1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printable and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
26 . /////////////////////////////////////////////////////////////////////////////
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generates the outermost <book> element that wraps the entire document.
39 . /////////////////////////////////////////////////////////////////////////////
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.94"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
54 .set drivernamemax "64"
60 . /////////////////////////////////////////////////////////////////////////////
61 . Additional xfpt markup used by this document, over and above the default
62 . provided in the xfpt library.
63 . /////////////////////////////////////////////////////////////////////////////
65 . --- Override the &$ flag to automatically insert a $ with the variable name.
67 .flag &$ $& "<varname>$" "</varname>"
69 . --- Short flags for daggers in option headings. They will always be inside
70 . --- an italic string, but we want the daggers to be in Roman.
72 .flag &!! "</emphasis>†<emphasis>"
73 .flag &!? "</emphasis>‡<emphasis>"
75 . --- A macro for an Exim option definition heading, generating a one-line
76 . --- table with four columns. For cases when the option name is given with
77 . --- a space, so that it can be split, a fifth argument is used for the
87 .itable all 0 0 4 8* left 6* center 6* center 6* right
88 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
92 . --- A macro for the common 2-column tables. The width of the first column
93 . --- is suitable for the many tables at the start of the main options chapter;
94 . --- a small number of other 2-column tables override it.
96 .macro table2 196pt 254pt
97 .itable none 0 0 2 $1 left $2 left
100 . --- A macro that generates .row, but puts &I; at the start of the first
101 . --- argument, thus indenting it. Assume a minimum of two arguments, and
102 . --- allow up to four arguments, which is as many as we'll ever need.
106 .row "&I;$1" "$2" "$3" "$4"
110 .row "&I;$1" "$2" "$3"
118 . --- Macros for option, variable, and concept index entries. For a "range"
119 . --- style of entry, use .scindex for the start and .ecindex for the end. The
120 . --- first argument of .scindex and the only argument of .ecindex must be the
121 . --- ID that ties them together.
124 &<indexterm role="concept">&
125 &<primary>&$1&</primary>&
127 &<secondary>&$2&</secondary>&
133 &<indexterm role="concept" id="$1" class="startofrange">&
134 &<primary>&$2&</primary>&
136 &<secondary>&$3&</secondary>&
142 &<indexterm role="concept" startref="$1" class="endofrange"/>&
146 &<indexterm role="option">&
147 &<primary>&$1&</primary>&
149 &<secondary>&$2&</secondary>&
155 &<indexterm role="variable">&
156 &<primary>&$1&</primary>&
158 &<secondary>&$2&</secondary>&
164 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
168 . use this for a concept-index entry for a header line
170 .cindex "&'$1'& header line"
171 .cindex "header lines" $1
173 . ////////////////////////////////////////////////////////////////////////////
176 . ////////////////////////////////////////////////////////////////////////////
177 . The <bookinfo> element is removed from the XML before processing for ASCII
179 . ////////////////////////////////////////////////////////////////////////////
183 <title>Specification of the Exim Mail Transfer Agent</title>
184 <titleabbrev>The Exim MTA</titleabbrev>
188 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
189 <authorinitials>EM</authorinitials>
190 <revhistory><revision>
192 <authorinitials>EM</authorinitials>
193 </revision></revhistory>
196 </year><holder>University of Cambridge</holder></copyright>
201 . /////////////////////////////////////////////////////////////////////////////
202 . This chunk of literal XML implements index entries of the form "x, see y" and
203 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
204 . at the top level, so we have to put the .chapter directive first.
206 . These do not turn up in the HTML output, unfortunately. The PDF does get them.
207 . /////////////////////////////////////////////////////////////////////////////
209 .chapter "Introduction" "CHID1"
212 <indexterm role="variable">
213 <primary>$1, $2, etc.</primary>
214 <see><emphasis>numerical variables</emphasis></see>
216 <indexterm role="concept">
217 <primary>address</primary>
218 <secondary>rewriting</secondary>
219 <see><emphasis>rewriting</emphasis></see>
221 <indexterm role="concept">
222 <primary>Bounce Address Tag Validation</primary>
223 <see><emphasis>BATV</emphasis></see>
225 <indexterm role="concept">
226 <primary>Client SMTP Authorization</primary>
227 <see><emphasis>CSA</emphasis></see>
229 <indexterm role="concept">
230 <primary>CR character</primary>
231 <see><emphasis>carriage return</emphasis></see>
233 <indexterm role="concept">
234 <primary>CRL</primary>
235 <see><emphasis>certificate revocation list</emphasis></see>
237 <indexterm role="concept">
238 <primary>delivery</primary>
239 <secondary>failure report</secondary>
240 <see><emphasis>bounce message</emphasis></see>
242 <indexterm role="concept">
243 <primary>de-tainting</primary>
244 <see><emphasis>tainting, de-tainting</emphasis></see>
246 <indexterm role="concept">
247 <primary>detainting</primary>
248 <see><emphasis>tainting, de-tainting</emphasis></see>
250 <indexterm role="concept">
251 <primary>dialup</primary>
252 <see><emphasis>intermittently connected hosts</emphasis></see>
254 <indexterm role="concept">
255 <primary>exiscan</primary>
256 <see><emphasis>content scanning</emphasis></see>
258 <indexterm role="concept">
259 <primary>failover</primary>
260 <see><emphasis>fallback</emphasis></see>
262 <indexterm role="concept">
263 <primary>fallover</primary>
264 <see><emphasis>fallback</emphasis></see>
266 <indexterm role="concept">
267 <primary>filter</primary>
268 <secondary>Sieve</secondary>
269 <see><emphasis>Sieve filter</emphasis></see>
271 <indexterm role="concept">
272 <primary>ident</primary>
273 <see><emphasis>RFC 1413</emphasis></see>
275 <indexterm role="concept">
276 <primary>LF character</primary>
277 <see><emphasis>linefeed</emphasis></see>
279 <indexterm role="concept">
280 <primary>maximum</primary>
281 <seealso><emphasis>limit</emphasis></seealso>
283 <indexterm role="concept">
284 <primary>monitor</primary>
285 <see><emphasis>Exim monitor</emphasis></see>
287 <indexterm role="concept">
288 <primary>no_<emphasis>xxx</emphasis></primary>
289 <see>entry for xxx</see>
291 <indexterm role="concept">
292 <primary>NUL</primary>
293 <see><emphasis>binary zero</emphasis></see>
295 <indexterm role="concept">
296 <primary>passwd file</primary>
297 <see><emphasis>/etc/passwd</emphasis></see>
299 <indexterm role="concept">
300 <primary>process id</primary>
301 <see><emphasis>pid</emphasis></see>
303 <indexterm role="concept">
304 <primary>RBL</primary>
305 <see><emphasis>DNS list</emphasis></see>
307 <indexterm role="concept">
308 <primary>redirection</primary>
309 <see><emphasis>address redirection</emphasis></see>
311 <indexterm role="concept">
312 <primary>return path</primary>
313 <seealso><emphasis>envelope sender</emphasis></seealso>
315 <indexterm role="concept">
316 <primary>scanning</primary>
317 <see><emphasis>content scanning</emphasis></see>
319 <indexterm role="concept">
320 <primary>SSL</primary>
321 <see><emphasis>TLS</emphasis></see>
323 <indexterm role="concept">
324 <primary>string</primary>
325 <secondary>expansion</secondary>
326 <see><emphasis>expansion</emphasis></see>
328 <indexterm role="concept">
329 <primary>top bit</primary>
330 <see><emphasis>8-bit characters</emphasis></see>
332 <indexterm role="concept">
333 <primary>variables</primary>
334 <see><emphasis>expansion, variables</emphasis></see>
336 <indexterm role="concept">
337 <primary>zero, binary</primary>
338 <see><emphasis>binary zero</emphasis></see>
340 <indexterm role="concept">
341 <primary>headers</primary>
342 <see><emphasis>header lines</emphasis></see>
348 . /////////////////////////////////////////////////////////////////////////////
349 . This is the real start of the first chapter. See the comment above as to why
350 . we can't have the .chapter line here.
351 . chapter "Introduction"
352 . /////////////////////////////////////////////////////////////////////////////
354 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
355 Unix-like operating systems. It was designed on the assumption that it would be
356 run on hosts that are permanently connected to the Internet. However, it can be
357 used on intermittently connected hosts with suitable configuration adjustments.
359 Configuration files currently exist for the following operating systems: AIX,
360 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
361 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
362 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
363 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
364 Some of these operating systems are no longer current and cannot easily be
365 tested, so the configuration files may no longer work in practice.
367 There are also configuration files for compiling Exim in the Cygwin environment
368 that can be installed on systems running Windows. However, this document does
369 not contain any information about running Exim in the Cygwin environment.
371 The terms and conditions for the use and distribution of Exim are contained in
372 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
373 Public Licence, a copy of which may be found in the file &_LICENCE_&.
375 The use, supply, or promotion of Exim for the purpose of sending bulk,
376 unsolicited electronic mail is incompatible with the basic aims of Exim,
377 which revolve around the free provision of a service that enhances the quality
378 of personal communications. The author of Exim regards indiscriminate
379 mass-mailing as an antisocial, irresponsible abuse of the Internet.
381 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
382 experience of running and working on the Smail 3 code, I could never have
383 contemplated starting to write a new MTA. Many of the ideas and user interfaces
384 were originally taken from Smail 3, though the actual code of Exim is entirely
385 new, and has developed far beyond the initial concept.
387 Many people, both in Cambridge and around the world, have contributed to the
388 development and the testing of Exim, and to porting it to various operating
389 systems. I am grateful to them all. The distribution now contains a file called
390 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
394 .section "Exim documentation" "SECID1"
395 . Keep this example change bar when updating the documentation!
398 .cindex "documentation"
399 This edition of the Exim specification applies to version &version() of Exim.
400 Substantive changes from the &previousversion; edition are marked in some
401 renditions of this document; this paragraph is so marked if the rendition is
402 capable of showing a change indicator.
405 This document is very much a reference manual; it is not a tutorial. The reader
406 is expected to have some familiarity with the SMTP mail transfer protocol and
407 with general Unix system administration. Although there are some discussions
408 and examples in places, the information is mostly organized in a way that makes
409 it easy to look up, rather than in a natural order for sequential reading.
410 Furthermore, this manual aims to cover every aspect of Exim in detail, including
411 a number of rarely-used, special-purpose features that are unlikely to be of
414 .cindex "books about Exim"
415 An &"easier"& discussion of Exim which provides more in-depth explanatory,
416 introductory, and tutorial material can be found in a book entitled &'The Exim
417 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
418 (&url(https://www.uit.co.uk/exim-book/)).
420 The book also contains a chapter that gives a general introduction to SMTP and
421 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
422 with the latest release of Exim. (Note that the earlier book about Exim,
423 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
425 .cindex "Debian" "information sources"
426 If you are using a Debian distribution of Exim, you will find information about
427 Debian-specific features in the file
428 &_/usr/share/doc/exim4-base/README.Debian_&.
429 The command &(man update-exim.conf)& is another source of Debian-specific
432 .cindex "&_doc/NewStuff_&"
433 .cindex "&_doc/ChangeLog_&"
435 As Exim develops, there may be features in newer versions that have not
436 yet made it into this document, which is updated only when the most significant
437 digit of the fractional part of the version number changes. Specifications of
438 new features that are not yet in this manual are placed in the file
439 &_doc/NewStuff_& in the Exim distribution.
441 Some features may be classified as &"experimental"&. These may change
442 incompatibly while they are developing, or even be withdrawn. For this reason,
443 they are not documented in this manual. Information about experimental features
444 can be found in the file &_doc/experimental.txt_&.
446 All changes to Exim (whether new features, bug fixes, or other kinds of
447 change) are noted briefly in the file called &_doc/ChangeLog_&.
449 .cindex "&_doc/spec.txt_&"
450 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
451 that it can easily be searched with a text editor. Other files in the &_doc_&
455 .row &_OptionLists.txt_& "list of all options in alphabetical order"
456 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
457 .row &_exim.8_& "a man page of Exim's command line options"
458 .row &_experimental.txt_& "documentation of experimental features"
459 .row &_filter.txt_& "specification of the filter language"
460 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
461 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
462 .row &_openssl.txt_& "installing a current OpenSSL release"
465 The main specification and the specification of the filtering language are also
466 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
467 &<<SECTavail>>& below tells you how to get hold of these.
471 .section "FTP site and websites" "SECID2"
474 The primary site for Exim source distributions is the &%exim.org%& FTP site,
475 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
476 website, are hosted at the University of Cambridge.
480 As well as Exim distribution tar files, the Exim website contains a number of
481 differently formatted versions of the documentation. A recent addition to the
482 online information is the Exim wiki (&url(https://wiki.exim.org)),
483 which contains what used to be a separate FAQ, as well as various other
484 examples, tips, and know-how that have been contributed by Exim users.
485 The wiki site should always redirect to the correct place, which is currently
486 provided by GitHub, and is open to editing by anyone with a GitHub account.
489 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
490 this to report bugs, and also to add items to the wish list. Please search
491 first to check that you are not duplicating a previous entry.
492 Please do not ask for configuration help in the bug-tracker.
495 .section "Mailing lists" "SECID3"
496 .cindex "mailing lists" "for Exim users"
497 The following Exim mailing lists exist:
500 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
501 .row &'exim-users@exim.org'& "General discussion list"
502 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
503 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
506 You can subscribe to these lists, change your existing subscriptions, and view
507 or search the archives via the mailing lists link on the Exim home page.
508 .cindex "Debian" "mailing list for"
509 If you are using a Debian distribution of Exim, you may wish to subscribe to
510 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
513 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
515 Please ask Debian-specific questions on that list and not on the general Exim
518 .section "Bug reports" "SECID5"
519 .cindex "bug reports"
520 .cindex "reporting bugs"
521 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
522 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
523 whether some behaviour is a bug or not, the best thing to do is to post a
524 message to the &'exim-dev'& mailing list and have it discussed.
528 .section "Where to find the Exim distribution" "SECTavail"
530 .cindex "HTTPS download site"
531 .cindex "distribution" "FTP site"
532 .cindex "distribution" "https site"
533 The master distribution site for the Exim distribution is
535 &url(https://downloads.exim.org/)
537 The service is available over HTTPS, HTTP and FTP.
538 We encourage people to migrate to HTTPS.
540 The content served at &url(https://downloads.exim.org/) is identical to the
541 content served at &url(https://ftp.exim.org/pub/exim) and
542 &url(ftp://ftp.exim.org/pub/exim).
544 If accessing via a hostname containing &'ftp'&, then the file references that
545 follow are relative to the &_exim_& directories at these sites.
546 If accessing via the hostname &'downloads'& then the subdirectories described
547 here are top-level directories.
549 There are now quite a number of independent mirror sites around
550 the world. Those that I know about are listed in the file called &_Mirrors_&.
552 Within the top exim directory there are subdirectories called &_exim3_& (for
553 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
554 distributions), and &_Testing_& for testing versions. In the &_exim4_&
555 subdirectory, the current release can always be found in files called
559 &_exim-n.nn.tar.bz2_&
561 where &'n.nn'& is the highest such version number in the directory. The three
562 files contain identical data; the only difference is the type of compression.
563 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
564 most portable to old systems.
566 .cindex "distribution" "signing details"
567 .cindex "distribution" "public key"
568 .cindex "public key for signed distribution"
569 The distributions will be PGP signed by an individual key of the Release
570 Coordinator. This key will have a uid containing an email address in the
571 &'exim.org'& domain and will have signatures from other people, including
572 other Exim maintainers. We expect that the key will be in the "strong set" of
573 PGP keys. There should be a trust path to that key from the Exim Maintainer's
574 PGP keys, a version of which can be found in the release directory in the file
575 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
576 such as &'pool.sks-keyservers.net'&.
578 At the time of the last update, releases were being made by Jeremy Harris and signed
579 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
580 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
581 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
583 The signatures for the tar bundles are in:
585 &_exim-n.nn.tar.xz.asc_&
586 &_exim-n.nn.tar.gz.asc_&
587 &_exim-n.nn.tar.bz2.asc_&
589 For each released version, the log of changes is made available in a
590 separate file in the directory &_ChangeLogs_& so that it is possible to
591 find out what has changed without having to download the entire distribution.
593 .cindex "documentation" "available formats"
594 The main distribution contains ASCII versions of this specification and other
595 documentation; other formats of the documents are available in separate files
596 inside the &_exim4_& directory of the FTP site:
598 &_exim-html-n.nn.tar.gz_&
599 &_exim-pdf-n.nn.tar.gz_&
600 &_exim-postscript-n.nn.tar.gz_&
601 &_exim-texinfo-n.nn.tar.gz_&
603 These tar files contain only the &_doc_& directory, not the complete
604 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
607 .section "Limitations" "SECID6"
609 .cindex "limitations of Exim"
610 .cindex "bang paths" "not handled by Exim"
611 Exim is designed for use as an Internet MTA, and therefore handles addresses in
612 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
613 simple two-component bang paths can be converted by a straightforward rewriting
614 configuration. This restriction does not prevent Exim from being interfaced to
615 UUCP as a transport mechanism, provided that domain addresses are used.
617 .cindex "domainless addresses"
618 .cindex "address" "without domain"
619 Exim insists that every address it handles has a domain attached. For incoming
620 local messages, domainless addresses are automatically qualified with a
621 configured domain value. Configuration options specify from which remote
622 systems unqualified addresses are acceptable. These are then qualified on
625 .cindex "transport" "external"
626 .cindex "external transports"
627 The only external transport mechanisms that are currently implemented are SMTP
628 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
629 transport is available, and there are facilities for writing messages to files
630 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
631 to send messages to other transport mechanisms such as UUCP, provided they can
632 handle domain-style addresses. Batched SMTP input is also catered for.
634 Exim is not designed for storing mail for dial-in hosts. When the volumes of
635 such mail are large, it is better to get the messages &"delivered"& into files
636 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
639 Although Exim does have basic facilities for scanning incoming messages, these
640 are not comprehensive enough to do full virus or spam scanning. Such operations
641 are best carried out using additional specialized software packages. If you
642 compile Exim with the content-scanning extension, straightforward interfaces to
643 a number of common scanners are provided.
647 .section "Runtime configuration" "SECID7"
648 Exim's runtime configuration is held in a single text file that is divided
649 into a number of sections. The entries in this file consist of keywords and
650 values, in the style of Smail 3 configuration files. A default configuration
651 file which is suitable for simple online installations is provided in the
652 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
655 .section "Calling interface" "SECID8"
656 .cindex "Sendmail compatibility" "command line interface"
657 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
658 can be a straight replacement for &_/usr/lib/sendmail_& or
659 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
660 about Sendmail in order to run Exim. For actions other than sending messages,
661 Sendmail-compatible options also exist, but those that produce output (for
662 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
663 format. There are also some additional options that are compatible with Smail
664 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
665 documents all Exim's command line options. This information is automatically
666 made into the man page that forms part of the Exim distribution.
668 Control of messages in the queue can be done via certain privileged command
669 line options. There is also an optional monitor program called &'eximon'&,
670 which displays current information in an X window, and which contains a menu
671 interface to Exim's command line administration options.
675 .section "Terminology" "SECID9"
676 .cindex "terminology definitions"
677 .cindex "body of message" "definition of"
678 The &'body'& of a message is the actual data that the sender wants to transmit.
679 It is the last part of a message and is separated from the &'header'& (see
680 below) by a blank line.
682 .cindex "bounce message" "definition of"
683 When a message cannot be delivered, it is normally returned to the sender in a
684 delivery failure message or a &"non-delivery report"& (NDR). The term
685 &'bounce'& is commonly used for this action, and the error reports are often
686 called &'bounce messages'&. This is a convenient shorthand for &"delivery
687 failure error report"&. Such messages have an empty sender address in the
688 message's &'envelope'& (see below) to ensure that they cannot themselves give
689 rise to further bounce messages.
691 The term &'default'& appears frequently in this manual. It is used to qualify a
692 value which is used in the absence of any setting in the configuration. It may
693 also qualify an action which is taken unless a configuration setting specifies
696 The term &'defer'& is used when the delivery of a message to a specific
697 destination cannot immediately take place for some reason (a remote host may be
698 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
701 The word &'domain'& is sometimes used to mean all but the first component of a
702 host's name. It is &'not'& used in that sense here, where it normally refers to
703 the part of an email address following the @ sign.
705 .cindex "envelope, definition of"
706 .cindex "sender" "definition of"
707 A message in transit has an associated &'envelope'&, as well as a header and a
708 body. The envelope contains a sender address (to which bounce messages should
709 be delivered), and any number of recipient addresses. References to the
710 sender or the recipients of a message usually mean the addresses in the
711 envelope. An MTA uses these addresses for delivery, and for returning bounce
712 messages, not the addresses that appear in the header lines.
714 .cindex "message" "header, definition of"
715 .cindex "header section" "definition of"
716 The &'header'& of a message is the first part of a message's text, consisting
717 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
718 &'Subject:'&, etc. Long header lines can be split over several text lines by
719 indenting the continuations. The header is separated from the body by a blank
722 .cindex "local part" "definition of"
723 .cindex "domain" "definition of"
724 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
725 part of an email address that precedes the @ sign. The part that follows the
726 @ sign is called the &'domain'& or &'mail domain'&.
728 .cindex "local delivery" "definition of"
729 .cindex "remote delivery, definition of"
730 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
731 delivery to a file or a pipe on the local host from delivery by SMTP over
732 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
733 host it is running on are &'remote'&.
735 .cindex "return path" "definition of"
736 &'Return path'& is another name that is used for the sender address in a
739 .cindex "queue" "definition of"
740 The term &'queue'& is used to refer to the set of messages awaiting delivery
741 because this term is in widespread use in the context of MTAs. However, in
742 Exim's case, the reality is more like a pool than a queue, because there is
743 normally no ordering of waiting messages.
745 .cindex "queue runner" "definition of"
746 The term &'queue runner'& is used to describe a process that scans the queue
747 and attempts to deliver those messages whose retry times have come. This term
748 is used by other MTAs and also relates to the command &%runq%&, but in Exim
749 the waiting messages are normally processed in an unpredictable order.
751 .cindex "spool directory" "definition of"
752 The term &'spool directory'& is used for a directory in which Exim keeps the
753 messages in its queue &-- that is, those that it is in the process of
754 delivering. This should not be confused with the directory in which local
755 mailboxes are stored, which is called a &"spool directory"& by some people. In
756 the Exim documentation, &"spool"& is always used in the first sense.
763 . ////////////////////////////////////////////////////////////////////////////
764 . ////////////////////////////////////////////////////////////////////////////
766 .chapter "Incorporated code" "CHID2"
767 .cindex "incorporated code"
768 .cindex "regular expressions" "library"
771 A number of pieces of external code are included in the Exim distribution.
774 Regular expressions are supported in the main Exim program and in the
775 Exim monitor using the freely-distributable PCRE library, copyright
776 © University of Cambridge. The source to PCRE is no longer shipped with
777 Exim, so you will need to use the version of PCRE shipped with your system,
778 or obtain and install the full version of the library from
779 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
781 .cindex "cdb" "acknowledgment"
782 Support for the cdb (Constant DataBase) lookup method is provided by code
783 contributed by Nigel Metheringham of (at the time he contributed it) Planet
784 Online Ltd. The implementation is completely contained within the code of Exim.
785 It does not link against an external cdb library. The code contains the
786 following statements:
789 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
791 This program is free software; you can redistribute it and/or modify it under
792 the terms of the GNU General Public License as published by the Free Software
793 Foundation; either version 2 of the License, or (at your option) any later
795 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
796 the spec and sample code for cdb can be obtained from
797 &url(https://cr.yp.to/cdb.html). This implementation borrows
798 some code from Dan Bernstein's implementation (which has no license
799 restrictions applied to it).
802 .cindex "SPA authentication"
803 .cindex "Samba project"
804 .cindex "Microsoft Secure Password Authentication"
805 Client support for Microsoft's &'Secure Password Authentication'& is provided
806 by code contributed by Marc Prud'hommeaux. Server support was contributed by
807 Tom Kistner. This includes code taken from the Samba project, which is released
811 .cindex "&'pwcheck'& daemon"
812 .cindex "&'pwauthd'& daemon"
813 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
814 by code taken from the Cyrus-SASL library and adapted by Alexander S.
815 Sabourenkov. The permission notice appears below, in accordance with the
816 conditions expressed therein.
819 Copyright © 2001 Carnegie Mellon University. All rights reserved.
821 Redistribution and use in source and binary forms, with or without
822 modification, are permitted provided that the following conditions
826 Redistributions of source code must retain the above copyright
827 notice, this list of conditions and the following disclaimer.
829 Redistributions in binary form must reproduce the above copyright
830 notice, this list of conditions and the following disclaimer in
831 the documentation and/or other materials provided with the
834 The name &"Carnegie Mellon University"& must not be used to
835 endorse or promote products derived from this software without
836 prior written permission. For permission or any other legal
837 details, please contact
839 Office of Technology Transfer
840 Carnegie Mellon University
842 Pittsburgh, PA 15213-3890
843 (412) 268-4387, fax: (412) 268-7395
844 tech-transfer@andrew.cmu.edu
847 Redistributions of any form whatsoever must retain the following
850 &"This product includes software developed by Computing Services
851 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
853 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
854 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
855 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
856 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
857 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
858 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
859 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
864 .cindex "Exim monitor" "acknowledgment"
867 The Exim Monitor program, which is an X-Window application, includes
868 modified versions of the Athena StripChart and TextPop widgets.
869 This code is copyright by DEC and MIT, and their permission notice appears
870 below, in accordance with the conditions expressed therein.
873 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
874 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
878 Permission to use, copy, modify, and distribute this software and its
879 documentation for any purpose and without fee is hereby granted,
880 provided that the above copyright notice appear in all copies and that
881 both that copyright notice and this permission notice appear in
882 supporting documentation, and that the names of Digital or MIT not be
883 used in advertising or publicity pertaining to distribution of the
884 software without specific, written prior permission.
886 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
887 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
888 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
889 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
890 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
891 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
896 .cindex "opendmarc" "acknowledgment"
897 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
898 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
899 derived code are indicated in the respective source files. The full OpenDMARC
900 license is provided in the LICENSE.opendmarc file contained in the distributed
904 Many people have contributed code fragments, some large, some small, that were
905 not covered by any specific license requirements. It is assumed that the
906 contributors are happy to see their code incorporated into Exim under the GPL.
913 . ////////////////////////////////////////////////////////////////////////////
914 . ////////////////////////////////////////////////////////////////////////////
916 .chapter "How Exim receives and delivers mail" "CHID11" &&&
917 "Receiving and delivering mail"
920 .section "Overall philosophy" "SECID10"
921 .cindex "design philosophy"
922 Exim is designed to work efficiently on systems that are permanently connected
923 to the Internet and are handling a general mix of mail. In such circumstances,
924 most messages can be delivered immediately. Consequently, Exim does not
925 maintain independent queues of messages for specific domains or hosts, though
926 it does try to send several messages in a single SMTP connection after a host
927 has been down, and it also maintains per-host retry information.
930 .section "Policy control" "SECID11"
931 .cindex "policy control" "overview"
932 Policy controls are now an important feature of MTAs that are connected to the
933 Internet. Perhaps their most important job is to stop MTAs from being abused as
934 &"open relays"& by misguided individuals who send out vast amounts of
935 unsolicited junk and want to disguise its source. Exim provides flexible
936 facilities for specifying policy controls on incoming mail:
939 .cindex "&ACL;" "introduction"
940 Exim 4 (unlike previous versions of Exim) implements policy controls on
941 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
942 series of statements that may either grant or deny access. ACLs can be used at
943 several places in the SMTP dialogue while receiving a message from a remote
944 host. However, the most common places are after each RCPT command, and at the
945 very end of the message. The sysadmin can specify conditions for accepting or
946 rejecting individual recipients or the entire message, respectively, at these
947 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
950 An ACL is also available for locally generated, non-SMTP messages. In this
951 case, the only available actions are to accept or deny the entire message.
953 When Exim is compiled with the content-scanning extension, facilities are
954 provided in the ACL mechanism for passing the message to external virus and/or
955 spam scanning software. The result of such a scan is passed back to the ACL,
956 which can then use it to decide what to do with the message.
958 When a message has been received, either from a remote host or from the local
959 host, but before the final acknowledgment has been sent, a locally supplied C
960 function called &[local_scan()]& can be run to inspect the message and decide
961 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
962 is accepted, the list of recipients can be modified by the function.
964 Using the &[local_scan()]& mechanism is another way of calling external scanner
965 software. The &%SA-Exim%& add-on package works this way. It does not require
966 Exim to be compiled with the content-scanning extension.
968 After a message has been accepted, a further checking mechanism is available in
969 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
970 runs at the start of every delivery process.
975 .section "User filters" "SECID12"
976 .cindex "filter" "introduction"
977 .cindex "Sieve filter"
978 In a conventional Exim configuration, users are able to run private filters by
979 setting up appropriate &_.forward_& files in their home directories. See
980 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
981 configuration needed to support this, and the separate document entitled
982 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
983 of filtering are available:
986 Sieve filters are written in the standard filtering language that is defined
989 Exim filters are written in a syntax that is unique to Exim, but which is more
990 powerful than Sieve, which it pre-dates.
993 User filters are run as part of the routing process, described below.
997 .section "Message identification" "SECTmessiden"
998 .cindex "message ids" "details of format"
999 .cindex "format" "of message id"
1000 .cindex "id of message"
1005 Every message handled by Exim is given a &'message id'& which is sixteen
1006 characters long. It is divided into three parts, separated by hyphens, for
1007 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
1008 normally encoding numbers in base 62. However, in the Darwin operating
1009 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1010 (avoiding the use of lower case letters) is used instead, because the message
1011 id is used to construct filenames, and the names of files in those systems are
1012 not always case-sensitive.
1014 .cindex "pid (process id)" "re-use of"
1015 The detail of the contents of the message id have changed as Exim has evolved.
1016 Earlier versions relied on the operating system not re-using a process id (pid)
1017 within one second. On modern operating systems, this assumption can no longer
1018 be made, so the algorithm had to be changed. To retain backward compatibility,
1019 the format of the message id was retained, which is why the following rules are
1023 The first six characters of the message id are the time at which the message
1024 started to be received, to a granularity of one second. That is, this field
1025 contains the number of seconds since the start of the epoch (the normal Unix
1026 way of representing the date and time of day).
1028 After the first hyphen, the next six characters are the id of the process that
1029 received the message.
1031 There are two different possibilities for the final two characters:
1033 .oindex "&%localhost_number%&"
1034 If &%localhost_number%& is not set, this value is the fractional part of the
1035 time of reception, normally in units of 1/2000 of a second, but for systems
1036 that must use base 36 instead of base 62 (because of case-insensitive file
1037 systems), the units are 1/1000 of a second.
1039 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1040 the fractional part of the time, which in this case is in units of 1/200
1041 (1/100) of a second.
1045 After a message has been received, Exim waits for the clock to tick at the
1046 appropriate resolution before proceeding, so that if another message is
1047 received by the same process, or by another process with the same (re-used)
1048 pid, it is guaranteed that the time will be different. In most cases, the clock
1049 will already have ticked while the message was being received.
1052 .section "Receiving mail" "SECID13"
1053 .cindex "receiving mail"
1054 .cindex "message" "reception"
1055 The only way Exim can receive mail from another host is using SMTP over
1056 TCP/IP, in which case the sender and recipient addresses are transferred using
1057 SMTP commands. However, from a locally running process (such as a user's MUA),
1058 there are several possibilities:
1061 If the process runs Exim with the &%-bm%& option, the message is read
1062 non-interactively (usually via a pipe), with the recipients taken from the
1063 command line, or from the body of the message if &%-t%& is also used.
1065 If the process runs Exim with the &%-bS%& option, the message is also read
1066 non-interactively, but in this case the recipients are listed at the start of
1067 the message in a series of SMTP RCPT commands, terminated by a DATA
1068 command. This is called &"batch SMTP"& format,
1069 but it isn't really SMTP. The SMTP commands are just another way of passing
1070 envelope addresses in a non-interactive submission.
1072 If the process runs Exim with the &%-bs%& option, the message is read
1073 interactively, using the SMTP protocol. A two-way pipe is normally used for
1074 passing data between the local process and the Exim process.
1075 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1076 example, the ACLs for SMTP commands are used for this form of submission.
1078 A local process may also make a TCP/IP call to the host's loopback address
1079 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1080 does not treat the loopback address specially. It treats all such connections
1081 in the same way as connections from other hosts.
1085 .cindex "message sender, constructed by Exim"
1086 .cindex "sender" "constructed by Exim"
1087 In the three cases that do not involve TCP/IP, the sender address is
1088 constructed from the login name of the user that called Exim and a default
1089 qualification domain (which can be set by the &%qualify_domain%& configuration
1090 option). For local or batch SMTP, a sender address that is passed using the
1091 SMTP MAIL command is ignored. However, the system administrator may allow
1092 certain users (&"trusted users"&) to specify a different sender addresses
1093 unconditionally, or all users to specify certain forms of different sender
1094 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1095 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1096 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1097 users to change sender addresses.
1099 Messages received by either of the non-interactive mechanisms are subject to
1100 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1101 (either over TCP/IP or interacting with a local process) can be checked by a
1102 number of ACLs that operate at different times during the SMTP session. Either
1103 individual recipients or the entire message can be rejected if local policy
1104 requirements are not met. The &[local_scan()]& function (see chapter
1105 &<<CHAPlocalscan>>&) is run for all incoming messages.
1107 Exim can be configured not to start a delivery process when a message is
1108 received; this can be unconditional, or depend on the number of incoming SMTP
1109 connections or the system load. In these situations, new messages wait on the
1110 queue until a queue runner process picks them up. However, in standard
1111 configurations under normal conditions, delivery is started as soon as a
1112 message is received.
1118 .section "Handling an incoming message" "SECID14"
1119 .cindex "spool directory" "files that hold a message"
1120 .cindex "file" "how a message is held"
1121 When Exim accepts a message, it writes two files in its spool directory. The
1122 first contains the envelope information, the current status of the message, and
1123 the header lines, and the second contains the body of the message. The names of
1124 the two spool files consist of the message id, followed by &`-H`& for the
1125 file containing the envelope and header, and &`-D`& for the data file.
1127 .cindex "spool directory" "&_input_& sub-directory"
1128 By default, all these message files are held in a single directory called
1129 &_input_& inside the general Exim spool directory. Some operating systems do
1130 not perform very well if the number of files in a directory gets large; to
1131 improve performance in such cases, the &%split_spool_directory%& option can be
1132 used. This causes Exim to split up the input files into 62 sub-directories
1133 whose names are single letters or digits. When this is done, the queue is
1134 processed one sub-directory at a time instead of all at once, which can improve
1135 overall performance even when there are not enough files in each directory to
1136 affect file system performance.
1138 The envelope information consists of the address of the message's sender and
1139 the addresses of the recipients. This information is entirely separate from
1140 any addresses contained in the header lines. The status of the message includes
1141 a list of recipients who have already received the message. The format of the
1142 first spool file is described in chapter &<<CHAPspool>>&.
1144 .cindex "rewriting" "addresses"
1145 Address rewriting that is specified in the rewrite section of the configuration
1146 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1147 both in the header lines and the envelope, at the time the message is accepted.
1148 If during the course of delivery additional addresses are generated (for
1149 example, via aliasing), these new addresses are rewritten as soon as they are
1150 generated. At the time a message is actually delivered (transported) further
1151 rewriting can take place; because this is a transport option, it can be
1152 different for different forms of delivery. It is also possible to specify the
1153 addition or removal of certain header lines at the time the message is
1154 delivered (see chapters &<<CHAProutergeneric>>& and
1155 &<<CHAPtransportgeneric>>&).
1159 .section "Life of a message" "SECID15"
1160 .cindex "message" "life of"
1161 .cindex "message" "frozen"
1162 A message remains in the spool directory until it is completely delivered to
1163 its recipients or to an error address, or until it is deleted by an
1164 administrator or by the user who originally created it. In cases when delivery
1165 cannot proceed &-- for example when a message can neither be delivered to its
1166 recipients nor returned to its sender, the message is marked &"frozen"& on the
1167 spool, and no more deliveries are attempted.
1169 .cindex "frozen messages" "thawing"
1170 .cindex "message" "thawing frozen"
1171 An administrator can &"thaw"& such messages when the problem has been
1172 corrected, and can also freeze individual messages by hand if necessary. In
1173 addition, an administrator can force a delivery error, causing a bounce message
1176 .oindex "&%timeout_frozen_after%&"
1177 .oindex "&%ignore_bounce_errors_after%&"
1178 There are options called &%ignore_bounce_errors_after%& and
1179 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1180 The first applies only to frozen bounces, the second to all frozen messages.
1182 .cindex "message" "log file for"
1183 .cindex "log" "file for each message"
1184 While Exim is working on a message, it writes information about each delivery
1185 attempt to its main log file. This includes successful, unsuccessful, and
1186 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1187 lines are also written to a separate &'message log'& file for each message.
1188 These logs are solely for the benefit of the administrator and are normally
1189 deleted along with the spool files when processing of a message is complete.
1190 The use of individual message logs can be disabled by setting
1191 &%no_message_logs%&; this might give an improvement in performance on very busy
1194 .cindex "journal file"
1195 .cindex "file" "journal"
1196 All the information Exim itself needs to set up a delivery is kept in the first
1197 spool file, along with the header lines. When a successful delivery occurs, the
1198 address is immediately written at the end of a journal file, whose name is the
1199 message id followed by &`-J`&. At the end of a delivery run, if there are some
1200 addresses left to be tried again later, the first spool file (the &`-H`& file)
1201 is updated to indicate which these are, and the journal file is then deleted.
1202 Updating the spool file is done by writing a new file and renaming it, to
1203 minimize the possibility of data loss.
1205 Should the system or Exim crash after a successful delivery but before
1206 the spool file has been updated, the journal is left lying around. The next
1207 time Exim attempts to deliver the message, it reads the journal file and
1208 updates the spool file before proceeding. This minimizes the chances of double
1209 deliveries caused by crashes.
1213 .section "Processing an address for delivery" "SECTprocaddress"
1214 .cindex "drivers" "definition of"
1215 .cindex "router" "definition of"
1216 .cindex "transport" "definition of"
1217 The main delivery processing elements of Exim are called &'routers'& and
1218 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1219 number of them is provided in the source distribution, and compile-time options
1220 specify which ones are included in the binary. Runtime options specify which
1221 ones are actually used for delivering messages.
1223 .cindex "drivers" "instance definition"
1224 Each driver that is specified in the runtime configuration is an &'instance'&
1225 of that particular driver type. Multiple instances are allowed; for example,
1226 you can set up several different &(smtp)& transports, each with different
1227 option values that might specify different ports or different timeouts. Each
1228 instance has its own identifying name. In what follows we will normally use the
1229 instance name when discussing one particular instance (that is, one specific
1230 configuration of the driver), and the generic driver name when discussing
1231 the driver's features in general.
1233 A &'router'& is a driver that operates on an address, either determining how
1234 its delivery should happen, by assigning it to a specific transport, or
1235 converting the address into one or more new addresses (for example, via an
1236 alias file). A router may also explicitly choose to fail an address, causing it
1239 A &'transport'& is a driver that transmits a copy of the message from Exim's
1240 spool to some destination. There are two kinds of transport: for a &'local'&
1241 transport, the destination is a file or a pipe on the local host, whereas for a
1242 &'remote'& transport the destination is some other host. A message is passed
1243 to a specific transport as a result of successful routing. If a message has
1244 several recipients, it may be passed to a number of different transports.
1246 .cindex "preconditions" "definition of"
1247 An address is processed by passing it to each configured router instance in
1248 turn, subject to certain preconditions, until a router accepts the address or
1249 specifies that it should be bounced. We will describe this process in more
1250 detail shortly. First, as a simple example, we consider how each recipient
1251 address in a message is processed in a small configuration of three routers.
1253 To make this a more concrete example, it is described in terms of some actual
1254 routers, but remember, this is only an example. You can configure Exim's
1255 routers in many different ways, and there may be any number of routers in a
1258 The first router that is specified in a configuration is often one that handles
1259 addresses in domains that are not recognized specifically by the local host.
1260 Typically these are addresses for arbitrary domains on the Internet. A precondition
1261 is set up which looks for the special domains known to the host (for example,
1262 its own domain name), and the router is run for addresses that do &'not'&
1263 match. Typically, this is a router that looks up domains in the DNS in order to
1264 find the hosts to which this address routes. If it succeeds, the address is
1265 assigned to a suitable SMTP transport; if it does not succeed, the router is
1266 configured to fail the address.
1268 The second router is reached only when the domain is recognized as one that
1269 &"belongs"& to the local host. This router does redirection &-- also known as
1270 aliasing and forwarding. When it generates one or more new addresses from the
1271 original, each of them is routed independently from the start. Otherwise, the
1272 router may cause an address to fail, or it may simply decline to handle the
1273 address, in which case the address is passed to the next router.
1275 The final router in many configurations is one that checks to see if the
1276 address belongs to a local mailbox. The precondition may involve a check to
1277 see if the local part is the name of a login account, or it may look up the
1278 local part in a file or a database. If its preconditions are not met, or if
1279 the router declines, we have reached the end of the routers. When this happens,
1280 the address is bounced.
1284 .section "Processing an address for verification" "SECID16"
1285 .cindex "router" "for verification"
1286 .cindex "verifying address" "overview"
1287 As well as being used to decide how to deliver to an address, Exim's routers
1288 are also used for &'address verification'&. Verification can be requested as
1289 one of the checks to be performed in an ACL for incoming messages, on both
1290 sender and recipient addresses, and it can be tested using the &%-bv%& and
1291 &%-bvs%& command line options.
1293 When an address is being verified, the routers are run in &"verify mode"&. This
1294 does not affect the way the routers work, but it is a state that can be
1295 detected. By this means, a router can be skipped or made to behave differently
1296 when verifying. A common example is a configuration in which the first router
1297 sends all messages to a message-scanning program unless they have been
1298 previously scanned. Thus, the first router accepts all addresses without any
1299 checking, making it useless for verifying. Normally, the &%no_verify%& option
1300 would be set for such a router, causing it to be skipped in verify mode.
1305 .section "Running an individual router" "SECTrunindrou"
1306 .cindex "router" "running details"
1307 .cindex "preconditions" "checking"
1308 .cindex "router" "result of running"
1309 As explained in the example above, a number of preconditions are checked before
1310 running a router. If any are not met, the router is skipped, and the address is
1311 passed to the next router. When all the preconditions on a router &'are'& met,
1312 the router is run. What happens next depends on the outcome, which is one of
1316 &'accept'&: The router accepts the address, and either assigns it to a
1317 transport or generates one or more &"child"& addresses. Processing the
1318 original address ceases
1319 .oindex "&%unseen%&"
1320 unless the &%unseen%& option is set on the router. This option
1321 can be used to set up multiple deliveries with different routing (for example,
1322 for keeping archive copies of messages). When &%unseen%& is set, the address is
1323 passed to the next router. Normally, however, an &'accept'& return marks the
1326 Any child addresses generated by the router are processed independently,
1327 starting with the first router by default. It is possible to change this by
1328 setting the &%redirect_router%& option to specify which router to start at for
1329 child addresses. Unlike &%pass_router%& (see below) the router specified by
1330 &%redirect_router%& may be anywhere in the router configuration.
1332 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1333 requests that the address be passed to another router. By default, the address
1334 is passed to the next router, but this can be changed by setting the
1335 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1336 must be below the current router (to avoid loops).
1338 &'decline'&: The router declines to accept the address because it does not
1339 recognize it at all. By default, the address is passed to the next router, but
1340 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1341 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1342 &'decline'& into &'fail'&.
1344 &'fail'&: The router determines that the address should fail, and queues it for
1345 the generation of a bounce message. There is no further processing of the
1346 original address unless &%unseen%& is set on the router.
1348 &'defer'&: The router cannot handle the address at the present time. (A
1349 database may be offline, or a DNS lookup may have timed out.) No further
1350 processing of the address happens in this delivery attempt. It is tried again
1351 next time the message is considered for delivery.
1353 &'error'&: There is some error in the router (for example, a syntax error in
1354 its configuration). The action is as for defer.
1357 If an address reaches the end of the routers without having been accepted by
1358 any of them, it is bounced as unrouteable. The default error message in this
1359 situation is &"unrouteable address"&, but you can set your own message by
1360 making use of the &%cannot_route_message%& option. This can be set for any
1361 router; the value from the last router that &"saw"& the address is used.
1363 Sometimes while routing you want to fail a delivery when some conditions are
1364 met but others are not, instead of passing the address on for further routing.
1365 You can do this by having a second router that explicitly fails the delivery
1366 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1367 facility for this purpose.
1370 .section "Duplicate addresses" "SECID17"
1371 .cindex "case of local parts"
1372 .cindex "address duplicate, discarding"
1373 .cindex "duplicate addresses"
1374 Once routing is complete, Exim scans the addresses that are assigned to local
1375 and remote transports and discards any duplicates that it finds. During this
1376 check, local parts are treated case-sensitively. This happens only when
1377 actually delivering a message; when testing routers with &%-bt%&, all the
1378 routed addresses are shown.
1382 .section "Router preconditions" "SECTrouprecon"
1383 .cindex "router" "preconditions, order of processing"
1384 .cindex "preconditions" "order of processing"
1385 The preconditions that are tested for each router are listed below, in the
1386 order in which they are tested. The individual configuration options are
1387 described in more detail in chapter &<<CHAProutergeneric>>&.
1390 .cindex affix "router precondition"
1391 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1392 the local parts handled by the router may or must have certain prefixes and/or
1393 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1394 skipped. These conditions are tested first. When an affix is present, it is
1395 removed from the local part before further processing, including the evaluation
1396 of any other conditions.
1398 Routers can be designated for use only when not verifying an address, that is,
1399 only when routing it for delivery (or testing its delivery routing). If the
1400 &%verify%& option is set false, the router is skipped when Exim is verifying an
1402 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1403 &%verify_recipient%&, which independently control the use of the router for
1404 sender and recipient verification. You can set these options directly if
1405 you want a router to be used for only one type of verification.
1406 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1408 If the &%address_test%& option is set false, the router is skipped when Exim is
1409 run with the &%-bt%& option to test an address routing. This can be helpful
1410 when the first router sends all new messages to a scanner of some sort; it
1411 makes it possible to use &%-bt%& to test subsequent delivery routing without
1412 having to simulate the effect of the scanner.
1414 Routers can be designated for use only when verifying an address, as
1415 opposed to routing it for delivery. The &%verify_only%& option controls this.
1416 Again, cutthrough delivery counts as a verification.
1418 Individual routers can be explicitly skipped when running the routers to
1419 check an address given in the SMTP EXPN command (see the &%expn%& option).
1422 If the &%domains%& option is set, the domain of the address must be in the set
1423 of domains that it defines.
1425 .cindex "tainted data" "de-tainting"
1426 A match verifies the variable &$domain$& (which carries tainted data)
1427 and assigns an untainted value to the &$domain_data$& variable.
1428 Such an untainted value is often needed in the transport.
1429 For specifics of the matching operation and the resulting untainted value,
1430 refer to section &<<SECTdomainlist>>&.
1432 When an untainted value is wanted, use this option
1433 rather than the generic &%condition%& option.
1437 .vindex "&$local_part_prefix$&"
1438 .vindex "&$local_part_prefix_v$&"
1439 .vindex "&$local_part$&"
1440 .vindex "&$local_part_suffix$&"
1441 .vindex "&$local_part_suffix_v$&"
1442 .cindex affix "router precondition"
1443 If the &%local_parts%& option is set, the local part of the address must be in
1444 the set of local parts that it defines.
1446 A match verifies the variable &$local_part$& (which carries tainted data)
1447 and assigns an untainted value to the &$local_part_data$& variable.
1448 Such an untainted value is often needed in the transport.
1449 For specifics of the matching operation and the resulting untainted value,
1450 refer to section &<<SECTlocparlis>>&.
1452 When an untainted value is wanted, use this option
1453 rather than the generic &%condition%& option.
1456 If &%local_part_prefix%& or
1457 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1458 part before this check. If you want to do precondition tests on local parts
1459 that include affixes, you can do so by using a &%condition%& option (see below)
1460 that uses the variables &$local_part$&, &$local_part_prefix$&,
1461 &$local_part_prefix_v$&, &$local_part_suffix$&
1462 and &$local_part_suffix_v$& as necessary.
1465 .vindex "&$local_user_uid$&"
1466 .vindex "&$local_user_gid$&"
1468 If the &%check_local_user%& option is set, the local part must be the name of
1469 an account on the local host. If this check succeeds, the uid and gid of the
1470 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1471 user's home directory is placed in &$home$&; these values can be used in the
1472 remaining preconditions.
1475 If the &%router_home_directory%& option is set, it is expanded at this point,
1476 because it overrides the value of &$home$&. If this expansion were left till
1477 later, the value of &$home$& as set by &%check_local_user%& would be used in
1478 subsequent tests. Having two different values of &$home$& in the same router
1479 could lead to confusion.
1482 If the &%senders%& option is set, the envelope sender address must be in the
1483 set of addresses that it defines.
1486 If the &%require_files%& option is set, the existence or non-existence of
1487 specified files is tested.
1490 .cindex "customizing" "precondition"
1491 If the &%condition%& option is set, it is evaluated and tested. This option
1492 uses an expanded string to allow you to set up your own custom preconditions.
1493 Expanded strings are described in chapter &<<CHAPexpand>>&.
1496 Note that while using
1497 this option for address matching technically works,
1498 it does not set any de-tainted values.
1499 Such values are often needed, either for router-specific options or
1500 for transport options.
1501 Using the &%domains%& and &%local_parts%& options is usually the most
1502 convenient way to obtain them.
1507 Note that &%require_files%& comes near the end of the list, so you cannot use
1508 it to check for the existence of a file in which to lookup up a domain, local
1509 part, or sender. However, as these options are all expanded, you can use the
1510 &%exists%& expansion condition to make such tests within each condition. The
1511 &%require_files%& option is intended for checking files that the router may be
1512 going to use internally, or which are needed by a specific transport (for
1513 example, &_.procmailrc_&).
1517 .section "Delivery in detail" "SECID18"
1518 .cindex "delivery" "in detail"
1519 When a message is to be delivered, the sequence of events is as follows:
1522 If a system-wide filter file is specified, the message is passed to it. The
1523 filter may add recipients to the message, replace the recipients, discard the
1524 message, cause a new message to be generated, or cause the message delivery to
1525 fail. The format of the system filter file is the same as for Exim user filter
1526 files, described in the separate document entitled &'Exim's interfaces to mail
1528 .cindex "Sieve filter" "not available for system filter"
1529 (&*Note*&: Sieve cannot be used for system filter files.)
1531 Some additional features are available in system filters &-- see chapter
1532 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1533 filter only once per delivery attempt, however many recipients it has. However,
1534 if there are several delivery attempts because one or more addresses could not
1535 be immediately delivered, the system filter is run each time. The filter
1536 condition &%first_delivery%& can be used to detect the first run of the system
1539 Each recipient address is offered to each configured router, in turn, subject to
1540 its preconditions, until one is able to handle it. If no router can handle the
1541 address, that is, if they all decline, the address is failed. Because routers
1542 can be targeted at particular domains, several locally handled domains can be
1543 processed entirely independently of each other.
1545 .cindex "routing" "loops in"
1546 .cindex "loop" "while routing"
1547 A router that accepts an address may assign it to a local or a remote
1548 transport. However, the transport is not run at this time. Instead, the address
1549 is placed on a list for the particular transport, which will be run later.
1550 Alternatively, the router may generate one or more new addresses (typically
1551 from alias, forward, or filter files). New addresses are fed back into this
1552 process from the top, but in order to avoid loops, a router ignores any address
1553 which has an identically-named ancestor that was processed by itself.
1555 When all the routing has been done, addresses that have been successfully
1556 handled are passed to their assigned transports. When local transports are
1557 doing real local deliveries, they handle only one address at a time, but if a
1558 local transport is being used as a pseudo-remote transport (for example, to
1559 collect batched SMTP messages for transmission by some other means) multiple
1560 addresses can be handled. Remote transports can always handle more than one
1561 address at a time, but can be configured not to do so, or to restrict multiple
1562 addresses to the same domain.
1564 Each local delivery to a file or a pipe runs in a separate process under a
1565 non-privileged uid, and these deliveries are run one at a time. Remote
1566 deliveries also run in separate processes, normally under a uid that is private
1567 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1568 run in parallel. The maximum number of simultaneous remote deliveries for any
1569 one message is set by the &%remote_max_parallel%& option.
1570 The order in which deliveries are done is not defined, except that all local
1571 deliveries happen before any remote deliveries.
1573 .cindex "queue runner"
1574 When it encounters a local delivery during a queue run, Exim checks its retry
1575 database to see if there has been a previous temporary delivery failure for the
1576 address before running the local transport. If there was a previous failure,
1577 Exim does not attempt a new delivery until the retry time for the address is
1578 reached. However, this happens only for delivery attempts that are part of a
1579 queue run. Local deliveries are always attempted when delivery immediately
1580 follows message reception, even if retry times are set for them. This makes for
1581 better behaviour if one particular message is causing problems (for example,
1582 causing quota overflow, or provoking an error in a filter file).
1584 .cindex "delivery" "retry in remote transports"
1585 Remote transports do their own retry handling, since an address may be
1586 deliverable to one of a number of hosts, each of which may have a different
1587 retry time. If there have been previous temporary failures and no host has
1588 reached its retry time, no delivery is attempted, whether in a queue run or
1589 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1591 If there were any permanent errors, a bounce message is returned to an
1592 appropriate address (the sender in the common case), with details of the error
1593 for each failing address. Exim can be configured to send copies of bounce
1594 messages to other addresses.
1596 .cindex "delivery" "deferral"
1597 If one or more addresses suffered a temporary failure, the message is left on
1598 the queue, to be tried again later. Delivery of these addresses is said to be
1601 When all the recipient addresses have either been delivered or bounced,
1602 handling of the message is complete. The spool files and message log are
1603 deleted, though the message log can optionally be preserved if required.
1609 .section "Retry mechanism" "SECID19"
1610 .cindex "delivery" "retry mechanism"
1611 .cindex "retry" "description of mechanism"
1612 .cindex "queue runner"
1613 Exim's mechanism for retrying messages that fail to get delivered at the first
1614 attempt is the queue runner process. You must either run an Exim daemon that
1615 uses the &%-q%& option with a time interval to start queue runners at regular
1616 intervals or use some other means (such as &'cron'&) to start them. If you do
1617 not arrange for queue runners to be run, messages that fail temporarily at the
1618 first attempt will remain in your queue forever. A queue runner process works
1619 its way through the queue, one message at a time, trying each delivery that has
1620 passed its retry time.
1621 You can run several queue runners at once.
1623 Exim uses a set of configured rules to determine when next to retry the failing
1624 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1625 should give up trying to deliver to the address, at which point it generates a
1626 bounce message. If no retry rules are set for a particular host, address, and
1627 error combination, no retries are attempted, and temporary errors are treated
1632 .section "Temporary delivery failure" "SECID20"
1633 .cindex "delivery" "temporary failure"
1634 There are many reasons why a message may not be immediately deliverable to a
1635 particular address. Failure to connect to a remote machine (because it, or the
1636 connection to it, is down) is one of the most common. Temporary failures may be
1637 detected during routing as well as during the transport stage of delivery.
1638 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1639 is on a file system where the user is over quota. Exim can be configured to
1640 impose its own quotas on local mailboxes; where system quotas are set they will
1643 If a host is unreachable for a period of time, a number of messages may be
1644 waiting for it by the time it recovers, and sending them in a single SMTP
1645 connection is clearly beneficial. Whenever a delivery to a remote host is
1647 .cindex "hints database" "deferred deliveries"
1648 Exim makes a note in its hints database, and whenever a successful
1649 SMTP delivery has happened, it looks to see if any other messages are waiting
1650 for the same host. If any are found, they are sent over the same SMTP
1651 connection, subject to a configuration limit as to the maximum number in any
1656 .section "Permanent delivery failure" "SECID21"
1657 .cindex "delivery" "permanent failure"
1658 .cindex "bounce message" "when generated"
1659 When a message cannot be delivered to some or all of its intended recipients, a
1660 bounce message is generated. Temporary delivery failures turn into permanent
1661 errors when their timeout expires. All the addresses that fail in a given
1662 delivery attempt are listed in a single message. If the original message has
1663 many recipients, it is possible for some addresses to fail in one delivery
1664 attempt and others to fail subsequently, giving rise to more than one bounce
1665 message. The wording of bounce messages can be customized by the administrator.
1666 See chapter &<<CHAPemsgcust>>& for details.
1668 .cindex "&'X-Failed-Recipients:'& header line"
1669 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1670 failed addresses, for the benefit of programs that try to analyse such messages
1673 .cindex "bounce message" "recipient of"
1674 A bounce message is normally sent to the sender of the original message, as
1675 obtained from the message's envelope. For incoming SMTP messages, this is the
1676 address given in the MAIL command. However, when an address is expanded via a
1677 forward or alias file, an alternative address can be specified for delivery
1678 failures of the generated addresses. For a mailing list expansion (see section
1679 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1684 .section "Failures to deliver bounce messages" "SECID22"
1685 .cindex "bounce message" "failure to deliver"
1686 If a bounce message (either locally generated or received from a remote host)
1687 itself suffers a permanent delivery failure, the message is left in the queue,
1688 but it is frozen, awaiting the attention of an administrator. There are options
1689 that can be used to make Exim discard such failed messages, or to keep them
1690 for only a short time (see &%timeout_frozen_after%& and
1691 &%ignore_bounce_errors_after%&).
1697 . ////////////////////////////////////////////////////////////////////////////
1698 . ////////////////////////////////////////////////////////////////////////////
1700 .chapter "Building and installing Exim" "CHID3"
1701 .scindex IIDbuex "building Exim"
1703 .section "Unpacking" "SECID23"
1704 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1705 creates a directory with the name of the current release (for example,
1706 &_exim-&version()_&) into which the following files are placed:
1709 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1710 .irow &_CHANGES_& "contains a reference to where changes are &&&
1712 .irow &_LICENCE_& "the GNU General Public Licence"
1713 .irow &_Makefile_& "top-level make file"
1714 .irow &_NOTICE_& "conditions for the use of Exim"
1715 .irow &_README_& "list of files, directories and simple build &&&
1719 Other files whose names begin with &_README_& may also be present. The
1720 following subdirectories are created:
1723 .irow &_Local_& "an empty directory for local configuration files"
1724 .irow &_OS_& "OS-specific files"
1725 .irow &_doc_& "documentation files"
1726 .irow &_exim_monitor_& "source files for the Exim monitor"
1727 .irow &_scripts_& "scripts used in the build process"
1728 .irow &_src_& "remaining source files"
1729 .irow &_util_& "independent utilities"
1732 The main utility programs are contained in the &_src_& directory and are built
1733 with the Exim binary. The &_util_& directory contains a few optional scripts
1734 that may be useful to some sites.
1737 .section "Multiple machine architectures and operating systems" "SECID24"
1738 .cindex "building Exim" "multiple OS/architectures"
1739 The building process for Exim is arranged to make it easy to build binaries for
1740 a number of different architectures and operating systems from the same set of
1741 source files. Compilation does not take place in the &_src_& directory.
1742 Instead, a &'build directory'& is created for each architecture and operating
1744 .cindex "symbolic link" "to build directory"
1745 Symbolic links to the sources are installed in this directory, which is where
1746 the actual building takes place. In most cases, Exim can discover the machine
1747 architecture and operating system for itself, but the defaults can be
1748 overridden if necessary.
1749 .cindex compiler requirements
1750 .cindex compiler version
1751 A C99-capable compiler will be required for the build.
1754 .section "PCRE library" "SECTpcre"
1755 .cindex "PCRE library"
1756 Exim no longer has an embedded PCRE library as the vast majority of
1757 modern systems include PCRE as a system library, although you may need to
1758 install the PCRE package or the PCRE development package for your operating
1759 system. If your system has a normal PCRE installation the Exim build
1760 process will need no further configuration. If the library or the
1761 headers are in an unusual location you will need to either set the PCRE_LIBS
1762 and INCLUDE directives appropriately,
1763 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1764 If your operating system has no
1765 PCRE support then you will need to obtain and build the current PCRE
1766 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1767 More information on PCRE is available at &url(https://www.pcre.org/).
1769 .section "DBM libraries" "SECTdb"
1770 .cindex "DBM libraries" "discussion of"
1771 .cindex "hints database" "DBM files used for"
1772 Even if you do not use any DBM files in your configuration, Exim still needs a
1773 DBM library in order to operate, because it uses indexed files for its hints
1774 databases. Unfortunately, there are a number of DBM libraries in existence, and
1775 different operating systems often have different ones installed.
1777 .cindex "Solaris" "DBM library for"
1778 .cindex "IRIX, DBM library for"
1779 .cindex "BSD, DBM library for"
1780 .cindex "Linux, DBM library for"
1781 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1782 Linux distribution, the DBM configuration should happen automatically, and you
1783 may be able to ignore this section. Otherwise, you may have to learn more than
1784 you would like about DBM libraries from what follows.
1786 .cindex "&'ndbm'& DBM library"
1787 Licensed versions of Unix normally contain a library of DBM functions operating
1788 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1789 versions of Unix seem to vary in what they contain as standard. In particular,
1790 some early versions of Linux have no default DBM library, and different
1791 distributors have chosen to bundle different libraries with their packaged
1792 versions. However, the more recent releases seem to have standardized on the
1793 Berkeley DB library.
1795 Different DBM libraries have different conventions for naming the files they
1796 use. When a program opens a file called &_dbmfile_&, there are several
1800 A traditional &'ndbm'& implementation, such as that supplied as part of
1801 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1803 .cindex "&'gdbm'& DBM library"
1804 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1805 compatibility interface it makes two different hard links to it with names
1806 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1807 filename is used unmodified.
1809 .cindex "Berkeley DB library"
1810 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1811 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1812 programmer exactly the same as the traditional &'ndbm'& implementation.
1814 If the Berkeley package is used in its native mode, it operates on a single
1815 file called &_dbmfile_&; the programmer's interface is somewhat different to
1816 the traditional &'ndbm'& interface.
1818 To complicate things further, there are several very different versions of the
1819 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1820 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1821 Maintenance of some of the earlier releases has ceased. All versions of
1822 Berkeley DB could be obtained from
1823 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1824 page with far newer versions listed.
1825 It is probably wise to plan to move your storage configurations away from
1826 Berkeley DB format, as today there are smaller and simpler alternatives more
1827 suited to Exim's usage model.
1829 .cindex "&'tdb'& DBM library"
1830 Yet another DBM library, called &'tdb'&, is available from
1831 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1832 operates on a single file.
1836 .cindex "DBM libraries" "configuration for building"
1837 Exim and its utilities can be compiled to use any of these interfaces. In order
1838 to use any version of the Berkeley DB package in native mode, you must set
1839 USE_DB in an appropriate configuration file (typically
1840 &_Local/Makefile_&). For example:
1844 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1845 error is diagnosed if you set more than one of these.
1847 At the lowest level, the build-time configuration sets none of these options,
1848 thereby assuming an interface of type (1). However, some operating system
1849 configuration files (for example, those for the BSD operating systems and
1850 Linux) assume type (4) by setting USE_DB as their default, and the
1851 configuration files for Cygwin set USE_GDBM. Anything you set in
1852 &_Local/Makefile_&, however, overrides these system defaults.
1854 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1855 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1856 in one of these lines:
1861 Settings like that will work if the DBM library is installed in the standard
1862 place. Sometimes it is not, and the library's header file may also not be in
1863 the default path. You may need to set INCLUDE to specify where the header
1864 file is, and to specify the path to the library more fully in DBMLIB, as in
1867 INCLUDE=-I/usr/local/include/db-4.1
1868 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1870 There is further detailed discussion about the various DBM libraries in the
1871 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1875 .section "Pre-building configuration" "SECID25"
1876 .cindex "building Exim" "pre-building configuration"
1877 .cindex "configuration for building Exim"
1878 .cindex "&_Local/Makefile_&"
1879 .cindex "&_src/EDITME_&"
1880 Before building Exim, a local configuration file that specifies options
1881 independent of any operating system has to be created with the name
1882 &_Local/Makefile_&. A template for this file is supplied as the file
1883 &_src/EDITME_&, and it contains full descriptions of all the option settings
1884 therein. These descriptions are therefore not repeated here. If you are
1885 building Exim for the first time, the simplest thing to do is to copy
1886 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1888 There are three settings that you must supply, because Exim will not build
1889 without them. They are the location of the runtime configuration file
1890 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1891 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1892 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1893 a colon-separated list of filenames; Exim uses the first of them that exists.
1895 There are a few other parameters that can be specified either at build time or
1896 at runtime, to enable the same binary to be used on a number of different
1897 machines. However, if the locations of Exim's spool directory and log file
1898 directory (if not within the spool directory) are fixed, it is recommended that
1899 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1900 detected early in Exim's execution (such as a malformed configuration file) can
1903 .cindex "content scanning" "specifying at build time"
1904 Exim's interfaces for calling virus and spam scanning software directly from
1905 access control lists are not compiled by default. If you want to include these
1906 facilities, you need to set
1908 WITH_CONTENT_SCAN=yes
1910 in your &_Local/Makefile_&. For details of the facilities themselves, see
1911 chapter &<<CHAPexiscan>>&.
1914 .cindex "&_Local/eximon.conf_&"
1915 .cindex "&_exim_monitor/EDITME_&"
1916 If you are going to build the Exim monitor, a similar configuration process is
1917 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1918 your installation and saved under the name &_Local/eximon.conf_&. If you are
1919 happy with the default settings described in &_exim_monitor/EDITME_&,
1920 &_Local/eximon.conf_& can be empty, but it must exist.
1922 This is all the configuration that is needed in straightforward cases for known
1923 operating systems. However, the building process is set up so that it is easy
1924 to override options that are set by default or by operating-system-specific
1925 configuration files, for example, to change the C compiler, which
1926 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1931 .section "Support for iconv()" "SECID26"
1932 .cindex "&[iconv()]& support"
1934 The contents of header lines in messages may be encoded according to the rules
1935 described RFC 2047. This makes it possible to transmit characters that are not
1936 in the ASCII character set, and to label them as being in a particular
1937 character set. When Exim is inspecting header lines by means of the &%$h_%&
1938 mechanism, it decodes them, and translates them into a specified character set
1939 (default is set at build time). The translation is possible only if the operating system
1940 supports the &[iconv()]& function.
1942 However, some of the operating systems that supply &[iconv()]& do not support
1943 very many conversions. The GNU &%libiconv%& library (available from
1944 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1945 systems to remedy this deficiency, as well as on systems that do not supply
1946 &[iconv()]& at all. After installing &%libiconv%&, you should add
1950 to your &_Local/Makefile_& and rebuild Exim.
1954 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1955 .cindex "TLS" "including support for TLS"
1956 .cindex "encryption" "including support for"
1957 .cindex "OpenSSL" "building Exim with"
1958 .cindex "GnuTLS" "building Exim with"
1959 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1960 command as per RFC 2487. It can also support clients that expect to
1961 start a TLS session immediately on connection to a non-standard port (see the
1962 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1965 If you want to build Exim with TLS support, you must first install either the
1966 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1969 If you do not want TLS support you should set
1973 in &_Local/Makefile_&.
1975 If OpenSSL is installed, you should set
1978 TLS_LIBS=-lssl -lcrypto
1980 in &_Local/Makefile_&. You may also need to specify the locations of the
1981 OpenSSL library and include files. For example:
1984 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1985 TLS_INCLUDE=-I/usr/local/openssl/include/
1987 .cindex "pkg-config" "OpenSSL"
1988 If you have &'pkg-config'& available, then instead you can just use:
1991 USE_OPENSSL_PC=openssl
1993 .cindex "USE_GNUTLS"
1994 If GnuTLS is installed, you should set
1997 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1999 in &_Local/Makefile_&, and again you may need to specify the locations of the
2000 library and include files. For example:
2003 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
2004 TLS_INCLUDE=-I/usr/gnu/include
2006 .cindex "pkg-config" "GnuTLS"
2007 If you have &'pkg-config'& available, then instead you can just use:
2010 USE_GNUTLS_PC=gnutls
2013 You do not need to set TLS_INCLUDE if the relevant directory is already
2014 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
2015 given in chapter &<<CHAPTLS>>&.
2020 .section "Use of tcpwrappers" "SECID27"
2022 .cindex "tcpwrappers, building Exim to support"
2023 .cindex "USE_TCP_WRAPPERS"
2024 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2025 .cindex "tcp_wrappers_daemon_name"
2026 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2027 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2028 alternative to Exim's own checking facilities for installations that are
2029 already making use of &'tcpwrappers'& for other purposes. To do this, you
2030 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2031 &_tcpd.h_& to be available at compile time, and also ensure that the library
2032 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2033 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2036 USE_TCP_WRAPPERS=yes
2037 CFLAGS=-O -I/usr/local/include
2038 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2040 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2041 files is &"exim"&. For example, the line
2043 exim : LOCAL 192.168.1. .friendly.domain.example
2045 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2046 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2047 All other connections are denied. The daemon name used by &'tcpwrappers'&
2048 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2049 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2050 configure file. Consult the &'tcpwrappers'& documentation for
2054 .section "Including support for IPv6" "SECID28"
2055 .cindex "IPv6" "including support for"
2056 Exim contains code for use on systems that have IPv6 support. Setting
2057 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2058 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2059 where the IPv6 support is not fully integrated into the normal include and
2062 Two different types of DNS record for handling IPv6 addresses have been
2063 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2064 currently seen as the mainstream. Another record type called A6 was proposed
2065 as better than AAAA because it had more flexibility. However, it was felt to be
2066 over-complex, and its status was reduced to &"experimental"&.
2068 have a compile option for including A6 record support but this has now been
2073 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2074 .cindex "lookup modules"
2075 .cindex "dynamic modules"
2076 .cindex ".so building"
2077 On some platforms, Exim supports not compiling all lookup types directly into
2078 the main binary, instead putting some into external modules which can be loaded
2080 This permits packagers to build Exim with support for lookups with extensive
2081 library dependencies without requiring all users to install all of those
2083 Most, but not all, lookup types can be built this way.
2085 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2086 installed; Exim will only load modules from that directory, as a security
2087 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2088 for your OS; see &_OS/Makefile-Linux_& for an example.
2089 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2090 see &_src/EDITME_& for details.
2092 Then, for each module to be loaded dynamically, define the relevant
2093 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2094 For example, this will build in lsearch but load sqlite and mysql support
2103 .section "The building process" "SECID29"
2104 .cindex "build directory"
2105 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2106 created, run &'make'& at the top level. It determines the architecture and
2107 operating system types, and creates a build directory if one does not exist.
2108 For example, on a Sun system running Solaris 8, the directory
2109 &_build-SunOS5-5.8-sparc_& is created.
2110 .cindex "symbolic link" "to source files"
2111 Symbolic links to relevant source files are installed in the build directory.
2113 If this is the first time &'make'& has been run, it calls a script that builds
2114 a make file inside the build directory, using the configuration files from the
2115 &_Local_& directory. The new make file is then passed to another instance of
2116 &'make'&. This does the real work, building a number of utility scripts, and
2117 then compiling and linking the binaries for the Exim monitor (if configured), a
2118 number of utility programs, and finally Exim itself. The command &`make
2119 makefile`& can be used to force a rebuild of the make file in the build
2120 directory, should this ever be necessary.
2122 If you have problems building Exim, check for any comments there may be in the
2123 &_README_& file concerning your operating system, and also take a look at the
2124 FAQ, where some common problems are covered.
2128 .section 'Output from &"make"&' "SECID283"
2129 The output produced by the &'make'& process for compile lines is often very
2130 unreadable, because these lines can be very long. For this reason, the normal
2131 output is suppressed by default, and instead output similar to that which
2132 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2133 each module that is being compiled or linked. However, it is still possible to
2134 get the full output, by calling &'make'& like this:
2138 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2139 command reflection in &'make'&. When you ask for the full output, it is
2140 given in addition to the short output.
2144 .section "Overriding build-time options for Exim" "SECToverride"
2145 .cindex "build-time options, overriding"
2146 The main make file that is created at the beginning of the building process
2147 consists of the concatenation of a number of files which set configuration
2148 values, followed by a fixed set of &'make'& instructions. If a value is set
2149 more than once, the last setting overrides any previous ones. This provides a
2150 convenient way of overriding defaults. The files that are concatenated are, in
2153 &_OS/Makefile-Default_&
2154 &_OS/Makefile-_&<&'ostype'&>
2156 &_Local/Makefile-_&<&'ostype'&>
2157 &_Local/Makefile-_&<&'archtype'&>
2158 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2159 &_OS/Makefile-Base_&
2161 .cindex "&_Local/Makefile_&"
2162 .cindex "building Exim" "operating system type"
2163 .cindex "building Exim" "architecture type"
2164 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2165 architecture type. &_Local/Makefile_& is required to exist, and the building
2166 process fails if it is absent. The other three &_Local_& files are optional,
2167 and are often not needed.
2169 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2170 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2171 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2172 values are used, thereby providing a means of forcing particular settings.
2173 Otherwise, the scripts try to get values from the &%uname%& command. If this
2174 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2175 of &'ad hoc'& transformations are then applied, to produce the standard names
2176 that Exim expects. You can run these scripts directly from the shell in order
2177 to find out what values are being used on your system.
2180 &_OS/Makefile-Default_& contains comments about the variables that are set
2181 therein. Some (but not all) are mentioned below. If there is something that
2182 needs changing, review the contents of this file and the contents of the make
2183 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2187 .cindex "building Exim" "overriding default settings"
2188 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2189 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2190 need to change the original files. Instead, you should make the changes by
2191 putting the new values in an appropriate &_Local_& file. For example,
2192 .cindex "Tru64-Unix build-time settings"
2193 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2194 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2195 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2196 called with the option &%-std1%&, to make it recognize some of the features of
2197 Standard C that Exim uses. (Most other compilers recognize Standard C by
2198 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2199 containing the lines
2204 If you are compiling for just one operating system, it may be easier to put
2205 these lines directly into &_Local/Makefile_&.
2207 Keeping all your local configuration settings separate from the distributed
2208 files makes it easy to transfer them to new versions of Exim simply by copying
2209 the contents of the &_Local_& directory.
2212 .cindex "NIS lookup type" "including support for"
2213 .cindex "NIS+ lookup type" "including support for"
2214 .cindex "LDAP" "including support for"
2215 .cindex "lookup" "inclusion in binary"
2216 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2217 lookup, but not all systems have these components installed, so the default is
2218 not to include the relevant code in the binary. All the different kinds of file
2219 and database lookup that Exim supports are implemented as separate code modules
2220 which are included only if the relevant compile-time options are set. In the
2221 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2227 and similar settings apply to the other lookup types. They are all listed in
2228 &_src/EDITME_&. In many cases the relevant include files and interface
2229 libraries need to be installed before compiling Exim.
2230 .cindex "cdb" "including support for"
2231 However, there are some optional lookup types (such as cdb) for which
2232 the code is entirely contained within Exim, and no external include
2233 files or libraries are required. When a lookup type is not included in the
2234 binary, attempts to configure Exim to use it cause runtime configuration
2237 .cindex "pkg-config" "lookups"
2238 .cindex "pkg-config" "authenticators"
2239 Many systems now use a tool called &'pkg-config'& to encapsulate information
2240 about how to compile against a library; Exim has some initial support for
2241 being able to use pkg-config for lookups and authenticators. For any given
2242 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2243 variable with the &`_PC`& suffix in the name and assign as the value the
2244 name of the package to be queried. The results of querying via the
2245 &'pkg-config'& command will be added to the appropriate Makefile variables
2246 with &`+=`& directives, so your version of &'make'& will need to support that
2247 syntax. For instance:
2250 LOOKUP_SQLITE_PC=sqlite3
2252 AUTH_GSASL_PC=libgsasl
2253 AUTH_HEIMDAL_GSSAPI=yes
2254 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2257 .cindex "Perl" "including support for"
2258 Exim can be linked with an embedded Perl interpreter, allowing Perl
2259 subroutines to be called during string expansion. To enable this facility,
2263 must be defined in &_Local/Makefile_&. Details of this facility are given in
2264 chapter &<<CHAPperl>>&.
2266 .cindex "X11 libraries, location of"
2267 The location of the X11 libraries is something that varies a lot between
2268 operating systems, and there may be different versions of X11 to cope
2269 with. Exim itself makes no use of X11, but if you are compiling the Exim
2270 monitor, the X11 libraries must be available.
2271 The following three variables are set in &_OS/Makefile-Default_&:
2274 XINCLUDE=-I$(X11)/include
2275 XLFLAGS=-L$(X11)/lib
2277 These are overridden in some of the operating-system configuration files. For
2278 example, in &_OS/Makefile-SunOS5_& there is
2281 XINCLUDE=-I$(X11)/include
2282 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2284 If you need to override the default setting for your operating system, place a
2285 definition of all three of these variables into your
2286 &_Local/Makefile-<ostype>_& file.
2289 If you need to add any extra libraries to the link steps, these can be put in a
2290 variable called EXTRALIBS, which appears in all the link commands, but by
2291 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2292 command for linking the main Exim binary, and not for any associated utilities.
2294 .cindex "DBM libraries" "configuration for building"
2295 There is also DBMLIB, which appears in the link commands for binaries that
2296 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2297 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2298 binary, and which can be used, for example, to include additional X11
2301 .cindex "configuration file" "editing"
2302 The make file copes with rebuilding Exim correctly if any of the configuration
2303 files are edited. However, if an optional configuration file is deleted, it is
2304 necessary to touch the associated non-optional file (that is,
2305 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2308 .section "OS-specific header files" "SECID30"
2310 .cindex "building Exim" "OS-specific C header files"
2311 The &_OS_& directory contains a number of files with names of the form
2312 &_os.h-<ostype>_&. These are system-specific C header files that should not
2313 normally need to be changed. There is a list of macro settings that are
2314 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2315 are porting Exim to a new operating system.
2319 .section "Overriding build-time options for the monitor" "SECID31"
2320 .cindex "building Eximon"
2321 A similar process is used for overriding things when building the Exim monitor,
2322 where the files that are involved are
2324 &_OS/eximon.conf-Default_&
2325 &_OS/eximon.conf-_&<&'ostype'&>
2326 &_Local/eximon.conf_&
2327 &_Local/eximon.conf-_&<&'ostype'&>
2328 &_Local/eximon.conf-_&<&'archtype'&>
2329 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2331 .cindex "&_Local/eximon.conf_&"
2332 As with Exim itself, the final three files need not exist, and in this case the
2333 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2334 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2335 variables of the same name, preceded by EXIMON_. For example, setting
2336 EXIMON_LOG_DEPTH in the environment overrides the value of
2337 LOG_DEPTH at runtime.
2341 .section "Installing Exim binaries and scripts" "SECID32"
2342 .cindex "installing Exim"
2343 .cindex "BIN_DIRECTORY"
2344 The command &`make install`& runs the &(exim_install)& script with no
2345 arguments. The script copies binaries and utility scripts into the directory
2346 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2347 .cindex "setuid" "installing Exim with"
2348 The install script copies files only if they are newer than the files they are
2349 going to replace. The Exim binary is required to be owned by root and have the
2350 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2351 install`& as root so that it can set up the Exim binary in this way. However, in
2352 some special situations (for example, if a host is doing no local deliveries)
2353 it may be possible to run Exim without making the binary setuid root (see
2354 chapter &<<CHAPsecurity>>& for details).
2356 .cindex "CONFIGURE_FILE"
2357 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2358 in &_Local/Makefile_&. If this names a single file, and the file does not
2359 exist, the default configuration file &_src/configure.default_& is copied there
2360 by the installation script. If a runtime configuration file already exists, it
2361 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2362 alternative files, no default is installed.
2364 .cindex "system aliases file"
2365 .cindex "&_/etc/aliases_&"
2366 One change is made to the default configuration file when it is installed: the
2367 default configuration contains a router that references a system aliases file.
2368 The path to this file is set to the value specified by
2369 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2370 If the system aliases file does not exist, the installation script creates it,
2371 and outputs a comment to the user.
2373 The created file contains no aliases, but it does contain comments about the
2374 aliases a site should normally have. Mail aliases have traditionally been
2375 kept in &_/etc/aliases_&. However, some operating systems are now using
2376 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2377 Exim's configuration if necessary.
2379 The default configuration uses the local host's name as the only local domain,
2380 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2381 running as the local user. System aliases and &_.forward_& files in users' home
2382 directories are supported, but no NIS or NIS+ support is configured. Domains
2383 other than the name of the local host are routed using the DNS, with delivery
2386 It is possible to install Exim for special purposes (such as building a binary
2387 distribution) in a private part of the file system. You can do this by a
2390 make DESTDIR=/some/directory/ install
2392 This has the effect of pre-pending the specified directory to all the file
2393 paths, except the name of the system aliases file that appears in the default
2394 configuration. (If a default alias file is created, its name &'is'& modified.)
2395 For backwards compatibility, ROOT is used if DESTDIR is not set,
2396 but this usage is deprecated.
2398 .cindex "installing Exim" "what is not installed"
2399 Running &'make install'& does not copy the Exim 4 conversion script
2400 &'convert4r4'&. You will probably run this only once if you are
2401 upgrading from Exim 3. None of the documentation files in the &_doc_&
2402 directory are copied, except for the info files when you have set
2403 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2405 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2406 to their names. The Exim binary itself, however, is handled differently. It is
2407 installed under a name that includes the version number and the compile number,
2408 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2409 called &_exim_& to point to the binary. If you are updating a previous version
2410 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2411 from the directory (as seen by other processes).
2413 .cindex "installing Exim" "testing the script"
2414 If you want to see what the &'make install'& will do before running it for
2415 real, you can pass the &%-n%& option to the installation script by this
2418 make INSTALL_ARG=-n install
2420 The contents of the variable INSTALL_ARG are passed to the installation
2421 script. You do not need to be root to run this test. Alternatively, you can run
2422 the installation script directly, but this must be from within the build
2423 directory. For example, from the top-level Exim directory you could use this
2426 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2428 .cindex "installing Exim" "install script options"
2429 There are two other options that can be supplied to the installation script.
2432 &%-no_chown%& bypasses the call to change the owner of the installed binary
2433 to root, and the call to make it a setuid binary.
2435 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2439 INSTALL_ARG can be used to pass these options to the script. For example:
2441 make INSTALL_ARG=-no_symlink install
2443 The installation script can also be given arguments specifying which files are
2444 to be copied. For example, to install just the Exim binary, and nothing else,
2445 without creating the symbolic link, you could use:
2447 make INSTALL_ARG='-no_symlink exim' install
2452 .section "Installing info documentation" "SECTinsinfdoc"
2453 .cindex "installing Exim" "&'info'& documentation"
2454 Not all systems use the GNU &'info'& system for documentation, and for this
2455 reason, the Texinfo source of Exim's documentation is not included in the main
2456 distribution. Instead it is available separately from the FTP site (see section
2459 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2460 source of the documentation is found in the source tree, running &`make
2461 install`& automatically builds the info files and installs them.
2465 .section "Setting up the spool directory" "SECID33"
2466 .cindex "spool directory" "creating"
2467 When it starts up, Exim tries to create its spool directory if it does not
2468 exist. The Exim uid and gid are used for the owner and group of the spool
2469 directory. Sub-directories are automatically created in the spool directory as
2475 .section "Testing" "SECID34"
2476 .cindex "testing" "installation"
2477 Having installed Exim, you can check that the runtime configuration file is
2478 syntactically valid by running the following command, which assumes that the
2479 Exim binary directory is within your PATH environment variable:
2483 If there are any errors in the configuration file, Exim outputs error messages.
2484 Otherwise it outputs the version number and build date,
2485 the DBM library that is being used, and information about which drivers and
2486 other optional code modules are included in the binary.
2487 Some simple routing tests can be done by using the address testing option. For
2490 &`exim -bt`& <&'local username'&>
2492 should verify that it recognizes a local mailbox, and
2494 &`exim -bt`& <&'remote address'&>
2496 a remote one. Then try getting it to deliver mail, both locally and remotely.
2497 This can be done by passing messages directly to Exim, without going through a
2498 user agent. For example:
2500 exim -v postmaster@your.domain.example
2501 From: user@your.domain.example
2502 To: postmaster@your.domain.example
2503 Subject: Testing Exim
2505 This is a test message.
2508 The &%-v%& option causes Exim to output some verification of what it is doing.
2509 In this case you should see copies of three log lines, one for the message's
2510 arrival, one for its delivery, and one containing &"Completed"&.
2512 .cindex "delivery" "problems with"
2513 If you encounter problems, look at Exim's log files (&'mainlog'& and
2514 &'paniclog'&) to see if there is any relevant information there. Another source
2515 of information is running Exim with debugging turned on, by specifying the
2516 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2517 with debugging turned on by a command of the form
2519 &`exim -d -M`& <&'exim-message-id'&>
2521 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2522 produces rather a lot of output, but you can cut this down to specific areas.
2523 For example, if you use &%-d-all+route%& only the debugging information
2524 relevant to routing is included. (See the &%-d%& option in chapter
2525 &<<CHAPcommandline>>& for more details.)
2527 .cindex '&"sticky"& bit'
2528 .cindex "lock files"
2529 One specific problem that has shown up on some sites is the inability to do
2530 local deliveries into a shared mailbox directory, because it does not have the
2531 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2532 writing to a mailbox file, and if it cannot create the lock file, the delivery
2533 is deferred. You can get round this either by setting the &"sticky bit"& on the
2534 directory, or by setting a specific group for local deliveries and allowing
2535 that group to create files in the directory (see the comments above the
2536 &(local_delivery)& transport in the default configuration file). Another
2537 approach is to configure Exim not to use lock files, but just to rely on
2538 &[fcntl()]& locking instead. However, you should do this only if all user
2539 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2540 see chapter &<<CHAPappendfile>>&.
2542 One thing that cannot be tested on a system that is already running an MTA is
2543 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2544 &%-oX%& option can be used to run an Exim daemon that listens on some other
2545 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2546 &'exim_checkaccess'& utility can be used to check out policy controls on
2549 Testing a new version on a system that is already running Exim can most easily
2550 be done by building a binary with a different CONFIGURE_FILE setting. From
2551 within the runtime configuration, all other file and directory names
2552 that Exim uses can be altered, in order to keep it entirely clear of the
2556 .section "Replacing another MTA with Exim" "SECID35"
2557 .cindex "replacing another MTA"
2558 Building and installing Exim for the first time does not of itself put it in
2559 general use. The name by which the system's MTA is called by mail user agents
2560 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2561 operating system), and it is necessary to make this name point to the &'exim'&
2562 binary in order to get the user agents to pass messages to Exim. This is
2563 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2564 or &_/usr/lib/sendmail_&
2565 .cindex "symbolic link" "to &'exim'& binary"
2566 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2567 privilege and executable status from the old MTA. It is then necessary to stop
2568 and restart the mailer daemon, if one is running.
2570 .cindex "FreeBSD, MTA indirection"
2571 .cindex "&_/etc/mail/mailer.conf_&"
2572 Some operating systems have introduced alternative ways of switching MTAs. For
2573 example, if you are running FreeBSD, you need to edit the file
2574 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2575 described. A typical example of the contents of this file for running Exim is
2578 sendmail /usr/exim/bin/exim
2579 send-mail /usr/exim/bin/exim
2580 mailq /usr/exim/bin/exim -bp
2581 newaliases /usr/bin/true
2583 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2584 your Exim installation is &"live"&. Check it by sending a message from your
2585 favourite user agent.
2587 You should consider what to tell your users about the change of MTA. Exim may
2588 have different capabilities to what was previously running, and there are
2589 various operational differences such as the text of messages produced by
2590 command line options and in bounce messages. If you allow your users to make
2591 use of Exim's filtering capabilities, you should make the document entitled
2592 &'Exim's interface to mail filtering'& available to them.
2596 .section "Upgrading Exim" "SECID36"
2597 .cindex "upgrading Exim"
2598 If you are already running Exim on your host, building and installing a new
2599 version automatically makes it available to MUAs, or any other programs that
2600 call the MTA directly. However, if you are running an Exim daemon, you do need
2601 .cindex restart "on HUP signal"
2602 .cindex signal "HUP, to restart"
2603 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2604 new binary. You do not need to stop processing mail in order to install a new
2605 version of Exim. The install script does not modify an existing runtime
2611 .section "Stopping the Exim daemon on Solaris" "SECID37"
2612 .cindex "Solaris" "stopping Exim on"
2613 The standard command for stopping the mailer daemon on Solaris is
2615 /etc/init.d/sendmail stop
2617 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2618 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2619 for the text &"sendmail"&; this is not present because the actual program name
2620 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2621 solution is to replace the line that finds the process id with something like
2623 pid=`cat /var/spool/exim/exim-daemon.pid`
2625 to obtain the daemon's pid directly from the file that Exim saves it in.
2627 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2628 still be received from local processes, and if automatic delivery is configured
2629 (the normal case), deliveries will still occur.
2634 . ////////////////////////////////////////////////////////////////////////////
2635 . ////////////////////////////////////////////////////////////////////////////
2637 .chapter "The Exim command line" "CHAPcommandline"
2638 .scindex IIDclo1 "command line" "options"
2639 .scindex IIDclo2 "options" "command line"
2640 Exim's command line takes the standard Unix form of a sequence of options,
2641 each starting with a hyphen character, followed by a number of arguments. The
2642 options are compatible with the main options of Sendmail, and there are also
2643 some additional options, some of which are compatible with Smail 3. Certain
2644 combinations of options do not make sense, and provoke an error if used.
2645 The form of the arguments depends on which options are set.
2648 .section "Setting options by program name" "SECID38"
2650 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2651 were present before any other options.
2652 The &%-bp%& option requests a listing of the contents of the mail queue on the
2654 This feature is for compatibility with some systems that contain a command of
2655 that name in one of the standard libraries, symbolically linked to
2656 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2659 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2660 were present before any other options, for compatibility with Smail. The
2661 &%-bS%& option is used for reading in a number of messages in batched SMTP
2665 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2666 &%-oee%& options were present before any other options, for compatibility with
2667 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2670 .cindex "queue runner"
2671 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2672 were present before any other options, for compatibility with Smail. The &%-q%&
2673 option causes a single queue runner process to be started.
2675 .cindex "&'newaliases'&"
2676 .cindex "alias file" "building"
2677 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2678 If Exim is called under the name &'newaliases'& it behaves as if the option
2679 &%-bi%& were present before any other options, for compatibility with Sendmail.
2680 This option is used for rebuilding Sendmail's alias file. Exim does not have
2681 the concept of a single alias file, but can be configured to run a given
2682 command if called with the &%-bi%& option.
2685 .section "Trusted and admin users" "SECTtrustedadmin"
2686 Some Exim options are available only to &'trusted users'& and others are
2687 available only to &'admin users'&. In the description below, the phrases &"Exim
2688 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2689 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2690 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2693 .cindex "trusted users" "definition of"
2694 .cindex "user" "trusted definition of"
2695 The trusted users are root, the Exim user, any user listed in the
2696 &%trusted_users%& configuration option, and any user whose current group or any
2697 supplementary group is one of those listed in the &%trusted_groups%&
2698 configuration option. Note that the Exim group is not automatically trusted.
2700 .cindex '&"From"& line'
2701 .cindex "envelope from"
2702 .cindex "envelope sender"
2703 Trusted users are always permitted to use the &%-f%& option or a leading
2704 &"From&~"& line to specify the envelope sender of a message that is passed to
2705 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2706 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2707 users to set envelope senders.
2711 For a trusted user, there is never any check on the contents of the &'From:'&
2712 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2713 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2715 Trusted users may also specify a host name, host address, interface address,
2716 protocol name, ident value, and authentication data when submitting a message
2717 locally. Thus, they are able to insert messages into Exim's queue locally that
2718 have the characteristics of messages received from a remote host. Untrusted
2719 users may in some circumstances use &%-f%&, but can never set the other values
2720 that are available to trusted users.
2722 .cindex "user" "admin definition of"
2723 .cindex "admin user" "definition of"
2724 The admin users are root, the Exim user, and any user that is a member of the
2725 Exim group or of any group listed in the &%admin_groups%& configuration option.
2726 The current group does not have to be one of these groups.
2728 Admin users are permitted to list the queue, and to carry out certain
2729 operations on messages, for example, to force delivery failures. It is also
2730 necessary to be an admin user in order to see the full information provided by
2731 the Exim monitor, and full debugging output.
2733 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2734 Exim to attempt delivery of messages on its queue is restricted to admin users.
2735 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2736 option false (that is, specifying &%no_prod_requires_admin%&).
2738 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2739 is restricted to admin users unless &%queue_list_requires_admin%& is set
2744 &*Warning*&: If you configure your system so that admin users are able to
2745 edit Exim's configuration file, you are giving those users an easy way of
2746 getting root. There is further discussion of this issue at the start of chapter
2752 .section "Command line options" "SECID39"
2753 Exim's command line options are described in alphabetical order below. If none
2754 of the options that specifies a specific action (such as starting the daemon or
2755 a queue runner, or testing an address, or receiving a message in a specific
2756 format, or listing the queue) are present, and there is at least one argument
2757 on the command line, &%-bm%& (accept a local message on the standard input,
2758 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2759 outputs a brief message about itself and exits.
2761 . ////////////////////////////////////////////////////////////////////////////
2762 . Insert a stylized XML comment here, to identify the start of the command line
2763 . options. This is for the benefit of the Perl script that automatically
2764 . creates a man page for the options.
2765 . ////////////////////////////////////////////////////////////////////////////
2768 <!-- === Start of command line options === -->
2775 .cindex "options" "command line; terminating"
2776 This is a pseudo-option whose only purpose is to terminate the options and
2777 therefore to cause subsequent command line items to be treated as arguments
2778 rather than options, even if they begin with hyphens.
2781 .oindex "&%--help%&"
2782 This option causes Exim to output a few sentences stating what it is.
2783 The same output is generated if the Exim binary is called with no options and
2786 .vitem &%--version%&
2787 .oindex "&%--version%&"
2788 This option is an alias for &%-bV%& and causes version information to be
2795 These options are used by Sendmail for selecting configuration files and are
2798 .vitem &%-B%&<&'type'&>
2800 .cindex "8-bit characters"
2801 .cindex "Sendmail compatibility" "8-bit characters"
2802 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2803 clean; it ignores this option.
2808 .cindex "SMTP" "listener"
2809 .cindex "queue runner"
2810 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2811 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2812 that the daemon should also initiate periodic queue runs.
2814 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2815 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2816 disconnect from the controlling terminal. When running this way, it can be
2817 stopped by pressing ctrl-C.
2819 By default, Exim listens for incoming connections to the standard SMTP port on
2820 all the host's running interfaces. However, it is possible to listen on other
2821 ports, on multiple ports, and only on specific interfaces. Chapter
2822 &<<CHAPinterfaces>>& contains a description of the options that control this.
2824 When a listening daemon
2825 .cindex "daemon" "process id (pid)"
2826 .cindex "pid (process id)" "of daemon"
2827 is started without the use of &%-oX%& (that is, without overriding the normal
2828 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2829 in Exim's spool directory. This location can be overridden by setting
2830 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2833 When &%-oX%& is used on the command line to start a listening daemon, the
2834 process id is not written to the normal pid file path. However, &%-oP%& can be
2835 used to specify a path on the command line if a pid file is required.
2839 .cindex restart "on HUP signal"
2840 .cindex signal "HUP, to restart"
2841 .cindex "daemon" "restarting"
2842 .cindex signal "to reload configuration"
2843 .cindex daemon "reload configuration"
2844 .cindex reload configuration
2845 can be used to cause the daemon to re-execute itself. This should be done
2846 whenever Exim's configuration file, or any file that is incorporated into it by
2847 means of the &%.include%& facility, is changed, and also whenever a new version
2848 of Exim is installed. It is not necessary to do this when other files that are
2849 referenced from the configuration (for example, alias files) are changed,
2850 because these are reread each time they are used.
2854 This option has the same effect as &%-bd%& except that it never disconnects
2855 from the controlling terminal, even when no debugging is specified.
2859 .cindex "testing" "string expansion"
2860 .cindex "expansion" "testing"
2861 Run Exim in expansion testing mode. Exim discards its root privilege, to
2862 prevent ordinary users from using this mode to read otherwise inaccessible
2863 files. If no arguments are given, Exim runs interactively, prompting for lines
2864 of data. Otherwise, it processes each argument in turn.
2866 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2867 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2868 used without command line arguments. If successful, it uses the &[readline()]&
2869 function, which provides extensive line-editing facilities, for reading the
2870 test data. A line history is supported.
2872 Long expansion expressions can be split over several lines by using backslash
2873 continuations. As in Exim's runtime configuration, white space at the start of
2874 continuation lines is ignored. Each argument or data line is passed through the
2875 string expansion mechanism, and the result is output. Variable values from the
2876 configuration file (for example, &$qualify_domain$&) are available, but no
2877 message-specific values (such as &$message_exim_id$&) are set, because no message
2878 is being processed (but see &%-bem%& and &%-Mset%&).
2880 &*Note*&: If you use this mechanism to test lookups, and you change the data
2881 files or databases you are using, you must exit and restart Exim before trying
2882 the same lookup again. Otherwise, because each Exim process caches the results
2883 of lookups, you will just get the same result as before.
2885 Macro processing is done on lines before string-expansion: new macros can be
2886 defined and macros will be expanded.
2887 Because macros in the config file are often used for secrets, those are only
2888 available to admin users.
2890 .vitem &%-bem%&&~<&'filename'&>
2892 .cindex "testing" "string expansion"
2893 .cindex "expansion" "testing"
2894 This option operates like &%-be%& except that it must be followed by the name
2895 of a file. For example:
2897 exim -bem /tmp/testmessage
2899 The file is read as a message (as if receiving a locally-submitted non-SMTP
2900 message) before any of the test expansions are done. Thus, message-specific
2901 variables such as &$message_size$& and &$header_from:$& are available. However,
2902 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2903 recipients are read from the headers in the normal way, and are shown in the
2904 &$recipients$& variable. Note that recipients cannot be given on the command
2905 line, because further arguments are taken as strings to expand (just like
2908 .vitem &%-bF%&&~<&'filename'&>
2910 .cindex "system filter" "testing"
2911 .cindex "testing" "system filter"
2912 This option is the same as &%-bf%& except that it assumes that the filter being
2913 tested is a system filter. The additional commands that are available only in
2914 system filters are recognized.
2916 .vitem &%-bf%&&~<&'filename'&>
2918 .cindex "filter" "testing"
2919 .cindex "testing" "filter file"
2920 .cindex "forward file" "testing"
2921 .cindex "testing" "forward file"
2922 .cindex "Sieve filter" "testing"
2923 This option runs Exim in user filter testing mode; the file is the filter file
2924 to be tested, and a test message must be supplied on the standard input. If
2925 there are no message-dependent tests in the filter, an empty file can be
2928 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2929 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2930 filter and a user filter in the same run. For example:
2932 exim -bF /system/filter -bf /user/filter </test/message
2934 This is helpful when the system filter adds header lines or sets filter
2935 variables that are used by the user filter.
2937 If the test filter file does not begin with one of the special lines
2942 it is taken to be a normal &_.forward_& file, and is tested for validity under
2943 that interpretation. See sections &<<SECTitenonfilred>>& to
2944 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2947 The result of an Exim command that uses &%-bf%&, provided no errors are
2948 detected, is a list of the actions that Exim would try to take if presented
2949 with the message for real. More details of filter testing are given in the
2950 separate document entitled &'Exim's interfaces to mail filtering'&.
2952 When testing a filter file,
2953 .cindex "&""From""& line"
2954 .cindex "envelope from"
2955 .cindex "envelope sender"
2956 .oindex "&%-f%&" "for filter testing"
2957 the envelope sender can be set by the &%-f%& option,
2958 or by a &"From&~"& line at the start of the test message. Various parameters
2959 that would normally be taken from the envelope recipient address of the message
2960 can be set by means of additional command line options (see the next four
2963 .vitem &%-bfd%&&~<&'domain'&>
2965 .vindex "&$qualify_domain$&"
2966 This sets the domain of the recipient address when a filter file is being
2967 tested by means of the &%-bf%& option. The default is the value of
2970 .vitem &%-bfl%&&~<&'local&~part'&>
2972 This sets the local part of the recipient address when a filter file is being
2973 tested by means of the &%-bf%& option. The default is the username of the
2974 process that calls Exim. A local part should be specified with any prefix or
2975 suffix stripped, because that is how it appears to the filter when a message is
2976 actually being delivered.
2978 .vitem &%-bfp%&&~<&'prefix'&>
2980 .cindex affix "filter testing"
2981 This sets the prefix of the local part of the recipient address when a filter
2982 file is being tested by means of the &%-bf%& option. The default is an empty
2985 .vitem &%-bfs%&&~<&'suffix'&>
2987 .cindex affix "filter testing"
2988 This sets the suffix of the local part of the recipient address when a filter
2989 file is being tested by means of the &%-bf%& option. The default is an empty
2992 .vitem &%-bh%&&~<&'IP&~address'&>
2994 .cindex "testing" "incoming SMTP"
2995 .cindex "SMTP" "testing incoming"
2996 .cindex "testing" "relay control"
2997 .cindex "relaying" "testing configuration"
2998 .cindex "policy control" "testing"
2999 .cindex "debugging" "&%-bh%& option"
3000 This option runs a fake SMTP session as if from the given IP address, using the
3001 standard input and output. The IP address may include a port number at the end,
3002 after a full stop. For example:
3004 exim -bh 10.9.8.7.1234
3005 exim -bh fe80::a00:20ff:fe86:a061.5678
3007 When an IPv6 address is given, it is converted into canonical form. In the case
3008 of the second example above, the value of &$sender_host_address$& after
3009 conversion to the canonical form is
3010 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
3012 Comments as to what is going on are written to the standard error file. These
3013 include lines beginning with &"LOG"& for anything that would have been logged.
3014 This facility is provided for testing configuration options for incoming
3015 messages, to make sure they implement the required policy. For example, you can
3016 test your relay controls using &%-bh%&.
3020 You can test features of the configuration that rely on ident (RFC 1413)
3021 information by using the &%-oMt%& option. However, Exim cannot actually perform
3022 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3025 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3026 are also skipped when testing using &%-bh%&. If you want these callouts to
3027 occur, use &%-bhc%& instead.
3029 Messages supplied during the testing session are discarded, and nothing is
3030 written to any of the real log files. There may be pauses when DNS (and other)
3031 lookups are taking place, and of course these may time out. The &%-oMi%& option
3032 can be used to specify a specific IP interface and port if this is important,
3033 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3034 session were authenticated.
3036 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3037 output just states whether a given recipient address from a given host is
3038 acceptable or not. See section &<<SECTcheckaccess>>&.
3040 Features such as authentication and encryption, where the client input is not
3041 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3042 specialized SMTP test program such as
3043 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3045 .vitem &%-bhc%&&~<&'IP&~address'&>
3047 This option operates in the same way as &%-bh%&, except that address
3048 verification callouts are performed if required. This includes consulting and
3049 updating the callout cache database.
3053 .cindex "alias file" "building"
3054 .cindex "building alias file"
3055 .cindex "Sendmail compatibility" "&%-bi%& option"
3056 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3057 Exim does not have the concept of a single alias file, and so it cannot mimic
3058 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3059 tend to appear in various scripts such as NIS make files, so the option must be
3062 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3063 configuration option is run, under the uid and gid of the caller of Exim. If
3064 the &%-oA%& option is used, its value is passed to the command as an argument.
3065 The command set by &%bi_command%& may not contain arguments. The command can
3066 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3067 if this is required. If the &%bi_command%& option is not set, calling Exim with
3070 . // Keep :help first, then the rest in alphabetical order
3072 .oindex "&%-bI:help%&"
3073 .cindex "querying exim information"
3074 We shall provide various options starting &`-bI:`& for querying Exim for
3075 information. The output of many of these will be intended for machine
3076 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3077 synopsis of supported options beginning &`-bI:`&. Use of any of these
3078 options shall cause Exim to exit after producing the requested output.
3081 .oindex "&%-bI:dscp%&"
3082 .cindex "DSCP" "values"
3083 This option causes Exim to emit an alphabetically sorted list of all
3084 recognised DSCP names.
3086 .vitem &%-bI:sieve%&
3087 .oindex "&%-bI:sieve%&"
3088 .cindex "Sieve filter" "capabilities"
3089 This option causes Exim to emit an alphabetically sorted list of all supported
3090 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3091 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3092 &`SIEVE`& capability response line. As the precise list may depend upon
3093 compile-time build options, which this option will adapt to, this is the only
3094 way to guarantee a correct response.
3098 .cindex "local message reception"
3099 This option runs an Exim receiving process that accepts an incoming,
3100 locally-generated message on the standard input. The recipients are given as the
3101 command arguments (except when &%-t%& is also present &-- see below). Each
3102 argument can be a comma-separated list of RFC 2822 addresses. This is the
3103 default option for selecting the overall action of an Exim call; it is assumed
3104 if no other conflicting option is present.
3106 If any addresses in the message are unqualified (have no domain), they are
3107 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3108 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3109 suppressing this for special cases.
3111 Policy checks on the contents of local messages can be enforced by means of
3112 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3114 .cindex "return code" "for &%-bm%&"
3115 The return code is zero if the message is successfully accepted. Otherwise, the
3116 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3119 .cindex "message" "format"
3120 .cindex "format" "message"
3121 .cindex "&""From""& line"
3122 .cindex "UUCP" "&""From""& line"
3123 .cindex "Sendmail compatibility" "&""From""& line"
3124 of the message must be as defined in RFC 2822, except that, for
3125 compatibility with Sendmail and Smail, a line in one of the forms
3127 From sender Fri Jan 5 12:55 GMT 1997
3128 From sender Fri, 5 Jan 97 12:55:01
3130 (with the weekday optional, and possibly with additional text after the date)
3131 is permitted to appear at the start of the message. There appears to be no
3132 authoritative specification of the format of this line. Exim recognizes it by
3133 matching against the regular expression defined by the &%uucp_from_pattern%&
3134 option, which can be changed if necessary.
3136 .oindex "&%-f%&" "overriding &""From""& line"
3137 The specified sender is treated as if it were given as the argument to the
3138 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3139 preference to the address taken from the message. The caller of Exim must be a
3140 trusted user for the sender of a message to be set in this way.
3142 .vitem &%-bmalware%&&~<&'filename'&>
3143 .oindex "&%-bmalware%&"
3144 .cindex "testing", "malware"
3145 .cindex "malware scan test"
3146 This debugging option causes Exim to scan the given file or directory
3147 (depending on the used scanner interface),
3148 using the malware scanning framework. The option of &%av_scanner%& influences
3149 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3150 the expansion should have defaults which apply to this invocation. ACLs are
3151 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3152 will never be populated and &%-bmalware%& will fail.
3154 Exim will have changed working directory before resolving the filename, so
3155 using fully qualified pathnames is advisable. Exim will be running as the Exim
3156 user when it tries to open the file, rather than as the invoking user.
3157 This option requires admin privileges.
3159 The &%-bmalware%& option will not be extended to be more generally useful,
3160 there are better tools for file-scanning. This option exists to help
3161 administrators verify their Exim and AV scanner configuration.
3165 .cindex "address qualification, suppressing"
3166 By default, Exim automatically qualifies unqualified addresses (those
3167 without domains) that appear in messages that are submitted locally (that
3168 is, not over TCP/IP). This qualification applies both to addresses in
3169 envelopes, and addresses in header lines. Sender addresses are qualified using
3170 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3171 defaults to the value of &%qualify_domain%&).
3173 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3174 being used to re-submit messages that originally came from remote hosts after
3175 content scanning, you probably do not want to qualify unqualified addresses in
3176 header lines. (Such lines will be present only if you have not enabled a header
3177 syntax check in the appropriate ACL.)
3179 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3180 messages that originate on the local host. When this is used, unqualified
3181 addresses in the envelope provoke errors (causing message rejection) and
3182 unqualified addresses in header lines are left alone.
3187 .cindex "configuration options" "extracting"
3188 .cindex "options" "configuration &-- extracting"
3189 If this option is given with no arguments, it causes the values of all Exim's
3190 main configuration options to be written to the standard output. The values
3191 of one or more specific options can be requested by giving their names as
3192 arguments, for example:
3194 exim -bP qualify_domain hold_domains
3196 .cindex "hiding configuration option values"
3197 .cindex "configuration options" "hiding value of"
3198 .cindex "options" "hiding value of"
3199 However, any option setting that is preceded by the word &"hide"& in the
3200 configuration file is not shown in full, except to an admin user. For other
3201 users, the output is as in this example:
3203 mysql_servers = <value not displayable>
3205 If &%config%& is given as an argument, the config is
3206 output, as it was parsed, any include file resolved, any comment removed.
3208 If &%config_file%& is given as an argument, the name of the runtime
3209 configuration file is output. (&%configure_file%& works too, for
3210 backward compatibility.)
3211 If a list of configuration files was supplied, the value that is output here
3212 is the name of the file that was actually used.
3214 .cindex "options" "hiding name of"
3215 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3216 name will not be output.
3218 .cindex "daemon" "process id (pid)"
3219 .cindex "pid (process id)" "of daemon"
3220 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3221 directories where log files and daemon pid files are written are output,
3222 respectively. If these values are unset, log files are written in a
3223 sub-directory of the spool directory called &%log%&, and the pid file is
3224 written directly into the spool directory.
3226 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3228 exim -bP +local_domains
3230 it searches for a matching named list of any type (domain, host, address, or
3231 local part) and outputs what it finds.
3233 .cindex "options" "router &-- extracting"
3234 .cindex "options" "transport &-- extracting"
3235 .cindex "options" "authenticator &-- extracting"
3236 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3237 followed by the name of an appropriate driver instance, the option settings for
3238 that driver are output. For example:
3240 exim -bP transport local_delivery
3242 The generic driver options are output first, followed by the driver's private
3243 options. A list of the names of drivers of a particular type can be obtained by
3244 using one of the words &%router_list%&, &%transport_list%&, or
3245 &%authenticator_list%&, and a complete list of all drivers with their option
3246 settings can be obtained by using &%routers%&, &%transports%&, or
3249 .cindex "environment"
3250 If &%environment%& is given as an argument, the set of environment
3251 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3254 .cindex "options" "macro &-- extracting"
3255 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3256 are available, similarly to the drivers. Because macros are sometimes used
3257 for storing passwords, this option is restricted.
3258 The output format is one item per line.
3259 For the "-bP macro <name>" form, if no such macro is found
3260 the exit status will be nonzero.
3264 .cindex "queue" "listing messages in"
3265 .cindex "listing" "messages in the queue"
3266 This option requests a listing of the contents of the mail queue on the
3267 standard output. If the &%-bp%& option is followed by a list of message ids,
3268 just those messages are listed. By default, this option can be used only by an
3269 admin user. However, the &%queue_list_requires_admin%& option can be set false
3270 to allow any user to see the queue.
3272 Each message in the queue is displayed as in the following example:
3274 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3275 red.king@looking-glass.fict.example
3278 .cindex "message" "size in queue listing"
3279 .cindex "size" "of message"
3280 The first line contains the length of time the message has been in the queue
3281 (in this case 25 minutes), the size of the message (2.9K), the unique local
3282 identifier for the message, and the message sender, as contained in the
3283 envelope. For bounce messages, the sender address is empty, and appears as
3284 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3285 the default sender address, the user's login name is shown in parentheses
3286 before the sender address.
3288 .cindex "frozen messages" "in queue listing"
3289 If the message is frozen (attempts to deliver it are suspended) then the text
3290 &"*** frozen ***"& is displayed at the end of this line.
3292 The recipients of the message (taken from the envelope, not the headers) are
3293 displayed on subsequent lines. Those addresses to which the message has already
3294 been delivered are marked with the letter D. If an original address gets
3295 expanded into several addresses via an alias or forward file, the original is
3296 displayed with a D only when deliveries for all of its child addresses are
3302 This option operates like &%-bp%&, but in addition it shows delivered addresses
3303 that were generated from the original top level address(es) in each message by
3304 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3310 .cindex "queue" "count of messages on"
3311 This option counts the number of messages in the queue, and writes the total
3312 to the standard output. It is restricted to admin users, unless
3313 &%queue_list_requires_admin%& is set false.
3318 This option operates like &%-bp%&, but the output is not sorted into
3319 chronological order of message arrival. This can speed it up when there are
3320 lots of messages in the queue, and is particularly useful if the output is
3321 going to be post-processed in a way that doesn't need the sorting.
3325 This option is a combination of &%-bpr%& and &%-bpa%&.
3329 This option is a combination of &%-bpr%& and &%-bpu%&.
3334 This option operates like &%-bp%& but shows only undelivered top-level
3335 addresses for each message displayed. Addresses generated by aliasing or
3336 forwarding are not shown, unless the message was deferred after processing by a
3337 router with the &%one_time%& option set.
3342 .cindex "testing" "retry configuration"
3343 .cindex "retry" "configuration testing"
3344 This option is for testing retry rules, and it must be followed by up to three
3345 arguments. It causes Exim to look for a retry rule that matches the values
3346 and to write it to the standard output. For example:
3348 exim -brt bach.comp.mus.example
3349 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3351 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3352 argument, which is required, can be a complete address in the form
3353 &'local_part@domain'&, or it can be just a domain name. If the second argument
3354 contains a dot, it is interpreted as an optional second domain name; if no
3355 retry rule is found for the first argument, the second is tried. This ties in
3356 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3357 rule is found that matches the host, one that matches the mail domain is
3358 sought. Finally, an argument that is the name of a specific delivery error, as
3359 used in setting up retry rules, can be given. For example:
3361 exim -brt haydn.comp.mus.example quota_3d
3362 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3367 .cindex "testing" "rewriting"
3368 .cindex "rewriting" "testing"
3369 This option is for testing address rewriting rules, and it must be followed by
3370 a single argument, consisting of either a local part without a domain, or a
3371 complete address with a fully qualified domain. Exim outputs how this address
3372 would be rewritten for each possible place it might appear. See chapter
3373 &<<CHAPrewrite>>& for further details.
3377 .cindex "SMTP" "batched incoming"
3378 .cindex "batched SMTP input"
3379 This option is used for batched SMTP input, which is an alternative interface
3380 for non-interactive local message submission. A number of messages can be
3381 submitted in a single run. However, despite its name, this is not really SMTP
3382 input. Exim reads each message's envelope from SMTP commands on the standard
3383 input, but generates no responses. If the caller is trusted, or
3384 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3385 believed; otherwise the sender is always the caller of Exim.
3387 The message itself is read from the standard input, in SMTP format (leading
3388 dots doubled), terminated by a line containing just a single dot. An error is
3389 provoked if the terminating dot is missing. A further message may then follow.
3391 As for other local message submissions, the contents of incoming batch SMTP
3392 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3393 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3394 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3396 Some other SMTP commands are recognized in the input. HELO and EHLO act
3397 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3398 QUIT quits, ignoring the rest of the standard input.
3400 .cindex "return code" "for &%-bS%&"
3401 If any error is encountered, reports are written to the standard output and
3402 error streams, and Exim gives up immediately. The return code is 0 if no error
3403 was detected; it is 1 if one or more messages were accepted before the error
3404 was detected; otherwise it is 2.
3406 More details of input using batched SMTP are given in section
3407 &<<SECTincomingbatchedSMTP>>&.
3411 .cindex "SMTP" "local input"
3412 .cindex "local SMTP input"
3413 This option causes Exim to accept one or more messages by reading SMTP commands
3414 on the standard input, and producing SMTP replies on the standard output. SMTP
3415 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3416 Some user agents use this interface as a way of passing locally-generated
3417 messages to the MTA.
3420 .cindex "sender" "source of"
3421 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3422 set, the senders of messages are taken from the SMTP MAIL commands.
3423 Otherwise the content of these commands is ignored and the sender is set up as
3424 the calling user. Unqualified addresses are automatically qualified using
3425 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3426 &%-bnq%& option is used.
3430 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3431 using a listening daemon. Exim can distinguish the two cases by checking
3432 whether the standard input is a TCP/IP socket. When Exim is called from
3433 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3434 above concerning senders and qualification do not apply. In this situation,
3435 Exim behaves in exactly the same way as it does when receiving a message via
3436 the listening daemon.
3440 .cindex "testing" "addresses"
3441 .cindex "address" "testing"
3442 This option runs Exim in address testing mode, in which each argument is taken
3443 as a recipient address to be tested for deliverability. The results are
3444 written to the standard output. If a test fails, and the caller is not an admin
3445 user, no details of the failure are output, because these might contain
3446 sensitive information such as usernames and passwords for database lookups.
3448 If no arguments are given, Exim runs in an interactive manner, prompting with a
3449 right angle bracket for addresses to be tested.
3451 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3452 &[readline()]& function, because it is running as &'root'& and there are
3455 Each address is handled as if it were the recipient address of a message
3456 (compare the &%-bv%& option). It is passed to the routers and the result is
3457 written to the standard output. However, any router that has
3458 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3459 genuine routing tests if your first router passes everything to a scanner
3462 .cindex "return code" "for &%-bt%&"
3463 The return code is 2 if any address failed outright; it is 1 if no address
3464 failed outright but at least one could not be resolved for some reason. Return
3465 code 0 is given only when all addresses succeed.
3467 .cindex "duplicate addresses"
3468 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3469 addresses after routing is complete, so that only one delivery takes place.
3470 This does not happen when testing with &%-bt%&; the full results of routing are
3473 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3474 routers in the configuration makes any tests on the sender address of a
3476 .oindex "&%-f%&" "for address testing"
3477 you can use the &%-f%& option to set an appropriate sender when running
3478 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3479 default qualifying domain. However, if you have set up (for example) routers
3480 whose behaviour depends on the contents of an incoming message, you cannot test
3481 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3486 .cindex "version number of Exim"
3487 This option causes Exim to write the current version number, compilation
3488 number, and compilation date of the &'exim'& binary to the standard output.
3489 It also lists the DBM library that is being used, the optional modules (such as
3490 specific lookup types), the drivers that are included in the binary, and the
3491 name of the runtime configuration file that is in use.
3493 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3494 configuration file. However, this is a static check only. It cannot check
3495 values that are to be expanded. For example, although a misspelt ACL verb is
3496 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3497 alone to discover (for example) all the typos in the configuration; some
3498 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3499 dynamic testing facilities.
3503 .cindex "verifying address" "using &%-bv%&"
3504 .cindex "address" "verification"
3505 This option runs Exim in address verification mode, in which each argument is
3506 taken as a recipient address to be verified by the routers. (This does
3507 not involve any verification callouts). During normal operation, verification
3508 happens mostly as a consequence processing a &%verify%& condition in an ACL
3509 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3510 including callouts, see the &%-bh%& and &%-bhc%& options.
3512 If verification fails, and the caller is not an admin user, no details of the
3513 failure are output, because these might contain sensitive information such as
3514 usernames and passwords for database lookups.
3516 If no arguments are given, Exim runs in an interactive manner, prompting with a
3517 right angle bracket for addresses to be verified.
3519 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3520 &[readline()]& function, because it is running as &'exim'& and there are
3523 Verification differs from address testing (the &%-bt%& option) in that routers
3524 that have &%no_verify%& set are skipped, and if the address is accepted by a
3525 router that has &%fail_verify%& set, verification fails. The address is
3526 verified as a recipient if &%-bv%& is used; to test verification for a sender
3527 address, &%-bvs%& should be used.
3529 If the &%-v%& option is not set, the output consists of a single line for each
3530 address, stating whether it was verified or not, and giving a reason in the
3531 latter case. Without &%-v%&, generating more than one address by redirection
3532 causes verification to end successfully, without considering the generated
3533 addresses. However, if just one address is generated, processing continues,
3534 and the generated address must verify successfully for the overall verification
3537 When &%-v%& is set, more details are given of how the address has been handled,
3538 and in the case of address redirection, all the generated addresses are also
3539 considered. Verification may succeed for some and fail for others.
3542 .cindex "return code" "for &%-bv%&"
3543 return code is 2 if any address failed outright; it is 1 if no address
3544 failed outright but at least one could not be resolved for some reason. Return
3545 code 0 is given only when all addresses succeed.
3547 If any of the routers in the configuration makes any tests on the sender
3548 address of a message, you should use the &%-f%& option to set an appropriate
3549 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3550 calling user at the default qualifying domain.
3554 This option acts like &%-bv%&, but verifies the address as a sender rather
3555 than a recipient address. This affects any rewriting and qualification that
3562 .cindex "inetd" "wait mode"
3563 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3564 similarly to the &%-bd%& option. All port specifications on the command-line
3565 and in the configuration file are ignored. Queue-running may not be specified.
3567 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3568 listening for connections. This permits the system to start up and have
3569 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3570 each port only when the first connection is received.
3572 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3573 which the daemon will exit, which should cause inetd to listen once more.
3575 .vitem &%-C%&&~<&'filelist'&>
3577 .cindex "configuration file" "alternate"
3578 .cindex "CONFIGURE_FILE"
3579 .cindex "alternate configuration file"
3580 This option causes Exim to find the runtime configuration file from the given
3581 list instead of from the list specified by the CONFIGURE_FILE
3582 compile-time setting. Usually, the list will consist of just a single filename,
3583 but it can be a colon-separated list of names. In this case, the first
3584 file that exists is used. Failure to open an existing file stops Exim from
3585 proceeding any further along the list, and an error is generated.
3587 When this option is used by a caller other than root, and the list is different
3588 from the compiled-in list, Exim gives up its root privilege immediately, and
3589 runs with the real and effective uid and gid set to those of the caller.
3590 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3591 file contains a list of full pathnames, one per line, for configuration files
3592 which are trusted. Root privilege is retained for any configuration file so
3593 listed, as long as the caller is the Exim user (or the user specified in the
3594 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3595 not writeable by inappropriate users or groups.
3597 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3598 configuration using &%-C%& right through message reception and delivery,
3599 even if the caller is root. The reception works, but by that time, Exim is
3600 running as the Exim user, so when it re-executes to regain privilege for the
3601 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3602 test reception and delivery using two separate commands (one to put a message
3603 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3605 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3606 prefix string with which any file named in a &%-C%& command line option
3607 must start. In addition, the filename must not contain the sequence &`/../`&.
3608 However, if the value of the &%-C%& option is identical to the value of
3609 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3610 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3611 unset, any filename can be used with &%-C%&.
3613 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3614 to a directory to which only root has access. This prevents someone who has
3615 broken into the Exim account from running a privileged Exim with an arbitrary
3618 The &%-C%& facility is useful for ensuring that configuration files are
3619 syntactically correct, but cannot be used for test deliveries, unless the
3620 caller is privileged, or unless it is an exotic configuration that does not
3621 require privilege. No check is made on the owner or group of the files
3622 specified by this option.
3625 .vitem &%-D%&<&'macro'&>=<&'value'&>
3627 .cindex "macro" "setting on command line"
3628 This option can be used to override macro definitions in the configuration file
3629 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3630 unprivileged caller, it causes Exim to give up its root privilege.
3631 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3632 completely disabled, and its use causes an immediate error exit.
3634 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3635 colon-separated list of macros which are considered safe and, if &%-D%& only
3636 supplies macros from this list, and the values are acceptable, then Exim will
3637 not give up root privilege if the caller is root, the Exim run-time user, or
3638 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3639 to be removed in the future. Acceptable values for the macros satisfy the
3640 regexp: &`^[A-Za-z0-9_/.-]*$`&
3642 The entire option (including equals sign if present) must all be within one
3643 command line item. &%-D%& can be used to set the value of a macro to the empty
3644 string, in which case the equals sign is optional. These two commands are
3650 To include spaces in a macro definition item, quotes must be used. If you use
3651 quotes, spaces are permitted around the macro name and the equals sign. For
3654 exim '-D ABC = something' ...
3656 &%-D%& may be repeated up to 10 times on a command line.
3657 Only macro names up to 22 letters long can be set.
3660 .vitem &%-d%&<&'debug&~options'&>
3662 .cindex "debugging" "list of selectors"
3663 .cindex "debugging" "&%-d%& option"
3664 This option causes debugging information to be written to the standard
3665 error stream. It is restricted to admin users because debugging output may show
3666 database queries that contain password information. Also, the details of users'
3667 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3668 writes an error message to the standard error stream and exits with a non-zero
3671 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3672 standard debugging data is output. This can be reduced, or increased to include
3673 some more rarely needed information, by directly following &%-d%& with a string
3674 made up of names preceded by plus or minus characters. These add or remove sets
3675 of debugging data, respectively. For example, &%-d+filter%& adds filter
3676 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3677 no spaces are allowed in the debug setting. The available debugging categories
3680 &`acl `& ACL interpretation
3681 &`auth `& authenticators
3682 &`deliver `& general delivery logic
3683 &`dns `& DNS lookups (see also resolver)
3684 &`dnsbl `& DNS black list (aka RBL) code
3685 &`exec `& arguments for &[execv()]& calls
3686 &`expand `& detailed debugging for string expansions
3687 &`filter `& filter handling
3688 &`hints_lookup `& hints data lookups
3689 &`host_lookup `& all types of name-to-IP address handling
3690 &`ident `& ident lookup
3691 &`interface `& lists of local interfaces
3692 &`lists `& matching things in lists
3693 &`load `& system load checks
3694 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3695 &<<CHAPlocalscan>>&)
3696 &`lookup `& general lookup code and all lookups
3697 &`memory `& memory handling
3698 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3699 &`pid `& modifier: add pid to debug output lines
3700 &`process_info `& setting info for the process log
3701 &`queue_run `& queue runs
3702 &`receive `& general message reception logic
3703 &`resolver `& turn on the DNS resolver's debugging output
3704 &`retry `& retry handling
3705 &`rewrite `& address rewriting
3706 &`route `& address routing
3707 &`timestamp `& modifier: add timestamp to debug output lines
3709 &`transport `& transports
3710 &`uid `& changes of uid/gid and looking up uid/gid
3711 &`verify `& address verification logic
3712 &`all `& almost all of the above (see below), and also &%-v%&
3714 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3715 for &`-all`&. The reason for this is that &`+all`& is something that people
3716 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3717 is included, an awful lot of output that is very rarely of interest is
3718 generated, so it now has to be explicitly requested. However, &`-all`& does
3719 turn everything off.
3721 .cindex "resolver, debugging output"
3722 .cindex "DNS resolver, debugging output"
3723 The &`resolver`& option produces output only if the DNS resolver was compiled
3724 with DEBUG enabled. This is not the case in some operating systems. Also,
3725 unfortunately, debugging output from the DNS resolver is written to stdout
3728 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3729 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3730 However, the &`pid`& selector is forced when debugging is turned on for a
3731 daemon, which then passes it on to any re-executed Exims. Exim also
3732 automatically adds the pid to debug lines when several remote deliveries are
3735 The &`timestamp`& selector causes the current time to be inserted at the start
3736 of all debug output lines. This can be useful when trying to track down delays
3739 .cindex debugging "UTF-8 in"
3740 .cindex UTF-8 "in debug output"
3741 The &`noutf8`& selector disables the use of
3742 UTF-8 line-drawing characters to group related information.
3743 When disabled. ascii-art is used instead.
3744 Using the &`+all`& option does not set this modifier,
3746 If the &%debug_print%& option is set in any driver, it produces output whenever
3747 any debugging is selected, or if &%-v%& is used.
3749 .vitem &%-dd%&<&'debug&~options'&>
3751 This option behaves exactly like &%-d%& except when used on a command that
3752 starts a daemon process. In that case, debugging is turned off for the
3753 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3754 behaviour of the daemon without creating as much output as full debugging does.
3757 .oindex "&%-dropcr%&"
3758 This is an obsolete option that is now a no-op. It used to affect the way Exim
3759 handled CR and LF characters in incoming messages. What happens now is
3760 described in section &<<SECTlineendings>>&.
3764 .cindex "bounce message" "generating"
3765 This option specifies that an incoming message is a locally-generated delivery
3766 failure report. It is used internally by Exim when handling delivery failures
3767 and is not intended for external use. Its only effect is to stop Exim
3768 generating certain messages to the postmaster, as otherwise message cascades
3769 could occur in some situations. As part of the same option, a message id may
3770 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3771 new message contains the id, following &"R="&, as a cross-reference.
3774 .oindex "&%-e%&&'x'&"
3775 There are a number of Sendmail options starting with &%-oe%& which seem to be
3776 called by various programs without the leading &%o%& in the option. For
3777 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3778 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3780 .vitem &%-F%&&~<&'string'&>
3782 .cindex "sender" "name"
3783 .cindex "name" "of sender"
3784 This option sets the sender's full name for use when a locally-generated
3785 message is being accepted. In the absence of this option, the user's &'gecos'&
3786 entry from the password data is used. As users are generally permitted to alter
3787 their &'gecos'& entries, no security considerations are involved. White space
3788 between &%-F%& and the <&'string'&> is optional.
3790 .vitem &%-f%&&~<&'address'&>
3792 .cindex "sender" "address"
3793 .cindex "address" "sender"
3794 .cindex "trusted users"
3795 .cindex "envelope from"
3796 .cindex "envelope sender"
3797 .cindex "user" "trusted"
3798 This option sets the address of the envelope sender of a locally-generated
3799 message (also known as the return path). The option can normally be used only
3800 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3803 Processes running as root or the Exim user are always trusted. Other
3804 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3805 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3806 of a local message is set to the caller's login name at the default qualify
3809 There is one exception to the restriction on the use of &%-f%&: an empty sender
3810 can be specified by any user, trusted or not, to create a message that can
3811 never provoke a bounce. An empty sender can be specified either as an empty
3812 string, or as a pair of angle brackets with nothing between them, as in these
3813 examples of shell commands:
3815 exim -f '<>' user@domain
3816 exim -f "" user@domain
3818 In addition, the use of &%-f%& is not restricted when testing a filter file
3819 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3822 Allowing untrusted users to change the sender address does not of itself make
3823 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3824 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3825 though this can be overridden by setting &%no_local_from_check%&.
3828 .cindex "&""From""& line"
3829 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3830 given as two arguments or one combined argument). The sender of a
3831 locally-generated message can also be set (when permitted) by an initial
3832 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3833 if &%-f%& is also present, it overrides &"From&~"&.
3837 .cindex "submission fixups, suppressing (command-line)"
3838 This option is equivalent to an ACL applying:
3840 control = suppress_local_fixups
3842 for every message received. Note that Sendmail will complain about such
3843 bad formatting, where Exim silently just does not fix it up. This may change
3846 As this affects audit information, the caller must be a trusted user to use
3849 .vitem &%-h%&&~<&'number'&>
3851 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3852 This option is accepted for compatibility with Sendmail, but has no effect. (In
3853 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3858 .cindex "Solaris" "&'mail'& command"
3859 .cindex "dot" "in incoming non-SMTP message"
3860 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3861 line by itself should not terminate an incoming, non-SMTP message.
3862 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3863 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3864 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3865 by its &'mailx'& command.
3867 .vitem &%-L%&&~<&'tag'&>
3869 .cindex "syslog" "process name; set with flag"
3870 This option is equivalent to setting &%syslog_processname%& in the config
3871 file and setting &%log_file_path%& to &`syslog`&.
3872 Its use is restricted to administrators. The configuration file has to be
3873 read and parsed, to determine access rights, before this is set and takes
3874 effect, so early configuration file errors will not honour this flag.
3876 The tag should not be longer than 32 characters.
3878 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3880 .cindex "forcing delivery"
3881 .cindex "delivery" "forcing attempt"
3882 .cindex "frozen messages" "forcing delivery"
3883 This option requests Exim to run a delivery attempt on each message in turn. If
3884 any of the messages are frozen, they are automatically thawed before the
3885 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3886 and &%hold_domains%& are ignored.
3889 .cindex "hints database" "overriding retry hints"
3890 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3891 the normal retry time has not yet been reached. This option requires the caller
3892 to be an admin user. However, there is an option called &%prod_requires_admin%&
3893 which can be set false to relax this restriction (and also the same requirement
3894 for the &%-q%&, &%-R%&, and &%-S%& options).
3896 The deliveries happen synchronously, that is, the original Exim process does
3897 not terminate until all the delivery attempts have finished. No output is
3898 produced unless there is a serious error. If you want to see what is happening,
3899 use the &%-v%& option as well, or inspect Exim's main log.
3901 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3903 .cindex "message" "adding recipients"
3904 .cindex "recipient" "adding"
3905 This option requests Exim to add the addresses to the list of recipients of the
3906 message (&"ar"& for &"add recipients"&). The first argument must be a message
3907 id, and the remaining ones must be email addresses. However, if the message is
3908 active (in the middle of a delivery attempt), it is not altered. This option
3909 can be used only by an admin user.
3911 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3913 &~<&'sequence&~number'&>&&&
3914 &~<&'message&~id'&>"
3916 .cindex "SMTP" "passed connection"
3917 .cindex "SMTP" "multiple deliveries"
3918 .cindex "multiple SMTP deliveries"
3919 This option is not intended for use by external callers. It is used internally
3920 by Exim to invoke another instance of itself to deliver a waiting message using
3921 an existing SMTP connection, which is passed as the standard input. Details are
3922 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3923 must be root or the Exim user in order to use it.
3927 This option is not intended for use by external callers. It is used internally
3928 by Exim in conjunction with the &%-MC%& option. It signifies that the
3929 connection to the remote host has been authenticated.
3933 This option is not intended for use by external callers. It is used internally
3934 by Exim in conjunction with the &%-MC%& option. It signifies that the
3935 remote host supports the ESMTP &_DSN_& extension.
3939 This option is not intended for use by external callers. It is used internally
3940 by Exim in conjunction with the &%-d%& option
3941 to pass on an information string on the purpose of the process.
3943 .vitem &%-MCG%&&~<&'queue&~name'&>
3945 This option is not intended for use by external callers. It is used internally
3946 by Exim in conjunction with the &%-MC%& option. It signifies that an
3947 alternate queue is used, named by the following argument.
3951 This option is not intended for use by external callers. It is used internally
3952 by Exim in conjunction with the &%-MC%& option. It signifies that a
3953 remote host supports the ESMTP &_CHUNKING_& extension.
3958 This option is not intended for use by external callers. It is used internally
3959 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3960 which Exim is connected advertised limits on numbers of mails, recipients or
3962 The limits are given by the following three arguments.
3967 This option is not intended for use by external callers. It is used internally
3968 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3969 which Exim is connected supports pipelining.
3974 This option is not intended for use by external callers. It is used internally
3975 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3976 t a remote server is via a SOCKS proxy, using addresses and ports given by
3977 the following four arguments.
3980 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3982 This option is not intended for use by external callers. It is used internally
3983 by Exim in conjunction with the &%-MC%& option when the original delivery was
3984 started by a queue runner. It passes on the process id of the queue runner,
3985 together with the file descriptor number of an open pipe. Closure of the pipe
3986 signals the final completion of the sequence of processes that are passing
3987 messages through the same SMTP connection.
3990 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3992 This option is not intended for use by external callers. It is used internally
3993 by Exim to implement quota checking for local users.
3998 This option is not intended for use by external callers. It is used internally
3999 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4000 ESMTP SIZE option should be used on messages delivered down the existing
4005 This option is not intended for use by external callers. It is used internally
4006 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4007 host to which Exim is connected supports TLS encryption.
4010 .vitem &%-MCr%&&~<&'SNI'&> &&&
4014 These options are not intended for use by external callers. It is used internally
4015 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
4016 a TLS Server Name Indication was sent as part of the channel establishment.
4017 The argument gives the SNI string.
4018 The "r" variant indicates a DANE-verified connection.
4021 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
4023 This option is not intended for use by external callers. It is used internally
4024 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4025 connection is being proxied by a parent process for handling TLS encryption.
4026 The arguments give the local address and port being proxied, and the TLS cipher.
4028 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4030 .cindex "hints database" "not overridden by &%-Mc%&"
4031 .cindex "delivery" "manually started &-- not forced"
4032 This option requests Exim to run a delivery attempt on each message, in turn,
4033 but unlike the &%-M%& option, it does check for retry hints, and respects any
4034 that are found. This option is not very useful to external callers. It is
4035 provided mainly for internal use by Exim when it needs to re-invoke itself in
4036 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
4037 However, &%-Mc%& can be useful when testing, in order to run a delivery that
4038 respects retry times and other options such as &%hold_domains%& that are
4039 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
4040 If you want to run a specific delivery as if in a queue run, you should use
4041 &%-q%& with a message id argument. A distinction between queue run deliveries
4042 and other deliveries is made in one or two places.
4044 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4046 .cindex "message" "changing sender"
4047 .cindex "sender" "changing"
4048 This option requests Exim to change the sender address in the message to the
4049 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4050 &"edit sender"&). There must be exactly two arguments. The first argument must
4051 be a message id, and the second one an email address. However, if the message
4052 is active (in the middle of a delivery attempt), its status is not altered.
4053 This option can be used only by an admin user.
4055 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4057 .cindex "freezing messages"
4058 .cindex "message" "manually freezing"
4059 This option requests Exim to mark each listed message as &"frozen"&. This
4060 prevents any delivery attempts taking place until the message is &"thawed"&,
4061 either manually or as a result of the &%auto_thaw%& configuration option.
4062 However, if any of the messages are active (in the middle of a delivery
4063 attempt), their status is not altered. This option can be used only by an admin
4066 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4068 .cindex "giving up on messages"
4069 .cindex "message" "abandoning delivery attempts"
4070 .cindex "delivery" "abandoning further attempts"
4071 This option requests Exim to give up trying to deliver the listed messages,
4072 including any that are frozen. However, if any of the messages are active,
4073 their status is not altered. For non-bounce messages, a delivery error message
4074 is sent to the sender, containing the text &"cancelled by administrator"&.
4075 Bounce messages are just discarded. This option can be used only by an admin
4078 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4081 .cindex "named queues" "moving messages"
4082 .cindex "queue" "moving messages"
4083 This option requests that each listed message be moved from its current
4084 queue to the given named queue.
4085 The destination queue name argument is required, but can be an empty
4086 string to define the default queue.
4087 If the messages are not currently located in the default queue,
4088 a &%-qG<name>%& option will be required to define the source queue.
4090 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4092 .cindex "delivery" "cancelling all"
4093 This option requests Exim to mark all the recipient addresses in the messages
4094 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4095 message is active (in the middle of a delivery attempt), its status is not
4096 altered. This option can be used only by an admin user.
4098 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4100 .cindex "delivery" "cancelling by address"
4101 .cindex "recipient" "removing"
4102 .cindex "removing recipients"
4103 This option requests Exim to mark the given addresses as already delivered
4104 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4105 the remaining ones must be email addresses. These are matched to recipient
4106 addresses in the message in a case-sensitive manner. If the message is active
4107 (in the middle of a delivery attempt), its status is not altered. This option
4108 can be used only by an admin user.
4110 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4112 .cindex "removing messages"
4113 .cindex "abandoning mail"
4114 .cindex "message" "manually discarding"
4115 This option requests Exim to remove the given messages from the queue. No
4116 bounce messages are sent; each message is simply forgotten. However, if any of
4117 the messages are active, their status is not altered. This option can be used
4118 only by an admin user or by the user who originally caused the message to be
4119 placed in the queue.
4124 . .cindex REQUIRETLS
4125 . This option is used to request REQUIRETLS processing on the message.
4126 . It is used internally by Exim in conjunction with -E when generating
4130 .vitem &%-Mset%&&~<&'message&~id'&>
4132 .cindex "testing" "string expansion"
4133 .cindex "expansion" "testing"
4134 This option is useful only in conjunction with &%-be%& (that is, when testing
4135 string expansions). Exim loads the given message from its spool before doing
4136 the test expansions, thus setting message-specific variables such as
4137 &$message_size$& and the header variables. The &$recipients$& variable is made
4138 available. This feature is provided to make it easier to test expansions that
4139 make use of these variables. However, this option can be used only by an admin
4140 user. See also &%-bem%&.
4142 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4144 .cindex "thawing messages"
4145 .cindex "unfreezing messages"
4146 .cindex "frozen messages" "thawing"
4147 .cindex "message" "thawing frozen"
4148 This option requests Exim to &"thaw"& any of the listed messages that are
4149 &"frozen"&, so that delivery attempts can resume. However, if any of the
4150 messages are active, their status is not altered. This option can be used only
4153 .vitem &%-Mvb%&&~<&'message&~id'&>
4155 .cindex "listing" "message body"
4156 .cindex "message" "listing body of"
4157 This option causes the contents of the message body (-D) spool file to be
4158 written to the standard output. This option can be used only by an admin user.
4160 .vitem &%-Mvc%&&~<&'message&~id'&>
4162 .cindex "message" "listing in RFC 2822 format"
4163 .cindex "listing" "message in RFC 2822 format"
4164 This option causes a copy of the complete message (header lines plus body) to
4165 be written to the standard output in RFC 2822 format. This option can be used
4166 only by an admin user.
4168 .vitem &%-Mvh%&&~<&'message&~id'&>
4170 .cindex "listing" "message headers"
4171 .cindex "header lines" "listing"
4172 .cindex "message" "listing header lines"
4173 This option causes the contents of the message headers (-H) spool file to be
4174 written to the standard output. This option can be used only by an admin user.
4176 .vitem &%-Mvl%&&~<&'message&~id'&>
4178 .cindex "listing" "message log"
4179 .cindex "message" "listing message log"
4180 This option causes the contents of the message log spool file to be written to
4181 the standard output. This option can be used only by an admin user.
4185 This is a synonym for &%-om%& that is accepted by Sendmail
4186 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4187 p. 1M-258), so Exim treats it that way too.
4191 .cindex "debugging" "&%-N%& option"
4192 .cindex "debugging" "suppressing delivery"
4193 This is a debugging option that inhibits delivery of a message at the transport
4194 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4195 it just doesn't actually transport the message, but instead behaves as if it
4196 had successfully done so. However, it does not make any updates to the retry
4197 database, and the log entries for deliveries are flagged with &"*>"& rather
4200 Because &%-N%& discards any message to which it applies, only root or the Exim
4201 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4202 words, an ordinary user can use it only when supplying an incoming message to
4203 which it will apply. Although transportation never fails when &%-N%& is set, an
4204 address may be deferred because of a configuration problem on a transport, or a
4205 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4206 the message, and applies to any subsequent delivery attempts that may happen
4211 This option is interpreted by Sendmail to mean &"no aliasing"&.
4212 For normal modes of operation, it is ignored by Exim.
4213 When combined with &%-bP%& it makes the output more terse (suppresses
4214 option names, environment values and config pretty printing).
4216 .vitem &%-O%&&~<&'data'&>
4218 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4221 .vitem &%-oA%&&~<&'file&~name'&>
4223 .cindex "Sendmail compatibility" "&%-oA%& option"
4224 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4225 alternative alias filename. Exim handles &%-bi%& differently; see the
4228 .vitem &%-oB%&&~<&'n'&>
4230 .cindex "SMTP" "passed connection"
4231 .cindex "SMTP" "multiple deliveries"
4232 .cindex "multiple SMTP deliveries"
4233 This is a debugging option which limits the maximum number of messages that can
4234 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4235 transport. If <&'n'&> is omitted, the limit is set to 1.
4239 .cindex "background delivery"
4240 .cindex "delivery" "in the background"
4241 This option applies to all modes in which Exim accepts incoming messages,
4242 including the listening daemon. It requests &"background"& delivery of such
4243 messages, which means that the accepting process automatically starts a
4244 delivery process for each message received, but does not wait for the delivery
4245 processes to finish.
4247 When all the messages have been received, the reception process exits,
4248 leaving the delivery processes to finish in their own time. The standard output
4249 and error streams are closed at the start of each delivery process.
4250 This is the default action if none of the &%-od%& options are present.
4252 If one of the queueing options in the configuration file
4253 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4254 overrides it if &%queue_only_override%& is set true, which is the default
4255 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4259 .cindex "foreground delivery"
4260 .cindex "delivery" "in the foreground"
4261 This option requests &"foreground"& (synchronous) delivery when Exim has
4262 accepted a locally-generated message. (For the daemon it is exactly the same as
4263 &%-odb%&.) A delivery process is automatically started to deliver the message,
4264 and Exim waits for it to complete before proceeding.
4266 The original Exim reception process does not finish until the delivery
4267 process for the final message has ended. The standard error stream is left open
4270 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4271 false and one of the queueing options in the configuration file is in effect.
4273 If there is a temporary delivery error during foreground delivery, the
4274 message is left in the queue for later delivery, and the original reception
4275 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4276 restricted configuration that never queues messages.
4281 This option is synonymous with &%-odf%&. It is provided for compatibility with
4286 .cindex "non-immediate delivery"
4287 .cindex "delivery" "suppressing immediate"
4288 .cindex "queueing incoming messages"
4289 This option applies to all modes in which Exim accepts incoming messages,
4290 including the listening daemon. It specifies that the accepting process should
4291 not automatically start a delivery process for each message received. Messages
4292 are placed in the queue, and remain there until a subsequent queue runner
4293 process encounters them. There are several configuration options (such as
4294 &%queue_only%&) that can be used to queue incoming messages under certain
4295 conditions. This option overrides all of them and also &%-odqs%&. It always
4300 .cindex "SMTP" "delaying delivery"
4301 .cindex "first pass routing"
4302 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4303 However, like &%-odb%& and &%-odi%&, this option has no effect if
4304 &%queue_only_override%& is false and one of the queueing options in the
4305 configuration file is in effect.
4307 When &%-odqs%& does operate, a delivery process is started for each incoming
4308 message, in the background by default, but in the foreground if &%-odi%& is
4309 also present. The recipient addresses are routed, and local deliveries are done
4310 in the normal way. However, if any SMTP deliveries are required, they are not
4311 done at this time, so the message remains in the queue until a subsequent queue
4312 runner process encounters it. Because routing was done, Exim knows which
4313 messages are waiting for which hosts, and so a number of messages for the same
4314 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4315 configuration option has the same effect for specific domains. See also the
4320 .cindex "error" "reporting"
4321 If an error is detected while a non-SMTP message is being received (for
4322 example, a malformed address), the error is reported to the sender in a mail
4325 .cindex "return code" "for &%-oee%&"
4327 this error message is successfully sent, the Exim receiving process
4328 exits with a return code of zero. If not, the return code is 2 if the problem
4329 is that the original message has no recipients, or 1 for any other error.
4330 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4334 .cindex "error" "reporting"
4335 .cindex "return code" "for &%-oem%&"
4336 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4337 return code, whether or not the error message was successfully sent.
4338 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4342 .cindex "error" "reporting"
4343 If an error is detected while a non-SMTP message is being received, the
4344 error is reported by writing a message to the standard error file (stderr).
4345 .cindex "return code" "for &%-oep%&"
4346 The return code is 1 for all errors.
4350 .cindex "error" "reporting"
4351 This option is supported for compatibility with Sendmail, but has the same
4356 .cindex "error" "reporting"
4357 This option is supported for compatibility with Sendmail, but has the same
4362 .cindex "dot" "in incoming non-SMTP message"
4363 This option, which has the same effect as &%-i%&, specifies that a dot on a
4364 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4365 single dot does terminate, though Exim does no special processing for other
4366 lines that start with a dot. This option is set by default if Exim is called as
4367 &'rmail'&. See also &%-ti%&.
4370 .oindex "&%-oitrue%&"
4371 This option is treated as synonymous with &%-oi%&.
4373 .vitem &%-oMa%&&~<&'host&~address'&>
4375 .cindex "sender" "host address, specifying for local message"
4376 A number of options starting with &%-oM%& can be used to set values associated
4377 with remote hosts on locally-submitted messages (that is, messages not received
4378 over TCP/IP). These options can be used by any caller in conjunction with the
4379 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4380 other circumstances, they are ignored unless the caller is trusted.
4382 The &%-oMa%& option sets the sender host address. This may include a port
4383 number at the end, after a full stop (period). For example:
4385 exim -bs -oMa 10.9.8.7.1234
4387 An alternative syntax is to enclose the IP address in square brackets,
4388 followed by a colon and the port number:
4390 exim -bs -oMa [10.9.8.7]:1234
4392 The IP address is placed in the &$sender_host_address$& variable, and the
4393 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4394 are present on the command line, the sender host IP address is taken from
4395 whichever one is last.
4397 .vitem &%-oMaa%&&~<&'name'&>
4399 .cindex "authentication" "name, specifying for local message"
4400 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4401 option sets the value of &$sender_host_authenticated$& (the authenticator
4402 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4403 This option can be used with &%-bh%& and &%-bs%& to set up an
4404 authenticated SMTP session without actually using the SMTP AUTH command.
4406 .vitem &%-oMai%&&~<&'string'&>
4408 .cindex "authentication" "id, specifying for local message"
4409 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4410 option sets the value of &$authenticated_id$& (the id that was authenticated).
4411 This overrides the default value (the caller's login id, except with &%-bh%&,
4412 where there is no default) for messages from local sources. See chapter
4413 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4415 .vitem &%-oMas%&&~<&'address'&>
4417 .cindex "authentication" "sender, specifying for local message"
4418 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4419 option sets the authenticated sender value in &$authenticated_sender$&. It
4420 overrides the sender address that is created from the caller's login id for
4421 messages from local sources, except when &%-bh%& is used, when there is no
4422 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4423 specified on a MAIL command overrides this value. See chapter
4424 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4426 .vitem &%-oMi%&&~<&'interface&~address'&>
4428 .cindex "interface" "address, specifying for local message"
4429 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4430 option sets the IP interface address value. A port number may be included,
4431 using the same syntax as for &%-oMa%&. The interface address is placed in
4432 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4434 .vitem &%-oMm%&&~<&'message&~reference'&>
4436 .cindex "message reference" "message reference, specifying for local message"
4437 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4438 option sets the message reference, e.g. message-id, and is logged during
4439 delivery. This is useful when some kind of audit trail is required to tie
4440 messages together. The format of the message reference is checked and will
4441 abort if the format is invalid. The option will only be accepted if exim is
4442 running in trusted mode, not as any regular user.
4444 The best example of a message reference is when Exim sends a bounce message.
4445 The message reference is the message-id of the original message for which Exim
4446 is sending the bounce.
4448 .vitem &%-oMr%&&~<&'protocol&~name'&>
4450 .cindex "protocol, specifying for local message"
4451 .vindex "&$received_protocol$&"
4452 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4453 option sets the received protocol value that is stored in
4454 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4455 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4456 SMTP protocol names (see the description of &$received_protocol$& in section
4457 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4458 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4459 be set by &%-oMr%&. Repeated use of this option is not supported.
4461 .vitem &%-oMs%&&~<&'host&~name'&>
4463 .cindex "sender" "host name, specifying for local message"
4464 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4465 option sets the sender host name in &$sender_host_name$&. When this option is
4466 present, Exim does not attempt to look up a host name from an IP address; it
4467 uses the name it is given.
4469 .vitem &%-oMt%&&~<&'ident&~string'&>
4471 .cindex "sender" "ident string, specifying for local message"
4472 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4473 option sets the sender ident value in &$sender_ident$&. The default setting for
4474 local callers is the login id of the calling process, except when &%-bh%& is
4475 used, when there is no default.
4479 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4480 In Sendmail, this option means &"me too"&, indicating that the sender of a
4481 message should receive a copy of the message if the sender appears in an alias
4482 expansion. Exim always does this, so the option does nothing.
4486 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4487 This option is ignored. In Sendmail it specifies &"old style headers"&,
4488 whatever that means.
4490 .vitem &%-oP%&&~<&'path'&>
4492 .cindex "pid (process id)" "of daemon"
4493 .cindex "daemon" "process id (pid)"
4494 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4495 value. The option specifies the file to which the process id of the daemon is
4496 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4497 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4498 because in those cases, the normal pid file is not used.
4502 .cindex "pid (process id)" "of daemon"
4503 .cindex "daemon" "process id (pid)"
4504 This option is not intended for general use.
4505 The daemon uses it when terminating due to a SIGTEM, possibly in
4506 combination with &%-oP%&&~<&'path'&>.
4507 It causes the pid file to be removed.
4509 .vitem &%-or%&&~<&'time'&>
4511 .cindex "timeout" "for non-SMTP input"
4512 This option sets a timeout value for incoming non-SMTP messages. If it is not
4513 set, Exim will wait forever for the standard input. The value can also be set
4514 by the &%receive_timeout%& option. The format used for specifying times is
4515 described in section &<<SECTtimeformat>>&.
4517 .vitem &%-os%&&~<&'time'&>
4519 .cindex "timeout" "for SMTP input"
4520 .cindex "SMTP" "input timeout"
4521 This option sets a timeout value for incoming SMTP messages. The timeout
4522 applies to each SMTP command and block of data. The value can also be set by
4523 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4524 for specifying times is described in section &<<SECTtimeformat>>&.
4528 This option has exactly the same effect as &%-v%&.
4530 .vitem &%-oX%&&~<&'number&~or&~string'&>
4532 .cindex "TCP/IP" "setting listening ports"
4533 .cindex "TCP/IP" "setting listening interfaces"
4534 .cindex "port" "receiving TCP/IP"
4535 This option is relevant only when the &%-bd%& (start listening daemon) option
4536 is also given. It controls which ports and interfaces the daemon uses. Details
4537 of the syntax, and how it interacts with configuration file options, are given
4538 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4539 file is written unless &%-oP%& is also present to specify a pid filename.
4544 .cindex "daemon notifier socket"
4545 This option controls the creation of an inter-process communications endpoint
4547 It is only relevant when the &%-bd%& (start listening daemon) option is also
4549 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4550 option is also present.
4551 If this option is given then the socket will not be created. This could be
4552 required if the system is running multiple daemons.
4554 The socket is currently used for
4556 fast ramp-up of queue runner processes
4558 obtaining a current queue size
4564 .cindex "Perl" "starting the interpreter"
4565 This option applies when an embedded Perl interpreter is linked with Exim (see
4566 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4567 option, forcing the starting of the interpreter to be delayed until it is
4572 .cindex "Perl" "starting the interpreter"
4573 This option applies when an embedded Perl interpreter is linked with Exim (see
4574 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4575 option, forcing the starting of the interpreter to occur as soon as Exim is
4578 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4580 For compatibility with Sendmail, this option is equivalent to
4582 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4584 It sets the incoming protocol and host name (for trusted callers). The
4585 host name and its colon can be omitted when only the protocol is to be set.
4586 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4587 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4588 or &`s`& using this option (but that does not seem a real limitation).
4589 Repeated use of this option is not supported.
4593 .cindex "queue runner" "starting manually"
4594 This option is normally restricted to admin users. However, there is a
4595 configuration option called &%prod_requires_admin%& which can be set false to
4596 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4597 and &%-S%& options).
4599 .cindex "queue runner" "description of operation"
4600 If other commandline options do not specify an action,
4601 the &%-q%& option starts one queue runner process. This scans the queue of
4602 waiting messages, and runs a delivery process for each one in turn. It waits
4603 for each delivery process to finish before starting the next one. A delivery
4604 process may not actually do any deliveries if the retry times for the addresses
4605 have not been reached. Use &%-qf%& (see below) if you want to override this.
4608 .cindex "SMTP" "passed connection"
4609 .cindex "SMTP" "multiple deliveries"
4610 .cindex "multiple SMTP deliveries"
4611 the delivery process spawns other processes to deliver other messages down
4612 passed SMTP connections, the queue runner waits for these to finish before
4615 When all the queued messages have been considered, the original queue runner
4616 process terminates. In other words, a single pass is made over the waiting
4617 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4618 this to be repeated periodically.
4620 Exim processes the waiting messages in an unpredictable order. It isn't very
4621 random, but it is likely to be different each time, which is all that matters.
4622 If one particular message screws up a remote MTA, other messages to the same
4623 MTA have a chance of getting through if they get tried first.
4625 It is possible to cause the messages to be processed in lexical message id
4626 order, which is essentially the order in which they arrived, by setting the
4627 &%queue_run_in_order%& option, but this is not recommended for normal use.
4629 .vitem &%-q%&<&'qflags'&>
4630 The &%-q%& option may be followed by one or more flag letters that change its
4631 behaviour. They are all optional, but if more than one is present, they must
4632 appear in the correct order. Each flag is described in a separate item below.
4636 .cindex "queue" "double scanning"
4637 .cindex "queue" "routing"
4638 .cindex "routing" "whole queue before delivery"
4639 .cindex "first pass routing"
4640 .cindex "queue runner" "two phase"
4641 An option starting with &%-qq%& requests a two-stage queue run. In the first
4642 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4643 every domain. Addresses are routed, local deliveries happen, but no remote
4646 Performance will be best if the &%queue_run_in_order%& option is false.
4647 If that is so and the &%queue_fast_ramp%& option is true then
4648 in the first phase of the run,
4649 once a threshold number of messages are routed for a given host,
4650 a delivery process is forked in parallel with the rest of the scan.
4652 .cindex "hints database" "remembering routing"
4653 The hints database that remembers which messages are waiting for specific hosts
4654 is updated, as if delivery to those hosts had been deferred. After this is
4655 complete, a second, normal queue scan happens, with routing and delivery taking
4656 place as normal. Messages that are routed to the same host should mostly be
4657 delivered down a single SMTP
4658 .cindex "SMTP" "passed connection"
4659 .cindex "SMTP" "multiple deliveries"
4660 .cindex "multiple SMTP deliveries"
4661 connection because of the hints that were set up during the first queue scan.
4662 This option may be useful for hosts that are connected to the Internet
4665 .vitem &%-q[q]i...%&
4667 .cindex "queue" "initial delivery"
4668 If the &'i'& flag is present, the queue runner runs delivery processes only for
4669 those messages that haven't previously been tried. (&'i'& stands for &"initial
4670 delivery"&.) This can be helpful if you are putting messages in the queue using
4671 &%-odq%& and want a queue runner just to process the new messages.
4673 .vitem &%-q[q][i]f...%&
4675 .cindex "queue" "forcing delivery"
4676 .cindex "delivery" "forcing in queue run"
4677 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4678 message, whereas without &'f'& only those non-frozen addresses that have passed
4679 their retry times are tried.
4681 .vitem &%-q[q][i]ff...%&
4683 .cindex "frozen messages" "forcing delivery"
4684 If &'ff'& is present, a delivery attempt is forced for every message, whether
4687 .vitem &%-q[q][i][f[f]]l%&
4689 .cindex "queue" "local deliveries only"
4690 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4691 be done. If a message requires any remote deliveries, it remains in the queue
4694 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4697 .cindex "named queues" "deliver from"
4698 .cindex "queue" "delivering specific messages"
4699 If the &'G'& flag and a name is present, the queue runner operates on the
4700 queue with the given name rather than the default queue.
4701 The name should not contain a &'/'& character.
4702 For a periodic queue run (see below)
4703 append to the name a slash and a time value.
4705 If other commandline options specify an action, a &'-qG<name>'& option
4706 will specify a queue to operate on.
4709 exim -bp -qGquarantine
4711 exim -qGoffpeak -Rf @special.domain.example
4714 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4715 When scanning the queue, Exim can be made to skip over messages whose ids are
4716 lexically less than a given value by following the &%-q%& option with a
4717 starting message id. For example:
4719 exim -q 0t5C6f-0000c8-00
4721 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4722 second message id is given, messages whose ids are lexically greater than it
4723 are also skipped. If the same id is given twice, for example,
4725 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4727 just one delivery process is started, for that message. This differs from
4728 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4729 that it counts as a delivery from a queue run. Note that the selection
4730 mechanism does not affect the order in which the messages are scanned. There
4731 are also other ways of selecting specific sets of messages for delivery in a
4732 queue run &-- see &%-R%& and &%-S%&.
4734 .vitem &%-q%&<&'qflags'&><&'time'&>
4735 .cindex "queue runner" "starting periodically"
4736 .cindex "periodic queue running"
4737 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4738 starting a queue runner process at intervals specified by the given time value
4739 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4740 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4741 single daemon process handles both functions. A common way of starting up a
4742 combined daemon at system boot time is to use a command such as
4744 /usr/exim/bin/exim -bd -q30m
4746 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4747 process every 30 minutes.
4749 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4750 pid file is written unless one is explicitly requested by the &%-oP%& option.
4752 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4754 This option is synonymous with &%-R%&. It is provided for Sendmail
4757 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4759 This option is synonymous with &%-S%&.
4761 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4763 .cindex "queue runner" "for specific recipients"
4764 .cindex "delivery" "to given domain"
4765 .cindex "domain" "delivery to"
4766 The <&'rsflags'&> may be empty, in which case the white space before the string
4767 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4768 which are the possible values for <&'rsflags'&>. White space is required if
4769 <&'rsflags'&> is not empty.
4771 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4772 perform a single queue run, except that, when scanning the messages on the
4773 queue, Exim processes only those that have at least one undelivered recipient
4774 address containing the given string, which is checked in a case-independent
4775 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4776 regular expression; otherwise it is a literal string.
4778 If you want to do periodic queue runs for messages with specific recipients,
4779 you can combine &%-R%& with &%-q%& and a time value. For example:
4781 exim -q25m -R @special.domain.example
4783 This example does a queue run for messages with recipients in the given domain
4784 every 25 minutes. Any additional flags that are specified with &%-q%& are
4785 applied to each queue run.
4787 Once a message is selected for delivery by this mechanism, all its addresses
4788 are processed. For the first selected message, Exim overrides any retry
4789 information and forces a delivery attempt for each undelivered address. This
4790 means that if delivery of any address in the first message is successful, any
4791 existing retry information is deleted, and so delivery attempts for that
4792 address in subsequently selected messages (which are processed without forcing)
4793 will run. However, if delivery of any address does not succeed, the retry
4794 information is updated, and in subsequently selected messages, the failing
4795 address will be skipped.
4797 .cindex "frozen messages" "forcing delivery"
4798 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4799 all selected messages, not just the first; frozen messages are included when
4802 The &%-R%& option makes it straightforward to initiate delivery of all messages
4803 to a given domain after a host has been down for some time. When the SMTP
4804 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4805 effect is to run Exim with the &%-R%& option, but it can be configured to run
4806 an arbitrary command instead.
4810 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4812 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4814 .cindex "delivery" "from given sender"
4815 .cindex "queue runner" "for specific senders"
4816 This option acts like &%-R%& except that it checks the string against each
4817 message's sender instead of against the recipients. If &%-R%& is also set, both
4818 conditions must be met for a message to be selected. If either of the options
4819 has &'f'& or &'ff'& in its flags, the associated action is taken.
4821 .vitem &%-Tqt%&&~<&'times'&>
4823 This is an option that is exclusively for use by the Exim testing suite. It is not
4824 recognized when Exim is run normally. It allows for the setting up of explicit
4825 &"queue times"& so that various warning/retry features can be tested.
4829 .cindex "recipient" "extracting from header lines"
4833 When Exim is receiving a locally-generated, non-SMTP message on its standard
4834 input, the &%-t%& option causes the recipients of the message to be obtained
4835 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4836 from the command arguments. The addresses are extracted before any rewriting
4837 takes place and the &'Bcc:'& header line, if present, is then removed.
4839 .cindex "Sendmail compatibility" "&%-t%& option"
4840 If the command has any arguments, they specify addresses to which the message
4841 is &'not'& to be delivered. That is, the argument addresses are removed from
4842 the recipients list obtained from the headers. This is compatible with Smail 3
4843 and in accordance with the documented behaviour of several versions of
4844 Sendmail, as described in man pages on a number of operating systems (e.g.
4845 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4846 argument addresses to those obtained from the headers, and the O'Reilly
4847 Sendmail book documents it that way. Exim can be made to add argument addresses
4848 instead of subtracting them by setting the option
4849 &%extract_addresses_remove_arguments%& false.
4851 .cindex "&%Resent-%& header lines" "with &%-t%&"
4852 If there are any &%Resent-%& header lines in the message, Exim extracts
4853 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4854 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4855 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4856 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4858 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4859 message is resent several times). The RFC also specifies that they should be
4860 added at the front of the message, and separated by &'Received:'& lines. It is
4861 not at all clear how &%-t%& should operate in the present of multiple sets,
4862 nor indeed exactly what constitutes a &"set"&.
4863 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4864 are often added at the end of the header, and if a message is resent more than
4865 once, it is common for the original set of &%Resent-%& headers to be renamed as
4866 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4870 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4871 compatibility with Sendmail.
4873 .vitem &%-tls-on-connect%&
4874 .oindex "&%-tls-on-connect%&"
4875 .cindex "TLS" "use without STARTTLS"
4876 .cindex "TLS" "automatic start"
4877 This option is available when Exim is compiled with TLS support. It forces all
4878 incoming SMTP connections to behave as if the incoming port is listed in the
4879 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4880 &<<CHAPTLS>>& for further details.
4885 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4886 Sendmail uses this option for &"initial message submission"&, and its
4887 documentation states that in future releases, it may complain about
4888 syntactically invalid messages rather than fixing them when this flag is not
4889 set. Exim ignores this option.
4893 This option causes Exim to write information to the standard error stream,
4894 describing what it is doing. In particular, it shows the log lines for
4895 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4896 dialogue is shown. Some of the log lines shown may not actually be written to
4897 the log if the setting of &%log_selector%& discards them. Any relevant
4898 selectors are shown with each log line. If none are shown, the logging is
4903 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4904 National Language Support extended characters in the body of the mail item"&).
4905 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4908 .vitem &%-X%&&~<&'logfile'&>
4910 This option is interpreted by Sendmail to cause debug information to be sent
4911 to the named file. It is ignored by Exim.
4913 .vitem &%-z%&&~<&'log-line'&>
4915 This option writes its argument to Exim's logfile.
4916 Use is restricted to administrators; the intent is for operational notes.
4917 Quotes should be used to maintain a multi-word item as a single argument,
4925 . ////////////////////////////////////////////////////////////////////////////
4926 . Insert a stylized DocBook comment here, to identify the end of the command
4927 . line options. This is for the benefit of the Perl script that automatically
4928 . creates a man page for the options.
4929 . ////////////////////////////////////////////////////////////////////////////
4932 <!-- === End of command line options === -->
4939 . ////////////////////////////////////////////////////////////////////////////
4940 . ////////////////////////////////////////////////////////////////////////////
4943 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4944 "The runtime configuration file"
4946 .cindex "runtime configuration"
4947 .cindex "configuration file" "general description"
4948 .cindex "CONFIGURE_FILE"
4949 .cindex "configuration file" "errors in"
4950 .cindex "error" "in configuration file"
4951 .cindex "return code" "for bad configuration"
4952 Exim uses a single runtime configuration file that is read whenever an Exim
4953 binary is executed. Note that in normal operation, this happens frequently,
4954 because Exim is designed to operate in a distributed manner, without central
4957 If a syntax error is detected while reading the configuration file, Exim
4958 writes a message on the standard error, and exits with a non-zero return code.
4959 The message is also written to the panic log. &*Note*&: Only simple syntax
4960 errors can be detected at this time. The values of any expanded options are
4961 not checked until the expansion happens, even when the expansion does not
4962 actually alter the string.
4964 The name of the configuration file is compiled into the binary for security
4965 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4966 most configurations, this specifies a single file. However, it is permitted to
4967 give a colon-separated list of filenames, in which case Exim uses the first
4968 existing file in the list.
4971 .cindex "EXIM_GROUP"
4972 .cindex "CONFIGURE_OWNER"
4973 .cindex "CONFIGURE_GROUP"
4974 .cindex "configuration file" "ownership"
4975 .cindex "ownership" "configuration file"
4976 The runtime configuration file must be owned by root or by the user that is
4977 specified at compile time by the CONFIGURE_OWNER option (if set). The
4978 configuration file must not be world-writeable, or group-writeable unless its
4979 group is the root group or the one specified at compile time by the
4980 CONFIGURE_GROUP option.
4982 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4983 to root, anybody who is able to edit the runtime configuration file has an
4984 easy way to run commands as root. If you specify a user or group in the
4985 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4986 who are members of that group will trivially be able to obtain root privileges.
4988 Up to Exim version 4.72, the runtime configuration file was also permitted to
4989 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4990 since it offered a simple privilege escalation for any attacker who managed to
4991 compromise the Exim user account.
4993 A default configuration file, which will work correctly in simple situations,
4994 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4995 defines just one filename, the installation process copies the default
4996 configuration to a new file of that name if it did not previously exist. If
4997 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4998 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
5003 .section "Using a different configuration file" "SECID40"
5004 .cindex "configuration file" "alternate"
5005 A one-off alternate configuration can be specified by the &%-C%& command line
5006 option, which may specify a single file or a list of files. However, when
5007 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
5008 unless the argument for &%-C%& is identical to the built-in value from
5009 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
5010 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
5011 is useful mainly for checking the syntax of configuration files before
5012 installing them. No owner or group checks are done on a configuration file
5013 specified by &%-C%&, if root privilege has been dropped.
5015 Even the Exim user is not trusted to specify an arbitrary configuration file
5016 with the &%-C%& option to be used with root privileges, unless that file is
5017 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
5018 testing a configuration using &%-C%& right through message reception and
5019 delivery, even if the caller is root. The reception works, but by that time,
5020 Exim is running as the Exim user, so when it re-execs to regain privilege for
5021 the delivery, the use of &%-C%& causes privilege to be lost. However, root
5022 can test reception and delivery using two separate commands (one to put a
5023 message in the queue, using &%-odq%&, and another to do the delivery, using
5026 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
5027 prefix string with which any file named in a &%-C%& command line option must
5028 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
5029 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
5030 filename can be used with &%-C%&.
5032 One-off changes to a configuration can be specified by the &%-D%& command line
5033 option, which defines and overrides values for macros used inside the
5034 configuration file. However, like &%-C%&, the use of this option by a
5035 non-privileged user causes Exim to discard its root privilege.
5036 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
5037 completely disabled, and its use causes an immediate error exit.
5039 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
5040 to declare certain macro names trusted, such that root privilege will not
5041 necessarily be discarded.
5042 WHITELIST_D_MACROS defines a colon-separated list of macros which are
5043 considered safe and, if &%-D%& only supplies macros from this list, and the
5044 values are acceptable, then Exim will not give up root privilege if the caller
5045 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5046 transition mechanism and is expected to be removed in the future. Acceptable
5047 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5049 Some sites may wish to use the same Exim binary on different machines that
5050 share a file system, but to use different configuration files on each machine.
5051 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5052 looks for a file whose name is the configuration filename followed by a dot
5053 and the machine's node name, as obtained from the &[uname()]& function. If this
5054 file does not exist, the standard name is tried. This processing occurs for
5055 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5057 In some esoteric situations different versions of Exim may be run under
5058 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5059 help with this. See the comments in &_src/EDITME_& for details.
5063 .section "Configuration file format" "SECTconffilfor"
5064 .cindex "configuration file" "format of"
5065 .cindex "format" "configuration file"
5066 Exim's configuration file is divided into a number of different parts. General
5067 option settings must always appear at the start of the file. The other parts
5068 are all optional, and may appear in any order. Each part other than the first
5069 is introduced by the word &"begin"& followed by at least one literal
5070 space, and the name of the part. The optional parts are:
5073 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5076 .cindex "AUTH" "configuration"
5077 &'authenticators'&: Configuration settings for the authenticator drivers. These
5078 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5080 &'routers'&: Configuration settings for the router drivers. Routers process
5081 addresses and determine how the message is to be delivered (see chapters
5082 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5084 &'transports'&: Configuration settings for the transport drivers. Transports
5085 define mechanisms for copying messages to destinations (see chapters
5086 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5088 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5089 If there is no retry section, or if it is empty (that is, no retry rules are
5090 defined), Exim will not retry deliveries. In this situation, temporary errors
5091 are treated the same as permanent errors. Retry rules are discussed in chapter
5094 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5095 when new addresses are generated during delivery. Rewriting is discussed in
5096 chapter &<<CHAPrewrite>>&.
5098 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5099 want to use this feature, you must set
5101 LOCAL_SCAN_HAS_OPTIONS=yes
5103 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5104 facility are given in chapter &<<CHAPlocalscan>>&.
5107 .cindex "configuration file" "leading white space in"
5108 .cindex "configuration file" "trailing white space in"
5109 .cindex "white space" "in configuration file"
5110 Leading and trailing white space in configuration lines is always ignored.
5112 Blank lines in the file, and lines starting with a # character (ignoring
5113 leading white space) are treated as comments and are ignored. &*Note*&: A
5114 # character other than at the beginning of a line is not treated specially,
5115 and does not introduce a comment.
5117 Any non-comment line can be continued by ending it with a backslash. Note that
5118 the general rule for white space means that trailing white space after the
5119 backslash and leading white space at the start of continuation
5120 lines is ignored. Comment lines beginning with # (but not empty lines) may
5121 appear in the middle of a sequence of continuation lines.
5123 A convenient way to create a configuration file is to start from the
5124 default, which is supplied in &_src/configure.default_&, and add, delete, or
5125 change settings as required.
5127 The ACLs, retry rules, and rewriting rules have their own syntax which is
5128 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5129 respectively. The other parts of the configuration file have some syntactic
5130 items in common, and these are described below, from section &<<SECTcos>>&
5131 onwards. Before that, the inclusion, macro, and conditional facilities are
5136 .section "File inclusions in the configuration file" "SECID41"
5137 .cindex "inclusions in configuration file"
5138 .cindex "configuration file" "including other files"
5139 .cindex "&`.include`& in configuration file"
5140 .cindex "&`.include_if_exists`& in configuration file"
5141 You can include other files inside Exim's runtime configuration file by
5144 &`.include`& <&'filename'&>
5145 &`.include_if_exists`& <&'filename'&>
5147 on a line by itself. Double quotes round the filename are optional. If you use
5148 the first form, a configuration error occurs if the file does not exist; the
5149 second form does nothing for non-existent files.
5150 The first form allows a relative name. It is resolved relative to
5151 the directory of the including file. For the second form an absolute filename
5154 Includes may be nested to any depth, but remember that Exim reads its
5155 configuration file often, so it is a good idea to keep them to a minimum.
5156 If you change the contents of an included file, you must HUP the daemon,
5157 because an included file is read only when the configuration itself is read.
5159 The processing of inclusions happens early, at a physical line level, so, like
5160 comment lines, an inclusion can be used in the middle of an option setting,
5163 hosts_lookup = a.b.c \
5166 Include processing happens after macro processing (see below). Its effect is to
5167 process the lines of the included file as if they occurred inline where the
5172 .section "Macros in the configuration file" "SECTmacrodefs"
5173 .cindex "macro" "description of"
5174 .cindex "configuration file" "macros"
5175 If a line in the main part of the configuration (that is, before the first
5176 &"begin"& line) begins with an upper case letter, it is taken as a macro
5177 definition, and must be of the form
5179 <&'name'&> = <&'rest of line'&>
5181 The name must consist of letters, digits, and underscores, and need not all be
5182 in upper case, though that is recommended. The rest of the line, including any
5183 continuations, is the replacement text, and has leading and trailing white
5184 space removed. Quotes are not removed. The replacement text can never end with
5185 a backslash character, but this doesn't seem to be a serious limitation.
5187 Macros may also be defined between router, transport, authenticator, or ACL
5188 definitions. They may not, however, be defined within an individual driver or
5189 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5191 .section "Macro substitution" "SECID42"
5192 Once a macro is defined, all subsequent lines in the file (and any included
5193 files) are scanned for the macro name; if there are several macros, the line is
5194 scanned for each, in turn, in the order in which the macros are defined. The
5195 replacement text is not re-scanned for the current macro, though it is scanned
5196 for subsequently defined macros. For this reason, a macro name may not contain
5197 the name of a previously defined macro as a substring. You could, for example,
5200 &`ABCD_XYZ = `&<&'something'&>
5201 &`ABCD = `&<&'something else'&>
5203 but putting the definitions in the opposite order would provoke a configuration
5204 error. Macro expansion is applied to individual physical lines from the file,
5205 before checking for line continuation or file inclusion (see above). If a line
5206 consists solely of a macro name, and the expansion of the macro is empty, the
5207 line is ignored. A macro at the start of a line may turn the line into a
5208 comment line or a &`.include`& line.
5211 .section "Redefining macros" "SECID43"
5212 Once defined, the value of a macro can be redefined later in the configuration
5213 (or in an included file). Redefinition is specified by using &'=='& instead of
5218 MAC == updated value
5220 Redefinition does not alter the order in which the macros are applied to the
5221 subsequent lines of the configuration file. It is still the same order in which
5222 the macros were originally defined. All that changes is the macro's value.
5223 Redefinition makes it possible to accumulate values. For example:
5227 MAC == MAC and something added
5229 This can be helpful in situations where the configuration file is built
5230 from a number of other files.
5232 .section "Overriding macro values" "SECID44"
5233 The values set for macros in the configuration file can be overridden by the
5234 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5235 used, unless called by root or the Exim user. A definition on the command line
5236 using the &%-D%& option causes all definitions and redefinitions within the
5241 .section "Example of macro usage" "SECID45"
5242 As an example of macro usage, consider a configuration where aliases are looked
5243 up in a MySQL database. It helps to keep the file less cluttered if long
5244 strings such as SQL statements are defined separately as macros, for example:
5246 ALIAS_QUERY = select mailbox from user where \
5247 login='${quote_mysql:$local_part}';
5249 This can then be used in a &(redirect)& router setting like this:
5251 data = ${lookup mysql{ALIAS_QUERY}}
5253 In earlier versions of Exim macros were sometimes used for domain, host, or
5254 address lists. In Exim 4 these are handled better by named lists &-- see
5255 section &<<SECTnamedlists>>&.
5258 .section "Builtin macros" "SECTbuiltinmacros"
5259 Exim defines some macros depending on facilities available, which may
5260 differ due to build-time definitions and from one release to another.
5261 All of these macros start with an underscore.
5262 They can be used to conditionally include parts of a configuration
5265 The following classes of macros are defined:
5267 &` _HAVE_* `& build-time defines
5268 &` _DRIVER_ROUTER_* `& router drivers
5269 &` _DRIVER_TRANSPORT_* `& transport drivers
5270 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5271 &` _LOG_* `& log_selector values
5272 &` _OPT_MAIN_* `& main config options
5273 &` _OPT_ROUTERS_* `& generic router options
5274 &` _OPT_TRANSPORTS_* `& generic transport options
5275 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5276 &` _OPT_ROUTER_*_* `& private router options
5277 &` _OPT_TRANSPORT_*_* `& private transport options
5278 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5281 Use an &"exim -bP macros"& command to get the list of macros.
5284 .section "Conditional skips in the configuration file" "SECID46"
5285 .cindex "configuration file" "conditional skips"
5286 .cindex "&`.ifdef`&"
5287 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5288 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5289 portions of the configuration file. The processing happens whenever the file is
5290 read (that is, when an Exim binary starts to run).
5292 The implementation is very simple. Instances of the first four directives must
5293 be followed by text that includes the names of one or macros. The condition
5294 that is tested is whether or not any macro substitution has taken place in the
5298 message_size_limit = 50M
5300 message_size_limit = 100M
5303 sets a message size limit of 50M if the macro &`AAA`& is defined
5304 (or &`A`& or &`AA`&), and 100M
5305 otherwise. If there is more than one macro named on the line, the condition
5306 is true if any of them are defined. That is, it is an &"or"& condition. To
5307 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5309 Although you can use a macro expansion to generate one of these directives,
5310 it is not very useful, because the condition &"there was a macro substitution
5311 in this line"& will always be true.
5313 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5314 to clarify complicated nestings.
5318 .section "Common option syntax" "SECTcos"
5319 .cindex "common option syntax"
5320 .cindex "syntax of common options"
5321 .cindex "configuration file" "common option syntax"
5322 For the main set of options, driver options, and &[local_scan()]& options,
5323 each setting is on a line by itself, and starts with a name consisting of
5324 lower-case letters and underscores. Many options require a data value, and in
5325 these cases the name must be followed by an equals sign (with optional white
5326 space) and then the value. For example:
5328 qualify_domain = mydomain.example.com
5330 .cindex "hiding configuration option values"
5331 .cindex "configuration options" "hiding value of"
5332 .cindex "options" "hiding value of"
5333 Some option settings may contain sensitive data, for example, passwords for
5334 accessing databases. To stop non-admin users from using the &%-bP%& command
5335 line option to read these values, you can precede the option settings with the
5336 word &"hide"&. For example:
5338 hide mysql_servers = localhost/users/admin/secret-password
5340 For non-admin users, such options are displayed like this:
5342 mysql_servers = <value not displayable>
5344 If &"hide"& is used on a driver option, it hides the value of that option on
5345 all instances of the same driver.
5347 The following sections describe the syntax used for the different data types
5348 that are found in option settings.
5351 .section "Boolean options" "SECID47"
5352 .cindex "format" "boolean"
5353 .cindex "boolean configuration values"
5354 .oindex "&%no_%&&'xxx'&"
5355 .oindex "&%not_%&&'xxx'&"
5356 Options whose type is given as boolean are on/off switches. There are two
5357 different ways of specifying such options: with and without a data value. If
5358 the option name is specified on its own without data, the switch is turned on;
5359 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5360 boolean options may be followed by an equals sign and one of the words
5361 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5362 the following two settings have exactly the same effect:
5367 The following two lines also have the same (opposite) effect:
5372 You can use whichever syntax you prefer.
5377 .section "Integer values" "SECID48"
5378 .cindex "integer configuration values"
5379 .cindex "format" "integer"
5380 If an option's type is given as &"integer"&, the value can be given in decimal,
5381 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5382 number is assumed. Otherwise, it is treated as an octal number unless it starts
5383 with the characters &"0x"&, in which case the remainder is interpreted as a
5386 If an integer value is followed by the letter K, it is multiplied by 1024; if
5387 it is followed by the letter M, it is multiplied by 1024x1024;
5388 if by the letter G, 1024x1024x1024.
5390 of integer option settings are output, values which are an exact multiple of
5391 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5392 and M. The printing style is independent of the actual input format that was
5396 .section "Octal integer values" "SECID49"
5397 .cindex "integer format"
5398 .cindex "format" "octal integer"
5399 If an option's type is given as &"octal integer"&, its value is always
5400 interpreted as an octal number, whether or not it starts with the digit zero.
5401 Such options are always output in octal.
5404 .section "Fixed point numbers" "SECID50"
5405 .cindex "fixed point configuration values"
5406 .cindex "format" "fixed point"
5407 If an option's type is given as &"fixed-point"&, its value must be a decimal
5408 integer, optionally followed by a decimal point and up to three further digits.
5412 .section "Time intervals" "SECTtimeformat"
5413 .cindex "time interval" "specifying in configuration"
5414 .cindex "format" "time interval"
5415 A time interval is specified as a sequence of numbers, each followed by one of
5416 the following letters, with no intervening white space:
5426 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5427 intervals are output in the same format. Exim does not restrict the values; it
5428 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5432 .section "String values" "SECTstrings"
5433 .cindex "string" "format of configuration values"
5434 .cindex "format" "string"
5435 If an option's type is specified as &"string"&, the value can be specified with
5436 or without double-quotes. If it does not start with a double-quote, the value
5437 consists of the remainder of the line plus any continuation lines, starting at
5438 the first character after any leading white space, with trailing white space
5439 removed, and with no interpretation of the characters in the string. Because
5440 Exim removes comment lines (those beginning with #) at an early stage, they can
5441 appear in the middle of a multi-line string. The following two settings are
5442 therefore equivalent:
5444 trusted_users = uucp:mail
5445 trusted_users = uucp:\
5446 # This comment line is ignored
5449 .cindex "string" "quoted"
5450 .cindex "escape characters in quoted strings"
5451 If a string does start with a double-quote, it must end with a closing
5452 double-quote, and any backslash characters other than those used for line
5453 continuation are interpreted as escape characters, as follows:
5456 .irow &`\\`& "single backslash"
5457 .irow &`\n`& "newline"
5458 .irow &`\r`& "carriage return"
5460 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5461 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5465 If a backslash is followed by some other character, including a double-quote
5466 character, that character replaces the pair.
5468 Quoting is necessary only if you want to make use of the backslash escapes to
5469 insert special characters, or if you need to specify a value with leading or
5470 trailing spaces. These cases are rare, so quoting is almost never needed in
5471 current versions of Exim. In versions of Exim before 3.14, quoting was required
5472 in order to continue lines, so you may come across older configuration files
5473 and examples that apparently quote unnecessarily.
5476 .section "Expanded strings" "SECID51"
5477 .cindex "expansion" "definition of"
5478 Some strings in the configuration file are subjected to &'string expansion'&,
5479 by which means various parts of the string may be changed according to the
5480 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5481 is as just described; in particular, the handling of backslashes in quoted
5482 strings is done as part of the input process, before expansion takes place.
5483 However, backslash is also an escape character for the expander, so any
5484 backslashes that are required for that reason must be doubled if they are
5485 within a quoted configuration string.
5488 .section "User and group names" "SECID52"
5489 .cindex "user name" "format of"
5490 .cindex "format" "user name"
5491 .cindex "groups" "name format"
5492 .cindex "format" "group name"
5493 User and group names are specified as strings, using the syntax described
5494 above, but the strings are interpreted specially. A user or group name must
5495 either consist entirely of digits, or be a name that can be looked up using the
5496 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5499 .section "List construction" "SECTlistconstruct"
5500 .cindex "list" "syntax of in configuration"
5501 .cindex "format" "list item in configuration"
5502 .cindex "string" "list, definition of"
5503 The data for some configuration options is a list of items, with colon as the
5504 default separator. Many of these options are shown with type &"string list"& in
5505 the descriptions later in this document. Others are listed as &"domain list"&,
5506 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5507 are all the same; however, those other than &"string list"& are subject to
5508 particular kinds of interpretation, as described in chapter
5509 &<<CHAPdomhosaddlists>>&.
5511 In all these cases, the entire list is treated as a single string as far as the
5512 input syntax is concerned. The &%trusted_users%& setting in section
5513 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5514 in a list, it must be entered as two colons. Leading and trailing white space
5515 on each item in a list is ignored. This makes it possible to include items that
5516 start with a colon, and in particular, certain forms of IPv6 address. For
5519 local_interfaces = 127.0.0.1 : ::::1
5521 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5523 &*Note*&: Although leading and trailing white space is ignored in individual
5524 list items, it is not ignored when parsing the list. The spaces around the first
5525 colon in the example above are necessary. If they were not there, the list would
5526 be interpreted as the two items 127.0.0.1:: and 1.
5528 .section "Changing list separators" "SECTlistsepchange"
5529 .cindex "list separator" "changing"
5530 .cindex "IPv6" "addresses in lists"
5531 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5532 introduced to allow the separator character to be changed. If a list begins
5533 with a left angle bracket, followed by any punctuation character, that
5534 character is used instead of colon as the list separator. For example, the list
5535 above can be rewritten to use a semicolon separator like this:
5537 local_interfaces = <; 127.0.0.1 ; ::1
5539 This facility applies to all lists, with the exception of the list in
5540 &%log_file_path%&. It is recommended that the use of non-colon separators be
5541 confined to circumstances where they really are needed.
5543 .cindex "list separator" "newline as"
5544 .cindex "newline" "as list separator"
5545 It is also possible to use newline and other control characters (those with
5546 code values less than 32, plus DEL) as separators in lists. Such separators
5547 must be provided literally at the time the list is processed. For options that
5548 are string-expanded, you can write the separator using a normal escape
5549 sequence. This will be processed by the expander before the string is
5550 interpreted as a list. For example, if a newline-separated list of domains is
5551 generated by a lookup, you can process it directly by a line such as this:
5553 domains = <\n ${lookup mysql{.....}}
5555 This avoids having to change the list separator in such data. You are unlikely
5556 to want to use a control character as a separator in an option that is not
5557 expanded, because the value is literal text. However, it can be done by giving
5558 the value in quotes. For example:
5560 local_interfaces = "<\n 127.0.0.1 \n ::1"
5562 Unlike printing character separators, which can be included in list items by
5563 doubling, it is not possible to include a control character as data when it is
5564 set as the separator. Two such characters in succession are interpreted as
5565 enclosing an empty list item.
5569 .section "Empty items in lists" "SECTempitelis"
5570 .cindex "list" "empty item in"
5571 An empty item at the end of a list is always ignored. In other words, trailing
5572 separator characters are ignored. Thus, the list in
5574 senders = user@domain :
5576 contains only a single item. If you want to include an empty string as one item
5577 in a list, it must not be the last item. For example, this list contains three
5578 items, the second of which is empty:
5580 senders = user1@domain : : user2@domain
5582 &*Note*&: There must be white space between the two colons, as otherwise they
5583 are interpreted as representing a single colon data character (and the list
5584 would then contain just one item). If you want to specify a list that contains
5585 just one, empty item, you can do it as in this example:
5589 In this case, the first item is empty, and the second is discarded because it
5590 is at the end of the list.
5595 .section "Format of driver configurations" "SECTfordricon"
5596 .cindex "drivers" "configuration format"
5597 There are separate parts in the configuration for defining routers, transports,
5598 and authenticators. In each part, you are defining a number of driver
5599 instances, each with its own set of options. Each driver instance is defined by
5600 a sequence of lines like this:
5602 <&'instance name'&>:
5607 In the following example, the instance name is &(localuser)&, and it is
5608 followed by three options settings:
5613 transport = local_delivery
5615 For each driver instance, you specify which Exim code module it uses &-- by the
5616 setting of the &%driver%& option &-- and (optionally) some configuration
5617 settings. For example, in the case of transports, if you want a transport to
5618 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5619 a local file you would use the &(appendfile)& driver. Each of the drivers is
5620 described in detail in its own separate chapter later in this manual.
5622 You can have several routers, transports, or authenticators that are based on
5623 the same underlying driver (each must have a different instance name).
5625 The order in which routers are defined is important, because addresses are
5626 passed to individual routers one by one, in order. The order in which
5627 transports are defined does not matter at all. The order in which
5628 authenticators are defined is used only when Exim, as a client, is searching
5629 them to find one that matches an authentication mechanism offered by the
5632 .cindex "generic options"
5633 .cindex "options" "generic &-- definition of"
5634 Within a driver instance definition, there are two kinds of option: &'generic'&
5635 and &'private'&. The generic options are those that apply to all drivers of the
5636 same type (that is, all routers, all transports or all authenticators). The
5637 &%driver%& option is a generic option that must appear in every definition.
5638 .cindex "private options"
5639 The private options are special for each driver, and none need appear, because
5640 they all have default values.
5642 The options may appear in any order, except that the &%driver%& option must
5643 precede any private options, since these depend on the particular driver. For
5644 this reason, it is recommended that &%driver%& always be the first option.
5646 Driver instance names, which are used for reference in log entries and
5647 elsewhere, can be any sequence of letters, digits, and underscores (starting
5648 with a letter) and must be unique among drivers of the same type. A router and
5649 a transport (for example) can each have the same name, but no two router
5650 instances can have the same name. The name of a driver instance should not be
5651 confused with the name of the underlying driver module. For example, the
5652 configuration lines:
5657 create an instance of the &(smtp)& transport driver whose name is
5658 &(remote_smtp)&. The same driver code can be used more than once, with
5659 different instance names and different option settings each time. A second
5660 instance of the &(smtp)& transport, with different options, might be defined
5666 command_timeout = 10s
5668 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5669 these transport instances from routers, and these names would appear in log
5672 Comment lines may be present in the middle of driver specifications. The full
5673 list of option settings for any particular driver instance, including all the
5674 defaulted values, can be extracted by making use of the &%-bP%& command line
5682 . ////////////////////////////////////////////////////////////////////////////
5683 . ////////////////////////////////////////////////////////////////////////////
5685 .chapter "The default configuration file" "CHAPdefconfil"
5686 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5687 .cindex "default" "configuration file &""walk through""&"
5688 The default configuration file supplied with Exim as &_src/configure.default_&
5689 is sufficient for a host with simple mail requirements. As an introduction to
5690 the way Exim is configured, this chapter &"walks through"& the default
5691 configuration, giving brief explanations of the settings. Detailed descriptions
5692 of the options are given in subsequent chapters. The default configuration file
5693 itself contains extensive comments about ways you might want to modify the
5694 initial settings. However, note that there are many options that are not
5695 mentioned at all in the default configuration.
5699 .section "Macros" "SECTdefconfmacros"
5700 All macros should be defined before any options.
5702 One macro is specified, but commented out, in the default configuration:
5704 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5706 If all off-site mail is expected to be delivered to a "smarthost", then set the
5707 hostname here and uncomment the macro. This will affect which router is used
5708 later on. If this is left commented out, then Exim will perform direct-to-MX
5709 deliveries using a &(dnslookup)& router.
5711 In addition to macros defined here, Exim includes a number of built-in macros
5712 to enable configuration to be guarded by a binary built with support for a
5713 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5716 .section "Main configuration settings" "SECTdefconfmain"
5717 The main (global) configuration option settings section must always come first
5718 in the file, after the macros.
5719 The first thing you'll see in the file, after some initial comments, is the line
5721 # primary_hostname =
5723 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5724 to know the official, fully qualified name of your host, and this is where you
5725 can specify it. However, in most cases you do not need to set this option. When
5726 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5728 The first three non-comment configuration lines are as follows:
5730 domainlist local_domains = @
5731 domainlist relay_to_domains =
5732 hostlist relay_from_hosts = 127.0.0.1
5734 These are not, in fact, option settings. They are definitions of two named
5735 domain lists and one named host list. Exim allows you to give names to lists of
5736 domains, hosts, and email addresses, in order to make it easier to manage the
5737 configuration file (see section &<<SECTnamedlists>>&).
5739 The first line defines a domain list called &'local_domains'&; this is used
5740 later in the configuration to identify domains that are to be delivered
5743 .cindex "@ in a domain list"
5744 There is just one item in this list, the string &"@"&. This is a special form
5745 of entry which means &"the name of the local host"&. Thus, if the local host is
5746 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5747 be delivered locally. Because the local host's name is referenced indirectly,
5748 the same configuration file can be used on different hosts.
5750 The second line defines a domain list called &'relay_to_domains'&, but the
5751 list itself is empty. Later in the configuration we will come to the part that
5752 controls mail relaying through the local host; it allows relaying to any
5753 domains in this list. By default, therefore, no relaying on the basis of a mail
5754 domain is permitted.
5756 The third line defines a host list called &'relay_from_hosts'&. This list is
5757 used later in the configuration to permit relaying from any host or IP address
5758 that matches the list. The default contains just the IP address of the IPv4
5759 loopback interface, which means that processes on the local host are able to
5760 submit mail for relaying by sending it over TCP/IP to that interface. No other
5761 hosts are permitted to submit messages for relaying.
5763 Just to be sure there's no misunderstanding: at this point in the configuration
5764 we aren't actually setting up any controls. We are just defining some domains
5765 and hosts that will be used in the controls that are specified later.
5767 The next two configuration lines are genuine option settings:
5769 acl_smtp_rcpt = acl_check_rcpt
5770 acl_smtp_data = acl_check_data
5772 These options specify &'Access Control Lists'& (ACLs) that are to be used
5773 during an incoming SMTP session for every recipient of a message (every RCPT
5774 command), and after the contents of the message have been received,
5775 respectively. The names of the lists are &'acl_check_rcpt'& and
5776 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5777 section of the configuration. The RCPT ACL controls which recipients are
5778 accepted for an incoming message &-- if a configuration does not provide an ACL
5779 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5780 contents of a message to be checked.
5782 Two commented-out option settings are next:
5784 # av_scanner = clamd:/tmp/clamd
5785 # spamd_address = 127.0.0.1 783
5787 These are example settings that can be used when Exim is compiled with the
5788 content-scanning extension. The first specifies the interface to the virus
5789 scanner, and the second specifies the interface to SpamAssassin. Further
5790 details are given in chapter &<<CHAPexiscan>>&.
5792 Three more commented-out option settings follow:
5794 # tls_advertise_hosts = *
5795 # tls_certificate = /etc/ssl/exim.crt
5796 # tls_privatekey = /etc/ssl/exim.pem
5798 These are example settings that can be used when Exim is compiled with
5799 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5800 first one specifies the list of clients that are allowed to use TLS when
5801 connecting to this server; in this case, the wildcard means all clients. The
5802 other options specify where Exim should find its TLS certificate and private
5803 key, which together prove the server's identity to any clients that connect.
5804 More details are given in chapter &<<CHAPTLS>>&.
5806 Another two commented-out option settings follow:
5808 # daemon_smtp_ports = 25 : 465 : 587
5809 # tls_on_connect_ports = 465
5811 .cindex "port" "465 and 587"
5812 .cindex "port" "for message submission"
5813 .cindex "message" "submission, ports for"
5814 .cindex "submissions protocol"
5815 .cindex "smtps protocol"
5816 .cindex "ssmtp protocol"
5817 .cindex "SMTP" "submissions protocol"
5818 .cindex "SMTP" "ssmtp protocol"
5819 .cindex "SMTP" "smtps protocol"
5820 These options provide better support for roaming users who wish to use this
5821 server for message submission. They are not much use unless you have turned on
5822 TLS (as described in the previous paragraph) and authentication (about which
5823 more in section &<<SECTdefconfauth>>&).
5824 Mail submission from mail clients (MUAs) should be separate from inbound mail
5825 to your domain (MX delivery) for various good reasons (eg, ability to impose
5826 much saner TLS protocol and ciphersuite requirements without unintended
5828 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5829 which uses STARTTLS, so this is the &"submission"& port.
5830 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5831 which should be used in preference to 587.
5832 You should also consider deploying SRV records to help clients find
5834 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5836 Two more commented-out options settings follow:
5839 # qualify_recipient =
5841 The first of these specifies a domain that Exim uses when it constructs a
5842 complete email address from a local login name. This is often needed when Exim
5843 receives a message from a local process. If you do not set &%qualify_domain%&,
5844 the value of &%primary_hostname%& is used. If you set both of these options,
5845 you can have different qualification domains for sender and recipient
5846 addresses. If you set only the first one, its value is used in both cases.
5848 .cindex "domain literal" "recognizing format"
5849 The following line must be uncommented if you want Exim to recognize
5850 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5851 (an IP address within square brackets) instead of a named domain.
5853 # allow_domain_literals
5855 The RFCs still require this form, but many people think that in the modern
5856 Internet it makes little sense to permit mail to be sent to specific hosts by
5857 quoting their IP addresses. This ancient format has been used by people who
5858 try to abuse hosts by using them for unwanted relaying. However, some
5859 people believe there are circumstances (for example, messages addressed to
5860 &'postmaster'&) where domain literals are still useful.
5862 The next configuration line is a kind of trigger guard:
5866 It specifies that no delivery must ever be run as the root user. The normal
5867 convention is to set up &'root'& as an alias for the system administrator. This
5868 setting is a guard against slips in the configuration.
5869 The list of users specified by &%never_users%& is not, however, the complete
5870 list; the build-time configuration in &_Local/Makefile_& has an option called
5871 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5872 contents of &%never_users%& are added to this list. By default
5873 FIXED_NEVER_USERS also specifies root.
5875 When a remote host connects to Exim in order to send mail, the only information
5876 Exim has about the host's identity is its IP address. The next configuration
5881 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5882 in order to get a host name. This improves the quality of the logging
5883 information, but if you feel it is too expensive, you can remove it entirely,
5884 or restrict the lookup to hosts on &"nearby"& networks.
5885 Note that it is not always possible to find a host name from an IP address,
5886 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5889 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5890 1413 (hence their names):
5893 rfc1413_query_timeout = 0s
5895 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5896 Few hosts offer RFC1413 service these days; calls have to be
5897 terminated by a timeout and this needlessly delays the startup
5898 of an incoming SMTP connection.
5899 If you have hosts for which you trust RFC1413 and need this
5900 information, you can change this.
5902 This line enables an efficiency SMTP option. It is negotiated by clients
5903 and not expected to cause problems but can be disabled if needed.
5908 When Exim receives messages over SMTP connections, it expects all addresses to
5909 be fully qualified with a domain, as required by the SMTP definition. However,
5910 if you are running a server to which simple clients submit messages, you may
5911 find that they send unqualified addresses. The two commented-out options:
5913 # sender_unqualified_hosts =
5914 # recipient_unqualified_hosts =
5916 show how you can specify hosts that are permitted to send unqualified sender
5917 and recipient addresses, respectively.
5919 The &%log_selector%& option is used to increase the detail of logging
5922 log_selector = +smtp_protocol_error +smtp_syntax_error \
5923 +tls_certificate_verified
5926 The &%percent_hack_domains%& option is also commented out:
5928 # percent_hack_domains =
5930 It provides a list of domains for which the &"percent hack"& is to operate.
5931 This is an almost obsolete form of explicit email routing. If you do not know
5932 anything about it, you can safely ignore this topic.
5934 The next two settings in the main part of the default configuration are
5935 concerned with messages that have been &"frozen"& on Exim's queue. When a
5936 message is frozen, Exim no longer continues to try to deliver it. Freezing
5937 occurs when a bounce message encounters a permanent failure because the sender
5938 address of the original message that caused the bounce is invalid, so the
5939 bounce cannot be delivered. This is probably the most common case, but there
5940 are also other conditions that cause freezing, and frozen messages are not
5941 always bounce messages.
5943 ignore_bounce_errors_after = 2d
5944 timeout_frozen_after = 7d
5946 The first of these options specifies that failing bounce messages are to be
5947 discarded after 2 days in the queue. The second specifies that any frozen
5948 message (whether a bounce message or not) is to be timed out (and discarded)
5949 after a week. In this configuration, the first setting ensures that no failing
5950 bounce message ever lasts a week.
5952 Exim queues it's messages in a spool directory. If you expect to have
5953 large queues, you may consider using this option. It splits the spool
5954 directory into subdirectories to avoid file system degradation from
5955 many files in a single directory, resulting in better performance.
5956 Manual manipulation of queued messages becomes more complex (though fortunately
5959 # split_spool_directory = true
5962 In an ideal world everybody follows the standards. For non-ASCII
5963 messages RFC 2047 is a standard, allowing a maximum line length of 76
5964 characters. Exim adheres that standard and won't process messages which
5965 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5966 In particular, the Exim maintainers have had multiple reports of
5967 problems from Russian administrators of issues until they disable this
5968 check, because of some popular, yet buggy, mail composition software.
5970 # check_rfc2047_length = false
5973 If you need to be strictly RFC compliant you may wish to disable the
5974 8BITMIME advertisement. Use this, if you exchange mails with systems
5975 that are not 8-bit clean.
5977 # accept_8bitmime = false
5980 Libraries you use may depend on specific environment settings. This
5981 imposes a security risk (e.g. PATH). There are two lists:
5982 &%keep_environment%& for the variables to import as they are, and
5983 &%add_environment%& for variables we want to set to a fixed value.
5984 Note that TZ is handled separately, by the &%timezone%& runtime
5985 option and by the TIMEZONE_DEFAULT buildtime option.
5987 # keep_environment = ^LDAP
5988 # add_environment = PATH=/usr/bin::/bin
5992 .section "ACL configuration" "SECID54"
5993 .cindex "default" "ACLs"
5994 .cindex "&ACL;" "default configuration"
5995 In the default configuration, the ACL section follows the main configuration.
5996 It starts with the line
6000 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
6001 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
6002 and &%acl_smtp_data%& above.
6004 .cindex "RCPT" "ACL for"
6005 The first ACL is used for every RCPT command in an incoming SMTP message. Each
6006 RCPT command specifies one of the message's recipients. The ACL statements
6007 are considered in order, until the recipient address is either accepted or
6008 rejected. The RCPT command is then accepted or rejected, according to the
6009 result of the ACL processing.
6013 This line, consisting of a name terminated by a colon, marks the start of the
6018 This ACL statement accepts the recipient if the sending host matches the list.
6019 But what does that strange list mean? It doesn't actually contain any host
6020 names or IP addresses. The presence of the colon puts an empty item in the
6021 list; Exim matches this only if the incoming message did not come from a remote
6022 host, because in that case, the remote hostname is empty. The colon is
6023 important. Without it, the list itself is empty, and can never match anything.
6025 What this statement is doing is to accept unconditionally all recipients in
6026 messages that are submitted by SMTP from local processes using the standard
6027 input and output (that is, not using TCP/IP). A number of MUAs operate in this
6030 deny domains = +local_domains
6031 local_parts = ^[.] : ^.*[@%!/|]
6032 message = Restricted characters in address
6034 deny domains = !+local_domains
6035 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
6036 message = Restricted characters in address
6038 These statements are concerned with local parts that contain any of the
6039 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
6040 Although these characters are entirely legal in local parts (in the case of
6041 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
6042 in Internet mail addresses.
6044 The first three have in the past been associated with explicitly routed
6045 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6046 option). Addresses containing these characters are regularly tried by spammers
6047 in an attempt to bypass relaying restrictions, and also by open relay testing
6048 programs. Unless you really need them it is safest to reject these characters
6049 at this early stage. This configuration is heavy-handed in rejecting these
6050 characters for all messages it accepts from remote hosts. This is a deliberate
6051 policy of being as safe as possible.
6053 The first rule above is stricter, and is applied to messages that are addressed
6054 to one of the local domains handled by this host. This is implemented by the
6055 first condition, which restricts it to domains that are listed in the
6056 &'local_domains'& domain list. The &"+"& character is used to indicate a
6057 reference to a named list. In this configuration, there is just one domain in
6058 &'local_domains'&, but in general there may be many.
6060 The second condition on the first statement uses two regular expressions to
6061 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6062 or &"|"&. If you have local accounts that include these characters, you will
6063 have to modify this rule.
6065 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6066 allows them because they have been encountered in practice. (Consider the
6067 common convention of local parts constructed as
6068 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6069 the author of Exim, who has no second initial.) However, a local part starting
6070 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6071 filename (for example, for a mailing list). This is also true for local parts
6072 that contain slashes. A pipe symbol can also be troublesome if the local part
6073 is incorporated unthinkingly into a shell command line.
6075 The second rule above applies to all other domains, and is less strict. This
6076 allows your own users to send outgoing messages to sites that use slashes
6077 and vertical bars in their local parts. It blocks local parts that begin
6078 with a dot, slash, or vertical bar, but allows these characters within the
6079 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6080 and &"!"& is blocked, as before. The motivation here is to prevent your users
6081 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6083 accept local_parts = postmaster
6084 domains = +local_domains
6086 This statement, which has two conditions, accepts an incoming address if the
6087 local part is &'postmaster'& and the domain is one of those listed in the
6088 &'local_domains'& domain list. The &"+"& character is used to indicate a
6089 reference to a named list. In this configuration, there is just one domain in
6090 &'local_domains'&, but in general there may be many.
6092 The presence of this statement means that mail to postmaster is never blocked
6093 by any of the subsequent tests. This can be helpful while sorting out problems
6094 in cases where the subsequent tests are incorrectly denying access.
6096 require verify = sender
6098 This statement requires the sender address to be verified before any subsequent
6099 ACL statement can be used. If verification fails, the incoming recipient
6100 address is refused. Verification consists of trying to route the address, to
6101 see if a bounce message could be delivered to it. In the case of remote
6102 addresses, basic verification checks only the domain, but &'callouts'& can be
6103 used for more verification if required. Section &<<SECTaddressverification>>&
6104 discusses the details of address verification.
6106 accept hosts = +relay_from_hosts
6107 control = submission
6109 This statement accepts the address if the message is coming from one of the
6110 hosts that are defined as being allowed to relay through this host. Recipient
6111 verification is omitted here, because in many cases the clients are dumb MUAs
6112 that do not cope well with SMTP error responses. For the same reason, the
6113 second line specifies &"submission mode"& for messages that are accepted. This
6114 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6115 messages that are deficient in some way, for example, because they lack a
6116 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6117 probably add recipient verification here, and disable submission mode.
6119 accept authenticated = *
6120 control = submission
6122 This statement accepts the address if the client host has authenticated itself.
6123 Submission mode is again specified, on the grounds that such messages are most
6124 likely to come from MUAs. The default configuration does not define any
6125 authenticators, though it does include some nearly complete commented-out
6126 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6127 fact authenticate until you complete the authenticator definitions.
6129 require message = relay not permitted
6130 domains = +local_domains : +relay_to_domains
6132 This statement rejects the address if its domain is neither a local domain nor
6133 one of the domains for which this host is a relay.
6135 require verify = recipient
6137 This statement requires the recipient address to be verified; if verification
6138 fails, the address is rejected.
6140 # deny dnslists = black.list.example
6141 # message = rejected because $sender_host_address \
6142 # is in a black list at $dnslist_domain\n\
6145 # warn dnslists = black.list.example
6146 # add_header = X-Warning: $sender_host_address is in \
6147 # a black list at $dnslist_domain
6148 # log_message = found in $dnslist_domain
6150 These commented-out lines are examples of how you could configure Exim to check
6151 sending hosts against a DNS black list. The first statement rejects messages
6152 from blacklisted hosts, whereas the second just inserts a warning header
6155 # require verify = csa
6157 This commented-out line is an example of how you could turn on client SMTP
6158 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6163 The final statement in the first ACL unconditionally accepts any recipient
6164 address that has successfully passed all the previous tests.
6168 This line marks the start of the second ACL, and names it. Most of the contents
6169 of this ACL are commented out:
6172 # message = This message contains a virus \
6175 These lines are examples of how to arrange for messages to be scanned for
6176 viruses when Exim has been compiled with the content-scanning extension, and a
6177 suitable virus scanner is installed. If the message is found to contain a
6178 virus, it is rejected with the given custom error message.
6180 # warn spam = nobody
6181 # message = X-Spam_score: $spam_score\n\
6182 # X-Spam_score_int: $spam_score_int\n\
6183 # X-Spam_bar: $spam_bar\n\
6184 # X-Spam_report: $spam_report
6186 These lines are an example of how to arrange for messages to be scanned by
6187 SpamAssassin when Exim has been compiled with the content-scanning extension,
6188 and SpamAssassin has been installed. The SpamAssassin check is run with
6189 &`nobody`& as its user parameter, and the results are added to the message as a
6190 series of extra header line. In this case, the message is not rejected,
6191 whatever the spam score.
6195 This final line in the DATA ACL accepts the message unconditionally.
6198 .section "Router configuration" "SECID55"
6199 .cindex "default" "routers"
6200 .cindex "routers" "default"
6201 The router configuration comes next in the default configuration, introduced
6206 Routers are the modules in Exim that make decisions about where to send
6207 messages. An address is passed to each router, in turn, until it is either
6208 accepted, or failed. This means that the order in which you define the routers
6209 matters. Each router is fully described in its own chapter later in this
6210 manual. Here we give only brief overviews.
6213 # driver = ipliteral
6214 # domains = !+local_domains
6215 # transport = remote_smtp
6217 .cindex "domain literal" "default router"
6218 This router is commented out because the majority of sites do not want to
6219 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6220 you uncomment this router, you also need to uncomment the setting of
6221 &%allow_domain_literals%& in the main part of the configuration.
6223 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6224 macro has been defined, per
6226 .ifdef ROUTER_SMARTHOST
6235 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6236 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6237 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6238 skip these routers because of the &%domains%& option.
6242 driver = manualroute
6243 domains = ! +local_domains
6244 transport = smarthost_smtp
6245 route_data = ROUTER_SMARTHOST
6246 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6249 This router only handles mail which is not to any local domains; this is
6250 specified by the line
6252 domains = ! +local_domains
6254 The &%domains%& option lists the domains to which this router applies, but the
6255 exclamation mark is a negation sign, so the router is used only for domains
6256 that are not in the domain list called &'local_domains'& (which was defined at
6257 the start of the configuration). The plus sign before &'local_domains'&
6258 indicates that it is referring to a named list. Addresses in other domains are
6259 passed on to the following routers.
6261 The name of the router driver is &(manualroute)& because we are manually
6262 specifying how mail should be routed onwards, instead of using DNS MX.
6263 While the name of this router instance is arbitrary, the &%driver%& option must
6264 be one of the driver modules that is in the Exim binary.
6266 With no pre-conditions other than &%domains%&, all mail for non-local domains
6267 will be handled by this router, and the &%no_more%& setting will ensure that no
6268 other routers will be used for messages matching the pre-conditions. See
6269 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6270 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6271 and the macro supplies the value; the address is then queued for the
6272 &(smarthost_smtp)& transport.
6277 domains = ! +local_domains
6278 transport = remote_smtp
6279 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6282 The &%domains%& option behaves as per smarthost, above.
6284 The name of the router driver is &(dnslookup)&,
6285 and is specified by the &%driver%& option. Do not be confused by the fact that
6286 the name of this router instance is the same as the name of the driver. The
6287 instance name is arbitrary, but the name set in the &%driver%& option must be
6288 one of the driver modules that is in the Exim binary.
6290 The &(dnslookup)& router routes addresses by looking up their domains in the
6291 DNS in order to obtain a list of hosts to which the address is routed. If the
6292 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6293 specified by the &%transport%& option. If the router does not find the domain
6294 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6295 the address fails and is bounced.
6297 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6298 be entirely ignored. This option is present because a number of cases have been
6299 encountered where MX records in the DNS point to host names
6300 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6301 Completely ignoring these IP addresses causes Exim to fail to route the
6302 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6303 continue to try to deliver the message periodically until the address timed
6310 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6312 file_transport = address_file
6313 pipe_transport = address_pipe
6315 Control reaches this and subsequent routers only for addresses in the local
6316 domains. This router checks to see whether the local part is defined as an
6317 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6318 data that it looks up from that file. If no data is found for the local part,
6319 the value of the &%data%& option is empty, causing the address to be passed to
6322 &_/etc/aliases_& is a conventional name for the system aliases file that is
6323 often used. That is why it is referenced by from the default configuration
6324 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6325 &_Local/Makefile_& before building Exim.
6330 # local_part_suffix = +* : -*
6331 # local_part_suffix_optional
6332 file = $home/.forward
6337 file_transport = address_file
6338 pipe_transport = address_pipe
6339 reply_transport = address_reply
6341 This is the most complicated router in the default configuration. It is another
6342 redirection router, but this time it is looking for forwarding data set up by
6343 individual users. The &%check_local_user%& setting specifies a check that the
6344 local part of the address is the login name of a local user. If it is not, the
6345 router is skipped. The two commented options that follow &%check_local_user%&,
6348 # local_part_suffix = +* : -*
6349 # local_part_suffix_optional
6351 .vindex "&$local_part_suffix$&"
6352 show how you can specify the recognition of local part suffixes. If the first
6353 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6354 by any sequence of characters, is removed from the local part and placed in the
6355 variable &$local_part_suffix$&. The second suffix option specifies that the
6356 presence of a suffix in the local part is optional. When a suffix is present,
6357 the check for a local login uses the local part with the suffix removed.
6359 When a local user account is found, the file called &_.forward_& in the user's
6360 home directory is consulted. If it does not exist, or is empty, the router
6361 declines. Otherwise, the contents of &_.forward_& are interpreted as
6362 redirection data (see chapter &<<CHAPredirect>>& for more details).
6364 .cindex "Sieve filter" "enabling in default router"
6365 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6366 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6367 is commented out by default), the contents of the file are interpreted as a set
6368 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6369 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6370 separate document entitled &'Exim's interfaces to mail filtering'&.
6372 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6373 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6374 There are two reasons for doing this:
6377 Whether or not a local user has a &_.forward_& file is not really relevant when
6378 checking an address for validity; it makes sense not to waste resources doing
6381 More importantly, when Exim is verifying addresses or handling an EXPN
6382 command during an SMTP session, it is running as the Exim user, not as root.
6383 The group is the Exim group, and no additional groups are set up.
6384 It may therefore not be possible for Exim to read users' &_.forward_& files at
6388 The setting of &%check_ancestor%& prevents the router from generating a new
6389 address that is the same as any previous address that was redirected. (This
6390 works round a problem concerning a bad interaction between aliasing and
6391 forwarding &-- see section &<<SECTredlocmai>>&).
6393 The final three option settings specify the transports that are to be used when
6394 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6395 auto-reply, respectively. For example, if a &_.forward_& file contains
6397 a.nother@elsewhere.example, /home/spqr/archive
6399 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6405 # local_part_suffix = +* : -*
6406 # local_part_suffix_optional
6407 transport = local_delivery
6409 The final router sets up delivery into local mailboxes, provided that the local
6410 part is the name of a local login, by accepting the address and assigning it to
6411 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6412 routers, so the address is bounced. The commented suffix settings fulfil the
6413 same purpose as they do for the &(userforward)& router.
6416 .section "Transport configuration" "SECID56"
6417 .cindex "default" "transports"
6418 .cindex "transports" "default"
6419 Transports define mechanisms for actually delivering messages. They operate
6420 only when referenced from routers, so the order in which they are defined does
6421 not matter. The transports section of the configuration starts with
6425 Two remote transports and four local transports are defined.
6429 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6434 This transport is used for delivering messages over SMTP connections.
6435 The list of remote hosts comes from the router.
6436 The &%message_size_limit%& usage is a hack to avoid sending on messages
6437 with over-long lines.
6439 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6440 negotiated between client and server and not expected to cause problems
6441 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6442 use of the &%hosts_try_prdr%& configuration option.
6444 The other remote transport is used when delivering to a specific smarthost
6445 with whom there must be some kind of existing relationship, instead of the
6446 usual federated system.
6451 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6455 # Comment out any of these which you have to, then file a Support
6456 # request with your smarthost provider to get things fixed:
6457 hosts_require_tls = *
6458 tls_verify_hosts = *
6459 # As long as tls_verify_hosts is enabled, this this will have no effect,
6460 # but if you have to comment it out then this will at least log whether
6461 # you succeed or not:
6462 tls_try_verify_hosts = *
6464 # The SNI name should match the name which we'll expect to verify;
6465 # many mail systems don't use SNI and this doesn't matter, but if it does,
6466 # we need to send a name which the remote site will recognize.
6467 # This _should_ be the name which the smarthost operators specified as
6468 # the hostname for sending your mail to.
6469 tls_sni = ROUTER_SMARTHOST
6471 .ifdef _HAVE_OPENSSL
6472 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6475 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6482 After the same &%message_size_limit%& hack, we then specify that this Transport
6483 can handle messages to multiple domains in one run. The assumption here is
6484 that you're routing all non-local mail to the same place and that place is
6485 happy to take all messages from you as quickly as possible.
6486 All other options depend upon built-in macros; if Exim was built without TLS support
6487 then no other options are defined.
6488 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6489 and versions using the &%tls_require_ciphers%& option, where the value to be
6490 used depends upon the library providing TLS.
6491 Beyond that, the options adopt the stance that you should have TLS support available
6492 from your smarthost on today's Internet, so we turn on requiring TLS for the
6493 mail to be delivered, and requiring that the certificate be valid, and match
6494 the expected hostname. The &%tls_sni%& option can be used by service providers
6495 to select an appropriate certificate to present to you and here we re-use the
6496 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6497 You want to specify the hostname which you'll expect to validate for, and that
6498 should not be subject to insecure tampering via DNS results.
6500 For the &%hosts_try_prdr%& option see the previous transport.
6502 All other options are defaulted.
6506 file = /var/mail/$local_part_data
6513 This &(appendfile)& transport is used for local delivery to user mailboxes in
6514 traditional BSD mailbox format.
6516 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6517 as it is provided by a potential bad actor.
6518 Instead we use &$local_part_data$&,
6519 the result of looking up &$local_part$& in the user database
6520 (done by using &%check_local_user%& in the the router).
6522 By default &(appendfile)& runs under the uid and gid of the
6523 local user, which requires the sticky bit to be set on the &_/var/mail_&
6524 directory. Some systems use the alternative approach of running mail deliveries
6525 under a particular group instead of using the sticky bit. The commented options
6526 show how this can be done.
6528 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6529 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6530 similarly-named options above.
6536 This transport is used for handling deliveries to pipes that are generated by
6537 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6538 option specifies that any output on stdout or stderr generated by the pipe is to
6539 be returned to the sender.
6547 This transport is used for handling deliveries to files that are generated by
6548 redirection. The name of the file is not specified in this instance of
6549 &(appendfile)&, because it comes from the &(redirect)& router.
6554 This transport is used for handling automatic replies generated by users'
6559 .section "Default retry rule" "SECID57"
6560 .cindex "retry" "default rule"
6561 .cindex "default" "retry rule"
6562 The retry section of the configuration file contains rules which affect the way
6563 Exim retries deliveries that cannot be completed at the first attempt. It is
6564 introduced by the line
6568 In the default configuration, there is just one rule, which applies to all
6571 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6573 This causes any temporarily failing address to be retried every 15 minutes for
6574 2 hours, then at intervals starting at one hour and increasing by a factor of
6575 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6576 is not delivered after 4 days of temporary failure, it is bounced. The time is
6577 measured from first failure, not from the time the message was received.
6579 If the retry section is removed from the configuration, or is empty (that is,
6580 if no retry rules are defined), Exim will not retry deliveries. This turns
6581 temporary errors into permanent errors.
6584 .section "Rewriting configuration" "SECID58"
6585 The rewriting section of the configuration, introduced by
6589 contains rules for rewriting addresses in messages as they arrive. There are no
6590 rewriting rules in the default configuration file.
6594 .section "Authenticators configuration" "SECTdefconfauth"
6595 .cindex "AUTH" "configuration"
6596 The authenticators section of the configuration, introduced by
6598 begin authenticators
6600 defines mechanisms for the use of the SMTP AUTH command. The default
6601 configuration file contains two commented-out example authenticators
6602 which support plaintext username/password authentication using the
6603 standard PLAIN mechanism and the traditional but non-standard LOGIN
6604 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6605 to support most MUA software.
6607 The example PLAIN authenticator looks like this:
6610 # driver = plaintext
6611 # server_set_id = $auth2
6612 # server_prompts = :
6613 # server_condition = Authentication is not yet configured
6614 # server_advertise_condition = ${if def:tls_in_cipher }
6616 And the example LOGIN authenticator looks like this:
6619 # driver = plaintext
6620 # server_set_id = $auth1
6621 # server_prompts = <| Username: | Password:
6622 # server_condition = Authentication is not yet configured
6623 # server_advertise_condition = ${if def:tls_in_cipher }
6626 The &%server_set_id%& option makes Exim remember the authenticated username
6627 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6628 &%server_prompts%& option configures the &(plaintext)& authenticator so
6629 that it implements the details of the specific authentication mechanism,
6630 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6631 when Exim offers authentication to clients; in the examples, this is only
6632 when TLS or SSL has been started, so to enable the authenticators you also
6633 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6635 The &%server_condition%& setting defines how to verify that the username and
6636 password are correct. In the examples it just produces an error message.
6637 To make the authenticators work, you can use a string expansion
6638 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6640 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6641 usercode and password are in different positions.
6642 Chapter &<<CHAPplaintext>>& covers both.
6644 .ecindex IIDconfiwal
6648 . ////////////////////////////////////////////////////////////////////////////
6649 . ////////////////////////////////////////////////////////////////////////////
6651 .chapter "Regular expressions" "CHAPregexp"
6653 .cindex "regular expressions" "library"
6655 Exim supports the use of regular expressions in many of its options. It
6656 uses the PCRE regular expression library; this provides regular expression
6657 matching that is compatible with Perl 5. The syntax and semantics of
6658 regular expressions is discussed in
6659 online Perl manpages, in
6660 many Perl reference books, and also in
6661 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6662 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6663 . --- the http: URL here redirects to another page with the ISBN in the URL
6664 . --- where trying to use https: just redirects back to http:, so sticking
6665 . --- to the old URL for now. 2018-09-07.
6667 The documentation for the syntax and semantics of the regular expressions that
6668 are supported by PCRE is included in the PCRE distribution, and no further
6669 description is included here. The PCRE functions are called from Exim using
6670 the default option settings (that is, with no PCRE options set), except that
6671 the PCRE_CASELESS option is set when the matching is required to be
6674 In most cases, when a regular expression is required in an Exim configuration,
6675 it has to start with a circumflex, in order to distinguish it from plain text
6676 or an &"ends with"& wildcard. In this example of a configuration setting, the
6677 second item in the colon-separated list is a regular expression.
6679 domains = a.b.c : ^\\d{3} : *.y.z : ...
6681 The doubling of the backslash is required because of string expansion that
6682 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6683 of this issue, and a way of avoiding the need for doubling backslashes. The
6684 regular expression that is eventually used in this example contains just one
6685 backslash. The circumflex is included in the regular expression, and has the
6686 normal effect of &"anchoring"& it to the start of the string that is being
6689 There are, however, two cases where a circumflex is not required for the
6690 recognition of a regular expression: these are the &%match%& condition in a
6691 string expansion, and the &%matches%& condition in an Exim filter file. In
6692 these cases, the relevant string is always treated as a regular expression; if
6693 it does not start with a circumflex, the expression is not anchored, and can
6694 match anywhere in the subject string.
6696 In all cases, if you want a regular expression to match at the end of a string,
6697 you must code the $ metacharacter to indicate this. For example:
6699 domains = ^\\d{3}\\.example
6701 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6704 domains = ^\\d{3}\\.example\$
6706 if you want &'example'& to be the top-level domain. The backslash before the
6707 $ is needed because string expansion also interprets dollar characters.
6711 . ////////////////////////////////////////////////////////////////////////////
6712 . ////////////////////////////////////////////////////////////////////////////
6714 .chapter "File and database lookups" "CHAPfdlookup"
6715 .scindex IIDfidalo1 "file" "lookups"
6716 .scindex IIDfidalo2 "database" "lookups"
6717 .cindex "lookup" "description of"
6718 Exim can be configured to look up data in files or databases as it processes
6719 messages. Two different kinds of syntax are used:
6722 A string that is to be expanded may contain explicit lookup requests. These
6723 cause parts of the string to be replaced by data that is obtained from the
6724 lookup. Lookups of this type are conditional expansion items. Different results
6725 can be defined for the cases of lookup success and failure. See chapter
6726 &<<CHAPexpand>>&, where string expansions are described in detail.
6727 The key for the lookup is &*specified*& as part of the string expansion.
6729 Lists of domains, hosts, and email addresses can contain lookup requests as a
6730 way of avoiding excessively long linear lists. In this case, the data that is
6731 returned by the lookup is often (but not always) discarded; whether the lookup
6732 succeeds or fails is what really counts. These kinds of list are described in
6733 chapter &<<CHAPdomhosaddlists>>&.
6734 The key for the lookup is &*implicit*&,
6735 given by the context in which the list is expanded.
6738 String expansions, lists, and lookups interact with each other in such a way
6739 that there is no order in which to describe any one of them that does not
6740 involve references to the others. Each of these three chapters makes more sense
6741 if you have read the other two first. If you are reading this for the first
6742 time, be aware that some of it will make a lot more sense after you have read
6743 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6745 .section "Examples of different lookup syntax" "SECID60"
6746 It is easy to confuse the two different kinds of lookup, especially as the
6747 lists that may contain the second kind are always expanded before being
6748 processed as lists. Therefore, they may also contain lookups of the first kind.
6749 Be careful to distinguish between the following two examples:
6751 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6752 domains = lsearch;/some/file
6754 The first uses a string expansion, the result of which must be a domain list.
6755 No strings have been specified for a successful or a failing lookup; the
6756 defaults in this case are the looked-up data and an empty string, respectively.
6757 The expansion takes place before the string is processed as a list, and the
6758 file that is searched could contain lines like this:
6760 192.168.3.4: domain1:domain2:...
6761 192.168.1.9: domain3:domain4:...
6763 When the lookup succeeds, the result of the expansion is a list of domains (and
6764 possibly other types of item that are allowed in domain lists).
6765 .cindex "tainted data" "de-tainting"
6766 The result of the expansion is not tainted.
6768 In the second example, the lookup is a single item in a domain list. It causes
6769 Exim to use a lookup to see if the domain that is being processed can be found
6771 The file could contains lines like this:
6776 Any data that follows the keys is not relevant when checking that the domain
6777 matches the list item.
6779 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6780 Consider a file containing lines like this:
6782 192.168.5.6: lsearch;/another/file
6784 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6785 first &%domains%& setting above generates the second setting, which therefore
6786 causes a second lookup to occur.
6789 The lookup type may optionally be followed by a comma
6790 and a comma-separated list of options.
6791 Each option is a &"name=value"& pair.
6792 Whether an option is meaningful depends on the lookup type.
6794 All lookups support the option &"cache=no_rd"&.
6795 If this is given then the cache that Exim manages for lookup results
6796 is not checked before doing the lookup.
6797 The result of the lookup is still written to the cache.
6800 The rest of this chapter describes the different lookup types that are
6801 available. Any of them can be used in any part of the configuration where a
6802 lookup is permitted.
6805 .section "Lookup types" "SECID61"
6806 .cindex "lookup" "types of"
6807 .cindex "single-key lookup" "definition of"
6808 Two different types of data lookup are implemented:
6811 The &'single-key'& type requires the specification of a file in which to look,
6812 and a single key to search for. The key must be a non-empty string for the
6813 lookup to succeed. The lookup type determines how the file is searched.
6814 .cindex "tainted data" "single-key lookups"
6815 The file string may not be tainted
6817 .cindex "tainted data" "de-tainting"
6818 All single-key lookups support the option &"ret=key"&.
6819 If this is given and the lookup
6820 (either underlying implementation or cached value)
6821 returns data, the result is replaced with a non-tainted
6822 version of the lookup key.
6823 .cindex "tainted data" "de-tainting"
6825 .cindex "query-style lookup" "definition of"
6826 The &'query-style'& type accepts a generalized database query. No particular
6827 key value is assumed by Exim for query-style lookups. You can use whichever
6828 Exim variables you need to construct the database query.
6831 The code for each lookup type is in a separate source file that is included in
6832 the binary of Exim only if the corresponding compile-time option is set. The
6833 default settings in &_src/EDITME_& are:
6838 which means that only linear searching and DBM lookups are included by default.
6839 For some types of lookup (e.g. SQL databases), you need to install appropriate
6840 libraries and header files before building Exim.
6845 .section "Single-key lookup types" "SECTsinglekeylookups"
6846 .cindex "lookup" "single-key types"
6847 .cindex "single-key lookup" "list of types"
6848 The following single-key lookup types are implemented:
6851 .cindex "cdb" "description of"
6852 .cindex "lookup" "cdb"
6853 .cindex "binary zero" "in lookup key"
6854 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6855 string without a terminating binary zero. The cdb format is designed for
6856 indexed files that are read frequently and never updated, except by total
6857 re-creation. As such, it is particularly suitable for large files containing
6858 aliases or other indexed data referenced by an MTA. Information about cdb and
6859 tools for building the files can be found in several places:
6861 &url(https://cr.yp.to/cdb.html)
6862 &url(https://www.corpit.ru/mjt/tinycdb.html)
6863 &url(https://packages.debian.org/stable/utils/freecdb)
6864 &url(https://github.com/philpennock/cdbtools) (in Go)
6866 A cdb distribution is not needed in order to build Exim with cdb support,
6867 because the code for reading cdb files is included directly in Exim itself.
6868 However, no means of building or testing cdb files is provided with Exim, so
6869 you need to obtain a cdb distribution in order to do this.
6871 .cindex "DBM" "lookup type"
6872 .cindex "lookup" "dbm"
6873 .cindex "binary zero" "in lookup key"
6874 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6875 DBM file by looking up the record with the given key. A terminating binary
6876 zero is included in the key that is passed to the DBM library. See section
6877 &<<SECTdb>>& for a discussion of DBM libraries.
6879 .cindex "Berkeley DB library" "file format"
6880 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6881 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6882 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6883 the DB_UNKNOWN option. This enables it to handle any of the types of database
6884 that the library supports, and can be useful for accessing DBM files created by
6885 other applications. (For earlier DB versions, DB_HASH is always used.)
6887 .cindex "lookup" "dbmjz"
6888 .cindex "lookup" "dbm &-- embedded NULs"
6890 .cindex "dbmjz lookup type"
6891 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6892 interpreted as an Exim list; the elements of the list are joined together with
6893 ASCII NUL characters to form the lookup key. An example usage would be to
6894 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6895 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6896 &(cram_md5)& authenticator.
6898 .cindex "lookup" "dbmnz"
6899 .cindex "lookup" "dbm &-- terminating zero"
6900 .cindex "binary zero" "in lookup key"
6902 .cindex "&_/etc/userdbshadow.dat_&"
6903 .cindex "dbmnz lookup type"
6904 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6905 is not included in the key that is passed to the DBM library. You may need this
6906 if you want to look up data in files that are created by or shared with some
6907 other application that does not use terminating zeros. For example, you need to
6908 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6909 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6910 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6911 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6913 .cindex "lookup" "dsearch"
6914 .cindex "dsearch lookup type"
6915 &(dsearch)&: The given file must be an
6917 directory path; this is searched for an entry
6918 whose name is the key by calling the &[lstat()]& function.
6920 contain any forward slash characters.
6921 If &[lstat()]& succeeds then so does the lookup.
6922 .cindex "tainted data" "dsearch result"
6923 The result is regarded as untainted.
6925 Options for the lookup can be given by appending them after the word "dsearch",
6926 separated by a comma. Options, if present, are a comma-separated list having
6927 each element starting with a tag name and an equals.
6929 Two options are supported, for the return value and for filtering match
6931 The "ret" option requests an alternate result value of
6932 the entire path for the entry. Example:
6934 ${lookup {passwd} dsearch,ret=full {/etc}}
6936 The default result is just the requested entry.
6937 The "filter" option requests that only directory entries of a given type
6938 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6939 not matching "." or ".."). Example:
6941 ${lookup {passwd} dsearch,filter=file {/etc}}
6943 The default matching is for any entry type, including directories
6946 An example of how this
6947 lookup can be used to support virtual domains is given in section
6948 &<<SECTvirtualdomains>>&.
6950 .cindex "lookup" "iplsearch"
6951 .cindex "iplsearch lookup type"
6952 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6953 terminated by a colon or white space or the end of the line. The keys in the
6954 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6955 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6956 being interpreted as a key terminator. For example:
6958 1.2.3.4: data for 1.2.3.4
6959 192.168.0.0/16: data for 192.168.0.0/16
6960 "abcd::cdab": data for abcd::cdab
6961 "abcd:abcd::/32" data for abcd:abcd::/32
6963 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6964 file is searched linearly, using the CIDR masks where present, until a matching
6965 key is found. The first key that matches is used; there is no attempt to find a
6966 &"best"& match. Apart from the way the keys are matched, the processing for
6967 &(iplsearch)& is the same as for &(lsearch)&.
6969 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6970 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6971 lookup types support only literal keys.
6973 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6974 the implicit key is the host's IP address rather than its name (see section
6975 &<<SECThoslispatsikey>>&).
6977 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6978 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6979 notation before executing the lookup.)
6982 One option is supported, "ret=full", to request the return of the entire line
6983 rather than omitting the key porttion.
6984 Note however that the key portion will have been de-quoted.
6989 .cindex json "lookup type"
6990 .cindex JSON expansions
6991 &(json)&: The given file is a text file with a JSON structure.
6992 An element of the structure is extracted, defined by the search key.
6993 The key is a list of subelement selectors
6994 (colon-separated by default but changeable in the usual way)
6995 which are applied in turn to select smaller and smaller portions
6996 of the JSON structure.
6997 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6998 nunbered array element is selected.
6999 Otherwise it must apply to a JSON object; the named element is selected.
7000 The final resulting element can be a simple JSON type or a JSON object
7001 or array; for the latter two a string-representation of the JSON
7003 For elements of type string, the returned value is de-quoted.
7010 .cindex database lmdb
7011 &(lmdb)&: The given file is an LMDB database.
7012 LMDB is a memory-mapped key-value store,
7013 with API modeled loosely on that of BerkeleyDB.
7014 See &url(https://symas.com/products/lightning-memory-mapped-database/)
7015 for the feature set and operation modes.
7017 Exim provides read-only access via the LMDB C library.
7018 The library can be obtained from &url(https://github.com/LMDB/lmdb)
7019 or your operating system package repository.
7020 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
7022 You will need to separately create the LMDB database file,
7023 possibly using the &"mdb_load"& utility.
7028 .cindex "linear search"
7029 .cindex "lookup" "lsearch"
7030 .cindex "lsearch lookup type"
7031 .cindex "case sensitivity" "in lsearch lookup"
7032 &(lsearch)&: The given file is a text file that is searched linearly for a
7033 line beginning with the search key, terminated by a colon or white space or the
7034 end of the line. The search is case-insensitive; that is, upper and lower case
7035 letters are treated as the same. The first occurrence of the key that is found
7036 in the file is used.
7038 White space between the key and the colon is permitted. The remainder of the
7039 line, with leading and trailing white space removed, is the data. This can be
7040 continued onto subsequent lines by starting them with any amount of white
7041 space, but only a single space character is included in the data at such a
7042 junction. If the data begins with a colon, the key must be terminated by a
7047 Empty lines and lines beginning with # are ignored, even if they occur in the
7048 middle of an item. This is the traditional textual format of alias files. Note
7049 that the keys in an &(lsearch)& file are literal strings. There is no
7050 wildcarding of any kind.
7052 .cindex "lookup" "lsearch &-- colons in keys"
7053 .cindex "white space" "in lsearch key"
7054 In most &(lsearch)& files, keys are not required to contain colons or #
7055 characters, or white space. However, if you need this feature, it is available.
7056 If a key begins with a doublequote character, it is terminated only by a
7057 matching quote (or end of line), and the normal escaping rules apply to its
7058 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7059 quoted keys (exactly as for unquoted keys). There is no special handling of
7060 quotes for the data part of an &(lsearch)& line.
7063 .cindex "NIS lookup type"
7064 .cindex "lookup" "NIS"
7065 .cindex "binary zero" "in lookup key"
7066 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7067 the given key, without a terminating binary zero. There is a variant called
7068 &(nis0)& which does include the terminating binary zero in the key. This is
7069 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7070 aliases; the full map names must be used.
7073 .cindex "wildlsearch lookup type"
7074 .cindex "lookup" "wildlsearch"
7075 .cindex "nwildlsearch lookup type"
7076 .cindex "lookup" "nwildlsearch"
7077 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7078 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7079 the file may be wildcarded. The difference between these two lookup types is
7080 that for &(wildlsearch)&, each key in the file is string-expanded before being
7081 used, whereas for &(nwildlsearch)&, no expansion takes place.
7083 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7084 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7085 file that are regular expressions can be made case-sensitive by the use of
7086 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7088 . ==== As this is a nested list, any displays it contains must be indented
7089 . ==== as otherwise they are too far to the left.
7092 The string may begin with an asterisk to mean &"ends with"&. For example:
7094 *.a.b.c data for anything.a.b.c
7095 *fish data for anythingfish
7098 The string may begin with a circumflex to indicate a regular expression. For
7099 example, for &(wildlsearch)&:
7101 ^\N\d+\.a\.b\N data for <digits>.a.b
7103 Note the use of &`\N`& to disable expansion of the contents of the regular
7104 expression. If you are using &(nwildlsearch)&, where the keys are not
7105 string-expanded, the equivalent entry is:
7107 ^\d+\.a\.b data for <digits>.a.b
7109 The case-insensitive flag is set at the start of compiling the regular
7110 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7111 For example, to make the entire pattern case-sensitive:
7113 ^(?-i)\d+\.a\.b data for <digits>.a.b
7116 If the regular expression contains white space or colon characters, you must
7117 either quote it (see &(lsearch)& above), or represent these characters in other
7118 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7119 colon. This may be easier than quoting, because if you quote, you have to
7120 escape all the backslashes inside the quotes.
7122 &*Note*&: It is not possible to capture substrings in a regular expression
7123 match for later use, because the results of all lookups are cached. If a lookup
7124 is repeated, the result is taken from the cache, and no actual pattern matching
7125 takes place. The values of all the numeric variables are unset after a
7126 &((n)wildlsearch)& match.
7129 Although I cannot see it being of much use, the general matching function that
7130 is used to implement &((n)wildlsearch)& means that the string may begin with a
7131 lookup name terminated by a semicolon, and followed by lookup data. For
7134 cdb;/some/file data for keys that match the file
7136 The data that is obtained from the nested lookup is discarded.
7139 Keys that do not match any of these patterns are interpreted literally. The
7140 continuation rules for the data are the same as for &(lsearch)&, and keys may
7141 be followed by optional colons.
7143 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7144 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7145 lookup types support only literal keys.
7148 .cindex "spf lookup type"
7149 .cindex "lookup" "spf"
7150 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7151 (as opposed to the standard ACL condition method).
7152 For details see section &<<SECSPF>>&.
7156 .section "Query-style lookup types" "SECTquerystylelookups"
7157 .cindex "lookup" "query-style types"
7158 .cindex "query-style lookup" "list of types"
7159 The supported query-style lookup types are listed below. Further details about
7160 many of them are given in later sections.
7163 .cindex "DNS" "as a lookup type"
7164 .cindex "lookup" "DNS"
7165 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7166 are given in the supplied query. The resulting data is the contents of the
7167 records. See section &<<SECTdnsdb>>&.
7169 .cindex "InterBase lookup type"
7170 .cindex "lookup" "InterBase"
7171 &(ibase)&: This does a lookup in an InterBase database.
7173 .cindex "LDAP" "lookup type"
7174 .cindex "lookup" "LDAP"
7175 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7176 returns attributes from a single entry. There is a variant called &(ldapm)&
7177 that permits values from multiple entries to be returned. A third variant
7178 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7179 any attribute values. See section &<<SECTldap>>&.
7181 .cindex "MySQL" "lookup type"
7182 .cindex "lookup" "MySQL"
7183 &(mysql)&: The format of the query is an SQL statement that is passed to a
7184 MySQL database. See section &<<SECTsql>>&.
7186 .cindex "NIS+ lookup type"
7187 .cindex "lookup" "NIS+"
7188 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7189 the field to be returned. See section &<<SECTnisplus>>&.
7191 .cindex "Oracle" "lookup type"
7192 .cindex "lookup" "Oracle"
7193 &(oracle)&: The format of the query is an SQL statement that is passed to an
7194 Oracle database. See section &<<SECTsql>>&.
7196 .cindex "lookup" "passwd"
7197 .cindex "passwd lookup type"
7198 .cindex "&_/etc/passwd_&"
7199 &(passwd)& is a query-style lookup with queries that are just user names. The
7200 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7201 success, the result string is the same as you would get from an &(lsearch)&
7202 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7203 password value. For example:
7205 *:42:42:King Rat:/home/kr:/bin/bash
7208 .cindex "PostgreSQL lookup type"
7209 .cindex "lookup" "PostgreSQL"
7210 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7211 PostgreSQL database. See section &<<SECTsql>>&.
7214 .cindex "Redis lookup type"
7215 .cindex lookup Redis
7216 &(redis)&: The format of the query is either a simple get or simple set,
7217 passed to a Redis database. See section &<<SECTsql>>&.
7220 .cindex "sqlite lookup type"
7221 .cindex "lookup" "sqlite"
7222 &(sqlite)&: The format of the query is
7223 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7226 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7227 not likely to be useful in normal operation.
7229 .cindex "whoson lookup type"
7230 .cindex "lookup" "whoson"
7231 . --- still http:-only, 2018-09-07
7232 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7233 allows a server to check whether a particular (dynamically allocated) IP
7234 address is currently allocated to a known (trusted) user and, optionally, to
7235 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7236 at one time for &"POP before SMTP"& authentication, but that approach has been
7237 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7238 &"POP before SMTP"& checking using ACL statements such as
7240 require condition = \
7241 ${lookup whoson {$sender_host_address}{yes}{no}}
7243 The query consists of a single IP address. The value returned is the name of
7244 the authenticated user, which is stored in the variable &$value$&. However, in
7245 this example, the data in &$value$& is not used; the result of the lookup is
7246 one of the fixed strings &"yes"& or &"no"&.
7251 .section "Temporary errors in lookups" "SECID63"
7252 .cindex "lookup" "temporary error in"
7253 Lookup functions can return temporary error codes if the lookup cannot be
7254 completed. For example, an SQL or LDAP database might be unavailable. For this
7255 reason, it is not advisable to use a lookup that might do this for critical
7256 options such as a list of local domains.
7258 When a lookup cannot be completed in a router or transport, delivery
7259 of the message (to the relevant address) is deferred, as for any other
7260 temporary error. In other circumstances Exim may assume the lookup has failed,
7261 or may give up altogether.
7265 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7266 .cindex "wildcard lookups"
7267 .cindex "lookup" "default values"
7268 .cindex "lookup" "wildcard"
7269 .cindex "lookup" "* added to type"
7270 .cindex "default" "in single-key lookups"
7271 In this context, a &"default value"& is a value specified by the administrator
7272 that is to be used if a lookup fails.
7274 &*Note:*& This section applies only to single-key lookups. For query-style
7275 lookups, the facilities of the query language must be used. An attempt to
7276 specify a default for a query-style lookup provokes an error.
7278 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7279 and the initial lookup fails, the key &"*"& is looked up in the file to
7280 provide a default value. See also the section on partial matching below.
7282 .cindex "*@ with single-key lookup"
7283 .cindex "lookup" "*@ added to type"
7284 .cindex "alias file" "per-domain default"
7285 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7286 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7287 character, a second lookup is done with everything before the last @ replaced
7288 by *. This makes it possible to provide per-domain defaults in alias files
7289 that include the domains in the keys. If the second lookup fails (or doesn't
7290 take place because there is no @ in the key), &"*"& is looked up.
7291 For example, a &(redirect)& router might contain:
7293 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7295 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7296 looks up these keys, in this order:
7302 The data is taken from whichever key it finds first. &*Note*&: In an
7303 &(lsearch)& file, this does not mean the first of these keys in the file. A
7304 complete scan is done for each key, and only if it is not found at all does
7305 Exim move on to try the next key.
7309 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7310 .cindex "partial matching"
7311 .cindex "wildcard lookups"
7312 .cindex "lookup" "partial matching"
7313 .cindex "lookup" "wildcard"
7314 .cindex "asterisk" "in search type"
7315 The normal operation of a single-key lookup is to search the file for an exact
7316 match with the given key. However, in a number of situations where domains are
7317 being looked up, it is useful to be able to do partial matching. In this case,
7318 information in the file that has a key starting with &"*."& is matched by any
7319 domain that ends with the components that follow the full stop. For example, if
7320 a key in a DBM file is
7322 *.dates.fict.example
7324 then when partial matching is enabled this is matched by (amongst others)
7325 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7326 by &'dates.fict.example'&, if that does not appear as a separate key in the
7329 &*Note*&: Partial matching is not available for query-style lookups. It is
7330 also not available for any lookup items in address lists (see section
7331 &<<SECTaddresslist>>&).
7333 Partial matching is implemented by doing a series of separate lookups using
7334 keys constructed by modifying the original subject key. This means that it can
7335 be used with any of the single-key lookup types, provided that
7336 partial matching keys
7337 beginning with a special prefix (default &"*."&) are included in the data file.
7338 Keys in the file that do not begin with the prefix are matched only by
7339 unmodified subject keys when partial matching is in use.
7341 Partial matching is requested by adding the string &"partial-"& to the front of
7342 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7343 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7344 is added at the start of the subject key, and it is looked up again. If that
7345 fails, further lookups are tried with dot-separated components removed from the
7346 start of the subject key, one-by-one, and &"*."& added on the front of what
7349 A minimum number of two non-* components are required. This can be adjusted
7350 by including a number before the hyphen in the search type. For example,
7351 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7352 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7353 subject key is &'2250.dates.fict.example'& then the following keys are looked
7354 up when the minimum number of non-* components is two:
7356 2250.dates.fict.example
7357 *.2250.dates.fict.example
7358 *.dates.fict.example
7361 As soon as one key in the sequence is successfully looked up, the lookup
7364 .cindex "lookup" "partial matching &-- changing prefix"
7365 .cindex "prefix" "for partial matching"
7366 The use of &"*."& as the partial matching prefix is a default that can be
7367 changed. The motivation for this feature is to allow Exim to operate with file
7368 formats that are used by other MTAs. A different prefix can be supplied in
7369 parentheses instead of the hyphen after &"partial"&. For example:
7371 domains = partial(.)lsearch;/some/file
7373 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7374 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7375 components is unchanged). The prefix may consist of any punctuation characters
7376 other than a closing parenthesis. It may be empty, for example:
7378 domains = partial1()cdb;/some/file
7380 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7381 &`a.b.c`&, &`b.c`&, and &`c`&.
7383 If &"partial0"& is specified, what happens at the end (when the lookup with
7384 just one non-wild component has failed, and the original key is shortened right
7385 down to the null string) depends on the prefix:
7388 If the prefix has zero length, the whole lookup fails.
7390 If the prefix has length 1, a lookup for just the prefix is done. For
7391 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7393 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7394 remainder is looked up. With the default prefix, therefore, the final lookup is
7395 for &"*"& on its own.
7397 Otherwise, the whole prefix is looked up.
7401 If the search type ends in &"*"& or &"*@"& (see section
7402 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7403 this implies happens after all partial lookups have failed. If &"partial0"& is
7404 specified, adding &"*"& to the search type has no effect with the default
7405 prefix, because the &"*"& key is already included in the sequence of partial
7406 lookups. However, there might be a use for lookup types such as
7407 &"partial0(.)lsearch*"&.
7409 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7410 in domain lists and the like. Partial matching works only in terms of
7411 dot-separated components; a key such as &`*fict.example`&
7412 in a database file is useless, because the asterisk in a partial matching
7413 subject key is always followed by a dot.
7418 .section "Lookup caching" "SECID64"
7419 .cindex "lookup" "caching"
7420 .cindex "caching" "lookup data"
7421 Exim caches all lookup results in order to avoid needless repetition of
7422 lookups. However, because (apart from the daemon) Exim operates as a collection
7423 of independent, short-lived processes, this caching applies only within a
7424 single Exim process. There is no inter-process lookup caching facility.
7426 For single-key lookups, Exim keeps the relevant files open in case there is
7427 another lookup that needs them. In some types of configuration this can lead to
7428 many files being kept open for messages with many recipients. To avoid hitting
7429 the operating system limit on the number of simultaneously open files, Exim
7430 closes the least recently used file when it needs to open more files than its
7431 own internal limit, which can be changed via the &%lookup_open_max%& option.
7433 The single-key lookup files are closed and the lookup caches are flushed at
7434 strategic points during delivery &-- for example, after all routing is
7440 .section "Quoting lookup data" "SECID65"
7441 .cindex "lookup" "quoting"
7442 .cindex "quoting" "in lookups"
7443 When data from an incoming message is included in a query-style lookup, there
7444 is the possibility of special characters in the data messing up the syntax of
7445 the query. For example, a NIS+ query that contains
7449 will be broken if the local part happens to contain a closing square bracket.
7450 For NIS+, data can be enclosed in double quotes like this:
7452 [name="$local_part"]
7454 but this still leaves the problem of a double quote in the data. The rule for
7455 NIS+ is that double quotes must be doubled. Other lookup types have different
7456 rules, and to cope with the differing requirements, an expansion operator
7457 of the following form is provided:
7459 ${quote_<lookup-type>:<string>}
7461 For example, the safest way to write the NIS+ query is
7463 [name="${quote_nisplus:$local_part}"]
7465 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7466 operator can be used for all lookup types, but has no effect for single-key
7467 lookups, since no quoting is ever needed in their key strings.
7472 .section "More about dnsdb" "SECTdnsdb"
7473 .cindex "dnsdb lookup"
7474 .cindex "lookup" "dnsdb"
7475 .cindex "DNS" "as a lookup type"
7476 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7477 of a record type and a domain name, separated by an equals sign. For example,
7478 an expansion string could contain:
7480 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7482 If the lookup succeeds, the result is placed in &$value$&, which in this case
7483 is used on its own as the result. If the lookup does not succeed, the
7484 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7485 &<<SECTforexpfai>>& for an explanation of what this means.
7487 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7488 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7489 If no type is given, TXT is assumed.
7491 For any record type, if multiple records are found, the data is returned as a
7492 concatenation, with newline as the default separator. The order, of course,
7493 depends on the DNS resolver. You can specify a different separator character
7494 between multiple records by putting a right angle-bracket followed immediately
7495 by the new separator at the start of the query. For example:
7497 ${lookup dnsdb{>: a=host1.example}}
7499 It is permitted to specify a space as the separator character. Further
7500 white space is ignored.
7501 For lookup types that return multiple fields per record,
7502 an alternate field separator can be specified using a comma after the main
7503 separator character, followed immediately by the field separator.
7505 .cindex "PTR record" "in &(dnsdb)& lookup"
7506 When the type is PTR,
7507 the data can be an IP address, written as normal; inversion and the addition of
7508 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7510 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7512 If the data for a PTR record is not a syntactically valid IP address, it is not
7513 altered and nothing is added.
7515 .cindex "MX record" "in &(dnsdb)& lookup"
7516 .cindex "SRV record" "in &(dnsdb)& lookup"
7517 For an MX lookup, both the preference value and the host name are returned for
7518 each record, separated by a space. For an SRV lookup, the priority, weight,
7519 port, and host name are returned for each record, separated by spaces.
7520 The field separator can be modified as above.
7522 .cindex "TXT record" "in &(dnsdb)& lookup"
7523 .cindex "SPF record" "in &(dnsdb)& lookup"
7524 For TXT records with multiple items of data, only the first item is returned,
7525 unless a field separator is specified.
7526 To concatenate items without a separator, use a semicolon instead.
7528 default behaviour is to concatenate multiple items without using a separator.
7530 ${lookup dnsdb{>\n,: txt=a.b.example}}
7531 ${lookup dnsdb{>\n; txt=a.b.example}}
7532 ${lookup dnsdb{spf=example.org}}
7534 It is permitted to specify a space as the separator character. Further
7535 white space is ignored.
7537 .cindex "SOA record" "in &(dnsdb)& lookup"
7538 For an SOA lookup, while no result is obtained the lookup is redone with
7539 successively more leading components dropped from the given domain.
7540 Only the primary-nameserver field is returned unless a field separator is
7543 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7546 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7547 .cindex "dnsdb modifiers"
7548 .cindex "modifiers" "dnsdb"
7549 .cindex "options" "dnsdb"
7550 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7551 each followed by a comma,
7552 that may appear before the record type.
7554 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7555 temporary DNS error for any of them, the behaviour is controlled by
7556 a defer-option modifier.
7557 The possible keywords are
7558 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7559 With &"strict"& behaviour, any temporary DNS error causes the
7560 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7561 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7562 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7563 error causes the whole lookup to defer only if none of the other lookups
7564 succeed. The default is &"lax"&, so the following lookups are equivalent:
7566 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7567 ${lookup dnsdb{a=one.host.com:two.host.com}}
7569 Thus, in the default case, as long as at least one of the DNS lookups
7570 yields some data, the lookup succeeds.
7572 .cindex "DNSSEC" "dns lookup"
7573 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7574 The possible keywords are
7575 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7576 With &"strict"& or &"lax"& DNSSEC information is requested
7578 With &"strict"& a response from the DNS resolver that
7579 is not labelled as authenticated data
7580 is treated as equivalent to a temporary DNS error.
7581 The default is &"lax"&.
7583 See also the &$lookup_dnssec_authenticated$& variable.
7585 .cindex timeout "dns lookup"
7586 .cindex "DNS" timeout
7587 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7588 The form is &"retrans_VAL"& where VAL is an Exim time specification
7590 The default value is set by the main configuration option &%dns_retrans%&.
7592 Retries for the dnsdb lookup can be controlled by a retry modifier.
7593 The form if &"retry_VAL"& where VAL is an integer.
7594 The default count is set by the main configuration option &%dns_retry%&.
7596 .cindex caching "of dns lookup"
7597 .cindex TTL "of dns lookup"
7599 Dnsdb lookup results are cached within a single process (and its children).
7600 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7601 value of the set of returned DNS records.
7604 .section "Pseudo dnsdb record types" "SECID66"
7605 .cindex "MX record" "in &(dnsdb)& lookup"
7606 By default, both the preference value and the host name are returned for
7607 each MX record, separated by a space. If you want only host names, you can use
7608 the pseudo-type MXH:
7610 ${lookup dnsdb{mxh=a.b.example}}
7612 In this case, the preference values are omitted, and just the host names are
7615 .cindex "name server for enclosing domain"
7616 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7617 records on the given domain, but if none are found, it removes the first
7618 component of the domain name, and tries again. This process continues until NS
7619 records are found or there are no more components left (or there is a DNS
7620 error). In other words, it may return the name servers for a top-level domain,
7621 but it never returns the root name servers. If there are no NS records for the
7622 top-level domain, the lookup fails. Consider these examples:
7624 ${lookup dnsdb{zns=xxx.quercite.com}}
7625 ${lookup dnsdb{zns=xxx.edu}}
7627 Assuming that in each case there are no NS records for the full domain name,
7628 the first returns the name servers for &%quercite.com%&, and the second returns
7629 the name servers for &%edu%&.
7631 You should be careful about how you use this lookup because, unless the
7632 top-level domain does not exist, the lookup always returns some host names. The
7633 sort of use to which this might be put is for seeing if the name servers for a
7634 given domain are on a blacklist. You can probably assume that the name servers
7635 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7638 .cindex "CSA" "in &(dnsdb)& lookup"
7639 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7640 records according to the CSA rules, which are described in section
7641 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7642 not sufficient because of the extra parent domain search behaviour of CSA. The
7643 result of a successful lookup such as:
7645 ${lookup dnsdb {csa=$sender_helo_name}}
7647 has two space-separated fields: an authorization code and a target host name.
7648 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7649 authorization required but absent, or &"?"& for unknown.
7651 .cindex "A+" "in &(dnsdb)& lookup"
7652 The pseudo-type A+ performs an AAAA
7653 and then an A lookup. All results are returned; defer processing
7654 (see below) is handled separately for each lookup. Example:
7656 ${lookup dnsdb {>; a+=$sender_helo_name}}
7660 .section "Multiple dnsdb lookups" "SECID67"
7661 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7662 However, you can specify a list of domains or IP addresses in a single
7663 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7664 the default separator, but with the ability to change this. For example:
7666 ${lookup dnsdb{one.domain.com:two.domain.com}}
7667 ${lookup dnsdb{a=one.host.com:two.host.com}}
7668 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7670 In order to retain backwards compatibility, there is one special case: if
7671 the lookup type is PTR and no change of separator is specified, Exim looks
7672 to see if the rest of the string is precisely one IPv6 address. In this
7673 case, it does not treat it as a list.
7675 The data from each lookup is concatenated, with newline separators by default,
7676 in the same way that multiple DNS records for a single item are handled. A
7677 different separator can be specified, as described above.
7682 .section "More about LDAP" "SECTldap"
7683 .cindex "LDAP" "lookup, more about"
7684 .cindex "lookup" "LDAP"
7685 .cindex "Solaris" "LDAP"
7686 The original LDAP implementation came from the University of Michigan; this has
7687 become &"Open LDAP"&, and there are now two different releases. Another
7688 implementation comes from Netscape, and Solaris 7 and subsequent releases
7689 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7690 the lookup function level, their error handling is different. For this reason
7691 it is necessary to set a compile-time variable when building Exim with LDAP, to
7692 indicate which LDAP library is in use. One of the following should appear in
7693 your &_Local/Makefile_&:
7695 LDAP_LIB_TYPE=UMICHIGAN
7696 LDAP_LIB_TYPE=OPENLDAP1
7697 LDAP_LIB_TYPE=OPENLDAP2
7698 LDAP_LIB_TYPE=NETSCAPE
7699 LDAP_LIB_TYPE=SOLARIS
7701 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7702 same interface as the University of Michigan version.
7704 There are three LDAP lookup types in Exim. These behave slightly differently in
7705 the way they handle the results of a query:
7708 &(ldap)& requires the result to contain just one entry; if there are more, it
7711 &(ldapdn)& also requires the result to contain just one entry, but it is the
7712 Distinguished Name that is returned rather than any attribute values.
7714 &(ldapm)& permits the result to contain more than one entry; the attributes
7715 from all of them are returned.
7719 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7720 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7721 the data returned by a successful lookup is described in the next section.
7722 First we explain how LDAP queries are coded.
7725 .section "Format of LDAP queries" "SECTforldaque"
7726 .cindex "LDAP" "query format"
7727 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7728 the configuration of a &(redirect)& router one might have this setting:
7730 data = ${lookup ldap \
7731 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7732 c=UK?mailbox?base?}}
7734 .cindex "LDAP" "with TLS"
7735 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7736 secure (encrypted) LDAP connections. The second of these ensures that an
7737 encrypted TLS connection is used.
7739 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7740 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7741 See the &%ldap_start_tls%& option.
7743 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7744 controlled. Every part of the TLS configuration can be configured by settings in
7745 &_exim.conf_&. Depending on the version of the client libraries installed on
7746 your system, some of the initialization may have required setting options in
7747 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7748 certificates. This revealed a nuance where the current UID that exim was
7749 running as could affect which config files it read. With Exim 4.83, these
7750 methods become optional, only taking effect if not specifically set in
7754 .section "LDAP quoting" "SECID68"
7755 .cindex "LDAP" "quoting"
7756 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7757 and the second because the LDAP query is represented as a URL. Furthermore,
7758 within an LDAP query, two different kinds of quoting are required. For this
7759 reason, there are two different LDAP-specific quoting operators.
7761 The &%quote_ldap%& operator is designed for use on strings that are part of
7762 filter specifications. Conceptually, it first does the following conversions on
7770 in accordance with RFC 2254. The resulting string is then quoted according
7771 to the rules for URLs, that is, all non-alphanumeric characters except
7775 are converted to their hex values, preceded by a percent sign. For example:
7777 ${quote_ldap: a(bc)*, a<yz>; }
7781 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7783 Removing the URL quoting, this is (with a leading and a trailing space):
7785 a\28bc\29\2A, a<yz>;
7787 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7788 base DN specifications in queries. Conceptually, it first converts the string
7789 by inserting a backslash in front of any of the following characters:
7793 It also inserts a backslash before any leading spaces or # characters, and
7794 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7795 is then quoted according to the rules for URLs. For example:
7797 ${quote_ldap_dn: a(bc)*, a<yz>; }
7801 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7803 Removing the URL quoting, this is (with a trailing space):
7805 \ a(bc)*\, a\<yz\>\;\
7807 There are some further comments about quoting in the section on LDAP
7808 authentication below.
7811 .section "LDAP connections" "SECID69"
7812 .cindex "LDAP" "connections"
7813 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7814 is in use, via a Unix domain socket. The example given above does not specify
7815 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7818 ldap://<hostname>:<port>/...
7820 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7821 used. When no server is specified in a query, a list of default servers is
7822 taken from the &%ldap_default_servers%& configuration option. This supplies a
7823 colon-separated list of servers which are tried in turn until one successfully
7824 handles a query, or there is a serious error. Successful handling either
7825 returns the requested data, or indicates that it does not exist. Serious errors
7826 are syntactical, or multiple values when only a single value is expected.
7827 Errors which cause the next server to be tried are connection failures, bind
7828 failures, and timeouts.
7830 For each server name in the list, a port number can be given. The standard way
7831 of specifying a host and port is to use a colon separator (RFC 1738). Because
7832 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7833 doubled. For example
7835 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7837 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7838 to the LDAP library with no server name, and the library's default (normally
7839 the local host) is used.
7841 If you are using the OpenLDAP library, you can connect to an LDAP server using
7842 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7843 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7844 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7847 For this type of connection, instead of a host name for the server, a pathname
7848 for the socket is required, and the port number is not relevant. The pathname
7849 can be specified either as an item in &%ldap_default_servers%&, or inline in
7850 the query. In the former case, you can have settings such as
7852 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7854 When the pathname is given in the query, you have to escape the slashes as
7855 &`%2F`& to fit in with the LDAP URL syntax. For example:
7857 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7859 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7860 a pathname, it uses the Unix domain socket code, even if the query actually
7861 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7862 socket connection. This behaviour means that you can use a setting of
7863 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7864 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7865 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7868 If an explicit &`ldapi`& type is given in a query when a host name is
7869 specified, an error is diagnosed. However, if there are more items in
7870 &%ldap_default_servers%&, they are tried. In other words:
7873 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7876 Using &`ldapi`& with a host name causes an error.
7880 Using &`ldapi`& with no host or path in the query, and no setting of
7881 &%ldap_default_servers%&, does whatever the library does by default.
7885 .section "LDAP authentication and control information" "SECID70"
7886 .cindex "LDAP" "authentication"
7887 The LDAP URL syntax provides no way of passing authentication and other control
7888 information to the server. To make this possible, the URL in an LDAP query may
7889 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7890 spaces. If a value contains spaces it must be enclosed in double quotes, and
7891 when double quotes are used, backslash is interpreted in the usual way inside
7892 them. The following names are recognized:
7894 &`DEREFERENCE`& set the dereferencing parameter
7895 &`NETTIME `& set a timeout for a network operation
7896 &`USER `& set the DN, for authenticating the LDAP bind
7897 &`PASS `& set the password, likewise
7898 &`REFERRALS `& set the referrals parameter
7899 &`SERVERS `& set alternate server list for this query only
7900 &`SIZE `& set the limit for the number of entries returned
7901 &`TIME `& set the maximum waiting time for a query
7903 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7904 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7905 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7906 library from trying to follow referrals issued by the LDAP server.
7908 .cindex LDAP timeout
7909 .cindex timeout "LDAP lookup"
7910 The name CONNECT is an obsolete name for NETTIME, retained for
7911 backwards compatibility. This timeout (specified as a number of seconds) is
7912 enforced from the client end for operations that can be carried out over a
7913 network. Specifically, it applies to network connections and calls to the
7914 &'ldap_result()'& function. If the value is greater than zero, it is used if
7915 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7916 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7917 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7918 Netscape SDK; for OpenLDAP no action is taken.
7920 The TIME parameter (also a number of seconds) is passed to the server to
7921 set a server-side limit on the time taken to complete a search.
7923 The SERVERS parameter allows you to specify an alternate list of ldap servers
7924 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7925 default list of ldap servers, and a single lookup can specify a single ldap
7926 server to use. But when you need to do a lookup with a list of servers that is
7927 different than the default list (maybe different order, maybe a completely
7928 different set of servers), the SERVERS parameter allows you to specify this
7929 alternate list (colon-separated).
7931 Here is an example of an LDAP query in an Exim lookup that uses some of these
7932 values. This is a single line, folded to fit on the page:
7935 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7936 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7939 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7940 any of the auxiliary data. Exim configuration settings that include lookups
7941 which contain password information should be preceded by &"hide"& to prevent
7942 non-admin users from using the &%-bP%& option to see their values.
7944 The auxiliary data items may be given in any order. The default is no
7945 connection timeout (the system timeout is used), no user or password, no limit
7946 on the number of entries returned, and no time limit on queries.
7948 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7949 removes any URL quoting that it may contain before passing it LDAP. Apparently
7950 some libraries do this for themselves, but some do not. Removing the URL
7951 quoting has two advantages:
7954 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7955 DNs as with DNs inside actual queries.
7957 It permits spaces inside USER= DNs.
7960 For example, a setting such as
7962 USER=cn=${quote_ldap_dn:$1}
7964 should work even if &$1$& contains spaces.
7966 Expanded data for the PASS= value should be quoted using the &%quote%&
7967 expansion operator, rather than the LDAP quote operators. The only reason this
7968 field needs quoting is to ensure that it conforms to the Exim syntax, which
7969 does not allow unquoted spaces. For example:
7973 The LDAP authentication mechanism can be used to check passwords as part of
7974 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7979 .section "Format of data returned by LDAP" "SECID71"
7980 .cindex "LDAP" "returned data formats"
7981 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7982 as a sequence of values, for example
7984 cn=manager,o=University of Cambridge,c=UK
7986 The &(ldap)& lookup type generates an error if more than one entry matches the
7987 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7988 the result between the data from different entries. It is possible for multiple
7989 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7990 you know that whatever values are returned all came from a single entry in the
7993 In the common case where you specify a single attribute in your LDAP query, the
7994 result is not quoted, and does not contain the attribute name. If the attribute
7995 has multiple values, they are separated by commas. Any comma that is
7996 part of an attribute's value is doubled.
7998 If you specify multiple attributes, the result contains space-separated, quoted
7999 strings, each preceded by the attribute name and an equals sign. Within the
8000 quotes, the quote character, backslash, and newline are escaped with
8001 backslashes, and commas are used to separate multiple values for the attribute.
8002 Any commas in attribute values are doubled
8003 (permitting treatment of the values as a comma-separated list).
8004 Apart from the escaping, the string within quotes takes the same form as the
8005 output when a single attribute is requested. Specifying no attributes is the
8006 same as specifying all of an entry's attributes.
8008 Here are some examples of the output format. The first line of each pair is an
8009 LDAP query, and the second is the data that is returned. The attribute called
8010 &%attr1%& has two values, one of them with an embedded comma, whereas
8011 &%attr2%& has only one value. Both attributes are derived from &%attr%&
8012 (they have SUP &%attr%& in their schema definitions).
8015 ldap:///o=base?attr1?sub?(uid=fred)
8018 ldap:///o=base?attr2?sub?(uid=fred)
8021 ldap:///o=base?attr?sub?(uid=fred)
8022 value1.1,value1,,2,value two
8024 ldap:///o=base?attr1,attr2?sub?(uid=fred)
8025 attr1="value1.1,value1,,2" attr2="value two"
8027 ldap:///o=base??sub?(uid=fred)
8028 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
8031 make use of Exim's &%-be%& option to run expansion tests and thereby check the
8032 results of LDAP lookups.
8033 The &%extract%& operator in string expansions can be used to pick out
8034 individual fields from data that consists of &'key'&=&'value'& pairs.
8035 The &%listextract%& operator should be used to pick out individual values
8036 of attributes, even when only a single value is expected.
8037 The doubling of embedded commas allows you to use the returned data as a
8038 comma separated list (using the "<," syntax for changing the input list separator).
8043 .section "More about NIS+" "SECTnisplus"
8044 .cindex "NIS+ lookup type"
8045 .cindex "lookup" "NIS+"
8046 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8047 and field name. If this is given, the result of a successful query is the
8048 contents of the named field; otherwise the result consists of a concatenation
8049 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8050 values containing spaces are quoted. For example, the query
8052 [name=mg1456],passwd.org_dir
8054 might return the string
8056 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8057 home=/home/mg1456 shell=/bin/bash shadow=""
8059 (split over two lines here to fit on the page), whereas
8061 [name=mg1456],passwd.org_dir:gcos
8067 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8068 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8069 operator is to double any quote characters within the text.
8073 .section "SQL lookups" "SECTsql"
8074 .cindex "SQL lookup types"
8075 .cindex "MySQL" "lookup type"
8076 .cindex "PostgreSQL lookup type"
8077 .cindex "lookup" "MySQL"
8078 .cindex "lookup" "PostgreSQL"
8079 .cindex "Oracle" "lookup type"
8080 .cindex "lookup" "Oracle"
8081 .cindex "InterBase lookup type"
8082 .cindex "lookup" "InterBase"
8083 .cindex "Redis lookup type"
8084 .cindex lookup Redis
8085 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8087 databases. Queries for these databases contain SQL statements, so an example
8090 ${lookup mysql{select mailbox from users where id='userx'}\
8093 If the result of the query contains more than one field, the data for each
8094 field in the row is returned, preceded by its name, so the result of
8096 ${lookup pgsql{select home,name from users where id='userx'}\
8101 home=/home/userx name="Mister X"
8103 Empty values and values containing spaces are double quoted, with embedded
8104 quotes escaped by a backslash. If the result of the query contains just one
8105 field, the value is passed back verbatim, without a field name, for example:
8109 If the result of the query yields more than one row, it is all concatenated,
8110 with a newline between the data for each row.
8113 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8114 .cindex "MySQL" "lookup type"
8115 .cindex "PostgreSQL lookup type"
8116 .cindex "lookup" "MySQL"
8117 .cindex "lookup" "PostgreSQL"
8118 .cindex "Oracle" "lookup type"
8119 .cindex "lookup" "Oracle"
8120 .cindex "InterBase lookup type"
8121 .cindex "lookup" "InterBase"
8122 .cindex "Redis lookup type"
8123 .cindex lookup Redis
8124 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8125 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8126 or &%redis_servers%&
8127 option (as appropriate) must be set to a colon-separated list of server
8129 .oindex &%mysql_servers%&
8130 .oindex &%pgsql_servers%&
8131 .oindex &%oracle_servers%&
8132 .oindex &%ibase_servers%&
8133 .oindex &%redis_servers%&
8134 (For MySQL and PostgreSQL, the global option need not be set if all
8135 queries contain their own server information &-- see section
8136 &<<SECTspeserque>>&.)
8138 each item in the list is a slash-separated list of four
8139 items: host name, database name, user name, and password. In the case of
8140 Oracle, the host name field is used for the &"service name"&, and the database
8141 name field is not used and should be empty. For example:
8143 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8145 Because password data is sensitive, you should always precede the setting with
8146 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8147 option. Here is an example where two MySQL servers are listed:
8149 hide mysql_servers = localhost/users/root/secret:\
8150 otherhost/users/root/othersecret
8152 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8153 because this is a colon-separated list, the colon has to be doubled. For each
8154 query, these parameter groups are tried in order until a connection is made and
8155 a query is successfully processed. The result of a query may be that no data is
8156 found, but that is still a successful query. In other words, the list of
8157 servers provides a backup facility, not a list of different places to look.
8159 For Redis the global option need not be specified if all queries contain their
8160 own server information &-- see section &<<SECTspeserque>>&.
8161 If specified, the option must be set to a colon-separated list of server
8163 Each item in the list is a slash-separated list of three items:
8164 host, database number, and password.
8166 The host is required and may be either an IPv4 address and optional
8167 port number (separated by a colon, which needs doubling due to the
8168 higher-level list), or a Unix socket pathname enclosed in parentheses
8170 The database number is optional; if present that number is selected in the backend
8172 The password is optional; if present it is used to authenticate to the backend
8175 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8176 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8177 respectively, and the characters single-quote, double-quote, and backslash
8178 itself are escaped with backslashes.
8180 The &%quote_redis%& expansion operator
8181 escapes whitespace and backslash characters with a backslash.
8183 .section "Specifying the server in the query" "SECTspeserque"
8184 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8185 it is possible to specify a list of servers with an individual query. This is
8186 done by appending a comma-separated option to the query type:
8188 &`,servers=`&&'server1:server2:server3:...'&
8190 Each item in the list may take one of two forms:
8192 If it contains no slashes it is assumed to be just a host name. The appropriate
8193 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8194 of the same name, and the remaining parameters (database, user, password) are
8197 If it contains any slashes, it is taken as a complete parameter set.
8199 The list of servers is used in exactly the same way as the global list.
8200 Once a connection to a server has happened and a query has been
8201 successfully executed, processing of the lookup ceases.
8203 This feature is intended for use in master/slave situations where updates
8204 are occurring and you want to update the master rather than a slave. If the
8205 master is in the list as a backup for reading, you might have a global setting
8208 mysql_servers = slave1/db/name/pw:\
8212 In an updating lookup, you could then write:
8214 ${lookup mysql,servers=master {UPDATE ...} }
8216 That query would then be sent only to the master server. If, on the other hand,
8217 the master is not to be used for reading, and so is not present in the global
8218 option, you can still update it by a query of this form:
8220 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8223 An older syntax places the servers specification before the query,
8224 semicolon separated:
8226 ${lookup mysql{servers=master; UPDATE ...} }
8228 The new version avoids potential issues with tainted
8229 arguments in the query, for explicit expansion.
8230 &*Note*&: server specifications in list-style lookups are still problematic.
8233 .section "Special MySQL features" "SECID73"
8234 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8235 causes a connection to the server on the local host by means of a Unix domain
8236 socket. An alternate socket can be specified in parentheses.
8237 An option group name for MySQL option files can be specified in square brackets;
8238 the default value is &"exim"&.
8239 The full syntax of each item in &%mysql_servers%& is:
8241 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8242 <&'database'&>/<&'user'&>/<&'password'&>
8244 Any of the four sub-parts of the first field can be omitted. For normal use on
8245 the local host it can be left blank or set to just &"localhost"&.
8247 No database need be supplied &-- but if it is absent here, it must be given in
8250 If a MySQL query is issued that does not request any data (an insert, update,
8251 or delete command), the result of the lookup is the number of rows affected.
8253 &*Warning*&: This can be misleading. If an update does not actually change
8254 anything (for example, setting a field to the value it already has), the result
8255 is zero because no rows are affected.
8258 .section "Special PostgreSQL features" "SECID74"
8259 PostgreSQL lookups can also use Unix domain socket connections to the database.
8260 This is usually faster and costs less CPU time than a TCP/IP connection.
8261 However it can be used only if the mail server runs on the same machine as the
8262 database server. A configuration line for PostgreSQL via Unix domain sockets
8265 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8267 In other words, instead of supplying a host name, a path to the socket is
8268 given. The path name is enclosed in parentheses so that its slashes aren't
8269 visually confused with the delimiters for the other server parameters.
8271 If a PostgreSQL query is issued that does not request any data (an insert,
8272 update, or delete command), the result of the lookup is the number of rows
8275 .section "More about SQLite" "SECTsqlite"
8276 .cindex "lookup" "SQLite"
8277 .cindex "sqlite lookup type"
8278 SQLite is different to the other SQL lookups because a filename is required in
8279 addition to the SQL query. An SQLite database is a single file, and there is no
8280 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.
8294 A deprecated method is available, prefixing the query with the filename
8295 separated by white space.
8297 .cindex "tainted data" "sqlite file"
8298 the query cannot use any tainted values, as that taints
8299 the entire query including the filename - resulting in a refusal to open
8302 In all the above cases the filename must be an absolute path.
8304 Here is a lookup expansion example:
8306 sqlite_dbfile = /some/thing/sqlitedb
8308 ${lookup sqlite {select name from aliases where id='userx';}}
8310 In a list, the syntax is similar. For example:
8312 domainlist relay_to_domains = sqlite;\
8313 select * from relays where ip='$sender_host_address';
8315 The only character affected by the &%quote_sqlite%& operator is a single
8316 quote, which it doubles.
8318 .cindex timeout SQLite
8319 .cindex sqlite "lookup timeout"
8320 The SQLite library handles multiple simultaneous accesses to the database
8321 internally. Multiple readers are permitted, but only one process can
8322 update at once. Attempts to access the database while it is being updated
8323 are rejected after a timeout period, during which the SQLite library
8324 waits for the lock to be released. In Exim, the default timeout is set
8325 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8328 .section "More about Redis" "SECTredis"
8329 .cindex "lookup" "Redis"
8330 .cindex "redis lookup type"
8331 Redis is a non-SQL database. Commands are simple get and set.
8334 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8335 ${lookup redis{get keyname}}
8338 As of release 4.91, "lightweight" support for Redis Cluster is available.
8339 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8340 of which must be reachable from the running exim instance. If the cluster has
8341 master/slave replication, the list must contain all the master and slave
8344 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8345 immediately follow the redirection but treats the response as a DEFER, moving on
8346 to the next server in the &%redis_servers%& list until the correct server is
8353 . ////////////////////////////////////////////////////////////////////////////
8354 . ////////////////////////////////////////////////////////////////////////////
8356 .chapter "Domain, host, address, and local part lists" &&&
8357 "CHAPdomhosaddlists" &&&
8358 "Domain, host, and address lists"
8359 .scindex IIDdohoadli "lists of domains; hosts; etc."
8360 A number of Exim configuration options contain lists of domains, hosts,
8361 email addresses, or local parts. For example, the &%hold_domains%& option
8362 contains a list of domains whose delivery is currently suspended. These lists
8363 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8364 arguments to expansion conditions such as &%match_domain%&.
8366 Each item in one of these lists is a pattern to be matched against a domain,
8367 host, email address, or local part, respectively. In the sections below, the
8368 different types of pattern for each case are described, but first we cover some
8369 general facilities that apply to all four kinds of list.
8371 Note that other parts of Exim use a &'string list'& which does not
8372 support all the complexity available in
8373 domain, host, address and local part lists.
8377 .section "Expansion of lists" "SECTlistexpand"
8378 .cindex "expansion" "of lists"
8379 Each list is expanded as a single string before it is used.
8381 &'Exception: the router headers_remove option, where list-item
8382 splitting is done before string-expansion.'&
8385 expansion must be a list, possibly containing empty items, which is split up
8386 into separate items for matching. By default, colon is the separator character,
8387 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8388 &<<SECTempitelis>>& for details of the list syntax; the second of these
8389 discusses the way to specify empty list items.
8392 If the string expansion is forced to fail, Exim behaves as if the item it is
8393 testing (domain, host, address, or local part) is not in the list. Other
8394 expansion failures cause temporary errors.
8396 If an item in a list is a regular expression, backslashes, dollars and possibly
8397 other special characters in the expression must be protected against
8398 misinterpretation by the string expander. The easiest way to do this is to use
8399 the &`\N`& expansion feature to indicate that the contents of the regular
8400 expression should not be expanded. For example, in an ACL you might have:
8402 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8403 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8405 The first item is a regular expression that is protected from expansion by
8406 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8407 senders based on the receiving domain.
8412 .section "Negated items in lists" "SECID76"
8413 .cindex "list" "negation"
8414 .cindex "negation" "in lists"
8415 Items in a list may be positive or negative. Negative items are indicated by a
8416 leading exclamation mark, which may be followed by optional white space. A list
8417 defines a set of items (domains, etc). When Exim processes one of these lists,
8418 it is trying to find out whether a domain, host, address, or local part
8419 (respectively) is in the set that is defined by the list. It works like this:
8421 The list is scanned from left to right. If a positive item is matched, the
8422 subject that is being checked is in the set; if a negative item is matched, the
8423 subject is not in the set. If the end of the list is reached without the
8424 subject having matched any of the patterns, it is in the set if the last item
8425 was a negative one, but not if it was a positive one. For example, the list in
8427 domainlist relay_to_domains = !a.b.c : *.b.c
8429 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8430 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8431 list is positive. However, if the setting were
8433 domainlist relay_to_domains = !a.b.c
8435 then all domains other than &'a.b.c'& would match because the last item in the
8436 list is negative. In other words, a list that ends with a negative item behaves
8437 as if it had an extra item &`:*`& on the end.
8439 Another way of thinking about positive and negative items in lists is to read
8440 the connector as &"or"& after a positive item and as &"and"& after a negative
8445 .section "File names in lists" "SECTfilnamlis"
8446 .cindex "list" "filename in"
8447 If an item in a domain, host, address, or local part list is an absolute
8448 filename (beginning with a slash character), each line of the file is read and
8449 processed as if it were an independent item in the list, except that further
8450 filenames are not allowed,
8451 and no expansion of the data from the file takes place.
8452 Empty lines in the file are ignored, and the file may also contain comment
8456 For domain and host lists, if a # character appears anywhere in a line of the
8457 file, it and all following characters are ignored.
8459 Because local parts may legitimately contain # characters, a comment in an
8460 address list or local part list file is recognized only if # is preceded by
8461 white space or the start of the line. For example:
8463 not#comment@x.y.z # but this is a comment
8467 Putting a filename in a list has the same effect as inserting each line of the
8468 file as an item in the list (blank lines and comments excepted). However, there
8469 is one important difference: the file is read each time the list is processed,
8470 so if its contents vary over time, Exim's behaviour changes.
8472 If a filename is preceded by an exclamation mark, the sense of any match
8473 within the file is inverted. For example, if
8475 hold_domains = !/etc/nohold-domains
8477 and the file contains the lines
8482 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8483 any domain matching &`*.b.c`& is not.
8487 .section "An lsearch file is not an out-of-line list" "SECID77"
8488 As will be described in the sections that follow, lookups can be used in lists
8489 to provide indexed methods of checking list membership. There has been some
8490 confusion about the way &(lsearch)& lookups work in lists. Because
8491 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8492 sometimes thought that it is allowed to contain wild cards and other kinds of
8493 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8494 always fixed strings, just as for any other single-key lookup type.
8496 If you want to use a file to contain wild-card patterns that form part of a
8497 list, just give the filename on its own, without a search type, as described
8498 in the previous section. You could also use the &(wildlsearch)& or
8499 &(nwildlsearch)&, but there is no advantage in doing this.
8504 .section "Results of list checking" SECTlistresults
8505 The primary result of doing a list check is a truth value.
8506 In some contexts additional information is stored
8507 about the list element that matched:
8510 A &%hosts%& ACL condition
8511 will store a result in the &$host_data$& variable.
8513 A &%local_parts%& router option or &%local_parts%& ACL condition
8514 will store a result in the &$local_part_data$& variable.
8517 A &%domains%& router option or &%domains%& ACL condition
8518 will store a result in the &$domain_data$& variable.
8521 A &%senders%& router option or &%senders%& ACL condition
8522 will store a result in the &$sender_data$& variable.
8524 A &%recipients%& ACL condition
8525 will store a result in the &$recipient_data$& variable.
8528 The detail of the additional information depends on the
8529 type of match and is given below as the &*value*& information.
8534 .section "Named lists" "SECTnamedlists"
8535 .cindex "named lists"
8536 .cindex "list" "named"
8537 A list of domains, hosts, email addresses, or local parts can be given a name
8538 which is then used to refer to the list elsewhere in the configuration. This is
8539 particularly convenient if the same list is required in several different
8540 places. It also allows lists to be given meaningful names, which can improve
8541 the readability of the configuration. For example, it is conventional to define
8542 a domain list called &'local_domains'& for all the domains that are handled
8543 locally on a host, using a configuration line such as
8545 domainlist local_domains = localhost:my.dom.example
8547 Named lists are referenced by giving their name preceded by a plus sign, so,
8548 for example, a router that is intended to handle local domains would be
8549 configured with the line
8551 domains = +local_domains
8553 The first router in a configuration is often one that handles all domains
8554 except the local ones, using a configuration with a negated item like this:
8558 domains = ! +local_domains
8559 transport = remote_smtp
8562 The four kinds of named list are created by configuration lines starting with
8563 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8564 respectively. Then there follows the name that you are defining, followed by an
8565 equals sign and the list itself. For example:
8567 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8568 addresslist bad_senders = cdb;/etc/badsenders
8570 A named list may refer to other named lists:
8572 domainlist dom1 = first.example : second.example
8573 domainlist dom2 = +dom1 : third.example
8574 domainlist dom3 = fourth.example : +dom2 : fifth.example
8576 &*Warning*&: If the last item in a referenced list is a negative one, the
8577 effect may not be what you intended, because the negation does not propagate
8578 out to the higher level. For example, consider:
8580 domainlist dom1 = !a.b
8581 domainlist dom2 = +dom1 : *.b
8583 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8584 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8585 means it matches the second list as well. The effect is not the same as
8587 domainlist dom2 = !a.b : *.b
8589 where &'x.y'& does not match. It's best to avoid negation altogether in
8590 referenced lists if you can.
8592 .cindex "hiding named list values"
8593 .cindex "named lists" "hiding value of"
8594 Some named list definitions may contain sensitive data, for example, passwords for
8595 accessing databases. To stop non-admin users from using the &%-bP%& command
8596 line option to read these values, you can precede the definition with the
8597 word &"hide"&. For example:
8599 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8603 Named lists may have a performance advantage. When Exim is routing an
8604 address or checking an incoming message, it caches the result of tests on named
8605 lists. So, if you have a setting such as
8607 domains = +local_domains
8609 on several of your routers
8610 or in several ACL statements,
8611 the actual test is done only for the first one. However, the caching works only
8612 if there are no expansions within the list itself or any sublists that it
8613 references. In other words, caching happens only for lists that are known to be
8614 the same each time they are referenced.
8616 By default, there may be up to 16 named lists of each type. This limit can be
8617 extended by changing a compile-time variable. The use of domain and host lists
8618 is recommended for concepts such as local domains, relay domains, and relay
8619 hosts. The default configuration is set up like this.
8623 .section "Named lists compared with macros" "SECID78"
8624 .cindex "list" "named compared with macro"
8625 .cindex "macro" "compared with named list"
8626 At first sight, named lists might seem to be no different from macros in the
8627 configuration file. However, macros are just textual substitutions. If you
8630 ALIST = host1 : host2
8631 auth_advertise_hosts = !ALIST
8633 it probably won't do what you want, because that is exactly the same as
8635 auth_advertise_hosts = !host1 : host2
8637 Notice that the second host name is not negated. However, if you use a host
8640 hostlist alist = host1 : host2
8641 auth_advertise_hosts = ! +alist
8643 the negation applies to the whole list, and so that is equivalent to
8645 auth_advertise_hosts = !host1 : !host2
8649 .section "Named list caching" "SECID79"
8650 .cindex "list" "caching of named"
8651 .cindex "caching" "named lists"
8652 While processing a message, Exim caches the result of checking a named list if
8653 it is sure that the list is the same each time. In practice, this means that
8654 the cache operates only if the list contains no $ characters, which guarantees
8655 that it will not change when it is expanded. Sometimes, however, you may have
8656 an expanded list that you know will be the same each time within a given
8657 message. For example:
8659 domainlist special_domains = \
8660 ${lookup{$sender_host_address}cdb{/some/file}}
8662 This provides a list of domains that depends only on the sending host's IP
8663 address. If this domain list is referenced a number of times (for example,
8664 in several ACL lines, or in several routers) the result of the check is not
8665 cached by default, because Exim does not know that it is going to be the
8666 same list each time.
8668 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8669 cache the result anyway. For example:
8671 domainlist_cache special_domains = ${lookup{...
8673 If you do this, you should be absolutely sure that caching is going to do
8674 the right thing in all cases. When in doubt, leave it out.
8678 .section "Domain lists" "SECTdomainlist"
8679 .cindex "domain list" "patterns for"
8680 .cindex "list" "domain list"
8681 Domain lists contain patterns that are to be matched against a mail domain.
8682 The following types of item may appear in domain lists:
8685 .cindex "primary host name"
8686 .cindex "host name" "matched in domain list"
8687 .oindex "&%primary_hostname%&"
8688 .cindex "domain list" "matching primary host name"
8689 .cindex "@ in a domain list"
8690 If a pattern consists of a single @ character, it matches the local host name,
8691 as set by the &%primary_hostname%& option (or defaulted). This makes it
8692 possible to use the same configuration file on several different hosts that
8693 differ only in their names.
8695 The value for a match will be the primary host name.
8699 .cindex "@[] in a domain list"
8700 .cindex "domain list" "matching local IP interfaces"
8701 .cindex "domain literal"
8702 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8703 in square brackets (as in an email address that contains a domain literal), but
8704 only if that IP address is recognized as local for email routing purposes. The
8705 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8706 control which of a host's several IP addresses are treated as local.
8707 In today's Internet, the use of domain literals is controversial;
8708 see the &%allow_domain_literals%& main option.
8710 The value for a match will be the string &`@[]`&.
8715 .cindex "@mx_primary"
8716 .cindex "@mx_secondary"
8717 .cindex "domain list" "matching MX pointers to local host"
8718 If a pattern consists of the string &`@mx_any`& it matches any domain that
8719 has an MX record pointing to the local host or to any host that is listed in
8720 .oindex "&%hosts_treat_as_local%&"
8721 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8722 are similar, except that the first matches only when a primary MX target is the
8723 local host, and the second only when no primary MX target is the local host,
8724 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8725 preference value &-- there may of course be more than one of them.
8727 The MX lookup that takes place when matching a pattern of this type is
8728 performed with the resolver options for widening names turned off. Thus, for
8729 example, a single-component domain will &'not'& be expanded by adding the
8730 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8731 options of the &(dnslookup)& router for a discussion of domain widening.
8733 Sometimes you may want to ignore certain IP addresses when using one of these
8734 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8735 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8736 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8737 on a router). For example:
8739 domains = @mx_any/ignore=127.0.0.1
8741 This example matches any domain that has an MX record pointing to one of
8742 the local host's IP addresses other than 127.0.0.1.
8744 The list of IP addresses is in fact processed by the same code that processes
8745 host lists, so it may contain CIDR-coded network specifications and it may also
8746 contain negative items.
8748 Because the list of IP addresses is a sublist within a domain list, you have to
8749 be careful about delimiters if there is more than one address. Like any other
8750 list, the default delimiter can be changed. Thus, you might have:
8752 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8753 an.other.domain : ...
8755 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8756 involved, it is easiest to change the delimiter for the main list as well:
8758 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8759 an.other.domain ? ...
8761 The value for a match will be the list element string (starting &`@mx_`&).
8765 .cindex "asterisk" "in domain list"
8766 .cindex "domain list" "asterisk in"
8767 .cindex "domain list" "matching &""ends with""&"
8768 If a pattern starts with an asterisk, the remaining characters of the pattern
8769 are compared with the terminating characters of the domain. The use of &"*"& in
8770 domain lists differs from its use in partial matching lookups. In a domain
8771 list, the character following the asterisk need not be a dot, whereas partial
8772 matching works only in terms of dot-separated components. For example, a domain
8773 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8776 The value for a match will be the list element string (starting with the asterisk).
8777 Additionally, &$0$& will be set to the matched string
8778 and &$1$& to the variable portion which the asterisk matched.
8781 .cindex "regular expressions" "in domain list"
8782 .cindex "domain list" "matching regular expression"
8783 If a pattern starts with a circumflex character, it is treated as a regular
8784 expression, and matched against the domain using a regular expression matching
8785 function. The circumflex is treated as part of the regular expression.
8786 Email domains are case-independent, so this regular expression match is by
8787 default case-independent, but you can make it case-dependent by starting it
8788 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8789 are given in chapter &<<CHAPregexp>>&.
8791 &*Warning*&: Because domain lists are expanded before being processed, you
8792 must escape any backslash and dollar characters in the regular expression, or
8793 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8794 it is not to be expanded (unless you really do want to build a regular
8795 expression by expansion, of course).
8797 The value for a match will be the list element string (starting with the circumflex).
8798 Additionally, &$0$& will be set to the string matching the regular expression,
8799 and &$1$& (onwards) to any submatches identified by parentheses.
8804 .cindex "lookup" "in domain list"
8805 .cindex "domain list" "matching by lookup"
8806 If a pattern starts with the name of a single-key lookup type followed by a
8807 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8808 must be a filename in a suitable format for the lookup type. For example, for
8809 &"cdb;"& it must be an absolute path:
8811 domains = cdb;/etc/mail/local_domains.cdb
8813 The appropriate type of lookup is done on the file using the domain name as the
8814 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8815 only in whether or not the key is present in the file. However, when a lookup
8816 is used for the &%domains%& option on a router
8817 or a &%domains%& condition in an ACL statement, the value is preserved in the
8818 &$domain_data$& variable and can be referred to in other router options or
8819 other statements in the same ACL.
8820 .cindex "tainted data" "de-tainting"
8821 The value will be untainted.
8824 &*Note*&: If the data result of the lookup (as opposed to the key)
8825 is empty, then this empty value is stored in &$domain_data$&.
8826 The option to return the key for the lookup, as the value,
8827 may be what is wanted.
8832 Any of the single-key lookup type names may be preceded by
8833 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8835 domains = partial-dbm;/partial/domains
8837 This causes partial matching logic to be invoked; a description of how this
8838 works is given in section &<<SECTpartiallookup>>&.
8841 .cindex "asterisk" "in lookup type"
8842 Any of the single-key lookup types may be followed by an asterisk. This causes
8843 a default lookup for a key consisting of a single asterisk to be done if the
8844 original lookup fails. This is not a useful feature when using a domain list to
8845 select particular domains (because any domain would match), but it might have
8846 value if the result of the lookup is being used via the &$domain_data$&
8850 If the pattern starts with the name of a query-style lookup type followed by a
8851 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8852 pattern must be an appropriate query for the lookup type, as described in
8853 chapter &<<CHAPfdlookup>>&. For example:
8855 hold_domains = mysql;select domain from holdlist \
8856 where domain = '${quote_mysql:$domain}';
8858 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8859 example, it doesn't matter what field you select). Exim is interested only in
8860 whether or not the query succeeds. However, when a lookup is used for the
8861 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8862 variable and can be referred to in other options.
8863 .cindex "tainted data" "de-tainting"
8864 The value will be untainted.
8867 If the pattern starts with the name of a lookup type
8868 of either kind (single-key or query-style) it may be
8869 followed by a comma and options,
8870 The options are lookup-type specific and consist of a comma-separated list.
8871 Each item starts with a tag and and equals "=" sign.
8874 .cindex "domain list" "matching literal domain name"
8875 If none of the above cases apply, a caseless textual comparison is made
8876 between the pattern and the domain.
8878 The value for a match will be the list element string.
8879 .cindex "tainted data" "de-tainting"
8880 Note that this is commonly untainted
8881 (depending on the way the list was created).
8882 Specifically, explicit text in the configuration file in not tainted.
8883 This is a useful way of obtaining an untainted equivalent to
8884 the domain, for later operations.
8886 However if the list (including one-element lists)
8887 is created by expanding a variable containing tainted data,
8888 it is tainted and so will the match value be.
8892 Here is an example that uses several different kinds of pattern:
8894 domainlist funny_domains = \
8897 *.foundation.fict.example : \
8898 \N^[1-2]\d{3}\.fict\.example$\N : \
8899 partial-dbm;/opt/data/penguin/book : \
8900 nis;domains.byname : \
8901 nisplus;[name=$domain,status=local],domains.org_dir
8903 There are obvious processing trade-offs among the various matching modes. Using
8904 an asterisk is faster than a regular expression, and listing a few names
8905 explicitly probably is too. The use of a file or database lookup is expensive,
8906 but may be the only option if hundreds of names are required. Because the
8907 patterns are tested in order, it makes sense to put the most commonly matched
8912 .section "Host lists" "SECThostlist"
8913 .cindex "host list" "patterns in"
8914 .cindex "list" "host list"
8915 Host lists are used to control what remote hosts are allowed to do. For
8916 example, some hosts may be allowed to use the local host as a relay, and some
8917 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8918 two different ways, by name or by IP address. In a host list, some types of
8919 pattern are matched to a host name, and some are matched to an IP address.
8920 You need to be particularly careful with this when single-key lookups are
8921 involved, to ensure that the right value is being used as the key.
8924 .section "Special host list patterns" "SECID80"
8925 .cindex "empty item in hosts list"
8926 .cindex "host list" "empty string in"
8927 If a host list item is the empty string, it matches only when no remote host is
8928 involved. This is the case when a message is being received from a local
8929 process using SMTP on the standard input, that is, when a TCP/IP connection is
8932 .cindex "asterisk" "in host list"
8933 The special pattern &"*"& in a host list matches any host or no host. Neither
8934 the IP address nor the name is actually inspected.
8938 .section "Host list patterns that match by IP address" "SECThoslispatip"
8939 .cindex "host list" "matching IP addresses"
8940 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8941 the incoming address actually appears in the IPv6 host as
8942 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8943 list, it is converted into a traditional IPv4 address first. (Not all operating
8944 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8947 The following types of pattern in a host list check the remote host by
8948 inspecting its IP address:
8951 If the pattern is a plain domain name (not a regular expression, not starting
8952 with *, not a lookup of any kind), Exim calls the operating system function
8953 to find the associated IP address(es). Exim uses the newer
8954 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8955 This typically causes a forward DNS lookup of the name. The result is compared
8956 with the IP address of the subject host.
8958 If there is a temporary problem (such as a DNS timeout) with the host name
8959 lookup, a temporary error occurs. For example, if the list is being used in an
8960 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8961 temporary SMTP error code. If no IP address can be found for the host name,
8962 what happens is described in section &<<SECTbehipnot>>& below.
8965 .cindex "@ in a host list"
8966 If the pattern is &"@"&, the primary host name is substituted and used as a
8967 domain name, as just described.
8970 If the pattern is an IP address, it is matched against the IP address of the
8971 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8972 IPv6 addresses can be given in colon-separated format, but the colons have to
8973 be doubled so as not to be taken as item separators when the default list
8974 separator is used. IPv6 addresses are recognized even when Exim is compiled
8975 without IPv6 support. This means that if they appear in a host list on an
8976 IPv4-only host, Exim will not treat them as host names. They are just addresses
8977 that can never match a client host.
8980 .cindex "@[] in a host list"
8981 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8982 the local host. For example, if the local host is an IPv4 host with one
8983 interface address 10.45.23.56, these two ACL statements have the same effect:
8985 accept hosts = 127.0.0.1 : 10.45.23.56
8989 .cindex "CIDR notation"
8990 If the pattern is an IP address followed by a slash and a mask length, for
8995 , it is matched against the IP address of the subject
8996 host under the given mask. This allows an entire network of hosts to be
8997 included (or excluded) by a single item. The mask uses CIDR notation; it
8998 specifies the number of address bits that must match, starting from the most
8999 significant end of the address.
9001 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
9002 of a range of addresses. It is the number of bits in the network portion of the
9003 address. The above example specifies a 24-bit netmask, so it matches all 256
9004 addresses in the 10.11.42.0 network. An item such as
9008 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
9009 32 for an IPv4 address is the same as no mask at all; just a single address
9012 Here is another example which shows an IPv4 and an IPv6 network:
9014 recipient_unqualified_hosts = 192.168.0.0/16: \
9015 3ffe::ffff::836f::::/48
9017 The doubling of list separator characters applies only when these items
9018 appear inline in a host list. It is not required when indirecting via a file.
9021 recipient_unqualified_hosts = /opt/exim/unqualnets
9023 could make use of a file containing
9028 to have exactly the same effect as the previous example. When listing IPv6
9029 addresses inline, it is usually more convenient to use the facility for
9030 changing separator characters. This list contains the same two networks:
9032 recipient_unqualified_hosts = <; 172.16.0.0/12; \
9035 The separator is changed to semicolon by the leading &"<;"& at the start of the
9041 .section "Host list patterns for single-key lookups by host address" &&&
9042 "SECThoslispatsikey"
9043 .cindex "host list" "lookup of IP address"
9044 When a host is to be identified by a single-key lookup of its complete IP
9045 address, the pattern takes this form:
9047 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9051 hosts_lookup = net-cdb;/hosts-by-ip.db
9053 The text form of the IP address of the subject host is used as the lookup key.
9054 IPv6 addresses are converted to an unabbreviated form, using lower case
9055 letters, with dots as separators because colon is the key terminator in
9056 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9057 quoting the keys, but this is a facility that was added later.] The data
9058 returned by the lookup is not used.
9060 .cindex "IP address" "masking"
9061 .cindex "host list" "masked IP address"
9062 Single-key lookups can also be performed using masked IP addresses, using
9063 patterns of this form:
9065 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9069 net24-dbm;/networks.db
9071 The IP address of the subject host is masked using <&'number'&> as the mask
9072 length. A textual string is constructed from the masked value, followed by the
9073 mask, and this is used as the lookup key. For example, if the host's IP address
9074 is 192.168.34.6, the key that is looked up for the above example is
9075 &"192.168.34.0/24"&.
9077 When an IPv6 address is converted to a string, dots are normally used instead
9078 of colons, so that keys in &(lsearch)& files need not contain colons (which
9079 terminate &(lsearch)& keys). This was implemented some time before the ability
9080 to quote keys was made available in &(lsearch)& files. However, the more
9081 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9082 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9083 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9084 converted using colons and not dots.
9085 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9086 addresses are always used.
9087 The latter are converted to IPv4 addresses, in dotted-quad form.
9089 Ideally, it would be nice to tidy up this anomalous situation by changing to
9090 colons in all cases, given that quoting is now available for &(lsearch)&.
9091 However, this would be an incompatible change that might break some existing
9094 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9095 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9096 the former case the key strings include the mask value, whereas in the latter
9097 case the IP address is used on its own.
9101 .section "Host list patterns that match by host name" "SECThoslispatnam"
9102 .cindex "host" "lookup failures"
9103 .cindex "unknown host name"
9104 .cindex "host list" "matching host name"
9105 There are several types of pattern that require Exim to know the name of the
9106 remote host. These are either wildcard patterns or lookups by name. (If a
9107 complete hostname is given without any wildcarding, it is used to find an IP
9108 address to match against, as described in section &<<SECThoslispatip>>&
9111 If the remote host name is not already known when Exim encounters one of these
9112 patterns, it has to be found from the IP address.
9113 Although many sites on the Internet are conscientious about maintaining reverse
9114 DNS data for their hosts, there are also many that do not do this.
9115 Consequently, a name cannot always be found, and this may lead to unwanted
9116 effects. Take care when configuring host lists with wildcarded name patterns.
9117 Consider what will happen if a name cannot be found.
9119 Because of the problems of determining host names from IP addresses, matching
9120 against host names is not as common as matching against IP addresses.
9122 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9123 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9124 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9125 are done can be changed by setting the &%host_lookup_order%& option. For
9126 security, once Exim has found one or more names, it looks up the IP addresses
9127 for these names and compares them with the IP address that it started with.
9128 Only those names whose IP addresses match are accepted. Any other names are
9129 discarded. If no names are left, Exim behaves as if the host name cannot be
9130 found. In the most common case there is only one name and one IP address.
9132 There are some options that control what happens if a host name cannot be
9133 found. These are described in section &<<SECTbehipnot>>& below.
9135 .cindex "host" "alias for"
9136 .cindex "alias for host"
9137 As a result of aliasing, hosts may have more than one name. When processing any
9138 of the following types of pattern, all the host's names are checked:
9141 .cindex "asterisk" "in host list"
9142 If a pattern starts with &"*"& the remainder of the item must match the end of
9143 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9144 &'.b.c'&. This special simple form is provided because this is a very common
9145 requirement. Other kinds of wildcarding require the use of a regular
9148 .cindex "regular expressions" "in host list"
9149 .cindex "host list" "regular expression in"
9150 If the item starts with &"^"& it is taken to be a regular expression which is
9151 matched against the host name. Host names are case-independent, so this regular
9152 expression match is by default case-independent, but you can make it
9153 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9154 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9159 is a regular expression that matches either of the two hosts &'a.c.d'& or
9160 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9161 that backslash and dollar characters are not misinterpreted as part of the
9162 string expansion. The simplest way to do this is to use &`\N`& to mark that
9163 part of the string as non-expandable. For example:
9165 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9167 &*Warning*&: If you want to match a complete host name, you must include the
9168 &`$`& terminating metacharacter in the regular expression, as in the above
9169 example. Without it, a match at the start of the host name is all that is
9176 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9177 .cindex "host" "lookup failures, permanent"
9178 While processing a host list, Exim may need to look up an IP address from a
9179 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9180 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9181 behaviour when it fails to find the information it is seeking is the same.
9183 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9184 apply to temporary DNS errors, whose handling is described in the next section.
9186 .cindex "&`+include_unknown`&"
9187 .cindex "&`+ignore_unknown`&"
9188 Exim parses a host list from left to right. If it encounters a permanent
9189 lookup failure in any item in the host list before it has found a match,
9190 Exim treats it as a failure and the default behavior is as if the host
9191 does not match the list. This may not always be what you want to happen.
9192 To change Exim's behaviour, the special items &`+include_unknown`& or
9193 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9194 not recognized in an indirected file).
9197 If any item that follows &`+include_unknown`& requires information that
9198 cannot found, Exim behaves as if the host does match the list. For example,
9200 host_reject_connection = +include_unknown:*.enemy.ex
9202 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9203 any hosts whose name it cannot find.
9206 If any item that follows &`+ignore_unknown`& requires information that cannot
9207 be found, Exim ignores that item and proceeds to the rest of the list. For
9210 accept hosts = +ignore_unknown : friend.example : \
9213 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9214 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9215 name can be found for 192.168.4.5, it is rejected.
9218 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9219 list. The effect of each one lasts until the next, or until the end of the
9222 .section "Mixing wildcarded host names and addresses in host lists" &&&
9224 .cindex "host list" "mixing names and addresses in"
9226 This section explains the host/ip processing logic with the same concepts
9227 as the previous section, but specifically addresses what happens when a
9228 wildcarded hostname is one of the items in the hostlist.
9231 If you have name lookups or wildcarded host names and
9232 IP addresses in the same host list, you should normally put the IP
9233 addresses first. For example, in an ACL you could have:
9235 accept hosts = 10.9.8.7 : *.friend.example
9237 The reason you normally would order it this way lies in the
9238 left-to-right way that Exim processes lists. It can test IP addresses
9239 without doing any DNS lookups, but when it reaches an item that requires
9240 a host name, it fails if it cannot find a host name to compare with the
9241 pattern. If the above list is given in the opposite order, the
9242 &%accept%& statement fails for a host whose name cannot be found, even
9243 if its IP address is 10.9.8.7.
9246 If you really do want to do the name check first, and still recognize the IP
9247 address, you can rewrite the ACL like this:
9249 accept hosts = *.friend.example
9250 accept hosts = 10.9.8.7
9252 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9253 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9254 &`+ignore_unknown`&, which was discussed in depth in the first example in
9259 .section "Temporary DNS errors when looking up host information" &&&
9261 .cindex "host" "lookup failures, temporary"
9262 .cindex "&`+include_defer`&"
9263 .cindex "&`+ignore_defer`&"
9264 A temporary DNS lookup failure normally causes a defer action (except when
9265 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9266 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9267 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9268 section. These options should be used with care, probably only in non-critical
9269 host lists such as whitelists.
9273 .section "Host list patterns for single-key lookups by host name" &&&
9274 "SECThoslispatnamsk"
9275 .cindex "unknown host name"
9276 .cindex "host list" "matching host name"
9277 If a pattern is of the form
9279 <&'single-key-search-type'&>;<&'search-data'&>
9283 dbm;/host/accept/list
9285 a single-key lookup is performed, using the host name as its key. If the
9286 lookup succeeds, the host matches the item. The actual data that is looked up
9289 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9290 keys in the file, not IP addresses. If you want to do lookups based on IP
9291 addresses, you must precede the search type with &"net-"& (see section
9292 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9293 two items in the same list, one doing an address lookup and one doing a name
9294 lookup, both using the same file.
9298 .section "Host list patterns for query-style lookups" "SECID81"
9299 If a pattern is of the form
9301 <&'query-style-search-type'&>;<&'query'&>
9303 the query is obeyed, and if it succeeds, the host matches the item. The actual
9304 data that is looked up is not used. The variables &$sender_host_address$& and
9305 &$sender_host_name$& can be used in the query. For example:
9307 hosts_lookup = pgsql;\
9308 select ip from hostlist where ip='$sender_host_address'
9310 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9311 can use the &%sg%& expansion item to change this if you need to. If you want to
9312 use masked IP addresses in database queries, you can use the &%mask%& expansion
9315 If the query contains a reference to &$sender_host_name$&, Exim automatically
9316 looks up the host name if it has not already done so. (See section
9317 &<<SECThoslispatnam>>& for comments on finding host names.)
9319 Historical note: prior to release 4.30, Exim would always attempt to find a
9320 host name before running the query, unless the search type was preceded by
9321 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9322 still recognized for query-style lookups, but its presence or absence has no
9323 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9324 See section &<<SECThoslispatsikey>>&.)
9330 .section "Address lists" "SECTaddresslist"
9331 .cindex "list" "address list"
9332 .cindex "address list" "empty item"
9333 .cindex "address list" "patterns"
9334 Address lists contain patterns that are matched against mail addresses. There
9335 is one special case to be considered: the sender address of a bounce message is
9336 always empty. You can test for this by providing an empty item in an address
9337 list. For example, you can set up a router to process bounce messages by
9338 using this option setting:
9342 The presence of the colon creates an empty item. If you do not provide any
9343 data, the list is empty and matches nothing. The empty sender can also be
9344 detected by a regular expression that matches an empty string,
9345 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9347 Non-empty items in an address list can be straightforward email addresses. For
9350 senders = jbc@askone.example : hs@anacreon.example
9352 A certain amount of wildcarding is permitted. If a pattern contains an @
9353 character, but is not a regular expression and does not begin with a
9354 semicolon-terminated lookup type (described below), the local part of the
9355 subject address is compared with the local part of the pattern, which may start
9356 with an asterisk. If the local parts match, the domain is checked in exactly
9357 the same way as for a pattern in a domain list. For example, the domain can be
9358 wildcarded, refer to a named list, or be a lookup:
9360 deny senders = *@*.spamming.site:\
9361 *@+hostile_domains:\
9362 bozo@partial-lsearch;/list/of/dodgy/sites:\
9363 *@dbm;/bad/domains.db
9365 .cindex "local part" "starting with !"
9366 .cindex "address list" "local part starting with !"
9367 If a local part that begins with an exclamation mark is required, it has to be
9368 specified using a regular expression, because otherwise the exclamation mark is
9369 treated as a sign of negation, as is standard in lists.
9371 If a non-empty pattern that is not a regular expression or a lookup does not
9372 contain an @ character, it is matched against the domain part of the subject
9373 address. The only two formats that are recognized this way are a literal
9374 domain, or a domain pattern that starts with *. In both these cases, the effect
9375 is the same as if &`*@`& preceded the pattern. For example:
9377 deny senders = enemy.domain : *.enemy.domain
9380 The following kinds of more complicated address list pattern can match any
9381 address, including the empty address that is characteristic of bounce message
9385 .cindex "regular expressions" "in address list"
9386 .cindex "address list" "regular expression in"
9387 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9388 done against the complete address, with the pattern as the regular expression.
9389 You must take care that backslash and dollar characters are not misinterpreted
9390 as part of the string expansion. The simplest way to do this is to use &`\N`&
9391 to mark that part of the string as non-expandable. For example:
9393 deny senders = \N^.*this.*@example\.com$\N : \
9394 \N^\d{8}.+@spamhaus.example$\N : ...
9396 The &`\N`& sequences are removed by the expansion, so these items do indeed
9397 start with &"^"& by the time they are being interpreted as address patterns.
9400 .cindex "address list" "lookup for complete address"
9401 Complete addresses can be looked up by using a pattern that starts with a
9402 lookup type terminated by a semicolon, followed by the data for the lookup. For
9405 deny senders = cdb;/etc/blocked.senders : \
9406 mysql;select address from blocked where \
9407 address='${quote_mysql:$sender_address}'
9409 Both query-style and single-key lookup types can be used. For a single-key
9410 lookup type, Exim uses the complete address as the key. However, empty keys are
9411 not supported for single-key lookups, so a match against the empty address
9412 always fails. This restriction does not apply to query-style lookups.
9414 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9415 cannot be used, and is ignored if specified, with an entry being written to the
9417 .cindex "*@ with single-key lookup"
9418 However, you can configure lookup defaults, as described in section
9419 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9420 default. For example, with this lookup:
9422 accept senders = lsearch*@;/some/file
9424 the file could contains lines like this:
9426 user1@domain1.example
9429 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9432 nimrod@jaeger.example
9436 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9437 would mean that every address matches, thus rendering the test useless.
9439 &*Warning 2*&: Do not confuse these two kinds of item:
9441 deny recipients = dbm*@;/some/file
9442 deny recipients = *@dbm;/some/file
9444 The first does a whole address lookup, with defaulting, as just described,
9445 because it starts with a lookup type. The second matches the local part and
9446 domain independently, as described in a bullet point below.
9450 The following kinds of address list pattern can match only non-empty addresses.
9451 If the subject address is empty, a match against any of these pattern types
9456 .cindex "@@ with single-key lookup"
9457 .cindex "address list" "@@ lookup type"
9458 .cindex "address list" "split local part and domain"
9459 If a pattern starts with &"@@"& followed by a single-key lookup item
9460 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9461 split into a local part and a domain. The domain is looked up in the file. If
9462 it is not found, there is no match. If it is found, the data that is looked up
9463 from the file is treated as a colon-separated list of local part patterns, each
9464 of which is matched against the subject local part in turn.
9466 .cindex "asterisk" "in address list"
9467 The lookup may be a partial one, and/or one involving a search for a default
9468 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9469 patterns that are looked up can be regular expressions or begin with &"*"&, or
9470 even be further lookups. They may also be independently negated. For example,
9473 deny senders = @@dbm;/etc/reject-by-domain
9475 the data from which the DBM file is built could contain lines like
9477 baddomain.com: !postmaster : *
9479 to reject all senders except &%postmaster%& from that domain.
9481 .cindex "local part" "starting with !"
9482 If a local part that actually begins with an exclamation mark is required, it
9483 has to be specified using a regular expression. In &(lsearch)& files, an entry
9484 may be split over several lines by indenting the second and subsequent lines,
9485 but the separating colon must still be included at line breaks. White space
9486 surrounding the colons is ignored. For example:
9488 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9491 As in all colon-separated lists in Exim, a colon can be included in an item by
9494 If the last item in the list starts with a right angle-bracket, the remainder
9495 of the item is taken as a new key to look up in order to obtain a continuation
9496 list of local parts. The new key can be any sequence of characters. Thus one
9497 might have entries like
9499 aol.com: spammer1 : spammer 2 : >*
9500 xyz.com: spammer3 : >*
9503 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9504 local parts for all domains, in addition to the specific local parts listed for
9505 each domain. Of course, using this feature costs another lookup each time a
9506 chain is followed, but the effort needed to maintain the data is reduced.
9508 .cindex "loop" "in lookups"
9509 It is possible to construct loops using this facility, and in order to catch
9510 them, the chains may be no more than fifty items long.
9513 The @@<&'lookup'&> style of item can also be used with a query-style
9514 lookup, but in this case, the chaining facility is not available. The lookup
9515 can only return a single list of local parts.
9518 &*Warning*&: There is an important difference between the address list items
9519 in these two examples:
9522 senders = *@+my_list
9524 In the first one, &`my_list`& is a named address list, whereas in the second
9525 example it is a named domain list.
9530 .section "Case of letters in address lists" "SECTcasletadd"
9531 .cindex "case of local parts"
9532 .cindex "address list" "case forcing"
9533 .cindex "case forcing in address lists"
9534 Domains in email addresses are always handled caselessly, but for local parts
9535 case may be significant on some systems (see &%caseful_local_part%& for how
9536 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9537 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9538 blocking lists should be done in a case-independent manner. Since most address
9539 lists in Exim are used for this kind of control, Exim attempts to do this by
9542 The domain portion of an address is always lowercased before matching it to an
9543 address list. The local part is lowercased by default, and any string
9544 comparisons that take place are done caselessly. This means that the data in
9545 the address list itself, in files included as plain filenames, and in any file
9546 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9547 keys in files that are looked up by a search type other than &(lsearch)& (which
9548 works caselessly) must be in lower case, because these lookups are not
9551 .cindex "&`+caseful`&"
9552 To allow for the possibility of caseful address list matching, if an item in
9553 an address list is the string &"+caseful"&, the original case of the local
9554 part is restored for any comparisons that follow, and string comparisons are no
9555 longer case-independent. This does not affect the domain, which remains in
9556 lower case. However, although independent matches on the domain alone are still
9557 performed caselessly, regular expressions that match against an entire address
9558 become case-sensitive after &"+caseful"& has been seen.
9562 .section "Local part lists" "SECTlocparlis"
9563 .cindex "list" "local part list"
9564 .cindex "local part" "list"
9565 These behave in the same way as domain and host lists, with the following
9568 Case-sensitivity in local part lists is handled in the same way as for address
9569 lists, as just described. The &"+caseful"& item can be used if required. In a
9570 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9571 set false, the subject is lowercased and the matching is initially
9572 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9573 matching in the local part list, but not elsewhere in the router. If
9574 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9575 option is case-sensitive from the start.
9577 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9578 comments are handled in the same way as address lists &-- they are recognized
9579 only if the # is preceded by white space or the start of the line.
9580 Otherwise, local part lists are matched in the same way as domain lists, except
9581 that the special items that refer to the local host (&`@`&, &`@[]`&,
9582 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9583 Refer to section &<<SECTdomainlist>>& for details of the other available item
9585 .ecindex IIDdohoadli
9590 . ////////////////////////////////////////////////////////////////////////////
9591 . ////////////////////////////////////////////////////////////////////////////
9593 .chapter "String expansions" "CHAPexpand"
9594 .scindex IIDstrexp "expansion" "of strings"
9595 Many strings in Exim's runtime configuration are expanded before use. Some of
9596 them are expanded every time they are used; others are expanded only once.
9598 When a string is being expanded it is copied verbatim from left to right except
9599 .cindex expansion "string concatenation"
9600 when a dollar or backslash character is encountered. A dollar specifies the
9601 start of a portion of the string that is interpreted and replaced as described
9602 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9603 escape character, as described in the following section.
9605 Whether a string is expanded depends upon the context. Usually this is solely
9606 dependent upon the option for which a value is sought; in this documentation,
9607 options for which string expansion is performed are marked with † after
9608 the data type. ACL rules always expand strings. A couple of expansion
9609 conditions do not expand some of the brace-delimited branches, for security
9611 .cindex "tainted data" expansion
9612 .cindex "tainted data" definition
9613 .cindex expansion "tainted data"
9614 and expansion of data deriving from the sender (&"tainted data"&)
9616 is not permitted (including acessing a file using a tainted name).
9617 The main config option &%allow_insecure_tainted_data%& can be used as
9618 mitigation during uprades to more secure configurations.
9622 Common ways of obtaining untainted equivalents of variables with
9624 .cindex "tainted data" "de-tainting"
9625 come down to using the tainted value as a lookup key in a trusted database.
9626 This database could be the filesystem structure,
9627 or the password file,
9628 or accessed via a DBMS.
9629 Specific methods are indexed under &"de-tainting"&.
9634 .section "Literal text in expanded strings" "SECTlittext"
9635 .cindex "expansion" "including literal text"
9636 An uninterpreted dollar can be included in an expanded string by putting a
9637 backslash in front of it. A backslash can be used to prevent any special
9638 character being treated specially in an expansion, including backslash itself.
9639 If the string appears in quotes in the configuration file, two backslashes are
9640 required because the quotes themselves cause interpretation of backslashes when
9641 the string is read in (see section &<<SECTstrings>>&).
9643 .cindex "expansion" "non-expandable substrings"
9644 A portion of the string can specified as non-expandable by placing it between
9645 two occurrences of &`\N`&. This is particularly useful for protecting regular
9646 expressions, which often contain backslashes and dollar signs. For example:
9648 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9650 On encountering the first &`\N`&, the expander copies subsequent characters
9651 without interpretation until it reaches the next &`\N`& or the end of the
9656 .section "Character escape sequences in expanded strings" "SECID82"
9657 .cindex "expansion" "escape sequences"
9658 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9659 expanded string is recognized as an escape sequence for the character newline,
9660 carriage return, or tab, respectively. A backslash followed by up to three
9661 octal digits is recognized as an octal encoding for a single character, and a
9662 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9665 These escape sequences are also recognized in quoted strings when they are read
9666 in. Their interpretation in expansions as well is useful for unquoted strings,
9667 and for other cases such as looked-up strings that are then expanded.
9670 .section "Testing string expansions" "SECID83"
9671 .cindex "expansion" "testing"
9672 .cindex "testing" "string expansion"
9674 Many expansions can be tested by calling Exim with the &%-be%& option. This
9675 takes the command arguments, or lines from the standard input if there are no
9676 arguments, runs them through the string expansion code, and writes the results
9677 to the standard output. Variables based on configuration values are set up, but
9678 since no message is being processed, variables such as &$local_part$& have no
9679 value. Nevertheless the &%-be%& option can be useful for checking out file and
9680 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9683 Exim gives up its root privilege when it is called with the &%-be%& option, and
9684 instead runs under the uid and gid it was called with, to prevent users from
9685 using &%-be%& for reading files to which they do not have access.
9688 If you want to test expansions that include variables whose values are taken
9689 from a message, there are two other options that can be used. The &%-bem%&
9690 option is like &%-be%& except that it is followed by a filename. The file is
9691 read as a message before doing the test expansions. For example:
9693 exim -bem /tmp/test.message '$h_subject:'
9695 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9696 Exim message identifier. For example:
9698 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9700 This loads the message from Exim's spool before doing the test expansions, and
9701 is therefore restricted to admin users.
9704 .section "Forced expansion failure" "SECTforexpfai"
9705 .cindex "expansion" "forced failure"
9706 A number of expansions that are described in the following section have
9707 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9708 (which are sometimes called &"curly brackets"&). Which of the two strings is
9709 used depends on some condition that is evaluated as part of the expansion. If,
9710 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9711 the entire string expansion fails in a way that can be detected by the code
9712 that requested the expansion. This is called &"forced expansion failure"&, and
9713 its consequences depend on the circumstances. In some cases it is no different
9714 from any other expansion failure, but in others a different action may be
9715 taken. Such variations are mentioned in the documentation of the option that is
9721 .section "Expansion items" "SECTexpansionitems"
9722 The following items are recognized in expanded strings. White space may be used
9723 between sub-items that are keywords or substrings enclosed in braces inside an
9724 outer set of braces, to improve readability. &*Warning*&: Within braces,
9725 white space is significant.
9728 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9729 .cindex "expansion" "variables"
9730 Substitute the contents of the named variable, for example:
9735 The second form can be used to separate the name from subsequent alphanumeric
9736 characters. This form (using braces) is available only for variables; it does
9737 &'not'& apply to message headers. The names of the variables are given in
9738 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9739 given, the expansion fails.
9741 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9742 .cindex "expansion" "operators"
9743 The string is first itself expanded, and then the operation specified by
9744 <&'op'&> is applied to it. For example:
9748 The string starts with the first character after the colon, which may be
9749 leading white space. A list of operators is given in section &<<SECTexpop>>&
9750 below. The operator notation is used for simple expansion items that have just
9751 one argument, because it reduces the number of braces and therefore makes the
9752 string easier to understand.
9754 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9755 This item inserts &"basic"& header lines. It is described with the &%header%&
9756 expansion item below.
9759 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9760 .cindex "expansion" "calling an acl"
9761 .cindex "&%acl%&" "call from expansion"
9762 The name and zero to nine argument strings are first expanded separately. The expanded
9763 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9764 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9765 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9766 and may use the variables; if another acl expansion is used the values
9767 are restored after it returns. If the ACL sets
9768 a value using a "message =" modifier and returns accept or deny, the value becomes
9769 the result of the expansion.
9770 If no message is set and the ACL returns accept or deny
9771 the expansion result is an empty string.
9772 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9775 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9776 .cindex authentication "results header"
9777 .chindex Authentication-Results:
9778 .cindex authentication "expansion item"
9779 This item returns a string suitable for insertion as an
9780 &'Authentication-Results:'&
9782 The given <&'authserv-id'&> is included in the result; typically this
9783 will be a domain name identifying the system performing the authentications.
9784 Methods that might be present in the result include:
9793 Example use (as an ACL modifier):
9795 add_header = :at_start:${authresults {$primary_hostname}}
9797 This is safe even if no authentication results are available.
9800 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9801 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9802 .cindex "expansion" "extracting certificate fields"
9803 .cindex "&%certextract%&" "certificate fields"
9804 .cindex "certificate" "extracting fields"
9805 The <&'certificate'&> must be a variable of type certificate.
9806 The field name is expanded and used to retrieve the relevant field from
9807 the certificate. Supported fields are:
9811 &`subject `& RFC4514 DN
9812 &`issuer `& RFC4514 DN
9817 &`subj_altname `& tagged list
9821 If the field is found,
9822 <&'string2'&> is expanded, and replaces the whole item;
9823 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9824 variable &$value$& contains the value that has been extracted. Afterwards, it
9825 is restored to any previous value it might have had.
9827 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9828 key is not found. If {<&'string2'&>} is also omitted, the value that was
9831 Some field names take optional modifiers, appended and separated by commas.
9833 The field selectors marked as "RFC4514" above
9834 output a Distinguished Name string which is
9836 parseable by Exim as a comma-separated tagged list
9837 (the exceptions being elements containing commas).
9838 RDN elements of a single type may be selected by
9839 a modifier of the type label; if so the expansion
9840 result is a list (newline-separated by default).
9841 The separator may be changed by another modifier of
9842 a right angle-bracket followed immediately by the new separator.
9843 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9845 The field selectors marked as "time" above
9846 take an optional modifier of "int"
9847 for which the result is the number of seconds since epoch.
9848 Otherwise the result is a human-readable string
9849 in the timezone selected by the main "timezone" option.
9851 The field selectors marked as "list" above return a list,
9852 newline-separated by default,
9853 (embedded separator characters in elements are doubled).
9854 The separator may be changed by a modifier of
9855 a right angle-bracket followed immediately by the new separator.
9857 The field selectors marked as "tagged" above
9858 prefix each list element with a type string and an equals sign.
9859 Elements of only one type may be selected by a modifier
9860 which is one of "dns", "uri" or "mail";
9861 if so the element tags are omitted.
9863 If not otherwise noted field values are presented in human-readable form.
9865 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9866 {*&<&'arg'&>&*}...}*&"
9868 This expansion dynamically loads and then calls a locally-written C function.
9869 This functionality is available only if Exim is compiled with
9873 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9874 object so that it doesn't reload the same object file in the same Exim process
9875 (but of course Exim does start new processes frequently).
9877 There may be from zero to eight arguments to the function.
9880 a local function that is to be called in this way,
9881 first &_DLFUNC_IMPL_& should be defined,
9882 and second &_local_scan.h_& should be included.
9883 The Exim variables and functions that are defined by that API
9884 are also available for dynamically loaded functions. The function itself
9885 must have the following type:
9887 int dlfunction(uschar **yield, int argc, uschar *argv[])
9889 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9890 function should return one of the following values:
9892 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9893 into the expanded string that is being built.
9895 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9896 from &'yield'&, if it is set.
9898 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9899 taken from &'yield'& if it is set.
9901 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9903 When compiling a function that is to be used in this way with gcc,
9904 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9905 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9908 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9909 .cindex "expansion" "extracting value from environment"
9910 .cindex "environment" "values from"
9911 The key is first expanded separately, and leading and trailing white space
9913 This is then searched for as a name in the environment.
9914 If a variable is found then its value is placed in &$value$&
9915 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9917 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9918 appear, for example:
9920 ${env{USER}{$value} fail }
9922 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9923 {<&'string1'&>} must be present for &"fail"& to be recognized.
9925 If {<&'string2'&>} is omitted an empty string is substituted on
9927 If {<&'string1'&>} is omitted the search result is substituted on
9930 The environment is adjusted by the &%keep_environment%& and
9931 &%add_environment%& main section options.
9934 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9935 {*&<&'string3'&>&*}}*&"
9936 .cindex "expansion" "extracting substrings by key"
9937 .cindex "&%extract%&" "substrings by key"
9938 The key and <&'string1'&> are first expanded separately. Leading and trailing
9939 white space is removed from the key (but not from any of the strings). The key
9940 must not be empty and must not consist entirely of digits.
9941 The expanded <&'string1'&> must be of the form:
9943 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9946 where the equals signs and spaces (but not both) are optional. If any of the
9947 values contain white space, they must be enclosed in double quotes, and any
9948 values that are enclosed in double quotes are subject to escape processing as
9949 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9950 for the value that corresponds to the key. The search is case-insensitive. If
9951 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9952 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9953 variable &$value$& contains the value that has been extracted. Afterwards, it
9954 is restored to any previous value it might have had.
9956 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9957 key is not found. If {<&'string2'&>} is also omitted, the value that was
9958 extracted is used. Thus, for example, these two expansions are identical, and
9961 ${extract{gid}{uid=1984 gid=2001}}
9962 ${extract{gid}{uid=1984 gid=2001}{$value}}
9964 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9965 appear, for example:
9967 ${extract{Z}{A=... B=...}{$value} fail }
9969 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9970 {<&'string2'&>} must be present for &"fail"& to be recognized.
9972 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9973 {*&<&'string3'&>&*}}*&" &&&
9974 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9975 {*&<&'string3'&>&*}}*&"
9976 .cindex "expansion" "extracting from JSON object"
9977 .cindex JSON expansions
9978 The key and <&'string1'&> are first expanded separately. Leading and trailing
9979 white space is removed from the key (but not from any of the strings). The key
9980 must not be empty and must not consist entirely of digits.
9981 The expanded <&'string1'&> must be of the form:
9983 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9986 The braces, commas and colons, and the quoting of the member name are required;
9987 the spaces are optional.
9988 Matching of the key against the member names is done case-sensitively.
9989 For the &"json"& variant,
9990 if a returned value is a JSON string, it retains its leading and
9992 For the &"jsons"& variant, which is intended for use with JSON strings, the
9993 leading and trailing quotes are removed from the returned value.
9994 . XXX should be a UTF-8 compare
9996 The results of matching are handled as above.
9999 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
10000 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10001 .cindex "expansion" "extracting substrings by number"
10002 .cindex "&%extract%&" "substrings by number"
10003 The <&'number'&> argument must consist entirely of decimal digits,
10004 apart from leading and trailing white space, which is ignored.
10005 This is what distinguishes this form of &%extract%& from the previous kind. It
10006 behaves in the same way, except that, instead of extracting a named field, it
10007 extracts from <&'string1'&> the field whose number is given as the first
10008 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
10009 <&'string3'&> as before.
10011 The fields in the string are separated by any one of the characters in the
10012 separator string. These may include space or tab characters.
10013 The first field is numbered one. If the number is negative, the fields are
10014 counted from the end of the string, with the rightmost one numbered -1. If the
10015 number given is zero, the entire string is returned. If the modulus of the
10016 number is greater than the number of fields in the string, the result is the
10017 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
10018 provided. For example:
10020 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
10024 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
10026 yields &"99"&. Two successive separators mean that the field between them is
10027 empty (for example, the fifth field above).
10030 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
10031 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
10032 "&*${extract jsons{*&<&'number'&>&*}}&&&
10033 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10034 .cindex "expansion" "extracting from JSON array"
10035 .cindex JSON expansions
10036 The <&'number'&> argument must consist entirely of decimal digits,
10037 apart from leading and trailing white space, which is ignored.
10039 Field selection and result handling is as above;
10040 there is no choice of field separator.
10041 For the &"json"& variant,
10042 if a returned value is a JSON string, it retains its leading and
10044 For the &"jsons"& variant, which is intended for use with JSON strings, the
10045 leading and trailing quotes are removed from the returned value.
10048 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
10049 .cindex "list" "selecting by condition"
10050 .cindex "expansion" "selecting from list by condition"
10052 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10053 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10055 in this list, its value is place in &$item$&, and then the condition is
10056 evaluated. If the condition is true, &$item$& is added to the output as an
10057 item in a new list; if the condition is false, the item is discarded. The
10058 separator used for the output list is the same as the one used for the
10059 input, but a separator setting is not included in the output. For example:
10061 ${filter{a:b:c}{!eq{$item}{b}}}
10063 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10064 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10067 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10068 .cindex "hash function" "textual"
10069 .cindex "expansion" "textual hash"
10070 This is a textual hashing function, and was the first to be implemented in
10071 early versions of Exim. In current releases, there are other hashing functions
10072 (numeric, MD5, and SHA-1), which are described below.
10074 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10075 <&'n'&>. If you are using fixed values for these numbers, that is, if
10076 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10077 use the simpler operator notation that avoids some of the braces:
10079 ${hash_<n>_<m>:<string>}
10081 The second number is optional (in both notations). If <&'n'&> is greater than
10082 or equal to the length of the string, the expansion item returns the string.
10083 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10084 function to the string. The new string consists of characters taken from the
10085 first <&'m'&> characters of the string
10087 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10089 If <&'m'&> is not present the value 26 is used, so that only lower case
10090 letters appear. For example:
10092 &`$hash{3}{monty}} `& yields &`jmg`&
10093 &`$hash{5}{monty}} `& yields &`monty`&
10094 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10097 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10098 &*$h_*&<&'header&~name'&>&*:*&" &&&
10099 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10100 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10101 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10102 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10103 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10104 &*$rh_*&<&'header&~name'&>&*:*&"
10105 .cindex "expansion" "header insertion"
10106 .vindex "&$header_$&"
10107 .vindex "&$bheader_$&"
10108 .vindex "&$lheader_$&"
10109 .vindex "&$rheader_$&"
10110 .cindex "header lines" "in expansion strings"
10111 .cindex "header lines" "character sets"
10112 .cindex "header lines" "decoding"
10113 Substitute the contents of the named message header line, for example
10117 The newline that terminates a header line is not included in the expansion, but
10118 internal newlines (caused by splitting the header line over several physical
10119 lines) may be present.
10121 The difference between the four pairs of expansions is in the way
10122 the data in the header line is interpreted.
10125 .cindex "white space" "in header lines"
10126 &%rheader%& gives the original &"raw"& content of the header line, with no
10127 processing at all, and without the removal of leading and trailing white space.
10130 .cindex "list" "of header lines"
10131 &%lheader%& gives a colon-separated list, one element per header when there
10132 are multiple headers with a given name.
10133 Any embedded colon characters within an element are doubled, so normal Exim
10134 list-processing facilities can be used.
10135 The terminating newline of each element is removed; in other respects
10136 the content is &"raw"&.
10139 .cindex "base64 encoding" "in header lines"
10140 &%bheader%& removes leading and trailing white space, and then decodes base64
10141 or quoted-printable MIME &"words"& within the header text, but does no
10142 character set translation. If decoding of what looks superficially like a MIME
10143 &"word"& fails, the raw string is returned. If decoding
10144 .cindex "binary zero" "in header line"
10145 produces a binary zero character, it is replaced by a question mark &-- this is
10146 what Exim does for binary zeros that are actually received in header lines.
10149 &%header%& tries to translate the string as decoded by &%bheader%& to a
10150 standard character set. This is an attempt to produce the same string as would
10151 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10152 returned. Translation is attempted only on operating systems that support the
10153 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10154 a system Makefile or in &_Local/Makefile_&.
10157 In a filter file, the target character set for &%header%& can be specified by a
10158 command of the following form:
10160 headers charset "UTF-8"
10162 This command affects all references to &$h_$& (or &$header_$&) expansions in
10163 subsequently obeyed filter commands. In the absence of this command, the target
10164 character set in a filter is taken from the setting of the &%headers_charset%&
10165 option in the runtime configuration. The value of this option defaults to the
10166 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10169 Header names follow the syntax of RFC 2822, which states that they may contain
10170 any printing characters except space and colon. Consequently, curly brackets
10171 &'do not'& terminate header names, and should not be used to enclose them as
10172 if they were variables. Attempting to do so causes a syntax error.
10174 Only header lines that are common to all copies of a message are visible to
10175 this mechanism. These are the original header lines that are received with the
10176 message, and any that are added by an ACL statement or by a system
10177 filter. Header lines that are added to a particular copy of a message by a
10178 router or transport are not accessible.
10180 For incoming SMTP messages, no header lines are visible in
10181 ACLs that are obeyed before the data phase completes,
10182 because the header structure is not set up until the message is received.
10183 They are visible in DKIM, PRDR and DATA ACLs.
10184 Header lines that are added in a RCPT ACL (for example)
10185 are saved until the message's incoming header lines are available, at which
10186 point they are added.
10187 When any of the above ACLs are
10188 running, however, header lines added by earlier ACLs are visible.
10190 Upper case and lower case letters are synonymous in header names. If the
10191 following character is white space, the terminating colon may be omitted, but
10192 this is not recommended, because you may then forget it when it is needed. When
10193 white space terminates the header name, this white space is included in the
10194 expanded string. If the message does not contain the given header, the
10195 expansion item is replaced by an empty string. (See the &%def%& condition in
10196 section &<<SECTexpcond>>& for a means of testing for the existence of a
10199 If there is more than one header with the same name, they are all concatenated
10200 to form the substitution string, up to a maximum length of 64K. Unless
10201 &%rheader%& is being used, leading and trailing white space is removed from
10202 each header before concatenation, and a completely empty header is ignored. A
10203 newline character is then inserted between non-empty headers, but there is no
10204 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10205 those headers that contain lists of addresses, a comma is also inserted at the
10206 junctions between headers. This does not happen for the &%rheader%& expansion.
10208 .cindex "tainted data" "message headers"
10209 When the headers are from an incoming message,
10210 the result of expanding any of these variables is tainted.
10213 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10214 .cindex "expansion" "hmac hashing"
10216 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10217 shared secret and some text into a message authentication code, as specified in
10218 RFC 2104. This differs from &`${md5:secret_text...}`& or
10219 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10220 cryptographic hash, allowing for authentication that is not possible with MD5
10221 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10222 present. For example:
10224 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10226 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10229 dd97e3ba5d1a61b5006108f8c8252953
10231 As an example of how this might be used, you might put in the main part of
10232 an Exim configuration:
10234 SPAMSCAN_SECRET=cohgheeLei2thahw
10236 In a router or a transport you could then have:
10239 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10240 ${hmac{md5}{SPAMSCAN_SECRET}\
10241 {${primary_hostname},${message_exim_id},$h_message-id:}}
10243 Then given a message, you can check where it was scanned by looking at the
10244 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10245 this header line is authentic by recomputing the authentication code from the
10246 host name, message ID and the &'Message-id:'& header line. This can be done
10247 using Exim's &%-be%& option, or by other means, for example, by using the
10248 &'hmac_md5_hex()'& function in Perl.
10251 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10252 .cindex "expansion" "conditional"
10253 .cindex "&%if%&, expansion item"
10254 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10255 item; otherwise <&'string2'&> is used. The available conditions are described
10256 in section &<<SECTexpcond>>& below. For example:
10258 ${if eq {$local_part}{postmaster} {yes}{no} }
10260 The second string need not be present; if it is not and the condition is not
10261 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10262 be present instead of the second string (without any curly brackets). In this
10263 case, the expansion is forced to fail if the condition is not true (see section
10264 &<<SECTforexpfai>>&).
10266 If both strings are omitted, the result is the string &`true`& if the condition
10267 is true, and the empty string if the condition is false. This makes it less
10268 cumbersome to write custom ACL and router conditions. For example, instead of
10270 condition = ${if >{$acl_m4}{3}{true}{false}}
10274 condition = ${if >{$acl_m4}{3}}
10279 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10280 .cindex expansion "imap folder"
10281 .cindex "&%imapfolder%& expansion item"
10282 This item converts a (possibly multilevel, or with non-ASCII characters)
10283 folder specification to a Maildir name for filesystem use.
10284 For information on internationalisation support see &<<SECTi18nMDA>>&.
10288 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10289 .cindex "expansion" "string truncation"
10290 .cindex "&%length%& expansion item"
10291 The &%length%& item is used to extract the initial portion of a string. Both
10292 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10293 you are using a fixed value for the number, that is, if <&'string1'&> does not
10294 change when expanded, you can use the simpler operator notation that avoids
10295 some of the braces:
10297 ${length_<n>:<string>}
10299 The result of this item is either the first <&'n'&> bytes or the whole
10300 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10301 &%strlen%&, which gives the length of a string.
10302 All measurement is done in bytes and is not UTF-8 aware.
10305 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10306 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10307 .cindex "expansion" "extracting list elements by number"
10308 .cindex "&%listextract%&" "extract list elements by number"
10309 .cindex "list" "extracting elements by number"
10310 The <&'number'&> argument must consist entirely of decimal digits,
10311 apart from an optional leading minus,
10312 and leading and trailing white space (which is ignored).
10314 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10315 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10317 The first field of the list is numbered one.
10318 If the number is negative, the fields are
10319 counted from the end of the list, with the rightmost one numbered -1.
10320 The numbered element of the list is extracted and placed in &$value$&,
10321 then <&'string2'&> is expanded as the result.
10323 If the modulus of the
10324 number is zero or greater than the number of fields in the string,
10325 the result is the expansion of <&'string3'&>.
10329 ${listextract{2}{x:42:99}}
10333 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10335 yields &"result: 42"&.
10337 If {<&'string3'&>} is omitted, an empty string is used for string3.
10338 If {<&'string2'&>} is also omitted, the value that was
10340 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10344 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10345 .cindex quoting "for list"
10346 .cindex list quoting
10347 This item doubles any occurrence of the separator character
10348 in the given string.
10349 An empty string is replaced with a single space.
10350 This converts the string into a safe form for use as a list element,
10351 in a list using the given separator.
10355 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10356 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10357 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10358 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10359 .cindex "expansion" "lookup in"
10360 .cindex "file" "lookups"
10361 .cindex "lookup" "in expanded string"
10362 The two forms of lookup item specify data lookups in files and databases, as
10363 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10364 lookups, and the second is used for query-style lookups. The <&'key'&>,
10365 <&'file'&>, and <&'query'&> strings are expanded before use.
10367 If there is any white space in a lookup item which is part of a filter command,
10368 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10369 other place where white space is significant, the lookup item must be enclosed
10370 in double quotes. The use of data lookups in users' filter files may be locked
10371 out by the system administrator.
10373 .vindex "&$value$&"
10374 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10375 During its expansion, the variable &$value$& contains the data returned by the
10376 lookup. Afterwards it reverts to the value it had previously (at the outer
10377 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10378 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10379 string on failure. If <&'string2'&> is provided, it can itself be a nested
10380 lookup, thus providing a mechanism for looking up a default value when the
10381 original lookup fails.
10383 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10384 data for the outer lookup while the parameters of the second lookup are
10385 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10386 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10387 appear, and in this case, if the lookup fails, the entire expansion is forced
10388 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10389 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10390 successful lookup, and nothing in the case of failure.
10392 For single-key lookups, the string &"partial"& is permitted to precede the
10393 search type in order to do partial matching, and * or *@ may follow a search
10394 type to request default lookups if the key does not match (see sections
10395 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10397 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10398 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10399 and non-wild parts of the key during the expansion of the replacement text.
10400 They return to their previous values at the end of the lookup item.
10402 This example looks up the postmaster alias in the conventional alias file:
10404 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10406 This example uses NIS+ to look up the full name of the user corresponding to
10407 the local part of an address, forcing the expansion to fail if it is not found:
10409 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10414 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10415 .cindex "expansion" "list creation"
10417 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10418 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10420 in this list, its value is place in &$item$&, and then <&'string2'&> is
10421 expanded and added to the output as an item in a new list. The separator used
10422 for the output list is the same as the one used for the input, but a separator
10423 setting is not included in the output. For example:
10425 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10427 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10428 value of &$item$& is restored to what it was before. See also the &%filter%&
10429 and &%reduce%& expansion items.
10431 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10432 .cindex "expansion" "numeric hash"
10433 .cindex "hash function" "numeric"
10434 The three strings are expanded; the first two must yield numbers. Call them
10435 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10436 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10437 can use the simpler operator notation that avoids some of the braces:
10439 ${nhash_<n>_<m>:<string>}
10441 The second number is optional (in both notations). If there is only one number,
10442 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10443 processed by a div/mod hash function that returns two numbers, separated by a
10444 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10447 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10449 returns the string &"6/33"&.
10453 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10454 .cindex "Perl" "use in expanded string"
10455 .cindex "expansion" "calling Perl from"
10456 This item is available only if Exim has been built to include an embedded Perl
10457 interpreter. The subroutine name and the arguments are first separately
10458 expanded, and then the Perl subroutine is called with those arguments. No
10459 additional arguments need be given; the maximum number permitted, including the
10460 name of the subroutine, is nine.
10462 The return value of the subroutine is inserted into the expanded string, unless
10463 the return value is &%undef%&. In that case, the entire expansion is
10464 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10465 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10466 in a scalar context, thus the return value is a scalar. For example, if you
10467 return a Perl vector, the return value is the size of the vector,
10470 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10471 with the error message that was passed to &%die%&. More details of the embedded
10472 Perl facility are given in chapter &<<CHAPperl>>&.
10474 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10475 out the use of this expansion item in filter files.
10478 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10479 .cindex "&%prvs%& expansion item"
10480 The first argument is a complete email address and the second is secret
10481 keystring. The third argument, specifying a key number, is optional. If absent,
10482 it defaults to 0. The result of the expansion is a prvs-signed email address,
10483 to be typically used with the &%return_path%& option on an &(smtp)& transport
10484 as part of a bounce address tag validation (BATV) scheme. For more discussion
10485 and an example, see section &<<SECTverifyPRVS>>&.
10487 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10488 {*&<&'string'&>&*}}*&"
10489 .cindex "&%prvscheck%& expansion item"
10490 This expansion item is the complement of the &%prvs%& item. It is used for
10491 checking prvs-signed addresses. If the expansion of the first argument does not
10492 yield a syntactically valid prvs-signed address, the whole item expands to the
10493 empty string. When the first argument does expand to a syntactically valid
10494 prvs-signed address, the second argument is expanded, with the prvs-decoded
10495 version of the address and the key number extracted from the address in the
10496 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10498 These two variables can be used in the expansion of the second argument to
10499 retrieve the secret. The validity of the prvs-signed address is then checked
10500 against the secret. The result is stored in the variable &$prvscheck_result$&,
10501 which is empty for failure or &"1"& for success.
10503 The third argument is optional; if it is missing, it defaults to an empty
10504 string. This argument is now expanded. If the result is an empty string, the
10505 result of the expansion is the decoded version of the address. This is the case
10506 whether or not the signature was valid. Otherwise, the result of the expansion
10507 is the expansion of the third argument.
10509 All three variables can be used in the expansion of the third argument.
10510 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10511 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10513 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10514 .cindex "expansion" "inserting an entire file"
10515 .cindex "file" "inserting into expansion"
10516 .cindex "&%readfile%& expansion item"
10517 The filename and end-of-line (eol) string are first expanded separately. The file is
10518 then read, and its contents replace the entire item. All newline characters in
10519 the file are replaced by the end-of-line string if it is present. Otherwise,
10520 newlines are left in the string.
10521 String expansion is not applied to the contents of the file. If you want this,
10522 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10523 the string expansion fails.
10525 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10526 locks out the use of this expansion item in filter files.
10530 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10531 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10532 .cindex "expansion" "inserting from a socket"
10533 .cindex "socket, use of in expansion"
10534 .cindex "&%readsocket%& expansion item"
10535 This item inserts data from a Unix domain or TCP socket into the expanded
10536 string. The minimal way of using it uses just two arguments, as in these
10539 ${readsocket{/socket/name}{request string}}
10540 ${readsocket{inet:some.host:1234}{request string}}
10542 For a Unix domain socket, the first substring must be the path to the socket.
10543 For an Internet socket, the first substring must contain &`inet:`& followed by
10544 a host name or IP address, followed by a colon and a port, which can be a
10545 number or the name of a TCP port in &_/etc/services_&. An IP address may
10546 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10549 ${readsocket{inet:[::1]:1234}{request string}}
10551 Only a single host name may be given, but if looking it up yields more than
10552 one IP address, they are each tried in turn until a connection is made. For
10553 both kinds of socket, Exim makes a connection, writes the request string
10554 (unless it is an empty string; no terminating NUL is ever sent)
10555 and reads from the socket until an end-of-file
10556 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10557 extend what can be done. Firstly, you can vary the timeout. For example:
10559 ${readsocket{/socket/name}{request string}{3s}}
10562 The third argument is a list of options, of which the first element is the timeout
10563 and must be present if any options are given.
10564 Further elements are options of form &'name=value'&.
10567 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10570 The following option names are recognised:
10573 Defines if the result data can be cached for use by a later identical
10574 request in the same process.
10575 Values are &"yes"& or &"no"& (the default).
10576 If not, all cached results for this connection specification
10577 will be invalidated.
10581 Defines whether or not a write-shutdown is done on the connection after
10582 sending the request. Values are &"yes"& (the default) or &"no"&
10583 (preferred, eg. by some webservers).
10587 Controls the use of TLS on the connection.
10588 Values are &"yes"& or &"no"& (the default).
10589 If it is enabled, a shutdown as descripbed above is never done.
10593 A fourth argument allows you to change any newlines that are in the data
10594 that is read, in the same way as for &%readfile%& (see above). This example
10595 turns them into spaces:
10597 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10599 As with all expansions, the substrings are expanded before the processing
10600 happens. Errors in these sub-expansions cause the expansion to fail. In
10601 addition, the following errors can occur:
10604 Failure to create a socket file descriptor;
10606 Failure to connect the socket;
10608 Failure to write the request string;
10610 Timeout on reading from the socket.
10613 By default, any of these errors causes the expansion to fail. However, if
10614 you supply a fifth substring, it is expanded and used when any of the above
10615 errors occurs. For example:
10617 ${readsocket{/socket/name}{request string}{3s}{\n}\
10620 You can test for the existence of a Unix domain socket by wrapping this
10621 expansion in &`${if exists`&, but there is a race condition between that test
10622 and the actual opening of the socket, so it is safer to use the fifth argument
10623 if you want to be absolutely sure of avoiding an expansion error for a
10624 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10626 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10627 locks out the use of this expansion item in filter files.
10630 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10631 .cindex "expansion" "reducing a list to a scalar"
10632 .cindex "list" "reducing to a scalar"
10633 .vindex "&$value$&"
10635 This operation reduces a list to a single, scalar string. After expansion,
10636 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10637 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10638 Then <&'string2'&> is expanded and
10639 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10640 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10641 them. The result of that expansion is assigned to &$value$& before the next
10642 iteration. When the end of the list is reached, the final value of &$value$& is
10643 added to the expansion output. The &%reduce%& expansion item can be used in a
10644 number of ways. For example, to add up a list of numbers:
10646 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10648 The result of that expansion would be &`6`&. The maximum of a list of numbers
10651 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10653 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10654 restored to what they were before. See also the &%filter%& and &%map%&
10657 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10658 This item inserts &"raw"& header lines. It is described with the &%header%&
10659 expansion item in section &<<SECTexpansionitems>>& above.
10661 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10662 {*&<&'string2'&>&*}}*&"
10663 .cindex "expansion" "running a command"
10664 .cindex "&%run%& expansion item"
10665 The command and its arguments are first expanded as one string. The string is
10666 split apart into individual arguments by spaces, and then the command is run
10667 in a separate process, but under the same uid and gid. As in other command
10668 executions from Exim, a shell is not used by default. If the command requires
10669 a shell, you must explicitly code it.
10671 Since the arguments are split by spaces, when there is a variable expansion
10672 which has an empty result, it will cause the situation that the argument will
10673 simply be omitted when the program is actually executed by Exim. If the
10674 script/program requires a specific number of arguments and the expanded
10675 variable could possibly result in this empty expansion, the variable must be
10676 quoted. This is more difficult if the expanded variable itself could result
10677 in a string containing quotes, because it would interfere with the quotes
10678 around the command arguments. A possible guard against this is to wrap the
10679 variable in the &%sg%& operator to change any quote marks to some other
10682 The standard input for the command exists, but is empty. The standard output
10683 and standard error are set to the same file descriptor.
10684 .cindex "return code" "from &%run%& expansion"
10685 .vindex "&$value$&"
10686 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10687 and replaces the entire item; during this expansion, the standard output/error
10688 from the command is in the variable &$value$&. If the command fails,
10689 <&'string2'&>, if present, is expanded and used. Once again, during the
10690 expansion, the standard output/error from the command is in the variable
10693 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10694 can be the word &"fail"& (not in braces) to force expansion failure if the
10695 command does not succeed. If both strings are omitted, the result is contents
10696 of the standard output/error on success, and nothing on failure.
10698 .vindex "&$run_in_acl$&"
10699 The standard output/error of the command is put in the variable &$value$&.
10700 In this ACL example, the output of a command is logged for the admin to
10703 warn condition = ${run{/usr/bin/id}{yes}{no}}
10704 log_message = Output of id: $value
10706 If the command requires shell idioms, such as the > redirect operator, the
10707 shell must be invoked directly, such as with:
10709 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10712 .vindex "&$runrc$&"
10713 The return code from the command is put in the variable &$runrc$&, and this
10714 remains set afterwards, so in a filter file you can do things like this:
10716 if "${run{x y z}{}}$runrc" is 1 then ...
10717 elif $runrc is 2 then ...
10721 If execution of the command fails (for example, the command does not exist),
10722 the return code is 127 &-- the same code that shells use for non-existent
10725 &*Warning*&: In a router or transport, you cannot assume the order in which
10726 option values are expanded, except for those preconditions whose order of
10727 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10728 by the expansion of one option, and use it in another.
10730 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10731 out the use of this expansion item in filter files.
10734 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10735 .cindex "expansion" "string substitution"
10736 .cindex "&%sg%& expansion item"
10737 This item works like Perl's substitution operator (s) with the global (/g)
10738 option; hence its name. However, unlike the Perl equivalent, Exim does not
10739 modify the subject string; instead it returns the modified string for insertion
10740 into the overall expansion. The item takes three arguments: the subject string,
10741 a regular expression, and a substitution string. For example:
10743 ${sg{abcdefabcdef}{abc}{xyz}}
10745 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10746 if any $, } or \ characters are required in the regular expression or in the
10747 substitution string, they have to be escaped. For example:
10749 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10751 yields &"defabc"&, and
10753 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10755 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10756 the regular expression from string expansion.
10758 The regular expression is compiled in 8-bit mode, working against bytes
10759 rather than any Unicode-aware character handling.
10762 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10763 .cindex sorting "a list"
10764 .cindex list sorting
10765 .cindex expansion "list sorting"
10766 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10767 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10768 The <&'comparator'&> argument is interpreted as the operator
10769 of a two-argument expansion condition.
10770 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10771 The comparison should return true when applied to two values
10772 if the first value should sort before the second value.
10773 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10774 the element being placed in &$item$&,
10775 to give values for comparison.
10777 The item result is a sorted list,
10778 with the original list separator,
10779 of the list elements (in full) of the original.
10783 ${sort{3:2:1:4}{<}{$item}}
10785 sorts a list of numbers, and
10787 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10789 will sort an MX lookup into priority order.
10794 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10795 SRS encoding. See SECT &<<SECTSRS>>& for details.
10800 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10801 .cindex "&%substr%& expansion item"
10802 .cindex "substring extraction"
10803 .cindex "expansion" "substring extraction"
10804 The three strings are expanded; the first two must yield numbers. Call them
10805 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10806 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10807 can use the simpler operator notation that avoids some of the braces:
10809 ${substr_<n>_<m>:<string>}
10811 The second number is optional (in both notations).
10812 If it is absent in the simpler format, the preceding underscore must also be
10815 The &%substr%& item can be used to extract more general substrings than
10816 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10817 length required. For example
10819 ${substr{3}{2}{$local_part}}
10821 If the starting offset is greater than the string length the result is the
10822 null string; if the length plus starting offset is greater than the string
10823 length, the result is the right-hand part of the string, starting from the
10824 given offset. The first byte (character) in the string has offset zero.
10826 The &%substr%& expansion item can take negative offset values to count
10827 from the right-hand end of its operand. The last byte (character) is offset -1,
10828 the second-last is offset -2, and so on. Thus, for example,
10830 ${substr{-5}{2}{1234567}}
10832 yields &"34"&. If the absolute value of a negative offset is greater than the
10833 length of the string, the substring starts at the beginning of the string, and
10834 the length is reduced by the amount of overshoot. Thus, for example,
10836 ${substr{-5}{2}{12}}
10838 yields an empty string, but
10840 ${substr{-3}{2}{12}}
10844 When the second number is omitted from &%substr%&, the remainder of the string
10845 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10846 string preceding the offset point are taken. For example, an offset of -1 and
10847 no length, as in these semantically identical examples:
10850 ${substr{-1}{abcde}}
10852 yields all but the last character of the string, that is, &"abcd"&.
10854 All measurement is done in bytes and is not UTF-8 aware.
10858 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10859 {*&<&'replacements'&>&*}}*&"
10860 .cindex "expansion" "character translation"
10861 .cindex "&%tr%& expansion item"
10862 This item does single-character (in bytes) translation on its subject string. The second
10863 argument is a list of characters to be translated in the subject string. Each
10864 matching character is replaced by the corresponding character from the
10865 replacement list. For example
10867 ${tr{abcdea}{ac}{13}}
10869 yields &`1b3de1`&. If there are duplicates in the second character string, the
10870 last occurrence is used. If the third string is shorter than the second, its
10871 last character is replicated. However, if it is empty, no translation takes
10874 All character handling is done in bytes and is not UTF-8 aware.
10880 .section "Expansion operators" "SECTexpop"
10881 .cindex "expansion" "operators"
10882 For expansion items that perform transformations on a single argument string,
10883 the &"operator"& notation is used because it is simpler and uses fewer braces.
10884 The substring is first expanded before the operation is applied to it. The
10885 following operations can be performed:
10888 .vitem &*${address:*&<&'string'&>&*}*&
10889 .cindex "expansion" "RFC 2822 address handling"
10890 .cindex "&%address%& expansion item"
10891 The string is interpreted as an RFC 2822 address, as it might appear in a
10892 header line, and the effective address is extracted from it. If the string does
10893 not parse successfully, the result is empty.
10895 The parsing correctly handles SMTPUTF8 Unicode in the string.
10898 .vitem &*${addresses:*&<&'string'&>&*}*&
10899 .cindex "expansion" "RFC 2822 address handling"
10900 .cindex "&%addresses%& expansion item"
10901 The string (after expansion) is interpreted as a list of addresses in RFC
10902 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10903 operative address (&'local-part@domain'&) is extracted from each item, and the
10904 result of the expansion is a colon-separated list, with appropriate
10905 doubling of colons should any happen to be present in the email addresses.
10906 Syntactically invalid RFC2822 address items are omitted from the output.
10908 It is possible to specify a character other than colon for the output
10909 separator by starting the string with > followed by the new separator
10910 character. For example:
10912 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10914 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10915 first, so if the expanded string starts with >, it may change the output
10916 separator unintentionally. This can be avoided by setting the output
10917 separator explicitly:
10919 ${addresses:>:$h_from:}
10922 Compare the &%address%& (singular)
10923 expansion item, which extracts the working address from a single RFC2822
10924 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10927 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10928 a strict interpretation of header line formatting. Exim parses the bare,
10929 unquoted portion of an email address and if it finds a comma, treats it as an
10930 email address separator. For the example header line:
10932 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10934 The first example below demonstrates that Q-encoded email addresses are parsed
10935 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10936 It does not see the comma because it's still encoded as "=2C". The second
10937 example below is passed the contents of &`$header_from:`&, meaning it gets
10938 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10939 The third example shows that the presence of a comma is skipped when it is
10940 quoted. The fourth example shows SMTPUTF8 handling.
10942 # exim -be '${addresses:From: \
10943 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10945 # exim -be '${addresses:From: Last, First <user@example.com>}'
10946 Last:user@example.com
10947 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10949 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10953 .vitem &*${base32:*&<&'digits'&>&*}*&
10954 .cindex "&%base32%& expansion item"
10955 .cindex "expansion" "conversion to base 32"
10956 The string must consist entirely of decimal digits. The number is converted to
10957 base 32 and output as a (empty, for zero) string of characters.
10958 Only lowercase letters are used.
10960 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10961 .cindex "&%base32d%& expansion item"
10962 .cindex "expansion" "conversion to base 32"
10963 The string must consist entirely of base-32 digits.
10964 The number is converted to decimal and output as a string.
10966 .vitem &*${base62:*&<&'digits'&>&*}*&
10967 .cindex "&%base62%& expansion item"
10968 .cindex "expansion" "conversion to base 62"
10969 The string must consist entirely of decimal digits. The number is converted to
10970 base 62 and output as a string of six characters, including leading zeros. In
10971 the few operating environments where Exim uses base 36 instead of base 62 for
10972 its message identifiers (because those systems do not have case-sensitive
10973 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10974 to be absolutely clear: this is &'not'& base64 encoding.
10976 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10977 .cindex "&%base62d%& expansion item"
10978 .cindex "expansion" "conversion to base 62"
10979 The string must consist entirely of base-62 digits, or, in operating
10980 environments where Exim uses base 36 instead of base 62 for its message
10981 identifiers, base-36 digits. The number is converted to decimal and output as a
10984 .vitem &*${base64:*&<&'string'&>&*}*&
10985 .cindex "expansion" "base64 encoding"
10986 .cindex "base64 encoding" "in string expansion"
10987 .cindex "&%base64%& expansion item"
10988 .cindex certificate "base64 of DER"
10989 This operator converts a string into one that is base64 encoded.
10991 If the string is a single variable of type certificate,
10992 returns the base64 encoding of the DER form of the certificate.
10995 .vitem &*${base64d:*&<&'string'&>&*}*&
10996 .cindex "expansion" "base64 decoding"
10997 .cindex "base64 decoding" "in string expansion"
10998 .cindex "&%base64d%& expansion item"
10999 This operator converts a base64-encoded string into the un-coded form.
11002 .vitem &*${domain:*&<&'string'&>&*}*&
11003 .cindex "domain" "extraction"
11004 .cindex "expansion" "domain extraction"
11005 The string is interpreted as an RFC 2822 address and the domain is extracted
11006 from it. If the string does not parse successfully, the result is empty.
11009 .vitem &*${escape:*&<&'string'&>&*}*&
11010 .cindex "expansion" "escaping non-printing characters"
11011 .cindex "&%escape%& expansion item"
11012 If the string contains any non-printing characters, they are converted to
11013 escape sequences starting with a backslash. Whether characters with the most
11014 significant bit set (so-called &"8-bit characters"&) count as printing or not
11015 is controlled by the &%print_topbitchars%& option.
11017 .vitem &*${escape8bit:*&<&'string'&>&*}*&
11018 .cindex "expansion" "escaping 8-bit characters"
11019 .cindex "&%escape8bit%& expansion item"
11020 If the string contains any characters with the most significant bit set,
11021 they are converted to escape sequences starting with a backslash.
11022 Backslashes and DEL characters are also converted.
11025 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
11026 .cindex "expansion" "expression evaluation"
11027 .cindex "expansion" "arithmetic expression"
11028 .cindex "&%eval%& expansion item"
11029 These items supports simple arithmetic and bitwise logical operations in
11030 expansion strings. The string (after expansion) must be a conventional
11031 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
11032 logical operators, and parentheses. All operations are carried out using
11033 integer arithmetic. The operator priorities are as follows (the same as in the
11034 C programming language):
11036 .irow &'highest:'& "not (~), negate (-)"
11037 .irow "" "multiply (*), divide (/), remainder (%)"
11038 .irow "" "plus (+), minus (-)"
11039 .irow "" "shift-left (<<), shift-right (>>)"
11040 .irow "" "and (&&)"
11042 .irow &'lowest:'& "or (|)"
11044 Binary operators with the same priority are evaluated from left to right. White
11045 space is permitted before or after operators.
11047 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11048 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11049 decimal, even if they start with a leading zero; hexadecimal numbers are not
11050 permitted. This can be useful when processing numbers extracted from dates or
11051 times, which often do have leading zeros.
11053 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11055 respectively. Negative numbers are supported. The result of the computation is
11056 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11059 &`${eval:1+1} `& yields 2
11060 &`${eval:1+2*3} `& yields 7
11061 &`${eval:(1+2)*3} `& yields 9
11062 &`${eval:2+42%5} `& yields 4
11063 &`${eval:0xc&5} `& yields 4
11064 &`${eval:0xc|5} `& yields 13
11065 &`${eval:0xc^5} `& yields 9
11066 &`${eval:0xc>>1} `& yields 6
11067 &`${eval:0xc<<1} `& yields 24
11068 &`${eval:~255&0x1234} `& yields 4608
11069 &`${eval:-(~255&0x1234)} `& yields -4608
11072 As a more realistic example, in an ACL you might have
11076 {>{$rcpt_count}{10}} \
11079 {$recipients_count} \
11080 {${eval:$rcpt_count/2}} \
11083 message = Too many bad recipients
11085 The condition is true if there have been more than 10 RCPT commands and
11086 fewer than half of them have resulted in a valid recipient.
11089 .vitem &*${expand:*&<&'string'&>&*}*&
11090 .cindex "expansion" "re-expansion of substring"
11091 The &%expand%& operator causes a string to be expanded for a second time. For
11094 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11096 first looks up a string in a file while expanding the operand for &%expand%&,
11097 and then re-expands what it has found.
11100 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11102 .cindex "UTF-8" "conversion from"
11103 .cindex "expansion" "UTF-8 conversion"
11104 .cindex "&%from_utf8%& expansion item"
11105 The world is slowly moving towards Unicode, although there are no standards for
11106 email yet. However, other applications (including some databases) are starting
11107 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11108 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11109 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11110 the result is an undefined sequence of bytes.
11112 Unicode code points with values less than 256 are compatible with ASCII and
11113 ISO-8859-1 (also known as Latin-1).
11114 For example, character 169 is the copyright symbol in both cases, though the
11115 way it is encoded is different. In UTF-8, more than one byte is needed for
11116 characters with code values greater than 127, whereas ISO-8859-1 is a
11117 single-byte encoding (but thereby limited to 256 characters). This makes
11118 translation from UTF-8 to ISO-8859-1 straightforward.
11121 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11122 .cindex "hash function" "textual"
11123 .cindex "expansion" "textual hash"
11124 The &%hash%& operator is a simpler interface to the hashing function that can
11125 be used when the two parameters are fixed numbers (as opposed to strings that
11126 change when expanded). The effect is the same as
11128 ${hash{<n>}{<m>}{<string>}}
11130 See the description of the general &%hash%& item above for details. The
11131 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11135 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11136 .cindex "base64 encoding" "conversion from hex"
11137 .cindex "expansion" "hex to base64"
11138 .cindex "&%hex2b64%& expansion item"
11139 This operator converts a hex string into one that is base64 encoded. This can
11140 be useful for processing the output of the various hashing functions.
11144 .vitem &*${hexquote:*&<&'string'&>&*}*&
11145 .cindex "quoting" "hex-encoded unprintable characters"
11146 .cindex "&%hexquote%& expansion item"
11147 This operator converts non-printable characters in a string into a hex
11148 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11149 as is, and other byte values are converted to &`\xNN`&, for example, a
11150 byte value 127 is converted to &`\x7f`&.
11153 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11154 .cindex "&%ipv6denorm%& expansion item"
11155 .cindex "IP address" normalisation
11156 This expands an IPv6 address to a full eight-element colon-separated set
11157 of hex digits including leading zeroes.
11158 A trailing ipv4-style dotted-decimal set is converted to hex.
11159 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11161 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11162 .cindex "&%ipv6norm%& expansion item"
11163 .cindex "IP address" normalisation
11164 .cindex "IP address" "canonical form"
11165 This converts an IPv6 address to canonical form.
11166 Leading zeroes of groups are omitted, and the longest
11167 set of zero-valued groups is replaced with a double colon.
11168 A trailing ipv4-style dotted-decimal set is converted to hex.
11169 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11172 .vitem &*${lc:*&<&'string'&>&*}*&
11173 .cindex "case forcing in strings"
11174 .cindex "string" "case forcing"
11175 .cindex "lower casing"
11176 .cindex "expansion" "case forcing"
11177 .cindex "&%lc%& expansion item"
11178 This forces the letters in the string into lower-case, for example:
11182 Case is defined per the system C locale.
11184 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11185 .cindex "expansion" "string truncation"
11186 .cindex "&%length%& expansion item"
11187 The &%length%& operator is a simpler interface to the &%length%& function that
11188 can be used when the parameter is a fixed number (as opposed to a string that
11189 changes when expanded). The effect is the same as
11191 ${length{<number>}{<string>}}
11193 See the description of the general &%length%& item above for details. Note that
11194 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11195 when &%length%& is used as an operator.
11196 All measurement is done in bytes and is not UTF-8 aware.
11199 .vitem &*${listcount:*&<&'string'&>&*}*&
11200 .cindex "expansion" "list item count"
11201 .cindex "list" "item count"
11202 .cindex "list" "count of items"
11203 .cindex "&%listcount%& expansion item"
11204 The string is interpreted as a list and the number of items is returned.
11207 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11208 .cindex "expansion" "named list"
11209 .cindex "&%listnamed%& expansion item"
11210 The name is interpreted as a named list and the content of the list is returned,
11211 expanding any referenced lists, re-quoting as needed for colon-separation.
11212 If the optional type is given it must be one of "a", "d", "h" or "l"
11213 and selects address-, domain-, host- or localpart- lists to search among respectively.
11214 Otherwise all types are searched in an undefined order and the first
11215 matching list is returned.
11217 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11218 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11222 .vitem &*${local_part:*&<&'string'&>&*}*&
11223 .cindex "expansion" "local part extraction"
11224 .cindex "&%local_part%& expansion item"
11225 The string is interpreted as an RFC 2822 address and the local part is
11226 extracted from it. If the string does not parse successfully, the result is
11228 The parsing correctly handles SMTPUTF8 Unicode in the string.
11231 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11232 .cindex "masked IP address"
11233 .cindex "IP address" "masking"
11234 .cindex "CIDR notation"
11235 .cindex "expansion" "IP address masking"
11236 .cindex "&%mask%& expansion item"
11237 If the form of the string to be operated on is not an IP address followed by a
11238 slash and an integer (that is, a network address in CIDR notation), the
11239 expansion fails. Otherwise, this operator converts the IP address to binary,
11240 masks off the least significant bits according to the bit count, and converts
11241 the result back to text, with mask appended. For example,
11243 ${mask:10.111.131.206/28}
11245 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11246 be mostly used for looking up masked addresses in files, the result for an IPv6
11247 address uses dots to separate components instead of colons, because colon
11248 terminates a key string in lsearch files. So, for example,
11250 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11254 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11256 Letters in IPv6 addresses are always output in lower case.
11259 .vitem &*${md5:*&<&'string'&>&*}*&
11261 .cindex "expansion" "MD5 hash"
11262 .cindex certificate fingerprint
11263 .cindex "&%md5%& expansion item"
11264 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11265 as a 32-digit hexadecimal number, in which any letters are in lower case.
11267 If the string is a single variable of type certificate,
11268 returns the MD5 hash fingerprint of the certificate.
11271 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11272 .cindex "expansion" "numeric hash"
11273 .cindex "hash function" "numeric"
11274 The &%nhash%& operator is a simpler interface to the numeric hashing function
11275 that can be used when the two parameters are fixed numbers (as opposed to
11276 strings that change when expanded). The effect is the same as
11278 ${nhash{<n>}{<m>}{<string>}}
11280 See the description of the general &%nhash%& item above for details.
11283 .vitem &*${quote:*&<&'string'&>&*}*&
11284 .cindex "quoting" "in string expansions"
11285 .cindex "expansion" "quoting"
11286 .cindex "&%quote%& expansion item"
11287 The &%quote%& operator puts its argument into double quotes if it
11288 is an empty string or
11289 contains anything other than letters, digits, underscores, dots, and hyphens.
11290 Any occurrences of double quotes and backslashes are escaped with a backslash.
11291 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11292 respectively For example,
11300 The place where this is useful is when the argument is a substitution from a
11301 variable or a message header.
11303 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11304 .cindex "&%quote_local_part%& expansion item"
11305 This operator is like &%quote%&, except that it quotes the string only if
11306 required to do so by the rules of RFC 2822 for quoting local parts. For
11307 example, a plus sign would not cause quoting (but it would for &%quote%&).
11308 If you are creating a new email address from the contents of &$local_part$&
11309 (or any other unknown data), you should always use this operator.
11311 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11312 will likely use the quoting form.
11313 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11316 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11317 .cindex "quoting" "lookup-specific"
11318 This operator applies lookup-specific quoting rules to the string. Each
11319 query-style lookup type has its own quoting rules which are described with
11320 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11322 ${quote_ldap:two * two}
11328 For single-key lookup types, no quoting is ever necessary and this operator
11329 yields an unchanged string.
11332 .vitem &*${randint:*&<&'n'&>&*}*&
11333 .cindex "random number"
11334 This operator returns a somewhat random number which is less than the
11335 supplied number and is at least 0. The quality of this randomness depends
11336 on how Exim was built; the values are not suitable for keying material.
11337 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11338 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11339 for versions of GnuTLS with that function.
11340 Otherwise, the implementation may be arc4random(), random() seeded by
11341 srandomdev() or srandom(), or a custom implementation even weaker than
11345 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11346 .cindex "expansion" "IP address"
11347 This operator reverses an IP address; for IPv4 addresses, the result is in
11348 dotted-quad decimal form, while for IPv6 addresses the result is in
11349 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11350 for DNS. For example,
11352 ${reverse_ip:192.0.2.4}
11353 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11358 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11362 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11363 .cindex "expansion" "RFC 2047"
11364 .cindex "RFC 2047" "expansion operator"
11365 .cindex "&%rfc2047%& expansion item"
11366 This operator encodes text according to the rules of RFC 2047. This is an
11367 encoding that is used in header lines to encode non-ASCII characters. It is
11368 assumed that the input string is in the encoding specified by the
11369 &%headers_charset%& option, which gets its default at build time. If the string
11370 contains only characters in the range 33&--126, and no instances of the
11373 ? = ( ) < > @ , ; : \ " . [ ] _
11375 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11376 string, using as many &"encoded words"& as necessary to encode all the
11380 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11381 .cindex "expansion" "RFC 2047"
11382 .cindex "RFC 2047" "decoding"
11383 .cindex "&%rfc2047d%& expansion item"
11384 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11385 bytes are replaced by question marks. Characters are converted into the
11386 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11387 not recognized unless &%check_rfc2047_length%& is set false.
11389 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11390 access a header line, RFC 2047 decoding is done automatically. You do not need
11391 to use this operator as well.
11395 .vitem &*${rxquote:*&<&'string'&>&*}*&
11396 .cindex "quoting" "in regular expressions"
11397 .cindex "regular expressions" "quoting"
11398 .cindex "&%rxquote%& expansion item"
11399 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11400 characters in its argument. This is useful when substituting the values of
11401 variables or headers inside regular expressions.
11404 .vitem &*${sha1:*&<&'string'&>&*}*&
11405 .cindex "SHA-1 hash"
11406 .cindex "expansion" "SHA-1 hashing"
11407 .cindex certificate fingerprint
11408 .cindex "&%sha1%& expansion item"
11409 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11410 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11412 If the string is a single variable of type certificate,
11413 returns the SHA-1 hash fingerprint of the certificate.
11416 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11417 &*${sha2:*&<&'string'&>&*}*& &&&
11418 &*${sha2_<n>:*&<&'string'&>&*}*&
11419 .cindex "SHA-256 hash"
11420 .cindex "SHA-2 hash"
11421 .cindex certificate fingerprint
11422 .cindex "expansion" "SHA-256 hashing"
11423 .cindex "&%sha256%& expansion item"
11424 .cindex "&%sha2%& expansion item"
11425 The &%sha256%& operator computes the SHA-256 hash value of the string
11427 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11429 If the string is a single variable of type certificate,
11430 returns the SHA-256 hash fingerprint of the certificate.
11432 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11433 (except for certificates, which are not supported).
11434 Finally, if an underbar
11435 and a number is appended it specifies the output length, selecting a
11436 member of the SHA-2 family of hash functions.
11437 Values of 256, 384 and 512 are accepted, with 256 being the default.
11440 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11441 &*${sha3_<n>:*&<&'string'&>&*}*&
11442 .cindex "SHA3 hash"
11443 .cindex "expansion" "SHA3 hashing"
11444 .cindex "&%sha3%& expansion item"
11445 The &%sha3%& operator computes the SHA3-256 hash value of the string
11447 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11449 If a number is appended, separated by an underbar, it specifies
11450 the output length. Values of 224, 256, 384 and 512 are accepted;
11451 with 256 being the default.
11453 The &%sha3%& expansion item is only supported if Exim has been
11454 compiled with GnuTLS 3.5.0 or later,
11455 or OpenSSL 1.1.1 or later.
11456 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11459 .vitem &*${stat:*&<&'string'&>&*}*&
11460 .cindex "expansion" "statting a file"
11461 .cindex "file" "extracting characteristics"
11462 .cindex "&%stat%& expansion item"
11463 The string, after expansion, must be a file path. A call to the &[stat()]&
11464 function is made for this path. If &[stat()]& fails, an error occurs and the
11465 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11466 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11467 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11468 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11469 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11470 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11471 can extract individual fields using the &%extract%& expansion item.
11473 The use of the &%stat%& expansion in users' filter files can be locked out by
11474 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11475 systems for files larger than 2GB.
11477 .vitem &*${str2b64:*&<&'string'&>&*}*&
11478 .cindex "&%str2b64%& expansion item"
11479 Now deprecated, a synonym for the &%base64%& expansion operator.
11483 .vitem &*${strlen:*&<&'string'&>&*}*&
11484 .cindex "expansion" "string length"
11485 .cindex "string" "length in expansion"
11486 .cindex "&%strlen%& expansion item"
11487 The item is replaced by the length of the expanded string, expressed as a
11488 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11489 All measurement is done in bytes and is not UTF-8 aware.
11492 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11493 .cindex "&%substr%& expansion item"
11494 .cindex "substring extraction"
11495 .cindex "expansion" "substring expansion"
11496 The &%substr%& operator is a simpler interface to the &%substr%& function that
11497 can be used when the two parameters are fixed numbers (as opposed to strings
11498 that change when expanded). The effect is the same as
11500 ${substr{<start>}{<length>}{<string>}}
11502 See the description of the general &%substr%& item above for details. The
11503 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11504 All measurement is done in bytes and is not UTF-8 aware.
11506 .vitem &*${time_eval:*&<&'string'&>&*}*&
11507 .cindex "&%time_eval%& expansion item"
11508 .cindex "time interval" "decoding"
11509 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11512 .vitem &*${time_interval:*&<&'string'&>&*}*&
11513 .cindex "&%time_interval%& expansion item"
11514 .cindex "time interval" "formatting"
11515 The argument (after sub-expansion) must be a sequence of decimal digits that
11516 represents an interval of time as a number of seconds. It is converted into a
11517 number of larger units and output in Exim's normal time format, for example,
11520 .vitem &*${uc:*&<&'string'&>&*}*&
11521 .cindex "case forcing in strings"
11522 .cindex "string" "case forcing"
11523 .cindex "upper casing"
11524 .cindex "expansion" "case forcing"
11525 .cindex "&%uc%& expansion item"
11526 This forces the letters in the string into upper-case.
11527 Case is defined per the system C locale.
11529 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11530 .cindex "correction of invalid utf-8 sequences in strings"
11531 .cindex "utf-8" "utf-8 sequences"
11532 .cindex "incorrect utf-8"
11533 .cindex "expansion" "utf-8 forcing"
11534 .cindex "&%utf8clean%& expansion item"
11535 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11536 In versions of Exim before 4.92, this did not correctly do so for a truncated
11537 final codepoint's encoding, and the character would be silently dropped.
11538 If you must handle detection of this scenario across both sets of Exim behavior,
11539 the complexity will depend upon the task.
11540 For instance, to detect if the first character is multibyte and a 1-byte
11541 extraction can be successfully used as a path component (as is common for
11542 dividing up delivery folders), you might use:
11544 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11546 (which will false-positive if the first character of the local part is a
11547 literal question mark).
11549 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11550 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11551 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11552 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11553 .cindex expansion UTF-8
11554 .cindex UTF-8 expansion
11556 .cindex internationalisation
11557 .cindex "&%utf8_domain_to_alabel%& expansion item"
11558 .cindex "&%utf8_domain_from_alabel%& expansion item"
11559 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11560 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11561 These convert EAI mail name components between UTF-8 and a-label forms.
11562 For information on internationalisation support see &<<SECTi18nMTA>>&.
11570 .section "Expansion conditions" "SECTexpcond"
11571 .scindex IIDexpcond "expansion" "conditions"
11572 The following conditions are available for testing by the &%${if%& construct
11573 while expanding strings:
11576 .vitem &*!*&<&'condition'&>
11577 .cindex "expansion" "negating a condition"
11578 .cindex "negation" "in expansion condition"
11579 Preceding any condition with an exclamation mark negates the result of the
11582 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11583 .cindex "numeric comparison"
11584 .cindex "expansion" "numeric comparison"
11585 There are a number of symbolic operators for doing numeric comparisons. They
11591 &`>= `& greater or equal
11593 &`<= `& less or equal
11597 ${if >{$message_size}{10M} ...
11599 Note that the general negation operator provides for inequality testing. The
11600 two strings must take the form of optionally signed decimal integers,
11601 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11602 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11603 As a special case, the numerical value of an empty string is taken as
11606 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11607 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11608 10M, not if 10M is larger than &$message_size$&.
11611 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11612 {*&<&'arg2'&>&*}...}*&
11613 .cindex "expansion" "calling an acl"
11614 .cindex "&%acl%&" "expansion condition"
11615 The name and zero to nine argument strings are first expanded separately. The expanded
11616 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11617 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11618 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11619 and may use the variables; if another acl expansion is used the values
11620 are restored after it returns. If the ACL sets
11621 a value using a "message =" modifier the variable $value becomes
11622 the result of the expansion, otherwise it is empty.
11623 If the ACL returns accept the condition is true; if deny, false.
11624 If the ACL returns defer the result is a forced-fail.
11626 .vitem &*bool&~{*&<&'string'&>&*}*&
11627 .cindex "expansion" "boolean parsing"
11628 .cindex "&%bool%& expansion condition"
11629 This condition turns a string holding a true or false representation into
11630 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11631 (case-insensitively); also integer numbers map to true if non-zero,
11633 An empty string is treated as false.
11634 Leading and trailing whitespace is ignored;
11635 thus a string consisting only of whitespace is false.
11636 All other string values will result in expansion failure.
11638 When combined with ACL variables, this expansion condition will let you
11639 make decisions in one place and act on those decisions in another place.
11642 ${if bool{$acl_m_privileged_sender} ...
11646 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11647 .cindex "expansion" "boolean parsing"
11648 .cindex "&%bool_lax%& expansion condition"
11649 Like &%bool%&, this condition turns a string into a boolean state. But
11650 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11651 loose definition that the Router &%condition%& option uses. The empty string
11652 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11653 true. Leading and trailing whitespace is ignored.
11655 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11657 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11658 .cindex "expansion" "encrypted comparison"
11659 .cindex "encrypted strings, comparing"
11660 .cindex "&%crypteq%& expansion condition"
11661 This condition is included in the Exim binary if it is built to support any
11662 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11663 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11664 included in the binary.
11666 The &%crypteq%& condition has two arguments. The first is encrypted and
11667 compared against the second, which is already encrypted. The second string may
11668 be in the LDAP form for storing encrypted strings, which starts with the
11669 encryption type in curly brackets, followed by the data. If the second string
11670 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11671 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11672 Typically this will be a field from a password file. An example of an encrypted
11673 string in LDAP form is:
11675 {md5}CY9rzUYh03PK3k6DJie09g==
11677 If such a string appears directly in an expansion, the curly brackets have to
11678 be quoted, because they are part of the expansion syntax. For example:
11680 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11682 The following encryption types (whose names are matched case-independently) are
11687 .cindex "base64 encoding" "in encrypted password"
11688 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11689 printable characters to compare with the remainder of the second string. If the
11690 length of the comparison string is 24, Exim assumes that it is base64 encoded
11691 (as in the above example). If the length is 32, Exim assumes that it is a
11692 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11696 .cindex "SHA-1 hash"
11697 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11698 printable characters to compare with the remainder of the second string. If the
11699 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11700 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11701 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11704 .cindex "&[crypt()]&"
11705 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11706 only the first eight characters of the password. However, in modern operating
11707 systems this is no longer true, and in many cases the entire password is used,
11708 whatever its length.
11711 .cindex "&[crypt16()]&"
11712 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11713 use up to 16 characters of the password in some operating systems. Again, in
11714 modern operating systems, more characters may be used.
11716 Exim has its own version of &[crypt16()]&, which is just a double call to
11717 &[crypt()]&. For operating systems that have their own version, setting
11718 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11719 operating system version instead of its own. This option is set by default in
11720 the OS-dependent &_Makefile_& for those operating systems that are known to
11721 support &[crypt16()]&.
11723 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11724 it was not using the same algorithm as some operating systems' versions. It
11725 turns out that as well as &[crypt16()]& there is a function called
11726 &[bigcrypt()]& in some operating systems. This may or may not use the same
11727 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11729 However, since there is now a move away from the traditional &[crypt()]&
11730 functions towards using SHA1 and other algorithms, tidying up this area of
11731 Exim is seen as very low priority.
11733 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11734 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11735 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11736 default is &`{crypt}`&. Whatever the default, you can always use either
11737 function by specifying it explicitly in curly brackets.
11739 .vitem &*def:*&<&'variable&~name'&>
11740 .cindex "expansion" "checking for empty variable"
11741 .cindex "&%def%& expansion condition"
11742 The &%def%& condition must be followed by the name of one of the expansion
11743 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11744 variable does not contain the empty string. For example:
11746 ${if def:sender_ident {from $sender_ident}}
11748 Note that the variable name is given without a leading &%$%& character. If the
11749 variable does not exist, the expansion fails.
11751 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11752 &~&*def:h_*&<&'header&~name'&>&*:*&"
11753 .cindex "expansion" "checking header line existence"
11754 This condition is true if a message is being processed and the named header
11755 exists in the message. For example,
11757 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11759 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11760 the header name must be terminated by a colon if white space does not follow.
11762 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11763 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11764 .cindex "string" "comparison"
11765 .cindex "expansion" "string comparison"
11766 .cindex "&%eq%& expansion condition"
11767 .cindex "&%eqi%& expansion condition"
11768 The two substrings are first expanded. The condition is true if the two
11769 resulting strings are identical. For &%eq%& the comparison includes the case of
11770 letters, whereas for &%eqi%& the comparison is case-independent, where
11771 case is defined per the system C locale.
11773 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11774 .cindex "expansion" "file existence test"
11775 .cindex "file" "existence test"
11776 .cindex "&%exists%&, expansion condition"
11777 The substring is first expanded and then interpreted as an absolute path. The
11778 condition is true if the named file (or directory) exists. The existence test
11779 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11780 users' filter files may be locked out by the system administrator.
11783 &*Note:*& Testing a path using this condition is not a sufficient way of
11785 Consider using a dsearch lookup.
11788 .vitem &*first_delivery*&
11789 .cindex "delivery" "first"
11790 .cindex "first delivery"
11791 .cindex "expansion" "first delivery test"
11792 .cindex "&%first_delivery%& expansion condition"
11793 This condition, which has no data, is true during a message's first delivery
11794 attempt. It is false during any subsequent delivery attempts.
11797 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11798 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11799 .cindex "list" "iterative conditions"
11800 .cindex "expansion" "&*forall*& condition"
11801 .cindex "expansion" "&*forany*& condition"
11803 These conditions iterate over a list. The first argument is expanded to form
11804 the list. By default, the list separator is a colon, but it can be changed by
11805 the normal method (&<<SECTlistsepchange>>&).
11806 The second argument is interpreted as a condition that is to
11807 be applied to each item in the list in turn. During the interpretation of the
11808 condition, the current list item is placed in a variable called &$item$&.
11810 For &*forany*&, interpretation stops if the condition is true for any item, and
11811 the result of the whole condition is true. If the condition is false for all
11812 items in the list, the overall condition is false.
11814 For &*forall*&, interpretation stops if the condition is false for any item,
11815 and the result of the whole condition is false. If the condition is true for
11816 all items in the list, the overall condition is true.
11818 Note that negation of &*forany*& means that the condition must be false for all
11819 items for the overall condition to succeed, and negation of &*forall*& means
11820 that the condition must be false for at least one item. In this example, the
11821 list separator is changed to a comma:
11823 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11825 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11826 being processed, to enable these expansion items to be nested.
11828 To scan a named list, expand it with the &*listnamed*& operator.
11830 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11831 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11832 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11833 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11834 .cindex JSON "iterative conditions"
11835 .cindex JSON expansions
11836 .cindex expansion "&*forall_json*& condition"
11837 .cindex expansion "&*forany_json*& condition"
11838 .cindex expansion "&*forall_jsons*& condition"
11839 .cindex expansion "&*forany_jsons*& condition"
11840 As for the above, except that the first argument must, after expansion,
11842 The array separator is not changeable.
11843 For the &"jsons"& variants the elements are expected to be JSON strings
11844 and have their quotes removed before the evaluation of the condition.
11848 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11849 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11850 .cindex "string" "comparison"
11851 .cindex "expansion" "string comparison"
11852 .cindex "&%ge%& expansion condition"
11853 .cindex "&%gei%& expansion condition"
11854 The two substrings are first expanded. The condition is true if the first
11855 string is lexically greater than or equal to the second string. For &%ge%& the
11856 comparison includes the case of letters, whereas for &%gei%& the comparison is
11858 Case and collation order are defined per the system C locale.
11860 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11861 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11862 .cindex "string" "comparison"
11863 .cindex "expansion" "string comparison"
11864 .cindex "&%gt%& expansion condition"
11865 .cindex "&%gti%& expansion condition"
11866 The two substrings are first expanded. The condition is true if the first
11867 string is lexically greater than the second string. For &%gt%& the comparison
11868 includes the case of letters, whereas for &%gti%& the comparison is
11870 Case and collation order are defined per the system C locale.
11874 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11875 SRS decode. See SECT &<<SECTSRS>>& for details.
11879 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11880 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11881 .cindex "string" "comparison"
11882 .cindex "list" "iterative conditions"
11883 Both strings are expanded; the second string is treated as a list of simple
11884 strings; if the first string is a member of the second, then the condition
11886 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11888 These are simpler to use versions of the more powerful &*forany*& condition.
11889 Examples, and the &*forany*& equivalents:
11891 ${if inlist{needle}{foo:needle:bar}}
11892 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11893 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11894 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11897 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11898 &*isip4&~{*&<&'string'&>&*}*& &&&
11899 &*isip6&~{*&<&'string'&>&*}*&
11900 .cindex "IP address" "testing string format"
11901 .cindex "string" "testing for IP address"
11902 .cindex "&%isip%& expansion condition"
11903 .cindex "&%isip4%& expansion condition"
11904 .cindex "&%isip6%& expansion condition"
11905 The substring is first expanded, and then tested to see if it has the form of
11906 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11907 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11909 For an IPv4 address, the test is for four dot-separated components, each of
11910 which consists of from one to three digits. For an IPv6 address, up to eight
11911 colon-separated components are permitted, each containing from one to four
11912 hexadecimal digits. There may be fewer than eight components if an empty
11913 component (adjacent colons) is present. Only one empty component is permitted.
11915 &*Note*&: The checks used to be just on the form of the address; actual numerical
11916 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11918 This is no longer the case.
11920 The main use of these tests is to distinguish between IP addresses and
11921 host names, or between IPv4 and IPv6 addresses. For example, you could use
11923 ${if isip4{$sender_host_address}...
11925 to test which IP version an incoming SMTP connection is using.
11927 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11928 .cindex "LDAP" "use for authentication"
11929 .cindex "expansion" "LDAP authentication test"
11930 .cindex "&%ldapauth%& expansion condition"
11931 This condition supports user authentication using LDAP. See section
11932 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11933 queries. For this use, the query must contain a user name and password. The
11934 query itself is not used, and can be empty. The condition is true if the
11935 password is not empty, and the user name and password are accepted by the LDAP
11936 server. An empty password is rejected without calling LDAP because LDAP binds
11937 with an empty password are considered anonymous regardless of the username, and
11938 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11939 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11943 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11944 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11945 .cindex "string" "comparison"
11946 .cindex "expansion" "string comparison"
11947 .cindex "&%le%& expansion condition"
11948 .cindex "&%lei%& expansion condition"
11949 The two substrings are first expanded. The condition is true if the first
11950 string is lexically less than or equal to the second string. For &%le%& the
11951 comparison includes the case of letters, whereas for &%lei%& the comparison is
11953 Case and collation order are defined per the system C locale.
11955 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11956 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11957 .cindex "string" "comparison"
11958 .cindex "expansion" "string comparison"
11959 .cindex "&%lt%& expansion condition"
11960 .cindex "&%lti%& expansion condition"
11961 The two substrings are first expanded. The condition is true if the first
11962 string is lexically less than the second string. For &%lt%& the comparison
11963 includes the case of letters, whereas for &%lti%& the comparison is
11965 Case and collation order are defined per the system C locale.
11968 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11969 .cindex "expansion" "regular expression comparison"
11970 .cindex "regular expressions" "match in expanded string"
11971 .cindex "&%match%& expansion condition"
11972 The two substrings are first expanded. The second is then treated as a regular
11973 expression and applied to the first. Because of the pre-expansion, if the
11974 regular expression contains dollar, or backslash characters, they must be
11975 escaped. Care must also be taken if the regular expression contains braces
11976 (curly brackets). A closing brace must be escaped so that it is not taken as a
11977 premature termination of <&'string2'&>. The easiest approach is to use the
11978 &`\N`& feature to disable expansion of the regular expression.
11981 ${if match {$local_part}{\N^\d{3}\N} ...
11983 If the whole expansion string is in double quotes, further escaping of
11984 backslashes is also required.
11986 The condition is true if the regular expression match succeeds.
11987 The regular expression is not required to begin with a circumflex
11988 metacharacter, but if there is no circumflex, the expression is not anchored,
11989 and it may match anywhere in the subject, not just at the start. If you want
11990 the pattern to match at the end of the subject, you must include the &`$`&
11991 metacharacter at an appropriate point.
11992 All character handling is done in bytes and is not UTF-8 aware,
11993 but we might change this in a future Exim release.
11995 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11996 At the start of an &%if%& expansion the values of the numeric variable
11997 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11998 succeeds causes them to be reset to the substrings of that condition and they
11999 will have these values during the expansion of the success string. At the end
12000 of the &%if%& expansion, the previous values are restored. After testing a
12001 combination of conditions using &%or%&, the subsequent values of the numeric
12002 variables are those of the condition that succeeded.
12004 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12005 .cindex "&%match_address%& expansion condition"
12006 See &*match_local_part*&.
12008 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12009 .cindex "&%match_domain%& expansion condition"
12010 See &*match_local_part*&.
12012 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12013 .cindex "&%match_ip%& expansion condition"
12014 This condition matches an IP address to a list of IP address patterns. It must
12015 be followed by two argument strings. The first (after expansion) must be an IP
12016 address or an empty string. The second (not expanded) is a restricted host
12017 list that can match only an IP address, not a host name. For example:
12019 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
12021 The specific types of host list item that are permitted in the list are:
12024 An IP address, optionally with a CIDR mask.
12026 A single asterisk, which matches any IP address.
12028 An empty item, which matches only if the IP address is empty. This could be
12029 useful for testing for a locally submitted message or one from specific hosts
12030 in a single test such as
12031 . ==== As this is a nested list, any displays it contains must be indented
12032 . ==== as otherwise they are too far to the left. This comment applies to
12033 . ==== the use of xmlto plus fop. There's no problem when formatting with
12034 . ==== sdop, with or without the extra indent.
12036 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12038 where the first item in the list is the empty string.
12040 The item @[] matches any of the local host's interface addresses.
12042 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12043 even if &`net-`& is not specified. There is never any attempt to turn the IP
12044 address into a host name. The most common type of linear search for
12045 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12046 masks. For example:
12048 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12050 It is of course possible to use other kinds of lookup, and in such a case, you
12051 do need to specify the &`net-`& prefix if you want to specify a specific
12052 address mask, for example:
12054 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12056 However, unless you are combining a &%match_ip%& condition with others, it is
12057 just as easy to use the fact that a lookup is itself a condition, and write:
12059 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12063 Note that <&'string2'&> is not itself subject to string expansion, unless
12064 Exim was built with the EXPAND_LISTMATCH_RHS option.
12066 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12068 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12069 .cindex "domain list" "in expansion condition"
12070 .cindex "address list" "in expansion condition"
12071 .cindex "local part" "list, in expansion condition"
12072 .cindex "&%match_local_part%& expansion condition"
12073 This condition, together with &%match_address%& and &%match_domain%&, make it
12074 possible to test domain, address, and local part lists within expansions. Each
12075 condition requires two arguments: an item and a list to match. A trivial
12078 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12080 In each case, the second argument may contain any of the allowable items for a
12081 list of the appropriate type. Also, because the second argument
12082 is a standard form of list, it is possible to refer to a named list.
12083 Thus, you can use conditions like this:
12085 ${if match_domain{$domain}{+local_domains}{...
12087 .cindex "&`+caseful`&"
12088 For address lists, the matching starts off caselessly, but the &`+caseful`&
12089 item can be used, as in all address lists, to cause subsequent items to
12090 have their local parts matched casefully. Domains are always matched
12093 Note that <&'string2'&> is not itself subject to string expansion, unless
12094 Exim was built with the EXPAND_LISTMATCH_RHS option.
12096 &*Note*&: Host lists are &'not'& supported in this way. This is because
12097 hosts have two identities: a name and an IP address, and it is not clear
12098 how to specify cleanly how such a test would work. However, IP addresses can be
12099 matched using &%match_ip%&.
12101 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12102 .cindex "PAM authentication"
12103 .cindex "AUTH" "with PAM"
12104 .cindex "Solaris" "PAM support"
12105 .cindex "expansion" "PAM authentication test"
12106 .cindex "&%pam%& expansion condition"
12107 &'Pluggable Authentication Modules'&
12108 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12109 available in the latest releases of Solaris and in some GNU/Linux
12110 distributions. The Exim support, which is intended for use in conjunction with
12111 the SMTP AUTH command, is available only if Exim is compiled with
12115 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12116 in some releases of GNU/Linux &%-ldl%& is also needed.
12118 The argument string is first expanded, and the result must be a
12119 colon-separated list of strings. Leading and trailing white space is ignored.
12120 The PAM module is initialized with the service name &"exim"& and the user name
12121 taken from the first item in the colon-separated data string (<&'string1'&>).
12122 The remaining items in the data string are passed over in response to requests
12123 from the authentication function. In the simple case there will only be one
12124 request, for a password, so the data consists of just two strings.
12126 There can be problems if any of the strings are permitted to contain colon
12127 characters. In the usual way, these have to be doubled to avoid being taken as
12129 The &%listquote%& expansion item can be used for this.
12130 For example, the configuration
12131 of a LOGIN authenticator might contain this setting:
12133 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12135 In some operating systems, PAM authentication can be done only from a process
12136 running as root. Since Exim is running as the Exim user when receiving
12137 messages, this means that PAM cannot be used directly in those systems.
12138 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12141 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12142 .cindex "&'pwcheck'& daemon"
12144 .cindex "expansion" "&'pwcheck'& authentication test"
12145 .cindex "&%pwcheck%& expansion condition"
12146 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12147 This is one way of making it possible for passwords to be checked by a process
12148 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12149 deprecated. Its replacement is &'saslauthd'& (see below).
12151 The pwcheck support is not included in Exim by default. You need to specify
12152 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12153 building Exim. For example:
12155 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12157 You do not need to install the full Cyrus software suite in order to use
12158 the pwcheck daemon. You can compile and install just the daemon alone
12159 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12160 access to the &_/var/pwcheck_& directory.
12162 The &%pwcheck%& condition takes one argument, which must be the user name and
12163 password, separated by a colon. For example, in a LOGIN authenticator
12164 configuration, you might have this:
12166 server_condition = ${if pwcheck{$auth1:$auth2}}
12168 Again, for a PLAIN authenticator configuration, this would be:
12170 server_condition = ${if pwcheck{$auth2:$auth3}}
12172 .vitem &*queue_running*&
12173 .cindex "queue runner" "detecting when delivering from"
12174 .cindex "expansion" "queue runner test"
12175 .cindex "&%queue_running%& expansion condition"
12176 This condition, which has no data, is true during delivery attempts that are
12177 initiated by queue runner processes, and false otherwise.
12180 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12182 .cindex "expansion" "Radius authentication"
12183 .cindex "&%radius%& expansion condition"
12184 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12185 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12186 the Radius client configuration file in order to build Exim with Radius
12189 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12190 library, using the original API. If you are using release 0.4.0 or later of
12191 this library, you need to set
12193 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12195 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12196 &%libradius%& library that comes with FreeBSD. To do this, set
12198 RADIUS_LIB_TYPE=RADLIB
12200 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12201 You may also have to supply a suitable setting in EXTRALIBS so that the
12202 Radius library can be found when Exim is linked.
12204 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12205 Radius client library, which calls the Radius server. The condition is true if
12206 the authentication is successful. For example:
12208 server_condition = ${if radius{<arguments>}}
12212 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12213 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12214 .cindex "&'saslauthd'& daemon"
12216 .cindex "expansion" "&'saslauthd'& authentication test"
12217 .cindex "&%saslauthd%& expansion condition"
12218 This condition supports user authentication using the Cyrus &'saslauthd'&
12219 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12220 Using this daemon is one way of making it possible for passwords to be checked
12221 by a process that is not running as root.
12223 The saslauthd support is not included in Exim by default. You need to specify
12224 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12225 building Exim. For example:
12227 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12229 You do not need to install the full Cyrus software suite in order to use
12230 the saslauthd daemon. You can compile and install just the daemon alone
12231 from the Cyrus SASL library.
12233 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12234 two are mandatory. For example:
12236 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12238 The service and the realm are optional (which is why the arguments are enclosed
12239 in their own set of braces). For details of the meaning of the service and
12240 realm, and how to run the daemon, consult the Cyrus documentation.
12245 .section "Combining expansion conditions" "SECID84"
12246 .cindex "expansion" "combining conditions"
12247 Several conditions can be tested at once by combining them using the &%and%&
12248 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12249 conditions on their own, and precede their lists of sub-conditions. Each
12250 sub-condition must be enclosed in braces within the overall braces that contain
12251 the list. No repetition of &%if%& is used.
12255 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12256 .cindex "&""or""& expansion condition"
12257 .cindex "expansion" "&""or""& of conditions"
12258 The sub-conditions are evaluated from left to right. The condition is true if
12259 any one of the sub-conditions is true.
12262 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12264 When a true sub-condition is found, the following ones are parsed but not
12265 evaluated. If there are several &"match"& sub-conditions the values of the
12266 numeric variables afterwards are taken from the first one that succeeds.
12268 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12269 .cindex "&""and""& expansion condition"
12270 .cindex "expansion" "&""and""& of conditions"
12271 The sub-conditions are evaluated from left to right. The condition is true if
12272 all of the sub-conditions are true. If there are several &"match"&
12273 sub-conditions, the values of the numeric variables afterwards are taken from
12274 the last one. When a false sub-condition is found, the following ones are
12275 parsed but not evaluated.
12277 .ecindex IIDexpcond
12282 .section "Expansion variables" "SECTexpvar"
12283 .cindex "expansion" "variables, list of"
12284 This section contains an alphabetical list of all the expansion variables. Some
12285 of them are available only when Exim is compiled with specific options such as
12286 support for TLS or the content scanning extension.
12289 .vitem "&$0$&, &$1$&, etc"
12290 .cindex "numerical variables (&$1$& &$2$& etc)"
12291 When a &%match%& expansion condition succeeds, these variables contain the
12292 captured substrings identified by the regular expression during subsequent
12293 processing of the success string of the containing &%if%& expansion item.
12294 In the expansion condition case
12295 they do not retain their values afterwards; in fact, their previous
12296 values are restored at the end of processing an &%if%& item. The numerical
12297 variables may also be set externally by some other matching process which
12298 precedes the expansion of the string. For example, the commands available in
12299 Exim filter files include an &%if%& command with its own regular expression
12300 matching condition.
12302 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12303 Within an acl condition, expansion condition or expansion item
12304 any arguments are copied to these variables,
12305 any unused variables being made empty.
12307 .vitem "&$acl_c...$&"
12308 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12309 can be given any name that starts with &$acl_c$& and is at least six characters
12310 long, but the sixth character must be either a digit or an underscore. For
12311 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12312 variables persist throughout the lifetime of an SMTP connection. They can be
12313 used to pass information between ACLs and between different invocations of the
12314 same ACL. When a message is received, the values of these variables are saved
12315 with the message, and can be accessed by filters, routers, and transports
12316 during subsequent delivery.
12318 .vitem "&$acl_m...$&"
12319 These variables are like the &$acl_c...$& variables, except that their values
12320 are reset after a message has been received. Thus, if several messages are
12321 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12322 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12323 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12324 message is received, the values of these variables are saved with the message,
12325 and can be accessed by filters, routers, and transports during subsequent
12328 .vitem &$acl_narg$&
12329 Within an acl condition, expansion condition or expansion item
12330 this variable has the number of arguments.
12332 .vitem &$acl_verify_message$&
12333 .vindex "&$acl_verify_message$&"
12334 After an address verification has failed, this variable contains the failure
12335 message. It retains its value for use in subsequent modifiers of the verb.
12336 The message can be preserved by coding like this:
12338 warn !verify = sender
12339 set acl_m0 = $acl_verify_message
12341 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12342 &%log_message%& modifiers, to include information about the verification
12345 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12348 .vitem &$address_data$&
12349 .vindex "&$address_data$&"
12350 This variable is set by means of the &%address_data%& option in routers. The
12351 value then remains with the address while it is processed by subsequent routers
12352 and eventually a transport. If the transport is handling multiple addresses,
12353 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12354 for more details. &*Note*&: The contents of &$address_data$& are visible in
12357 If &$address_data$& is set when the routers are called from an ACL to verify
12358 a recipient address, the final value is still in the variable for subsequent
12359 conditions and modifiers of the ACL statement. If routing the address caused it
12360 to be redirected to just one address, the child address is also routed as part
12361 of the verification, and in this case the final value of &$address_data$& is
12362 from the child's routing.
12364 If &$address_data$& is set when the routers are called from an ACL to verify a
12365 sender address, the final value is also preserved, but this time in
12366 &$sender_address_data$&, to distinguish it from data from a recipient
12369 In both cases (recipient and sender verification), the value does not persist
12370 after the end of the current ACL statement. If you want to preserve
12371 these values for longer, you can save them in ACL variables.
12373 .vitem &$address_file$&
12374 .vindex "&$address_file$&"
12375 When, as a result of aliasing, forwarding, or filtering, a message is directed
12376 to a specific file, this variable holds the name of the file when the transport
12377 is running. At other times, the variable is empty. For example, using the
12378 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12380 /home/r2d2/savemail
12382 then when the &(address_file)& transport is running, &$address_file$&
12383 contains the text string &`/home/r2d2/savemail`&.
12384 .cindex "Sieve filter" "value of &$address_file$&"
12385 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12386 then up to the transport configuration to generate an appropriate absolute path
12387 to the relevant file.
12389 .vitem &$address_pipe$&
12390 .vindex "&$address_pipe$&"
12391 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12392 this variable holds the pipe command when the transport is running.
12394 .vitem "&$auth1$& &-- &$auth4$&"
12395 .vindex "&$auth1$&, &$auth2$&, etc"
12396 These variables are used in SMTP authenticators (see chapters
12397 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12399 .vitem &$authenticated_id$&
12400 .cindex "authentication" "id"
12401 .vindex "&$authenticated_id$&"
12402 When a server successfully authenticates a client it may be configured to
12403 preserve some of the authentication information in the variable
12404 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12405 user/password authenticator configuration might preserve the user name for use
12406 in the routers. Note that this is not the same information that is saved in
12407 &$sender_host_authenticated$&.
12409 When a message is submitted locally (that is, not over a TCP connection)
12410 the value of &$authenticated_id$& is normally the login name of the calling
12411 process. However, a trusted user can override this by means of the &%-oMai%&
12412 command line option.
12413 This second case also sets up information used by the
12414 &$authresults$& expansion item.
12416 .vitem &$authenticated_fail_id$&
12417 .cindex "authentication" "fail" "id"
12418 .vindex "&$authenticated_fail_id$&"
12419 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12420 will contain the failed authentication id. If more than one authentication
12421 id is attempted, it will contain only the last one. The variable is
12422 available for processing in the ACL's, generally the quit or notquit ACL.
12423 A message to a local recipient could still be accepted without requiring
12424 authentication, which means this variable could also be visible in all of
12428 .vitem &$authenticated_sender$&
12429 .cindex "sender" "authenticated"
12430 .cindex "authentication" "sender"
12431 .cindex "AUTH" "on MAIL command"
12432 .vindex "&$authenticated_sender$&"
12433 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12434 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12435 described in section &<<SECTauthparamail>>&. Unless the data is the string
12436 &"<>"&, it is set as the authenticated sender of the message, and the value is
12437 available during delivery in the &$authenticated_sender$& variable. If the
12438 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12440 .vindex "&$qualify_domain$&"
12441 When a message is submitted locally (that is, not over a TCP connection), the
12442 value of &$authenticated_sender$& is an address constructed from the login
12443 name of the calling process and &$qualify_domain$&, except that a trusted user
12444 can override this by means of the &%-oMas%& command line option.
12447 .vitem &$authentication_failed$&
12448 .cindex "authentication" "failure"
12449 .vindex "&$authentication_failed$&"
12450 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12451 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12452 possible to distinguish between &"did not try to authenticate"&
12453 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12454 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12455 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12456 negative response to an AUTH command, including (for example) an attempt to use
12457 an undefined mechanism.
12459 .vitem &$av_failed$&
12460 .cindex "content scanning" "AV scanner failure"
12461 This variable is available when Exim is compiled with the content-scanning
12462 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12463 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12464 the ACL malware condition.
12466 .vitem &$body_linecount$&
12467 .cindex "message body" "line count"
12468 .cindex "body of message" "line count"
12469 .vindex "&$body_linecount$&"
12470 When a message is being received or delivered, this variable contains the
12471 number of lines in the message's body. See also &$message_linecount$&.
12473 .vitem &$body_zerocount$&
12474 .cindex "message body" "binary zero count"
12475 .cindex "body of message" "binary zero count"
12476 .cindex "binary zero" "in message body"
12477 .vindex "&$body_zerocount$&"
12478 When a message is being received or delivered, this variable contains the
12479 number of binary zero bytes (ASCII NULs) in the message's body.
12481 .vitem &$bounce_recipient$&
12482 .vindex "&$bounce_recipient$&"
12483 This is set to the recipient address of a bounce message while Exim is creating
12484 it. It is useful if a customized bounce message text file is in use (see
12485 chapter &<<CHAPemsgcust>>&).
12487 .vitem &$bounce_return_size_limit$&
12488 .vindex "&$bounce_return_size_limit$&"
12489 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12490 up to a multiple of 1000. It is useful when a customized error message text
12491 file is in use (see chapter &<<CHAPemsgcust>>&).
12493 .vitem &$caller_gid$&
12494 .cindex "gid (group id)" "caller"
12495 .vindex "&$caller_gid$&"
12496 The real group id under which the process that called Exim was running. This is
12497 not the same as the group id of the originator of a message (see
12498 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12499 incarnation normally contains the Exim gid.
12501 .vitem &$caller_uid$&
12502 .cindex "uid (user id)" "caller"
12503 .vindex "&$caller_uid$&"
12504 The real user id under which the process that called Exim was running. This is
12505 not the same as the user id of the originator of a message (see
12506 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12507 incarnation normally contains the Exim uid.
12509 .vitem &$callout_address$&
12510 .vindex "&$callout_address$&"
12511 After a callout for verification, spamd or malware daemon service, the
12512 address that was connected to.
12514 .vitem &$compile_number$&
12515 .vindex "&$compile_number$&"
12516 The building process for Exim keeps a count of the number
12517 of times it has been compiled. This serves to distinguish different
12518 compilations of the same version of Exim.
12520 .vitem &$config_dir$&
12521 .vindex "&$config_dir$&"
12522 The directory name of the main configuration file. That is, the content of
12523 &$config_file$& with the last component stripped. The value does not
12524 contain the trailing slash. If &$config_file$& does not contain a slash,
12525 &$config_dir$& is ".".
12527 .vitem &$config_file$&
12528 .vindex "&$config_file$&"
12529 The name of the main configuration file Exim is using.
12531 .vitem &$dkim_verify_status$&
12532 Results of DKIM verification.
12533 For details see section &<<SECDKIMVFY>>&.
12535 .vitem &$dkim_cur_signer$& &&&
12536 &$dkim_verify_reason$& &&&
12537 &$dkim_domain$& &&&
12538 &$dkim_identity$& &&&
12539 &$dkim_selector$& &&&
12541 &$dkim_canon_body$& &&&
12542 &$dkim_canon_headers$& &&&
12543 &$dkim_copiedheaders$& &&&
12544 &$dkim_bodylength$& &&&
12545 &$dkim_created$& &&&
12546 &$dkim_expires$& &&&
12547 &$dkim_headernames$& &&&
12548 &$dkim_key_testing$& &&&
12549 &$dkim_key_nosubdomains$& &&&
12550 &$dkim_key_srvtype$& &&&
12551 &$dkim_key_granularity$& &&&
12552 &$dkim_key_notes$& &&&
12553 &$dkim_key_length$&
12554 These variables are only available within the DKIM ACL.
12555 For details see section &<<SECDKIMVFY>>&.
12557 .vitem &$dkim_signers$&
12558 .vindex &$dkim_signers$&
12559 When a message has been received this variable contains
12560 a colon-separated list of signer domains and identities for the message.
12561 For details see section &<<SECDKIMVFY>>&.
12563 .vitem &$dmarc_domain_policy$& &&&
12564 &$dmarc_status$& &&&
12565 &$dmarc_status_text$& &&&
12566 &$dmarc_used_domains$&
12567 Results of DMARC verification.
12568 For details see section &<<SECDMARC>>&.
12570 .vitem &$dnslist_domain$& &&&
12571 &$dnslist_matched$& &&&
12572 &$dnslist_text$& &&&
12574 .vindex "&$dnslist_domain$&"
12575 .vindex "&$dnslist_matched$&"
12576 .vindex "&$dnslist_text$&"
12577 .vindex "&$dnslist_value$&"
12578 .cindex "black list (DNS)"
12579 When a DNS (black) list lookup succeeds, these variables are set to contain
12580 the following data from the lookup: the list's domain name, the key that was
12581 looked up, the contents of any associated TXT record, and the value from the
12582 main A record. See section &<<SECID204>>& for more details.
12585 .vindex "&$domain$&"
12586 When an address is being routed, or delivered on its own, this variable
12587 contains the domain. Uppercase letters in the domain are converted into lower
12588 case for &$domain$&.
12590 Global address rewriting happens when a message is received, so the value of
12591 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12592 is set during user filtering, but not during system filtering, because a
12593 message may have many recipients and the system filter is called just once.
12595 When more than one address is being delivered at once (for example, several
12596 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12597 have the same domain. Transports can be restricted to handling only one domain
12598 at a time if the value of &$domain$& is required at transport time &-- this is
12599 the default for local transports. For further details of the environment in
12600 which local transports are run, see chapter &<<CHAPenvironment>>&.
12602 .oindex "&%delay_warning_condition%&"
12603 At the end of a delivery, if all deferred addresses have the same domain, it is
12604 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12606 The &$domain$& variable is also used in some other circumstances:
12609 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12610 the recipient address. The domain of the &'sender'& address is in
12611 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12612 normally set during the running of the MAIL ACL. However, if the sender address
12613 is verified with a callout during the MAIL ACL, the sender domain is placed in
12614 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12615 the &(smtp)& transport.
12618 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12619 &$domain$& contains the domain portion of the address that is being rewritten;
12620 it can be used in the expansion of the replacement address, for example, to
12621 rewrite domains by file lookup.
12624 With one important exception, whenever a domain list is being scanned,
12625 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12626 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12627 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12628 that, in a RCPT ACL, the sender domain list can be dependent on the
12629 recipient domain (which is what is in &$domain$& at this time).
12632 .cindex "ETRN" "value of &$domain$&"
12633 .oindex "&%smtp_etrn_command%&"
12634 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12635 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12638 .cindex "tainted data"
12639 If the origin of the data is an incoming message,
12640 the result of expanding this variable is tainted and may not
12641 be further expanded or used as a filename.
12642 When an untainted version is needed, one should be obtained from
12643 looking up the value in a local (therefore trusted) database.
12644 Often &$domain_data$& is usable in this role.
12647 .vitem &$domain_data$&
12648 .vindex "&$domain_data$&"
12649 When the &%domains%& condition on a router
12653 against a list, the match value is copied to &$domain_data$&.
12654 This is an enhancement over previous versions of Exim, when it only
12655 applied to the data read by a lookup.
12656 For details on match values see section &<<SECTlistresults>>& et. al.
12659 If the router routes the
12660 address to a transport, the value is available in that transport. If the
12661 transport is handling multiple addresses, the value from the first address is
12664 &$domain_data$& set in an ACL is available during
12665 the rest of the ACL statement.
12667 .vitem &$exim_gid$&
12668 .vindex "&$exim_gid$&"
12669 This variable contains the numerical value of the Exim group id.
12671 .vitem &$exim_path$&
12672 .vindex "&$exim_path$&"
12673 This variable contains the path to the Exim binary.
12675 .vitem &$exim_uid$&
12676 .vindex "&$exim_uid$&"
12677 This variable contains the numerical value of the Exim user id.
12679 .vitem &$exim_version$&
12680 .vindex "&$exim_version$&"
12681 This variable contains the version string of the Exim build.
12682 The first character is a major version number, currently 4.
12683 Then after a dot, the next group of digits is a minor version number.
12684 There may be other characters following the minor version.
12685 This value may be overridden by the &%exim_version%& main config option.
12687 .vitem &$header_$&<&'name'&>
12688 This is not strictly an expansion variable. It is expansion syntax for
12689 inserting the message header line with the given name. Note that the name must
12690 be terminated by colon or white space, because it may contain a wide variety of
12691 characters. Note also that braces must &'not'& be used.
12692 See the full description in section &<<SECTexpansionitems>>& above.
12694 .vitem &$headers_added$&
12695 .vindex "&$headers_added$&"
12696 Within an ACL this variable contains the headers added so far by
12697 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12698 The headers are a newline-separated list.
12702 When the &%check_local_user%& option is set for a router, the user's home
12703 directory is placed in &$home$& when the check succeeds. In particular, this
12704 means it is set during the running of users' filter files. A router may also
12705 explicitly set a home directory for use by a transport; this can be overridden
12706 by a setting on the transport itself.
12708 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12709 of the environment variable HOME, which is subject to the
12710 &%keep_environment%& and &%add_environment%& main config options.
12714 If a router assigns an address to a transport (any transport), and passes a
12715 list of hosts with the address, the value of &$host$& when the transport starts
12716 to run is the name of the first host on the list. Note that this applies both
12717 to local and remote transports.
12719 .cindex "transport" "filter"
12720 .cindex "filter" "transport filter"
12721 For the &(smtp)& transport, if there is more than one host, the value of
12722 &$host$& changes as the transport works its way through the list. In
12723 particular, when the &(smtp)& transport is expanding its options for encryption
12724 using TLS, or for specifying a transport filter (see chapter
12725 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12728 When used in the client part of an authenticator configuration (see chapter
12729 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12730 client is connected.
12733 .vitem &$host_address$&
12734 .vindex "&$host_address$&"
12735 This variable is set to the remote host's IP address whenever &$host$& is set
12736 for a remote connection. It is also set to the IP address that is being checked
12737 when the &%ignore_target_hosts%& option is being processed.
12739 .vitem &$host_data$&
12740 .vindex "&$host_data$&"
12741 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12742 result of the lookup is made available in the &$host_data$& variable. This
12743 allows you, for example, to do things like this:
12745 deny hosts = net-lsearch;/some/file
12746 message = $host_data
12748 .vitem &$host_lookup_deferred$&
12749 .cindex "host name" "lookup, failure of"
12750 .vindex "&$host_lookup_deferred$&"
12751 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12752 message comes from a remote host and there is an attempt to look up the host's
12753 name from its IP address, and the attempt is not successful, one of these
12754 variables is set to &"1"&.
12757 If the lookup receives a definite negative response (for example, a DNS lookup
12758 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12761 If there is any kind of problem during the lookup, such that Exim cannot
12762 tell whether or not the host name is defined (for example, a timeout for a DNS
12763 lookup), &$host_lookup_deferred$& is set to &"1"&.
12766 Looking up a host's name from its IP address consists of more than just a
12767 single reverse lookup. Exim checks that a forward lookup of at least one of the
12768 names it receives from a reverse lookup yields the original IP address. If this
12769 is not the case, Exim does not accept the looked up name(s), and
12770 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12771 IP address (for example, the existence of a PTR record in the DNS) is not
12772 sufficient on its own for the success of a host name lookup. If the reverse
12773 lookup succeeds, but there is a lookup problem such as a timeout when checking
12774 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12775 &"1"&. See also &$sender_host_name$&.
12777 .cindex authentication "expansion item"
12778 Performing these checks sets up information used by the
12779 &%authresults%& expansion item.
12782 .vitem &$host_lookup_failed$&
12783 .vindex "&$host_lookup_failed$&"
12784 See &$host_lookup_deferred$&.
12786 .vitem &$host_port$&
12787 .vindex "&$host_port$&"
12788 This variable is set to the remote host's TCP port whenever &$host$& is set
12789 for an outbound connection.
12791 .vitem &$initial_cwd$&
12792 .vindex "&$initial_cwd$&
12793 This variable contains the full path name of the initial working
12794 directory of the current Exim process. This may differ from the current
12795 working directory, as Exim changes this to "/" during early startup, and
12796 to &$spool_directory$& later.
12799 .vindex "&$inode$&"
12800 The only time this variable is set is while expanding the &%directory_file%&
12801 option in the &(appendfile)& transport. The variable contains the inode number
12802 of the temporary file which is about to be renamed. It can be used to construct
12803 a unique name for the file.
12805 .vitem &$interface_address$&
12806 .vindex "&$interface_address$&"
12807 This is an obsolete name for &$received_ip_address$&.
12809 .vitem &$interface_port$&
12810 .vindex "&$interface_port$&"
12811 This is an obsolete name for &$received_port$&.
12815 This variable is used during the expansion of &*forall*& and &*forany*&
12816 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12817 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12821 .vindex "&$ldap_dn$&"
12822 This variable, which is available only when Exim is compiled with LDAP support,
12823 contains the DN from the last entry in the most recently successful LDAP
12826 .vitem &$load_average$&
12827 .vindex "&$load_average$&"
12828 This variable contains the system load average, multiplied by 1000 so that it
12829 is an integer. For example, if the load average is 0.21, the value of the
12830 variable is 210. The value is recomputed every time the variable is referenced.
12832 .vitem &$local_part$&
12833 .vindex "&$local_part$&"
12834 When an address is being routed, or delivered on its own, this
12835 variable contains the local part. When a number of addresses are being
12836 delivered together (for example, multiple RCPT commands in an SMTP
12837 session), &$local_part$& is not set.
12839 Global address rewriting happens when a message is received, so the value of
12840 &$local_part$& during routing and delivery is the value after rewriting.
12841 &$local_part$& is set during user filtering, but not during system filtering,
12842 because a message may have many recipients and the system filter is called just
12845 .cindex "tainted data"
12846 If the origin of the data is an incoming message,
12847 the result of expanding this variable is tainted and
12848 may not be further expanded or used as a filename.
12850 &*Warning*&: the content of this variable is usually provided by a potential
12852 Consider carefully the implications of using it unvalidated as a name
12854 This presents issues for users' &_.forward_& and filter files.
12855 For traditional full user accounts, use &%check_local_users%& and the
12856 &$local_part_data$& variable rather than this one.
12857 For virtual users, store a suitable pathname component in the database
12858 which is used for account name validation, and use that retrieved value
12859 rather than this variable.
12860 Often &$local_part_data$& is usable in this role.
12861 If needed, use a router &%address_data%& or &%set%& option for
12862 the retrieved data.
12864 When a message is being delivered to a file, pipe, or autoreply transport as a
12865 result of aliasing or forwarding, &$local_part$& is set to the local part of
12866 the parent address, not to the filename or command (see &$address_file$& and
12869 When an ACL is running for a RCPT command, &$local_part$& contains the
12870 local part of the recipient address.
12872 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12873 &$local_part$& contains the local part of the address that is being rewritten;
12874 it can be used in the expansion of the replacement address, for example.
12876 In all cases, all quoting is removed from the local part. For example, for both
12879 "abc:xyz"@test.example
12880 abc\:xyz@test.example
12882 the value of &$local_part$& is
12886 If you use &$local_part$& to create another address, you should always wrap it
12887 inside a quoting operator. For example, in a &(redirect)& router you could
12890 data = ${quote_local_part:$local_part}@new.domain.example
12892 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12893 to process local parts in a case-dependent manner in a router, you can set the
12894 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12896 .vitem &$local_part_data$&
12897 .vindex "&$local_part_data$&"
12898 When the &%local_parts%& condition on a router or ACL
12899 matches a local part list
12901 the match value is copied to &$local_part_data$&.
12902 This is an enhancement over previous versions of Exim, when it only
12903 applied to the data read by a lookup.
12904 For details on match values see section &<<SECTlistresults>>& et. al.
12907 The &%check_local_user%& router option also sets this variable.
12909 .vindex &$local_part_prefix$& &&&
12910 &$local_part_prefix_v$& &&&
12911 &$local_part_suffix$& &&&
12912 &$local_part_suffix_v$&
12913 .cindex affix variables
12914 If a local part prefix or suffix has been recognized, it is not included in the
12915 value of &$local_part$& during routing and subsequent delivery. The values of
12916 any prefix or suffix are in &$local_part_prefix$& and
12917 &$local_part_suffix$&, respectively.
12918 .cindex "tainted data"
12919 If the specification did not include a wildcard then
12920 the affix variable value is not tainted.
12922 If the affix specification included a wildcard then the portion of
12923 the affix matched by the wildcard is in
12924 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12925 and both the whole and varying values are tainted.
12927 .vitem &$local_scan_data$&
12928 .vindex "&$local_scan_data$&"
12929 This variable contains the text returned by the &[local_scan()]& function when
12930 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12932 .vitem &$local_user_gid$&
12933 .vindex "&$local_user_gid$&"
12934 See &$local_user_uid$&.
12936 .vitem &$local_user_uid$&
12937 .vindex "&$local_user_uid$&"
12938 This variable and &$local_user_gid$& are set to the uid and gid after the
12939 &%check_local_user%& router precondition succeeds. This means that their values
12940 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12941 and &%condition%&), for the &%address_data%& expansion, and for any
12942 router-specific expansions. At all other times, the values in these variables
12943 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12945 .vitem &$localhost_number$&
12946 .vindex "&$localhost_number$&"
12947 This contains the expanded value of the
12948 &%localhost_number%& option. The expansion happens after the main options have
12951 .vitem &$log_inodes$&
12952 .vindex "&$log_inodes$&"
12953 The number of free inodes in the disk partition where Exim's
12954 log files are being written. The value is recalculated whenever the variable is
12955 referenced. If the relevant file system does not have the concept of inodes,
12956 the value of is -1. See also the &%check_log_inodes%& option.
12958 .vitem &$log_space$&
12959 .vindex "&$log_space$&"
12960 The amount of free space (as a number of kilobytes) in the disk
12961 partition where Exim's log files are being written. The value is recalculated
12962 whenever the variable is referenced. If the operating system does not have the
12963 ability to find the amount of free space (only true for experimental systems),
12964 the space value is -1. See also the &%check_log_space%& option.
12967 .vitem &$lookup_dnssec_authenticated$&
12968 .vindex "&$lookup_dnssec_authenticated$&"
12969 This variable is set after a DNS lookup done by
12970 a dnsdb lookup expansion, dnslookup router or smtp transport.
12971 .cindex "DNS" "DNSSEC"
12972 It will be empty if &(DNSSEC)& was not requested,
12973 &"no"& if the result was not labelled as authenticated data
12974 and &"yes"& if it was.
12975 Results that are labelled as authoritative answer that match
12976 the &%dns_trust_aa%& configuration variable count also
12977 as authenticated data.
12979 .vitem &$mailstore_basename$&
12980 .vindex "&$mailstore_basename$&"
12981 This variable is set only when doing deliveries in &"mailstore"& format in the
12982 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12983 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12984 contains the basename of the files that are being written, that is, the name
12985 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12988 .vitem &$malware_name$&
12989 .vindex "&$malware_name$&"
12990 This variable is available when Exim is compiled with the
12991 content-scanning extension. It is set to the name of the virus that was found
12992 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12994 .vitem &$max_received_linelength$&
12995 .vindex "&$max_received_linelength$&"
12996 .cindex "maximum" "line length"
12997 .cindex "line length" "maximum"
12998 This variable contains the number of bytes in the longest line that was
12999 received as part of the message, not counting the line termination
13001 It is not valid if the &%spool_files_wireformat%& option is used.
13003 .vitem &$message_age$&
13004 .cindex "message" "age of"
13005 .vindex "&$message_age$&"
13006 This variable is set at the start of a delivery attempt to contain the number
13007 of seconds since the message was received. It does not change during a single
13010 .vitem &$message_body$&
13011 .cindex "body of message" "expansion variable"
13012 .cindex "message body" "in expansion"
13013 .cindex "binary zero" "in message body"
13014 .vindex "&$message_body$&"
13015 .oindex "&%message_body_visible%&"
13016 This variable contains the initial portion of a message's body while it is
13017 being delivered, and is intended mainly for use in filter files. The maximum
13018 number of characters of the body that are put into the variable is set by the
13019 &%message_body_visible%& configuration option; the default is 500.
13021 .oindex "&%message_body_newlines%&"
13022 By default, newlines are converted into spaces in &$message_body$&, to make it
13023 easier to search for phrases that might be split over a line break. However,
13024 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13025 zeros are always converted into spaces.
13027 .vitem &$message_body_end$&
13028 .cindex "body of message" "expansion variable"
13029 .cindex "message body" "in expansion"
13030 .vindex "&$message_body_end$&"
13031 This variable contains the final portion of a message's
13032 body while it is being delivered. The format and maximum size are as for
13035 .vitem &$message_body_size$&
13036 .cindex "body of message" "size"
13037 .cindex "message body" "size"
13038 .vindex "&$message_body_size$&"
13039 When a message is being delivered, this variable contains the size of the body
13040 in bytes. The count starts from the character after the blank line that
13041 separates the body from the header. Newlines are included in the count. See
13042 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13044 If the spool file is wireformat
13045 (see the &%spool_files_wireformat%& main option)
13046 the CRLF line-terminators are included in the count.
13048 .vitem &$message_exim_id$&
13049 .vindex "&$message_exim_id$&"
13050 When a message is being received or delivered, this variable contains the
13051 unique message id that is generated and used by Exim to identify the message.
13052 An id is not created for a message until after its header has been successfully
13053 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13054 line; it is the local id that Exim assigns to the message, for example:
13055 &`1BXTIK-0001yO-VA`&.
13057 .vitem &$message_headers$&
13058 .vindex &$message_headers$&
13059 This variable contains a concatenation of all the header lines when a message
13060 is being processed, except for lines added by routers or transports. The header
13061 lines are separated by newline characters. Their contents are decoded in the
13062 same way as a header line that is inserted by &%bheader%&.
13064 .vitem &$message_headers_raw$&
13065 .vindex &$message_headers_raw$&
13066 This variable is like &$message_headers$& except that no processing of the
13067 contents of header lines is done.
13069 .vitem &$message_id$&
13070 This is an old name for &$message_exim_id$&. It is now deprecated.
13072 .vitem &$message_linecount$&
13073 .vindex "&$message_linecount$&"
13074 This variable contains the total number of lines in the header and body of the
13075 message. Compare &$body_linecount$&, which is the count for the body only.
13076 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13077 number of lines received. Before delivery happens (that is, before filters,
13078 routers, and transports run) the count is increased to include the
13079 &'Received:'& header line that Exim standardly adds, and also any other header
13080 lines that are added by ACLs. The blank line that separates the message header
13081 from the body is not counted.
13083 As with the special case of &$message_size$&, during the expansion of the
13084 appendfile transport's maildir_tag option in maildir format, the value of
13085 &$message_linecount$& is the precise size of the number of newlines in the
13086 file that has been written (minus one for the blank line between the
13087 header and the body).
13089 Here is an example of the use of this variable in a DATA ACL:
13092 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13093 message = Too many lines in message header
13095 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13096 message has not yet been received.
13098 This variable is not valid if the &%spool_files_wireformat%& option is used.
13100 .vitem &$message_size$&
13101 .cindex "size" "of message"
13102 .cindex "message" "size"
13103 .vindex "&$message_size$&"
13104 When a message is being processed, this variable contains its size in bytes. In
13105 most cases, the size includes those headers that were received with the
13106 message, but not those (such as &'Envelope-to:'&) that are added to individual
13107 deliveries as they are written. However, there is one special case: during the
13108 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13109 doing a delivery in maildir format, the value of &$message_size$& is the
13110 precise size of the file that has been written. See also
13111 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13113 .cindex "RCPT" "value of &$message_size$&"
13114 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13115 contains the size supplied on the MAIL command, or -1 if no size was given. The
13116 value may not, of course, be truthful.
13118 .vitem &$mime_$&&'xxx'&
13119 A number of variables whose names start with &$mime$& are
13120 available when Exim is compiled with the content-scanning extension. For
13121 details, see section &<<SECTscanmimepart>>&.
13123 .vitem "&$n0$& &-- &$n9$&"
13124 These variables are counters that can be incremented by means
13125 of the &%add%& command in filter files.
13127 .vitem &$original_domain$&
13128 .vindex "&$domain$&"
13129 .vindex "&$original_domain$&"
13130 When a top-level address is being processed for delivery, this contains the
13131 same value as &$domain$&. However, if a &"child"& address (for example,
13132 generated by an alias, forward, or filter file) is being processed, this
13133 variable contains the domain of the original address (lower cased). This
13134 differs from &$parent_domain$& only when there is more than one level of
13135 aliasing or forwarding. When more than one address is being delivered in a
13136 single transport run, &$original_domain$& is not set.
13138 If a new address is created by means of a &%deliver%& command in a system
13139 filter, it is set up with an artificial &"parent"& address. This has the local
13140 part &'system-filter'& and the default qualify domain.
13142 .vitem &$original_local_part$&
13143 .vindex "&$local_part$&"
13144 .vindex "&$original_local_part$&"
13145 When a top-level address is being processed for delivery, this contains the
13146 same value as &$local_part$&, unless a prefix or suffix was removed from the
13147 local part, because &$original_local_part$& always contains the full local
13148 part. When a &"child"& address (for example, generated by an alias, forward, or
13149 filter file) is being processed, this variable contains the full local part of
13150 the original address.
13152 If the router that did the redirection processed the local part
13153 case-insensitively, the value in &$original_local_part$& is in lower case.
13154 This variable differs from &$parent_local_part$& only when there is more than
13155 one level of aliasing or forwarding. When more than one address is being
13156 delivered in a single transport run, &$original_local_part$& is not set.
13158 If a new address is created by means of a &%deliver%& command in a system
13159 filter, it is set up with an artificial &"parent"& address. This has the local
13160 part &'system-filter'& and the default qualify domain.
13162 .vitem &$originator_gid$&
13163 .cindex "gid (group id)" "of originating user"
13164 .cindex "sender" "gid"
13165 .vindex "&$caller_gid$&"
13166 .vindex "&$originator_gid$&"
13167 This variable contains the value of &$caller_gid$& that was set when the
13168 message was received. For messages received via the command line, this is the
13169 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13170 normally the gid of the Exim user.
13172 .vitem &$originator_uid$&
13173 .cindex "uid (user id)" "of originating user"
13174 .cindex "sender" "uid"
13175 .vindex "&$caller_uid$&"
13176 .vindex "&$originator_uid$&"
13177 The value of &$caller_uid$& that was set when the message was received. For
13178 messages received via the command line, this is the uid of the sending user.
13179 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13182 .vitem &$parent_domain$&
13183 .vindex "&$parent_domain$&"
13184 This variable is similar to &$original_domain$& (see
13185 above), except that it refers to the immediately preceding parent address.
13187 .vitem &$parent_local_part$&
13188 .vindex "&$parent_local_part$&"
13189 This variable is similar to &$original_local_part$&
13190 (see above), except that it refers to the immediately preceding parent address.
13193 .cindex "pid (process id)" "of current process"
13195 This variable contains the current process id.
13197 .vitem &$pipe_addresses$&
13198 .cindex "filter" "transport filter"
13199 .cindex "transport" "filter"
13200 .vindex "&$pipe_addresses$&"
13201 This is not an expansion variable, but is mentioned here because the string
13202 &`$pipe_addresses`& is handled specially in the command specification for the
13203 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13204 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13205 It cannot be used in general expansion strings, and provokes an &"unknown
13206 variable"& error if encountered.
13208 .vitem &$primary_hostname$&
13209 .vindex "&$primary_hostname$&"
13210 This variable contains the value set by &%primary_hostname%& in the
13211 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13212 a single-component name, Exim calls &[gethostbyname()]& (or
13213 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13214 qualified host name. See also &$smtp_active_hostname$&.
13217 .vitem &$proxy_external_address$& &&&
13218 &$proxy_external_port$& &&&
13219 &$proxy_local_address$& &&&
13220 &$proxy_local_port$& &&&
13222 These variables are only available when built with Proxy Protocol
13224 For details see chapter &<<SECTproxyInbound>>&.
13226 .vitem &$prdr_requested$&
13227 .cindex "PRDR" "variable for"
13228 This variable is set to &"yes"& if PRDR was requested by the client for the
13229 current message, otherwise &"no"&.
13231 .vitem &$prvscheck_address$&
13232 This variable is used in conjunction with the &%prvscheck%& expansion item,
13233 which is described in sections &<<SECTexpansionitems>>& and
13234 &<<SECTverifyPRVS>>&.
13236 .vitem &$prvscheck_keynum$&
13237 This variable is used in conjunction with the &%prvscheck%& expansion item,
13238 which is described in sections &<<SECTexpansionitems>>& and
13239 &<<SECTverifyPRVS>>&.
13241 .vitem &$prvscheck_result$&
13242 This variable is used in conjunction with the &%prvscheck%& expansion item,
13243 which is described in sections &<<SECTexpansionitems>>& and
13244 &<<SECTverifyPRVS>>&.
13246 .vitem &$qualify_domain$&
13247 .vindex "&$qualify_domain$&"
13248 The value set for the &%qualify_domain%& option in the configuration file.
13250 .vitem &$qualify_recipient$&
13251 .vindex "&$qualify_recipient$&"
13252 The value set for the &%qualify_recipient%& option in the configuration file,
13253 or if not set, the value of &$qualify_domain$&.
13255 .vitem &$queue_name$&
13256 .vindex &$queue_name$&
13257 .cindex "named queues" variable
13258 .cindex queues named
13259 The name of the spool queue in use; empty for the default queue.
13261 .vitem &$queue_size$&
13262 .vindex "&$queue_size$&"
13263 .cindex "queue" "size of"
13264 .cindex "spool" "number of messages"
13265 This variable contains the number of messages queued.
13266 It is evaluated on demand, but no more often than once every minute.
13267 If there is no daemon notifier socket open, the value will be
13272 .cindex router variables
13273 Values can be placed in these variables by the &%set%& option of a router.
13274 They can be given any name that starts with &$r_$&.
13275 The values persist for the address being handled through subsequent routers
13276 and the eventual transport.
13278 .vitem &$rcpt_count$&
13279 .vindex "&$rcpt_count$&"
13280 When a message is being received by SMTP, this variable contains the number of
13281 RCPT commands received for the current message. If this variable is used in a
13282 RCPT ACL, its value includes the current command.
13284 .vitem &$rcpt_defer_count$&
13285 .vindex "&$rcpt_defer_count$&"
13286 .cindex "4&'xx'& responses" "count of"
13287 When a message is being received by SMTP, this variable contains the number of
13288 RCPT commands in the current message that have previously been rejected with a
13289 temporary (4&'xx'&) response.
13291 .vitem &$rcpt_fail_count$&
13292 .vindex "&$rcpt_fail_count$&"
13293 When a message is being received by SMTP, this variable contains the number of
13294 RCPT commands in the current message that have previously been rejected with a
13295 permanent (5&'xx'&) response.
13297 .vitem &$received_count$&
13298 .vindex "&$received_count$&"
13299 This variable contains the number of &'Received:'& header lines in the message,
13300 including the one added by Exim (so its value is always greater than zero). It
13301 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13304 .vitem &$received_for$&
13305 .vindex "&$received_for$&"
13306 If there is only a single recipient address in an incoming message, this
13307 variable contains that address when the &'Received:'& header line is being
13308 built. The value is copied after recipient rewriting has happened, but before
13309 the &[local_scan()]& function is run.
13311 .vitem &$received_ip_address$&
13312 .vindex "&$received_ip_address$&"
13313 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13314 variable is set to the address of the local IP interface, and &$received_port$&
13315 is set to the local port number. (The remote IP address and port are in
13316 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13317 the port value is -1 unless it has been set using the &%-oMi%& command line
13320 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13321 could be used, for example, to make the filename for a TLS certificate depend
13322 on which interface and/or port is being used for the incoming connection. The
13323 values of &$received_ip_address$& and &$received_port$& are saved with any
13324 messages that are received, thus making these variables available at delivery
13326 For outbound connections see &$sending_ip_address$&.
13328 .vitem &$received_port$&
13329 .vindex "&$received_port$&"
13330 See &$received_ip_address$&.
13332 .vitem &$received_protocol$&
13333 .vindex "&$received_protocol$&"
13334 When a message is being processed, this variable contains the name of the
13335 protocol by which it was received. Most of the names used by Exim are defined
13336 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13337 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13338 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13339 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13340 connection and the client was successfully authenticated.
13342 Exim uses the protocol name &"smtps"& for the case when encryption is
13343 automatically set up on connection without the use of STARTTLS (see
13344 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13345 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13346 where the client initially uses EHLO, sets up an encrypted connection using
13347 STARTTLS, and then uses HELO afterwards.
13349 The &%-oMr%& option provides a way of specifying a custom protocol name for
13350 messages that are injected locally by trusted callers. This is commonly used to
13351 identify messages that are being re-injected after some kind of scanning.
13353 .vitem &$received_time$&
13354 .vindex "&$received_time$&"
13355 This variable contains the date and time when the current message was received,
13356 as a number of seconds since the start of the Unix epoch.
13358 .vitem &$recipient_data$&
13359 .vindex "&$recipient_data$&"
13360 This variable is set after an indexing lookup success in an ACL &%recipients%&
13361 condition. It contains the data from the lookup, and the value remains set
13362 until the next &%recipients%& test. Thus, you can do things like this:
13364 &`require recipients = cdb*@;/some/file`&
13365 &`deny `&&'some further test involving'& &`$recipient_data`&
13367 &*Warning*&: This variable is set only when a lookup is used as an indexing
13368 method in the address list, using the semicolon syntax as in the example above.
13369 The variable is not set for a lookup that is used as part of the string
13370 expansion that all such lists undergo before being interpreted.
13372 .vitem &$recipient_verify_failure$&
13373 .vindex "&$recipient_verify_failure$&"
13374 In an ACL, when a recipient verification fails, this variable contains
13375 information about the failure. It is set to one of the following words:
13378 &"qualify"&: The address was unqualified (no domain), and the message
13379 was neither local nor came from an exempted host.
13382 &"route"&: Routing failed.
13385 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13386 or before the MAIL command (that is, on initial connection, HELO, or
13390 &"recipient"&: The RCPT command in a callout was rejected.
13393 &"postmaster"&: The postmaster check in a callout was rejected.
13396 The main use of this variable is expected to be to distinguish between
13397 rejections of MAIL and rejections of RCPT.
13399 .vitem &$recipients$&
13400 .vindex "&$recipients$&"
13401 This variable contains a list of envelope recipients for a message. A comma and
13402 a space separate the addresses in the replacement text. However, the variable
13403 is not generally available, to prevent exposure of Bcc recipients in
13404 unprivileged users' filter files. You can use &$recipients$& only in these
13408 In a system filter file.
13410 In the ACLs associated with the DATA command and with non-SMTP messages, that
13411 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13412 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13413 &%acl_not_smtp_mime%&.
13415 From within a &[local_scan()]& function.
13419 .vitem &$recipients_count$&
13420 .vindex "&$recipients_count$&"
13421 When a message is being processed, this variable contains the number of
13422 envelope recipients that came with the message. Duplicates are not excluded
13423 from the count. While a message is being received over SMTP, the number
13424 increases for each accepted recipient. It can be referenced in an ACL.
13427 .vitem &$regex_match_string$&
13428 .vindex "&$regex_match_string$&"
13429 This variable is set to contain the matching regular expression after a
13430 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13432 .vitem "&$regex1$&, &$regex2$&, etc"
13433 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13434 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13435 these variables contain the
13436 captured substrings identified by the regular expression.
13439 .vitem &$reply_address$&
13440 .vindex "&$reply_address$&"
13441 When a message is being processed, this variable contains the contents of the
13442 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13443 contents of the &'From:'& header line. Apart from the removal of leading
13444 white space, the value is not processed in any way. In particular, no RFC 2047
13445 decoding or character code translation takes place.
13447 .vitem &$return_path$&
13448 .vindex "&$return_path$&"
13449 When a message is being delivered, this variable contains the return path &--
13450 the sender field that will be sent as part of the envelope. It is not enclosed
13451 in <> characters. At the start of routing an address, &$return_path$& has the
13452 same value as &$sender_address$&, but if, for example, an incoming message to a
13453 mailing list has been expanded by a router which specifies a different address
13454 for bounce messages, &$return_path$& subsequently contains the new bounce
13455 address, whereas &$sender_address$& always contains the original sender address
13456 that was received with the message. In other words, &$sender_address$& contains
13457 the incoming envelope sender, and &$return_path$& contains the outgoing
13460 .vitem &$return_size_limit$&
13461 .vindex "&$return_size_limit$&"
13462 This is an obsolete name for &$bounce_return_size_limit$&.
13464 .vitem &$router_name$&
13465 .cindex "router" "name"
13466 .cindex "name" "of router"
13467 .vindex "&$router_name$&"
13468 During the running of a router this variable contains its name.
13471 .cindex "return code" "from &%run%& expansion"
13472 .vindex "&$runrc$&"
13473 This variable contains the return code from a command that is run by the
13474 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13475 assume the order in which option values are expanded, except for those
13476 preconditions whose order of testing is documented. Therefore, you cannot
13477 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13480 .vitem &$self_hostname$&
13481 .oindex "&%self%&" "value of host name"
13482 .vindex "&$self_hostname$&"
13483 When an address is routed to a supposedly remote host that turns out to be the
13484 local host, what happens is controlled by the &%self%& generic router option.
13485 One of its values causes the address to be passed to another router. When this
13486 happens, &$self_hostname$& is set to the name of the local host that the
13487 original router encountered. In other circumstances its contents are null.
13489 .vitem &$sender_address$&
13490 .vindex "&$sender_address$&"
13491 When a message is being processed, this variable contains the sender's address
13492 that was received in the message's envelope. The case of letters in the address
13493 is retained, in both the local part and the domain. For bounce messages, the
13494 value of this variable is the empty string. See also &$return_path$&.
13496 .vitem &$sender_address_data$&
13497 .vindex "&$address_data$&"
13498 .vindex "&$sender_address_data$&"
13499 If &$address_data$& is set when the routers are called from an ACL to verify a
13500 sender address, the final value is preserved in &$sender_address_data$&, to
13501 distinguish it from data from a recipient address. The value does not persist
13502 after the end of the current ACL statement. If you want to preserve it for
13503 longer, you can save it in an ACL variable.
13505 .vitem &$sender_address_domain$&
13506 .vindex "&$sender_address_domain$&"
13507 The domain portion of &$sender_address$&.
13509 .vitem &$sender_address_local_part$&
13510 .vindex "&$sender_address_local_part$&"
13511 The local part portion of &$sender_address$&.
13513 .vitem &$sender_data$&
13514 .vindex "&$sender_data$&"
13515 This variable is set after a lookup success in an ACL &%senders%& condition or
13516 in a router &%senders%& option. It contains the data from the lookup, and the
13517 value remains set until the next &%senders%& test. Thus, you can do things like
13520 &`require senders = cdb*@;/some/file`&
13521 &`deny `&&'some further test involving'& &`$sender_data`&
13523 &*Warning*&: This variable is set only when a lookup is used as an indexing
13524 method in the address list, using the semicolon syntax as in the example above.
13525 The variable is not set for a lookup that is used as part of the string
13526 expansion that all such lists undergo before being interpreted.
13528 .vitem &$sender_fullhost$&
13529 .vindex "&$sender_fullhost$&"
13530 When a message is received from a remote host, this variable contains the host
13531 name and IP address in a single string. It ends with the IP address in square
13532 brackets, followed by a colon and a port number if the logging of ports is
13533 enabled. The format of the rest of the string depends on whether the host
13534 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13535 looking up its IP address. (Looking up the IP address can be forced by the
13536 &%host_lookup%& option, independent of verification.) A plain host name at the
13537 start of the string is a verified host name; if this is not present,
13538 verification either failed or was not requested. A host name in parentheses is
13539 the argument of a HELO or EHLO command. This is omitted if it is identical to
13540 the verified host name or to the host's IP address in square brackets.
13542 .vitem &$sender_helo_dnssec$&
13543 .vindex "&$sender_helo_dnssec$&"
13544 This boolean variable is true if a successful HELO verification was
13545 .cindex "DNS" "DNSSEC"
13546 done using DNS information the resolver library stated was authenticated data.
13548 .vitem &$sender_helo_name$&
13549 .vindex "&$sender_helo_name$&"
13550 When a message is received from a remote host that has issued a HELO or EHLO
13551 command, the argument of that command is placed in this variable. It is also
13552 set if HELO or EHLO is used when a message is received using SMTP locally via
13553 the &%-bs%& or &%-bS%& options.
13555 .vitem &$sender_host_address$&
13556 .vindex "&$sender_host_address$&"
13557 When a message is received from a remote host using SMTP,
13558 this variable contains that
13559 host's IP address. For locally non-SMTP submitted messages, it is empty.
13561 .vitem &$sender_host_authenticated$&
13562 .vindex "&$sender_host_authenticated$&"
13563 This variable contains the name (not the public name) of the authenticator
13564 driver that successfully authenticated the client from which the message was
13565 received. It is empty if there was no successful authentication. See also
13566 &$authenticated_id$&.
13568 .vitem &$sender_host_dnssec$&
13569 .vindex "&$sender_host_dnssec$&"
13570 If an attempt to populate &$sender_host_name$& has been made
13571 (by reference, &%hosts_lookup%& or
13572 otherwise) then this boolean will have been set true if, and only if, the
13573 resolver library states that both
13574 the reverse and forward DNS were authenticated data. At all
13575 other times, this variable is false.
13577 .cindex "DNS" "DNSSEC"
13578 It is likely that you will need to coerce DNSSEC support on in the resolver
13579 library, by setting:
13584 In addition, on Linux with glibc 2.31 or newer the resolver library will
13585 default to stripping out a successful validation status.
13586 This will break a previously working Exim installation.
13587 Provided that you do trust the resolver (ie, is on localhost) you can tell
13588 glibc to pass through any successful validation with a new option in
13589 &_/etc/resolv.conf_&:
13594 Exim does not perform DNSSEC validation itself, instead leaving that to a
13595 validating resolver (e.g. unbound, or bind with suitable configuration).
13597 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13598 mechanism in the list, then this variable will be false.
13600 This requires that your system resolver library support EDNS0 (and that
13601 DNSSEC flags exist in the system headers). If the resolver silently drops
13602 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13603 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13606 .vitem &$sender_host_name$&
13607 .vindex "&$sender_host_name$&"
13608 When a message is received from a remote host, this variable contains the
13609 host's name as obtained by looking up its IP address. For messages received by
13610 other means, this variable is empty.
13612 .vindex "&$host_lookup_failed$&"
13613 If the host name has not previously been looked up, a reference to
13614 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13615 A looked up name is accepted only if it leads back to the original IP address
13616 via a forward lookup. If either the reverse or the forward lookup fails to find
13617 any data, or if the forward lookup does not yield the original IP address,
13618 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13620 .vindex "&$host_lookup_deferred$&"
13621 However, if either of the lookups cannot be completed (for example, there is a
13622 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13623 &$host_lookup_failed$& remains set to &"0"&.
13625 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13626 host name again if there is a subsequent reference to &$sender_host_name$&
13627 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13630 Exim does not automatically look up every calling host's name. If you want
13631 maximum efficiency, you should arrange your configuration so that it avoids
13632 these lookups altogether. The lookup happens only if one or more of the
13633 following are true:
13636 A string containing &$sender_host_name$& is expanded.
13638 The calling host matches the list in &%host_lookup%&. In the default
13639 configuration, this option is set to *, so it must be changed if lookups are
13640 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13642 Exim needs the host name in order to test an item in a host list. The items
13643 that require this are described in sections &<<SECThoslispatnam>>& and
13644 &<<SECThoslispatnamsk>>&.
13646 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13647 In this case, the host name is required to compare with the name quoted in any
13648 EHLO or HELO commands that the client issues.
13650 The remote host issues a EHLO or HELO command that quotes one of the
13651 domains in &%helo_lookup_domains%&. The default value of this option is
13652 . ==== As this is a nested list, any displays it contains must be indented
13653 . ==== as otherwise they are too far to the left.
13655 helo_lookup_domains = @ : @[]
13657 which causes a lookup if a remote host (incorrectly) gives the server's name or
13658 IP address in an EHLO or HELO command.
13662 .vitem &$sender_host_port$&
13663 .vindex "&$sender_host_port$&"
13664 When a message is received from a remote host, this variable contains the port
13665 number that was used on the remote host.
13667 .vitem &$sender_ident$&
13668 .vindex "&$sender_ident$&"
13669 When a message is received from a remote host, this variable contains the
13670 identification received in response to an RFC 1413 request. When a message has
13671 been received locally, this variable contains the login name of the user that
13674 .vitem &$sender_rate_$&&'xxx'&
13675 A number of variables whose names begin &$sender_rate_$& are set as part of the
13676 &%ratelimit%& ACL condition. Details are given in section
13677 &<<SECTratelimiting>>&.
13679 .vitem &$sender_rcvhost$&
13680 .cindex "DNS" "reverse lookup"
13681 .cindex "reverse DNS lookup"
13682 .vindex "&$sender_rcvhost$&"
13683 This is provided specifically for use in &'Received:'& headers. It starts with
13684 either the verified host name (as obtained from a reverse DNS lookup) or, if
13685 there is no verified host name, the IP address in square brackets. After that
13686 there may be text in parentheses. When the first item is a verified host name,
13687 the first thing in the parentheses is the IP address in square brackets,
13688 followed by a colon and a port number if port logging is enabled. When the
13689 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13692 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13693 was used and its argument was not identical to the real host name or IP
13694 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13695 all three items are present in the parentheses, a newline and tab are inserted
13696 into the string, to improve the formatting of the &'Received:'& header.
13698 .vitem &$sender_verify_failure$&
13699 .vindex "&$sender_verify_failure$&"
13700 In an ACL, when a sender verification fails, this variable contains information
13701 about the failure. The details are the same as for
13702 &$recipient_verify_failure$&.
13704 .vitem &$sending_ip_address$&
13705 .vindex "&$sending_ip_address$&"
13706 This variable is set whenever an outgoing SMTP connection to another host has
13707 been set up. It contains the IP address of the local interface that is being
13708 used. This is useful if a host that has more than one IP address wants to take
13709 on different personalities depending on which one is being used. For incoming
13710 connections, see &$received_ip_address$&.
13712 .vitem &$sending_port$&
13713 .vindex "&$sending_port$&"
13714 This variable is set whenever an outgoing SMTP connection to another host has
13715 been set up. It contains the local port that is being used. For incoming
13716 connections, see &$received_port$&.
13718 .vitem &$smtp_active_hostname$&
13719 .vindex "&$smtp_active_hostname$&"
13720 During an incoming SMTP session, this variable contains the value of the active
13721 host name, as specified by the &%smtp_active_hostname%& option. The value of
13722 &$smtp_active_hostname$& is saved with any message that is received, so its
13723 value can be consulted during routing and delivery.
13725 .vitem &$smtp_command$&
13726 .vindex "&$smtp_command$&"
13727 During the processing of an incoming SMTP command, this variable contains the
13728 entire command. This makes it possible to distinguish between HELO and EHLO in
13729 the HELO ACL, and also to distinguish between commands such as these:
13734 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13735 command, the address in &$smtp_command$& is the original address before any
13736 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13737 the address after SMTP-time rewriting.
13739 .vitem &$smtp_command_argument$&
13740 .cindex "SMTP" "command, argument for"
13741 .vindex "&$smtp_command_argument$&"
13742 While an ACL is running to check an SMTP command, this variable contains the
13743 argument, that is, the text that follows the command name, with leading white
13744 space removed. Following the introduction of &$smtp_command$&, this variable is
13745 somewhat redundant, but is retained for backwards compatibility.
13747 .vitem &$smtp_command_history$&
13748 .cindex SMTP "command history"
13749 .vindex "&$smtp_command_history$&"
13750 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13751 received, in time-order left to right. Only a limited number of commands
13754 .vitem &$smtp_count_at_connection_start$&
13755 .vindex "&$smtp_count_at_connection_start$&"
13756 This variable is set greater than zero only in processes spawned by the Exim
13757 daemon for handling incoming SMTP connections. The name is deliberately long,
13758 in order to emphasize what the contents are. When the daemon accepts a new
13759 connection, it increments this variable. A copy of the variable is passed to
13760 the child process that handles the connection, but its value is fixed, and
13761 never changes. It is only an approximation of how many incoming connections
13762 there actually are, because many other connections may come and go while a
13763 single connection is being processed. When a child process terminates, the
13764 daemon decrements its copy of the variable.
13766 .vitem "&$sn0$& &-- &$sn9$&"
13767 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13768 that were current at the end of the system filter file. This allows a system
13769 filter file to set values that can be tested in users' filter files. For
13770 example, a system filter could set a value indicating how likely it is that a
13771 message is junk mail.
13773 .vitem &$spam_score$& &&&
13774 &$spam_score_int$& &&&
13776 &$spam_report$& &&&
13778 A number of variables whose names start with &$spam$& are available when Exim
13779 is compiled with the content-scanning extension. For details, see section
13780 &<<SECTscanspamass>>&.
13782 .vitem &$spf_header_comment$& &&&
13783 &$spf_received$& &&&
13785 &$spf_result_guessed$& &&&
13786 &$spf_smtp_comment$&
13787 These variables are only available if Exim is built with SPF support.
13788 For details see section &<<SECSPF>>&.
13790 .vitem &$spool_directory$&
13791 .vindex "&$spool_directory$&"
13792 The name of Exim's spool directory.
13794 .vitem &$spool_inodes$&
13795 .vindex "&$spool_inodes$&"
13796 The number of free inodes in the disk partition where Exim's spool files are
13797 being written. The value is recalculated whenever the variable is referenced.
13798 If the relevant file system does not have the concept of inodes, the value of
13799 is -1. See also the &%check_spool_inodes%& option.
13801 .vitem &$spool_space$&
13802 .vindex "&$spool_space$&"
13803 The amount of free space (as a number of kilobytes) in the disk partition where
13804 Exim's spool files are being written. The value is recalculated whenever the
13805 variable is referenced. If the operating system does not have the ability to
13806 find the amount of free space (only true for experimental systems), the space
13807 value is -1. For example, to check in an ACL that there is at least 50
13808 megabytes free on the spool, you could write:
13810 condition = ${if > {$spool_space}{50000}}
13812 See also the &%check_spool_space%& option.
13815 .vitem &$thisaddress$&
13816 .vindex "&$thisaddress$&"
13817 This variable is set only during the processing of the &%foranyaddress%&
13818 command in a filter file. Its use is explained in the description of that
13819 command, which can be found in the separate document entitled &'Exim's
13820 interfaces to mail filtering'&.
13822 .vitem &$tls_in_bits$&
13823 .vindex "&$tls_in_bits$&"
13824 Contains an approximation of the TLS cipher's bit-strength
13825 on the inbound connection; the meaning of
13826 this depends upon the TLS implementation used.
13827 If TLS has not been negotiated, the value will be 0.
13828 The value of this is automatically fed into the Cyrus SASL authenticator
13829 when acting as a server, to specify the "external SSF" (a SASL term).
13831 The deprecated &$tls_bits$& variable refers to the inbound side
13832 except when used in the context of an outbound SMTP delivery, when it refers to
13835 .vitem &$tls_out_bits$&
13836 .vindex "&$tls_out_bits$&"
13837 Contains an approximation of the TLS cipher's bit-strength
13838 on an outbound SMTP connection; the meaning of
13839 this depends upon the TLS implementation used.
13840 If TLS has not been negotiated, the value will be 0.
13842 .vitem &$tls_in_ourcert$&
13843 .vindex "&$tls_in_ourcert$&"
13844 .cindex certificate variables
13845 This variable refers to the certificate presented to the peer of an
13846 inbound connection when the message was received.
13847 It is only useful as the argument of a
13848 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13849 or a &%def%& condition.
13851 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13852 when a list of more than one
13853 file is used for &%tls_certificate%&, this variable is not reliable.
13854 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13856 .vitem &$tls_in_peercert$&
13857 .vindex "&$tls_in_peercert$&"
13858 This variable refers to the certificate presented by the peer of an
13859 inbound connection when the message was received.
13860 It is only useful as the argument of a
13861 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13862 or a &%def%& condition.
13863 If certificate verification fails it may refer to a failing chain element
13864 which is not the leaf.
13866 .vitem &$tls_out_ourcert$&
13867 .vindex "&$tls_out_ourcert$&"
13868 This variable refers to the certificate presented to the peer of an
13869 outbound connection. It is only useful as the argument of a
13870 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13871 or a &%def%& condition.
13873 .vitem &$tls_out_peercert$&
13874 .vindex "&$tls_out_peercert$&"
13875 This variable refers to the certificate presented by the peer of an
13876 outbound connection. It is only useful as the argument of a
13877 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13878 or a &%def%& condition.
13879 If certificate verification fails it may refer to a failing chain element
13880 which is not the leaf.
13882 .vitem &$tls_in_certificate_verified$&
13883 .vindex "&$tls_in_certificate_verified$&"
13884 This variable is set to &"1"& if a TLS certificate was verified when the
13885 message was received, and &"0"& otherwise.
13887 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13888 except when used in the context of an outbound SMTP delivery, when it refers to
13891 .vitem &$tls_out_certificate_verified$&
13892 .vindex "&$tls_out_certificate_verified$&"
13893 This variable is set to &"1"& if a TLS certificate was verified when an
13894 outbound SMTP connection was made,
13895 and &"0"& otherwise.
13897 .vitem &$tls_in_cipher$&
13898 .vindex "&$tls_in_cipher$&"
13899 .vindex "&$tls_cipher$&"
13900 When a message is received from a remote host over an encrypted SMTP
13901 connection, this variable is set to the cipher suite that was negotiated, for
13902 example DES-CBC3-SHA. In other circumstances, in particular, for message
13903 received over unencrypted connections, the variable is empty. Testing
13904 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13905 non-encrypted connections during ACL processing.
13907 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13908 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13909 becomes the same as &$tls_out_cipher$&.
13911 .vitem &$tls_in_cipher_std$&
13912 .vindex "&$tls_in_cipher_std$&"
13913 As above, but returning the RFC standard name for the cipher suite.
13915 .vitem &$tls_out_cipher$&
13916 .vindex "&$tls_out_cipher$&"
13918 cleared before any outgoing SMTP connection is made,
13919 and then set to the outgoing cipher suite if one is negotiated. See chapter
13920 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13921 details of the &(smtp)& transport.
13923 .vitem &$tls_out_cipher_std$&
13924 .vindex "&$tls_out_cipher_std$&"
13925 As above, but returning the RFC standard name for the cipher suite.
13927 .vitem &$tls_out_dane$&
13928 .vindex &$tls_out_dane$&
13929 DANE active status. See section &<<SECDANE>>&.
13931 .vitem &$tls_in_ocsp$&
13932 .vindex "&$tls_in_ocsp$&"
13933 When a message is received from a remote client connection
13934 the result of any OCSP request from the client is encoded in this variable:
13936 0 OCSP proof was not requested (default value)
13937 1 No response to request
13938 2 Response not verified
13939 3 Verification failed
13940 4 Verification succeeded
13943 .vitem &$tls_out_ocsp$&
13944 .vindex "&$tls_out_ocsp$&"
13945 When a message is sent to a remote host connection
13946 the result of any OCSP request made is encoded in this variable.
13947 See &$tls_in_ocsp$& for values.
13949 .vitem &$tls_in_peerdn$&
13950 .vindex "&$tls_in_peerdn$&"
13951 .vindex "&$tls_peerdn$&"
13952 .cindex certificate "extracting fields"
13953 When a message is received from a remote host over an encrypted SMTP
13954 connection, and Exim is configured to request a certificate from the client,
13955 the value of the Distinguished Name of the certificate is made available in the
13956 &$tls_in_peerdn$& during subsequent processing.
13957 If certificate verification fails it may refer to a failing chain element
13958 which is not the leaf.
13960 The deprecated &$tls_peerdn$& variable refers to the inbound side
13961 except when used in the context of an outbound SMTP delivery, when it refers to
13964 .vitem &$tls_out_peerdn$&
13965 .vindex "&$tls_out_peerdn$&"
13966 When a message is being delivered to a remote host over an encrypted SMTP
13967 connection, and Exim is configured to request a certificate from the server,
13968 the value of the Distinguished Name of the certificate is made available in the
13969 &$tls_out_peerdn$& during subsequent processing.
13970 If certificate verification fails it may refer to a failing chain element
13971 which is not the leaf.
13975 .vitem &$tls_in_resumption$& &&&
13976 &$tls_out_resumption$&
13977 .vindex &$tls_in_resumption$&
13978 .vindex &$tls_out_resumption$&
13979 .cindex TLS resumption
13980 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13984 .vitem &$tls_in_sni$&
13985 .vindex "&$tls_in_sni$&"
13986 .vindex "&$tls_sni$&"
13987 .cindex "TLS" "Server Name Indication"
13989 .cindex SNI "observability on server"
13990 When a TLS session is being established, if the client sends the Server
13991 Name Indication extension, the value will be placed in this variable.
13992 If the variable appears in &%tls_certificate%& then this option and
13993 some others, described in &<<SECTtlssni>>&,
13994 will be re-expanded early in the TLS session, to permit
13995 a different certificate to be presented (and optionally a different key to be
13996 used) to the client, based upon the value of the SNI extension.
13998 The deprecated &$tls_sni$& variable refers to the inbound side
13999 except when used in the context of an outbound SMTP delivery, when it refers to
14002 .vitem &$tls_out_sni$&
14003 .vindex "&$tls_out_sni$&"
14004 .cindex "TLS" "Server Name Indication"
14006 .cindex SNI "observability in client"
14008 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
14011 .vitem &$tls_out_tlsa_usage$&
14012 .vindex &$tls_out_tlsa_usage$&
14013 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
14015 .vitem &$tls_in_ver$&
14016 .vindex "&$tls_in_ver$&"
14017 When a message is received from a remote host over an encrypted SMTP connection
14018 this variable is set to the protocol version, eg &'TLS1.2'&.
14020 .vitem &$tls_out_ver$&
14021 .vindex "&$tls_out_ver$&"
14022 When a message is being delivered to a remote host over an encrypted SMTP connection
14023 this variable is set to the protocol version.
14026 .vitem &$tod_bsdinbox$&
14027 .vindex "&$tod_bsdinbox$&"
14028 The time of day and the date, in the format required for BSD-style mailbox
14029 files, for example: Thu Oct 17 17:14:09 1995.
14031 .vitem &$tod_epoch$&
14032 .vindex "&$tod_epoch$&"
14033 The time and date as a number of seconds since the start of the Unix epoch.
14035 .vitem &$tod_epoch_l$&
14036 .vindex "&$tod_epoch_l$&"
14037 The time and date as a number of microseconds since the start of the Unix epoch.
14039 .vitem &$tod_full$&
14040 .vindex "&$tod_full$&"
14041 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14042 +0100. The timezone is always given as a numerical offset from UTC, with
14043 positive values used for timezones that are ahead (east) of UTC, and negative
14044 values for those that are behind (west).
14047 .vindex "&$tod_log$&"
14048 The time and date in the format used for writing Exim's log files, for example:
14049 1995-10-12 15:32:29, but without a timezone.
14051 .vitem &$tod_logfile$&
14052 .vindex "&$tod_logfile$&"
14053 This variable contains the date in the format yyyymmdd. This is the format that
14054 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14057 .vitem &$tod_zone$&
14058 .vindex "&$tod_zone$&"
14059 This variable contains the numerical value of the local timezone, for example:
14062 .vitem &$tod_zulu$&
14063 .vindex "&$tod_zulu$&"
14064 This variable contains the UTC date and time in &"Zulu"& format, as specified
14065 by ISO 8601, for example: 20030221154023Z.
14067 .vitem &$transport_name$&
14068 .cindex "transport" "name"
14069 .cindex "name" "of transport"
14070 .vindex "&$transport_name$&"
14071 During the running of a transport, this variable contains its name.
14074 .vindex "&$value$&"
14075 This variable contains the result of an expansion lookup, extraction operation,
14076 or external command, as described above. It is also used during a
14077 &*reduce*& expansion.
14079 .vitem &$verify_mode$&
14080 .vindex "&$verify_mode$&"
14081 While a router or transport is being run in verify mode or for cutthrough delivery,
14082 contains "S" for sender-verification or "R" for recipient-verification.
14085 .vitem &$version_number$&
14086 .vindex "&$version_number$&"
14087 The version number of Exim. Same as &$exim_version$&, may be overridden
14088 by the &%exim_version%& main config option.
14090 .vitem &$warn_message_delay$&
14091 .vindex "&$warn_message_delay$&"
14092 This variable is set only during the creation of a message warning about a
14093 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14095 .vitem &$warn_message_recipients$&
14096 .vindex "&$warn_message_recipients$&"
14097 This variable is set only during the creation of a message warning about a
14098 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14104 . ////////////////////////////////////////////////////////////////////////////
14105 . ////////////////////////////////////////////////////////////////////////////
14107 .chapter "Embedded Perl" "CHAPperl"
14108 .scindex IIDperl "Perl" "calling from Exim"
14109 Exim can be built to include an embedded Perl interpreter. When this is done,
14110 Perl subroutines can be called as part of the string expansion process. To make
14111 use of the Perl support, you need version 5.004 or later of Perl installed on
14112 your system. To include the embedded interpreter in the Exim binary, include
14117 in your &_Local/Makefile_& and then build Exim in the normal way.
14120 .section "Setting up so Perl can be used" "SECID85"
14121 .oindex "&%perl_startup%&"
14122 Access to Perl subroutines is via a global configuration option called
14123 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14124 no &%perl_startup%& option in the Exim configuration file then no Perl
14125 interpreter is started and there is almost no overhead for Exim (since none of
14126 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14127 option then the associated value is taken to be Perl code which is executed in
14128 a newly created Perl interpreter.
14130 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14131 need backslashes before any characters to escape special meanings. The option
14132 should usually be something like
14134 perl_startup = do '/etc/exim.pl'
14136 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14137 use from Exim. Exim can be configured either to start up a Perl interpreter as
14138 soon as it is entered, or to wait until the first time it is needed. Starting
14139 the interpreter at the beginning ensures that it is done while Exim still has
14140 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14141 fact used in a particular run. Also, note that this does not mean that Exim is
14142 necessarily running as root when Perl is called at a later time. By default,
14143 the interpreter is started only when it is needed, but this can be changed in
14147 .oindex "&%perl_at_start%&"
14148 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14149 a startup when Exim is entered.
14151 The command line option &%-ps%& also requests a startup when Exim is entered,
14152 overriding the setting of &%perl_at_start%&.
14155 There is also a command line option &%-pd%& (for delay) which suppresses the
14156 initial startup, even if &%perl_at_start%& is set.
14159 .oindex "&%perl_taintmode%&"
14160 .cindex "Perl" "taintmode"
14161 To provide more security executing Perl code via the embedded Perl
14162 interpreter, the &%perl_taintmode%& option can be set. This enables the
14163 taint mode of the Perl interpreter. You are encouraged to set this
14164 option to a true value. To avoid breaking existing installations, it
14168 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14172 .section "Calling Perl subroutines" "SECID86"
14173 When the configuration file includes a &%perl_startup%& option you can make use
14174 of the string expansion item to call the Perl subroutines that are defined
14175 by the &%perl_startup%& code. The operator is used in any of the following
14179 ${perl{foo}{argument}}
14180 ${perl{foo}{argument1}{argument2} ... }
14182 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14183 arguments may be passed. Passing more than this results in an expansion failure
14184 with an error message of the form
14186 Too many arguments passed to Perl subroutine "foo" (max is 8)
14188 The return value of the Perl subroutine is evaluated in a scalar context before
14189 it is passed back to Exim to be inserted into the expanded string. If the
14190 return value is &'undef'&, the expansion is forced to fail in the same way as
14191 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14192 by obeying Perl's &%die%& function, the expansion fails with the error message
14193 that was passed to &%die%&.
14196 .section "Calling Exim functions from Perl" "SECID87"
14197 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14198 is available to call back into Exim's string expansion function. For example,
14201 my $lp = Exim::expand_string('$local_part');
14203 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14204 Note those are single quotes and not double quotes to protect against
14205 &$local_part$& being interpolated as a Perl variable.
14207 If the string expansion is forced to fail by a &"fail"& item, the result of
14208 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14209 expansion string, the Perl call from the original expansion string fails with
14210 an appropriate error message, in the same way as if &%die%& were used.
14212 .cindex "debugging" "from embedded Perl"
14213 .cindex "log" "writing from embedded Perl"
14214 Two other Exim functions are available for use from within Perl code.
14215 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14216 debugging is enabled. If you want a newline at the end, you must supply it.
14217 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14218 timestamp. In this case, you should not supply a terminating newline.
14221 .section "Use of standard output and error by Perl" "SECID88"
14222 .cindex "Perl" "standard output and error"
14223 You should not write to the standard error or output streams from within your
14224 Perl code, as it is not defined how these are set up. In versions of Exim
14225 before 4.50, it is possible for the standard output or error to refer to the
14226 SMTP connection during message reception via the daemon. Writing to this stream
14227 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14228 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14229 avoided, but the output is lost.
14231 .cindex "Perl" "use of &%warn%&"
14232 The Perl &%warn%& statement writes to the standard error stream by default.
14233 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14234 you have no control. When Exim starts up the Perl interpreter, it arranges for
14235 output from the &%warn%& statement to be written to the Exim main log. You can
14236 change this by including appropriate Perl magic somewhere in your Perl code.
14237 For example, to discard &%warn%& output completely, you need this:
14239 $SIG{__WARN__} = sub { };
14241 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14242 example, the code for the subroutine is empty, so it does nothing, but you can
14243 include any Perl code that you like. The text of the &%warn%& message is passed
14244 as the first subroutine argument.
14248 . ////////////////////////////////////////////////////////////////////////////
14249 . ////////////////////////////////////////////////////////////////////////////
14251 .chapter "Starting the daemon and the use of network interfaces" &&&
14252 "CHAPinterfaces" &&&
14253 "Starting the daemon"
14254 .cindex "daemon" "starting"
14255 .cindex "interface" "listening"
14256 .cindex "network interface"
14257 .cindex "interface" "network"
14258 .cindex "IP address" "for listening"
14259 .cindex "daemon" "listening IP addresses"
14260 .cindex "TCP/IP" "setting listening interfaces"
14261 .cindex "TCP/IP" "setting listening ports"
14262 A host that is connected to a TCP/IP network may have one or more physical
14263 hardware network interfaces. Each of these interfaces may be configured as one
14264 or more &"logical"& interfaces, which are the entities that a program actually
14265 works with. Each of these logical interfaces is associated with an IP address.
14266 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14267 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14268 knowledge about the host's interfaces for use in three different circumstances:
14271 When a listening daemon is started, Exim needs to know which interfaces
14272 and ports to listen on.
14274 When Exim is routing an address, it needs to know which IP addresses
14275 are associated with local interfaces. This is required for the correct
14276 processing of MX lists by removing the local host and others with the
14277 same or higher priority values. Also, Exim needs to detect cases
14278 when an address is routed to an IP address that in fact belongs to the
14279 local host. Unless the &%self%& router option or the &%allow_localhost%&
14280 option of the smtp transport is set (as appropriate), this is treated
14281 as an error situation.
14283 When Exim connects to a remote host, it may need to know which interface to use
14284 for the outgoing connection.
14288 Exim's default behaviour is likely to be appropriate in the vast majority
14289 of cases. If your host has only one interface, and you want all its IP
14290 addresses to be treated in the same way, and you are using only the
14291 standard SMTP port, you should not need to take any special action. The
14292 rest of this chapter does not apply to you.
14294 In a more complicated situation you may want to listen only on certain
14295 interfaces, or on different ports, and for this reason there are a number of
14296 options that can be used to influence Exim's behaviour. The rest of this
14297 chapter describes how they operate.
14299 When a message is received over TCP/IP, the interface and port that were
14300 actually used are set in &$received_ip_address$& and &$received_port$&.
14304 .section "Starting a listening daemon" "SECID89"
14305 When a listening daemon is started (by means of the &%-bd%& command line
14306 option), the interfaces and ports on which it listens are controlled by the
14310 &%daemon_smtp_ports%& contains a list of default ports
14312 (For backward compatibility, this option can also be specified in the singular.)
14314 &%local_interfaces%& contains list of interface IP addresses on which to
14315 listen. Each item may optionally also specify a port.
14318 The default list separator in both cases is a colon, but this can be changed as
14319 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14320 it is usually best to change the separator to avoid having to double all the
14321 colons. For example:
14323 local_interfaces = <; 127.0.0.1 ; \
14326 3ffe:ffff:836f::fe86:a061
14328 There are two different formats for specifying a port along with an IP address
14329 in &%local_interfaces%&:
14332 The port is added onto the address with a dot separator. For example, to listen
14333 on port 1234 on two different IP addresses:
14335 local_interfaces = <; 192.168.23.65.1234 ; \
14336 3ffe:ffff:836f::fe86:a061.1234
14339 The IP address is enclosed in square brackets, and the port is added
14340 with a colon separator, for example:
14342 local_interfaces = <; [192.168.23.65]:1234 ; \
14343 [3ffe:ffff:836f::fe86:a061]:1234
14347 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14348 default setting contains just one port:
14350 daemon_smtp_ports = smtp
14352 If more than one port is listed, each interface that does not have its own port
14353 specified listens on all of them. Ports that are listed in
14354 &%daemon_smtp_ports%& can be identified either by name (defined in
14355 &_/etc/services_&) or by number. However, when ports are given with individual
14356 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14360 .section "Special IP listening addresses" "SECID90"
14361 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14362 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14363 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14364 instead of setting up separate listening sockets for each interface. The
14365 default value of &%local_interfaces%& is
14367 local_interfaces = 0.0.0.0
14369 when Exim is built without IPv6 support; otherwise it is:
14371 local_interfaces = <; ::0 ; 0.0.0.0
14373 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14377 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14378 The &%-oX%& command line option can be used to override the values of
14379 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14380 instance. Another way of doing this would be to use macros and the &%-D%&
14381 option. However, &%-oX%& can be used by any admin user, whereas modification of
14382 the runtime configuration by &%-D%& is allowed only when the caller is root or
14385 The value of &%-oX%& is a list of items. The default colon separator can be
14386 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14387 If there are any items that do not
14388 contain dots or colons (that is, are not IP addresses), the value of
14389 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14390 items that do contain dots or colons, the value of &%local_interfaces%& is
14391 replaced by those items. Thus, for example,
14395 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14398 -oX 192.168.34.5.1125
14400 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14401 (However, since &%local_interfaces%& now contains no items without ports, the
14402 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14406 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14407 .cindex "submissions protocol"
14408 .cindex "ssmtp protocol"
14409 .cindex "smtps protocol"
14410 .cindex "SMTP" "ssmtp protocol"
14411 .cindex "SMTP" "smtps protocol"
14412 Exim supports the use of TLS-on-connect, used by mail clients in the
14413 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14414 For some years, IETF Standards Track documents only blessed the
14415 STARTTLS-based Submission service (port 587) while common practice was to support
14416 the same feature set on port 465, but using TLS-on-connect.
14417 If your installation needs to provide service to mail clients
14418 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14421 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14422 service names, connections to those ports must first establish TLS, before
14423 proceeding to the application layer use of the SMTP protocol.
14425 The common use of this option is expected to be
14427 tls_on_connect_ports = 465
14430 There is also a command line option &%-tls-on-connect%&, which forces all ports
14431 to behave in this way when a daemon is started.
14433 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14434 daemon to listen on those ports. You must still specify them in
14435 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14436 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14437 connections via the daemon.)
14442 .section "IPv6 address scopes" "SECID92"
14443 .cindex "IPv6" "address scopes"
14444 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14445 can, in principle, have the same link-local IPv6 address on different
14446 interfaces. Thus, additional information is needed, over and above the IP
14447 address, to distinguish individual interfaces. A convention of using a
14448 percent sign followed by something (often the interface name) has been
14449 adopted in some cases, leading to addresses like this:
14451 fe80::202:b3ff:fe03:45c1%eth0
14453 To accommodate this usage, a percent sign followed by an arbitrary string is
14454 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14455 to convert a textual IPv6 address for actual use. This function recognizes the
14456 percent convention in operating systems that support it, and it processes the
14457 address appropriately. Unfortunately, some older libraries have problems with
14458 &[getaddrinfo()]&. If
14460 IPV6_USE_INET_PTON=yes
14462 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14463 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14464 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14465 function.) Of course, this means that the additional functionality of
14466 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14468 .section "Disabling IPv6" "SECID93"
14469 .cindex "IPv6" "disabling"
14470 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14471 run on a host whose kernel does not support IPv6. The binary will fall back to
14472 using IPv4, but it may waste resources looking up AAAA records, and trying to
14473 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14474 .oindex "&%disable_ipv6%&"
14475 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14476 activities take place. AAAA records are never looked up, and any IPv6 addresses
14477 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14478 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14479 to handle IPv6 literal addresses.
14481 On the other hand, when IPv6 is in use, there may be times when you want to
14482 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14483 option to globally suppress the lookup of AAAA records for specified domains,
14484 and you can use the &%ignore_target_hosts%& generic router option to ignore
14485 IPv6 addresses in an individual router.
14489 .section "Examples of starting a listening daemon" "SECID94"
14490 The default case in an IPv6 environment is
14492 daemon_smtp_ports = smtp
14493 local_interfaces = <; ::0 ; 0.0.0.0
14495 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14496 Either one or two sockets may be used, depending on the characteristics of
14497 the TCP/IP stack. (This is complicated and messy; for more information,
14498 read the comments in the &_daemon.c_& source file.)
14500 To specify listening on ports 25 and 26 on all interfaces:
14502 daemon_smtp_ports = 25 : 26
14504 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14506 local_interfaces = <; ::0.25 ; ::0.26 \
14507 0.0.0.0.25 ; 0.0.0.0.26
14509 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14510 IPv4 loopback address only:
14512 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14514 To specify listening on the default port on specific interfaces only:
14516 local_interfaces = 10.0.0.67 : 192.168.34.67
14518 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14522 .section "Recognizing the local host" "SECTreclocipadd"
14523 The &%local_interfaces%& option is also used when Exim needs to determine
14524 whether or not an IP address refers to the local host. That is, the IP
14525 addresses of all the interfaces on which a daemon is listening are always
14528 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14529 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14530 available interfaces from the operating system, and extracts the relevant
14531 (that is, IPv4 or IPv6) addresses to use for checking.
14533 Some systems set up large numbers of virtual interfaces in order to provide
14534 many virtual web servers. In this situation, you may want to listen for
14535 email on only a few of the available interfaces, but nevertheless treat all
14536 interfaces as local when routing. You can do this by setting
14537 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14538 &"all"& wildcard values. These addresses are recognized as local, but are not
14539 used for listening. Consider this example:
14541 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14543 3ffe:2101:12:1:a00:20ff:fe86:a061
14545 extra_local_interfaces = <; ::0 ; 0.0.0.0
14547 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14548 address, but all available interface addresses are treated as local when
14551 In some environments the local host name may be in an MX list, but with an IP
14552 address that is not assigned to any local interface. In other cases it may be
14553 desirable to treat other host names as if they referred to the local host. Both
14554 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14555 This contains host names rather than IP addresses. When a host is referenced
14556 during routing, either via an MX record or directly, it is treated as the local
14557 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14558 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14562 .section "Delivering to a remote host" "SECID95"
14563 Delivery to a remote host is handled by the smtp transport. By default, it
14564 allows the system's TCP/IP functions to choose which interface to use (if
14565 there is more than one) when connecting to a remote host. However, the
14566 &%interface%& option can be set to specify which interface is used. See the
14567 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14573 . ////////////////////////////////////////////////////////////////////////////
14574 . ////////////////////////////////////////////////////////////////////////////
14576 .chapter "Main configuration" "CHAPmainconfig"
14577 .scindex IIDconfima "configuration file" "main section"
14578 .scindex IIDmaiconf "main configuration"
14579 The first part of the runtime configuration file contains three types of item:
14582 Macro definitions: These lines start with an upper case letter. See section
14583 &<<SECTmacrodefs>>& for details of macro processing.
14585 Named list definitions: These lines start with one of the words &"domainlist"&,
14586 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14587 section &<<SECTnamedlists>>&.
14589 Main configuration settings: Each setting occupies one line of the file
14590 (with possible continuations). If any setting is preceded by the word
14591 &"hide"&, the &%-bP%& command line option displays its value to admin users
14592 only. See section &<<SECTcos>>& for a description of the syntax of these option
14596 This chapter specifies all the main configuration options, along with their
14597 types and default values. For ease of finding a particular option, they appear
14598 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14599 are now so many options, they are first listed briefly in functional groups, as
14600 an aid to finding the name of the option you are looking for. Some options are
14601 listed in more than one group.
14603 .section "Miscellaneous" "SECID96"
14605 .row &%add_environment%& "environment variables"
14606 .row &%allow_insecure_tainted_data%& "turn taint errors into warnings"
14607 .row &%bi_command%& "to run for &%-bi%& command line option"
14608 .row &%debug_store%& "do extra internal checks"
14609 .row &%disable_ipv6%& "do no IPv6 processing"
14610 .row &%keep_environment%& "environment variables"
14611 .row &%keep_malformed%& "for broken files &-- should not happen"
14612 .row &%localhost_number%& "for unique message ids in clusters"
14613 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14614 .row &%message_body_visible%& "how much to show in &$message_body$&"
14615 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14616 .row &%print_topbitchars%& "top-bit characters are printing"
14617 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14618 .row &%timezone%& "force time zone"
14622 .section "Exim parameters" "SECID97"
14624 .row &%exim_group%& "override compiled-in value"
14625 .row &%exim_path%& "override compiled-in value"
14626 .row &%exim_user%& "override compiled-in value"
14627 .row &%primary_hostname%& "default from &[uname()]&"
14628 .row &%split_spool_directory%& "use multiple directories"
14629 .row &%spool_directory%& "override compiled-in value"
14634 .section "Privilege controls" "SECID98"
14636 .row &%admin_groups%& "groups that are Exim admin users"
14637 .row &%commandline_checks_require_admin%& "require admin for various checks"
14638 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14639 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14640 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14641 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14642 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14643 .row &%never_users%& "do not run deliveries as these"
14644 .row &%prod_requires_admin%& "forced delivery requires admin user"
14645 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14646 .row &%trusted_groups%& "groups that are trusted"
14647 .row &%trusted_users%& "users that are trusted"
14652 .section "Logging" "SECID99"
14654 .row &%event_action%& "custom logging"
14655 .row &%hosts_connection_nolog%& "exemption from connect logging"
14656 .row &%log_file_path%& "override compiled-in value"
14657 .row &%log_selector%& "set/unset optional logging"
14658 .row &%log_timezone%& "add timezone to log lines"
14659 .row &%message_logs%& "create per-message logs"
14660 .row &%preserve_message_logs%& "after message completion"
14661 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14662 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14663 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14664 .row &%syslog_facility%& "set syslog &""facility""& field"
14665 .row &%syslog_pid%& "pid in syslog lines"
14666 .row &%syslog_processname%& "set syslog &""ident""& field"
14667 .row &%syslog_timestamp%& "timestamp syslog lines"
14668 .row &%write_rejectlog%& "control use of message log"
14673 .section "Frozen messages" "SECID100"
14675 .row &%auto_thaw%& "sets time for retrying frozen messages"
14676 .row &%freeze_tell%& "send message when freezing"
14677 .row &%move_frozen_messages%& "to another directory"
14678 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14683 .section "Data lookups" "SECID101"
14685 .row &%ibase_servers%& "InterBase servers"
14686 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14687 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14688 .row &%ldap_cert_file%& "client cert file for LDAP"
14689 .row &%ldap_cert_key%& "client key file for LDAP"
14690 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14691 .row &%ldap_default_servers%& "used if no server in query"
14692 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14693 .row &%ldap_start_tls%& "require TLS within LDAP"
14694 .row &%ldap_version%& "set protocol version"
14695 .row &%lookup_open_max%& "lookup files held open"
14696 .row &%mysql_servers%& "default MySQL servers"
14697 .row &%oracle_servers%& "Oracle servers"
14698 .row &%pgsql_servers%& "default PostgreSQL servers"
14699 .row &%sqlite_lock_timeout%& "as it says"
14704 .section "Message ids" "SECID102"
14706 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14707 .row &%message_id_header_text%& "ditto"
14712 .section "Embedded Perl Startup" "SECID103"
14714 .row &%perl_at_start%& "always start the interpreter"
14715 .row &%perl_startup%& "code to obey when starting Perl"
14716 .row &%perl_taintmode%& "enable taint mode in Perl"
14721 .section "Daemon" "SECID104"
14723 .row &%daemon_smtp_ports%& "default ports"
14724 .row &%daemon_startup_retries%& "number of times to retry"
14725 .row &%daemon_startup_sleep%& "time to sleep between tries"
14726 .row &%extra_local_interfaces%& "not necessarily listened on"
14727 .row &%local_interfaces%& "on which to listen, with optional ports"
14728 .row &%notifier_socket%& "override compiled-in value"
14729 .row &%pid_file_path%& "override compiled-in value"
14730 .row &%queue_run_max%& "maximum simultaneous queue runners"
14731 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14736 .section "Resource control" "SECID105"
14738 .row &%check_log_inodes%& "before accepting a message"
14739 .row &%check_log_space%& "before accepting a message"
14740 .row &%check_spool_inodes%& "before accepting a message"
14741 .row &%check_spool_space%& "before accepting a message"
14742 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14743 .row &%queue_only_load%& "queue incoming if load high"
14744 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14745 .row &%queue_run_max%& "maximum simultaneous queue runners"
14746 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14747 .row &%smtp_accept_max%& "simultaneous incoming connections"
14748 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14749 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14750 .row &%smtp_accept_max_per_connection%& "messages per connection"
14751 .row &%smtp_accept_max_per_host%& "connections from one host"
14752 .row &%smtp_accept_queue%& "queue mail if more connections"
14753 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14755 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14756 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14757 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14758 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14759 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14764 .section "Policy controls" "SECID106"
14766 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14767 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14768 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14769 .row &%acl_smtp_auth%& "ACL for AUTH"
14770 .row &%acl_smtp_connect%& "ACL for connection"
14771 .row &%acl_smtp_data%& "ACL for DATA"
14772 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14773 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14774 .row &%acl_smtp_etrn%& "ACL for ETRN"
14775 .row &%acl_smtp_expn%& "ACL for EXPN"
14776 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14777 .row &%acl_smtp_mail%& "ACL for MAIL"
14778 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14779 .row &%acl_smtp_mime%& "ACL for MIME parts"
14780 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14781 .row &%acl_smtp_predata%& "ACL for start of data"
14782 .row &%acl_smtp_quit%& "ACL for QUIT"
14783 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14784 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14785 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14786 .row &%av_scanner%& "specify virus scanner"
14787 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14789 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14790 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14791 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14792 .row &%header_maxsize%& "total size of message header"
14793 .row &%header_line_maxsize%& "individual header line limit"
14794 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14795 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14796 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14797 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14798 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14799 .row &%host_lookup%& "host name looked up for these hosts"
14800 .row &%host_lookup_order%& "order of DNS and local name lookups"
14801 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14802 .row &%host_reject_connection%& "reject connection from these hosts"
14803 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14804 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14805 .row &%message_size_limit%& "for all messages"
14806 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14807 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14808 .row &%spamd_address%& "set interface to SpamAssassin"
14809 .row &%strict_acl_vars%& "object to unset ACL variables"
14810 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14815 .section "Callout cache" "SECID107"
14817 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14819 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14821 .row &%callout_negative_expire%& "timeout for negative address cache item"
14822 .row &%callout_positive_expire%& "timeout for positive address cache item"
14823 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14828 .section "TLS" "SECID108"
14830 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14831 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14832 .row &%hosts_require_alpn%& "mandatory ALPN"
14833 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14834 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14835 .row &%tls_alpn%& "acceptable protocol names"
14836 .row &%tls_certificate%& "location of server certificate"
14837 .row &%tls_crl%& "certificate revocation list"
14838 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14839 .row &%tls_dhparam%& "DH parameters for server"
14840 .row &%tls_eccurve%& "EC curve selection for server"
14841 .row &%tls_ocsp_file%& "location of server certificate status proof"
14842 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14843 .row &%tls_privatekey%& "location of server private key"
14844 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14845 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14846 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14847 .row &%tls_verify_certificates%& "expected client certificates"
14848 .row &%tls_verify_hosts%& "insist on client certificate verify"
14853 .section "Local user handling" "SECID109"
14855 .row &%finduser_retries%& "useful in NIS environments"
14856 .row &%gecos_name%& "used when creating &'Sender:'&"
14857 .row &%gecos_pattern%& "ditto"
14858 .row &%max_username_length%& "for systems that truncate"
14859 .row &%unknown_login%& "used when no login name found"
14860 .row &%unknown_username%& "ditto"
14861 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14862 .row &%uucp_from_sender%& "ditto"
14867 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14869 .row &%header_maxsize%& "total size of message header"
14870 .row &%header_line_maxsize%& "individual header line limit"
14871 .row &%message_size_limit%& "applies to all messages"
14872 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14873 .row &%received_header_text%& "expanded to make &'Received:'&"
14874 .row &%received_headers_max%& "for mail loop detection"
14875 .row &%recipients_max%& "limit per message"
14876 .row &%recipients_max_reject%& "permanently reject excess recipients"
14882 .section "Non-SMTP incoming messages" "SECID111"
14884 .row &%receive_timeout%& "for non-SMTP messages"
14891 .section "Incoming SMTP messages" "SECID112"
14892 See also the &'Policy controls'& section above.
14895 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14896 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14897 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14898 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14899 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14900 .row &%dmarc_history_file%& "DMARC results log"
14901 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14902 .row &%host_lookup%& "host name looked up for these hosts"
14903 .row &%host_lookup_order%& "order of DNS and local name lookups"
14904 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14905 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14906 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14907 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14908 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14909 .row &%smtp_accept_max%& "simultaneous incoming connections"
14910 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14911 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14912 .row &%smtp_accept_max_per_connection%& "messages per connection"
14913 .row &%smtp_accept_max_per_host%& "connections from one host"
14914 .row &%smtp_accept_queue%& "queue mail if more connections"
14915 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14917 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14918 .row &%smtp_active_hostname%& "host name to use in messages"
14919 .row &%smtp_banner%& "text for welcome banner"
14920 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14921 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14922 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14923 .row &%smtp_etrn_command%& "what to run for ETRN"
14924 .row &%smtp_etrn_serialize%& "only one at once"
14925 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14926 .row &%smtp_max_unknown_commands%& "before dropping connection"
14927 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14928 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14929 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14930 .row &%smtp_receive_timeout%& "per command or data line"
14931 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14932 .row &%smtp_return_error_details%& "give detail on rejections"
14937 .section "SMTP extensions" "SECID113"
14939 .row &%accept_8bitmime%& "advertise 8BITMIME"
14940 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14941 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14942 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14943 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14944 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14945 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14946 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14947 .row &%prdr_enable%& "advertise PRDR to all hosts"
14948 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14949 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14954 .section "Processing messages" "SECID114"
14956 .row &%allow_domain_literals%& "recognize domain literal syntax"
14957 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14958 .row &%allow_utf8_domains%& "in addresses"
14959 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14961 .row &%delivery_date_remove%& "from incoming messages"
14962 .row &%envelope_to_remove%& "from incoming messages"
14963 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14964 .row &%headers_charset%& "default for translations"
14965 .row &%qualify_domain%& "default for senders"
14966 .row &%qualify_recipient%& "default for recipients"
14967 .row &%return_path_remove%& "from incoming messages"
14968 .row &%strip_excess_angle_brackets%& "in addresses"
14969 .row &%strip_trailing_dot%& "at end of addresses"
14970 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14975 .section "System filter" "SECID115"
14977 .row &%system_filter%& "locate system filter"
14978 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14980 .row &%system_filter_file_transport%& "transport for delivery to a file"
14981 .row &%system_filter_group%& "group for filter running"
14982 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14983 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14984 .row &%system_filter_user%& "user for filter running"
14989 .section "Routing and delivery" "SECID116"
14991 .row &%disable_ipv6%& "do no IPv6 processing"
14992 .row &%dns_again_means_nonexist%& "for broken domains"
14993 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14994 .row &%dns_dnssec_ok%& "parameter for resolver"
14995 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14996 .row &%dns_retrans%& "parameter for resolver"
14997 .row &%dns_retry%& "parameter for resolver"
14998 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14999 .row &%dns_use_edns0%& "parameter for resolver"
15000 .row &%hold_domains%& "hold delivery for these domains"
15001 .row &%local_interfaces%& "for routing checks"
15002 .row &%queue_domains%& "no immediate delivery for these"
15003 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
15004 .row &%queue_only%& "no immediate delivery at all"
15005 .row &%queue_only_file%& "no immediate delivery if file exists"
15006 .row &%queue_only_load%& "no immediate delivery if load is high"
15007 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
15008 .row &%queue_only_override%& "allow command line to override"
15009 .row &%queue_run_in_order%& "order of arrival"
15010 .row &%queue_run_max%& "of simultaneous queue runners"
15011 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
15012 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
15013 .row &%remote_sort_domains%& "order of remote deliveries"
15014 .row &%retry_data_expire%& "timeout for retry data"
15015 .row &%retry_interval_max%& "safety net for retry rules"
15020 .section "Bounce and warning messages" "SECID117"
15022 .row &%bounce_message_file%& "content of bounce"
15023 .row &%bounce_message_text%& "content of bounce"
15024 .row &%bounce_return_body%& "include body if returning message"
15025 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
15026 .row &%bounce_return_message%& "include original message in bounce"
15027 .row &%bounce_return_size_limit%& "limit on returned message"
15028 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
15029 .row &%dsn_from%& "set &'From:'& contents in bounces"
15030 .row &%errors_copy%& "copy bounce messages"
15031 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
15032 .row &%delay_warning%& "time schedule"
15033 .row &%delay_warning_condition%& "condition for warning messages"
15034 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15035 .row &%smtp_return_error_details%& "give detail on rejections"
15036 .row &%warn_message_file%& "content of warning message"
15041 .section "Alphabetical list of main options" "SECTalomo"
15042 Those options that undergo string expansion before use are marked with
15045 .option accept_8bitmime main boolean true
15047 .cindex "8-bit characters"
15048 .cindex "log" "selectors"
15049 .cindex "log" "8BITMIME"
15050 .cindex "ESMTP extensions" 8BITMIME
15051 This option causes Exim to send 8BITMIME in its response to an SMTP
15052 EHLO command, and to accept the BODY= parameter on MAIL commands.
15053 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15054 takes no steps to do anything special with messages received by this route.
15056 Historically Exim kept this option off by default, but the maintainers
15057 feel that in today's Internet, this causes more problems than it solves.
15058 It now defaults to true.
15059 A more detailed analysis of the issues is provided by Dan Bernstein:
15061 &url(https://cr.yp.to/smtp/8bitmime.html)
15064 To log received 8BITMIME status use
15066 log_selector = +8bitmime
15069 .option acl_not_smtp main string&!! unset
15070 .cindex "&ACL;" "for non-SMTP messages"
15071 .cindex "non-SMTP messages" "ACLs for"
15072 This option defines the ACL that is run when a non-SMTP message has been
15073 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15076 .option acl_not_smtp_mime main string&!! unset
15077 This option defines the ACL that is run for individual MIME parts of non-SMTP
15078 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15081 .option acl_not_smtp_start main string&!! unset
15082 .cindex "&ACL;" "at start of non-SMTP message"
15083 .cindex "non-SMTP messages" "ACLs for"
15084 This option defines the ACL that is run before Exim starts reading a
15085 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15087 .option acl_smtp_auth main string&!! unset
15088 .cindex "&ACL;" "setting up for SMTP commands"
15089 .cindex "AUTH" "ACL for"
15090 This option defines the ACL that is run when an SMTP AUTH command is
15091 received. See chapter &<<CHAPACL>>& for further details.
15093 .option acl_smtp_connect main string&!! unset
15094 .cindex "&ACL;" "on SMTP connection"
15095 This option defines the ACL that is run when an SMTP connection is received.
15096 See chapter &<<CHAPACL>>& for further details.
15098 .option acl_smtp_data main string&!! unset
15099 .cindex "DATA" "ACL for"
15100 This option defines the ACL that is run after an SMTP DATA command has been
15101 processed and the message itself has been received, but before the final
15102 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15104 .option acl_smtp_data_prdr main string&!! accept
15105 .cindex "PRDR" "ACL for"
15106 .cindex "DATA" "PRDR ACL for"
15107 .cindex "&ACL;" "PRDR-related"
15108 .cindex "&ACL;" "per-user data processing"
15109 This option defines the ACL that,
15110 if the PRDR feature has been negotiated,
15111 is run for each recipient after an SMTP DATA command has been
15112 processed and the message itself has been received, but before the
15113 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15115 .option acl_smtp_dkim main string&!! unset
15116 .cindex DKIM "ACL for"
15117 This option defines the ACL that is run for each DKIM signature
15118 (by default, or as specified in the dkim_verify_signers option)
15119 of a received message.
15120 See section &<<SECDKIMVFY>>& for further details.
15122 .option acl_smtp_etrn main string&!! unset
15123 .cindex "ETRN" "ACL for"
15124 This option defines the ACL that is run when an SMTP ETRN command is
15125 received. See chapter &<<CHAPACL>>& for further details.
15127 .option acl_smtp_expn main string&!! unset
15128 .cindex "EXPN" "ACL for"
15129 This option defines the ACL that is run when an SMTP EXPN command is
15130 received. See chapter &<<CHAPACL>>& for further details.
15132 .option acl_smtp_helo main string&!! unset
15133 .cindex "EHLO" "ACL for"
15134 .cindex "HELO" "ACL for"
15135 This option defines the ACL that is run when an SMTP EHLO or HELO
15136 command is received. See chapter &<<CHAPACL>>& for further details.
15139 .option acl_smtp_mail main string&!! unset
15140 .cindex "MAIL" "ACL for"
15141 This option defines the ACL that is run when an SMTP MAIL command is
15142 received. See chapter &<<CHAPACL>>& for further details.
15144 .option acl_smtp_mailauth main string&!! unset
15145 .cindex "AUTH" "on MAIL command"
15146 This option defines the ACL that is run when there is an AUTH parameter on
15147 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15148 &<<CHAPSMTPAUTH>>& for details of authentication.
15150 .option acl_smtp_mime main string&!! unset
15151 .cindex "MIME content scanning" "ACL for"
15152 This option is available when Exim is built with the content-scanning
15153 extension. It defines the ACL that is run for each MIME part in a message. See
15154 section &<<SECTscanmimepart>>& for details.
15156 .option acl_smtp_notquit main string&!! unset
15157 .cindex "not-QUIT, ACL for"
15158 This option defines the ACL that is run when an SMTP session
15159 ends without a QUIT command being received.
15160 See chapter &<<CHAPACL>>& for further details.
15162 .option acl_smtp_predata main string&!! unset
15163 This option defines the ACL that is run when an SMTP DATA command is
15164 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15167 .option acl_smtp_quit main string&!! unset
15168 .cindex "QUIT, ACL for"
15169 This option defines the ACL that is run when an SMTP QUIT command is
15170 received. See chapter &<<CHAPACL>>& for further details.
15172 .option acl_smtp_rcpt main string&!! unset
15173 .cindex "RCPT" "ACL for"
15174 This option defines the ACL that is run when an SMTP RCPT command is
15175 received. See chapter &<<CHAPACL>>& for further details.
15177 .option acl_smtp_starttls main string&!! unset
15178 .cindex "STARTTLS, ACL for"
15179 This option defines the ACL that is run when an SMTP STARTTLS command is
15180 received. See chapter &<<CHAPACL>>& for further details.
15182 .option acl_smtp_vrfy main string&!! unset
15183 .cindex "VRFY" "ACL for"
15184 This option defines the ACL that is run when an SMTP VRFY command is
15185 received. See chapter &<<CHAPACL>>& for further details.
15187 .option add_environment main "string list" empty
15188 .cindex "environment" "set values"
15189 This option adds individual environment variables that the
15190 currently linked libraries and programs in child processes may use.
15191 Each list element should be of the form &"name=value"&.
15193 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15195 .option admin_groups main "string list&!!" unset
15196 .cindex "admin user"
15197 This option is expanded just once, at the start of Exim's processing. If the
15198 current group or any of the supplementary groups of an Exim caller is in this
15199 colon-separated list, the caller has admin privileges. If all your system
15200 programmers are in a specific group, for example, you can give them all Exim
15201 admin privileges by putting that group in &%admin_groups%&. However, this does
15202 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15203 To permit this, you have to add individuals to the Exim group.
15205 .option allow_domain_literals main boolean false
15206 .cindex "domain literal"
15207 If this option is set, the RFC 2822 domain literal format is permitted in
15208 email addresses. The option is not set by default, because the domain literal
15209 format is not normally required these days, and few people know about it. It
15210 has, however, been exploited by mail abusers.
15212 Unfortunately, it seems that some DNS black list maintainers are using this
15213 format to report black listing to postmasters. If you want to accept messages
15214 addressed to your hosts by IP address, you need to set
15215 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15216 domains (defined in the named domain list &%local_domains%& in the default
15217 configuration). This &"magic string"& matches the domain literal form of all
15218 the local host's IP addresses.
15221 .option allow_insecure_tainted_data main boolean false
15222 .cindex "de-tainting"
15223 .oindex "allow_insecure_tainted_data"
15224 The handling of tainted data may break older (pre 4.94) configurations.
15225 Setting this option to "true" turns taint errors (which result in a temporary
15226 message rejection) into warnings. This option is meant as mitigation only
15227 and deprecated already today. Future releases of Exim may ignore it.
15228 The &%taint%& log selector can be used to suppress even the warnings.
15233 .option allow_mx_to_ip main boolean false
15234 .cindex "MX record" "pointing to IP address"
15235 It appears that more and more DNS zone administrators are breaking the rules
15236 and putting domain names that look like IP addresses on the right hand side of
15237 MX records. Exim follows the rules and rejects this, giving an error message
15238 that explains the misconfiguration. However, some other MTAs support this
15239 practice, so to avoid &"Why can't Exim do this?"& complaints,
15240 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15241 recommended, except when you have no other choice.
15243 .option allow_utf8_domains main boolean false
15244 .cindex "domain" "UTF-8 characters in"
15245 .cindex "UTF-8" "in domain name"
15246 Lots of discussion is going on about internationalized domain names. One
15247 camp is strongly in favour of just using UTF-8 characters, and it seems
15248 that at least two other MTAs permit this.
15249 This option allows Exim users to experiment if they wish.
15251 If it is set true, Exim's domain parsing function allows valid
15252 UTF-8 multicharacters to appear in domain name components, in addition to
15253 letters, digits, and hyphens.
15255 If Exim is built with internationalization support
15256 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15257 this option can be left as default.
15259 if you want to look up such domain names in the DNS, you must also
15260 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15261 suitable setting is:
15263 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15264 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15266 Alternatively, you can just disable this feature by setting
15268 dns_check_names_pattern =
15270 That is, set the option to an empty string so that no check is done.
15273 .option auth_advertise_hosts main "host list&!!" *
15274 .cindex "authentication" "advertising"
15275 .cindex "AUTH" "advertising"
15276 .cindex "ESMTP extensions" AUTH
15277 If any server authentication mechanisms are configured, Exim advertises them in
15278 response to an EHLO command only if the calling host matches this list.
15279 Otherwise, Exim does not advertise AUTH.
15280 Exim does not accept AUTH commands from clients to which it has not
15281 advertised the availability of AUTH. The advertising of individual
15282 authentication mechanisms can be controlled by the use of the
15283 &%server_advertise_condition%& generic authenticator option on the individual
15284 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15286 Certain mail clients (for example, Netscape) require the user to provide a name
15287 and password for authentication if AUTH is advertised, even though it may
15288 not be needed (the host may accept messages from hosts on its local LAN without
15289 authentication, for example). The &%auth_advertise_hosts%& option can be used
15290 to make these clients more friendly by excluding them from the set of hosts to
15291 which Exim advertises AUTH.
15293 .cindex "AUTH" "advertising when encrypted"
15294 If you want to advertise the availability of AUTH only when the connection
15295 is encrypted using TLS, you can make use of the fact that the value of this
15296 option is expanded, with a setting like this:
15298 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15300 .vindex "&$tls_in_cipher$&"
15301 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15302 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15303 expansion is *, which matches all hosts.
15306 .option auto_thaw main time 0s
15307 .cindex "thawing messages"
15308 .cindex "unfreezing messages"
15309 If this option is set to a time greater than zero, a queue runner will try a
15310 new delivery attempt on any frozen message, other than a bounce message, if
15311 this much time has passed since it was frozen. This may result in the message
15312 being re-frozen if nothing has changed since the last attempt. It is a way of
15313 saying &"keep on trying, even though there are big problems"&.
15315 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15316 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15317 thought to be very useful any more, and its use should probably be avoided.
15320 .option av_scanner main string "see below"
15321 This option is available if Exim is built with the content-scanning extension.
15322 It specifies which anti-virus scanner to use. The default value is:
15324 sophie:/var/run/sophie
15326 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15327 before use. See section &<<SECTscanvirus>>& for further details.
15330 .option bi_command main string unset
15332 This option supplies the name of a command that is run when Exim is called with
15333 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15334 just the command name, it is not a complete command line. If an argument is
15335 required, it must come from the &%-oA%& command line option.
15338 .option bounce_message_file main string&!! unset
15339 .cindex "bounce message" "customizing"
15340 .cindex "customizing" "bounce message"
15341 This option defines a template file containing paragraphs of text to be used
15342 for constructing bounce messages. Details of the file's contents are given in
15343 chapter &<<CHAPemsgcust>>&.
15344 .cindex bounce_message_file "tainted data"
15345 The option is expanded to give the file path, which must be
15346 absolute and untainted.
15347 See also &%warn_message_file%&.
15350 .option bounce_message_text main string unset
15351 When this option is set, its contents are included in the default bounce
15352 message immediately after &"This message was created automatically by mail
15353 delivery software."& It is not used if &%bounce_message_file%& is set.
15355 .option bounce_return_body main boolean true
15356 .cindex "bounce message" "including body"
15357 This option controls whether the body of an incoming message is included in a
15358 bounce message when &%bounce_return_message%& is true. The default setting
15359 causes the entire message, both header and body, to be returned (subject to the
15360 value of &%bounce_return_size_limit%&). If this option is false, only the
15361 message header is included. In the case of a non-SMTP message containing an
15362 error that is detected during reception, only those header lines preceding the
15363 point at which the error was detected are returned.
15364 .cindex "bounce message" "including original"
15366 .option bounce_return_linesize_limit main integer 998
15367 .cindex "size" "of bounce lines, limit"
15368 .cindex "bounce message" "line length limit"
15369 .cindex "limit" "bounce message line length"
15370 This option sets a limit in bytes on the line length of messages
15371 that are returned to senders due to delivery problems,
15372 when &%bounce_return_message%& is true.
15373 The default value corresponds to RFC limits.
15374 If the message being returned has lines longer than this value it is
15375 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15377 The option also applies to bounces returned when an error is detected
15378 during reception of a message.
15379 In this case lines from the original are truncated.
15381 The option does not apply to messages generated by an &(autoreply)& transport.
15384 .option bounce_return_message main boolean true
15385 If this option is set false, none of the original message is included in
15386 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15387 &%bounce_return_body%&.
15390 .option bounce_return_size_limit main integer 100K
15391 .cindex "size" "of bounce, limit"
15392 .cindex "bounce message" "size limit"
15393 .cindex "limit" "bounce message size"
15394 This option sets a limit in bytes on the size of messages that are returned to
15395 senders as part of bounce messages when &%bounce_return_message%& is true. The
15396 limit should be less than the value of the global &%message_size_limit%& and of
15397 any &%message_size_limit%& settings on transports, to allow for the bounce text
15398 that Exim generates. If this option is set to zero there is no limit.
15400 When the body of any message that is to be included in a bounce message is
15401 greater than the limit, it is truncated, and a comment pointing this out is
15402 added at the top. The actual cutoff may be greater than the value given, owing
15403 to the use of buffering for transferring the message in chunks (typically 8K in
15404 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15407 .option bounce_sender_authentication main string unset
15408 .cindex "bounce message" "sender authentication"
15409 .cindex "authentication" "bounce message"
15410 .cindex "AUTH" "on bounce message"
15411 This option provides an authenticated sender address that is sent with any
15412 bounce messages generated by Exim that are sent over an authenticated SMTP
15413 connection. A typical setting might be:
15415 bounce_sender_authentication = mailer-daemon@my.domain.example
15417 which would cause bounce messages to be sent using the SMTP command:
15419 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15421 The value of &%bounce_sender_authentication%& must always be a complete email
15424 .option callout_domain_negative_expire main time 3h
15425 .cindex "caching" "callout timeouts"
15426 .cindex "callout" "caching timeouts"
15427 This option specifies the expiry time for negative callout cache data for a
15428 domain. See section &<<SECTcallver>>& for details of callout verification, and
15429 section &<<SECTcallvercache>>& for details of the caching.
15432 .option callout_domain_positive_expire main time 7d
15433 This option specifies the expiry time for positive callout cache data for a
15434 domain. See section &<<SECTcallver>>& for details of callout verification, and
15435 section &<<SECTcallvercache>>& for details of the caching.
15438 .option callout_negative_expire main time 2h
15439 This option specifies the expiry time for negative callout cache data for an
15440 address. See section &<<SECTcallver>>& for details of callout verification, and
15441 section &<<SECTcallvercache>>& for details of the caching.
15444 .option callout_positive_expire main time 24h
15445 This option specifies the expiry time for positive callout cache data for an
15446 address. See section &<<SECTcallver>>& for details of callout verification, and
15447 section &<<SECTcallvercache>>& for details of the caching.
15450 .option callout_random_local_part main string&!! "see below"
15451 This option defines the &"random"& local part that can be used as part of
15452 callout verification. The default value is
15454 $primary_hostname-$tod_epoch-testing
15456 See section &<<CALLaddparcall>>& for details of how this value is used.
15459 .option check_log_inodes main integer 100
15460 See &%check_spool_space%& below.
15463 .option check_log_space main integer 10M
15464 See &%check_spool_space%& below.
15466 .oindex "&%check_rfc2047_length%&"
15467 .cindex "RFC 2047" "disabling length check"
15468 .option check_rfc2047_length main boolean true
15469 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15470 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15471 word; strings to be encoded that exceed this length are supposed to use
15472 multiple encoded words. By default, Exim does not recognize encoded words that
15473 exceed the maximum length. However, it seems that some software, in violation
15474 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15475 set false, Exim recognizes encoded words of any length.
15478 .option check_spool_inodes main integer 100
15479 See &%check_spool_space%& below.
15482 .option check_spool_space main integer 10M
15483 .cindex "checking disk space"
15484 .cindex "disk space, checking"
15485 .cindex "spool directory" "checking space"
15486 The four &%check_...%& options allow for checking of disk resources before a
15487 message is accepted.
15489 .vindex "&$log_inodes$&"
15490 .vindex "&$log_space$&"
15491 .vindex "&$spool_inodes$&"
15492 .vindex "&$spool_space$&"
15493 When any of these options are nonzero, they apply to all incoming messages. If you
15494 want to apply different checks to different kinds of message, you can do so by
15495 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15496 &$spool_space$& in an ACL with appropriate additional conditions.
15499 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15500 either value is greater than zero, for example:
15502 check_spool_space = 100M
15503 check_spool_inodes = 100
15505 The spool partition is the one that contains the directory defined by
15506 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15509 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15510 files are written if either is greater than zero. These should be set only if
15511 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15513 If there is less space or fewer inodes than requested, Exim refuses to accept
15514 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15515 error response to the MAIL command. If ESMTP is in use and there was a
15516 SIZE parameter on the MAIL command, its value is added to the
15517 &%check_spool_space%& value, and the check is performed even if
15518 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15520 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15521 number of kilobytes (though specified in bytes).
15522 If a non-multiple of 1024 is specified, it is rounded up.
15524 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15525 failure a message is written to stderr and Exim exits with a non-zero code, as
15526 it obviously cannot send an error message of any kind.
15528 There is a slight performance penalty for these checks.
15529 Versions of Exim preceding 4.88 had these disabled by default;
15530 high-rate installations confident they will never run out of resources
15531 may wish to deliberately disable them.
15533 .option chunking_advertise_hosts main "host list&!!" *
15534 .cindex CHUNKING advertisement
15535 .cindex "RFC 3030" "CHUNKING"
15536 .cindex "ESMTP extensions" CHUNKING
15537 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15539 Hosts may use the BDAT command as an alternate to DATA.
15541 .option commandline_checks_require_admin main boolean &`false`&
15542 .cindex "restricting access to features"
15543 This option restricts various basic checking features to require an
15544 administrative user.
15545 This affects most of the &%-b*%& options, such as &%-be%&.
15547 .option debug_store main boolean &`false`&
15548 .cindex debugging "memory corruption"
15549 .cindex memory debugging
15550 This option, when true, enables extra checking in Exim's internal memory
15551 management. For use when a memory corruption issue is being investigated,
15552 it should normally be left as default.
15554 .option daemon_smtp_ports main string &`smtp`&
15555 .cindex "port" "for daemon"
15556 .cindex "TCP/IP" "setting listening ports"
15557 This option specifies one or more default SMTP ports on which the Exim daemon
15558 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15559 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15561 .option daemon_startup_retries main integer 9
15562 .cindex "daemon startup, retrying"
15563 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15564 the daemon at startup when it cannot immediately bind a listening socket
15565 (typically because the socket is already in use): &%daemon_startup_retries%&
15566 defines the number of retries after the first failure, and
15567 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15569 .option daemon_startup_sleep main time 30s
15570 See &%daemon_startup_retries%&.
15572 .option delay_warning main "time list" 24h
15573 .cindex "warning of delay"
15574 .cindex "delay warning, specifying"
15575 .cindex "queue" "delay warning"
15576 When a message is delayed, Exim sends a warning message to the sender at
15577 intervals specified by this option. The data is a colon-separated list of times
15578 after which to send warning messages. If the value of the option is an empty
15579 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15580 message has been in the queue for longer than the last time, the last interval
15581 between the times is used to compute subsequent warning times. For example,
15584 delay_warning = 4h:8h:24h
15586 the first message is sent after 4 hours, the second after 8 hours, and
15587 the third one after 24 hours. After that, messages are sent every 16 hours,
15588 because that is the interval between the last two times on the list. If you set
15589 just one time, it specifies the repeat interval. For example, with:
15593 messages are repeated every six hours. To stop warnings after a given time, set
15594 a very large time at the end of the list. For example:
15596 delay_warning = 2h:12h:99d
15598 Note that the option is only evaluated at the time a delivery attempt fails,
15599 which depends on retry and queue-runner configuration.
15600 Typically retries will be configured more frequently than warning messages.
15602 .option delay_warning_condition main string&!! "see below"
15603 .vindex "&$domain$&"
15604 The string is expanded at the time a warning message might be sent. If all the
15605 deferred addresses have the same domain, it is set in &$domain$& during the
15606 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15607 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15608 &"false"& (the comparison being done caselessly) then the warning message is
15609 not sent. The default is:
15611 delay_warning_condition = ${if or {\
15612 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15613 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15614 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15617 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15618 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15619 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15620 &"auto-replied"& in an &'Auto-Submitted:'& header.
15622 .option deliver_drop_privilege main boolean false
15623 .cindex "unprivileged delivery"
15624 .cindex "delivery" "unprivileged"
15625 If this option is set true, Exim drops its root privilege at the start of a
15626 delivery process, and runs as the Exim user throughout. This severely restricts
15627 the kinds of local delivery that are possible, but is viable in certain types
15628 of configuration. There is a discussion about the use of root privilege in
15629 chapter &<<CHAPsecurity>>&.
15631 .option deliver_queue_load_max main fixed-point unset
15632 .cindex "load average"
15633 .cindex "queue runner" "abandoning"
15634 When this option is set, a queue run is abandoned if the system load average
15635 becomes greater than the value of the option. The option has no effect on
15636 ancient operating systems on which Exim cannot determine the load average.
15637 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15640 .option delivery_date_remove main boolean true
15641 .cindex "&'Delivery-date:'& header line"
15642 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15643 message when it is delivered, in exactly the same way as &'Return-path:'& is
15644 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15645 should not be present in incoming messages, and this option causes them to be
15646 removed at the time the message is received, to avoid any problems that might
15647 occur when a delivered message is subsequently sent on to some other recipient.
15649 .option disable_fsync main boolean false
15650 .cindex "&[fsync()]&, disabling"
15651 This option is available only if Exim was built with the compile-time option
15652 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15653 a runtime configuration generates an &"unknown option"& error. You should not
15654 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15655 really, really, really understand what you are doing. &'No pre-compiled
15656 distributions of Exim should ever make this option available.'&
15658 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15659 updated files' data to be written to disc before continuing. Unexpected events
15660 such as crashes and power outages may cause data to be lost or scrambled.
15661 Here be Dragons. &*Beware.*&
15664 .option disable_ipv6 main boolean false
15665 .cindex "IPv6" "disabling"
15666 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15667 activities take place. AAAA records are never looked up, and any IPv6 addresses
15668 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15669 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15670 to handle IPv6 literal addresses.
15673 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15674 .cindex DKIM "selecting signature algorithms"
15675 This option gives a list of hash types which are acceptable in signatures,
15676 and an order of processing.
15677 Signatures with algorithms not in the list will be ignored.
15679 Acceptable values include:
15686 Note that the acceptance of sha1 violates RFC 8301.
15688 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15689 This option gives a list of key types which are acceptable in signatures,
15690 and an order of processing.
15691 Signatures with algorithms not in the list will be ignored.
15694 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15695 This option gives a list of key sizes which are acceptable in signatures.
15696 The list is keyed by the algorithm type for the key; the values are in bits.
15697 Signatures with keys smaller than given by this option will fail verification.
15699 The default enforces the RFC 8301 minimum key size for RSA signatures.
15701 .option dkim_verify_minimal main boolean false
15702 If set to true, verification of signatures will terminate after the
15705 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15706 .cindex DKIM "controlling calls to the ACL"
15707 This option gives a list of DKIM domains for which the DKIM ACL is run.
15708 It is expanded after the message is received; by default it runs
15709 the ACL once for each signature in the message.
15710 See section &<<SECDKIMVFY>>&.
15713 .option dmarc_forensic_sender main string&!! unset
15714 .option dmarc_history_file main string unset
15715 .option dmarc_tld_file main string unset
15716 .cindex DMARC "main section options"
15717 These options control DMARC processing.
15718 See section &<<SECDMARC>>& for details.
15721 .option dns_again_means_nonexist main "domain list&!!" unset
15722 .cindex "DNS" "&""try again""& response; overriding"
15723 DNS lookups give a &"try again"& response for the DNS errors
15724 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15725 keep trying to deliver a message, or to give repeated temporary errors to
15726 incoming mail. Sometimes the effect is caused by a badly set up name server and
15727 may persist for a long time. If a domain which exhibits this problem matches
15728 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15729 This option should be used with care. You can make it apply to reverse lookups
15730 by a setting such as this:
15732 dns_again_means_nonexist = *.in-addr.arpa
15734 This option applies to all DNS lookups that Exim does. It also applies when the
15735 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15736 since these are most likely to be caused by DNS lookup problems. The
15737 &(dnslookup)& router has some options of its own for controlling what happens
15738 when lookups for MX or SRV records give temporary errors. These more specific
15739 options are applied after this global option.
15741 .option dns_check_names_pattern main string "see below"
15742 .cindex "DNS" "pre-check of name syntax"
15743 When this option is set to a non-empty string, it causes Exim to check domain
15744 names for characters that are not allowed in host names before handing them to
15745 the DNS resolver, because some resolvers give temporary errors for names that
15746 contain unusual characters. If a domain name contains any unwanted characters,
15747 a &"not found"& result is forced, and the resolver is not called. The check is
15748 done by matching the domain name against a regular expression, which is the
15749 value of this option. The default pattern is
15751 dns_check_names_pattern = \
15752 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15754 which permits only letters, digits, slashes, and hyphens in components, but
15755 they must start and end with a letter or digit. Slashes are not, in fact,
15756 permitted in host names, but they are found in certain NS records (which can be
15757 accessed in Exim by using a &%dnsdb%& lookup). If you set
15758 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15761 .option dns_csa_search_limit main integer 5
15762 This option controls the depth of parental searching for CSA SRV records in the
15763 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15765 .option dns_csa_use_reverse main boolean true
15766 This option controls whether or not an IP address, given as a CSA domain, is
15767 reversed and looked up in the reverse DNS, as described in more detail in
15768 section &<<SECTverifyCSA>>&.
15770 .option dns_cname_loops main integer 1
15771 .cindex DNS "CNAME following"
15772 This option controls the following of CNAME chains, needed if the resolver does
15773 not do it internally.
15774 As of 2018 most should, and the default can be left.
15775 If you have an ancient one, a value of 10 is likely needed.
15777 The default value of one CNAME-follow is needed
15778 thanks to the observed return for an MX request,
15779 given no MX presence but a CNAME to an A, of the CNAME.
15782 .option dns_dnssec_ok main integer -1
15783 .cindex "DNS" "resolver options"
15784 .cindex "DNS" "DNSSEC"
15785 If this option is set to a non-negative number then Exim will initialise the
15786 DNS resolver library to either use or not use DNSSEC, overriding the system
15787 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15789 If the resolver library does not support DNSSEC then this option has no effect.
15791 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15792 will default to stripping out a successful validation status.
15793 This will break a previously working Exim installation.
15794 Provided that you do trust the resolver (ie, is on localhost) you can tell
15795 glibc to pass through any successful validation with a new option in
15796 &_/etc/resolv.conf_&:
15802 .option dns_ipv4_lookup main "domain list&!!" unset
15803 .cindex "IPv6" "DNS lookup for AAAA records"
15804 .cindex "DNS" "IPv6 lookup for AAAA records"
15805 .cindex DNS "IPv6 disabling"
15806 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15807 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15808 (A records) when trying to find IP addresses for hosts, unless the host's
15809 domain matches this list.
15811 This is a fudge to help with name servers that give big delays or otherwise do
15812 not work for the AAAA record type. In due course, when the world's name
15813 servers have all been upgraded, there should be no need for this option.
15814 Note that all lookups, including those done for verification, are affected;
15815 this will result in verify failure for IPv6 connections or ones using names
15816 only valid for IPv6 addresses.
15819 .option dns_retrans main time 0s
15820 .cindex "DNS" "resolver options"
15821 .cindex timeout "dns lookup"
15822 .cindex "DNS" timeout
15823 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15824 retransmission and retry parameters for DNS lookups. Values of zero (the
15825 defaults) leave the system default settings unchanged. The first value is the
15826 time between retries, and the second is the number of retries. It isn't
15827 totally clear exactly how these settings affect the total time a DNS lookup may
15828 take. I haven't found any documentation about timeouts on DNS lookups; these
15829 parameter values are available in the external resolver interface structure,
15830 but nowhere does it seem to describe how they are used or what you might want
15832 See also the &%slow_lookup_log%& option.
15835 .option dns_retry main integer 0
15836 See &%dns_retrans%& above.
15839 .option dns_trust_aa main "domain list&!!" unset
15840 .cindex "DNS" "resolver options"
15841 .cindex "DNS" "DNSSEC"
15842 If this option is set then lookup results marked with the AA bit
15843 (Authoritative Answer) are trusted the same way as if they were
15844 DNSSEC-verified. The authority section's name of the answer must
15845 match with this expanded domain list.
15847 Use this option only if you talk directly to a resolver that is
15848 authoritative for some zones and does not set the AD (Authentic Data)
15849 bit in the answer. Some DNS servers may have an configuration option to
15850 mark the answers from their own zones as verified (they set the AD bit).
15851 Others do not have this option. It is considered as poor practice using
15852 a resolver that is an authoritative server for some zones.
15854 Use this option only if you really have to (e.g. if you want
15855 to use DANE for remote delivery to a server that is listed in the DNS
15856 zones that your resolver is authoritative for).
15858 If the DNS answer packet has the AA bit set and contains resource record
15859 in the answer section, the name of the first NS record appearing in the
15860 authority section is compared against the list. If the answer packet is
15861 authoritative but the answer section is empty, the name of the first SOA
15862 record in the authoritative section is used instead.
15864 .cindex "DNS" "resolver options"
15865 .option dns_use_edns0 main integer -1
15866 .cindex "DNS" "resolver options"
15867 .cindex "DNS" "EDNS0"
15868 .cindex "DNS" "OpenBSD
15869 If this option is set to a non-negative number then Exim will initialise the
15870 DNS resolver library to either use or not use EDNS0 extensions, overriding
15871 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15874 If the resolver library does not support EDNS0 then this option has no effect.
15876 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15877 means that DNSSEC will not work with Exim on that platform either, unless Exim
15878 is linked against an alternative DNS client library.
15881 .option drop_cr main boolean false
15882 This is an obsolete option that is now a no-op. It used to affect the way Exim
15883 handled CR and LF characters in incoming messages. What happens now is
15884 described in section &<<SECTlineendings>>&.
15886 .option dsn_advertise_hosts main "host list&!!" unset
15887 .cindex "bounce messages" "success"
15888 .cindex "DSN" "success"
15889 .cindex "Delivery Status Notification" "success"
15890 .cindex "ESMTP extensions" DSN
15891 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15892 and accepted from, these hosts.
15893 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15894 and RET and ORCPT options on MAIL FROM commands.
15895 A NOTIFY=SUCCESS option requests success-DSN messages.
15896 A NOTIFY= option with no argument requests that no delay or failure DSNs
15898 &*Note*&: Supplying success-DSN messages has been criticised
15899 on privacy grounds; it can leak details of internal forwarding.
15901 .option dsn_from main "string&!!" "see below"
15902 .cindex "&'From:'& header line" "in bounces"
15903 .cindex "bounce messages" "&'From:'& line, specifying"
15904 This option can be used to vary the contents of &'From:'& header lines in
15905 bounces and other automatically generated messages (&"Delivery Status
15906 Notifications"& &-- hence the name of the option). The default setting is:
15908 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15910 The value is expanded every time it is needed. If the expansion fails, a
15911 panic is logged, and the default value is used.
15913 .option envelope_to_remove main boolean true
15914 .cindex "&'Envelope-to:'& header line"
15915 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15916 message when it is delivered, in exactly the same way as &'Return-path:'& is
15917 handled. &'Envelope-to:'& records the original recipient address from the
15918 message's envelope that caused the delivery to happen. Such headers should not
15919 be present in incoming messages, and this option causes them to be removed at
15920 the time the message is received, to avoid any problems that might occur when a
15921 delivered message is subsequently sent on to some other recipient.
15924 .option errors_copy main "string list&!!" unset
15925 .cindex "bounce message" "copy to other address"
15926 .cindex "copy of bounce message"
15927 Setting this option causes Exim to send bcc copies of bounce messages that it
15928 generates to other addresses. &*Note*&: This does not apply to bounce messages
15929 coming from elsewhere. The value of the option is a colon-separated list of
15930 items. Each item consists of a pattern, terminated by white space, followed by
15931 a comma-separated list of email addresses. If a pattern contains spaces, it
15932 must be enclosed in double quotes.
15934 Each pattern is processed in the same way as a single item in an address list
15935 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15936 the bounce message, the message is copied to the addresses on the list. The
15937 items are scanned in order, and once a matching one is found, no further items
15938 are examined. For example:
15940 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15941 rqps@mydomain hostmaster@mydomain.example,\
15942 postmaster@mydomain.example
15944 .vindex "&$domain$&"
15945 .vindex "&$local_part$&"
15946 The address list is expanded before use. The expansion variables &$local_part$&
15947 and &$domain$& are set from the original recipient of the error message, and if
15948 there was any wildcard matching in the pattern, the expansion
15949 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15950 variables &$0$&, &$1$&, etc. are set in the normal way.
15953 .option errors_reply_to main string unset
15954 .cindex "bounce message" "&'Reply-to:'& in"
15955 By default, Exim's bounce and delivery warning messages contain the header line
15957 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15959 .oindex &%quota_warn_message%&
15960 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15961 A warning message that is generated by the &%quota_warn_message%& option in an
15962 &(appendfile)& transport may contain its own &'From:'& header line that
15963 overrides the default.
15965 Experience shows that people reply to bounce messages. If the
15966 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15967 and warning messages. For example:
15969 errors_reply_to = postmaster@my.domain.example
15971 The value of the option is not expanded. It must specify a valid RFC 2822
15972 address. However, if a warning message that is generated by the
15973 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15974 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15978 .option event_action main string&!! unset
15980 This option declares a string to be expanded for Exim's events mechanism.
15981 For details see chapter &<<CHAPevents>>&.
15984 .option exim_group main string "compile-time configured"
15985 .cindex "gid (group id)" "Exim's own"
15986 .cindex "Exim group"
15987 This option changes the gid under which Exim runs when it gives up root
15988 privilege. The default value is compiled into the binary. The value of this
15989 option is used only when &%exim_user%& is also set. Unless it consists entirely
15990 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15991 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15995 .option exim_path main string "see below"
15996 .cindex "Exim binary, path name"
15997 This option specifies the path name of the Exim binary, which is used when Exim
15998 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15999 the directory configured at compile time by the BIN_DIRECTORY setting. It
16000 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
16002 &*Warning*&: Do not use a macro to define the value of this option, because
16003 you will break those Exim utilities that scan the configuration file to find
16004 where the binary is. (They then use the &%-bP%& option to extract option
16005 settings such as the value of &%spool_directory%&.)
16008 .option exim_user main string "compile-time configured"
16009 .cindex "uid (user id)" "Exim's own"
16010 .cindex "Exim user"
16011 This option changes the uid under which Exim runs when it gives up root
16012 privilege. The default value is compiled into the binary. Ownership of the run
16013 time configuration file and the use of the &%-C%& and &%-D%& command line
16014 options is checked against the values in the binary, not what is set here.
16016 Unless it consists entirely of digits, the string is looked up using
16017 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
16018 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
16019 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
16022 .option exim_version main string "current version"
16023 .cindex "Exim version"
16024 .cindex customizing "version number"
16025 .cindex "version number of Exim" override
16026 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
16027 various places. Use with care; this may fool stupid security scanners.
16030 .option extra_local_interfaces main "string list" unset
16031 This option defines network interfaces that are to be considered local when
16032 routing, but which are not used for listening by the daemon. See section
16033 &<<SECTreclocipadd>>& for details.
16036 . Allow this long option name to split; give it unsplit as a fifth argument
16037 . for the automatic .oindex that is generated by .option.
16039 .option "extract_addresses_remove_arguments" main boolean true &&&
16040 extract_addresses_remove_arguments
16042 .cindex "command line" "addresses with &%-t%&"
16043 .cindex "Sendmail compatibility" "&%-t%& option"
16044 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
16045 are present on the command line when the &%-t%& option is used to build an
16046 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
16047 line addresses are removed from the recipients list. This is also how Smail
16048 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16049 command line addresses are added to those obtained from the header lines. When
16050 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16051 argument headers. If it is set false, Exim adds rather than removes argument
16055 .option finduser_retries main integer 0
16056 .cindex "NIS, retrying user lookups"
16057 On systems running NIS or other schemes in which user and group information is
16058 distributed from a remote system, there can be times when &[getpwnam()]& and
16059 related functions fail, even when given valid data, because things time out.
16060 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16061 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16062 many extra times to find a user or a group, waiting for one second between
16065 .cindex "&_/etc/passwd_&" "multiple reading of"
16066 You should not set this option greater than zero if your user information is in
16067 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16068 search the file multiple times for non-existent users, and also cause delay.
16072 .option freeze_tell main "string list, comma separated" unset
16073 .cindex "freezing messages" "sending a message when freezing"
16074 On encountering certain errors, or when configured to do so in a system filter,
16075 ACL, or special router, Exim freezes a message. This means that no further
16076 delivery attempts take place until an administrator thaws the message, or the
16077 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16078 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16079 warning message whenever it freezes something, unless the message it is
16080 freezing is a locally-generated bounce message. (Without this exception there
16081 is the possibility of looping.) The warning message is sent to the addresses
16082 supplied as the comma-separated value of this option. If several of the
16083 message's addresses cause freezing, only a single message is sent. If the
16084 freezing was automatic, the reason(s) for freezing can be found in the message
16085 log. If you configure freezing in a filter or ACL, you must arrange for any
16086 logging that you require.
16089 .option gecos_name main string&!! unset
16091 .cindex "&""gecos""& field, parsing"
16092 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16093 password file to hold other information in addition to users' real names. Exim
16094 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16095 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16096 of the field are used unchanged, except that, if an ampersand is encountered,
16097 it is replaced by the user's login name with the first character forced to
16098 upper case, since this is a convention that is observed on many systems.
16100 When these options are set, &%gecos_pattern%& is treated as a regular
16101 expression that is to be applied to the field (again with && replaced by the
16102 login name), and if it matches, &%gecos_name%& is expanded and used as the
16105 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16106 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16107 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16108 name terminates at the first comma, the following can be used:
16110 gecos_pattern = ([^,]*)
16114 .option gecos_pattern main string unset
16115 See &%gecos_name%& above.
16118 .option gnutls_compat_mode main boolean unset
16119 This option controls whether GnuTLS is used in compatibility mode in an Exim
16120 server. This reduces security slightly, but improves interworking with older
16121 implementations of TLS.
16124 .option gnutls_allow_auto_pkcs11 main boolean unset
16125 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16126 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16129 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16134 .option headers_charset main string "see below"
16135 This option sets a default character set for translating from encoded MIME
16136 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16137 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16138 ultimate default is ISO-8859-1. For more details see the description of header
16139 insertions in section &<<SECTexpansionitems>>&.
16143 .option header_maxsize main integer "see below"
16144 .cindex "header section" "maximum size of"
16145 .cindex "limit" "size of message header section"
16146 This option controls the overall maximum size of a message's header
16147 section. The default is the value of HEADER_MAXSIZE in
16148 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16149 sections are rejected.
16152 .option header_line_maxsize main integer 0
16153 .cindex "header lines" "maximum size of"
16154 .cindex "limit" "size of one header line"
16155 This option limits the length of any individual header line in a message, after
16156 all the continuations have been joined together. Messages with individual
16157 header lines that are longer than the limit are rejected. The default value of
16158 zero means &"no limit"&.
16163 .option helo_accept_junk_hosts main "host list&!!" unset
16164 .cindex "HELO" "accepting junk data"
16165 .cindex "EHLO" "accepting junk data"
16166 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16167 mail, and gives an error response for invalid data. Unfortunately, there are
16168 some SMTP clients that send syntactic junk. They can be accommodated by setting
16169 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16170 if you want to do semantic checking.
16171 See also &%helo_allow_chars%& for a way of extending the permitted character
16175 .option helo_allow_chars main string unset
16176 .cindex "HELO" "underscores in"
16177 .cindex "EHLO" "underscores in"
16178 .cindex "underscore in EHLO/HELO"
16179 This option can be set to a string of rogue characters that are permitted in
16180 all EHLO and HELO names in addition to the standard letters, digits,
16181 hyphens, and dots. If you really must allow underscores, you can set
16183 helo_allow_chars = _
16185 Note that the value is one string, not a list.
16188 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16189 .cindex "HELO" "forcing reverse lookup"
16190 .cindex "EHLO" "forcing reverse lookup"
16191 If the domain given by a client in a HELO or EHLO command matches this
16192 list, a reverse lookup is done in order to establish the host's true name. The
16193 default forces a lookup if the client host gives the server's name or any of
16194 its IP addresses (in brackets), something that broken clients have been seen to
16198 .option helo_try_verify_hosts main "host list&!!" unset
16199 .cindex "HELO verifying" "optional"
16200 .cindex "EHLO" "verifying, optional"
16201 By default, Exim just checks the syntax of HELO and EHLO commands (see
16202 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16203 to do more extensive checking of the data supplied by these commands. The ACL
16204 condition &`verify = helo`& is provided to make this possible.
16205 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16206 to force the check to occur. From release 4.53 onwards, this is no longer
16207 necessary. If the check has not been done before &`verify = helo`& is
16208 encountered, it is done at that time. Consequently, this option is obsolete.
16209 Its specification is retained here for backwards compatibility.
16211 When an EHLO or HELO command is received, if the calling host matches
16212 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16213 EHLO command either:
16216 is an IP literal matching the calling address of the host, or
16218 .cindex "DNS" "reverse lookup"
16219 .cindex "reverse DNS lookup"
16220 matches the host name that Exim obtains by doing a reverse lookup of the
16221 calling host address, or
16223 when looked up in DNS yields the calling host address.
16226 However, the EHLO or HELO command is not rejected if any of the checks
16227 fail. Processing continues, but the result of the check is remembered, and can
16228 be detected later in an ACL by the &`verify = helo`& condition.
16230 If DNS was used for successful verification, the variable
16231 .cindex "DNS" "DNSSEC"
16232 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16234 .option helo_verify_hosts main "host list&!!" unset
16235 .cindex "HELO verifying" "mandatory"
16236 .cindex "EHLO" "verifying, mandatory"
16237 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16238 backwards compatibility. For hosts that match this option, Exim checks the host
16239 name given in the HELO or EHLO in the same way as for
16240 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16241 rejected with a 550 error, and entries are written to the main and reject logs.
16242 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16245 .option hold_domains main "domain list&!!" unset
16246 .cindex "domain" "delaying delivery"
16247 .cindex "delivery" "delaying certain domains"
16248 This option allows mail for particular domains to be held in the queue
16249 manually. The option is overridden if a message delivery is forced with the
16250 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16251 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16252 item in &%hold_domains%&, no routing or delivery for that address is done, and
16253 it is deferred every time the message is looked at.
16255 This option is intended as a temporary operational measure for delaying the
16256 delivery of mail while some problem is being sorted out, or some new
16257 configuration tested. If you just want to delay the processing of some
16258 domains until a queue run occurs, you should use &%queue_domains%& or
16259 &%queue_smtp_domains%&, not &%hold_domains%&.
16261 A setting of &%hold_domains%& does not override Exim's code for removing
16262 messages from the queue if they have been there longer than the longest retry
16263 time in any retry rule. If you want to hold messages for longer than the normal
16264 retry times, insert a dummy retry rule with a long retry time.
16267 .option host_lookup main "host list&!!" unset
16268 .cindex "host name" "lookup, forcing"
16269 Exim does not look up the name of a calling host from its IP address unless it
16270 is required to compare against some host list, or the host matches
16271 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16272 option (which normally contains IP addresses rather than host names). The
16273 default configuration file contains
16277 which causes a lookup to happen for all hosts. If the expense of these lookups
16278 is felt to be too great, the setting can be changed or removed.
16280 After a successful reverse lookup, Exim does a forward lookup on the name it
16281 has obtained, to verify that it yields the IP address that it started with. If
16282 this check fails, Exim behaves as if the name lookup failed.
16284 .vindex "&$host_lookup_failed$&"
16285 .vindex "&$sender_host_name$&"
16286 After any kind of failure, the host name (in &$sender_host_name$&) remains
16287 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16288 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16289 &`verify = reverse_host_lookup`& in ACLs.
16292 .option host_lookup_order main "string list" &`bydns:byaddr`&
16293 This option specifies the order of different lookup methods when Exim is trying
16294 to find a host name from an IP address. The default is to do a DNS lookup
16295 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16296 if that fails. You can change the order of these lookups, or omit one entirely,
16299 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16300 multiple PTR records in the DNS and the IP address is not listed in
16301 &_/etc/hosts_&. Different operating systems give different results in this
16302 case. That is why the default tries a DNS lookup first.
16306 .option host_reject_connection main "host list&!!" unset
16307 .cindex "host" "rejecting connections from"
16308 If this option is set, incoming SMTP calls from the hosts listed are rejected
16309 as soon as the connection is made.
16310 This option is obsolete, and retained only for backward compatibility, because
16311 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16312 connections immediately.
16314 The ability to give an immediate rejection (either by this option or using an
16315 ACL) is provided for use in unusual cases. Many hosts will just try again,
16316 sometimes without much delay. Normally, it is better to use an ACL to reject
16317 incoming messages at a later stage, such as after RCPT commands. See
16318 chapter &<<CHAPACL>>&.
16321 .option hosts_connection_nolog main "host list&!!" unset
16322 .cindex "host" "not logging connections from"
16323 This option defines a list of hosts for which connection logging does not
16324 happen, even though the &%smtp_connection%& log selector is set. For example,
16325 you might want not to log SMTP connections from local processes, or from
16326 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16327 the daemon; you should therefore strive to restrict its value to a short inline
16328 list of IP addresses and networks. To disable logging SMTP connections from
16329 local processes, you must create a host list with an empty item. For example:
16331 hosts_connection_nolog = :
16333 If the &%smtp_connection%& log selector is not set, this option has no effect.
16337 .option hosts_require_alpn main "host list&!!" unset
16338 .cindex ALPN "require negotiation in server"
16340 .cindex TLS "Application Layer Protocol Names"
16341 If the TLS library supports ALPN
16342 then a successful negotiation of ALPN will be required for any client
16343 matching the list, for TLS to be used.
16344 See also the &%tls_alpn%& option.
16346 &*Note*&: prevention of fallback to in-clear connection is not
16347 managed by this option, and should be done separately.
16351 .option hosts_proxy main "host list&!!" unset
16352 .cindex proxy "proxy protocol"
16353 This option enables use of Proxy Protocol proxies for incoming
16354 connections. For details see section &<<SECTproxyInbound>>&.
16357 .option hosts_treat_as_local main "domain list&!!" unset
16358 .cindex "local host" "domains treated as"
16359 .cindex "host" "treated as local"
16360 If this option is set, any host names that match the domain list are treated as
16361 if they were the local host when Exim is scanning host lists obtained from MX
16363 or other sources. Note that the value of this option is a domain list, not a
16364 host list, because it is always used to check host names, not IP addresses.
16366 This option also applies when Exim is matching the special items
16367 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16368 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16369 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16370 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16371 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16372 interfaces and recognizing the local host.
16375 .option ibase_servers main "string list" unset
16376 .cindex "InterBase" "server list"
16377 This option provides a list of InterBase servers and associated connection data,
16378 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16379 The option is available only if Exim has been built with InterBase support.
16383 .option ignore_bounce_errors_after main time 10w
16384 .cindex "bounce message" "discarding"
16385 .cindex "discarding bounce message"
16386 This option affects the processing of bounce messages that cannot be delivered,
16387 that is, those that suffer a permanent delivery failure. (Bounce messages that
16388 suffer temporary delivery failures are of course retried in the usual way.)
16390 After a permanent delivery failure, bounce messages are frozen,
16391 because there is no sender to whom they can be returned. When a frozen bounce
16392 message has been in the queue for more than the given time, it is unfrozen at
16393 the next queue run, and a further delivery is attempted. If delivery fails
16394 again, the bounce message is discarded. This makes it possible to keep failed
16395 bounce messages around for a shorter time than the normal maximum retry time
16396 for frozen messages. For example,
16398 ignore_bounce_errors_after = 12h
16400 retries failed bounce message deliveries after 12 hours, discarding any further
16401 failures. If the value of this option is set to a zero time period, bounce
16402 failures are discarded immediately. Setting a very long time (as in the default
16403 value) has the effect of disabling this option. For ways of automatically
16404 dealing with other kinds of frozen message, see &%auto_thaw%& and
16405 &%timeout_frozen_after%&.
16408 .option ignore_fromline_hosts main "host list&!!" unset
16409 .cindex "&""From""& line"
16410 .cindex "UUCP" "&""From""& line"
16411 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16412 the headers of a message. By default this is treated as the start of the
16413 message's body, which means that any following headers are not recognized as
16414 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16415 match those hosts that insist on sending it. If the sender is actually a local
16416 process rather than a remote host, and is using &%-bs%& to inject the messages,
16417 &%ignore_fromline_local%& must be set to achieve this effect.
16420 .option ignore_fromline_local main boolean false
16421 See &%ignore_fromline_hosts%& above.
16423 .option keep_environment main "string list" unset
16424 .cindex "environment" "values from"
16425 This option contains a string list of environment variables to keep.
16426 You have to trust these variables or you have to be sure that
16427 these variables do not impose any security risk. Keep in mind that
16428 during the startup phase Exim is running with an effective UID 0 in most
16429 installations. As the default value is an empty list, the default
16430 environment for using libraries, running embedded Perl code, or running
16431 external binaries is empty, and does not not even contain PATH or HOME.
16433 Actually the list is interpreted as a list of patterns
16434 (&<<SECTlistexpand>>&), except that it is not expanded first.
16436 WARNING: Macro substitution is still done first, so having a macro
16437 FOO and having FOO_HOME in your &%keep_environment%& option may have
16438 unexpected results. You may work around this using a regular expression
16439 that does not match the macro name: ^[F]OO_HOME$.
16441 Current versions of Exim issue a warning during startup if you do not mention
16442 &%keep_environment%& in your runtime configuration file and if your
16443 current environment is not empty. Future versions may not issue that warning
16446 See the &%add_environment%& main config option for a way to set
16447 environment variables to a fixed value. The environment for &(pipe)&
16448 transports is handled separately, see section &<<SECTpipeenv>>& for
16452 .option keep_malformed main time 4d
16453 This option specifies the length of time to keep messages whose spool files
16454 have been corrupted in some way. This should, of course, never happen. At the
16455 next attempt to deliver such a message, it gets removed. The incident is
16459 .option ldap_ca_cert_dir main string unset
16460 .cindex "LDAP", "TLS CA certificate directory"
16461 .cindex certificate "directory for LDAP"
16462 This option indicates which directory contains CA certificates for verifying
16463 a TLS certificate presented by an LDAP server.
16464 While Exim does not provide a default value, your SSL library may.
16465 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16466 and constrained to be a directory.
16469 .option ldap_ca_cert_file main string unset
16470 .cindex "LDAP", "TLS CA certificate file"
16471 .cindex certificate "file for LDAP"
16472 This option indicates which file contains CA certificates for verifying
16473 a TLS certificate presented by an LDAP server.
16474 While Exim does not provide a default value, your SSL library may.
16475 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16476 and constrained to be a file.
16479 .option ldap_cert_file main string unset
16480 .cindex "LDAP" "TLS client certificate file"
16481 .cindex certificate "file for LDAP"
16482 This option indicates which file contains an TLS client certificate which
16483 Exim should present to the LDAP server during TLS negotiation.
16484 Should be used together with &%ldap_cert_key%&.
16487 .option ldap_cert_key main string unset
16488 .cindex "LDAP" "TLS client key file"
16489 .cindex certificate "key for LDAP"
16490 This option indicates which file contains the secret/private key to use
16491 to prove identity to the LDAP server during TLS negotiation.
16492 Should be used together with &%ldap_cert_file%&, which contains the
16493 identity to be proven.
16496 .option ldap_cipher_suite main string unset
16497 .cindex "LDAP" "TLS cipher suite"
16498 This controls the TLS cipher-suite negotiation during TLS negotiation with
16499 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16500 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16503 .option ldap_default_servers main "string list" unset
16504 .cindex "LDAP" "default servers"
16505 This option provides a list of LDAP servers which are tried in turn when an
16506 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16507 details of LDAP queries. This option is available only when Exim has been built
16511 .option ldap_require_cert main string unset.
16512 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16513 This should be one of the values "hard", "demand", "allow", "try" or "never".
16514 A value other than one of these is interpreted as "never".
16515 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16516 Although Exim does not set a default, the LDAP library probably defaults
16520 .option ldap_start_tls main boolean false
16521 .cindex "LDAP" "whether or not to negotiate TLS"
16522 If set, Exim will attempt to negotiate TLS with the LDAP server when
16523 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16524 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16526 In the event of failure to negotiate TLS, the action taken is controlled
16527 by &%ldap_require_cert%&.
16528 This option is ignored for &`ldapi`& connections.
16531 .option ldap_version main integer unset
16532 .cindex "LDAP" "protocol version, forcing"
16533 This option can be used to force Exim to set a specific protocol version for
16534 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16535 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16536 the LDAP headers; otherwise it is 2. This option is available only when Exim
16537 has been built with LDAP support.
16541 .option local_from_check main boolean true
16542 .cindex "&'Sender:'& header line" "disabling addition of"
16543 .cindex "&'From:'& header line" "disabling checking of"
16544 When a message is submitted locally (that is, not over a TCP/IP connection) by
16545 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16546 checks that the &'From:'& header line matches the login of the calling user and
16547 the domain specified by &%qualify_domain%&.
16549 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16550 locally submitted message is automatically qualified by Exim, unless the
16551 &%-bnq%& command line option is used.
16553 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16554 on the local part. If the &'From:'& header line does not match, Exim adds a
16555 &'Sender:'& header with an address constructed from the calling user's login
16556 and the default qualify domain.
16558 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16559 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16560 &'Sender:'& header lines supplied by untrusted users, you must also set
16561 &%local_sender_retain%& to be true.
16563 .cindex "envelope from"
16564 .cindex "envelope sender"
16565 These options affect only the header lines in the message. The envelope sender
16566 is still forced to be the login id at the qualify domain unless
16567 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16569 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16570 request similar header line checking. See section &<<SECTthesenhea>>&, which
16571 has more details about &'Sender:'& processing.
16576 .option local_from_prefix main string unset
16577 When Exim checks the &'From:'& header line of locally submitted messages for
16578 matching the login id (see &%local_from_check%& above), it can be configured to
16579 ignore certain prefixes and suffixes in the local part of the address. This is
16580 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16581 appropriate lists, in the same form as the &%local_part_prefix%& and
16582 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16585 local_from_prefix = *-
16587 is set, a &'From:'& line containing
16589 From: anything-user@your.domain.example
16591 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16592 matches the actual sender address that is constructed from the login name and
16596 .option local_from_suffix main string unset
16597 See &%local_from_prefix%& above.
16600 .option local_interfaces main "string list" "see below"
16601 This option controls which network interfaces are used by the daemon for
16602 listening; they are also used to identify the local host when routing. Chapter
16603 &<<CHAPinterfaces>>& contains a full description of this option and the related
16604 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16605 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16606 &%local_interfaces%& is
16608 local_interfaces = 0.0.0.0
16610 when Exim is built without IPv6 support; otherwise it is
16612 local_interfaces = <; ::0 ; 0.0.0.0
16615 .option local_scan_timeout main time 5m
16616 .cindex "timeout" "for &[local_scan()]& function"
16617 .cindex "&[local_scan()]& function" "timeout"
16618 This timeout applies to the &[local_scan()]& function (see chapter
16619 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16620 the incoming message is rejected with a temporary error if it is an SMTP
16621 message. For a non-SMTP message, the message is dropped and Exim ends with a
16622 non-zero code. The incident is logged on the main and reject logs.
16626 .option local_sender_retain main boolean false
16627 .cindex "&'Sender:'& header line" "retaining from local submission"
16628 When a message is submitted locally (that is, not over a TCP/IP connection) by
16629 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16630 do not want this to happen, you must set &%local_sender_retain%&, and you must
16631 also set &%local_from_check%& to be false (Exim will complain if you do not).
16632 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16633 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16638 .option localhost_number main string&!! unset
16639 .cindex "host" "locally unique number for"
16640 .cindex "message ids" "with multiple hosts"
16641 .vindex "&$localhost_number$&"
16642 Exim's message ids are normally unique only within the local host. If
16643 uniqueness among a set of hosts is required, each host must set a different
16644 value for the &%localhost_number%& option. The string is expanded immediately
16645 after reading the configuration file (so that a number can be computed from the
16646 host name, for example) and the result of the expansion must be a number in the
16647 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16648 systems). This is available in subsequent string expansions via the variable
16649 &$localhost_number$&. When &%localhost_number is set%&, the final two
16650 characters of the message id, instead of just being a fractional part of the
16651 time, are computed from the time and the local host number as described in
16652 section &<<SECTmessiden>>&.
16656 .option log_file_path main "string list&!!" "set at compile time"
16657 .cindex "log" "file path for"
16658 This option sets the path which is used to determine the names of Exim's log
16659 files, or indicates that logging is to be to syslog, or both. It is expanded
16660 when Exim is entered, so it can, for example, contain a reference to the host
16661 name. If no specific path is set for the log files at compile or runtime,
16662 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16663 they are written in a sub-directory called &_log_& in Exim's spool directory.
16664 A path must start with a slash.
16665 To send to syslog, use the word &"syslog"&.
16666 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16667 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16668 used. If this string is fixed at your installation (contains no expansion
16669 variables) it is recommended that you do not set this option in the
16670 configuration file, but instead supply the path using LOG_FILE_PATH in
16671 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16672 early on &-- in particular, failure to read the configuration file.
16675 .option log_selector main string unset
16676 .cindex "log" "selectors"
16677 This option can be used to reduce or increase the number of things that Exim
16678 writes to its log files. Its argument is made up of names preceded by plus or
16679 minus characters. For example:
16681 log_selector = +arguments -retry_defer
16683 A list of possible names and what they control is given in the chapter on
16684 logging, in section &<<SECTlogselector>>&.
16687 .option log_timezone main boolean false
16688 .cindex "log" "timezone for entries"
16689 .vindex "&$tod_log$&"
16690 .vindex "&$tod_zone$&"
16691 By default, the timestamps on log lines are in local time without the
16692 timezone. This means that if your timezone changes twice a year, the timestamps
16693 in log lines are ambiguous for an hour when the clocks go back. One way of
16694 avoiding this problem is to set the timezone to UTC. An alternative is to set
16695 &%log_timezone%& true. This turns on the addition of the timezone offset to
16696 timestamps in log lines. Turning on this option can add quite a lot to the size
16697 of log files because each line is extended by 6 characters. Note that the
16698 &$tod_log$& variable contains the log timestamp without the zone, but there is
16699 another variable called &$tod_zone$& that contains just the timezone offset.
16702 .option lookup_open_max main integer 25
16703 .cindex "too many open files"
16704 .cindex "open files, too many"
16705 .cindex "file" "too many open"
16706 .cindex "lookup" "maximum open files"
16707 .cindex "limit" "open files for lookups"
16708 This option limits the number of simultaneously open files for single-key
16709 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16710 Exim normally keeps these files open during routing, because often the same
16711 file is required several times. If the limit is reached, Exim closes the least
16712 recently used file. Note that if you are using the &'ndbm'& library, it
16713 actually opens two files for each logical DBM database, though it still counts
16714 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16715 open files"& errors with NDBM, you need to reduce the value of
16716 &%lookup_open_max%&.
16719 .option max_username_length main integer 0
16720 .cindex "length of login name"
16721 .cindex "user name" "maximum length"
16722 .cindex "limit" "user name length"
16723 Some operating systems are broken in that they truncate long arguments to
16724 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16725 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16726 an argument that is longer behaves as if &[getpwnam()]& failed.
16729 .option message_body_newlines main bool false
16730 .cindex "message body" "newlines in variables"
16731 .cindex "newline" "in message body variables"
16732 .vindex "&$message_body$&"
16733 .vindex "&$message_body_end$&"
16734 By default, newlines in the message body are replaced by spaces when setting
16735 the &$message_body$& and &$message_body_end$& expansion variables. If this
16736 option is set true, this no longer happens.
16739 .option message_body_visible main integer 500
16740 .cindex "body of message" "visible size"
16741 .cindex "message body" "visible size"
16742 .vindex "&$message_body$&"
16743 .vindex "&$message_body_end$&"
16744 This option specifies how much of a message's body is to be included in the
16745 &$message_body$& and &$message_body_end$& expansion variables.
16748 .option message_id_header_domain main string&!! unset
16749 .cindex "&'Message-ID:'& header line"
16750 If this option is set, the string is expanded and used as the right hand side
16751 (domain) of the &'Message-ID:'& header that Exim creates if a
16752 locally-originated incoming message does not have one. &"Locally-originated"&
16753 means &"not received over TCP/IP."&
16754 Otherwise, the primary host name is used.
16755 Only letters, digits, dot and hyphen are accepted; any other characters are
16756 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16757 empty string, the option is ignored.
16760 .option message_id_header_text main string&!! unset
16761 If this variable is set, the string is expanded and used to augment the text of
16762 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16763 message does not have one. The text of this header is required by RFC 2822 to
16764 take the form of an address. By default, Exim uses its internal message id as
16765 the local part, and the primary host name as the domain. If this option is set,
16766 it is expanded, and provided the expansion is not forced to fail, and does not
16767 yield an empty string, the result is inserted into the header immediately
16768 before the @, separated from the internal message id by a dot. Any characters
16769 that are illegal in an address are automatically converted into hyphens. This
16770 means that variables such as &$tod_log$& can be used, because the spaces and
16771 colons will become hyphens.
16774 .option message_logs main boolean true
16775 .cindex "message logs" "disabling"
16776 .cindex "log" "message log; disabling"
16777 If this option is turned off, per-message log files are not created in the
16778 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16779 Exim, by reducing the number of files involved in handling a message from a
16780 minimum of four (header spool file, body spool file, delivery journal, and
16781 per-message log) to three. The other major I/O activity is Exim's main log,
16782 which is not affected by this option.
16785 .option message_size_limit main string&!! 50M
16786 .cindex "message" "size limit"
16787 .cindex "limit" "message size"
16788 .cindex "size" "of message, limit"
16789 This option limits the maximum size of message that Exim will process. The
16790 value is expanded for each incoming connection so, for example, it can be made
16791 to depend on the IP address of the remote host for messages arriving via
16792 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16793 optionally followed by K or M.
16795 .cindex "SIZE" "ESMTP extension, advertising"
16796 .cindex "ESMTP extensions" SIZE
16797 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16798 service extension keyword.
16800 &*Note*&: This limit cannot be made to depend on a message's sender or any
16801 other properties of an individual message, because it has to be advertised in
16802 the server's response to EHLO. String expansion failure causes a temporary
16803 error. A value of zero means no limit, but its use is not recommended. See also
16804 &%bounce_return_size_limit%&.
16806 Incoming SMTP messages are failed with a 552 error if the limit is
16807 exceeded; locally-generated messages either get a stderr message or a delivery
16808 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16809 an oversized message is logged in both the main and the reject logs. See also
16810 the generic transport option &%message_size_limit%&, which limits the size of
16811 message that an individual transport can process.
16813 If you use a virus-scanner and set this option to to a value larger than the
16814 maximum size that your virus-scanner is configured to support, you may get
16815 failures triggered by large mails. The right size to configure for the
16816 virus-scanner depends upon what data is passed and the options in use but it's
16817 probably safest to just set it to a little larger than this value. E.g., with a
16818 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16819 some problems may result.
16821 A value of 0 will disable size limit checking; Exim will still advertise the
16822 SIZE extension in an EHLO response, but without a limit, so as to permit
16823 SMTP clients to still indicate the message size along with the MAIL verb.
16826 .option move_frozen_messages main boolean false
16827 .cindex "frozen messages" "moving"
16828 This option, which is available only if Exim has been built with the setting
16830 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16832 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16833 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16834 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16835 standard utilities for handling such moved messages, and they do not show up in
16836 lists generated by &%-bp%& or by the Exim monitor.
16839 .option mua_wrapper main boolean false
16840 Setting this option true causes Exim to run in a very restrictive mode in which
16841 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16842 contains a full description of this facility.
16846 .option mysql_servers main "string list" unset
16847 .cindex "MySQL" "server list"
16848 This option provides a list of MySQL servers and associated connection data, to
16849 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16850 option is available only if Exim has been built with MySQL support.
16853 .option never_users main "string list&!!" unset
16854 This option is expanded just once, at the start of Exim's processing. Local
16855 message deliveries are normally run in processes that are setuid to the
16856 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16857 It is usually desirable to prevent any deliveries from running as root, as a
16860 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16861 list of users that must not be used for local deliveries. This list is fixed in
16862 the binary and cannot be overridden by the configuration file. By default, it
16863 contains just the single user name &"root"&. The &%never_users%& runtime option
16864 can be used to add more users to the fixed list.
16866 If a message is to be delivered as one of the users on the fixed list or the
16867 &%never_users%& list, an error occurs, and delivery is deferred. A common
16870 never_users = root:daemon:bin
16872 Including root is redundant if it is also on the fixed list, but it does no
16873 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16877 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16878 This option gives the name for a unix-domain socket on which the daemon
16879 listens for work and information-requests.
16880 Only installations running multiple daemons sharing a spool directory
16881 should need to modify the default.
16883 The option is expanded before use.
16884 If the platform supports Linux-style abstract socket names, the result
16885 is used with a nul byte prefixed.
16887 .new "if nonempty,"
16888 it should be a full path name and use a directory accessible
16892 If this option is set as empty,
16893 or the command line &%-oY%& option is used, or
16895 the command line uses a &%-oX%& option and does not use &%-oP%&,
16896 then a notifier socket is not created.
16899 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16900 .cindex "OpenSSL "compatibility options"
16901 This option allows an administrator to adjust the SSL options applied
16902 by OpenSSL to connections. It is given as a space-separated list of items,
16903 each one to be +added or -subtracted from the current value.
16905 This option is only available if Exim is built against OpenSSL. The values
16906 available for this option vary according to the age of your OpenSSL install.
16907 The &"all"& value controls a subset of flags which are available, typically
16908 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16909 list the values known on your system and Exim should support all the
16910 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16911 names lose the leading &"SSL_OP_"& and are lower-cased.
16913 Note that adjusting the options can have severe impact upon the security of
16914 SSL as used by Exim. It is possible to disable safety checks and shoot
16915 yourself in the foot in various unpleasant ways. This option should not be
16916 adjusted lightly. An unrecognised item will be detected at startup, by
16917 invoking Exim with the &%-bV%& flag.
16919 The option affects Exim operating both as a server and as a client.
16921 Historical note: prior to release 4.80, Exim defaulted this value to
16922 "+dont_insert_empty_fragments", which may still be needed for compatibility
16923 with some clients, but which lowers security by increasing exposure to
16924 some now infamous attacks.
16928 # Make both old MS and old Eudora happy:
16929 openssl_options = -all +microsoft_big_sslv3_buffer \
16930 +dont_insert_empty_fragments
16932 # Disable older protocol versions:
16933 openssl_options = +no_sslv2 +no_sslv3
16936 Possible options may include:
16940 &`allow_unsafe_legacy_renegotiation`&
16942 &`cipher_server_preference`&
16944 &`dont_insert_empty_fragments`&
16948 &`legacy_server_connect`&
16950 &`microsoft_big_sslv3_buffer`&
16952 &`microsoft_sess_id_bug`&
16954 &`msie_sslv2_rsa_padding`&
16956 &`netscape_challenge_bug`&
16958 &`netscape_reuse_cipher_change_bug`&
16962 &`no_session_resumption_on_renegotiation`&
16976 &`safari_ecdhe_ecdsa_bug`&
16980 &`single_ecdh_use`&
16982 &`ssleay_080_client_dh_bug`&
16984 &`sslref2_reuse_cert_type_bug`&
16986 &`tls_block_padding_bug`&
16990 &`tls_rollback_bug`&
16993 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16994 all clients connecting using the MacOS SecureTransport TLS facility prior
16995 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16996 to negotiate TLS then this option value might help, provided that your OpenSSL
16997 release is new enough to contain this work-around. This may be a situation
16998 where you have to upgrade OpenSSL to get buggy clients working.
17001 .option oracle_servers main "string list" unset
17002 .cindex "Oracle" "server list"
17003 This option provides a list of Oracle servers and associated connection data,
17004 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
17005 The option is available only if Exim has been built with Oracle support.
17008 .option percent_hack_domains main "domain list&!!" unset
17009 .cindex "&""percent hack""&"
17010 .cindex "source routing" "in email address"
17011 .cindex "address" "source-routed"
17012 The &"percent hack"& is the convention whereby a local part containing a
17013 percent sign is re-interpreted as a new email address, with the percent
17014 replaced by @. This is sometimes called &"source routing"&, though that term is
17015 also applied to RFC 2822 addresses that begin with an @ character. If this
17016 option is set, Exim implements the percent facility for those domains listed,
17017 but no others. This happens before an incoming SMTP address is tested against
17020 &*Warning*&: The &"percent hack"& has often been abused by people who are
17021 trying to get round relaying restrictions. For this reason, it is best avoided
17022 if at all possible. Unfortunately, a number of less security-conscious MTAs
17023 implement it unconditionally. If you are running Exim on a gateway host, and
17024 routing mail through to internal MTAs without processing the local parts, it is
17025 a good idea to reject recipient addresses with percent characters in their
17026 local parts. Exim's default configuration does this.
17029 .option perl_at_start main boolean false
17031 This option is available only when Exim is built with an embedded Perl
17032 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17035 .option perl_startup main string unset
17037 This option is available only when Exim is built with an embedded Perl
17038 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17040 .option perl_taintmode main boolean false
17042 This option enables the taint mode of the embedded Perl interpreter.
17045 .option pgsql_servers main "string list" unset
17046 .cindex "PostgreSQL lookup type" "server list"
17047 This option provides a list of PostgreSQL servers and associated connection
17048 data, to be used in conjunction with &(pgsql)& lookups (see section
17049 &<<SECID72>>&). The option is available only if Exim has been built with
17050 PostgreSQL support.
17053 .option pid_file_path main string&!! "set at compile time"
17054 .cindex "daemon" "pid file path"
17055 .cindex "pid file, path for"
17056 This option sets the name of the file to which the Exim daemon writes its
17057 process id. The string is expanded, so it can contain, for example, references
17060 pid_file_path = /var/log/$primary_hostname/exim.pid
17062 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17064 The value set by the option can be overridden by the &%-oP%& command line
17065 option. A pid file is not written if a &"non-standard"& daemon is run by means
17066 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17069 .option pipelining_advertise_hosts main "host list&!!" *
17070 .cindex "PIPELINING" "suppressing advertising"
17071 .cindex "ESMTP extensions" PIPELINING
17072 This option can be used to suppress the advertisement of the SMTP
17073 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17074 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17075 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17076 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17077 that clients will use it; &"out of order"& commands that are &"expected"& do
17078 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17080 .option pipelining_connect_advertise_hosts main "host list&!!" *
17081 .cindex "pipelining" "early connection"
17082 .cindex "pipelining" PIPE_CONNECT
17083 .cindex "ESMTP extensions" PIPE_CONNECT
17084 If Exim is built with the SUPPORT_PIPE_CONNECT build option
17085 this option controls which hosts the facility is advertised to
17086 and from which pipeline early-connection (before MAIL) SMTP
17087 commands are acceptable.
17088 When used, the pipelining saves on roundtrip times.
17090 See also the &%hosts_pipe_connect%& smtp transport option.
17093 The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
17097 .option prdr_enable main boolean false
17098 .cindex "PRDR" "enabling on server"
17099 .cindex "ESMTP extensions" PRDR
17100 This option can be used to enable the Per-Recipient Data Response extension
17101 to SMTP, defined by Eric Hall.
17102 If the option is set, PRDR is advertised by Exim when operating as a server.
17103 If the client requests PRDR, and more than one recipient, for a message
17104 an additional ACL is called for each recipient after the message content
17105 is received. See section &<<SECTPRDRACL>>&.
17107 .option preserve_message_logs main boolean false
17108 .cindex "message logs" "preserving"
17109 If this option is set, message log files are not deleted when messages are
17110 completed. Instead, they are moved to a sub-directory of the spool directory
17111 called &_msglog.OLD_&, where they remain available for statistical or debugging
17112 purposes. This is a dangerous option to set on systems with any appreciable
17113 volume of mail. Use with care!
17116 .option primary_hostname main string "see below"
17117 .cindex "name" "of local host"
17118 .cindex "host" "name of local"
17119 .cindex "local host" "name of"
17120 .vindex "&$primary_hostname$&"
17121 This specifies the name of the current host. It is used in the default EHLO or
17122 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17123 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17124 The value is also used by default in some SMTP response messages from an Exim
17125 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17127 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17128 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17129 contains only one component, Exim passes it to &[gethostbyname()]& (or
17130 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17131 version. The variable &$primary_hostname$& contains the host name, whether set
17132 explicitly by this option, or defaulted.
17135 .option print_topbitchars main boolean false
17136 .cindex "printing characters"
17137 .cindex "8-bit characters"
17138 By default, Exim considers only those characters whose codes lie in the range
17139 32&--126 to be printing characters. In a number of circumstances (for example,
17140 when writing log entries) non-printing characters are converted into escape
17141 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17142 is set, code values of 128 and above are also considered to be printing
17145 This option also affects the header syntax checks performed by the
17146 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17147 the user's full name when constructing From: and Sender: addresses (as
17148 described in section &<<SECTconstr>>&). Setting this option can cause
17149 Exim to generate eight bit message headers that do not conform to the
17153 .option process_log_path main string unset
17154 .cindex "process log path"
17155 .cindex "log" "process log"
17156 .cindex "&'exiwhat'&"
17157 This option sets the name of the file to which an Exim process writes its
17158 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17159 utility script. If this option is unset, the file called &_exim-process.info_&
17160 in Exim's spool directory is used. The ability to specify the name explicitly
17161 can be useful in environments where two different Exims are running, using
17162 different spool directories.
17165 .option prod_requires_admin main boolean true
17166 .cindex "restricting access to features"
17170 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17171 admin user unless &%prod_requires_admin%& is set false. See also
17172 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17176 .option proxy_protocol_timeout main time 3s
17177 .cindex proxy "proxy protocol"
17178 This option sets the timeout for proxy protocol negotiation.
17179 For details see section &<<SECTproxyInbound>>&.
17183 .option qualify_domain main string "see below"
17184 .cindex "domain" "for qualifying addresses"
17185 .cindex "address" "qualification"
17186 This option specifies the domain name that is added to any envelope sender
17187 addresses that do not have a domain qualification. It also applies to
17188 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17189 are accepted by default only for locally-generated messages. Qualification is
17190 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17191 locally-generated messages, unless the &%-bnq%& command line option is used.
17193 Messages from external sources must always contain fully qualified addresses,
17194 unless the sending host matches &%sender_unqualified_hosts%& or
17195 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17196 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17197 necessary. Internally, Exim always works with fully qualified envelope
17198 addresses. If &%qualify_domain%& is not set, it defaults to the
17199 &%primary_hostname%& value.
17202 .option qualify_recipient main string "see below"
17203 This option allows you to specify a different domain for qualifying recipient
17204 addresses to the one that is used for senders. See &%qualify_domain%& above.
17208 .option queue_domains main "domain list&!!" unset
17209 .cindex "domain" "specifying non-immediate delivery"
17210 .cindex "queueing incoming messages"
17211 .cindex "message" "queueing certain domains"
17212 This option lists domains for which immediate delivery is not required.
17213 A delivery process is started whenever a message is received, but only those
17214 domains that do not match are processed. All other deliveries wait until the
17215 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17219 .option queue_fast_ramp main boolean false
17220 .cindex "queue runner" "two phase"
17221 .cindex "queue" "double scanning"
17222 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17223 command line, may start parallel delivery processes during their first
17224 phase. This will be done when a threshold number of messages have been
17225 routed for a single host.
17229 .option queue_list_requires_admin main boolean true
17230 .cindex "restricting access to features"
17232 The &%-bp%& command-line option, which lists the messages that are on the
17233 queue, requires the caller to be an admin user unless
17234 &%queue_list_requires_admin%& is set false.
17235 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17238 .option queue_only main boolean false
17239 .cindex "queueing incoming messages"
17240 .cindex "message" "queueing unconditionally"
17241 If &%queue_only%& is set, a delivery process is not automatically started
17242 whenever a message is received. Instead, the message waits in the queue for the
17243 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17244 delivered immediately when certain conditions (such as heavy load) occur.
17246 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17247 and &%-odi%& command line options override &%queue_only%& unless
17248 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17249 &%queue_only_load%&, and &%smtp_accept_queue%&.
17252 .option queue_only_file main string unset
17253 .cindex "queueing incoming messages"
17254 .cindex "message" "queueing by file existence"
17255 This option can be set to a colon-separated list of absolute path names, each
17256 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17257 it tests for the existence of each listed path using a call to &[stat()]&. For
17258 each path that exists, the corresponding queueing option is set.
17259 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17260 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17262 queue_only_file = smtp/some/file
17264 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17265 &_/some/file_& exists.
17268 .option queue_only_load main fixed-point unset
17269 .cindex "load average"
17270 .cindex "queueing incoming messages"
17271 .cindex "message" "queueing by load"
17272 If the system load average is higher than this value, incoming messages from
17273 all sources are queued, and no automatic deliveries are started. If this
17274 happens during local or remote SMTP input, all subsequent messages received on
17275 the same SMTP connection are queued by default, whatever happens to the load in
17276 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17279 Deliveries will subsequently be performed by queue runner processes. This
17280 option has no effect on ancient operating systems on which Exim cannot
17281 determine the load average. See also &%deliver_queue_load_max%& and
17282 &%smtp_load_reserve%&.
17285 .option queue_only_load_latch main boolean true
17286 .cindex "load average" "re-evaluating per message"
17287 When this option is true (the default), once one message has been queued
17288 because the load average is higher than the value set by &%queue_only_load%&,
17289 all subsequent messages received on the same SMTP connection are also queued.
17290 This is a deliberate choice; even though the load average may fall below the
17291 threshold, it doesn't seem right to deliver later messages on the same
17292 connection when not delivering earlier ones. However, there are special
17293 circumstances such as very long-lived connections from scanning appliances
17294 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17295 should be set false. This causes the value of the load average to be
17296 re-evaluated for each message.
17299 .option queue_only_override main boolean true
17300 .cindex "queueing incoming messages"
17301 When this option is true, the &%-od%&&'x'& command line options override the
17302 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17303 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17304 to override; they are accepted, but ignored.
17307 .option queue_run_in_order main boolean false
17308 .cindex "queue runner" "processing messages in order"
17309 If this option is set, queue runs happen in order of message arrival instead of
17310 in an arbitrary order. For this to happen, a complete list of the entire queue
17311 must be set up before the deliveries start. When the queue is all held in a
17312 single directory (the default), a single list is created for both the ordered
17313 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17314 single list is not created when &%queue_run_in_order%& is false. In this case,
17315 the sub-directories are processed one at a time (in a random order), and this
17316 avoids setting up one huge list for the whole queue. Thus, setting
17317 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17318 when the queue is large, because of the extra work in setting up the single,
17319 large list. In most situations, &%queue_run_in_order%& should not be set.
17323 .option queue_run_max main integer&!! 5
17324 .cindex "queue runner" "maximum number of"
17325 This controls the maximum number of queue runner processes that an Exim daemon
17326 can run simultaneously. This does not mean that it starts them all at once,
17327 but rather that if the maximum number are still running when the time comes to
17328 start another one, it refrains from starting another one. This can happen with
17329 very large queues and/or very sluggish deliveries. This option does not,
17330 however, interlock with other processes, so additional queue runners can be
17331 started by other means, or by killing and restarting the daemon.
17333 Setting this option to zero does not suppress queue runs; rather, it disables
17334 the limit, allowing any number of simultaneous queue runner processes to be
17335 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17336 the daemon's command line.
17338 .cindex queues named
17339 .cindex "named queues" "resource limit"
17340 To set limits for different named queues use
17341 an expansion depending on the &$queue_name$& variable.
17343 .option queue_smtp_domains main "domain list&!!" unset
17344 .cindex "queueing incoming messages"
17345 .cindex "message" "queueing remote deliveries"
17346 .cindex "first pass routing"
17347 When this option is set, a delivery process is started whenever a message is
17348 received, routing is performed, and local deliveries take place.
17349 However, if any SMTP deliveries are required for domains that match
17350 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17351 message waits in the queue for the next queue run. Since routing of the message
17352 has taken place, Exim knows to which remote hosts it must be delivered, and so
17353 when the queue run happens, multiple messages for the same host are delivered
17354 over a single SMTP connection. The &%-odqs%& command line option causes all
17355 SMTP deliveries to be queued in this way, and is equivalent to setting
17356 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17360 .option receive_timeout main time 0s
17361 .cindex "timeout" "for non-SMTP input"
17362 This option sets the timeout for accepting a non-SMTP message, that is, the
17363 maximum time that Exim waits when reading a message on the standard input. If
17364 the value is zero, it will wait forever. This setting is overridden by the
17365 &%-or%& command line option. The timeout for incoming SMTP messages is
17366 controlled by &%smtp_receive_timeout%&.
17368 .option received_header_text main string&!! "see below"
17369 .cindex "customizing" "&'Received:'& header"
17370 .cindex "&'Received:'& header line" "customizing"
17371 This string defines the contents of the &'Received:'& message header that is
17372 added to each message, except for the timestamp, which is automatically added
17373 on at the end (preceded by a semicolon). The string is expanded each time it is
17374 used. If the expansion yields an empty string, no &'Received:'& header line is
17375 added to the message. Otherwise, the string should start with the text
17376 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17378 The default setting is:
17381 received_header_text = Received: \
17382 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17383 {${if def:sender_ident \
17384 {from ${quote_local_part:$sender_ident} }}\
17385 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17386 by $primary_hostname \
17387 ${if def:received_protocol {with $received_protocol }}\
17388 ${if def:tls_in_ver { ($tls_in_ver)}}\
17389 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17390 (Exim $version_number)\n\t\
17391 ${if def:sender_address \
17392 {(envelope-from <$sender_address>)\n\t}}\
17393 id $message_exim_id\
17394 ${if def:received_for {\n\tfor $received_for}}
17397 The references to the TLS version and cipher are
17398 omitted when Exim is built without TLS
17399 support. The use of conditional expansions ensures that this works for both
17400 locally generated messages and messages received from remote hosts, giving
17401 header lines such as the following:
17403 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17404 by marley.carol.example with esmtp (Exim 4.00)
17405 (envelope-from <bob@carol.example>)
17406 id 16IOWa-00019l-00
17407 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17408 Received: by scrooge.carol.example with local (Exim 4.00)
17409 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17411 Until the body of the message has been received, the timestamp is the time when
17412 the message started to be received. Once the body has arrived, and all policy
17413 checks have taken place, the timestamp is updated to the time at which the
17414 message was accepted.
17417 .option received_headers_max main integer 30
17418 .cindex "loop" "prevention"
17419 .cindex "mail loop prevention"
17420 .cindex "&'Received:'& header line" "counting"
17421 When a message is to be delivered, the number of &'Received:'& headers is
17422 counted, and if it is greater than this parameter, a mail loop is assumed to
17423 have occurred, the delivery is abandoned, and an error message is generated.
17424 This applies to both local and remote deliveries.
17427 .option recipient_unqualified_hosts main "host list&!!" unset
17428 .cindex "unqualified addresses"
17429 .cindex "host" "unqualified addresses from"
17430 This option lists those hosts from which Exim is prepared to accept unqualified
17431 recipient addresses in message envelopes. The addresses are made fully
17432 qualified by the addition of the &%qualify_recipient%& value. This option also
17433 affects message header lines. Exim does not reject unqualified recipient
17434 addresses in headers, but it qualifies them only if the message came from a
17435 host that matches &%recipient_unqualified_hosts%&,
17436 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17437 option was not set.
17440 .option recipients_max main integer 50000
17441 .cindex "limit" "number of recipients"
17442 .cindex "recipient" "maximum number"
17443 If this option is set greater than zero, it specifies the maximum number of
17444 original recipients for any message. Additional recipients that are generated
17445 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17446 all recipients over the limit; earlier recipients are delivered as normal.
17447 Non-SMTP messages with too many recipients are failed, and no deliveries are
17450 .cindex "RCPT" "maximum number of incoming"
17451 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17452 RCPT commands in a single message.
17455 .option recipients_max_reject main boolean false
17456 If this option is set true, Exim rejects SMTP messages containing too many
17457 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17458 error to the eventual DATA command. Otherwise (the default) it gives a 452
17459 error to the surplus RCPT commands and accepts the message on behalf of the
17460 initial set of recipients. The remote server should then re-send the message
17461 for the remaining recipients at a later time.
17464 .option remote_max_parallel main integer 2
17465 .cindex "delivery" "parallelism for remote"
17466 This option controls parallel delivery of one message to a number of remote
17467 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17468 does all the remote deliveries for a message one by one. Otherwise, if a single
17469 message has to be delivered to more than one remote host, or if several copies
17470 have to be sent to the same remote host, up to &%remote_max_parallel%&
17471 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17472 deliveries are required, the maximum number of processes are started, and as
17473 each one finishes, another is begun. The order of starting processes is the
17474 same as if sequential delivery were being done, and can be controlled by the
17475 &%remote_sort_domains%& option. If parallel delivery takes place while running
17476 with debugging turned on, the debugging output from each delivery process is
17477 tagged with its process id.
17479 This option controls only the maximum number of parallel deliveries for one
17480 message in one Exim delivery process. Because Exim has no central queue
17481 manager, there is no way of controlling the total number of simultaneous
17482 deliveries if the configuration allows a delivery attempt as soon as a message
17485 See also the &%max_parallel%& generic transport option,
17486 and the &%serialize_hosts%& smtp transport option.
17488 .cindex "number of deliveries"
17489 .cindex "delivery" "maximum number of"
17490 If you want to control the total number of deliveries on the system, you
17491 need to set the &%queue_only%& option. This ensures that all incoming messages
17492 are added to the queue without starting a delivery process. Then set up an Exim
17493 daemon to start queue runner processes at appropriate intervals (probably
17494 fairly often, for example, every minute), and limit the total number of queue
17495 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17496 delivers only one message at a time, the maximum number of deliveries that can
17497 then take place at once is &%queue_run_max%& multiplied by
17498 &%remote_max_parallel%&.
17500 If it is purely remote deliveries you want to control, use
17501 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17502 doing the SMTP routing before queueing, so that several messages for the same
17503 host will eventually get delivered down the same connection.
17506 .option remote_sort_domains main "domain list&!!" unset
17507 .cindex "sorting remote deliveries"
17508 .cindex "delivery" "sorting remote"
17509 When there are a number of remote deliveries for a message, they are sorted by
17510 domain into the order given by this list. For example,
17512 remote_sort_domains = *.cam.ac.uk:*.uk
17514 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17515 then to those in the &%uk%& domain, then to any others.
17518 .option retry_data_expire main time 7d
17519 .cindex "hints database" "data expiry"
17520 This option sets a &"use before"& time on retry information in Exim's hints
17521 database. Any older retry data is ignored. This means that, for example, once a
17522 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17526 .option retry_interval_max main time 24h
17527 .cindex "retry" "limit on interval"
17528 .cindex "limit" "on retry interval"
17529 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17530 intervals between delivery attempts for messages that cannot be delivered
17531 straight away. This option sets an overall limit to the length of time between
17532 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17536 .option return_path_remove main boolean true
17537 .cindex "&'Return-path:'& header line" "removing"
17538 RFC 2821, section 4.4, states that an SMTP server must insert a
17539 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17540 The &'Return-path:'& header preserves the sender address as received in the
17541 MAIL command. This description implies that this header should not be present
17542 in an incoming message. If &%return_path_remove%& is true, any existing
17543 &'Return-path:'& headers are removed from messages at the time they are
17544 received. Exim's transports have options for adding &'Return-path:'& headers at
17545 the time of delivery. They are normally used only for final local deliveries.
17548 .option return_size_limit main integer 100K
17549 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17552 .option rfc1413_hosts main "host list&!!" @[]
17554 .cindex "host" "for RFC 1413 calls"
17555 RFC 1413 identification calls are made to any client host which matches
17556 an item in the list.
17557 The default value specifies just this host, being any local interface
17560 .option rfc1413_query_timeout main time 0s
17561 .cindex "RFC 1413" "query timeout"
17562 .cindex "timeout" "for RFC 1413 call"
17563 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17564 no RFC 1413 calls are ever made.
17567 .option sender_unqualified_hosts main "host list&!!" unset
17568 .cindex "unqualified addresses"
17569 .cindex "host" "unqualified addresses from"
17570 This option lists those hosts from which Exim is prepared to accept unqualified
17571 sender addresses. The addresses are made fully qualified by the addition of
17572 &%qualify_domain%&. This option also affects message header lines. Exim does
17573 not reject unqualified addresses in headers that contain sender addresses, but
17574 it qualifies them only if the message came from a host that matches
17575 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17576 using TCP/IP), and the &%-bnq%& option was not set.
17579 .option slow_lookup_log main integer 0
17580 .cindex "logging" "slow lookups"
17581 .cindex "dns" "logging slow lookups"
17582 This option controls logging of slow lookups.
17583 If the value is nonzero it is taken as a number of milliseconds
17584 and lookups taking longer than this are logged.
17585 Currently this applies only to DNS lookups.
17589 .option smtp_accept_keepalive main boolean true
17590 .cindex "keepalive" "on incoming connection"
17591 This option controls the setting of the SO_KEEPALIVE option on incoming
17592 TCP/IP socket connections. When set, it causes the kernel to probe idle
17593 connections periodically, by sending packets with &"old"& sequence numbers. The
17594 other end of the connection should send an acknowledgment if the connection is
17595 still okay or a reset if the connection has been aborted. The reason for doing
17596 this is that it has the beneficial effect of freeing up certain types of
17597 connection that can get stuck when the remote host is disconnected without
17598 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17599 hours to detect unreachable hosts.
17603 .option smtp_accept_max main integer 20
17604 .cindex "limit" "incoming SMTP connections"
17605 .cindex "SMTP" "incoming connection count"
17607 This option specifies the maximum number of simultaneous incoming SMTP calls
17608 that Exim will accept. It applies only to the listening daemon; there is no
17609 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17610 value is set to zero, no limit is applied. However, it is required to be
17611 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17612 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17614 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17615 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17616 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17617 and &%smtp_load_reserve%& are then checked before accepting the connection.
17620 .option smtp_accept_max_nonmail main integer 10
17621 .cindex "limit" "non-mail SMTP commands"
17622 .cindex "SMTP" "limiting non-mail commands"
17623 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17624 the connection if there are too many. This option defines &"too many"&. The
17625 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17626 client looping sending EHLO, for example. The check is applied only if the
17627 client host matches &%smtp_accept_max_nonmail_hosts%&.
17629 When a new message is expected, one occurrence of RSET is not counted. This
17630 allows a client to send one RSET between messages (this is not necessary,
17631 but some clients do it). Exim also allows one uncounted occurrence of HELO
17632 or EHLO, and one occurrence of STARTTLS between messages. After
17633 starting up a TLS session, another EHLO is expected, and so it too is not
17634 counted. The first occurrence of AUTH in a connection, or immediately
17635 following STARTTLS is not counted. Otherwise, all commands other than
17636 MAIL, RCPT, DATA, and QUIT are counted.
17639 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17640 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17641 check by setting this option. The default value makes it apply to all hosts. By
17642 changing the value, you can exclude any badly-behaved hosts that you have to
17646 . Allow this long option name to split; give it unsplit as a fifth argument
17647 . for the automatic .oindex that is generated by .option.
17648 . We insert " &~&~" which is both pretty nasty visually and results in
17649 . non-searchable text. HowItWorks.txt mentions an option for inserting
17650 . zero-width-space, which would be nicer visually and results in (at least)
17651 . html that Firefox will split on when it's forced to reflow (rather than
17652 . inserting a horizontal scrollbar). However, the text is still not
17653 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17654 . the option name to split.
17656 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17657 smtp_accept_max_per_connection
17658 .cindex "SMTP" "limiting incoming message count"
17659 .cindex "limit" "messages per SMTP connection"
17660 The value of this option limits the number of MAIL commands that Exim is
17661 prepared to accept over a single SMTP connection, whether or not each command
17662 results in the transfer of a message. After the limit is reached, a 421
17663 response is given to subsequent MAIL commands. This limit is a safety
17664 precaution against a client that goes mad (incidents of this type have been
17667 The option is expanded after the HELO or EHLO is received
17668 and may depend on values available at that time.
17669 An empty or zero value after expansion removes the limit.
17673 .option smtp_accept_max_per_host main string&!! unset
17674 .cindex "limit" "SMTP connections from one host"
17675 .cindex "host" "limiting SMTP connections from"
17676 This option restricts the number of simultaneous IP connections from a single
17677 host (strictly, from a single IP address) to the Exim daemon. The option is
17678 expanded, to enable different limits to be applied to different hosts by
17679 reference to &$sender_host_address$&. Once the limit is reached, additional
17680 connection attempts from the same host are rejected with error code 421. This
17681 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17682 of zero imposes no limit. If this option is set greater than zero, it is
17683 required that &%smtp_accept_max%& be non-zero.
17685 &*Warning*&: When setting this option you should not use any expansion
17686 constructions that take an appreciable amount of time. The expansion and test
17687 happen in the main daemon loop, in order to reject additional connections
17688 without forking additional processes (otherwise a denial-of-service attack
17689 could cause a vast number or processes to be created). While the daemon is
17690 doing this processing, it cannot accept any other incoming connections.
17694 .option smtp_accept_queue main integer 0
17695 .cindex "SMTP" "incoming connection count"
17696 .cindex "queueing incoming messages"
17697 .cindex "message" "queueing by SMTP connection count"
17698 If the number of simultaneous incoming SMTP connections being handled via the
17699 listening daemon exceeds this value, messages received by SMTP are just placed
17700 in the queue; no delivery processes are started automatically. The count is
17701 fixed at the start of an SMTP connection. It cannot be updated in the
17702 subprocess that receives messages, and so the queueing or not queueing applies
17703 to all messages received in the same connection.
17705 A value of zero implies no limit, and clearly any non-zero value is useful only
17706 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17707 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17708 various &%-od%&&'x'& command line options.
17711 . See the comment on smtp_accept_max_per_connection
17713 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17714 smtp_accept_queue_per_connection
17715 .cindex "queueing incoming messages"
17716 .cindex "message" "queueing by message count"
17717 This option limits the number of delivery processes that Exim starts
17718 automatically when receiving messages via SMTP, whether via the daemon or by
17719 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17720 and the number of messages received in a single SMTP session exceeds this
17721 number, subsequent messages are placed in the queue, but no delivery processes
17722 are started. This helps to limit the number of Exim processes when a server
17723 restarts after downtime and there is a lot of mail waiting for it on other
17724 systems. On large systems, the default should probably be increased, and on
17725 dial-in client systems it should probably be set to zero (that is, disabled).
17728 .option smtp_accept_reserve main integer 0
17729 .cindex "SMTP" "incoming call count"
17730 .cindex "host" "reserved"
17731 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17732 number of SMTP connections that are reserved for connections from the hosts
17733 that are specified in &%smtp_reserve_hosts%&. The value set in
17734 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17735 restricted to this number of connections; the option specifies a minimum number
17736 of connection slots for them, not a maximum. It is a guarantee that this group
17737 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17738 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17741 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17742 set to 5, once there are 45 active connections (from any hosts), new
17743 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17744 provided the other criteria for acceptance are met.
17747 .option smtp_active_hostname main string&!! unset
17748 .cindex "host" "name in SMTP responses"
17749 .cindex "SMTP" "host name in responses"
17750 .vindex "&$primary_hostname$&"
17751 This option is provided for multi-homed servers that want to masquerade as
17752 several different hosts. At the start of an incoming SMTP connection, its value
17753 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17754 responses. For example, it is used as domain name in the response to an
17755 incoming HELO or EHLO command.
17757 .vindex "&$smtp_active_hostname$&"
17758 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17759 is saved with any messages that are received. It is therefore available for use
17760 in routers and transports when the message is later delivered.
17762 If this option is unset, or if its expansion is forced to fail, or if the
17763 expansion results in an empty string, the value of &$primary_hostname$& is
17764 used. Other expansion failures cause a message to be written to the main and
17765 panic logs, and the SMTP command receives a temporary error. Typically, the
17766 value of &%smtp_active_hostname%& depends on the incoming interface address.
17769 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17770 {cox.mydomain}{box.mydomain}}
17773 Although &$smtp_active_hostname$& is primarily concerned with incoming
17774 messages, it is also used as the default for HELO commands in callout
17775 verification if there is no remote transport from which to obtain a
17776 &%helo_data%& value.
17778 .option smtp_backlog_monitor main integer 0
17779 .cindex "connection backlog" monitoring
17780 If this option is set to greater than zero, and the backlog of available
17781 TCP connections on a socket listening for SMTP is larger than it, a line
17782 is logged giving the value and the socket address and port.
17783 The value is retrived jsut before an accept call.
17784 This facility is only available on Linux.
17786 .option smtp_banner main string&!! "see below"
17787 .cindex "SMTP" "welcome banner"
17788 .cindex "banner for SMTP"
17789 .cindex "welcome banner for SMTP"
17790 .cindex "customizing" "SMTP banner"
17791 This string, which is expanded every time it is used, is output as the initial
17792 positive response to an SMTP connection. The default setting is:
17794 smtp_banner = $smtp_active_hostname ESMTP Exim \
17795 $version_number $tod_full
17797 Failure to expand the string causes a panic error. If you want to create a
17798 multiline response to the initial SMTP connection, use &"\n"& in the string at
17799 appropriate points, but not at the end. Note that the 220 code is not included
17800 in this string. Exim adds it automatically (several times in the case of a
17801 multiline response).
17804 .option smtp_check_spool_space main boolean true
17805 .cindex "checking disk space"
17806 .cindex "disk space, checking"
17807 .cindex "spool directory" "checking space"
17808 When this option is set, if an incoming SMTP session encounters the SIZE
17809 option on a MAIL command, it checks that there is enough space in the
17810 spool directory's partition to accept a message of that size, while still
17811 leaving free the amount specified by &%check_spool_space%& (even if that value
17812 is zero). If there isn't enough space, a temporary error code is returned.
17815 .option smtp_connect_backlog main integer 20
17816 .cindex "connection backlog" "set maximum"
17817 .cindex "SMTP" "connection backlog"
17818 .cindex "backlog of connections"
17819 This option specifies a maximum number of waiting SMTP connections. Exim passes
17820 this value to the TCP/IP system when it sets up its listener. Once this number
17821 of connections are waiting for the daemon's attention, subsequent connection
17822 attempts are refused at the TCP/IP level. At least, that is what the manuals
17823 say; in some circumstances such connection attempts have been observed to time
17824 out instead. For large systems it is probably a good idea to increase the
17825 value (to 50, say). It also gives some protection against denial-of-service
17826 attacks by SYN flooding.
17829 .option smtp_enforce_sync main boolean true
17830 .cindex "SMTP" "synchronization checking"
17831 .cindex "synchronization checking in SMTP"
17832 The SMTP protocol specification requires the client to wait for a response from
17833 the server at certain points in the dialogue. Without PIPELINING these
17834 synchronization points are after every command; with PIPELINING they are
17835 fewer, but they still exist.
17837 Some spamming sites send out a complete set of SMTP commands without waiting
17838 for any response. Exim protects against this by rejecting a message if the
17839 client has sent further input when it should not have. The error response &"554
17840 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17841 for this error cannot be perfect because of transmission delays (unexpected
17842 input may be on its way but not yet received when Exim checks). However, it
17843 does detect many instances.
17845 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17846 If you want to disable the check selectively (for example, only for certain
17847 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17848 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17852 .option smtp_etrn_command main string&!! unset
17853 .cindex "ETRN" "command to be run"
17854 .cindex "ESMTP extensions" ETRN
17855 .vindex "&$domain$&"
17856 If this option is set, the given command is run whenever an SMTP ETRN
17857 command is received from a host that is permitted to issue such commands (see
17858 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17859 are independently expanded. The expansion variable &$domain$& is set to the
17860 argument of the ETRN command, and no syntax checking is done on it. For
17863 smtp_etrn_command = /etc/etrn_command $domain \
17864 $sender_host_address
17866 If the option is not set, the argument for the ETRN command must
17867 be a &'#'& followed by an address string.
17868 In this case an &'exim -R <string>'& command is used;
17869 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17871 A new process is created to run the command, but Exim does not wait for it to
17872 complete. Consequently, its status cannot be checked. If the command cannot be
17873 run, a line is written to the panic log, but the ETRN caller still receives
17874 a 250 success response. Exim is normally running under its own uid when
17875 receiving SMTP, so it is not possible for it to change the uid before running
17879 .option smtp_etrn_serialize main boolean true
17880 .cindex "ETRN" "serializing"
17881 When this option is set, it prevents the simultaneous execution of more than
17882 one identical command as a result of ETRN in an SMTP connection. See
17883 section &<<SECTETRN>>& for details.
17886 .option smtp_load_reserve main fixed-point unset
17887 .cindex "load average"
17888 If the system load average ever gets higher than this, incoming SMTP calls are
17889 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17890 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17891 the load is over the limit. The option has no effect on ancient operating
17892 systems on which Exim cannot determine the load average. See also
17893 &%deliver_queue_load_max%& and &%queue_only_load%&.
17897 .option smtp_max_synprot_errors main integer 3
17898 .cindex "SMTP" "limiting syntax and protocol errors"
17899 .cindex "limit" "SMTP syntax and protocol errors"
17900 Exim rejects SMTP commands that contain syntax or protocol errors. In
17901 particular, a syntactically invalid email address, as in this command:
17903 RCPT TO:<abc xyz@a.b.c>
17905 causes immediate rejection of the command, before any other tests are done.
17906 (The ACL cannot be run if there is no valid address to set up for it.) An
17907 example of a protocol error is receiving RCPT before MAIL. If there are
17908 too many syntax or protocol errors in one SMTP session, the connection is
17909 dropped. The limit is set by this option.
17911 .cindex "PIPELINING" "expected errors"
17912 When the PIPELINING extension to SMTP is in use, some protocol errors are
17913 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17914 Exim assumes that PIPELINING will be used if it advertises it (see
17915 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17916 not count towards the limit.
17920 .option smtp_max_unknown_commands main integer 3
17921 .cindex "SMTP" "limiting unknown commands"
17922 .cindex "limit" "unknown SMTP commands"
17923 If there are too many unrecognized commands in an incoming SMTP session, an
17924 Exim server drops the connection. This is a defence against some kinds of abuse
17927 into making connections to SMTP ports; in these circumstances, a number of
17928 non-SMTP command lines are sent first.
17932 .option smtp_ratelimit_hosts main "host list&!!" unset
17933 .cindex "SMTP" "rate limiting"
17934 .cindex "limit" "rate of message arrival"
17935 .cindex "RCPT" "rate limiting"
17936 Some sites find it helpful to be able to limit the rate at which certain hosts
17937 can send them messages, and the rate at which an individual message can specify
17940 Exim has two rate-limiting facilities. This section describes the older
17941 facility, which can limit rates within a single connection. The newer
17942 &%ratelimit%& ACL condition can limit rates across all connections. See section
17943 &<<SECTratelimiting>>& for details of the newer facility.
17945 When a host matches &%smtp_ratelimit_hosts%&, the values of
17946 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17947 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17948 respectively. Each option, if set, must contain a set of four comma-separated
17952 A threshold, before which there is no rate limiting.
17954 An initial time delay. Unlike other times in Exim, numbers with decimal
17955 fractional parts are allowed here.
17957 A factor by which to increase the delay each time.
17959 A maximum value for the delay. This should normally be less than 5 minutes,
17960 because after that time, the client is liable to timeout the SMTP command.
17963 For example, these settings have been used successfully at the site which
17964 first suggested this feature, for controlling mail from their customers:
17966 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17967 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17969 The first setting specifies delays that are applied to MAIL commands after
17970 two have been received over a single connection. The initial delay is 0.5
17971 seconds, increasing by a factor of 1.05 each time. The second setting applies
17972 delays to RCPT commands when more than four occur in a single message.
17975 .option smtp_ratelimit_mail main string unset
17976 See &%smtp_ratelimit_hosts%& above.
17979 .option smtp_ratelimit_rcpt main string unset
17980 See &%smtp_ratelimit_hosts%& above.
17983 .option smtp_receive_timeout main time&!! 5m
17984 .cindex "timeout" "for SMTP input"
17985 .cindex "SMTP" "input timeout"
17986 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17987 input, including batch SMTP. If a line of input (either an SMTP command or a
17988 data line) is not received within this time, the SMTP connection is dropped and
17989 the message is abandoned.
17990 A line is written to the log containing one of the following messages:
17992 SMTP command timeout on connection from...
17993 SMTP data timeout on connection from...
17995 The former means that Exim was expecting to read an SMTP command; the latter
17996 means that it was in the DATA phase, reading the contents of a message.
17998 If the first character of the option is a &"$"& the option is
17999 expanded before use and may depend on
18000 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
18004 The value set by this option can be overridden by the
18005 &%-os%& command-line option. A setting of zero time disables the timeout, but
18006 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
18007 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
18008 timeout is controlled by &%receive_timeout%& and &%-or%&.
18011 .option smtp_reserve_hosts main "host list&!!" unset
18012 This option defines hosts for which SMTP connections are reserved; see
18013 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
18016 .option smtp_return_error_details main boolean false
18017 .cindex "SMTP" "details policy failures"
18018 .cindex "policy control" "rejection, returning details"
18019 In the default state, Exim uses bland messages such as
18020 &"Administrative prohibition"& when it rejects SMTP commands for policy
18021 reasons. Many sysadmins like this because it gives away little information
18022 to spammers. However, some other sysadmins who are applying strict checking
18023 policies want to give out much fuller information about failures. Setting
18024 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
18025 example, instead of &"Administrative prohibition"&, it might give:
18027 550-Rejected after DATA: '>' missing at end of address:
18028 550 failing address in "From" header is: <user@dom.ain
18032 .option smtputf8_advertise_hosts main "host list&!!" *
18033 .cindex "SMTPUTF8" "ESMTP extension, advertising"
18034 .cindex "ESMTP extensions" SMTPUTF8
18035 When Exim is built with support for internationalised mail names,
18036 the availability thereof is advertised in
18037 response to EHLO only to those client hosts that match this option. See
18038 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
18041 .option spamd_address main string "127.0.0.1 783"
18042 This option is available when Exim is compiled with the content-scanning
18043 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18044 See section &<<SECTscanspamass>>& for more details.
18048 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18049 This option is available when Exim is compiled with SPF support.
18050 See section &<<SECSPF>>& for more details.
18052 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18053 This option is available when Exim is compiled with SPF support. It
18054 allows the customisation of the SMTP comment that the SPF library
18055 generates. You are strongly encouraged to link to your own explanative
18056 site. The template must not contain spaces. If you need spaces in the
18057 output, use the proper placeholder. If libspf2 can not parse the
18058 template, it uses a built-in default broken link. The following placeholders
18059 (along with Exim variables (but see below)) are allowed in the template:
18063 &*%{L}*&: Envelope sender's local part.
18065 &*%{S}*&: Envelope sender.
18067 &*%{O}*&: Envelope sender's domain.
18069 &*%{D}*&: Current(?) domain.
18071 &*%{I}*&: SMTP client Ip.
18073 &*%{C}*&: SMTP client pretty IP.
18075 &*%{T}*&: Epoch time (UTC).
18077 &*%{P}*&: SMTP client domain name.
18079 &*%{V}*&: IP version.
18081 &*%{H}*&: EHLO/HELO domain.
18083 &*%{R}*&: Receiving domain.
18085 The capitalized placeholders do proper URL encoding, if you use them
18086 lowercased, no encoding takes place. This list was compiled from the
18089 A note on using Exim variables: As
18090 currently the SPF library is initialized before the SMTP EHLO phase,
18091 the variables useful for expansion are quite limited.
18094 .option split_spool_directory main boolean false
18095 .cindex "multiple spool directories"
18096 .cindex "spool directory" "split"
18097 .cindex "directories, multiple"
18098 If this option is set, it causes Exim to split its input directory into 62
18099 subdirectories, each with a single alphanumeric character as its name. The
18100 sixth character of the message id is used to allocate messages to
18101 subdirectories; this is the least significant base-62 digit of the time of
18102 arrival of the message.
18104 Splitting up the spool in this way may provide better performance on systems
18105 where there are long mail queues, by reducing the number of files in any one
18106 directory. The msglog directory is also split up in a similar way to the input
18107 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18108 are still placed in the single directory &_msglog.OLD_&.
18110 It is not necessary to take any special action for existing messages when
18111 changing &%split_spool_directory%&. Exim notices messages that are in the
18112 &"wrong"& place, and continues to process them. If the option is turned off
18113 after a period of being on, the subdirectories will eventually empty and be
18114 automatically deleted.
18116 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18117 changes. Instead of creating a list of all messages in the queue, and then
18118 trying to deliver each one, in turn, it constructs a list of those in one
18119 sub-directory and tries to deliver them, before moving on to the next
18120 sub-directory. The sub-directories are processed in a random order. This
18121 spreads out the scanning of the input directories, and uses less memory. It is
18122 particularly beneficial when there are lots of messages in the queue. However,
18123 if &%queue_run_in_order%& is set, none of this new processing happens. The
18124 entire queue has to be scanned and sorted before any deliveries can start.
18127 .option spool_directory main string&!! "set at compile time"
18128 .cindex "spool directory" "path to"
18129 This defines the directory in which Exim keeps its spool, that is, the messages
18130 it is waiting to deliver. The default value is taken from the compile-time
18131 configuration setting, if there is one. If not, this option must be set. The
18132 string is expanded, so it can contain, for example, a reference to
18133 &$primary_hostname$&.
18135 If the spool directory name is fixed on your installation, it is recommended
18136 that you set it at build time rather than from this option, particularly if the
18137 log files are being written to the spool directory (see &%log_file_path%&).
18138 Otherwise log files cannot be used for errors that are detected early on, such
18139 as failures in the configuration file.
18141 By using this option to override the compiled-in path, it is possible to run
18142 tests of Exim without using the standard spool.
18144 .option spool_wireformat main boolean false
18145 .cindex "spool directory" "file formats"
18146 If this option is set, Exim may for some messages use an alternative format
18147 for data-files in the spool which matches the wire format.
18148 Doing this permits more efficient message reception and transmission.
18149 Currently it is only done for messages received using the ESMTP CHUNKING
18152 The following variables will not have useful values:
18154 $max_received_linelength
18159 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18160 and any external programs which are passed a reference to a message data file
18161 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18162 will need to be aware of the different formats potentially available.
18164 Using any of the ACL conditions noted will negate the reception benefit
18165 (as a Unix-mbox-format file is constructed for them).
18166 The transmission benefit is maintained.
18168 .option sqlite_lock_timeout main time 5s
18169 .cindex "sqlite lookup type" "lock timeout"
18170 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18171 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18173 .option strict_acl_vars main boolean false
18174 .cindex "&ACL;" "variables, handling unset"
18175 This option controls what happens if a syntactically valid but undefined ACL
18176 variable is referenced. If it is false (the default), an empty string
18177 is substituted; if it is true, an error is generated. See section
18178 &<<SECTaclvariables>>& for details of ACL variables.
18180 .option strip_excess_angle_brackets main boolean false
18181 .cindex "angle brackets, excess"
18182 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18183 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18184 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18185 passed on to another MTA, the excess angle brackets are not passed on. If this
18186 option is not set, multiple pairs of angle brackets cause a syntax error.
18189 .option strip_trailing_dot main boolean false
18190 .cindex "trailing dot on domain"
18191 .cindex "dot" "trailing on domain"
18192 If this option is set, a trailing dot at the end of a domain in an address is
18193 ignored. If this is in the envelope and the message is passed on to another
18194 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18195 domain causes a syntax error.
18196 However, addresses in header lines are checked only when an ACL requests header
18200 .option syslog_duplication main boolean true
18201 .cindex "syslog" "duplicate log lines; suppressing"
18202 When Exim is logging to syslog, it writes the log lines for its three
18203 separate logs at different syslog priorities so that they can in principle
18204 be separated on the logging hosts. Some installations do not require this
18205 separation, and in those cases, the duplication of certain log lines is a
18206 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18207 particular log line is written to syslog. For lines that normally go to
18208 both the main log and the reject log, the reject log version (possibly
18209 containing message header lines) is written, at LOG_NOTICE priority.
18210 Lines that normally go to both the main and the panic log are written at
18211 the LOG_ALERT priority.
18214 .option syslog_facility main string unset
18215 .cindex "syslog" "facility; setting"
18216 This option sets the syslog &"facility"& name, used when Exim is logging to
18217 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18218 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18219 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18220 details of Exim's logging.
18223 .option syslog_pid main boolean true
18224 .cindex "syslog" "pid"
18225 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18226 omitted when these lines are sent to syslog. (Syslog normally prefixes
18227 the log lines with the PID of the logging process automatically.) You need
18228 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18229 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18233 .option syslog_processname main string &`exim`&
18234 .cindex "syslog" "process name; setting"
18235 This option sets the syslog &"ident"& name, used when Exim is logging to
18236 syslog. The value must be no longer than 32 characters. See chapter
18237 &<<CHAPlog>>& for details of Exim's logging.
18241 .option syslog_timestamp main boolean true
18242 .cindex "syslog" "timestamps"
18243 .cindex timestamps syslog
18244 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18245 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18246 details of Exim's logging.
18249 .option system_filter main string&!! unset
18250 .cindex "filter" "system filter"
18251 .cindex "system filter" "specifying"
18252 .cindex "Sieve filter" "not available for system filter"
18253 This option specifies an Exim filter file that is applied to all messages at
18254 the start of each delivery attempt, before any routing is done. System filters
18255 must be Exim filters; they cannot be Sieve filters. If the system filter
18256 generates any deliveries to files or pipes, or any new mail messages, the
18257 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18258 which transports are to be used. Details of this facility are given in chapter
18259 &<<CHAPsystemfilter>>&.
18260 A forced expansion failure results in no filter operation.
18263 .option system_filter_directory_transport main string&!! unset
18264 .vindex "&$address_file$&"
18265 This sets the name of the transport driver that is to be used when the
18266 &%save%& command in a system message filter specifies a path ending in &"/"&,
18267 implying delivery of each message into a separate file in some directory.
18268 During the delivery, the variable &$address_file$& contains the path name.
18271 .option system_filter_file_transport main string&!! unset
18272 .cindex "file" "transport for system filter"
18273 This sets the name of the transport driver that is to be used when the &%save%&
18274 command in a system message filter specifies a path not ending in &"/"&. During
18275 the delivery, the variable &$address_file$& contains the path name.
18277 .option system_filter_group main string unset
18278 .cindex "gid (group id)" "system filter"
18279 This option is used only when &%system_filter_user%& is also set. It sets the
18280 gid under which the system filter is run, overriding any gid that is associated
18281 with the user. The value may be numerical or symbolic.
18283 .option system_filter_pipe_transport main string&!! unset
18284 .cindex "&(pipe)& transport" "for system filter"
18285 .vindex "&$address_pipe$&"
18286 This specifies the transport driver that is to be used when a &%pipe%& command
18287 is used in a system filter. During the delivery, the variable &$address_pipe$&
18288 contains the pipe command.
18291 .option system_filter_reply_transport main string&!! unset
18292 .cindex "&(autoreply)& transport" "for system filter"
18293 This specifies the transport driver that is to be used when a &%mail%& command
18294 is used in a system filter.
18297 .option system_filter_user main string unset
18298 .cindex "uid (user id)" "system filter"
18299 If this option is set to root, the system filter is run in the main Exim
18300 delivery process, as root. Otherwise, the system filter runs in a separate
18301 process, as the given user, defaulting to the Exim run-time user.
18302 Unless the string consists entirely of digits, it
18303 is looked up in the password data. Failure to find the named user causes a
18304 configuration error. The gid is either taken from the password data, or
18305 specified by &%system_filter_group%&. When the uid is specified numerically,
18306 &%system_filter_group%& is required to be set.
18308 If the system filter generates any pipe, file, or reply deliveries, the uid
18309 under which the filter is run is used when transporting them, unless a
18310 transport option overrides.
18313 .option tcp_nodelay main boolean true
18314 .cindex "daemon" "TCP_NODELAY on sockets"
18315 .cindex "Nagle algorithm"
18316 .cindex "TCP_NODELAY on listening sockets"
18317 If this option is set false, it stops the Exim daemon setting the
18318 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18319 turns off the &"Nagle algorithm"&, which is a way of improving network
18320 performance in interactive (character-by-character) situations. Turning it off
18321 should improve Exim's performance a bit, so that is what happens by default.
18322 However, it appears that some broken clients cannot cope, and time out. Hence
18323 this option. It affects only those sockets that are set up for listening by the
18324 daemon. Sockets created by the smtp transport for delivering mail always set
18328 .option timeout_frozen_after main time 0s
18329 .cindex "frozen messages" "timing out"
18330 .cindex "timeout" "frozen messages"
18331 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18332 message of any kind that has been in the queue for longer than the given time
18333 is automatically cancelled at the next queue run. If the frozen message is a
18334 bounce message, it is just discarded; otherwise, a bounce is sent to the
18335 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18336 If you want to timeout frozen bounce messages earlier than other kinds of
18337 frozen message, see &%ignore_bounce_errors_after%&.
18339 &*Note:*& the default value of zero means no timeouts; with this setting,
18340 frozen messages remain in the queue forever (except for any frozen bounce
18341 messages that are released by &%ignore_bounce_errors_after%&).
18344 .option timezone main string unset
18345 .cindex "timezone, setting"
18346 .cindex "environment" "values from"
18347 The value of &%timezone%& is used to set the environment variable TZ while
18348 running Exim (if it is different on entry). This ensures that all timestamps
18349 created by Exim are in the required timezone. If you want all your timestamps
18350 to be in UTC (aka GMT) you should set
18354 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18355 or, if that is not set, from the value of the TZ environment variable when Exim
18356 is built. If &%timezone%& is set to the empty string, either at build or run
18357 time, any existing TZ variable is removed from the environment when Exim
18358 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18359 unfortunately not all, operating systems.
18362 .option tls_advertise_hosts main "host list&!!" *
18363 .cindex "TLS" "advertising"
18364 .cindex "encryption" "on SMTP connection"
18365 .cindex "SMTP" "encrypted connection"
18366 .cindex "ESMTP extensions" STARTTLS
18367 When Exim is built with support for TLS encrypted connections, the availability
18368 of the STARTTLS command to set up an encrypted session is advertised in
18369 response to EHLO only to those client hosts that match this option. See
18370 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18371 Note that the default value requires that a certificate be supplied
18372 using the &%tls_certificate%& option. If TLS support for incoming connections
18373 is not required the &%tls_advertise_hosts%& option should be set empty.
18377 .option tls_alpn main "string list&!!" "smtp : esmtp"
18378 .cindex TLS "Application Layer Protocol Names"
18380 .cindex ALPN "set acceptable names for server"
18381 If this option is set,
18382 the TLS library supports ALPN,
18383 and the client offers either more than
18384 ALPN name or a name which does not match the list,
18385 the TLS connection is declined.
18389 .option tls_certificate main "string list&!!" unset
18390 .cindex "TLS" "server certificate; location of"
18391 .cindex "certificate" "server, location of"
18392 The value of this option is expanded, and must then be a list of absolute paths to
18393 files which contain the server's certificates (in PEM format).
18394 Commonly only one file is needed.
18395 The server's private key is also
18396 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18397 &<<CHAPTLS>>& for further details.
18399 &*Note*&: The certificates defined by this option are used only when Exim is
18400 receiving incoming messages as a server. If you want to supply certificates for
18401 use when sending messages as a client, you must set the &%tls_certificate%&
18402 option in the relevant &(smtp)& transport.
18404 &*Note*&: If you use filenames based on IP addresses, change the list
18405 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18407 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18408 when a list of more than one
18409 file is used, the &$tls_in_ourcert$& variable is unreliable.
18410 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18412 .cindex SNI "selecting server certificate based on"
18413 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18414 if the OpenSSL build supports TLS extensions and the TLS client sends the
18415 Server Name Indication extension, then this option and others documented in
18416 &<<SECTtlssni>>& will be re-expanded.
18418 If this option is unset or empty a self-signed certificate will be
18421 Under Linux this is generated at daemon startup; on other platforms it will be
18422 generated fresh for every connection.
18425 .option tls_crl main string&!! unset
18426 .cindex "TLS" "server certificate revocation list"
18427 .cindex "certificate" "revocation list for server"
18428 This option specifies a certificate revocation list. The expanded value must
18429 be the name of a file that contains CRLs in PEM format.
18431 Under OpenSSL the option can specify a directory with CRL files.
18433 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18434 for each signing element of the certificate chain (i.e. all but the leaf).
18435 For the file variant this can be multiple PEM blocks in the one file.
18437 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18440 .option tls_dh_max_bits main integer 2236
18441 .cindex "TLS" "D-H bit count"
18442 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18443 the chosen TLS library. That value might prove to be too high for
18444 interoperability. This option provides a maximum clamp on the value
18445 suggested, trading off security for interoperability.
18447 The value must be at least 1024.
18449 The value 2236 was chosen because, at time of adding the option, it was the
18450 hard-coded maximum value supported by the NSS cryptographic library, as used
18451 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18453 If you prefer more security and are willing to break some clients, raise this
18456 Note that the value passed to GnuTLS for *generating* a new prime may be a
18457 little less than this figure, because GnuTLS is inexact and may produce a
18458 larger prime than requested.
18461 .option tls_dhparam main string&!! unset
18462 .cindex "TLS" "D-H parameters for server"
18463 The value of this option is expanded and indicates the source of DH parameters
18464 to be used by Exim.
18466 This option is ignored for GnuTLS version 3.6.0 and later.
18467 The library manages parameter negotiation internally.
18469 &*Note: The Exim Maintainers strongly recommend,
18470 for other TLS library versions,
18471 using a filename with site-generated
18472 local DH parameters*&, which has been supported across all versions of Exim. The
18473 other specific constants available are a fallback so that even when
18474 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18476 If &%tls_dhparam%& is a filename starting with a &`/`&,
18477 then it names a file from which DH
18478 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18479 PKCS#3 representation of the DH prime. If the file does not exist, for
18480 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18481 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18482 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18483 and treated as though the &%tls_dhparam%& were set to "none".
18485 If this option expands to the string "none", then no DH parameters will be
18488 If this option expands to the string "historic" and Exim is using GnuTLS, then
18489 Exim will attempt to load a file from inside the spool directory. If the file
18490 does not exist, Exim will attempt to create it.
18491 See section &<<SECTgnutlsparam>>& for further details.
18493 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18494 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18496 In older versions of Exim the default was the 2048 bit prime described in section
18497 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18498 in IKE is assigned number 23.
18500 Otherwise, the option must expand to the name used by Exim for any of a number
18501 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18502 sources. As names, Exim uses a standard specified name, else "ike" followed by
18503 the number used by IKE, or "default" which corresponds to
18504 &`exim.dev.20160529.3`&.
18506 The available standard primes are:
18507 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18508 &`ike1`&, &`ike2`&, &`ike5`&,
18509 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18510 &`ike22`&, &`ike23`& and &`ike24`&.
18512 The available additional primes are:
18513 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18515 Some of these will be too small to be accepted by clients.
18516 Some may be too large to be accepted by clients.
18517 The open cryptographic community has suspicions about the integrity of some
18518 of the later IKE values, which led into RFC7919 providing new fixed constants
18519 (the "ffdhe" identifiers).
18521 At this point, all of the "ike" values should be considered obsolete;
18522 they're still in Exim to avoid breaking unusual configurations, but are
18523 candidates for removal the next time we have backwards-incompatible changes.
18525 The TLS protocol does not negotiate an acceptable size for this; clients tend
18526 to hard-drop connections if what is offered by the server is unacceptable,
18527 whether too large or too small, and there's no provision for the client to
18528 tell the server what these constraints are. Thus, as a server operator, you
18529 need to make an educated guess as to what is most likely to work for your
18532 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18533 is most likely to maximise interoperability. The upper bound comes from
18534 applications using the Mozilla Network Security Services (NSS) library, which
18535 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18536 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18537 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18538 acceptable bound from 1024 to 2048.
18541 .option tls_eccurve main string&!! &`auto`&
18542 .cindex TLS "EC cryptography"
18543 This option selects a EC curve for use by Exim when used with OpenSSL.
18544 It has no effect when Exim is used with GnuTLS.
18546 After expansion it must contain a valid EC curve parameter, such as
18547 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18548 for valid selections.
18550 For OpenSSL versions before (and not including) 1.0.2, the string
18551 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18552 &`auto`& tells the library to choose.
18554 If the option expands to an empty string, no EC curves will be enabled.
18557 .option tls_ocsp_file main string&!! unset
18558 .cindex TLS "certificate status"
18559 .cindex TLS "OCSP proof file"
18561 must if set expand to the absolute path to a file which contains a current
18562 status proof for the server's certificate, as obtained from the
18563 Certificate Authority.
18565 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18566 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18568 For OpenSSL 1.1.0 or later, and
18569 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18570 of files, to match a list given for the &%tls_certificate%& option.
18571 The ordering of the two lists must match.
18572 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18574 The file(s) should be in DER format,
18575 except for GnuTLS 3.6.3 or later
18577 when an optional filetype prefix can be used.
18578 The prefix must be one of "DER" or "PEM", followed by
18579 a single space. If one is used it sets the format for subsequent
18580 files in the list; the initial format is DER.
18581 If multiple proofs are wanted, for multiple chain elements
18582 (this only works under TLS1.3)
18583 they must be coded as a combined OCSP response.
18585 Although GnuTLS will accept PEM files with multiple separate
18586 PEM blobs (ie. separate OCSP responses), it sends them in the
18587 TLS Certificate record interleaved with the certificates of the chain;
18588 although a GnuTLS client is happy with that, an OpenSSL client is not.
18590 .option tls_on_connect_ports main "string list" unset
18593 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18594 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18595 set up without waiting for the client to issue a STARTTLS command. For
18596 further details, see section &<<SECTsupobssmt>>&.
18600 .option tls_privatekey main "string list&!!" unset
18601 .cindex "TLS" "server private key; location of"
18602 The value of this option is expanded, and must then be a list of absolute paths to
18603 files which contains the server's private keys.
18604 If this option is unset, or if
18605 the expansion is forced to fail, or the result is an empty string, the private
18606 key is assumed to be in the same file as the server's certificates. See chapter
18607 &<<CHAPTLS>>& for further details.
18609 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18612 .option tls_remember_esmtp main boolean false
18613 .cindex "TLS" "esmtp state; remembering"
18614 .cindex "TLS" "broken clients"
18615 If this option is set true, Exim violates the RFCs by remembering that it is in
18616 &"esmtp"& state after successfully negotiating a TLS session. This provides
18617 support for broken clients that fail to send a new EHLO after starting a
18621 .option tls_require_ciphers main string&!! unset
18622 .cindex "TLS" "requiring specific ciphers"
18623 .cindex "cipher" "requiring specific"
18624 This option controls which ciphers can be used for incoming TLS connections.
18625 The &(smtp)& transport has an option of the same name for controlling outgoing
18626 connections. This option is expanded for each connection, so can be varied for
18627 different clients if required. The value of this option must be a list of
18628 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18629 in somewhat different ways. If GnuTLS is being used, the client controls the
18630 preference order of the available ciphers. Details are given in sections
18631 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18635 .option tls_resumption_hosts main "host list&!!" unset
18636 .cindex TLS resumption
18637 This option controls which connections to offer the TLS resumption feature.
18638 See &<<SECTresumption>>& for details.
18642 .option tls_try_verify_hosts main "host list&!!" unset
18643 .cindex "TLS" "client certificate verification"
18644 .cindex "certificate" "verification of client"
18645 See &%tls_verify_hosts%& below.
18648 .option tls_verify_certificates main string&!! system
18649 .cindex "TLS" "client certificate verification"
18650 .cindex "certificate" "verification of client"
18651 The value of this option is expanded, and must then be either the
18653 or the absolute path to
18654 a file or directory containing permitted certificates for clients that
18655 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18657 The "system" value for the option will use a
18658 system default location compiled into the SSL library.
18659 This is not available for GnuTLS versions preceding 3.0.20,
18660 and will be taken as empty; an explicit location
18663 The use of a directory for the option value is not available for GnuTLS versions
18664 preceding 3.3.6 and a single file must be used.
18666 With OpenSSL the certificates specified
18668 either by file or directory
18669 are added to those given by the system default location.
18671 These certificates should be for the certificate authorities trusted, rather
18672 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18673 the value is a file then the certificates are sent by Exim as a server to
18674 connecting clients, defining the list of accepted certificate authorities.
18675 Thus the values defined should be considered public data. To avoid this,
18676 use the explicit directory version. (If your peer is Exim up to 4.85,
18677 using GnuTLS, you may need to send the CAs (thus using the file
18678 variant). Otherwise the peer doesn't send its certificate.)
18680 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18682 A forced expansion failure or setting to an empty string is equivalent to
18686 .option tls_verify_hosts main "host list&!!" unset
18687 .cindex "TLS" "client certificate verification"
18688 .cindex "certificate" "verification of client"
18689 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18690 certificates from clients. The expected certificates are defined by
18691 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18692 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18693 &%tls_verify_certificates%& is not set.
18695 Any client that matches &%tls_verify_hosts%& is constrained by
18696 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18697 present one of the listed certificates. If it does not, the connection is
18698 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18699 the host to use TLS. It can still send SMTP commands through unencrypted
18700 connections. Forcing a client to use TLS has to be done separately using an
18701 ACL to reject inappropriate commands when the connection is not encrypted.
18703 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18704 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18705 certificate and checks it against &%tls_verify_certificates%&, but does not
18706 abort the connection if there is no certificate or if it does not match. This
18707 state can be detected in an ACL, which makes it possible to implement policies
18708 such as &"accept for relay only if a verified certificate has been received,
18709 but accept for local delivery if encrypted, even without a verified
18712 Client hosts that match neither of these lists are not asked to present
18716 .option trusted_groups main "string list&!!" unset
18717 .cindex "trusted groups"
18718 .cindex "groups" "trusted"
18719 This option is expanded just once, at the start of Exim's processing. If this
18720 option is set, any process that is running in one of the listed groups, or
18721 which has one of them as a supplementary group, is trusted. The groups can be
18722 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18723 details of what trusted callers are permitted to do. If neither
18724 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18727 .option trusted_users main "string list&!!" unset
18728 .cindex "trusted users"
18729 .cindex "user" "trusted"
18730 This option is expanded just once, at the start of Exim's processing. If this
18731 option is set, any process that is running as one of the listed users is
18732 trusted. The users can be specified numerically or by name. See section
18733 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18734 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18735 Exim user are trusted.
18737 .option unknown_login main string&!! unset
18738 .cindex "uid (user id)" "unknown caller"
18739 .vindex "&$caller_uid$&"
18740 This is a specialized feature for use in unusual configurations. By default, if
18741 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18742 gives up. The &%unknown_login%& option can be used to set a login name to be
18743 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18744 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18745 is used for the user's real name (gecos field), unless this has been set by the
18748 .option unknown_username main string unset
18749 See &%unknown_login%&.
18751 .option untrusted_set_sender main "address list&!!" unset
18752 .cindex "trusted users"
18753 .cindex "sender" "setting by untrusted user"
18754 .cindex "untrusted user setting sender"
18755 .cindex "user" "untrusted setting sender"
18756 .cindex "envelope from"
18757 .cindex "envelope sender"
18758 When an untrusted user submits a message to Exim using the standard input, Exim
18759 normally creates an envelope sender address from the user's login and the
18760 default qualification domain. Data from the &%-f%& option (for setting envelope
18761 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18762 is used) is ignored.
18764 However, untrusted users are permitted to set an empty envelope sender address,
18765 to declare that a message should never generate any bounces. For example:
18767 exim -f '<>' user@domain.example
18769 .vindex "&$sender_ident$&"
18770 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18771 other envelope sender addresses in a controlled way. When it is set, untrusted
18772 users are allowed to set envelope sender addresses that match any of the
18773 patterns in the list. Like all address lists, the string is expanded. The
18774 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18775 users to setting senders that start with their login ids
18776 followed by a hyphen
18777 by a setting like this:
18779 untrusted_set_sender = ^$sender_ident-
18781 If you want to allow untrusted users to set envelope sender addresses without
18782 restriction, you can use
18784 untrusted_set_sender = *
18786 The &%untrusted_set_sender%& option applies to all forms of local input, but
18787 only to the setting of the envelope sender. It does not permit untrusted users
18788 to use the other options which trusted user can use to override message
18789 parameters. Furthermore, it does not stop Exim from removing an existing
18790 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18791 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18792 overriding these actions. The handling of the &'Sender:'& header is also
18793 described in section &<<SECTthesenhea>>&.
18795 The log line for a message's arrival shows the envelope sender following
18796 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18797 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18798 envelope sender address, the user's login is shown in parentheses after the
18802 .option uucp_from_pattern main string "see below"
18803 .cindex "&""From""& line"
18804 .cindex "UUCP" "&""From""& line"
18805 Some applications that pass messages to an MTA via a command line interface use
18806 an initial line starting with &"From&~"& to pass the envelope sender. In
18807 particular, this is used by UUCP software. Exim recognizes such a line by means
18808 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18809 matches, the sender address is constructed by expanding the contents of
18810 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18811 default pattern recognizes lines in the following two forms:
18813 From ph10 Fri Jan 5 12:35 GMT 1996
18814 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18816 The pattern can be seen by running
18818 exim -bP uucp_from_pattern
18820 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18821 year in the second case. The first word after &"From&~"& is matched in the
18822 regular expression by a parenthesized subpattern. The default value for
18823 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18824 (&"ph10"& in the example above) as the message's sender. See also
18825 &%ignore_fromline_hosts%&.
18828 .option uucp_from_sender main string&!! &`$1`&
18829 See &%uucp_from_pattern%& above.
18832 .option warn_message_file main string&!! unset
18833 .cindex "warning of delay" "customizing the message"
18834 .cindex "customizing" "warning message"
18835 This option defines a template file containing paragraphs of text to be used
18836 for constructing the warning message which is sent by Exim when a message has
18837 been in the queue for a specified amount of time, as specified by
18838 &%delay_warning%&. Details of the file's contents are given in chapter
18839 &<<CHAPemsgcust>>&.
18840 .cindex warn_message_file "tainted data"
18841 The option is expanded to give the file path, which must be
18842 absolute and untainted.
18843 See also &%bounce_message_file%&.
18846 .option write_rejectlog main boolean true
18847 .cindex "reject log" "disabling"
18848 If this option is set false, Exim no longer writes anything to the reject log.
18849 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18850 .ecindex IIDconfima
18851 .ecindex IIDmaiconf
18856 . ////////////////////////////////////////////////////////////////////////////
18857 . ////////////////////////////////////////////////////////////////////////////
18859 .chapter "Generic options for routers" "CHAProutergeneric"
18860 .scindex IIDgenoprou1 "options" "generic; for routers"
18861 .scindex IIDgenoprou2 "generic options" "router"
18862 This chapter describes the generic options that apply to all routers.
18863 Those that are preconditions are marked with ‡ in the &"use"& field.
18865 For a general description of how a router operates, see sections
18866 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18867 which the preconditions are tested. The order of expansion of the options that
18868 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18869 &%headers_remove%&, &%transport%&.
18872 The name of a router is limited to be &drivernamemax; ASCII characters long;
18873 prior to Exim 4.95 names would be silently truncated at this length, but now
18878 .option address_data routers string&!! unset
18879 .cindex "router" "data attached to address"
18880 The string is expanded just before the router is run, that is, after all the
18881 precondition tests have succeeded. If the expansion is forced to fail, the
18882 router declines, the value of &%address_data%& remains unchanged, and the
18883 &%more%& option controls what happens next. Other expansion failures cause
18884 delivery of the address to be deferred.
18886 .vindex "&$address_data$&"
18887 When the expansion succeeds, the value is retained with the address, and can be
18888 accessed using the variable &$address_data$& in the current router, subsequent
18889 routers, and the eventual transport.
18891 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18892 that runs a user's filter file, the contents of &$address_data$& are accessible
18893 in the filter. This is not normally a problem, because such data is usually
18894 either not confidential or it &"belongs"& to the current user, but if you do
18895 put confidential data into &$address_data$& you need to remember this point.
18897 Even if the router declines or passes, the value of &$address_data$& remains
18898 with the address, though it can be changed by another &%address_data%& setting
18899 on a subsequent router. If a router generates child addresses, the value of
18900 &$address_data$& propagates to them. This also applies to the special kind of
18901 &"child"& that is generated by a router with the &%unseen%& option.
18903 The idea of &%address_data%& is that you can use it to look up a lot of data
18904 for the address once, and then pick out parts of the data later. For example,
18905 you could use a single LDAP lookup to return a string of the form
18907 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18909 In the transport you could pick out the mailbox by a setting such as
18911 file = ${extract{mailbox}{$address_data}}
18913 This makes the configuration file less messy, and also reduces the number of
18914 lookups (though Exim does cache lookups).
18916 See also the &%set%& option below.
18918 .vindex "&$sender_address_data$&"
18919 .vindex "&$address_data$&"
18920 The &%address_data%& facility is also useful as a means of passing information
18921 from one router to another, and from a router to a transport. In addition, if
18922 &$address_data$& is set by a router when verifying a recipient address from an
18923 ACL, it remains available for use in the rest of the ACL statement. After
18924 verifying a sender, the value is transferred to &$sender_address_data$&.
18928 .option address_test routers&!? boolean true
18930 .cindex "router" "skipping when address testing"
18931 If this option is set false, the router is skipped when routing is being tested
18932 by means of the &%-bt%& command line option. This can be a convenience when
18933 your first router sends messages to an external scanner, because it saves you
18934 having to set the &"already scanned"& indicator when testing real address
18939 .option cannot_route_message routers string&!! unset
18940 .cindex "router" "customizing &""cannot route""& message"
18941 .cindex "customizing" "&""cannot route""& message"
18942 This option specifies a text message that is used when an address cannot be
18943 routed because Exim has run out of routers. The default message is
18944 &"Unrouteable address"&. This option is useful only on routers that have
18945 &%more%& set false, or on the very last router in a configuration, because the
18946 value that is used is taken from the last router that is considered. This
18947 includes a router that is skipped because its preconditions are not met, as
18948 well as a router that declines. For example, using the default configuration,
18951 cannot_route_message = Remote domain not found in DNS
18953 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18956 cannot_route_message = Unknown local user
18958 on the final router that checks for local users. If string expansion fails for
18959 this option, the default message is used. Unless the expansion failure was
18960 explicitly forced, a message about the failure is written to the main and panic
18961 logs, in addition to the normal message about the routing failure.
18964 .option caseful_local_part routers boolean false
18965 .cindex "case of local parts"
18966 .cindex "router" "case of local parts"
18967 By default, routers handle the local parts of addresses in a case-insensitive
18968 manner, though the actual case is preserved for transmission with the message.
18969 If you want the case of letters to be significant in a router, you must set
18970 this option true. For individual router options that contain address or local
18971 part lists (for example, &%local_parts%&), case-sensitive matching can be
18972 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18975 .vindex "&$local_part$&"
18976 .vindex "&$original_local_part$&"
18977 .vindex "&$parent_local_part$&"
18978 The value of the &$local_part$& variable is forced to lower case while a
18979 router is running unless &%caseful_local_part%& is set. When a router assigns
18980 an address to a transport, the value of &$local_part$& when the transport runs
18981 is the same as it was in the router. Similarly, when a router generates child
18982 addresses by aliasing or forwarding, the values of &$original_local_part$&
18983 and &$parent_local_part$& are those that were used by the redirecting router.
18985 This option applies to the processing of an address by a router. When a
18986 recipient address is being processed in an ACL, there is a separate &%control%&
18987 modifier that can be used to specify case-sensitive processing within the ACL
18988 (see section &<<SECTcontrols>>&).
18992 .option check_local_user routers&!? boolean false
18993 .cindex "local user, checking in router"
18994 .cindex "router" "checking for local user"
18995 .cindex "&_/etc/passwd_&"
18997 When this option is true, Exim checks that the local part of the recipient
18998 address (with affixes removed if relevant) is the name of an account on the
18999 local system. The check is done by calling the &[getpwnam()]& function rather
19000 than trying to read &_/etc/passwd_& directly. This means that other methods of
19001 holding password data (such as NIS) are supported. If the local part is a local
19003 .cindex "tainted data" "de-tainting"
19004 &$local_part_data$& is set to an untainted version of the local part and
19005 &$home$& is set from the password data. The latter can be tested in other
19006 preconditions that are evaluated after this one (the order of evaluation is
19007 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
19008 overridden by &%router_home_directory%&. If the local part is not a local user,
19009 the router is skipped.
19011 If you want to check that the local part is either the name of a local user
19012 or matches something else, you cannot combine &%check_local_user%& with a
19013 setting of &%local_parts%&, because that specifies the logical &'and'& of the
19014 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
19015 setting to achieve this. For example:
19017 local_parts = passwd;$local_part : lsearch;/etc/other/users
19019 Note, however, that the side effects of &%check_local_user%& (such as setting
19020 up a home directory) do not occur when a &(passwd)& lookup is used in a
19021 &%local_parts%& (or any other) precondition.
19025 .option condition routers&!? string&!! unset
19026 .cindex "router" "customized precondition"
19027 This option specifies a general precondition test that has to succeed for the
19028 router to be called. The &%condition%& option is the last precondition to be
19029 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
19030 result is a forced failure, or an empty string, or one of the strings &"0"& or
19031 &"no"& or &"false"& (checked without regard to the case of the letters), the
19032 router is skipped, and the address is offered to the next one.
19034 If the result is any other value, the router is run (as this is the last
19035 precondition to be evaluated, all the other preconditions must be true).
19037 This option is unusual in that multiple &%condition%& options may be present.
19038 All &%condition%& options must succeed.
19040 The &%condition%& option provides a means of applying custom conditions to the
19041 running of routers. Note that in the case of a simple conditional expansion,
19042 the default expansion values are exactly what is wanted. For example:
19044 condition = ${if >{$message_age}{600}}
19046 Because of the default behaviour of the string expansion, this is equivalent to
19048 condition = ${if >{$message_age}{600}{true}{}}
19051 A multiple condition example, which succeeds:
19053 condition = ${if >{$message_age}{600}}
19054 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19058 If the expansion fails (other than forced failure) delivery is deferred. Some
19059 of the other precondition options are common special cases that could in fact
19060 be specified using &%condition%&.
19062 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19063 are far older, and use one set of semantics. ACLs are newer and when
19064 they were created, the ACL &%condition%& process was given far stricter
19065 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19066 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19067 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19068 Router rules processing behavior.
19070 This is best illustrated in an example:
19072 # If used in an ACL condition will fail with a syntax error, but
19073 # in a router condition any extra characters are treated as a string
19075 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19078 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19081 In each example above, the &%if%& statement actually ends after
19082 &"{google.com}}"&. Since no true or false braces were defined, the
19083 default &%if%& behavior is to return a boolean true or a null answer
19084 (which evaluates to false). The rest of the line is then treated as a
19085 string. So the first example resulted in the boolean answer &"true"&
19086 with the string &" {yes} {no}}"& appended to it. The second example
19087 resulted in the null output (indicating false) with the string
19088 &" {yes} {no}}"& appended to it.
19090 In fact you can put excess forward braces in too. In the router
19091 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19092 mean something, like after a &"$"& or when required as part of a
19093 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19096 Thus, in a Router, the above expansion strings will both always evaluate
19097 true, as the result of expansion is a non-empty string which doesn't
19098 match an explicit false value. This can be tricky to debug. By
19099 contrast, in an ACL either of those strings will always result in an
19100 expansion error because the result doesn't look sufficiently boolean.
19103 .option debug_print routers string&!! unset
19104 .cindex "testing" "variables in drivers"
19105 If this option is set and debugging is enabled (see the &%-d%& command line
19106 option) or in address-testing mode (see the &%-bt%& command line option),
19107 the string is expanded and included in the debugging output.
19108 If expansion of the string fails, the error message is written to the debugging
19109 output, and Exim carries on processing.
19110 This option is provided to help with checking out the values of variables and
19111 so on when debugging router configurations. For example, if a &%condition%&
19112 option appears not to be working, &%debug_print%& can be used to output the
19113 variables it references. The output happens after checks for &%domains%&,
19114 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19115 are tested. A newline is added to the text if it does not end with one.
19116 The variable &$router_name$& contains the name of the router.
19120 .option disable_logging routers boolean false
19121 If this option is set true, nothing is logged for any routing errors
19122 or for any deliveries caused by this router. You should not set this option
19123 unless you really, really know what you are doing. See also the generic
19124 transport option of the same name.
19126 .option dnssec_request_domains routers "domain list&!!" *
19127 .cindex "MX record" "security"
19128 .cindex "DNSSEC" "MX lookup"
19129 .cindex "security" "MX lookup"
19130 .cindex "DNS" "DNSSEC"
19131 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19132 the DNSSEC request bit set.
19133 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19135 .option dnssec_require_domains routers "domain list&!!" unset
19136 .cindex "MX record" "security"
19137 .cindex "DNSSEC" "MX lookup"
19138 .cindex "security" "MX lookup"
19139 .cindex "DNS" "DNSSEC"
19140 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19141 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19142 (AD bit) set will be ignored and logged as a host-lookup failure.
19143 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19146 .option domains routers&!? "domain list&!!" unset
19147 .cindex "router" "restricting to specific domains"
19148 .vindex "&$domain_data$&"
19149 If this option is set, the router is skipped unless the current domain matches
19150 the list. If the match is achieved by means of a file lookup, the data that the
19151 lookup returned for the domain is placed in &$domain_data$& for use in string
19152 expansions of the driver's private options and in the transport.
19153 See section &<<SECTrouprecon>>& for
19154 a list of the order in which preconditions are evaluated.
19158 .option driver routers string unset
19159 This option must always be set. It specifies which of the available routers is
19163 .option dsn_lasthop routers boolean false
19164 .cindex "DSN" "success"
19165 .cindex "Delivery Status Notification" "success"
19166 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19167 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19168 instead send a success DSN as if the next hop does not support DSN.
19169 Not effective on redirect routers.
19173 .option errors_to routers string&!! unset
19174 .cindex "envelope from"
19175 .cindex "envelope sender"
19176 .cindex "router" "changing address for errors"
19177 If a router successfully handles an address, it may assign the address to a
19178 transport for delivery or it may generate child addresses. In both cases, if
19179 there is a delivery problem during later processing, the resulting bounce
19180 message is sent to the address that results from expanding this string,
19181 provided that the address verifies successfully. The &%errors_to%& option is
19182 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19184 The &%errors_to%& setting associated with an address can be overridden if it
19185 subsequently passes through other routers that have their own &%errors_to%&
19186 settings, or if the message is delivered by a transport with a &%return_path%&
19189 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19190 the expansion fails to verify, the errors address associated with the incoming
19191 address is used. At top level, this is the envelope sender. A non-forced
19192 expansion failure causes delivery to be deferred.
19194 If an address for which &%errors_to%& has been set ends up being delivered over
19195 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19196 any bounces that are generated by other MTAs on the delivery route are also
19197 sent there. You can set &%errors_to%& to the empty string by either of these
19203 An expansion item that yields an empty string has the same effect. If you do
19204 this, a locally detected delivery error for addresses processed by this router
19205 no longer gives rise to a bounce message; the error is discarded. If the
19206 address is delivered to a remote host, the return path is set to &`<>`&, unless
19207 overridden by the &%return_path%& option on the transport.
19209 .vindex "&$address_data$&"
19210 If for some reason you want to discard local errors, but use a non-empty
19211 MAIL command for remote delivery, you can preserve the original return
19212 path in &$address_data$& in the router, and reinstate it in the transport by
19213 setting &%return_path%&.
19215 The most common use of &%errors_to%& is to direct mailing list bounces to the
19216 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19217 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19221 .option expn routers&!? boolean true
19222 .cindex "address" "testing"
19223 .cindex "testing" "addresses"
19224 .cindex "EXPN" "router skipping"
19225 .cindex "router" "skipping for EXPN"
19226 If this option is turned off, the router is skipped when testing an address
19227 as a result of processing an SMTP EXPN command. You might, for example,
19228 want to turn it off on a router for users' &_.forward_& files, while leaving it
19229 on for the system alias file.
19230 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19233 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19234 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19235 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19239 .option fail_verify routers boolean false
19240 .cindex "router" "forcing verification failure"
19241 Setting this option has the effect of setting both &%fail_verify_sender%& and
19242 &%fail_verify_recipient%& to the same value.
19246 .option fail_verify_recipient routers boolean false
19247 If this option is true and an address is accepted by this router when
19248 verifying a recipient, verification fails.
19252 .option fail_verify_sender routers boolean false
19253 If this option is true and an address is accepted by this router when
19254 verifying a sender, verification fails.
19258 .option fallback_hosts routers "string list" unset
19259 .cindex "router" "fallback hosts"
19260 .cindex "fallback" "hosts specified on router"
19261 String expansion is not applied to this option. The argument must be a
19262 colon-separated list of host names or IP addresses. The list separator can be
19263 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19264 each name or address. In fact, the format of each item is exactly the same as
19265 defined for the list of hosts in a &(manualroute)& router (see section
19266 &<<SECTformatonehostitem>>&).
19268 If a router queues an address for a remote transport, this host list is
19269 associated with the address, and used instead of the transport's fallback host
19270 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19271 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19272 transport for further details.
19275 .option group routers string&!! "see below"
19276 .cindex "gid (group id)" "local delivery"
19277 .cindex "local transports" "uid and gid"
19278 .cindex "transport" "local"
19279 .cindex "router" "setting group"
19280 When a router queues an address for a transport, and the transport does not
19281 specify a group, the group given here is used when running the delivery
19283 The group may be specified numerically or by name. If expansion fails, the
19284 error is logged and delivery is deferred.
19285 The default is unset, unless &%check_local_user%& is set, when the default
19286 is taken from the password information. See also &%initgroups%& and &%user%&
19287 and the discussion in chapter &<<CHAPenvironment>>&.
19291 .option headers_add routers list&!! unset
19292 .cindex "header lines" "adding"
19293 .cindex "router" "adding header lines"
19294 This option specifies a list of text headers,
19295 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19296 that is associated with any addresses that are accepted by the router.
19297 Each item is separately expanded, at routing time. However, this
19298 option has no effect when an address is just being verified. The way in which
19299 the text is used to add header lines at transport time is described in section
19300 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19301 message is in the process of being transported. This means that references to
19302 header lines in string expansions in the transport's configuration do not
19303 &"see"& the added header lines.
19305 The &%headers_add%& option is expanded after &%errors_to%&, but before
19306 &%headers_remove%& and &%transport%&. If an item is empty, or if
19307 an item expansion is forced to fail, the item has no effect. Other expansion
19308 failures are treated as configuration errors.
19310 Unlike most options, &%headers_add%& can be specified multiple times
19311 for a router; all listed headers are added.
19313 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19314 router that has the &%one_time%& option set.
19316 .cindex "duplicate addresses"
19317 .oindex "&%unseen%&"
19318 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19319 additions are deleted when the address is passed on to subsequent routers.
19320 For a &%redirect%& router, if a generated address is the same as the incoming
19321 address, this can lead to duplicate addresses with different header
19322 modifications. Exim does not do duplicate deliveries (except, in certain
19323 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19324 which of the duplicates is discarded, so this ambiguous situation should be
19325 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19329 .option headers_remove routers list&!! unset
19330 .cindex "header lines" "removing"
19331 .cindex "router" "removing header lines"
19332 This option specifies a list of text headers,
19333 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19334 that is associated with any addresses that are accepted by the router.
19335 However, the option has no effect when an address is just being verified.
19336 Each list item is separately expanded, at transport time.
19337 If an item ends in *, it will match any header with the given prefix.
19339 the text is used to remove header lines at transport time is described in
19340 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19341 the message is in the process of being transported. This means that references
19342 to header lines in string expansions in the transport's configuration still
19343 &"see"& the original header lines.
19345 The &%headers_remove%& option is handled after &%errors_to%& and
19346 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19347 the item has no effect. Other expansion failures are treated as configuration
19350 Unlike most options, &%headers_remove%& can be specified multiple times
19351 for a router; all listed headers are removed.
19353 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19354 router that has the &%one_time%& option set.
19356 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19357 removal requests are deleted when the address is passed on to subsequent
19358 routers, and this can lead to problems with duplicates -- see the similar
19359 warning for &%headers_add%& above.
19361 &*Warning 3*&: Because of the separate expansion of the list items,
19362 items that contain a list separator must have it doubled.
19363 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19367 .option ignore_target_hosts routers "host list&!!" unset
19368 .cindex "IP address" "discarding"
19369 .cindex "router" "discarding IP addresses"
19370 Although this option is a host list, it should normally contain IP address
19371 entries rather than names. If any host that is looked up by the router has an
19372 IP address that matches an item in this list, Exim behaves as if that IP
19373 address did not exist. This option allows you to cope with rogue DNS entries
19376 remote.domain.example. A 127.0.0.1
19380 ignore_target_hosts = 127.0.0.1
19382 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19383 discarded in this way, the router declines. In a conventional configuration, an
19384 attempt to mail to such a domain would normally provoke the &"unrouteable
19385 domain"& error, and an attempt to verify an address in the domain would fail.
19386 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19387 router declines if presented with one of the listed addresses.
19389 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19390 means of the first or the second of the following settings, respectively:
19392 ignore_target_hosts = 0.0.0.0/0
19393 ignore_target_hosts = <; 0::0/0
19395 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19396 in the second line matches all IPv6 addresses.
19398 This option may also be useful for ignoring link-local and site-local IPv6
19399 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19400 is expanded before use as a list, it is possible to make it dependent on the
19401 domain that is being routed.
19403 .vindex "&$host_address$&"
19404 During its expansion, &$host_address$& is set to the IP address that is being
19407 .option initgroups routers boolean false
19408 .cindex "additional groups"
19409 .cindex "groups" "additional"
19410 .cindex "local transports" "uid and gid"
19411 .cindex "transport" "local"
19412 If the router queues an address for a transport, and this option is true, and
19413 the uid supplied by the router is not overridden by the transport, the
19414 &[initgroups()]& function is called when running the transport to ensure that
19415 any additional groups associated with the uid are set up. See also &%group%&
19416 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19420 .option local_part_prefix routers&!? "string list" unset
19421 .cindex affix "router precondition"
19422 .cindex "router" "prefix for local part"
19423 .cindex "prefix" "for local part, used in router"
19424 If this option is set, the router is skipped unless the local part starts with
19425 one of the given strings, or &%local_part_prefix_optional%& is true. See
19426 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19429 The list is scanned from left to right, and the first prefix that matches is
19430 used. A limited form of wildcard is available; if the prefix begins with an
19431 asterisk, it matches the longest possible sequence of arbitrary characters at
19432 the start of the local part. An asterisk should therefore always be followed by
19433 some character that does not occur in normal local parts.
19434 .cindex "multiple mailboxes"
19435 .cindex "mailbox" "multiple"
19436 Wildcarding can be used to set up multiple user mailboxes, as described in
19437 section &<<SECTmulbox>>&.
19439 .vindex "&$local_part$&"
19440 .vindex "&$local_part_prefix$&"
19441 During the testing of the &%local_parts%& option, and while the router is
19442 running, the prefix is removed from the local part, and is available in the
19443 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19444 the router accepts the address, this remains true during subsequent delivery by
19445 a transport. In particular, the local part that is transmitted in the RCPT
19446 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19447 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19448 the relevant transport.
19450 .vindex &$local_part_prefix_v$&
19451 If wildcarding (above) was used then the part of the prefix matching the
19452 wildcard is available in &$local_part_prefix_v$&.
19454 When an address is being verified, &%local_part_prefix%& affects only the
19455 behaviour of the router. If the callout feature of verification is in use, this
19456 means that the full address, including the prefix, will be used during the
19459 The prefix facility is commonly used to handle local parts of the form
19460 &%owner-something%&. Another common use is to support local parts of the form
19461 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19462 to tell a user their forwarding is broken &-- by placing a router like this one
19463 immediately before the router that handles &_.forward_& files:
19467 local_part_prefix = real-
19469 transport = local_delivery
19471 For security, it would probably be a good idea to restrict the use of this
19472 router to locally-generated messages, using a condition such as this:
19474 condition = ${if match {$sender_host_address}\
19475 {\N^(|127\.0\.0\.1)$\N}}
19478 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19479 both conditions must be met if not optional. Care must be taken if wildcards
19480 are used in both a prefix and a suffix on the same router. Different
19481 separator characters must be used to avoid ambiguity.
19484 .option local_part_prefix_optional routers boolean false
19485 See &%local_part_prefix%& above.
19489 .option local_part_suffix routers&!? "string list" unset
19490 .cindex "router" "suffix for local part"
19491 .cindex "suffix for local part" "used in router"
19492 This option operates in the same way as &%local_part_prefix%&, except that the
19493 local part must end (rather than start) with the given string, the
19494 &%local_part_suffix_optional%& option determines whether the suffix is
19495 mandatory, and the wildcard * character, if present, must be the last
19496 character of the suffix. This option facility is commonly used to handle local
19497 parts of the form &%something-request%& and multiple user mailboxes of the form
19501 .option local_part_suffix_optional routers boolean false
19502 See &%local_part_suffix%& above.
19506 .option local_parts routers&!? "local part list&!!" unset
19507 .cindex "router" "restricting to specific local parts"
19508 .cindex "local part" "checking in router"
19509 The router is run only if the local part of the address matches the list.
19510 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19512 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19513 string is expanded, it is possible to make it depend on the domain, for
19516 local_parts = dbm;/usr/local/specials/$domain_data
19518 .vindex "&$local_part_data$&"
19519 If the match is achieved by a lookup, the data that the lookup returned
19520 for the local part is placed in the variable &$local_part_data$& for use in
19521 expansions of the router's private options or in the transport.
19522 You might use this option, for
19523 example, if you have a large number of local virtual domains, and you want to
19524 send all postmaster mail to the same place without having to set up an alias in
19525 each virtual domain:
19529 local_parts = postmaster
19530 data = postmaster@real.domain.example
19534 .option log_as_local routers boolean "see below"
19535 .cindex "log" "delivery line"
19536 .cindex "delivery" "log line format"
19537 Exim has two logging styles for delivery, the idea being to make local
19538 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19539 recipient address is given just as the local part, without a domain. The use of
19540 this style is controlled by this option. It defaults to true for the &(accept)&
19541 router, and false for all the others. This option applies only when a
19542 router assigns an address to a transport. It has no effect on routers that
19543 redirect addresses.
19547 .option more routers boolean&!! true
19548 The result of string expansion for this option must be a valid boolean value,
19549 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19550 result causes an error, and delivery is deferred. If the expansion is forced to
19551 fail, the default value for the option (true) is used. Other failures cause
19552 delivery to be deferred.
19554 If this option is set false, and the router declines to handle the address, no
19555 further routers are tried, routing fails, and the address is bounced.
19557 However, if the router explicitly passes an address to the following router by
19558 means of the setting
19562 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19563 does not affect the behaviour if one of the precondition tests fails. In that
19564 case, the address is always passed to the next router.
19566 Note that &%address_data%& is not considered to be a precondition. If its
19567 expansion is forced to fail, the router declines, and the value of &%more%&
19568 controls what happens next.
19571 .option pass_on_timeout routers boolean false
19572 .cindex "timeout" "of router"
19573 .cindex "router" "timeout"
19574 If a router times out during a host lookup, it normally causes deferral of the
19575 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19576 router, overriding &%no_more%&. This may be helpful for systems that are
19577 intermittently connected to the Internet, or those that want to pass to a smart
19578 host any messages that cannot immediately be delivered.
19580 There are occasional other temporary errors that can occur while doing DNS
19581 lookups. They are treated in the same way as a timeout, and this option
19582 applies to all of them.
19586 .option pass_router routers string unset
19587 .cindex "router" "go to after &""pass""&"
19588 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19589 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19590 routing to continue, and overriding a false setting of &%more%&. When one of
19591 these routers returns &"pass"&, the address is normally handed on to the next
19592 router in sequence. This can be changed by setting &%pass_router%& to the name
19593 of another router. However (unlike &%redirect_router%&) the named router must
19594 be below the current router, to avoid loops. Note that this option applies only
19595 to the special case of &"pass"&. It does not apply when a router returns
19596 &"decline"& because it cannot handle an address.
19600 .option redirect_router routers string unset
19601 .cindex "router" "start at after redirection"
19602 Sometimes an administrator knows that it is pointless to reprocess addresses
19603 generated from alias or forward files with the same router again. For
19604 example, if an alias file translates real names into login ids there is no
19605 point searching the alias file a second time, especially if it is a large file.
19607 The &%redirect_router%& option can be set to the name of any router instance.
19608 It causes the routing of any generated addresses to start at the named router
19609 instead of at the first router. This option has no effect if the router in
19610 which it is set does not generate new addresses.
19614 .option require_files routers&!? "string list&!!" unset
19615 .cindex "file" "requiring for router"
19616 .cindex "router" "requiring file existence"
19617 This option provides a general mechanism for predicating the running of a
19618 router on the existence or non-existence of certain files or directories.
19619 Before running a router, as one of its precondition tests, Exim works its way
19620 through the &%require_files%& list, expanding each item separately.
19622 Because the list is split before expansion, any colons in expansion items must
19623 be doubled, or the facility for using a different list separator must be used
19624 (&<<SECTlistsepchange>>&).
19625 If any expansion is forced to fail, the item is ignored. Other expansion
19626 failures cause routing of the address to be deferred.
19628 If any expanded string is empty, it is ignored. Otherwise, except as described
19629 below, each string must be a fully qualified file path, optionally preceded by
19630 &"!"&. The paths are passed to the &[stat()]& function to test for the
19631 existence of the files or directories. The router is skipped if any paths not
19632 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19635 If &[stat()]& cannot determine whether a file exists or not, delivery of
19636 the message is deferred. This can happen when NFS-mounted filesystems are
19639 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19640 options, so you cannot use it to check for the existence of a file in which to
19641 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19642 full list of the order in which preconditions are evaluated.) However, as
19643 these options are all expanded, you can use the &%exists%& expansion condition
19644 to make such tests. The &%require_files%& option is intended for checking files
19645 that the router may be going to use internally, or which are needed by a
19646 transport (e.g., &_.procmailrc_&).
19648 During delivery, the &[stat()]& function is run as root, but there is a
19649 facility for some checking of the accessibility of a file by another user.
19650 This is not a proper permissions check, but just a &"rough"& check that
19651 operates as follows:
19653 If an item in a &%require_files%& list does not contain any forward slash
19654 characters, it is taken to be the user (and optional group, separated by a
19655 comma) to be checked for subsequent files in the list. If no group is specified
19656 but the user is specified symbolically, the gid associated with the uid is
19659 require_files = mail:/some/file
19660 require_files = $local_part_data:$home/.procmailrc
19662 If a user or group name in a &%require_files%& list does not exist, the
19663 &%require_files%& condition fails.
19665 Exim performs the check by scanning along the components of the file path, and
19666 checking the access for the given uid and gid. It checks for &"x"& access on
19667 directories, and &"r"& access on the final file. Note that this means that file
19668 access control lists, if the operating system has them, are ignored.
19670 &*Warning 1*&: When the router is being run to verify addresses for an
19671 incoming SMTP message, Exim is not running as root, but under its own uid. This
19672 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19673 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19674 user is not permitted to read one of the directories on the file's path.
19676 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19677 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19678 without root access. In this case, if a check for access by a particular user
19679 is requested, Exim creates a subprocess that runs as that user, and tries the
19680 check again in that process.
19682 The default action for handling an unresolved EACCES is to consider it to
19683 be caused by a configuration error, and routing is deferred because the
19684 existence or non-existence of the file cannot be determined. However, in some
19685 circumstances it may be desirable to treat this condition as if the file did
19686 not exist. If the filename (or the exclamation mark that precedes the filename
19687 for non-existence) is preceded by a plus sign, the EACCES error is treated
19688 as if the file did not exist. For example:
19690 require_files = +/some/file
19692 If the router is not an essential part of verification (for example, it
19693 handles users' &_.forward_& files), another solution is to set the &%verify%&
19694 option false so that the router is skipped when verifying.
19698 .option retry_use_local_part routers boolean "see below"
19699 .cindex "hints database" "retry keys"
19700 .cindex "local part" "in retry keys"
19701 When a delivery suffers a temporary routing failure, a retry record is created
19702 in Exim's hints database. For addresses whose routing depends only on the
19703 domain, the key for the retry record should not involve the local part, but for
19704 other addresses, both the domain and the local part should be included.
19705 Usually, remote routing is of the former kind, and local routing is of the
19708 This option controls whether the local part is used to form the key for retry
19709 hints for addresses that suffer temporary errors while being handled by this
19710 router. The default value is true for any router that has any of
19711 &%check_local_user%&,
19714 &%local_part_prefix%&,
19715 &%local_part_suffix%&,
19718 set, and false otherwise. Note that this option does not apply to hints keys
19719 for transport delays; they are controlled by a generic transport option of the
19722 Failing to set this option when it is needed
19723 (because a remote router handles only some of the local-parts for a domain)
19724 can result in incorrect error messages being generated.
19726 The setting of &%retry_use_local_part%& applies only to the router on which it
19727 appears. If the router generates child addresses, they are routed
19728 independently; this setting does not become attached to them.
19732 .option router_home_directory routers string&!! unset
19733 .cindex "router" "home directory for"
19734 .cindex "home directory" "for router"
19736 This option sets a home directory for use while the router is running. (Compare
19737 &%transport_home_directory%&, which sets a home directory for later
19738 transporting.) In particular, if used on a &(redirect)& router, this option
19739 sets a value for &$home$& while a filter is running. The value is expanded;
19740 forced expansion failure causes the option to be ignored &-- other failures
19741 cause the router to defer.
19743 Expansion of &%router_home_directory%& happens immediately after the
19744 &%check_local_user%& test (if configured), before any further expansions take
19746 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19748 While the router is running, &%router_home_directory%& overrides the value of
19749 &$home$& that came from &%check_local_user%&.
19751 When a router accepts an address and assigns it to a local transport (including
19752 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19753 delivery), the home directory setting for the transport is taken from the first
19754 of these values that is set:
19757 The &%home_directory%& option on the transport;
19759 The &%transport_home_directory%& option on the router;
19761 The password data if &%check_local_user%& is set on the router;
19763 The &%router_home_directory%& option on the router.
19766 In other words, &%router_home_directory%& overrides the password data for the
19767 router, but not for the transport.
19771 .option self routers string freeze
19772 .cindex "MX record" "pointing to local host"
19773 .cindex "local host" "MX pointing to"
19774 This option applies to those routers that use a recipient address to find a
19775 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19776 and &(manualroute)& routers.
19777 Certain configurations of the &(queryprogram)& router can also specify a list
19779 Usually such routers are configured to send the message to a remote host via an
19780 &(smtp)& transport. The &%self%& option specifies what happens when the first
19781 host on the list turns out to be the local host.
19782 The way in which Exim checks for the local host is described in section
19783 &<<SECTreclocipadd>>&.
19785 Normally this situation indicates either an error in Exim's configuration (for
19786 example, the router should be configured not to process this domain), or an
19787 error in the DNS (for example, the MX should not point to this host). For this
19788 reason, the default action is to log the incident, defer the address, and
19789 freeze the message. The following alternatives are provided for use in special
19794 Delivery of the message is tried again later, but the message is not frozen.
19796 .vitem "&%reroute%&: <&'domain'&>"
19797 The domain is changed to the given domain, and the address is passed back to
19798 be reprocessed by the routers. No rewriting of headers takes place. This
19799 behaviour is essentially a redirection.
19801 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19802 The domain is changed to the given domain, and the address is passed back to be
19803 reprocessed by the routers. Any headers that contain the original domain are
19808 .vindex "&$self_hostname$&"
19809 The router passes the address to the next router, or to the router named in the
19810 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19811 subsequent routing and delivery, the variable &$self_hostname$& contains the
19812 name of the local host that the router encountered. This can be used to
19813 distinguish between different cases for hosts with multiple names. The
19819 ensures that only those addresses that routed to the local host are passed on.
19820 Without &%no_more%&, addresses that were declined for other reasons would also
19821 be passed to the next router.
19824 Delivery fails and an error report is generated.
19827 .cindex "local host" "sending to"
19828 The anomaly is ignored and the address is queued for the transport. This
19829 setting should be used with extreme caution. For an &(smtp)& transport, it
19830 makes sense only in cases where the program that is listening on the SMTP port
19831 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19832 different configuration file that handles the domain in another way.
19837 .option senders routers&!? "address list&!!" unset
19838 .cindex "router" "checking senders"
19839 If this option is set, the router is skipped unless the message's sender
19840 address matches something on the list.
19841 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19844 There are issues concerning verification when the running of routers is
19845 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19846 setting, it sets the sender to the null string. When using the &%-bt%& option
19847 to check a configuration file, it is necessary also to use the &%-f%& option to
19848 set an appropriate sender. For incoming mail, the sender is unset when
19849 verifying the sender, but is available when verifying any recipients. If the
19850 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19854 .option set routers "string list" unset
19855 .cindex router variables
19856 This option may be used multiple times on a router;
19857 because of this the list aspect is mostly irrelevant.
19858 The list separator is a semicolon but can be changed in the
19861 Each list-element given must be of the form &"name = value"&
19862 and the names used must start with the string &"r_"&.
19863 Values containing a list-separator should have them doubled.
19864 When a router runs, the strings are evaluated in order,
19865 to create variables which are added to the set associated with
19868 This is done immediately after all the preconditions, before the
19869 evaluation of the &%address_data%& option.
19871 The variable is set with the expansion of the value.
19872 The variables can be used by the router options
19873 (not including any preconditions)
19874 and by the transport.
19875 Later definitions of a given named variable will override former ones.
19876 Variable use is via the usual &$r_...$& syntax.
19878 This is similar to the &%address_data%& option, except that
19879 many independent variables can be used, with choice of naming.
19882 .option translate_ip_address routers string&!! unset
19883 .cindex "IP address" "translating"
19884 .cindex "packet radio"
19885 .cindex "router" "IP address translation"
19886 There exist some rare networking situations (for example, packet radio) where
19887 it is helpful to be able to translate IP addresses generated by normal routing
19888 mechanisms into other IP addresses, thus performing a kind of manual IP
19889 routing. This should be done only if the normal IP routing of the TCP/IP stack
19890 is inadequate or broken. Because this is an extremely uncommon requirement, the
19891 code to support this option is not included in the Exim binary unless
19892 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19894 .vindex "&$host_address$&"
19895 The &%translate_ip_address%& string is expanded for every IP address generated
19896 by the router, with the generated address set in &$host_address$&. If the
19897 expansion is forced to fail, no action is taken.
19898 For any other expansion error, delivery of the message is deferred.
19899 If the result of the expansion is an IP address, that replaces the original
19900 address; otherwise the result is assumed to be a host name &-- this is looked
19901 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19902 produce one or more replacement IP addresses. For example, to subvert all IP
19903 addresses in some specific networks, this could be added to a router:
19905 translate_ip_address = \
19906 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19909 The file would contain lines like
19911 10.2.3.128/26 some.host
19912 10.8.4.34/26 10.44.8.15
19914 You should not make use of this facility unless you really understand what you
19919 .option transport routers string&!! unset
19920 This option specifies the transport to be used when a router accepts an address
19921 and sets it up for delivery. A transport is never needed if a router is used
19922 only for verification. The value of the option is expanded at routing time,
19923 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19924 and result must be the name of one of the configured transports. If it is not,
19925 delivery is deferred.
19927 The &%transport%& option is not used by the &(redirect)& router, but it does
19928 have some private options that set up transports for pipe and file deliveries
19929 (see chapter &<<CHAPredirect>>&).
19933 .option transport_current_directory routers string&!! unset
19934 .cindex "current directory for local transport"
19935 This option associates a current directory with any address that is routed
19936 to a local transport. This can happen either because a transport is
19937 explicitly configured for the router, or because it generates a delivery to a
19938 file or a pipe. During the delivery process (that is, at transport time), this
19939 option string is expanded and is set as the current directory, unless
19940 overridden by a setting on the transport.
19941 If the expansion fails for any reason, including forced failure, an error is
19942 logged, and delivery is deferred.
19943 See chapter &<<CHAPenvironment>>& for details of the local delivery
19949 .option transport_home_directory routers string&!! "see below"
19950 .cindex "home directory" "for local transport"
19951 This option associates a home directory with any address that is routed to a
19952 local transport. This can happen either because a transport is explicitly
19953 configured for the router, or because it generates a delivery to a file or a
19954 pipe. During the delivery process (that is, at transport time), the option
19955 string is expanded and is set as the home directory, unless overridden by a
19956 setting of &%home_directory%& on the transport.
19957 If the expansion fails for any reason, including forced failure, an error is
19958 logged, and delivery is deferred.
19960 If the transport does not specify a home directory, and
19961 &%transport_home_directory%& is not set for the router, the home directory for
19962 the transport is taken from the password data if &%check_local_user%& is set for
19963 the router. Otherwise it is taken from &%router_home_directory%& if that option
19964 is set; if not, no home directory is set for the transport.
19966 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19972 .option unseen routers boolean&!! false
19973 .cindex "router" "carrying on after success"
19974 The result of string expansion for this option must be a valid boolean value,
19975 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19976 result causes an error, and delivery is deferred. If the expansion is forced to
19977 fail, the default value for the option (false) is used. Other failures cause
19978 delivery to be deferred.
19980 When this option is set true, routing does not cease if the router accepts the
19981 address. Instead, a copy of the incoming address is passed to the next router,
19982 overriding a false setting of &%more%&. There is little point in setting
19983 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19984 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19985 sometimes true and sometimes false).
19987 .cindex "copy of message (&%unseen%& option)"
19988 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19989 qualifier in filter files. It can be used to cause copies of messages to be
19990 delivered to some other destination, while also carrying out a normal delivery.
19991 In effect, the current address is made into a &"parent"& that has two children
19992 &-- one that is delivered as specified by this router, and a clone that goes on
19993 to be routed further. For this reason, &%unseen%& may not be combined with the
19994 &%one_time%& option in a &(redirect)& router.
19996 &*Warning*&: Header lines added to the address (or specified for removal) by
19997 this router or by previous routers affect the &"unseen"& copy of the message
19998 only. The clone that continues to be processed by further routers starts with
19999 no added headers and none specified for removal. For a &%redirect%& router, if
20000 a generated address is the same as the incoming address, this can lead to
20001 duplicate addresses with different header modifications. Exim does not do
20002 duplicate deliveries (except, in certain circumstances, to pipes -- see section
20003 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
20004 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
20005 &%redirect%& router may be of help.
20007 Unlike the handling of header modifications, any data that was set by the
20008 &%address_data%& option in the current or previous routers &'is'& passed on to
20009 subsequent routers.
20012 .option user routers string&!! "see below"
20013 .cindex "uid (user id)" "local delivery"
20014 .cindex "local transports" "uid and gid"
20015 .cindex "transport" "local"
20016 .cindex "router" "user for filter processing"
20017 .cindex "filter" "user for processing"
20018 When a router queues an address for a transport, and the transport does not
20019 specify a user, the user given here is used when running the delivery process.
20020 The user may be specified numerically or by name. If expansion fails, the
20021 error is logged and delivery is deferred.
20022 This user is also used by the &(redirect)& router when running a filter file.
20023 The default is unset, except when &%check_local_user%& is set. In this case,
20024 the default is taken from the password information. If the user is specified as
20025 a name, and &%group%& is not set, the group associated with the user is used.
20026 See also &%initgroups%& and &%group%& and the discussion in chapter
20027 &<<CHAPenvironment>>&.
20031 .option verify routers&!? boolean true
20032 Setting this option has the effect of setting &%verify_sender%& and
20033 &%verify_recipient%& to the same value.
20036 .option verify_only routers&!? boolean false
20037 .cindex "EXPN" "with &%verify_only%&"
20039 .cindex "router" "used only when verifying"
20040 If this option is set, the router is used only when verifying an address,
20041 delivering in cutthrough mode or
20042 testing with the &%-bv%& option, not when actually doing a delivery, testing
20043 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20044 restricted to verifying only senders or recipients by means of
20045 &%verify_sender%& and &%verify_recipient%&.
20047 &*Warning*&: When the router is being run to verify addresses for an incoming
20048 SMTP message, Exim is not running as root, but under its own uid. If the router
20049 accesses any files, you need to make sure that they are accessible to the Exim
20053 .option verify_recipient routers&!? boolean true
20054 If this option is false, the router is skipped when verifying recipient
20056 delivering in cutthrough mode
20057 or testing recipient verification using &%-bv%&.
20058 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20060 See also the &$verify_mode$& variable.
20063 .option verify_sender routers&!? boolean true
20064 If this option is false, the router is skipped when verifying sender addresses
20065 or testing sender verification using &%-bvs%&.
20066 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20068 See also the &$verify_mode$& variable.
20069 .ecindex IIDgenoprou1
20070 .ecindex IIDgenoprou2
20077 . ////////////////////////////////////////////////////////////////////////////
20078 . ////////////////////////////////////////////////////////////////////////////
20080 .chapter "The accept router" "CHID4"
20081 .cindex "&(accept)& router"
20082 .cindex "routers" "&(accept)&"
20083 The &(accept)& router has no private options of its own. Unless it is being
20084 used purely for verification (see &%verify_only%&) a transport is required to
20085 be defined by the generic &%transport%& option. If the preconditions that are
20086 specified by generic options are met, the router accepts the address and queues
20087 it for the given transport. The most common use of this router is for setting
20088 up deliveries to local mailboxes. For example:
20092 domains = mydomain.example
20094 transport = local_delivery
20096 The &%domains%& condition in this example checks the domain of the address, and
20097 &%check_local_user%& checks that the local part is the login of a local user.
20098 When both preconditions are met, the &(accept)& router runs, and queues the
20099 address for the &(local_delivery)& transport.
20106 . ////////////////////////////////////////////////////////////////////////////
20107 . ////////////////////////////////////////////////////////////////////////////
20109 .chapter "The dnslookup router" "CHAPdnslookup"
20110 .scindex IIDdnsrou1 "&(dnslookup)& router"
20111 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20112 The &(dnslookup)& router looks up the hosts that handle mail for the
20113 recipient's domain in the DNS. A transport must always be set for this router,
20114 unless &%verify_only%& is set.
20116 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20117 SRV records. If none are found, or if SRV support is not configured,
20118 MX records are looked up. If no MX records exist, address records are sought.
20119 However, &%mx_domains%& can be set to disable the direct use of address
20122 MX records of equal priority are sorted by Exim into a random order. Exim then
20123 looks for address records for the host names obtained from MX or SRV records.
20124 When a host has more than one IP address, they are sorted into a random order,
20125 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20126 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20127 generic option, the router declines.
20129 Unless they have the highest priority (lowest MX value), MX records that point
20130 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20131 are discarded, together with any other MX records of equal or lower priority.
20133 .cindex "MX record" "pointing to local host"
20134 .cindex "local host" "MX pointing to"
20135 .oindex "&%self%&" "in &(dnslookup)& router"
20136 If the host pointed to by the highest priority MX record, or looked up as an
20137 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20138 happens is controlled by the generic &%self%& option.
20141 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20142 There have been problems with DNS servers when SRV records are looked up.
20143 Some misbehaving servers return a DNS error or timeout when a non-existent
20144 SRV record is sought. Similar problems have in the past been reported for
20145 MX records. The global &%dns_again_means_nonexist%& option can help with this
20146 problem, but it is heavy-handed because it is a global option.
20148 For this reason, there are two options, &%srv_fail_domains%& and
20149 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20150 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20151 an attempt to look up an SRV or MX record causes one of these results, and the
20152 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20153 such record"&. In the case of an SRV lookup, this means that the router
20154 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20155 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20156 case routing fails.
20159 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20160 .cindex "&(dnslookup)& router" "declines"
20161 There are a few cases where a &(dnslookup)& router will decline to accept
20162 an address; if such a router is expected to handle "all remaining non-local
20163 domains", then it is important to set &%no_more%&.
20165 The router will defer rather than decline if the domain
20166 is found in the &%fail_defer_domains%& router option.
20168 Reasons for a &(dnslookup)& router to decline currently include:
20170 The domain does not exist in DNS
20172 The domain exists but the MX record's host part is just "."; this is a common
20173 convention (borrowed from SRV) used to indicate that there is no such service
20174 for this domain and to not fall back to trying A/AAAA records.
20176 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20178 MX record points to a non-existent host.
20180 MX record points to an IP address and the main section option
20181 &%allow_mx_to_ip%& is not set.
20183 MX records exist and point to valid hosts, but all hosts resolve only to
20184 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20186 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20187 &%dns_check_names_pattern%& for handling one variant of this)
20189 &%check_secondary_mx%& is set on this router but the local host can
20190 not be found in the MX records (see below)
20196 .section "Private options for dnslookup" "SECID118"
20197 .cindex "options" "&(dnslookup)& router"
20198 The private options for the &(dnslookup)& router are as follows:
20200 .option check_secondary_mx dnslookup boolean false
20201 .cindex "MX record" "checking for secondary"
20202 If this option is set, the router declines unless the local host is found in
20203 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20204 process domains for which the local host is a secondary mail exchanger
20205 differently to other domains. The way in which Exim decides whether a host is
20206 the local host is described in section &<<SECTreclocipadd>>&.
20209 .option check_srv dnslookup string&!! unset
20210 .cindex "SRV record" "enabling use of"
20211 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20212 addition to MX and address records. The support is disabled by default. To
20213 enable SRV support, set the &%check_srv%& option to the name of the service
20214 required. For example,
20218 looks for SRV records that refer to the normal smtp service. The option is
20219 expanded, so the service name can vary from message to message or address
20220 to address. This might be helpful if SRV records are being used for a
20221 submission service. If the expansion is forced to fail, the &%check_srv%&
20222 option is ignored, and the router proceeds to look for MX records in the
20225 When the expansion succeeds, the router searches first for SRV records for
20226 the given service (it assumes TCP protocol). A single SRV record with a
20227 host name that consists of just a single dot indicates &"no such service for
20228 this domain"&; if this is encountered, the router declines. If other kinds of
20229 SRV record are found, they are used to construct a host list for delivery
20230 according to the rules of RFC 2782. MX records are not sought in this case.
20232 When no SRV records are found, MX records (and address records) are sought in
20233 the traditional way. In other words, SRV records take precedence over MX
20234 records, just as MX records take precedence over address records. Note that
20235 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20236 defined it. It is apparently believed that MX records are sufficient for email
20237 and that SRV records should not be used for this purpose. However, SRV records
20238 have an additional &"weight"& feature which some people might find useful when
20239 trying to split an SMTP load between hosts of different power.
20241 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20242 when there is a DNS lookup error.
20247 .option fail_defer_domains dnslookup "domain list&!!" unset
20248 .cindex "MX record" "not found"
20249 DNS lookups for domains matching &%fail_defer_domains%&
20250 which find no matching record will cause the router to defer
20251 rather than the default behaviour of decline.
20252 This maybe be useful for queueing messages for a newly created
20253 domain while the DNS configuration is not ready.
20254 However, it will result in any message with mistyped domains
20258 .option ipv4_only "string&!!" unset
20259 .cindex IPv6 disabling
20260 .cindex DNS "IPv6 disabling"
20261 The string is expanded, and if the result is anything but a forced failure,
20262 or an empty string, or one of the strings “0” or “no” or “false”
20263 (checked without regard to the case of the letters),
20264 only A records are used.
20266 .option ipv4_prefer "string&!!" unset
20267 .cindex IPv4 preference
20268 .cindex DNS "IPv4 preference"
20269 The string is expanded, and if the result is anything but a forced failure,
20270 or an empty string, or one of the strings “0” or “no” or “false”
20271 (checked without regard to the case of the letters),
20272 A records are sorted before AAAA records (inverting the default).
20274 .option mx_domains dnslookup "domain list&!!" unset
20275 .cindex "MX record" "required to exist"
20276 .cindex "SRV record" "required to exist"
20277 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20278 record in order to be recognized. (The name of this option could be improved.)
20279 For example, if all the mail hosts in &'fict.example'& are known to have MX
20280 records, except for those in &'discworld.fict.example'&, you could use this
20283 mx_domains = ! *.discworld.fict.example : *.fict.example
20285 This specifies that messages addressed to a domain that matches the list but
20286 has no MX record should be bounced immediately instead of being routed using
20287 the address record.
20290 .option mx_fail_domains dnslookup "domain list&!!" unset
20291 If the DNS lookup for MX records for one of the domains in this list causes a
20292 DNS lookup error, Exim behaves as if no MX records were found. See section
20293 &<<SECTprowitdnsloo>>& for more discussion.
20298 .option qualify_single dnslookup boolean true
20299 .cindex "DNS" "resolver options"
20300 .cindex "DNS" "qualifying single-component names"
20301 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20302 lookups. Typically, but not standardly, this causes the resolver to qualify
20303 single-component names with the default domain. For example, on a machine
20304 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20305 &'thesaurus.ref.example'& inside the resolver. For details of what your
20306 resolver actually does, consult your man pages for &'resolver'& and
20311 .option rewrite_headers dnslookup boolean true
20312 .cindex "rewriting" "header lines"
20313 .cindex "header lines" "rewriting"
20314 If the domain name in the address that is being processed is not fully
20315 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20316 an address is specified as &'dormouse@teaparty'&, the domain might be
20317 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20318 occur as a result of setting the &%widen_domains%& option. If
20319 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20320 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20321 header lines of the message are rewritten with the full domain name.
20323 This option should be turned off only when it is known that no message is
20324 ever going to be sent outside an environment where the abbreviation makes
20327 When an MX record is looked up in the DNS and matches a wildcard record, name
20328 servers normally return a record containing the name that has been looked up,
20329 making it impossible to detect whether a wildcard was present or not. However,
20330 some name servers have recently been seen to return the wildcard entry. If the
20331 name returned by a DNS lookup begins with an asterisk, it is not used for
20335 .option same_domain_copy_routing dnslookup boolean false
20336 .cindex "address" "copying routing"
20337 Addresses with the same domain are normally routed by the &(dnslookup)& router
20338 to the same list of hosts. However, this cannot be presumed, because the router
20339 options and preconditions may refer to the local part of the address. By
20340 default, therefore, Exim routes each address in a message independently. DNS
20341 servers run caches, so repeated DNS lookups are not normally expensive, and in
20342 any case, personal messages rarely have more than a few recipients.
20344 If you are running mailing lists with large numbers of subscribers at the same
20345 domain, and you are using a &(dnslookup)& router which is independent of the
20346 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20347 lookups for identical domains in one message. In this case, when &(dnslookup)&
20348 routes an address to a remote transport, any other unrouted addresses in the
20349 message that have the same domain are automatically given the same routing
20350 without processing them independently,
20351 provided the following conditions are met:
20354 No router that processed the address specified &%headers_add%& or
20355 &%headers_remove%&.
20357 The router did not change the address in any way, for example, by &"widening"&
20364 .option search_parents dnslookup boolean false
20365 .cindex "DNS" "resolver options"
20366 When this option is true, the resolver option RES_DNSRCH is set for DNS
20367 lookups. This is different from the &%qualify_single%& option in that it
20368 applies to domains containing dots. Typically, but not standardly, it causes
20369 the resolver to search for the name in the current domain and in parent
20370 domains. For example, on a machine in the &'fict.example'& domain, if looking
20371 up &'teaparty.wonderland'& failed, the resolver would try
20372 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20373 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20375 Setting this option true can cause problems in domains that have a wildcard MX
20376 record, because any domain that does not have its own MX record matches the
20381 .option srv_fail_domains dnslookup "domain list&!!" unset
20382 If the DNS lookup for SRV records for one of the domains in this list causes a
20383 DNS lookup error, Exim behaves as if no SRV records were found. See section
20384 &<<SECTprowitdnsloo>>& for more discussion.
20389 .option widen_domains dnslookup "string list" unset
20390 .cindex "domain" "partial; widening"
20391 If a DNS lookup fails and this option is set, each of its strings in turn is
20392 added onto the end of the domain, and the lookup is tried again. For example,
20395 widen_domains = fict.example:ref.example
20397 is set and a lookup of &'klingon.dictionary'& fails,
20398 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20399 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20400 and &%search_parents%& options can cause some widening to be undertaken inside
20401 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20402 when verifying, unless &%rewrite_headers%& is false (not the default).
20405 .section "Effect of qualify_single and search_parents" "SECID119"
20406 When a domain from an envelope recipient is changed by the resolver as a result
20407 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20408 corresponding address in the message's header lines unless &%rewrite_headers%&
20409 is set false. Exim then re-routes the address, using the full domain.
20411 These two options affect only the DNS lookup that takes place inside the router
20412 for the domain of the address that is being routed. They do not affect lookups
20413 such as that implied by
20417 that may happen while processing a router precondition before the router is
20418 entered. No widening ever takes place for these lookups.
20419 .ecindex IIDdnsrou1
20420 .ecindex IIDdnsrou2
20430 . ////////////////////////////////////////////////////////////////////////////
20431 . ////////////////////////////////////////////////////////////////////////////
20433 .chapter "The ipliteral router" "CHID5"
20434 .cindex "&(ipliteral)& router"
20435 .cindex "domain literal" "routing"
20436 .cindex "routers" "&(ipliteral)&"
20437 This router has no private options. Unless it is being used purely for
20438 verification (see &%verify_only%&) a transport is required to be defined by the
20439 generic &%transport%& option. The router accepts the address if its domain part
20440 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20441 router handles the address
20445 by setting up delivery to the host with that IP address. IPv4 domain literals
20446 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20447 are similar, but the address is preceded by &`ipv6:`&. For example:
20449 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20451 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20452 grounds that sooner or later somebody will try it.
20454 .oindex "&%self%&" "in &(ipliteral)& router"
20455 If the IP address matches something in &%ignore_target_hosts%&, the router
20456 declines. If an IP literal turns out to refer to the local host, the generic
20457 &%self%& option determines what happens.
20459 The RFCs require support for domain literals; however, their use is
20460 controversial in today's Internet. If you want to use this router, you must
20461 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20462 Exim will not recognize the domain literal syntax in addresses.
20466 . ////////////////////////////////////////////////////////////////////////////
20467 . ////////////////////////////////////////////////////////////////////////////
20469 .chapter "The iplookup router" "CHID6"
20470 .cindex "&(iplookup)& router"
20471 .cindex "routers" "&(iplookup)&"
20472 The &(iplookup)& router was written to fulfil a specific requirement in
20473 Cambridge University (which in fact no longer exists). For this reason, it is
20474 not included in the binary of Exim by default. If you want to include it, you
20477 ROUTER_IPLOOKUP=yes
20479 in your &_Local/Makefile_& configuration file.
20481 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20482 connection to one or more specific hosts. The host can then return the same or
20483 a different address &-- in effect rewriting the recipient address in the
20484 message's envelope. The new address is then passed on to subsequent routers. If
20485 this process fails, the address can be passed on to other routers, or delivery
20486 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20487 must not be specified for it.
20489 .cindex "options" "&(iplookup)& router"
20490 .option hosts iplookup string unset
20491 This option must be supplied. Its value is a colon-separated list of host
20492 names. The hosts are looked up using &[gethostbyname()]&
20493 (or &[getipnodebyname()]& when available)
20494 and are tried in order until one responds to the query. If none respond, what
20495 happens is controlled by &%optional%&.
20498 .option optional iplookup boolean false
20499 If &%optional%& is true, if no response is obtained from any host, the address
20500 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20501 delivery to the address is deferred.
20504 .option port iplookup integer 0
20505 .cindex "port" "&(iplookup)& router"
20506 This option must be supplied. It specifies the port number for the TCP or UDP
20510 .option protocol iplookup string udp
20511 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20512 protocols is to be used.
20515 .option query iplookup string&!! "see below"
20516 This defines the content of the query that is sent to the remote hosts. The
20519 $local_part@$domain $local_part@$domain
20521 The repetition serves as a way of checking that a response is to the correct
20522 query in the default case (see &%response_pattern%& below).
20525 .option reroute iplookup string&!! unset
20526 If this option is not set, the rerouted address is precisely the byte string
20527 returned by the remote host, up to the first white space, if any. If set, the
20528 string is expanded to form the rerouted address. It can include parts matched
20529 in the response by &%response_pattern%& by means of numeric variables such as
20530 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20531 whether or not a pattern is in use. In all cases, the rerouted address must end
20532 up in the form &'local_part@domain'&.
20535 .option response_pattern iplookup string unset
20536 This option can be set to a regular expression that is applied to the string
20537 returned from the remote host. If the pattern does not match the response, the
20538 router declines. If &%response_pattern%& is not set, no checking of the
20539 response is done, unless the query was defaulted, in which case there is a
20540 check that the text returned after the first white space is the original
20541 address. This checks that the answer that has been received is in response to
20542 the correct question. For example, if the response is just a new domain, the
20543 following could be used:
20545 response_pattern = ^([^@]+)$
20546 reroute = $local_part@$1
20549 .option timeout iplookup time 5s
20550 This specifies the amount of time to wait for a response from the remote
20551 machine. The same timeout is used for the &[connect()]& function for a TCP
20552 call. It does not apply to UDP.
20557 . ////////////////////////////////////////////////////////////////////////////
20558 . ////////////////////////////////////////////////////////////////////////////
20560 .chapter "The manualroute router" "CHID7"
20561 .scindex IIDmanrou1 "&(manualroute)& router"
20562 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20563 .cindex "domain" "manually routing"
20564 The &(manualroute)& router is so-called because it provides a way of manually
20565 routing an address according to its domain. It is mainly used when you want to
20566 route addresses to remote hosts according to your own rules, bypassing the
20567 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20568 route to local transports, a facility that may be useful if you want to save
20569 messages for dial-in hosts in local files.
20571 The &(manualroute)& router compares a list of domain patterns with the domain
20572 it is trying to route. If there is no match, the router declines. Each pattern
20573 has associated with it a list of hosts and some other optional data, which may
20574 include a transport. The combination of a pattern and its data is called a
20575 &"routing rule"&. For patterns that do not have an associated transport, the
20576 generic &%transport%& option must specify a transport, unless the router is
20577 being used purely for verification (see &%verify_only%&).
20580 In the case of verification, matching the domain pattern is sufficient for the
20581 router to accept the address. When actually routing an address for delivery,
20582 an address that matches a domain pattern is queued for the associated
20583 transport. If the transport is not a local one, a host list must be associated
20584 with the pattern; IP addresses are looked up for the hosts, and these are
20585 passed to the transport along with the mail address. For local transports, a
20586 host list is optional. If it is present, it is passed in &$host$& as a single
20589 The list of routing rules can be provided as an inline string in
20590 &%route_list%&, or the data can be obtained by looking up the domain in a file
20591 or database by setting &%route_data%&. Only one of these settings may appear in
20592 any one instance of &(manualroute)&. The format of routing rules is described
20593 below, following the list of private options.
20596 .section "Private options for manualroute" "SECTprioptman"
20598 .cindex "options" "&(manualroute)& router"
20599 The private options for the &(manualroute)& router are as follows:
20601 .option host_all_ignored manualroute string defer
20602 See &%host_find_failed%&.
20604 .option host_find_failed manualroute string freeze
20605 This option controls what happens when &(manualroute)& tries to find an IP
20606 address for a host, and the host does not exist. The option can be set to one
20607 of the following values:
20616 The default (&"freeze"&) assumes that this state is a serious configuration
20617 error. The difference between &"pass"& and &"decline"& is that the former
20618 forces the address to be passed to the next router (or the router defined by
20621 overriding &%no_more%&, whereas the latter passes the address to the next
20622 router only if &%more%& is true.
20624 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20625 cannot be found. If all the hosts in the list are ignored, the behaviour is
20626 controlled by the &%host_all_ignored%& option. This takes the same values
20627 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20629 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20630 state; if a host lookup gets a temporary error, delivery is deferred unless the
20631 generic &%pass_on_timeout%& option is set.
20634 .option hosts_randomize manualroute boolean false
20635 .cindex "randomized host list"
20636 .cindex "host" "list of; randomized"
20637 If this option is set, the order of the items in a host list in a routing rule
20638 is randomized each time the list is used, unless an option in the routing rule
20639 overrides (see below). Randomizing the order of a host list can be used to do
20640 crude load sharing. However, if more than one mail address is routed by the
20641 same router to the same host list, the host lists are considered to be the same
20642 (even though they may be randomized into different orders) for the purpose of
20643 deciding whether to batch the deliveries into a single SMTP transaction.
20645 When &%hosts_randomize%& is true, a host list may be split
20646 into groups whose order is separately randomized. This makes it possible to
20647 set up MX-like behaviour. The boundaries between groups are indicated by an
20648 item that is just &`+`& in the host list. For example:
20650 route_list = * host1:host2:host3:+:host4:host5
20652 The order of the first three hosts and the order of the last two hosts is
20653 randomized for each use, but the first three always end up before the last two.
20654 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20655 randomized host list is passed to an &(smtp)& transport that also has
20656 &%hosts_randomize set%&, the list is not re-randomized.
20659 .option route_data manualroute string&!! unset
20660 If this option is set, it must expand to yield the data part of a routing rule.
20661 Typically, the expansion string includes a lookup based on the domain. For
20664 route_data = ${lookup{$domain}dbm{/etc/routes}}
20666 If the expansion is forced to fail, or the result is an empty string, the
20667 router declines. Other kinds of expansion failure cause delivery to be
20671 .option route_list manualroute "string list" unset
20672 This string is a list of routing rules, in the form defined below. Note that,
20673 unlike most string lists, the items are separated by semicolons. This is so
20674 that they may contain colon-separated host lists.
20677 .option same_domain_copy_routing manualroute boolean false
20678 .cindex "address" "copying routing"
20679 Addresses with the same domain are normally routed by the &(manualroute)&
20680 router to the same list of hosts. However, this cannot be presumed, because the
20681 router options and preconditions may refer to the local part of the address. By
20682 default, therefore, Exim routes each address in a message independently. DNS
20683 servers run caches, so repeated DNS lookups are not normally expensive, and in
20684 any case, personal messages rarely have more than a few recipients.
20686 If you are running mailing lists with large numbers of subscribers at the same
20687 domain, and you are using a &(manualroute)& router which is independent of the
20688 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20689 lookups for identical domains in one message. In this case, when
20690 &(manualroute)& routes an address to a remote transport, any other unrouted
20691 addresses in the message that have the same domain are automatically given the
20692 same routing without processing them independently. However, this is only done
20693 if &%headers_add%& and &%headers_remove%& are unset.
20698 .section "Routing rules in route_list" "SECID120"
20699 The value of &%route_list%& is a string consisting of a sequence of routing
20700 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20701 entered as two semicolons. Alternatively, the list separator can be changed as
20702 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20703 Empty rules are ignored. The format of each rule is
20705 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20707 The following example contains two rules, each with a simple domain pattern and
20711 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20712 thes.ref.example mail-3.ref.example:mail-4.ref.example
20714 The three parts of a rule are separated by white space. The pattern and the
20715 list of hosts can be enclosed in quotes if necessary, and if they are, the
20716 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20717 single domain pattern, which is the only mandatory item in the rule. The
20718 pattern is in the same format as one item in a domain list (see section
20719 &<<SECTdomainlist>>&),
20720 except that it may not be the name of an interpolated file.
20721 That is, it may be wildcarded, or a regular expression, or a file or database
20722 lookup (with semicolons doubled, because of the use of semicolon as a separator
20723 in a &%route_list%&).
20725 The rules in &%route_list%& are searched in order until one of the patterns
20726 matches the domain that is being routed. The list of hosts and then options are
20727 then used as described below. If there is no match, the router declines. When
20728 &%route_list%& is set, &%route_data%& must not be set.
20732 .section "Routing rules in route_data" "SECID121"
20733 The use of &%route_list%& is convenient when there are only a small number of
20734 routing rules. For larger numbers, it is easier to use a file or database to
20735 hold the routing information, and use the &%route_data%& option instead.
20736 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20737 Most commonly, &%route_data%& is set as a string that contains an
20738 expansion lookup. For example, suppose we place two routing rules in a file
20741 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20742 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20744 This data can be accessed by setting
20746 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20748 Failure of the lookup results in an empty string, causing the router to
20749 decline. However, you do not have to use a lookup in &%route_data%&. The only
20750 requirement is that the result of expanding the string is a list of hosts,
20751 possibly followed by options, separated by white space. The list of hosts must
20752 be enclosed in quotes if it contains white space.
20757 .section "Format of the list of hosts" "SECID122"
20758 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20759 always separately expanded before use. If the expansion fails, the router
20760 declines. The result of the expansion must be a colon-separated list of names
20761 and/or IP addresses, optionally also including ports.
20762 If the list is written with spaces, it must be protected with quotes.
20763 The format of each item
20764 in the list is described in the next section. The list separator can be changed
20765 as described in section &<<SECTlistsepchange>>&.
20767 If the list of hosts was obtained from a &%route_list%& item, the following
20768 variables are set during its expansion:
20771 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20772 If the domain was matched against a regular expression, the numeric variables
20773 &$1$&, &$2$&, etc. may be set. For example:
20775 route_list = ^domain(\d+) host-$1.text.example
20778 &$0$& is always set to the entire domain.
20780 &$1$& is also set when partial matching is done in a file lookup.
20783 .vindex "&$value$&"
20784 If the pattern that matched the domain was a lookup item, the data that was
20785 looked up is available in the expansion variable &$value$&. For example:
20787 route_list = lsearch;;/some/file.routes $value
20791 Note the doubling of the semicolon in the pattern that is necessary because
20792 semicolon is the default route list separator.
20796 .section "Format of one host item" "SECTformatonehostitem"
20797 Each item in the list of hosts can be either a host name or an IP address,
20798 optionally with an attached port number, or it can be a single "+"
20799 (see &%hosts_randomize%&).
20800 When no port is given, an IP address
20801 is not enclosed in brackets. When a port is specified, it overrides the port
20802 specification on the transport. The port is separated from the name or address
20803 by a colon. This leads to some complications:
20806 Because colon is the default separator for the list of hosts, either
20807 the colon that specifies a port must be doubled, or the list separator must
20808 be changed. The following two examples have the same effect:
20810 route_list = * "host1.tld::1225 : host2.tld::1226"
20811 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20814 When IPv6 addresses are involved, it gets worse, because they contain
20815 colons of their own. To make this case easier, it is permitted to
20816 enclose an IP address (either v4 or v6) in square brackets if a port
20817 number follows. For example:
20819 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20823 .section "How the list of hosts is used" "SECThostshowused"
20824 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20825 the hosts is tried, in the order specified, when carrying out the SMTP
20826 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20827 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20830 Hosts may be listed by name or by IP address. An unadorned name in the list of
20831 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20832 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20833 records in the DNS. For example:
20835 route_list = * x.y.z:p.q.r/MX:e.f.g
20837 If this feature is used with a port specifier, the port must come last. For
20840 route_list = * dom1.tld/mx::1225
20842 If the &%hosts_randomize%& option is set, the order of the items in the list is
20843 randomized before any lookups are done. Exim then scans the list; for any name
20844 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20845 be an interface on the local host and the item is not the first in the list,
20846 Exim discards it and any subsequent items. If it is the first item, what
20847 happens is controlled by the
20848 .oindex "&%self%&" "in &(manualroute)& router"
20849 &%self%& option of the router.
20851 A name on the list that is followed by &`/MX`& is replaced with the list of
20852 hosts obtained by looking up MX records for the name. This is always a DNS
20853 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20854 below) are not relevant here. The order of these hosts is determined by the
20855 preference values in the MX records, according to the usual rules. Because
20856 randomizing happens before the MX lookup, it does not affect the order that is
20857 defined by MX preferences.
20859 If the local host is present in the sublist obtained from MX records, but is
20860 not the most preferred host in that list, it and any equally or less
20861 preferred hosts are removed before the sublist is inserted into the main list.
20863 If the local host is the most preferred host in the MX list, what happens
20864 depends on where in the original list of hosts the &`/MX`& item appears. If it
20865 is not the first item (that is, there are previous hosts in the main list),
20866 Exim discards this name and any subsequent items in the main list.
20868 If the MX item is first in the list of hosts, and the local host is the
20869 most preferred host, what happens is controlled by the &%self%& option of the
20872 DNS failures when lookup up the MX records are treated in the same way as DNS
20873 failures when looking up IP addresses: &%pass_on_timeout%& and
20874 &%host_find_failed%& are used when relevant.
20876 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20877 whether obtained from an MX lookup or not.
20881 .section "How the options are used" "SECThowoptused"
20882 The options are a sequence of words, space-separated.
20883 One of the words can be the name of a transport; this overrides the
20884 &%transport%& option on the router for this particular routing rule only. The
20885 other words (if present) control randomization of the list of hosts on a
20886 per-rule basis, and how the IP addresses of the hosts are to be found when
20887 routing to a remote transport. These options are as follows:
20890 &%randomize%&: randomize the order of the hosts in this list, overriding the
20891 setting of &%hosts_randomize%& for this routing rule only.
20893 &%no_randomize%&: do not randomize the order of the hosts in this list,
20894 overriding the setting of &%hosts_randomize%& for this routing rule only.
20896 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20897 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20898 also look in &_/etc/hosts_& or other sources of information.
20900 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20901 no address records are found. If there is a temporary DNS error (such as a
20902 timeout), delivery is deferred.
20904 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20906 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20911 route_list = domain1 host1:host2:host3 randomize bydns;\
20912 domain2 host4:host5
20914 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20915 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20916 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20917 or &[gethostbyname()]&, and the result of the lookup is the result of that
20920 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20921 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20922 instead of TRY_AGAIN. That is why the default action is to try a DNS
20923 lookup first. Only if that gives a definite &"no such host"& is the local
20926 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20927 inadvertent constraint that a transport name as an option had to be the last
20932 If no IP address for a host can be found, what happens is controlled by the
20933 &%host_find_failed%& option.
20936 When an address is routed to a local transport, IP addresses are not looked up.
20937 The host list is passed to the transport in the &$host$& variable.
20941 .section "Manualroute examples" "SECID123"
20942 In some of the examples that follow, the presence of the &%remote_smtp%&
20943 transport, as defined in the default configuration file, is assumed:
20946 .cindex "smart host" "example router"
20947 The &(manualroute)& router can be used to forward all external mail to a
20948 &'smart host'&. If you have set up, in the main part of the configuration, a
20949 named domain list that contains your local domains, for example:
20951 domainlist local_domains = my.domain.example
20953 You can arrange for all other domains to be routed to a smart host by making
20954 your first router something like this:
20957 driver = manualroute
20958 domains = !+local_domains
20959 transport = remote_smtp
20960 route_list = * smarthost.ref.example
20962 This causes all non-local addresses to be sent to the single host
20963 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20964 they are tried in order
20965 (but you can use &%hosts_randomize%& to vary the order each time).
20966 Another way of configuring the same thing is this:
20969 driver = manualroute
20970 transport = remote_smtp
20971 route_list = !+local_domains smarthost.ref.example
20973 There is no difference in behaviour between these two routers as they stand.
20974 However, they behave differently if &%no_more%& is added to them. In the first
20975 example, the router is skipped if the domain does not match the &%domains%&
20976 precondition; the following router is always tried. If the router runs, it
20977 always matches the domain and so can never decline. Therefore, &%no_more%&
20978 would have no effect. In the second case, the router is never skipped; it
20979 always runs. However, if it doesn't match the domain, it declines. In this case
20980 &%no_more%& would prevent subsequent routers from running.
20983 .cindex "mail hub example"
20984 A &'mail hub'& is a host which receives mail for a number of domains via MX
20985 records in the DNS and delivers it via its own private routing mechanism. Often
20986 the final destinations are behind a firewall, with the mail hub being the one
20987 machine that can connect to machines both inside and outside the firewall. The
20988 &(manualroute)& router is usually used on a mail hub to route incoming messages
20989 to the correct hosts. For a small number of domains, the routing can be inline,
20990 using the &%route_list%& option, but for a larger number a file or database
20991 lookup is easier to manage.
20993 If the domain names are in fact the names of the machines to which the mail is
20994 to be sent by the mail hub, the configuration can be quite simple. For
20998 driver = manualroute
20999 transport = remote_smtp
21000 route_list = *.rhodes.tvs.example $domain
21002 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
21003 whose names are the same as the mail domains. A similar approach can be taken
21004 if the host name can be obtained from the domain name by a string manipulation
21005 that the expansion facilities can handle. Otherwise, a lookup based on the
21006 domain can be used to find the host:
21009 driver = manualroute
21010 transport = remote_smtp
21011 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
21013 The result of the lookup must be the name or IP address of the host (or
21014 hosts) to which the address is to be routed. If the lookup fails, the route
21015 data is empty, causing the router to decline. The address then passes to the
21019 .cindex "batched SMTP output example"
21020 .cindex "SMTP" "batched outgoing; example"
21021 You can use &(manualroute)& to deliver messages to pipes or files in batched
21022 SMTP format for onward transportation by some other means. This is one way of
21023 storing mail for a dial-up host when it is not connected. The route list entry
21024 can be as simple as a single domain name in a configuration like this:
21027 driver = manualroute
21028 transport = batchsmtp_appendfile
21029 route_list = saved.domain.example
21031 though often a pattern is used to pick up more than one domain. If there are
21032 several domains or groups of domains with different transport requirements,
21033 different transports can be listed in the routing information:
21036 driver = manualroute
21038 *.saved.domain1.example $domain batch_appendfile; \
21039 *.saved.domain2.example \
21040 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21043 .vindex "&$domain$&"
21045 The first of these just passes the domain in the &$host$& variable, which
21046 doesn't achieve much (since it is also in &$domain$&), but the second does a
21047 file lookup to find a value to pass, causing the router to decline to handle
21048 the address if the lookup fails.
21051 .cindex "UUCP" "example of router for"
21052 Routing mail directly to UUCP software is a specific case of the use of
21053 &(manualroute)& in a gateway to another mail environment. This is an example of
21054 one way it can be done:
21060 command = /usr/local/bin/uux -r - \
21061 ${substr_-5:$host}!rmail ${local_part}
21062 return_fail_output = true
21067 driver = manualroute
21069 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21071 The file &_/usr/local/exim/uucphosts_& contains entries like
21073 darksite.ethereal.example: darksite.UUCP
21075 It can be set up more simply without adding and removing &".UUCP"& but this way
21076 makes clear the distinction between the domain name
21077 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21079 .ecindex IIDmanrou1
21080 .ecindex IIDmanrou2
21089 . ////////////////////////////////////////////////////////////////////////////
21090 . ////////////////////////////////////////////////////////////////////////////
21092 .chapter "The queryprogram router" "CHAPdriverlast"
21093 .scindex IIDquerou1 "&(queryprogram)& router"
21094 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21095 .cindex "routing" "by external program"
21096 The &(queryprogram)& router routes an address by running an external command
21097 and acting on its output. This is an expensive way to route, and is intended
21098 mainly for use in lightly-loaded systems, or for performing experiments.
21099 However, if it is possible to use the precondition options (&%domains%&,
21100 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21101 be used in special cases, even on a busy host. There are the following private
21103 .cindex "options" "&(queryprogram)& router"
21105 .option command queryprogram string&!! unset
21106 This option must be set. It specifies the command that is to be run. The
21107 command is split up into a command name and arguments, and then each is
21108 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21109 &<<CHAPpipetransport>>&).
21112 .option command_group queryprogram string unset
21113 .cindex "gid (group id)" "in &(queryprogram)& router"
21114 This option specifies a gid to be set when running the command while routing an
21115 address for deliver. It must be set if &%command_user%& specifies a numerical
21116 uid. If it begins with a digit, it is interpreted as the numerical value of the
21117 gid. Otherwise it is looked up using &[getgrnam()]&.
21120 .option command_user queryprogram string unset
21121 .cindex "uid (user id)" "for &(queryprogram)&"
21122 This option must be set. It specifies the uid which is set when running the
21123 command while routing an address for delivery. If the value begins with a digit,
21124 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21125 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21126 not set, a value for the gid also.
21128 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21129 root, which it does during a normal delivery in a conventional configuration.
21130 However, when an address is being verified during message reception, Exim is
21131 usually running as the Exim user, not as root. If the &(queryprogram)& router
21132 is called from a non-root process, Exim cannot change uid or gid before running
21133 the command. In this circumstance the command runs under the current uid and
21137 .option current_directory queryprogram string /
21138 This option specifies an absolute path which is made the current directory
21139 before running the command.
21142 .option timeout queryprogram time 1h
21143 If the command does not complete within the timeout period, its process group
21144 is killed and the message is frozen. A value of zero time specifies no
21148 The standard output of the command is connected to a pipe, which is read when
21149 the command terminates. It should consist of a single line of output,
21150 containing up to five fields, separated by white space. The maximum length of
21151 the line is 1023 characters. Longer lines are silently truncated. The first
21152 field is one of the following words (case-insensitive):
21155 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21158 &'Decline'&: the router declines; pass the address to the next router, unless
21159 &%no_more%& is set.
21161 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21162 subsequent text on the line is an error message. If the router is run as part
21163 of address verification during an incoming SMTP message, the message is
21164 included in the SMTP response.
21166 &'Defer'&: routing could not be completed at this time; try again later. Any
21167 subsequent text on the line is an error message which is logged. It is not
21168 included in any SMTP response.
21170 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21172 &'Pass'&: pass the address to the next router (or the router specified by
21173 &%pass_router%&), overriding &%no_more%&.
21175 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21176 new addresses, which are routed independently, starting with the first router,
21177 or the router specified by &%redirect_router%&, if set.
21180 When the first word is &'accept'&, the remainder of the line consists of a
21181 number of keyed data values, as follows (split into two lines here, to fit on
21184 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21185 LOOKUP=byname|bydns DATA=<text>
21187 The data items can be given in any order, and all are optional. If no transport
21188 is included, the transport specified by the generic &%transport%& option is
21189 used. The list of hosts and the lookup type are needed only if the transport is
21190 an &(smtp)& transport that does not itself supply a list of hosts.
21192 The format of the list of hosts is the same as for the &(manualroute)& router.
21193 As well as host names and IP addresses with optional port numbers, as described
21194 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21195 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21196 (see section &<<SECThostshowused>>&).
21198 If the lookup type is not specified, Exim behaves as follows when trying to
21199 find an IP address for each host: First, a DNS lookup is done. If this yields
21200 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21201 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21202 result of the lookup is the result of that call.
21204 .vindex "&$address_data$&"
21205 If the DATA field is set, its value is placed in the &$address_data$&
21206 variable. For example, this return line
21208 accept hosts=x1.y.example:x2.y.example data="rule1"
21210 routes the address to the default transport, passing a list of two hosts. When
21211 the transport runs, the string &"rule1"& is in &$address_data$&.
21212 .ecindex IIDquerou1
21213 .ecindex IIDquerou2
21218 . ////////////////////////////////////////////////////////////////////////////
21219 . ////////////////////////////////////////////////////////////////////////////
21221 .chapter "The redirect router" "CHAPredirect"
21222 .scindex IIDredrou1 "&(redirect)& router"
21223 .scindex IIDredrou2 "routers" "&(redirect)&"
21224 .cindex "alias file" "in a &(redirect)& router"
21225 .cindex "address redirection" "&(redirect)& router"
21226 The &(redirect)& router handles several kinds of address redirection. Its most
21227 common uses are for resolving local part aliases from a central alias file
21228 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21229 files, but it has many other potential uses. The incoming address can be
21230 redirected in several different ways:
21233 It can be replaced by one or more new addresses which are themselves routed
21236 It can be routed to be delivered to a given file or directory.
21238 It can be routed to be delivered to a specified pipe command.
21240 It can cause an automatic reply to be generated.
21242 It can be forced to fail, optionally with a custom error message.
21244 It can be temporarily deferred, optionally with a custom message.
21246 It can be discarded.
21249 The generic &%transport%& option must not be set for &(redirect)& routers.
21250 However, there are some private options which define transports for delivery to
21251 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21252 &%pipe_transport%& and &%reply_transport%& descriptions below.
21254 If success DSNs have been requested
21255 .cindex "DSN" "success"
21256 .cindex "Delivery Status Notification" "success"
21257 redirection triggers one and the DSN options are not passed any further.
21261 .section "Redirection data" "SECID124"
21262 The router operates by interpreting a text string which it obtains either by
21263 expanding the contents of the &%data%& option, or by reading the entire
21264 contents of a file whose name is given in the &%file%& option. These two
21265 options are mutually exclusive. The first is commonly used for handling system
21266 aliases, in a configuration like this:
21270 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21272 If the lookup fails, the expanded string in this example is empty. When the
21273 expansion of &%data%& results in an empty string, the router declines. A forced
21274 expansion failure also causes the router to decline; other expansion failures
21275 cause delivery to be deferred.
21277 A configuration using &%file%& is commonly used for handling users'
21278 &_.forward_& files, like this:
21283 file = $home/.forward
21286 If the file does not exist, or causes no action to be taken (for example, it is
21287 empty or consists only of comments), the router declines. &*Warning*&: This
21288 is not the case when the file contains syntactically valid items that happen to
21289 yield empty addresses, for example, items containing only RFC 2822 address
21292 .cindex "tainted data" "in filenames"
21293 .cindex redirect "tainted data"
21294 Tainted data may not be used for a filename.
21296 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21297 directly for redirection,
21298 as they are provided by a potential attacker.
21299 In the examples above, &$local_part$& is used for looking up data held locally
21300 on the system, and not used directly (the second example derives &$home$& via
21301 the passsword file or database, using &$local_part$&).
21305 .section "Forward files and address verification" "SECID125"
21306 .cindex "address redirection" "while verifying"
21307 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21308 &_.forward_& files, as in the example above. There are two reasons for this:
21311 When Exim is receiving an incoming SMTP message from a remote host, it is
21312 running under the Exim uid, not as root. Exim is unable to change uid to read
21313 the file as the user, and it may not be able to read it as the Exim user. So in
21314 practice the router may not be able to operate.
21316 However, even when the router can operate, the existence of a &_.forward_& file
21317 is unimportant when verifying an address. What should be checked is whether the
21318 local part is a valid user name or not. Cutting out the redirection processing
21319 saves some resources.
21327 .section "Interpreting redirection data" "SECID126"
21328 .cindex "Sieve filter" "specifying in redirection data"
21329 .cindex "filter" "specifying in redirection data"
21330 The contents of the data string, whether obtained from &%data%& or &%file%&,
21331 can be interpreted in two different ways:
21334 If the &%allow_filter%& option is set true, and the data begins with the text
21335 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21336 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21337 respectively. Details of the syntax and semantics of filter files are described
21338 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21339 document is intended for use by end users.
21341 Otherwise, the data must be a comma-separated list of redirection items, as
21342 described in the next section.
21345 When a message is redirected to a file (a &"mail folder"&), the filename given
21346 in a non-filter redirection list must always be an absolute path. A filter may
21347 generate a relative path &-- how this is handled depends on the transport's
21348 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21349 for the &(appendfile)& transport.
21353 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21354 .cindex "address redirection" "non-filter list items"
21355 When the redirection data is not an Exim or Sieve filter, for example, if it
21356 comes from a conventional alias or forward file, it consists of a list of
21357 addresses, filenames, pipe commands, or certain special items (see section
21358 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21359 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21360 depending on their default values. The items in the list are separated by
21361 commas or newlines.
21362 If a comma is required in an item, the entire item must be enclosed in double
21365 Lines starting with a # character are comments, and are ignored, and # may
21366 also appear following a comma, in which case everything between the # and the
21367 next newline character is ignored.
21369 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21370 double quotes are retained because some forms of mail address require their use
21371 (but never to enclose the entire address). In the following description,
21372 &"item"& refers to what remains after any surrounding double quotes have been
21375 .vindex "&$local_part$&"
21376 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21377 and the expansion contains a reference to &$local_part$&, you should make use
21378 of the &%quote_local_part%& expansion operator, in case the local part contains
21379 special characters. For example, to redirect all mail for the domain
21380 &'obsolete.example'&, retaining the existing local part, you could use this
21383 data = ${quote_local_part:$local_part}@newdomain.example
21387 .section "Redirecting to a local mailbox" "SECTredlocmai"
21388 .cindex "routing" "loops in"
21389 .cindex "loop" "while routing, avoidance of"
21390 .cindex "address redirection" "to local mailbox"
21391 A redirection item may safely be the same as the address currently under
21392 consideration. This does not cause a routing loop, because a router is
21393 automatically skipped if any ancestor of the address that is being processed
21394 is the same as the current address and was processed by the current router.
21395 Such an address is therefore passed to the following routers, so it is handled
21396 as if there were no redirection. When making this loop-avoidance test, the
21397 complete local part, including any prefix or suffix, is used.
21399 .cindex "address redirection" "local part without domain"
21400 Specifying the same local part without a domain is a common usage in personal
21401 filter files when the user wants to have messages delivered to the local
21402 mailbox and also forwarded elsewhere. For example, the user whose login is
21403 &'cleo'& might have a &_.forward_& file containing this:
21405 cleo, cleopatra@egypt.example
21407 .cindex "backslash in alias file"
21408 .cindex "alias file" "backslash in"
21409 For compatibility with other MTAs, such unqualified local parts may be
21410 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21411 it does make a difference if more than one domain is being handled
21414 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21415 2822 address that does not include a domain, the item is qualified using the
21416 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21417 addresses are qualified using the value in &%qualify_recipient%&, but you can
21418 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21420 Care must be taken if there are alias names for local users.
21421 Consider an MTA handling a single local domain where the system alias file
21426 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21427 messages in the local mailbox, and also forward copies elsewhere. He creates
21430 Sam.Reman, spqr@reme.elsewhere.example
21432 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21433 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21434 second time round, because it has previously routed it,
21435 and the following routers presumably cannot handle the alias. The forward file
21436 should really contain
21438 spqr, spqr@reme.elsewhere.example
21440 but because this is such a common error, the &%check_ancestor%& option (see
21441 below) exists to provide a way to get round it. This is normally set on a
21442 &(redirect)& router that is handling users' &_.forward_& files.
21446 .section "Special items in redirection lists" "SECTspecitredli"
21447 In addition to addresses, the following types of item may appear in redirection
21448 lists (that is, in non-filter redirection data):
21451 .cindex "pipe" "in redirection list"
21452 .cindex "address redirection" "to pipe"
21453 An item is treated as a pipe command if it begins with &"|"& and does not parse
21454 as a valid RFC 2822 address that includes a domain. A transport for running the
21455 command must be specified by the &%pipe_transport%& option.
21456 Normally, either the router or the transport specifies a user and a group under
21457 which to run the delivery. The default is to use the Exim user and group.
21459 Single or double quotes can be used for enclosing the individual arguments of
21460 the pipe command; no interpretation of escapes is done for single quotes. If
21461 the command contains a comma character, it is necessary to put the whole item
21462 in double quotes, for example:
21464 "|/some/command ready,steady,go"
21466 since items in redirection lists are terminated by commas. Do not, however,
21467 quote just the command. An item such as
21469 |"/some/command ready,steady,go"
21471 is interpreted as a pipe with a rather strange command name, and no arguments.
21473 Note that the above example assumes that the text comes from a lookup source
21474 of some sort, so that the quotes are part of the data. If composing a
21475 redirect router with a &%data%& option directly specifying this command, the
21476 quotes will be used by the configuration parser to define the extent of one
21477 string, but will not be passed down into the redirect router itself. There
21478 are two main approaches to get around this: escape quotes to be part of the
21479 data itself, or avoid using this mechanism and instead create a custom
21480 transport with the &%command%& option set and reference that transport from
21481 an &%accept%& router.
21484 .cindex "file" "in redirection list"
21485 .cindex "address redirection" "to file"
21486 An item is interpreted as a path name if it begins with &"/"& and does not
21487 parse as a valid RFC 2822 address that includes a domain. For example,
21489 /home/world/minbari
21491 is treated as a filename, but
21493 /s=molari/o=babylon/@x400gate.way
21495 is treated as an address. For a filename, a transport must be specified using
21496 the &%file_transport%& option. However, if the generated path name ends with a
21497 forward slash character, it is interpreted as a directory name rather than a
21498 filename, and &%directory_transport%& is used instead.
21500 Normally, either the router or the transport specifies a user and a group under
21501 which to run the delivery. The default is to use the Exim user and group.
21503 .cindex "&_/dev/null_&"
21504 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21505 bypassed at a high level, and the log entry shows &"**bypassed**"&
21506 instead of a transport name. In this case the user and group are not used.
21509 .cindex "included address list"
21510 .cindex "address redirection" "included external list"
21511 If an item is of the form
21513 :include:<path name>
21515 a list of further items is taken from the given file and included at that
21516 point. &*Note*&: Such a file can not be a filter file; it is just an
21517 out-of-line addition to the list. The items in the included list are separated
21518 by commas or newlines and are not subject to expansion. If this is the first
21519 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21520 the alias name. This example is incorrect:
21522 list1 :include:/opt/lists/list1
21524 It must be given as
21526 list1: :include:/opt/lists/list1
21528 .cindex "tainted data" "in filenames"
21529 .cindex redirect "tainted data"
21530 Tainted data may not be used for a filename.
21532 .cindex "address redirection" "to black hole"
21533 .cindex "delivery" "discard"
21534 .cindex "delivery" "blackhole"
21535 .cindex "black hole"
21536 .cindex "abandoning mail"
21537 Sometimes you want to throw away mail to a particular local part. Making the
21538 &%data%& option expand to an empty string does not work, because that causes
21539 the router to decline. Instead, the alias item
21543 can be used. It does what its name implies. No delivery is
21544 done, and no error message is generated. This has the same effect as specifying
21545 &_/dev/null_& as a destination, but it can be independently disabled.
21547 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21548 delivery is done for the original local part, even if other redirection items
21549 are present. If you are generating a multi-item list (for example, by reading a
21550 database) and need the ability to provide a no-op item, you must use
21554 .cindex "delivery" "forcing failure"
21555 .cindex "delivery" "forcing deferral"
21556 .cindex "failing delivery" "forcing"
21557 .cindex "deferred delivery, forcing"
21558 .cindex "customizing" "failure message"
21559 An attempt to deliver a particular address can be deferred or forced to fail by
21560 redirection items of the form
21565 respectively. When a redirection list contains such an item, it applies
21566 to the entire redirection; any other items in the list are ignored. Any
21567 text following &':fail:'& or &':defer:'& is placed in the error text
21568 associated with the failure. For example, an alias file might contain:
21570 X.Employee: :fail: Gone away, no forwarding address
21572 In the case of an address that is being verified from an ACL or as the subject
21574 .cindex "VRFY" "error text, display of"
21575 VRFY command, the text is included in the SMTP error response by
21577 .cindex "EXPN" "error text, display of"
21578 The text is not included in the response to an EXPN command. In non-SMTP cases
21579 the text is included in the error message that Exim generates.
21581 .cindex "SMTP" "error codes"
21582 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21583 &':fail:'&. However, if the message starts with three digits followed by a
21584 space, optionally followed by an extended code of the form &'n.n.n'&, also
21585 followed by a space, and the very first digit is the same as the default error
21586 code, the code from the message is used instead. If the very first digit is
21587 incorrect, a panic error is logged, and the default code is used. You can
21588 suppress the use of the supplied code in a redirect router by setting the
21589 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21592 .vindex "&$acl_verify_message$&"
21593 In an ACL, an explicitly provided message overrides the default, but the
21594 default message is available in the variable &$acl_verify_message$& and can
21595 therefore be included in a custom message if this is desired.
21597 Normally the error text is the rest of the redirection list &-- a comma does
21598 not terminate it &-- but a newline does act as a terminator. Newlines are not
21599 normally present in alias expansions. In &(lsearch)& lookups they are removed
21600 as part of the continuation process, but they may exist in other kinds of
21601 lookup and in &':include:'& files.
21603 During routing for message delivery (as opposed to verification), a redirection
21604 containing &':fail:'& causes an immediate failure of the incoming address,
21605 whereas &':defer:'& causes the message to remain in the queue so that a
21606 subsequent delivery attempt can happen at a later time. If an address is
21607 deferred for too long, it will ultimately fail, because the normal retry
21611 .cindex "alias file" "exception to default"
21612 Sometimes it is useful to use a single-key search type with a default (see
21613 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21614 for exceptions to the default. These can be handled by aliasing them to
21615 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21616 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21617 results in an empty redirection list has the same effect.
21621 .section "Duplicate addresses" "SECTdupaddr"
21622 .cindex "duplicate addresses"
21623 .cindex "address duplicate, discarding"
21624 .cindex "pipe" "duplicated"
21625 Exim removes duplicate addresses from the list to which it is delivering, so as
21626 to deliver just one copy to each address. This does not apply to deliveries
21627 routed to pipes by different immediate parent addresses, but an indirect
21628 aliasing scheme of the type
21630 pipe: |/some/command $local_part
21634 does not work with a message that is addressed to both local parts, because
21635 when the second is aliased to the intermediate local part &"pipe"& it gets
21636 discarded as being the same as a previously handled address. However, a scheme
21639 localpart1: |/some/command $local_part
21640 localpart2: |/some/command $local_part
21642 does result in two different pipe deliveries, because the immediate parents of
21643 the pipes are distinct.
21647 .section "Repeated redirection expansion" "SECID128"
21648 .cindex "repeated redirection expansion"
21649 .cindex "address redirection" "repeated for each delivery attempt"
21650 When a message cannot be delivered to all of its recipients immediately,
21651 leading to two or more delivery attempts, redirection expansion is carried out
21652 afresh each time for those addresses whose children were not all previously
21653 delivered. If redirection is being used as a mailing list, this can lead to new
21654 members of the list receiving copies of old messages. The &%one_time%& option
21655 can be used to avoid this.
21658 .section "Errors in redirection lists" "SECID129"
21659 .cindex "address redirection" "errors"
21660 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21661 error is skipped, and an entry is written to the main log. This may be useful
21662 for mailing lists that are automatically managed. Otherwise, if an error is
21663 detected while generating the list of new addresses, the original address is
21664 deferred. See also &%syntax_errors_to%&.
21668 .section "Private options for the redirect router" "SECID130"
21670 .cindex "options" "&(redirect)& router"
21671 The private options for the &(redirect)& router are as follows:
21674 .option allow_defer redirect boolean false
21675 Setting this option allows the use of &':defer:'& in non-filter redirection
21676 data, or the &%defer%& command in an Exim filter file.
21679 .option allow_fail redirect boolean false
21680 .cindex "failing delivery" "from filter"
21681 If this option is true, the &':fail:'& item can be used in a redirection list,
21682 and the &%fail%& command may be used in an Exim filter file.
21685 .option allow_filter redirect boolean false
21686 .cindex "filter" "enabling use of"
21687 .cindex "Sieve filter" "enabling use of"
21688 Setting this option allows Exim to interpret redirection data that starts with
21689 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21690 are some features of Exim filter files that some administrators may wish to
21691 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21693 It is also possible to lock out Exim filters or Sieve filters while allowing
21694 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21697 The filter is run using the uid and gid set by the generic &%user%& and
21698 &%group%& options. These take their defaults from the password data if
21699 &%check_local_user%& is set, so in the normal case of users' personal filter
21700 files, the filter is run as the relevant user. When &%allow_filter%& is set
21701 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21705 .option allow_freeze redirect boolean false
21706 .cindex "freezing messages" "allowing in filter"
21707 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21708 This command is more normally encountered in system filters, and is disabled by
21709 default for redirection filters because it isn't something you usually want to
21710 let ordinary users do.
21714 .option check_ancestor redirect boolean false
21715 This option is concerned with handling generated addresses that are the same
21716 as some address in the list of redirection ancestors of the current address.
21717 Although it is turned off by default in the code, it is set in the default
21718 configuration file for handling users' &_.forward_& files. It is recommended
21719 for this use of the &(redirect)& router.
21721 When &%check_ancestor%& is set, if a generated address (including the domain)
21722 is the same as any ancestor of the current address, it is replaced by a copy of
21723 the current address. This helps in the case where local part A is aliased to B,
21724 and B has a &_.forward_& file pointing back to A. For example, within a single
21725 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21726 &_&~jb/.forward_& contains:
21728 \Joe.Bloggs, <other item(s)>
21730 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21731 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21732 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21733 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21734 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21735 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21736 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21737 original address. See also the &%repeat_use%& option below.
21740 .option check_group redirect boolean "see below"
21741 When the &%file%& option is used, the group owner of the file is checked only
21742 when this option is set. The permitted groups are those listed in the
21743 &%owngroups%& option, together with the user's default group if
21744 &%check_local_user%& is set. If the file has the wrong group, routing is
21745 deferred. The default setting for this option is true if &%check_local_user%&
21746 is set and the &%modemask%& option permits the group write bit, or if the
21747 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21751 .option check_owner redirect boolean "see below"
21752 When the &%file%& option is used, the owner of the file is checked only when
21753 this option is set. If &%check_local_user%& is set, the local user is
21754 permitted; otherwise the owner must be one of those listed in the &%owners%&
21755 option. The default value for this option is true if &%check_local_user%& or
21756 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21759 .option data redirect string&!! unset
21760 This option is mutually exclusive with &%file%&. One or other of them must be
21761 set, but not both. The contents of &%data%& are expanded, and then used as the
21762 list of forwarding items, or as a set of filtering instructions. If the
21763 expansion is forced to fail, or the result is an empty string or a string that
21764 has no effect (consists entirely of comments), the router declines.
21766 When filtering instructions are used, the string must begin with &"#Exim
21767 filter"&, and all comments in the string, including this initial one, must be
21768 terminated with newline characters. For example:
21770 data = #Exim filter\n\
21771 if $h_to: contains Exim then save $home/mail/exim endif
21773 If you are reading the data from a database where newlines cannot be included,
21774 you can use the &${sg}$& expansion item to turn the escape string of your
21775 choice into a newline.
21778 .option directory_transport redirect string&!! unset
21779 A &(redirect)& router sets up a direct delivery to a directory when a path name
21780 ending with a slash is specified as a new &"address"&. The transport used is
21781 specified by this option, which, after expansion, must be the name of a
21782 configured transport. This should normally be an &(appendfile)& transport.
21785 .option file redirect string&!! unset
21786 This option specifies the name of a file that contains the redirection data. It
21787 is mutually exclusive with the &%data%& option. The string is expanded before
21788 use; if the expansion is forced to fail, the router declines. Other expansion
21789 failures cause delivery to be deferred. The result of a successful expansion
21790 must be an absolute path. The entire file is read and used as the redirection
21791 data. If the data is an empty string or a string that has no effect (consists
21792 entirely of comments), the router declines.
21794 .cindex "NFS" "checking for file existence"
21795 If the attempt to open the file fails with a &"does not exist"& error, Exim
21796 runs a check on the containing directory,
21797 unless &%ignore_enotdir%& is true (see below).
21798 If the directory does not appear to exist, delivery is deferred. This can
21799 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21800 is a mount problem. If the containing directory does exist, but the file does
21801 not, the router declines.
21804 .option file_transport redirect string&!! unset
21805 .vindex "&$address_file$&"
21806 A &(redirect)& router sets up a direct delivery to a file when a path name not
21807 ending in a slash is specified as a new &"address"&. The transport used is
21808 specified by this option, which, after expansion, must be the name of a
21809 configured transport. This should normally be an &(appendfile)& transport. When
21810 it is running, the filename is in &$address_file$&.
21813 .option filter_prepend_home redirect boolean true
21814 When this option is true, if a &(save)& command in an Exim filter specifies a
21815 relative path, and &$home$& is defined, it is automatically prepended to the
21816 relative path. If this option is set false, this action does not happen. The
21817 relative path is then passed to the transport unmodified.
21820 .option forbid_blackhole redirect boolean false
21821 .cindex "restricting access to features"
21822 .cindex "filter" "locking out certain features"
21823 If this option is true, the &':blackhole:'& item may not appear in a
21827 .option forbid_exim_filter redirect boolean false
21828 .cindex "restricting access to features"
21829 .cindex "filter" "locking out certain features"
21830 If this option is set true, only Sieve filters are permitted when
21831 &%allow_filter%& is true.
21836 .option forbid_file redirect boolean false
21837 .cindex "restricting access to features"
21838 .cindex "delivery" "to file; forbidding"
21839 .cindex "filter" "locking out certain features"
21840 .cindex "Sieve filter" "forbidding delivery to a file"
21841 .cindex "Sieve filter" "&""keep""& facility; disabling"
21842 If this option is true, this router may not generate a new address that
21843 specifies delivery to a local file or directory, either from a filter or from a
21844 conventional forward file. This option is forced to be true if &%one_time%& is
21845 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21846 locks out the Sieve's &"keep"& facility.
21849 .option forbid_filter_dlfunc redirect boolean false
21850 .cindex "restricting access to features"
21851 .cindex "filter" "locking out certain features"
21852 If this option is true, string expansions in Exim filters are not allowed to
21853 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21856 .option forbid_filter_existstest redirect boolean false
21857 .cindex "restricting access to features"
21858 .cindex "filter" "locking out certain features"
21859 .cindex "expansion" "statting a file"
21860 If this option is true, string expansions in Exim filters are not allowed to
21861 make use of the &%exists%& condition or the &%stat%& expansion item.
21863 .option forbid_filter_logwrite redirect boolean false
21864 .cindex "restricting access to features"
21865 .cindex "filter" "locking out certain features"
21866 If this option is true, use of the logging facility in Exim filters is not
21867 permitted. Logging is in any case available only if the filter is being run
21868 under some unprivileged uid (which is normally the case for ordinary users'
21869 &_.forward_& files).
21872 .option forbid_filter_lookup redirect boolean false
21873 .cindex "restricting access to features"
21874 .cindex "filter" "locking out certain features"
21875 If this option is true, string expansions in Exim filter files are not allowed
21876 to make use of &%lookup%& items.
21879 .option forbid_filter_perl redirect boolean false
21880 .cindex "restricting access to features"
21881 .cindex "filter" "locking out certain features"
21882 This option has an effect only if Exim is built with embedded Perl support. If
21883 it is true, string expansions in Exim filter files are not allowed to make use
21884 of the embedded Perl support.
21887 .option forbid_filter_readfile redirect boolean false
21888 .cindex "restricting access to features"
21889 .cindex "filter" "locking out certain features"
21890 If this option is true, string expansions in Exim filter files are not allowed
21891 to make use of &%readfile%& items.
21894 .option forbid_filter_readsocket redirect boolean false
21895 .cindex "restricting access to features"
21896 .cindex "filter" "locking out certain features"
21897 If this option is true, string expansions in Exim filter files are not allowed
21898 to make use of &%readsocket%& items.
21901 .option forbid_filter_reply redirect boolean false
21902 .cindex "restricting access to features"
21903 .cindex "filter" "locking out certain features"
21904 If this option is true, this router may not generate an automatic reply
21905 message. Automatic replies can be generated only from Exim or Sieve filter
21906 files, not from traditional forward files. This option is forced to be true if
21907 &%one_time%& is set.
21910 .option forbid_filter_run redirect boolean false
21911 .cindex "restricting access to features"
21912 .cindex "filter" "locking out certain features"
21913 If this option is true, string expansions in Exim filter files are not allowed
21914 to make use of &%run%& items.
21917 .option forbid_include redirect boolean false
21918 .cindex "restricting access to features"
21919 .cindex "filter" "locking out certain features"
21920 If this option is true, items of the form
21922 :include:<path name>
21924 are not permitted in non-filter redirection lists.
21927 .option forbid_pipe redirect boolean false
21928 .cindex "restricting access to features"
21929 .cindex "filter" "locking out certain features"
21930 .cindex "delivery" "to pipe; forbidding"
21931 If this option is true, this router may not generate a new address which
21932 specifies delivery to a pipe, either from an Exim filter or from a conventional
21933 forward file. This option is forced to be true if &%one_time%& is set.
21936 .option forbid_sieve_filter redirect boolean false
21937 .cindex "restricting access to features"
21938 .cindex "filter" "locking out certain features"
21939 If this option is set true, only Exim filters are permitted when
21940 &%allow_filter%& is true.
21943 .cindex "SMTP" "error codes"
21944 .option forbid_smtp_code redirect boolean false
21945 If this option is set true, any SMTP error codes that are present at the start
21946 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21947 the default codes (451 and 550, respectively) are always used.
21952 .option hide_child_in_errmsg redirect boolean false
21953 .cindex "bounce message" "redirection details; suppressing"
21954 If this option is true, it prevents Exim from quoting a child address if it
21955 generates a bounce or delay message for it. Instead it says &"an address
21956 generated from <&'the top level address'&>"&. Of course, this applies only to
21957 bounces generated locally. If a message is forwarded to another host, &'its'&
21958 bounce may well quote the generated address.
21961 .option ignore_eacces redirect boolean false
21963 If this option is set and an attempt to open a redirection file yields the
21964 EACCES error (permission denied), the &(redirect)& router behaves as if the
21965 file did not exist.
21968 .option ignore_enotdir redirect boolean false
21970 If this option is set and an attempt to open a redirection file yields the
21971 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21972 router behaves as if the file did not exist.
21974 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21975 router that has the &%file%& option set discovers that the file does not exist
21976 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21977 against unmounted NFS directories. If the parent can not be statted, delivery
21978 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21979 is set, because that option tells Exim to ignore &"something on the path is not
21980 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21981 that some operating systems give ENOENT where others give ENOTDIR.
21985 .option include_directory redirect string unset
21986 If this option is set, the path names of any &':include:'& items in a
21987 redirection list must start with this directory.
21990 .option modemask redirect "octal integer" 022
21991 This specifies mode bits which must not be set for a file specified by the
21992 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21995 .option one_time redirect boolean false
21996 .cindex "one-time aliasing/forwarding expansion"
21997 .cindex "alias file" "one-time expansion"
21998 .cindex "forward file" "one-time expansion"
21999 .cindex "mailing lists" "one-time expansion"
22000 .cindex "address redirection" "one-time expansion"
22001 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
22002 files each time it tries to deliver a message causes a problem when one or more
22003 of the generated addresses fails be delivered at the first attempt. The problem
22004 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
22005 but of what happens when the redirection list changes during the time that the
22006 message is on Exim's queue. This is particularly true in the case of mailing
22007 lists, where new subscribers might receive copies of messages that were posted
22008 before they subscribed.
22010 If &%one_time%& is set and any addresses generated by the router fail to
22011 deliver at the first attempt, the failing addresses are added to the message as
22012 &"top level"& addresses, and the parent address that generated them is marked
22013 &"delivered"&. Thus, redirection does not happen again at the next delivery
22016 &*Warning 1*&: Any header line addition or removal that is specified by this
22017 router would be lost if delivery did not succeed at the first attempt. For this
22018 reason, the &%headers_add%& and &%headers_remove%& generic options are not
22019 permitted when &%one_time%& is set.
22021 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
22022 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
22023 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
22025 &*Warning 3*&: The &%unseen%& generic router option may not be set with
22028 The original top-level address is remembered with each of the generated
22029 addresses, and is output in any log messages. However, any intermediate parent
22030 addresses are not recorded. This makes a difference to the log only if
22031 &%all_parents%& log selector is set. It is expected that &%one_time%& will
22032 typically be used for mailing lists, where there is normally just one level of
22036 .option owners redirect "string list" unset
22037 .cindex "ownership" "alias file"
22038 .cindex "ownership" "forward file"
22039 .cindex "alias file" "ownership"
22040 .cindex "forward file" "ownership"
22041 This specifies a list of permitted owners for the file specified by &%file%&.
22042 This list is in addition to the local user when &%check_local_user%& is set.
22043 See &%check_owner%& above.
22046 .option owngroups redirect "string list" unset
22047 This specifies a list of permitted groups for the file specified by &%file%&.
22048 The list is in addition to the local user's primary group when
22049 &%check_local_user%& is set. See &%check_group%& above.
22052 .option pipe_transport redirect string&!! unset
22053 .vindex "&$address_pipe$&"
22054 A &(redirect)& router sets up a direct delivery to a pipe when a string
22055 starting with a vertical bar character is specified as a new &"address"&. The
22056 transport used is specified by this option, which, after expansion, must be the
22057 name of a configured transport. This should normally be a &(pipe)& transport.
22058 When the transport is run, the pipe command is in &$address_pipe$&.
22061 .option qualify_domain redirect string&!! unset
22062 .vindex "&$qualify_recipient$&"
22063 If this option is set, and an unqualified address (one without a domain) is
22064 generated, and that address would normally be qualified by the global setting
22065 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22066 expanding this string. If the expansion fails, the router declines. If you want
22067 to revert to the default, you can have the expansion generate
22068 &$qualify_recipient$&.
22070 This option applies to all unqualified addresses generated by Exim filters,
22071 but for traditional &_.forward_& files, it applies only to addresses that are
22072 not preceded by a backslash. Sieve filters cannot generate unqualified
22075 .option qualify_preserve_domain redirect boolean false
22076 .cindex "domain" "in redirection; preserving"
22077 .cindex "preserving domain in redirection"
22078 .cindex "address redirection" "domain; preserving"
22079 If this option is set, the router's local &%qualify_domain%& option must not be
22080 set (a configuration error occurs if it is). If an unqualified address (one
22081 without a domain) is generated, it is qualified with the domain of the parent
22082 address (the immediately preceding ancestor) instead of the global
22083 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22084 this applies whether or not the address is preceded by a backslash.
22087 .option repeat_use redirect boolean true
22088 If this option is set false, the router is skipped for a child address that has
22089 any ancestor that was routed by this router. This test happens before any of
22090 the other preconditions are tested. Exim's default anti-looping rules skip
22091 only when the ancestor is the same as the current address. See also
22092 &%check_ancestor%& above and the generic &%redirect_router%& option.
22095 .option reply_transport redirect string&!! unset
22096 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22097 &%vacation%& command is used in a filter file. The transport used is specified
22098 by this option, which, after expansion, must be the name of a configured
22099 transport. This should normally be an &(autoreply)& transport. Other transports
22100 are unlikely to do anything sensible or useful.
22103 .option rewrite redirect boolean true
22104 .cindex "address redirection" "disabling rewriting"
22105 If this option is set false, addresses generated by the router are not
22106 subject to address rewriting. Otherwise, they are treated like new addresses
22107 and are rewritten according to the global rewriting rules.
22110 .option sieve_subaddress redirect string&!! unset
22111 The value of this option is passed to a Sieve filter to specify the
22112 :subaddress part of an address.
22114 .option sieve_useraddress redirect string&!! unset
22115 The value of this option is passed to a Sieve filter to specify the :user part
22116 of an address. However, if it is unset, the entire original local part
22117 (including any prefix or suffix) is used for :user.
22120 .option sieve_vacation_directory redirect string&!! unset
22121 .cindex "Sieve filter" "vacation directory"
22122 To enable the &"vacation"& extension for Sieve filters, you must set
22123 &%sieve_vacation_directory%& to the directory where vacation databases are held
22124 (do not put anything else in that directory), and ensure that the
22125 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22126 needs their own directory; Exim will create it if necessary.
22130 .option skip_syntax_errors redirect boolean false
22131 .cindex "forward file" "broken"
22132 .cindex "address redirection" "broken files"
22133 .cindex "alias file" "broken"
22134 .cindex "broken alias or forward files"
22135 .cindex "ignoring faulty addresses"
22136 .cindex "skipping faulty addresses"
22137 .cindex "error" "skipping bad syntax"
22138 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22139 non-filter redirection data are skipped, and each failing address is logged. If
22140 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22141 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22142 are expanded and placed at the head of the error message generated by
22143 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22144 be the same address as the generic &%errors_to%& option. The
22145 &%skip_syntax_errors%& option is often used when handling mailing lists.
22147 If all the addresses in a redirection list are skipped because of syntax
22148 errors, the router declines to handle the original address, and it is passed to
22149 the following routers.
22151 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22152 error in the filter causes filtering to be abandoned without any action being
22153 taken. The incident is logged, and the router declines to handle the address,
22154 so it is passed to the following routers.
22156 .cindex "Sieve filter" "syntax errors in"
22157 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22158 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22159 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22161 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22162 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22163 option, used with an address that does not get redirected, can be used to
22164 notify users of these errors, by means of a router like this:
22170 file = $home/.forward
22171 file_transport = address_file
22172 pipe_transport = address_pipe
22173 reply_transport = address_reply
22176 syntax_errors_to = real-$local_part@$domain
22177 syntax_errors_text = \
22178 This is an automatically generated message. An error has\n\
22179 been found in your .forward file. Details of the error are\n\
22180 reported below. While this error persists, you will receive\n\
22181 a copy of this message for every message that is addressed\n\
22182 to you. If your .forward file is a filter file, or if it is\n\
22183 a non-filter file containing no valid forwarding addresses,\n\
22184 a copy of each incoming message will be put in your normal\n\
22185 mailbox. If a non-filter file contains at least one valid\n\
22186 forwarding address, forwarding to the valid addresses will\n\
22187 happen, and those will be the only deliveries that occur.
22189 You also need a router to ensure that local addresses that are prefixed by
22190 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22191 put this immediately before the &(userforward)& router:
22196 local_part_prefix = real-
22197 transport = local_delivery
22199 For security, it would probably be a good idea to restrict the use of this
22200 router to locally-generated messages, using a condition such as this:
22202 condition = ${if match {$sender_host_address}\
22203 {\N^(|127\.0\.0\.1)$\N}}
22207 .option syntax_errors_text redirect string&!! unset
22208 See &%skip_syntax_errors%& above.
22211 .option syntax_errors_to redirect string unset
22212 See &%skip_syntax_errors%& above.
22213 .ecindex IIDredrou1
22214 .ecindex IIDredrou2
22221 . ////////////////////////////////////////////////////////////////////////////
22222 . ////////////////////////////////////////////////////////////////////////////
22224 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22225 "Environment for local transports"
22226 .scindex IIDenvlotra1 "local transports" "environment for"
22227 .scindex IIDenvlotra2 "environment" "local transports"
22228 .scindex IIDenvlotra3 "transport" "local; environment for"
22229 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22230 transport can be thought of as similar to a pipe.) Exim always runs transports
22231 in subprocesses, under specified uids and gids. Typical deliveries to local
22232 mailboxes run under the uid and gid of the local user.
22234 Exim also sets a specific current directory while running the transport; for
22235 some transports a home directory setting is also relevant. The &(pipe)&
22236 transport is the only one that sets up environment variables; see section
22237 &<<SECTpipeenv>>& for details.
22239 The values used for the uid, gid, and the directories may come from several
22240 different places. In many cases, the router that handles the address associates
22241 settings with that address as a result of its &%check_local_user%&, &%group%&,
22242 or &%user%& options. However, values may also be given in the transport's own
22243 configuration, and these override anything that comes from the router.
22247 .section "Concurrent deliveries" "SECID131"
22248 .cindex "concurrent deliveries"
22249 .cindex "simultaneous deliveries"
22250 If two different messages for the same local recipient arrive more or less
22251 simultaneously, the two delivery processes are likely to run concurrently. When
22252 the &(appendfile)& transport is used to write to a file, Exim applies locking
22253 rules to stop concurrent processes from writing to the same file at the same
22256 However, when you use a &(pipe)& transport, it is up to you to arrange any
22257 locking that is needed. Here is a silly example:
22261 command = /bin/sh -c 'cat >>/some/file'
22263 This is supposed to write the message at the end of the file. However, if two
22264 messages arrive at the same time, the file will be scrambled. You can use the
22265 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22266 file using the same algorithm that Exim itself uses.
22271 .section "Uids and gids" "SECTenvuidgid"
22272 .cindex "local transports" "uid and gid"
22273 .cindex "transport" "local; uid and gid"
22274 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22275 overrides any group that the router set in the address, even if &%user%& is not
22276 set for the transport. This makes it possible, for example, to run local mail
22277 delivery under the uid of the recipient (set by the router), but in a special
22278 group (set by the transport). For example:
22281 # User/group are set by check_local_user in this router
22285 transport = group_delivery
22288 # This transport overrides the group
22290 driver = appendfile
22291 file = /var/spool/mail/$local_part_data
22294 If &%user%& is set for a transport, its value overrides what is set in the
22295 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22296 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22299 .oindex "&%initgroups%&"
22300 When the uid is taken from the transport's configuration, the &[initgroups()]&
22301 function is called for the groups associated with that uid if the
22302 &%initgroups%& option is set for the transport. When the uid is not specified
22303 by the transport, but is associated with the address by a router, the option
22304 for calling &[initgroups()]& is taken from the router configuration.
22306 .cindex "&(pipe)& transport" "uid for"
22307 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22308 is set and &%user%& is not set, the uid of the process that called Exim to
22309 receive the message is used, and if &%group%& is not set, the corresponding
22310 original gid is also used.
22312 This is the detailed preference order for obtaining a gid; the first of the
22313 following that is set is used:
22316 A &%group%& setting of the transport;
22318 A &%group%& setting of the router;
22320 A gid associated with a user setting of the router, either as a result of
22321 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22323 The group associated with a non-numeric &%user%& setting of the transport;
22325 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22326 the uid is the creator's uid;
22328 The Exim gid if the Exim uid is being used as a default.
22331 If, for example, the user is specified numerically on the router and there are
22332 no group settings, no gid is available. In this situation, an error occurs.
22333 This is different for the uid, for which there always is an ultimate default.
22334 The first of the following that is set is used:
22337 A &%user%& setting of the transport;
22339 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22341 A &%user%& setting of the router;
22343 A &%check_local_user%& setting of the router;
22348 Of course, an error will still occur if the uid that is chosen is on the
22349 &%never_users%& list.
22355 .section "Current and home directories" "SECID132"
22356 .cindex "current directory for local transport"
22357 .cindex "home directory" "for local transport"
22358 .cindex "transport" "local; home directory for"
22359 .cindex "transport" "local; current directory for"
22360 Routers may set current and home directories for local transports by means of
22361 the &%transport_current_directory%& and &%transport_home_directory%& options.
22362 However, if the transport's &%current_directory%& or &%home_directory%& options
22363 are set, they override the router's values. In detail, the home directory
22364 for a local transport is taken from the first of these values that is set:
22367 The &%home_directory%& option on the transport;
22369 The &%transport_home_directory%& option on the router;
22371 The password data if &%check_local_user%& is set on the router;
22373 The &%router_home_directory%& option on the router.
22376 The current directory is taken from the first of these values that is set:
22379 The &%current_directory%& option on the transport;
22381 The &%transport_current_directory%& option on the router.
22385 If neither the router nor the transport sets a current directory, Exim uses the
22386 value of the home directory, if it is set. Otherwise it sets the current
22387 directory to &_/_& before running a local transport.
22391 .section "Expansion variables derived from the address" "SECID133"
22392 .vindex "&$domain$&"
22393 .vindex "&$local_part$&"
22394 .vindex "&$original_domain$&"
22395 Normally a local delivery is handling a single address, and in that case the
22396 variables such as &$domain$& and &$local_part$& are set during local
22397 deliveries. However, in some circumstances more than one address may be handled
22398 at once (for example, while writing batch SMTP for onward transmission by some
22399 other means). In this case, the variables associated with the local part are
22400 never set, &$domain$& is set only if all the addresses have the same domain,
22401 and &$original_domain$& is never set.
22402 .ecindex IIDenvlotra1
22403 .ecindex IIDenvlotra2
22404 .ecindex IIDenvlotra3
22412 . ////////////////////////////////////////////////////////////////////////////
22413 . ////////////////////////////////////////////////////////////////////////////
22415 .chapter "Generic options for transports" "CHAPtransportgeneric"
22416 .scindex IIDgenoptra1 "generic options" "transport"
22417 .scindex IIDgenoptra2 "options" "generic; for transports"
22418 .scindex IIDgenoptra3 "transport" "generic options for"
22420 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22421 prior to Exim 4.95 names would be silently truncated at this length, but now
22425 The following generic options apply to all transports:
22428 .option body_only transports boolean false
22429 .cindex "transport" "body only"
22430 .cindex "message" "transporting body only"
22431 .cindex "body of message" "transporting"
22432 If this option is set, the message's headers are not transported. It is
22433 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22434 or &(pipe)& transports, the settings of &%message_prefix%& and
22435 &%message_suffix%& should be checked, because this option does not
22436 automatically suppress them.
22439 .option current_directory transports string&!! unset
22440 .cindex "transport" "current directory for"
22441 This specifies the current directory that is to be set while running the
22442 transport, overriding any value that may have been set by the router.
22443 If the expansion fails for any reason, including forced failure, an error is
22444 logged, and delivery is deferred.
22447 .option disable_logging transports boolean false
22448 If this option is set true, nothing is logged for any
22449 deliveries by the transport or for any
22450 transport errors. You should not set this option unless you really, really know
22451 what you are doing.
22454 .option debug_print transports string&!! unset
22455 .cindex "testing" "variables in drivers"
22456 If this option is set and debugging is enabled (see the &%-d%& command line
22457 option), the string is expanded and included in the debugging output when the
22459 If expansion of the string fails, the error message is written to the debugging
22460 output, and Exim carries on processing.
22461 This facility is provided to help with checking out the values of variables and
22462 so on when debugging driver configurations. For example, if a &%headers_add%&
22463 option is not working properly, &%debug_print%& could be used to output the
22464 variables it references. A newline is added to the text if it does not end with
22466 The variables &$transport_name$& and &$router_name$& contain the name of the
22467 transport and the router that called it.
22469 .option delivery_date_add transports boolean false
22470 .cindex "&'Delivery-date:'& header line"
22471 If this option is true, a &'Delivery-date:'& header is added to the message.
22472 This gives the actual time the delivery was made. As this is not a standard
22473 header, Exim has a configuration option (&%delivery_date_remove%&) which
22474 requests its removal from incoming messages, so that delivered messages can
22475 safely be resent to other recipients.
22478 .option driver transports string unset
22479 This specifies which of the available transport drivers is to be used.
22480 There is no default, and this option must be set for every transport.
22483 .option envelope_to_add transports boolean false
22484 .cindex "&'Envelope-to:'& header line"
22485 If this option is true, an &'Envelope-to:'& header is added to the message.
22486 This gives the original address(es) in the incoming envelope that caused this
22487 delivery to happen. More than one address may be present if the transport is
22488 configured to handle several addresses at once, or if more than one original
22489 address was redirected to the same final address. As this is not a standard
22490 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22491 its removal from incoming messages, so that delivered messages can safely be
22492 resent to other recipients.
22495 .option event_action transports string&!! unset
22497 This option declares a string to be expanded for Exim's events mechanism.
22498 For details see chapter &<<CHAPevents>>&.
22501 .option group transports string&!! "Exim group"
22502 .cindex "transport" "group; specifying"
22503 This option specifies a gid for running the transport process, overriding any
22504 value that the router supplies, and also overriding any value associated with
22505 &%user%& (see below).
22508 .option headers_add transports list&!! unset
22509 .cindex "header lines" "adding in transport"
22510 .cindex "transport" "header lines; adding"
22511 This option specifies a list of text headers,
22512 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22513 which are (separately) expanded and added to the header
22514 portion of a message as it is transported, as described in section
22515 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22516 routers. If the result of the expansion is an empty string, or if the expansion
22517 is forced to fail, no action is taken. Other expansion failures are treated as
22518 errors and cause the delivery to be deferred.
22520 Unlike most options, &%headers_add%& can be specified multiple times
22521 for a transport; all listed headers are added.
22524 .option headers_only transports boolean false
22525 .cindex "transport" "header lines only"
22526 .cindex "message" "transporting headers only"
22527 .cindex "header lines" "transporting"
22528 If this option is set, the message's body is not transported. It is mutually
22529 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22530 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22531 checked, since this option does not automatically suppress them.
22534 .option headers_remove transports list&!! unset
22535 .cindex "header lines" "removing"
22536 .cindex "transport" "header lines; removing"
22537 This option specifies a list of text headers,
22538 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22539 to be removed from the message.
22540 However, the option has no effect when an address is just being verified.
22541 Each list item is separately expanded.
22542 If the result of the expansion is an empty string, or if the expansion
22543 is forced to fail, no action is taken. Other expansion failures are treated as
22544 errors and cause the delivery to be deferred.
22545 If an item ends in *, it will match any header with the given prefix.
22547 Matching headers are omitted from the message as it is transported, as described
22548 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22551 Unlike most options, &%headers_remove%& can be specified multiple times
22552 for a transport; all listed headers are removed.
22554 &*Warning*&: Because of the separate expansion of the list items,
22555 items that contain a list separator must have it doubled.
22556 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22560 .option headers_rewrite transports string unset
22561 .cindex "transport" "header lines; rewriting"
22562 .cindex "rewriting" "at transport time"
22563 This option allows addresses in header lines to be rewritten at transport time,
22564 that is, as the message is being copied to its destination. The contents of the
22565 option are a colon-separated list of rewriting rules. Each rule is in exactly
22566 the same form as one of the general rewriting rules that are applied when a
22567 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22570 headers_rewrite = a@b c@d f : \
22573 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22574 &'w@z'& in all address-bearing header lines. The rules are applied to the
22575 header lines just before they are written out at transport time, so they affect
22576 only those copies of the message that pass through the transport. However, only
22577 the message's original header lines, and any that were added by a system
22578 filter, are rewritten. If a router or transport adds header lines, they are not
22579 affected by this option. These rewriting rules are &'not'& applied to the
22580 envelope. You can change the return path using &%return_path%&, but you cannot
22581 change envelope recipients at this time.
22584 .option home_directory transports string&!! unset
22585 .cindex "transport" "home directory for"
22587 This option specifies a home directory setting for a local transport,
22588 overriding any value that may be set by the router. The home directory is
22589 placed in &$home$& while expanding the transport's private options. It is also
22590 used as the current directory if no current directory is set by the
22591 &%current_directory%& option on the transport or the
22592 &%transport_current_directory%& option on the router. If the expansion fails
22593 for any reason, including forced failure, an error is logged, and delivery is
22597 .option initgroups transports boolean false
22598 .cindex "additional groups"
22599 .cindex "groups" "additional"
22600 .cindex "transport" "group; additional"
22601 If this option is true and the uid for the delivery process is provided by the
22602 transport, the &[initgroups()]& function is called when running the transport
22603 to ensure that any additional groups associated with the uid are set up.
22606 .option max_parallel transports integer&!! unset
22607 .cindex limit "transport parallelism"
22608 .cindex transport "parallel processes"
22609 .cindex transport "concurrency limit"
22610 .cindex "delivery" "parallelism for transport"
22611 If this option is set and expands to an integer greater than zero
22612 it limits the number of concurrent runs of the transport.
22613 The control does not apply to shadow transports.
22615 .cindex "hints database" "transport concurrency control"
22616 Exim implements this control by means of a hints database in which a record is
22617 incremented whenever a transport process is being created. The record
22618 is decremented and possibly removed when the process terminates.
22619 Obviously there is scope for
22620 records to get left lying around if there is a system or program crash. To
22621 guard against this, Exim ignores any records that are more than six hours old.
22623 If you use this option, you should also arrange to delete the
22624 relevant hints database whenever your system reboots. The names of the files
22625 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22626 may be one or two files, depending on the type of DBM in use. The same files
22627 are used for ETRN and smtp transport serialization.
22630 .option message_size_limit transports string&!! 0
22631 .cindex "limit" "message size per transport"
22632 .cindex "size" "of message, limit"
22633 .cindex "transport" "message size; limiting"
22634 This option controls the size of messages passed through the transport. It is
22635 expanded before use; the result of the expansion must be a sequence of decimal
22636 digits, optionally followed by K or M. If the expansion fails for any reason,
22637 including forced failure, or if the result is not of the required form,
22638 delivery is deferred. If the value is greater than zero and the size of a
22639 message exceeds this limit, the address is failed. If there is any chance that
22640 the resulting bounce message could be routed to the same transport, you should
22641 ensure that &%return_size_limit%& is less than the transport's
22642 &%message_size_limit%&, as otherwise the bounce message will fail to get
22647 .option rcpt_include_affixes transports boolean false
22648 .cindex "prefix" "for local part, including in envelope"
22649 .cindex "suffix for local part" "including in envelope"
22650 .cindex "local part" "prefix"
22651 .cindex "local part" "suffix"
22652 When this option is false (the default), and an address that has had any
22653 affixes (prefixes or suffixes) removed from the local part is delivered by any
22654 form of SMTP or LMTP, the affixes are not included. For example, if a router
22657 local_part_prefix = *-
22659 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22662 RCPT TO:<xyz@some.domain>
22664 This is also the case when an ACL-time callout is being used to verify a
22665 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22666 whole local part is included in the RCPT command. This option applies to BSMTP
22667 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22668 &(lmtp)& and &(smtp)& transports.
22671 .option retry_use_local_part transports boolean "see below"
22672 .cindex "hints database" "retry keys"
22673 When a delivery suffers a temporary failure, a retry record is created
22674 in Exim's hints database. For remote deliveries, the key for the retry record
22675 is based on the name and/or IP address of the failing remote host. For local
22676 deliveries, the key is normally the entire address, including both the local
22677 part and the domain. This is suitable for most common cases of local delivery
22678 temporary failure &-- for example, exceeding a mailbox quota should delay only
22679 deliveries to that mailbox, not to the whole domain.
22681 However, in some special cases you may want to treat a temporary local delivery
22682 as a failure associated with the domain, and not with a particular local part.
22683 (For example, if you are storing all mail for some domain in files.) You can do
22684 this by setting &%retry_use_local_part%& false.
22686 For all the local transports, its default value is true. For remote transports,
22687 the default value is false for tidiness, but changing the value has no effect
22688 on a remote transport in the current implementation.
22691 .option return_path transports string&!! unset
22692 .cindex "envelope sender"
22693 .cindex "envelope from"
22694 .cindex "transport" "return path; changing"
22695 .cindex "return path" "changing in transport"
22696 If this option is set, the string is expanded at transport time and replaces
22697 the existing return path (envelope sender) value in the copy of the message
22698 that is being delivered. An empty return path is permitted. This feature is
22699 designed for remote deliveries, where the value of this option is used in the
22700 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22701 only effect is to change the address that is placed in the &'Return-path:'&
22702 header line, if one is added to the message (see the next option).
22704 &*Note:*& A changed return path is not logged unless you add
22705 &%return_path_on_delivery%& to the log selector.
22707 .vindex "&$return_path$&"
22708 The expansion can refer to the existing value via &$return_path$&. This is
22709 either the message's envelope sender, or an address set by the
22710 &%errors_to%& option on a router. If the expansion is forced to fail, no
22711 replacement occurs; if it fails for another reason, delivery is deferred. This
22712 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22713 section &<<SECTverp>>&.
22715 &*Note*&: If a delivery error is detected locally, including the case when a
22716 remote server rejects a message at SMTP time, the bounce message is not sent to
22717 the value of this option. It is sent to the previously set errors address.
22718 This defaults to the incoming sender address, but can be changed by setting
22719 &%errors_to%& in a router.
22723 .option return_path_add transports boolean false
22724 .chindex Return-path:
22725 If this option is true, a &'Return-path:'& header is added to the message.
22726 Although the return path is normally available in the prefix line of BSD
22727 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22728 have easy access to it.
22730 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22731 the delivery SMTP server makes the final delivery"&. This implies that this
22732 header should not be present in incoming messages. Exim has a configuration
22733 option, &%return_path_remove%&, which requests removal of this header from
22734 incoming messages, so that delivered messages can safely be resent to other
22738 .option shadow_condition transports string&!! unset
22739 See &%shadow_transport%& below.
22742 .option shadow_transport transports string unset
22743 .cindex "shadow transport"
22744 .cindex "transport" "shadow"
22745 A local transport may set the &%shadow_transport%& option to the name of
22746 another local transport. Shadow remote transports are not supported.
22748 Whenever a delivery to the main transport succeeds, and either
22749 &%shadow_condition%& is unset, or its expansion does not result in the empty
22750 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22751 passed to the shadow transport, with the same delivery address or addresses. If
22752 expansion fails, no action is taken except that non-forced expansion failures
22753 cause a log line to be written.
22755 The result of the shadow transport is discarded and does not affect the
22756 subsequent processing of the message. Only a single level of shadowing is
22757 provided; the &%shadow_transport%& option is ignored on any transport when it
22758 is running as a shadow. Options concerned with output from pipes are also
22759 ignored. The log line for the successful delivery has an item added on the end,
22762 ST=<shadow transport name>
22764 If the shadow transport did not succeed, the error message is put in
22765 parentheses afterwards. Shadow transports can be used for a number of different
22766 purposes, including keeping more detailed log information than Exim normally
22767 provides, and implementing automatic acknowledgment policies based on message
22768 headers that some sites insist on.
22771 .option transport_filter transports string&!! unset
22772 .cindex "transport" "filter"
22773 .cindex "filter" "transport filter"
22774 This option sets up a filtering (in the Unix shell sense) process for messages
22775 at transport time. It should not be confused with mail filtering as set up by
22776 individual users or via a system filter.
22777 If unset, or expanding to an empty string, no filtering is done.
22779 When the message is about to be written out, the command specified by
22780 &%transport_filter%& is started up in a separate, parallel process, and
22781 the entire message, including the header lines, is passed to it on its standard
22782 input (this in fact is done from a third process, to avoid deadlock). The
22783 command must be specified as an absolute path.
22785 The lines of the message that are written to the transport filter are
22786 terminated by newline (&"\n"&). The message is passed to the filter before any
22787 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22788 lines beginning with a dot, and also before any processing implied by the
22789 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22790 &(pipe)& transports.
22792 The standard error for the filter process is set to the same destination as its
22793 standard output; this is read and written to the message's ultimate
22794 destination. The process that writes the message to the filter, the
22795 filter itself, and the original process that reads the result and delivers it
22796 are all run in parallel, like a shell pipeline.
22798 The filter can perform any transformations it likes, but of course should take
22799 care not to break RFC 2822 syntax. Exim does not check the result, except to
22800 test for a final newline when SMTP is in use. All messages transmitted over
22801 SMTP must end with a newline, so Exim supplies one if it is missing.
22803 .cindex "content scanning" "per user"
22804 A transport filter can be used to provide content-scanning on a per-user basis
22805 at delivery time if the only required effect of the scan is to modify the
22806 message. For example, a content scan could insert a new header line containing
22807 a spam score. This could be interpreted by a filter in the user's MUA. It is
22808 not possible to discard a message at this stage.
22810 .cindex "SIZE" "ESMTP extension"
22811 A problem might arise if the filter increases the size of a message that is
22812 being sent down an SMTP connection. If the receiving SMTP server has indicated
22813 support for the SIZE parameter, Exim will have sent the size of the message
22814 at the start of the SMTP session. If what is actually sent is substantially
22815 more, the server might reject the message. This can be worked round by setting
22816 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22817 additions to the message, or to disable the use of SIZE altogether.
22819 .vindex "&$pipe_addresses$&"
22820 The value of the &%transport_filter%& option is the command string for starting
22821 the filter, which is run directly from Exim, not under a shell. The string is
22822 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22823 Exim breaks it up into arguments and then expands each argument separately (see
22824 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22825 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22826 of arguments, one for each address that applies to this delivery. (This isn't
22827 an ideal name for this feature here, but as it was already implemented for the
22828 &(pipe)& transport, it seemed sensible not to change it.)
22831 .vindex "&$host_address$&"
22832 The expansion variables &$host$& and &$host_address$& are available when the
22833 transport is a remote one. They contain the name and IP address of the host to
22834 which the message is being sent. For example:
22836 transport_filter = /some/directory/transport-filter.pl \
22837 $host $host_address $sender_address $pipe_addresses
22840 Two problems arise if you want to use more complicated expansion items to
22841 generate transport filter commands, both of which due to the fact that the
22842 command is split up &'before'& expansion.
22844 If an expansion item contains white space, you must quote it, so that it is all
22845 part of the same command item. If the entire option setting is one such
22846 expansion item, you have to take care what kind of quoting you use. For
22849 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22851 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22852 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22853 stripped by Exim when it read the option's value. When the value is used, if
22854 the single quotes were missing, the line would be split into two items,
22855 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22856 Exim tried to expand the first one.
22858 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22859 expansion cannot generate multiple arguments, or a command name followed by
22860 arguments. Consider this example:
22862 transport_filter = ${lookup{$host}lsearch{/a/file}\
22863 {$value}{/bin/cat}}
22865 The result of the lookup is interpreted as the name of the command, even
22866 if it contains white space. The simplest way round this is to use a shell:
22868 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22869 {$value}{/bin/cat}}
22873 The filter process is run under the same uid and gid as the normal delivery.
22874 For remote deliveries this is the Exim uid/gid by default. The command should
22875 normally yield a zero return code. Transport filters are not supposed to fail.
22876 A non-zero code is taken to mean that the transport filter encountered some
22877 serious problem. Delivery of the message is deferred; the message remains on
22878 the queue and is tried again later. It is not possible to cause a message to be
22879 bounced from a transport filter.
22881 If a transport filter is set on an autoreply transport, the original message is
22882 passed through the filter as it is being copied into the newly generated
22883 message, which happens if the &%return_message%& option is set.
22886 .option transport_filter_timeout transports time 5m
22887 .cindex "transport" "filter, timeout"
22888 When Exim is reading the output of a transport filter, it applies a timeout
22889 that can be set by this option. Exceeding the timeout is normally treated as a
22890 temporary delivery failure. However, if a transport filter is used with a
22891 &(pipe)& transport, a timeout in the transport filter is treated in the same
22892 way as a timeout in the pipe command itself. By default, a timeout is a hard
22893 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22894 becomes a temporary error.
22897 .option user transports string&!! "Exim user"
22898 .cindex "uid (user id)" "local delivery"
22899 .cindex "transport" "user, specifying"
22900 This option specifies the user under whose uid the delivery process is to be
22901 run, overriding any uid that may have been set by the router. If the user is
22902 given as a name, the uid is looked up from the password data, and the
22903 associated group is taken as the value of the gid to be used if the &%group%&
22906 For deliveries that use local transports, a user and group are normally
22907 specified explicitly or implicitly (for example, as a result of
22908 &%check_local_user%&) by the router or transport.
22910 .cindex "hints database" "access by remote transport"
22911 For remote transports, you should leave this option unset unless you really are
22912 sure you know what you are doing. When a remote transport is running, it needs
22913 to be able to access Exim's hints databases, because each host may have its own
22915 .ecindex IIDgenoptra1
22916 .ecindex IIDgenoptra2
22917 .ecindex IIDgenoptra3
22924 . ////////////////////////////////////////////////////////////////////////////
22925 . ////////////////////////////////////////////////////////////////////////////
22927 .chapter "Address batching in local transports" "CHAPbatching" &&&
22929 .cindex "transport" "local; address batching in"
22930 The only remote transport (&(smtp)&) is normally configured to handle more than
22931 one address at a time, so that when several addresses are routed to the same
22932 remote host, just one copy of the message is sent. Local transports, however,
22933 normally handle one address at a time. That is, a separate instance of the
22934 transport is run for each address that is routed to the transport. A separate
22935 copy of the message is delivered each time.
22937 .cindex "batched local delivery"
22938 .oindex "&%batch_max%&"
22939 .oindex "&%batch_id%&"
22940 In special cases, it may be desirable to handle several addresses at once in a
22941 local transport, for example:
22944 In an &(appendfile)& transport, when storing messages in files for later
22945 delivery by some other means, a single copy of the message with multiple
22946 recipients saves space.
22948 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22949 a single copy saves time, and is the normal way LMTP is expected to work.
22951 In a &(pipe)& transport, when passing the message
22952 to a scanner program or
22953 to some other delivery mechanism such as UUCP, multiple recipients may be
22957 These three local transports all have the same options for controlling multiple
22958 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22959 repeating the information for each transport, these options are described here.
22961 The &%batch_max%& option specifies the maximum number of addresses that can be
22962 delivered together in a single run of the transport. Its default value is one
22963 (no batching). When more than one address is routed to a transport that has a
22964 &%batch_max%& value greater than one, the addresses are delivered in a batch
22965 (that is, in a single run of the transport with multiple recipients), subject
22966 to certain conditions:
22969 .vindex "&$local_part$&"
22970 If any of the transport's options contain a reference to &$local_part$&, no
22971 batching is possible.
22973 .vindex "&$domain$&"
22974 If any of the transport's options contain a reference to &$domain$&, only
22975 addresses with the same domain are batched.
22977 .cindex "customizing" "batching condition"
22978 If &%batch_id%& is set, it is expanded for each address, and only those
22979 addresses with the same expanded value are batched. This allows you to specify
22980 customized batching conditions. Failure of the expansion for any reason,
22981 including forced failure, disables batching, but it does not stop the delivery
22984 Batched addresses must also have the same errors address (where to send
22985 delivery errors), the same header additions and removals, the same user and
22986 group for the transport, and if a host list is present, the first host must
22990 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22991 both when the file or pipe command is specified in the transport, and when it
22992 is specified by a &(redirect)& router, but all the batched addresses must of
22993 course be routed to the same file or pipe command. These two transports have an
22994 option called &%use_bsmtp%&, which causes them to deliver the message in
22995 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22996 &%check_string%& and &%escape_string%& options are forced to the values
22999 escape_string = ".."
23001 when batched SMTP is in use. A full description of the batch SMTP mechanism is
23002 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
23003 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
23005 .cindex "&'Envelope-to:'& header line"
23006 If the generic &%envelope_to_add%& option is set for a batching transport, the
23007 &'Envelope-to:'& header that is added to the message contains all the addresses
23008 that are being processed together. If you are using a batching &(appendfile)&
23009 transport without &%use_bsmtp%&, the only way to preserve the recipient
23010 addresses is to set the &%envelope_to_add%& option.
23012 .cindex "&(pipe)& transport" "with multiple addresses"
23013 .vindex "&$pipe_addresses$&"
23014 If you are using a &(pipe)& transport without BSMTP, and setting the
23015 transport's &%command%& option, you can include &$pipe_addresses$& as part of
23016 the command. This is not a true variable; it is a bit of magic that causes each
23017 of the recipient addresses to be inserted into the command as a separate
23018 argument. This provides a way of accessing all the addresses that are being
23019 delivered in the batch. &*Note:*& This is not possible for pipe commands that
23020 are specified by a &(redirect)& router.
23025 . ////////////////////////////////////////////////////////////////////////////
23026 . ////////////////////////////////////////////////////////////////////////////
23028 .chapter "The appendfile transport" "CHAPappendfile"
23029 .scindex IIDapptra1 "&(appendfile)& transport"
23030 .scindex IIDapptra2 "transports" "&(appendfile)&"
23031 .cindex "directory creation"
23032 .cindex "creating directories"
23033 The &(appendfile)& transport delivers a message by appending it to an existing
23034 file, or by creating an entirely new file in a specified directory. Single
23035 files to which messages are appended can be in the traditional Unix mailbox
23036 format, or optionally in the MBX format supported by the Pine MUA and
23037 University of Washington IMAP daemon, &'inter alia'&. When each message is
23038 being delivered as a separate file, &"maildir"& format can optionally be used
23039 to give added protection against failures that happen part-way through the
23040 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23041 supported. For all file formats, Exim attempts to create as many levels of
23042 directory as necessary, provided that &%create_directory%& is set.
23044 The code for the optional formats is not included in the Exim binary by
23045 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23046 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23049 .cindex "quota" "system"
23050 Exim recognizes system quota errors, and generates an appropriate message. Exim
23051 also supports its own quota control within the transport, for use when the
23052 system facility is unavailable or cannot be used for some reason.
23054 If there is an error while appending to a file (for example, quota exceeded or
23055 partition filled), Exim attempts to reset the file's length and last
23056 modification time back to what they were before. If there is an error while
23057 creating an entirely new file, the new file is removed.
23059 Before appending to a file, a number of security checks are made, and the
23060 file is locked. A detailed description is given below, after the list of
23063 The &(appendfile)& transport is most commonly used for local deliveries to
23064 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23065 putting messages into files for remote delivery by some means other than Exim.
23066 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23071 .section "The file and directory options" "SECTfildiropt"
23072 The &%file%& option specifies a single file, to which the message is appended;
23073 the &%directory%& option specifies a directory, in which a new file containing
23074 the message is created. Only one of these two options can be set, and for
23075 normal deliveries to mailboxes, one of them &'must'& be set.
23077 .vindex "&$address_file$&"
23078 .vindex "&$local_part$&"
23079 However, &(appendfile)& is also used for delivering messages to files or
23080 directories whose names (or parts of names) are obtained from alias,
23081 forwarding, or filtering operations (for example, a &%save%& command in a
23082 user's Exim filter). When such a transport is running, &$local_part$& contains
23083 the local part that was aliased or forwarded, and &$address_file$& contains the
23084 name (or partial name) of the file or directory generated by the redirection
23085 operation. There are two cases:
23088 If neither &%file%& nor &%directory%& is set, the redirection operation
23089 must specify an absolute path (one that begins with &`/`&). This is the most
23090 common case when users with local accounts use filtering to sort mail into
23091 different folders. See for example, the &(address_file)& transport in the
23092 default configuration. If the path ends with a slash, it is assumed to be the
23093 name of a directory. A delivery to a directory can also be forced by setting
23094 &%maildir_format%& or &%mailstore_format%&.
23096 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23097 used to determine the file or directory name for the delivery. Normally, the
23098 contents of &$address_file$& are used in some way in the string expansion.
23100 If the &%create_file%& option is set to a path which
23101 matches (see the option definition below for details)
23102 a file or directory name
23103 for the delivery, that name becomes de-tainted.
23105 .cindex "tainted data" "in filenames"
23106 .cindex appendfile "tainted data"
23107 Tainted data may not be used for a file or directory name.
23108 This means that, for instance, &$local_part$& cannot be used directly
23109 as a component of a path. It can however be used as the key for a lookup
23110 which returns a path (or component).
23113 .cindex "Sieve filter" "configuring &(appendfile)&"
23114 .cindex "Sieve filter" "relative mailbox path handling"
23115 As an example of the second case, consider an environment where users do not
23116 have home directories. They may be permitted to use Exim filter commands of the
23121 or Sieve filter commands of the form:
23123 require "fileinto";
23124 fileinto "folder23";
23126 In this situation, the expansion of &%file%& or &%directory%& in the transport
23127 must transform the relative path into an appropriate absolute filename. In the
23128 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23129 is used as a result of a &"keep"& action in the filter. This example shows one
23130 way of handling this requirement:
23132 file = ${if eq{$address_file}{inbox} \
23133 {/var/mail/$local_part_data} \
23134 {${if eq{${substr_0_1:$address_file}}{/} \
23136 {$home/mail/$address_file} \
23140 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23141 location, absolute paths are used without change, and other folders are in the
23142 &_mail_& directory within the home directory.
23144 &*Note 1*&: While processing an Exim filter, a relative path such as
23145 &_folder23_& is turned into an absolute path if a home directory is known to
23146 the router. In particular, this is the case if &%check_local_user%& is set. If
23147 you want to prevent this happening at routing time, you can set
23148 &%router_home_directory%& empty. This forces the router to pass the relative
23149 path to the transport.
23151 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23152 the &%file%& or &%directory%& option is still used if it is set.
23157 .section "Private options for appendfile" "SECID134"
23158 .cindex "options" "&(appendfile)& transport"
23162 .option allow_fifo appendfile boolean false
23163 .cindex "fifo (named pipe)"
23164 .cindex "named pipe (fifo)"
23165 .cindex "pipe" "named (fifo)"
23166 Setting this option permits delivery to named pipes (FIFOs) as well as to
23167 regular files. If no process is reading the named pipe at delivery time, the
23168 delivery is deferred.
23171 .option allow_symlink appendfile boolean false
23172 .cindex "symbolic link" "to mailbox"
23173 .cindex "mailbox" "symbolic link"
23174 By default, &(appendfile)& will not deliver if the path name for the file is
23175 that of a symbolic link. Setting this option relaxes that constraint, but there
23176 are security issues involved in the use of symbolic links. Be sure you know
23177 what you are doing if you set this. Details of exactly what this option affects
23178 are included in the discussion which follows this list of options.
23181 .option batch_id appendfile string&!! unset
23182 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23183 However, batching is automatically disabled for &(appendfile)& deliveries that
23184 happen as a result of forwarding or aliasing or other redirection directly to a
23188 .option batch_max appendfile integer 1
23189 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23192 .option check_group appendfile boolean false
23193 When this option is set, the group owner of the file defined by the &%file%&
23194 option is checked to see that it is the same as the group under which the
23195 delivery process is running. The default setting is false because the default
23196 file mode is 0600, which means that the group is irrelevant.
23199 .option check_owner appendfile boolean true
23200 When this option is set, the owner of the file defined by the &%file%& option
23201 is checked to ensure that it is the same as the user under which the delivery
23202 process is running.
23205 .option check_string appendfile string "see below"
23206 .cindex "&""From""& line"
23207 As &(appendfile)& writes the message, the start of each line is tested for
23208 matching &%check_string%&, and if it does, the initial matching characters are
23209 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23210 a literal string, not a regular expression, and the case of any letters it
23211 contains is significant.
23213 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23214 are forced to &"."& and &".."& respectively, and any settings in the
23215 configuration are ignored. Otherwise, they default to &"From&~"& and
23216 &">From&~"& when the &%file%& option is set, and unset when any of the
23217 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23219 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23220 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23221 &"From&~"& indicates the start of a new message. All four options need changing
23222 if another format is used. For example, to deliver to mailboxes in MMDF format:
23223 .cindex "MMDF format mailbox"
23224 .cindex "mailbox" "MMDF format"
23226 check_string = "\1\1\1\1\n"
23227 escape_string = "\1\1\1\1 \n"
23228 message_prefix = "\1\1\1\1\n"
23229 message_suffix = "\1\1\1\1\n"
23231 .option create_directory appendfile boolean true
23232 .cindex "directory creation"
23233 When this option is true, Exim attempts to create any missing superior
23234 directories for the file that it is about to write. A created directory's mode
23235 is given by the &%directory_mode%& option.
23237 The group ownership of a newly created directory is highly dependent on the
23238 operating system (and possibly the file system) that is being used. For
23239 example, in Solaris, if the parent directory has the setgid bit set, its group
23240 is propagated to the child; if not, the currently set group is used. However,
23241 in FreeBSD, the parent's group is always used.
23245 .option create_file appendfile string anywhere
23246 This option constrains the location of files and directories that are created
23247 by this transport. It applies to files defined by the &%file%& option and
23248 directories defined by the &%directory%& option. In the case of maildir
23249 delivery, it applies to the top level directory, not the maildir directories
23253 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23254 &"belowhome"&, or to an absolute path.
23257 In the second and third cases, a home directory must have been
23258 set for the transport, and the file or directory being created must
23260 The "belowhome" checking additionally checks for attempts to use "../"
23261 to evade the testing.
23262 This option is not useful when an explicit filename is
23263 given for normal mailbox deliveries. It is intended for the case when filenames
23264 are generated from users' &_.forward_& files. These are usually handled
23265 by an &(appendfile)& transport called &%address_file%&. See also
23266 &%file_must_exist%&.
23269 In the fourth case,
23270 the value given for this option must be an absolute path for an
23271 existing directory.
23272 The value is used for checking instead of a home directory;
23273 checking is done in "belowhome" mode.
23275 .cindex "tainted data" "de-tainting"
23276 If "belowhome" checking is used, the file or directory path
23277 becomes de-tainted.
23281 .option directory appendfile string&!! unset
23282 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23283 or &%directory%& must be set, unless the delivery is the direct result of a
23284 redirection (see section &<<SECTfildiropt>>&).
23286 When &%directory%& is set, the string is expanded, and the message is delivered
23287 into a new file or files in or below the given directory, instead of being
23288 appended to a single mailbox file. A number of different formats are provided
23289 (see &%maildir_format%& and &%mailstore_format%&), and see section
23290 &<<SECTopdir>>& for further details of this form of delivery.
23293 The result of expansion must not be tainted, unless the &%create_file%& option
23298 .option directory_file appendfile string&!! "see below"
23300 .vindex "&$inode$&"
23301 When &%directory%& is set, but neither &%maildir_format%& nor
23302 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23303 whose name is obtained by expanding this string. The default value is:
23305 q${base62:$tod_epoch}-$inode
23307 This generates a unique name from the current time, in base 62 form, and the
23308 inode of the file. The variable &$inode$& is available only when expanding this
23312 .option directory_mode appendfile "octal integer" 0700
23313 If &(appendfile)& creates any directories as a result of the
23314 &%create_directory%& option, their mode is specified by this option.
23317 .option escape_string appendfile string "see description"
23318 See &%check_string%& above.
23321 .option file appendfile string&!! unset
23322 This option is mutually exclusive with the &%directory%& option, but one of
23323 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23324 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23325 specifies a single file, to which the message is appended. One or more of
23326 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23330 The result of expansion must not be tainted, unless the &%create_file%& option
23334 .cindex "NFS" "lock file"
23335 .cindex "locking files"
23336 .cindex "lock files"
23337 If you are using more than one host to deliver over NFS into the same
23338 mailboxes, you should always use lock files.
23340 The string value is expanded for each delivery, and must yield an absolute
23341 path. The most common settings of this option are variations on one of these
23344 file = /var/spool/mail/$local_part_data
23345 file = /home/$local_part_data/inbox
23348 .cindex "&""sticky""& bit"
23349 In the first example, all deliveries are done into the same directory. If Exim
23350 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23351 create a file in the directory, so the &"sticky"& bit must be turned on for
23352 deliveries to be possible, or alternatively the &%group%& option can be used to
23353 run the delivery under a group id which has write access to the directory.
23357 .option file_format appendfile string unset
23358 .cindex "file" "mailbox; checking existing format"
23359 This option requests the transport to check the format of an existing file
23360 before adding to it. The check consists of matching a specific string at the
23361 start of the file. The value of the option consists of an even number of
23362 colon-separated strings. The first of each pair is the test string, and the
23363 second is the name of a transport. If the transport associated with a matched
23364 string is not the current transport, control is passed over to the other
23365 transport. For example, suppose the standard &(local_delivery)& transport has
23368 file_format = "From : local_delivery :\
23369 \1\1\1\1\n : local_mmdf_delivery"
23371 Mailboxes that begin with &"From"& are still handled by this transport, but if
23372 a mailbox begins with four binary ones followed by a newline, control is passed
23373 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23374 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23375 is assumed to match the current transport. If the start of a mailbox doesn't
23376 match any string, or if the transport named for a given string is not defined,
23377 delivery is deferred.
23380 .option file_must_exist appendfile boolean false
23381 If this option is true, the file specified by the &%file%& option must exist.
23382 A temporary error occurs if it does not, causing delivery to be deferred.
23383 If this option is false, the file is created if it does not exist.
23386 .option lock_fcntl_timeout appendfile time 0s
23387 .cindex "timeout" "mailbox locking"
23388 .cindex "mailbox" "locking, blocking and non-blocking"
23389 .cindex "locking files"
23390 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23391 when locking an open mailbox file. If the call fails, the delivery process
23392 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23393 Non-blocking calls are used so that the file is not kept open during the wait
23394 for the lock; the reason for this is to make it as safe as possible for
23395 deliveries over NFS in the case when processes might be accessing an NFS
23396 mailbox without using a lock file. This should not be done, but
23397 misunderstandings and hence misconfigurations are not unknown.
23399 On a busy system, however, the performance of a non-blocking lock approach is
23400 not as good as using a blocking lock with a timeout. In this case, the waiting
23401 is done inside the system call, and Exim's delivery process acquires the lock
23402 and can proceed as soon as the previous lock holder releases it.
23404 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23405 timeout, are used. There may still be some retrying: the maximum number of
23408 (lock_retries * lock_interval) / lock_fcntl_timeout
23410 rounded up to the next whole number. In other words, the total time during
23411 which &(appendfile)& is trying to get a lock is roughly the same, unless
23412 &%lock_fcntl_timeout%& is set very large.
23414 You should consider setting this option if you are getting a lot of delayed
23415 local deliveries because of errors of the form
23417 failed to lock mailbox /some/file (fcntl)
23420 .option lock_flock_timeout appendfile time 0s
23421 This timeout applies to file locking when using &[flock()]& (see
23422 &%use_flock%&); the timeout operates in a similar manner to
23423 &%lock_fcntl_timeout%&.
23426 .option lock_interval appendfile time 3s
23427 This specifies the time to wait between attempts to lock the file. See below
23428 for details of locking.
23431 .option lock_retries appendfile integer 10
23432 This specifies the maximum number of attempts to lock the file. A value of zero
23433 is treated as 1. See below for details of locking.
23436 .option lockfile_mode appendfile "octal integer" 0600
23437 This specifies the mode of the created lock file, when a lock file is being
23438 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23441 .option lockfile_timeout appendfile time 30m
23442 .cindex "timeout" "mailbox locking"
23443 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23444 exists and is older than this value, it is assumed to have been left behind by
23445 accident, and Exim attempts to remove it.
23448 .option mailbox_filecount appendfile string&!! unset
23449 .cindex "mailbox" "specifying size of"
23450 .cindex "size" "of mailbox"
23451 If this option is set, it is expanded, and the result is taken as the current
23452 number of files in the mailbox. It must be a decimal number, optionally
23453 followed by K or M. This provides a way of obtaining this information from an
23454 external source that maintains the data.
23457 .option mailbox_size appendfile string&!! unset
23458 .cindex "mailbox" "specifying size of"
23459 .cindex "size" "of mailbox"
23460 If this option is set, it is expanded, and the result is taken as the current
23461 size the mailbox. It must be a decimal number, optionally followed by K or M.
23462 This provides a way of obtaining this information from an external source that
23463 maintains the data. This is likely to be helpful for maildir deliveries where
23464 it is computationally expensive to compute the size of a mailbox.
23468 .option maildir_format appendfile boolean false
23469 .cindex "maildir format" "specifying"
23470 If this option is set with the &%directory%& option, the delivery is into a new
23471 file, in the &"maildir"& format that is used by other mail software. When the
23472 transport is activated directly from a &(redirect)& router (for example, the
23473 &(address_file)& transport in the default configuration), setting
23474 &%maildir_format%& causes the path received from the router to be treated as a
23475 directory, whether or not it ends with &`/`&. This option is available only if
23476 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23477 &<<SECTmaildirdelivery>>& below for further details.
23480 .option maildir_quota_directory_regex appendfile string "See below"
23481 .cindex "maildir format" "quota; directories included in"
23482 .cindex "quota" "maildir; directories included in"
23483 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23484 a regular expression for specifying directories, relative to the quota
23485 directory (see &%quota_directory%&), that should be included in the quota
23486 calculation. The default value is:
23488 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23490 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23491 (directories whose names begin with a dot). If you want to exclude the
23493 folder from the count (as some sites do), you need to change this setting to
23495 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23497 This uses a negative lookahead in the regular expression to exclude the
23498 directory whose name is &_.Trash_&. When a directory is excluded from quota
23499 calculations, quota processing is bypassed for any messages that are delivered
23500 directly into that directory.
23503 .option maildir_retries appendfile integer 10
23504 This option specifies the number of times to retry when writing a file in
23505 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23508 .option maildir_tag appendfile string&!! unset
23509 This option applies only to deliveries in maildir format, and is described in
23510 section &<<SECTmaildirdelivery>>& below.
23513 .option maildir_use_size_file appendfile&!! boolean false
23514 .cindex "maildir format" "&_maildirsize_& file"
23515 The result of string expansion for this option must be a valid boolean value.
23516 If it is true, it enables support for &_maildirsize_& files. Exim
23517 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23518 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23519 value is zero. See &%maildir_quota_directory_regex%& above and section
23520 &<<SECTmaildirdelivery>>& below for further details.
23522 .option maildirfolder_create_regex appendfile string unset
23523 .cindex "maildir format" "&_maildirfolder_& file"
23524 .cindex "&_maildirfolder_&, creating"
23525 The value of this option is a regular expression. If it is unset, it has no
23526 effect. Otherwise, before a maildir delivery takes place, the pattern is
23527 matched against the name of the maildir directory, that is, the directory
23528 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23529 delivery. If there is a match, Exim checks for the existence of a file called
23530 &_maildirfolder_& in the directory, and creates it if it does not exist.
23531 See section &<<SECTmaildirdelivery>>& for more details.
23534 .option mailstore_format appendfile boolean false
23535 .cindex "mailstore format" "specifying"
23536 If this option is set with the &%directory%& option, the delivery is into two
23537 new files in &"mailstore"& format. The option is available only if
23538 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23539 below for further details.
23542 .option mailstore_prefix appendfile string&!! unset
23543 This option applies only to deliveries in mailstore format, and is described in
23544 section &<<SECTopdir>>& below.
23547 .option mailstore_suffix appendfile string&!! unset
23548 This option applies only to deliveries in mailstore format, and is described in
23549 section &<<SECTopdir>>& below.
23552 .option mbx_format appendfile boolean false
23553 .cindex "locking files"
23554 .cindex "file" "locking"
23555 .cindex "file" "MBX format"
23556 .cindex "MBX format, specifying"
23557 This option is available only if Exim has been compiled with SUPPORT_MBX
23558 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23559 the message is appended to the mailbox file in MBX format instead of
23560 traditional Unix format. This format is supported by Pine4 and its associated
23561 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23563 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23564 automatically changed by the use of &%mbx_format%&. They should normally be set
23565 empty when using MBX format, so this option almost always appears in this
23572 If none of the locking options are mentioned in the configuration,
23573 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23574 is possible to specify the other kinds of locking with &%mbx_format%&, but
23575 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23576 interworks with &'c-client'&, providing for shared access to the mailbox. It
23577 should not be used if any program that does not use this form of locking is
23578 going to access the mailbox, nor should it be used if the mailbox file is NFS
23579 mounted, because it works only when the mailbox is accessed from a single host.
23581 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23582 the standard version of &'c-client'&, because as long as it has a mailbox open
23583 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23584 append messages to it.
23587 .option message_prefix appendfile string&!! "see below"
23588 .cindex "&""From""& line"
23589 The string specified here is expanded and output at the start of every message.
23590 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23591 in which case it is:
23593 message_prefix = "From ${if def:return_path{$return_path}\
23594 {MAILER-DAEMON}} $tod_bsdinbox\n"
23596 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23597 &`\n`& to &`\r\n`& in &%message_prefix%&.
23599 .option message_suffix appendfile string&!! "see below"
23600 The string specified here is expanded and output at the end of every message.
23601 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23602 in which case it is a single newline character. The suffix can be suppressed by
23607 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23608 &`\n`& to &`\r\n`& in &%message_suffix%&.
23610 .option mode appendfile "octal integer" 0600
23611 If the output file is created, it is given this mode. If it already exists and
23612 has wider permissions, they are reduced to this mode. If it has narrower
23613 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23614 if the delivery is the result of a &%save%& command in a filter file specifying
23615 a particular mode, the mode of the output file is always forced to take that
23616 value, and this option is ignored.
23619 .option mode_fail_narrower appendfile boolean true
23620 This option applies in the case when an existing mailbox file has a narrower
23621 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23622 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23623 continues with the delivery attempt, using the existing mode of the file.
23626 .option notify_comsat appendfile boolean false
23627 If this option is true, the &'comsat'& daemon is notified after every
23628 successful delivery to a user mailbox. This is the daemon that notifies logged
23629 on users about incoming mail.
23632 .option quota appendfile string&!! unset
23633 .cindex "quota" "imposed by Exim"
23634 This option imposes a limit on the size of the file to which Exim is appending,
23635 or to the total space used in the directory tree when the &%directory%& option
23636 is set. In the latter case, computation of the space used is expensive, because
23637 all the files in the directory (and any sub-directories) have to be
23638 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23639 &%maildir_use_size_file%& for ways to avoid this in environments where users
23640 have no shell access to their mailboxes).
23642 As there is no interlock against two simultaneous deliveries into a
23643 multi-file mailbox, it is possible for the quota to be overrun in this case.
23644 For single-file mailboxes, of course, an interlock is a necessity.
23646 A file's size is taken as its &'used'& value. Because of blocking effects, this
23647 may be a lot less than the actual amount of disk space allocated to the file.
23648 If the sizes of a number of files are being added up, the rounding effect can
23649 become quite noticeable, especially on systems that have large block sizes.
23650 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23651 the obvious value which users understand most easily.
23653 The value of the option is expanded, and must then be a numerical value
23654 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23655 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23656 and further option modifiers. If Exim is running on a system with
23657 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23660 The option modifier &%no_check%& can be used to force delivery even if the over
23661 quota condition is met. The quota gets updated as usual.
23663 &*Note*&: A value of zero is interpreted as &"no quota"&.
23665 The expansion happens while Exim is running as root, before it changes uid for
23666 the delivery. This means that files that are inaccessible to the end user can
23667 be used to hold quota values that are looked up in the expansion. When delivery
23668 fails because this quota is exceeded, the handling of the error is as for
23669 system quota failures.
23671 By default, Exim's quota checking mimics system quotas, and restricts the
23672 mailbox to the specified maximum size, though the value is not accurate to the
23673 last byte, owing to separator lines and additional headers that may get added
23674 during message delivery. When a mailbox is nearly full, large messages may get
23675 refused even though small ones are accepted, because the size of the current
23676 message is added to the quota when the check is made. This behaviour can be
23677 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23678 for exceeding the quota does not include the current message. Thus, deliveries
23679 continue until the quota has been exceeded; thereafter, no further messages are
23680 delivered. See also &%quota_warn_threshold%&.
23683 .option quota_directory appendfile string&!! unset
23684 This option defines the directory to check for quota purposes when delivering
23685 into individual files. The default is the delivery directory, or, if a file
23686 called &_maildirfolder_& exists in a maildir directory, the parent of the
23687 delivery directory.
23690 .option quota_filecount appendfile string&!! 0
23691 This option applies when the &%directory%& option is set. It limits the total
23692 number of files in the directory (compare the inode limit in system quotas). It
23693 can only be used if &%quota%& is also set. The value is expanded; an expansion
23694 failure causes delivery to be deferred. A value of zero is interpreted as
23697 The option modifier &%no_check%& can be used to force delivery even if the over
23698 quota condition is met. The quota gets updated as usual.
23700 .option quota_is_inclusive appendfile boolean true
23701 See &%quota%& above.
23704 .option quota_size_regex appendfile string unset
23705 This option applies when one of the delivery modes that writes a separate file
23706 for each message is being used. When Exim wants to find the size of one of
23707 these files in order to test the quota, it first checks &%quota_size_regex%&.
23708 If this is set to a regular expression that matches the filename, and it
23709 captures one string, that string is interpreted as a representation of the
23710 file's size. The value of &%quota_size_regex%& is not expanded.
23712 This feature is useful only when users have no shell access to their mailboxes
23713 &-- otherwise they could defeat the quota simply by renaming the files. This
23714 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23715 the file length to the filename. For example:
23717 maildir_tag = ,S=$message_size
23718 quota_size_regex = ,S=(\d+)
23720 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23721 number of lines in the message.
23723 The regular expression should not assume that the length is at the end of the
23724 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23725 sometimes add other information onto the ends of message filenames.
23727 Section &<<SECID136>>& contains further information.
23729 This option should not be used when other message-handling software
23730 may duplicate messages by making hardlinks to the files. When that is done Exim
23731 will count the message size once for each filename, in contrast with the actual
23732 disk usage. When the option is not set, calculating total usage requires
23733 a system-call per file to get the size; the number of links is then available also
23734 as is used to adjust the effective size.
23737 .option quota_warn_message appendfile string&!! "see below"
23738 See below for the use of this option. If it is not set when
23739 &%quota_warn_threshold%& is set, it defaults to
23741 quota_warn_message = "\
23742 To: $local_part@$domain\n\
23743 Subject: Your mailbox\n\n\
23744 This message is automatically created \
23745 by mail delivery software.\n\n\
23746 The size of your mailbox has exceeded \
23747 a warning threshold that is\n\
23748 set by the system administrator.\n"
23752 .option quota_warn_threshold appendfile string&!! 0
23753 .cindex "quota" "warning threshold"
23754 .cindex "mailbox" "size warning"
23755 .cindex "size" "of mailbox"
23756 This option is expanded in the same way as &%quota%& (see above). If the
23757 resulting value is greater than zero, and delivery of the message causes the
23758 size of the file or total space in the directory tree to cross the given
23759 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23760 may be specified as a percentage of it by following the value with a percent
23764 quota_warn_threshold = 75%
23766 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23767 percent sign is ignored.
23769 The warning message itself is specified by the &%quota_warn_message%& option,
23770 and it must start with a &'To:'& header line containing the recipient(s) of the
23771 warning message. These do not necessarily have to include the recipient(s) of
23772 the original message. A &'Subject:'& line should also normally be supplied. You
23773 can include any other header lines that you want. If you do not include a
23774 &'From:'& line, the default is:
23776 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23778 .oindex &%errors_reply_to%&
23779 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23782 The &%quota%& option does not have to be set in order to use this option; they
23783 are independent of one another except when the threshold is specified as a
23787 .option use_bsmtp appendfile boolean false
23788 .cindex "envelope from"
23789 .cindex "envelope sender"
23790 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23791 format, with the envelope sender and recipient(s) included as SMTP commands. If
23792 you want to include a leading HELO command with such messages, you can do
23793 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23794 for details of batch SMTP.
23797 .option use_crlf appendfile boolean false
23798 .cindex "carriage return"
23800 This option causes lines to be terminated with the two-character CRLF sequence
23801 (carriage return, linefeed) instead of just a linefeed character. In the case
23802 of batched SMTP, the byte sequence written to the file is then an exact image
23803 of what would be sent down a real SMTP connection.
23805 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23806 (which are used to supply the traditional &"From&~"& and blank line separators
23807 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23808 carriage return characters if these are needed. In cases where these options
23809 have non-empty defaults, the values end with a single linefeed, so they must be
23810 changed to end with &`\r\n`& if &%use_crlf%& is set.
23813 .option use_fcntl_lock appendfile boolean "see below"
23814 This option controls the use of the &[fcntl()]& function to lock a file for
23815 exclusive use when a message is being appended. It is set by default unless
23816 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23817 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23818 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23821 .option use_flock_lock appendfile boolean false
23822 This option is provided to support the use of &[flock()]& for file locking, for
23823 the few situations where it is needed. Most modern operating systems support
23824 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23825 each other. Exim uses &[fcntl()]& locking by default.
23827 This option is required only if you are using an operating system where
23828 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23829 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23830 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23832 .cindex "Solaris" "&[flock()]& support"
23833 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23834 have it (and some, I think, provide a not quite right version built on top of
23835 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23836 the ability to use it, and any attempt to do so will cause a configuration
23839 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23840 is just being mapped onto &[fcntl()]& by the OS).
23843 .option use_lockfile appendfile boolean "see below"
23844 If this option is turned off, Exim does not attempt to create a lock file when
23845 appending to a mailbox file. In this situation, the only locking is by
23846 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23847 sure that every MUA that is ever going to look at your users' mailboxes uses
23848 &[fcntl()]& rather than a lock file, and even then only when you are not
23849 delivering over NFS from more than one host.
23851 .cindex "NFS" "lock file"
23852 In order to append to an NFS file safely from more than one host, it is
23853 necessary to take out a lock &'before'& opening the file, and the lock file
23854 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23857 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23858 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23859 except when &%mbx_format%& is set.
23862 .option use_mbx_lock appendfile boolean "see below"
23863 This option is available only if Exim has been compiled with SUPPORT_MBX
23864 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23865 locking rules be used. It is set by default if &%mbx_format%& is set and none
23866 of the locking options are mentioned in the configuration. The locking rules
23867 are the same as are used by the &'c-client'& library that underlies Pine and
23868 the IMAP4 and POP daemons that come with it (see the discussion below). The
23869 rules allow for shared access to the mailbox. However, this kind of locking
23870 does not work when the mailbox is NFS mounted.
23872 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23873 &%use_flock_lock%& to control what kind of locking is used in implementing the
23874 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23875 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23880 .section "Operational details for appending" "SECTopappend"
23881 .cindex "appending to a file"
23882 .cindex "file" "appending"
23883 Before appending to a file, the following preparations are made:
23886 If the name of the file is &_/dev/null_&, no action is taken, and a success
23890 .cindex "directory creation"
23891 If any directories on the file's path are missing, Exim creates them if the
23892 &%create_directory%& option is set. A created directory's mode is given by the
23893 &%directory_mode%& option.
23896 If &%file_format%& is set, the format of an existing file is checked. If this
23897 indicates that a different transport should be used, control is passed to that
23901 .cindex "file" "locking"
23902 .cindex "locking files"
23903 .cindex "NFS" "lock file"
23904 If &%use_lockfile%& is set, a lock file is built in a way that will work
23905 reliably over NFS, as follows:
23908 Create a &"hitching post"& file whose name is that of the lock file with the
23909 current time, primary host name, and process id added, by opening for writing
23910 as a new file. If this fails with an access error, delivery is deferred.
23912 Close the hitching post file, and hard link it to the lock filename.
23914 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23915 Unlink the hitching post name.
23917 Otherwise, use &[stat()]& to get information about the hitching post file, and
23918 then unlink hitching post name. If the number of links is exactly two, creation
23919 of the lock file succeeded but something (for example, an NFS server crash and
23920 restart) caused this fact not to be communicated to the &[link()]& call.
23922 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23923 up to &%lock_retries%& times. However, since any program that writes to a
23924 mailbox should complete its task very quickly, it is reasonable to time out old
23925 lock files that are normally the result of user agent and system crashes. If an
23926 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23927 it before trying again.
23931 A call is made to &[lstat()]& to discover whether the main file exists, and if
23932 so, what its characteristics are. If &[lstat()]& fails for any reason other
23933 than non-existence, delivery is deferred.
23936 .cindex "symbolic link" "to mailbox"
23937 .cindex "mailbox" "symbolic link"
23938 If the file does exist and is a symbolic link, delivery is deferred, unless the
23939 &%allow_symlink%& option is set, in which case the ownership of the link is
23940 checked, and then &[stat()]& is called to find out about the real file, which
23941 is then subjected to the checks below. The check on the top-level link
23942 ownership prevents one user creating a link for another's mailbox in a sticky
23943 directory, though allowing symbolic links in this case is definitely not a good
23944 idea. If there is a chain of symbolic links, the intermediate ones are not
23948 If the file already exists but is not a regular file, or if the file's owner
23949 and group (if the group is being checked &-- see &%check_group%& above) are
23950 different from the user and group under which the delivery is running,
23951 delivery is deferred.
23954 If the file's permissions are more generous than specified, they are reduced.
23955 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23956 is set false, in which case the delivery is tried using the existing
23960 The file's inode number is saved, and the file is then opened for appending.
23961 If this fails because the file has vanished, &(appendfile)& behaves as if it
23962 hadn't existed (see below). For any other failures, delivery is deferred.
23965 If the file is opened successfully, check that the inode number hasn't
23966 changed, that it is still a regular file, and that the owner and permissions
23967 have not changed. If anything is wrong, defer delivery and freeze the message.
23970 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23971 option is set. Otherwise, check that the file is being created in a permitted
23972 directory if the &%create_file%& option is set (deferring on failure), and then
23973 open for writing as a new file, with the O_EXCL and O_CREAT options,
23974 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23975 set). In this case, which can happen if the link points to a non-existent file,
23976 the file is opened for writing using O_CREAT but not O_EXCL, because
23977 that prevents link following.
23980 .cindex "loop" "while file testing"
23981 If opening fails because the file exists, obey the tests given above for
23982 existing files. However, to avoid looping in a situation where the file is
23983 being continuously created and destroyed, the exists/not-exists loop is broken
23984 after 10 repetitions, and the message is then frozen.
23987 If opening fails with any other error, defer delivery.
23990 .cindex "file" "locking"
23991 .cindex "locking files"
23992 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23993 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23994 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23995 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23996 file, and an exclusive lock on the file whose name is
23998 /tmp/.<device-number>.<inode-number>
24000 using the device and inode numbers of the open mailbox file, in accordance with
24001 the MBX locking rules. This file is created with a mode that is specified by
24002 the &%lockfile_mode%& option.
24004 If Exim fails to lock the file, there are two possible courses of action,
24005 depending on the value of the locking timeout. This is obtained from
24006 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
24008 If the timeout value is zero, the file is closed, Exim waits for
24009 &%lock_interval%&, and then goes back and re-opens the file as above and tries
24010 to lock it again. This happens up to &%lock_retries%& times, after which the
24011 delivery is deferred.
24013 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
24014 &[flock()]& are used (with the given timeout), so there has already been some
24015 waiting involved by the time locking fails. Nevertheless, Exim does not give up
24016 immediately. It retries up to
24018 (lock_retries * lock_interval) / <timeout>
24020 times (rounded up).
24023 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
24024 and/or &[flock()]& locks) and then deletes the lock file if one was created.
24027 .section "Operational details for delivery to a new file" "SECTopdir"
24028 .cindex "delivery" "to single file"
24029 .cindex "&""From""& line"
24030 When the &%directory%& option is set instead of &%file%&, each message is
24031 delivered into a newly-created file or set of files. When &(appendfile)& is
24032 activated directly from a &(redirect)& router, neither &%file%& nor
24033 &%directory%& is normally set, because the path for delivery is supplied by the
24034 router. (See for example, the &(address_file)& transport in the default
24035 configuration.) In this case, delivery is to a new file if either the path name
24036 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
24038 No locking is required while writing the message to a new file, so the various
24039 locking options of the transport are ignored. The &"From"& line that by default
24040 separates messages in a single file is not normally needed, nor is the escaping
24041 of message lines that start with &"From"&, and there is no need to ensure a
24042 newline at the end of each message. Consequently, the default values for
24043 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24044 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24046 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24047 the files in the delivery directory by default. However, you can specify a
24048 different directory by setting &%quota_directory%&. Also, for maildir
24049 deliveries (see below) the &_maildirfolder_& convention is honoured.
24052 .cindex "maildir format"
24053 .cindex "mailstore format"
24054 There are three different ways in which delivery to individual files can be
24055 done, controlled by the settings of the &%maildir_format%& and
24056 &%mailstore_format%& options. Note that code to support maildir or mailstore
24057 formats is not included in the binary unless SUPPORT_MAILDIR or
24058 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24060 .cindex "directory creation"
24061 In all three cases an attempt is made to create the directory and any necessary
24062 sub-directories if they do not exist, provided that the &%create_directory%&
24063 option is set (the default). The location of a created directory can be
24064 constrained by setting &%create_file%&. A created directory's mode is given by
24065 the &%directory_mode%& option. If creation fails, or if the
24066 &%create_directory%& option is not set when creation is required, delivery is
24071 .section "Maildir delivery" "SECTmaildirdelivery"
24072 .cindex "maildir format" "description of"
24073 If the &%maildir_format%& option is true, Exim delivers each message by writing
24074 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24075 directory that is defined by the &%directory%& option (the &"delivery
24076 directory"&). If the delivery is successful, the file is renamed into the
24077 &_new_& subdirectory.
24079 In the filename, <&'stime'&> is the current time of day in seconds, and
24080 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24081 Exim checks that the time-of-day clock has moved on by at least one microsecond
24082 before terminating the delivery process. This guarantees uniqueness for the
24083 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24084 opening it. If any response other than ENOENT (does not exist) is given,
24085 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24087 Before Exim carries out a maildir delivery, it ensures that subdirectories
24088 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24089 do not exist, Exim tries to create them and any superior directories in their
24090 path, subject to the &%create_directory%& and &%create_file%& options. If the
24091 &%maildirfolder_create_regex%& option is set, and the regular expression it
24092 contains matches the delivery directory, Exim also ensures that a file called
24093 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24094 &_maildirfolder_& file cannot be created, delivery is deferred.
24096 These features make it possible to use Exim to create all the necessary files
24097 and directories in a maildir mailbox, including subdirectories for maildir++
24098 folders. Consider this example:
24100 maildir_format = true
24101 directory = /var/mail/$local_part_data\
24102 ${if eq{$local_part_suffix}{}{}\
24103 {/.${substr_1:$local_part_suffix}}}
24104 maildirfolder_create_regex = /\.[^/]+$
24106 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24107 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24108 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24109 not match this name, so Exim will not look for or create the file
24110 &_/var/mail/pimbo/maildirfolder_&, though it will create
24111 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24113 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24114 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24115 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24116 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24117 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24119 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24120 not inadvertently match the toplevel maildir directory, because a
24121 &_maildirfolder_& file at top level would completely break quota calculations.
24123 .cindex "quota" "in maildir delivery"
24124 .cindex "maildir++"
24125 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24126 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24127 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24128 Exim assumes the directory is a maildir++ folder directory, which is one level
24129 down from the user's top level mailbox directory. This causes it to start at
24130 the parent directory instead of the current directory when calculating the
24131 amount of space used.
24133 One problem with delivering into a multi-file mailbox is that it is
24134 computationally expensive to compute the size of the mailbox for quota
24135 checking. Various approaches have been taken to reduce the amount of work
24136 needed. The next two sections describe two of them. A third alternative is to
24137 use some external process for maintaining the size data, and use the expansion
24138 of the &%mailbox_size%& option as a way of importing it into Exim.
24143 .section "Using tags to record message sizes" "SECID135"
24144 If &%maildir_tag%& is set, the string is expanded for each delivery.
24145 When the maildir file is renamed into the &_new_& sub-directory, the
24146 tag is added to its name. However, if adding the tag takes the length of the
24147 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24148 the tag is dropped and the maildir file is created with no tag.
24151 .vindex "&$message_size$&"
24152 Tags can be used to encode the size of files in their names; see
24153 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24154 happens after the message has been written. The value of the &$message_size$&
24155 variable is set to the number of bytes actually written. If the expansion is
24156 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24157 be deferred. The expanded tag may contain any printing characters except &"/"&.
24158 Non-printing characters in the string are ignored; if the resulting string is
24159 empty, it is ignored. If it starts with an alphanumeric character, a leading
24160 colon is inserted; this default has not proven to be the path that popular
24161 maildir implementations have chosen (but changing it in Exim would break
24162 backwards compatibility).
24164 For one common implementation, you might set:
24166 maildir_tag = ,S=${message_size}
24168 but you should check the documentation of the other software to be sure.
24170 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24171 as this allows Exim to extract the size from your tag, instead of having to
24172 &[stat()]& each message file.
24175 .section "Using a maildirsize file" "SECID136"
24176 .cindex "quota" "in maildir delivery"
24177 .cindex "maildir format" "&_maildirsize_& file"
24178 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24179 storing quota and message size information in a file called &_maildirsize_&
24180 within the toplevel maildir directory. If this file does not exist, Exim
24181 creates it, setting the quota from the &%quota%& option of the transport. If
24182 the maildir directory itself does not exist, it is created before any attempt
24183 to write a &_maildirsize_& file.
24185 The &_maildirsize_& file is used to hold information about the sizes of
24186 messages in the maildir, thus speeding up quota calculations. The quota value
24187 in the file is just a cache; if the quota is changed in the transport, the new
24188 value overrides the cached value when the next message is delivered. The cache
24189 is maintained for the benefit of other programs that access the maildir and
24190 need to know the quota.
24192 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24193 file is maintained (with a zero quota setting), but no quota is imposed.
24195 A regular expression is available for controlling which directories in the
24196 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24197 See the description of the &%maildir_quota_directory_regex%& option above for
24201 .section "Mailstore delivery" "SECID137"
24202 .cindex "mailstore format" "description of"
24203 If the &%mailstore_format%& option is true, each message is written as two
24204 files in the given directory. A unique base name is constructed from the
24205 message id and the current delivery process, and the files that are written use
24206 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24207 contains the message's envelope, and the &_.msg_& file contains the message
24208 itself. The base name is placed in the variable &$mailstore_basename$&.
24210 During delivery, the envelope is first written to a file with the suffix
24211 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24212 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24213 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24214 file before accessing either of them. An alternative approach is to wait for
24215 the absence of a &_.tmp_& file.
24217 The envelope file starts with any text defined by the &%mailstore_prefix%&
24218 option, expanded and terminated by a newline if there isn't one. Then follows
24219 the sender address on one line, then all the recipient addresses, one per line.
24220 There can be more than one recipient only if the &%batch_max%& option is set
24221 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24222 appended to the file, followed by a newline if it does not end with one.
24224 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24225 failure, it is ignored. Other expansion errors are treated as serious
24226 configuration errors, and delivery is deferred. The variable
24227 &$mailstore_basename$& is available for use during these expansions.
24230 .section "Non-special new file delivery" "SECID138"
24231 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24232 file is created directly in the named directory. For example, when delivering
24233 messages into files in batched SMTP format for later delivery to some host (see
24234 section &<<SECTbatchSMTP>>&), a setting such as
24236 directory = /var/bsmtp/$host
24238 might be used. A message is written to a file with a temporary name, which is
24239 then renamed when the delivery is complete. The final name is obtained by
24240 expanding the contents of the &%directory_file%& option.
24241 .ecindex IIDapptra1
24242 .ecindex IIDapptra2
24249 . ////////////////////////////////////////////////////////////////////////////
24250 . ////////////////////////////////////////////////////////////////////////////
24252 .chapter "The autoreply transport" "CHID8"
24253 .scindex IIDauttra1 "transports" "&(autoreply)&"
24254 .scindex IIDauttra2 "&(autoreply)& transport"
24255 The &(autoreply)& transport is not a true transport in that it does not cause
24256 the message to be transmitted. Instead, it generates a new mail message as an
24257 automatic reply to the incoming message. &'References:'& and
24258 &'Auto-Submitted:'& header lines are included. These are constructed according
24259 to the rules in RFCs 2822 and 3834, respectively.
24261 If the router that passes the message to this transport does not have the
24262 &%unseen%& option set, the original message (for the current recipient) is not
24263 delivered anywhere. However, when the &%unseen%& option is set on the router
24264 that passes the message to this transport, routing of the address continues, so
24265 another router can set up a normal message delivery.
24268 The &(autoreply)& transport is usually run as the result of mail filtering, a
24269 &"vacation"& message being the standard example. However, it can also be run
24270 directly from a router like any other transport. To reduce the possibility of
24271 message cascades, messages created by the &(autoreply)& transport always have
24272 empty envelope sender addresses, like bounce messages.
24274 The parameters of the message to be sent can be specified in the configuration
24275 by options described below. However, these are used only when the address
24276 passed to the transport does not contain its own reply information. When the
24277 transport is run as a consequence of a
24279 or &%vacation%& command in a filter file, the parameters of the message are
24280 supplied by the filter, and passed with the address. The transport's options
24281 that define the message are then ignored (so they are not usually set in this
24282 case). The message is specified entirely by the filter or by the transport; it
24283 is never built from a mixture of options. However, the &%file_optional%&,
24284 &%mode%&, and &%return_message%& options apply in all cases.
24286 &(Autoreply)& is implemented as a local transport. When used as a result of a
24287 command in a user's filter file, &(autoreply)& normally runs under the uid and
24288 gid of the user, and with appropriate current and home directories (see chapter
24289 &<<CHAPenvironment>>&).
24291 There is a subtle difference between routing a message to a &(pipe)& transport
24292 that generates some text to be returned to the sender, and routing it to an
24293 &(autoreply)& transport. This difference is noticeable only if more than one
24294 address from the same message is so handled. In the case of a pipe, the
24295 separate outputs from the different addresses are gathered up and returned to
24296 the sender in a single message, whereas if &(autoreply)& is used, a separate
24297 message is generated for each address that is passed to it.
24299 Non-printing characters are not permitted in the header lines generated for the
24300 message that &(autoreply)& creates, with the exception of newlines that are
24301 immediately followed by white space. If any non-printing characters are found,
24302 the transport defers.
24303 Whether characters with the top bit set count as printing characters or not is
24304 controlled by the &%print_topbitchars%& global option.
24306 If any of the generic options for manipulating headers (for example,
24307 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24308 of the original message that is included in the generated message when
24309 &%return_message%& is set. They do not apply to the generated message itself.
24311 .vindex "&$sender_address$&"
24312 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24313 the message, indicating that there were no recipients, it does not treat this
24314 as an error. This means that autoreplies sent to &$sender_address$& when this
24315 is empty (because the incoming message is a bounce message) do not cause
24316 problems. They are just discarded.
24320 .section "Private options for autoreply" "SECID139"
24321 .cindex "options" "&(autoreply)& transport"
24323 .option bcc autoreply string&!! unset
24324 This specifies the addresses that are to receive &"blind carbon copies"& of the
24325 message when the message is specified by the transport.
24328 .option cc autoreply string&!! unset
24329 This specifies recipients of the message and the contents of the &'Cc:'& header
24330 when the message is specified by the transport.
24333 .option file autoreply string&!! unset
24334 The contents of the file are sent as the body of the message when the message
24335 is specified by the transport. If both &%file%& and &%text%& are set, the text
24336 string comes first.
24339 .option file_expand autoreply boolean false
24340 If this is set, the contents of the file named by the &%file%& option are
24341 subjected to string expansion as they are added to the message.
24344 .option file_optional autoreply boolean false
24345 If this option is true, no error is generated if the file named by the &%file%&
24346 option or passed with the address does not exist or cannot be read.
24349 .option from autoreply string&!! unset
24350 This specifies the contents of the &'From:'& header when the message is
24351 specified by the transport.
24354 .option headers autoreply string&!! unset
24355 This specifies additional RFC 2822 headers that are to be added to the message
24356 when the message is specified by the transport. Several can be given by using
24357 &"\n"& to separate them. There is no check on the format.
24360 .option log autoreply string&!! unset
24361 This option names a file in which a record of every message sent is logged when
24362 the message is specified by the transport.
24365 .option mode autoreply "octal integer" 0600
24366 If either the log file or the &"once"& file has to be created, this mode is
24370 .option never_mail autoreply "address list&!!" unset
24371 If any run of the transport creates a message with a recipient that matches any
24372 item in the list, that recipient is quietly discarded. If all recipients are
24373 discarded, no message is created. This applies both when the recipients are
24374 generated by a filter and when they are specified in the transport.
24378 .option once autoreply string&!! unset
24379 This option names a file or DBM database in which a record of each &'To:'&
24380 recipient is kept when the message is specified by the transport. &*Note*&:
24381 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24383 If &%once%& is unset, or is set to an empty string, the message is always sent.
24384 By default, if &%once%& is set to a non-empty filename, the message
24385 is not sent if a potential recipient is already listed in the database.
24386 However, if the &%once_repeat%& option specifies a time greater than zero, the
24387 message is sent if that much time has elapsed since a message was last sent to
24388 this recipient. A setting of zero time for &%once_repeat%& (the default)
24389 prevents a message from being sent a second time &-- in this case, zero means
24392 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24393 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24394 greater than zero, it changes the way Exim implements the &%once%& option.
24395 Instead of using a DBM file to record every recipient it sends to, it uses a
24396 regular file, whose size will never get larger than the given value.
24398 In the file, Exim keeps a linear list of recipient addresses and the times at
24399 which they were sent messages. If the file is full when a new address needs to
24400 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24401 means that a given recipient may receive multiple messages, but at
24402 unpredictable intervals that depend on the rate of turnover of addresses in the
24403 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24406 .option once_file_size autoreply integer 0
24407 See &%once%& above.
24410 .option once_repeat autoreply time&!! 0s
24411 See &%once%& above.
24412 After expansion, the value of this option must be a valid time value.
24415 .option reply_to autoreply string&!! unset
24416 This specifies the contents of the &'Reply-To:'& header when the message is
24417 specified by the transport.
24420 .option return_message autoreply boolean false
24421 If this is set, a copy of the original message is returned with the new
24422 message, subject to the maximum size set in the &%return_size_limit%& global
24423 configuration option.
24426 .option subject autoreply string&!! unset
24427 This specifies the contents of the &'Subject:'& header when the message is
24428 specified by the transport. It is tempting to quote the original subject in
24429 automatic responses. For example:
24431 subject = Re: $h_subject:
24433 There is a danger in doing this, however. It may allow a third party to
24434 subscribe your users to an opt-in mailing list, provided that the list accepts
24435 bounce messages as subscription confirmations. Well-managed lists require a
24436 non-bounce message to confirm a subscription, so the danger is relatively
24441 .option text autoreply string&!! unset
24442 This specifies a single string to be used as the body of the message when the
24443 message is specified by the transport. If both &%text%& and &%file%& are set,
24444 the text comes first.
24447 .option to autoreply string&!! unset
24448 This specifies recipients of the message and the contents of the &'To:'& header
24449 when the message is specified by the transport.
24450 .ecindex IIDauttra1
24451 .ecindex IIDauttra2
24456 . ////////////////////////////////////////////////////////////////////////////
24457 . ////////////////////////////////////////////////////////////////////////////
24459 .chapter "The lmtp transport" "CHAPLMTP"
24460 .cindex "transports" "&(lmtp)&"
24461 .cindex "&(lmtp)& transport"
24462 .cindex "LMTP" "over a pipe"
24463 .cindex "LMTP" "over a socket"
24464 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24466 or by interacting with a Unix domain socket.
24467 This transport is something of a cross between the &(pipe)& and &(smtp)&
24468 transports. Exim also has support for using LMTP over TCP/IP; this is
24469 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24470 to be of minority interest, the default build-time configure in &_src/EDITME_&
24471 has it commented out. You need to ensure that
24475 .cindex "options" "&(lmtp)& transport"
24476 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24477 included in the Exim binary. The private options of the &(lmtp)& transport are
24480 .option batch_id lmtp string&!! unset
24481 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24484 .option batch_max lmtp integer 1
24485 This limits the number of addresses that can be handled in a single delivery.
24486 Most LMTP servers can handle several addresses at once, so it is normally a
24487 good idea to increase this value. See the description of local delivery
24488 batching in chapter &<<CHAPbatching>>&.
24491 .option command lmtp string&!! unset
24492 This option must be set if &%socket%& is not set. The string is a command which
24493 is run in a separate process. It is split up into a command name and list of
24494 arguments, each of which is separately expanded (so expansion cannot change the
24495 number of arguments). The command is run directly, not via a shell. The message
24496 is passed to the new process using the standard input and output to operate the
24499 .option ignore_quota lmtp boolean false
24500 .cindex "LMTP" "ignoring quota errors"
24501 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24502 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24503 in its response to the LHLO command.
24505 .option socket lmtp string&!! unset
24506 This option must be set if &%command%& is not set. The result of expansion must
24507 be the name of a Unix domain socket. The transport connects to the socket and
24508 delivers the message to it using the LMTP protocol.
24511 .option timeout lmtp time 5m
24512 The transport is aborted if the created process or Unix domain socket does not
24513 respond to LMTP commands or message input within this timeout. Delivery
24514 is deferred, and will be tried again later. Here is an example of a typical
24519 command = /some/local/lmtp/delivery/program
24523 This delivers up to 20 addresses at a time, in a mixture of domains if
24524 necessary, running as the user &'exim'&.
24528 . ////////////////////////////////////////////////////////////////////////////
24529 . ////////////////////////////////////////////////////////////////////////////
24531 .chapter "The pipe transport" "CHAPpipetransport"
24532 .scindex IIDpiptra1 "transports" "&(pipe)&"
24533 .scindex IIDpiptra2 "&(pipe)& transport"
24534 The &(pipe)& transport is used to deliver messages via a pipe to a command
24535 running in another process. One example is the use of &(pipe)& as a
24536 pseudo-remote transport for passing messages to some other delivery mechanism
24537 (such as UUCP). Another is the use by individual users to automatically process
24538 their incoming messages. The &(pipe)& transport can be used in one of the
24542 .vindex "&$local_part$&"
24543 A router routes one address to a transport in the normal way, and the
24544 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24545 contains the local part of the address (as usual), and the command that is run
24546 is specified by the &%command%& option on the transport.
24548 .vindex "&$pipe_addresses$&"
24549 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24550 transport can handle more than one address in a single run. In this case, when
24551 more than one address is routed to the transport, &$local_part$& is not set
24552 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24553 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24554 that are routed to the transport.
24556 .vindex "&$address_pipe$&"
24557 A router redirects an address directly to a pipe command (for example, from an
24558 alias or forward file). In this case, &$address_pipe$& contains the text of the
24559 pipe command, and the &%command%& option on the transport is ignored unless
24560 &%force_command%& is set. If only one address is being transported
24561 (&%batch_max%& is not greater than one, or only one address was redirected to
24562 this pipe command), &$local_part$& contains the local part that was redirected.
24566 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24567 deliver messages over pipes using the LMTP interactive protocol. This is
24568 implemented by the &(lmtp)& transport.
24570 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24571 &_.forward_& file, the command runs under the uid and gid of that user. In
24572 other cases, the uid and gid have to be specified explicitly, either on the
24573 transport or on the router that handles the address. Current and &"home"&
24574 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24575 details of the local delivery environment and chapter &<<CHAPbatching>>&
24576 for a discussion of local delivery batching.
24578 .cindex "tainted data" "in pipe command"
24579 .cindex pipe "tainted data"
24580 Tainted data may not be used for the command name.
24583 .section "Concurrent delivery" "SECID140"
24584 If two messages arrive at almost the same time, and both are routed to a pipe
24585 delivery, the two pipe transports may be run concurrently. You must ensure that
24586 any pipe commands you set up are robust against this happening. If the commands
24587 write to a file, the &%exim_lock%& utility might be of use.
24588 Alternatively the &%max_parallel%& option could be used with a value
24589 of "1" to enforce serialization.
24594 .section "Returned status and data" "SECID141"
24595 .cindex "&(pipe)& transport" "returned data"
24596 If the command exits with a non-zero return code, the delivery is deemed to
24597 have failed, unless either the &%ignore_status%& option is set (in which case
24598 the return code is treated as zero), or the return code is one of those listed
24599 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24600 later"&. In this case, delivery is deferred. Details of a permanent failure are
24601 logged, but are not included in the bounce message, which merely contains
24602 &"local delivery failed"&.
24604 If the command exits on a signal and the &%freeze_signal%& option is set then
24605 the message will be frozen in the queue. If that option is not set, a bounce
24606 will be sent as normal.
24608 If the return code is greater than 128 and the command being run is a shell
24609 script, it normally means that the script was terminated by a signal whose
24610 value is the return code minus 128. The &%freeze_signal%& option does not
24611 apply in this case.
24613 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24614 return code is set to 127. This is the value that a shell returns if it is
24615 asked to run a non-existent command. The wording for the log line suggests that
24616 a non-existent command may be the problem.
24618 The &%return_output%& option can affect the result of a pipe delivery. If it is
24619 set and the command produces any output on its standard output or standard
24620 error streams, the command is considered to have failed, even if it gave a zero
24621 return code or if &%ignore_status%& is set. The output from the command is
24622 included as part of the bounce message. The &%return_fail_output%& option is
24623 similar, except that output is returned only when the command exits with a
24624 failure return code, that is, a value other than zero or a code that matches
24629 .section "How the command is run" "SECThowcommandrun"
24630 .cindex "&(pipe)& transport" "path for command"
24631 The command line is (by default) broken down into a command name and arguments
24632 by the &(pipe)& transport itself. The &%allow_commands%& and
24633 &%restrict_to_path%& options can be used to restrict the commands that may be
24636 .cindex "quoting" "in pipe command"
24637 Unquoted arguments are delimited by white space. If an argument appears in
24638 double quotes, backslash is interpreted as an escape character in the usual
24639 way. If an argument appears in single quotes, no escaping is done.
24641 String expansion is applied to the command line except when it comes from a
24642 traditional &_.forward_& file (commands from a filter file are expanded). The
24643 expansion is applied to each argument in turn rather than to the whole line.
24644 For this reason, any string expansion item that contains white space must be
24645 quoted so as to be contained within a single argument. A setting such as
24647 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24649 will not work, because the expansion item gets split between several
24650 arguments. You have to write
24652 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24654 to ensure that it is all in one argument. The expansion is done in this way,
24655 argument by argument, so that the number of arguments cannot be changed as a
24656 result of expansion, and quotes or backslashes in inserted variables do not
24657 interact with external quoting. However, this leads to problems if you want to
24658 generate multiple arguments (or the command name plus arguments) from a single
24659 expansion. In this situation, the simplest solution is to use a shell. For
24662 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24665 .cindex "transport" "filter"
24666 .cindex "filter" "transport filter"
24667 .vindex "&$pipe_addresses$&"
24668 Special handling takes place when an argument consists of precisely the text
24669 &`$pipe_addresses`& (no quotes).
24670 This is not a general expansion variable; the only
24671 place this string is recognized is when it appears as an argument for a pipe or
24672 transport filter command. It causes each address that is being handled to be
24673 inserted in the argument list at that point &'as a separate argument'&. This
24674 avoids any problems with spaces or shell metacharacters, and is of use when a
24675 &(pipe)& transport is handling groups of addresses in a batch.
24677 If &%force_command%& is enabled on the transport, special handling takes place
24678 for an argument that consists of precisely the text &`$address_pipe`&. It
24679 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24680 argument is inserted in the argument list at that point
24681 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24682 the only item in the argument; in fact, if it were then &%force_command%&
24683 should behave as a no-op. Rather, it should be used to adjust the command
24684 run while preserving the argument vector separation.
24686 After splitting up into arguments and expansion, the resulting command is run
24687 in a subprocess directly from the transport, &'not'& under a shell. The
24688 message that is being delivered is supplied on the standard input, and the
24689 standard output and standard error are both connected to a single pipe that is
24690 read by Exim. The &%max_output%& option controls how much output the command
24691 may produce, and the &%return_output%& and &%return_fail_output%& options
24692 control what is done with it.
24694 Not running the command under a shell (by default) lessens the security risks
24695 in cases when a command from a user's filter file is built out of data that was
24696 taken from an incoming message. If a shell is required, it can of course be
24697 explicitly specified as the command to be run. However, there are circumstances
24698 where existing commands (for example, in &_.forward_& files) expect to be run
24699 under a shell and cannot easily be modified. To allow for these cases, there is
24700 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24701 works. Instead of breaking up the command line as just described, it expands it
24702 as a single string and passes the result to &_/bin/sh_&. The
24703 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24704 with &%use_shell%&, and the whole mechanism is inherently less secure.
24708 .section "Environment variables" "SECTpipeenv"
24709 .cindex "&(pipe)& transport" "environment for command"
24710 .cindex "environment" "&(pipe)& transport"
24711 The environment variables listed below are set up when the command is invoked.
24712 This list is a compromise for maximum compatibility with other MTAs. Note that
24713 the &%environment%& option can be used to add additional variables to this
24714 environment. The environment for the &(pipe)& transport is not subject
24715 to the &%add_environment%& and &%keep_environment%& main config options.
24717 &`DOMAIN `& the domain of the address
24718 &`HOME `& the home directory, if set
24719 &`HOST `& the host name when called from a router (see below)
24720 &`LOCAL_PART `& see below
24721 &`LOCAL_PART_PREFIX `& see below
24722 &`LOCAL_PART_SUFFIX `& see below
24723 &`LOGNAME `& see below
24724 &`MESSAGE_ID `& Exim's local ID for the message
24725 &`PATH `& as specified by the &%path%& option below
24726 &`QUALIFY_DOMAIN `& the sender qualification domain
24727 &`RECIPIENT `& the complete recipient address
24728 &`SENDER `& the sender of the message (empty if a bounce)
24729 &`SHELL `& &`/bin/sh`&
24730 &`TZ `& the value of the &%timezone%& option, if set
24731 &`USER `& see below
24733 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24734 router, LOCAL_PART is set to the local part of the address. When it is
24735 called as a result of a forward or alias expansion, LOCAL_PART is set to
24736 the local part of the address that was expanded. In both cases, any affixes are
24737 removed from the local part, and made available in LOCAL_PART_PREFIX and
24738 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24739 same value as LOCAL_PART for compatibility with other MTAs.
24742 HOST is set only when a &(pipe)& transport is called from a router that
24743 associates hosts with an address, typically when using &(pipe)& as a
24744 pseudo-remote transport. HOST is set to the first host name specified by
24748 If the transport's generic &%home_directory%& option is set, its value is used
24749 for the HOME environment variable. Otherwise, a home directory may be set
24750 by the router's &%transport_home_directory%& option, which defaults to the
24751 user's home directory if &%check_local_user%& is set.
24754 .section "Private options for pipe" "SECID142"
24755 .cindex "options" "&(pipe)& transport"
24759 .option allow_commands pipe "string list&!!" unset
24760 .cindex "&(pipe)& transport" "permitted commands"
24761 The string is expanded, and is then interpreted as a colon-separated list of
24762 permitted commands. If &%restrict_to_path%& is not set, the only commands
24763 permitted are those in the &%allow_commands%& list. They need not be absolute
24764 paths; the &%path%& option is still used for relative paths. If
24765 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24766 in the &%allow_commands%& list, or a name without any slashes that is found on
24767 the path. In other words, if neither &%allow_commands%& nor
24768 &%restrict_to_path%& is set, there is no restriction on the command, but
24769 otherwise only commands that are permitted by one or the other are allowed. For
24772 allow_commands = /usr/bin/vacation
24774 and &%restrict_to_path%& is not set, the only permitted command is
24775 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24776 &%use_shell%& is set.
24779 .option batch_id pipe string&!! unset
24780 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24783 .option batch_max pipe integer 1
24784 This limits the number of addresses that can be handled in a single delivery.
24785 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24788 .option check_string pipe string unset
24789 As &(pipe)& writes the message, the start of each line is tested for matching
24790 &%check_string%&, and if it does, the initial matching characters are replaced
24791 by the contents of &%escape_string%&, provided both are set. The value of
24792 &%check_string%& is a literal string, not a regular expression, and the case of
24793 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24794 of &%check_string%& and &%escape_string%& are forced to values that implement
24795 the SMTP escaping protocol. Any settings made in the configuration file are
24799 .option command pipe string&!! unset
24800 This option need not be set when &(pipe)& is being used to deliver to pipes
24801 obtained directly from address redirections. In other cases, the option must be
24802 set, to provide a command to be run. It need not yield an absolute path (see
24803 the &%path%& option below). The command is split up into separate arguments by
24804 Exim, and each argument is separately expanded, as described in section
24805 &<<SECThowcommandrun>>& above.
24808 .option environment pipe string&!! unset
24809 .cindex "&(pipe)& transport" "environment for command"
24810 .cindex "environment" "&(pipe)& transport"
24811 This option is used to add additional variables to the environment in which the
24812 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24813 a string which is expanded, and then interpreted as a colon-separated list of
24814 environment settings of the form <&'name'&>=<&'value'&>.
24817 .option escape_string pipe string unset
24818 See &%check_string%& above.
24821 .option freeze_exec_fail pipe boolean false
24822 .cindex "exec failure"
24823 .cindex "failure of exec"
24824 .cindex "&(pipe)& transport" "failure of exec"
24825 Failure to exec the command in a pipe transport is by default treated like
24826 any other failure while running the command. However, if &%freeze_exec_fail%&
24827 is set, failure to exec is treated specially, and causes the message to be
24828 frozen, whatever the setting of &%ignore_status%&.
24831 .option freeze_signal pipe boolean false
24832 .cindex "signal exit"
24833 .cindex "&(pipe)& transport", "signal exit"
24834 Normally if the process run by a command in a pipe transport exits on a signal,
24835 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24836 frozen in Exim's queue instead.
24839 .option force_command pipe boolean false
24840 .cindex "force command"
24841 .cindex "&(pipe)& transport", "force command"
24842 Normally when a router redirects an address directly to a pipe command
24843 the &%command%& option on the transport is ignored. If &%force_command%&
24844 is set, the &%command%& option will used. This is especially
24845 useful for forcing a wrapper or additional argument to be added to the
24846 command. For example:
24848 command = /usr/bin/remote_exec myhost -- $address_pipe
24852 Note that &$address_pipe$& is handled specially in &%command%& when
24853 &%force_command%& is set, expanding out to the original argument vector as
24854 separate items, similarly to a Unix shell &`"$@"`& construct.
24857 .option ignore_status pipe boolean false
24858 If this option is true, the status returned by the subprocess that is set up to
24859 run the command is ignored, and Exim behaves as if zero had been returned.
24860 Otherwise, a non-zero status or termination by signal causes an error return
24861 from the transport unless the status value is one of those listed in
24862 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24864 &*Note*&: This option does not apply to timeouts, which do not return a status.
24865 See the &%timeout_defer%& option for how timeouts are handled.
24868 .option log_defer_output pipe boolean false
24869 .cindex "&(pipe)& transport" "logging output"
24870 If this option is set, and the status returned by the command is
24871 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24872 and any output was produced on stdout or stderr, the first line of it is
24873 written to the main log.
24876 .option log_fail_output pipe boolean false
24877 If this option is set, and the command returns any output on stdout or
24878 stderr, and also ends with a return code that is neither zero nor one of
24879 the return codes listed in &%temp_errors%& (that is, the delivery
24880 failed), the first line of output is written to the main log. This
24881 option and &%log_output%& are mutually exclusive. Only one of them may
24885 .option log_output pipe boolean false
24886 If this option is set and the command returns any output on stdout or
24887 stderr, the first line of output is written to the main log, whatever
24888 the return code. This option and &%log_fail_output%& are mutually
24889 exclusive. Only one of them may be set.
24892 .option max_output pipe integer 20K
24893 This specifies the maximum amount of output that the command may produce on its
24894 standard output and standard error file combined. If the limit is exceeded, the
24895 process running the command is killed. This is intended as a safety measure to
24896 catch runaway processes. The limit is applied independently of the settings of
24897 the options that control what is done with such output (for example,
24898 &%return_output%&). Because of buffering effects, the amount of output may
24899 exceed the limit by a small amount before Exim notices.
24902 .option message_prefix pipe string&!! "see below"
24903 The string specified here is expanded and output at the start of every message.
24904 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24907 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24911 .cindex "&%tmail%&"
24912 .cindex "&""From""& line"
24913 This is required by the commonly used &_/usr/bin/vacation_& program.
24914 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24915 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24920 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24921 &`\n`& to &`\r\n`& in &%message_prefix%&.
24924 .option message_suffix pipe string&!! "see below"
24925 The string specified here is expanded and output at the end of every message.
24926 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24927 The suffix can be suppressed by setting
24931 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24932 &`\n`& to &`\r\n`& in &%message_suffix%&.
24935 .option path pipe string&!! "/bin:/usr/bin"
24936 This option is expanded and
24937 specifies the string that is set up in the PATH environment
24938 variable of the subprocess.
24939 If the &%command%& option does not yield an absolute path name, the command is
24940 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24941 apply to a command specified as a transport filter.
24944 .option permit_coredump pipe boolean false
24945 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24946 a core-dump of a pipe command, enable this command. This enables core-dumps
24947 during delivery and affects both the Exim binary and the pipe command run.
24948 It is recommended that this option remain off unless and until you have a need
24949 for it and that this only be enabled when needed, as the risk of excessive
24950 resource consumption can be quite high. Note also that Exim is typically
24951 installed as a setuid binary and most operating systems will inhibit coredumps
24952 of these by default, so further OS-specific action may be required.
24955 .option pipe_as_creator pipe boolean false
24956 .cindex "uid (user id)" "local delivery"
24957 If the generic &%user%& option is not set and this option is true, the delivery
24958 process is run under the uid that was in force when Exim was originally called
24959 to accept the message. If the group id is not otherwise set (via the generic
24960 &%group%& option), the gid that was in force when Exim was originally called to
24961 accept the message is used.
24964 .option restrict_to_path pipe boolean false
24965 When this option is set, any command name not listed in &%allow_commands%& must
24966 contain no slashes. The command is searched for only in the directories listed
24967 in the &%path%& option. This option is intended for use in the case when a pipe
24968 command has been generated from a user's &_.forward_& file. This is usually
24969 handled by a &(pipe)& transport called &%address_pipe%&.
24972 .option return_fail_output pipe boolean false
24973 If this option is true, and the command produced any output and ended with a
24974 return code other than zero or one of the codes listed in &%temp_errors%& (that
24975 is, the delivery failed), the output is returned in the bounce message.
24976 However, if the message has a null sender (that is, it is itself a bounce
24977 message), output from the command is discarded. This option and
24978 &%return_output%& are mutually exclusive. Only one of them may be set.
24982 .option return_output pipe boolean false
24983 If this option is true, and the command produced any output, the delivery is
24984 deemed to have failed whatever the return code from the command, and the output
24985 is returned in the bounce message. Otherwise, the output is just discarded.
24986 However, if the message has a null sender (that is, it is a bounce message),
24987 output from the command is always discarded, whatever the setting of this
24988 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24989 of them may be set.
24993 .option temp_errors pipe "string list" "see below"
24994 .cindex "&(pipe)& transport" "temporary failure"
24995 This option contains either a colon-separated list of numbers, or a single
24996 asterisk. If &%ignore_status%& is false
24997 and &%return_output%& is not set,
24998 and the command exits with a non-zero return code, the failure is treated as
24999 temporary and the delivery is deferred if the return code matches one of the
25000 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
25001 codes are treated as permanent errors. The default setting contains the codes
25002 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
25003 compiled on a system that does not define these macros, it assumes values of 75
25004 and 73, respectively.
25007 .option timeout pipe time 1h
25008 If the command fails to complete within this time, it is killed. This normally
25009 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
25010 specifies no timeout. In order to ensure that any subprocesses created by the
25011 command are also killed, Exim makes the initial process a process group leader,
25012 and kills the whole process group on a timeout. However, this can be defeated
25013 if one of the processes starts a new process group.
25015 .option timeout_defer pipe boolean false
25016 A timeout in a &(pipe)& transport, either in the command that the transport
25017 runs, or in a transport filter that is associated with it, is by default
25018 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
25019 is set true, both kinds of timeout become temporary errors, causing the
25020 delivery to be deferred.
25022 .option umask pipe "octal integer" 022
25023 This specifies the umask setting for the subprocess that runs the command.
25026 .option use_bsmtp pipe boolean false
25027 .cindex "envelope sender"
25028 If this option is set true, the &(pipe)& transport writes messages in &"batch
25029 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
25030 commands. If you want to include a leading HELO command with such messages,
25031 you can do so by setting the &%message_prefix%& option. See section
25032 &<<SECTbatchSMTP>>& for details of batch SMTP.
25034 .option use_classresources pipe boolean false
25035 .cindex "class resources (BSD)"
25036 This option is available only when Exim is running on FreeBSD, NetBSD, or
25037 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
25038 resource limits when a &(pipe)& transport is run to perform a delivery. The
25039 limits for the uid under which the pipe is to run are obtained from the login
25043 .option use_crlf pipe boolean false
25044 .cindex "carriage return"
25046 This option causes lines to be terminated with the two-character CRLF sequence
25047 (carriage return, linefeed) instead of just a linefeed character. In the case
25048 of batched SMTP, the byte sequence written to the pipe is then an exact image
25049 of what would be sent down a real SMTP connection.
25051 The contents of the &%message_prefix%& and &%message_suffix%& options are
25052 written verbatim, so must contain their own carriage return characters if these
25053 are needed. When &%use_bsmtp%& is not set, the default values for both
25054 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25055 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25058 .option use_shell pipe boolean false
25059 .vindex "&$pipe_addresses$&"
25060 If this option is set, it causes the command to be passed to &_/bin/sh_&
25061 instead of being run directly from the transport, as described in section
25062 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25063 where the command is expected to be run under a shell and cannot easily be
25064 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25065 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25066 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25071 .section "Using an external local delivery agent" "SECID143"
25072 .cindex "local delivery" "using an external agent"
25073 .cindex "&'procmail'&"
25074 .cindex "external local delivery"
25075 .cindex "delivery" "&'procmail'&"
25076 .cindex "delivery" "by external agent"
25077 The &(pipe)& transport can be used to pass all messages that require local
25078 delivery to a separate local delivery agent such as &%procmail%&. When doing
25079 this, care must be taken to ensure that the pipe is run under an appropriate
25080 uid and gid. In some configurations one wants this to be a uid that is trusted
25081 by the delivery agent to supply the correct sender of the message. It may be
25082 necessary to recompile or reconfigure the delivery agent so that it trusts an
25083 appropriate user. The following is an example transport and router
25084 configuration for &%procmail%&:
25089 command = /usr/local/bin/procmail -d $local_part_data
25093 check_string = "From "
25094 escape_string = ">From "
25096 user = $local_part_data
25103 transport = procmail_pipe
25105 In this example, the pipe is run as the local user, but with the group set to
25106 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25107 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25108 user to supply a correct sender address. If you do not specify either a
25109 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25110 home directory is the user's home directory by default.
25112 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25116 as shown in some &%procmail%& documentation, because Exim does not by default
25117 use a shell to run pipe commands.
25120 The next example shows a transport and a router for a system where local
25121 deliveries are handled by the Cyrus IMAP server.
25124 local_delivery_cyrus:
25126 command = /usr/cyrus/bin/deliver \
25127 -m ${substr_1:$local_part_suffix} -- $local_part
25139 local_part_suffix = .*
25140 transport = local_delivery_cyrus
25142 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25143 &%return_output%& to cause any text written by Cyrus to be returned to the
25145 .ecindex IIDpiptra1
25146 .ecindex IIDpiptra2
25149 . ////////////////////////////////////////////////////////////////////////////
25150 . ////////////////////////////////////////////////////////////////////////////
25152 .chapter "The smtp transport" "CHAPsmtptrans"
25153 .scindex IIDsmttra1 "transports" "&(smtp)&"
25154 .scindex IIDsmttra2 "&(smtp)& transport"
25155 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25156 or LMTP protocol. The list of hosts to try can either be taken from the address
25157 that is being processed (having been set up by the router), or specified
25158 explicitly for the transport. Timeout and retry processing (see chapter
25159 &<<CHAPretry>>&) is applied to each IP address independently.
25162 .section "Multiple messages on a single connection" "SECID144"
25163 The sending of multiple messages over a single TCP/IP connection can arise in
25167 If a message contains more than &%max_rcpt%& (see below) addresses that are
25168 routed to the same host, more than one copy of the message has to be sent to
25169 that host. In this situation, multiple copies may be sent in a single run of
25170 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25171 does when it has too many addresses to send in one message also depends on the
25172 value of the global &%remote_max_parallel%& option. Details are given in
25173 section &<<SECToutSMTPTCP>>&.)
25175 .cindex "hints database" "remembering routing"
25176 When a message has been successfully delivered over a TCP/IP connection, Exim
25177 looks in its hints database to see if there are any other messages awaiting a
25178 connection to the same host. If there are, a new delivery process is started
25179 for one of them, and the current TCP/IP connection is passed on to it. The new
25180 process may in turn send multiple copies and possibly create yet another
25185 For each copy sent over the same TCP/IP connection, a sequence counter is
25186 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25187 no further messages are sent over that connection.
25191 .section "Use of the $host and $host_address variables" "SECID145"
25193 .vindex "&$host_address$&"
25194 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25195 &$host_address$& are the name and IP address of the first host on the host list
25196 passed by the router. However, when the transport is about to connect to a
25197 specific host, and while it is connected to that host, &$host$& and
25198 &$host_address$& are set to the values for that host. These are the values
25199 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25200 &%serialize_hosts%&, and the various TLS options are expanded.
25203 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25204 .vindex &$tls_bits$&
25205 .vindex &$tls_cipher$&
25206 .vindex &$tls_peerdn$&
25207 .vindex &$tls_sni$&
25208 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25209 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25210 are the values that were set when the message was received.
25211 These are the values that are used for options that are expanded before any
25212 SMTP connections are made. Just before each connection is made, these four
25213 variables are emptied. If TLS is subsequently started, they are set to the
25214 appropriate values for the outgoing connection, and these are the values that
25215 are in force when any authenticators are run and when the
25216 &%authenticated_sender%& option is expanded.
25218 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25219 and will be removed in a future release.
25222 .section "Private options for smtp" "SECID146"
25223 .cindex "options" "&(smtp)& transport"
25224 The private options of the &(smtp)& transport are as follows:
25227 .option address_retry_include_sender smtp boolean true
25228 .cindex "4&'xx'& responses" "retrying after"
25229 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25230 is the combination of sender and recipient that is delayed in subsequent queue
25231 runs until the retry time is reached. You can delay the recipient without
25232 reference to the sender (which is what earlier versions of Exim did), by
25233 setting &%address_retry_include_sender%& false. However, this can lead to
25234 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25236 .option allow_localhost smtp boolean false
25237 .cindex "local host" "sending to"
25238 .cindex "fallback" "hosts specified on transport"
25239 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25240 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25241 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25242 the delivery anyway. This should be used only in special cases when the
25243 configuration ensures that no looping will result (for example, a differently
25244 configured Exim is listening on the port to which the message is sent).
25247 .option authenticated_sender smtp string&!! unset
25249 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25250 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25251 overriding any existing authenticated sender value. If the string expansion is
25252 forced to fail, the option is ignored. Other expansion failures cause delivery
25253 to be deferred. If the result of expansion is an empty string, that is also
25256 The expansion happens after the outgoing connection has been made and TLS
25257 started, if required. This means that the &$host$&, &$host_address$&,
25258 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25259 particular connection.
25261 If the SMTP session is not authenticated, the expansion of
25262 &%authenticated_sender%& still happens (and can cause the delivery to be
25263 deferred if it fails), but no AUTH= item is added to MAIL commands
25264 unless &%authenticated_sender_force%& is true.
25266 This option allows you to use the &(smtp)& transport in LMTP mode to
25267 deliver mail to Cyrus IMAP and provide the proper local part as the
25268 &"authenticated sender"&, via a setting such as:
25270 authenticated_sender = $local_part
25272 This removes the need for IMAP subfolders to be assigned special ACLs to
25273 allow direct delivery to those subfolders.
25275 Because of expected uses such as that just described for Cyrus (when no
25276 domain is involved), there is no checking on the syntax of the provided
25280 .option authenticated_sender_force smtp boolean false
25281 If this option is set true, the &%authenticated_sender%& option's value
25282 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25283 authenticated as a client.
25286 .option command_timeout smtp time 5m
25287 .cindex timeout "smtp transport command"
25288 This sets a timeout for receiving a response to an SMTP command that has been
25289 sent out. It is also used when waiting for the initial banner line from the
25290 remote host. Its value must not be zero.
25293 .option connect_timeout smtp time 5m
25294 .cindex timeout "smtp transport connect"
25295 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25296 to a remote host. A setting of zero allows the system timeout (typically
25297 several minutes) to act. To have any effect, the value of this option must be
25298 less than the system timeout. However, it has been observed that on some
25299 systems there is no system timeout, which is why the default value for this
25300 option is 5 minutes, a value recommended by RFC 1123.
25303 .option connection_max_messages smtp integer 500
25304 .cindex "SMTP" "passed connection"
25305 .cindex "SMTP" "multiple deliveries"
25306 .cindex "multiple SMTP deliveries"
25307 This controls the maximum number of separate message deliveries that are sent
25308 over a single TCP/IP connection. If the value is zero, there is no limit.
25309 For testing purposes, this value can be overridden by the &%-oB%& command line
25313 .option dane_require_tls_ciphers smtp string&!! unset
25314 .cindex "TLS" "requiring specific ciphers for DANE"
25315 .cindex "cipher" "requiring specific"
25316 .cindex DANE "TLS ciphers"
25317 This option may be used to override &%tls_require_ciphers%& for connections
25318 where DANE has been determined to be in effect.
25319 If not set, then &%tls_require_ciphers%& will be used.
25320 Normal SMTP delivery is not able to make strong demands of TLS cipher
25321 configuration, because delivery will fall back to plaintext. Once DANE has
25322 been determined to be in effect, there is no plaintext fallback and making the
25323 TLS cipherlist configuration stronger will increase security, rather than
25324 counter-intuitively decreasing it.
25325 If the option expands to be empty or is forced to fail, then it will
25326 be treated as unset and &%tls_require_ciphers%& will be used instead.
25329 .option data_timeout smtp time 5m
25330 .cindex timeout "for transmitted SMTP data blocks"
25331 This sets a timeout for the transmission of each block in the data portion of
25332 the message. As a result, the overall timeout for a message depends on the size
25333 of the message. Its value must not be zero. See also &%final_timeout%&.
25336 .option dkim_canon smtp string&!! unset
25337 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25338 .option dkim_domain smtp "string list&!!" unset
25339 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25340 .option dkim_hash smtp string&!! sha256
25341 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25342 .option dkim_identity smtp string&!! unset
25343 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25344 .option dkim_private_key smtp string&!! unset
25345 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25346 .option dkim_selector smtp string&!! unset
25347 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25348 .option dkim_strict smtp string&!! unset
25349 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25350 .option dkim_sign_headers smtp string&!! "per RFC"
25351 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25352 .option dkim_timestamps smtp string&!! unset
25353 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25356 .option delay_after_cutoff smtp boolean true
25357 .cindex "final cutoff" "retries, controlling"
25358 .cindex retry "final cutoff"
25359 This option controls what happens when all remote IP addresses for a given
25360 domain have been inaccessible for so long that they have passed their retry
25363 In the default state, if the next retry time has not been reached for any of
25364 them, the address is bounced without trying any deliveries. In other words,
25365 Exim delays retrying an IP address after the final cutoff time until a new
25366 retry time is reached, and can therefore bounce an address without ever trying
25367 a delivery, when machines have been down for a long time. Some people are
25368 unhappy at this prospect, so...
25370 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25371 addresses are past their final cutoff time, Exim tries to deliver to those
25372 IP addresses that have not been tried since the message arrived. If there are
25373 none, of if they all fail, the address is bounced. In other words, it does not
25374 delay when a new message arrives, but immediately tries those expired IP
25375 addresses that haven't been tried since the message arrived. If there is a
25376 continuous stream of messages for the dead hosts, unsetting
25377 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25381 .option dns_qualify_single smtp boolean true
25382 If the &%hosts%& or &%fallback_hosts%& option is being used,
25383 and the &%gethostbyname%& option is false,
25384 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25385 in chapter &<<CHAPdnslookup>>& for more details.
25388 .option dns_search_parents smtp boolean false
25389 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25390 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25391 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25395 .option dnssec_request_domains smtp "domain list&!!" *
25396 .cindex "MX record" "security"
25397 .cindex "DNSSEC" "MX lookup"
25398 .cindex "security" "MX lookup"
25399 .cindex "DNS" "DNSSEC"
25400 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25401 the DNSSEC request bit set. Setting this transport option is only useful if the
25402 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25407 .option dnssec_require_domains smtp "domain list&!!" unset
25408 .cindex "MX record" "security"
25409 .cindex "DNSSEC" "MX lookup"
25410 .cindex "security" "MX lookup"
25411 .cindex "DNS" "DNSSEC"
25412 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25413 the DNSSEC request bit set. Setting this transport option is only
25414 useful if the transport overrides or sets the host names. See the
25415 &%dnssec_require_domains%& router option.
25419 .option dscp smtp string&!! unset
25420 .cindex "DCSP" "outbound"
25421 This option causes the DSCP value associated with a socket to be set to one
25422 of a number of fixed strings or to numeric value.
25423 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25424 Common values include &`throughput`&, &`mincost`&, and on newer systems
25425 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25427 The outbound packets from Exim will be marked with this value in the header
25428 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25429 that these values will have any effect, not be stripped by networking
25430 equipment, or do much of anything without cooperation with your Network
25431 Engineer and those of all network operators between the source and destination.
25434 .option fallback_hosts smtp "string list" unset
25435 .cindex "fallback" "hosts specified on transport"
25436 String expansion is not applied to this option. The argument must be a
25437 colon-separated list of host names or IP addresses, optionally also including
25438 port numbers, though the separator can be changed, as described in section
25439 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25440 item in a &%route_list%& setting for the &(manualroute)& router, as described
25441 in section &<<SECTformatonehostitem>>&.
25443 Fallback hosts can also be specified on routers, which associate them with the
25444 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25445 &%fallback_hosts%& specified on the transport is used only if the address does
25446 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25447 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25448 However, &%hosts_randomize%& does apply to fallback host lists.
25450 If Exim is unable to deliver to any of the hosts for a particular address, and
25451 the errors are not permanent rejections, the address is put on a separate
25452 transport queue with its host list replaced by the fallback hosts, unless the
25453 address was routed via MX records and the current host was in the original MX
25454 list. In that situation, the fallback host list is not used.
25456 Once normal deliveries are complete, the fallback queue is delivered by
25457 re-running the same transports with the new host lists. If several failing
25458 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25459 copy of the message is sent.
25461 The resolution of the host names on the fallback list is controlled by the
25462 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25463 both to cases when the host list comes with the address and when it is taken
25464 from &%hosts%&. This option provides a &"use a smart host only if delivery
25468 .option final_timeout smtp time 10m
25469 .cindex timeout "for transmitted SMTP data accept"
25470 This is the timeout that applies while waiting for the response to the final
25471 line containing just &"."& that terminates a message. Its value must not be
25474 .option gethostbyname smtp boolean false
25475 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25476 being used, names are looked up using &[gethostbyname()]&
25477 (or &[getipnodebyname()]& when available)
25478 instead of using the DNS. Of course, that function may in fact use the DNS, but
25479 it may also consult other sources of information such as &_/etc/hosts_&.
25481 .option gnutls_compat_mode smtp boolean unset
25482 This option controls whether GnuTLS is used in compatibility mode in an Exim
25483 server. This reduces security slightly, but improves interworking with older
25484 implementations of TLS.
25486 .option helo_data smtp string&!! "see below"
25487 .cindex "HELO" "argument, setting"
25488 .cindex "EHLO" "argument, setting"
25489 .cindex "LHLO argument setting"
25490 The value of this option is expanded after a connection to a another host has
25491 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25492 command that starts the outgoing SMTP or LMTP session. The default value of the
25497 During the expansion, the variables &$host$& and &$host_address$& are set to
25498 the identity of the remote host, and the variables &$sending_ip_address$& and
25499 &$sending_port$& are set to the local IP address and port number that are being
25500 used. These variables can be used to generate different values for different
25501 servers or different local IP addresses. For example, if you want the string
25502 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25503 interface address, you could use this:
25505 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25506 {$primary_hostname}}
25508 The use of &%helo_data%& applies both to sending messages and when doing
25511 .option hosts smtp "string list&!!" unset
25512 Hosts are associated with an address by a router such as &(dnslookup)&, which
25513 finds the hosts by looking up the address domain in the DNS, or by
25514 &(manualroute)&, which has lists of hosts in its configuration. However,
25515 email addresses can be passed to the &(smtp)& transport by any router, and not
25516 all of them can provide an associated list of hosts.
25518 The &%hosts%& option specifies a list of hosts to be used if the address being
25519 processed does not have any hosts associated with it. The hosts specified by
25520 &%hosts%& are also used, whether or not the address has its own hosts, if
25521 &%hosts_override%& is set.
25523 The string is first expanded, before being interpreted as a colon-separated
25524 list of host names or IP addresses, possibly including port numbers. The
25525 separator may be changed to something other than colon, as described in section
25526 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25527 item in a &%route_list%& setting for the &(manualroute)& router, as described
25528 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25529 of the &(manualroute)& router is not available here.
25531 If the expansion fails, delivery is deferred. Unless the failure was caused by
25532 the inability to complete a lookup, the error is logged to the panic log as
25533 well as the main log. Host names are looked up either by searching directly for
25534 address records in the DNS or by calling &[gethostbyname()]& (or
25535 &[getipnodebyname()]& when available), depending on the setting of the
25536 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25537 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25540 During delivery, the hosts are tried in order, subject to their retry status,
25541 unless &%hosts_randomize%& is set.
25544 .option hosts_avoid_esmtp smtp "host list&!!" unset
25545 .cindex "ESMTP, avoiding use of"
25546 .cindex "HELO" "forcing use of"
25547 .cindex "EHLO" "avoiding use of"
25548 .cindex "PIPELINING" "avoiding the use of"
25549 This option is for use with broken hosts that announce ESMTP facilities (for
25550 example, PIPELINING) and then fail to implement them properly. When a host
25551 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25552 start of the SMTP session. This means that it cannot use any of the ESMTP
25553 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25556 .option hosts_avoid_pipelining smtp "host list&!!" unset
25557 .cindex "PIPELINING" "avoiding the use of"
25558 .cindex "ESMTP extensions" PIPELINING
25559 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25560 that matches this list, even if the server host advertises PIPELINING support.
25562 .option hosts_pipe_connect smtp "host list&!!" unset
25563 .cindex "pipelining" "early connection"
25564 .cindex "pipelining" PIPE_CONNECT
25565 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25566 this option controls which to hosts the facility watched for
25567 and recorded, and used for subsequent connections.
25569 The retry hints database is used for the record,
25570 and records are subject to the &%retry_data_expire%& option.
25571 When used, the pipelining saves on roundtrip times.
25572 It also turns SMTP into a client-first protocol
25573 so combines well with TCP Fast Open.
25575 See also the &%pipelining_connect_advertise_hosts%& main option.
25578 When the facility is used, the transport &%helo_data%& option
25579 will be expanded before the &$sending_ip_address$& variable
25581 A check is made for the use of that variable, without the
25582 presence of a &"def:"& test on it, but suitably complex coding
25583 can avoid the check and produce unexpected results.
25584 You have been warned.
25587 .option hosts_avoid_tls smtp "host list&!!" unset
25588 .cindex "TLS" "avoiding for certain hosts"
25589 Exim will not try to start a TLS session when delivering to any host that
25590 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25592 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25593 .cindex "TLS" "avoiding for certain hosts"
25594 Exim will not try to start a TLS session for a verify callout,
25595 or when delivering in cutthrough mode,
25596 to any host that matches this list.
25599 .option hosts_max_try smtp integer 5
25600 .cindex "host" "maximum number to try"
25601 .cindex "limit" "number of hosts tried"
25602 .cindex "limit" "number of MX tried"
25603 .cindex "MX record" "maximum tried"
25604 This option limits the number of IP addresses that are tried for any one
25605 delivery in cases where there are temporary delivery errors. Section
25606 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25609 .option hosts_max_try_hardlimit smtp integer 50
25610 This is an additional check on the maximum number of IP addresses that Exim
25611 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25616 .option hosts_nopass_tls smtp "host list&!!" unset
25617 .cindex "TLS" "passing connection"
25618 .cindex "multiple SMTP deliveries"
25619 .cindex "TLS" "multiple message deliveries"
25620 For any host that matches this list, a connection on which a TLS session has
25621 been started will not be passed to a new delivery process for sending another
25622 message on the same connection. See section &<<SECTmulmessam>>& for an
25623 explanation of when this might be needed.
25625 .option hosts_noproxy_tls smtp "host list&!!" unset
25626 .cindex "TLS" "passing connection"
25627 .cindex "multiple SMTP deliveries"
25628 .cindex "TLS" "multiple message deliveries"
25629 For any host that matches this list, a TLS session which has
25630 been started will not be passed to a new delivery process for sending another
25631 message on the same session.
25633 The traditional implementation closes down TLS and re-starts it in the new
25634 process, on the same open TCP connection, for each successive message
25635 sent. If permitted by this option a pipe to to the new process is set up
25636 instead, and the original process maintains the TLS connection and proxies
25637 the SMTP connection from and to the new process and any subsequents.
25638 The new process has no access to TLS information, so cannot include it in
25643 .option hosts_override smtp boolean false
25644 If this option is set and the &%hosts%& option is also set, any hosts that are
25645 attached to the address are ignored, and instead the hosts specified by the
25646 &%hosts%& option are always used. This option does not apply to
25647 &%fallback_hosts%&.
25650 .option hosts_randomize smtp boolean false
25651 .cindex "randomized host list"
25652 .cindex "host" "list of; randomized"
25653 .cindex "fallback" "randomized hosts"
25654 If this option is set, and either the list of hosts is taken from the
25655 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25656 were not obtained from MX records (this includes fallback hosts from the
25657 router), and were not randomized by the router, the order of trying the hosts
25658 is randomized each time the transport runs. Randomizing the order of a host
25659 list can be used to do crude load sharing.
25661 When &%hosts_randomize%& is true, a host list may be split into groups whose
25662 order is separately randomized. This makes it possible to set up MX-like
25663 behaviour. The boundaries between groups are indicated by an item that is just
25664 &`+`& in the host list. For example:
25666 hosts = host1:host2:host3:+:host4:host5
25668 The order of the first three hosts and the order of the last two hosts is
25669 randomized for each use, but the first three always end up before the last two.
25670 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25672 .option hosts_require_auth smtp "host list&!!" unset
25673 .cindex "authentication" "required by client"
25674 This option provides a list of servers for which authentication must succeed
25675 before Exim will try to transfer a message. If authentication fails for
25676 servers which are not in this list, Exim tries to send unauthenticated. If
25677 authentication fails for one of these servers, delivery is deferred. This
25678 temporary error is detectable in the retry rules, so it can be turned into a
25679 hard failure if required. See also &%hosts_try_auth%&, and chapter
25680 &<<CHAPSMTPAUTH>>& for details of authentication.
25683 .option hosts_request_ocsp smtp "host list&!!" *
25684 .cindex "TLS" "requiring for certain servers"
25685 Exim will request a Certificate Status on a
25686 TLS session for any host that matches this list.
25687 &%tls_verify_certificates%& should also be set for the transport.
25690 .option hosts_require_alpn smtp "host list&!!" unset
25691 .cindex ALPN "require negotiation in client"
25693 .cindex TLS "Application Layer Protocol Names"
25694 If the TLS library supports ALPN
25695 then a successful negotiation of ALPN will be required for any host
25696 matching the list, for TLS to be used.
25697 See also the &%tls_alpn%& option.
25699 &*Note*&: prevention of fallback to in-clear connection is not
25700 managed by this option; see &%hosts_require_tls%&.
25703 .option hosts_require_dane smtp "host list&!!" unset
25704 .cindex DANE "transport options"
25705 .cindex DANE "requiring for certain servers"
25706 If built with DANE support, Exim will require that a DNSSEC-validated
25707 TLSA record is present for any host matching the list,
25708 and that a DANE-verified TLS connection is made.
25709 There will be no fallback to in-clear communication.
25710 See the &%dnssec_request_domains%& router and transport options.
25711 See section &<<SECDANE>>&.
25713 .option hosts_require_helo smtp "host list&!!" *
25714 .cindex "HELO/EHLO" requiring
25715 Exim will require an accepted HELO or EHLO command from a host matching
25716 this list, before accepting a MAIL command.
25718 .option hosts_require_ocsp smtp "host list&!!" unset
25719 .cindex "TLS" "requiring for certain servers"
25720 Exim will request, and check for a valid Certificate Status being given, on a
25721 TLS session for any host that matches this list.
25722 &%tls_verify_certificates%& should also be set for the transport.
25724 .option hosts_require_tls smtp "host list&!!" unset
25725 .cindex "TLS" "requiring for certain servers"
25726 Exim will insist on using a TLS session when delivering to any host that
25727 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25728 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25729 incoming messages, use an appropriate ACL.
25731 .option hosts_try_auth smtp "host list&!!" unset
25732 .cindex "authentication" "optional in client"
25733 This option provides a list of servers to which, provided they announce
25734 authentication support, Exim will attempt to authenticate as a client when it
25735 connects. If authentication fails
25737 and &%hosts_require_auth%& permits,
25739 Exim will try to transfer the message unauthenticated.
25740 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25742 .option hosts_try_chunking smtp "host list&!!" *
25743 .cindex CHUNKING "enabling, in client"
25744 .cindex BDAT "SMTP command"
25745 .cindex "RFC 3030" "CHUNKING"
25746 This option provides a list of servers to which, provided they announce
25747 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25748 Unless DKIM signing is being done,
25749 BDAT will not be used in conjunction with a transport filter.
25751 .option hosts_try_dane smtp "host list&!!" *
25752 .cindex DANE "transport options"
25753 .cindex DANE "attempting for certain servers"
25755 If built with DANE support, Exim will look up a
25756 TLSA record for any host matching the list,
25757 If one is found and that lookup was DNSSEC-validated,
25758 then Exim requires that a DANE-verified TLS connection is made for that host;
25759 there will be no fallback to in-clear communication.
25761 See the &%dnssec_request_domains%& router and transport options.
25762 See section &<<SECDANE>>&.
25764 .option hosts_try_fastopen smtp "host list&!!" *
25765 .cindex "fast open, TCP" "enabling, in client"
25766 .cindex "TCP Fast Open" "enabling, in client"
25767 .cindex "RFC 7413" "TCP Fast Open"
25768 This option provides a list of servers to which, provided
25769 the facility is supported by this system, Exim will attempt to
25770 perform a TCP Fast Open.
25771 No data is sent on the SYN segment but, if the remote server also
25772 supports the facility, it can send its SMTP banner immediately after
25773 the SYN,ACK segment. This can save up to one round-trip time.
25775 The facility is only active for previously-contacted servers,
25776 as the initiator must present a cookie in the SYN segment.
25778 On (at least some) current Linux distributions the facility must be enabled
25779 in the kernel by the sysadmin before the support is usable.
25780 There is no option for control of the server side; if the system supports
25781 it it is always enabled. Note that lengthy operations in the connect ACL,
25782 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25784 .option hosts_try_prdr smtp "host list&!!" *
25785 .cindex "PRDR" "enabling, optional in client"
25786 .cindex "ESMTP extensions" PRDR
25787 This option provides a list of servers to which, provided they announce
25788 PRDR support, Exim will attempt to negotiate PRDR
25789 for multi-recipient messages.
25790 The option can usually be left as default.
25792 .option interface smtp "string list&!!" unset
25793 .cindex "bind IP address"
25794 .cindex "IP address" "binding"
25796 .vindex "&$host_address$&"
25797 This option specifies which interface to bind to when making an outgoing SMTP
25798 call. The value is an IP address, not an interface name such as
25799 &`eth0`&. Do not confuse this with the interface address that was used when a
25800 message was received, which is in &$received_ip_address$&, formerly known as
25801 &$interface_address$&. The name was changed to minimize confusion with the
25802 outgoing interface address. There is no variable that contains an outgoing
25803 interface address because, unless it is set by this option, its value is
25806 During the expansion of the &%interface%& option the variables &$host$& and
25807 &$host_address$& refer to the host to which a connection is about to be made
25808 during the expansion of the string. Forced expansion failure, or an empty
25809 string result causes the option to be ignored. Otherwise, after expansion, the
25810 string must be a list of IP addresses, colon-separated by default, but the
25811 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25814 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25816 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25817 connection. If none of them are the correct type, the option is ignored. If
25818 &%interface%& is not set, or is ignored, the system's IP functions choose which
25819 interface to use if the host has more than one.
25822 .option keepalive smtp boolean true
25823 .cindex "keepalive" "on outgoing connection"
25824 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25825 connections. When set, it causes the kernel to probe idle connections
25826 periodically, by sending packets with &"old"& sequence numbers. The other end
25827 of the connection should send a acknowledgment if the connection is still okay
25828 or a reset if the connection has been aborted. The reason for doing this is
25829 that it has the beneficial effect of freeing up certain types of connection
25830 that can get stuck when the remote host is disconnected without tidying up the
25831 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25835 .option lmtp_ignore_quota smtp boolean false
25836 .cindex "LMTP" "ignoring quota errors"
25837 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25838 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25839 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25841 .option max_rcpt smtp integer 100
25842 .cindex "RCPT" "maximum number of outgoing"
25843 This option limits the number of RCPT commands that are sent in a single
25844 SMTP message transaction. Each set of addresses is treated independently, and
25845 so can cause parallel connections to the same host if &%remote_max_parallel%&
25846 permits this. A value setting of zero disables the limit.
25850 .option message_linelength_limit smtp integer 998
25851 .cindex "line length" limit
25852 This option sets the maximum line length, in bytes, that the transport
25853 will send. Any messages with lines exceeding the given value
25854 will fail and a failure-DSN ("bounce") message will if possible be returned
25856 The default value is that defined by the SMTP standards.
25858 It is generally wise to also check in the data ACL so that messages
25859 received via SMTP can be refused without producing a bounce.
25863 .option multi_domain smtp boolean&!! true
25864 .vindex "&$domain$&"
25865 When this option is set, the &(smtp)& transport can handle a number of
25866 addresses containing a mixture of different domains provided they all resolve
25867 to the same list of hosts. Turning the option off restricts the transport to
25868 handling only one domain at a time. This is useful if you want to use
25869 &$domain$& in an expansion for the transport, because it is set only when there
25870 is a single domain involved in a remote delivery.
25872 It is expanded per-address and can depend on any of
25873 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25874 &$host$&, &$host_address$& and &$host_port$&.
25877 If the connection is DANE-enabled then this option is ignored;
25878 only messages having the domain used for the DANE TLSA lookup are
25879 sent on the connection.
25882 .option port smtp string&!! "see below"
25883 .cindex "port" "sending TCP/IP"
25884 .cindex "TCP/IP" "setting outgoing port"
25885 This option specifies the TCP/IP port on the server to which Exim connects.
25886 &*Note:*& Do not confuse this with the port that was used when a message was
25887 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25888 The name was changed to minimize confusion with the outgoing port. There is no
25889 variable that contains an outgoing port.
25891 If the value of this option begins with a digit it is taken as a port number;
25892 otherwise it is looked up using &[getservbyname()]&. The default value is
25894 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25895 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25896 If the expansion fails, or if a port number cannot be found, delivery
25899 Note that at least one Linux distribution has been seen failing
25900 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25904 .option protocol smtp string smtp
25905 .cindex "LMTP" "over TCP/IP"
25906 .cindex "ssmtp protocol" "outbound"
25907 .cindex "TLS" "SSL-on-connect outbound"
25909 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25910 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25911 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25912 deliveries into closed message stores. Exim also has support for running LMTP
25913 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25915 If this option is set to &"smtps"&, the default value for the &%port%& option
25916 changes to &"smtps"&, and the transport initiates TLS immediately after
25917 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25918 The Internet standards bodies used to strongly discourage use of this mode,
25919 but as of RFC 8314 it is preferred over STARTTLS for message submission
25920 (as distinct from MTA-MTA communication).
25923 .option retry_include_ip_address smtp boolean&!! true
25924 Exim normally includes both the host name and the IP address in the key it
25925 constructs for indexing retry data after a temporary delivery failure. This
25926 means that when one of several IP addresses for a host is failing, it gets
25927 tried periodically (controlled by the retry rules), but use of the other IP
25928 addresses is not affected.
25930 However, in some dialup environments hosts are assigned a different IP address
25931 each time they connect. In this situation the use of the IP address as part of
25932 the retry key leads to undesirable behaviour. Setting this option false causes
25933 Exim to use only the host name.
25934 Since it is expanded it can be made to depend on the host or domain.
25937 .option serialize_hosts smtp "host list&!!" unset
25938 .cindex "serializing connections"
25939 .cindex "host" "serializing connections"
25940 Because Exim operates in a distributed manner, if several messages for the same
25941 host arrive at around the same time, more than one simultaneous connection to
25942 the remote host can occur. This is not usually a problem except when there is a
25943 slow link between the hosts. In that situation it may be helpful to restrict
25944 Exim to one connection at a time. This can be done by setting
25945 &%serialize_hosts%& to match the relevant hosts.
25947 .cindex "hints database" "serializing deliveries to a host"
25948 Exim implements serialization by means of a hints database in which a record is
25949 written whenever a process connects to one of the restricted hosts. The record
25950 is deleted when the connection is completed. Obviously there is scope for
25951 records to get left lying around if there is a system or program crash. To
25952 guard against this, Exim ignores any records that are more than six hours old.
25954 If you set up this kind of serialization, you should also arrange to delete the
25955 relevant hints database whenever your system reboots. The names of the files
25956 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25957 may be one or two files, depending on the type of DBM in use. The same files
25958 are used for ETRN serialization.
25960 See also the &%max_parallel%& generic transport option.
25963 .option size_addition smtp integer 1024
25964 .cindex "SIZE" "ESMTP extension"
25965 .cindex "message" "size issue for transport filter"
25966 .cindex "size" "of message"
25967 .cindex "transport" "filter"
25968 .cindex "filter" "transport filter"
25969 If a remote SMTP server indicates that it supports the SIZE option of the
25970 MAIL command, Exim uses this to pass over the message size at the start of
25971 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25972 sends, to allow for headers and other text that may be added during delivery by
25973 configuration options or in a transport filter. It may be necessary to increase
25974 this if a lot of text is added to messages.
25976 Alternatively, if the value of &%size_addition%& is set negative, it disables
25977 the use of the SIZE option altogether.
25980 .option socks_proxy smtp string&!! unset
25981 .cindex proxy SOCKS
25982 This option enables use of SOCKS proxies for connections made by the
25983 transport. For details see section &<<SECTproxySOCKS>>&.
25987 .option tls_alpn smtp string&!! unset
25988 .cindex TLS "Application Layer Protocol Names"
25990 .cindex ALPN "set name in client"
25991 If this option is set
25992 and the TLS library supports ALPN,
25993 the value given is used.
25995 As of writing no value has been standardised for email use.
25996 The authors suggest using &"smtp"&.
26001 .option tls_certificate smtp string&!! unset
26002 .cindex "TLS" "client certificate, location of"
26003 .cindex "certificate" "client, location of"
26005 .vindex "&$host_address$&"
26006 The value of this option must be the absolute path to a file which contains the
26007 client's certificate, for possible use when sending a message over an encrypted
26008 connection. The values of &$host$& and &$host_address$& are set to the name and
26009 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
26012 &*Note*&: This option must be set if you want Exim to be able to use a TLS
26013 certificate when sending messages as a client. The global option of the same
26014 name specifies the certificate for Exim as a server; it is not automatically
26015 assumed that the same certificate should be used when Exim is operating as a
26019 .option tls_crl smtp string&!! unset
26020 .cindex "TLS" "client certificate revocation list"
26021 .cindex "certificate" "revocation list for client"
26022 This option specifies a certificate revocation list. The expanded value must
26023 be the name of a file that contains a CRL in PEM format.
26026 .option tls_dh_min_bits smtp integer 1024
26027 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
26028 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
26029 key agreement is negotiated, the server will provide a large prime number
26030 for use. This option establishes the minimum acceptable size of that number.
26031 If the parameter offered by the server is too small, then the TLS handshake
26034 Only supported when using GnuTLS.
26037 .option tls_privatekey smtp string&!! unset
26038 .cindex "TLS" "client private key, location of"
26040 .vindex "&$host_address$&"
26041 The value of this option must be the absolute path to a file which contains the
26042 client's private key. This is used when sending a message over an encrypted
26043 connection using a client certificate. The values of &$host$& and
26044 &$host_address$& are set to the name and address of the server during the
26045 expansion. If this option is unset, or the expansion is forced to fail, or the
26046 result is an empty string, the private key is assumed to be in the same file as
26047 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
26050 .option tls_require_ciphers smtp string&!! unset
26051 .cindex "TLS" "requiring specific ciphers"
26052 .cindex "cipher" "requiring specific"
26054 .vindex "&$host_address$&"
26055 The value of this option must be a list of permitted cipher suites, for use
26056 when setting up an outgoing encrypted connection. (There is a global option of
26057 the same name for controlling incoming connections.) The values of &$host$& and
26058 &$host_address$& are set to the name and address of the server during the
26059 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26060 is used in different ways by OpenSSL and GnuTLS (see sections
26061 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26062 ciphers is a preference order.
26066 .option tls_resumption_hosts smtp "host list&!!" unset
26067 .cindex TLS resumption
26068 This option controls which connections to use the TLS resumption feature.
26069 See &<<SECTresumption>>& for details.
26074 .option tls_sni smtp string&!! unset
26075 .cindex "TLS" "Server Name Indication"
26077 .cindex SNI "setting in client"
26078 .vindex "&$tls_sni$&"
26079 If this option is set
26081 and the connection is not DANE-validated
26083 then it sets the $tls_out_sni variable and causes any
26084 TLS session to pass this value as the Server Name Indication extension to
26085 the remote side, which can be used by the remote side to select an appropriate
26086 certificate and private key for the session.
26088 See &<<SECTtlssni>>& for more information.
26090 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26096 .option tls_tempfail_tryclear smtp boolean true
26097 .cindex "4&'xx'& responses" "to STARTTLS"
26098 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26099 setting up a TLS session, this option determines whether or not Exim should try
26100 to deliver the message unencrypted. If it is set false, delivery to the
26101 current host is deferred; if there are other hosts, they are tried. If this
26102 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26103 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26104 TLS negotiation fails, Exim closes the current connection (because it is in an
26105 unknown state), opens a new one to the same host, and then tries the delivery
26109 .option tls_try_verify_hosts smtp "host list&!!" *
26110 .cindex "TLS" "server certificate verification"
26111 .cindex "certificate" "verification of server"
26112 This option gives a list of hosts for which, on encrypted connections,
26113 certificate verification will be tried but need not succeed.
26114 The &%tls_verify_certificates%& option must also be set.
26115 Note that unless the host is in this list
26116 TLS connections will be denied to hosts using self-signed certificates
26117 when &%tls_verify_certificates%& is matched.
26118 The &$tls_out_certificate_verified$& variable is set when
26119 certificate verification succeeds.
26122 .option tls_verify_cert_hostnames smtp "host list&!!" *
26123 .cindex "TLS" "server certificate hostname verification"
26124 .cindex "certificate" "verification of server"
26125 This option give a list of hosts for which,
26126 while verifying the server certificate,
26127 checks will be included on the host name
26128 (note that this will generally be the result of a DNS MX lookup)
26129 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26130 limited to being the initial component of a 3-or-more component FQDN.
26132 There is no equivalent checking on client certificates.
26135 .option tls_verify_certificates smtp string&!! system
26136 .cindex "TLS" "server certificate verification"
26137 .cindex "certificate" "verification of server"
26139 .vindex "&$host_address$&"
26140 The value of this option must be either the
26142 or the absolute path to
26143 a file or directory containing permitted certificates for servers,
26144 for use when setting up an encrypted connection.
26146 The "system" value for the option will use a location compiled into the SSL library.
26147 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26148 is taken as empty and an explicit location
26151 The use of a directory for the option value is not available for GnuTLS versions
26152 preceding 3.3.6 and a single file must be used.
26154 With OpenSSL the certificates specified
26156 either by file or directory
26157 are added to those given by the system default location.
26159 The values of &$host$& and
26160 &$host_address$& are set to the name and address of the server during the
26161 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26163 For back-compatibility,
26164 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26165 (a single-colon empty list counts as being set)
26166 and certificate verification fails the TLS connection is closed.
26169 .option tls_verify_hosts smtp "host list&!!" unset
26170 .cindex "TLS" "server certificate verification"
26171 .cindex "certificate" "verification of server"
26172 This option gives a list of hosts for which, on encrypted connections,
26173 certificate verification must succeed.
26174 The &%tls_verify_certificates%& option must also be set.
26175 If both this option and &%tls_try_verify_hosts%& are unset
26176 operation is as if this option selected all hosts.
26178 .option utf8_downconvert smtp integer&!! -1
26179 .cindex utf8 "address downconversion"
26180 .cindex i18n "utf8 address downconversion"
26181 If built with internationalization support,
26182 this option controls conversion of UTF-8 in message envelope addresses
26184 If, after expansion, the value is 1, 0, or -1 then this value overrides
26185 any value previously set for the message. Otherwise, any previously
26186 set value is used. To permit use of a previous value,
26187 set this option to an empty string.
26188 For details on the values see section &<<SECTi18nMTA>>&.
26193 .section "How the limits for the number of hosts to try are used" &&&
26195 .cindex "host" "maximum number to try"
26196 .cindex "limit" "hosts; maximum number tried"
26197 There are two options that are concerned with the number of hosts that are
26198 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26199 &%hosts_max_try_hardlimit%&.
26202 The &%hosts_max_try%& option limits the number of hosts that are tried
26203 for a single delivery. However, despite the term &"host"& in its name, the
26204 option actually applies to each IP address independently. In other words, a
26205 multihomed host is treated as several independent hosts, just as it is for
26208 Many of the larger ISPs have multiple MX records which often point to
26209 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26210 created as a result of routing one of these domains.
26212 Trying every single IP address on such a long list does not seem sensible; if
26213 several at the top of the list fail, it is reasonable to assume there is some
26214 problem that is likely to affect all of them. Roughly speaking, the value of
26215 &%hosts_max_try%& is the maximum number that are tried before deferring the
26216 delivery. However, the logic cannot be quite that simple.
26218 Firstly, IP addresses that are skipped because their retry times have not
26219 arrived do not count, and in addition, addresses that are past their retry
26220 limits are also not counted, even when they are tried. This means that when
26221 some IP addresses are past their retry limits, more than the value of
26222 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26223 that all IP addresses are considered before timing out an email address (but
26224 see below for an exception).
26226 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26227 list to see if there is a subsequent host with a different (higher valued) MX.
26228 If there is, that host is considered next, and the current IP address is used
26229 but not counted. This behaviour helps in the case of a domain with a retry rule
26230 that hardly ever delays any hosts, as is now explained:
26232 Consider the case of a long list of hosts with one MX value, and a few with a
26233 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26234 hosts at the top of the list are tried at first. With the default retry rule,
26235 which specifies increasing retry times, the higher MX hosts are eventually
26236 tried when those at the top of the list are skipped because they have not
26237 reached their retry times.
26239 However, it is common practice to put a fixed short retry time on domains for
26240 large ISPs, on the grounds that their servers are rarely down for very long.
26241 Unfortunately, these are exactly the domains that tend to resolve to long lists
26242 of hosts. The short retry time means that the lowest MX hosts are tried every
26243 time. The attempts may be in a different order because of random sorting, but
26244 without the special MX check, the higher MX hosts would never be tried until
26245 all the lower MX hosts had timed out (which might be several days), because
26246 there are always some lower MX hosts that have reached their retry times. With
26247 the special check, Exim considers at least one IP address from each MX value at
26248 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26251 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26252 particular, Exim normally eventually tries all the IP addresses before timing
26253 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26254 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26255 been set up with hundreds of IP addresses for some domains. It can
26256 take a very long time indeed for an address to time out in these cases.
26258 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26259 Exim never tries more than this number of IP addresses; if it hits this limit
26260 and they are all timed out, the email address is bounced, even though not all
26261 possible IP addresses have been tried.
26262 .ecindex IIDsmttra1
26263 .ecindex IIDsmttra2
26269 . ////////////////////////////////////////////////////////////////////////////
26270 . ////////////////////////////////////////////////////////////////////////////
26272 .chapter "Address rewriting" "CHAPrewrite"
26273 .scindex IIDaddrew "rewriting" "addresses"
26274 There are some circumstances in which Exim automatically rewrites domains in
26275 addresses. The two most common are when an address is given without a domain
26276 (referred to as an &"unqualified address"&) or when an address contains an
26277 abbreviated domain that is expanded by DNS lookup.
26279 Unqualified envelope addresses are accepted only for locally submitted
26280 messages, or for messages that are received from hosts matching
26281 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26282 appropriate. Unqualified addresses in header lines are qualified if they are in
26283 locally submitted messages, or messages from hosts that are permitted to send
26284 unqualified envelope addresses. Otherwise, unqualified addresses in header
26285 lines are neither qualified nor rewritten.
26287 One situation in which Exim does &'not'& automatically rewrite a domain is
26288 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26289 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26290 do this. The new RFCs do not contain this suggestion.
26293 .section "Explicitly configured address rewriting" "SECID147"
26294 This chapter describes the rewriting rules that can be used in the
26295 main rewrite section of the configuration file, and also in the generic
26296 &%headers_rewrite%& option that can be set on any transport.
26298 Some people believe that configured address rewriting is a Mortal Sin.
26299 Others believe that life is not possible without it. Exim provides the
26300 facility; you do not have to use it.
26302 The main rewriting rules that appear in the &"rewrite"& section of the
26303 configuration file are applied to addresses in incoming messages, both envelope
26304 addresses and addresses in header lines. Each rule specifies the types of
26305 address to which it applies.
26307 Whether or not addresses in header lines are rewritten depends on the origin of
26308 the headers and the type of rewriting. Global rewriting, that is, rewriting
26309 rules from the rewrite section of the configuration file, is applied only to
26310 those headers that were received with the message. Header lines that are added
26311 by ACLs or by a system filter or by individual routers or transports (which
26312 are specific to individual recipient addresses) are not rewritten by the global
26315 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26316 applies all headers except those added by routers and transports. That is, as
26317 well as the headers that were received with the message, it also applies to
26318 headers that were added by an ACL or a system filter.
26321 In general, rewriting addresses from your own system or domain has some
26322 legitimacy. Rewriting other addresses should be done only with great care and
26323 in special circumstances. The author of Exim believes that rewriting should be
26324 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26325 Although it can sometimes be used as a routing tool, this is very strongly
26328 There are two commonly encountered circumstances where rewriting is used, as
26329 illustrated by these examples:
26332 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26333 exchange mail with each other behind a firewall, but there is only a single
26334 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26335 &'hitch.fict.example'& when sending mail off-site.
26337 A host rewrites the local parts of its own users so that, for example,
26338 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26343 .section "When does rewriting happen?" "SECID148"
26344 .cindex "rewriting" "timing of"
26345 .cindex "&ACL;" "rewriting addresses in"
26346 Configured address rewriting can take place at several different stages of a
26347 message's processing.
26349 .vindex "&$sender_address$&"
26350 At the start of an ACL for MAIL, the sender address may have been rewritten
26351 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26352 ordinary rewrite rules have yet been applied. If, however, the sender address
26353 is verified in the ACL, it is rewritten before verification, and remains
26354 rewritten thereafter. The subsequent value of &$sender_address$& is the
26355 rewritten address. This also applies if sender verification happens in a
26356 RCPT ACL. Otherwise, when the sender address is not verified, it is
26357 rewritten as soon as a message's header lines have been received.
26359 .vindex "&$domain$&"
26360 .vindex "&$local_part$&"
26361 Similarly, at the start of an ACL for RCPT, the current recipient's address
26362 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26363 rewrite rules have yet been applied to it. However, the behaviour is different
26364 from the sender address when a recipient is verified. The address is rewritten
26365 for the verification, but the rewriting is not remembered at this stage. The
26366 value of &$local_part$& and &$domain$& after verification are always the same
26367 as they were before (that is, they contain the unrewritten &-- except for
26368 SMTP-time rewriting &-- address).
26370 As soon as a message's header lines have been received, all the envelope
26371 recipient addresses are permanently rewritten, and rewriting is also applied to
26372 the addresses in the header lines (if configured). This happens before adding
26373 any header lines that were specified in MAIL or RCPT ACLs, and
26374 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26375 before the DATA ACL and &[local_scan()]& functions are run.
26377 When an address is being routed, either for delivery or for verification,
26378 rewriting is applied immediately to child addresses that are generated by
26379 redirection, unless &%no_rewrite%& is set on the router.
26381 .cindex "envelope from"
26382 .cindex "envelope sender" "rewriting at transport time"
26383 .cindex "rewriting" "at transport time"
26384 .cindex "header lines" "rewriting at transport time"
26385 At transport time, additional rewriting of addresses in header lines can be
26386 specified by setting the generic &%headers_rewrite%& option on a transport.
26387 This option contains rules that are identical in form to those in the rewrite
26388 section of the configuration file. They are applied to the original message
26389 header lines and any that were added by ACLs or a system filter. They are not
26390 applied to header lines that are added by routers or the transport.
26392 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26393 transport option. However, it is not possible to rewrite envelope recipients at
26399 .section "Testing the rewriting rules that apply on input" "SECID149"
26400 .cindex "rewriting" "testing"
26401 .cindex "testing" "rewriting"
26402 Exim's input rewriting configuration appears in a part of the runtime
26403 configuration file headed by &"begin rewrite"&. It can be tested by the
26404 &%-brw%& command line option. This takes an address (which can be a full RFC
26405 2822 address) as its argument. The output is a list of how the address would be
26406 transformed by the rewriting rules for each of the different places it might
26407 appear in an incoming message, that is, for each different header and for the
26408 envelope sender and recipient fields. For example,
26410 exim -brw ph10@exim.workshop.example
26412 might produce the output
26414 sender: Philip.Hazel@exim.workshop.example
26415 from: Philip.Hazel@exim.workshop.example
26416 to: ph10@exim.workshop.example
26417 cc: ph10@exim.workshop.example
26418 bcc: ph10@exim.workshop.example
26419 reply-to: Philip.Hazel@exim.workshop.example
26420 env-from: Philip.Hazel@exim.workshop.example
26421 env-to: ph10@exim.workshop.example
26423 which shows that rewriting has been set up for that address when used in any of
26424 the source fields, but not when it appears as a recipient address. At the
26425 present time, there is no equivalent way of testing rewriting rules that are
26426 set for a particular transport.
26429 .section "Rewriting rules" "SECID150"
26430 .cindex "rewriting" "rules"
26431 The rewrite section of the configuration file consists of lines of rewriting
26434 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26436 Rewriting rules that are specified for the &%headers_rewrite%& generic
26437 transport option are given as a colon-separated list. Each item in the list
26438 takes the same form as a line in the main rewriting configuration (except that
26439 any colons must be doubled, of course).
26441 The formats of source patterns and replacement strings are described below.
26442 Each is terminated by white space, unless enclosed in double quotes, in which
26443 case normal quoting conventions apply inside the quotes. The flags are single
26444 characters which may appear in any order. Spaces and tabs between them are
26447 For each address that could potentially be rewritten, the rules are scanned in
26448 order, and replacements for the address from earlier rules can themselves be
26449 replaced by later rules (but see the &"q"& and &"R"& flags).
26451 The order in which addresses are rewritten is undefined, may change between
26452 releases, and must not be relied on, with one exception: when a message is
26453 received, the envelope sender is always rewritten first, before any header
26454 lines are rewritten. For example, the replacement string for a rewrite of an
26455 address in &'To:'& must not assume that the message's address in &'From:'& has
26456 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26457 that the envelope sender has already been rewritten.
26459 .vindex "&$domain$&"
26460 .vindex "&$local_part$&"
26461 The variables &$local_part$& and &$domain$& can be used in the replacement
26462 string to refer to the address that is being rewritten. Note that lookup-driven
26463 rewriting can be done by a rule of the form
26467 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26468 refer to the address that is being rewritten.
26471 .section "Rewriting patterns" "SECID151"
26472 .cindex "rewriting" "patterns"
26473 .cindex "address list" "in a rewriting pattern"
26474 The source pattern in a rewriting rule is any item which may appear in an
26475 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26476 single-item address list, which means that it is expanded before being tested
26477 against the address. As always, if you use a regular expression as a pattern,
26478 you must take care to escape dollar and backslash characters, or use the &`\N`&
26479 facility to suppress string expansion within the regular expression.
26481 Domains in patterns should be given in lower case. Local parts in patterns are
26482 case-sensitive. If you want to do case-insensitive matching of local parts, you
26483 can use a regular expression that starts with &`^(?i)`&.
26485 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26486 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26487 depending on the type of match which occurred. These can be used in the
26488 replacement string to insert portions of the incoming address. &$0$& always
26489 refers to the complete incoming address. When a regular expression is used, the
26490 numerical variables are set from its capturing subexpressions. For other types
26491 of pattern they are set as follows:
26494 If a local part or domain starts with an asterisk, the numerical variables
26495 refer to the character strings matched by asterisks, with &$1$& associated with
26496 the first asterisk, and &$2$& with the second, if present. For example, if the
26499 *queen@*.fict.example
26501 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26503 $0 = hearts-queen@wonderland.fict.example
26507 Note that if the local part does not start with an asterisk, but the domain
26508 does, it is &$1$& that contains the wild part of the domain.
26511 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26512 of the domain are placed in the next available numerical variables. Suppose,
26513 for example, that the address &'foo@bar.baz.example'& is processed by a
26514 rewriting rule of the form
26516 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26518 and the key in the file that matches the domain is &`*.baz.example`&. Then
26524 If the address &'foo@baz.example'& is looked up, this matches the same
26525 wildcard file entry, and in this case &$2$& is set to the empty string, but
26526 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26527 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26528 whole domain. For non-partial domain lookups, no numerical variables are set.
26532 .section "Rewriting replacements" "SECID152"
26533 .cindex "rewriting" "replacements"
26534 If the replacement string for a rule is a single asterisk, addresses that
26535 match the pattern and the flags are &'not'& rewritten, and no subsequent
26536 rewriting rules are scanned. For example,
26538 hatta@lookingglass.fict.example * f
26540 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26543 .vindex "&$domain$&"
26544 .vindex "&$local_part$&"
26545 If the replacement string is not a single asterisk, it is expanded, and must
26546 yield a fully qualified address. Within the expansion, the variables
26547 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26548 Any letters they contain retain their original case &-- they are not lower
26549 cased. The numerical variables are set up according to the type of pattern that
26550 matched the address, as described above. If the expansion is forced to fail by
26551 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26552 current rule is abandoned, but subsequent rules may take effect. Any other
26553 expansion failure causes the entire rewriting operation to be abandoned, and an
26554 entry written to the panic log.
26558 .section "Rewriting flags" "SECID153"
26559 There are three different kinds of flag that may appear on rewriting rules:
26562 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26565 A flag that specifies rewriting at SMTP time: S.
26567 Flags that control the rewriting process: Q, q, R, w.
26570 For rules that are part of the &%headers_rewrite%& generic transport option,
26571 E, F, T, and S are not permitted.
26575 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26577 .cindex "rewriting" "flags"
26578 If none of the following flag letters, nor the &"S"& flag (see section
26579 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26580 and to both the sender and recipient fields of the envelope, whereas a
26581 transport-time rewriting rule just applies to all headers. Otherwise, the
26582 rewriting rule is skipped unless the relevant addresses are being processed.
26584 &`E`& rewrite all envelope fields
26585 &`F`& rewrite the envelope From field
26586 &`T`& rewrite the envelope To field
26587 &`b`& rewrite the &'Bcc:'& header
26588 &`c`& rewrite the &'Cc:'& header
26589 &`f`& rewrite the &'From:'& header
26590 &`h`& rewrite all headers
26591 &`r`& rewrite the &'Reply-To:'& header
26592 &`s`& rewrite the &'Sender:'& header
26593 &`t`& rewrite the &'To:'& header
26595 "All headers" means all of the headers listed above that can be selected
26596 individually, plus their &'Resent-'& versions. It does not include
26597 other headers such as &'Subject:'& etc.
26599 You should be particularly careful about rewriting &'Sender:'& headers, and
26600 restrict this to special known cases in your own domains.
26603 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26604 .cindex "SMTP" "rewriting malformed addresses"
26605 .cindex "RCPT" "rewriting argument of"
26606 .cindex "MAIL" "rewriting argument of"
26607 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26608 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26609 before any other processing; even before syntax checking. The pattern is
26610 required to be a regular expression, and it is matched against the whole of the
26611 data for the command, including any surrounding angle brackets.
26613 .vindex "&$domain$&"
26614 .vindex "&$local_part$&"
26615 This form of rewrite rule allows for the handling of addresses that are not
26616 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26617 input). Because the input is not required to be a syntactically valid address,
26618 the variables &$local_part$& and &$domain$& are not available during the
26619 expansion of the replacement string. The result of rewriting replaces the
26620 original address in the MAIL or RCPT command.
26623 .section "Flags controlling the rewriting process" "SECID155"
26624 There are four flags which control the way the rewriting process works. These
26625 take effect only when a rule is invoked, that is, when the address is of the
26626 correct type (matches the flags) and matches the pattern:
26629 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26630 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26631 absence of &"Q"& the rewritten address must always include a domain.
26633 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26634 even if no rewriting actually takes place because of a &"fail"& in the
26635 expansion. The &"q"& flag is not effective if the address is of the wrong type
26636 (does not match the flags) or does not match the pattern.
26638 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26639 address, up to ten times. It can be combined with the &"q"& flag, to stop
26640 rewriting once it fails to match (after at least one successful rewrite).
26642 .cindex "rewriting" "whole addresses"
26643 When an address in a header is rewritten, the rewriting normally applies only
26644 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26645 left unchanged. For example, rewriting might change
26647 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26651 From: Ford Prefect <prefectf@hitch.fict.example>
26654 Sometimes there is a need to replace the whole address item, and this can be
26655 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26656 causes an address in a header line to be rewritten, the entire address is
26657 replaced, not just the working part. The replacement must be a complete RFC
26658 2822 address, including the angle brackets if necessary. If text outside angle
26659 brackets contains a character whose value is greater than 126 or less than 32
26660 (except for tab), the text is encoded according to RFC 2047. The character set
26661 is taken from &%headers_charset%&, which gets its default at build time.
26663 When the &"w"& flag is set on a rule that causes an envelope address to be
26664 rewritten, all but the working part of the replacement address is discarded.
26668 .section "Rewriting examples" "SECID156"
26669 Here is an example of the two common rewriting paradigms:
26671 *@*.hitch.fict.example $1@hitch.fict.example
26672 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26673 {$value}fail}@hitch.fict.example bctfrF
26675 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26676 the string expansion to fail if the lookup does not succeed. In this context it
26677 has the effect of leaving the original address unchanged, but Exim goes on to
26678 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26679 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26680 explicitly, which would cause the rewritten address to be the same as before,
26681 at the cost of a small bit of processing. Not supplying either of these is an
26682 error, since the rewritten address would then contain no local part.
26684 The first example above replaces the domain with a superior, more general
26685 domain. This may not be desirable for certain local parts. If the rule
26687 root@*.hitch.fict.example *
26689 were inserted before the first rule, rewriting would be suppressed for the
26690 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26692 Rewriting can be made conditional on a number of tests, by making use of
26693 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26694 messages that originate outside the local host:
26696 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26697 {$1@hitch.fict.example}fail}"
26699 The replacement string is quoted in this example because it contains white
26702 .cindex "rewriting" "bang paths"
26703 .cindex "bang paths" "rewriting"
26704 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26705 an address it treats it as an unqualified local part which it qualifies with
26706 the local qualification domain (if the source of the message is local or if the
26707 remote host is permitted to send unqualified addresses). Rewriting can
26708 sometimes be used to handle simple bang paths with a fixed number of
26709 components. For example, the rule
26711 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26713 rewrites a two-component bang path &'host.name!user'& as the domain address
26714 &'user@host.name'&. However, there is a security implication in using this as
26715 a global rewriting rule for envelope addresses. It can provide a backdoor
26716 method for using your system as a relay, because the incoming addresses appear
26717 to be local. If the bang path addresses are received via SMTP, it is safer to
26718 use the &"S"& flag to rewrite them as they are received, so that relay checking
26719 can be done on the rewritten addresses.
26726 . ////////////////////////////////////////////////////////////////////////////
26727 . ////////////////////////////////////////////////////////////////////////////
26729 .chapter "Retry configuration" "CHAPretry"
26730 .scindex IIDretconf1 "retry" "configuration, description of"
26731 .scindex IIDregconf2 "configuration file" "retry section"
26732 The &"retry"& section of the runtime configuration file contains a list of
26733 retry rules that control how often Exim tries to deliver messages that cannot
26734 be delivered at the first attempt. If there are no retry rules (the section is
26735 empty or not present), there are no retries. In this situation, temporary
26736 errors are treated as permanent. The default configuration contains a single,
26737 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26738 line option can be used to test which retry rule will be used for a given
26739 address, domain and error.
26741 The most common cause of retries is temporary failure to deliver to a remote
26742 host because the host is down, or inaccessible because of a network problem.
26743 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26744 address) basis, not on a per-message basis. Thus, if one message has recently
26745 been delayed, delivery of a new message to the same host is not immediately
26746 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26747 log selector is set, the message
26748 .cindex "retry" "time not reached"
26749 &"retry time not reached"& is written to the main log whenever a delivery is
26750 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26751 the handling of errors during remote deliveries.
26753 Retry processing applies to routing as well as to delivering, except as covered
26754 in the next paragraph. The retry rules do not distinguish between these
26755 actions. It is not possible, for example, to specify different behaviour for
26756 failures to route the domain &'snark.fict.example'& and failures to deliver to
26757 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26758 added complication, so did not implement it. However, although they share the
26759 same retry rule, the actual retry times for routing and transporting a given
26760 domain are maintained independently.
26762 When a delivery is not part of a queue run (typically an immediate delivery on
26763 receipt of a message), the routers are always run, and local deliveries are
26764 always attempted, even if retry times are set for them. This makes for better
26765 behaviour if one particular message is causing problems (for example, causing
26766 quota overflow, or provoking an error in a filter file). If such a delivery
26767 suffers a temporary failure, the retry data is updated as normal, and
26768 subsequent delivery attempts from queue runs occur only when the retry time for
26769 the local address is reached.
26771 .section "Changing retry rules" "SECID157"
26772 If you change the retry rules in your configuration, you should consider
26773 whether or not to delete the retry data that is stored in Exim's spool area in
26774 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26775 always safe; that is why they are called &"hints"&.
26777 The hints retry data contains suggested retry times based on the previous
26778 rules. In the case of a long-running problem with a remote host, it might
26779 record the fact that the host has timed out. If your new rules increase the
26780 timeout time for such a host, you should definitely remove the old retry data
26781 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26782 messages that it should now be retaining.
26786 .section "Format of retry rules" "SECID158"
26787 .cindex "retry" "rules"
26788 Each retry rule occupies one line and consists of three or four parts,
26789 separated by white space: a pattern, an error name, an optional list of sender
26790 addresses, and a list of retry parameters. The pattern and sender lists must be
26791 enclosed in double quotes if they contain white space. The rules are searched
26792 in order until one is found where the pattern, error name, and sender list (if
26793 present) match the failing host or address, the error that occurred, and the
26794 message's sender, respectively.
26797 The pattern is any single item that may appear in an address list (see section
26798 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26799 which means that it is expanded before being tested against the address that
26800 has been delayed. A negated address list item is permitted. Address
26801 list processing treats a plain domain name as if it were preceded by &"*@"&,
26802 which makes it possible for many retry rules to start with just a domain. For
26805 lookingglass.fict.example * F,24h,30m;
26807 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26810 alice@lookingglass.fict.example * F,24h,30m;
26812 applies only to temporary failures involving the local part &%alice%&.
26813 In practice, almost all rules start with a domain name pattern without a local
26816 .cindex "regular expressions" "in retry rules"
26817 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26818 must match a complete address, not just a domain, because that is how regular
26819 expressions work in address lists.
26821 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26822 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26826 .section "Choosing which retry rule to use for address errors" "SECID159"
26827 When Exim is looking for a retry rule after a routing attempt has failed (for
26828 example, after a DNS timeout), each line in the retry configuration is tested
26829 against the complete address only if &%retry_use_local_part%& is set for the
26830 router. Otherwise, only the domain is used, except when matching against a
26831 regular expression, when the local part of the address is replaced with &"*"&.
26832 A domain on its own can match a domain pattern, or a pattern that starts with
26833 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26834 &%check_local_user%& is true, and false for other routers.
26836 Similarly, when Exim is looking for a retry rule after a local delivery has
26837 failed (for example, after a mailbox full error), each line in the retry
26838 configuration is tested against the complete address only if
26839 &%retry_use_local_part%& is set for the transport (it defaults true for all
26842 .cindex "4&'xx'& responses" "retry rules for"
26843 However, when Exim is looking for a retry rule after a remote delivery attempt
26844 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26845 whole address is always used as the key when searching the retry rules. The
26846 rule that is found is used to create a retry time for the combination of the
26847 failing address and the message's sender. It is the combination of sender and
26848 recipient that is delayed in subsequent queue runs until its retry time is
26849 reached. You can delay the recipient without regard to the sender by setting
26850 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26851 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26856 .section "Choosing which retry rule to use for host and message errors" &&&
26858 For a temporary error that is not related to an individual address (for
26859 example, a connection timeout), each line in the retry configuration is checked
26860 twice. First, the name of the remote host is used as a domain name (preceded by
26861 &"*@"& when matching a regular expression). If this does not match the line,
26862 the domain from the email address is tried in a similar fashion. For example,
26863 suppose the MX records for &'a.b.c.example'& are
26865 a.b.c.example MX 5 x.y.z.example
26869 and the retry rules are
26871 p.q.r.example * F,24h,30m;
26872 a.b.c.example * F,4d,45m;
26874 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26875 first rule matches neither the host nor the domain, so Exim looks at the second
26876 rule. This does not match the host, but it does match the domain, so it is used
26877 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26878 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26879 first retry rule is used, because it matches the host.
26881 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26882 first rule to determine retry times, but for all the other hosts for the domain
26883 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26884 routing to &'a.b.c.example'& suffers a temporary failure.
26886 &*Note*&: The host name is used when matching the patterns, not its IP address.
26887 However, if a message is routed directly to an IP address without the use of a
26888 host name, for example, if a &(manualroute)& router contains a setting such as:
26890 route_list = *.a.example 192.168.34.23
26892 then the &"host name"& that is used when searching for a retry rule is the
26893 textual form of the IP address.
26895 .section "Retry rules for specific errors" "SECID161"
26896 .cindex "retry" "specific errors; specifying"
26897 The second field in a retry rule is the name of a particular error, or an
26898 asterisk, which matches any error. The errors that can be tested for are:
26901 .vitem &%auth_failed%&
26902 Authentication failed when trying to send to a host in the
26903 &%hosts_require_auth%& list in an &(smtp)& transport.
26905 .vitem &%data_4xx%&
26906 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26907 after the command, or after sending the message's data.
26909 .vitem &%mail_4xx%&
26910 A 4&'xx'& error was received for an outgoing MAIL command.
26912 .vitem &%rcpt_4xx%&
26913 A 4&'xx'& error was received for an outgoing RCPT command.
26916 For the three 4&'xx'& errors, either the first or both of the x's can be given
26917 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26918 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26919 and have retries every ten minutes with a one-hour timeout, you could set up a
26920 retry rule of this form:
26922 the.domain.name rcpt_452 F,1h,10m
26924 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26925 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26928 .vitem &%lost_connection%&
26929 A server unexpectedly closed the SMTP connection. There may, of course,
26930 legitimate reasons for this (host died, network died), but if it repeats a lot
26931 for the same host, it indicates something odd.
26934 A DNS lookup for a host failed.
26935 Note that a &%dnslookup%& router will need to have matched
26936 its &%fail_defer_domains%& option for this retry type to be usable.
26937 Also note that a &%manualroute%& router will probably need
26938 its &%host_find_failed%& option set to &%defer%&.
26940 .vitem &%refused_MX%&
26941 A connection to a host obtained from an MX record was refused.
26943 .vitem &%refused_A%&
26944 A connection to a host not obtained from an MX record was refused.
26947 A connection was refused.
26949 .vitem &%timeout_connect_MX%&
26950 A connection attempt to a host obtained from an MX record timed out.
26952 .vitem &%timeout_connect_A%&
26953 A connection attempt to a host not obtained from an MX record timed out.
26955 .vitem &%timeout_connect%&
26956 A connection attempt timed out.
26958 .vitem &%timeout_MX%&
26959 There was a timeout while connecting or during an SMTP session with a host
26960 obtained from an MX record.
26962 .vitem &%timeout_A%&
26963 There was a timeout while connecting or during an SMTP session with a host not
26964 obtained from an MX record.
26967 There was a timeout while connecting or during an SMTP session.
26969 .vitem &%tls_required%&
26970 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26971 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26972 to STARTTLS, or there was a problem setting up the TLS connection.
26975 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26978 .vitem &%quota_%&<&'time'&>
26979 .cindex "quota" "error testing in retry rule"
26980 .cindex "retry" "quota error testing"
26981 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26982 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26983 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26987 .cindex "mailbox" "time of last read"
26988 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26989 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26990 it should be based on the last time that the user accessed the mailbox.
26991 However, it is not always possible to determine this. Exim uses the following
26995 If the mailbox is a single file, the time of last access (the &"atime"&) is
26996 used. As no new messages are being delivered (because the mailbox is over
26997 quota), Exim does not access the file, so this is the time of last user access.
26999 .cindex "maildir format" "time of last read"
27000 For a maildir delivery, the time of last modification of the &_new_&
27001 subdirectory is used. As the mailbox is over quota, no new files are created in
27002 the &_new_& subdirectory, because no new messages are being delivered. Any
27003 change to the &_new_& subdirectory is therefore assumed to be the result of an
27004 MUA moving a new message to the &_cur_& directory when it is first read. The
27005 time that is used is therefore the last time that the user read a new message.
27007 For other kinds of multi-file mailbox, the time of last access cannot be
27008 obtained, so a retry rule that uses this type of error field is never matched.
27011 The quota errors apply both to system-enforced quotas and to Exim's own quota
27012 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
27013 when a local delivery is deferred because a partition is full (the ENOSPC
27018 .section "Retry rules for specified senders" "SECID162"
27019 .cindex "retry" "rules; sender-specific"
27020 You can specify retry rules that apply only when the failing message has a
27021 specific sender. In particular, this can be used to define retry rules that
27022 apply only to bounce messages. The third item in a retry rule can be of this
27025 &`senders=`&<&'address list'&>
27027 The retry timings themselves are then the fourth item. For example:
27029 * rcpt_4xx senders=: F,1h,30m
27031 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
27032 host. If the address list contains white space, it must be enclosed in quotes.
27035 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
27037 &*Warning*&: This facility can be unhelpful if it is used for host errors
27038 (which do not depend on the recipient). The reason is that the sender is used
27039 only to match the retry rule. Once the rule has been found for a host error,
27040 its contents are used to set a retry time for the host, and this will apply to
27041 all messages, not just those with specific senders.
27043 When testing retry rules using &%-brt%&, you can supply a sender using the
27044 &%-f%& command line option, like this:
27046 exim -f "" -brt user@dom.ain
27048 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
27049 list is never matched.
27055 .section "Retry parameters" "SECID163"
27056 .cindex "retry" "parameters in rules"
27057 The third (or fourth, if a senders list is present) field in a retry rule is a
27058 sequence of retry parameter sets, separated by semicolons. Each set consists of
27060 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27062 The letter identifies the algorithm for computing a new retry time; the cutoff
27063 time is the time beyond which this algorithm no longer applies, and the
27064 arguments vary the algorithm's action. The cutoff time is measured from the
27065 time that the first failure for the domain (combined with the local part if
27066 relevant) was detected, not from the time the message was received.
27068 .cindex "retry" "algorithms"
27069 .cindex "retry" "fixed intervals"
27070 .cindex "retry" "increasing intervals"
27071 .cindex "retry" "random intervals"
27072 The available algorithms are:
27075 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27078 &'G'&: retry at geometrically increasing intervals. The first argument
27079 specifies a starting value for the interval, and the second a multiplier, which
27080 is used to increase the size of the interval at each retry.
27082 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27083 retry, the previous interval is multiplied by the factor in order to get a
27084 maximum for the next interval. The minimum interval is the first argument of
27085 the parameter, and an actual interval is chosen randomly between them. Such a
27086 rule has been found to be helpful in cluster configurations when all the
27087 members of the cluster restart at once, and may therefore synchronize their
27088 queue processing times.
27091 When computing the next retry time, the algorithm definitions are scanned in
27092 order until one whose cutoff time has not yet passed is reached. This is then
27093 used to compute a new retry time that is later than the current time. In the
27094 case of fixed interval retries, this simply means adding the interval to the
27095 current time. For geometrically increasing intervals, retry intervals are
27096 computed from the rule's parameters until one that is greater than the previous
27097 interval is found. The main configuration variable
27098 .cindex "limit" "retry interval"
27099 .cindex "retry" "interval, maximum"
27100 .oindex "&%retry_interval_max%&"
27101 &%retry_interval_max%& limits the maximum interval between retries. It
27102 cannot be set greater than &`24h`&, which is its default value.
27104 A single remote domain may have a number of hosts associated with it, and each
27105 host may have more than one IP address. Retry algorithms are selected on the
27106 basis of the domain name, but are applied to each IP address independently. If,
27107 for example, a host has two IP addresses and one is unusable, Exim will
27108 generate retry times for it and will not try to use it until its next retry
27109 time comes. Thus the good IP address is likely to be tried first most of the
27112 .cindex "hints database" "use for retrying"
27113 Retry times are hints rather than promises. Exim does not make any attempt to
27114 run deliveries exactly at the computed times. Instead, a queue runner process
27115 starts delivery processes for delayed messages periodically, and these attempt
27116 new deliveries only for those addresses that have passed their next retry time.
27117 If a new message arrives for a deferred address, an immediate delivery attempt
27118 occurs only if the address has passed its retry time. In the absence of new
27119 messages, the minimum time between retries is the interval between queue runner
27120 processes. There is not much point in setting retry times of five minutes if
27121 your queue runners happen only once an hour, unless there are a significant
27122 number of incoming messages (which might be the case on a system that is
27123 sending everything to a smart host, for example).
27125 The data in the retry hints database can be inspected by using the
27126 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27127 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27128 &'exinext'& utility script can be used to find out what the next retry times
27129 are for the hosts associated with a particular mail domain, and also for local
27130 deliveries that have been deferred.
27133 .section "Retry rule examples" "SECID164"
27134 Here are some example retry rules:
27136 alice@wonderland.fict.example quota_5d F,7d,3h
27137 wonderland.fict.example quota_5d
27138 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27139 lookingglass.fict.example * F,24h,30m;
27140 * refused_A F,2h,20m;
27141 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27143 The first rule sets up special handling for mail to
27144 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27145 mailbox has not been read for at least 5 days. Retries continue every three
27146 hours for 7 days. The second rule handles over-quota errors for all other local
27147 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27148 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27149 fail are bounced immediately if the mailbox has not been read for at least 5
27152 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27153 happen every 15 minutes for an hour, then with geometrically increasing
27154 intervals until two days have passed since a delivery first failed. After the
27155 first hour there is a delay of one hour, then two hours, then four hours, and
27156 so on (this is a rather extreme example).
27158 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27159 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27160 all other domains, with special action for connection refusal from hosts that
27161 were not obtained from an MX record.
27163 The final rule in a retry configuration should always have asterisks in the
27164 first two fields so as to provide a general catch-all for any addresses that do
27165 not have their own special handling. This example tries every 15 minutes for 2
27166 hours, then with intervals starting at one hour and increasing by a factor of
27167 1.5 up to 16 hours, then every 8 hours up to 5 days.
27171 .section "Timeout of retry data" "SECID165"
27172 .cindex "timeout" "of retry data"
27173 .oindex "&%retry_data_expire%&"
27174 .cindex "hints database" "data expiry"
27175 .cindex "retry" "timeout of data"
27176 Exim timestamps the data that it writes to its retry hints database. When it
27177 consults the data during a delivery it ignores any that is older than the value
27178 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27179 been tried for 7 days, Exim will try to deliver to it immediately a message
27180 arrives, and if that fails, it will calculate a retry time as if it were
27181 failing for the first time.
27183 This improves the behaviour for messages routed to rarely-used hosts such as MX
27184 backups. If such a host was down at one time, and happens to be down again when
27185 Exim tries a month later, using the old retry data would imply that it had been
27186 down all the time, which is not a justified assumption.
27188 If a host really is permanently dead, this behaviour causes a burst of retries
27189 every now and again, but only if messages routed to it are rare. If there is a
27190 message at least once every 7 days the retry data never expires.
27195 .section "Long-term failures" "SECID166"
27196 .cindex "delivery failure, long-term"
27197 .cindex "retry" "after long-term failure"
27198 Special processing happens when an email address has been failing for so long
27199 that the cutoff time for the last algorithm is reached. For example, using the
27200 default retry rule:
27202 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27204 the cutoff time is four days. Reaching the retry cutoff is independent of how
27205 long any specific message has been failing; it is the length of continuous
27206 failure for the recipient address that counts.
27208 When the cutoff time is reached for a local delivery, or for all the IP
27209 addresses associated with a remote delivery, a subsequent delivery failure
27210 causes Exim to give up on the address, and a bounce message is generated.
27211 In order to cater for new messages that use the failing address, a next retry
27212 time is still computed from the final algorithm, and is used as follows:
27214 For local deliveries, one delivery attempt is always made for any subsequent
27215 messages. If this delivery fails, the address fails immediately. The
27216 post-cutoff retry time is not used.
27218 .cindex "final cutoff" "retries, controlling"
27219 .cindex retry "final cutoff"
27220 If the delivery is remote, there are two possibilities, controlled by the
27221 .oindex "&%delay_after_cutoff%&"
27222 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27223 default. Until the post-cutoff retry time for one of the IP addresses,
27224 as set by the &%retry_data_expire%& option, is
27225 reached, the failing email address is bounced immediately, without a delivery
27226 attempt taking place. After that time, one new delivery attempt is made to
27227 those IP addresses that are past their retry times, and if that still fails,
27228 the address is bounced and new retry times are computed.
27230 In other words, when all the hosts for a given email address have been failing
27231 for a long time, Exim bounces rather then defers until one of the hosts' retry
27232 times is reached. Then it tries once, and bounces if that attempt fails. This
27233 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27234 to a broken destination, but if the host does recover, Exim will eventually
27237 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27238 addresses are past their final cutoff time, Exim tries to deliver to those IP
27239 addresses that have not been tried since the message arrived. If there are
27240 no suitable IP addresses, or if they all fail, the address is bounced. In other
27241 words, it does not delay when a new message arrives, but tries the expired
27242 addresses immediately, unless they have been tried since the message arrived.
27243 If there is a continuous stream of messages for the failing domains, setting
27244 &%delay_after_cutoff%& false means that there will be many more attempts to
27245 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27248 .section "Deliveries that work intermittently" "SECID167"
27249 .cindex "retry" "intermittently working deliveries"
27250 Some additional logic is needed to cope with cases where a host is
27251 intermittently available, or when a message has some attribute that prevents
27252 its delivery when others to the same address get through. In this situation,
27253 because some messages are successfully delivered, the &"retry clock"& for the
27254 host or address keeps getting reset by the successful deliveries, and so
27255 failing messages remain in the queue for ever because the cutoff time is never
27258 Two exceptional actions are applied to prevent this happening. The first
27259 applies to errors that are related to a message rather than a remote host.
27260 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27261 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27262 commands, and quota failures. For this type of error, if a message's arrival
27263 time is earlier than the &"first failed"& time for the error, the earlier time
27264 is used when scanning the retry rules to decide when to try next and when to
27265 time out the address.
27267 The exceptional second action applies in all cases. If a message has been on
27268 the queue for longer than the cutoff time of any applicable retry rule for a
27269 given address, a delivery is attempted for that address, even if it is not yet
27270 time, and if this delivery fails, the address is timed out. A new retry time is
27271 not computed in this case, so that other messages for the same address are
27272 considered immediately.
27273 .ecindex IIDretconf1
27274 .ecindex IIDregconf2
27281 . ////////////////////////////////////////////////////////////////////////////
27282 . ////////////////////////////////////////////////////////////////////////////
27284 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27285 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27286 .scindex IIDauthconf2 "authentication"
27287 The &"authenticators"& section of Exim's runtime configuration is concerned
27288 with SMTP authentication. This facility is an extension to the SMTP protocol,
27289 described in RFC 2554, which allows a client SMTP host to authenticate itself
27290 to a server. This is a common way for a server to recognize clients that are
27291 permitted to use it as a relay. SMTP authentication is not of relevance to the
27292 transfer of mail between servers that have no managerial connection with each
27296 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27297 prior to Exim 4.95 names would be silently truncated at this length, but now
27301 .cindex "AUTH" "description of"
27302 .cindex "ESMTP extensions" AUTH
27303 Very briefly, the way SMTP authentication works is as follows:
27306 The server advertises a number of authentication &'mechanisms'& in response to
27307 the client's EHLO command.
27309 The client issues an AUTH command, naming a specific mechanism. The command
27310 may, optionally, contain some authentication data.
27312 The server may issue one or more &'challenges'&, to which the client must send
27313 appropriate responses. In simple authentication mechanisms, the challenges are
27314 just prompts for user names and passwords. The server does not have to issue
27315 any challenges &-- in some mechanisms the relevant data may all be transmitted
27316 with the AUTH command.
27318 The server either accepts or denies authentication.
27320 If authentication succeeds, the client may optionally make use of the AUTH
27321 option on the MAIL command to pass an authenticated sender in subsequent
27322 mail transactions. Authentication lasts for the remainder of the SMTP
27325 If authentication fails, the client may give up, or it may try a different
27326 authentication mechanism, or it may try transferring mail over the
27327 unauthenticated connection.
27330 If you are setting up a client, and want to know which authentication
27331 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27332 SMTP port) on the server, and issue an EHLO command. The response to this
27333 includes the list of supported mechanisms. For example:
27335 &`$ `&&*&`telnet server.example 25`&*&
27336 &`Trying 192.168.34.25...`&
27337 &`Connected to server.example.`&
27338 &`Escape character is '^]'.`&
27339 &`220 server.example ESMTP Exim 4.20 ...`&
27340 &*&`ehlo client.example`&*&
27341 &`250-server.example Hello client.example [10.8.4.5]`&
27342 &`250-SIZE 52428800`&
27347 The second-last line of this example output shows that the server supports
27348 authentication using the PLAIN mechanism. In Exim, the different authentication
27349 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27350 routers and transports, which authenticators are included in the binary is
27351 controlled by build-time definitions. The following are currently available,
27352 included by setting
27355 AUTH_CYRUS_SASL=yes
27359 AUTH_HEIMDAL_GSSAPI=yes
27364 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27365 authentication mechanism (RFC 2195), and the second provides an interface to
27366 the Cyrus SASL authentication library.
27367 The third is an interface to Dovecot's authentication system, delegating the
27368 work via a socket interface.
27369 The fourth provides for negotiation of authentication done via non-SMTP means,
27370 as defined by RFC 4422 Appendix A.
27371 The fifth provides an interface to the GNU SASL authentication library, which
27372 provides mechanisms but typically not data sources.
27373 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27374 supporting setting a server keytab.
27375 The seventh can be configured to support
27376 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27377 not formally documented, but used by several MUAs.
27378 The eighth authenticator
27379 supports Microsoft's &'Secure Password Authentication'& mechanism.
27380 The last is an Exim authenticator but not an SMTP one;
27381 instead it can use information from a TLS negotiation.
27383 The authenticators are configured using the same syntax as other drivers (see
27384 section &<<SECTfordricon>>&). If no authenticators are required, no
27385 authentication section need be present in the configuration file. Each
27386 authenticator can in principle have both server and client functions. When Exim
27387 is receiving SMTP mail, it is acting as a server; when it is sending out
27388 messages over SMTP, it is acting as a client. Authenticator configuration
27389 options are provided for use in both these circumstances.
27391 To make it clear which options apply to which situation, the prefixes
27392 &%server_%& and &%client_%& are used on option names that are specific to
27393 either the server or the client function, respectively. Server and client
27394 functions are disabled if none of their options are set. If an authenticator is
27395 to be used for both server and client functions, a single definition, using
27396 both sets of options, is required. For example:
27400 public_name = CRAM-MD5
27401 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27403 client_secret = secret2
27405 The &%server_%& option is used when Exim is acting as a server, and the
27406 &%client_%& options when it is acting as a client.
27408 Descriptions of the individual authenticators are given in subsequent chapters.
27409 The remainder of this chapter covers the generic options for the
27410 authenticators, followed by general discussion of the way authentication works
27413 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27414 per-mechanism basis. Please read carefully to determine which variables hold
27415 account labels such as usercodes and which hold passwords or other
27416 authenticating data.
27418 Note that some mechanisms support two different identifiers for accounts: the
27419 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27420 and &'authz'& are commonly encountered. The American spelling is standard here.
27421 Conceptually, authentication data such as passwords are tied to the identifier
27422 used to authenticate; servers may have rules to permit one user to act as a
27423 second user, so that after login the session is treated as though that second
27424 user had logged in. That second user is the &'authorization id'&. A robust
27425 configuration might confirm that the &'authz'& field is empty or matches the
27426 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27427 as verified data, the &'authz'& as an unverified request which the server might
27430 A &'realm'& is a text string, typically a domain name, presented by a server
27431 to a client to help it select an account and credentials to use. In some
27432 mechanisms, the client and server provably agree on the realm, but clients
27433 typically can not treat the realm as secure data to be blindly trusted.
27437 .section "Generic options for authenticators" "SECID168"
27438 .cindex "authentication" "generic options"
27439 .cindex "options" "generic; for authenticators"
27441 .option client_condition authenticators string&!! unset
27442 When Exim is authenticating as a client, it skips any authenticator whose
27443 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27444 used, for example, to skip plain text authenticators when the connection is not
27445 encrypted by a setting such as:
27447 client_condition = ${if !eq{$tls_out_cipher}{}}
27451 .option client_set_id authenticators string&!! unset
27452 When client authentication succeeds, this condition is expanded; the
27453 result is used in the log lines for outbound messages.
27454 Typically it will be the user name used for authentication.
27457 .option driver authenticators string unset
27458 This option must always be set. It specifies which of the available
27459 authenticators is to be used.
27462 .option public_name authenticators string unset
27463 This option specifies the name of the authentication mechanism that the driver
27464 implements, and by which it is known to the outside world. These names should
27465 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27466 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27467 defaults to the driver's instance name.
27470 .option server_advertise_condition authenticators string&!! unset
27471 When a server is about to advertise an authentication mechanism, the condition
27472 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27473 mechanism is not advertised.
27474 If the expansion fails, the mechanism is not advertised. If the failure was not
27475 forced, and was not caused by a lookup defer, the incident is logged.
27476 See section &<<SECTauthexiser>>& below for further discussion.
27479 .option server_condition authenticators string&!! unset
27480 This option must be set for a &%plaintext%& server authenticator, where it
27481 is used directly to control authentication. See section &<<SECTplainserver>>&
27484 For the &(gsasl)& authenticator, this option is required for various
27485 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27487 For the other authenticators, &%server_condition%& can be used as an additional
27488 authentication or authorization mechanism that is applied after the other
27489 authenticator conditions succeed. If it is set, it is expanded when the
27490 authenticator would otherwise return a success code. If the expansion is forced
27491 to fail, authentication fails. Any other expansion failure causes a temporary
27492 error code to be returned. If the result of a successful expansion is an empty
27493 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27494 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27495 other result, a temporary error code is returned, with the expanded string as
27499 .option server_debug_print authenticators string&!! unset
27500 If this option is set and authentication debugging is enabled (see the &%-d%&
27501 command line option), the string is expanded and included in the debugging
27502 output when the authenticator is run as a server. This can help with checking
27503 out the values of variables.
27504 If expansion of the string fails, the error message is written to the debugging
27505 output, and Exim carries on processing.
27508 .option server_set_id authenticators string&!! unset
27509 .vindex "&$authenticated_id$&"
27510 .vindex "&$authenticated_fail_id$&"
27511 When an Exim server successfully authenticates a client, this string is
27512 expanded using data from the authentication, and preserved for any incoming
27513 messages in the variable &$authenticated_id$&. It is also included in the log
27514 lines for incoming messages. For example, a user/password authenticator
27515 configuration might preserve the user name that was used to authenticate, and
27516 refer to it subsequently during delivery of the message.
27517 On a failing authentication the expansion result is instead saved in
27518 the &$authenticated_fail_id$& variable.
27519 If expansion fails, the option is ignored.
27522 .option server_mail_auth_condition authenticators string&!! unset
27523 This option allows a server to discard authenticated sender addresses supplied
27524 as part of MAIL commands in SMTP connections that are authenticated by the
27525 driver on which &%server_mail_auth_condition%& is set. The option is not used
27526 as part of the authentication process; instead its (unexpanded) value is
27527 remembered for later use.
27528 How it is used is described in the following section.
27534 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27535 .cindex "authentication" "sender; authenticated"
27536 .cindex "AUTH" "on MAIL command"
27537 When a client supplied an AUTH= item on a MAIL command, Exim applies
27538 the following checks before accepting it as the authenticated sender of the
27542 If the connection is not using extended SMTP (that is, HELO was used rather
27543 than EHLO), the use of AUTH= is a syntax error.
27545 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27547 .vindex "&$authenticated_sender$&"
27548 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27549 running, the value of &$authenticated_sender$& is set to the value obtained
27550 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27551 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27552 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27553 given for the MAIL command.
27555 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27556 is accepted and placed in &$authenticated_sender$& only if the client has
27559 If the AUTH= value was accepted by either of the two previous rules, and
27560 the client has authenticated, and the authenticator has a setting for the
27561 &%server_mail_auth_condition%&, the condition is checked at this point. The
27562 valued that was saved from the authenticator is expanded. If the expansion
27563 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27564 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27565 the value of &$authenticated_sender$& is retained and passed on with the
27570 When &$authenticated_sender$& is set for a message, it is passed on to other
27571 hosts to which Exim authenticates as a client. Do not confuse this value with
27572 &$authenticated_id$&, which is a string obtained from the authentication
27573 process, and which is not usually a complete email address.
27575 .vindex "&$sender_address$&"
27576 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27577 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27578 therefore make use of &$authenticated_sender$&. The converse is not true: the
27579 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27584 .section "Authentication on an Exim server" "SECTauthexiser"
27585 .cindex "authentication" "on an Exim server"
27586 When Exim receives an EHLO command, it advertises the public names of those
27587 authenticators that are configured as servers, subject to the following
27591 The client host must match &%auth_advertise_hosts%& (default *).
27593 If the &%server_advertise_condition%& option is set, its expansion must not
27594 yield the empty string, &"0"&, &"no"&, or &"false"&.
27597 The order in which the authenticators are defined controls the order in which
27598 the mechanisms are advertised.
27600 Some mail clients (for example, some versions of Netscape) require the user to
27601 provide a name and password for authentication whenever AUTH is advertised,
27602 even though authentication may not in fact be needed (for example, Exim may be
27603 set up to allow unconditional relaying from the client by an IP address check).
27604 You can make such clients more friendly by not advertising AUTH to them.
27605 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27606 that runs for RCPT) to relay without authentication, you should set
27608 auth_advertise_hosts = ! 10.9.8.0/24
27610 so that no authentication mechanisms are advertised to them.
27612 The &%server_advertise_condition%& controls the advertisement of individual
27613 authentication mechanisms. For example, it can be used to restrict the
27614 advertisement of a particular mechanism to encrypted connections, by a setting
27617 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27619 .vindex "&$tls_in_cipher$&"
27620 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27621 yields &"yes"&, which allows the advertisement to happen.
27623 When an Exim server receives an AUTH command from a client, it rejects it
27624 immediately if AUTH was not advertised in response to an earlier EHLO
27625 command. This is the case if
27628 The client host does not match &%auth_advertise_hosts%&; or
27630 No authenticators are configured with server options; or
27632 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27633 server authenticators.
27637 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27638 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27639 AUTH is accepted from any client host.
27641 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27642 server authentication mechanism that was advertised in response to EHLO and
27643 that matches the one named in the AUTH command. If it finds one, it runs
27644 the appropriate authentication protocol, and authentication either succeeds or
27645 fails. If there is no matching advertised mechanism, the AUTH command is
27646 rejected with a 504 error.
27648 .vindex "&$received_protocol$&"
27649 .vindex "&$sender_host_authenticated$&"
27650 When a message is received from an authenticated host, the value of
27651 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27652 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27653 public name) of the authenticator driver that successfully authenticated the
27654 client from which the message was received. This variable is empty if there was
27655 no successful authentication.
27657 .cindex authentication "expansion item"
27658 Successful authentication sets up information used by the
27659 &%authresults%& expansion item.
27664 .section "Testing server authentication" "SECID169"
27665 .cindex "authentication" "testing a server"
27666 .cindex "AUTH" "testing a server"
27667 .cindex "base64 encoding" "creating authentication test data"
27668 Exim's &%-bh%& option can be useful for testing server authentication
27669 configurations. The data for the AUTH command has to be sent using base64
27670 encoding. A quick way to produce such data for testing is the following Perl
27674 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27676 .cindex "binary zero" "in authentication data"
27677 This interprets its argument as a Perl string, and then encodes it. The
27678 interpretation as a Perl string allows binary zeros, which are required for
27679 some kinds of authentication, to be included in the data. For example, a
27680 command line to run this script on such data might be
27682 encode '\0user\0password'
27684 Note the use of single quotes to prevent the shell interpreting the
27685 backslashes, so that they can be interpreted by Perl to specify characters
27686 whose code value is zero.
27688 &*Warning 1*&: If either of the user or password strings starts with an octal
27689 digit, you must use three zeros instead of one after the leading backslash. If
27690 you do not, the octal digit that starts your string will be incorrectly
27691 interpreted as part of the code for the first character.
27693 &*Warning 2*&: If there are characters in the strings that Perl interprets
27694 specially, you must use a Perl escape to prevent them being misinterpreted. For
27695 example, a command such as
27697 encode '\0user@domain.com\0pas$$word'
27699 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27701 If you have the &%mimencode%& command installed, another way to produce
27702 base64-encoded strings is to run the command
27704 echo -e -n `\0user\0password' | mimencode
27706 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27707 in the argument, and the &%-n%& option specifies no newline at the end of its
27708 output. However, not all versions of &%echo%& recognize these options, so you
27709 should check your version before relying on this suggestion.
27713 .section "Authentication by an Exim client" "SECID170"
27714 .cindex "authentication" "on an Exim client"
27715 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27716 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27717 announces support for authentication, and the host matches an entry in either
27718 of these options, Exim (as a client) tries to authenticate as follows:
27721 For each authenticator that is configured as a client, in the order in which
27722 they are defined in the configuration, it searches the authentication
27723 mechanisms announced by the server for one whose name matches the public name
27724 of the authenticator.
27727 .vindex "&$host_address$&"
27728 When it finds one that matches, it runs the authenticator's client code. The
27729 variables &$host$& and &$host_address$& are available for any string expansions
27730 that the client might do. They are set to the server's name and IP address. If
27731 any expansion is forced to fail, the authentication attempt is abandoned, and
27732 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27733 delivery to be deferred.
27735 If the result of the authentication attempt is a temporary error or a timeout,
27736 Exim abandons trying to send the message to the host for the moment. It will
27737 try again later. If there are any backup hosts available, they are tried in the
27740 If the response to authentication is a permanent error (5&'xx'& code), Exim
27741 carries on searching the list of authenticators and tries another one if
27742 possible. If all authentication attempts give permanent errors, or if there are
27743 no attempts because no mechanisms match (or option expansions force failure),
27744 what happens depends on whether the host matches &%hosts_require_auth%& or
27745 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27746 delivery is deferred. The error can be detected in the retry rules, and thereby
27747 turned into a permanent error if you wish. In the second case, Exim tries to
27748 deliver the message unauthenticated.
27751 Note that the hostlist test for whether to do authentication can be
27752 confused if name-IP lookups change between the time the peer is decided
27753 upon and the time that the transport runs. For example, with a manualroute
27754 router given a host name, and with DNS "round-robin" used by that name: if
27755 the local resolver cache times out between the router and the transport
27756 running, the transport may get an IP for the name for its authentication
27757 check which does not match the connection peer IP.
27758 No authentication will then be done, despite the names being identical.
27760 For such cases use a separate transport which always authenticates.
27762 .cindex "AUTH" "on MAIL command"
27763 When Exim has authenticated itself to a remote server, it adds the AUTH
27764 parameter to the MAIL commands it sends, if it has an authenticated sender for
27765 the message. If the message came from a remote host, the authenticated sender
27766 is the one that was receiving on an incoming MAIL command, provided that the
27767 incoming connection was authenticated and the &%server_mail_auth%& condition
27768 allowed the authenticated sender to be retained. If a local process calls Exim
27769 to send a message, the sender address that is built from the login name and
27770 &%qualify_domain%& is treated as authenticated. However, if the
27771 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27772 the authenticated sender that was received with the message.
27773 .ecindex IIDauthconf1
27774 .ecindex IIDauthconf2
27781 . ////////////////////////////////////////////////////////////////////////////
27782 . ////////////////////////////////////////////////////////////////////////////
27784 .chapter "The plaintext authenticator" "CHAPplaintext"
27785 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27786 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27787 The &(plaintext)& authenticator can be configured to support the PLAIN and
27788 LOGIN authentication mechanisms, both of which transfer authentication data as
27789 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27790 security risk; you are strongly advised to insist on the use of SMTP encryption
27791 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27792 use unencrypted plain text, you should not use the same passwords for SMTP
27793 connections as you do for login accounts.
27795 .section "Avoiding cleartext use" "SECTplain_TLS"
27796 The following generic option settings will disable &(plaintext)& authenticators when
27797 TLS is not being used:
27799 server_advertise_condition = ${if def:tls_in_cipher }
27800 client_condition = ${if def:tls_out_cipher}
27803 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27804 but is still vulnerable to a Man In The Middle attack unless certificates
27805 (including their names) have been properly verified.
27807 .section "Plaintext server options" "SECID171"
27808 .cindex "options" "&(plaintext)& authenticator (server)"
27809 When configured as a server, &(plaintext)& uses the following options:
27811 .option server_condition authenticators string&!! unset
27812 This is actually a global authentication option, but it must be set in order to
27813 configure the &(plaintext)& driver as a server. Its use is described below.
27815 .option server_prompts plaintext "string list&!!" unset
27816 The contents of this option, after expansion, must be a colon-separated list of
27817 prompt strings. If expansion fails, a temporary authentication rejection is
27820 .section "Using plaintext in a server" "SECTplainserver"
27821 .cindex "AUTH" "in &(plaintext)& authenticator"
27822 .cindex "binary zero" "in &(plaintext)& authenticator"
27823 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27824 "in &(plaintext)& authenticator"
27825 .vindex "&$auth1$&, &$auth2$&, etc"
27826 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27828 When running as a server, &(plaintext)& performs the authentication test by
27829 expanding a string. The data sent by the client with the AUTH command, or in
27830 response to subsequent prompts, is base64 encoded, and so may contain any byte
27831 values when decoded. If any data is supplied with the command, it is treated as
27832 a list of strings, separated by NULs (binary zeros), the first three of which
27833 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27834 (neither LOGIN nor PLAIN uses more than three strings).
27836 For compatibility with previous releases of Exim, the values are also placed in
27837 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27838 variables for this purpose is now deprecated, as it can lead to confusion in
27839 string expansions that also use them for other things.
27841 If there are more strings in &%server_prompts%& than the number of strings
27842 supplied with the AUTH command, the remaining prompts are used to obtain more
27843 data. Each response from the client may be a list of NUL-separated strings.
27845 .vindex "&$authenticated_id$&"
27846 Once a sufficient number of data strings have been received,
27847 &%server_condition%& is expanded. If the expansion is forced to fail,
27848 authentication fails. Any other expansion failure causes a temporary error code
27849 to be returned. If the result of a successful expansion is an empty string,
27850 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27851 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27852 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27853 For any other result, a temporary error code is returned, with the expanded
27854 string as the error text.
27856 &*Warning*&: If you use a lookup in the expansion to find the user's
27857 password, be sure to make the authentication fail if the user is unknown.
27858 There are good and bad examples at the end of the next section.
27862 .section "The PLAIN authentication mechanism" "SECID172"
27863 .cindex "PLAIN authentication mechanism"
27864 .cindex authentication PLAIN
27865 .cindex "binary zero" "in &(plaintext)& authenticator"
27866 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27867 sent as one item of data (that is, one combined string containing two NUL
27868 separators). The data is sent either as part of the AUTH command, or
27869 subsequently in response to an empty prompt from the server.
27871 The second and third strings are a user name and a corresponding password.
27872 Using a single fixed user name and password as an example, this could be
27873 configured as follows:
27877 public_name = PLAIN
27879 server_condition = \
27880 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27881 server_set_id = $auth2
27883 Note that the default result strings from &%if%& (&"true"& or an empty string)
27884 are exactly what we want here, so they need not be specified. Obviously, if the
27885 password contains expansion-significant characters such as dollar, backslash,
27886 or closing brace, they have to be escaped.
27888 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27889 the end of a string list are ignored). If all the data comes as part of the
27890 AUTH command, as is commonly the case, the prompt is not used. This
27891 authenticator is advertised in the response to EHLO as
27895 and a client host can authenticate itself by sending the command
27897 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27899 As this contains three strings (more than the number of prompts), no further
27900 data is required from the client. Alternatively, the client may just send
27904 to initiate authentication, in which case the server replies with an empty
27905 prompt. The client must respond with the combined data string.
27907 The data string is base64 encoded, as required by the RFC. This example,
27908 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27909 represents a zero byte. This is split up into three strings, the first of which
27910 is empty. The &%server_condition%& option in the authenticator checks that the
27911 second two are &`username`& and &`mysecret`& respectively.
27913 Having just one fixed user name and password, as in this example, is not very
27914 realistic, though for a small organization with only a handful of
27915 authenticating clients it could make sense.
27917 A more sophisticated instance of this authenticator could use the user name in
27918 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27919 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27920 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27921 This is an incorrect example:
27923 server_condition = \
27924 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27926 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27927 which it then compares to the supplied password (&$auth3$&). Why is this example
27928 incorrect? It works fine for existing users, but consider what happens if a
27929 non-existent user name is given. The lookup fails, but as no success/failure
27930 strings are given for the lookup, it yields an empty string. Thus, to defeat
27931 the authentication, all a client has to do is to supply a non-existent user
27932 name and an empty password. The correct way of writing this test is:
27934 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27935 {${if eq{$value}{$auth3}}} {false}}
27937 In this case, if the lookup succeeds, the result is checked; if the lookup
27938 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27939 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27940 always fails if its second argument is empty. However, the second way of
27941 writing the test makes the logic clearer.
27944 .section "The LOGIN authentication mechanism" "SECID173"
27945 .cindex "LOGIN authentication mechanism"
27946 .cindex authentication LOGIN
27947 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27948 in a number of programs. No data is sent with the AUTH command. Instead, a
27949 user name and password are supplied separately, in response to prompts. The
27950 plaintext authenticator can be configured to support this as in this example:
27954 public_name = LOGIN
27955 server_prompts = User Name : Password
27956 server_condition = \
27957 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27958 server_set_id = $auth1
27960 Because of the way plaintext operates, this authenticator accepts data supplied
27961 with the AUTH command (in contravention of the specification of LOGIN), but
27962 if the client does not supply it (as is the case for LOGIN clients), the prompt
27963 strings are used to obtain two data items.
27965 Some clients are very particular about the precise text of the prompts. For
27966 example, Outlook Express is reported to recognize only &"Username:"& and
27967 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27968 strings. It uses the &%ldapauth%& expansion condition to check the user
27969 name and password by binding to an LDAP server:
27973 public_name = LOGIN
27974 server_prompts = Username:: : Password::
27975 server_condition = ${if and{{ \
27978 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27979 pass=${quote:$auth2} \
27980 ldap://ldap.example.org/} }} }
27981 server_set_id = uid=$auth1,ou=people,o=example.org
27983 We have to check that the username is not empty before using it, because LDAP
27984 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27985 operator to correctly quote the DN for authentication. However, the basic
27986 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27987 correct one to use for the password, because quoting is needed only to make
27988 the password conform to the Exim syntax. At the LDAP level, the password is an
27989 uninterpreted string.
27992 .section "Support for different kinds of authentication" "SECID174"
27993 A number of string expansion features are provided for the purpose of
27994 interfacing to different ways of user authentication. These include checking
27995 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27996 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
28002 .section "Using plaintext in a client" "SECID175"
28003 .cindex "options" "&(plaintext)& authenticator (client)"
28004 The &(plaintext)& authenticator has two client options:
28006 .option client_ignore_invalid_base64 plaintext boolean false
28007 If the client receives a server prompt that is not a valid base64 string,
28008 authentication is abandoned by default. However, if this option is set true,
28009 the error in the challenge is ignored and the client sends the response as
28012 .option client_send plaintext string&!! unset
28013 The string is a colon-separated list of authentication data strings. Each
28014 string is independently expanded before being sent to the server. The first
28015 string is sent with the AUTH command; any more strings are sent in response
28016 to prompts from the server. Before each string is expanded, the value of the
28017 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
28018 with &$auth1$& for the first prompt. Up to three prompts are stored in this
28019 way. Thus, the prompt that is received in response to sending the first string
28020 (with the AUTH command) can be used in the expansion of the second string, and
28021 so on. If an invalid base64 string is received when
28022 &%client_ignore_invalid_base64%& is set, an empty string is put in the
28023 &$auth$&<&'n'&> variable.
28025 &*Note*&: You cannot use expansion to create multiple strings, because
28026 splitting takes priority and happens first.
28028 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
28029 the data, further processing is applied to each string before it is sent. If
28030 there are any single circumflex characters in the string, they are converted to
28031 NULs. Should an actual circumflex be required as data, it must be doubled in
28034 This is an example of a client configuration that implements the PLAIN
28035 authentication mechanism with a fixed user name and password:
28039 public_name = PLAIN
28040 client_send = ^username^mysecret
28042 The lack of colons means that the entire text is sent with the AUTH
28043 command, with the circumflex characters converted to NULs.
28045 Note that due to the ambiguity of parsing three consectutive circumflex characters
28046 there is no way to provide a password having a leading circumflex.
28051 that uses the LOGIN mechanism is:
28055 public_name = LOGIN
28056 client_send = : username : mysecret
28058 The initial colon means that the first string is empty, so no data is sent with
28059 the AUTH command itself. The remaining strings are sent in response to
28061 .ecindex IIDplaiauth1
28062 .ecindex IIDplaiauth2
28067 . ////////////////////////////////////////////////////////////////////////////
28068 . ////////////////////////////////////////////////////////////////////////////
28070 .chapter "The cram_md5 authenticator" "CHID9"
28071 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28072 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28073 .cindex "CRAM-MD5 authentication mechanism"
28074 .cindex authentication CRAM-MD5
28075 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28076 sends a challenge string to the client, and the response consists of a user
28077 name and the CRAM-MD5 digest of the challenge string combined with a secret
28078 string (password) which is known to both server and client. Thus, the secret
28079 is not sent over the network as plain text, which makes this authenticator more
28080 secure than &(plaintext)&. However, the downside is that the secret has to be
28081 available in plain text at either end.
28084 .section "Using cram_md5 as a server" "SECID176"
28085 .cindex "options" "&(cram_md5)& authenticator (server)"
28086 This authenticator has one server option, which must be set to configure the
28087 authenticator as a server:
28089 .option server_secret cram_md5 string&!! unset
28090 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28091 When the server receives the client's response, the user name is placed in
28092 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28093 obtain the password for that user. The server then computes the CRAM-MD5 digest
28094 that the client should have sent, and checks that it received the correct
28095 string. If the expansion of &%server_secret%& is forced to fail, authentication
28096 fails. If the expansion fails for some other reason, a temporary error code is
28097 returned to the client.
28099 For compatibility with previous releases of Exim, the user name is also placed
28100 in &$1$&. However, the use of this variables for this purpose is now
28101 deprecated, as it can lead to confusion in string expansions that also use
28102 numeric variables for other things.
28104 For example, the following authenticator checks that the user name given by the
28105 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28106 user name, authentication fails.
28110 public_name = CRAM-MD5
28111 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28112 server_set_id = $auth1
28114 .vindex "&$authenticated_id$&"
28115 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28116 name in &$authenticated_id$&. A more typical configuration might look up the
28117 secret string in a file, using the user name as the key. For example:
28121 public_name = CRAM-MD5
28122 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28124 server_set_id = $auth1
28126 Note that this expansion explicitly forces failure if the lookup fails
28127 because &$auth1$& contains an unknown user name.
28129 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28130 using the relevant libraries, you need to know the realm to specify in the
28131 lookup and then ask for the &"userPassword"& attribute for that user in that
28136 public_name = CRAM-MD5
28137 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28138 dbmjz{/etc/sasldb2}{$value}fail}
28139 server_set_id = $auth1
28142 .section "Using cram_md5 as a client" "SECID177"
28143 .cindex "options" "&(cram_md5)& authenticator (client)"
28144 When used as a client, the &(cram_md5)& authenticator has two options:
28148 .option client_name cram_md5 string&!! "the primary host name"
28149 This string is expanded, and the result used as the user name data when
28150 computing the response to the server's challenge.
28153 .option client_secret cram_md5 string&!! unset
28154 This option must be set for the authenticator to work as a client. Its value is
28155 expanded and the result used as the secret string when computing the response.
28159 .vindex "&$host_address$&"
28160 Different user names and secrets can be used for different servers by referring
28161 to &$host$& or &$host_address$& in the options. Forced failure of either
28162 expansion string is treated as an indication that this authenticator is not
28163 prepared to handle this case. Exim moves on to the next configured client
28164 authenticator. Any other expansion failure causes Exim to give up trying to
28165 send the message to the current server.
28167 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28172 public_name = CRAM-MD5
28174 client_secret = secret
28176 .ecindex IIDcramauth1
28177 .ecindex IIDcramauth2
28181 . ////////////////////////////////////////////////////////////////////////////
28182 . ////////////////////////////////////////////////////////////////////////////
28184 .chapter "The cyrus_sasl authenticator" "CHID10"
28185 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28186 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28187 .cindex "Cyrus" "SASL library"
28189 The code for this authenticator was provided by Matthew Byng-Maddick while
28190 at A L Digital Ltd.
28192 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28193 library implementation of the RFC 2222 (&"Simple Authentication and Security
28194 Layer"&). This library supports a number of authentication mechanisms,
28195 including PLAIN and LOGIN, but also several others that Exim does not support
28196 directly. In particular, there is support for Kerberos authentication.
28198 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28199 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28200 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28201 name of the driver to determine which mechanism to support.
28203 Where access to some kind of secret file is required, for example, in GSSAPI
28204 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28205 user, and that the Cyrus SASL library has no way of escalating privileges
28206 by default. You may also find you need to set environment variables,
28207 depending on the driver you are using.
28209 The application name provided by Exim is &"exim"&, so various SASL options may
28210 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28211 Kerberos, note that because of limitations in the GSSAPI interface,
28212 changing the server keytab might need to be communicated down to the Kerberos
28213 layer independently. The mechanism for doing so is dependent upon the Kerberos
28216 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28217 may be set to point to an alternative keytab file. Exim will pass this
28218 variable through from its own inherited environment when started as root or the
28219 Exim user. The keytab file needs to be readable by the Exim user.
28220 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28221 environment variable. In practice, for those releases, the Cyrus authenticator
28222 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28223 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28226 .section "Using cyrus_sasl as a server" "SECID178"
28227 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28228 (on a successful authentication) into &$auth1$&. For compatibility with
28229 previous releases of Exim, the username is also placed in &$1$&. However, the
28230 use of this variable for this purpose is now deprecated, as it can lead to
28231 confusion in string expansions that also use numeric variables for other
28235 .option server_hostname cyrus_sasl string&!! "see below"
28236 This option selects the hostname that is used when communicating with the
28237 library. The default value is &`$primary_hostname`&. It is up to the underlying
28238 SASL plug-in what it does with this data.
28241 .option server_mech cyrus_sasl string "see below"
28242 This option selects the authentication mechanism this driver should use. The
28243 default is the value of the generic &%public_name%& option. This option allows
28244 you to use a different underlying mechanism from the advertised name. For
28248 driver = cyrus_sasl
28249 public_name = X-ANYTHING
28250 server_mech = CRAM-MD5
28251 server_set_id = $auth1
28254 .option server_realm cyrus_sasl string&!! unset
28255 This specifies the SASL realm that the server claims to be in.
28258 .option server_service cyrus_sasl string &`smtp`&
28259 This is the SASL service that the server claims to implement.
28262 For straightforward cases, you do not need to set any of the authenticator's
28263 private options. All you need to do is to specify an appropriate mechanism as
28264 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28265 PLAIN, you could have two authenticators as follows:
28268 driver = cyrus_sasl
28269 public_name = CRAM-MD5
28270 server_set_id = $auth1
28273 driver = cyrus_sasl
28274 public_name = PLAIN
28275 server_set_id = $auth2
28277 Cyrus SASL does implement the LOGIN authentication method, even though it is
28278 not a standard method. It is disabled by default in the source distribution,
28279 but it is present in many binary distributions.
28280 .ecindex IIDcyrauth1
28281 .ecindex IIDcyrauth2
28286 . ////////////////////////////////////////////////////////////////////////////
28287 . ////////////////////////////////////////////////////////////////////////////
28288 .chapter "The dovecot authenticator" "CHAPdovecot"
28289 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28290 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28291 This authenticator is an interface to the authentication facility of the
28292 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28293 Note that Dovecot must be configured to use auth-client not auth-userdb.
28294 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28295 to use the same mechanisms for SMTP authentication. This is a server
28296 authenticator only. There is only one option:
28298 .option server_socket dovecot string unset
28300 This option must specify the UNIX socket that is the interface to Dovecot
28301 authentication. The &%public_name%& option must specify an authentication
28302 mechanism that Dovecot is configured to support. You can have several
28303 authenticators for different mechanisms. For example:
28307 public_name = PLAIN
28308 server_socket = /var/run/dovecot/auth-client
28309 server_set_id = $auth1
28314 server_socket = /var/run/dovecot/auth-client
28315 server_set_id = $auth1
28317 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28318 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28319 option is passed in the Dovecot authentication command. If, for a TLS
28320 connection, a client certificate has been verified, the &"valid-client-cert"&
28321 option is passed. When authentication succeeds, the identity of the user
28322 who authenticated is placed in &$auth1$&.
28324 The Dovecot configuration to match the above will look
28327 conf.d/10-master.conf :-
28332 unix_listener auth-client {
28339 conf.d/10-auth.conf :-
28341 auth_mechanisms = plain login ntlm
28344 .ecindex IIDdcotauth1
28345 .ecindex IIDdcotauth2
28348 . ////////////////////////////////////////////////////////////////////////////
28349 . ////////////////////////////////////////////////////////////////////////////
28350 .chapter "The gsasl authenticator" "CHAPgsasl"
28351 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28352 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28353 .cindex "authentication" "GNU SASL"
28354 .cindex "authentication" "SASL"
28355 .cindex "authentication" "EXTERNAL"
28356 .cindex "authentication" "ANONYMOUS"
28357 .cindex "authentication" "PLAIN"
28358 .cindex "authentication" "LOGIN"
28359 .cindex "authentication" "DIGEST-MD5"
28360 .cindex "authentication" "CRAM-MD5"
28361 .cindex "authentication" "SCRAM family"
28362 The &(gsasl)& authenticator provides integration for the GNU SASL
28363 library and the mechanisms it provides. This is new as of the 4.80 release
28364 and there are a few areas where the library does not let Exim smoothly
28365 scale to handle future authentication mechanisms, so no guarantee can be
28366 made that any particular new authentication mechanism will be supported
28367 without code changes in Exim.
28369 The library is expected to add support in an upcoming
28370 realease for the SCRAM-SHA-256 method.
28371 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28375 To see the list of mechanisms supported by the library run Exim with "auth" debug
28376 enabled and look for a line containing "GNU SASL supports".
28377 Note however that some may not have been tested from Exim.
28381 .option client_authz gsasl string&!! unset
28382 This option can be used to supply an &'authorization id'&
28383 which is different to the &'authentication_id'& provided
28384 by &%client_username%& option.
28385 If unset or (after expansion) empty it is not used,
28386 which is the common case.
28388 .option client_channelbinding gsasl boolean false
28389 See &%server_channelbinding%& below.
28391 .option client_password gsasl string&!! unset
28392 This option is exapanded before use, and should result in
28393 the password to be used, in clear.
28395 .option client_username gsasl string&!! unset
28396 This option is exapanded before use, and should result in
28397 the account name to be used.
28400 .option client_spassword gsasl string&!! unset
28402 This option is only supported for library versions 1.9.1 and greater.
28403 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28406 If a SCRAM mechanism is being used and this option is set
28407 and correctly sized
28408 it is used in preference to &%client_password%&.
28409 The value after expansion should be
28410 a 40 (for SHA-1) or 64 (for SHA-256) character string
28411 with the PBKDF2-prepared password, hex-encoded.
28413 Note that this value will depend on the salt and iteration-count
28414 supplied by the server.
28415 The option is expanded before use.
28417 During the expansion &$auth1$& is set with the client username,
28418 &$auth2$& with the iteration count, and
28419 &$auth3$& with the salt.
28421 The intent of this option
28422 is to support clients that can cache thes salted password
28423 to save on recalculation costs.
28424 The cache lookup should return an unusable value
28425 (eg. an empty string)
28426 if the salt or iteration count has changed
28428 If the authentication succeeds then the above variables are set,
28429 .vindex "&$auth4$&"
28430 plus the calculated salted password value value in &$auth4$&,
28431 during the expansion of the &%client_set_id%& option.
28432 A side-effect of this expansion can be used to prime the cache.
28436 .option server_channelbinding gsasl boolean false
28437 Some authentication mechanisms are able to use external context at both ends
28438 of the session to bind the authentication to that context, and fail the
28439 authentication process if that context differs. Specifically, some TLS
28440 ciphersuites can provide identifying information about the cryptographic
28443 This should have meant that certificate identity and verification becomes a
28444 non-issue, as a man-in-the-middle attack will cause the correct client and
28445 server to see different identifiers and authentication will fail.
28448 only usable by mechanisms which support "channel binding"; at time of
28449 writing, that's the SCRAM family.
28450 When using this feature the "-PLUS" variants of the method names need to be used.
28452 This defaults off to ensure smooth upgrade across Exim releases, in case
28453 this option causes some clients to start failing. Some future release
28454 of Exim might have switched the default to be true.
28456 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28457 . Do not plan to rely upon this feature for security, ever, without consulting
28458 . with a subject matter expert (a cryptographic engineer).
28461 This option was deprecated in previous releases due to doubts over
28462 the "Triple Handshake" vulnerability.
28463 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28464 Session Resumption was used) for safety.
28468 .option server_hostname gsasl string&!! "see below"
28469 This option selects the hostname that is used when communicating with the
28470 library. The default value is &`$primary_hostname`&.
28471 Some mechanisms will use this data.
28474 .option server_mech gsasl string "see below"
28475 This option selects the authentication mechanism this driver should use. The
28476 default is the value of the generic &%public_name%& option. This option allows
28477 you to use a different underlying mechanism from the advertised name. For
28482 public_name = X-ANYTHING
28483 server_mech = CRAM-MD5
28484 server_set_id = $auth1
28488 .option server_password gsasl string&!! unset
28489 Various mechanisms need access to the cleartext password on the server, so
28490 that proof-of-possession can be demonstrated on the wire, without sending
28491 the password itself.
28493 The data available for lookup varies per mechanism.
28494 In all cases, &$auth1$& is set to the &'authentication id'&.
28495 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28496 if available, else the empty string.
28497 The &$auth3$& variable will always be the &'realm'& if available,
28498 else the empty string.
28500 A forced failure will cause authentication to defer.
28502 If using this option, it may make sense to set the &%server_condition%&
28503 option to be simply "true".
28506 .option server_realm gsasl string&!! unset
28507 This specifies the SASL realm that the server claims to be in.
28508 Some mechanisms will use this data.
28511 .option server_scram_iter gsasl string&!! 4096
28512 This option provides data for the SCRAM family of mechanisms.
28513 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28514 when this option is expanded.
28516 The result of expansion should be a decimal number,
28517 and represents both a lower-bound on the security, and
28518 a compute cost factor imposed on the client
28519 (if it does not cache results, or the server changes
28520 either the iteration count or the salt).
28521 A minimum value of 4096 is required by the standards
28522 for all current SCRAM mechanism variants.
28524 .option server_scram_salt gsasl string&!! unset
28525 This option provides data for the SCRAM family of mechanisms.
28526 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28527 when this option is expanded.
28528 The value should be a base64-encoded string,
28529 of random data typically 4-to-16 bytes long.
28530 If unset or empty after expansion the library will provides a value for the
28531 protocol conversation.
28534 .option server_key gsasl string&!! unset
28535 .option server_skey gsasl string&!! unset
28536 These options can be used for the SCRAM family of mechanisms
28537 to provide stored information related to a password,
28538 the storage of which is preferable to plaintext.
28540 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28541 &%server_skey%& is StoredKey.
28543 They are only available for version 1.9.0 (or later) of the gsasl library.
28544 When this is so, the macros
28545 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28546 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28549 The &$authN$& variables are available when these options are expanded.
28551 If set, the results of expansion should for each
28552 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28553 of base64-coded data, and will be used in preference to the
28554 &%server_password%& option.
28555 If unset or not of the right length, &%server_password%& will be used.
28557 The libgsasl library release includes a utility &'gsasl'& which can be used
28558 to generate these values.
28561 .option server_service gsasl string &`smtp`&
28562 This is the SASL service that the server claims to implement.
28563 Some mechanisms will use this data.
28566 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28567 .vindex "&$auth1$&, &$auth2$&, etc"
28568 These may be set when evaluating specific options, as detailed above.
28569 They will also be set when evaluating &%server_condition%&.
28571 Unless otherwise stated below, the &(gsasl)& integration will use the following
28572 meanings for these variables:
28575 .vindex "&$auth1$&"
28576 &$auth1$&: the &'authentication id'&
28578 .vindex "&$auth2$&"
28579 &$auth2$&: the &'authorization id'&
28581 .vindex "&$auth3$&"
28582 &$auth3$&: the &'realm'&
28585 On a per-mechanism basis:
28588 .cindex "authentication" "EXTERNAL"
28589 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28590 the &%server_condition%& option must be present.
28592 .cindex "authentication" "ANONYMOUS"
28593 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28594 the &%server_condition%& option must be present.
28596 .cindex "authentication" "GSSAPI"
28597 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28598 &$auth2$& will be set to the &'authorization id'&,
28599 the &%server_condition%& option must be present.
28602 An &'anonymous token'& is something passed along as an unauthenticated
28603 identifier; this is analogous to FTP anonymous authentication passing an
28604 email address, or software-identifier@, as the "password".
28607 An example showing the password having the realm specified in the callback
28608 and demonstrating a Cyrus SASL to GSASL migration approach is:
28610 gsasl_cyrusless_crammd5:
28612 public_name = CRAM-MD5
28613 server_realm = imap.example.org
28614 server_password = ${lookup{$auth1:$auth3:userPassword}\
28615 dbmjz{/etc/sasldb2}{$value}fail}
28616 server_set_id = ${quote:$auth1}
28617 server_condition = yes
28621 . ////////////////////////////////////////////////////////////////////////////
28622 . ////////////////////////////////////////////////////////////////////////////
28624 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28625 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28626 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28627 .cindex "authentication" "GSSAPI"
28628 .cindex "authentication" "Kerberos"
28629 The &(heimdal_gssapi)& authenticator provides server integration for the
28630 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28633 .option server_hostname heimdal_gssapi string&!! "see below"
28634 This option selects the hostname that is used, with &%server_service%&,
28635 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28636 identifier. The default value is &`$primary_hostname`&.
28638 .option server_keytab heimdal_gssapi string&!! unset
28639 If set, then Heimdal will not use the system default keytab (typically
28640 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28641 The value should be a pathname, with no &"file:"& prefix.
28643 .option server_service heimdal_gssapi string&!! "smtp"
28644 This option specifies the service identifier used, in conjunction with
28645 &%server_hostname%&, for building the identifier for finding credentials
28649 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28650 Beware that these variables will typically include a realm, thus will appear
28651 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28652 not verified, so a malicious client can set it to anything.
28654 The &$auth1$& field should be safely trustable as a value from the Key
28655 Distribution Center. Note that these are not quite email addresses.
28656 Each identifier is for a role, and so the left-hand-side may include a
28657 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28659 .vindex "&$auth1$&, &$auth2$&, etc"
28661 .vindex "&$auth1$&"
28662 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28664 .vindex "&$auth2$&"
28665 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28666 authentication. If that was empty, this will also be set to the
28671 . ////////////////////////////////////////////////////////////////////////////
28672 . ////////////////////////////////////////////////////////////////////////////
28674 .chapter "The spa authenticator" "CHAPspa"
28675 .scindex IIDspaauth1 "&(spa)& authenticator"
28676 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28677 .cindex "authentication" "Microsoft Secure Password"
28678 .cindex "authentication" "NTLM"
28679 .cindex "Microsoft Secure Password Authentication"
28680 .cindex "NTLM authentication"
28681 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28682 Password Authentication'& mechanism,
28683 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28684 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28685 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28686 server side was subsequently contributed by Tom Kistner. The mechanism works as
28690 After the AUTH command has been accepted, the client sends an SPA
28691 authentication request based on the user name and optional domain.
28693 The server sends back a challenge.
28695 The client builds a challenge response which makes use of the user's password
28696 and sends it to the server, which then accepts or rejects it.
28699 Encryption is used to protect the password in transit.
28703 .section "Using spa as a server" "SECID179"
28704 .cindex "options" "&(spa)& authenticator (server)"
28705 The &(spa)& authenticator has just one server option:
28707 .option server_password spa string&!! unset
28708 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28709 This option is expanded, and the result must be the cleartext password for the
28710 authenticating user, whose name is at this point in &$auth1$&. For
28711 compatibility with previous releases of Exim, the user name is also placed in
28712 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28713 it can lead to confusion in string expansions that also use numeric variables
28714 for other things. For example:
28719 server_password = \
28720 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28722 If the expansion is forced to fail, authentication fails. Any other expansion
28723 failure causes a temporary error code to be returned.
28729 .section "Using spa as a client" "SECID180"
28730 .cindex "options" "&(spa)& authenticator (client)"
28731 The &(spa)& authenticator has the following client options:
28735 .option client_domain spa string&!! unset
28736 This option specifies an optional domain for the authentication.
28739 .option client_password spa string&!! unset
28740 This option specifies the user's password, and must be set.
28743 .option client_username spa string&!! unset
28744 This option specifies the user name, and must be set. Here is an example of a
28745 configuration of this authenticator for use with the mail servers at
28751 client_username = msn/msn_username
28752 client_password = msn_plaintext_password
28753 client_domain = DOMAIN_OR_UNSET
28755 .ecindex IIDspaauth1
28756 .ecindex IIDspaauth2
28762 . ////////////////////////////////////////////////////////////////////////////
28763 . ////////////////////////////////////////////////////////////////////////////
28765 .chapter "The external authenticator" "CHAPexternauth"
28766 .scindex IIDexternauth1 "&(external)& authenticator"
28767 .scindex IIDexternauth2 "authenticators" "&(external)&"
28768 .cindex "authentication" "Client Certificate"
28769 .cindex "authentication" "X509"
28770 .cindex "Certificate-based authentication"
28771 The &(external)& authenticator provides support for
28772 authentication based on non-SMTP information.
28773 The specification is in RFC 4422 Appendix A
28774 (&url(https://tools.ietf.org/html/rfc4422)).
28775 It is only a transport and negotiation mechanism;
28776 the process of authentication is entirely controlled
28777 by the server configuration.
28779 The client presents an identity in-clear.
28780 It is probably wise for a server to only advertise,
28781 and for clients to only attempt,
28782 this authentication method on a secure (eg. under TLS) connection.
28784 One possible use, compatible with the
28785 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28786 is for using X509 client certificates.
28788 It thus overlaps in function with the TLS authenticator
28789 (see &<<CHAPtlsauth>>&)
28790 but is a full SMTP SASL authenticator
28791 rather than being implicit for TLS-connection carried
28792 client certificates only.
28794 The examples and discussion in this chapter assume that
28795 client-certificate authentication is being done.
28797 The client must present a certificate,
28798 for which it must have been requested via the
28799 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28800 (see &<<CHAPTLS>>&).
28801 For authentication to be effective the certificate should be
28802 verifiable against a trust-anchor certificate known to the server.
28804 .section "External options" "SECTexternsoptions"
28805 .cindex "options" "&(external)& authenticator (server)"
28806 The &(external)& authenticator has two server options:
28808 .option server_param2 external string&!! unset
28809 .option server_param3 external string&!! unset
28810 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28811 These options are expanded before the &%server_condition%& option
28812 and the result are placed in &$auth2$& and &$auth3$& resectively.
28813 If the expansion is forced to fail, authentication fails. Any other expansion
28814 failure causes a temporary error code to be returned.
28816 They can be used to clarify the coding of a complex &%server_condition%&.
28818 .section "Using external in a server" "SECTexternserver"
28819 .cindex "AUTH" "in &(external)& authenticator"
28820 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28821 "in &(external)& authenticator"
28822 .vindex "&$auth1$&, &$auth2$&, etc"
28823 .cindex "base64 encoding" "in &(external)& authenticator"
28825 When running as a server, &(external)& performs the authentication test by
28826 expanding a string. The data sent by the client with the AUTH command, or in
28827 response to subsequent prompts, is base64 encoded, and so may contain any byte
28828 values when decoded. The decoded value is treated as
28829 an identity for authentication and
28830 placed in the expansion variable &$auth1$&.
28832 For compatibility with previous releases of Exim, the value is also placed in
28833 the expansion variable &$1$&. However, the use of this
28834 variable for this purpose is now deprecated, as it can lead to confusion in
28835 string expansions that also use them for other things.
28837 .vindex "&$authenticated_id$&"
28838 Once an identity has been received,
28839 &%server_condition%& is expanded. If the expansion is forced to fail,
28840 authentication fails. Any other expansion failure causes a temporary error code
28841 to be returned. If the result of a successful expansion is an empty string,
28842 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28843 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28844 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28845 For any other result, a temporary error code is returned, with the expanded
28846 string as the error text.
28850 ext_ccert_san_mail:
28852 public_name = EXTERNAL
28854 server_advertise_condition = $tls_in_certificate_verified
28855 server_param2 = ${certextract {subj_altname,mail,>:} \
28856 {$tls_in_peercert}}
28857 server_condition = ${if forany {$auth2} \
28858 {eq {$item}{$auth1}}}
28859 server_set_id = $auth1
28861 This accepts a client certificate that is verifiable against any
28862 of your configured trust-anchors
28863 (which usually means the full set of public CAs)
28864 and which has a mail-SAN matching the claimed identity sent by the client.
28866 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28867 The account name is therefore guessable by an opponent.
28868 TLS 1.3 protects both server and client certificates, and is not vulnerable
28872 .section "Using external in a client" "SECTexternclient"
28873 .cindex "options" "&(external)& authenticator (client)"
28874 The &(external)& authenticator has one client option:
28876 .option client_send external string&!! unset
28877 This option is expanded and sent with the AUTH command as the
28878 identity being asserted.
28884 public_name = EXTERNAL
28886 client_condition = ${if !eq{$tls_out_cipher}{}}
28887 client_send = myaccount@smarthost.example.net
28891 .ecindex IIDexternauth1
28892 .ecindex IIDexternauth2
28898 . ////////////////////////////////////////////////////////////////////////////
28899 . ////////////////////////////////////////////////////////////////////////////
28901 .chapter "The tls authenticator" "CHAPtlsauth"
28902 .scindex IIDtlsauth1 "&(tls)& authenticator"
28903 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28904 .cindex "authentication" "Client Certificate"
28905 .cindex "authentication" "X509"
28906 .cindex "Certificate-based authentication"
28907 The &(tls)& authenticator provides server support for
28908 authentication based on client certificates.
28910 It is not an SMTP authentication mechanism and is not
28911 advertised by the server as part of the SMTP EHLO response.
28912 It is an Exim authenticator in the sense that it affects
28913 the protocol element of the log line, can be tested for
28914 by the &%authenticated%& ACL condition, and can set
28915 the &$authenticated_id$& variable.
28917 The client must present a verifiable certificate,
28918 for which it must have been requested via the
28919 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28920 (see &<<CHAPTLS>>&).
28922 If an authenticator of this type is configured it is
28923 run before any SMTP-level communication is done,
28924 and can authenticate the connection.
28925 If it does, SMTP authentication is not offered.
28927 A maximum of one authenticator of this type may be present.
28930 .cindex "options" "&(tls)& authenticator (server)"
28931 The &(tls)& authenticator has three server options:
28933 .option server_param1 tls string&!! unset
28934 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28935 This option is expanded after the TLS negotiation and
28936 the result is placed in &$auth1$&.
28937 If the expansion is forced to fail, authentication fails. Any other expansion
28938 failure causes a temporary error code to be returned.
28940 .option server_param2 tls string&!! unset
28941 .option server_param3 tls string&!! unset
28942 As above, for &$auth2$& and &$auth3$&.
28944 &%server_param1%& may also be spelled &%server_param%&.
28951 server_param1 = ${certextract {subj_altname,mail,>:} \
28952 {$tls_in_peercert}}
28953 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28956 {${lookup ldap{ldap:///\
28957 mailname=${quote_ldap_dn:${lc:$item}},\
28958 ou=users,LDAP_DC?mailid} {$value}{0} \
28960 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28962 This accepts a client certificate that is verifiable against any
28963 of your configured trust-anchors
28964 (which usually means the full set of public CAs)
28965 and which has a SAN with a good account name.
28967 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28968 The account name is therefore guessable by an opponent.
28969 TLS 1.3 protects both server and client certificates, and is not vulnerable
28971 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28973 . An alternative might use
28975 . server_param1 = ${sha256:$tls_in_peercert}
28977 . to require one of a set of specific certs that define a given account
28978 . (the verification is still required, but mostly irrelevant).
28979 . This would help for per-device use.
28981 . However, for the future we really need support for checking a
28982 . user cert in LDAP - which probably wants a base-64 DER.
28984 .ecindex IIDtlsauth1
28985 .ecindex IIDtlsauth2
28988 Note that because authentication is traditionally an SMTP operation,
28989 the &%authenticated%& ACL condition cannot be used in
28990 a connect- or helo-ACL.
28994 . ////////////////////////////////////////////////////////////////////////////
28995 . ////////////////////////////////////////////////////////////////////////////
28997 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28998 "Encrypted SMTP connections"
28999 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
29000 .scindex IIDencsmtp2 "SMTP" "encryption"
29001 .cindex "TLS" "on SMTP connection"
29004 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
29005 Sockets Layer), is implemented by making use of the OpenSSL library or the
29006 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
29007 cryptographic code in the Exim distribution itself for implementing TLS. In
29008 order to use this feature you must install OpenSSL or GnuTLS, and then build a
29009 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
29010 You also need to understand the basic concepts of encryption at a managerial
29011 level, and in particular, the way that public keys, private keys, and
29012 certificates are used.
29014 RFC 3207 defines how SMTP connections can make use of encryption. Once a
29015 connection is established, the client issues a STARTTLS command. If the
29016 server accepts this, the client and the server negotiate an encryption
29017 mechanism. If the negotiation succeeds, the data that subsequently passes
29018 between them is encrypted.
29020 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
29021 and if so, what cipher suite is in use, whether the client supplied a
29022 certificate, and whether or not that certificate was verified. This makes it
29023 possible for an Exim server to deny or accept certain commands based on the
29026 &*Warning*&: Certain types of firewall and certain anti-virus products can
29027 disrupt TLS connections. You need to turn off SMTP scanning for these products
29028 in order to get TLS to work.
29032 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
29034 .cindex "submissions protocol"
29035 .cindex "ssmtp protocol"
29036 .cindex "smtps protocol"
29037 .cindex "SMTP" "submissions protocol"
29038 .cindex "SMTP" "ssmtp protocol"
29039 .cindex "SMTP" "smtps protocol"
29040 The history of port numbers for TLS in SMTP is a little messy and has been
29041 contentious. As of RFC 8314, the common practice of using the historically
29042 allocated port 465 for "email submission but with TLS immediately upon connect
29043 instead of using STARTTLS" is officially blessed by the IETF, and recommended
29044 by them in preference to STARTTLS.
29046 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
29047 clarity emerged over the dual roles of SMTP, for MX delivery and Email
29048 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
29050 This approach was, for a while, officially abandoned when encrypted SMTP was
29051 standardized, but many clients kept using it, even as the TCP port number was
29052 reassigned for other use.
29053 Thus you may encounter guidance claiming that you shouldn't enable use of
29055 In practice, a number of mail-clients have only ever supported submissions,
29056 not submission with STARTTLS upgrade.
29057 Ideally, offer both submission (587) and submissions (465) service.
29059 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
29060 global option. Its value must be a list of port numbers;
29061 the most common use is expected to be:
29063 tls_on_connect_ports = 465
29065 The port numbers specified by this option apply to all SMTP connections, both
29066 via the daemon and via &'inetd'&. You still need to specify all the ports that
29067 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29068 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29069 an extra port &-- rather, it specifies different behaviour on a port that is
29072 There is also a &%-tls-on-connect%& command line option. This overrides
29073 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29080 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29081 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29082 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29083 To build Exim to use OpenSSL you need to set
29089 To build Exim to use GnuTLS, you need to set
29095 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29096 include files and libraries for GnuTLS can be found.
29098 There are some differences in usage when using GnuTLS instead of OpenSSL:
29101 The &%tls_verify_certificates%& option
29102 cannot be the path of a directory
29103 for GnuTLS versions before 3.3.6
29104 (for later versions, or OpenSSL, it can be either).
29106 The default value for &%tls_dhparam%& differs for historical reasons.
29108 .vindex "&$tls_in_peerdn$&"
29109 .vindex "&$tls_out_peerdn$&"
29110 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29111 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29112 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29114 OpenSSL identifies cipher suites using hyphens as separators, for example:
29115 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29116 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29117 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29118 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29119 to handle its own older variants) when processing lists of cipher suites in the
29120 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29123 The &%tls_require_ciphers%& options operate differently, as described in the
29124 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29126 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29127 When using OpenSSL, this option is ignored.
29128 (If an API is found to let OpenSSL be configured in this way,
29129 let the Exim Maintainers know and we'll likely use it).
29131 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29132 main option, it must be ordered to match the &%tls_certificate%& list.
29134 Some other recently added features may only be available in one or the other.
29135 This should be documented with the feature. If the documentation does not
29136 explicitly state that the feature is infeasible in the other TLS
29137 implementation, then patches are welcome.
29140 The output from "exim -bV" will show which (if any) support was included
29142 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29147 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29148 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29149 an explicit path; if the latter, then the text about generation still applies,
29150 but not the chosen filename.
29151 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29152 See the documentation of &%tls_dhparam%& for more information.
29154 GnuTLS uses D-H parameters that may take a substantial amount of time
29155 to compute. It is unreasonable to re-compute them for every TLS session.
29156 Therefore, Exim keeps this data in a file in its spool directory, called
29157 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29159 The file is owned by the Exim user and is readable only by
29160 its owner. Every Exim process that start up GnuTLS reads the D-H
29161 parameters from this file. If the file does not exist, the first Exim process
29162 that needs it computes the data and writes it to a temporary file which is
29163 renamed once it is complete. It does not matter if several Exim processes do
29164 this simultaneously (apart from wasting a few resources). Once a file is in
29165 place, new Exim processes immediately start using it.
29167 For maximum security, the parameters that are stored in this file should be
29168 recalculated periodically, the frequency depending on your paranoia level.
29169 If you are avoiding using the fixed D-H primes published in RFCs, then you
29170 are concerned about some advanced attacks and will wish to do this; if you do
29171 not regenerate then you might as well stick to the standard primes.
29173 Arranging this is easy in principle; just delete the file when you want new
29174 values to be computed. However, there may be a problem. The calculation of new
29175 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29176 If the system is not very active, &_/dev/random_& may delay returning data
29177 until enough randomness (entropy) is available. This may cause Exim to hang for
29178 a substantial amount of time, causing timeouts on incoming connections.
29180 The solution is to generate the parameters externally to Exim. They are stored
29181 in &_gnutls-params-N_& in PEM format, which means that they can be
29182 generated externally using the &(certtool)& command that is part of GnuTLS.
29184 To replace the parameters with new ones, instead of deleting the file
29185 and letting Exim re-create it, you can generate new parameters using
29186 &(certtool)& and, when this has been done, replace Exim's cache file by
29187 renaming. The relevant commands are something like this:
29190 [ look for file; assume gnutls-params-2236 is the most recent ]
29193 # chown exim:exim new-params
29194 # chmod 0600 new-params
29195 # certtool --generate-dh-params --bits 2236 >>new-params
29196 # openssl dhparam -noout -text -in new-params | head
29197 [ check the first line, make sure it's not more than 2236;
29198 if it is, then go back to the start ("rm") and repeat
29199 until the size generated is at most the size requested ]
29200 # chmod 0400 new-params
29201 # mv new-params gnutls-params-2236
29203 If Exim never has to generate the parameters itself, the possibility of
29204 stalling is removed.
29206 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29207 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29208 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29209 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29210 and Exim does so. This attempt to remove Exim from TLS policy decisions
29211 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29212 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29213 which applies to all D-H usage, client or server. If the value returned by
29214 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29215 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29216 limit, which is still much higher than Exim historically used.
29218 The filename and bits used will change as the GnuTLS maintainers change the
29219 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29220 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29221 2432 bits, while NSS is limited to 2236 bits.
29223 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29224 increase the chance of the generated prime actually being within acceptable
29225 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29226 procedure above. There is no sane procedure available to Exim to double-check
29227 the size of the generated prime, so it might still be too large.
29230 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29231 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29232 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29233 There is a function in the OpenSSL library that can be passed a list of cipher
29234 suites before the cipher negotiation takes place. This specifies which ciphers
29235 are acceptable for TLS versions prior to 1.3.
29236 The list is colon separated and may contain names like
29237 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29238 directly to this function call.
29239 Many systems will install the OpenSSL manual-pages, so you may have
29240 &'ciphers(1)'& available to you.
29241 The following quotation from the OpenSSL
29242 documentation specifies what forms of item are allowed in the cipher string:
29245 It can consist of a single cipher suite such as RC4-SHA.
29247 It can represent a list of cipher suites containing a certain algorithm,
29248 or cipher suites of a certain type. For example SHA1 represents all
29249 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29252 Lists of cipher suites can be combined in a single cipher string using
29253 the + character. This is used as a logical and operation. For example
29254 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29258 Each cipher string can be optionally preceded by one of the characters &`!`&,
29261 If &`!`& is used, the ciphers are permanently deleted from the list. The
29262 ciphers deleted can never reappear in the list even if they are explicitly
29265 If &`-`& is used, the ciphers are deleted from the list, but some or all
29266 of the ciphers can be added again by later options.
29268 If &`+`& is used, the ciphers are moved to the end of the list. This
29269 option does not add any new ciphers; it just moves matching existing ones.
29272 If none of these characters is present, the string is interpreted as
29273 a list of ciphers to be appended to the current preference list. If the list
29274 includes any ciphers already present they will be ignored: that is, they will
29275 not be moved to the end of the list.
29278 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29281 # note single-quotes to get ! past any shell history expansion
29282 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29285 This example will let the library defaults be permitted on the MX port, where
29286 there's probably no identity verification anyway, but ups the ante on the
29287 submission ports where the administrator might have some influence on the
29288 choice of clients used:
29290 # OpenSSL variant; see man ciphers(1)
29291 tls_require_ciphers = ${if =={$received_port}{25}\
29296 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29298 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29301 For TLS version 1.3 the control available is less fine-grained
29302 and Exim does not provide access to it at present.
29303 The value of the &%tls_require_ciphers%& option is ignored when
29304 TLS version 1.3 is negotiated.
29306 As of writing the library default cipher suite list for TLSv1.3 is
29308 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29312 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29314 .cindex "GnuTLS" "specifying parameters for"
29315 .cindex "TLS" "specifying ciphers (GnuTLS)"
29316 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29317 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29318 .cindex "TLS" "specifying protocols (GnuTLS)"
29319 .cindex "TLS" "specifying priority string (GnuTLS)"
29320 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29321 The GnuTLS library allows the caller to provide a "priority string", documented
29322 as part of the &[gnutls_priority_init]& function. This is very similar to the
29323 ciphersuite specification in OpenSSL.
29325 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29326 and controls both protocols and ciphers.
29328 The &%tls_require_ciphers%& option is available both as an global option,
29329 controlling how Exim behaves as a server, and also as an option of the
29330 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29331 the value is string expanded. The resulting string is not an Exim list and
29332 the string is given to the GnuTLS library, so that Exim does not need to be
29333 aware of future feature enhancements of GnuTLS.
29335 Documentation of the strings accepted may be found in the GnuTLS manual, under
29336 "Priority strings". This is online as
29337 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29338 but beware that this relates to GnuTLS 3, which may be newer than the version
29339 installed on your system. If you are using GnuTLS 3,
29340 then the example code
29341 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29342 on that site can be used to test a given string.
29346 # Disable older versions of protocols
29347 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29350 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29351 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29352 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29354 This example will let the library defaults be permitted on the MX port, where
29355 there's probably no identity verification anyway, and lowers security further
29356 by increasing compatibility; but this ups the ante on the submission ports
29357 where the administrator might have some influence on the choice of clients
29361 tls_require_ciphers = ${if =={$received_port}{25}\
29367 .section "Configuring an Exim server to use TLS" "SECID182"
29368 .cindex "TLS" "configuring an Exim server"
29369 .cindex "ESMTP extensions" STARTTLS
29370 When Exim has been built with TLS support, it advertises the availability of
29371 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29372 but not to any others. The default value of this option is *, which means
29373 that STARTTLS is always advertised. Set it to blank to never advertise;
29374 this is reasonable for systems that want to use TLS only as a client.
29376 If STARTTLS is to be used you
29377 need to set some other options in order to make TLS available.
29379 If a client issues a STARTTLS command and there is some configuration
29380 problem in the server, the command is rejected with a 454 error. If the client
29381 persists in trying to issue SMTP commands, all except QUIT are rejected
29384 554 Security failure
29386 If a STARTTLS command is issued within an existing TLS session, it is
29387 rejected with a 554 error code.
29389 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29390 must be set to match some hosts. The default is * which matches all hosts.
29392 If this is all you do, TLS encryption will be enabled but not authentication -
29393 meaning that the peer has no assurance it is actually you he is talking to.
29394 You gain protection from a passive sniffer listening on the wire but not
29395 from someone able to intercept the communication.
29397 Further protection requires some further configuration at the server end.
29399 To make TLS work you need to set, in the server,
29401 tls_certificate = /some/file/name
29402 tls_privatekey = /some/file/name
29404 These options are, in fact, expanded strings, so you can make them depend on
29405 the identity of the client that is connected if you wish. The first file
29406 contains the server's X509 certificate, and the second contains the private key
29407 that goes with it. These files need to be
29408 PEM format and readable by the Exim user, and must
29409 always be given as full path names.
29410 The key must not be password-protected.
29411 They can be the same file if both the
29412 certificate and the key are contained within it. If &%tls_privatekey%& is not
29413 set, or if its expansion is forced to fail or results in an empty string, this
29414 is assumed to be the case. The certificate file may also contain intermediate
29415 certificates that need to be sent to the client to enable it to authenticate
29416 the server's certificate.
29418 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29419 colon-separated lists of file paths. Ciphers using given authentication
29420 algorithms require the presence of a suitable certificate to supply the
29421 public-key. The server selects among the certificates to present to the
29422 client depending on the selected cipher, hence the priority ordering for
29423 ciphers will affect which certificate is used.
29425 If you do not understand about certificates and keys, please try to find a
29426 source of this background information, which is not Exim-specific. (There are a
29427 few comments below in section &<<SECTcerandall>>&.)
29429 &*Note*&: These options do not apply when Exim is operating as a client &--
29430 they apply only in the case of a server. If you need to use a certificate in an
29431 Exim client, you must set the options of the same names in an &(smtp)&
29434 With just these options, an Exim server will be able to use TLS. It does not
29435 require the client to have a certificate (but see below for how to insist on
29436 this). There is one other option that may be needed in other situations. If
29438 tls_dhparam = /some/file/name
29440 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29441 with the parameters contained in the file.
29442 Set this to &`none`& to disable use of DH entirely, by making no prime
29447 This may also be set to a string identifying a standard prime to be used for
29448 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29449 used is &`ike23`&. There are a few standard primes available, see the
29450 documentation for &%tls_dhparam%& for the complete list.
29456 for a way of generating file data.
29458 The strings supplied for these three options are expanded every time a client
29459 host connects. It is therefore possible to use different certificates and keys
29460 for different hosts, if you so wish, by making use of the client's IP address
29461 in &$sender_host_address$& to control the expansion. If a string expansion is
29462 forced to fail, Exim behaves as if the option is not set.
29464 .cindex "cipher" "logging"
29465 .cindex "log" "TLS cipher"
29466 .vindex "&$tls_in_cipher$&"
29467 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29468 an incoming TLS connection. It is included in the &'Received:'& header of an
29469 incoming message (by default &-- you can, of course, change this), and it is
29470 also included in the log line that records a message's arrival, keyed by
29471 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29472 condition can be used to test for specific cipher suites in ACLs.
29474 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29475 can check the name of the cipher suite and vary their actions accordingly. The
29476 cipher suite names vary, depending on which TLS library is being used. For
29477 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29478 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29479 documentation for more details.
29481 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29482 (again depending on the &%tls_cipher%& log selector).
29485 .section "Requesting and verifying client certificates" "SECID183"
29486 .cindex "certificate" "verification of client"
29487 .cindex "TLS" "client certificate verification"
29488 If you want an Exim server to request a certificate when negotiating a TLS
29489 session with a client, you must set either &%tls_verify_hosts%& or
29490 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29491 apply to all TLS connections. For any host that matches one of these options,
29492 Exim requests a certificate as part of the setup of the TLS session. The
29493 contents of the certificate are verified by comparing it with a list of
29494 expected trust-anchors or certificates.
29495 These may be the system default set (depending on library version),
29496 an explicit file or,
29497 depending on library version, a directory, identified by
29498 &%tls_verify_certificates%&.
29500 A file can contain multiple certificates, concatenated end to end. If a
29503 each certificate must be in a separate file, with a name (or a symbolic link)
29504 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29505 certificate. You can compute the relevant hash by running the command
29507 openssl x509 -hash -noout -in /cert/file
29509 where &_/cert/file_& contains a single certificate.
29511 There is no checking of names of the client against the certificate
29512 Subject Name or Subject Alternate Names.
29514 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29515 what happens if the client does not supply a certificate, or if the certificate
29516 does not match any of the certificates in the collection named by
29517 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29518 attempt to set up a TLS session is aborted, and the incoming connection is
29519 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29520 session continues. ACLs that run for subsequent SMTP commands can detect the
29521 fact that no certificate was verified, and vary their actions accordingly. For
29522 example, you can insist on a certificate before accepting a message for
29523 relaying, but not when the message is destined for local delivery.
29525 .vindex "&$tls_in_peerdn$&"
29526 When a client supplies a certificate (whether it verifies or not), the value of
29527 the Distinguished Name of the certificate is made available in the variable
29528 &$tls_in_peerdn$& during subsequent processing of the message.
29530 .cindex "log" "distinguished name"
29531 Because it is often a long text string, it is not included in the log line or
29532 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29533 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29534 &%received_header_text%& to change the &'Received:'& header. When no
29535 certificate is supplied, &$tls_in_peerdn$& is empty.
29538 .section "Revoked certificates" "SECID184"
29539 .cindex "TLS" "revoked certificates"
29540 .cindex "revocation list"
29541 .cindex "certificate" "revocation list"
29542 .cindex "OCSP" "stapling"
29543 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29544 certificates are revoked. If you have such a list, you can pass it to an Exim
29545 server using the global option called &%tls_crl%& and to an Exim client using
29546 an identically named option for the &(smtp)& transport. In each case, the value
29547 of the option is expanded and must then be the name of a file that contains a
29549 The downside is that clients have to periodically re-download a potentially huge
29550 file from every certificate authority they know of.
29552 The way with most moving parts at query time is Online Certificate
29553 Status Protocol (OCSP), where the client verifies the certificate
29554 against an OCSP server run by the CA. This lets the CA track all
29555 usage of the certs. It requires running software with access to the
29556 private key of the CA, to sign the responses to the OCSP queries. OCSP
29557 is based on HTTP and can be proxied accordingly.
29559 The only widespread OCSP server implementation (known to this writer)
29560 comes as part of OpenSSL and aborts on an invalid request, such as
29561 connecting to the port and then disconnecting. This requires
29562 re-entering the passphrase each time some random client does this.
29564 The third way is OCSP Stapling; in this, the server using a certificate
29565 issued by the CA periodically requests an OCSP proof of validity from
29566 the OCSP server, then serves it up inline as part of the TLS
29567 negotiation. This approach adds no extra round trips, does not let the
29568 CA track users, scales well with number of certs issued by the CA and is
29569 resilient to temporary OCSP server failures, as long as the server
29570 starts retrying to fetch an OCSP proof some time before its current
29571 proof expires. The downside is that it requires server support.
29573 Unless Exim is built with the support disabled,
29574 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29575 support for OCSP stapling is included.
29577 There is a global option called &%tls_ocsp_file%&.
29578 The file specified therein is expected to be in DER format, and contain
29579 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29580 option will be re-expanded for SNI, if the &%tls_certificate%& option
29581 contains &`tls_in_sni`&, as per other TLS options.
29583 Exim does not at this time implement any support for fetching a new OCSP
29584 proof. The burden is on the administrator to handle this, outside of
29585 Exim. The file specified should be replaced atomically, so that the
29586 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29587 on each connection, so a new file will be handled transparently on the
29590 When built with OpenSSL Exim will check for a valid next update timestamp
29591 in the OCSP proof; if not present, or if the proof has expired, it will be
29594 For the client to be able to verify the stapled OCSP the server must
29595 also supply, in its stapled information, any intermediate
29596 certificates for the chain leading to the OCSP proof from the signer
29597 of the server certificate. There may be zero or one such. These
29598 intermediate certificates should be added to the server OCSP stapling
29599 file named by &%tls_ocsp_file%&.
29601 Note that the proof only covers the terminal server certificate,
29602 not any of the chain from CA to it.
29604 There is no current way to staple a proof for a client certificate.
29607 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29608 OCSP server is supplied. The server URL may be included in the
29609 server certificate, if the CA is helpful.
29611 One failure mode seen was the OCSP Signer cert expiring before the end
29612 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29613 noted this as invalid overall, but the re-fetch script did not.
29618 .section "Caching of static server configuration items" "SECTserverTLScache"
29619 .cindex certificate caching
29620 .cindex privatekey caching
29621 .cindex crl caching
29622 .cindex ocsp caching
29623 .cindex ciphers caching
29624 .cindex "CA bundle" caching
29625 .cindex "certificate authorities" caching
29626 .cindex tls_certificate caching
29627 .cindex tls_privatekey caching
29628 .cindex tls_crl caching
29629 .cindex tls_ocsp_file caching
29630 .cindex tls_require_ciphers caching
29631 .cindex tls_verify_certificate caching
29632 .cindex caching certificate
29633 .cindex caching privatekey
29634 .cindex caching crl
29635 .cindex caching ocsp
29636 .cindex caching ciphers
29637 .cindex caching "certificate authorities
29638 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29639 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29640 expandable elements,
29641 then the associated information is loaded at daemon startup.
29642 It is made available
29643 to child processes forked for handling received SMTP connections.
29645 This caching is currently only supported under Linux and FreeBSD.
29647 If caching is not possible, for example if an item has to be dependent
29648 on the peer host so contains a &$sender_host_name$& expansion, the load
29649 of the associated information is done at the startup of the TLS connection.
29651 The cache is invalidated and reloaded after any changes to the directories
29652 containing files specified by these options.
29654 The information specified by the main option &%tls_verify_certificates%&
29655 is similarly cached so long as it specifies files explicitly
29656 or (under GnuTLS) is the string &"system,cache"&.
29657 The latter case is not automatically invalidated;
29658 it is the operator's responsibility to arrange for a daemon restart
29659 any time the system certificate authority bundle is updated.
29660 A HUP signal is sufficient for this.
29661 The value &"system"& results in no caching under GnuTLS.
29663 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29664 is acceptable in configurations for the Exim executavble.
29666 Caching of the system Certificate Authorities bundle can
29667 save siginificant time and processing on every TLS connection
29674 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29675 .cindex "cipher" "logging"
29676 .cindex "log" "TLS cipher"
29677 .cindex "log" "distinguished name"
29678 .cindex "TLS" "configuring an Exim client"
29679 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29680 deliveries as well as to incoming, the latter one causing logging of the
29681 server certificate's DN. The remaining client configuration for TLS is all
29682 within the &(smtp)& transport.
29684 .cindex "ESMTP extensions" STARTTLS
29685 It is not necessary to set any options to have TLS work in the &(smtp)&
29686 transport. If Exim is built with TLS support, and TLS is advertised by a
29687 server, the &(smtp)& transport always tries to start a TLS session. However,
29688 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29689 transport) to a list of server hosts for which TLS should not be used.
29691 If you do not want Exim to attempt to send messages unencrypted when an attempt
29692 to set up an encrypted connection fails in any way, you can set
29693 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29694 those hosts, delivery is always deferred if an encrypted connection cannot be
29695 set up. If there are any other hosts for the address, they are tried in the
29698 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29699 the message unencrypted. It always does this if the response to STARTTLS is
29700 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29701 session after a success response code, what happens is controlled by the
29702 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29703 delivery to this host is deferred, and other hosts (if available) are tried. If
29704 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29705 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29706 negotiation fails, Exim closes the current connection (because it is in an
29707 unknown state), opens a new one to the same host, and then tries the delivery
29710 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29711 transport provide the client with a certificate, which is passed to the server
29713 This is an optional thing for TLS connections, although either end
29715 If the server is Exim, it will request a certificate only if
29716 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29718 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29719 for client use (they are usable for server use).
29720 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29721 in failed connections.
29723 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29724 specifies a collection of expected server certificates.
29726 the system default set (depending on library version),
29728 or (depending on library version) a directory.
29729 The client verifies the server's certificate
29730 against this collection, taking into account any revoked certificates that are
29731 in the list defined by &%tls_crl%&.
29732 Failure to verify fails the TLS connection unless either of the
29733 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29735 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29736 certificate verification to the listed servers. Verification either must
29737 or need not succeed respectively.
29739 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29740 name checks are made on the server certificate.
29742 The match against this list is, as per other Exim usage, the
29743 IP for the host. That is most closely associated with the
29744 name on the DNS A (or AAAA) record for the host.
29745 However, the name that needs to be in the certificate
29746 is the one at the head of any CNAME chain leading to the A record.
29748 The option defaults to always checking.
29750 The &(smtp)& transport has two OCSP-related options:
29751 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29752 is requested and required for the connection to proceed. The default
29754 &%hosts_request_ocsp%&; a host-list for which (additionally)
29755 a Certificate Status is requested (but not necessarily verified). The default
29756 value is "*" meaning that requests are made unless configured
29759 The host(s) should also be in &%hosts_require_tls%&, and
29760 &%tls_verify_certificates%& configured for the transport,
29761 for OCSP to be relevant.
29764 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29765 list of permitted cipher suites. If either of these checks fails, delivery to
29766 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29767 alternative hosts, if any.
29770 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29771 is operating as a client. Exim does not assume that a server certificate (set
29772 by the global options of the same name) should also be used when operating as a
29776 .vindex "&$host_address$&"
29777 All the TLS options in the &(smtp)& transport are expanded before use, with
29778 &$host$& and &$host_address$& containing the name and address of the server to
29779 which the client is connected. Forced failure of an expansion causes Exim to
29780 behave as if the relevant option were unset.
29782 .vindex &$tls_out_bits$&
29783 .vindex &$tls_out_cipher$&
29784 .vindex &$tls_out_peerdn$&
29785 .vindex &$tls_out_sni$&
29786 Before an SMTP connection is established, the
29787 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29788 variables are emptied. (Until the first connection, they contain the values
29789 that were set when the message was received.) If STARTTLS is subsequently
29790 successfully obeyed, these variables are set to the relevant values for the
29791 outgoing connection.
29796 .section "Caching of static client configuration items" "SECTclientTLScache"
29797 .cindex certificate caching
29798 .cindex privatekey caching
29799 .cindex crl caching
29800 .cindex ciphers caching
29801 .cindex "CA bundle" caching
29802 .cindex "certificate authorities" caching
29803 .cindex tls_certificate caching
29804 .cindex tls_privatekey caching
29805 .cindex tls_crl caching
29806 .cindex tls_require_ciphers caching
29807 .cindex tls_verify_certificate caching
29808 .cindex caching certificate
29809 .cindex caching privatekey
29810 .cindex caching crl
29811 .cindex caching ciphers
29812 .cindex caching "certificate authorities
29813 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29814 and &%tls_crl%& have values with no
29815 expandable elements,
29816 then the associated information is loaded per smtp transport
29817 at daemon startup, at the start of a queue run, or on a
29818 command-line specified message delivery.
29819 It is made available
29820 to child processes forked for handling making SMTP connections.
29822 This caching is currently only supported under Linux.
29824 If caching is not possible, the load
29825 of the associated information is done at the startup of the TLS connection.
29827 The cache is invalidated in the daemon
29828 and reloaded after any changes to the directories
29829 containing files specified by these options.
29831 The information specified by the main option &%tls_verify_certificates%&
29832 is similarly cached so long as it specifies files explicitly
29833 or (under GnuTLS) is the string &"system,cache"&.
29834 The latter case is not automatically invaludated;
29835 it is the operator's responsibility to arrange for a daemon restart
29836 any time the system certificate authority bundle is updated.
29837 A HUP signal is sufficient for this.
29838 The value &"system"& results in no caching under GnuTLS.
29840 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29841 is acceptable in configurations for the Exim executavble.
29843 Caching of the system Certificate Authorities bundle can
29844 save siginificant time and processing on every TLS connection
29851 .section "Use of TLS Server Name Indication" "SECTtlssni"
29852 .cindex "TLS" "Server Name Indication"
29855 .vindex "&$tls_in_sni$&"
29856 .oindex "&%tls_in_sni%&"
29857 With TLS1.0 or above, there is an extension mechanism by which extra
29858 information can be included at various points in the protocol. One of these
29859 extensions, documented in RFC 6066 (and before that RFC 4366) is
29860 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29861 client in the initial handshake, so that the server can examine the servername
29862 within and possibly choose to use different certificates and keys (and more)
29865 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29866 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29869 With SMTP to MX, there are the same problems here as in choosing the identity
29870 against which to validate a certificate: you can't rely on insecure DNS to
29871 provide the identity which you then cryptographically verify. So this will
29872 be of limited use in that environment.
29874 With SMTP to Submission, there is a well-defined hostname which clients are
29875 connecting to and can validate certificates against. Thus clients &*can*&
29876 choose to include this information in the TLS negotiation. If this becomes
29877 wide-spread, then hosters can choose to present different certificates to
29878 different clients. Or even negotiate different cipher suites.
29880 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29881 if not empty, will be sent on a TLS session as part of the handshake. There's
29882 nothing more to it. Choosing a sensible value not derived insecurely is the
29883 only point of caution. The &$tls_out_sni$& variable will be set to this string
29884 for the lifetime of the client connection (including during authentication).
29887 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29888 is forced to the domain part of the recipient address.
29891 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29892 received from a client.
29893 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29895 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29896 option (prior to expansion) then the following options will be re-expanded
29897 during TLS session handshake, to permit alternative values to be chosen:
29900 &%tls_certificate%&
29906 &%tls_verify_certificates%&
29911 Great care should be taken to deal with matters of case, various injection
29912 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29913 can always be referenced; it is important to remember that &$tls_in_sni$& is
29914 arbitrary unverified data provided prior to authentication.
29915 Further, the initial certificate is loaded before SNI has arrived, so
29916 an expansion for &%tls_certificate%& must have a default which is used
29917 when &$tls_in_sni$& is empty.
29919 The Exim developers are proceeding cautiously and so far no other TLS options
29922 When Exim is built against OpenSSL, OpenSSL must have been built with support
29923 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29924 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29925 see &`-servername`& in the output, then OpenSSL has support.
29927 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29928 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29929 built, then you have SNI support).
29933 .cindex ALPN "general information"
29934 .cindex TLS "Application Layer Protocol Names"
29935 There is a TLS feature related to SNI
29936 called Application Layer Protocol Name (ALPN).
29937 This is intended to declare, or select, what protocol layer will be using a TLS
29939 The client for the connection proposes a set of protocol names, and
29940 the server responds with a selected one.
29941 It is not, as of 2021, commonly used for SMTP connections.
29942 However, to guard against misirected or malicious use of web clients
29943 (which often do use ALPN) against MTA ports, Exim by default check that
29944 there is no incompatible ALPN specified by a client for a TLS connection.
29945 If there is, the connection is rejected.
29947 As a client Exim does not supply ALPN by default.
29948 The behaviour of both client and server can be configured using the options
29949 &%tls_alpn%& and &%hosts_require_alpn%&.
29950 There are no variables providing observability.
29951 Some feature-specific logging may appear on denied connections, but this
29952 depends on the behavious of the peer
29953 (not all peers can send a feature-specific TLS Alert).
29955 This feature is available when Exim is built with
29956 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29957 the macro _HAVE_TLS_ALPN will be defined when this is so.
29962 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29964 .cindex "multiple SMTP deliveries with TLS"
29965 .cindex "TLS" "multiple message deliveries"
29966 Exim sends multiple messages down the same TCP/IP connection by starting up
29967 an entirely new delivery process for each message, passing the socket from
29968 one process to the next. This implementation does not fit well with the use
29969 of TLS, because there is quite a lot of state information associated with a TLS
29970 connection, not just a socket identification. Passing all the state information
29971 to a new process is not feasible. Consequently, for sending using TLS Exim
29972 starts an additional proxy process for handling the encryption, piping the
29973 unencrypted data stream from and to the delivery processes.
29975 An older mode of operation can be enabled on a per-host basis by the
29976 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29977 this list the proxy process described above is not used; instead Exim
29978 shuts down an existing TLS session being run by the delivery process
29979 before passing the socket to a new process. The new process may then
29980 try to start a new TLS session, and if successful, may try to re-authenticate
29981 if AUTH is in use, before sending the next message.
29983 The RFC is not clear as to whether or not an SMTP session continues in clear
29984 after TLS has been shut down, or whether TLS may be restarted again later, as
29985 just described. However, if the server is Exim, this shutdown and
29986 reinitialization works. It is not known which (if any) other servers operate
29987 successfully if the client closes a TLS session and continues with unencrypted
29988 SMTP, but there are certainly some that do not work. For such servers, Exim
29989 should not pass the socket to another process, because the failure of the
29990 subsequent attempt to use it would cause Exim to record a temporary host error,
29991 and delay other deliveries to that host.
29993 To test for this case, Exim sends an EHLO command to the server after
29994 closing down the TLS session. If this fails in any way, the connection is
29995 closed instead of being passed to a new delivery process, but no retry
29996 information is recorded.
29998 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29999 &(smtp)& transport to match those hosts for which Exim should not pass
30000 connections to new processes if TLS has been used.
30005 .section "Certificates and all that" "SECTcerandall"
30006 .cindex "certificate" "references to discussion"
30007 In order to understand fully how TLS works, you need to know about
30008 certificates, certificate signing, and certificate authorities.
30009 This is a large topic and an introductory guide is unsuitable for the Exim
30010 reference manual, so instead we provide pointers to existing documentation.
30012 The Apache web-server was for a long time the canonical guide, so their
30013 documentation is a good place to start; their SSL module's Introduction
30014 document is currently at
30016 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
30018 and their FAQ is at
30020 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
30023 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
30024 0-201-61598-3) in 2001, contains both introductory and more in-depth
30026 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
30027 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
30028 Ivan is the author of the popular TLS testing tools at
30029 &url(https://www.ssllabs.com/).
30032 .section "Certificate chains" "SECID186"
30033 A file named by &%tls_certificate%& may contain more than one
30034 certificate. This is useful in the case where the certificate that is being
30035 sent is validated by an intermediate certificate which the other end does
30036 not have. Multiple certificates must be in the correct order in the file.
30037 First the host's certificate itself, then the first intermediate
30038 certificate to validate the issuer of the host certificate, then the next
30039 intermediate certificate to validate the issuer of the first intermediate
30040 certificate, and so on, until finally (optionally) the root certificate.
30041 The root certificate must already be trusted by the recipient for
30042 validation to succeed, of course, but if it's not preinstalled, sending the
30043 root certificate along with the rest makes it available for the user to
30044 install if the receiving end is a client MUA that can interact with a user.
30046 Note that certificates using MD5 are unlikely to work on today's Internet;
30047 even if your libraries allow loading them for use in Exim when acting as a
30048 server, increasingly clients will not accept such certificates. The error
30049 diagnostics in such a case can be frustratingly vague.
30053 .section "Self-signed certificates" "SECID187"
30054 .cindex "certificate" "self-signed"
30055 You can create a self-signed certificate using the &'req'& command provided
30056 with OpenSSL, like this:
30057 . ==== Do not shorten the duration here without reading and considering
30058 . ==== the text below. Please leave it at 9999 days.
30060 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
30063 &_file1_& and &_file2_& can be the same file; the key and the certificate are
30064 delimited and so can be identified independently. The &%-days%& option
30065 specifies a period for which the certificate is valid. The &%-nodes%& option is
30066 important: if you do not set it, the key is encrypted with a passphrase
30067 that you are prompted for, and any use that is made of the key causes more
30068 prompting for the passphrase. This is not helpful if you are going to use
30069 this certificate and key in an MTA, where prompting is not possible.
30071 . ==== I expect to still be working 26 years from now. The less technical
30072 . ==== debt I create, in terms of storing up trouble for my later years, the
30073 . ==== happier I will be then. We really have reached the point where we
30074 . ==== should start, at the very least, provoking thought and making folks
30075 . ==== pause before proceeding, instead of leaving all the fixes until two
30076 . ==== years before 2^31 seconds after the 1970 Unix epoch.
30078 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30079 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30080 the above command might produce a date in the past. Think carefully about
30081 the lifetime of the systems you're deploying, and either reduce the duration
30082 of the certificate or reconsider your platform deployment. (At time of
30083 writing, reducing the duration is the most likely choice, but the inexorable
30084 progression of time takes us steadily towards an era where this will not
30085 be a sensible resolution).
30087 A self-signed certificate made in this way is sufficient for testing, and
30088 may be adequate for all your requirements if you are mainly interested in
30089 encrypting transfers, and not in secure identification.
30091 However, many clients require that the certificate presented by the server be a
30092 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30093 certificate. In this situation, the self-signed certificate described above
30094 must be installed on the client host as a trusted root &'certification
30095 authority'& (CA), and the certificate used by Exim must be a user certificate
30096 signed with that self-signed certificate.
30098 For information on creating self-signed CA certificates and using them to sign
30099 user certificates, see the &'General implementation overview'& chapter of the
30100 Open-source PKI book, available online at
30101 &url(https://sourceforge.net/projects/ospkibook/).
30102 .ecindex IIDencsmtp1
30103 .ecindex IIDencsmtp2
30107 .section "TLS Resumption" "SECTresumption"
30108 .cindex TLS resumption
30109 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30110 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30113 Session resumption (this is the "stateless" variant) involves the server sending
30114 a "session ticket" to the client on one connection, which can be stored by the
30115 client and used for a later session. The ticket contains sufficient state for
30116 the server to reconstruct the TLS session, avoiding some expensive crypto
30117 calculation and (on TLS1.2) one full packet roundtrip time.
30120 Operational cost/benefit:
30122 The extra data being transmitted costs a minor amount, and the client has
30123 extra costs in storing and retrieving the data.
30125 In the Exim/Gnutls implementation the extra cost on an initial connection
30126 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30127 The saved cost on a subsequent connection is about 4ms; three or more
30128 connections become a net win. On longer network paths, two or more
30129 connections will have an average lower startup time thanks to the one
30130 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30133 .cindex "hints database" tls
30134 Since a new hints DB is used on the TLS client,
30135 the hints DB maintenance should be updated to additionally handle "tls".
30140 The session ticket is encrypted, but is obviously an additional security
30141 vulnarability surface. An attacker able to decrypt it would have access
30142 all connections using the resumed session.
30143 The session ticket encryption key is not committed to storage by the server
30144 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30145 overlap; GnuTLS 6hr but does not specify any overlap).
30146 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30147 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30149 There is a question-mark over the security of the Diffie-Helman parameters
30150 used for session negotiation.
30155 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30158 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30159 have bits 0-4 indicating respectively
30160 support built, client requested ticket, client offered session,
30161 server issued ticket, resume used. A suitable decode list is provided
30162 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30167 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30168 exim, operating as a server, will offer resumption to clients.
30169 Current best practice is to not offer the feature to MUA connection.
30170 Commonly this can be done like this:
30172 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30174 If the peer host matches the list after expansion then resumption
30175 is offered and/or accepted.
30177 The &%tls_resumption_hosts%& smtp transport option performs the
30178 equivalent function for operation as a client.
30179 If the peer host matches the list after expansion then resumption
30180 is attempted (if a stored session is available) or the information
30181 stored (if supplied by the peer).
30187 In a resumed session:
30189 The variables &$tls_{in,out}_cipher$& will have values different
30190 to the original (under GnuTLS).
30192 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30193 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30194 . XXX need to do something with that hosts_require_ocsp
30201 .section DANE "SECDANE"
30203 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30204 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30205 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30206 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30207 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30208 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30210 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30211 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30212 by (a) is thought to be smaller than that of the set of root CAs.
30214 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30215 fail to pass on a server's STARTTLS.
30217 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30218 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30219 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30221 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30222 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30223 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30225 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30226 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30228 There are no changes to Exim specific to server-side operation of DANE.
30229 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30230 in &_Local/Makefile_&.
30231 If it has been included, the macro "_HAVE_DANE" will be defined.
30233 A TLSA record consist of 4 fields, the "Certificate Usage", the
30234 "Selector", the "Matching type", and the "Certificate Association Data".
30235 For a detailed description of the TLSA record see
30236 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30238 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30239 These are the "Trust Anchor" and "End Entity" variants.
30240 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30241 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30242 this is appropriate for a single system, using a self-signed certificate.
30243 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30245 A private CA at simplest is just a self-signed certificate (with certain
30246 attributes) which is used to sign server certificates, but running one securely
30247 does require careful arrangement.
30248 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30249 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30250 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30251 all of which point to a single TLSA record.
30252 DANE-TA and DANE-EE can both be used together.
30254 Our recommendation is to use DANE with a certificate from a public CA,
30255 because this enables a variety of strategies for remote clients to verify
30257 You can then publish information both via DANE and another technology,
30258 "MTA-STS", described below.
30260 When you use DANE-TA to publish trust anchor information, you ask entities
30261 outside your administrative control to trust the Certificate Authority for
30262 connections to you.
30263 If using a private CA then you should expect others to still apply the
30264 technical criteria they'd use for a public CA to your certificates.
30265 In particular, you should probably try to follow current best practices for CA
30266 operation around hash algorithms and key sizes.
30267 Do not expect other organizations to lower their security expectations just
30268 because a particular profile might be reasonable for your own internal use.
30270 When this text was last updated, this in practice means to avoid use of SHA-1
30271 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30272 than 4096, for interoperability); to use keyUsage fields correctly; to use
30273 random serial numbers.
30274 The list of requirements is subject to change as best practices evolve.
30275 If you're not already using a private CA, or it doesn't meet these
30276 requirements, then we encourage you to avoid all these issues and use a public
30277 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30279 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30280 a "Matching Type" (3rd) field of SHA2-512(2).
30282 For the "Certificate Authority Data" (4th) field, commands like
30285 openssl x509 -pubkey -noout <certificate.pem \
30286 | openssl rsa -outform der -pubin 2>/dev/null \
30291 are workable to create a hash of the certificate's public key.
30293 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30296 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30299 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30300 is useful for quickly generating TLSA records.
30303 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30305 The Certificate issued by the CA published in the DANE-TA model should be
30306 issued using a strong hash algorithm.
30307 Exim, and importantly various other MTAs sending to you, will not
30308 re-enable hash algorithms which have been disabled by default in TLS
30310 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30311 interoperability (and probably the maximum too, in 2018).
30313 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30314 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30315 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30318 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30319 {= {4}{$tls_out_tlsa_usage}} } \
30323 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30324 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30325 found. If the definition of &%hosts_request_ocsp%& includes the
30326 string "tls_out_tlsa_usage", they are re-expanded in time to
30327 control the OCSP request.
30329 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30330 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30333 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30334 and &%dane_require_tls_ciphers%&.
30335 The &"require"& variant will result in failure if the target host is not
30336 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30337 the &%dnssec_request_domains%& router or transport option.
30339 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30341 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30342 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30343 will be required for the host. If it does not, the host will not
30344 be used; there is no fallback to non-DANE or non-TLS.
30346 If DANE is requested and usable, then the TLS cipher list configuration
30347 prefers to use the option &%dane_require_tls_ciphers%& and falls
30348 back to &%tls_require_ciphers%& only if that is unset.
30349 This lets you configure "decent crypto" for DANE and "better than nothing
30350 crypto" as the default. Note though that while GnuTLS lets the string control
30351 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30352 limited to ciphersuite constraints.
30354 If DANE is requested and useable (see above) the following transport options are ignored:
30358 tls_try_verify_hosts
30359 tls_verify_certificates
30361 tls_verify_cert_hostnames
30365 If DANE is not usable, whether requested or not, and CA-anchored
30366 verification evaluation is wanted, the above variables should be set appropriately.
30368 The router and transport option &%dnssec_request_domains%& must not be
30369 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30371 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30373 There is a new variable &$tls_out_dane$& which will have "yes" if
30374 verification succeeded using DANE and "no" otherwise (only useful
30375 in combination with events; see &<<CHAPevents>>&),
30376 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30378 .cindex DANE reporting
30379 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30380 to achieve DANE-verified connection, if one was either requested and offered, or
30381 required. This is intended to support TLS-reporting as defined in
30382 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30383 The &$event_data$& will be one of the Result Types defined in
30384 Section 4.3 of that document.
30386 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30388 DANE is specified in published RFCs and decouples certificate authority trust
30389 selection from a "race to the bottom" of "you must trust everything for mail
30390 to get through". There is an alternative technology called MTA-STS, which
30391 instead publishes MX trust anchor information on an HTTPS website. At the
30392 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30393 Exim has no support for MTA-STS as a client, but Exim mail server operators
30394 can choose to publish information describing their TLS configuration using
30395 MTA-STS to let those clients who do use that protocol derive trust
30398 The MTA-STS design requires a certificate from a public Certificate Authority
30399 which is recognized by clients sending to you.
30400 That selection of which CAs are trusted by others is outside your control.
30402 The most interoperable course of action is probably to use
30403 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30404 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30405 records for DANE clients (such as Exim and Postfix) and to publish anchor
30406 information for MTA-STS as well. This is what is done for the &'exim.org'&
30407 domain itself (with caveats around occasionally broken MTA-STS because of
30408 incompatible specification changes prior to reaching RFC status).
30412 . ////////////////////////////////////////////////////////////////////////////
30413 . ////////////////////////////////////////////////////////////////////////////
30415 .chapter "Access control lists" "CHAPACL"
30416 .scindex IIDacl "&ACL;" "description"
30417 .cindex "control of incoming mail"
30418 .cindex "message" "controlling incoming"
30419 .cindex "policy control" "access control lists"
30420 Access Control Lists (ACLs) are defined in a separate section of the runtime
30421 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30422 name, terminated by a colon. Here is a complete ACL section that contains just
30423 one very small ACL:
30427 accept hosts = one.host.only
30429 You can have as many lists as you like in the ACL section, and the order in
30430 which they appear does not matter. The lists are self-terminating.
30432 The majority of ACLs are used to control Exim's behaviour when it receives
30433 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30434 when a local process submits a message using SMTP by specifying the &%-bs%&
30435 option. The most common use is for controlling which recipients are accepted
30436 in incoming messages. In addition, you can define an ACL that is used to check
30437 local non-SMTP messages. The default configuration file contains an example of
30438 a realistic ACL for checking RCPT commands. This is discussed in chapter
30439 &<<CHAPdefconfil>>&.
30442 .section "Testing ACLs" "SECID188"
30443 The &%-bh%& command line option provides a way of testing your ACL
30444 configuration locally by running a fake SMTP session with which you interact.
30447 .section "Specifying when ACLs are used" "SECID189"
30448 .cindex "&ACL;" "options for specifying"
30449 In order to cause an ACL to be used, you have to name it in one of the relevant
30450 options in the main part of the configuration. These options are:
30451 .cindex "AUTH" "ACL for"
30452 .cindex "DATA" "ACLs for"
30453 .cindex "ETRN" "ACL for"
30454 .cindex "EXPN" "ACL for"
30455 .cindex "HELO" "ACL for"
30456 .cindex "EHLO" "ACL for"
30457 .cindex "DKIM" "ACL for"
30458 .cindex "MAIL" "ACL for"
30459 .cindex "QUIT, ACL for"
30460 .cindex "RCPT" "ACL for"
30461 .cindex "STARTTLS, ACL for"
30462 .cindex "VRFY" "ACL for"
30463 .cindex "SMTP" "connection, ACL for"
30464 .cindex "non-SMTP messages" "ACLs for"
30465 .cindex "MIME content scanning" "ACL for"
30466 .cindex "PRDR" "ACL for"
30469 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30470 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30471 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30472 .irow &%acl_smtp_auth%& "ACL for AUTH"
30473 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30474 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30475 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30476 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30477 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30478 .irow &%acl_smtp_expn%& "ACL for EXPN"
30479 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30480 .irow &%acl_smtp_mail%& "ACL for MAIL"
30481 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30482 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30483 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30484 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30485 .irow &%acl_smtp_quit%& "ACL for QUIT"
30486 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30487 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30488 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30491 For example, if you set
30493 acl_smtp_rcpt = small_acl
30495 the little ACL defined above is used whenever Exim receives a RCPT command
30496 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30497 done when RCPT commands arrive. A rejection of RCPT should cause the
30498 sending MTA to give up on the recipient address contained in the RCPT
30499 command, whereas rejection at other times may cause the client MTA to keep on
30500 trying to deliver the message. It is therefore recommended that you do as much
30501 testing as possible at RCPT time.
30504 .section "The non-SMTP ACLs" "SECID190"
30505 .cindex "non-SMTP messages" "ACLs for"
30506 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30507 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30508 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30509 the state of the SMTP connection such as encryption and authentication) are not
30510 relevant and are forbidden in these ACLs. However, the sender and recipients
30511 are known, so the &%senders%& and &%sender_domains%& conditions and the
30512 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30513 &$authenticated_sender$& are also available. You can specify added header lines
30514 in any of these ACLs.
30516 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30517 non-SMTP message, before any of the message has been read. (This is the
30518 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30519 batched SMTP input, it runs after the DATA command has been reached. The
30520 result of this ACL is ignored; it cannot be used to reject a message. If you
30521 really need to, you could set a value in an ACL variable here and reject based
30522 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30523 controls, and in particular, it can be used to set
30525 control = suppress_local_fixups
30527 This cannot be used in the other non-SMTP ACLs because by the time they are
30528 run, it is too late.
30530 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30531 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30533 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30534 kind of rejection is treated as permanent, because there is no way of sending a
30535 temporary error for these kinds of message.
30538 .section "The SMTP connect ACL" "SECID191"
30539 .cindex "SMTP" "connection, ACL for"
30540 .oindex &%smtp_banner%&
30541 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30542 session, after the test specified by &%host_reject_connection%& (which is now
30543 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30544 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30545 the message override the banner message that is otherwise specified by the
30546 &%smtp_banner%& option.
30549 .section "The EHLO/HELO ACL" "SECID192"
30550 .cindex "EHLO" "ACL for"
30551 .cindex "HELO" "ACL for"
30552 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30553 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30554 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30555 Note that a client may issue more than one EHLO or HELO command in an SMTP
30556 session, and indeed is required to issue a new EHLO or HELO after successfully
30557 setting up encryption following a STARTTLS command.
30559 Note also that a deny neither forces the client to go away nor means that
30560 mail will be refused on the connection. Consider checking for
30561 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30563 If the command is accepted by an &%accept%& verb that has a &%message%&
30564 modifier, the message may not contain more than one line (it will be truncated
30565 at the first newline and a panic logged if it does). Such a message cannot
30566 affect the EHLO options that are listed on the second and subsequent lines of
30570 .section "The DATA ACLs" "SECID193"
30571 .cindex "DATA" "ACLs for"
30572 Two ACLs are associated with the DATA command, because it is two-stage
30573 command, with two responses being sent to the client.
30574 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30575 is obeyed. This gives you control after all the RCPT commands, but before
30576 the message itself is received. It offers the opportunity to give a negative
30577 response to the DATA command before the data is transmitted. Header lines
30578 added by MAIL or RCPT ACLs are not visible at this time, but any that
30579 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30581 You cannot test the contents of the message, for example, to verify addresses
30582 in the headers, at RCPT time or when the DATA command is received. Such
30583 tests have to appear in the ACL that is run after the message itself has been
30584 received, before the final response to the DATA command is sent. This is
30585 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30586 associated with the DATA command.
30588 .cindex CHUNKING "BDAT command"
30589 .cindex BDAT "SMTP command"
30590 .cindex "RFC 3030" CHUNKING
30591 If CHUNKING was advertised and a BDAT command sequence is received,
30592 the &%acl_smtp_predata%& ACL is not run.
30593 . XXX why not? It should be possible, for the first BDAT.
30594 The &%acl_smtp_data%& is run after the last BDAT command and all of
30595 the data specified is received.
30597 For both of these ACLs, it is not possible to reject individual recipients. An
30598 error response rejects the entire message. Unfortunately, it is known that some
30599 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30600 before or after the data) correctly &-- they keep the message on their queues
30601 and try again later, but that is their problem, though it does waste some of
30604 The &%acl_smtp_data%& ACL is run after
30605 the &%acl_smtp_data_prdr%&,
30606 the &%acl_smtp_dkim%&
30607 and the &%acl_smtp_mime%& ACLs.
30609 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30610 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30611 enabled (which is the default).
30613 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30614 received, and is executed for each DKIM signature found in a message. If not
30615 otherwise specified, the default action is to accept.
30617 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30619 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30622 .section "The SMTP MIME ACL" "SECID194"
30623 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30624 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30626 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30629 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30630 .cindex "PRDR" "ACL for"
30631 .oindex "&%prdr_enable%&"
30632 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30633 with PRDR support enabled (which is the default).
30634 It becomes active only when the PRDR feature is negotiated between
30635 client and server for a message, and more than one recipient
30638 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30639 has been received, and is executed once for each recipient of the message
30640 with &$local_part$& and &$domain$& valid.
30641 The test may accept, defer or deny for individual recipients.
30642 The &%acl_smtp_data%& will still be called after this ACL and
30643 can reject the message overall, even if this ACL has accepted it
30644 for some or all recipients.
30646 PRDR may be used to support per-user content filtering. Without it
30647 one must defer any recipient after the first that has a different
30648 content-filter configuration. With PRDR, the RCPT-time check
30649 .cindex "PRDR" "variable for"
30650 for this can be disabled when the variable &$prdr_requested$&
30652 Any required difference in behaviour of the main DATA-time
30653 ACL should however depend on the PRDR-time ACL having run, as Exim
30654 will avoid doing so in some situations (e.g. single-recipient mails).
30656 See also the &%prdr_enable%& global option
30657 and the &%hosts_try_prdr%& smtp transport option.
30659 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30660 If the ACL is not defined, processing completes as if
30661 the feature was not requested by the client.
30663 .section "The QUIT ACL" "SECTQUITACL"
30664 .cindex "QUIT, ACL for"
30665 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30666 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30667 does not in fact control any access.
30668 For this reason, it may only accept
30669 or warn as its final result.
30671 This ACL can be used for tasks such as custom logging at the end of an SMTP
30672 session. For example, you can use ACL variables in other ACLs to count
30673 messages, recipients, etc., and log the totals at QUIT time using one or
30674 more &%logwrite%& modifiers on a &%warn%& verb.
30676 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30677 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30679 You do not need to have a final &%accept%&, but if you do, you can use a
30680 &%message%& modifier to specify custom text that is sent as part of the 221
30683 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30684 failure (for example, failure to open a log file, or when Exim is bombing out
30685 because it has detected an unrecoverable error), all SMTP commands from the
30686 client are given temporary error responses until QUIT is received or the
30687 connection is closed. In these special cases, the QUIT ACL does not run.
30690 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30691 .vindex &$acl_smtp_notquit$&
30692 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30693 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30694 trouble, such as being unable to write to its log files, this ACL is not run,
30695 because it might try to do things (such as write to log files) that make the
30696 situation even worse.
30698 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30699 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30700 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30703 .vindex &$smtp_notquit_reason$&
30704 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30705 to a string that indicates the reason for the termination of the SMTP
30706 connection. The possible values are:
30708 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30709 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30710 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30711 .irow &`connection-lost`& "The SMTP connection has been lost"
30712 .irow &`data-timeout`& "Timeout while reading message data"
30713 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30714 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30715 .irow &`signal-exit`& "SIGTERM or SIGINT"
30716 .irow &`synchronization-error`& "SMTP synchronization error"
30717 .irow &`tls-failed`& "TLS failed to start"
30719 In most cases when an SMTP connection is closed without having received QUIT,
30720 Exim sends an SMTP response message before actually closing the connection.
30721 With the exception of the &`acl-drop`& case, the default message can be
30722 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30723 &%drop%& verb in another ACL, it is the message from the other ACL that is
30727 .section "Finding an ACL to use" "SECID195"
30728 .cindex "&ACL;" "finding which to use"
30729 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30730 you can use different ACLs in different circumstances. For example,
30732 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30733 {acl_check_rcpt} {acl_check_rcpt_submit} }
30735 In the default configuration file there are some example settings for
30736 providing an RFC 4409 message &"submission"& service on port 587 and
30737 an RFC 8314 &"submissions"& service on port 465. You can use a string
30738 expansion like this to choose an ACL for MUAs on these ports which is
30739 more appropriate for this purpose than the default ACL on port 25.
30741 The expanded string does not have to be the name of an ACL in the
30742 configuration file; there are other possibilities. Having expanded the
30743 string, Exim searches for an ACL as follows:
30746 If the string begins with a slash, Exim uses it as a filename, and reads its
30747 contents as an ACL. The lines are processed in the same way as lines in the
30748 Exim configuration file. In particular, continuation lines are supported, blank
30749 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30750 If the file does not exist or cannot be read, an error occurs (typically
30751 causing a temporary failure of whatever caused the ACL to be run). For example:
30753 acl_smtp_data = /etc/acls/\
30754 ${lookup{$sender_host_address}lsearch\
30755 {/etc/acllist}{$value}{default}}
30757 This looks up an ACL file to use on the basis of the host's IP address, falling
30758 back to a default if the lookup fails. If an ACL is successfully read from a
30759 file, it is retained in memory for the duration of the Exim process, so that it
30760 can be re-used without having to re-read the file.
30762 If the string does not start with a slash, and does not contain any spaces,
30763 Exim searches the ACL section of the configuration for an ACL whose name
30764 matches the string.
30766 If no named ACL is found, or if the string contains spaces, Exim parses
30767 the string as an inline ACL. This can save typing in cases where you just
30768 want to have something like
30770 acl_smtp_vrfy = accept
30772 in order to allow free use of the VRFY command. Such a string may contain
30773 newlines; it is processed in the same way as an ACL that is read from a file.
30779 .section "ACL return codes" "SECID196"
30780 .cindex "&ACL;" "return codes"
30781 Except for the QUIT ACL, which does not affect the SMTP return code (see
30782 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30783 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30784 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30785 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30786 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30787 This also causes a 4&'xx'& return code.
30789 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30790 &"deny"&, because there is no mechanism for passing temporary errors to the
30791 submitters of non-SMTP messages.
30794 ACLs that are relevant to message reception may also return &"discard"&. This
30795 has the effect of &"accept"&, but causes either the entire message or an
30796 individual recipient address to be discarded. In other words, it is a
30797 blackholing facility. Use it with care.
30799 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30800 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30801 RCPT ACL is to discard just the one recipient address. If there are no
30802 recipients left when the message's data is received, the DATA ACL is not
30803 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30804 remaining recipients. The &"discard"& return is not permitted for the
30805 &%acl_smtp_predata%& ACL.
30807 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30808 is done on the address and the result determines the SMTP response.
30811 .cindex "&[local_scan()]& function" "when all recipients discarded"
30812 The &[local_scan()]& function is always run, even if there are no remaining
30813 recipients; it may create new recipients.
30817 .section "Unset ACL options" "SECID197"
30818 .cindex "&ACL;" "unset options"
30819 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30820 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30821 not defined at all. For any defined ACL, the default action when control
30822 reaches the end of the ACL statements is &"deny"&.
30824 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30825 these two are ACLs that are used only for their side effects. They cannot be
30826 used to accept or reject anything.
30828 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30829 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30830 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30831 when the ACL is not defined is &"accept"&.
30833 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30834 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30835 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30836 messages over an SMTP connection. For an example, see the ACL in the default
30837 configuration file.
30842 .section "Data for message ACLs" "SECID198"
30843 .cindex "&ACL;" "data for message ACL"
30845 .vindex &$local_part$&
30846 .vindex &$sender_address$&
30847 .vindex &$sender_host_address$&
30848 .vindex &$smtp_command$&
30849 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30850 that contain information about the host and the message's sender (for example,
30851 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30852 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30853 &$local_part$& are set from the argument address. The entire SMTP command
30854 is available in &$smtp_command$&.
30856 When an ACL for the AUTH parameter of MAIL is running, the variables that
30857 contain information about the host are set, but &$sender_address$& is not yet
30858 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30861 .vindex "&$message_size$&"
30862 The &$message_size$& variable is set to the value of the SIZE parameter on
30863 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30864 that parameter is not given. The value is updated to the true message size by
30865 the time the final DATA ACL is run (after the message data has been
30868 .vindex "&$rcpt_count$&"
30869 .vindex "&$recipients_count$&"
30870 The &$rcpt_count$& variable increases by one for each RCPT command received.
30871 The &$recipients_count$& variable increases by one each time a RCPT command is
30872 accepted, so while an ACL for RCPT is being processed, it contains the number
30873 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30874 &$rcpt_count$& contains the total number of RCPT commands, and
30875 &$recipients_count$& contains the total number of accepted recipients.
30881 .section "Data for non-message ACLs" "SECTdatfornon"
30882 .cindex "&ACL;" "data for non-message ACL"
30883 .vindex &$smtp_command_argument$&
30884 .vindex &$smtp_command$&
30885 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30886 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30887 and the entire SMTP command is available in &$smtp_command$&.
30888 These variables can be tested using a &%condition%& condition. For example,
30889 here is an ACL for use with AUTH, which insists that either the session is
30890 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30891 does not permit authentication methods that use cleartext passwords on
30892 unencrypted connections.
30895 accept encrypted = *
30896 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30898 deny message = TLS encryption or CRAM-MD5 required
30900 (Another way of applying this restriction is to arrange for the authenticators
30901 that use cleartext passwords not to be advertised when the connection is not
30902 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30903 option to do this.)
30907 .section "Format of an ACL" "SECID199"
30908 .cindex "&ACL;" "format of"
30909 .cindex "&ACL;" "verbs, definition of"
30910 An individual ACL consists of a number of statements. Each statement starts
30911 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30912 Modifiers can change the way the verb operates, define error and log messages,
30913 set variables, insert delays, and vary the processing of accepted messages.
30915 If all the conditions are met, the verb is obeyed. The same condition may be
30916 used (with different arguments) more than once in the same statement. This
30917 provides a means of specifying an &"and"& conjunction between conditions. For
30920 deny dnslists = list1.example
30921 dnslists = list2.example
30923 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30924 the conditions and modifiers when it reaches a condition that fails. What
30925 happens then depends on the verb (and in one case, on a special modifier). Not
30926 all the conditions make sense at every testing point. For example, you cannot
30927 test a sender address in the ACL that is run for a VRFY command.
30930 .section "ACL verbs" "SECID200"
30931 The ACL verbs are as follows:
30934 .cindex "&%accept%& ACL verb"
30935 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30936 of the conditions are not met, what happens depends on whether &%endpass%&
30937 appears among the conditions (for syntax see below). If the failing condition
30938 is before &%endpass%&, control is passed to the next ACL statement; if it is
30939 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30940 check a RCPT command:
30942 accept domains = +local_domains
30946 If the recipient domain does not match the &%domains%& condition, control
30947 passes to the next statement. If it does match, the recipient is verified, and
30948 the command is accepted if verification succeeds. However, if verification
30949 fails, the ACL yields &"deny"&, because the failing condition is after
30952 The &%endpass%& feature has turned out to be confusing to many people, so its
30953 use is not recommended nowadays. It is always possible to rewrite an ACL so
30954 that &%endpass%& is not needed, and it is no longer used in the default
30957 .cindex "&%message%& ACL modifier" "with &%accept%&"
30958 If a &%message%& modifier appears on an &%accept%& statement, its action
30959 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30960 (when an &%accept%& verb either accepts or passes control to the next
30961 statement), &%message%& can be used to vary the message that is sent when an
30962 SMTP command is accepted. For example, in a RCPT ACL you could have:
30964 &`accept `&<&'some conditions'&>
30965 &` message = OK, I will allow you through today`&
30967 You can specify an SMTP response code, optionally followed by an &"extended
30968 response code"& at the start of the message, but the first digit must be the
30969 same as would be sent by default, which is 2 for an &%accept%& verb.
30971 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30972 an error message that is used when access is denied. This behaviour is retained
30973 for backward compatibility, but current &"best practice"& is to avoid the use
30978 .cindex "&%defer%& ACL verb"
30979 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30980 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30981 &%defer%& is the same as &%deny%&, because there is no way of sending a
30982 temporary error. For a RCPT command, &%defer%& is much the same as using a
30983 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30984 be used in any ACL, and even for a recipient it might be a simpler approach.
30988 .cindex "&%deny%& ACL verb"
30989 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30990 the conditions are not met, control is passed to the next ACL statement. For
30993 deny dnslists = blackholes.mail-abuse.org
30995 rejects commands from hosts that are on a DNS black list.
30999 .cindex "&%discard%& ACL verb"
31000 &%discard%&: This verb behaves like &%accept%&, except that it returns
31001 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
31002 that are concerned with receiving messages. When all the conditions are true,
31003 the sending entity receives a &"success"& response. However, &%discard%& causes
31004 recipients to be discarded. If it is used in an ACL for RCPT, just the one
31005 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
31006 message's recipients are discarded. Recipients that are discarded before DATA
31007 do not appear in the log line when the &%received_recipients%& log selector is set.
31009 If the &%log_message%& modifier is set when &%discard%& operates,
31010 its contents are added to the line that is automatically written to the log.
31011 The &%message%& modifier operates exactly as it does for &%accept%&.
31015 .cindex "&%drop%& ACL verb"
31016 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
31017 forcibly closed after the 5&'xx'& error message has been sent. For example:
31019 drop condition = ${if > {$rcpt_count}{20}}
31020 message = I don't take more than 20 RCPTs
31022 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
31023 The connection is always dropped after sending a 550 response.
31026 .cindex "&%require%& ACL verb"
31027 &%require%&: If all the conditions are met, control is passed to the next ACL
31028 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
31029 example, when checking a RCPT command,
31031 require message = Sender did not verify
31034 passes control to subsequent statements only if the message's sender can be
31035 verified. Otherwise, it rejects the command. Note the positioning of the
31036 &%message%& modifier, before the &%verify%& condition. The reason for this is
31037 discussed in section &<<SECTcondmodproc>>&.
31040 .cindex "&%warn%& ACL verb"
31041 &%warn%&: If all the conditions are true, a line specified by the
31042 &%log_message%& modifier is written to Exim's main log. Control always passes
31043 to the next ACL statement. If any condition is false, the log line is not
31044 written. If an identical log line is requested several times in the same
31045 message, only one copy is actually written to the log. If you want to force
31046 duplicates to be written, use the &%logwrite%& modifier instead.
31048 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
31049 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
31050 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
31051 first failing condition. There is more about adding header lines in section
31052 &<<SECTaddheadacl>>&.
31054 If any condition on a &%warn%& statement cannot be completed (that is, there is
31055 some sort of defer), the log line specified by &%log_message%& is not written.
31056 This does not include the case of a forced failure from a lookup, which
31057 is considered to be a successful completion. After a defer, no further
31058 conditions or modifiers in the &%warn%& statement are processed. The incident
31059 is logged, and the ACL continues to be processed, from the next statement
31063 .vindex "&$acl_verify_message$&"
31064 When one of the &%warn%& conditions is an address verification that fails, the
31065 text of the verification failure message is in &$acl_verify_message$&. If you
31066 want this logged, you must set it up explicitly. For example:
31068 warn !verify = sender
31069 log_message = sender verify failed: $acl_verify_message
31073 At the end of each ACL there is an implicit unconditional &%deny%&.
31075 As you can see from the examples above, the conditions and modifiers are
31076 written one to a line, with the first one on the same line as the verb, and
31077 subsequent ones on following lines. If you have a very long condition, you can
31078 continue it onto several physical lines by the usual backslash continuation
31079 mechanism. It is conventional to align the conditions vertically.
31083 .section "ACL variables" "SECTaclvariables"
31084 .cindex "&ACL;" "variables"
31085 There are some special variables that can be set during ACL processing. They
31086 can be used to pass information between different ACLs, different invocations
31087 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31088 transports, and filters that are used to deliver a message. The names of these
31089 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31090 an underscore, but the remainder of the name can be any sequence of
31091 alphanumeric characters and underscores that you choose. There is no limit on
31092 the number of ACL variables. The two sets act as follows:
31094 The values of those variables whose names begin with &$acl_c$& persist
31095 throughout an SMTP connection. They are never reset. Thus, a value that is set
31096 while receiving one message is still available when receiving the next message
31097 on the same SMTP connection.
31099 The values of those variables whose names begin with &$acl_m$& persist only
31100 while a message is being received. They are reset afterwards. They are also
31101 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31104 When a message is accepted, the current values of all the ACL variables are
31105 preserved with the message and are subsequently made available at delivery
31106 time. The ACL variables are set by a modifier called &%set%&. For example:
31108 accept hosts = whatever
31109 set acl_m4 = some value
31110 accept authenticated = *
31111 set acl_c_auth = yes
31113 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31114 be set. If you want to set a variable without taking any action, you can use a
31115 &%warn%& verb without any other modifiers or conditions.
31117 .oindex &%strict_acl_vars%&
31118 What happens if a syntactically valid but undefined ACL variable is
31119 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31120 false (the default), an empty string is substituted; if it is true, an
31121 error is generated.
31123 Versions of Exim before 4.64 have a limited set of numbered variables, but
31124 their names are compatible, so there is no problem with upgrading.
31127 .section "Condition and modifier processing" "SECTcondmodproc"
31128 .cindex "&ACL;" "conditions; processing"
31129 .cindex "&ACL;" "modifiers; processing"
31130 An exclamation mark preceding a condition negates its result. For example:
31132 deny domains = *.dom.example
31133 !verify = recipient
31135 causes the ACL to return &"deny"& if the recipient domain ends in
31136 &'dom.example'& and the recipient address cannot be verified. Sometimes
31137 negation can be used on the right-hand side of a condition. For example, these
31138 two statements are equivalent:
31140 deny hosts = !192.168.3.4
31141 deny !hosts = 192.168.3.4
31143 However, for many conditions (&%verify%& being a good example), only left-hand
31144 side negation of the whole condition is possible.
31146 The arguments of conditions and modifiers are expanded. A forced failure
31147 of an expansion causes a condition to be ignored, that is, it behaves as if the
31148 condition is true. Consider these two statements:
31150 accept senders = ${lookup{$host_name}lsearch\
31151 {/some/file}{$value}fail}
31152 accept senders = ${lookup{$host_name}lsearch\
31153 {/some/file}{$value}{}}
31155 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31156 the returned list is searched, but if the lookup fails the behaviour is
31157 different in the two cases. The &%fail%& in the first statement causes the
31158 condition to be ignored, leaving no further conditions. The &%accept%& verb
31159 therefore succeeds. The second statement, however, generates an empty list when
31160 the lookup fails. No sender can match an empty list, so the condition fails,
31161 and therefore the &%accept%& also fails.
31163 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31164 specify actions that are taken as the conditions for a statement are checked;
31165 others specify text for messages that are used when access is denied or a
31166 warning is generated. The &%control%& modifier affects the way an incoming
31167 message is handled.
31169 The positioning of the modifiers in an ACL statement is important, because the
31170 processing of a verb ceases as soon as its outcome is known. Only those
31171 modifiers that have already been encountered will take effect. For example,
31172 consider this use of the &%message%& modifier:
31174 require message = Can't verify sender
31176 message = Can't verify recipient
31178 message = This message cannot be used
31180 If sender verification fails, Exim knows that the result of the statement is
31181 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31182 so its text is used as the error message. If sender verification succeeds, but
31183 recipient verification fails, the second message is used. If recipient
31184 verification succeeds, the third message becomes &"current"&, but is never used
31185 because there are no more conditions to cause failure.
31187 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31188 modifier that is used, because all the conditions must be true for rejection to
31189 happen. Specifying more than one &%message%& modifier does not make sense, and
31190 the message can even be specified after all the conditions. For example:
31193 !senders = *@my.domain.example
31194 message = Invalid sender from client host
31196 The &"deny"& result does not happen until the end of the statement is reached,
31197 by which time Exim has set up the message.
31201 .section "ACL modifiers" "SECTACLmodi"
31202 .cindex "&ACL;" "modifiers; list of"
31203 The ACL modifiers are as follows:
31206 .vitem &*add_header*&&~=&~<&'text'&>
31207 This modifier specifies one or more header lines that are to be added to an
31208 incoming message, assuming, of course, that the message is ultimately
31209 accepted. For details, see section &<<SECTaddheadacl>>&.
31211 .vitem &*continue*&&~=&~<&'text'&>
31212 .cindex "&%continue%& ACL modifier"
31213 .cindex "database" "updating in ACL"
31214 This modifier does nothing of itself, and processing of the ACL always
31215 continues with the next condition or modifier. The value of &%continue%& is in
31216 the side effects of expanding its argument. Typically this could be used to
31217 update a database. It is really just a syntactic tidiness, to avoid having to
31218 write rather ugly lines like this:
31220 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31222 Instead, all you need is
31224 &`continue = `&<&'some expansion'&>
31227 .vitem &*control*&&~=&~<&'text'&>
31228 .cindex "&%control%& ACL modifier"
31229 This modifier affects the subsequent processing of the SMTP connection or of an
31230 incoming message that is accepted. The effect of the first type of control
31231 lasts for the duration of the connection, whereas the effect of the second type
31232 lasts only until the current message has been received. The message-specific
31233 controls always apply to the whole message, not to individual recipients,
31234 even if the &%control%& modifier appears in a RCPT ACL.
31236 As there are now quite a few controls that can be applied, they are described
31237 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31238 in several different ways. For example:
31240 . ==== As this is a nested list, any displays it contains must be indented
31241 . ==== as otherwise they are too far to the left. That comment applies only
31242 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31246 It can be at the end of an &%accept%& statement:
31248 accept ...some conditions
31251 In this case, the control is applied when this statement yields &"accept"&, in
31252 other words, when the conditions are all true.
31255 It can be in the middle of an &%accept%& statement:
31257 accept ...some conditions...
31259 ...some more conditions...
31261 If the first set of conditions are true, the control is applied, even if the
31262 statement does not accept because one of the second set of conditions is false.
31263 In this case, some subsequent statement must yield &"accept"& for the control
31267 It can be used with &%warn%& to apply the control, leaving the
31268 decision about accepting or denying to a subsequent verb. For
31271 warn ...some conditions...
31275 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31276 &%logwrite%&, so it does not add anything to the message and does not write a
31280 If you want to apply a control unconditionally, you can use it with a
31281 &%require%& verb. For example:
31283 require control = no_multiline_responses
31287 .vitem &*delay*&&~=&~<&'time'&>
31288 .cindex "&%delay%& ACL modifier"
31290 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31291 the time interval before proceeding. However, when testing Exim using the
31292 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31293 output instead). The time is given in the usual Exim notation, and the delay
31294 happens as soon as the modifier is processed. In an SMTP session, pending
31295 output is flushed before the delay is imposed.
31297 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31300 deny ...some conditions...
31303 The delay happens if all the conditions are true, before the statement returns
31304 &"deny"&. Compare this with:
31307 ...some conditions...
31309 which waits for 30s before processing the conditions. The &%delay%& modifier
31310 can also be used with &%warn%& and together with &%control%&:
31312 warn ...some conditions...
31318 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31319 responses to several commands are no longer buffered and sent in one packet (as
31320 they would normally be) because all output is flushed before imposing the
31321 delay. This optimization is disabled so that a number of small delays do not
31322 appear to the client as one large aggregated delay that might provoke an
31323 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31324 using a &%control%& modifier to set &%no_delay_flush%&.
31328 .cindex "&%endpass%& ACL modifier"
31329 This modifier, which has no argument, is recognized only in &%accept%& and
31330 &%discard%& statements. It marks the boundary between the conditions whose
31331 failure causes control to pass to the next statement, and the conditions whose
31332 failure causes the ACL to return &"deny"&. This concept has proved to be
31333 confusing to some people, so the use of &%endpass%& is no longer recommended as
31334 &"best practice"&. See the description of &%accept%& above for more details.
31337 .vitem &*log_message*&&~=&~<&'text'&>
31338 .cindex "&%log_message%& ACL modifier"
31339 This modifier sets up a message that is used as part of the log message if the
31340 ACL denies access or a &%warn%& statement's conditions are true. For example:
31342 require log_message = wrong cipher suite $tls_in_cipher
31343 encrypted = DES-CBC3-SHA
31345 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31348 &`discard `&<&'some conditions'&>
31349 &` log_message = Discarded $local_part@$domain because...`&
31351 When access is denied, &%log_message%& adds to any underlying error message
31352 that may exist because of a condition failure. For example, while verifying a
31353 recipient address, a &':fail:'& redirection might have already set up a
31356 The message may be defined before the conditions to which it applies, because
31357 the string expansion does not happen until Exim decides that access is to be
31358 denied. This means that any variables that are set by the condition are
31359 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31360 variables are set after a DNS black list lookup succeeds. If the expansion of
31361 &%log_message%& fails, or if the result is an empty string, the modifier is
31364 .vindex "&$acl_verify_message$&"
31365 If you want to use a &%warn%& statement to log the result of an address
31366 verification, you can use &$acl_verify_message$& to include the verification
31369 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31370 the start of the logged message. If the same warning log message is requested
31371 more than once while receiving a single email message, only one copy is
31372 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31373 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31374 is logged for a successful &%warn%& statement.
31376 If &%log_message%& is not present and there is no underlying error message (for
31377 example, from the failure of address verification), but &%message%& is present,
31378 the &%message%& text is used for logging rejections. However, if any text for
31379 logging contains newlines, only the first line is logged. In the absence of
31380 both &%log_message%& and &%message%&, a default built-in message is used for
31381 logging rejections.
31384 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31385 .cindex "&%log_reject_target%& ACL modifier"
31386 .cindex "logging in ACL" "specifying which log"
31387 This modifier makes it possible to specify which logs are used for messages
31388 about ACL rejections. Its argument is a colon-separated list of words that can
31389 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31390 may be empty, in which case a rejection is not logged at all. For example, this
31391 ACL fragment writes no logging information when access is denied:
31393 &`deny `&<&'some conditions'&>
31394 &` log_reject_target =`&
31396 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31397 permanent and temporary rejections. Its effect lasts for the rest of the
31401 .vitem &*logwrite*&&~=&~<&'text'&>
31402 .cindex "&%logwrite%& ACL modifier"
31403 .cindex "logging in ACL" "immediate"
31404 This modifier writes a message to a log file as soon as it is encountered when
31405 processing an ACL. (Compare &%log_message%&, which, except in the case of
31406 &%warn%& and &%discard%&, is used only if the ACL statement denies
31407 access.) The &%logwrite%& modifier can be used to log special incidents in
31410 &`accept `&<&'some special conditions'&>
31411 &` control = freeze`&
31412 &` logwrite = froze message because ...`&
31414 By default, the message is written to the main log. However, it may begin
31415 with a colon, followed by a comma-separated list of log names, and then
31416 another colon, to specify exactly which logs are to be written. For
31419 logwrite = :main,reject: text for main and reject logs
31420 logwrite = :panic: text for panic log only
31424 .vitem &*message*&&~=&~<&'text'&>
31425 .cindex "&%message%& ACL modifier"
31426 This modifier sets up a text string that is expanded and used as a response
31427 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31428 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31429 there is some complication if &%endpass%& is involved; see the description of
31430 &%accept%& for details.)
31432 The expansion of the message happens at the time Exim decides that the ACL is
31433 to end, not at the time it processes &%message%&. If the expansion fails, or
31434 generates an empty string, the modifier is ignored. Here is an example where
31435 &%message%& must be specified first, because the ACL ends with a rejection if
31436 the &%hosts%& condition fails:
31438 require message = Host not recognized
31441 (Once a condition has failed, no further conditions or modifiers are
31444 .cindex "SMTP" "error codes"
31445 .oindex "&%smtp_banner%&
31446 For ACLs that are triggered by SMTP commands, the message is returned as part
31447 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31448 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31449 is accepted. In the case of the connect ACL, accepting with a message modifier
31450 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31451 accept message may not contain more than one line (otherwise it will be
31452 truncated at the first newline and a panic logged), and it cannot affect the
31455 When SMTP is involved, the message may begin with an overriding response code,
31456 consisting of three digits optionally followed by an &"extended response code"&
31457 of the form &'n.n.n'&, each code being followed by a space. For example:
31459 deny message = 599 1.2.3 Host not welcome
31460 hosts = 192.168.34.0/24
31462 The first digit of the supplied response code must be the same as would be sent
31463 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31464 access, but for the predata ACL, note that the default success code is 354, not
31467 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31468 the message modifier cannot override the 221 response code.
31470 The text in a &%message%& modifier is literal; any quotes are taken as
31471 literals, but because the string is expanded, backslash escapes are processed
31472 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31475 .vindex "&$acl_verify_message$&"
31477 While the text is being expanded, the &$acl_verify_message$& variable
31478 contains any message previously set.
31479 Afterwards, &$acl_verify_message$& is cleared.
31482 If &%message%& is used on a statement that verifies an address, the message
31483 specified overrides any message that is generated by the verification process.
31484 However, the original message is available in the variable
31485 &$acl_verify_message$&, so you can incorporate it into your message if you
31486 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31487 routers to be passed back as part of the SMTP response, you should either not
31488 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31490 For compatibility with previous releases of Exim, a &%message%& modifier that
31491 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31492 modifier, but this usage is now deprecated. However, &%message%& acts only when
31493 all the conditions are true, wherever it appears in an ACL command, whereas
31494 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31495 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31499 .vitem &*queue*&&~=&~<&'text'&>
31500 .cindex "&%queue%& ACL modifier"
31501 .cindex "named queues" "selecting in ACL"
31502 This modifier specifies the use of a named queue for spool files
31504 It can only be used before the message is received (i.e. not in
31506 This could be used, for example, for known high-volume burst sources
31507 of traffic, or for quarantine of messages.
31508 Separate queue-runner processes will be needed for named queues.
31509 If the text after expansion is empty, the default queue is used.
31512 .vitem &*remove_header*&&~=&~<&'text'&>
31513 This modifier specifies one or more header names in a colon-separated list
31514 that are to be removed from an incoming message, assuming, of course, that
31515 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31518 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31519 .cindex "&%set%& ACL modifier"
31520 This modifier puts a value into one of the ACL variables (see section
31521 &<<SECTaclvariables>>&).
31524 .vitem &*udpsend*&&~=&~<&'parameters'&>
31525 .cindex "UDP communications"
31526 This modifier sends a UDP packet, for purposes such as statistics
31527 collection or behaviour monitoring. The parameters are expanded, and
31528 the result of the expansion must be a colon-separated list consisting
31529 of a destination server, port number, and the packet contents. The
31530 server can be specified as a host name or IPv4 or IPv6 address. The
31531 separator can be changed with the usual angle bracket syntax. For
31532 example, you might want to collect information on which hosts connect
31535 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31536 $tod_zulu $sender_host_address
31543 .section "Use of the control modifier" "SECTcontrols"
31544 .cindex "&%control%& ACL modifier"
31545 The &%control%& modifier supports the following settings:
31548 .vitem &*control&~=&~allow_auth_unadvertised*&
31549 This modifier allows a client host to use the SMTP AUTH command even when it
31550 has not been advertised in response to EHLO. Furthermore, because there are
31551 apparently some really broken clients that do this, Exim will accept AUTH after
31552 HELO (rather than EHLO) when this control is set. It should be used only if you
31553 really need it, and you should limit its use to those broken clients that do
31554 not work without it. For example:
31556 warn hosts = 192.168.34.25
31557 control = allow_auth_unadvertised
31559 Normally, when an Exim server receives an AUTH command, it checks the name of
31560 the authentication mechanism that is given in the command to ensure that it
31561 matches an advertised mechanism. When this control is set, the check that a
31562 mechanism has been advertised is bypassed. Any configured mechanism can be used
31563 by the client. This control is permitted only in the connection and HELO ACLs.
31566 .vitem &*control&~=&~caseful_local_part*& &&&
31567 &*control&~=&~caselower_local_part*&
31568 .cindex "&ACL;" "case of local part in"
31569 .cindex "case of local parts"
31570 .vindex "&$local_part$&"
31571 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31572 (that is, during RCPT processing). By default, the contents of &$local_part$&
31573 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31574 any uppercase letters in the original local part are restored in &$local_part$&
31575 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31578 These controls affect only the current recipient. Moreover, they apply only to
31579 local part handling that takes place directly in the ACL (for example, as a key
31580 in lookups). If a test to verify the recipient is obeyed, the case-related
31581 handling of the local part during the verification is controlled by the router
31582 configuration (see the &%caseful_local_part%& generic router option).
31584 This facility could be used, for example, to add a spam score to local parts
31585 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31588 warn control = caseful_local_part
31589 set acl_m4 = ${eval:\
31591 ${if match{$local_part}{[A-Z]}{1}{0}}\
31593 control = caselower_local_part
31595 Notice that we put back the lower cased version afterwards, assuming that
31596 is what is wanted for subsequent tests.
31599 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31600 .cindex "&ACL;" "cutthrough routing"
31601 .cindex "cutthrough" "requesting"
31602 This option requests delivery be attempted while the item is being received.
31604 The option is usable in the RCPT ACL.
31605 If enabled for a message received via smtp and routed to an smtp transport,
31606 and only one transport, interface, destination host and port combination
31607 is used for all recipients of the message,
31608 then the delivery connection is made while the receiving connection is open
31609 and data is copied from one to the other.
31611 An attempt to set this option for any recipient but the first
31612 for a mail will be quietly ignored.
31613 If a recipient-verify callout
31615 connection is subsequently
31616 requested in the same ACL it is held open and used for
31617 any subsequent recipients and the data,
31618 otherwise one is made after the initial RCPT ACL completes.
31620 Note that routers are used in verify mode,
31621 and cannot depend on content of received headers.
31622 Note also that headers cannot be
31623 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31624 Headers may be modified by routers (subject to the above) and transports.
31625 The &'Received-By:'& header is generated as soon as the body reception starts,
31626 rather than the traditional time after the full message is received;
31627 this will affect the timestamp.
31629 All the usual ACLs are called; if one results in the message being
31630 rejected, all effort spent in delivery (including the costs on
31631 the ultimate destination) will be wasted.
31632 Note that in the case of data-time ACLs this includes the entire
31635 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31636 of outgoing messages is done, because it sends data to the ultimate destination
31637 before the entire message has been received from the source.
31638 It is not supported for messages received with the SMTP PRDR
31642 Should the ultimate destination system positively accept or reject the mail,
31643 a corresponding indication is given to the source system and nothing is queued.
31644 If the item is successfully delivered in cutthrough mode
31645 the delivery log lines are tagged with ">>" rather than "=>" and appear
31646 before the acceptance "<=" line.
31648 If there is a temporary error the item is queued for later delivery in the
31650 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31651 to the control; the default value is &"spool"& and the alternate value
31652 &"pass"& copies an SMTP defer response from the target back to the initiator
31653 and does not queue the message.
31654 Note that this is independent of any recipient verify conditions in the ACL.
31656 Delivery in this mode avoids the generation of a bounce mail to a
31658 sender when the destination system is doing content-scan based rejection.
31661 .vitem &*control&~=&~debug/*&<&'options'&>
31662 .cindex "&ACL;" "enabling debug logging"
31663 .cindex "debugging" "enabling from an ACL"
31664 This control turns on debug logging, almost as though Exim had been invoked
31665 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31666 by default called &'debuglog'&.
31667 The filename can be adjusted with the &'tag'& option, which
31668 may access any variables already defined. The logging may be adjusted with
31669 the &'opts'& option, which takes the same values as the &`-d`& command-line
31671 Logging started this way may be stopped, and the file removed,
31672 with the &'kill'& option.
31673 Some examples (which depend on variables that don't exist in all
31677 control = debug/tag=.$sender_host_address
31678 control = debug/opts=+expand+acl
31679 control = debug/tag=.$message_exim_id/opts=+expand
31680 control = debug/kill
31684 .vitem &*control&~=&~dkim_disable_verify*&
31685 .cindex "disable DKIM verify"
31686 .cindex "DKIM" "disable verify"
31687 This control turns off DKIM verification processing entirely. For details on
31688 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31691 .vitem &*control&~=&~dmarc_disable_verify*&
31692 .cindex "disable DMARC verify"
31693 .cindex "DMARC" "disable verify"
31694 This control turns off DMARC verification processing entirely. For details on
31695 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31698 .vitem &*control&~=&~dscp/*&<&'value'&>
31699 .cindex "&ACL;" "setting DSCP value"
31700 .cindex "DSCP" "inbound"
31701 This option causes the DSCP value associated with the socket for the inbound
31702 connection to be adjusted to a given value, given as one of a number of fixed
31703 strings or to numeric value.
31704 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31705 Common values include &`throughput`&, &`mincost`&, and on newer systems
31706 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31708 The outbound packets from Exim will be marked with this value in the header
31709 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31710 that these values will have any effect, not be stripped by networking
31711 equipment, or do much of anything without cooperation with your Network
31712 Engineer and those of all network operators between the source and destination.
31715 .vitem &*control&~=&~enforce_sync*& &&&
31716 &*control&~=&~no_enforce_sync*&
31717 .cindex "SMTP" "synchronization checking"
31718 .cindex "synchronization checking in SMTP"
31719 These controls make it possible to be selective about when SMTP synchronization
31720 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31721 state of the switch (it is true by default). See the description of this option
31722 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31724 The effect of these two controls lasts for the remainder of the SMTP
31725 connection. They can appear in any ACL except the one for the non-SMTP
31726 messages. The most straightforward place to put them is in the ACL defined by
31727 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31728 before the first synchronization check. The expected use is to turn off the
31729 synchronization checks for badly-behaved hosts that you nevertheless need to
31733 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31734 .cindex "fake defer"
31735 .cindex "defer, fake"
31736 This control works in exactly the same way as &%fakereject%& (described below)
31737 except that it causes an SMTP 450 response after the message data instead of a
31738 550 response. You must take care when using &%fakedefer%& because it causes the
31739 messages to be duplicated when the sender retries. Therefore, you should not
31740 use &%fakedefer%& if the message is to be delivered normally.
31742 .vitem &*control&~=&~fakereject/*&<&'message'&>
31743 .cindex "fake rejection"
31744 .cindex "rejection, fake"
31745 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31746 words, only when an SMTP message is being received. If Exim accepts the
31747 message, instead the final 250 response, a 550 rejection message is sent.
31748 However, Exim proceeds to deliver the message as normal. The control applies
31749 only to the current message, not to any subsequent ones that may be received in
31750 the same SMTP connection.
31752 The text for the 550 response is taken from the &%control%& modifier. If no
31753 message is supplied, the following is used:
31755 550-Your message has been rejected but is being
31756 550-kept for evaluation.
31757 550-If it was a legitimate message, it may still be
31758 550 delivered to the target recipient(s).
31760 This facility should be used with extreme caution.
31762 .vitem &*control&~=&~freeze*&
31763 .cindex "frozen messages" "forcing in ACL"
31764 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31765 other words, only when a message is being received. If the message is accepted,
31766 it is placed on Exim's queue and frozen. The control applies only to the
31767 current message, not to any subsequent ones that may be received in the same
31770 This modifier can optionally be followed by &`/no_tell`&. If the global option
31771 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31772 is told about the freezing), provided all the &*control=freeze*& modifiers that
31773 are obeyed for the current message have the &`/no_tell`& option.
31775 .vitem &*control&~=&~no_delay_flush*&
31776 .cindex "SMTP" "output flushing, disabling for delay"
31777 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31778 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31779 use. This control, as long as it is encountered before the &%delay%& modifier,
31780 disables such output flushing.
31782 .vitem &*control&~=&~no_callout_flush*&
31783 .cindex "SMTP" "output flushing, disabling for callout"
31784 Exim normally flushes SMTP output before performing a callout in an ACL, to
31785 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31786 use. This control, as long as it is encountered before the &%verify%& condition
31787 that causes the callout, disables such output flushing.
31789 .vitem &*control&~=&~no_mbox_unspool*&
31790 This control is available when Exim is compiled with the content scanning
31791 extension. Content scanning may require a copy of the current message, or parts
31792 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31793 or spam scanner. Normally, such copies are deleted when they are no longer
31794 needed. If this control is set, the copies are not deleted. The control applies
31795 only to the current message, not to any subsequent ones that may be received in
31796 the same SMTP connection. It is provided for debugging purposes and is unlikely
31797 to be useful in production.
31799 .vitem &*control&~=&~no_multiline_responses*&
31800 .cindex "multiline responses, suppressing"
31801 This control is permitted for any ACL except the one for non-SMTP messages.
31802 It seems that there are broken clients in use that cannot handle multiline
31803 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31805 If this control is set, multiline SMTP responses from ACL rejections are
31806 suppressed. One way of doing this would have been to put out these responses as
31807 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31808 (&"use multiline responses for more"& it says &-- ha!), and some of the
31809 responses might get close to that. So this facility, which is after all only a
31810 sop to broken clients, is implemented by doing two very easy things:
31813 Extra information that is normally output as part of a rejection caused by
31814 sender verification failure is omitted. Only the final line (typically &"sender
31815 verification failed"&) is sent.
31817 If a &%message%& modifier supplies a multiline response, only the first
31821 The setting of the switch can, of course, be made conditional on the
31822 calling host. Its effect lasts until the end of the SMTP connection.
31824 .vitem &*control&~=&~no_pipelining*&
31825 .cindex "PIPELINING" "suppressing advertising"
31826 .cindex "ESMTP extensions" PIPELINING
31827 This control turns off the advertising of the PIPELINING extension to SMTP in
31828 the current session. To be useful, it must be obeyed before Exim sends its
31829 response to an EHLO command. Therefore, it should normally appear in an ACL
31830 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31831 &%pipelining_advertise_hosts%&.
31833 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31834 &*control&~=&~queue_only*&
31835 .oindex "&%queue%&"
31836 .oindex "&%queue_only%&"
31837 .cindex "queueing incoming messages"
31838 .cindex queueing "forcing in ACL"
31839 .cindex "first pass routing"
31840 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31841 other words, only when a message is being received. If the message is accepted,
31842 it is placed on Exim's queue and left there for delivery by a subsequent queue
31844 If used with no options set,
31845 no immediate delivery process is started. In other words, it has the
31846 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31848 If the &'first_pass_route'& option is given then
31849 the behaviour is like the command-line &'-oqds'& option;
31850 a delivery process is started which stops short of making
31851 any SMTP delivery. The benefit is that the hints database will be updated for
31852 the message being waiting for a specific host, and a later queue run will be
31853 able to send all such messages on a single connection.
31855 The control only applies to the current message, not to any subsequent ones that
31856 may be received in the same SMTP connection.
31858 .vitem &*control&~=&~submission/*&<&'options'&>
31859 .cindex "message" "submission"
31860 .cindex "submission mode"
31861 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31862 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31863 the current message is a submission from a local MUA. In this case, Exim
31864 operates in &"submission mode"&, and applies certain fixups to the message if
31865 necessary. For example, it adds a &'Date:'& header line if one is not present.
31866 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31867 late (the message has already been created).
31869 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31870 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31871 submission mode; the available options for this control are described there.
31872 The control applies only to the current message, not to any subsequent ones
31873 that may be received in the same SMTP connection.
31875 .vitem &*control&~=&~suppress_local_fixups*&
31876 .cindex "submission fixups, suppressing"
31877 This control applies to locally submitted (non TCP/IP) messages, and is the
31878 complement of &`control = submission`&. It disables the fixups that are
31879 normally applied to locally-submitted messages. Specifically:
31882 Any &'Sender:'& header line is left alone (in this respect, it is a
31883 dynamic version of &%local_sender_retain%&).
31885 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31887 There is no check that &'From:'& corresponds to the actual sender.
31890 This control may be useful when a remotely-originated message is accepted,
31891 passed to some scanning program, and then re-submitted for delivery. It can be
31892 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31893 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31896 &*Note:*& This control applies only to the current message, not to any others
31897 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31899 .vitem &*control&~=&~utf8_downconvert*&
31900 This control enables conversion of UTF-8 in message envelope addresses
31902 For details see section &<<SECTi18nMTA>>&.
31906 .section "Summary of message fixup control" "SECTsummesfix"
31907 All four possibilities for message fixups can be specified:
31910 Locally submitted, fixups applied: the default.
31912 Locally submitted, no fixups applied: use
31913 &`control = suppress_local_fixups`&.
31915 Remotely submitted, no fixups applied: the default.
31917 Remotely submitted, fixups applied: use &`control = submission`&.
31922 .section "Adding header lines in ACLs" "SECTaddheadacl"
31923 .cindex "header lines" "adding in an ACL"
31924 .cindex "header lines" "position of added lines"
31925 .cindex "&%add_header%& ACL modifier"
31926 The &%add_header%& modifier can be used to add one or more extra header lines
31927 to an incoming message, as in this example:
31929 warn dnslists = sbl.spamhaus.org : \
31930 dialup.mail-abuse.org
31931 add_header = X-blacklisted-at: $dnslist_domain
31933 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31934 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31935 receiving a message). The message must ultimately be accepted for
31936 &%add_header%& to have any significant effect. You can use &%add_header%& with
31937 any ACL verb, including &%deny%& (though this is potentially useful only in a
31940 Headers will not be added to the message if the modifier is used in
31941 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31943 Leading and trailing newlines are removed from
31944 the data for the &%add_header%& modifier; if it then
31945 contains one or more newlines that
31946 are not followed by a space or a tab, it is assumed to contain multiple header
31947 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31948 front of any line that is not a valid header line.
31950 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31951 They are added to the message before processing the DATA and MIME ACLs.
31952 However, if an identical header line is requested more than once, only one copy
31953 is actually added to the message. Further header lines may be accumulated
31954 during the DATA and MIME ACLs, after which they are added to the message, again
31955 with duplicates suppressed. Thus, it is possible to add two identical header
31956 lines to an SMTP message, but only if one is added before DATA and one after.
31957 In the case of non-SMTP messages, new headers are accumulated during the
31958 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31959 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31960 are included in the entry that is written to the reject log.
31962 .cindex "header lines" "added; visibility of"
31963 Header lines are not visible in string expansions
31965 until they are added to the
31966 message. It follows that header lines defined in the MAIL, RCPT, and predata
31967 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31968 header lines that are added by the DATA or MIME ACLs are not visible in those
31969 ACLs. Because of this restriction, you cannot use header lines as a way of
31970 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31971 this, you can use ACL variables, as described in section
31972 &<<SECTaclvariables>>&.
31974 The list of headers yet to be added is given by the &%$headers_added%& variable.
31976 The &%add_header%& modifier acts immediately as it is encountered during the
31977 processing of an ACL. Notice the difference between these two cases:
31979 &`accept add_header = ADDED: some text`&
31980 &` `&<&'some condition'&>
31982 &`accept `&<&'some condition'&>
31983 &` add_header = ADDED: some text`&
31985 In the first case, the header line is always added, whether or not the
31986 condition is true. In the second case, the header line is added only if the
31987 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31988 ACL statement. All those that are encountered before a condition fails are
31991 .cindex "&%warn%& ACL verb"
31992 For compatibility with previous versions of Exim, a &%message%& modifier for a
31993 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31994 effect only if all the conditions are true, even if it appears before some of
31995 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31996 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31997 are present on a &%warn%& verb, both are processed according to their
32000 By default, new header lines are added to a message at the end of the existing
32001 header lines. However, you can specify that any particular header line should
32002 be added right at the start (before all the &'Received:'& lines), immediately
32003 after the first block of &'Received:'& lines, or immediately before any line
32004 that is not a &'Received:'& or &'Resent-something:'& header.
32006 This is done by specifying &":at_start:"&, &":after_received:"&, or
32007 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
32008 header line, respectively. (Header text cannot start with a colon, as there has
32009 to be a header name first.) For example:
32011 warn add_header = \
32012 :after_received:X-My-Header: something or other...
32014 If more than one header line is supplied in a single &%add_header%& modifier,
32015 each one is treated independently and can therefore be placed differently. If
32016 you add more than one line at the start, or after the Received: block, they end
32017 up in reverse order.
32019 &*Warning*&: This facility currently applies only to header lines that are
32020 added in an ACL. It does NOT work for header lines that are added in a
32021 system filter or in a router or transport.
32025 .section "Removing header lines in ACLs" "SECTremoveheadacl"
32026 .cindex "header lines" "removing in an ACL"
32027 .cindex "header lines" "position of removed lines"
32028 .cindex "&%remove_header%& ACL modifier"
32029 The &%remove_header%& modifier can be used to remove one or more header lines
32030 from an incoming message, as in this example:
32032 warn message = Remove internal headers
32033 remove_header = x-route-mail1 : x-route-mail2
32035 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32036 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32037 receiving a message). The message must ultimately be accepted for
32038 &%remove_header%& to have any significant effect. You can use &%remove_header%&
32039 with any ACL verb, including &%deny%&, though this is really not useful for
32040 any verb that doesn't result in a delivered message.
32042 Headers will not be removed from the message if the modifier is used in
32043 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32045 More than one header can be removed at the same time by using a colon separated
32046 list of header names. The header matching is case insensitive. Wildcards are
32047 not permitted, nor is list expansion performed, so you cannot use hostlists to
32048 create a list of headers, however both connection and message variable expansion
32049 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
32051 warn hosts = +internal_hosts
32052 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
32053 warn message = Remove internal headers
32054 remove_header = $acl_c_ihdrs
32056 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
32057 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
32058 If multiple header lines match, all are removed.
32059 There is no harm in attempting to remove the same header twice nor in removing
32060 a non-existent header. Further header lines to be removed may be accumulated
32061 during the DATA and MIME ACLs, after which they are removed from the message,
32062 if present. In the case of non-SMTP messages, headers to be removed are
32063 accumulated during the non-SMTP ACLs, and are removed from the message after
32064 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
32065 ACL, there really is no effect because there is no logging of what headers
32066 would have been removed.
32068 .cindex "header lines" "removed; visibility of"
32069 Header lines are not visible in string expansions until the DATA phase when it
32070 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
32071 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
32072 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
32073 this restriction, you cannot use header lines as a way of controlling data
32074 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
32075 you should instead use ACL variables, as described in section
32076 &<<SECTaclvariables>>&.
32078 The &%remove_header%& modifier acts immediately as it is encountered during the
32079 processing of an ACL. Notice the difference between these two cases:
32081 &`accept remove_header = X-Internal`&
32082 &` `&<&'some condition'&>
32084 &`accept `&<&'some condition'&>
32085 &` remove_header = X-Internal`&
32087 In the first case, the header line is always removed, whether or not the
32088 condition is true. In the second case, the header line is removed only if the
32089 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32090 same ACL statement. All those that are encountered before a condition fails
32093 &*Warning*&: This facility currently applies only to header lines that are
32094 present during ACL processing. It does NOT remove header lines that are added
32095 in a system filter or in a router or transport.
32100 .section "ACL conditions" "SECTaclconditions"
32101 .cindex "&ACL;" "conditions; list of"
32102 Some of the conditions listed in this section are available only when Exim is
32103 compiled with the content-scanning extension. They are included here briefly
32104 for completeness. More detailed descriptions can be found in the discussion on
32105 content scanning in chapter &<<CHAPexiscan>>&.
32107 Not all conditions are relevant in all circumstances. For example, testing
32108 senders and recipients does not make sense in an ACL that is being run as the
32109 result of the arrival of an ETRN command, and checks on message headers can be
32110 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32111 can use the same condition (with different parameters) more than once in the
32112 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32113 The conditions are as follows:
32117 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32118 .cindex "&ACL;" "nested"
32119 .cindex "&ACL;" "indirect"
32120 .cindex "&ACL;" "arguments"
32121 .cindex "&%acl%& ACL condition"
32122 The possible values of the argument are the same as for the
32123 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32124 &"accept"& the condition is true; if it returns &"deny"& the condition is
32125 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32126 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32127 condition false. This means that further processing of the &%warn%& verb
32128 ceases, but processing of the ACL continues.
32130 If the argument is a named ACL, up to nine space-separated optional values
32131 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32132 and $acl_narg is set to the count of values.
32133 Previous values of these variables are restored after the call returns.
32134 The name and values are expanded separately.
32135 Note that spaces in complex expansions which are used as arguments
32136 will act as argument separators.
32138 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32139 the connection is dropped. If it returns &"discard"&, the verb must be
32140 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32141 conditions are tested.
32143 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32144 loops. This condition allows you to use different ACLs in different
32145 circumstances. For example, different ACLs can be used to handle RCPT commands
32146 for different local users or different local domains.
32148 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32149 .cindex "&%authenticated%& ACL condition"
32150 .cindex "authentication" "ACL checking"
32151 .cindex "&ACL;" "testing for authentication"
32152 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32153 the name of the authenticator is tested against the list. To test for
32154 authentication by any authenticator, you can set
32159 .vitem &*condition&~=&~*&<&'string'&>
32160 .cindex "&%condition%& ACL condition"
32161 .cindex "customizing" "ACL condition"
32162 .cindex "&ACL;" "customized test"
32163 .cindex "&ACL;" "testing, customized"
32164 This feature allows you to make up custom conditions. If the result of
32165 expanding the string is an empty string, the number zero, or one of the strings
32166 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32167 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32168 any other value, some error is assumed to have occurred, and the ACL returns
32169 &"defer"&. However, if the expansion is forced to fail, the condition is
32170 ignored. The effect is to treat it as true, whether it is positive or
32173 .vitem &*decode&~=&~*&<&'location'&>
32174 .cindex "&%decode%& ACL condition"
32175 This condition is available only when Exim is compiled with the
32176 content-scanning extension, and it is allowed only in the ACL defined by
32177 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32178 If all goes well, the condition is true. It is false only if there are
32179 problems such as a syntax error or a memory shortage. For more details, see
32180 chapter &<<CHAPexiscan>>&.
32182 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32183 .cindex "&%dnslists%& ACL condition"
32184 .cindex "DNS list" "in ACL"
32185 .cindex "black list (DNS)"
32186 .cindex "&ACL;" "testing a DNS list"
32187 This condition checks for entries in DNS black lists. These are also known as
32188 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32189 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32190 different variants of this condition to describe briefly here. See sections
32191 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32193 .vitem &*domains&~=&~*&<&'domain&~list'&>
32194 .cindex "&%domains%& ACL condition"
32195 .cindex "domain" "ACL checking"
32196 .cindex "&ACL;" "testing a recipient domain"
32197 .vindex "&$domain_data$&"
32198 This condition is relevant only after a RCPT command. It checks that the domain
32199 of the recipient address is in the domain list. If percent-hack processing is
32200 enabled, it is done before this test is done. If the check succeeds with a
32201 lookup, the result of the lookup is placed in &$domain_data$& until the next
32204 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32205 use &%domains%& in a DATA ACL.
32208 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32209 .cindex "&%encrypted%& ACL condition"
32210 .cindex "encryption" "checking in an ACL"
32211 .cindex "&ACL;" "testing for encryption"
32212 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32213 name of the cipher suite in use is tested against the list. To test for
32214 encryption without testing for any specific cipher suite(s), set
32220 .vitem &*hosts&~=&~*&<&'host&~list'&>
32221 .cindex "&%hosts%& ACL condition"
32222 .cindex "host" "ACL checking"
32223 .cindex "&ACL;" "testing the client host"
32224 This condition tests that the calling host matches the host list. If you have
32225 name lookups or wildcarded host names and IP addresses in the same host list,
32226 you should normally put the IP addresses first. For example, you could have:
32228 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32230 The lookup in this example uses the host name for its key. This is implied by
32231 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32232 and it wouldn't matter which way round you had these two items.)
32234 The reason for the problem with host names lies in the left-to-right way that
32235 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32236 but when it reaches an item that requires a host name, it fails if it cannot
32237 find a host name to compare with the pattern. If the above list is given in the
32238 opposite order, the &%accept%& statement fails for a host whose name cannot be
32239 found, even if its IP address is 10.9.8.7.
32241 If you really do want to do the name check first, and still recognize the IP
32242 address even if the name lookup fails, you can rewrite the ACL like this:
32244 accept hosts = dbm;/etc/friendly/hosts
32245 accept hosts = 10.9.8.7
32247 The default action on failing to find the host name is to assume that the host
32248 is not in the list, so the first &%accept%& statement fails. The second
32249 statement can then check the IP address.
32251 .vindex "&$host_data$&"
32252 If a &%hosts%& condition is satisfied by means of a lookup, the result
32253 of the lookup is made available in the &$host_data$& variable. This
32254 allows you, for example, to set up a statement like this:
32256 deny hosts = net-lsearch;/some/file
32257 message = $host_data
32259 which gives a custom error message for each denied host.
32261 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32262 .cindex "&%local_parts%& ACL condition"
32263 .cindex "local part" "ACL checking"
32264 .cindex "&ACL;" "testing a local part"
32265 .vindex "&$local_part_data$&"
32266 This condition is relevant only after a RCPT command. It checks that the local
32267 part of the recipient address is in the list. If percent-hack processing is
32268 enabled, it is done before this test. If the check succeeds with a lookup, the
32269 result of the lookup is placed in &$local_part_data$&, which remains set until
32270 the next &%local_parts%& test.
32272 .vitem &*malware&~=&~*&<&'option'&>
32273 .cindex "&%malware%& ACL condition"
32274 .cindex "&ACL;" "virus scanning"
32275 .cindex "&ACL;" "scanning for viruses"
32276 This condition is available only when Exim is compiled with the
32277 content-scanning extension
32278 and only after a DATA command.
32279 It causes the incoming message to be scanned for
32280 viruses. For details, see chapter &<<CHAPexiscan>>&.
32282 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32283 .cindex "&%mime_regex%& ACL condition"
32284 .cindex "&ACL;" "testing by regex matching"
32285 This condition is available only when Exim is compiled with the
32286 content-scanning extension, and it is allowed only in the ACL defined by
32287 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32288 with any of the regular expressions. For details, see chapter
32291 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32292 .cindex "rate limiting"
32293 This condition can be used to limit the rate at which a user or host submits
32294 messages. Details are given in section &<<SECTratelimiting>>&.
32296 .vitem &*recipients&~=&~*&<&'address&~list'&>
32297 .cindex "&%recipients%& ACL condition"
32298 .cindex "recipient" "ACL checking"
32299 .cindex "&ACL;" "testing a recipient"
32300 This condition is relevant only after a RCPT command. It checks the entire
32301 recipient address against a list of recipients.
32303 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32304 .cindex "&%regex%& ACL condition"
32305 .cindex "&ACL;" "testing by regex matching"
32306 This condition is available only when Exim is compiled with the
32307 content-scanning extension, and is available only in the DATA, MIME, and
32308 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32309 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32311 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32312 .cindex "&%sender_domains%& ACL condition"
32313 .cindex "sender" "ACL checking"
32314 .cindex "&ACL;" "testing a sender domain"
32315 .vindex "&$domain$&"
32316 .vindex "&$sender_address_domain$&"
32317 This condition tests the domain of the sender of the message against the given
32318 domain list. &*Note*&: The domain of the sender address is in
32319 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32320 of this condition. This is an exception to the general rule for testing domain
32321 lists. It is done this way so that, if this condition is used in an ACL for a
32322 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32323 influence the sender checking.
32325 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32326 relaying, because sender addresses are easily, and commonly, forged.
32328 .vitem &*senders&~=&~*&<&'address&~list'&>
32329 .cindex "&%senders%& ACL condition"
32330 .cindex "sender" "ACL checking"
32331 .cindex "&ACL;" "testing a sender"
32332 This condition tests the sender of the message against the given list. To test
32333 for a bounce message, which has an empty sender, set
32337 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32338 relaying, because sender addresses are easily, and commonly, forged.
32340 .vitem &*spam&~=&~*&<&'username'&>
32341 .cindex "&%spam%& ACL condition"
32342 .cindex "&ACL;" "scanning for spam"
32343 This condition is available only when Exim is compiled with the
32344 content-scanning extension. It causes the incoming message to be scanned by
32345 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32347 .vitem &*verify&~=&~certificate*&
32348 .cindex "&%verify%& ACL condition"
32349 .cindex "TLS" "client certificate verification"
32350 .cindex "certificate" "verification of client"
32351 .cindex "&ACL;" "certificate verification"
32352 .cindex "&ACL;" "testing a TLS certificate"
32353 This condition is true in an SMTP session if the session is encrypted, and a
32354 certificate was received from the client, and the certificate was verified. The
32355 server requests a certificate only if the client matches &%tls_verify_hosts%&
32356 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32358 .vitem &*verify&~=&~csa*&
32359 .cindex "CSA verification"
32360 This condition checks whether the sending host (the client) is authorized to
32361 send email. Details of how this works are given in section
32362 &<<SECTverifyCSA>>&.
32364 .vitem &*verify&~=&~header_names_ascii*&
32365 .cindex "&%verify%& ACL condition"
32366 .cindex "&ACL;" "verifying header names only ASCII"
32367 .cindex "header lines" "verifying header names only ASCII"
32368 .cindex "verifying" "header names only ASCII"
32369 This condition is relevant only in an ACL that is run after a message has been
32371 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32372 It checks all header names (not the content) to make sure
32373 there are no non-ASCII characters, also excluding control characters. The
32374 allowable characters are decimal ASCII values 33 through 126.
32376 Exim itself will handle headers with non-ASCII characters, but it can cause
32377 problems for downstream applications, so this option will allow their
32378 detection and rejection in the DATA ACL's.
32380 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32381 .cindex "&%verify%& ACL condition"
32382 .cindex "&ACL;" "verifying sender in the header"
32383 .cindex "header lines" "verifying the sender in"
32384 .cindex "sender" "verifying in header"
32385 .cindex "verifying" "sender in header"
32386 This condition is relevant only in an ACL that is run after a message has been
32387 received, that is, in an ACL specified by &%acl_smtp_data%& or
32388 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32389 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32390 is loosely thought of as a &"sender"& address (hence the name of the test).
32391 However, an address that appears in one of these headers need not be an address
32392 that accepts bounce messages; only sender addresses in envelopes are required
32393 to accept bounces. Therefore, if you use the callout option on this check, you
32394 might want to arrange for a non-empty address in the MAIL command.
32396 Details of address verification and the options are given later, starting at
32397 section &<<SECTaddressverification>>& (callouts are described in section
32398 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32399 condition to restrict it to bounce messages only:
32402 !verify = header_sender
32403 message = A valid sender header is required for bounces
32406 .vitem &*verify&~=&~header_syntax*&
32407 .cindex "&%verify%& ACL condition"
32408 .cindex "&ACL;" "verifying header syntax"
32409 .cindex "header lines" "verifying syntax"
32410 .cindex "verifying" "header syntax"
32411 This condition is relevant only in an ACL that is run after a message has been
32412 received, that is, in an ACL specified by &%acl_smtp_data%& or
32413 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32414 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32415 and &'Bcc:'&), returning true if there are no problems.
32416 Unqualified addresses (local parts without domains) are
32417 permitted only in locally generated messages and from hosts that match
32418 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32421 Note that this condition is a syntax check only. However, a common spamming
32422 ploy used to be to send syntactically invalid headers such as
32426 and this condition can be used to reject such messages, though they are not as
32427 common as they used to be.
32429 .vitem &*verify&~=&~helo*&
32430 .cindex "&%verify%& ACL condition"
32431 .cindex "&ACL;" "verifying HELO/EHLO"
32432 .cindex "HELO" "verifying"
32433 .cindex "EHLO" "verifying"
32434 .cindex "verifying" "EHLO"
32435 .cindex "verifying" "HELO"
32436 This condition is true if a HELO or EHLO command has been received from the
32437 client host, and its contents have been verified. If there has been no previous
32438 attempt to verify the HELO/EHLO contents, it is carried out when this
32439 condition is encountered. See the description of the &%helo_verify_hosts%& and
32440 &%helo_try_verify_hosts%& options for details of how to request verification
32441 independently of this condition, and for detail of the verification.
32443 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32444 option), this condition is always true.
32447 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32448 .cindex "verifying" "not blind"
32449 .cindex "bcc recipients, verifying none"
32450 This condition checks that there are no blind (bcc) recipients in the message.
32451 Every envelope recipient must appear either in a &'To:'& header line or in a
32452 &'Cc:'& header line for this condition to be true. Local parts are checked
32453 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32454 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32455 used only in a DATA or non-SMTP ACL.
32457 There is one possible option, &`case_insensitive`&. If this is present then
32458 local parts are checked case-insensitively.
32460 There are, of course, many legitimate messages that make use of blind (bcc)
32461 recipients. This check should not be used on its own for blocking messages.
32464 .vitem &*verify&~=&~recipient/*&<&'options'&>
32465 .cindex "&%verify%& ACL condition"
32466 .cindex "&ACL;" "verifying recipient"
32467 .cindex "recipient" "verifying"
32468 .cindex "verifying" "recipient"
32469 .vindex "&$address_data$&"
32470 This condition is relevant only after a RCPT command. It verifies the current
32471 recipient. Details of address verification are given later, starting at section
32472 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32473 of &$address_data$& is the last value that was set while routing the address.
32474 This applies even if the verification fails. When an address that is being
32475 verified is redirected to a single address, verification continues with the new
32476 address, and in that case, the subsequent value of &$address_data$& is the
32477 value for the child address.
32479 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32480 .cindex "&%verify%& ACL condition"
32481 .cindex "&ACL;" "verifying host reverse lookup"
32482 .cindex "host" "verifying reverse lookup"
32483 This condition ensures that a verified host name has been looked up from the IP
32484 address of the client host. (This may have happened already if the host name
32485 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32486 Verification ensures that the host name obtained from a reverse DNS lookup, or
32487 one of its aliases, does, when it is itself looked up in the DNS, yield the
32488 original IP address.
32490 There is one possible option, &`defer_ok`&. If this is present and a
32491 DNS operation returns a temporary error, the verify condition succeeds.
32493 If this condition is used for a locally generated message (that is, when there
32494 is no client host involved), it always succeeds.
32496 .vitem &*verify&~=&~sender/*&<&'options'&>
32497 .cindex "&%verify%& ACL condition"
32498 .cindex "&ACL;" "verifying sender"
32499 .cindex "sender" "verifying"
32500 .cindex "verifying" "sender"
32501 This condition is relevant only after a MAIL or RCPT command, or after a
32502 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32503 the message's sender is empty (that is, this is a bounce message), the
32504 condition is true. Otherwise, the sender address is verified.
32506 .vindex "&$address_data$&"
32507 .vindex "&$sender_address_data$&"
32508 If there is data in the &$address_data$& variable at the end of routing, its
32509 value is placed in &$sender_address_data$& at the end of verification. This
32510 value can be used in subsequent conditions and modifiers in the same ACL
32511 statement. It does not persist after the end of the current statement. If you
32512 want to preserve the value for longer, you can save it in an ACL variable.
32514 Details of verification are given later, starting at section
32515 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32516 to avoid doing it more than once per message.
32518 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32519 .cindex "&%verify%& ACL condition"
32520 This is a variation of the previous option, in which a modified address is
32521 verified as a sender.
32523 Note that '/' is legal in local-parts; if the address may have such
32524 (eg. is generated from the received message)
32525 they must be protected from the options parsing by doubling:
32527 verify = sender=${listquote{/}{${address:$h_sender:}}}
32533 .section "Using DNS lists" "SECTmorednslists"
32534 .cindex "DNS list" "in ACL"
32535 .cindex "black list (DNS)"
32536 .cindex "&ACL;" "testing a DNS list"
32537 In its simplest form, the &%dnslists%& condition tests whether the calling host
32538 is on at least one of a number of DNS lists by looking up the inverted IP
32539 address in one or more DNS domains. (Note that DNS list domains are not mail
32540 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32541 special options instead.) For example, if the calling host's IP
32542 address is 192.168.62.43, and the ACL statement is
32544 deny dnslists = blackholes.mail-abuse.org : \
32545 dialups.mail-abuse.org
32547 the following records are looked up:
32549 43.62.168.192.blackholes.mail-abuse.org
32550 43.62.168.192.dialups.mail-abuse.org
32552 As soon as Exim finds an existing DNS record, processing of the list stops.
32553 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32554 to test that a host is on more than one list (an &"and"& conjunction), you can
32555 use two separate conditions:
32557 deny dnslists = blackholes.mail-abuse.org
32558 dnslists = dialups.mail-abuse.org
32560 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32561 behaves as if the host does not match the list item, that is, as if the DNS
32562 record does not exist. If there are further items in the DNS list, they are
32565 This is usually the required action when &%dnslists%& is used with &%deny%&
32566 (which is the most common usage), because it prevents a DNS failure from
32567 blocking mail. However, you can change this behaviour by putting one of the
32568 following special items in the list:
32570 &`+include_unknown `& behave as if the item is on the list
32571 &`+exclude_unknown `& behave as if the item is not on the list (default)
32572 &`+defer_unknown `& give a temporary error
32574 .cindex "&`+include_unknown`&"
32575 .cindex "&`+exclude_unknown`&"
32576 .cindex "&`+defer_unknown`&"
32577 Each of these applies to any subsequent items on the list. For example:
32579 deny dnslists = +defer_unknown : foo.bar.example
32581 Testing the list of domains stops as soon as a match is found. If you want to
32582 warn for one list and block for another, you can use two different statements:
32584 deny dnslists = blackholes.mail-abuse.org
32585 warn dnslists = dialups.mail-abuse.org
32586 message = X-Warn: sending host is on dialups list
32588 .cindex caching "of dns lookup"
32590 DNS list lookups are cached by Exim for the duration of the SMTP session
32591 (but limited by the DNS return TTL value),
32592 so a lookup based on the IP address is done at most once for any incoming
32593 connection (assuming long-enough TTL).
32594 Exim does not share information between multiple incoming
32595 connections (but your local name server cache should be active).
32597 There are a number of DNS lists to choose from, some commercial, some free,
32598 or free for small deployments. An overview can be found at
32599 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32603 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32604 .cindex "DNS list" "keyed by explicit IP address"
32605 By default, the IP address that is used in a DNS list lookup is the IP address
32606 of the calling host. However, you can specify another IP address by listing it
32607 after the domain name, introduced by a slash. For example:
32609 deny dnslists = black.list.tld/192.168.1.2
32611 This feature is not very helpful with explicit IP addresses; it is intended for
32612 use with IP addresses that are looked up, for example, the IP addresses of the
32613 MX hosts or nameservers of an email sender address. For an example, see section
32614 &<<SECTmulkeyfor>>& below.
32619 .section "DNS lists keyed on domain names" "SECID202"
32620 .cindex "DNS list" "keyed by domain name"
32621 There are some lists that are keyed on domain names rather than inverted IP
32622 addresses (see, e.g., the &'domain based zones'& link at
32623 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32624 with these lists. You can change the name that is looked up in a DNS list by
32625 listing it after the domain name, introduced by a slash. For example,
32627 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32628 message = Sender's domain is listed at $dnslist_domain
32630 This particular example is useful only in ACLs that are obeyed after the
32631 RCPT or DATA commands, when a sender address is available. If (for
32632 example) the message's sender is &'user@tld.example'& the name that is looked
32633 up by this example is
32635 tld.example.dsn.rfc-ignorant.org
32637 A single &%dnslists%& condition can contain entries for both names and IP
32638 addresses. For example:
32640 deny dnslists = sbl.spamhaus.org : \
32641 dsn.rfc-ignorant.org/$sender_address_domain
32643 The first item checks the sending host's IP address; the second checks a domain
32644 name. The whole condition is true if either of the DNS lookups succeeds.
32649 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32650 .cindex "DNS list" "multiple keys for"
32651 The syntax described above for looking up explicitly-defined values (either
32652 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32653 name for the DNS list, what follows the slash can in fact be a list of items.
32654 As with all lists in Exim, the default separator is a colon. However, because
32655 this is a sublist within the list of DNS blacklist domains, it is necessary
32656 either to double the separators like this:
32658 dnslists = black.list.tld/name.1::name.2
32660 or to change the separator character, like this:
32662 dnslists = black.list.tld/<;name.1;name.2
32664 If an item in the list is an IP address, it is inverted before the DNS
32665 blacklist domain is appended. If it is not an IP address, no inversion
32666 occurs. Consider this condition:
32668 dnslists = black.list.tld/<;192.168.1.2;a.domain
32670 The DNS lookups that occur are:
32672 2.1.168.192.black.list.tld
32673 a.domain.black.list.tld
32675 Once a DNS record has been found (that matches a specific IP return
32676 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32677 are done. If there is a temporary DNS error, the rest of the sublist of domains
32678 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32679 only if no other DNS lookup in this sublist succeeds. In other words, a
32680 successful lookup for any of the items in the sublist overrides a temporary
32681 error for a previous item.
32683 The ability to supply a list of items after the slash is in some sense just a
32684 syntactic convenience. These two examples have the same effect:
32686 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32687 dnslists = black.list.tld/a.domain::b.domain
32689 However, when the data for the list is obtained from a lookup, the second form
32690 is usually much more convenient. Consider this example:
32692 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32693 ${lookup dnsdb {>|mxh=\
32694 $sender_address_domain} }} }
32695 message = The mail servers for the domain \
32696 $sender_address_domain \
32697 are listed at $dnslist_domain ($dnslist_value); \
32700 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32701 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32702 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32703 of expanding the condition might be something like this:
32705 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32707 Thus, this example checks whether or not the IP addresses of the sender
32708 domain's mail servers are on the Spamhaus black list.
32710 The key that was used for a successful DNS list lookup is put into the variable
32711 &$dnslist_matched$& (see section &<<SECID204>>&).
32716 .section "Data returned by DNS lists" "SECID203"
32717 .cindex "DNS list" "data returned from"
32718 DNS lists are constructed using address records in the DNS. The original RBL
32719 just used the address 127.0.0.1 on the right hand side of each record, but the
32720 RBL+ list and some other lists use a number of values with different meanings.
32721 The values used on the RBL+ list are:
32725 127.1.0.3 DUL and RBL
32727 127.1.0.5 RSS and RBL
32728 127.1.0.6 RSS and DUL
32729 127.1.0.7 RSS and DUL and RBL
32731 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32732 different values. Some DNS lists may return more than one address record;
32733 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32736 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32737 range. If a DNSBL operator loses control of the domain, lookups on it
32738 may start returning other addresses. Because of this, Exim now ignores
32739 returned values outside the 127/8 region.
32743 .section "Variables set from DNS lists" "SECID204"
32744 .cindex "expansion" "variables, set from DNS list"
32745 .cindex "DNS list" "variables set from"
32746 .vindex "&$dnslist_domain$&"
32747 .vindex "&$dnslist_matched$&"
32748 .vindex "&$dnslist_text$&"
32749 .vindex "&$dnslist_value$&"
32750 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32751 the name of the overall domain that matched (for example,
32752 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32753 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32754 the DNS record. When the key is an IP address, it is not reversed in
32755 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32756 cases, for example:
32758 deny dnslists = spamhaus.example
32760 the key is also available in another variable (in this case,
32761 &$sender_host_address$&). In more complicated cases, however, this is not true.
32762 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32763 might generate a dnslists lookup like this:
32765 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32767 If this condition succeeds, the value in &$dnslist_matched$& might be
32768 &`192.168.6.7`& (for example).
32770 If more than one address record is returned by the DNS lookup, all the IP
32771 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32772 The variable &$dnslist_text$& contains the contents of any associated TXT
32773 record. For lists such as RBL+ the TXT record for a merged entry is often not
32774 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32777 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32778 &-- even if these appear before the condition in the ACL, they are not
32779 expanded until after it has failed. For example:
32781 deny hosts = !+local_networks
32782 message = $sender_host_address is listed \
32784 dnslists = rbl-plus.mail-abuse.example
32789 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32790 .cindex "DNS list" "matching specific returned data"
32791 You can add an equals sign and an IP address after a &%dnslists%& domain name
32792 in order to restrict its action to DNS records with a matching right hand side.
32795 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32797 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32798 any address record is considered to be a match. For the moment, we assume
32799 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32800 describes how multiple records are handled.
32802 More than one IP address may be given for checking, using a comma as a
32803 separator. These are alternatives &-- if any one of them matches, the
32804 &%dnslists%& condition is true. For example:
32806 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32808 If you want to specify a constraining address list and also specify names or IP
32809 addresses to be looked up, the constraining address list must be specified
32810 first. For example:
32812 deny dnslists = dsn.rfc-ignorant.org\
32813 =127.0.0.2/$sender_address_domain
32816 If the character &`&&`& is used instead of &`=`&, the comparison for each
32817 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32818 In other words, the listed addresses are used as bit masks. The comparison is
32819 true if all the bits in the mask are present in the address that is being
32820 tested. For example:
32822 dnslists = a.b.c&0.0.0.3
32824 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32825 want to test whether one bit or another bit is present (as opposed to both
32826 being present), you must use multiple values. For example:
32828 dnslists = a.b.c&0.0.0.1,0.0.0.2
32830 matches if the final component of the address is an odd number or two times
32835 .section "Negated DNS matching conditions" "SECID205"
32836 You can supply a negative list of IP addresses as part of a &%dnslists%&
32839 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32841 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32842 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32844 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32846 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32847 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32848 words, the result of the test is inverted if an exclamation mark appears before
32849 the &`=`& (or the &`&&`&) sign.
32851 &*Note*&: This kind of negation is not the same as negation in a domain,
32852 host, or address list (which is why the syntax is different).
32854 If you are using just one list, the negation syntax does not gain you much. The
32855 previous example is precisely equivalent to
32857 deny dnslists = a.b.c
32858 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32860 However, if you are using multiple lists, the negation syntax is clearer.
32861 Consider this example:
32863 deny dnslists = sbl.spamhaus.org : \
32865 dnsbl.njabl.org!=127.0.0.3 : \
32868 Using only positive lists, this would have to be:
32870 deny dnslists = sbl.spamhaus.org : \
32872 deny dnslists = dnsbl.njabl.org
32873 !dnslists = dnsbl.njabl.org=127.0.0.3
32874 deny dnslists = relays.ordb.org
32876 which is less clear, and harder to maintain.
32878 Negation can also be used with a bitwise-and restriction.
32879 The dnslists condition with only be trus if a result is returned
32880 by the lookup which, anded with the restriction, is all zeroes.
32883 deny dnslists = zen.spamhaus.org!&0.255.255.0
32889 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32890 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32891 thereby providing more than one IP address. When an item in a &%dnslists%& list
32892 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32893 the match to specific results from the DNS lookup, there are two ways in which
32894 the checking can be handled. For example, consider the condition:
32896 dnslists = a.b.c=127.0.0.1
32898 What happens if the DNS lookup for the incoming IP address yields both
32899 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32900 condition true because at least one given value was found, or is it false
32901 because at least one of the found values was not listed? And how does this
32902 affect negated conditions? Both possibilities are provided for with the help of
32903 additional separators &`==`& and &`=&&`&.
32906 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32907 IP addresses matches one of the listed addresses. For the example above, the
32908 condition is true because 127.0.0.1 matches.
32910 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32911 looked up IP addresses matches one of the listed addresses. If the condition is
32914 dnslists = a.b.c==127.0.0.1
32916 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32917 false because 127.0.0.2 is not listed. You would need to have:
32919 dnslists = a.b.c==127.0.0.1,127.0.0.2
32921 for the condition to be true.
32924 When &`!`& is used to negate IP address matching, it inverts the result, giving
32925 the precise opposite of the behaviour above. Thus:
32927 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32928 addresses matches one of the listed addresses. Consider:
32930 dnslists = a.b.c!&0.0.0.1
32932 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32933 false because 127.0.0.1 matches.
32935 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32936 looked up IP address that does not match. Consider:
32938 dnslists = a.b.c!=&0.0.0.1
32940 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32941 true, because 127.0.0.2 does not match. You would need to have:
32943 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32945 for the condition to be false.
32947 When the DNS lookup yields only a single IP address, there is no difference
32948 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32953 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32954 .cindex "DNS list" "information from merged"
32955 When the facility for restricting the matching IP values in a DNS list is used,
32956 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32957 the true reason for rejection. This happens when lists are merged and the IP
32958 address in the A record is used to distinguish them; unfortunately there is
32959 only one TXT record. One way round this is not to use merged lists, but that
32960 can be inefficient because it requires multiple DNS lookups where one would do
32961 in the vast majority of cases when the host of interest is not on any of the
32964 A less inefficient way of solving this problem is available. If
32965 two domain names, comma-separated, are given, the second is used first to
32966 do an initial check, making use of any IP value restrictions that are set.
32967 If there is a match, the first domain is used, without any IP value
32968 restrictions, to get the TXT record. As a byproduct of this, there is also
32969 a check that the IP being tested is indeed on the first list. The first
32970 domain is the one that is put in &$dnslist_domain$&. For example:
32973 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32974 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32976 rejected because $sender_host_address is blacklisted \
32977 at $dnslist_domain\n$dnslist_text
32979 For the first blacklist item, this starts by doing a lookup in
32980 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32981 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32982 value, and as long as something is found, it looks for the corresponding TXT
32983 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32984 The second blacklist item is processed similarly.
32986 If you are interested in more than one merged list, the same list must be
32987 given several times, but because the results of the DNS lookups are cached,
32988 the DNS calls themselves are not repeated. For example:
32991 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32992 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32993 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32994 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32996 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32997 values matches (or if no record is found), this is the only lookup that is
32998 done. Only if there is a match is one of the more specific lists consulted.
33002 .section "DNS lists and IPv6" "SECTmorednslistslast"
33003 .cindex "IPv6" "DNS black lists"
33004 .cindex "DNS list" "IPv6 usage"
33005 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
33006 nibble by nibble. For example, if the calling host's IP address is
33007 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
33009 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
33010 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
33012 (split over two lines here to fit on the page). Unfortunately, some of the DNS
33013 lists contain wildcard records, intended for IPv4, that interact badly with
33014 IPv6. For example, the DNS entry
33016 *.3.some.list.example. A 127.0.0.1
33018 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
33019 Unfortunately, it also matches the entire 3::/4 IPv6 network.
33021 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
33022 &%condition%& condition, as in this example:
33024 deny condition = ${if isip4{$sender_host_address}}
33025 dnslists = some.list.example
33028 If an explicit key is being used for a DNS lookup and it may be an IPv6
33029 address you should specify alternate list separators for both the outer
33030 (DNS list name) list and inner (lookup keys) list:
33032 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
33035 .section "Rate limiting incoming messages" "SECTratelimiting"
33036 .cindex "rate limiting" "client sending"
33037 .cindex "limiting client sending rates"
33038 .oindex "&%smtp_ratelimit_*%&"
33039 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33040 which clients can send email. This is more powerful than the
33041 &%smtp_ratelimit_*%& options, because those options control the rate of
33042 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33043 works across all connections (concurrent and sequential) from the same client
33044 host. The syntax of the &%ratelimit%& condition is:
33046 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33048 If the average client sending rate is less than &'m'& messages per time
33049 period &'p'& then the condition is false; otherwise it is true.
33051 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33052 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33053 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33056 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33057 time interval, for example, &`8h`& for eight hours. A larger time constant
33058 means that it takes Exim longer to forget a client's past behaviour. The
33059 parameter &'m'& is the maximum number of messages that a client is permitted to
33060 send in each time interval. It also specifies the number of messages permitted
33061 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33062 constant, you can allow a client to send more messages in a burst without
33063 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33064 both small, messages must be sent at an even rate.
33066 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33067 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33068 when deploying the &%ratelimit%& ACL condition. The script prints usage
33069 instructions when it is run with no arguments.
33071 The key is used to look up the data for calculating the client's average
33072 sending rate. This data is stored in Exim's spool directory, alongside the
33073 retry and other hints databases. The default key is &$sender_host_address$&,
33074 which means Exim computes the sending rate of each client host IP address.
33075 By changing the key you can change how Exim identifies clients for the purpose
33076 of ratelimiting. For example, to limit the sending rate of each authenticated
33077 user, independent of the computer they are sending from, set the key to
33078 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33079 example, &$authenticated_id$& is only meaningful if the client has
33080 authenticated (which you can check with the &%authenticated%& ACL condition).
33082 The lookup key does not have to identify clients: If you want to limit the
33083 rate at which a recipient receives messages, you can use the key
33084 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33087 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33088 specifies what Exim measures the rate of, for example, messages or recipients
33089 or bytes. You can adjust the measurement using the &%unique=%& and/or
33090 &%count=%& options. You can also control when Exim updates the recorded rate
33091 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33092 separated by a slash, like the other parameters. They may appear in any order.
33094 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33095 any options that alter the meaning of the stored data. The limit &'m'& is not
33096 stored, so you can alter the configured maximum rate and Exim will still
33097 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33098 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33099 behaviour. The lookup key is not affected by changes to the update mode and
33100 the &%count=%& option.
33103 .section "Ratelimit options for what is being measured" "ratoptmea"
33104 .cindex "rate limiting" "per_* options"
33105 The &%per_conn%& option limits the client's connection rate. It is not
33106 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33107 &%acl_not_smtp_start%& ACLs.
33109 The &%per_mail%& option limits the client's rate of sending messages. This is
33110 the default if none of the &%per_*%& options is specified. It can be used in
33111 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33112 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33114 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33115 the same ACLs as the &%per_mail%& option, though it is best to use this option
33116 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33117 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33118 in its MAIL command, which may be inaccurate or completely missing. You can
33119 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33120 in kilobytes, megabytes, or gigabytes, respectively.
33122 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33123 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33124 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33125 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33126 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33127 in either case the rate limiting engine will see a message with many
33128 recipients as a large high-speed burst.
33130 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33131 number of different recipients that the client has sent messages to in the
33132 last time period. That is, if the client repeatedly sends messages to the same
33133 recipient, its measured rate is not increased. This option can only be used in
33136 The &%per_cmd%& option causes Exim to recompute the rate every time the
33137 condition is processed. This can be used to limit the rate of any SMTP
33138 command. If it is used in multiple ACLs it can limit the aggregate rate of
33139 multiple different commands.
33141 The &%count=%& option can be used to alter how much Exim adds to the client's
33142 measured rate. For example, the &%per_byte%& option is equivalent to
33143 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33144 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33145 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33147 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33150 .section "Ratelimit update modes" "ratoptupd"
33151 .cindex "rate limiting" "reading data without updating"
33152 You can specify one of three options with the &%ratelimit%& condition to
33153 control when its database is updated. This section describes the &%readonly%&
33154 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33156 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33157 previously-computed rate to check against the limit.
33159 For example, you can test the client's sending rate and deny it access (when
33160 it is too fast) in the connect ACL. If the client passes this check then it
33161 can go on to send a message, in which case its recorded rate will be updated
33162 in the MAIL ACL. Subsequent connections from the same client will check this
33166 deny ratelimit = 100 / 5m / readonly
33167 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33168 (max $sender_rate_limit)
33171 warn ratelimit = 100 / 5m / strict
33172 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33173 (max $sender_rate_limit)
33176 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33177 processing a message then it may increase the client's measured rate more than
33178 it should. For example, this will happen if you check the &%per_rcpt%& option
33179 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33180 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33181 multiple update problems by using the &%readonly%& option on later ratelimit
33184 The &%per_*%& options described above do not make sense in some ACLs. If you
33185 use a &%per_*%& option in an ACL where it is not normally permitted then the
33186 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33187 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33188 next section) so you must specify the &%readonly%& option explicitly.
33191 .section "Ratelimit options for handling fast clients" "ratoptfast"
33192 .cindex "rate limiting" "strict and leaky modes"
33193 If a client's average rate is greater than the maximum, the rate limiting
33194 engine can react in two possible ways, depending on the presence of the
33195 &%strict%& or &%leaky%& update modes. This is independent of the other
33196 counter-measures (such as rejecting the message) that may be specified by the
33199 The &%leaky%& (default) option means that the client's recorded rate is not
33200 updated if it is above the limit. The effect of this is that Exim measures the
33201 client's average rate of successfully sent email,
33202 up to the given limit.
33203 This is appropriate if the countermeasure when the condition is true
33204 consists of refusing the message, and
33205 is generally the better choice if you have clients that retry automatically.
33206 If the action when true is anything more complex then this option is
33207 likely not what is wanted.
33209 The &%strict%& option means that the client's recorded rate is always
33210 updated. The effect of this is that Exim measures the client's average rate
33211 of attempts to send email, which can be much higher than the maximum it is
33212 actually allowed. If the client is over the limit it may be subjected to
33213 counter-measures by the ACL. It must slow down and allow sufficient time to
33214 pass that its computed rate falls below the maximum before it can send email
33215 again. The time (the number of smoothing periods) it must wait and not
33216 attempt to send mail can be calculated with this formula:
33218 ln(peakrate/maxrate)
33222 .section "Limiting the rate of different events" "ratoptuniq"
33223 .cindex "rate limiting" "counting unique events"
33224 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33225 rate of different events. For example, the &%per_addr%& option uses this
33226 mechanism to count the number of different recipients that the client has
33227 sent messages to in the last time period; it is equivalent to
33228 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33229 measure the rate that a client uses different sender addresses with the
33230 options &`per_mail/unique=$sender_address`&.
33232 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33233 has seen for that key. The whole set is thrown away when it is older than the
33234 rate smoothing period &'p'&, so each different event is counted at most once
33235 per period. In the &%leaky%& update mode, an event that causes the client to
33236 go over the limit is not added to the set, in the same way that the client's
33237 recorded rate is not updated in the same situation.
33239 When you combine the &%unique=%& and &%readonly%& options, the specific
33240 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33243 The &%unique=%& mechanism needs more space in the ratelimit database than the
33244 other &%ratelimit%& options in order to store the event set. The number of
33245 unique values is potentially as large as the rate limit, so the extra space
33246 required increases with larger limits.
33248 The uniqueification is not perfect: there is a small probability that Exim
33249 will think a new event has happened before. If the sender's rate is less than
33250 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33251 the measured rate can go above the limit, in which case Exim may under-count
33252 events by a significant margin. Fortunately, if the rate is high enough (2.7
33253 times the limit) that the false positive rate goes above 9%, then Exim will
33254 throw away the over-full event set before the measured rate falls below the
33255 limit. Therefore the only harm should be that exceptionally high sending rates
33256 are logged incorrectly; any countermeasures you configure will be as effective
33260 .section "Using rate limiting" "useratlim"
33261 Exim's other ACL facilities are used to define what counter-measures are taken
33262 when the rate limit is exceeded. This might be anything from logging a warning
33263 (for example, while measuring existing sending rates in order to define
33264 policy), through time delays to slow down fast senders, up to rejecting the
33265 message. For example:
33267 # Log all senders' rates
33268 warn ratelimit = 0 / 1h / strict
33269 log_message = Sender rate $sender_rate / $sender_rate_period
33271 # Slow down fast senders; note the need to truncate $sender_rate
33272 # at the decimal point.
33273 warn ratelimit = 100 / 1h / per_rcpt / strict
33274 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33275 $sender_rate_limit }s
33277 # Keep authenticated users under control
33278 deny authenticated = *
33279 ratelimit = 100 / 1d / strict / $authenticated_id
33281 # System-wide rate limit
33282 defer ratelimit = 10 / 1s / $primary_hostname
33283 message = Sorry, too busy. Try again later.
33285 # Restrict incoming rate from each host, with a default
33286 # set using a macro and special cases looked up in a table.
33287 defer ratelimit = ${lookup {$sender_host_address} \
33288 cdb {DB/ratelimits.cdb} \
33289 {$value} {RATELIMIT} }
33290 message = Sender rate exceeds $sender_rate_limit \
33291 messages per $sender_rate_period
33293 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33294 especially with the &%per_rcpt%& option, you may suffer from a performance
33295 bottleneck caused by locking on the ratelimit hints database. Apart from
33296 making your ACLs less complicated, you can reduce the problem by using a
33297 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33298 this means that Exim will lose its hints data after a reboot (including retry
33299 hints, the callout cache, and ratelimit data).
33303 .section "Address verification" "SECTaddressverification"
33304 .cindex "verifying address" "options for"
33305 .cindex "policy control" "address verification"
33306 Several of the &%verify%& conditions described in section
33307 &<<SECTaclconditions>>& cause addresses to be verified. Section
33308 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33309 The verification conditions can be followed by options that modify the
33310 verification process. The options are separated from the keyword and from each
33311 other by slashes, and some of them contain parameters. For example:
33313 verify = sender/callout
33314 verify = recipient/defer_ok/callout=10s,defer_ok
33316 The first stage of address verification, which always happens, is to run the
33317 address through the routers, in &"verify mode"&. Routers can detect the
33318 difference between verification and routing for delivery, and their actions can
33319 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33320 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33321 The available options are as follows:
33324 If the &%callout%& option is specified, successful routing to one or more
33325 remote hosts is followed by a &"callout"& to those hosts as an additional
33326 check. Callouts and their sub-options are discussed in the next section.
33328 If there is a defer error while doing verification routing, the ACL
33329 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33330 options, the condition is forced to be true instead. Note that this is a main
33331 verification option as well as a suboption for callouts.
33333 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33334 discusses the reporting of sender address verification failures.
33336 The &%success_on_redirect%& option causes verification always to succeed
33337 immediately after a successful redirection. By default, if a redirection
33338 generates just one address, that address is also verified. See further
33339 discussion in section &<<SECTredirwhilveri>>&.
33342 If the &%quota%& option is specified for recipient verify,
33343 successful routing to an appendfile transport is followed by a call into
33344 the transport to evaluate the quota status for the recipient.
33345 No actual delivery is done, but verification will succeed if the quota
33346 is sufficient for the message (if the sender gave a message size) or
33347 not already exceeded (otherwise).
33351 .cindex "verifying address" "differentiating failures"
33352 .vindex "&$recipient_verify_failure$&"
33353 .vindex "&$sender_verify_failure$&"
33354 .vindex "&$acl_verify_message$&"
33355 After an address verification failure, &$acl_verify_message$& contains the
33356 error message that is associated with the failure. It can be preserved by
33359 warn !verify = sender
33360 set acl_m0 = $acl_verify_message
33362 If you are writing your own custom rejection message or log message when
33363 denying access, you can use this variable to include information about the
33364 verification failure.
33365 This variable is cleared at the end of processing the ACL verb.
33367 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33368 appropriate) contains one of the following words:
33371 &%qualify%&: The address was unqualified (no domain), and the message
33372 was neither local nor came from an exempted host.
33374 &%route%&: Routing failed.
33376 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33377 occurred at or before the MAIL command (that is, on initial
33378 connection, HELO, or MAIL).
33380 &%recipient%&: The RCPT command in a callout was rejected.
33382 &%postmaster%&: The postmaster check in a callout was rejected.
33385 &%quota%&: The quota check for a local recipient did non pass.
33388 The main use of these variables is expected to be to distinguish between
33389 rejections of MAIL and rejections of RCPT in callouts.
33391 The above variables may also be set after a &*successful*&
33392 address verification to:
33395 &%random%&: A random local-part callout succeeded
33401 .section "Callout verification" "SECTcallver"
33402 .cindex "verifying address" "by callout"
33403 .cindex "callout" "verification"
33404 .cindex "SMTP" "callout verification"
33405 For non-local addresses, routing verifies the domain, but is unable to do any
33406 checking of the local part. There are situations where some means of verifying
33407 the local part is desirable. One way this can be done is to make an SMTP
33408 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33409 a subsequent host for a recipient address, to see if the host accepts the
33410 address. We use the term &'callout'& to cover both cases. Note that for a
33411 sender address, the callback is not to the client host that is trying to
33412 deliver the message, but to one of the hosts that accepts incoming mail for the
33415 Exim does not do callouts by default. If you want them to happen, you must
33416 request them by setting appropriate options on the &%verify%& condition, as
33417 described below. This facility should be used with care, because it can add a
33418 lot of resource usage to the cost of verifying an address. However, Exim does
33419 cache the results of callouts, which helps to reduce the cost. Details of
33420 caching are in section &<<SECTcallvercache>>&.
33422 Recipient callouts are usually used only between hosts that are controlled by
33423 the same administration. For example, a corporate gateway host could use
33424 callouts to check for valid recipients on an internal mailserver. A successful
33425 callout does not guarantee that a real delivery to the address would succeed;
33426 on the other hand, a failing callout does guarantee that a delivery would fail.
33428 If the &%callout%& option is present on a condition that verifies an address, a
33429 second stage of verification occurs if the address is successfully routed to
33430 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33431 &(manualroute)& router, where the router specifies the hosts. However, if a
33432 router that does not set up hosts routes to an &(smtp)& transport with a
33433 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33434 &%hosts_override%& set, its hosts are always used, whether or not the router
33435 supplies a host list.
33436 Callouts are only supported on &(smtp)& transports.
33438 The port that is used is taken from the transport, if it is specified and is a
33439 remote transport. (For routers that do verification only, no transport need be
33440 specified.) Otherwise, the default SMTP port is used. If a remote transport
33441 specifies an outgoing interface, this is used; otherwise the interface is not
33442 specified. Likewise, the text that is used for the HELO command is taken from
33443 the transport's &%helo_data%& option; if there is no transport, the value of
33444 &$smtp_active_hostname$& is used.
33446 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33447 test whether a bounce message could be delivered to the sender address. The
33448 following SMTP commands are sent:
33450 &`HELO `&<&'local host name'&>
33452 &`RCPT TO:`&<&'the address to be tested'&>
33455 LHLO is used instead of HELO if the transport's &%protocol%& option is
33458 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33461 A recipient callout check is similar. By default, it also uses an empty address
33462 for the sender. This default is chosen because most hosts do not make use of
33463 the sender address when verifying a recipient. Using the same address means
33464 that a single cache entry can be used for each recipient. Some sites, however,
33465 do make use of the sender address when verifying. These are catered for by the
33466 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33468 If the response to the RCPT command is a 2&'xx'& code, the verification
33469 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33470 Exim tries the next host, if any. If there is a problem with all the remote
33471 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33472 &%callout%& option is given, in which case the condition is forced to succeed.
33474 .cindex "SMTP" "output flushing, disabling for callout"
33475 A callout may take a little time. For this reason, Exim normally flushes SMTP
33476 output before performing a callout in an ACL, to avoid unexpected timeouts in
33477 clients when the SMTP PIPELINING extension is in use. The flushing can be
33478 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33483 .section "Additional parameters for callouts" "CALLaddparcall"
33484 .cindex "callout" "additional parameters for"
33485 The &%callout%& option can be followed by an equals sign and a number of
33486 optional parameters, separated by commas. For example:
33488 verify = recipient/callout=10s,defer_ok
33490 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33491 separate verify options, is retained for backwards compatibility, but is now
33492 deprecated. The additional parameters for &%callout%& are as follows:
33496 .vitem <&'a&~time&~interval'&>
33497 .cindex "callout" "timeout, specifying"
33498 This specifies the timeout that applies for the callout attempt to each host.
33501 verify = sender/callout=5s
33503 The default is 30 seconds. The timeout is used for each response from the
33504 remote host. It is also used for the initial connection, unless overridden by
33505 the &%connect%& parameter.
33508 .vitem &*connect&~=&~*&<&'time&~interval'&>
33509 .cindex "callout" "connection timeout, specifying"
33510 This parameter makes it possible to set a different (usually smaller) timeout
33511 for making the SMTP connection. For example:
33513 verify = sender/callout=5s,connect=1s
33515 If not specified, this timeout defaults to the general timeout value.
33517 .vitem &*defer_ok*&
33518 .cindex "callout" "defer, action on"
33519 When this parameter is present, failure to contact any host, or any other kind
33520 of temporary error, is treated as success by the ACL. However, the cache is not
33521 updated in this circumstance.
33523 .vitem &*fullpostmaster*&
33524 .cindex "callout" "full postmaster check"
33525 This operates like the &%postmaster%& option (see below), but if the check for
33526 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33527 accordance with the specification in RFC 2821. The RFC states that the
33528 unqualified address &'postmaster'& should be accepted.
33531 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33532 .cindex "callout" "sender when verifying header"
33533 When verifying addresses in header lines using the &%header_sender%&
33534 verification option, Exim behaves by default as if the addresses are envelope
33535 sender addresses from a message. Callout verification therefore tests to see
33536 whether a bounce message could be delivered, by using an empty address in the
33537 MAIL command. However, it is arguable that these addresses might never be used
33538 as envelope senders, and could therefore justifiably reject bounce messages
33539 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33540 address to use in the MAIL command. For example:
33542 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33544 This parameter is available only for the &%header_sender%& verification option.
33547 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33548 .cindex "callout" "overall timeout, specifying"
33549 This parameter sets an overall timeout for performing a callout verification.
33552 verify = sender/callout=5s,maxwait=30s
33554 This timeout defaults to four times the callout timeout for individual SMTP
33555 commands. The overall timeout applies when there is more than one host that can
33556 be tried. The timeout is checked before trying the next host. This prevents
33557 very long delays if there are a large number of hosts and all are timing out
33558 (for example, when network connections are timing out).
33561 .vitem &*no_cache*&
33562 .cindex "callout" "cache, suppressing"
33563 .cindex "caching callout, suppressing"
33564 When this parameter is given, the callout cache is neither read nor updated.
33566 .vitem &*postmaster*&
33567 .cindex "callout" "postmaster; checking"
33568 When this parameter is set, a successful callout check is followed by a similar
33569 check for the local part &'postmaster'& at the same domain. If this address is
33570 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33571 the postmaster check is recorded in a cache record; if it is a failure, this is
33572 used to fail subsequent callouts for the domain without a connection being
33573 made, until the cache record expires.
33575 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33576 The postmaster check uses an empty sender in the MAIL command by default.
33577 You can use this parameter to do a postmaster check using a different address.
33580 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33582 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33583 one overrides. The &%postmaster%& parameter is equivalent to this example:
33585 require verify = sender/callout=postmaster_mailfrom=
33587 &*Warning*&: The caching arrangements for postmaster checking do not take
33588 account of the sender address. It is assumed that either the empty address or
33589 a fixed non-empty address will be used. All that Exim remembers is that the
33590 postmaster check for the domain succeeded or failed.
33594 .cindex "callout" "&""random""& check"
33595 When this parameter is set, before doing the normal callout check, Exim does a
33596 check for a &"random"& local part at the same domain. The local part is not
33597 really random &-- it is defined by the expansion of the option
33598 &%callout_random_local_part%&, which defaults to
33600 $primary_hostname-$tod_epoch-testing
33602 The idea here is to try to determine whether the remote host accepts all local
33603 parts without checking. If it does, there is no point in doing callouts for
33604 specific local parts. If the &"random"& check succeeds, the result is saved in
33605 a cache record, and used to force the current and subsequent callout checks to
33606 succeed without a connection being made, until the cache record expires.
33608 .vitem &*use_postmaster*&
33609 .cindex "callout" "sender for recipient check"
33610 This parameter applies to recipient callouts only. For example:
33612 deny !verify = recipient/callout=use_postmaster
33614 .vindex "&$qualify_domain$&"
33615 It causes a non-empty postmaster address to be used in the MAIL command when
33616 performing the callout for the recipient, and also for a &"random"& check if
33617 that is configured. The local part of the address is &`postmaster`& and the
33618 domain is the contents of &$qualify_domain$&.
33620 .vitem &*use_sender*&
33621 This option applies to recipient callouts only. For example:
33623 require verify = recipient/callout=use_sender
33625 It causes the message's actual sender address to be used in the MAIL
33626 command when performing the callout, instead of an empty address. There is no
33627 need to use this option unless you know that the called hosts make use of the
33628 sender when checking recipients. If used indiscriminately, it reduces the
33629 usefulness of callout caching.
33632 This option applies to recipient callouts only. For example:
33634 require verify = recipient/callout=use_sender,hold
33636 It causes the connection to be held open and used for any further recipients
33637 and for eventual delivery (should that be done quickly).
33638 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33639 when that is used for the connections.
33640 The advantage is only gained if there are no callout cache hits
33641 (which could be enforced by the no_cache option),
33642 if the use_sender option is used,
33643 if neither the random nor the use_postmaster option is used,
33644 and if no other callouts intervene.
33647 If you use any of the parameters that set a non-empty sender for the MAIL
33648 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33649 &%use_sender%&), you should think about possible loops. Recipient checking is
33650 usually done between two hosts that are under the same management, and the host
33651 that receives the callouts is not normally configured to do callouts itself.
33652 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33653 these circumstances.
33655 However, if you use a non-empty sender address for a callout to an arbitrary
33656 host, there is the likelihood that the remote host will itself initiate a
33657 callout check back to your host. As it is checking what appears to be a message
33658 sender, it is likely to use an empty address in MAIL, thus avoiding a
33659 callout loop. However, to be on the safe side it would be best to set up your
33660 own ACLs so that they do not do sender verification checks when the recipient
33661 is the address you use for header sender or postmaster callout checking.
33663 Another issue to think about when using non-empty senders for callouts is
33664 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33665 by the sender/recipient combination; thus, for any given recipient, many more
33666 actual callouts are performed than when an empty sender or postmaster is used.
33671 .section "Callout caching" "SECTcallvercache"
33672 .cindex "hints database" "callout cache"
33673 .cindex "callout" "cache, description of"
33674 .cindex "caching" "callout"
33675 Exim caches the results of callouts in order to reduce the amount of resources
33676 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33677 option. A hints database called &"callout"& is used for the cache. Two
33678 different record types are used: one records the result of a callout check for
33679 a specific address, and the other records information that applies to the
33680 entire domain (for example, that it accepts the local part &'postmaster'&).
33682 When an original callout fails, a detailed SMTP error message is given about
33683 the failure. However, for subsequent failures use the cache data, this message
33686 The expiry times for negative and positive address cache records are
33687 independent, and can be set by the global options &%callout_negative_expire%&
33688 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33690 If a host gives a negative response to an SMTP connection, or rejects any
33691 commands up to and including
33695 (but not including the MAIL command with a non-empty address),
33696 any callout attempt is bound to fail. Exim remembers such failures in a
33697 domain cache record, which it uses to fail callouts for the domain without
33698 making new connections, until the domain record times out. There are two
33699 separate expiry times for domain cache records:
33700 &%callout_domain_negative_expire%& (default 3h) and
33701 &%callout_domain_positive_expire%& (default 7d).
33703 Domain records expire when the negative expiry time is reached if callouts
33704 cannot be made for the domain, or if the postmaster check failed.
33705 Otherwise, they expire when the positive expiry time is reached. This
33706 ensures that, for example, a host that stops accepting &"random"& local parts
33707 will eventually be noticed.
33709 The callout caching mechanism is based on the domain of the address that is
33710 being tested. If the domain routes to several hosts, it is assumed that their
33711 behaviour will be the same.
33716 .section "Quota caching" "SECTquotacache"
33717 .cindex "hints database" "quota cache"
33718 .cindex "quota" "cache, description of"
33719 .cindex "caching" "quota"
33720 Exim caches the results of quota verification
33721 in order to reduce the amount of resources used.
33722 The &"callout"& hints database is used.
33724 The default cache periods are five minutes for a positive (good) result
33725 and one hour for a negative result.
33726 To change the periods the &%quota%& option can be followed by an equals sign
33727 and a number of optional paramemters, separated by commas.
33730 verify = recipient/quota=cachepos=1h,cacheneg=1d
33732 Possible parameters are:
33734 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33735 .cindex "quota cache" "positive entry expiry, specifying"
33736 Set the lifetime for a positive cache entry.
33737 A value of zero seconds is legitimate.
33739 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33740 .cindex "quota cache" "negative entry expiry, specifying"
33741 As above, for a negative entry.
33743 .vitem &*no_cache*&
33744 Set both positive and negative lifetimes to zero.
33747 .section "Sender address verification reporting" "SECTsenaddver"
33748 .cindex "verifying" "suppressing error details"
33749 See section &<<SECTaddressverification>>& for a general discussion of
33750 verification. When sender verification fails in an ACL, the details of the
33751 failure are given as additional output lines before the 550 response to the
33752 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33755 MAIL FROM:<xyz@abc.example>
33757 RCPT TO:<pqr@def.example>
33758 550-Verification failed for <xyz@abc.example>
33759 550-Called: 192.168.34.43
33760 550-Sent: RCPT TO:<xyz@abc.example>
33761 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33762 550 Sender verification failed
33764 If more than one RCPT command fails in the same way, the details are given
33765 only for the first of them. However, some administrators do not want to send
33766 out this much information. You can suppress the details by adding
33767 &`/no_details`& to the ACL statement that requests sender verification. For
33770 verify = sender/no_details
33773 .section "Redirection while verifying" "SECTredirwhilveri"
33774 .cindex "verifying" "redirection while"
33775 .cindex "address redirection" "while verifying"
33776 A dilemma arises when a local address is redirected by aliasing or forwarding
33777 during verification: should the generated addresses themselves be verified,
33778 or should the successful expansion of the original address be enough to verify
33779 it? By default, Exim takes the following pragmatic approach:
33782 When an incoming address is redirected to just one child address, verification
33783 continues with the child address, and if that fails to verify, the original
33784 verification also fails.
33786 When an incoming address is redirected to more than one child address,
33787 verification does not continue. A success result is returned.
33790 This seems the most reasonable behaviour for the common use of aliasing as a
33791 way of redirecting different local parts to the same mailbox. It means, for
33792 example, that a pair of alias entries of the form
33795 aw123: :fail: Gone away, no forwarding address
33797 work as expected, with both local parts causing verification failure. When a
33798 redirection generates more than one address, the behaviour is more like a
33799 mailing list, where the existence of the alias itself is sufficient for
33800 verification to succeed.
33802 It is possible, however, to change the default behaviour so that all successful
33803 redirections count as successful verifications, however many new addresses are
33804 generated. This is specified by the &%success_on_redirect%& verification
33805 option. For example:
33807 require verify = recipient/success_on_redirect/callout=10s
33809 In this example, verification succeeds if a router generates a new address, and
33810 the callout does not occur, because no address was routed to a remote host.
33812 When verification is being tested via the &%-bv%& option, the treatment of
33813 redirections is as just described, unless the &%-v%& or any debugging option is
33814 also specified. In that case, full verification is done for every generated
33815 address and a report is output for each of them.
33819 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33820 .cindex "CSA" "verifying"
33821 Client SMTP Authorization is a system that allows a site to advertise
33822 which machines are and are not permitted to send email. This is done by placing
33823 special SRV records in the DNS; these are looked up using the client's HELO
33824 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33825 Authorization checks in Exim are performed by the ACL condition:
33829 This fails if the client is not authorized. If there is a DNS problem, or if no
33830 valid CSA SRV record is found, or if the client is authorized, the condition
33831 succeeds. These three cases can be distinguished using the expansion variable
33832 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33833 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33834 be likely to cause problems for legitimate email.
33836 The error messages produced by the CSA code include slightly more
33837 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33838 looking up the CSA SRV record, or problems looking up the CSA target
33839 address record. There are four reasons for &$csa_status$& being &"fail"&:
33842 The client's host name is explicitly not authorized.
33844 The client's IP address does not match any of the CSA target IP addresses.
33846 The client's host name is authorized but it has no valid target IP addresses
33847 (for example, the target's addresses are IPv6 and the client is using IPv4).
33849 The client's host name has no CSA SRV record but a parent domain has asserted
33850 that all subdomains must be explicitly authorized.
33853 The &%csa%& verification condition can take an argument which is the domain to
33854 use for the DNS query. The default is:
33856 verify = csa/$sender_helo_name
33858 This implementation includes an extension to CSA. If the query domain
33859 is an address literal such as [192.0.2.95], or if it is a bare IP
33860 address, Exim searches for CSA SRV records in the reverse DNS as if
33861 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33864 verify = csa/$sender_host_address
33866 In fact, this is the check that Exim performs if the client does not say HELO.
33867 This extension can be turned off by setting the main configuration option
33868 &%dns_csa_use_reverse%& to be false.
33870 If a CSA SRV record is not found for the domain itself, a search
33871 is performed through its parent domains for a record which might be
33872 making assertions about subdomains. The maximum depth of this search is limited
33873 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33874 default. Exim does not look for CSA SRV records in a top level domain, so the
33875 default settings handle HELO domains as long as seven
33876 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33877 of legitimate HELO domains.
33879 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33880 direct SRV lookups, this is not sufficient because of the extra parent domain
33881 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33882 addresses into lookups in the reverse DNS space. The result of a successful
33885 ${lookup dnsdb {csa=$sender_helo_name}}
33887 has two space-separated fields: an authorization code and a target host name.
33888 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33889 authorization required but absent, or &"?"& for unknown.
33894 .section "Bounce address tag validation" "SECTverifyPRVS"
33895 .cindex "BATV, verifying"
33896 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33897 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33898 Genuine incoming bounce messages should therefore always be addressed to
33899 recipients that have a valid tag. This scheme is a way of detecting unwanted
33900 bounce messages caused by sender address forgeries (often called &"collateral
33901 spam"&), because the recipients of such messages do not include valid tags.
33903 There are two expansion items to help with the implementation of the BATV
33904 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33905 the original envelope sender address by using a simple key to add a hash of the
33906 address and some time-based randomizing information. The &%prvs%& expansion
33907 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33908 The syntax of these expansion items is described in section
33909 &<<SECTexpansionitems>>&.
33910 The validity period on signed addresses is seven days.
33912 As an example, suppose the secret per-address keys are stored in an MySQL
33913 database. A query to look up the key for an address could be defined as a macro
33916 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33917 WHERE sender='${quote_mysql:$prvscheck_address}'\
33920 Suppose also that the senders who make use of BATV are defined by an address
33921 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33924 # Bounces: drop unsigned addresses for BATV senders
33926 recipients = +batv_senders
33927 message = This address does not send an unsigned reverse path
33929 # Bounces: In case of prvs-signed address, check signature.
33931 condition = ${prvscheck {$local_part@$domain}\
33932 {PRVSCHECK_SQL}{1}}
33933 !condition = $prvscheck_result
33934 message = Invalid reverse path signature.
33936 The first statement rejects recipients for bounce messages that are addressed
33937 to plain BATV sender addresses, because it is known that BATV senders do not
33938 send out messages with plain sender addresses. The second statement rejects
33939 recipients that are prvs-signed, but with invalid signatures (either because
33940 the key is wrong, or the signature has timed out).
33942 A non-prvs-signed address is not rejected by the second statement, because the
33943 &%prvscheck%& expansion yields an empty string if its first argument is not a
33944 prvs-signed address, thus causing the &%condition%& condition to be false. If
33945 the first argument is a syntactically valid prvs-signed address, the yield is
33946 the third string (in this case &"1"&), whether or not the cryptographic and
33947 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33948 of the checks (empty for failure, &"1"& for success).
33950 There is one more issue you must consider when implementing prvs-signing:
33951 you have to ensure that the routers accept prvs-signed addresses and
33952 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33953 router to remove the signature with a configuration along these lines:
33957 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33959 This works because, if the third argument of &%prvscheck%& is empty, the result
33960 of the expansion of a prvs-signed address is the decoded value of the original
33961 address. This router should probably be the first of your routers that handles
33964 To create BATV-signed addresses in the first place, a transport of this form
33967 external_smtp_batv:
33969 return_path = ${prvs {$return_path} \
33970 {${lookup mysql{SELECT \
33971 secret FROM batv_prvs WHERE \
33972 sender='${quote_mysql:$sender_address}'} \
33975 If no key can be found for the existing return path, no signing takes place.
33979 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33980 .cindex "&ACL;" "relay control"
33981 .cindex "relaying" "control by ACL"
33982 .cindex "policy control" "relay control"
33983 An MTA is said to &'relay'& a message if it receives it from some host and
33984 delivers it directly to another host as a result of a remote address contained
33985 within it. Redirecting a local address via an alias or forward file and then
33986 passing the message on to another host is not relaying,
33987 .cindex "&""percent hack""&"
33988 but a redirection as a result of the &"percent hack"& is.
33990 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33991 A host which is acting as a gateway or an MX backup is concerned with incoming
33992 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33993 a host which is acting as a smart host for a number of clients is concerned
33994 with outgoing relaying from those clients to the Internet at large. Often the
33995 same host is fulfilling both functions,
33997 . as illustrated in the diagram below,
33999 but in principle these two kinds of relaying are entirely independent. What is
34000 not wanted is the transmission of mail from arbitrary remote hosts through your
34001 system to arbitrary domains.
34004 You can implement relay control by means of suitable statements in the ACL that
34005 runs for each RCPT command. For convenience, it is often easiest to use
34006 Exim's named list facility to define the domains and hosts involved. For
34007 example, suppose you want to do the following:
34010 Deliver a number of domains to mailboxes on the local host (or process them
34011 locally in some other way). Let's say these are &'my.dom1.example'& and
34012 &'my.dom2.example'&.
34014 Relay mail for a number of other domains for which you are the secondary MX.
34015 These might be &'friend1.example'& and &'friend2.example'&.
34017 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34018 Suppose your LAN is 192.168.45.0/24.
34022 In the main part of the configuration, you put the following definitions:
34024 domainlist local_domains = my.dom1.example : my.dom2.example
34025 domainlist relay_to_domains = friend1.example : friend2.example
34026 hostlist relay_from_hosts = 192.168.45.0/24
34028 Now you can use these definitions in the ACL that is run for every RCPT
34032 accept domains = +local_domains : +relay_to_domains
34033 accept hosts = +relay_from_hosts
34035 The first statement accepts any RCPT command that contains an address in
34036 the local or relay domains. For any other domain, control passes to the second
34037 statement, which accepts the command only if it comes from one of the relay
34038 hosts. In practice, you will probably want to make your ACL more sophisticated
34039 than this, for example, by including sender and recipient verification. The
34040 default configuration includes a more comprehensive example, which is described
34041 in chapter &<<CHAPdefconfil>>&.
34045 .section "Checking a relay configuration" "SECTcheralcon"
34046 .cindex "relaying" "checking control of"
34047 You can check the relay characteristics of your configuration in the same way
34048 that you can test any ACL behaviour for an incoming SMTP connection, by using
34049 the &%-bh%& option to run a fake SMTP session with which you interact.
34054 . ////////////////////////////////////////////////////////////////////////////
34055 . ////////////////////////////////////////////////////////////////////////////
34057 .chapter "Content scanning at ACL time" "CHAPexiscan"
34058 .scindex IIDcosca "content scanning" "at ACL time"
34059 The extension of Exim to include content scanning at ACL time, formerly known
34060 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34061 was integrated into the main source for Exim release 4.50, and Tom continues to
34062 maintain it. Most of the wording of this chapter is taken from Tom's
34065 It is also possible to scan the content of messages at other times. The
34066 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34067 scanning after all the ACLs have run. A transport filter can be used to scan
34068 messages at delivery time (see the &%transport_filter%& option, described in
34069 chapter &<<CHAPtransportgeneric>>&).
34071 If you want to include the ACL-time content-scanning features when you compile
34072 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34073 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34076 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34077 for all MIME parts for SMTP and non-SMTP messages, respectively.
34079 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34080 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34081 run at the end of message reception (the &%acl_smtp_data%& ACL).
34083 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34084 of messages, or parts of messages, for debugging purposes.
34086 Additional expansion variables that are set in the new ACL and by the new
34089 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34092 Content-scanning is continually evolving, and new features are still being
34093 added. While such features are still unstable and liable to incompatible
34094 changes, they are made available in Exim by setting options whose names begin
34095 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34096 this manual. You can find out about them by reading the file called
34097 &_doc/experimental.txt_&.
34099 All the content-scanning facilities work on a MBOX copy of the message that is
34100 temporarily created in a file called:
34102 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34104 The &_.eml_& extension is a friendly hint to virus scanners that they can
34105 expect an MBOX-like structure inside that file. The file is created when the
34106 first content scanning facility is called. Subsequent calls to content
34107 scanning conditions open the same file again. The directory is recursively
34108 removed when the &%acl_smtp_data%& ACL has finished running, unless
34110 control = no_mbox_unspool
34112 has been encountered. When the MIME ACL decodes files, they are put into the
34113 same directory by default.
34117 .section "Scanning for viruses" "SECTscanvirus"
34118 .cindex "virus scanning"
34119 .cindex "content scanning" "for viruses"
34120 .cindex "content scanning" "the &%malware%& condition"
34121 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34122 It supports a &"generic"& interface to scanners called via the shell, and
34123 specialized interfaces for &"daemon"& type virus scanners, which are resident
34124 in memory and thus are much faster.
34126 Since message data needs to have arrived,
34127 the condition may be only called in ACL defined by
34129 &%acl_smtp_data_prdr%&,
34130 &%acl_smtp_mime%& or
34133 A timeout of 2 minutes is applied to a scanner call (by default);
34134 if it expires then a defer action is taken.
34136 .oindex "&%av_scanner%&"
34137 You can set the &%av_scanner%& option in the main part of the configuration
34138 to specify which scanner to use, together with any additional options that
34139 are needed. The basic syntax is as follows:
34141 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34143 If you do not set &%av_scanner%&, it defaults to
34145 av_scanner = sophie:/var/run/sophie
34147 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34149 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34150 The following scanner types are supported in this release,
34151 though individual ones can be included or not at build time:
34155 .cindex "virus scanners" "avast"
34156 This is the scanner daemon of Avast. It has been tested with Avast Core
34157 Security (currently at version 2.2.0).
34158 You can get a trial version at &url(https://www.avast.com) or for Linux
34159 at &url(https://www.avast.com/linux-server-antivirus).
34160 This scanner type takes one option,
34161 which can be either a full path to a UNIX socket,
34162 or host and port specifiers separated by white space.
34163 The host may be a name or an IP address; the port is either a
34164 single number or a pair of numbers with a dash between.
34165 A list of options may follow. These options are interpreted on the
34166 Exim's side of the malware scanner, or are given on separate lines to
34167 the daemon as options before the main scan command.
34169 .cindex &`pass_unscanned`& "avast"
34170 If &`pass_unscanned`&
34171 is set, any files the Avast scanner can't scan (e.g.
34172 decompression bombs, or invalid archives) are considered clean. Use with
34177 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34178 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34179 av_scanner = avast:192.168.2.22 5036
34181 If you omit the argument, the default path
34182 &_/var/run/avast/scan.sock_&
34184 If you use a remote host,
34185 you need to make Exim's spool directory available to it,
34186 as the scanner is passed a file path, not file contents.
34187 For information about available commands and their options you may use
34189 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34195 If the scanner returns a temporary failure (e.g. license issues, or
34196 permission problems), the message is deferred and a paniclog entry is
34197 written. The usual &`defer_ok`& option is available.
34199 .vitem &%aveserver%&
34200 .cindex "virus scanners" "Kaspersky"
34201 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34202 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34203 which is the path to the daemon's UNIX socket. The default is shown in this
34206 av_scanner = aveserver:/var/run/aveserver
34211 .cindex "virus scanners" "clamd"
34212 This daemon-type scanner is GPL and free. You can get it at
34213 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34214 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34215 in the MIME ACL. This is no longer believed to be necessary.
34217 The options are a list of server specifiers, which may be
34218 a UNIX socket specification,
34219 a TCP socket specification,
34220 or a (global) option.
34222 A socket specification consists of a space-separated list.
34223 For a Unix socket the first element is a full path for the socket,
34224 for a TCP socket the first element is the IP address
34225 and the second a port number,
34226 Any further elements are per-server (non-global) options.
34227 These per-server options are supported:
34229 retry=<timespec> Retry on connect fail
34232 The &`retry`& option specifies a time after which a single retry for
34233 a failed connect is made. The default is to not retry.
34235 If a Unix socket file is specified, only one server is supported.
34239 av_scanner = clamd:/opt/clamd/socket
34240 av_scanner = clamd:192.0.2.3 1234
34241 av_scanner = clamd:192.0.2.3 1234:local
34242 av_scanner = clamd:192.0.2.3 1234 retry=10s
34243 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34245 If the value of av_scanner points to a UNIX socket file or contains the
34247 option, then the ClamAV interface will pass a filename containing the data
34248 to be scanned, which should normally result in less I/O happening and be
34249 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34250 Exim does not assume that there is a common filesystem with the remote host.
34252 The final example shows that multiple TCP targets can be specified. Exim will
34253 randomly use one for each incoming email (i.e. it load balances them). Note
34254 that only TCP targets may be used if specifying a list of scanners; a UNIX
34255 socket cannot be mixed in with TCP targets. If one of the servers becomes
34256 unavailable, Exim will try the remaining one(s) until it finds one that works.
34257 When a clamd server becomes unreachable, Exim will log a message. Exim does
34258 not keep track of scanner state between multiple messages, and the scanner
34259 selection is random, so the message will get logged in the mainlog for each
34260 email that the down scanner gets chosen first (message wrapped to be readable):
34262 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34263 clamd: connection to localhost, port 3310 failed
34264 (Connection refused)
34267 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34268 contributing the code for this scanner.
34271 .cindex "virus scanners" "command line interface"
34272 This is the keyword for the generic command line scanner interface. It can be
34273 used to attach virus scanners that are invoked from the shell. This scanner
34274 type takes 3 mandatory options:
34277 The full path and name of the scanner binary, with all command line options,
34278 and a placeholder (&`%s`&) for the directory to scan.
34281 A regular expression to match against the STDOUT and STDERR output of the
34282 virus scanner. If the expression matches, a virus was found. You must make
34283 absolutely sure that this expression matches on &"virus found"&. This is called
34284 the &"trigger"& expression.
34287 Another regular expression, containing exactly one pair of parentheses, to
34288 match the name of the virus found in the scanners output. This is called the
34289 &"name"& expression.
34292 For example, Sophos Sweep reports a virus on a line like this:
34294 Virus 'W32/Magistr-B' found in file ./those.bat
34296 For the trigger expression, we can match the phrase &"found in file"&. For the
34297 name expression, we want to extract the W32/Magistr-B string, so we can match
34298 for the single quotes left and right of it. Altogether, this makes the
34299 configuration setting:
34301 av_scanner = cmdline:\
34302 /path/to/sweep -ss -all -rec -archive %s:\
34303 found in file:'(.+)'
34306 .cindex "virus scanners" "DrWeb"
34307 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34309 either a full path to a UNIX socket,
34310 or host and port specifiers separated by white space.
34311 The host may be a name or an IP address; the port is either a
34312 single number or a pair of numbers with a dash between.
34315 av_scanner = drweb:/var/run/drwebd.sock
34316 av_scanner = drweb:192.168.2.20 31337
34318 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34319 is used. Thanks to Alex Miller for contributing the code for this scanner.
34322 .cindex "virus scanners" "f-protd"
34323 The f-protd scanner is accessed via HTTP over TCP.
34324 One argument is taken, being a space-separated hostname and port number
34328 av_scanner = f-protd:localhost 10200-10204
34330 If you omit the argument, the default values shown above are used.
34332 .vitem &%f-prot6d%&
34333 .cindex "virus scanners" "f-prot6d"
34334 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34335 One argument is taken, being a space-separated hostname and port number.
34338 av_scanner = f-prot6d:localhost 10200
34340 If you omit the argument, the default values show above are used.
34343 .cindex "virus scanners" "F-Secure"
34344 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34345 argument which is the path to a UNIX socket. For example:
34347 av_scanner = fsecure:/path/to/.fsav
34349 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34350 Thelmen for contributing the code for this scanner.
34352 .vitem &%kavdaemon%&
34353 .cindex "virus scanners" "Kaspersky"
34354 This is the scanner daemon of Kaspersky Version 4. This version of the
34355 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34356 scanner type takes one option, which is the path to the daemon's UNIX socket.
34359 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34361 The default path is &_/var/run/AvpCtl_&.
34364 .cindex "virus scanners" "mksd"
34365 This was a daemon type scanner that is aimed mainly at Polish users,
34366 though some documentation was available in English.
34367 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34368 and this appears to be a candidate for removal from Exim, unless
34369 we are informed of other virus scanners which use the same protocol
34371 The only option for this scanner type is
34372 the maximum number of processes used simultaneously to scan the attachments,
34373 provided that mksd has
34374 been run with at least the same number of child processes. For example:
34376 av_scanner = mksd:2
34378 You can safely omit this option (the default value is 1).
34381 .cindex "virus scanners" "simple socket-connected"
34382 This is a general-purpose way of talking to simple scanner daemons
34383 running on the local machine.
34384 There are four options:
34385 an address (which may be an IP address and port, or the path of a Unix socket),
34386 a commandline to send (may include a single %s which will be replaced with
34387 the path to the mail file to be scanned),
34388 an RE to trigger on from the returned data,
34389 and an RE to extract malware_name from the returned data.
34392 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34394 Note that surrounding whitespace is stripped from each option, meaning
34395 there is no way to specify a trailing newline.
34396 The socket specifier and both regular-expressions are required.
34397 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34398 specify an empty element to get this.
34401 .cindex "virus scanners" "Sophos and Sophie"
34402 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34403 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34404 for this scanner type is the path to the UNIX socket that Sophie uses for
34405 client communication. For example:
34407 av_scanner = sophie:/tmp/sophie
34409 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34413 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34414 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34417 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34418 makes it possible to use different scanners. See further below for an example.
34419 The &%malware%& condition caches its results, so when you use it multiple times
34420 for the same message, the actual scanning process is only carried out once.
34421 However, using expandable items in &%av_scanner%& disables this caching, in
34422 which case each use of the &%malware%& condition causes a new scan of the
34425 The &%malware%& condition takes a right-hand argument that is expanded before
34426 use and taken as a list, slash-separated by default.
34427 The first element can then be one of
34430 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34431 The condition succeeds if a virus was found, and fail otherwise. This is the
34434 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34435 the condition fails immediately.
34437 A regular expression, in which case the message is scanned for viruses. The
34438 condition succeeds if a virus is found and its name matches the regular
34439 expression. This allows you to take special actions on certain types of virus.
34440 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34441 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34444 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34445 messages even if there is a problem with the virus scanner.
34446 Otherwise, such a problem causes the ACL to defer.
34448 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34449 specify a non-default timeout. The default is two minutes.
34452 malware = * / defer_ok / tmo=10s
34454 A timeout causes the ACL to defer.
34456 .vindex "&$callout_address$&"
34457 When a connection is made to the scanner the expansion variable &$callout_address$&
34458 is set to record the actual address used.
34460 .vindex "&$malware_name$&"
34461 When a virus is found, the condition sets up an expansion variable called
34462 &$malware_name$& that contains the name of the virus. You can use it in a
34463 &%message%& modifier that specifies the error returned to the sender, and/or in
34466 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34467 imposed by your anti-virus scanner.
34469 Here is a very simple scanning example:
34472 message = This message contains malware ($malware_name)
34474 The next example accepts messages when there is a problem with the scanner:
34476 deny malware = */defer_ok
34477 message = This message contains malware ($malware_name)
34479 The next example shows how to use an ACL variable to scan with both sophie and
34480 aveserver. It assumes you have set:
34482 av_scanner = $acl_m0
34484 in the main Exim configuration.
34486 deny set acl_m0 = sophie
34488 message = This message contains malware ($malware_name)
34490 deny set acl_m0 = aveserver
34492 message = This message contains malware ($malware_name)
34496 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34497 .cindex "content scanning" "for spam"
34498 .cindex "spam scanning"
34499 .cindex "SpamAssassin"
34501 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34502 score and a report for the message.
34503 Support is also provided for Rspamd.
34505 For more information about installation and configuration of SpamAssassin or
34506 Rspamd refer to their respective websites at
34507 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34509 SpamAssassin can be installed with CPAN by running:
34511 perl -MCPAN -e 'install Mail::SpamAssassin'
34513 SpamAssassin has its own set of configuration files. Please review its
34514 documentation to see how you can tweak it. The default installation should work
34517 .oindex "&%spamd_address%&"
34518 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34519 intend to use an instance running on the local host you do not need to set
34520 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34521 you must set the &%spamd_address%& option in the global part of the Exim
34522 configuration as follows (example):
34524 spamd_address = 192.168.99.45 783
34526 The SpamAssassin protocol relies on a TCP half-close from the client.
34527 If your SpamAssassin client side is running a Linux system with an
34528 iptables firewall, consider setting
34529 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34530 timeout, Exim uses when waiting for a response from the SpamAssassin
34531 server (currently defaulting to 120s). With a lower value the Linux
34532 connection tracking may consider your half-closed connection as dead too
34536 To use Rspamd (which by default listens on all local addresses
34538 you should add &%variant=rspamd%& after the address/port pair, for example:
34540 spamd_address = 127.0.0.1 11333 variant=rspamd
34543 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34544 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34545 filename instead of an address/port pair:
34547 spamd_address = /var/run/spamd_socket
34549 You can have multiple &%spamd%& servers to improve scalability. These can
34550 reside on other hardware reachable over the network. To specify multiple
34551 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34552 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34554 spamd_address = 192.168.2.10 783 : \
34555 192.168.2.11 783 : \
34558 Up to 32 &%spamd%& servers are supported.
34559 When a server fails to respond to the connection attempt, all other
34560 servers are tried until one succeeds. If no server responds, the &%spam%&
34563 Unix and TCP socket specifications may be mixed in any order.
34564 Each element of the list is a list itself, space-separated by default
34565 and changeable in the usual way (&<<SECTlistsepchange>>&);
34566 take care to not double the separator.
34568 For TCP socket specifications a host name or IP (v4 or v6, but
34569 subject to list-separator quoting rules) address can be used,
34570 and the port can be one or a dash-separated pair.
34571 In the latter case, the range is tried in strict order.
34573 Elements after the first for Unix sockets, or second for TCP socket,
34575 The supported options are:
34577 pri=<priority> Selection priority
34578 weight=<value> Selection bias
34579 time=<start>-<end> Use only between these times of day
34580 retry=<timespec> Retry on connect fail
34581 tmo=<timespec> Connection time limit
34582 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34585 The &`pri`& option specifies a priority for the server within the list,
34586 higher values being tried first.
34587 The default priority is 1.
34589 The &`weight`& option specifies a selection bias.
34590 Within a priority set
34591 servers are queried in a random fashion, weighted by this value.
34592 The default value for selection bias is 1.
34594 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34595 in the local time zone; each element being one or more digits.
34596 Either the seconds or both minutes and seconds, plus the leading &`.`&
34597 characters, may be omitted and will be taken as zero.
34599 Timeout specifications for the &`retry`& and &`tmo`& options
34600 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34602 The &`tmo`& option specifies an overall timeout for communication.
34603 The default value is two minutes.
34605 The &`retry`& option specifies a time after which a single retry for
34606 a failed connect is made.
34607 The default is to not retry.
34609 The &%spamd_address%& variable is expanded before use if it starts with
34610 a dollar sign. In this case, the expansion may return a string that is
34611 used as the list so that multiple spamd servers can be the result of an
34614 .vindex "&$callout_address$&"
34615 When a connection is made to the server the expansion variable &$callout_address$&
34616 is set to record the actual address used.
34618 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34619 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34622 message = This message was classified as SPAM
34624 The right-hand side of the &%spam%& condition specifies a name. This is
34625 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34626 to scan using a specific profile, but rather use the SpamAssassin system-wide
34627 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34628 Rspamd does not use this setting. However, you must put something on the
34631 The name allows you to use per-domain or per-user antispam profiles in
34632 principle, but this is not straightforward in practice, because a message may
34633 have multiple recipients, not necessarily all in the same domain. Because the
34634 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34635 read the contents of the message, the variables &$local_part$& and &$domain$&
34637 Careful enforcement of single-recipient messages
34638 (e.g. by responding with defer in the recipient ACL for all recipients
34640 or the use of PRDR,
34641 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34642 are needed to use this feature.
34644 The right-hand side of the &%spam%& condition is expanded before being used, so
34645 you can put lookups or conditions there. When the right-hand side evaluates to
34646 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34649 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34650 large ones may cause significant performance degradation. As most spam messages
34651 are quite small, it is recommended that you do not scan the big ones. For
34654 deny condition = ${if < {$message_size}{10K}}
34656 message = This message was classified as SPAM
34659 The &%spam%& condition returns true if the threshold specified in the user's
34660 SpamAssassin profile has been matched or exceeded. If you want to use the
34661 &%spam%& condition for its side effects (see the variables below), you can make
34662 it always return &"true"& by appending &`:true`& to the username.
34664 .cindex "spam scanning" "returned variables"
34665 When the &%spam%& condition is run, it sets up a number of expansion
34667 Except for &$spam_report$&,
34668 these variables are saved with the received message so are
34669 available for use at delivery time.
34672 .vitem &$spam_score$&
34673 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34674 for inclusion in log or reject messages.
34676 .vitem &$spam_score_int$&
34677 The spam score of the message, multiplied by ten, as an integer value. For
34678 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34679 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34680 The integer value is useful for numeric comparisons in conditions.
34682 .vitem &$spam_bar$&
34683 A string consisting of a number of &"+"& or &"-"& characters, representing the
34684 integer part of the spam score value. A spam score of 4.4 would have a
34685 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34686 headers, since MUAs can match on such strings. The maximum length of the
34687 spam bar is 50 characters.
34689 .vitem &$spam_report$&
34690 A multiline text table, containing the full SpamAssassin report for the
34691 message. Useful for inclusion in headers or reject messages.
34692 This variable is only usable in a DATA-time ACL.
34693 Beware that SpamAssassin may return non-ASCII characters, especially
34694 when running in country-specific locales, which are not legal
34695 unencoded in headers.
34697 .vitem &$spam_action$&
34698 For SpamAssassin either 'reject' or 'no action' depending on the
34699 spam score versus threshold.
34700 For Rspamd, the recommended action.
34704 The &%spam%& condition caches its results unless expansion in
34705 spamd_address was used. If you call it again with the same user name, it
34706 does not scan again, but rather returns the same values as before.
34708 The &%spam%& condition returns DEFER if there is any error while running
34709 the message through SpamAssassin or if the expansion of spamd_address
34710 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34711 statement block), append &`/defer_ok`& to the right-hand side of the
34712 spam condition, like this:
34714 deny spam = joe/defer_ok
34715 message = This message was classified as SPAM
34717 This causes messages to be accepted even if there is a problem with &%spamd%&.
34719 Here is a longer, commented example of the use of the &%spam%&
34722 # put headers in all messages (no matter if spam or not)
34723 warn spam = nobody:true
34724 add_header = X-Spam-Score: $spam_score ($spam_bar)
34725 add_header = X-Spam-Report: $spam_report
34727 # add second subject line with *SPAM* marker when message
34728 # is over threshold
34730 add_header = Subject: *SPAM* $h_Subject:
34732 # reject spam at high scores (> 12)
34733 deny spam = nobody:true
34734 condition = ${if >{$spam_score_int}{120}{1}{0}}
34735 message = This message scored $spam_score spam points.
34740 .section "Scanning MIME parts" "SECTscanmimepart"
34741 .cindex "content scanning" "MIME parts"
34742 .cindex "MIME content scanning"
34743 .oindex "&%acl_smtp_mime%&"
34744 .oindex "&%acl_not_smtp_mime%&"
34745 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34746 each MIME part of an SMTP message, including multipart types, in the sequence
34747 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34748 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34749 options may both refer to the same ACL if you want the same processing in both
34752 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34753 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34754 the case of a non-SMTP message. However, a MIME ACL is called only if the
34755 message contains a &'Content-Type:'& header line. When a call to a MIME
34756 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34757 result code is sent to the client. In the case of an SMTP message, the
34758 &%acl_smtp_data%& ACL is not called when this happens.
34760 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34761 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34762 condition to match against the raw MIME part. You can also use the
34763 &%mime_regex%& condition to match against the decoded MIME part (see section
34764 &<<SECTscanregex>>&).
34766 At the start of a MIME ACL, a number of variables are set from the header
34767 information for the relevant MIME part. These are described below. The contents
34768 of the MIME part are not by default decoded into a disk file except for MIME
34769 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34770 part into a disk file, you can use the &%decode%& condition. The general
34773 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34775 The right hand side is expanded before use. After expansion,
34779 &"0"& or &"false"&, in which case no decoding is done.
34781 The string &"default"&. In that case, the file is put in the temporary
34782 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34783 a sequential filename consisting of the message id and a sequence number. The
34784 full path and name is available in &$mime_decoded_filename$& after decoding.
34786 A full path name starting with a slash. If the full name is an existing
34787 directory, it is used as a replacement for the default directory. The filename
34788 is then sequentially assigned. If the path does not exist, it is used as
34789 the full path and filename.
34791 If the string does not start with a slash, it is used as the
34792 filename, and the default path is then used.
34794 The &%decode%& condition normally succeeds. It is only false for syntax
34795 errors or unusual circumstances such as memory shortages. You can easily decode
34796 a file with its original, proposed filename using
34798 decode = $mime_filename
34800 However, you should keep in mind that &$mime_filename$& might contain
34801 anything. If you place files outside of the default path, they are not
34802 automatically unlinked.
34804 For RFC822 attachments (these are messages attached to messages, with a
34805 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34806 as for the primary message, only that the &$mime_is_rfc822$& expansion
34807 variable is set (see below). Attached messages are always decoded to disk
34808 before being checked, and the files are unlinked once the check is done.
34810 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34811 used to match regular expressions against raw and decoded MIME parts,
34812 respectively. They are described in section &<<SECTscanregex>>&.
34814 .cindex "MIME content scanning" "returned variables"
34815 The following list describes all expansion variables that are
34816 available in the MIME ACL:
34819 .vitem &$mime_anomaly_level$& &&&
34820 &$mime_anomaly_text$&
34821 .vindex &$mime_anomaly_level$&
34822 .vindex &$mime_anomaly_text$&
34823 If there are problems decoding, these variables contain information on
34824 the detected issue.
34826 .vitem &$mime_boundary$&
34827 .vindex &$mime_boundary$&
34828 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34829 have a boundary string, which is stored in this variable. If the current part
34830 has no boundary parameter in the &'Content-Type:'& header, this variable
34831 contains the empty string.
34833 .vitem &$mime_charset$&
34834 .vindex &$mime_charset$&
34835 This variable contains the character set identifier, if one was found in the
34836 &'Content-Type:'& header. Examples for charset identifiers are:
34842 Please note that this value is not normalized, so you should do matches
34843 case-insensitively.
34845 .vitem &$mime_content_description$&
34846 .vindex &$mime_content_description$&
34847 This variable contains the normalized content of the &'Content-Description:'&
34848 header. It can contain a human-readable description of the parts content. Some
34849 implementations repeat the filename for attachments here, but they are usually
34850 only used for display purposes.
34852 .vitem &$mime_content_disposition$&
34853 .vindex &$mime_content_disposition$&
34854 This variable contains the normalized content of the &'Content-Disposition:'&
34855 header. You can expect strings like &"attachment"& or &"inline"& here.
34857 .vitem &$mime_content_id$&
34858 .vindex &$mime_content_id$&
34859 This variable contains the normalized content of the &'Content-ID:'& header.
34860 This is a unique ID that can be used to reference a part from another part.
34862 .vitem &$mime_content_size$&
34863 .vindex &$mime_content_size$&
34864 This variable is set only after the &%decode%& modifier (see above) has been
34865 successfully run. It contains the size of the decoded part in kilobytes. The
34866 size is always rounded up to full kilobytes, so only a completely empty part
34867 has a &$mime_content_size$& of zero.
34869 .vitem &$mime_content_transfer_encoding$&
34870 .vindex &$mime_content_transfer_encoding$&
34871 This variable contains the normalized content of the
34872 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34873 type. Typical values are &"base64"& and &"quoted-printable"&.
34875 .vitem &$mime_content_type$&
34876 .vindex &$mime_content_type$&
34877 If the MIME part has a &'Content-Type:'& header, this variable contains its
34878 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34879 are some examples of popular MIME types, as they may appear in this variable:
34883 application/octet-stream
34887 If the MIME part has no &'Content-Type:'& header, this variable contains the
34890 .vitem &$mime_decoded_filename$&
34891 .vindex &$mime_decoded_filename$&
34892 This variable is set only after the &%decode%& modifier (see above) has been
34893 successfully run. It contains the full path and filename of the file
34894 containing the decoded data.
34899 .vitem &$mime_filename$&
34900 .vindex &$mime_filename$&
34901 This is perhaps the most important of the MIME variables. It contains a
34902 proposed filename for an attachment, if one was found in either the
34903 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34906 decoded, but no additional sanity checks are done.
34908 found, this variable contains the empty string.
34910 .vitem &$mime_is_coverletter$&
34911 .vindex &$mime_is_coverletter$&
34912 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34913 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34914 content in the cover letter, while not restricting attachments at all.
34916 The variable contains 1 (true) for a MIME part believed to be part of the
34917 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34921 The outermost MIME part of a message is always a cover letter.
34924 If a multipart/alternative or multipart/related MIME part is a cover letter,
34925 so are all MIME subparts within that multipart.
34928 If any other multipart is a cover letter, the first subpart is a cover letter,
34929 and the rest are attachments.
34932 All parts contained within an attachment multipart are attachments.
34935 As an example, the following will ban &"HTML mail"& (including that sent with
34936 alternative plain text), while allowing HTML files to be attached. HTML
34937 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34939 deny !condition = $mime_is_rfc822
34940 condition = $mime_is_coverletter
34941 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34942 message = HTML mail is not accepted here
34945 .vitem &$mime_is_multipart$&
34946 .vindex &$mime_is_multipart$&
34947 This variable has the value 1 (true) when the current part has the main type
34948 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34949 Since multipart entities only serve as containers for other parts, you may not
34950 want to carry out specific actions on them.
34952 .vitem &$mime_is_rfc822$&
34953 .vindex &$mime_is_rfc822$&
34954 This variable has the value 1 (true) if the current part is not a part of the
34955 checked message itself, but part of an attached message. Attached message
34956 decoding is fully recursive.
34958 .vitem &$mime_part_count$&
34959 .vindex &$mime_part_count$&
34960 This variable is a counter that is raised for each processed MIME part. It
34961 starts at zero for the very first part (which is usually a multipart). The
34962 counter is per-message, so it is reset when processing RFC822 attachments (see
34963 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34964 complete, so you can use it in the DATA ACL to determine the number of MIME
34965 parts of a message. For non-MIME messages, this variable contains the value -1.
34970 .section "Scanning with regular expressions" "SECTscanregex"
34971 .cindex "content scanning" "with regular expressions"
34972 .cindex "regular expressions" "content scanning with"
34973 You can specify your own custom regular expression matches on the full body of
34974 the message, or on individual MIME parts.
34976 The &%regex%& condition takes one or more regular expressions as arguments and
34977 matches them against the full message (when called in the DATA ACL) or a raw
34978 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34979 linewise, with a maximum line length of 32K characters. That means you cannot
34980 have multiline matches with the &%regex%& condition.
34982 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34983 to 32K of decoded content (the whole content at once, not linewise). If the
34984 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34985 is decoded automatically when &%mime_regex%& is executed (using default path
34986 and filename values). If the decoded data is larger than 32K, only the first
34987 32K characters are checked.
34989 The regular expressions are passed as a colon-separated list. To include a
34990 literal colon, you must double it. Since the whole right-hand side string is
34991 expanded before being used, you must also escape dollar signs and backslashes
34992 with more backslashes, or use the &`\N`& facility to disable expansion.
34993 Here is a simple example that contains two regular expressions:
34995 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34996 message = contains blacklisted regex ($regex_match_string)
34998 The conditions returns true if any one of the regular expressions matches. The
34999 &$regex_match_string$& expansion variable is then set up and contains the
35000 matching regular expression.
35001 The expansion variables &$regex1$& &$regex2$& etc
35002 are set to any substrings captured by the regular expression.
35004 &*Warning*&: With large messages, these conditions can be fairly
35012 . ////////////////////////////////////////////////////////////////////////////
35013 . ////////////////////////////////////////////////////////////////////////////
35015 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
35016 "Local scan function"
35017 .scindex IIDlosca "&[local_scan()]& function" "description of"
35018 .cindex "customizing" "input scan using C function"
35019 .cindex "policy control" "by local scan function"
35020 In these days of email worms, viruses, and ever-increasing spam, some sites
35021 want to apply a lot of checking to messages before accepting them.
35023 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35024 passing messages to external virus and spam scanning software. You can also do
35025 a certain amount in Exim itself through string expansions and the &%condition%&
35026 condition in the ACL that runs after the SMTP DATA command or the ACL for
35027 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35029 To allow for further customization to a site's own requirements, there is the
35030 possibility of linking Exim with a private message scanning function, written
35031 in C. If you want to run code that is written in something other than C, you
35032 can of course use a little C stub to call it.
35034 The local scan function is run once for every incoming message, at the point
35035 when Exim is just about to accept the message.
35036 It can therefore be used to control non-SMTP messages from local processes as
35037 well as messages arriving via SMTP.
35039 Exim applies a timeout to calls of the local scan function, and there is an
35040 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35041 Zero means &"no timeout"&.
35042 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35043 before calling the local scan function, so that the most common types of crash
35044 are caught. If the timeout is exceeded or one of those signals is caught, the
35045 incoming message is rejected with a temporary error if it is an SMTP message.
35046 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35047 code. The incident is logged on the main and reject logs.
35051 .section "Building Exim to use a local scan function" "SECID207"
35052 .cindex "&[local_scan()]& function" "building Exim to use"
35053 To make use of the local scan function feature, you must tell Exim where your
35054 function is before building Exim, by setting
35055 both HAVE_LOCAL_SCAN and
35056 LOCAL_SCAN_SOURCE in your
35057 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35058 directory, so you might set
35060 HAVE_LOCAL_SCAN=yes
35061 LOCAL_SCAN_SOURCE=Local/local_scan.c
35063 for example. The function must be called &[local_scan()]&;
35064 the source file(s) for it should first #define LOCAL_SCAN
35065 and then #include "local_scan.h".
35067 Exim after it has received a message, when the success return code is about to
35068 be sent. This is after all the ACLs have been run. The return code from your
35069 function controls whether the message is actually accepted or not. There is a
35070 commented template function (that just accepts the message) in the file
35071 _src/local_scan.c_.
35073 If you want to make use of Exim's runtime configuration file to set options
35074 for your &[local_scan()]& function, you must also set
35076 LOCAL_SCAN_HAS_OPTIONS=yes
35078 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35083 .section "API for local_scan()" "SECTapiforloc"
35084 .cindex "&[local_scan()]& function" "API description"
35085 .cindex &%dlfunc%& "API description"
35086 You must include this line near the start of your code:
35089 #include "local_scan.h"
35091 This header file defines a number of variables and other values, and the
35092 prototype for the function itself. Exim is coded to use unsigned char values
35093 almost exclusively, and one of the things this header defines is a shorthand
35094 for &`unsigned char`& called &`uschar`&.
35095 It also makes available the following macro definitions, to simplify casting character
35096 strings and pointers to character strings:
35098 #define CS (char *)
35099 #define CCS (const char *)
35100 #define CSS (char **)
35101 #define US (unsigned char *)
35102 #define CUS (const unsigned char *)
35103 #define USS (unsigned char **)
35105 The function prototype for &[local_scan()]& is:
35107 extern int local_scan(int fd, uschar **return_text);
35109 The arguments are as follows:
35112 &%fd%& is a file descriptor for the file that contains the body of the message
35113 (the -D file). The file is open for reading and writing, but updating it is not
35114 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35116 The descriptor is positioned at character 19 of the file, which is the first
35117 character of the body itself, because the first 19 characters are the message
35118 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35119 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35120 case this changes in some future version.
35122 &%return_text%& is an address which you can use to return a pointer to a text
35123 string at the end of the function. The value it points to on entry is NULL.
35126 The function must return an &%int%& value which is one of the following macros:
35129 .vitem &`LOCAL_SCAN_ACCEPT`&
35130 .vindex "&$local_scan_data$&"
35131 The message is accepted. If you pass back a string of text, it is saved with
35132 the message, and made available in the variable &$local_scan_data$&. No
35133 newlines are permitted (if there are any, they are turned into spaces) and the
35134 maximum length of text is 1000 characters.
35136 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35137 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35138 queued without immediate delivery, and is frozen.
35140 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35141 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35142 queued without immediate delivery.
35144 .vitem &`LOCAL_SCAN_REJECT`&
35145 The message is rejected; the returned text is used as an error message which is
35146 passed back to the sender and which is also logged. Newlines are permitted &--
35147 they cause a multiline response for SMTP rejections, but are converted to
35148 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35151 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35152 The message is temporarily rejected; the returned text is used as an error
35153 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35156 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35157 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35158 message is not written to the reject log. It has the effect of unsetting the
35159 &%rejected_header%& log selector for just this rejection. If
35160 &%rejected_header%& is already unset (see the discussion of the
35161 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35162 same as LOCAL_SCAN_REJECT.
35164 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35165 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35166 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35169 If the message is not being received by interactive SMTP, rejections are
35170 reported by writing to &%stderr%& or by sending an email, as configured by the
35171 &%-oe%& command line options.
35175 .section "Configuration options for local_scan()" "SECTconoptloc"
35176 .cindex "&[local_scan()]& function" "configuration options"
35177 It is possible to have option settings in the main configuration file
35178 that set values in static variables in the &[local_scan()]& module. If you
35179 want to do this, you must have the line
35181 LOCAL_SCAN_HAS_OPTIONS=yes
35183 in your &_Local/Makefile_& when you build Exim. (This line is in
35184 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35185 file, you must define static variables to hold the option values, and a table
35188 The table must be a vector called &%local_scan_options%&, of type
35189 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35190 and a pointer to the variable that holds the value. The entries must appear in
35191 alphabetical order. Following &%local_scan_options%& you must also define a
35192 variable called &%local_scan_options_count%& that contains the number of
35193 entries in the table. Here is a short example, showing two kinds of option:
35195 static int my_integer_option = 42;
35196 static uschar *my_string_option = US"a default string";
35198 optionlist local_scan_options[] = {
35199 { "my_integer", opt_int, &my_integer_option },
35200 { "my_string", opt_stringptr, &my_string_option }
35203 int local_scan_options_count =
35204 sizeof(local_scan_options)/sizeof(optionlist);
35206 The values of the variables can now be changed from Exim's runtime
35207 configuration file by including a local scan section as in this example:
35211 my_string = some string of text...
35213 The available types of option data are as follows:
35216 .vitem &*opt_bool*&
35217 This specifies a boolean (true/false) option. The address should point to a
35218 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35219 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35220 whether such a variable has been set at all, you can initialize it to
35221 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35224 .vitem &*opt_fixed*&
35225 This specifies a fixed point number, such as is used for load averages.
35226 The address should point to a variable of type &`int`&. The value is stored
35227 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35230 This specifies an integer; the address should point to a variable of type
35231 &`int`&. The value may be specified in any of the integer formats accepted by
35234 .vitem &*opt_mkint*&
35235 This is the same as &%opt_int%&, except that when such a value is output in a
35236 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35237 printed with the suffix K or M.
35239 .vitem &*opt_octint*&
35240 This also specifies an integer, but the value is always interpreted as an
35241 octal integer, whether or not it starts with the digit zero, and it is
35242 always output in octal.
35244 .vitem &*opt_stringptr*&
35245 This specifies a string value; the address must be a pointer to a
35246 variable that points to a string (for example, of type &`uschar *`&).
35248 .vitem &*opt_time*&
35249 This specifies a time interval value. The address must point to a variable of
35250 type &`int`&. The value that is placed there is a number of seconds.
35253 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35254 out the values of all the &[local_scan()]& options.
35258 .section "Available Exim variables" "SECID208"
35259 .cindex "&[local_scan()]& function" "available Exim variables"
35260 The header &_local_scan.h_& gives you access to a number of C variables. These
35261 are the only ones that are guaranteed to be maintained from release to release.
35262 Note, however, that you can obtain the value of any Exim expansion variable,
35263 including &$recipients$&, by calling &'expand_string()'&. The exported
35264 C variables are as follows:
35267 .vitem &*int&~body_linecount*&
35268 This variable contains the number of lines in the message's body.
35269 It is not valid if the &%spool_files_wireformat%& option is used.
35271 .vitem &*int&~body_zerocount*&
35272 This variable contains the number of binary zero bytes in the message's body.
35273 It is not valid if the &%spool_files_wireformat%& option is used.
35275 .vitem &*unsigned&~int&~debug_selector*&
35276 This variable is set to zero when no debugging is taking place. Otherwise, it
35277 is a bitmap of debugging selectors. Two bits are identified for use in
35278 &[local_scan()]&; they are defined as macros:
35281 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35282 testing option that is not privileged &-- any caller may set it. All the
35283 other selector bits can be set only by admin users.
35286 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35287 by the &`+local_scan`& debug selector. It is not included in the default set
35291 Thus, to write to the debugging output only when &`+local_scan`& has been
35292 selected, you should use code like this:
35294 if ((debug_selector & D_local_scan) != 0)
35295 debug_printf("xxx", ...);
35297 .vitem &*uschar&~*expand_string_message*&
35298 After a failing call to &'expand_string()'& (returned value NULL), the
35299 variable &%expand_string_message%& contains the error message, zero-terminated.
35301 .vitem &*header_line&~*header_list*&
35302 A pointer to a chain of header lines. The &%header_line%& structure is
35305 .vitem &*header_line&~*header_last*&
35306 A pointer to the last of the header lines.
35308 .vitem &*uschar&~*headers_charset*&
35309 The value of the &%headers_charset%& configuration option.
35311 .vitem &*BOOL&~host_checking*&
35312 This variable is TRUE during a host checking session that is initiated by the
35313 &%-bh%& command line option.
35315 .vitem &*uschar&~*interface_address*&
35316 The IP address of the interface that received the message, as a string. This
35317 is NULL for locally submitted messages.
35319 .vitem &*int&~interface_port*&
35320 The port on which this message was received. When testing with the &%-bh%&
35321 command line option, the value of this variable is -1 unless a port has been
35322 specified via the &%-oMi%& option.
35324 .vitem &*uschar&~*message_id*&
35325 This variable contains Exim's message id for the incoming message (the value of
35326 &$message_exim_id$&) as a zero-terminated string.
35328 .vitem &*uschar&~*received_protocol*&
35329 The name of the protocol by which the message was received.
35331 .vitem &*int&~recipients_count*&
35332 The number of accepted recipients.
35334 .vitem &*recipient_item&~*recipients_list*&
35335 .cindex "recipient" "adding in local scan"
35336 .cindex "recipient" "removing in local scan"
35337 The list of accepted recipients, held in a vector of length
35338 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35339 can add additional recipients by calling &'receive_add_recipient()'& (see
35340 below). You can delete recipients by removing them from the vector and
35341 adjusting the value in &%recipients_count%&. In particular, by setting
35342 &%recipients_count%& to zero you remove all recipients. If you then return the
35343 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35344 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35345 and then call &'receive_add_recipient()'& as often as needed.
35347 .vitem &*uschar&~*sender_address*&
35348 The envelope sender address. For bounce messages this is the empty string.
35350 .vitem &*uschar&~*sender_host_address*&
35351 The IP address of the sending host, as a string. This is NULL for
35352 locally-submitted messages.
35354 .vitem &*uschar&~*sender_host_authenticated*&
35355 The name of the authentication mechanism that was used, or NULL if the message
35356 was not received over an authenticated SMTP connection.
35358 .vitem &*uschar&~*sender_host_name*&
35359 The name of the sending host, if known.
35361 .vitem &*int&~sender_host_port*&
35362 The port on the sending host.
35364 .vitem &*BOOL&~smtp_input*&
35365 This variable is TRUE for all SMTP input, including BSMTP.
35367 .vitem &*BOOL&~smtp_batched_input*&
35368 This variable is TRUE for BSMTP input.
35370 .vitem &*int&~store_pool*&
35371 The contents of this variable control which pool of memory is used for new
35372 requests. See section &<<SECTmemhanloc>>& for details.
35376 .section "Structure of header lines" "SECID209"
35377 The &%header_line%& structure contains the members listed below.
35378 You can add additional header lines by calling the &'header_add()'& function
35379 (see below). You can cause header lines to be ignored (deleted) by setting
35384 .vitem &*struct&~header_line&~*next*&
35385 A pointer to the next header line, or NULL for the last line.
35387 .vitem &*int&~type*&
35388 A code identifying certain headers that Exim recognizes. The codes are printing
35389 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35390 Notice in particular that any header line whose type is * is not transmitted
35391 with the message. This flagging is used for header lines that have been
35392 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35393 lines.) Effectively, * means &"deleted"&.
35395 .vitem &*int&~slen*&
35396 The number of characters in the header line, including the terminating and any
35399 .vitem &*uschar&~*text*&
35400 A pointer to the text of the header. It always ends with a newline, followed by
35401 a zero byte. Internal newlines are preserved.
35406 .section "Structure of recipient items" "SECID210"
35407 The &%recipient_item%& structure contains these members:
35410 .vitem &*uschar&~*address*&
35411 This is a pointer to the recipient address as it was received.
35413 .vitem &*int&~pno*&
35414 This is used in later Exim processing when top level addresses are created by
35415 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35416 and must always contain -1 at this stage.
35418 .vitem &*uschar&~*errors_to*&
35419 If this value is not NULL, bounce messages caused by failing to deliver to the
35420 recipient are sent to the address it contains. In other words, it overrides the
35421 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35422 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35423 an unqualified address, Exim qualifies it using the domain from
35424 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35425 is NULL for all recipients.
35430 .section "Available Exim functions" "SECID211"
35431 .cindex "&[local_scan()]& function" "available Exim functions"
35432 The header &_local_scan.h_& gives you access to a number of Exim functions.
35433 These are the only ones that are guaranteed to be maintained from release to
35437 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35438 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35440 This function creates a child process that runs the command specified by
35441 &%argv%&. The environment for the process is specified by &%envp%&, which can
35442 be NULL if no environment variables are to be passed. A new umask is supplied
35443 for the process in &%newumask%&.
35445 Pipes to the standard input and output of the new process are set up
35446 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35447 standard error is cloned to the standard output. If there are any file
35448 descriptors &"in the way"& in the new process, they are closed. If the final
35449 argument is TRUE, the new process is made into a process group leader.
35451 The function returns the pid of the new process, or -1 if things go wrong.
35453 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35454 This function waits for a child process to terminate, or for a timeout (in
35455 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35456 return value is as follows:
35461 The process terminated by a normal exit and the value is the process
35467 The process was terminated by a signal and the value is the negation of the
35473 The process timed out.
35477 The was some other error in wait(); &%errno%& is still set.
35480 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35481 This function provide you with a means of submitting a new message to
35482 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35483 want, but this packages it all up for you.) The function creates a pipe,
35484 forks a subprocess that is running
35486 exim -t -oem -oi -f <>
35488 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35489 that is connected to the standard input. The yield of the function is the PID
35490 of the subprocess. You can then write a message to the file descriptor, with
35491 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35493 When you have finished, call &'child_close()'& to wait for the process to
35494 finish and to collect its ending status. A timeout value of zero is usually
35495 fine in this circumstance. Unless you have made a mistake with the recipient
35496 addresses, you should get a return code of zero.
35499 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35500 *sender_authentication)*&
35501 This function is a more sophisticated version of &'child_open()'&. The command
35504 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35506 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35509 .vitem &*void&~debug_printf(char&~*,&~...)*&
35510 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35511 output is written to the standard error stream. If no debugging is selected,
35512 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35513 conditional on the &`local_scan`& debug selector by coding like this:
35515 if ((debug_selector & D_local_scan) != 0)
35516 debug_printf("xxx", ...);
35519 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35520 This is an interface to Exim's string expansion code. The return value is the
35521 expanded string, or NULL if there was an expansion failure.
35522 The C variable &%expand_string_message%& contains an error message after an
35523 expansion failure. If expansion does not change the string, the return value is
35524 the pointer to the input string. Otherwise, the return value points to a new
35525 block of memory that was obtained by a call to &'store_get()'&. See section
35526 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35528 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35529 This function allows you to an add additional header line at the end of the
35530 existing ones. The first argument is the type, and should normally be a space
35531 character. The second argument is a format string and any number of
35532 substitution arguments as for &[sprintf()]&. You may include internal newlines
35533 if you want, and you must ensure that the string ends with a newline.
35535 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35536 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35537 This function adds a new header line at a specified point in the header
35538 chain. The header itself is specified as for &'header_add()'&.
35540 If &%name%& is NULL, the new header is added at the end of the chain if
35541 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35542 NULL, the header lines are searched for the first non-deleted header that
35543 matches the name. If one is found, the new header is added before it if
35544 &%after%& is false. If &%after%& is true, the new header is added after the
35545 found header and any adjacent subsequent ones with the same name (even if
35546 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35547 option controls where the header is added. If it is true, addition is at the
35548 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35549 headers, or at the top if there are no &'Received:'& headers, you could use
35551 header_add_at_position(TRUE, US"Received", TRUE,
35552 ' ', "X-xxx: ...");
35554 Normally, there is always at least one non-deleted &'Received:'& header, but
35555 there may not be if &%received_header_text%& expands to an empty string.
35558 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35559 This function removes header lines. If &%occurrence%& is zero or negative, all
35560 occurrences of the header are removed. If occurrence is greater than zero, that
35561 particular instance of the header is removed. If no header(s) can be found that
35562 match the specification, the function does nothing.
35565 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35566 int&~length,&~BOOL&~notdel)*&"
35567 This function tests whether the given header has the given name. It is not just
35568 a string comparison, because white space is permitted between the name and the
35569 colon. If the &%notdel%& argument is true, a false return is forced for all
35570 &"deleted"& headers; otherwise they are not treated specially. For example:
35572 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35574 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35575 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35576 This function base64-encodes a string, which is passed by address and length.
35577 The text may contain bytes of any value, including zero. The result is passed
35578 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35581 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35582 This function decodes a base64-encoded string. Its arguments are a
35583 zero-terminated base64-encoded string and the address of a variable that is set
35584 to point to the result, which is in dynamic memory. The length of the decoded
35585 string is the yield of the function. If the input is invalid base64 data, the
35586 yield is -1. A zero byte is added to the end of the output string to make it
35587 easy to interpret as a C string (assuming it contains no zeros of its own). The
35588 added zero byte is not included in the returned count.
35590 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35591 This function checks for a match in a domain list. Domains are always
35592 matched caselessly. The return value is one of the following:
35594 &`OK `& match succeeded
35595 &`FAIL `& match failed
35596 &`DEFER `& match deferred
35598 DEFER is usually caused by some kind of lookup defer, such as the
35599 inability to contact a database.
35601 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35603 This function checks for a match in a local part list. The third argument
35604 controls case-sensitivity. The return values are as for
35605 &'lss_match_domain()'&.
35607 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35609 This function checks for a match in an address list. The third argument
35610 controls the case-sensitivity of the local part match. The domain is always
35611 matched caselessly. The return values are as for &'lss_match_domain()'&.
35613 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35615 This function checks for a match in a host list. The most common usage is
35618 lss_match_host(sender_host_name, sender_host_address, ...)
35620 .vindex "&$sender_host_address$&"
35621 An empty address field matches an empty item in the host list. If the host name
35622 is NULL, the name corresponding to &$sender_host_address$& is automatically
35623 looked up if a host name is required to match an item in the list. The return
35624 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35625 returns ERROR in the case when it had to look up a host name, but the lookup
35628 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35630 This function writes to Exim's log files. The first argument should be zero (it
35631 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35632 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35633 them. It specifies to which log or logs the message is written. The remaining
35634 arguments are a format and relevant insertion arguments. The string should not
35635 contain any newlines, not even at the end.
35638 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35639 This function adds an additional recipient to the message. The first argument
35640 is the recipient address. If it is unqualified (has no domain), it is qualified
35641 with the &%qualify_recipient%& domain. The second argument must always be -1.
35643 This function does not allow you to specify a private &%errors_to%& address (as
35644 described with the structure of &%recipient_item%& above), because it pre-dates
35645 the addition of that field to the structure. However, it is easy to add such a
35646 value afterwards. For example:
35648 receive_add_recipient(US"monitor@mydom.example", -1);
35649 recipients_list[recipients_count-1].errors_to =
35650 US"postmaster@mydom.example";
35653 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35654 This is a convenience function to remove a named recipient from the list of
35655 recipients. It returns true if a recipient was removed, and false if no
35656 matching recipient could be found. The argument must be a complete email
35663 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35664 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35665 This function decodes strings that are encoded according to RFC 2047. Typically
35666 these are the contents of header lines. First, each &"encoded word"& is decoded
35667 from the Q or B encoding into a byte-string. Then, if provided with the name of
35668 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35669 made to translate the result to the named character set. If this fails, the
35670 binary string is returned with an error message.
35672 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35673 maximum MIME word length is enforced. The third argument is the target
35674 encoding, or NULL if no translation is wanted.
35676 .cindex "binary zero" "in RFC 2047 decoding"
35677 .cindex "RFC 2047" "binary zero in"
35678 If a binary zero is encountered in the decoded string, it is replaced by the
35679 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35680 not be 0 because header lines are handled as zero-terminated strings.
35682 The function returns the result of processing the string, zero-terminated; if
35683 &%lenptr%& is not NULL, the length of the result is set in the variable to
35684 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35686 If an error is encountered, the function returns NULL and uses the &%error%&
35687 argument to return an error message. The variable pointed to by &%error%& is
35688 set to NULL if there is no error; it may be set non-NULL even when the function
35689 returns a non-NULL value if decoding was successful, but there was a problem
35693 .vitem &*int&~smtp_fflush(void)*&
35694 This function is used in conjunction with &'smtp_printf()'&, as described
35697 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35698 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35699 output stream. You should use this function only when there is an SMTP output
35700 stream, that is, when the incoming message is being received via interactive
35701 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35702 is FALSE. If you want to test for an incoming message from another host (as
35703 opposed to a local process that used the &%-bs%& command line option), you can
35704 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35707 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35708 output function, so it can be used for all forms of SMTP connection.
35710 The second argument is used to request that the data be buffered
35711 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35712 This is advisory only, but likely to save on system-calls and packets
35713 sent when a sequence of calls to the function are made.
35715 The argument was added in Exim version 4.90 - changing the API/ABI.
35716 Nobody noticed until 4.93 was imminent, at which point the
35717 ABI version number was incremented.
35719 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35720 must start with an appropriate response code: 550 if you are going to return
35721 LOCAL_SCAN_REJECT, 451 if you are going to return
35722 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35723 initial lines of a multi-line response, the code must be followed by a hyphen
35724 to indicate that the line is not the final response line. You must also ensure
35725 that the lines you write terminate with CRLF. For example:
35727 smtp_printf("550-this is some extra info\r\n");
35728 return LOCAL_SCAN_REJECT;
35730 Note that you can also create multi-line responses by including newlines in
35731 the data returned via the &%return_text%& argument. The added value of using
35732 &'smtp_printf()'& is that, for instance, you could introduce delays between
35733 multiple output lines.
35735 The &'smtp_printf()'& function does not return any error indication, because it
35737 guarantee a flush of
35738 pending output, and therefore does not test
35739 the state of the stream. (In the main code of Exim, flushing and error
35740 detection is done when Exim is ready for the next SMTP input command.) If
35741 you want to flush the output and check for an error (for example, the
35742 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35743 arguments. It flushes the output stream, and returns a non-zero value if there
35746 .vitem &*void&~*store_get(int,BOOL)*&
35747 This function accesses Exim's internal store (memory) manager. It gets a new
35748 chunk of memory whose size is given by the first argument.
35749 The second argument should be given as TRUE if the memory will be used for
35750 data possibly coming from an attacker (eg. the message content),
35751 FALSE if it is locally-sourced.
35752 Exim bombs out if it ever
35753 runs out of memory. See the next section for a discussion of memory handling.
35755 .vitem &*void&~*store_get_perm(int,BOOL)*&
35756 This function is like &'store_get()'&, but it always gets memory from the
35757 permanent pool. See the next section for a discussion of memory handling.
35759 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35762 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35765 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35766 These three functions create strings using Exim's dynamic memory facilities.
35767 The first makes a copy of an entire string. The second copies up to a maximum
35768 number of characters, indicated by the second argument. The third uses a format
35769 and insertion arguments to create a new string. In each case, the result is a
35770 pointer to a new string in the current memory pool. See the next section for
35776 .section "More about Exim's memory handling" "SECTmemhanloc"
35777 .cindex "&[local_scan()]& function" "memory handling"
35778 No function is provided for freeing memory, because that is never needed.
35779 The dynamic memory that Exim uses when receiving a message is automatically
35780 recycled if another message is received by the same process (this applies only
35781 to incoming SMTP connections &-- other input methods can supply only one
35782 message at a time). After receiving the last message, a reception process
35785 Because it is recycled, the normal dynamic memory cannot be used for holding
35786 data that must be preserved over a number of incoming messages on the same SMTP
35787 connection. However, Exim in fact uses two pools of dynamic memory; the second
35788 one is not recycled, and can be used for this purpose.
35790 If you want to allocate memory that remains available for subsequent messages
35791 in the same SMTP connection, you should set
35793 store_pool = POOL_PERM
35795 before calling the function that does the allocation. There is no need to
35796 restore the value if you do not need to; however, if you do want to revert to
35797 the normal pool, you can either restore the previous value of &%store_pool%& or
35798 set it explicitly to POOL_MAIN.
35800 The pool setting applies to all functions that get dynamic memory, including
35801 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35802 There is also a convenience function called &'store_get_perm()'& that gets a
35803 block of memory from the permanent pool while preserving the value of
35810 . ////////////////////////////////////////////////////////////////////////////
35811 . ////////////////////////////////////////////////////////////////////////////
35813 .chapter "System-wide message filtering" "CHAPsystemfilter"
35814 .scindex IIDsysfil1 "filter" "system filter"
35815 .scindex IIDsysfil2 "filtering all mail"
35816 .scindex IIDsysfil3 "system filter"
35817 The previous chapters (on ACLs and the local scan function) describe checks
35818 that can be applied to messages before they are accepted by a host. There is
35819 also a mechanism for checking messages once they have been received, but before
35820 they are delivered. This is called the &'system filter'&.
35822 The system filter operates in a similar manner to users' filter files, but it
35823 is run just once per message (however many recipients the message has).
35824 It should not normally be used as a substitute for routing, because &%deliver%&
35825 commands in a system router provide new envelope recipient addresses.
35826 The system filter must be an Exim filter. It cannot be a Sieve filter.
35828 The system filter is run at the start of a delivery attempt, before any routing
35829 is done. If a message fails to be completely delivered at the first attempt,
35830 the system filter is run again at the start of every retry.
35831 If you want your filter to do something only once per message, you can make use
35832 of the &%first_delivery%& condition in an &%if%& command in the filter to
35833 prevent it happening on retries.
35835 .vindex "&$domain$&"
35836 .vindex "&$local_part$&"
35837 &*Warning*&: Because the system filter runs just once, variables that are
35838 specific to individual recipient addresses, such as &$local_part$& and
35839 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35840 you want to run a centrally-specified filter for each recipient address
35841 independently, you can do so by setting up a suitable &(redirect)& router, as
35842 described in section &<<SECTperaddfil>>& below.
35845 .section "Specifying a system filter" "SECID212"
35846 .cindex "uid (user id)" "system filter"
35847 .cindex "gid (group id)" "system filter"
35848 The name of the file that contains the system filter must be specified by
35849 setting &%system_filter%&. If you want the filter to run under a uid and gid
35850 other than root, you must also set &%system_filter_user%& and
35851 &%system_filter_group%& as appropriate. For example:
35853 system_filter = /etc/mail/exim.filter
35854 system_filter_user = exim
35856 If a system filter generates any deliveries directly to files or pipes (via the
35857 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35858 specified by setting &%system_filter_file_transport%& and
35859 &%system_filter_pipe_transport%&, respectively. Similarly,
35860 &%system_filter_reply_transport%& must be set to handle any messages generated
35861 by the &%reply%& command.
35864 .section "Testing a system filter" "SECID213"
35865 You can run simple tests of a system filter in the same way as for a user
35866 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35867 are permitted only in system filters are recognized.
35869 If you want to test the combined effect of a system filter and a user filter,
35870 you can use both &%-bF%& and &%-bf%& on the same command line.
35874 .section "Contents of a system filter" "SECID214"
35875 The language used to specify system filters is the same as for users' filter
35876 files. It is described in the separate end-user document &'Exim's interface to
35877 mail filtering'&. However, there are some additional features that are
35878 available only in system filters; these are described in subsequent sections.
35879 If they are encountered in a user's filter file or when testing with &%-bf%&,
35882 .cindex "frozen messages" "manual thaw; testing in filter"
35883 There are two special conditions which, though available in users' filter
35884 files, are designed for use in system filters. The condition &%first_delivery%&
35885 is true only for the first attempt at delivering a message, and
35886 &%manually_thawed%& is true only if the message has been frozen, and
35887 subsequently thawed by an admin user. An explicit forced delivery counts as a
35888 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35890 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35891 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35892 succeed, it will not be tried again.
35893 If you want Exim to retry an unseen delivery until it succeeds, you should
35894 arrange to set it up every time the filter runs.
35896 When a system filter finishes running, the values of the variables &$n0$& &--
35897 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35898 users' filter files. Thus a system filter can, for example, set up &"scores"&
35899 to which users' filter files can refer.
35903 .section "Additional variable for system filters" "SECID215"
35904 .vindex "&$recipients$&"
35905 The expansion variable &$recipients$&, containing a list of all the recipients
35906 of the message (separated by commas and white space), is available in system
35907 filters. It is not available in users' filters for privacy reasons.
35911 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35912 .cindex "freezing messages"
35913 .cindex "message" "freezing"
35914 .cindex "message" "forced failure"
35915 .cindex "&%fail%&" "in system filter"
35916 .cindex "&%freeze%& in system filter"
35917 .cindex "&%defer%& in system filter"
35918 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35919 always available in system filters, but are not normally enabled in users'
35920 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35921 for the &(redirect)& router.) These commands can optionally be followed by the
35922 word &%text%& and a string containing an error message, for example:
35924 fail text "this message looks like spam to me"
35926 The keyword &%text%& is optional if the next character is a double quote.
35928 The &%defer%& command defers delivery of the original recipients of the
35929 message. The &%fail%& command causes all the original recipients to be failed,
35930 and a bounce message to be created. The &%freeze%& command suspends all
35931 delivery attempts for the original recipients. In all cases, any new deliveries
35932 that are specified by the filter are attempted as normal after the filter has
35935 The &%freeze%& command is ignored if the message has been manually unfrozen and
35936 not manually frozen since. This means that automatic freezing by a system
35937 filter can be used as a way of checking out suspicious messages. If a message
35938 is found to be all right, manually unfreezing it allows it to be delivered.
35940 .cindex "log" "&%fail%& command log line"
35941 .cindex "&%fail%&" "log line; reducing"
35942 The text given with a fail command is used as part of the bounce message as
35943 well as being written to the log. If the message is quite long, this can fill
35944 up a lot of log space when such failures are common. To reduce the size of the
35945 log message, Exim interprets the text in a special way if it starts with the
35946 two characters &`<<`& and contains &`>>`& later. The text between these two
35947 strings is written to the log, and the rest of the text is used in the bounce
35948 message. For example:
35950 fail "<<filter test 1>>Your message is rejected \
35951 because it contains attachments that we are \
35952 not prepared to receive."
35955 .cindex "loop" "caused by &%fail%&"
35956 Take great care with the &%fail%& command when basing the decision to fail on
35957 the contents of the message, because the bounce message will of course include
35958 the contents of the original message and will therefore trigger the &%fail%&
35959 command again (causing a mail loop) unless steps are taken to prevent this.
35960 Testing the &%error_message%& condition is one way to prevent this. You could
35963 if $message_body contains "this is spam" and not error_message
35964 then fail text "spam is not wanted here" endif
35966 though of course that might let through unwanted bounce messages. The
35967 alternative is clever checking of the body and/or headers to detect bounces
35968 generated by the filter.
35970 The interpretation of a system filter file ceases after a
35972 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35973 set up earlier in the filter file are honoured, so you can use a sequence such
35979 to send a specified message when the system filter is freezing (or deferring or
35980 failing) a message. The normal deliveries for the message do not, of course,
35985 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35986 .cindex "header lines" "adding; in system filter"
35987 .cindex "header lines" "removing; in system filter"
35988 .cindex "filter" "header lines; adding/removing"
35989 Two filter commands that are available only in system filters are:
35991 headers add <string>
35992 headers remove <string>
35994 The argument for the &%headers add%& is a string that is expanded and then
35995 added to the end of the message's headers. It is the responsibility of the
35996 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35997 space is ignored, and if the string is otherwise empty, or if the expansion is
35998 forced to fail, the command has no effect.
36000 You can use &"\n"& within the string, followed by white space, to specify
36001 continued header lines. More than one header may be added in one command by
36002 including &"\n"& within the string without any following white space. For
36005 headers add "X-header-1: ....\n \
36006 continuation of X-header-1 ...\n\
36009 Note that the header line continuation white space after the first newline must
36010 be placed before the backslash that continues the input string, because white
36011 space after input continuations is ignored.
36013 The argument for &%headers remove%& is a colon-separated list of header names.
36014 This command applies only to those headers that are stored with the message;
36015 those that are added at delivery time (such as &'Envelope-To:'& and
36016 &'Return-Path:'&) cannot be removed by this means. If there is more than one
36017 header with the same name, they are all removed.
36019 The &%headers%& command in a system filter makes an immediate change to the set
36020 of header lines that was received with the message (with possible additions
36021 from ACL processing). Subsequent commands in the system filter operate on the
36022 modified set, which also forms the basis for subsequent message delivery.
36023 Unless further modified during routing or transporting, this set of headers is
36024 used for all recipients of the message.
36026 During routing and transporting, the variables that refer to the contents of
36027 header lines refer only to those lines that are in this set. Thus, header lines
36028 that are added by a system filter are visible to users' filter files and to all
36029 routers and transports. This contrasts with the manipulation of header lines by
36030 routers and transports, which is not immediate, but which instead is saved up
36031 until the message is actually being written (see section
36032 &<<SECTheadersaddrem>>&).
36034 If the message is not delivered at the first attempt, header lines that were
36035 added by the system filter are stored with the message, and so are still
36036 present at the next delivery attempt. Header lines that were removed are still
36037 present, but marked &"deleted"& so that they are not transported with the
36038 message. For this reason, it is usual to make the &%headers%& command
36039 conditional on &%first_delivery%& so that the set of header lines is not
36040 modified more than once.
36042 Because header modification in a system filter acts immediately, you have to
36043 use an indirect approach if you want to modify the contents of a header line.
36046 headers add "Old-Subject: $h_subject:"
36047 headers remove "Subject"
36048 headers add "Subject: new subject (was: $h_old-subject:)"
36049 headers remove "Old-Subject"
36054 .section "Setting an errors address in a system filter" "SECID217"
36055 .cindex "envelope from"
36056 .cindex "envelope sender"
36057 In a system filter, if a &%deliver%& command is followed by
36059 errors_to <some address>
36061 in order to change the envelope sender (and hence the error reporting) for that
36062 delivery, any address may be specified. (In a user filter, only the current
36063 user's address can be set.) For example, if some mail is being monitored, you
36066 unseen deliver monitor@spying.example errors_to root@local.example
36068 to take a copy which would not be sent back to the normal error reporting
36069 address if its delivery failed.
36073 .section "Per-address filtering" "SECTperaddfil"
36074 .vindex "&$domain_data$&"
36075 .vindex "&$local_part_data$&"
36076 In contrast to the system filter, which is run just once per message for each
36077 delivery attempt, it is also possible to set up a system-wide filtering
36078 operation that runs once for each recipient address. In this case, variables
36079 such as &$local_part_data$& and &$domain_data$& can be used,
36080 and indeed, the choice of filter file could be made dependent on them.
36081 This is an example of a router which implements such a filter:
36086 domains = +local_domains
36087 file = /central/filters/$local_part_data
36092 The filter is run in a separate process under its own uid. Therefore, either
36093 &%check_local_user%& must be set (as above), in which case the filter is run as
36094 the local user, or the &%user%& option must be used to specify which user to
36095 use. If both are set, &%user%& overrides.
36097 Care should be taken to ensure that none of the commands in the filter file
36098 specify a significant delivery if the message is to go on to be delivered to
36099 its intended recipient. The router will not then claim to have dealt with the
36100 address, so it will be passed on to subsequent routers to be delivered in the
36102 .ecindex IIDsysfil1
36103 .ecindex IIDsysfil2
36104 .ecindex IIDsysfil3
36111 . ////////////////////////////////////////////////////////////////////////////
36112 . ////////////////////////////////////////////////////////////////////////////
36114 .chapter "Message processing" "CHAPmsgproc"
36115 .scindex IIDmesproc "message" "general processing"
36116 Exim performs various transformations on the sender and recipient addresses of
36117 all messages that it handles, and also on the messages' header lines. Some of
36118 these are optional and configurable, while others always take place. All of
36119 this processing, except rewriting as a result of routing, and the addition or
36120 removal of header lines while delivering, happens when a message is received,
36121 before it is placed on Exim's queue.
36123 Some of the automatic processing takes place by default only for
36124 &"locally-originated"& messages. This adjective is used to describe messages
36125 that are not received over TCP/IP, but instead are passed to an Exim process on
36126 its standard input. This includes the interactive &"local SMTP"& case that is
36127 set up by the &%-bs%& command line option.
36129 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36130 or ::1) are not considered to be locally-originated. Exim does not treat the
36131 loopback interface specially in any way.
36133 If you want the loopback interface to be treated specially, you must ensure
36134 that there are appropriate entries in your ACLs.
36139 .section "Submission mode for non-local messages" "SECTsubmodnon"
36140 .cindex "message" "submission"
36141 .cindex "submission mode"
36142 Processing that happens automatically for locally-originated messages (unless
36143 &%suppress_local_fixups%& is set) can also be requested for messages that are
36144 received over TCP/IP. The term &"submission mode"& is used to describe this
36145 state. Submission mode is set by the modifier
36147 control = submission
36149 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36150 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36151 a local submission, and is normally used when the source of the message is
36152 known to be an MUA running on a client host (as opposed to an MTA). For
36153 example, to set submission mode for messages originating on the IPv4 loopback
36154 interface, you could include the following in the MAIL ACL:
36156 warn hosts = 127.0.0.1
36157 control = submission
36159 .cindex "&%sender_retain%& submission option"
36160 There are some options that can be used when setting submission mode. A slash
36161 is used to separate options. For example:
36163 control = submission/sender_retain
36165 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36166 true and &%local_from_check%& false for the current incoming message. The first
36167 of these allows an existing &'Sender:'& header in the message to remain, and
36168 the second suppresses the check to ensure that &'From:'& matches the
36169 authenticated sender. With this setting, Exim still fixes up messages by adding
36170 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36171 attempt to check sender authenticity in header lines.
36173 When &%sender_retain%& is not set, a submission mode setting may specify a
36174 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36177 control = submission/domain=some.domain
36179 The domain may be empty. How this value is used is described in sections
36180 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36181 that allows you to specify the user's full name for inclusion in a created
36182 &'Sender:'& or &'From:'& header line. For example:
36184 accept authenticated = *
36185 control = submission/domain=wonderland.example/\
36186 name=${lookup {$authenticated_id} \
36187 lsearch {/etc/exim/namelist}}
36189 Because the name may contain any characters, including slashes, the &%name%&
36190 option must be given last. The remainder of the string is used as the name. For
36191 the example above, if &_/etc/exim/namelist_& contains:
36193 bigegg: Humpty Dumpty
36195 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36198 Sender: Humpty Dumpty <bigegg@wonderland.example>
36200 .cindex "return path" "in submission mode"
36201 By default, submission mode forces the return path to the same address as is
36202 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36203 specified, the return path is also left unchanged.
36205 &*Note*&: The changes caused by submission mode take effect after the predata
36206 ACL. This means that any sender checks performed before the fix-ups use the
36207 untrusted sender address specified by the user, not the trusted sender address
36208 specified by submission mode. Although this might be slightly unexpected, it
36209 does mean that you can configure ACL checks to spot that a user is trying to
36210 spoof another's address.
36212 .section "Line endings" "SECTlineendings"
36213 .cindex "line endings"
36214 .cindex "carriage return"
36216 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36217 linefeed) is the line ending for messages transmitted over the Internet using
36218 SMTP over TCP/IP. However, within individual operating systems, different
36219 conventions are used. For example, Unix-like systems use just LF, but others
36220 use CRLF or just CR.
36222 Exim was designed for Unix-like systems, and internally, it stores messages
36223 using the system's convention of a single LF as a line terminator. When
36224 receiving a message, all line endings are translated to this standard format.
36225 Originally, it was thought that programs that passed messages directly to an
36226 MTA within an operating system would use that system's convention. Experience
36227 has shown that this is not the case; for example, there are Unix applications
36228 that use CRLF in this circumstance. For this reason, and for compatibility with
36229 other MTAs, the way Exim handles line endings for all messages is now as
36233 LF not preceded by CR is treated as a line ending.
36235 CR is treated as a line ending; if it is immediately followed by LF, the LF
36238 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36239 nor a local message in the state where a line containing only a dot is a
36242 If a bare CR is encountered within a header line, an extra space is added after
36243 the line terminator so as not to end the header line. The reasoning behind this
36244 is that bare CRs in header lines are most likely either to be mistakes, or
36245 people trying to play silly games.
36247 If the first header line received in a message ends with CRLF, a subsequent
36248 bare LF in a header line is treated in the same way as a bare CR in a header
36256 .section "Unqualified addresses" "SECID218"
36257 .cindex "unqualified addresses"
36258 .cindex "address" "qualification"
36259 By default, Exim expects every envelope address it receives from an external
36260 host to be fully qualified. Unqualified addresses cause negative responses to
36261 SMTP commands. However, because SMTP is used as a means of transporting
36262 messages from MUAs running on personal workstations, there is sometimes a
36263 requirement to accept unqualified addresses from specific hosts or IP networks.
36265 Exim has two options that separately control which hosts may send unqualified
36266 sender or recipient addresses in SMTP commands, namely
36267 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36268 cases, if an unqualified address is accepted, it is qualified by adding the
36269 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36271 .oindex "&%qualify_domain%&"
36272 .oindex "&%qualify_recipient%&"
36273 Unqualified addresses in header lines are automatically qualified for messages
36274 that are locally originated, unless the &%-bnq%& option is given on the command
36275 line. For messages received over SMTP, unqualified addresses in header lines
36276 are qualified only if unqualified addresses are permitted in SMTP commands. In
36277 other words, such qualification is also controlled by
36278 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36283 .section "The UUCP From line" "SECID219"
36284 .cindex "&""From""& line"
36285 .cindex "UUCP" "&""From""& line"
36286 .cindex "sender" "address"
36287 .oindex "&%uucp_from_pattern%&"
36288 .oindex "&%uucp_from_sender%&"
36289 .cindex "envelope from"
36290 .cindex "envelope sender"
36291 .cindex "Sendmail compatibility" "&""From""& line"
36292 Messages that have come from UUCP (and some other applications) often begin
36293 with a line containing the envelope sender and a timestamp, following the word
36294 &"From"&. Examples of two common formats are:
36296 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36297 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36299 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36300 Exim recognizes such lines at the start of messages that are submitted to it
36301 via the command line (that is, on the standard input). It does not recognize
36302 such lines in incoming SMTP messages, unless the sending host matches
36303 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36304 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36305 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36306 default value matches the two common cases shown above and puts the address
36307 that follows &"From"& into &$1$&.
36309 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36310 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36311 a trusted user, the message's sender address is constructed by expanding the
36312 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36313 then parsed as an RFC 2822 address. If there is no domain, the local part is
36314 qualified with &%qualify_domain%& unless it is the empty string. However, if
36315 the command line &%-f%& option is used, it overrides the &"From"& line.
36317 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36318 sender address is not changed. This is also the case for incoming SMTP messages
36319 that are permitted to contain &"From"& lines.
36321 Only one &"From"& line is recognized. If there is more than one, the second is
36322 treated as a data line that starts the body of the message, as it is not valid
36323 as a header line. This also happens if a &"From"& line is present in an
36324 incoming SMTP message from a source that is not permitted to send them.
36328 .section "Resent- header lines" "SECID220"
36330 RFC 2822 makes provision for sets of header lines starting with the string
36331 &`Resent-`& to be added to a message when it is resent by the original
36332 recipient to somebody else. These headers are &'Resent-Date:'&,
36333 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36334 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36337 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36338 processing of replies or other such automatic actions on messages.'&
36341 This leaves things a bit vague as far as other processing actions such as
36342 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36346 A &'Resent-From:'& line that just contains the login id of the submitting user
36347 is automatically rewritten in the same way as &'From:'& (see below).
36349 If there's a rewriting rule for a particular header line, it is also applied to
36350 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36351 &'From:'& also rewrites &'Resent-From:'&.
36353 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36356 For a locally-submitted message,
36357 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36358 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36359 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36360 included in log lines in this case.
36362 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36363 &%Resent-%& header lines are present.
36369 .section "The Auto-Submitted: header line" "SECID221"
36370 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36371 includes the header line:
36373 Auto-Submitted: auto-replied
36376 .section "The Bcc: header line" "SECID222"
36377 .cindex "&'Bcc:'& header line"
36378 If Exim is called with the &%-t%& option, to take recipient addresses from a
36379 message's header, it removes any &'Bcc:'& header line that may exist (after
36380 extracting its addresses). If &%-t%& is not present on the command line, any
36381 existing &'Bcc:'& is not removed.
36384 .section "The Date: header line" "SECID223"
36386 If a locally-generated or submission-mode message has no &'Date:'& header line,
36387 Exim adds one, using the current date and time, unless the
36388 &%suppress_local_fixups%& control has been specified.
36390 .section "The Delivery-date: header line" "SECID224"
36391 .cindex "&'Delivery-date:'& header line"
36392 .oindex "&%delivery_date_remove%&"
36393 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36394 set. Exim can be configured to add them to the final delivery of messages. (See
36395 the generic &%delivery_date_add%& transport option.) They should not be present
36396 in messages in transit. If the &%delivery_date_remove%& configuration option is
36397 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36401 .section "The Envelope-to: header line" "SECID225"
36402 .chindex Envelope-to:
36403 .oindex "&%envelope_to_remove%&"
36404 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36405 Exim can be configured to add them to the final delivery of messages. (See the
36406 generic &%envelope_to_add%& transport option.) They should not be present in
36407 messages in transit. If the &%envelope_to_remove%& configuration option is set
36408 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36412 .section "The From: header line" "SECTthefrohea"
36414 .cindex "Sendmail compatibility" "&""From""& line"
36415 .cindex "message" "submission"
36416 .cindex "submission mode"
36417 If a submission-mode message does not contain a &'From:'& header line, Exim
36418 adds one if either of the following conditions is true:
36421 The envelope sender address is not empty (that is, this is not a bounce
36422 message). The added header line copies the envelope sender address.
36424 .vindex "&$authenticated_id$&"
36425 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36427 .vindex "&$qualify_domain$&"
36428 If no domain is specified by the submission control, the local part is
36429 &$authenticated_id$& and the domain is &$qualify_domain$&.
36431 If a non-empty domain is specified by the submission control, the local
36432 part is &$authenticated_id$&, and the domain is the specified domain.
36434 If an empty domain is specified by the submission control,
36435 &$authenticated_id$& is assumed to be the complete address.
36439 A non-empty envelope sender takes precedence.
36441 If a locally-generated incoming message does not contain a &'From:'& header
36442 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36443 containing the sender's address. The calling user's login name and full name
36444 are used to construct the address, as described in section &<<SECTconstr>>&.
36445 They are obtained from the password data by calling &[getpwuid()]& (but see the
36446 &%unknown_login%& configuration option). The address is qualified with
36447 &%qualify_domain%&.
36449 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36450 &'From:'& header line containing just the unqualified login name of the calling
36451 user, this is replaced by an address containing the user's login name and full
36452 name as described in section &<<SECTconstr>>&.
36455 .section "The Message-ID: header line" "SECID226"
36456 .chindex Message-ID:
36457 .cindex "message" "submission"
36458 .oindex "&%message_id_header_text%&"
36459 If a locally-generated or submission-mode incoming message does not contain a
36460 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36461 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36462 to the message. If there are any &'Resent-:'& headers in the message, it
36463 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36464 message id, preceded by the letter E to ensure it starts with a letter, and
36465 followed by @ and the primary host name. Additional information can be included
36466 in this header line by setting the &%message_id_header_text%& and/or
36467 &%message_id_header_domain%& options.
36470 .section "The Received: header line" "SECID227"
36472 A &'Received:'& header line is added at the start of every message. The
36473 contents are defined by the &%received_header_text%& configuration option, and
36474 Exim automatically adds a semicolon and a timestamp to the configured string.
36476 The &'Received:'& header is generated as soon as the message's header lines
36477 have been received. At this stage, the timestamp in the &'Received:'& header
36478 line is the time that the message started to be received. This is the value
36479 that is seen by the DATA ACL and by the &[local_scan()]& function.
36481 Once a message is accepted, the timestamp in the &'Received:'& header line is
36482 changed to the time of acceptance, which is (apart from a small delay while the
36483 -H spool file is written) the earliest time at which delivery could start.
36486 .section "The References: header line" "SECID228"
36487 .chindex References:
36488 Messages created by the &(autoreply)& transport include a &'References:'&
36489 header line. This is constructed according to the rules that are described in
36490 section 3.64 of RFC 2822 (which states that replies should contain such a
36491 header line), and section 3.14 of RFC 3834 (which states that automatic
36492 responses are not different in this respect). However, because some mail
36493 processing software does not cope well with very long header lines, no more
36494 than 12 message IDs are copied from the &'References:'& header line in the
36495 incoming message. If there are more than 12, the first one and then the final
36496 11 are copied, before adding the message ID of the incoming message.
36500 .section "The Return-path: header line" "SECID229"
36501 .chindex Return-path:
36502 .oindex "&%return_path_remove%&"
36503 &'Return-path:'& header lines are defined as something an MTA may insert when
36504 it does the final delivery of messages. (See the generic &%return_path_add%&
36505 transport option.) Therefore, they should not be present in messages in
36506 transit. If the &%return_path_remove%& configuration option is set (the
36507 default), Exim removes &'Return-path:'& header lines from incoming messages.
36511 .section "The Sender: header line" "SECTthesenhea"
36512 .cindex "&'Sender:'& header line"
36513 .cindex "message" "submission"
36515 For a locally-originated message from an untrusted user, Exim may remove an
36516 existing &'Sender:'& header line, and it may add a new one. You can modify
36517 these actions by setting the &%local_sender_retain%& option true, the
36518 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36521 When a local message is received from an untrusted user and
36522 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36523 control has not been set, a check is made to see if the address given in the
36524 &'From:'& header line is the correct (local) sender of the message. The address
36525 that is expected has the login name as the local part and the value of
36526 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36527 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36528 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36529 line is added to the message.
36531 If you set &%local_from_check%& false, this checking does not occur. However,
36532 the removal of an existing &'Sender:'& line still happens, unless you also set
36533 &%local_sender_retain%& to be true. It is not possible to set both of these
36534 options true at the same time.
36536 .cindex "submission mode"
36537 By default, no processing of &'Sender:'& header lines is done for messages
36538 received over TCP/IP or for messages submitted by trusted users. However, when
36539 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36540 not specified on the submission control, the following processing takes place:
36542 .vindex "&$authenticated_id$&"
36543 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36544 authenticated, and &$authenticated_id$& is not empty, a sender address is
36545 created as follows:
36548 .vindex "&$qualify_domain$&"
36549 If no domain is specified by the submission control, the local part is
36550 &$authenticated_id$& and the domain is &$qualify_domain$&.
36552 If a non-empty domain is specified by the submission control, the local part
36553 is &$authenticated_id$&, and the domain is the specified domain.
36555 If an empty domain is specified by the submission control,
36556 &$authenticated_id$& is assumed to be the complete address.
36559 This address is compared with the address in the &'From:'& header line. If they
36560 are different, a &'Sender:'& header line containing the created address is
36561 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36562 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36564 .cindex "return path" "created from &'Sender:'&"
36565 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36566 the message (the envelope sender address) is changed to be the same address,
36567 except in the case of submission mode when &%sender_retain%& is specified.
36571 .section "Adding and removing header lines in routers and transports" &&&
36572 "SECTheadersaddrem"
36573 .cindex "header lines" "adding; in router or transport"
36574 .cindex "header lines" "removing; in router or transport"
36575 When a message is delivered, the addition and removal of header lines can be
36576 specified in a system filter, or on any of the routers and transports that
36577 process the message. Section &<<SECTaddremheasys>>& contains details about
36578 modifying headers in a system filter. Header lines can also be added in an ACL
36579 as a message is received (see section &<<SECTaddheadacl>>&).
36581 In contrast to what happens in a system filter, header modifications that are
36582 specified on routers and transports apply only to the particular recipient
36583 addresses that are being processed by those routers and transports. These
36584 changes do not actually take place until a copy of the message is being
36585 transported. Therefore, they do not affect the basic set of header lines, and
36586 they do not affect the values of the variables that refer to header lines.
36588 &*Note*&: In particular, this means that any expansions in the configuration of
36589 the transport cannot refer to the modified header lines, because such
36590 expansions all occur before the message is actually transported.
36592 For both routers and transports, the argument of a &%headers_add%&
36593 option must be in the form of one or more RFC 2822 header lines, separated by
36594 newlines (coded as &"\n"&). For example:
36596 headers_add = X-added-header: added by $primary_hostname\n\
36597 X-added-second: another added header line
36599 Exim does not check the syntax of these added header lines.
36601 Multiple &%headers_add%& options for a single router or transport can be
36602 specified; the values will append to a single list of header lines.
36603 Each header-line is separately expanded.
36605 The argument of a &%headers_remove%& option must consist of a colon-separated
36606 list of header names. This is confusing, because header names themselves are
36607 often terminated by colons. In this case, the colons are the list separators,
36608 not part of the names. For example:
36610 headers_remove = return-receipt-to:acknowledge-to
36613 Multiple &%headers_remove%& options for a single router or transport can be
36614 specified; the arguments will append to a single header-names list.
36615 Each item is separately expanded.
36616 Note that colons in complex expansions which are used to
36617 form all or part of a &%headers_remove%& list
36618 will act as list separators.
36620 When &%headers_add%& or &%headers_remove%& is specified on a router,
36621 items are expanded at routing time,
36622 and then associated with all addresses that are
36623 accepted by that router, and also with any new addresses that it generates. If
36624 an address passes through several routers as a result of aliasing or
36625 forwarding, the changes are cumulative.
36627 .oindex "&%unseen%&"
36628 However, this does not apply to multiple routers that result from the use of
36629 the &%unseen%& option. Any header modifications that were specified by the
36630 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36632 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36633 settings cannot be delivered together in a batch, so a transport is always
36634 dealing with a set of addresses that have the same header-processing
36637 The transport starts by writing the original set of header lines that arrived
36638 with the message, possibly modified by the system filter. As it writes out
36639 these lines, it consults the list of header names that were attached to the
36640 recipient address(es) by &%headers_remove%& options in routers, and it also
36641 consults the transport's own &%headers_remove%& option. Header lines whose
36642 names are on either of these lists are not written out. If there are multiple
36643 instances of any listed header, they are all skipped.
36645 After the remaining original header lines have been written, new header
36646 lines that were specified by routers' &%headers_add%& options are written, in
36647 the order in which they were attached to the address. These are followed by any
36648 header lines specified by the transport's &%headers_add%& option.
36650 This way of handling header line modifications in routers and transports has
36651 the following consequences:
36654 The original set of header lines, possibly modified by the system filter,
36655 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36656 to it, at all times.
36658 Header lines that are added by a router's
36659 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36660 expansion syntax in subsequent routers or the transport.
36662 Conversely, header lines that are specified for removal by &%headers_remove%&
36663 in a router remain visible to subsequent routers and the transport.
36665 Headers added to an address by &%headers_add%& in a router cannot be removed by
36666 a later router or by a transport.
36668 An added header can refer to the contents of an original header that is to be
36669 removed, even it has the same name as the added header. For example:
36671 headers_remove = subject
36672 headers_add = Subject: new subject (was: $h_subject:)
36676 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36677 for a &(redirect)& router that has the &%one_time%& option set.
36683 .section "Constructed addresses" "SECTconstr"
36684 .cindex "address" "constructed"
36685 .cindex "constructed address"
36686 When Exim constructs a sender address for a locally-generated message, it uses
36689 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36693 Zaphod Beeblebrox <zaphod@end.univ.example>
36695 The user name is obtained from the &%-F%& command line option if set, or
36696 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36697 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36698 ampersand character, this is replaced by the login name with the first letter
36699 upper cased, as is conventional in a number of operating systems. See the
36700 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36701 The &%unknown_username%& option can be used to specify user names in cases when
36702 there is no password file entry.
36705 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36706 parts of it if necessary. In addition, if it contains any non-printing
36707 characters, it is encoded as described in RFC 2047, which defines a way of
36708 including non-ASCII characters in header lines. The value of the
36709 &%headers_charset%& option specifies the name of the encoding that is used (the
36710 characters are assumed to be in this encoding). The setting of
36711 &%print_topbitchars%& controls whether characters with the top bit set (that
36712 is, with codes greater than 127) count as printing characters or not.
36716 .section "Case of local parts" "SECID230"
36717 .cindex "case of local parts"
36718 .cindex "local part" "case of"
36719 RFC 2822 states that the case of letters in the local parts of addresses cannot
36720 be assumed to be non-significant. Exim preserves the case of local parts of
36721 addresses, but by default it uses a lower-cased form when it is routing,
36722 because on most Unix systems, usernames are in lower case and case-insensitive
36723 routing is required. However, any particular router can be made to use the
36724 original case for local parts by setting the &%caseful_local_part%& generic
36727 .cindex "mixed-case login names"
36728 If you must have mixed-case user names on your system, the best way to proceed,
36729 assuming you want case-independent handling of incoming email, is to set up
36730 your first router to convert incoming local parts in your domains to the
36731 correct case by means of a file lookup. For example:
36735 domains = +local_domains
36736 data = ${lookup{$local_part}cdb\
36737 {/etc/usercased.cdb}{$value}fail}\
36740 For this router, the local part is forced to lower case by the default action
36741 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36742 up a new local part in the correct case. If you then set &%caseful_local_part%&
36743 on any subsequent routers which process your domains, they will operate on
36744 local parts with the correct case in a case-sensitive manner.
36748 .section "Dots in local parts" "SECID231"
36749 .cindex "dot" "in local part"
36750 .cindex "local part" "dots in"
36751 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36752 part may not begin or end with a dot, nor have two consecutive dots in the
36753 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36754 empty components for compatibility.
36758 .section "Rewriting addresses" "SECID232"
36759 .cindex "rewriting" "addresses"
36760 Rewriting of sender and recipient addresses, and addresses in headers, can
36761 happen automatically, or as the result of configuration options, as described
36762 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36763 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36765 Automatic rewriting includes qualification, as mentioned above. The other case
36766 in which it can happen is when an incomplete non-local domain is given. The
36767 routing process may cause this to be expanded into the full domain name. For
36768 example, a header such as
36772 might get rewritten as
36774 To: hare@teaparty.wonderland.fict.example
36776 Rewriting as a result of routing is the one kind of message processing that
36777 does not happen at input time, as it cannot be done until the address has
36780 Strictly, one should not do &'any'& deliveries of a message until all its
36781 addresses have been routed, in case any of the headers get changed as a
36782 result of routing. However, doing this in practice would hold up many
36783 deliveries for unreasonable amounts of time, just because one address could not
36784 immediately be routed. Exim therefore does not delay other deliveries when
36785 routing of one or more addresses is deferred.
36786 .ecindex IIDmesproc
36790 . ////////////////////////////////////////////////////////////////////////////
36791 . ////////////////////////////////////////////////////////////////////////////
36793 .chapter "SMTP processing" "CHAPSMTP"
36794 .scindex IIDsmtpproc1 "SMTP" "processing details"
36795 .scindex IIDsmtpproc2 "LMTP" "processing details"
36796 Exim supports a number of different ways of using the SMTP protocol, and its
36797 LMTP variant, which is an interactive protocol for transferring messages into a
36798 closed mail store application. This chapter contains details of how SMTP is
36799 processed. For incoming mail, the following are available:
36802 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36804 SMTP over the standard input and output (the &%-bs%& option);
36806 Batched SMTP on the standard input (the &%-bS%& option).
36809 For mail delivery, the following are available:
36812 SMTP over TCP/IP (the &(smtp)& transport);
36814 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36817 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36820 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36821 the &%use_bsmtp%& option set).
36824 &'Batched SMTP'& is the name for a process in which batches of messages are
36825 stored in or read from files (or pipes), in a format in which SMTP commands are
36826 used to contain the envelope information.
36830 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36831 .cindex "SMTP" "outgoing over TCP/IP"
36832 .cindex "outgoing SMTP over TCP/IP"
36833 .cindex "LMTP" "over TCP/IP"
36834 .cindex "outgoing LMTP over TCP/IP"
36837 .cindex "SIZE" "option on MAIL command"
36838 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36839 The &%protocol%& option selects which protocol is to be used, but the actual
36840 processing is the same in both cases.
36842 .cindex "ESMTP extensions" SIZE
36843 If, in response to its EHLO command, Exim is told that the SIZE
36844 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36845 command. The value of <&'n'&> is the message size plus the value of the
36846 &%size_addition%& option (default 1024) to allow for additions to the message
36847 such as per-transport header lines, or changes made in a
36848 .cindex "transport" "filter"
36849 .cindex "filter" "transport filter"
36850 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36853 If the remote server advertises support for PIPELINING, Exim uses the
36854 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36855 required for the transaction.
36857 If the remote server advertises support for the STARTTLS command, and Exim
36858 was built to support TLS encryption, it tries to start a TLS session unless the
36859 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36860 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36861 is called for verification.
36863 If the remote server advertises support for the AUTH command, Exim scans
36864 the authenticators configuration for any suitable client settings, as described
36865 in chapter &<<CHAPSMTPAUTH>>&.
36867 .cindex "carriage return"
36869 Responses from the remote host are supposed to be terminated by CR followed by
36870 LF. However, there are known to be hosts that do not send CR characters, so in
36871 order to be able to interwork with such hosts, Exim treats LF on its own as a
36874 If a message contains a number of different addresses, all those with the same
36875 characteristics (for example, the same envelope sender) that resolve to the
36876 same set of hosts, in the same order, are sent in a single SMTP transaction,
36877 even if they are for different domains, unless there are more than the setting
36878 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36879 they are split into groups containing no more than &%max_rcpt%&s addresses
36880 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36881 in parallel sessions. The order of hosts with identical MX values is not
36882 significant when checking whether addresses can be batched in this way.
36884 When the &(smtp)& transport suffers a temporary failure that is not
36885 message-related, Exim updates its transport-specific database, which contains
36886 records indexed by host name that remember which messages are waiting for each
36887 particular host. It also updates the retry database with new retry times.
36889 .cindex "hints database" "retry keys"
36890 Exim's retry hints are based on host name plus IP address, so if one address of
36891 a multi-homed host is broken, it will soon be skipped most of the time.
36892 See the next section for more detail about error handling.
36894 .cindex "SMTP" "passed connection"
36895 .cindex "SMTP" "batching over TCP/IP"
36896 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36897 looks in the hints database for the transport to see if there are any queued
36898 messages waiting for the host to which it is connected. If it finds one, it
36899 creates a new Exim process using the &%-MC%& option (which can only be used by
36900 a process running as root or the Exim user) and passes the TCP/IP socket to it
36901 so that it can deliver another message using the same socket. The new process
36902 does only those deliveries that are routed to the connected host, and may in
36903 turn pass the socket on to a third process, and so on.
36905 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36906 limit the number of messages sent down a single TCP/IP connection.
36908 .cindex "asterisk" "after IP address"
36909 The second and subsequent messages delivered down an existing connection are
36910 identified in the main log by the addition of an asterisk after the closing
36911 square bracket of the IP address.
36916 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36917 .cindex "error" "in outgoing SMTP"
36918 .cindex "SMTP" "errors in outgoing"
36919 .cindex "host" "error"
36920 Three different kinds of error are recognized for outgoing SMTP: host errors,
36921 message errors, and recipient errors.
36924 .vitem "&*Host errors*&"
36925 A host error is not associated with a particular message or with a
36926 particular recipient of a message. The host errors are:
36929 Connection refused or timed out,
36931 Any error response code on connection,
36933 Any error response code to EHLO or HELO,
36935 Loss of connection at any time, except after &"."&,
36937 I/O errors at any time,
36939 Timeouts during the session, other than in response to MAIL, RCPT or
36940 the &"."& at the end of the data.
36943 For a host error, a permanent error response on connection, or in response to
36944 EHLO, causes all addresses routed to the host to be failed. Any other host
36945 error causes all addresses to be deferred, and retry data to be created for the
36946 host. It is not tried again, for any message, until its retry time arrives. If
36947 the current set of addresses are not all delivered in this run (to some
36948 alternative host), the message is added to the list of those waiting for this
36949 host, so if it is still undelivered when a subsequent successful delivery is
36950 made to the host, it will be sent down the same SMTP connection.
36952 .vitem "&*Message errors*&"
36953 .cindex "message" "error"
36954 A message error is associated with a particular message when sent to a
36955 particular host, but not with a particular recipient of the message. The
36956 message errors are:
36959 Any error response code to MAIL, DATA, or the &"."& that terminates
36962 Timeout after MAIL,
36964 Timeout or loss of connection after the &"."& that terminates the data. A
36965 timeout after the DATA command itself is treated as a host error, as is loss of
36966 connection at any other time.
36969 For a message error, a permanent error response (5&'xx'&) causes all addresses
36970 to be failed, and a delivery error report to be returned to the sender. A
36971 temporary error response (4&'xx'&), or one of the timeouts, causes all
36972 addresses to be deferred. Retry data is not created for the host, but instead,
36973 a retry record for the combination of host plus message id is created. The
36974 message is not added to the list of those waiting for this host. This ensures
36975 that the failing message will not be sent to this host again until the retry
36976 time arrives. However, other messages that are routed to the host are not
36977 affected, so if it is some property of the message that is causing the error,
36978 it will not stop the delivery of other mail.
36980 If the remote host specified support for the SIZE parameter in its response
36981 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36982 over-large message will cause a message error because the error arrives as a
36985 .vitem "&*Recipient errors*&"
36986 .cindex "recipient" "error"
36987 A recipient error is associated with a particular recipient of a message. The
36988 recipient errors are:
36991 Any error response to RCPT,
36993 Timeout after RCPT.
36996 For a recipient error, a permanent error response (5&'xx'&) causes the
36997 recipient address to be failed, and a bounce message to be returned to the
36998 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36999 address to be deferred, and routing retry data to be created for it. This is
37000 used to delay processing of the address in subsequent queue runs, until its
37001 routing retry time arrives. This applies to all messages, but because it
37002 operates only in queue runs, one attempt will be made to deliver a new message
37003 to the failing address before the delay starts to operate. This ensures that,
37004 if the failure is really related to the message rather than the recipient
37005 (&"message too big for this recipient"& is a possible example), other messages
37006 have a chance of getting delivered. If a delivery to the address does succeed,
37007 the retry information gets cleared, so all stuck messages get tried again, and
37008 the retry clock is reset.
37010 The message is not added to the list of those waiting for this host. Use of the
37011 host for other messages is unaffected, and except in the case of a timeout,
37012 other recipients are processed independently, and may be successfully delivered
37013 in the current SMTP session. After a timeout it is of course impossible to
37014 proceed with the session, so all addresses get deferred. However, those other
37015 than the one that failed do not suffer any subsequent retry delays. Therefore,
37016 if one recipient is causing trouble, the others have a chance of getting
37017 through when a subsequent delivery attempt occurs before the failing
37018 recipient's retry time.
37021 In all cases, if there are other hosts (or IP addresses) available for the
37022 current set of addresses (for example, from multiple MX records), they are
37023 tried in this run for any undelivered addresses, subject of course to their
37024 own retry data. In other words, recipient error retry data does not take effect
37025 until the next delivery attempt.
37027 Some hosts have been observed to give temporary error responses to every
37028 MAIL command at certain times (&"insufficient space"& has been seen). It
37029 would be nice if such circumstances could be recognized, and defer data for the
37030 host itself created, but this is not possible within the current Exim design.
37031 What actually happens is that retry data for every (host, message) combination
37034 The reason that timeouts after MAIL and RCPT are treated specially is that
37035 these can sometimes arise as a result of the remote host's verification
37036 procedures. Exim makes this assumption, and treats them as if a temporary error
37037 response had been received. A timeout after &"."& is treated specially because
37038 it is known that some broken implementations fail to recognize the end of the
37039 message if the last character of the last line is a binary zero. Thus, it is
37040 helpful to treat this case as a message error.
37042 Timeouts at other times are treated as host errors, assuming a problem with the
37043 host, or the connection to it. If a timeout after MAIL, RCPT,
37044 or &"."& is really a connection problem, the assumption is that at the next try
37045 the timeout is likely to occur at some other point in the dialogue, causing it
37046 then to be treated as a host error.
37048 There is experimental evidence that some MTAs drop the connection after the
37049 terminating &"."& if they do not like the contents of the message for some
37050 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37051 should be given. That is why Exim treats this case as a message rather than a
37052 host error, in order not to delay other messages to the same host.
37057 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37058 .cindex "SMTP" "incoming over TCP/IP"
37059 .cindex "incoming SMTP over TCP/IP"
37062 Incoming SMTP messages can be accepted in one of two ways: by running a
37063 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37064 &_/etc/inetd.conf_& should be like this:
37066 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37068 Exim distinguishes between this case and the case of a locally running user
37069 agent using the &%-bs%& option by checking whether or not the standard input is
37070 a socket. When it is, either the port must be privileged (less than 1024), or
37071 the caller must be root or the Exim user. If any other user passes a socket
37072 with an unprivileged port number, Exim prints a message on the standard error
37073 stream and exits with an error code.
37075 By default, Exim does not make a log entry when a remote host connects or
37076 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37077 unexpected. It can be made to write such log entries by setting the
37078 &%smtp_connection%& log selector.
37080 .cindex "carriage return"
37082 Commands from the remote host are supposed to be terminated by CR followed by
37083 LF. However, there are known to be hosts that do not send CR characters. In
37084 order to be able to interwork with such hosts, Exim treats LF on its own as a
37086 Furthermore, because common code is used for receiving messages from all
37087 sources, a CR on its own is also interpreted as a line terminator. However, the
37088 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37090 .cindex "EHLO" "invalid data"
37091 .cindex "HELO" "invalid data"
37092 One area that sometimes gives rise to problems concerns the EHLO or
37093 HELO commands. Some clients send syntactically invalid versions of these
37094 commands, which Exim rejects by default. (This is nothing to do with verifying
37095 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37096 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37097 match the broken hosts that send invalid commands.
37099 .cindex "SIZE option on MAIL command"
37100 .cindex "MAIL" "SIZE option"
37101 The amount of disk space available is checked whenever SIZE is received on
37102 a MAIL command, independently of whether &%message_size_limit%& or
37103 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37104 false. A temporary error is given if there is not enough space. If
37105 &%check_spool_space%& is set, the check is for that amount of space plus the
37106 value given with SIZE, that is, it checks that the addition of the incoming
37107 message will not reduce the space below the threshold.
37109 When a message is successfully received, Exim includes the local message id in
37110 its response to the final &"."& that terminates the data. If the remote host
37111 logs this text it can help with tracing what has happened to a message.
37113 The Exim daemon can limit the number of simultaneous incoming connections it is
37114 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37115 number of simultaneous incoming connections from a single remote host (see the
37116 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37117 rejected using the SMTP temporary error code 421.
37119 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37120 subprocess has finished, as this can get lost at busy times. Instead, it looks
37121 for completed subprocesses every time it wakes up. Provided there are other
37122 things happening (new incoming calls, starts of queue runs), completed
37123 processes will be noticed and tidied away. On very quiet systems you may
37124 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37125 it will be noticed when the daemon next wakes up.
37127 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37128 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37129 high system load &-- for details see the &%smtp_accept_reserve%&,
37130 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37131 applies in both the daemon and &'inetd'& cases.
37133 Exim normally starts a delivery process for each message received, though this
37134 can be varied by means of the &%-odq%& command line option and the
37135 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37136 number of simultaneously running delivery processes started in this way from
37137 SMTP input can be limited by the &%smtp_accept_queue%& and
37138 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37139 subsequently received messages are just put on the input queue without starting
37140 a delivery process.
37142 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37143 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37144 started up from the &'inetd'& daemon, because in that case each connection is
37145 handled by an entirely independent Exim process. Control by load average is,
37146 however, available with &'inetd'&.
37148 Exim can be configured to verify addresses in incoming SMTP commands as they
37149 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37150 to rewrite addresses at this time &-- before any syntax checking is done. See
37151 section &<<SECTrewriteS>>&.
37153 Exim can also be configured to limit the rate at which a client host submits
37154 MAIL and RCPT commands in a single SMTP session. See the
37155 &%smtp_ratelimit_hosts%& option.
37159 .section "Unrecognized SMTP commands" "SECID234"
37160 .cindex "SMTP" "unrecognized commands"
37161 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37162 commands during a single SMTP connection, it drops the connection after sending
37163 the error response to the last command. The default value for
37164 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37165 abuse that subvert web servers into making connections to SMTP ports; in these
37166 circumstances, a number of non-SMTP lines are sent first.
37169 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37170 .cindex "SMTP" "syntax errors"
37171 .cindex "SMTP" "protocol errors"
37172 A syntax error is detected if an SMTP command is recognized, but there is
37173 something syntactically wrong with its data, for example, a malformed email
37174 address in a RCPT command. Protocol errors include invalid command
37175 sequencing such as RCPT before MAIL. If Exim receives more than
37176 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37177 drops the connection after sending the error response to the last command. The
37178 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37179 broken clients that loop sending bad commands (yes, it has been seen).
37183 .section "Use of non-mail SMTP commands" "SECID236"
37184 .cindex "SMTP" "non-mail commands"
37185 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37186 DATA. Exim counts such commands, and drops the connection if there are too
37187 many of them in a single SMTP session. This action catches some
37188 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37189 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37190 defines what &"too many"& means. Its default value is 10.
37192 When a new message is expected, one occurrence of RSET is not counted. This
37193 allows a client to send one RSET between messages (this is not necessary,
37194 but some clients do it). Exim also allows one uncounted occurrence of HELO
37195 or EHLO, and one occurrence of STARTTLS between messages. After
37196 starting up a TLS session, another EHLO is expected, and so it too is not
37199 The first occurrence of AUTH in a connection, or immediately following
37200 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37201 RCPT, DATA, and QUIT are counted.
37203 You can control which hosts are subject to the limit set by
37204 &%smtp_accept_max_nonmail%& by setting
37205 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37206 the limit apply to all hosts. This option means that you can exclude any
37207 specific badly-behaved hosts that you have to live with.
37212 .section "The VRFY and EXPN commands" "SECID237"
37213 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37214 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37215 appropriate) in order to decide whether the command should be accepted or not.
37217 .cindex "VRFY" "processing"
37218 When no ACL is defined for VRFY, or if it rejects without
37219 setting an explicit response code, the command is accepted
37220 (with a 252 SMTP response code)
37221 in order to support awkward clients that do a VRFY before every RCPT.
37222 When VRFY is accepted, it runs exactly the same code as when Exim is
37223 called with the &%-bv%& option, and returns 250/451/550
37224 SMTP response codes.
37226 .cindex "EXPN" "processing"
37227 If no ACL for EXPN is defined, the command is rejected.
37228 When EXPN is accepted, a single-level expansion of the address is done.
37229 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37230 than a verification (the &%-bv%& option). If an unqualified local part is given
37231 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37232 of VRFY and EXPN commands are logged on the main and reject logs, and
37233 VRFY verification failures are logged on the main log for consistency with
37238 .section "The ETRN command" "SECTETRN"
37239 .cindex "ETRN" "processing"
37240 .cindex "ESMTP extensions" ETRN
37241 RFC 1985 describes an ESMTP command called ETRN that is designed to
37242 overcome the security problems of the TURN command (which has fallen into
37243 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37244 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37245 should be accepted or not. If no ACL is defined, the command is rejected.
37247 The ETRN command is concerned with &"releasing"& messages that are awaiting
37248 delivery to certain hosts. As Exim does not organize its message queue by host,
37249 the only form of ETRN that is supported by default is the one where the
37250 text starts with the &"#"& prefix, in which case the remainder of the text is
37251 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37252 the &%-R%& option to happen, with the remainder of the ETRN text as its
37253 argument. For example,
37261 which causes a delivery attempt on all messages with undelivered addresses
37262 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37263 default), Exim prevents the simultaneous execution of more than one queue run
37264 for the same argument string as a result of an ETRN command. This stops
37265 a misbehaving client from starting more than one queue runner at once.
37267 .cindex "hints database" "ETRN serialization"
37268 Exim implements the serialization by means of a hints database in which a
37269 record is written whenever a process is started by ETRN, and deleted when
37270 the process completes. However, Exim does not keep the SMTP session waiting for
37271 the ETRN process to complete. Once ETRN is accepted, the client is sent
37272 a &"success"& return code. Obviously there is scope for hints records to get
37273 left lying around if there is a system or program crash. To guard against this,
37274 Exim ignores any records that are more than six hours old.
37276 .oindex "&%smtp_etrn_command%&"
37277 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37278 used. This specifies a command that is run whenever ETRN is received,
37279 whatever the form of its argument. For
37282 smtp_etrn_command = /etc/etrn_command $domain \
37283 $sender_host_address
37285 .vindex "&$domain$&"
37286 The string is split up into arguments which are independently expanded. The
37287 expansion variable &$domain$& is set to the argument of the ETRN command,
37288 and no syntax checking is done on the contents of this argument. Exim does not
37289 wait for the command to complete, so its status code is not checked. Exim runs
37290 under its own uid and gid when receiving incoming SMTP, so it is not possible
37291 for it to change them before running the command.
37295 .section "Incoming local SMTP" "SECID238"
37296 .cindex "SMTP" "local incoming"
37297 Some user agents use SMTP to pass messages to their local MTA using the
37298 standard input and output, as opposed to passing the envelope on the command
37299 line and writing the message to the standard input. This is supported by the
37300 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37301 messages over TCP/IP (including the use of ACLs), except that the envelope
37302 sender given in a MAIL command is ignored unless the caller is trusted. In
37303 an ACL you can detect this form of SMTP input by testing for an empty host
37304 identification. It is common to have this as the first line in the ACL that
37305 runs for RCPT commands:
37309 This accepts SMTP messages from local processes without doing any other tests.
37313 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37314 .cindex "SMTP" "batched outgoing"
37315 .cindex "batched SMTP output"
37316 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37317 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37318 be output in BSMTP format. No SMTP responses are possible for this form of
37319 delivery. All it is doing is using SMTP commands as a way of transmitting the
37320 envelope along with the message.
37322 The message is written to the file or pipe preceded by the SMTP commands
37323 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37324 the message that start with a dot have an extra dot added. The SMTP command
37325 HELO is not normally used. If it is required, the &%message_prefix%& option
37326 can be used to specify it.
37328 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37329 one recipient address at a time by default. However, you can arrange for them
37330 to handle several addresses at once by setting the &%batch_max%& option. When
37331 this is done for BSMTP, messages may contain multiple RCPT commands. See
37332 chapter &<<CHAPbatching>>& for more details.
37335 When one or more addresses are routed to a BSMTP transport by a router that
37336 sets up a host list, the name of the first host on the list is available to the
37337 transport in the variable &$host$&. Here is an example of such a transport and
37342 driver = manualroute
37343 transport = smtp_appendfile
37344 route_list = domain.example batch.host.example
37348 driver = appendfile
37349 directory = /var/bsmtp/$host
37354 This causes messages addressed to &'domain.example'& to be written in BSMTP
37355 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37356 message (unless there are more than 1000 recipients).
37360 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37361 .cindex "SMTP" "batched incoming"
37362 .cindex "batched SMTP input"
37363 The &%-bS%& command line option causes Exim to accept one or more messages by
37364 reading SMTP on the standard input, but to generate no responses. If the caller
37365 is trusted, the senders in the MAIL commands are believed; otherwise the
37366 sender is always the caller of Exim. Unqualified senders and receivers are not
37367 rejected (there seems little point) but instead just get qualified. HELO
37368 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37369 as NOOP; QUIT quits.
37371 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37372 ACL is run in the same way as for non-SMTP local input.
37374 If an error is detected while reading a message, including a missing &"."& at
37375 the end, Exim gives up immediately. It writes details of the error to the
37376 standard output in a stylized way that the calling program should be able to
37377 make some use of automatically, for example:
37379 554 Unexpected end of file
37380 Transaction started in line 10
37381 Error detected in line 14
37383 It writes a more verbose version, for human consumption, to the standard error
37386 An error was detected while processing a file of BSMTP input.
37387 The error message was:
37389 501 '>' missing at end of address
37391 The SMTP transaction started in line 10.
37392 The error was detected in line 12.
37393 The SMTP command at fault was:
37395 rcpt to:<malformed@in.com.plete
37397 1 previous message was successfully processed.
37398 The rest of the batch was abandoned.
37400 The return code from Exim is zero only if there were no errors. It is 1 if some
37401 messages were accepted before an error was detected, and 2 if no messages were
37403 .ecindex IIDsmtpproc1
37404 .ecindex IIDsmtpproc2
37408 . ////////////////////////////////////////////////////////////////////////////
37409 . ////////////////////////////////////////////////////////////////////////////
37411 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37412 "Customizing messages"
37413 When a message fails to be delivered, or remains in the queue for more than a
37414 configured amount of time, Exim sends a message to the original sender, or
37415 to an alternative configured address. The text of these messages is built into
37416 the code of Exim, but it is possible to change it, either by adding a single
37417 string, or by replacing each of the paragraphs by text supplied in a file.
37419 The &'From:'& and &'To:'& header lines are automatically generated; you can
37420 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37421 option. Exim also adds the line
37423 Auto-Submitted: auto-generated
37425 to all warning and bounce messages,
37428 .section "Customizing bounce messages" "SECID239"
37429 .cindex "customizing" "bounce message"
37430 .cindex "bounce message" "customizing"
37431 If &%bounce_message_text%& is set, its contents are included in the default
37432 message immediately after &"This message was created automatically by mail
37433 delivery software."& The string is not expanded. It is not used if
37434 &%bounce_message_file%& is set.
37436 When &%bounce_message_file%& is set, it must point to a template file for
37437 constructing error messages. The file consists of a series of text items,
37438 separated by lines consisting of exactly four asterisks. If the file cannot be
37439 opened, default text is used and a message is written to the main and panic
37440 logs. If any text item in the file is empty, default text is used for that
37443 .vindex "&$bounce_recipient$&"
37444 .vindex "&$bounce_return_size_limit$&"
37445 Each item of text that is read from the file is expanded, and there are two
37446 expansion variables which can be of use here: &$bounce_recipient$& is set to
37447 the recipient of an error message while it is being created, and
37448 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37449 option, rounded to a whole number.
37451 The items must appear in the file in the following order:
37454 The first item is included in the headers, and should include at least a
37455 &'Subject:'& header. Exim does not check the syntax of these headers.
37457 The second item forms the start of the error message. After it, Exim lists the
37458 failing addresses with their error messages.
37460 The third item is used to introduce any text from pipe transports that is to be
37461 returned to the sender. It is omitted if there is no such text.
37463 The fourth, fifth and sixth items will be ignored and may be empty.
37464 The fields exist for back-compatibility
37467 The default state (&%bounce_message_file%& unset) is equivalent to the
37468 following file, in which the sixth item is empty. The &'Subject:'& and some
37469 other lines have been split in order to fit them on the page:
37471 Subject: Mail delivery failed
37472 ${if eq{$sender_address}{$bounce_recipient}
37473 {: returning message to sender}}
37475 This message was created automatically by mail delivery software.
37477 A message ${if eq{$sender_address}{$bounce_recipient}
37478 {that you sent }{sent by
37482 }}could not be delivered to all of its recipients.
37483 This is a permanent error. The following address(es) failed:
37485 The following text was generated during the delivery attempt(s):
37487 ------ This is a copy of the message, including all the headers.
37490 ------ The body of the message is $message_size characters long;
37492 ------ $bounce_return_size_limit or so are included here.
37495 .section "Customizing warning messages" "SECTcustwarn"
37496 .cindex "customizing" "warning message"
37497 .cindex "warning of delay" "customizing the message"
37498 The option &%warn_message_file%& can be pointed at a template file for use when
37499 warnings about message delays are created. In this case there are only three
37503 The first item is included in the headers, and should include at least a
37504 &'Subject:'& header. Exim does not check the syntax of these headers.
37506 The second item forms the start of the warning message. After it, Exim lists
37507 the delayed addresses.
37509 The third item then ends the message.
37512 The default state is equivalent to the following file, except that some lines
37513 have been split here, in order to fit them on the page:
37515 Subject: Warning: message $message_exim_id delayed
37516 $warn_message_delay
37518 This message was created automatically by mail delivery software.
37520 A message ${if eq{$sender_address}{$warn_message_recipients}
37521 {that you sent }{sent by
37525 }}has not been delivered to all of its recipients after
37526 more than $warn_message_delay in the queue on $primary_hostname.
37528 The message identifier is: $message_exim_id
37529 The subject of the message is: $h_subject
37530 The date of the message is: $h_date
37532 The following address(es) have not yet been delivered:
37534 No action is required on your part. Delivery attempts will
37535 continue for some time, and this warning may be repeated at
37536 intervals if the message remains undelivered. Eventually the
37537 mail delivery software will give up, and when that happens,
37538 the message will be returned to you.
37540 .vindex "&$warn_message_delay$&"
37541 .vindex "&$warn_message_recipients$&"
37542 However, in the default state the subject and date lines are omitted if no
37543 appropriate headers exist. During the expansion of this file,
37544 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37545 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37546 of recipients for the warning message. There may be more than one if there are
37547 multiple addresses with different &%errors_to%& settings on the routers that
37553 . ////////////////////////////////////////////////////////////////////////////
37554 . ////////////////////////////////////////////////////////////////////////////
37556 .chapter "Some common configuration settings" "CHAPcomconreq"
37557 This chapter discusses some configuration settings that seem to be fairly
37558 common. More examples and discussion can be found in the Exim book.
37562 .section "Sending mail to a smart host" "SECID240"
37563 .cindex "smart host" "example router"
37564 If you want to send all mail for non-local domains to a &"smart host"&, you
37565 should replace the default &(dnslookup)& router with a router which does the
37566 routing explicitly:
37568 send_to_smart_host:
37569 driver = manualroute
37570 route_list = !+local_domains smart.host.name
37571 transport = remote_smtp
37573 You can use the smart host's IP address instead of the name if you wish.
37574 If you are using Exim only to submit messages to a smart host, and not for
37575 receiving incoming messages, you can arrange for it to do the submission
37576 synchronously by setting the &%mua_wrapper%& option (see chapter
37577 &<<CHAPnonqueueing>>&).
37582 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37583 .cindex "mailing lists"
37584 Exim can be used to run simple mailing lists, but for large and/or complicated
37585 requirements, the use of additional specialized mailing list software such as
37586 Majordomo or Mailman is recommended.
37588 The &(redirect)& router can be used to handle mailing lists where each list
37589 is maintained in a separate file, which can therefore be managed by an
37590 independent manager. The &%domains%& router option can be used to run these
37591 lists in a separate domain from normal mail. For example:
37595 domains = lists.example
37596 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37599 errors_to = ${quote_local_part:$local_part-request}@lists.example
37602 This router is skipped for domains other than &'lists.example'&. For addresses
37603 in that domain, it looks for a file that matches the local part. If there is no
37604 such file, the router declines, but because &%no_more%& is set, no subsequent
37605 routers are tried, and so the whole delivery fails.
37607 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37608 expanded into a filename or a pipe delivery, which is usually inappropriate in
37611 .oindex "&%errors_to%&"
37612 The &%errors_to%& option specifies that any delivery errors caused by addresses
37613 taken from a mailing list are to be sent to the given address rather than the
37614 original sender of the message. However, before acting on this, Exim verifies
37615 the error address, and ignores it if verification fails.
37617 For example, using the configuration above, mail sent to
37618 &'dicts@lists.example'& is passed on to those addresses contained in
37619 &_/usr/lists/dicts_&, with error reports directed to
37620 &'dicts-request@lists.example'&, provided that this address can be verified.
37621 There could be a file called &_/usr/lists/dicts-request_& containing
37622 the address(es) of this particular list's manager(s), but other approaches,
37623 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37624 or &%local_part_suffix%& options) to handle addresses of the form
37625 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37629 .section "Syntax errors in mailing lists" "SECID241"
37630 .cindex "mailing lists" "syntax errors in"
37631 If an entry in redirection data contains a syntax error, Exim normally defers
37632 delivery of the original address. That means that a syntax error in a mailing
37633 list holds up all deliveries to the list. This may not be appropriate when a
37634 list is being maintained automatically from data supplied by users, and the
37635 addresses are not rigorously checked.
37637 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37638 entries that fail to parse, noting the incident in the log. If in addition
37639 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37640 whenever a broken address is skipped. It is usually appropriate to set
37641 &%syntax_errors_to%& to the same address as &%errors_to%&.
37645 .section "Re-expansion of mailing lists" "SECID242"
37646 .cindex "mailing lists" "re-expansion of"
37647 Exim remembers every individual address to which a message has been delivered,
37648 in order to avoid duplication, but it normally stores only the original
37649 recipient addresses with a message. If all the deliveries to a mailing list
37650 cannot be done at the first attempt, the mailing list is re-expanded when the
37651 delivery is next tried. This means that alterations to the list are taken into
37652 account at each delivery attempt, so addresses that have been added to
37653 the list since the message arrived will therefore receive a copy of the
37654 message, even though it pre-dates their subscription.
37656 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37657 on the &(redirect)& router. If this is done, any addresses generated by the
37658 router that fail to deliver at the first attempt are added to the message as
37659 &"top level"& addresses, and the parent address that generated them is marked
37660 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37661 subsequent delivery attempts. The disadvantage of this is that if any of the
37662 failing addresses are incorrect, correcting them in the file has no effect on
37663 pre-existing messages.
37665 The original top-level address is remembered with each of the generated
37666 addresses, and is output in any log messages. However, any intermediate parent
37667 addresses are not recorded. This makes a difference to the log only if the
37668 &%all_parents%& selector is set, but for mailing lists there is normally only
37669 one level of expansion anyway.
37673 .section "Closed mailing lists" "SECID243"
37674 .cindex "mailing lists" "closed"
37675 The examples so far have assumed open mailing lists, to which anybody may
37676 send mail. It is also possible to set up closed lists, where mail is accepted
37677 from specified senders only. This is done by making use of the generic
37678 &%senders%& option to restrict the router that handles the list.
37680 The following example uses the same file as a list of recipients and as a list
37681 of permitted senders. It requires three routers:
37685 domains = lists.example
37686 local_part_suffix = -request
37687 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37688 file = /usr/lists/${local_part_data}-request
37693 domains = lists.example
37694 senders = ${if exists {/usr/lists/$local_part}\
37695 {lsearch;/usr/lists/$local_part}{*}}
37696 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37699 errors_to = ${quote_local_part:$local_part-request}@lists.example
37704 domains = lists.example
37706 data = :fail: $local_part@lists.example is a closed mailing list
37708 All three routers have the same &%domains%& setting, so for any other domains,
37709 they are all skipped. The first router runs only if the local part ends in
37710 &%-request%&. It handles messages to the list manager(s) by means of an open
37713 The second router runs only if the &%senders%& precondition is satisfied. It
37714 checks for the existence of a list that corresponds to the local part, and then
37715 checks that the sender is on the list by means of a linear search. It is
37716 necessary to check for the existence of the file before trying to search it,
37717 because otherwise Exim thinks there is a configuration error. If the file does
37718 not exist, the expansion of &%senders%& is *, which matches all senders. This
37719 means that the router runs, but because there is no list, declines, and
37720 &%no_more%& ensures that no further routers are run. The address fails with an
37721 &"unrouteable address"& error.
37723 The third router runs only if the second router is skipped, which happens when
37724 a mailing list exists, but the sender is not on it. This router forcibly fails
37725 the address, giving a suitable error message.
37730 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37732 .cindex "Variable Envelope Return Paths"
37733 .cindex "envelope from"
37734 .cindex "envelope sender"
37735 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37736 are a way of helping mailing list administrators discover which subscription
37737 address is the cause of a particular delivery failure. The idea is to encode
37738 the original recipient address in the outgoing envelope sender address, so that
37739 if the message is forwarded by another host and then subsequently bounces, the
37740 original recipient can be extracted from the recipient address of the bounce.
37742 .oindex &%errors_to%&
37743 .oindex &%return_path%&
37744 Envelope sender addresses can be modified by Exim using two different
37745 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37746 list examples), or the &%return_path%& option on a transport. The second of
37747 these is effective only if the message is successfully delivered to another
37748 host; it is not used for errors detected on the local host (see the description
37749 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37750 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37756 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37757 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37759 This has the effect of rewriting the return path (envelope sender) on outgoing
37760 SMTP messages, if the local part of the original return path ends in
37761 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37762 local part and domain of the recipient into the return path. Suppose, for
37763 example, that a message whose return path has been set to
37764 &'somelist-request@your.dom.example'& is sent to
37765 &'subscriber@other.dom.example'&. In the transport, the return path is
37768 somelist-request+subscriber=other.dom.example@your.dom.example
37770 .vindex "&$local_part$&"
37771 For this to work, you must tell Exim to send multiple copies of messages that
37772 have more than one recipient, so that each copy has just one recipient. This is
37773 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37774 might be sent to several different recipients in the same domain, in which case
37775 &$local_part$& is not available in the transport, because it is not unique.
37777 Unless your host is doing nothing but mailing list deliveries, you should
37778 probably use a separate transport for the VERP deliveries, so as not to use
37779 extra resources in making one-per-recipient copies for other deliveries. This
37780 can easily be done by expanding the &%transport%& option in the router:
37784 domains = ! +local_domains
37786 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37787 {verp_smtp}{remote_smtp}}
37790 If you want to change the return path using &%errors_to%& in a router instead
37791 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37792 routers that handle mailing list addresses. This will ensure that all delivery
37793 errors, including those detected on the local host, are sent to the VERP
37796 On a host that does no local deliveries and has no manual routing, only the
37797 &(dnslookup)& router needs to be changed. A special transport is not needed for
37798 SMTP deliveries. Every mailing list recipient has its own return path value,
37799 and so Exim must hand them to the transport one at a time. Here is an example
37800 of a &(dnslookup)& router that implements VERP:
37804 domains = ! +local_domains
37805 transport = remote_smtp
37807 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37808 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37811 Before you start sending out messages with VERPed return paths, you must also
37812 configure Exim to accept the bounce messages that come back to those paths.
37813 Typically this is done by setting a &%local_part_suffix%& option for a
37814 router, and using this to route the messages to wherever you want to handle
37817 The overhead incurred in using VERP depends very much on the size of the
37818 message, the number of recipient addresses that resolve to the same remote
37819 host, and the speed of the connection over which the message is being sent. If
37820 a lot of addresses resolve to the same host and the connection is slow, sending
37821 a separate copy of the message for each address may take substantially longer
37822 than sending a single copy with many recipients (for which VERP cannot be
37830 .section "Virtual domains" "SECTvirtualdomains"
37831 .cindex "virtual domains"
37832 .cindex "domain" "virtual"
37833 The phrase &'virtual domain'& is unfortunately used with two rather different
37837 A domain for which there are no real mailboxes; all valid local parts are
37838 aliases for other email addresses. Common examples are organizational
37839 top-level domains and &"vanity"& domains.
37841 One of a number of independent domains that are all handled by the same host,
37842 with mailboxes on that host, but where the mailbox owners do not necessarily
37843 have login accounts on that host.
37846 The first usage is probably more common, and does seem more &"virtual"& than
37847 the second. This kind of domain can be handled in Exim with a straightforward
37848 aliasing router. One approach is to create a separate alias file for each
37849 virtual domain. Exim can test for the existence of the alias file to determine
37850 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37851 to a router of this form:
37855 domains = dsearch;/etc/mail/virtual
37856 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37859 The &%domains%& option specifies that the router is to be skipped, unless there
37860 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37861 domain that is being processed.
37862 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37863 being placed into the &$domain_data$& variable.
37865 When the router runs, it looks up the local
37866 part in the file to find a new address (or list of addresses). The &%no_more%&
37867 setting ensures that if the lookup fails (leading to &%data%& being an empty
37868 string), Exim gives up on the address without trying any subsequent routers.
37870 This one router can handle all the virtual domains because the alias filenames
37871 follow a fixed pattern. Permissions can be arranged so that appropriate people
37872 can edit the different alias files. A successful aliasing operation results in
37873 a new envelope recipient address, which is then routed from scratch.
37875 The other kind of &"virtual"& domain can also be handled in a straightforward
37876 way. One approach is to create a file for each domain containing a list of
37877 valid local parts, and use it in a router like this:
37881 domains = dsearch;/etc/mail/domains
37882 local_parts = lsearch;/etc/mail/domains/$domain
37883 transport = my_mailboxes
37885 The address is accepted if there is a file for the domain, and the local part
37886 can be found in the file. The &%domains%& option is used to check for the
37887 file's existence because &%domains%& is tested before the &%local_parts%&
37888 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37889 because that option is tested after &%local_parts%&. The transport is as
37893 driver = appendfile
37894 file = /var/mail/$domain_data/$local_part_data
37897 This uses a directory of mailboxes for each domain. The &%user%& setting is
37898 required, to specify which uid is to be used for writing to the mailboxes.
37900 The configuration shown here is just one example of how you might support this
37901 requirement. There are many other ways this kind of configuration can be set
37902 up, for example, by using a database instead of separate files to hold all the
37903 information about the domains.
37907 .section "Multiple user mailboxes" "SECTmulbox"
37908 .cindex "multiple mailboxes"
37909 .cindex "mailbox" "multiple"
37910 .cindex "local part" "prefix"
37911 .cindex "local part" "suffix"
37912 Heavy email users often want to operate with multiple mailboxes, into which
37913 incoming mail is automatically sorted. A popular way of handling this is to
37914 allow users to use multiple sender addresses, so that replies can easily be
37915 identified. Users are permitted to add prefixes or suffixes to their local
37916 parts for this purpose. The wildcard facility of the generic router options
37917 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37918 example, consider this router:
37923 file = $home/.forward
37924 local_part_suffix = -*
37925 local_part_suffix_optional
37928 .vindex "&$local_part_suffix$&"
37929 It runs a user's &_.forward_& file for all local parts of the form
37930 &'username-*'&. Within the filter file the user can distinguish different
37931 cases by testing the variable &$local_part_suffix$&. For example:
37933 if $local_part_suffix contains -special then
37934 save /home/$local_part_data/Mail/special
37937 If the filter file does not exist, or does not deal with such addresses, they
37938 fall through to subsequent routers, and, assuming no subsequent use of the
37939 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37940 control over which suffixes are valid.
37942 Alternatively, a suffix can be used to trigger the use of a different
37943 &_.forward_& file &-- which is the way a similar facility is implemented in
37949 local_part_suffix = -*
37950 local_part_suffix_optional
37951 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37954 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37955 example, &_.forward-special_& is used. Once again, if the appropriate file
37956 does not exist, or does not deal with the address, it is passed on to
37957 subsequent routers, which could, if required, look for an unqualified
37958 &_.forward_& file to use as a default.
37962 .section "Simplified vacation processing" "SECID244"
37963 .cindex "vacation processing"
37964 The traditional way of running the &'vacation'& program is for a user to set up
37965 a pipe command in a &_.forward_& file
37966 (see section &<<SECTspecitredli>>& for syntax details).
37967 This is prone to error by inexperienced users. There are two features of Exim
37968 that can be used to make this process simpler for users:
37971 A local part prefix such as &"vacation-"& can be specified on a router which
37972 can cause the message to be delivered directly to the &'vacation'& program, or
37973 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37974 &_.forward_& file are then much simpler. For example:
37976 spqr, vacation-spqr
37979 The &%require_files%& generic router option can be used to trigger a
37980 vacation delivery by checking for the existence of a certain file in the
37981 user's home directory. The &%unseen%& generic option should also be used, to
37982 ensure that the original delivery also proceeds. In this case, all the user has
37983 to do is to create a file called, say, &_.vacation_&, containing a vacation
37987 Another advantage of both these methods is that they both work even when the
37988 use of arbitrary pipes by users is locked out.
37992 .section "Taking copies of mail" "SECID245"
37993 .cindex "message" "copying every"
37994 Some installations have policies that require archive copies of all messages to
37995 be made. A single copy of each message can easily be taken by an appropriate
37996 command in a system filter, which could, for example, use a different file for
37997 each day's messages.
37999 There is also a shadow transport mechanism that can be used to take copies of
38000 messages that are successfully delivered by local transports, one copy per
38001 delivery. This could be used, &'inter alia'&, to implement automatic
38002 notification of delivery by sites that insist on doing such things.
38006 .section "Intermittently connected hosts" "SECID246"
38007 .cindex "intermittently connected hosts"
38008 It has become quite common (because it is cheaper) for hosts to connect to the
38009 Internet periodically rather than remain connected all the time. The normal
38010 arrangement is that mail for such hosts accumulates on a system that is
38011 permanently connected.
38013 Exim was designed for use on permanently connected hosts, and so it is not
38014 particularly well-suited to use in an intermittently connected environment.
38015 Nevertheless there are some features that can be used.
38018 .section "Exim on the upstream server host" "SECID247"
38019 It is tempting to arrange for incoming mail for the intermittently connected
38020 host to remain in Exim's queue until the client connects. However, this
38021 approach does not scale very well. Two different kinds of waiting message are
38022 being mixed up in the same queue &-- those that cannot be delivered because of
38023 some temporary problem, and those that are waiting for their destination host
38024 to connect. This makes it hard to manage the queue, as well as wasting
38025 resources, because each queue runner scans the entire queue.
38027 A better approach is to separate off those messages that are waiting for an
38028 intermittently connected host. This can be done by delivering these messages
38029 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38030 format, from where they are transmitted by other software when their
38031 destination connects. This makes it easy to collect all the mail for one host
38032 in a single directory, and to apply local timeout rules on a per-message basis
38035 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38036 you are doing this, you should configure Exim with a long retry period for the
38037 intermittent host. For example:
38039 cheshire.wonderland.fict.example * F,5d,24h
38041 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38042 which messages it has queued up for that host. Once the intermittent host comes
38043 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38044 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38045 causes all the queued up messages to be delivered, often down a single SMTP
38046 connection. While the host remains connected, any new messages get delivered
38049 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38050 issued with a different IP address each time it connects, Exim's retry
38051 mechanisms on the holding host get confused, because the IP address is normally
38052 used as part of the key string for holding retry information. This can be
38053 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38054 Since this has disadvantages for permanently connected hosts, it is best to
38055 arrange a separate transport for the intermittently connected ones.
38059 .section "Exim on the intermittently connected client host" "SECID248"
38060 The value of &%smtp_accept_queue_per_connection%& should probably be
38061 increased, or even set to zero (that is, disabled) on the intermittently
38062 connected host, so that all incoming messages down a single connection get
38063 delivered immediately.
38065 .cindex "SMTP" "passed connection"
38066 .cindex "SMTP" "multiple deliveries"
38067 .cindex "multiple SMTP deliveries"
38068 .cindex "first pass routing"
38069 Mail waiting to be sent from an intermittently connected host will probably
38070 not have been routed, because without a connection DNS lookups are not
38071 possible. This means that if a normal queue run is done at connection time,
38072 each message is likely to be sent in a separate SMTP session. This can be
38073 avoided by starting the queue run with a command line option beginning with
38074 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38075 first pass, routing is done but no deliveries take place. The second pass is a
38076 normal queue run; since all the messages have been previously routed, those
38077 destined for the same host are likely to get sent as multiple deliveries in a
38078 single SMTP connection.
38082 . ////////////////////////////////////////////////////////////////////////////
38083 . ////////////////////////////////////////////////////////////////////////////
38085 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38086 "Exim as a non-queueing client"
38087 .cindex "client, non-queueing"
38088 .cindex "smart host" "suppressing queueing"
38089 On a personal computer, it is a common requirement for all
38090 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38091 configured to operate that way, for all the popular operating systems.
38092 However, there are some MUAs for Unix-like systems that cannot be so
38093 configured: they submit messages using the command line interface of
38094 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38097 If the personal computer runs continuously, there is no problem, because it can
38098 run a conventional MTA that handles delivery to the smart host, and deal with
38099 any delays via its queueing mechanism. However, if the computer does not run
38100 continuously or runs different operating systems at different times, queueing
38101 email is not desirable.
38103 There is therefore a requirement for something that can provide the
38104 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38105 any queueing or retrying facilities. Furthermore, the delivery to the smart
38106 host should be synchronous, so that if it fails, the sending MUA is immediately
38107 informed. In other words, we want something that extends an MUA that submits
38108 to a local MTA via the command line so that it behaves like one that submits
38109 to a remote smart host using TCP/SMTP.
38111 There are a number of applications (for example, there is one called &'ssmtp'&)
38112 that do this job. However, people have found them to be lacking in various
38113 ways. For instance, you might want to allow aliasing and forwarding to be done
38114 before sending a message to the smart host.
38116 Exim already had the necessary infrastructure for doing this job. Just a few
38117 tweaks were needed to make it behave as required, though it is somewhat of an
38118 overkill to use a fully-featured MTA for this purpose.
38120 .oindex "&%mua_wrapper%&"
38121 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38122 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38123 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38124 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38125 compatible router and transport configuration. Typically there will be just one
38126 router and one transport, sending everything to a smart host.
38128 When run in MUA wrapping mode, the behaviour of Exim changes in the
38132 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38133 In other words, the only way to submit messages is via the command line.
38135 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38136 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38137 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38138 does not finish until the delivery attempt is complete. If the delivery is
38139 successful, a zero return code is given.
38141 Address redirection is permitted, but the final routing for all addresses must
38142 be to the same remote transport, and to the same list of hosts. Furthermore,
38143 the return address (envelope sender) must be the same for all recipients, as
38144 must any added or deleted header lines. In other words, it must be possible to
38145 deliver the message in a single SMTP transaction, however many recipients there
38148 If these conditions are not met, or if routing any address results in a
38149 failure or defer status, or if Exim is unable to deliver all the recipients
38150 successfully to one of the smart hosts, delivery of the entire message fails.
38152 Because no queueing is allowed, all failures are treated as permanent; there
38153 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38154 smart host. Furthermore, because only a single yes/no response can be given to
38155 the caller, it is not possible to deliver to some recipients and not others. If
38156 there is an error (temporary or permanent) for any recipient, all are failed.
38158 If more than one smart host is listed, Exim will try another host after a
38159 connection failure or a timeout, in the normal way. However, if this kind of
38160 failure happens for all the hosts, the delivery fails.
38162 When delivery fails, an error message is written to the standard error stream
38163 (as well as to Exim's log), and Exim exits to the caller with a return code
38164 value 1. The message is expunged from Exim's spool files. No bounce messages
38165 are ever generated.
38167 No retry data is maintained, and any retry rules are ignored.
38169 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38170 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38171 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38174 The overall effect is that Exim makes a single synchronous attempt to deliver
38175 the message, failing if there is any kind of problem. Because no local
38176 deliveries are done and no daemon can be run, Exim does not need root
38177 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38178 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38179 the advantages and disadvantages of running without root privilege.
38184 . ////////////////////////////////////////////////////////////////////////////
38185 . ////////////////////////////////////////////////////////////////////////////
38187 .chapter "Log files" "CHAPlog"
38188 .scindex IIDloggen "log" "general description"
38189 .cindex "log" "types of"
38190 Exim writes three different logs, referred to as the main log, the reject log,
38195 The main log records the arrival of each message and each delivery in a single
38196 line in each case. The format is as compact as possible, in an attempt to keep
38197 down the size of log files. Two-character flag sequences make it easy to pick
38198 out these lines. A number of other events are recorded in the main log. Some of
38199 them are optional, in which case the &%log_selector%& option controls whether
38200 they are included or not. A Perl script called &'eximstats'&, which does simple
38201 analysis of main log files, is provided in the Exim distribution (see section
38202 &<<SECTmailstat>>&).
38204 .cindex "reject log"
38205 The reject log records information from messages that are rejected as a result
38206 of a configuration option (that is, for policy reasons).
38207 The first line of each rejection is a copy of the line that is also written to
38208 the main log. Then, if the message's header has been read at the time the log
38209 is written, its contents are written to this log. Only the original header
38210 lines are available; header lines added by ACLs are not logged. You can use the
38211 reject log to check that your policy controls are working correctly; on a busy
38212 host this may be easier than scanning the main log for rejection messages. You
38213 can suppress the writing of the reject log by setting &%write_rejectlog%&
38216 .cindex "panic log"
38217 .cindex "system log"
38218 When certain serious errors occur, Exim writes entries to its panic log. If the
38219 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38220 are usually written to the main log as well, but can get lost amid the mass of
38221 other entries. The panic log should be empty under normal circumstances. It is
38222 therefore a good idea to check it (or to have a &'cron'& script check it)
38223 regularly, in order to become aware of any problems. When Exim cannot open its
38224 panic log, it tries as a last resort to write to the system log (syslog). This
38225 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38226 message itself is written at priority LOG_CRIT.
38229 Every log line starts with a timestamp, in the format shown in the following
38230 example. Note that many of the examples shown in this chapter are line-wrapped.
38231 In the log file, this would be all on one line:
38233 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38236 By default, the timestamps are in the local timezone. There are two
38237 ways of changing this:
38240 You can set the &%timezone%& option to a different time zone; in particular, if
38245 the timestamps will be in UTC (aka GMT).
38247 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38250 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38254 .cindex "log" "process ids in"
38255 .cindex "pid (process id)" "in log lines"
38256 Exim does not include its process id in log lines by default, but you can
38257 request that it does so by specifying the &`pid`& log selector (see section
38258 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38259 brackets, immediately after the time and date.
38264 .section "Where the logs are written" "SECTwhelogwri"
38265 .cindex "log" "destination"
38266 .cindex "log" "to file"
38267 .cindex "log" "to syslog"
38269 The logs may be written to local files, or to syslog, or both. However, it
38270 should be noted that many syslog implementations use UDP as a transport, and
38271 are therefore unreliable in the sense that messages are not guaranteed to
38272 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38273 It has also been reported that on large log files (tens of megabytes) you may
38274 need to tweak syslog to prevent it syncing the file with each write &-- on
38275 Linux this has been seen to make syslog take 90% plus of CPU time.
38277 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38278 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38279 configuration. This latter string is expanded, so it can contain, for example,
38280 references to the host name:
38282 log_file_path = /var/log/$primary_hostname/exim_%slog
38284 It is generally advisable, however, to set the string in &_Local/Makefile_&
38285 rather than at runtime, because then the setting is available right from the
38286 start of Exim's execution. Otherwise, if there's something it wants to log
38287 before it has read the configuration file (for example, an error in the
38288 configuration file) it will not use the path you want, and may not be able to
38291 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38292 list, currently limited to at most two items. This is one option where the
38293 facility for changing a list separator may not be used. The list must always be
38294 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38295 otherwise the item must either be an absolute path, containing &`%s`& at the
38296 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38297 implying the use of a default path.
38299 When Exim encounters an empty item in the list, it searches the list defined by
38300 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38301 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38302 mean &"use the path specified at build time"&. If no such item exists, log
38303 files are written in the &_log_& subdirectory of the spool directory. This is
38304 equivalent to the setting:
38306 log_file_path = $spool_directory/log/%slog
38308 If you do not specify anything at build time or runtime,
38309 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38310 that is where the logs are written.
38312 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38313 are in use &-- see section &<<SECTdatlogfil>>& below.
38315 Here are some examples of possible settings:
38317 &`LOG_FILE_PATH=syslog `& syslog only
38318 &`LOG_FILE_PATH=:syslog `& syslog and default path
38319 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38320 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38322 If there are more than two paths in the list, the first is used and a panic
38327 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38328 .cindex "log" "cycling local files"
38329 .cindex "cycling logs"
38330 .cindex "&'exicyclog'&"
38331 .cindex "log" "local files; writing to"
38332 Some operating systems provide centralized and standardized methods for cycling
38333 log files. For those that do not, a utility script called &'exicyclog'& is
38334 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38335 main and reject logs each time it is called. The maximum number of old logs to
38336 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38338 An Exim delivery process opens the main log when it first needs to write to it,
38339 and it keeps the file open in case subsequent entries are required &-- for
38340 example, if a number of different deliveries are being done for the same
38341 message. However, remote SMTP deliveries can take a long time, and this means
38342 that the file may be kept open long after it is renamed if &'exicyclog'& or
38343 something similar is being used to rename log files on a regular basis. To
38344 ensure that a switch of log files is noticed as soon as possible, Exim calls
38345 &[stat()]& on the main log's name before reusing an open file, and if the file
38346 does not exist, or its inode has changed, the old file is closed and Exim
38347 tries to open the main log from scratch. Thus, an old log file may remain open
38348 for quite some time, but no Exim processes should write to it once it has been
38353 .section "Datestamped log files" "SECTdatlogfil"
38354 .cindex "log" "datestamped files"
38355 Instead of cycling the main and reject log files by renaming them
38356 periodically, some sites like to use files whose names contain a datestamp,
38357 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38358 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38359 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38360 point where the datestamp is required. For example:
38362 log_file_path = /var/spool/exim/log/%slog-%D
38363 log_file_path = /var/log/exim-%s-%D.log
38364 log_file_path = /var/spool/exim/log/%D-%slog
38365 log_file_path = /var/log/exim/%s.%M
38367 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38368 examples of names generated by the above examples:
38370 /var/spool/exim/log/mainlog-20021225
38371 /var/log/exim-reject-20021225.log
38372 /var/spool/exim/log/20021225-mainlog
38373 /var/log/exim/main.200212
38375 When this form of log file is specified, Exim automatically switches to new
38376 files at midnight. It does not make any attempt to compress old logs; you
38377 will need to write your own script if you require this. You should not
38378 run &'exicyclog'& with this form of logging.
38380 The location of the panic log is also determined by &%log_file_path%&, but it
38381 is not datestamped, because rotation of the panic log does not make sense.
38382 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38383 the string. In addition, if it immediately follows a slash, a following
38384 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38385 character is removed. Thus, the four examples above would give these panic
38388 /var/spool/exim/log/paniclog
38389 /var/log/exim-panic.log
38390 /var/spool/exim/log/paniclog
38391 /var/log/exim/panic
38395 .section "Logging to syslog" "SECID249"
38396 .cindex "log" "syslog; writing to"
38397 The use of syslog does not change what Exim logs or the format of its messages,
38398 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38399 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38400 that, the same strings are written to syslog as to log files. The syslog
38401 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38402 by default, but you can change these by setting the &%syslog_facility%& and
38403 &%syslog_processname%& options, respectively. If Exim was compiled with
38404 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38405 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38406 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38407 the time and host name to each line.
38408 The three log streams are mapped onto syslog priorities as follows:
38411 &'mainlog'& is mapped to LOG_INFO
38413 &'rejectlog'& is mapped to LOG_NOTICE
38415 &'paniclog'& is mapped to LOG_ALERT
38418 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38419 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38420 these are routed by syslog to the same place. You can suppress this duplication
38421 by setting &%syslog_duplication%& false.
38423 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38424 entries contain multiple lines when headers are included. To cope with both
38425 these cases, entries written to syslog are split into separate &[syslog()]&
38426 calls at each internal newline, and also after a maximum of
38427 870 data characters. (This allows for a total syslog line length of 1024, when
38428 additions such as timestamps are added.) If you are running a syslog
38429 replacement that can handle lines longer than the 1024 characters allowed by
38430 RFC 3164, you should set
38432 SYSLOG_LONG_LINES=yes
38434 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38435 lines, but it still splits at internal newlines in &'reject'& log entries.
38437 To make it easy to re-assemble split lines later, each component of a split
38438 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38439 where <&'n'&> is the component number and <&'m'&> is the total number of
38440 components in the entry. The / delimiter is used when the line was split
38441 because it was too long; if it was split because of an internal newline, the \
38442 delimiter is used. For example, supposing the length limit to be 50 instead of
38443 870, the following would be the result of a typical rejection message to
38444 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38445 name, and pid as added by syslog:
38447 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38448 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38449 [3/5] when scanning for sender: missing or malformed lo
38450 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38453 The same error might cause the following lines to be written to &"rejectlog"&
38456 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38457 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38458 [3/18] er when scanning for sender: missing or malformed
38459 [4/18] local part in "<>" (envelope sender is <ph10@cam
38461 [6\18] Recipients: ph10@some.domain.cam.example
38462 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38463 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38464 [9\18] id 16RdAL-0006pc-00
38465 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38466 [11\18] 09:43 +0100
38468 [13\18] Subject: this is a test header
38469 [18\18] X-something: this is another header
38470 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38473 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38475 Log lines that are neither too long nor contain newlines are written to syslog
38476 without modification.
38478 If only syslog is being used, the Exim monitor is unable to provide a log tail
38479 display, unless syslog is routing &'mainlog'& to a file on the local host and
38480 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38485 .section "Log line flags" "SECID250"
38486 One line is written to the main log for each message received, and for each
38487 successful, unsuccessful, and delayed delivery. These lines can readily be
38488 picked out by the distinctive two-character flags that immediately follow the
38489 timestamp. The flags are:
38491 &`<=`& message arrival
38492 &`(=`& message fakereject
38493 &`=>`& normal message delivery
38494 &`->`& additional address in same delivery
38495 &`>>`& cutthrough message delivery
38496 &`*>`& delivery suppressed by &%-N%&
38497 &`**`& delivery failed; address bounced
38498 &`==`& delivery deferred; temporary problem
38502 .section "Logging message reception" "SECID251"
38503 .cindex "log" "reception line"
38504 The format of the single-line entry in the main log that is written for every
38505 message received is shown in the basic example below, which is split over
38506 several lines in order to fit it on the page:
38508 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38509 H=mailer.fict.example [192.168.123.123] U=exim
38510 P=smtp S=5678 id=<incoming message id>
38512 The address immediately following &"<="& is the envelope sender address. A
38513 bounce message is shown with the sender address &"<>"&, and if it is locally
38514 generated, this is followed by an item of the form
38518 which is a reference to the message that caused the bounce to be sent.
38522 For messages from other hosts, the H and U fields identify the remote host and
38523 record the RFC 1413 identity of the user that sent the message, if one was
38524 received. The number given in square brackets is the IP address of the sending
38525 host. If there is a single, unparenthesized host name in the H field, as
38526 above, it has been verified to correspond to the IP address (see the
38527 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38528 by the remote host in the SMTP HELO or EHLO command, and has not been
38529 verified. If verification yields a different name to that given for HELO or
38530 EHLO, the verified name appears first, followed by the HELO or EHLO
38531 name in parentheses.
38533 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38534 without brackets, in the HELO or EHLO command, leading to entries in
38535 the log containing text like these examples:
38537 H=(10.21.32.43) [192.168.8.34]
38538 H=([10.21.32.43]) [192.168.8.34]
38540 This can be confusing. Only the final address in square brackets can be relied
38543 For locally generated messages (that is, messages not received over TCP/IP),
38544 the H field is omitted, and the U field contains the login name of the caller
38547 .cindex "authentication" "logging"
38548 .cindex "AUTH" "logging"
38549 For all messages, the P field specifies the protocol used to receive the
38550 message. This is the value that is stored in &$received_protocol$&. In the case
38551 of incoming SMTP messages, the value indicates whether or not any SMTP
38552 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38553 session was encrypted, there is an additional X field that records the cipher
38554 suite that was used.
38556 .cindex log protocol
38557 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38558 hosts that have authenticated themselves using the SMTP AUTH command. The first
38559 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38560 there is an additional item A= followed by the name of the authenticator that
38561 was used. If an authenticated identification was set up by the authenticator's
38562 &%server_set_id%& option, this is logged too, separated by a colon from the
38563 authenticator name.
38565 .cindex "size" "of message"
38566 The id field records the existing message id, if present. The size of the
38567 received message is given by the S field. When the message is delivered,
38568 headers may be removed or added, so that the size of delivered copies of the
38569 message may not correspond with this value (and indeed may be different to each
38572 The &%log_selector%& option can be used to request the logging of additional
38573 data when a message is received. See section &<<SECTlogselector>>& below.
38577 .section "Logging deliveries" "SECID252"
38578 .cindex "log" "delivery line"
38579 The format of the single-line entry in the main log that is written for every
38580 delivery is shown in one of the examples below, for local and remote
38581 deliveries, respectively. Each example has been split into multiple lines in order
38582 to fit it on the page:
38584 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38585 <marv@hitch.fict.example> R=localuser T=local_delivery
38586 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38587 monk@holistic.fict.example R=dnslookup T=remote_smtp
38588 H=holistic.fict.example [192.168.234.234]
38590 For ordinary local deliveries, the original address is given in angle brackets
38591 after the final delivery address, which might be a pipe or a file. If
38592 intermediate address(es) exist between the original and the final address, the
38593 last of these is given in parentheses after the final address. The R and T
38594 fields record the router and transport that were used to process the address.
38596 If SMTP AUTH was used for the delivery there is an additional item A=
38597 followed by the name of the authenticator that was used.
38598 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38599 option, this is logged too, as a second colon-separated list item.
38600 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38602 If a shadow transport was run after a successful local delivery, the log line
38603 for the successful delivery has an item added on the end, of the form
38605 &`ST=<`&&'shadow transport name'&&`>`&
38607 If the shadow transport did not succeed, the error message is put in
38608 parentheses afterwards.
38610 .cindex "asterisk" "after IP address"
38611 When more than one address is included in a single delivery (for example, two
38612 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38613 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38614 down a single SMTP connection, an asterisk follows the
38616 remote IP address (and port if enabled)
38618 in the log lines for the second and subsequent messages.
38619 When two or more messages are delivered down a single TLS connection, the
38620 DNS and some TLS-related information logged for the first message delivered
38621 will not be present in the log lines for the second and subsequent messages.
38622 TLS cipher information is still available.
38624 .cindex "delivery" "cutthrough; logging"
38625 .cindex "cutthrough" "logging"
38626 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38627 line precedes the reception line, since cutthrough waits for a possible
38628 rejection from the destination in case it can reject the sourced item.
38630 The generation of a reply message by a filter file gets logged as a
38631 &"delivery"& to the addressee, preceded by &">"&.
38633 The &%log_selector%& option can be used to request the logging of additional
38634 data when a message is delivered. See section &<<SECTlogselector>>& below.
38637 .section "Discarded deliveries" "SECID253"
38638 .cindex "discarded messages"
38639 .cindex "message" "discarded"
38640 .cindex "delivery" "discarded; logging"
38641 When a message is discarded as a result of the command &"seen finish"& being
38642 obeyed in a filter file which generates no deliveries, a log entry of the form
38644 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38645 <low.club@bridge.example> R=userforward
38647 is written, to record why no deliveries are logged. When a message is discarded
38648 because it is aliased to &":blackhole:"& the log line is like this:
38650 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38651 <hole@nowhere.example> R=blackhole_router
38655 .section "Deferred deliveries" "SECID254"
38656 When a delivery is deferred, a line of the following form is logged:
38658 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38659 R=dnslookup T=smtp defer (146): Connection refused
38661 In the case of remote deliveries, the error is the one that was given for the
38662 last IP address that was tried. Details of individual SMTP failures are also
38663 written to the log, so the above line would be preceded by something like
38665 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38666 mail1.endrest.example [192.168.239.239]: Connection refused
38668 When a deferred address is skipped because its retry time has not been reached,
38669 a message is written to the log, but this can be suppressed by setting an
38670 appropriate value in &%log_selector%&.
38674 .section "Delivery failures" "SECID255"
38675 .cindex "delivery" "failure; logging"
38676 If a delivery fails because an address cannot be routed, a line of the
38677 following form is logged:
38679 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38680 <jim@trek99.example>: unknown mail domain
38682 If a delivery fails at transport time, the router and transport are shown, and
38683 the response from the remote host is included, as in this example:
38685 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38686 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38687 after pipelined RCPT TO:<ace400@pb.example>: host
38688 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38689 <ace400@pb.example>...Addressee unknown
38691 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38692 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38693 disabling PIPELINING. The log lines for all forms of delivery failure are
38694 flagged with &`**`&.
38698 .section "Fake deliveries" "SECID256"
38699 .cindex "delivery" "fake; logging"
38700 If a delivery does not actually take place because the &%-N%& option has been
38701 used to suppress it, a normal delivery line is written to the log, except that
38702 &"=>"& is replaced by &"*>"&.
38706 .section "Completion" "SECID257"
38709 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38711 is written to the main log when a message is about to be removed from the spool
38712 at the end of its processing.
38717 .section "Summary of Fields in Log Lines" "SECID258"
38718 .cindex "log" "summary of fields"
38719 A summary of the field identifiers that are used in log lines is shown in
38720 the following table:
38722 &`A `& authenticator name (and optional id and sender)
38723 &`C `& SMTP confirmation on delivery
38724 &` `& command list for &"no mail in SMTP session"&
38725 &`CV `& certificate verification status
38726 &`D `& duration of &"no mail in SMTP session"&
38727 &`DKIM`& domain verified in incoming message
38728 &`DN `& distinguished name from peer certificate
38729 &`DS `& DNSSEC secured lookups
38730 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38731 &`F `& sender address (on delivery lines)
38732 &`H `& host name and IP address
38733 &`I `& local interface used
38734 &`id `& message id (from header) for incoming message
38735 &`K `& CHUNKING extension used
38736 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38737 &`M8S `& 8BITMIME status for incoming message
38738 &`P `& on &`<=`& lines: protocol used
38739 &` `& on &`=>`& and &`**`& lines: return path
38740 &`PRDR`& PRDR extension used
38741 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38742 &`Q `& alternate queue name
38743 &`QT `& on &`=>`& lines: time spent on queue so far
38744 &` `& on &"Completed"& lines: time spent on queue
38745 &`R `& on &`<=`& lines: reference for local bounce
38746 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38747 &`RT `& on &`<=`& lines: time taken for reception
38748 &`S `& size of message in bytes
38749 &`SNI `& server name indication from TLS client hello
38750 &`ST `& shadow transport name
38751 &`T `& on &`<=`& lines: message subject (topic)
38752 &`TFO `& connection took advantage of TCP Fast Open
38753 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38754 &`U `& local user or RFC 1413 identity
38755 &`X `& TLS cipher suite
38759 .section "Other log entries" "SECID259"
38760 Various other types of log entry are written from time to time. Most should be
38761 self-explanatory. Among the more common are:
38764 .cindex "retry" "time not reached"
38765 &'retry time not reached'&&~&~An address previously suffered a temporary error
38766 during routing or local delivery, and the time to retry has not yet arrived.
38767 This message is not written to an individual message log file unless it happens
38768 during the first delivery attempt.
38770 &'retry time not reached for any host'&&~&~An address previously suffered
38771 temporary errors during remote delivery, and the retry time has not yet arrived
38772 for any of the hosts to which it is routed.
38774 .cindex "spool directory" "file locked"
38775 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38776 some other Exim process is already working on the message. This can be quite
38777 common if queue running processes are started at frequent intervals. The
38778 &'exiwhat'& utility script can be used to find out what Exim processes are
38781 .cindex "error" "ignored"
38782 &'error ignored'&&~&~There are several circumstances that give rise to this
38785 Exim failed to deliver a bounce message whose age was greater than
38786 &%ignore_bounce_errors_after%&. The bounce was discarded.
38788 A filter file set up a delivery using the &"noerror"& option, and the delivery
38789 failed. The delivery was discarded.
38791 A delivery set up by a router configured with
38792 . ==== As this is a nested list, any displays it contains must be indented
38793 . ==== as otherwise they are too far to the left.
38797 failed. The delivery was discarded.
38800 .cindex DKIM "log line"
38801 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38802 logging and the message has a DKIM signature header.
38809 .section "Reducing or increasing what is logged" "SECTlogselector"
38810 .cindex "log" "selectors"
38811 By setting the &%log_selector%& global option, you can disable some of Exim's
38812 default logging, or you can request additional logging. The value of
38813 &%log_selector%& is made up of names preceded by plus or minus characters. For
38816 log_selector = +arguments -retry_defer
38818 The list of optional log items is in the following table, with the default
38819 selection marked by asterisks:
38821 &` 8bitmime `& received 8BITMIME status
38822 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38823 &` address_rewrite `& address rewriting
38824 &` all_parents `& all parents in => lines
38825 &` arguments `& command line arguments
38826 &`*connection_reject `& connection rejections
38827 &`*delay_delivery `& immediate delivery delayed
38828 &` deliver_time `& time taken to attempt delivery
38829 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38830 &`*dkim `& DKIM verified domain on <= lines
38831 &` dkim_verbose `& separate full DKIM verification result line, per signature
38832 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38833 &` dnssec `& DNSSEC secured lookups
38834 &`*etrn `& ETRN commands
38835 &`*host_lookup_failed `& as it says
38836 &` ident_timeout `& timeout for ident connection
38837 &` incoming_interface `& local interface on <= and => lines
38838 &` incoming_port `& remote port on <= lines
38839 &`*lost_incoming_connection `& as it says (includes timeouts)
38840 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38841 &`*msg_id `& on <= lines, Message-ID: header value
38842 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38843 &` outgoing_interface `& local interface on => lines
38844 &` outgoing_port `& add remote port to => lines
38845 &`*queue_run `& start and end queue runs
38846 &` queue_time `& time on queue for one recipient
38847 &`*queue_time_exclusive `& exclude recieve time from QT times
38848 &` queue_time_overall `& time on queue for whole message
38849 &` pid `& Exim process id
38850 &` pipelining `& PIPELINING use, on <= and => lines
38851 &` proxy `& proxy address on <= and => lines
38852 &` receive_time `& time taken to receive message
38853 &` received_recipients `& recipients on <= lines
38854 &` received_sender `& sender on <= lines
38855 &`*rejected_header `& header contents on reject log
38856 &`*retry_defer `& &"retry time not reached"&
38857 &` return_path_on_delivery `& put return path on => and ** lines
38858 &` sender_on_delivery `& add sender to => lines
38859 &`*sender_verify_fail `& sender verification failures
38860 &`*size_reject `& rejection because too big
38861 &`*skip_delivery `& delivery skipped in a queue run
38862 &`*smtp_confirmation `& SMTP confirmation on => lines
38863 &` smtp_connection `& incoming SMTP connections
38864 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38865 &` smtp_mailauth `& AUTH argument to MAIL commands
38866 &` smtp_no_mail `& session with no MAIL commands
38867 &` smtp_protocol_error `& SMTP protocol errors
38868 &` smtp_syntax_error `& SMTP syntax errors
38869 &` subject `& contents of &'Subject:'& on <= lines
38870 &`*taint `& taint errors or warnings
38871 &`*tls_certificate_verified `& certificate verification status
38872 &`*tls_cipher `& TLS cipher suite on <= and => lines
38873 &` tls_peerdn `& TLS peer DN on <= and => lines
38874 &` tls_resumption `& append * to cipher field
38875 &` tls_sni `& TLS SNI on <= lines
38876 &` unknown_in_list `& DNS lookup failed in list match
38878 &` all `& all of the above
38880 See also the &%slow_lookup_log%& main configuration option,
38881 section &<<SECID99>>&
38883 More details on each of these items follows:
38887 .cindex "log" "8BITMIME"
38888 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38889 which may help in tracking down interoperability issues with ancient MTAs
38890 that are not 8bit clean. This is added to the &"<="& line, tagged with
38891 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38892 &`7BIT`& and &`8BITMIME`& respectively.
38894 .cindex "&%warn%& ACL verb" "log when skipping"
38895 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38896 its conditions cannot be evaluated, a log line to this effect is written if
38897 this log selector is set.
38899 .cindex "log" "rewriting"
38900 .cindex "rewriting" "logging"
38901 &%address_rewrite%&: This applies both to global rewrites and per-transport
38902 rewrites, but not to rewrites in filters run as an unprivileged user (because
38903 such users cannot access the log).
38905 .cindex "log" "full parentage"
38906 &%all_parents%&: Normally only the original and final addresses are logged on
38907 delivery lines; with this selector, intermediate parents are given in
38908 parentheses between them.
38910 .cindex "log" "Exim arguments"
38911 .cindex "Exim arguments, logging"
38912 &%arguments%&: This causes Exim to write the arguments with which it was called
38913 to the main log, preceded by the current working directory. This is a debugging
38914 feature, added to make it easier to find out how certain MUAs call
38915 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38916 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38917 that are empty or that contain white space are quoted. Non-printing characters
38918 are shown as escape sequences. This facility cannot log unrecognized arguments,
38919 because the arguments are checked before the configuration file is read. The
38920 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38921 between the caller and Exim.
38923 .cindex "log" "connection rejections"
38924 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38925 connection is rejected, for whatever reason.
38927 .cindex "log" "delayed delivery"
38928 .cindex "delayed delivery, logging"
38929 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38930 started for an incoming message because the load is too high or too many
38931 messages were received on one connection. Logging does not occur if no delivery
38932 process is started because &%queue_only%& is set or &%-odq%& was used.
38934 .cindex "log" "delivery duration"
38935 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38936 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38937 If millisecond logging is enabled, short times will be shown with greater
38938 precision, eg. &`DT=0.304s`&.
38940 .cindex "log" "message size on delivery"
38941 .cindex "size" "of message"
38942 &%delivery_size%&: For each delivery, the size of message delivered is added to
38943 the &"=>"& line, tagged with S=.
38945 .cindex log "DKIM verification"
38946 .cindex DKIM "verification logging"
38947 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38948 verifies successfully a tag of DKIM is added, with one of the verified domains.
38950 .cindex log "DKIM verification"
38951 .cindex DKIM "verification logging"
38952 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38954 .cindex "log" "dnslist defer"
38955 .cindex "DNS list" "logging defer"
38956 .cindex "black list (DNS)"
38957 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38958 DNS black list suffers a temporary error.
38961 .cindex dnssec logging
38962 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38963 dns lookups gave secure results a tag of DS is added.
38964 For acceptance this covers the reverse and forward lookups for host name verification.
38965 It does not cover helo-name verification.
38966 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38968 .cindex "log" "ETRN commands"
38969 .cindex "ETRN" "logging"
38970 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38971 is run to determine whether or not it is actually accepted. An invalid ETRN
38972 command, or one received within a message transaction is not logged by this
38973 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38975 .cindex "log" "host lookup failure"
38976 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38977 any addresses, or when a lookup of an IP address fails to find a host name, a
38978 log line is written. This logging does not apply to direct DNS lookups when
38979 routing email addresses, but it does apply to &"byname"& lookups.
38981 .cindex "log" "ident timeout"
38982 .cindex "RFC 1413" "logging timeout"
38983 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38984 client's ident port times out.
38986 .cindex "log" "incoming interface"
38987 .cindex "log" "outgoing interface"
38988 .cindex "log" "local interface"
38989 .cindex "log" "local address and port"
38990 .cindex "TCP/IP" "logging local address and port"
38991 .cindex "interface" "logging"
38992 &%incoming_interface%&: The interface on which a message was received is added
38993 to the &"<="& line as an IP address in square brackets, tagged by I= and
38994 followed by a colon and the port number. The local interface and port are also
38995 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38996 rejection lines, and (despite the name) to outgoing
38998 &"=>"&, &"->"&, &"=="& and &"**"& lines.
39000 The latter can be disabled by turning off the &%outgoing_interface%& option.
39002 .cindex log "incoming proxy address"
39003 .cindex proxy "logging proxy address"
39004 .cindex "TCP/IP" "logging proxy address"
39005 &%proxy%&: The internal (closest to the system running Exim) IP address
39006 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
39007 on a proxied connection
39008 or the &"=>"& line for a message delivered on a proxied connection.
39009 See &<<SECTproxyInbound>>& for more information.
39011 .cindex "log" "incoming remote port"
39012 .cindex "port" "logging remote"
39013 .cindex "TCP/IP" "logging incoming remote port"
39014 .vindex "&$sender_fullhost$&"
39015 .vindex "&$sender_rcvhost$&"
39016 &%incoming_port%&: The remote port number from which a message was received is
39017 added to log entries and &'Received:'& header lines, following the IP address
39018 in square brackets, and separated from it by a colon. This is implemented by
39019 changing the value that is put in the &$sender_fullhost$& and
39020 &$sender_rcvhost$& variables. Recording the remote port number has become more
39021 important with the widening use of NAT (see RFC 2505).
39023 .cindex "log" "dropped connection"
39024 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39025 connection is unexpectedly dropped.
39027 .cindex "log" "millisecond timestamps"
39028 .cindex millisecond logging
39029 .cindex timestamps "millisecond, in logs"
39030 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39031 appended to the seconds value.
39033 .cindex "log" "message id"
39034 &%msg_id%&: The value of the Message-ID: header.
39036 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39037 This will be either because the message is a bounce, or was submitted locally
39038 (submission mode) without one.
39039 The field identifier will have an asterix appended: &"id*="&.
39041 .cindex "log" "outgoing interface"
39042 .cindex "log" "local interface"
39043 .cindex "log" "local address and port"
39044 .cindex "TCP/IP" "logging local address and port"
39045 .cindex "interface" "logging"
39046 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39047 interface on which a message was sent is added to delivery lines as an I= tag
39048 followed by IP address in square brackets. You can disable this by turning
39049 off the &%outgoing_interface%& option.
39051 .cindex "log" "outgoing remote port"
39052 .cindex "port" "logging outgoing remote"
39053 .cindex "TCP/IP" "logging outgoing remote port"
39054 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39055 containing => tags) following the IP address.
39056 The local port is also added if &%incoming_interface%& and
39057 &%outgoing_interface%& are both enabled.
39058 This option is not included in the default setting, because for most ordinary
39059 configurations, the remote port number is always 25 (the SMTP port), and the
39060 local port is a random ephemeral port.
39062 .cindex "log" "process ids in"
39063 .cindex "pid (process id)" "in log lines"
39064 &%pid%&: The current process id is added to every log line, in square brackets,
39065 immediately after the time and date.
39067 .cindex log pipelining
39068 .cindex pipelining "logging outgoing"
39069 &%pipelining%&: A field is added to delivery and accept
39070 log lines when the ESMTP PIPELINING extension was used.
39071 The field is a single "L".
39073 On accept lines, where PIPELINING was offered but not used by the client,
39074 the field has a minus appended.
39076 .cindex "pipelining" "early connection"
39077 If Exim is built with the SUPPORT_PIPE_CONNECT build option
39078 accept "L" fields have a period appended if the feature was
39079 offered but not used, or an asterisk appended if used.
39080 Delivery "L" fields have an asterisk appended if used.
39083 .cindex "log" "queue run"
39084 .cindex "queue runner" "logging"
39085 &%queue_run%&: The start and end of every queue run are logged.
39087 .cindex "log" "queue time"
39088 &%queue_time%&: The amount of time the message has been in the queue on the
39089 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39091 If millisecond logging is enabled, short times will be shown with greater
39092 precision, eg. &`QT=1.578s`&.
39094 &%queue_time_overall%&: The amount of time the message has been in the queue on
39095 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39096 example, &`QT=3m45s`&.
39098 .cindex "log" "receive duration"
39099 &%receive_time%&: For each message, the amount of real time it has taken to
39100 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39101 If millisecond logging is enabled, short times will be shown with greater
39102 precision, eg. &`RT=0.204s`&.
39104 .cindex "log" "recipients"
39105 &%received_recipients%&: The recipients of a message are listed in the main log
39106 as soon as the message is received. The list appears at the end of the log line
39107 that is written when a message is received, preceded by the word &"for"&. The
39108 addresses are listed after they have been qualified, but before any rewriting
39110 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39113 .cindex "log" "sender reception"
39114 &%received_sender%&: The unrewritten original sender of a message is added to
39115 the end of the log line that records the message's arrival, after the word
39116 &"from"& (before the recipients if &%received_recipients%& is also set).
39118 .cindex "log" "header lines for rejection"
39119 &%rejected_header%&: If a message's header has been received at the time a
39120 rejection is written to the reject log, the complete header is added to the
39121 log. Header logging can be turned off individually for messages that are
39122 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39124 .cindex "log" "retry defer"
39125 &%retry_defer%&: A log line is written if a delivery is deferred because a
39126 retry time has not yet been reached. However, this &"retry time not reached"&
39127 message is always omitted from individual message logs after the first delivery
39130 .cindex "log" "return path"
39131 &%return_path_on_delivery%&: The return path that is being transmitted with
39132 the message is included in delivery and bounce lines, using the tag P=.
39133 This is omitted if no delivery actually happens, for example, if routing fails,
39134 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39136 .cindex "log" "sender on delivery"
39137 &%sender_on_delivery%&: The message's sender address is added to every delivery
39138 and bounce line, tagged by F= (for &"from"&).
39139 This is the original sender that was received with the message; it is not
39140 necessarily the same as the outgoing return path.
39142 .cindex "log" "sender verify failure"
39143 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39144 gives details of a sender verification failure is not written. Log lines for
39145 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39148 .cindex "log" "size rejection"
39149 &%size_reject%&: A log line is written whenever a message is rejected because
39152 .cindex "log" "frozen messages; skipped"
39153 .cindex "frozen messages" "logging skipping"
39154 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39155 queue run because it another process is already delivering it or because
39157 .cindex "&""spool file is locked""&"
39158 .cindex "&""message is frozen""&"
39159 The message that is written is either &"spool file is locked"& or
39160 &"message is frozen"&.
39162 .cindex "log" "smtp confirmation"
39163 .cindex "SMTP" "logging confirmation"
39164 .cindex "LMTP" "logging confirmation"
39165 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39166 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39167 A number of MTAs (including Exim) return an identifying string in this
39170 .cindex "log" "SMTP connections"
39171 .cindex "SMTP" "logging connections"
39172 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39173 established or closed, unless the connection is from a host that matches
39174 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39175 only when the closure is unexpected.) This applies to connections from local
39176 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39177 dropped in the middle of a message, a log line is always written, whether or
39178 not this selector is set, but otherwise nothing is written at the start and end
39179 of connections unless this selector is enabled.
39181 For TCP/IP connections to an Exim daemon, the current number of connections is
39182 included in the log message for each new connection, but note that the count is
39183 reset if the daemon is restarted.
39184 Also, because connections are closed (and the closure is logged) in
39185 subprocesses, the count may not include connections that have been closed but
39186 whose termination the daemon has not yet noticed. Thus, while it is possible to
39187 match up the opening and closing of connections in the log, the value of the
39188 logged counts may not be entirely accurate.
39190 .cindex "log" "SMTP transaction; incomplete"
39191 .cindex "SMTP" "logging incomplete transactions"
39192 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39193 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39194 and the message sender plus any accepted recipients are included in the log
39195 line. This can provide evidence of dictionary attacks.
39197 .cindex "log" "non-MAIL SMTP sessions"
39198 .cindex "MAIL" "logging session without"
39199 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39200 connection terminates without having issued a MAIL command. This includes both
39201 the case when the connection is dropped, and the case when QUIT is used. It
39202 does not include cases where the connection is rejected right at the start (by
39203 an ACL, or because there are too many connections, or whatever). These cases
39204 already have their own log lines.
39206 The log line that is written contains the identity of the client in the usual
39207 way, followed by D= and a time, which records the duration of the connection.
39208 If the connection was authenticated, this fact is logged exactly as it is for
39209 an incoming message, with an A= item. If the connection was encrypted, CV=,
39210 DN=, and X= items may appear as they do for an incoming message, controlled by
39211 the same logging options.
39213 Finally, if any SMTP commands were issued during the connection, a C= item
39214 is added to the line, listing the commands that were used. For example,
39218 shows that the client issued QUIT straight after EHLO. If there were fewer
39219 than 20 commands, they are all listed. If there were more than 20 commands,
39220 the last 20 are listed, preceded by &"..."&. However, with the default
39221 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39222 have been aborted before 20 non-mail commands are processed.
39224 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39225 colon-separated, is appended to the A= item for a message arrival or delivery
39226 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39227 was accepted or used.
39229 .cindex "log" "SMTP protocol error"
39230 .cindex "SMTP" "logging protocol error"
39231 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39232 encountered. Exim does not have perfect detection of all protocol errors
39233 because of transmission delays and the use of pipelining. If PIPELINING has
39234 been advertised to a client, an Exim server assumes that the client will use
39235 it, and therefore it does not count &"expected"& errors (for example, RCPT
39236 received after rejecting MAIL) as protocol errors.
39238 .cindex "SMTP" "logging syntax errors"
39239 .cindex "SMTP" "syntax errors; logging"
39240 .cindex "SMTP" "unknown command; logging"
39241 .cindex "log" "unknown SMTP command"
39242 .cindex "log" "SMTP syntax error"
39243 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39244 encountered. An unrecognized command is treated as a syntax error. For an
39245 external connection, the host identity is given; for an internal connection
39246 using &%-bs%& the sender identification (normally the calling user) is given.
39248 .cindex "log" "subject"
39249 .cindex "subject, logging"
39250 &%subject%&: The subject of the message is added to the arrival log line,
39251 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39252 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39253 specifies whether characters with values greater than 127 should be logged
39254 unchanged, or whether they should be rendered as escape sequences.
39256 .cindex "log" "certificate verification"
39258 .cindex DANE logging
39259 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39260 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39262 using a CA trust anchor,
39263 &`CV=dane`& if using a DNS trust anchor,
39264 and &`CV=no`& if not.
39266 .cindex "log" "Taint warnings"
39267 &%taint%&: Log warnings about tainted data. This selector can't be
39268 turned of if &%allow_insecure_tainted_data%& is false (which is the
39271 .cindex "log" "TLS cipher"
39272 .cindex "TLS" "logging cipher"
39273 &%tls_cipher%&: When a message is sent or received over an encrypted
39274 connection, the cipher suite used is added to the log line, preceded by X=.
39276 .cindex "log" "TLS peer DN"
39277 .cindex "TLS" "logging peer DN"
39278 &%tls_peerdn%&: When a message is sent or received over an encrypted
39279 connection, and a certificate is supplied by the remote host, the peer DN is
39280 added to the log line, preceded by DN=.
39282 .cindex "log" "TLS resumption"
39283 .cindex "TLS" "logging session resumption"
39285 &%tls_resumption%&: When a message is sent or received over an encrypted
39286 connection and the TLS session resumed one used on a previous TCP connection,
39287 an asterisk is appended to the X= cipher field in the log line.
39290 .cindex "log" "TLS SNI"
39291 .cindex "TLS" "logging SNI"
39292 .cindex SNI logging
39293 &%tls_sni%&: When a message is received over an encrypted connection, and
39294 the remote host provided the Server Name Indication extension, the SNI is
39295 added to the log line, preceded by SNI=.
39297 .cindex "log" "DNS failure in list"
39298 &%unknown_in_list%&: This setting causes a log entry to be written when the
39299 result of a list match is failure because a DNS lookup failed.
39303 .section "Message log" "SECID260"
39304 .cindex "message" "log file for"
39305 .cindex "log" "message log; description of"
39306 .cindex "&_msglog_& directory"
39307 .oindex "&%preserve_message_logs%&"
39308 In addition to the general log files, Exim writes a log file for each message
39309 that it handles. The names of these per-message logs are the message ids, and
39310 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39311 message log contains copies of the log lines that apply to the message. This
39312 makes it easier to inspect the status of an individual message without having
39313 to search the main log. A message log is deleted when processing of the message
39314 is complete, unless &%preserve_message_logs%& is set, but this should be used
39315 only with great care because they can fill up your disk very quickly.
39317 On a heavily loaded system, it may be desirable to disable the use of
39318 per-message logs, in order to reduce disk I/O. This can be done by setting the
39319 &%message_logs%& option false.
39325 . ////////////////////////////////////////////////////////////////////////////
39326 . ////////////////////////////////////////////////////////////////////////////
39328 .chapter "Exim utilities" "CHAPutils"
39329 .scindex IIDutils "utilities"
39330 A number of utility scripts and programs are supplied with Exim and are
39331 described in this chapter. There is also the Exim Monitor, which is covered in
39332 the next chapter. The utilities described here are:
39334 .itable none 0 0 3 7* left 15* left 40* left
39335 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39336 "list what Exim processes are doing"
39337 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39338 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39339 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39340 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39342 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39343 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39344 "extract statistics from the log"
39345 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39346 "check address acceptance from given IP"
39347 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39348 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39349 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39350 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39351 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39352 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39355 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39356 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39357 &url(https://duncanthrax.net/exilog/) for details.
39362 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39363 .cindex "&'exiwhat'&"
39364 .cindex "process, querying"
39366 On operating systems that can restart a system call after receiving a signal
39367 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39368 a line describing what it is doing to the file &_exim-process.info_& in the
39369 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39370 processes it can find, having first emptied the file. It then waits for one
39371 second to allow the Exim processes to react before displaying the results. In
39372 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39373 send the signal to the Exim processes, so it is normally run as root.
39375 &*Warning*&: This is not an efficient process. It is intended for occasional
39376 use by system administrators. It is not sensible, for example, to set up a
39377 script that sends SIGUSR1 signals to Exim processes at short intervals.
39380 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39381 varies in different operating systems. Not only are different options used,
39382 but the format of the output is different. For this reason, there are some
39383 system configuration options that configure exactly how &'exiwhat'& works. If
39384 it doesn't seem to be working for you, check the following compile-time
39387 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39388 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39389 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39390 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39392 An example of typical output from &'exiwhat'& is
39394 164 daemon: -q1h, listening on port 25
39395 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39396 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39397 [10.19.42.42] (editor@ref.example)
39398 10592 handling incoming call from [192.168.243.242]
39399 10628 accepting a local non-SMTP message
39401 The first number in the output line is the process number. The third line has
39402 been split here, in order to fit it on the page.
39406 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39407 .cindex "&'exiqgrep'&"
39408 .cindex "queue" "grepping"
39409 This utility is a Perl script contributed by Matt Hubbard. It runs
39413 or (in case &*-a*& switch is specified)
39417 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
39418 contain alternate exim configuration the queue management might be using.
39420 to obtain a queue listing, and then greps the output to select messages
39421 that match given criteria. The following selection options are available:
39424 .vitem &*-f*&&~<&'regex'&>
39425 Match the sender address using a case-insensitive search. The field that is
39426 tested is enclosed in angle brackets, so you can test for bounce messages with
39430 .vitem &*-r*&&~<&'regex'&>
39431 Match a recipient address using a case-insensitive search. The field that is
39432 tested is not enclosed in angle brackets.
39434 .vitem &*-s*&&~<&'regex'&>
39435 Match against the size field.
39437 .vitem &*-y*&&~<&'seconds'&>
39438 Match messages that are younger than the given time.
39440 .vitem &*-o*&&~<&'seconds'&>
39441 Match messages that are older than the given time.
39444 Match only frozen messages.
39447 Match only non-frozen messages.
39449 .vitem &*-G*&&~<&'queuename'&>
39450 Match only messages in the given queue. Without this, the default queue is searched.
39453 The following options control the format of the output:
39457 Display only the count of matching messages.
39460 Long format &-- display the full message information as output by Exim. This is
39464 Display message ids only.
39467 Brief format &-- one line per message.
39470 Display messages in reverse order.
39473 Include delivered recipients in queue listing.
39476 There is one more option, &%-h%&, which outputs a list of options.
39480 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39481 .cindex "&'exiqsumm'&"
39482 .cindex "queue" "summary"
39483 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39484 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39485 running a command such as
39487 exim -bp | exiqsumm
39489 The output consists of one line for each domain that has messages waiting for
39490 it, as in the following example:
39492 3 2322 74m 66m msn.com.example
39494 Each line lists the number of pending deliveries for a domain, their total
39495 volume, and the length of time that the oldest and the newest messages have
39496 been waiting. Note that the number of pending deliveries is greater than the
39497 number of messages when messages have more than one recipient.
39499 A summary line is output at the end. By default the output is sorted on the
39500 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39501 the output to be sorted by oldest message and by count of messages,
39502 respectively. There are also three options that split the messages for each
39503 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39504 separates frozen messages, and &%-s%& separates messages according to their
39507 The output of &'exim -bp'& contains the original addresses in the message, so
39508 this also applies to the output from &'exiqsumm'&. No domains from addresses
39509 generated by aliasing or forwarding are included (unless the &%one_time%&
39510 option of the &(redirect)& router has been used to convert them into &"top
39511 level"& addresses).
39516 .section "Extracting specific information from the log (exigrep)" &&&
39518 .cindex "&'exigrep'&"
39519 .cindex "log" "extracts; grepping for"
39520 The &'exigrep'& utility is a Perl script that searches one or more main log
39521 files for entries that match a given pattern. When it finds a match, it
39522 extracts all the log entries for the relevant message, not just those that
39523 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39524 given message, or all mail for a given user, or for a given host, for example.
39525 The input files can be in Exim log format or syslog format.
39526 If a matching log line is not associated with a specific message, it is
39527 included in &'exigrep'&'s output without any additional lines. The usage is:
39529 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39531 If no log filenames are given on the command line, the standard input is read.
39533 The &%-t%& argument specifies a number of seconds. It adds an additional
39534 condition for message selection. Messages that are complete are shown only if
39535 they spent more than <&'n'&> seconds in the queue.
39537 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39538 makes it case-sensitive. This may give a performance improvement when searching
39539 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39540 option; with &%-I%& they do not. In both cases it is possible to change the
39541 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39543 The &%-l%& option means &"literal"&, that is, treat all characters in the
39544 pattern as standing for themselves. Otherwise the pattern must be a Perl
39545 regular expression.
39547 The &%-v%& option inverts the matching condition. That is, a line is selected
39548 if it does &'not'& match the pattern.
39550 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39551 that are generated as a result/response to a message that &'exigrep'& matched
39555 user_a sends a message to user_b, which generates a bounce back to user_b. If
39556 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39557 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39558 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39559 when searching for &"user_a"& will show both messages since the bounce is
39560 &"related"& to or a &"result"& of the first message that was found by the
39563 If the location of a &'zcat'& command is known from the definition of
39564 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39565 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39566 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39567 autodetection of some well known compression extensions.
39570 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39571 .cindex "&'exipick'&"
39572 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39573 lists messages from the queue according to a variety of criteria. For details
39574 of &'exipick'&'s facilities, run &'exipick'& with
39575 the &%--help%& option.
39578 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39579 .cindex "log" "cycling local files"
39580 .cindex "cycling logs"
39581 .cindex "&'exicyclog'&"
39582 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39583 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39584 you are using log files with datestamps in their names (see section
39585 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39586 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39587 There are two command line options for &'exicyclog'&:
39589 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39590 default that is set when Exim is built. The default default is 10.
39592 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39593 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39594 overriding the script's default, which is to find the setting from Exim's
39598 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39599 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39600 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39601 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39602 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39603 logs are handled similarly.
39605 If the limit is greater than 99, the script uses 3-digit numbers such as
39606 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39607 to one that is greater, or &'vice versa'&, you will have to fix the names of
39608 any existing log files.
39610 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39611 the end are deleted. All files with numbers greater than 01 are compressed,
39612 using a compression command which is configured by the COMPRESS_COMMAND
39613 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39614 root &%crontab%& entry of the form
39616 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39618 assuming you have used the name &"exim"& for the Exim user. You can run
39619 &'exicyclog'& as root if you wish, but there is no need.
39623 .section "Mail statistics (eximstats)" "SECTmailstat"
39624 .cindex "statistics"
39625 .cindex "&'eximstats'&"
39626 A Perl script called &'eximstats'& is provided for extracting statistical
39627 information from log files. The output is either plain text, or HTML.
39628 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39629 . --- 404 error and everything else points to that.
39631 The &'eximstats'& script has been hacked about quite a bit over time. The
39632 latest version is the result of some extensive revision by Steve Campbell. A
39633 lot of information is given by default, but there are options for suppressing
39634 various parts of it. Following any options, the arguments to the script are a
39635 list of files, which should be main log files. For example:
39637 eximstats -nr /var/spool/exim/log/mainlog.01
39639 By default, &'eximstats'& extracts information about the number and volume of
39640 messages received from or delivered to various hosts. The information is sorted
39641 both by message count and by volume, and the top fifty hosts in each category
39642 are listed on the standard output. Similar information, based on email
39643 addresses or domains instead of hosts can be requested by means of various
39644 options. For messages delivered and received locally, similar statistics are
39645 also produced per user.
39647 The output also includes total counts and statistics about delivery errors, and
39648 histograms showing the number of messages received and deliveries made in each
39649 hour of the day. A delivery with more than one address in its envelope (for
39650 example, an SMTP transaction with more than one RCPT command) is counted
39651 as a single delivery by &'eximstats'&.
39653 Though normally more deliveries than receipts are reported (as messages may
39654 have multiple recipients), it is possible for &'eximstats'& to report more
39655 messages received than delivered, even though the queue is empty at the start
39656 and end of the period in question. If an incoming message contains no valid
39657 recipients, no deliveries are recorded for it. A bounce message is handled as
39658 an entirely separate message.
39660 &'eximstats'& always outputs a grand total summary giving the volume and number
39661 of messages received and deliveries made, and the number of hosts involved in
39662 each case. It also outputs the number of messages that were delayed (that is,
39663 not completely delivered at the first attempt), and the number that had at
39664 least one address that failed.
39666 The remainder of the output is in sections that can be independently disabled
39667 or modified by various options. It consists of a summary of deliveries by
39668 transport, histograms of messages received and delivered per time interval
39669 (default per hour), information about the time messages spent in the queue,
39670 a list of relayed messages, lists of the top fifty sending hosts, local
39671 senders, destination hosts, and destination local users by count and by volume,
39672 and a list of delivery errors that occurred.
39674 The relay information lists messages that were actually relayed, that is, they
39675 came from a remote host and were directly delivered to some other remote host,
39676 without being processed (for example, for aliasing or forwarding) locally.
39678 There are quite a few options for &'eximstats'& to control exactly what it
39679 outputs. These are documented in the Perl script itself, and can be extracted
39680 by running the command &(perldoc)& on the script. For example:
39682 perldoc /usr/exim/bin/eximstats
39685 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39686 .cindex "&'exim_checkaccess'&"
39687 .cindex "policy control" "checking access"
39688 .cindex "checking access"
39689 The &%-bh%& command line argument allows you to run a fake SMTP session with
39690 debugging output, in order to check what Exim is doing when it is applying
39691 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39692 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39693 sometimes you just want to answer the question &"Does this address have
39694 access?"& without bothering with any further details.
39696 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39697 two arguments, an IP address and an email address:
39699 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39701 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39702 given email address would be accepted in a RCPT command in a TCP/IP
39703 connection from the host with the given IP address. The output of the utility
39704 is either the word &"accepted"&, or the SMTP error response, for example:
39707 550 Relay not permitted
39709 When running this test, the utility uses &`<>`& as the envelope sender address
39710 for the MAIL command, but you can change this by providing additional
39711 options. These are passed directly to the Exim command. For example, to specify
39712 that the test is to be run with the sender address &'himself@there.example'&
39715 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39716 -f himself@there.example
39718 Note that these additional Exim command line items must be given after the two
39719 mandatory arguments.
39721 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39722 while running its checks. You can run checks that include callouts by using
39723 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39727 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39728 .cindex "DBM" "building dbm files"
39729 .cindex "building DBM files"
39730 .cindex "&'exim_dbmbuild'&"
39731 .cindex "lower casing"
39732 .cindex "binary zero" "in lookup key"
39733 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39734 the format used by the &(lsearch)& lookup (see section
39735 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39736 names as keys and the remainder of the information as data. The lower-casing
39737 can be prevented by calling the program with the &%-nolc%& option.
39739 A terminating zero is included as part of the key string. This is expected by
39740 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39741 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39742 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39745 The program requires two arguments: the name of the input file (which can be a
39746 single hyphen to indicate the standard input), and the name of the output file.
39747 It creates the output under a temporary name, and then renames it if all went
39751 If the native DB interface is in use (USE_DB is set in a compile-time
39752 configuration file &-- this is common in free versions of Unix) the two
39753 filenames must be different, because in this mode the Berkeley DB functions
39754 create a single output file using exactly the name given. For example,
39756 exim_dbmbuild /etc/aliases /etc/aliases.db
39758 reads the system alias file and creates a DBM version of it in
39759 &_/etc/aliases.db_&.
39761 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39762 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39763 environment, the suffixes are added to the second argument of
39764 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39765 when the Berkeley functions are used in compatibility mode (though this is not
39766 recommended), because in that case it adds a &_.db_& suffix to the filename.
39768 If a duplicate key is encountered, the program outputs a warning, and when it
39769 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39770 option is used. By default, only the first of a set of duplicates is used &--
39771 this makes it compatible with &(lsearch)& lookups. There is an option
39772 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39773 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39774 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39780 .section "Finding individual retry times (exinext)" "SECTfinindret"
39781 .cindex "retry" "times"
39782 .cindex "&'exinext'&"
39783 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39784 fish specific information out of the retry database. Given a mail domain (or a
39785 complete address), it looks up the hosts for that domain, and outputs any retry
39786 information for the hosts or for the domain. At present, the retry information
39787 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39788 output. For example:
39790 $ exinext piglet@milne.fict.example
39791 kanga.milne.example:192.168.8.1 error 146: Connection refused
39792 first failed: 21-Feb-1996 14:57:34
39793 last tried: 21-Feb-1996 14:57:34
39794 next try at: 21-Feb-1996 15:02:34
39795 roo.milne.example:192.168.8.3 error 146: Connection refused
39796 first failed: 20-Jan-1996 13:12:08
39797 last tried: 21-Feb-1996 11:42:03
39798 next try at: 21-Feb-1996 19:42:03
39799 past final cutoff time
39801 You can also give &'exinext'& a local part, without a domain, and it
39802 will give any retry information for that local part in your default domain.
39803 A message id can be used to obtain retry information pertaining to a specific
39804 message. This exists only when an attempt to deliver a message to a remote host
39805 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39806 &'exinext'& is not particularly efficient, but then it is not expected to be
39809 The &'exinext'& utility calls Exim to find out information such as the location
39810 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39811 passed on to the &'exim'& commands. The first specifies an alternate Exim
39812 configuration file, and the second sets macros for use within the configuration
39813 file. These features are mainly to help in testing, but might also be useful in
39814 environments where more than one configuration file is in use.
39818 .section "Hints database maintenance" "SECThindatmai"
39819 .cindex "hints database" "maintenance"
39820 .cindex "maintaining Exim's hints database"
39821 Three utility programs are provided for maintaining the DBM files that Exim
39822 uses to contain its delivery hint information. Each program requires two
39823 arguments. The first specifies the name of Exim's spool directory, and the
39824 second is the name of the database it is to operate on. These are as follows:
39827 &'retry'&: the database of retry information
39829 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39832 &'callout'&: the callout cache
39834 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39837 &'tls'&: TLS session resumption data
39840 &'misc'&: other hints data
39843 The &'misc'& database is used for
39846 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39848 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39849 &(smtp)& transport)
39851 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39857 .section "exim_dumpdb" "SECTdumpdb"
39858 .cindex "&'exim_dumpdb'&"
39859 The entire contents of a database are written to the standard output by the
39860 &'exim_dumpdb'& program, which has no options or arguments other than the
39861 spool and database names. For example, to dump the retry database:
39863 exim_dumpdb /var/spool/exim retry
39865 Two lines of output are produced for each entry:
39867 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39868 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39870 The first item on the first line is the key of the record. It starts with one
39871 of the letters R, or T, depending on whether it refers to a routing or
39872 transport retry. For a local delivery, the next part is the local address; for
39873 a remote delivery it is the name of the remote host, followed by its failing IP
39874 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39875 transport). If the remote port is not the standard one (port 25), it is added
39876 to the IP address. Then there follows an error code, an additional error code,
39877 and a textual description of the error.
39879 The three times on the second line are the time of first failure, the time of
39880 the last delivery attempt, and the computed time for the next attempt. The line
39881 ends with an asterisk if the cutoff time for the last retry rule has been
39884 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39885 consists of a host name followed by a list of ids for messages that are or were
39886 waiting to be delivered to that host. If there are a very large number for any
39887 one host, continuation records, with a sequence number added to the host name,
39888 may be seen. The data in these records is often out of date, because a message
39889 may be routed to several alternative hosts, and Exim makes no effort to keep
39894 .section "exim_tidydb" "SECTtidydb"
39895 .cindex "&'exim_tidydb'&"
39896 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39897 database. If run with no options, it removes all records that are more than 30
39898 days old. The age is calculated from the date and time that the record was last
39899 updated. Note that, in the case of the retry database, it is &'not'& the time
39900 since the first delivery failure. Information about a host that has been down
39901 for more than 30 days will remain in the database, provided that the record is
39902 updated sufficiently often.
39904 The cutoff date can be altered by means of the &%-t%& option, which must be
39905 followed by a time. For example, to remove all records older than a week from
39906 the retry database:
39908 exim_tidydb -t 7d /var/spool/exim retry
39910 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39911 message ids. In the former these appear as data in records keyed by host &--
39912 they were messages that were waiting for that host &-- and in the latter they
39913 are the keys for retry information for messages that have suffered certain
39914 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39915 message ids in database records are those of messages that are still on the
39916 queue. Message ids for messages that no longer exist are removed from
39917 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39918 For the &'retry'& database, records whose keys are non-existent message ids are
39919 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39920 whenever it removes information from the database.
39922 Certain records are automatically removed by Exim when they are no longer
39923 needed, but others are not. For example, if all the MX hosts for a domain are
39924 down, a retry record is created for each one. If the primary MX host comes back
39925 first, its record is removed when Exim successfully delivers to it, but the
39926 records for the others remain because Exim has not tried to use those hosts.
39928 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39929 hints databases. You should do this at a quiet time of day, because it requires
39930 a database to be locked (and therefore inaccessible to Exim) while it does its
39931 work. Removing records from a DBM file does not normally make the file smaller,
39932 but all the common DBM libraries are able to re-use the space that is released.
39933 After an initial phase of increasing in size, the databases normally reach a
39934 point at which they no longer get any bigger, as long as they are regularly
39937 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39938 databases is likely to keep on increasing.
39943 .section "exim_fixdb" "SECTfixdb"
39944 .cindex "&'exim_fixdb'&"
39945 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39946 Its main use is for testing Exim, but it might also be occasionally useful for
39947 getting round problems in a live system. It has no options, and its interface
39948 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39949 key of a database record can then be entered, and the data for that record is
39952 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39953 except the &'retry'& database, that is the only operation that can be carried
39954 out. For the &'retry'& database, each field is output preceded by a number, and
39955 data for individual fields can be changed by typing the field number followed
39956 by new data, for example:
39960 resets the time of the next delivery attempt. Time values are given as a
39961 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39962 used as optional separators.
39967 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39968 .cindex "mailbox" "maintenance"
39969 .cindex "&'exim_lock'&"
39970 .cindex "locking mailboxes"
39971 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39972 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39973 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39974 a user agent while investigating a problem. The utility requires the name of
39975 the file as its first argument. If the locking is successful, the second
39976 argument is run as a command (using C's &[system()]& function); if there is no
39977 second argument, the value of the SHELL environment variable is used; if this
39978 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39979 is unlocked and the utility ends. The following options are available:
39983 Use &[fcntl()]& locking on the open mailbox.
39986 Use &[flock()]& locking on the open mailbox, provided the operating system
39989 .vitem &%-interval%&
39990 This must be followed by a number, which is a number of seconds; it sets the
39991 interval to sleep between retries (default 3).
39993 .vitem &%-lockfile%&
39994 Create a lock file before opening the mailbox.
39997 Lock the mailbox using MBX rules.
40000 Suppress verification output.
40002 .vitem &%-retries%&
40003 This must be followed by a number; it sets the number of times to try to get
40004 the lock (default 10).
40006 .vitem &%-restore_time%&
40007 This option causes &%exim_lock%& to restore the modified and read times to the
40008 locked file before exiting. This allows you to access a locked mailbox (for
40009 example, to take a backup copy) without disturbing the times that the user
40012 .vitem &%-timeout%&
40013 This must be followed by a number, which is a number of seconds; it sets a
40014 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40015 default), a non-blocking call is used.
40018 Generate verbose output.
40021 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40022 default is to create a lock file and also to use &[fcntl()]& locking on the
40023 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40024 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40025 requires that the directory containing the file be writeable. Locking by lock
40026 file does not last forever; Exim assumes that a lock file is expired if it is
40027 more than 30 minutes old.
40029 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40030 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40031 to be taken out on the open mailbox, and an exclusive lock on the file
40032 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40033 number of the mailbox file. When the locking is released, if an exclusive lock
40034 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40036 The default output contains verification of the locking that takes place. The
40037 &%-v%& option causes some additional information to be given. The &%-q%& option
40038 suppresses all output except error messages.
40042 exim_lock /var/spool/mail/spqr
40044 runs an interactive shell while the file is locked, whereas
40046 &`exim_lock -q /var/spool/mail/spqr <<End`&
40047 <&'some commands'&>
40050 runs a specific non-interactive sequence of commands while the file is locked,
40051 suppressing all verification output. A single command can be run by a command
40054 exim_lock -q /var/spool/mail/spqr \
40055 "cp /var/spool/mail/spqr /some/where"
40057 Note that if a command is supplied, it must be entirely contained within the
40058 second argument &-- hence the quotes.
40062 . ////////////////////////////////////////////////////////////////////////////
40063 . ////////////////////////////////////////////////////////////////////////////
40065 .chapter "The Exim monitor" "CHAPeximon"
40066 .scindex IIDeximon "Exim monitor" "description"
40067 .cindex "X-windows"
40068 .cindex "&'eximon'&"
40069 .cindex "Local/eximon.conf"
40070 .cindex "&_exim_monitor/EDITME_&"
40071 The Exim monitor is an application which displays in an X window information
40072 about the state of Exim's queue and what Exim is doing. An admin user can
40073 perform certain operations on messages from this GUI interface; however all
40074 such facilities are also available from the command line, and indeed, the
40075 monitor itself makes use of the command line to perform any actions requested.
40079 .section "Running the monitor" "SECID264"
40080 The monitor is started by running the script called &'eximon'&. This is a shell
40081 script that sets up a number of environment variables, and then runs the
40082 binary called &_eximon.bin_&. The default appearance of the monitor window can
40083 be changed by editing the &_Local/eximon.conf_& file created by editing
40084 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40085 parameters are for.
40087 The parameters that get built into the &'eximon'& script can be overridden for
40088 a particular invocation by setting up environment variables of the same names,
40089 preceded by &`EXIMON_`&. For example, a shell command such as
40091 EXIMON_LOG_DEPTH=400 eximon
40093 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40094 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40095 overrides the Exim log file configuration. This makes it possible to have
40096 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40097 syslog messages are routed to a file on the local host.
40099 X resources can be used to change the appearance of the window in the normal
40100 way. For example, a resource setting of the form
40102 Eximon*background: gray94
40104 changes the colour of the background to light grey rather than white. The
40105 stripcharts are drawn with both the data lines and the reference lines in
40106 black. This means that the reference lines are not visible when on top of the
40107 data. However, their colour can be changed by setting a resource called
40108 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40109 For example, if your X server is running Unix, you could set up lighter
40110 reference lines in the stripcharts by obeying
40113 Eximon*highlight: gray
40116 .cindex "admin user"
40117 In order to see the contents of messages in the queue, and to operate on them,
40118 &'eximon'& must either be run as root or by an admin user.
40120 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40121 contain X11 resource parameters interpreted by the X11 library. In addition,
40122 if the first parameter starts with the string "gdb" then it is removed and the
40123 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40124 versioned variants of gdb can be invoked).
40126 The monitor's window is divided into three parts. The first contains one or
40127 more stripcharts and two action buttons, the second contains a &"tail"& of the
40128 main log file, and the third is a display of the queue of messages awaiting
40129 delivery, with two more action buttons. The following sections describe these
40130 different parts of the display.
40135 .section "The stripcharts" "SECID265"
40136 .cindex "stripchart"
40137 The first stripchart is always a count of messages in the queue. Its name can
40138 be configured by setting QUEUE_STRIPCHART_NAME in the
40139 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40140 configuration script by regular expression matches on log file entries, making
40141 it possible to display, for example, counts of messages delivered to certain
40142 hosts or using certain transports. The supplied defaults display counts of
40143 received and delivered messages, and of local and SMTP deliveries. The default
40144 period between stripchart updates is one minute; this can be adjusted by a
40145 parameter in the &_Local/eximon.conf_& file.
40147 The stripchart displays rescale themselves automatically as the value they are
40148 displaying changes. There are always 10 horizontal lines in each chart; the
40149 title string indicates the value of each division when it is greater than one.
40150 For example, &"x2"& means that each division represents a value of 2.
40152 It is also possible to have a stripchart which shows the percentage fullness of
40153 a particular disk partition, which is useful when local deliveries are confined
40154 to a single partition.
40156 .cindex "&%statvfs%& function"
40157 This relies on the availability of the &[statvfs()]& function or equivalent in
40158 the operating system. Most, but not all versions of Unix that support Exim have
40159 this. For this particular stripchart, the top of the chart always represents
40160 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40161 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40162 &_Local/eximon.conf_& file.
40167 .section "Main action buttons" "SECID266"
40168 .cindex "size" "of monitor window"
40169 .cindex "Exim monitor" "window size"
40170 .cindex "window size"
40171 Below the stripcharts there is an action button for quitting the monitor. Next
40172 to this is another button marked &"Size"&. They are placed here so that
40173 shrinking the window to its default minimum size leaves just the queue count
40174 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40175 the window to expand to its maximum size, unless it is already at the maximum,
40176 in which case it is reduced to its minimum.
40178 When expanding to the maximum, if the window cannot be fully seen where it
40179 currently is, it is moved back to where it was the last time it was at full
40180 size. When it is expanding from its minimum size, the old position is
40181 remembered, and next time it is reduced to the minimum it is moved back there.
40183 The idea is that you can keep a reduced window just showing one or two
40184 stripcharts at a convenient place on your screen, easily expand it to show
40185 the full window when required, and just as easily put it back to what it was.
40186 The idea is copied from what the &'twm'& window manager does for its
40187 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40188 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40190 Normally, the monitor starts up with the window at its full size, but it can be
40191 built so that it starts up with the window at its smallest size, by setting
40192 START_SMALL=yes in &_Local/eximon.conf_&.
40196 .section "The log display" "SECID267"
40197 .cindex "log" "tail of; in monitor"
40198 The second section of the window is an area in which a display of the tail of
40199 the main log is maintained.
40200 To save space on the screen, the timestamp on each log line is shortened by
40201 removing the date and, if &%log_timezone%& is set, the timezone.
40202 The log tail is not available when the only destination for logging data is
40203 syslog, unless the syslog lines are routed to a local file whose name is passed
40204 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40206 The log sub-window has a scroll bar at its lefthand side which can be used to
40207 move back to look at earlier text, and the up and down arrow keys also have a
40208 scrolling effect. The amount of log that is kept depends on the setting of
40209 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40210 to use. When this is full, the earlier 50% of data is discarded &-- this is
40211 much more efficient than throwing it away line by line. The sub-window also has
40212 a horizontal scroll bar for accessing the ends of long log lines. This is the
40213 only means of horizontal scrolling; the right and left arrow keys are not
40214 available. Text can be cut from this part of the window using the mouse in the
40215 normal way. The size of this subwindow is controlled by parameters in the
40216 configuration file &_Local/eximon.conf_&.
40218 Searches of the text in the log window can be carried out by means of the ^R
40219 and ^S keystrokes, which default to a reverse and a forward search,
40220 respectively. The search covers only the text that is displayed in the window.
40221 It cannot go further back up the log.
40223 The point from which the search starts is indicated by a caret marker. This is
40224 normally at the end of the text in the window, but can be positioned explicitly
40225 by pointing and clicking with the left mouse button, and is moved automatically
40226 by a successful search. If new text arrives in the window when it is scrolled
40227 back, the caret remains where it is, but if the window is not scrolled back,
40228 the caret is moved to the end of the new text.
40230 Pressing ^R or ^S pops up a window into which the search text can be typed.
40231 There are buttons for selecting forward or reverse searching, for carrying out
40232 the search, and for cancelling. If the &"Search"& button is pressed, the search
40233 happens and the window remains so that further searches can be done. If the
40234 &"Return"& key is pressed, a single search is done and the window is closed. If
40235 ^C is typed the search is cancelled.
40237 The searching facility is implemented using the facilities of the Athena text
40238 widget. By default this pops up a window containing both &"search"& and
40239 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40240 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40241 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40242 provided version of &%TextPop%& when the remaining parts of the text widget
40243 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40244 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40245 on these systems, at the expense of having unwanted items in the search popup
40250 .section "The queue display" "SECID268"
40251 .cindex "queue" "display in monitor"
40252 The bottom section of the monitor window contains a list of all messages that
40253 are in the queue, which includes those currently being received or delivered,
40254 as well as those awaiting delivery. The size of this subwindow is controlled by
40255 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40256 at which it is updated is controlled by another parameter in the same file &--
40257 the default is 5 minutes, since queue scans can be quite expensive. However,
40258 there is an &"Update"& action button just above the display which can be used
40259 to force an update of the queue display at any time.
40261 When a host is down for some time, a lot of pending mail can build up for it,
40262 and this can make it hard to deal with other messages in the queue. To help
40263 with this situation there is a button next to &"Update"& called &"Hide"&. If
40264 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40265 type anything in here and press &"Return"&, the text is added to a chain of
40266 such texts, and if every undelivered address in a message matches at least one
40267 of the texts, the message is not displayed.
40269 If there is an address that does not match any of the texts, all the addresses
40270 are displayed as normal. The matching happens on the ends of addresses so, for
40271 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40272 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40273 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40274 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40275 a hide request is automatically cancelled after one hour.
40277 While the dialogue box is displayed, you can't press any buttons or do anything
40278 else to the monitor window. For this reason, if you want to cut text from the
40279 queue display to use in the dialogue box, you have to do the cutting before
40280 pressing the &"Hide"& button.
40282 The queue display contains, for each unhidden queued message, the length of
40283 time it has been in the queue, the size of the message, the message id, the
40284 message sender, and the first undelivered recipient, all on one line. If it is
40285 a bounce message, the sender is shown as &"<>"&. If there is more than one
40286 recipient to which the message has not yet been delivered, subsequent ones are
40287 listed on additional lines, up to a maximum configured number, following which
40288 an ellipsis is displayed. Recipients that have already received the message are
40291 .cindex "frozen messages" "display"
40292 If a message is frozen, an asterisk is displayed at the left-hand side.
40294 The queue display has a vertical scroll bar, and can also be scrolled by means
40295 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40296 The text searching facilities, as described above for the log window, are also
40297 available, but the caret is always moved to the end of the text when the queue
40298 display is updated.
40302 .section "The queue menu" "SECID269"
40303 .cindex "queue" "menu in monitor"
40304 If the &%shift%& key is held down and the left button is clicked when the mouse
40305 pointer is over the text for any message, an action menu pops up, and the first
40306 line of the queue display for the message is highlighted. This does not affect
40309 If you want to use some other event for popping up the menu, you can set the
40310 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40311 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40312 value set in this parameter is a standard X event description. For example, to
40313 run eximon using &%ctrl%& rather than &%shift%& you could use
40315 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40317 The title of the menu is the message id, and it contains entries which act as
40321 &'message log'&: The contents of the message log for the message are displayed
40322 in a new text window.
40324 &'headers'&: Information from the spool file that contains the envelope
40325 information and headers is displayed in a new text window. See chapter
40326 &<<CHAPspool>>& for a description of the format of spool files.
40328 &'body'&: The contents of the spool file containing the body of the message are
40329 displayed in a new text window. There is a default limit of 20,000 bytes to the
40330 amount of data displayed. This can be changed by setting the BODY_MAX
40331 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40333 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40334 delivery of the message. This causes an automatic thaw if the message is
40335 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40336 a new text window. The delivery is run in a separate process, to avoid holding
40337 up the monitor while the delivery proceeds.
40339 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40340 that the message be frozen.
40342 .cindex "thawing messages"
40343 .cindex "unfreezing messages"
40344 .cindex "frozen messages" "thawing"
40345 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40346 that the message be thawed.
40348 .cindex "delivery" "forcing failure"
40349 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40350 that Exim gives up trying to deliver the message. A bounce message is generated
40351 for any remaining undelivered addresses.
40353 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40354 that the message be deleted from the system without generating a bounce
40357 &'add recipient'&: A dialog box is displayed into which a recipient address can
40358 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40359 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40360 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40361 causes a call to Exim to be made using the &%-Mar%& option to request that an
40362 additional recipient be added to the message, unless the entry box is empty, in
40363 which case no action is taken.
40365 &'mark delivered'&: A dialog box is displayed into which a recipient address
40366 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40367 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40368 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40369 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40370 recipient address as already delivered, unless the entry box is empty, in which
40371 case no action is taken.
40373 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40374 mark all recipient addresses as already delivered.
40376 &'edit sender'&: A dialog box is displayed initialized with the current
40377 sender's address. Pressing RETURN causes a call to Exim to be made using the
40378 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40379 in which case no action is taken. If you want to set an empty sender (as in
40380 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40381 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40382 the address is qualified with that domain.
40385 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40386 other cases when a call to Exim is made, if there is any output from Exim (in
40387 particular, if the command fails) a window containing the command and the
40388 output is displayed. Otherwise, the results of the action are normally apparent
40389 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40390 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40391 if no output is generated.
40393 The queue display is automatically updated for actions such as freezing and
40394 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40395 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40396 force an update of the display after one of these actions.
40398 In any text window that is displayed as result of a menu action, the normal
40399 cut-and-paste facility is available, and searching can be carried out using ^R
40400 and ^S, as described above for the log tail window.
40407 . ////////////////////////////////////////////////////////////////////////////
40408 . ////////////////////////////////////////////////////////////////////////////
40410 .chapter "Security considerations" "CHAPsecurity"
40411 .scindex IIDsecurcon "security" "discussion of"
40412 This chapter discusses a number of issues concerned with security, some of
40413 which are also covered in other parts of this manual.
40415 For reasons that this author does not understand, some people have promoted
40416 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40417 existence of this chapter in the documentation. However, the intent of the
40418 chapter is simply to describe the way Exim works in relation to certain
40419 security concerns, not to make any specific claims about the effectiveness of
40420 its security as compared with other MTAs.
40422 What follows is a description of the way Exim is supposed to be. Best efforts
40423 have been made to try to ensure that the code agrees with the theory, but an
40424 absence of bugs can never be guaranteed. Any that are reported will get fixed
40425 as soon as possible.
40428 .section "Building a more &""hardened""& Exim" "SECID286"
40429 .cindex "security" "build-time features"
40430 There are a number of build-time options that can be set in &_Local/Makefile_&
40431 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40432 Exim administrator who does not have the root password, or by someone who has
40433 penetrated the Exim (but not the root) account. These options are as follows:
40436 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40437 start of any filenames used with the &%-C%& option. When it is set, these
40438 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40439 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40440 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40441 default setting for &%ALT_CONFIG_PREFIX%&.
40443 If the permitted configuration files are confined to a directory to
40444 which only root has access, this guards against someone who has broken
40445 into the Exim account from running a privileged Exim with an arbitrary
40446 configuration file, and using it to break into other accounts.
40449 If a non-trusted configuration file (i.e. not the default configuration file
40450 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40451 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40452 the next item), then root privilege is retained only if the caller of Exim is
40453 root. This locks out the possibility of testing a configuration using &%-C%&
40454 right through message reception and delivery, even if the caller is root. The
40455 reception works, but by that time, Exim is running as the Exim user, so when
40456 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40457 privilege to be lost. However, root can test reception and delivery using two
40461 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40462 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40463 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40464 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40465 the restrictive side. Requiring build-time selection of safe macros is onerous
40466 but this option is intended solely as a transition mechanism to permit
40467 previously-working configurations to continue to work after release 4.73.
40469 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40472 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40473 never to be used for any deliveries. This is like the &%never_users%& runtime
40474 option, but it cannot be overridden; the runtime option adds additional users
40475 to the list. The default setting is &"root"&; this prevents a non-root user who
40476 is permitted to modify the runtime file from using Exim as a way to get root.
40481 .section "Root privilege" "SECID270"
40483 .cindex "root privilege"
40484 The Exim binary is normally setuid to root, which means that it gains root
40485 privilege (runs as root) when it starts execution. In some special cases (for
40486 example, when the daemon is not in use and there are no local deliveries), it
40487 may be possible to run Exim setuid to some user other than root. This is
40488 discussed in the next section. However, in most installations, root privilege
40489 is required for two things:
40492 To set up a socket connected to the standard SMTP port (25) when initialising
40493 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40496 To be able to change uid and gid in order to read users' &_.forward_& files and
40497 perform local deliveries as the receiving user or as specified in the
40501 It is not necessary to be root to do any of the other things Exim does, such as
40502 receiving messages and delivering them externally over SMTP, and it is
40503 obviously more secure if Exim does not run as root except when necessary.
40504 For this reason, a user and group for Exim to use must be defined in
40505 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40506 group"&. Their values can be changed by the runtime configuration, though this
40507 is not recommended. Often a user called &'exim'& is used, but some sites use
40508 &'mail'& or another user name altogether.
40510 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40511 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40512 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40514 After a new Exim process has interpreted its command line options, it changes
40515 uid and gid in the following cases:
40520 If the &%-C%& option is used to specify an alternate configuration file, or if
40521 the &%-D%& option is used to define macro values for the configuration, and the
40522 calling process is not running as root, the uid and gid are changed to those of
40523 the calling process.
40524 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40525 option may not be used at all.
40526 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40527 can be supplied if the calling process is running as root, the Exim run-time
40528 user or CONFIGURE_OWNER, if defined.
40533 If the expansion test option (&%-be%&) or one of the filter testing options
40534 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40537 If the process is not a daemon process or a queue runner process or a delivery
40538 process or a process for testing address routing (started with &%-bt%&), the
40539 uid and gid are changed to the Exim user and group. This means that Exim always
40540 runs under its own uid and gid when receiving messages. This also applies when
40541 testing address verification
40544 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40547 For a daemon, queue runner, delivery, or address testing process, the uid
40548 remains as root at this stage, but the gid is changed to the Exim group.
40551 The processes that initially retain root privilege behave as follows:
40554 A daemon process changes the gid to the Exim group and the uid to the Exim
40555 user after setting up one or more listening sockets. The &[initgroups()]&
40556 function is called, so that if the Exim user is in any additional groups, they
40557 will be used during message reception.
40559 A queue runner process retains root privilege throughout its execution. Its
40560 job is to fork a controlled sequence of delivery processes.
40562 A delivery process retains root privilege throughout most of its execution,
40563 but any actual deliveries (that is, the transports themselves) are run in
40564 subprocesses which always change to a non-root uid and gid. For local
40565 deliveries this is typically the uid and gid of the owner of the mailbox; for
40566 remote deliveries, the Exim uid and gid are used. Once all the delivery
40567 subprocesses have been run, a delivery process changes to the Exim uid and gid
40568 while doing post-delivery tidying up such as updating the retry database and
40569 generating bounce and warning messages.
40571 While the recipient addresses in a message are being routed, the delivery
40572 process runs as root. However, if a user's filter file has to be processed,
40573 this is done in a subprocess that runs under the individual user's uid and
40574 gid. A system filter is run as root unless &%system_filter_user%& is set.
40576 A process that is testing addresses (the &%-bt%& option) runs as root so that
40577 the routing is done in the same environment as a message delivery.
40583 .section "Running Exim without privilege" "SECTrunexiwitpri"
40584 .cindex "privilege, running without"
40585 .cindex "unprivileged running"
40586 .cindex "root privilege" "running without"
40587 Some installations like to run Exim in an unprivileged state for more of its
40588 operation, for added security. Support for this mode of operation is provided
40589 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40590 gid are changed to the Exim user and group at the start of a delivery process
40591 (and also queue runner and address testing processes). This means that address
40592 routing is no longer run as root, and the deliveries themselves cannot change
40596 .cindex "daemon" "restarting"
40597 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40598 that the daemon can still be started in the usual way, and it can respond
40599 correctly to SIGHUP because the re-invocation regains root privilege.
40601 An alternative approach is to make Exim setuid to the Exim user and also setgid
40602 to the Exim group. If you do this, the daemon must be started from a root
40603 process. (Calling Exim from a root process makes it behave in the way it does
40604 when it is setuid root.) However, the daemon cannot restart itself after a
40605 SIGHUP signal because it cannot regain privilege.
40607 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40608 stops Exim from trying to re-invoke itself to do a delivery after a message has
40609 been received. Such a re-invocation is a waste of resources because it has no
40612 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40613 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40614 to the Exim user seems a clean approach, but there is one complication:
40616 In this style of operation, Exim is running with the real uid and gid set to
40617 those of the calling process, and the effective uid/gid set to Exim's values.
40618 Ideally, any association with the calling process' uid/gid should be dropped,
40619 that is, the real uid/gid should be reset to the effective values so as to
40620 discard any privileges that the caller may have. While some operating systems
40621 have a function that permits this action for a non-root effective uid, quite a
40622 number of them do not. Because of this lack of standardization, Exim does not
40623 address this problem at this time.
40625 For this reason, the recommended approach for &"mostly unprivileged"& running
40626 is to keep the Exim binary setuid to root, and to set
40627 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40628 be used in the most straightforward way.
40630 If you configure Exim not to run delivery processes as root, there are a
40631 number of restrictions on what you can do:
40634 You can deliver only as the Exim user/group. You should explicitly use the
40635 &%user%& and &%group%& options to override routers or local transports that
40636 normally deliver as the recipient. This makes sure that configurations that
40637 work in this mode function the same way in normal mode. Any implicit or
40638 explicit specification of another user causes an error.
40640 Use of &_.forward_& files is severely restricted, such that it is usually
40641 not worthwhile to include them in the configuration.
40643 Users who wish to use &_.forward_& would have to make their home directory and
40644 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40645 and their equivalents in Exim filters, cannot be used. While they could be
40646 enabled in the Exim user's name, that would be insecure and not very useful.
40648 Unless the local user mailboxes are all owned by the Exim user (possible in
40649 some POP3 or IMAP-only environments):
40652 They must be owned by the Exim group and be writeable by that group. This
40653 implies you must set &%mode%& in the appendfile configuration, as well as the
40654 mode of the mailbox files themselves.
40656 You must set &%no_check_owner%&, since most or all of the files will not be
40657 owned by the Exim user.
40659 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40660 on a newly created mailbox when unprivileged. This also implies that new
40661 mailboxes need to be created manually.
40666 These restrictions severely restrict what can be done in local deliveries.
40667 However, there are no restrictions on remote deliveries. If you are running a
40668 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40669 gives more security at essentially no cost.
40671 If you are using the &%mua_wrapper%& facility (see chapter
40672 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40677 .section "Delivering to local files" "SECID271"
40678 Full details of the checks applied by &(appendfile)& before it writes to a file
40679 are given in chapter &<<CHAPappendfile>>&.
40683 .section "Running local commands" "SECTsecconslocalcmds"
40684 .cindex "security" "local commands"
40685 .cindex "security" "command injection attacks"
40686 There are a number of ways in which an administrator can configure Exim to run
40687 commands based upon received, untrustworthy, data. Further, in some
40688 configurations a user who can control a &_.forward_& file can also arrange to
40689 run commands. Configuration to check includes, but is not limited to:
40692 Use of &%use_shell%& in the pipe transport: various forms of shell command
40693 injection may be possible with this option present. It is dangerous and should
40694 be used only with considerable caution. Consider constraints which whitelist
40695 allowed characters in a variable which is to be used in a pipe transport that
40696 has &%use_shell%& enabled.
40698 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40699 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40700 &_.forward_& files in a redirect router. If Exim is running on a central mail
40701 hub to which ordinary users do not have shell access, but home directories are
40702 NFS mounted (for instance) then administrators should review the list of these
40703 forbid options available, and should bear in mind that the options that may
40704 need forbidding can change as new features are added between releases.
40706 The &%${run...}%& expansion item does not use a shell by default, but
40707 administrators can configure use of &_/bin/sh_& as part of the command.
40708 Such invocations should be viewed with prejudicial suspicion.
40710 Administrators who use embedded Perl are advised to explore how Perl's
40711 taint checking might apply to their usage.
40713 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40714 administrators are well advised to view its use with suspicion, in case (for
40715 instance) it allows a local-part to contain embedded Exim directives.
40717 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40718 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40719 each can reference arbitrary lists and files, rather than just being a list
40721 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40722 real-world security vulnerabilities caused by its use with untrustworthy data
40723 injected in, for SQL injection attacks.
40724 Consider the use of the &%inlisti%& expansion condition instead.
40730 .section "Trust in configuration data" "SECTsecconfdata"
40731 .cindex "security" "data sources"
40732 .cindex "security" "regular expressions"
40733 .cindex "regular expressions" "security"
40734 .cindex "PCRE" "security"
40735 If configuration data for Exim can come from untrustworthy sources, there
40736 are some issues to be aware of:
40739 Use of &%${expand...}%& may provide a path for shell injection attacks.
40741 Letting untrusted data provide a regular expression is unwise.
40743 Using &%${match...}%& to apply a fixed regular expression against untrusted
40744 data may result in pathological behaviour within PCRE. Be aware of what
40745 "backtracking" means and consider options for being more strict with a regular
40746 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40747 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40748 possessive quantifiers or just not using regular expressions against untrusted
40751 It can be important to correctly use &%${quote:...}%&,
40752 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40753 items to ensure that data is correctly constructed.
40755 Some lookups might return multiple results, even though normal usage is only
40756 expected to yield one result.
40762 .section "IPv4 source routing" "SECID272"
40763 .cindex "source routing" "in IP packets"
40764 .cindex "IP source routing"
40765 Many operating systems suppress IP source-routed packets in the kernel, but
40766 some cannot be made to do this, so Exim does its own check. It logs incoming
40767 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40768 IPv6. No special checking is currently done.
40772 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40773 Support for these SMTP commands is disabled by default. If required, they can
40774 be enabled by defining suitable ACLs.
40779 .section "Privileged users" "SECID274"
40780 .cindex "trusted users"
40781 .cindex "admin user"
40782 .cindex "privileged user"
40783 .cindex "user" "trusted"
40784 .cindex "user" "admin"
40785 Exim recognizes two sets of users with special privileges. Trusted users are
40786 able to submit new messages to Exim locally, but supply their own sender
40787 addresses and information about a sending host. For other users submitting
40788 local messages, Exim sets up the sender address from the uid, and doesn't
40789 permit a remote host to be specified.
40792 However, an untrusted user is permitted to use the &%-f%& command line option
40793 in the special form &%-f <>%& to indicate that a delivery failure for the
40794 message should not cause an error report. This affects the message's envelope,
40795 but it does not affect the &'Sender:'& header. Untrusted users may also be
40796 permitted to use specific forms of address with the &%-f%& option by setting
40797 the &%untrusted_set_sender%& option.
40799 Trusted users are used to run processes that receive mail messages from some
40800 other mail domain and pass them on to Exim for delivery either locally, or over
40801 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40802 as any user listed in the &%trusted_users%& configuration option, or under any
40803 group listed in the &%trusted_groups%& option.
40805 Admin users are permitted to do things to the messages on Exim's queue. They
40806 can freeze or thaw messages, cause them to be returned to their senders, remove
40807 them entirely, or modify them in various ways. In addition, admin users can run
40808 the Exim monitor and see all the information it is capable of providing, which
40809 includes the contents of files on the spool.
40813 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40814 delivery of messages on its queue is restricted to admin users. This
40815 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40816 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40817 queue is also restricted to admin users. This restriction can be relaxed by
40818 setting &%no_queue_list_requires_admin%&.
40820 Exim recognizes an admin user if the calling process is running as root or as
40821 the Exim user or if any of the groups associated with the calling process is
40822 the Exim group. It is not necessary actually to be running under the Exim
40823 group. However, if admin users who are not root or the Exim user are to access
40824 the contents of files on the spool via the Exim monitor (which runs
40825 unprivileged), Exim must be built to allow group read access to its spool
40828 By default, regular users are trusted to perform basic testing and
40829 introspection commands, as themselves. This setting can be tightened by
40830 setting the &%commandline_checks_require_admin%& option.
40831 This affects most of the checking options,
40832 such as &%-be%& and anything else &%-b*%&.
40835 .section "Spool files" "SECID275"
40836 .cindex "spool directory" "files"
40837 Exim's spool directory and everything it contains is owned by the Exim user and
40838 set to the Exim group. The mode for spool files is defined in the
40839 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40840 any user who is a member of the Exim group can access these files.
40844 .section "Use of argv[0]" "SECID276"
40845 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40846 of specific strings, Exim assumes certain options. For example, calling Exim
40847 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40848 to calling it with the option &%-bS%&. There are no security implications in
40853 .section "Use of %f formatting" "SECID277"
40854 The only use made of &"%f"& by Exim is in formatting load average values. These
40855 are actually stored in integer variables as 1000 times the load average.
40856 Consequently, their range is limited and so therefore is the length of the
40861 .section "Embedded Exim path" "SECID278"
40862 Exim uses its own path name, which is embedded in the code, only when it needs
40863 to re-exec in order to regain root privilege. Therefore, it is not root when it
40864 does so. If some bug allowed the path to get overwritten, it would lead to an
40865 arbitrary program's being run as exim, not as root.
40869 .section "Dynamic module directory" "SECTdynmoddir"
40870 Any dynamically loadable modules must be installed into the directory
40871 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40875 .section "Use of sprintf()" "SECID279"
40876 .cindex "&[sprintf()]&"
40877 A large number of occurrences of &"sprintf"& in the code are actually calls to
40878 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40879 The intermediate formatting is done into a large fixed buffer by a function
40880 that runs through the format string itself, and checks the length of each
40881 conversion before performing it, thus preventing buffer overruns.
40883 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40884 the output buffer is known to be sufficiently long to contain the converted
40889 .section "Use of debug_printf() and log_write()" "SECID280"
40890 Arbitrary strings are passed to both these functions, but they do their
40891 formatting by calling the function &'string_vformat()'&, which runs through
40892 the format string itself, and checks the length of each conversion.
40896 .section "Use of strcat() and strcpy()" "SECID281"
40897 These are used only in cases where the output buffer is known to be large
40898 enough to hold the result.
40899 .ecindex IIDsecurcon
40904 . ////////////////////////////////////////////////////////////////////////////
40905 . ////////////////////////////////////////////////////////////////////////////
40907 .chapter "Format of spool files" "CHAPspool"
40908 .scindex IIDforspo1 "format" "spool files"
40909 .scindex IIDforspo2 "spool directory" "format of files"
40910 .scindex IIDforspo3 "spool files" "format of"
40911 .cindex "spool files" "editing"
40912 A message on Exim's queue consists of two files, whose names are the message id
40913 followed by -D and -H, respectively. The data portion of the message is kept in
40914 the -D file on its own. The message's envelope, status, and headers are all
40915 kept in the -H file, whose format is described in this chapter. Each of these
40916 two files contains the final component of its own name as its first line. This
40917 is insurance against disk crashes where the directory is lost but the files
40918 themselves are recoverable.
40920 The file formats may be changed, or new formats added, at any release.
40921 Spool files are not intended as an interface to other programs
40922 and should not be used as such.
40924 Some people are tempted into editing -D files in order to modify messages. You
40925 need to be extremely careful if you do this; it is not recommended and you are
40926 on your own if you do it. Here are some of the pitfalls:
40929 You must ensure that Exim does not try to deliver the message while you are
40930 fiddling with it. The safest way is to take out a write lock on the -D file,
40931 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40932 place, the lock will be retained. If you write a new file and rename it, the
40933 lock will be lost at the instant of rename.
40935 .vindex "&$body_linecount$&"
40936 If you change the number of lines in the file, the value of
40937 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40938 cause incomplete transmission of messages or undeliverable messages.
40940 If the message is in MIME format, you must take care not to break it.
40942 If the message is cryptographically signed, any change will invalidate the
40945 All in all, modifying -D files is fraught with danger.
40947 Files whose names end with -J may also be seen in the &_input_& directory (or
40948 its subdirectories when &%split_spool_directory%& is set). These are journal
40949 files, used to record addresses to which the message has been delivered during
40950 the course of a delivery attempt. If there are still undelivered recipients at
40951 the end, the -H file is updated, and the -J file is deleted. If, however, there
40952 is some kind of crash (for example, a power outage) before this happens, the -J
40953 file remains in existence. When Exim next processes the message, it notices the
40954 -J file and uses it to update the -H file before starting the next delivery
40957 Files whose names end with -K or .eml may also be seen in the spool.
40958 These are temporaries used for DKIM or malware processing, when that is used.
40959 They should be tidied up by normal operations; any old ones are probably
40960 relics of crashes and can be removed.
40962 .section "Format of the -H file" "SECID282"
40963 .cindex "uid (user id)" "in spool file"
40964 .cindex "gid (group id)" "in spool file"
40965 The second line of the -H file contains the login name for the uid of the
40966 process that called Exim to read the message, followed by the numerical uid and
40967 gid. For a locally generated message, this is normally the user who sent the
40968 message. For a message received over TCP/IP via the daemon, it is
40969 normally the Exim user.
40971 The third line of the file contains the address of the message's sender as
40972 transmitted in the envelope, contained in angle brackets. The sender address is
40973 empty for bounce messages. For incoming SMTP mail, the sender address is given
40974 in the MAIL command. For locally generated mail, the sender address is
40975 created by Exim from the login name of the current user and the configured
40976 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40977 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40978 &"<>"& or an address that matches &%untrusted_set_senders%&.
40980 The fourth line contains two numbers. The first is the time that the message
40981 was received, in the conventional Unix form &-- the number of seconds since the
40982 start of the epoch. The second number is a count of the number of messages
40983 warning of delayed delivery that have been sent to the sender.
40985 There follow a number of lines starting with a hyphen. These can appear in any
40986 order, and are omitted when not relevant:
40989 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40990 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40991 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40992 recognized, to provide backward compatibility. In the old format, a line of
40993 this form is present for every ACL variable that is not empty. The number
40994 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40995 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40996 the data string for the variable. The string itself starts at the beginning of
40997 the next line, and is followed by a newline character. It may contain internal
41000 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
41001 A line of this form is present for every ACL connection variable that is
41002 defined. Note that there is a space between &%-aclc%& and the rest of the name.
41003 The length is the length of the data string for the variable. The string itself
41004 starts at the beginning of the next line, and is followed by a newline
41005 character. It may contain internal newlines.
41007 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41008 A line of this form is present for every ACL message variable that is defined.
41009 Note that there is a space between &%-aclm%& and the rest of the name. The
41010 length is the length of the data string for the variable. The string itself
41011 starts at the beginning of the next line, and is followed by a newline
41012 character. It may contain internal newlines.
41014 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41015 This is present if, when the message was received over SMTP, the value of
41016 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41018 .vitem &%-allow_unqualified_recipient%&
41019 This is present if unqualified recipient addresses are permitted in header
41020 lines (to stop such addresses from being qualified if rewriting occurs at
41021 transport time). Local messages that were input using &%-bnq%& and remote
41022 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41024 .vitem &%-allow_unqualified_sender%&
41025 This is present if unqualified sender addresses are permitted in header lines
41026 (to stop such addresses from being qualified if rewriting occurs at transport
41027 time). Local messages that were input using &%-bnq%& and remote messages from
41028 hosts that match &%sender_unqualified_hosts%& set this flag.
41030 .vitem "&%-auth_id%&&~<&'text'&>"
41031 The id information for a message received on an authenticated SMTP connection
41032 &-- the value of the &$authenticated_id$& variable.
41034 .vitem "&%-auth_sender%&&~<&'address'&>"
41035 The address of an authenticated sender &-- the value of the
41036 &$authenticated_sender$& variable.
41038 .vitem "&%-body_linecount%&&~<&'number'&>"
41039 This records the number of lines in the body of the message, and is
41040 present unless &%-spool_file_wireformat%& is.
41042 .vitem "&%-body_zerocount%&&~<&'number'&>"
41043 This records the number of binary zero bytes in the body of the message, and is
41044 present if the number is greater than zero.
41046 .vitem &%-deliver_firsttime%&
41047 This is written when a new message is first added to the spool. When the spool
41048 file is updated after a deferral, it is omitted.
41050 .vitem "&%-frozen%&&~<&'time'&>"
41051 .cindex "frozen messages" "spool data"
41052 The message is frozen, and the freezing happened at <&'time'&>.
41054 .vitem "&%-helo_name%&&~<&'text'&>"
41055 This records the host name as specified by a remote host in a HELO or EHLO
41058 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41059 This records the IP address of the host from which the message was received and
41060 the remote port number that was used. It is omitted for locally generated
41063 .vitem "&%-host_auth%&&~<&'text'&>"
41064 If the message was received on an authenticated SMTP connection, this records
41065 the name of the authenticator &-- the value of the
41066 &$sender_host_authenticated$& variable.
41068 .vitem &%-host_lookup_failed%&
41069 This is present if an attempt to look up the sending host's name from its IP
41070 address failed. It corresponds to the &$host_lookup_failed$& variable.
41072 .vitem "&%-host_name%&&~<&'text'&>"
41073 .cindex "reverse DNS lookup"
41074 .cindex "DNS" "reverse lookup"
41075 This records the name of the remote host from which the message was received,
41076 if the host name was looked up from the IP address when the message was being
41077 received. It is not present if no reverse lookup was done.
41079 .vitem "&%-ident%&&~<&'text'&>"
41080 For locally submitted messages, this records the login of the originating user,
41081 unless it was a trusted user and the &%-oMt%& option was used to specify an
41082 ident value. For messages received over TCP/IP, this records the ident string
41083 supplied by the remote host, if any.
41085 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41086 This records the IP address of the local interface and the port number through
41087 which a message was received from a remote host. It is omitted for locally
41088 generated messages.
41091 The message is from a local sender.
41093 .vitem &%-localerror%&
41094 The message is a locally-generated bounce message.
41096 .vitem "&%-local_scan%&&~<&'string'&>"
41097 This records the data string that was returned by the &[local_scan()]& function
41098 when the message was received &-- the value of the &$local_scan_data$&
41099 variable. It is omitted if no data was returned.
41101 .vitem &%-manual_thaw%&
41102 The message was frozen but has been thawed manually, that is, by an explicit
41103 Exim command rather than via the auto-thaw process.
41106 A testing delivery process was started using the &%-N%& option to suppress any
41107 actual deliveries, but delivery was deferred. At any further delivery attempts,
41110 .vitem &%-received_protocol%&
41111 This records the value of the &$received_protocol$& variable, which contains
41112 the name of the protocol by which the message was received.
41114 .vitem &%-sender_set_untrusted%&
41115 The envelope sender of this message was set by an untrusted local caller (used
41116 to ensure that the caller is displayed in queue listings).
41118 .vitem "&%-spam_score_int%&&~<&'number'&>"
41119 If a message was scanned by SpamAssassin, this is present. It records the value
41120 of &$spam_score_int$&.
41122 .vitem &%-spool_file_wireformat%&
41123 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41124 rather than Unix-format.
41125 The line-ending is CRLF rather than newline.
41126 There is still, however, no leading-dot-stuffing.
41128 .vitem &%-tls_certificate_verified%&
41129 A TLS certificate was received from the client that sent this message, and the
41130 certificate was verified by the server.
41132 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41133 When the message was received over an encrypted connection, this records the
41134 name of the cipher suite that was used.
41136 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41137 When the message was received over an encrypted connection, and a certificate
41138 was received from the client, this records the Distinguished Name from that
41142 Any of the above may have an extra hyphen prepended, to indicate the the
41143 corresponding data is untrusted.
41145 Following the options there is a list of those addresses to which the message
41146 is not to be delivered. This set of addresses is initialized from the command
41147 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41148 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41149 the address is added to this set. The addresses are kept internally as a
41150 balanced binary tree, and it is a representation of that tree which is written
41151 to the spool file. If an address is expanded via an alias or forward file, the
41152 original address is added to the tree when deliveries to all its child
41153 addresses are complete.
41155 If the tree is empty, there is a single line in the spool file containing just
41156 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41157 Y or N, followed by an address. The address is the value for the node of the
41158 tree, and the letters indicate whether the node has a left branch and/or a
41159 right branch attached to it, respectively. If branches exist, they immediately
41160 follow. Here is an example of a three-node tree:
41162 YY darcy@austen.fict.example
41163 NN alice@wonderland.fict.example
41164 NN editor@thesaurus.ref.example
41166 After the non-recipients tree, there is a list of the message's recipients.
41167 This is a simple list, preceded by a count. It includes all the original
41168 recipients of the message, including those to whom the message has already been
41169 delivered. In the simplest case, the list contains one address per line. For
41173 editor@thesaurus.ref.example
41174 darcy@austen.fict.example
41176 alice@wonderland.fict.example
41178 However, when a child address has been added to the top-level addresses as a
41179 result of the use of the &%one_time%& option on a &(redirect)& router, each
41180 line is of the following form:
41182 <&'top-level address'&> <&'errors_to address'&> &&&
41183 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41185 The 01 flag bit indicates the presence of the three other fields that follow
41186 the top-level address. Other bits may be used in future to support additional
41187 fields. The <&'parent number'&> is the offset in the recipients list of the
41188 original parent of the &"one time"& address. The first two fields are the
41189 envelope sender that is associated with this address and its length. If the
41190 length is zero, there is no special envelope sender (there are then two space
41191 characters in the line). A non-empty field can arise from a &(redirect)& router
41192 that has an &%errors_to%& setting.
41195 A blank line separates the envelope and status information from the headers
41196 which follow. A header may occupy several lines of the file, and to save effort
41197 when reading it in, each header is preceded by a number and an identifying
41198 character. The number is the number of characters in the header, including any
41199 embedded newlines and the terminating newline. The character is one of the
41203 .row <&'blank'&> "header in which Exim has no special interest"
41204 .row &`B`& "&'Bcc:'& header"
41205 .row &`C`& "&'Cc:'& header"
41206 .row &`F`& "&'From:'& header"
41207 .row &`I`& "&'Message-id:'& header"
41208 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41209 .row &`R`& "&'Reply-To:'& header"
41210 .row &`S`& "&'Sender:'& header"
41211 .row &`T`& "&'To:'& header"
41212 .row &`*`& "replaced or deleted header"
41215 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41216 purposes. They are not transmitted when the message is delivered. Here is a
41217 typical set of headers:
41219 111P Received: by hobbit.fict.example with local (Exim 4.00)
41220 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41221 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41222 038* X-rewrote-sender: bb@hobbit.fict.example
41223 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41224 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41225 099* To: alice@wonderland.fict.example, rdo@foundation,
41226 darcy@austen.fict.example, editor@thesaurus.ref.example
41227 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41228 darcy@austen.fict.example, editor@thesaurus.ref.example
41229 038 Date: Fri, 11 May 2001 10:28:59 +0100
41231 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41232 &'To:'& header have been rewritten, the last one because routing expanded the
41233 unqualified domain &'foundation'&.
41234 .ecindex IIDforspo1
41235 .ecindex IIDforspo2
41236 .ecindex IIDforspo3
41238 .section "Format of the -D file" "SECID282a"
41239 The data file is traditionally in Unix-standard format: lines are ended with
41240 an ASCII newline character.
41241 However, when the &%spool_wireformat%& main option is used some -D files
41242 can have an alternate format.
41243 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41244 The -D file lines (not including the first name-component line) are
41245 suitable for direct copying to the wire when transmitting using the
41246 ESMTP CHUNKING option, meaning lower processing overhead.
41247 Lines are terminated with an ASCII CRLF pair.
41248 There is no dot-stuffing (and no dot-termination).
41250 . ////////////////////////////////////////////////////////////////////////////
41251 . ////////////////////////////////////////////////////////////////////////////
41253 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41254 "DKIM, SPF, SRS and DMARC Support"
41256 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41259 DKIM is a mechanism by which messages sent by some entity can be provably
41260 linked to a domain which that entity controls. It permits reputation to
41261 be tracked on a per-domain basis, rather than merely upon source IP address.
41262 DKIM is documented in RFC 6376.
41264 As DKIM relies on the message being unchanged in transit, messages handled
41265 by a mailing-list (which traditionally adds to the message) will not match
41266 any original DKIM signature.
41268 DKIM support is compiled into Exim by default if TLS support is present.
41269 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41271 Exim's DKIM implementation allows for
41273 Signing outgoing messages: This function is implemented in the SMTP transport.
41274 It can co-exist with all other Exim features
41275 (including transport filters)
41276 except cutthrough delivery.
41278 Verifying signatures in incoming messages: This is implemented by an additional
41279 ACL (acl_smtp_dkim), which can be called several times per message, with
41280 different signature contexts.
41283 In typical Exim style, the verification implementation does not include any
41284 default "policy". Instead it enables you to build your own policy using
41285 Exim's standard controls.
41287 Please note that verification of DKIM signatures in incoming mail is turned
41288 on by default for logging (in the <= line) purposes.
41290 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41291 When set, for each signature in incoming email,
41292 exim will log a line displaying the most important signature details, and the
41293 signature status. Here is an example (with line-breaks added for clarity):
41295 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41296 d=facebookmail.com s=q1-2009b
41297 c=relaxed/relaxed a=rsa-sha1
41298 i=@facebookmail.com t=1252484542 [verification succeeded]
41301 You might want to turn off DKIM verification processing entirely for internal
41302 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41303 control modifier. This should typically be done in the RCPT ACL, at points
41304 where you accept mail from relay sources (internal hosts or authenticated
41308 .section "Signing outgoing messages" "SECDKIMSIGN"
41309 .cindex "DKIM" "signing"
41311 For signing to be usable you must have published a DKIM record in DNS.
41312 Note that RFC 8301 (which does not cover EC keys) says:
41314 rsa-sha1 MUST NOT be used for signing or verifying.
41316 Signers MUST use RSA keys of at least 1024 bits for all keys.
41317 Signers SHOULD use RSA keys of at least 2048 bits.
41320 Note also that the key content (the 'p=' field)
41321 in the DNS record is different between RSA and EC keys;
41322 for the former it is the base64 of the ASN.1 for the RSA public key
41323 (equivalent to the private-key .pem with the header/trailer stripped)
41324 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41326 Signing is enabled by setting private options on the SMTP transport.
41327 These options take (expandable) strings as arguments.
41329 .option dkim_domain smtp "string list&!!" unset
41330 The domain(s) you want to sign with.
41331 After expansion, this can be a list.
41332 Each element in turn,
41334 is put into the &%$dkim_domain%& expansion variable
41335 while expanding the remaining signing options.
41336 If it is empty after expansion, DKIM signing is not done,
41337 and no error will result even if &%dkim_strict%& is set.
41339 .option dkim_selector smtp "string list&!!" unset
41340 This sets the key selector string.
41341 After expansion, which can use &$dkim_domain$&, this can be a list.
41342 Each element in turn is put in the expansion
41343 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41344 option along with &%$dkim_domain%&.
41345 If the option is empty after expansion, DKIM signing is not done for this domain,
41346 and no error will result even if &%dkim_strict%& is set.
41349 To do, for example, dual-signing with RSA and EC keys
41350 this could be be used:
41352 dkim_selector = ec_sel : rsa_sel
41353 dkim_private_key = KEYS_DIR/$dkim_selector
41357 .option dkim_private_key smtp string&!! unset
41358 This sets the private key to use.
41359 You can use the &%$dkim_domain%& and
41360 &%$dkim_selector%& expansion variables to determine the private key to use.
41361 The result can either
41363 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41365 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41366 be a valid Ed25519 private key (same format as above)
41368 start with a slash, in which case it is treated as a file that contains
41371 be "0", "false" or the empty string, in which case the message will not
41372 be signed. This case will not result in an error, even if &%dkim_strict%&
41376 To generate keys under OpenSSL:
41378 openssl genrsa -out dkim_rsa.private 2048
41379 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41381 The result file from the first command should be retained, and
41382 this option set to use it.
41383 Take the base-64 lines from the output of the second command, concatenated,
41384 for the DNS TXT record.
41385 See section 3.6 of RFC6376 for the record specification.
41389 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41390 certtool --load-privkey=dkim_rsa.private --pubkey-info
41393 Note that RFC 8301 says:
41395 Signers MUST use RSA keys of at least 1024 bits for all keys.
41396 Signers SHOULD use RSA keys of at least 2048 bits.
41399 EC keys for DKIM are defined by RFC 8463.
41400 They are considerably smaller than RSA keys for equivalent protection.
41401 As they are a recent development, users should consider dual-signing
41402 (by setting a list of selectors, and an expansion for this option)
41403 for some transition period.
41404 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41407 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41409 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41410 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41413 To produce the required public key value for a DNS record:
41415 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41416 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41419 Exim also supports an alternate format
41420 of Ed25519 keys in DNS which was a candidate during development
41421 of the standard, but not adopted.
41422 A future release will probably drop that support.
41424 .option dkim_hash smtp string&!! sha256
41425 Can be set to any one of the supported hash methods, which are:
41427 &`sha1`& &-- should not be used, is old and insecure
41429 &`sha256`& &-- the default
41431 &`sha512`& &-- possibly more secure but less well supported
41434 Note that RFC 8301 says:
41436 rsa-sha1 MUST NOT be used for signing or verifying.
41439 .option dkim_identity smtp string&!! unset
41440 If set after expansion, the value is used to set an "i=" tag in
41441 the signing header. The DKIM standards restrict the permissible
41442 syntax of this optional tag to a mail address, with possibly-empty
41443 local part, an @, and a domain identical to or subdomain of the "d="
41444 tag value. Note that Exim does not check the value.
41446 .option dkim_canon smtp string&!! unset
41447 This option sets the canonicalization method used when signing a message.
41448 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41449 The option defaults to "relaxed" when unset. Note: the current implementation
41450 only supports signing with the same canonicalization method for both headers and body.
41452 .option dkim_strict smtp string&!! unset
41453 This option defines how Exim behaves when signing a message that
41454 should be signed fails for some reason. When the expansion evaluates to
41455 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41456 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41459 .option dkim_sign_headers smtp string&!! "see below"
41460 If set, this option must expand to a colon-separated
41461 list of header names.
41462 Headers with these names, or the absence or such a header, will be included
41463 in the message signature.
41464 When unspecified, the header names listed in RFC4871 will be used,
41465 whether or not each header is present in the message.
41466 The default list is available for the expansion in the macro
41467 &"_DKIM_SIGN_HEADERS"&
41468 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41470 If a name is repeated, multiple headers by that name (or the absence thereof)
41471 will be signed. The textually later headers in the headers part of the
41472 message are signed first, if there are multiples.
41474 A name can be prefixed with either an &"="& or a &"+"& character.
41475 If an &"="& prefix is used, all headers that are present with this name
41477 If a &"+"& prefix if used, all headers that are present with this name
41478 will be signed, and one signature added for a missing header with the
41479 name will be appended.
41481 .option dkim_timestamps smtp integer&!! unset
41482 This option controls the inclusion of timestamp information in the signature.
41483 If not set, no such information will be included.
41484 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41486 (eg. 1209600 for two weeks);
41487 both creation (t=) and expiry (x=) tags will be included.
41489 RFC 6376 lists these tags as RECOMMENDED.
41492 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41493 .cindex "DKIM" "verification"
41495 Verification of DKIM signatures in SMTP incoming email is done for all
41496 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41497 .cindex DKIM "selecting signature algorithms"
41498 Individual classes of signature algorithm can be ignored by changing
41499 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41500 The &%dkim_verify_minimal%& option can be set to cease verification
41501 processing for a message once the first passing signature is found.
41503 .cindex authentication "expansion item"
41504 Performing verification sets up information used by the
41505 &%authresults%& expansion item.
41507 For most purposes the default option settings suffice and the remainder
41508 of this section can be ignored.
41510 The results of verification are made available to the
41511 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41512 A missing ACL definition defaults to accept.
41513 By default, the ACL is called once for each
41514 syntactically(!) correct signature in the incoming message.
41515 If any ACL call does not accept, the message is not accepted.
41516 If a cutthrough delivery was in progress for the message, that is
41517 summarily dropped (having wasted the transmission effort).
41519 To evaluate the verification result in the ACL
41520 a large number of expansion variables
41521 containing the signature status and its details are set up during the
41522 runtime of the ACL.
41524 Calling the ACL only for existing signatures is not sufficient to build
41525 more advanced policies. For that reason, the main option
41526 &%dkim_verify_signers%&, and an expansion variable
41527 &%$dkim_signers%& exist.
41529 The main option &%dkim_verify_signers%& can be set to a colon-separated
41530 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41531 called. It is expanded when the message has been received. At this point,
41532 the expansion variable &%$dkim_signers%& already contains a colon-separated
41533 list of signer domains and identities for the message. When
41534 &%dkim_verify_signers%& is not specified in the main configuration,
41537 dkim_verify_signers = $dkim_signers
41539 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41540 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41541 call the ACL for known domains or identities. This would be achieved as follows:
41543 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41545 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41546 and "ebay.com", plus all domains and identities that have signatures in the message.
41547 You can also be more creative in constructing your policy. For example:
41549 dkim_verify_signers = $sender_address_domain:$dkim_signers
41552 If a domain or identity is listed several times in the (expanded) value of
41553 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41555 Note that if the option is set using untrustworthy data
41556 (such as the From: header)
41557 care should be taken to force lowercase for domains
41558 and for the domain part if identities.
41559 The default setting can be regarded as trustworthy in this respect.
41561 If multiple signatures match a domain (or identity), the ACL is called once
41562 for each matching signature.
41565 Inside the DKIM ACL, the following expansion variables are
41566 available (from most to least important):
41570 .vitem &%$dkim_cur_signer%&
41571 The signer that is being evaluated in this ACL run. This can be a domain or
41572 an identity. This is one of the list items from the expanded main option
41573 &%dkim_verify_signers%& (see above).
41575 .vitem &%$dkim_verify_status%&
41576 Within the DKIM ACL,
41577 a string describing the general status of the signature. One of
41579 &%none%&: There is no signature in the message for the current domain or
41580 identity (as reflected by &%$dkim_cur_signer%&).
41582 &%invalid%&: The signature could not be verified due to a processing error.
41583 More detail is available in &%$dkim_verify_reason%&.
41585 &%fail%&: Verification of the signature failed. More detail is
41586 available in &%$dkim_verify_reason%&.
41588 &%pass%&: The signature passed verification. It is valid.
41591 This variable can be overwritten using an ACL 'set' modifier.
41592 This might, for instance, be done to enforce a policy restriction on
41593 hash-method or key-size:
41595 warn condition = ${if eq {$dkim_verify_status}{pass}}
41596 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41597 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41598 {< {$dkim_key_length}{1024}}}}
41599 logwrite = NOTE: forcing DKIM verify fail (was pass)
41600 set dkim_verify_status = fail
41601 set dkim_verify_reason = hash too weak or key too short
41604 So long as a DKIM ACL is defined (it need do no more than accept),
41605 after all the DKIM ACL runs have completed, the value becomes a
41606 colon-separated list of the values after each run.
41607 This is maintained for the mime, prdr and data ACLs.
41609 .vitem &%$dkim_verify_reason%&
41610 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41611 "fail" or "invalid". One of
41613 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41614 key for the domain could not be retrieved. This may be a temporary problem.
41616 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41617 record for the domain is syntactically invalid.
41619 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41620 body hash does not match the one specified in the signature header. This
41621 means that the message body was modified in transit.
41623 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41624 could not be verified. This may mean that headers were modified,
41625 re-written or otherwise changed in a way which is incompatible with
41626 DKIM verification. It may of course also mean that the signature is forged.
41629 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41631 .vitem &%$dkim_domain%&
41632 The signing domain. IMPORTANT: This variable is only populated if there is
41633 an actual signature in the message for the current domain or identity (as
41634 reflected by &%$dkim_cur_signer%&).
41636 .vitem &%$dkim_identity%&
41637 The signing identity, if present. IMPORTANT: This variable is only populated
41638 if there is an actual signature in the message for the current domain or
41639 identity (as reflected by &%$dkim_cur_signer%&).
41641 .vitem &%$dkim_selector%&
41642 The key record selector string.
41644 .vitem &%$dkim_algo%&
41645 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41646 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41647 may also be 'ed25519-sha256'.
41648 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41651 Note that RFC 8301 says:
41653 rsa-sha1 MUST NOT be used for signing or verifying.
41655 DKIM signatures identified as having been signed with historic
41656 algorithms (currently, rsa-sha1) have permanently failed evaluation
41659 To enforce this you must either have a DKIM ACL which checks this variable
41660 and overwrites the &$dkim_verify_status$& variable as discussed above,
41661 or have set the main option &%dkim_verify_hashes%& to exclude
41662 processing of such signatures.
41664 .vitem &%$dkim_canon_body%&
41665 The body canonicalization method. One of 'relaxed' or 'simple'.
41667 .vitem &%$dkim_canon_headers%&
41668 The header canonicalization method. One of 'relaxed' or 'simple'.
41670 .vitem &%$dkim_copiedheaders%&
41671 A transcript of headers and their values which are included in the signature
41672 (copied from the 'z=' tag of the signature).
41673 Note that RFC6376 requires that verification fail if the From: header is
41674 not included in the signature. Exim does not enforce this; sites wishing
41675 strict enforcement should code the check explicitly.
41677 .vitem &%$dkim_bodylength%&
41678 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41679 limit was set by the signer, "9999999999999" is returned. This makes sure
41680 that this variable always expands to an integer value.
41681 &*Note:*& The presence of the signature tag specifying a signing body length
41682 is one possible route to spoofing of valid DKIM signatures.
41683 A paranoid implementation might wish to regard signature where this variable
41684 shows less than the "no limit" return as being invalid.
41686 .vitem &%$dkim_created%&
41687 UNIX timestamp reflecting the date and time when the signature was created.
41688 When this was not specified by the signer, "0" is returned.
41690 .vitem &%$dkim_expires%&
41691 UNIX timestamp reflecting the date and time when the signer wants the
41692 signature to be treated as "expired". When this was not specified by the
41693 signer, "9999999999999" is returned. This makes it possible to do useful
41694 integer size comparisons against this value.
41695 Note that Exim does not check this value.
41697 .vitem &%$dkim_headernames%&
41698 A colon-separated list of names of headers included in the signature.
41700 .vitem &%$dkim_key_testing%&
41701 "1" if the key record has the "testing" flag set, "0" if not.
41703 .vitem &%$dkim_key_nosubdomains%&
41704 "1" if the key record forbids subdomaining, "0" otherwise.
41706 .vitem &%$dkim_key_srvtype%&
41707 Service type (tag s=) from the key record. Defaults to "*" if not specified
41710 .vitem &%$dkim_key_granularity%&
41711 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41714 .vitem &%$dkim_key_notes%&
41715 Notes from the key record (tag n=).
41717 .vitem &%$dkim_key_length%&
41718 Number of bits in the key.
41719 Valid only once the key is loaded, which is at the time the header signature
41720 is verified, which is after the body hash is.
41722 Note that RFC 8301 says:
41724 Verifiers MUST NOT consider signatures using RSA keys of
41725 less than 1024 bits as valid signatures.
41728 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41733 In addition, two ACL conditions are provided:
41736 .vitem &%dkim_signers%&
41737 ACL condition that checks a colon-separated list of domains or identities
41738 for a match against the domain or identity that the ACL is currently verifying
41739 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41740 verb to a group of domains or identities. For example:
41743 # Warn when Mail purportedly from GMail has no gmail signature
41744 warn sender_domains = gmail.com
41745 dkim_signers = gmail.com
41747 log_message = GMail sender without gmail.com DKIM signature
41750 Note that the above does not check for a total lack of DKIM signing;
41751 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41753 .vitem &%dkim_status%&
41754 ACL condition that checks a colon-separated list of possible DKIM verification
41755 results against the actual result of verification. This is typically used
41756 to restrict an ACL verb to a list of verification outcomes, for example:
41759 deny sender_domains = paypal.com:paypal.de
41760 dkim_signers = paypal.com:paypal.de
41761 dkim_status = none:invalid:fail
41762 message = Mail from Paypal with invalid/missing signature
41765 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41766 see the documentation of the &%$dkim_verify_status%& expansion variable above
41767 for more information of what they mean.
41773 .section "SPF (Sender Policy Framework)" SECSPF
41774 .cindex SPF verification
41776 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41777 messages with its domain in the envelope from, documented by RFC 7208.
41778 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41779 the &url(http://openspf.org).
41780 . --- 2019-10-28: still not https, open-spf.org is told to be a
41781 . --- web-archive copy of the now dead openspf.org site
41782 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41785 Messages sent by a system not authorised will fail checking of such assertions.
41786 This includes retransmissions done by traditional forwarders.
41788 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41789 &_Local/Makefile_&. The support uses the &_libspf2_& library
41790 &url(https://www.libspf2.org/).
41791 There is no Exim involvement in the transmission of messages;
41792 publishing certain DNS records is all that is required.
41794 For verification, an ACL condition and an expansion lookup are provided.
41795 .cindex authentication "expansion item"
41796 Performing verification sets up information used by the
41797 &%authresults%& expansion item.
41800 .cindex SPF "ACL condition"
41801 .cindex ACL "spf condition"
41802 The ACL condition "spf" can be used at or after the MAIL ACL.
41803 It takes as an argument a list of strings giving the outcome of the SPF check,
41804 and will succeed for any matching outcome.
41808 The SPF check passed, the sending host is positively verified by SPF.
41811 The SPF check failed, the sending host is NOT allowed to send mail for the
41812 domain in the envelope-from address.
41814 .vitem &%softfail%&
41815 The SPF check failed, but the queried domain can't absolutely confirm that this
41819 The queried domain does not publish SPF records.
41822 The SPF check returned a "neutral" state. This means the queried domain has
41823 published a SPF record, but wants to allow outside servers to send mail under
41824 its domain as well. This should be treated like "none".
41826 .vitem &%permerror%&
41827 This indicates a syntax error in the SPF record of the queried domain.
41828 You may deny messages when this occurs.
41830 .vitem &%temperror%&
41831 This indicates a temporary error during all processing, including Exim's
41832 SPF processing. You may defer messages when this occurs.
41835 There was an error during processing of the SPF lookup
41838 You can prefix each string with an exclamation mark to invert
41839 its meaning, for example "!fail" will match all results but
41840 "fail". The string list is evaluated left-to-right, in a
41841 short-circuit fashion.
41846 message = $sender_host_address is not allowed to send mail from \
41847 ${if def:sender_address_domain \
41848 {$sender_address_domain}{$sender_helo_name}}. \
41849 Please see http://www.open-spf.org/Why;\
41850 identity=${if def:sender_address_domain \
41851 {$sender_address}{$sender_helo_name}};\
41852 ip=$sender_host_address
41855 Note: The above mentioned URL may not be as helpful as expected. You are
41856 encouraged to replace the link with a link to a site with more
41859 When the spf condition has run, it sets up several expansion
41862 .cindex SPF "verification variables"
41864 .vitem &$spf_header_comment$&
41865 .vindex &$spf_header_comment$&
41866 This contains a human-readable string describing the outcome
41867 of the SPF check. You can add it to a custom header or use
41868 it for logging purposes.
41870 .vitem &$spf_received$&
41871 .vindex &$spf_received$&
41872 This contains a complete Received-SPF: header that can be
41873 added to the message. Please note that according to the SPF
41874 draft, this header must be added at the top of the header
41875 list. Please see section 10 on how you can do this.
41877 Note: in case of "Best-guess" (see below), the convention is
41878 to put this string in a header called X-SPF-Guess: instead.
41880 .vitem &$spf_result$&
41881 .vindex &$spf_result$&
41882 This contains the outcome of the SPF check in string form,
41883 currently one of pass, fail, softfail, none, neutral, permerror,
41884 temperror, or &"(invalid)"&.
41886 .vitem &$spf_result_guessed$&
41887 .vindex &$spf_result_guessed$&
41888 This boolean is true only if a best-guess operation was used
41889 and required in order to obtain a result.
41891 .vitem &$spf_smtp_comment$&
41892 .vindex &$spf_smtp_comment$&
41893 .vindex &%spf_smtp_comment_template%&
41894 This contains a string that can be used in a SMTP response
41895 to the calling party. Useful for "fail".
41896 The string is generated by the SPF library from the template configured in the main config
41897 option &%spf_smtp_comment_template%&.
41901 .cindex SPF "ACL condition"
41902 .cindex ACL "spf_guess condition"
41903 .cindex SPF "best guess"
41904 In addition to SPF, you can also perform checks for so-called
41905 "Best-guess". Strictly speaking, "Best-guess" is not standard
41906 SPF, but it is supported by the same framework that enables SPF
41908 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41909 for a description of what it means.
41910 . --- 2019-10-28: still not https:
41912 To access this feature, simply use the spf_guess condition in place
41913 of the spf one. For example:
41916 deny spf_guess = fail
41917 message = $sender_host_address doesn't look trustworthy to me
41920 In case you decide to reject messages based on this check, you
41921 should note that although it uses the same framework, "Best-guess"
41922 is not SPF, and therefore you should not mention SPF at all in your
41925 When the spf_guess condition has run, it sets up the same expansion
41926 variables as when spf condition is run, described above.
41928 Additionally, since Best-guess is not standardized, you may redefine
41929 what "Best-guess" means to you by redefining the main configuration
41930 &%spf_guess%& option.
41931 For example, the following:
41934 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41937 would relax host matching rules to a broader network range.
41940 .cindex SPF "lookup expansion"
41942 A lookup expansion is also available. It takes an email
41943 address as the key and an IP address
41948 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41951 The lookup will return the same result strings as can appear in
41952 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41958 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41959 .cindex SRS "sender rewriting scheme"
41962 SRS can be used to modify sender addresses when forwarding so that
41963 SPF verification does not object to them.
41964 It operates by encoding the original envelope sender in a new
41965 sender local part and using a domain run by the forwarding site
41966 as the new domain for the sender. Any DSN message should be returned
41967 to this new sender at the forwarding site, which can extract the
41968 original sender from the coded local part and forward the DSN to
41971 This is a way of avoiding the breakage that SPF does to forwarding.
41972 The constructed local-part will be longer than the original,
41973 leading to possible problems with very long addresses.
41974 The changing of the sender address also hinders the tracing of mail
41977 Exim can be built to include native SRS support. To do this
41978 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41979 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41981 The support is limited to SRS0-encoding; SRS1 is not supported.
41983 .cindex SRS excoding
41984 To encode an address use this expansion item:
41986 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41987 .cindex "&%srs_encode%& expansion item"
41988 .cindex SRS "expansion item"
41989 The first argument should be a secret known and used by all systems
41990 handling the recipient domain for the original message.
41991 There is no need to periodically change this key; a timestamp is also
41993 The second argument should be given as the envelope sender address before this
41994 encoding operation.
41995 The third argument should be the recipient domain of the message when
41996 it arrived at this system.
41999 .cindex SRS decoding
42000 To decode an address use this expansion condition:
42002 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
42003 The first argument should be the recipient local prt as is was received.
42004 The second argument is the site secret.
42006 If the messages is not for an SRS-encoded recipient the condition will
42007 return false. If it is, the condition will return true and the variable
42008 &$srs_recipient$& will be set to the decoded (original) value.
42014 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42020 # if outbound, and forwarding has been done, use an alternate transport
42021 domains = ! +my_domains
42022 transport = ${if eq {$local_part@$domain} \
42023 {$original_local_part@$original_domain} \
42024 {remote_smtp} {remote_forwarded_smtp}}
42029 domains = +my_domains
42030 # detect inbound bounces which are SRS'd, and decode them
42031 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42032 data = $srs_recipient
42034 inbound_srs_failure:
42037 domains = +my_domains
42038 # detect inbound bounces which look SRS'd but are invalid
42039 condition = ${if inbound_srs {$local_part} {}}
42041 data = :fail: Invalid SRS recipient address
42043 #... further routers here
42046 # transport; should look like the non-forward outbound
42047 # one, plus the max_rcpt and return_path options
42048 remote_forwarded_smtp:
42050 # modify the envelope from, for mails that we forward
42052 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42060 .section DMARC SECDMARC
42061 .cindex DMARC verification
42063 DMARC combines feedback from SPF, DKIM, and header From: in order
42064 to attempt to provide better indicators of the authenticity of an
42065 email. This document does not explain the fundamentals; you
42066 should read and understand how it works by visiting the website at
42067 &url(http://www.dmarc.org/).
42069 If Exim is built with DMARC support,
42070 the libopendmarc library is used.
42072 For building Exim yourself, obtain the library from
42073 &url(http://sourceforge.net/projects/opendmarc/)
42074 to obtain a copy, or find it in your favorite package
42075 repository. You will need to attend to the local/Makefile feature
42076 SUPPORT_DMARC and the associated LDFLAGS addition.
42077 This description assumes
42078 that headers will be in /usr/local/include, and that the libraries
42079 are in /usr/local/lib.
42083 There are three main-configuration options:
42084 .cindex DMARC "configuration options"
42086 The &%dmarc_tld_file%& option
42087 .oindex &%dmarc_tld_file%&
42088 defines the location of a text file of valid
42089 top level domains the opendmarc library uses
42090 during domain parsing. Maintained by Mozilla,
42091 the most current version can be downloaded
42092 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42093 See also the util/renew-opendmarc-tlds.sh script.
42094 The default for the option is unset.
42095 If not set, DMARC processing is disabled.
42098 The &%dmarc_history_file%& option, if set
42099 .oindex &%dmarc_history_file%&
42100 defines the location of a file to log results
42101 of dmarc verification on inbound emails. The
42102 contents are importable by the opendmarc tools
42103 which will manage the data, send out DMARC
42104 reports, and expire the data. Make sure the
42105 directory of this file is writable by the user
42107 The default is unset.
42109 The &%dmarc_forensic_sender%& option
42110 .oindex &%dmarc_forensic_sender%&
42111 defines an alternate email address to use when sending a
42112 forensic report detailing alignment failures
42113 if a sender domain's dmarc record specifies it
42114 and you have configured Exim to send them.
42115 If set, this is expanded and used for the
42116 From: header line; the address is extracted
42117 from it and used for the envelope from.
42118 If not set (the default), the From: header is expanded from
42119 the dsn_from option, and <> is used for the
42122 . I wish we had subsections...
42124 .cindex DMARC controls
42125 By default, the DMARC processing will run for any remote,
42126 non-authenticated user. It makes sense to only verify DMARC
42127 status of messages coming from remote, untrusted sources. You can
42128 use standard conditions such as hosts, senders, etc, to decide that
42129 DMARC verification should *not* be performed for them and disable
42130 DMARC with an ACL control modifier:
42132 control = dmarc_disable_verify
42134 A DMARC record can also specify a "forensic address", which gives
42135 exim an email address to submit reports about failed alignment.
42136 Exim does not do this by default because in certain conditions it
42137 results in unintended information leakage (what lists a user might
42138 be subscribed to, etc). You must configure exim to submit forensic
42139 reports to the owner of the domain. If the DMARC record contains a
42140 forensic address and you specify the control statement below, then
42141 exim will send these forensic emails. It is also advised that you
42142 configure a &%dmarc_forensic_sender%& because the default sender address
42143 construction might be inadequate.
42145 control = dmarc_enable_forensic
42147 (AGAIN: You can choose not to send these forensic reports by simply
42148 not putting the dmarc_enable_forensic control line at any point in
42149 your exim config. If you don't tell exim to send them, it will not
42152 There are no options to either control. Both must appear before
42157 DMARC checks cam be run on incoming SMTP messages by using the
42158 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42159 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42160 condition. Putting this condition in the ACLs is required in order
42161 for a DMARC check to actually occur. All of the variables are set
42162 up before the DATA ACL, but there is no actual DMARC check that
42163 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42165 The &"dmarc_status"& condition takes a list of strings on its
42166 right-hand side. These strings describe recommended action based
42167 on the DMARC check. To understand what the policy recommendations
42168 mean, refer to the DMARC website above. Valid strings are:
42170 &'accept '& The DMARC check passed and the library recommends accepting the email.
42171 &'reject '& The DMARC check failed and the library recommends rejecting the email.
42172 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
42173 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
42174 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
42175 &'nofrom '& Unable to determine the domain of the sender.
42176 &'temperror '& Library error or dns error.
42177 &'off '& The DMARC check was disabled for this email.
42179 You can prefix each string with an exclamation mark to invert its
42180 meaning, for example "!accept" will match all results but
42181 "accept". The string list is evaluated left-to-right in a
42182 short-circuit fashion. When a string matches the outcome of the
42183 DMARC check, the condition succeeds. If none of the listed
42184 strings matches the outcome of the DMARC check, the condition
42187 Of course, you can also use any other lookup method that Exim
42188 supports, including LDAP, Postgres, MySQL, etc, as long as the
42189 result is a list of colon-separated strings.
42191 Performing the check sets up information used by the
42192 &%authresults%& expansion item.
42194 Several expansion variables are set before the DATA ACL is
42195 processed, and you can use them in this ACL. The following
42196 expansion variables are available:
42199 .vitem &$dmarc_status$&
42200 .vindex &$dmarc_status$&
42201 .cindex DMARC result
42202 A one word status indicating what the DMARC library
42203 thinks of the email. It is a combination of the results of
42204 DMARC record lookup and the SPF/DKIM/DMARC processing results
42205 (if a DMARC record was found). The actual policy declared
42206 in the DMARC record is in a separate expansion variable.
42208 .vitem &$dmarc_status_text$&
42209 .vindex &$dmarc_status_text$&
42210 Slightly longer, human readable status.
42212 .vitem &$dmarc_used_domain$&
42213 .vindex &$dmarc_used_domain$&
42214 The domain which DMARC used to look up the DMARC policy record.
42216 .vitem &$dmarc_domain_policy$&
42217 .vindex &$dmarc_domain_policy$&
42218 The policy declared in the DMARC record. Valid values
42219 are "none", "reject" and "quarantine". It is blank when there
42220 is any error, including no DMARC record.
42225 By default, Exim's DMARC configuration is intended to be
42226 non-intrusive and conservative. To facilitate this, Exim will not
42227 create any type of logging files without explicit configuration by
42228 you, the admin. Nor will Exim send out any emails/reports about
42229 DMARC issues without explicit configuration by you, the admin (other
42230 than typical bounce messages that may come about due to ACL
42231 processing or failure delivery issues).
42233 In order to log statistics suitable to be imported by the opendmarc
42234 tools, you need to:
42236 Configure the global option &%dmarc_history_file%&
42238 Configure cron jobs to call the appropriate opendmarc history
42239 import scripts and truncating the dmarc_history_file
42242 In order to send forensic reports, you need to:
42244 Configure the global option &%dmarc_forensic_sender%&
42246 Configure, somewhere before the DATA ACL, the control option to
42247 enable sending DMARC forensic reports
42255 warn domains = +local_domains
42256 hosts = +local_hosts
42257 control = dmarc_disable_verify
42259 warn !domains = +screwed_up_dmarc_records
42260 control = dmarc_enable_forensic
42262 warn condition = (lookup if destined to mailing list)
42263 set acl_m_mailing_list = 1
42266 warn dmarc_status = accept : none : off
42268 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42270 warn dmarc_status = !accept
42272 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42274 warn dmarc_status = quarantine
42276 set $acl_m_quarantine = 1
42277 # Do something in a transport with this flag variable
42279 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42280 condition = ${if eq{$acl_m_mailing_list}{1}}
42281 message = Messages from $dmarc_used_domain break mailing lists
42283 deny dmarc_status = reject
42285 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42287 warn add_header = :at_start:${authresults {$primary_hostname}}
42294 . ////////////////////////////////////////////////////////////////////////////
42295 . ////////////////////////////////////////////////////////////////////////////
42297 .chapter "Proxies" "CHAPproxies" &&&
42299 .cindex "proxy support"
42300 .cindex "proxy" "access via"
42302 A proxy is an intermediate system through which communication is passed.
42303 Proxies may provide a security, availability or load-distribution function.
42306 .section "Inbound proxies" SECTproxyInbound
42307 .cindex proxy inbound
42308 .cindex proxy "server side"
42309 .cindex proxy "Proxy protocol"
42310 .cindex "Proxy protocol" proxy
42312 Exim has support for receiving inbound SMTP connections via a proxy
42313 that uses &"Proxy Protocol"& to speak to it.
42314 To include this support, include &"SUPPORT_PROXY=yes"&
42317 It was built on the HAProxy specification, found at
42318 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42320 The purpose of this facility is so that an application load balancer,
42321 such as HAProxy, can sit in front of several Exim servers
42322 to distribute load.
42323 Exim uses the local protocol communication with the proxy to obtain
42324 the remote SMTP system IP address and port information.
42325 There is no logging if a host passes or
42326 fails Proxy Protocol negotiation, but it can easily be determined and
42327 recorded in an ACL (example is below).
42329 Use of a proxy is enabled by setting the &%hosts_proxy%&
42330 main configuration option to a hostlist; connections from these
42331 hosts will use Proxy Protocol.
42332 Exim supports both version 1 and version 2 of the Proxy Protocol and
42333 automatically determines which version is in use.
42335 The Proxy Protocol header is the first data received on a TCP connection
42336 and is inserted before any TLS-on-connect handshake from the client; Exim
42337 negotiates TLS between Exim-as-server and the remote client, not between
42338 Exim and the proxy server. The Proxy Protocol header must be received
42339 within &%proxy_protocol_timeout%&, which defaults to 3s.
42341 The following expansion variables are usable
42342 (&"internal"& and &"external"& here refer to the interfaces
42345 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42346 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42347 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42348 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42349 &'proxy_session '& boolean: SMTP connection via proxy
42351 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42352 there was a protocol error.
42353 The variables &$sender_host_address$& and &$sender_host_port$&
42354 will have values for the actual client system, not the proxy.
42356 Since the real connections are all coming from the proxy, and the
42357 per host connection tracking is done before Proxy Protocol is
42358 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42359 handle all of the parallel volume you expect per inbound proxy.
42360 With the option set so high, you lose the ability
42361 to protect your server from many connections from one IP.
42362 In order to prevent your server from overload, you
42363 need to add a per connection ratelimit to your connect ACL.
42364 A possible solution is:
42366 # Set max number of connections per host
42368 # Or do some kind of IP lookup in a flat file or database
42369 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42371 defer ratelimit = LIMIT / 5s / per_conn / strict
42372 message = Too many connections from this IP right now
42377 .section "Outbound proxies" SECTproxySOCKS
42378 .cindex proxy outbound
42379 .cindex proxy "client side"
42380 .cindex proxy SOCKS
42381 .cindex SOCKS proxy
42382 Exim has support for sending outbound SMTP via a proxy
42383 using a protocol called SOCKS5 (defined by RFC1928).
42384 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42387 Use of a proxy is enabled by setting the &%socks_proxy%& option
42388 on an smtp transport.
42389 The option value is expanded and should then be a list
42390 (colon-separated by default) of proxy specifiers.
42391 Each proxy specifier is a list
42392 (space-separated by default) where the initial element
42393 is an IP address and any subsequent elements are options.
42395 Options are a string <name>=<value>.
42396 The list of options is in the following table:
42398 &'auth '& authentication method
42399 &'name '& authentication username
42400 &'pass '& authentication password
42402 &'tmo '& connection timeout
42404 &'weight '& selection bias
42407 More details on each of these options follows:
42410 .cindex authentication "to proxy"
42411 .cindex proxy authentication
42412 &%auth%&: Either &"none"& (default) or &"name"&.
42413 Using &"name"& selects username/password authentication per RFC 1929
42414 for access to the proxy.
42415 Default is &"none"&.
42417 &%name%&: sets the username for the &"name"& authentication method.
42420 &%pass%&: sets the password for the &"name"& authentication method.
42423 &%port%&: the TCP port number to use for the connection to the proxy.
42426 &%tmo%&: sets a connection timeout in seconds for this proxy.
42429 &%pri%&: specifies a priority for the proxy within the list,
42430 higher values being tried first.
42431 The default priority is 1.
42433 &%weight%&: specifies a selection bias.
42434 Within a priority set servers are queried in a random fashion,
42435 weighted by this value.
42436 The default value for selection bias is 1.
42439 Proxies from the list are tried according to their priority
42440 and weight settings until one responds. The timeout for the
42441 overall connection applies to the set of proxied attempts.
42443 .section Logging SECTproxyLog
42444 To log the (local) IP of a proxy in the incoming or delivery logline,
42445 add &"+proxy"& to the &%log_selector%& option.
42446 This will add a component tagged with &"PRX="& to the line.
42448 . ////////////////////////////////////////////////////////////////////////////
42449 . ////////////////////////////////////////////////////////////////////////////
42451 .chapter "Internationalisation" "CHAPi18n" &&&
42452 "Internationalisation""
42453 .cindex internationalisation "email address"
42456 .cindex utf8 "mail name handling"
42458 Exim has support for Internationalised mail names.
42459 To include this it must be built with SUPPORT_I18N and the libidn library.
42460 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42462 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42463 instead of it) then IDNA2008 is supported; this adds an extra library
42464 requirement, upon libidn2.
42466 .section "MTA operations" SECTi18nMTA
42467 .cindex SMTPUTF8 "ESMTP option"
42468 .cindex "ESMTP extensions" SMTPUTF8
42469 The main configuration option &%smtputf8_advertise_hosts%& specifies
42470 a host list. If this matches the sending host and
42471 accept_8bitmime is true (the default) then the ESMTP option
42472 SMTPUTF8 will be advertised.
42474 If the sender specifies the SMTPUTF8 option on a MAIL command
42475 international handling for the message is enabled and
42476 the expansion variable &$message_smtputf8$& will have value TRUE.
42478 The option &%allow_utf8_domains%& is set to true for this
42479 message. All DNS lookups are converted to a-label form
42480 whatever the setting of &%allow_utf8_domains%&
42481 when Exim is built with SUPPORT_I18N.
42483 Both localparts and domain are maintained as the original
42484 UTF-8 form internally; any comparison or regular-expression use will
42485 require appropriate care. Filenames created, eg. by
42486 the appendfile transport, will have UTF-8 names.
42488 HELO names sent by the smtp transport will have any UTF-8
42489 components expanded to a-label form,
42490 and any certificate name checks will be done using the a-label
42493 .cindex log protocol
42494 .cindex SMTPUTF8 logging
42495 .cindex i18n logging
42496 Log lines and Received-by: header lines will acquire a "utf8"
42497 prefix on the protocol element, eg. utf8esmtp.
42499 The following expansion operators can be used:
42501 ${utf8_domain_to_alabel:str}
42502 ${utf8_domain_from_alabel:str}
42503 ${utf8_localpart_to_alabel:str}
42504 ${utf8_localpart_from_alabel:str}
42507 .cindex utf8 "address downconversion"
42508 .cindex i18n "utf8 address downconversion"
42510 may use the following modifier:
42512 control = utf8_downconvert
42513 control = utf8_downconvert/<value>
42515 This sets a flag requiring that envelope addresses are converted to
42516 a-label form before smtp delivery.
42517 This is usually for use in a Message Submission Agent context,
42518 but could be used for any message.
42520 If a value is appended it may be:
42522 &`1 `& mandatory downconversion
42523 &`0 `& no downconversion
42524 &`-1 `& if SMTPUTF8 not supported by destination host
42526 If no value is given, 1 is used.
42528 If mua_wrapper is set, the utf8_downconvert control
42529 is initially set to -1.
42531 The smtp transport has an option &%utf8_downconvert%&.
42532 If set it must expand to one of the three values described above,
42533 or an empty string.
42534 If non-empty it overrides value previously set
42535 (due to mua_wrapper or by an ACL control).
42538 There is no explicit support for VRFY and EXPN.
42539 Configurations supporting these should inspect
42540 &$smtp_command_argument$& for an SMTPUTF8 argument.
42542 There is no support for LMTP on Unix sockets.
42543 Using the "lmtp" protocol option on an smtp transport,
42544 for LMTP over TCP, should work as expected.
42546 There is no support for DSN unitext handling,
42547 and no provision for converting logging from or to UTF-8.
42551 .section "MDA operations" SECTi18nMDA
42552 To aid in constructing names suitable for IMAP folders
42553 the following expansion operator can be used:
42555 ${imapfolder {<string>} {<sep>} {<specials>}}
42558 The string is converted from the charset specified by
42559 the "headers charset" command (in a filter file)
42560 or &%headers_charset%& main configuration option (otherwise),
42562 modified UTF-7 encoding specified by RFC 2060,
42563 with the following exception: All occurrences of <sep>
42564 (which has to be a single character)
42565 are replaced with periods ("."), and all periods and slashes that are not
42566 <sep> and are not in the <specials> string are BASE64 encoded.
42568 The third argument can be omitted, defaulting to an empty string.
42569 The second argument can be omitted, defaulting to "/".
42571 This is the encoding used by Courier for Maildir names on disk, and followed
42572 by many other IMAP servers.
42576 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42577 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42578 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42581 Note that the source charset setting is vital, and also that characters
42582 must be representable in UTF-16.
42585 . ////////////////////////////////////////////////////////////////////////////
42586 . ////////////////////////////////////////////////////////////////////////////
42588 .chapter "Events" "CHAPevents" &&&
42592 The events mechanism in Exim can be used to intercept processing at a number
42593 of points. It was originally invented to give a way to do customised logging
42594 actions (for example, to a database) but can also be used to modify some
42595 processing actions.
42597 Most installations will never need to use Events.
42598 The support can be left out of a build by defining DISABLE_EVENT=yes
42599 in &_Local/Makefile_&.
42601 There are two major classes of events: main and transport.
42602 The main configuration option &%event_action%& controls reception events;
42603 a transport option &%event_action%& controls delivery events.
42605 Both options are a string which is expanded when the event fires.
42606 An example might look like:
42607 .cindex logging custom
42609 event_action = ${if eq {msg:delivery}{$event_name} \
42610 {${lookup pgsql {SELECT * FROM record_Delivery( \
42611 '${quote_pgsql:$sender_address_domain}',\
42612 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42613 '${quote_pgsql:$domain}', \
42614 '${quote_pgsql:${lc:$local_part}}', \
42615 '${quote_pgsql:$host_address}', \
42616 '${quote_pgsql:${lc:$host}}', \
42617 '${quote_pgsql:$message_exim_id}')}} \
42621 Events have names which correspond to the point in process at which they fire.
42622 The name is placed in the variable &$event_name$& and the event action
42623 expansion must check this, as it will be called for every possible event type.
42625 The current list of events is:
42627 &`dane:fail after transport `& per connection
42628 &`msg:complete after main `& per message
42629 &`msg:defer after transport `& per message per delivery try
42630 &`msg:delivery after transport `& per recipient
42631 &`msg:rcpt:host:defer after transport `& per recipient per host
42632 &`msg:rcpt:defer after transport `& per recipient
42633 &`msg:host:defer after transport `& per host per delivery try; host errors
42634 &`msg:fail:delivery after transport `& per recipient
42635 &`msg:fail:internal after main `& per recipient
42636 &`tcp:connect before transport `& per connection
42637 &`tcp:close after transport `& per connection
42638 &`tls:cert before both `& per certificate in verification chain
42639 &`smtp:connect after transport `& per connection
42640 &`smtp:ehlo after transport `& per connection
42642 New event types may be added in future.
42644 The event name is a colon-separated list, defining the type of
42645 event in a tree of possibilities. It may be used as a list
42646 or just matched on as a whole. There will be no spaces in the name.
42648 The second column in the table above describes whether the event fires
42649 before or after the action is associates with. Those which fire before
42650 can be used to affect that action (more on this below).
42652 The third column in the table above says what section of the configuration
42653 should define the event action.
42655 An additional variable, &$event_data$&, is filled with information varying
42656 with the event type:
42658 &`dane:fail `& failure reason
42659 &`msg:defer `& error string
42660 &`msg:delivery `& smtp confirmation message
42661 &`msg:fail:internal `& failure reason
42662 &`msg:fail:delivery `& smtp error message
42663 &`msg:host:defer `& error string
42664 &`msg:rcpt:host:defer `& error string
42665 &`msg:rcpt:defer `& error string
42666 &`tls:cert `& verification chain depth
42667 &`smtp:connect `& smtp banner
42668 &`smtp:ehlo `& smtp ehlo response
42671 The :defer events populate one extra variable: &$event_defer_errno$&.
42673 For complex operations an ACL expansion can be used in &%event_action%&
42674 however due to the multiple contexts that Exim operates in during
42675 the course of its processing:
42677 variables set in transport events will not be visible outside that
42680 acl_m variables in a server context are lost on a new connection,
42681 and after smtp helo/ehlo/mail/starttls/rset commands
42683 Using an ACL expansion with the logwrite modifier can be
42684 a useful way of writing to the main log.
42686 The expansion of the event_action option should normally
42687 return an empty string. Should it return anything else the
42688 following will be forced:
42690 &`tcp:connect `& do not connect
42691 &`tls:cert `& refuse verification
42692 &`smtp:connect `& close connection
42694 All other message types ignore the result string, and
42695 no other use is made of it.
42697 For a tcp:connect event, if the connection is being made to a proxy
42698 then the address and port variables will be that of the proxy and not
42701 For tls:cert events, if GnuTLS is in use this will trigger only per
42702 chain element received on the connection.
42703 For OpenSSL it will trigger for every chain element including those
42706 . ////////////////////////////////////////////////////////////////////////////
42707 . ////////////////////////////////////////////////////////////////////////////
42709 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42710 "Adding drivers or lookups"
42711 .cindex "adding drivers"
42712 .cindex "new drivers, adding"
42713 .cindex "drivers" "adding new"
42714 The following actions have to be taken in order to add a new router, transport,
42715 authenticator, or lookup type to Exim:
42718 Choose a name for the driver or lookup type that does not conflict with any
42719 existing name; I will use &"newdriver"& in what follows.
42721 Add to &_src/EDITME_& the line:
42723 <&'type'&>&`_NEWDRIVER=yes`&
42725 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42726 code is not to be included in the binary by default, comment this line out. You
42727 should also add any relevant comments about the driver or lookup type.
42729 Add to &_src/config.h.defaults_& the line:
42731 #define <type>_NEWDRIVER
42734 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42735 and create a table entry as is done for all the other drivers and lookup types.
42737 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42738 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42739 Add your &`NEWDRIVER`& to that list.
42740 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42741 simple form that most lookups have.
42743 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42744 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42745 driver or lookup type and add it to the definition of OBJ.
42747 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42748 definition of OBJ_MACRO. Add a set of line to do the compile also.
42750 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42753 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42754 as for other drivers and lookups.
42757 Then all you need to do is write the code! A good way to start is to make a
42758 proforma by copying an existing module of the same type, globally changing all
42759 occurrences of the name, and cutting out most of the code. Note that any
42760 options you create must be listed in alphabetical order, because the tables are
42761 searched using a binary chop procedure.
42763 There is a &_README_& file in each of the sub-directories of &_src_& describing
42764 the interface that is expected.
42769 . ////////////////////////////////////////////////////////////////////////////
42770 . ////////////////////////////////////////////////////////////////////////////
42772 . /////////////////////////////////////////////////////////////////////////////
42773 . These lines are processing instructions for the Simple DocBook Processor that
42774 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42775 . PDFs than using xmlto and fop. They will be ignored by all other XML
42777 . /////////////////////////////////////////////////////////////////////////////
42782 foot_right_recto="&chaptertitle;"
42783 foot_right_verso="&chaptertitle;"
42787 .makeindex "Options index" "option"
42788 .makeindex "Variables index" "variable"
42789 .makeindex "Concept index" "concept"
42792 . /////////////////////////////////////////////////////////////////////////////
42793 . /////////////////////////////////////////////////////////////////////////////