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 "4.93"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name.
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be in Roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- a small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
164 . ////////////////////////////////////////////////////////////////////////////
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for ASCII
170 . ////////////////////////////////////////////////////////////////////////////
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
187 </year><holder>University of Cambridge</holder></copyright>
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
198 .chapter "Introduction" "CHID1"
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
352 The use, supply, or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of Exim,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of this document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, this manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(https://www.uit.co.uk/exim-book/)).
397 The book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
412 As Exim develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
423 All changes to Exim (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
448 .section "FTP site and websites" "SECID2"
451 The primary site for Exim source distributions is the &%exim.org%& FTP site,
452 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
453 website, are hosted at the University of Cambridge.
457 As well as Exim distribution tar files, the Exim website contains a number of
458 differently formatted versions of the documentation. A recent addition to the
459 online information is the Exim wiki (&url(https://wiki.exim.org)),
460 which contains what used to be a separate FAQ, as well as various other
461 examples, tips, and know-how that have been contributed by Exim users.
462 The wiki site should always redirect to the correct place, which is currently
463 provided by GitHub, and is open to editing by anyone with a GitHub account.
466 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
469 Please do not ask for configuration help in the bug-tracker.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on that list and not on the general Exim
495 .section "Bug reports" "SECID5"
496 .cindex "bug reports"
497 .cindex "reporting bugs"
498 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
499 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
500 whether some behaviour is a bug or not, the best thing to do is to post a
501 message to the &'exim-dev'& mailing list and have it discussed.
505 .section "Where to find the Exim distribution" "SECTavail"
507 .cindex "HTTPS download site"
508 .cindex "distribution" "FTP site"
509 .cindex "distribution" "https site"
510 The master distribution site for the Exim distribution is
512 &url(https://downloads.exim.org/)
514 The service is available over HTTPS, HTTP and FTP.
515 We encourage people to migrate to HTTPS.
517 The content served at &url(https://downloads.exim.org/) is identical to the
518 content served at &url(https://ftp.exim.org/pub/exim) and
519 &url(ftp://ftp.exim.org/pub/exim).
521 If accessing via a hostname containing &'ftp'&, then the file references that
522 follow are relative to the &_exim_& directories at these sites.
523 If accessing via the hostname &'downloads'& then the subdirectories described
524 here are top-level directories.
526 There are now quite a number of independent mirror sites around
527 the world. Those that I know about are listed in the file called &_Mirrors_&.
529 Within the top exim directory there are subdirectories called &_exim3_& (for
530 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
531 distributions), and &_Testing_& for testing versions. In the &_exim4_&
532 subdirectory, the current release can always be found in files called
536 &_exim-n.nn.tar.bz2_&
538 where &'n.nn'& is the highest such version number in the directory. The three
539 files contain identical data; the only difference is the type of compression.
540 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
541 most portable to old systems.
543 .cindex "distribution" "signing details"
544 .cindex "distribution" "public key"
545 .cindex "public key for signed distribution"
546 The distributions will be PGP signed by an individual key of the Release
547 Coordinator. This key will have a uid containing an email address in the
548 &'exim.org'& domain and will have signatures from other people, including
549 other Exim maintainers. We expect that the key will be in the "strong set" of
550 PGP keys. There should be a trust path to that key from the Exim Maintainer's
551 PGP keys, a version of which can be found in the release directory in the file
552 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
553 such as &'pool.sks-keyservers.net'&.
555 At the time of the last update, releases were being made by Jeremy Harris and signed
556 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
557 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
558 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.xz.asc_&
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
566 For each released version, the log of changes is made available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
584 .section "Limitations" "SECID6"
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
624 .section "Runtime configuration" "SECID7"
625 Exim's runtime configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
645 Control of messages in the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message and is separated from the &'header'& (see
657 below) by a blank line.
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case, the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages in its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
748 A number of pieces of external code are included in the Exim distribution.
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 © University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
766 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(https://cr.yp.to/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
796 Copyright © 2001 Carnegie Mellon University. All rights reserved.
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
816 Office of Technology Transfer
817 Carnegie Mellon University
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
824 Redistributions of any form whatsoever must retain the following
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
841 .cindex "Exim monitor" "acknowledgment"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific license requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs from being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
963 Sieve filters are written in the standard filtering language that is defined
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
970 User filters are run as part of the routing process, described below.
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct filenames, and the names of files in those systems are
989 not always case-sensitive.
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1008 There are two different possibilities for the final two characters:
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender addresses
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1078 (either over TCP/IP or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients or the entire message can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default, all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to all frozen messages.
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1182 Should the system or Exim crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Runtime options specify which
1198 ones are actually used for delivering messages.
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the runtime configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specifically by the local host.
1237 Typically these are addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport or generates one or more &"child"& addresses. Processing the
1295 original address ceases
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default, the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports and discards any duplicates that it finds. During this
1353 check, local parts are treated case-sensitively. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1367 .cindex affix "router precondition"
1368 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1369 the local parts handled by the router may or must have certain prefixes and/or
1370 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1371 skipped. These conditions are tested first. When an affix is present, it is
1372 removed from the local part before further processing, including the evaluation
1373 of any other conditions.
1375 Routers can be designated for use only when not verifying an address, that is,
1376 only when routing it for delivery (or testing its delivery routing). If the
1377 &%verify%& option is set false, the router is skipped when Exim is verifying an
1379 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1380 &%verify_recipient%&, which independently control the use of the router for
1381 sender and recipient verification. You can set these options directly if
1382 you want a router to be used for only one type of verification.
1383 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1385 If the &%address_test%& option is set false, the router is skipped when Exim is
1386 run with the &%-bt%& option to test an address routing. This can be helpful
1387 when the first router sends all new messages to a scanner of some sort; it
1388 makes it possible to use &%-bt%& to test subsequent delivery routing without
1389 having to simulate the effect of the scanner.
1391 Routers can be designated for use only when verifying an address, as
1392 opposed to routing it for delivery. The &%verify_only%& option controls this.
1393 Again, cutthrough delivery counts as a verification.
1395 Individual routers can be explicitly skipped when running the routers to
1396 check an address given in the SMTP EXPN command (see the &%expn%& option).
1398 If the &%domains%& option is set, the domain of the address must be in the set
1399 of domains that it defines.
1401 .vindex "&$local_part_prefix$&"
1402 .vindex "&$local_part_prefix_v$&"
1403 .vindex "&$local_part$&"
1404 .vindex "&$local_part_suffix$&"
1405 .vindex "&$local_part_suffix_v$&"
1406 .cindex affix "router precondition"
1407 If the &%local_parts%& option is set, the local part of the address must be in
1408 the set of local parts that it defines. If &%local_part_prefix%& or
1409 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1410 part before this check. If you want to do precondition tests on local parts
1411 that include affixes, you can do so by using a &%condition%& option (see below)
1413 that uses the variables &$local_part$&, &$local_part_prefix$&,
1414 &$local_part_prefix_v$&, &$local_part_suffix$&
1415 and &$local_part_suffix_v$& as necessary.
1418 .vindex "&$local_user_uid$&"
1419 .vindex "&$local_user_gid$&"
1421 If the &%check_local_user%& option is set, the local part must be the name of
1422 an account on the local host. If this check succeeds, the uid and gid of the
1423 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1424 user's home directory is placed in &$home$&; these values can be used in the
1425 remaining preconditions.
1427 If the &%router_home_directory%& option is set, it is expanded at this point,
1428 because it overrides the value of &$home$&. If this expansion were left till
1429 later, the value of &$home$& as set by &%check_local_user%& would be used in
1430 subsequent tests. Having two different values of &$home$& in the same router
1431 could lead to confusion.
1433 If the &%senders%& option is set, the envelope sender address must be in the
1434 set of addresses that it defines.
1436 If the &%require_files%& option is set, the existence or non-existence of
1437 specified files is tested.
1439 .cindex "customizing" "precondition"
1440 If the &%condition%& option is set, it is evaluated and tested. This option
1441 uses an expanded string to allow you to set up your own custom preconditions.
1442 Expanded strings are described in chapter &<<CHAPexpand>>&.
1446 Note that &%require_files%& comes near the end of the list, so you cannot use
1447 it to check for the existence of a file in which to lookup up a domain, local
1448 part, or sender. However, as these options are all expanded, you can use the
1449 &%exists%& expansion condition to make such tests within each condition. The
1450 &%require_files%& option is intended for checking files that the router may be
1451 going to use internally, or which are needed by a specific transport (for
1452 example, &_.procmailrc_&).
1456 .section "Delivery in detail" "SECID18"
1457 .cindex "delivery" "in detail"
1458 When a message is to be delivered, the sequence of events is as follows:
1461 If a system-wide filter file is specified, the message is passed to it. The
1462 filter may add recipients to the message, replace the recipients, discard the
1463 message, cause a new message to be generated, or cause the message delivery to
1464 fail. The format of the system filter file is the same as for Exim user filter
1465 files, described in the separate document entitled &'Exim's interfaces to mail
1467 .cindex "Sieve filter" "not available for system filter"
1468 (&*Note*&: Sieve cannot be used for system filter files.)
1470 Some additional features are available in system filters &-- see chapter
1471 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1472 filter only once per delivery attempt, however many recipients it has. However,
1473 if there are several delivery attempts because one or more addresses could not
1474 be immediately delivered, the system filter is run each time. The filter
1475 condition &%first_delivery%& can be used to detect the first run of the system
1478 Each recipient address is offered to each configured router, in turn, subject to
1479 its preconditions, until one is able to handle it. If no router can handle the
1480 address, that is, if they all decline, the address is failed. Because routers
1481 can be targeted at particular domains, several locally handled domains can be
1482 processed entirely independently of each other.
1484 .cindex "routing" "loops in"
1485 .cindex "loop" "while routing"
1486 A router that accepts an address may assign it to a local or a remote
1487 transport. However, the transport is not run at this time. Instead, the address
1488 is placed on a list for the particular transport, which will be run later.
1489 Alternatively, the router may generate one or more new addresses (typically
1490 from alias, forward, or filter files). New addresses are fed back into this
1491 process from the top, but in order to avoid loops, a router ignores any address
1492 which has an identically-named ancestor that was processed by itself.
1494 When all the routing has been done, addresses that have been successfully
1495 handled are passed to their assigned transports. When local transports are
1496 doing real local deliveries, they handle only one address at a time, but if a
1497 local transport is being used as a pseudo-remote transport (for example, to
1498 collect batched SMTP messages for transmission by some other means) multiple
1499 addresses can be handled. Remote transports can always handle more than one
1500 address at a time, but can be configured not to do so, or to restrict multiple
1501 addresses to the same domain.
1503 Each local delivery to a file or a pipe runs in a separate process under a
1504 non-privileged uid, and these deliveries are run one at a time. Remote
1505 deliveries also run in separate processes, normally under a uid that is private
1506 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1507 run in parallel. The maximum number of simultaneous remote deliveries for any
1508 one message is set by the &%remote_max_parallel%& option.
1509 The order in which deliveries are done is not defined, except that all local
1510 deliveries happen before any remote deliveries.
1512 .cindex "queue runner"
1513 When it encounters a local delivery during a queue run, Exim checks its retry
1514 database to see if there has been a previous temporary delivery failure for the
1515 address before running the local transport. If there was a previous failure,
1516 Exim does not attempt a new delivery until the retry time for the address is
1517 reached. However, this happens only for delivery attempts that are part of a
1518 queue run. Local deliveries are always attempted when delivery immediately
1519 follows message reception, even if retry times are set for them. This makes for
1520 better behaviour if one particular message is causing problems (for example,
1521 causing quota overflow, or provoking an error in a filter file).
1523 .cindex "delivery" "retry in remote transports"
1524 Remote transports do their own retry handling, since an address may be
1525 deliverable to one of a number of hosts, each of which may have a different
1526 retry time. If there have been previous temporary failures and no host has
1527 reached its retry time, no delivery is attempted, whether in a queue run or
1528 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1530 If there were any permanent errors, a bounce message is returned to an
1531 appropriate address (the sender in the common case), with details of the error
1532 for each failing address. Exim can be configured to send copies of bounce
1533 messages to other addresses.
1535 .cindex "delivery" "deferral"
1536 If one or more addresses suffered a temporary failure, the message is left on
1537 the queue, to be tried again later. Delivery of these addresses is said to be
1540 When all the recipient addresses have either been delivered or bounced,
1541 handling of the message is complete. The spool files and message log are
1542 deleted, though the message log can optionally be preserved if required.
1548 .section "Retry mechanism" "SECID19"
1549 .cindex "delivery" "retry mechanism"
1550 .cindex "retry" "description of mechanism"
1551 .cindex "queue runner"
1552 Exim's mechanism for retrying messages that fail to get delivered at the first
1553 attempt is the queue runner process. You must either run an Exim daemon that
1554 uses the &%-q%& option with a time interval to start queue runners at regular
1555 intervals or use some other means (such as &'cron'&) to start them. If you do
1556 not arrange for queue runners to be run, messages that fail temporarily at the
1557 first attempt will remain in your queue forever. A queue runner process works
1558 its way through the queue, one message at a time, trying each delivery that has
1559 passed its retry time.
1560 You can run several queue runners at once.
1562 Exim uses a set of configured rules to determine when next to retry the failing
1563 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1564 should give up trying to deliver to the address, at which point it generates a
1565 bounce message. If no retry rules are set for a particular host, address, and
1566 error combination, no retries are attempted, and temporary errors are treated
1571 .section "Temporary delivery failure" "SECID20"
1572 .cindex "delivery" "temporary failure"
1573 There are many reasons why a message may not be immediately deliverable to a
1574 particular address. Failure to connect to a remote machine (because it, or the
1575 connection to it, is down) is one of the most common. Temporary failures may be
1576 detected during routing as well as during the transport stage of delivery.
1577 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1578 is on a file system where the user is over quota. Exim can be configured to
1579 impose its own quotas on local mailboxes; where system quotas are set they will
1582 If a host is unreachable for a period of time, a number of messages may be
1583 waiting for it by the time it recovers, and sending them in a single SMTP
1584 connection is clearly beneficial. Whenever a delivery to a remote host is
1586 .cindex "hints database" "deferred deliveries"
1587 Exim makes a note in its hints database, and whenever a successful
1588 SMTP delivery has happened, it looks to see if any other messages are waiting
1589 for the same host. If any are found, they are sent over the same SMTP
1590 connection, subject to a configuration limit as to the maximum number in any
1595 .section "Permanent delivery failure" "SECID21"
1596 .cindex "delivery" "permanent failure"
1597 .cindex "bounce message" "when generated"
1598 When a message cannot be delivered to some or all of its intended recipients, a
1599 bounce message is generated. Temporary delivery failures turn into permanent
1600 errors when their timeout expires. All the addresses that fail in a given
1601 delivery attempt are listed in a single message. If the original message has
1602 many recipients, it is possible for some addresses to fail in one delivery
1603 attempt and others to fail subsequently, giving rise to more than one bounce
1604 message. The wording of bounce messages can be customized by the administrator.
1605 See chapter &<<CHAPemsgcust>>& for details.
1607 .cindex "&'X-Failed-Recipients:'& header line"
1608 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1609 failed addresses, for the benefit of programs that try to analyse such messages
1612 .cindex "bounce message" "recipient of"
1613 A bounce message is normally sent to the sender of the original message, as
1614 obtained from the message's envelope. For incoming SMTP messages, this is the
1615 address given in the MAIL command. However, when an address is expanded via a
1616 forward or alias file, an alternative address can be specified for delivery
1617 failures of the generated addresses. For a mailing list expansion (see section
1618 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1623 .section "Failures to deliver bounce messages" "SECID22"
1624 .cindex "bounce message" "failure to deliver"
1625 If a bounce message (either locally generated or received from a remote host)
1626 itself suffers a permanent delivery failure, the message is left in the queue,
1627 but it is frozen, awaiting the attention of an administrator. There are options
1628 that can be used to make Exim discard such failed messages, or to keep them
1629 for only a short time (see &%timeout_frozen_after%& and
1630 &%ignore_bounce_errors_after%&).
1636 . ////////////////////////////////////////////////////////////////////////////
1637 . ////////////////////////////////////////////////////////////////////////////
1639 .chapter "Building and installing Exim" "CHID3"
1640 .scindex IIDbuex "building Exim"
1642 .section "Unpacking" "SECID23"
1643 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1644 creates a directory with the name of the current release (for example,
1645 &_exim-&version()_&) into which the following files are placed:
1648 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1649 .irow &_CHANGES_& "contains a reference to where changes are &&&
1651 .irow &_LICENCE_& "the GNU General Public Licence"
1652 .irow &_Makefile_& "top-level make file"
1653 .irow &_NOTICE_& "conditions for the use of Exim"
1654 .irow &_README_& "list of files, directories and simple build &&&
1658 Other files whose names begin with &_README_& may also be present. The
1659 following subdirectories are created:
1662 .irow &_Local_& "an empty directory for local configuration files"
1663 .irow &_OS_& "OS-specific files"
1664 .irow &_doc_& "documentation files"
1665 .irow &_exim_monitor_& "source files for the Exim monitor"
1666 .irow &_scripts_& "scripts used in the build process"
1667 .irow &_src_& "remaining source files"
1668 .irow &_util_& "independent utilities"
1671 The main utility programs are contained in the &_src_& directory and are built
1672 with the Exim binary. The &_util_& directory contains a few optional scripts
1673 that may be useful to some sites.
1676 .section "Multiple machine architectures and operating systems" "SECID24"
1677 .cindex "building Exim" "multiple OS/architectures"
1678 The building process for Exim is arranged to make it easy to build binaries for
1679 a number of different architectures and operating systems from the same set of
1680 source files. Compilation does not take place in the &_src_& directory.
1681 Instead, a &'build directory'& is created for each architecture and operating
1683 .cindex "symbolic link" "to build directory"
1684 Symbolic links to the sources are installed in this directory, which is where
1685 the actual building takes place. In most cases, Exim can discover the machine
1686 architecture and operating system for itself, but the defaults can be
1687 overridden if necessary.
1688 .cindex compiler requirements
1689 .cindex compiler version
1690 A C99-capable compiler will be required for the build.
1693 .section "PCRE library" "SECTpcre"
1694 .cindex "PCRE library"
1695 Exim no longer has an embedded PCRE library as the vast majority of
1696 modern systems include PCRE as a system library, although you may need to
1697 install the PCRE package or the PCRE development package for your operating
1698 system. If your system has a normal PCRE installation the Exim build
1699 process will need no further configuration. If the library or the
1700 headers are in an unusual location you will need to either set the PCRE_LIBS
1701 and INCLUDE directives appropriately,
1702 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1703 If your operating system has no
1704 PCRE support then you will need to obtain and build the current PCRE
1705 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1706 More information on PCRE is available at &url(https://www.pcre.org/).
1708 .section "DBM libraries" "SECTdb"
1709 .cindex "DBM libraries" "discussion of"
1710 .cindex "hints database" "DBM files used for"
1711 Even if you do not use any DBM files in your configuration, Exim still needs a
1712 DBM library in order to operate, because it uses indexed files for its hints
1713 databases. Unfortunately, there are a number of DBM libraries in existence, and
1714 different operating systems often have different ones installed.
1716 .cindex "Solaris" "DBM library for"
1717 .cindex "IRIX, DBM library for"
1718 .cindex "BSD, DBM library for"
1719 .cindex "Linux, DBM library for"
1720 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1721 Linux distribution, the DBM configuration should happen automatically, and you
1722 may be able to ignore this section. Otherwise, you may have to learn more than
1723 you would like about DBM libraries from what follows.
1725 .cindex "&'ndbm'& DBM library"
1726 Licensed versions of Unix normally contain a library of DBM functions operating
1727 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1728 versions of Unix seem to vary in what they contain as standard. In particular,
1729 some early versions of Linux have no default DBM library, and different
1730 distributors have chosen to bundle different libraries with their packaged
1731 versions. However, the more recent releases seem to have standardized on the
1732 Berkeley DB library.
1734 Different DBM libraries have different conventions for naming the files they
1735 use. When a program opens a file called &_dbmfile_&, there are several
1739 A traditional &'ndbm'& implementation, such as that supplied as part of
1740 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1742 .cindex "&'gdbm'& DBM library"
1743 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1744 compatibility interface it makes two different hard links to it with names
1745 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1746 filename is used unmodified.
1748 .cindex "Berkeley DB library"
1749 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1750 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1751 programmer exactly the same as the traditional &'ndbm'& implementation.
1753 If the Berkeley package is used in its native mode, it operates on a single
1754 file called &_dbmfile_&; the programmer's interface is somewhat different to
1755 the traditional &'ndbm'& interface.
1757 To complicate things further, there are several very different versions of the
1758 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1759 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1760 Maintenance of some of the earlier releases has ceased. All versions of
1761 Berkeley DB could be obtained from
1762 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1763 page with far newer versions listed.
1764 It is probably wise to plan to move your storage configurations away from
1765 Berkeley DB format, as today there are smaller and simpler alternatives more
1766 suited to Exim's usage model.
1768 .cindex "&'tdb'& DBM library"
1769 Yet another DBM library, called &'tdb'&, is available from
1770 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1771 operates on a single file.
1775 .cindex "DBM libraries" "configuration for building"
1776 Exim and its utilities can be compiled to use any of these interfaces. In order
1777 to use any version of the Berkeley DB package in native mode, you must set
1778 USE_DB in an appropriate configuration file (typically
1779 &_Local/Makefile_&). For example:
1783 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1784 error is diagnosed if you set more than one of these.
1786 At the lowest level, the build-time configuration sets none of these options,
1787 thereby assuming an interface of type (1). However, some operating system
1788 configuration files (for example, those for the BSD operating systems and
1789 Linux) assume type (4) by setting USE_DB as their default, and the
1790 configuration files for Cygwin set USE_GDBM. Anything you set in
1791 &_Local/Makefile_&, however, overrides these system defaults.
1793 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1794 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1795 in one of these lines:
1800 Settings like that will work if the DBM library is installed in the standard
1801 place. Sometimes it is not, and the library's header file may also not be in
1802 the default path. You may need to set INCLUDE to specify where the header
1803 file is, and to specify the path to the library more fully in DBMLIB, as in
1806 INCLUDE=-I/usr/local/include/db-4.1
1807 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1809 There is further detailed discussion about the various DBM libraries in the
1810 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1814 .section "Pre-building configuration" "SECID25"
1815 .cindex "building Exim" "pre-building configuration"
1816 .cindex "configuration for building Exim"
1817 .cindex "&_Local/Makefile_&"
1818 .cindex "&_src/EDITME_&"
1819 Before building Exim, a local configuration file that specifies options
1820 independent of any operating system has to be created with the name
1821 &_Local/Makefile_&. A template for this file is supplied as the file
1822 &_src/EDITME_&, and it contains full descriptions of all the option settings
1823 therein. These descriptions are therefore not repeated here. If you are
1824 building Exim for the first time, the simplest thing to do is to copy
1825 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1827 There are three settings that you must supply, because Exim will not build
1828 without them. They are the location of the runtime configuration file
1829 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1830 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1831 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1832 a colon-separated list of filenames; Exim uses the first of them that exists.
1834 There are a few other parameters that can be specified either at build time or
1835 at runtime, to enable the same binary to be used on a number of different
1836 machines. However, if the locations of Exim's spool directory and log file
1837 directory (if not within the spool directory) are fixed, it is recommended that
1838 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1839 detected early in Exim's execution (such as a malformed configuration file) can
1842 .cindex "content scanning" "specifying at build time"
1843 Exim's interfaces for calling virus and spam scanning software directly from
1844 access control lists are not compiled by default. If you want to include these
1845 facilities, you need to set
1847 WITH_CONTENT_SCAN=yes
1849 in your &_Local/Makefile_&. For details of the facilities themselves, see
1850 chapter &<<CHAPexiscan>>&.
1853 .cindex "&_Local/eximon.conf_&"
1854 .cindex "&_exim_monitor/EDITME_&"
1855 If you are going to build the Exim monitor, a similar configuration process is
1856 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1857 your installation and saved under the name &_Local/eximon.conf_&. If you are
1858 happy with the default settings described in &_exim_monitor/EDITME_&,
1859 &_Local/eximon.conf_& can be empty, but it must exist.
1861 This is all the configuration that is needed in straightforward cases for known
1862 operating systems. However, the building process is set up so that it is easy
1863 to override options that are set by default or by operating-system-specific
1864 configuration files, for example, to change the C compiler, which
1865 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1870 .section "Support for iconv()" "SECID26"
1871 .cindex "&[iconv()]& support"
1873 The contents of header lines in messages may be encoded according to the rules
1874 described RFC 2047. This makes it possible to transmit characters that are not
1875 in the ASCII character set, and to label them as being in a particular
1876 character set. When Exim is inspecting header lines by means of the &%$h_%&
1877 mechanism, it decodes them, and translates them into a specified character set
1878 (default is set at build time). The translation is possible only if the operating system
1879 supports the &[iconv()]& function.
1881 However, some of the operating systems that supply &[iconv()]& do not support
1882 very many conversions. The GNU &%libiconv%& library (available from
1883 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1884 systems to remedy this deficiency, as well as on systems that do not supply
1885 &[iconv()]& at all. After installing &%libiconv%&, you should add
1889 to your &_Local/Makefile_& and rebuild Exim.
1893 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1894 .cindex "TLS" "including support for TLS"
1895 .cindex "encryption" "including support for"
1896 .cindex "OpenSSL" "building Exim with"
1897 .cindex "GnuTLS" "building Exim with"
1898 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1899 command as per RFC 2487. It can also support clients that expect to
1900 start a TLS session immediately on connection to a non-standard port (see the
1901 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1904 If you want to build Exim with TLS support, you must first install either the
1905 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1908 If you do not want TLS support you should set
1912 in &_Local/Makefile_&.
1914 If OpenSSL is installed, you should set
1917 TLS_LIBS=-lssl -lcrypto
1919 in &_Local/Makefile_&. You may also need to specify the locations of the
1920 OpenSSL library and include files. For example:
1923 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1924 TLS_INCLUDE=-I/usr/local/openssl/include/
1926 .cindex "pkg-config" "OpenSSL"
1927 If you have &'pkg-config'& available, then instead you can just use:
1930 USE_OPENSSL_PC=openssl
1932 .cindex "USE_GNUTLS"
1933 If GnuTLS is installed, you should set
1936 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1938 in &_Local/Makefile_&, and again you may need to specify the locations of the
1939 library and include files. For example:
1942 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1943 TLS_INCLUDE=-I/usr/gnu/include
1945 .cindex "pkg-config" "GnuTLS"
1946 If you have &'pkg-config'& available, then instead you can just use:
1949 USE_GNUTLS_PC=gnutls
1952 You do not need to set TLS_INCLUDE if the relevant directory is already
1953 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1954 given in chapter &<<CHAPTLS>>&.
1959 .section "Use of tcpwrappers" "SECID27"
1961 .cindex "tcpwrappers, building Exim to support"
1962 .cindex "USE_TCP_WRAPPERS"
1963 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1964 .cindex "tcp_wrappers_daemon_name"
1965 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1966 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1967 alternative to Exim's own checking facilities for installations that are
1968 already making use of &'tcpwrappers'& for other purposes. To do this, you
1969 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1970 &_tcpd.h_& to be available at compile time, and also ensure that the library
1971 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1972 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1975 USE_TCP_WRAPPERS=yes
1976 CFLAGS=-O -I/usr/local/include
1977 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1979 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1980 files is &"exim"&. For example, the line
1982 exim : LOCAL 192.168.1. .friendly.domain.example
1984 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1985 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1986 All other connections are denied. The daemon name used by &'tcpwrappers'&
1987 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1988 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1989 configure file. Consult the &'tcpwrappers'& documentation for
1993 .section "Including support for IPv6" "SECID28"
1994 .cindex "IPv6" "including support for"
1995 Exim contains code for use on systems that have IPv6 support. Setting
1996 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1997 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1998 where the IPv6 support is not fully integrated into the normal include and
2001 Two different types of DNS record for handling IPv6 addresses have been
2002 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2003 currently seen as the mainstream. Another record type called A6 was proposed
2004 as better than AAAA because it had more flexibility. However, it was felt to be
2005 over-complex, and its status was reduced to &"experimental"&.
2007 have a compile option for including A6 record support but this has now been
2012 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2013 .cindex "lookup modules"
2014 .cindex "dynamic modules"
2015 .cindex ".so building"
2016 On some platforms, Exim supports not compiling all lookup types directly into
2017 the main binary, instead putting some into external modules which can be loaded
2019 This permits packagers to build Exim with support for lookups with extensive
2020 library dependencies without requiring all users to install all of those
2022 Most, but not all, lookup types can be built this way.
2024 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2025 installed; Exim will only load modules from that directory, as a security
2026 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2027 for your OS; see &_OS/Makefile-Linux_& for an example.
2028 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2029 see &_src/EDITME_& for details.
2031 Then, for each module to be loaded dynamically, define the relevant
2032 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2033 For example, this will build in lsearch but load sqlite and mysql support
2042 .section "The building process" "SECID29"
2043 .cindex "build directory"
2044 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2045 created, run &'make'& at the top level. It determines the architecture and
2046 operating system types, and creates a build directory if one does not exist.
2047 For example, on a Sun system running Solaris 8, the directory
2048 &_build-SunOS5-5.8-sparc_& is created.
2049 .cindex "symbolic link" "to source files"
2050 Symbolic links to relevant source files are installed in the build directory.
2052 If this is the first time &'make'& has been run, it calls a script that builds
2053 a make file inside the build directory, using the configuration files from the
2054 &_Local_& directory. The new make file is then passed to another instance of
2055 &'make'&. This does the real work, building a number of utility scripts, and
2056 then compiling and linking the binaries for the Exim monitor (if configured), a
2057 number of utility programs, and finally Exim itself. The command &`make
2058 makefile`& can be used to force a rebuild of the make file in the build
2059 directory, should this ever be necessary.
2061 If you have problems building Exim, check for any comments there may be in the
2062 &_README_& file concerning your operating system, and also take a look at the
2063 FAQ, where some common problems are covered.
2067 .section 'Output from &"make"&' "SECID283"
2068 The output produced by the &'make'& process for compile lines is often very
2069 unreadable, because these lines can be very long. For this reason, the normal
2070 output is suppressed by default, and instead output similar to that which
2071 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2072 each module that is being compiled or linked. However, it is still possible to
2073 get the full output, by calling &'make'& like this:
2077 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2078 command reflection in &'make'&. When you ask for the full output, it is
2079 given in addition to the short output.
2083 .section "Overriding build-time options for Exim" "SECToverride"
2084 .cindex "build-time options, overriding"
2085 The main make file that is created at the beginning of the building process
2086 consists of the concatenation of a number of files which set configuration
2087 values, followed by a fixed set of &'make'& instructions. If a value is set
2088 more than once, the last setting overrides any previous ones. This provides a
2089 convenient way of overriding defaults. The files that are concatenated are, in
2092 &_OS/Makefile-Default_&
2093 &_OS/Makefile-_&<&'ostype'&>
2095 &_Local/Makefile-_&<&'ostype'&>
2096 &_Local/Makefile-_&<&'archtype'&>
2097 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2098 &_OS/Makefile-Base_&
2100 .cindex "&_Local/Makefile_&"
2101 .cindex "building Exim" "operating system type"
2102 .cindex "building Exim" "architecture type"
2103 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2104 architecture type. &_Local/Makefile_& is required to exist, and the building
2105 process fails if it is absent. The other three &_Local_& files are optional,
2106 and are often not needed.
2108 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2109 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2110 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2111 values are used, thereby providing a means of forcing particular settings.
2112 Otherwise, the scripts try to get values from the &%uname%& command. If this
2113 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2114 of &'ad hoc'& transformations are then applied, to produce the standard names
2115 that Exim expects. You can run these scripts directly from the shell in order
2116 to find out what values are being used on your system.
2119 &_OS/Makefile-Default_& contains comments about the variables that are set
2120 therein. Some (but not all) are mentioned below. If there is something that
2121 needs changing, review the contents of this file and the contents of the make
2122 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2126 .cindex "building Exim" "overriding default settings"
2127 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2128 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2129 need to change the original files. Instead, you should make the changes by
2130 putting the new values in an appropriate &_Local_& file. For example,
2131 .cindex "Tru64-Unix build-time settings"
2132 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2133 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2134 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2135 called with the option &%-std1%&, to make it recognize some of the features of
2136 Standard C that Exim uses. (Most other compilers recognize Standard C by
2137 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2138 containing the lines
2143 If you are compiling for just one operating system, it may be easier to put
2144 these lines directly into &_Local/Makefile_&.
2146 Keeping all your local configuration settings separate from the distributed
2147 files makes it easy to transfer them to new versions of Exim simply by copying
2148 the contents of the &_Local_& directory.
2151 .cindex "NIS lookup type" "including support for"
2152 .cindex "NIS+ lookup type" "including support for"
2153 .cindex "LDAP" "including support for"
2154 .cindex "lookup" "inclusion in binary"
2155 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2156 lookup, but not all systems have these components installed, so the default is
2157 not to include the relevant code in the binary. All the different kinds of file
2158 and database lookup that Exim supports are implemented as separate code modules
2159 which are included only if the relevant compile-time options are set. In the
2160 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2166 and similar settings apply to the other lookup types. They are all listed in
2167 &_src/EDITME_&. In many cases the relevant include files and interface
2168 libraries need to be installed before compiling Exim.
2169 .cindex "cdb" "including support for"
2170 However, there are some optional lookup types (such as cdb) for which
2171 the code is entirely contained within Exim, and no external include
2172 files or libraries are required. When a lookup type is not included in the
2173 binary, attempts to configure Exim to use it cause runtime configuration
2176 .cindex "pkg-config" "lookups"
2177 .cindex "pkg-config" "authenticators"
2178 Many systems now use a tool called &'pkg-config'& to encapsulate information
2179 about how to compile against a library; Exim has some initial support for
2180 being able to use pkg-config for lookups and authenticators. For any given
2181 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2182 variable with the &`_PC`& suffix in the name and assign as the value the
2183 name of the package to be queried. The results of querying via the
2184 &'pkg-config'& command will be added to the appropriate Makefile variables
2185 with &`+=`& directives, so your version of &'make'& will need to support that
2186 syntax. For instance:
2189 LOOKUP_SQLITE_PC=sqlite3
2191 AUTH_GSASL_PC=libgsasl
2192 AUTH_HEIMDAL_GSSAPI=yes
2193 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2196 .cindex "Perl" "including support for"
2197 Exim can be linked with an embedded Perl interpreter, allowing Perl
2198 subroutines to be called during string expansion. To enable this facility,
2202 must be defined in &_Local/Makefile_&. Details of this facility are given in
2203 chapter &<<CHAPperl>>&.
2205 .cindex "X11 libraries, location of"
2206 The location of the X11 libraries is something that varies a lot between
2207 operating systems, and there may be different versions of X11 to cope
2208 with. Exim itself makes no use of X11, but if you are compiling the Exim
2209 monitor, the X11 libraries must be available.
2210 The following three variables are set in &_OS/Makefile-Default_&:
2213 XINCLUDE=-I$(X11)/include
2214 XLFLAGS=-L$(X11)/lib
2216 These are overridden in some of the operating-system configuration files. For
2217 example, in &_OS/Makefile-SunOS5_& there is
2220 XINCLUDE=-I$(X11)/include
2221 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2223 If you need to override the default setting for your operating system, place a
2224 definition of all three of these variables into your
2225 &_Local/Makefile-<ostype>_& file.
2228 If you need to add any extra libraries to the link steps, these can be put in a
2229 variable called EXTRALIBS, which appears in all the link commands, but by
2230 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2231 command for linking the main Exim binary, and not for any associated utilities.
2233 .cindex "DBM libraries" "configuration for building"
2234 There is also DBMLIB, which appears in the link commands for binaries that
2235 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2236 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2237 binary, and which can be used, for example, to include additional X11
2240 .cindex "configuration file" "editing"
2241 The make file copes with rebuilding Exim correctly if any of the configuration
2242 files are edited. However, if an optional configuration file is deleted, it is
2243 necessary to touch the associated non-optional file (that is,
2244 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2247 .section "OS-specific header files" "SECID30"
2249 .cindex "building Exim" "OS-specific C header files"
2250 The &_OS_& directory contains a number of files with names of the form
2251 &_os.h-<ostype>_&. These are system-specific C header files that should not
2252 normally need to be changed. There is a list of macro settings that are
2253 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2254 are porting Exim to a new operating system.
2258 .section "Overriding build-time options for the monitor" "SECID31"
2259 .cindex "building Eximon"
2260 A similar process is used for overriding things when building the Exim monitor,
2261 where the files that are involved are
2263 &_OS/eximon.conf-Default_&
2264 &_OS/eximon.conf-_&<&'ostype'&>
2265 &_Local/eximon.conf_&
2266 &_Local/eximon.conf-_&<&'ostype'&>
2267 &_Local/eximon.conf-_&<&'archtype'&>
2268 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2270 .cindex "&_Local/eximon.conf_&"
2271 As with Exim itself, the final three files need not exist, and in this case the
2272 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2273 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2274 variables of the same name, preceded by EXIMON_. For example, setting
2275 EXIMON_LOG_DEPTH in the environment overrides the value of
2276 LOG_DEPTH at runtime.
2280 .section "Installing Exim binaries and scripts" "SECID32"
2281 .cindex "installing Exim"
2282 .cindex "BIN_DIRECTORY"
2283 The command &`make install`& runs the &(exim_install)& script with no
2284 arguments. The script copies binaries and utility scripts into the directory
2285 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2286 .cindex "setuid" "installing Exim with"
2287 The install script copies files only if they are newer than the files they are
2288 going to replace. The Exim binary is required to be owned by root and have the
2289 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2290 install`& as root so that it can set up the Exim binary in this way. However, in
2291 some special situations (for example, if a host is doing no local deliveries)
2292 it may be possible to run Exim without making the binary setuid root (see
2293 chapter &<<CHAPsecurity>>& for details).
2295 .cindex "CONFIGURE_FILE"
2296 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2297 in &_Local/Makefile_&. If this names a single file, and the file does not
2298 exist, the default configuration file &_src/configure.default_& is copied there
2299 by the installation script. If a runtime configuration file already exists, it
2300 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2301 alternative files, no default is installed.
2303 .cindex "system aliases file"
2304 .cindex "&_/etc/aliases_&"
2305 One change is made to the default configuration file when it is installed: the
2306 default configuration contains a router that references a system aliases file.
2307 The path to this file is set to the value specified by
2308 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2309 If the system aliases file does not exist, the installation script creates it,
2310 and outputs a comment to the user.
2312 The created file contains no aliases, but it does contain comments about the
2313 aliases a site should normally have. Mail aliases have traditionally been
2314 kept in &_/etc/aliases_&. However, some operating systems are now using
2315 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2316 Exim's configuration if necessary.
2318 The default configuration uses the local host's name as the only local domain,
2319 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2320 running as the local user. System aliases and &_.forward_& files in users' home
2321 directories are supported, but no NIS or NIS+ support is configured. Domains
2322 other than the name of the local host are routed using the DNS, with delivery
2325 It is possible to install Exim for special purposes (such as building a binary
2326 distribution) in a private part of the file system. You can do this by a
2329 make DESTDIR=/some/directory/ install
2331 This has the effect of pre-pending the specified directory to all the file
2332 paths, except the name of the system aliases file that appears in the default
2333 configuration. (If a default alias file is created, its name &'is'& modified.)
2334 For backwards compatibility, ROOT is used if DESTDIR is not set,
2335 but this usage is deprecated.
2337 .cindex "installing Exim" "what is not installed"
2338 Running &'make install'& does not copy the Exim 4 conversion script
2339 &'convert4r4'&. You will probably run this only once if you are
2340 upgrading from Exim 3. None of the documentation files in the &_doc_&
2341 directory are copied, except for the info files when you have set
2342 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2344 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2345 to their names. The Exim binary itself, however, is handled differently. It is
2346 installed under a name that includes the version number and the compile number,
2347 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2348 called &_exim_& to point to the binary. If you are updating a previous version
2349 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2350 from the directory (as seen by other processes).
2352 .cindex "installing Exim" "testing the script"
2353 If you want to see what the &'make install'& will do before running it for
2354 real, you can pass the &%-n%& option to the installation script by this
2357 make INSTALL_ARG=-n install
2359 The contents of the variable INSTALL_ARG are passed to the installation
2360 script. You do not need to be root to run this test. Alternatively, you can run
2361 the installation script directly, but this must be from within the build
2362 directory. For example, from the top-level Exim directory you could use this
2365 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2367 .cindex "installing Exim" "install script options"
2368 There are two other options that can be supplied to the installation script.
2371 &%-no_chown%& bypasses the call to change the owner of the installed binary
2372 to root, and the call to make it a setuid binary.
2374 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2378 INSTALL_ARG can be used to pass these options to the script. For example:
2380 make INSTALL_ARG=-no_symlink install
2382 The installation script can also be given arguments specifying which files are
2383 to be copied. For example, to install just the Exim binary, and nothing else,
2384 without creating the symbolic link, you could use:
2386 make INSTALL_ARG='-no_symlink exim' install
2391 .section "Installing info documentation" "SECTinsinfdoc"
2392 .cindex "installing Exim" "&'info'& documentation"
2393 Not all systems use the GNU &'info'& system for documentation, and for this
2394 reason, the Texinfo source of Exim's documentation is not included in the main
2395 distribution. Instead it is available separately from the FTP site (see section
2398 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2399 source of the documentation is found in the source tree, running &`make
2400 install`& automatically builds the info files and installs them.
2404 .section "Setting up the spool directory" "SECID33"
2405 .cindex "spool directory" "creating"
2406 When it starts up, Exim tries to create its spool directory if it does not
2407 exist. The Exim uid and gid are used for the owner and group of the spool
2408 directory. Sub-directories are automatically created in the spool directory as
2414 .section "Testing" "SECID34"
2415 .cindex "testing" "installation"
2416 Having installed Exim, you can check that the runtime configuration file is
2417 syntactically valid by running the following command, which assumes that the
2418 Exim binary directory is within your PATH environment variable:
2422 If there are any errors in the configuration file, Exim outputs error messages.
2423 Otherwise it outputs the version number and build date,
2424 the DBM library that is being used, and information about which drivers and
2425 other optional code modules are included in the binary.
2426 Some simple routing tests can be done by using the address testing option. For
2429 &`exim -bt`& <&'local username'&>
2431 should verify that it recognizes a local mailbox, and
2433 &`exim -bt`& <&'remote address'&>
2435 a remote one. Then try getting it to deliver mail, both locally and remotely.
2436 This can be done by passing messages directly to Exim, without going through a
2437 user agent. For example:
2439 exim -v postmaster@your.domain.example
2440 From: user@your.domain.example
2441 To: postmaster@your.domain.example
2442 Subject: Testing Exim
2444 This is a test message.
2447 The &%-v%& option causes Exim to output some verification of what it is doing.
2448 In this case you should see copies of three log lines, one for the message's
2449 arrival, one for its delivery, and one containing &"Completed"&.
2451 .cindex "delivery" "problems with"
2452 If you encounter problems, look at Exim's log files (&'mainlog'& and
2453 &'paniclog'&) to see if there is any relevant information there. Another source
2454 of information is running Exim with debugging turned on, by specifying the
2455 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2456 with debugging turned on by a command of the form
2458 &`exim -d -M`& <&'exim-message-id'&>
2460 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2461 produces rather a lot of output, but you can cut this down to specific areas.
2462 For example, if you use &%-d-all+route%& only the debugging information
2463 relevant to routing is included. (See the &%-d%& option in chapter
2464 &<<CHAPcommandline>>& for more details.)
2466 .cindex '&"sticky"& bit'
2467 .cindex "lock files"
2468 One specific problem that has shown up on some sites is the inability to do
2469 local deliveries into a shared mailbox directory, because it does not have the
2470 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2471 writing to a mailbox file, and if it cannot create the lock file, the delivery
2472 is deferred. You can get round this either by setting the &"sticky bit"& on the
2473 directory, or by setting a specific group for local deliveries and allowing
2474 that group to create files in the directory (see the comments above the
2475 &(local_delivery)& transport in the default configuration file). Another
2476 approach is to configure Exim not to use lock files, but just to rely on
2477 &[fcntl()]& locking instead. However, you should do this only if all user
2478 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2479 see chapter &<<CHAPappendfile>>&.
2481 One thing that cannot be tested on a system that is already running an MTA is
2482 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2483 &%-oX%& option can be used to run an Exim daemon that listens on some other
2484 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2485 &'exim_checkaccess'& utility can be used to check out policy controls on
2488 Testing a new version on a system that is already running Exim can most easily
2489 be done by building a binary with a different CONFIGURE_FILE setting. From
2490 within the runtime configuration, all other file and directory names
2491 that Exim uses can be altered, in order to keep it entirely clear of the
2495 .section "Replacing another MTA with Exim" "SECID35"
2496 .cindex "replacing another MTA"
2497 Building and installing Exim for the first time does not of itself put it in
2498 general use. The name by which the system's MTA is called by mail user agents
2499 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2500 operating system), and it is necessary to make this name point to the &'exim'&
2501 binary in order to get the user agents to pass messages to Exim. This is
2502 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2503 or &_/usr/lib/sendmail_&
2504 .cindex "symbolic link" "to &'exim'& binary"
2505 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2506 privilege and executable status from the old MTA. It is then necessary to stop
2507 and restart the mailer daemon, if one is running.
2509 .cindex "FreeBSD, MTA indirection"
2510 .cindex "&_/etc/mail/mailer.conf_&"
2511 Some operating systems have introduced alternative ways of switching MTAs. For
2512 example, if you are running FreeBSD, you need to edit the file
2513 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2514 described. A typical example of the contents of this file for running Exim is
2517 sendmail /usr/exim/bin/exim
2518 send-mail /usr/exim/bin/exim
2519 mailq /usr/exim/bin/exim -bp
2520 newaliases /usr/bin/true
2522 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2523 your Exim installation is &"live"&. Check it by sending a message from your
2524 favourite user agent.
2526 You should consider what to tell your users about the change of MTA. Exim may
2527 have different capabilities to what was previously running, and there are
2528 various operational differences such as the text of messages produced by
2529 command line options and in bounce messages. If you allow your users to make
2530 use of Exim's filtering capabilities, you should make the document entitled
2531 &'Exim's interface to mail filtering'& available to them.
2535 .section "Upgrading Exim" "SECID36"
2536 .cindex "upgrading Exim"
2537 If you are already running Exim on your host, building and installing a new
2538 version automatically makes it available to MUAs, or any other programs that
2539 call the MTA directly. However, if you are running an Exim daemon, you do need
2540 .cindex restart "on HUP signal"
2541 .cindex signal "HUP, to restart"
2542 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2543 new binary. You do not need to stop processing mail in order to install a new
2544 version of Exim. The install script does not modify an existing runtime
2550 .section "Stopping the Exim daemon on Solaris" "SECID37"
2551 .cindex "Solaris" "stopping Exim on"
2552 The standard command for stopping the mailer daemon on Solaris is
2554 /etc/init.d/sendmail stop
2556 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2557 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2558 for the text &"sendmail"&; this is not present because the actual program name
2559 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2560 solution is to replace the line that finds the process id with something like
2562 pid=`cat /var/spool/exim/exim-daemon.pid`
2564 to obtain the daemon's pid directly from the file that Exim saves it in.
2566 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2567 still be received from local processes, and if automatic delivery is configured
2568 (the normal case), deliveries will still occur.
2573 . ////////////////////////////////////////////////////////////////////////////
2574 . ////////////////////////////////////////////////////////////////////////////
2576 .chapter "The Exim command line" "CHAPcommandline"
2577 .scindex IIDclo1 "command line" "options"
2578 .scindex IIDclo2 "options" "command line"
2579 Exim's command line takes the standard Unix form of a sequence of options,
2580 each starting with a hyphen character, followed by a number of arguments. The
2581 options are compatible with the main options of Sendmail, and there are also
2582 some additional options, some of which are compatible with Smail 3. Certain
2583 combinations of options do not make sense, and provoke an error if used.
2584 The form of the arguments depends on which options are set.
2587 .section "Setting options by program name" "SECID38"
2589 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2590 were present before any other options.
2591 The &%-bp%& option requests a listing of the contents of the mail queue on the
2593 This feature is for compatibility with some systems that contain a command of
2594 that name in one of the standard libraries, symbolically linked to
2595 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2598 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2599 were present before any other options, for compatibility with Smail. The
2600 &%-bS%& option is used for reading in a number of messages in batched SMTP
2604 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2605 &%-oee%& options were present before any other options, for compatibility with
2606 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2609 .cindex "queue runner"
2610 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2611 were present before any other options, for compatibility with Smail. The &%-q%&
2612 option causes a single queue runner process to be started.
2614 .cindex "&'newaliases'&"
2615 .cindex "alias file" "building"
2616 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2617 If Exim is called under the name &'newaliases'& it behaves as if the option
2618 &%-bi%& were present before any other options, for compatibility with Sendmail.
2619 This option is used for rebuilding Sendmail's alias file. Exim does not have
2620 the concept of a single alias file, but can be configured to run a given
2621 command if called with the &%-bi%& option.
2624 .section "Trusted and admin users" "SECTtrustedadmin"
2625 Some Exim options are available only to &'trusted users'& and others are
2626 available only to &'admin users'&. In the description below, the phrases &"Exim
2627 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2628 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2629 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2632 .cindex "trusted users" "definition of"
2633 .cindex "user" "trusted definition of"
2634 The trusted users are root, the Exim user, any user listed in the
2635 &%trusted_users%& configuration option, and any user whose current group or any
2636 supplementary group is one of those listed in the &%trusted_groups%&
2637 configuration option. Note that the Exim group is not automatically trusted.
2639 .cindex '&"From"& line'
2640 .cindex "envelope from"
2641 .cindex "envelope sender"
2642 Trusted users are always permitted to use the &%-f%& option or a leading
2643 &"From&~"& line to specify the envelope sender of a message that is passed to
2644 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2645 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2646 users to set envelope senders.
2648 .cindex "&'From:'& header line"
2649 .cindex "&'Sender:'& header line"
2650 .cindex "header lines" "From:"
2651 .cindex "header lines" "Sender:"
2652 For a trusted user, there is never any check on the contents of the &'From:'&
2653 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2654 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2656 Trusted users may also specify a host name, host address, interface address,
2657 protocol name, ident value, and authentication data when submitting a message
2658 locally. Thus, they are able to insert messages into Exim's queue locally that
2659 have the characteristics of messages received from a remote host. Untrusted
2660 users may in some circumstances use &%-f%&, but can never set the other values
2661 that are available to trusted users.
2663 .cindex "user" "admin definition of"
2664 .cindex "admin user" "definition of"
2665 The admin users are root, the Exim user, and any user that is a member of the
2666 Exim group or of any group listed in the &%admin_groups%& configuration option.
2667 The current group does not have to be one of these groups.
2669 Admin users are permitted to list the queue, and to carry out certain
2670 operations on messages, for example, to force delivery failures. It is also
2671 necessary to be an admin user in order to see the full information provided by
2672 the Exim monitor, and full debugging output.
2674 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2675 Exim to attempt delivery of messages on its queue is restricted to admin users.
2676 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2677 option false (that is, specifying &%no_prod_requires_admin%&).
2679 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2680 is restricted to admin users unless &%queue_list_requires_admin%& is set
2685 &*Warning*&: If you configure your system so that admin users are able to
2686 edit Exim's configuration file, you are giving those users an easy way of
2687 getting root. There is further discussion of this issue at the start of chapter
2693 .section "Command line options" "SECID39"
2694 Exim's command line options are described in alphabetical order below. If none
2695 of the options that specifies a specific action (such as starting the daemon or
2696 a queue runner, or testing an address, or receiving a message in a specific
2697 format, or listing the queue) are present, and there is at least one argument
2698 on the command line, &%-bm%& (accept a local message on the standard input,
2699 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2700 outputs a brief message about itself and exits.
2702 . ////////////////////////////////////////////////////////////////////////////
2703 . Insert a stylized XML comment here, to identify the start of the command line
2704 . options. This is for the benefit of the Perl script that automatically
2705 . creates a man page for the options.
2706 . ////////////////////////////////////////////////////////////////////////////
2709 <!-- === Start of command line options === -->
2716 .cindex "options" "command line; terminating"
2717 This is a pseudo-option whose only purpose is to terminate the options and
2718 therefore to cause subsequent command line items to be treated as arguments
2719 rather than options, even if they begin with hyphens.
2722 .oindex "&%--help%&"
2723 This option causes Exim to output a few sentences stating what it is.
2724 The same output is generated if the Exim binary is called with no options and
2727 .vitem &%--version%&
2728 .oindex "&%--version%&"
2729 This option is an alias for &%-bV%& and causes version information to be
2736 These options are used by Sendmail for selecting configuration files and are
2739 .vitem &%-B%&<&'type'&>
2741 .cindex "8-bit characters"
2742 .cindex "Sendmail compatibility" "8-bit characters"
2743 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2744 clean; it ignores this option.
2749 .cindex "SMTP" "listener"
2750 .cindex "queue runner"
2751 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2752 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2753 that the daemon should also initiate periodic queue runs.
2755 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2756 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2757 disconnect from the controlling terminal. When running this way, it can be
2758 stopped by pressing ctrl-C.
2760 By default, Exim listens for incoming connections to the standard SMTP port on
2761 all the host's running interfaces. However, it is possible to listen on other
2762 ports, on multiple ports, and only on specific interfaces. Chapter
2763 &<<CHAPinterfaces>>& contains a description of the options that control this.
2765 When a listening daemon
2766 .cindex "daemon" "process id (pid)"
2767 .cindex "pid (process id)" "of daemon"
2768 is started without the use of &%-oX%& (that is, without overriding the normal
2769 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2770 in Exim's spool directory. This location can be overridden by setting
2771 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2774 When &%-oX%& is used on the command line to start a listening daemon, the
2775 process id is not written to the normal pid file path. However, &%-oP%& can be
2776 used to specify a path on the command line if a pid file is required.
2780 .cindex restart "on HUP signal"
2781 .cindex signal "HUP, to restart"
2782 .cindex "daemon" "restarting"
2783 .cindex signal "to reload configuration"
2784 .cindex daemon "reload configuration"
2785 .cindex reload configuration
2786 can be used to cause the daemon to re-execute itself. This should be done
2787 whenever Exim's configuration file, or any file that is incorporated into it by
2788 means of the &%.include%& facility, is changed, and also whenever a new version
2789 of Exim is installed. It is not necessary to do this when other files that are
2790 referenced from the configuration (for example, alias files) are changed,
2791 because these are reread each time they are used.
2795 This option has the same effect as &%-bd%& except that it never disconnects
2796 from the controlling terminal, even when no debugging is specified.
2800 .cindex "testing" "string expansion"
2801 .cindex "expansion" "testing"
2802 Run Exim in expansion testing mode. Exim discards its root privilege, to
2803 prevent ordinary users from using this mode to read otherwise inaccessible
2804 files. If no arguments are given, Exim runs interactively, prompting for lines
2805 of data. Otherwise, it processes each argument in turn.
2807 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2808 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2809 used without command line arguments. If successful, it uses the &[readline()]&
2810 function, which provides extensive line-editing facilities, for reading the
2811 test data. A line history is supported.
2813 Long expansion expressions can be split over several lines by using backslash
2814 continuations. As in Exim's runtime configuration, white space at the start of
2815 continuation lines is ignored. Each argument or data line is passed through the
2816 string expansion mechanism, and the result is output. Variable values from the
2817 configuration file (for example, &$qualify_domain$&) are available, but no
2818 message-specific values (such as &$message_exim_id$&) are set, because no message
2819 is being processed (but see &%-bem%& and &%-Mset%&).
2821 &*Note*&: If you use this mechanism to test lookups, and you change the data
2822 files or databases you are using, you must exit and restart Exim before trying
2823 the same lookup again. Otherwise, because each Exim process caches the results
2824 of lookups, you will just get the same result as before.
2826 Macro processing is done on lines before string-expansion: new macros can be
2827 defined and macros will be expanded.
2828 Because macros in the config file are often used for secrets, those are only
2829 available to admin users.
2831 .vitem &%-bem%&&~<&'filename'&>
2833 .cindex "testing" "string expansion"
2834 .cindex "expansion" "testing"
2835 This option operates like &%-be%& except that it must be followed by the name
2836 of a file. For example:
2838 exim -bem /tmp/testmessage
2840 The file is read as a message (as if receiving a locally-submitted non-SMTP
2841 message) before any of the test expansions are done. Thus, message-specific
2842 variables such as &$message_size$& and &$header_from:$& are available. However,
2843 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2844 recipients are read from the headers in the normal way, and are shown in the
2845 &$recipients$& variable. Note that recipients cannot be given on the command
2846 line, because further arguments are taken as strings to expand (just like
2849 .vitem &%-bF%&&~<&'filename'&>
2851 .cindex "system filter" "testing"
2852 .cindex "testing" "system filter"
2853 This option is the same as &%-bf%& except that it assumes that the filter being
2854 tested is a system filter. The additional commands that are available only in
2855 system filters are recognized.
2857 .vitem &%-bf%&&~<&'filename'&>
2859 .cindex "filter" "testing"
2860 .cindex "testing" "filter file"
2861 .cindex "forward file" "testing"
2862 .cindex "testing" "forward file"
2863 .cindex "Sieve filter" "testing"
2864 This option runs Exim in user filter testing mode; the file is the filter file
2865 to be tested, and a test message must be supplied on the standard input. If
2866 there are no message-dependent tests in the filter, an empty file can be
2869 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2870 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2871 filter and a user filter in the same run. For example:
2873 exim -bF /system/filter -bf /user/filter </test/message
2875 This is helpful when the system filter adds header lines or sets filter
2876 variables that are used by the user filter.
2878 If the test filter file does not begin with one of the special lines
2883 it is taken to be a normal &_.forward_& file, and is tested for validity under
2884 that interpretation. See sections &<<SECTitenonfilred>>& to
2885 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2888 The result of an Exim command that uses &%-bf%&, provided no errors are
2889 detected, is a list of the actions that Exim would try to take if presented
2890 with the message for real. More details of filter testing are given in the
2891 separate document entitled &'Exim's interfaces to mail filtering'&.
2893 When testing a filter file,
2894 .cindex "&""From""& line"
2895 .cindex "envelope from"
2896 .cindex "envelope sender"
2897 .oindex "&%-f%&" "for filter testing"
2898 the envelope sender can be set by the &%-f%& option,
2899 or by a &"From&~"& line at the start of the test message. Various parameters
2900 that would normally be taken from the envelope recipient address of the message
2901 can be set by means of additional command line options (see the next four
2904 .vitem &%-bfd%&&~<&'domain'&>
2906 .vindex "&$qualify_domain$&"
2907 This sets the domain of the recipient address when a filter file is being
2908 tested by means of the &%-bf%& option. The default is the value of
2911 .vitem &%-bfl%&&~<&'local&~part'&>
2913 This sets the local part of the recipient address when a filter file is being
2914 tested by means of the &%-bf%& option. The default is the username of the
2915 process that calls Exim. A local part should be specified with any prefix or
2916 suffix stripped, because that is how it appears to the filter when a message is
2917 actually being delivered.
2919 .vitem &%-bfp%&&~<&'prefix'&>
2921 .cindex affix "filter testing"
2922 This sets the prefix of the local part of the recipient address when a filter
2923 file is being tested by means of the &%-bf%& option. The default is an empty
2926 .vitem &%-bfs%&&~<&'suffix'&>
2928 .cindex affix "filter testing"
2929 This sets the suffix of the local part of the recipient address when a filter
2930 file is being tested by means of the &%-bf%& option. The default is an empty
2933 .vitem &%-bh%&&~<&'IP&~address'&>
2935 .cindex "testing" "incoming SMTP"
2936 .cindex "SMTP" "testing incoming"
2937 .cindex "testing" "relay control"
2938 .cindex "relaying" "testing configuration"
2939 .cindex "policy control" "testing"
2940 .cindex "debugging" "&%-bh%& option"
2941 This option runs a fake SMTP session as if from the given IP address, using the
2942 standard input and output. The IP address may include a port number at the end,
2943 after a full stop. For example:
2945 exim -bh 10.9.8.7.1234
2946 exim -bh fe80::a00:20ff:fe86:a061.5678
2948 When an IPv6 address is given, it is converted into canonical form. In the case
2949 of the second example above, the value of &$sender_host_address$& after
2950 conversion to the canonical form is
2951 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2953 Comments as to what is going on are written to the standard error file. These
2954 include lines beginning with &"LOG"& for anything that would have been logged.
2955 This facility is provided for testing configuration options for incoming
2956 messages, to make sure they implement the required policy. For example, you can
2957 test your relay controls using &%-bh%&.
2961 You can test features of the configuration that rely on ident (RFC 1413)
2962 information by using the &%-oMt%& option. However, Exim cannot actually perform
2963 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2966 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2967 are also skipped when testing using &%-bh%&. If you want these callouts to
2968 occur, use &%-bhc%& instead.
2970 Messages supplied during the testing session are discarded, and nothing is
2971 written to any of the real log files. There may be pauses when DNS (and other)
2972 lookups are taking place, and of course these may time out. The &%-oMi%& option
2973 can be used to specify a specific IP interface and port if this is important,
2974 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2975 session were authenticated.
2977 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2978 output just states whether a given recipient address from a given host is
2979 acceptable or not. See section &<<SECTcheckaccess>>&.
2981 Features such as authentication and encryption, where the client input is not
2982 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2983 specialized SMTP test program such as
2984 &url(https://www.jetmore.org/john/code/swaks/,swaks).
2986 .vitem &%-bhc%&&~<&'IP&~address'&>
2988 This option operates in the same way as &%-bh%&, except that address
2989 verification callouts are performed if required. This includes consulting and
2990 updating the callout cache database.
2994 .cindex "alias file" "building"
2995 .cindex "building alias file"
2996 .cindex "Sendmail compatibility" "&%-bi%& option"
2997 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2998 Exim does not have the concept of a single alias file, and so it cannot mimic
2999 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3000 tend to appear in various scripts such as NIS make files, so the option must be
3003 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3004 configuration option is run, under the uid and gid of the caller of Exim. If
3005 the &%-oA%& option is used, its value is passed to the command as an argument.
3006 The command set by &%bi_command%& may not contain arguments. The command can
3007 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3008 if this is required. If the &%bi_command%& option is not set, calling Exim with
3011 . // Keep :help first, then the rest in alphabetical order
3013 .oindex "&%-bI:help%&"
3014 .cindex "querying exim information"
3015 We shall provide various options starting &`-bI:`& for querying Exim for
3016 information. The output of many of these will be intended for machine
3017 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3018 synopsis of supported options beginning &`-bI:`&. Use of any of these
3019 options shall cause Exim to exit after producing the requested output.
3022 .oindex "&%-bI:dscp%&"
3023 .cindex "DSCP" "values"
3024 This option causes Exim to emit an alphabetically sorted list of all
3025 recognised DSCP names.
3027 .vitem &%-bI:sieve%&
3028 .oindex "&%-bI:sieve%&"
3029 .cindex "Sieve filter" "capabilities"
3030 This option causes Exim to emit an alphabetically sorted list of all supported
3031 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3032 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3033 &`SIEVE`& capability response line. As the precise list may depend upon
3034 compile-time build options, which this option will adapt to, this is the only
3035 way to guarantee a correct response.
3039 .cindex "local message reception"
3040 This option runs an Exim receiving process that accepts an incoming,
3041 locally-generated message on the standard input. The recipients are given as the
3042 command arguments (except when &%-t%& is also present &-- see below). Each
3043 argument can be a comma-separated list of RFC 2822 addresses. This is the
3044 default option for selecting the overall action of an Exim call; it is assumed
3045 if no other conflicting option is present.
3047 If any addresses in the message are unqualified (have no domain), they are
3048 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3049 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3050 suppressing this for special cases.
3052 Policy checks on the contents of local messages can be enforced by means of
3053 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3055 .cindex "return code" "for &%-bm%&"
3056 The return code is zero if the message is successfully accepted. Otherwise, the
3057 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3060 .cindex "message" "format"
3061 .cindex "format" "message"
3062 .cindex "&""From""& line"
3063 .cindex "UUCP" "&""From""& line"
3064 .cindex "Sendmail compatibility" "&""From""& line"
3065 of the message must be as defined in RFC 2822, except that, for
3066 compatibility with Sendmail and Smail, a line in one of the forms
3068 From sender Fri Jan 5 12:55 GMT 1997
3069 From sender Fri, 5 Jan 97 12:55:01
3071 (with the weekday optional, and possibly with additional text after the date)
3072 is permitted to appear at the start of the message. There appears to be no
3073 authoritative specification of the format of this line. Exim recognizes it by
3074 matching against the regular expression defined by the &%uucp_from_pattern%&
3075 option, which can be changed if necessary.
3077 .oindex "&%-f%&" "overriding &""From""& line"
3078 The specified sender is treated as if it were given as the argument to the
3079 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3080 preference to the address taken from the message. The caller of Exim must be a
3081 trusted user for the sender of a message to be set in this way.
3083 .vitem &%-bmalware%&&~<&'filename'&>
3084 .oindex "&%-bmalware%&"
3085 .cindex "testing", "malware"
3086 .cindex "malware scan test"
3087 This debugging option causes Exim to scan the given file or directory
3088 (depending on the used scanner interface),
3089 using the malware scanning framework. The option of &%av_scanner%& influences
3090 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3091 the expansion should have defaults which apply to this invocation. ACLs are
3092 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3093 will never be populated and &%-bmalware%& will fail.
3095 Exim will have changed working directory before resolving the filename, so
3096 using fully qualified pathnames is advisable. Exim will be running as the Exim
3097 user when it tries to open the file, rather than as the invoking user.
3098 This option requires admin privileges.
3100 The &%-bmalware%& option will not be extended to be more generally useful,
3101 there are better tools for file-scanning. This option exists to help
3102 administrators verify their Exim and AV scanner configuration.
3106 .cindex "address qualification, suppressing"
3107 By default, Exim automatically qualifies unqualified addresses (those
3108 without domains) that appear in messages that are submitted locally (that
3109 is, not over TCP/IP). This qualification applies both to addresses in
3110 envelopes, and addresses in header lines. Sender addresses are qualified using
3111 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3112 defaults to the value of &%qualify_domain%&).
3114 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3115 being used to re-submit messages that originally came from remote hosts after
3116 content scanning, you probably do not want to qualify unqualified addresses in
3117 header lines. (Such lines will be present only if you have not enabled a header
3118 syntax check in the appropriate ACL.)
3120 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3121 messages that originate on the local host. When this is used, unqualified
3122 addresses in the envelope provoke errors (causing message rejection) and
3123 unqualified addresses in header lines are left alone.
3128 .cindex "configuration options" "extracting"
3129 .cindex "options" "configuration &-- extracting"
3130 If this option is given with no arguments, it causes the values of all Exim's
3131 main configuration options to be written to the standard output. The values
3132 of one or more specific options can be requested by giving their names as
3133 arguments, for example:
3135 exim -bP qualify_domain hold_domains
3137 .cindex "hiding configuration option values"
3138 .cindex "configuration options" "hiding value of"
3139 .cindex "options" "hiding value of"
3140 However, any option setting that is preceded by the word &"hide"& in the
3141 configuration file is not shown in full, except to an admin user. For other
3142 users, the output is as in this example:
3144 mysql_servers = <value not displayable>
3146 If &%config%& is given as an argument, the config is
3147 output, as it was parsed, any include file resolved, any comment removed.
3149 If &%config_file%& is given as an argument, the name of the runtime
3150 configuration file is output. (&%configure_file%& works too, for
3151 backward compatibility.)
3152 If a list of configuration files was supplied, the value that is output here
3153 is the name of the file that was actually used.
3155 .cindex "options" "hiding name of"
3156 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3157 name will not be output.
3159 .cindex "daemon" "process id (pid)"
3160 .cindex "pid (process id)" "of daemon"
3161 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3162 directories where log files and daemon pid files are written are output,
3163 respectively. If these values are unset, log files are written in a
3164 sub-directory of the spool directory called &%log%&, and the pid file is
3165 written directly into the spool directory.
3167 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3169 exim -bP +local_domains
3171 it searches for a matching named list of any type (domain, host, address, or
3172 local part) and outputs what it finds.
3174 .cindex "options" "router &-- extracting"
3175 .cindex "options" "transport &-- extracting"
3176 .cindex "options" "authenticator &-- extracting"
3177 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3178 followed by the name of an appropriate driver instance, the option settings for
3179 that driver are output. For example:
3181 exim -bP transport local_delivery
3183 The generic driver options are output first, followed by the driver's private
3184 options. A list of the names of drivers of a particular type can be obtained by
3185 using one of the words &%router_list%&, &%transport_list%&, or
3186 &%authenticator_list%&, and a complete list of all drivers with their option
3187 settings can be obtained by using &%routers%&, &%transports%&, or
3190 .cindex "environment"
3191 If &%environment%& is given as an argument, the set of environment
3192 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3195 .cindex "options" "macro &-- extracting"
3196 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3197 are available, similarly to the drivers. Because macros are sometimes used
3198 for storing passwords, this option is restricted.
3199 The output format is one item per line.
3200 For the "-bP macro <name>" form, if no such macro is found
3201 the exit status will be nonzero.
3205 .cindex "queue" "listing messages in"
3206 .cindex "listing" "messages in the queue"
3207 This option requests a listing of the contents of the mail queue on the
3208 standard output. If the &%-bp%& option is followed by a list of message ids,
3209 just those messages are listed. By default, this option can be used only by an
3210 admin user. However, the &%queue_list_requires_admin%& option can be set false
3211 to allow any user to see the queue.
3213 Each message in the queue is displayed as in the following example:
3215 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3216 red.king@looking-glass.fict.example
3219 .cindex "message" "size in queue listing"
3220 .cindex "size" "of message"
3221 The first line contains the length of time the message has been in the queue
3222 (in this case 25 minutes), the size of the message (2.9K), the unique local
3223 identifier for the message, and the message sender, as contained in the
3224 envelope. For bounce messages, the sender address is empty, and appears as
3225 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3226 the default sender address, the user's login name is shown in parentheses
3227 before the sender address.
3229 .cindex "frozen messages" "in queue listing"
3230 If the message is frozen (attempts to deliver it are suspended) then the text
3231 &"*** frozen ***"& is displayed at the end of this line.
3233 The recipients of the message (taken from the envelope, not the headers) are
3234 displayed on subsequent lines. Those addresses to which the message has already
3235 been delivered are marked with the letter D. If an original address gets
3236 expanded into several addresses via an alias or forward file, the original is
3237 displayed with a D only when deliveries for all of its child addresses are
3243 This option operates like &%-bp%&, but in addition it shows delivered addresses
3244 that were generated from the original top level address(es) in each message by
3245 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3251 .cindex "queue" "count of messages on"
3252 This option counts the number of messages in the queue, and writes the total
3253 to the standard output. It is restricted to admin users, unless
3254 &%queue_list_requires_admin%& is set false.
3259 This option operates like &%-bp%&, but the output is not sorted into
3260 chronological order of message arrival. This can speed it up when there are
3261 lots of messages in the queue, and is particularly useful if the output is
3262 going to be post-processed in a way that doesn't need the sorting.
3266 This option is a combination of &%-bpr%& and &%-bpa%&.
3270 This option is a combination of &%-bpr%& and &%-bpu%&.
3275 This option operates like &%-bp%& but shows only undelivered top-level
3276 addresses for each message displayed. Addresses generated by aliasing or
3277 forwarding are not shown, unless the message was deferred after processing by a
3278 router with the &%one_time%& option set.
3283 .cindex "testing" "retry configuration"
3284 .cindex "retry" "configuration testing"
3285 This option is for testing retry rules, and it must be followed by up to three
3286 arguments. It causes Exim to look for a retry rule that matches the values
3287 and to write it to the standard output. For example:
3289 exim -brt bach.comp.mus.example
3290 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3292 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3293 argument, which is required, can be a complete address in the form
3294 &'local_part@domain'&, or it can be just a domain name. If the second argument
3295 contains a dot, it is interpreted as an optional second domain name; if no
3296 retry rule is found for the first argument, the second is tried. This ties in
3297 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3298 rule is found that matches the host, one that matches the mail domain is
3299 sought. Finally, an argument that is the name of a specific delivery error, as
3300 used in setting up retry rules, can be given. For example:
3302 exim -brt haydn.comp.mus.example quota_3d
3303 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3308 .cindex "testing" "rewriting"
3309 .cindex "rewriting" "testing"
3310 This option is for testing address rewriting rules, and it must be followed by
3311 a single argument, consisting of either a local part without a domain, or a
3312 complete address with a fully qualified domain. Exim outputs how this address
3313 would be rewritten for each possible place it might appear. See chapter
3314 &<<CHAPrewrite>>& for further details.
3318 .cindex "SMTP" "batched incoming"
3319 .cindex "batched SMTP input"
3320 This option is used for batched SMTP input, which is an alternative interface
3321 for non-interactive local message submission. A number of messages can be
3322 submitted in a single run. However, despite its name, this is not really SMTP
3323 input. Exim reads each message's envelope from SMTP commands on the standard
3324 input, but generates no responses. If the caller is trusted, or
3325 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3326 believed; otherwise the sender is always the caller of Exim.
3328 The message itself is read from the standard input, in SMTP format (leading
3329 dots doubled), terminated by a line containing just a single dot. An error is
3330 provoked if the terminating dot is missing. A further message may then follow.
3332 As for other local message submissions, the contents of incoming batch SMTP
3333 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3334 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3335 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3337 Some other SMTP commands are recognized in the input. HELO and EHLO act
3338 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3339 QUIT quits, ignoring the rest of the standard input.
3341 .cindex "return code" "for &%-bS%&"
3342 If any error is encountered, reports are written to the standard output and
3343 error streams, and Exim gives up immediately. The return code is 0 if no error
3344 was detected; it is 1 if one or more messages were accepted before the error
3345 was detected; otherwise it is 2.
3347 More details of input using batched SMTP are given in section
3348 &<<SECTincomingbatchedSMTP>>&.
3352 .cindex "SMTP" "local input"
3353 .cindex "local SMTP input"
3354 This option causes Exim to accept one or more messages by reading SMTP commands
3355 on the standard input, and producing SMTP replies on the standard output. SMTP
3356 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3357 Some user agents use this interface as a way of passing locally-generated
3358 messages to the MTA.
3361 .cindex "sender" "source of"
3362 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3363 set, the senders of messages are taken from the SMTP MAIL commands.
3364 Otherwise the content of these commands is ignored and the sender is set up as
3365 the calling user. Unqualified addresses are automatically qualified using
3366 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3367 &%-bnq%& option is used.
3371 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3372 using a listening daemon. Exim can distinguish the two cases by checking
3373 whether the standard input is a TCP/IP socket. When Exim is called from
3374 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3375 above concerning senders and qualification do not apply. In this situation,
3376 Exim behaves in exactly the same way as it does when receiving a message via
3377 the listening daemon.
3381 .cindex "testing" "addresses"
3382 .cindex "address" "testing"
3383 This option runs Exim in address testing mode, in which each argument is taken
3384 as a recipient address to be tested for deliverability. The results are
3385 written to the standard output. If a test fails, and the caller is not an admin
3386 user, no details of the failure are output, because these might contain
3387 sensitive information such as usernames and passwords for database lookups.
3389 If no arguments are given, Exim runs in an interactive manner, prompting with a
3390 right angle bracket for addresses to be tested.
3392 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3393 &[readline()]& function, because it is running as &'root'& and there are
3396 Each address is handled as if it were the recipient address of a message
3397 (compare the &%-bv%& option). It is passed to the routers and the result is
3398 written to the standard output. However, any router that has
3399 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3400 genuine routing tests if your first router passes everything to a scanner
3403 .cindex "return code" "for &%-bt%&"
3404 The return code is 2 if any address failed outright; it is 1 if no address
3405 failed outright but at least one could not be resolved for some reason. Return
3406 code 0 is given only when all addresses succeed.
3408 .cindex "duplicate addresses"
3409 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3410 addresses after routing is complete, so that only one delivery takes place.
3411 This does not happen when testing with &%-bt%&; the full results of routing are
3414 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3415 routers in the configuration makes any tests on the sender address of a
3417 .oindex "&%-f%&" "for address testing"
3418 you can use the &%-f%& option to set an appropriate sender when running
3419 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3420 default qualifying domain. However, if you have set up (for example) routers
3421 whose behaviour depends on the contents of an incoming message, you cannot test
3422 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3427 .cindex "version number of Exim"
3428 This option causes Exim to write the current version number, compilation
3429 number, and compilation date of the &'exim'& binary to the standard output.
3430 It also lists the DBM library that is being used, the optional modules (such as
3431 specific lookup types), the drivers that are included in the binary, and the
3432 name of the runtime configuration file that is in use.
3434 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3435 configuration file. However, this is a static check only. It cannot check
3436 values that are to be expanded. For example, although a misspelt ACL verb is
3437 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3438 alone to discover (for example) all the typos in the configuration; some
3439 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3440 dynamic testing facilities.
3444 .cindex "verifying address" "using &%-bv%&"
3445 .cindex "address" "verification"
3446 This option runs Exim in address verification mode, in which each argument is
3447 taken as a recipient address to be verified by the routers. (This does
3448 not involve any verification callouts). During normal operation, verification
3449 happens mostly as a consequence processing a &%verify%& condition in an ACL
3450 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3451 including callouts, see the &%-bh%& and &%-bhc%& options.
3453 If verification fails, and the caller is not an admin user, no details of the
3454 failure are output, because these might contain sensitive information such as
3455 usernames and passwords for database lookups.
3457 If no arguments are given, Exim runs in an interactive manner, prompting with a
3458 right angle bracket for addresses to be verified.
3460 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3461 &[readline()]& function, because it is running as &'exim'& and there are
3464 Verification differs from address testing (the &%-bt%& option) in that routers
3465 that have &%no_verify%& set are skipped, and if the address is accepted by a
3466 router that has &%fail_verify%& set, verification fails. The address is
3467 verified as a recipient if &%-bv%& is used; to test verification for a sender
3468 address, &%-bvs%& should be used.
3470 If the &%-v%& option is not set, the output consists of a single line for each
3471 address, stating whether it was verified or not, and giving a reason in the
3472 latter case. Without &%-v%&, generating more than one address by redirection
3473 causes verification to end successfully, without considering the generated
3474 addresses. However, if just one address is generated, processing continues,
3475 and the generated address must verify successfully for the overall verification
3478 When &%-v%& is set, more details are given of how the address has been handled,
3479 and in the case of address redirection, all the generated addresses are also
3480 considered. Verification may succeed for some and fail for others.
3483 .cindex "return code" "for &%-bv%&"
3484 return code is 2 if any address failed outright; it is 1 if no address
3485 failed outright but at least one could not be resolved for some reason. Return
3486 code 0 is given only when all addresses succeed.
3488 If any of the routers in the configuration makes any tests on the sender
3489 address of a message, you should use the &%-f%& option to set an appropriate
3490 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3491 calling user at the default qualifying domain.
3495 This option acts like &%-bv%&, but verifies the address as a sender rather
3496 than a recipient address. This affects any rewriting and qualification that
3503 .cindex "inetd" "wait mode"
3504 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3505 similarly to the &%-bd%& option. All port specifications on the command-line
3506 and in the configuration file are ignored. Queue-running may not be specified.
3508 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3509 listening for connections. This permits the system to start up and have
3510 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3511 each port only when the first connection is received.
3513 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3514 which the daemon will exit, which should cause inetd to listen once more.
3516 .vitem &%-C%&&~<&'filelist'&>
3518 .cindex "configuration file" "alternate"
3519 .cindex "CONFIGURE_FILE"
3520 .cindex "alternate configuration file"
3521 This option causes Exim to find the runtime configuration file from the given
3522 list instead of from the list specified by the CONFIGURE_FILE
3523 compile-time setting. Usually, the list will consist of just a single filename,
3524 but it can be a colon-separated list of names. In this case, the first
3525 file that exists is used. Failure to open an existing file stops Exim from
3526 proceeding any further along the list, and an error is generated.
3528 When this option is used by a caller other than root, and the list is different
3529 from the compiled-in list, Exim gives up its root privilege immediately, and
3530 runs with the real and effective uid and gid set to those of the caller.
3531 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3532 file contains a list of full pathnames, one per line, for configuration files
3533 which are trusted. Root privilege is retained for any configuration file so
3534 listed, as long as the caller is the Exim user (or the user specified in the
3535 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3536 not writeable by inappropriate users or groups.
3538 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3539 configuration using &%-C%& right through message reception and delivery,
3540 even if the caller is root. The reception works, but by that time, Exim is
3541 running as the Exim user, so when it re-executes to regain privilege for the
3542 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3543 test reception and delivery using two separate commands (one to put a message
3544 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3546 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3547 prefix string with which any file named in a &%-C%& command line option
3548 must start. In addition, the filename must not contain the sequence &`/../`&.
3549 However, if the value of the &%-C%& option is identical to the value of
3550 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3551 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3552 unset, any filename can be used with &%-C%&.
3554 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3555 to a directory to which only root has access. This prevents someone who has
3556 broken into the Exim account from running a privileged Exim with an arbitrary
3559 The &%-C%& facility is useful for ensuring that configuration files are
3560 syntactically correct, but cannot be used for test deliveries, unless the
3561 caller is privileged, or unless it is an exotic configuration that does not
3562 require privilege. No check is made on the owner or group of the files
3563 specified by this option.
3566 .vitem &%-D%&<&'macro'&>=<&'value'&>
3568 .cindex "macro" "setting on command line"
3569 This option can be used to override macro definitions in the configuration file
3570 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3571 unprivileged caller, it causes Exim to give up its root privilege.
3572 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3573 completely disabled, and its use causes an immediate error exit.
3575 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3576 colon-separated list of macros which are considered safe and, if &%-D%& only
3577 supplies macros from this list, and the values are acceptable, then Exim will
3578 not give up root privilege if the caller is root, the Exim run-time user, or
3579 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3580 to be removed in the future. Acceptable values for the macros satisfy the
3581 regexp: &`^[A-Za-z0-9_/.-]*$`&
3583 The entire option (including equals sign if present) must all be within one
3584 command line item. &%-D%& can be used to set the value of a macro to the empty
3585 string, in which case the equals sign is optional. These two commands are
3591 To include spaces in a macro definition item, quotes must be used. If you use
3592 quotes, spaces are permitted around the macro name and the equals sign. For
3595 exim '-D ABC = something' ...
3597 &%-D%& may be repeated up to 10 times on a command line.
3598 Only macro names up to 22 letters long can be set.
3601 .vitem &%-d%&<&'debug&~options'&>
3603 .cindex "debugging" "list of selectors"
3604 .cindex "debugging" "&%-d%& option"
3605 This option causes debugging information to be written to the standard
3606 error stream. It is restricted to admin users because debugging output may show
3607 database queries that contain password information. Also, the details of users'
3608 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3609 writes an error message to the standard error stream and exits with a non-zero
3612 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3613 standard debugging data is output. This can be reduced, or increased to include
3614 some more rarely needed information, by directly following &%-d%& with a string
3615 made up of names preceded by plus or minus characters. These add or remove sets
3616 of debugging data, respectively. For example, &%-d+filter%& adds filter
3617 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3618 no spaces are allowed in the debug setting. The available debugging categories
3621 &`acl `& ACL interpretation
3622 &`auth `& authenticators
3623 &`deliver `& general delivery logic
3624 &`dns `& DNS lookups (see also resolver)
3625 &`dnsbl `& DNS black list (aka RBL) code
3626 &`exec `& arguments for &[execv()]& calls
3627 &`expand `& detailed debugging for string expansions
3628 &`filter `& filter handling
3629 &`hints_lookup `& hints data lookups
3630 &`host_lookup `& all types of name-to-IP address handling
3631 &`ident `& ident lookup
3632 &`interface `& lists of local interfaces
3633 &`lists `& matching things in lists
3634 &`load `& system load checks
3635 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3636 &<<CHAPlocalscan>>&)
3637 &`lookup `& general lookup code and all lookups
3638 &`memory `& memory handling
3639 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3640 &`pid `& modifier: add pid to debug output lines
3641 &`process_info `& setting info for the process log
3642 &`queue_run `& queue runs
3643 &`receive `& general message reception logic
3644 &`resolver `& turn on the DNS resolver's debugging output
3645 &`retry `& retry handling
3646 &`rewrite `& address rewriting
3647 &`route `& address routing
3648 &`timestamp `& modifier: add timestamp to debug output lines
3650 &`transport `& transports
3651 &`uid `& changes of uid/gid and looking up uid/gid
3652 &`verify `& address verification logic
3653 &`all `& almost all of the above (see below), and also &%-v%&
3655 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3656 for &`-all`&. The reason for this is that &`+all`& is something that people
3657 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3658 is included, an awful lot of output that is very rarely of interest is
3659 generated, so it now has to be explicitly requested. However, &`-all`& does
3660 turn everything off.
3662 .cindex "resolver, debugging output"
3663 .cindex "DNS resolver, debugging output"
3664 The &`resolver`& option produces output only if the DNS resolver was compiled
3665 with DEBUG enabled. This is not the case in some operating systems. Also,
3666 unfortunately, debugging output from the DNS resolver is written to stdout
3669 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3670 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3671 However, the &`pid`& selector is forced when debugging is turned on for a
3672 daemon, which then passes it on to any re-executed Exims. Exim also
3673 automatically adds the pid to debug lines when several remote deliveries are
3676 The &`timestamp`& selector causes the current time to be inserted at the start
3677 of all debug output lines. This can be useful when trying to track down delays
3680 .cindex debugging "UTF-8 in"
3681 .cindex UTF-8 "in debug output"
3682 The &`noutf8`& selector disables the use of
3683 UTF-8 line-drawing characters to group related information.
3684 When disabled. ascii-art is used instead.
3685 Using the &`+all`& option does not set this modifier,
3687 If the &%debug_print%& option is set in any driver, it produces output whenever
3688 any debugging is selected, or if &%-v%& is used.
3690 .vitem &%-dd%&<&'debug&~options'&>
3692 This option behaves exactly like &%-d%& except when used on a command that
3693 starts a daemon process. In that case, debugging is turned off for the
3694 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3695 behaviour of the daemon without creating as much output as full debugging does.
3698 .oindex "&%-dropcr%&"
3699 This is an obsolete option that is now a no-op. It used to affect the way Exim
3700 handled CR and LF characters in incoming messages. What happens now is
3701 described in section &<<SECTlineendings>>&.
3705 .cindex "bounce message" "generating"
3706 This option specifies that an incoming message is a locally-generated delivery
3707 failure report. It is used internally by Exim when handling delivery failures
3708 and is not intended for external use. Its only effect is to stop Exim
3709 generating certain messages to the postmaster, as otherwise message cascades
3710 could occur in some situations. As part of the same option, a message id may
3711 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3712 new message contains the id, following &"R="&, as a cross-reference.
3715 .oindex "&%-e%&&'x'&"
3716 There are a number of Sendmail options starting with &%-oe%& which seem to be
3717 called by various programs without the leading &%o%& in the option. For
3718 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3719 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3721 .vitem &%-F%&&~<&'string'&>
3723 .cindex "sender" "name"
3724 .cindex "name" "of sender"
3725 This option sets the sender's full name for use when a locally-generated
3726 message is being accepted. In the absence of this option, the user's &'gecos'&
3727 entry from the password data is used. As users are generally permitted to alter
3728 their &'gecos'& entries, no security considerations are involved. White space
3729 between &%-F%& and the <&'string'&> is optional.
3731 .vitem &%-f%&&~<&'address'&>
3733 .cindex "sender" "address"
3734 .cindex "address" "sender"
3735 .cindex "trusted users"
3736 .cindex "envelope from"
3737 .cindex "envelope sender"
3738 .cindex "user" "trusted"
3739 This option sets the address of the envelope sender of a locally-generated
3740 message (also known as the return path). The option can normally be used only
3741 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3744 Processes running as root or the Exim user are always trusted. Other
3745 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3746 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3747 of a local message is set to the caller's login name at the default qualify
3750 There is one exception to the restriction on the use of &%-f%&: an empty sender
3751 can be specified by any user, trusted or not, to create a message that can
3752 never provoke a bounce. An empty sender can be specified either as an empty
3753 string, or as a pair of angle brackets with nothing between them, as in these
3754 examples of shell commands:
3756 exim -f '<>' user@domain
3757 exim -f "" user@domain
3759 In addition, the use of &%-f%& is not restricted when testing a filter file
3760 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3763 Allowing untrusted users to change the sender address does not of itself make
3764 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3765 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3766 though this can be overridden by setting &%no_local_from_check%&.
3769 .cindex "&""From""& line"
3770 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3771 given as two arguments or one combined argument). The sender of a
3772 locally-generated message can also be set (when permitted) by an initial
3773 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3774 if &%-f%& is also present, it overrides &"From&~"&.
3778 .cindex "submission fixups, suppressing (command-line)"
3779 This option is equivalent to an ACL applying:
3781 control = suppress_local_fixups
3783 for every message received. Note that Sendmail will complain about such
3784 bad formatting, where Exim silently just does not fix it up. This may change
3787 As this affects audit information, the caller must be a trusted user to use
3790 .vitem &%-h%&&~<&'number'&>
3792 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3793 This option is accepted for compatibility with Sendmail, but has no effect. (In
3794 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3799 .cindex "Solaris" "&'mail'& command"
3800 .cindex "dot" "in incoming non-SMTP message"
3801 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3802 line by itself should not terminate an incoming, non-SMTP message. I can find
3803 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3804 command in Solaris 2.4 uses it. See also &%-ti%&.
3806 .vitem &%-L%&&~<&'tag'&>
3808 .cindex "syslog" "process name; set with flag"
3809 This option is equivalent to setting &%syslog_processname%& in the config
3810 file and setting &%log_file_path%& to &`syslog`&.
3811 Its use is restricted to administrators. The configuration file has to be
3812 read and parsed, to determine access rights, before this is set and takes
3813 effect, so early configuration file errors will not honour this flag.
3815 The tag should not be longer than 32 characters.
3817 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3819 .cindex "forcing delivery"
3820 .cindex "delivery" "forcing attempt"
3821 .cindex "frozen messages" "forcing delivery"
3822 This option requests Exim to run a delivery attempt on each message in turn. If
3823 any of the messages are frozen, they are automatically thawed before the
3824 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3825 and &%hold_domains%& are ignored.
3828 .cindex "hints database" "overriding retry hints"
3829 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3830 the normal retry time has not yet been reached. This option requires the caller
3831 to be an admin user. However, there is an option called &%prod_requires_admin%&
3832 which can be set false to relax this restriction (and also the same requirement
3833 for the &%-q%&, &%-R%&, and &%-S%& options).
3835 The deliveries happen synchronously, that is, the original Exim process does
3836 not terminate until all the delivery attempts have finished. No output is
3837 produced unless there is a serious error. If you want to see what is happening,
3838 use the &%-v%& option as well, or inspect Exim's main log.
3840 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3842 .cindex "message" "adding recipients"
3843 .cindex "recipient" "adding"
3844 This option requests Exim to add the addresses to the list of recipients of the
3845 message (&"ar"& for &"add recipients"&). The first argument must be a message
3846 id, and the remaining ones must be email addresses. However, if the message is
3847 active (in the middle of a delivery attempt), it is not altered. This option
3848 can be used only by an admin user.
3850 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3851 &~<&'message&~id'&>"
3853 .cindex "SMTP" "passed connection"
3854 .cindex "SMTP" "multiple deliveries"
3855 .cindex "multiple SMTP deliveries"
3856 This option is not intended for use by external callers. It is used internally
3857 by Exim to invoke another instance of itself to deliver a waiting message using
3858 an existing SMTP connection, which is passed as the standard input. Details are
3859 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3860 must be root or the Exim user in order to use it.
3864 This option is not intended for use by external callers. It is used internally
3865 by Exim in conjunction with the &%-MC%& option. It signifies that the
3866 connection to the remote host has been authenticated.
3870 This option is not intended for use by external callers. It is used internally
3871 by Exim in conjunction with the &%-MC%& option. It signifies that the
3872 remote host supports the ESMTP &_DSN_& extension.
3877 This option is not intended for use by external callers. It is used internally
3878 by Exim in conjunction with the &%-d%& option
3879 to pass on an information string on the purpose of the process.
3882 .vitem &%-MCG%&&~<&'queue&~name'&>
3884 This option is not intended for use by external callers. It is used internally
3885 by Exim in conjunction with the &%-MC%& option. It signifies that an
3886 alternate queue is used, named by the following argument.
3890 This option is not intended for use by external callers. It is used internally
3891 by Exim in conjunction with the &%-MC%& option. It signifies that a
3892 remote host supports the ESMTP &_CHUNKING_& extension.
3896 This option is not intended for use by external callers. It is used internally
3897 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3898 which Exim is connected supports pipelining.
3900 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3902 This option is not intended for use by external callers. It is used internally
3903 by Exim in conjunction with the &%-MC%& option when the original delivery was
3904 started by a queue runner. It passes on the process id of the queue runner,
3905 together with the file descriptor number of an open pipe. Closure of the pipe
3906 signals the final completion of the sequence of processes that are passing
3907 messages through the same SMTP connection.
3910 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3912 This option is not intended for use by external callers. It is used internally
3913 by Exim to implement quota checking for local users.
3918 This option is not intended for use by external callers. It is used internally
3919 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3920 ESMTP SIZE option should be used on messages delivered down the existing
3925 This option is not intended for use by external callers. It is used internally
3926 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3927 host to which Exim is connected supports TLS encryption.
3929 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3931 This option is not intended for use by external callers. It is used internally
3932 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3933 connection is being proxied by a parent process for handling TLS encryption.
3934 The arguments give the local address and port being proxied, and the TLS cipher.
3936 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3938 .cindex "hints database" "not overridden by &%-Mc%&"
3939 .cindex "delivery" "manually started &-- not forced"
3940 This option requests Exim to run a delivery attempt on each message, in turn,
3941 but unlike the &%-M%& option, it does check for retry hints, and respects any
3942 that are found. This option is not very useful to external callers. It is
3943 provided mainly for internal use by Exim when it needs to re-invoke itself in
3944 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3945 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3946 respects retry times and other options such as &%hold_domains%& that are
3947 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3948 If you want to run a specific delivery as if in a queue run, you should use
3949 &%-q%& with a message id argument. A distinction between queue run deliveries
3950 and other deliveries is made in one or two places.
3952 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3954 .cindex "message" "changing sender"
3955 .cindex "sender" "changing"
3956 This option requests Exim to change the sender address in the message to the
3957 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3958 &"edit sender"&). There must be exactly two arguments. The first argument must
3959 be a message id, and the second one an email address. However, if the message
3960 is active (in the middle of a delivery attempt), its status is not altered.
3961 This option can be used only by an admin user.
3963 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3965 .cindex "freezing messages"
3966 .cindex "message" "manually freezing"
3967 This option requests Exim to mark each listed message as &"frozen"&. This
3968 prevents any delivery attempts taking place until the message is &"thawed"&,
3969 either manually or as a result of the &%auto_thaw%& configuration option.
3970 However, if any of the messages are active (in the middle of a delivery
3971 attempt), their status is not altered. This option can be used only by an admin
3974 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3976 .cindex "giving up on messages"
3977 .cindex "message" "abandoning delivery attempts"
3978 .cindex "delivery" "abandoning further attempts"
3979 This option requests Exim to give up trying to deliver the listed messages,
3980 including any that are frozen. However, if any of the messages are active,
3981 their status is not altered. For non-bounce messages, a delivery error message
3982 is sent to the sender, containing the text &"cancelled by administrator"&.
3983 Bounce messages are just discarded. This option can be used only by an admin
3986 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
3989 .cindex "named queues" "moving messages"
3990 .cindex "queue" "moving messages"
3991 This option requests that each listed message be moved from its current
3992 queue to the given named queue.
3993 The destination queue name argument is required, but can be an empty
3994 string to define the default queue.
3995 If the messages are not currently located in the default queue,
3996 a &%-qG<name>%& option will be required to define the source queue.
3998 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4000 .cindex "delivery" "cancelling all"
4001 This option requests Exim to mark all the recipient addresses in the messages
4002 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4003 message is active (in the middle of a delivery attempt), its status is not
4004 altered. This option can be used only by an admin user.
4006 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4008 .cindex "delivery" "cancelling by address"
4009 .cindex "recipient" "removing"
4010 .cindex "removing recipients"
4011 This option requests Exim to mark the given addresses as already delivered
4012 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4013 the remaining ones must be email addresses. These are matched to recipient
4014 addresses in the message in a case-sensitive manner. If the message is active
4015 (in the middle of a delivery attempt), its status is not altered. This option
4016 can be used only by an admin user.
4018 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4020 .cindex "removing messages"
4021 .cindex "abandoning mail"
4022 .cindex "message" "manually discarding"
4023 This option requests Exim to remove the given messages from the queue. No
4024 bounce messages are sent; each message is simply forgotten. However, if any of
4025 the messages are active, their status is not altered. This option can be used
4026 only by an admin user or by the user who originally caused the message to be
4027 placed in the queue.
4032 . .cindex REQUIRETLS
4033 . This option is used to request REQUIRETLS processing on the message.
4034 . It is used internally by Exim in conjunction with -E when generating
4038 .vitem &%-Mset%&&~<&'message&~id'&>
4040 .cindex "testing" "string expansion"
4041 .cindex "expansion" "testing"
4042 This option is useful only in conjunction with &%-be%& (that is, when testing
4043 string expansions). Exim loads the given message from its spool before doing
4044 the test expansions, thus setting message-specific variables such as
4045 &$message_size$& and the header variables. The &$recipients$& variable is made
4046 available. This feature is provided to make it easier to test expansions that
4047 make use of these variables. However, this option can be used only by an admin
4048 user. See also &%-bem%&.
4050 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4052 .cindex "thawing messages"
4053 .cindex "unfreezing messages"
4054 .cindex "frozen messages" "thawing"
4055 .cindex "message" "thawing frozen"
4056 This option requests Exim to &"thaw"& any of the listed messages that are
4057 &"frozen"&, so that delivery attempts can resume. However, if any of the
4058 messages are active, their status is not altered. This option can be used only
4061 .vitem &%-Mvb%&&~<&'message&~id'&>
4063 .cindex "listing" "message body"
4064 .cindex "message" "listing body of"
4065 This option causes the contents of the message body (-D) spool file to be
4066 written to the standard output. This option can be used only by an admin user.
4068 .vitem &%-Mvc%&&~<&'message&~id'&>
4070 .cindex "message" "listing in RFC 2822 format"
4071 .cindex "listing" "message in RFC 2822 format"
4072 This option causes a copy of the complete message (header lines plus body) to
4073 be written to the standard output in RFC 2822 format. This option can be used
4074 only by an admin user.
4076 .vitem &%-Mvh%&&~<&'message&~id'&>
4078 .cindex "listing" "message headers"
4079 .cindex "header lines" "listing"
4080 .cindex "message" "listing header lines"
4081 This option causes the contents of the message headers (-H) spool file to be
4082 written to the standard output. This option can be used only by an admin user.
4084 .vitem &%-Mvl%&&~<&'message&~id'&>
4086 .cindex "listing" "message log"
4087 .cindex "message" "listing message log"
4088 This option causes the contents of the message log spool file to be written to
4089 the standard output. This option can be used only by an admin user.
4093 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4094 treats it that way too.
4098 .cindex "debugging" "&%-N%& option"
4099 .cindex "debugging" "suppressing delivery"
4100 This is a debugging option that inhibits delivery of a message at the transport
4101 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4102 it just doesn't actually transport the message, but instead behaves as if it
4103 had successfully done so. However, it does not make any updates to the retry
4104 database, and the log entries for deliveries are flagged with &"*>"& rather
4107 Because &%-N%& discards any message to which it applies, only root or the Exim
4108 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4109 words, an ordinary user can use it only when supplying an incoming message to
4110 which it will apply. Although transportation never fails when &%-N%& is set, an
4111 address may be deferred because of a configuration problem on a transport, or a
4112 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4113 the message, and applies to any subsequent delivery attempts that may happen
4118 This option is interpreted by Sendmail to mean &"no aliasing"&.
4119 For normal modes of operation, it is ignored by Exim.
4120 When combined with &%-bP%& it makes the output more terse (suppresses
4121 option names, environment values and config pretty printing).
4123 .vitem &%-O%&&~<&'data'&>
4125 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4128 .vitem &%-oA%&&~<&'file&~name'&>
4130 .cindex "Sendmail compatibility" "&%-oA%& option"
4131 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4132 alternative alias filename. Exim handles &%-bi%& differently; see the
4135 .vitem &%-oB%&&~<&'n'&>
4137 .cindex "SMTP" "passed connection"
4138 .cindex "SMTP" "multiple deliveries"
4139 .cindex "multiple SMTP deliveries"
4140 This is a debugging option which limits the maximum number of messages that can
4141 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4142 transport. If <&'n'&> is omitted, the limit is set to 1.
4146 .cindex "background delivery"
4147 .cindex "delivery" "in the background"
4148 This option applies to all modes in which Exim accepts incoming messages,
4149 including the listening daemon. It requests &"background"& delivery of such
4150 messages, which means that the accepting process automatically starts a
4151 delivery process for each message received, but does not wait for the delivery
4152 processes to finish.
4154 When all the messages have been received, the reception process exits,
4155 leaving the delivery processes to finish in their own time. The standard output
4156 and error streams are closed at the start of each delivery process.
4157 This is the default action if none of the &%-od%& options are present.
4159 If one of the queueing options in the configuration file
4160 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4161 overrides it if &%queue_only_override%& is set true, which is the default
4162 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4166 .cindex "foreground delivery"
4167 .cindex "delivery" "in the foreground"
4168 This option requests &"foreground"& (synchronous) delivery when Exim has
4169 accepted a locally-generated message. (For the daemon it is exactly the same as
4170 &%-odb%&.) A delivery process is automatically started to deliver the message,
4171 and Exim waits for it to complete before proceeding.
4173 The original Exim reception process does not finish until the delivery
4174 process for the final message has ended. The standard error stream is left open
4177 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4178 false and one of the queueing options in the configuration file is in effect.
4180 If there is a temporary delivery error during foreground delivery, the
4181 message is left in the queue for later delivery, and the original reception
4182 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4183 restricted configuration that never queues messages.
4188 This option is synonymous with &%-odf%&. It is provided for compatibility with
4193 .cindex "non-immediate delivery"
4194 .cindex "delivery" "suppressing immediate"
4195 .cindex "queueing incoming messages"
4196 This option applies to all modes in which Exim accepts incoming messages,
4197 including the listening daemon. It specifies that the accepting process should
4198 not automatically start a delivery process for each message received. Messages
4199 are placed in the queue, and remain there until a subsequent queue runner
4200 process encounters them. There are several configuration options (such as
4201 &%queue_only%&) that can be used to queue incoming messages under certain
4202 conditions. This option overrides all of them and also &%-odqs%&. It always
4207 .cindex "SMTP" "delaying delivery"
4208 .cindex "first pass routing"
4209 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4210 However, like &%-odb%& and &%-odi%&, this option has no effect if
4211 &%queue_only_override%& is false and one of the queueing options in the
4212 configuration file is in effect.
4214 When &%-odqs%& does operate, a delivery process is started for each incoming
4215 message, in the background by default, but in the foreground if &%-odi%& is
4216 also present. The recipient addresses are routed, and local deliveries are done
4217 in the normal way. However, if any SMTP deliveries are required, they are not
4218 done at this time, so the message remains in the queue until a subsequent queue
4219 runner process encounters it. Because routing was done, Exim knows which
4220 messages are waiting for which hosts, and so a number of messages for the same
4221 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4222 configuration option has the same effect for specific domains. See also the
4227 .cindex "error" "reporting"
4228 If an error is detected while a non-SMTP message is being received (for
4229 example, a malformed address), the error is reported to the sender in a mail
4232 .cindex "return code" "for &%-oee%&"
4234 this error message is successfully sent, the Exim receiving process
4235 exits with a return code of zero. If not, the return code is 2 if the problem
4236 is that the original message has no recipients, or 1 for any other error.
4237 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4241 .cindex "error" "reporting"
4242 .cindex "return code" "for &%-oem%&"
4243 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4244 return code, whether or not the error message was successfully sent.
4245 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4249 .cindex "error" "reporting"
4250 If an error is detected while a non-SMTP message is being received, the
4251 error is reported by writing a message to the standard error file (stderr).
4252 .cindex "return code" "for &%-oep%&"
4253 The return code is 1 for all errors.
4257 .cindex "error" "reporting"
4258 This option is supported for compatibility with Sendmail, but has the same
4263 .cindex "error" "reporting"
4264 This option is supported for compatibility with Sendmail, but has the same
4269 .cindex "dot" "in incoming non-SMTP message"
4270 This option, which has the same effect as &%-i%&, specifies that a dot on a
4271 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4272 single dot does terminate, though Exim does no special processing for other
4273 lines that start with a dot. This option is set by default if Exim is called as
4274 &'rmail'&. See also &%-ti%&.
4277 .oindex "&%-oitrue%&"
4278 This option is treated as synonymous with &%-oi%&.
4280 .vitem &%-oMa%&&~<&'host&~address'&>
4282 .cindex "sender" "host address, specifying for local message"
4283 A number of options starting with &%-oM%& can be used to set values associated
4284 with remote hosts on locally-submitted messages (that is, messages not received
4285 over TCP/IP). These options can be used by any caller in conjunction with the
4286 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4287 other circumstances, they are ignored unless the caller is trusted.
4289 The &%-oMa%& option sets the sender host address. This may include a port
4290 number at the end, after a full stop (period). For example:
4292 exim -bs -oMa 10.9.8.7.1234
4294 An alternative syntax is to enclose the IP address in square brackets,
4295 followed by a colon and the port number:
4297 exim -bs -oMa [10.9.8.7]:1234
4299 The IP address is placed in the &$sender_host_address$& variable, and the
4300 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4301 are present on the command line, the sender host IP address is taken from
4302 whichever one is last.
4304 .vitem &%-oMaa%&&~<&'name'&>
4306 .cindex "authentication" "name, specifying for local message"
4307 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4308 option sets the value of &$sender_host_authenticated$& (the authenticator
4309 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4310 This option can be used with &%-bh%& and &%-bs%& to set up an
4311 authenticated SMTP session without actually using the SMTP AUTH command.
4313 .vitem &%-oMai%&&~<&'string'&>
4315 .cindex "authentication" "id, specifying for local message"
4316 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4317 option sets the value of &$authenticated_id$& (the id that was authenticated).
4318 This overrides the default value (the caller's login id, except with &%-bh%&,
4319 where there is no default) for messages from local sources. See chapter
4320 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4322 .vitem &%-oMas%&&~<&'address'&>
4324 .cindex "authentication" "sender, specifying for local message"
4325 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4326 option sets the authenticated sender value in &$authenticated_sender$&. It
4327 overrides the sender address that is created from the caller's login id for
4328 messages from local sources, except when &%-bh%& is used, when there is no
4329 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4330 specified on a MAIL command overrides this value. See chapter
4331 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4333 .vitem &%-oMi%&&~<&'interface&~address'&>
4335 .cindex "interface" "address, specifying for local message"
4336 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4337 option sets the IP interface address value. A port number may be included,
4338 using the same syntax as for &%-oMa%&. The interface address is placed in
4339 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4341 .vitem &%-oMm%&&~<&'message&~reference'&>
4343 .cindex "message reference" "message reference, specifying for local message"
4344 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4345 option sets the message reference, e.g. message-id, and is logged during
4346 delivery. This is useful when some kind of audit trail is required to tie
4347 messages together. The format of the message reference is checked and will
4348 abort if the format is invalid. The option will only be accepted if exim is
4349 running in trusted mode, not as any regular user.
4351 The best example of a message reference is when Exim sends a bounce message.
4352 The message reference is the message-id of the original message for which Exim
4353 is sending the bounce.
4355 .vitem &%-oMr%&&~<&'protocol&~name'&>
4357 .cindex "protocol, specifying for local message"
4358 .vindex "&$received_protocol$&"
4359 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4360 option sets the received protocol value that is stored in
4361 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4362 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4363 SMTP protocol names (see the description of &$received_protocol$& in section
4364 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4365 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4366 be set by &%-oMr%&. Repeated use of this option is not supported.
4368 .vitem &%-oMs%&&~<&'host&~name'&>
4370 .cindex "sender" "host name, specifying for local message"
4371 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4372 option sets the sender host name in &$sender_host_name$&. When this option is
4373 present, Exim does not attempt to look up a host name from an IP address; it
4374 uses the name it is given.
4376 .vitem &%-oMt%&&~<&'ident&~string'&>
4378 .cindex "sender" "ident string, specifying for local message"
4379 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4380 option sets the sender ident value in &$sender_ident$&. The default setting for
4381 local callers is the login id of the calling process, except when &%-bh%& is
4382 used, when there is no default.
4386 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4387 In Sendmail, this option means &"me too"&, indicating that the sender of a
4388 message should receive a copy of the message if the sender appears in an alias
4389 expansion. Exim always does this, so the option does nothing.
4393 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4394 This option is ignored. In Sendmail it specifies &"old style headers"&,
4395 whatever that means.
4397 .vitem &%-oP%&&~<&'path'&>
4399 .cindex "pid (process id)" "of daemon"
4400 .cindex "daemon" "process id (pid)"
4401 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4402 value. The option specifies the file to which the process id of the daemon is
4403 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4404 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4405 because in those cases, the normal pid file is not used.
4410 .cindex "pid (process id)" "of daemon"
4411 .cindex "daemon" "process id (pid)"
4412 This option is not intended for general use.
4413 The daemon uses it when terminating due to a SIGTEM, possibly in
4414 combination with &%-oP%&&~<&'path'&>.
4415 It causes the pid file to be removed.
4418 .vitem &%-or%&&~<&'time'&>
4420 .cindex "timeout" "for non-SMTP input"
4421 This option sets a timeout value for incoming non-SMTP messages. If it is not
4422 set, Exim will wait forever for the standard input. The value can also be set
4423 by the &%receive_timeout%& option. The format used for specifying times is
4424 described in section &<<SECTtimeformat>>&.
4426 .vitem &%-os%&&~<&'time'&>
4428 .cindex "timeout" "for SMTP input"
4429 .cindex "SMTP" "input timeout"
4430 This option sets a timeout value for incoming SMTP messages. The timeout
4431 applies to each SMTP command and block of data. The value can also be set by
4432 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4433 for specifying times is described in section &<<SECTtimeformat>>&.
4437 This option has exactly the same effect as &%-v%&.
4439 .vitem &%-oX%&&~<&'number&~or&~string'&>
4441 .cindex "TCP/IP" "setting listening ports"
4442 .cindex "TCP/IP" "setting listening interfaces"
4443 .cindex "port" "receiving TCP/IP"
4444 This option is relevant only when the &%-bd%& (start listening daemon) option
4445 is also given. It controls which ports and interfaces the daemon uses. Details
4446 of the syntax, and how it interacts with configuration file options, are given
4447 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4448 file is written unless &%-oP%& is also present to specify a pid filename.
4452 .cindex "Perl" "starting the interpreter"
4453 This option applies when an embedded Perl interpreter is linked with Exim (see
4454 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4455 option, forcing the starting of the interpreter to be delayed until it is
4460 .cindex "Perl" "starting the interpreter"
4461 This option applies when an embedded Perl interpreter is linked with Exim (see
4462 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4463 option, forcing the starting of the interpreter to occur as soon as Exim is
4466 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4468 For compatibility with Sendmail, this option is equivalent to
4470 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4472 It sets the incoming protocol and host name (for trusted callers). The
4473 host name and its colon can be omitted when only the protocol is to be set.
4474 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4475 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4476 or &`s`& using this option (but that does not seem a real limitation).
4477 Repeated use of this option is not supported.
4481 .cindex "queue runner" "starting manually"
4482 This option is normally restricted to admin users. However, there is a
4483 configuration option called &%prod_requires_admin%& which can be set false to
4484 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4485 and &%-S%& options).
4487 .cindex "queue runner" "description of operation"
4488 If other commandline options do not specify an action,
4489 the &%-q%& option starts one queue runner process. This scans the queue of
4490 waiting messages, and runs a delivery process for each one in turn. It waits
4491 for each delivery process to finish before starting the next one. A delivery
4492 process may not actually do any deliveries if the retry times for the addresses
4493 have not been reached. Use &%-qf%& (see below) if you want to override this.
4496 .cindex "SMTP" "passed connection"
4497 .cindex "SMTP" "multiple deliveries"
4498 .cindex "multiple SMTP deliveries"
4499 the delivery process spawns other processes to deliver other messages down
4500 passed SMTP connections, the queue runner waits for these to finish before
4503 When all the queued messages have been considered, the original queue runner
4504 process terminates. In other words, a single pass is made over the waiting
4505 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4506 this to be repeated periodically.
4508 Exim processes the waiting messages in an unpredictable order. It isn't very
4509 random, but it is likely to be different each time, which is all that matters.
4510 If one particular message screws up a remote MTA, other messages to the same
4511 MTA have a chance of getting through if they get tried first.
4513 It is possible to cause the messages to be processed in lexical message id
4514 order, which is essentially the order in which they arrived, by setting the
4515 &%queue_run_in_order%& option, but this is not recommended for normal use.
4517 .vitem &%-q%&<&'qflags'&>
4518 The &%-q%& option may be followed by one or more flag letters that change its
4519 behaviour. They are all optional, but if more than one is present, they must
4520 appear in the correct order. Each flag is described in a separate item below.
4524 .cindex "queue" "double scanning"
4525 .cindex "queue" "routing"
4526 .cindex "routing" "whole queue before delivery"
4527 .cindex "first pass routing"
4528 .cindex "queue runner" "two phase"
4529 An option starting with &%-qq%& requests a two-stage queue run. In the first
4530 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4531 every domain. Addresses are routed, local deliveries happen, but no remote
4535 Performance will be best if the &%queue_run_in_order%& option is false.
4536 If that is so and the &%queue_fast_ramp%& option is true then
4537 in the first phase of the run,
4538 once a threshold number of messages are routed for a given host,
4539 a delivery process is forked in parallel with the rest of the scan.
4542 .cindex "hints database" "remembering routing"
4543 The hints database that remembers which messages are waiting for specific hosts
4544 is updated, as if delivery to those hosts had been deferred. After this is
4545 complete, a second, normal queue scan happens, with routing and delivery taking
4546 place as normal. Messages that are routed to the same host should mostly be
4547 delivered down a single SMTP
4548 .cindex "SMTP" "passed connection"
4549 .cindex "SMTP" "multiple deliveries"
4550 .cindex "multiple SMTP deliveries"
4551 connection because of the hints that were set up during the first queue scan.
4552 This option may be useful for hosts that are connected to the Internet
4555 .vitem &%-q[q]i...%&
4557 .cindex "queue" "initial delivery"
4558 If the &'i'& flag is present, the queue runner runs delivery processes only for
4559 those messages that haven't previously been tried. (&'i'& stands for &"initial
4560 delivery"&.) This can be helpful if you are putting messages in the queue using
4561 &%-odq%& and want a queue runner just to process the new messages.
4563 .vitem &%-q[q][i]f...%&
4565 .cindex "queue" "forcing delivery"
4566 .cindex "delivery" "forcing in queue run"
4567 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4568 message, whereas without &'f'& only those non-frozen addresses that have passed
4569 their retry times are tried.
4571 .vitem &%-q[q][i]ff...%&
4573 .cindex "frozen messages" "forcing delivery"
4574 If &'ff'& is present, a delivery attempt is forced for every message, whether
4577 .vitem &%-q[q][i][f[f]]l%&
4579 .cindex "queue" "local deliveries only"
4580 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4581 be done. If a message requires any remote deliveries, it remains in the queue
4584 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4587 .cindex "named queues" "deliver from"
4588 .cindex "queue" "delivering specific messages"
4589 If the &'G'& flag and a name is present, the queue runner operates on the
4590 queue with the given name rather than the default queue.
4591 The name should not contain a &'/'& character.
4592 For a periodic queue run (see below)
4593 append to the name a slash and a time value.
4595 If other commandline options specify an action, a &'-qG<name>'& option
4596 will specify a queue to operate on.
4599 exim -bp -qGquarantine
4601 exim -qGoffpeak -Rf @special.domain.example
4604 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4605 When scanning the queue, Exim can be made to skip over messages whose ids are
4606 lexically less than a given value by following the &%-q%& option with a
4607 starting message id. For example:
4609 exim -q 0t5C6f-0000c8-00
4611 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4612 second message id is given, messages whose ids are lexically greater than it
4613 are also skipped. If the same id is given twice, for example,
4615 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4617 just one delivery process is started, for that message. This differs from
4618 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4619 that it counts as a delivery from a queue run. Note that the selection
4620 mechanism does not affect the order in which the messages are scanned. There
4621 are also other ways of selecting specific sets of messages for delivery in a
4622 queue run &-- see &%-R%& and &%-S%&.
4624 .vitem &%-q%&<&'qflags'&><&'time'&>
4625 .cindex "queue runner" "starting periodically"
4626 .cindex "periodic queue running"
4627 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4628 starting a queue runner process at intervals specified by the given time value
4629 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4630 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4631 single daemon process handles both functions. A common way of starting up a
4632 combined daemon at system boot time is to use a command such as
4634 /usr/exim/bin/exim -bd -q30m
4636 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4637 process every 30 minutes.
4639 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4640 pid file is written unless one is explicitly requested by the &%-oP%& option.
4642 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4644 This option is synonymous with &%-R%&. It is provided for Sendmail
4647 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4649 This option is synonymous with &%-S%&.
4651 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4653 .cindex "queue runner" "for specific recipients"
4654 .cindex "delivery" "to given domain"
4655 .cindex "domain" "delivery to"
4656 The <&'rsflags'&> may be empty, in which case the white space before the string
4657 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4658 which are the possible values for <&'rsflags'&>. White space is required if
4659 <&'rsflags'&> is not empty.
4661 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4662 perform a single queue run, except that, when scanning the messages on the
4663 queue, Exim processes only those that have at least one undelivered recipient
4664 address containing the given string, which is checked in a case-independent
4665 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4666 regular expression; otherwise it is a literal string.
4668 If you want to do periodic queue runs for messages with specific recipients,
4669 you can combine &%-R%& with &%-q%& and a time value. For example:
4671 exim -q25m -R @special.domain.example
4673 This example does a queue run for messages with recipients in the given domain
4674 every 25 minutes. Any additional flags that are specified with &%-q%& are
4675 applied to each queue run.
4677 Once a message is selected for delivery by this mechanism, all its addresses
4678 are processed. For the first selected message, Exim overrides any retry
4679 information and forces a delivery attempt for each undelivered address. This
4680 means that if delivery of any address in the first message is successful, any
4681 existing retry information is deleted, and so delivery attempts for that
4682 address in subsequently selected messages (which are processed without forcing)
4683 will run. However, if delivery of any address does not succeed, the retry
4684 information is updated, and in subsequently selected messages, the failing
4685 address will be skipped.
4687 .cindex "frozen messages" "forcing delivery"
4688 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4689 all selected messages, not just the first; frozen messages are included when
4692 The &%-R%& option makes it straightforward to initiate delivery of all messages
4693 to a given domain after a host has been down for some time. When the SMTP
4694 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4695 effect is to run Exim with the &%-R%& option, but it can be configured to run
4696 an arbitrary command instead.
4700 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4702 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4704 .cindex "delivery" "from given sender"
4705 .cindex "queue runner" "for specific senders"
4706 This option acts like &%-R%& except that it checks the string against each
4707 message's sender instead of against the recipients. If &%-R%& is also set, both
4708 conditions must be met for a message to be selected. If either of the options
4709 has &'f'& or &'ff'& in its flags, the associated action is taken.
4711 .vitem &%-Tqt%&&~<&'times'&>
4713 This is an option that is exclusively for use by the Exim testing suite. It is not
4714 recognized when Exim is run normally. It allows for the setting up of explicit
4715 &"queue times"& so that various warning/retry features can be tested.
4719 .cindex "recipient" "extracting from header lines"
4720 .cindex "&'Bcc:'& header line"
4721 .cindex "&'Cc:'& header line"
4722 .cindex "&'To:'& header line"
4723 When Exim is receiving a locally-generated, non-SMTP message on its standard
4724 input, the &%-t%& option causes the recipients of the message to be obtained
4725 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4726 from the command arguments. The addresses are extracted before any rewriting
4727 takes place and the &'Bcc:'& header line, if present, is then removed.
4729 .cindex "Sendmail compatibility" "&%-t%& option"
4730 If the command has any arguments, they specify addresses to which the message
4731 is &'not'& to be delivered. That is, the argument addresses are removed from
4732 the recipients list obtained from the headers. This is compatible with Smail 3
4733 and in accordance with the documented behaviour of several versions of
4734 Sendmail, as described in man pages on a number of operating systems (e.g.
4735 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4736 argument addresses to those obtained from the headers, and the O'Reilly
4737 Sendmail book documents it that way. Exim can be made to add argument addresses
4738 instead of subtracting them by setting the option
4739 &%extract_addresses_remove_arguments%& false.
4741 .cindex "&%Resent-%& header lines" "with &%-t%&"
4742 If there are any &%Resent-%& header lines in the message, Exim extracts
4743 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4744 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4745 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4746 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4748 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4749 message is resent several times). The RFC also specifies that they should be
4750 added at the front of the message, and separated by &'Received:'& lines. It is
4751 not at all clear how &%-t%& should operate in the present of multiple sets,
4752 nor indeed exactly what constitutes a &"set"&.
4753 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4754 are often added at the end of the header, and if a message is resent more than
4755 once, it is common for the original set of &%Resent-%& headers to be renamed as
4756 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4760 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4761 compatibility with Sendmail.
4763 .vitem &%-tls-on-connect%&
4764 .oindex "&%-tls-on-connect%&"
4765 .cindex "TLS" "use without STARTTLS"
4766 .cindex "TLS" "automatic start"
4767 This option is available when Exim is compiled with TLS support. It forces all
4768 incoming SMTP connections to behave as if the incoming port is listed in the
4769 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4770 &<<CHAPTLS>>& for further details.
4775 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4776 Sendmail uses this option for &"initial message submission"&, and its
4777 documentation states that in future releases, it may complain about
4778 syntactically invalid messages rather than fixing them when this flag is not
4779 set. Exim ignores this option.
4783 This option causes Exim to write information to the standard error stream,
4784 describing what it is doing. In particular, it shows the log lines for
4785 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4786 dialogue is shown. Some of the log lines shown may not actually be written to
4787 the log if the setting of &%log_selector%& discards them. Any relevant
4788 selectors are shown with each log line. If none are shown, the logging is
4793 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4794 National Language Support extended characters in the body of the mail item"&).
4795 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4798 .vitem &%-X%&&~<&'logfile'&>
4800 This option is interpreted by Sendmail to cause debug information to be sent
4801 to the named file. It is ignored by Exim.
4803 .vitem &%-z%&&~<&'log-line'&>
4805 This option writes its argument to Exim's logfile.
4806 Use is restricted to administrators; the intent is for operational notes.
4807 Quotes should be used to maintain a multi-word item as a single argument,
4815 . ////////////////////////////////////////////////////////////////////////////
4816 . Insert a stylized DocBook comment here, to identify the end of the command
4817 . line options. This is for the benefit of the Perl script that automatically
4818 . creates a man page for the options.
4819 . ////////////////////////////////////////////////////////////////////////////
4822 <!-- === End of command line options === -->
4829 . ////////////////////////////////////////////////////////////////////////////
4830 . ////////////////////////////////////////////////////////////////////////////
4833 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4834 "The runtime configuration file"
4836 .cindex "runtime configuration"
4837 .cindex "configuration file" "general description"
4838 .cindex "CONFIGURE_FILE"
4839 .cindex "configuration file" "errors in"
4840 .cindex "error" "in configuration file"
4841 .cindex "return code" "for bad configuration"
4842 Exim uses a single runtime configuration file that is read whenever an Exim
4843 binary is executed. Note that in normal operation, this happens frequently,
4844 because Exim is designed to operate in a distributed manner, without central
4847 If a syntax error is detected while reading the configuration file, Exim
4848 writes a message on the standard error, and exits with a non-zero return code.
4849 The message is also written to the panic log. &*Note*&: Only simple syntax
4850 errors can be detected at this time. The values of any expanded options are
4851 not checked until the expansion happens, even when the expansion does not
4852 actually alter the string.
4854 The name of the configuration file is compiled into the binary for security
4855 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4856 most configurations, this specifies a single file. However, it is permitted to
4857 give a colon-separated list of filenames, in which case Exim uses the first
4858 existing file in the list.
4861 .cindex "EXIM_GROUP"
4862 .cindex "CONFIGURE_OWNER"
4863 .cindex "CONFIGURE_GROUP"
4864 .cindex "configuration file" "ownership"
4865 .cindex "ownership" "configuration file"
4866 The runtime configuration file must be owned by root or by the user that is
4867 specified at compile time by the CONFIGURE_OWNER option (if set). The
4868 configuration file must not be world-writeable, or group-writeable unless its
4869 group is the root group or the one specified at compile time by the
4870 CONFIGURE_GROUP option.
4872 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4873 to root, anybody who is able to edit the runtime configuration file has an
4874 easy way to run commands as root. If you specify a user or group in the
4875 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4876 who are members of that group will trivially be able to obtain root privileges.
4878 Up to Exim version 4.72, the runtime configuration file was also permitted to
4879 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4880 since it offered a simple privilege escalation for any attacker who managed to
4881 compromise the Exim user account.
4883 A default configuration file, which will work correctly in simple situations,
4884 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4885 defines just one filename, the installation process copies the default
4886 configuration to a new file of that name if it did not previously exist. If
4887 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4888 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4893 .section "Using a different configuration file" "SECID40"
4894 .cindex "configuration file" "alternate"
4895 A one-off alternate configuration can be specified by the &%-C%& command line
4896 option, which may specify a single file or a list of files. However, when
4897 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4898 unless the argument for &%-C%& is identical to the built-in value from
4899 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4900 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4901 is useful mainly for checking the syntax of configuration files before
4902 installing them. No owner or group checks are done on a configuration file
4903 specified by &%-C%&, if root privilege has been dropped.
4905 Even the Exim user is not trusted to specify an arbitrary configuration file
4906 with the &%-C%& option to be used with root privileges, unless that file is
4907 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4908 testing a configuration using &%-C%& right through message reception and
4909 delivery, even if the caller is root. The reception works, but by that time,
4910 Exim is running as the Exim user, so when it re-execs to regain privilege for
4911 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4912 can test reception and delivery using two separate commands (one to put a
4913 message in the queue, using &%-odq%&, and another to do the delivery, using
4916 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4917 prefix string with which any file named in a &%-C%& command line option must
4918 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4919 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4920 filename can be used with &%-C%&.
4922 One-off changes to a configuration can be specified by the &%-D%& command line
4923 option, which defines and overrides values for macros used inside the
4924 configuration file. However, like &%-C%&, the use of this option by a
4925 non-privileged user causes Exim to discard its root privilege.
4926 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4927 completely disabled, and its use causes an immediate error exit.
4929 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4930 to declare certain macro names trusted, such that root privilege will not
4931 necessarily be discarded.
4932 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4933 considered safe and, if &%-D%& only supplies macros from this list, and the
4934 values are acceptable, then Exim will not give up root privilege if the caller
4935 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4936 transition mechanism and is expected to be removed in the future. Acceptable
4937 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4939 Some sites may wish to use the same Exim binary on different machines that
4940 share a file system, but to use different configuration files on each machine.
4941 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4942 looks for a file whose name is the configuration filename followed by a dot
4943 and the machine's node name, as obtained from the &[uname()]& function. If this
4944 file does not exist, the standard name is tried. This processing occurs for
4945 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4947 In some esoteric situations different versions of Exim may be run under
4948 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4949 help with this. See the comments in &_src/EDITME_& for details.
4953 .section "Configuration file format" "SECTconffilfor"
4954 .cindex "configuration file" "format of"
4955 .cindex "format" "configuration file"
4956 Exim's configuration file is divided into a number of different parts. General
4957 option settings must always appear at the start of the file. The other parts
4958 are all optional, and may appear in any order. Each part other than the first
4959 is introduced by the word &"begin"& followed by at least one literal
4960 space, and the name of the part. The optional parts are:
4963 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4966 .cindex "AUTH" "configuration"
4967 &'authenticators'&: Configuration settings for the authenticator drivers. These
4968 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4970 &'routers'&: Configuration settings for the router drivers. Routers process
4971 addresses and determine how the message is to be delivered (see chapters
4972 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4974 &'transports'&: Configuration settings for the transport drivers. Transports
4975 define mechanisms for copying messages to destinations (see chapters
4976 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4978 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4979 If there is no retry section, or if it is empty (that is, no retry rules are
4980 defined), Exim will not retry deliveries. In this situation, temporary errors
4981 are treated the same as permanent errors. Retry rules are discussed in chapter
4984 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4985 when new addresses are generated during delivery. Rewriting is discussed in
4986 chapter &<<CHAPrewrite>>&.
4988 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4989 want to use this feature, you must set
4991 LOCAL_SCAN_HAS_OPTIONS=yes
4993 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4994 facility are given in chapter &<<CHAPlocalscan>>&.
4997 .cindex "configuration file" "leading white space in"
4998 .cindex "configuration file" "trailing white space in"
4999 .cindex "white space" "in configuration file"
5000 Leading and trailing white space in configuration lines is always ignored.
5002 Blank lines in the file, and lines starting with a # character (ignoring
5003 leading white space) are treated as comments and are ignored. &*Note*&: A
5004 # character other than at the beginning of a line is not treated specially,
5005 and does not introduce a comment.
5007 Any non-comment line can be continued by ending it with a backslash. Note that
5008 the general rule for white space means that trailing white space after the
5009 backslash and leading white space at the start of continuation
5010 lines is ignored. Comment lines beginning with # (but not empty lines) may
5011 appear in the middle of a sequence of continuation lines.
5013 A convenient way to create a configuration file is to start from the
5014 default, which is supplied in &_src/configure.default_&, and add, delete, or
5015 change settings as required.
5017 The ACLs, retry rules, and rewriting rules have their own syntax which is
5018 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5019 respectively. The other parts of the configuration file have some syntactic
5020 items in common, and these are described below, from section &<<SECTcos>>&
5021 onwards. Before that, the inclusion, macro, and conditional facilities are
5026 .section "File inclusions in the configuration file" "SECID41"
5027 .cindex "inclusions in configuration file"
5028 .cindex "configuration file" "including other files"
5029 .cindex "&`.include`& in configuration file"
5030 .cindex "&`.include_if_exists`& in configuration file"
5031 You can include other files inside Exim's runtime configuration file by
5034 &`.include`& <&'filename'&>
5035 &`.include_if_exists`& <&'filename'&>
5037 on a line by itself. Double quotes round the filename are optional. If you use
5038 the first form, a configuration error occurs if the file does not exist; the
5039 second form does nothing for non-existent files.
5040 The first form allows a relative name. It is resolved relative to
5041 the directory of the including file. For the second form an absolute filename
5044 Includes may be nested to any depth, but remember that Exim reads its
5045 configuration file often, so it is a good idea to keep them to a minimum.
5046 If you change the contents of an included file, you must HUP the daemon,
5047 because an included file is read only when the configuration itself is read.
5049 The processing of inclusions happens early, at a physical line level, so, like
5050 comment lines, an inclusion can be used in the middle of an option setting,
5053 hosts_lookup = a.b.c \
5056 Include processing happens after macro processing (see below). Its effect is to
5057 process the lines of the included file as if they occurred inline where the
5062 .section "Macros in the configuration file" "SECTmacrodefs"
5063 .cindex "macro" "description of"
5064 .cindex "configuration file" "macros"
5065 If a line in the main part of the configuration (that is, before the first
5066 &"begin"& line) begins with an upper case letter, it is taken as a macro
5067 definition, and must be of the form
5069 <&'name'&> = <&'rest of line'&>
5071 The name must consist of letters, digits, and underscores, and need not all be
5072 in upper case, though that is recommended. The rest of the line, including any
5073 continuations, is the replacement text, and has leading and trailing white
5074 space removed. Quotes are not removed. The replacement text can never end with
5075 a backslash character, but this doesn't seem to be a serious limitation.
5077 Macros may also be defined between router, transport, authenticator, or ACL
5078 definitions. They may not, however, be defined within an individual driver or
5079 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5081 .section "Macro substitution" "SECID42"
5082 Once a macro is defined, all subsequent lines in the file (and any included
5083 files) are scanned for the macro name; if there are several macros, the line is
5084 scanned for each, in turn, in the order in which the macros are defined. The
5085 replacement text is not re-scanned for the current macro, though it is scanned
5086 for subsequently defined macros. For this reason, a macro name may not contain
5087 the name of a previously defined macro as a substring. You could, for example,
5090 &`ABCD_XYZ = `&<&'something'&>
5091 &`ABCD = `&<&'something else'&>
5093 but putting the definitions in the opposite order would provoke a configuration
5094 error. Macro expansion is applied to individual physical lines from the file,
5095 before checking for line continuation or file inclusion (see above). If a line
5096 consists solely of a macro name, and the expansion of the macro is empty, the
5097 line is ignored. A macro at the start of a line may turn the line into a
5098 comment line or a &`.include`& line.
5101 .section "Redefining macros" "SECID43"
5102 Once defined, the value of a macro can be redefined later in the configuration
5103 (or in an included file). Redefinition is specified by using &'=='& instead of
5108 MAC == updated value
5110 Redefinition does not alter the order in which the macros are applied to the
5111 subsequent lines of the configuration file. It is still the same order in which
5112 the macros were originally defined. All that changes is the macro's value.
5113 Redefinition makes it possible to accumulate values. For example:
5117 MAC == MAC and something added
5119 This can be helpful in situations where the configuration file is built
5120 from a number of other files.
5122 .section "Overriding macro values" "SECID44"
5123 The values set for macros in the configuration file can be overridden by the
5124 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5125 used, unless called by root or the Exim user. A definition on the command line
5126 using the &%-D%& option causes all definitions and redefinitions within the
5131 .section "Example of macro usage" "SECID45"
5132 As an example of macro usage, consider a configuration where aliases are looked
5133 up in a MySQL database. It helps to keep the file less cluttered if long
5134 strings such as SQL statements are defined separately as macros, for example:
5136 ALIAS_QUERY = select mailbox from user where \
5137 login='${quote_mysql:$local_part}';
5139 This can then be used in a &(redirect)& router setting like this:
5141 data = ${lookup mysql{ALIAS_QUERY}}
5143 In earlier versions of Exim macros were sometimes used for domain, host, or
5144 address lists. In Exim 4 these are handled better by named lists &-- see
5145 section &<<SECTnamedlists>>&.
5148 .section "Builtin macros" "SECTbuiltinmacros"
5149 Exim defines some macros depending on facilities available, which may
5150 differ due to build-time definitions and from one release to another.
5151 All of these macros start with an underscore.
5152 They can be used to conditionally include parts of a configuration
5155 The following classes of macros are defined:
5157 &` _HAVE_* `& build-time defines
5158 &` _DRIVER_ROUTER_* `& router drivers
5159 &` _DRIVER_TRANSPORT_* `& transport drivers
5160 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5161 &` _LOG_* `& log_selector values
5162 &` _OPT_MAIN_* `& main config options
5163 &` _OPT_ROUTERS_* `& generic router options
5164 &` _OPT_TRANSPORTS_* `& generic transport options
5165 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5166 &` _OPT_ROUTER_*_* `& private router options
5167 &` _OPT_TRANSPORT_*_* `& private transport options
5168 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5171 Use an &"exim -bP macros"& command to get the list of macros.
5174 .section "Conditional skips in the configuration file" "SECID46"
5175 .cindex "configuration file" "conditional skips"
5176 .cindex "&`.ifdef`&"
5177 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5178 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5179 portions of the configuration file. The processing happens whenever the file is
5180 read (that is, when an Exim binary starts to run).
5182 The implementation is very simple. Instances of the first four directives must
5183 be followed by text that includes the names of one or macros. The condition
5184 that is tested is whether or not any macro substitution has taken place in the
5188 message_size_limit = 50M
5190 message_size_limit = 100M
5193 sets a message size limit of 50M if the macro &`AAA`& is defined
5194 (or &`A`& or &`AA`&), and 100M
5195 otherwise. If there is more than one macro named on the line, the condition
5196 is true if any of them are defined. That is, it is an &"or"& condition. To
5197 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5199 Although you can use a macro expansion to generate one of these directives,
5200 it is not very useful, because the condition &"there was a macro substitution
5201 in this line"& will always be true.
5203 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5204 to clarify complicated nestings.
5208 .section "Common option syntax" "SECTcos"
5209 .cindex "common option syntax"
5210 .cindex "syntax of common options"
5211 .cindex "configuration file" "common option syntax"
5212 For the main set of options, driver options, and &[local_scan()]& options,
5213 each setting is on a line by itself, and starts with a name consisting of
5214 lower-case letters and underscores. Many options require a data value, and in
5215 these cases the name must be followed by an equals sign (with optional white
5216 space) and then the value. For example:
5218 qualify_domain = mydomain.example.com
5220 .cindex "hiding configuration option values"
5221 .cindex "configuration options" "hiding value of"
5222 .cindex "options" "hiding value of"
5223 Some option settings may contain sensitive data, for example, passwords for
5224 accessing databases. To stop non-admin users from using the &%-bP%& command
5225 line option to read these values, you can precede the option settings with the
5226 word &"hide"&. For example:
5228 hide mysql_servers = localhost/users/admin/secret-password
5230 For non-admin users, such options are displayed like this:
5232 mysql_servers = <value not displayable>
5234 If &"hide"& is used on a driver option, it hides the value of that option on
5235 all instances of the same driver.
5237 The following sections describe the syntax used for the different data types
5238 that are found in option settings.
5241 .section "Boolean options" "SECID47"
5242 .cindex "format" "boolean"
5243 .cindex "boolean configuration values"
5244 .oindex "&%no_%&&'xxx'&"
5245 .oindex "&%not_%&&'xxx'&"
5246 Options whose type is given as boolean are on/off switches. There are two
5247 different ways of specifying such options: with and without a data value. If
5248 the option name is specified on its own without data, the switch is turned on;
5249 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5250 boolean options may be followed by an equals sign and one of the words
5251 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5252 the following two settings have exactly the same effect:
5257 The following two lines also have the same (opposite) effect:
5262 You can use whichever syntax you prefer.
5267 .section "Integer values" "SECID48"
5268 .cindex "integer configuration values"
5269 .cindex "format" "integer"
5270 If an option's type is given as &"integer"&, the value can be given in decimal,
5271 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5272 number is assumed. Otherwise, it is treated as an octal number unless it starts
5273 with the characters &"0x"&, in which case the remainder is interpreted as a
5276 If an integer value is followed by the letter K, it is multiplied by 1024; if
5277 it is followed by the letter M, it is multiplied by 1024x1024;
5278 if by the letter G, 1024x1024x1024.
5280 of integer option settings are output, values which are an exact multiple of
5281 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5282 and M. The printing style is independent of the actual input format that was
5286 .section "Octal integer values" "SECID49"
5287 .cindex "integer format"
5288 .cindex "format" "octal integer"
5289 If an option's type is given as &"octal integer"&, its value is always
5290 interpreted as an octal number, whether or not it starts with the digit zero.
5291 Such options are always output in octal.
5294 .section "Fixed point numbers" "SECID50"
5295 .cindex "fixed point configuration values"
5296 .cindex "format" "fixed point"
5297 If an option's type is given as &"fixed-point"&, its value must be a decimal
5298 integer, optionally followed by a decimal point and up to three further digits.
5302 .section "Time intervals" "SECTtimeformat"
5303 .cindex "time interval" "specifying in configuration"
5304 .cindex "format" "time interval"
5305 A time interval is specified as a sequence of numbers, each followed by one of
5306 the following letters, with no intervening white space:
5316 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5317 intervals are output in the same format. Exim does not restrict the values; it
5318 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5322 .section "String values" "SECTstrings"
5323 .cindex "string" "format of configuration values"
5324 .cindex "format" "string"
5325 If an option's type is specified as &"string"&, the value can be specified with
5326 or without double-quotes. If it does not start with a double-quote, the value
5327 consists of the remainder of the line plus any continuation lines, starting at
5328 the first character after any leading white space, with trailing white space
5329 removed, and with no interpretation of the characters in the string. Because
5330 Exim removes comment lines (those beginning with #) at an early stage, they can
5331 appear in the middle of a multi-line string. The following two settings are
5332 therefore equivalent:
5334 trusted_users = uucp:mail
5335 trusted_users = uucp:\
5336 # This comment line is ignored
5339 .cindex "string" "quoted"
5340 .cindex "escape characters in quoted strings"
5341 If a string does start with a double-quote, it must end with a closing
5342 double-quote, and any backslash characters other than those used for line
5343 continuation are interpreted as escape characters, as follows:
5346 .irow &`\\`& "single backslash"
5347 .irow &`\n`& "newline"
5348 .irow &`\r`& "carriage return"
5350 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5351 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5355 If a backslash is followed by some other character, including a double-quote
5356 character, that character replaces the pair.
5358 Quoting is necessary only if you want to make use of the backslash escapes to
5359 insert special characters, or if you need to specify a value with leading or
5360 trailing spaces. These cases are rare, so quoting is almost never needed in
5361 current versions of Exim. In versions of Exim before 3.14, quoting was required
5362 in order to continue lines, so you may come across older configuration files
5363 and examples that apparently quote unnecessarily.
5366 .section "Expanded strings" "SECID51"
5367 .cindex "expansion" "definition of"
5368 Some strings in the configuration file are subjected to &'string expansion'&,
5369 by which means various parts of the string may be changed according to the
5370 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5371 is as just described; in particular, the handling of backslashes in quoted
5372 strings is done as part of the input process, before expansion takes place.
5373 However, backslash is also an escape character for the expander, so any
5374 backslashes that are required for that reason must be doubled if they are
5375 within a quoted configuration string.
5378 .section "User and group names" "SECID52"
5379 .cindex "user name" "format of"
5380 .cindex "format" "user name"
5381 .cindex "groups" "name format"
5382 .cindex "format" "group name"
5383 User and group names are specified as strings, using the syntax described
5384 above, but the strings are interpreted specially. A user or group name must
5385 either consist entirely of digits, or be a name that can be looked up using the
5386 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5389 .section "List construction" "SECTlistconstruct"
5390 .cindex "list" "syntax of in configuration"
5391 .cindex "format" "list item in configuration"
5392 .cindex "string" "list, definition of"
5393 The data for some configuration options is a list of items, with colon as the
5394 default separator. Many of these options are shown with type &"string list"& in
5395 the descriptions later in this document. Others are listed as &"domain list"&,
5396 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5397 are all the same; however, those other than &"string list"& are subject to
5398 particular kinds of interpretation, as described in chapter
5399 &<<CHAPdomhosaddlists>>&.
5401 In all these cases, the entire list is treated as a single string as far as the
5402 input syntax is concerned. The &%trusted_users%& setting in section
5403 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5404 in a list, it must be entered as two colons. Leading and trailing white space
5405 on each item in a list is ignored. This makes it possible to include items that
5406 start with a colon, and in particular, certain forms of IPv6 address. For
5409 local_interfaces = 127.0.0.1 : ::::1
5411 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5413 &*Note*&: Although leading and trailing white space is ignored in individual
5414 list items, it is not ignored when parsing the list. The space after the first
5415 colon in the example above is necessary. If it were not there, the list would
5416 be interpreted as the two items 127.0.0.1:: and 1.
5418 .section "Changing list separators" "SECTlistsepchange"
5419 .cindex "list separator" "changing"
5420 .cindex "IPv6" "addresses in lists"
5421 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5422 introduced to allow the separator character to be changed. If a list begins
5423 with a left angle bracket, followed by any punctuation character, that
5424 character is used instead of colon as the list separator. For example, the list
5425 above can be rewritten to use a semicolon separator like this:
5427 local_interfaces = <; 127.0.0.1 ; ::1
5429 This facility applies to all lists, with the exception of the list in
5430 &%log_file_path%&. It is recommended that the use of non-colon separators be
5431 confined to circumstances where they really are needed.
5433 .cindex "list separator" "newline as"
5434 .cindex "newline" "as list separator"
5435 It is also possible to use newline and other control characters (those with
5436 code values less than 32, plus DEL) as separators in lists. Such separators
5437 must be provided literally at the time the list is processed. For options that
5438 are string-expanded, you can write the separator using a normal escape
5439 sequence. This will be processed by the expander before the string is
5440 interpreted as a list. For example, if a newline-separated list of domains is
5441 generated by a lookup, you can process it directly by a line such as this:
5443 domains = <\n ${lookup mysql{.....}}
5445 This avoids having to change the list separator in such data. You are unlikely
5446 to want to use a control character as a separator in an option that is not
5447 expanded, because the value is literal text. However, it can be done by giving
5448 the value in quotes. For example:
5450 local_interfaces = "<\n 127.0.0.1 \n ::1"
5452 Unlike printing character separators, which can be included in list items by
5453 doubling, it is not possible to include a control character as data when it is
5454 set as the separator. Two such characters in succession are interpreted as
5455 enclosing an empty list item.
5459 .section "Empty items in lists" "SECTempitelis"
5460 .cindex "list" "empty item in"
5461 An empty item at the end of a list is always ignored. In other words, trailing
5462 separator characters are ignored. Thus, the list in
5464 senders = user@domain :
5466 contains only a single item. If you want to include an empty string as one item
5467 in a list, it must not be the last item. For example, this list contains three
5468 items, the second of which is empty:
5470 senders = user1@domain : : user2@domain
5472 &*Note*&: There must be white space between the two colons, as otherwise they
5473 are interpreted as representing a single colon data character (and the list
5474 would then contain just one item). If you want to specify a list that contains
5475 just one, empty item, you can do it as in this example:
5479 In this case, the first item is empty, and the second is discarded because it
5480 is at the end of the list.
5485 .section "Format of driver configurations" "SECTfordricon"
5486 .cindex "drivers" "configuration format"
5487 There are separate parts in the configuration for defining routers, transports,
5488 and authenticators. In each part, you are defining a number of driver
5489 instances, each with its own set of options. Each driver instance is defined by
5490 a sequence of lines like this:
5492 <&'instance name'&>:
5497 In the following example, the instance name is &(localuser)&, and it is
5498 followed by three options settings:
5503 transport = local_delivery
5505 For each driver instance, you specify which Exim code module it uses &-- by the
5506 setting of the &%driver%& option &-- and (optionally) some configuration
5507 settings. For example, in the case of transports, if you want a transport to
5508 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5509 a local file you would use the &(appendfile)& driver. Each of the drivers is
5510 described in detail in its own separate chapter later in this manual.
5512 You can have several routers, transports, or authenticators that are based on
5513 the same underlying driver (each must have a different instance name).
5515 The order in which routers are defined is important, because addresses are
5516 passed to individual routers one by one, in order. The order in which
5517 transports are defined does not matter at all. The order in which
5518 authenticators are defined is used only when Exim, as a client, is searching
5519 them to find one that matches an authentication mechanism offered by the
5522 .cindex "generic options"
5523 .cindex "options" "generic &-- definition of"
5524 Within a driver instance definition, there are two kinds of option: &'generic'&
5525 and &'private'&. The generic options are those that apply to all drivers of the
5526 same type (that is, all routers, all transports or all authenticators). The
5527 &%driver%& option is a generic option that must appear in every definition.
5528 .cindex "private options"
5529 The private options are special for each driver, and none need appear, because
5530 they all have default values.
5532 The options may appear in any order, except that the &%driver%& option must
5533 precede any private options, since these depend on the particular driver. For
5534 this reason, it is recommended that &%driver%& always be the first option.
5536 Driver instance names, which are used for reference in log entries and
5537 elsewhere, can be any sequence of letters, digits, and underscores (starting
5538 with a letter) and must be unique among drivers of the same type. A router and
5539 a transport (for example) can each have the same name, but no two router
5540 instances can have the same name. The name of a driver instance should not be
5541 confused with the name of the underlying driver module. For example, the
5542 configuration lines:
5547 create an instance of the &(smtp)& transport driver whose name is
5548 &(remote_smtp)&. The same driver code can be used more than once, with
5549 different instance names and different option settings each time. A second
5550 instance of the &(smtp)& transport, with different options, might be defined
5556 command_timeout = 10s
5558 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5559 these transport instances from routers, and these names would appear in log
5562 Comment lines may be present in the middle of driver specifications. The full
5563 list of option settings for any particular driver instance, including all the
5564 defaulted values, can be extracted by making use of the &%-bP%& command line
5572 . ////////////////////////////////////////////////////////////////////////////
5573 . ////////////////////////////////////////////////////////////////////////////
5575 .chapter "The default configuration file" "CHAPdefconfil"
5576 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5577 .cindex "default" "configuration file &""walk through""&"
5578 The default configuration file supplied with Exim as &_src/configure.default_&
5579 is sufficient for a host with simple mail requirements. As an introduction to
5580 the way Exim is configured, this chapter &"walks through"& the default
5581 configuration, giving brief explanations of the settings. Detailed descriptions
5582 of the options are given in subsequent chapters. The default configuration file
5583 itself contains extensive comments about ways you might want to modify the
5584 initial settings. However, note that there are many options that are not
5585 mentioned at all in the default configuration.
5589 .section "Macros" "SECTdefconfmacros"
5590 All macros should be defined before any options.
5592 One macro is specified, but commented out, in the default configuration:
5594 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5596 If all off-site mail is expected to be delivered to a "smarthost", then set the
5597 hostname here and uncomment the macro. This will affect which router is used
5598 later on. If this is left commented out, then Exim will perform direct-to-MX
5599 deliveries using a &(dnslookup)& router.
5601 In addition to macros defined here, Exim includes a number of built-in macros
5602 to enable configuration to be guarded by a binary built with support for a
5603 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5606 .section "Main configuration settings" "SECTdefconfmain"
5607 The main (global) configuration option settings section must always come first
5608 in the file, after the macros.
5609 The first thing you'll see in the file, after some initial comments, is the line
5611 # primary_hostname =
5613 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5614 to know the official, fully qualified name of your host, and this is where you
5615 can specify it. However, in most cases you do not need to set this option. When
5616 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5618 The first three non-comment configuration lines are as follows:
5620 domainlist local_domains = @
5621 domainlist relay_to_domains =
5622 hostlist relay_from_hosts = 127.0.0.1
5624 These are not, in fact, option settings. They are definitions of two named
5625 domain lists and one named host list. Exim allows you to give names to lists of
5626 domains, hosts, and email addresses, in order to make it easier to manage the
5627 configuration file (see section &<<SECTnamedlists>>&).
5629 The first line defines a domain list called &'local_domains'&; this is used
5630 later in the configuration to identify domains that are to be delivered
5633 .cindex "@ in a domain list"
5634 There is just one item in this list, the string &"@"&. This is a special form
5635 of entry which means &"the name of the local host"&. Thus, if the local host is
5636 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5637 be delivered locally. Because the local host's name is referenced indirectly,
5638 the same configuration file can be used on different hosts.
5640 The second line defines a domain list called &'relay_to_domains'&, but the
5641 list itself is empty. Later in the configuration we will come to the part that
5642 controls mail relaying through the local host; it allows relaying to any
5643 domains in this list. By default, therefore, no relaying on the basis of a mail
5644 domain is permitted.
5646 The third line defines a host list called &'relay_from_hosts'&. This list is
5647 used later in the configuration to permit relaying from any host or IP address
5648 that matches the list. The default contains just the IP address of the IPv4
5649 loopback interface, which means that processes on the local host are able to
5650 submit mail for relaying by sending it over TCP/IP to that interface. No other
5651 hosts are permitted to submit messages for relaying.
5653 Just to be sure there's no misunderstanding: at this point in the configuration
5654 we aren't actually setting up any controls. We are just defining some domains
5655 and hosts that will be used in the controls that are specified later.
5657 The next two configuration lines are genuine option settings:
5659 acl_smtp_rcpt = acl_check_rcpt
5660 acl_smtp_data = acl_check_data
5662 These options specify &'Access Control Lists'& (ACLs) that are to be used
5663 during an incoming SMTP session for every recipient of a message (every RCPT
5664 command), and after the contents of the message have been received,
5665 respectively. The names of the lists are &'acl_check_rcpt'& and
5666 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5667 section of the configuration. The RCPT ACL controls which recipients are
5668 accepted for an incoming message &-- if a configuration does not provide an ACL
5669 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5670 contents of a message to be checked.
5672 Two commented-out option settings are next:
5674 # av_scanner = clamd:/tmp/clamd
5675 # spamd_address = 127.0.0.1 783
5677 These are example settings that can be used when Exim is compiled with the
5678 content-scanning extension. The first specifies the interface to the virus
5679 scanner, and the second specifies the interface to SpamAssassin. Further
5680 details are given in chapter &<<CHAPexiscan>>&.
5682 Three more commented-out option settings follow:
5684 # tls_advertise_hosts = *
5685 # tls_certificate = /etc/ssl/exim.crt
5686 # tls_privatekey = /etc/ssl/exim.pem
5688 These are example settings that can be used when Exim is compiled with
5689 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5690 first one specifies the list of clients that are allowed to use TLS when
5691 connecting to this server; in this case, the wildcard means all clients. The
5692 other options specify where Exim should find its TLS certificate and private
5693 key, which together prove the server's identity to any clients that connect.
5694 More details are given in chapter &<<CHAPTLS>>&.
5696 Another two commented-out option settings follow:
5698 # daemon_smtp_ports = 25 : 465 : 587
5699 # tls_on_connect_ports = 465
5701 .cindex "port" "465 and 587"
5702 .cindex "port" "for message submission"
5703 .cindex "message" "submission, ports for"
5704 .cindex "submissions protocol"
5705 .cindex "smtps protocol"
5706 .cindex "ssmtp protocol"
5707 .cindex "SMTP" "submissions protocol"
5708 .cindex "SMTP" "ssmtp protocol"
5709 .cindex "SMTP" "smtps protocol"
5710 These options provide better support for roaming users who wish to use this
5711 server for message submission. They are not much use unless you have turned on
5712 TLS (as described in the previous paragraph) and authentication (about which
5713 more in section &<<SECTdefconfauth>>&).
5714 Mail submission from mail clients (MUAs) should be separate from inbound mail
5715 to your domain (MX delivery) for various good reasons (eg, ability to impose
5716 much saner TLS protocol and ciphersuite requirements without unintended
5718 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5719 which uses STARTTLS, so this is the &"submission"& port.
5720 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5721 which should be used in preference to 587.
5722 You should also consider deploying SRV records to help clients find
5724 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5726 Two more commented-out options settings follow:
5729 # qualify_recipient =
5731 The first of these specifies a domain that Exim uses when it constructs a
5732 complete email address from a local login name. This is often needed when Exim
5733 receives a message from a local process. If you do not set &%qualify_domain%&,
5734 the value of &%primary_hostname%& is used. If you set both of these options,
5735 you can have different qualification domains for sender and recipient
5736 addresses. If you set only the first one, its value is used in both cases.
5738 .cindex "domain literal" "recognizing format"
5739 The following line must be uncommented if you want Exim to recognize
5740 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5741 (an IP address within square brackets) instead of a named domain.
5743 # allow_domain_literals
5745 The RFCs still require this form, but many people think that in the modern
5746 Internet it makes little sense to permit mail to be sent to specific hosts by
5747 quoting their IP addresses. This ancient format has been used by people who
5748 try to abuse hosts by using them for unwanted relaying. However, some
5749 people believe there are circumstances (for example, messages addressed to
5750 &'postmaster'&) where domain literals are still useful.
5752 The next configuration line is a kind of trigger guard:
5756 It specifies that no delivery must ever be run as the root user. The normal
5757 convention is to set up &'root'& as an alias for the system administrator. This
5758 setting is a guard against slips in the configuration.
5759 The list of users specified by &%never_users%& is not, however, the complete
5760 list; the build-time configuration in &_Local/Makefile_& has an option called
5761 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5762 contents of &%never_users%& are added to this list. By default
5763 FIXED_NEVER_USERS also specifies root.
5765 When a remote host connects to Exim in order to send mail, the only information
5766 Exim has about the host's identity is its IP address. The next configuration
5771 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5772 in order to get a host name. This improves the quality of the logging
5773 information, but if you feel it is too expensive, you can remove it entirely,
5774 or restrict the lookup to hosts on &"nearby"& networks.
5775 Note that it is not always possible to find a host name from an IP address,
5776 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5779 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5780 1413 (hence their names):
5783 rfc1413_query_timeout = 0s
5785 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5786 Few hosts offer RFC1413 service these days; calls have to be
5787 terminated by a timeout and this needlessly delays the startup
5788 of an incoming SMTP connection.
5789 If you have hosts for which you trust RFC1413 and need this
5790 information, you can change this.
5792 This line enables an efficiency SMTP option. It is negotiated by clients
5793 and not expected to cause problems but can be disabled if needed.
5798 When Exim receives messages over SMTP connections, it expects all addresses to
5799 be fully qualified with a domain, as required by the SMTP definition. However,
5800 if you are running a server to which simple clients submit messages, you may
5801 find that they send unqualified addresses. The two commented-out options:
5803 # sender_unqualified_hosts =
5804 # recipient_unqualified_hosts =
5806 show how you can specify hosts that are permitted to send unqualified sender
5807 and recipient addresses, respectively.
5809 The &%log_selector%& option is used to increase the detail of logging
5812 log_selector = +smtp_protocol_error +smtp_syntax_error \
5813 +tls_certificate_verified
5816 The &%percent_hack_domains%& option is also commented out:
5818 # percent_hack_domains =
5820 It provides a list of domains for which the &"percent hack"& is to operate.
5821 This is an almost obsolete form of explicit email routing. If you do not know
5822 anything about it, you can safely ignore this topic.
5824 The next two settings in the main part of the default configuration are
5825 concerned with messages that have been &"frozen"& on Exim's queue. When a
5826 message is frozen, Exim no longer continues to try to deliver it. Freezing
5827 occurs when a bounce message encounters a permanent failure because the sender
5828 address of the original message that caused the bounce is invalid, so the
5829 bounce cannot be delivered. This is probably the most common case, but there
5830 are also other conditions that cause freezing, and frozen messages are not
5831 always bounce messages.
5833 ignore_bounce_errors_after = 2d
5834 timeout_frozen_after = 7d
5836 The first of these options specifies that failing bounce messages are to be
5837 discarded after 2 days in the queue. The second specifies that any frozen
5838 message (whether a bounce message or not) is to be timed out (and discarded)
5839 after a week. In this configuration, the first setting ensures that no failing
5840 bounce message ever lasts a week.
5842 Exim queues it's messages in a spool directory. If you expect to have
5843 large queues, you may consider using this option. It splits the spool
5844 directory into subdirectories to avoid file system degradation from
5845 many files in a single directory, resulting in better performance.
5846 Manual manipulation of queued messages becomes more complex (though fortunately
5849 # split_spool_directory = true
5852 In an ideal world everybody follows the standards. For non-ASCII
5853 messages RFC 2047 is a standard, allowing a maximum line length of 76
5854 characters. Exim adheres that standard and won't process messages which
5855 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5856 In particular, the Exim maintainers have had multiple reports of
5857 problems from Russian administrators of issues until they disable this
5858 check, because of some popular, yet buggy, mail composition software.
5860 # check_rfc2047_length = false
5863 If you need to be strictly RFC compliant you may wish to disable the
5864 8BITMIME advertisement. Use this, if you exchange mails with systems
5865 that are not 8-bit clean.
5867 # accept_8bitmime = false
5870 Libraries you use may depend on specific environment settings. This
5871 imposes a security risk (e.g. PATH). There are two lists:
5872 &%keep_environment%& for the variables to import as they are, and
5873 &%add_environment%& for variables we want to set to a fixed value.
5874 Note that TZ is handled separately, by the $%timezone%$ runtime
5875 option and by the TIMEZONE_DEFAULT buildtime option.
5877 # keep_environment = ^LDAP
5878 # add_environment = PATH=/usr/bin::/bin
5882 .section "ACL configuration" "SECID54"
5883 .cindex "default" "ACLs"
5884 .cindex "&ACL;" "default configuration"
5885 In the default configuration, the ACL section follows the main configuration.
5886 It starts with the line
5890 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5891 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5892 and &%acl_smtp_data%& above.
5894 .cindex "RCPT" "ACL for"
5895 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5896 RCPT command specifies one of the message's recipients. The ACL statements
5897 are considered in order, until the recipient address is either accepted or
5898 rejected. The RCPT command is then accepted or rejected, according to the
5899 result of the ACL processing.
5903 This line, consisting of a name terminated by a colon, marks the start of the
5908 This ACL statement accepts the recipient if the sending host matches the list.
5909 But what does that strange list mean? It doesn't actually contain any host
5910 names or IP addresses. The presence of the colon puts an empty item in the
5911 list; Exim matches this only if the incoming message did not come from a remote
5912 host, because in that case, the remote hostname is empty. The colon is
5913 important. Without it, the list itself is empty, and can never match anything.
5915 What this statement is doing is to accept unconditionally all recipients in
5916 messages that are submitted by SMTP from local processes using the standard
5917 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5920 deny message = Restricted characters in address
5921 domains = +local_domains
5922 local_parts = ^[.] : ^.*[@%!/|]
5924 deny message = Restricted characters in address
5925 domains = !+local_domains
5926 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5928 These statements are concerned with local parts that contain any of the
5929 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5930 Although these characters are entirely legal in local parts (in the case of
5931 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5932 in Internet mail addresses.
5934 The first three have in the past been associated with explicitly routed
5935 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5936 option). Addresses containing these characters are regularly tried by spammers
5937 in an attempt to bypass relaying restrictions, and also by open relay testing
5938 programs. Unless you really need them it is safest to reject these characters
5939 at this early stage. This configuration is heavy-handed in rejecting these
5940 characters for all messages it accepts from remote hosts. This is a deliberate
5941 policy of being as safe as possible.
5943 The first rule above is stricter, and is applied to messages that are addressed
5944 to one of the local domains handled by this host. This is implemented by the
5945 first condition, which restricts it to domains that are listed in the
5946 &'local_domains'& domain list. The &"+"& character is used to indicate a
5947 reference to a named list. In this configuration, there is just one domain in
5948 &'local_domains'&, but in general there may be many.
5950 The second condition on the first statement uses two regular expressions to
5951 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5952 or &"|"&. If you have local accounts that include these characters, you will
5953 have to modify this rule.
5955 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5956 allows them because they have been encountered in practice. (Consider the
5957 common convention of local parts constructed as
5958 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5959 the author of Exim, who has no second initial.) However, a local part starting
5960 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5961 filename (for example, for a mailing list). This is also true for local parts
5962 that contain slashes. A pipe symbol can also be troublesome if the local part
5963 is incorporated unthinkingly into a shell command line.
5965 The second rule above applies to all other domains, and is less strict. This
5966 allows your own users to send outgoing messages to sites that use slashes
5967 and vertical bars in their local parts. It blocks local parts that begin
5968 with a dot, slash, or vertical bar, but allows these characters within the
5969 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5970 and &"!"& is blocked, as before. The motivation here is to prevent your users
5971 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5973 accept local_parts = postmaster
5974 domains = +local_domains
5976 This statement, which has two conditions, accepts an incoming address if the
5977 local part is &'postmaster'& and the domain is one of those listed in the
5978 &'local_domains'& domain list. The &"+"& character is used to indicate a
5979 reference to a named list. In this configuration, there is just one domain in
5980 &'local_domains'&, but in general there may be many.
5982 The presence of this statement means that mail to postmaster is never blocked
5983 by any of the subsequent tests. This can be helpful while sorting out problems
5984 in cases where the subsequent tests are incorrectly denying access.
5986 require verify = sender
5988 This statement requires the sender address to be verified before any subsequent
5989 ACL statement can be used. If verification fails, the incoming recipient
5990 address is refused. Verification consists of trying to route the address, to
5991 see if a bounce message could be delivered to it. In the case of remote
5992 addresses, basic verification checks only the domain, but &'callouts'& can be
5993 used for more verification if required. Section &<<SECTaddressverification>>&
5994 discusses the details of address verification.
5996 accept hosts = +relay_from_hosts
5997 control = submission
5999 This statement accepts the address if the message is coming from one of the
6000 hosts that are defined as being allowed to relay through this host. Recipient
6001 verification is omitted here, because in many cases the clients are dumb MUAs
6002 that do not cope well with SMTP error responses. For the same reason, the
6003 second line specifies &"submission mode"& for messages that are accepted. This
6004 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6005 messages that are deficient in some way, for example, because they lack a
6006 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6007 probably add recipient verification here, and disable submission mode.
6009 accept authenticated = *
6010 control = submission
6012 This statement accepts the address if the client host has authenticated itself.
6013 Submission mode is again specified, on the grounds that such messages are most
6014 likely to come from MUAs. The default configuration does not define any
6015 authenticators, though it does include some nearly complete commented-out
6016 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6017 fact authenticate until you complete the authenticator definitions.
6019 require message = relay not permitted
6020 domains = +local_domains : +relay_to_domains
6022 This statement rejects the address if its domain is neither a local domain nor
6023 one of the domains for which this host is a relay.
6025 require verify = recipient
6027 This statement requires the recipient address to be verified; if verification
6028 fails, the address is rejected.
6030 # deny message = rejected because $sender_host_address \
6031 # is in a black list at $dnslist_domain\n\
6033 # dnslists = black.list.example
6035 # warn dnslists = black.list.example
6036 # add_header = X-Warning: $sender_host_address is in \
6037 # a black list at $dnslist_domain
6038 # log_message = found in $dnslist_domain
6040 These commented-out lines are examples of how you could configure Exim to check
6041 sending hosts against a DNS black list. The first statement rejects messages
6042 from blacklisted hosts, whereas the second just inserts a warning header
6045 # require verify = csa
6047 This commented-out line is an example of how you could turn on client SMTP
6048 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6053 The final statement in the first ACL unconditionally accepts any recipient
6054 address that has successfully passed all the previous tests.
6058 This line marks the start of the second ACL, and names it. Most of the contents
6059 of this ACL are commented out:
6062 # message = This message contains a virus \
6065 These lines are examples of how to arrange for messages to be scanned for
6066 viruses when Exim has been compiled with the content-scanning extension, and a
6067 suitable virus scanner is installed. If the message is found to contain a
6068 virus, it is rejected with the given custom error message.
6070 # warn spam = nobody
6071 # message = X-Spam_score: $spam_score\n\
6072 # X-Spam_score_int: $spam_score_int\n\
6073 # X-Spam_bar: $spam_bar\n\
6074 # X-Spam_report: $spam_report
6076 These lines are an example of how to arrange for messages to be scanned by
6077 SpamAssassin when Exim has been compiled with the content-scanning extension,
6078 and SpamAssassin has been installed. The SpamAssassin check is run with
6079 &`nobody`& as its user parameter, and the results are added to the message as a
6080 series of extra header line. In this case, the message is not rejected,
6081 whatever the spam score.
6085 This final line in the DATA ACL accepts the message unconditionally.
6088 .section "Router configuration" "SECID55"
6089 .cindex "default" "routers"
6090 .cindex "routers" "default"
6091 The router configuration comes next in the default configuration, introduced
6096 Routers are the modules in Exim that make decisions about where to send
6097 messages. An address is passed to each router, in turn, until it is either
6098 accepted, or failed. This means that the order in which you define the routers
6099 matters. Each router is fully described in its own chapter later in this
6100 manual. Here we give only brief overviews.
6103 # driver = ipliteral
6104 # domains = !+local_domains
6105 # transport = remote_smtp
6107 .cindex "domain literal" "default router"
6108 This router is commented out because the majority of sites do not want to
6109 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6110 you uncomment this router, you also need to uncomment the setting of
6111 &%allow_domain_literals%& in the main part of the configuration.
6113 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6114 macro has been defined, per
6116 .ifdef ROUTER_SMARTHOST
6125 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6126 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6127 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6128 skip these routers because of the &%domains%& option.
6132 driver = manualroute
6133 domains = ! +local_domains
6134 transport = smarthost_smtp
6135 route_data = ROUTER_SMARTHOST
6136 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6139 This router only handles mail which is not to any local domains; this is
6140 specified by the line
6142 domains = ! +local_domains
6144 The &%domains%& option lists the domains to which this router applies, but the
6145 exclamation mark is a negation sign, so the router is used only for domains
6146 that are not in the domain list called &'local_domains'& (which was defined at
6147 the start of the configuration). The plus sign before &'local_domains'&
6148 indicates that it is referring to a named list. Addresses in other domains are
6149 passed on to the following routers.
6151 The name of the router driver is &(manualroute)& because we are manually
6152 specifying how mail should be routed onwards, instead of using DNS MX.
6153 While the name of this router instance is arbitrary, the &%driver%& option must
6154 be one of the driver modules that is in the Exim binary.
6156 With no pre-conditions other than &%domains%&, all mail for non-local domains
6157 will be handled by this router, and the &%no_more%& setting will ensure that no
6158 other routers will be used for messages matching the pre-conditions. See
6159 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6160 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6161 and the macro supplies the value; the address is then queued for the
6162 &(smarthost_smtp)& transport.
6167 domains = ! +local_domains
6168 transport = remote_smtp
6169 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6172 The &%domains%& option behaves as per smarthost, above.
6174 The name of the router driver is &(dnslookup)&,
6175 and is specified by the &%driver%& option. Do not be confused by the fact that
6176 the name of this router instance is the same as the name of the driver. The
6177 instance name is arbitrary, but the name set in the &%driver%& option must be
6178 one of the driver modules that is in the Exim binary.
6180 The &(dnslookup)& router routes addresses by looking up their domains in the
6181 DNS in order to obtain a list of hosts to which the address is routed. If the
6182 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6183 specified by the &%transport%& option. If the router does not find the domain
6184 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6185 the address fails and is bounced.
6187 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6188 be entirely ignored. This option is present because a number of cases have been
6189 encountered where MX records in the DNS point to host names
6190 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6191 Completely ignoring these IP addresses causes Exim to fail to route the
6192 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6193 continue to try to deliver the message periodically until the address timed
6200 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6202 file_transport = address_file
6203 pipe_transport = address_pipe
6205 Control reaches this and subsequent routers only for addresses in the local
6206 domains. This router checks to see whether the local part is defined as an
6207 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6208 data that it looks up from that file. If no data is found for the local part,
6209 the value of the &%data%& option is empty, causing the address to be passed to
6212 &_/etc/aliases_& is a conventional name for the system aliases file that is
6213 often used. That is why it is referenced by from the default configuration
6214 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6215 &_Local/Makefile_& before building Exim.
6220 # local_part_suffix = +* : -*
6221 # local_part_suffix_optional
6222 file = $home/.forward
6227 file_transport = address_file
6228 pipe_transport = address_pipe
6229 reply_transport = address_reply
6231 This is the most complicated router in the default configuration. It is another
6232 redirection router, but this time it is looking for forwarding data set up by
6233 individual users. The &%check_local_user%& setting specifies a check that the
6234 local part of the address is the login name of a local user. If it is not, the
6235 router is skipped. The two commented options that follow &%check_local_user%&,
6238 # local_part_suffix = +* : -*
6239 # local_part_suffix_optional
6241 .vindex "&$local_part_suffix$&"
6242 show how you can specify the recognition of local part suffixes. If the first
6243 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6244 by any sequence of characters, is removed from the local part and placed in the
6245 variable &$local_part_suffix$&. The second suffix option specifies that the
6246 presence of a suffix in the local part is optional. When a suffix is present,
6247 the check for a local login uses the local part with the suffix removed.
6249 When a local user account is found, the file called &_.forward_& in the user's
6250 home directory is consulted. If it does not exist, or is empty, the router
6251 declines. Otherwise, the contents of &_.forward_& are interpreted as
6252 redirection data (see chapter &<<CHAPredirect>>& for more details).
6254 .cindex "Sieve filter" "enabling in default router"
6255 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6256 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6257 is commented out by default), the contents of the file are interpreted as a set
6258 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6259 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6260 separate document entitled &'Exim's interfaces to mail filtering'&.
6262 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6263 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6264 There are two reasons for doing this:
6267 Whether or not a local user has a &_.forward_& file is not really relevant when
6268 checking an address for validity; it makes sense not to waste resources doing
6271 More importantly, when Exim is verifying addresses or handling an EXPN
6272 command during an SMTP session, it is running as the Exim user, not as root.
6273 The group is the Exim group, and no additional groups are set up.
6274 It may therefore not be possible for Exim to read users' &_.forward_& files at
6278 The setting of &%check_ancestor%& prevents the router from generating a new
6279 address that is the same as any previous address that was redirected. (This
6280 works round a problem concerning a bad interaction between aliasing and
6281 forwarding &-- see section &<<SECTredlocmai>>&).
6283 The final three option settings specify the transports that are to be used when
6284 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6285 auto-reply, respectively. For example, if a &_.forward_& file contains
6287 a.nother@elsewhere.example, /home/spqr/archive
6289 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6295 # local_part_suffix = +* : -*
6296 # local_part_suffix_optional
6297 transport = local_delivery
6299 The final router sets up delivery into local mailboxes, provided that the local
6300 part is the name of a local login, by accepting the address and assigning it to
6301 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6302 routers, so the address is bounced. The commented suffix settings fulfil the
6303 same purpose as they do for the &(userforward)& router.
6306 .section "Transport configuration" "SECID56"
6307 .cindex "default" "transports"
6308 .cindex "transports" "default"
6309 Transports define mechanisms for actually delivering messages. They operate
6310 only when referenced from routers, so the order in which they are defined does
6311 not matter. The transports section of the configuration starts with
6315 Two remote transports and four local transports are defined.
6319 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6324 This transport is used for delivering messages over SMTP connections.
6325 The list of remote hosts comes from the router.
6326 The &%message_size_limit%& usage is a hack to avoid sending on messages
6327 with over-long lines.
6329 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6330 negotiated between client and server and not expected to cause problems
6331 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6332 use of the &%hosts_try_prdr%& configuration option.
6334 The other remote transport is used when delivering to a specific smarthost
6335 with whom there must be some kind of existing relationship, instead of the
6336 usual federated system.
6341 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6345 # Comment out any of these which you have to, then file a Support
6346 # request with your smarthost provider to get things fixed:
6347 hosts_require_tls = *
6348 tls_verify_hosts = *
6349 # As long as tls_verify_hosts is enabled, this won't matter, but if you
6350 # have to comment it out then this will at least log whether you succeed
6352 tls_try_verify_hosts = *
6354 # The SNI name should match the name which we'll expect to verify;
6355 # many mail systems don't use SNI and this doesn't matter, but if it does,
6356 # we need to send a name which the remote site will recognize.
6357 # This _should_ be the name which the smarthost operators specified as
6358 # the hostname for sending your mail to.
6359 tls_sni = ROUTER_SMARTHOST
6361 .ifdef _HAVE_OPENSSL
6362 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6365 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6372 After the same &%message_size_limit%& hack, we then specify that this Transport
6373 can handle messages to multiple domains in one run. The assumption here is
6374 that you're routing all non-local mail to the same place and that place is
6375 happy to take all messages from you as quickly as possible.
6376 All other options depend upon built-in macros; if Exim was built without TLS support
6377 then no other options are defined.
6378 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6379 and versions using the &%tls_require_ciphers%& option, where the value to be
6380 used depends upon the library providing TLS.
6381 Beyond that, the options adopt the stance that you should have TLS support available
6382 from your smarthost on today's Internet, so we turn on requiring TLS for the
6383 mail to be delivered, and requiring that the certificate be valid, and match
6384 the expected hostname. The &%tls_sni%& option can be used by service providers
6385 to select an appropriate certificate to present to you and here we re-use the
6386 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6387 You want to specify the hostname which you'll expect to validate for, and that
6388 should not be subject to insecure tampering via DNS results.
6390 For the &%hosts_try_prdr%& option see the previous transport.
6392 All other options are defaulted.
6396 file = /var/mail/$local_part_data
6403 This &(appendfile)& transport is used for local delivery to user mailboxes in
6404 traditional BSD mailbox format.
6407 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6408 as it is provided by a potential bad actor.
6409 Instead we use &$local_part_data$&,
6410 the result of looking up &$local_part$& in the user database
6411 (done by using &%check_local_user%& in the the router).
6414 By default &(appendfile)& runs under the uid and gid of the
6415 local user, which requires the sticky bit to be set on the &_/var/mail_&
6416 directory. Some systems use the alternative approach of running mail deliveries
6417 under a particular group instead of using the sticky bit. The commented options
6418 show how this can be done.
6420 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6421 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6422 similarly-named options above.
6428 This transport is used for handling deliveries to pipes that are generated by
6429 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6430 option specifies that any output on stdout or stderr generated by the pipe is to
6431 be returned to the sender.
6439 This transport is used for handling deliveries to files that are generated by
6440 redirection. The name of the file is not specified in this instance of
6441 &(appendfile)&, because it comes from the &(redirect)& router.
6446 This transport is used for handling automatic replies generated by users'
6451 .section "Default retry rule" "SECID57"
6452 .cindex "retry" "default rule"
6453 .cindex "default" "retry rule"
6454 The retry section of the configuration file contains rules which affect the way
6455 Exim retries deliveries that cannot be completed at the first attempt. It is
6456 introduced by the line
6460 In the default configuration, there is just one rule, which applies to all
6463 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6465 This causes any temporarily failing address to be retried every 15 minutes for
6466 2 hours, then at intervals starting at one hour and increasing by a factor of
6467 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6468 is not delivered after 4 days of temporary failure, it is bounced. The time is
6469 measured from first failure, not from the time the message was received.
6471 If the retry section is removed from the configuration, or is empty (that is,
6472 if no retry rules are defined), Exim will not retry deliveries. This turns
6473 temporary errors into permanent errors.
6476 .section "Rewriting configuration" "SECID58"
6477 The rewriting section of the configuration, introduced by
6481 contains rules for rewriting addresses in messages as they arrive. There are no
6482 rewriting rules in the default configuration file.
6486 .section "Authenticators configuration" "SECTdefconfauth"
6487 .cindex "AUTH" "configuration"
6488 The authenticators section of the configuration, introduced by
6490 begin authenticators
6492 defines mechanisms for the use of the SMTP AUTH command. The default
6493 configuration file contains two commented-out example authenticators
6494 which support plaintext username/password authentication using the
6495 standard PLAIN mechanism and the traditional but non-standard LOGIN
6496 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6497 to support most MUA software.
6499 The example PLAIN authenticator looks like this:
6502 # driver = plaintext
6503 # server_set_id = $auth2
6504 # server_prompts = :
6505 # server_condition = Authentication is not yet configured
6506 # server_advertise_condition = ${if def:tls_in_cipher }
6508 And the example LOGIN authenticator looks like this:
6511 # driver = plaintext
6512 # server_set_id = $auth1
6513 # server_prompts = <| Username: | Password:
6514 # server_condition = Authentication is not yet configured
6515 # server_advertise_condition = ${if def:tls_in_cipher }
6518 The &%server_set_id%& option makes Exim remember the authenticated username
6519 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6520 &%server_prompts%& option configures the &(plaintext)& authenticator so
6521 that it implements the details of the specific authentication mechanism,
6522 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6523 when Exim offers authentication to clients; in the examples, this is only
6524 when TLS or SSL has been started, so to enable the authenticators you also
6525 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6527 The &%server_condition%& setting defines how to verify that the username and
6528 password are correct. In the examples it just produces an error message.
6529 To make the authenticators work, you can use a string expansion
6530 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6532 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6533 usercode and password are in different positions.
6534 Chapter &<<CHAPplaintext>>& covers both.
6536 .ecindex IIDconfiwal
6540 . ////////////////////////////////////////////////////////////////////////////
6541 . ////////////////////////////////////////////////////////////////////////////
6543 .chapter "Regular expressions" "CHAPregexp"
6545 .cindex "regular expressions" "library"
6547 Exim supports the use of regular expressions in many of its options. It
6548 uses the PCRE regular expression library; this provides regular expression
6549 matching that is compatible with Perl 5. The syntax and semantics of
6550 regular expressions is discussed in
6551 online Perl manpages, in
6552 many Perl reference books, and also in
6553 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6554 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6555 . --- the http: URL here redirects to another page with the ISBN in the URL
6556 . --- where trying to use https: just redirects back to http:, so sticking
6557 . --- to the old URL for now. 2018-09-07.
6559 The documentation for the syntax and semantics of the regular expressions that
6560 are supported by PCRE is included in the PCRE distribution, and no further
6561 description is included here. The PCRE functions are called from Exim using
6562 the default option settings (that is, with no PCRE options set), except that
6563 the PCRE_CASELESS option is set when the matching is required to be
6566 In most cases, when a regular expression is required in an Exim configuration,
6567 it has to start with a circumflex, in order to distinguish it from plain text
6568 or an &"ends with"& wildcard. In this example of a configuration setting, the
6569 second item in the colon-separated list is a regular expression.
6571 domains = a.b.c : ^\\d{3} : *.y.z : ...
6573 The doubling of the backslash is required because of string expansion that
6574 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6575 of this issue, and a way of avoiding the need for doubling backslashes. The
6576 regular expression that is eventually used in this example contains just one
6577 backslash. The circumflex is included in the regular expression, and has the
6578 normal effect of &"anchoring"& it to the start of the string that is being
6581 There are, however, two cases where a circumflex is not required for the
6582 recognition of a regular expression: these are the &%match%& condition in a
6583 string expansion, and the &%matches%& condition in an Exim filter file. In
6584 these cases, the relevant string is always treated as a regular expression; if
6585 it does not start with a circumflex, the expression is not anchored, and can
6586 match anywhere in the subject string.
6588 In all cases, if you want a regular expression to match at the end of a string,
6589 you must code the $ metacharacter to indicate this. For example:
6591 domains = ^\\d{3}\\.example
6593 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6596 domains = ^\\d{3}\\.example\$
6598 if you want &'example'& to be the top-level domain. The backslash before the
6599 $ is needed because string expansion also interprets dollar characters.
6603 . ////////////////////////////////////////////////////////////////////////////
6604 . ////////////////////////////////////////////////////////////////////////////
6606 .chapter "File and database lookups" "CHAPfdlookup"
6607 .scindex IIDfidalo1 "file" "lookups"
6608 .scindex IIDfidalo2 "database" "lookups"
6609 .cindex "lookup" "description of"
6610 Exim can be configured to look up data in files or databases as it processes
6611 messages. Two different kinds of syntax are used:
6614 A string that is to be expanded may contain explicit lookup requests. These
6615 cause parts of the string to be replaced by data that is obtained from the
6616 lookup. Lookups of this type are conditional expansion items. Different results
6617 can be defined for the cases of lookup success and failure. See chapter
6618 &<<CHAPexpand>>&, where string expansions are described in detail.
6619 The key for the lookup is specified as part of the string expansion.
6621 Lists of domains, hosts, and email addresses can contain lookup requests as a
6622 way of avoiding excessively long linear lists. In this case, the data that is
6623 returned by the lookup is often (but not always) discarded; whether the lookup
6624 succeeds or fails is what really counts. These kinds of list are described in
6625 chapter &<<CHAPdomhosaddlists>>&.
6626 The key for the lookup is given by the context in which the list is expanded.
6629 String expansions, lists, and lookups interact with each other in such a way
6630 that there is no order in which to describe any one of them that does not
6631 involve references to the others. Each of these three chapters makes more sense
6632 if you have read the other two first. If you are reading this for the first
6633 time, be aware that some of it will make a lot more sense after you have read
6634 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6636 .section "Examples of different lookup syntax" "SECID60"
6637 It is easy to confuse the two different kinds of lookup, especially as the
6638 lists that may contain the second kind are always expanded before being
6639 processed as lists. Therefore, they may also contain lookups of the first kind.
6640 Be careful to distinguish between the following two examples:
6642 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6643 domains = lsearch;/some/file
6645 The first uses a string expansion, the result of which must be a domain list.
6646 No strings have been specified for a successful or a failing lookup; the
6647 defaults in this case are the looked-up data and an empty string, respectively.
6648 The expansion takes place before the string is processed as a list, and the
6649 file that is searched could contain lines like this:
6651 192.168.3.4: domain1:domain2:...
6652 192.168.1.9: domain3:domain4:...
6654 When the lookup succeeds, the result of the expansion is a list of domains (and
6655 possibly other types of item that are allowed in domain lists).
6656 .cindex "tainted data" "de-tainting"
6657 The result of the expansion is not tainted.
6659 In the second example, the lookup is a single item in a domain list. It causes
6660 Exim to use a lookup to see if the domain that is being processed can be found
6661 in the file. The file could contains lines like this:
6666 Any data that follows the keys is not relevant when checking that the domain
6667 matches the list item.
6669 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6670 Consider a file containing lines like this:
6672 192.168.5.6: lsearch;/another/file
6674 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6675 first &%domains%& setting above generates the second setting, which therefore
6676 causes a second lookup to occur.
6679 The lookup type may optionally be followed by a comma
6680 and a comma-separated list of options.
6681 Each option is a &"name=value"& pair.
6682 Whether an option is meaningful depands on the lookup type.
6684 All lookups support the option &"cache=no_rd"&.
6685 If this is given then the cache that Exim manages for lookup results
6686 is not checked before diong the lookup.
6687 The result of the lookup is still written to the cache.
6690 The rest of this chapter describes the different lookup types that are
6691 available. Any of them can be used in any part of the configuration where a
6692 lookup is permitted.
6695 .section "Lookup types" "SECID61"
6696 .cindex "lookup" "types of"
6697 .cindex "single-key lookup" "definition of"
6698 Two different types of data lookup are implemented:
6701 The &'single-key'& type requires the specification of a file in which to look,
6702 and a single key to search for. The key must be a non-empty string for the
6703 lookup to succeed. The lookup type determines how the file is searched.
6705 .cindex "tainted data" "single-key lookups"
6706 The file string may not be tainted
6708 All single-key lookups support the option &"ret=key"&.
6709 If this is given and the lookup
6710 (either underlying implementation or cached value)
6711 returns data, the result is replaced with a non-tainted
6712 version of the lookup key.
6713 .cindex "tainted data" "de-tainting"
6716 .cindex "query-style lookup" "definition of"
6717 The &'query-style'& type accepts a generalized database query. No particular
6718 key value is assumed by Exim for query-style lookups. You can use whichever
6719 Exim variables you need to construct the database query.
6722 The code for each lookup type is in a separate source file that is included in
6723 the binary of Exim only if the corresponding compile-time option is set. The
6724 default settings in &_src/EDITME_& are:
6729 which means that only linear searching and DBM lookups are included by default.
6730 For some types of lookup (e.g. SQL databases), you need to install appropriate
6731 libraries and header files before building Exim.
6736 .section "Single-key lookup types" "SECTsinglekeylookups"
6737 .cindex "lookup" "single-key types"
6738 .cindex "single-key lookup" "list of types"
6739 The following single-key lookup types are implemented:
6742 .cindex "cdb" "description of"
6743 .cindex "lookup" "cdb"
6744 .cindex "binary zero" "in lookup key"
6745 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6746 string without a terminating binary zero. The cdb format is designed for
6747 indexed files that are read frequently and never updated, except by total
6748 re-creation. As such, it is particularly suitable for large files containing
6749 aliases or other indexed data referenced by an MTA. Information about cdb and
6750 tools for building the files can be found in several places:
6752 &url(https://cr.yp.to/cdb.html)
6753 &url(https://www.corpit.ru/mjt/tinycdb.html)
6754 &url(https://packages.debian.org/stable/utils/freecdb)
6755 &url(https://github.com/philpennock/cdbtools) (in Go)
6757 A cdb distribution is not needed in order to build Exim with cdb support,
6758 because the code for reading cdb files is included directly in Exim itself.
6759 However, no means of building or testing cdb files is provided with Exim, so
6760 you need to obtain a cdb distribution in order to do this.
6762 .cindex "DBM" "lookup type"
6763 .cindex "lookup" "dbm"
6764 .cindex "binary zero" "in lookup key"
6765 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6766 DBM file by looking up the record with the given key. A terminating binary
6767 zero is included in the key that is passed to the DBM library. See section
6768 &<<SECTdb>>& for a discussion of DBM libraries.
6770 .cindex "Berkeley DB library" "file format"
6771 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6772 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6773 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6774 the DB_UNKNOWN option. This enables it to handle any of the types of database
6775 that the library supports, and can be useful for accessing DBM files created by
6776 other applications. (For earlier DB versions, DB_HASH is always used.)
6778 .cindex "lookup" "dbmjz"
6779 .cindex "lookup" "dbm &-- embedded NULs"
6781 .cindex "dbmjz lookup type"
6782 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6783 interpreted as an Exim list; the elements of the list are joined together with
6784 ASCII NUL characters to form the lookup key. An example usage would be to
6785 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6786 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6787 &(cram_md5)& authenticator.
6789 .cindex "lookup" "dbmnz"
6790 .cindex "lookup" "dbm &-- terminating zero"
6791 .cindex "binary zero" "in lookup key"
6793 .cindex "&_/etc/userdbshadow.dat_&"
6794 .cindex "dbmnz lookup type"
6795 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6796 is not included in the key that is passed to the DBM library. You may need this
6797 if you want to look up data in files that are created by or shared with some
6798 other application that does not use terminating zeros. For example, you need to
6799 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6800 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6801 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6802 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6804 .cindex "lookup" "dsearch"
6805 .cindex "dsearch lookup type"
6806 &(dsearch)&: The given file must be an
6810 directory path; this is searched for an entry
6811 whose name is the key by calling the &[lstat()]& function.
6813 contain any forward slash characters.
6814 If &[lstat()]& succeeds then so does the lookup.
6816 .cindex "tainted data" "dsearch result"
6817 The result is regarded as untainted.
6819 Options for the lookup can be given by appending them after the word "dsearch",
6820 separated by a comma. Options, if present, are a comma-separated list having
6821 each element starting with a tag name and an equals.
6823 Two options are supported, for the return value and for filtering match
6825 The "ret" option requests an alternate result value of
6826 the entire path for the entry. Example:
6828 ${lookup {passwd} dsearch,ret=full {/etc}}
6830 The default result is just the requested entry.
6831 The "filter" option requests that only directory entries of a given type
6832 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6833 not matching "." or ".."). Example:
6835 ${lookup {passwd} dsearch,filter=file {/etc}}
6837 The default matching is for any entry type, including directories
6841 An example of how this
6842 lookup can be used to support virtual domains is given in section
6843 &<<SECTvirtualdomains>>&.
6845 .cindex "lookup" "iplsearch"
6846 .cindex "iplsearch lookup type"
6847 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6848 terminated by a colon or white space or the end of the line. The keys in the
6849 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6850 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6851 being interpreted as a key terminator. For example:
6853 1.2.3.4: data for 1.2.3.4
6854 192.168.0.0/16: data for 192.168.0.0/16
6855 "abcd::cdab": data for abcd::cdab
6856 "abcd:abcd::/32" data for abcd:abcd::/32
6858 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6859 file is searched linearly, using the CIDR masks where present, until a matching
6860 key is found. The first key that matches is used; there is no attempt to find a
6861 &"best"& match. Apart from the way the keys are matched, the processing for
6862 &(iplsearch)& is the same as for &(lsearch)&.
6864 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6865 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6866 lookup types support only literal keys.
6868 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6869 the implicit key is the host's IP address rather than its name (see section
6870 &<<SECThoslispatsikey>>&).
6872 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6873 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6874 notation before executing the lookup.)
6877 .cindex json "lookup type"
6878 .cindex JSON expansions
6879 &(json)&: The given file is a text file with a JSON structure.
6880 An element of the structure is extracted, defined by the search key.
6881 The key is a list of subelement selectors
6882 (colon-separated by default but changeable in the usual way)
6883 which are applied in turn to select smaller and smaller portions
6884 of the JSON structure.
6885 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6886 nunbered array element is selected.
6887 Otherwise it must apply to a JSON object; the named element is selected.
6888 The final resulting element can be a simple JSON type or a JSON object
6889 or array; for the latter two a string-representation of the JSON
6891 For elements of type string, the returned value is de-quoted.
6898 .cindex database lmdb
6899 &(lmdb)&: The given file is an LMDB database.
6900 LMDB is a memory-mapped key-value store,
6901 with API modeled loosely on that of BerkeleyDB.
6902 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6903 for the feature set and operation modes.
6905 Exim provides read-only access via the LMDB C library.
6906 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6907 or your operating system package repository.
6908 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6910 You will need to separately create the LMDB database file,
6911 possibly using the &"mdb_load"& utility.
6916 .cindex "linear search"
6917 .cindex "lookup" "lsearch"
6918 .cindex "lsearch lookup type"
6919 .cindex "case sensitivity" "in lsearch lookup"
6920 &(lsearch)&: The given file is a text file that is searched linearly for a
6921 line beginning with the search key, terminated by a colon or white space or the
6922 end of the line. The search is case-insensitive; that is, upper and lower case
6923 letters are treated as the same. The first occurrence of the key that is found
6924 in the file is used.
6926 White space between the key and the colon is permitted. The remainder of the
6927 line, with leading and trailing white space removed, is the data. This can be
6928 continued onto subsequent lines by starting them with any amount of white
6929 space, but only a single space character is included in the data at such a
6930 junction. If the data begins with a colon, the key must be terminated by a
6935 Empty lines and lines beginning with # are ignored, even if they occur in the
6936 middle of an item. This is the traditional textual format of alias files. Note
6937 that the keys in an &(lsearch)& file are literal strings. There is no
6938 wildcarding of any kind.
6940 .cindex "lookup" "lsearch &-- colons in keys"
6941 .cindex "white space" "in lsearch key"
6942 In most &(lsearch)& files, keys are not required to contain colons or #
6943 characters, or white space. However, if you need this feature, it is available.
6944 If a key begins with a doublequote character, it is terminated only by a
6945 matching quote (or end of line), and the normal escaping rules apply to its
6946 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6947 quoted keys (exactly as for unquoted keys). There is no special handling of
6948 quotes for the data part of an &(lsearch)& line.
6951 .cindex "NIS lookup type"
6952 .cindex "lookup" "NIS"
6953 .cindex "binary zero" "in lookup key"
6954 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6955 the given key, without a terminating binary zero. There is a variant called
6956 &(nis0)& which does include the terminating binary zero in the key. This is
6957 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6958 aliases; the full map names must be used.
6961 .cindex "wildlsearch lookup type"
6962 .cindex "lookup" "wildlsearch"
6963 .cindex "nwildlsearch lookup type"
6964 .cindex "lookup" "nwildlsearch"
6965 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6966 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6967 the file may be wildcarded. The difference between these two lookup types is
6968 that for &(wildlsearch)&, each key in the file is string-expanded before being
6969 used, whereas for &(nwildlsearch)&, no expansion takes place.
6971 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6972 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6973 file that are regular expressions can be made case-sensitive by the use of
6974 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6976 . ==== As this is a nested list, any displays it contains must be indented
6977 . ==== as otherwise they are too far to the left.
6980 The string may begin with an asterisk to mean &"ends with"&. For example:
6982 *.a.b.c data for anything.a.b.c
6983 *fish data for anythingfish
6986 The string may begin with a circumflex to indicate a regular expression. For
6987 example, for &(wildlsearch)&:
6989 ^\N\d+\.a\.b\N data for <digits>.a.b
6991 Note the use of &`\N`& to disable expansion of the contents of the regular
6992 expression. If you are using &(nwildlsearch)&, where the keys are not
6993 string-expanded, the equivalent entry is:
6995 ^\d+\.a\.b data for <digits>.a.b
6997 The case-insensitive flag is set at the start of compiling the regular
6998 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6999 For example, to make the entire pattern case-sensitive:
7001 ^(?-i)\d+\.a\.b data for <digits>.a.b
7004 If the regular expression contains white space or colon characters, you must
7005 either quote it (see &(lsearch)& above), or represent these characters in other
7006 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7007 colon. This may be easier than quoting, because if you quote, you have to
7008 escape all the backslashes inside the quotes.
7010 &*Note*&: It is not possible to capture substrings in a regular expression
7011 match for later use, because the results of all lookups are cached. If a lookup
7012 is repeated, the result is taken from the cache, and no actual pattern matching
7013 takes place. The values of all the numeric variables are unset after a
7014 &((n)wildlsearch)& match.
7017 Although I cannot see it being of much use, the general matching function that
7018 is used to implement &((n)wildlsearch)& means that the string may begin with a
7019 lookup name terminated by a semicolon, and followed by lookup data. For
7022 cdb;/some/file data for keys that match the file
7024 The data that is obtained from the nested lookup is discarded.
7027 Keys that do not match any of these patterns are interpreted literally. The
7028 continuation rules for the data are the same as for &(lsearch)&, and keys may
7029 be followed by optional colons.
7031 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7032 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7033 lookup types support only literal keys.
7036 .cindex "spf lookup type"
7037 .cindex "lookup" "spf"
7038 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7039 (as opposed to the standard ACL condition method).
7040 For details see section &<<SECSPF>>&.
7044 .section "Query-style lookup types" "SECTquerystylelookups"
7045 .cindex "lookup" "query-style types"
7046 .cindex "query-style lookup" "list of types"
7047 The supported query-style lookup types are listed below. Further details about
7048 many of them are given in later sections.
7051 .cindex "DNS" "as a lookup type"
7052 .cindex "lookup" "DNS"
7053 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7054 are given in the supplied query. The resulting data is the contents of the
7055 records. See section &<<SECTdnsdb>>&.
7057 .cindex "InterBase lookup type"
7058 .cindex "lookup" "InterBase"
7059 &(ibase)&: This does a lookup in an InterBase database.
7061 .cindex "LDAP" "lookup type"
7062 .cindex "lookup" "LDAP"
7063 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7064 returns attributes from a single entry. There is a variant called &(ldapm)&
7065 that permits values from multiple entries to be returned. A third variant
7066 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7067 any attribute values. See section &<<SECTldap>>&.
7069 .cindex "MySQL" "lookup type"
7070 .cindex "lookup" "MySQL"
7071 &(mysql)&: The format of the query is an SQL statement that is passed to a
7072 MySQL database. See section &<<SECTsql>>&.
7074 .cindex "NIS+ lookup type"
7075 .cindex "lookup" "NIS+"
7076 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7077 the field to be returned. See section &<<SECTnisplus>>&.
7079 .cindex "Oracle" "lookup type"
7080 .cindex "lookup" "Oracle"
7081 &(oracle)&: The format of the query is an SQL statement that is passed to an
7082 Oracle database. See section &<<SECTsql>>&.
7084 .cindex "lookup" "passwd"
7085 .cindex "passwd lookup type"
7086 .cindex "&_/etc/passwd_&"
7087 &(passwd)& is a query-style lookup with queries that are just user names. The
7088 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7089 success, the result string is the same as you would get from an &(lsearch)&
7090 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7091 password value. For example:
7093 *:42:42:King Rat:/home/kr:/bin/bash
7096 .cindex "PostgreSQL lookup type"
7097 .cindex "lookup" "PostgreSQL"
7098 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7099 PostgreSQL database. See section &<<SECTsql>>&.
7102 .cindex "Redis lookup type"
7103 .cindex lookup Redis
7104 &(redis)&: The format of the query is either a simple get or simple set,
7105 passed to a Redis database. See section &<<SECTsql>>&.
7108 .cindex "sqlite lookup type"
7109 .cindex "lookup" "sqlite"
7110 &(sqlite)&: The format of the query is
7112 an optional filename
7114 followed by an SQL statement
7115 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7118 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7119 not likely to be useful in normal operation.
7121 .cindex "whoson lookup type"
7122 .cindex "lookup" "whoson"
7123 . --- still http:-only, 2018-09-07
7124 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7125 allows a server to check whether a particular (dynamically allocated) IP
7126 address is currently allocated to a known (trusted) user and, optionally, to
7127 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7128 at one time for &"POP before SMTP"& authentication, but that approach has been
7129 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7130 &"POP before SMTP"& checking using ACL statements such as
7132 require condition = \
7133 ${lookup whoson {$sender_host_address}{yes}{no}}
7135 The query consists of a single IP address. The value returned is the name of
7136 the authenticated user, which is stored in the variable &$value$&. However, in
7137 this example, the data in &$value$& is not used; the result of the lookup is
7138 one of the fixed strings &"yes"& or &"no"&.
7143 .section "Temporary errors in lookups" "SECID63"
7144 .cindex "lookup" "temporary error in"
7145 Lookup functions can return temporary error codes if the lookup cannot be
7146 completed. For example, an SQL or LDAP database might be unavailable. For this
7147 reason, it is not advisable to use a lookup that might do this for critical
7148 options such as a list of local domains.
7150 When a lookup cannot be completed in a router or transport, delivery
7151 of the message (to the relevant address) is deferred, as for any other
7152 temporary error. In other circumstances Exim may assume the lookup has failed,
7153 or may give up altogether.
7157 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7158 .cindex "wildcard lookups"
7159 .cindex "lookup" "default values"
7160 .cindex "lookup" "wildcard"
7161 .cindex "lookup" "* added to type"
7162 .cindex "default" "in single-key lookups"
7163 In this context, a &"default value"& is a value specified by the administrator
7164 that is to be used if a lookup fails.
7166 &*Note:*& This section applies only to single-key lookups. For query-style
7167 lookups, the facilities of the query language must be used. An attempt to
7168 specify a default for a query-style lookup provokes an error.
7170 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7171 and the initial lookup fails, the key &"*"& is looked up in the file to
7172 provide a default value. See also the section on partial matching below.
7174 .cindex "*@ with single-key lookup"
7175 .cindex "lookup" "*@ added to type"
7176 .cindex "alias file" "per-domain default"
7177 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7178 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7179 character, a second lookup is done with everything before the last @ replaced
7180 by *. This makes it possible to provide per-domain defaults in alias files
7181 that include the domains in the keys. If the second lookup fails (or doesn't
7182 take place because there is no @ in the key), &"*"& is looked up.
7183 For example, a &(redirect)& router might contain:
7185 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7187 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7188 looks up these keys, in this order:
7194 The data is taken from whichever key it finds first. &*Note*&: In an
7195 &(lsearch)& file, this does not mean the first of these keys in the file. A
7196 complete scan is done for each key, and only if it is not found at all does
7197 Exim move on to try the next key.
7201 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7202 .cindex "partial matching"
7203 .cindex "wildcard lookups"
7204 .cindex "lookup" "partial matching"
7205 .cindex "lookup" "wildcard"
7206 .cindex "asterisk" "in search type"
7207 The normal operation of a single-key lookup is to search the file for an exact
7208 match with the given key. However, in a number of situations where domains are
7209 being looked up, it is useful to be able to do partial matching. In this case,
7210 information in the file that has a key starting with &"*."& is matched by any
7211 domain that ends with the components that follow the full stop. For example, if
7212 a key in a DBM file is
7214 *.dates.fict.example
7216 then when partial matching is enabled this is matched by (amongst others)
7217 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7218 by &'dates.fict.example'&, if that does not appear as a separate key in the
7221 &*Note*&: Partial matching is not available for query-style lookups. It is
7222 also not available for any lookup items in address lists (see section
7223 &<<SECTaddresslist>>&).
7225 Partial matching is implemented by doing a series of separate lookups using
7226 keys constructed by modifying the original subject key. This means that it can
7227 be used with any of the single-key lookup types, provided that
7228 partial matching keys
7229 beginning with a special prefix (default &"*."&) are included in the data file.
7230 Keys in the file that do not begin with the prefix are matched only by
7231 unmodified subject keys when partial matching is in use.
7233 Partial matching is requested by adding the string &"partial-"& to the front of
7234 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7235 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7236 is added at the start of the subject key, and it is looked up again. If that
7237 fails, further lookups are tried with dot-separated components removed from the
7238 start of the subject key, one-by-one, and &"*."& added on the front of what
7241 A minimum number of two non-* components are required. This can be adjusted
7242 by including a number before the hyphen in the search type. For example,
7243 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7244 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7245 subject key is &'2250.dates.fict.example'& then the following keys are looked
7246 up when the minimum number of non-* components is two:
7248 2250.dates.fict.example
7249 *.2250.dates.fict.example
7250 *.dates.fict.example
7253 As soon as one key in the sequence is successfully looked up, the lookup
7256 .cindex "lookup" "partial matching &-- changing prefix"
7257 .cindex "prefix" "for partial matching"
7258 The use of &"*."& as the partial matching prefix is a default that can be
7259 changed. The motivation for this feature is to allow Exim to operate with file
7260 formats that are used by other MTAs. A different prefix can be supplied in
7261 parentheses instead of the hyphen after &"partial"&. For example:
7263 domains = partial(.)lsearch;/some/file
7265 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7266 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7267 components is unchanged). The prefix may consist of any punctuation characters
7268 other than a closing parenthesis. It may be empty, for example:
7270 domains = partial1()cdb;/some/file
7272 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7273 &`a.b.c`&, &`b.c`&, and &`c`&.
7275 If &"partial0"& is specified, what happens at the end (when the lookup with
7276 just one non-wild component has failed, and the original key is shortened right
7277 down to the null string) depends on the prefix:
7280 If the prefix has zero length, the whole lookup fails.
7282 If the prefix has length 1, a lookup for just the prefix is done. For
7283 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7285 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7286 remainder is looked up. With the default prefix, therefore, the final lookup is
7287 for &"*"& on its own.
7289 Otherwise, the whole prefix is looked up.
7293 If the search type ends in &"*"& or &"*@"& (see section
7294 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7295 this implies happens after all partial lookups have failed. If &"partial0"& is
7296 specified, adding &"*"& to the search type has no effect with the default
7297 prefix, because the &"*"& key is already included in the sequence of partial
7298 lookups. However, there might be a use for lookup types such as
7299 &"partial0(.)lsearch*"&.
7301 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7302 in domain lists and the like. Partial matching works only in terms of
7303 dot-separated components; a key such as &`*fict.example`&
7304 in a database file is useless, because the asterisk in a partial matching
7305 subject key is always followed by a dot.
7310 .section "Lookup caching" "SECID64"
7311 .cindex "lookup" "caching"
7312 .cindex "caching" "lookup data"
7313 Exim caches all lookup results in order to avoid needless repetition of
7314 lookups. However, because (apart from the daemon) Exim operates as a collection
7315 of independent, short-lived processes, this caching applies only within a
7316 single Exim process. There is no inter-process lookup caching facility.
7318 For single-key lookups, Exim keeps the relevant files open in case there is
7319 another lookup that needs them. In some types of configuration this can lead to
7320 many files being kept open for messages with many recipients. To avoid hitting
7321 the operating system limit on the number of simultaneously open files, Exim
7322 closes the least recently used file when it needs to open more files than its
7323 own internal limit, which can be changed via the &%lookup_open_max%& option.
7325 The single-key lookup files are closed and the lookup caches are flushed at
7326 strategic points during delivery &-- for example, after all routing is
7332 .section "Quoting lookup data" "SECID65"
7333 .cindex "lookup" "quoting"
7334 .cindex "quoting" "in lookups"
7335 When data from an incoming message is included in a query-style lookup, there
7336 is the possibility of special characters in the data messing up the syntax of
7337 the query. For example, a NIS+ query that contains
7341 will be broken if the local part happens to contain a closing square bracket.
7342 For NIS+, data can be enclosed in double quotes like this:
7344 [name="$local_part"]
7346 but this still leaves the problem of a double quote in the data. The rule for
7347 NIS+ is that double quotes must be doubled. Other lookup types have different
7348 rules, and to cope with the differing requirements, an expansion operator
7349 of the following form is provided:
7351 ${quote_<lookup-type>:<string>}
7353 For example, the safest way to write the NIS+ query is
7355 [name="${quote_nisplus:$local_part}"]
7357 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7358 operator can be used for all lookup types, but has no effect for single-key
7359 lookups, since no quoting is ever needed in their key strings.
7364 .section "More about dnsdb" "SECTdnsdb"
7365 .cindex "dnsdb lookup"
7366 .cindex "lookup" "dnsdb"
7367 .cindex "DNS" "as a lookup type"
7368 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7369 of a record type and a domain name, separated by an equals sign. For example,
7370 an expansion string could contain:
7372 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7374 If the lookup succeeds, the result is placed in &$value$&, which in this case
7375 is used on its own as the result. If the lookup does not succeed, the
7376 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7377 &<<SECTforexpfai>>& for an explanation of what this means.
7379 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7380 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7381 If no type is given, TXT is assumed.
7383 For any record type, if multiple records are found, the data is returned as a
7384 concatenation, with newline as the default separator. The order, of course,
7385 depends on the DNS resolver. You can specify a different separator character
7386 between multiple records by putting a right angle-bracket followed immediately
7387 by the new separator at the start of the query. For example:
7389 ${lookup dnsdb{>: a=host1.example}}
7391 It is permitted to specify a space as the separator character. Further
7392 white space is ignored.
7393 For lookup types that return multiple fields per record,
7394 an alternate field separator can be specified using a comma after the main
7395 separator character, followed immediately by the field separator.
7397 .cindex "PTR record" "in &(dnsdb)& lookup"
7398 When the type is PTR,
7399 the data can be an IP address, written as normal; inversion and the addition of
7400 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7402 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7404 If the data for a PTR record is not a syntactically valid IP address, it is not
7405 altered and nothing is added.
7407 .cindex "MX record" "in &(dnsdb)& lookup"
7408 .cindex "SRV record" "in &(dnsdb)& lookup"
7409 For an MX lookup, both the preference value and the host name are returned for
7410 each record, separated by a space. For an SRV lookup, the priority, weight,
7411 port, and host name are returned for each record, separated by spaces.
7412 The field separator can be modified as above.
7414 .cindex "TXT record" "in &(dnsdb)& lookup"
7415 .cindex "SPF record" "in &(dnsdb)& lookup"
7416 For TXT records with multiple items of data, only the first item is returned,
7417 unless a field separator is specified.
7418 To concatenate items without a separator, use a semicolon instead.
7420 default behaviour is to concatenate multiple items without using a separator.
7422 ${lookup dnsdb{>\n,: txt=a.b.example}}
7423 ${lookup dnsdb{>\n; txt=a.b.example}}
7424 ${lookup dnsdb{spf=example.org}}
7426 It is permitted to specify a space as the separator character. Further
7427 white space is ignored.
7429 .cindex "SOA record" "in &(dnsdb)& lookup"
7430 For an SOA lookup, while no result is obtained the lookup is redone with
7431 successively more leading components dropped from the given domain.
7432 Only the primary-nameserver field is returned unless a field separator is
7435 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7438 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7439 .cindex "dnsdb modifiers"
7440 .cindex "modifiers" "dnsdb"
7441 .cindex "options" "dnsdb"
7442 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7443 each followed by a comma,
7444 that may appear before the record type.
7446 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7447 temporary DNS error for any of them, the behaviour is controlled by
7448 a defer-option modifier.
7449 The possible keywords are
7450 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7451 With &"strict"& behaviour, any temporary DNS error causes the
7452 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7453 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7454 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7455 error causes the whole lookup to defer only if none of the other lookups
7456 succeed. The default is &"lax"&, so the following lookups are equivalent:
7458 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7459 ${lookup dnsdb{a=one.host.com:two.host.com}}
7461 Thus, in the default case, as long as at least one of the DNS lookups
7462 yields some data, the lookup succeeds.
7464 .cindex "DNSSEC" "dns lookup"
7465 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7466 The possible keywords are
7467 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7468 With &"strict"& or &"lax"& DNSSEC information is requested
7470 With &"strict"& a response from the DNS resolver that
7471 is not labelled as authenticated data
7472 is treated as equivalent to a temporary DNS error.
7473 The default is &"lax"&.
7475 See also the &$lookup_dnssec_authenticated$& variable.
7477 .cindex timeout "dns lookup"
7478 .cindex "DNS" timeout
7479 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7480 The form is &"retrans_VAL"& where VAL is an Exim time specification
7482 The default value is set by the main configuration option &%dns_retrans%&.
7484 Retries for the dnsdb lookup can be controlled by a retry modifier.
7485 The form if &"retry_VAL"& where VAL is an integer.
7486 The default count is set by the main configuration option &%dns_retry%&.
7488 .cindex caching "of dns lookup"
7489 .cindex TTL "of dns lookup"
7491 Dnsdb lookup results are cached within a single process (and its children).
7492 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7493 value of the set of returned DNS records.
7496 .section "Pseudo dnsdb record types" "SECID66"
7497 .cindex "MX record" "in &(dnsdb)& lookup"
7498 By default, both the preference value and the host name are returned for
7499 each MX record, separated by a space. If you want only host names, you can use
7500 the pseudo-type MXH:
7502 ${lookup dnsdb{mxh=a.b.example}}
7504 In this case, the preference values are omitted, and just the host names are
7507 .cindex "name server for enclosing domain"
7508 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7509 records on the given domain, but if none are found, it removes the first
7510 component of the domain name, and tries again. This process continues until NS
7511 records are found or there are no more components left (or there is a DNS
7512 error). In other words, it may return the name servers for a top-level domain,
7513 but it never returns the root name servers. If there are no NS records for the
7514 top-level domain, the lookup fails. Consider these examples:
7516 ${lookup dnsdb{zns=xxx.quercite.com}}
7517 ${lookup dnsdb{zns=xxx.edu}}
7519 Assuming that in each case there are no NS records for the full domain name,
7520 the first returns the name servers for &%quercite.com%&, and the second returns
7521 the name servers for &%edu%&.
7523 You should be careful about how you use this lookup because, unless the
7524 top-level domain does not exist, the lookup always returns some host names. The
7525 sort of use to which this might be put is for seeing if the name servers for a
7526 given domain are on a blacklist. You can probably assume that the name servers
7527 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7530 .cindex "CSA" "in &(dnsdb)& lookup"
7531 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7532 records according to the CSA rules, which are described in section
7533 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7534 not sufficient because of the extra parent domain search behaviour of CSA. The
7535 result of a successful lookup such as:
7537 ${lookup dnsdb {csa=$sender_helo_name}}
7539 has two space-separated fields: an authorization code and a target host name.
7540 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7541 authorization required but absent, or &"?"& for unknown.
7543 .cindex "A+" "in &(dnsdb)& lookup"
7544 The pseudo-type A+ performs an AAAA
7545 and then an A lookup. All results are returned; defer processing
7546 (see below) is handled separately for each lookup. Example:
7548 ${lookup dnsdb {>; a+=$sender_helo_name}}
7552 .section "Multiple dnsdb lookups" "SECID67"
7553 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7554 However, you can specify a list of domains or IP addresses in a single
7555 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7556 the default separator, but with the ability to change this. For example:
7558 ${lookup dnsdb{one.domain.com:two.domain.com}}
7559 ${lookup dnsdb{a=one.host.com:two.host.com}}
7560 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7562 In order to retain backwards compatibility, there is one special case: if
7563 the lookup type is PTR and no change of separator is specified, Exim looks
7564 to see if the rest of the string is precisely one IPv6 address. In this
7565 case, it does not treat it as a list.
7567 The data from each lookup is concatenated, with newline separators by default,
7568 in the same way that multiple DNS records for a single item are handled. A
7569 different separator can be specified, as described above.
7574 .section "More about LDAP" "SECTldap"
7575 .cindex "LDAP" "lookup, more about"
7576 .cindex "lookup" "LDAP"
7577 .cindex "Solaris" "LDAP"
7578 The original LDAP implementation came from the University of Michigan; this has
7579 become &"Open LDAP"&, and there are now two different releases. Another
7580 implementation comes from Netscape, and Solaris 7 and subsequent releases
7581 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7582 the lookup function level, their error handling is different. For this reason
7583 it is necessary to set a compile-time variable when building Exim with LDAP, to
7584 indicate which LDAP library is in use. One of the following should appear in
7585 your &_Local/Makefile_&:
7587 LDAP_LIB_TYPE=UMICHIGAN
7588 LDAP_LIB_TYPE=OPENLDAP1
7589 LDAP_LIB_TYPE=OPENLDAP2
7590 LDAP_LIB_TYPE=NETSCAPE
7591 LDAP_LIB_TYPE=SOLARIS
7593 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7594 same interface as the University of Michigan version.
7596 There are three LDAP lookup types in Exim. These behave slightly differently in
7597 the way they handle the results of a query:
7600 &(ldap)& requires the result to contain just one entry; if there are more, it
7603 &(ldapdn)& also requires the result to contain just one entry, but it is the
7604 Distinguished Name that is returned rather than any attribute values.
7606 &(ldapm)& permits the result to contain more than one entry; the attributes
7607 from all of them are returned.
7611 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7612 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7613 the data returned by a successful lookup is described in the next section.
7614 First we explain how LDAP queries are coded.
7617 .section "Format of LDAP queries" "SECTforldaque"
7618 .cindex "LDAP" "query format"
7619 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7620 the configuration of a &(redirect)& router one might have this setting:
7622 data = ${lookup ldap \
7623 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7624 c=UK?mailbox?base?}}
7626 .cindex "LDAP" "with TLS"
7627 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7628 secure (encrypted) LDAP connections. The second of these ensures that an
7629 encrypted TLS connection is used.
7631 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7632 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7633 See the &%ldap_start_tls%& option.
7635 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7636 controlled. Every part of the TLS configuration can be configured by settings in
7637 &_exim.conf_&. Depending on the version of the client libraries installed on
7638 your system, some of the initialization may have required setting options in
7639 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7640 certificates. This revealed a nuance where the current UID that exim was
7641 running as could affect which config files it read. With Exim 4.83, these
7642 methods become optional, only taking effect if not specifically set in
7646 .section "LDAP quoting" "SECID68"
7647 .cindex "LDAP" "quoting"
7648 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7649 and the second because the LDAP query is represented as a URL. Furthermore,
7650 within an LDAP query, two different kinds of quoting are required. For this
7651 reason, there are two different LDAP-specific quoting operators.
7653 The &%quote_ldap%& operator is designed for use on strings that are part of
7654 filter specifications. Conceptually, it first does the following conversions on
7662 in accordance with RFC 2254. The resulting string is then quoted according
7663 to the rules for URLs, that is, all non-alphanumeric characters except
7667 are converted to their hex values, preceded by a percent sign. For example:
7669 ${quote_ldap: a(bc)*, a<yz>; }
7673 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7675 Removing the URL quoting, this is (with a leading and a trailing space):
7677 a\28bc\29\2A, a<yz>;
7679 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7680 base DN specifications in queries. Conceptually, it first converts the string
7681 by inserting a backslash in front of any of the following characters:
7685 It also inserts a backslash before any leading spaces or # characters, and
7686 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7687 is then quoted according to the rules for URLs. For example:
7689 ${quote_ldap_dn: a(bc)*, a<yz>; }
7693 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7695 Removing the URL quoting, this is (with a trailing space):
7697 \ a(bc)*\, a\<yz\>\;\
7699 There are some further comments about quoting in the section on LDAP
7700 authentication below.
7703 .section "LDAP connections" "SECID69"
7704 .cindex "LDAP" "connections"
7705 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7706 is in use, via a Unix domain socket. The example given above does not specify
7707 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7710 ldap://<hostname>:<port>/...
7712 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7713 used. When no server is specified in a query, a list of default servers is
7714 taken from the &%ldap_default_servers%& configuration option. This supplies a
7715 colon-separated list of servers which are tried in turn until one successfully
7716 handles a query, or there is a serious error. Successful handling either
7717 returns the requested data, or indicates that it does not exist. Serious errors
7718 are syntactical, or multiple values when only a single value is expected.
7719 Errors which cause the next server to be tried are connection failures, bind
7720 failures, and timeouts.
7722 For each server name in the list, a port number can be given. The standard way
7723 of specifying a host and port is to use a colon separator (RFC 1738). Because
7724 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7725 doubled. For example
7727 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7729 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7730 to the LDAP library with no server name, and the library's default (normally
7731 the local host) is used.
7733 If you are using the OpenLDAP library, you can connect to an LDAP server using
7734 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7735 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7736 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7739 For this type of connection, instead of a host name for the server, a pathname
7740 for the socket is required, and the port number is not relevant. The pathname
7741 can be specified either as an item in &%ldap_default_servers%&, or inline in
7742 the query. In the former case, you can have settings such as
7744 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7746 When the pathname is given in the query, you have to escape the slashes as
7747 &`%2F`& to fit in with the LDAP URL syntax. For example:
7749 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7751 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7752 a pathname, it uses the Unix domain socket code, even if the query actually
7753 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7754 socket connection. This behaviour means that you can use a setting of
7755 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7756 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7757 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7760 If an explicit &`ldapi`& type is given in a query when a host name is
7761 specified, an error is diagnosed. However, if there are more items in
7762 &%ldap_default_servers%&, they are tried. In other words:
7765 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7768 Using &`ldapi`& with a host name causes an error.
7772 Using &`ldapi`& with no host or path in the query, and no setting of
7773 &%ldap_default_servers%&, does whatever the library does by default.
7777 .section "LDAP authentication and control information" "SECID70"
7778 .cindex "LDAP" "authentication"
7779 The LDAP URL syntax provides no way of passing authentication and other control
7780 information to the server. To make this possible, the URL in an LDAP query may
7781 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7782 spaces. If a value contains spaces it must be enclosed in double quotes, and
7783 when double quotes are used, backslash is interpreted in the usual way inside
7784 them. The following names are recognized:
7786 &`DEREFERENCE`& set the dereferencing parameter
7787 &`NETTIME `& set a timeout for a network operation
7788 &`USER `& set the DN, for authenticating the LDAP bind
7789 &`PASS `& set the password, likewise
7790 &`REFERRALS `& set the referrals parameter
7791 &`SERVERS `& set alternate server list for this query only
7792 &`SIZE `& set the limit for the number of entries returned
7793 &`TIME `& set the maximum waiting time for a query
7795 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7796 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7797 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7798 library from trying to follow referrals issued by the LDAP server.
7800 .cindex LDAP timeout
7801 .cindex timeout "LDAP lookup"
7802 The name CONNECT is an obsolete name for NETTIME, retained for
7803 backwards compatibility. This timeout (specified as a number of seconds) is
7804 enforced from the client end for operations that can be carried out over a
7805 network. Specifically, it applies to network connections and calls to the
7806 &'ldap_result()'& function. If the value is greater than zero, it is used if
7807 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7808 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7809 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7810 Netscape SDK; for OpenLDAP no action is taken.
7812 The TIME parameter (also a number of seconds) is passed to the server to
7813 set a server-side limit on the time taken to complete a search.
7815 The SERVERS parameter allows you to specify an alternate list of ldap servers
7816 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7817 default list of ldap servers, and a single lookup can specify a single ldap
7818 server to use. But when you need to do a lookup with a list of servers that is
7819 different than the default list (maybe different order, maybe a completely
7820 different set of servers), the SERVERS parameter allows you to specify this
7821 alternate list (colon-separated).
7823 Here is an example of an LDAP query in an Exim lookup that uses some of these
7824 values. This is a single line, folded to fit on the page:
7827 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7828 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7831 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7832 any of the auxiliary data. Exim configuration settings that include lookups
7833 which contain password information should be preceded by &"hide"& to prevent
7834 non-admin users from using the &%-bP%& option to see their values.
7836 The auxiliary data items may be given in any order. The default is no
7837 connection timeout (the system timeout is used), no user or password, no limit
7838 on the number of entries returned, and no time limit on queries.
7840 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7841 removes any URL quoting that it may contain before passing it LDAP. Apparently
7842 some libraries do this for themselves, but some do not. Removing the URL
7843 quoting has two advantages:
7846 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7847 DNs as with DNs inside actual queries.
7849 It permits spaces inside USER= DNs.
7852 For example, a setting such as
7854 USER=cn=${quote_ldap_dn:$1}
7856 should work even if &$1$& contains spaces.
7858 Expanded data for the PASS= value should be quoted using the &%quote%&
7859 expansion operator, rather than the LDAP quote operators. The only reason this
7860 field needs quoting is to ensure that it conforms to the Exim syntax, which
7861 does not allow unquoted spaces. For example:
7865 The LDAP authentication mechanism can be used to check passwords as part of
7866 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7871 .section "Format of data returned by LDAP" "SECID71"
7872 .cindex "LDAP" "returned data formats"
7873 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7874 as a sequence of values, for example
7876 cn=manager,o=University of Cambridge,c=UK
7878 The &(ldap)& lookup type generates an error if more than one entry matches the
7879 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7880 the result between the data from different entries. It is possible for multiple
7881 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7882 you know that whatever values are returned all came from a single entry in the
7885 In the common case where you specify a single attribute in your LDAP query, the
7886 result is not quoted, and does not contain the attribute name. If the attribute
7887 has multiple values, they are separated by commas. Any comma that is
7888 part of an attribute's value is doubled.
7890 If you specify multiple attributes, the result contains space-separated, quoted
7891 strings, each preceded by the attribute name and an equals sign. Within the
7892 quotes, the quote character, backslash, and newline are escaped with
7893 backslashes, and commas are used to separate multiple values for the attribute.
7894 Any commas in attribute values are doubled
7895 (permitting treatment of the values as a comma-separated list).
7896 Apart from the escaping, the string within quotes takes the same form as the
7897 output when a single attribute is requested. Specifying no attributes is the
7898 same as specifying all of an entry's attributes.
7900 Here are some examples of the output format. The first line of each pair is an
7901 LDAP query, and the second is the data that is returned. The attribute called
7902 &%attr1%& has two values, one of them with an embedded comma, whereas
7903 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7904 (they have SUP &%attr%& in their schema definitions).
7907 ldap:///o=base?attr1?sub?(uid=fred)
7910 ldap:///o=base?attr2?sub?(uid=fred)
7913 ldap:///o=base?attr?sub?(uid=fred)
7914 value1.1,value1,,2,value two
7916 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7917 attr1="value1.1,value1,,2" attr2="value two"
7919 ldap:///o=base??sub?(uid=fred)
7920 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7923 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7924 results of LDAP lookups.
7925 The &%extract%& operator in string expansions can be used to pick out
7926 individual fields from data that consists of &'key'&=&'value'& pairs.
7927 The &%listextract%& operator should be used to pick out individual values
7928 of attributes, even when only a single value is expected.
7929 The doubling of embedded commas allows you to use the returned data as a
7930 comma separated list (using the "<," syntax for changing the input list separator).
7935 .section "More about NIS+" "SECTnisplus"
7936 .cindex "NIS+ lookup type"
7937 .cindex "lookup" "NIS+"
7938 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7939 and field name. If this is given, the result of a successful query is the
7940 contents of the named field; otherwise the result consists of a concatenation
7941 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7942 values containing spaces are quoted. For example, the query
7944 [name=mg1456],passwd.org_dir
7946 might return the string
7948 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7949 home=/home/mg1456 shell=/bin/bash shadow=""
7951 (split over two lines here to fit on the page), whereas
7953 [name=mg1456],passwd.org_dir:gcos
7959 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7960 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7961 operator is to double any quote characters within the text.
7965 .section "SQL lookups" "SECTsql"
7966 .cindex "SQL lookup types"
7967 .cindex "MySQL" "lookup type"
7968 .cindex "PostgreSQL lookup type"
7969 .cindex "lookup" "MySQL"
7970 .cindex "lookup" "PostgreSQL"
7971 .cindex "Oracle" "lookup type"
7972 .cindex "lookup" "Oracle"
7973 .cindex "InterBase lookup type"
7974 .cindex "lookup" "InterBase"
7975 .cindex "Redis lookup type"
7976 .cindex lookup Redis
7977 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7979 databases. Queries for these databases contain SQL statements, so an example
7982 ${lookup mysql{select mailbox from users where id='userx'}\
7985 If the result of the query contains more than one field, the data for each
7986 field in the row is returned, preceded by its name, so the result of
7988 ${lookup pgsql{select home,name from users where id='userx'}\
7993 home=/home/userx name="Mister X"
7995 Empty values and values containing spaces are double quoted, with embedded
7996 quotes escaped by a backslash. If the result of the query contains just one
7997 field, the value is passed back verbatim, without a field name, for example:
8001 If the result of the query yields more than one row, it is all concatenated,
8002 with a newline between the data for each row.
8005 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8006 .cindex "MySQL" "lookup type"
8007 .cindex "PostgreSQL lookup type"
8008 .cindex "lookup" "MySQL"
8009 .cindex "lookup" "PostgreSQL"
8010 .cindex "Oracle" "lookup type"
8011 .cindex "lookup" "Oracle"
8012 .cindex "InterBase lookup type"
8013 .cindex "lookup" "InterBase"
8014 .cindex "Redis lookup type"
8015 .cindex lookup Redis
8016 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8017 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8018 or &%redis_servers%&
8019 option (as appropriate) must be set to a colon-separated list of server
8021 .oindex &%mysql_servers%&
8022 .oindex &%pgsql_servers%&
8023 .oindex &%oracle_servers%&
8024 .oindex &%ibase_servers%&
8025 .oindex &%redis_servers%&
8026 (For MySQL and PostgreSQL, the global option need not be set if all
8027 queries contain their own server information &-- see section
8028 &<<SECTspeserque>>&.)
8030 each item in the list is a slash-separated list of four
8031 items: host name, database name, user name, and password. In the case of
8032 Oracle, the host name field is used for the &"service name"&, and the database
8033 name field is not used and should be empty. For example:
8035 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8037 Because password data is sensitive, you should always precede the setting with
8038 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8039 option. Here is an example where two MySQL servers are listed:
8041 hide mysql_servers = localhost/users/root/secret:\
8042 otherhost/users/root/othersecret
8044 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8045 because this is a colon-separated list, the colon has to be doubled. For each
8046 query, these parameter groups are tried in order until a connection is made and
8047 a query is successfully processed. The result of a query may be that no data is
8048 found, but that is still a successful query. In other words, the list of
8049 servers provides a backup facility, not a list of different places to look.
8051 For Redis the global option need not be specified if all queries contain their
8052 own server information &-- see section &<<SECTspeserque>>&.
8053 If specified, the option must be set to a colon-separated list of server
8055 Each item in the list is a slash-separated list of three items:
8056 host, database number, and password.
8058 The host is required and may be either an IPv4 address and optional
8059 port number (separated by a colon, which needs doubling due to the
8060 higher-level list), or a Unix socket pathname enclosed in parentheses
8062 The database number is optional; if present that number is selected in the backend
8064 The password is optional; if present it is used to authenticate to the backend
8067 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8068 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8069 respectively, and the characters single-quote, double-quote, and backslash
8070 itself are escaped with backslashes.
8072 The &%quote_redis%& expansion operator
8073 escapes whitespace and backslash characters with a backslash.
8075 .section "Specifying the server in the query" "SECTspeserque"
8077 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8078 it is possible to specify a list of servers with an individual query. This is
8079 done by appending a comma-separated option to the query type:
8082 &`,servers=`&&'server1:server2:server3:...'&
8084 Each item in the list may take one of two forms:
8086 If it contains no slashes it is assumed to be just a host name. The appropriate
8087 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8088 of the same name, and the remaining parameters (database, user, password) are
8091 If it contains any slashes, it is taken as a complete parameter set.
8093 The list of servers is used in exactly the same way as the global list.
8094 Once a connection to a server has happened and a query has been
8095 successfully executed, processing of the lookup ceases.
8097 This feature is intended for use in master/slave situations where updates
8098 are occurring and you want to update the master rather than a slave. If the
8099 master is in the list as a backup for reading, you might have a global setting
8102 mysql_servers = slave1/db/name/pw:\
8106 In an updating lookup, you could then write:
8108 ${lookup mysql,servers=master {UPDATE ...} }
8110 That query would then be sent only to the master server. If, on the other hand,
8111 the master is not to be used for reading, and so is not present in the global
8112 option, you can still update it by a query of this form:
8114 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8118 An older syntax places the servers speciification before the qury,
8119 semicolon separated:
8121 ${lookup mysql{servers=master; UPDATE ...} }
8123 The new version avoids potential issues with tainted
8124 arguments in the query, for explicit expansion.
8125 &*Note*&: server specifications in list-style lookups are still problematic.
8129 .section "Special MySQL features" "SECID73"
8130 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8131 causes a connection to the server on the local host by means of a Unix domain
8132 socket. An alternate socket can be specified in parentheses.
8133 An option group name for MySQL option files can be specified in square brackets;
8134 the default value is &"exim"&.
8135 The full syntax of each item in &%mysql_servers%& is:
8137 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8138 <&'database'&>/<&'user'&>/<&'password'&>
8140 Any of the four sub-parts of the first field can be omitted. For normal use on
8141 the local host it can be left blank or set to just &"localhost"&.
8143 No database need be supplied &-- but if it is absent here, it must be given in
8146 If a MySQL query is issued that does not request any data (an insert, update,
8147 or delete command), the result of the lookup is the number of rows affected.
8149 &*Warning*&: This can be misleading. If an update does not actually change
8150 anything (for example, setting a field to the value it already has), the result
8151 is zero because no rows are affected.
8154 .section "Special PostgreSQL features" "SECID74"
8155 PostgreSQL lookups can also use Unix domain socket connections to the database.
8156 This is usually faster and costs less CPU time than a TCP/IP connection.
8157 However it can be used only if the mail server runs on the same machine as the
8158 database server. A configuration line for PostgreSQL via Unix domain sockets
8161 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8163 In other words, instead of supplying a host name, a path to the socket is
8164 given. The path name is enclosed in parentheses so that its slashes aren't
8165 visually confused with the delimiters for the other server parameters.
8167 If a PostgreSQL query is issued that does not request any data (an insert,
8168 update, or delete command), the result of the lookup is the number of rows
8171 .section "More about SQLite" "SECTsqlite"
8172 .cindex "lookup" "SQLite"
8173 .cindex "sqlite lookup type"
8174 SQLite is different to the other SQL lookups because a filename is required in
8175 addition to the SQL query. An SQLite database is a single file, and there is no
8176 daemon as in the other SQL databases.
8179 .oindex &%sqlite_dbfile%&
8180 The preferred way of specifying the file is by using the
8181 &%sqlite_dbfile%& option, set to
8184 A deprecated method is available, prefixing the query with the filename
8185 separated by white space.
8186 This means that the path name cannot contain white space.
8187 .cindex "tainted data" "sqlite file"
8188 It also means that the query cannot use any tainted values, as that taints
8189 the entire query including the filename - resulting in a refusal to open
8193 Here is a lookup expansion example:
8195 sqlite_dbfile = /some/thing/sqlitedb
8197 ${lookup sqlite {select name from aliases where id='userx';}}
8199 In a list, the syntax is similar. For example:
8201 domainlist relay_to_domains = sqlite;\
8202 select * from relays where ip='$sender_host_address';
8205 The only character affected by the &%quote_sqlite%& operator is a single
8206 quote, which it doubles.
8208 .cindex timeout SQLite
8209 .cindex sqlite "lookup timeout"
8210 The SQLite library handles multiple simultaneous accesses to the database
8211 internally. Multiple readers are permitted, but only one process can
8212 update at once. Attempts to access the database while it is being updated
8213 are rejected after a timeout period, during which the SQLite library
8214 waits for the lock to be released. In Exim, the default timeout is set
8215 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8218 .section "More about Redis" "SECTredis"
8219 .cindex "lookup" "Redis"
8220 .cindex "redis lookup type"
8221 Redis is a non-SQL database. Commands are simple get and set.
8224 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8225 ${lookup redis{get keyname}}
8228 As of release 4.91, "lightweight" support for Redis Cluster is available.
8229 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8230 of which must be reachable from the running exim instance. If the cluster has
8231 master/slave replication, the list must contain all the master and slave
8234 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8235 immediately follow the redirection but treats the response as a DEFER, moving on
8236 to the next server in the &%redis_servers%& list until the correct server is
8243 . ////////////////////////////////////////////////////////////////////////////
8244 . ////////////////////////////////////////////////////////////////////////////
8246 .chapter "Domain, host, address, and local part lists" &&&
8247 "CHAPdomhosaddlists" &&&
8248 "Domain, host, and address lists"
8249 .scindex IIDdohoadli "lists of domains; hosts; etc."
8250 A number of Exim configuration options contain lists of domains, hosts,
8251 email addresses, or local parts. For example, the &%hold_domains%& option
8252 contains a list of domains whose delivery is currently suspended. These lists
8253 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8254 arguments to expansion conditions such as &%match_domain%&.
8256 Each item in one of these lists is a pattern to be matched against a domain,
8257 host, email address, or local part, respectively. In the sections below, the
8258 different types of pattern for each case are described, but first we cover some
8259 general facilities that apply to all four kinds of list.
8261 Note that other parts of Exim use a &'string list'& which does not
8262 support all the complexity available in
8263 domain, host, address and local part lists.
8267 .section "Expansion of lists" "SECTlistexpand"
8268 .cindex "expansion" "of lists"
8269 Each list is expanded as a single string before it is used.
8271 &'Exception: the router headers_remove option, where list-item
8272 splitting is done before string-expansion.'&
8275 expansion must be a list, possibly containing empty items, which is split up
8276 into separate items for matching. By default, colon is the separator character,
8277 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8278 &<<SECTempitelis>>& for details of the list syntax; the second of these
8279 discusses the way to specify empty list items.
8282 If the string expansion is forced to fail, Exim behaves as if the item it is
8283 testing (domain, host, address, or local part) is not in the list. Other
8284 expansion failures cause temporary errors.
8286 If an item in a list is a regular expression, backslashes, dollars and possibly
8287 other special characters in the expression must be protected against
8288 misinterpretation by the string expander. The easiest way to do this is to use
8289 the &`\N`& expansion feature to indicate that the contents of the regular
8290 expression should not be expanded. For example, in an ACL you might have:
8292 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8293 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8295 The first item is a regular expression that is protected from expansion by
8296 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8297 senders based on the receiving domain.
8302 .section "Negated items in lists" "SECID76"
8303 .cindex "list" "negation"
8304 .cindex "negation" "in lists"
8305 Items in a list may be positive or negative. Negative items are indicated by a
8306 leading exclamation mark, which may be followed by optional white space. A list
8307 defines a set of items (domains, etc). When Exim processes one of these lists,
8308 it is trying to find out whether a domain, host, address, or local part
8309 (respectively) is in the set that is defined by the list. It works like this:
8311 The list is scanned from left to right. If a positive item is matched, the
8312 subject that is being checked is in the set; if a negative item is matched, the
8313 subject is not in the set. If the end of the list is reached without the
8314 subject having matched any of the patterns, it is in the set if the last item
8315 was a negative one, but not if it was a positive one. For example, the list in
8317 domainlist relay_to_domains = !a.b.c : *.b.c
8319 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8320 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8321 list is positive. However, if the setting were
8323 domainlist relay_to_domains = !a.b.c
8325 then all domains other than &'a.b.c'& would match because the last item in the
8326 list is negative. In other words, a list that ends with a negative item behaves
8327 as if it had an extra item &`:*`& on the end.
8329 Another way of thinking about positive and negative items in lists is to read
8330 the connector as &"or"& after a positive item and as &"and"& after a negative
8335 .section "File names in lists" "SECTfilnamlis"
8336 .cindex "list" "filename in"
8337 If an item in a domain, host, address, or local part list is an absolute
8338 filename (beginning with a slash character), each line of the file is read and
8339 processed as if it were an independent item in the list, except that further
8340 filenames are not allowed,
8341 and no expansion of the data from the file takes place.
8342 Empty lines in the file are ignored, and the file may also contain comment
8346 For domain and host lists, if a # character appears anywhere in a line of the
8347 file, it and all following characters are ignored.
8349 Because local parts may legitimately contain # characters, a comment in an
8350 address list or local part list file is recognized only if # is preceded by
8351 white space or the start of the line. For example:
8353 not#comment@x.y.z # but this is a comment
8357 Putting a filename in a list has the same effect as inserting each line of the
8358 file as an item in the list (blank lines and comments excepted). However, there
8359 is one important difference: the file is read each time the list is processed,
8360 so if its contents vary over time, Exim's behaviour changes.
8362 If a filename is preceded by an exclamation mark, the sense of any match
8363 within the file is inverted. For example, if
8365 hold_domains = !/etc/nohold-domains
8367 and the file contains the lines
8372 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8373 any domain matching &`*.b.c`& is not.
8377 .section "An lsearch file is not an out-of-line list" "SECID77"
8378 As will be described in the sections that follow, lookups can be used in lists
8379 to provide indexed methods of checking list membership. There has been some
8380 confusion about the way &(lsearch)& lookups work in lists. Because
8381 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8382 sometimes thought that it is allowed to contain wild cards and other kinds of
8383 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8384 always fixed strings, just as for any other single-key lookup type.
8386 If you want to use a file to contain wild-card patterns that form part of a
8387 list, just give the filename on its own, without a search type, as described
8388 in the previous section. You could also use the &(wildlsearch)& or
8389 &(nwildlsearch)&, but there is no advantage in doing this.
8395 .section "Results of list checking" SECTlistresults
8396 The primary result of doing a list check is a truth value.
8397 In some contexts additional information is stored
8398 about the list element that matched:
8401 A &%hosts%& ACL condition
8402 will store a result in the &$host_data$& variable.
8404 A &%local_parts%& router option or &%local_parts%& ACL condition
8405 will store a result in the &$local_part_data$& variable.
8407 A &%domains%& router option or &%domains%& ACL condition
8409 A &%senders%& router option or &%senders%& ACL condition
8410 will store a result in the &$sender_data$& variable.
8412 A &%recipients%& ACL condition
8413 will store a result in the &$recipient_data$& variable.
8416 The detail of the additional information depends on the
8417 type of match and is given below as the &*value*& information.
8423 .section "Named lists" "SECTnamedlists"
8424 .cindex "named lists"
8425 .cindex "list" "named"
8426 A list of domains, hosts, email addresses, or local parts can be given a name
8427 which is then used to refer to the list elsewhere in the configuration. This is
8428 particularly convenient if the same list is required in several different
8429 places. It also allows lists to be given meaningful names, which can improve
8430 the readability of the configuration. For example, it is conventional to define
8431 a domain list called &'local_domains'& for all the domains that are handled
8432 locally on a host, using a configuration line such as
8434 domainlist local_domains = localhost:my.dom.example
8436 Named lists are referenced by giving their name preceded by a plus sign, so,
8437 for example, a router that is intended to handle local domains would be
8438 configured with the line
8440 domains = +local_domains
8442 The first router in a configuration is often one that handles all domains
8443 except the local ones, using a configuration with a negated item like this:
8447 domains = ! +local_domains
8448 transport = remote_smtp
8451 The four kinds of named list are created by configuration lines starting with
8452 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8453 respectively. Then there follows the name that you are defining, followed by an
8454 equals sign and the list itself. For example:
8456 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8457 addresslist bad_senders = cdb;/etc/badsenders
8459 A named list may refer to other named lists:
8461 domainlist dom1 = first.example : second.example
8462 domainlist dom2 = +dom1 : third.example
8463 domainlist dom3 = fourth.example : +dom2 : fifth.example
8465 &*Warning*&: If the last item in a referenced list is a negative one, the
8466 effect may not be what you intended, because the negation does not propagate
8467 out to the higher level. For example, consider:
8469 domainlist dom1 = !a.b
8470 domainlist dom2 = +dom1 : *.b
8472 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8473 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8474 means it matches the second list as well. The effect is not the same as
8476 domainlist dom2 = !a.b : *.b
8478 where &'x.y'& does not match. It's best to avoid negation altogether in
8479 referenced lists if you can.
8482 .cindex "hiding named list values"
8483 .cindex "named lists" "hiding value of"
8484 Some named list definitions may contain sensitive data, for example, passwords for
8485 accessing databases. To stop non-admin users from using the &%-bP%& command
8486 line option to read these values, you can precede the definition with the
8487 word &"hide"&. For example:
8489 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8494 Named lists may have a performance advantage. When Exim is routing an
8495 address or checking an incoming message, it caches the result of tests on named
8496 lists. So, if you have a setting such as
8498 domains = +local_domains
8500 on several of your routers
8501 or in several ACL statements,
8502 the actual test is done only for the first one. However, the caching works only
8503 if there are no expansions within the list itself or any sublists that it
8504 references. In other words, caching happens only for lists that are known to be
8505 the same each time they are referenced.
8507 By default, there may be up to 16 named lists of each type. This limit can be
8508 extended by changing a compile-time variable. The use of domain and host lists
8509 is recommended for concepts such as local domains, relay domains, and relay
8510 hosts. The default configuration is set up like this.
8514 .section "Named lists compared with macros" "SECID78"
8515 .cindex "list" "named compared with macro"
8516 .cindex "macro" "compared with named list"
8517 At first sight, named lists might seem to be no different from macros in the
8518 configuration file. However, macros are just textual substitutions. If you
8521 ALIST = host1 : host2
8522 auth_advertise_hosts = !ALIST
8524 it probably won't do what you want, because that is exactly the same as
8526 auth_advertise_hosts = !host1 : host2
8528 Notice that the second host name is not negated. However, if you use a host
8531 hostlist alist = host1 : host2
8532 auth_advertise_hosts = ! +alist
8534 the negation applies to the whole list, and so that is equivalent to
8536 auth_advertise_hosts = !host1 : !host2
8540 .section "Named list caching" "SECID79"
8541 .cindex "list" "caching of named"
8542 .cindex "caching" "named lists"
8543 While processing a message, Exim caches the result of checking a named list if
8544 it is sure that the list is the same each time. In practice, this means that
8545 the cache operates only if the list contains no $ characters, which guarantees
8546 that it will not change when it is expanded. Sometimes, however, you may have
8547 an expanded list that you know will be the same each time within a given
8548 message. For example:
8550 domainlist special_domains = \
8551 ${lookup{$sender_host_address}cdb{/some/file}}
8553 This provides a list of domains that depends only on the sending host's IP
8554 address. If this domain list is referenced a number of times (for example,
8555 in several ACL lines, or in several routers) the result of the check is not
8556 cached by default, because Exim does not know that it is going to be the
8557 same list each time.
8559 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8560 cache the result anyway. For example:
8562 domainlist_cache special_domains = ${lookup{...
8564 If you do this, you should be absolutely sure that caching is going to do
8565 the right thing in all cases. When in doubt, leave it out.
8569 .section "Domain lists" "SECTdomainlist"
8570 .cindex "domain list" "patterns for"
8571 .cindex "list" "domain list"
8572 Domain lists contain patterns that are to be matched against a mail domain.
8573 The following types of item may appear in domain lists:
8576 .cindex "primary host name"
8577 .cindex "host name" "matched in domain list"
8578 .oindex "&%primary_hostname%&"
8579 .cindex "domain list" "matching primary host name"
8580 .cindex "@ in a domain list"
8581 If a pattern consists of a single @ character, it matches the local host name,
8582 as set by the &%primary_hostname%& option (or defaulted). This makes it
8583 possible to use the same configuration file on several different hosts that
8584 differ only in their names.
8587 The value for a match will be the primary host name.
8592 .cindex "@[] in a domain list"
8593 .cindex "domain list" "matching local IP interfaces"
8594 .cindex "domain literal"
8595 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8596 in square brackets (as in an email address that contains a domain literal), but
8597 only if that IP address is recognized as local for email routing purposes. The
8598 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8599 control which of a host's several IP addresses are treated as local.
8600 In today's Internet, the use of domain literals is controversial;
8601 see the &%allow_domain_literals%& main option.
8604 The value for a match will be the string &`@[]`&.
8610 .cindex "@mx_primary"
8611 .cindex "@mx_secondary"
8612 .cindex "domain list" "matching MX pointers to local host"
8613 If a pattern consists of the string &`@mx_any`& it matches any domain that
8614 has an MX record pointing to the local host or to any host that is listed in
8615 .oindex "&%hosts_treat_as_local%&"
8616 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8617 are similar, except that the first matches only when a primary MX target is the
8618 local host, and the second only when no primary MX target is the local host,
8619 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8620 preference value &-- there may of course be more than one of them.
8622 The MX lookup that takes place when matching a pattern of this type is
8623 performed with the resolver options for widening names turned off. Thus, for
8624 example, a single-component domain will &'not'& be expanded by adding the
8625 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8626 options of the &(dnslookup)& router for a discussion of domain widening.
8628 Sometimes you may want to ignore certain IP addresses when using one of these
8629 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8630 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8631 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8632 on a router). For example:
8634 domains = @mx_any/ignore=127.0.0.1
8636 This example matches any domain that has an MX record pointing to one of
8637 the local host's IP addresses other than 127.0.0.1.
8639 The list of IP addresses is in fact processed by the same code that processes
8640 host lists, so it may contain CIDR-coded network specifications and it may also
8641 contain negative items.
8643 Because the list of IP addresses is a sublist within a domain list, you have to
8644 be careful about delimiters if there is more than one address. Like any other
8645 list, the default delimiter can be changed. Thus, you might have:
8647 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8648 an.other.domain : ...
8650 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8651 involved, it is easiest to change the delimiter for the main list as well:
8653 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8654 an.other.domain ? ...
8657 The value for a match will be the list element string (starting &`@mx_`&).
8662 .cindex "asterisk" "in domain list"
8663 .cindex "domain list" "asterisk in"
8664 .cindex "domain list" "matching &""ends with""&"
8665 If a pattern starts with an asterisk, the remaining characters of the pattern
8666 are compared with the terminating characters of the domain. The use of &"*"& in
8667 domain lists differs from its use in partial matching lookups. In a domain
8668 list, the character following the asterisk need not be a dot, whereas partial
8669 matching works only in terms of dot-separated components. For example, a domain
8670 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8674 The value for a match will be the list element string (starting with the asterisk).
8675 Additionally, &$0$& will be set to the matched string
8676 and &$1$& to the variable portion which the asterisk matched.
8680 .cindex "regular expressions" "in domain list"
8681 .cindex "domain list" "matching regular expression"
8682 If a pattern starts with a circumflex character, it is treated as a regular
8683 expression, and matched against the domain using a regular expression matching
8684 function. The circumflex is treated as part of the regular expression.
8685 Email domains are case-independent, so this regular expression match is by
8686 default case-independent, but you can make it case-dependent by starting it
8687 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8688 are given in chapter &<<CHAPregexp>>&.
8690 &*Warning*&: Because domain lists are expanded before being processed, you
8691 must escape any backslash and dollar characters in the regular expression, or
8692 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8693 it is not to be expanded (unless you really do want to build a regular
8694 expression by expansion, of course).
8697 The value for a match will be the list element string (starting with the circumflex).
8698 Additionally, &$0$& will be set to the string matching the regular expression,
8699 and &$1$& (onwards) to any submatches identified by parentheses.
8705 .cindex "lookup" "in domain list"
8706 .cindex "domain list" "matching by lookup"
8707 If a pattern starts with the name of a single-key lookup type followed by a
8708 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8709 must be a filename in a suitable format for the lookup type. For example, for
8710 &"cdb;"& it must be an absolute path:
8712 domains = cdb;/etc/mail/local_domains.cdb
8714 The appropriate type of lookup is done on the file using the domain name as the
8715 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8716 only in whether or not the key is present in the file. However, when a lookup
8717 is used for the &%domains%& option on a router
8718 or a &%domains%& condition in an ACL statement, the value is preserved in the
8719 &$domain_data$& variable and can be referred to in other router options or
8720 other statements in the same ACL.
8721 .cindex "tainted data" "de-tainting"
8722 The value will be untainted.
8726 Any of the single-key lookup type names may be preceded by
8727 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8729 domains = partial-dbm;/partial/domains
8731 This causes partial matching logic to be invoked; a description of how this
8732 works is given in section &<<SECTpartiallookup>>&.
8735 .cindex "asterisk" "in lookup type"
8736 Any of the single-key lookup types may be followed by an asterisk. This causes
8737 a default lookup for a key consisting of a single asterisk to be done if the
8738 original lookup fails. This is not a useful feature when using a domain list to
8739 select particular domains (because any domain would match), but it might have
8740 value if the result of the lookup is being used via the &$domain_data$&
8744 If the pattern starts with the name of a query-style lookup type followed by a
8745 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8746 pattern must be an appropriate query for the lookup type, as described in
8747 chapter &<<CHAPfdlookup>>&. For example:
8749 hold_domains = mysql;select domain from holdlist \
8750 where domain = '${quote_mysql:$domain}';
8752 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8753 example, it doesn't matter what field you select). Exim is interested only in
8754 whether or not the query succeeds. However, when a lookup is used for the
8755 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8756 variable and can be referred to in other options.
8757 .cindex "tainted data" "de-tainting"
8758 The value will be untainted.
8762 If the pattern starts with the name of a lookup type
8763 of either kind (single-key or query-style) it may be
8764 followed by a comma and options,
8765 The options are lookup-type specific and consist of a comma-separated list.
8766 Each item starts with a tag and and equals "=".
8770 .cindex "domain list" "matching literal domain name"
8771 If none of the above cases apply, a caseless textual comparison is made
8772 between the pattern and the domain.
8774 The value for a match will be the list element string.
8775 .cindex "tainted data" "de-tainting"
8776 Note that this is commonly untainted
8777 (depending on the way the list was created).
8778 This is a useful way of obtaining an untainted equivalent to
8779 the domain, for later operations.
8783 Here is an example that uses several different kinds of pattern:
8785 domainlist funny_domains = \
8788 *.foundation.fict.example : \
8789 \N^[1-2]\d{3}\.fict\.example$\N : \
8790 partial-dbm;/opt/data/penguin/book : \
8791 nis;domains.byname : \
8792 nisplus;[name=$domain,status=local],domains.org_dir
8794 There are obvious processing trade-offs among the various matching modes. Using
8795 an asterisk is faster than a regular expression, and listing a few names
8796 explicitly probably is too. The use of a file or database lookup is expensive,
8797 but may be the only option if hundreds of names are required. Because the
8798 patterns are tested in order, it makes sense to put the most commonly matched
8803 .section "Host lists" "SECThostlist"
8804 .cindex "host list" "patterns in"
8805 .cindex "list" "host list"
8806 Host lists are used to control what remote hosts are allowed to do. For
8807 example, some hosts may be allowed to use the local host as a relay, and some
8808 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8809 two different ways, by name or by IP address. In a host list, some types of
8810 pattern are matched to a host name, and some are matched to an IP address.
8811 You need to be particularly careful with this when single-key lookups are
8812 involved, to ensure that the right value is being used as the key.
8815 .section "Special host list patterns" "SECID80"
8816 .cindex "empty item in hosts list"
8817 .cindex "host list" "empty string in"
8818 If a host list item is the empty string, it matches only when no remote host is
8819 involved. This is the case when a message is being received from a local
8820 process using SMTP on the standard input, that is, when a TCP/IP connection is
8823 .cindex "asterisk" "in host list"
8824 The special pattern &"*"& in a host list matches any host or no host. Neither
8825 the IP address nor the name is actually inspected.
8829 .section "Host list patterns that match by IP address" "SECThoslispatip"
8830 .cindex "host list" "matching IP addresses"
8831 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8832 the incoming address actually appears in the IPv6 host as
8833 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8834 list, it is converted into a traditional IPv4 address first. (Not all operating
8835 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8838 The following types of pattern in a host list check the remote host by
8839 inspecting its IP address:
8842 If the pattern is a plain domain name (not a regular expression, not starting
8843 with *, not a lookup of any kind), Exim calls the operating system function
8844 to find the associated IP address(es). Exim uses the newer
8845 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8846 This typically causes a forward DNS lookup of the name. The result is compared
8847 with the IP address of the subject host.
8849 If there is a temporary problem (such as a DNS timeout) with the host name
8850 lookup, a temporary error occurs. For example, if the list is being used in an
8851 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8852 temporary SMTP error code. If no IP address can be found for the host name,
8853 what happens is described in section &<<SECTbehipnot>>& below.
8856 .cindex "@ in a host list"
8857 If the pattern is &"@"&, the primary host name is substituted and used as a
8858 domain name, as just described.
8861 If the pattern is an IP address, it is matched against the IP address of the
8862 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8863 IPv6 addresses can be given in colon-separated format, but the colons have to
8864 be doubled so as not to be taken as item separators when the default list
8865 separator is used. IPv6 addresses are recognized even when Exim is compiled
8866 without IPv6 support. This means that if they appear in a host list on an
8867 IPv4-only host, Exim will not treat them as host names. They are just addresses
8868 that can never match a client host.
8871 .cindex "@[] in a host list"
8872 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8873 the local host. For example, if the local host is an IPv4 host with one
8874 interface address 10.45.23.56, these two ACL statements have the same effect:
8876 accept hosts = 127.0.0.1 : 10.45.23.56
8880 .cindex "CIDR notation"
8881 If the pattern is an IP address followed by a slash and a mask length (for
8882 example 10.11.42.0/24), it is matched against the IP address of the subject
8883 host under the given mask. This allows, an entire network of hosts to be
8884 included (or excluded) by a single item. The mask uses CIDR notation; it
8885 specifies the number of address bits that must match, starting from the most
8886 significant end of the address.
8888 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8889 of a range of addresses. It is the number of bits in the network portion of the
8890 address. The above example specifies a 24-bit netmask, so it matches all 256
8891 addresses in the 10.11.42.0 network. An item such as
8895 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8896 32 for an IPv4 address is the same as no mask at all; just a single address
8899 Here is another example which shows an IPv4 and an IPv6 network:
8901 recipient_unqualified_hosts = 192.168.0.0/16: \
8902 3ffe::ffff::836f::::/48
8904 The doubling of list separator characters applies only when these items
8905 appear inline in a host list. It is not required when indirecting via a file.
8908 recipient_unqualified_hosts = /opt/exim/unqualnets
8910 could make use of a file containing
8915 to have exactly the same effect as the previous example. When listing IPv6
8916 addresses inline, it is usually more convenient to use the facility for
8917 changing separator characters. This list contains the same two networks:
8919 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8922 The separator is changed to semicolon by the leading &"<;"& at the start of the
8928 .section "Host list patterns for single-key lookups by host address" &&&
8929 "SECThoslispatsikey"
8930 .cindex "host list" "lookup of IP address"
8931 When a host is to be identified by a single-key lookup of its complete IP
8932 address, the pattern takes this form:
8934 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8938 hosts_lookup = net-cdb;/hosts-by-ip.db
8940 The text form of the IP address of the subject host is used as the lookup key.
8941 IPv6 addresses are converted to an unabbreviated form, using lower case
8942 letters, with dots as separators because colon is the key terminator in
8943 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8944 quoting the keys, but this is a facility that was added later.] The data
8945 returned by the lookup is not used.
8947 .cindex "IP address" "masking"
8948 .cindex "host list" "masked IP address"
8949 Single-key lookups can also be performed using masked IP addresses, using
8950 patterns of this form:
8952 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8956 net24-dbm;/networks.db
8958 The IP address of the subject host is masked using <&'number'&> as the mask
8959 length. A textual string is constructed from the masked value, followed by the
8960 mask, and this is used as the lookup key. For example, if the host's IP address
8961 is 192.168.34.6, the key that is looked up for the above example is
8962 &"192.168.34.0/24"&.
8964 When an IPv6 address is converted to a string, dots are normally used instead
8965 of colons, so that keys in &(lsearch)& files need not contain colons (which
8966 terminate &(lsearch)& keys). This was implemented some time before the ability
8967 to quote keys was made available in &(lsearch)& files. However, the more
8968 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8969 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8970 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8971 converted using colons and not dots.
8972 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
8973 addresses are always used.
8974 The latter are converted to IPv4 addresses, in dotted-quad form.
8976 Ideally, it would be nice to tidy up this anomalous situation by changing to
8977 colons in all cases, given that quoting is now available for &(lsearch)&.
8978 However, this would be an incompatible change that might break some existing
8981 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8982 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8983 the former case the key strings include the mask value, whereas in the latter
8984 case the IP address is used on its own.
8988 .section "Host list patterns that match by host name" "SECThoslispatnam"
8989 .cindex "host" "lookup failures"
8990 .cindex "unknown host name"
8991 .cindex "host list" "matching host name"
8992 There are several types of pattern that require Exim to know the name of the
8993 remote host. These are either wildcard patterns or lookups by name. (If a
8994 complete hostname is given without any wildcarding, it is used to find an IP
8995 address to match against, as described in section &<<SECThoslispatip>>&
8998 If the remote host name is not already known when Exim encounters one of these
8999 patterns, it has to be found from the IP address.
9000 Although many sites on the Internet are conscientious about maintaining reverse
9001 DNS data for their hosts, there are also many that do not do this.
9002 Consequently, a name cannot always be found, and this may lead to unwanted
9003 effects. Take care when configuring host lists with wildcarded name patterns.
9004 Consider what will happen if a name cannot be found.
9006 Because of the problems of determining host names from IP addresses, matching
9007 against host names is not as common as matching against IP addresses.
9009 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9010 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9011 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9012 are done can be changed by setting the &%host_lookup_order%& option. For
9013 security, once Exim has found one or more names, it looks up the IP addresses
9014 for these names and compares them with the IP address that it started with.
9015 Only those names whose IP addresses match are accepted. Any other names are
9016 discarded. If no names are left, Exim behaves as if the host name cannot be
9017 found. In the most common case there is only one name and one IP address.
9019 There are some options that control what happens if a host name cannot be
9020 found. These are described in section &<<SECTbehipnot>>& below.
9022 .cindex "host" "alias for"
9023 .cindex "alias for host"
9024 As a result of aliasing, hosts may have more than one name. When processing any
9025 of the following types of pattern, all the host's names are checked:
9028 .cindex "asterisk" "in host list"
9029 If a pattern starts with &"*"& the remainder of the item must match the end of
9030 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9031 &'.b.c'&. This special simple form is provided because this is a very common
9032 requirement. Other kinds of wildcarding require the use of a regular
9035 .cindex "regular expressions" "in host list"
9036 .cindex "host list" "regular expression in"
9037 If the item starts with &"^"& it is taken to be a regular expression which is
9038 matched against the host name. Host names are case-independent, so this regular
9039 expression match is by default case-independent, but you can make it
9040 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9041 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9046 is a regular expression that matches either of the two hosts &'a.c.d'& or
9047 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9048 that backslash and dollar characters are not misinterpreted as part of the
9049 string expansion. The simplest way to do this is to use &`\N`& to mark that
9050 part of the string as non-expandable. For example:
9052 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9054 &*Warning*&: If you want to match a complete host name, you must include the
9055 &`$`& terminating metacharacter in the regular expression, as in the above
9056 example. Without it, a match at the start of the host name is all that is
9063 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9064 .cindex "host" "lookup failures, permanent"
9065 While processing a host list, Exim may need to look up an IP address from a
9066 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9067 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9068 behaviour when it fails to find the information it is seeking is the same.
9070 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9071 apply to temporary DNS errors, whose handling is described in the next section.
9073 .cindex "&`+include_unknown`&"
9074 .cindex "&`+ignore_unknown`&"
9075 Exim parses a host list from left to right. If it encounters a permanent
9076 lookup failure in any item in the host list before it has found a match,
9077 Exim treats it as a failure and the default behavior is as if the host
9078 does not match the list. This may not always be what you want to happen.
9079 To change Exim's behaviour, the special items &`+include_unknown`& or
9080 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9081 not recognized in an indirected file).
9084 If any item that follows &`+include_unknown`& requires information that
9085 cannot found, Exim behaves as if the host does match the list. For example,
9087 host_reject_connection = +include_unknown:*.enemy.ex
9089 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9090 any hosts whose name it cannot find.
9093 If any item that follows &`+ignore_unknown`& requires information that cannot
9094 be found, Exim ignores that item and proceeds to the rest of the list. For
9097 accept hosts = +ignore_unknown : friend.example : \
9100 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9101 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9102 name can be found for 192.168.4.5, it is rejected.
9105 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9106 list. The effect of each one lasts until the next, or until the end of the
9109 .section "Mixing wildcarded host names and addresses in host lists" &&&
9111 .cindex "host list" "mixing names and addresses in"
9113 This section explains the host/ip processing logic with the same concepts
9114 as the previous section, but specifically addresses what happens when a
9115 wildcarded hostname is one of the items in the hostlist.
9118 If you have name lookups or wildcarded host names and
9119 IP addresses in the same host list, you should normally put the IP
9120 addresses first. For example, in an ACL you could have:
9122 accept hosts = 10.9.8.7 : *.friend.example
9124 The reason you normally would order it this way lies in the
9125 left-to-right way that Exim processes lists. It can test IP addresses
9126 without doing any DNS lookups, but when it reaches an item that requires
9127 a host name, it fails if it cannot find a host name to compare with the
9128 pattern. If the above list is given in the opposite order, the
9129 &%accept%& statement fails for a host whose name cannot be found, even
9130 if its IP address is 10.9.8.7.
9133 If you really do want to do the name check first, and still recognize the IP
9134 address, you can rewrite the ACL like this:
9136 accept hosts = *.friend.example
9137 accept hosts = 10.9.8.7
9139 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9140 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9141 &`+ignore_unknown`&, which was discussed in depth in the first example in
9146 .section "Temporary DNS errors when looking up host information" &&&
9148 .cindex "host" "lookup failures, temporary"
9149 .cindex "&`+include_defer`&"
9150 .cindex "&`+ignore_defer`&"
9151 A temporary DNS lookup failure normally causes a defer action (except when
9152 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9153 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9154 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9155 section. These options should be used with care, probably only in non-critical
9156 host lists such as whitelists.
9160 .section "Host list patterns for single-key lookups by host name" &&&
9161 "SECThoslispatnamsk"
9162 .cindex "unknown host name"
9163 .cindex "host list" "matching host name"
9164 If a pattern is of the form
9166 <&'single-key-search-type'&>;<&'search-data'&>
9170 dbm;/host/accept/list
9172 a single-key lookup is performed, using the host name as its key. If the
9173 lookup succeeds, the host matches the item. The actual data that is looked up
9176 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9177 keys in the file, not IP addresses. If you want to do lookups based on IP
9178 addresses, you must precede the search type with &"net-"& (see section
9179 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9180 two items in the same list, one doing an address lookup and one doing a name
9181 lookup, both using the same file.
9185 .section "Host list patterns for query-style lookups" "SECID81"
9186 If a pattern is of the form
9188 <&'query-style-search-type'&>;<&'query'&>
9190 the query is obeyed, and if it succeeds, the host matches the item. The actual
9191 data that is looked up is not used. The variables &$sender_host_address$& and
9192 &$sender_host_name$& can be used in the query. For example:
9194 hosts_lookup = pgsql;\
9195 select ip from hostlist where ip='$sender_host_address'
9197 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9198 can use the &%sg%& expansion item to change this if you need to. If you want to
9199 use masked IP addresses in database queries, you can use the &%mask%& expansion
9202 If the query contains a reference to &$sender_host_name$&, Exim automatically
9203 looks up the host name if it has not already done so. (See section
9204 &<<SECThoslispatnam>>& for comments on finding host names.)
9206 Historical note: prior to release 4.30, Exim would always attempt to find a
9207 host name before running the query, unless the search type was preceded by
9208 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9209 still recognized for query-style lookups, but its presence or absence has no
9210 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9211 See section &<<SECThoslispatsikey>>&.)
9217 .section "Address lists" "SECTaddresslist"
9218 .cindex "list" "address list"
9219 .cindex "address list" "empty item"
9220 .cindex "address list" "patterns"
9221 Address lists contain patterns that are matched against mail addresses. There
9222 is one special case to be considered: the sender address of a bounce message is
9223 always empty. You can test for this by providing an empty item in an address
9224 list. For example, you can set up a router to process bounce messages by
9225 using this option setting:
9229 The presence of the colon creates an empty item. If you do not provide any
9230 data, the list is empty and matches nothing. The empty sender can also be
9231 detected by a regular expression that matches an empty string,
9232 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9234 Non-empty items in an address list can be straightforward email addresses. For
9237 senders = jbc@askone.example : hs@anacreon.example
9239 A certain amount of wildcarding is permitted. If a pattern contains an @
9240 character, but is not a regular expression and does not begin with a
9241 semicolon-terminated lookup type (described below), the local part of the
9242 subject address is compared with the local part of the pattern, which may start
9243 with an asterisk. If the local parts match, the domain is checked in exactly
9244 the same way as for a pattern in a domain list. For example, the domain can be
9245 wildcarded, refer to a named list, or be a lookup:
9247 deny senders = *@*.spamming.site:\
9248 *@+hostile_domains:\
9249 bozo@partial-lsearch;/list/of/dodgy/sites:\
9250 *@dbm;/bad/domains.db
9252 .cindex "local part" "starting with !"
9253 .cindex "address list" "local part starting with !"
9254 If a local part that begins with an exclamation mark is required, it has to be
9255 specified using a regular expression, because otherwise the exclamation mark is
9256 treated as a sign of negation, as is standard in lists.
9258 If a non-empty pattern that is not a regular expression or a lookup does not
9259 contain an @ character, it is matched against the domain part of the subject
9260 address. The only two formats that are recognized this way are a literal
9261 domain, or a domain pattern that starts with *. In both these cases, the effect
9262 is the same as if &`*@`& preceded the pattern. For example:
9264 deny senders = enemy.domain : *.enemy.domain
9267 The following kinds of more complicated address list pattern can match any
9268 address, including the empty address that is characteristic of bounce message
9272 .cindex "regular expressions" "in address list"
9273 .cindex "address list" "regular expression in"
9274 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9275 done against the complete address, with the pattern as the regular expression.
9276 You must take care that backslash and dollar characters are not misinterpreted
9277 as part of the string expansion. The simplest way to do this is to use &`\N`&
9278 to mark that part of the string as non-expandable. For example:
9280 deny senders = \N^.*this.*@example\.com$\N : \
9281 \N^\d{8}.+@spamhaus.example$\N : ...
9283 The &`\N`& sequences are removed by the expansion, so these items do indeed
9284 start with &"^"& by the time they are being interpreted as address patterns.
9287 .cindex "address list" "lookup for complete address"
9288 Complete addresses can be looked up by using a pattern that starts with a
9289 lookup type terminated by a semicolon, followed by the data for the lookup. For
9292 deny senders = cdb;/etc/blocked.senders : \
9293 mysql;select address from blocked where \
9294 address='${quote_mysql:$sender_address}'
9296 Both query-style and single-key lookup types can be used. For a single-key
9297 lookup type, Exim uses the complete address as the key. However, empty keys are
9298 not supported for single-key lookups, so a match against the empty address
9299 always fails. This restriction does not apply to query-style lookups.
9301 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9302 cannot be used, and is ignored if specified, with an entry being written to the
9304 .cindex "*@ with single-key lookup"
9305 However, you can configure lookup defaults, as described in section
9306 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9307 default. For example, with this lookup:
9309 accept senders = lsearch*@;/some/file
9311 the file could contains lines like this:
9313 user1@domain1.example
9316 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9319 nimrod@jaeger.example
9323 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9324 would mean that every address matches, thus rendering the test useless.
9326 &*Warning 2*&: Do not confuse these two kinds of item:
9328 deny recipients = dbm*@;/some/file
9329 deny recipients = *@dbm;/some/file
9331 The first does a whole address lookup, with defaulting, as just described,
9332 because it starts with a lookup type. The second matches the local part and
9333 domain independently, as described in a bullet point below.
9337 The following kinds of address list pattern can match only non-empty addresses.
9338 If the subject address is empty, a match against any of these pattern types
9343 .cindex "@@ with single-key lookup"
9344 .cindex "address list" "@@ lookup type"
9345 .cindex "address list" "split local part and domain"
9346 If a pattern starts with &"@@"& followed by a single-key lookup item
9347 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9348 split into a local part and a domain. The domain is looked up in the file. If
9349 it is not found, there is no match. If it is found, the data that is looked up
9350 from the file is treated as a colon-separated list of local part patterns, each
9351 of which is matched against the subject local part in turn.
9353 .cindex "asterisk" "in address list"
9354 The lookup may be a partial one, and/or one involving a search for a default
9355 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9356 patterns that are looked up can be regular expressions or begin with &"*"&, or
9357 even be further lookups. They may also be independently negated. For example,
9360 deny senders = @@dbm;/etc/reject-by-domain
9362 the data from which the DBM file is built could contain lines like
9364 baddomain.com: !postmaster : *
9366 to reject all senders except &%postmaster%& from that domain.
9368 .cindex "local part" "starting with !"
9369 If a local part that actually begins with an exclamation mark is required, it
9370 has to be specified using a regular expression. In &(lsearch)& files, an entry
9371 may be split over several lines by indenting the second and subsequent lines,
9372 but the separating colon must still be included at line breaks. White space
9373 surrounding the colons is ignored. For example:
9375 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9378 As in all colon-separated lists in Exim, a colon can be included in an item by
9381 If the last item in the list starts with a right angle-bracket, the remainder
9382 of the item is taken as a new key to look up in order to obtain a continuation
9383 list of local parts. The new key can be any sequence of characters. Thus one
9384 might have entries like
9386 aol.com: spammer1 : spammer 2 : >*
9387 xyz.com: spammer3 : >*
9390 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9391 local parts for all domains, in addition to the specific local parts listed for
9392 each domain. Of course, using this feature costs another lookup each time a
9393 chain is followed, but the effort needed to maintain the data is reduced.
9395 .cindex "loop" "in lookups"
9396 It is possible to construct loops using this facility, and in order to catch
9397 them, the chains may be no more than fifty items long.
9400 The @@<&'lookup'&> style of item can also be used with a query-style
9401 lookup, but in this case, the chaining facility is not available. The lookup
9402 can only return a single list of local parts.
9405 &*Warning*&: There is an important difference between the address list items
9406 in these two examples:
9409 senders = *@+my_list
9411 In the first one, &`my_list`& is a named address list, whereas in the second
9412 example it is a named domain list.
9417 .section "Case of letters in address lists" "SECTcasletadd"
9418 .cindex "case of local parts"
9419 .cindex "address list" "case forcing"
9420 .cindex "case forcing in address lists"
9421 Domains in email addresses are always handled caselessly, but for local parts
9422 case may be significant on some systems (see &%caseful_local_part%& for how
9423 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9424 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9425 blocking lists should be done in a case-independent manner. Since most address
9426 lists in Exim are used for this kind of control, Exim attempts to do this by
9429 The domain portion of an address is always lowercased before matching it to an
9430 address list. The local part is lowercased by default, and any string
9431 comparisons that take place are done caselessly. This means that the data in
9432 the address list itself, in files included as plain filenames, and in any file
9433 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9434 keys in files that are looked up by a search type other than &(lsearch)& (which
9435 works caselessly) must be in lower case, because these lookups are not
9438 .cindex "&`+caseful`&"
9439 To allow for the possibility of caseful address list matching, if an item in
9440 an address list is the string &"+caseful"&, the original case of the local
9441 part is restored for any comparisons that follow, and string comparisons are no
9442 longer case-independent. This does not affect the domain, which remains in
9443 lower case. However, although independent matches on the domain alone are still
9444 performed caselessly, regular expressions that match against an entire address
9445 become case-sensitive after &"+caseful"& has been seen.
9449 .section "Local part lists" "SECTlocparlis"
9450 .cindex "list" "local part list"
9451 .cindex "local part" "list"
9452 Case-sensitivity in local part lists is handled in the same way as for address
9453 lists, as just described. The &"+caseful"& item can be used if required. In a
9454 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9455 set false, the subject is lowercased and the matching is initially
9456 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9457 matching in the local part list, but not elsewhere in the router. If
9458 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9459 option is case-sensitive from the start.
9461 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9462 comments are handled in the same way as address lists &-- they are recognized
9463 only if the # is preceded by white space or the start of the line.
9464 Otherwise, local part lists are matched in the same way as domain lists, except
9465 that the special items that refer to the local host (&`@`&, &`@[]`&,
9466 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9467 Refer to section &<<SECTdomainlist>>& for details of the other available item
9469 .ecindex IIDdohoadli
9474 . ////////////////////////////////////////////////////////////////////////////
9475 . ////////////////////////////////////////////////////////////////////////////
9477 .chapter "String expansions" "CHAPexpand"
9478 .scindex IIDstrexp "expansion" "of strings"
9479 Many strings in Exim's runtime configuration are expanded before use. Some of
9480 them are expanded every time they are used; others are expanded only once.
9482 When a string is being expanded it is copied verbatim from left to right except
9483 .cindex expansion "string concatenation"
9484 when a dollar or backslash character is encountered. A dollar specifies the
9485 start of a portion of the string that is interpreted and replaced as described
9486 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9487 escape character, as described in the following section.
9489 Whether a string is expanded depends upon the context. Usually this is solely
9490 dependent upon the option for which a value is sought; in this documentation,
9491 options for which string expansion is performed are marked with † after
9492 the data type. ACL rules always expand strings. A couple of expansion
9493 conditions do not expand some of the brace-delimited branches, for security
9495 .cindex "tainted data" expansion
9496 .cindex expansion "tainted data"
9497 and expansion of data deriving from the sender (&"tainted data"&)
9502 .section "Literal text in expanded strings" "SECTlittext"
9503 .cindex "expansion" "including literal text"
9504 An uninterpreted dollar can be included in an expanded string by putting a
9505 backslash in front of it. A backslash can be used to prevent any special
9506 character being treated specially in an expansion, including backslash itself.
9507 If the string appears in quotes in the configuration file, two backslashes are
9508 required because the quotes themselves cause interpretation of backslashes when
9509 the string is read in (see section &<<SECTstrings>>&).
9511 .cindex "expansion" "non-expandable substrings"
9512 A portion of the string can specified as non-expandable by placing it between
9513 two occurrences of &`\N`&. This is particularly useful for protecting regular
9514 expressions, which often contain backslashes and dollar signs. For example:
9516 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9518 On encountering the first &`\N`&, the expander copies subsequent characters
9519 without interpretation until it reaches the next &`\N`& or the end of the
9524 .section "Character escape sequences in expanded strings" "SECID82"
9525 .cindex "expansion" "escape sequences"
9526 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9527 expanded string is recognized as an escape sequence for the character newline,
9528 carriage return, or tab, respectively. A backslash followed by up to three
9529 octal digits is recognized as an octal encoding for a single character, and a
9530 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9533 These escape sequences are also recognized in quoted strings when they are read
9534 in. Their interpretation in expansions as well is useful for unquoted strings,
9535 and for other cases such as looked-up strings that are then expanded.
9538 .section "Testing string expansions" "SECID83"
9539 .cindex "expansion" "testing"
9540 .cindex "testing" "string expansion"
9542 Many expansions can be tested by calling Exim with the &%-be%& option. This
9543 takes the command arguments, or lines from the standard input if there are no
9544 arguments, runs them through the string expansion code, and writes the results
9545 to the standard output. Variables based on configuration values are set up, but
9546 since no message is being processed, variables such as &$local_part$& have no
9547 value. Nevertheless the &%-be%& option can be useful for checking out file and
9548 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9551 Exim gives up its root privilege when it is called with the &%-be%& option, and
9552 instead runs under the uid and gid it was called with, to prevent users from
9553 using &%-be%& for reading files to which they do not have access.
9556 If you want to test expansions that include variables whose values are taken
9557 from a message, there are two other options that can be used. The &%-bem%&
9558 option is like &%-be%& except that it is followed by a filename. The file is
9559 read as a message before doing the test expansions. For example:
9561 exim -bem /tmp/test.message '$h_subject:'
9563 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9564 Exim message identifier. For example:
9566 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9568 This loads the message from Exim's spool before doing the test expansions, and
9569 is therefore restricted to admin users.
9572 .section "Forced expansion failure" "SECTforexpfai"
9573 .cindex "expansion" "forced failure"
9574 A number of expansions that are described in the following section have
9575 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9576 (which are sometimes called &"curly brackets"&). Which of the two strings is
9577 used depends on some condition that is evaluated as part of the expansion. If,
9578 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9579 the entire string expansion fails in a way that can be detected by the code
9580 that requested the expansion. This is called &"forced expansion failure"&, and
9581 its consequences depend on the circumstances. In some cases it is no different
9582 from any other expansion failure, but in others a different action may be
9583 taken. Such variations are mentioned in the documentation of the option that is
9589 .section "Expansion items" "SECTexpansionitems"
9590 The following items are recognized in expanded strings. White space may be used
9591 between sub-items that are keywords or substrings enclosed in braces inside an
9592 outer set of braces, to improve readability. &*Warning*&: Within braces,
9593 white space is significant.
9596 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9597 .cindex "expansion" "variables"
9598 Substitute the contents of the named variable, for example:
9603 The second form can be used to separate the name from subsequent alphanumeric
9604 characters. This form (using braces) is available only for variables; it does
9605 &'not'& apply to message headers. The names of the variables are given in
9606 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9607 given, the expansion fails.
9609 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9610 .cindex "expansion" "operators"
9611 The string is first itself expanded, and then the operation specified by
9612 <&'op'&> is applied to it. For example:
9616 The string starts with the first character after the colon, which may be
9617 leading white space. A list of operators is given in section &<<SECTexpop>>&
9618 below. The operator notation is used for simple expansion items that have just
9619 one argument, because it reduces the number of braces and therefore makes the
9620 string easier to understand.
9622 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9623 This item inserts &"basic"& header lines. It is described with the &%header%&
9624 expansion item below.
9627 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9628 .cindex "expansion" "calling an acl"
9629 .cindex "&%acl%&" "call from expansion"
9630 The name and zero to nine argument strings are first expanded separately. The expanded
9631 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9632 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9633 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9634 and may use the variables; if another acl expansion is used the values
9635 are restored after it returns. If the ACL sets
9636 a value using a "message =" modifier and returns accept or deny, the value becomes
9637 the result of the expansion.
9638 If no message is set and the ACL returns accept or deny
9639 the expansion result is an empty string.
9640 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9643 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9644 .cindex authentication "results header"
9645 .cindex headers "authentication-results:"
9646 .cindex authentication "expansion item"
9647 This item returns a string suitable for insertion as an
9648 &'Authentication-Results:'&
9650 The given <&'authserv-id'&> is included in the result; typically this
9651 will be a domain name identifying the system performing the authentications.
9652 Methods that might be present in the result include:
9661 Example use (as an ACL modifier):
9663 add_header = :at_start:${authresults {$primary_hostname}}
9665 This is safe even if no authentication results are available.
9668 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9669 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9670 .cindex "expansion" "extracting certificate fields"
9671 .cindex "&%certextract%&" "certificate fields"
9672 .cindex "certificate" "extracting fields"
9673 The <&'certificate'&> must be a variable of type certificate.
9674 The field name is expanded and used to retrieve the relevant field from
9675 the certificate. Supported fields are:
9679 &`subject `& RFC4514 DN
9680 &`issuer `& RFC4514 DN
9685 &`subj_altname `& tagged list
9689 If the field is found,
9690 <&'string2'&> is expanded, and replaces the whole item;
9691 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9692 variable &$value$& contains the value that has been extracted. Afterwards, it
9693 is restored to any previous value it might have had.
9695 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9696 key is not found. If {<&'string2'&>} is also omitted, the value that was
9699 Some field names take optional modifiers, appended and separated by commas.
9701 The field selectors marked as "RFC4514" above
9702 output a Distinguished Name string which is
9704 parseable by Exim as a comma-separated tagged list
9705 (the exceptions being elements containing commas).
9706 RDN elements of a single type may be selected by
9707 a modifier of the type label; if so the expansion
9708 result is a list (newline-separated by default).
9709 The separator may be changed by another modifier of
9710 a right angle-bracket followed immediately by the new separator.
9711 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9713 The field selectors marked as "time" above
9714 take an optional modifier of "int"
9715 for which the result is the number of seconds since epoch.
9716 Otherwise the result is a human-readable string
9717 in the timezone selected by the main "timezone" option.
9719 The field selectors marked as "list" above return a list,
9720 newline-separated by default,
9721 (embedded separator characters in elements are doubled).
9722 The separator may be changed by a modifier of
9723 a right angle-bracket followed immediately by the new separator.
9725 The field selectors marked as "tagged" above
9726 prefix each list element with a type string and an equals sign.
9727 Elements of only one type may be selected by a modifier
9728 which is one of "dns", "uri" or "mail";
9729 if so the element tags are omitted.
9731 If not otherwise noted field values are presented in human-readable form.
9733 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9734 {*&<&'arg'&>&*}...}*&"
9736 This expansion dynamically loads and then calls a locally-written C function.
9737 This functionality is available only if Exim is compiled with
9741 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9742 object so that it doesn't reload the same object file in the same Exim process
9743 (but of course Exim does start new processes frequently).
9745 There may be from zero to eight arguments to the function.
9748 a local function that is to be called in this way,
9749 first &_DLFUNC_IMPL_& should be defined,
9750 and second &_local_scan.h_& should be included.
9751 The Exim variables and functions that are defined by that API
9752 are also available for dynamically loaded functions. The function itself
9753 must have the following type:
9755 int dlfunction(uschar **yield, int argc, uschar *argv[])
9757 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9758 function should return one of the following values:
9760 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9761 into the expanded string that is being built.
9763 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9764 from &'yield'&, if it is set.
9766 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9767 taken from &'yield'& if it is set.
9769 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9771 When compiling a function that is to be used in this way with gcc,
9772 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9773 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9776 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9777 .cindex "expansion" "extracting value from environment"
9778 .cindex "environment" "values from"
9779 The key is first expanded separately, and leading and trailing white space
9781 This is then searched for as a name in the environment.
9782 If a variable is found then its value is placed in &$value$&
9783 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9785 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9786 appear, for example:
9788 ${env{USER}{$value} fail }
9790 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9791 {<&'string1'&>} must be present for &"fail"& to be recognized.
9793 If {<&'string2'&>} is omitted an empty string is substituted on
9795 If {<&'string1'&>} is omitted the search result is substituted on
9798 The environment is adjusted by the &%keep_environment%& and
9799 &%add_environment%& main section options.
9802 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9803 {*&<&'string3'&>&*}}*&"
9804 .cindex "expansion" "extracting substrings by key"
9805 .cindex "&%extract%&" "substrings by key"
9806 The key and <&'string1'&> are first expanded separately. Leading and trailing
9807 white space is removed from the key (but not from any of the strings). The key
9808 must not be empty and must not consist entirely of digits.
9809 The expanded <&'string1'&> must be of the form:
9811 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9814 where the equals signs and spaces (but not both) are optional. If any of the
9815 values contain white space, they must be enclosed in double quotes, and any
9816 values that are enclosed in double quotes are subject to escape processing as
9817 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9818 for the value that corresponds to the key. The search is case-insensitive. If
9819 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9820 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9821 variable &$value$& contains the value that has been extracted. Afterwards, it
9822 is restored to any previous value it might have had.
9824 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9825 key is not found. If {<&'string2'&>} is also omitted, the value that was
9826 extracted is used. Thus, for example, these two expansions are identical, and
9829 ${extract{gid}{uid=1984 gid=2001}}
9830 ${extract{gid}{uid=1984 gid=2001}{$value}}
9832 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9833 appear, for example:
9835 ${extract{Z}{A=... B=...}{$value} fail }
9837 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9838 {<&'string2'&>} must be present for &"fail"& to be recognized.
9840 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9841 {*&<&'string3'&>&*}}*&" &&&
9842 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9843 {*&<&'string3'&>&*}}*&"
9844 .cindex "expansion" "extracting from JSON object"
9845 .cindex JSON expansions
9846 The key and <&'string1'&> are first expanded separately. Leading and trailing
9847 white space is removed from the key (but not from any of the strings). The key
9848 must not be empty and must not consist entirely of digits.
9849 The expanded <&'string1'&> must be of the form:
9851 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9854 The braces, commas and colons, and the quoting of the member name are required;
9855 the spaces are optional.
9856 Matching of the key against the member names is done case-sensitively.
9857 For the &"json"& variant,
9858 if a returned value is a JSON string, it retains its leading and
9860 For the &"jsons"& variant, which is intended for use with JSON strings, the
9861 leading and trailing quotes are removed from the returned value.
9862 . XXX should be a UTF-8 compare
9864 The results of matching are handled as above.
9867 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9868 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9869 .cindex "expansion" "extracting substrings by number"
9870 .cindex "&%extract%&" "substrings by number"
9871 The <&'number'&> argument must consist entirely of decimal digits,
9872 apart from leading and trailing white space, which is ignored.
9873 This is what distinguishes this form of &%extract%& from the previous kind. It
9874 behaves in the same way, except that, instead of extracting a named field, it
9875 extracts from <&'string1'&> the field whose number is given as the first
9876 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9877 <&'string3'&> as before.
9879 The fields in the string are separated by any one of the characters in the
9880 separator string. These may include space or tab characters.
9881 The first field is numbered one. If the number is negative, the fields are
9882 counted from the end of the string, with the rightmost one numbered -1. If the
9883 number given is zero, the entire string is returned. If the modulus of the
9884 number is greater than the number of fields in the string, the result is the
9885 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9886 provided. For example:
9888 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9892 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9894 yields &"99"&. Two successive separators mean that the field between them is
9895 empty (for example, the fifth field above).
9898 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9899 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9900 "&*${extract jsons{*&<&'number'&>&*}}&&&
9901 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9902 .cindex "expansion" "extracting from JSON array"
9903 .cindex JSON expansions
9904 The <&'number'&> argument must consist entirely of decimal digits,
9905 apart from leading and trailing white space, which is ignored.
9907 Field selection and result handling is as above;
9908 there is no choice of field separator.
9909 For the &"json"& variant,
9910 if a returned value is a JSON string, it retains its leading and
9912 For the &"jsons"& variant, which is intended for use with JSON strings, the
9913 leading and trailing quotes are removed from the returned value.
9916 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9917 .cindex "list" "selecting by condition"
9918 .cindex "expansion" "selecting from list by condition"
9920 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9921 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9923 in this list, its value is place in &$item$&, and then the condition is
9924 evaluated. If the condition is true, &$item$& is added to the output as an
9925 item in a new list; if the condition is false, the item is discarded. The
9926 separator used for the output list is the same as the one used for the
9927 input, but a separator setting is not included in the output. For example:
9929 ${filter{a:b:c}{!eq{$item}{b}}}
9931 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9932 to what it was before. See also the &%map%& and &%reduce%& expansion items.
9935 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9936 .cindex "hash function" "textual"
9937 .cindex "expansion" "textual hash"
9938 This is a textual hashing function, and was the first to be implemented in
9939 early versions of Exim. In current releases, there are other hashing functions
9940 (numeric, MD5, and SHA-1), which are described below.
9942 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9943 <&'n'&>. If you are using fixed values for these numbers, that is, if
9944 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9945 use the simpler operator notation that avoids some of the braces:
9947 ${hash_<n>_<m>:<string>}
9949 The second number is optional (in both notations). If <&'n'&> is greater than
9950 or equal to the length of the string, the expansion item returns the string.
9951 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9952 function to the string. The new string consists of characters taken from the
9953 first <&'m'&> characters of the string
9955 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9957 If <&'m'&> is not present the value 26 is used, so that only lower case
9958 letters appear. For example:
9960 &`$hash{3}{monty}} `& yields &`jmg`&
9961 &`$hash{5}{monty}} `& yields &`monty`&
9962 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9965 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9966 &*$h_*&<&'header&~name'&>&*:*&" &&&
9967 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9968 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9969 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9970 &*$lh_*&<&'header&~name'&>&*:*&" &&&
9971 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9972 &*$rh_*&<&'header&~name'&>&*:*&"
9973 .cindex "expansion" "header insertion"
9974 .vindex "&$header_$&"
9975 .vindex "&$bheader_$&"
9976 .vindex "&$lheader_$&"
9977 .vindex "&$rheader_$&"
9978 .cindex "header lines" "in expansion strings"
9979 .cindex "header lines" "character sets"
9980 .cindex "header lines" "decoding"
9981 Substitute the contents of the named message header line, for example
9985 The newline that terminates a header line is not included in the expansion, but
9986 internal newlines (caused by splitting the header line over several physical
9987 lines) may be present.
9989 The difference between the four pairs of expansions is in the way
9990 the data in the header line is interpreted.
9993 .cindex "white space" "in header lines"
9994 &%rheader%& gives the original &"raw"& content of the header line, with no
9995 processing at all, and without the removal of leading and trailing white space.
9998 .cindex "list" "of header lines"
9999 &%lheader%& gives a colon-separated list, one element per header when there
10000 are multiple headers with a given name.
10001 Any embedded colon characters within an element are doubled, so normal Exim
10002 list-processing facilities can be used.
10003 The terminating newline of each element is removed; in other respects
10004 the content is &"raw"&.
10007 .cindex "base64 encoding" "in header lines"
10008 &%bheader%& removes leading and trailing white space, and then decodes base64
10009 or quoted-printable MIME &"words"& within the header text, but does no
10010 character set translation. If decoding of what looks superficially like a MIME
10011 &"word"& fails, the raw string is returned. If decoding
10012 .cindex "binary zero" "in header line"
10013 produces a binary zero character, it is replaced by a question mark &-- this is
10014 what Exim does for binary zeros that are actually received in header lines.
10017 &%header%& tries to translate the string as decoded by &%bheader%& to a
10018 standard character set. This is an attempt to produce the same string as would
10019 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10020 returned. Translation is attempted only on operating systems that support the
10021 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10022 a system Makefile or in &_Local/Makefile_&.
10025 In a filter file, the target character set for &%header%& can be specified by a
10026 command of the following form:
10028 headers charset "UTF-8"
10030 This command affects all references to &$h_$& (or &$header_$&) expansions in
10031 subsequently obeyed filter commands. In the absence of this command, the target
10032 character set in a filter is taken from the setting of the &%headers_charset%&
10033 option in the runtime configuration. The value of this option defaults to the
10034 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10037 Header names follow the syntax of RFC 2822, which states that they may contain
10038 any printing characters except space and colon. Consequently, curly brackets
10039 &'do not'& terminate header names, and should not be used to enclose them as
10040 if they were variables. Attempting to do so causes a syntax error.
10042 Only header lines that are common to all copies of a message are visible to
10043 this mechanism. These are the original header lines that are received with the
10044 message, and any that are added by an ACL statement or by a system
10045 filter. Header lines that are added to a particular copy of a message by a
10046 router or transport are not accessible.
10048 For incoming SMTP messages, no header lines are visible in
10049 ACLs that are obeyed before the data phase completes,
10050 because the header structure is not set up until the message is received.
10051 They are visible in DKIM, PRDR and DATA ACLs.
10052 Header lines that are added in a RCPT ACL (for example)
10053 are saved until the message's incoming header lines are available, at which
10054 point they are added.
10055 When any of the above ACLs ar
10056 running, however, header lines added by earlier ACLs are visible.
10058 Upper case and lower case letters are synonymous in header names. If the
10059 following character is white space, the terminating colon may be omitted, but
10060 this is not recommended, because you may then forget it when it is needed. When
10061 white space terminates the header name, this white space is included in the
10062 expanded string. If the message does not contain the given header, the
10063 expansion item is replaced by an empty string. (See the &%def%& condition in
10064 section &<<SECTexpcond>>& for a means of testing for the existence of a
10067 If there is more than one header with the same name, they are all concatenated
10068 to form the substitution string, up to a maximum length of 64K. Unless
10069 &%rheader%& is being used, leading and trailing white space is removed from
10070 each header before concatenation, and a completely empty header is ignored. A
10071 newline character is then inserted between non-empty headers, but there is no
10072 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10073 those headers that contain lists of addresses, a comma is also inserted at the
10074 junctions between headers. This does not happen for the &%rheader%& expansion.
10077 .cindex "tainted data"
10078 When the headers are from an incoming message,
10079 the result of expanding any of these variables is tainted.
10083 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10084 .cindex "expansion" "hmac hashing"
10086 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10087 shared secret and some text into a message authentication code, as specified in
10088 RFC 2104. This differs from &`${md5:secret_text...}`& or
10089 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10090 cryptographic hash, allowing for authentication that is not possible with MD5
10091 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10092 present. For example:
10094 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10096 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10099 dd97e3ba5d1a61b5006108f8c8252953
10101 As an example of how this might be used, you might put in the main part of
10102 an Exim configuration:
10104 SPAMSCAN_SECRET=cohgheeLei2thahw
10106 In a router or a transport you could then have:
10109 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10110 ${hmac{md5}{SPAMSCAN_SECRET}\
10111 {${primary_hostname},${message_exim_id},$h_message-id:}}
10113 Then given a message, you can check where it was scanned by looking at the
10114 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10115 this header line is authentic by recomputing the authentication code from the
10116 host name, message ID and the &'Message-id:'& header line. This can be done
10117 using Exim's &%-be%& option, or by other means, for example, by using the
10118 &'hmac_md5_hex()'& function in Perl.
10121 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10122 .cindex "expansion" "conditional"
10123 .cindex "&%if%&, expansion item"
10124 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10125 item; otherwise <&'string2'&> is used. The available conditions are described
10126 in section &<<SECTexpcond>>& below. For example:
10128 ${if eq {$local_part}{postmaster} {yes}{no} }
10130 The second string need not be present; if it is not and the condition is not
10131 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10132 be present instead of the second string (without any curly brackets). In this
10133 case, the expansion is forced to fail if the condition is not true (see section
10134 &<<SECTforexpfai>>&).
10136 If both strings are omitted, the result is the string &`true`& if the condition
10137 is true, and the empty string if the condition is false. This makes it less
10138 cumbersome to write custom ACL and router conditions. For example, instead of
10140 condition = ${if >{$acl_m4}{3}{true}{false}}
10144 condition = ${if >{$acl_m4}{3}}
10149 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10150 .cindex expansion "imap folder"
10151 .cindex "&%imapfolder%& expansion item"
10152 This item converts a (possibly multilevel, or with non-ASCII characters)
10153 folder specification to a Maildir name for filesystem use.
10154 For information on internationalisation support see &<<SECTi18nMDA>>&.
10158 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10159 .cindex "expansion" "string truncation"
10160 .cindex "&%length%& expansion item"
10161 The &%length%& item is used to extract the initial portion of a string. Both
10162 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10163 you are using a fixed value for the number, that is, if <&'string1'&> does not
10164 change when expanded, you can use the simpler operator notation that avoids
10165 some of the braces:
10167 ${length_<n>:<string>}
10169 The result of this item is either the first <&'n'&> bytes or the whole
10170 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10171 &%strlen%&, which gives the length of a string.
10172 All measurement is done in bytes and is not UTF-8 aware.
10175 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10176 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10177 .cindex "expansion" "extracting list elements by number"
10178 .cindex "&%listextract%&" "extract list elements by number"
10179 .cindex "list" "extracting elements by number"
10180 The <&'number'&> argument must consist entirely of decimal digits,
10181 apart from an optional leading minus,
10182 and leading and trailing white space (which is ignored).
10184 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10185 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10187 The first field of the list is numbered one.
10188 If the number is negative, the fields are
10189 counted from the end of the list, with the rightmost one numbered -1.
10190 The numbered element of the list is extracted and placed in &$value$&,
10191 then <&'string2'&> is expanded as the result.
10193 If the modulus of the
10194 number is zero or greater than the number of fields in the string,
10195 the result is the expansion of <&'string3'&>.
10199 ${listextract{2}{x:42:99}}
10203 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10205 yields &"result: 42"&.
10207 If {<&'string3'&>} is omitted, an empty string is used for string3.
10208 If {<&'string2'&>} is also omitted, the value that was
10210 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10213 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10214 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10215 This is the first of one of two different types of lookup item, which are both
10216 described in the next item.
10218 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10219 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10220 .cindex "expansion" "lookup in"
10221 .cindex "file" "lookups"
10222 .cindex "lookup" "in expanded string"
10223 The two forms of lookup item specify data lookups in files and databases, as
10224 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10225 lookups, and the second is used for query-style lookups. The <&'key'&>,
10226 <&'file'&>, and <&'query'&> strings are expanded before use.
10228 If there is any white space in a lookup item which is part of a filter command,
10229 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10230 other place where white space is significant, the lookup item must be enclosed
10231 in double quotes. The use of data lookups in users' filter files may be locked
10232 out by the system administrator.
10234 .vindex "&$value$&"
10235 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10236 During its expansion, the variable &$value$& contains the data returned by the
10237 lookup. Afterwards it reverts to the value it had previously (at the outer
10238 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10239 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10240 string on failure. If <&'string2'&> is provided, it can itself be a nested
10241 lookup, thus providing a mechanism for looking up a default value when the
10242 original lookup fails.
10244 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10245 data for the outer lookup while the parameters of the second lookup are
10246 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10247 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10248 appear, and in this case, if the lookup fails, the entire expansion is forced
10249 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10250 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10251 successful lookup, and nothing in the case of failure.
10253 For single-key lookups, the string &"partial"& is permitted to precede the
10254 search type in order to do partial matching, and * or *@ may follow a search
10255 type to request default lookups if the key does not match (see sections
10256 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10258 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10259 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10260 and non-wild parts of the key during the expansion of the replacement text.
10261 They return to their previous values at the end of the lookup item.
10263 This example looks up the postmaster alias in the conventional alias file:
10265 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10267 This example uses NIS+ to look up the full name of the user corresponding to
10268 the local part of an address, forcing the expansion to fail if it is not found:
10270 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10275 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10276 .cindex "expansion" "list creation"
10278 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10279 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10281 in this list, its value is place in &$item$&, and then <&'string2'&> is
10282 expanded and added to the output as an item in a new list. The separator used
10283 for the output list is the same as the one used for the input, but a separator
10284 setting is not included in the output. For example:
10286 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10288 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10289 value of &$item$& is restored to what it was before. See also the &%filter%&
10290 and &%reduce%& expansion items.
10292 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10293 .cindex "expansion" "numeric hash"
10294 .cindex "hash function" "numeric"
10295 The three strings are expanded; the first two must yield numbers. Call them
10296 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10297 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10298 can use the simpler operator notation that avoids some of the braces:
10300 ${nhash_<n>_<m>:<string>}
10302 The second number is optional (in both notations). If there is only one number,
10303 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10304 processed by a div/mod hash function that returns two numbers, separated by a
10305 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10308 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10310 returns the string &"6/33"&.
10314 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10315 .cindex "Perl" "use in expanded string"
10316 .cindex "expansion" "calling Perl from"
10317 This item is available only if Exim has been built to include an embedded Perl
10318 interpreter. The subroutine name and the arguments are first separately
10319 expanded, and then the Perl subroutine is called with those arguments. No
10320 additional arguments need be given; the maximum number permitted, including the
10321 name of the subroutine, is nine.
10323 The return value of the subroutine is inserted into the expanded string, unless
10324 the return value is &%undef%&. In that case, the expansion fails in the same
10325 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
10326 Whatever you return is evaluated in a scalar context. For example, if you
10327 return the name of a Perl vector, the return value is the size of the vector,
10330 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10331 with the error message that was passed to &%die%&. More details of the embedded
10332 Perl facility are given in chapter &<<CHAPperl>>&.
10334 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10335 out the use of this expansion item in filter files.
10338 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10339 .cindex "&%prvs%& expansion item"
10340 The first argument is a complete email address and the second is secret
10341 keystring. The third argument, specifying a key number, is optional. If absent,
10342 it defaults to 0. The result of the expansion is a prvs-signed email address,
10343 to be typically used with the &%return_path%& option on an &(smtp)& transport
10344 as part of a bounce address tag validation (BATV) scheme. For more discussion
10345 and an example, see section &<<SECTverifyPRVS>>&.
10347 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10348 {*&<&'string'&>&*}}*&"
10349 .cindex "&%prvscheck%& expansion item"
10350 This expansion item is the complement of the &%prvs%& item. It is used for
10351 checking prvs-signed addresses. If the expansion of the first argument does not
10352 yield a syntactically valid prvs-signed address, the whole item expands to the
10353 empty string. When the first argument does expand to a syntactically valid
10354 prvs-signed address, the second argument is expanded, with the prvs-decoded
10355 version of the address and the key number extracted from the address in the
10356 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10358 These two variables can be used in the expansion of the second argument to
10359 retrieve the secret. The validity of the prvs-signed address is then checked
10360 against the secret. The result is stored in the variable &$prvscheck_result$&,
10361 which is empty for failure or &"1"& for success.
10363 The third argument is optional; if it is missing, it defaults to an empty
10364 string. This argument is now expanded. If the result is an empty string, the
10365 result of the expansion is the decoded version of the address. This is the case
10366 whether or not the signature was valid. Otherwise, the result of the expansion
10367 is the expansion of the third argument.
10369 All three variables can be used in the expansion of the third argument.
10370 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10371 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10373 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10374 .cindex "expansion" "inserting an entire file"
10375 .cindex "file" "inserting into expansion"
10376 .cindex "&%readfile%& expansion item"
10377 The filename and end-of-line string are first expanded separately. The file is
10378 then read, and its contents replace the entire item. All newline characters in
10379 the file are replaced by the end-of-line string if it is present. Otherwise,
10380 newlines are left in the string.
10381 String expansion is not applied to the contents of the file. If you want this,
10382 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10383 the string expansion fails.
10385 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10386 locks out the use of this expansion item in filter files.
10390 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10391 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10392 .cindex "expansion" "inserting from a socket"
10393 .cindex "socket, use of in expansion"
10394 .cindex "&%readsocket%& expansion item"
10395 This item inserts data from a Unix domain or TCP socket into the expanded
10396 string. The minimal way of using it uses just two arguments, as in these
10399 ${readsocket{/socket/name}{request string}}
10400 ${readsocket{inet:some.host:1234}{request string}}
10402 For a Unix domain socket, the first substring must be the path to the socket.
10403 For an Internet socket, the first substring must contain &`inet:`& followed by
10404 a host name or IP address, followed by a colon and a port, which can be a
10405 number or the name of a TCP port in &_/etc/services_&. An IP address may
10406 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10409 ${readsocket{inet:[::1]:1234}{request string}}
10411 Only a single host name may be given, but if looking it up yields more than
10412 one IP address, they are each tried in turn until a connection is made. For
10413 both kinds of socket, Exim makes a connection, writes the request string
10414 unless it is an empty string; and no terminating NUL is ever sent)
10415 and reads from the socket until an end-of-file
10416 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10417 extend what can be done. Firstly, you can vary the timeout. For example:
10419 ${readsocket{/socket/name}{request string}{3s}}
10422 The third argument is a list of options, of which the first element is the timeout
10423 and must be present if any options are given.
10424 Further elements are options of form &'name=value'&.
10427 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10431 The following option names are recognised:
10434 Defines if the result data can be cached for use by a later identical
10435 request in the same process.
10436 Values are &"yes"& or &"no"& (the default).
10437 If not, all cached results for this connection specification
10438 will be invalidated.
10442 Defines whether or not a write-shutdown is done on the connection after
10443 sending the request. Values are &"yes"& (the default) or &"no"&
10444 (preferred, eg. by some webservers).
10448 Controls the use of TLS on the connection.
10449 Values are &"yes"& or &"no"& (the default).
10450 If it is enabled, a shutdown as descripbed above is never done.
10455 A fourth argument allows you to change any newlines that are in the data
10456 that is read, in the same way as for &%readfile%& (see above). This example
10457 turns them into spaces:
10459 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10461 As with all expansions, the substrings are expanded before the processing
10462 happens. Errors in these sub-expansions cause the expansion to fail. In
10463 addition, the following errors can occur:
10466 Failure to create a socket file descriptor;
10468 Failure to connect the socket;
10470 Failure to write the request string;
10472 Timeout on reading from the socket.
10475 By default, any of these errors causes the expansion to fail. However, if
10476 you supply a fifth substring, it is expanded and used when any of the above
10477 errors occurs. For example:
10479 ${readsocket{/socket/name}{request string}{3s}{\n}\
10482 You can test for the existence of a Unix domain socket by wrapping this
10483 expansion in &`${if exists`&, but there is a race condition between that test
10484 and the actual opening of the socket, so it is safer to use the fifth argument
10485 if you want to be absolutely sure of avoiding an expansion error for a
10486 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10488 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10489 locks out the use of this expansion item in filter files.
10492 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10493 .cindex "expansion" "reducing a list to a scalar"
10494 .cindex "list" "reducing to a scalar"
10495 .vindex "&$value$&"
10497 This operation reduces a list to a single, scalar string. After expansion,
10498 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10499 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10500 Then <&'string2'&> is expanded and
10501 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10502 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10503 them. The result of that expansion is assigned to &$value$& before the next
10504 iteration. When the end of the list is reached, the final value of &$value$& is
10505 added to the expansion output. The &%reduce%& expansion item can be used in a
10506 number of ways. For example, to add up a list of numbers:
10508 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10510 The result of that expansion would be &`6`&. The maximum of a list of numbers
10513 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10515 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10516 restored to what they were before. See also the &%filter%& and &%map%&
10519 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10520 This item inserts &"raw"& header lines. It is described with the &%header%&
10521 expansion item in section &<<SECTexpansionitems>>& above.
10523 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10524 {*&<&'string2'&>&*}}*&"
10525 .cindex "expansion" "running a command"
10526 .cindex "&%run%& expansion item"
10527 The command and its arguments are first expanded as one string. The string is
10528 split apart into individual arguments by spaces, and then the command is run
10529 in a separate process, but under the same uid and gid. As in other command
10530 executions from Exim, a shell is not used by default. If the command requires
10531 a shell, you must explicitly code it.
10533 Since the arguments are split by spaces, when there is a variable expansion
10534 which has an empty result, it will cause the situation that the argument will
10535 simply be omitted when the program is actually executed by Exim. If the
10536 script/program requires a specific number of arguments and the expanded
10537 variable could possibly result in this empty expansion, the variable must be
10538 quoted. This is more difficult if the expanded variable itself could result
10539 in a string containing quotes, because it would interfere with the quotes
10540 around the command arguments. A possible guard against this is to wrap the
10541 variable in the &%sg%& operator to change any quote marks to some other
10544 The standard input for the command exists, but is empty. The standard output
10545 and standard error are set to the same file descriptor.
10546 .cindex "return code" "from &%run%& expansion"
10547 .vindex "&$value$&"
10548 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10549 and replaces the entire item; during this expansion, the standard output/error
10550 from the command is in the variable &$value$&. If the command fails,
10551 <&'string2'&>, if present, is expanded and used. Once again, during the
10552 expansion, the standard output/error from the command is in the variable
10555 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10556 can be the word &"fail"& (not in braces) to force expansion failure if the
10557 command does not succeed. If both strings are omitted, the result is contents
10558 of the standard output/error on success, and nothing on failure.
10560 .vindex "&$run_in_acl$&"
10561 The standard output/error of the command is put in the variable &$value$&.
10562 In this ACL example, the output of a command is logged for the admin to
10565 warn condition = ${run{/usr/bin/id}{yes}{no}}
10566 log_message = Output of id: $value
10568 If the command requires shell idioms, such as the > redirect operator, the
10569 shell must be invoked directly, such as with:
10571 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10574 .vindex "&$runrc$&"
10575 The return code from the command is put in the variable &$runrc$&, and this
10576 remains set afterwards, so in a filter file you can do things like this:
10578 if "${run{x y z}{}}$runrc" is 1 then ...
10579 elif $runrc is 2 then ...
10583 If execution of the command fails (for example, the command does not exist),
10584 the return code is 127 &-- the same code that shells use for non-existent
10587 &*Warning*&: In a router or transport, you cannot assume the order in which
10588 option values are expanded, except for those preconditions whose order of
10589 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10590 by the expansion of one option, and use it in another.
10592 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10593 out the use of this expansion item in filter files.
10596 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10597 .cindex "expansion" "string substitution"
10598 .cindex "&%sg%& expansion item"
10599 This item works like Perl's substitution operator (s) with the global (/g)
10600 option; hence its name. However, unlike the Perl equivalent, Exim does not
10601 modify the subject string; instead it returns the modified string for insertion
10602 into the overall expansion. The item takes three arguments: the subject string,
10603 a regular expression, and a substitution string. For example:
10605 ${sg{abcdefabcdef}{abc}{xyz}}
10607 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10608 if any $, } or \ characters are required in the regular expression or in the
10609 substitution string, they have to be escaped. For example:
10611 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10613 yields &"defabc"&, and
10615 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10617 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10618 the regular expression from string expansion.
10620 The regular expression is compiled in 8-bit mode, working against bytes
10621 rather than any Unicode-aware character handling.
10624 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10625 .cindex sorting "a list"
10626 .cindex list sorting
10627 .cindex expansion "list sorting"
10628 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10629 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10630 The <&'comparator'&> argument is interpreted as the operator
10631 of a two-argument expansion condition.
10632 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10633 The comparison should return true when applied to two values
10634 if the first value should sort before the second value.
10635 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10636 the element being placed in &$item$&,
10637 to give values for comparison.
10639 The item result is a sorted list,
10640 with the original list separator,
10641 of the list elements (in full) of the original.
10645 ${sort{3:2:1:4}{<}{$item}}
10647 sorts a list of numbers, and
10649 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10651 will sort an MX lookup into priority order.
10656 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10657 SRS encoding. See SECT &<<SECTSRS>>& for details.
10662 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10663 .cindex "&%substr%& expansion item"
10664 .cindex "substring extraction"
10665 .cindex "expansion" "substring extraction"
10666 The three strings are expanded; the first two must yield numbers. Call them
10667 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10668 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10669 can use the simpler operator notation that avoids some of the braces:
10671 ${substr_<n>_<m>:<string>}
10673 The second number is optional (in both notations).
10674 If it is absent in the simpler format, the preceding underscore must also be
10677 The &%substr%& item can be used to extract more general substrings than
10678 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10679 length required. For example
10681 ${substr{3}{2}{$local_part}}
10683 If the starting offset is greater than the string length the result is the
10684 null string; if the length plus starting offset is greater than the string
10685 length, the result is the right-hand part of the string, starting from the
10686 given offset. The first byte (character) in the string has offset zero.
10688 The &%substr%& expansion item can take negative offset values to count
10689 from the right-hand end of its operand. The last byte (character) is offset -1,
10690 the second-last is offset -2, and so on. Thus, for example,
10692 ${substr{-5}{2}{1234567}}
10694 yields &"34"&. If the absolute value of a negative offset is greater than the
10695 length of the string, the substring starts at the beginning of the string, and
10696 the length is reduced by the amount of overshoot. Thus, for example,
10698 ${substr{-5}{2}{12}}
10700 yields an empty string, but
10702 ${substr{-3}{2}{12}}
10706 When the second number is omitted from &%substr%&, the remainder of the string
10707 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10708 string preceding the offset point are taken. For example, an offset of -1 and
10709 no length, as in these semantically identical examples:
10712 ${substr{-1}{abcde}}
10714 yields all but the last character of the string, that is, &"abcd"&.
10716 All measurement is done in bytes and is not UTF-8 aware.
10720 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10721 {*&<&'replacements'&>&*}}*&"
10722 .cindex "expansion" "character translation"
10723 .cindex "&%tr%& expansion item"
10724 This item does single-character (in bytes) translation on its subject string. The second
10725 argument is a list of characters to be translated in the subject string. Each
10726 matching character is replaced by the corresponding character from the
10727 replacement list. For example
10729 ${tr{abcdea}{ac}{13}}
10731 yields &`1b3de1`&. If there are duplicates in the second character string, the
10732 last occurrence is used. If the third string is shorter than the second, its
10733 last character is replicated. However, if it is empty, no translation takes
10736 All character handling is done in bytes and is not UTF-8 aware.
10742 .section "Expansion operators" "SECTexpop"
10743 .cindex "expansion" "operators"
10744 For expansion items that perform transformations on a single argument string,
10745 the &"operator"& notation is used because it is simpler and uses fewer braces.
10746 The substring is first expanded before the operation is applied to it. The
10747 following operations can be performed:
10750 .vitem &*${address:*&<&'string'&>&*}*&
10751 .cindex "expansion" "RFC 2822 address handling"
10752 .cindex "&%address%& expansion item"
10753 The string is interpreted as an RFC 2822 address, as it might appear in a
10754 header line, and the effective address is extracted from it. If the string does
10755 not parse successfully, the result is empty.
10757 The parsing correctly handles SMTPUTF8 Unicode in the string.
10760 .vitem &*${addresses:*&<&'string'&>&*}*&
10761 .cindex "expansion" "RFC 2822 address handling"
10762 .cindex "&%addresses%& expansion item"
10763 The string (after expansion) is interpreted as a list of addresses in RFC
10764 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10765 operative address (&'local-part@domain'&) is extracted from each item, and the
10766 result of the expansion is a colon-separated list, with appropriate
10767 doubling of colons should any happen to be present in the email addresses.
10768 Syntactically invalid RFC2822 address items are omitted from the output.
10770 It is possible to specify a character other than colon for the output
10771 separator by starting the string with > followed by the new separator
10772 character. For example:
10774 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10776 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10777 first, so if the expanded string starts with >, it may change the output
10778 separator unintentionally. This can be avoided by setting the output
10779 separator explicitly:
10781 ${addresses:>:$h_from:}
10784 Compare the &%address%& (singular)
10785 expansion item, which extracts the working address from a single RFC2822
10786 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10789 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10790 a strict interpretation of header line formatting. Exim parses the bare,
10791 unquoted portion of an email address and if it finds a comma, treats it as an
10792 email address separator. For the example header line:
10794 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10796 The first example below demonstrates that Q-encoded email addresses are parsed
10797 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10798 It does not see the comma because it's still encoded as "=2C". The second
10799 example below is passed the contents of &`$header_from:`&, meaning it gets
10800 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10801 The third example shows that the presence of a comma is skipped when it is
10802 quoted. The fourth example shows SMTPUTF8 handling.
10804 # exim -be '${addresses:From: \
10805 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10807 # exim -be '${addresses:From: Last, First <user@example.com>}'
10808 Last:user@example.com
10809 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10811 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10815 .vitem &*${base32:*&<&'digits'&>&*}*&
10816 .cindex "&%base32%& expansion item"
10817 .cindex "expansion" "conversion to base 32"
10818 The string must consist entirely of decimal digits. The number is converted to
10819 base 32 and output as a (empty, for zero) string of characters.
10820 Only lowercase letters are used.
10822 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10823 .cindex "&%base32d%& expansion item"
10824 .cindex "expansion" "conversion to base 32"
10825 The string must consist entirely of base-32 digits.
10826 The number is converted to decimal and output as a string.
10828 .vitem &*${base62:*&<&'digits'&>&*}*&
10829 .cindex "&%base62%& expansion item"
10830 .cindex "expansion" "conversion to base 62"
10831 The string must consist entirely of decimal digits. The number is converted to
10832 base 62 and output as a string of six characters, including leading zeros. In
10833 the few operating environments where Exim uses base 36 instead of base 62 for
10834 its message identifiers (because those systems do not have case-sensitive
10835 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10836 to be absolutely clear: this is &'not'& base64 encoding.
10838 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10839 .cindex "&%base62d%& expansion item"
10840 .cindex "expansion" "conversion to base 62"
10841 The string must consist entirely of base-62 digits, or, in operating
10842 environments where Exim uses base 36 instead of base 62 for its message
10843 identifiers, base-36 digits. The number is converted to decimal and output as a
10846 .vitem &*${base64:*&<&'string'&>&*}*&
10847 .cindex "expansion" "base64 encoding"
10848 .cindex "base64 encoding" "in string expansion"
10849 .cindex "&%base64%& expansion item"
10850 .cindex certificate "base64 of DER"
10851 This operator converts a string into one that is base64 encoded.
10853 If the string is a single variable of type certificate,
10854 returns the base64 encoding of the DER form of the certificate.
10857 .vitem &*${base64d:*&<&'string'&>&*}*&
10858 .cindex "expansion" "base64 decoding"
10859 .cindex "base64 decoding" "in string expansion"
10860 .cindex "&%base64d%& expansion item"
10861 This operator converts a base64-encoded string into the un-coded form.
10864 .vitem &*${domain:*&<&'string'&>&*}*&
10865 .cindex "domain" "extraction"
10866 .cindex "expansion" "domain extraction"
10867 The string is interpreted as an RFC 2822 address and the domain is extracted
10868 from it. If the string does not parse successfully, the result is empty.
10871 .vitem &*${escape:*&<&'string'&>&*}*&
10872 .cindex "expansion" "escaping non-printing characters"
10873 .cindex "&%escape%& expansion item"
10874 If the string contains any non-printing characters, they are converted to
10875 escape sequences starting with a backslash. Whether characters with the most
10876 significant bit set (so-called &"8-bit characters"&) count as printing or not
10877 is controlled by the &%print_topbitchars%& option.
10879 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10880 .cindex "expansion" "escaping 8-bit characters"
10881 .cindex "&%escape8bit%& expansion item"
10882 If the string contains and characters with the most significant bit set,
10883 they are converted to escape sequences starting with a backslash.
10884 Backslashes and DEL characters are also converted.
10887 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10888 .cindex "expansion" "expression evaluation"
10889 .cindex "expansion" "arithmetic expression"
10890 .cindex "&%eval%& expansion item"
10891 These items supports simple arithmetic and bitwise logical operations in
10892 expansion strings. The string (after expansion) must be a conventional
10893 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10894 logical operators, and parentheses. All operations are carried out using
10895 integer arithmetic. The operator priorities are as follows (the same as in the
10896 C programming language):
10898 .irow &'highest:'& "not (~), negate (-)"
10899 .irow "" "multiply (*), divide (/), remainder (%)"
10900 .irow "" "plus (+), minus (-)"
10901 .irow "" "shift-left (<<), shift-right (>>)"
10902 .irow "" "and (&&)"
10904 .irow &'lowest:'& "or (|)"
10906 Binary operators with the same priority are evaluated from left to right. White
10907 space is permitted before or after operators.
10909 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10910 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10911 decimal, even if they start with a leading zero; hexadecimal numbers are not
10912 permitted. This can be useful when processing numbers extracted from dates or
10913 times, which often do have leading zeros.
10915 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10917 respectively. Negative numbers are supported. The result of the computation is
10918 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10921 &`${eval:1+1} `& yields 2
10922 &`${eval:1+2*3} `& yields 7
10923 &`${eval:(1+2)*3} `& yields 9
10924 &`${eval:2+42%5} `& yields 4
10925 &`${eval:0xc&5} `& yields 4
10926 &`${eval:0xc|5} `& yields 13
10927 &`${eval:0xc^5} `& yields 9
10928 &`${eval:0xc>>1} `& yields 6
10929 &`${eval:0xc<<1} `& yields 24
10930 &`${eval:~255&0x1234} `& yields 4608
10931 &`${eval:-(~255&0x1234)} `& yields -4608
10934 As a more realistic example, in an ACL you might have
10936 deny message = Too many bad recipients
10939 {>{$rcpt_count}{10}} \
10942 {$recipients_count} \
10943 {${eval:$rcpt_count/2}} \
10947 The condition is true if there have been more than 10 RCPT commands and
10948 fewer than half of them have resulted in a valid recipient.
10951 .vitem &*${expand:*&<&'string'&>&*}*&
10952 .cindex "expansion" "re-expansion of substring"
10953 The &%expand%& operator causes a string to be expanded for a second time. For
10956 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10958 first looks up a string in a file while expanding the operand for &%expand%&,
10959 and then re-expands what it has found.
10962 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10964 .cindex "UTF-8" "conversion from"
10965 .cindex "expansion" "UTF-8 conversion"
10966 .cindex "&%from_utf8%& expansion item"
10967 The world is slowly moving towards Unicode, although there are no standards for
10968 email yet. However, other applications (including some databases) are starting
10969 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10970 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10971 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10972 the result is an undefined sequence of bytes.
10974 Unicode code points with values less than 256 are compatible with ASCII and
10975 ISO-8859-1 (also known as Latin-1).
10976 For example, character 169 is the copyright symbol in both cases, though the
10977 way it is encoded is different. In UTF-8, more than one byte is needed for
10978 characters with code values greater than 127, whereas ISO-8859-1 is a
10979 single-byte encoding (but thereby limited to 256 characters). This makes
10980 translation from UTF-8 to ISO-8859-1 straightforward.
10983 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10984 .cindex "hash function" "textual"
10985 .cindex "expansion" "textual hash"
10986 The &%hash%& operator is a simpler interface to the hashing function that can
10987 be used when the two parameters are fixed numbers (as opposed to strings that
10988 change when expanded). The effect is the same as
10990 ${hash{<n>}{<m>}{<string>}}
10992 See the description of the general &%hash%& item above for details. The
10993 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10997 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10998 .cindex "base64 encoding" "conversion from hex"
10999 .cindex "expansion" "hex to base64"
11000 .cindex "&%hex2b64%& expansion item"
11001 This operator converts a hex string into one that is base64 encoded. This can
11002 be useful for processing the output of the various hashing functions.
11006 .vitem &*${hexquote:*&<&'string'&>&*}*&
11007 .cindex "quoting" "hex-encoded unprintable characters"
11008 .cindex "&%hexquote%& expansion item"
11009 This operator converts non-printable characters in a string into a hex
11010 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11011 as is, and other byte values are converted to &`\xNN`&, for example, a
11012 byte value 127 is converted to &`\x7f`&.
11015 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11016 .cindex "&%ipv6denorm%& expansion item"
11017 .cindex "IP address" normalisation
11018 This expands an IPv6 address to a full eight-element colon-separated set
11019 of hex digits including leading zeroes.
11020 A trailing ipv4-style dotted-decimal set is converted to hex.
11021 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11023 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11024 .cindex "&%ipv6norm%& expansion item"
11025 .cindex "IP address" normalisation
11026 .cindex "IP address" "canonical form"
11027 This converts an IPv6 address to canonical form.
11028 Leading zeroes of groups are omitted, and the longest
11029 set of zero-valued groups is replaced with a double colon.
11030 A trailing ipv4-style dotted-decimal set is converted to hex.
11031 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11034 .vitem &*${lc:*&<&'string'&>&*}*&
11035 .cindex "case forcing in strings"
11036 .cindex "string" "case forcing"
11037 .cindex "lower casing"
11038 .cindex "expansion" "case forcing"
11039 .cindex "&%lc%& expansion item"
11040 This forces the letters in the string into lower-case, for example:
11044 Case is defined per the system C locale.
11046 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11047 .cindex "expansion" "string truncation"
11048 .cindex "&%length%& expansion item"
11049 The &%length%& operator is a simpler interface to the &%length%& function that
11050 can be used when the parameter is a fixed number (as opposed to a string that
11051 changes when expanded). The effect is the same as
11053 ${length{<number>}{<string>}}
11055 See the description of the general &%length%& item above for details. Note that
11056 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11057 when &%length%& is used as an operator.
11058 All measurement is done in bytes and is not UTF-8 aware.
11061 .vitem &*${listcount:*&<&'string'&>&*}*&
11062 .cindex "expansion" "list item count"
11063 .cindex "list" "item count"
11064 .cindex "list" "count of items"
11065 .cindex "&%listcount%& expansion item"
11066 The string is interpreted as a list and the number of items is returned.
11069 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11070 .cindex "expansion" "named list"
11071 .cindex "&%listnamed%& expansion item"
11072 The name is interpreted as a named list and the content of the list is returned,
11073 expanding any referenced lists, re-quoting as needed for colon-separation.
11074 If the optional type is given it must be one of "a", "d", "h" or "l"
11075 and selects address-, domain-, host- or localpart- lists to search among respectively.
11076 Otherwise all types are searched in an undefined order and the first
11077 matching list is returned.
11080 .vitem &*${local_part:*&<&'string'&>&*}*&
11081 .cindex "expansion" "local part extraction"
11082 .cindex "&%local_part%& expansion item"
11083 The string is interpreted as an RFC 2822 address and the local part is
11084 extracted from it. If the string does not parse successfully, the result is
11086 The parsing correctly handles SMTPUTF8 Unicode in the string.
11089 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11090 .cindex "masked IP address"
11091 .cindex "IP address" "masking"
11092 .cindex "CIDR notation"
11093 .cindex "expansion" "IP address masking"
11094 .cindex "&%mask%& expansion item"
11095 If the form of the string to be operated on is not an IP address followed by a
11096 slash and an integer (that is, a network address in CIDR notation), the
11097 expansion fails. Otherwise, this operator converts the IP address to binary,
11098 masks off the least significant bits according to the bit count, and converts
11099 the result back to text, with mask appended. For example,
11101 ${mask:10.111.131.206/28}
11103 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11104 be mostly used for looking up masked addresses in files, the result for an IPv6
11105 address uses dots to separate components instead of colons, because colon
11106 terminates a key string in lsearch files. So, for example,
11108 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11112 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11114 Letters in IPv6 addresses are always output in lower case.
11117 .vitem &*${md5:*&<&'string'&>&*}*&
11119 .cindex "expansion" "MD5 hash"
11120 .cindex certificate fingerprint
11121 .cindex "&%md5%& expansion item"
11122 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11123 as a 32-digit hexadecimal number, in which any letters are in lower case.
11125 If the string is a single variable of type certificate,
11126 returns the MD5 hash fingerprint of the certificate.
11129 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11130 .cindex "expansion" "numeric hash"
11131 .cindex "hash function" "numeric"
11132 The &%nhash%& operator is a simpler interface to the numeric hashing function
11133 that can be used when the two parameters are fixed numbers (as opposed to
11134 strings that change when expanded). The effect is the same as
11136 ${nhash{<n>}{<m>}{<string>}}
11138 See the description of the general &%nhash%& item above for details.
11141 .vitem &*${quote:*&<&'string'&>&*}*&
11142 .cindex "quoting" "in string expansions"
11143 .cindex "expansion" "quoting"
11144 .cindex "&%quote%& expansion item"
11145 The &%quote%& operator puts its argument into double quotes if it
11146 is an empty string or
11147 contains anything other than letters, digits, underscores, dots, and hyphens.
11148 Any occurrences of double quotes and backslashes are escaped with a backslash.
11149 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11150 respectively For example,
11158 The place where this is useful is when the argument is a substitution from a
11159 variable or a message header.
11161 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11162 .cindex "&%quote_local_part%& expansion item"
11163 This operator is like &%quote%&, except that it quotes the string only if
11164 required to do so by the rules of RFC 2822 for quoting local parts. For
11165 example, a plus sign would not cause quoting (but it would for &%quote%&).
11166 If you are creating a new email address from the contents of &$local_part$&
11167 (or any other unknown data), you should always use this operator.
11169 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11170 will likely use the quoting form.
11171 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11174 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11175 .cindex "quoting" "lookup-specific"
11176 This operator applies lookup-specific quoting rules to the string. Each
11177 query-style lookup type has its own quoting rules which are described with
11178 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11180 ${quote_ldap:two * two}
11186 For single-key lookup types, no quoting is ever necessary and this operator
11187 yields an unchanged string.
11190 .vitem &*${randint:*&<&'n'&>&*}*&
11191 .cindex "random number"
11192 This operator returns a somewhat random number which is less than the
11193 supplied number and is at least 0. The quality of this randomness depends
11194 on how Exim was built; the values are not suitable for keying material.
11195 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11196 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11197 for versions of GnuTLS with that function.
11198 Otherwise, the implementation may be arc4random(), random() seeded by
11199 srandomdev() or srandom(), or a custom implementation even weaker than
11203 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11204 .cindex "expansion" "IP address"
11205 This operator reverses an IP address; for IPv4 addresses, the result is in
11206 dotted-quad decimal form, while for IPv6 addresses the result is in
11207 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11208 for DNS. For example,
11210 ${reverse_ip:192.0.2.4}
11211 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11216 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11220 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11221 .cindex "expansion" "RFC 2047"
11222 .cindex "RFC 2047" "expansion operator"
11223 .cindex "&%rfc2047%& expansion item"
11224 This operator encodes text according to the rules of RFC 2047. This is an
11225 encoding that is used in header lines to encode non-ASCII characters. It is
11226 assumed that the input string is in the encoding specified by the
11227 &%headers_charset%& option, which gets its default at build time. If the string
11228 contains only characters in the range 33&--126, and no instances of the
11231 ? = ( ) < > @ , ; : \ " . [ ] _
11233 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11234 string, using as many &"encoded words"& as necessary to encode all the
11238 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11239 .cindex "expansion" "RFC 2047"
11240 .cindex "RFC 2047" "decoding"
11241 .cindex "&%rfc2047d%& expansion item"
11242 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11243 bytes are replaced by question marks. Characters are converted into the
11244 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11245 not recognized unless &%check_rfc2047_length%& is set false.
11247 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11248 access a header line, RFC 2047 decoding is done automatically. You do not need
11249 to use this operator as well.
11253 .vitem &*${rxquote:*&<&'string'&>&*}*&
11254 .cindex "quoting" "in regular expressions"
11255 .cindex "regular expressions" "quoting"
11256 .cindex "&%rxquote%& expansion item"
11257 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11258 characters in its argument. This is useful when substituting the values of
11259 variables or headers inside regular expressions.
11262 .vitem &*${sha1:*&<&'string'&>&*}*&
11263 .cindex "SHA-1 hash"
11264 .cindex "expansion" "SHA-1 hashing"
11265 .cindex certificate fingerprint
11266 .cindex "&%sha1%& expansion item"
11267 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11268 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11270 If the string is a single variable of type certificate,
11271 returns the SHA-1 hash fingerprint of the certificate.
11274 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11275 &*${sha2:*&<&'string'&>&*}*& &&&
11276 &*${sha2_<n>:*&<&'string'&>&*}*&
11277 .cindex "SHA-256 hash"
11278 .cindex "SHA-2 hash"
11279 .cindex certificate fingerprint
11280 .cindex "expansion" "SHA-256 hashing"
11281 .cindex "&%sha256%& expansion item"
11282 .cindex "&%sha2%& expansion item"
11283 The &%sha256%& operator computes the SHA-256 hash value of the string
11285 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11287 If the string is a single variable of type certificate,
11288 returns the SHA-256 hash fingerprint of the certificate.
11290 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11291 (except for certificates, which are not supported).
11292 Finally, if an underbar
11293 and a number is appended it specifies the output length, selecting a
11294 member of the SHA-2 family of hash functions.
11295 Values of 256, 384 and 512 are accepted, with 256 being the default.
11298 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11299 &*${sha3_<n>:*&<&'string'&>&*}*&
11300 .cindex "SHA3 hash"
11301 .cindex "expansion" "SHA3 hashing"
11302 .cindex "&%sha3%& expansion item"
11303 The &%sha3%& operator computes the SHA3-256 hash value of the string
11305 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11307 If a number is appended, separated by an underbar, it specifies
11308 the output length. Values of 224, 256, 384 and 512 are accepted;
11309 with 256 being the default.
11311 The &%sha3%& expansion item is only supported if Exim has been
11312 compiled with GnuTLS 3.5.0 or later,
11313 or OpenSSL 1.1.1 or later.
11314 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11317 .vitem &*${stat:*&<&'string'&>&*}*&
11318 .cindex "expansion" "statting a file"
11319 .cindex "file" "extracting characteristics"
11320 .cindex "&%stat%& expansion item"
11321 The string, after expansion, must be a file path. A call to the &[stat()]&
11322 function is made for this path. If &[stat()]& fails, an error occurs and the
11323 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11324 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11325 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11326 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11327 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11328 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11329 can extract individual fields using the &%extract%& expansion item.
11331 The use of the &%stat%& expansion in users' filter files can be locked out by
11332 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11333 systems for files larger than 2GB.
11335 .vitem &*${str2b64:*&<&'string'&>&*}*&
11336 .cindex "&%str2b64%& expansion item"
11337 Now deprecated, a synonym for the &%base64%& expansion operator.
11341 .vitem &*${strlen:*&<&'string'&>&*}*&
11342 .cindex "expansion" "string length"
11343 .cindex "string" "length in expansion"
11344 .cindex "&%strlen%& expansion item"
11345 The item is replace by the length of the expanded string, expressed as a
11346 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11347 All measurement is done in bytes and is not UTF-8 aware.
11350 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11351 .cindex "&%substr%& expansion item"
11352 .cindex "substring extraction"
11353 .cindex "expansion" "substring expansion"
11354 The &%substr%& operator is a simpler interface to the &%substr%& function that
11355 can be used when the two parameters are fixed numbers (as opposed to strings
11356 that change when expanded). The effect is the same as
11358 ${substr{<start>}{<length>}{<string>}}
11360 See the description of the general &%substr%& item above for details. The
11361 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11362 All measurement is done in bytes and is not UTF-8 aware.
11364 .vitem &*${time_eval:*&<&'string'&>&*}*&
11365 .cindex "&%time_eval%& expansion item"
11366 .cindex "time interval" "decoding"
11367 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11370 .vitem &*${time_interval:*&<&'string'&>&*}*&
11371 .cindex "&%time_interval%& expansion item"
11372 .cindex "time interval" "formatting"
11373 The argument (after sub-expansion) must be a sequence of decimal digits that
11374 represents an interval of time as a number of seconds. It is converted into a
11375 number of larger units and output in Exim's normal time format, for example,
11378 .vitem &*${uc:*&<&'string'&>&*}*&
11379 .cindex "case forcing in strings"
11380 .cindex "string" "case forcing"
11381 .cindex "upper casing"
11382 .cindex "expansion" "case forcing"
11383 .cindex "&%uc%& expansion item"
11384 This forces the letters in the string into upper-case.
11385 Case is defined per the system C locale.
11387 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11388 .cindex "correction of invalid utf-8 sequences in strings"
11389 .cindex "utf-8" "utf-8 sequences"
11390 .cindex "incorrect utf-8"
11391 .cindex "expansion" "utf-8 forcing"
11392 .cindex "&%utf8clean%& expansion item"
11393 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11394 In versions of Exim before 4.92, this did not correctly do so for a truncated
11395 final codepoint's encoding, and the character would be silently dropped.
11396 If you must handle detection of this scenario across both sets of Exim behavior,
11397 the complexity will depend upon the task.
11398 For instance, to detect if the first character is multibyte and a 1-byte
11399 extraction can be successfully used as a path component (as is common for
11400 dividing up delivery folders), you might use:
11402 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11404 (which will false-positive if the first character of the local part is a
11405 literal question mark).
11407 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11408 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11409 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11410 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11411 .cindex expansion UTF-8
11412 .cindex UTF-8 expansion
11414 .cindex internationalisation
11415 .cindex "&%utf8_domain_to_alabel%& expansion item"
11416 .cindex "&%utf8_domain_from_alabel%& expansion item"
11417 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11418 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11419 These convert EAI mail name components between UTF-8 and a-label forms.
11420 For information on internationalisation support see &<<SECTi18nMTA>>&.
11428 .section "Expansion conditions" "SECTexpcond"
11429 .scindex IIDexpcond "expansion" "conditions"
11430 The following conditions are available for testing by the &%${if%& construct
11431 while expanding strings:
11434 .vitem &*!*&<&'condition'&>
11435 .cindex "expansion" "negating a condition"
11436 .cindex "negation" "in expansion condition"
11437 Preceding any condition with an exclamation mark negates the result of the
11440 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11441 .cindex "numeric comparison"
11442 .cindex "expansion" "numeric comparison"
11443 There are a number of symbolic operators for doing numeric comparisons. They
11449 &`>= `& greater or equal
11451 &`<= `& less or equal
11455 ${if >{$message_size}{10M} ...
11457 Note that the general negation operator provides for inequality testing. The
11458 two strings must take the form of optionally signed decimal integers,
11459 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11460 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11461 As a special case, the numerical value of an empty string is taken as
11464 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11465 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11466 10M, not if 10M is larger than &$message_size$&.
11469 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11470 {*&<&'arg2'&>&*}...}*&
11471 .cindex "expansion" "calling an acl"
11472 .cindex "&%acl%&" "expansion condition"
11473 The name and zero to nine argument strings are first expanded separately. The expanded
11474 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11475 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11476 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11477 and may use the variables; if another acl expansion is used the values
11478 are restored after it returns. If the ACL sets
11479 a value using a "message =" modifier the variable $value becomes
11480 the result of the expansion, otherwise it is empty.
11481 If the ACL returns accept the condition is true; if deny, false.
11482 If the ACL returns defer the result is a forced-fail.
11484 .vitem &*bool&~{*&<&'string'&>&*}*&
11485 .cindex "expansion" "boolean parsing"
11486 .cindex "&%bool%& expansion condition"
11487 This condition turns a string holding a true or false representation into
11488 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11489 (case-insensitively); also integer numbers map to true if non-zero,
11491 An empty string is treated as false.
11492 Leading and trailing whitespace is ignored;
11493 thus a string consisting only of whitespace is false.
11494 All other string values will result in expansion failure.
11496 When combined with ACL variables, this expansion condition will let you
11497 make decisions in one place and act on those decisions in another place.
11500 ${if bool{$acl_m_privileged_sender} ...
11504 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11505 .cindex "expansion" "boolean parsing"
11506 .cindex "&%bool_lax%& expansion condition"
11507 Like &%bool%&, this condition turns a string into a boolean state. But
11508 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11509 loose definition that the Router &%condition%& option uses. The empty string
11510 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11511 true. Leading and trailing whitespace is ignored.
11513 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11515 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11516 .cindex "expansion" "encrypted comparison"
11517 .cindex "encrypted strings, comparing"
11518 .cindex "&%crypteq%& expansion condition"
11519 This condition is included in the Exim binary if it is built to support any
11520 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11521 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11522 included in the binary.
11524 The &%crypteq%& condition has two arguments. The first is encrypted and
11525 compared against the second, which is already encrypted. The second string may
11526 be in the LDAP form for storing encrypted strings, which starts with the
11527 encryption type in curly brackets, followed by the data. If the second string
11528 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11529 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11530 Typically this will be a field from a password file. An example of an encrypted
11531 string in LDAP form is:
11533 {md5}CY9rzUYh03PK3k6DJie09g==
11535 If such a string appears directly in an expansion, the curly brackets have to
11536 be quoted, because they are part of the expansion syntax. For example:
11538 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11540 The following encryption types (whose names are matched case-independently) are
11545 .cindex "base64 encoding" "in encrypted password"
11546 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11547 printable characters to compare with the remainder of the second string. If the
11548 length of the comparison string is 24, Exim assumes that it is base64 encoded
11549 (as in the above example). If the length is 32, Exim assumes that it is a
11550 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11554 .cindex "SHA-1 hash"
11555 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11556 printable characters to compare with the remainder of the second string. If the
11557 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11558 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11559 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11562 .cindex "&[crypt()]&"
11563 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11564 only the first eight characters of the password. However, in modern operating
11565 systems this is no longer true, and in many cases the entire password is used,
11566 whatever its length.
11569 .cindex "&[crypt16()]&"
11570 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11571 use up to 16 characters of the password in some operating systems. Again, in
11572 modern operating systems, more characters may be used.
11574 Exim has its own version of &[crypt16()]&, which is just a double call to
11575 &[crypt()]&. For operating systems that have their own version, setting
11576 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11577 operating system version instead of its own. This option is set by default in
11578 the OS-dependent &_Makefile_& for those operating systems that are known to
11579 support &[crypt16()]&.
11581 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11582 it was not using the same algorithm as some operating systems' versions. It
11583 turns out that as well as &[crypt16()]& there is a function called
11584 &[bigcrypt()]& in some operating systems. This may or may not use the same
11585 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11587 However, since there is now a move away from the traditional &[crypt()]&
11588 functions towards using SHA1 and other algorithms, tidying up this area of
11589 Exim is seen as very low priority.
11591 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11592 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11593 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11594 default is &`{crypt}`&. Whatever the default, you can always use either
11595 function by specifying it explicitly in curly brackets.
11597 .vitem &*def:*&<&'variable&~name'&>
11598 .cindex "expansion" "checking for empty variable"
11599 .cindex "&%def%& expansion condition"
11600 The &%def%& condition must be followed by the name of one of the expansion
11601 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11602 variable does not contain the empty string. For example:
11604 ${if def:sender_ident {from $sender_ident}}
11606 Note that the variable name is given without a leading &%$%& character. If the
11607 variable does not exist, the expansion fails.
11609 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11610 &~&*def:h_*&<&'header&~name'&>&*:*&"
11611 .cindex "expansion" "checking header line existence"
11612 This condition is true if a message is being processed and the named header
11613 exists in the message. For example,
11615 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11617 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11618 the header name must be terminated by a colon if white space does not follow.
11620 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11621 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11622 .cindex "string" "comparison"
11623 .cindex "expansion" "string comparison"
11624 .cindex "&%eq%& expansion condition"
11625 .cindex "&%eqi%& expansion condition"
11626 The two substrings are first expanded. The condition is true if the two
11627 resulting strings are identical. For &%eq%& the comparison includes the case of
11628 letters, whereas for &%eqi%& the comparison is case-independent, where
11629 case is defined per the system C locale.
11631 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11632 .cindex "expansion" "file existence test"
11633 .cindex "file" "existence test"
11634 .cindex "&%exists%&, expansion condition"
11635 The substring is first expanded and then interpreted as an absolute path. The
11636 condition is true if the named file (or directory) exists. The existence test
11637 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11638 users' filter files may be locked out by the system administrator.
11640 .vitem &*first_delivery*&
11641 .cindex "delivery" "first"
11642 .cindex "first delivery"
11643 .cindex "expansion" "first delivery test"
11644 .cindex "&%first_delivery%& expansion condition"
11645 This condition, which has no data, is true during a message's first delivery
11646 attempt. It is false during any subsequent delivery attempts.
11649 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11650 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11651 .cindex "list" "iterative conditions"
11652 .cindex "expansion" "&*forall*& condition"
11653 .cindex "expansion" "&*forany*& condition"
11655 These conditions iterate over a list. The first argument is expanded to form
11656 the list. By default, the list separator is a colon, but it can be changed by
11657 the normal method (&<<SECTlistsepchange>>&).
11658 The second argument is interpreted as a condition that is to
11659 be applied to each item in the list in turn. During the interpretation of the
11660 condition, the current list item is placed in a variable called &$item$&.
11662 For &*forany*&, interpretation stops if the condition is true for any item, and
11663 the result of the whole condition is true. If the condition is false for all
11664 items in the list, the overall condition is false.
11666 For &*forall*&, interpretation stops if the condition is false for any item,
11667 and the result of the whole condition is false. If the condition is true for
11668 all items in the list, the overall condition is true.
11670 Note that negation of &*forany*& means that the condition must be false for all
11671 items for the overall condition to succeed, and negation of &*forall*& means
11672 that the condition must be false for at least one item. In this example, the
11673 list separator is changed to a comma:
11675 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11677 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11678 being processed, to enable these expansion items to be nested.
11680 To scan a named list, expand it with the &*listnamed*& operator.
11682 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11683 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11684 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11685 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11686 .cindex JSON "iterative conditions"
11687 .cindex JSON expansions
11688 .cindex expansion "&*forall_json*& condition"
11689 .cindex expansion "&*forany_json*& condition"
11690 .cindex expansion "&*forall_jsons*& condition"
11691 .cindex expansion "&*forany_jsons*& condition"
11692 As for the above, except that the first argument must, after expansion,
11694 The array separator is not changeable.
11695 For the &"jsons"& variants the elements are expected to be JSON strings
11696 and have their quotes removed before the evaluation of the condition.
11700 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11701 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11702 .cindex "string" "comparison"
11703 .cindex "expansion" "string comparison"
11704 .cindex "&%ge%& expansion condition"
11705 .cindex "&%gei%& expansion condition"
11706 The two substrings are first expanded. The condition is true if the first
11707 string is lexically greater than or equal to the second string. For &%ge%& the
11708 comparison includes the case of letters, whereas for &%gei%& the comparison is
11710 Case and collation order are defined per the system C locale.
11712 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11713 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11714 .cindex "string" "comparison"
11715 .cindex "expansion" "string comparison"
11716 .cindex "&%gt%& expansion condition"
11717 .cindex "&%gti%& expansion condition"
11718 The two substrings are first expanded. The condition is true if the first
11719 string is lexically greater than the second string. For &%gt%& the comparison
11720 includes the case of letters, whereas for &%gti%& the comparison is
11722 Case and collation order are defined per the system C locale.
11726 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11727 SRS decode. See SECT &<<SECTSRS>>& for details.
11731 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11732 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11733 .cindex "string" "comparison"
11734 .cindex "list" "iterative conditions"
11735 Both strings are expanded; the second string is treated as a list of simple
11736 strings; if the first string is a member of the second, then the condition
11738 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11740 These are simpler to use versions of the more powerful &*forany*& condition.
11741 Examples, and the &*forany*& equivalents:
11743 ${if inlist{needle}{foo:needle:bar}}
11744 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11745 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11746 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11749 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11750 &*isip4&~{*&<&'string'&>&*}*& &&&
11751 &*isip6&~{*&<&'string'&>&*}*&
11752 .cindex "IP address" "testing string format"
11753 .cindex "string" "testing for IP address"
11754 .cindex "&%isip%& expansion condition"
11755 .cindex "&%isip4%& expansion condition"
11756 .cindex "&%isip6%& expansion condition"
11757 The substring is first expanded, and then tested to see if it has the form of
11758 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11759 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11761 For an IPv4 address, the test is for four dot-separated components, each of
11762 which consists of from one to three digits. For an IPv6 address, up to eight
11763 colon-separated components are permitted, each containing from one to four
11764 hexadecimal digits. There may be fewer than eight components if an empty
11765 component (adjacent colons) is present. Only one empty component is permitted.
11767 &*Note*&: The checks used to be just on the form of the address; actual numerical
11768 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11770 This is no longer the case.
11772 The main use of these tests is to distinguish between IP addresses and
11773 host names, or between IPv4 and IPv6 addresses. For example, you could use
11775 ${if isip4{$sender_host_address}...
11777 to test which IP version an incoming SMTP connection is using.
11779 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11780 .cindex "LDAP" "use for authentication"
11781 .cindex "expansion" "LDAP authentication test"
11782 .cindex "&%ldapauth%& expansion condition"
11783 This condition supports user authentication using LDAP. See section
11784 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11785 queries. For this use, the query must contain a user name and password. The
11786 query itself is not used, and can be empty. The condition is true if the
11787 password is not empty, and the user name and password are accepted by the LDAP
11788 server. An empty password is rejected without calling LDAP because LDAP binds
11789 with an empty password are considered anonymous regardless of the username, and
11790 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11791 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11795 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11796 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11797 .cindex "string" "comparison"
11798 .cindex "expansion" "string comparison"
11799 .cindex "&%le%& expansion condition"
11800 .cindex "&%lei%& expansion condition"
11801 The two substrings are first expanded. The condition is true if the first
11802 string is lexically less than or equal to the second string. For &%le%& the
11803 comparison includes the case of letters, whereas for &%lei%& the comparison is
11805 Case and collation order are defined per the system C locale.
11807 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11808 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11809 .cindex "string" "comparison"
11810 .cindex "expansion" "string comparison"
11811 .cindex "&%lt%& expansion condition"
11812 .cindex "&%lti%& expansion condition"
11813 The two substrings are first expanded. The condition is true if the first
11814 string is lexically less than the second string. For &%lt%& the comparison
11815 includes the case of letters, whereas for &%lti%& the comparison is
11817 Case and collation order are defined per the system C locale.
11820 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11821 .cindex "expansion" "regular expression comparison"
11822 .cindex "regular expressions" "match in expanded string"
11823 .cindex "&%match%& expansion condition"
11824 The two substrings are first expanded. The second is then treated as a regular
11825 expression and applied to the first. Because of the pre-expansion, if the
11826 regular expression contains dollar, or backslash characters, they must be
11827 escaped. Care must also be taken if the regular expression contains braces
11828 (curly brackets). A closing brace must be escaped so that it is not taken as a
11829 premature termination of <&'string2'&>. The easiest approach is to use the
11830 &`\N`& feature to disable expansion of the regular expression.
11833 ${if match {$local_part}{\N^\d{3}\N} ...
11835 If the whole expansion string is in double quotes, further escaping of
11836 backslashes is also required.
11838 The condition is true if the regular expression match succeeds.
11839 The regular expression is not required to begin with a circumflex
11840 metacharacter, but if there is no circumflex, the expression is not anchored,
11841 and it may match anywhere in the subject, not just at the start. If you want
11842 the pattern to match at the end of the subject, you must include the &`$`&
11843 metacharacter at an appropriate point.
11844 All character handling is done in bytes and is not UTF-8 aware,
11845 but we might change this in a future Exim release.
11847 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11848 At the start of an &%if%& expansion the values of the numeric variable
11849 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11850 succeeds causes them to be reset to the substrings of that condition and they
11851 will have these values during the expansion of the success string. At the end
11852 of the &%if%& expansion, the previous values are restored. After testing a
11853 combination of conditions using &%or%&, the subsequent values of the numeric
11854 variables are those of the condition that succeeded.
11856 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11857 .cindex "&%match_address%& expansion condition"
11858 See &*match_local_part*&.
11860 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11861 .cindex "&%match_domain%& expansion condition"
11862 See &*match_local_part*&.
11864 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11865 .cindex "&%match_ip%& expansion condition"
11866 This condition matches an IP address to a list of IP address patterns. It must
11867 be followed by two argument strings. The first (after expansion) must be an IP
11868 address or an empty string. The second (not expanded) is a restricted host
11869 list that can match only an IP address, not a host name. For example:
11871 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11873 The specific types of host list item that are permitted in the list are:
11876 An IP address, optionally with a CIDR mask.
11878 A single asterisk, which matches any IP address.
11880 An empty item, which matches only if the IP address is empty. This could be
11881 useful for testing for a locally submitted message or one from specific hosts
11882 in a single test such as
11883 . ==== As this is a nested list, any displays it contains must be indented
11884 . ==== as otherwise they are too far to the left. This comment applies to
11885 . ==== the use of xmlto plus fop. There's no problem when formatting with
11886 . ==== sdop, with or without the extra indent.
11888 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11890 where the first item in the list is the empty string.
11892 The item @[] matches any of the local host's interface addresses.
11894 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11895 even if &`net-`& is not specified. There is never any attempt to turn the IP
11896 address into a host name. The most common type of linear search for
11897 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11898 masks. For example:
11900 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11902 It is of course possible to use other kinds of lookup, and in such a case, you
11903 do need to specify the &`net-`& prefix if you want to specify a specific
11904 address mask, for example:
11906 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11908 However, unless you are combining a &%match_ip%& condition with others, it is
11909 just as easy to use the fact that a lookup is itself a condition, and write:
11911 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11915 Note that <&'string2'&> is not itself subject to string expansion, unless
11916 Exim was built with the EXPAND_LISTMATCH_RHS option.
11918 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11920 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11921 .cindex "domain list" "in expansion condition"
11922 .cindex "address list" "in expansion condition"
11923 .cindex "local part" "list, in expansion condition"
11924 .cindex "&%match_local_part%& expansion condition"
11925 This condition, together with &%match_address%& and &%match_domain%&, make it
11926 possible to test domain, address, and local part lists within expansions. Each
11927 condition requires two arguments: an item and a list to match. A trivial
11930 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11932 In each case, the second argument may contain any of the allowable items for a
11933 list of the appropriate type. Also, because the second argument
11934 is a standard form of list, it is possible to refer to a named list.
11935 Thus, you can use conditions like this:
11937 ${if match_domain{$domain}{+local_domains}{...
11939 .cindex "&`+caseful`&"
11940 For address lists, the matching starts off caselessly, but the &`+caseful`&
11941 item can be used, as in all address lists, to cause subsequent items to
11942 have their local parts matched casefully. Domains are always matched
11945 Note that <&'string2'&> is not itself subject to string expansion, unless
11946 Exim was built with the EXPAND_LISTMATCH_RHS option.
11948 &*Note*&: Host lists are &'not'& supported in this way. This is because
11949 hosts have two identities: a name and an IP address, and it is not clear
11950 how to specify cleanly how such a test would work. However, IP addresses can be
11951 matched using &%match_ip%&.
11953 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11954 .cindex "PAM authentication"
11955 .cindex "AUTH" "with PAM"
11956 .cindex "Solaris" "PAM support"
11957 .cindex "expansion" "PAM authentication test"
11958 .cindex "&%pam%& expansion condition"
11959 &'Pluggable Authentication Modules'&
11960 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
11961 available in the latest releases of Solaris and in some GNU/Linux
11962 distributions. The Exim support, which is intended for use in conjunction with
11963 the SMTP AUTH command, is available only if Exim is compiled with
11967 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11968 in some releases of GNU/Linux &%-ldl%& is also needed.
11970 The argument string is first expanded, and the result must be a
11971 colon-separated list of strings. Leading and trailing white space is ignored.
11972 The PAM module is initialized with the service name &"exim"& and the user name
11973 taken from the first item in the colon-separated data string (<&'string1'&>).
11974 The remaining items in the data string are passed over in response to requests
11975 from the authentication function. In the simple case there will only be one
11976 request, for a password, so the data consists of just two strings.
11978 There can be problems if any of the strings are permitted to contain colon
11979 characters. In the usual way, these have to be doubled to avoid being taken as
11980 separators. If the data is being inserted from a variable, the &%sg%& expansion
11981 item can be used to double any existing colons. For example, the configuration
11982 of a LOGIN authenticator might contain this setting:
11984 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11986 For a PLAIN authenticator you could use:
11988 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11990 In some operating systems, PAM authentication can be done only from a process
11991 running as root. Since Exim is running as the Exim user when receiving
11992 messages, this means that PAM cannot be used directly in those systems.
11993 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
11996 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11997 .cindex "&'pwcheck'& daemon"
11999 .cindex "expansion" "&'pwcheck'& authentication test"
12000 .cindex "&%pwcheck%& expansion condition"
12001 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12002 This is one way of making it possible for passwords to be checked by a process
12003 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12004 deprecated. Its replacement is &'saslauthd'& (see below).
12006 The pwcheck support is not included in Exim by default. You need to specify
12007 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12008 building Exim. For example:
12010 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12012 You do not need to install the full Cyrus software suite in order to use
12013 the pwcheck daemon. You can compile and install just the daemon alone
12014 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12015 access to the &_/var/pwcheck_& directory.
12017 The &%pwcheck%& condition takes one argument, which must be the user name and
12018 password, separated by a colon. For example, in a LOGIN authenticator
12019 configuration, you might have this:
12021 server_condition = ${if pwcheck{$auth1:$auth2}}
12023 Again, for a PLAIN authenticator configuration, this would be:
12025 server_condition = ${if pwcheck{$auth2:$auth3}}
12027 .vitem &*queue_running*&
12028 .cindex "queue runner" "detecting when delivering from"
12029 .cindex "expansion" "queue runner test"
12030 .cindex "&%queue_running%& expansion condition"
12031 This condition, which has no data, is true during delivery attempts that are
12032 initiated by queue runner processes, and false otherwise.
12035 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12037 .cindex "expansion" "Radius authentication"
12038 .cindex "&%radius%& expansion condition"
12039 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12040 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12041 the Radius client configuration file in order to build Exim with Radius
12044 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12045 library, using the original API. If you are using release 0.4.0 or later of
12046 this library, you need to set
12048 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12050 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12051 &%libradius%& library that comes with FreeBSD. To do this, set
12053 RADIUS_LIB_TYPE=RADLIB
12055 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12056 You may also have to supply a suitable setting in EXTRALIBS so that the
12057 Radius library can be found when Exim is linked.
12059 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12060 Radius client library, which calls the Radius server. The condition is true if
12061 the authentication is successful. For example:
12063 server_condition = ${if radius{<arguments>}}
12067 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12068 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12069 .cindex "&'saslauthd'& daemon"
12071 .cindex "expansion" "&'saslauthd'& authentication test"
12072 .cindex "&%saslauthd%& expansion condition"
12073 This condition supports user authentication using the Cyrus &'saslauthd'&
12074 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12075 Using this daemon is one way of making it possible for passwords to be checked
12076 by a process that is not running as root.
12078 The saslauthd support is not included in Exim by default. You need to specify
12079 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12080 building Exim. For example:
12082 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12084 You do not need to install the full Cyrus software suite in order to use
12085 the saslauthd daemon. You can compile and install just the daemon alone
12086 from the Cyrus SASL library.
12088 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12089 two are mandatory. For example:
12091 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12093 The service and the realm are optional (which is why the arguments are enclosed
12094 in their own set of braces). For details of the meaning of the service and
12095 realm, and how to run the daemon, consult the Cyrus documentation.
12100 .section "Combining expansion conditions" "SECID84"
12101 .cindex "expansion" "combining conditions"
12102 Several conditions can be tested at once by combining them using the &%and%&
12103 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12104 conditions on their own, and precede their lists of sub-conditions. Each
12105 sub-condition must be enclosed in braces within the overall braces that contain
12106 the list. No repetition of &%if%& is used.
12110 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12111 .cindex "&""or""& expansion condition"
12112 .cindex "expansion" "&""or""& of conditions"
12113 The sub-conditions are evaluated from left to right. The condition is true if
12114 any one of the sub-conditions is true.
12117 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12119 When a true sub-condition is found, the following ones are parsed but not
12120 evaluated. If there are several &"match"& sub-conditions the values of the
12121 numeric variables afterwards are taken from the first one that succeeds.
12123 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12124 .cindex "&""and""& expansion condition"
12125 .cindex "expansion" "&""and""& of conditions"
12126 The sub-conditions are evaluated from left to right. The condition is true if
12127 all of the sub-conditions are true. If there are several &"match"&
12128 sub-conditions, the values of the numeric variables afterwards are taken from
12129 the last one. When a false sub-condition is found, the following ones are
12130 parsed but not evaluated.
12132 .ecindex IIDexpcond
12137 .section "Expansion variables" "SECTexpvar"
12138 .cindex "expansion" "variables, list of"
12139 This section contains an alphabetical list of all the expansion variables. Some
12140 of them are available only when Exim is compiled with specific options such as
12141 support for TLS or the content scanning extension.
12144 .vitem "&$0$&, &$1$&, etc"
12145 .cindex "numerical variables (&$1$& &$2$& etc)"
12146 When a &%match%& expansion condition succeeds, these variables contain the
12147 captured substrings identified by the regular expression during subsequent
12148 processing of the success string of the containing &%if%& expansion item.
12149 In the expansion condition case
12150 they do not retain their values afterwards; in fact, their previous
12151 values are restored at the end of processing an &%if%& item. The numerical
12152 variables may also be set externally by some other matching process which
12153 precedes the expansion of the string. For example, the commands available in
12154 Exim filter files include an &%if%& command with its own regular expression
12155 matching condition.
12157 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12158 Within an acl condition, expansion condition or expansion item
12159 any arguments are copied to these variables,
12160 any unused variables being made empty.
12162 .vitem "&$acl_c...$&"
12163 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12164 can be given any name that starts with &$acl_c$& and is at least six characters
12165 long, but the sixth character must be either a digit or an underscore. For
12166 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12167 variables persist throughout the lifetime of an SMTP connection. They can be
12168 used to pass information between ACLs and between different invocations of the
12169 same ACL. When a message is received, the values of these variables are saved
12170 with the message, and can be accessed by filters, routers, and transports
12171 during subsequent delivery.
12173 .vitem "&$acl_m...$&"
12174 These variables are like the &$acl_c...$& variables, except that their values
12175 are reset after a message has been received. Thus, if several messages are
12176 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12177 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12178 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12179 message is received, the values of these variables are saved with the message,
12180 and can be accessed by filters, routers, and transports during subsequent
12183 .vitem &$acl_narg$&
12184 Within an acl condition, expansion condition or expansion item
12185 this variable has the number of arguments.
12187 .vitem &$acl_verify_message$&
12188 .vindex "&$acl_verify_message$&"
12189 After an address verification has failed, this variable contains the failure
12190 message. It retains its value for use in subsequent modifiers. The message can
12191 be preserved by coding like this:
12193 warn !verify = sender
12194 set acl_m0 = $acl_verify_message
12196 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12197 &%log_message%& modifiers, to include information about the verification
12200 .vitem &$address_data$&
12201 .vindex "&$address_data$&"
12202 This variable is set by means of the &%address_data%& option in routers. The
12203 value then remains with the address while it is processed by subsequent routers
12204 and eventually a transport. If the transport is handling multiple addresses,
12205 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12206 for more details. &*Note*&: The contents of &$address_data$& are visible in
12209 If &$address_data$& is set when the routers are called from an ACL to verify
12210 a recipient address, the final value is still in the variable for subsequent
12211 conditions and modifiers of the ACL statement. If routing the address caused it
12212 to be redirected to just one address, the child address is also routed as part
12213 of the verification, and in this case the final value of &$address_data$& is
12214 from the child's routing.
12216 If &$address_data$& is set when the routers are called from an ACL to verify a
12217 sender address, the final value is also preserved, but this time in
12218 &$sender_address_data$&, to distinguish it from data from a recipient
12221 In both cases (recipient and sender verification), the value does not persist
12222 after the end of the current ACL statement. If you want to preserve
12223 these values for longer, you can save them in ACL variables.
12225 .vitem &$address_file$&
12226 .vindex "&$address_file$&"
12227 When, as a result of aliasing, forwarding, or filtering, a message is directed
12228 to a specific file, this variable holds the name of the file when the transport
12229 is running. At other times, the variable is empty. For example, using the
12230 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12232 /home/r2d2/savemail
12234 then when the &(address_file)& transport is running, &$address_file$&
12235 contains the text string &`/home/r2d2/savemail`&.
12236 .cindex "Sieve filter" "value of &$address_file$&"
12237 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12238 then up to the transport configuration to generate an appropriate absolute path
12239 to the relevant file.
12241 .vitem &$address_pipe$&
12242 .vindex "&$address_pipe$&"
12243 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12244 this variable holds the pipe command when the transport is running.
12246 .vitem "&$auth1$& &-- &$auth3$&"
12247 .vindex "&$auth1$&, &$auth2$&, etc"
12248 These variables are used in SMTP authenticators (see chapters
12249 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12251 .vitem &$authenticated_id$&
12252 .cindex "authentication" "id"
12253 .vindex "&$authenticated_id$&"
12254 When a server successfully authenticates a client it may be configured to
12255 preserve some of the authentication information in the variable
12256 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12257 user/password authenticator configuration might preserve the user name for use
12258 in the routers. Note that this is not the same information that is saved in
12259 &$sender_host_authenticated$&.
12261 When a message is submitted locally (that is, not over a TCP connection)
12262 the value of &$authenticated_id$& is normally the login name of the calling
12263 process. However, a trusted user can override this by means of the &%-oMai%&
12264 command line option.
12265 This second case also sets up information used by the
12266 &$authresults$& expansion item.
12268 .vitem &$authenticated_fail_id$&
12269 .cindex "authentication" "fail" "id"
12270 .vindex "&$authenticated_fail_id$&"
12271 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12272 will contain the failed authentication id. If more than one authentication
12273 id is attempted, it will contain only the last one. The variable is
12274 available for processing in the ACL's, generally the quit or notquit ACL.
12275 A message to a local recipient could still be accepted without requiring
12276 authentication, which means this variable could also be visible in all of
12280 .vitem &$authenticated_sender$&
12281 .cindex "sender" "authenticated"
12282 .cindex "authentication" "sender"
12283 .cindex "AUTH" "on MAIL command"
12284 .vindex "&$authenticated_sender$&"
12285 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12286 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12287 described in section &<<SECTauthparamail>>&. Unless the data is the string
12288 &"<>"&, it is set as the authenticated sender of the message, and the value is
12289 available during delivery in the &$authenticated_sender$& variable. If the
12290 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12292 .vindex "&$qualify_domain$&"
12293 When a message is submitted locally (that is, not over a TCP connection), the
12294 value of &$authenticated_sender$& is an address constructed from the login
12295 name of the calling process and &$qualify_domain$&, except that a trusted user
12296 can override this by means of the &%-oMas%& command line option.
12299 .vitem &$authentication_failed$&
12300 .cindex "authentication" "failure"
12301 .vindex "&$authentication_failed$&"
12302 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12303 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12304 possible to distinguish between &"did not try to authenticate"&
12305 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12306 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12307 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12308 negative response to an AUTH command, including (for example) an attempt to use
12309 an undefined mechanism.
12311 .vitem &$av_failed$&
12312 .cindex "content scanning" "AV scanner failure"
12313 This variable is available when Exim is compiled with the content-scanning
12314 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12315 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12316 the ACL malware condition.
12318 .vitem &$body_linecount$&
12319 .cindex "message body" "line count"
12320 .cindex "body of message" "line count"
12321 .vindex "&$body_linecount$&"
12322 When a message is being received or delivered, this variable contains the
12323 number of lines in the message's body. See also &$message_linecount$&.
12325 .vitem &$body_zerocount$&
12326 .cindex "message body" "binary zero count"
12327 .cindex "body of message" "binary zero count"
12328 .cindex "binary zero" "in message body"
12329 .vindex "&$body_zerocount$&"
12330 When a message is being received or delivered, this variable contains the
12331 number of binary zero bytes (ASCII NULs) in the message's body.
12333 .vitem &$bounce_recipient$&
12334 .vindex "&$bounce_recipient$&"
12335 This is set to the recipient address of a bounce message while Exim is creating
12336 it. It is useful if a customized bounce message text file is in use (see
12337 chapter &<<CHAPemsgcust>>&).
12339 .vitem &$bounce_return_size_limit$&
12340 .vindex "&$bounce_return_size_limit$&"
12341 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12342 up to a multiple of 1000. It is useful when a customized error message text
12343 file is in use (see chapter &<<CHAPemsgcust>>&).
12345 .vitem &$caller_gid$&
12346 .cindex "gid (group id)" "caller"
12347 .vindex "&$caller_gid$&"
12348 The real group id under which the process that called Exim was running. This is
12349 not the same as the group id of the originator of a message (see
12350 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12351 incarnation normally contains the Exim gid.
12353 .vitem &$caller_uid$&
12354 .cindex "uid (user id)" "caller"
12355 .vindex "&$caller_uid$&"
12356 The real user id under which the process that called Exim was running. This is
12357 not the same as the user id of the originator of a message (see
12358 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12359 incarnation normally contains the Exim uid.
12361 .vitem &$callout_address$&
12362 .vindex "&$callout_address$&"
12363 After a callout for verification, spamd or malware daemon service, the
12364 address that was connected to.
12366 .vitem &$compile_number$&
12367 .vindex "&$compile_number$&"
12368 The building process for Exim keeps a count of the number
12369 of times it has been compiled. This serves to distinguish different
12370 compilations of the same version of Exim.
12372 .vitem &$config_dir$&
12373 .vindex "&$config_dir$&"
12374 The directory name of the main configuration file. That is, the content of
12375 &$config_file$& with the last component stripped. The value does not
12376 contain the trailing slash. If &$config_file$& does not contain a slash,
12377 &$config_dir$& is ".".
12379 .vitem &$config_file$&
12380 .vindex "&$config_file$&"
12381 The name of the main configuration file Exim is using.
12383 .vitem &$dmarc_domain_policy$& &&&
12384 &$dmarc_status$& &&&
12385 &$dmarc_status_text$& &&&
12386 &$dmarc_used_domains$&
12387 Results of DMARC verification.
12388 For details see section &<<SECDMARC>>&.
12390 .vitem &$dkim_verify_status$&
12391 Results of DKIM verification.
12392 For details see section &<<SECDKIMVFY>>&.
12394 .vitem &$dkim_cur_signer$& &&&
12395 &$dkim_verify_reason$& &&&
12396 &$dkim_domain$& &&&
12397 &$dkim_identity$& &&&
12398 &$dkim_selector$& &&&
12400 &$dkim_canon_body$& &&&
12401 &$dkim_canon_headers$& &&&
12402 &$dkim_copiedheaders$& &&&
12403 &$dkim_bodylength$& &&&
12404 &$dkim_created$& &&&
12405 &$dkim_expires$& &&&
12406 &$dkim_headernames$& &&&
12407 &$dkim_key_testing$& &&&
12408 &$dkim_key_nosubdomains$& &&&
12409 &$dkim_key_srvtype$& &&&
12410 &$dkim_key_granularity$& &&&
12411 &$dkim_key_notes$& &&&
12412 &$dkim_key_length$&
12413 These variables are only available within the DKIM ACL.
12414 For details see section &<<SECDKIMVFY>>&.
12416 .vitem &$dkim_signers$&
12417 .vindex &$dkim_signers$&
12418 When a message has been received this variable contains
12419 a colon-separated list of signer domains and identities for the message.
12420 For details see section &<<SECDKIMVFY>>&.
12422 .vitem &$dnslist_domain$& &&&
12423 &$dnslist_matched$& &&&
12424 &$dnslist_text$& &&&
12426 .vindex "&$dnslist_domain$&"
12427 .vindex "&$dnslist_matched$&"
12428 .vindex "&$dnslist_text$&"
12429 .vindex "&$dnslist_value$&"
12430 .cindex "black list (DNS)"
12431 When a DNS (black) list lookup succeeds, these variables are set to contain
12432 the following data from the lookup: the list's domain name, the key that was
12433 looked up, the contents of any associated TXT record, and the value from the
12434 main A record. See section &<<SECID204>>& for more details.
12437 .vindex "&$domain$&"
12438 When an address is being routed, or delivered on its own, this variable
12439 contains the domain. Uppercase letters in the domain are converted into lower
12440 case for &$domain$&.
12442 Global address rewriting happens when a message is received, so the value of
12443 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12444 is set during user filtering, but not during system filtering, because a
12445 message may have many recipients and the system filter is called just once.
12447 When more than one address is being delivered at once (for example, several
12448 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12449 have the same domain. Transports can be restricted to handling only one domain
12450 at a time if the value of &$domain$& is required at transport time &-- this is
12451 the default for local transports. For further details of the environment in
12452 which local transports are run, see chapter &<<CHAPenvironment>>&.
12454 .oindex "&%delay_warning_condition%&"
12455 At the end of a delivery, if all deferred addresses have the same domain, it is
12456 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12458 The &$domain$& variable is also used in some other circumstances:
12461 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12462 the recipient address. The domain of the &'sender'& address is in
12463 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12464 normally set during the running of the MAIL ACL. However, if the sender address
12465 is verified with a callout during the MAIL ACL, the sender domain is placed in
12466 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12467 the &(smtp)& transport.
12470 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12471 &$domain$& contains the domain portion of the address that is being rewritten;
12472 it can be used in the expansion of the replacement address, for example, to
12473 rewrite domains by file lookup.
12476 With one important exception, whenever a domain list is being scanned,
12477 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12478 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12479 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12480 that, in a RCPT ACL, the sender domain list can be dependent on the
12481 recipient domain (which is what is in &$domain$& at this time).
12484 .cindex "ETRN" "value of &$domain$&"
12485 .oindex "&%smtp_etrn_command%&"
12486 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12487 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12491 .cindex "tainted data"
12492 If the origin of the data is an incoming message,
12493 the result of expanding this variable is tainted.
12494 When un untainted version is needed, one should be obtained from
12495 looking up the value in a local (therefore trusted) database.
12496 Often &$domain_data$& is usable in this role.
12500 .vitem &$domain_data$&
12501 .vindex "&$domain_data$&"
12502 When the &%domains%& option on a router matches a domain by
12503 means of a lookup, the data read by the lookup is available during the running
12504 of the router as &$domain_data$&. In addition, if the driver routes the
12505 address to a transport, the value is available in that transport. If the
12506 transport is handling multiple addresses, the value from the first address is
12509 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
12510 domain by means of a lookup. The data read by the lookup is available during
12511 the rest of the ACL statement. In all other situations, this variable expands
12514 .vitem &$exim_gid$&
12515 .vindex "&$exim_gid$&"
12516 This variable contains the numerical value of the Exim group id.
12518 .vitem &$exim_path$&
12519 .vindex "&$exim_path$&"
12520 This variable contains the path to the Exim binary.
12522 .vitem &$exim_uid$&
12523 .vindex "&$exim_uid$&"
12524 This variable contains the numerical value of the Exim user id.
12526 .vitem &$exim_version$&
12527 .vindex "&$exim_version$&"
12528 This variable contains the version string of the Exim build.
12529 The first character is a major version number, currently 4.
12530 Then after a dot, the next group of digits is a minor version number.
12531 There may be other characters following the minor version.
12532 This value may be overridden by the &%exim_version%& main config option.
12534 .vitem &$header_$&<&'name'&>
12535 This is not strictly an expansion variable. It is expansion syntax for
12536 inserting the message header line with the given name. Note that the name must
12537 be terminated by colon or white space, because it may contain a wide variety of
12538 characters. Note also that braces must &'not'& be used.
12539 See the full description in section &<<SECTexpansionitems>>& above.
12541 .vitem &$headers_added$&
12542 .vindex "&$headers_added$&"
12543 Within an ACL this variable contains the headers added so far by
12544 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12545 The headers are a newline-separated list.
12549 When the &%check_local_user%& option is set for a router, the user's home
12550 directory is placed in &$home$& when the check succeeds. In particular, this
12551 means it is set during the running of users' filter files. A router may also
12552 explicitly set a home directory for use by a transport; this can be overridden
12553 by a setting on the transport itself.
12555 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12556 of the environment variable HOME, which is subject to the
12557 &%keep_environment%& and &%add_environment%& main config options.
12561 If a router assigns an address to a transport (any transport), and passes a
12562 list of hosts with the address, the value of &$host$& when the transport starts
12563 to run is the name of the first host on the list. Note that this applies both
12564 to local and remote transports.
12566 .cindex "transport" "filter"
12567 .cindex "filter" "transport filter"
12568 For the &(smtp)& transport, if there is more than one host, the value of
12569 &$host$& changes as the transport works its way through the list. In
12570 particular, when the &(smtp)& transport is expanding its options for encryption
12571 using TLS, or for specifying a transport filter (see chapter
12572 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12575 When used in the client part of an authenticator configuration (see chapter
12576 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12577 client is connected.
12580 .vitem &$host_address$&
12581 .vindex "&$host_address$&"
12582 This variable is set to the remote host's IP address whenever &$host$& is set
12583 for a remote connection. It is also set to the IP address that is being checked
12584 when the &%ignore_target_hosts%& option is being processed.
12586 .vitem &$host_data$&
12587 .vindex "&$host_data$&"
12588 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12589 result of the lookup is made available in the &$host_data$& variable. This
12590 allows you, for example, to do things like this:
12592 deny hosts = net-lsearch;/some/file
12593 message = $host_data
12595 .vitem &$host_lookup_deferred$&
12596 .cindex "host name" "lookup, failure of"
12597 .vindex "&$host_lookup_deferred$&"
12598 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12599 message comes from a remote host and there is an attempt to look up the host's
12600 name from its IP address, and the attempt is not successful, one of these
12601 variables is set to &"1"&.
12604 If the lookup receives a definite negative response (for example, a DNS lookup
12605 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12608 If there is any kind of problem during the lookup, such that Exim cannot
12609 tell whether or not the host name is defined (for example, a timeout for a DNS
12610 lookup), &$host_lookup_deferred$& is set to &"1"&.
12613 Looking up a host's name from its IP address consists of more than just a
12614 single reverse lookup. Exim checks that a forward lookup of at least one of the
12615 names it receives from a reverse lookup yields the original IP address. If this
12616 is not the case, Exim does not accept the looked up name(s), and
12617 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12618 IP address (for example, the existence of a PTR record in the DNS) is not
12619 sufficient on its own for the success of a host name lookup. If the reverse
12620 lookup succeeds, but there is a lookup problem such as a timeout when checking
12621 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12622 &"1"&. See also &$sender_host_name$&.
12624 .cindex authentication "expansion item"
12625 Performing these checks sets up information used by the
12626 &%authresults%& expansion item.
12629 .vitem &$host_lookup_failed$&
12630 .vindex "&$host_lookup_failed$&"
12631 See &$host_lookup_deferred$&.
12633 .vitem &$host_port$&
12634 .vindex "&$host_port$&"
12635 This variable is set to the remote host's TCP port whenever &$host$& is set
12636 for an outbound connection.
12638 .vitem &$initial_cwd$&
12639 .vindex "&$initial_cwd$&
12640 This variable contains the full path name of the initial working
12641 directory of the current Exim process. This may differ from the current
12642 working directory, as Exim changes this to "/" during early startup, and
12643 to &$spool_directory$& later.
12646 .vindex "&$inode$&"
12647 The only time this variable is set is while expanding the &%directory_file%&
12648 option in the &(appendfile)& transport. The variable contains the inode number
12649 of the temporary file which is about to be renamed. It can be used to construct
12650 a unique name for the file.
12652 .vitem &$interface_address$&
12653 .vindex "&$interface_address$&"
12654 This is an obsolete name for &$received_ip_address$&.
12656 .vitem &$interface_port$&
12657 .vindex "&$interface_port$&"
12658 This is an obsolete name for &$received_port$&.
12662 This variable is used during the expansion of &*forall*& and &*forany*&
12663 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12664 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12668 .vindex "&$ldap_dn$&"
12669 This variable, which is available only when Exim is compiled with LDAP support,
12670 contains the DN from the last entry in the most recently successful LDAP
12673 .vitem &$load_average$&
12674 .vindex "&$load_average$&"
12675 This variable contains the system load average, multiplied by 1000 so that it
12676 is an integer. For example, if the load average is 0.21, the value of the
12677 variable is 210. The value is recomputed every time the variable is referenced.
12679 .vitem &$local_part$&
12680 .vindex "&$local_part$&"
12681 When an address is being routed, or delivered on its own, this
12682 variable contains the local part. When a number of addresses are being
12683 delivered together (for example, multiple RCPT commands in an SMTP
12684 session), &$local_part$& is not set.
12686 Global address rewriting happens when a message is received, so the value of
12687 &$local_part$& during routing and delivery is the value after rewriting.
12688 &$local_part$& is set during user filtering, but not during system filtering,
12689 because a message may have many recipients and the system filter is called just
12693 .cindex "tainted data"
12694 If the origin of the data is an incoming message,
12695 the result of expanding this variable is tainted.
12697 &*Warning*&: the content of this variable is usually provided by a potential
12699 Consider carefully the implications of using it unvalidated as a name
12701 This presents issues for users' &_.forward_& and filter files.
12702 For traditional full user accounts, use &%check_local_users%& and the
12703 &$local_part_data$& variable rather than this one.
12704 For virtual users, store a suitable pathname component in the database
12705 which is used for account name validation, and use that retrieved value
12706 rather than this variable.
12707 Often &$local_part_data$& is usable in this role.
12708 If needed, use a router &%address_data%& or &%set%& option for
12709 the retrieved data.
12712 When a message is being delivered to a file, pipe, or autoreply transport as a
12713 result of aliasing or forwarding, &$local_part$& is set to the local part of
12714 the parent address, not to the filename or command (see &$address_file$& and
12717 When an ACL is running for a RCPT command, &$local_part$& contains the
12718 local part of the recipient address.
12720 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12721 &$local_part$& contains the local part of the address that is being rewritten;
12722 it can be used in the expansion of the replacement address, for example.
12724 In all cases, all quoting is removed from the local part. For example, for both
12727 "abc:xyz"@test.example
12728 abc\:xyz@test.example
12730 the value of &$local_part$& is
12734 If you use &$local_part$& to create another address, you should always wrap it
12735 inside a quoting operator. For example, in a &(redirect)& router you could
12738 data = ${quote_local_part:$local_part}@new.domain.example
12740 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12741 to process local parts in a case-dependent manner in a router, you can set the
12742 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12744 .vitem &$local_part_data$&
12745 .vindex "&$local_part_data$&"
12746 When the &%local_parts%& option on a router matches a local part by means of a
12747 lookup, the data read by the lookup is available during the running of the
12748 router as &$local_part_data$&. In addition, if the driver routes the address
12749 to a transport, the value is available in that transport. If the transport is
12750 handling multiple addresses, the value from the first address is used.
12753 The &%check_local_user%& router option also sets this variable.
12756 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
12757 matches a local part by means of a lookup. The data read by the lookup is
12758 available during the rest of the ACL statement. In all other situations, this
12759 variable expands to nothing.
12761 .vindex &$local_part_prefix$& &&&
12762 &$local_part_prefix_v$& &&&
12763 &$local_part_suffix$& &&&
12764 &$local_part_suffix_v$&
12765 .cindex affix variables
12766 If a local part prefix or suffix has been recognized, it is not included in the
12767 value of &$local_part$& during routing and subsequent delivery. The values of
12768 any prefix or suffix are in &$local_part_prefix$& and
12769 &$local_part_suffix$&, respectively.
12771 .cindex "tainted data"
12772 If the specification did not include a wildcard then
12773 the affix variable value is not tainted.
12775 If the affix specification included a wildcard then the portion of
12776 the affix matched by the wildcard is in
12777 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12778 and both the whole and varying values are tainted.
12781 .vitem &$local_scan_data$&
12782 .vindex "&$local_scan_data$&"
12783 This variable contains the text returned by the &[local_scan()]& function when
12784 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12786 .vitem &$local_user_gid$&
12787 .vindex "&$local_user_gid$&"
12788 See &$local_user_uid$&.
12790 .vitem &$local_user_uid$&
12791 .vindex "&$local_user_uid$&"
12792 This variable and &$local_user_gid$& are set to the uid and gid after the
12793 &%check_local_user%& router precondition succeeds. This means that their values
12794 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12795 and &%condition%&), for the &%address_data%& expansion, and for any
12796 router-specific expansions. At all other times, the values in these variables
12797 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12799 .vitem &$localhost_number$&
12800 .vindex "&$localhost_number$&"
12801 This contains the expanded value of the
12802 &%localhost_number%& option. The expansion happens after the main options have
12805 .vitem &$log_inodes$&
12806 .vindex "&$log_inodes$&"
12807 The number of free inodes in the disk partition where Exim's
12808 log files are being written. The value is recalculated whenever the variable is
12809 referenced. If the relevant file system does not have the concept of inodes,
12810 the value of is -1. See also the &%check_log_inodes%& option.
12812 .vitem &$log_space$&
12813 .vindex "&$log_space$&"
12814 The amount of free space (as a number of kilobytes) in the disk
12815 partition where Exim's log files are being written. The value is recalculated
12816 whenever the variable is referenced. If the operating system does not have the
12817 ability to find the amount of free space (only true for experimental systems),
12818 the space value is -1. See also the &%check_log_space%& option.
12821 .vitem &$lookup_dnssec_authenticated$&
12822 .vindex "&$lookup_dnssec_authenticated$&"
12823 This variable is set after a DNS lookup done by
12824 a dnsdb lookup expansion, dnslookup router or smtp transport.
12825 .cindex "DNS" "DNSSEC"
12826 It will be empty if &(DNSSEC)& was not requested,
12827 &"no"& if the result was not labelled as authenticated data
12828 and &"yes"& if it was.
12829 Results that are labelled as authoritative answer that match
12830 the &%dns_trust_aa%& configuration variable count also
12831 as authenticated data.
12833 .vitem &$mailstore_basename$&
12834 .vindex "&$mailstore_basename$&"
12835 This variable is set only when doing deliveries in &"mailstore"& format in the
12836 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12837 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12838 contains the basename of the files that are being written, that is, the name
12839 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12842 .vitem &$malware_name$&
12843 .vindex "&$malware_name$&"
12844 This variable is available when Exim is compiled with the
12845 content-scanning extension. It is set to the name of the virus that was found
12846 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12848 .vitem &$max_received_linelength$&
12849 .vindex "&$max_received_linelength$&"
12850 .cindex "maximum" "line length"
12851 .cindex "line length" "maximum"
12852 This variable contains the number of bytes in the longest line that was
12853 received as part of the message, not counting the line termination
12855 It is not valid if the &%spool_files_wireformat%& option is used.
12857 .vitem &$message_age$&
12858 .cindex "message" "age of"
12859 .vindex "&$message_age$&"
12860 This variable is set at the start of a delivery attempt to contain the number
12861 of seconds since the message was received. It does not change during a single
12864 .vitem &$message_body$&
12865 .cindex "body of message" "expansion variable"
12866 .cindex "message body" "in expansion"
12867 .cindex "binary zero" "in message body"
12868 .vindex "&$message_body$&"
12869 .oindex "&%message_body_visible%&"
12870 This variable contains the initial portion of a message's body while it is
12871 being delivered, and is intended mainly for use in filter files. The maximum
12872 number of characters of the body that are put into the variable is set by the
12873 &%message_body_visible%& configuration option; the default is 500.
12875 .oindex "&%message_body_newlines%&"
12876 By default, newlines are converted into spaces in &$message_body$&, to make it
12877 easier to search for phrases that might be split over a line break. However,
12878 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12879 zeros are always converted into spaces.
12881 .vitem &$message_body_end$&
12882 .cindex "body of message" "expansion variable"
12883 .cindex "message body" "in expansion"
12884 .vindex "&$message_body_end$&"
12885 This variable contains the final portion of a message's
12886 body while it is being delivered. The format and maximum size are as for
12889 .vitem &$message_body_size$&
12890 .cindex "body of message" "size"
12891 .cindex "message body" "size"
12892 .vindex "&$message_body_size$&"
12893 When a message is being delivered, this variable contains the size of the body
12894 in bytes. The count starts from the character after the blank line that
12895 separates the body from the header. Newlines are included in the count. See
12896 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12898 If the spool file is wireformat
12899 (see the &%spool_files_wireformat%& main option)
12900 the CRLF line-terminators are included in the count.
12902 .vitem &$message_exim_id$&
12903 .vindex "&$message_exim_id$&"
12904 When a message is being received or delivered, this variable contains the
12905 unique message id that is generated and used by Exim to identify the message.
12906 An id is not created for a message until after its header has been successfully
12907 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12908 line; it is the local id that Exim assigns to the message, for example:
12909 &`1BXTIK-0001yO-VA`&.
12911 .vitem &$message_headers$&
12912 .vindex &$message_headers$&
12913 This variable contains a concatenation of all the header lines when a message
12914 is being processed, except for lines added by routers or transports. The header
12915 lines are separated by newline characters. Their contents are decoded in the
12916 same way as a header line that is inserted by &%bheader%&.
12918 .vitem &$message_headers_raw$&
12919 .vindex &$message_headers_raw$&
12920 This variable is like &$message_headers$& except that no processing of the
12921 contents of header lines is done.
12923 .vitem &$message_id$&
12924 This is an old name for &$message_exim_id$&. It is now deprecated.
12926 .vitem &$message_linecount$&
12927 .vindex "&$message_linecount$&"
12928 This variable contains the total number of lines in the header and body of the
12929 message. Compare &$body_linecount$&, which is the count for the body only.
12930 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12931 number of lines received. Before delivery happens (that is, before filters,
12932 routers, and transports run) the count is increased to include the
12933 &'Received:'& header line that Exim standardly adds, and also any other header
12934 lines that are added by ACLs. The blank line that separates the message header
12935 from the body is not counted.
12937 As with the special case of &$message_size$&, during the expansion of the
12938 appendfile transport's maildir_tag option in maildir format, the value of
12939 &$message_linecount$& is the precise size of the number of newlines in the
12940 file that has been written (minus one for the blank line between the
12941 header and the body).
12943 Here is an example of the use of this variable in a DATA ACL:
12945 deny message = Too many lines in message header
12947 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12949 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12950 message has not yet been received.
12952 This variable is not valid if the &%spool_files_wireformat%& option is used.
12954 .vitem &$message_size$&
12955 .cindex "size" "of message"
12956 .cindex "message" "size"
12957 .vindex "&$message_size$&"
12958 When a message is being processed, this variable contains its size in bytes. In
12959 most cases, the size includes those headers that were received with the
12960 message, but not those (such as &'Envelope-to:'&) that are added to individual
12961 deliveries as they are written. However, there is one special case: during the
12962 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12963 doing a delivery in maildir format, the value of &$message_size$& is the
12964 precise size of the file that has been written. See also
12965 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12967 .cindex "RCPT" "value of &$message_size$&"
12968 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12969 contains the size supplied on the MAIL command, or -1 if no size was given. The
12970 value may not, of course, be truthful.
12972 .vitem &$mime_$&&'xxx'&
12973 A number of variables whose names start with &$mime$& are
12974 available when Exim is compiled with the content-scanning extension. For
12975 details, see section &<<SECTscanmimepart>>&.
12977 .vitem "&$n0$& &-- &$n9$&"
12978 These variables are counters that can be incremented by means
12979 of the &%add%& command in filter files.
12981 .vitem &$original_domain$&
12982 .vindex "&$domain$&"
12983 .vindex "&$original_domain$&"
12984 When a top-level address is being processed for delivery, this contains the
12985 same value as &$domain$&. However, if a &"child"& address (for example,
12986 generated by an alias, forward, or filter file) is being processed, this
12987 variable contains the domain of the original address (lower cased). This
12988 differs from &$parent_domain$& only when there is more than one level of
12989 aliasing or forwarding. When more than one address is being delivered in a
12990 single transport run, &$original_domain$& is not set.
12992 If a new address is created by means of a &%deliver%& command in a system
12993 filter, it is set up with an artificial &"parent"& address. This has the local
12994 part &'system-filter'& and the default qualify domain.
12996 .vitem &$original_local_part$&
12997 .vindex "&$local_part$&"
12998 .vindex "&$original_local_part$&"
12999 When a top-level address is being processed for delivery, this contains the
13000 same value as &$local_part$&, unless a prefix or suffix was removed from the
13001 local part, because &$original_local_part$& always contains the full local
13002 part. When a &"child"& address (for example, generated by an alias, forward, or
13003 filter file) is being processed, this variable contains the full local part of
13004 the original address.
13006 If the router that did the redirection processed the local part
13007 case-insensitively, the value in &$original_local_part$& is in lower case.
13008 This variable differs from &$parent_local_part$& only when there is more than
13009 one level of aliasing or forwarding. When more than one address is being
13010 delivered in a single transport run, &$original_local_part$& is not set.
13012 If a new address is created by means of a &%deliver%& command in a system
13013 filter, it is set up with an artificial &"parent"& address. This has the local
13014 part &'system-filter'& and the default qualify domain.
13016 .vitem &$originator_gid$&
13017 .cindex "gid (group id)" "of originating user"
13018 .cindex "sender" "gid"
13019 .vindex "&$caller_gid$&"
13020 .vindex "&$originator_gid$&"
13021 This variable contains the value of &$caller_gid$& that was set when the
13022 message was received. For messages received via the command line, this is the
13023 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13024 normally the gid of the Exim user.
13026 .vitem &$originator_uid$&
13027 .cindex "uid (user id)" "of originating user"
13028 .cindex "sender" "uid"
13029 .vindex "&$caller_uid$&"
13030 .vindex "&$originator_uid$&"
13031 The value of &$caller_uid$& that was set when the message was received. For
13032 messages received via the command line, this is the uid of the sending user.
13033 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13036 .vitem &$parent_domain$&
13037 .vindex "&$parent_domain$&"
13038 This variable is similar to &$original_domain$& (see
13039 above), except that it refers to the immediately preceding parent address.
13041 .vitem &$parent_local_part$&
13042 .vindex "&$parent_local_part$&"
13043 This variable is similar to &$original_local_part$&
13044 (see above), except that it refers to the immediately preceding parent address.
13047 .cindex "pid (process id)" "of current process"
13049 This variable contains the current process id.
13051 .vitem &$pipe_addresses$&
13052 .cindex "filter" "transport filter"
13053 .cindex "transport" "filter"
13054 .vindex "&$pipe_addresses$&"
13055 This is not an expansion variable, but is mentioned here because the string
13056 &`$pipe_addresses`& is handled specially in the command specification for the
13057 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13058 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13059 It cannot be used in general expansion strings, and provokes an &"unknown
13060 variable"& error if encountered.
13062 .vitem &$primary_hostname$&
13063 .vindex "&$primary_hostname$&"
13064 This variable contains the value set by &%primary_hostname%& in the
13065 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13066 a single-component name, Exim calls &[gethostbyname()]& (or
13067 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13068 qualified host name. See also &$smtp_active_hostname$&.
13071 .vitem &$proxy_external_address$& &&&
13072 &$proxy_external_port$& &&&
13073 &$proxy_local_address$& &&&
13074 &$proxy_local_port$& &&&
13076 These variables are only available when built with Proxy Protocol
13078 For details see chapter &<<SECTproxyInbound>>&.
13080 .vitem &$prdr_requested$&
13081 .cindex "PRDR" "variable for"
13082 This variable is set to &"yes"& if PRDR was requested by the client for the
13083 current message, otherwise &"no"&.
13085 .vitem &$prvscheck_address$&
13086 This variable is used in conjunction with the &%prvscheck%& expansion item,
13087 which is described in sections &<<SECTexpansionitems>>& and
13088 &<<SECTverifyPRVS>>&.
13090 .vitem &$prvscheck_keynum$&
13091 This variable is used in conjunction with the &%prvscheck%& expansion item,
13092 which is described in sections &<<SECTexpansionitems>>& and
13093 &<<SECTverifyPRVS>>&.
13095 .vitem &$prvscheck_result$&
13096 This variable is used in conjunction with the &%prvscheck%& expansion item,
13097 which is described in sections &<<SECTexpansionitems>>& and
13098 &<<SECTverifyPRVS>>&.
13100 .vitem &$qualify_domain$&
13101 .vindex "&$qualify_domain$&"
13102 The value set for the &%qualify_domain%& option in the configuration file.
13104 .vitem &$qualify_recipient$&
13105 .vindex "&$qualify_recipient$&"
13106 The value set for the &%qualify_recipient%& option in the configuration file,
13107 or if not set, the value of &$qualify_domain$&.
13109 .vitem &$queue_name$&
13110 .vindex &$queue_name$&
13111 .cindex "named queues" variable
13112 .cindex queues named
13113 The name of the spool queue in use; empty for the default queue.
13115 .vitem &$queue_size$&
13116 .vindex "&$queue_size$&"
13117 .cindex "queue" "size of"
13118 .cindex "spool" "number of messages"
13119 This variable contains the number of messages queued.
13120 It is evaluated on demand, but no more often than once every minute.
13124 .cindex router variables
13125 Values can be placed in these variables by the &%set%& option of a router.
13126 They can be given any name that starts with &$r_$&.
13127 The values persist for the address being handled through subsequent routers
13128 and the eventual transport.
13130 .vitem &$rcpt_count$&
13131 .vindex "&$rcpt_count$&"
13132 When a message is being received by SMTP, this variable contains the number of
13133 RCPT commands received for the current message. If this variable is used in a
13134 RCPT ACL, its value includes the current command.
13136 .vitem &$rcpt_defer_count$&
13137 .vindex "&$rcpt_defer_count$&"
13138 .cindex "4&'xx'& responses" "count of"
13139 When a message is being received by SMTP, this variable contains the number of
13140 RCPT commands in the current message that have previously been rejected with a
13141 temporary (4&'xx'&) response.
13143 .vitem &$rcpt_fail_count$&
13144 .vindex "&$rcpt_fail_count$&"
13145 When a message is being received by SMTP, this variable contains the number of
13146 RCPT commands in the current message that have previously been rejected with a
13147 permanent (5&'xx'&) response.
13149 .vitem &$received_count$&
13150 .vindex "&$received_count$&"
13151 This variable contains the number of &'Received:'& header lines in the message,
13152 including the one added by Exim (so its value is always greater than zero). It
13153 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13156 .vitem &$received_for$&
13157 .vindex "&$received_for$&"
13158 If there is only a single recipient address in an incoming message, this
13159 variable contains that address when the &'Received:'& header line is being
13160 built. The value is copied after recipient rewriting has happened, but before
13161 the &[local_scan()]& function is run.
13163 .vitem &$received_ip_address$&
13164 .vindex "&$received_ip_address$&"
13165 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13166 variable is set to the address of the local IP interface, and &$received_port$&
13167 is set to the local port number. (The remote IP address and port are in
13168 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13169 the port value is -1 unless it has been set using the &%-oMi%& command line
13172 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13173 could be used, for example, to make the filename for a TLS certificate depend
13174 on which interface and/or port is being used for the incoming connection. The
13175 values of &$received_ip_address$& and &$received_port$& are saved with any
13176 messages that are received, thus making these variables available at delivery
13178 For outbound connections see &$sending_ip_address$&.
13180 .vitem &$received_port$&
13181 .vindex "&$received_port$&"
13182 See &$received_ip_address$&.
13184 .vitem &$received_protocol$&
13185 .vindex "&$received_protocol$&"
13186 When a message is being processed, this variable contains the name of the
13187 protocol by which it was received. Most of the names used by Exim are defined
13188 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13189 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13190 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13191 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13192 connection and the client was successfully authenticated.
13194 Exim uses the protocol name &"smtps"& for the case when encryption is
13195 automatically set up on connection without the use of STARTTLS (see
13196 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13197 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13198 where the client initially uses EHLO, sets up an encrypted connection using
13199 STARTTLS, and then uses HELO afterwards.
13201 The &%-oMr%& option provides a way of specifying a custom protocol name for
13202 messages that are injected locally by trusted callers. This is commonly used to
13203 identify messages that are being re-injected after some kind of scanning.
13205 .vitem &$received_time$&
13206 .vindex "&$received_time$&"
13207 This variable contains the date and time when the current message was received,
13208 as a number of seconds since the start of the Unix epoch.
13210 .vitem &$recipient_data$&
13211 .vindex "&$recipient_data$&"
13212 This variable is set after an indexing lookup success in an ACL &%recipients%&
13213 condition. It contains the data from the lookup, and the value remains set
13214 until the next &%recipients%& test. Thus, you can do things like this:
13216 &`require recipients = cdb*@;/some/file`&
13217 &`deny `&&'some further test involving'& &`$recipient_data`&
13219 &*Warning*&: This variable is set only when a lookup is used as an indexing
13220 method in the address list, using the semicolon syntax as in the example above.
13221 The variable is not set for a lookup that is used as part of the string
13222 expansion that all such lists undergo before being interpreted.
13224 .vitem &$recipient_verify_failure$&
13225 .vindex "&$recipient_verify_failure$&"
13226 In an ACL, when a recipient verification fails, this variable contains
13227 information about the failure. It is set to one of the following words:
13230 &"qualify"&: The address was unqualified (no domain), and the message
13231 was neither local nor came from an exempted host.
13234 &"route"&: Routing failed.
13237 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13238 or before the MAIL command (that is, on initial connection, HELO, or
13242 &"recipient"&: The RCPT command in a callout was rejected.
13245 &"postmaster"&: The postmaster check in a callout was rejected.
13248 The main use of this variable is expected to be to distinguish between
13249 rejections of MAIL and rejections of RCPT.
13251 .vitem &$recipients$&
13252 .vindex "&$recipients$&"
13253 This variable contains a list of envelope recipients for a message. A comma and
13254 a space separate the addresses in the replacement text. However, the variable
13255 is not generally available, to prevent exposure of Bcc recipients in
13256 unprivileged users' filter files. You can use &$recipients$& only in these
13260 In a system filter file.
13262 In the ACLs associated with the DATA command and with non-SMTP messages, that
13263 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13264 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13265 &%acl_not_smtp_mime%&.
13267 From within a &[local_scan()]& function.
13271 .vitem &$recipients_count$&
13272 .vindex "&$recipients_count$&"
13273 When a message is being processed, this variable contains the number of
13274 envelope recipients that came with the message. Duplicates are not excluded
13275 from the count. While a message is being received over SMTP, the number
13276 increases for each accepted recipient. It can be referenced in an ACL.
13279 .vitem &$regex_match_string$&
13280 .vindex "&$regex_match_string$&"
13281 This variable is set to contain the matching regular expression after a
13282 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13284 .vitem "&$regex1$&, &$regex2$&, etc"
13285 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13286 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13287 these variables contain the
13288 captured substrings identified by the regular expression.
13291 .vitem &$reply_address$&
13292 .vindex "&$reply_address$&"
13293 When a message is being processed, this variable contains the contents of the
13294 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13295 contents of the &'From:'& header line. Apart from the removal of leading
13296 white space, the value is not processed in any way. In particular, no RFC 2047
13297 decoding or character code translation takes place.
13299 .vitem &$return_path$&
13300 .vindex "&$return_path$&"
13301 When a message is being delivered, this variable contains the return path &--
13302 the sender field that will be sent as part of the envelope. It is not enclosed
13303 in <> characters. At the start of routing an address, &$return_path$& has the
13304 same value as &$sender_address$&, but if, for example, an incoming message to a
13305 mailing list has been expanded by a router which specifies a different address
13306 for bounce messages, &$return_path$& subsequently contains the new bounce
13307 address, whereas &$sender_address$& always contains the original sender address
13308 that was received with the message. In other words, &$sender_address$& contains
13309 the incoming envelope sender, and &$return_path$& contains the outgoing
13312 .vitem &$return_size_limit$&
13313 .vindex "&$return_size_limit$&"
13314 This is an obsolete name for &$bounce_return_size_limit$&.
13316 .vitem &$router_name$&
13317 .cindex "router" "name"
13318 .cindex "name" "of router"
13319 .vindex "&$router_name$&"
13320 During the running of a router this variable contains its name.
13323 .cindex "return code" "from &%run%& expansion"
13324 .vindex "&$runrc$&"
13325 This variable contains the return code from a command that is run by the
13326 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13327 assume the order in which option values are expanded, except for those
13328 preconditions whose order of testing is documented. Therefore, you cannot
13329 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13332 .vitem &$self_hostname$&
13333 .oindex "&%self%&" "value of host name"
13334 .vindex "&$self_hostname$&"
13335 When an address is routed to a supposedly remote host that turns out to be the
13336 local host, what happens is controlled by the &%self%& generic router option.
13337 One of its values causes the address to be passed to another router. When this
13338 happens, &$self_hostname$& is set to the name of the local host that the
13339 original router encountered. In other circumstances its contents are null.
13341 .vitem &$sender_address$&
13342 .vindex "&$sender_address$&"
13343 When a message is being processed, this variable contains the sender's address
13344 that was received in the message's envelope. The case of letters in the address
13345 is retained, in both the local part and the domain. For bounce messages, the
13346 value of this variable is the empty string. See also &$return_path$&.
13348 .vitem &$sender_address_data$&
13349 .vindex "&$address_data$&"
13350 .vindex "&$sender_address_data$&"
13351 If &$address_data$& is set when the routers are called from an ACL to verify a
13352 sender address, the final value is preserved in &$sender_address_data$&, to
13353 distinguish it from data from a recipient address. The value does not persist
13354 after the end of the current ACL statement. If you want to preserve it for
13355 longer, you can save it in an ACL variable.
13357 .vitem &$sender_address_domain$&
13358 .vindex "&$sender_address_domain$&"
13359 The domain portion of &$sender_address$&.
13361 .vitem &$sender_address_local_part$&
13362 .vindex "&$sender_address_local_part$&"
13363 The local part portion of &$sender_address$&.
13365 .vitem &$sender_data$&
13366 .vindex "&$sender_data$&"
13367 This variable is set after a lookup success in an ACL &%senders%& condition or
13368 in a router &%senders%& option. It contains the data from the lookup, and the
13369 value remains set until the next &%senders%& test. Thus, you can do things like
13372 &`require senders = cdb*@;/some/file`&
13373 &`deny `&&'some further test involving'& &`$sender_data`&
13375 &*Warning*&: This variable is set only when a lookup is used as an indexing
13376 method in the address list, using the semicolon syntax as in the example above.
13377 The variable is not set for a lookup that is used as part of the string
13378 expansion that all such lists undergo before being interpreted.
13380 .vitem &$sender_fullhost$&
13381 .vindex "&$sender_fullhost$&"
13382 When a message is received from a remote host, this variable contains the host
13383 name and IP address in a single string. It ends with the IP address in square
13384 brackets, followed by a colon and a port number if the logging of ports is
13385 enabled. The format of the rest of the string depends on whether the host
13386 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13387 looking up its IP address. (Looking up the IP address can be forced by the
13388 &%host_lookup%& option, independent of verification.) A plain host name at the
13389 start of the string is a verified host name; if this is not present,
13390 verification either failed or was not requested. A host name in parentheses is
13391 the argument of a HELO or EHLO command. This is omitted if it is identical to
13392 the verified host name or to the host's IP address in square brackets.
13394 .vitem &$sender_helo_dnssec$&
13395 .vindex "&$sender_helo_dnssec$&"
13396 This boolean variable is true if a successful HELO verification was
13397 .cindex "DNS" "DNSSEC"
13398 done using DNS information the resolver library stated was authenticated data.
13400 .vitem &$sender_helo_name$&
13401 .vindex "&$sender_helo_name$&"
13402 When a message is received from a remote host that has issued a HELO or EHLO
13403 command, the argument of that command is placed in this variable. It is also
13404 set if HELO or EHLO is used when a message is received using SMTP locally via
13405 the &%-bs%& or &%-bS%& options.
13407 .vitem &$sender_host_address$&
13408 .vindex "&$sender_host_address$&"
13409 When a message is received from a remote host using SMTP,
13410 this variable contains that
13411 host's IP address. For locally non-SMTP submitted messages, it is empty.
13413 .vitem &$sender_host_authenticated$&
13414 .vindex "&$sender_host_authenticated$&"
13415 This variable contains the name (not the public name) of the authenticator
13416 driver that successfully authenticated the client from which the message was
13417 received. It is empty if there was no successful authentication. See also
13418 &$authenticated_id$&.
13420 .vitem &$sender_host_dnssec$&
13421 .vindex "&$sender_host_dnssec$&"
13422 If an attempt to populate &$sender_host_name$& has been made
13423 (by reference, &%hosts_lookup%& or
13424 otherwise) then this boolean will have been set true if, and only if, the
13425 resolver library states that both
13426 the reverse and forward DNS were authenticated data. At all
13427 other times, this variable is false.
13429 .cindex "DNS" "DNSSEC"
13430 It is likely that you will need to coerce DNSSEC support on in the resolver
13431 library, by setting:
13437 In addition, on Linux with glibc 2.31 or newer the resolver library will
13438 default to stripping out a successful validation status.
13439 This will break a previously working Exim installation.
13440 Provided that you do trust the resolver (ie, is on localhost) you can tell
13441 glibc to pass through any successful validation with a new option in
13442 &_/etc/resolv.conf_&:
13448 Exim does not perform DNSSEC validation itself, instead leaving that to a
13449 validating resolver (e.g. unbound, or bind with suitable configuration).
13451 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13452 mechanism in the list, then this variable will be false.
13454 This requires that your system resolver library support EDNS0 (and that
13455 DNSSEC flags exist in the system headers). If the resolver silently drops
13456 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13457 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13460 .vitem &$sender_host_name$&
13461 .vindex "&$sender_host_name$&"
13462 When a message is received from a remote host, this variable contains the
13463 host's name as obtained by looking up its IP address. For messages received by
13464 other means, this variable is empty.
13466 .vindex "&$host_lookup_failed$&"
13467 If the host name has not previously been looked up, a reference to
13468 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13469 A looked up name is accepted only if it leads back to the original IP address
13470 via a forward lookup. If either the reverse or the forward lookup fails to find
13471 any data, or if the forward lookup does not yield the original IP address,
13472 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13474 .vindex "&$host_lookup_deferred$&"
13475 However, if either of the lookups cannot be completed (for example, there is a
13476 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13477 &$host_lookup_failed$& remains set to &"0"&.
13479 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13480 host name again if there is a subsequent reference to &$sender_host_name$&
13481 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13484 Exim does not automatically look up every calling host's name. If you want
13485 maximum efficiency, you should arrange your configuration so that it avoids
13486 these lookups altogether. The lookup happens only if one or more of the
13487 following are true:
13490 A string containing &$sender_host_name$& is expanded.
13492 The calling host matches the list in &%host_lookup%&. In the default
13493 configuration, this option is set to *, so it must be changed if lookups are
13494 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13496 Exim needs the host name in order to test an item in a host list. The items
13497 that require this are described in sections &<<SECThoslispatnam>>& and
13498 &<<SECThoslispatnamsk>>&.
13500 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13501 In this case, the host name is required to compare with the name quoted in any
13502 EHLO or HELO commands that the client issues.
13504 The remote host issues a EHLO or HELO command that quotes one of the
13505 domains in &%helo_lookup_domains%&. The default value of this option is
13506 . ==== As this is a nested list, any displays it contains must be indented
13507 . ==== as otherwise they are too far to the left.
13509 helo_lookup_domains = @ : @[]
13511 which causes a lookup if a remote host (incorrectly) gives the server's name or
13512 IP address in an EHLO or HELO command.
13516 .vitem &$sender_host_port$&
13517 .vindex "&$sender_host_port$&"
13518 When a message is received from a remote host, this variable contains the port
13519 number that was used on the remote host.
13521 .vitem &$sender_ident$&
13522 .vindex "&$sender_ident$&"
13523 When a message is received from a remote host, this variable contains the
13524 identification received in response to an RFC 1413 request. When a message has
13525 been received locally, this variable contains the login name of the user that
13528 .vitem &$sender_rate_$&&'xxx'&
13529 A number of variables whose names begin &$sender_rate_$& are set as part of the
13530 &%ratelimit%& ACL condition. Details are given in section
13531 &<<SECTratelimiting>>&.
13533 .vitem &$sender_rcvhost$&
13534 .cindex "DNS" "reverse lookup"
13535 .cindex "reverse DNS lookup"
13536 .vindex "&$sender_rcvhost$&"
13537 This is provided specifically for use in &'Received:'& headers. It starts with
13538 either the verified host name (as obtained from a reverse DNS lookup) or, if
13539 there is no verified host name, the IP address in square brackets. After that
13540 there may be text in parentheses. When the first item is a verified host name,
13541 the first thing in the parentheses is the IP address in square brackets,
13542 followed by a colon and a port number if port logging is enabled. When the
13543 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13546 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13547 was used and its argument was not identical to the real host name or IP
13548 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13549 all three items are present in the parentheses, a newline and tab are inserted
13550 into the string, to improve the formatting of the &'Received:'& header.
13552 .vitem &$sender_verify_failure$&
13553 .vindex "&$sender_verify_failure$&"
13554 In an ACL, when a sender verification fails, this variable contains information
13555 about the failure. The details are the same as for
13556 &$recipient_verify_failure$&.
13558 .vitem &$sending_ip_address$&
13559 .vindex "&$sending_ip_address$&"
13560 This variable is set whenever an outgoing SMTP connection to another host has
13561 been set up. It contains the IP address of the local interface that is being
13562 used. This is useful if a host that has more than one IP address wants to take
13563 on different personalities depending on which one is being used. For incoming
13564 connections, see &$received_ip_address$&.
13566 .vitem &$sending_port$&
13567 .vindex "&$sending_port$&"
13568 This variable is set whenever an outgoing SMTP connection to another host has
13569 been set up. It contains the local port that is being used. For incoming
13570 connections, see &$received_port$&.
13572 .vitem &$smtp_active_hostname$&
13573 .vindex "&$smtp_active_hostname$&"
13574 During an incoming SMTP session, this variable contains the value of the active
13575 host name, as specified by the &%smtp_active_hostname%& option. The value of
13576 &$smtp_active_hostname$& is saved with any message that is received, so its
13577 value can be consulted during routing and delivery.
13579 .vitem &$smtp_command$&
13580 .vindex "&$smtp_command$&"
13581 During the processing of an incoming SMTP command, this variable contains the
13582 entire command. This makes it possible to distinguish between HELO and EHLO in
13583 the HELO ACL, and also to distinguish between commands such as these:
13588 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13589 command, the address in &$smtp_command$& is the original address before any
13590 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13591 the address after SMTP-time rewriting.
13593 .vitem &$smtp_command_argument$&
13594 .cindex "SMTP" "command, argument for"
13595 .vindex "&$smtp_command_argument$&"
13596 While an ACL is running to check an SMTP command, this variable contains the
13597 argument, that is, the text that follows the command name, with leading white
13598 space removed. Following the introduction of &$smtp_command$&, this variable is
13599 somewhat redundant, but is retained for backwards compatibility.
13601 .vitem &$smtp_command_history$&
13602 .cindex SMTP "command history"
13603 .vindex "&$smtp_command_history$&"
13604 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13605 received, in time-order left to right. Only a limited number of commands
13608 .vitem &$smtp_count_at_connection_start$&
13609 .vindex "&$smtp_count_at_connection_start$&"
13610 This variable is set greater than zero only in processes spawned by the Exim
13611 daemon for handling incoming SMTP connections. The name is deliberately long,
13612 in order to emphasize what the contents are. When the daemon accepts a new
13613 connection, it increments this variable. A copy of the variable is passed to
13614 the child process that handles the connection, but its value is fixed, and
13615 never changes. It is only an approximation of how many incoming connections
13616 there actually are, because many other connections may come and go while a
13617 single connection is being processed. When a child process terminates, the
13618 daemon decrements its copy of the variable.
13620 .vitem "&$sn0$& &-- &$sn9$&"
13621 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13622 that were current at the end of the system filter file. This allows a system
13623 filter file to set values that can be tested in users' filter files. For
13624 example, a system filter could set a value indicating how likely it is that a
13625 message is junk mail.
13627 .vitem &$spam_$&&'xxx'&
13628 A number of variables whose names start with &$spam$& are available when Exim
13629 is compiled with the content-scanning extension. For details, see section
13630 &<<SECTscanspamass>>&.
13632 .vitem &$spf_header_comment$& &&&
13633 &$spf_received$& &&&
13635 &$spf_result_guessed$& &&&
13636 &$spf_smtp_comment$&
13637 These variables are only available if Exim is built with SPF support.
13638 For details see section &<<SECSPF>>&.
13640 .vitem &$spool_directory$&
13641 .vindex "&$spool_directory$&"
13642 The name of Exim's spool directory.
13644 .vitem &$spool_inodes$&
13645 .vindex "&$spool_inodes$&"
13646 The number of free inodes in the disk partition where Exim's spool files are
13647 being written. The value is recalculated whenever the variable is referenced.
13648 If the relevant file system does not have the concept of inodes, the value of
13649 is -1. See also the &%check_spool_inodes%& option.
13651 .vitem &$spool_space$&
13652 .vindex "&$spool_space$&"
13653 The amount of free space (as a number of kilobytes) in the disk partition where
13654 Exim's spool files are being written. The value is recalculated whenever the
13655 variable is referenced. If the operating system does not have the ability to
13656 find the amount of free space (only true for experimental systems), the space
13657 value is -1. For example, to check in an ACL that there is at least 50
13658 megabytes free on the spool, you could write:
13660 condition = ${if > {$spool_space}{50000}}
13662 See also the &%check_spool_space%& option.
13665 .vitem &$thisaddress$&
13666 .vindex "&$thisaddress$&"
13667 This variable is set only during the processing of the &%foranyaddress%&
13668 command in a filter file. Its use is explained in the description of that
13669 command, which can be found in the separate document entitled &'Exim's
13670 interfaces to mail filtering'&.
13672 .vitem &$tls_in_bits$&
13673 .vindex "&$tls_in_bits$&"
13674 Contains an approximation of the TLS cipher's bit-strength
13675 on the inbound connection; the meaning of
13676 this depends upon the TLS implementation used.
13677 If TLS has not been negotiated, the value will be 0.
13678 The value of this is automatically fed into the Cyrus SASL authenticator
13679 when acting as a server, to specify the "external SSF" (a SASL term).
13681 The deprecated &$tls_bits$& variable refers to the inbound side
13682 except when used in the context of an outbound SMTP delivery, when it refers to
13685 .vitem &$tls_out_bits$&
13686 .vindex "&$tls_out_bits$&"
13687 Contains an approximation of the TLS cipher's bit-strength
13688 on an outbound SMTP connection; the meaning of
13689 this depends upon the TLS implementation used.
13690 If TLS has not been negotiated, the value will be 0.
13692 .vitem &$tls_in_ourcert$&
13693 .vindex "&$tls_in_ourcert$&"
13694 .cindex certificate variables
13695 This variable refers to the certificate presented to the peer of an
13696 inbound connection when the message was received.
13697 It is only useful as the argument of a
13698 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13699 or a &%def%& condition.
13701 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13702 when a list of more than one
13703 file is used for &%tls_certificate%&, this variable is not reliable.
13704 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13706 .vitem &$tls_in_peercert$&
13707 .vindex "&$tls_in_peercert$&"
13708 This variable refers to the certificate presented by the peer of an
13709 inbound connection when the message was received.
13710 It is only useful as the argument of a
13711 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13712 or a &%def%& condition.
13713 If certificate verification fails it may refer to a failing chain element
13714 which is not the leaf.
13716 .vitem &$tls_out_ourcert$&
13717 .vindex "&$tls_out_ourcert$&"
13718 This variable refers to the certificate presented to the peer of an
13719 outbound connection. It is only useful as the argument of a
13720 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13721 or a &%def%& condition.
13723 .vitem &$tls_out_peercert$&
13724 .vindex "&$tls_out_peercert$&"
13725 This variable refers to the certificate presented by the peer of an
13726 outbound connection. It is only useful as the argument of a
13727 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13728 or a &%def%& condition.
13729 If certificate verification fails it may refer to a failing chain element
13730 which is not the leaf.
13732 .vitem &$tls_in_certificate_verified$&
13733 .vindex "&$tls_in_certificate_verified$&"
13734 This variable is set to &"1"& if a TLS certificate was verified when the
13735 message was received, and &"0"& otherwise.
13737 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13738 except when used in the context of an outbound SMTP delivery, when it refers to
13741 .vitem &$tls_out_certificate_verified$&
13742 .vindex "&$tls_out_certificate_verified$&"
13743 This variable is set to &"1"& if a TLS certificate was verified when an
13744 outbound SMTP connection was made,
13745 and &"0"& otherwise.
13747 .vitem &$tls_in_cipher$&
13748 .vindex "&$tls_in_cipher$&"
13749 .vindex "&$tls_cipher$&"
13750 When a message is received from a remote host over an encrypted SMTP
13751 connection, this variable is set to the cipher suite that was negotiated, for
13752 example DES-CBC3-SHA. In other circumstances, in particular, for message
13753 received over unencrypted connections, the variable is empty. Testing
13754 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13755 non-encrypted connections during ACL processing.
13757 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13758 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13759 becomes the same as &$tls_out_cipher$&.
13761 .vitem &$tls_in_cipher_std$&
13762 .vindex "&$tls_in_cipher_std$&"
13763 As above, but returning the RFC standard name for the cipher suite.
13765 .vitem &$tls_out_cipher$&
13766 .vindex "&$tls_out_cipher$&"
13768 cleared before any outgoing SMTP connection is made,
13769 and then set to the outgoing cipher suite if one is negotiated. See chapter
13770 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13771 details of the &(smtp)& transport.
13773 .vitem &$tls_out_cipher_std$&
13774 .vindex "&$tls_out_cipher_std$&"
13775 As above, but returning the RFC standard name for the cipher suite.
13777 .vitem &$tls_out_dane$&
13778 .vindex &$tls_out_dane$&
13779 DANE active status. See section &<<SECDANE>>&.
13781 .vitem &$tls_in_ocsp$&
13782 .vindex "&$tls_in_ocsp$&"
13783 When a message is received from a remote client connection
13784 the result of any OCSP request from the client is encoded in this variable:
13786 0 OCSP proof was not requested (default value)
13787 1 No response to request
13788 2 Response not verified
13789 3 Verification failed
13790 4 Verification succeeded
13793 .vitem &$tls_out_ocsp$&
13794 .vindex "&$tls_out_ocsp$&"
13795 When a message is sent to a remote host connection
13796 the result of any OCSP request made is encoded in this variable.
13797 See &$tls_in_ocsp$& for values.
13799 .vitem &$tls_in_peerdn$&
13800 .vindex "&$tls_in_peerdn$&"
13801 .vindex "&$tls_peerdn$&"
13802 .cindex certificate "extracting fields"
13803 When a message is received from a remote host over an encrypted SMTP
13804 connection, and Exim is configured to request a certificate from the client,
13805 the value of the Distinguished Name of the certificate is made available in the
13806 &$tls_in_peerdn$& during subsequent processing.
13807 If certificate verification fails it may refer to a failing chain element
13808 which is not the leaf.
13810 The deprecated &$tls_peerdn$& variable refers to the inbound side
13811 except when used in the context of an outbound SMTP delivery, when it refers to
13814 .vitem &$tls_out_peerdn$&
13815 .vindex "&$tls_out_peerdn$&"
13816 When a message is being delivered to a remote host over an encrypted SMTP
13817 connection, and Exim is configured to request a certificate from the server,
13818 the value of the Distinguished Name of the certificate is made available in the
13819 &$tls_out_peerdn$& during subsequent processing.
13820 If certificate verification fails it may refer to a failing chain element
13821 which is not the leaf.
13825 .vitem &$tls_in_resumption$& &&&
13826 &$tls_out_resumption$&
13827 .vindex &$tls_in_resumption$&
13828 .vindex &$tls_out_resumption$&
13829 .cindex TLS resumption
13830 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13834 .vitem &$tls_in_sni$&
13835 .vindex "&$tls_in_sni$&"
13836 .vindex "&$tls_sni$&"
13837 .cindex "TLS" "Server Name Indication"
13838 When a TLS session is being established, if the client sends the Server
13839 Name Indication extension, the value will be placed in this variable.
13840 If the variable appears in &%tls_certificate%& then this option and
13841 some others, described in &<<SECTtlssni>>&,
13842 will be re-expanded early in the TLS session, to permit
13843 a different certificate to be presented (and optionally a different key to be
13844 used) to the client, based upon the value of the SNI extension.
13846 The deprecated &$tls_sni$& variable refers to the inbound side
13847 except when used in the context of an outbound SMTP delivery, when it refers to
13850 .vitem &$tls_out_sni$&
13851 .vindex "&$tls_out_sni$&"
13852 .cindex "TLS" "Server Name Indication"
13854 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13857 .vitem &$tls_out_tlsa_usage$&
13858 .vindex &$tls_out_tlsa_usage$&
13859 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13861 .vitem &$tls_in_ver$&
13862 .vindex "&$tls_in_ver$&"
13863 When a message is received from a remote host over an encrypted SMTP connection
13864 this variable is set to the protocol version, eg &'TLS1.2'&.
13866 .vitem &$tls_out_ver$&
13867 .vindex "&$tls_out_ver$&"
13868 When a message is being delivered to a remote host over an encrypted SMTP connection
13869 this variable is set to the protocol version.
13872 .vitem &$tod_bsdinbox$&
13873 .vindex "&$tod_bsdinbox$&"
13874 The time of day and the date, in the format required for BSD-style mailbox
13875 files, for example: Thu Oct 17 17:14:09 1995.
13877 .vitem &$tod_epoch$&
13878 .vindex "&$tod_epoch$&"
13879 The time and date as a number of seconds since the start of the Unix epoch.
13881 .vitem &$tod_epoch_l$&
13882 .vindex "&$tod_epoch_l$&"
13883 The time and date as a number of microseconds since the start of the Unix epoch.
13885 .vitem &$tod_full$&
13886 .vindex "&$tod_full$&"
13887 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13888 +0100. The timezone is always given as a numerical offset from UTC, with
13889 positive values used for timezones that are ahead (east) of UTC, and negative
13890 values for those that are behind (west).
13893 .vindex "&$tod_log$&"
13894 The time and date in the format used for writing Exim's log files, for example:
13895 1995-10-12 15:32:29, but without a timezone.
13897 .vitem &$tod_logfile$&
13898 .vindex "&$tod_logfile$&"
13899 This variable contains the date in the format yyyymmdd. This is the format that
13900 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13903 .vitem &$tod_zone$&
13904 .vindex "&$tod_zone$&"
13905 This variable contains the numerical value of the local timezone, for example:
13908 .vitem &$tod_zulu$&
13909 .vindex "&$tod_zulu$&"
13910 This variable contains the UTC date and time in &"Zulu"& format, as specified
13911 by ISO 8601, for example: 20030221154023Z.
13913 .vitem &$transport_name$&
13914 .cindex "transport" "name"
13915 .cindex "name" "of transport"
13916 .vindex "&$transport_name$&"
13917 During the running of a transport, this variable contains its name.
13920 .vindex "&$value$&"
13921 This variable contains the result of an expansion lookup, extraction operation,
13922 or external command, as described above. It is also used during a
13923 &*reduce*& expansion.
13925 .vitem &$verify_mode$&
13926 .vindex "&$verify_mode$&"
13927 While a router or transport is being run in verify mode or for cutthrough delivery,
13928 contains "S" for sender-verification or "R" for recipient-verification.
13931 .vitem &$version_number$&
13932 .vindex "&$version_number$&"
13933 The version number of Exim. Same as &$exim_version$&, may be overridden
13934 by the &%exim_version%& main config option.
13936 .vitem &$warn_message_delay$&
13937 .vindex "&$warn_message_delay$&"
13938 This variable is set only during the creation of a message warning about a
13939 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13941 .vitem &$warn_message_recipients$&
13942 .vindex "&$warn_message_recipients$&"
13943 This variable is set only during the creation of a message warning about a
13944 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13950 . ////////////////////////////////////////////////////////////////////////////
13951 . ////////////////////////////////////////////////////////////////////////////
13953 .chapter "Embedded Perl" "CHAPperl"
13954 .scindex IIDperl "Perl" "calling from Exim"
13955 Exim can be built to include an embedded Perl interpreter. When this is done,
13956 Perl subroutines can be called as part of the string expansion process. To make
13957 use of the Perl support, you need version 5.004 or later of Perl installed on
13958 your system. To include the embedded interpreter in the Exim binary, include
13963 in your &_Local/Makefile_& and then build Exim in the normal way.
13966 .section "Setting up so Perl can be used" "SECID85"
13967 .oindex "&%perl_startup%&"
13968 Access to Perl subroutines is via a global configuration option called
13969 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13970 no &%perl_startup%& option in the Exim configuration file then no Perl
13971 interpreter is started and there is almost no overhead for Exim (since none of
13972 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13973 option then the associated value is taken to be Perl code which is executed in
13974 a newly created Perl interpreter.
13976 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13977 need backslashes before any characters to escape special meanings. The option
13978 should usually be something like
13980 perl_startup = do '/etc/exim.pl'
13982 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13983 use from Exim. Exim can be configured either to start up a Perl interpreter as
13984 soon as it is entered, or to wait until the first time it is needed. Starting
13985 the interpreter at the beginning ensures that it is done while Exim still has
13986 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13987 fact used in a particular run. Also, note that this does not mean that Exim is
13988 necessarily running as root when Perl is called at a later time. By default,
13989 the interpreter is started only when it is needed, but this can be changed in
13993 .oindex "&%perl_at_start%&"
13994 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13995 a startup when Exim is entered.
13997 The command line option &%-ps%& also requests a startup when Exim is entered,
13998 overriding the setting of &%perl_at_start%&.
14001 There is also a command line option &%-pd%& (for delay) which suppresses the
14002 initial startup, even if &%perl_at_start%& is set.
14005 .oindex "&%perl_taintmode%&"
14006 .cindex "Perl" "taintmode"
14007 To provide more security executing Perl code via the embedded Perl
14008 interpreter, the &%perl_taintmode%& option can be set. This enables the
14009 taint mode of the Perl interpreter. You are encouraged to set this
14010 option to a true value. To avoid breaking existing installations, it
14014 .section "Calling Perl subroutines" "SECID86"
14015 When the configuration file includes a &%perl_startup%& option you can make use
14016 of the string expansion item to call the Perl subroutines that are defined
14017 by the &%perl_startup%& code. The operator is used in any of the following
14021 ${perl{foo}{argument}}
14022 ${perl{foo}{argument1}{argument2} ... }
14024 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14025 arguments may be passed. Passing more than this results in an expansion failure
14026 with an error message of the form
14028 Too many arguments passed to Perl subroutine "foo" (max is 8)
14030 The return value of the Perl subroutine is evaluated in a scalar context before
14031 it is passed back to Exim to be inserted into the expanded string. If the
14032 return value is &'undef'&, the expansion is forced to fail in the same way as
14033 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14034 by obeying Perl's &%die%& function, the expansion fails with the error message
14035 that was passed to &%die%&.
14038 .section "Calling Exim functions from Perl" "SECID87"
14039 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14040 is available to call back into Exim's string expansion function. For example,
14043 my $lp = Exim::expand_string('$local_part');
14045 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14046 Note those are single quotes and not double quotes to protect against
14047 &$local_part$& being interpolated as a Perl variable.
14049 If the string expansion is forced to fail by a &"fail"& item, the result of
14050 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14051 expansion string, the Perl call from the original expansion string fails with
14052 an appropriate error message, in the same way as if &%die%& were used.
14054 .cindex "debugging" "from embedded Perl"
14055 .cindex "log" "writing from embedded Perl"
14056 Two other Exim functions are available for use from within Perl code.
14057 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14058 debugging is enabled. If you want a newline at the end, you must supply it.
14059 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14060 timestamp. In this case, you should not supply a terminating newline.
14063 .section "Use of standard output and error by Perl" "SECID88"
14064 .cindex "Perl" "standard output and error"
14065 You should not write to the standard error or output streams from within your
14066 Perl code, as it is not defined how these are set up. In versions of Exim
14067 before 4.50, it is possible for the standard output or error to refer to the
14068 SMTP connection during message reception via the daemon. Writing to this stream
14069 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14070 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14071 avoided, but the output is lost.
14073 .cindex "Perl" "use of &%warn%&"
14074 The Perl &%warn%& statement writes to the standard error stream by default.
14075 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14076 you have no control. When Exim starts up the Perl interpreter, it arranges for
14077 output from the &%warn%& statement to be written to the Exim main log. You can
14078 change this by including appropriate Perl magic somewhere in your Perl code.
14079 For example, to discard &%warn%& output completely, you need this:
14081 $SIG{__WARN__} = sub { };
14083 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14084 example, the code for the subroutine is empty, so it does nothing, but you can
14085 include any Perl code that you like. The text of the &%warn%& message is passed
14086 as the first subroutine argument.
14090 . ////////////////////////////////////////////////////////////////////////////
14091 . ////////////////////////////////////////////////////////////////////////////
14093 .chapter "Starting the daemon and the use of network interfaces" &&&
14094 "CHAPinterfaces" &&&
14095 "Starting the daemon"
14096 .cindex "daemon" "starting"
14097 .cindex "interface" "listening"
14098 .cindex "network interface"
14099 .cindex "interface" "network"
14100 .cindex "IP address" "for listening"
14101 .cindex "daemon" "listening IP addresses"
14102 .cindex "TCP/IP" "setting listening interfaces"
14103 .cindex "TCP/IP" "setting listening ports"
14104 A host that is connected to a TCP/IP network may have one or more physical
14105 hardware network interfaces. Each of these interfaces may be configured as one
14106 or more &"logical"& interfaces, which are the entities that a program actually
14107 works with. Each of these logical interfaces is associated with an IP address.
14108 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14109 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14110 knowledge about the host's interfaces for use in three different circumstances:
14113 When a listening daemon is started, Exim needs to know which interfaces
14114 and ports to listen on.
14116 When Exim is routing an address, it needs to know which IP addresses
14117 are associated with local interfaces. This is required for the correct
14118 processing of MX lists by removing the local host and others with the
14119 same or higher priority values. Also, Exim needs to detect cases
14120 when an address is routed to an IP address that in fact belongs to the
14121 local host. Unless the &%self%& router option or the &%allow_localhost%&
14122 option of the smtp transport is set (as appropriate), this is treated
14123 as an error situation.
14125 When Exim connects to a remote host, it may need to know which interface to use
14126 for the outgoing connection.
14130 Exim's default behaviour is likely to be appropriate in the vast majority
14131 of cases. If your host has only one interface, and you want all its IP
14132 addresses to be treated in the same way, and you are using only the
14133 standard SMTP port, you should not need to take any special action. The
14134 rest of this chapter does not apply to you.
14136 In a more complicated situation you may want to listen only on certain
14137 interfaces, or on different ports, and for this reason there are a number of
14138 options that can be used to influence Exim's behaviour. The rest of this
14139 chapter describes how they operate.
14141 When a message is received over TCP/IP, the interface and port that were
14142 actually used are set in &$received_ip_address$& and &$received_port$&.
14146 .section "Starting a listening daemon" "SECID89"
14147 When a listening daemon is started (by means of the &%-bd%& command line
14148 option), the interfaces and ports on which it listens are controlled by the
14152 &%daemon_smtp_ports%& contains a list of default ports
14154 (For backward compatibility, this option can also be specified in the singular.)
14156 &%local_interfaces%& contains list of interface IP addresses on which to
14157 listen. Each item may optionally also specify a port.
14160 The default list separator in both cases is a colon, but this can be changed as
14161 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14162 it is usually best to change the separator to avoid having to double all the
14163 colons. For example:
14165 local_interfaces = <; 127.0.0.1 ; \
14168 3ffe:ffff:836f::fe86:a061
14170 There are two different formats for specifying a port along with an IP address
14171 in &%local_interfaces%&:
14174 The port is added onto the address with a dot separator. For example, to listen
14175 on port 1234 on two different IP addresses:
14177 local_interfaces = <; 192.168.23.65.1234 ; \
14178 3ffe:ffff:836f::fe86:a061.1234
14181 The IP address is enclosed in square brackets, and the port is added
14182 with a colon separator, for example:
14184 local_interfaces = <; [192.168.23.65]:1234 ; \
14185 [3ffe:ffff:836f::fe86:a061]:1234
14189 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14190 default setting contains just one port:
14192 daemon_smtp_ports = smtp
14194 If more than one port is listed, each interface that does not have its own port
14195 specified listens on all of them. Ports that are listed in
14196 &%daemon_smtp_ports%& can be identified either by name (defined in
14197 &_/etc/services_&) or by number. However, when ports are given with individual
14198 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14202 .section "Special IP listening addresses" "SECID90"
14203 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14204 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14205 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14206 instead of setting up separate listening sockets for each interface. The
14207 default value of &%local_interfaces%& is
14209 local_interfaces = 0.0.0.0
14211 when Exim is built without IPv6 support; otherwise it is:
14213 local_interfaces = <; ::0 ; 0.0.0.0
14215 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14219 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14220 The &%-oX%& command line option can be used to override the values of
14221 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14222 instance. Another way of doing this would be to use macros and the &%-D%&
14223 option. However, &%-oX%& can be used by any admin user, whereas modification of
14224 the runtime configuration by &%-D%& is allowed only when the caller is root or
14227 The value of &%-oX%& is a list of items. The default colon separator can be
14228 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14229 If there are any items that do not
14230 contain dots or colons (that is, are not IP addresses), the value of
14231 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14232 items that do contain dots or colons, the value of &%local_interfaces%& is
14233 replaced by those items. Thus, for example,
14237 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14240 -oX 192.168.34.5.1125
14242 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14243 (However, since &%local_interfaces%& now contains no items without ports, the
14244 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14248 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14249 .cindex "submissions protocol"
14250 .cindex "ssmtp protocol"
14251 .cindex "smtps protocol"
14252 .cindex "SMTP" "ssmtp protocol"
14253 .cindex "SMTP" "smtps protocol"
14254 Exim supports the use of TLS-on-connect, used by mail clients in the
14255 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14256 For some years, IETF Standards Track documents only blessed the
14257 STARTTLS-based Submission service (port 587) while common practice was to support
14258 the same feature set on port 465, but using TLS-on-connect.
14259 If your installation needs to provide service to mail clients
14260 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14263 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14264 service names, connections to those ports must first establish TLS, before
14265 proceeding to the application layer use of the SMTP protocol.
14267 The common use of this option is expected to be
14269 tls_on_connect_ports = 465
14272 There is also a command line option &%-tls-on-connect%&, which forces all ports
14273 to behave in this way when a daemon is started.
14275 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14276 daemon to listen on those ports. You must still specify them in
14277 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14278 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14279 connections via the daemon.)
14284 .section "IPv6 address scopes" "SECID92"
14285 .cindex "IPv6" "address scopes"
14286 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14287 can, in principle, have the same link-local IPv6 address on different
14288 interfaces. Thus, additional information is needed, over and above the IP
14289 address, to distinguish individual interfaces. A convention of using a
14290 percent sign followed by something (often the interface name) has been
14291 adopted in some cases, leading to addresses like this:
14293 fe80::202:b3ff:fe03:45c1%eth0
14295 To accommodate this usage, a percent sign followed by an arbitrary string is
14296 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14297 to convert a textual IPv6 address for actual use. This function recognizes the
14298 percent convention in operating systems that support it, and it processes the
14299 address appropriately. Unfortunately, some older libraries have problems with
14300 &[getaddrinfo()]&. If
14302 IPV6_USE_INET_PTON=yes
14304 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14305 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14306 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14307 function.) Of course, this means that the additional functionality of
14308 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14310 .section "Disabling IPv6" "SECID93"
14311 .cindex "IPv6" "disabling"
14312 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14313 run on a host whose kernel does not support IPv6. The binary will fall back to
14314 using IPv4, but it may waste resources looking up AAAA records, and trying to
14315 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14316 .oindex "&%disable_ipv6%&"
14317 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14318 activities take place. AAAA records are never looked up, and any IPv6 addresses
14319 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14320 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14321 to handle IPv6 literal addresses.
14323 On the other hand, when IPv6 is in use, there may be times when you want to
14324 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14325 option to globally suppress the lookup of AAAA records for specified domains,
14326 and you can use the &%ignore_target_hosts%& generic router option to ignore
14327 IPv6 addresses in an individual router.
14331 .section "Examples of starting a listening daemon" "SECID94"
14332 The default case in an IPv6 environment is
14334 daemon_smtp_ports = smtp
14335 local_interfaces = <; ::0 ; 0.0.0.0
14337 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14338 Either one or two sockets may be used, depending on the characteristics of
14339 the TCP/IP stack. (This is complicated and messy; for more information,
14340 read the comments in the &_daemon.c_& source file.)
14342 To specify listening on ports 25 and 26 on all interfaces:
14344 daemon_smtp_ports = 25 : 26
14346 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14348 local_interfaces = <; ::0.25 ; ::0.26 \
14349 0.0.0.0.25 ; 0.0.0.0.26
14351 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14352 IPv4 loopback address only:
14354 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14356 To specify listening on the default port on specific interfaces only:
14358 local_interfaces = 10.0.0.67 : 192.168.34.67
14360 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14364 .section "Recognizing the local host" "SECTreclocipadd"
14365 The &%local_interfaces%& option is also used when Exim needs to determine
14366 whether or not an IP address refers to the local host. That is, the IP
14367 addresses of all the interfaces on which a daemon is listening are always
14370 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14371 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14372 available interfaces from the operating system, and extracts the relevant
14373 (that is, IPv4 or IPv6) addresses to use for checking.
14375 Some systems set up large numbers of virtual interfaces in order to provide
14376 many virtual web servers. In this situation, you may want to listen for
14377 email on only a few of the available interfaces, but nevertheless treat all
14378 interfaces as local when routing. You can do this by setting
14379 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14380 &"all"& wildcard values. These addresses are recognized as local, but are not
14381 used for listening. Consider this example:
14383 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14385 3ffe:2101:12:1:a00:20ff:fe86:a061
14387 extra_local_interfaces = <; ::0 ; 0.0.0.0
14389 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14390 address, but all available interface addresses are treated as local when
14393 In some environments the local host name may be in an MX list, but with an IP
14394 address that is not assigned to any local interface. In other cases it may be
14395 desirable to treat other host names as if they referred to the local host. Both
14396 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14397 This contains host names rather than IP addresses. When a host is referenced
14398 during routing, either via an MX record or directly, it is treated as the local
14399 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14400 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14404 .section "Delivering to a remote host" "SECID95"
14405 Delivery to a remote host is handled by the smtp transport. By default, it
14406 allows the system's TCP/IP functions to choose which interface to use (if
14407 there is more than one) when connecting to a remote host. However, the
14408 &%interface%& option can be set to specify which interface is used. See the
14409 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14415 . ////////////////////////////////////////////////////////////////////////////
14416 . ////////////////////////////////////////////////////////////////////////////
14418 .chapter "Main configuration" "CHAPmainconfig"
14419 .scindex IIDconfima "configuration file" "main section"
14420 .scindex IIDmaiconf "main configuration"
14421 The first part of the runtime configuration file contains three types of item:
14424 Macro definitions: These lines start with an upper case letter. See section
14425 &<<SECTmacrodefs>>& for details of macro processing.
14427 Named list definitions: These lines start with one of the words &"domainlist"&,
14428 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14429 section &<<SECTnamedlists>>&.
14431 Main configuration settings: Each setting occupies one line of the file
14432 (with possible continuations). If any setting is preceded by the word
14433 &"hide"&, the &%-bP%& command line option displays its value to admin users
14434 only. See section &<<SECTcos>>& for a description of the syntax of these option
14438 This chapter specifies all the main configuration options, along with their
14439 types and default values. For ease of finding a particular option, they appear
14440 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14441 are now so many options, they are first listed briefly in functional groups, as
14442 an aid to finding the name of the option you are looking for. Some options are
14443 listed in more than one group.
14445 .section "Miscellaneous" "SECID96"
14447 .row &%bi_command%& "to run for &%-bi%& command line option"
14448 .row &%debug_store%& "do extra internal checks"
14449 .row &%disable_ipv6%& "do no IPv6 processing"
14450 .row &%keep_malformed%& "for broken files &-- should not happen"
14451 .row &%localhost_number%& "for unique message ids in clusters"
14452 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14453 .row &%message_body_visible%& "how much to show in &$message_body$&"
14454 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14455 .row &%print_topbitchars%& "top-bit characters are printing"
14456 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14457 .row &%timezone%& "force time zone"
14461 .section "Exim parameters" "SECID97"
14463 .row &%exim_group%& "override compiled-in value"
14464 .row &%exim_path%& "override compiled-in value"
14465 .row &%exim_user%& "override compiled-in value"
14466 .row &%primary_hostname%& "default from &[uname()]&"
14467 .row &%split_spool_directory%& "use multiple directories"
14468 .row &%spool_directory%& "override compiled-in value"
14473 .section "Privilege controls" "SECID98"
14475 .row &%admin_groups%& "groups that are Exim admin users"
14476 .row &%commandline_checks_require_admin%& "require admin for various checks"
14477 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14478 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14479 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14480 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14481 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14482 .row &%never_users%& "do not run deliveries as these"
14483 .row &%prod_requires_admin%& "forced delivery requires admin user"
14484 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14485 .row &%trusted_groups%& "groups that are trusted"
14486 .row &%trusted_users%& "users that are trusted"
14491 .section "Logging" "SECID99"
14493 .row &%event_action%& "custom logging"
14494 .row &%hosts_connection_nolog%& "exemption from connect logging"
14495 .row &%log_file_path%& "override compiled-in value"
14496 .row &%log_selector%& "set/unset optional logging"
14497 .row &%log_timezone%& "add timezone to log lines"
14498 .row &%message_logs%& "create per-message logs"
14499 .row &%preserve_message_logs%& "after message completion"
14500 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14501 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14502 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14503 .row &%syslog_facility%& "set syslog &""facility""& field"
14504 .row &%syslog_pid%& "pid in syslog lines"
14505 .row &%syslog_processname%& "set syslog &""ident""& field"
14506 .row &%syslog_timestamp%& "timestamp syslog lines"
14507 .row &%write_rejectlog%& "control use of message log"
14512 .section "Frozen messages" "SECID100"
14514 .row &%auto_thaw%& "sets time for retrying frozen messages"
14515 .row &%freeze_tell%& "send message when freezing"
14516 .row &%move_frozen_messages%& "to another directory"
14517 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14522 .section "Data lookups" "SECID101"
14524 .row &%ibase_servers%& "InterBase servers"
14525 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14526 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14527 .row &%ldap_cert_file%& "client cert file for LDAP"
14528 .row &%ldap_cert_key%& "client key file for LDAP"
14529 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14530 .row &%ldap_default_servers%& "used if no server in query"
14531 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14532 .row &%ldap_start_tls%& "require TLS within LDAP"
14533 .row &%ldap_version%& "set protocol version"
14534 .row &%lookup_open_max%& "lookup files held open"
14535 .row &%mysql_servers%& "default MySQL servers"
14536 .row &%oracle_servers%& "Oracle servers"
14537 .row &%pgsql_servers%& "default PostgreSQL servers"
14538 .row &%sqlite_lock_timeout%& "as it says"
14543 .section "Message ids" "SECID102"
14545 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14546 .row &%message_id_header_text%& "ditto"
14551 .section "Embedded Perl Startup" "SECID103"
14553 .row &%perl_at_start%& "always start the interpreter"
14554 .row &%perl_startup%& "code to obey when starting Perl"
14555 .row &%perl_taintmode%& "enable taint mode in Perl"
14560 .section "Daemon" "SECID104"
14562 .row &%daemon_smtp_ports%& "default ports"
14563 .row &%daemon_startup_retries%& "number of times to retry"
14564 .row &%daemon_startup_sleep%& "time to sleep between tries"
14565 .row &%extra_local_interfaces%& "not necessarily listened on"
14566 .row &%local_interfaces%& "on which to listen, with optional ports"
14567 .row &%notifier_socket%& "override compiled-in value"
14568 .row &%pid_file_path%& "override compiled-in value"
14569 .row &%queue_run_max%& "maximum simultaneous queue runners"
14574 .section "Resource control" "SECID105"
14576 .row &%check_log_inodes%& "before accepting a message"
14577 .row &%check_log_space%& "before accepting a message"
14578 .row &%check_spool_inodes%& "before accepting a message"
14579 .row &%check_spool_space%& "before accepting a message"
14580 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14581 .row &%queue_only_load%& "queue incoming if load high"
14582 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14583 .row &%queue_run_max%& "maximum simultaneous queue runners"
14584 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14585 .row &%smtp_accept_max%& "simultaneous incoming connections"
14586 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14587 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14588 .row &%smtp_accept_max_per_connection%& "messages per connection"
14589 .row &%smtp_accept_max_per_host%& "connections from one host"
14590 .row &%smtp_accept_queue%& "queue mail if more connections"
14591 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14593 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14594 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14595 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14596 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14597 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14602 .section "Policy controls" "SECID106"
14604 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14605 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14606 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14607 .row &%acl_smtp_auth%& "ACL for AUTH"
14608 .row &%acl_smtp_connect%& "ACL for connection"
14609 .row &%acl_smtp_data%& "ACL for DATA"
14610 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14611 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14612 .row &%acl_smtp_etrn%& "ACL for ETRN"
14613 .row &%acl_smtp_expn%& "ACL for EXPN"
14614 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14615 .row &%acl_smtp_mail%& "ACL for MAIL"
14616 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14617 .row &%acl_smtp_mime%& "ACL for MIME parts"
14618 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14619 .row &%acl_smtp_predata%& "ACL for start of data"
14620 .row &%acl_smtp_quit%& "ACL for QUIT"
14621 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14622 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14623 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14624 .row &%av_scanner%& "specify virus scanner"
14625 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14627 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14628 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14629 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14630 .row &%header_maxsize%& "total size of message header"
14631 .row &%header_line_maxsize%& "individual header line limit"
14632 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14633 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14634 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14635 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14636 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14637 .row &%host_lookup%& "host name looked up for these hosts"
14638 .row &%host_lookup_order%& "order of DNS and local name lookups"
14639 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14640 .row &%host_reject_connection%& "reject connection from these hosts"
14641 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14642 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14643 .row &%message_size_limit%& "for all messages"
14644 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14645 .row &%spamd_address%& "set interface to SpamAssassin"
14646 .row &%strict_acl_vars%& "object to unset ACL variables"
14651 .section "Callout cache" "SECID107"
14653 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14655 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14657 .row &%callout_negative_expire%& "timeout for negative address cache item"
14658 .row &%callout_positive_expire%& "timeout for positive address cache item"
14659 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14664 .section "TLS" "SECID108"
14666 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14667 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14668 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14669 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14670 .row &%tls_certificate%& "location of server certificate"
14671 .row &%tls_crl%& "certificate revocation list"
14672 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14673 .row &%tls_dhparam%& "DH parameters for server"
14674 .row &%tls_eccurve%& "EC curve selection for server"
14675 .row &%tls_ocsp_file%& "location of server certificate status proof"
14676 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14677 .row &%tls_privatekey%& "location of server private key"
14678 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14679 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14680 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14681 .row &%tls_verify_certificates%& "expected client certificates"
14682 .row &%tls_verify_hosts%& "insist on client certificate verify"
14687 .section "Local user handling" "SECID109"
14689 .row &%finduser_retries%& "useful in NIS environments"
14690 .row &%gecos_name%& "used when creating &'Sender:'&"
14691 .row &%gecos_pattern%& "ditto"
14692 .row &%max_username_length%& "for systems that truncate"
14693 .row &%unknown_login%& "used when no login name found"
14694 .row &%unknown_username%& "ditto"
14695 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14696 .row &%uucp_from_sender%& "ditto"
14701 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14703 .row &%header_maxsize%& "total size of message header"
14704 .row &%header_line_maxsize%& "individual header line limit"
14705 .row &%message_size_limit%& "applies to all messages"
14706 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14707 .row &%received_header_text%& "expanded to make &'Received:'&"
14708 .row &%received_headers_max%& "for mail loop detection"
14709 .row &%recipients_max%& "limit per message"
14710 .row &%recipients_max_reject%& "permanently reject excess recipients"
14716 .section "Non-SMTP incoming messages" "SECID111"
14718 .row &%receive_timeout%& "for non-SMTP messages"
14725 .section "Incoming SMTP messages" "SECID112"
14726 See also the &'Policy controls'& section above.
14729 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14730 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14731 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14732 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14733 .row &%host_lookup%& "host name looked up for these hosts"
14734 .row &%host_lookup_order%& "order of DNS and local name lookups"
14735 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14736 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14737 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14738 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14739 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14740 .row &%smtp_accept_max%& "simultaneous incoming connections"
14741 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14742 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14743 .row &%smtp_accept_max_per_connection%& "messages per connection"
14744 .row &%smtp_accept_max_per_host%& "connections from one host"
14745 .row &%smtp_accept_queue%& "queue mail if more connections"
14746 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14748 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14749 .row &%smtp_active_hostname%& "host name to use in messages"
14750 .row &%smtp_banner%& "text for welcome banner"
14751 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14752 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14753 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14754 .row &%smtp_etrn_command%& "what to run for ETRN"
14755 .row &%smtp_etrn_serialize%& "only one at once"
14756 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14757 .row &%smtp_max_unknown_commands%& "before dropping connection"
14758 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14759 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14760 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14761 .row &%smtp_receive_timeout%& "per command or data line"
14762 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14763 .row &%smtp_return_error_details%& "give detail on rejections"
14768 .section "SMTP extensions" "SECID113"
14770 .row &%accept_8bitmime%& "advertise 8BITMIME"
14771 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14772 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14773 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14774 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14775 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14776 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14777 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14778 .row &%prdr_enable%& "advertise PRDR to all hosts"
14779 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14780 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14785 .section "Processing messages" "SECID114"
14787 .row &%allow_domain_literals%& "recognize domain literal syntax"
14788 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14789 .row &%allow_utf8_domains%& "in addresses"
14790 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14792 .row &%delivery_date_remove%& "from incoming messages"
14793 .row &%envelope_to_remove%& "from incoming messages"
14794 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14795 .row &%headers_charset%& "default for translations"
14796 .row &%qualify_domain%& "default for senders"
14797 .row &%qualify_recipient%& "default for recipients"
14798 .row &%return_path_remove%& "from incoming messages"
14799 .row &%strip_excess_angle_brackets%& "in addresses"
14800 .row &%strip_trailing_dot%& "at end of addresses"
14801 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14806 .section "System filter" "SECID115"
14808 .row &%system_filter%& "locate system filter"
14809 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14811 .row &%system_filter_file_transport%& "transport for delivery to a file"
14812 .row &%system_filter_group%& "group for filter running"
14813 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14814 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14815 .row &%system_filter_user%& "user for filter running"
14820 .section "Routing and delivery" "SECID116"
14822 .row &%disable_ipv6%& "do no IPv6 processing"
14823 .row &%dns_again_means_nonexist%& "for broken domains"
14824 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14825 .row &%dns_dnssec_ok%& "parameter for resolver"
14826 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14827 .row &%dns_retrans%& "parameter for resolver"
14828 .row &%dns_retry%& "parameter for resolver"
14829 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14830 .row &%dns_use_edns0%& "parameter for resolver"
14831 .row &%hold_domains%& "hold delivery for these domains"
14832 .row &%local_interfaces%& "for routing checks"
14833 .row &%queue_domains%& "no immediate delivery for these"
14834 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14835 .row &%queue_only%& "no immediate delivery at all"
14836 .row &%queue_only_file%& "no immediate delivery if file exists"
14837 .row &%queue_only_load%& "no immediate delivery if load is high"
14838 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14839 .row &%queue_only_override%& "allow command line to override"
14840 .row &%queue_run_in_order%& "order of arrival"
14841 .row &%queue_run_max%& "of simultaneous queue runners"
14842 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14843 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14844 .row &%remote_sort_domains%& "order of remote deliveries"
14845 .row &%retry_data_expire%& "timeout for retry data"
14846 .row &%retry_interval_max%& "safety net for retry rules"
14851 .section "Bounce and warning messages" "SECID117"
14853 .row &%bounce_message_file%& "content of bounce"
14854 .row &%bounce_message_text%& "content of bounce"
14855 .row &%bounce_return_body%& "include body if returning message"
14856 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14857 .row &%bounce_return_message%& "include original message in bounce"
14858 .row &%bounce_return_size_limit%& "limit on returned message"
14859 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14860 .row &%dsn_from%& "set &'From:'& contents in bounces"
14861 .row &%errors_copy%& "copy bounce messages"
14862 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14863 .row &%delay_warning%& "time schedule"
14864 .row &%delay_warning_condition%& "condition for warning messages"
14865 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14866 .row &%smtp_return_error_details%& "give detail on rejections"
14867 .row &%warn_message_file%& "content of warning message"
14872 .section "Alphabetical list of main options" "SECTalomo"
14873 Those options that undergo string expansion before use are marked with
14876 .option accept_8bitmime main boolean true
14878 .cindex "8-bit characters"
14879 .cindex "log" "selectors"
14880 .cindex "log" "8BITMIME"
14881 .cindex "ESMTP extensions" 8BITMIME
14882 This option causes Exim to send 8BITMIME in its response to an SMTP
14883 EHLO command, and to accept the BODY= parameter on MAIL commands.
14884 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14885 takes no steps to do anything special with messages received by this route.
14887 Historically Exim kept this option off by default, but the maintainers
14888 feel that in today's Internet, this causes more problems than it solves.
14889 It now defaults to true.
14890 A more detailed analysis of the issues is provided by Dan Bernstein:
14892 &url(https://cr.yp.to/smtp/8bitmime.html)
14895 To log received 8BITMIME status use
14897 log_selector = +8bitmime
14900 .option acl_not_smtp main string&!! unset
14901 .cindex "&ACL;" "for non-SMTP messages"
14902 .cindex "non-SMTP messages" "ACLs for"
14903 This option defines the ACL that is run when a non-SMTP message has been
14904 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14907 .option acl_not_smtp_mime main string&!! unset
14908 This option defines the ACL that is run for individual MIME parts of non-SMTP
14909 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14912 .option acl_not_smtp_start main string&!! unset
14913 .cindex "&ACL;" "at start of non-SMTP message"
14914 .cindex "non-SMTP messages" "ACLs for"
14915 This option defines the ACL that is run before Exim starts reading a
14916 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14918 .option acl_smtp_auth main string&!! unset
14919 .cindex "&ACL;" "setting up for SMTP commands"
14920 .cindex "AUTH" "ACL for"
14921 This option defines the ACL that is run when an SMTP AUTH command is
14922 received. See chapter &<<CHAPACL>>& for further details.
14924 .option acl_smtp_connect main string&!! unset
14925 .cindex "&ACL;" "on SMTP connection"
14926 This option defines the ACL that is run when an SMTP connection is received.
14927 See chapter &<<CHAPACL>>& for further details.
14929 .option acl_smtp_data main string&!! unset
14930 .cindex "DATA" "ACL for"
14931 This option defines the ACL that is run after an SMTP DATA command has been
14932 processed and the message itself has been received, but before the final
14933 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14935 .option acl_smtp_data_prdr main string&!! accept
14936 .cindex "PRDR" "ACL for"
14937 .cindex "DATA" "PRDR ACL for"
14938 .cindex "&ACL;" "PRDR-related"
14939 .cindex "&ACL;" "per-user data processing"
14940 This option defines the ACL that,
14941 if the PRDR feature has been negotiated,
14942 is run for each recipient after an SMTP DATA command has been
14943 processed and the message itself has been received, but before the
14944 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14946 .option acl_smtp_dkim main string&!! unset
14947 .cindex DKIM "ACL for"
14948 This option defines the ACL that is run for each DKIM signature
14949 (by default, or as specified in the dkim_verify_signers option)
14950 of a received message.
14951 See section &<<SECDKIMVFY>>& for further details.
14953 .option acl_smtp_etrn main string&!! unset
14954 .cindex "ETRN" "ACL for"
14955 This option defines the ACL that is run when an SMTP ETRN command is
14956 received. See chapter &<<CHAPACL>>& for further details.
14958 .option acl_smtp_expn main string&!! unset
14959 .cindex "EXPN" "ACL for"
14960 This option defines the ACL that is run when an SMTP EXPN command is
14961 received. See chapter &<<CHAPACL>>& for further details.
14963 .option acl_smtp_helo main string&!! unset
14964 .cindex "EHLO" "ACL for"
14965 .cindex "HELO" "ACL for"
14966 This option defines the ACL that is run when an SMTP EHLO or HELO
14967 command is received. See chapter &<<CHAPACL>>& for further details.
14970 .option acl_smtp_mail main string&!! unset
14971 .cindex "MAIL" "ACL for"
14972 This option defines the ACL that is run when an SMTP MAIL command is
14973 received. See chapter &<<CHAPACL>>& for further details.
14975 .option acl_smtp_mailauth main string&!! unset
14976 .cindex "AUTH" "on MAIL command"
14977 This option defines the ACL that is run when there is an AUTH parameter on
14978 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14979 &<<CHAPSMTPAUTH>>& for details of authentication.
14981 .option acl_smtp_mime main string&!! unset
14982 .cindex "MIME content scanning" "ACL for"
14983 This option is available when Exim is built with the content-scanning
14984 extension. It defines the ACL that is run for each MIME part in a message. See
14985 section &<<SECTscanmimepart>>& for details.
14987 .option acl_smtp_notquit main string&!! unset
14988 .cindex "not-QUIT, ACL for"
14989 This option defines the ACL that is run when an SMTP session
14990 ends without a QUIT command being received.
14991 See chapter &<<CHAPACL>>& for further details.
14993 .option acl_smtp_predata main string&!! unset
14994 This option defines the ACL that is run when an SMTP DATA command is
14995 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14998 .option acl_smtp_quit main string&!! unset
14999 .cindex "QUIT, ACL for"
15000 This option defines the ACL that is run when an SMTP QUIT command is
15001 received. See chapter &<<CHAPACL>>& for further details.
15003 .option acl_smtp_rcpt main string&!! unset
15004 .cindex "RCPT" "ACL for"
15005 This option defines the ACL that is run when an SMTP RCPT command is
15006 received. See chapter &<<CHAPACL>>& for further details.
15008 .option acl_smtp_starttls main string&!! unset
15009 .cindex "STARTTLS, ACL for"
15010 This option defines the ACL that is run when an SMTP STARTTLS command is
15011 received. See chapter &<<CHAPACL>>& for further details.
15013 .option acl_smtp_vrfy main string&!! unset
15014 .cindex "VRFY" "ACL for"
15015 This option defines the ACL that is run when an SMTP VRFY command is
15016 received. See chapter &<<CHAPACL>>& for further details.
15018 .option add_environment main "string list" empty
15019 .cindex "environment" "set values"
15020 This option adds individual environment variables that the
15021 currently linked libraries and programs in child processes may use.
15022 Each list element should be of the form &"name=value"&.
15024 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15026 .option admin_groups main "string list&!!" unset
15027 .cindex "admin user"
15028 This option is expanded just once, at the start of Exim's processing. If the
15029 current group or any of the supplementary groups of an Exim caller is in this
15030 colon-separated list, the caller has admin privileges. If all your system
15031 programmers are in a specific group, for example, you can give them all Exim
15032 admin privileges by putting that group in &%admin_groups%&. However, this does
15033 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15034 To permit this, you have to add individuals to the Exim group.
15036 .option allow_domain_literals main boolean false
15037 .cindex "domain literal"
15038 If this option is set, the RFC 2822 domain literal format is permitted in
15039 email addresses. The option is not set by default, because the domain literal
15040 format is not normally required these days, and few people know about it. It
15041 has, however, been exploited by mail abusers.
15043 Unfortunately, it seems that some DNS black list maintainers are using this
15044 format to report black listing to postmasters. If you want to accept messages
15045 addressed to your hosts by IP address, you need to set
15046 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15047 domains (defined in the named domain list &%local_domains%& in the default
15048 configuration). This &"magic string"& matches the domain literal form of all
15049 the local host's IP addresses.
15052 .option allow_mx_to_ip main boolean false
15053 .cindex "MX record" "pointing to IP address"
15054 It appears that more and more DNS zone administrators are breaking the rules
15055 and putting domain names that look like IP addresses on the right hand side of
15056 MX records. Exim follows the rules and rejects this, giving an error message
15057 that explains the misconfiguration. However, some other MTAs support this
15058 practice, so to avoid &"Why can't Exim do this?"& complaints,
15059 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15060 recommended, except when you have no other choice.
15062 .option allow_utf8_domains main boolean false
15063 .cindex "domain" "UTF-8 characters in"
15064 .cindex "UTF-8" "in domain name"
15065 Lots of discussion is going on about internationalized domain names. One
15066 camp is strongly in favour of just using UTF-8 characters, and it seems
15067 that at least two other MTAs permit this.
15068 This option allows Exim users to experiment if they wish.
15070 If it is set true, Exim's domain parsing function allows valid
15071 UTF-8 multicharacters to appear in domain name components, in addition to
15072 letters, digits, and hyphens.
15074 If Exim is built with internationalization support
15075 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15076 this option can be left as default.
15078 if you want to look up such domain names in the DNS, you must also
15079 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15080 suitable setting is:
15082 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15083 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15085 Alternatively, you can just disable this feature by setting
15087 dns_check_names_pattern =
15089 That is, set the option to an empty string so that no check is done.
15092 .option auth_advertise_hosts main "host list&!!" *
15093 .cindex "authentication" "advertising"
15094 .cindex "AUTH" "advertising"
15095 .cindex "ESMTP extensions" AUTH
15096 If any server authentication mechanisms are configured, Exim advertises them in
15097 response to an EHLO command only if the calling host matches this list.
15098 Otherwise, Exim does not advertise AUTH.
15099 Exim does not accept AUTH commands from clients to which it has not
15100 advertised the availability of AUTH. The advertising of individual
15101 authentication mechanisms can be controlled by the use of the
15102 &%server_advertise_condition%& generic authenticator option on the individual
15103 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15105 Certain mail clients (for example, Netscape) require the user to provide a name
15106 and password for authentication if AUTH is advertised, even though it may
15107 not be needed (the host may accept messages from hosts on its local LAN without
15108 authentication, for example). The &%auth_advertise_hosts%& option can be used
15109 to make these clients more friendly by excluding them from the set of hosts to
15110 which Exim advertises AUTH.
15112 .cindex "AUTH" "advertising when encrypted"
15113 If you want to advertise the availability of AUTH only when the connection
15114 is encrypted using TLS, you can make use of the fact that the value of this
15115 option is expanded, with a setting like this:
15117 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15119 .vindex "&$tls_in_cipher$&"
15120 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15121 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15122 expansion is *, which matches all hosts.
15125 .option auto_thaw main time 0s
15126 .cindex "thawing messages"
15127 .cindex "unfreezing messages"
15128 If this option is set to a time greater than zero, a queue runner will try a
15129 new delivery attempt on any frozen message, other than a bounce message, if
15130 this much time has passed since it was frozen. This may result in the message
15131 being re-frozen if nothing has changed since the last attempt. It is a way of
15132 saying &"keep on trying, even though there are big problems"&.
15134 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15135 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15136 thought to be very useful any more, and its use should probably be avoided.
15139 .option av_scanner main string "see below"
15140 This option is available if Exim is built with the content-scanning extension.
15141 It specifies which anti-virus scanner to use. The default value is:
15143 sophie:/var/run/sophie
15145 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15146 before use. See section &<<SECTscanvirus>>& for further details.
15149 .option bi_command main string unset
15151 This option supplies the name of a command that is run when Exim is called with
15152 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15153 just the command name, it is not a complete command line. If an argument is
15154 required, it must come from the &%-oA%& command line option.
15157 .option bounce_message_file main string&!! unset
15158 .cindex "bounce message" "customizing"
15159 .cindex "customizing" "bounce message"
15160 This option defines a template file containing paragraphs of text to be used
15161 for constructing bounce messages. Details of the file's contents are given in
15162 chapter &<<CHAPemsgcust>>&.
15164 .cindex bounce_message_file "tainted data"
15165 The option is expanded to give the file path, which must be
15166 absolute and untainted.
15168 See also &%warn_message_file%&.
15171 .option bounce_message_text main string unset
15172 When this option is set, its contents are included in the default bounce
15173 message immediately after &"This message was created automatically by mail
15174 delivery software."& It is not used if &%bounce_message_file%& is set.
15176 .option bounce_return_body main boolean true
15177 .cindex "bounce message" "including body"
15178 This option controls whether the body of an incoming message is included in a
15179 bounce message when &%bounce_return_message%& is true. The default setting
15180 causes the entire message, both header and body, to be returned (subject to the
15181 value of &%bounce_return_size_limit%&). If this option is false, only the
15182 message header is included. In the case of a non-SMTP message containing an
15183 error that is detected during reception, only those header lines preceding the
15184 point at which the error was detected are returned.
15185 .cindex "bounce message" "including original"
15187 .option bounce_return_linesize_limit main integer 998
15188 .cindex "size" "of bounce lines, limit"
15189 .cindex "bounce message" "line length limit"
15190 .cindex "limit" "bounce message line length"
15191 This option sets a limit in bytes on the line length of messages
15192 that are returned to senders due to delivery problems,
15193 when &%bounce_return_message%& is true.
15194 The default value corresponds to RFC limits.
15195 If the message being returned has lines longer than this value it is
15196 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15198 The option also applies to bounces returned when an error is detected
15199 during reception of a message.
15200 In this case lines from the original are truncated.
15202 The option does not apply to messages generated by an &(autoreply)& transport.
15205 .option bounce_return_message main boolean true
15206 If this option is set false, none of the original message is included in
15207 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15208 &%bounce_return_body%&.
15211 .option bounce_return_size_limit main integer 100K
15212 .cindex "size" "of bounce, limit"
15213 .cindex "bounce message" "size limit"
15214 .cindex "limit" "bounce message size"
15215 This option sets a limit in bytes on the size of messages that are returned to
15216 senders as part of bounce messages when &%bounce_return_message%& is true. The
15217 limit should be less than the value of the global &%message_size_limit%& and of
15218 any &%message_size_limit%& settings on transports, to allow for the bounce text
15219 that Exim generates. If this option is set to zero there is no limit.
15221 When the body of any message that is to be included in a bounce message is
15222 greater than the limit, it is truncated, and a comment pointing this out is
15223 added at the top. The actual cutoff may be greater than the value given, owing
15224 to the use of buffering for transferring the message in chunks (typically 8K in
15225 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15228 .option bounce_sender_authentication main string unset
15229 .cindex "bounce message" "sender authentication"
15230 .cindex "authentication" "bounce message"
15231 .cindex "AUTH" "on bounce message"
15232 This option provides an authenticated sender address that is sent with any
15233 bounce messages generated by Exim that are sent over an authenticated SMTP
15234 connection. A typical setting might be:
15236 bounce_sender_authentication = mailer-daemon@my.domain.example
15238 which would cause bounce messages to be sent using the SMTP command:
15240 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15242 The value of &%bounce_sender_authentication%& must always be a complete email
15245 .option callout_domain_negative_expire main time 3h
15246 .cindex "caching" "callout timeouts"
15247 .cindex "callout" "caching timeouts"
15248 This option specifies the expiry time for negative callout cache data for a
15249 domain. See section &<<SECTcallver>>& for details of callout verification, and
15250 section &<<SECTcallvercache>>& for details of the caching.
15253 .option callout_domain_positive_expire main time 7d
15254 This option specifies the expiry time for positive callout cache data for a
15255 domain. See section &<<SECTcallver>>& for details of callout verification, and
15256 section &<<SECTcallvercache>>& for details of the caching.
15259 .option callout_negative_expire main time 2h
15260 This option specifies the expiry time for negative callout cache data for an
15261 address. See section &<<SECTcallver>>& for details of callout verification, and
15262 section &<<SECTcallvercache>>& for details of the caching.
15265 .option callout_positive_expire main time 24h
15266 This option specifies the expiry time for positive callout cache data for an
15267 address. See section &<<SECTcallver>>& for details of callout verification, and
15268 section &<<SECTcallvercache>>& for details of the caching.
15271 .option callout_random_local_part main string&!! "see below"
15272 This option defines the &"random"& local part that can be used as part of
15273 callout verification. The default value is
15275 $primary_hostname-$tod_epoch-testing
15277 See section &<<CALLaddparcall>>& for details of how this value is used.
15280 .option check_log_inodes main integer 100
15281 See &%check_spool_space%& below.
15284 .option check_log_space main integer 10M
15285 See &%check_spool_space%& below.
15287 .oindex "&%check_rfc2047_length%&"
15288 .cindex "RFC 2047" "disabling length check"
15289 .option check_rfc2047_length main boolean true
15290 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15291 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15292 word; strings to be encoded that exceed this length are supposed to use
15293 multiple encoded words. By default, Exim does not recognize encoded words that
15294 exceed the maximum length. However, it seems that some software, in violation
15295 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15296 set false, Exim recognizes encoded words of any length.
15299 .option check_spool_inodes main integer 100
15300 See &%check_spool_space%& below.
15303 .option check_spool_space main integer 10M
15304 .cindex "checking disk space"
15305 .cindex "disk space, checking"
15306 .cindex "spool directory" "checking space"
15307 The four &%check_...%& options allow for checking of disk resources before a
15308 message is accepted.
15310 .vindex "&$log_inodes$&"
15311 .vindex "&$log_space$&"
15312 .vindex "&$spool_inodes$&"
15313 .vindex "&$spool_space$&"
15314 When any of these options are nonzero, they apply to all incoming messages. If you
15315 want to apply different checks to different kinds of message, you can do so by
15316 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15317 &$spool_space$& in an ACL with appropriate additional conditions.
15320 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15321 either value is greater than zero, for example:
15323 check_spool_space = 100M
15324 check_spool_inodes = 100
15326 The spool partition is the one that contains the directory defined by
15327 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15330 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15331 files are written if either is greater than zero. These should be set only if
15332 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15334 If there is less space or fewer inodes than requested, Exim refuses to accept
15335 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15336 error response to the MAIL command. If ESMTP is in use and there was a
15337 SIZE parameter on the MAIL command, its value is added to the
15338 &%check_spool_space%& value, and the check is performed even if
15339 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15341 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15342 number of kilobytes (though specified in bytes).
15343 If a non-multiple of 1024 is specified, it is rounded up.
15345 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15346 failure a message is written to stderr and Exim exits with a non-zero code, as
15347 it obviously cannot send an error message of any kind.
15349 There is a slight performance penalty for these checks.
15350 Versions of Exim preceding 4.88 had these disabled by default;
15351 high-rate installations confident they will never run out of resources
15352 may wish to deliberately disable them.
15354 .option chunking_advertise_hosts main "host list&!!" *
15355 .cindex CHUNKING advertisement
15356 .cindex "RFC 3030" "CHUNKING"
15357 .cindex "ESMTP extensions" CHUNKING
15358 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15360 Hosts may use the BDAT command as an alternate to DATA.
15362 .option commandline_checks_require_admin main boolean &`false`&
15363 .cindex "restricting access to features"
15364 This option restricts various basic checking features to require an
15365 administrative user.
15366 This affects most of the &%-b*%& options, such as &%-be%&.
15368 .option debug_store main boolean &`false`&
15369 .cindex debugging "memory corruption"
15370 .cindex memory debugging
15371 This option, when true, enables extra checking in Exim's internal memory
15372 management. For use when a memory corruption issue is being investigated,
15373 it should normally be left as default.
15375 .option daemon_smtp_ports main string &`smtp`&
15376 .cindex "port" "for daemon"
15377 .cindex "TCP/IP" "setting listening ports"
15378 This option specifies one or more default SMTP ports on which the Exim daemon
15379 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15380 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15382 .option daemon_startup_retries main integer 9
15383 .cindex "daemon startup, retrying"
15384 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15385 the daemon at startup when it cannot immediately bind a listening socket
15386 (typically because the socket is already in use): &%daemon_startup_retries%&
15387 defines the number of retries after the first failure, and
15388 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15390 .option daemon_startup_sleep main time 30s
15391 See &%daemon_startup_retries%&.
15393 .option delay_warning main "time list" 24h
15394 .cindex "warning of delay"
15395 .cindex "delay warning, specifying"
15396 .cindex "queue" "delay warning"
15397 When a message is delayed, Exim sends a warning message to the sender at
15398 intervals specified by this option. The data is a colon-separated list of times
15399 after which to send warning messages. If the value of the option is an empty
15400 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15401 message has been in the queue for longer than the last time, the last interval
15402 between the times is used to compute subsequent warning times. For example,
15405 delay_warning = 4h:8h:24h
15407 the first message is sent after 4 hours, the second after 8 hours, and
15408 the third one after 24 hours. After that, messages are sent every 16 hours,
15409 because that is the interval between the last two times on the list. If you set
15410 just one time, it specifies the repeat interval. For example, with:
15414 messages are repeated every six hours. To stop warnings after a given time, set
15415 a very large time at the end of the list. For example:
15417 delay_warning = 2h:12h:99d
15419 Note that the option is only evaluated at the time a delivery attempt fails,
15420 which depends on retry and queue-runner configuration.
15421 Typically retries will be configured more frequently than warning messages.
15423 .option delay_warning_condition main string&!! "see below"
15424 .vindex "&$domain$&"
15425 The string is expanded at the time a warning message might be sent. If all the
15426 deferred addresses have the same domain, it is set in &$domain$& during the
15427 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15428 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15429 &"false"& (the comparison being done caselessly) then the warning message is
15430 not sent. The default is:
15432 delay_warning_condition = ${if or {\
15433 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15434 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15435 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15438 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15439 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15440 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15441 &"auto-replied"& in an &'Auto-Submitted:'& header.
15443 .option deliver_drop_privilege main boolean false
15444 .cindex "unprivileged delivery"
15445 .cindex "delivery" "unprivileged"
15446 If this option is set true, Exim drops its root privilege at the start of a
15447 delivery process, and runs as the Exim user throughout. This severely restricts
15448 the kinds of local delivery that are possible, but is viable in certain types
15449 of configuration. There is a discussion about the use of root privilege in
15450 chapter &<<CHAPsecurity>>&.
15452 .option deliver_queue_load_max main fixed-point unset
15453 .cindex "load average"
15454 .cindex "queue runner" "abandoning"
15455 When this option is set, a queue run is abandoned if the system load average
15456 becomes greater than the value of the option. The option has no effect on
15457 ancient operating systems on which Exim cannot determine the load average.
15458 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15461 .option delivery_date_remove main boolean true
15462 .cindex "&'Delivery-date:'& header line"
15463 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15464 message when it is delivered, in exactly the same way as &'Return-path:'& is
15465 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15466 should not be present in incoming messages, and this option causes them to be
15467 removed at the time the message is received, to avoid any problems that might
15468 occur when a delivered message is subsequently sent on to some other recipient.
15470 .option disable_fsync main boolean false
15471 .cindex "&[fsync()]&, disabling"
15472 This option is available only if Exim was built with the compile-time option
15473 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15474 a runtime configuration generates an &"unknown option"& error. You should not
15475 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15476 really, really, really understand what you are doing. &'No pre-compiled
15477 distributions of Exim should ever make this option available.'&
15479 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15480 updated files' data to be written to disc before continuing. Unexpected events
15481 such as crashes and power outages may cause data to be lost or scrambled.
15482 Here be Dragons. &*Beware.*&
15485 .option disable_ipv6 main boolean false
15486 .cindex "IPv6" "disabling"
15487 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15488 activities take place. AAAA records are never looked up, and any IPv6 addresses
15489 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15490 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15491 to handle IPv6 literal addresses.
15495 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15496 .cindex DKIM "selecting signature algorithms"
15497 This option gives a list of hash types which are acceptable in signatures,
15499 and an order of processing.
15500 Signatures with algorithms not in the list will be ignored.
15502 Acceptable values include:
15509 Note that the acceptance of sha1 violates RFC 8301.
15511 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15512 This option gives a list of key types which are acceptable in signatures,
15513 and an order of processing.
15514 Signatures with algorithms not in the list will be ignored.
15518 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15519 This option gives a list of key sizes which are acceptable in signatures.
15520 The list is keyed by the algorithm type for the key; the values are in bits.
15521 Signatures with keys smaller than given by this option will fail verification.
15523 The default enforces the RFC 8301 minimum key size for RSA signatures.
15526 .option dkim_verify_minimal main boolean false
15527 If set to true, verification of signatures will terminate after the
15530 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15531 .cindex DKIM "controlling calls to the ACL"
15532 This option gives a list of DKIM domains for which the DKIM ACL is run.
15533 It is expanded after the message is received; by default it runs
15534 the ACL once for each signature in the message.
15535 See section &<<SECDKIMVFY>>&.
15538 .option dns_again_means_nonexist main "domain list&!!" unset
15539 .cindex "DNS" "&""try again""& response; overriding"
15540 DNS lookups give a &"try again"& response for the DNS errors
15541 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15542 keep trying to deliver a message, or to give repeated temporary errors to
15543 incoming mail. Sometimes the effect is caused by a badly set up name server and
15544 may persist for a long time. If a domain which exhibits this problem matches
15545 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15546 This option should be used with care. You can make it apply to reverse lookups
15547 by a setting such as this:
15549 dns_again_means_nonexist = *.in-addr.arpa
15551 This option applies to all DNS lookups that Exim does. It also applies when the
15552 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15553 since these are most likely to be caused by DNS lookup problems. The
15554 &(dnslookup)& router has some options of its own for controlling what happens
15555 when lookups for MX or SRV records give temporary errors. These more specific
15556 options are applied after this global option.
15558 .option dns_check_names_pattern main string "see below"
15559 .cindex "DNS" "pre-check of name syntax"
15560 When this option is set to a non-empty string, it causes Exim to check domain
15561 names for characters that are not allowed in host names before handing them to
15562 the DNS resolver, because some resolvers give temporary errors for names that
15563 contain unusual characters. If a domain name contains any unwanted characters,
15564 a &"not found"& result is forced, and the resolver is not called. The check is
15565 done by matching the domain name against a regular expression, which is the
15566 value of this option. The default pattern is
15568 dns_check_names_pattern = \
15569 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15571 which permits only letters, digits, slashes, and hyphens in components, but
15572 they must start and end with a letter or digit. Slashes are not, in fact,
15573 permitted in host names, but they are found in certain NS records (which can be
15574 accessed in Exim by using a &%dnsdb%& lookup). If you set
15575 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15578 .option dns_csa_search_limit main integer 5
15579 This option controls the depth of parental searching for CSA SRV records in the
15580 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15582 .option dns_csa_use_reverse main boolean true
15583 This option controls whether or not an IP address, given as a CSA domain, is
15584 reversed and looked up in the reverse DNS, as described in more detail in
15585 section &<<SECTverifyCSA>>&.
15587 .option dns_cname_loops main integer 1
15588 .cindex DNS "CNAME following"
15589 This option controls the following of CNAME chains, needed if the resolver does
15590 not do it internally.
15591 As of 2018 most should, and the default can be left.
15592 If you have an ancient one, a value of 10 is likely needed.
15594 The default value of one CNAME-follow is needed
15595 thanks to the observed return for an MX request,
15596 given no MX presence but a CNAME to an A, of the CNAME.
15599 .option dns_dnssec_ok main integer -1
15600 .cindex "DNS" "resolver options"
15601 .cindex "DNS" "DNSSEC"
15602 If this option is set to a non-negative number then Exim will initialise the
15603 DNS resolver library to either use or not use DNSSEC, overriding the system
15604 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15606 If the resolver library does not support DNSSEC then this option has no effect.
15609 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15610 will default to stripping out a successful validation status.
15611 This will break a previously working Exim installation.
15612 Provided that you do trust the resolver (ie, is on localhost) you can tell
15613 glibc to pass through any successful validation with a new option in
15614 &_/etc/resolv.conf_&:
15621 .option dns_ipv4_lookup main "domain list&!!" unset
15622 .cindex "IPv6" "DNS lookup for AAAA records"
15623 .cindex "DNS" "IPv6 lookup for AAAA records"
15624 .cindex DNS "IPv6 disabling"
15625 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15626 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15627 (A records) when trying to find IP addresses for hosts, unless the host's
15628 domain matches this list.
15630 This is a fudge to help with name servers that give big delays or otherwise do
15631 not work for the AAAA record type. In due course, when the world's name
15632 servers have all been upgraded, there should be no need for this option.
15633 Note that all lookups, including those done for verification, are affected;
15634 this will result in verify failure for IPv6 connections or ones using names
15635 only valid for IPv6 addresses.
15638 .option dns_retrans main time 0s
15639 .cindex "DNS" "resolver options"
15640 .cindex timeout "dns lookup"
15641 .cindex "DNS" timeout
15642 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15643 retransmission and retry parameters for DNS lookups. Values of zero (the
15644 defaults) leave the system default settings unchanged. The first value is the
15645 time between retries, and the second is the number of retries. It isn't
15646 totally clear exactly how these settings affect the total time a DNS lookup may
15647 take. I haven't found any documentation about timeouts on DNS lookups; these
15648 parameter values are available in the external resolver interface structure,
15649 but nowhere does it seem to describe how they are used or what you might want
15651 See also the &%slow_lookup_log%& option.
15654 .option dns_retry main integer 0
15655 See &%dns_retrans%& above.
15658 .option dns_trust_aa main "domain list&!!" unset
15659 .cindex "DNS" "resolver options"
15660 .cindex "DNS" "DNSSEC"
15661 If this option is set then lookup results marked with the AA bit
15662 (Authoritative Answer) are trusted the same way as if they were
15663 DNSSEC-verified. The authority section's name of the answer must
15664 match with this expanded domain list.
15666 Use this option only if you talk directly to a resolver that is
15667 authoritative for some zones and does not set the AD (Authentic Data)
15668 bit in the answer. Some DNS servers may have an configuration option to
15669 mark the answers from their own zones as verified (they set the AD bit).
15670 Others do not have this option. It is considered as poor practice using
15671 a resolver that is an authoritative server for some zones.
15673 Use this option only if you really have to (e.g. if you want
15674 to use DANE for remote delivery to a server that is listed in the DNS
15675 zones that your resolver is authoritative for).
15677 If the DNS answer packet has the AA bit set and contains resource record
15678 in the answer section, the name of the first NS record appearing in the
15679 authority section is compared against the list. If the answer packet is
15680 authoritative but the answer section is empty, the name of the first SOA
15681 record in the authoritative section is used instead.
15683 .cindex "DNS" "resolver options"
15684 .option dns_use_edns0 main integer -1
15685 .cindex "DNS" "resolver options"
15686 .cindex "DNS" "EDNS0"
15687 .cindex "DNS" "OpenBSD
15688 If this option is set to a non-negative number then Exim will initialise the
15689 DNS resolver library to either use or not use EDNS0 extensions, overriding
15690 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15693 If the resolver library does not support EDNS0 then this option has no effect.
15695 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15696 means that DNSSEC will not work with Exim on that platform either, unless Exim
15697 is linked against an alternative DNS client library.
15700 .option drop_cr main boolean false
15701 This is an obsolete option that is now a no-op. It used to affect the way Exim
15702 handled CR and LF characters in incoming messages. What happens now is
15703 described in section &<<SECTlineendings>>&.
15705 .option dsn_advertise_hosts main "host list&!!" unset
15706 .cindex "bounce messages" "success"
15707 .cindex "DSN" "success"
15708 .cindex "Delivery Status Notification" "success"
15709 .cindex "ESMTP extensions" DSN
15710 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15711 and accepted from, these hosts.
15712 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15713 and RET and ORCPT options on MAIL FROM commands.
15714 A NOTIFY=SUCCESS option requests success-DSN messages.
15715 A NOTIFY= option with no argument requests that no delay or failure DSNs
15718 &*Note*&: Supplying success-DSN messages has been criticised
15719 on privacy grounds; it can leak details of internal forwarding.
15722 .option dsn_from main "string&!!" "see below"
15723 .cindex "&'From:'& header line" "in bounces"
15724 .cindex "bounce messages" "&'From:'& line, specifying"
15725 This option can be used to vary the contents of &'From:'& header lines in
15726 bounces and other automatically generated messages (&"Delivery Status
15727 Notifications"& &-- hence the name of the option). The default setting is:
15729 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15731 The value is expanded every time it is needed. If the expansion fails, a
15732 panic is logged, and the default value is used.
15734 .option envelope_to_remove main boolean true
15735 .cindex "&'Envelope-to:'& header line"
15736 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15737 message when it is delivered, in exactly the same way as &'Return-path:'& is
15738 handled. &'Envelope-to:'& records the original recipient address from the
15739 message's envelope that caused the delivery to happen. Such headers should not
15740 be present in incoming messages, and this option causes them to be removed at
15741 the time the message is received, to avoid any problems that might occur when a
15742 delivered message is subsequently sent on to some other recipient.
15745 .option errors_copy main "string list&!!" unset
15746 .cindex "bounce message" "copy to other address"
15747 .cindex "copy of bounce message"
15748 Setting this option causes Exim to send bcc copies of bounce messages that it
15749 generates to other addresses. &*Note*&: This does not apply to bounce messages
15750 coming from elsewhere. The value of the option is a colon-separated list of
15751 items. Each item consists of a pattern, terminated by white space, followed by
15752 a comma-separated list of email addresses. If a pattern contains spaces, it
15753 must be enclosed in double quotes.
15755 Each pattern is processed in the same way as a single item in an address list
15756 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15757 the bounce message, the message is copied to the addresses on the list. The
15758 items are scanned in order, and once a matching one is found, no further items
15759 are examined. For example:
15761 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15762 rqps@mydomain hostmaster@mydomain.example,\
15763 postmaster@mydomain.example
15765 .vindex "&$domain$&"
15766 .vindex "&$local_part$&"
15767 The address list is expanded before use. The expansion variables &$local_part$&
15768 and &$domain$& are set from the original recipient of the error message, and if
15769 there was any wildcard matching in the pattern, the expansion
15770 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15771 variables &$0$&, &$1$&, etc. are set in the normal way.
15774 .option errors_reply_to main string unset
15775 .cindex "bounce message" "&'Reply-to:'& in"
15776 By default, Exim's bounce and delivery warning messages contain the header line
15778 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15780 .oindex &%quota_warn_message%&
15781 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15782 A warning message that is generated by the &%quota_warn_message%& option in an
15783 &(appendfile)& transport may contain its own &'From:'& header line that
15784 overrides the default.
15786 Experience shows that people reply to bounce messages. If the
15787 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15788 and warning messages. For example:
15790 errors_reply_to = postmaster@my.domain.example
15792 The value of the option is not expanded. It must specify a valid RFC 2822
15793 address. However, if a warning message that is generated by the
15794 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15795 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15799 .option event_action main string&!! unset
15801 This option declares a string to be expanded for Exim's events mechanism.
15802 For details see chapter &<<CHAPevents>>&.
15805 .option exim_group main string "compile-time configured"
15806 .cindex "gid (group id)" "Exim's own"
15807 .cindex "Exim group"
15808 This option changes the gid under which Exim runs when it gives up root
15809 privilege. The default value is compiled into the binary. The value of this
15810 option is used only when &%exim_user%& is also set. Unless it consists entirely
15811 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15812 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15816 .option exim_path main string "see below"
15817 .cindex "Exim binary, path name"
15818 This option specifies the path name of the Exim binary, which is used when Exim
15819 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15820 the directory configured at compile time by the BIN_DIRECTORY setting. It
15821 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15823 &*Warning*&: Do not use a macro to define the value of this option, because
15824 you will break those Exim utilities that scan the configuration file to find
15825 where the binary is. (They then use the &%-bP%& option to extract option
15826 settings such as the value of &%spool_directory%&.)
15829 .option exim_user main string "compile-time configured"
15830 .cindex "uid (user id)" "Exim's own"
15831 .cindex "Exim user"
15832 This option changes the uid under which Exim runs when it gives up root
15833 privilege. The default value is compiled into the binary. Ownership of the run
15834 time configuration file and the use of the &%-C%& and &%-D%& command line
15835 options is checked against the values in the binary, not what is set here.
15837 Unless it consists entirely of digits, the string is looked up using
15838 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15839 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15840 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15843 .option exim_version main string "current version"
15844 .cindex "Exim version"
15845 .cindex customizing "version number"
15846 .cindex "version number of Exim" override
15847 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15848 various places. Use with care; this may fool stupid security scanners.
15851 .option extra_local_interfaces main "string list" unset
15852 This option defines network interfaces that are to be considered local when
15853 routing, but which are not used for listening by the daemon. See section
15854 &<<SECTreclocipadd>>& for details.
15857 . Allow this long option name to split; give it unsplit as a fifth argument
15858 . for the automatic .oindex that is generated by .option.
15860 .option "extract_addresses_remove_arguments" main boolean true &&&
15861 extract_addresses_remove_arguments
15863 .cindex "command line" "addresses with &%-t%&"
15864 .cindex "Sendmail compatibility" "&%-t%& option"
15865 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15866 are present on the command line when the &%-t%& option is used to build an
15867 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15868 line addresses are removed from the recipients list. This is also how Smail
15869 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15870 command line addresses are added to those obtained from the header lines. When
15871 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15872 argument headers. If it is set false, Exim adds rather than removes argument
15876 .option finduser_retries main integer 0
15877 .cindex "NIS, retrying user lookups"
15878 On systems running NIS or other schemes in which user and group information is
15879 distributed from a remote system, there can be times when &[getpwnam()]& and
15880 related functions fail, even when given valid data, because things time out.
15881 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15882 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15883 many extra times to find a user or a group, waiting for one second between
15886 .cindex "&_/etc/passwd_&" "multiple reading of"
15887 You should not set this option greater than zero if your user information is in
15888 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15889 search the file multiple times for non-existent users, and also cause delay.
15893 .option freeze_tell main "string list, comma separated" unset
15894 .cindex "freezing messages" "sending a message when freezing"
15895 On encountering certain errors, or when configured to do so in a system filter,
15896 ACL, or special router, Exim freezes a message. This means that no further
15897 delivery attempts take place until an administrator thaws the message, or the
15898 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15899 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15900 warning message whenever it freezes something, unless the message it is
15901 freezing is a locally-generated bounce message. (Without this exception there
15902 is the possibility of looping.) The warning message is sent to the addresses
15903 supplied as the comma-separated value of this option. If several of the
15904 message's addresses cause freezing, only a single message is sent. If the
15905 freezing was automatic, the reason(s) for freezing can be found in the message
15906 log. If you configure freezing in a filter or ACL, you must arrange for any
15907 logging that you require.
15910 .option gecos_name main string&!! unset
15912 .cindex "&""gecos""& field, parsing"
15913 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15914 password file to hold other information in addition to users' real names. Exim
15915 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15916 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15917 of the field are used unchanged, except that, if an ampersand is encountered,
15918 it is replaced by the user's login name with the first character forced to
15919 upper case, since this is a convention that is observed on many systems.
15921 When these options are set, &%gecos_pattern%& is treated as a regular
15922 expression that is to be applied to the field (again with && replaced by the
15923 login name), and if it matches, &%gecos_name%& is expanded and used as the
15926 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15927 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15928 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15929 name terminates at the first comma, the following can be used:
15931 gecos_pattern = ([^,]*)
15935 .option gecos_pattern main string unset
15936 See &%gecos_name%& above.
15939 .option gnutls_compat_mode main boolean unset
15940 This option controls whether GnuTLS is used in compatibility mode in an Exim
15941 server. This reduces security slightly, but improves interworking with older
15942 implementations of TLS.
15945 .option gnutls_allow_auto_pkcs11 main boolean unset
15946 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15947 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15950 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15955 .option headers_charset main string "see below"
15956 This option sets a default character set for translating from encoded MIME
15957 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15958 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15959 ultimate default is ISO-8859-1. For more details see the description of header
15960 insertions in section &<<SECTexpansionitems>>&.
15964 .option header_maxsize main integer "see below"
15965 .cindex "header section" "maximum size of"
15966 .cindex "limit" "size of message header section"
15967 This option controls the overall maximum size of a message's header
15968 section. The default is the value of HEADER_MAXSIZE in
15969 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
15970 sections are rejected.
15973 .option header_line_maxsize main integer 0
15974 .cindex "header lines" "maximum size of"
15975 .cindex "limit" "size of one header line"
15976 This option limits the length of any individual header line in a message, after
15977 all the continuations have been joined together. Messages with individual
15978 header lines that are longer than the limit are rejected. The default value of
15979 zero means &"no limit"&.
15984 .option helo_accept_junk_hosts main "host list&!!" unset
15985 .cindex "HELO" "accepting junk data"
15986 .cindex "EHLO" "accepting junk data"
15987 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
15988 mail, and gives an error response for invalid data. Unfortunately, there are
15989 some SMTP clients that send syntactic junk. They can be accommodated by setting
15990 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
15991 if you want to do semantic checking.
15992 See also &%helo_allow_chars%& for a way of extending the permitted character
15996 .option helo_allow_chars main string unset
15997 .cindex "HELO" "underscores in"
15998 .cindex "EHLO" "underscores in"
15999 .cindex "underscore in EHLO/HELO"
16000 This option can be set to a string of rogue characters that are permitted in
16001 all EHLO and HELO names in addition to the standard letters, digits,
16002 hyphens, and dots. If you really must allow underscores, you can set
16004 helo_allow_chars = _
16006 Note that the value is one string, not a list.
16009 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16010 .cindex "HELO" "forcing reverse lookup"
16011 .cindex "EHLO" "forcing reverse lookup"
16012 If the domain given by a client in a HELO or EHLO command matches this
16013 list, a reverse lookup is done in order to establish the host's true name. The
16014 default forces a lookup if the client host gives the server's name or any of
16015 its IP addresses (in brackets), something that broken clients have been seen to
16019 .option helo_try_verify_hosts main "host list&!!" unset
16020 .cindex "HELO verifying" "optional"
16021 .cindex "EHLO" "verifying, optional"
16022 By default, Exim just checks the syntax of HELO and EHLO commands (see
16023 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16024 to do more extensive checking of the data supplied by these commands. The ACL
16025 condition &`verify = helo`& is provided to make this possible.
16026 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16027 to force the check to occur. From release 4.53 onwards, this is no longer
16028 necessary. If the check has not been done before &`verify = helo`& is
16029 encountered, it is done at that time. Consequently, this option is obsolete.
16030 Its specification is retained here for backwards compatibility.
16032 When an EHLO or HELO command is received, if the calling host matches
16033 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16034 EHLO command either:
16037 is an IP literal matching the calling address of the host, or
16039 .cindex "DNS" "reverse lookup"
16040 .cindex "reverse DNS lookup"
16041 matches the host name that Exim obtains by doing a reverse lookup of the
16042 calling host address, or
16044 when looked up in DNS yields the calling host address.
16047 However, the EHLO or HELO command is not rejected if any of the checks
16048 fail. Processing continues, but the result of the check is remembered, and can
16049 be detected later in an ACL by the &`verify = helo`& condition.
16051 If DNS was used for successful verification, the variable
16052 .cindex "DNS" "DNSSEC"
16053 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16055 .option helo_verify_hosts main "host list&!!" unset
16056 .cindex "HELO verifying" "mandatory"
16057 .cindex "EHLO" "verifying, mandatory"
16058 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16059 backwards compatibility. For hosts that match this option, Exim checks the host
16060 name given in the HELO or EHLO in the same way as for
16061 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16062 rejected with a 550 error, and entries are written to the main and reject logs.
16063 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16066 .option hold_domains main "domain list&!!" unset
16067 .cindex "domain" "delaying delivery"
16068 .cindex "delivery" "delaying certain domains"
16069 This option allows mail for particular domains to be held in the queue
16070 manually. The option is overridden if a message delivery is forced with the
16071 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16072 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16073 item in &%hold_domains%&, no routing or delivery for that address is done, and
16074 it is deferred every time the message is looked at.
16076 This option is intended as a temporary operational measure for delaying the
16077 delivery of mail while some problem is being sorted out, or some new
16078 configuration tested. If you just want to delay the processing of some
16079 domains until a queue run occurs, you should use &%queue_domains%& or
16080 &%queue_smtp_domains%&, not &%hold_domains%&.
16082 A setting of &%hold_domains%& does not override Exim's code for removing
16083 messages from the queue if they have been there longer than the longest retry
16084 time in any retry rule. If you want to hold messages for longer than the normal
16085 retry times, insert a dummy retry rule with a long retry time.
16088 .option host_lookup main "host list&!!" unset
16089 .cindex "host name" "lookup, forcing"
16090 Exim does not look up the name of a calling host from its IP address unless it
16091 is required to compare against some host list, or the host matches
16092 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16093 option (which normally contains IP addresses rather than host names). The
16094 default configuration file contains
16098 which causes a lookup to happen for all hosts. If the expense of these lookups
16099 is felt to be too great, the setting can be changed or removed.
16101 After a successful reverse lookup, Exim does a forward lookup on the name it
16102 has obtained, to verify that it yields the IP address that it started with. If
16103 this check fails, Exim behaves as if the name lookup failed.
16105 .vindex "&$host_lookup_failed$&"
16106 .vindex "&$sender_host_name$&"
16107 After any kind of failure, the host name (in &$sender_host_name$&) remains
16108 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16109 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16110 &`verify = reverse_host_lookup`& in ACLs.
16113 .option host_lookup_order main "string list" &`bydns:byaddr`&
16114 This option specifies the order of different lookup methods when Exim is trying
16115 to find a host name from an IP address. The default is to do a DNS lookup
16116 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16117 if that fails. You can change the order of these lookups, or omit one entirely,
16120 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16121 multiple PTR records in the DNS and the IP address is not listed in
16122 &_/etc/hosts_&. Different operating systems give different results in this
16123 case. That is why the default tries a DNS lookup first.
16127 .option host_reject_connection main "host list&!!" unset
16128 .cindex "host" "rejecting connections from"
16129 If this option is set, incoming SMTP calls from the hosts listed are rejected
16130 as soon as the connection is made.
16131 This option is obsolete, and retained only for backward compatibility, because
16132 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16133 connections immediately.
16135 The ability to give an immediate rejection (either by this option or using an
16136 ACL) is provided for use in unusual cases. Many hosts will just try again,
16137 sometimes without much delay. Normally, it is better to use an ACL to reject
16138 incoming messages at a later stage, such as after RCPT commands. See
16139 chapter &<<CHAPACL>>&.
16142 .option hosts_connection_nolog main "host list&!!" unset
16143 .cindex "host" "not logging connections from"
16144 This option defines a list of hosts for which connection logging does not
16145 happen, even though the &%smtp_connection%& log selector is set. For example,
16146 you might want not to log SMTP connections from local processes, or from
16147 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16148 the daemon; you should therefore strive to restrict its value to a short inline
16149 list of IP addresses and networks. To disable logging SMTP connections from
16150 local processes, you must create a host list with an empty item. For example:
16152 hosts_connection_nolog = :
16154 If the &%smtp_connection%& log selector is not set, this option has no effect.
16158 .option hosts_proxy main "host list&!!" unset
16159 .cindex proxy "proxy protocol"
16160 This option enables use of Proxy Protocol proxies for incoming
16161 connections. For details see section &<<SECTproxyInbound>>&.
16164 .option hosts_treat_as_local main "domain list&!!" unset
16165 .cindex "local host" "domains treated as"
16166 .cindex "host" "treated as local"
16167 If this option is set, any host names that match the domain list are treated as
16168 if they were the local host when Exim is scanning host lists obtained from MX
16170 or other sources. Note that the value of this option is a domain list, not a
16171 host list, because it is always used to check host names, not IP addresses.
16173 This option also applies when Exim is matching the special items
16174 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16175 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16176 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16177 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16178 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16179 interfaces and recognizing the local host.
16182 .option ibase_servers main "string list" unset
16183 .cindex "InterBase" "server list"
16184 This option provides a list of InterBase servers and associated connection data,
16185 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16186 The option is available only if Exim has been built with InterBase support.
16190 .option ignore_bounce_errors_after main time 10w
16191 .cindex "bounce message" "discarding"
16192 .cindex "discarding bounce message"
16193 This option affects the processing of bounce messages that cannot be delivered,
16194 that is, those that suffer a permanent delivery failure. (Bounce messages that
16195 suffer temporary delivery failures are of course retried in the usual way.)
16197 After a permanent delivery failure, bounce messages are frozen,
16198 because there is no sender to whom they can be returned. When a frozen bounce
16199 message has been in the queue for more than the given time, it is unfrozen at
16200 the next queue run, and a further delivery is attempted. If delivery fails
16201 again, the bounce message is discarded. This makes it possible to keep failed
16202 bounce messages around for a shorter time than the normal maximum retry time
16203 for frozen messages. For example,
16205 ignore_bounce_errors_after = 12h
16207 retries failed bounce message deliveries after 12 hours, discarding any further
16208 failures. If the value of this option is set to a zero time period, bounce
16209 failures are discarded immediately. Setting a very long time (as in the default
16210 value) has the effect of disabling this option. For ways of automatically
16211 dealing with other kinds of frozen message, see &%auto_thaw%& and
16212 &%timeout_frozen_after%&.
16215 .option ignore_fromline_hosts main "host list&!!" unset
16216 .cindex "&""From""& line"
16217 .cindex "UUCP" "&""From""& line"
16218 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16219 the headers of a message. By default this is treated as the start of the
16220 message's body, which means that any following headers are not recognized as
16221 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16222 match those hosts that insist on sending it. If the sender is actually a local
16223 process rather than a remote host, and is using &%-bs%& to inject the messages,
16224 &%ignore_fromline_local%& must be set to achieve this effect.
16227 .option ignore_fromline_local main boolean false
16228 See &%ignore_fromline_hosts%& above.
16230 .option keep_environment main "string list" unset
16231 .cindex "environment" "values from"
16232 This option contains a string list of environment variables to keep.
16233 You have to trust these variables or you have to be sure that
16234 these variables do not impose any security risk. Keep in mind that
16235 during the startup phase Exim is running with an effective UID 0 in most
16236 installations. As the default value is an empty list, the default
16237 environment for using libraries, running embedded Perl code, or running
16238 external binaries is empty, and does not not even contain PATH or HOME.
16240 Actually the list is interpreted as a list of patterns
16241 (&<<SECTlistexpand>>&), except that it is not expanded first.
16243 WARNING: Macro substitution is still done first, so having a macro
16244 FOO and having FOO_HOME in your &%keep_environment%& option may have
16245 unexpected results. You may work around this using a regular expression
16246 that does not match the macro name: ^[F]OO_HOME$.
16248 Current versions of Exim issue a warning during startup if you do not mention
16249 &%keep_environment%& in your runtime configuration file and if your
16250 current environment is not empty. Future versions may not issue that warning
16253 See the &%add_environment%& main config option for a way to set
16254 environment variables to a fixed value. The environment for &(pipe)&
16255 transports is handled separately, see section &<<SECTpipeenv>>& for
16259 .option keep_malformed main time 4d
16260 This option specifies the length of time to keep messages whose spool files
16261 have been corrupted in some way. This should, of course, never happen. At the
16262 next attempt to deliver such a message, it gets removed. The incident is
16266 .option ldap_ca_cert_dir main string unset
16267 .cindex "LDAP", "TLS CA certificate directory"
16268 .cindex certificate "directory for LDAP"
16269 This option indicates which directory contains CA certificates for verifying
16270 a TLS certificate presented by an LDAP server.
16271 While Exim does not provide a default value, your SSL library may.
16272 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16273 and constrained to be a directory.
16276 .option ldap_ca_cert_file main string unset
16277 .cindex "LDAP", "TLS CA certificate file"
16278 .cindex certificate "file for LDAP"
16279 This option indicates which file contains CA certificates for verifying
16280 a TLS certificate presented by an LDAP server.
16281 While Exim does not provide a default value, your SSL library may.
16282 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16283 and constrained to be a file.
16286 .option ldap_cert_file main string unset
16287 .cindex "LDAP" "TLS client certificate file"
16288 .cindex certificate "file for LDAP"
16289 This option indicates which file contains an TLS client certificate which
16290 Exim should present to the LDAP server during TLS negotiation.
16291 Should be used together with &%ldap_cert_key%&.
16294 .option ldap_cert_key main string unset
16295 .cindex "LDAP" "TLS client key file"
16296 .cindex certificate "key for LDAP"
16297 This option indicates which file contains the secret/private key to use
16298 to prove identity to the LDAP server during TLS negotiation.
16299 Should be used together with &%ldap_cert_file%&, which contains the
16300 identity to be proven.
16303 .option ldap_cipher_suite main string unset
16304 .cindex "LDAP" "TLS cipher suite"
16305 This controls the TLS cipher-suite negotiation during TLS negotiation with
16306 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16307 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16310 .option ldap_default_servers main "string list" unset
16311 .cindex "LDAP" "default servers"
16312 This option provides a list of LDAP servers which are tried in turn when an
16313 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16314 details of LDAP queries. This option is available only when Exim has been built
16318 .option ldap_require_cert main string unset.
16319 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16320 This should be one of the values "hard", "demand", "allow", "try" or "never".
16321 A value other than one of these is interpreted as "never".
16322 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16323 Although Exim does not set a default, the LDAP library probably defaults
16327 .option ldap_start_tls main boolean false
16328 .cindex "LDAP" "whether or not to negotiate TLS"
16329 If set, Exim will attempt to negotiate TLS with the LDAP server when
16330 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16331 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16333 In the event of failure to negotiate TLS, the action taken is controlled
16334 by &%ldap_require_cert%&.
16335 This option is ignored for &`ldapi`& connections.
16338 .option ldap_version main integer unset
16339 .cindex "LDAP" "protocol version, forcing"
16340 This option can be used to force Exim to set a specific protocol version for
16341 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16342 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16343 the LDAP headers; otherwise it is 2. This option is available only when Exim
16344 has been built with LDAP support.
16348 .option local_from_check main boolean true
16349 .cindex "&'Sender:'& header line" "disabling addition of"
16350 .cindex "&'From:'& header line" "disabling checking of"
16351 When a message is submitted locally (that is, not over a TCP/IP connection) by
16352 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16353 checks that the &'From:'& header line matches the login of the calling user and
16354 the domain specified by &%qualify_domain%&.
16356 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16357 locally submitted message is automatically qualified by Exim, unless the
16358 &%-bnq%& command line option is used.
16360 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16361 on the local part. If the &'From:'& header line does not match, Exim adds a
16362 &'Sender:'& header with an address constructed from the calling user's login
16363 and the default qualify domain.
16365 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16366 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16367 &'Sender:'& header lines supplied by untrusted users, you must also set
16368 &%local_sender_retain%& to be true.
16370 .cindex "envelope from"
16371 .cindex "envelope sender"
16372 These options affect only the header lines in the message. The envelope sender
16373 is still forced to be the login id at the qualify domain unless
16374 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16376 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16377 request similar header line checking. See section &<<SECTthesenhea>>&, which
16378 has more details about &'Sender:'& processing.
16383 .option local_from_prefix main string unset
16384 When Exim checks the &'From:'& header line of locally submitted messages for
16385 matching the login id (see &%local_from_check%& above), it can be configured to
16386 ignore certain prefixes and suffixes in the local part of the address. This is
16387 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16388 appropriate lists, in the same form as the &%local_part_prefix%& and
16389 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16392 local_from_prefix = *-
16394 is set, a &'From:'& line containing
16396 From: anything-user@your.domain.example
16398 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16399 matches the actual sender address that is constructed from the login name and
16403 .option local_from_suffix main string unset
16404 See &%local_from_prefix%& above.
16407 .option local_interfaces main "string list" "see below"
16408 This option controls which network interfaces are used by the daemon for
16409 listening; they are also used to identify the local host when routing. Chapter
16410 &<<CHAPinterfaces>>& contains a full description of this option and the related
16411 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16412 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16413 &%local_interfaces%& is
16415 local_interfaces = 0.0.0.0
16417 when Exim is built without IPv6 support; otherwise it is
16419 local_interfaces = <; ::0 ; 0.0.0.0
16422 .option local_scan_timeout main time 5m
16423 .cindex "timeout" "for &[local_scan()]& function"
16424 .cindex "&[local_scan()]& function" "timeout"
16425 This timeout applies to the &[local_scan()]& function (see chapter
16426 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16427 the incoming message is rejected with a temporary error if it is an SMTP
16428 message. For a non-SMTP message, the message is dropped and Exim ends with a
16429 non-zero code. The incident is logged on the main and reject logs.
16433 .option local_sender_retain main boolean false
16434 .cindex "&'Sender:'& header line" "retaining from local submission"
16435 When a message is submitted locally (that is, not over a TCP/IP connection) by
16436 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16437 do not want this to happen, you must set &%local_sender_retain%&, and you must
16438 also set &%local_from_check%& to be false (Exim will complain if you do not).
16439 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16440 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16445 .option localhost_number main string&!! unset
16446 .cindex "host" "locally unique number for"
16447 .cindex "message ids" "with multiple hosts"
16448 .vindex "&$localhost_number$&"
16449 Exim's message ids are normally unique only within the local host. If
16450 uniqueness among a set of hosts is required, each host must set a different
16451 value for the &%localhost_number%& option. The string is expanded immediately
16452 after reading the configuration file (so that a number can be computed from the
16453 host name, for example) and the result of the expansion must be a number in the
16454 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16455 systems). This is available in subsequent string expansions via the variable
16456 &$localhost_number$&. When &%localhost_number is set%&, the final two
16457 characters of the message id, instead of just being a fractional part of the
16458 time, are computed from the time and the local host number as described in
16459 section &<<SECTmessiden>>&.
16463 .option log_file_path main "string list&!!" "set at compile time"
16464 .cindex "log" "file path for"
16465 This option sets the path which is used to determine the names of Exim's log
16466 files, or indicates that logging is to be to syslog, or both. It is expanded
16467 when Exim is entered, so it can, for example, contain a reference to the host
16468 name. If no specific path is set for the log files at compile or runtime,
16469 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16470 they are written in a sub-directory called &_log_& in Exim's spool directory.
16471 A path must start with a slash.
16472 To send to syslog, use the word &"syslog"&.
16473 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16474 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16475 used. If this string is fixed at your installation (contains no expansion
16476 variables) it is recommended that you do not set this option in the
16477 configuration file, but instead supply the path using LOG_FILE_PATH in
16478 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16479 early on &-- in particular, failure to read the configuration file.
16482 .option log_selector main string unset
16483 .cindex "log" "selectors"
16484 This option can be used to reduce or increase the number of things that Exim
16485 writes to its log files. Its argument is made up of names preceded by plus or
16486 minus characters. For example:
16488 log_selector = +arguments -retry_defer
16490 A list of possible names and what they control is given in the chapter on
16491 logging, in section &<<SECTlogselector>>&.
16494 .option log_timezone main boolean false
16495 .cindex "log" "timezone for entries"
16496 .vindex "&$tod_log$&"
16497 .vindex "&$tod_zone$&"
16498 By default, the timestamps on log lines are in local time without the
16499 timezone. This means that if your timezone changes twice a year, the timestamps
16500 in log lines are ambiguous for an hour when the clocks go back. One way of
16501 avoiding this problem is to set the timezone to UTC. An alternative is to set
16502 &%log_timezone%& true. This turns on the addition of the timezone offset to
16503 timestamps in log lines. Turning on this option can add quite a lot to the size
16504 of log files because each line is extended by 6 characters. Note that the
16505 &$tod_log$& variable contains the log timestamp without the zone, but there is
16506 another variable called &$tod_zone$& that contains just the timezone offset.
16509 .option lookup_open_max main integer 25
16510 .cindex "too many open files"
16511 .cindex "open files, too many"
16512 .cindex "file" "too many open"
16513 .cindex "lookup" "maximum open files"
16514 .cindex "limit" "open files for lookups"
16515 This option limits the number of simultaneously open files for single-key
16516 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16517 Exim normally keeps these files open during routing, because often the same
16518 file is required several times. If the limit is reached, Exim closes the least
16519 recently used file. Note that if you are using the &'ndbm'& library, it
16520 actually opens two files for each logical DBM database, though it still counts
16521 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16522 open files"& errors with NDBM, you need to reduce the value of
16523 &%lookup_open_max%&.
16526 .option max_username_length main integer 0
16527 .cindex "length of login name"
16528 .cindex "user name" "maximum length"
16529 .cindex "limit" "user name length"
16530 Some operating systems are broken in that they truncate long arguments to
16531 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16532 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16533 an argument that is longer behaves as if &[getpwnam()]& failed.
16536 .option message_body_newlines main bool false
16537 .cindex "message body" "newlines in variables"
16538 .cindex "newline" "in message body variables"
16539 .vindex "&$message_body$&"
16540 .vindex "&$message_body_end$&"
16541 By default, newlines in the message body are replaced by spaces when setting
16542 the &$message_body$& and &$message_body_end$& expansion variables. If this
16543 option is set true, this no longer happens.
16546 .option message_body_visible main integer 500
16547 .cindex "body of message" "visible size"
16548 .cindex "message body" "visible size"
16549 .vindex "&$message_body$&"
16550 .vindex "&$message_body_end$&"
16551 This option specifies how much of a message's body is to be included in the
16552 &$message_body$& and &$message_body_end$& expansion variables.
16555 .option message_id_header_domain main string&!! unset
16556 .cindex "&'Message-ID:'& header line"
16557 If this option is set, the string is expanded and used as the right hand side
16558 (domain) of the &'Message-ID:'& header that Exim creates if a
16559 locally-originated incoming message does not have one. &"Locally-originated"&
16560 means &"not received over TCP/IP."&
16561 Otherwise, the primary host name is used.
16562 Only letters, digits, dot and hyphen are accepted; any other characters are
16563 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16564 empty string, the option is ignored.
16567 .option message_id_header_text main string&!! unset
16568 If this variable is set, the string is expanded and used to augment the text of
16569 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16570 message does not have one. The text of this header is required by RFC 2822 to
16571 take the form of an address. By default, Exim uses its internal message id as
16572 the local part, and the primary host name as the domain. If this option is set,
16573 it is expanded, and provided the expansion is not forced to fail, and does not
16574 yield an empty string, the result is inserted into the header immediately
16575 before the @, separated from the internal message id by a dot. Any characters
16576 that are illegal in an address are automatically converted into hyphens. This
16577 means that variables such as &$tod_log$& can be used, because the spaces and
16578 colons will become hyphens.
16581 .option message_logs main boolean true
16582 .cindex "message logs" "disabling"
16583 .cindex "log" "message log; disabling"
16584 If this option is turned off, per-message log files are not created in the
16585 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16586 Exim, by reducing the number of files involved in handling a message from a
16587 minimum of four (header spool file, body spool file, delivery journal, and
16588 per-message log) to three. The other major I/O activity is Exim's main log,
16589 which is not affected by this option.
16592 .option message_size_limit main string&!! 50M
16593 .cindex "message" "size limit"
16594 .cindex "limit" "message size"
16595 .cindex "size" "of message, limit"
16596 This option limits the maximum size of message that Exim will process. The
16597 value is expanded for each incoming connection so, for example, it can be made
16598 to depend on the IP address of the remote host for messages arriving via
16599 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16600 optionally followed by K or M.
16602 .cindex "SIZE" "ESMTP extension, advertising"
16603 .cindex "ESMTP extensions" SIZE
16604 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16605 service extension keyword.
16607 &*Note*&: This limit cannot be made to depend on a message's sender or any
16608 other properties of an individual message, because it has to be advertised in
16609 the server's response to EHLO. String expansion failure causes a temporary
16610 error. A value of zero means no limit, but its use is not recommended. See also
16611 &%bounce_return_size_limit%&.
16613 Incoming SMTP messages are failed with a 552 error if the limit is
16614 exceeded; locally-generated messages either get a stderr message or a delivery
16615 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16616 an oversized message is logged in both the main and the reject logs. See also
16617 the generic transport option &%message_size_limit%&, which limits the size of
16618 message that an individual transport can process.
16620 If you use a virus-scanner and set this option to to a value larger than the
16621 maximum size that your virus-scanner is configured to support, you may get
16622 failures triggered by large mails. The right size to configure for the
16623 virus-scanner depends upon what data is passed and the options in use but it's
16624 probably safest to just set it to a little larger than this value. E.g., with a
16625 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16626 some problems may result.
16628 A value of 0 will disable size limit checking; Exim will still advertise the
16629 SIZE extension in an EHLO response, but without a limit, so as to permit
16630 SMTP clients to still indicate the message size along with the MAIL verb.
16633 .option move_frozen_messages main boolean false
16634 .cindex "frozen messages" "moving"
16635 This option, which is available only if Exim has been built with the setting
16637 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16639 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16640 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16641 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16642 standard utilities for handling such moved messages, and they do not show up in
16643 lists generated by &%-bp%& or by the Exim monitor.
16646 .option mua_wrapper main boolean false
16647 Setting this option true causes Exim to run in a very restrictive mode in which
16648 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16649 contains a full description of this facility.
16653 .option mysql_servers main "string list" unset
16654 .cindex "MySQL" "server list"
16655 This option provides a list of MySQL servers and associated connection data, to
16656 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16657 option is available only if Exim has been built with MySQL support.
16660 .option never_users main "string list&!!" unset
16661 This option is expanded just once, at the start of Exim's processing. Local
16662 message deliveries are normally run in processes that are setuid to the
16663 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16664 It is usually desirable to prevent any deliveries from running as root, as a
16667 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16668 list of users that must not be used for local deliveries. This list is fixed in
16669 the binary and cannot be overridden by the configuration file. By default, it
16670 contains just the single user name &"root"&. The &%never_users%& runtime option
16671 can be used to add more users to the fixed list.
16673 If a message is to be delivered as one of the users on the fixed list or the
16674 &%never_users%& list, an error occurs, and delivery is deferred. A common
16677 never_users = root:daemon:bin
16679 Including root is redundant if it is also on the fixed list, but it does no
16680 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16685 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16686 This option gives the name for a unix-domain socket on which the daemon
16687 listens for work and information-requests.
16688 Only installations running multiple daemons sharing a spool directory
16689 should need to modify the default.
16691 The option is expanded before use.
16692 If the platform supports Linux-style abstract socket names, the result
16693 is used with a nul byte prefixed.
16694 Otherwise, it should be a full path name and use a directory accessible
16697 If the Exim command line uses a &%-oX%& option and does not use &%-oP%&
16698 then a notifier socket is not created.
16702 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16703 .cindex "OpenSSL "compatibility options"
16704 This option allows an administrator to adjust the SSL options applied
16705 by OpenSSL to connections. It is given as a space-separated list of items,
16706 each one to be +added or -subtracted from the current value.
16708 This option is only available if Exim is built against OpenSSL. The values
16709 available for this option vary according to the age of your OpenSSL install.
16710 The &"all"& value controls a subset of flags which are available, typically
16711 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16712 list the values known on your system and Exim should support all the
16713 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16714 names lose the leading &"SSL_OP_"& and are lower-cased.
16716 Note that adjusting the options can have severe impact upon the security of
16717 SSL as used by Exim. It is possible to disable safety checks and shoot
16718 yourself in the foot in various unpleasant ways. This option should not be
16719 adjusted lightly. An unrecognised item will be detected at startup, by
16720 invoking Exim with the &%-bV%& flag.
16722 The option affects Exim operating both as a server and as a client.
16724 Historical note: prior to release 4.80, Exim defaulted this value to
16725 "+dont_insert_empty_fragments", which may still be needed for compatibility
16726 with some clients, but which lowers security by increasing exposure to
16727 some now infamous attacks.
16731 # Make both old MS and old Eudora happy:
16732 openssl_options = -all +microsoft_big_sslv3_buffer \
16733 +dont_insert_empty_fragments
16735 # Disable older protocol versions:
16736 openssl_options = +no_sslv2 +no_sslv3
16739 Possible options may include:
16743 &`allow_unsafe_legacy_renegotiation`&
16745 &`cipher_server_preference`&
16747 &`dont_insert_empty_fragments`&
16751 &`legacy_server_connect`&
16753 &`microsoft_big_sslv3_buffer`&
16755 &`microsoft_sess_id_bug`&
16757 &`msie_sslv2_rsa_padding`&
16759 &`netscape_challenge_bug`&
16761 &`netscape_reuse_cipher_change_bug`&
16765 &`no_session_resumption_on_renegotiation`&
16779 &`safari_ecdhe_ecdsa_bug`&
16783 &`single_ecdh_use`&
16785 &`ssleay_080_client_dh_bug`&
16787 &`sslref2_reuse_cert_type_bug`&
16789 &`tls_block_padding_bug`&
16793 &`tls_rollback_bug`&
16796 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16797 all clients connecting using the MacOS SecureTransport TLS facility prior
16798 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16799 to negotiate TLS then this option value might help, provided that your OpenSSL
16800 release is new enough to contain this work-around. This may be a situation
16801 where you have to upgrade OpenSSL to get buggy clients working.
16804 .option oracle_servers main "string list" unset
16805 .cindex "Oracle" "server list"
16806 This option provides a list of Oracle servers and associated connection data,
16807 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16808 The option is available only if Exim has been built with Oracle support.
16811 .option percent_hack_domains main "domain list&!!" unset
16812 .cindex "&""percent hack""&"
16813 .cindex "source routing" "in email address"
16814 .cindex "address" "source-routed"
16815 The &"percent hack"& is the convention whereby a local part containing a
16816 percent sign is re-interpreted as a new email address, with the percent
16817 replaced by @. This is sometimes called &"source routing"&, though that term is
16818 also applied to RFC 2822 addresses that begin with an @ character. If this
16819 option is set, Exim implements the percent facility for those domains listed,
16820 but no others. This happens before an incoming SMTP address is tested against
16823 &*Warning*&: The &"percent hack"& has often been abused by people who are
16824 trying to get round relaying restrictions. For this reason, it is best avoided
16825 if at all possible. Unfortunately, a number of less security-conscious MTAs
16826 implement it unconditionally. If you are running Exim on a gateway host, and
16827 routing mail through to internal MTAs without processing the local parts, it is
16828 a good idea to reject recipient addresses with percent characters in their
16829 local parts. Exim's default configuration does this.
16832 .option perl_at_start main boolean false
16834 This option is available only when Exim is built with an embedded Perl
16835 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16838 .option perl_startup main string unset
16840 This option is available only when Exim is built with an embedded Perl
16841 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16843 .option perl_taintmode main boolean false
16845 This option enables the taint mode of the embedded Perl interpreter.
16848 .option pgsql_servers main "string list" unset
16849 .cindex "PostgreSQL lookup type" "server list"
16850 This option provides a list of PostgreSQL servers and associated connection
16851 data, to be used in conjunction with &(pgsql)& lookups (see section
16852 &<<SECID72>>&). The option is available only if Exim has been built with
16853 PostgreSQL support.
16856 .option pid_file_path main string&!! "set at compile time"
16857 .cindex "daemon" "pid file path"
16858 .cindex "pid file, path for"
16859 This option sets the name of the file to which the Exim daemon writes its
16860 process id. The string is expanded, so it can contain, for example, references
16863 pid_file_path = /var/log/$primary_hostname/exim.pid
16865 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16867 The value set by the option can be overridden by the &%-oP%& command line
16868 option. A pid file is not written if a &"non-standard"& daemon is run by means
16869 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16872 .option pipelining_advertise_hosts main "host list&!!" *
16873 .cindex "PIPELINING" "suppressing advertising"
16874 .cindex "ESMTP extensions" PIPELINING
16875 This option can be used to suppress the advertisement of the SMTP
16876 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16877 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16878 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16879 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16880 that clients will use it; &"out of order"& commands that are &"expected"& do
16881 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16883 .option pipelining_connect_advertise_hosts main "host list&!!" *
16884 .cindex "pipelining" "early connection"
16885 .cindex "pipelining" PIPE_CONNECT
16886 .cindex "ESMTP extensions" X_PIPE_CONNECT
16887 If Exim is built with the SUPPORT_PIPE_CONNECT build option
16888 this option controls which hosts the facility is advertised to
16889 and from which pipeline early-connection (before MAIL) SMTP
16890 commands are acceptable.
16891 When used, the pipelining saves on roundtrip times.
16893 See also the &%hosts_pipe_connect%& smtp transport option.
16895 Currently the option name &"X_PIPE_CONNECT"& is used.
16898 .option prdr_enable main boolean false
16899 .cindex "PRDR" "enabling on server"
16900 .cindex "ESMTP extensions" PRDR
16901 This option can be used to enable the Per-Recipient Data Response extension
16902 to SMTP, defined by Eric Hall.
16903 If the option is set, PRDR is advertised by Exim when operating as a server.
16904 If the client requests PRDR, and more than one recipient, for a message
16905 an additional ACL is called for each recipient after the message content
16906 is received. See section &<<SECTPRDRACL>>&.
16908 .option preserve_message_logs main boolean false
16909 .cindex "message logs" "preserving"
16910 If this option is set, message log files are not deleted when messages are
16911 completed. Instead, they are moved to a sub-directory of the spool directory
16912 called &_msglog.OLD_&, where they remain available for statistical or debugging
16913 purposes. This is a dangerous option to set on systems with any appreciable
16914 volume of mail. Use with care!
16917 .option primary_hostname main string "see below"
16918 .cindex "name" "of local host"
16919 .cindex "host" "name of local"
16920 .cindex "local host" "name of"
16921 .vindex "&$primary_hostname$&"
16922 This specifies the name of the current host. It is used in the default EHLO or
16923 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16924 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16925 The value is also used by default in some SMTP response messages from an Exim
16926 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16928 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16929 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16930 contains only one component, Exim passes it to &[gethostbyname()]& (or
16931 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16932 version. The variable &$primary_hostname$& contains the host name, whether set
16933 explicitly by this option, or defaulted.
16936 .option print_topbitchars main boolean false
16937 .cindex "printing characters"
16938 .cindex "8-bit characters"
16939 By default, Exim considers only those characters whose codes lie in the range
16940 32&--126 to be printing characters. In a number of circumstances (for example,
16941 when writing log entries) non-printing characters are converted into escape
16942 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16943 is set, code values of 128 and above are also considered to be printing
16946 This option also affects the header syntax checks performed by the
16947 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16948 the user's full name when constructing From: and Sender: addresses (as
16949 described in section &<<SECTconstr>>&). Setting this option can cause
16950 Exim to generate eight bit message headers that do not conform to the
16954 .option process_log_path main string unset
16955 .cindex "process log path"
16956 .cindex "log" "process log"
16957 .cindex "&'exiwhat'&"
16958 This option sets the name of the file to which an Exim process writes its
16959 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
16960 utility script. If this option is unset, the file called &_exim-process.info_&
16961 in Exim's spool directory is used. The ability to specify the name explicitly
16962 can be useful in environments where two different Exims are running, using
16963 different spool directories.
16966 .option prod_requires_admin main boolean true
16967 .cindex "restricting access to features"
16971 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
16972 admin user unless &%prod_requires_admin%& is set false. See also
16973 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
16976 .option qualify_domain main string "see below"
16977 .cindex "domain" "for qualifying addresses"
16978 .cindex "address" "qualification"
16979 This option specifies the domain name that is added to any envelope sender
16980 addresses that do not have a domain qualification. It also applies to
16981 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
16982 are accepted by default only for locally-generated messages. Qualification is
16983 also applied to addresses in header lines such as &'From:'& and &'To:'& for
16984 locally-generated messages, unless the &%-bnq%& command line option is used.
16986 Messages from external sources must always contain fully qualified addresses,
16987 unless the sending host matches &%sender_unqualified_hosts%& or
16988 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
16989 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
16990 necessary. Internally, Exim always works with fully qualified envelope
16991 addresses. If &%qualify_domain%& is not set, it defaults to the
16992 &%primary_hostname%& value.
16995 .option qualify_recipient main string "see below"
16996 This option allows you to specify a different domain for qualifying recipient
16997 addresses to the one that is used for senders. See &%qualify_domain%& above.
17001 .option queue_domains main "domain list&!!" unset
17002 .cindex "domain" "specifying non-immediate delivery"
17003 .cindex "queueing incoming messages"
17004 .cindex "message" "queueing certain domains"
17005 This option lists domains for which immediate delivery is not required.
17006 A delivery process is started whenever a message is received, but only those
17007 domains that do not match are processed. All other deliveries wait until the
17008 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17012 .option queue_fast_ramp main boolean false
17013 .cindex "queue runner" "two phase"
17014 .cindex "queue" "double scanning"
17015 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17016 command line, may start parallel delivery processes during their first
17017 phase. This will be done when a threshold number of messages have been
17018 routed for a single host.
17022 .option queue_list_requires_admin main boolean true
17023 .cindex "restricting access to features"
17025 The &%-bp%& command-line option, which lists the messages that are on the
17026 queue, requires the caller to be an admin user unless
17027 &%queue_list_requires_admin%& is set false.
17028 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17031 .option queue_only main boolean false
17032 .cindex "queueing incoming messages"
17033 .cindex "message" "queueing unconditionally"
17034 If &%queue_only%& is set, a delivery process is not automatically started
17035 whenever a message is received. Instead, the message waits in the queue for the
17036 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17037 delivered immediately when certain conditions (such as heavy load) occur.
17039 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17040 and &%-odi%& command line options override &%queue_only%& unless
17041 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17042 &%queue_only_load%&, and &%smtp_accept_queue%&.
17045 .option queue_only_file main string unset
17046 .cindex "queueing incoming messages"
17047 .cindex "message" "queueing by file existence"
17048 This option can be set to a colon-separated list of absolute path names, each
17049 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17050 it tests for the existence of each listed path using a call to &[stat()]&. For
17051 each path that exists, the corresponding queueing option is set.
17052 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17053 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17055 queue_only_file = smtp/some/file
17057 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17058 &_/some/file_& exists.
17061 .option queue_only_load main fixed-point unset
17062 .cindex "load average"
17063 .cindex "queueing incoming messages"
17064 .cindex "message" "queueing by load"
17065 If the system load average is higher than this value, incoming messages from
17066 all sources are queued, and no automatic deliveries are started. If this
17067 happens during local or remote SMTP input, all subsequent messages received on
17068 the same SMTP connection are queued by default, whatever happens to the load in
17069 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17072 Deliveries will subsequently be performed by queue runner processes. This
17073 option has no effect on ancient operating systems on which Exim cannot
17074 determine the load average. See also &%deliver_queue_load_max%& and
17075 &%smtp_load_reserve%&.
17078 .option queue_only_load_latch main boolean true
17079 .cindex "load average" "re-evaluating per message"
17080 When this option is true (the default), once one message has been queued
17081 because the load average is higher than the value set by &%queue_only_load%&,
17082 all subsequent messages received on the same SMTP connection are also queued.
17083 This is a deliberate choice; even though the load average may fall below the
17084 threshold, it doesn't seem right to deliver later messages on the same
17085 connection when not delivering earlier ones. However, there are special
17086 circumstances such as very long-lived connections from scanning appliances
17087 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17088 should be set false. This causes the value of the load average to be
17089 re-evaluated for each message.
17092 .option queue_only_override main boolean true
17093 .cindex "queueing incoming messages"
17094 When this option is true, the &%-od%&&'x'& command line options override the
17095 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17096 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17097 to override; they are accepted, but ignored.
17100 .option queue_run_in_order main boolean false
17101 .cindex "queue runner" "processing messages in order"
17102 If this option is set, queue runs happen in order of message arrival instead of
17103 in an arbitrary order. For this to happen, a complete list of the entire queue
17104 must be set up before the deliveries start. When the queue is all held in a
17105 single directory (the default), a single list is created for both the ordered
17106 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17107 single list is not created when &%queue_run_in_order%& is false. In this case,
17108 the sub-directories are processed one at a time (in a random order), and this
17109 avoids setting up one huge list for the whole queue. Thus, setting
17110 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17111 when the queue is large, because of the extra work in setting up the single,
17112 large list. In most situations, &%queue_run_in_order%& should not be set.
17116 .option queue_run_max main integer&!! 5
17117 .cindex "queue runner" "maximum number of"
17118 This controls the maximum number of queue runner processes that an Exim daemon
17119 can run simultaneously. This does not mean that it starts them all at once,
17120 but rather that if the maximum number are still running when the time comes to
17121 start another one, it refrains from starting another one. This can happen with
17122 very large queues and/or very sluggish deliveries. This option does not,
17123 however, interlock with other processes, so additional queue runners can be
17124 started by other means, or by killing and restarting the daemon.
17126 Setting this option to zero does not suppress queue runs; rather, it disables
17127 the limit, allowing any number of simultaneous queue runner processes to be
17128 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17129 the daemon's command line.
17131 .cindex queues named
17132 .cindex "named queues" "resource limit"
17133 To set limits for different named queues use
17134 an expansion depending on the &$queue_name$& variable.
17136 .option queue_smtp_domains main "domain list&!!" unset
17137 .cindex "queueing incoming messages"
17138 .cindex "message" "queueing remote deliveries"
17139 .cindex "first pass routing"
17140 When this option is set, a delivery process is started whenever a message is
17141 received, routing is performed, and local deliveries take place.
17142 However, if any SMTP deliveries are required for domains that match
17143 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17144 message waits in the queue for the next queue run. Since routing of the message
17145 has taken place, Exim knows to which remote hosts it must be delivered, and so
17146 when the queue run happens, multiple messages for the same host are delivered
17147 over a single SMTP connection. The &%-odqs%& command line option causes all
17148 SMTP deliveries to be queued in this way, and is equivalent to setting
17149 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17153 .option receive_timeout main time 0s
17154 .cindex "timeout" "for non-SMTP input"
17155 This option sets the timeout for accepting a non-SMTP message, that is, the
17156 maximum time that Exim waits when reading a message on the standard input. If
17157 the value is zero, it will wait forever. This setting is overridden by the
17158 &%-or%& command line option. The timeout for incoming SMTP messages is
17159 controlled by &%smtp_receive_timeout%&.
17161 .option received_header_text main string&!! "see below"
17162 .cindex "customizing" "&'Received:'& header"
17163 .cindex "&'Received:'& header line" "customizing"
17164 This string defines the contents of the &'Received:'& message header that is
17165 added to each message, except for the timestamp, which is automatically added
17166 on at the end (preceded by a semicolon). The string is expanded each time it is
17167 used. If the expansion yields an empty string, no &'Received:'& header line is
17168 added to the message. Otherwise, the string should start with the text
17169 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17171 The default setting is:
17174 received_header_text = Received: \
17175 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17176 {${if def:sender_ident \
17177 {from ${quote_local_part:$sender_ident} }}\
17178 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17179 by $primary_hostname \
17180 ${if def:received_protocol {with $received_protocol }}\
17181 ${if def:tls_in_ver { ($tls_in_ver)}}\
17182 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17183 (Exim $version_number)\n\t\
17184 ${if def:sender_address \
17185 {(envelope-from <$sender_address>)\n\t}}\
17186 id $message_exim_id\
17187 ${if def:received_for {\n\tfor $received_for}}
17190 The references to the TLS version and cipher are
17191 omitted when Exim is built without TLS
17192 support. The use of conditional expansions ensures that this works for both
17193 locally generated messages and messages received from remote hosts, giving
17194 header lines such as the following:
17196 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17197 by marley.carol.example with esmtp (Exim 4.00)
17198 (envelope-from <bob@carol.example>)
17199 id 16IOWa-00019l-00
17200 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17201 Received: by scrooge.carol.example with local (Exim 4.00)
17202 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17204 Until the body of the message has been received, the timestamp is the time when
17205 the message started to be received. Once the body has arrived, and all policy
17206 checks have taken place, the timestamp is updated to the time at which the
17207 message was accepted.
17210 .option received_headers_max main integer 30
17211 .cindex "loop" "prevention"
17212 .cindex "mail loop prevention"
17213 .cindex "&'Received:'& header line" "counting"
17214 When a message is to be delivered, the number of &'Received:'& headers is
17215 counted, and if it is greater than this parameter, a mail loop is assumed to
17216 have occurred, the delivery is abandoned, and an error message is generated.
17217 This applies to both local and remote deliveries.
17220 .option recipient_unqualified_hosts main "host list&!!" unset
17221 .cindex "unqualified addresses"
17222 .cindex "host" "unqualified addresses from"
17223 This option lists those hosts from which Exim is prepared to accept unqualified
17224 recipient addresses in message envelopes. The addresses are made fully
17225 qualified by the addition of the &%qualify_recipient%& value. This option also
17226 affects message header lines. Exim does not reject unqualified recipient
17227 addresses in headers, but it qualifies them only if the message came from a
17228 host that matches &%recipient_unqualified_hosts%&,
17229 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17230 option was not set.
17233 .option recipients_max main integer 0
17234 .cindex "limit" "number of recipients"
17235 .cindex "recipient" "maximum number"
17236 If this option is set greater than zero, it specifies the maximum number of
17237 original recipients for any message. Additional recipients that are generated
17238 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17239 all recipients over the limit; earlier recipients are delivered as normal.
17240 Non-SMTP messages with too many recipients are failed, and no deliveries are
17243 .cindex "RCPT" "maximum number of incoming"
17244 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17245 RCPT commands in a single message.
17248 .option recipients_max_reject main boolean false
17249 If this option is set true, Exim rejects SMTP messages containing too many
17250 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17251 error to the eventual DATA command. Otherwise (the default) it gives a 452
17252 error to the surplus RCPT commands and accepts the message on behalf of the
17253 initial set of recipients. The remote server should then re-send the message
17254 for the remaining recipients at a later time.
17257 .option remote_max_parallel main integer 2
17258 .cindex "delivery" "parallelism for remote"
17259 This option controls parallel delivery of one message to a number of remote
17260 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17261 does all the remote deliveries for a message one by one. Otherwise, if a single
17262 message has to be delivered to more than one remote host, or if several copies
17263 have to be sent to the same remote host, up to &%remote_max_parallel%&
17264 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17265 deliveries are required, the maximum number of processes are started, and as
17266 each one finishes, another is begun. The order of starting processes is the
17267 same as if sequential delivery were being done, and can be controlled by the
17268 &%remote_sort_domains%& option. If parallel delivery takes place while running
17269 with debugging turned on, the debugging output from each delivery process is
17270 tagged with its process id.
17272 This option controls only the maximum number of parallel deliveries for one
17273 message in one Exim delivery process. Because Exim has no central queue
17274 manager, there is no way of controlling the total number of simultaneous
17275 deliveries if the configuration allows a delivery attempt as soon as a message
17278 .cindex "number of deliveries"
17279 .cindex "delivery" "maximum number of"
17280 If you want to control the total number of deliveries on the system, you
17281 need to set the &%queue_only%& option. This ensures that all incoming messages
17282 are added to the queue without starting a delivery process. Then set up an Exim
17283 daemon to start queue runner processes at appropriate intervals (probably
17284 fairly often, for example, every minute), and limit the total number of queue
17285 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17286 delivers only one message at a time, the maximum number of deliveries that can
17287 then take place at once is &%queue_run_max%& multiplied by
17288 &%remote_max_parallel%&.
17290 If it is purely remote deliveries you want to control, use
17291 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17292 doing the SMTP routing before queueing, so that several messages for the same
17293 host will eventually get delivered down the same connection.
17296 .option remote_sort_domains main "domain list&!!" unset
17297 .cindex "sorting remote deliveries"
17298 .cindex "delivery" "sorting remote"
17299 When there are a number of remote deliveries for a message, they are sorted by
17300 domain into the order given by this list. For example,
17302 remote_sort_domains = *.cam.ac.uk:*.uk
17304 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17305 then to those in the &%uk%& domain, then to any others.
17308 .option retry_data_expire main time 7d
17309 .cindex "hints database" "data expiry"
17310 This option sets a &"use before"& time on retry information in Exim's hints
17311 database. Any older retry data is ignored. This means that, for example, once a
17312 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17316 .option retry_interval_max main time 24h
17317 .cindex "retry" "limit on interval"
17318 .cindex "limit" "on retry interval"
17319 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17320 intervals between delivery attempts for messages that cannot be delivered
17321 straight away. This option sets an overall limit to the length of time between
17322 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17326 .option return_path_remove main boolean true
17327 .cindex "&'Return-path:'& header line" "removing"
17328 RFC 2821, section 4.4, states that an SMTP server must insert a
17329 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17330 The &'Return-path:'& header preserves the sender address as received in the
17331 MAIL command. This description implies that this header should not be present
17332 in an incoming message. If &%return_path_remove%& is true, any existing
17333 &'Return-path:'& headers are removed from messages at the time they are
17334 received. Exim's transports have options for adding &'Return-path:'& headers at
17335 the time of delivery. They are normally used only for final local deliveries.
17338 .option return_size_limit main integer 100K
17339 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17342 .option rfc1413_hosts main "host list&!!" @[]
17344 .cindex "host" "for RFC 1413 calls"
17345 RFC 1413 identification calls are made to any client host which matches
17346 an item in the list.
17347 The default value specifies just this host, being any local interface
17350 .option rfc1413_query_timeout main time 0s
17351 .cindex "RFC 1413" "query timeout"
17352 .cindex "timeout" "for RFC 1413 call"
17353 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17354 no RFC 1413 calls are ever made.
17357 .option sender_unqualified_hosts main "host list&!!" unset
17358 .cindex "unqualified addresses"
17359 .cindex "host" "unqualified addresses from"
17360 This option lists those hosts from which Exim is prepared to accept unqualified
17361 sender addresses. The addresses are made fully qualified by the addition of
17362 &%qualify_domain%&. This option also affects message header lines. Exim does
17363 not reject unqualified addresses in headers that contain sender addresses, but
17364 it qualifies them only if the message came from a host that matches
17365 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17366 using TCP/IP), and the &%-bnq%& option was not set.
17369 .option slow_lookup_log main integer 0
17370 .cindex "logging" "slow lookups"
17371 .cindex "dns" "logging slow lookups"
17372 This option controls logging of slow lookups.
17373 If the value is nonzero it is taken as a number of milliseconds
17374 and lookups taking longer than this are logged.
17375 Currently this applies only to DNS lookups.
17379 .option smtp_accept_keepalive main boolean true
17380 .cindex "keepalive" "on incoming connection"
17381 This option controls the setting of the SO_KEEPALIVE option on incoming
17382 TCP/IP socket connections. When set, it causes the kernel to probe idle
17383 connections periodically, by sending packets with &"old"& sequence numbers. The
17384 other end of the connection should send an acknowledgment if the connection is
17385 still okay or a reset if the connection has been aborted. The reason for doing
17386 this is that it has the beneficial effect of freeing up certain types of
17387 connection that can get stuck when the remote host is disconnected without
17388 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17389 hours to detect unreachable hosts.
17393 .option smtp_accept_max main integer 20
17394 .cindex "limit" "incoming SMTP connections"
17395 .cindex "SMTP" "incoming connection count"
17397 This option specifies the maximum number of simultaneous incoming SMTP calls
17398 that Exim will accept. It applies only to the listening daemon; there is no
17399 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17400 value is set to zero, no limit is applied. However, it is required to be
17401 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17402 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17404 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17405 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17406 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17407 and &%smtp_load_reserve%& are then checked before accepting the connection.
17410 .option smtp_accept_max_nonmail main integer 10
17411 .cindex "limit" "non-mail SMTP commands"
17412 .cindex "SMTP" "limiting non-mail commands"
17413 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17414 the connection if there are too many. This option defines &"too many"&. The
17415 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17416 client looping sending EHLO, for example. The check is applied only if the
17417 client host matches &%smtp_accept_max_nonmail_hosts%&.
17419 When a new message is expected, one occurrence of RSET is not counted. This
17420 allows a client to send one RSET between messages (this is not necessary,
17421 but some clients do it). Exim also allows one uncounted occurrence of HELO
17422 or EHLO, and one occurrence of STARTTLS between messages. After
17423 starting up a TLS session, another EHLO is expected, and so it too is not
17424 counted. The first occurrence of AUTH in a connection, or immediately
17425 following STARTTLS is not counted. Otherwise, all commands other than
17426 MAIL, RCPT, DATA, and QUIT are counted.
17429 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17430 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17431 check by setting this option. The default value makes it apply to all hosts. By
17432 changing the value, you can exclude any badly-behaved hosts that you have to
17436 . Allow this long option name to split; give it unsplit as a fifth argument
17437 . for the automatic .oindex that is generated by .option.
17438 . We insert " &~&~" which is both pretty nasty visually and results in
17439 . non-searchable text. HowItWorks.txt mentions an option for inserting
17440 . zero-width-space, which would be nicer visually and results in (at least)
17441 . html that Firefox will split on when it's forced to reflow (rather than
17442 . inserting a horizontal scrollbar). However, the text is still not
17443 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17444 . the option name to split.
17446 .option "smtp_accept_max_per_connection" main integer 1000 &&&
17447 smtp_accept_max_per_connection
17448 .cindex "SMTP" "limiting incoming message count"
17449 .cindex "limit" "messages per SMTP connection"
17450 The value of this option limits the number of MAIL commands that Exim is
17451 prepared to accept over a single SMTP connection, whether or not each command
17452 results in the transfer of a message. After the limit is reached, a 421
17453 response is given to subsequent MAIL commands. This limit is a safety
17454 precaution against a client that goes mad (incidents of this type have been
17458 .option smtp_accept_max_per_host main string&!! unset
17459 .cindex "limit" "SMTP connections from one host"
17460 .cindex "host" "limiting SMTP connections from"
17461 This option restricts the number of simultaneous IP connections from a single
17462 host (strictly, from a single IP address) to the Exim daemon. The option is
17463 expanded, to enable different limits to be applied to different hosts by
17464 reference to &$sender_host_address$&. Once the limit is reached, additional
17465 connection attempts from the same host are rejected with error code 421. This
17466 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17467 of zero imposes no limit. If this option is set greater than zero, it is
17468 required that &%smtp_accept_max%& be non-zero.
17470 &*Warning*&: When setting this option you should not use any expansion
17471 constructions that take an appreciable amount of time. The expansion and test
17472 happen in the main daemon loop, in order to reject additional connections
17473 without forking additional processes (otherwise a denial-of-service attack
17474 could cause a vast number or processes to be created). While the daemon is
17475 doing this processing, it cannot accept any other incoming connections.
17479 .option smtp_accept_queue main integer 0
17480 .cindex "SMTP" "incoming connection count"
17481 .cindex "queueing incoming messages"
17482 .cindex "message" "queueing by SMTP connection count"
17483 If the number of simultaneous incoming SMTP connections being handled via the
17484 listening daemon exceeds this value, messages received by SMTP are just placed
17485 in the queue; no delivery processes are started automatically. The count is
17486 fixed at the start of an SMTP connection. It cannot be updated in the
17487 subprocess that receives messages, and so the queueing or not queueing applies
17488 to all messages received in the same connection.
17490 A value of zero implies no limit, and clearly any non-zero value is useful only
17491 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17492 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17493 various &%-od%&&'x'& command line options.
17496 . See the comment on smtp_accept_max_per_connection
17498 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17499 smtp_accept_queue_per_connection
17500 .cindex "queueing incoming messages"
17501 .cindex "message" "queueing by message count"
17502 This option limits the number of delivery processes that Exim starts
17503 automatically when receiving messages via SMTP, whether via the daemon or by
17504 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17505 and the number of messages received in a single SMTP session exceeds this
17506 number, subsequent messages are placed in the queue, but no delivery processes
17507 are started. This helps to limit the number of Exim processes when a server
17508 restarts after downtime and there is a lot of mail waiting for it on other
17509 systems. On large systems, the default should probably be increased, and on
17510 dial-in client systems it should probably be set to zero (that is, disabled).
17513 .option smtp_accept_reserve main integer 0
17514 .cindex "SMTP" "incoming call count"
17515 .cindex "host" "reserved"
17516 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17517 number of SMTP connections that are reserved for connections from the hosts
17518 that are specified in &%smtp_reserve_hosts%&. The value set in
17519 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17520 restricted to this number of connections; the option specifies a minimum number
17521 of connection slots for them, not a maximum. It is a guarantee that this group
17522 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17523 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17526 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17527 set to 5, once there are 45 active connections (from any hosts), new
17528 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17529 provided the other criteria for acceptance are met.
17532 .option smtp_active_hostname main string&!! unset
17533 .cindex "host" "name in SMTP responses"
17534 .cindex "SMTP" "host name in responses"
17535 .vindex "&$primary_hostname$&"
17536 This option is provided for multi-homed servers that want to masquerade as
17537 several different hosts. At the start of an incoming SMTP connection, its value
17538 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17539 responses. For example, it is used as domain name in the response to an
17540 incoming HELO or EHLO command.
17542 .vindex "&$smtp_active_hostname$&"
17543 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17544 is saved with any messages that are received. It is therefore available for use
17545 in routers and transports when the message is later delivered.
17547 If this option is unset, or if its expansion is forced to fail, or if the
17548 expansion results in an empty string, the value of &$primary_hostname$& is
17549 used. Other expansion failures cause a message to be written to the main and
17550 panic logs, and the SMTP command receives a temporary error. Typically, the
17551 value of &%smtp_active_hostname%& depends on the incoming interface address.
17554 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17555 {cox.mydomain}{box.mydomain}}
17558 Although &$smtp_active_hostname$& is primarily concerned with incoming
17559 messages, it is also used as the default for HELO commands in callout
17560 verification if there is no remote transport from which to obtain a
17561 &%helo_data%& value.
17563 .option smtp_banner main string&!! "see below"
17564 .cindex "SMTP" "welcome banner"
17565 .cindex "banner for SMTP"
17566 .cindex "welcome banner for SMTP"
17567 .cindex "customizing" "SMTP banner"
17568 This string, which is expanded every time it is used, is output as the initial
17569 positive response to an SMTP connection. The default setting is:
17571 smtp_banner = $smtp_active_hostname ESMTP Exim \
17572 $version_number $tod_full
17574 Failure to expand the string causes a panic error. If you want to create a
17575 multiline response to the initial SMTP connection, use &"\n"& in the string at
17576 appropriate points, but not at the end. Note that the 220 code is not included
17577 in this string. Exim adds it automatically (several times in the case of a
17578 multiline response).
17581 .option smtp_check_spool_space main boolean true
17582 .cindex "checking disk space"
17583 .cindex "disk space, checking"
17584 .cindex "spool directory" "checking space"
17585 When this option is set, if an incoming SMTP session encounters the SIZE
17586 option on a MAIL command, it checks that there is enough space in the
17587 spool directory's partition to accept a message of that size, while still
17588 leaving free the amount specified by &%check_spool_space%& (even if that value
17589 is zero). If there isn't enough space, a temporary error code is returned.
17592 .option smtp_connect_backlog main integer 20
17593 .cindex "connection backlog"
17594 .cindex "SMTP" "connection backlog"
17595 .cindex "backlog of connections"
17596 This option specifies a maximum number of waiting SMTP connections. Exim passes
17597 this value to the TCP/IP system when it sets up its listener. Once this number
17598 of connections are waiting for the daemon's attention, subsequent connection
17599 attempts are refused at the TCP/IP level. At least, that is what the manuals
17600 say; in some circumstances such connection attempts have been observed to time
17601 out instead. For large systems it is probably a good idea to increase the
17602 value (to 50, say). It also gives some protection against denial-of-service
17603 attacks by SYN flooding.
17606 .option smtp_enforce_sync main boolean true
17607 .cindex "SMTP" "synchronization checking"
17608 .cindex "synchronization checking in SMTP"
17609 The SMTP protocol specification requires the client to wait for a response from
17610 the server at certain points in the dialogue. Without PIPELINING these
17611 synchronization points are after every command; with PIPELINING they are
17612 fewer, but they still exist.
17614 Some spamming sites send out a complete set of SMTP commands without waiting
17615 for any response. Exim protects against this by rejecting a message if the
17616 client has sent further input when it should not have. The error response &"554
17617 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17618 for this error cannot be perfect because of transmission delays (unexpected
17619 input may be on its way but not yet received when Exim checks). However, it
17620 does detect many instances.
17622 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17623 If you want to disable the check selectively (for example, only for certain
17624 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17625 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17629 .option smtp_etrn_command main string&!! unset
17630 .cindex "ETRN" "command to be run"
17631 .cindex "ESMTP extensions" ETRN
17632 .vindex "&$domain$&"
17633 If this option is set, the given command is run whenever an SMTP ETRN
17634 command is received from a host that is permitted to issue such commands (see
17635 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17636 are independently expanded. The expansion variable &$domain$& is set to the
17637 argument of the ETRN command, and no syntax checking is done on it. For
17640 smtp_etrn_command = /etc/etrn_command $domain \
17641 $sender_host_address
17644 If the option is not set, the argument for the ETRN command must
17645 be a &'#'& followed by an address string.
17646 In this case an &'exim -R <string>'& command is used;
17647 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17650 A new process is created to run the command, but Exim does not wait for it to
17651 complete. Consequently, its status cannot be checked. If the command cannot be
17652 run, a line is written to the panic log, but the ETRN caller still receives
17653 a 250 success response. Exim is normally running under its own uid when
17654 receiving SMTP, so it is not possible for it to change the uid before running
17658 .option smtp_etrn_serialize main boolean true
17659 .cindex "ETRN" "serializing"
17660 When this option is set, it prevents the simultaneous execution of more than
17661 one identical command as a result of ETRN in an SMTP connection. See
17662 section &<<SECTETRN>>& for details.
17665 .option smtp_load_reserve main fixed-point unset
17666 .cindex "load average"
17667 If the system load average ever gets higher than this, incoming SMTP calls are
17668 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17669 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17670 the load is over the limit. The option has no effect on ancient operating
17671 systems on which Exim cannot determine the load average. See also
17672 &%deliver_queue_load_max%& and &%queue_only_load%&.
17676 .option smtp_max_synprot_errors main integer 3
17677 .cindex "SMTP" "limiting syntax and protocol errors"
17678 .cindex "limit" "SMTP syntax and protocol errors"
17679 Exim rejects SMTP commands that contain syntax or protocol errors. In
17680 particular, a syntactically invalid email address, as in this command:
17682 RCPT TO:<abc xyz@a.b.c>
17684 causes immediate rejection of the command, before any other tests are done.
17685 (The ACL cannot be run if there is no valid address to set up for it.) An
17686 example of a protocol error is receiving RCPT before MAIL. If there are
17687 too many syntax or protocol errors in one SMTP session, the connection is
17688 dropped. The limit is set by this option.
17690 .cindex "PIPELINING" "expected errors"
17691 When the PIPELINING extension to SMTP is in use, some protocol errors are
17692 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17693 Exim assumes that PIPELINING will be used if it advertises it (see
17694 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17695 not count towards the limit.
17699 .option smtp_max_unknown_commands main integer 3
17700 .cindex "SMTP" "limiting unknown commands"
17701 .cindex "limit" "unknown SMTP commands"
17702 If there are too many unrecognized commands in an incoming SMTP session, an
17703 Exim server drops the connection. This is a defence against some kinds of abuse
17706 into making connections to SMTP ports; in these circumstances, a number of
17707 non-SMTP command lines are sent first.
17711 .option smtp_ratelimit_hosts main "host list&!!" unset
17712 .cindex "SMTP" "rate limiting"
17713 .cindex "limit" "rate of message arrival"
17714 .cindex "RCPT" "rate limiting"
17715 Some sites find it helpful to be able to limit the rate at which certain hosts
17716 can send them messages, and the rate at which an individual message can specify
17719 Exim has two rate-limiting facilities. This section describes the older
17720 facility, which can limit rates within a single connection. The newer
17721 &%ratelimit%& ACL condition can limit rates across all connections. See section
17722 &<<SECTratelimiting>>& for details of the newer facility.
17724 When a host matches &%smtp_ratelimit_hosts%&, the values of
17725 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17726 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17727 respectively. Each option, if set, must contain a set of four comma-separated
17731 A threshold, before which there is no rate limiting.
17733 An initial time delay. Unlike other times in Exim, numbers with decimal
17734 fractional parts are allowed here.
17736 A factor by which to increase the delay each time.
17738 A maximum value for the delay. This should normally be less than 5 minutes,
17739 because after that time, the client is liable to timeout the SMTP command.
17742 For example, these settings have been used successfully at the site which
17743 first suggested this feature, for controlling mail from their customers:
17745 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17746 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17748 The first setting specifies delays that are applied to MAIL commands after
17749 two have been received over a single connection. The initial delay is 0.5
17750 seconds, increasing by a factor of 1.05 each time. The second setting applies
17751 delays to RCPT commands when more than four occur in a single message.
17754 .option smtp_ratelimit_mail main string unset
17755 See &%smtp_ratelimit_hosts%& above.
17758 .option smtp_ratelimit_rcpt main string unset
17759 See &%smtp_ratelimit_hosts%& above.
17762 .option smtp_receive_timeout main time&!! 5m
17763 .cindex "timeout" "for SMTP input"
17764 .cindex "SMTP" "input timeout"
17765 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17766 input, including batch SMTP. If a line of input (either an SMTP command or a
17767 data line) is not received within this time, the SMTP connection is dropped and
17768 the message is abandoned.
17769 A line is written to the log containing one of the following messages:
17771 SMTP command timeout on connection from...
17772 SMTP data timeout on connection from...
17774 The former means that Exim was expecting to read an SMTP command; the latter
17775 means that it was in the DATA phase, reading the contents of a message.
17777 If the first character of the option is a &"$"& the option is
17778 expanded before use and may depend on
17779 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17783 The value set by this option can be overridden by the
17784 &%-os%& command-line option. A setting of zero time disables the timeout, but
17785 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17786 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17787 timeout is controlled by &%receive_timeout%& and &%-or%&.
17790 .option smtp_reserve_hosts main "host list&!!" unset
17791 This option defines hosts for which SMTP connections are reserved; see
17792 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17795 .option smtp_return_error_details main boolean false
17796 .cindex "SMTP" "details policy failures"
17797 .cindex "policy control" "rejection, returning details"
17798 In the default state, Exim uses bland messages such as
17799 &"Administrative prohibition"& when it rejects SMTP commands for policy
17800 reasons. Many sysadmins like this because it gives away little information
17801 to spammers. However, some other sysadmins who are applying strict checking
17802 policies want to give out much fuller information about failures. Setting
17803 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17804 example, instead of &"Administrative prohibition"&, it might give:
17806 550-Rejected after DATA: '>' missing at end of address:
17807 550 failing address in "From" header is: <user@dom.ain
17811 .option smtputf8_advertise_hosts main "host list&!!" *
17812 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17813 .cindex "ESMTP extensions" SMTPUTF8
17814 When Exim is built with support for internationalised mail names,
17815 the availability thereof is advertised in
17816 response to EHLO only to those client hosts that match this option. See
17817 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17820 .option spamd_address main string "127.0.0.1 783"
17821 This option is available when Exim is compiled with the content-scanning
17822 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17823 See section &<<SECTscanspamass>>& for more details.
17827 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17828 This option is available when Exim is compiled with SPF support.
17829 See section &<<SECSPF>>& for more details.
17833 .option split_spool_directory main boolean false
17834 .cindex "multiple spool directories"
17835 .cindex "spool directory" "split"
17836 .cindex "directories, multiple"
17837 If this option is set, it causes Exim to split its input directory into 62
17838 subdirectories, each with a single alphanumeric character as its name. The
17839 sixth character of the message id is used to allocate messages to
17840 subdirectories; this is the least significant base-62 digit of the time of
17841 arrival of the message.
17843 Splitting up the spool in this way may provide better performance on systems
17844 where there are long mail queues, by reducing the number of files in any one
17845 directory. The msglog directory is also split up in a similar way to the input
17846 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17847 are still placed in the single directory &_msglog.OLD_&.
17849 It is not necessary to take any special action for existing messages when
17850 changing &%split_spool_directory%&. Exim notices messages that are in the
17851 &"wrong"& place, and continues to process them. If the option is turned off
17852 after a period of being on, the subdirectories will eventually empty and be
17853 automatically deleted.
17855 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17856 changes. Instead of creating a list of all messages in the queue, and then
17857 trying to deliver each one, in turn, it constructs a list of those in one
17858 sub-directory and tries to deliver them, before moving on to the next
17859 sub-directory. The sub-directories are processed in a random order. This
17860 spreads out the scanning of the input directories, and uses less memory. It is
17861 particularly beneficial when there are lots of messages in the queue. However,
17862 if &%queue_run_in_order%& is set, none of this new processing happens. The
17863 entire queue has to be scanned and sorted before any deliveries can start.
17866 .option spool_directory main string&!! "set at compile time"
17867 .cindex "spool directory" "path to"
17868 This defines the directory in which Exim keeps its spool, that is, the messages
17869 it is waiting to deliver. The default value is taken from the compile-time
17870 configuration setting, if there is one. If not, this option must be set. The
17871 string is expanded, so it can contain, for example, a reference to
17872 &$primary_hostname$&.
17874 If the spool directory name is fixed on your installation, it is recommended
17875 that you set it at build time rather than from this option, particularly if the
17876 log files are being written to the spool directory (see &%log_file_path%&).
17877 Otherwise log files cannot be used for errors that are detected early on, such
17878 as failures in the configuration file.
17880 By using this option to override the compiled-in path, it is possible to run
17881 tests of Exim without using the standard spool.
17883 .option spool_wireformat main boolean false
17884 .cindex "spool directory" "file formats"
17885 If this option is set, Exim may for some messages use an alternative format
17886 for data-files in the spool which matches the wire format.
17887 Doing this permits more efficient message reception and transmission.
17888 Currently it is only done for messages received using the ESMTP CHUNKING
17891 The following variables will not have useful values:
17893 $max_received_linelength
17898 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17899 and any external programs which are passed a reference to a message data file
17900 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17901 will need to be aware of the different formats potentially available.
17903 Using any of the ACL conditions noted will negate the reception benefit
17904 (as a Unix-mbox-format file is constructed for them).
17905 The transmission benefit is maintained.
17907 .option sqlite_lock_timeout main time 5s
17908 .cindex "sqlite lookup type" "lock timeout"
17909 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17910 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17912 .option strict_acl_vars main boolean false
17913 .cindex "&ACL;" "variables, handling unset"
17914 This option controls what happens if a syntactically valid but undefined ACL
17915 variable is referenced. If it is false (the default), an empty string
17916 is substituted; if it is true, an error is generated. See section
17917 &<<SECTaclvariables>>& for details of ACL variables.
17919 .option strip_excess_angle_brackets main boolean false
17920 .cindex "angle brackets, excess"
17921 If this option is set, redundant pairs of angle brackets round &"route-addr"&
17922 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
17923 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
17924 passed on to another MTA, the excess angle brackets are not passed on. If this
17925 option is not set, multiple pairs of angle brackets cause a syntax error.
17928 .option strip_trailing_dot main boolean false
17929 .cindex "trailing dot on domain"
17930 .cindex "dot" "trailing on domain"
17931 If this option is set, a trailing dot at the end of a domain in an address is
17932 ignored. If this is in the envelope and the message is passed on to another
17933 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
17934 domain causes a syntax error.
17935 However, addresses in header lines are checked only when an ACL requests header
17939 .option syslog_duplication main boolean true
17940 .cindex "syslog" "duplicate log lines; suppressing"
17941 When Exim is logging to syslog, it writes the log lines for its three
17942 separate logs at different syslog priorities so that they can in principle
17943 be separated on the logging hosts. Some installations do not require this
17944 separation, and in those cases, the duplication of certain log lines is a
17945 nuisance. If &%syslog_duplication%& is set false, only one copy of any
17946 particular log line is written to syslog. For lines that normally go to
17947 both the main log and the reject log, the reject log version (possibly
17948 containing message header lines) is written, at LOG_NOTICE priority.
17949 Lines that normally go to both the main and the panic log are written at
17950 the LOG_ALERT priority.
17953 .option syslog_facility main string unset
17954 .cindex "syslog" "facility; setting"
17955 This option sets the syslog &"facility"& name, used when Exim is logging to
17956 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
17957 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
17958 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
17959 details of Exim's logging.
17962 .option syslog_pid main boolean true
17963 .cindex "syslog" "pid"
17964 If &%syslog_pid%& is set false, the PID on Exim's log lines are
17965 omitted when these lines are sent to syslog. (Syslog normally prefixes
17966 the log lines with the PID of the logging process automatically.) You need
17967 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
17968 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
17972 .option syslog_processname main string &`exim`&
17973 .cindex "syslog" "process name; setting"
17974 This option sets the syslog &"ident"& name, used when Exim is logging to
17975 syslog. The value must be no longer than 32 characters. See chapter
17976 &<<CHAPlog>>& for details of Exim's logging.
17980 .option syslog_timestamp main boolean true
17981 .cindex "syslog" "timestamps"
17982 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
17983 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
17984 details of Exim's logging.
17987 .option system_filter main string&!! unset
17988 .cindex "filter" "system filter"
17989 .cindex "system filter" "specifying"
17990 .cindex "Sieve filter" "not available for system filter"
17991 This option specifies an Exim filter file that is applied to all messages at
17992 the start of each delivery attempt, before any routing is done. System filters
17993 must be Exim filters; they cannot be Sieve filters. If the system filter
17994 generates any deliveries to files or pipes, or any new mail messages, the
17995 appropriate &%system_filter_..._transport%& option(s) must be set, to define
17996 which transports are to be used. Details of this facility are given in chapter
17997 &<<CHAPsystemfilter>>&.
17998 A forced expansion failure results in no filter operation.
18001 .option system_filter_directory_transport main string&!! unset
18002 .vindex "&$address_file$&"
18003 This sets the name of the transport driver that is to be used when the
18004 &%save%& command in a system message filter specifies a path ending in &"/"&,
18005 implying delivery of each message into a separate file in some directory.
18006 During the delivery, the variable &$address_file$& contains the path name.
18009 .option system_filter_file_transport main string&!! unset
18010 .cindex "file" "transport for system filter"
18011 This sets the name of the transport driver that is to be used when the &%save%&
18012 command in a system message filter specifies a path not ending in &"/"&. During
18013 the delivery, the variable &$address_file$& contains the path name.
18015 .option system_filter_group main string unset
18016 .cindex "gid (group id)" "system filter"
18017 This option is used only when &%system_filter_user%& is also set. It sets the
18018 gid under which the system filter is run, overriding any gid that is associated
18019 with the user. The value may be numerical or symbolic.
18021 .option system_filter_pipe_transport main string&!! unset
18022 .cindex "&(pipe)& transport" "for system filter"
18023 .vindex "&$address_pipe$&"
18024 This specifies the transport driver that is to be used when a &%pipe%& command
18025 is used in a system filter. During the delivery, the variable &$address_pipe$&
18026 contains the pipe command.
18029 .option system_filter_reply_transport main string&!! unset
18030 .cindex "&(autoreply)& transport" "for system filter"
18031 This specifies the transport driver that is to be used when a &%mail%& command
18032 is used in a system filter.
18035 .option system_filter_user main string unset
18036 .cindex "uid (user id)" "system filter"
18037 If this option is set to root, the system filter is run in the main Exim
18038 delivery process, as root. Otherwise, the system filter runs in a separate
18039 process, as the given user, defaulting to the Exim run-time user.
18040 Unless the string consists entirely of digits, it
18041 is looked up in the password data. Failure to find the named user causes a
18042 configuration error. The gid is either taken from the password data, or
18043 specified by &%system_filter_group%&. When the uid is specified numerically,
18044 &%system_filter_group%& is required to be set.
18046 If the system filter generates any pipe, file, or reply deliveries, the uid
18047 under which the filter is run is used when transporting them, unless a
18048 transport option overrides.
18051 .option tcp_nodelay main boolean true
18052 .cindex "daemon" "TCP_NODELAY on sockets"
18053 .cindex "Nagle algorithm"
18054 .cindex "TCP_NODELAY on listening sockets"
18055 If this option is set false, it stops the Exim daemon setting the
18056 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18057 turns off the &"Nagle algorithm"&, which is a way of improving network
18058 performance in interactive (character-by-character) situations. Turning it off
18059 should improve Exim's performance a bit, so that is what happens by default.
18060 However, it appears that some broken clients cannot cope, and time out. Hence
18061 this option. It affects only those sockets that are set up for listening by the
18062 daemon. Sockets created by the smtp transport for delivering mail always set
18066 .option timeout_frozen_after main time 0s
18067 .cindex "frozen messages" "timing out"
18068 .cindex "timeout" "frozen messages"
18069 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18070 message of any kind that has been in the queue for longer than the given time
18071 is automatically cancelled at the next queue run. If the frozen message is a
18072 bounce message, it is just discarded; otherwise, a bounce is sent to the
18073 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18074 If you want to timeout frozen bounce messages earlier than other kinds of
18075 frozen message, see &%ignore_bounce_errors_after%&.
18077 &*Note:*& the default value of zero means no timeouts; with this setting,
18078 frozen messages remain in the queue forever (except for any frozen bounce
18079 messages that are released by &%ignore_bounce_errors_after%&).
18082 .option timezone main string unset
18083 .cindex "timezone, setting"
18084 .cindex "environment" "values from"
18085 The value of &%timezone%& is used to set the environment variable TZ while
18086 running Exim (if it is different on entry). This ensures that all timestamps
18087 created by Exim are in the required timezone. If you want all your timestamps
18088 to be in UTC (aka GMT) you should set
18092 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18093 or, if that is not set, from the value of the TZ environment variable when Exim
18094 is built. If &%timezone%& is set to the empty string, either at build or run
18095 time, any existing TZ variable is removed from the environment when Exim
18096 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18097 unfortunately not all, operating systems.
18100 .option tls_advertise_hosts main "host list&!!" *
18101 .cindex "TLS" "advertising"
18102 .cindex "encryption" "on SMTP connection"
18103 .cindex "SMTP" "encrypted connection"
18104 .cindex "ESMTP extensions" STARTTLS
18105 When Exim is built with support for TLS encrypted connections, the availability
18106 of the STARTTLS command to set up an encrypted session is advertised in
18107 response to EHLO only to those client hosts that match this option. See
18108 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18109 Note that the default value requires that a certificate be supplied
18110 using the &%tls_certificate%& option. If TLS support for incoming connections
18111 is not required the &%tls_advertise_hosts%& option should be set empty.
18114 .option tls_certificate main string list&!! unset
18115 .cindex "TLS" "server certificate; location of"
18116 .cindex "certificate" "server, location of"
18117 The value of this option is expanded, and must then be a list of absolute paths to
18118 files which contain the server's certificates (in PEM format).
18119 Commonly only one file is needed.
18120 The server's private key is also
18121 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18122 &<<CHAPTLS>>& for further details.
18124 &*Note*&: The certificates defined by this option are used only when Exim is
18125 receiving incoming messages as a server. If you want to supply certificates for
18126 use when sending messages as a client, you must set the &%tls_certificate%&
18127 option in the relevant &(smtp)& transport.
18129 &*Note*&: If you use filenames based on IP addresses, change the list
18130 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18132 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18133 when a list of more than one
18134 file is used, the &$tls_in_ourcert$& variable is unreliable.
18135 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18137 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18138 if the OpenSSL build supports TLS extensions and the TLS client sends the
18139 Server Name Indication extension, then this option and others documented in
18140 &<<SECTtlssni>>& will be re-expanded.
18142 If this option is unset or empty a fresh self-signed certificate will be
18143 generated for every connection.
18145 .option tls_crl main string&!! unset
18146 .cindex "TLS" "server certificate revocation list"
18147 .cindex "certificate" "revocation list for server"
18148 This option specifies a certificate revocation list. The expanded value must
18149 be the name of a file that contains CRLs in PEM format.
18151 Under OpenSSL the option can specify a directory with CRL files.
18153 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18154 for each signing element of the certificate chain (i.e. all but the leaf).
18155 For the file variant this can be multiple PEM blocks in the one file.
18157 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18160 .option tls_dh_max_bits main integer 2236
18161 .cindex "TLS" "D-H bit count"
18162 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18163 the chosen TLS library. That value might prove to be too high for
18164 interoperability. This option provides a maximum clamp on the value
18165 suggested, trading off security for interoperability.
18167 The value must be at least 1024.
18169 The value 2236 was chosen because, at time of adding the option, it was the
18170 hard-coded maximum value supported by the NSS cryptographic library, as used
18171 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18173 If you prefer more security and are willing to break some clients, raise this
18176 Note that the value passed to GnuTLS for *generating* a new prime may be a
18177 little less than this figure, because GnuTLS is inexact and may produce a
18178 larger prime than requested.
18181 .option tls_dhparam main string&!! unset
18182 .cindex "TLS" "D-H parameters for server"
18183 The value of this option is expanded and indicates the source of DH parameters
18184 to be used by Exim.
18186 This option is ignored for GnuTLS version 3.6.0 and later.
18187 The library manages parameter negotiation internally.
18189 &*Note: The Exim Maintainers strongly recommend,
18190 for other TLS library versions,
18191 using a filename with site-generated
18192 local DH parameters*&, which has been supported across all versions of Exim. The
18193 other specific constants available are a fallback so that even when
18194 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18196 If &%tls_dhparam%& is a filename starting with a &`/`&,
18197 then it names a file from which DH
18198 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18199 PKCS#3 representation of the DH prime. If the file does not exist, for
18200 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18201 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18202 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18203 and treated as though the &%tls_dhparam%& were set to "none".
18205 If this option expands to the string "none", then no DH parameters will be
18208 If this option expands to the string "historic" and Exim is using GnuTLS, then
18209 Exim will attempt to load a file from inside the spool directory. If the file
18210 does not exist, Exim will attempt to create it.
18211 See section &<<SECTgnutlsparam>>& for further details.
18213 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18214 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18216 In older versions of Exim the default was the 2048 bit prime described in section
18217 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18218 in IKE is assigned number 23.
18220 Otherwise, the option must expand to the name used by Exim for any of a number
18221 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18222 sources. As names, Exim uses a standard specified name, else "ike" followed by
18223 the number used by IKE, or "default" which corresponds to
18224 &`exim.dev.20160529.3`&.
18226 The available standard primes are:
18227 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18228 &`ike1`&, &`ike2`&, &`ike5`&,
18229 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18230 &`ike22`&, &`ike23`& and &`ike24`&.
18232 The available additional primes are:
18233 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18235 Some of these will be too small to be accepted by clients.
18236 Some may be too large to be accepted by clients.
18237 The open cryptographic community has suspicions about the integrity of some
18238 of the later IKE values, which led into RFC7919 providing new fixed constants
18239 (the "ffdhe" identifiers).
18241 At this point, all of the "ike" values should be considered obsolete;
18242 they're still in Exim to avoid breaking unusual configurations, but are
18243 candidates for removal the next time we have backwards-incompatible changes.
18245 The TLS protocol does not negotiate an acceptable size for this; clients tend
18246 to hard-drop connections if what is offered by the server is unacceptable,
18247 whether too large or too small, and there's no provision for the client to
18248 tell the server what these constraints are. Thus, as a server operator, you
18249 need to make an educated guess as to what is most likely to work for your
18252 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18253 is most likely to maximise interoperability. The upper bound comes from
18254 applications using the Mozilla Network Security Services (NSS) library, which
18255 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18256 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18257 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18258 acceptable bound from 1024 to 2048.
18261 .option tls_eccurve main string&!! &`auto`&
18262 .cindex TLS "EC cryptography"
18263 This option selects a EC curve for use by Exim when used with OpenSSL.
18264 It has no effect when Exim is used with GnuTLS.
18266 After expansion it must contain a valid EC curve parameter, such as
18267 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18268 for valid selections.
18270 For OpenSSL versions before (and not including) 1.0.2, the string
18271 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18272 &`auto`& tells the library to choose.
18274 If the option expands to an empty string, no EC curves will be enabled.
18277 .option tls_ocsp_file main string&!! unset
18278 .cindex TLS "certificate status"
18279 .cindex TLS "OCSP proof file"
18281 must if set expand to the absolute path to a file which contains a current
18282 status proof for the server's certificate, as obtained from the
18283 Certificate Authority.
18285 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18286 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18288 For OpenSSL 1.1.0 or later, and
18289 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18290 of files, to match a list given for the &%tls_certificate%& option.
18291 The ordering of the two lists must match.
18292 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18294 The file(s) should be in DER format,
18295 except for GnuTLS 3.6.3 or later
18297 when an optional filetype prefix can be used.
18298 The prefix must be one of "DER" or "PEM", followed by
18299 a single space. If one is used it sets the format for subsequent
18300 files in the list; the initial format is DER.
18301 If multiple proofs are wanted, for multiple chain elements
18302 (this only works under TLS1.3)
18303 they must be coded as a combined OCSP response.
18305 Although GnuTLS will accept PEM files with multiple separate
18306 PEM blobs (ie. separate OCSP responses), it sends them in the
18307 TLS Certificate record interleaved with the certificates of the chain;
18308 although a GnuTLS client is happy with that, an OpenSSL client is not.
18310 .option tls_on_connect_ports main "string list" unset
18313 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18314 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18315 set up without waiting for the client to issue a STARTTLS command. For
18316 further details, see section &<<SECTsupobssmt>>&.
18320 .option tls_privatekey main string list&!! unset
18321 .cindex "TLS" "server private key; location of"
18322 The value of this option is expanded, and must then be a list of absolute paths to
18323 files which contains the server's private keys.
18324 If this option is unset, or if
18325 the expansion is forced to fail, or the result is an empty string, the private
18326 key is assumed to be in the same file as the server's certificates. See chapter
18327 &<<CHAPTLS>>& for further details.
18329 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18332 .option tls_remember_esmtp main boolean false
18333 .cindex "TLS" "esmtp state; remembering"
18334 .cindex "TLS" "broken clients"
18335 If this option is set true, Exim violates the RFCs by remembering that it is in
18336 &"esmtp"& state after successfully negotiating a TLS session. This provides
18337 support for broken clients that fail to send a new EHLO after starting a
18341 .option tls_require_ciphers main string&!! unset
18342 .cindex "TLS" "requiring specific ciphers"
18343 .cindex "cipher" "requiring specific"
18344 This option controls which ciphers can be used for incoming TLS connections.
18345 The &(smtp)& transport has an option of the same name for controlling outgoing
18346 connections. This option is expanded for each connection, so can be varied for
18347 different clients if required. The value of this option must be a list of
18348 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18349 in somewhat different ways. If GnuTLS is being used, the client controls the
18350 preference order of the available ciphers. Details are given in sections
18351 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18355 .option tls_resumption_hosts main "host list&!!" unset
18356 .cindex TLS resumption
18357 This option controls which connections to offer the TLS resumption feature.
18358 See &<<SECTresumption>>& for details.
18362 .option tls_try_verify_hosts main "host list&!!" unset
18363 .cindex "TLS" "client certificate verification"
18364 .cindex "certificate" "verification of client"
18365 See &%tls_verify_hosts%& below.
18368 .option tls_verify_certificates main string&!! system
18369 .cindex "TLS" "client certificate verification"
18370 .cindex "certificate" "verification of client"
18371 The value of this option is expanded, and must then be either the
18373 or the absolute path to
18374 a file or directory containing permitted certificates for clients that
18375 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18377 The "system" value for the option will use a
18378 system default location compiled into the SSL library.
18379 This is not available for GnuTLS versions preceding 3.0.20,
18380 and will be taken as empty; an explicit location
18383 The use of a directory for the option value is not available for GnuTLS versions
18384 preceding 3.3.6 and a single file must be used.
18386 With OpenSSL the certificates specified
18388 either by file or directory
18389 are added to those given by the system default location.
18391 These certificates should be for the certificate authorities trusted, rather
18392 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18393 the value is a file then the certificates are sent by Exim as a server to
18394 connecting clients, defining the list of accepted certificate authorities.
18395 Thus the values defined should be considered public data. To avoid this,
18396 use the explicit directory version.
18398 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18400 A forced expansion failure or setting to an empty string is equivalent to
18404 .option tls_verify_hosts main "host list&!!" unset
18405 .cindex "TLS" "client certificate verification"
18406 .cindex "certificate" "verification of client"
18407 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18408 certificates from clients. The expected certificates are defined by
18409 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18410 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18411 &%tls_verify_certificates%& is not set.
18413 Any client that matches &%tls_verify_hosts%& is constrained by
18414 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18415 present one of the listed certificates. If it does not, the connection is
18416 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18417 the host to use TLS. It can still send SMTP commands through unencrypted
18418 connections. Forcing a client to use TLS has to be done separately using an
18419 ACL to reject inappropriate commands when the connection is not encrypted.
18421 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18422 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18423 certificate and checks it against &%tls_verify_certificates%&, but does not
18424 abort the connection if there is no certificate or if it does not match. This
18425 state can be detected in an ACL, which makes it possible to implement policies
18426 such as &"accept for relay only if a verified certificate has been received,
18427 but accept for local delivery if encrypted, even without a verified
18430 Client hosts that match neither of these lists are not asked to present
18434 .option trusted_groups main "string list&!!" unset
18435 .cindex "trusted groups"
18436 .cindex "groups" "trusted"
18437 This option is expanded just once, at the start of Exim's processing. If this
18438 option is set, any process that is running in one of the listed groups, or
18439 which has one of them as a supplementary group, is trusted. The groups can be
18440 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18441 details of what trusted callers are permitted to do. If neither
18442 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18445 .option trusted_users main "string list&!!" unset
18446 .cindex "trusted users"
18447 .cindex "user" "trusted"
18448 This option is expanded just once, at the start of Exim's processing. If this
18449 option is set, any process that is running as one of the listed users is
18450 trusted. The users can be specified numerically or by name. See section
18451 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18452 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18453 Exim user are trusted.
18455 .option unknown_login main string&!! unset
18456 .cindex "uid (user id)" "unknown caller"
18457 .vindex "&$caller_uid$&"
18458 This is a specialized feature for use in unusual configurations. By default, if
18459 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18460 gives up. The &%unknown_login%& option can be used to set a login name to be
18461 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18462 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18463 is used for the user's real name (gecos field), unless this has been set by the
18466 .option unknown_username main string unset
18467 See &%unknown_login%&.
18469 .option untrusted_set_sender main "address list&!!" unset
18470 .cindex "trusted users"
18471 .cindex "sender" "setting by untrusted user"
18472 .cindex "untrusted user setting sender"
18473 .cindex "user" "untrusted setting sender"
18474 .cindex "envelope from"
18475 .cindex "envelope sender"
18476 When an untrusted user submits a message to Exim using the standard input, Exim
18477 normally creates an envelope sender address from the user's login and the
18478 default qualification domain. Data from the &%-f%& option (for setting envelope
18479 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18480 is used) is ignored.
18482 However, untrusted users are permitted to set an empty envelope sender address,
18483 to declare that a message should never generate any bounces. For example:
18485 exim -f '<>' user@domain.example
18487 .vindex "&$sender_ident$&"
18488 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18489 other envelope sender addresses in a controlled way. When it is set, untrusted
18490 users are allowed to set envelope sender addresses that match any of the
18491 patterns in the list. Like all address lists, the string is expanded. The
18492 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18493 users to setting senders that start with their login ids
18494 followed by a hyphen
18495 by a setting like this:
18497 untrusted_set_sender = ^$sender_ident-
18499 If you want to allow untrusted users to set envelope sender addresses without
18500 restriction, you can use
18502 untrusted_set_sender = *
18504 The &%untrusted_set_sender%& option applies to all forms of local input, but
18505 only to the setting of the envelope sender. It does not permit untrusted users
18506 to use the other options which trusted user can use to override message
18507 parameters. Furthermore, it does not stop Exim from removing an existing
18508 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18509 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18510 overriding these actions. The handling of the &'Sender:'& header is also
18511 described in section &<<SECTthesenhea>>&.
18513 The log line for a message's arrival shows the envelope sender following
18514 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18515 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18516 envelope sender address, the user's login is shown in parentheses after the
18520 .option uucp_from_pattern main string "see below"
18521 .cindex "&""From""& line"
18522 .cindex "UUCP" "&""From""& line"
18523 Some applications that pass messages to an MTA via a command line interface use
18524 an initial line starting with &"From&~"& to pass the envelope sender. In
18525 particular, this is used by UUCP software. Exim recognizes such a line by means
18526 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18527 matches, the sender address is constructed by expanding the contents of
18528 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18529 default pattern recognizes lines in the following two forms:
18531 From ph10 Fri Jan 5 12:35 GMT 1996
18532 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18534 The pattern can be seen by running
18536 exim -bP uucp_from_pattern
18538 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18539 year in the second case. The first word after &"From&~"& is matched in the
18540 regular expression by a parenthesized subpattern. The default value for
18541 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18542 (&"ph10"& in the example above) as the message's sender. See also
18543 &%ignore_fromline_hosts%&.
18546 .option uucp_from_sender main string&!! &`$1`&
18547 See &%uucp_from_pattern%& above.
18550 .option warn_message_file main string&!! unset
18551 .cindex "warning of delay" "customizing the message"
18552 .cindex "customizing" "warning message"
18553 This option defines a template file containing paragraphs of text to be used
18554 for constructing the warning message which is sent by Exim when a message has
18555 been in the queue for a specified amount of time, as specified by
18556 &%delay_warning%&. Details of the file's contents are given in chapter
18557 &<<CHAPemsgcust>>&.
18559 .cindex warn_message_file "tainted data"
18560 The option is expanded to give the file path, which must be
18561 absolute and untainted.
18563 See also &%bounce_message_file%&.
18566 .option write_rejectlog main boolean true
18567 .cindex "reject log" "disabling"
18568 If this option is set false, Exim no longer writes anything to the reject log.
18569 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18570 .ecindex IIDconfima
18571 .ecindex IIDmaiconf
18576 . ////////////////////////////////////////////////////////////////////////////
18577 . ////////////////////////////////////////////////////////////////////////////
18579 .chapter "Generic options for routers" "CHAProutergeneric"
18580 .scindex IIDgenoprou1 "options" "generic; for routers"
18581 .scindex IIDgenoprou2 "generic options" "router"
18582 This chapter describes the generic options that apply to all routers.
18583 Those that are preconditions are marked with ‡ in the &"use"& field.
18585 For a general description of how a router operates, see sections
18586 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18587 which the preconditions are tested. The order of expansion of the options that
18588 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18589 &%headers_remove%&, &%transport%&.
18593 .option address_data routers string&!! unset
18594 .cindex "router" "data attached to address"
18595 The string is expanded just before the router is run, that is, after all the
18596 precondition tests have succeeded. If the expansion is forced to fail, the
18597 router declines, the value of &%address_data%& remains unchanged, and the
18598 &%more%& option controls what happens next. Other expansion failures cause
18599 delivery of the address to be deferred.
18601 .vindex "&$address_data$&"
18602 When the expansion succeeds, the value is retained with the address, and can be
18603 accessed using the variable &$address_data$& in the current router, subsequent
18604 routers, and the eventual transport.
18606 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18607 that runs a user's filter file, the contents of &$address_data$& are accessible
18608 in the filter. This is not normally a problem, because such data is usually
18609 either not confidential or it &"belongs"& to the current user, but if you do
18610 put confidential data into &$address_data$& you need to remember this point.
18612 Even if the router declines or passes, the value of &$address_data$& remains
18613 with the address, though it can be changed by another &%address_data%& setting
18614 on a subsequent router. If a router generates child addresses, the value of
18615 &$address_data$& propagates to them. This also applies to the special kind of
18616 &"child"& that is generated by a router with the &%unseen%& option.
18618 The idea of &%address_data%& is that you can use it to look up a lot of data
18619 for the address once, and then pick out parts of the data later. For example,
18620 you could use a single LDAP lookup to return a string of the form
18622 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18624 In the transport you could pick out the mailbox by a setting such as
18626 file = ${extract{mailbox}{$address_data}}
18628 This makes the configuration file less messy, and also reduces the number of
18629 lookups (though Exim does cache lookups).
18631 See also the &%set%& option below.
18633 .vindex "&$sender_address_data$&"
18634 .vindex "&$address_data$&"
18635 The &%address_data%& facility is also useful as a means of passing information
18636 from one router to another, and from a router to a transport. In addition, if
18637 &$address_data$& is set by a router when verifying a recipient address from an
18638 ACL, it remains available for use in the rest of the ACL statement. After
18639 verifying a sender, the value is transferred to &$sender_address_data$&.
18643 .option address_test routers&!? boolean true
18645 .cindex "router" "skipping when address testing"
18646 If this option is set false, the router is skipped when routing is being tested
18647 by means of the &%-bt%& command line option. This can be a convenience when
18648 your first router sends messages to an external scanner, because it saves you
18649 having to set the &"already scanned"& indicator when testing real address
18654 .option cannot_route_message routers string&!! unset
18655 .cindex "router" "customizing &""cannot route""& message"
18656 .cindex "customizing" "&""cannot route""& message"
18657 This option specifies a text message that is used when an address cannot be
18658 routed because Exim has run out of routers. The default message is
18659 &"Unrouteable address"&. This option is useful only on routers that have
18660 &%more%& set false, or on the very last router in a configuration, because the
18661 value that is used is taken from the last router that is considered. This
18662 includes a router that is skipped because its preconditions are not met, as
18663 well as a router that declines. For example, using the default configuration,
18666 cannot_route_message = Remote domain not found in DNS
18668 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18671 cannot_route_message = Unknown local user
18673 on the final router that checks for local users. If string expansion fails for
18674 this option, the default message is used. Unless the expansion failure was
18675 explicitly forced, a message about the failure is written to the main and panic
18676 logs, in addition to the normal message about the routing failure.
18679 .option caseful_local_part routers boolean false
18680 .cindex "case of local parts"
18681 .cindex "router" "case of local parts"
18682 By default, routers handle the local parts of addresses in a case-insensitive
18683 manner, though the actual case is preserved for transmission with the message.
18684 If you want the case of letters to be significant in a router, you must set
18685 this option true. For individual router options that contain address or local
18686 part lists (for example, &%local_parts%&), case-sensitive matching can be
18687 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18690 .vindex "&$local_part$&"
18691 .vindex "&$original_local_part$&"
18692 .vindex "&$parent_local_part$&"
18693 The value of the &$local_part$& variable is forced to lower case while a
18694 router is running unless &%caseful_local_part%& is set. When a router assigns
18695 an address to a transport, the value of &$local_part$& when the transport runs
18696 is the same as it was in the router. Similarly, when a router generates child
18697 addresses by aliasing or forwarding, the values of &$original_local_part$&
18698 and &$parent_local_part$& are those that were used by the redirecting router.
18700 This option applies to the processing of an address by a router. When a
18701 recipient address is being processed in an ACL, there is a separate &%control%&
18702 modifier that can be used to specify case-sensitive processing within the ACL
18703 (see section &<<SECTcontrols>>&).
18707 .option check_local_user routers&!? boolean false
18708 .cindex "local user, checking in router"
18709 .cindex "router" "checking for local user"
18710 .cindex "&_/etc/passwd_&"
18712 When this option is true, Exim checks that the local part of the recipient
18713 address (with affixes removed if relevant) is the name of an account on the
18714 local system. The check is done by calling the &[getpwnam()]& function rather
18715 than trying to read &_/etc/passwd_& directly. This means that other methods of
18716 holding password data (such as NIS) are supported. If the local part is a local
18717 user, &$home$& is set from the password data, and can be tested in other
18718 preconditions that are evaluated after this one (the order of evaluation is
18719 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18720 overridden by &%router_home_directory%&. If the local part is not a local user,
18721 the router is skipped.
18723 If you want to check that the local part is either the name of a local user
18724 or matches something else, you cannot combine &%check_local_user%& with a
18725 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18726 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18727 setting to achieve this. For example:
18729 local_parts = passwd;$local_part : lsearch;/etc/other/users
18731 Note, however, that the side effects of &%check_local_user%& (such as setting
18732 up a home directory) do not occur when a &(passwd)& lookup is used in a
18733 &%local_parts%& (or any other) precondition.
18737 .option condition routers&!? string&!! unset
18738 .cindex "router" "customized precondition"
18739 This option specifies a general precondition test that has to succeed for the
18740 router to be called. The &%condition%& option is the last precondition to be
18741 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18742 result is a forced failure, or an empty string, or one of the strings &"0"& or
18743 &"no"& or &"false"& (checked without regard to the case of the letters), the
18744 router is skipped, and the address is offered to the next one.
18746 If the result is any other value, the router is run (as this is the last
18747 precondition to be evaluated, all the other preconditions must be true).
18749 This option is unusual in that multiple &%condition%& options may be present.
18750 All &%condition%& options must succeed.
18752 The &%condition%& option provides a means of applying custom conditions to the
18753 running of routers. Note that in the case of a simple conditional expansion,
18754 the default expansion values are exactly what is wanted. For example:
18756 condition = ${if >{$message_age}{600}}
18758 Because of the default behaviour of the string expansion, this is equivalent to
18760 condition = ${if >{$message_age}{600}{true}{}}
18763 A multiple condition example, which succeeds:
18765 condition = ${if >{$message_age}{600}}
18766 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18770 If the expansion fails (other than forced failure) delivery is deferred. Some
18771 of the other precondition options are common special cases that could in fact
18772 be specified using &%condition%&.
18774 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18775 are far older, and use one set of semantics. ACLs are newer and when
18776 they were created, the ACL &%condition%& process was given far stricter
18777 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18778 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18779 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18780 Router rules processing behavior.
18782 This is best illustrated in an example:
18784 # If used in an ACL condition will fail with a syntax error, but
18785 # in a router condition any extra characters are treated as a string
18787 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18790 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18793 In each example above, the &%if%& statement actually ends after
18794 &"{google.com}}"&. Since no true or false braces were defined, the
18795 default &%if%& behavior is to return a boolean true or a null answer
18796 (which evaluates to false). The rest of the line is then treated as a
18797 string. So the first example resulted in the boolean answer &"true"&
18798 with the string &" {yes} {no}}"& appended to it. The second example
18799 resulted in the null output (indicating false) with the string
18800 &" {yes} {no}}"& appended to it.
18802 In fact you can put excess forward braces in too. In the router
18803 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18804 mean something, like after a &"$"& or when required as part of a
18805 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18808 Thus, in a Router, the above expansion strings will both always evaluate
18809 true, as the result of expansion is a non-empty string which doesn't
18810 match an explicit false value. This can be tricky to debug. By
18811 contrast, in an ACL either of those strings will always result in an
18812 expansion error because the result doesn't look sufficiently boolean.
18815 .option debug_print routers string&!! unset
18816 .cindex "testing" "variables in drivers"
18817 If this option is set and debugging is enabled (see the &%-d%& command line
18818 option) or in address-testing mode (see the &%-bt%& command line option),
18819 the string is expanded and included in the debugging output.
18820 If expansion of the string fails, the error message is written to the debugging
18821 output, and Exim carries on processing.
18822 This option is provided to help with checking out the values of variables and
18823 so on when debugging router configurations. For example, if a &%condition%&
18824 option appears not to be working, &%debug_print%& can be used to output the
18825 variables it references. The output happens after checks for &%domains%&,
18826 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18827 are tested. A newline is added to the text if it does not end with one.
18828 The variable &$router_name$& contains the name of the router.
18832 .option disable_logging routers boolean false
18833 If this option is set true, nothing is logged for any routing errors
18834 or for any deliveries caused by this router. You should not set this option
18835 unless you really, really know what you are doing. See also the generic
18836 transport option of the same name.
18838 .option dnssec_request_domains routers "domain list&!!" *
18839 .cindex "MX record" "security"
18840 .cindex "DNSSEC" "MX lookup"
18841 .cindex "security" "MX lookup"
18842 .cindex "DNS" "DNSSEC"
18843 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18844 the dnssec request bit set.
18845 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18847 .option dnssec_require_domains routers "domain list&!!" unset
18848 .cindex "MX record" "security"
18849 .cindex "DNSSEC" "MX lookup"
18850 .cindex "security" "MX lookup"
18851 .cindex "DNS" "DNSSEC"
18852 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
18853 the dnssec request bit set. Any returns not having the Authenticated Data bit
18854 (AD bit) set will be ignored and logged as a host-lookup failure.
18855 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18858 .option domains routers&!? "domain list&!!" unset
18859 .cindex "router" "restricting to specific domains"
18860 .vindex "&$domain_data$&"
18861 If this option is set, the router is skipped unless the current domain matches
18862 the list. If the match is achieved by means of a file lookup, the data that the
18863 lookup returned for the domain is placed in &$domain_data$& for use in string
18864 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
18865 a list of the order in which preconditions are evaluated.
18869 .option driver routers string unset
18870 This option must always be set. It specifies which of the available routers is
18874 .option dsn_lasthop routers boolean false
18875 .cindex "DSN" "success"
18876 .cindex "Delivery Status Notification" "success"
18877 If this option is set true, and extended DSN (RFC3461) processing is in effect,
18878 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
18879 instead send a success DSN as if the next hop does not support DSN.
18880 Not effective on redirect routers.
18884 .option errors_to routers string&!! unset
18885 .cindex "envelope from"
18886 .cindex "envelope sender"
18887 .cindex "router" "changing address for errors"
18888 If a router successfully handles an address, it may assign the address to a
18889 transport for delivery or it may generate child addresses. In both cases, if
18890 there is a delivery problem during later processing, the resulting bounce
18891 message is sent to the address that results from expanding this string,
18892 provided that the address verifies successfully. The &%errors_to%& option is
18893 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
18895 The &%errors_to%& setting associated with an address can be overridden if it
18896 subsequently passes through other routers that have their own &%errors_to%&
18897 settings, or if the message is delivered by a transport with a &%return_path%&
18900 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
18901 the expansion fails to verify, the errors address associated with the incoming
18902 address is used. At top level, this is the envelope sender. A non-forced
18903 expansion failure causes delivery to be deferred.
18905 If an address for which &%errors_to%& has been set ends up being delivered over
18906 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
18907 any bounces that are generated by other MTAs on the delivery route are also
18908 sent there. You can set &%errors_to%& to the empty string by either of these
18914 An expansion item that yields an empty string has the same effect. If you do
18915 this, a locally detected delivery error for addresses processed by this router
18916 no longer gives rise to a bounce message; the error is discarded. If the
18917 address is delivered to a remote host, the return path is set to &`<>`&, unless
18918 overridden by the &%return_path%& option on the transport.
18920 .vindex "&$address_data$&"
18921 If for some reason you want to discard local errors, but use a non-empty
18922 MAIL command for remote delivery, you can preserve the original return
18923 path in &$address_data$& in the router, and reinstate it in the transport by
18924 setting &%return_path%&.
18926 The most common use of &%errors_to%& is to direct mailing list bounces to the
18927 manager of the list, as described in section &<<SECTmailinglists>>&, or to
18928 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
18932 .option expn routers&!? boolean true
18933 .cindex "address" "testing"
18934 .cindex "testing" "addresses"
18935 .cindex "EXPN" "router skipping"
18936 .cindex "router" "skipping for EXPN"
18937 If this option is turned off, the router is skipped when testing an address
18938 as a result of processing an SMTP EXPN command. You might, for example,
18939 want to turn it off on a router for users' &_.forward_& files, while leaving it
18940 on for the system alias file.
18941 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18944 The use of the SMTP EXPN command is controlled by an ACL (see chapter
18945 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
18946 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
18950 .option fail_verify routers boolean false
18951 .cindex "router" "forcing verification failure"
18952 Setting this option has the effect of setting both &%fail_verify_sender%& and
18953 &%fail_verify_recipient%& to the same value.
18957 .option fail_verify_recipient routers boolean false
18958 If this option is true and an address is accepted by this router when
18959 verifying a recipient, verification fails.
18963 .option fail_verify_sender routers boolean false
18964 If this option is true and an address is accepted by this router when
18965 verifying a sender, verification fails.
18969 .option fallback_hosts routers "string list" unset
18970 .cindex "router" "fallback hosts"
18971 .cindex "fallback" "hosts specified on router"
18972 String expansion is not applied to this option. The argument must be a
18973 colon-separated list of host names or IP addresses. The list separator can be
18974 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
18975 each name or address. In fact, the format of each item is exactly the same as
18976 defined for the list of hosts in a &(manualroute)& router (see section
18977 &<<SECTformatonehostitem>>&).
18979 If a router queues an address for a remote transport, this host list is
18980 associated with the address, and used instead of the transport's fallback host
18981 list. If &%hosts_randomize%& is set on the transport, the order of the list is
18982 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
18983 transport for further details.
18986 .option group routers string&!! "see below"
18987 .cindex "gid (group id)" "local delivery"
18988 .cindex "local transports" "uid and gid"
18989 .cindex "transport" "local"
18990 .cindex "router" "setting group"
18991 When a router queues an address for a transport, and the transport does not
18992 specify a group, the group given here is used when running the delivery
18994 The group may be specified numerically or by name. If expansion fails, the
18995 error is logged and delivery is deferred.
18996 The default is unset, unless &%check_local_user%& is set, when the default
18997 is taken from the password information. See also &%initgroups%& and &%user%&
18998 and the discussion in chapter &<<CHAPenvironment>>&.
19002 .option headers_add routers list&!! unset
19003 .cindex "header lines" "adding"
19004 .cindex "router" "adding header lines"
19005 This option specifies a list of text headers,
19006 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19007 that is associated with any addresses that are accepted by the router.
19008 Each item is separately expanded, at routing time. However, this
19009 option has no effect when an address is just being verified. The way in which
19010 the text is used to add header lines at transport time is described in section
19011 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19012 message is in the process of being transported. This means that references to
19013 header lines in string expansions in the transport's configuration do not
19014 &"see"& the added header lines.
19016 The &%headers_add%& option is expanded after &%errors_to%&, but before
19017 &%headers_remove%& and &%transport%&. If an item is empty, or if
19018 an item expansion is forced to fail, the item has no effect. Other expansion
19019 failures are treated as configuration errors.
19021 Unlike most options, &%headers_add%& can be specified multiple times
19022 for a router; all listed headers are added.
19024 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19025 router that has the &%one_time%& option set.
19027 .cindex "duplicate addresses"
19028 .oindex "&%unseen%&"
19029 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19030 additions are deleted when the address is passed on to subsequent routers.
19031 For a &%redirect%& router, if a generated address is the same as the incoming
19032 address, this can lead to duplicate addresses with different header
19033 modifications. Exim does not do duplicate deliveries (except, in certain
19034 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19035 which of the duplicates is discarded, so this ambiguous situation should be
19036 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19040 .option headers_remove routers list&!! unset
19041 .cindex "header lines" "removing"
19042 .cindex "router" "removing header lines"
19043 This option specifies a list of text headers,
19044 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19045 that is associated with any addresses that are accepted by the router.
19046 However, the option has no effect when an address is just being verified.
19047 Each list item is separately expanded, at transport time.
19049 If an item ends in *, it will match any header with the given prefix.
19052 the text is used to remove header lines at transport time is described in
19053 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19054 the message is in the process of being transported. This means that references
19055 to header lines in string expansions in the transport's configuration still
19056 &"see"& the original header lines.
19058 The &%headers_remove%& option is handled after &%errors_to%& and
19059 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19060 the item has no effect. Other expansion failures are treated as configuration
19063 Unlike most options, &%headers_remove%& can be specified multiple times
19064 for a router; all listed headers are removed.
19066 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19067 router that has the &%one_time%& option set.
19069 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19070 removal requests are deleted when the address is passed on to subsequent
19071 routers, and this can lead to problems with duplicates -- see the similar
19072 warning for &%headers_add%& above.
19074 &*Warning 3*&: Because of the separate expansion of the list items,
19075 items that contain a list separator must have it doubled.
19076 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19080 .option ignore_target_hosts routers "host list&!!" unset
19081 .cindex "IP address" "discarding"
19082 .cindex "router" "discarding IP addresses"
19083 Although this option is a host list, it should normally contain IP address
19084 entries rather than names. If any host that is looked up by the router has an
19085 IP address that matches an item in this list, Exim behaves as if that IP
19086 address did not exist. This option allows you to cope with rogue DNS entries
19089 remote.domain.example. A 127.0.0.1
19093 ignore_target_hosts = 127.0.0.1
19095 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19096 discarded in this way, the router declines. In a conventional configuration, an
19097 attempt to mail to such a domain would normally provoke the &"unrouteable
19098 domain"& error, and an attempt to verify an address in the domain would fail.
19099 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19100 router declines if presented with one of the listed addresses.
19102 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19103 means of the first or the second of the following settings, respectively:
19105 ignore_target_hosts = 0.0.0.0/0
19106 ignore_target_hosts = <; 0::0/0
19108 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19109 in the second line matches all IPv6 addresses.
19111 This option may also be useful for ignoring link-local and site-local IPv6
19112 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19113 is expanded before use as a list, it is possible to make it dependent on the
19114 domain that is being routed.
19116 .vindex "&$host_address$&"
19117 During its expansion, &$host_address$& is set to the IP address that is being
19120 .option initgroups routers boolean false
19121 .cindex "additional groups"
19122 .cindex "groups" "additional"
19123 .cindex "local transports" "uid and gid"
19124 .cindex "transport" "local"
19125 If the router queues an address for a transport, and this option is true, and
19126 the uid supplied by the router is not overridden by the transport, the
19127 &[initgroups()]& function is called when running the transport to ensure that
19128 any additional groups associated with the uid are set up. See also &%group%&
19129 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19133 .option local_part_prefix routers&!? "string list" unset
19134 .cindex affix "router precondition"
19135 .cindex "router" "prefix for local part"
19136 .cindex "prefix" "for local part, used in router"
19137 If this option is set, the router is skipped unless the local part starts with
19138 one of the given strings, or &%local_part_prefix_optional%& is true. See
19139 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19142 The list is scanned from left to right, and the first prefix that matches is
19143 used. A limited form of wildcard is available; if the prefix begins with an
19144 asterisk, it matches the longest possible sequence of arbitrary characters at
19145 the start of the local part. An asterisk should therefore always be followed by
19146 some character that does not occur in normal local parts.
19147 .cindex "multiple mailboxes"
19148 .cindex "mailbox" "multiple"
19149 Wildcarding can be used to set up multiple user mailboxes, as described in
19150 section &<<SECTmulbox>>&.
19152 .vindex "&$local_part$&"
19153 .vindex "&$local_part_prefix$&"
19154 During the testing of the &%local_parts%& option, and while the router is
19155 running, the prefix is removed from the local part, and is available in the
19156 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19157 the router accepts the address, this remains true during subsequent delivery by
19158 a transport. In particular, the local part that is transmitted in the RCPT
19159 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19160 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19161 the relevant transport.
19164 .vindex &$local_part_prefix_v$&
19165 If wildcarding (above) was used then the part of the prefix matching the
19166 wildcard is available in &$local_part_prefix_v$&.
19169 When an address is being verified, &%local_part_prefix%& affects only the
19170 behaviour of the router. If the callout feature of verification is in use, this
19171 means that the full address, including the prefix, will be used during the
19174 The prefix facility is commonly used to handle local parts of the form
19175 &%owner-something%&. Another common use is to support local parts of the form
19176 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19177 to tell a user their forwarding is broken &-- by placing a router like this one
19178 immediately before the router that handles &_.forward_& files:
19182 local_part_prefix = real-
19184 transport = local_delivery
19186 For security, it would probably be a good idea to restrict the use of this
19187 router to locally-generated messages, using a condition such as this:
19189 condition = ${if match {$sender_host_address}\
19190 {\N^(|127\.0\.0\.1)$\N}}
19193 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19194 both conditions must be met if not optional. Care must be taken if wildcards
19195 are used in both a prefix and a suffix on the same router. Different
19196 separator characters must be used to avoid ambiguity.
19199 .option local_part_prefix_optional routers boolean false
19200 See &%local_part_prefix%& above.
19204 .option local_part_suffix routers&!? "string list" unset
19205 .cindex "router" "suffix for local part"
19206 .cindex "suffix for local part" "used in router"
19207 This option operates in the same way as &%local_part_prefix%&, except that the
19208 local part must end (rather than start) with the given string, the
19209 &%local_part_suffix_optional%& option determines whether the suffix is
19210 mandatory, and the wildcard * character, if present, must be the last
19211 character of the suffix. This option facility is commonly used to handle local
19212 parts of the form &%something-request%& and multiple user mailboxes of the form
19216 .option local_part_suffix_optional routers boolean false
19217 See &%local_part_suffix%& above.
19221 .option local_parts routers&!? "local part list&!!" unset
19222 .cindex "router" "restricting to specific local parts"
19223 .cindex "local part" "checking in router"
19224 The router is run only if the local part of the address matches the list.
19225 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19227 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19228 string is expanded, it is possible to make it depend on the domain, for
19231 local_parts = dbm;/usr/local/specials/$domain
19233 .vindex "&$local_part_data$&"
19234 If the match is achieved by a lookup, the data that the lookup returned
19235 for the local part is placed in the variable &$local_part_data$& for use in
19236 expansions of the router's private options. You might use this option, for
19237 example, if you have a large number of local virtual domains, and you want to
19238 send all postmaster mail to the same place without having to set up an alias in
19239 each virtual domain:
19243 local_parts = postmaster
19244 data = postmaster@real.domain.example
19248 .option log_as_local routers boolean "see below"
19249 .cindex "log" "delivery line"
19250 .cindex "delivery" "log line format"
19251 Exim has two logging styles for delivery, the idea being to make local
19252 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19253 recipient address is given just as the local part, without a domain. The use of
19254 this style is controlled by this option. It defaults to true for the &(accept)&
19255 router, and false for all the others. This option applies only when a
19256 router assigns an address to a transport. It has no effect on routers that
19257 redirect addresses.
19261 .option more routers boolean&!! true
19262 The result of string expansion for this option must be a valid boolean value,
19263 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19264 result causes an error, and delivery is deferred. If the expansion is forced to
19265 fail, the default value for the option (true) is used. Other failures cause
19266 delivery to be deferred.
19268 If this option is set false, and the router declines to handle the address, no
19269 further routers are tried, routing fails, and the address is bounced.
19271 However, if the router explicitly passes an address to the following router by
19272 means of the setting
19276 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19277 does not affect the behaviour if one of the precondition tests fails. In that
19278 case, the address is always passed to the next router.
19280 Note that &%address_data%& is not considered to be a precondition. If its
19281 expansion is forced to fail, the router declines, and the value of &%more%&
19282 controls what happens next.
19285 .option pass_on_timeout routers boolean false
19286 .cindex "timeout" "of router"
19287 .cindex "router" "timeout"
19288 If a router times out during a host lookup, it normally causes deferral of the
19289 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19290 router, overriding &%no_more%&. This may be helpful for systems that are
19291 intermittently connected to the Internet, or those that want to pass to a smart
19292 host any messages that cannot immediately be delivered.
19294 There are occasional other temporary errors that can occur while doing DNS
19295 lookups. They are treated in the same way as a timeout, and this option
19296 applies to all of them.
19300 .option pass_router routers string unset
19301 .cindex "router" "go to after &""pass""&"
19302 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19303 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19304 routing to continue, and overriding a false setting of &%more%&. When one of
19305 these routers returns &"pass"&, the address is normally handed on to the next
19306 router in sequence. This can be changed by setting &%pass_router%& to the name
19307 of another router. However (unlike &%redirect_router%&) the named router must
19308 be below the current router, to avoid loops. Note that this option applies only
19309 to the special case of &"pass"&. It does not apply when a router returns
19310 &"decline"& because it cannot handle an address.
19314 .option redirect_router routers string unset
19315 .cindex "router" "start at after redirection"
19316 Sometimes an administrator knows that it is pointless to reprocess addresses
19317 generated from alias or forward files with the same router again. For
19318 example, if an alias file translates real names into login ids there is no
19319 point searching the alias file a second time, especially if it is a large file.
19321 The &%redirect_router%& option can be set to the name of any router instance.
19322 It causes the routing of any generated addresses to start at the named router
19323 instead of at the first router. This option has no effect if the router in
19324 which it is set does not generate new addresses.
19328 .option require_files routers&!? "string list&!!" unset
19329 .cindex "file" "requiring for router"
19330 .cindex "router" "requiring file existence"
19331 This option provides a general mechanism for predicating the running of a
19332 router on the existence or non-existence of certain files or directories.
19333 Before running a router, as one of its precondition tests, Exim works its way
19334 through the &%require_files%& list, expanding each item separately.
19336 Because the list is split before expansion, any colons in expansion items must
19337 be doubled, or the facility for using a different list separator must be used
19338 (&<<SECTlistsepchange>>&).
19339 If any expansion is forced to fail, the item is ignored. Other expansion
19340 failures cause routing of the address to be deferred.
19342 If any expanded string is empty, it is ignored. Otherwise, except as described
19343 below, each string must be a fully qualified file path, optionally preceded by
19344 &"!"&. The paths are passed to the &[stat()]& function to test for the
19345 existence of the files or directories. The router is skipped if any paths not
19346 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19349 If &[stat()]& cannot determine whether a file exists or not, delivery of
19350 the message is deferred. This can happen when NFS-mounted filesystems are
19353 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19354 options, so you cannot use it to check for the existence of a file in which to
19355 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19356 full list of the order in which preconditions are evaluated.) However, as
19357 these options are all expanded, you can use the &%exists%& expansion condition
19358 to make such tests. The &%require_files%& option is intended for checking files
19359 that the router may be going to use internally, or which are needed by a
19360 transport (e.g., &_.procmailrc_&).
19362 During delivery, the &[stat()]& function is run as root, but there is a
19363 facility for some checking of the accessibility of a file by another user.
19364 This is not a proper permissions check, but just a &"rough"& check that
19365 operates as follows:
19367 If an item in a &%require_files%& list does not contain any forward slash
19368 characters, it is taken to be the user (and optional group, separated by a
19369 comma) to be checked for subsequent files in the list. If no group is specified
19370 but the user is specified symbolically, the gid associated with the uid is
19373 require_files = mail:/some/file
19374 require_files = $local_part_data:$home/.procmailrc
19376 If a user or group name in a &%require_files%& list does not exist, the
19377 &%require_files%& condition fails.
19379 Exim performs the check by scanning along the components of the file path, and
19380 checking the access for the given uid and gid. It checks for &"x"& access on
19381 directories, and &"r"& access on the final file. Note that this means that file
19382 access control lists, if the operating system has them, are ignored.
19384 &*Warning 1*&: When the router is being run to verify addresses for an
19385 incoming SMTP message, Exim is not running as root, but under its own uid. This
19386 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19387 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19388 user is not permitted to read one of the directories on the file's path.
19390 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19391 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19392 without root access. In this case, if a check for access by a particular user
19393 is requested, Exim creates a subprocess that runs as that user, and tries the
19394 check again in that process.
19396 The default action for handling an unresolved EACCES is to consider it to
19397 be caused by a configuration error, and routing is deferred because the
19398 existence or non-existence of the file cannot be determined. However, in some
19399 circumstances it may be desirable to treat this condition as if the file did
19400 not exist. If the filename (or the exclamation mark that precedes the filename
19401 for non-existence) is preceded by a plus sign, the EACCES error is treated
19402 as if the file did not exist. For example:
19404 require_files = +/some/file
19406 If the router is not an essential part of verification (for example, it
19407 handles users' &_.forward_& files), another solution is to set the &%verify%&
19408 option false so that the router is skipped when verifying.
19412 .option retry_use_local_part routers boolean "see below"
19413 .cindex "hints database" "retry keys"
19414 .cindex "local part" "in retry keys"
19415 When a delivery suffers a temporary routing failure, a retry record is created
19416 in Exim's hints database. For addresses whose routing depends only on the
19417 domain, the key for the retry record should not involve the local part, but for
19418 other addresses, both the domain and the local part should be included.
19419 Usually, remote routing is of the former kind, and local routing is of the
19422 This option controls whether the local part is used to form the key for retry
19423 hints for addresses that suffer temporary errors while being handled by this
19424 router. The default value is true for any router that has any of
19425 &%check_local_user%&,
19428 &%local_part_prefix%&,
19429 &%local_part_suffix%&,
19432 set, and false otherwise. Note that this option does not apply to hints keys
19433 for transport delays; they are controlled by a generic transport option of the
19436 Failing to set this option when it is needed
19437 (because a remote router handles only some of the local-parts for a domain)
19438 can result in incorrect error messages being generated.
19440 The setting of &%retry_use_local_part%& applies only to the router on which it
19441 appears. If the router generates child addresses, they are routed
19442 independently; this setting does not become attached to them.
19446 .option router_home_directory routers string&!! unset
19447 .cindex "router" "home directory for"
19448 .cindex "home directory" "for router"
19450 This option sets a home directory for use while the router is running. (Compare
19451 &%transport_home_directory%&, which sets a home directory for later
19452 transporting.) In particular, if used on a &(redirect)& router, this option
19453 sets a value for &$home$& while a filter is running. The value is expanded;
19454 forced expansion failure causes the option to be ignored &-- other failures
19455 cause the router to defer.
19457 Expansion of &%router_home_directory%& happens immediately after the
19458 &%check_local_user%& test (if configured), before any further expansions take
19460 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19462 While the router is running, &%router_home_directory%& overrides the value of
19463 &$home$& that came from &%check_local_user%&.
19465 When a router accepts an address and assigns it to a local transport (including
19466 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19467 delivery), the home directory setting for the transport is taken from the first
19468 of these values that is set:
19471 The &%home_directory%& option on the transport;
19473 The &%transport_home_directory%& option on the router;
19475 The password data if &%check_local_user%& is set on the router;
19477 The &%router_home_directory%& option on the router.
19480 In other words, &%router_home_directory%& overrides the password data for the
19481 router, but not for the transport.
19485 .option self routers string freeze
19486 .cindex "MX record" "pointing to local host"
19487 .cindex "local host" "MX pointing to"
19488 This option applies to those routers that use a recipient address to find a
19489 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19490 and &(manualroute)& routers.
19491 Certain configurations of the &(queryprogram)& router can also specify a list
19493 Usually such routers are configured to send the message to a remote host via an
19494 &(smtp)& transport. The &%self%& option specifies what happens when the first
19495 host on the list turns out to be the local host.
19496 The way in which Exim checks for the local host is described in section
19497 &<<SECTreclocipadd>>&.
19499 Normally this situation indicates either an error in Exim's configuration (for
19500 example, the router should be configured not to process this domain), or an
19501 error in the DNS (for example, the MX should not point to this host). For this
19502 reason, the default action is to log the incident, defer the address, and
19503 freeze the message. The following alternatives are provided for use in special
19508 Delivery of the message is tried again later, but the message is not frozen.
19510 .vitem "&%reroute%&: <&'domain'&>"
19511 The domain is changed to the given domain, and the address is passed back to
19512 be reprocessed by the routers. No rewriting of headers takes place. This
19513 behaviour is essentially a redirection.
19515 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19516 The domain is changed to the given domain, and the address is passed back to be
19517 reprocessed by the routers. Any headers that contain the original domain are
19522 .vindex "&$self_hostname$&"
19523 The router passes the address to the next router, or to the router named in the
19524 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19525 subsequent routing and delivery, the variable &$self_hostname$& contains the
19526 name of the local host that the router encountered. This can be used to
19527 distinguish between different cases for hosts with multiple names. The
19533 ensures that only those addresses that routed to the local host are passed on.
19534 Without &%no_more%&, addresses that were declined for other reasons would also
19535 be passed to the next router.
19538 Delivery fails and an error report is generated.
19541 .cindex "local host" "sending to"
19542 The anomaly is ignored and the address is queued for the transport. This
19543 setting should be used with extreme caution. For an &(smtp)& transport, it
19544 makes sense only in cases where the program that is listening on the SMTP port
19545 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19546 different configuration file that handles the domain in another way.
19551 .option senders routers&!? "address list&!!" unset
19552 .cindex "router" "checking senders"
19553 If this option is set, the router is skipped unless the message's sender
19554 address matches something on the list.
19555 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19558 There are issues concerning verification when the running of routers is
19559 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19560 setting, it sets the sender to the null string. When using the &%-bt%& option
19561 to check a configuration file, it is necessary also to use the &%-f%& option to
19562 set an appropriate sender. For incoming mail, the sender is unset when
19563 verifying the sender, but is available when verifying any recipients. If the
19564 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19568 .option set routers "string list" unset
19569 .cindex router variables
19570 This option may be used multiple times on a router;
19571 because of this the list aspect is mostly irrelevant.
19572 The list separator is a semicolon but can be changed in the
19575 Each list-element given must be of the form &"name = value"&
19576 and the names used must start with the string &"r_"&.
19577 Values containing a list-separator should have them doubled.
19578 When a router runs, the strings are evaluated in order,
19579 to create variables which are added to the set associated with
19581 The variable is set with the expansion of the value.
19582 The variables can be used by the router options
19583 (not including any preconditions)
19584 and by the transport.
19585 Later definitions of a given named variable will override former ones.
19586 Variable use is via the usual &$r_...$& syntax.
19588 This is similar to the &%address_data%& option, except that
19589 many independent variables can be used, with choice of naming.
19592 .option translate_ip_address routers string&!! unset
19593 .cindex "IP address" "translating"
19594 .cindex "packet radio"
19595 .cindex "router" "IP address translation"
19596 There exist some rare networking situations (for example, packet radio) where
19597 it is helpful to be able to translate IP addresses generated by normal routing
19598 mechanisms into other IP addresses, thus performing a kind of manual IP
19599 routing. This should be done only if the normal IP routing of the TCP/IP stack
19600 is inadequate or broken. Because this is an extremely uncommon requirement, the
19601 code to support this option is not included in the Exim binary unless
19602 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19604 .vindex "&$host_address$&"
19605 The &%translate_ip_address%& string is expanded for every IP address generated
19606 by the router, with the generated address set in &$host_address$&. If the
19607 expansion is forced to fail, no action is taken.
19608 For any other expansion error, delivery of the message is deferred.
19609 If the result of the expansion is an IP address, that replaces the original
19610 address; otherwise the result is assumed to be a host name &-- this is looked
19611 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19612 produce one or more replacement IP addresses. For example, to subvert all IP
19613 addresses in some specific networks, this could be added to a router:
19615 translate_ip_address = \
19616 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19619 The file would contain lines like
19621 10.2.3.128/26 some.host
19622 10.8.4.34/26 10.44.8.15
19624 You should not make use of this facility unless you really understand what you
19629 .option transport routers string&!! unset
19630 This option specifies the transport to be used when a router accepts an address
19631 and sets it up for delivery. A transport is never needed if a router is used
19632 only for verification. The value of the option is expanded at routing time,
19633 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19634 and result must be the name of one of the configured transports. If it is not,
19635 delivery is deferred.
19637 The &%transport%& option is not used by the &(redirect)& router, but it does
19638 have some private options that set up transports for pipe and file deliveries
19639 (see chapter &<<CHAPredirect>>&).
19643 .option transport_current_directory routers string&!! unset
19644 .cindex "current directory for local transport"
19645 This option associates a current directory with any address that is routed
19646 to a local transport. This can happen either because a transport is
19647 explicitly configured for the router, or because it generates a delivery to a
19648 file or a pipe. During the delivery process (that is, at transport time), this
19649 option string is expanded and is set as the current directory, unless
19650 overridden by a setting on the transport.
19651 If the expansion fails for any reason, including forced failure, an error is
19652 logged, and delivery is deferred.
19653 See chapter &<<CHAPenvironment>>& for details of the local delivery
19659 .option transport_home_directory routers string&!! "see below"
19660 .cindex "home directory" "for local transport"
19661 This option associates a home directory with any address that is routed to a
19662 local transport. This can happen either because a transport is explicitly
19663 configured for the router, or because it generates a delivery to a file or a
19664 pipe. During the delivery process (that is, at transport time), the option
19665 string is expanded and is set as the home directory, unless overridden by a
19666 setting of &%home_directory%& on the transport.
19667 If the expansion fails for any reason, including forced failure, an error is
19668 logged, and delivery is deferred.
19670 If the transport does not specify a home directory, and
19671 &%transport_home_directory%& is not set for the router, the home directory for
19672 the transport is taken from the password data if &%check_local_user%& is set for
19673 the router. Otherwise it is taken from &%router_home_directory%& if that option
19674 is set; if not, no home directory is set for the transport.
19676 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19682 .option unseen routers boolean&!! false
19683 .cindex "router" "carrying on after success"
19684 The result of string expansion for this option must be a valid boolean value,
19685 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19686 result causes an error, and delivery is deferred. If the expansion is forced to
19687 fail, the default value for the option (false) is used. Other failures cause
19688 delivery to be deferred.
19690 When this option is set true, routing does not cease if the router accepts the
19691 address. Instead, a copy of the incoming address is passed to the next router,
19692 overriding a false setting of &%more%&. There is little point in setting
19693 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19694 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19695 sometimes true and sometimes false).
19697 .cindex "copy of message (&%unseen%& option)"
19698 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19699 qualifier in filter files. It can be used to cause copies of messages to be
19700 delivered to some other destination, while also carrying out a normal delivery.
19701 In effect, the current address is made into a &"parent"& that has two children
19702 &-- one that is delivered as specified by this router, and a clone that goes on
19703 to be routed further. For this reason, &%unseen%& may not be combined with the
19704 &%one_time%& option in a &(redirect)& router.
19706 &*Warning*&: Header lines added to the address (or specified for removal) by
19707 this router or by previous routers affect the &"unseen"& copy of the message
19708 only. The clone that continues to be processed by further routers starts with
19709 no added headers and none specified for removal. For a &%redirect%& router, if
19710 a generated address is the same as the incoming address, this can lead to
19711 duplicate addresses with different header modifications. Exim does not do
19712 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19713 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19714 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19715 &%redirect%& router may be of help.
19717 Unlike the handling of header modifications, any data that was set by the
19718 &%address_data%& option in the current or previous routers &'is'& passed on to
19719 subsequent routers.
19722 .option user routers string&!! "see below"
19723 .cindex "uid (user id)" "local delivery"
19724 .cindex "local transports" "uid and gid"
19725 .cindex "transport" "local"
19726 .cindex "router" "user for filter processing"
19727 .cindex "filter" "user for processing"
19728 When a router queues an address for a transport, and the transport does not
19729 specify a user, the user given here is used when running the delivery process.
19730 The user may be specified numerically or by name. If expansion fails, the
19731 error is logged and delivery is deferred.
19732 This user is also used by the &(redirect)& router when running a filter file.
19733 The default is unset, except when &%check_local_user%& is set. In this case,
19734 the default is taken from the password information. If the user is specified as
19735 a name, and &%group%& is not set, the group associated with the user is used.
19736 See also &%initgroups%& and &%group%& and the discussion in chapter
19737 &<<CHAPenvironment>>&.
19741 .option verify routers&!? boolean true
19742 Setting this option has the effect of setting &%verify_sender%& and
19743 &%verify_recipient%& to the same value.
19746 .option verify_only routers&!? boolean false
19747 .cindex "EXPN" "with &%verify_only%&"
19749 .cindex "router" "used only when verifying"
19750 If this option is set, the router is used only when verifying an address,
19751 delivering in cutthrough mode or
19752 testing with the &%-bv%& option, not when actually doing a delivery, testing
19753 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19754 restricted to verifying only senders or recipients by means of
19755 &%verify_sender%& and &%verify_recipient%&.
19757 &*Warning*&: When the router is being run to verify addresses for an incoming
19758 SMTP message, Exim is not running as root, but under its own uid. If the router
19759 accesses any files, you need to make sure that they are accessible to the Exim
19763 .option verify_recipient routers&!? boolean true
19764 If this option is false, the router is skipped when verifying recipient
19766 delivering in cutthrough mode
19767 or testing recipient verification using &%-bv%&.
19768 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19770 See also the &$verify_mode$& variable.
19773 .option verify_sender routers&!? boolean true
19774 If this option is false, the router is skipped when verifying sender addresses
19775 or testing sender verification using &%-bvs%&.
19776 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19778 See also the &$verify_mode$& variable.
19779 .ecindex IIDgenoprou1
19780 .ecindex IIDgenoprou2
19787 . ////////////////////////////////////////////////////////////////////////////
19788 . ////////////////////////////////////////////////////////////////////////////
19790 .chapter "The accept router" "CHID4"
19791 .cindex "&(accept)& router"
19792 .cindex "routers" "&(accept)&"
19793 The &(accept)& router has no private options of its own. Unless it is being
19794 used purely for verification (see &%verify_only%&) a transport is required to
19795 be defined by the generic &%transport%& option. If the preconditions that are
19796 specified by generic options are met, the router accepts the address and queues
19797 it for the given transport. The most common use of this router is for setting
19798 up deliveries to local mailboxes. For example:
19802 domains = mydomain.example
19804 transport = local_delivery
19806 The &%domains%& condition in this example checks the domain of the address, and
19807 &%check_local_user%& checks that the local part is the login of a local user.
19808 When both preconditions are met, the &(accept)& router runs, and queues the
19809 address for the &(local_delivery)& transport.
19816 . ////////////////////////////////////////////////////////////////////////////
19817 . ////////////////////////////////////////////////////////////////////////////
19819 .chapter "The dnslookup router" "CHAPdnslookup"
19820 .scindex IIDdnsrou1 "&(dnslookup)& router"
19821 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19822 The &(dnslookup)& router looks up the hosts that handle mail for the
19823 recipient's domain in the DNS. A transport must always be set for this router,
19824 unless &%verify_only%& is set.
19826 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19827 SRV records. If none are found, or if SRV support is not configured,
19828 MX records are looked up. If no MX records exist, address records are sought.
19829 However, &%mx_domains%& can be set to disable the direct use of address
19832 MX records of equal priority are sorted by Exim into a random order. Exim then
19833 looks for address records for the host names obtained from MX or SRV records.
19834 When a host has more than one IP address, they are sorted into a random order,
19835 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19836 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19837 generic option, the router declines.
19839 Unless they have the highest priority (lowest MX value), MX records that point
19840 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19841 are discarded, together with any other MX records of equal or lower priority.
19843 .cindex "MX record" "pointing to local host"
19844 .cindex "local host" "MX pointing to"
19845 .oindex "&%self%&" "in &(dnslookup)& router"
19846 If the host pointed to by the highest priority MX record, or looked up as an
19847 address record, is the local host, or matches &%hosts_treat_as_local%&, what
19848 happens is controlled by the generic &%self%& option.
19851 .section "Problems with DNS lookups" "SECTprowitdnsloo"
19852 There have been problems with DNS servers when SRV records are looked up.
19853 Some misbehaving servers return a DNS error or timeout when a non-existent
19854 SRV record is sought. Similar problems have in the past been reported for
19855 MX records. The global &%dns_again_means_nonexist%& option can help with this
19856 problem, but it is heavy-handed because it is a global option.
19858 For this reason, there are two options, &%srv_fail_domains%& and
19859 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
19860 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
19861 an attempt to look up an SRV or MX record causes one of these results, and the
19862 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
19863 such record"&. In the case of an SRV lookup, this means that the router
19864 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
19865 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
19866 case routing fails.
19869 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
19870 .cindex "&(dnslookup)& router" "declines"
19871 There are a few cases where a &(dnslookup)& router will decline to accept
19872 an address; if such a router is expected to handle "all remaining non-local
19873 domains", then it is important to set &%no_more%&.
19875 The router will defer rather than decline if the domain
19876 is found in the &%fail_defer_domains%& router option.
19878 Reasons for a &(dnslookup)& router to decline currently include:
19880 The domain does not exist in DNS
19882 The domain exists but the MX record's host part is just "."; this is a common
19883 convention (borrowed from SRV) used to indicate that there is no such service
19884 for this domain and to not fall back to trying A/AAAA records.
19886 Ditto, but for SRV records, when &%check_srv%& is set on this router.
19888 MX record points to a non-existent host.
19890 MX record points to an IP address and the main section option
19891 &%allow_mx_to_ip%& is not set.
19893 MX records exist and point to valid hosts, but all hosts resolve only to
19894 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
19896 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
19897 &%dns_check_names_pattern%& for handling one variant of this)
19899 &%check_secondary_mx%& is set on this router but the local host can
19900 not be found in the MX records (see below)
19906 .section "Private options for dnslookup" "SECID118"
19907 .cindex "options" "&(dnslookup)& router"
19908 The private options for the &(dnslookup)& router are as follows:
19910 .option check_secondary_mx dnslookup boolean false
19911 .cindex "MX record" "checking for secondary"
19912 If this option is set, the router declines unless the local host is found in
19913 (and removed from) the list of hosts obtained by MX lookup. This can be used to
19914 process domains for which the local host is a secondary mail exchanger
19915 differently to other domains. The way in which Exim decides whether a host is
19916 the local host is described in section &<<SECTreclocipadd>>&.
19919 .option check_srv dnslookup string&!! unset
19920 .cindex "SRV record" "enabling use of"
19921 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
19922 addition to MX and address records. The support is disabled by default. To
19923 enable SRV support, set the &%check_srv%& option to the name of the service
19924 required. For example,
19928 looks for SRV records that refer to the normal smtp service. The option is
19929 expanded, so the service name can vary from message to message or address
19930 to address. This might be helpful if SRV records are being used for a
19931 submission service. If the expansion is forced to fail, the &%check_srv%&
19932 option is ignored, and the router proceeds to look for MX records in the
19935 When the expansion succeeds, the router searches first for SRV records for
19936 the given service (it assumes TCP protocol). A single SRV record with a
19937 host name that consists of just a single dot indicates &"no such service for
19938 this domain"&; if this is encountered, the router declines. If other kinds of
19939 SRV record are found, they are used to construct a host list for delivery
19940 according to the rules of RFC 2782. MX records are not sought in this case.
19942 When no SRV records are found, MX records (and address records) are sought in
19943 the traditional way. In other words, SRV records take precedence over MX
19944 records, just as MX records take precedence over address records. Note that
19945 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
19946 defined it. It is apparently believed that MX records are sufficient for email
19947 and that SRV records should not be used for this purpose. However, SRV records
19948 have an additional &"weight"& feature which some people might find useful when
19949 trying to split an SMTP load between hosts of different power.
19951 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
19952 when there is a DNS lookup error.
19957 .option fail_defer_domains dnslookup "domain list&!!" unset
19958 .cindex "MX record" "not found"
19959 DNS lookups for domains matching &%fail_defer_domains%&
19960 which find no matching record will cause the router to defer
19961 rather than the default behaviour of decline.
19962 This maybe be useful for queueing messages for a newly created
19963 domain while the DNS configuration is not ready.
19964 However, it will result in any message with mistyped domains
19968 .option ipv4_only "string&!!" unset
19969 .cindex IPv6 disabling
19970 .cindex DNS "IPv6 disabling"
19971 The string is expanded, and if the result is anything but a forced failure,
19972 or an empty string, or one of the strings “0” or “no” or “false”
19973 (checked without regard to the case of the letters),
19974 only A records are used.
19976 .option ipv4_prefer "string&!!" unset
19977 .cindex IPv4 preference
19978 .cindex DNS "IPv4 preference"
19979 The string is expanded, and if the result is anything but a forced failure,
19980 or an empty string, or one of the strings “0” or “no” or “false”
19981 (checked without regard to the case of the letters),
19982 A records are sorted before AAAA records (inverting the default).
19984 .option mx_domains dnslookup "domain list&!!" unset
19985 .cindex "MX record" "required to exist"
19986 .cindex "SRV record" "required to exist"
19987 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
19988 record in order to be recognized. (The name of this option could be improved.)
19989 For example, if all the mail hosts in &'fict.example'& are known to have MX
19990 records, except for those in &'discworld.fict.example'&, you could use this
19993 mx_domains = ! *.discworld.fict.example : *.fict.example
19995 This specifies that messages addressed to a domain that matches the list but
19996 has no MX record should be bounced immediately instead of being routed using
19997 the address record.
20000 .option mx_fail_domains dnslookup "domain list&!!" unset
20001 If the DNS lookup for MX records for one of the domains in this list causes a
20002 DNS lookup error, Exim behaves as if no MX records were found. See section
20003 &<<SECTprowitdnsloo>>& for more discussion.
20008 .option qualify_single dnslookup boolean true
20009 .cindex "DNS" "resolver options"
20010 .cindex "DNS" "qualifying single-component names"
20011 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20012 lookups. Typically, but not standardly, this causes the resolver to qualify
20013 single-component names with the default domain. For example, on a machine
20014 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20015 &'thesaurus.ref.example'& inside the resolver. For details of what your
20016 resolver actually does, consult your man pages for &'resolver'& and
20021 .option rewrite_headers dnslookup boolean true
20022 .cindex "rewriting" "header lines"
20023 .cindex "header lines" "rewriting"
20024 If the domain name in the address that is being processed is not fully
20025 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20026 an address is specified as &'dormouse@teaparty'&, the domain might be
20027 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20028 occur as a result of setting the &%widen_domains%& option. If
20029 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20030 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20031 header lines of the message are rewritten with the full domain name.
20033 This option should be turned off only when it is known that no message is
20034 ever going to be sent outside an environment where the abbreviation makes
20037 When an MX record is looked up in the DNS and matches a wildcard record, name
20038 servers normally return a record containing the name that has been looked up,
20039 making it impossible to detect whether a wildcard was present or not. However,
20040 some name servers have recently been seen to return the wildcard entry. If the
20041 name returned by a DNS lookup begins with an asterisk, it is not used for
20045 .option same_domain_copy_routing dnslookup boolean false
20046 .cindex "address" "copying routing"
20047 Addresses with the same domain are normally routed by the &(dnslookup)& router
20048 to the same list of hosts. However, this cannot be presumed, because the router
20049 options and preconditions may refer to the local part of the address. By
20050 default, therefore, Exim routes each address in a message independently. DNS
20051 servers run caches, so repeated DNS lookups are not normally expensive, and in
20052 any case, personal messages rarely have more than a few recipients.
20054 If you are running mailing lists with large numbers of subscribers at the same
20055 domain, and you are using a &(dnslookup)& router which is independent of the
20056 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20057 lookups for identical domains in one message. In this case, when &(dnslookup)&
20058 routes an address to a remote transport, any other unrouted addresses in the
20059 message that have the same domain are automatically given the same routing
20060 without processing them independently,
20061 provided the following conditions are met:
20064 No router that processed the address specified &%headers_add%& or
20065 &%headers_remove%&.
20067 The router did not change the address in any way, for example, by &"widening"&
20074 .option search_parents dnslookup boolean false
20075 .cindex "DNS" "resolver options"
20076 When this option is true, the resolver option RES_DNSRCH is set for DNS
20077 lookups. This is different from the &%qualify_single%& option in that it
20078 applies to domains containing dots. Typically, but not standardly, it causes
20079 the resolver to search for the name in the current domain and in parent
20080 domains. For example, on a machine in the &'fict.example'& domain, if looking
20081 up &'teaparty.wonderland'& failed, the resolver would try
20082 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20083 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20085 Setting this option true can cause problems in domains that have a wildcard MX
20086 record, because any domain that does not have its own MX record matches the
20091 .option srv_fail_domains dnslookup "domain list&!!" unset
20092 If the DNS lookup for SRV records for one of the domains in this list causes a
20093 DNS lookup error, Exim behaves as if no SRV records were found. See section
20094 &<<SECTprowitdnsloo>>& for more discussion.
20099 .option widen_domains dnslookup "string list" unset
20100 .cindex "domain" "partial; widening"
20101 If a DNS lookup fails and this option is set, each of its strings in turn is
20102 added onto the end of the domain, and the lookup is tried again. For example,
20105 widen_domains = fict.example:ref.example
20107 is set and a lookup of &'klingon.dictionary'& fails,
20108 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20109 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20110 and &%search_parents%& options can cause some widening to be undertaken inside
20111 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20112 when verifying, unless &%rewrite_headers%& is false (not the default).
20115 .section "Effect of qualify_single and search_parents" "SECID119"
20116 When a domain from an envelope recipient is changed by the resolver as a result
20117 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20118 corresponding address in the message's header lines unless &%rewrite_headers%&
20119 is set false. Exim then re-routes the address, using the full domain.
20121 These two options affect only the DNS lookup that takes place inside the router
20122 for the domain of the address that is being routed. They do not affect lookups
20123 such as that implied by
20127 that may happen while processing a router precondition before the router is
20128 entered. No widening ever takes place for these lookups.
20129 .ecindex IIDdnsrou1
20130 .ecindex IIDdnsrou2
20140 . ////////////////////////////////////////////////////////////////////////////
20141 . ////////////////////////////////////////////////////////////////////////////
20143 .chapter "The ipliteral router" "CHID5"
20144 .cindex "&(ipliteral)& router"
20145 .cindex "domain literal" "routing"
20146 .cindex "routers" "&(ipliteral)&"
20147 This router has no private options. Unless it is being used purely for
20148 verification (see &%verify_only%&) a transport is required to be defined by the
20149 generic &%transport%& option. The router accepts the address if its domain part
20150 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20151 router handles the address
20155 by setting up delivery to the host with that IP address. IPv4 domain literals
20156 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20157 are similar, but the address is preceded by &`ipv6:`&. For example:
20159 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20161 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20162 grounds that sooner or later somebody will try it.
20164 .oindex "&%self%&" "in &(ipliteral)& router"
20165 If the IP address matches something in &%ignore_target_hosts%&, the router
20166 declines. If an IP literal turns out to refer to the local host, the generic
20167 &%self%& option determines what happens.
20169 The RFCs require support for domain literals; however, their use is
20170 controversial in today's Internet. If you want to use this router, you must
20171 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20172 Exim will not recognize the domain literal syntax in addresses.
20176 . ////////////////////////////////////////////////////////////////////////////
20177 . ////////////////////////////////////////////////////////////////////////////
20179 .chapter "The iplookup router" "CHID6"
20180 .cindex "&(iplookup)& router"
20181 .cindex "routers" "&(iplookup)&"
20182 The &(iplookup)& router was written to fulfil a specific requirement in
20183 Cambridge University (which in fact no longer exists). For this reason, it is
20184 not included in the binary of Exim by default. If you want to include it, you
20187 ROUTER_IPLOOKUP=yes
20189 in your &_Local/Makefile_& configuration file.
20191 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20192 connection to one or more specific hosts. The host can then return the same or
20193 a different address &-- in effect rewriting the recipient address in the
20194 message's envelope. The new address is then passed on to subsequent routers. If
20195 this process fails, the address can be passed on to other routers, or delivery
20196 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20197 must not be specified for it.
20199 .cindex "options" "&(iplookup)& router"
20200 .option hosts iplookup string unset
20201 This option must be supplied. Its value is a colon-separated list of host
20202 names. The hosts are looked up using &[gethostbyname()]&
20203 (or &[getipnodebyname()]& when available)
20204 and are tried in order until one responds to the query. If none respond, what
20205 happens is controlled by &%optional%&.
20208 .option optional iplookup boolean false
20209 If &%optional%& is true, if no response is obtained from any host, the address
20210 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20211 delivery to the address is deferred.
20214 .option port iplookup integer 0
20215 .cindex "port" "&(iplookup)& router"
20216 This option must be supplied. It specifies the port number for the TCP or UDP
20220 .option protocol iplookup string udp
20221 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20222 protocols is to be used.
20225 .option query iplookup string&!! "see below"
20226 This defines the content of the query that is sent to the remote hosts. The
20229 $local_part@$domain $local_part@$domain
20231 The repetition serves as a way of checking that a response is to the correct
20232 query in the default case (see &%response_pattern%& below).
20235 .option reroute iplookup string&!! unset
20236 If this option is not set, the rerouted address is precisely the byte string
20237 returned by the remote host, up to the first white space, if any. If set, the
20238 string is expanded to form the rerouted address. It can include parts matched
20239 in the response by &%response_pattern%& by means of numeric variables such as
20240 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20241 whether or not a pattern is in use. In all cases, the rerouted address must end
20242 up in the form &'local_part@domain'&.
20245 .option response_pattern iplookup string unset
20246 This option can be set to a regular expression that is applied to the string
20247 returned from the remote host. If the pattern does not match the response, the
20248 router declines. If &%response_pattern%& is not set, no checking of the
20249 response is done, unless the query was defaulted, in which case there is a
20250 check that the text returned after the first white space is the original
20251 address. This checks that the answer that has been received is in response to
20252 the correct question. For example, if the response is just a new domain, the
20253 following could be used:
20255 response_pattern = ^([^@]+)$
20256 reroute = $local_part@$1
20259 .option timeout iplookup time 5s
20260 This specifies the amount of time to wait for a response from the remote
20261 machine. The same timeout is used for the &[connect()]& function for a TCP
20262 call. It does not apply to UDP.
20267 . ////////////////////////////////////////////////////////////////////////////
20268 . ////////////////////////////////////////////////////////////////////////////
20270 .chapter "The manualroute router" "CHID7"
20271 .scindex IIDmanrou1 "&(manualroute)& router"
20272 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20273 .cindex "domain" "manually routing"
20274 The &(manualroute)& router is so-called because it provides a way of manually
20275 routing an address according to its domain. It is mainly used when you want to
20276 route addresses to remote hosts according to your own rules, bypassing the
20277 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20278 route to local transports, a facility that may be useful if you want to save
20279 messages for dial-in hosts in local files.
20281 The &(manualroute)& router compares a list of domain patterns with the domain
20282 it is trying to route. If there is no match, the router declines. Each pattern
20283 has associated with it a list of hosts and some other optional data, which may
20284 include a transport. The combination of a pattern and its data is called a
20285 &"routing rule"&. For patterns that do not have an associated transport, the
20286 generic &%transport%& option must specify a transport, unless the router is
20287 being used purely for verification (see &%verify_only%&).
20290 In the case of verification, matching the domain pattern is sufficient for the
20291 router to accept the address. When actually routing an address for delivery,
20292 an address that matches a domain pattern is queued for the associated
20293 transport. If the transport is not a local one, a host list must be associated
20294 with the pattern; IP addresses are looked up for the hosts, and these are
20295 passed to the transport along with the mail address. For local transports, a
20296 host list is optional. If it is present, it is passed in &$host$& as a single
20299 The list of routing rules can be provided as an inline string in
20300 &%route_list%&, or the data can be obtained by looking up the domain in a file
20301 or database by setting &%route_data%&. Only one of these settings may appear in
20302 any one instance of &(manualroute)&. The format of routing rules is described
20303 below, following the list of private options.
20306 .section "Private options for manualroute" "SECTprioptman"
20308 .cindex "options" "&(manualroute)& router"
20309 The private options for the &(manualroute)& router are as follows:
20311 .option host_all_ignored manualroute string defer
20312 See &%host_find_failed%&.
20314 .option host_find_failed manualroute string freeze
20315 This option controls what happens when &(manualroute)& tries to find an IP
20316 address for a host, and the host does not exist. The option can be set to one
20317 of the following values:
20326 The default (&"freeze"&) assumes that this state is a serious configuration
20327 error. The difference between &"pass"& and &"decline"& is that the former
20328 forces the address to be passed to the next router (or the router defined by
20331 overriding &%no_more%&, whereas the latter passes the address to the next
20332 router only if &%more%& is true.
20334 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20335 cannot be found. If all the hosts in the list are ignored, the behaviour is
20336 controlled by the &%host_all_ignored%& option. This takes the same values
20337 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20339 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20340 state; if a host lookup gets a temporary error, delivery is deferred unless the
20341 generic &%pass_on_timeout%& option is set.
20344 .option hosts_randomize manualroute boolean false
20345 .cindex "randomized host list"
20346 .cindex "host" "list of; randomized"
20347 If this option is set, the order of the items in a host list in a routing rule
20348 is randomized each time the list is used, unless an option in the routing rule
20349 overrides (see below). Randomizing the order of a host list can be used to do
20350 crude load sharing. However, if more than one mail address is routed by the
20351 same router to the same host list, the host lists are considered to be the same
20352 (even though they may be randomized into different orders) for the purpose of
20353 deciding whether to batch the deliveries into a single SMTP transaction.
20355 When &%hosts_randomize%& is true, a host list may be split
20356 into groups whose order is separately randomized. This makes it possible to
20357 set up MX-like behaviour. The boundaries between groups are indicated by an
20358 item that is just &`+`& in the host list. For example:
20360 route_list = * host1:host2:host3:+:host4:host5
20362 The order of the first three hosts and the order of the last two hosts is
20363 randomized for each use, but the first three always end up before the last two.
20364 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20365 randomized host list is passed to an &(smtp)& transport that also has
20366 &%hosts_randomize set%&, the list is not re-randomized.
20369 .option route_data manualroute string&!! unset
20370 If this option is set, it must expand to yield the data part of a routing rule.
20371 Typically, the expansion string includes a lookup based on the domain. For
20374 route_data = ${lookup{$domain}dbm{/etc/routes}}
20376 If the expansion is forced to fail, or the result is an empty string, the
20377 router declines. Other kinds of expansion failure cause delivery to be
20381 .option route_list manualroute "string list" unset
20382 This string is a list of routing rules, in the form defined below. Note that,
20383 unlike most string lists, the items are separated by semicolons. This is so
20384 that they may contain colon-separated host lists.
20387 .option same_domain_copy_routing manualroute boolean false
20388 .cindex "address" "copying routing"
20389 Addresses with the same domain are normally routed by the &(manualroute)&
20390 router to the same list of hosts. However, this cannot be presumed, because the
20391 router options and preconditions may refer to the local part of the address. By
20392 default, therefore, Exim routes each address in a message independently. DNS
20393 servers run caches, so repeated DNS lookups are not normally expensive, and in
20394 any case, personal messages rarely have more than a few recipients.
20396 If you are running mailing lists with large numbers of subscribers at the same
20397 domain, and you are using a &(manualroute)& router which is independent of the
20398 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20399 lookups for identical domains in one message. In this case, when
20400 &(manualroute)& routes an address to a remote transport, any other unrouted
20401 addresses in the message that have the same domain are automatically given the
20402 same routing without processing them independently. However, this is only done
20403 if &%headers_add%& and &%headers_remove%& are unset.
20408 .section "Routing rules in route_list" "SECID120"
20409 The value of &%route_list%& is a string consisting of a sequence of routing
20410 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20411 entered as two semicolons. Alternatively, the list separator can be changed as
20412 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20413 Empty rules are ignored. The format of each rule is
20415 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20417 The following example contains two rules, each with a simple domain pattern and
20421 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20422 thes.ref.example mail-3.ref.example:mail-4.ref.example
20424 The three parts of a rule are separated by white space. The pattern and the
20425 list of hosts can be enclosed in quotes if necessary, and if they are, the
20426 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20427 single domain pattern, which is the only mandatory item in the rule. The
20428 pattern is in the same format as one item in a domain list (see section
20429 &<<SECTdomainlist>>&),
20430 except that it may not be the name of an interpolated file.
20431 That is, it may be wildcarded, or a regular expression, or a file or database
20432 lookup (with semicolons doubled, because of the use of semicolon as a separator
20433 in a &%route_list%&).
20435 The rules in &%route_list%& are searched in order until one of the patterns
20436 matches the domain that is being routed. The list of hosts and then options are
20437 then used as described below. If there is no match, the router declines. When
20438 &%route_list%& is set, &%route_data%& must not be set.
20442 .section "Routing rules in route_data" "SECID121"
20443 The use of &%route_list%& is convenient when there are only a small number of
20444 routing rules. For larger numbers, it is easier to use a file or database to
20445 hold the routing information, and use the &%route_data%& option instead.
20446 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20447 Most commonly, &%route_data%& is set as a string that contains an
20448 expansion lookup. For example, suppose we place two routing rules in a file
20451 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20452 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20454 This data can be accessed by setting
20456 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20458 Failure of the lookup results in an empty string, causing the router to
20459 decline. However, you do not have to use a lookup in &%route_data%&. The only
20460 requirement is that the result of expanding the string is a list of hosts,
20461 possibly followed by options, separated by white space. The list of hosts must
20462 be enclosed in quotes if it contains white space.
20467 .section "Format of the list of hosts" "SECID122"
20468 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20469 always separately expanded before use. If the expansion fails, the router
20470 declines. The result of the expansion must be a colon-separated list of names
20471 and/or IP addresses, optionally also including ports.
20472 If the list is written with spaces, it must be protected with quotes.
20473 The format of each item
20474 in the list is described in the next section. The list separator can be changed
20475 as described in section &<<SECTlistsepchange>>&.
20477 If the list of hosts was obtained from a &%route_list%& item, the following
20478 variables are set during its expansion:
20481 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20482 If the domain was matched against a regular expression, the numeric variables
20483 &$1$&, &$2$&, etc. may be set. For example:
20485 route_list = ^domain(\d+) host-$1.text.example
20488 &$0$& is always set to the entire domain.
20490 &$1$& is also set when partial matching is done in a file lookup.
20493 .vindex "&$value$&"
20494 If the pattern that matched the domain was a lookup item, the data that was
20495 looked up is available in the expansion variable &$value$&. For example:
20497 route_list = lsearch;;/some/file.routes $value
20501 Note the doubling of the semicolon in the pattern that is necessary because
20502 semicolon is the default route list separator.
20506 .section "Format of one host item" "SECTformatonehostitem"
20507 Each item in the list of hosts can be either a host name or an IP address,
20508 optionally with an attached port number, or it can be a single "+"
20509 (see &%hosts_randomize%&).
20510 When no port is given, an IP address
20511 is not enclosed in brackets. When a port is specified, it overrides the port
20512 specification on the transport. The port is separated from the name or address
20513 by a colon. This leads to some complications:
20516 Because colon is the default separator for the list of hosts, either
20517 the colon that specifies a port must be doubled, or the list separator must
20518 be changed. The following two examples have the same effect:
20520 route_list = * "host1.tld::1225 : host2.tld::1226"
20521 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20524 When IPv6 addresses are involved, it gets worse, because they contain
20525 colons of their own. To make this case easier, it is permitted to
20526 enclose an IP address (either v4 or v6) in square brackets if a port
20527 number follows. For example:
20529 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20533 .section "How the list of hosts is used" "SECThostshowused"
20534 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20535 the hosts is tried, in the order specified, when carrying out the SMTP
20536 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20537 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20540 Hosts may be listed by name or by IP address. An unadorned name in the list of
20541 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20542 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20543 records in the DNS. For example:
20545 route_list = * x.y.z:p.q.r/MX:e.f.g
20547 If this feature is used with a port specifier, the port must come last. For
20550 route_list = * dom1.tld/mx::1225
20552 If the &%hosts_randomize%& option is set, the order of the items in the list is
20553 randomized before any lookups are done. Exim then scans the list; for any name
20554 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20555 be an interface on the local host and the item is not the first in the list,
20556 Exim discards it and any subsequent items. If it is the first item, what
20557 happens is controlled by the
20558 .oindex "&%self%&" "in &(manualroute)& router"
20559 &%self%& option of the router.
20561 A name on the list that is followed by &`/MX`& is replaced with the list of
20562 hosts obtained by looking up MX records for the name. This is always a DNS
20563 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20564 below) are not relevant here. The order of these hosts is determined by the
20565 preference values in the MX records, according to the usual rules. Because
20566 randomizing happens before the MX lookup, it does not affect the order that is
20567 defined by MX preferences.
20569 If the local host is present in the sublist obtained from MX records, but is
20570 not the most preferred host in that list, it and any equally or less
20571 preferred hosts are removed before the sublist is inserted into the main list.
20573 If the local host is the most preferred host in the MX list, what happens
20574 depends on where in the original list of hosts the &`/MX`& item appears. If it
20575 is not the first item (that is, there are previous hosts in the main list),
20576 Exim discards this name and any subsequent items in the main list.
20578 If the MX item is first in the list of hosts, and the local host is the
20579 most preferred host, what happens is controlled by the &%self%& option of the
20582 DNS failures when lookup up the MX records are treated in the same way as DNS
20583 failures when looking up IP addresses: &%pass_on_timeout%& and
20584 &%host_find_failed%& are used when relevant.
20586 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20587 whether obtained from an MX lookup or not.
20591 .section "How the options are used" "SECThowoptused"
20592 The options are a sequence of words, space-separated.
20593 One of the words can be the name of a transport; this overrides the
20594 &%transport%& option on the router for this particular routing rule only. The
20595 other words (if present) control randomization of the list of hosts on a
20596 per-rule basis, and how the IP addresses of the hosts are to be found when
20597 routing to a remote transport. These options are as follows:
20600 &%randomize%&: randomize the order of the hosts in this list, overriding the
20601 setting of &%hosts_randomize%& for this routing rule only.
20603 &%no_randomize%&: do not randomize the order of the hosts in this list,
20604 overriding the setting of &%hosts_randomize%& for this routing rule only.
20606 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20607 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20608 also look in &_/etc/hosts_& or other sources of information.
20610 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20611 no address records are found. If there is a temporary DNS error (such as a
20612 timeout), delivery is deferred.
20614 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20616 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20621 route_list = domain1 host1:host2:host3 randomize bydns;\
20622 domain2 host4:host5
20624 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20625 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20626 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20627 or &[gethostbyname()]&, and the result of the lookup is the result of that
20630 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20631 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20632 instead of TRY_AGAIN. That is why the default action is to try a DNS
20633 lookup first. Only if that gives a definite &"no such host"& is the local
20636 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20637 inadvertent constraint that a transport name as an option had to be the last
20642 If no IP address for a host can be found, what happens is controlled by the
20643 &%host_find_failed%& option.
20646 When an address is routed to a local transport, IP addresses are not looked up.
20647 The host list is passed to the transport in the &$host$& variable.
20651 .section "Manualroute examples" "SECID123"
20652 In some of the examples that follow, the presence of the &%remote_smtp%&
20653 transport, as defined in the default configuration file, is assumed:
20656 .cindex "smart host" "example router"
20657 The &(manualroute)& router can be used to forward all external mail to a
20658 &'smart host'&. If you have set up, in the main part of the configuration, a
20659 named domain list that contains your local domains, for example:
20661 domainlist local_domains = my.domain.example
20663 You can arrange for all other domains to be routed to a smart host by making
20664 your first router something like this:
20667 driver = manualroute
20668 domains = !+local_domains
20669 transport = remote_smtp
20670 route_list = * smarthost.ref.example
20672 This causes all non-local addresses to be sent to the single host
20673 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20674 they are tried in order
20675 (but you can use &%hosts_randomize%& to vary the order each time).
20676 Another way of configuring the same thing is this:
20679 driver = manualroute
20680 transport = remote_smtp
20681 route_list = !+local_domains smarthost.ref.example
20683 There is no difference in behaviour between these two routers as they stand.
20684 However, they behave differently if &%no_more%& is added to them. In the first
20685 example, the router is skipped if the domain does not match the &%domains%&
20686 precondition; the following router is always tried. If the router runs, it
20687 always matches the domain and so can never decline. Therefore, &%no_more%&
20688 would have no effect. In the second case, the router is never skipped; it
20689 always runs. However, if it doesn't match the domain, it declines. In this case
20690 &%no_more%& would prevent subsequent routers from running.
20693 .cindex "mail hub example"
20694 A &'mail hub'& is a host which receives mail for a number of domains via MX
20695 records in the DNS and delivers it via its own private routing mechanism. Often
20696 the final destinations are behind a firewall, with the mail hub being the one
20697 machine that can connect to machines both inside and outside the firewall. The
20698 &(manualroute)& router is usually used on a mail hub to route incoming messages
20699 to the correct hosts. For a small number of domains, the routing can be inline,
20700 using the &%route_list%& option, but for a larger number a file or database
20701 lookup is easier to manage.
20703 If the domain names are in fact the names of the machines to which the mail is
20704 to be sent by the mail hub, the configuration can be quite simple. For
20708 driver = manualroute
20709 transport = remote_smtp
20710 route_list = *.rhodes.tvs.example $domain
20712 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20713 whose names are the same as the mail domains. A similar approach can be taken
20714 if the host name can be obtained from the domain name by a string manipulation
20715 that the expansion facilities can handle. Otherwise, a lookup based on the
20716 domain can be used to find the host:
20719 driver = manualroute
20720 transport = remote_smtp
20721 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20723 The result of the lookup must be the name or IP address of the host (or
20724 hosts) to which the address is to be routed. If the lookup fails, the route
20725 data is empty, causing the router to decline. The address then passes to the
20729 .cindex "batched SMTP output example"
20730 .cindex "SMTP" "batched outgoing; example"
20731 You can use &(manualroute)& to deliver messages to pipes or files in batched
20732 SMTP format for onward transportation by some other means. This is one way of
20733 storing mail for a dial-up host when it is not connected. The route list entry
20734 can be as simple as a single domain name in a configuration like this:
20737 driver = manualroute
20738 transport = batchsmtp_appendfile
20739 route_list = saved.domain.example
20741 though often a pattern is used to pick up more than one domain. If there are
20742 several domains or groups of domains with different transport requirements,
20743 different transports can be listed in the routing information:
20746 driver = manualroute
20748 *.saved.domain1.example $domain batch_appendfile; \
20749 *.saved.domain2.example \
20750 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20753 .vindex "&$domain$&"
20755 The first of these just passes the domain in the &$host$& variable, which
20756 doesn't achieve much (since it is also in &$domain$&), but the second does a
20757 file lookup to find a value to pass, causing the router to decline to handle
20758 the address if the lookup fails.
20761 .cindex "UUCP" "example of router for"
20762 Routing mail directly to UUCP software is a specific case of the use of
20763 &(manualroute)& in a gateway to another mail environment. This is an example of
20764 one way it can be done:
20770 command = /usr/local/bin/uux -r - \
20771 ${substr_-5:$host}!rmail ${local_part}
20772 return_fail_output = true
20777 driver = manualroute
20779 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20781 The file &_/usr/local/exim/uucphosts_& contains entries like
20783 darksite.ethereal.example: darksite.UUCP
20785 It can be set up more simply without adding and removing &".UUCP"& but this way
20786 makes clear the distinction between the domain name
20787 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20789 .ecindex IIDmanrou1
20790 .ecindex IIDmanrou2
20799 . ////////////////////////////////////////////////////////////////////////////
20800 . ////////////////////////////////////////////////////////////////////////////
20802 .chapter "The queryprogram router" "CHAPdriverlast"
20803 .scindex IIDquerou1 "&(queryprogram)& router"
20804 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20805 .cindex "routing" "by external program"
20806 The &(queryprogram)& router routes an address by running an external command
20807 and acting on its output. This is an expensive way to route, and is intended
20808 mainly for use in lightly-loaded systems, or for performing experiments.
20809 However, if it is possible to use the precondition options (&%domains%&,
20810 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20811 be used in special cases, even on a busy host. There are the following private
20813 .cindex "options" "&(queryprogram)& router"
20815 .option command queryprogram string&!! unset
20816 This option must be set. It specifies the command that is to be run. The
20817 command is split up into a command name and arguments, and then each is
20818 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20819 &<<CHAPpipetransport>>&).
20822 .option command_group queryprogram string unset
20823 .cindex "gid (group id)" "in &(queryprogram)& router"
20824 This option specifies a gid to be set when running the command while routing an
20825 address for deliver. It must be set if &%command_user%& specifies a numerical
20826 uid. If it begins with a digit, it is interpreted as the numerical value of the
20827 gid. Otherwise it is looked up using &[getgrnam()]&.
20830 .option command_user queryprogram string unset
20831 .cindex "uid (user id)" "for &(queryprogram)&"
20832 This option must be set. It specifies the uid which is set when running the
20833 command while routing an address for delivery. If the value begins with a digit,
20834 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20835 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20836 not set, a value for the gid also.
20838 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20839 root, which it does during a normal delivery in a conventional configuration.
20840 However, when an address is being verified during message reception, Exim is
20841 usually running as the Exim user, not as root. If the &(queryprogram)& router
20842 is called from a non-root process, Exim cannot change uid or gid before running
20843 the command. In this circumstance the command runs under the current uid and
20847 .option current_directory queryprogram string /
20848 This option specifies an absolute path which is made the current directory
20849 before running the command.
20852 .option timeout queryprogram time 1h
20853 If the command does not complete within the timeout period, its process group
20854 is killed and the message is frozen. A value of zero time specifies no
20858 The standard output of the command is connected to a pipe, which is read when
20859 the command terminates. It should consist of a single line of output,
20860 containing up to five fields, separated by white space. The maximum length of
20861 the line is 1023 characters. Longer lines are silently truncated. The first
20862 field is one of the following words (case-insensitive):
20865 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
20868 &'Decline'&: the router declines; pass the address to the next router, unless
20869 &%no_more%& is set.
20871 &'Fail'&: routing failed; do not pass the address to any more routers. Any
20872 subsequent text on the line is an error message. If the router is run as part
20873 of address verification during an incoming SMTP message, the message is
20874 included in the SMTP response.
20876 &'Defer'&: routing could not be completed at this time; try again later. Any
20877 subsequent text on the line is an error message which is logged. It is not
20878 included in any SMTP response.
20880 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
20882 &'Pass'&: pass the address to the next router (or the router specified by
20883 &%pass_router%&), overriding &%no_more%&.
20885 &'Redirect'&: the message is redirected. The remainder of the line is a list of
20886 new addresses, which are routed independently, starting with the first router,
20887 or the router specified by &%redirect_router%&, if set.
20890 When the first word is &'accept'&, the remainder of the line consists of a
20891 number of keyed data values, as follows (split into two lines here, to fit on
20894 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
20895 LOOKUP=byname|bydns DATA=<text>
20897 The data items can be given in any order, and all are optional. If no transport
20898 is included, the transport specified by the generic &%transport%& option is
20899 used. The list of hosts and the lookup type are needed only if the transport is
20900 an &(smtp)& transport that does not itself supply a list of hosts.
20902 The format of the list of hosts is the same as for the &(manualroute)& router.
20903 As well as host names and IP addresses with optional port numbers, as described
20904 in section &<<SECTformatonehostitem>>&, it may contain names followed by
20905 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
20906 (see section &<<SECThostshowused>>&).
20908 If the lookup type is not specified, Exim behaves as follows when trying to
20909 find an IP address for each host: First, a DNS lookup is done. If this yields
20910 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
20911 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
20912 result of the lookup is the result of that call.
20914 .vindex "&$address_data$&"
20915 If the DATA field is set, its value is placed in the &$address_data$&
20916 variable. For example, this return line
20918 accept hosts=x1.y.example:x2.y.example data="rule1"
20920 routes the address to the default transport, passing a list of two hosts. When
20921 the transport runs, the string &"rule1"& is in &$address_data$&.
20922 .ecindex IIDquerou1
20923 .ecindex IIDquerou2
20928 . ////////////////////////////////////////////////////////////////////////////
20929 . ////////////////////////////////////////////////////////////////////////////
20931 .chapter "The redirect router" "CHAPredirect"
20932 .scindex IIDredrou1 "&(redirect)& router"
20933 .scindex IIDredrou2 "routers" "&(redirect)&"
20934 .cindex "alias file" "in a &(redirect)& router"
20935 .cindex "address redirection" "&(redirect)& router"
20936 The &(redirect)& router handles several kinds of address redirection. Its most
20937 common uses are for resolving local part aliases from a central alias file
20938 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
20939 files, but it has many other potential uses. The incoming address can be
20940 redirected in several different ways:
20943 It can be replaced by one or more new addresses which are themselves routed
20946 It can be routed to be delivered to a given file or directory.
20948 It can be routed to be delivered to a specified pipe command.
20950 It can cause an automatic reply to be generated.
20952 It can be forced to fail, optionally with a custom error message.
20954 It can be temporarily deferred, optionally with a custom message.
20956 It can be discarded.
20959 The generic &%transport%& option must not be set for &(redirect)& routers.
20960 However, there are some private options which define transports for delivery to
20961 files and pipes, and for generating autoreplies. See the &%file_transport%&,
20962 &%pipe_transport%& and &%reply_transport%& descriptions below.
20964 If success DSNs have been requested
20965 .cindex "DSN" "success"
20966 .cindex "Delivery Status Notification" "success"
20967 redirection triggers one and the DSN options are not passed any further.
20971 .section "Redirection data" "SECID124"
20972 The router operates by interpreting a text string which it obtains either by
20973 expanding the contents of the &%data%& option, or by reading the entire
20974 contents of a file whose name is given in the &%file%& option. These two
20975 options are mutually exclusive. The first is commonly used for handling system
20976 aliases, in a configuration like this:
20980 data = ${lookup{$local_part}lsearch{/etc/aliases}}
20982 If the lookup fails, the expanded string in this example is empty. When the
20983 expansion of &%data%& results in an empty string, the router declines. A forced
20984 expansion failure also causes the router to decline; other expansion failures
20985 cause delivery to be deferred.
20987 A configuration using &%file%& is commonly used for handling users'
20988 &_.forward_& files, like this:
20993 file = $home/.forward
20996 If the file does not exist, or causes no action to be taken (for example, it is
20997 empty or consists only of comments), the router declines. &*Warning*&: This
20998 is not the case when the file contains syntactically valid items that happen to
20999 yield empty addresses, for example, items containing only RFC 2822 address
21003 .cindex "tainted data" "in filenames"
21004 .cindex redirect "tainted data"
21005 Tainted data may not be used for a filename.
21007 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21008 directly for redirection,
21009 as they are provided by a potential attacker.
21010 In the examples above, &$local_part$& is used for looking up data held locally
21011 on the system, and not used directly (the second example derives &$home$& via
21012 the passsword file or database, using &$local_part$&).
21017 .section "Forward files and address verification" "SECID125"
21018 .cindex "address redirection" "while verifying"
21019 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21020 &_.forward_& files, as in the example above. There are two reasons for this:
21023 When Exim is receiving an incoming SMTP message from a remote host, it is
21024 running under the Exim uid, not as root. Exim is unable to change uid to read
21025 the file as the user, and it may not be able to read it as the Exim user. So in
21026 practice the router may not be able to operate.
21028 However, even when the router can operate, the existence of a &_.forward_& file
21029 is unimportant when verifying an address. What should be checked is whether the
21030 local part is a valid user name or not. Cutting out the redirection processing
21031 saves some resources.
21039 .section "Interpreting redirection data" "SECID126"
21040 .cindex "Sieve filter" "specifying in redirection data"
21041 .cindex "filter" "specifying in redirection data"
21042 The contents of the data string, whether obtained from &%data%& or &%file%&,
21043 can be interpreted in two different ways:
21046 If the &%allow_filter%& option is set true, and the data begins with the text
21047 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21048 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21049 respectively. Details of the syntax and semantics of filter files are described
21050 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21051 document is intended for use by end users.
21053 Otherwise, the data must be a comma-separated list of redirection items, as
21054 described in the next section.
21057 When a message is redirected to a file (a &"mail folder"&), the filename given
21058 in a non-filter redirection list must always be an absolute path. A filter may
21059 generate a relative path &-- how this is handled depends on the transport's
21060 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21061 for the &(appendfile)& transport.
21065 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21066 .cindex "address redirection" "non-filter list items"
21067 When the redirection data is not an Exim or Sieve filter, for example, if it
21068 comes from a conventional alias or forward file, it consists of a list of
21069 addresses, filenames, pipe commands, or certain special items (see section
21070 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21071 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21072 depending on their default values. The items in the list are separated by
21073 commas or newlines.
21074 If a comma is required in an item, the entire item must be enclosed in double
21077 Lines starting with a # character are comments, and are ignored, and # may
21078 also appear following a comma, in which case everything between the # and the
21079 next newline character is ignored.
21081 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21082 double quotes are retained because some forms of mail address require their use
21083 (but never to enclose the entire address). In the following description,
21084 &"item"& refers to what remains after any surrounding double quotes have been
21087 .vindex "&$local_part$&"
21088 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21089 and the expansion contains a reference to &$local_part$&, you should make use
21090 of the &%quote_local_part%& expansion operator, in case the local part contains
21091 special characters. For example, to redirect all mail for the domain
21092 &'obsolete.example'&, retaining the existing local part, you could use this
21095 data = ${quote_local_part:$local_part}@newdomain.example
21099 .section "Redirecting to a local mailbox" "SECTredlocmai"
21100 .cindex "routing" "loops in"
21101 .cindex "loop" "while routing, avoidance of"
21102 .cindex "address redirection" "to local mailbox"
21103 A redirection item may safely be the same as the address currently under
21104 consideration. This does not cause a routing loop, because a router is
21105 automatically skipped if any ancestor of the address that is being processed
21106 is the same as the current address and was processed by the current router.
21107 Such an address is therefore passed to the following routers, so it is handled
21108 as if there were no redirection. When making this loop-avoidance test, the
21109 complete local part, including any prefix or suffix, is used.
21111 .cindex "address redirection" "local part without domain"
21112 Specifying the same local part without a domain is a common usage in personal
21113 filter files when the user wants to have messages delivered to the local
21114 mailbox and also forwarded elsewhere. For example, the user whose login is
21115 &'cleo'& might have a &_.forward_& file containing this:
21117 cleo, cleopatra@egypt.example
21119 .cindex "backslash in alias file"
21120 .cindex "alias file" "backslash in"
21121 For compatibility with other MTAs, such unqualified local parts may be
21122 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21123 it does make a difference if more than one domain is being handled
21126 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21127 2822 address that does not include a domain, the item is qualified using the
21128 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21129 addresses are qualified using the value in &%qualify_recipient%&, but you can
21130 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21132 Care must be taken if there are alias names for local users.
21133 Consider an MTA handling a single local domain where the system alias file
21138 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21139 messages in the local mailbox, and also forward copies elsewhere. He creates
21142 Sam.Reman, spqr@reme.elsewhere.example
21144 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21145 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21146 second time round, because it has previously routed it,
21147 and the following routers presumably cannot handle the alias. The forward file
21148 should really contain
21150 spqr, spqr@reme.elsewhere.example
21152 but because this is such a common error, the &%check_ancestor%& option (see
21153 below) exists to provide a way to get round it. This is normally set on a
21154 &(redirect)& router that is handling users' &_.forward_& files.
21158 .section "Special items in redirection lists" "SECTspecitredli"
21159 In addition to addresses, the following types of item may appear in redirection
21160 lists (that is, in non-filter redirection data):
21163 .cindex "pipe" "in redirection list"
21164 .cindex "address redirection" "to pipe"
21165 An item is treated as a pipe command if it begins with &"|"& and does not parse
21166 as a valid RFC 2822 address that includes a domain. A transport for running the
21167 command must be specified by the &%pipe_transport%& option.
21168 Normally, either the router or the transport specifies a user and a group under
21169 which to run the delivery. The default is to use the Exim user and group.
21171 Single or double quotes can be used for enclosing the individual arguments of
21172 the pipe command; no interpretation of escapes is done for single quotes. If
21173 the command contains a comma character, it is necessary to put the whole item
21174 in double quotes, for example:
21176 "|/some/command ready,steady,go"
21178 since items in redirection lists are terminated by commas. Do not, however,
21179 quote just the command. An item such as
21181 |"/some/command ready,steady,go"
21183 is interpreted as a pipe with a rather strange command name, and no arguments.
21185 Note that the above example assumes that the text comes from a lookup source
21186 of some sort, so that the quotes are part of the data. If composing a
21187 redirect router with a &%data%& option directly specifying this command, the
21188 quotes will be used by the configuration parser to define the extent of one
21189 string, but will not be passed down into the redirect router itself. There
21190 are two main approaches to get around this: escape quotes to be part of the
21191 data itself, or avoid using this mechanism and instead create a custom
21192 transport with the &%command%& option set and reference that transport from
21193 an &%accept%& router.
21196 .cindex "file" "in redirection list"
21197 .cindex "address redirection" "to file"
21198 An item is interpreted as a path name if it begins with &"/"& and does not
21199 parse as a valid RFC 2822 address that includes a domain. For example,
21201 /home/world/minbari
21203 is treated as a filename, but
21205 /s=molari/o=babylon/@x400gate.way
21207 is treated as an address. For a filename, a transport must be specified using
21208 the &%file_transport%& option. However, if the generated path name ends with a
21209 forward slash character, it is interpreted as a directory name rather than a
21210 filename, and &%directory_transport%& is used instead.
21212 Normally, either the router or the transport specifies a user and a group under
21213 which to run the delivery. The default is to use the Exim user and group.
21215 .cindex "&_/dev/null_&"
21216 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21217 bypassed at a high level, and the log entry shows &"**bypassed**"&
21218 instead of a transport name. In this case the user and group are not used.
21221 .cindex "included address list"
21222 .cindex "address redirection" "included external list"
21223 If an item is of the form
21225 :include:<path name>
21227 a list of further items is taken from the given file and included at that
21228 point. &*Note*&: Such a file can not be a filter file; it is just an
21229 out-of-line addition to the list. The items in the included list are separated
21230 by commas or newlines and are not subject to expansion. If this is the first
21231 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21232 the alias name. This example is incorrect:
21234 list1 :include:/opt/lists/list1
21236 It must be given as
21238 list1: :include:/opt/lists/list1
21241 .cindex "tainted data" "in filenames"
21242 .cindex redirect "tainted data"
21243 Tainted data may not be used for a filename.
21246 .cindex "address redirection" "to black hole"
21247 .cindex "delivery" "discard"
21248 .cindex "delivery" "blackhole"
21249 .cindex "black hole"
21250 .cindex "abandoning mail"
21251 Sometimes you want to throw away mail to a particular local part. Making the
21252 &%data%& option expand to an empty string does not work, because that causes
21253 the router to decline. Instead, the alias item
21257 can be used. It does what its name implies. No delivery is
21258 done, and no error message is generated. This has the same effect as specifying
21259 &_/dev/null_& as a destination, but it can be independently disabled.
21261 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21262 delivery is done for the original local part, even if other redirection items
21263 are present. If you are generating a multi-item list (for example, by reading a
21264 database) and need the ability to provide a no-op item, you must use
21268 .cindex "delivery" "forcing failure"
21269 .cindex "delivery" "forcing deferral"
21270 .cindex "failing delivery" "forcing"
21271 .cindex "deferred delivery, forcing"
21272 .cindex "customizing" "failure message"
21273 An attempt to deliver a particular address can be deferred or forced to fail by
21274 redirection items of the form
21279 respectively. When a redirection list contains such an item, it applies
21280 to the entire redirection; any other items in the list are ignored. Any
21281 text following &':fail:'& or &':defer:'& is placed in the error text
21282 associated with the failure. For example, an alias file might contain:
21284 X.Employee: :fail: Gone away, no forwarding address
21286 In the case of an address that is being verified from an ACL or as the subject
21288 .cindex "VRFY" "error text, display of"
21289 VRFY command, the text is included in the SMTP error response by
21291 .cindex "EXPN" "error text, display of"
21292 The text is not included in the response to an EXPN command. In non-SMTP cases
21293 the text is included in the error message that Exim generates.
21295 .cindex "SMTP" "error codes"
21296 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21297 &':fail:'&. However, if the message starts with three digits followed by a
21298 space, optionally followed by an extended code of the form &'n.n.n'&, also
21299 followed by a space, and the very first digit is the same as the default error
21300 code, the code from the message is used instead. If the very first digit is
21301 incorrect, a panic error is logged, and the default code is used. You can
21302 suppress the use of the supplied code in a redirect router by setting the
21303 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21306 .vindex "&$acl_verify_message$&"
21307 In an ACL, an explicitly provided message overrides the default, but the
21308 default message is available in the variable &$acl_verify_message$& and can
21309 therefore be included in a custom message if this is desired.
21311 Normally the error text is the rest of the redirection list &-- a comma does
21312 not terminate it &-- but a newline does act as a terminator. Newlines are not
21313 normally present in alias expansions. In &(lsearch)& lookups they are removed
21314 as part of the continuation process, but they may exist in other kinds of
21315 lookup and in &':include:'& files.
21317 During routing for message delivery (as opposed to verification), a redirection
21318 containing &':fail:'& causes an immediate failure of the incoming address,
21319 whereas &':defer:'& causes the message to remain in the queue so that a
21320 subsequent delivery attempt can happen at a later time. If an address is
21321 deferred for too long, it will ultimately fail, because the normal retry
21325 .cindex "alias file" "exception to default"
21326 Sometimes it is useful to use a single-key search type with a default (see
21327 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21328 for exceptions to the default. These can be handled by aliasing them to
21329 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21330 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21331 results in an empty redirection list has the same effect.
21335 .section "Duplicate addresses" "SECTdupaddr"
21336 .cindex "duplicate addresses"
21337 .cindex "address duplicate, discarding"
21338 .cindex "pipe" "duplicated"
21339 Exim removes duplicate addresses from the list to which it is delivering, so as
21340 to deliver just one copy to each address. This does not apply to deliveries
21341 routed to pipes by different immediate parent addresses, but an indirect
21342 aliasing scheme of the type
21344 pipe: |/some/command $local_part
21348 does not work with a message that is addressed to both local parts, because
21349 when the second is aliased to the intermediate local part &"pipe"& it gets
21350 discarded as being the same as a previously handled address. However, a scheme
21353 localpart1: |/some/command $local_part
21354 localpart2: |/some/command $local_part
21356 does result in two different pipe deliveries, because the immediate parents of
21357 the pipes are distinct.
21361 .section "Repeated redirection expansion" "SECID128"
21362 .cindex "repeated redirection expansion"
21363 .cindex "address redirection" "repeated for each delivery attempt"
21364 When a message cannot be delivered to all of its recipients immediately,
21365 leading to two or more delivery attempts, redirection expansion is carried out
21366 afresh each time for those addresses whose children were not all previously
21367 delivered. If redirection is being used as a mailing list, this can lead to new
21368 members of the list receiving copies of old messages. The &%one_time%& option
21369 can be used to avoid this.
21372 .section "Errors in redirection lists" "SECID129"
21373 .cindex "address redirection" "errors"
21374 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21375 error is skipped, and an entry is written to the main log. This may be useful
21376 for mailing lists that are automatically managed. Otherwise, if an error is
21377 detected while generating the list of new addresses, the original address is
21378 deferred. See also &%syntax_errors_to%&.
21382 .section "Private options for the redirect router" "SECID130"
21384 .cindex "options" "&(redirect)& router"
21385 The private options for the &(redirect)& router are as follows:
21388 .option allow_defer redirect boolean false
21389 Setting this option allows the use of &':defer:'& in non-filter redirection
21390 data, or the &%defer%& command in an Exim filter file.
21393 .option allow_fail redirect boolean false
21394 .cindex "failing delivery" "from filter"
21395 If this option is true, the &':fail:'& item can be used in a redirection list,
21396 and the &%fail%& command may be used in an Exim filter file.
21399 .option allow_filter redirect boolean false
21400 .cindex "filter" "enabling use of"
21401 .cindex "Sieve filter" "enabling use of"
21402 Setting this option allows Exim to interpret redirection data that starts with
21403 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21404 are some features of Exim filter files that some administrators may wish to
21405 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21407 It is also possible to lock out Exim filters or Sieve filters while allowing
21408 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21411 The filter is run using the uid and gid set by the generic &%user%& and
21412 &%group%& options. These take their defaults from the password data if
21413 &%check_local_user%& is set, so in the normal case of users' personal filter
21414 files, the filter is run as the relevant user. When &%allow_filter%& is set
21415 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21419 .option allow_freeze redirect boolean false
21420 .cindex "freezing messages" "allowing in filter"
21421 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21422 This command is more normally encountered in system filters, and is disabled by
21423 default for redirection filters because it isn't something you usually want to
21424 let ordinary users do.
21428 .option check_ancestor redirect boolean false
21429 This option is concerned with handling generated addresses that are the same
21430 as some address in the list of redirection ancestors of the current address.
21431 Although it is turned off by default in the code, it is set in the default
21432 configuration file for handling users' &_.forward_& files. It is recommended
21433 for this use of the &(redirect)& router.
21435 When &%check_ancestor%& is set, if a generated address (including the domain)
21436 is the same as any ancestor of the current address, it is replaced by a copy of
21437 the current address. This helps in the case where local part A is aliased to B,
21438 and B has a &_.forward_& file pointing back to A. For example, within a single
21439 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21440 &_&~jb/.forward_& contains:
21442 \Joe.Bloggs, <other item(s)>
21444 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21445 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21446 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21447 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21448 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21449 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21450 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21451 original address. See also the &%repeat_use%& option below.
21454 .option check_group redirect boolean "see below"
21455 When the &%file%& option is used, the group owner of the file is checked only
21456 when this option is set. The permitted groups are those listed in the
21457 &%owngroups%& option, together with the user's default group if
21458 &%check_local_user%& is set. If the file has the wrong group, routing is
21459 deferred. The default setting for this option is true if &%check_local_user%&
21460 is set and the &%modemask%& option permits the group write bit, or if the
21461 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21465 .option check_owner redirect boolean "see below"
21466 When the &%file%& option is used, the owner of the file is checked only when
21467 this option is set. If &%check_local_user%& is set, the local user is
21468 permitted; otherwise the owner must be one of those listed in the &%owners%&
21469 option. The default value for this option is true if &%check_local_user%& or
21470 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21473 .option data redirect string&!! unset
21474 This option is mutually exclusive with &%file%&. One or other of them must be
21475 set, but not both. The contents of &%data%& are expanded, and then used as the
21476 list of forwarding items, or as a set of filtering instructions. If the
21477 expansion is forced to fail, or the result is an empty string or a string that
21478 has no effect (consists entirely of comments), the router declines.
21480 When filtering instructions are used, the string must begin with &"#Exim
21481 filter"&, and all comments in the string, including this initial one, must be
21482 terminated with newline characters. For example:
21484 data = #Exim filter\n\
21485 if $h_to: contains Exim then save $home/mail/exim endif
21487 If you are reading the data from a database where newlines cannot be included,
21488 you can use the &${sg}$& expansion item to turn the escape string of your
21489 choice into a newline.
21492 .option directory_transport redirect string&!! unset
21493 A &(redirect)& router sets up a direct delivery to a directory when a path name
21494 ending with a slash is specified as a new &"address"&. The transport used is
21495 specified by this option, which, after expansion, must be the name of a
21496 configured transport. This should normally be an &(appendfile)& transport.
21499 .option file redirect string&!! unset
21500 This option specifies the name of a file that contains the redirection data. It
21501 is mutually exclusive with the &%data%& option. The string is expanded before
21502 use; if the expansion is forced to fail, the router declines. Other expansion
21503 failures cause delivery to be deferred. The result of a successful expansion
21504 must be an absolute path. The entire file is read and used as the redirection
21505 data. If the data is an empty string or a string that has no effect (consists
21506 entirely of comments), the router declines.
21508 .cindex "NFS" "checking for file existence"
21509 If the attempt to open the file fails with a &"does not exist"& error, Exim
21510 runs a check on the containing directory,
21511 unless &%ignore_enotdir%& is true (see below).
21512 If the directory does not appear to exist, delivery is deferred. This can
21513 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21514 is a mount problem. If the containing directory does exist, but the file does
21515 not, the router declines.
21518 .option file_transport redirect string&!! unset
21519 .vindex "&$address_file$&"
21520 A &(redirect)& router sets up a direct delivery to a file when a path name not
21521 ending in a slash is specified as a new &"address"&. The transport used is
21522 specified by this option, which, after expansion, must be the name of a
21523 configured transport. This should normally be an &(appendfile)& transport. When
21524 it is running, the filename is in &$address_file$&.
21527 .option filter_prepend_home redirect boolean true
21528 When this option is true, if a &(save)& command in an Exim filter specifies a
21529 relative path, and &$home$& is defined, it is automatically prepended to the
21530 relative path. If this option is set false, this action does not happen. The
21531 relative path is then passed to the transport unmodified.
21534 .option forbid_blackhole redirect boolean false
21535 .cindex "restricting access to features"
21536 .cindex "filter" "locking out certain features"
21537 If this option is true, the &':blackhole:'& item may not appear in a
21541 .option forbid_exim_filter redirect boolean false
21542 .cindex "restricting access to features"
21543 .cindex "filter" "locking out certain features"
21544 If this option is set true, only Sieve filters are permitted when
21545 &%allow_filter%& is true.
21550 .option forbid_file redirect boolean false
21551 .cindex "restricting access to features"
21552 .cindex "delivery" "to file; forbidding"
21553 .cindex "filter" "locking out certain features"
21554 .cindex "Sieve filter" "forbidding delivery to a file"
21555 .cindex "Sieve filter" "&""keep""& facility; disabling"
21556 If this option is true, this router may not generate a new address that
21557 specifies delivery to a local file or directory, either from a filter or from a
21558 conventional forward file. This option is forced to be true if &%one_time%& is
21559 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21560 locks out the Sieve's &"keep"& facility.
21563 .option forbid_filter_dlfunc redirect boolean false
21564 .cindex "restricting access to features"
21565 .cindex "filter" "locking out certain features"
21566 If this option is true, string expansions in Exim filters are not allowed to
21567 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21570 .option forbid_filter_existstest redirect boolean false
21571 .cindex "restricting access to features"
21572 .cindex "filter" "locking out certain features"
21573 .cindex "expansion" "statting a file"
21574 If this option is true, string expansions in Exim filters are not allowed to
21575 make use of the &%exists%& condition or the &%stat%& expansion item.
21577 .option forbid_filter_logwrite redirect boolean false
21578 .cindex "restricting access to features"
21579 .cindex "filter" "locking out certain features"
21580 If this option is true, use of the logging facility in Exim filters is not
21581 permitted. Logging is in any case available only if the filter is being run
21582 under some unprivileged uid (which is normally the case for ordinary users'
21583 &_.forward_& files).
21586 .option forbid_filter_lookup redirect boolean false
21587 .cindex "restricting access to features"
21588 .cindex "filter" "locking out certain features"
21589 If this option is true, string expansions in Exim filter files are not allowed
21590 to make use of &%lookup%& items.
21593 .option forbid_filter_perl redirect boolean false
21594 .cindex "restricting access to features"
21595 .cindex "filter" "locking out certain features"
21596 This option has an effect only if Exim is built with embedded Perl support. If
21597 it is true, string expansions in Exim filter files are not allowed to make use
21598 of the embedded Perl support.
21601 .option forbid_filter_readfile redirect boolean false
21602 .cindex "restricting access to features"
21603 .cindex "filter" "locking out certain features"
21604 If this option is true, string expansions in Exim filter files are not allowed
21605 to make use of &%readfile%& items.
21608 .option forbid_filter_readsocket redirect boolean false
21609 .cindex "restricting access to features"
21610 .cindex "filter" "locking out certain features"
21611 If this option is true, string expansions in Exim filter files are not allowed
21612 to make use of &%readsocket%& items.
21615 .option forbid_filter_reply redirect boolean false
21616 .cindex "restricting access to features"
21617 .cindex "filter" "locking out certain features"
21618 If this option is true, this router may not generate an automatic reply
21619 message. Automatic replies can be generated only from Exim or Sieve filter
21620 files, not from traditional forward files. This option is forced to be true if
21621 &%one_time%& is set.
21624 .option forbid_filter_run redirect boolean false
21625 .cindex "restricting access to features"
21626 .cindex "filter" "locking out certain features"
21627 If this option is true, string expansions in Exim filter files are not allowed
21628 to make use of &%run%& items.
21631 .option forbid_include redirect boolean false
21632 .cindex "restricting access to features"
21633 .cindex "filter" "locking out certain features"
21634 If this option is true, items of the form
21636 :include:<path name>
21638 are not permitted in non-filter redirection lists.
21641 .option forbid_pipe redirect boolean false
21642 .cindex "restricting access to features"
21643 .cindex "filter" "locking out certain features"
21644 .cindex "delivery" "to pipe; forbidding"
21645 If this option is true, this router may not generate a new address which
21646 specifies delivery to a pipe, either from an Exim filter or from a conventional
21647 forward file. This option is forced to be true if &%one_time%& is set.
21650 .option forbid_sieve_filter redirect boolean false
21651 .cindex "restricting access to features"
21652 .cindex "filter" "locking out certain features"
21653 If this option is set true, only Exim filters are permitted when
21654 &%allow_filter%& is true.
21657 .cindex "SMTP" "error codes"
21658 .option forbid_smtp_code redirect boolean false
21659 If this option is set true, any SMTP error codes that are present at the start
21660 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21661 the default codes (451 and 550, respectively) are always used.
21666 .option hide_child_in_errmsg redirect boolean false
21667 .cindex "bounce message" "redirection details; suppressing"
21668 If this option is true, it prevents Exim from quoting a child address if it
21669 generates a bounce or delay message for it. Instead it says &"an address
21670 generated from <&'the top level address'&>"&. Of course, this applies only to
21671 bounces generated locally. If a message is forwarded to another host, &'its'&
21672 bounce may well quote the generated address.
21675 .option ignore_eacces redirect boolean false
21677 If this option is set and an attempt to open a redirection file yields the
21678 EACCES error (permission denied), the &(redirect)& router behaves as if the
21679 file did not exist.
21682 .option ignore_enotdir redirect boolean false
21684 If this option is set and an attempt to open a redirection file yields the
21685 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21686 router behaves as if the file did not exist.
21688 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21689 router that has the &%file%& option set discovers that the file does not exist
21690 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21691 against unmounted NFS directories. If the parent can not be statted, delivery
21692 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21693 is set, because that option tells Exim to ignore &"something on the path is not
21694 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21695 that some operating systems give ENOENT where others give ENOTDIR.
21699 .option include_directory redirect string unset
21700 If this option is set, the path names of any &':include:'& items in a
21701 redirection list must start with this directory.
21704 .option modemask redirect "octal integer" 022
21705 This specifies mode bits which must not be set for a file specified by the
21706 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21709 .option one_time redirect boolean false
21710 .cindex "one-time aliasing/forwarding expansion"
21711 .cindex "alias file" "one-time expansion"
21712 .cindex "forward file" "one-time expansion"
21713 .cindex "mailing lists" "one-time expansion"
21714 .cindex "address redirection" "one-time expansion"
21715 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21716 files each time it tries to deliver a message causes a problem when one or more
21717 of the generated addresses fails be delivered at the first attempt. The problem
21718 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21719 but of what happens when the redirection list changes during the time that the
21720 message is on Exim's queue. This is particularly true in the case of mailing
21721 lists, where new subscribers might receive copies of messages that were posted
21722 before they subscribed.
21724 If &%one_time%& is set and any addresses generated by the router fail to
21725 deliver at the first attempt, the failing addresses are added to the message as
21726 &"top level"& addresses, and the parent address that generated them is marked
21727 &"delivered"&. Thus, redirection does not happen again at the next delivery
21730 &*Warning 1*&: Any header line addition or removal that is specified by this
21731 router would be lost if delivery did not succeed at the first attempt. For this
21732 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21733 permitted when &%one_time%& is set.
21735 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21736 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21737 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21739 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21742 The original top-level address is remembered with each of the generated
21743 addresses, and is output in any log messages. However, any intermediate parent
21744 addresses are not recorded. This makes a difference to the log only if
21745 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21746 typically be used for mailing lists, where there is normally just one level of
21750 .option owners redirect "string list" unset
21751 .cindex "ownership" "alias file"
21752 .cindex "ownership" "forward file"
21753 .cindex "alias file" "ownership"
21754 .cindex "forward file" "ownership"
21755 This specifies a list of permitted owners for the file specified by &%file%&.
21756 This list is in addition to the local user when &%check_local_user%& is set.
21757 See &%check_owner%& above.
21760 .option owngroups redirect "string list" unset
21761 This specifies a list of permitted groups for the file specified by &%file%&.
21762 The list is in addition to the local user's primary group when
21763 &%check_local_user%& is set. See &%check_group%& above.
21766 .option pipe_transport redirect string&!! unset
21767 .vindex "&$address_pipe$&"
21768 A &(redirect)& router sets up a direct delivery to a pipe when a string
21769 starting with a vertical bar character is specified as a new &"address"&. The
21770 transport used is specified by this option, which, after expansion, must be the
21771 name of a configured transport. This should normally be a &(pipe)& transport.
21772 When the transport is run, the pipe command is in &$address_pipe$&.
21775 .option qualify_domain redirect string&!! unset
21776 .vindex "&$qualify_recipient$&"
21777 If this option is set, and an unqualified address (one without a domain) is
21778 generated, and that address would normally be qualified by the global setting
21779 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21780 expanding this string. If the expansion fails, the router declines. If you want
21781 to revert to the default, you can have the expansion generate
21782 &$qualify_recipient$&.
21784 This option applies to all unqualified addresses generated by Exim filters,
21785 but for traditional &_.forward_& files, it applies only to addresses that are
21786 not preceded by a backslash. Sieve filters cannot generate unqualified
21789 .option qualify_preserve_domain redirect boolean false
21790 .cindex "domain" "in redirection; preserving"
21791 .cindex "preserving domain in redirection"
21792 .cindex "address redirection" "domain; preserving"
21793 If this option is set, the router's local &%qualify_domain%& option must not be
21794 set (a configuration error occurs if it is). If an unqualified address (one
21795 without a domain) is generated, it is qualified with the domain of the parent
21796 address (the immediately preceding ancestor) instead of the global
21797 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21798 this applies whether or not the address is preceded by a backslash.
21801 .option repeat_use redirect boolean true
21802 If this option is set false, the router is skipped for a child address that has
21803 any ancestor that was routed by this router. This test happens before any of
21804 the other preconditions are tested. Exim's default anti-looping rules skip
21805 only when the ancestor is the same as the current address. See also
21806 &%check_ancestor%& above and the generic &%redirect_router%& option.
21809 .option reply_transport redirect string&!! unset
21810 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21811 &%vacation%& command is used in a filter file. The transport used is specified
21812 by this option, which, after expansion, must be the name of a configured
21813 transport. This should normally be an &(autoreply)& transport. Other transports
21814 are unlikely to do anything sensible or useful.
21817 .option rewrite redirect boolean true
21818 .cindex "address redirection" "disabling rewriting"
21819 If this option is set false, addresses generated by the router are not
21820 subject to address rewriting. Otherwise, they are treated like new addresses
21821 and are rewritten according to the global rewriting rules.
21824 .option sieve_subaddress redirect string&!! unset
21825 The value of this option is passed to a Sieve filter to specify the
21826 :subaddress part of an address.
21828 .option sieve_useraddress redirect string&!! unset
21829 The value of this option is passed to a Sieve filter to specify the :user part
21830 of an address. However, if it is unset, the entire original local part
21831 (including any prefix or suffix) is used for :user.
21834 .option sieve_vacation_directory redirect string&!! unset
21835 .cindex "Sieve filter" "vacation directory"
21836 To enable the &"vacation"& extension for Sieve filters, you must set
21837 &%sieve_vacation_directory%& to the directory where vacation databases are held
21838 (do not put anything else in that directory), and ensure that the
21839 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21840 needs their own directory; Exim will create it if necessary.
21844 .option skip_syntax_errors redirect boolean false
21845 .cindex "forward file" "broken"
21846 .cindex "address redirection" "broken files"
21847 .cindex "alias file" "broken"
21848 .cindex "broken alias or forward files"
21849 .cindex "ignoring faulty addresses"
21850 .cindex "skipping faulty addresses"
21851 .cindex "error" "skipping bad syntax"
21852 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
21853 non-filter redirection data are skipped, and each failing address is logged. If
21854 &%syntax_errors_to%& is set, a message is sent to the address it defines,
21855 giving details of the failures. If &%syntax_errors_text%& is set, its contents
21856 are expanded and placed at the head of the error message generated by
21857 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
21858 be the same address as the generic &%errors_to%& option. The
21859 &%skip_syntax_errors%& option is often used when handling mailing lists.
21861 If all the addresses in a redirection list are skipped because of syntax
21862 errors, the router declines to handle the original address, and it is passed to
21863 the following routers.
21865 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
21866 error in the filter causes filtering to be abandoned without any action being
21867 taken. The incident is logged, and the router declines to handle the address,
21868 so it is passed to the following routers.
21870 .cindex "Sieve filter" "syntax errors in"
21871 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
21872 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
21873 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
21875 &%skip_syntax_errors%& can be used to specify that errors in users' forward
21876 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
21877 option, used with an address that does not get redirected, can be used to
21878 notify users of these errors, by means of a router like this:
21884 file = $home/.forward
21885 file_transport = address_file
21886 pipe_transport = address_pipe
21887 reply_transport = address_reply
21890 syntax_errors_to = real-$local_part@$domain
21891 syntax_errors_text = \
21892 This is an automatically generated message. An error has\n\
21893 been found in your .forward file. Details of the error are\n\
21894 reported below. While this error persists, you will receive\n\
21895 a copy of this message for every message that is addressed\n\
21896 to you. If your .forward file is a filter file, or if it is\n\
21897 a non-filter file containing no valid forwarding addresses,\n\
21898 a copy of each incoming message will be put in your normal\n\
21899 mailbox. If a non-filter file contains at least one valid\n\
21900 forwarding address, forwarding to the valid addresses will\n\
21901 happen, and those will be the only deliveries that occur.
21903 You also need a router to ensure that local addresses that are prefixed by
21904 &`real-`& are recognized, but not forwarded or filtered. For example, you could
21905 put this immediately before the &(userforward)& router:
21910 local_part_prefix = real-
21911 transport = local_delivery
21913 For security, it would probably be a good idea to restrict the use of this
21914 router to locally-generated messages, using a condition such as this:
21916 condition = ${if match {$sender_host_address}\
21917 {\N^(|127\.0\.0\.1)$\N}}
21921 .option syntax_errors_text redirect string&!! unset
21922 See &%skip_syntax_errors%& above.
21925 .option syntax_errors_to redirect string unset
21926 See &%skip_syntax_errors%& above.
21927 .ecindex IIDredrou1
21928 .ecindex IIDredrou2
21935 . ////////////////////////////////////////////////////////////////////////////
21936 . ////////////////////////////////////////////////////////////////////////////
21938 .chapter "Environment for running local transports" "CHAPenvironment" &&&
21939 "Environment for local transports"
21940 .scindex IIDenvlotra1 "local transports" "environment for"
21941 .scindex IIDenvlotra2 "environment" "local transports"
21942 .scindex IIDenvlotra3 "transport" "local; environment for"
21943 Local transports handle deliveries to files and pipes. (The &(autoreply)&
21944 transport can be thought of as similar to a pipe.) Exim always runs transports
21945 in subprocesses, under specified uids and gids. Typical deliveries to local
21946 mailboxes run under the uid and gid of the local user.
21948 Exim also sets a specific current directory while running the transport; for
21949 some transports a home directory setting is also relevant. The &(pipe)&
21950 transport is the only one that sets up environment variables; see section
21951 &<<SECTpipeenv>>& for details.
21953 The values used for the uid, gid, and the directories may come from several
21954 different places. In many cases, the router that handles the address associates
21955 settings with that address as a result of its &%check_local_user%&, &%group%&,
21956 or &%user%& options. However, values may also be given in the transport's own
21957 configuration, and these override anything that comes from the router.
21961 .section "Concurrent deliveries" "SECID131"
21962 .cindex "concurrent deliveries"
21963 .cindex "simultaneous deliveries"
21964 If two different messages for the same local recipient arrive more or less
21965 simultaneously, the two delivery processes are likely to run concurrently. When
21966 the &(appendfile)& transport is used to write to a file, Exim applies locking
21967 rules to stop concurrent processes from writing to the same file at the same
21970 However, when you use a &(pipe)& transport, it is up to you to arrange any
21971 locking that is needed. Here is a silly example:
21975 command = /bin/sh -c 'cat >>/some/file'
21977 This is supposed to write the message at the end of the file. However, if two
21978 messages arrive at the same time, the file will be scrambled. You can use the
21979 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
21980 file using the same algorithm that Exim itself uses.
21985 .section "Uids and gids" "SECTenvuidgid"
21986 .cindex "local transports" "uid and gid"
21987 .cindex "transport" "local; uid and gid"
21988 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
21989 overrides any group that the router set in the address, even if &%user%& is not
21990 set for the transport. This makes it possible, for example, to run local mail
21991 delivery under the uid of the recipient (set by the router), but in a special
21992 group (set by the transport). For example:
21995 # User/group are set by check_local_user in this router
21999 transport = group_delivery
22002 # This transport overrides the group
22004 driver = appendfile
22005 file = /var/spool/mail/$local_part_data
22008 If &%user%& is set for a transport, its value overrides what is set in the
22009 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22010 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22013 .oindex "&%initgroups%&"
22014 When the uid is taken from the transport's configuration, the &[initgroups()]&
22015 function is called for the groups associated with that uid if the
22016 &%initgroups%& option is set for the transport. When the uid is not specified
22017 by the transport, but is associated with the address by a router, the option
22018 for calling &[initgroups()]& is taken from the router configuration.
22020 .cindex "&(pipe)& transport" "uid for"
22021 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22022 is set and &%user%& is not set, the uid of the process that called Exim to
22023 receive the message is used, and if &%group%& is not set, the corresponding
22024 original gid is also used.
22026 This is the detailed preference order for obtaining a gid; the first of the
22027 following that is set is used:
22030 A &%group%& setting of the transport;
22032 A &%group%& setting of the router;
22034 A gid associated with a user setting of the router, either as a result of
22035 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22037 The group associated with a non-numeric &%user%& setting of the transport;
22039 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22040 the uid is the creator's uid;
22042 The Exim gid if the Exim uid is being used as a default.
22045 If, for example, the user is specified numerically on the router and there are
22046 no group settings, no gid is available. In this situation, an error occurs.
22047 This is different for the uid, for which there always is an ultimate default.
22048 The first of the following that is set is used:
22051 A &%user%& setting of the transport;
22053 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22055 A &%user%& setting of the router;
22057 A &%check_local_user%& setting of the router;
22062 Of course, an error will still occur if the uid that is chosen is on the
22063 &%never_users%& list.
22069 .section "Current and home directories" "SECID132"
22070 .cindex "current directory for local transport"
22071 .cindex "home directory" "for local transport"
22072 .cindex "transport" "local; home directory for"
22073 .cindex "transport" "local; current directory for"
22074 Routers may set current and home directories for local transports by means of
22075 the &%transport_current_directory%& and &%transport_home_directory%& options.
22076 However, if the transport's &%current_directory%& or &%home_directory%& options
22077 are set, they override the router's values. In detail, the home directory
22078 for a local transport is taken from the first of these values that is set:
22081 The &%home_directory%& option on the transport;
22083 The &%transport_home_directory%& option on the router;
22085 The password data if &%check_local_user%& is set on the router;
22087 The &%router_home_directory%& option on the router.
22090 The current directory is taken from the first of these values that is set:
22093 The &%current_directory%& option on the transport;
22095 The &%transport_current_directory%& option on the router.
22099 If neither the router nor the transport sets a current directory, Exim uses the
22100 value of the home directory, if it is set. Otherwise it sets the current
22101 directory to &_/_& before running a local transport.
22105 .section "Expansion variables derived from the address" "SECID133"
22106 .vindex "&$domain$&"
22107 .vindex "&$local_part$&"
22108 .vindex "&$original_domain$&"
22109 Normally a local delivery is handling a single address, and in that case the
22110 variables such as &$domain$& and &$local_part$& are set during local
22111 deliveries. However, in some circumstances more than one address may be handled
22112 at once (for example, while writing batch SMTP for onward transmission by some
22113 other means). In this case, the variables associated with the local part are
22114 never set, &$domain$& is set only if all the addresses have the same domain,
22115 and &$original_domain$& is never set.
22116 .ecindex IIDenvlotra1
22117 .ecindex IIDenvlotra2
22118 .ecindex IIDenvlotra3
22126 . ////////////////////////////////////////////////////////////////////////////
22127 . ////////////////////////////////////////////////////////////////////////////
22129 .chapter "Generic options for transports" "CHAPtransportgeneric"
22130 .scindex IIDgenoptra1 "generic options" "transport"
22131 .scindex IIDgenoptra2 "options" "generic; for transports"
22132 .scindex IIDgenoptra3 "transport" "generic options for"
22133 The following generic options apply to all transports:
22136 .option body_only transports boolean false
22137 .cindex "transport" "body only"
22138 .cindex "message" "transporting body only"
22139 .cindex "body of message" "transporting"
22140 If this option is set, the message's headers are not transported. It is
22141 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22142 or &(pipe)& transports, the settings of &%message_prefix%& and
22143 &%message_suffix%& should be checked, because this option does not
22144 automatically suppress them.
22147 .option current_directory transports string&!! unset
22148 .cindex "transport" "current directory for"
22149 This specifies the current directory that is to be set while running the
22150 transport, overriding any value that may have been set by the router.
22151 If the expansion fails for any reason, including forced failure, an error is
22152 logged, and delivery is deferred.
22155 .option disable_logging transports boolean false
22156 If this option is set true, nothing is logged for any
22157 deliveries by the transport or for any
22158 transport errors. You should not set this option unless you really, really know
22159 what you are doing.
22162 .option debug_print transports string&!! unset
22163 .cindex "testing" "variables in drivers"
22164 If this option is set and debugging is enabled (see the &%-d%& command line
22165 option), the string is expanded and included in the debugging output when the
22167 If expansion of the string fails, the error message is written to the debugging
22168 output, and Exim carries on processing.
22169 This facility is provided to help with checking out the values of variables and
22170 so on when debugging driver configurations. For example, if a &%headers_add%&
22171 option is not working properly, &%debug_print%& could be used to output the
22172 variables it references. A newline is added to the text if it does not end with
22174 The variables &$transport_name$& and &$router_name$& contain the name of the
22175 transport and the router that called it.
22177 .option delivery_date_add transports boolean false
22178 .cindex "&'Delivery-date:'& header line"
22179 If this option is true, a &'Delivery-date:'& header is added to the message.
22180 This gives the actual time the delivery was made. As this is not a standard
22181 header, Exim has a configuration option (&%delivery_date_remove%&) which
22182 requests its removal from incoming messages, so that delivered messages can
22183 safely be resent to other recipients.
22186 .option driver transports string unset
22187 This specifies which of the available transport drivers is to be used.
22188 There is no default, and this option must be set for every transport.
22191 .option envelope_to_add transports boolean false
22192 .cindex "&'Envelope-to:'& header line"
22193 If this option is true, an &'Envelope-to:'& header is added to the message.
22194 This gives the original address(es) in the incoming envelope that caused this
22195 delivery to happen. More than one address may be present if the transport is
22196 configured to handle several addresses at once, or if more than one original
22197 address was redirected to the same final address. As this is not a standard
22198 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22199 its removal from incoming messages, so that delivered messages can safely be
22200 resent to other recipients.
22203 .option event_action transports string&!! unset
22205 This option declares a string to be expanded for Exim's events mechanism.
22206 For details see chapter &<<CHAPevents>>&.
22209 .option group transports string&!! "Exim group"
22210 .cindex "transport" "group; specifying"
22211 This option specifies a gid for running the transport process, overriding any
22212 value that the router supplies, and also overriding any value associated with
22213 &%user%& (see below).
22216 .option headers_add transports list&!! unset
22217 .cindex "header lines" "adding in transport"
22218 .cindex "transport" "header lines; adding"
22219 This option specifies a list of text headers,
22220 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22221 which are (separately) expanded and added to the header
22222 portion of a message as it is transported, as described in section
22223 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22224 routers. If the result of the expansion is an empty string, or if the expansion
22225 is forced to fail, no action is taken. Other expansion failures are treated as
22226 errors and cause the delivery to be deferred.
22228 Unlike most options, &%headers_add%& can be specified multiple times
22229 for a transport; all listed headers are added.
22232 .option headers_only transports boolean false
22233 .cindex "transport" "header lines only"
22234 .cindex "message" "transporting headers only"
22235 .cindex "header lines" "transporting"
22236 If this option is set, the message's body is not transported. It is mutually
22237 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22238 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22239 checked, since this option does not automatically suppress them.
22242 .option headers_remove transports list&!! unset
22243 .cindex "header lines" "removing"
22244 .cindex "transport" "header lines; removing"
22245 This option specifies a list of text headers,
22246 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22247 to be removed from the message.
22248 However, the option has no effect when an address is just being verified.
22249 Each list item is separately expanded.
22250 If the result of the expansion is an empty string, or if the expansion
22251 is forced to fail, no action is taken. Other expansion failures are treated as
22252 errors and cause the delivery to be deferred.
22254 If an item ends in *, it will match any header with the given prefix.
22257 Matching headers are omitted from the message as it is transported, as described
22258 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22261 Unlike most options, &%headers_remove%& can be specified multiple times
22262 for a transport; all listed headers are removed.
22264 &*Warning*&: Because of the separate expansion of the list items,
22265 items that contain a list separator must have it doubled.
22266 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22270 .option headers_rewrite transports string unset
22271 .cindex "transport" "header lines; rewriting"
22272 .cindex "rewriting" "at transport time"
22273 This option allows addresses in header lines to be rewritten at transport time,
22274 that is, as the message is being copied to its destination. The contents of the
22275 option are a colon-separated list of rewriting rules. Each rule is in exactly
22276 the same form as one of the general rewriting rules that are applied when a
22277 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22280 headers_rewrite = a@b c@d f : \
22283 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22284 &'w@z'& in all address-bearing header lines. The rules are applied to the
22285 header lines just before they are written out at transport time, so they affect
22286 only those copies of the message that pass through the transport. However, only
22287 the message's original header lines, and any that were added by a system
22288 filter, are rewritten. If a router or transport adds header lines, they are not
22289 affected by this option. These rewriting rules are &'not'& applied to the
22290 envelope. You can change the return path using &%return_path%&, but you cannot
22291 change envelope recipients at this time.
22294 .option home_directory transports string&!! unset
22295 .cindex "transport" "home directory for"
22297 This option specifies a home directory setting for a local transport,
22298 overriding any value that may be set by the router. The home directory is
22299 placed in &$home$& while expanding the transport's private options. It is also
22300 used as the current directory if no current directory is set by the
22301 &%current_directory%& option on the transport or the
22302 &%transport_current_directory%& option on the router. If the expansion fails
22303 for any reason, including forced failure, an error is logged, and delivery is
22307 .option initgroups transports boolean false
22308 .cindex "additional groups"
22309 .cindex "groups" "additional"
22310 .cindex "transport" "group; additional"
22311 If this option is true and the uid for the delivery process is provided by the
22312 transport, the &[initgroups()]& function is called when running the transport
22313 to ensure that any additional groups associated with the uid are set up.
22316 .option max_parallel transports integer&!! unset
22317 .cindex limit "transport parallelism"
22318 .cindex transport "parallel processes"
22319 .cindex transport "concurrency limit"
22320 .cindex "delivery" "parallelism for transport"
22321 If this option is set and expands to an integer greater than zero
22322 it limits the number of concurrent runs of the transport.
22323 The control does not apply to shadow transports.
22325 .cindex "hints database" "transport concurrency control"
22326 Exim implements this control by means of a hints database in which a record is
22327 incremented whenever a transport process is being created. The record
22328 is decremented and possibly removed when the process terminates.
22329 Obviously there is scope for
22330 records to get left lying around if there is a system or program crash. To
22331 guard against this, Exim ignores any records that are more than six hours old.
22333 If you use this option, you should also arrange to delete the
22334 relevant hints database whenever your system reboots. The names of the files
22335 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22336 may be one or two files, depending on the type of DBM in use. The same files
22337 are used for ETRN and smtp transport serialization.
22340 .option message_size_limit transports string&!! 0
22341 .cindex "limit" "message size per transport"
22342 .cindex "size" "of message, limit"
22343 .cindex "transport" "message size; limiting"
22344 This option controls the size of messages passed through the transport. It is
22345 expanded before use; the result of the expansion must be a sequence of decimal
22346 digits, optionally followed by K or M. If the expansion fails for any reason,
22347 including forced failure, or if the result is not of the required form,
22348 delivery is deferred. If the value is greater than zero and the size of a
22349 message exceeds this limit, the address is failed. If there is any chance that
22350 the resulting bounce message could be routed to the same transport, you should
22351 ensure that &%return_size_limit%& is less than the transport's
22352 &%message_size_limit%&, as otherwise the bounce message will fail to get
22357 .option rcpt_include_affixes transports boolean false
22358 .cindex "prefix" "for local part, including in envelope"
22359 .cindex "suffix for local part" "including in envelope"
22360 .cindex "local part" "prefix"
22361 .cindex "local part" "suffix"
22362 When this option is false (the default), and an address that has had any
22363 affixes (prefixes or suffixes) removed from the local part is delivered by any
22364 form of SMTP or LMTP, the affixes are not included. For example, if a router
22367 local_part_prefix = *-
22369 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22372 RCPT TO:<xyz@some.domain>
22374 This is also the case when an ACL-time callout is being used to verify a
22375 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22376 whole local part is included in the RCPT command. This option applies to BSMTP
22377 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22378 &(lmtp)& and &(smtp)& transports.
22381 .option retry_use_local_part transports boolean "see below"
22382 .cindex "hints database" "retry keys"
22383 When a delivery suffers a temporary failure, a retry record is created
22384 in Exim's hints database. For remote deliveries, the key for the retry record
22385 is based on the name and/or IP address of the failing remote host. For local
22386 deliveries, the key is normally the entire address, including both the local
22387 part and the domain. This is suitable for most common cases of local delivery
22388 temporary failure &-- for example, exceeding a mailbox quota should delay only
22389 deliveries to that mailbox, not to the whole domain.
22391 However, in some special cases you may want to treat a temporary local delivery
22392 as a failure associated with the domain, and not with a particular local part.
22393 (For example, if you are storing all mail for some domain in files.) You can do
22394 this by setting &%retry_use_local_part%& false.
22396 For all the local transports, its default value is true. For remote transports,
22397 the default value is false for tidiness, but changing the value has no effect
22398 on a remote transport in the current implementation.
22401 .option return_path transports string&!! unset
22402 .cindex "envelope sender"
22403 .cindex "envelope from"
22404 .cindex "transport" "return path; changing"
22405 .cindex "return path" "changing in transport"
22406 If this option is set, the string is expanded at transport time and replaces
22407 the existing return path (envelope sender) value in the copy of the message
22408 that is being delivered. An empty return path is permitted. This feature is
22409 designed for remote deliveries, where the value of this option is used in the
22410 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22411 only effect is to change the address that is placed in the &'Return-path:'&
22412 header line, if one is added to the message (see the next option).
22414 &*Note:*& A changed return path is not logged unless you add
22415 &%return_path_on_delivery%& to the log selector.
22417 .vindex "&$return_path$&"
22418 The expansion can refer to the existing value via &$return_path$&. This is
22419 either the message's envelope sender, or an address set by the
22420 &%errors_to%& option on a router. If the expansion is forced to fail, no
22421 replacement occurs; if it fails for another reason, delivery is deferred. This
22422 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22423 section &<<SECTverp>>&.
22425 &*Note*&: If a delivery error is detected locally, including the case when a
22426 remote server rejects a message at SMTP time, the bounce message is not sent to
22427 the value of this option. It is sent to the previously set errors address.
22428 This defaults to the incoming sender address, but can be changed by setting
22429 &%errors_to%& in a router.
22433 .option return_path_add transports boolean false
22434 .cindex "&'Return-path:'& header line"
22435 If this option is true, a &'Return-path:'& header is added to the message.
22436 Although the return path is normally available in the prefix line of BSD
22437 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22438 have easy access to it.
22440 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22441 the delivery SMTP server makes the final delivery"&. This implies that this
22442 header should not be present in incoming messages. Exim has a configuration
22443 option, &%return_path_remove%&, which requests removal of this header from
22444 incoming messages, so that delivered messages can safely be resent to other
22448 .option shadow_condition transports string&!! unset
22449 See &%shadow_transport%& below.
22452 .option shadow_transport transports string unset
22453 .cindex "shadow transport"
22454 .cindex "transport" "shadow"
22455 A local transport may set the &%shadow_transport%& option to the name of
22456 another local transport. Shadow remote transports are not supported.
22458 Whenever a delivery to the main transport succeeds, and either
22459 &%shadow_condition%& is unset, or its expansion does not result in the empty
22460 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22461 passed to the shadow transport, with the same delivery address or addresses. If
22462 expansion fails, no action is taken except that non-forced expansion failures
22463 cause a log line to be written.
22465 The result of the shadow transport is discarded and does not affect the
22466 subsequent processing of the message. Only a single level of shadowing is
22467 provided; the &%shadow_transport%& option is ignored on any transport when it
22468 is running as a shadow. Options concerned with output from pipes are also
22469 ignored. The log line for the successful delivery has an item added on the end,
22472 ST=<shadow transport name>
22474 If the shadow transport did not succeed, the error message is put in
22475 parentheses afterwards. Shadow transports can be used for a number of different
22476 purposes, including keeping more detailed log information than Exim normally
22477 provides, and implementing automatic acknowledgment policies based on message
22478 headers that some sites insist on.
22481 .option transport_filter transports string&!! unset
22482 .cindex "transport" "filter"
22483 .cindex "filter" "transport filter"
22484 This option sets up a filtering (in the Unix shell sense) process for messages
22485 at transport time. It should not be confused with mail filtering as set up by
22486 individual users or via a system filter.
22487 If unset, or expanding to an empty string, no filtering is done.
22489 When the message is about to be written out, the command specified by
22490 &%transport_filter%& is started up in a separate, parallel process, and
22491 the entire message, including the header lines, is passed to it on its standard
22492 input (this in fact is done from a third process, to avoid deadlock). The
22493 command must be specified as an absolute path.
22495 The lines of the message that are written to the transport filter are
22496 terminated by newline (&"\n"&). The message is passed to the filter before any
22497 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22498 lines beginning with a dot, and also before any processing implied by the
22499 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22500 &(pipe)& transports.
22502 The standard error for the filter process is set to the same destination as its
22503 standard output; this is read and written to the message's ultimate
22504 destination. The process that writes the message to the filter, the
22505 filter itself, and the original process that reads the result and delivers it
22506 are all run in parallel, like a shell pipeline.
22508 The filter can perform any transformations it likes, but of course should take
22509 care not to break RFC 2822 syntax. Exim does not check the result, except to
22510 test for a final newline when SMTP is in use. All messages transmitted over
22511 SMTP must end with a newline, so Exim supplies one if it is missing.
22513 .cindex "content scanning" "per user"
22514 A transport filter can be used to provide content-scanning on a per-user basis
22515 at delivery time if the only required effect of the scan is to modify the
22516 message. For example, a content scan could insert a new header line containing
22517 a spam score. This could be interpreted by a filter in the user's MUA. It is
22518 not possible to discard a message at this stage.
22520 .cindex "SIZE" "ESMTP extension"
22521 A problem might arise if the filter increases the size of a message that is
22522 being sent down an SMTP connection. If the receiving SMTP server has indicated
22523 support for the SIZE parameter, Exim will have sent the size of the message
22524 at the start of the SMTP session. If what is actually sent is substantially
22525 more, the server might reject the message. This can be worked round by setting
22526 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22527 additions to the message, or to disable the use of SIZE altogether.
22529 .vindex "&$pipe_addresses$&"
22530 The value of the &%transport_filter%& option is the command string for starting
22531 the filter, which is run directly from Exim, not under a shell. The string is
22532 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22533 Exim breaks it up into arguments and then expands each argument separately (see
22534 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22535 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22536 of arguments, one for each address that applies to this delivery. (This isn't
22537 an ideal name for this feature here, but as it was already implemented for the
22538 &(pipe)& transport, it seemed sensible not to change it.)
22541 .vindex "&$host_address$&"
22542 The expansion variables &$host$& and &$host_address$& are available when the
22543 transport is a remote one. They contain the name and IP address of the host to
22544 which the message is being sent. For example:
22546 transport_filter = /some/directory/transport-filter.pl \
22547 $host $host_address $sender_address $pipe_addresses
22550 Two problems arise if you want to use more complicated expansion items to
22551 generate transport filter commands, both of which due to the fact that the
22552 command is split up &'before'& expansion.
22554 If an expansion item contains white space, you must quote it, so that it is all
22555 part of the same command item. If the entire option setting is one such
22556 expansion item, you have to take care what kind of quoting you use. For
22559 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22561 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22562 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22563 stripped by Exim when it read the option's value. When the value is used, if
22564 the single quotes were missing, the line would be split into two items,
22565 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22566 Exim tried to expand the first one.
22568 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22569 expansion cannot generate multiple arguments, or a command name followed by
22570 arguments. Consider this example:
22572 transport_filter = ${lookup{$host}lsearch{/a/file}\
22573 {$value}{/bin/cat}}
22575 The result of the lookup is interpreted as the name of the command, even
22576 if it contains white space. The simplest way round this is to use a shell:
22578 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22579 {$value}{/bin/cat}}
22583 The filter process is run under the same uid and gid as the normal delivery.
22584 For remote deliveries this is the Exim uid/gid by default. The command should
22585 normally yield a zero return code. Transport filters are not supposed to fail.
22586 A non-zero code is taken to mean that the transport filter encountered some
22587 serious problem. Delivery of the message is deferred; the message remains on
22588 the queue and is tried again later. It is not possible to cause a message to be
22589 bounced from a transport filter.
22591 If a transport filter is set on an autoreply transport, the original message is
22592 passed through the filter as it is being copied into the newly generated
22593 message, which happens if the &%return_message%& option is set.
22596 .option transport_filter_timeout transports time 5m
22597 .cindex "transport" "filter, timeout"
22598 When Exim is reading the output of a transport filter, it applies a timeout
22599 that can be set by this option. Exceeding the timeout is normally treated as a
22600 temporary delivery failure. However, if a transport filter is used with a
22601 &(pipe)& transport, a timeout in the transport filter is treated in the same
22602 way as a timeout in the pipe command itself. By default, a timeout is a hard
22603 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22604 becomes a temporary error.
22607 .option user transports string&!! "Exim user"
22608 .cindex "uid (user id)" "local delivery"
22609 .cindex "transport" "user, specifying"
22610 This option specifies the user under whose uid the delivery process is to be
22611 run, overriding any uid that may have been set by the router. If the user is
22612 given as a name, the uid is looked up from the password data, and the
22613 associated group is taken as the value of the gid to be used if the &%group%&
22616 For deliveries that use local transports, a user and group are normally
22617 specified explicitly or implicitly (for example, as a result of
22618 &%check_local_user%&) by the router or transport.
22620 .cindex "hints database" "access by remote transport"
22621 For remote transports, you should leave this option unset unless you really are
22622 sure you know what you are doing. When a remote transport is running, it needs
22623 to be able to access Exim's hints databases, because each host may have its own
22625 .ecindex IIDgenoptra1
22626 .ecindex IIDgenoptra2
22627 .ecindex IIDgenoptra3
22634 . ////////////////////////////////////////////////////////////////////////////
22635 . ////////////////////////////////////////////////////////////////////////////
22637 .chapter "Address batching in local transports" "CHAPbatching" &&&
22639 .cindex "transport" "local; address batching in"
22640 The only remote transport (&(smtp)&) is normally configured to handle more than
22641 one address at a time, so that when several addresses are routed to the same
22642 remote host, just one copy of the message is sent. Local transports, however,
22643 normally handle one address at a time. That is, a separate instance of the
22644 transport is run for each address that is routed to the transport. A separate
22645 copy of the message is delivered each time.
22647 .cindex "batched local delivery"
22648 .oindex "&%batch_max%&"
22649 .oindex "&%batch_id%&"
22650 In special cases, it may be desirable to handle several addresses at once in a
22651 local transport, for example:
22654 In an &(appendfile)& transport, when storing messages in files for later
22655 delivery by some other means, a single copy of the message with multiple
22656 recipients saves space.
22658 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22659 a single copy saves time, and is the normal way LMTP is expected to work.
22661 In a &(pipe)& transport, when passing the message
22662 to a scanner program or
22663 to some other delivery mechanism such as UUCP, multiple recipients may be
22667 These three local transports all have the same options for controlling multiple
22668 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22669 repeating the information for each transport, these options are described here.
22671 The &%batch_max%& option specifies the maximum number of addresses that can be
22672 delivered together in a single run of the transport. Its default value is one
22673 (no batching). When more than one address is routed to a transport that has a
22674 &%batch_max%& value greater than one, the addresses are delivered in a batch
22675 (that is, in a single run of the transport with multiple recipients), subject
22676 to certain conditions:
22679 .vindex "&$local_part$&"
22680 If any of the transport's options contain a reference to &$local_part$&, no
22681 batching is possible.
22683 .vindex "&$domain$&"
22684 If any of the transport's options contain a reference to &$domain$&, only
22685 addresses with the same domain are batched.
22687 .cindex "customizing" "batching condition"
22688 If &%batch_id%& is set, it is expanded for each address, and only those
22689 addresses with the same expanded value are batched. This allows you to specify
22690 customized batching conditions. Failure of the expansion for any reason,
22691 including forced failure, disables batching, but it does not stop the delivery
22694 Batched addresses must also have the same errors address (where to send
22695 delivery errors), the same header additions and removals, the same user and
22696 group for the transport, and if a host list is present, the first host must
22700 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22701 both when the file or pipe command is specified in the transport, and when it
22702 is specified by a &(redirect)& router, but all the batched addresses must of
22703 course be routed to the same file or pipe command. These two transports have an
22704 option called &%use_bsmtp%&, which causes them to deliver the message in
22705 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22706 &%check_string%& and &%escape_string%& options are forced to the values
22709 escape_string = ".."
22711 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22712 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22713 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22715 .cindex "&'Envelope-to:'& header line"
22716 If the generic &%envelope_to_add%& option is set for a batching transport, the
22717 &'Envelope-to:'& header that is added to the message contains all the addresses
22718 that are being processed together. If you are using a batching &(appendfile)&
22719 transport without &%use_bsmtp%&, the only way to preserve the recipient
22720 addresses is to set the &%envelope_to_add%& option.
22722 .cindex "&(pipe)& transport" "with multiple addresses"
22723 .vindex "&$pipe_addresses$&"
22724 If you are using a &(pipe)& transport without BSMTP, and setting the
22725 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22726 the command. This is not a true variable; it is a bit of magic that causes each
22727 of the recipient addresses to be inserted into the command as a separate
22728 argument. This provides a way of accessing all the addresses that are being
22729 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22730 are specified by a &(redirect)& router.
22735 . ////////////////////////////////////////////////////////////////////////////
22736 . ////////////////////////////////////////////////////////////////////////////
22738 .chapter "The appendfile transport" "CHAPappendfile"
22739 .scindex IIDapptra1 "&(appendfile)& transport"
22740 .scindex IIDapptra2 "transports" "&(appendfile)&"
22741 .cindex "directory creation"
22742 .cindex "creating directories"
22743 The &(appendfile)& transport delivers a message by appending it to an existing
22744 file, or by creating an entirely new file in a specified directory. Single
22745 files to which messages are appended can be in the traditional Unix mailbox
22746 format, or optionally in the MBX format supported by the Pine MUA and
22747 University of Washington IMAP daemon, &'inter alia'&. When each message is
22748 being delivered as a separate file, &"maildir"& format can optionally be used
22749 to give added protection against failures that happen part-way through the
22750 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22751 supported. For all file formats, Exim attempts to create as many levels of
22752 directory as necessary, provided that &%create_directory%& is set.
22754 The code for the optional formats is not included in the Exim binary by
22755 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22756 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22759 .cindex "quota" "system"
22760 Exim recognizes system quota errors, and generates an appropriate message. Exim
22761 also supports its own quota control within the transport, for use when the
22762 system facility is unavailable or cannot be used for some reason.
22764 If there is an error while appending to a file (for example, quota exceeded or
22765 partition filled), Exim attempts to reset the file's length and last
22766 modification time back to what they were before. If there is an error while
22767 creating an entirely new file, the new file is removed.
22769 Before appending to a file, a number of security checks are made, and the
22770 file is locked. A detailed description is given below, after the list of
22773 The &(appendfile)& transport is most commonly used for local deliveries to
22774 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22775 putting messages into files for remote delivery by some means other than Exim.
22776 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22781 .section "The file and directory options" "SECTfildiropt"
22782 The &%file%& option specifies a single file, to which the message is appended;
22783 the &%directory%& option specifies a directory, in which a new file containing
22784 the message is created. Only one of these two options can be set, and for
22785 normal deliveries to mailboxes, one of them &'must'& be set.
22787 .vindex "&$address_file$&"
22788 .vindex "&$local_part$&"
22789 However, &(appendfile)& is also used for delivering messages to files or
22790 directories whose names (or parts of names) are obtained from alias,
22791 forwarding, or filtering operations (for example, a &%save%& command in a
22792 user's Exim filter). When such a transport is running, &$local_part$& contains
22793 the local part that was aliased or forwarded, and &$address_file$& contains the
22794 name (or partial name) of the file or directory generated by the redirection
22795 operation. There are two cases:
22798 If neither &%file%& nor &%directory%& is set, the redirection operation
22799 must specify an absolute path (one that begins with &`/`&). This is the most
22800 common case when users with local accounts use filtering to sort mail into
22801 different folders. See for example, the &(address_file)& transport in the
22802 default configuration. If the path ends with a slash, it is assumed to be the
22803 name of a directory. A delivery to a directory can also be forced by setting
22804 &%maildir_format%& or &%mailstore_format%&.
22806 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22807 used to determine the file or directory name for the delivery. Normally, the
22808 contents of &$address_file$& are used in some way in the string expansion.
22811 .cindex "tainted data" "in filenames"
22812 .cindex appendfile "tainted data"
22813 Tainted data may not be used for a file or directory name.
22814 This means that, for instance, &$local_part$& cannot be used directly
22815 as a component of a path. It can however be used as the key for a lookup
22816 which returns a path (or component).
22820 .cindex "Sieve filter" "configuring &(appendfile)&"
22821 .cindex "Sieve filter" "relative mailbox path handling"
22822 As an example of the second case, consider an environment where users do not
22823 have home directories. They may be permitted to use Exim filter commands of the
22828 or Sieve filter commands of the form:
22830 require "fileinto";
22831 fileinto "folder23";
22833 In this situation, the expansion of &%file%& or &%directory%& in the transport
22834 must transform the relative path into an appropriate absolute filename. In the
22835 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
22836 is used as a result of a &"keep"& action in the filter. This example shows one
22837 way of handling this requirement:
22839 file = ${if eq{$address_file}{inbox} \
22840 {/var/mail/$local_part_data} \
22841 {${if eq{${substr_0_1:$address_file}}{/} \
22843 {$home/mail/$address_file} \
22847 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
22848 location, absolute paths are used without change, and other folders are in the
22849 &_mail_& directory within the home directory.
22851 &*Note 1*&: While processing an Exim filter, a relative path such as
22852 &_folder23_& is turned into an absolute path if a home directory is known to
22853 the router. In particular, this is the case if &%check_local_user%& is set. If
22854 you want to prevent this happening at routing time, you can set
22855 &%router_home_directory%& empty. This forces the router to pass the relative
22856 path to the transport.
22858 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
22859 the &%file%& or &%directory%& option is still used if it is set.
22864 .section "Private options for appendfile" "SECID134"
22865 .cindex "options" "&(appendfile)& transport"
22869 .option allow_fifo appendfile boolean false
22870 .cindex "fifo (named pipe)"
22871 .cindex "named pipe (fifo)"
22872 .cindex "pipe" "named (fifo)"
22873 Setting this option permits delivery to named pipes (FIFOs) as well as to
22874 regular files. If no process is reading the named pipe at delivery time, the
22875 delivery is deferred.
22878 .option allow_symlink appendfile boolean false
22879 .cindex "symbolic link" "to mailbox"
22880 .cindex "mailbox" "symbolic link"
22881 By default, &(appendfile)& will not deliver if the path name for the file is
22882 that of a symbolic link. Setting this option relaxes that constraint, but there
22883 are security issues involved in the use of symbolic links. Be sure you know
22884 what you are doing if you set this. Details of exactly what this option affects
22885 are included in the discussion which follows this list of options.
22888 .option batch_id appendfile string&!! unset
22889 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22890 However, batching is automatically disabled for &(appendfile)& deliveries that
22891 happen as a result of forwarding or aliasing or other redirection directly to a
22895 .option batch_max appendfile integer 1
22896 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22899 .option check_group appendfile boolean false
22900 When this option is set, the group owner of the file defined by the &%file%&
22901 option is checked to see that it is the same as the group under which the
22902 delivery process is running. The default setting is false because the default
22903 file mode is 0600, which means that the group is irrelevant.
22906 .option check_owner appendfile boolean true
22907 When this option is set, the owner of the file defined by the &%file%& option
22908 is checked to ensure that it is the same as the user under which the delivery
22909 process is running.
22912 .option check_string appendfile string "see below"
22913 .cindex "&""From""& line"
22914 As &(appendfile)& writes the message, the start of each line is tested for
22915 matching &%check_string%&, and if it does, the initial matching characters are
22916 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
22917 a literal string, not a regular expression, and the case of any letters it
22918 contains is significant.
22920 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
22921 are forced to &"."& and &".."& respectively, and any settings in the
22922 configuration are ignored. Otherwise, they default to &"From&~"& and
22923 &">From&~"& when the &%file%& option is set, and unset when any of the
22924 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
22926 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
22927 suitable for traditional &"BSD"& mailboxes, where a line beginning with
22928 &"From&~"& indicates the start of a new message. All four options need changing
22929 if another format is used. For example, to deliver to mailboxes in MMDF format:
22930 .cindex "MMDF format mailbox"
22931 .cindex "mailbox" "MMDF format"
22933 check_string = "\1\1\1\1\n"
22934 escape_string = "\1\1\1\1 \n"
22935 message_prefix = "\1\1\1\1\n"
22936 message_suffix = "\1\1\1\1\n"
22938 .option create_directory appendfile boolean true
22939 .cindex "directory creation"
22940 When this option is true, Exim attempts to create any missing superior
22941 directories for the file that it is about to write. A created directory's mode
22942 is given by the &%directory_mode%& option.
22944 The group ownership of a newly created directory is highly dependent on the
22945 operating system (and possibly the file system) that is being used. For
22946 example, in Solaris, if the parent directory has the setgid bit set, its group
22947 is propagated to the child; if not, the currently set group is used. However,
22948 in FreeBSD, the parent's group is always used.
22952 .option create_file appendfile string anywhere
22953 This option constrains the location of files and directories that are created
22954 by this transport. It applies to files defined by the &%file%& option and
22955 directories defined by the &%directory%& option. In the case of maildir
22956 delivery, it applies to the top level directory, not the maildir directories
22959 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
22960 &"belowhome"&. In the second and third cases, a home directory must have been
22961 set for the transport. This option is not useful when an explicit filename is
22962 given for normal mailbox deliveries. It is intended for the case when filenames
22963 are generated from users' &_.forward_& files. These are usually handled
22964 by an &(appendfile)& transport called &%address_file%&. See also
22965 &%file_must_exist%&.
22968 .option directory appendfile string&!! unset
22969 This option is mutually exclusive with the &%file%& option, but one of &%file%&
22970 or &%directory%& must be set, unless the delivery is the direct result of a
22971 redirection (see section &<<SECTfildiropt>>&).
22973 When &%directory%& is set, the string is expanded, and the message is delivered
22974 into a new file or files in or below the given directory, instead of being
22975 appended to a single mailbox file. A number of different formats are provided
22976 (see &%maildir_format%& and &%mailstore_format%&), and see section
22977 &<<SECTopdir>>& for further details of this form of delivery.
22980 .option directory_file appendfile string&!! "see below"
22982 .vindex "&$inode$&"
22983 When &%directory%& is set, but neither &%maildir_format%& nor
22984 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
22985 whose name is obtained by expanding this string. The default value is:
22987 q${base62:$tod_epoch}-$inode
22989 This generates a unique name from the current time, in base 62 form, and the
22990 inode of the file. The variable &$inode$& is available only when expanding this
22994 .option directory_mode appendfile "octal integer" 0700
22995 If &(appendfile)& creates any directories as a result of the
22996 &%create_directory%& option, their mode is specified by this option.
22999 .option escape_string appendfile string "see description"
23000 See &%check_string%& above.
23003 .option file appendfile string&!! unset
23004 This option is mutually exclusive with the &%directory%& option, but one of
23005 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23006 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23007 specifies a single file, to which the message is appended. One or more of
23008 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23011 .cindex "NFS" "lock file"
23012 .cindex "locking files"
23013 .cindex "lock files"
23014 If you are using more than one host to deliver over NFS into the same
23015 mailboxes, you should always use lock files.
23017 The string value is expanded for each delivery, and must yield an absolute
23018 path. The most common settings of this option are variations on one of these
23021 file = /var/spool/mail/$local_part_data
23022 file = /home/$local_part_data/inbox
23025 .cindex "&""sticky""& bit"
23026 In the first example, all deliveries are done into the same directory. If Exim
23027 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23028 create a file in the directory, so the &"sticky"& bit must be turned on for
23029 deliveries to be possible, or alternatively the &%group%& option can be used to
23030 run the delivery under a group id which has write access to the directory.
23034 .option file_format appendfile string unset
23035 .cindex "file" "mailbox; checking existing format"
23036 This option requests the transport to check the format of an existing file
23037 before adding to it. The check consists of matching a specific string at the
23038 start of the file. The value of the option consists of an even number of
23039 colon-separated strings. The first of each pair is the test string, and the
23040 second is the name of a transport. If the transport associated with a matched
23041 string is not the current transport, control is passed over to the other
23042 transport. For example, suppose the standard &(local_delivery)& transport has
23045 file_format = "From : local_delivery :\
23046 \1\1\1\1\n : local_mmdf_delivery"
23048 Mailboxes that begin with &"From"& are still handled by this transport, but if
23049 a mailbox begins with four binary ones followed by a newline, control is passed
23050 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23051 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23052 is assumed to match the current transport. If the start of a mailbox doesn't
23053 match any string, or if the transport named for a given string is not defined,
23054 delivery is deferred.
23057 .option file_must_exist appendfile boolean false
23058 If this option is true, the file specified by the &%file%& option must exist.
23059 A temporary error occurs if it does not, causing delivery to be deferred.
23060 If this option is false, the file is created if it does not exist.
23063 .option lock_fcntl_timeout appendfile time 0s
23064 .cindex "timeout" "mailbox locking"
23065 .cindex "mailbox" "locking, blocking and non-blocking"
23066 .cindex "locking files"
23067 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23068 when locking an open mailbox file. If the call fails, the delivery process
23069 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23070 Non-blocking calls are used so that the file is not kept open during the wait
23071 for the lock; the reason for this is to make it as safe as possible for
23072 deliveries over NFS in the case when processes might be accessing an NFS
23073 mailbox without using a lock file. This should not be done, but
23074 misunderstandings and hence misconfigurations are not unknown.
23076 On a busy system, however, the performance of a non-blocking lock approach is
23077 not as good as using a blocking lock with a timeout. In this case, the waiting
23078 is done inside the system call, and Exim's delivery process acquires the lock
23079 and can proceed as soon as the previous lock holder releases it.
23081 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23082 timeout, are used. There may still be some retrying: the maximum number of
23085 (lock_retries * lock_interval) / lock_fcntl_timeout
23087 rounded up to the next whole number. In other words, the total time during
23088 which &(appendfile)& is trying to get a lock is roughly the same, unless
23089 &%lock_fcntl_timeout%& is set very large.
23091 You should consider setting this option if you are getting a lot of delayed
23092 local deliveries because of errors of the form
23094 failed to lock mailbox /some/file (fcntl)
23097 .option lock_flock_timeout appendfile time 0s
23098 This timeout applies to file locking when using &[flock()]& (see
23099 &%use_flock%&); the timeout operates in a similar manner to
23100 &%lock_fcntl_timeout%&.
23103 .option lock_interval appendfile time 3s
23104 This specifies the time to wait between attempts to lock the file. See below
23105 for details of locking.
23108 .option lock_retries appendfile integer 10
23109 This specifies the maximum number of attempts to lock the file. A value of zero
23110 is treated as 1. See below for details of locking.
23113 .option lockfile_mode appendfile "octal integer" 0600
23114 This specifies the mode of the created lock file, when a lock file is being
23115 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23118 .option lockfile_timeout appendfile time 30m
23119 .cindex "timeout" "mailbox locking"
23120 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23121 exists and is older than this value, it is assumed to have been left behind by
23122 accident, and Exim attempts to remove it.
23125 .option mailbox_filecount appendfile string&!! unset
23126 .cindex "mailbox" "specifying size of"
23127 .cindex "size" "of mailbox"
23128 If this option is set, it is expanded, and the result is taken as the current
23129 number of files in the mailbox. It must be a decimal number, optionally
23130 followed by K or M. This provides a way of obtaining this information from an
23131 external source that maintains the data.
23134 .option mailbox_size appendfile string&!! unset
23135 .cindex "mailbox" "specifying size of"
23136 .cindex "size" "of mailbox"
23137 If this option is set, it is expanded, and the result is taken as the current
23138 size the mailbox. It must be a decimal number, optionally followed by K or M.
23139 This provides a way of obtaining this information from an external source that
23140 maintains the data. This is likely to be helpful for maildir deliveries where
23141 it is computationally expensive to compute the size of a mailbox.
23145 .option maildir_format appendfile boolean false
23146 .cindex "maildir format" "specifying"
23147 If this option is set with the &%directory%& option, the delivery is into a new
23148 file, in the &"maildir"& format that is used by other mail software. When the
23149 transport is activated directly from a &(redirect)& router (for example, the
23150 &(address_file)& transport in the default configuration), setting
23151 &%maildir_format%& causes the path received from the router to be treated as a
23152 directory, whether or not it ends with &`/`&. This option is available only if
23153 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23154 &<<SECTmaildirdelivery>>& below for further details.
23157 .option maildir_quota_directory_regex appendfile string "See below"
23158 .cindex "maildir format" "quota; directories included in"
23159 .cindex "quota" "maildir; directories included in"
23160 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23161 a regular expression for specifying directories, relative to the quota
23162 directory (see &%quota_directory%&), that should be included in the quota
23163 calculation. The default value is:
23165 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23167 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23168 (directories whose names begin with a dot). If you want to exclude the
23170 folder from the count (as some sites do), you need to change this setting to
23172 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23174 This uses a negative lookahead in the regular expression to exclude the
23175 directory whose name is &_.Trash_&. When a directory is excluded from quota
23176 calculations, quota processing is bypassed for any messages that are delivered
23177 directly into that directory.
23180 .option maildir_retries appendfile integer 10
23181 This option specifies the number of times to retry when writing a file in
23182 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23185 .option maildir_tag appendfile string&!! unset
23186 This option applies only to deliveries in maildir format, and is described in
23187 section &<<SECTmaildirdelivery>>& below.
23190 .option maildir_use_size_file appendfile&!! boolean false
23191 .cindex "maildir format" "&_maildirsize_& file"
23192 The result of string expansion for this option must be a valid boolean value.
23193 If it is true, it enables support for &_maildirsize_& files. Exim
23194 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23195 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23196 value is zero. See &%maildir_quota_directory_regex%& above and section
23197 &<<SECTmaildirdelivery>>& below for further details.
23199 .option maildirfolder_create_regex appendfile string unset
23200 .cindex "maildir format" "&_maildirfolder_& file"
23201 .cindex "&_maildirfolder_&, creating"
23202 The value of this option is a regular expression. If it is unset, it has no
23203 effect. Otherwise, before a maildir delivery takes place, the pattern is
23204 matched against the name of the maildir directory, that is, the directory
23205 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23206 delivery. If there is a match, Exim checks for the existence of a file called
23207 &_maildirfolder_& in the directory, and creates it if it does not exist.
23208 See section &<<SECTmaildirdelivery>>& for more details.
23211 .option mailstore_format appendfile boolean false
23212 .cindex "mailstore format" "specifying"
23213 If this option is set with the &%directory%& option, the delivery is into two
23214 new files in &"mailstore"& format. The option is available only if
23215 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23216 below for further details.
23219 .option mailstore_prefix appendfile string&!! unset
23220 This option applies only to deliveries in mailstore format, and is described in
23221 section &<<SECTopdir>>& below.
23224 .option mailstore_suffix appendfile string&!! unset
23225 This option applies only to deliveries in mailstore format, and is described in
23226 section &<<SECTopdir>>& below.
23229 .option mbx_format appendfile boolean false
23230 .cindex "locking files"
23231 .cindex "file" "locking"
23232 .cindex "file" "MBX format"
23233 .cindex "MBX format, specifying"
23234 This option is available only if Exim has been compiled with SUPPORT_MBX
23235 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23236 the message is appended to the mailbox file in MBX format instead of
23237 traditional Unix format. This format is supported by Pine4 and its associated
23238 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23240 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23241 automatically changed by the use of &%mbx_format%&. They should normally be set
23242 empty when using MBX format, so this option almost always appears in this
23249 If none of the locking options are mentioned in the configuration,
23250 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23251 is possible to specify the other kinds of locking with &%mbx_format%&, but
23252 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23253 interworks with &'c-client'&, providing for shared access to the mailbox. It
23254 should not be used if any program that does not use this form of locking is
23255 going to access the mailbox, nor should it be used if the mailbox file is NFS
23256 mounted, because it works only when the mailbox is accessed from a single host.
23258 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23259 the standard version of &'c-client'&, because as long as it has a mailbox open
23260 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23261 append messages to it.
23264 .option message_prefix appendfile string&!! "see below"
23265 .cindex "&""From""& line"
23266 The string specified here is expanded and output at the start of every message.
23267 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23268 in which case it is:
23270 message_prefix = "From ${if def:return_path{$return_path}\
23271 {MAILER-DAEMON}} $tod_bsdinbox\n"
23273 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23274 &`\n`& to &`\r\n`& in &%message_prefix%&.
23276 .option message_suffix appendfile string&!! "see below"
23277 The string specified here is expanded and output at the end of every message.
23278 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23279 in which case it is a single newline character. The suffix can be suppressed by
23284 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23285 &`\n`& to &`\r\n`& in &%message_suffix%&.
23287 .option mode appendfile "octal integer" 0600
23288 If the output file is created, it is given this mode. If it already exists and
23289 has wider permissions, they are reduced to this mode. If it has narrower
23290 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23291 if the delivery is the result of a &%save%& command in a filter file specifying
23292 a particular mode, the mode of the output file is always forced to take that
23293 value, and this option is ignored.
23296 .option mode_fail_narrower appendfile boolean true
23297 This option applies in the case when an existing mailbox file has a narrower
23298 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23299 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23300 continues with the delivery attempt, using the existing mode of the file.
23303 .option notify_comsat appendfile boolean false
23304 If this option is true, the &'comsat'& daemon is notified after every
23305 successful delivery to a user mailbox. This is the daemon that notifies logged
23306 on users about incoming mail.
23309 .option quota appendfile string&!! unset
23310 .cindex "quota" "imposed by Exim"
23311 This option imposes a limit on the size of the file to which Exim is appending,
23312 or to the total space used in the directory tree when the &%directory%& option
23313 is set. In the latter case, computation of the space used is expensive, because
23314 all the files in the directory (and any sub-directories) have to be
23315 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23316 &%maildir_use_size_file%& for ways to avoid this in environments where users
23317 have no shell access to their mailboxes).
23319 As there is no interlock against two simultaneous deliveries into a
23320 multi-file mailbox, it is possible for the quota to be overrun in this case.
23321 For single-file mailboxes, of course, an interlock is a necessity.
23323 A file's size is taken as its &'used'& value. Because of blocking effects, this
23324 may be a lot less than the actual amount of disk space allocated to the file.
23325 If the sizes of a number of files are being added up, the rounding effect can
23326 become quite noticeable, especially on systems that have large block sizes.
23327 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23328 the obvious value which users understand most easily.
23330 The value of the option is expanded, and must then be a numerical value
23331 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23332 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23333 and further option modifiers. If Exim is running on a system with
23334 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23337 The option modifier &%no_check%& can be used to force delivery even if the over
23338 quota condition is met. The quota gets updated as usual.
23340 &*Note*&: A value of zero is interpreted as &"no quota"&.
23342 The expansion happens while Exim is running as root, before it changes uid for
23343 the delivery. This means that files that are inaccessible to the end user can
23344 be used to hold quota values that are looked up in the expansion. When delivery
23345 fails because this quota is exceeded, the handling of the error is as for
23346 system quota failures.
23348 By default, Exim's quota checking mimics system quotas, and restricts the
23349 mailbox to the specified maximum size, though the value is not accurate to the
23350 last byte, owing to separator lines and additional headers that may get added
23351 during message delivery. When a mailbox is nearly full, large messages may get
23352 refused even though small ones are accepted, because the size of the current
23353 message is added to the quota when the check is made. This behaviour can be
23354 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23355 for exceeding the quota does not include the current message. Thus, deliveries
23356 continue until the quota has been exceeded; thereafter, no further messages are
23357 delivered. See also &%quota_warn_threshold%&.
23360 .option quota_directory appendfile string&!! unset
23361 This option defines the directory to check for quota purposes when delivering
23362 into individual files. The default is the delivery directory, or, if a file
23363 called &_maildirfolder_& exists in a maildir directory, the parent of the
23364 delivery directory.
23367 .option quota_filecount appendfile string&!! 0
23368 This option applies when the &%directory%& option is set. It limits the total
23369 number of files in the directory (compare the inode limit in system quotas). It
23370 can only be used if &%quota%& is also set. The value is expanded; an expansion
23371 failure causes delivery to be deferred. A value of zero is interpreted as
23374 The option modifier &%no_check%& can be used to force delivery even if the over
23375 quota condition is met. The quota gets updated as usual.
23377 .option quota_is_inclusive appendfile boolean true
23378 See &%quota%& above.
23381 .option quota_size_regex appendfile string unset
23382 This option applies when one of the delivery modes that writes a separate file
23383 for each message is being used. When Exim wants to find the size of one of
23384 these files in order to test the quota, it first checks &%quota_size_regex%&.
23385 If this is set to a regular expression that matches the filename, and it
23386 captures one string, that string is interpreted as a representation of the
23387 file's size. The value of &%quota_size_regex%& is not expanded.
23389 This feature is useful only when users have no shell access to their mailboxes
23390 &-- otherwise they could defeat the quota simply by renaming the files. This
23391 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23392 the file length to the filename. For example:
23394 maildir_tag = ,S=$message_size
23395 quota_size_regex = ,S=(\d+)
23397 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23398 number of lines in the message.
23400 The regular expression should not assume that the length is at the end of the
23401 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23402 sometimes add other information onto the ends of message filenames.
23404 Section &<<SECID136>>& contains further information.
23406 This option should not be used when other message-handling software
23407 may duplicate messages by making hardlinks to the files. When that is done Exim
23408 will count the message size once for each filename, in contrast with the actual
23409 disk usage. When the option is not set, calculating total usage requires
23410 a system-call per file to get the size; the number of links is then available also
23411 as is used to adjust the effective size.
23414 .option quota_warn_message appendfile string&!! "see below"
23415 See below for the use of this option. If it is not set when
23416 &%quota_warn_threshold%& is set, it defaults to
23418 quota_warn_message = "\
23419 To: $local_part@$domain\n\
23420 Subject: Your mailbox\n\n\
23421 This message is automatically created \
23422 by mail delivery software.\n\n\
23423 The size of your mailbox has exceeded \
23424 a warning threshold that is\n\
23425 set by the system administrator.\n"
23429 .option quota_warn_threshold appendfile string&!! 0
23430 .cindex "quota" "warning threshold"
23431 .cindex "mailbox" "size warning"
23432 .cindex "size" "of mailbox"
23433 This option is expanded in the same way as &%quota%& (see above). If the
23434 resulting value is greater than zero, and delivery of the message causes the
23435 size of the file or total space in the directory tree to cross the given
23436 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23437 may be specified as a percentage of it by following the value with a percent
23441 quota_warn_threshold = 75%
23443 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23444 percent sign is ignored.
23446 The warning message itself is specified by the &%quota_warn_message%& option,
23447 and it must start with a &'To:'& header line containing the recipient(s) of the
23448 warning message. These do not necessarily have to include the recipient(s) of
23449 the original message. A &'Subject:'& line should also normally be supplied. You
23450 can include any other header lines that you want. If you do not include a
23451 &'From:'& line, the default is:
23453 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23455 .oindex &%errors_reply_to%&
23456 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23459 The &%quota%& option does not have to be set in order to use this option; they
23460 are independent of one another except when the threshold is specified as a
23464 .option use_bsmtp appendfile boolean false
23465 .cindex "envelope from"
23466 .cindex "envelope sender"
23467 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23468 format, with the envelope sender and recipient(s) included as SMTP commands. If
23469 you want to include a leading HELO command with such messages, you can do
23470 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23471 for details of batch SMTP.
23474 .option use_crlf appendfile boolean false
23475 .cindex "carriage return"
23477 This option causes lines to be terminated with the two-character CRLF sequence
23478 (carriage return, linefeed) instead of just a linefeed character. In the case
23479 of batched SMTP, the byte sequence written to the file is then an exact image
23480 of what would be sent down a real SMTP connection.
23482 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23483 (which are used to supply the traditional &"From&~"& and blank line separators
23484 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23485 carriage return characters if these are needed. In cases where these options
23486 have non-empty defaults, the values end with a single linefeed, so they must be
23487 changed to end with &`\r\n`& if &%use_crlf%& is set.
23490 .option use_fcntl_lock appendfile boolean "see below"
23491 This option controls the use of the &[fcntl()]& function to lock a file for
23492 exclusive use when a message is being appended. It is set by default unless
23493 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23494 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23495 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23498 .option use_flock_lock appendfile boolean false
23499 This option is provided to support the use of &[flock()]& for file locking, for
23500 the few situations where it is needed. Most modern operating systems support
23501 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23502 each other. Exim uses &[fcntl()]& locking by default.
23504 This option is required only if you are using an operating system where
23505 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23506 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23507 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23509 .cindex "Solaris" "&[flock()]& support"
23510 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23511 have it (and some, I think, provide a not quite right version built on top of
23512 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23513 the ability to use it, and any attempt to do so will cause a configuration
23516 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23517 is just being mapped onto &[fcntl()]& by the OS).
23520 .option use_lockfile appendfile boolean "see below"
23521 If this option is turned off, Exim does not attempt to create a lock file when
23522 appending to a mailbox file. In this situation, the only locking is by
23523 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23524 sure that every MUA that is ever going to look at your users' mailboxes uses
23525 &[fcntl()]& rather than a lock file, and even then only when you are not
23526 delivering over NFS from more than one host.
23528 .cindex "NFS" "lock file"
23529 In order to append to an NFS file safely from more than one host, it is
23530 necessary to take out a lock &'before'& opening the file, and the lock file
23531 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23534 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23535 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23536 except when &%mbx_format%& is set.
23539 .option use_mbx_lock appendfile boolean "see below"
23540 This option is available only if Exim has been compiled with SUPPORT_MBX
23541 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23542 locking rules be used. It is set by default if &%mbx_format%& is set and none
23543 of the locking options are mentioned in the configuration. The locking rules
23544 are the same as are used by the &'c-client'& library that underlies Pine and
23545 the IMAP4 and POP daemons that come with it (see the discussion below). The
23546 rules allow for shared access to the mailbox. However, this kind of locking
23547 does not work when the mailbox is NFS mounted.
23549 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23550 &%use_flock_lock%& to control what kind of locking is used in implementing the
23551 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23552 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23557 .section "Operational details for appending" "SECTopappend"
23558 .cindex "appending to a file"
23559 .cindex "file" "appending"
23560 Before appending to a file, the following preparations are made:
23563 If the name of the file is &_/dev/null_&, no action is taken, and a success
23567 .cindex "directory creation"
23568 If any directories on the file's path are missing, Exim creates them if the
23569 &%create_directory%& option is set. A created directory's mode is given by the
23570 &%directory_mode%& option.
23573 If &%file_format%& is set, the format of an existing file is checked. If this
23574 indicates that a different transport should be used, control is passed to that
23578 .cindex "file" "locking"
23579 .cindex "locking files"
23580 .cindex "NFS" "lock file"
23581 If &%use_lockfile%& is set, a lock file is built in a way that will work
23582 reliably over NFS, as follows:
23585 Create a &"hitching post"& file whose name is that of the lock file with the
23586 current time, primary host name, and process id added, by opening for writing
23587 as a new file. If this fails with an access error, delivery is deferred.
23589 Close the hitching post file, and hard link it to the lock filename.
23591 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23592 Unlink the hitching post name.
23594 Otherwise, use &[stat()]& to get information about the hitching post file, and
23595 then unlink hitching post name. If the number of links is exactly two, creation
23596 of the lock file succeeded but something (for example, an NFS server crash and
23597 restart) caused this fact not to be communicated to the &[link()]& call.
23599 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23600 up to &%lock_retries%& times. However, since any program that writes to a
23601 mailbox should complete its task very quickly, it is reasonable to time out old
23602 lock files that are normally the result of user agent and system crashes. If an
23603 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23604 it before trying again.
23608 A call is made to &[lstat()]& to discover whether the main file exists, and if
23609 so, what its characteristics are. If &[lstat()]& fails for any reason other
23610 than non-existence, delivery is deferred.
23613 .cindex "symbolic link" "to mailbox"
23614 .cindex "mailbox" "symbolic link"
23615 If the file does exist and is a symbolic link, delivery is deferred, unless the
23616 &%allow_symlink%& option is set, in which case the ownership of the link is
23617 checked, and then &[stat()]& is called to find out about the real file, which
23618 is then subjected to the checks below. The check on the top-level link
23619 ownership prevents one user creating a link for another's mailbox in a sticky
23620 directory, though allowing symbolic links in this case is definitely not a good
23621 idea. If there is a chain of symbolic links, the intermediate ones are not
23625 If the file already exists but is not a regular file, or if the file's owner
23626 and group (if the group is being checked &-- see &%check_group%& above) are
23627 different from the user and group under which the delivery is running,
23628 delivery is deferred.
23631 If the file's permissions are more generous than specified, they are reduced.
23632 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23633 is set false, in which case the delivery is tried using the existing
23637 The file's inode number is saved, and the file is then opened for appending.
23638 If this fails because the file has vanished, &(appendfile)& behaves as if it
23639 hadn't existed (see below). For any other failures, delivery is deferred.
23642 If the file is opened successfully, check that the inode number hasn't
23643 changed, that it is still a regular file, and that the owner and permissions
23644 have not changed. If anything is wrong, defer delivery and freeze the message.
23647 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23648 option is set. Otherwise, check that the file is being created in a permitted
23649 directory if the &%create_file%& option is set (deferring on failure), and then
23650 open for writing as a new file, with the O_EXCL and O_CREAT options,
23651 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23652 set). In this case, which can happen if the link points to a non-existent file,
23653 the file is opened for writing using O_CREAT but not O_EXCL, because
23654 that prevents link following.
23657 .cindex "loop" "while file testing"
23658 If opening fails because the file exists, obey the tests given above for
23659 existing files. However, to avoid looping in a situation where the file is
23660 being continuously created and destroyed, the exists/not-exists loop is broken
23661 after 10 repetitions, and the message is then frozen.
23664 If opening fails with any other error, defer delivery.
23667 .cindex "file" "locking"
23668 .cindex "locking files"
23669 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23670 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23671 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23672 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23673 file, and an exclusive lock on the file whose name is
23675 /tmp/.<device-number>.<inode-number>
23677 using the device and inode numbers of the open mailbox file, in accordance with
23678 the MBX locking rules. This file is created with a mode that is specified by
23679 the &%lockfile_mode%& option.
23681 If Exim fails to lock the file, there are two possible courses of action,
23682 depending on the value of the locking timeout. This is obtained from
23683 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23685 If the timeout value is zero, the file is closed, Exim waits for
23686 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23687 to lock it again. This happens up to &%lock_retries%& times, after which the
23688 delivery is deferred.
23690 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23691 &[flock()]& are used (with the given timeout), so there has already been some
23692 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23693 immediately. It retries up to
23695 (lock_retries * lock_interval) / <timeout>
23697 times (rounded up).
23700 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23701 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23704 .section "Operational details for delivery to a new file" "SECTopdir"
23705 .cindex "delivery" "to single file"
23706 .cindex "&""From""& line"
23707 When the &%directory%& option is set instead of &%file%&, each message is
23708 delivered into a newly-created file or set of files. When &(appendfile)& is
23709 activated directly from a &(redirect)& router, neither &%file%& nor
23710 &%directory%& is normally set, because the path for delivery is supplied by the
23711 router. (See for example, the &(address_file)& transport in the default
23712 configuration.) In this case, delivery is to a new file if either the path name
23713 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23715 No locking is required while writing the message to a new file, so the various
23716 locking options of the transport are ignored. The &"From"& line that by default
23717 separates messages in a single file is not normally needed, nor is the escaping
23718 of message lines that start with &"From"&, and there is no need to ensure a
23719 newline at the end of each message. Consequently, the default values for
23720 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23721 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23723 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23724 the files in the delivery directory by default. However, you can specify a
23725 different directory by setting &%quota_directory%&. Also, for maildir
23726 deliveries (see below) the &_maildirfolder_& convention is honoured.
23729 .cindex "maildir format"
23730 .cindex "mailstore format"
23731 There are three different ways in which delivery to individual files can be
23732 done, controlled by the settings of the &%maildir_format%& and
23733 &%mailstore_format%& options. Note that code to support maildir or mailstore
23734 formats is not included in the binary unless SUPPORT_MAILDIR or
23735 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23737 .cindex "directory creation"
23738 In all three cases an attempt is made to create the directory and any necessary
23739 sub-directories if they do not exist, provided that the &%create_directory%&
23740 option is set (the default). The location of a created directory can be
23741 constrained by setting &%create_file%&. A created directory's mode is given by
23742 the &%directory_mode%& option. If creation fails, or if the
23743 &%create_directory%& option is not set when creation is required, delivery is
23748 .section "Maildir delivery" "SECTmaildirdelivery"
23749 .cindex "maildir format" "description of"
23750 If the &%maildir_format%& option is true, Exim delivers each message by writing
23751 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23752 directory that is defined by the &%directory%& option (the &"delivery
23753 directory"&). If the delivery is successful, the file is renamed into the
23754 &_new_& subdirectory.
23756 In the filename, <&'stime'&> is the current time of day in seconds, and
23757 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23758 Exim checks that the time-of-day clock has moved on by at least one microsecond
23759 before terminating the delivery process. This guarantees uniqueness for the
23760 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23761 opening it. If any response other than ENOENT (does not exist) is given,
23762 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23764 Before Exim carries out a maildir delivery, it ensures that subdirectories
23765 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23766 do not exist, Exim tries to create them and any superior directories in their
23767 path, subject to the &%create_directory%& and &%create_file%& options. If the
23768 &%maildirfolder_create_regex%& option is set, and the regular expression it
23769 contains matches the delivery directory, Exim also ensures that a file called
23770 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23771 &_maildirfolder_& file cannot be created, delivery is deferred.
23773 These features make it possible to use Exim to create all the necessary files
23774 and directories in a maildir mailbox, including subdirectories for maildir++
23775 folders. Consider this example:
23777 maildir_format = true
23778 directory = /var/mail/$local_part_data\
23779 ${if eq{$local_part_suffix}{}{}\
23780 {/.${substr_1:$local_part_suffix}}}
23781 maildirfolder_create_regex = /\.[^/]+$
23783 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23784 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23785 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23786 not match this name, so Exim will not look for or create the file
23787 &_/var/mail/pimbo/maildirfolder_&, though it will create
23788 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23790 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23791 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23792 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23793 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23794 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23796 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23797 not inadvertently match the toplevel maildir directory, because a
23798 &_maildirfolder_& file at top level would completely break quota calculations.
23800 .cindex "quota" "in maildir delivery"
23801 .cindex "maildir++"
23802 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23803 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23804 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23805 Exim assumes the directory is a maildir++ folder directory, which is one level
23806 down from the user's top level mailbox directory. This causes it to start at
23807 the parent directory instead of the current directory when calculating the
23808 amount of space used.
23810 One problem with delivering into a multi-file mailbox is that it is
23811 computationally expensive to compute the size of the mailbox for quota
23812 checking. Various approaches have been taken to reduce the amount of work
23813 needed. The next two sections describe two of them. A third alternative is to
23814 use some external process for maintaining the size data, and use the expansion
23815 of the &%mailbox_size%& option as a way of importing it into Exim.
23820 .section "Using tags to record message sizes" "SECID135"
23821 If &%maildir_tag%& is set, the string is expanded for each delivery.
23822 When the maildir file is renamed into the &_new_& sub-directory, the
23823 tag is added to its name. However, if adding the tag takes the length of the
23824 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
23825 the tag is dropped and the maildir file is created with no tag.
23828 .vindex "&$message_size$&"
23829 Tags can be used to encode the size of files in their names; see
23830 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
23831 happens after the message has been written. The value of the &$message_size$&
23832 variable is set to the number of bytes actually written. If the expansion is
23833 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
23834 be deferred. The expanded tag may contain any printing characters except &"/"&.
23835 Non-printing characters in the string are ignored; if the resulting string is
23836 empty, it is ignored. If it starts with an alphanumeric character, a leading
23837 colon is inserted; this default has not proven to be the path that popular
23838 maildir implementations have chosen (but changing it in Exim would break
23839 backwards compatibility).
23841 For one common implementation, you might set:
23843 maildir_tag = ,S=${message_size}
23845 but you should check the documentation of the other software to be sure.
23847 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
23848 as this allows Exim to extract the size from your tag, instead of having to
23849 &[stat()]& each message file.
23852 .section "Using a maildirsize file" "SECID136"
23853 .cindex "quota" "in maildir delivery"
23854 .cindex "maildir format" "&_maildirsize_& file"
23855 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
23856 storing quota and message size information in a file called &_maildirsize_&
23857 within the toplevel maildir directory. If this file does not exist, Exim
23858 creates it, setting the quota from the &%quota%& option of the transport. If
23859 the maildir directory itself does not exist, it is created before any attempt
23860 to write a &_maildirsize_& file.
23862 The &_maildirsize_& file is used to hold information about the sizes of
23863 messages in the maildir, thus speeding up quota calculations. The quota value
23864 in the file is just a cache; if the quota is changed in the transport, the new
23865 value overrides the cached value when the next message is delivered. The cache
23866 is maintained for the benefit of other programs that access the maildir and
23867 need to know the quota.
23869 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
23870 file is maintained (with a zero quota setting), but no quota is imposed.
23872 A regular expression is available for controlling which directories in the
23873 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
23874 See the description of the &%maildir_quota_directory_regex%& option above for
23878 .section "Mailstore delivery" "SECID137"
23879 .cindex "mailstore format" "description of"
23880 If the &%mailstore_format%& option is true, each message is written as two
23881 files in the given directory. A unique base name is constructed from the
23882 message id and the current delivery process, and the files that are written use
23883 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
23884 contains the message's envelope, and the &_.msg_& file contains the message
23885 itself. The base name is placed in the variable &$mailstore_basename$&.
23887 During delivery, the envelope is first written to a file with the suffix
23888 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
23889 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
23890 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
23891 file before accessing either of them. An alternative approach is to wait for
23892 the absence of a &_.tmp_& file.
23894 The envelope file starts with any text defined by the &%mailstore_prefix%&
23895 option, expanded and terminated by a newline if there isn't one. Then follows
23896 the sender address on one line, then all the recipient addresses, one per line.
23897 There can be more than one recipient only if the &%batch_max%& option is set
23898 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
23899 appended to the file, followed by a newline if it does not end with one.
23901 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
23902 failure, it is ignored. Other expansion errors are treated as serious
23903 configuration errors, and delivery is deferred. The variable
23904 &$mailstore_basename$& is available for use during these expansions.
23907 .section "Non-special new file delivery" "SECID138"
23908 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
23909 file is created directly in the named directory. For example, when delivering
23910 messages into files in batched SMTP format for later delivery to some host (see
23911 section &<<SECTbatchSMTP>>&), a setting such as
23913 directory = /var/bsmtp/$host
23915 might be used. A message is written to a file with a temporary name, which is
23916 then renamed when the delivery is complete. The final name is obtained by
23917 expanding the contents of the &%directory_file%& option.
23918 .ecindex IIDapptra1
23919 .ecindex IIDapptra2
23926 . ////////////////////////////////////////////////////////////////////////////
23927 . ////////////////////////////////////////////////////////////////////////////
23929 .chapter "The autoreply transport" "CHID8"
23930 .scindex IIDauttra1 "transports" "&(autoreply)&"
23931 .scindex IIDauttra2 "&(autoreply)& transport"
23932 The &(autoreply)& transport is not a true transport in that it does not cause
23933 the message to be transmitted. Instead, it generates a new mail message as an
23934 automatic reply to the incoming message. &'References:'& and
23935 &'Auto-Submitted:'& header lines are included. These are constructed according
23936 to the rules in RFCs 2822 and 3834, respectively.
23938 If the router that passes the message to this transport does not have the
23939 &%unseen%& option set, the original message (for the current recipient) is not
23940 delivered anywhere. However, when the &%unseen%& option is set on the router
23941 that passes the message to this transport, routing of the address continues, so
23942 another router can set up a normal message delivery.
23945 The &(autoreply)& transport is usually run as the result of mail filtering, a
23946 &"vacation"& message being the standard example. However, it can also be run
23947 directly from a router like any other transport. To reduce the possibility of
23948 message cascades, messages created by the &(autoreply)& transport always have
23949 empty envelope sender addresses, like bounce messages.
23951 The parameters of the message to be sent can be specified in the configuration
23952 by options described below. However, these are used only when the address
23953 passed to the transport does not contain its own reply information. When the
23954 transport is run as a consequence of a
23956 or &%vacation%& command in a filter file, the parameters of the message are
23957 supplied by the filter, and passed with the address. The transport's options
23958 that define the message are then ignored (so they are not usually set in this
23959 case). The message is specified entirely by the filter or by the transport; it
23960 is never built from a mixture of options. However, the &%file_optional%&,
23961 &%mode%&, and &%return_message%& options apply in all cases.
23963 &(Autoreply)& is implemented as a local transport. When used as a result of a
23964 command in a user's filter file, &(autoreply)& normally runs under the uid and
23965 gid of the user, and with appropriate current and home directories (see chapter
23966 &<<CHAPenvironment>>&).
23968 There is a subtle difference between routing a message to a &(pipe)& transport
23969 that generates some text to be returned to the sender, and routing it to an
23970 &(autoreply)& transport. This difference is noticeable only if more than one
23971 address from the same message is so handled. In the case of a pipe, the
23972 separate outputs from the different addresses are gathered up and returned to
23973 the sender in a single message, whereas if &(autoreply)& is used, a separate
23974 message is generated for each address that is passed to it.
23976 Non-printing characters are not permitted in the header lines generated for the
23977 message that &(autoreply)& creates, with the exception of newlines that are
23978 immediately followed by white space. If any non-printing characters are found,
23979 the transport defers.
23980 Whether characters with the top bit set count as printing characters or not is
23981 controlled by the &%print_topbitchars%& global option.
23983 If any of the generic options for manipulating headers (for example,
23984 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
23985 of the original message that is included in the generated message when
23986 &%return_message%& is set. They do not apply to the generated message itself.
23988 .vindex "&$sender_address$&"
23989 If the &(autoreply)& transport receives return code 2 from Exim when it submits
23990 the message, indicating that there were no recipients, it does not treat this
23991 as an error. This means that autoreplies sent to &$sender_address$& when this
23992 is empty (because the incoming message is a bounce message) do not cause
23993 problems. They are just discarded.
23997 .section "Private options for autoreply" "SECID139"
23998 .cindex "options" "&(autoreply)& transport"
24000 .option bcc autoreply string&!! unset
24001 This specifies the addresses that are to receive &"blind carbon copies"& of the
24002 message when the message is specified by the transport.
24005 .option cc autoreply string&!! unset
24006 This specifies recipients of the message and the contents of the &'Cc:'& header
24007 when the message is specified by the transport.
24010 .option file autoreply string&!! unset
24011 The contents of the file are sent as the body of the message when the message
24012 is specified by the transport. If both &%file%& and &%text%& are set, the text
24013 string comes first.
24016 .option file_expand autoreply boolean false
24017 If this is set, the contents of the file named by the &%file%& option are
24018 subjected to string expansion as they are added to the message.
24021 .option file_optional autoreply boolean false
24022 If this option is true, no error is generated if the file named by the &%file%&
24023 option or passed with the address does not exist or cannot be read.
24026 .option from autoreply string&!! unset
24027 This specifies the contents of the &'From:'& header when the message is
24028 specified by the transport.
24031 .option headers autoreply string&!! unset
24032 This specifies additional RFC 2822 headers that are to be added to the message
24033 when the message is specified by the transport. Several can be given by using
24034 &"\n"& to separate them. There is no check on the format.
24037 .option log autoreply string&!! unset
24038 This option names a file in which a record of every message sent is logged when
24039 the message is specified by the transport.
24042 .option mode autoreply "octal integer" 0600
24043 If either the log file or the &"once"& file has to be created, this mode is
24047 .option never_mail autoreply "address list&!!" unset
24048 If any run of the transport creates a message with a recipient that matches any
24049 item in the list, that recipient is quietly discarded. If all recipients are
24050 discarded, no message is created. This applies both when the recipients are
24051 generated by a filter and when they are specified in the transport.
24055 .option once autoreply string&!! unset
24056 This option names a file or DBM database in which a record of each &'To:'&
24057 recipient is kept when the message is specified by the transport. &*Note*&:
24058 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24060 If &%once%& is unset, or is set to an empty string, the message is always sent.
24061 By default, if &%once%& is set to a non-empty filename, the message
24062 is not sent if a potential recipient is already listed in the database.
24063 However, if the &%once_repeat%& option specifies a time greater than zero, the
24064 message is sent if that much time has elapsed since a message was last sent to
24065 this recipient. A setting of zero time for &%once_repeat%& (the default)
24066 prevents a message from being sent a second time &-- in this case, zero means
24069 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24070 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24071 greater than zero, it changes the way Exim implements the &%once%& option.
24072 Instead of using a DBM file to record every recipient it sends to, it uses a
24073 regular file, whose size will never get larger than the given value.
24075 In the file, Exim keeps a linear list of recipient addresses and the times at
24076 which they were sent messages. If the file is full when a new address needs to
24077 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24078 means that a given recipient may receive multiple messages, but at
24079 unpredictable intervals that depend on the rate of turnover of addresses in the
24080 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24083 .option once_file_size autoreply integer 0
24084 See &%once%& above.
24087 .option once_repeat autoreply time&!! 0s
24088 See &%once%& above.
24089 After expansion, the value of this option must be a valid time value.
24092 .option reply_to autoreply string&!! unset
24093 This specifies the contents of the &'Reply-To:'& header when the message is
24094 specified by the transport.
24097 .option return_message autoreply boolean false
24098 If this is set, a copy of the original message is returned with the new
24099 message, subject to the maximum size set in the &%return_size_limit%& global
24100 configuration option.
24103 .option subject autoreply string&!! unset
24104 This specifies the contents of the &'Subject:'& header when the message is
24105 specified by the transport. It is tempting to quote the original subject in
24106 automatic responses. For example:
24108 subject = Re: $h_subject:
24110 There is a danger in doing this, however. It may allow a third party to
24111 subscribe your users to an opt-in mailing list, provided that the list accepts
24112 bounce messages as subscription confirmations. Well-managed lists require a
24113 non-bounce message to confirm a subscription, so the danger is relatively
24118 .option text autoreply string&!! unset
24119 This specifies a single string to be used as the body of the message when the
24120 message is specified by the transport. If both &%text%& and &%file%& are set,
24121 the text comes first.
24124 .option to autoreply string&!! unset
24125 This specifies recipients of the message and the contents of the &'To:'& header
24126 when the message is specified by the transport.
24127 .ecindex IIDauttra1
24128 .ecindex IIDauttra2
24133 . ////////////////////////////////////////////////////////////////////////////
24134 . ////////////////////////////////////////////////////////////////////////////
24136 .chapter "The lmtp transport" "CHAPLMTP"
24137 .cindex "transports" "&(lmtp)&"
24138 .cindex "&(lmtp)& transport"
24139 .cindex "LMTP" "over a pipe"
24140 .cindex "LMTP" "over a socket"
24141 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24143 or by interacting with a Unix domain socket.
24144 This transport is something of a cross between the &(pipe)& and &(smtp)&
24145 transports. Exim also has support for using LMTP over TCP/IP; this is
24146 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24147 to be of minority interest, the default build-time configure in &_src/EDITME_&
24148 has it commented out. You need to ensure that
24152 .cindex "options" "&(lmtp)& transport"
24153 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24154 included in the Exim binary. The private options of the &(lmtp)& transport are
24157 .option batch_id lmtp string&!! unset
24158 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24161 .option batch_max lmtp integer 1
24162 This limits the number of addresses that can be handled in a single delivery.
24163 Most LMTP servers can handle several addresses at once, so it is normally a
24164 good idea to increase this value. See the description of local delivery
24165 batching in chapter &<<CHAPbatching>>&.
24168 .option command lmtp string&!! unset
24169 This option must be set if &%socket%& is not set. The string is a command which
24170 is run in a separate process. It is split up into a command name and list of
24171 arguments, each of which is separately expanded (so expansion cannot change the
24172 number of arguments). The command is run directly, not via a shell. The message
24173 is passed to the new process using the standard input and output to operate the
24176 .option ignore_quota lmtp boolean false
24177 .cindex "LMTP" "ignoring quota errors"
24178 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24179 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24180 in its response to the LHLO command.
24182 .option socket lmtp string&!! unset
24183 This option must be set if &%command%& is not set. The result of expansion must
24184 be the name of a Unix domain socket. The transport connects to the socket and
24185 delivers the message to it using the LMTP protocol.
24188 .option timeout lmtp time 5m
24189 The transport is aborted if the created process or Unix domain socket does not
24190 respond to LMTP commands or message input within this timeout. Delivery
24191 is deferred, and will be tried again later. Here is an example of a typical
24196 command = /some/local/lmtp/delivery/program
24200 This delivers up to 20 addresses at a time, in a mixture of domains if
24201 necessary, running as the user &'exim'&.
24205 . ////////////////////////////////////////////////////////////////////////////
24206 . ////////////////////////////////////////////////////////////////////////////
24208 .chapter "The pipe transport" "CHAPpipetransport"
24209 .scindex IIDpiptra1 "transports" "&(pipe)&"
24210 .scindex IIDpiptra2 "&(pipe)& transport"
24211 The &(pipe)& transport is used to deliver messages via a pipe to a command
24212 running in another process. One example is the use of &(pipe)& as a
24213 pseudo-remote transport for passing messages to some other delivery mechanism
24214 (such as UUCP). Another is the use by individual users to automatically process
24215 their incoming messages. The &(pipe)& transport can be used in one of the
24219 .vindex "&$local_part$&"
24220 A router routes one address to a transport in the normal way, and the
24221 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24222 contains the local part of the address (as usual), and the command that is run
24223 is specified by the &%command%& option on the transport.
24225 .vindex "&$pipe_addresses$&"
24226 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24227 transport can handle more than one address in a single run. In this case, when
24228 more than one address is routed to the transport, &$local_part$& is not set
24229 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24230 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24231 that are routed to the transport.
24233 .vindex "&$address_pipe$&"
24234 A router redirects an address directly to a pipe command (for example, from an
24235 alias or forward file). In this case, &$address_pipe$& contains the text of the
24236 pipe command, and the &%command%& option on the transport is ignored unless
24237 &%force_command%& is set. If only one address is being transported
24238 (&%batch_max%& is not greater than one, or only one address was redirected to
24239 this pipe command), &$local_part$& contains the local part that was redirected.
24243 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24244 deliver messages over pipes using the LMTP interactive protocol. This is
24245 implemented by the &(lmtp)& transport.
24247 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24248 &_.forward_& file, the command runs under the uid and gid of that user. In
24249 other cases, the uid and gid have to be specified explicitly, either on the
24250 transport or on the router that handles the address. Current and &"home"&
24251 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24252 details of the local delivery environment and chapter &<<CHAPbatching>>&
24253 for a discussion of local delivery batching.
24256 .cindex "tainted data" "in pipe command"
24257 .cindex pipe "tainted data"
24258 Tainted data may not be used for the command name.
24262 .section "Concurrent delivery" "SECID140"
24263 If two messages arrive at almost the same time, and both are routed to a pipe
24264 delivery, the two pipe transports may be run concurrently. You must ensure that
24265 any pipe commands you set up are robust against this happening. If the commands
24266 write to a file, the &%exim_lock%& utility might be of use.
24267 Alternatively the &%max_parallel%& option could be used with a value
24268 of "1" to enforce serialization.
24273 .section "Returned status and data" "SECID141"
24274 .cindex "&(pipe)& transport" "returned data"
24275 If the command exits with a non-zero return code, the delivery is deemed to
24276 have failed, unless either the &%ignore_status%& option is set (in which case
24277 the return code is treated as zero), or the return code is one of those listed
24278 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24279 later"&. In this case, delivery is deferred. Details of a permanent failure are
24280 logged, but are not included in the bounce message, which merely contains
24281 &"local delivery failed"&.
24283 If the command exits on a signal and the &%freeze_signal%& option is set then
24284 the message will be frozen in the queue. If that option is not set, a bounce
24285 will be sent as normal.
24287 If the return code is greater than 128 and the command being run is a shell
24288 script, it normally means that the script was terminated by a signal whose
24289 value is the return code minus 128. The &%freeze_signal%& option does not
24290 apply in this case.
24292 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24293 return code is set to 127. This is the value that a shell returns if it is
24294 asked to run a non-existent command. The wording for the log line suggests that
24295 a non-existent command may be the problem.
24297 The &%return_output%& option can affect the result of a pipe delivery. If it is
24298 set and the command produces any output on its standard output or standard
24299 error streams, the command is considered to have failed, even if it gave a zero
24300 return code or if &%ignore_status%& is set. The output from the command is
24301 included as part of the bounce message. The &%return_fail_output%& option is
24302 similar, except that output is returned only when the command exits with a
24303 failure return code, that is, a value other than zero or a code that matches
24308 .section "How the command is run" "SECThowcommandrun"
24309 .cindex "&(pipe)& transport" "path for command"
24310 The command line is (by default) broken down into a command name and arguments
24311 by the &(pipe)& transport itself. The &%allow_commands%& and
24312 &%restrict_to_path%& options can be used to restrict the commands that may be
24315 .cindex "quoting" "in pipe command"
24316 Unquoted arguments are delimited by white space. If an argument appears in
24317 double quotes, backslash is interpreted as an escape character in the usual
24318 way. If an argument appears in single quotes, no escaping is done.
24320 String expansion is applied to the command line except when it comes from a
24321 traditional &_.forward_& file (commands from a filter file are expanded). The
24322 expansion is applied to each argument in turn rather than to the whole line.
24323 For this reason, any string expansion item that contains white space must be
24324 quoted so as to be contained within a single argument. A setting such as
24326 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24328 will not work, because the expansion item gets split between several
24329 arguments. You have to write
24331 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24333 to ensure that it is all in one argument. The expansion is done in this way,
24334 argument by argument, so that the number of arguments cannot be changed as a
24335 result of expansion, and quotes or backslashes in inserted variables do not
24336 interact with external quoting. However, this leads to problems if you want to
24337 generate multiple arguments (or the command name plus arguments) from a single
24338 expansion. In this situation, the simplest solution is to use a shell. For
24341 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24344 .cindex "transport" "filter"
24345 .cindex "filter" "transport filter"
24346 .vindex "&$pipe_addresses$&"
24347 Special handling takes place when an argument consists of precisely the text
24348 &`$pipe_addresses`& (no quotes).
24349 This is not a general expansion variable; the only
24350 place this string is recognized is when it appears as an argument for a pipe or
24351 transport filter command. It causes each address that is being handled to be
24352 inserted in the argument list at that point &'as a separate argument'&. This
24353 avoids any problems with spaces or shell metacharacters, and is of use when a
24354 &(pipe)& transport is handling groups of addresses in a batch.
24356 If &%force_command%& is enabled on the transport, special handling takes place
24357 for an argument that consists of precisely the text &`$address_pipe`&. It
24358 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24359 argument is inserted in the argument list at that point
24360 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24361 the only item in the argument; in fact, if it were then &%force_command%&
24362 should behave as a no-op. Rather, it should be used to adjust the command
24363 run while preserving the argument vector separation.
24365 After splitting up into arguments and expansion, the resulting command is run
24366 in a subprocess directly from the transport, &'not'& under a shell. The
24367 message that is being delivered is supplied on the standard input, and the
24368 standard output and standard error are both connected to a single pipe that is
24369 read by Exim. The &%max_output%& option controls how much output the command
24370 may produce, and the &%return_output%& and &%return_fail_output%& options
24371 control what is done with it.
24373 Not running the command under a shell (by default) lessens the security risks
24374 in cases when a command from a user's filter file is built out of data that was
24375 taken from an incoming message. If a shell is required, it can of course be
24376 explicitly specified as the command to be run. However, there are circumstances
24377 where existing commands (for example, in &_.forward_& files) expect to be run
24378 under a shell and cannot easily be modified. To allow for these cases, there is
24379 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24380 works. Instead of breaking up the command line as just described, it expands it
24381 as a single string and passes the result to &_/bin/sh_&. The
24382 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24383 with &%use_shell%&, and the whole mechanism is inherently less secure.
24387 .section "Environment variables" "SECTpipeenv"
24388 .cindex "&(pipe)& transport" "environment for command"
24389 .cindex "environment" "&(pipe)& transport"
24390 The environment variables listed below are set up when the command is invoked.
24391 This list is a compromise for maximum compatibility with other MTAs. Note that
24392 the &%environment%& option can be used to add additional variables to this
24393 environment. The environment for the &(pipe)& transport is not subject
24394 to the &%add_environment%& and &%keep_environment%& main config options.
24396 &`DOMAIN `& the domain of the address
24397 &`HOME `& the home directory, if set
24398 &`HOST `& the host name when called from a router (see below)
24399 &`LOCAL_PART `& see below
24400 &`LOCAL_PART_PREFIX `& see below
24401 &`LOCAL_PART_SUFFIX `& see below
24402 &`LOGNAME `& see below
24403 &`MESSAGE_ID `& Exim's local ID for the message
24404 &`PATH `& as specified by the &%path%& option below
24405 &`QUALIFY_DOMAIN `& the sender qualification domain
24406 &`RECIPIENT `& the complete recipient address
24407 &`SENDER `& the sender of the message (empty if a bounce)
24408 &`SHELL `& &`/bin/sh`&
24409 &`TZ `& the value of the &%timezone%& option, if set
24410 &`USER `& see below
24412 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24413 router, LOCAL_PART is set to the local part of the address. When it is
24414 called as a result of a forward or alias expansion, LOCAL_PART is set to
24415 the local part of the address that was expanded. In both cases, any affixes are
24416 removed from the local part, and made available in LOCAL_PART_PREFIX and
24417 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24418 same value as LOCAL_PART for compatibility with other MTAs.
24421 HOST is set only when a &(pipe)& transport is called from a router that
24422 associates hosts with an address, typically when using &(pipe)& as a
24423 pseudo-remote transport. HOST is set to the first host name specified by
24427 If the transport's generic &%home_directory%& option is set, its value is used
24428 for the HOME environment variable. Otherwise, a home directory may be set
24429 by the router's &%transport_home_directory%& option, which defaults to the
24430 user's home directory if &%check_local_user%& is set.
24433 .section "Private options for pipe" "SECID142"
24434 .cindex "options" "&(pipe)& transport"
24438 .option allow_commands pipe "string list&!!" unset
24439 .cindex "&(pipe)& transport" "permitted commands"
24440 The string is expanded, and is then interpreted as a colon-separated list of
24441 permitted commands. If &%restrict_to_path%& is not set, the only commands
24442 permitted are those in the &%allow_commands%& list. They need not be absolute
24443 paths; the &%path%& option is still used for relative paths. If
24444 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24445 in the &%allow_commands%& list, or a name without any slashes that is found on
24446 the path. In other words, if neither &%allow_commands%& nor
24447 &%restrict_to_path%& is set, there is no restriction on the command, but
24448 otherwise only commands that are permitted by one or the other are allowed. For
24451 allow_commands = /usr/bin/vacation
24453 and &%restrict_to_path%& is not set, the only permitted command is
24454 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24455 &%use_shell%& is set.
24458 .option batch_id pipe string&!! unset
24459 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24462 .option batch_max pipe integer 1
24463 This limits the number of addresses that can be handled in a single delivery.
24464 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24467 .option check_string pipe string unset
24468 As &(pipe)& writes the message, the start of each line is tested for matching
24469 &%check_string%&, and if it does, the initial matching characters are replaced
24470 by the contents of &%escape_string%&, provided both are set. The value of
24471 &%check_string%& is a literal string, not a regular expression, and the case of
24472 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24473 of &%check_string%& and &%escape_string%& are forced to values that implement
24474 the SMTP escaping protocol. Any settings made in the configuration file are
24478 .option command pipe string&!! unset
24479 This option need not be set when &(pipe)& is being used to deliver to pipes
24480 obtained directly from address redirections. In other cases, the option must be
24481 set, to provide a command to be run. It need not yield an absolute path (see
24482 the &%path%& option below). The command is split up into separate arguments by
24483 Exim, and each argument is separately expanded, as described in section
24484 &<<SECThowcommandrun>>& above.
24487 .option environment pipe string&!! unset
24488 .cindex "&(pipe)& transport" "environment for command"
24489 .cindex "environment" "&(pipe)& transport"
24490 This option is used to add additional variables to the environment in which the
24491 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24492 a string which is expanded, and then interpreted as a colon-separated list of
24493 environment settings of the form <&'name'&>=<&'value'&>.
24496 .option escape_string pipe string unset
24497 See &%check_string%& above.
24500 .option freeze_exec_fail pipe boolean false
24501 .cindex "exec failure"
24502 .cindex "failure of exec"
24503 .cindex "&(pipe)& transport" "failure of exec"
24504 Failure to exec the command in a pipe transport is by default treated like
24505 any other failure while running the command. However, if &%freeze_exec_fail%&
24506 is set, failure to exec is treated specially, and causes the message to be
24507 frozen, whatever the setting of &%ignore_status%&.
24510 .option freeze_signal pipe boolean false
24511 .cindex "signal exit"
24512 .cindex "&(pipe)& transport", "signal exit"
24513 Normally if the process run by a command in a pipe transport exits on a signal,
24514 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24515 frozen in Exim's queue instead.
24518 .option force_command pipe boolean false
24519 .cindex "force command"
24520 .cindex "&(pipe)& transport", "force command"
24521 Normally when a router redirects an address directly to a pipe command
24522 the &%command%& option on the transport is ignored. If &%force_command%&
24523 is set, the &%command%& option will used. This is especially
24524 useful for forcing a wrapper or additional argument to be added to the
24525 command. For example:
24527 command = /usr/bin/remote_exec myhost -- $address_pipe
24531 Note that &$address_pipe$& is handled specially in &%command%& when
24532 &%force_command%& is set, expanding out to the original argument vector as
24533 separate items, similarly to a Unix shell &`"$@"`& construct.
24536 .option ignore_status pipe boolean false
24537 If this option is true, the status returned by the subprocess that is set up to
24538 run the command is ignored, and Exim behaves as if zero had been returned.
24539 Otherwise, a non-zero status or termination by signal causes an error return
24540 from the transport unless the status value is one of those listed in
24541 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24543 &*Note*&: This option does not apply to timeouts, which do not return a status.
24544 See the &%timeout_defer%& option for how timeouts are handled.
24547 .option log_defer_output pipe boolean false
24548 .cindex "&(pipe)& transport" "logging output"
24549 If this option is set, and the status returned by the command is
24550 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24551 and any output was produced on stdout or stderr, the first line of it is
24552 written to the main log.
24555 .option log_fail_output pipe boolean false
24556 If this option is set, and the command returns any output on stdout or
24557 stderr, and also ends with a return code that is neither zero nor one of
24558 the return codes listed in &%temp_errors%& (that is, the delivery
24559 failed), the first line of output is written to the main log. This
24560 option and &%log_output%& are mutually exclusive. Only one of them may
24564 .option log_output pipe boolean false
24565 If this option is set and the command returns any output on stdout or
24566 stderr, the first line of output is written to the main log, whatever
24567 the return code. This option and &%log_fail_output%& are mutually
24568 exclusive. Only one of them may be set.
24571 .option max_output pipe integer 20K
24572 This specifies the maximum amount of output that the command may produce on its
24573 standard output and standard error file combined. If the limit is exceeded, the
24574 process running the command is killed. This is intended as a safety measure to
24575 catch runaway processes. The limit is applied independently of the settings of
24576 the options that control what is done with such output (for example,
24577 &%return_output%&). Because of buffering effects, the amount of output may
24578 exceed the limit by a small amount before Exim notices.
24581 .option message_prefix pipe string&!! "see below"
24582 The string specified here is expanded and output at the start of every message.
24583 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24586 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24590 .cindex "&%tmail%&"
24591 .cindex "&""From""& line"
24592 This is required by the commonly used &_/usr/bin/vacation_& program.
24593 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24594 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24599 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24600 &`\n`& to &`\r\n`& in &%message_prefix%&.
24603 .option message_suffix pipe string&!! "see below"
24604 The string specified here is expanded and output at the end of every message.
24605 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24606 The suffix can be suppressed by setting
24610 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24611 &`\n`& to &`\r\n`& in &%message_suffix%&.
24614 .option path pipe string&!! "/bin:/usr/bin"
24615 This option is expanded and
24616 specifies the string that is set up in the PATH environment
24617 variable of the subprocess.
24618 If the &%command%& option does not yield an absolute path name, the command is
24619 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24620 apply to a command specified as a transport filter.
24623 .option permit_coredump pipe boolean false
24624 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24625 a core-dump of a pipe command, enable this command. This enables core-dumps
24626 during delivery and affects both the Exim binary and the pipe command run.
24627 It is recommended that this option remain off unless and until you have a need
24628 for it and that this only be enabled when needed, as the risk of excessive
24629 resource consumption can be quite high. Note also that Exim is typically
24630 installed as a setuid binary and most operating systems will inhibit coredumps
24631 of these by default, so further OS-specific action may be required.
24634 .option pipe_as_creator pipe boolean false
24635 .cindex "uid (user id)" "local delivery"
24636 If the generic &%user%& option is not set and this option is true, the delivery
24637 process is run under the uid that was in force when Exim was originally called
24638 to accept the message. If the group id is not otherwise set (via the generic
24639 &%group%& option), the gid that was in force when Exim was originally called to
24640 accept the message is used.
24643 .option restrict_to_path pipe boolean false
24644 When this option is set, any command name not listed in &%allow_commands%& must
24645 contain no slashes. The command is searched for only in the directories listed
24646 in the &%path%& option. This option is intended for use in the case when a pipe
24647 command has been generated from a user's &_.forward_& file. This is usually
24648 handled by a &(pipe)& transport called &%address_pipe%&.
24651 .option return_fail_output pipe boolean false
24652 If this option is true, and the command produced any output and ended with a
24653 return code other than zero or one of the codes listed in &%temp_errors%& (that
24654 is, the delivery failed), the output is returned in the bounce message.
24655 However, if the message has a null sender (that is, it is itself a bounce
24656 message), output from the command is discarded. This option and
24657 &%return_output%& are mutually exclusive. Only one of them may be set.
24661 .option return_output pipe boolean false
24662 If this option is true, and the command produced any output, the delivery is
24663 deemed to have failed whatever the return code from the command, and the output
24664 is returned in the bounce message. Otherwise, the output is just discarded.
24665 However, if the message has a null sender (that is, it is a bounce message),
24666 output from the command is always discarded, whatever the setting of this
24667 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24668 of them may be set.
24672 .option temp_errors pipe "string list" "see below"
24673 .cindex "&(pipe)& transport" "temporary failure"
24674 This option contains either a colon-separated list of numbers, or a single
24675 asterisk. If &%ignore_status%& is false
24676 and &%return_output%& is not set,
24677 and the command exits with a non-zero return code, the failure is treated as
24678 temporary and the delivery is deferred if the return code matches one of the
24679 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24680 codes are treated as permanent errors. The default setting contains the codes
24681 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24682 compiled on a system that does not define these macros, it assumes values of 75
24683 and 73, respectively.
24686 .option timeout pipe time 1h
24687 If the command fails to complete within this time, it is killed. This normally
24688 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24689 specifies no timeout. In order to ensure that any subprocesses created by the
24690 command are also killed, Exim makes the initial process a process group leader,
24691 and kills the whole process group on a timeout. However, this can be defeated
24692 if one of the processes starts a new process group.
24694 .option timeout_defer pipe boolean false
24695 A timeout in a &(pipe)& transport, either in the command that the transport
24696 runs, or in a transport filter that is associated with it, is by default
24697 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24698 is set true, both kinds of timeout become temporary errors, causing the
24699 delivery to be deferred.
24701 .option umask pipe "octal integer" 022
24702 This specifies the umask setting for the subprocess that runs the command.
24705 .option use_bsmtp pipe boolean false
24706 .cindex "envelope sender"
24707 If this option is set true, the &(pipe)& transport writes messages in &"batch
24708 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24709 commands. If you want to include a leading HELO command with such messages,
24710 you can do so by setting the &%message_prefix%& option. See section
24711 &<<SECTbatchSMTP>>& for details of batch SMTP.
24713 .option use_classresources pipe boolean false
24714 .cindex "class resources (BSD)"
24715 This option is available only when Exim is running on FreeBSD, NetBSD, or
24716 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24717 resource limits when a &(pipe)& transport is run to perform a delivery. The
24718 limits for the uid under which the pipe is to run are obtained from the login
24722 .option use_crlf pipe boolean false
24723 .cindex "carriage return"
24725 This option causes lines to be terminated with the two-character CRLF sequence
24726 (carriage return, linefeed) instead of just a linefeed character. In the case
24727 of batched SMTP, the byte sequence written to the pipe is then an exact image
24728 of what would be sent down a real SMTP connection.
24730 The contents of the &%message_prefix%& and &%message_suffix%& options are
24731 written verbatim, so must contain their own carriage return characters if these
24732 are needed. When &%use_bsmtp%& is not set, the default values for both
24733 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24734 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24737 .option use_shell pipe boolean false
24738 .vindex "&$pipe_addresses$&"
24739 If this option is set, it causes the command to be passed to &_/bin/sh_&
24740 instead of being run directly from the transport, as described in section
24741 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24742 where the command is expected to be run under a shell and cannot easily be
24743 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24744 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24745 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24750 .section "Using an external local delivery agent" "SECID143"
24751 .cindex "local delivery" "using an external agent"
24752 .cindex "&'procmail'&"
24753 .cindex "external local delivery"
24754 .cindex "delivery" "&'procmail'&"
24755 .cindex "delivery" "by external agent"
24756 The &(pipe)& transport can be used to pass all messages that require local
24757 delivery to a separate local delivery agent such as &%procmail%&. When doing
24758 this, care must be taken to ensure that the pipe is run under an appropriate
24759 uid and gid. In some configurations one wants this to be a uid that is trusted
24760 by the delivery agent to supply the correct sender of the message. It may be
24761 necessary to recompile or reconfigure the delivery agent so that it trusts an
24762 appropriate user. The following is an example transport and router
24763 configuration for &%procmail%&:
24768 command = /usr/local/bin/procmail -d $local_part_data
24772 check_string = "From "
24773 escape_string = ">From "
24775 user = $local_part_data
24782 transport = procmail_pipe
24784 In this example, the pipe is run as the local user, but with the group set to
24785 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24786 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24787 user to supply a correct sender address. If you do not specify either a
24788 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24789 home directory is the user's home directory by default.
24791 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24795 as shown in some &%procmail%& documentation, because Exim does not by default
24796 use a shell to run pipe commands.
24799 The next example shows a transport and a router for a system where local
24800 deliveries are handled by the Cyrus IMAP server.
24803 local_delivery_cyrus:
24805 command = /usr/cyrus/bin/deliver \
24806 -m ${substr_1:$local_part_suffix} -- $local_part
24818 local_part_suffix = .*
24819 transport = local_delivery_cyrus
24821 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
24822 &%return_output%& to cause any text written by Cyrus to be returned to the
24824 .ecindex IIDpiptra1
24825 .ecindex IIDpiptra2
24828 . ////////////////////////////////////////////////////////////////////////////
24829 . ////////////////////////////////////////////////////////////////////////////
24831 .chapter "The smtp transport" "CHAPsmtptrans"
24832 .scindex IIDsmttra1 "transports" "&(smtp)&"
24833 .scindex IIDsmttra2 "&(smtp)& transport"
24834 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
24835 or LMTP protocol. The list of hosts to try can either be taken from the address
24836 that is being processed (having been set up by the router), or specified
24837 explicitly for the transport. Timeout and retry processing (see chapter
24838 &<<CHAPretry>>&) is applied to each IP address independently.
24841 .section "Multiple messages on a single connection" "SECID144"
24842 The sending of multiple messages over a single TCP/IP connection can arise in
24846 If a message contains more than &%max_rcpt%& (see below) addresses that are
24847 routed to the same host, more than one copy of the message has to be sent to
24848 that host. In this situation, multiple copies may be sent in a single run of
24849 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
24850 does when it has too many addresses to send in one message also depends on the
24851 value of the global &%remote_max_parallel%& option. Details are given in
24852 section &<<SECToutSMTPTCP>>&.)
24854 .cindex "hints database" "remembering routing"
24855 When a message has been successfully delivered over a TCP/IP connection, Exim
24856 looks in its hints database to see if there are any other messages awaiting a
24857 connection to the same host. If there are, a new delivery process is started
24858 for one of them, and the current TCP/IP connection is passed on to it. The new
24859 process may in turn send multiple copies and possibly create yet another
24864 For each copy sent over the same TCP/IP connection, a sequence counter is
24865 incremented, and if it ever gets to the value of &%connection_max_messages%&,
24866 no further messages are sent over that connection.
24870 .section "Use of the $host and $host_address variables" "SECID145"
24872 .vindex "&$host_address$&"
24873 At the start of a run of the &(smtp)& transport, the values of &$host$& and
24874 &$host_address$& are the name and IP address of the first host on the host list
24875 passed by the router. However, when the transport is about to connect to a
24876 specific host, and while it is connected to that host, &$host$& and
24877 &$host_address$& are set to the values for that host. These are the values
24878 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
24879 &%serialize_hosts%&, and the various TLS options are expanded.
24882 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
24883 .vindex &$tls_bits$&
24884 .vindex &$tls_cipher$&
24885 .vindex &$tls_peerdn$&
24886 .vindex &$tls_sni$&
24887 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
24888 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
24889 are the values that were set when the message was received.
24890 These are the values that are used for options that are expanded before any
24891 SMTP connections are made. Just before each connection is made, these four
24892 variables are emptied. If TLS is subsequently started, they are set to the
24893 appropriate values for the outgoing connection, and these are the values that
24894 are in force when any authenticators are run and when the
24895 &%authenticated_sender%& option is expanded.
24897 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
24898 and will be removed in a future release.
24901 .section "Private options for smtp" "SECID146"
24902 .cindex "options" "&(smtp)& transport"
24903 The private options of the &(smtp)& transport are as follows:
24906 .option address_retry_include_sender smtp boolean true
24907 .cindex "4&'xx'& responses" "retrying after"
24908 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
24909 is the combination of sender and recipient that is delayed in subsequent queue
24910 runs until the retry time is reached. You can delay the recipient without
24911 reference to the sender (which is what earlier versions of Exim did), by
24912 setting &%address_retry_include_sender%& false. However, this can lead to
24913 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
24915 .option allow_localhost smtp boolean false
24916 .cindex "local host" "sending to"
24917 .cindex "fallback" "hosts specified on transport"
24918 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
24919 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
24920 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
24921 the delivery anyway. This should be used only in special cases when the
24922 configuration ensures that no looping will result (for example, a differently
24923 configured Exim is listening on the port to which the message is sent).
24926 .option authenticated_sender smtp string&!! unset
24928 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
24929 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
24930 overriding any existing authenticated sender value. If the string expansion is
24931 forced to fail, the option is ignored. Other expansion failures cause delivery
24932 to be deferred. If the result of expansion is an empty string, that is also
24935 The expansion happens after the outgoing connection has been made and TLS
24936 started, if required. This means that the &$host$&, &$host_address$&,
24937 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
24938 particular connection.
24940 If the SMTP session is not authenticated, the expansion of
24941 &%authenticated_sender%& still happens (and can cause the delivery to be
24942 deferred if it fails), but no AUTH= item is added to MAIL commands
24943 unless &%authenticated_sender_force%& is true.
24945 This option allows you to use the &(smtp)& transport in LMTP mode to
24946 deliver mail to Cyrus IMAP and provide the proper local part as the
24947 &"authenticated sender"&, via a setting such as:
24949 authenticated_sender = $local_part
24951 This removes the need for IMAP subfolders to be assigned special ACLs to
24952 allow direct delivery to those subfolders.
24954 Because of expected uses such as that just described for Cyrus (when no
24955 domain is involved), there is no checking on the syntax of the provided
24959 .option authenticated_sender_force smtp boolean false
24960 If this option is set true, the &%authenticated_sender%& option's value
24961 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
24962 authenticated as a client.
24965 .option command_timeout smtp time 5m
24966 This sets a timeout for receiving a response to an SMTP command that has been
24967 sent out. It is also used when waiting for the initial banner line from the
24968 remote host. Its value must not be zero.
24971 .option connect_timeout smtp time 5m
24972 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
24973 to a remote host. A setting of zero allows the system timeout (typically
24974 several minutes) to act. To have any effect, the value of this option must be
24975 less than the system timeout. However, it has been observed that on some
24976 systems there is no system timeout, which is why the default value for this
24977 option is 5 minutes, a value recommended by RFC 1123.
24980 .option connection_max_messages smtp integer 500
24981 .cindex "SMTP" "passed connection"
24982 .cindex "SMTP" "multiple deliveries"
24983 .cindex "multiple SMTP deliveries"
24984 This controls the maximum number of separate message deliveries that are sent
24985 over a single TCP/IP connection. If the value is zero, there is no limit.
24986 For testing purposes, this value can be overridden by the &%-oB%& command line
24990 .option dane_require_tls_ciphers smtp string&!! unset
24991 .cindex "TLS" "requiring specific ciphers for DANE"
24992 .cindex "cipher" "requiring specific"
24993 .cindex DANE "TLS ciphers"
24994 This option may be used to override &%tls_require_ciphers%& for connections
24995 where DANE has been determined to be in effect.
24996 If not set, then &%tls_require_ciphers%& will be used.
24997 Normal SMTP delivery is not able to make strong demands of TLS cipher
24998 configuration, because delivery will fall back to plaintext. Once DANE has
24999 been determined to be in effect, there is no plaintext fallback and making the
25000 TLS cipherlist configuration stronger will increase security, rather than
25001 counter-intuitively decreasing it.
25002 If the option expands to be empty or is forced to fail, then it will
25003 be treated as unset and &%tls_require_ciphers%& will be used instead.
25006 .option data_timeout smtp time 5m
25007 This sets a timeout for the transmission of each block in the data portion of
25008 the message. As a result, the overall timeout for a message depends on the size
25009 of the message. Its value must not be zero. See also &%final_timeout%&.
25012 .option dkim_canon smtp string&!! unset
25013 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25014 .option dkim_domain smtp string list&!! unset
25015 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25016 .option dkim_hash smtp string&!! sha256
25017 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25018 .option dkim_identity smtp string&!! unset
25019 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25020 .option dkim_private_key smtp string&!! unset
25021 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25022 .option dkim_selector smtp string&!! unset
25023 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25024 .option dkim_strict smtp string&!! unset
25025 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25026 .option dkim_sign_headers smtp string&!! "per RFC"
25027 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25028 .option dkim_timestamps smtp string&!! unset
25029 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25032 .option delay_after_cutoff smtp boolean true
25033 .cindex "final cutoff" "retries, controlling"
25034 .cindex retry "final cutoff"
25035 This option controls what happens when all remote IP addresses for a given
25036 domain have been inaccessible for so long that they have passed their retry
25039 In the default state, if the next retry time has not been reached for any of
25040 them, the address is bounced without trying any deliveries. In other words,
25041 Exim delays retrying an IP address after the final cutoff time until a new
25042 retry time is reached, and can therefore bounce an address without ever trying
25043 a delivery, when machines have been down for a long time. Some people are
25044 unhappy at this prospect, so...
25046 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25047 addresses are past their final cutoff time, Exim tries to deliver to those
25048 IP addresses that have not been tried since the message arrived. If there are
25049 none, of if they all fail, the address is bounced. In other words, it does not
25050 delay when a new message arrives, but immediately tries those expired IP
25051 addresses that haven't been tried since the message arrived. If there is a
25052 continuous stream of messages for the dead hosts, unsetting
25053 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25057 .option dns_qualify_single smtp boolean true
25058 If the &%hosts%& or &%fallback_hosts%& option is being used,
25059 and the &%gethostbyname%& option is false,
25060 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25061 in chapter &<<CHAPdnslookup>>& for more details.
25064 .option dns_search_parents smtp boolean false
25065 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25066 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25067 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25071 .option dnssec_request_domains smtp "domain list&!!" *
25072 .cindex "MX record" "security"
25073 .cindex "DNSSEC" "MX lookup"
25074 .cindex "security" "MX lookup"
25075 .cindex "DNS" "DNSSEC"
25076 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25077 the dnssec request bit set. Setting this transport option is only useful if the
25078 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25083 .option dnssec_require_domains smtp "domain list&!!" unset
25084 .cindex "MX record" "security"
25085 .cindex "DNSSEC" "MX lookup"
25086 .cindex "security" "MX lookup"
25087 .cindex "DNS" "DNSSEC"
25088 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25089 the dnssec request bit set. Setting this transport option is only
25090 useful if the transport overrides or sets the host names. See the
25091 &%dnssec_require_domains%& router option.
25095 .option dscp smtp string&!! unset
25096 .cindex "DCSP" "outbound"
25097 This option causes the DSCP value associated with a socket to be set to one
25098 of a number of fixed strings or to numeric value.
25099 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25100 Common values include &`throughput`&, &`mincost`&, and on newer systems
25101 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25103 The outbound packets from Exim will be marked with this value in the header
25104 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25105 that these values will have any effect, not be stripped by networking
25106 equipment, or do much of anything without cooperation with your Network
25107 Engineer and those of all network operators between the source and destination.
25110 .option fallback_hosts smtp "string list" unset
25111 .cindex "fallback" "hosts specified on transport"
25112 String expansion is not applied to this option. The argument must be a
25113 colon-separated list of host names or IP addresses, optionally also including
25114 port numbers, though the separator can be changed, as described in section
25115 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25116 item in a &%route_list%& setting for the &(manualroute)& router, as described
25117 in section &<<SECTformatonehostitem>>&.
25119 Fallback hosts can also be specified on routers, which associate them with the
25120 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25121 &%fallback_hosts%& specified on the transport is used only if the address does
25122 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25123 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25124 However, &%hosts_randomize%& does apply to fallback host lists.
25126 If Exim is unable to deliver to any of the hosts for a particular address, and
25127 the errors are not permanent rejections, the address is put on a separate
25128 transport queue with its host list replaced by the fallback hosts, unless the
25129 address was routed via MX records and the current host was in the original MX
25130 list. In that situation, the fallback host list is not used.
25132 Once normal deliveries are complete, the fallback queue is delivered by
25133 re-running the same transports with the new host lists. If several failing
25134 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25135 copy of the message is sent.
25137 The resolution of the host names on the fallback list is controlled by the
25138 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25139 both to cases when the host list comes with the address and when it is taken
25140 from &%hosts%&. This option provides a &"use a smart host only if delivery
25144 .option final_timeout smtp time 10m
25145 This is the timeout that applies while waiting for the response to the final
25146 line containing just &"."& that terminates a message. Its value must not be
25149 .option gethostbyname smtp boolean false
25150 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25151 being used, names are looked up using &[gethostbyname()]&
25152 (or &[getipnodebyname()]& when available)
25153 instead of using the DNS. Of course, that function may in fact use the DNS, but
25154 it may also consult other sources of information such as &_/etc/hosts_&.
25156 .option gnutls_compat_mode smtp boolean unset
25157 This option controls whether GnuTLS is used in compatibility mode in an Exim
25158 server. This reduces security slightly, but improves interworking with older
25159 implementations of TLS.
25161 .option helo_data smtp string&!! "see below"
25162 .cindex "HELO" "argument, setting"
25163 .cindex "EHLO" "argument, setting"
25164 .cindex "LHLO argument setting"
25165 The value of this option is expanded after a connection to a another host has
25166 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25167 command that starts the outgoing SMTP or LMTP session. The default value of the
25172 During the expansion, the variables &$host$& and &$host_address$& are set to
25173 the identity of the remote host, and the variables &$sending_ip_address$& and
25174 &$sending_port$& are set to the local IP address and port number that are being
25175 used. These variables can be used to generate different values for different
25176 servers or different local IP addresses. For example, if you want the string
25177 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25178 interface address, you could use this:
25180 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25181 {$primary_hostname}}
25183 The use of &%helo_data%& applies both to sending messages and when doing
25186 .option hosts smtp "string list&!!" unset
25187 Hosts are associated with an address by a router such as &(dnslookup)&, which
25188 finds the hosts by looking up the address domain in the DNS, or by
25189 &(manualroute)&, which has lists of hosts in its configuration. However,
25190 email addresses can be passed to the &(smtp)& transport by any router, and not
25191 all of them can provide an associated list of hosts.
25193 The &%hosts%& option specifies a list of hosts to be used if the address being
25194 processed does not have any hosts associated with it. The hosts specified by
25195 &%hosts%& are also used, whether or not the address has its own hosts, if
25196 &%hosts_override%& is set.
25198 The string is first expanded, before being interpreted as a colon-separated
25199 list of host names or IP addresses, possibly including port numbers. The
25200 separator may be changed to something other than colon, as described in section
25201 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25202 item in a &%route_list%& setting for the &(manualroute)& router, as described
25203 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25204 of the &(manualroute)& router is not available here.
25206 If the expansion fails, delivery is deferred. Unless the failure was caused by
25207 the inability to complete a lookup, the error is logged to the panic log as
25208 well as the main log. Host names are looked up either by searching directly for
25209 address records in the DNS or by calling &[gethostbyname()]& (or
25210 &[getipnodebyname()]& when available), depending on the setting of the
25211 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25212 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25215 During delivery, the hosts are tried in order, subject to their retry status,
25216 unless &%hosts_randomize%& is set.
25219 .option hosts_avoid_esmtp smtp "host list&!!" unset
25220 .cindex "ESMTP, avoiding use of"
25221 .cindex "HELO" "forcing use of"
25222 .cindex "EHLO" "avoiding use of"
25223 .cindex "PIPELINING" "avoiding the use of"
25224 This option is for use with broken hosts that announce ESMTP facilities (for
25225 example, PIPELINING) and then fail to implement them properly. When a host
25226 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25227 start of the SMTP session. This means that it cannot use any of the ESMTP
25228 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25231 .option hosts_avoid_pipelining smtp "host list&!!" unset
25232 .cindex "PIPELINING" "avoiding the use of"
25233 .cindex "ESMTP extensions" PIPELINING
25234 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25235 that matches this list, even if the server host advertises PIPELINING support.
25237 .option hosts_pipe_connect smtp "host list&!!" unset
25238 .cindex "pipelining" "early connection"
25239 .cindex "pipelining" PIPE_CONNECT
25240 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25241 this option controls which to hosts the facility watched for
25242 and recorded, and used for subsequent connections.
25244 The retry hints database is used for the record,
25245 and records are subject to the &%retry_data_expire%& option.
25246 When used, the pipelining saves on roundtrip times.
25247 It also turns SMTP into a client-first protocol
25248 so combines well with TCP Fast Open.
25250 See also the &%pipelining_connect_advertise_hosts%& main option.
25253 When the facility is used, the transport &%helo_data%& option
25254 will be expanded before the &$sending_ip_address$& variable
25256 A check is made for the use of that variable, without the
25257 presence of a &"def:"& test on it, but suitably complex coding
25258 can avoid the check and produce unexpected results.
25259 You have been warned.
25262 .option hosts_avoid_tls smtp "host list&!!" unset
25263 .cindex "TLS" "avoiding for certain hosts"
25264 Exim will not try to start a TLS session when delivering to any host that
25265 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25267 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25268 .cindex "TLS" "avoiding for certain hosts"
25269 Exim will not try to start a TLS session for a verify callout,
25270 or when delivering in cutthrough mode,
25271 to any host that matches this list.
25274 .option hosts_max_try smtp integer 5
25275 .cindex "host" "maximum number to try"
25276 .cindex "limit" "number of hosts tried"
25277 .cindex "limit" "number of MX tried"
25278 .cindex "MX record" "maximum tried"
25279 This option limits the number of IP addresses that are tried for any one
25280 delivery in cases where there are temporary delivery errors. Section
25281 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25284 .option hosts_max_try_hardlimit smtp integer 50
25285 This is an additional check on the maximum number of IP addresses that Exim
25286 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25291 .option hosts_nopass_tls smtp "host list&!!" unset
25292 .cindex "TLS" "passing connection"
25293 .cindex "multiple SMTP deliveries"
25294 .cindex "TLS" "multiple message deliveries"
25295 For any host that matches this list, a connection on which a TLS session has
25296 been started will not be passed to a new delivery process for sending another
25297 message on the same connection. See section &<<SECTmulmessam>>& for an
25298 explanation of when this might be needed.
25300 .option hosts_noproxy_tls smtp "host list&!!" unset
25301 .cindex "TLS" "passing connection"
25302 .cindex "multiple SMTP deliveries"
25303 .cindex "TLS" "multiple message deliveries"
25304 For any host that matches this list, a TLS session which has
25305 been started will not be passed to a new delivery process for sending another
25306 message on the same session.
25308 The traditional implementation closes down TLS and re-starts it in the new
25309 process, on the same open TCP connection, for each successive message
25310 sent. If permitted by this option a pipe to to the new process is set up
25311 instead, and the original process maintains the TLS connection and proxies
25312 the SMTP connection from and to the new process and any subsequents.
25313 The new process has no access to TLS information, so cannot include it in
25318 .option hosts_override smtp boolean false
25319 If this option is set and the &%hosts%& option is also set, any hosts that are
25320 attached to the address are ignored, and instead the hosts specified by the
25321 &%hosts%& option are always used. This option does not apply to
25322 &%fallback_hosts%&.
25325 .option hosts_randomize smtp boolean false
25326 .cindex "randomized host list"
25327 .cindex "host" "list of; randomized"
25328 .cindex "fallback" "randomized hosts"
25329 If this option is set, and either the list of hosts is taken from the
25330 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25331 were not obtained from MX records (this includes fallback hosts from the
25332 router), and were not randomized by the router, the order of trying the hosts
25333 is randomized each time the transport runs. Randomizing the order of a host
25334 list can be used to do crude load sharing.
25336 When &%hosts_randomize%& is true, a host list may be split into groups whose
25337 order is separately randomized. This makes it possible to set up MX-like
25338 behaviour. The boundaries between groups are indicated by an item that is just
25339 &`+`& in the host list. For example:
25341 hosts = host1:host2:host3:+:host4:host5
25343 The order of the first three hosts and the order of the last two hosts is
25344 randomized for each use, but the first three always end up before the last two.
25345 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25347 .option hosts_require_auth smtp "host list&!!" unset
25348 .cindex "authentication" "required by client"
25349 This option provides a list of servers for which authentication must succeed
25350 before Exim will try to transfer a message. If authentication fails for
25351 servers which are not in this list, Exim tries to send unauthenticated. If
25352 authentication fails for one of these servers, delivery is deferred. This
25353 temporary error is detectable in the retry rules, so it can be turned into a
25354 hard failure if required. See also &%hosts_try_auth%&, and chapter
25355 &<<CHAPSMTPAUTH>>& for details of authentication.
25358 .option hosts_request_ocsp smtp "host list&!!" *
25359 .cindex "TLS" "requiring for certain servers"
25360 Exim will request a Certificate Status on a
25361 TLS session for any host that matches this list.
25362 &%tls_verify_certificates%& should also be set for the transport.
25364 .option hosts_require_dane smtp "host list&!!" unset
25365 .cindex DANE "transport options"
25366 .cindex DANE "requiring for certain servers"
25367 If built with DANE support, Exim will require that a DNSSEC-validated
25368 TLSA record is present for any host matching the list,
25369 and that a DANE-verified TLS connection is made. See
25370 the &%dnssec_request_domains%& router and transport options.
25371 There will be no fallback to in-clear communication.
25372 See section &<<SECDANE>>&.
25374 .option hosts_require_ocsp smtp "host list&!!" unset
25375 .cindex "TLS" "requiring for certain servers"
25376 Exim will request, and check for a valid Certificate Status being given, on a
25377 TLS session for any host that matches this list.
25378 &%tls_verify_certificates%& should also be set for the transport.
25380 .option hosts_require_tls smtp "host list&!!" unset
25381 .cindex "TLS" "requiring for certain servers"
25382 Exim will insist on using a TLS session when delivering to any host that
25383 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25384 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25385 incoming messages, use an appropriate ACL.
25387 .option hosts_try_auth smtp "host list&!!" unset
25388 .cindex "authentication" "optional in client"
25389 This option provides a list of servers to which, provided they announce
25390 authentication support, Exim will attempt to authenticate as a client when it
25391 connects. If authentication fails, Exim will try to transfer the message
25392 unauthenticated. See also &%hosts_require_auth%&, and chapter
25393 &<<CHAPSMTPAUTH>>& for details of authentication.
25395 .option hosts_try_chunking smtp "host list&!!" *
25396 .cindex CHUNKING "enabling, in client"
25397 .cindex BDAT "SMTP command"
25398 .cindex "RFC 3030" "CHUNKING"
25399 This option provides a list of servers to which, provided they announce
25400 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25402 Unless DKIM signing is being done,
25404 BDAT will not be used in conjunction with a transport filter.
25406 .option hosts_try_dane smtp "host list&!!" *
25407 .cindex DANE "transport options"
25408 .cindex DANE "attempting for certain servers"
25409 If built with DANE support, Exim will require that a DNSSEC-validated
25410 TLSA record is present for any host matching the list,
25411 and that a DANE-verified TLS connection is made. See
25412 the &%dnssec_request_domains%& router and transport options.
25413 There will be no fallback to in-clear communication.
25414 See section &<<SECDANE>>&.
25416 .option hosts_try_fastopen smtp "host list&!!" *
25417 .cindex "fast open, TCP" "enabling, in client"
25418 .cindex "TCP Fast Open" "enabling, in client"
25419 .cindex "RFC 7413" "TCP Fast Open"
25420 This option provides a list of servers to which, provided
25421 the facility is supported by this system, Exim will attempt to
25422 perform a TCP Fast Open.
25423 No data is sent on the SYN segment but, if the remote server also
25424 supports the facility, it can send its SMTP banner immediately after
25425 the SYN,ACK segment. This can save up to one round-trip time.
25427 The facility is only active for previously-contacted servers,
25428 as the initiator must present a cookie in the SYN segment.
25430 On (at least some) current Linux distributions the facility must be enabled
25431 in the kernel by the sysadmin before the support is usable.
25432 There is no option for control of the server side; if the system supports
25433 it it is always enabled. Note that lengthy operations in the connect ACL,
25434 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25436 .option hosts_try_prdr smtp "host list&!!" *
25437 .cindex "PRDR" "enabling, optional in client"
25438 .cindex "ESMTP extensions" PRDR
25439 This option provides a list of servers to which, provided they announce
25440 PRDR support, Exim will attempt to negotiate PRDR
25441 for multi-recipient messages.
25442 The option can usually be left as default.
25444 .option interface smtp "string list&!!" unset
25445 .cindex "bind IP address"
25446 .cindex "IP address" "binding"
25448 .vindex "&$host_address$&"
25449 This option specifies which interface to bind to when making an outgoing SMTP
25450 call. The value is an IP address, not an interface name such as
25451 &`eth0`&. Do not confuse this with the interface address that was used when a
25452 message was received, which is in &$received_ip_address$&, formerly known as
25453 &$interface_address$&. The name was changed to minimize confusion with the
25454 outgoing interface address. There is no variable that contains an outgoing
25455 interface address because, unless it is set by this option, its value is
25458 During the expansion of the &%interface%& option the variables &$host$& and
25459 &$host_address$& refer to the host to which a connection is about to be made
25460 during the expansion of the string. Forced expansion failure, or an empty
25461 string result causes the option to be ignored. Otherwise, after expansion, the
25462 string must be a list of IP addresses, colon-separated by default, but the
25463 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25466 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25468 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25469 connection. If none of them are the correct type, the option is ignored. If
25470 &%interface%& is not set, or is ignored, the system's IP functions choose which
25471 interface to use if the host has more than one.
25474 .option keepalive smtp boolean true
25475 .cindex "keepalive" "on outgoing connection"
25476 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25477 connections. When set, it causes the kernel to probe idle connections
25478 periodically, by sending packets with &"old"& sequence numbers. The other end
25479 of the connection should send a acknowledgment if the connection is still okay
25480 or a reset if the connection has been aborted. The reason for doing this is
25481 that it has the beneficial effect of freeing up certain types of connection
25482 that can get stuck when the remote host is disconnected without tidying up the
25483 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25487 .option lmtp_ignore_quota smtp boolean false
25488 .cindex "LMTP" "ignoring quota errors"
25489 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25490 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25491 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25493 .option max_rcpt smtp integer 100
25494 .cindex "RCPT" "maximum number of outgoing"
25495 This option limits the number of RCPT commands that are sent in a single
25496 SMTP message transaction. Each set of addresses is treated independently, and
25497 so can cause parallel connections to the same host if &%remote_max_parallel%&
25502 .option message_linelength_limit smtp integer 998
25503 .cindex "line length" limit
25504 This option sets the maximum line length, in bytes, that the transport
25505 will send. Any messages with lines exceeding the given value
25506 will fail and a failure-DSN ("bounce") message will if possible be returned
25508 The default value is that defined by the SMTP standards.
25510 It is generally wise to also check in the data ACL so that messages
25511 received via SMTP can be refused without producing a bounce.
25515 .option multi_domain smtp boolean&!! true
25516 .vindex "&$domain$&"
25517 When this option is set, the &(smtp)& transport can handle a number of
25518 addresses containing a mixture of different domains provided they all resolve
25519 to the same list of hosts. Turning the option off restricts the transport to
25520 handling only one domain at a time. This is useful if you want to use
25521 &$domain$& in an expansion for the transport, because it is set only when there
25522 is a single domain involved in a remote delivery.
25524 It is expanded per-address and can depend on any of
25525 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25526 &$host$&, &$host_address$& and &$host_port$&.
25528 .option port smtp string&!! "see below"
25529 .cindex "port" "sending TCP/IP"
25530 .cindex "TCP/IP" "setting outgoing port"
25531 This option specifies the TCP/IP port on the server to which Exim connects.
25532 &*Note:*& Do not confuse this with the port that was used when a message was
25533 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25534 The name was changed to minimize confusion with the outgoing port. There is no
25535 variable that contains an outgoing port.
25537 If the value of this option begins with a digit it is taken as a port number;
25538 otherwise it is looked up using &[getservbyname()]&. The default value is
25540 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25541 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25542 If the expansion fails, or if a port number cannot be found, delivery
25545 Note that at least one Linux distribution has been seen failing
25546 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25550 .option protocol smtp string smtp
25551 .cindex "LMTP" "over TCP/IP"
25552 .cindex "ssmtp protocol" "outbound"
25553 .cindex "TLS" "SSL-on-connect outbound"
25555 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25556 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25557 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25558 deliveries into closed message stores. Exim also has support for running LMTP
25559 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25561 If this option is set to &"smtps"&, the default value for the &%port%& option
25562 changes to &"smtps"&, and the transport initiates TLS immediately after
25563 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25564 The Internet standards bodies used to strongly discourage use of this mode,
25565 but as of RFC 8314 it is perferred over STARTTLS for message submission
25566 (as distinct from MTA-MTA communication).
25569 .option retry_include_ip_address smtp boolean&!! true
25570 Exim normally includes both the host name and the IP address in the key it
25571 constructs for indexing retry data after a temporary delivery failure. This
25572 means that when one of several IP addresses for a host is failing, it gets
25573 tried periodically (controlled by the retry rules), but use of the other IP
25574 addresses is not affected.
25576 However, in some dialup environments hosts are assigned a different IP address
25577 each time they connect. In this situation the use of the IP address as part of
25578 the retry key leads to undesirable behaviour. Setting this option false causes
25579 Exim to use only the host name.
25580 Since it is expanded it can be made to depend on the host or domain.
25583 .option serialize_hosts smtp "host list&!!" unset
25584 .cindex "serializing connections"
25585 .cindex "host" "serializing connections"
25586 Because Exim operates in a distributed manner, if several messages for the same
25587 host arrive at around the same time, more than one simultaneous connection to
25588 the remote host can occur. This is not usually a problem except when there is a
25589 slow link between the hosts. In that situation it may be helpful to restrict
25590 Exim to one connection at a time. This can be done by setting
25591 &%serialize_hosts%& to match the relevant hosts.
25593 .cindex "hints database" "serializing deliveries to a host"
25594 Exim implements serialization by means of a hints database in which a record is
25595 written whenever a process connects to one of the restricted hosts. The record
25596 is deleted when the connection is completed. Obviously there is scope for
25597 records to get left lying around if there is a system or program crash. To
25598 guard against this, Exim ignores any records that are more than six hours old.
25600 If you set up this kind of serialization, you should also arrange to delete the
25601 relevant hints database whenever your system reboots. The names of the files
25602 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25603 may be one or two files, depending on the type of DBM in use. The same files
25604 are used for ETRN serialization.
25606 See also the &%max_parallel%& generic transport option.
25609 .option size_addition smtp integer 1024
25610 .cindex "SIZE" "ESMTP extension"
25611 .cindex "message" "size issue for transport filter"
25612 .cindex "size" "of message"
25613 .cindex "transport" "filter"
25614 .cindex "filter" "transport filter"
25615 If a remote SMTP server indicates that it supports the SIZE option of the
25616 MAIL command, Exim uses this to pass over the message size at the start of
25617 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25618 sends, to allow for headers and other text that may be added during delivery by
25619 configuration options or in a transport filter. It may be necessary to increase
25620 this if a lot of text is added to messages.
25622 Alternatively, if the value of &%size_addition%& is set negative, it disables
25623 the use of the SIZE option altogether.
25626 .option socks_proxy smtp string&!! unset
25627 .cindex proxy SOCKS
25628 This option enables use of SOCKS proxies for connections made by the
25629 transport. For details see section &<<SECTproxySOCKS>>&.
25632 .option tls_certificate smtp string&!! unset
25633 .cindex "TLS" "client certificate, location of"
25634 .cindex "certificate" "client, location of"
25636 .vindex "&$host_address$&"
25637 The value of this option must be the absolute path to a file which contains the
25638 client's certificate, for possible use when sending a message over an encrypted
25639 connection. The values of &$host$& and &$host_address$& are set to the name and
25640 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25643 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25644 certificate when sending messages as a client. The global option of the same
25645 name specifies the certificate for Exim as a server; it is not automatically
25646 assumed that the same certificate should be used when Exim is operating as a
25650 .option tls_crl smtp string&!! unset
25651 .cindex "TLS" "client certificate revocation list"
25652 .cindex "certificate" "revocation list for client"
25653 This option specifies a certificate revocation list. The expanded value must
25654 be the name of a file that contains a CRL in PEM format.
25657 .option tls_dh_min_bits smtp integer 1024
25658 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25659 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25660 key agreement is negotiated, the server will provide a large prime number
25661 for use. This option establishes the minimum acceptable size of that number.
25662 If the parameter offered by the server is too small, then the TLS handshake
25665 Only supported when using GnuTLS.
25668 .option tls_privatekey smtp string&!! unset
25669 .cindex "TLS" "client private key, location of"
25671 .vindex "&$host_address$&"
25672 The value of this option must be the absolute path to a file which contains the
25673 client's private key. This is used when sending a message over an encrypted
25674 connection using a client certificate. The values of &$host$& and
25675 &$host_address$& are set to the name and address of the server during the
25676 expansion. If this option is unset, or the expansion is forced to fail, or the
25677 result is an empty string, the private key is assumed to be in the same file as
25678 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25681 .option tls_require_ciphers smtp string&!! unset
25682 .cindex "TLS" "requiring specific ciphers"
25683 .cindex "cipher" "requiring specific"
25685 .vindex "&$host_address$&"
25686 The value of this option must be a list of permitted cipher suites, for use
25687 when setting up an outgoing encrypted connection. (There is a global option of
25688 the same name for controlling incoming connections.) The values of &$host$& and
25689 &$host_address$& are set to the name and address of the server during the
25690 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25691 is used in different ways by OpenSSL and GnuTLS (see sections
25692 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25693 ciphers is a preference order.
25697 .option tls_resumption_hosts smtp "host list&!!" unset
25698 .cindex TLS resumption
25699 This option controls which connections to use the TLS resumption feature.
25700 See &<<SECTresumption>>& for details.
25705 .option tls_sni smtp string&!! unset
25706 .cindex "TLS" "Server Name Indication"
25707 .vindex "&$tls_sni$&"
25708 If this option is set then it sets the $tls_out_sni variable and causes any
25709 TLS session to pass this value as the Server Name Indication extension to
25710 the remote side, which can be used by the remote side to select an appropriate
25711 certificate and private key for the session.
25713 See &<<SECTtlssni>>& for more information.
25715 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25721 .option tls_tempfail_tryclear smtp boolean true
25722 .cindex "4&'xx'& responses" "to STARTTLS"
25723 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25724 setting up a TLS session, this option determines whether or not Exim should try
25725 to deliver the message unencrypted. If it is set false, delivery to the
25726 current host is deferred; if there are other hosts, they are tried. If this
25727 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25728 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25729 TLS negotiation fails, Exim closes the current connection (because it is in an
25730 unknown state), opens a new one to the same host, and then tries the delivery
25734 .option tls_try_verify_hosts smtp "host list&!!" *
25735 .cindex "TLS" "server certificate verification"
25736 .cindex "certificate" "verification of server"
25737 This option gives a list of hosts for which, on encrypted connections,
25738 certificate verification will be tried but need not succeed.
25739 The &%tls_verify_certificates%& option must also be set.
25740 Note that unless the host is in this list
25741 TLS connections will be denied to hosts using self-signed certificates
25742 when &%tls_verify_certificates%& is matched.
25743 The &$tls_out_certificate_verified$& variable is set when
25744 certificate verification succeeds.
25747 .option tls_verify_cert_hostnames smtp "host list&!!" *
25748 .cindex "TLS" "server certificate hostname verification"
25749 .cindex "certificate" "verification of server"
25750 This option give a list of hosts for which,
25751 while verifying the server certificate,
25752 checks will be included on the host name
25753 (note that this will generally be the result of a DNS MX lookup)
25754 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
25755 limited to being the initial component of a 3-or-more component FQDN.
25757 There is no equivalent checking on client certificates.
25760 .option tls_verify_certificates smtp string&!! system
25761 .cindex "TLS" "server certificate verification"
25762 .cindex "certificate" "verification of server"
25764 .vindex "&$host_address$&"
25765 The value of this option must be either the
25767 or the absolute path to
25768 a file or directory containing permitted certificates for servers,
25769 for use when setting up an encrypted connection.
25771 The "system" value for the option will use a location compiled into the SSL library.
25772 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
25773 is taken as empty and an explicit location
25776 The use of a directory for the option value is not available for GnuTLS versions
25777 preceding 3.3.6 and a single file must be used.
25779 With OpenSSL the certificates specified
25781 either by file or directory
25782 are added to those given by the system default location.
25784 The values of &$host$& and
25785 &$host_address$& are set to the name and address of the server during the
25786 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
25788 For back-compatibility,
25789 if neither tls_verify_hosts nor tls_try_verify_hosts are set
25790 (a single-colon empty list counts as being set)
25791 and certificate verification fails the TLS connection is closed.
25794 .option tls_verify_hosts smtp "host list&!!" unset
25795 .cindex "TLS" "server certificate verification"
25796 .cindex "certificate" "verification of server"
25797 This option gives a list of hosts for which, on encrypted connections,
25798 certificate verification must succeed.
25799 The &%tls_verify_certificates%& option must also be set.
25800 If both this option and &%tls_try_verify_hosts%& are unset
25801 operation is as if this option selected all hosts.
25803 .option utf8_downconvert smtp integer&!! -1
25804 .cindex utf8 "address downconversion"
25805 .cindex i18n "utf8 address downconversion"
25806 If built with internationalization support,
25807 this option controls conversion of UTF-8 in message envelope addresses
25809 If, after expansion, the value is 1, 0, or -1 then this value overrides
25810 any value previously set for the message. Otherwise, any previously
25811 set value is used. To permit use of a previous value,
25812 set this option to an empty string.
25813 For details on the values see section &<<SECTi18nMTA>>&.
25818 .section "How the limits for the number of hosts to try are used" &&&
25820 .cindex "host" "maximum number to try"
25821 .cindex "limit" "hosts; maximum number tried"
25822 There are two options that are concerned with the number of hosts that are
25823 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
25824 &%hosts_max_try_hardlimit%&.
25827 The &%hosts_max_try%& option limits the number of hosts that are tried
25828 for a single delivery. However, despite the term &"host"& in its name, the
25829 option actually applies to each IP address independently. In other words, a
25830 multihomed host is treated as several independent hosts, just as it is for
25833 Many of the larger ISPs have multiple MX records which often point to
25834 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
25835 created as a result of routing one of these domains.
25837 Trying every single IP address on such a long list does not seem sensible; if
25838 several at the top of the list fail, it is reasonable to assume there is some
25839 problem that is likely to affect all of them. Roughly speaking, the value of
25840 &%hosts_max_try%& is the maximum number that are tried before deferring the
25841 delivery. However, the logic cannot be quite that simple.
25843 Firstly, IP addresses that are skipped because their retry times have not
25844 arrived do not count, and in addition, addresses that are past their retry
25845 limits are also not counted, even when they are tried. This means that when
25846 some IP addresses are past their retry limits, more than the value of
25847 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
25848 that all IP addresses are considered before timing out an email address (but
25849 see below for an exception).
25851 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
25852 list to see if there is a subsequent host with a different (higher valued) MX.
25853 If there is, that host is considered next, and the current IP address is used
25854 but not counted. This behaviour helps in the case of a domain with a retry rule
25855 that hardly ever delays any hosts, as is now explained:
25857 Consider the case of a long list of hosts with one MX value, and a few with a
25858 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
25859 hosts at the top of the list are tried at first. With the default retry rule,
25860 which specifies increasing retry times, the higher MX hosts are eventually
25861 tried when those at the top of the list are skipped because they have not
25862 reached their retry times.
25864 However, it is common practice to put a fixed short retry time on domains for
25865 large ISPs, on the grounds that their servers are rarely down for very long.
25866 Unfortunately, these are exactly the domains that tend to resolve to long lists
25867 of hosts. The short retry time means that the lowest MX hosts are tried every
25868 time. The attempts may be in a different order because of random sorting, but
25869 without the special MX check, the higher MX hosts would never be tried until
25870 all the lower MX hosts had timed out (which might be several days), because
25871 there are always some lower MX hosts that have reached their retry times. With
25872 the special check, Exim considers at least one IP address from each MX value at
25873 every delivery attempt, even if the &%hosts_max_try%& limit has already been
25876 The above logic means that &%hosts_max_try%& is not a hard limit, and in
25877 particular, Exim normally eventually tries all the IP addresses before timing
25878 out an email address. When &%hosts_max_try%& was implemented, this seemed a
25879 reasonable thing to do. Recently, however, some lunatic DNS configurations have
25880 been set up with hundreds of IP addresses for some domains. It can
25881 take a very long time indeed for an address to time out in these cases.
25883 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
25884 Exim never tries more than this number of IP addresses; if it hits this limit
25885 and they are all timed out, the email address is bounced, even though not all
25886 possible IP addresses have been tried.
25887 .ecindex IIDsmttra1
25888 .ecindex IIDsmttra2
25894 . ////////////////////////////////////////////////////////////////////////////
25895 . ////////////////////////////////////////////////////////////////////////////
25897 .chapter "Address rewriting" "CHAPrewrite"
25898 .scindex IIDaddrew "rewriting" "addresses"
25899 There are some circumstances in which Exim automatically rewrites domains in
25900 addresses. The two most common are when an address is given without a domain
25901 (referred to as an &"unqualified address"&) or when an address contains an
25902 abbreviated domain that is expanded by DNS lookup.
25904 Unqualified envelope addresses are accepted only for locally submitted
25905 messages, or for messages that are received from hosts matching
25906 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
25907 appropriate. Unqualified addresses in header lines are qualified if they are in
25908 locally submitted messages, or messages from hosts that are permitted to send
25909 unqualified envelope addresses. Otherwise, unqualified addresses in header
25910 lines are neither qualified nor rewritten.
25912 One situation in which Exim does &'not'& automatically rewrite a domain is
25913 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
25914 such a domain should be rewritten using the &"canonical"& name, and some MTAs
25915 do this. The new RFCs do not contain this suggestion.
25918 .section "Explicitly configured address rewriting" "SECID147"
25919 This chapter describes the rewriting rules that can be used in the
25920 main rewrite section of the configuration file, and also in the generic
25921 &%headers_rewrite%& option that can be set on any transport.
25923 Some people believe that configured address rewriting is a Mortal Sin.
25924 Others believe that life is not possible without it. Exim provides the
25925 facility; you do not have to use it.
25927 The main rewriting rules that appear in the &"rewrite"& section of the
25928 configuration file are applied to addresses in incoming messages, both envelope
25929 addresses and addresses in header lines. Each rule specifies the types of
25930 address to which it applies.
25932 Whether or not addresses in header lines are rewritten depends on the origin of
25933 the headers and the type of rewriting. Global rewriting, that is, rewriting
25934 rules from the rewrite section of the configuration file, is applied only to
25935 those headers that were received with the message. Header lines that are added
25936 by ACLs or by a system filter or by individual routers or transports (which
25937 are specific to individual recipient addresses) are not rewritten by the global
25940 Rewriting at transport time, by means of the &%headers_rewrite%& option,
25941 applies all headers except those added by routers and transports. That is, as
25942 well as the headers that were received with the message, it also applies to
25943 headers that were added by an ACL or a system filter.
25946 In general, rewriting addresses from your own system or domain has some
25947 legitimacy. Rewriting other addresses should be done only with great care and
25948 in special circumstances. The author of Exim believes that rewriting should be
25949 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
25950 Although it can sometimes be used as a routing tool, this is very strongly
25953 There are two commonly encountered circumstances where rewriting is used, as
25954 illustrated by these examples:
25957 The company whose domain is &'hitch.fict.example'& has a number of hosts that
25958 exchange mail with each other behind a firewall, but there is only a single
25959 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
25960 &'hitch.fict.example'& when sending mail off-site.
25962 A host rewrites the local parts of its own users so that, for example,
25963 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
25968 .section "When does rewriting happen?" "SECID148"
25969 .cindex "rewriting" "timing of"
25970 .cindex "&ACL;" "rewriting addresses in"
25971 Configured address rewriting can take place at several different stages of a
25972 message's processing.
25974 .vindex "&$sender_address$&"
25975 At the start of an ACL for MAIL, the sender address may have been rewritten
25976 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
25977 ordinary rewrite rules have yet been applied. If, however, the sender address
25978 is verified in the ACL, it is rewritten before verification, and remains
25979 rewritten thereafter. The subsequent value of &$sender_address$& is the
25980 rewritten address. This also applies if sender verification happens in a
25981 RCPT ACL. Otherwise, when the sender address is not verified, it is
25982 rewritten as soon as a message's header lines have been received.
25984 .vindex "&$domain$&"
25985 .vindex "&$local_part$&"
25986 Similarly, at the start of an ACL for RCPT, the current recipient's address
25987 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
25988 rewrite rules have yet been applied to it. However, the behaviour is different
25989 from the sender address when a recipient is verified. The address is rewritten
25990 for the verification, but the rewriting is not remembered at this stage. The
25991 value of &$local_part$& and &$domain$& after verification are always the same
25992 as they were before (that is, they contain the unrewritten &-- except for
25993 SMTP-time rewriting &-- address).
25995 As soon as a message's header lines have been received, all the envelope
25996 recipient addresses are permanently rewritten, and rewriting is also applied to
25997 the addresses in the header lines (if configured). This happens before adding
25998 any header lines that were specified in MAIL or RCPT ACLs, and
25999 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26000 before the DATA ACL and &[local_scan()]& functions are run.
26002 When an address is being routed, either for delivery or for verification,
26003 rewriting is applied immediately to child addresses that are generated by
26004 redirection, unless &%no_rewrite%& is set on the router.
26006 .cindex "envelope from"
26007 .cindex "envelope sender" "rewriting at transport time"
26008 .cindex "rewriting" "at transport time"
26009 .cindex "header lines" "rewriting at transport time"
26010 At transport time, additional rewriting of addresses in header lines can be
26011 specified by setting the generic &%headers_rewrite%& option on a transport.
26012 This option contains rules that are identical in form to those in the rewrite
26013 section of the configuration file. They are applied to the original message
26014 header lines and any that were added by ACLs or a system filter. They are not
26015 applied to header lines that are added by routers or the transport.
26017 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26018 transport option. However, it is not possible to rewrite envelope recipients at
26024 .section "Testing the rewriting rules that apply on input" "SECID149"
26025 .cindex "rewriting" "testing"
26026 .cindex "testing" "rewriting"
26027 Exim's input rewriting configuration appears in a part of the runtime
26028 configuration file headed by &"begin rewrite"&. It can be tested by the
26029 &%-brw%& command line option. This takes an address (which can be a full RFC
26030 2822 address) as its argument. The output is a list of how the address would be
26031 transformed by the rewriting rules for each of the different places it might
26032 appear in an incoming message, that is, for each different header and for the
26033 envelope sender and recipient fields. For example,
26035 exim -brw ph10@exim.workshop.example
26037 might produce the output
26039 sender: Philip.Hazel@exim.workshop.example
26040 from: Philip.Hazel@exim.workshop.example
26041 to: ph10@exim.workshop.example
26042 cc: ph10@exim.workshop.example
26043 bcc: ph10@exim.workshop.example
26044 reply-to: Philip.Hazel@exim.workshop.example
26045 env-from: Philip.Hazel@exim.workshop.example
26046 env-to: ph10@exim.workshop.example
26048 which shows that rewriting has been set up for that address when used in any of
26049 the source fields, but not when it appears as a recipient address. At the
26050 present time, there is no equivalent way of testing rewriting rules that are
26051 set for a particular transport.
26054 .section "Rewriting rules" "SECID150"
26055 .cindex "rewriting" "rules"
26056 The rewrite section of the configuration file consists of lines of rewriting
26059 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26061 Rewriting rules that are specified for the &%headers_rewrite%& generic
26062 transport option are given as a colon-separated list. Each item in the list
26063 takes the same form as a line in the main rewriting configuration (except that
26064 any colons must be doubled, of course).
26066 The formats of source patterns and replacement strings are described below.
26067 Each is terminated by white space, unless enclosed in double quotes, in which
26068 case normal quoting conventions apply inside the quotes. The flags are single
26069 characters which may appear in any order. Spaces and tabs between them are
26072 For each address that could potentially be rewritten, the rules are scanned in
26073 order, and replacements for the address from earlier rules can themselves be
26074 replaced by later rules (but see the &"q"& and &"R"& flags).
26076 The order in which addresses are rewritten is undefined, may change between
26077 releases, and must not be relied on, with one exception: when a message is
26078 received, the envelope sender is always rewritten first, before any header
26079 lines are rewritten. For example, the replacement string for a rewrite of an
26080 address in &'To:'& must not assume that the message's address in &'From:'& has
26081 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26082 that the envelope sender has already been rewritten.
26084 .vindex "&$domain$&"
26085 .vindex "&$local_part$&"
26086 The variables &$local_part$& and &$domain$& can be used in the replacement
26087 string to refer to the address that is being rewritten. Note that lookup-driven
26088 rewriting can be done by a rule of the form
26092 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26093 refer to the address that is being rewritten.
26096 .section "Rewriting patterns" "SECID151"
26097 .cindex "rewriting" "patterns"
26098 .cindex "address list" "in a rewriting pattern"
26099 The source pattern in a rewriting rule is any item which may appear in an
26100 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26101 single-item address list, which means that it is expanded before being tested
26102 against the address. As always, if you use a regular expression as a pattern,
26103 you must take care to escape dollar and backslash characters, or use the &`\N`&
26104 facility to suppress string expansion within the regular expression.
26106 Domains in patterns should be given in lower case. Local parts in patterns are
26107 case-sensitive. If you want to do case-insensitive matching of local parts, you
26108 can use a regular expression that starts with &`^(?i)`&.
26110 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26111 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26112 depending on the type of match which occurred. These can be used in the
26113 replacement string to insert portions of the incoming address. &$0$& always
26114 refers to the complete incoming address. When a regular expression is used, the
26115 numerical variables are set from its capturing subexpressions. For other types
26116 of pattern they are set as follows:
26119 If a local part or domain starts with an asterisk, the numerical variables
26120 refer to the character strings matched by asterisks, with &$1$& associated with
26121 the first asterisk, and &$2$& with the second, if present. For example, if the
26124 *queen@*.fict.example
26126 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26128 $0 = hearts-queen@wonderland.fict.example
26132 Note that if the local part does not start with an asterisk, but the domain
26133 does, it is &$1$& that contains the wild part of the domain.
26136 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26137 of the domain are placed in the next available numerical variables. Suppose,
26138 for example, that the address &'foo@bar.baz.example'& is processed by a
26139 rewriting rule of the form
26141 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26143 and the key in the file that matches the domain is &`*.baz.example`&. Then
26149 If the address &'foo@baz.example'& is looked up, this matches the same
26150 wildcard file entry, and in this case &$2$& is set to the empty string, but
26151 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26152 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26153 whole domain. For non-partial domain lookups, no numerical variables are set.
26157 .section "Rewriting replacements" "SECID152"
26158 .cindex "rewriting" "replacements"
26159 If the replacement string for a rule is a single asterisk, addresses that
26160 match the pattern and the flags are &'not'& rewritten, and no subsequent
26161 rewriting rules are scanned. For example,
26163 hatta@lookingglass.fict.example * f
26165 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26168 .vindex "&$domain$&"
26169 .vindex "&$local_part$&"
26170 If the replacement string is not a single asterisk, it is expanded, and must
26171 yield a fully qualified address. Within the expansion, the variables
26172 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26173 Any letters they contain retain their original case &-- they are not lower
26174 cased. The numerical variables are set up according to the type of pattern that
26175 matched the address, as described above. If the expansion is forced to fail by
26176 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26177 current rule is abandoned, but subsequent rules may take effect. Any other
26178 expansion failure causes the entire rewriting operation to be abandoned, and an
26179 entry written to the panic log.
26183 .section "Rewriting flags" "SECID153"
26184 There are three different kinds of flag that may appear on rewriting rules:
26187 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26190 A flag that specifies rewriting at SMTP time: S.
26192 Flags that control the rewriting process: Q, q, R, w.
26195 For rules that are part of the &%headers_rewrite%& generic transport option,
26196 E, F, T, and S are not permitted.
26200 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26202 .cindex "rewriting" "flags"
26203 If none of the following flag letters, nor the &"S"& flag (see section
26204 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26205 and to both the sender and recipient fields of the envelope, whereas a
26206 transport-time rewriting rule just applies to all headers. Otherwise, the
26207 rewriting rule is skipped unless the relevant addresses are being processed.
26209 &`E`& rewrite all envelope fields
26210 &`F`& rewrite the envelope From field
26211 &`T`& rewrite the envelope To field
26212 &`b`& rewrite the &'Bcc:'& header
26213 &`c`& rewrite the &'Cc:'& header
26214 &`f`& rewrite the &'From:'& header
26215 &`h`& rewrite all headers
26216 &`r`& rewrite the &'Reply-To:'& header
26217 &`s`& rewrite the &'Sender:'& header
26218 &`t`& rewrite the &'To:'& header
26220 "All headers" means all of the headers listed above that can be selected
26221 individually, plus their &'Resent-'& versions. It does not include
26222 other headers such as &'Subject:'& etc.
26224 You should be particularly careful about rewriting &'Sender:'& headers, and
26225 restrict this to special known cases in your own domains.
26228 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26229 .cindex "SMTP" "rewriting malformed addresses"
26230 .cindex "RCPT" "rewriting argument of"
26231 .cindex "MAIL" "rewriting argument of"
26232 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26233 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26234 before any other processing; even before syntax checking. The pattern is
26235 required to be a regular expression, and it is matched against the whole of the
26236 data for the command, including any surrounding angle brackets.
26238 .vindex "&$domain$&"
26239 .vindex "&$local_part$&"
26240 This form of rewrite rule allows for the handling of addresses that are not
26241 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26242 input). Because the input is not required to be a syntactically valid address,
26243 the variables &$local_part$& and &$domain$& are not available during the
26244 expansion of the replacement string. The result of rewriting replaces the
26245 original address in the MAIL or RCPT command.
26248 .section "Flags controlling the rewriting process" "SECID155"
26249 There are four flags which control the way the rewriting process works. These
26250 take effect only when a rule is invoked, that is, when the address is of the
26251 correct type (matches the flags) and matches the pattern:
26254 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26255 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26256 absence of &"Q"& the rewritten address must always include a domain.
26258 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26259 even if no rewriting actually takes place because of a &"fail"& in the
26260 expansion. The &"q"& flag is not effective if the address is of the wrong type
26261 (does not match the flags) or does not match the pattern.
26263 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26264 address, up to ten times. It can be combined with the &"q"& flag, to stop
26265 rewriting once it fails to match (after at least one successful rewrite).
26267 .cindex "rewriting" "whole addresses"
26268 When an address in a header is rewritten, the rewriting normally applies only
26269 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26270 left unchanged. For example, rewriting might change
26272 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26276 From: Ford Prefect <prefectf@hitch.fict.example>
26279 Sometimes there is a need to replace the whole address item, and this can be
26280 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26281 causes an address in a header line to be rewritten, the entire address is
26282 replaced, not just the working part. The replacement must be a complete RFC
26283 2822 address, including the angle brackets if necessary. If text outside angle
26284 brackets contains a character whose value is greater than 126 or less than 32
26285 (except for tab), the text is encoded according to RFC 2047. The character set
26286 is taken from &%headers_charset%&, which gets its default at build time.
26288 When the &"w"& flag is set on a rule that causes an envelope address to be
26289 rewritten, all but the working part of the replacement address is discarded.
26293 .section "Rewriting examples" "SECID156"
26294 Here is an example of the two common rewriting paradigms:
26296 *@*.hitch.fict.example $1@hitch.fict.example
26297 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26298 {$value}fail}@hitch.fict.example bctfrF
26300 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26301 the string expansion to fail if the lookup does not succeed. In this context it
26302 has the effect of leaving the original address unchanged, but Exim goes on to
26303 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26304 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26305 explicitly, which would cause the rewritten address to be the same as before,
26306 at the cost of a small bit of processing. Not supplying either of these is an
26307 error, since the rewritten address would then contain no local part.
26309 The first example above replaces the domain with a superior, more general
26310 domain. This may not be desirable for certain local parts. If the rule
26312 root@*.hitch.fict.example *
26314 were inserted before the first rule, rewriting would be suppressed for the
26315 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26317 Rewriting can be made conditional on a number of tests, by making use of
26318 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26319 messages that originate outside the local host:
26321 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26322 {$1@hitch.fict.example}fail}"
26324 The replacement string is quoted in this example because it contains white
26327 .cindex "rewriting" "bang paths"
26328 .cindex "bang paths" "rewriting"
26329 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26330 an address it treats it as an unqualified local part which it qualifies with
26331 the local qualification domain (if the source of the message is local or if the
26332 remote host is permitted to send unqualified addresses). Rewriting can
26333 sometimes be used to handle simple bang paths with a fixed number of
26334 components. For example, the rule
26336 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26338 rewrites a two-component bang path &'host.name!user'& as the domain address
26339 &'user@host.name'&. However, there is a security implication in using this as
26340 a global rewriting rule for envelope addresses. It can provide a backdoor
26341 method for using your system as a relay, because the incoming addresses appear
26342 to be local. If the bang path addresses are received via SMTP, it is safer to
26343 use the &"S"& flag to rewrite them as they are received, so that relay checking
26344 can be done on the rewritten addresses.
26351 . ////////////////////////////////////////////////////////////////////////////
26352 . ////////////////////////////////////////////////////////////////////////////
26354 .chapter "Retry configuration" "CHAPretry"
26355 .scindex IIDretconf1 "retry" "configuration, description of"
26356 .scindex IIDregconf2 "configuration file" "retry section"
26357 The &"retry"& section of the runtime configuration file contains a list of
26358 retry rules that control how often Exim tries to deliver messages that cannot
26359 be delivered at the first attempt. If there are no retry rules (the section is
26360 empty or not present), there are no retries. In this situation, temporary
26361 errors are treated as permanent. The default configuration contains a single,
26362 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26363 line option can be used to test which retry rule will be used for a given
26364 address, domain and error.
26366 The most common cause of retries is temporary failure to deliver to a remote
26367 host because the host is down, or inaccessible because of a network problem.
26368 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26369 address) basis, not on a per-message basis. Thus, if one message has recently
26370 been delayed, delivery of a new message to the same host is not immediately
26371 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26372 log selector is set, the message
26373 .cindex "retry" "time not reached"
26374 &"retry time not reached"& is written to the main log whenever a delivery is
26375 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26376 the handling of errors during remote deliveries.
26378 Retry processing applies to routing as well as to delivering, except as covered
26379 in the next paragraph. The retry rules do not distinguish between these
26380 actions. It is not possible, for example, to specify different behaviour for
26381 failures to route the domain &'snark.fict.example'& and failures to deliver to
26382 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26383 added complication, so did not implement it. However, although they share the
26384 same retry rule, the actual retry times for routing and transporting a given
26385 domain are maintained independently.
26387 When a delivery is not part of a queue run (typically an immediate delivery on
26388 receipt of a message), the routers are always run, and local deliveries are
26389 always attempted, even if retry times are set for them. This makes for better
26390 behaviour if one particular message is causing problems (for example, causing
26391 quota overflow, or provoking an error in a filter file). If such a delivery
26392 suffers a temporary failure, the retry data is updated as normal, and
26393 subsequent delivery attempts from queue runs occur only when the retry time for
26394 the local address is reached.
26396 .section "Changing retry rules" "SECID157"
26397 If you change the retry rules in your configuration, you should consider
26398 whether or not to delete the retry data that is stored in Exim's spool area in
26399 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26400 always safe; that is why they are called &"hints"&.
26402 The hints retry data contains suggested retry times based on the previous
26403 rules. In the case of a long-running problem with a remote host, it might
26404 record the fact that the host has timed out. If your new rules increase the
26405 timeout time for such a host, you should definitely remove the old retry data
26406 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26407 messages that it should now be retaining.
26411 .section "Format of retry rules" "SECID158"
26412 .cindex "retry" "rules"
26413 Each retry rule occupies one line and consists of three or four parts,
26414 separated by white space: a pattern, an error name, an optional list of sender
26415 addresses, and a list of retry parameters. The pattern and sender lists must be
26416 enclosed in double quotes if they contain white space. The rules are searched
26417 in order until one is found where the pattern, error name, and sender list (if
26418 present) match the failing host or address, the error that occurred, and the
26419 message's sender, respectively.
26422 The pattern is any single item that may appear in an address list (see section
26423 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26424 which means that it is expanded before being tested against the address that
26425 has been delayed. A negated address list item is permitted. Address
26426 list processing treats a plain domain name as if it were preceded by &"*@"&,
26427 which makes it possible for many retry rules to start with just a domain. For
26430 lookingglass.fict.example * F,24h,30m;
26432 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26435 alice@lookingglass.fict.example * F,24h,30m;
26437 applies only to temporary failures involving the local part &%alice%&.
26438 In practice, almost all rules start with a domain name pattern without a local
26441 .cindex "regular expressions" "in retry rules"
26442 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26443 must match a complete address, not just a domain, because that is how regular
26444 expressions work in address lists.
26446 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26447 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26451 .section "Choosing which retry rule to use for address errors" "SECID159"
26452 When Exim is looking for a retry rule after a routing attempt has failed (for
26453 example, after a DNS timeout), each line in the retry configuration is tested
26454 against the complete address only if &%retry_use_local_part%& is set for the
26455 router. Otherwise, only the domain is used, except when matching against a
26456 regular expression, when the local part of the address is replaced with &"*"&.
26457 A domain on its own can match a domain pattern, or a pattern that starts with
26458 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26459 &%check_local_user%& is true, and false for other routers.
26461 Similarly, when Exim is looking for a retry rule after a local delivery has
26462 failed (for example, after a mailbox full error), each line in the retry
26463 configuration is tested against the complete address only if
26464 &%retry_use_local_part%& is set for the transport (it defaults true for all
26467 .cindex "4&'xx'& responses" "retry rules for"
26468 However, when Exim is looking for a retry rule after a remote delivery attempt
26469 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26470 whole address is always used as the key when searching the retry rules. The
26471 rule that is found is used to create a retry time for the combination of the
26472 failing address and the message's sender. It is the combination of sender and
26473 recipient that is delayed in subsequent queue runs until its retry time is
26474 reached. You can delay the recipient without regard to the sender by setting
26475 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26476 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26481 .section "Choosing which retry rule to use for host and message errors" &&&
26483 For a temporary error that is not related to an individual address (for
26484 example, a connection timeout), each line in the retry configuration is checked
26485 twice. First, the name of the remote host is used as a domain name (preceded by
26486 &"*@"& when matching a regular expression). If this does not match the line,
26487 the domain from the email address is tried in a similar fashion. For example,
26488 suppose the MX records for &'a.b.c.example'& are
26490 a.b.c.example MX 5 x.y.z.example
26494 and the retry rules are
26496 p.q.r.example * F,24h,30m;
26497 a.b.c.example * F,4d,45m;
26499 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26500 first rule matches neither the host nor the domain, so Exim looks at the second
26501 rule. This does not match the host, but it does match the domain, so it is used
26502 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26503 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26504 first retry rule is used, because it matches the host.
26506 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26507 first rule to determine retry times, but for all the other hosts for the domain
26508 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26509 routing to &'a.b.c.example'& suffers a temporary failure.
26511 &*Note*&: The host name is used when matching the patterns, not its IP address.
26512 However, if a message is routed directly to an IP address without the use of a
26513 host name, for example, if a &(manualroute)& router contains a setting such as:
26515 route_list = *.a.example 192.168.34.23
26517 then the &"host name"& that is used when searching for a retry rule is the
26518 textual form of the IP address.
26520 .section "Retry rules for specific errors" "SECID161"
26521 .cindex "retry" "specific errors; specifying"
26522 The second field in a retry rule is the name of a particular error, or an
26523 asterisk, which matches any error. The errors that can be tested for are:
26526 .vitem &%auth_failed%&
26527 Authentication failed when trying to send to a host in the
26528 &%hosts_require_auth%& list in an &(smtp)& transport.
26530 .vitem &%data_4xx%&
26531 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26532 after the command, or after sending the message's data.
26534 .vitem &%mail_4xx%&
26535 A 4&'xx'& error was received for an outgoing MAIL command.
26537 .vitem &%rcpt_4xx%&
26538 A 4&'xx'& error was received for an outgoing RCPT command.
26541 For the three 4&'xx'& errors, either the first or both of the x's can be given
26542 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26543 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26544 and have retries every ten minutes with a one-hour timeout, you could set up a
26545 retry rule of this form:
26547 the.domain.name rcpt_452 F,1h,10m
26549 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26550 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26553 .vitem &%lost_connection%&
26554 A server unexpectedly closed the SMTP connection. There may, of course,
26555 legitimate reasons for this (host died, network died), but if it repeats a lot
26556 for the same host, it indicates something odd.
26559 A DNS lookup for a host failed.
26560 Note that a &%dnslookup%& router will need to have matched
26561 its &%fail_defer_domains%& option for this retry type to be usable.
26562 Also note that a &%manualroute%& router will probably need
26563 its &%host_find_failed%& option set to &%defer%&.
26565 .vitem &%refused_MX%&
26566 A connection to a host obtained from an MX record was refused.
26568 .vitem &%refused_A%&
26569 A connection to a host not obtained from an MX record was refused.
26572 A connection was refused.
26574 .vitem &%timeout_connect_MX%&
26575 A connection attempt to a host obtained from an MX record timed out.
26577 .vitem &%timeout_connect_A%&
26578 A connection attempt to a host not obtained from an MX record timed out.
26580 .vitem &%timeout_connect%&
26581 A connection attempt timed out.
26583 .vitem &%timeout_MX%&
26584 There was a timeout while connecting or during an SMTP session with a host
26585 obtained from an MX record.
26587 .vitem &%timeout_A%&
26588 There was a timeout while connecting or during an SMTP session with a host not
26589 obtained from an MX record.
26592 There was a timeout while connecting or during an SMTP session.
26594 .vitem &%tls_required%&
26595 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26596 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26597 to STARTTLS, or there was a problem setting up the TLS connection.
26600 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26603 .vitem &%quota_%&<&'time'&>
26604 .cindex "quota" "error testing in retry rule"
26605 .cindex "retry" "quota error testing"
26606 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26607 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26608 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26612 .cindex "mailbox" "time of last read"
26613 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26614 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26615 it should be based on the last time that the user accessed the mailbox.
26616 However, it is not always possible to determine this. Exim uses the following
26620 If the mailbox is a single file, the time of last access (the &"atime"&) is
26621 used. As no new messages are being delivered (because the mailbox is over
26622 quota), Exim does not access the file, so this is the time of last user access.
26624 .cindex "maildir format" "time of last read"
26625 For a maildir delivery, the time of last modification of the &_new_&
26626 subdirectory is used. As the mailbox is over quota, no new files are created in
26627 the &_new_& subdirectory, because no new messages are being delivered. Any
26628 change to the &_new_& subdirectory is therefore assumed to be the result of an
26629 MUA moving a new message to the &_cur_& directory when it is first read. The
26630 time that is used is therefore the last time that the user read a new message.
26632 For other kinds of multi-file mailbox, the time of last access cannot be
26633 obtained, so a retry rule that uses this type of error field is never matched.
26636 The quota errors apply both to system-enforced quotas and to Exim's own quota
26637 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26638 when a local delivery is deferred because a partition is full (the ENOSPC
26643 .section "Retry rules for specified senders" "SECID162"
26644 .cindex "retry" "rules; sender-specific"
26645 You can specify retry rules that apply only when the failing message has a
26646 specific sender. In particular, this can be used to define retry rules that
26647 apply only to bounce messages. The third item in a retry rule can be of this
26650 &`senders=`&<&'address list'&>
26652 The retry timings themselves are then the fourth item. For example:
26654 * rcpt_4xx senders=: F,1h,30m
26656 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26657 host. If the address list contains white space, it must be enclosed in quotes.
26660 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26662 &*Warning*&: This facility can be unhelpful if it is used for host errors
26663 (which do not depend on the recipient). The reason is that the sender is used
26664 only to match the retry rule. Once the rule has been found for a host error,
26665 its contents are used to set a retry time for the host, and this will apply to
26666 all messages, not just those with specific senders.
26668 When testing retry rules using &%-brt%&, you can supply a sender using the
26669 &%-f%& command line option, like this:
26671 exim -f "" -brt user@dom.ain
26673 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26674 list is never matched.
26680 .section "Retry parameters" "SECID163"
26681 .cindex "retry" "parameters in rules"
26682 The third (or fourth, if a senders list is present) field in a retry rule is a
26683 sequence of retry parameter sets, separated by semicolons. Each set consists of
26685 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26687 The letter identifies the algorithm for computing a new retry time; the cutoff
26688 time is the time beyond which this algorithm no longer applies, and the
26689 arguments vary the algorithm's action. The cutoff time is measured from the
26690 time that the first failure for the domain (combined with the local part if
26691 relevant) was detected, not from the time the message was received.
26693 .cindex "retry" "algorithms"
26694 .cindex "retry" "fixed intervals"
26695 .cindex "retry" "increasing intervals"
26696 .cindex "retry" "random intervals"
26697 The available algorithms are:
26700 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26703 &'G'&: retry at geometrically increasing intervals. The first argument
26704 specifies a starting value for the interval, and the second a multiplier, which
26705 is used to increase the size of the interval at each retry.
26707 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26708 retry, the previous interval is multiplied by the factor in order to get a
26709 maximum for the next interval. The minimum interval is the first argument of
26710 the parameter, and an actual interval is chosen randomly between them. Such a
26711 rule has been found to be helpful in cluster configurations when all the
26712 members of the cluster restart at once, and may therefore synchronize their
26713 queue processing times.
26716 When computing the next retry time, the algorithm definitions are scanned in
26717 order until one whose cutoff time has not yet passed is reached. This is then
26718 used to compute a new retry time that is later than the current time. In the
26719 case of fixed interval retries, this simply means adding the interval to the
26720 current time. For geometrically increasing intervals, retry intervals are
26721 computed from the rule's parameters until one that is greater than the previous
26722 interval is found. The main configuration variable
26723 .cindex "limit" "retry interval"
26724 .cindex "retry" "interval, maximum"
26725 .oindex "&%retry_interval_max%&"
26726 &%retry_interval_max%& limits the maximum interval between retries. It
26727 cannot be set greater than &`24h`&, which is its default value.
26729 A single remote domain may have a number of hosts associated with it, and each
26730 host may have more than one IP address. Retry algorithms are selected on the
26731 basis of the domain name, but are applied to each IP address independently. If,
26732 for example, a host has two IP addresses and one is unusable, Exim will
26733 generate retry times for it and will not try to use it until its next retry
26734 time comes. Thus the good IP address is likely to be tried first most of the
26737 .cindex "hints database" "use for retrying"
26738 Retry times are hints rather than promises. Exim does not make any attempt to
26739 run deliveries exactly at the computed times. Instead, a queue runner process
26740 starts delivery processes for delayed messages periodically, and these attempt
26741 new deliveries only for those addresses that have passed their next retry time.
26742 If a new message arrives for a deferred address, an immediate delivery attempt
26743 occurs only if the address has passed its retry time. In the absence of new
26744 messages, the minimum time between retries is the interval between queue runner
26745 processes. There is not much point in setting retry times of five minutes if
26746 your queue runners happen only once an hour, unless there are a significant
26747 number of incoming messages (which might be the case on a system that is
26748 sending everything to a smart host, for example).
26750 The data in the retry hints database can be inspected by using the
26751 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
26752 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
26753 &'exinext'& utility script can be used to find out what the next retry times
26754 are for the hosts associated with a particular mail domain, and also for local
26755 deliveries that have been deferred.
26758 .section "Retry rule examples" "SECID164"
26759 Here are some example retry rules:
26761 alice@wonderland.fict.example quota_5d F,7d,3h
26762 wonderland.fict.example quota_5d
26763 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
26764 lookingglass.fict.example * F,24h,30m;
26765 * refused_A F,2h,20m;
26766 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
26768 The first rule sets up special handling for mail to
26769 &'alice@wonderland.fict.example'& when there is an over-quota error and the
26770 mailbox has not been read for at least 5 days. Retries continue every three
26771 hours for 7 days. The second rule handles over-quota errors for all other local
26772 parts at &'wonderland.fict.example'&; the absence of a local part has the same
26773 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
26774 fail are bounced immediately if the mailbox has not been read for at least 5
26777 The third rule handles all other errors at &'wonderland.fict.example'&; retries
26778 happen every 15 minutes for an hour, then with geometrically increasing
26779 intervals until two days have passed since a delivery first failed. After the
26780 first hour there is a delay of one hour, then two hours, then four hours, and
26781 so on (this is a rather extreme example).
26783 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
26784 They happen every 30 minutes for 24 hours only. The remaining two rules handle
26785 all other domains, with special action for connection refusal from hosts that
26786 were not obtained from an MX record.
26788 The final rule in a retry configuration should always have asterisks in the
26789 first two fields so as to provide a general catch-all for any addresses that do
26790 not have their own special handling. This example tries every 15 minutes for 2
26791 hours, then with intervals starting at one hour and increasing by a factor of
26792 1.5 up to 16 hours, then every 8 hours up to 5 days.
26796 .section "Timeout of retry data" "SECID165"
26797 .cindex "timeout" "of retry data"
26798 .oindex "&%retry_data_expire%&"
26799 .cindex "hints database" "data expiry"
26800 .cindex "retry" "timeout of data"
26801 Exim timestamps the data that it writes to its retry hints database. When it
26802 consults the data during a delivery it ignores any that is older than the value
26803 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
26804 been tried for 7 days, Exim will try to deliver to it immediately a message
26805 arrives, and if that fails, it will calculate a retry time as if it were
26806 failing for the first time.
26808 This improves the behaviour for messages routed to rarely-used hosts such as MX
26809 backups. If such a host was down at one time, and happens to be down again when
26810 Exim tries a month later, using the old retry data would imply that it had been
26811 down all the time, which is not a justified assumption.
26813 If a host really is permanently dead, this behaviour causes a burst of retries
26814 every now and again, but only if messages routed to it are rare. If there is a
26815 message at least once every 7 days the retry data never expires.
26820 .section "Long-term failures" "SECID166"
26821 .cindex "delivery failure, long-term"
26822 .cindex "retry" "after long-term failure"
26823 Special processing happens when an email address has been failing for so long
26824 that the cutoff time for the last algorithm is reached. For example, using the
26825 default retry rule:
26827 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
26829 the cutoff time is four days. Reaching the retry cutoff is independent of how
26830 long any specific message has been failing; it is the length of continuous
26831 failure for the recipient address that counts.
26833 When the cutoff time is reached for a local delivery, or for all the IP
26834 addresses associated with a remote delivery, a subsequent delivery failure
26835 causes Exim to give up on the address, and a bounce message is generated.
26836 In order to cater for new messages that use the failing address, a next retry
26837 time is still computed from the final algorithm, and is used as follows:
26839 For local deliveries, one delivery attempt is always made for any subsequent
26840 messages. If this delivery fails, the address fails immediately. The
26841 post-cutoff retry time is not used.
26843 .cindex "final cutoff" "retries, controlling"
26844 .cindex retry "final cutoff"
26845 If the delivery is remote, there are two possibilities, controlled by the
26846 .oindex "&%delay_after_cutoff%&"
26847 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
26848 default. Until the post-cutoff retry time for one of the IP addresses,
26849 as set by the &%retry_data_expire%& option, is
26850 reached, the failing email address is bounced immediately, without a delivery
26851 attempt taking place. After that time, one new delivery attempt is made to
26852 those IP addresses that are past their retry times, and if that still fails,
26853 the address is bounced and new retry times are computed.
26855 In other words, when all the hosts for a given email address have been failing
26856 for a long time, Exim bounces rather then defers until one of the hosts' retry
26857 times is reached. Then it tries once, and bounces if that attempt fails. This
26858 behaviour ensures that few resources are wasted in repeatedly trying to deliver
26859 to a broken destination, but if the host does recover, Exim will eventually
26862 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
26863 addresses are past their final cutoff time, Exim tries to deliver to those IP
26864 addresses that have not been tried since the message arrived. If there are
26865 no suitable IP addresses, or if they all fail, the address is bounced. In other
26866 words, it does not delay when a new message arrives, but tries the expired
26867 addresses immediately, unless they have been tried since the message arrived.
26868 If there is a continuous stream of messages for the failing domains, setting
26869 &%delay_after_cutoff%& false means that there will be many more attempts to
26870 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
26873 .section "Deliveries that work intermittently" "SECID167"
26874 .cindex "retry" "intermittently working deliveries"
26875 Some additional logic is needed to cope with cases where a host is
26876 intermittently available, or when a message has some attribute that prevents
26877 its delivery when others to the same address get through. In this situation,
26878 because some messages are successfully delivered, the &"retry clock"& for the
26879 host or address keeps getting reset by the successful deliveries, and so
26880 failing messages remain in the queue for ever because the cutoff time is never
26883 Two exceptional actions are applied to prevent this happening. The first
26884 applies to errors that are related to a message rather than a remote host.
26885 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
26886 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
26887 commands, and quota failures. For this type of error, if a message's arrival
26888 time is earlier than the &"first failed"& time for the error, the earlier time
26889 is used when scanning the retry rules to decide when to try next and when to
26890 time out the address.
26892 The exceptional second action applies in all cases. If a message has been on
26893 the queue for longer than the cutoff time of any applicable retry rule for a
26894 given address, a delivery is attempted for that address, even if it is not yet
26895 time, and if this delivery fails, the address is timed out. A new retry time is
26896 not computed in this case, so that other messages for the same address are
26897 considered immediately.
26898 .ecindex IIDretconf1
26899 .ecindex IIDregconf2
26906 . ////////////////////////////////////////////////////////////////////////////
26907 . ////////////////////////////////////////////////////////////////////////////
26909 .chapter "SMTP authentication" "CHAPSMTPAUTH"
26910 .scindex IIDauthconf1 "SMTP" "authentication configuration"
26911 .scindex IIDauthconf2 "authentication"
26912 The &"authenticators"& section of Exim's runtime configuration is concerned
26913 with SMTP authentication. This facility is an extension to the SMTP protocol,
26914 described in RFC 2554, which allows a client SMTP host to authenticate itself
26915 to a server. This is a common way for a server to recognize clients that are
26916 permitted to use it as a relay. SMTP authentication is not of relevance to the
26917 transfer of mail between servers that have no managerial connection with each
26920 .cindex "AUTH" "description of"
26921 .cindex "ESMTP extensions" AUTH
26922 Very briefly, the way SMTP authentication works is as follows:
26925 The server advertises a number of authentication &'mechanisms'& in response to
26926 the client's EHLO command.
26928 The client issues an AUTH command, naming a specific mechanism. The command
26929 may, optionally, contain some authentication data.
26931 The server may issue one or more &'challenges'&, to which the client must send
26932 appropriate responses. In simple authentication mechanisms, the challenges are
26933 just prompts for user names and passwords. The server does not have to issue
26934 any challenges &-- in some mechanisms the relevant data may all be transmitted
26935 with the AUTH command.
26937 The server either accepts or denies authentication.
26939 If authentication succeeds, the client may optionally make use of the AUTH
26940 option on the MAIL command to pass an authenticated sender in subsequent
26941 mail transactions. Authentication lasts for the remainder of the SMTP
26944 If authentication fails, the client may give up, or it may try a different
26945 authentication mechanism, or it may try transferring mail over the
26946 unauthenticated connection.
26949 If you are setting up a client, and want to know which authentication
26950 mechanisms the server supports, you can use Telnet to connect to port 25 (the
26951 SMTP port) on the server, and issue an EHLO command. The response to this
26952 includes the list of supported mechanisms. For example:
26954 &`$ `&&*&`telnet server.example 25`&*&
26955 &`Trying 192.168.34.25...`&
26956 &`Connected to server.example.`&
26957 &`Escape character is '^]'.`&
26958 &`220 server.example ESMTP Exim 4.20 ...`&
26959 &*&`ehlo client.example`&*&
26960 &`250-server.example Hello client.example [10.8.4.5]`&
26961 &`250-SIZE 52428800`&
26966 The second-last line of this example output shows that the server supports
26967 authentication using the PLAIN mechanism. In Exim, the different authentication
26968 mechanisms are configured by specifying &'authenticator'& drivers. Like the
26969 routers and transports, which authenticators are included in the binary is
26970 controlled by build-time definitions. The following are currently available,
26971 included by setting
26974 AUTH_CYRUS_SASL=yes
26978 AUTH_HEIMDAL_GSSAPI=yes
26983 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
26984 authentication mechanism (RFC 2195), and the second provides an interface to
26985 the Cyrus SASL authentication library.
26986 The third is an interface to Dovecot's authentication system, delegating the
26987 work via a socket interface.
26988 The fourth provides for negotiation of authentication done via non-SMTP means,
26989 as defined by RFC 4422 Appendix A.
26990 The fifth provides an interface to the GNU SASL authentication library, which
26991 provides mechanisms but typically not data sources.
26992 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
26993 supporting setting a server keytab.
26994 The seventh can be configured to support
26995 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
26996 not formally documented, but used by several MUAs.
26997 The eighth authenticator
26998 supports Microsoft's &'Secure Password Authentication'& mechanism.
26999 The last is an Exim authenticator but not an SMTP one;
27000 instead it can use information from a TLS negotiation.
27002 The authenticators are configured using the same syntax as other drivers (see
27003 section &<<SECTfordricon>>&). If no authenticators are required, no
27004 authentication section need be present in the configuration file. Each
27005 authenticator can in principle have both server and client functions. When Exim
27006 is receiving SMTP mail, it is acting as a server; when it is sending out
27007 messages over SMTP, it is acting as a client. Authenticator configuration
27008 options are provided for use in both these circumstances.
27010 To make it clear which options apply to which situation, the prefixes
27011 &%server_%& and &%client_%& are used on option names that are specific to
27012 either the server or the client function, respectively. Server and client
27013 functions are disabled if none of their options are set. If an authenticator is
27014 to be used for both server and client functions, a single definition, using
27015 both sets of options, is required. For example:
27019 public_name = CRAM-MD5
27020 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27022 client_secret = secret2
27024 The &%server_%& option is used when Exim is acting as a server, and the
27025 &%client_%& options when it is acting as a client.
27027 Descriptions of the individual authenticators are given in subsequent chapters.
27028 The remainder of this chapter covers the generic options for the
27029 authenticators, followed by general discussion of the way authentication works
27032 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27033 per-mechanism basis. Please read carefully to determine which variables hold
27034 account labels such as usercodes and which hold passwords or other
27035 authenticating data.
27037 Note that some mechanisms support two different identifiers for accounts: the
27038 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27039 and &'authz'& are commonly encountered. The American spelling is standard here.
27040 Conceptually, authentication data such as passwords are tied to the identifier
27041 used to authenticate; servers may have rules to permit one user to act as a
27042 second user, so that after login the session is treated as though that second
27043 user had logged in. That second user is the &'authorization id'&. A robust
27044 configuration might confirm that the &'authz'& field is empty or matches the
27045 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27046 as verified data, the &'authz'& as an unverified request which the server might
27049 A &'realm'& is a text string, typically a domain name, presented by a server
27050 to a client to help it select an account and credentials to use. In some
27051 mechanisms, the client and server provably agree on the realm, but clients
27052 typically can not treat the realm as secure data to be blindly trusted.
27056 .section "Generic options for authenticators" "SECID168"
27057 .cindex "authentication" "generic options"
27058 .cindex "options" "generic; for authenticators"
27060 .option client_condition authenticators string&!! unset
27061 When Exim is authenticating as a client, it skips any authenticator whose
27062 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27063 used, for example, to skip plain text authenticators when the connection is not
27064 encrypted by a setting such as:
27066 client_condition = ${if !eq{$tls_out_cipher}{}}
27070 .option client_set_id authenticators string&!! unset
27071 When client authentication succeeds, this condition is expanded; the
27072 result is used in the log lines for outbound messages.
27073 Typically it will be the user name used for authentication.
27076 .option driver authenticators string unset
27077 This option must always be set. It specifies which of the available
27078 authenticators is to be used.
27081 .option public_name authenticators string unset
27082 This option specifies the name of the authentication mechanism that the driver
27083 implements, and by which it is known to the outside world. These names should
27084 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27085 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27086 defaults to the driver's instance name.
27089 .option server_advertise_condition authenticators string&!! unset
27090 When a server is about to advertise an authentication mechanism, the condition
27091 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27092 mechanism is not advertised.
27093 If the expansion fails, the mechanism is not advertised. If the failure was not
27094 forced, and was not caused by a lookup defer, the incident is logged.
27095 See section &<<SECTauthexiser>>& below for further discussion.
27098 .option server_condition authenticators string&!! unset
27099 This option must be set for a &%plaintext%& server authenticator, where it
27100 is used directly to control authentication. See section &<<SECTplainserver>>&
27103 For the &(gsasl)& authenticator, this option is required for various
27104 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27106 For the other authenticators, &%server_condition%& can be used as an additional
27107 authentication or authorization mechanism that is applied after the other
27108 authenticator conditions succeed. If it is set, it is expanded when the
27109 authenticator would otherwise return a success code. If the expansion is forced
27110 to fail, authentication fails. Any other expansion failure causes a temporary
27111 error code to be returned. If the result of a successful expansion is an empty
27112 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27113 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27114 other result, a temporary error code is returned, with the expanded string as
27118 .option server_debug_print authenticators string&!! unset
27119 If this option is set and authentication debugging is enabled (see the &%-d%&
27120 command line option), the string is expanded and included in the debugging
27121 output when the authenticator is run as a server. This can help with checking
27122 out the values of variables.
27123 If expansion of the string fails, the error message is written to the debugging
27124 output, and Exim carries on processing.
27127 .option server_set_id authenticators string&!! unset
27128 .vindex "&$authenticated_id$&"
27129 .vindex "&$authenticated_fail_id$&"
27130 When an Exim server successfully authenticates a client, this string is
27131 expanded using data from the authentication, and preserved for any incoming
27132 messages in the variable &$authenticated_id$&. It is also included in the log
27133 lines for incoming messages. For example, a user/password authenticator
27134 configuration might preserve the user name that was used to authenticate, and
27135 refer to it subsequently during delivery of the message.
27136 On a failing authentication the expansion result is instead saved in
27137 the &$authenticated_fail_id$& variable.
27138 If expansion fails, the option is ignored.
27141 .option server_mail_auth_condition authenticators string&!! unset
27142 This option allows a server to discard authenticated sender addresses supplied
27143 as part of MAIL commands in SMTP connections that are authenticated by the
27144 driver on which &%server_mail_auth_condition%& is set. The option is not used
27145 as part of the authentication process; instead its (unexpanded) value is
27146 remembered for later use.
27147 How it is used is described in the following section.
27153 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27154 .cindex "authentication" "sender; authenticated"
27155 .cindex "AUTH" "on MAIL command"
27156 When a client supplied an AUTH= item on a MAIL command, Exim applies
27157 the following checks before accepting it as the authenticated sender of the
27161 If the connection is not using extended SMTP (that is, HELO was used rather
27162 than EHLO), the use of AUTH= is a syntax error.
27164 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27166 .vindex "&$authenticated_sender$&"
27167 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27168 running, the value of &$authenticated_sender$& is set to the value obtained
27169 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27170 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27171 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27172 given for the MAIL command.
27174 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27175 is accepted and placed in &$authenticated_sender$& only if the client has
27178 If the AUTH= value was accepted by either of the two previous rules, and
27179 the client has authenticated, and the authenticator has a setting for the
27180 &%server_mail_auth_condition%&, the condition is checked at this point. The
27181 valued that was saved from the authenticator is expanded. If the expansion
27182 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27183 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27184 the value of &$authenticated_sender$& is retained and passed on with the
27189 When &$authenticated_sender$& is set for a message, it is passed on to other
27190 hosts to which Exim authenticates as a client. Do not confuse this value with
27191 &$authenticated_id$&, which is a string obtained from the authentication
27192 process, and which is not usually a complete email address.
27194 .vindex "&$sender_address$&"
27195 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27196 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27197 therefore make use of &$authenticated_sender$&. The converse is not true: the
27198 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27203 .section "Authentication on an Exim server" "SECTauthexiser"
27204 .cindex "authentication" "on an Exim server"
27205 When Exim receives an EHLO command, it advertises the public names of those
27206 authenticators that are configured as servers, subject to the following
27210 The client host must match &%auth_advertise_hosts%& (default *).
27212 It the &%server_advertise_condition%& option is set, its expansion must not
27213 yield the empty string, &"0"&, &"no"&, or &"false"&.
27216 The order in which the authenticators are defined controls the order in which
27217 the mechanisms are advertised.
27219 Some mail clients (for example, some versions of Netscape) require the user to
27220 provide a name and password for authentication whenever AUTH is advertised,
27221 even though authentication may not in fact be needed (for example, Exim may be
27222 set up to allow unconditional relaying from the client by an IP address check).
27223 You can make such clients more friendly by not advertising AUTH to them.
27224 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27225 that runs for RCPT) to relay without authentication, you should set
27227 auth_advertise_hosts = ! 10.9.8.0/24
27229 so that no authentication mechanisms are advertised to them.
27231 The &%server_advertise_condition%& controls the advertisement of individual
27232 authentication mechanisms. For example, it can be used to restrict the
27233 advertisement of a particular mechanism to encrypted connections, by a setting
27236 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27238 .vindex "&$tls_in_cipher$&"
27239 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27240 yields &"yes"&, which allows the advertisement to happen.
27242 When an Exim server receives an AUTH command from a client, it rejects it
27243 immediately if AUTH was not advertised in response to an earlier EHLO
27244 command. This is the case if
27247 The client host does not match &%auth_advertise_hosts%&; or
27249 No authenticators are configured with server options; or
27251 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27252 server authenticators.
27256 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27257 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27258 AUTH is accepted from any client host.
27260 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27261 server authentication mechanism that was advertised in response to EHLO and
27262 that matches the one named in the AUTH command. If it finds one, it runs
27263 the appropriate authentication protocol, and authentication either succeeds or
27264 fails. If there is no matching advertised mechanism, the AUTH command is
27265 rejected with a 504 error.
27267 .vindex "&$received_protocol$&"
27268 .vindex "&$sender_host_authenticated$&"
27269 When a message is received from an authenticated host, the value of
27270 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27271 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27272 public name) of the authenticator driver that successfully authenticated the
27273 client from which the message was received. This variable is empty if there was
27274 no successful authentication.
27276 .cindex authentication "expansion item"
27277 Successful authentication sets up information used by the
27278 &%authresults%& expansion item.
27283 .section "Testing server authentication" "SECID169"
27284 .cindex "authentication" "testing a server"
27285 .cindex "AUTH" "testing a server"
27286 .cindex "base64 encoding" "creating authentication test data"
27287 Exim's &%-bh%& option can be useful for testing server authentication
27288 configurations. The data for the AUTH command has to be sent using base64
27289 encoding. A quick way to produce such data for testing is the following Perl
27293 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27295 .cindex "binary zero" "in authentication data"
27296 This interprets its argument as a Perl string, and then encodes it. The
27297 interpretation as a Perl string allows binary zeros, which are required for
27298 some kinds of authentication, to be included in the data. For example, a
27299 command line to run this script on such data might be
27301 encode '\0user\0password'
27303 Note the use of single quotes to prevent the shell interpreting the
27304 backslashes, so that they can be interpreted by Perl to specify characters
27305 whose code value is zero.
27307 &*Warning 1*&: If either of the user or password strings starts with an octal
27308 digit, you must use three zeros instead of one after the leading backslash. If
27309 you do not, the octal digit that starts your string will be incorrectly
27310 interpreted as part of the code for the first character.
27312 &*Warning 2*&: If there are characters in the strings that Perl interprets
27313 specially, you must use a Perl escape to prevent them being misinterpreted. For
27314 example, a command such as
27316 encode '\0user@domain.com\0pas$$word'
27318 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27320 If you have the &%mimencode%& command installed, another way to do produce
27321 base64-encoded strings is to run the command
27323 echo -e -n `\0user\0password' | mimencode
27325 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27326 in the argument, and the &%-n%& option specifies no newline at the end of its
27327 output. However, not all versions of &%echo%& recognize these options, so you
27328 should check your version before relying on this suggestion.
27332 .section "Authentication by an Exim client" "SECID170"
27333 .cindex "authentication" "on an Exim client"
27334 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27335 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27336 announces support for authentication, and the host matches an entry in either
27337 of these options, Exim (as a client) tries to authenticate as follows:
27340 For each authenticator that is configured as a client, in the order in which
27341 they are defined in the configuration, it searches the authentication
27342 mechanisms announced by the server for one whose name matches the public name
27343 of the authenticator.
27346 .vindex "&$host_address$&"
27347 When it finds one that matches, it runs the authenticator's client code. The
27348 variables &$host$& and &$host_address$& are available for any string expansions
27349 that the client might do. They are set to the server's name and IP address. If
27350 any expansion is forced to fail, the authentication attempt is abandoned, and
27351 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27352 delivery to be deferred.
27354 If the result of the authentication attempt is a temporary error or a timeout,
27355 Exim abandons trying to send the message to the host for the moment. It will
27356 try again later. If there are any backup hosts available, they are tried in the
27359 If the response to authentication is a permanent error (5&'xx'& code), Exim
27360 carries on searching the list of authenticators and tries another one if
27361 possible. If all authentication attempts give permanent errors, or if there are
27362 no attempts because no mechanisms match (or option expansions force failure),
27363 what happens depends on whether the host matches &%hosts_require_auth%& or
27364 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27365 delivery is deferred. The error can be detected in the retry rules, and thereby
27366 turned into a permanent error if you wish. In the second case, Exim tries to
27367 deliver the message unauthenticated.
27370 Note that the hostlist test for whether to do authentication can be
27371 confused if name-IP lookups change between the time the peer is decided
27372 upon and the time that the transport runs. For example, with a manualroute
27373 router given a host name, and with DNS "round-robin" used by that name: if
27374 the local resolver cache times out between the router and the transport
27375 running, the transport may get an IP for the name for its authentication
27376 check which does not match the connection peer IP.
27377 No authentication will then be done, despite the names being identical.
27379 For such cases use a separate transport which always authenticates.
27381 .cindex "AUTH" "on MAIL command"
27382 When Exim has authenticated itself to a remote server, it adds the AUTH
27383 parameter to the MAIL commands it sends, if it has an authenticated sender for
27384 the message. If the message came from a remote host, the authenticated sender
27385 is the one that was receiving on an incoming MAIL command, provided that the
27386 incoming connection was authenticated and the &%server_mail_auth%& condition
27387 allowed the authenticated sender to be retained. If a local process calls Exim
27388 to send a message, the sender address that is built from the login name and
27389 &%qualify_domain%& is treated as authenticated. However, if the
27390 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27391 the authenticated sender that was received with the message.
27392 .ecindex IIDauthconf1
27393 .ecindex IIDauthconf2
27400 . ////////////////////////////////////////////////////////////////////////////
27401 . ////////////////////////////////////////////////////////////////////////////
27403 .chapter "The plaintext authenticator" "CHAPplaintext"
27404 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27405 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27406 The &(plaintext)& authenticator can be configured to support the PLAIN and
27407 LOGIN authentication mechanisms, both of which transfer authentication data as
27408 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27409 security risk; you are strongly advised to insist on the use of SMTP encryption
27410 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27411 use unencrypted plain text, you should not use the same passwords for SMTP
27412 connections as you do for login accounts.
27414 .section "Avoiding cleartext use" "SECTplain_TLS"
27415 The following generic option settings will disable &(plaintext)& authenticators when
27416 TLS is not being used:
27418 server_advertise_condition = ${if def:tls_in_cipher }
27419 client_condition = ${if def:tls_out_cipher}
27422 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27423 but is still vulnerable to a Man In The Middle attack unless certificates
27424 (including their names) have been properly verified.
27426 .section "Plaintext server options" "SECID171"
27427 .cindex "options" "&(plaintext)& authenticator (server)"
27428 When configured as a server, &(plaintext)& uses the following options:
27430 .option server_condition authenticators string&!! unset
27431 This is actually a global authentication option, but it must be set in order to
27432 configure the &(plaintext)& driver as a server. Its use is described below.
27434 .option server_prompts plaintext "string list&!!" unset
27435 The contents of this option, after expansion, must be a colon-separated list of
27436 prompt strings. If expansion fails, a temporary authentication rejection is
27439 .section "Using plaintext in a server" "SECTplainserver"
27440 .cindex "AUTH" "in &(plaintext)& authenticator"
27441 .cindex "binary zero" "in &(plaintext)& authenticator"
27442 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27443 "in &(plaintext)& authenticator"
27444 .vindex "&$auth1$&, &$auth2$&, etc"
27445 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27447 When running as a server, &(plaintext)& performs the authentication test by
27448 expanding a string. The data sent by the client with the AUTH command, or in
27449 response to subsequent prompts, is base64 encoded, and so may contain any byte
27450 values when decoded. If any data is supplied with the command, it is treated as
27451 a list of strings, separated by NULs (binary zeros), the first three of which
27452 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27453 (neither LOGIN nor PLAIN uses more than three strings).
27455 For compatibility with previous releases of Exim, the values are also placed in
27456 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27457 variables for this purpose is now deprecated, as it can lead to confusion in
27458 string expansions that also use them for other things.
27460 If there are more strings in &%server_prompts%& than the number of strings
27461 supplied with the AUTH command, the remaining prompts are used to obtain more
27462 data. Each response from the client may be a list of NUL-separated strings.
27464 .vindex "&$authenticated_id$&"
27465 Once a sufficient number of data strings have been received,
27466 &%server_condition%& is expanded. If the expansion is forced to fail,
27467 authentication fails. Any other expansion failure causes a temporary error code
27468 to be returned. If the result of a successful expansion is an empty string,
27469 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27470 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27471 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27472 For any other result, a temporary error code is returned, with the expanded
27473 string as the error text.
27475 &*Warning*&: If you use a lookup in the expansion to find the user's
27476 password, be sure to make the authentication fail if the user is unknown.
27477 There are good and bad examples at the end of the next section.
27481 .section "The PLAIN authentication mechanism" "SECID172"
27482 .cindex "PLAIN authentication mechanism"
27483 .cindex authentication PLAIN
27484 .cindex "binary zero" "in &(plaintext)& authenticator"
27485 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27486 sent as one item of data (that is, one combined string containing two NUL
27487 separators). The data is sent either as part of the AUTH command, or
27488 subsequently in response to an empty prompt from the server.
27490 The second and third strings are a user name and a corresponding password.
27491 Using a single fixed user name and password as an example, this could be
27492 configured as follows:
27496 public_name = PLAIN
27498 server_condition = \
27499 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27500 server_set_id = $auth2
27502 Note that the default result strings from &%if%& (&"true"& or an empty string)
27503 are exactly what we want here, so they need not be specified. Obviously, if the
27504 password contains expansion-significant characters such as dollar, backslash,
27505 or closing brace, they have to be escaped.
27507 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27508 the end of a string list are ignored). If all the data comes as part of the
27509 AUTH command, as is commonly the case, the prompt is not used. This
27510 authenticator is advertised in the response to EHLO as
27514 and a client host can authenticate itself by sending the command
27516 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27518 As this contains three strings (more than the number of prompts), no further
27519 data is required from the client. Alternatively, the client may just send
27523 to initiate authentication, in which case the server replies with an empty
27524 prompt. The client must respond with the combined data string.
27526 The data string is base64 encoded, as required by the RFC. This example,
27527 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27528 represents a zero byte. This is split up into three strings, the first of which
27529 is empty. The &%server_condition%& option in the authenticator checks that the
27530 second two are &`username`& and &`mysecret`& respectively.
27532 Having just one fixed user name and password, as in this example, is not very
27533 realistic, though for a small organization with only a handful of
27534 authenticating clients it could make sense.
27536 A more sophisticated instance of this authenticator could use the user name in
27537 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27538 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27539 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27540 This is an incorrect example:
27542 server_condition = \
27543 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27545 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27546 which it then compares to the supplied password (&$auth3$&). Why is this example
27547 incorrect? It works fine for existing users, but consider what happens if a
27548 non-existent user name is given. The lookup fails, but as no success/failure
27549 strings are given for the lookup, it yields an empty string. Thus, to defeat
27550 the authentication, all a client has to do is to supply a non-existent user
27551 name and an empty password. The correct way of writing this test is:
27553 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27554 {${if eq{$value}{$auth3}}} {false}}
27556 In this case, if the lookup succeeds, the result is checked; if the lookup
27557 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27558 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27559 always fails if its second argument is empty. However, the second way of
27560 writing the test makes the logic clearer.
27563 .section "The LOGIN authentication mechanism" "SECID173"
27564 .cindex "LOGIN authentication mechanism"
27565 .cindex authentication LOGIN
27566 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27567 in a number of programs. No data is sent with the AUTH command. Instead, a
27568 user name and password are supplied separately, in response to prompts. The
27569 plaintext authenticator can be configured to support this as in this example:
27573 public_name = LOGIN
27574 server_prompts = User Name : Password
27575 server_condition = \
27576 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27577 server_set_id = $auth1
27579 Because of the way plaintext operates, this authenticator accepts data supplied
27580 with the AUTH command (in contravention of the specification of LOGIN), but
27581 if the client does not supply it (as is the case for LOGIN clients), the prompt
27582 strings are used to obtain two data items.
27584 Some clients are very particular about the precise text of the prompts. For
27585 example, Outlook Express is reported to recognize only &"Username:"& and
27586 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27587 strings. It uses the &%ldapauth%& expansion condition to check the user
27588 name and password by binding to an LDAP server:
27592 public_name = LOGIN
27593 server_prompts = Username:: : Password::
27594 server_condition = ${if and{{ \
27597 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27598 pass=${quote:$auth2} \
27599 ldap://ldap.example.org/} }} }
27600 server_set_id = uid=$auth1,ou=people,o=example.org
27602 We have to check that the username is not empty before using it, because LDAP
27603 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27604 operator to correctly quote the DN for authentication. However, the basic
27605 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27606 correct one to use for the password, because quoting is needed only to make
27607 the password conform to the Exim syntax. At the LDAP level, the password is an
27608 uninterpreted string.
27611 .section "Support for different kinds of authentication" "SECID174"
27612 A number of string expansion features are provided for the purpose of
27613 interfacing to different ways of user authentication. These include checking
27614 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27615 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27621 .section "Using plaintext in a client" "SECID175"
27622 .cindex "options" "&(plaintext)& authenticator (client)"
27623 The &(plaintext)& authenticator has two client options:
27625 .option client_ignore_invalid_base64 plaintext boolean false
27626 If the client receives a server prompt that is not a valid base64 string,
27627 authentication is abandoned by default. However, if this option is set true,
27628 the error in the challenge is ignored and the client sends the response as
27631 .option client_send plaintext string&!! unset
27632 The string is a colon-separated list of authentication data strings. Each
27633 string is independently expanded before being sent to the server. The first
27634 string is sent with the AUTH command; any more strings are sent in response
27635 to prompts from the server. Before each string is expanded, the value of the
27636 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27637 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27638 way. Thus, the prompt that is received in response to sending the first string
27639 (with the AUTH command) can be used in the expansion of the second string, and
27640 so on. If an invalid base64 string is received when
27641 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27642 &$auth$&<&'n'&> variable.
27644 &*Note*&: You cannot use expansion to create multiple strings, because
27645 splitting takes priority and happens first.
27647 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27648 the data, further processing is applied to each string before it is sent. If
27649 there are any single circumflex characters in the string, they are converted to
27650 NULs. Should an actual circumflex be required as data, it must be doubled in
27653 This is an example of a client configuration that implements the PLAIN
27654 authentication mechanism with a fixed user name and password:
27658 public_name = PLAIN
27659 client_send = ^username^mysecret
27661 The lack of colons means that the entire text is sent with the AUTH
27662 command, with the circumflex characters converted to NULs. A similar example
27663 that uses the LOGIN mechanism is:
27667 public_name = LOGIN
27668 client_send = : username : mysecret
27670 The initial colon means that the first string is empty, so no data is sent with
27671 the AUTH command itself. The remaining strings are sent in response to
27673 .ecindex IIDplaiauth1
27674 .ecindex IIDplaiauth2
27679 . ////////////////////////////////////////////////////////////////////////////
27680 . ////////////////////////////////////////////////////////////////////////////
27682 .chapter "The cram_md5 authenticator" "CHID9"
27683 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27684 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27685 .cindex "CRAM-MD5 authentication mechanism"
27686 .cindex authentication CRAM-MD5
27687 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27688 sends a challenge string to the client, and the response consists of a user
27689 name and the CRAM-MD5 digest of the challenge string combined with a secret
27690 string (password) which is known to both server and client. Thus, the secret
27691 is not sent over the network as plain text, which makes this authenticator more
27692 secure than &(plaintext)&. However, the downside is that the secret has to be
27693 available in plain text at either end.
27696 .section "Using cram_md5 as a server" "SECID176"
27697 .cindex "options" "&(cram_md5)& authenticator (server)"
27698 This authenticator has one server option, which must be set to configure the
27699 authenticator as a server:
27701 .option server_secret cram_md5 string&!! unset
27702 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
27703 When the server receives the client's response, the user name is placed in
27704 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
27705 obtain the password for that user. The server then computes the CRAM-MD5 digest
27706 that the client should have sent, and checks that it received the correct
27707 string. If the expansion of &%server_secret%& is forced to fail, authentication
27708 fails. If the expansion fails for some other reason, a temporary error code is
27709 returned to the client.
27711 For compatibility with previous releases of Exim, the user name is also placed
27712 in &$1$&. However, the use of this variables for this purpose is now
27713 deprecated, as it can lead to confusion in string expansions that also use
27714 numeric variables for other things.
27716 For example, the following authenticator checks that the user name given by the
27717 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
27718 user name, authentication fails.
27722 public_name = CRAM-MD5
27723 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
27724 server_set_id = $auth1
27726 .vindex "&$authenticated_id$&"
27727 If authentication succeeds, the setting of &%server_set_id%& preserves the user
27728 name in &$authenticated_id$&. A more typical configuration might look up the
27729 secret string in a file, using the user name as the key. For example:
27733 public_name = CRAM-MD5
27734 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
27736 server_set_id = $auth1
27738 Note that this expansion explicitly forces failure if the lookup fails
27739 because &$auth1$& contains an unknown user name.
27741 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
27742 using the relevant libraries, you need to know the realm to specify in the
27743 lookup and then ask for the &"userPassword"& attribute for that user in that
27748 public_name = CRAM-MD5
27749 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
27750 dbmjz{/etc/sasldb2}{$value}fail}
27751 server_set_id = $auth1
27754 .section "Using cram_md5 as a client" "SECID177"
27755 .cindex "options" "&(cram_md5)& authenticator (client)"
27756 When used as a client, the &(cram_md5)& authenticator has two options:
27760 .option client_name cram_md5 string&!! "the primary host name"
27761 This string is expanded, and the result used as the user name data when
27762 computing the response to the server's challenge.
27765 .option client_secret cram_md5 string&!! unset
27766 This option must be set for the authenticator to work as a client. Its value is
27767 expanded and the result used as the secret string when computing the response.
27771 .vindex "&$host_address$&"
27772 Different user names and secrets can be used for different servers by referring
27773 to &$host$& or &$host_address$& in the options. Forced failure of either
27774 expansion string is treated as an indication that this authenticator is not
27775 prepared to handle this case. Exim moves on to the next configured client
27776 authenticator. Any other expansion failure causes Exim to give up trying to
27777 send the message to the current server.
27779 A simple example configuration of a &(cram_md5)& authenticator, using fixed
27784 public_name = CRAM-MD5
27786 client_secret = secret
27788 .ecindex IIDcramauth1
27789 .ecindex IIDcramauth2
27793 . ////////////////////////////////////////////////////////////////////////////
27794 . ////////////////////////////////////////////////////////////////////////////
27796 .chapter "The cyrus_sasl authenticator" "CHID10"
27797 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
27798 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
27799 .cindex "Cyrus" "SASL library"
27801 The code for this authenticator was provided by Matthew Byng-Maddick while
27802 at A L Digital Ltd.
27804 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
27805 library implementation of the RFC 2222 (&"Simple Authentication and Security
27806 Layer"&). This library supports a number of authentication mechanisms,
27807 including PLAIN and LOGIN, but also several others that Exim does not support
27808 directly. In particular, there is support for Kerberos authentication.
27810 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
27811 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
27812 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
27813 name of the driver to determine which mechanism to support.
27815 Where access to some kind of secret file is required, for example, in GSSAPI
27816 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
27817 user, and that the Cyrus SASL library has no way of escalating privileges
27818 by default. You may also find you need to set environment variables,
27819 depending on the driver you are using.
27821 The application name provided by Exim is &"exim"&, so various SASL options may
27822 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
27823 Kerberos, note that because of limitations in the GSSAPI interface,
27824 changing the server keytab might need to be communicated down to the Kerberos
27825 layer independently. The mechanism for doing so is dependent upon the Kerberos
27828 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
27829 may be set to point to an alternative keytab file. Exim will pass this
27830 variable through from its own inherited environment when started as root or the
27831 Exim user. The keytab file needs to be readable by the Exim user.
27832 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
27833 environment variable. In practice, for those releases, the Cyrus authenticator
27834 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
27835 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
27838 .section "Using cyrus_sasl as a server" "SECID178"
27839 The &(cyrus_sasl)& authenticator has four private options. It puts the username
27840 (on a successful authentication) into &$auth1$&. For compatibility with
27841 previous releases of Exim, the username is also placed in &$1$&. However, the
27842 use of this variable for this purpose is now deprecated, as it can lead to
27843 confusion in string expansions that also use numeric variables for other
27847 .option server_hostname cyrus_sasl string&!! "see below"
27848 This option selects the hostname that is used when communicating with the
27849 library. The default value is &`$primary_hostname`&. It is up to the underlying
27850 SASL plug-in what it does with this data.
27853 .option server_mech cyrus_sasl string "see below"
27854 This option selects the authentication mechanism this driver should use. The
27855 default is the value of the generic &%public_name%& option. This option allows
27856 you to use a different underlying mechanism from the advertised name. For
27860 driver = cyrus_sasl
27861 public_name = X-ANYTHING
27862 server_mech = CRAM-MD5
27863 server_set_id = $auth1
27866 .option server_realm cyrus_sasl string&!! unset
27867 This specifies the SASL realm that the server claims to be in.
27870 .option server_service cyrus_sasl string &`smtp`&
27871 This is the SASL service that the server claims to implement.
27874 For straightforward cases, you do not need to set any of the authenticator's
27875 private options. All you need to do is to specify an appropriate mechanism as
27876 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
27877 PLAIN, you could have two authenticators as follows:
27880 driver = cyrus_sasl
27881 public_name = CRAM-MD5
27882 server_set_id = $auth1
27885 driver = cyrus_sasl
27886 public_name = PLAIN
27887 server_set_id = $auth2
27889 Cyrus SASL does implement the LOGIN authentication method, even though it is
27890 not a standard method. It is disabled by default in the source distribution,
27891 but it is present in many binary distributions.
27892 .ecindex IIDcyrauth1
27893 .ecindex IIDcyrauth2
27898 . ////////////////////////////////////////////////////////////////////////////
27899 . ////////////////////////////////////////////////////////////////////////////
27900 .chapter "The dovecot authenticator" "CHAPdovecot"
27901 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
27902 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
27903 This authenticator is an interface to the authentication facility of the
27904 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
27905 Note that Dovecot must be configured to use auth-client not auth-userdb.
27906 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
27907 to use the same mechanisms for SMTP authentication. This is a server
27908 authenticator only. There is only one option:
27910 .option server_socket dovecot string unset
27912 This option must specify the UNIX socket that is the interface to Dovecot
27913 authentication. The &%public_name%& option must specify an authentication
27914 mechanism that Dovecot is configured to support. You can have several
27915 authenticators for different mechanisms. For example:
27919 public_name = PLAIN
27920 server_socket = /var/run/dovecot/auth-client
27921 server_set_id = $auth1
27926 server_socket = /var/run/dovecot/auth-client
27927 server_set_id = $auth1
27929 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
27930 &$received_ip_address$& (that is, the connection is local), the &"secured"&
27931 option is passed in the Dovecot authentication command. If, for a TLS
27932 connection, a client certificate has been verified, the &"valid-client-cert"&
27933 option is passed. When authentication succeeds, the identity of the user
27934 who authenticated is placed in &$auth1$&.
27937 The Dovecot configuration to match the above wil look
27940 conf.d/10-master.conf :-
27945 unix_listener auth-client {
27952 conf.d/10-auth.conf :-
27954 auth_mechanisms = plain login ntlm
27958 .ecindex IIDdcotauth1
27959 .ecindex IIDdcotauth2
27962 . ////////////////////////////////////////////////////////////////////////////
27963 . ////////////////////////////////////////////////////////////////////////////
27964 .chapter "The gsasl authenticator" "CHAPgsasl"
27965 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
27966 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
27967 .cindex "authentication" "GNU SASL"
27968 .cindex "authentication" "SASL"
27969 .cindex "authentication" "EXTERNAL"
27970 .cindex "authentication" "ANONYMOUS"
27971 .cindex "authentication" "PLAIN"
27972 .cindex "authentication" "LOGIN"
27973 .cindex "authentication" "DIGEST-MD5"
27974 .cindex "authentication" "CRAM-MD5"
27975 .cindex "authentication" "SCRAM family"
27976 The &(gsasl)& authenticator provides integration for the GNU SASL
27977 library and the mechanisms it provides. This is new as of the 4.80 release
27978 and there are a few areas where the library does not let Exim smoothly
27979 scale to handle future authentication mechanisms, so no guarantee can be
27980 made that any particular new authentication mechanism will be supported
27981 without code changes in Exim.
27984 The library is expected to add support in an upcoming
27985 realease for the SCRAM-SHA-256 method.
27986 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
27990 .option client_authz gsasl string&!! unset
27991 This option can be used to supply an &'authorization id'&
27992 which is different to the &'authentication_id'& provided
27993 by &%client_username%& option.
27994 If unset or (after expansion) empty it is not used,
27995 which is the common case.
27997 .option client_channelbinding gsasl boolean false
27998 See &%server_channelbinding%& below.
28000 .option client_password gsasl string&!! unset
28001 This option is exapanded before use, and should result in
28002 the password to be used, in clear.
28004 .option client_username gsasl string&!! unset
28005 This option is exapanded before use, and should result in
28006 the account name to be used.
28010 .option client_spassword gsasl string&!! unset
28011 If a SCRAM mechanism is being used and this option is set
28012 it is used in preference to &%client_password%&.
28013 The value after expansion should be
28014 a 40 (for SHA-1) or 64 (for SHA-256) character string
28015 with the PBKDF2-prepared password, hex-encoded.
28016 Note that this value will depend on the salt and iteration-count
28017 supplied by the server.
28022 .option server_channelbinding gsasl boolean false
28023 Do not set this true and rely on the properties
28024 without consulting a cryptographic engineer.
28026 Some authentication mechanisms are able to use external context at both ends
28027 of the session to bind the authentication to that context, and fail the
28028 authentication process if that context differs. Specifically, some TLS
28029 ciphersuites can provide identifying information about the cryptographic
28032 This should have meant that certificate identity and verification becomes a
28033 non-issue, as a man-in-the-middle attack will cause the correct client and
28034 server to see different identifiers and authentication will fail.
28038 only usable by mechanisms which support "channel binding"; at time of
28039 writing, that's the SCRAM family.
28040 When using this feature the "-PLUS" variants of the method names need to be used.
28043 This defaults off to ensure smooth upgrade across Exim releases, in case
28044 this option causes some clients to start failing. Some future release
28045 of Exim might have switched the default to be true.
28047 However, Channel Binding in TLS has proven to be vulnerable in current versions.
28048 Do not plan to rely upon this feature for security, ever, without consulting
28049 with a subject matter expert (a cryptographic engineer).
28052 .option server_hostname gsasl string&!! "see below"
28053 This option selects the hostname that is used when communicating with the
28054 library. The default value is &`$primary_hostname`&.
28055 Some mechanisms will use this data.
28058 .option server_mech gsasl string "see below"
28059 This option selects the authentication mechanism this driver should use. The
28060 default is the value of the generic &%public_name%& option. This option allows
28061 you to use a different underlying mechanism from the advertised name. For
28066 public_name = X-ANYTHING
28067 server_mech = CRAM-MD5
28068 server_set_id = $auth1
28072 .option server_password gsasl string&!! unset
28073 Various mechanisms need access to the cleartext password on the server, so
28074 that proof-of-possession can be demonstrated on the wire, without sending
28075 the password itself.
28077 The data available for lookup varies per mechanism.
28078 In all cases, &$auth1$& is set to the &'authentication id'&.
28079 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28080 if available, else the empty string.
28081 The &$auth3$& variable will always be the &'realm'& if available,
28082 else the empty string.
28084 A forced failure will cause authentication to defer.
28086 If using this option, it may make sense to set the &%server_condition%&
28087 option to be simply "true".
28090 .option server_realm gsasl string&!! unset
28091 This specifies the SASL realm that the server claims to be in.
28092 Some mechanisms will use this data.
28095 .option server_scram_iter gsasl string&!! 4096
28096 This option provides data for the SCRAM family of mechanisms.
28098 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28099 when this option is expanded.
28101 The result of expansion should be a decimal number,
28102 and represents both a lower-bound on the security, and
28103 a compute cost factor imposed on the client
28104 (if it does not cache results, or the server changes
28105 either the iteration count or the salt).
28106 A minimum value of 4096 is required by the standards
28107 for all current SCRAM mechanism variants.
28110 .option server_scram_salt gsasl string&!! unset
28111 This option provides data for the SCRAM family of mechanisms.
28113 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28114 when this option is expanded.
28115 The value should be a base64-encoded string,
28116 of random data typically 4-to-16 bytes long.
28117 If unset or empty after expansion the library will provides a value for the
28118 protocol conversation.
28123 .option server_key gsasl string&!! unset
28124 .option server_skey gsasl string&!! unset
28125 These options can be used for the SCRAM family of mechanisms
28126 to provide stored information related to a password,
28127 the storage of which is preferable to plaintext.
28129 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28130 &%server_skey%& is StoredKey.
28132 They are only available for version 1.9.0 (or later) of the gsasl library.
28133 When this is so, the macros
28134 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28135 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28138 The &$authN$& variables are available when these options are expanded.
28140 If set, the results of expansion should for each
28141 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28142 of base64-coded data, and will be used in preference to the
28143 &%server_password%& option.
28144 If unset or not of the right length, &%server_password%& will be used.
28146 The libgsasl library release includes a utility &'gsasl'& which can be used
28147 to generate these values.
28151 .option server_service gsasl string &`smtp`&
28152 This is the SASL service that the server claims to implement.
28153 Some mechanisms will use this data.
28156 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28157 .vindex "&$auth1$&, &$auth2$&, etc"
28158 These may be set when evaluating specific options, as detailed above.
28159 They will also be set when evaluating &%server_condition%&.
28161 Unless otherwise stated below, the &(gsasl)& integration will use the following
28162 meanings for these variables:
28165 .vindex "&$auth1$&"
28166 &$auth1$&: the &'authentication id'&
28168 .vindex "&$auth2$&"
28169 &$auth2$&: the &'authorization id'&
28171 .vindex "&$auth3$&"
28172 &$auth3$&: the &'realm'&
28175 On a per-mechanism basis:
28178 .cindex "authentication" "EXTERNAL"
28179 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28180 the &%server_condition%& option must be present.
28182 .cindex "authentication" "ANONYMOUS"
28183 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28184 the &%server_condition%& option must be present.
28186 .cindex "authentication" "GSSAPI"
28187 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28188 &$auth2$& will be set to the &'authorization id'&,
28189 the &%server_condition%& option must be present.
28192 An &'anonymous token'& is something passed along as an unauthenticated
28193 identifier; this is analogous to FTP anonymous authentication passing an
28194 email address, or software-identifier@, as the "password".
28197 An example showing the password having the realm specified in the callback
28198 and demonstrating a Cyrus SASL to GSASL migration approach is:
28200 gsasl_cyrusless_crammd5:
28202 public_name = CRAM-MD5
28203 server_realm = imap.example.org
28204 server_password = ${lookup{$auth1:$auth3:userPassword}\
28205 dbmjz{/etc/sasldb2}{$value}fail}
28206 server_set_id = ${quote:$auth1}
28207 server_condition = yes
28211 . ////////////////////////////////////////////////////////////////////////////
28212 . ////////////////////////////////////////////////////////////////////////////
28214 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28215 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28216 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28217 .cindex "authentication" "GSSAPI"
28218 .cindex "authentication" "Kerberos"
28219 The &(heimdal_gssapi)& authenticator provides server integration for the
28220 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28223 .option server_hostname heimdal_gssapi string&!! "see below"
28224 This option selects the hostname that is used, with &%server_service%&,
28225 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28226 identifier. The default value is &`$primary_hostname`&.
28228 .option server_keytab heimdal_gssapi string&!! unset
28229 If set, then Heimdal will not use the system default keytab (typically
28230 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28231 The value should be a pathname, with no &"file:"& prefix.
28233 .option server_service heimdal_gssapi string&!! "smtp"
28234 This option specifies the service identifier used, in conjunction with
28235 &%server_hostname%&, for building the identifier for finding credentials
28239 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28240 Beware that these variables will typically include a realm, thus will appear
28241 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28242 not verified, so a malicious client can set it to anything.
28244 The &$auth1$& field should be safely trustable as a value from the Key
28245 Distribution Center. Note that these are not quite email addresses.
28246 Each identifier is for a role, and so the left-hand-side may include a
28247 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28249 .vindex "&$auth1$&, &$auth2$&, etc"
28251 .vindex "&$auth1$&"
28252 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28254 .vindex "&$auth2$&"
28255 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28256 authentication. If that was empty, this will also be set to the
28261 . ////////////////////////////////////////////////////////////////////////////
28262 . ////////////////////////////////////////////////////////////////////////////
28264 .chapter "The spa authenticator" "CHAPspa"
28265 .scindex IIDspaauth1 "&(spa)& authenticator"
28266 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28267 .cindex "authentication" "Microsoft Secure Password"
28268 .cindex "authentication" "NTLM"
28269 .cindex "Microsoft Secure Password Authentication"
28270 .cindex "NTLM authentication"
28271 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28272 Password Authentication'& mechanism,
28273 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28274 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28275 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28276 server side was subsequently contributed by Tom Kistner. The mechanism works as
28280 After the AUTH command has been accepted, the client sends an SPA
28281 authentication request based on the user name and optional domain.
28283 The server sends back a challenge.
28285 The client builds a challenge response which makes use of the user's password
28286 and sends it to the server, which then accepts or rejects it.
28289 Encryption is used to protect the password in transit.
28293 .section "Using spa as a server" "SECID179"
28294 .cindex "options" "&(spa)& authenticator (server)"
28295 The &(spa)& authenticator has just one server option:
28297 .option server_password spa string&!! unset
28298 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28299 This option is expanded, and the result must be the cleartext password for the
28300 authenticating user, whose name is at this point in &$auth1$&. For
28301 compatibility with previous releases of Exim, the user name is also placed in
28302 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28303 it can lead to confusion in string expansions that also use numeric variables
28304 for other things. For example:
28309 server_password = \
28310 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28312 If the expansion is forced to fail, authentication fails. Any other expansion
28313 failure causes a temporary error code to be returned.
28319 .section "Using spa as a client" "SECID180"
28320 .cindex "options" "&(spa)& authenticator (client)"
28321 The &(spa)& authenticator has the following client options:
28325 .option client_domain spa string&!! unset
28326 This option specifies an optional domain for the authentication.
28329 .option client_password spa string&!! unset
28330 This option specifies the user's password, and must be set.
28333 .option client_username spa string&!! unset
28334 This option specifies the user name, and must be set. Here is an example of a
28335 configuration of this authenticator for use with the mail servers at
28341 client_username = msn/msn_username
28342 client_password = msn_plaintext_password
28343 client_domain = DOMAIN_OR_UNSET
28345 .ecindex IIDspaauth1
28346 .ecindex IIDspaauth2
28352 . ////////////////////////////////////////////////////////////////////////////
28353 . ////////////////////////////////////////////////////////////////////////////
28355 .chapter "The external authenticator" "CHAPexternauth"
28356 .scindex IIDexternauth1 "&(external)& authenticator"
28357 .scindex IIDexternauth2 "authenticators" "&(external)&"
28358 .cindex "authentication" "Client Certificate"
28359 .cindex "authentication" "X509"
28360 .cindex "Certificate-based authentication"
28361 The &(external)& authenticator provides support for
28362 authentication based on non-SMTP information.
28363 The specification is in RFC 4422 Appendix A
28364 (&url(https://tools.ietf.org/html/rfc4422)).
28365 It is only a transport and negotiation mechanism;
28366 the process of authentication is entirely controlled
28367 by the server configuration.
28369 The client presents an identity in-clear.
28370 It is probably wise for a server to only advertise,
28371 and for clients to only attempt,
28372 this authentication method on a secure (eg. under TLS) connection.
28374 One possible use, compatible with the
28375 K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
28376 is for using X509 client certificates.
28378 It thus overlaps in function with the TLS authenticator
28379 (see &<<CHAPtlsauth>>&)
28380 but is a full SMTP SASL authenticator
28381 rather than being implicit for TLS-connection carried
28382 client certificates only.
28384 The examples and discussion in this chapter assume that
28385 client-certificate authentication is being done.
28387 The client must present a certificate,
28388 for which it must have been requested via the
28389 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28390 (see &<<CHAPTLS>>&).
28391 For authentication to be effective the certificate should be
28392 verifiable against a trust-anchor certificate known to the server.
28394 .section "External options" "SECTexternsoptions"
28395 .cindex "options" "&(external)& authenticator (server)"
28396 The &(external)& authenticator has two server options:
28398 .option server_param2 external string&!! unset
28399 .option server_param3 external string&!! unset
28400 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28401 These options are expanded before the &%server_condition%& option
28402 and the result are placed in &$auth2$& and &$auth3$& resectively.
28403 If the expansion is forced to fail, authentication fails. Any other expansion
28404 failure causes a temporary error code to be returned.
28406 They can be used to clarify the coding of a complex &%server_condition%&.
28408 .section "Using external in a server" "SECTexternserver"
28409 .cindex "AUTH" "in &(external)& authenticator"
28410 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28411 "in &(external)& authenticator"
28412 .vindex "&$auth1$&, &$auth2$&, etc"
28413 .cindex "base64 encoding" "in &(external)& authenticator"
28415 When running as a server, &(external)& performs the authentication test by
28416 expanding a string. The data sent by the client with the AUTH command, or in
28417 response to subsequent prompts, is base64 encoded, and so may contain any byte
28418 values when decoded. The decoded value is treated as
28419 an identity for authentication and
28420 placed in the expansion variable &$auth1$&.
28422 For compatibility with previous releases of Exim, the value is also placed in
28423 the expansion variable &$1$&. However, the use of this
28424 variable for this purpose is now deprecated, as it can lead to confusion in
28425 string expansions that also use them for other things.
28427 .vindex "&$authenticated_id$&"
28428 Once an identity has been received,
28429 &%server_condition%& is expanded. If the expansion is forced to fail,
28430 authentication fails. Any other expansion failure causes a temporary error code
28431 to be returned. If the result of a successful expansion is an empty string,
28432 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28433 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28434 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28435 For any other result, a temporary error code is returned, with the expanded
28436 string as the error text.
28440 ext_ccert_san_mail:
28442 public_name = EXTERNAL
28444 server_advertise_condition = $tls_in_certificate_verified
28445 server_param2 = ${certextract {subj_altname,mail,>:} \
28446 {$tls_in_peercert}}
28447 server_condition = ${if forany {$auth2} \
28448 {eq {$item}{$auth1}}}
28449 server_set_id = $auth1
28451 This accepts a client certificate that is verifiable against any
28452 of your configured trust-anchors
28453 (which usually means the full set of public CAs)
28454 and which has a mail-SAN matching the claimed identity sent by the client.
28456 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28457 The account name is therefore guessable by an opponent.
28458 TLS 1.3 protects both server and client certificates, and is not vulnerable
28462 .section "Using external in a client" "SECTexternclient"
28463 .cindex "options" "&(external)& authenticator (client)"
28464 The &(external)& authenticator has one client option:
28466 .option client_send external string&!! unset
28467 This option is expanded and sent with the AUTH command as the
28468 identity being asserted.
28474 public_name = EXTERNAL
28476 client_condition = ${if !eq{$tls_out_cipher}{}}
28477 client_send = myaccount@smarthost.example.net
28481 .ecindex IIDexternauth1
28482 .ecindex IIDexternauth2
28488 . ////////////////////////////////////////////////////////////////////////////
28489 . ////////////////////////////////////////////////////////////////////////////
28491 .chapter "The tls authenticator" "CHAPtlsauth"
28492 .scindex IIDtlsauth1 "&(tls)& authenticator"
28493 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28494 .cindex "authentication" "Client Certificate"
28495 .cindex "authentication" "X509"
28496 .cindex "Certificate-based authentication"
28497 The &(tls)& authenticator provides server support for
28498 authentication based on client certificates.
28500 It is not an SMTP authentication mechanism and is not
28501 advertised by the server as part of the SMTP EHLO response.
28502 It is an Exim authenticator in the sense that it affects
28503 the protocol element of the log line, can be tested for
28504 by the &%authenticated%& ACL condition, and can set
28505 the &$authenticated_id$& variable.
28507 The client must present a verifiable certificate,
28508 for which it must have been requested via the
28509 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28510 (see &<<CHAPTLS>>&).
28512 If an authenticator of this type is configured it is
28513 run before any SMTP-level communication is done,
28514 and can authenticate the connection.
28515 If it does, SMTP authentication is not offered.
28517 A maximum of one authenticator of this type may be present.
28520 .cindex "options" "&(tls)& authenticator (server)"
28521 The &(tls)& authenticator has three server options:
28523 .option server_param1 tls string&!! unset
28524 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28525 This option is expanded after the TLS negotiation and
28526 the result is placed in &$auth1$&.
28527 If the expansion is forced to fail, authentication fails. Any other expansion
28528 failure causes a temporary error code to be returned.
28530 .option server_param2 tls string&!! unset
28531 .option server_param3 tls string&!! unset
28532 As above, for &$auth2$& and &$auth3$&.
28534 &%server_param1%& may also be spelled &%server_param%&.
28541 server_param1 = ${certextract {subj_altname,mail,>:} \
28542 {$tls_in_peercert}}
28543 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28546 {${lookup ldap{ldap:///\
28547 mailname=${quote_ldap_dn:${lc:$item}},\
28548 ou=users,LDAP_DC?mailid} {$value}{0} \
28550 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28552 This accepts a client certificate that is verifiable against any
28553 of your configured trust-anchors
28554 (which usually means the full set of public CAs)
28555 and which has a SAN with a good account name.
28557 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28558 The account name is therefore guessable by an opponent.
28559 TLS 1.3 protects both server and client certificates, and is not vulnerable
28561 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28563 . An alternative might use
28565 . server_param1 = ${sha256:$tls_in_peercert}
28567 . to require one of a set of specific certs that define a given account
28568 . (the verification is still required, but mostly irrelevant).
28569 . This would help for per-device use.
28571 . However, for the future we really need support for checking a
28572 . user cert in LDAP - which probably wants a base-64 DER.
28574 .ecindex IIDtlsauth1
28575 .ecindex IIDtlsauth2
28578 Note that because authentication is traditionally an SMTP operation,
28579 the &%authenticated%& ACL condition cannot be used in
28580 a connect- or helo-ACL.
28584 . ////////////////////////////////////////////////////////////////////////////
28585 . ////////////////////////////////////////////////////////////////////////////
28587 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28588 "Encrypted SMTP connections"
28589 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28590 .scindex IIDencsmtp2 "SMTP" "encryption"
28591 .cindex "TLS" "on SMTP connection"
28594 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28595 Sockets Layer), is implemented by making use of the OpenSSL library or the
28596 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28597 cryptographic code in the Exim distribution itself for implementing TLS. In
28598 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28599 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28600 You also need to understand the basic concepts of encryption at a managerial
28601 level, and in particular, the way that public keys, private keys, and
28602 certificates are used.
28604 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28605 connection is established, the client issues a STARTTLS command. If the
28606 server accepts this, the client and the server negotiate an encryption
28607 mechanism. If the negotiation succeeds, the data that subsequently passes
28608 between them is encrypted.
28610 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28611 and if so, what cipher suite is in use, whether the client supplied a
28612 certificate, and whether or not that certificate was verified. This makes it
28613 possible for an Exim server to deny or accept certain commands based on the
28616 &*Warning*&: Certain types of firewall and certain anti-virus products can
28617 disrupt TLS connections. You need to turn off SMTP scanning for these products
28618 in order to get TLS to work.
28622 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28624 .cindex "submissions protocol"
28625 .cindex "ssmtp protocol"
28626 .cindex "smtps protocol"
28627 .cindex "SMTP" "submissions protocol"
28628 .cindex "SMTP" "ssmtp protocol"
28629 .cindex "SMTP" "smtps protocol"
28630 The history of port numbers for TLS in SMTP is a little messy and has been
28631 contentious. As of RFC 8314, the common practice of using the historically
28632 allocated port 465 for "email submission but with TLS immediately upon connect
28633 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28634 by them in preference to STARTTLS.
28636 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28637 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28638 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28640 This approach was, for a while, officially abandoned when encrypted SMTP was
28641 standardized, but many clients kept using it, even as the TCP port number was
28642 reassigned for other use.
28643 Thus you may encounter guidance claiming that you shouldn't enable use of
28645 In practice, a number of mail-clients have only ever supported submissions,
28646 not submission with STARTTLS upgrade.
28647 Ideally, offer both submission (587) and submissions (465) service.
28649 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28650 global option. Its value must be a list of port numbers;
28651 the most common use is expected to be:
28653 tls_on_connect_ports = 465
28655 The port numbers specified by this option apply to all SMTP connections, both
28656 via the daemon and via &'inetd'&. You still need to specify all the ports that
28657 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28658 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28659 an extra port &-- rather, it specifies different behaviour on a port that is
28662 There is also a &%-tls-on-connect%& command line option. This overrides
28663 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28670 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28671 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28672 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28673 To build Exim to use OpenSSL you need to set
28679 To build Exim to use GnuTLS, you need to set
28685 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28686 include files and libraries for GnuTLS can be found.
28688 There are some differences in usage when using GnuTLS instead of OpenSSL:
28691 The &%tls_verify_certificates%& option
28692 cannot be the path of a directory
28693 for GnuTLS versions before 3.3.6
28694 (for later versions, or OpenSSL, it can be either).
28696 The default value for &%tls_dhparam%& differs for historical reasons.
28698 .vindex "&$tls_in_peerdn$&"
28699 .vindex "&$tls_out_peerdn$&"
28700 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
28701 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
28702 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
28704 OpenSSL identifies cipher suites using hyphens as separators, for example:
28705 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
28706 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
28707 in a cipher list. To make life simpler, Exim changes underscores to hyphens
28708 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
28709 to handle its own older variants) when processing lists of cipher suites in the
28710 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
28713 The &%tls_require_ciphers%& options operate differently, as described in the
28714 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
28716 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
28717 When using OpenSSL, this option is ignored.
28718 (If an API is found to let OpenSSL be configured in this way,
28719 let the Exim Maintainers know and we'll likely use it).
28721 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
28722 main option, it must be ordered to match the &%tls_certificate%& list.
28724 Some other recently added features may only be available in one or the other.
28725 This should be documented with the feature. If the documentation does not
28726 explicitly state that the feature is infeasible in the other TLS
28727 implementation, then patches are welcome.
28731 .section "GnuTLS parameter computation" "SECTgnutlsparam"
28732 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
28733 an explicit path; if the latter, then the text about generation still applies,
28734 but not the chosen filename.
28735 By default, as of Exim 4.80 a hard-coded D-H prime is used.
28736 See the documentation of &%tls_dhparam%& for more information.
28738 GnuTLS uses D-H parameters that may take a substantial amount of time
28739 to compute. It is unreasonable to re-compute them for every TLS session.
28740 Therefore, Exim keeps this data in a file in its spool directory, called
28741 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
28743 The file is owned by the Exim user and is readable only by
28744 its owner. Every Exim process that start up GnuTLS reads the D-H
28745 parameters from this file. If the file does not exist, the first Exim process
28746 that needs it computes the data and writes it to a temporary file which is
28747 renamed once it is complete. It does not matter if several Exim processes do
28748 this simultaneously (apart from wasting a few resources). Once a file is in
28749 place, new Exim processes immediately start using it.
28751 For maximum security, the parameters that are stored in this file should be
28752 recalculated periodically, the frequency depending on your paranoia level.
28753 If you are avoiding using the fixed D-H primes published in RFCs, then you
28754 are concerned about some advanced attacks and will wish to do this; if you do
28755 not regenerate then you might as well stick to the standard primes.
28757 Arranging this is easy in principle; just delete the file when you want new
28758 values to be computed. However, there may be a problem. The calculation of new
28759 parameters needs random numbers, and these are obtained from &_/dev/random_&.
28760 If the system is not very active, &_/dev/random_& may delay returning data
28761 until enough randomness (entropy) is available. This may cause Exim to hang for
28762 a substantial amount of time, causing timeouts on incoming connections.
28764 The solution is to generate the parameters externally to Exim. They are stored
28765 in &_gnutls-params-N_& in PEM format, which means that they can be
28766 generated externally using the &(certtool)& command that is part of GnuTLS.
28768 To replace the parameters with new ones, instead of deleting the file
28769 and letting Exim re-create it, you can generate new parameters using
28770 &(certtool)& and, when this has been done, replace Exim's cache file by
28771 renaming. The relevant commands are something like this:
28774 [ look for file; assume gnutls-params-2236 is the most recent ]
28777 # chown exim:exim new-params
28778 # chmod 0600 new-params
28779 # certtool --generate-dh-params --bits 2236 >>new-params
28780 # openssl dhparam -noout -text -in new-params | head
28781 [ check the first line, make sure it's not more than 2236;
28782 if it is, then go back to the start ("rm") and repeat
28783 until the size generated is at most the size requested ]
28784 # chmod 0400 new-params
28785 # mv new-params gnutls-params-2236
28787 If Exim never has to generate the parameters itself, the possibility of
28788 stalling is removed.
28790 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
28791 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
28792 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
28793 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
28794 and Exim does so. This attempt to remove Exim from TLS policy decisions
28795 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
28796 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
28797 which applies to all D-H usage, client or server. If the value returned by
28798 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
28799 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
28800 limit, which is still much higher than Exim historically used.
28802 The filename and bits used will change as the GnuTLS maintainers change the
28803 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
28804 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
28805 2432 bits, while NSS is limited to 2236 bits.
28807 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
28808 increase the chance of the generated prime actually being within acceptable
28809 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
28810 procedure above. There is no sane procedure available to Exim to double-check
28811 the size of the generated prime, so it might still be too large.
28814 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
28815 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
28816 .oindex "&%tls_require_ciphers%&" "OpenSSL"
28817 There is a function in the OpenSSL library that can be passed a list of cipher
28818 suites before the cipher negotiation takes place. This specifies which ciphers
28819 are acceptable for TLS versions prior to 1.3.
28820 The list is colon separated and may contain names like
28821 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
28822 directly to this function call.
28823 Many systems will install the OpenSSL manual-pages, so you may have
28824 &'ciphers(1)'& available to you.
28825 The following quotation from the OpenSSL
28826 documentation specifies what forms of item are allowed in the cipher string:
28829 It can consist of a single cipher suite such as RC4-SHA.
28831 It can represent a list of cipher suites containing a certain algorithm,
28832 or cipher suites of a certain type. For example SHA1 represents all
28833 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
28836 Lists of cipher suites can be combined in a single cipher string using
28837 the + character. This is used as a logical and operation. For example
28838 SHA1+DES represents all cipher suites containing the SHA1 and the DES
28842 Each cipher string can be optionally preceded by one of the characters &`!`&,
28845 If &`!`& is used, the ciphers are permanently deleted from the list. The
28846 ciphers deleted can never reappear in the list even if they are explicitly
28849 If &`-`& is used, the ciphers are deleted from the list, but some or all
28850 of the ciphers can be added again by later options.
28852 If &`+`& is used, the ciphers are moved to the end of the list. This
28853 option does not add any new ciphers; it just moves matching existing ones.
28856 If none of these characters is present, the string is interpreted as
28857 a list of ciphers to be appended to the current preference list. If the list
28858 includes any ciphers already present they will be ignored: that is, they will
28859 not be moved to the end of the list.
28862 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
28865 # note single-quotes to get ! past any shell history expansion
28866 $ openssl ciphers 'HIGH:!MD5:!SHA1'
28869 This example will let the library defaults be permitted on the MX port, where
28870 there's probably no identity verification anyway, but ups the ante on the
28871 submission ports where the administrator might have some influence on the
28872 choice of clients used:
28874 # OpenSSL variant; see man ciphers(1)
28875 tls_require_ciphers = ${if =={$received_port}{25}\
28880 This example will prefer ECDSA-authenticated ciphers over RSA ones:
28882 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
28885 For TLS version 1.3 the control available is less fine-grained
28886 and Exim does not provide access to it at present.
28887 The value of the &%tls_require_ciphers%& option is ignored when
28888 TLS version 1.3 is negotiated.
28890 As of writing the library default cipher suite list for TLSv1.3 is
28892 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
28896 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
28898 .cindex "GnuTLS" "specifying parameters for"
28899 .cindex "TLS" "specifying ciphers (GnuTLS)"
28900 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
28901 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
28902 .cindex "TLS" "specifying protocols (GnuTLS)"
28903 .cindex "TLS" "specifying priority string (GnuTLS)"
28904 .oindex "&%tls_require_ciphers%&" "GnuTLS"
28905 The GnuTLS library allows the caller to provide a "priority string", documented
28906 as part of the &[gnutls_priority_init]& function. This is very similar to the
28907 ciphersuite specification in OpenSSL.
28909 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
28910 and controls both protocols and ciphers.
28912 The &%tls_require_ciphers%& option is available both as an global option,
28913 controlling how Exim behaves as a server, and also as an option of the
28914 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
28915 the value is string expanded. The resulting string is not an Exim list and
28916 the string is given to the GnuTLS library, so that Exim does not need to be
28917 aware of future feature enhancements of GnuTLS.
28919 Documentation of the strings accepted may be found in the GnuTLS manual, under
28920 "Priority strings". This is online as
28921 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
28922 but beware that this relates to GnuTLS 3, which may be newer than the version
28923 installed on your system. If you are using GnuTLS 3,
28924 then the example code
28925 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
28926 on that site can be used to test a given string.
28930 # Disable older versions of protocols
28931 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
28934 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
28935 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
28936 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
28938 This example will let the library defaults be permitted on the MX port, where
28939 there's probably no identity verification anyway, and lowers security further
28940 by increasing compatibility; but this ups the ante on the submission ports
28941 where the administrator might have some influence on the choice of clients
28945 tls_require_ciphers = ${if =={$received_port}{25}\
28951 .section "Configuring an Exim server to use TLS" "SECID182"
28952 .cindex "TLS" "configuring an Exim server"
28953 .cindex "ESMTP extensions" STARTTLS
28954 When Exim has been built with TLS support, it advertises the availability of
28955 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
28956 but not to any others. The default value of this option is *, which means
28957 that STARTTLS is always advertised. Set it to blank to never advertise;
28958 this is reasonable for systems that want to use TLS only as a client.
28960 If STARTTLS is to be used you
28961 need to set some other options in order to make TLS available.
28963 If a client issues a STARTTLS command and there is some configuration
28964 problem in the server, the command is rejected with a 454 error. If the client
28965 persists in trying to issue SMTP commands, all except QUIT are rejected
28968 554 Security failure
28970 If a STARTTLS command is issued within an existing TLS session, it is
28971 rejected with a 554 error code.
28973 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
28974 must be set to match some hosts. The default is * which matches all hosts.
28976 If this is all you do, TLS encryption will be enabled but not authentication -
28977 meaning that the peer has no assurance it is actually you he is talking to.
28978 You gain protection from a passive sniffer listening on the wire but not
28979 from someone able to intercept the communication.
28981 Further protection requires some further configuration at the server end.
28983 To make TLS work you need to set, in the server,
28985 tls_certificate = /some/file/name
28986 tls_privatekey = /some/file/name
28988 These options are, in fact, expanded strings, so you can make them depend on
28989 the identity of the client that is connected if you wish. The first file
28990 contains the server's X509 certificate, and the second contains the private key
28991 that goes with it. These files need to be
28992 PEM format and readable by the Exim user, and must
28993 always be given as full path names.
28994 The key must not be password-protected.
28995 They can be the same file if both the
28996 certificate and the key are contained within it. If &%tls_privatekey%& is not
28997 set, or if its expansion is forced to fail or results in an empty string, this
28998 is assumed to be the case. The certificate file may also contain intermediate
28999 certificates that need to be sent to the client to enable it to authenticate
29000 the server's certificate.
29002 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29003 colon-separated lists of file paths. Ciphers using given authentication
29004 algorithms require the presence of a suitable certificate to supply the
29005 public-key. The server selects among the certificates to present to the
29006 client depending on the selected cipher, hence the priority ordering for
29007 ciphers will affect which certificate is used.
29009 If you do not understand about certificates and keys, please try to find a
29010 source of this background information, which is not Exim-specific. (There are a
29011 few comments below in section &<<SECTcerandall>>&.)
29013 &*Note*&: These options do not apply when Exim is operating as a client &--
29014 they apply only in the case of a server. If you need to use a certificate in an
29015 Exim client, you must set the options of the same names in an &(smtp)&
29018 With just these options, an Exim server will be able to use TLS. It does not
29019 require the client to have a certificate (but see below for how to insist on
29020 this). There is one other option that may be needed in other situations. If
29022 tls_dhparam = /some/file/name
29024 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29025 with the parameters contained in the file.
29026 Set this to &`none`& to disable use of DH entirely, by making no prime
29031 This may also be set to a string identifying a standard prime to be used for
29032 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29033 used is &`ike23`&. There are a few standard primes available, see the
29034 documentation for &%tls_dhparam%& for the complete list.
29040 for a way of generating file data.
29042 The strings supplied for these three options are expanded every time a client
29043 host connects. It is therefore possible to use different certificates and keys
29044 for different hosts, if you so wish, by making use of the client's IP address
29045 in &$sender_host_address$& to control the expansion. If a string expansion is
29046 forced to fail, Exim behaves as if the option is not set.
29048 .cindex "cipher" "logging"
29049 .cindex "log" "TLS cipher"
29050 .vindex "&$tls_in_cipher$&"
29051 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29052 an incoming TLS connection. It is included in the &'Received:'& header of an
29053 incoming message (by default &-- you can, of course, change this), and it is
29054 also included in the log line that records a message's arrival, keyed by
29055 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29056 condition can be used to test for specific cipher suites in ACLs.
29058 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29059 can check the name of the cipher suite and vary their actions accordingly. The
29060 cipher suite names vary, depending on which TLS library is being used. For
29061 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29062 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29063 documentation for more details.
29065 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29066 (again depending on the &%tls_cipher%& log selector).
29069 .section "Requesting and verifying client certificates" "SECID183"
29070 .cindex "certificate" "verification of client"
29071 .cindex "TLS" "client certificate verification"
29072 If you want an Exim server to request a certificate when negotiating a TLS
29073 session with a client, you must set either &%tls_verify_hosts%& or
29074 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29075 apply to all TLS connections. For any host that matches one of these options,
29076 Exim requests a certificate as part of the setup of the TLS session. The
29077 contents of the certificate are verified by comparing it with a list of
29078 expected trust-anchors or certificates.
29079 These may be the system default set (depending on library version),
29080 an explicit file or,
29081 depending on library version, a directory, identified by
29082 &%tls_verify_certificates%&.
29084 A file can contain multiple certificates, concatenated end to end. If a
29087 each certificate must be in a separate file, with a name (or a symbolic link)
29088 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29089 certificate. You can compute the relevant hash by running the command
29091 openssl x509 -hash -noout -in /cert/file
29093 where &_/cert/file_& contains a single certificate.
29095 There is no checking of names of the client against the certificate
29096 Subject Name or Subject Alternate Names.
29098 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29099 what happens if the client does not supply a certificate, or if the certificate
29100 does not match any of the certificates in the collection named by
29101 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29102 attempt to set up a TLS session is aborted, and the incoming connection is
29103 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29104 session continues. ACLs that run for subsequent SMTP commands can detect the
29105 fact that no certificate was verified, and vary their actions accordingly. For
29106 example, you can insist on a certificate before accepting a message for
29107 relaying, but not when the message is destined for local delivery.
29109 .vindex "&$tls_in_peerdn$&"
29110 When a client supplies a certificate (whether it verifies or not), the value of
29111 the Distinguished Name of the certificate is made available in the variable
29112 &$tls_in_peerdn$& during subsequent processing of the message.
29114 .cindex "log" "distinguished name"
29115 Because it is often a long text string, it is not included in the log line or
29116 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29117 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29118 &%received_header_text%& to change the &'Received:'& header. When no
29119 certificate is supplied, &$tls_in_peerdn$& is empty.
29122 .section "Revoked certificates" "SECID184"
29123 .cindex "TLS" "revoked certificates"
29124 .cindex "revocation list"
29125 .cindex "certificate" "revocation list"
29126 .cindex "OCSP" "stapling"
29127 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29128 certificates are revoked. If you have such a list, you can pass it to an Exim
29129 server using the global option called &%tls_crl%& and to an Exim client using
29130 an identically named option for the &(smtp)& transport. In each case, the value
29131 of the option is expanded and must then be the name of a file that contains a
29133 The downside is that clients have to periodically re-download a potentially huge
29134 file from every certificate authority they know of.
29136 The way with most moving parts at query time is Online Certificate
29137 Status Protocol (OCSP), where the client verifies the certificate
29138 against an OCSP server run by the CA. This lets the CA track all
29139 usage of the certs. It requires running software with access to the
29140 private key of the CA, to sign the responses to the OCSP queries. OCSP
29141 is based on HTTP and can be proxied accordingly.
29143 The only widespread OCSP server implementation (known to this writer)
29144 comes as part of OpenSSL and aborts on an invalid request, such as
29145 connecting to the port and then disconnecting. This requires
29146 re-entering the passphrase each time some random client does this.
29148 The third way is OCSP Stapling; in this, the server using a certificate
29149 issued by the CA periodically requests an OCSP proof of validity from
29150 the OCSP server, then serves it up inline as part of the TLS
29151 negotiation. This approach adds no extra round trips, does not let the
29152 CA track users, scales well with number of certs issued by the CA and is
29153 resilient to temporary OCSP server failures, as long as the server
29154 starts retrying to fetch an OCSP proof some time before its current
29155 proof expires. The downside is that it requires server support.
29157 Unless Exim is built with the support disabled,
29158 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29159 support for OCSP stapling is included.
29161 There is a global option called &%tls_ocsp_file%&.
29162 The file specified therein is expected to be in DER format, and contain
29163 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29164 option will be re-expanded for SNI, if the &%tls_certificate%& option
29165 contains &`tls_in_sni`&, as per other TLS options.
29167 Exim does not at this time implement any support for fetching a new OCSP
29168 proof. The burden is on the administrator to handle this, outside of
29169 Exim. The file specified should be replaced atomically, so that the
29170 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29171 on each connection, so a new file will be handled transparently on the
29174 When built with OpenSSL Exim will check for a valid next update timestamp
29175 in the OCSP proof; if not present, or if the proof has expired, it will be
29178 For the client to be able to verify the stapled OCSP the server must
29179 also supply, in its stapled information, any intermediate
29180 certificates for the chain leading to the OCSP proof from the signer
29181 of the server certificate. There may be zero or one such. These
29182 intermediate certificates should be added to the server OCSP stapling
29183 file named by &%tls_ocsp_file%&.
29185 Note that the proof only covers the terminal server certificate,
29186 not any of the chain from CA to it.
29188 There is no current way to staple a proof for a client certificate.
29191 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29192 OCSP server is supplied. The server URL may be included in the
29193 server certificate, if the CA is helpful.
29195 One failure mode seen was the OCSP Signer cert expiring before the end
29196 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29197 noted this as invalid overall, but the re-fetch script did not.
29203 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29204 .cindex "cipher" "logging"
29205 .cindex "log" "TLS cipher"
29206 .cindex "log" "distinguished name"
29207 .cindex "TLS" "configuring an Exim client"
29208 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29209 deliveries as well as to incoming, the latter one causing logging of the
29210 server certificate's DN. The remaining client configuration for TLS is all
29211 within the &(smtp)& transport.
29213 .cindex "ESMTP extensions" STARTTLS
29214 It is not necessary to set any options to have TLS work in the &(smtp)&
29215 transport. If Exim is built with TLS support, and TLS is advertised by a
29216 server, the &(smtp)& transport always tries to start a TLS session. However,
29217 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29218 transport) to a list of server hosts for which TLS should not be used.
29220 If you do not want Exim to attempt to send messages unencrypted when an attempt
29221 to set up an encrypted connection fails in any way, you can set
29222 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29223 those hosts, delivery is always deferred if an encrypted connection cannot be
29224 set up. If there are any other hosts for the address, they are tried in the
29227 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29228 the message unencrypted. It always does this if the response to STARTTLS is
29229 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29230 session after a success response code, what happens is controlled by the
29231 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29232 delivery to this host is deferred, and other hosts (if available) are tried. If
29233 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29234 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29235 negotiation fails, Exim closes the current connection (because it is in an
29236 unknown state), opens a new one to the same host, and then tries the delivery
29239 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29240 transport provide the client with a certificate, which is passed to the server
29241 if it requests it. If the server is Exim, it will request a certificate only if
29242 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29244 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29245 for client use (they are usable for server use).
29246 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29247 in failed connections.
29249 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29250 specifies a collection of expected server certificates.
29252 the system default set (depending on library version),
29254 or (depending on library version) a directory.
29255 The client verifies the server's certificate
29256 against this collection, taking into account any revoked certificates that are
29257 in the list defined by &%tls_crl%&.
29258 Failure to verify fails the TLS connection unless either of the
29259 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29261 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29262 certificate verification to the listed servers. Verification either must
29263 or need not succeed respectively.
29265 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29266 checks are made: that the host name (the one in the DNS A record)
29267 is valid for the certificate.
29268 The option defaults to always checking.
29270 The &(smtp)& transport has two OCSP-related options:
29271 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29272 is requested and required for the connection to proceed. The default
29274 &%hosts_request_ocsp%&; a host-list for which (additionally)
29275 a Certificate Status is requested (but not necessarily verified). The default
29276 value is "*" meaning that requests are made unless configured
29279 The host(s) should also be in &%hosts_require_tls%&, and
29280 &%tls_verify_certificates%& configured for the transport,
29281 for OCSP to be relevant.
29284 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29285 list of permitted cipher suites. If either of these checks fails, delivery to
29286 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29287 alternative hosts, if any.
29290 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29291 is operating as a client. Exim does not assume that a server certificate (set
29292 by the global options of the same name) should also be used when operating as a
29296 .vindex "&$host_address$&"
29297 All the TLS options in the &(smtp)& transport are expanded before use, with
29298 &$host$& and &$host_address$& containing the name and address of the server to
29299 which the client is connected. Forced failure of an expansion causes Exim to
29300 behave as if the relevant option were unset.
29302 .vindex &$tls_out_bits$&
29303 .vindex &$tls_out_cipher$&
29304 .vindex &$tls_out_peerdn$&
29305 .vindex &$tls_out_sni$&
29306 Before an SMTP connection is established, the
29307 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29308 variables are emptied. (Until the first connection, they contain the values
29309 that were set when the message was received.) If STARTTLS is subsequently
29310 successfully obeyed, these variables are set to the relevant values for the
29311 outgoing connection.
29315 .section "Use of TLS Server Name Indication" "SECTtlssni"
29316 .cindex "TLS" "Server Name Indication"
29317 .vindex "&$tls_in_sni$&"
29318 .oindex "&%tls_in_sni%&"
29319 With TLS1.0 or above, there is an extension mechanism by which extra
29320 information can be included at various points in the protocol. One of these
29321 extensions, documented in RFC 6066 (and before that RFC 4366) is
29322 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29323 client in the initial handshake, so that the server can examine the servername
29324 within and possibly choose to use different certificates and keys (and more)
29327 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29328 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29331 With SMTP to MX, there are the same problems here as in choosing the identity
29332 against which to validate a certificate: you can't rely on insecure DNS to
29333 provide the identity which you then cryptographically verify. So this will
29334 be of limited use in that environment.
29336 With SMTP to Submission, there is a well-defined hostname which clients are
29337 connecting to and can validate certificates against. Thus clients &*can*&
29338 choose to include this information in the TLS negotiation. If this becomes
29339 wide-spread, then hosters can choose to present different certificates to
29340 different clients. Or even negotiate different cipher suites.
29342 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29343 if not empty, will be sent on a TLS session as part of the handshake. There's
29344 nothing more to it. Choosing a sensible value not derived insecurely is the
29345 only point of caution. The &$tls_out_sni$& variable will be set to this string
29346 for the lifetime of the client connection (including during authentication).
29348 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29349 received from a client.
29350 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29352 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29353 option (prior to expansion) then the following options will be re-expanded
29354 during TLS session handshake, to permit alternative values to be chosen:
29357 &%tls_certificate%&
29363 &%tls_verify_certificates%&
29368 Great care should be taken to deal with matters of case, various injection
29369 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29370 can always be referenced; it is important to remember that &$tls_in_sni$& is
29371 arbitrary unverified data provided prior to authentication.
29372 Further, the initial certificate is loaded before SNI has arrived, so
29373 an expansion for &%tls_certificate%& must have a default which is used
29374 when &$tls_in_sni$& is empty.
29376 The Exim developers are proceeding cautiously and so far no other TLS options
29379 When Exim is built against OpenSSL, OpenSSL must have been built with support
29380 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29381 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29382 see &`-servername`& in the output, then OpenSSL has support.
29384 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29385 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29386 built, then you have SNI support).
29390 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29392 .cindex "multiple SMTP deliveries with TLS"
29393 .cindex "TLS" "multiple message deliveries"
29394 Exim sends multiple messages down the same TCP/IP connection by starting up
29395 an entirely new delivery process for each message, passing the socket from
29396 one process to the next. This implementation does not fit well with the use
29397 of TLS, because there is quite a lot of state information associated with a TLS
29398 connection, not just a socket identification. Passing all the state information
29399 to a new process is not feasible. Consequently, for sending using TLS Exim
29400 starts an additional proxy process for handling the encryption, piping the
29401 unencrypted data stream from and to the delivery processes.
29403 An older mode of operation can be enabled on a per-host basis by the
29404 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29405 this list the proxy process described above is not used; instead Exim
29406 shuts down an existing TLS session being run by the delivery process
29407 before passing the socket to a new process. The new process may then
29408 try to start a new TLS session, and if successful, may try to re-authenticate
29409 if AUTH is in use, before sending the next message.
29411 The RFC is not clear as to whether or not an SMTP session continues in clear
29412 after TLS has been shut down, or whether TLS may be restarted again later, as
29413 just described. However, if the server is Exim, this shutdown and
29414 reinitialization works. It is not known which (if any) other servers operate
29415 successfully if the client closes a TLS session and continues with unencrypted
29416 SMTP, but there are certainly some that do not work. For such servers, Exim
29417 should not pass the socket to another process, because the failure of the
29418 subsequent attempt to use it would cause Exim to record a temporary host error,
29419 and delay other deliveries to that host.
29421 To test for this case, Exim sends an EHLO command to the server after
29422 closing down the TLS session. If this fails in any way, the connection is
29423 closed instead of being passed to a new delivery process, but no retry
29424 information is recorded.
29426 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29427 &(smtp)& transport to match those hosts for which Exim should not pass
29428 connections to new processes if TLS has been used.
29433 .section "Certificates and all that" "SECTcerandall"
29434 .cindex "certificate" "references to discussion"
29435 In order to understand fully how TLS works, you need to know about
29436 certificates, certificate signing, and certificate authorities.
29437 This is a large topic and an introductory guide is unsuitable for the Exim
29438 reference manual, so instead we provide pointers to existing documentation.
29440 The Apache web-server was for a long time the canonical guide, so their
29441 documentation is a good place to start; their SSL module's Introduction
29442 document is currently at
29444 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29446 and their FAQ is at
29448 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29451 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29452 0-201-61598-3) in 2001, contains both introductory and more in-depth
29454 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29455 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29456 Ivan is the author of the popular TLS testing tools at
29457 &url(https://www.ssllabs.com/).
29460 .section "Certificate chains" "SECID186"
29461 The file named by &%tls_certificate%& may contain more than one
29462 certificate. This is useful in the case where the certificate that is being
29463 sent is validated by an intermediate certificate which the other end does
29464 not have. Multiple certificates must be in the correct order in the file.
29465 First the host's certificate itself, then the first intermediate
29466 certificate to validate the issuer of the host certificate, then the next
29467 intermediate certificate to validate the issuer of the first intermediate
29468 certificate, and so on, until finally (optionally) the root certificate.
29469 The root certificate must already be trusted by the recipient for
29470 validation to succeed, of course, but if it's not preinstalled, sending the
29471 root certificate along with the rest makes it available for the user to
29472 install if the receiving end is a client MUA that can interact with a user.
29474 Note that certificates using MD5 are unlikely to work on today's Internet;
29475 even if your libraries allow loading them for use in Exim when acting as a
29476 server, increasingly clients will not accept such certificates. The error
29477 diagnostics in such a case can be frustratingly vague.
29481 .section "Self-signed certificates" "SECID187"
29482 .cindex "certificate" "self-signed"
29483 You can create a self-signed certificate using the &'req'& command provided
29484 with OpenSSL, like this:
29485 . ==== Do not shorten the duration here without reading and considering
29486 . ==== the text below. Please leave it at 9999 days.
29488 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29491 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29492 delimited and so can be identified independently. The &%-days%& option
29493 specifies a period for which the certificate is valid. The &%-nodes%& option is
29494 important: if you do not set it, the key is encrypted with a passphrase
29495 that you are prompted for, and any use that is made of the key causes more
29496 prompting for the passphrase. This is not helpful if you are going to use
29497 this certificate and key in an MTA, where prompting is not possible.
29499 . ==== I expect to still be working 26 years from now. The less technical
29500 . ==== debt I create, in terms of storing up trouble for my later years, the
29501 . ==== happier I will be then. We really have reached the point where we
29502 . ==== should start, at the very least, provoking thought and making folks
29503 . ==== pause before proceeding, instead of leaving all the fixes until two
29504 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29506 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29507 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29508 the above command might produce a date in the past. Think carefully about
29509 the lifetime of the systems you're deploying, and either reduce the duration
29510 of the certificate or reconsider your platform deployment. (At time of
29511 writing, reducing the duration is the most likely choice, but the inexorable
29512 progression of time takes us steadily towards an era where this will not
29513 be a sensible resolution).
29515 A self-signed certificate made in this way is sufficient for testing, and
29516 may be adequate for all your requirements if you are mainly interested in
29517 encrypting transfers, and not in secure identification.
29519 However, many clients require that the certificate presented by the server be a
29520 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29521 certificate. In this situation, the self-signed certificate described above
29522 must be installed on the client host as a trusted root &'certification
29523 authority'& (CA), and the certificate used by Exim must be a user certificate
29524 signed with that self-signed certificate.
29526 For information on creating self-signed CA certificates and using them to sign
29527 user certificates, see the &'General implementation overview'& chapter of the
29528 Open-source PKI book, available online at
29529 &url(https://sourceforge.net/projects/ospkibook/).
29530 .ecindex IIDencsmtp1
29531 .ecindex IIDencsmtp2
29535 .section "TLS Resumption" "SECTresumption"
29536 .cindex TLS resumption
29537 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29538 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
29541 Session resumption (this is the "stateless" variant) involves the server sending
29542 a "session ticket" to the client on one connection, which can be stored by the
29543 client and used for a later session. The ticket contains sufficient state for
29544 the server to reconstruct the TLS session, avoiding some expensive crypto
29545 calculation and (on TLS1.2) one full packet roundtrip time.
29548 Operational cost/benefit:
29550 The extra data being transmitted costs a minor amount, and the client has
29551 extra costs in storing and retrieving the data.
29553 In the Exim/Gnutls implementation the extra cost on an initial connection
29554 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
29555 The saved cost on a subsequent connection is about 4ms; three or more
29556 connections become a net win. On longer network paths, two or more
29557 connections will have an average lower startup time thanks to the one
29558 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
29561 .cindex "hints database" tls
29562 Since a new hints DB is used on the TLS client,
29563 the hints DB maintenance should be updated to additionally handle "tls".
29568 The session ticket is encrypted, but is obviously an additional security
29569 vulnarability surface. An attacker able to decrypt it would have access
29570 all connections using the resumed session.
29571 The session ticket encryption key is not committed to storage by the server
29572 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
29573 overlap; GnuTLS 6hr but does not specify any overlap).
29574 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
29575 OpenSSL. GnuTLS 2hr, appears to not do overlap).
29577 There is a question-mark over the security of the Diffie-Helman parameters
29578 used for session negotiation.
29583 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
29586 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
29587 have bits 0-4 indicating respectively
29588 support built, client requested ticket, client offered session,
29589 server issued ticket, resume used. A suitable decode list is provided
29590 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
29595 The &%tls_resumption_hosts%& main option specifies a hostlist for which
29596 exim, operating as a server, will offer resumption to clients.
29597 Current best practice is to not offer the feature to MUA connection.
29598 Commonly this can be done like this:
29600 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
29602 If the peer host matches the list after expansion then resumption
29603 is offered and/or accepted.
29605 The &%tls_resumption_hosts%& smtp transport option performs the
29606 equivalent function for operation as a client.
29607 If the peer host matches the list after expansion then resumption
29608 is attempted (if a stored session is available) or the information
29609 stored (if supplied by the peer).
29615 In a resumed session:
29617 The variables &$tls_{in,out}_cipher$& will have values different
29618 to the original (under GnuTLS).
29620 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
29621 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
29622 . XXX need to do something with that hosts_require_ocsp
29629 .section DANE "SECDANE"
29631 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
29632 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
29633 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
29634 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
29635 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
29636 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
29638 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
29639 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
29640 by (a) is thought to be smaller than that of the set of root CAs.
29642 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
29643 fail to pass on a server's STARTTLS.
29645 DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
29646 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
29647 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
29649 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
29650 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
29651 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
29653 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
29654 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
29656 There are no changes to Exim specific to server-side operation of DANE.
29657 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
29658 in &_Local/Makefile_&.
29659 If it has been included, the macro "_HAVE_DANE" will be defined.
29661 A TLSA record consist of 4 fields, the "Certificate Usage", the
29662 "Selector", the "Matching type", and the "Certificate Association Data".
29663 For a detailed description of the TLSA record see
29664 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
29666 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
29667 These are the "Trust Anchor" and "End Entity" variants.
29668 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
29669 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
29670 this is appropriate for a single system, using a self-signed certificate.
29671 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
29673 A private CA at simplest is just a self-signed certificate (with certain
29674 attributes) which is used to sign server certificates, but running one securely
29675 does require careful arrangement.
29676 With DANE-TA, as implemented in Exim and commonly in other MTAs,
29677 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
29678 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
29679 all of which point to a single TLSA record.
29680 DANE-TA and DANE-EE can both be used together.
29682 Our recommendation is to use DANE with a certificate from a public CA,
29683 because this enables a variety of strategies for remote clients to verify
29685 You can then publish information both via DANE and another technology,
29686 "MTA-STS", described below.
29688 When you use DANE-TA to publish trust anchor information, you ask entities
29689 outside your administrative control to trust the Certificate Authority for
29690 connections to you.
29691 If using a private CA then you should expect others to still apply the
29692 technical criteria they'd use for a public CA to your certificates.
29693 In particular, you should probably try to follow current best practices for CA
29694 operation around hash algorithms and key sizes.
29695 Do not expect other organizations to lower their security expectations just
29696 because a particular profile might be reasonable for your own internal use.
29698 When this text was last updated, this in practice means to avoid use of SHA-1
29699 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
29700 than 4096, for interoperability); to use keyUsage fields correctly; to use
29701 random serial numbers.
29702 The list of requirements is subject to change as best practices evolve.
29703 If you're not already using a private CA, or it doesn't meet these
29704 requirements, then we encourage you to avoid all these issues and use a public
29705 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
29707 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
29708 a "Matching Type" (3rd) field of SHA2-512(2).
29710 For the "Certificate Authority Data" (4th) field, commands like
29713 openssl x509 -pubkey -noout <certificate.pem \
29714 | openssl rsa -outform der -pubin 2>/dev/null \
29719 are workable to create a hash of the certificate's public key.
29721 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
29724 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
29727 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
29728 is useful for quickly generating TLSA records.
29731 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
29733 The Certificate issued by the CA published in the DANE-TA model should be
29734 issued using a strong hash algorithm.
29735 Exim, and importantly various other MTAs sending to you, will not
29736 re-enable hash algorithms which have been disabled by default in TLS
29738 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
29739 interoperability (and probably the maximum too, in 2018).
29741 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
29742 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
29743 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
29746 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
29747 {= {4}{$tls_out_tlsa_usage}} } \
29751 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
29752 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
29753 found. If the definition of &%hosts_request_ocsp%& includes the
29754 string "tls_out_tlsa_usage", they are re-expanded in time to
29755 control the OCSP request.
29757 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
29758 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
29761 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
29762 and &%dane_require_tls_ciphers%&.
29763 The &"require"& variant will result in failure if the target host is not
29764 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
29765 the &%dnssec_request_domains%& router or transport option.
29767 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
29769 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
29770 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
29771 will be required for the host. If it does not, the host will not
29772 be used; there is no fallback to non-DANE or non-TLS.
29774 If DANE is requested and usable, then the TLS cipher list configuration
29775 prefers to use the option &%dane_require_tls_ciphers%& and falls
29776 back to &%tls_require_ciphers%& only if that is unset.
29777 This lets you configure "decent crypto" for DANE and "better than nothing
29778 crypto" as the default. Note though that while GnuTLS lets the string control
29779 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
29780 limited to ciphersuite constraints.
29782 If DANE is requested and useable (see above) the following transport options are ignored:
29786 tls_try_verify_hosts
29787 tls_verify_certificates
29789 tls_verify_cert_hostnames
29792 If DANE is not usable, whether requested or not, and CA-anchored
29793 verification evaluation is wanted, the above variables should be set appropriately.
29795 The router and transport option &%dnssec_request_domains%& must not be
29796 set to &"never"&, and &%dnssec_require_domains%& is ignored.
29798 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
29800 There is a new variable &$tls_out_dane$& which will have "yes" if
29801 verification succeeded using DANE and "no" otherwise (only useful
29802 in combination with events; see &<<CHAPevents>>&),
29803 and a new variable &$tls_out_tlsa_usage$& (detailed above).
29805 .cindex DANE reporting
29806 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
29807 to achieve DANE-verified connection, if one was either requested and offered, or
29808 required. This is intended to support TLS-reporting as defined in
29809 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
29810 The &$event_data$& will be one of the Result Types defined in
29811 Section 4.3 of that document.
29813 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
29815 DANE is specified in published RFCs and decouples certificate authority trust
29816 selection from a "race to the bottom" of "you must trust everything for mail
29817 to get through". There is an alternative technology called MTA-STS, which
29818 instead publishes MX trust anchor information on an HTTPS website. At the
29819 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
29820 Exim has no support for MTA-STS as a client, but Exim mail server operators
29821 can choose to publish information describing their TLS configuration using
29822 MTA-STS to let those clients who do use that protocol derive trust
29825 The MTA-STS design requires a certificate from a public Certificate Authority
29826 which is recognized by clients sending to you.
29827 That selection of which CAs are trusted by others is outside your control.
29829 The most interoperable course of action is probably to use
29830 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
29831 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
29832 records for DANE clients (such as Exim and Postfix) and to publish anchor
29833 information for MTA-STS as well. This is what is done for the &'exim.org'&
29834 domain itself (with caveats around occasionally broken MTA-STS because of
29835 incompatible specification changes prior to reaching RFC status).
29839 . ////////////////////////////////////////////////////////////////////////////
29840 . ////////////////////////////////////////////////////////////////////////////
29842 .chapter "Access control lists" "CHAPACL"
29843 .scindex IIDacl "&ACL;" "description"
29844 .cindex "control of incoming mail"
29845 .cindex "message" "controlling incoming"
29846 .cindex "policy control" "access control lists"
29847 Access Control Lists (ACLs) are defined in a separate section of the runtime
29848 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
29849 name, terminated by a colon. Here is a complete ACL section that contains just
29850 one very small ACL:
29854 accept hosts = one.host.only
29856 You can have as many lists as you like in the ACL section, and the order in
29857 which they appear does not matter. The lists are self-terminating.
29859 The majority of ACLs are used to control Exim's behaviour when it receives
29860 certain SMTP commands. This applies both to incoming TCP/IP connections, and
29861 when a local process submits a message using SMTP by specifying the &%-bs%&
29862 option. The most common use is for controlling which recipients are accepted
29863 in incoming messages. In addition, you can define an ACL that is used to check
29864 local non-SMTP messages. The default configuration file contains an example of
29865 a realistic ACL for checking RCPT commands. This is discussed in chapter
29866 &<<CHAPdefconfil>>&.
29869 .section "Testing ACLs" "SECID188"
29870 The &%-bh%& command line option provides a way of testing your ACL
29871 configuration locally by running a fake SMTP session with which you interact.
29874 .section "Specifying when ACLs are used" "SECID189"
29875 .cindex "&ACL;" "options for specifying"
29876 In order to cause an ACL to be used, you have to name it in one of the relevant
29877 options in the main part of the configuration. These options are:
29878 .cindex "AUTH" "ACL for"
29879 .cindex "DATA" "ACLs for"
29880 .cindex "ETRN" "ACL for"
29881 .cindex "EXPN" "ACL for"
29882 .cindex "HELO" "ACL for"
29883 .cindex "EHLO" "ACL for"
29884 .cindex "DKIM" "ACL for"
29885 .cindex "MAIL" "ACL for"
29886 .cindex "QUIT, ACL for"
29887 .cindex "RCPT" "ACL for"
29888 .cindex "STARTTLS, ACL for"
29889 .cindex "VRFY" "ACL for"
29890 .cindex "SMTP" "connection, ACL for"
29891 .cindex "non-SMTP messages" "ACLs for"
29892 .cindex "MIME content scanning" "ACL for"
29893 .cindex "PRDR" "ACL for"
29896 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
29897 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
29898 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
29899 .irow &%acl_smtp_auth%& "ACL for AUTH"
29900 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
29901 .irow &%acl_smtp_data%& "ACL after DATA is complete"
29902 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
29903 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
29904 .irow &%acl_smtp_etrn%& "ACL for ETRN"
29905 .irow &%acl_smtp_expn%& "ACL for EXPN"
29906 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
29907 .irow &%acl_smtp_mail%& "ACL for MAIL"
29908 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
29909 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
29910 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
29911 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
29912 .irow &%acl_smtp_quit%& "ACL for QUIT"
29913 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
29914 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
29915 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
29918 For example, if you set
29920 acl_smtp_rcpt = small_acl
29922 the little ACL defined above is used whenever Exim receives a RCPT command
29923 in an SMTP dialogue. The majority of policy tests on incoming messages can be
29924 done when RCPT commands arrive. A rejection of RCPT should cause the
29925 sending MTA to give up on the recipient address contained in the RCPT
29926 command, whereas rejection at other times may cause the client MTA to keep on
29927 trying to deliver the message. It is therefore recommended that you do as much
29928 testing as possible at RCPT time.
29931 .section "The non-SMTP ACLs" "SECID190"
29932 .cindex "non-SMTP messages" "ACLs for"
29933 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
29934 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
29935 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
29936 the state of the SMTP connection such as encryption and authentication) are not
29937 relevant and are forbidden in these ACLs. However, the sender and recipients
29938 are known, so the &%senders%& and &%sender_domains%& conditions and the
29939 &$sender_address$& and &$recipients$& variables can be used. Variables such as
29940 &$authenticated_sender$& are also available. You can specify added header lines
29941 in any of these ACLs.
29943 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
29944 non-SMTP message, before any of the message has been read. (This is the
29945 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
29946 batched SMTP input, it runs after the DATA command has been reached. The
29947 result of this ACL is ignored; it cannot be used to reject a message. If you
29948 really need to, you could set a value in an ACL variable here and reject based
29949 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
29950 controls, and in particular, it can be used to set
29952 control = suppress_local_fixups
29954 This cannot be used in the other non-SMTP ACLs because by the time they are
29955 run, it is too late.
29957 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
29958 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
29960 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
29961 kind of rejection is treated as permanent, because there is no way of sending a
29962 temporary error for these kinds of message.
29965 .section "The SMTP connect ACL" "SECID191"
29966 .cindex "SMTP" "connection, ACL for"
29967 .oindex &%smtp_banner%&
29968 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
29969 session, after the test specified by &%host_reject_connection%& (which is now
29970 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
29971 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
29972 the message override the banner message that is otherwise specified by the
29973 &%smtp_banner%& option.
29976 .section "The EHLO/HELO ACL" "SECID192"
29977 .cindex "EHLO" "ACL for"
29978 .cindex "HELO" "ACL for"
29979 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
29980 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
29981 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
29982 Note that a client may issue more than one EHLO or HELO command in an SMTP
29983 session, and indeed is required to issue a new EHLO or HELO after successfully
29984 setting up encryption following a STARTTLS command.
29986 Note also that a deny neither forces the client to go away nor means that
29987 mail will be refused on the connection. Consider checking for
29988 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
29990 If the command is accepted by an &%accept%& verb that has a &%message%&
29991 modifier, the message may not contain more than one line (it will be truncated
29992 at the first newline and a panic logged if it does). Such a message cannot
29993 affect the EHLO options that are listed on the second and subsequent lines of
29997 .section "The DATA ACLs" "SECID193"
29998 .cindex "DATA" "ACLs for"
29999 Two ACLs are associated with the DATA command, because it is two-stage
30000 command, with two responses being sent to the client.
30001 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30002 is obeyed. This gives you control after all the RCPT commands, but before
30003 the message itself is received. It offers the opportunity to give a negative
30004 response to the DATA command before the data is transmitted. Header lines
30005 added by MAIL or RCPT ACLs are not visible at this time, but any that
30006 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30008 You cannot test the contents of the message, for example, to verify addresses
30009 in the headers, at RCPT time or when the DATA command is received. Such
30010 tests have to appear in the ACL that is run after the message itself has been
30011 received, before the final response to the DATA command is sent. This is
30012 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30013 associated with the DATA command.
30015 .cindex CHUNKING "BDAT command"
30016 .cindex BDAT "SMTP command"
30017 .cindex "RFC 3030" CHUNKING
30018 If CHUNKING was advertised and a BDAT command sequence is received,
30019 the &%acl_smtp_predata%& ACL is not run.
30020 . XXX why not? It should be possible, for the first BDAT.
30021 The &%acl_smtp_data%& is run after the last BDAT command and all of
30022 the data specified is received.
30024 For both of these ACLs, it is not possible to reject individual recipients. An
30025 error response rejects the entire message. Unfortunately, it is known that some
30026 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30027 before or after the data) correctly &-- they keep the message on their queues
30028 and try again later, but that is their problem, though it does waste some of
30031 The &%acl_smtp_data%& ACL is run after
30032 the &%acl_smtp_data_prdr%&,
30033 the &%acl_smtp_dkim%&
30034 and the &%acl_smtp_mime%& ACLs.
30036 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30037 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30038 enabled (which is the default).
30040 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30041 received, and is executed for each DKIM signature found in a message. If not
30042 otherwise specified, the default action is to accept.
30044 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30046 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30049 .section "The SMTP MIME ACL" "SECID194"
30050 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30051 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30053 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30056 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30057 .cindex "PRDR" "ACL for"
30058 .oindex "&%prdr_enable%&"
30059 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30060 with PRDR support enabled (which is the default).
30061 It becomes active only when the PRDR feature is negotiated between
30062 client and server for a message, and more than one recipient
30065 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30066 has been received, and is executed once for each recipient of the message
30067 with &$local_part$& and &$domain$& valid.
30068 The test may accept, defer or deny for individual recipients.
30069 The &%acl_smtp_data%& will still be called after this ACL and
30070 can reject the message overall, even if this ACL has accepted it
30071 for some or all recipients.
30073 PRDR may be used to support per-user content filtering. Without it
30074 one must defer any recipient after the first that has a different
30075 content-filter configuration. With PRDR, the RCPT-time check
30076 .cindex "PRDR" "variable for"
30077 for this can be disabled when the variable &$prdr_requested$&
30079 Any required difference in behaviour of the main DATA-time
30080 ACL should however depend on the PRDR-time ACL having run, as Exim
30081 will avoid doing so in some situations (e.g. single-recipient mails).
30083 See also the &%prdr_enable%& global option
30084 and the &%hosts_try_prdr%& smtp transport option.
30086 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30087 If the ACL is not defined, processing completes as if
30088 the feature was not requested by the client.
30090 .section "The QUIT ACL" "SECTQUITACL"
30091 .cindex "QUIT, ACL for"
30092 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30093 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30094 does not in fact control any access.
30095 For this reason, it may only accept
30096 or warn as its final result.
30098 This ACL can be used for tasks such as custom logging at the end of an SMTP
30099 session. For example, you can use ACL variables in other ACLs to count
30100 messages, recipients, etc., and log the totals at QUIT time using one or
30101 more &%logwrite%& modifiers on a &%warn%& verb.
30103 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30104 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30106 You do not need to have a final &%accept%&, but if you do, you can use a
30107 &%message%& modifier to specify custom text that is sent as part of the 221
30110 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30111 failure (for example, failure to open a log file, or when Exim is bombing out
30112 because it has detected an unrecoverable error), all SMTP commands from the
30113 client are given temporary error responses until QUIT is received or the
30114 connection is closed. In these special cases, the QUIT ACL does not run.
30117 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30118 .vindex &$acl_smtp_notquit$&
30119 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30120 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30121 trouble, such as being unable to write to its log files, this ACL is not run,
30122 because it might try to do things (such as write to log files) that make the
30123 situation even worse.
30125 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30126 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30127 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30130 .vindex &$smtp_notquit_reason$&
30131 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30132 to a string that indicates the reason for the termination of the SMTP
30133 connection. The possible values are:
30135 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30136 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30137 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30138 .irow &`connection-lost`& "The SMTP connection has been lost"
30139 .irow &`data-timeout`& "Timeout while reading message data"
30140 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30141 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30142 .irow &`signal-exit`& "SIGTERM or SIGINT"
30143 .irow &`synchronization-error`& "SMTP synchronization error"
30144 .irow &`tls-failed`& "TLS failed to start"
30146 In most cases when an SMTP connection is closed without having received QUIT,
30147 Exim sends an SMTP response message before actually closing the connection.
30148 With the exception of the &`acl-drop`& case, the default message can be
30149 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30150 &%drop%& verb in another ACL, it is the message from the other ACL that is
30154 .section "Finding an ACL to use" "SECID195"
30155 .cindex "&ACL;" "finding which to use"
30156 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30157 you can use different ACLs in different circumstances. For example,
30159 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30160 {acl_check_rcpt} {acl_check_rcpt_submit} }
30162 In the default configuration file there are some example settings for
30163 providing an RFC 4409 message &"submission"& service on port 587 and
30164 an RFC 8314 &"submissions"& service on port 465. You can use a string
30165 expansion like this to choose an ACL for MUAs on these ports which is
30166 more appropriate for this purpose than the default ACL on port 25.
30168 The expanded string does not have to be the name of an ACL in the
30169 configuration file; there are other possibilities. Having expanded the
30170 string, Exim searches for an ACL as follows:
30173 If the string begins with a slash, Exim uses it as a filename, and reads its
30174 contents as an ACL. The lines are processed in the same way as lines in the
30175 Exim configuration file. In particular, continuation lines are supported, blank
30176 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30177 If the file does not exist or cannot be read, an error occurs (typically
30178 causing a temporary failure of whatever caused the ACL to be run). For example:
30180 acl_smtp_data = /etc/acls/\
30181 ${lookup{$sender_host_address}lsearch\
30182 {/etc/acllist}{$value}{default}}
30184 This looks up an ACL file to use on the basis of the host's IP address, falling
30185 back to a default if the lookup fails. If an ACL is successfully read from a
30186 file, it is retained in memory for the duration of the Exim process, so that it
30187 can be re-used without having to re-read the file.
30189 If the string does not start with a slash, and does not contain any spaces,
30190 Exim searches the ACL section of the configuration for an ACL whose name
30191 matches the string.
30193 If no named ACL is found, or if the string contains spaces, Exim parses
30194 the string as an inline ACL. This can save typing in cases where you just
30195 want to have something like
30197 acl_smtp_vrfy = accept
30199 in order to allow free use of the VRFY command. Such a string may contain
30200 newlines; it is processed in the same way as an ACL that is read from a file.
30206 .section "ACL return codes" "SECID196"
30207 .cindex "&ACL;" "return codes"
30208 Except for the QUIT ACL, which does not affect the SMTP return code (see
30209 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30210 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30211 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30212 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30213 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30214 This also causes a 4&'xx'& return code.
30216 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30217 &"deny"&, because there is no mechanism for passing temporary errors to the
30218 submitters of non-SMTP messages.
30221 ACLs that are relevant to message reception may also return &"discard"&. This
30222 has the effect of &"accept"&, but causes either the entire message or an
30223 individual recipient address to be discarded. In other words, it is a
30224 blackholing facility. Use it with care.
30226 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30227 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30228 RCPT ACL is to discard just the one recipient address. If there are no
30229 recipients left when the message's data is received, the DATA ACL is not
30230 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30231 remaining recipients. The &"discard"& return is not permitted for the
30232 &%acl_smtp_predata%& ACL.
30234 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30235 is done on the address and the result determines the SMTP response.
30238 .cindex "&[local_scan()]& function" "when all recipients discarded"
30239 The &[local_scan()]& function is always run, even if there are no remaining
30240 recipients; it may create new recipients.
30244 .section "Unset ACL options" "SECID197"
30245 .cindex "&ACL;" "unset options"
30246 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30247 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30248 not defined at all. For any defined ACL, the default action when control
30249 reaches the end of the ACL statements is &"deny"&.
30251 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30252 these two are ACLs that are used only for their side effects. They cannot be
30253 used to accept or reject anything.
30255 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30256 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30257 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30258 when the ACL is not defined is &"accept"&.
30260 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30261 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30262 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30263 messages over an SMTP connection. For an example, see the ACL in the default
30264 configuration file.
30269 .section "Data for message ACLs" "SECID198"
30270 .cindex "&ACL;" "data for message ACL"
30272 .vindex &$local_part$&
30273 .vindex &$sender_address$&
30274 .vindex &$sender_host_address$&
30275 .vindex &$smtp_command$&
30276 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30277 that contain information about the host and the message's sender (for example,
30278 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30279 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30280 &$local_part$& are set from the argument address. The entire SMTP command
30281 is available in &$smtp_command$&.
30283 When an ACL for the AUTH parameter of MAIL is running, the variables that
30284 contain information about the host are set, but &$sender_address$& is not yet
30285 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30288 .vindex "&$message_size$&"
30289 The &$message_size$& variable is set to the value of the SIZE parameter on
30290 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30291 that parameter is not given. The value is updated to the true message size by
30292 the time the final DATA ACL is run (after the message data has been
30295 .vindex "&$rcpt_count$&"
30296 .vindex "&$recipients_count$&"
30297 The &$rcpt_count$& variable increases by one for each RCPT command received.
30298 The &$recipients_count$& variable increases by one each time a RCPT command is
30299 accepted, so while an ACL for RCPT is being processed, it contains the number
30300 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30301 &$rcpt_count$& contains the total number of RCPT commands, and
30302 &$recipients_count$& contains the total number of accepted recipients.
30308 .section "Data for non-message ACLs" "SECTdatfornon"
30309 .cindex "&ACL;" "data for non-message ACL"
30310 .vindex &$smtp_command_argument$&
30311 .vindex &$smtp_command$&
30312 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30313 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30314 and the entire SMTP command is available in &$smtp_command$&.
30315 These variables can be tested using a &%condition%& condition. For example,
30316 here is an ACL for use with AUTH, which insists that either the session is
30317 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30318 does not permit authentication methods that use cleartext passwords on
30319 unencrypted connections.
30322 accept encrypted = *
30323 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30325 deny message = TLS encryption or CRAM-MD5 required
30327 (Another way of applying this restriction is to arrange for the authenticators
30328 that use cleartext passwords not to be advertised when the connection is not
30329 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30330 option to do this.)
30334 .section "Format of an ACL" "SECID199"
30335 .cindex "&ACL;" "format of"
30336 .cindex "&ACL;" "verbs, definition of"
30337 An individual ACL consists of a number of statements. Each statement starts
30338 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30339 Modifiers can change the way the verb operates, define error and log messages,
30340 set variables, insert delays, and vary the processing of accepted messages.
30342 If all the conditions are met, the verb is obeyed. The same condition may be
30343 used (with different arguments) more than once in the same statement. This
30344 provides a means of specifying an &"and"& conjunction between conditions. For
30347 deny dnslists = list1.example
30348 dnslists = list2.example
30350 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30351 the conditions and modifiers when it reaches a condition that fails. What
30352 happens then depends on the verb (and in one case, on a special modifier). Not
30353 all the conditions make sense at every testing point. For example, you cannot
30354 test a sender address in the ACL that is run for a VRFY command.
30357 .section "ACL verbs" "SECID200"
30358 The ACL verbs are as follows:
30361 .cindex "&%accept%& ACL verb"
30362 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30363 of the conditions are not met, what happens depends on whether &%endpass%&
30364 appears among the conditions (for syntax see below). If the failing condition
30365 is before &%endpass%&, control is passed to the next ACL statement; if it is
30366 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30367 check a RCPT command:
30369 accept domains = +local_domains
30373 If the recipient domain does not match the &%domains%& condition, control
30374 passes to the next statement. If it does match, the recipient is verified, and
30375 the command is accepted if verification succeeds. However, if verification
30376 fails, the ACL yields &"deny"&, because the failing condition is after
30379 The &%endpass%& feature has turned out to be confusing to many people, so its
30380 use is not recommended nowadays. It is always possible to rewrite an ACL so
30381 that &%endpass%& is not needed, and it is no longer used in the default
30384 .cindex "&%message%& ACL modifier" "with &%accept%&"
30385 If a &%message%& modifier appears on an &%accept%& statement, its action
30386 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30387 (when an &%accept%& verb either accepts or passes control to the next
30388 statement), &%message%& can be used to vary the message that is sent when an
30389 SMTP command is accepted. For example, in a RCPT ACL you could have:
30391 &`accept `&<&'some conditions'&>
30392 &` message = OK, I will allow you through today`&
30394 You can specify an SMTP response code, optionally followed by an &"extended
30395 response code"& at the start of the message, but the first digit must be the
30396 same as would be sent by default, which is 2 for an &%accept%& verb.
30398 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30399 an error message that is used when access is denied. This behaviour is retained
30400 for backward compatibility, but current &"best practice"& is to avoid the use
30405 .cindex "&%defer%& ACL verb"
30406 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30407 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30408 &%defer%& is the same as &%deny%&, because there is no way of sending a
30409 temporary error. For a RCPT command, &%defer%& is much the same as using a
30410 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30411 be used in any ACL, and even for a recipient it might be a simpler approach.
30415 .cindex "&%deny%& ACL verb"
30416 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30417 the conditions are not met, control is passed to the next ACL statement. For
30420 deny dnslists = blackholes.mail-abuse.org
30422 rejects commands from hosts that are on a DNS black list.
30426 .cindex "&%discard%& ACL verb"
30427 &%discard%&: This verb behaves like &%accept%&, except that it returns
30428 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30429 that are concerned with receiving messages. When all the conditions are true,
30430 the sending entity receives a &"success"& response. However, &%discard%& causes
30431 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30432 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30433 message's recipients are discarded. Recipients that are discarded before DATA
30434 do not appear in the log line when the &%received_recipients%& log selector is set.
30436 If the &%log_message%& modifier is set when &%discard%& operates,
30437 its contents are added to the line that is automatically written to the log.
30438 The &%message%& modifier operates exactly as it does for &%accept%&.
30442 .cindex "&%drop%& ACL verb"
30443 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30444 forcibly closed after the 5&'xx'& error message has been sent. For example:
30446 drop message = I don't take more than 20 RCPTs
30447 condition = ${if > {$rcpt_count}{20}}
30449 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30450 The connection is always dropped after sending a 550 response.
30453 .cindex "&%require%& ACL verb"
30454 &%require%&: If all the conditions are met, control is passed to the next ACL
30455 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30456 example, when checking a RCPT command,
30458 require message = Sender did not verify
30461 passes control to subsequent statements only if the message's sender can be
30462 verified. Otherwise, it rejects the command. Note the positioning of the
30463 &%message%& modifier, before the &%verify%& condition. The reason for this is
30464 discussed in section &<<SECTcondmodproc>>&.
30467 .cindex "&%warn%& ACL verb"
30468 &%warn%&: If all the conditions are true, a line specified by the
30469 &%log_message%& modifier is written to Exim's main log. Control always passes
30470 to the next ACL statement. If any condition is false, the log line is not
30471 written. If an identical log line is requested several times in the same
30472 message, only one copy is actually written to the log. If you want to force
30473 duplicates to be written, use the &%logwrite%& modifier instead.
30475 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30476 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30477 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30478 first failing condition. There is more about adding header lines in section
30479 &<<SECTaddheadacl>>&.
30481 If any condition on a &%warn%& statement cannot be completed (that is, there is
30482 some sort of defer), the log line specified by &%log_message%& is not written.
30483 This does not include the case of a forced failure from a lookup, which
30484 is considered to be a successful completion. After a defer, no further
30485 conditions or modifiers in the &%warn%& statement are processed. The incident
30486 is logged, and the ACL continues to be processed, from the next statement
30490 .vindex "&$acl_verify_message$&"
30491 When one of the &%warn%& conditions is an address verification that fails, the
30492 text of the verification failure message is in &$acl_verify_message$&. If you
30493 want this logged, you must set it up explicitly. For example:
30495 warn !verify = sender
30496 log_message = sender verify failed: $acl_verify_message
30500 At the end of each ACL there is an implicit unconditional &%deny%&.
30502 As you can see from the examples above, the conditions and modifiers are
30503 written one to a line, with the first one on the same line as the verb, and
30504 subsequent ones on following lines. If you have a very long condition, you can
30505 continue it onto several physical lines by the usual backslash continuation
30506 mechanism. It is conventional to align the conditions vertically.
30510 .section "ACL variables" "SECTaclvariables"
30511 .cindex "&ACL;" "variables"
30512 There are some special variables that can be set during ACL processing. They
30513 can be used to pass information between different ACLs, different invocations
30514 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30515 transports, and filters that are used to deliver a message. The names of these
30516 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30517 an underscore, but the remainder of the name can be any sequence of
30518 alphanumeric characters and underscores that you choose. There is no limit on
30519 the number of ACL variables. The two sets act as follows:
30521 The values of those variables whose names begin with &$acl_c$& persist
30522 throughout an SMTP connection. They are never reset. Thus, a value that is set
30523 while receiving one message is still available when receiving the next message
30524 on the same SMTP connection.
30526 The values of those variables whose names begin with &$acl_m$& persist only
30527 while a message is being received. They are reset afterwards. They are also
30528 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30531 When a message is accepted, the current values of all the ACL variables are
30532 preserved with the message and are subsequently made available at delivery
30533 time. The ACL variables are set by a modifier called &%set%&. For example:
30535 accept hosts = whatever
30536 set acl_m4 = some value
30537 accept authenticated = *
30538 set acl_c_auth = yes
30540 &*Note*&: A leading dollar sign is not used when naming a variable that is to
30541 be set. If you want to set a variable without taking any action, you can use a
30542 &%warn%& verb without any other modifiers or conditions.
30544 .oindex &%strict_acl_vars%&
30545 What happens if a syntactically valid but undefined ACL variable is
30546 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
30547 false (the default), an empty string is substituted; if it is true, an
30548 error is generated.
30550 Versions of Exim before 4.64 have a limited set of numbered variables, but
30551 their names are compatible, so there is no problem with upgrading.
30554 .section "Condition and modifier processing" "SECTcondmodproc"
30555 .cindex "&ACL;" "conditions; processing"
30556 .cindex "&ACL;" "modifiers; processing"
30557 An exclamation mark preceding a condition negates its result. For example:
30559 deny domains = *.dom.example
30560 !verify = recipient
30562 causes the ACL to return &"deny"& if the recipient domain ends in
30563 &'dom.example'& and the recipient address cannot be verified. Sometimes
30564 negation can be used on the right-hand side of a condition. For example, these
30565 two statements are equivalent:
30567 deny hosts = !192.168.3.4
30568 deny !hosts = 192.168.3.4
30570 However, for many conditions (&%verify%& being a good example), only left-hand
30571 side negation of the whole condition is possible.
30573 The arguments of conditions and modifiers are expanded. A forced failure
30574 of an expansion causes a condition to be ignored, that is, it behaves as if the
30575 condition is true. Consider these two statements:
30577 accept senders = ${lookup{$host_name}lsearch\
30578 {/some/file}{$value}fail}
30579 accept senders = ${lookup{$host_name}lsearch\
30580 {/some/file}{$value}{}}
30582 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
30583 the returned list is searched, but if the lookup fails the behaviour is
30584 different in the two cases. The &%fail%& in the first statement causes the
30585 condition to be ignored, leaving no further conditions. The &%accept%& verb
30586 therefore succeeds. The second statement, however, generates an empty list when
30587 the lookup fails. No sender can match an empty list, so the condition fails,
30588 and therefore the &%accept%& also fails.
30590 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
30591 specify actions that are taken as the conditions for a statement are checked;
30592 others specify text for messages that are used when access is denied or a
30593 warning is generated. The &%control%& modifier affects the way an incoming
30594 message is handled.
30596 The positioning of the modifiers in an ACL statement is important, because the
30597 processing of a verb ceases as soon as its outcome is known. Only those
30598 modifiers that have already been encountered will take effect. For example,
30599 consider this use of the &%message%& modifier:
30601 require message = Can't verify sender
30603 message = Can't verify recipient
30605 message = This message cannot be used
30607 If sender verification fails, Exim knows that the result of the statement is
30608 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
30609 so its text is used as the error message. If sender verification succeeds, but
30610 recipient verification fails, the second message is used. If recipient
30611 verification succeeds, the third message becomes &"current"&, but is never used
30612 because there are no more conditions to cause failure.
30614 For the &%deny%& verb, on the other hand, it is always the last &%message%&
30615 modifier that is used, because all the conditions must be true for rejection to
30616 happen. Specifying more than one &%message%& modifier does not make sense, and
30617 the message can even be specified after all the conditions. For example:
30620 !senders = *@my.domain.example
30621 message = Invalid sender from client host
30623 The &"deny"& result does not happen until the end of the statement is reached,
30624 by which time Exim has set up the message.
30628 .section "ACL modifiers" "SECTACLmodi"
30629 .cindex "&ACL;" "modifiers; list of"
30630 The ACL modifiers are as follows:
30633 .vitem &*add_header*&&~=&~<&'text'&>
30634 This modifier specifies one or more header lines that are to be added to an
30635 incoming message, assuming, of course, that the message is ultimately
30636 accepted. For details, see section &<<SECTaddheadacl>>&.
30638 .vitem &*continue*&&~=&~<&'text'&>
30639 .cindex "&%continue%& ACL modifier"
30640 .cindex "database" "updating in ACL"
30641 This modifier does nothing of itself, and processing of the ACL always
30642 continues with the next condition or modifier. The value of &%continue%& is in
30643 the side effects of expanding its argument. Typically this could be used to
30644 update a database. It is really just a syntactic tidiness, to avoid having to
30645 write rather ugly lines like this:
30647 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
30649 Instead, all you need is
30651 &`continue = `&<&'some expansion'&>
30654 .vitem &*control*&&~=&~<&'text'&>
30655 .cindex "&%control%& ACL modifier"
30656 This modifier affects the subsequent processing of the SMTP connection or of an
30657 incoming message that is accepted. The effect of the first type of control
30658 lasts for the duration of the connection, whereas the effect of the second type
30659 lasts only until the current message has been received. The message-specific
30660 controls always apply to the whole message, not to individual recipients,
30661 even if the &%control%& modifier appears in a RCPT ACL.
30663 As there are now quite a few controls that can be applied, they are described
30664 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
30665 in several different ways. For example:
30667 . ==== As this is a nested list, any displays it contains must be indented
30668 . ==== as otherwise they are too far to the left. That comment applies only
30669 . ==== when xmlto and fop are used; formatting with sdop gets it right either
30673 It can be at the end of an &%accept%& statement:
30675 accept ...some conditions
30678 In this case, the control is applied when this statement yields &"accept"&, in
30679 other words, when the conditions are all true.
30682 It can be in the middle of an &%accept%& statement:
30684 accept ...some conditions...
30686 ...some more conditions...
30688 If the first set of conditions are true, the control is applied, even if the
30689 statement does not accept because one of the second set of conditions is false.
30690 In this case, some subsequent statement must yield &"accept"& for the control
30694 It can be used with &%warn%& to apply the control, leaving the
30695 decision about accepting or denying to a subsequent verb. For
30698 warn ...some conditions...
30702 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
30703 &%logwrite%&, so it does not add anything to the message and does not write a
30707 If you want to apply a control unconditionally, you can use it with a
30708 &%require%& verb. For example:
30710 require control = no_multiline_responses
30714 .vitem &*delay*&&~=&~<&'time'&>
30715 .cindex "&%delay%& ACL modifier"
30717 This modifier may appear in any ACL except notquit. It causes Exim to wait for
30718 the time interval before proceeding. However, when testing Exim using the
30719 &%-bh%& option, the delay is not actually imposed (an appropriate message is
30720 output instead). The time is given in the usual Exim notation, and the delay
30721 happens as soon as the modifier is processed. In an SMTP session, pending
30722 output is flushed before the delay is imposed.
30724 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
30727 deny ...some conditions...
30730 The delay happens if all the conditions are true, before the statement returns
30731 &"deny"&. Compare this with:
30734 ...some conditions...
30736 which waits for 30s before processing the conditions. The &%delay%& modifier
30737 can also be used with &%warn%& and together with &%control%&:
30739 warn ...some conditions...
30745 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
30746 responses to several commands are no longer buffered and sent in one packet (as
30747 they would normally be) because all output is flushed before imposing the
30748 delay. This optimization is disabled so that a number of small delays do not
30749 appear to the client as one large aggregated delay that might provoke an
30750 unwanted timeout. You can, however, disable output flushing for &%delay%& by
30751 using a &%control%& modifier to set &%no_delay_flush%&.
30755 .cindex "&%endpass%& ACL modifier"
30756 This modifier, which has no argument, is recognized only in &%accept%& and
30757 &%discard%& statements. It marks the boundary between the conditions whose
30758 failure causes control to pass to the next statement, and the conditions whose
30759 failure causes the ACL to return &"deny"&. This concept has proved to be
30760 confusing to some people, so the use of &%endpass%& is no longer recommended as
30761 &"best practice"&. See the description of &%accept%& above for more details.
30764 .vitem &*log_message*&&~=&~<&'text'&>
30765 .cindex "&%log_message%& ACL modifier"
30766 This modifier sets up a message that is used as part of the log message if the
30767 ACL denies access or a &%warn%& statement's conditions are true. For example:
30769 require log_message = wrong cipher suite $tls_in_cipher
30770 encrypted = DES-CBC3-SHA
30772 &%log_message%& is also used when recipients are discarded by &%discard%&. For
30775 &`discard `&<&'some conditions'&>
30776 &` log_message = Discarded $local_part@$domain because...`&
30778 When access is denied, &%log_message%& adds to any underlying error message
30779 that may exist because of a condition failure. For example, while verifying a
30780 recipient address, a &':fail:'& redirection might have already set up a
30783 The message may be defined before the conditions to which it applies, because
30784 the string expansion does not happen until Exim decides that access is to be
30785 denied. This means that any variables that are set by the condition are
30786 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
30787 variables are set after a DNS black list lookup succeeds. If the expansion of
30788 &%log_message%& fails, or if the result is an empty string, the modifier is
30791 .vindex "&$acl_verify_message$&"
30792 If you want to use a &%warn%& statement to log the result of an address
30793 verification, you can use &$acl_verify_message$& to include the verification
30796 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
30797 the start of the logged message. If the same warning log message is requested
30798 more than once while receiving a single email message, only one copy is
30799 actually logged. If you want to log multiple copies, use &%logwrite%& instead
30800 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
30801 is logged for a successful &%warn%& statement.
30803 If &%log_message%& is not present and there is no underlying error message (for
30804 example, from the failure of address verification), but &%message%& is present,
30805 the &%message%& text is used for logging rejections. However, if any text for
30806 logging contains newlines, only the first line is logged. In the absence of
30807 both &%log_message%& and &%message%&, a default built-in message is used for
30808 logging rejections.
30811 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
30812 .cindex "&%log_reject_target%& ACL modifier"
30813 .cindex "logging in ACL" "specifying which log"
30814 This modifier makes it possible to specify which logs are used for messages
30815 about ACL rejections. Its argument is a colon-separated list of words that can
30816 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
30817 may be empty, in which case a rejection is not logged at all. For example, this
30818 ACL fragment writes no logging information when access is denied:
30820 &`deny `&<&'some conditions'&>
30821 &` log_reject_target =`&
30823 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
30824 permanent and temporary rejections. Its effect lasts for the rest of the
30828 .vitem &*logwrite*&&~=&~<&'text'&>
30829 .cindex "&%logwrite%& ACL modifier"
30830 .cindex "logging in ACL" "immediate"
30831 This modifier writes a message to a log file as soon as it is encountered when
30832 processing an ACL. (Compare &%log_message%&, which, except in the case of
30833 &%warn%& and &%discard%&, is used only if the ACL statement denies
30834 access.) The &%logwrite%& modifier can be used to log special incidents in
30837 &`accept `&<&'some special conditions'&>
30838 &` control = freeze`&
30839 &` logwrite = froze message because ...`&
30841 By default, the message is written to the main log. However, it may begin
30842 with a colon, followed by a comma-separated list of log names, and then
30843 another colon, to specify exactly which logs are to be written. For
30846 logwrite = :main,reject: text for main and reject logs
30847 logwrite = :panic: text for panic log only
30851 .vitem &*message*&&~=&~<&'text'&>
30852 .cindex "&%message%& ACL modifier"
30853 This modifier sets up a text string that is expanded and used as a response
30854 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
30855 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
30856 there is some complication if &%endpass%& is involved; see the description of
30857 &%accept%& for details.)
30859 The expansion of the message happens at the time Exim decides that the ACL is
30860 to end, not at the time it processes &%message%&. If the expansion fails, or
30861 generates an empty string, the modifier is ignored. Here is an example where
30862 &%message%& must be specified first, because the ACL ends with a rejection if
30863 the &%hosts%& condition fails:
30865 require message = Host not recognized
30868 (Once a condition has failed, no further conditions or modifiers are
30871 .cindex "SMTP" "error codes"
30872 .oindex "&%smtp_banner%&
30873 For ACLs that are triggered by SMTP commands, the message is returned as part
30874 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
30875 is meaningful only for SMTP, as no message is returned when a non-SMTP message
30876 is accepted. In the case of the connect ACL, accepting with a message modifier
30877 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
30878 accept message may not contain more than one line (otherwise it will be
30879 truncated at the first newline and a panic logged), and it cannot affect the
30882 When SMTP is involved, the message may begin with an overriding response code,
30883 consisting of three digits optionally followed by an &"extended response code"&
30884 of the form &'n.n.n'&, each code being followed by a space. For example:
30886 deny message = 599 1.2.3 Host not welcome
30887 hosts = 192.168.34.0/24
30889 The first digit of the supplied response code must be the same as would be sent
30890 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
30891 access, but for the predata ACL, note that the default success code is 354, not
30894 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
30895 the message modifier cannot override the 221 response code.
30897 The text in a &%message%& modifier is literal; any quotes are taken as
30898 literals, but because the string is expanded, backslash escapes are processed
30899 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
30902 .vindex "&$acl_verify_message$&"
30903 For ACLs that are called by an &%acl =%& ACL condition, the message is
30904 stored in &$acl_verify_message$&, from which the calling ACL may use it.
30906 If &%message%& is used on a statement that verifies an address, the message
30907 specified overrides any message that is generated by the verification process.
30908 However, the original message is available in the variable
30909 &$acl_verify_message$&, so you can incorporate it into your message if you
30910 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
30911 routers to be passed back as part of the SMTP response, you should either not
30912 use a &%message%& modifier, or make use of &$acl_verify_message$&.
30914 For compatibility with previous releases of Exim, a &%message%& modifier that
30915 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
30916 modifier, but this usage is now deprecated. However, &%message%& acts only when
30917 all the conditions are true, wherever it appears in an ACL command, whereas
30918 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
30919 &%warn%& in an ACL that is not concerned with receiving a message, it has no
30923 .vitem &*queue*&&~=&~<&'text'&>
30924 .cindex "&%queue%& ACL modifier"
30925 .cindex "named queues" "selecting in ACL"
30926 This modifier specifies the use of a named queue for spool files
30928 It can only be used before the message is received (i.e. not in
30930 This could be used, for example, for known high-volume burst sources
30931 of traffic, or for quarantine of messages.
30932 Separate queue-runner processes will be needed for named queues.
30933 If the text after expansion is empty, the default queue is used.
30936 .vitem &*remove_header*&&~=&~<&'text'&>
30937 This modifier specifies one or more header names in a colon-separated list
30938 that are to be removed from an incoming message, assuming, of course, that
30939 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
30942 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
30943 .cindex "&%set%& ACL modifier"
30944 This modifier puts a value into one of the ACL variables (see section
30945 &<<SECTaclvariables>>&).
30948 .vitem &*udpsend*&&~=&~<&'parameters'&>
30949 .cindex "UDP communications"
30950 This modifier sends a UDP packet, for purposes such as statistics
30951 collection or behaviour monitoring. The parameters are expanded, and
30952 the result of the expansion must be a colon-separated list consisting
30953 of a destination server, port number, and the packet contents. The
30954 server can be specified as a host name or IPv4 or IPv6 address. The
30955 separator can be changed with the usual angle bracket syntax. For
30956 example, you might want to collect information on which hosts connect
30959 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
30960 $tod_zulu $sender_host_address
30967 .section "Use of the control modifier" "SECTcontrols"
30968 .cindex "&%control%& ACL modifier"
30969 The &%control%& modifier supports the following settings:
30972 .vitem &*control&~=&~allow_auth_unadvertised*&
30973 This modifier allows a client host to use the SMTP AUTH command even when it
30974 has not been advertised in response to EHLO. Furthermore, because there are
30975 apparently some really broken clients that do this, Exim will accept AUTH after
30976 HELO (rather than EHLO) when this control is set. It should be used only if you
30977 really need it, and you should limit its use to those broken clients that do
30978 not work without it. For example:
30980 warn hosts = 192.168.34.25
30981 control = allow_auth_unadvertised
30983 Normally, when an Exim server receives an AUTH command, it checks the name of
30984 the authentication mechanism that is given in the command to ensure that it
30985 matches an advertised mechanism. When this control is set, the check that a
30986 mechanism has been advertised is bypassed. Any configured mechanism can be used
30987 by the client. This control is permitted only in the connection and HELO ACLs.
30990 .vitem &*control&~=&~caseful_local_part*& &&&
30991 &*control&~=&~caselower_local_part*&
30992 .cindex "&ACL;" "case of local part in"
30993 .cindex "case of local parts"
30994 .vindex "&$local_part$&"
30995 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
30996 (that is, during RCPT processing). By default, the contents of &$local_part$&
30997 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
30998 any uppercase letters in the original local part are restored in &$local_part$&
30999 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31002 These controls affect only the current recipient. Moreover, they apply only to
31003 local part handling that takes place directly in the ACL (for example, as a key
31004 in lookups). If a test to verify the recipient is obeyed, the case-related
31005 handling of the local part during the verification is controlled by the router
31006 configuration (see the &%caseful_local_part%& generic router option).
31008 This facility could be used, for example, to add a spam score to local parts
31009 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31012 warn control = caseful_local_part
31013 set acl_m4 = ${eval:\
31015 ${if match{$local_part}{[A-Z]}{1}{0}}\
31017 control = caselower_local_part
31019 Notice that we put back the lower cased version afterwards, assuming that
31020 is what is wanted for subsequent tests.
31023 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31024 .cindex "&ACL;" "cutthrough routing"
31025 .cindex "cutthrough" "requesting"
31026 This option requests delivery be attempted while the item is being received.
31028 The option is usable in the RCPT ACL.
31029 If enabled for a message received via smtp and routed to an smtp transport,
31030 and only one transport, interface, destination host and port combination
31031 is used for all recipients of the message,
31032 then the delivery connection is made while the receiving connection is open
31033 and data is copied from one to the other.
31035 An attempt to set this option for any recipient but the first
31036 for a mail will be quietly ignored.
31037 If a recipient-verify callout
31039 connection is subsequently
31040 requested in the same ACL it is held open and used for
31041 any subsequent recipients and the data,
31042 otherwise one is made after the initial RCPT ACL completes.
31044 Note that routers are used in verify mode,
31045 and cannot depend on content of received headers.
31046 Note also that headers cannot be
31047 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31048 Headers may be modified by routers (subject to the above) and transports.
31049 The &'Received-By:'& header is generated as soon as the body reception starts,
31050 rather than the traditional time after the full message is received;
31051 this will affect the timestamp.
31053 All the usual ACLs are called; if one results in the message being
31054 rejected, all effort spent in delivery (including the costs on
31055 the ultimate destination) will be wasted.
31056 Note that in the case of data-time ACLs this includes the entire
31059 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31060 of outgoing messages is done, because it sends data to the ultimate destination
31061 before the entire message has been received from the source.
31062 It is not supported for messages received with the SMTP PRDR
31066 Should the ultimate destination system positively accept or reject the mail,
31067 a corresponding indication is given to the source system and nothing is queued.
31068 If the item is successfully delivered in cutthrough mode
31069 the delivery log lines are tagged with ">>" rather than "=>" and appear
31070 before the acceptance "<=" line.
31072 If there is a temporary error the item is queued for later delivery in the
31074 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31075 to the control; the default value is &"spool"& and the alternate value
31076 &"pass"& copies an SMTP defer response from the target back to the initiator
31077 and does not queue the message.
31078 Note that this is independent of any recipient verify conditions in the ACL.
31080 Delivery in this mode avoids the generation of a bounce mail to a
31082 sender when the destination system is doing content-scan based rejection.
31085 .vitem &*control&~=&~debug/*&<&'options'&>
31086 .cindex "&ACL;" "enabling debug logging"
31087 .cindex "debugging" "enabling from an ACL"
31088 This control turns on debug logging, almost as though Exim had been invoked
31089 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31090 by default called &'debuglog'&.
31091 The filename can be adjusted with the &'tag'& option, which
31092 may access any variables already defined. The logging may be adjusted with
31093 the &'opts'& option, which takes the same values as the &`-d`& command-line
31095 Logging started this way may be stopped, and the file removed,
31096 with the &'kill'& option.
31097 Some examples (which depend on variables that don't exist in all
31101 control = debug/tag=.$sender_host_address
31102 control = debug/opts=+expand+acl
31103 control = debug/tag=.$message_exim_id/opts=+expand
31104 control = debug/kill
31108 .vitem &*control&~=&~dkim_disable_verify*&
31109 .cindex "disable DKIM verify"
31110 .cindex "DKIM" "disable verify"
31111 This control turns off DKIM verification processing entirely. For details on
31112 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31115 .vitem &*control&~=&~dmarc_disable_verify*&
31116 .cindex "disable DMARC verify"
31117 .cindex "DMARC" "disable verify"
31118 This control turns off DMARC verification processing entirely. For details on
31119 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31122 .vitem &*control&~=&~dscp/*&<&'value'&>
31123 .cindex "&ACL;" "setting DSCP value"
31124 .cindex "DSCP" "inbound"
31125 This option causes the DSCP value associated with the socket for the inbound
31126 connection to be adjusted to a given value, given as one of a number of fixed
31127 strings or to numeric value.
31128 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31129 Common values include &`throughput`&, &`mincost`&, and on newer systems
31130 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31132 The outbound packets from Exim will be marked with this value in the header
31133 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31134 that these values will have any effect, not be stripped by networking
31135 equipment, or do much of anything without cooperation with your Network
31136 Engineer and those of all network operators between the source and destination.
31139 .vitem &*control&~=&~enforce_sync*& &&&
31140 &*control&~=&~no_enforce_sync*&
31141 .cindex "SMTP" "synchronization checking"
31142 .cindex "synchronization checking in SMTP"
31143 These controls make it possible to be selective about when SMTP synchronization
31144 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31145 state of the switch (it is true by default). See the description of this option
31146 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31148 The effect of these two controls lasts for the remainder of the SMTP
31149 connection. They can appear in any ACL except the one for the non-SMTP
31150 messages. The most straightforward place to put them is in the ACL defined by
31151 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31152 before the first synchronization check. The expected use is to turn off the
31153 synchronization checks for badly-behaved hosts that you nevertheless need to
31157 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31158 .cindex "fake defer"
31159 .cindex "defer, fake"
31160 This control works in exactly the same way as &%fakereject%& (described below)
31161 except that it causes an SMTP 450 response after the message data instead of a
31162 550 response. You must take care when using &%fakedefer%& because it causes the
31163 messages to be duplicated when the sender retries. Therefore, you should not
31164 use &%fakedefer%& if the message is to be delivered normally.
31166 .vitem &*control&~=&~fakereject/*&<&'message'&>
31167 .cindex "fake rejection"
31168 .cindex "rejection, fake"
31169 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31170 words, only when an SMTP message is being received. If Exim accepts the
31171 message, instead the final 250 response, a 550 rejection message is sent.
31172 However, Exim proceeds to deliver the message as normal. The control applies
31173 only to the current message, not to any subsequent ones that may be received in
31174 the same SMTP connection.
31176 The text for the 550 response is taken from the &%control%& modifier. If no
31177 message is supplied, the following is used:
31179 550-Your message has been rejected but is being
31180 550-kept for evaluation.
31181 550-If it was a legitimate message, it may still be
31182 550 delivered to the target recipient(s).
31184 This facility should be used with extreme caution.
31186 .vitem &*control&~=&~freeze*&
31187 .cindex "frozen messages" "forcing in ACL"
31188 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31189 other words, only when a message is being received. If the message is accepted,
31190 it is placed on Exim's queue and frozen. The control applies only to the
31191 current message, not to any subsequent ones that may be received in the same
31194 This modifier can optionally be followed by &`/no_tell`&. If the global option
31195 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31196 is told about the freezing), provided all the &*control=freeze*& modifiers that
31197 are obeyed for the current message have the &`/no_tell`& option.
31199 .vitem &*control&~=&~no_delay_flush*&
31200 .cindex "SMTP" "output flushing, disabling for delay"
31201 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31202 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31203 use. This control, as long as it is encountered before the &%delay%& modifier,
31204 disables such output flushing.
31206 .vitem &*control&~=&~no_callout_flush*&
31207 .cindex "SMTP" "output flushing, disabling for callout"
31208 Exim normally flushes SMTP output before performing a callout in an ACL, to
31209 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31210 use. This control, as long as it is encountered before the &%verify%& condition
31211 that causes the callout, disables such output flushing.
31213 .vitem &*control&~=&~no_mbox_unspool*&
31214 This control is available when Exim is compiled with the content scanning
31215 extension. Content scanning may require a copy of the current message, or parts
31216 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31217 or spam scanner. Normally, such copies are deleted when they are no longer
31218 needed. If this control is set, the copies are not deleted. The control applies
31219 only to the current message, not to any subsequent ones that may be received in
31220 the same SMTP connection. It is provided for debugging purposes and is unlikely
31221 to be useful in production.
31223 .vitem &*control&~=&~no_multiline_responses*&
31224 .cindex "multiline responses, suppressing"
31225 This control is permitted for any ACL except the one for non-SMTP messages.
31226 It seems that there are broken clients in use that cannot handle multiline
31227 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31229 If this control is set, multiline SMTP responses from ACL rejections are
31230 suppressed. One way of doing this would have been to put out these responses as
31231 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31232 (&"use multiline responses for more"& it says &-- ha!), and some of the
31233 responses might get close to that. So this facility, which is after all only a
31234 sop to broken clients, is implemented by doing two very easy things:
31237 Extra information that is normally output as part of a rejection caused by
31238 sender verification failure is omitted. Only the final line (typically &"sender
31239 verification failed"&) is sent.
31241 If a &%message%& modifier supplies a multiline response, only the first
31245 The setting of the switch can, of course, be made conditional on the
31246 calling host. Its effect lasts until the end of the SMTP connection.
31248 .vitem &*control&~=&~no_pipelining*&
31249 .cindex "PIPELINING" "suppressing advertising"
31250 .cindex "ESMTP extensions" PIPELINING
31251 This control turns off the advertising of the PIPELINING extension to SMTP in
31252 the current session. To be useful, it must be obeyed before Exim sends its
31253 response to an EHLO command. Therefore, it should normally appear in an ACL
31254 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31255 &%pipelining_advertise_hosts%&.
31258 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31259 &*control&~=&~queue_only*&
31260 .oindex "&%queue%&"
31261 .oindex "&%queue_only%&"
31262 .cindex "queueing incoming messages"
31263 .cindex queueing "forcing in ACL"
31264 .cindex "first pass routing"
31265 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31266 other words, only when a message is being received. If the message is accepted,
31267 it is placed on Exim's queue and left there for delivery by a subsequent queue
31269 If used with no options set,
31270 no immediate delivery process is started. In other words, it has the
31271 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31273 If the &'first_pass_route'& option is given then
31274 the behaviour is like the command-line &'-oqds'& option;
31275 a delivery process is started which stops short of making
31276 any SMTP delivery. The benefit is that the hints database will be updated for
31277 the message being waiting for a specific host, and a later queue run will be
31278 able to send all such messages on a single connection.
31280 The control only applies to the current message, not to any subsequent ones that
31281 may be received in the same SMTP connection.
31284 .vitem &*control&~=&~submission/*&<&'options'&>
31285 .cindex "message" "submission"
31286 .cindex "submission mode"
31287 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31288 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31289 the current message is a submission from a local MUA. In this case, Exim
31290 operates in &"submission mode"&, and applies certain fixups to the message if
31291 necessary. For example, it adds a &'Date:'& header line if one is not present.
31292 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31293 late (the message has already been created).
31295 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31296 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31297 submission mode; the available options for this control are described there.
31298 The control applies only to the current message, not to any subsequent ones
31299 that may be received in the same SMTP connection.
31301 .vitem &*control&~=&~suppress_local_fixups*&
31302 .cindex "submission fixups, suppressing"
31303 This control applies to locally submitted (non TCP/IP) messages, and is the
31304 complement of &`control = submission`&. It disables the fixups that are
31305 normally applied to locally-submitted messages. Specifically:
31308 Any &'Sender:'& header line is left alone (in this respect, it is a
31309 dynamic version of &%local_sender_retain%&).
31311 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31313 There is no check that &'From:'& corresponds to the actual sender.
31316 This control may be useful when a remotely-originated message is accepted,
31317 passed to some scanning program, and then re-submitted for delivery. It can be
31318 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31319 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31322 &*Note:*& This control applies only to the current message, not to any others
31323 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31325 .vitem &*control&~=&~utf8_downconvert*&
31326 This control enables conversion of UTF-8 in message envelope addresses
31328 For details see section &<<SECTi18nMTA>>&.
31332 .section "Summary of message fixup control" "SECTsummesfix"
31333 All four possibilities for message fixups can be specified:
31336 Locally submitted, fixups applied: the default.
31338 Locally submitted, no fixups applied: use
31339 &`control = suppress_local_fixups`&.
31341 Remotely submitted, no fixups applied: the default.
31343 Remotely submitted, fixups applied: use &`control = submission`&.
31348 .section "Adding header lines in ACLs" "SECTaddheadacl"
31349 .cindex "header lines" "adding in an ACL"
31350 .cindex "header lines" "position of added lines"
31351 .cindex "&%add_header%& ACL modifier"
31352 The &%add_header%& modifier can be used to add one or more extra header lines
31353 to an incoming message, as in this example:
31355 warn dnslists = sbl.spamhaus.org : \
31356 dialup.mail-abuse.org
31357 add_header = X-blacklisted-at: $dnslist_domain
31359 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31360 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31361 receiving a message). The message must ultimately be accepted for
31362 &%add_header%& to have any significant effect. You can use &%add_header%& with
31363 any ACL verb, including &%deny%& (though this is potentially useful only in a
31366 Headers will not be added to the message if the modifier is used in
31367 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31369 Leading and trailing newlines are removed from
31370 the data for the &%add_header%& modifier; if it then
31371 contains one or more newlines that
31372 are not followed by a space or a tab, it is assumed to contain multiple header
31373 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31374 front of any line that is not a valid header line.
31376 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31377 They are added to the message before processing the DATA and MIME ACLs.
31378 However, if an identical header line is requested more than once, only one copy
31379 is actually added to the message. Further header lines may be accumulated
31380 during the DATA and MIME ACLs, after which they are added to the message, again
31381 with duplicates suppressed. Thus, it is possible to add two identical header
31382 lines to an SMTP message, but only if one is added before DATA and one after.
31383 In the case of non-SMTP messages, new headers are accumulated during the
31384 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31385 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31386 are included in the entry that is written to the reject log.
31388 .cindex "header lines" "added; visibility of"
31389 Header lines are not visible in string expansions
31391 until they are added to the
31392 message. It follows that header lines defined in the MAIL, RCPT, and predata
31393 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31394 header lines that are added by the DATA or MIME ACLs are not visible in those
31395 ACLs. Because of this restriction, you cannot use header lines as a way of
31396 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31397 this, you can use ACL variables, as described in section
31398 &<<SECTaclvariables>>&.
31400 The list of headers yet to be added is given by the &%$headers_added%& variable.
31402 The &%add_header%& modifier acts immediately as it is encountered during the
31403 processing of an ACL. Notice the difference between these two cases:
31405 &`accept add_header = ADDED: some text`&
31406 &` `&<&'some condition'&>
31408 &`accept `&<&'some condition'&>
31409 &` add_header = ADDED: some text`&
31411 In the first case, the header line is always added, whether or not the
31412 condition is true. In the second case, the header line is added only if the
31413 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31414 ACL statement. All those that are encountered before a condition fails are
31417 .cindex "&%warn%& ACL verb"
31418 For compatibility with previous versions of Exim, a &%message%& modifier for a
31419 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31420 effect only if all the conditions are true, even if it appears before some of
31421 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31422 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31423 are present on a &%warn%& verb, both are processed according to their
31426 By default, new header lines are added to a message at the end of the existing
31427 header lines. However, you can specify that any particular header line should
31428 be added right at the start (before all the &'Received:'& lines), immediately
31429 after the first block of &'Received:'& lines, or immediately before any line
31430 that is not a &'Received:'& or &'Resent-something:'& header.
31432 This is done by specifying &":at_start:"&, &":after_received:"&, or
31433 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31434 header line, respectively. (Header text cannot start with a colon, as there has
31435 to be a header name first.) For example:
31437 warn add_header = \
31438 :after_received:X-My-Header: something or other...
31440 If more than one header line is supplied in a single &%add_header%& modifier,
31441 each one is treated independently and can therefore be placed differently. If
31442 you add more than one line at the start, or after the Received: block, they end
31443 up in reverse order.
31445 &*Warning*&: This facility currently applies only to header lines that are
31446 added in an ACL. It does NOT work for header lines that are added in a
31447 system filter or in a router or transport.
31451 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31452 .cindex "header lines" "removing in an ACL"
31453 .cindex "header lines" "position of removed lines"
31454 .cindex "&%remove_header%& ACL modifier"
31455 The &%remove_header%& modifier can be used to remove one or more header lines
31456 from an incoming message, as in this example:
31458 warn message = Remove internal headers
31459 remove_header = x-route-mail1 : x-route-mail2
31461 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31462 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31463 receiving a message). The message must ultimately be accepted for
31464 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31465 with any ACL verb, including &%deny%&, though this is really not useful for
31466 any verb that doesn't result in a delivered message.
31468 Headers will not be removed from the message if the modifier is used in
31469 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31471 More than one header can be removed at the same time by using a colon separated
31472 list of header names. The header matching is case insensitive. Wildcards are
31473 not permitted, nor is list expansion performed, so you cannot use hostlists to
31474 create a list of headers, however both connection and message variable expansion
31475 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31477 warn hosts = +internal_hosts
31478 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31479 warn message = Remove internal headers
31480 remove_header = $acl_c_ihdrs
31482 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31483 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31484 If multiple header lines match, all are removed.
31485 There is no harm in attempting to remove the same header twice nor in removing
31486 a non-existent header. Further header lines to be removed may be accumulated
31487 during the DATA and MIME ACLs, after which they are removed from the message,
31488 if present. In the case of non-SMTP messages, headers to be removed are
31489 accumulated during the non-SMTP ACLs, and are removed from the message after
31490 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31491 ACL, there really is no effect because there is no logging of what headers
31492 would have been removed.
31494 .cindex "header lines" "removed; visibility of"
31495 Header lines are not visible in string expansions until the DATA phase when it
31496 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31497 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31498 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31499 this restriction, you cannot use header lines as a way of controlling data
31500 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31501 you should instead use ACL variables, as described in section
31502 &<<SECTaclvariables>>&.
31504 The &%remove_header%& modifier acts immediately as it is encountered during the
31505 processing of an ACL. Notice the difference between these two cases:
31507 &`accept remove_header = X-Internal`&
31508 &` `&<&'some condition'&>
31510 &`accept `&<&'some condition'&>
31511 &` remove_header = X-Internal`&
31513 In the first case, the header line is always removed, whether or not the
31514 condition is true. In the second case, the header line is removed only if the
31515 condition is true. Multiple occurrences of &%remove_header%& may occur in the
31516 same ACL statement. All those that are encountered before a condition fails
31519 &*Warning*&: This facility currently applies only to header lines that are
31520 present during ACL processing. It does NOT remove header lines that are added
31521 in a system filter or in a router or transport.
31526 .section "ACL conditions" "SECTaclconditions"
31527 .cindex "&ACL;" "conditions; list of"
31528 Some of the conditions listed in this section are available only when Exim is
31529 compiled with the content-scanning extension. They are included here briefly
31530 for completeness. More detailed descriptions can be found in the discussion on
31531 content scanning in chapter &<<CHAPexiscan>>&.
31533 Not all conditions are relevant in all circumstances. For example, testing
31534 senders and recipients does not make sense in an ACL that is being run as the
31535 result of the arrival of an ETRN command, and checks on message headers can be
31536 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
31537 can use the same condition (with different parameters) more than once in the
31538 same ACL statement. This provides a way of specifying an &"and"& conjunction.
31539 The conditions are as follows:
31543 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
31544 .cindex "&ACL;" "nested"
31545 .cindex "&ACL;" "indirect"
31546 .cindex "&ACL;" "arguments"
31547 .cindex "&%acl%& ACL condition"
31548 The possible values of the argument are the same as for the
31549 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
31550 &"accept"& the condition is true; if it returns &"deny"& the condition is
31551 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
31552 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
31553 condition false. This means that further processing of the &%warn%& verb
31554 ceases, but processing of the ACL continues.
31556 If the argument is a named ACL, up to nine space-separated optional values
31557 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
31558 and $acl_narg is set to the count of values.
31559 Previous values of these variables are restored after the call returns.
31560 The name and values are expanded separately.
31561 Note that spaces in complex expansions which are used as arguments
31562 will act as argument separators.
31564 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
31565 the connection is dropped. If it returns &"discard"&, the verb must be
31566 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
31567 conditions are tested.
31569 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
31570 loops. This condition allows you to use different ACLs in different
31571 circumstances. For example, different ACLs can be used to handle RCPT commands
31572 for different local users or different local domains.
31574 .vitem &*authenticated&~=&~*&<&'string&~list'&>
31575 .cindex "&%authenticated%& ACL condition"
31576 .cindex "authentication" "ACL checking"
31577 .cindex "&ACL;" "testing for authentication"
31578 If the SMTP connection is not authenticated, the condition is false. Otherwise,
31579 the name of the authenticator is tested against the list. To test for
31580 authentication by any authenticator, you can set
31585 .vitem &*condition&~=&~*&<&'string'&>
31586 .cindex "&%condition%& ACL condition"
31587 .cindex "customizing" "ACL condition"
31588 .cindex "&ACL;" "customized test"
31589 .cindex "&ACL;" "testing, customized"
31590 This feature allows you to make up custom conditions. If the result of
31591 expanding the string is an empty string, the number zero, or one of the strings
31592 &"no"& or &"false"&, the condition is false. If the result is any non-zero
31593 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
31594 any other value, some error is assumed to have occurred, and the ACL returns
31595 &"defer"&. However, if the expansion is forced to fail, the condition is
31596 ignored. The effect is to treat it as true, whether it is positive or
31599 .vitem &*decode&~=&~*&<&'location'&>
31600 .cindex "&%decode%& ACL condition"
31601 This condition is available only when Exim is compiled with the
31602 content-scanning extension, and it is allowed only in the ACL defined by
31603 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
31604 If all goes well, the condition is true. It is false only if there are
31605 problems such as a syntax error or a memory shortage. For more details, see
31606 chapter &<<CHAPexiscan>>&.
31608 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
31609 .cindex "&%dnslists%& ACL condition"
31610 .cindex "DNS list" "in ACL"
31611 .cindex "black list (DNS)"
31612 .cindex "&ACL;" "testing a DNS list"
31613 This condition checks for entries in DNS black lists. These are also known as
31614 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
31615 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
31616 different variants of this condition to describe briefly here. See sections
31617 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
31619 .vitem &*domains&~=&~*&<&'domain&~list'&>
31620 .cindex "&%domains%& ACL condition"
31621 .cindex "domain" "ACL checking"
31622 .cindex "&ACL;" "testing a recipient domain"
31623 .vindex "&$domain_data$&"
31624 This condition is relevant only after a RCPT command. It checks that the domain
31625 of the recipient address is in the domain list. If percent-hack processing is
31626 enabled, it is done before this test is done. If the check succeeds with a
31627 lookup, the result of the lookup is placed in &$domain_data$& until the next
31630 &*Note carefully*& (because many people seem to fall foul of this): you cannot
31631 use &%domains%& in a DATA ACL.
31634 .vitem &*encrypted&~=&~*&<&'string&~list'&>
31635 .cindex "&%encrypted%& ACL condition"
31636 .cindex "encryption" "checking in an ACL"
31637 .cindex "&ACL;" "testing for encryption"
31638 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
31639 name of the cipher suite in use is tested against the list. To test for
31640 encryption without testing for any specific cipher suite(s), set
31646 .vitem &*hosts&~=&~*&<&'host&~list'&>
31647 .cindex "&%hosts%& ACL condition"
31648 .cindex "host" "ACL checking"
31649 .cindex "&ACL;" "testing the client host"
31650 This condition tests that the calling host matches the host list. If you have
31651 name lookups or wildcarded host names and IP addresses in the same host list,
31652 you should normally put the IP addresses first. For example, you could have:
31654 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
31656 The lookup in this example uses the host name for its key. This is implied by
31657 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
31658 and it wouldn't matter which way round you had these two items.)
31660 The reason for the problem with host names lies in the left-to-right way that
31661 Exim processes lists. It can test IP addresses without doing any DNS lookups,
31662 but when it reaches an item that requires a host name, it fails if it cannot
31663 find a host name to compare with the pattern. If the above list is given in the
31664 opposite order, the &%accept%& statement fails for a host whose name cannot be
31665 found, even if its IP address is 10.9.8.7.
31667 If you really do want to do the name check first, and still recognize the IP
31668 address even if the name lookup fails, you can rewrite the ACL like this:
31670 accept hosts = dbm;/etc/friendly/hosts
31671 accept hosts = 10.9.8.7
31673 The default action on failing to find the host name is to assume that the host
31674 is not in the list, so the first &%accept%& statement fails. The second
31675 statement can then check the IP address.
31677 .vindex "&$host_data$&"
31678 If a &%hosts%& condition is satisfied by means of a lookup, the result
31679 of the lookup is made available in the &$host_data$& variable. This
31680 allows you, for example, to set up a statement like this:
31682 deny hosts = net-lsearch;/some/file
31683 message = $host_data
31685 which gives a custom error message for each denied host.
31687 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
31688 .cindex "&%local_parts%& ACL condition"
31689 .cindex "local part" "ACL checking"
31690 .cindex "&ACL;" "testing a local part"
31691 .vindex "&$local_part_data$&"
31692 This condition is relevant only after a RCPT command. It checks that the local
31693 part of the recipient address is in the list. If percent-hack processing is
31694 enabled, it is done before this test. If the check succeeds with a lookup, the
31695 result of the lookup is placed in &$local_part_data$&, which remains set until
31696 the next &%local_parts%& test.
31698 .vitem &*malware&~=&~*&<&'option'&>
31699 .cindex "&%malware%& ACL condition"
31700 .cindex "&ACL;" "virus scanning"
31701 .cindex "&ACL;" "scanning for viruses"
31702 This condition is available only when Exim is compiled with the
31703 content-scanning extension
31704 and only after a DATA command.
31705 It causes the incoming message to be scanned for
31706 viruses. For details, see chapter &<<CHAPexiscan>>&.
31708 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31709 .cindex "&%mime_regex%& ACL condition"
31710 .cindex "&ACL;" "testing by regex matching"
31711 This condition is available only when Exim is compiled with the
31712 content-scanning extension, and it is allowed only in the ACL defined by
31713 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
31714 with any of the regular expressions. For details, see chapter
31717 .vitem &*ratelimit&~=&~*&<&'parameters'&>
31718 .cindex "rate limiting"
31719 This condition can be used to limit the rate at which a user or host submits
31720 messages. Details are given in section &<<SECTratelimiting>>&.
31722 .vitem &*recipients&~=&~*&<&'address&~list'&>
31723 .cindex "&%recipients%& ACL condition"
31724 .cindex "recipient" "ACL checking"
31725 .cindex "&ACL;" "testing a recipient"
31726 This condition is relevant only after a RCPT command. It checks the entire
31727 recipient address against a list of recipients.
31729 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31730 .cindex "&%regex%& ACL condition"
31731 .cindex "&ACL;" "testing by regex matching"
31732 This condition is available only when Exim is compiled with the
31733 content-scanning extension, and is available only in the DATA, MIME, and
31734 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
31735 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
31737 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
31738 .cindex "&%sender_domains%& ACL condition"
31739 .cindex "sender" "ACL checking"
31740 .cindex "&ACL;" "testing a sender domain"
31741 .vindex "&$domain$&"
31742 .vindex "&$sender_address_domain$&"
31743 This condition tests the domain of the sender of the message against the given
31744 domain list. &*Note*&: The domain of the sender address is in
31745 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
31746 of this condition. This is an exception to the general rule for testing domain
31747 lists. It is done this way so that, if this condition is used in an ACL for a
31748 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
31749 influence the sender checking.
31751 &*Warning*&: It is a bad idea to use this condition on its own as a control on
31752 relaying, because sender addresses are easily, and commonly, forged.
31754 .vitem &*senders&~=&~*&<&'address&~list'&>
31755 .cindex "&%senders%& ACL condition"
31756 .cindex "sender" "ACL checking"
31757 .cindex "&ACL;" "testing a sender"
31758 This condition tests the sender of the message against the given list. To test
31759 for a bounce message, which has an empty sender, set
31763 &*Warning*&: It is a bad idea to use this condition on its own as a control on
31764 relaying, because sender addresses are easily, and commonly, forged.
31766 .vitem &*spam&~=&~*&<&'username'&>
31767 .cindex "&%spam%& ACL condition"
31768 .cindex "&ACL;" "scanning for spam"
31769 This condition is available only when Exim is compiled with the
31770 content-scanning extension. It causes the incoming message to be scanned by
31771 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
31773 .vitem &*verify&~=&~certificate*&
31774 .cindex "&%verify%& ACL condition"
31775 .cindex "TLS" "client certificate verification"
31776 .cindex "certificate" "verification of client"
31777 .cindex "&ACL;" "certificate verification"
31778 .cindex "&ACL;" "testing a TLS certificate"
31779 This condition is true in an SMTP session if the session is encrypted, and a
31780 certificate was received from the client, and the certificate was verified. The
31781 server requests a certificate only if the client matches &%tls_verify_hosts%&
31782 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
31784 .vitem &*verify&~=&~csa*&
31785 .cindex "CSA verification"
31786 This condition checks whether the sending host (the client) is authorized to
31787 send email. Details of how this works are given in section
31788 &<<SECTverifyCSA>>&.
31790 .vitem &*verify&~=&~header_names_ascii*&
31791 .cindex "&%verify%& ACL condition"
31792 .cindex "&ACL;" "verifying header names only ASCII"
31793 .cindex "header lines" "verifying header names only ASCII"
31794 .cindex "verifying" "header names only ASCII"
31795 This condition is relevant only in an ACL that is run after a message has been
31796 received, that is, in an ACL specified by &%acl_smtp_data%& or
31797 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
31798 there are no non-ASCII characters, also excluding control characters. The
31799 allowable characters are decimal ASCII values 33 through 126.
31801 Exim itself will handle headers with non-ASCII characters, but it can cause
31802 problems for downstream applications, so this option will allow their
31803 detection and rejection in the DATA ACL's.
31805 .vitem &*verify&~=&~header_sender/*&<&'options'&>
31806 .cindex "&%verify%& ACL condition"
31807 .cindex "&ACL;" "verifying sender in the header"
31808 .cindex "header lines" "verifying the sender in"
31809 .cindex "sender" "verifying in header"
31810 .cindex "verifying" "sender in header"
31811 This condition is relevant only in an ACL that is run after a message has been
31812 received, that is, in an ACL specified by &%acl_smtp_data%& or
31813 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
31814 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
31815 is loosely thought of as a &"sender"& address (hence the name of the test).
31816 However, an address that appears in one of these headers need not be an address
31817 that accepts bounce messages; only sender addresses in envelopes are required
31818 to accept bounces. Therefore, if you use the callout option on this check, you
31819 might want to arrange for a non-empty address in the MAIL command.
31821 Details of address verification and the options are given later, starting at
31822 section &<<SECTaddressverification>>& (callouts are described in section
31823 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
31824 condition to restrict it to bounce messages only:
31827 message = A valid sender header is required for bounces
31828 !verify = header_sender
31831 .vitem &*verify&~=&~header_syntax*&
31832 .cindex "&%verify%& ACL condition"
31833 .cindex "&ACL;" "verifying header syntax"
31834 .cindex "header lines" "verifying syntax"
31835 .cindex "verifying" "header syntax"
31836 This condition is relevant only in an ACL that is run after a message has been
31837 received, that is, in an ACL specified by &%acl_smtp_data%& or
31838 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
31839 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
31840 and &'Bcc:'&), returning true if there are no problems.
31841 Unqualified addresses (local parts without domains) are
31842 permitted only in locally generated messages and from hosts that match
31843 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
31846 Note that this condition is a syntax check only. However, a common spamming
31847 ploy used to be to send syntactically invalid headers such as
31851 and this condition can be used to reject such messages, though they are not as
31852 common as they used to be.
31854 .vitem &*verify&~=&~helo*&
31855 .cindex "&%verify%& ACL condition"
31856 .cindex "&ACL;" "verifying HELO/EHLO"
31857 .cindex "HELO" "verifying"
31858 .cindex "EHLO" "verifying"
31859 .cindex "verifying" "EHLO"
31860 .cindex "verifying" "HELO"
31861 This condition is true if a HELO or EHLO command has been received from the
31862 client host, and its contents have been verified. If there has been no previous
31863 attempt to verify the HELO/EHLO contents, it is carried out when this
31864 condition is encountered. See the description of the &%helo_verify_hosts%& and
31865 &%helo_try_verify_hosts%& options for details of how to request verification
31866 independently of this condition, and for detail of the verification.
31868 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
31869 option), this condition is always true.
31872 .vitem &*verify&~=&~not_blind/*&<&'options'&>
31873 .cindex "verifying" "not blind"
31874 .cindex "bcc recipients, verifying none"
31875 This condition checks that there are no blind (bcc) recipients in the message.
31876 Every envelope recipient must appear either in a &'To:'& header line or in a
31877 &'Cc:'& header line for this condition to be true. Local parts are checked
31878 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
31879 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
31880 used only in a DATA or non-SMTP ACL.
31882 There is one possible option, &`case_insensitive`&. If this is present then
31883 local parts are checked case-insensitively.
31885 There are, of course, many legitimate messages that make use of blind (bcc)
31886 recipients. This check should not be used on its own for blocking messages.
31889 .vitem &*verify&~=&~recipient/*&<&'options'&>
31890 .cindex "&%verify%& ACL condition"
31891 .cindex "&ACL;" "verifying recipient"
31892 .cindex "recipient" "verifying"
31893 .cindex "verifying" "recipient"
31894 .vindex "&$address_data$&"
31895 This condition is relevant only after a RCPT command. It verifies the current
31896 recipient. Details of address verification are given later, starting at section
31897 &<<SECTaddressverification>>&. After a recipient has been verified, the value
31898 of &$address_data$& is the last value that was set while routing the address.
31899 This applies even if the verification fails. When an address that is being
31900 verified is redirected to a single address, verification continues with the new
31901 address, and in that case, the subsequent value of &$address_data$& is the
31902 value for the child address.
31904 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
31905 .cindex "&%verify%& ACL condition"
31906 .cindex "&ACL;" "verifying host reverse lookup"
31907 .cindex "host" "verifying reverse lookup"
31908 This condition ensures that a verified host name has been looked up from the IP
31909 address of the client host. (This may have happened already if the host name
31910 was needed for checking a host list, or if the host matched &%host_lookup%&.)
31911 Verification ensures that the host name obtained from a reverse DNS lookup, or
31912 one of its aliases, does, when it is itself looked up in the DNS, yield the
31913 original IP address.
31915 There is one possible option, &`defer_ok`&. If this is present and a
31916 DNS operation returns a temporary error, the verify condition succeeds.
31918 If this condition is used for a locally generated message (that is, when there
31919 is no client host involved), it always succeeds.
31921 .vitem &*verify&~=&~sender/*&<&'options'&>
31922 .cindex "&%verify%& ACL condition"
31923 .cindex "&ACL;" "verifying sender"
31924 .cindex "sender" "verifying"
31925 .cindex "verifying" "sender"
31926 This condition is relevant only after a MAIL or RCPT command, or after a
31927 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
31928 the message's sender is empty (that is, this is a bounce message), the
31929 condition is true. Otherwise, the sender address is verified.
31931 .vindex "&$address_data$&"
31932 .vindex "&$sender_address_data$&"
31933 If there is data in the &$address_data$& variable at the end of routing, its
31934 value is placed in &$sender_address_data$& at the end of verification. This
31935 value can be used in subsequent conditions and modifiers in the same ACL
31936 statement. It does not persist after the end of the current statement. If you
31937 want to preserve the value for longer, you can save it in an ACL variable.
31939 Details of verification are given later, starting at section
31940 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
31941 to avoid doing it more than once per message.
31943 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
31944 .cindex "&%verify%& ACL condition"
31945 This is a variation of the previous option, in which a modified address is
31946 verified as a sender.
31948 Note that '/' is legal in local-parts; if the address may have such
31949 (eg. is generated from the received message)
31950 they must be protected from the options parsing by doubling:
31952 verify = sender=${sg{${address:$h_sender:}}{/}{//}}
31958 .section "Using DNS lists" "SECTmorednslists"
31959 .cindex "DNS list" "in ACL"
31960 .cindex "black list (DNS)"
31961 .cindex "&ACL;" "testing a DNS list"
31962 In its simplest form, the &%dnslists%& condition tests whether the calling host
31963 is on at least one of a number of DNS lists by looking up the inverted IP
31964 address in one or more DNS domains. (Note that DNS list domains are not mail
31965 domains, so the &`+`& syntax for named lists doesn't work - it is used for
31966 special options instead.) For example, if the calling host's IP
31967 address is 192.168.62.43, and the ACL statement is
31969 deny dnslists = blackholes.mail-abuse.org : \
31970 dialups.mail-abuse.org
31972 the following records are looked up:
31974 43.62.168.192.blackholes.mail-abuse.org
31975 43.62.168.192.dialups.mail-abuse.org
31977 As soon as Exim finds an existing DNS record, processing of the list stops.
31978 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
31979 to test that a host is on more than one list (an &"and"& conjunction), you can
31980 use two separate conditions:
31982 deny dnslists = blackholes.mail-abuse.org
31983 dnslists = dialups.mail-abuse.org
31985 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
31986 behaves as if the host does not match the list item, that is, as if the DNS
31987 record does not exist. If there are further items in the DNS list, they are
31990 This is usually the required action when &%dnslists%& is used with &%deny%&
31991 (which is the most common usage), because it prevents a DNS failure from
31992 blocking mail. However, you can change this behaviour by putting one of the
31993 following special items in the list:
31995 &`+include_unknown `& behave as if the item is on the list
31996 &`+exclude_unknown `& behave as if the item is not on the list (default)
31997 &`+defer_unknown `& give a temporary error
31999 .cindex "&`+include_unknown`&"
32000 .cindex "&`+exclude_unknown`&"
32001 .cindex "&`+defer_unknown`&"
32002 Each of these applies to any subsequent items on the list. For example:
32004 deny dnslists = +defer_unknown : foo.bar.example
32006 Testing the list of domains stops as soon as a match is found. If you want to
32007 warn for one list and block for another, you can use two different statements:
32009 deny dnslists = blackholes.mail-abuse.org
32010 warn message = X-Warn: sending host is on dialups list
32011 dnslists = dialups.mail-abuse.org
32013 .cindex caching "of dns lookup"
32015 DNS list lookups are cached by Exim for the duration of the SMTP session
32016 (but limited by the DNS return TTL value),
32017 so a lookup based on the IP address is done at most once for any incoming
32018 connection (assuming long-enough TTL).
32019 Exim does not share information between multiple incoming
32020 connections (but your local name server cache should be active).
32022 There are a number of DNS lists to choose from, some commercial, some free,
32023 or free for small deployments. An overview can be found at
32024 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32028 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32029 .cindex "DNS list" "keyed by explicit IP address"
32030 By default, the IP address that is used in a DNS list lookup is the IP address
32031 of the calling host. However, you can specify another IP address by listing it
32032 after the domain name, introduced by a slash. For example:
32034 deny dnslists = black.list.tld/192.168.1.2
32036 This feature is not very helpful with explicit IP addresses; it is intended for
32037 use with IP addresses that are looked up, for example, the IP addresses of the
32038 MX hosts or nameservers of an email sender address. For an example, see section
32039 &<<SECTmulkeyfor>>& below.
32044 .section "DNS lists keyed on domain names" "SECID202"
32045 .cindex "DNS list" "keyed by domain name"
32046 There are some lists that are keyed on domain names rather than inverted IP
32047 addresses (see, e.g., the &'domain based zones'& link at
32048 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32049 with these lists. You can change the name that is looked up in a DNS list by
32050 listing it after the domain name, introduced by a slash. For example,
32052 deny message = Sender's domain is listed at $dnslist_domain
32053 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32055 This particular example is useful only in ACLs that are obeyed after the
32056 RCPT or DATA commands, when a sender address is available. If (for
32057 example) the message's sender is &'user@tld.example'& the name that is looked
32058 up by this example is
32060 tld.example.dsn.rfc-ignorant.org
32062 A single &%dnslists%& condition can contain entries for both names and IP
32063 addresses. For example:
32065 deny dnslists = sbl.spamhaus.org : \
32066 dsn.rfc-ignorant.org/$sender_address_domain
32068 The first item checks the sending host's IP address; the second checks a domain
32069 name. The whole condition is true if either of the DNS lookups succeeds.
32074 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32075 .cindex "DNS list" "multiple keys for"
32076 The syntax described above for looking up explicitly-defined values (either
32077 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32078 name for the DNS list, what follows the slash can in fact be a list of items.
32079 As with all lists in Exim, the default separator is a colon. However, because
32080 this is a sublist within the list of DNS blacklist domains, it is necessary
32081 either to double the separators like this:
32083 dnslists = black.list.tld/name.1::name.2
32085 or to change the separator character, like this:
32087 dnslists = black.list.tld/<;name.1;name.2
32089 If an item in the list is an IP address, it is inverted before the DNS
32090 blacklist domain is appended. If it is not an IP address, no inversion
32091 occurs. Consider this condition:
32093 dnslists = black.list.tld/<;192.168.1.2;a.domain
32095 The DNS lookups that occur are:
32097 2.1.168.192.black.list.tld
32098 a.domain.black.list.tld
32100 Once a DNS record has been found (that matches a specific IP return
32101 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32102 are done. If there is a temporary DNS error, the rest of the sublist of domains
32103 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32104 only if no other DNS lookup in this sublist succeeds. In other words, a
32105 successful lookup for any of the items in the sublist overrides a temporary
32106 error for a previous item.
32108 The ability to supply a list of items after the slash is in some sense just a
32109 syntactic convenience. These two examples have the same effect:
32111 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32112 dnslists = black.list.tld/a.domain::b.domain
32114 However, when the data for the list is obtained from a lookup, the second form
32115 is usually much more convenient. Consider this example:
32117 deny message = The mail servers for the domain \
32118 $sender_address_domain \
32119 are listed at $dnslist_domain ($dnslist_value); \
32121 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32122 ${lookup dnsdb {>|mxh=\
32123 $sender_address_domain} }} }
32125 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32126 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32127 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32128 of expanding the condition might be something like this:
32130 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32132 Thus, this example checks whether or not the IP addresses of the sender
32133 domain's mail servers are on the Spamhaus black list.
32135 The key that was used for a successful DNS list lookup is put into the variable
32136 &$dnslist_matched$& (see section &<<SECID204>>&).
32141 .section "Data returned by DNS lists" "SECID203"
32142 .cindex "DNS list" "data returned from"
32143 DNS lists are constructed using address records in the DNS. The original RBL
32144 just used the address 127.0.0.1 on the right hand side of each record, but the
32145 RBL+ list and some other lists use a number of values with different meanings.
32146 The values used on the RBL+ list are:
32150 127.1.0.3 DUL and RBL
32152 127.1.0.5 RSS and RBL
32153 127.1.0.6 RSS and DUL
32154 127.1.0.7 RSS and DUL and RBL
32156 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32157 different values. Some DNS lists may return more than one address record;
32158 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32161 .section "Variables set from DNS lists" "SECID204"
32162 .cindex "expansion" "variables, set from DNS list"
32163 .cindex "DNS list" "variables set from"
32164 .vindex "&$dnslist_domain$&"
32165 .vindex "&$dnslist_matched$&"
32166 .vindex "&$dnslist_text$&"
32167 .vindex "&$dnslist_value$&"
32168 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32169 the name of the overall domain that matched (for example,
32170 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32171 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32172 the DNS record. When the key is an IP address, it is not reversed in
32173 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32174 cases, for example:
32176 deny dnslists = spamhaus.example
32178 the key is also available in another variable (in this case,
32179 &$sender_host_address$&). In more complicated cases, however, this is not true.
32180 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32181 might generate a dnslists lookup like this:
32183 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32185 If this condition succeeds, the value in &$dnslist_matched$& might be
32186 &`192.168.6.7`& (for example).
32188 If more than one address record is returned by the DNS lookup, all the IP
32189 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32190 The variable &$dnslist_text$& contains the contents of any associated TXT
32191 record. For lists such as RBL+ the TXT record for a merged entry is often not
32192 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32195 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32196 &-- although these appear before the condition in the ACL, they are not
32197 expanded until after it has failed. For example:
32199 deny hosts = !+local_networks
32200 message = $sender_host_address is listed \
32202 dnslists = rbl-plus.mail-abuse.example
32207 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32208 .cindex "DNS list" "matching specific returned data"
32209 You can add an equals sign and an IP address after a &%dnslists%& domain name
32210 in order to restrict its action to DNS records with a matching right hand side.
32213 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32215 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32216 any address record is considered to be a match. For the moment, we assume
32217 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32218 describes how multiple records are handled.
32220 More than one IP address may be given for checking, using a comma as a
32221 separator. These are alternatives &-- if any one of them matches, the
32222 &%dnslists%& condition is true. For example:
32224 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32226 If you want to specify a constraining address list and also specify names or IP
32227 addresses to be looked up, the constraining address list must be specified
32228 first. For example:
32230 deny dnslists = dsn.rfc-ignorant.org\
32231 =127.0.0.2/$sender_address_domain
32234 If the character &`&&`& is used instead of &`=`&, the comparison for each
32235 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32236 In other words, the listed addresses are used as bit masks. The comparison is
32237 true if all the bits in the mask are present in the address that is being
32238 tested. For example:
32240 dnslists = a.b.c&0.0.0.3
32242 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32243 want to test whether one bit or another bit is present (as opposed to both
32244 being present), you must use multiple values. For example:
32246 dnslists = a.b.c&0.0.0.1,0.0.0.2
32248 matches if the final component of the address is an odd number or two times
32253 .section "Negated DNS matching conditions" "SECID205"
32254 You can supply a negative list of IP addresses as part of a &%dnslists%&
32257 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32259 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32260 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32262 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32264 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32265 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32266 words, the result of the test is inverted if an exclamation mark appears before
32267 the &`=`& (or the &`&&`&) sign.
32269 &*Note*&: This kind of negation is not the same as negation in a domain,
32270 host, or address list (which is why the syntax is different).
32272 If you are using just one list, the negation syntax does not gain you much. The
32273 previous example is precisely equivalent to
32275 deny dnslists = a.b.c
32276 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32278 However, if you are using multiple lists, the negation syntax is clearer.
32279 Consider this example:
32281 deny dnslists = sbl.spamhaus.org : \
32283 dnsbl.njabl.org!=127.0.0.3 : \
32286 Using only positive lists, this would have to be:
32288 deny dnslists = sbl.spamhaus.org : \
32290 deny dnslists = dnsbl.njabl.org
32291 !dnslists = dnsbl.njabl.org=127.0.0.3
32292 deny dnslists = relays.ordb.org
32294 which is less clear, and harder to maintain.
32299 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32300 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32301 thereby providing more than one IP address. When an item in a &%dnslists%& list
32302 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32303 the match to specific results from the DNS lookup, there are two ways in which
32304 the checking can be handled. For example, consider the condition:
32306 dnslists = a.b.c=127.0.0.1
32308 What happens if the DNS lookup for the incoming IP address yields both
32309 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32310 condition true because at least one given value was found, or is it false
32311 because at least one of the found values was not listed? And how does this
32312 affect negated conditions? Both possibilities are provided for with the help of
32313 additional separators &`==`& and &`=&&`&.
32316 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32317 IP addresses matches one of the listed addresses. For the example above, the
32318 condition is true because 127.0.0.1 matches.
32320 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32321 looked up IP addresses matches one of the listed addresses. If the condition is
32324 dnslists = a.b.c==127.0.0.1
32326 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32327 false because 127.0.0.2 is not listed. You would need to have:
32329 dnslists = a.b.c==127.0.0.1,127.0.0.2
32331 for the condition to be true.
32334 When &`!`& is used to negate IP address matching, it inverts the result, giving
32335 the precise opposite of the behaviour above. Thus:
32337 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32338 addresses matches one of the listed addresses. Consider:
32340 dnslists = a.b.c!&0.0.0.1
32342 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32343 false because 127.0.0.1 matches.
32345 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32346 looked up IP address that does not match. Consider:
32348 dnslists = a.b.c!=&0.0.0.1
32350 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32351 true, because 127.0.0.2 does not match. You would need to have:
32353 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32355 for the condition to be false.
32357 When the DNS lookup yields only a single IP address, there is no difference
32358 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32363 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32364 .cindex "DNS list" "information from merged"
32365 When the facility for restricting the matching IP values in a DNS list is used,
32366 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32367 the true reason for rejection. This happens when lists are merged and the IP
32368 address in the A record is used to distinguish them; unfortunately there is
32369 only one TXT record. One way round this is not to use merged lists, but that
32370 can be inefficient because it requires multiple DNS lookups where one would do
32371 in the vast majority of cases when the host of interest is not on any of the
32374 A less inefficient way of solving this problem is available. If
32375 two domain names, comma-separated, are given, the second is used first to
32376 do an initial check, making use of any IP value restrictions that are set.
32377 If there is a match, the first domain is used, without any IP value
32378 restrictions, to get the TXT record. As a byproduct of this, there is also
32379 a check that the IP being tested is indeed on the first list. The first
32380 domain is the one that is put in &$dnslist_domain$&. For example:
32383 rejected because $sender_host_address is blacklisted \
32384 at $dnslist_domain\n$dnslist_text
32386 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32387 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32389 For the first blacklist item, this starts by doing a lookup in
32390 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32391 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32392 value, and as long as something is found, it looks for the corresponding TXT
32393 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32394 The second blacklist item is processed similarly.
32396 If you are interested in more than one merged list, the same list must be
32397 given several times, but because the results of the DNS lookups are cached,
32398 the DNS calls themselves are not repeated. For example:
32401 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32402 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32403 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32404 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32406 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32407 values matches (or if no record is found), this is the only lookup that is
32408 done. Only if there is a match is one of the more specific lists consulted.
32412 .section "DNS lists and IPv6" "SECTmorednslistslast"
32413 .cindex "IPv6" "DNS black lists"
32414 .cindex "DNS list" "IPv6 usage"
32415 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32416 nibble by nibble. For example, if the calling host's IP address is
32417 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32419 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32420 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32422 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32423 lists contain wildcard records, intended for IPv4, that interact badly with
32424 IPv6. For example, the DNS entry
32426 *.3.some.list.example. A 127.0.0.1
32428 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32429 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32431 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32432 &%condition%& condition, as in this example:
32434 deny condition = ${if isip4{$sender_host_address}}
32435 dnslists = some.list.example
32438 If an explicit key is being used for a DNS lookup and it may be an IPv6
32439 address you should specify alternate list separators for both the outer
32440 (DNS list name) list and inner (lookup keys) list:
32442 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32445 .section "Rate limiting incoming messages" "SECTratelimiting"
32446 .cindex "rate limiting" "client sending"
32447 .cindex "limiting client sending rates"
32448 .oindex "&%smtp_ratelimit_*%&"
32449 The &%ratelimit%& ACL condition can be used to measure and control the rate at
32450 which clients can send email. This is more powerful than the
32451 &%smtp_ratelimit_*%& options, because those options control the rate of
32452 commands in a single SMTP session only, whereas the &%ratelimit%& condition
32453 works across all connections (concurrent and sequential) from the same client
32454 host. The syntax of the &%ratelimit%& condition is:
32456 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
32458 If the average client sending rate is less than &'m'& messages per time
32459 period &'p'& then the condition is false; otherwise it is true.
32461 As a side-effect, the &%ratelimit%& condition sets the expansion variable
32462 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
32463 configured value of &'m'&, and &$sender_rate_period$& to the configured value
32466 The parameter &'p'& is the smoothing time constant, in the form of an Exim
32467 time interval, for example, &`8h`& for eight hours. A larger time constant
32468 means that it takes Exim longer to forget a client's past behaviour. The
32469 parameter &'m'& is the maximum number of messages that a client is permitted to
32470 send in each time interval. It also specifies the number of messages permitted
32471 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
32472 constant, you can allow a client to send more messages in a burst without
32473 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
32474 both small, messages must be sent at an even rate.
32476 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
32477 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
32478 when deploying the &%ratelimit%& ACL condition. The script prints usage
32479 instructions when it is run with no arguments.
32481 The key is used to look up the data for calculating the client's average
32482 sending rate. This data is stored in Exim's spool directory, alongside the
32483 retry and other hints databases. The default key is &$sender_host_address$&,
32484 which means Exim computes the sending rate of each client host IP address.
32485 By changing the key you can change how Exim identifies clients for the purpose
32486 of ratelimiting. For example, to limit the sending rate of each authenticated
32487 user, independent of the computer they are sending from, set the key to
32488 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
32489 example, &$authenticated_id$& is only meaningful if the client has
32490 authenticated (which you can check with the &%authenticated%& ACL condition).
32492 The lookup key does not have to identify clients: If you want to limit the
32493 rate at which a recipient receives messages, you can use the key
32494 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
32497 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
32498 specifies what Exim measures the rate of, for example, messages or recipients
32499 or bytes. You can adjust the measurement using the &%unique=%& and/or
32500 &%count=%& options. You can also control when Exim updates the recorded rate
32501 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
32502 separated by a slash, like the other parameters. They may appear in any order.
32504 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
32505 any options that alter the meaning of the stored data. The limit &'m'& is not
32506 stored, so you can alter the configured maximum rate and Exim will still
32507 remember clients' past behaviour. If you change the &%per_*%& mode or add or
32508 remove the &%unique=%& option, the lookup key changes so Exim will forget past
32509 behaviour. The lookup key is not affected by changes to the update mode and
32510 the &%count=%& option.
32513 .section "Ratelimit options for what is being measured" "ratoptmea"
32514 .cindex "rate limiting" "per_* options"
32515 The &%per_conn%& option limits the client's connection rate. It is not
32516 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
32517 &%acl_not_smtp_start%& ACLs.
32519 The &%per_mail%& option limits the client's rate of sending messages. This is
32520 the default if none of the &%per_*%& options is specified. It can be used in
32521 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
32522 &%acl_smtp_data%&, or &%acl_not_smtp%&.
32524 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
32525 the same ACLs as the &%per_mail%& option, though it is best to use this option
32526 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
32527 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
32528 in its MAIL command, which may be inaccurate or completely missing. You can
32529 follow the limit &'m'& in the configuration with K, M, or G to specify limits
32530 in kilobytes, megabytes, or gigabytes, respectively.
32532 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
32533 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
32534 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
32535 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
32536 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
32537 in either case the rate limiting engine will see a message with many
32538 recipients as a large high-speed burst.
32540 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
32541 number of different recipients that the client has sent messages to in the
32542 last time period. That is, if the client repeatedly sends messages to the same
32543 recipient, its measured rate is not increased. This option can only be used in
32546 The &%per_cmd%& option causes Exim to recompute the rate every time the
32547 condition is processed. This can be used to limit the rate of any SMTP
32548 command. If it is used in multiple ACLs it can limit the aggregate rate of
32549 multiple different commands.
32551 The &%count=%& option can be used to alter how much Exim adds to the client's
32552 measured rate. For example, the &%per_byte%& option is equivalent to
32553 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
32554 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
32555 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
32557 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
32560 .section "Ratelimit update modes" "ratoptupd"
32561 .cindex "rate limiting" "reading data without updating"
32562 You can specify one of three options with the &%ratelimit%& condition to
32563 control when its database is updated. This section describes the &%readonly%&
32564 mode, and the next section describes the &%strict%& and &%leaky%& modes.
32566 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
32567 previously-computed rate to check against the limit.
32569 For example, you can test the client's sending rate and deny it access (when
32570 it is too fast) in the connect ACL. If the client passes this check then it
32571 can go on to send a message, in which case its recorded rate will be updated
32572 in the MAIL ACL. Subsequent connections from the same client will check this
32576 deny ratelimit = 100 / 5m / readonly
32577 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
32578 (max $sender_rate_limit)
32581 warn ratelimit = 100 / 5m / strict
32582 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
32583 (max $sender_rate_limit)
32586 If Exim encounters multiple &%ratelimit%& conditions with the same key when
32587 processing a message then it may increase the client's measured rate more than
32588 it should. For example, this will happen if you check the &%per_rcpt%& option
32589 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
32590 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
32591 multiple update problems by using the &%readonly%& option on later ratelimit
32594 The &%per_*%& options described above do not make sense in some ACLs. If you
32595 use a &%per_*%& option in an ACL where it is not normally permitted then the
32596 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
32597 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
32598 next section) so you must specify the &%readonly%& option explicitly.
32601 .section "Ratelimit options for handling fast clients" "ratoptfast"
32602 .cindex "rate limiting" "strict and leaky modes"
32603 If a client's average rate is greater than the maximum, the rate limiting
32604 engine can react in two possible ways, depending on the presence of the
32605 &%strict%& or &%leaky%& update modes. This is independent of the other
32606 counter-measures (such as rejecting the message) that may be specified by the
32609 The &%leaky%& (default) option means that the client's recorded rate is not
32610 updated if it is above the limit. The effect of this is that Exim measures the
32611 client's average rate of successfully sent email,
32612 up to the given limit.
32613 This is appropriate if the countermeasure when the condition is true
32614 consists of refusing the message, and
32615 is generally the better choice if you have clients that retry automatically.
32616 If the action when true is anything more complex then this option is
32617 likely not what is wanted.
32619 The &%strict%& option means that the client's recorded rate is always
32620 updated. The effect of this is that Exim measures the client's average rate
32621 of attempts to send email, which can be much higher than the maximum it is
32622 actually allowed. If the client is over the limit it may be subjected to
32623 counter-measures by the ACL. It must slow down and allow sufficient time to
32624 pass that its computed rate falls below the maximum before it can send email
32625 again. The time (the number of smoothing periods) it must wait and not
32626 attempt to send mail can be calculated with this formula:
32628 ln(peakrate/maxrate)
32632 .section "Limiting the rate of different events" "ratoptuniq"
32633 .cindex "rate limiting" "counting unique events"
32634 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
32635 rate of different events. For example, the &%per_addr%& option uses this
32636 mechanism to count the number of different recipients that the client has
32637 sent messages to in the last time period; it is equivalent to
32638 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
32639 measure the rate that a client uses different sender addresses with the
32640 options &`per_mail/unique=$sender_address`&.
32642 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
32643 has seen for that key. The whole set is thrown away when it is older than the
32644 rate smoothing period &'p'&, so each different event is counted at most once
32645 per period. In the &%leaky%& update mode, an event that causes the client to
32646 go over the limit is not added to the set, in the same way that the client's
32647 recorded rate is not updated in the same situation.
32649 When you combine the &%unique=%& and &%readonly%& options, the specific
32650 &%unique=%& value is ignored, and Exim just retrieves the client's stored
32653 The &%unique=%& mechanism needs more space in the ratelimit database than the
32654 other &%ratelimit%& options in order to store the event set. The number of
32655 unique values is potentially as large as the rate limit, so the extra space
32656 required increases with larger limits.
32658 The uniqueification is not perfect: there is a small probability that Exim
32659 will think a new event has happened before. If the sender's rate is less than
32660 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
32661 the measured rate can go above the limit, in which case Exim may under-count
32662 events by a significant margin. Fortunately, if the rate is high enough (2.7
32663 times the limit) that the false positive rate goes above 9%, then Exim will
32664 throw away the over-full event set before the measured rate falls below the
32665 limit. Therefore the only harm should be that exceptionally high sending rates
32666 are logged incorrectly; any countermeasures you configure will be as effective
32670 .section "Using rate limiting" "useratlim"
32671 Exim's other ACL facilities are used to define what counter-measures are taken
32672 when the rate limit is exceeded. This might be anything from logging a warning
32673 (for example, while measuring existing sending rates in order to define
32674 policy), through time delays to slow down fast senders, up to rejecting the
32675 message. For example:
32677 # Log all senders' rates
32678 warn ratelimit = 0 / 1h / strict
32679 log_message = Sender rate $sender_rate / $sender_rate_period
32681 # Slow down fast senders; note the need to truncate $sender_rate
32682 # at the decimal point.
32683 warn ratelimit = 100 / 1h / per_rcpt / strict
32684 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
32685 $sender_rate_limit }s
32687 # Keep authenticated users under control
32688 deny authenticated = *
32689 ratelimit = 100 / 1d / strict / $authenticated_id
32691 # System-wide rate limit
32692 defer message = Sorry, too busy. Try again later.
32693 ratelimit = 10 / 1s / $primary_hostname
32695 # Restrict incoming rate from each host, with a default
32696 # set using a macro and special cases looked up in a table.
32697 defer message = Sender rate exceeds $sender_rate_limit \
32698 messages per $sender_rate_period
32699 ratelimit = ${lookup {$sender_host_address} \
32700 cdb {DB/ratelimits.cdb} \
32701 {$value} {RATELIMIT} }
32703 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
32704 especially with the &%per_rcpt%& option, you may suffer from a performance
32705 bottleneck caused by locking on the ratelimit hints database. Apart from
32706 making your ACLs less complicated, you can reduce the problem by using a
32707 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
32708 this means that Exim will lose its hints data after a reboot (including retry
32709 hints, the callout cache, and ratelimit data).
32713 .section "Address verification" "SECTaddressverification"
32714 .cindex "verifying address" "options for"
32715 .cindex "policy control" "address verification"
32716 Several of the &%verify%& conditions described in section
32717 &<<SECTaclconditions>>& cause addresses to be verified. Section
32718 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
32719 The verification conditions can be followed by options that modify the
32720 verification process. The options are separated from the keyword and from each
32721 other by slashes, and some of them contain parameters. For example:
32723 verify = sender/callout
32724 verify = recipient/defer_ok/callout=10s,defer_ok
32726 The first stage of address verification, which always happens, is to run the
32727 address through the routers, in &"verify mode"&. Routers can detect the
32728 difference between verification and routing for delivery, and their actions can
32729 be varied by a number of generic options such as &%verify%& and &%verify_only%&
32730 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
32731 The available options are as follows:
32734 If the &%callout%& option is specified, successful routing to one or more
32735 remote hosts is followed by a &"callout"& to those hosts as an additional
32736 check. Callouts and their sub-options are discussed in the next section.
32738 If there is a defer error while doing verification routing, the ACL
32739 normally returns &"defer"&. However, if you include &%defer_ok%& in the
32740 options, the condition is forced to be true instead. Note that this is a main
32741 verification option as well as a suboption for callouts.
32743 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
32744 discusses the reporting of sender address verification failures.
32746 The &%success_on_redirect%& option causes verification always to succeed
32747 immediately after a successful redirection. By default, if a redirection
32748 generates just one address, that address is also verified. See further
32749 discussion in section &<<SECTredirwhilveri>>&.
32752 If the &%quota%& option is specified for recipient verify,
32753 successful routing to an appendfile transport is followed by a call into
32754 the transport to evaluate the quota status for the recipient.
32755 No actual delivery is done, but verification will succeed if the quota
32756 is sufficient for the message (if the sender gave a message size) or
32757 not already exceeded (otherwise).
32761 .cindex "verifying address" "differentiating failures"
32762 .vindex "&$recipient_verify_failure$&"
32763 .vindex "&$sender_verify_failure$&"
32764 .vindex "&$acl_verify_message$&"
32765 After an address verification failure, &$acl_verify_message$& contains the
32766 error message that is associated with the failure. It can be preserved by
32769 warn !verify = sender
32770 set acl_m0 = $acl_verify_message
32772 If you are writing your own custom rejection message or log message when
32773 denying access, you can use this variable to include information about the
32774 verification failure.
32776 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
32777 appropriate) contains one of the following words:
32780 &%qualify%&: The address was unqualified (no domain), and the message
32781 was neither local nor came from an exempted host.
32783 &%route%&: Routing failed.
32785 &%mail%&: Routing succeeded, and a callout was attempted; rejection
32786 occurred at or before the MAIL command (that is, on initial
32787 connection, HELO, or MAIL).
32789 &%recipient%&: The RCPT command in a callout was rejected.
32791 &%postmaster%&: The postmaster check in a callout was rejected.
32794 &%quota%&: The quota check for a local recipient did non pass.
32797 The main use of these variables is expected to be to distinguish between
32798 rejections of MAIL and rejections of RCPT in callouts.
32800 The above variables may also be set after a &*successful*&
32801 address verification to:
32804 &%random%&: A random local-part callout succeeded
32810 .section "Callout verification" "SECTcallver"
32811 .cindex "verifying address" "by callout"
32812 .cindex "callout" "verification"
32813 .cindex "SMTP" "callout verification"
32814 For non-local addresses, routing verifies the domain, but is unable to do any
32815 checking of the local part. There are situations where some means of verifying
32816 the local part is desirable. One way this can be done is to make an SMTP
32817 &'callback'& to a delivery host for the sender address or a &'callforward'& to
32818 a subsequent host for a recipient address, to see if the host accepts the
32819 address. We use the term &'callout'& to cover both cases. Note that for a
32820 sender address, the callback is not to the client host that is trying to
32821 deliver the message, but to one of the hosts that accepts incoming mail for the
32824 Exim does not do callouts by default. If you want them to happen, you must
32825 request them by setting appropriate options on the &%verify%& condition, as
32826 described below. This facility should be used with care, because it can add a
32827 lot of resource usage to the cost of verifying an address. However, Exim does
32828 cache the results of callouts, which helps to reduce the cost. Details of
32829 caching are in section &<<SECTcallvercache>>&.
32831 Recipient callouts are usually used only between hosts that are controlled by
32832 the same administration. For example, a corporate gateway host could use
32833 callouts to check for valid recipients on an internal mailserver. A successful
32834 callout does not guarantee that a real delivery to the address would succeed;
32835 on the other hand, a failing callout does guarantee that a delivery would fail.
32837 If the &%callout%& option is present on a condition that verifies an address, a
32838 second stage of verification occurs if the address is successfully routed to
32839 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
32840 &(manualroute)& router, where the router specifies the hosts. However, if a
32841 router that does not set up hosts routes to an &(smtp)& transport with a
32842 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
32843 &%hosts_override%& set, its hosts are always used, whether or not the router
32844 supplies a host list.
32845 Callouts are only supported on &(smtp)& transports.
32847 The port that is used is taken from the transport, if it is specified and is a
32848 remote transport. (For routers that do verification only, no transport need be
32849 specified.) Otherwise, the default SMTP port is used. If a remote transport
32850 specifies an outgoing interface, this is used; otherwise the interface is not
32851 specified. Likewise, the text that is used for the HELO command is taken from
32852 the transport's &%helo_data%& option; if there is no transport, the value of
32853 &$smtp_active_hostname$& is used.
32855 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
32856 test whether a bounce message could be delivered to the sender address. The
32857 following SMTP commands are sent:
32859 &`HELO `&<&'local host name'&>
32861 &`RCPT TO:`&<&'the address to be tested'&>
32864 LHLO is used instead of HELO if the transport's &%protocol%& option is
32867 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
32870 A recipient callout check is similar. By default, it also uses an empty address
32871 for the sender. This default is chosen because most hosts do not make use of
32872 the sender address when verifying a recipient. Using the same address means
32873 that a single cache entry can be used for each recipient. Some sites, however,
32874 do make use of the sender address when verifying. These are catered for by the
32875 &%use_sender%& and &%use_postmaster%& options, described in the next section.
32877 If the response to the RCPT command is a 2&'xx'& code, the verification
32878 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
32879 Exim tries the next host, if any. If there is a problem with all the remote
32880 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
32881 &%callout%& option is given, in which case the condition is forced to succeed.
32883 .cindex "SMTP" "output flushing, disabling for callout"
32884 A callout may take a little time. For this reason, Exim normally flushes SMTP
32885 output before performing a callout in an ACL, to avoid unexpected timeouts in
32886 clients when the SMTP PIPELINING extension is in use. The flushing can be
32887 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
32892 .section "Additional parameters for callouts" "CALLaddparcall"
32893 .cindex "callout" "additional parameters for"
32894 The &%callout%& option can be followed by an equals sign and a number of
32895 optional parameters, separated by commas. For example:
32897 verify = recipient/callout=10s,defer_ok
32899 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
32900 separate verify options, is retained for backwards compatibility, but is now
32901 deprecated. The additional parameters for &%callout%& are as follows:
32905 .vitem <&'a&~time&~interval'&>
32906 .cindex "callout" "timeout, specifying"
32907 This specifies the timeout that applies for the callout attempt to each host.
32910 verify = sender/callout=5s
32912 The default is 30 seconds. The timeout is used for each response from the
32913 remote host. It is also used for the initial connection, unless overridden by
32914 the &%connect%& parameter.
32917 .vitem &*connect&~=&~*&<&'time&~interval'&>
32918 .cindex "callout" "connection timeout, specifying"
32919 This parameter makes it possible to set a different (usually smaller) timeout
32920 for making the SMTP connection. For example:
32922 verify = sender/callout=5s,connect=1s
32924 If not specified, this timeout defaults to the general timeout value.
32926 .vitem &*defer_ok*&
32927 .cindex "callout" "defer, action on"
32928 When this parameter is present, failure to contact any host, or any other kind
32929 of temporary error, is treated as success by the ACL. However, the cache is not
32930 updated in this circumstance.
32932 .vitem &*fullpostmaster*&
32933 .cindex "callout" "full postmaster check"
32934 This operates like the &%postmaster%& option (see below), but if the check for
32935 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
32936 accordance with the specification in RFC 2821. The RFC states that the
32937 unqualified address &'postmaster'& should be accepted.
32940 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
32941 .cindex "callout" "sender when verifying header"
32942 When verifying addresses in header lines using the &%header_sender%&
32943 verification option, Exim behaves by default as if the addresses are envelope
32944 sender addresses from a message. Callout verification therefore tests to see
32945 whether a bounce message could be delivered, by using an empty address in the
32946 MAIL command. However, it is arguable that these addresses might never be used
32947 as envelope senders, and could therefore justifiably reject bounce messages
32948 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
32949 address to use in the MAIL command. For example:
32951 require verify = header_sender/callout=mailfrom=abcd@x.y.z
32953 This parameter is available only for the &%header_sender%& verification option.
32956 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
32957 .cindex "callout" "overall timeout, specifying"
32958 This parameter sets an overall timeout for performing a callout verification.
32961 verify = sender/callout=5s,maxwait=30s
32963 This timeout defaults to four times the callout timeout for individual SMTP
32964 commands. The overall timeout applies when there is more than one host that can
32965 be tried. The timeout is checked before trying the next host. This prevents
32966 very long delays if there are a large number of hosts and all are timing out
32967 (for example, when network connections are timing out).
32970 .vitem &*no_cache*&
32971 .cindex "callout" "cache, suppressing"
32972 .cindex "caching callout, suppressing"
32973 When this parameter is given, the callout cache is neither read nor updated.
32975 .vitem &*postmaster*&
32976 .cindex "callout" "postmaster; checking"
32977 When this parameter is set, a successful callout check is followed by a similar
32978 check for the local part &'postmaster'& at the same domain. If this address is
32979 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
32980 the postmaster check is recorded in a cache record; if it is a failure, this is
32981 used to fail subsequent callouts for the domain without a connection being
32982 made, until the cache record expires.
32984 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
32985 The postmaster check uses an empty sender in the MAIL command by default.
32986 You can use this parameter to do a postmaster check using a different address.
32989 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
32991 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
32992 one overrides. The &%postmaster%& parameter is equivalent to this example:
32994 require verify = sender/callout=postmaster_mailfrom=
32996 &*Warning*&: The caching arrangements for postmaster checking do not take
32997 account of the sender address. It is assumed that either the empty address or
32998 a fixed non-empty address will be used. All that Exim remembers is that the
32999 postmaster check for the domain succeeded or failed.
33003 .cindex "callout" "&""random""& check"
33004 When this parameter is set, before doing the normal callout check, Exim does a
33005 check for a &"random"& local part at the same domain. The local part is not
33006 really random &-- it is defined by the expansion of the option
33007 &%callout_random_local_part%&, which defaults to
33009 $primary_hostname-$tod_epoch-testing
33011 The idea here is to try to determine whether the remote host accepts all local
33012 parts without checking. If it does, there is no point in doing callouts for
33013 specific local parts. If the &"random"& check succeeds, the result is saved in
33014 a cache record, and used to force the current and subsequent callout checks to
33015 succeed without a connection being made, until the cache record expires.
33017 .vitem &*use_postmaster*&
33018 .cindex "callout" "sender for recipient check"
33019 This parameter applies to recipient callouts only. For example:
33021 deny !verify = recipient/callout=use_postmaster
33023 .vindex "&$qualify_domain$&"
33024 It causes a non-empty postmaster address to be used in the MAIL command when
33025 performing the callout for the recipient, and also for a &"random"& check if
33026 that is configured. The local part of the address is &`postmaster`& and the
33027 domain is the contents of &$qualify_domain$&.
33029 .vitem &*use_sender*&
33030 This option applies to recipient callouts only. For example:
33032 require verify = recipient/callout=use_sender
33034 It causes the message's actual sender address to be used in the MAIL
33035 command when performing the callout, instead of an empty address. There is no
33036 need to use this option unless you know that the called hosts make use of the
33037 sender when checking recipients. If used indiscriminately, it reduces the
33038 usefulness of callout caching.
33041 This option applies to recipient callouts only. For example:
33043 require verify = recipient/callout=use_sender,hold
33045 It causes the connection to be held open and used for any further recipients
33046 and for eventual delivery (should that be done quickly).
33047 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33048 when that is used for the connections.
33049 The advantage is only gained if there are no callout cache hits
33050 (which could be enforced by the no_cache option),
33051 if the use_sender option is used,
33052 if neither the random nor the use_postmaster option is used,
33053 and if no other callouts intervene.
33056 If you use any of the parameters that set a non-empty sender for the MAIL
33057 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33058 &%use_sender%&), you should think about possible loops. Recipient checking is
33059 usually done between two hosts that are under the same management, and the host
33060 that receives the callouts is not normally configured to do callouts itself.
33061 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33062 these circumstances.
33064 However, if you use a non-empty sender address for a callout to an arbitrary
33065 host, there is the likelihood that the remote host will itself initiate a
33066 callout check back to your host. As it is checking what appears to be a message
33067 sender, it is likely to use an empty address in MAIL, thus avoiding a
33068 callout loop. However, to be on the safe side it would be best to set up your
33069 own ACLs so that they do not do sender verification checks when the recipient
33070 is the address you use for header sender or postmaster callout checking.
33072 Another issue to think about when using non-empty senders for callouts is
33073 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33074 by the sender/recipient combination; thus, for any given recipient, many more
33075 actual callouts are performed than when an empty sender or postmaster is used.
33080 .section "Callout caching" "SECTcallvercache"
33081 .cindex "hints database" "callout cache"
33082 .cindex "callout" "cache, description of"
33083 .cindex "caching" "callout"
33084 Exim caches the results of callouts in order to reduce the amount of resources
33085 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33086 option. A hints database called &"callout"& is used for the cache. Two
33087 different record types are used: one records the result of a callout check for
33088 a specific address, and the other records information that applies to the
33089 entire domain (for example, that it accepts the local part &'postmaster'&).
33091 When an original callout fails, a detailed SMTP error message is given about
33092 the failure. However, for subsequent failures use the cache data, this message
33095 The expiry times for negative and positive address cache records are
33096 independent, and can be set by the global options &%callout_negative_expire%&
33097 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33099 If a host gives a negative response to an SMTP connection, or rejects any
33100 commands up to and including
33104 (but not including the MAIL command with a non-empty address),
33105 any callout attempt is bound to fail. Exim remembers such failures in a
33106 domain cache record, which it uses to fail callouts for the domain without
33107 making new connections, until the domain record times out. There are two
33108 separate expiry times for domain cache records:
33109 &%callout_domain_negative_expire%& (default 3h) and
33110 &%callout_domain_positive_expire%& (default 7d).
33112 Domain records expire when the negative expiry time is reached if callouts
33113 cannot be made for the domain, or if the postmaster check failed.
33114 Otherwise, they expire when the positive expiry time is reached. This
33115 ensures that, for example, a host that stops accepting &"random"& local parts
33116 will eventually be noticed.
33118 The callout caching mechanism is based on the domain of the address that is
33119 being tested. If the domain routes to several hosts, it is assumed that their
33120 behaviour will be the same.
33125 .section "Quota caching" "SECTquotacache"
33126 .cindex "hints database" "quota cache"
33127 .cindex "quota" "cache, description of"
33128 .cindex "caching" "quota"
33129 Exim caches the results of quota verification
33130 in order to reduce the amount of resources used.
33131 The &"callout"& hints database is used.
33133 The default cache periods are five minutes for a positive (good) result
33134 and one hour for a negative result.
33135 To change the periods the &%quota%& option can be followed by an equals sign
33136 and a number of optional paramemters, separated by commas.
33139 verify = recipient/quota=cachepos=1h,cacheneg=1d
33141 Possible parameters are:
33143 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33144 .cindex "quota cache" "positive entry expiry, specifying"
33145 Set the lifetime for a positive cache entry.
33146 A value of zero seconds is legitimate.
33148 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33149 .cindex "quota cache" "negative entry expiry, specifying"
33150 As above, for a negative entry.
33152 .vitem &*no_cache*&
33153 Set both positive and negative lifetimes to zero.
33156 .section "Sender address verification reporting" "SECTsenaddver"
33157 .cindex "verifying" "suppressing error details"
33158 See section &<<SECTaddressverification>>& for a general discussion of
33159 verification. When sender verification fails in an ACL, the details of the
33160 failure are given as additional output lines before the 550 response to the
33161 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33164 MAIL FROM:<xyz@abc.example>
33166 RCPT TO:<pqr@def.example>
33167 550-Verification failed for <xyz@abc.example>
33168 550-Called: 192.168.34.43
33169 550-Sent: RCPT TO:<xyz@abc.example>
33170 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33171 550 Sender verification failed
33173 If more than one RCPT command fails in the same way, the details are given
33174 only for the first of them. However, some administrators do not want to send
33175 out this much information. You can suppress the details by adding
33176 &`/no_details`& to the ACL statement that requests sender verification. For
33179 verify = sender/no_details
33182 .section "Redirection while verifying" "SECTredirwhilveri"
33183 .cindex "verifying" "redirection while"
33184 .cindex "address redirection" "while verifying"
33185 A dilemma arises when a local address is redirected by aliasing or forwarding
33186 during verification: should the generated addresses themselves be verified,
33187 or should the successful expansion of the original address be enough to verify
33188 it? By default, Exim takes the following pragmatic approach:
33191 When an incoming address is redirected to just one child address, verification
33192 continues with the child address, and if that fails to verify, the original
33193 verification also fails.
33195 When an incoming address is redirected to more than one child address,
33196 verification does not continue. A success result is returned.
33199 This seems the most reasonable behaviour for the common use of aliasing as a
33200 way of redirecting different local parts to the same mailbox. It means, for
33201 example, that a pair of alias entries of the form
33204 aw123: :fail: Gone away, no forwarding address
33206 work as expected, with both local parts causing verification failure. When a
33207 redirection generates more than one address, the behaviour is more like a
33208 mailing list, where the existence of the alias itself is sufficient for
33209 verification to succeed.
33211 It is possible, however, to change the default behaviour so that all successful
33212 redirections count as successful verifications, however many new addresses are
33213 generated. This is specified by the &%success_on_redirect%& verification
33214 option. For example:
33216 require verify = recipient/success_on_redirect/callout=10s
33218 In this example, verification succeeds if a router generates a new address, and
33219 the callout does not occur, because no address was routed to a remote host.
33221 When verification is being tested via the &%-bv%& option, the treatment of
33222 redirections is as just described, unless the &%-v%& or any debugging option is
33223 also specified. In that case, full verification is done for every generated
33224 address and a report is output for each of them.
33228 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33229 .cindex "CSA" "verifying"
33230 Client SMTP Authorization is a system that allows a site to advertise
33231 which machines are and are not permitted to send email. This is done by placing
33232 special SRV records in the DNS; these are looked up using the client's HELO
33233 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33234 Authorization checks in Exim are performed by the ACL condition:
33238 This fails if the client is not authorized. If there is a DNS problem, or if no
33239 valid CSA SRV record is found, or if the client is authorized, the condition
33240 succeeds. These three cases can be distinguished using the expansion variable
33241 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33242 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33243 be likely to cause problems for legitimate email.
33245 The error messages produced by the CSA code include slightly more
33246 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33247 looking up the CSA SRV record, or problems looking up the CSA target
33248 address record. There are four reasons for &$csa_status$& being &"fail"&:
33251 The client's host name is explicitly not authorized.
33253 The client's IP address does not match any of the CSA target IP addresses.
33255 The client's host name is authorized but it has no valid target IP addresses
33256 (for example, the target's addresses are IPv6 and the client is using IPv4).
33258 The client's host name has no CSA SRV record but a parent domain has asserted
33259 that all subdomains must be explicitly authorized.
33262 The &%csa%& verification condition can take an argument which is the domain to
33263 use for the DNS query. The default is:
33265 verify = csa/$sender_helo_name
33267 This implementation includes an extension to CSA. If the query domain
33268 is an address literal such as [192.0.2.95], or if it is a bare IP
33269 address, Exim searches for CSA SRV records in the reverse DNS as if
33270 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33273 verify = csa/$sender_host_address
33275 In fact, this is the check that Exim performs if the client does not say HELO.
33276 This extension can be turned off by setting the main configuration option
33277 &%dns_csa_use_reverse%& to be false.
33279 If a CSA SRV record is not found for the domain itself, a search
33280 is performed through its parent domains for a record which might be
33281 making assertions about subdomains. The maximum depth of this search is limited
33282 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33283 default. Exim does not look for CSA SRV records in a top level domain, so the
33284 default settings handle HELO domains as long as seven
33285 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33286 of legitimate HELO domains.
33288 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33289 direct SRV lookups, this is not sufficient because of the extra parent domain
33290 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33291 addresses into lookups in the reverse DNS space. The result of a successful
33294 ${lookup dnsdb {csa=$sender_helo_name}}
33296 has two space-separated fields: an authorization code and a target host name.
33297 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33298 authorization required but absent, or &"?"& for unknown.
33303 .section "Bounce address tag validation" "SECTverifyPRVS"
33304 .cindex "BATV, verifying"
33305 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33306 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33307 Genuine incoming bounce messages should therefore always be addressed to
33308 recipients that have a valid tag. This scheme is a way of detecting unwanted
33309 bounce messages caused by sender address forgeries (often called &"collateral
33310 spam"&), because the recipients of such messages do not include valid tags.
33312 There are two expansion items to help with the implementation of the BATV
33313 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33314 the original envelope sender address by using a simple key to add a hash of the
33315 address and some time-based randomizing information. The &%prvs%& expansion
33316 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33317 The syntax of these expansion items is described in section
33318 &<<SECTexpansionitems>>&.
33319 The validity period on signed addresses is seven days.
33321 As an example, suppose the secret per-address keys are stored in an MySQL
33322 database. A query to look up the key for an address could be defined as a macro
33325 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33326 WHERE sender='${quote_mysql:$prvscheck_address}'\
33329 Suppose also that the senders who make use of BATV are defined by an address
33330 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33333 # Bounces: drop unsigned addresses for BATV senders
33334 deny message = This address does not send an unsigned reverse path
33336 recipients = +batv_senders
33338 # Bounces: In case of prvs-signed address, check signature.
33339 deny message = Invalid reverse path signature.
33341 condition = ${prvscheck {$local_part@$domain}\
33342 {PRVSCHECK_SQL}{1}}
33343 !condition = $prvscheck_result
33345 The first statement rejects recipients for bounce messages that are addressed
33346 to plain BATV sender addresses, because it is known that BATV senders do not
33347 send out messages with plain sender addresses. The second statement rejects
33348 recipients that are prvs-signed, but with invalid signatures (either because
33349 the key is wrong, or the signature has timed out).
33351 A non-prvs-signed address is not rejected by the second statement, because the
33352 &%prvscheck%& expansion yields an empty string if its first argument is not a
33353 prvs-signed address, thus causing the &%condition%& condition to be false. If
33354 the first argument is a syntactically valid prvs-signed address, the yield is
33355 the third string (in this case &"1"&), whether or not the cryptographic and
33356 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33357 of the checks (empty for failure, &"1"& for success).
33359 There is one more issue you must consider when implementing prvs-signing:
33360 you have to ensure that the routers accept prvs-signed addresses and
33361 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33362 router to remove the signature with a configuration along these lines:
33366 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33368 This works because, if the third argument of &%prvscheck%& is empty, the result
33369 of the expansion of a prvs-signed address is the decoded value of the original
33370 address. This router should probably be the first of your routers that handles
33373 To create BATV-signed addresses in the first place, a transport of this form
33376 external_smtp_batv:
33378 return_path = ${prvs {$return_path} \
33379 {${lookup mysql{SELECT \
33380 secret FROM batv_prvs WHERE \
33381 sender='${quote_mysql:$sender_address}'} \
33384 If no key can be found for the existing return path, no signing takes place.
33388 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33389 .cindex "&ACL;" "relay control"
33390 .cindex "relaying" "control by ACL"
33391 .cindex "policy control" "relay control"
33392 An MTA is said to &'relay'& a message if it receives it from some host and
33393 delivers it directly to another host as a result of a remote address contained
33394 within it. Redirecting a local address via an alias or forward file and then
33395 passing the message on to another host is not relaying,
33396 .cindex "&""percent hack""&"
33397 but a redirection as a result of the &"percent hack"& is.
33399 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33400 A host which is acting as a gateway or an MX backup is concerned with incoming
33401 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33402 a host which is acting as a smart host for a number of clients is concerned
33403 with outgoing relaying from those clients to the Internet at large. Often the
33404 same host is fulfilling both functions,
33406 . as illustrated in the diagram below,
33408 but in principle these two kinds of relaying are entirely independent. What is
33409 not wanted is the transmission of mail from arbitrary remote hosts through your
33410 system to arbitrary domains.
33413 You can implement relay control by means of suitable statements in the ACL that
33414 runs for each RCPT command. For convenience, it is often easiest to use
33415 Exim's named list facility to define the domains and hosts involved. For
33416 example, suppose you want to do the following:
33419 Deliver a number of domains to mailboxes on the local host (or process them
33420 locally in some other way). Let's say these are &'my.dom1.example'& and
33421 &'my.dom2.example'&.
33423 Relay mail for a number of other domains for which you are the secondary MX.
33424 These might be &'friend1.example'& and &'friend2.example'&.
33426 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33427 Suppose your LAN is 192.168.45.0/24.
33431 In the main part of the configuration, you put the following definitions:
33433 domainlist local_domains = my.dom1.example : my.dom2.example
33434 domainlist relay_to_domains = friend1.example : friend2.example
33435 hostlist relay_from_hosts = 192.168.45.0/24
33437 Now you can use these definitions in the ACL that is run for every RCPT
33441 accept domains = +local_domains : +relay_to_domains
33442 accept hosts = +relay_from_hosts
33444 The first statement accepts any RCPT command that contains an address in
33445 the local or relay domains. For any other domain, control passes to the second
33446 statement, which accepts the command only if it comes from one of the relay
33447 hosts. In practice, you will probably want to make your ACL more sophisticated
33448 than this, for example, by including sender and recipient verification. The
33449 default configuration includes a more comprehensive example, which is described
33450 in chapter &<<CHAPdefconfil>>&.
33454 .section "Checking a relay configuration" "SECTcheralcon"
33455 .cindex "relaying" "checking control of"
33456 You can check the relay characteristics of your configuration in the same way
33457 that you can test any ACL behaviour for an incoming SMTP connection, by using
33458 the &%-bh%& option to run a fake SMTP session with which you interact.
33463 . ////////////////////////////////////////////////////////////////////////////
33464 . ////////////////////////////////////////////////////////////////////////////
33466 .chapter "Content scanning at ACL time" "CHAPexiscan"
33467 .scindex IIDcosca "content scanning" "at ACL time"
33468 The extension of Exim to include content scanning at ACL time, formerly known
33469 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
33470 was integrated into the main source for Exim release 4.50, and Tom continues to
33471 maintain it. Most of the wording of this chapter is taken from Tom's
33474 It is also possible to scan the content of messages at other times. The
33475 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
33476 scanning after all the ACLs have run. A transport filter can be used to scan
33477 messages at delivery time (see the &%transport_filter%& option, described in
33478 chapter &<<CHAPtransportgeneric>>&).
33480 If you want to include the ACL-time content-scanning features when you compile
33481 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
33482 &_Local/Makefile_&. When you do that, the Exim binary is built with:
33485 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
33486 for all MIME parts for SMTP and non-SMTP messages, respectively.
33488 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
33489 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
33490 run at the end of message reception (the &%acl_smtp_data%& ACL).
33492 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
33493 of messages, or parts of messages, for debugging purposes.
33495 Additional expansion variables that are set in the new ACL and by the new
33498 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
33501 Content-scanning is continually evolving, and new features are still being
33502 added. While such features are still unstable and liable to incompatible
33503 changes, they are made available in Exim by setting options whose names begin
33504 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
33505 this manual. You can find out about them by reading the file called
33506 &_doc/experimental.txt_&.
33508 All the content-scanning facilities work on a MBOX copy of the message that is
33509 temporarily created in a file called:
33511 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
33513 The &_.eml_& extension is a friendly hint to virus scanners that they can
33514 expect an MBOX-like structure inside that file. The file is created when the
33515 first content scanning facility is called. Subsequent calls to content
33516 scanning conditions open the same file again. The directory is recursively
33517 removed when the &%acl_smtp_data%& ACL has finished running, unless
33519 control = no_mbox_unspool
33521 has been encountered. When the MIME ACL decodes files, they are put into the
33522 same directory by default.
33526 .section "Scanning for viruses" "SECTscanvirus"
33527 .cindex "virus scanning"
33528 .cindex "content scanning" "for viruses"
33529 .cindex "content scanning" "the &%malware%& condition"
33530 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
33531 It supports a &"generic"& interface to scanners called via the shell, and
33532 specialized interfaces for &"daemon"& type virus scanners, which are resident
33533 in memory and thus are much faster.
33535 Since message data needs to have arrived,
33536 the condition may be only called in ACL defined by
33538 &%acl_smtp_data_prdr%&,
33539 &%acl_smtp_mime%& or
33542 A timeout of 2 minutes is applied to a scanner call (by default);
33543 if it expires then a defer action is taken.
33545 .oindex "&%av_scanner%&"
33546 You can set the &%av_scanner%& option in the main part of the configuration
33547 to specify which scanner to use, together with any additional options that
33548 are needed. The basic syntax is as follows:
33550 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
33552 If you do not set &%av_scanner%&, it defaults to
33554 av_scanner = sophie:/var/run/sophie
33556 If the value of &%av_scanner%& starts with a dollar character, it is expanded
33558 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
33559 The following scanner types are supported in this release,
33560 though individual ones can be included or not at build time:
33564 .cindex "virus scanners" "avast"
33565 This is the scanner daemon of Avast. It has been tested with Avast Core
33566 Security (currently at version 2.2.0).
33567 You can get a trial version at &url(https://www.avast.com) or for Linux
33568 at &url(https://www.avast.com/linux-server-antivirus).
33569 This scanner type takes one option,
33570 which can be either a full path to a UNIX socket,
33571 or host and port specifiers separated by white space.
33572 The host may be a name or an IP address; the port is either a
33573 single number or a pair of numbers with a dash between.
33574 A list of options may follow. These options are interpreted on the
33575 Exim's side of the malware scanner, or are given on separate lines to
33576 the daemon as options before the main scan command.
33578 .cindex &`pass_unscanned`& "avast"
33579 If &`pass_unscanned`&
33580 is set, any files the Avast scanner can't scan (e.g.
33581 decompression bombs, or invalid archives) are considered clean. Use with
33586 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
33587 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
33588 av_scanner = avast:192.168.2.22 5036
33590 If you omit the argument, the default path
33591 &_/var/run/avast/scan.sock_&
33593 If you use a remote host,
33594 you need to make Exim's spool directory available to it,
33595 as the scanner is passed a file path, not file contents.
33596 For information about available commands and their options you may use
33598 $ socat UNIX:/var/run/avast/scan.sock STDIO:
33604 If the scanner returns a temporary failure (e.g. license issues, or
33605 permission problems), the message is deferred and a paniclog entry is
33606 written. The usual &`defer_ok`& option is available.
33608 .vitem &%aveserver%&
33609 .cindex "virus scanners" "Kaspersky"
33610 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
33611 at &url(https://www.kaspersky.com/). This scanner type takes one option,
33612 which is the path to the daemon's UNIX socket. The default is shown in this
33615 av_scanner = aveserver:/var/run/aveserver
33620 .cindex "virus scanners" "clamd"
33621 This daemon-type scanner is GPL and free. You can get it at
33622 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
33623 unpack MIME containers, so it used to be recommended to unpack MIME attachments
33624 in the MIME ACL. This is no longer believed to be necessary.
33626 The options are a list of server specifiers, which may be
33627 a UNIX socket specification,
33628 a TCP socket specification,
33629 or a (global) option.
33631 A socket specification consists of a space-separated list.
33632 For a Unix socket the first element is a full path for the socket,
33633 for a TCP socket the first element is the IP address
33634 and the second a port number,
33635 Any further elements are per-server (non-global) options.
33636 These per-server options are supported:
33638 retry=<timespec> Retry on connect fail
33641 The &`retry`& option specifies a time after which a single retry for
33642 a failed connect is made. The default is to not retry.
33644 If a Unix socket file is specified, only one server is supported.
33648 av_scanner = clamd:/opt/clamd/socket
33649 av_scanner = clamd:192.0.2.3 1234
33650 av_scanner = clamd:192.0.2.3 1234:local
33651 av_scanner = clamd:192.0.2.3 1234 retry=10s
33652 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
33654 If the value of av_scanner points to a UNIX socket file or contains the
33656 option, then the ClamAV interface will pass a filename containing the data
33657 to be scanned, which should normally result in less I/O happening and be
33658 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
33659 Exim does not assume that there is a common filesystem with the remote host.
33661 The final example shows that multiple TCP targets can be specified. Exim will
33662 randomly use one for each incoming email (i.e. it load balances them). Note
33663 that only TCP targets may be used if specifying a list of scanners; a UNIX
33664 socket cannot be mixed in with TCP targets. If one of the servers becomes
33665 unavailable, Exim will try the remaining one(s) until it finds one that works.
33666 When a clamd server becomes unreachable, Exim will log a message. Exim does
33667 not keep track of scanner state between multiple messages, and the scanner
33668 selection is random, so the message will get logged in the mainlog for each
33669 email that the down scanner gets chosen first (message wrapped to be readable):
33671 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
33672 clamd: connection to localhost, port 3310 failed
33673 (Connection refused)
33676 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
33677 contributing the code for this scanner.
33680 .cindex "virus scanners" "command line interface"
33681 This is the keyword for the generic command line scanner interface. It can be
33682 used to attach virus scanners that are invoked from the shell. This scanner
33683 type takes 3 mandatory options:
33686 The full path and name of the scanner binary, with all command line options,
33687 and a placeholder (&`%s`&) for the directory to scan.
33690 A regular expression to match against the STDOUT and STDERR output of the
33691 virus scanner. If the expression matches, a virus was found. You must make
33692 absolutely sure that this expression matches on &"virus found"&. This is called
33693 the &"trigger"& expression.
33696 Another regular expression, containing exactly one pair of parentheses, to
33697 match the name of the virus found in the scanners output. This is called the
33698 &"name"& expression.
33701 For example, Sophos Sweep reports a virus on a line like this:
33703 Virus 'W32/Magistr-B' found in file ./those.bat
33705 For the trigger expression, we can match the phrase &"found in file"&. For the
33706 name expression, we want to extract the W32/Magistr-B string, so we can match
33707 for the single quotes left and right of it. Altogether, this makes the
33708 configuration setting:
33710 av_scanner = cmdline:\
33711 /path/to/sweep -ss -all -rec -archive %s:\
33712 found in file:'(.+)'
33715 .cindex "virus scanners" "DrWeb"
33716 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
33718 either a full path to a UNIX socket,
33719 or host and port specifiers separated by white space.
33720 The host may be a name or an IP address; the port is either a
33721 single number or a pair of numbers with a dash between.
33724 av_scanner = drweb:/var/run/drwebd.sock
33725 av_scanner = drweb:192.168.2.20 31337
33727 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
33728 is used. Thanks to Alex Miller for contributing the code for this scanner.
33731 .cindex "virus scanners" "f-protd"
33732 The f-protd scanner is accessed via HTTP over TCP.
33733 One argument is taken, being a space-separated hostname and port number
33737 av_scanner = f-protd:localhost 10200-10204
33739 If you omit the argument, the default values shown above are used.
33741 .vitem &%f-prot6d%&
33742 .cindex "virus scanners" "f-prot6d"
33743 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
33744 One argument is taken, being a space-separated hostname and port number.
33747 av_scanner = f-prot6d:localhost 10200
33749 If you omit the argument, the default values show above are used.
33752 .cindex "virus scanners" "F-Secure"
33753 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
33754 argument which is the path to a UNIX socket. For example:
33756 av_scanner = fsecure:/path/to/.fsav
33758 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
33759 Thelmen for contributing the code for this scanner.
33761 .vitem &%kavdaemon%&
33762 .cindex "virus scanners" "Kaspersky"
33763 This is the scanner daemon of Kaspersky Version 4. This version of the
33764 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
33765 scanner type takes one option, which is the path to the daemon's UNIX socket.
33768 av_scanner = kavdaemon:/opt/AVP/AvpCtl
33770 The default path is &_/var/run/AvpCtl_&.
33773 .cindex "virus scanners" "mksd"
33774 This was a daemon type scanner that is aimed mainly at Polish users,
33775 though some documentation was available in English.
33776 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
33777 and this appears to be a candidate for removal from Exim, unless
33778 we are informed of other virus scanners which use the same protocol
33780 The only option for this scanner type is
33781 the maximum number of processes used simultaneously to scan the attachments,
33782 provided that mksd has
33783 been run with at least the same number of child processes. For example:
33785 av_scanner = mksd:2
33787 You can safely omit this option (the default value is 1).
33790 .cindex "virus scanners" "simple socket-connected"
33791 This is a general-purpose way of talking to simple scanner daemons
33792 running on the local machine.
33793 There are four options:
33794 an address (which may be an IP address and port, or the path of a Unix socket),
33795 a commandline to send (may include a single %s which will be replaced with
33796 the path to the mail file to be scanned),
33797 an RE to trigger on from the returned data,
33798 and an RE to extract malware_name from the returned data.
33801 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
33803 Note that surrounding whitespace is stripped from each option, meaning
33804 there is no way to specify a trailing newline.
33805 The socket specifier and both regular-expressions are required.
33806 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
33807 specify an empty element to get this.
33810 .cindex "virus scanners" "Sophos and Sophie"
33811 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
33812 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
33813 for this scanner type is the path to the UNIX socket that Sophie uses for
33814 client communication. For example:
33816 av_scanner = sophie:/tmp/sophie
33818 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
33822 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
33823 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
33826 The &%av_scanner%& option is expanded each time &%malware%& is called. This
33827 makes it possible to use different scanners. See further below for an example.
33828 The &%malware%& condition caches its results, so when you use it multiple times
33829 for the same message, the actual scanning process is only carried out once.
33830 However, using expandable items in &%av_scanner%& disables this caching, in
33831 which case each use of the &%malware%& condition causes a new scan of the
33834 The &%malware%& condition takes a right-hand argument that is expanded before
33835 use and taken as a list, slash-separated by default.
33836 The first element can then be one of
33839 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
33840 The condition succeeds if a virus was found, and fail otherwise. This is the
33843 &"false"& or &"0"& or an empty string, in which case no scanning is done and
33844 the condition fails immediately.
33846 A regular expression, in which case the message is scanned for viruses. The
33847 condition succeeds if a virus is found and its name matches the regular
33848 expression. This allows you to take special actions on certain types of virus.
33849 Note that &"/"& characters in the RE must be doubled due to the list-processing,
33850 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
33853 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
33854 messages even if there is a problem with the virus scanner.
33855 Otherwise, such a problem causes the ACL to defer.
33857 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
33858 specify a non-default timeout. The default is two minutes.
33861 malware = * / defer_ok / tmo=10s
33863 A timeout causes the ACL to defer.
33865 .vindex "&$callout_address$&"
33866 When a connection is made to the scanner the expansion variable &$callout_address$&
33867 is set to record the actual address used.
33869 .vindex "&$malware_name$&"
33870 When a virus is found, the condition sets up an expansion variable called
33871 &$malware_name$& that contains the name of the virus. You can use it in a
33872 &%message%& modifier that specifies the error returned to the sender, and/or in
33875 Beware the interaction of Exim's &%message_size_limit%& with any size limits
33876 imposed by your anti-virus scanner.
33878 Here is a very simple scanning example:
33880 deny message = This message contains malware ($malware_name)
33883 The next example accepts messages when there is a problem with the scanner:
33885 deny message = This message contains malware ($malware_name)
33886 malware = */defer_ok
33888 The next example shows how to use an ACL variable to scan with both sophie and
33889 aveserver. It assumes you have set:
33891 av_scanner = $acl_m0
33893 in the main Exim configuration.
33895 deny message = This message contains malware ($malware_name)
33896 set acl_m0 = sophie
33899 deny message = This message contains malware ($malware_name)
33900 set acl_m0 = aveserver
33905 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
33906 .cindex "content scanning" "for spam"
33907 .cindex "spam scanning"
33908 .cindex "SpamAssassin"
33910 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
33911 score and a report for the message.
33912 Support is also provided for Rspamd.
33914 For more information about installation and configuration of SpamAssassin or
33915 Rspamd refer to their respective websites at
33916 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
33918 SpamAssassin can be installed with CPAN by running:
33920 perl -MCPAN -e 'install Mail::SpamAssassin'
33922 SpamAssassin has its own set of configuration files. Please review its
33923 documentation to see how you can tweak it. The default installation should work
33926 .oindex "&%spamd_address%&"
33927 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
33928 intend to use an instance running on the local host you do not need to set
33929 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
33930 you must set the &%spamd_address%& option in the global part of the Exim
33931 configuration as follows (example):
33933 spamd_address = 192.168.99.45 783
33935 The SpamAssassin protocol relies on a TCP half-close from the client.
33936 If your SpamAssassin client side is running a Linux system with an
33937 iptables firewall, consider setting
33938 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
33939 timeout, Exim uses when waiting for a response from the SpamAssassin
33940 server (currently defaulting to 120s). With a lower value the Linux
33941 connection tracking may consider your half-closed connection as dead too
33945 To use Rspamd (which by default listens on all local addresses
33947 you should add &%variant=rspamd%& after the address/port pair, for example:
33949 spamd_address = 127.0.0.1 11333 variant=rspamd
33952 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
33953 sockets. If you want to us these, supply &%spamd_address%& with an absolute
33954 filename instead of an address/port pair:
33956 spamd_address = /var/run/spamd_socket
33958 You can have multiple &%spamd%& servers to improve scalability. These can
33959 reside on other hardware reachable over the network. To specify multiple
33960 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
33961 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
33963 spamd_address = 192.168.2.10 783 : \
33964 192.168.2.11 783 : \
33967 Up to 32 &%spamd%& servers are supported.
33968 When a server fails to respond to the connection attempt, all other
33969 servers are tried until one succeeds. If no server responds, the &%spam%&
33972 Unix and TCP socket specifications may be mixed in any order.
33973 Each element of the list is a list itself, space-separated by default
33974 and changeable in the usual way (&<<SECTlistsepchange>>&);
33975 take care to not double the separator.
33977 For TCP socket specifications a host name or IP (v4 or v6, but
33978 subject to list-separator quoting rules) address can be used,
33979 and the port can be one or a dash-separated pair.
33980 In the latter case, the range is tried in strict order.
33982 Elements after the first for Unix sockets, or second for TCP socket,
33984 The supported options are:
33986 pri=<priority> Selection priority
33987 weight=<value> Selection bias
33988 time=<start>-<end> Use only between these times of day
33989 retry=<timespec> Retry on connect fail
33990 tmo=<timespec> Connection time limit
33991 variant=rspamd Use Rspamd rather than SpamAssassin protocol
33994 The &`pri`& option specifies a priority for the server within the list,
33995 higher values being tried first.
33996 The default priority is 1.
33998 The &`weight`& option specifies a selection bias.
33999 Within a priority set
34000 servers are queried in a random fashion, weighted by this value.
34001 The default value for selection bias is 1.
34003 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34004 in the local time zone; each element being one or more digits.
34005 Either the seconds or both minutes and seconds, plus the leading &`.`&
34006 characters, may be omitted and will be taken as zero.
34008 Timeout specifications for the &`retry`& and &`tmo`& options
34009 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34011 The &`tmo`& option specifies an overall timeout for communication.
34012 The default value is two minutes.
34014 The &`retry`& option specifies a time after which a single retry for
34015 a failed connect is made.
34016 The default is to not retry.
34018 The &%spamd_address%& variable is expanded before use if it starts with
34019 a dollar sign. In this case, the expansion may return a string that is
34020 used as the list so that multiple spamd servers can be the result of an
34023 .vindex "&$callout_address$&"
34024 When a connection is made to the server the expansion variable &$callout_address$&
34025 is set to record the actual address used.
34027 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34028 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34030 deny message = This message was classified as SPAM
34033 The right-hand side of the &%spam%& condition specifies a name. This is
34034 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34035 to scan using a specific profile, but rather use the SpamAssassin system-wide
34036 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34037 Rspamd does not use this setting. However, you must put something on the
34040 The name allows you to use per-domain or per-user antispam profiles in
34041 principle, but this is not straightforward in practice, because a message may
34042 have multiple recipients, not necessarily all in the same domain. Because the
34043 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34044 read the contents of the message, the variables &$local_part$& and &$domain$&
34046 Careful enforcement of single-recipient messages
34047 (e.g. by responding with defer in the recipient ACL for all recipients
34049 or the use of PRDR,
34050 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34051 are needed to use this feature.
34053 The right-hand side of the &%spam%& condition is expanded before being used, so
34054 you can put lookups or conditions there. When the right-hand side evaluates to
34055 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34058 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34059 large ones may cause significant performance degradation. As most spam messages
34060 are quite small, it is recommended that you do not scan the big ones. For
34063 deny message = This message was classified as SPAM
34064 condition = ${if < {$message_size}{10K}}
34068 The &%spam%& condition returns true if the threshold specified in the user's
34069 SpamAssassin profile has been matched or exceeded. If you want to use the
34070 &%spam%& condition for its side effects (see the variables below), you can make
34071 it always return &"true"& by appending &`:true`& to the username.
34073 .cindex "spam scanning" "returned variables"
34074 When the &%spam%& condition is run, it sets up a number of expansion
34076 Except for &$spam_report$&,
34077 these variables are saved with the received message so are
34078 available for use at delivery time.
34081 .vitem &$spam_score$&
34082 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34083 for inclusion in log or reject messages.
34085 .vitem &$spam_score_int$&
34086 The spam score of the message, multiplied by ten, as an integer value. For
34087 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34088 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34089 The integer value is useful for numeric comparisons in conditions.
34091 .vitem &$spam_bar$&
34092 A string consisting of a number of &"+"& or &"-"& characters, representing the
34093 integer part of the spam score value. A spam score of 4.4 would have a
34094 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34095 headers, since MUAs can match on such strings. The maximum length of the
34096 spam bar is 50 characters.
34098 .vitem &$spam_report$&
34099 A multiline text table, containing the full SpamAssassin report for the
34100 message. Useful for inclusion in headers or reject messages.
34101 This variable is only usable in a DATA-time ACL.
34102 Beware that SpamAssassin may return non-ASCII characters, especially
34103 when running in country-specific locales, which are not legal
34104 unencoded in headers.
34106 .vitem &$spam_action$&
34107 For SpamAssassin either 'reject' or 'no action' depending on the
34108 spam score versus threshold.
34109 For Rspamd, the recommended action.
34113 The &%spam%& condition caches its results unless expansion in
34114 spamd_address was used. If you call it again with the same user name, it
34115 does not scan again, but rather returns the same values as before.
34117 The &%spam%& condition returns DEFER if there is any error while running
34118 the message through SpamAssassin or if the expansion of spamd_address
34119 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34120 statement block), append &`/defer_ok`& to the right-hand side of the
34121 spam condition, like this:
34123 deny message = This message was classified as SPAM
34124 spam = joe/defer_ok
34126 This causes messages to be accepted even if there is a problem with &%spamd%&.
34128 Here is a longer, commented example of the use of the &%spam%&
34131 # put headers in all messages (no matter if spam or not)
34132 warn spam = nobody:true
34133 add_header = X-Spam-Score: $spam_score ($spam_bar)
34134 add_header = X-Spam-Report: $spam_report
34136 # add second subject line with *SPAM* marker when message
34137 # is over threshold
34139 add_header = Subject: *SPAM* $h_Subject:
34141 # reject spam at high scores (> 12)
34142 deny message = This message scored $spam_score spam points.
34144 condition = ${if >{$spam_score_int}{120}{1}{0}}
34149 .section "Scanning MIME parts" "SECTscanmimepart"
34150 .cindex "content scanning" "MIME parts"
34151 .cindex "MIME content scanning"
34152 .oindex "&%acl_smtp_mime%&"
34153 .oindex "&%acl_not_smtp_mime%&"
34154 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34155 each MIME part of an SMTP message, including multipart types, in the sequence
34156 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34157 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34158 options may both refer to the same ACL if you want the same processing in both
34161 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34162 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34163 the case of a non-SMTP message. However, a MIME ACL is called only if the
34164 message contains a &'Content-Type:'& header line. When a call to a MIME
34165 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34166 result code is sent to the client. In the case of an SMTP message, the
34167 &%acl_smtp_data%& ACL is not called when this happens.
34169 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34170 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34171 condition to match against the raw MIME part. You can also use the
34172 &%mime_regex%& condition to match against the decoded MIME part (see section
34173 &<<SECTscanregex>>&).
34175 At the start of a MIME ACL, a number of variables are set from the header
34176 information for the relevant MIME part. These are described below. The contents
34177 of the MIME part are not by default decoded into a disk file except for MIME
34178 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34179 part into a disk file, you can use the &%decode%& condition. The general
34182 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34184 The right hand side is expanded before use. After expansion,
34188 &"0"& or &"false"&, in which case no decoding is done.
34190 The string &"default"&. In that case, the file is put in the temporary
34191 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34192 a sequential filename consisting of the message id and a sequence number. The
34193 full path and name is available in &$mime_decoded_filename$& after decoding.
34195 A full path name starting with a slash. If the full name is an existing
34196 directory, it is used as a replacement for the default directory. The filename
34197 is then sequentially assigned. If the path does not exist, it is used as
34198 the full path and filename.
34200 If the string does not start with a slash, it is used as the
34201 filename, and the default path is then used.
34203 The &%decode%& condition normally succeeds. It is only false for syntax
34204 errors or unusual circumstances such as memory shortages. You can easily decode
34205 a file with its original, proposed filename using
34207 decode = $mime_filename
34209 However, you should keep in mind that &$mime_filename$& might contain
34210 anything. If you place files outside of the default path, they are not
34211 automatically unlinked.
34213 For RFC822 attachments (these are messages attached to messages, with a
34214 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34215 as for the primary message, only that the &$mime_is_rfc822$& expansion
34216 variable is set (see below). Attached messages are always decoded to disk
34217 before being checked, and the files are unlinked once the check is done.
34219 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34220 used to match regular expressions against raw and decoded MIME parts,
34221 respectively. They are described in section &<<SECTscanregex>>&.
34223 .cindex "MIME content scanning" "returned variables"
34224 The following list describes all expansion variables that are
34225 available in the MIME ACL:
34228 .vitem &$mime_anomaly_level$& &&&
34229 &$mime_anomaly_text$&
34230 .vindex &$mime_anomaly_level$&
34231 .vindex &$mime_anomaly_text$&
34232 If there are problems decoding, these variables contain information on
34233 the detected issue.
34235 .vitem &$mime_boundary$&
34236 .vindex &$mime_boundary$&
34237 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34238 have a boundary string, which is stored in this variable. If the current part
34239 has no boundary parameter in the &'Content-Type:'& header, this variable
34240 contains the empty string.
34242 .vitem &$mime_charset$&
34243 .vindex &$mime_charset$&
34244 This variable contains the character set identifier, if one was found in the
34245 &'Content-Type:'& header. Examples for charset identifiers are:
34251 Please note that this value is not normalized, so you should do matches
34252 case-insensitively.
34254 .vitem &$mime_content_description$&
34255 .vindex &$mime_content_description$&
34256 This variable contains the normalized content of the &'Content-Description:'&
34257 header. It can contain a human-readable description of the parts content. Some
34258 implementations repeat the filename for attachments here, but they are usually
34259 only used for display purposes.
34261 .vitem &$mime_content_disposition$&
34262 .vindex &$mime_content_disposition$&
34263 This variable contains the normalized content of the &'Content-Disposition:'&
34264 header. You can expect strings like &"attachment"& or &"inline"& here.
34266 .vitem &$mime_content_id$&
34267 .vindex &$mime_content_id$&
34268 This variable contains the normalized content of the &'Content-ID:'& header.
34269 This is a unique ID that can be used to reference a part from another part.
34271 .vitem &$mime_content_size$&
34272 .vindex &$mime_content_size$&
34273 This variable is set only after the &%decode%& modifier (see above) has been
34274 successfully run. It contains the size of the decoded part in kilobytes. The
34275 size is always rounded up to full kilobytes, so only a completely empty part
34276 has a &$mime_content_size$& of zero.
34278 .vitem &$mime_content_transfer_encoding$&
34279 .vindex &$mime_content_transfer_encoding$&
34280 This variable contains the normalized content of the
34281 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34282 type. Typical values are &"base64"& and &"quoted-printable"&.
34284 .vitem &$mime_content_type$&
34285 .vindex &$mime_content_type$&
34286 If the MIME part has a &'Content-Type:'& header, this variable contains its
34287 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34288 are some examples of popular MIME types, as they may appear in this variable:
34292 application/octet-stream
34296 If the MIME part has no &'Content-Type:'& header, this variable contains the
34299 .vitem &$mime_decoded_filename$&
34300 .vindex &$mime_decoded_filename$&
34301 This variable is set only after the &%decode%& modifier (see above) has been
34302 successfully run. It contains the full path and filename of the file
34303 containing the decoded data.
34308 .vitem &$mime_filename$&
34309 .vindex &$mime_filename$&
34310 This is perhaps the most important of the MIME variables. It contains a
34311 proposed filename for an attachment, if one was found in either the
34312 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34315 decoded, but no additional sanity checks are done.
34317 found, this variable contains the empty string.
34319 .vitem &$mime_is_coverletter$&
34320 .vindex &$mime_is_coverletter$&
34321 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34322 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34323 content in the cover letter, while not restricting attachments at all.
34325 The variable contains 1 (true) for a MIME part believed to be part of the
34326 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34330 The outermost MIME part of a message is always a cover letter.
34333 If a multipart/alternative or multipart/related MIME part is a cover letter,
34334 so are all MIME subparts within that multipart.
34337 If any other multipart is a cover letter, the first subpart is a cover letter,
34338 and the rest are attachments.
34341 All parts contained within an attachment multipart are attachments.
34344 As an example, the following will ban &"HTML mail"& (including that sent with
34345 alternative plain text), while allowing HTML files to be attached. HTML
34346 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34348 deny message = HTML mail is not accepted here
34349 !condition = $mime_is_rfc822
34350 condition = $mime_is_coverletter
34351 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34354 .vitem &$mime_is_multipart$&
34355 .vindex &$mime_is_multipart$&
34356 This variable has the value 1 (true) when the current part has the main type
34357 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34358 Since multipart entities only serve as containers for other parts, you may not
34359 want to carry out specific actions on them.
34361 .vitem &$mime_is_rfc822$&
34362 .vindex &$mime_is_rfc822$&
34363 This variable has the value 1 (true) if the current part is not a part of the
34364 checked message itself, but part of an attached message. Attached message
34365 decoding is fully recursive.
34367 .vitem &$mime_part_count$&
34368 .vindex &$mime_part_count$&
34369 This variable is a counter that is raised for each processed MIME part. It
34370 starts at zero for the very first part (which is usually a multipart). The
34371 counter is per-message, so it is reset when processing RFC822 attachments (see
34372 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34373 complete, so you can use it in the DATA ACL to determine the number of MIME
34374 parts of a message. For non-MIME messages, this variable contains the value -1.
34379 .section "Scanning with regular expressions" "SECTscanregex"
34380 .cindex "content scanning" "with regular expressions"
34381 .cindex "regular expressions" "content scanning with"
34382 You can specify your own custom regular expression matches on the full body of
34383 the message, or on individual MIME parts.
34385 The &%regex%& condition takes one or more regular expressions as arguments and
34386 matches them against the full message (when called in the DATA ACL) or a raw
34387 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34388 linewise, with a maximum line length of 32K characters. That means you cannot
34389 have multiline matches with the &%regex%& condition.
34391 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34392 to 32K of decoded content (the whole content at once, not linewise). If the
34393 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34394 is decoded automatically when &%mime_regex%& is executed (using default path
34395 and filename values). If the decoded data is larger than 32K, only the first
34396 32K characters are checked.
34398 The regular expressions are passed as a colon-separated list. To include a
34399 literal colon, you must double it. Since the whole right-hand side string is
34400 expanded before being used, you must also escape dollar signs and backslashes
34401 with more backslashes, or use the &`\N`& facility to disable expansion.
34402 Here is a simple example that contains two regular expressions:
34404 deny message = contains blacklisted regex ($regex_match_string)
34405 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34407 The conditions returns true if any one of the regular expressions matches. The
34408 &$regex_match_string$& expansion variable is then set up and contains the
34409 matching regular expression.
34410 The expansion variables &$regex1$& &$regex2$& etc
34411 are set to any substrings captured by the regular expression.
34413 &*Warning*&: With large messages, these conditions can be fairly
34421 . ////////////////////////////////////////////////////////////////////////////
34422 . ////////////////////////////////////////////////////////////////////////////
34424 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34425 "Local scan function"
34426 .scindex IIDlosca "&[local_scan()]& function" "description of"
34427 .cindex "customizing" "input scan using C function"
34428 .cindex "policy control" "by local scan function"
34429 In these days of email worms, viruses, and ever-increasing spam, some sites
34430 want to apply a lot of checking to messages before accepting them.
34432 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34433 passing messages to external virus and spam scanning software. You can also do
34434 a certain amount in Exim itself through string expansions and the &%condition%&
34435 condition in the ACL that runs after the SMTP DATA command or the ACL for
34436 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
34438 To allow for further customization to a site's own requirements, there is the
34439 possibility of linking Exim with a private message scanning function, written
34440 in C. If you want to run code that is written in something other than C, you
34441 can of course use a little C stub to call it.
34443 The local scan function is run once for every incoming message, at the point
34444 when Exim is just about to accept the message.
34445 It can therefore be used to control non-SMTP messages from local processes as
34446 well as messages arriving via SMTP.
34448 Exim applies a timeout to calls of the local scan function, and there is an
34449 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
34450 Zero means &"no timeout"&.
34451 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
34452 before calling the local scan function, so that the most common types of crash
34453 are caught. If the timeout is exceeded or one of those signals is caught, the
34454 incoming message is rejected with a temporary error if it is an SMTP message.
34455 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
34456 code. The incident is logged on the main and reject logs.
34460 .section "Building Exim to use a local scan function" "SECID207"
34461 .cindex "&[local_scan()]& function" "building Exim to use"
34462 To make use of the local scan function feature, you must tell Exim where your
34463 function is before building Exim, by setting
34464 both HAVE_LOCAL_SCAN and
34465 LOCAL_SCAN_SOURCE in your
34466 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
34467 directory, so you might set
34469 HAVE_LOCAL_SCAN=yes
34470 LOCAL_SCAN_SOURCE=Local/local_scan.c
34472 for example. The function must be called &[local_scan()]&;
34474 the source file(s) for it should first #define LOCAL_SCAN
34475 and then #include "local_scan.h".
34478 Exim after it has received a message, when the success return code is about to
34479 be sent. This is after all the ACLs have been run. The return code from your
34480 function controls whether the message is actually accepted or not. There is a
34481 commented template function (that just accepts the message) in the file
34482 _src/local_scan.c_.
34484 If you want to make use of Exim's runtime configuration file to set options
34485 for your &[local_scan()]& function, you must also set
34487 LOCAL_SCAN_HAS_OPTIONS=yes
34489 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
34494 .section "API for local_scan()" "SECTapiforloc"
34495 .cindex "&[local_scan()]& function" "API description"
34496 .cindex &%dlfunc%& "API description"
34497 You must include this line near the start of your code:
34500 #include "local_scan.h"
34502 This header file defines a number of variables and other values, and the
34503 prototype for the function itself. Exim is coded to use unsigned char values
34504 almost exclusively, and one of the things this header defines is a shorthand
34505 for &`unsigned char`& called &`uschar`&.
34506 It also makes available the following macro definitions, to simplify casting character
34507 strings and pointers to character strings:
34509 #define CS (char *)
34510 #define CCS (const char *)
34511 #define CSS (char **)
34512 #define US (unsigned char *)
34513 #define CUS (const unsigned char *)
34514 #define USS (unsigned char **)
34516 The function prototype for &[local_scan()]& is:
34518 extern int local_scan(int fd, uschar **return_text);
34520 The arguments are as follows:
34523 &%fd%& is a file descriptor for the file that contains the body of the message
34524 (the -D file). The file is open for reading and writing, but updating it is not
34525 recommended. &*Warning*&: You must &'not'& close this file descriptor.
34527 The descriptor is positioned at character 19 of the file, which is the first
34528 character of the body itself, because the first 19 characters are the message
34529 id followed by &`-D`& and a newline. If you rewind the file, you should use the
34530 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
34531 case this changes in some future version.
34533 &%return_text%& is an address which you can use to return a pointer to a text
34534 string at the end of the function. The value it points to on entry is NULL.
34537 The function must return an &%int%& value which is one of the following macros:
34540 .vitem &`LOCAL_SCAN_ACCEPT`&
34541 .vindex "&$local_scan_data$&"
34542 The message is accepted. If you pass back a string of text, it is saved with
34543 the message, and made available in the variable &$local_scan_data$&. No
34544 newlines are permitted (if there are any, they are turned into spaces) and the
34545 maximum length of text is 1000 characters.
34547 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
34548 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34549 queued without immediate delivery, and is frozen.
34551 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
34552 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34553 queued without immediate delivery.
34555 .vitem &`LOCAL_SCAN_REJECT`&
34556 The message is rejected; the returned text is used as an error message which is
34557 passed back to the sender and which is also logged. Newlines are permitted &--
34558 they cause a multiline response for SMTP rejections, but are converted to
34559 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
34562 .vitem &`LOCAL_SCAN_TEMPREJECT`&
34563 The message is temporarily rejected; the returned text is used as an error
34564 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
34567 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
34568 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
34569 message is not written to the reject log. It has the effect of unsetting the
34570 &%rejected_header%& log selector for just this rejection. If
34571 &%rejected_header%& is already unset (see the discussion of the
34572 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
34573 same as LOCAL_SCAN_REJECT.
34575 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
34576 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
34577 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
34580 If the message is not being received by interactive SMTP, rejections are
34581 reported by writing to &%stderr%& or by sending an email, as configured by the
34582 &%-oe%& command line options.
34586 .section "Configuration options for local_scan()" "SECTconoptloc"
34587 .cindex "&[local_scan()]& function" "configuration options"
34588 It is possible to have option settings in the main configuration file
34589 that set values in static variables in the &[local_scan()]& module. If you
34590 want to do this, you must have the line
34592 LOCAL_SCAN_HAS_OPTIONS=yes
34594 in your &_Local/Makefile_& when you build Exim. (This line is in
34595 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
34596 file, you must define static variables to hold the option values, and a table
34599 The table must be a vector called &%local_scan_options%&, of type
34600 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
34601 and a pointer to the variable that holds the value. The entries must appear in
34602 alphabetical order. Following &%local_scan_options%& you must also define a
34603 variable called &%local_scan_options_count%& that contains the number of
34604 entries in the table. Here is a short example, showing two kinds of option:
34606 static int my_integer_option = 42;
34607 static uschar *my_string_option = US"a default string";
34609 optionlist local_scan_options[] = {
34610 { "my_integer", opt_int, &my_integer_option },
34611 { "my_string", opt_stringptr, &my_string_option }
34614 int local_scan_options_count =
34615 sizeof(local_scan_options)/sizeof(optionlist);
34617 The values of the variables can now be changed from Exim's runtime
34618 configuration file by including a local scan section as in this example:
34622 my_string = some string of text...
34624 The available types of option data are as follows:
34627 .vitem &*opt_bool*&
34628 This specifies a boolean (true/false) option. The address should point to a
34629 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
34630 that are defined as &"1"& and &"0"&, respectively. If you want to detect
34631 whether such a variable has been set at all, you can initialize it to
34632 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
34635 .vitem &*opt_fixed*&
34636 This specifies a fixed point number, such as is used for load averages.
34637 The address should point to a variable of type &`int`&. The value is stored
34638 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
34641 This specifies an integer; the address should point to a variable of type
34642 &`int`&. The value may be specified in any of the integer formats accepted by
34645 .vitem &*opt_mkint*&
34646 This is the same as &%opt_int%&, except that when such a value is output in a
34647 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
34648 printed with the suffix K or M.
34650 .vitem &*opt_octint*&
34651 This also specifies an integer, but the value is always interpreted as an
34652 octal integer, whether or not it starts with the digit zero, and it is
34653 always output in octal.
34655 .vitem &*opt_stringptr*&
34656 This specifies a string value; the address must be a pointer to a
34657 variable that points to a string (for example, of type &`uschar *`&).
34659 .vitem &*opt_time*&
34660 This specifies a time interval value. The address must point to a variable of
34661 type &`int`&. The value that is placed there is a number of seconds.
34664 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
34665 out the values of all the &[local_scan()]& options.
34669 .section "Available Exim variables" "SECID208"
34670 .cindex "&[local_scan()]& function" "available Exim variables"
34671 The header &_local_scan.h_& gives you access to a number of C variables. These
34672 are the only ones that are guaranteed to be maintained from release to release.
34673 Note, however, that you can obtain the value of any Exim expansion variable,
34674 including &$recipients$&, by calling &'expand_string()'&. The exported
34675 C variables are as follows:
34678 .vitem &*int&~body_linecount*&
34679 This variable contains the number of lines in the message's body.
34680 It is not valid if the &%spool_files_wireformat%& option is used.
34682 .vitem &*int&~body_zerocount*&
34683 This variable contains the number of binary zero bytes in the message's body.
34684 It is not valid if the &%spool_files_wireformat%& option is used.
34686 .vitem &*unsigned&~int&~debug_selector*&
34687 This variable is set to zero when no debugging is taking place. Otherwise, it
34688 is a bitmap of debugging selectors. Two bits are identified for use in
34689 &[local_scan()]&; they are defined as macros:
34692 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
34693 testing option that is not privileged &-- any caller may set it. All the
34694 other selector bits can be set only by admin users.
34697 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
34698 by the &`+local_scan`& debug selector. It is not included in the default set
34702 Thus, to write to the debugging output only when &`+local_scan`& has been
34703 selected, you should use code like this:
34705 if ((debug_selector & D_local_scan) != 0)
34706 debug_printf("xxx", ...);
34708 .vitem &*uschar&~*expand_string_message*&
34709 After a failing call to &'expand_string()'& (returned value NULL), the
34710 variable &%expand_string_message%& contains the error message, zero-terminated.
34712 .vitem &*header_line&~*header_list*&
34713 A pointer to a chain of header lines. The &%header_line%& structure is
34716 .vitem &*header_line&~*header_last*&
34717 A pointer to the last of the header lines.
34719 .vitem &*uschar&~*headers_charset*&
34720 The value of the &%headers_charset%& configuration option.
34722 .vitem &*BOOL&~host_checking*&
34723 This variable is TRUE during a host checking session that is initiated by the
34724 &%-bh%& command line option.
34726 .vitem &*uschar&~*interface_address*&
34727 The IP address of the interface that received the message, as a string. This
34728 is NULL for locally submitted messages.
34730 .vitem &*int&~interface_port*&
34731 The port on which this message was received. When testing with the &%-bh%&
34732 command line option, the value of this variable is -1 unless a port has been
34733 specified via the &%-oMi%& option.
34735 .vitem &*uschar&~*message_id*&
34736 This variable contains Exim's message id for the incoming message (the value of
34737 &$message_exim_id$&) as a zero-terminated string.
34739 .vitem &*uschar&~*received_protocol*&
34740 The name of the protocol by which the message was received.
34742 .vitem &*int&~recipients_count*&
34743 The number of accepted recipients.
34745 .vitem &*recipient_item&~*recipients_list*&
34746 .cindex "recipient" "adding in local scan"
34747 .cindex "recipient" "removing in local scan"
34748 The list of accepted recipients, held in a vector of length
34749 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
34750 can add additional recipients by calling &'receive_add_recipient()'& (see
34751 below). You can delete recipients by removing them from the vector and
34752 adjusting the value in &%recipients_count%&. In particular, by setting
34753 &%recipients_count%& to zero you remove all recipients. If you then return the
34754 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
34755 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
34756 and then call &'receive_add_recipient()'& as often as needed.
34758 .vitem &*uschar&~*sender_address*&
34759 The envelope sender address. For bounce messages this is the empty string.
34761 .vitem &*uschar&~*sender_host_address*&
34762 The IP address of the sending host, as a string. This is NULL for
34763 locally-submitted messages.
34765 .vitem &*uschar&~*sender_host_authenticated*&
34766 The name of the authentication mechanism that was used, or NULL if the message
34767 was not received over an authenticated SMTP connection.
34769 .vitem &*uschar&~*sender_host_name*&
34770 The name of the sending host, if known.
34772 .vitem &*int&~sender_host_port*&
34773 The port on the sending host.
34775 .vitem &*BOOL&~smtp_input*&
34776 This variable is TRUE for all SMTP input, including BSMTP.
34778 .vitem &*BOOL&~smtp_batched_input*&
34779 This variable is TRUE for BSMTP input.
34781 .vitem &*int&~store_pool*&
34782 The contents of this variable control which pool of memory is used for new
34783 requests. See section &<<SECTmemhanloc>>& for details.
34787 .section "Structure of header lines" "SECID209"
34788 The &%header_line%& structure contains the members listed below.
34789 You can add additional header lines by calling the &'header_add()'& function
34790 (see below). You can cause header lines to be ignored (deleted) by setting
34795 .vitem &*struct&~header_line&~*next*&
34796 A pointer to the next header line, or NULL for the last line.
34798 .vitem &*int&~type*&
34799 A code identifying certain headers that Exim recognizes. The codes are printing
34800 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
34801 Notice in particular that any header line whose type is * is not transmitted
34802 with the message. This flagging is used for header lines that have been
34803 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
34804 lines.) Effectively, * means &"deleted"&.
34806 .vitem &*int&~slen*&
34807 The number of characters in the header line, including the terminating and any
34810 .vitem &*uschar&~*text*&
34811 A pointer to the text of the header. It always ends with a newline, followed by
34812 a zero byte. Internal newlines are preserved.
34817 .section "Structure of recipient items" "SECID210"
34818 The &%recipient_item%& structure contains these members:
34821 .vitem &*uschar&~*address*&
34822 This is a pointer to the recipient address as it was received.
34824 .vitem &*int&~pno*&
34825 This is used in later Exim processing when top level addresses are created by
34826 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
34827 and must always contain -1 at this stage.
34829 .vitem &*uschar&~*errors_to*&
34830 If this value is not NULL, bounce messages caused by failing to deliver to the
34831 recipient are sent to the address it contains. In other words, it overrides the
34832 envelope sender for this one recipient. (Compare the &%errors_to%& generic
34833 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
34834 an unqualified address, Exim qualifies it using the domain from
34835 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
34836 is NULL for all recipients.
34841 .section "Available Exim functions" "SECID211"
34842 .cindex "&[local_scan()]& function" "available Exim functions"
34843 The header &_local_scan.h_& gives you access to a number of Exim functions.
34844 These are the only ones that are guaranteed to be maintained from release to
34848 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
34849 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
34851 This function creates a child process that runs the command specified by
34852 &%argv%&. The environment for the process is specified by &%envp%&, which can
34853 be NULL if no environment variables are to be passed. A new umask is supplied
34854 for the process in &%newumask%&.
34856 Pipes to the standard input and output of the new process are set up
34857 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
34858 standard error is cloned to the standard output. If there are any file
34859 descriptors &"in the way"& in the new process, they are closed. If the final
34860 argument is TRUE, the new process is made into a process group leader.
34862 The function returns the pid of the new process, or -1 if things go wrong.
34864 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
34865 This function waits for a child process to terminate, or for a timeout (in
34866 seconds) to expire. A timeout value of zero means wait as long as it takes. The
34867 return value is as follows:
34872 The process terminated by a normal exit and the value is the process
34878 The process was terminated by a signal and the value is the negation of the
34884 The process timed out.
34888 The was some other error in wait(); &%errno%& is still set.
34891 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
34892 This function provide you with a means of submitting a new message to
34893 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
34894 want, but this packages it all up for you.) The function creates a pipe,
34895 forks a subprocess that is running
34897 exim -t -oem -oi -f <>
34899 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
34900 that is connected to the standard input. The yield of the function is the PID
34901 of the subprocess. You can then write a message to the file descriptor, with
34902 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
34904 When you have finished, call &'child_close()'& to wait for the process to
34905 finish and to collect its ending status. A timeout value of zero is usually
34906 fine in this circumstance. Unless you have made a mistake with the recipient
34907 addresses, you should get a return code of zero.
34910 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
34911 *sender_authentication)*&
34912 This function is a more sophisticated version of &'child_open()'&. The command
34915 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
34917 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
34920 .vitem &*void&~debug_printf(char&~*,&~...)*&
34921 This is Exim's debugging function, with arguments as for &'(printf()'&. The
34922 output is written to the standard error stream. If no debugging is selected,
34923 calls to &'debug_printf()'& have no effect. Normally, you should make calls
34924 conditional on the &`local_scan`& debug selector by coding like this:
34926 if ((debug_selector & D_local_scan) != 0)
34927 debug_printf("xxx", ...);
34930 .vitem &*uschar&~*expand_string(uschar&~*string)*&
34931 This is an interface to Exim's string expansion code. The return value is the
34932 expanded string, or NULL if there was an expansion failure.
34933 The C variable &%expand_string_message%& contains an error message after an
34934 expansion failure. If expansion does not change the string, the return value is
34935 the pointer to the input string. Otherwise, the return value points to a new
34936 block of memory that was obtained by a call to &'store_get()'&. See section
34937 &<<SECTmemhanloc>>& below for a discussion of memory handling.
34939 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
34940 This function allows you to an add additional header line at the end of the
34941 existing ones. The first argument is the type, and should normally be a space
34942 character. The second argument is a format string and any number of
34943 substitution arguments as for &[sprintf()]&. You may include internal newlines
34944 if you want, and you must ensure that the string ends with a newline.
34946 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
34947 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
34948 This function adds a new header line at a specified point in the header
34949 chain. The header itself is specified as for &'header_add()'&.
34951 If &%name%& is NULL, the new header is added at the end of the chain if
34952 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
34953 NULL, the header lines are searched for the first non-deleted header that
34954 matches the name. If one is found, the new header is added before it if
34955 &%after%& is false. If &%after%& is true, the new header is added after the
34956 found header and any adjacent subsequent ones with the same name (even if
34957 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
34958 option controls where the header is added. If it is true, addition is at the
34959 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
34960 headers, or at the top if there are no &'Received:'& headers, you could use
34962 header_add_at_position(TRUE, US"Received", TRUE,
34963 ' ', "X-xxx: ...");
34965 Normally, there is always at least one non-deleted &'Received:'& header, but
34966 there may not be if &%received_header_text%& expands to an empty string.
34969 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
34970 This function removes header lines. If &%occurrence%& is zero or negative, all
34971 occurrences of the header are removed. If occurrence is greater than zero, that
34972 particular instance of the header is removed. If no header(s) can be found that
34973 match the specification, the function does nothing.
34976 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
34977 int&~length,&~BOOL&~notdel)*&"
34978 This function tests whether the given header has the given name. It is not just
34979 a string comparison, because white space is permitted between the name and the
34980 colon. If the &%notdel%& argument is true, a false return is forced for all
34981 &"deleted"& headers; otherwise they are not treated specially. For example:
34983 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
34985 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
34986 .cindex "base64 encoding" "functions for &[local_scan()]& use"
34987 This function base64-encodes a string, which is passed by address and length.
34988 The text may contain bytes of any value, including zero. The result is passed
34989 back in dynamic memory that is obtained by calling &'store_get()'&. It is
34992 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
34993 This function decodes a base64-encoded string. Its arguments are a
34994 zero-terminated base64-encoded string and the address of a variable that is set
34995 to point to the result, which is in dynamic memory. The length of the decoded
34996 string is the yield of the function. If the input is invalid base64 data, the
34997 yield is -1. A zero byte is added to the end of the output string to make it
34998 easy to interpret as a C string (assuming it contains no zeros of its own). The
34999 added zero byte is not included in the returned count.
35001 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35002 This function checks for a match in a domain list. Domains are always
35003 matched caselessly. The return value is one of the following:
35005 &`OK `& match succeeded
35006 &`FAIL `& match failed
35007 &`DEFER `& match deferred
35009 DEFER is usually caused by some kind of lookup defer, such as the
35010 inability to contact a database.
35012 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35014 This function checks for a match in a local part list. The third argument
35015 controls case-sensitivity. The return values are as for
35016 &'lss_match_domain()'&.
35018 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35020 This function checks for a match in an address list. The third argument
35021 controls the case-sensitivity of the local part match. The domain is always
35022 matched caselessly. The return values are as for &'lss_match_domain()'&.
35024 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35026 This function checks for a match in a host list. The most common usage is
35029 lss_match_host(sender_host_name, sender_host_address, ...)
35031 .vindex "&$sender_host_address$&"
35032 An empty address field matches an empty item in the host list. If the host name
35033 is NULL, the name corresponding to &$sender_host_address$& is automatically
35034 looked up if a host name is required to match an item in the list. The return
35035 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35036 returns ERROR in the case when it had to look up a host name, but the lookup
35039 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35041 This function writes to Exim's log files. The first argument should be zero (it
35042 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35043 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35044 them. It specifies to which log or logs the message is written. The remaining
35045 arguments are a format and relevant insertion arguments. The string should not
35046 contain any newlines, not even at the end.
35049 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35050 This function adds an additional recipient to the message. The first argument
35051 is the recipient address. If it is unqualified (has no domain), it is qualified
35052 with the &%qualify_recipient%& domain. The second argument must always be -1.
35054 This function does not allow you to specify a private &%errors_to%& address (as
35055 described with the structure of &%recipient_item%& above), because it pre-dates
35056 the addition of that field to the structure. However, it is easy to add such a
35057 value afterwards. For example:
35059 receive_add_recipient(US"monitor@mydom.example", -1);
35060 recipients_list[recipients_count-1].errors_to =
35061 US"postmaster@mydom.example";
35064 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35065 This is a convenience function to remove a named recipient from the list of
35066 recipients. It returns true if a recipient was removed, and false if no
35067 matching recipient could be found. The argument must be a complete email
35074 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35075 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35076 This function decodes strings that are encoded according to RFC 2047. Typically
35077 these are the contents of header lines. First, each &"encoded word"& is decoded
35078 from the Q or B encoding into a byte-string. Then, if provided with the name of
35079 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35080 made to translate the result to the named character set. If this fails, the
35081 binary string is returned with an error message.
35083 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35084 maximum MIME word length is enforced. The third argument is the target
35085 encoding, or NULL if no translation is wanted.
35087 .cindex "binary zero" "in RFC 2047 decoding"
35088 .cindex "RFC 2047" "binary zero in"
35089 If a binary zero is encountered in the decoded string, it is replaced by the
35090 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35091 not be 0 because header lines are handled as zero-terminated strings.
35093 The function returns the result of processing the string, zero-terminated; if
35094 &%lenptr%& is not NULL, the length of the result is set in the variable to
35095 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35097 If an error is encountered, the function returns NULL and uses the &%error%&
35098 argument to return an error message. The variable pointed to by &%error%& is
35099 set to NULL if there is no error; it may be set non-NULL even when the function
35100 returns a non-NULL value if decoding was successful, but there was a problem
35104 .vitem &*int&~smtp_fflush(void)*&
35105 This function is used in conjunction with &'smtp_printf()'&, as described
35108 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35109 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35110 output stream. You should use this function only when there is an SMTP output
35111 stream, that is, when the incoming message is being received via interactive
35112 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35113 is FALSE. If you want to test for an incoming message from another host (as
35114 opposed to a local process that used the &%-bs%& command line option), you can
35115 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35118 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35119 output function, so it can be used for all forms of SMTP connection.
35121 The second argument is used to request that the data be buffered
35122 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35123 This is advisory only, but likely to save on system-calls and packets
35124 sent when a sequence of calls to the function are made.
35126 The argument was added in Exim version 4.90 - changing the API/ABI.
35127 Nobody noticed until 4.93 was imminent, at which point the
35128 ABI version number was incremented.
35130 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35131 must start with an appropriate response code: 550 if you are going to return
35132 LOCAL_SCAN_REJECT, 451 if you are going to return
35133 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35134 initial lines of a multi-line response, the code must be followed by a hyphen
35135 to indicate that the line is not the final response line. You must also ensure
35136 that the lines you write terminate with CRLF. For example:
35138 smtp_printf("550-this is some extra info\r\n");
35139 return LOCAL_SCAN_REJECT;
35141 Note that you can also create multi-line responses by including newlines in
35142 the data returned via the &%return_text%& argument. The added value of using
35143 &'smtp_printf()'& is that, for instance, you could introduce delays between
35144 multiple output lines.
35146 The &'smtp_printf()'& function does not return any error indication, because it
35148 guarantee a flush of
35149 pending output, and therefore does not test
35150 the state of the stream. (In the main code of Exim, flushing and error
35151 detection is done when Exim is ready for the next SMTP input command.) If
35152 you want to flush the output and check for an error (for example, the
35153 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35154 arguments. It flushes the output stream, and returns a non-zero value if there
35158 .vitem &*void&~*store_get(int,BOOL)*&
35159 This function accesses Exim's internal store (memory) manager. It gets a new
35160 chunk of memory whose size is given by the first argument.
35161 The second argument should be given as TRUE if the memory will be used for
35162 data possibly coming from an attacker (eg. the message content),
35163 FALSE if it is locally-sourced.
35164 Exim bombs out if it ever
35165 runs out of memory. See the next section for a discussion of memory handling.
35168 .vitem &*void&~*store_get_perm(int,BOOL)*&
35169 This function is like &'store_get()'&, but it always gets memory from the
35170 permanent pool. See the next section for a discussion of memory handling.
35172 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35175 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35178 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35179 These three functions create strings using Exim's dynamic memory facilities.
35180 The first makes a copy of an entire string. The second copies up to a maximum
35181 number of characters, indicated by the second argument. The third uses a format
35182 and insertion arguments to create a new string. In each case, the result is a
35183 pointer to a new string in the current memory pool. See the next section for
35189 .section "More about Exim's memory handling" "SECTmemhanloc"
35190 .cindex "&[local_scan()]& function" "memory handling"
35191 No function is provided for freeing memory, because that is never needed.
35192 The dynamic memory that Exim uses when receiving a message is automatically
35193 recycled if another message is received by the same process (this applies only
35194 to incoming SMTP connections &-- other input methods can supply only one
35195 message at a time). After receiving the last message, a reception process
35198 Because it is recycled, the normal dynamic memory cannot be used for holding
35199 data that must be preserved over a number of incoming messages on the same SMTP
35200 connection. However, Exim in fact uses two pools of dynamic memory; the second
35201 one is not recycled, and can be used for this purpose.
35203 If you want to allocate memory that remains available for subsequent messages
35204 in the same SMTP connection, you should set
35206 store_pool = POOL_PERM
35208 before calling the function that does the allocation. There is no need to
35209 restore the value if you do not need to; however, if you do want to revert to
35210 the normal pool, you can either restore the previous value of &%store_pool%& or
35211 set it explicitly to POOL_MAIN.
35213 The pool setting applies to all functions that get dynamic memory, including
35214 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35215 There is also a convenience function called &'store_get_perm()'& that gets a
35216 block of memory from the permanent pool while preserving the value of
35223 . ////////////////////////////////////////////////////////////////////////////
35224 . ////////////////////////////////////////////////////////////////////////////
35226 .chapter "System-wide message filtering" "CHAPsystemfilter"
35227 .scindex IIDsysfil1 "filter" "system filter"
35228 .scindex IIDsysfil2 "filtering all mail"
35229 .scindex IIDsysfil3 "system filter"
35230 The previous chapters (on ACLs and the local scan function) describe checks
35231 that can be applied to messages before they are accepted by a host. There is
35232 also a mechanism for checking messages once they have been received, but before
35233 they are delivered. This is called the &'system filter'&.
35235 The system filter operates in a similar manner to users' filter files, but it
35236 is run just once per message (however many recipients the message has).
35237 It should not normally be used as a substitute for routing, because &%deliver%&
35238 commands in a system router provide new envelope recipient addresses.
35239 The system filter must be an Exim filter. It cannot be a Sieve filter.
35241 The system filter is run at the start of a delivery attempt, before any routing
35242 is done. If a message fails to be completely delivered at the first attempt,
35243 the system filter is run again at the start of every retry.
35244 If you want your filter to do something only once per message, you can make use
35245 of the &%first_delivery%& condition in an &%if%& command in the filter to
35246 prevent it happening on retries.
35248 .vindex "&$domain$&"
35249 .vindex "&$local_part$&"
35250 &*Warning*&: Because the system filter runs just once, variables that are
35251 specific to individual recipient addresses, such as &$local_part$& and
35252 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35253 you want to run a centrally-specified filter for each recipient address
35254 independently, you can do so by setting up a suitable &(redirect)& router, as
35255 described in section &<<SECTperaddfil>>& below.
35258 .section "Specifying a system filter" "SECID212"
35259 .cindex "uid (user id)" "system filter"
35260 .cindex "gid (group id)" "system filter"
35261 The name of the file that contains the system filter must be specified by
35262 setting &%system_filter%&. If you want the filter to run under a uid and gid
35263 other than root, you must also set &%system_filter_user%& and
35264 &%system_filter_group%& as appropriate. For example:
35266 system_filter = /etc/mail/exim.filter
35267 system_filter_user = exim
35269 If a system filter generates any deliveries directly to files or pipes (via the
35270 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35271 specified by setting &%system_filter_file_transport%& and
35272 &%system_filter_pipe_transport%&, respectively. Similarly,
35273 &%system_filter_reply_transport%& must be set to handle any messages generated
35274 by the &%reply%& command.
35277 .section "Testing a system filter" "SECID213"
35278 You can run simple tests of a system filter in the same way as for a user
35279 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35280 are permitted only in system filters are recognized.
35282 If you want to test the combined effect of a system filter and a user filter,
35283 you can use both &%-bF%& and &%-bf%& on the same command line.
35287 .section "Contents of a system filter" "SECID214"
35288 The language used to specify system filters is the same as for users' filter
35289 files. It is described in the separate end-user document &'Exim's interface to
35290 mail filtering'&. However, there are some additional features that are
35291 available only in system filters; these are described in subsequent sections.
35292 If they are encountered in a user's filter file or when testing with &%-bf%&,
35295 .cindex "frozen messages" "manual thaw; testing in filter"
35296 There are two special conditions which, though available in users' filter
35297 files, are designed for use in system filters. The condition &%first_delivery%&
35298 is true only for the first attempt at delivering a message, and
35299 &%manually_thawed%& is true only if the message has been frozen, and
35300 subsequently thawed by an admin user. An explicit forced delivery counts as a
35301 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35303 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35304 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35305 succeed, it will not be tried again.
35306 If you want Exim to retry an unseen delivery until it succeeds, you should
35307 arrange to set it up every time the filter runs.
35309 When a system filter finishes running, the values of the variables &$n0$& &--
35310 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35311 users' filter files. Thus a system filter can, for example, set up &"scores"&
35312 to which users' filter files can refer.
35316 .section "Additional variable for system filters" "SECID215"
35317 .vindex "&$recipients$&"
35318 The expansion variable &$recipients$&, containing a list of all the recipients
35319 of the message (separated by commas and white space), is available in system
35320 filters. It is not available in users' filters for privacy reasons.
35324 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35325 .cindex "freezing messages"
35326 .cindex "message" "freezing"
35327 .cindex "message" "forced failure"
35328 .cindex "&%fail%&" "in system filter"
35329 .cindex "&%freeze%& in system filter"
35330 .cindex "&%defer%& in system filter"
35331 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35332 always available in system filters, but are not normally enabled in users'
35333 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35334 for the &(redirect)& router.) These commands can optionally be followed by the
35335 word &%text%& and a string containing an error message, for example:
35337 fail text "this message looks like spam to me"
35339 The keyword &%text%& is optional if the next character is a double quote.
35341 The &%defer%& command defers delivery of the original recipients of the
35342 message. The &%fail%& command causes all the original recipients to be failed,
35343 and a bounce message to be created. The &%freeze%& command suspends all
35344 delivery attempts for the original recipients. In all cases, any new deliveries
35345 that are specified by the filter are attempted as normal after the filter has
35348 The &%freeze%& command is ignored if the message has been manually unfrozen and
35349 not manually frozen since. This means that automatic freezing by a system
35350 filter can be used as a way of checking out suspicious messages. If a message
35351 is found to be all right, manually unfreezing it allows it to be delivered.
35353 .cindex "log" "&%fail%& command log line"
35354 .cindex "&%fail%&" "log line; reducing"
35355 The text given with a fail command is used as part of the bounce message as
35356 well as being written to the log. If the message is quite long, this can fill
35357 up a lot of log space when such failures are common. To reduce the size of the
35358 log message, Exim interprets the text in a special way if it starts with the
35359 two characters &`<<`& and contains &`>>`& later. The text between these two
35360 strings is written to the log, and the rest of the text is used in the bounce
35361 message. For example:
35363 fail "<<filter test 1>>Your message is rejected \
35364 because it contains attachments that we are \
35365 not prepared to receive."
35368 .cindex "loop" "caused by &%fail%&"
35369 Take great care with the &%fail%& command when basing the decision to fail on
35370 the contents of the message, because the bounce message will of course include
35371 the contents of the original message and will therefore trigger the &%fail%&
35372 command again (causing a mail loop) unless steps are taken to prevent this.
35373 Testing the &%error_message%& condition is one way to prevent this. You could
35376 if $message_body contains "this is spam" and not error_message
35377 then fail text "spam is not wanted here" endif
35379 though of course that might let through unwanted bounce messages. The
35380 alternative is clever checking of the body and/or headers to detect bounces
35381 generated by the filter.
35383 The interpretation of a system filter file ceases after a
35385 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35386 set up earlier in the filter file are honoured, so you can use a sequence such
35392 to send a specified message when the system filter is freezing (or deferring or
35393 failing) a message. The normal deliveries for the message do not, of course,
35398 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35399 .cindex "header lines" "adding; in system filter"
35400 .cindex "header lines" "removing; in system filter"
35401 .cindex "filter" "header lines; adding/removing"
35402 Two filter commands that are available only in system filters are:
35404 headers add <string>
35405 headers remove <string>
35407 The argument for the &%headers add%& is a string that is expanded and then
35408 added to the end of the message's headers. It is the responsibility of the
35409 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35410 space is ignored, and if the string is otherwise empty, or if the expansion is
35411 forced to fail, the command has no effect.
35413 You can use &"\n"& within the string, followed by white space, to specify
35414 continued header lines. More than one header may be added in one command by
35415 including &"\n"& within the string without any following white space. For
35418 headers add "X-header-1: ....\n \
35419 continuation of X-header-1 ...\n\
35422 Note that the header line continuation white space after the first newline must
35423 be placed before the backslash that continues the input string, because white
35424 space after input continuations is ignored.
35426 The argument for &%headers remove%& is a colon-separated list of header names.
35427 This command applies only to those headers that are stored with the message;
35428 those that are added at delivery time (such as &'Envelope-To:'& and
35429 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35430 header with the same name, they are all removed.
35432 The &%headers%& command in a system filter makes an immediate change to the set
35433 of header lines that was received with the message (with possible additions
35434 from ACL processing). Subsequent commands in the system filter operate on the
35435 modified set, which also forms the basis for subsequent message delivery.
35436 Unless further modified during routing or transporting, this set of headers is
35437 used for all recipients of the message.
35439 During routing and transporting, the variables that refer to the contents of
35440 header lines refer only to those lines that are in this set. Thus, header lines
35441 that are added by a system filter are visible to users' filter files and to all
35442 routers and transports. This contrasts with the manipulation of header lines by
35443 routers and transports, which is not immediate, but which instead is saved up
35444 until the message is actually being written (see section
35445 &<<SECTheadersaddrem>>&).
35447 If the message is not delivered at the first attempt, header lines that were
35448 added by the system filter are stored with the message, and so are still
35449 present at the next delivery attempt. Header lines that were removed are still
35450 present, but marked &"deleted"& so that they are not transported with the
35451 message. For this reason, it is usual to make the &%headers%& command
35452 conditional on &%first_delivery%& so that the set of header lines is not
35453 modified more than once.
35455 Because header modification in a system filter acts immediately, you have to
35456 use an indirect approach if you want to modify the contents of a header line.
35459 headers add "Old-Subject: $h_subject:"
35460 headers remove "Subject"
35461 headers add "Subject: new subject (was: $h_old-subject:)"
35462 headers remove "Old-Subject"
35467 .section "Setting an errors address in a system filter" "SECID217"
35468 .cindex "envelope from"
35469 .cindex "envelope sender"
35470 In a system filter, if a &%deliver%& command is followed by
35472 errors_to <some address>
35474 in order to change the envelope sender (and hence the error reporting) for that
35475 delivery, any address may be specified. (In a user filter, only the current
35476 user's address can be set.) For example, if some mail is being monitored, you
35479 unseen deliver monitor@spying.example errors_to root@local.example
35481 to take a copy which would not be sent back to the normal error reporting
35482 address if its delivery failed.
35486 .section "Per-address filtering" "SECTperaddfil"
35487 .vindex "&$domain$&"
35488 .vindex "&$local_part$&"
35489 In contrast to the system filter, which is run just once per message for each
35490 delivery attempt, it is also possible to set up a system-wide filtering
35491 operation that runs once for each recipient address. In this case, variables
35492 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
35493 filter file could be made dependent on them. This is an example of a router
35494 which implements such a filter:
35499 domains = +local_domains
35500 file = /central/filters/$local_part_data
35505 The filter is run in a separate process under its own uid. Therefore, either
35506 &%check_local_user%& must be set (as above), in which case the filter is run as
35507 the local user, or the &%user%& option must be used to specify which user to
35508 use. If both are set, &%user%& overrides.
35510 Care should be taken to ensure that none of the commands in the filter file
35511 specify a significant delivery if the message is to go on to be delivered to
35512 its intended recipient. The router will not then claim to have dealt with the
35513 address, so it will be passed on to subsequent routers to be delivered in the
35515 .ecindex IIDsysfil1
35516 .ecindex IIDsysfil2
35517 .ecindex IIDsysfil3
35524 . ////////////////////////////////////////////////////////////////////////////
35525 . ////////////////////////////////////////////////////////////////////////////
35527 .chapter "Message processing" "CHAPmsgproc"
35528 .scindex IIDmesproc "message" "general processing"
35529 Exim performs various transformations on the sender and recipient addresses of
35530 all messages that it handles, and also on the messages' header lines. Some of
35531 these are optional and configurable, while others always take place. All of
35532 this processing, except rewriting as a result of routing, and the addition or
35533 removal of header lines while delivering, happens when a message is received,
35534 before it is placed on Exim's queue.
35536 Some of the automatic processing takes place by default only for
35537 &"locally-originated"& messages. This adjective is used to describe messages
35538 that are not received over TCP/IP, but instead are passed to an Exim process on
35539 its standard input. This includes the interactive &"local SMTP"& case that is
35540 set up by the &%-bs%& command line option.
35542 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
35543 or ::1) are not considered to be locally-originated. Exim does not treat the
35544 loopback interface specially in any way.
35546 If you want the loopback interface to be treated specially, you must ensure
35547 that there are appropriate entries in your ACLs.
35552 .section "Submission mode for non-local messages" "SECTsubmodnon"
35553 .cindex "message" "submission"
35554 .cindex "submission mode"
35555 Processing that happens automatically for locally-originated messages (unless
35556 &%suppress_local_fixups%& is set) can also be requested for messages that are
35557 received over TCP/IP. The term &"submission mode"& is used to describe this
35558 state. Submission mode is set by the modifier
35560 control = submission
35562 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
35563 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
35564 a local submission, and is normally used when the source of the message is
35565 known to be an MUA running on a client host (as opposed to an MTA). For
35566 example, to set submission mode for messages originating on the IPv4 loopback
35567 interface, you could include the following in the MAIL ACL:
35569 warn hosts = 127.0.0.1
35570 control = submission
35572 .cindex "&%sender_retain%& submission option"
35573 There are some options that can be used when setting submission mode. A slash
35574 is used to separate options. For example:
35576 control = submission/sender_retain
35578 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
35579 true and &%local_from_check%& false for the current incoming message. The first
35580 of these allows an existing &'Sender:'& header in the message to remain, and
35581 the second suppresses the check to ensure that &'From:'& matches the
35582 authenticated sender. With this setting, Exim still fixes up messages by adding
35583 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
35584 attempt to check sender authenticity in header lines.
35586 When &%sender_retain%& is not set, a submission mode setting may specify a
35587 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
35590 control = submission/domain=some.domain
35592 The domain may be empty. How this value is used is described in sections
35593 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
35594 that allows you to specify the user's full name for inclusion in a created
35595 &'Sender:'& or &'From:'& header line. For example:
35597 accept authenticated = *
35598 control = submission/domain=wonderland.example/\
35599 name=${lookup {$authenticated_id} \
35600 lsearch {/etc/exim/namelist}}
35602 Because the name may contain any characters, including slashes, the &%name%&
35603 option must be given last. The remainder of the string is used as the name. For
35604 the example above, if &_/etc/exim/namelist_& contains:
35606 bigegg: Humpty Dumpty
35608 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
35611 Sender: Humpty Dumpty <bigegg@wonderland.example>
35613 .cindex "return path" "in submission mode"
35614 By default, submission mode forces the return path to the same address as is
35615 used to create the &'Sender:'& header. However, if &%sender_retain%& is
35616 specified, the return path is also left unchanged.
35618 &*Note*&: The changes caused by submission mode take effect after the predata
35619 ACL. This means that any sender checks performed before the fix-ups use the
35620 untrusted sender address specified by the user, not the trusted sender address
35621 specified by submission mode. Although this might be slightly unexpected, it
35622 does mean that you can configure ACL checks to spot that a user is trying to
35623 spoof another's address.
35625 .section "Line endings" "SECTlineendings"
35626 .cindex "line endings"
35627 .cindex "carriage return"
35629 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
35630 linefeed) is the line ending for messages transmitted over the Internet using
35631 SMTP over TCP/IP. However, within individual operating systems, different
35632 conventions are used. For example, Unix-like systems use just LF, but others
35633 use CRLF or just CR.
35635 Exim was designed for Unix-like systems, and internally, it stores messages
35636 using the system's convention of a single LF as a line terminator. When
35637 receiving a message, all line endings are translated to this standard format.
35638 Originally, it was thought that programs that passed messages directly to an
35639 MTA within an operating system would use that system's convention. Experience
35640 has shown that this is not the case; for example, there are Unix applications
35641 that use CRLF in this circumstance. For this reason, and for compatibility with
35642 other MTAs, the way Exim handles line endings for all messages is now as
35646 LF not preceded by CR is treated as a line ending.
35648 CR is treated as a line ending; if it is immediately followed by LF, the LF
35651 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
35652 nor a local message in the state where a line containing only a dot is a
35655 If a bare CR is encountered within a header line, an extra space is added after
35656 the line terminator so as not to end the header line. The reasoning behind this
35657 is that bare CRs in header lines are most likely either to be mistakes, or
35658 people trying to play silly games.
35660 If the first header line received in a message ends with CRLF, a subsequent
35661 bare LF in a header line is treated in the same way as a bare CR in a header
35669 .section "Unqualified addresses" "SECID218"
35670 .cindex "unqualified addresses"
35671 .cindex "address" "qualification"
35672 By default, Exim expects every envelope address it receives from an external
35673 host to be fully qualified. Unqualified addresses cause negative responses to
35674 SMTP commands. However, because SMTP is used as a means of transporting
35675 messages from MUAs running on personal workstations, there is sometimes a
35676 requirement to accept unqualified addresses from specific hosts or IP networks.
35678 Exim has two options that separately control which hosts may send unqualified
35679 sender or recipient addresses in SMTP commands, namely
35680 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
35681 cases, if an unqualified address is accepted, it is qualified by adding the
35682 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
35684 .oindex "&%qualify_domain%&"
35685 .oindex "&%qualify_recipient%&"
35686 Unqualified addresses in header lines are automatically qualified for messages
35687 that are locally originated, unless the &%-bnq%& option is given on the command
35688 line. For messages received over SMTP, unqualified addresses in header lines
35689 are qualified only if unqualified addresses are permitted in SMTP commands. In
35690 other words, such qualification is also controlled by
35691 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
35696 .section "The UUCP From line" "SECID219"
35697 .cindex "&""From""& line"
35698 .cindex "UUCP" "&""From""& line"
35699 .cindex "sender" "address"
35700 .oindex "&%uucp_from_pattern%&"
35701 .oindex "&%uucp_from_sender%&"
35702 .cindex "envelope from"
35703 .cindex "envelope sender"
35704 .cindex "Sendmail compatibility" "&""From""& line"
35705 Messages that have come from UUCP (and some other applications) often begin
35706 with a line containing the envelope sender and a timestamp, following the word
35707 &"From"&. Examples of two common formats are:
35709 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
35710 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
35712 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
35713 Exim recognizes such lines at the start of messages that are submitted to it
35714 via the command line (that is, on the standard input). It does not recognize
35715 such lines in incoming SMTP messages, unless the sending host matches
35716 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
35717 and &%ignore_fromline_local%& is set. The recognition is controlled by a
35718 regular expression that is defined by the &%uucp_from_pattern%& option, whose
35719 default value matches the two common cases shown above and puts the address
35720 that follows &"From"& into &$1$&.
35722 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
35723 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
35724 a trusted user, the message's sender address is constructed by expanding the
35725 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
35726 then parsed as an RFC 2822 address. If there is no domain, the local part is
35727 qualified with &%qualify_domain%& unless it is the empty string. However, if
35728 the command line &%-f%& option is used, it overrides the &"From"& line.
35730 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
35731 sender address is not changed. This is also the case for incoming SMTP messages
35732 that are permitted to contain &"From"& lines.
35734 Only one &"From"& line is recognized. If there is more than one, the second is
35735 treated as a data line that starts the body of the message, as it is not valid
35736 as a header line. This also happens if a &"From"& line is present in an
35737 incoming SMTP message from a source that is not permitted to send them.
35741 .section "Resent- header lines" "SECID220"
35742 .cindex "&%Resent-%& header lines"
35743 .cindex "header lines" "Resent-"
35744 RFC 2822 makes provision for sets of header lines starting with the string
35745 &`Resent-`& to be added to a message when it is resent by the original
35746 recipient to somebody else. These headers are &'Resent-Date:'&,
35747 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
35748 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
35751 &'Resent fields are strictly informational. They MUST NOT be used in the normal
35752 processing of replies or other such automatic actions on messages.'&
35755 This leaves things a bit vague as far as other processing actions such as
35756 address rewriting are concerned. Exim treats &%Resent-%& header lines as
35760 A &'Resent-From:'& line that just contains the login id of the submitting user
35761 is automatically rewritten in the same way as &'From:'& (see below).
35763 If there's a rewriting rule for a particular header line, it is also applied to
35764 &%Resent-%& header lines of the same type. For example, a rule that rewrites
35765 &'From:'& also rewrites &'Resent-From:'&.
35767 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
35770 For a locally-submitted message,
35771 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
35772 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
35773 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
35774 included in log lines in this case.
35776 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
35777 &%Resent-%& header lines are present.
35783 .section "The Auto-Submitted: header line" "SECID221"
35784 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
35785 includes the header line:
35787 Auto-Submitted: auto-replied
35790 .section "The Bcc: header line" "SECID222"
35791 .cindex "&'Bcc:'& header line"
35792 If Exim is called with the &%-t%& option, to take recipient addresses from a
35793 message's header, it removes any &'Bcc:'& header line that may exist (after
35794 extracting its addresses). If &%-t%& is not present on the command line, any
35795 existing &'Bcc:'& is not removed.
35798 .section "The Date: header line" "SECID223"
35799 .cindex "&'Date:'& header line"
35800 .cindex "header lines" "Date:"
35801 If a locally-generated or submission-mode message has no &'Date:'& header line,
35802 Exim adds one, using the current date and time, unless the
35803 &%suppress_local_fixups%& control has been specified.
35805 .section "The Delivery-date: header line" "SECID224"
35806 .cindex "&'Delivery-date:'& header line"
35807 .oindex "&%delivery_date_remove%&"
35808 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
35809 set. Exim can be configured to add them to the final delivery of messages. (See
35810 the generic &%delivery_date_add%& transport option.) They should not be present
35811 in messages in transit. If the &%delivery_date_remove%& configuration option is
35812 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
35816 .section "The Envelope-to: header line" "SECID225"
35817 .cindex "&'Envelope-to:'& header line"
35818 .cindex "header lines" "Envelope-to:"
35819 .oindex "&%envelope_to_remove%&"
35820 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
35821 Exim can be configured to add them to the final delivery of messages. (See the
35822 generic &%envelope_to_add%& transport option.) They should not be present in
35823 messages in transit. If the &%envelope_to_remove%& configuration option is set
35824 (the default), Exim removes &'Envelope-to:'& header lines from incoming
35828 .section "The From: header line" "SECTthefrohea"
35829 .cindex "&'From:'& header line"
35830 .cindex "header lines" "From:"
35831 .cindex "Sendmail compatibility" "&""From""& line"
35832 .cindex "message" "submission"
35833 .cindex "submission mode"
35834 If a submission-mode message does not contain a &'From:'& header line, Exim
35835 adds one if either of the following conditions is true:
35838 The envelope sender address is not empty (that is, this is not a bounce
35839 message). The added header line copies the envelope sender address.
35841 .vindex "&$authenticated_id$&"
35842 The SMTP session is authenticated and &$authenticated_id$& is not empty.
35844 .vindex "&$qualify_domain$&"
35845 If no domain is specified by the submission control, the local part is
35846 &$authenticated_id$& and the domain is &$qualify_domain$&.
35848 If a non-empty domain is specified by the submission control, the local
35849 part is &$authenticated_id$&, and the domain is the specified domain.
35851 If an empty domain is specified by the submission control,
35852 &$authenticated_id$& is assumed to be the complete address.
35856 A non-empty envelope sender takes precedence.
35858 If a locally-generated incoming message does not contain a &'From:'& header
35859 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
35860 containing the sender's address. The calling user's login name and full name
35861 are used to construct the address, as described in section &<<SECTconstr>>&.
35862 They are obtained from the password data by calling &[getpwuid()]& (but see the
35863 &%unknown_login%& configuration option). The address is qualified with
35864 &%qualify_domain%&.
35866 For compatibility with Sendmail, if an incoming, non-SMTP message has a
35867 &'From:'& header line containing just the unqualified login name of the calling
35868 user, this is replaced by an address containing the user's login name and full
35869 name as described in section &<<SECTconstr>>&.
35872 .section "The Message-ID: header line" "SECID226"
35873 .cindex "&'Message-ID:'& header line"
35874 .cindex "header lines" "Message-ID:"
35875 .cindex "message" "submission"
35876 .oindex "&%message_id_header_text%&"
35877 If a locally-generated or submission-mode incoming message does not contain a
35878 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
35879 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
35880 to the message. If there are any &'Resent-:'& headers in the message, it
35881 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
35882 message id, preceded by the letter E to ensure it starts with a letter, and
35883 followed by @ and the primary host name. Additional information can be included
35884 in this header line by setting the &%message_id_header_text%& and/or
35885 &%message_id_header_domain%& options.
35888 .section "The Received: header line" "SECID227"
35889 .cindex "&'Received:'& header line"
35890 .cindex "header lines" "Received:"
35891 A &'Received:'& header line is added at the start of every message. The
35892 contents are defined by the &%received_header_text%& configuration option, and
35893 Exim automatically adds a semicolon and a timestamp to the configured string.
35895 The &'Received:'& header is generated as soon as the message's header lines
35896 have been received. At this stage, the timestamp in the &'Received:'& header
35897 line is the time that the message started to be received. This is the value
35898 that is seen by the DATA ACL and by the &[local_scan()]& function.
35900 Once a message is accepted, the timestamp in the &'Received:'& header line is
35901 changed to the time of acceptance, which is (apart from a small delay while the
35902 -H spool file is written) the earliest time at which delivery could start.
35905 .section "The References: header line" "SECID228"
35906 .cindex "&'References:'& header line"
35907 .cindex "header lines" "References:"
35908 Messages created by the &(autoreply)& transport include a &'References:'&
35909 header line. This is constructed according to the rules that are described in
35910 section 3.64 of RFC 2822 (which states that replies should contain such a
35911 header line), and section 3.14 of RFC 3834 (which states that automatic
35912 responses are not different in this respect). However, because some mail
35913 processing software does not cope well with very long header lines, no more
35914 than 12 message IDs are copied from the &'References:'& header line in the
35915 incoming message. If there are more than 12, the first one and then the final
35916 11 are copied, before adding the message ID of the incoming message.
35920 .section "The Return-path: header line" "SECID229"
35921 .cindex "&'Return-path:'& header line"
35922 .cindex "header lines" "Return-path:"
35923 .oindex "&%return_path_remove%&"
35924 &'Return-path:'& header lines are defined as something an MTA may insert when
35925 it does the final delivery of messages. (See the generic &%return_path_add%&
35926 transport option.) Therefore, they should not be present in messages in
35927 transit. If the &%return_path_remove%& configuration option is set (the
35928 default), Exim removes &'Return-path:'& header lines from incoming messages.
35932 .section "The Sender: header line" "SECTthesenhea"
35933 .cindex "&'Sender:'& header line"
35934 .cindex "message" "submission"
35935 .cindex "header lines" "Sender:"
35936 For a locally-originated message from an untrusted user, Exim may remove an
35937 existing &'Sender:'& header line, and it may add a new one. You can modify
35938 these actions by setting the &%local_sender_retain%& option true, the
35939 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
35942 When a local message is received from an untrusted user and
35943 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
35944 control has not been set, a check is made to see if the address given in the
35945 &'From:'& header line is the correct (local) sender of the message. The address
35946 that is expected has the login name as the local part and the value of
35947 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
35948 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
35949 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
35950 line is added to the message.
35952 If you set &%local_from_check%& false, this checking does not occur. However,
35953 the removal of an existing &'Sender:'& line still happens, unless you also set
35954 &%local_sender_retain%& to be true. It is not possible to set both of these
35955 options true at the same time.
35957 .cindex "submission mode"
35958 By default, no processing of &'Sender:'& header lines is done for messages
35959 received over TCP/IP or for messages submitted by trusted users. However, when
35960 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
35961 not specified on the submission control, the following processing takes place:
35963 .vindex "&$authenticated_id$&"
35964 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
35965 authenticated, and &$authenticated_id$& is not empty, a sender address is
35966 created as follows:
35969 .vindex "&$qualify_domain$&"
35970 If no domain is specified by the submission control, the local part is
35971 &$authenticated_id$& and the domain is &$qualify_domain$&.
35973 If a non-empty domain is specified by the submission control, the local part
35974 is &$authenticated_id$&, and the domain is the specified domain.
35976 If an empty domain is specified by the submission control,
35977 &$authenticated_id$& is assumed to be the complete address.
35980 This address is compared with the address in the &'From:'& header line. If they
35981 are different, a &'Sender:'& header line containing the created address is
35982 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
35983 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
35985 .cindex "return path" "created from &'Sender:'&"
35986 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
35987 the message (the envelope sender address) is changed to be the same address,
35988 except in the case of submission mode when &%sender_retain%& is specified.
35992 .section "Adding and removing header lines in routers and transports" &&&
35993 "SECTheadersaddrem"
35994 .cindex "header lines" "adding; in router or transport"
35995 .cindex "header lines" "removing; in router or transport"
35996 When a message is delivered, the addition and removal of header lines can be
35997 specified in a system filter, or on any of the routers and transports that
35998 process the message. Section &<<SECTaddremheasys>>& contains details about
35999 modifying headers in a system filter. Header lines can also be added in an ACL
36000 as a message is received (see section &<<SECTaddheadacl>>&).
36002 In contrast to what happens in a system filter, header modifications that are
36003 specified on routers and transports apply only to the particular recipient
36004 addresses that are being processed by those routers and transports. These
36005 changes do not actually take place until a copy of the message is being
36006 transported. Therefore, they do not affect the basic set of header lines, and
36007 they do not affect the values of the variables that refer to header lines.
36009 &*Note*&: In particular, this means that any expansions in the configuration of
36010 the transport cannot refer to the modified header lines, because such
36011 expansions all occur before the message is actually transported.
36013 For both routers and transports, the argument of a &%headers_add%&
36014 option must be in the form of one or more RFC 2822 header lines, separated by
36015 newlines (coded as &"\n"&). For example:
36017 headers_add = X-added-header: added by $primary_hostname\n\
36018 X-added-second: another added header line
36020 Exim does not check the syntax of these added header lines.
36022 Multiple &%headers_add%& options for a single router or transport can be
36023 specified; the values will append to a single list of header lines.
36024 Each header-line is separately expanded.
36026 The argument of a &%headers_remove%& option must consist of a colon-separated
36027 list of header names. This is confusing, because header names themselves are
36028 often terminated by colons. In this case, the colons are the list separators,
36029 not part of the names. For example:
36031 headers_remove = return-receipt-to:acknowledge-to
36034 Multiple &%headers_remove%& options for a single router or transport can be
36035 specified; the arguments will append to a single header-names list.
36036 Each item is separately expanded.
36037 Note that colons in complex expansions which are used to
36038 form all or part of a &%headers_remove%& list
36039 will act as list separators.
36041 When &%headers_add%& or &%headers_remove%& is specified on a router,
36042 items are expanded at routing time,
36043 and then associated with all addresses that are
36044 accepted by that router, and also with any new addresses that it generates. If
36045 an address passes through several routers as a result of aliasing or
36046 forwarding, the changes are cumulative.
36048 .oindex "&%unseen%&"
36049 However, this does not apply to multiple routers that result from the use of
36050 the &%unseen%& option. Any header modifications that were specified by the
36051 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36053 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36054 settings cannot be delivered together in a batch, so a transport is always
36055 dealing with a set of addresses that have the same header-processing
36058 The transport starts by writing the original set of header lines that arrived
36059 with the message, possibly modified by the system filter. As it writes out
36060 these lines, it consults the list of header names that were attached to the
36061 recipient address(es) by &%headers_remove%& options in routers, and it also
36062 consults the transport's own &%headers_remove%& option. Header lines whose
36063 names are on either of these lists are not written out. If there are multiple
36064 instances of any listed header, they are all skipped.
36066 After the remaining original header lines have been written, new header
36067 lines that were specified by routers' &%headers_add%& options are written, in
36068 the order in which they were attached to the address. These are followed by any
36069 header lines specified by the transport's &%headers_add%& option.
36071 This way of handling header line modifications in routers and transports has
36072 the following consequences:
36075 The original set of header lines, possibly modified by the system filter,
36076 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36077 to it, at all times.
36079 Header lines that are added by a router's
36080 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36081 expansion syntax in subsequent routers or the transport.
36083 Conversely, header lines that are specified for removal by &%headers_remove%&
36084 in a router remain visible to subsequent routers and the transport.
36086 Headers added to an address by &%headers_add%& in a router cannot be removed by
36087 a later router or by a transport.
36089 An added header can refer to the contents of an original header that is to be
36090 removed, even it has the same name as the added header. For example:
36092 headers_remove = subject
36093 headers_add = Subject: new subject (was: $h_subject:)
36097 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36098 for a &(redirect)& router that has the &%one_time%& option set.
36104 .section "Constructed addresses" "SECTconstr"
36105 .cindex "address" "constructed"
36106 .cindex "constructed address"
36107 When Exim constructs a sender address for a locally-generated message, it uses
36110 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36114 Zaphod Beeblebrox <zaphod@end.univ.example>
36116 The user name is obtained from the &%-F%& command line option if set, or
36117 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36118 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36119 ampersand character, this is replaced by the login name with the first letter
36120 upper cased, as is conventional in a number of operating systems. See the
36121 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36122 The &%unknown_username%& option can be used to specify user names in cases when
36123 there is no password file entry.
36126 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36127 parts of it if necessary. In addition, if it contains any non-printing
36128 characters, it is encoded as described in RFC 2047, which defines a way of
36129 including non-ASCII characters in header lines. The value of the
36130 &%headers_charset%& option specifies the name of the encoding that is used (the
36131 characters are assumed to be in this encoding). The setting of
36132 &%print_topbitchars%& controls whether characters with the top bit set (that
36133 is, with codes greater than 127) count as printing characters or not.
36137 .section "Case of local parts" "SECID230"
36138 .cindex "case of local parts"
36139 .cindex "local part" "case of"
36140 RFC 2822 states that the case of letters in the local parts of addresses cannot
36141 be assumed to be non-significant. Exim preserves the case of local parts of
36142 addresses, but by default it uses a lower-cased form when it is routing,
36143 because on most Unix systems, usernames are in lower case and case-insensitive
36144 routing is required. However, any particular router can be made to use the
36145 original case for local parts by setting the &%caseful_local_part%& generic
36148 .cindex "mixed-case login names"
36149 If you must have mixed-case user names on your system, the best way to proceed,
36150 assuming you want case-independent handling of incoming email, is to set up
36151 your first router to convert incoming local parts in your domains to the
36152 correct case by means of a file lookup. For example:
36156 domains = +local_domains
36157 data = ${lookup{$local_part}cdb\
36158 {/etc/usercased.cdb}{$value}fail}\
36161 For this router, the local part is forced to lower case by the default action
36162 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36163 up a new local part in the correct case. If you then set &%caseful_local_part%&
36164 on any subsequent routers which process your domains, they will operate on
36165 local parts with the correct case in a case-sensitive manner.
36169 .section "Dots in local parts" "SECID231"
36170 .cindex "dot" "in local part"
36171 .cindex "local part" "dots in"
36172 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36173 part may not begin or end with a dot, nor have two consecutive dots in the
36174 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36175 empty components for compatibility.
36179 .section "Rewriting addresses" "SECID232"
36180 .cindex "rewriting" "addresses"
36181 Rewriting of sender and recipient addresses, and addresses in headers, can
36182 happen automatically, or as the result of configuration options, as described
36183 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36184 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36186 Automatic rewriting includes qualification, as mentioned above. The other case
36187 in which it can happen is when an incomplete non-local domain is given. The
36188 routing process may cause this to be expanded into the full domain name. For
36189 example, a header such as
36193 might get rewritten as
36195 To: hare@teaparty.wonderland.fict.example
36197 Rewriting as a result of routing is the one kind of message processing that
36198 does not happen at input time, as it cannot be done until the address has
36201 Strictly, one should not do &'any'& deliveries of a message until all its
36202 addresses have been routed, in case any of the headers get changed as a
36203 result of routing. However, doing this in practice would hold up many
36204 deliveries for unreasonable amounts of time, just because one address could not
36205 immediately be routed. Exim therefore does not delay other deliveries when
36206 routing of one or more addresses is deferred.
36207 .ecindex IIDmesproc
36211 . ////////////////////////////////////////////////////////////////////////////
36212 . ////////////////////////////////////////////////////////////////////////////
36214 .chapter "SMTP processing" "CHAPSMTP"
36215 .scindex IIDsmtpproc1 "SMTP" "processing details"
36216 .scindex IIDsmtpproc2 "LMTP" "processing details"
36217 Exim supports a number of different ways of using the SMTP protocol, and its
36218 LMTP variant, which is an interactive protocol for transferring messages into a
36219 closed mail store application. This chapter contains details of how SMTP is
36220 processed. For incoming mail, the following are available:
36223 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36225 SMTP over the standard input and output (the &%-bs%& option);
36227 Batched SMTP on the standard input (the &%-bS%& option).
36230 For mail delivery, the following are available:
36233 SMTP over TCP/IP (the &(smtp)& transport);
36235 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36238 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36241 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36242 the &%use_bsmtp%& option set).
36245 &'Batched SMTP'& is the name for a process in which batches of messages are
36246 stored in or read from files (or pipes), in a format in which SMTP commands are
36247 used to contain the envelope information.
36251 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36252 .cindex "SMTP" "outgoing over TCP/IP"
36253 .cindex "outgoing SMTP over TCP/IP"
36254 .cindex "LMTP" "over TCP/IP"
36255 .cindex "outgoing LMTP over TCP/IP"
36258 .cindex "SIZE" "option on MAIL command"
36259 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36260 The &%protocol%& option selects which protocol is to be used, but the actual
36261 processing is the same in both cases.
36263 .cindex "ESMTP extensions" SIZE
36264 If, in response to its EHLO command, Exim is told that the SIZE
36265 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36266 command. The value of <&'n'&> is the message size plus the value of the
36267 &%size_addition%& option (default 1024) to allow for additions to the message
36268 such as per-transport header lines, or changes made in a
36269 .cindex "transport" "filter"
36270 .cindex "filter" "transport filter"
36271 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36274 If the remote server advertises support for PIPELINING, Exim uses the
36275 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36276 required for the transaction.
36278 If the remote server advertises support for the STARTTLS command, and Exim
36279 was built to support TLS encryption, it tries to start a TLS session unless the
36280 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36281 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36282 is called for verification.
36284 If the remote server advertises support for the AUTH command, Exim scans
36285 the authenticators configuration for any suitable client settings, as described
36286 in chapter &<<CHAPSMTPAUTH>>&.
36288 .cindex "carriage return"
36290 Responses from the remote host are supposed to be terminated by CR followed by
36291 LF. However, there are known to be hosts that do not send CR characters, so in
36292 order to be able to interwork with such hosts, Exim treats LF on its own as a
36295 If a message contains a number of different addresses, all those with the same
36296 characteristics (for example, the same envelope sender) that resolve to the
36297 same set of hosts, in the same order, are sent in a single SMTP transaction,
36298 even if they are for different domains, unless there are more than the setting
36299 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36300 they are split into groups containing no more than &%max_rcpt%&s addresses
36301 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36302 in parallel sessions. The order of hosts with identical MX values is not
36303 significant when checking whether addresses can be batched in this way.
36305 When the &(smtp)& transport suffers a temporary failure that is not
36306 message-related, Exim updates its transport-specific database, which contains
36307 records indexed by host name that remember which messages are waiting for each
36308 particular host. It also updates the retry database with new retry times.
36310 .cindex "hints database" "retry keys"
36311 Exim's retry hints are based on host name plus IP address, so if one address of
36312 a multi-homed host is broken, it will soon be skipped most of the time.
36313 See the next section for more detail about error handling.
36315 .cindex "SMTP" "passed connection"
36316 .cindex "SMTP" "batching over TCP/IP"
36317 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36318 looks in the hints database for the transport to see if there are any queued
36319 messages waiting for the host to which it is connected. If it finds one, it
36320 creates a new Exim process using the &%-MC%& option (which can only be used by
36321 a process running as root or the Exim user) and passes the TCP/IP socket to it
36322 so that it can deliver another message using the same socket. The new process
36323 does only those deliveries that are routed to the connected host, and may in
36324 turn pass the socket on to a third process, and so on.
36326 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36327 limit the number of messages sent down a single TCP/IP connection.
36329 .cindex "asterisk" "after IP address"
36330 The second and subsequent messages delivered down an existing connection are
36331 identified in the main log by the addition of an asterisk after the closing
36332 square bracket of the IP address.
36337 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36338 .cindex "error" "in outgoing SMTP"
36339 .cindex "SMTP" "errors in outgoing"
36340 .cindex "host" "error"
36341 Three different kinds of error are recognized for outgoing SMTP: host errors,
36342 message errors, and recipient errors.
36345 .vitem "&*Host errors*&"
36346 A host error is not associated with a particular message or with a
36347 particular recipient of a message. The host errors are:
36350 Connection refused or timed out,
36352 Any error response code on connection,
36354 Any error response code to EHLO or HELO,
36356 Loss of connection at any time, except after &"."&,
36358 I/O errors at any time,
36360 Timeouts during the session, other than in response to MAIL, RCPT or
36361 the &"."& at the end of the data.
36364 For a host error, a permanent error response on connection, or in response to
36365 EHLO, causes all addresses routed to the host to be failed. Any other host
36366 error causes all addresses to be deferred, and retry data to be created for the
36367 host. It is not tried again, for any message, until its retry time arrives. If
36368 the current set of addresses are not all delivered in this run (to some
36369 alternative host), the message is added to the list of those waiting for this
36370 host, so if it is still undelivered when a subsequent successful delivery is
36371 made to the host, it will be sent down the same SMTP connection.
36373 .vitem "&*Message errors*&"
36374 .cindex "message" "error"
36375 A message error is associated with a particular message when sent to a
36376 particular host, but not with a particular recipient of the message. The
36377 message errors are:
36380 Any error response code to MAIL, DATA, or the &"."& that terminates
36383 Timeout after MAIL,
36385 Timeout or loss of connection after the &"."& that terminates the data. A
36386 timeout after the DATA command itself is treated as a host error, as is loss of
36387 connection at any other time.
36390 For a message error, a permanent error response (5&'xx'&) causes all addresses
36391 to be failed, and a delivery error report to be returned to the sender. A
36392 temporary error response (4&'xx'&), or one of the timeouts, causes all
36393 addresses to be deferred. Retry data is not created for the host, but instead,
36394 a retry record for the combination of host plus message id is created. The
36395 message is not added to the list of those waiting for this host. This ensures
36396 that the failing message will not be sent to this host again until the retry
36397 time arrives. However, other messages that are routed to the host are not
36398 affected, so if it is some property of the message that is causing the error,
36399 it will not stop the delivery of other mail.
36401 If the remote host specified support for the SIZE parameter in its response
36402 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36403 over-large message will cause a message error because the error arrives as a
36406 .vitem "&*Recipient errors*&"
36407 .cindex "recipient" "error"
36408 A recipient error is associated with a particular recipient of a message. The
36409 recipient errors are:
36412 Any error response to RCPT,
36414 Timeout after RCPT.
36417 For a recipient error, a permanent error response (5&'xx'&) causes the
36418 recipient address to be failed, and a bounce message to be returned to the
36419 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36420 address to be deferred, and routing retry data to be created for it. This is
36421 used to delay processing of the address in subsequent queue runs, until its
36422 routing retry time arrives. This applies to all messages, but because it
36423 operates only in queue runs, one attempt will be made to deliver a new message
36424 to the failing address before the delay starts to operate. This ensures that,
36425 if the failure is really related to the message rather than the recipient
36426 (&"message too big for this recipient"& is a possible example), other messages
36427 have a chance of getting delivered. If a delivery to the address does succeed,
36428 the retry information gets cleared, so all stuck messages get tried again, and
36429 the retry clock is reset.
36431 The message is not added to the list of those waiting for this host. Use of the
36432 host for other messages is unaffected, and except in the case of a timeout,
36433 other recipients are processed independently, and may be successfully delivered
36434 in the current SMTP session. After a timeout it is of course impossible to
36435 proceed with the session, so all addresses get deferred. However, those other
36436 than the one that failed do not suffer any subsequent retry delays. Therefore,
36437 if one recipient is causing trouble, the others have a chance of getting
36438 through when a subsequent delivery attempt occurs before the failing
36439 recipient's retry time.
36442 In all cases, if there are other hosts (or IP addresses) available for the
36443 current set of addresses (for example, from multiple MX records), they are
36444 tried in this run for any undelivered addresses, subject of course to their
36445 own retry data. In other words, recipient error retry data does not take effect
36446 until the next delivery attempt.
36448 Some hosts have been observed to give temporary error responses to every
36449 MAIL command at certain times (&"insufficient space"& has been seen). It
36450 would be nice if such circumstances could be recognized, and defer data for the
36451 host itself created, but this is not possible within the current Exim design.
36452 What actually happens is that retry data for every (host, message) combination
36455 The reason that timeouts after MAIL and RCPT are treated specially is that
36456 these can sometimes arise as a result of the remote host's verification
36457 procedures. Exim makes this assumption, and treats them as if a temporary error
36458 response had been received. A timeout after &"."& is treated specially because
36459 it is known that some broken implementations fail to recognize the end of the
36460 message if the last character of the last line is a binary zero. Thus, it is
36461 helpful to treat this case as a message error.
36463 Timeouts at other times are treated as host errors, assuming a problem with the
36464 host, or the connection to it. If a timeout after MAIL, RCPT,
36465 or &"."& is really a connection problem, the assumption is that at the next try
36466 the timeout is likely to occur at some other point in the dialogue, causing it
36467 then to be treated as a host error.
36469 There is experimental evidence that some MTAs drop the connection after the
36470 terminating &"."& if they do not like the contents of the message for some
36471 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
36472 should be given. That is why Exim treats this case as a message rather than a
36473 host error, in order not to delay other messages to the same host.
36478 .section "Incoming SMTP messages over TCP/IP" "SECID233"
36479 .cindex "SMTP" "incoming over TCP/IP"
36480 .cindex "incoming SMTP over TCP/IP"
36483 Incoming SMTP messages can be accepted in one of two ways: by running a
36484 listening daemon, or by using &'inetd'&. In the latter case, the entry in
36485 &_/etc/inetd.conf_& should be like this:
36487 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
36489 Exim distinguishes between this case and the case of a locally running user
36490 agent using the &%-bs%& option by checking whether or not the standard input is
36491 a socket. When it is, either the port must be privileged (less than 1024), or
36492 the caller must be root or the Exim user. If any other user passes a socket
36493 with an unprivileged port number, Exim prints a message on the standard error
36494 stream and exits with an error code.
36496 By default, Exim does not make a log entry when a remote host connects or
36497 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
36498 unexpected. It can be made to write such log entries by setting the
36499 &%smtp_connection%& log selector.
36501 .cindex "carriage return"
36503 Commands from the remote host are supposed to be terminated by CR followed by
36504 LF. However, there are known to be hosts that do not send CR characters. In
36505 order to be able to interwork with such hosts, Exim treats LF on its own as a
36507 Furthermore, because common code is used for receiving messages from all
36508 sources, a CR on its own is also interpreted as a line terminator. However, the
36509 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
36511 .cindex "EHLO" "invalid data"
36512 .cindex "HELO" "invalid data"
36513 One area that sometimes gives rise to problems concerns the EHLO or
36514 HELO commands. Some clients send syntactically invalid versions of these
36515 commands, which Exim rejects by default. (This is nothing to do with verifying
36516 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
36517 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
36518 match the broken hosts that send invalid commands.
36520 .cindex "SIZE option on MAIL command"
36521 .cindex "MAIL" "SIZE option"
36522 The amount of disk space available is checked whenever SIZE is received on
36523 a MAIL command, independently of whether &%message_size_limit%& or
36524 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
36525 false. A temporary error is given if there is not enough space. If
36526 &%check_spool_space%& is set, the check is for that amount of space plus the
36527 value given with SIZE, that is, it checks that the addition of the incoming
36528 message will not reduce the space below the threshold.
36530 When a message is successfully received, Exim includes the local message id in
36531 its response to the final &"."& that terminates the data. If the remote host
36532 logs this text it can help with tracing what has happened to a message.
36534 The Exim daemon can limit the number of simultaneous incoming connections it is
36535 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
36536 number of simultaneous incoming connections from a single remote host (see the
36537 &%smtp_accept_max_per_host%& option). Additional connection attempts are
36538 rejected using the SMTP temporary error code 421.
36540 The Exim daemon does not rely on the SIGCHLD signal to detect when a
36541 subprocess has finished, as this can get lost at busy times. Instead, it looks
36542 for completed subprocesses every time it wakes up. Provided there are other
36543 things happening (new incoming calls, starts of queue runs), completed
36544 processes will be noticed and tidied away. On very quiet systems you may
36545 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
36546 it will be noticed when the daemon next wakes up.
36548 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
36549 and can also be set up to reject SMTP calls from non-reserved hosts at times of
36550 high system load &-- for details see the &%smtp_accept_reserve%&,
36551 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
36552 applies in both the daemon and &'inetd'& cases.
36554 Exim normally starts a delivery process for each message received, though this
36555 can be varied by means of the &%-odq%& command line option and the
36556 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
36557 number of simultaneously running delivery processes started in this way from
36558 SMTP input can be limited by the &%smtp_accept_queue%& and
36559 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
36560 subsequently received messages are just put on the input queue without starting
36561 a delivery process.
36563 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
36564 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
36565 started up from the &'inetd'& daemon, because in that case each connection is
36566 handled by an entirely independent Exim process. Control by load average is,
36567 however, available with &'inetd'&.
36569 Exim can be configured to verify addresses in incoming SMTP commands as they
36570 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
36571 to rewrite addresses at this time &-- before any syntax checking is done. See
36572 section &<<SECTrewriteS>>&.
36574 Exim can also be configured to limit the rate at which a client host submits
36575 MAIL and RCPT commands in a single SMTP session. See the
36576 &%smtp_ratelimit_hosts%& option.
36580 .section "Unrecognized SMTP commands" "SECID234"
36581 .cindex "SMTP" "unrecognized commands"
36582 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
36583 commands during a single SMTP connection, it drops the connection after sending
36584 the error response to the last command. The default value for
36585 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
36586 abuse that subvert web servers into making connections to SMTP ports; in these
36587 circumstances, a number of non-SMTP lines are sent first.
36590 .section "Syntax and protocol errors in SMTP commands" "SECID235"
36591 .cindex "SMTP" "syntax errors"
36592 .cindex "SMTP" "protocol errors"
36593 A syntax error is detected if an SMTP command is recognized, but there is
36594 something syntactically wrong with its data, for example, a malformed email
36595 address in a RCPT command. Protocol errors include invalid command
36596 sequencing such as RCPT before MAIL. If Exim receives more than
36597 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
36598 drops the connection after sending the error response to the last command. The
36599 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
36600 broken clients that loop sending bad commands (yes, it has been seen).
36604 .section "Use of non-mail SMTP commands" "SECID236"
36605 .cindex "SMTP" "non-mail commands"
36606 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
36607 DATA. Exim counts such commands, and drops the connection if there are too
36608 many of them in a single SMTP session. This action catches some
36609 denial-of-service attempts and things like repeated failing AUTHs, or a mad
36610 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
36611 defines what &"too many"& means. Its default value is 10.
36613 When a new message is expected, one occurrence of RSET is not counted. This
36614 allows a client to send one RSET between messages (this is not necessary,
36615 but some clients do it). Exim also allows one uncounted occurrence of HELO
36616 or EHLO, and one occurrence of STARTTLS between messages. After
36617 starting up a TLS session, another EHLO is expected, and so it too is not
36620 The first occurrence of AUTH in a connection, or immediately following
36621 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
36622 RCPT, DATA, and QUIT are counted.
36624 You can control which hosts are subject to the limit set by
36625 &%smtp_accept_max_nonmail%& by setting
36626 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
36627 the limit apply to all hosts. This option means that you can exclude any
36628 specific badly-behaved hosts that you have to live with.
36633 .section "The VRFY and EXPN commands" "SECID237"
36634 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
36635 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
36636 appropriate) in order to decide whether the command should be accepted or not.
36638 .cindex "VRFY" "processing"
36639 When no ACL is defined for VRFY, or if it rejects without
36640 setting an explicit response code, the command is accepted
36641 (with a 252 SMTP response code)
36642 in order to support awkward clients that do a VRFY before every RCPT.
36643 When VRFY is accepted, it runs exactly the same code as when Exim is
36644 called with the &%-bv%& option, and returns 250/451/550
36645 SMTP response codes.
36647 .cindex "EXPN" "processing"
36648 If no ACL for EXPN is defined, the command is rejected.
36649 When EXPN is accepted, a single-level expansion of the address is done.
36650 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
36651 than a verification (the &%-bv%& option). If an unqualified local part is given
36652 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
36653 of VRFY and EXPN commands are logged on the main and reject logs, and
36654 VRFY verification failures are logged on the main log for consistency with
36659 .section "The ETRN command" "SECTETRN"
36660 .cindex "ETRN" "processing"
36661 .cindex "ESMTP extensions" ETRN
36662 RFC 1985 describes an ESMTP command called ETRN that is designed to
36663 overcome the security problems of the TURN command (which has fallen into
36664 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
36665 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
36666 should be accepted or not. If no ACL is defined, the command is rejected.
36668 The ETRN command is concerned with &"releasing"& messages that are awaiting
36669 delivery to certain hosts. As Exim does not organize its message queue by host,
36670 the only form of ETRN that is supported by default is the one where the
36671 text starts with the &"#"& prefix, in which case the remainder of the text is
36672 specific to the SMTP server. A valid ETRN command causes a run of Exim with
36673 the &%-R%& option to happen, with the remainder of the ETRN text as its
36674 argument. For example,
36682 which causes a delivery attempt on all messages with undelivered addresses
36683 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
36684 default), Exim prevents the simultaneous execution of more than one queue run
36685 for the same argument string as a result of an ETRN command. This stops
36686 a misbehaving client from starting more than one queue runner at once.
36688 .cindex "hints database" "ETRN serialization"
36689 Exim implements the serialization by means of a hints database in which a
36690 record is written whenever a process is started by ETRN, and deleted when
36691 the process completes. However, Exim does not keep the SMTP session waiting for
36692 the ETRN process to complete. Once ETRN is accepted, the client is sent
36693 a &"success"& return code. Obviously there is scope for hints records to get
36694 left lying around if there is a system or program crash. To guard against this,
36695 Exim ignores any records that are more than six hours old.
36697 .oindex "&%smtp_etrn_command%&"
36698 For more control over what ETRN does, the &%smtp_etrn_command%& option can
36699 used. This specifies a command that is run whenever ETRN is received,
36700 whatever the form of its argument. For
36703 smtp_etrn_command = /etc/etrn_command $domain \
36704 $sender_host_address
36706 .vindex "&$domain$&"
36707 The string is split up into arguments which are independently expanded. The
36708 expansion variable &$domain$& is set to the argument of the ETRN command,
36709 and no syntax checking is done on the contents of this argument. Exim does not
36710 wait for the command to complete, so its status code is not checked. Exim runs
36711 under its own uid and gid when receiving incoming SMTP, so it is not possible
36712 for it to change them before running the command.
36716 .section "Incoming local SMTP" "SECID238"
36717 .cindex "SMTP" "local incoming"
36718 Some user agents use SMTP to pass messages to their local MTA using the
36719 standard input and output, as opposed to passing the envelope on the command
36720 line and writing the message to the standard input. This is supported by the
36721 &%-bs%& option. This form of SMTP is handled in the same way as incoming
36722 messages over TCP/IP (including the use of ACLs), except that the envelope
36723 sender given in a MAIL command is ignored unless the caller is trusted. In
36724 an ACL you can detect this form of SMTP input by testing for an empty host
36725 identification. It is common to have this as the first line in the ACL that
36726 runs for RCPT commands:
36730 This accepts SMTP messages from local processes without doing any other tests.
36734 .section "Outgoing batched SMTP" "SECTbatchSMTP"
36735 .cindex "SMTP" "batched outgoing"
36736 .cindex "batched SMTP output"
36737 Both the &(appendfile)& and &(pipe)& transports can be used for handling
36738 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
36739 be output in BSMTP format. No SMTP responses are possible for this form of
36740 delivery. All it is doing is using SMTP commands as a way of transmitting the
36741 envelope along with the message.
36743 The message is written to the file or pipe preceded by the SMTP commands
36744 MAIL and RCPT, and followed by a line containing a single dot. Lines in
36745 the message that start with a dot have an extra dot added. The SMTP command
36746 HELO is not normally used. If it is required, the &%message_prefix%& option
36747 can be used to specify it.
36749 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
36750 one recipient address at a time by default. However, you can arrange for them
36751 to handle several addresses at once by setting the &%batch_max%& option. When
36752 this is done for BSMTP, messages may contain multiple RCPT commands. See
36753 chapter &<<CHAPbatching>>& for more details.
36756 When one or more addresses are routed to a BSMTP transport by a router that
36757 sets up a host list, the name of the first host on the list is available to the
36758 transport in the variable &$host$&. Here is an example of such a transport and
36763 driver = manualroute
36764 transport = smtp_appendfile
36765 route_list = domain.example batch.host.example
36769 driver = appendfile
36770 directory = /var/bsmtp/$host
36775 This causes messages addressed to &'domain.example'& to be written in BSMTP
36776 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
36777 message (unless there are more than 1000 recipients).
36781 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
36782 .cindex "SMTP" "batched incoming"
36783 .cindex "batched SMTP input"
36784 The &%-bS%& command line option causes Exim to accept one or more messages by
36785 reading SMTP on the standard input, but to generate no responses. If the caller
36786 is trusted, the senders in the MAIL commands are believed; otherwise the
36787 sender is always the caller of Exim. Unqualified senders and receivers are not
36788 rejected (there seems little point) but instead just get qualified. HELO
36789 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
36790 as NOOP; QUIT quits.
36792 Minimal policy checking is done for BSMTP input. Only the non-SMTP
36793 ACL is run in the same way as for non-SMTP local input.
36795 If an error is detected while reading a message, including a missing &"."& at
36796 the end, Exim gives up immediately. It writes details of the error to the
36797 standard output in a stylized way that the calling program should be able to
36798 make some use of automatically, for example:
36800 554 Unexpected end of file
36801 Transaction started in line 10
36802 Error detected in line 14
36804 It writes a more verbose version, for human consumption, to the standard error
36807 An error was detected while processing a file of BSMTP input.
36808 The error message was:
36810 501 '>' missing at end of address
36812 The SMTP transaction started in line 10.
36813 The error was detected in line 12.
36814 The SMTP command at fault was:
36816 rcpt to:<malformed@in.com.plete
36818 1 previous message was successfully processed.
36819 The rest of the batch was abandoned.
36821 The return code from Exim is zero only if there were no errors. It is 1 if some
36822 messages were accepted before an error was detected, and 2 if no messages were
36824 .ecindex IIDsmtpproc1
36825 .ecindex IIDsmtpproc2
36829 . ////////////////////////////////////////////////////////////////////////////
36830 . ////////////////////////////////////////////////////////////////////////////
36832 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
36833 "Customizing messages"
36834 When a message fails to be delivered, or remains in the queue for more than a
36835 configured amount of time, Exim sends a message to the original sender, or
36836 to an alternative configured address. The text of these messages is built into
36837 the code of Exim, but it is possible to change it, either by adding a single
36838 string, or by replacing each of the paragraphs by text supplied in a file.
36840 The &'From:'& and &'To:'& header lines are automatically generated; you can
36841 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
36842 option. Exim also adds the line
36844 Auto-Submitted: auto-generated
36846 to all warning and bounce messages,
36849 .section "Customizing bounce messages" "SECID239"
36850 .cindex "customizing" "bounce message"
36851 .cindex "bounce message" "customizing"
36852 If &%bounce_message_text%& is set, its contents are included in the default
36853 message immediately after &"This message was created automatically by mail
36854 delivery software."& The string is not expanded. It is not used if
36855 &%bounce_message_file%& is set.
36857 When &%bounce_message_file%& is set, it must point to a template file for
36858 constructing error messages. The file consists of a series of text items,
36859 separated by lines consisting of exactly four asterisks. If the file cannot be
36860 opened, default text is used and a message is written to the main and panic
36861 logs. If any text item in the file is empty, default text is used for that
36864 .vindex "&$bounce_recipient$&"
36865 .vindex "&$bounce_return_size_limit$&"
36866 Each item of text that is read from the file is expanded, and there are two
36867 expansion variables which can be of use here: &$bounce_recipient$& is set to
36868 the recipient of an error message while it is being created, and
36869 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
36870 option, rounded to a whole number.
36872 The items must appear in the file in the following order:
36875 The first item is included in the headers, and should include at least a
36876 &'Subject:'& header. Exim does not check the syntax of these headers.
36878 The second item forms the start of the error message. After it, Exim lists the
36879 failing addresses with their error messages.
36881 The third item is used to introduce any text from pipe transports that is to be
36882 returned to the sender. It is omitted if there is no such text.
36884 The fourth, fifth and sixth items will be ignored and may be empty.
36885 The fields exist for back-compatibility
36888 The default state (&%bounce_message_file%& unset) is equivalent to the
36889 following file, in which the sixth item is empty. The &'Subject:'& and some
36890 other lines have been split in order to fit them on the page:
36892 Subject: Mail delivery failed
36893 ${if eq{$sender_address}{$bounce_recipient}
36894 {: returning message to sender}}
36896 This message was created automatically by mail delivery software.
36898 A message ${if eq{$sender_address}{$bounce_recipient}
36899 {that you sent }{sent by
36903 }}could not be delivered to all of its recipients.
36904 This is a permanent error. The following address(es) failed:
36906 The following text was generated during the delivery attempt(s):
36908 ------ This is a copy of the message, including all the headers.
36911 ------ The body of the message is $message_size characters long;
36913 ------ $bounce_return_size_limit or so are included here.
36916 .section "Customizing warning messages" "SECTcustwarn"
36917 .cindex "customizing" "warning message"
36918 .cindex "warning of delay" "customizing the message"
36919 The option &%warn_message_file%& can be pointed at a template file for use when
36920 warnings about message delays are created. In this case there are only three
36924 The first item is included in the headers, and should include at least a
36925 &'Subject:'& header. Exim does not check the syntax of these headers.
36927 The second item forms the start of the warning message. After it, Exim lists
36928 the delayed addresses.
36930 The third item then ends the message.
36933 The default state is equivalent to the following file, except that some lines
36934 have been split here, in order to fit them on the page:
36936 Subject: Warning: message $message_exim_id delayed
36937 $warn_message_delay
36939 This message was created automatically by mail delivery software.
36941 A message ${if eq{$sender_address}{$warn_message_recipients}
36942 {that you sent }{sent by
36946 }}has not been delivered to all of its recipients after
36947 more than $warn_message_delay in the queue on $primary_hostname.
36949 The message identifier is: $message_exim_id
36950 The subject of the message is: $h_subject
36951 The date of the message is: $h_date
36953 The following address(es) have not yet been delivered:
36955 No action is required on your part. Delivery attempts will
36956 continue for some time, and this warning may be repeated at
36957 intervals if the message remains undelivered. Eventually the
36958 mail delivery software will give up, and when that happens,
36959 the message will be returned to you.
36961 .vindex "&$warn_message_delay$&"
36962 .vindex "&$warn_message_recipients$&"
36963 However, in the default state the subject and date lines are omitted if no
36964 appropriate headers exist. During the expansion of this file,
36965 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
36966 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
36967 of recipients for the warning message. There may be more than one if there are
36968 multiple addresses with different &%errors_to%& settings on the routers that
36974 . ////////////////////////////////////////////////////////////////////////////
36975 . ////////////////////////////////////////////////////////////////////////////
36977 .chapter "Some common configuration settings" "CHAPcomconreq"
36978 This chapter discusses some configuration settings that seem to be fairly
36979 common. More examples and discussion can be found in the Exim book.
36983 .section "Sending mail to a smart host" "SECID240"
36984 .cindex "smart host" "example router"
36985 If you want to send all mail for non-local domains to a &"smart host"&, you
36986 should replace the default &(dnslookup)& router with a router which does the
36987 routing explicitly:
36989 send_to_smart_host:
36990 driver = manualroute
36991 route_list = !+local_domains smart.host.name
36992 transport = remote_smtp
36994 You can use the smart host's IP address instead of the name if you wish.
36995 If you are using Exim only to submit messages to a smart host, and not for
36996 receiving incoming messages, you can arrange for it to do the submission
36997 synchronously by setting the &%mua_wrapper%& option (see chapter
36998 &<<CHAPnonqueueing>>&).
37003 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37004 .cindex "mailing lists"
37005 Exim can be used to run simple mailing lists, but for large and/or complicated
37006 requirements, the use of additional specialized mailing list software such as
37007 Majordomo or Mailman is recommended.
37009 The &(redirect)& router can be used to handle mailing lists where each list
37010 is maintained in a separate file, which can therefore be managed by an
37011 independent manager. The &%domains%& router option can be used to run these
37012 lists in a separate domain from normal mail. For example:
37016 domains = lists.example
37017 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37020 errors_to = ${quote_local_part:$local_part-request}@lists.example
37023 This router is skipped for domains other than &'lists.example'&. For addresses
37024 in that domain, it looks for a file that matches the local part. If there is no
37025 such file, the router declines, but because &%no_more%& is set, no subsequent
37026 routers are tried, and so the whole delivery fails.
37028 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37029 expanded into a filename or a pipe delivery, which is usually inappropriate in
37032 .oindex "&%errors_to%&"
37033 The &%errors_to%& option specifies that any delivery errors caused by addresses
37034 taken from a mailing list are to be sent to the given address rather than the
37035 original sender of the message. However, before acting on this, Exim verifies
37036 the error address, and ignores it if verification fails.
37038 For example, using the configuration above, mail sent to
37039 &'dicts@lists.example'& is passed on to those addresses contained in
37040 &_/usr/lists/dicts_&, with error reports directed to
37041 &'dicts-request@lists.example'&, provided that this address can be verified.
37042 There could be a file called &_/usr/lists/dicts-request_& containing
37043 the address(es) of this particular list's manager(s), but other approaches,
37044 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37045 or &%local_part_suffix%& options) to handle addresses of the form
37046 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37050 .section "Syntax errors in mailing lists" "SECID241"
37051 .cindex "mailing lists" "syntax errors in"
37052 If an entry in redirection data contains a syntax error, Exim normally defers
37053 delivery of the original address. That means that a syntax error in a mailing
37054 list holds up all deliveries to the list. This may not be appropriate when a
37055 list is being maintained automatically from data supplied by users, and the
37056 addresses are not rigorously checked.
37058 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37059 entries that fail to parse, noting the incident in the log. If in addition
37060 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37061 whenever a broken address is skipped. It is usually appropriate to set
37062 &%syntax_errors_to%& to the same address as &%errors_to%&.
37066 .section "Re-expansion of mailing lists" "SECID242"
37067 .cindex "mailing lists" "re-expansion of"
37068 Exim remembers every individual address to which a message has been delivered,
37069 in order to avoid duplication, but it normally stores only the original
37070 recipient addresses with a message. If all the deliveries to a mailing list
37071 cannot be done at the first attempt, the mailing list is re-expanded when the
37072 delivery is next tried. This means that alterations to the list are taken into
37073 account at each delivery attempt, so addresses that have been added to
37074 the list since the message arrived will therefore receive a copy of the
37075 message, even though it pre-dates their subscription.
37077 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37078 on the &(redirect)& router. If this is done, any addresses generated by the
37079 router that fail to deliver at the first attempt are added to the message as
37080 &"top level"& addresses, and the parent address that generated them is marked
37081 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37082 subsequent delivery attempts. The disadvantage of this is that if any of the
37083 failing addresses are incorrect, correcting them in the file has no effect on
37084 pre-existing messages.
37086 The original top-level address is remembered with each of the generated
37087 addresses, and is output in any log messages. However, any intermediate parent
37088 addresses are not recorded. This makes a difference to the log only if the
37089 &%all_parents%& selector is set, but for mailing lists there is normally only
37090 one level of expansion anyway.
37094 .section "Closed mailing lists" "SECID243"
37095 .cindex "mailing lists" "closed"
37096 The examples so far have assumed open mailing lists, to which anybody may
37097 send mail. It is also possible to set up closed lists, where mail is accepted
37098 from specified senders only. This is done by making use of the generic
37099 &%senders%& option to restrict the router that handles the list.
37101 The following example uses the same file as a list of recipients and as a list
37102 of permitted senders. It requires three routers:
37106 domains = lists.example
37107 local_part_suffix = -request
37108 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37109 file = /usr/lists/${local_part_data}-request
37114 domains = lists.example
37115 senders = ${if exists {/usr/lists/$local_part}\
37116 {lsearch;/usr/lists/$local_part}{*}}
37117 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37120 errors_to = ${quote_local_part:$local_part-request}@lists.example
37125 domains = lists.example
37127 data = :fail: $local_part@lists.example is a closed mailing list
37129 All three routers have the same &%domains%& setting, so for any other domains,
37130 they are all skipped. The first router runs only if the local part ends in
37131 &%-request%&. It handles messages to the list manager(s) by means of an open
37134 The second router runs only if the &%senders%& precondition is satisfied. It
37135 checks for the existence of a list that corresponds to the local part, and then
37136 checks that the sender is on the list by means of a linear search. It is
37137 necessary to check for the existence of the file before trying to search it,
37138 because otherwise Exim thinks there is a configuration error. If the file does
37139 not exist, the expansion of &%senders%& is *, which matches all senders. This
37140 means that the router runs, but because there is no list, declines, and
37141 &%no_more%& ensures that no further routers are run. The address fails with an
37142 &"unrouteable address"& error.
37144 The third router runs only if the second router is skipped, which happens when
37145 a mailing list exists, but the sender is not on it. This router forcibly fails
37146 the address, giving a suitable error message.
37151 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37153 .cindex "Variable Envelope Return Paths"
37154 .cindex "envelope from"
37155 .cindex "envelope sender"
37156 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37157 are a way of helping mailing list administrators discover which subscription
37158 address is the cause of a particular delivery failure. The idea is to encode
37159 the original recipient address in the outgoing envelope sender address, so that
37160 if the message is forwarded by another host and then subsequently bounces, the
37161 original recipient can be extracted from the recipient address of the bounce.
37163 .oindex &%errors_to%&
37164 .oindex &%return_path%&
37165 Envelope sender addresses can be modified by Exim using two different
37166 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37167 list examples), or the &%return_path%& option on a transport. The second of
37168 these is effective only if the message is successfully delivered to another
37169 host; it is not used for errors detected on the local host (see the description
37170 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37171 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37177 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37178 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37180 This has the effect of rewriting the return path (envelope sender) on outgoing
37181 SMTP messages, if the local part of the original return path ends in
37182 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37183 local part and domain of the recipient into the return path. Suppose, for
37184 example, that a message whose return path has been set to
37185 &'somelist-request@your.dom.example'& is sent to
37186 &'subscriber@other.dom.example'&. In the transport, the return path is
37189 somelist-request+subscriber=other.dom.example@your.dom.example
37191 .vindex "&$local_part$&"
37192 For this to work, you must tell Exim to send multiple copies of messages that
37193 have more than one recipient, so that each copy has just one recipient. This is
37194 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37195 might be sent to several different recipients in the same domain, in which case
37196 &$local_part$& is not available in the transport, because it is not unique.
37198 Unless your host is doing nothing but mailing list deliveries, you should
37199 probably use a separate transport for the VERP deliveries, so as not to use
37200 extra resources in making one-per-recipient copies for other deliveries. This
37201 can easily be done by expanding the &%transport%& option in the router:
37205 domains = ! +local_domains
37207 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37208 {verp_smtp}{remote_smtp}}
37211 If you want to change the return path using &%errors_to%& in a router instead
37212 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37213 routers that handle mailing list addresses. This will ensure that all delivery
37214 errors, including those detected on the local host, are sent to the VERP
37217 On a host that does no local deliveries and has no manual routing, only the
37218 &(dnslookup)& router needs to be changed. A special transport is not needed for
37219 SMTP deliveries. Every mailing list recipient has its own return path value,
37220 and so Exim must hand them to the transport one at a time. Here is an example
37221 of a &(dnslookup)& router that implements VERP:
37225 domains = ! +local_domains
37226 transport = remote_smtp
37228 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37229 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37232 Before you start sending out messages with VERPed return paths, you must also
37233 configure Exim to accept the bounce messages that come back to those paths.
37234 Typically this is done by setting a &%local_part_suffix%& option for a
37235 router, and using this to route the messages to wherever you want to handle
37238 The overhead incurred in using VERP depends very much on the size of the
37239 message, the number of recipient addresses that resolve to the same remote
37240 host, and the speed of the connection over which the message is being sent. If
37241 a lot of addresses resolve to the same host and the connection is slow, sending
37242 a separate copy of the message for each address may take substantially longer
37243 than sending a single copy with many recipients (for which VERP cannot be
37251 .section "Virtual domains" "SECTvirtualdomains"
37252 .cindex "virtual domains"
37253 .cindex "domain" "virtual"
37254 The phrase &'virtual domain'& is unfortunately used with two rather different
37258 A domain for which there are no real mailboxes; all valid local parts are
37259 aliases for other email addresses. Common examples are organizational
37260 top-level domains and &"vanity"& domains.
37262 One of a number of independent domains that are all handled by the same host,
37263 with mailboxes on that host, but where the mailbox owners do not necessarily
37264 have login accounts on that host.
37267 The first usage is probably more common, and does seem more &"virtual"& than
37268 the second. This kind of domain can be handled in Exim with a straightforward
37269 aliasing router. One approach is to create a separate alias file for each
37270 virtual domain. Exim can test for the existence of the alias file to determine
37271 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37272 to a router of this form:
37276 domains = dsearch;/etc/mail/virtual
37277 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37281 The &%domains%& option specifies that the router is to be skipped, unless there
37282 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37283 domain that is being processed.
37284 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37285 being placed into the &$domain_data$& variable.
37288 When the router runs, it looks up the local
37289 part in the file to find a new address (or list of addresses). The &%no_more%&
37290 setting ensures that if the lookup fails (leading to &%data%& being an empty
37291 string), Exim gives up on the address without trying any subsequent routers.
37293 This one router can handle all the virtual domains because the alias filenames
37294 follow a fixed pattern. Permissions can be arranged so that appropriate people
37295 can edit the different alias files. A successful aliasing operation results in
37296 a new envelope recipient address, which is then routed from scratch.
37298 The other kind of &"virtual"& domain can also be handled in a straightforward
37299 way. One approach is to create a file for each domain containing a list of
37300 valid local parts, and use it in a router like this:
37304 domains = dsearch;/etc/mail/domains
37305 local_parts = lsearch;/etc/mail/domains/$domain
37306 transport = my_mailboxes
37308 The address is accepted if there is a file for the domain, and the local part
37309 can be found in the file. The &%domains%& option is used to check for the
37310 file's existence because &%domains%& is tested before the &%local_parts%&
37311 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37312 because that option is tested after &%local_parts%&. The transport is as
37316 driver = appendfile
37317 file = /var/mail/$domain/$local_part_data
37320 This uses a directory of mailboxes for each domain. The &%user%& setting is
37321 required, to specify which uid is to be used for writing to the mailboxes.
37323 The configuration shown here is just one example of how you might support this
37324 requirement. There are many other ways this kind of configuration can be set
37325 up, for example, by using a database instead of separate files to hold all the
37326 information about the domains.
37330 .section "Multiple user mailboxes" "SECTmulbox"
37331 .cindex "multiple mailboxes"
37332 .cindex "mailbox" "multiple"
37333 .cindex "local part" "prefix"
37334 .cindex "local part" "suffix"
37335 Heavy email users often want to operate with multiple mailboxes, into which
37336 incoming mail is automatically sorted. A popular way of handling this is to
37337 allow users to use multiple sender addresses, so that replies can easily be
37338 identified. Users are permitted to add prefixes or suffixes to their local
37339 parts for this purpose. The wildcard facility of the generic router options
37340 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37341 example, consider this router:
37346 file = $home/.forward
37347 local_part_suffix = -*
37348 local_part_suffix_optional
37351 .vindex "&$local_part_suffix$&"
37352 It runs a user's &_.forward_& file for all local parts of the form
37353 &'username-*'&. Within the filter file the user can distinguish different
37354 cases by testing the variable &$local_part_suffix$&. For example:
37356 if $local_part_suffix contains -special then
37357 save /home/$local_part/Mail/special
37360 If the filter file does not exist, or does not deal with such addresses, they
37361 fall through to subsequent routers, and, assuming no subsequent use of the
37362 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37363 control over which suffixes are valid.
37365 Alternatively, a suffix can be used to trigger the use of a different
37366 &_.forward_& file &-- which is the way a similar facility is implemented in
37372 local_part_suffix = -*
37373 local_part_suffix_optional
37374 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37377 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37378 example, &_.forward-special_& is used. Once again, if the appropriate file
37379 does not exist, or does not deal with the address, it is passed on to
37380 subsequent routers, which could, if required, look for an unqualified
37381 &_.forward_& file to use as a default.
37385 .section "Simplified vacation processing" "SECID244"
37386 .cindex "vacation processing"
37387 The traditional way of running the &'vacation'& program is for a user to set up
37388 a pipe command in a &_.forward_& file
37389 (see section &<<SECTspecitredli>>& for syntax details).
37390 This is prone to error by inexperienced users. There are two features of Exim
37391 that can be used to make this process simpler for users:
37394 A local part prefix such as &"vacation-"& can be specified on a router which
37395 can cause the message to be delivered directly to the &'vacation'& program, or
37396 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37397 &_.forward_& file are then much simpler. For example:
37399 spqr, vacation-spqr
37402 The &%require_files%& generic router option can be used to trigger a
37403 vacation delivery by checking for the existence of a certain file in the
37404 user's home directory. The &%unseen%& generic option should also be used, to
37405 ensure that the original delivery also proceeds. In this case, all the user has
37406 to do is to create a file called, say, &_.vacation_&, containing a vacation
37410 Another advantage of both these methods is that they both work even when the
37411 use of arbitrary pipes by users is locked out.
37415 .section "Taking copies of mail" "SECID245"
37416 .cindex "message" "copying every"
37417 Some installations have policies that require archive copies of all messages to
37418 be made. A single copy of each message can easily be taken by an appropriate
37419 command in a system filter, which could, for example, use a different file for
37420 each day's messages.
37422 There is also a shadow transport mechanism that can be used to take copies of
37423 messages that are successfully delivered by local transports, one copy per
37424 delivery. This could be used, &'inter alia'&, to implement automatic
37425 notification of delivery by sites that insist on doing such things.
37429 .section "Intermittently connected hosts" "SECID246"
37430 .cindex "intermittently connected hosts"
37431 It has become quite common (because it is cheaper) for hosts to connect to the
37432 Internet periodically rather than remain connected all the time. The normal
37433 arrangement is that mail for such hosts accumulates on a system that is
37434 permanently connected.
37436 Exim was designed for use on permanently connected hosts, and so it is not
37437 particularly well-suited to use in an intermittently connected environment.
37438 Nevertheless there are some features that can be used.
37441 .section "Exim on the upstream server host" "SECID247"
37442 It is tempting to arrange for incoming mail for the intermittently connected
37443 host to remain in Exim's queue until the client connects. However, this
37444 approach does not scale very well. Two different kinds of waiting message are
37445 being mixed up in the same queue &-- those that cannot be delivered because of
37446 some temporary problem, and those that are waiting for their destination host
37447 to connect. This makes it hard to manage the queue, as well as wasting
37448 resources, because each queue runner scans the entire queue.
37450 A better approach is to separate off those messages that are waiting for an
37451 intermittently connected host. This can be done by delivering these messages
37452 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
37453 format, from where they are transmitted by other software when their
37454 destination connects. This makes it easy to collect all the mail for one host
37455 in a single directory, and to apply local timeout rules on a per-message basis
37458 On a very small scale, leaving the mail on Exim's queue can be made to work. If
37459 you are doing this, you should configure Exim with a long retry period for the
37460 intermittent host. For example:
37462 cheshire.wonderland.fict.example * F,5d,24h
37464 This stops a lot of failed delivery attempts from occurring, but Exim remembers
37465 which messages it has queued up for that host. Once the intermittent host comes
37466 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
37467 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
37468 causes all the queued up messages to be delivered, often down a single SMTP
37469 connection. While the host remains connected, any new messages get delivered
37472 If the connecting hosts do not have fixed IP addresses, that is, if a host is
37473 issued with a different IP address each time it connects, Exim's retry
37474 mechanisms on the holding host get confused, because the IP address is normally
37475 used as part of the key string for holding retry information. This can be
37476 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
37477 Since this has disadvantages for permanently connected hosts, it is best to
37478 arrange a separate transport for the intermittently connected ones.
37482 .section "Exim on the intermittently connected client host" "SECID248"
37483 The value of &%smtp_accept_queue_per_connection%& should probably be
37484 increased, or even set to zero (that is, disabled) on the intermittently
37485 connected host, so that all incoming messages down a single connection get
37486 delivered immediately.
37488 .cindex "SMTP" "passed connection"
37489 .cindex "SMTP" "multiple deliveries"
37490 .cindex "multiple SMTP deliveries"
37491 .cindex "first pass routing"
37492 Mail waiting to be sent from an intermittently connected host will probably
37493 not have been routed, because without a connection DNS lookups are not
37494 possible. This means that if a normal queue run is done at connection time,
37495 each message is likely to be sent in a separate SMTP session. This can be
37496 avoided by starting the queue run with a command line option beginning with
37497 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
37498 first pass, routing is done but no deliveries take place. The second pass is a
37499 normal queue run; since all the messages have been previously routed, those
37500 destined for the same host are likely to get sent as multiple deliveries in a
37501 single SMTP connection.
37505 . ////////////////////////////////////////////////////////////////////////////
37506 . ////////////////////////////////////////////////////////////////////////////
37508 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
37509 "Exim as a non-queueing client"
37510 .cindex "client, non-queueing"
37511 .cindex "smart host" "suppressing queueing"
37512 On a personal computer, it is a common requirement for all
37513 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
37514 configured to operate that way, for all the popular operating systems.
37515 However, there are some MUAs for Unix-like systems that cannot be so
37516 configured: they submit messages using the command line interface of
37517 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
37520 If the personal computer runs continuously, there is no problem, because it can
37521 run a conventional MTA that handles delivery to the smart host, and deal with
37522 any delays via its queueing mechanism. However, if the computer does not run
37523 continuously or runs different operating systems at different times, queueing
37524 email is not desirable.
37526 There is therefore a requirement for something that can provide the
37527 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
37528 any queueing or retrying facilities. Furthermore, the delivery to the smart
37529 host should be synchronous, so that if it fails, the sending MUA is immediately
37530 informed. In other words, we want something that extends an MUA that submits
37531 to a local MTA via the command line so that it behaves like one that submits
37532 to a remote smart host using TCP/SMTP.
37534 There are a number of applications (for example, there is one called &'ssmtp'&)
37535 that do this job. However, people have found them to be lacking in various
37536 ways. For instance, you might want to allow aliasing and forwarding to be done
37537 before sending a message to the smart host.
37539 Exim already had the necessary infrastructure for doing this job. Just a few
37540 tweaks were needed to make it behave as required, though it is somewhat of an
37541 overkill to use a fully-featured MTA for this purpose.
37543 .oindex "&%mua_wrapper%&"
37544 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
37545 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
37546 assumes that it is being used to &"wrap"& a command-line MUA in the manner
37547 just described. As well as setting &%mua_wrapper%&, you also need to provide a
37548 compatible router and transport configuration. Typically there will be just one
37549 router and one transport, sending everything to a smart host.
37551 When run in MUA wrapping mode, the behaviour of Exim changes in the
37555 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
37556 In other words, the only way to submit messages is via the command line.
37558 Each message is synchronously delivered as soon as it is received (&%-odi%& is
37559 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
37560 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
37561 does not finish until the delivery attempt is complete. If the delivery is
37562 successful, a zero return code is given.
37564 Address redirection is permitted, but the final routing for all addresses must
37565 be to the same remote transport, and to the same list of hosts. Furthermore,
37566 the return address (envelope sender) must be the same for all recipients, as
37567 must any added or deleted header lines. In other words, it must be possible to
37568 deliver the message in a single SMTP transaction, however many recipients there
37571 If these conditions are not met, or if routing any address results in a
37572 failure or defer status, or if Exim is unable to deliver all the recipients
37573 successfully to one of the smart hosts, delivery of the entire message fails.
37575 Because no queueing is allowed, all failures are treated as permanent; there
37576 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
37577 smart host. Furthermore, because only a single yes/no response can be given to
37578 the caller, it is not possible to deliver to some recipients and not others. If
37579 there is an error (temporary or permanent) for any recipient, all are failed.
37581 If more than one smart host is listed, Exim will try another host after a
37582 connection failure or a timeout, in the normal way. However, if this kind of
37583 failure happens for all the hosts, the delivery fails.
37585 When delivery fails, an error message is written to the standard error stream
37586 (as well as to Exim's log), and Exim exits to the caller with a return code
37587 value 1. The message is expunged from Exim's spool files. No bounce messages
37588 are ever generated.
37590 No retry data is maintained, and any retry rules are ignored.
37592 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
37593 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
37594 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
37597 The overall effect is that Exim makes a single synchronous attempt to deliver
37598 the message, failing if there is any kind of problem. Because no local
37599 deliveries are done and no daemon can be run, Exim does not need root
37600 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
37601 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
37602 the advantages and disadvantages of running without root privilege.
37607 . ////////////////////////////////////////////////////////////////////////////
37608 . ////////////////////////////////////////////////////////////////////////////
37610 .chapter "Log files" "CHAPlog"
37611 .scindex IIDloggen "log" "general description"
37612 .cindex "log" "types of"
37613 Exim writes three different logs, referred to as the main log, the reject log,
37618 The main log records the arrival of each message and each delivery in a single
37619 line in each case. The format is as compact as possible, in an attempt to keep
37620 down the size of log files. Two-character flag sequences make it easy to pick
37621 out these lines. A number of other events are recorded in the main log. Some of
37622 them are optional, in which case the &%log_selector%& option controls whether
37623 they are included or not. A Perl script called &'eximstats'&, which does simple
37624 analysis of main log files, is provided in the Exim distribution (see section
37625 &<<SECTmailstat>>&).
37627 .cindex "reject log"
37628 The reject log records information from messages that are rejected as a result
37629 of a configuration option (that is, for policy reasons).
37630 The first line of each rejection is a copy of the line that is also written to
37631 the main log. Then, if the message's header has been read at the time the log
37632 is written, its contents are written to this log. Only the original header
37633 lines are available; header lines added by ACLs are not logged. You can use the
37634 reject log to check that your policy controls are working correctly; on a busy
37635 host this may be easier than scanning the main log for rejection messages. You
37636 can suppress the writing of the reject log by setting &%write_rejectlog%&
37639 .cindex "panic log"
37640 .cindex "system log"
37641 When certain serious errors occur, Exim writes entries to its panic log. If the
37642 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
37643 are usually written to the main log as well, but can get lost amid the mass of
37644 other entries. The panic log should be empty under normal circumstances. It is
37645 therefore a good idea to check it (or to have a &'cron'& script check it)
37646 regularly, in order to become aware of any problems. When Exim cannot open its
37647 panic log, it tries as a last resort to write to the system log (syslog). This
37648 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
37649 message itself is written at priority LOG_CRIT.
37652 Every log line starts with a timestamp, in the format shown in the following
37653 example. Note that many of the examples shown in this chapter are line-wrapped.
37654 In the log file, this would be all on one line:
37656 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
37659 By default, the timestamps are in the local timezone. There are two
37660 ways of changing this:
37663 You can set the &%timezone%& option to a different time zone; in particular, if
37668 the timestamps will be in UTC (aka GMT).
37670 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
37673 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
37677 .cindex "log" "process ids in"
37678 .cindex "pid (process id)" "in log lines"
37679 Exim does not include its process id in log lines by default, but you can
37680 request that it does so by specifying the &`pid`& log selector (see section
37681 &<<SECTlogselector>>&). When this is set, the process id is output, in square
37682 brackets, immediately after the time and date.
37687 .section "Where the logs are written" "SECTwhelogwri"
37688 .cindex "log" "destination"
37689 .cindex "log" "to file"
37690 .cindex "log" "to syslog"
37692 The logs may be written to local files, or to syslog, or both. However, it
37693 should be noted that many syslog implementations use UDP as a transport, and
37694 are therefore unreliable in the sense that messages are not guaranteed to
37695 arrive at the loghost, nor is the ordering of messages necessarily maintained.
37696 It has also been reported that on large log files (tens of megabytes) you may
37697 need to tweak syslog to prevent it syncing the file with each write &-- on
37698 Linux this has been seen to make syslog take 90% plus of CPU time.
37700 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
37701 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
37702 configuration. This latter string is expanded, so it can contain, for example,
37703 references to the host name:
37705 log_file_path = /var/log/$primary_hostname/exim_%slog
37707 It is generally advisable, however, to set the string in &_Local/Makefile_&
37708 rather than at runtime, because then the setting is available right from the
37709 start of Exim's execution. Otherwise, if there's something it wants to log
37710 before it has read the configuration file (for example, an error in the
37711 configuration file) it will not use the path you want, and may not be able to
37714 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
37715 list, currently limited to at most two items. This is one option where the
37716 facility for changing a list separator may not be used. The list must always be
37717 colon-separated. If an item in the list is &"syslog"& then syslog is used;
37718 otherwise the item must either be an absolute path, containing &`%s`& at the
37719 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
37720 implying the use of a default path.
37722 When Exim encounters an empty item in the list, it searches the list defined by
37723 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
37724 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
37725 mean &"use the path specified at build time"&. It no such item exists, log
37726 files are written in the &_log_& subdirectory of the spool directory. This is
37727 equivalent to the setting:
37729 log_file_path = $spool_directory/log/%slog
37731 If you do not specify anything at build time or runtime,
37732 or if you unset the option at runtime (i.e. &`log_file_path = `&),
37733 that is where the logs are written.
37735 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
37736 are in use &-- see section &<<SECTdatlogfil>>& below.
37738 Here are some examples of possible settings:
37740 &`LOG_FILE_PATH=syslog `& syslog only
37741 &`LOG_FILE_PATH=:syslog `& syslog and default path
37742 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
37743 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
37745 If there are more than two paths in the list, the first is used and a panic
37750 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
37751 .cindex "log" "cycling local files"
37752 .cindex "cycling logs"
37753 .cindex "&'exicyclog'&"
37754 .cindex "log" "local files; writing to"
37755 Some operating systems provide centralized and standardized methods for cycling
37756 log files. For those that do not, a utility script called &'exicyclog'& is
37757 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
37758 main and reject logs each time it is called. The maximum number of old logs to
37759 keep can be set. It is suggested this script is run as a daily &'cron'& job.
37761 An Exim delivery process opens the main log when it first needs to write to it,
37762 and it keeps the file open in case subsequent entries are required &-- for
37763 example, if a number of different deliveries are being done for the same
37764 message. However, remote SMTP deliveries can take a long time, and this means
37765 that the file may be kept open long after it is renamed if &'exicyclog'& or
37766 something similar is being used to rename log files on a regular basis. To
37767 ensure that a switch of log files is noticed as soon as possible, Exim calls
37768 &[stat()]& on the main log's name before reusing an open file, and if the file
37769 does not exist, or its inode has changed, the old file is closed and Exim
37770 tries to open the main log from scratch. Thus, an old log file may remain open
37771 for quite some time, but no Exim processes should write to it once it has been
37776 .section "Datestamped log files" "SECTdatlogfil"
37777 .cindex "log" "datestamped files"
37778 Instead of cycling the main and reject log files by renaming them
37779 periodically, some sites like to use files whose names contain a datestamp,
37780 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
37781 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
37782 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
37783 point where the datestamp is required. For example:
37785 log_file_path = /var/spool/exim/log/%slog-%D
37786 log_file_path = /var/log/exim-%s-%D.log
37787 log_file_path = /var/spool/exim/log/%D-%slog
37788 log_file_path = /var/log/exim/%s.%M
37790 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
37791 examples of names generated by the above examples:
37793 /var/spool/exim/log/mainlog-20021225
37794 /var/log/exim-reject-20021225.log
37795 /var/spool/exim/log/20021225-mainlog
37796 /var/log/exim/main.200212
37798 When this form of log file is specified, Exim automatically switches to new
37799 files at midnight. It does not make any attempt to compress old logs; you
37800 will need to write your own script if you require this. You should not
37801 run &'exicyclog'& with this form of logging.
37803 The location of the panic log is also determined by &%log_file_path%&, but it
37804 is not datestamped, because rotation of the panic log does not make sense.
37805 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
37806 the string. In addition, if it immediately follows a slash, a following
37807 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
37808 character is removed. Thus, the four examples above would give these panic
37811 /var/spool/exim/log/paniclog
37812 /var/log/exim-panic.log
37813 /var/spool/exim/log/paniclog
37814 /var/log/exim/panic
37818 .section "Logging to syslog" "SECID249"
37819 .cindex "log" "syslog; writing to"
37820 The use of syslog does not change what Exim logs or the format of its messages,
37821 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
37822 Exim's log lines are omitted when these lines are sent to syslog. Apart from
37823 that, the same strings are written to syslog as to log files. The syslog
37824 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
37825 by default, but you can change these by setting the &%syslog_facility%& and
37826 &%syslog_processname%& options, respectively. If Exim was compiled with
37827 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
37828 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
37829 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
37830 the time and host name to each line.
37831 The three log streams are mapped onto syslog priorities as follows:
37834 &'mainlog'& is mapped to LOG_INFO
37836 &'rejectlog'& is mapped to LOG_NOTICE
37838 &'paniclog'& is mapped to LOG_ALERT
37841 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
37842 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
37843 these are routed by syslog to the same place. You can suppress this duplication
37844 by setting &%syslog_duplication%& false.
37846 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
37847 entries contain multiple lines when headers are included. To cope with both
37848 these cases, entries written to syslog are split into separate &[syslog()]&
37849 calls at each internal newline, and also after a maximum of
37850 870 data characters. (This allows for a total syslog line length of 1024, when
37851 additions such as timestamps are added.) If you are running a syslog
37852 replacement that can handle lines longer than the 1024 characters allowed by
37853 RFC 3164, you should set
37855 SYSLOG_LONG_LINES=yes
37857 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
37858 lines, but it still splits at internal newlines in &'reject'& log entries.
37860 To make it easy to re-assemble split lines later, each component of a split
37861 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
37862 where <&'n'&> is the component number and <&'m'&> is the total number of
37863 components in the entry. The / delimiter is used when the line was split
37864 because it was too long; if it was split because of an internal newline, the \
37865 delimiter is used. For example, supposing the length limit to be 50 instead of
37866 870, the following would be the result of a typical rejection message to
37867 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
37868 name, and pid as added by syslog:
37870 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
37871 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
37872 [3/5] when scanning for sender: missing or malformed lo
37873 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
37876 The same error might cause the following lines to be written to &"rejectlog"&
37879 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
37880 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
37881 [3/18] er when scanning for sender: missing or malformed
37882 [4/18] local part in "<>" (envelope sender is <ph10@cam
37884 [6\18] Recipients: ph10@some.domain.cam.example
37885 [7\18] P Received: from [127.0.0.1] (ident=ph10)
37886 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
37887 [9\18] id 16RdAL-0006pc-00
37888 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
37889 [11\18] 09:43 +0100
37891 [13\18] Subject: this is a test header
37892 [18\18] X-something: this is another header
37893 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
37896 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
37898 Log lines that are neither too long nor contain newlines are written to syslog
37899 without modification.
37901 If only syslog is being used, the Exim monitor is unable to provide a log tail
37902 display, unless syslog is routing &'mainlog'& to a file on the local host and
37903 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
37908 .section "Log line flags" "SECID250"
37909 One line is written to the main log for each message received, and for each
37910 successful, unsuccessful, and delayed delivery. These lines can readily be
37911 picked out by the distinctive two-character flags that immediately follow the
37912 timestamp. The flags are:
37914 &`<=`& message arrival
37915 &`(=`& message fakereject
37916 &`=>`& normal message delivery
37917 &`->`& additional address in same delivery
37918 &`>>`& cutthrough message delivery
37919 &`*>`& delivery suppressed by &%-N%&
37920 &`**`& delivery failed; address bounced
37921 &`==`& delivery deferred; temporary problem
37925 .section "Logging message reception" "SECID251"
37926 .cindex "log" "reception line"
37927 The format of the single-line entry in the main log that is written for every
37928 message received is shown in the basic example below, which is split over
37929 several lines in order to fit it on the page:
37931 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
37932 H=mailer.fict.example [192.168.123.123] U=exim
37933 P=smtp S=5678 id=<incoming message id>
37935 The address immediately following &"<="& is the envelope sender address. A
37936 bounce message is shown with the sender address &"<>"&, and if it is locally
37937 generated, this is followed by an item of the form
37941 which is a reference to the message that caused the bounce to be sent.
37945 For messages from other hosts, the H and U fields identify the remote host and
37946 record the RFC 1413 identity of the user that sent the message, if one was
37947 received. The number given in square brackets is the IP address of the sending
37948 host. If there is a single, unparenthesized host name in the H field, as
37949 above, it has been verified to correspond to the IP address (see the
37950 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
37951 by the remote host in the SMTP HELO or EHLO command, and has not been
37952 verified. If verification yields a different name to that given for HELO or
37953 EHLO, the verified name appears first, followed by the HELO or EHLO
37954 name in parentheses.
37956 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
37957 without brackets, in the HELO or EHLO command, leading to entries in
37958 the log containing text like these examples:
37960 H=(10.21.32.43) [192.168.8.34]
37961 H=([10.21.32.43]) [192.168.8.34]
37963 This can be confusing. Only the final address in square brackets can be relied
37966 For locally generated messages (that is, messages not received over TCP/IP),
37967 the H field is omitted, and the U field contains the login name of the caller
37970 .cindex "authentication" "logging"
37971 .cindex "AUTH" "logging"
37972 For all messages, the P field specifies the protocol used to receive the
37973 message. This is the value that is stored in &$received_protocol$&. In the case
37974 of incoming SMTP messages, the value indicates whether or not any SMTP
37975 extensions (ESMTP), encryption, or authentication were used. If the SMTP
37976 session was encrypted, there is an additional X field that records the cipher
37977 suite that was used.
37979 .cindex log protocol
37980 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
37981 hosts that have authenticated themselves using the SMTP AUTH command. The first
37982 value is used when the SMTP connection was encrypted (&"secure"&). In this case
37983 there is an additional item A= followed by the name of the authenticator that
37984 was used. If an authenticated identification was set up by the authenticator's
37985 &%server_set_id%& option, this is logged too, separated by a colon from the
37986 authenticator name.
37988 .cindex "size" "of message"
37989 The id field records the existing message id, if present. The size of the
37990 received message is given by the S field. When the message is delivered,
37991 headers may be removed or added, so that the size of delivered copies of the
37992 message may not correspond with this value (and indeed may be different to each
37995 The &%log_selector%& option can be used to request the logging of additional
37996 data when a message is received. See section &<<SECTlogselector>>& below.
38000 .section "Logging deliveries" "SECID252"
38001 .cindex "log" "delivery line"
38002 The format of the single-line entry in the main log that is written for every
38003 delivery is shown in one of the examples below, for local and remote
38004 deliveries, respectively. Each example has been split into multiple lines in order
38005 to fit it on the page:
38007 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38008 <marv@hitch.fict.example> R=localuser T=local_delivery
38009 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38010 monk@holistic.fict.example R=dnslookup T=remote_smtp
38011 H=holistic.fict.example [192.168.234.234]
38013 For ordinary local deliveries, the original address is given in angle brackets
38014 after the final delivery address, which might be a pipe or a file. If
38015 intermediate address(es) exist between the original and the final address, the
38016 last of these is given in parentheses after the final address. The R and T
38017 fields record the router and transport that were used to process the address.
38019 If SMTP AUTH was used for the delivery there is an additional item A=
38020 followed by the name of the authenticator that was used.
38021 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38022 option, this is logged too, separated by a colon from the authenticator name.
38024 If a shadow transport was run after a successful local delivery, the log line
38025 for the successful delivery has an item added on the end, of the form
38027 &`ST=<`&&'shadow transport name'&&`>`&
38029 If the shadow transport did not succeed, the error message is put in
38030 parentheses afterwards.
38032 .cindex "asterisk" "after IP address"
38033 When more than one address is included in a single delivery (for example, two
38034 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38035 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38036 down a single SMTP connection, an asterisk follows the IP address in the log
38037 lines for the second and subsequent messages.
38038 When two or more messages are delivered down a single TLS connection, the
38039 DNS and some TLS-related information logged for the first message delivered
38040 will not be present in the log lines for the second and subsequent messages.
38041 TLS cipher information is still available.
38043 .cindex "delivery" "cutthrough; logging"
38044 .cindex "cutthrough" "logging"
38045 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38046 line precedes the reception line, since cutthrough waits for a possible
38047 rejection from the destination in case it can reject the sourced item.
38049 The generation of a reply message by a filter file gets logged as a
38050 &"delivery"& to the addressee, preceded by &">"&.
38052 The &%log_selector%& option can be used to request the logging of additional
38053 data when a message is delivered. See section &<<SECTlogselector>>& below.
38056 .section "Discarded deliveries" "SECID253"
38057 .cindex "discarded messages"
38058 .cindex "message" "discarded"
38059 .cindex "delivery" "discarded; logging"
38060 When a message is discarded as a result of the command &"seen finish"& being
38061 obeyed in a filter file which generates no deliveries, a log entry of the form
38063 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38064 <low.club@bridge.example> R=userforward
38066 is written, to record why no deliveries are logged. When a message is discarded
38067 because it is aliased to &":blackhole:"& the log line is like this:
38069 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38070 <hole@nowhere.example> R=blackhole_router
38074 .section "Deferred deliveries" "SECID254"
38075 When a delivery is deferred, a line of the following form is logged:
38077 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38078 R=dnslookup T=smtp defer (146): Connection refused
38080 In the case of remote deliveries, the error is the one that was given for the
38081 last IP address that was tried. Details of individual SMTP failures are also
38082 written to the log, so the above line would be preceded by something like
38084 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38085 mail1.endrest.example [192.168.239.239]: Connection refused
38087 When a deferred address is skipped because its retry time has not been reached,
38088 a message is written to the log, but this can be suppressed by setting an
38089 appropriate value in &%log_selector%&.
38093 .section "Delivery failures" "SECID255"
38094 .cindex "delivery" "failure; logging"
38095 If a delivery fails because an address cannot be routed, a line of the
38096 following form is logged:
38098 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38099 <jim@trek99.example>: unknown mail domain
38101 If a delivery fails at transport time, the router and transport are shown, and
38102 the response from the remote host is included, as in this example:
38104 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38105 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38106 after pipelined RCPT TO:<ace400@pb.example>: host
38107 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38108 <ace400@pb.example>...Addressee unknown
38110 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38111 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38112 disabling PIPELINING. The log lines for all forms of delivery failure are
38113 flagged with &`**`&.
38117 .section "Fake deliveries" "SECID256"
38118 .cindex "delivery" "fake; logging"
38119 If a delivery does not actually take place because the &%-N%& option has been
38120 used to suppress it, a normal delivery line is written to the log, except that
38121 &"=>"& is replaced by &"*>"&.
38125 .section "Completion" "SECID257"
38128 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38130 is written to the main log when a message is about to be removed from the spool
38131 at the end of its processing.
38136 .section "Summary of Fields in Log Lines" "SECID258"
38137 .cindex "log" "summary of fields"
38138 A summary of the field identifiers that are used in log lines is shown in
38139 the following table:
38141 &`A `& authenticator name (and optional id and sender)
38142 &`C `& SMTP confirmation on delivery
38143 &` `& command list for &"no mail in SMTP session"&
38144 &`CV `& certificate verification status
38145 &`D `& duration of &"no mail in SMTP session"&
38146 &`DKIM`& domain verified in incoming message
38147 &`DN `& distinguished name from peer certificate
38148 &`DS `& DNSSEC secured lookups
38149 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38150 &`F `& sender address (on delivery lines)
38151 &`H `& host name and IP address
38152 &`I `& local interface used
38153 &`id `& message id (from header) for incoming message
38154 &`K `& CHUNKING extension used
38155 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38156 &`M8S `& 8BITMIME status for incoming message
38157 &`P `& on &`<=`& lines: protocol used
38158 &` `& on &`=>`& and &`**`& lines: return path
38159 &`PRDR`& PRDR extension used
38160 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38161 &`Q `& alternate queue name
38162 &`QT `& on &`=>`& lines: time spent on queue so far
38163 &` `& on &"Completed"& lines: time spent on queue
38164 &`R `& on &`<=`& lines: reference for local bounce
38165 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38166 &`RT `& on &`<=`& lines: time taken for reception
38167 &`S `& size of message in bytes
38168 &`SNI `& server name indication from TLS client hello
38169 &`ST `& shadow transport name
38170 &`T `& on &`<=`& lines: message subject (topic)
38171 &`TFO `& connection took advantage of TCP Fast Open
38172 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38173 &`U `& local user or RFC 1413 identity
38174 &`X `& TLS cipher suite
38178 .section "Other log entries" "SECID259"
38179 Various other types of log entry are written from time to time. Most should be
38180 self-explanatory. Among the more common are:
38183 .cindex "retry" "time not reached"
38184 &'retry time not reached'&&~&~An address previously suffered a temporary error
38185 during routing or local delivery, and the time to retry has not yet arrived.
38186 This message is not written to an individual message log file unless it happens
38187 during the first delivery attempt.
38189 &'retry time not reached for any host'&&~&~An address previously suffered
38190 temporary errors during remote delivery, and the retry time has not yet arrived
38191 for any of the hosts to which it is routed.
38193 .cindex "spool directory" "file locked"
38194 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38195 some other Exim process is already working on the message. This can be quite
38196 common if queue running processes are started at frequent intervals. The
38197 &'exiwhat'& utility script can be used to find out what Exim processes are
38200 .cindex "error" "ignored"
38201 &'error ignored'&&~&~There are several circumstances that give rise to this
38204 Exim failed to deliver a bounce message whose age was greater than
38205 &%ignore_bounce_errors_after%&. The bounce was discarded.
38207 A filter file set up a delivery using the &"noerror"& option, and the delivery
38208 failed. The delivery was discarded.
38210 A delivery set up by a router configured with
38211 . ==== As this is a nested list, any displays it contains must be indented
38212 . ==== as otherwise they are too far to the left.
38216 failed. The delivery was discarded.
38219 .cindex DKIM "log line"
38220 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38221 logging and the message has a DKIM signature header.
38228 .section "Reducing or increasing what is logged" "SECTlogselector"
38229 .cindex "log" "selectors"
38230 By setting the &%log_selector%& global option, you can disable some of Exim's
38231 default logging, or you can request additional logging. The value of
38232 &%log_selector%& is made up of names preceded by plus or minus characters. For
38235 log_selector = +arguments -retry_defer
38237 The list of optional log items is in the following table, with the default
38238 selection marked by asterisks:
38240 &` 8bitmime `& received 8BITMIME status
38241 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38242 &` address_rewrite `& address rewriting
38243 &` all_parents `& all parents in => lines
38244 &` arguments `& command line arguments
38245 &`*connection_reject `& connection rejections
38246 &`*delay_delivery `& immediate delivery delayed
38247 &` deliver_time `& time taken to attempt delivery
38248 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38249 &`*dkim `& DKIM verified domain on <= lines
38250 &` dkim_verbose `& separate full DKIM verification result line, per signature
38251 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38252 &` dnssec `& DNSSEC secured lookups
38253 &`*etrn `& ETRN commands
38254 &`*host_lookup_failed `& as it says
38255 &` ident_timeout `& timeout for ident connection
38256 &` incoming_interface `& local interface on <= and => lines
38257 &` incoming_port `& remote port on <= lines
38258 &`*lost_incoming_connection `& as it says (includes timeouts)
38259 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38260 &`*msg_id `& on <= lines, Message-ID: header value
38261 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38262 &` outgoing_interface `& local interface on => lines
38263 &` outgoing_port `& add remote port to => lines
38264 &`*queue_run `& start and end queue runs
38265 &` queue_time `& time on queue for one recipient
38266 &` queue_time_overall `& time on queue for whole message
38267 &` pid `& Exim process id
38268 &` pipelining `& PIPELINING use, on <= and => lines
38269 &` proxy `& proxy address on <= and => lines
38270 &` receive_time `& time taken to receive message
38271 &` received_recipients `& recipients on <= lines
38272 &` received_sender `& sender on <= lines
38273 &`*rejected_header `& header contents on reject log
38274 &`*retry_defer `& &"retry time not reached"&
38275 &` return_path_on_delivery `& put return path on => and ** lines
38276 &` sender_on_delivery `& add sender to => lines
38277 &`*sender_verify_fail `& sender verification failures
38278 &`*size_reject `& rejection because too big
38279 &`*skip_delivery `& delivery skipped in a queue run
38280 &`*smtp_confirmation `& SMTP confirmation on => lines
38281 &` smtp_connection `& incoming SMTP connections
38282 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38283 &` smtp_mailauth `& AUTH argument to MAIL commands
38284 &` smtp_no_mail `& session with no MAIL commands
38285 &` smtp_protocol_error `& SMTP protocol errors
38286 &` smtp_syntax_error `& SMTP syntax errors
38287 &` subject `& contents of &'Subject:'& on <= lines
38288 &`*tls_certificate_verified `& certificate verification status
38289 &`*tls_cipher `& TLS cipher suite on <= and => lines
38290 &` tls_peerdn `& TLS peer DN on <= and => lines
38291 &` tls_resumption `& append * to cipher field
38292 &` tls_sni `& TLS SNI on <= lines
38293 &` unknown_in_list `& DNS lookup failed in list match
38295 &` all `& all of the above
38297 See also the &%slow_lookup_log%& main configuration option,
38298 section &<<SECID99>>&
38300 More details on each of these items follows:
38304 .cindex "log" "8BITMIME"
38305 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38306 which may help in tracking down interoperability issues with ancient MTAs
38307 that are not 8bit clean. This is added to the &"<="& line, tagged with
38308 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38309 &`7BIT`& and &`8BITMIME`& respectively.
38311 .cindex "&%warn%& ACL verb" "log when skipping"
38312 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38313 its conditions cannot be evaluated, a log line to this effect is written if
38314 this log selector is set.
38316 .cindex "log" "rewriting"
38317 .cindex "rewriting" "logging"
38318 &%address_rewrite%&: This applies both to global rewrites and per-transport
38319 rewrites, but not to rewrites in filters run as an unprivileged user (because
38320 such users cannot access the log).
38322 .cindex "log" "full parentage"
38323 &%all_parents%&: Normally only the original and final addresses are logged on
38324 delivery lines; with this selector, intermediate parents are given in
38325 parentheses between them.
38327 .cindex "log" "Exim arguments"
38328 .cindex "Exim arguments, logging"
38329 &%arguments%&: This causes Exim to write the arguments with which it was called
38330 to the main log, preceded by the current working directory. This is a debugging
38331 feature, added to make it easier to find out how certain MUAs call
38332 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38333 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38334 that are empty or that contain white space are quoted. Non-printing characters
38335 are shown as escape sequences. This facility cannot log unrecognized arguments,
38336 because the arguments are checked before the configuration file is read. The
38337 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38338 between the caller and Exim.
38340 .cindex "log" "connection rejections"
38341 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38342 connection is rejected, for whatever reason.
38344 .cindex "log" "delayed delivery"
38345 .cindex "delayed delivery, logging"
38346 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38347 started for an incoming message because the load is too high or too many
38348 messages were received on one connection. Logging does not occur if no delivery
38349 process is started because &%queue_only%& is set or &%-odq%& was used.
38351 .cindex "log" "delivery duration"
38352 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38353 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38354 If millisecond logging is enabled, short times will be shown with greater
38355 precision, eg. &`DT=0.304s`&.
38357 .cindex "log" "message size on delivery"
38358 .cindex "size" "of message"
38359 &%delivery_size%&: For each delivery, the size of message delivered is added to
38360 the &"=>"& line, tagged with S=.
38362 .cindex log "DKIM verification"
38363 .cindex DKIM "verification logging"
38364 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38365 verifies successfully a tag of DKIM is added, with one of the verified domains.
38367 .cindex log "DKIM verification"
38368 .cindex DKIM "verification logging"
38369 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38371 .cindex "log" "dnslist defer"
38372 .cindex "DNS list" "logging defer"
38373 .cindex "black list (DNS)"
38374 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38375 DNS black list suffers a temporary error.
38378 .cindex dnssec logging
38379 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38380 dns lookups gave secure results a tag of DS is added.
38381 For acceptance this covers the reverse and forward lookups for host name verification.
38382 It does not cover helo-name verification.
38383 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38385 .cindex "log" "ETRN commands"
38386 .cindex "ETRN" "logging"
38387 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38388 is run to determine whether or not it is actually accepted. An invalid ETRN
38389 command, or one received within a message transaction is not logged by this
38390 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38392 .cindex "log" "host lookup failure"
38393 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38394 any addresses, or when a lookup of an IP address fails to find a host name, a
38395 log line is written. This logging does not apply to direct DNS lookups when
38396 routing email addresses, but it does apply to &"byname"& lookups.
38398 .cindex "log" "ident timeout"
38399 .cindex "RFC 1413" "logging timeout"
38400 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38401 client's ident port times out.
38403 .cindex "log" "incoming interface"
38404 .cindex "log" "local interface"
38405 .cindex "log" "local address and port"
38406 .cindex "TCP/IP" "logging local address and port"
38407 .cindex "interface" "logging"
38408 &%incoming_interface%&: The interface on which a message was received is added
38409 to the &"<="& line as an IP address in square brackets, tagged by I= and
38410 followed by a colon and the port number. The local interface and port are also
38411 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38412 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
38413 The latter can be disabled by turning off the &%outgoing_interface%& option.
38415 .cindex log "incoming proxy address"
38416 .cindex proxy "logging proxy address"
38417 .cindex "TCP/IP" "logging proxy address"
38418 &%proxy%&: The internal (closest to the system running Exim) IP address
38419 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38420 on a proxied connection
38421 or the &"=>"& line for a message delivered on a proxied connection.
38422 See &<<SECTproxyInbound>>& for more information.
38424 .cindex "log" "incoming remote port"
38425 .cindex "port" "logging remote"
38426 .cindex "TCP/IP" "logging incoming remote port"
38427 .vindex "&$sender_fullhost$&"
38428 .vindex "&$sender_rcvhost$&"
38429 &%incoming_port%&: The remote port number from which a message was received is
38430 added to log entries and &'Received:'& header lines, following the IP address
38431 in square brackets, and separated from it by a colon. This is implemented by
38432 changing the value that is put in the &$sender_fullhost$& and
38433 &$sender_rcvhost$& variables. Recording the remote port number has become more
38434 important with the widening use of NAT (see RFC 2505).
38436 .cindex "log" "dropped connection"
38437 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38438 connection is unexpectedly dropped.
38440 .cindex "log" "millisecond timestamps"
38441 .cindex millisecond logging
38442 .cindex timestamps "millisecond, in logs"
38443 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
38444 appended to the seconds value.
38446 .cindex "log" "message id"
38447 &%msg_id%&: The value of the Message-ID: header.
38449 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
38450 This will be either because the message is a bounce, or was submitted locally
38451 (submission mode) without one.
38452 The field identifier will have an asterix appended: &"id*="&.
38454 .cindex "log" "outgoing interface"
38455 .cindex "log" "local interface"
38456 .cindex "log" "local address and port"
38457 .cindex "TCP/IP" "logging local address and port"
38458 .cindex "interface" "logging"
38459 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
38460 interface on which a message was sent is added to delivery lines as an I= tag
38461 followed by IP address in square brackets. You can disable this by turning
38462 off the &%outgoing_interface%& option.
38464 .cindex "log" "outgoing remote port"
38465 .cindex "port" "logging outgoing remote"
38466 .cindex "TCP/IP" "logging outgoing remote port"
38467 &%outgoing_port%&: The remote port number is added to delivery log lines (those
38468 containing => tags) following the IP address.
38469 The local port is also added if &%incoming_interface%& and
38470 &%outgoing_interface%& are both enabled.
38471 This option is not included in the default setting, because for most ordinary
38472 configurations, the remote port number is always 25 (the SMTP port), and the
38473 local port is a random ephemeral port.
38475 .cindex "log" "process ids in"
38476 .cindex "pid (process id)" "in log lines"
38477 &%pid%&: The current process id is added to every log line, in square brackets,
38478 immediately after the time and date.
38480 .cindex log pipelining
38481 .cindex pipelining "logging outgoing"
38482 &%pipelining%&: A field is added to delivery and accept
38483 log lines when the ESMTP PIPELINING extension was used.
38484 The field is a single "L".
38486 On accept lines, where PIPELINING was offered but not used by the client,
38487 the field has a minus appended.
38489 .cindex "pipelining" "early connection"
38490 If Exim is built with the SUPPORT_PIPE_CONNECT build option
38491 accept "L" fields have a period appended if the feature was
38492 offered but not used, or an asterisk appended if used.
38493 Delivery "L" fields have an asterisk appended if used.
38496 .cindex "log" "queue run"
38497 .cindex "queue runner" "logging"
38498 &%queue_run%&: The start and end of every queue run are logged.
38500 .cindex "log" "queue time"
38501 &%queue_time%&: The amount of time the message has been in the queue on the
38502 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
38503 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
38504 includes reception time as well as the delivery time for the current address.
38505 This means that it may be longer than the difference between the arrival and
38506 delivery log line times, because the arrival log line is not written until the
38507 message has been successfully received.
38508 If millisecond logging is enabled, short times will be shown with greater
38509 precision, eg. &`QT=1.578s`&.
38511 &%queue_time_overall%&: The amount of time the message has been in the queue on
38512 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
38513 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
38514 message, so it includes reception time as well as the total delivery time.
38516 .cindex "log" "receive duration"
38517 &%receive_time%&: For each message, the amount of real time it has taken to
38518 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
38519 If millisecond logging is enabled, short times will be shown with greater
38520 precision, eg. &`RT=0.204s`&.
38522 .cindex "log" "recipients"
38523 &%received_recipients%&: The recipients of a message are listed in the main log
38524 as soon as the message is received. The list appears at the end of the log line
38525 that is written when a message is received, preceded by the word &"for"&. The
38526 addresses are listed after they have been qualified, but before any rewriting
38528 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
38531 .cindex "log" "sender reception"
38532 &%received_sender%&: The unrewritten original sender of a message is added to
38533 the end of the log line that records the message's arrival, after the word
38534 &"from"& (before the recipients if &%received_recipients%& is also set).
38536 .cindex "log" "header lines for rejection"
38537 &%rejected_header%&: If a message's header has been received at the time a
38538 rejection is written to the reject log, the complete header is added to the
38539 log. Header logging can be turned off individually for messages that are
38540 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
38542 .cindex "log" "retry defer"
38543 &%retry_defer%&: A log line is written if a delivery is deferred because a
38544 retry time has not yet been reached. However, this &"retry time not reached"&
38545 message is always omitted from individual message logs after the first delivery
38548 .cindex "log" "return path"
38549 &%return_path_on_delivery%&: The return path that is being transmitted with
38550 the message is included in delivery and bounce lines, using the tag P=.
38551 This is omitted if no delivery actually happens, for example, if routing fails,
38552 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
38554 .cindex "log" "sender on delivery"
38555 &%sender_on_delivery%&: The message's sender address is added to every delivery
38556 and bounce line, tagged by F= (for &"from"&).
38557 This is the original sender that was received with the message; it is not
38558 necessarily the same as the outgoing return path.
38560 .cindex "log" "sender verify failure"
38561 &%sender_verify_fail%&: If this selector is unset, the separate log line that
38562 gives details of a sender verification failure is not written. Log lines for
38563 the rejection of SMTP commands contain just &"sender verify failed"&, so some
38566 .cindex "log" "size rejection"
38567 &%size_reject%&: A log line is written whenever a message is rejected because
38570 .cindex "log" "frozen messages; skipped"
38571 .cindex "frozen messages" "logging skipping"
38572 &%skip_delivery%&: A log line is written whenever a message is skipped during a
38573 queue run because it is frozen or because another process is already delivering
38575 .cindex "&""spool file is locked""&"
38576 The message that is written is &"spool file is locked"&.
38578 .cindex "log" "smtp confirmation"
38579 .cindex "SMTP" "logging confirmation"
38580 .cindex "LMTP" "logging confirmation"
38581 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
38582 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
38583 A number of MTAs (including Exim) return an identifying string in this
38586 .cindex "log" "SMTP connections"
38587 .cindex "SMTP" "logging connections"
38588 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
38589 established or closed, unless the connection is from a host that matches
38590 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
38591 only when the closure is unexpected.) This applies to connections from local
38592 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
38593 dropped in the middle of a message, a log line is always written, whether or
38594 not this selector is set, but otherwise nothing is written at the start and end
38595 of connections unless this selector is enabled.
38597 For TCP/IP connections to an Exim daemon, the current number of connections is
38598 included in the log message for each new connection, but note that the count is
38599 reset if the daemon is restarted.
38600 Also, because connections are closed (and the closure is logged) in
38601 subprocesses, the count may not include connections that have been closed but
38602 whose termination the daemon has not yet noticed. Thus, while it is possible to
38603 match up the opening and closing of connections in the log, the value of the
38604 logged counts may not be entirely accurate.
38606 .cindex "log" "SMTP transaction; incomplete"
38607 .cindex "SMTP" "logging incomplete transactions"
38608 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
38609 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
38610 and the message sender plus any accepted recipients are included in the log
38611 line. This can provide evidence of dictionary attacks.
38613 .cindex "log" "non-MAIL SMTP sessions"
38614 .cindex "MAIL" "logging session without"
38615 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
38616 connection terminates without having issued a MAIL command. This includes both
38617 the case when the connection is dropped, and the case when QUIT is used. It
38618 does not include cases where the connection is rejected right at the start (by
38619 an ACL, or because there are too many connections, or whatever). These cases
38620 already have their own log lines.
38622 The log line that is written contains the identity of the client in the usual
38623 way, followed by D= and a time, which records the duration of the connection.
38624 If the connection was authenticated, this fact is logged exactly as it is for
38625 an incoming message, with an A= item. If the connection was encrypted, CV=,
38626 DN=, and X= items may appear as they do for an incoming message, controlled by
38627 the same logging options.
38629 Finally, if any SMTP commands were issued during the connection, a C= item
38630 is added to the line, listing the commands that were used. For example,
38634 shows that the client issued QUIT straight after EHLO. If there were fewer
38635 than 20 commands, they are all listed. If there were more than 20 commands,
38636 the last 20 are listed, preceded by &"..."&. However, with the default
38637 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
38638 have been aborted before 20 non-mail commands are processed.
38640 &%smtp_mailauth%&: A third subfield with the authenticated sender,
38641 colon-separated, is appended to the A= item for a message arrival or delivery
38642 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
38643 was accepted or used.
38645 .cindex "log" "SMTP protocol error"
38646 .cindex "SMTP" "logging protocol error"
38647 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
38648 encountered. Exim does not have perfect detection of all protocol errors
38649 because of transmission delays and the use of pipelining. If PIPELINING has
38650 been advertised to a client, an Exim server assumes that the client will use
38651 it, and therefore it does not count &"expected"& errors (for example, RCPT
38652 received after rejecting MAIL) as protocol errors.
38654 .cindex "SMTP" "logging syntax errors"
38655 .cindex "SMTP" "syntax errors; logging"
38656 .cindex "SMTP" "unknown command; logging"
38657 .cindex "log" "unknown SMTP command"
38658 .cindex "log" "SMTP syntax error"
38659 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
38660 encountered. An unrecognized command is treated as a syntax error. For an
38661 external connection, the host identity is given; for an internal connection
38662 using &%-bs%& the sender identification (normally the calling user) is given.
38664 .cindex "log" "subject"
38665 .cindex "subject, logging"
38666 &%subject%&: The subject of the message is added to the arrival log line,
38667 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
38668 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
38669 specifies whether characters with values greater than 127 should be logged
38670 unchanged, or whether they should be rendered as escape sequences.
38672 .cindex "log" "certificate verification"
38674 .cindex DANE logging
38675 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
38676 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
38678 using a CA trust anchor,
38679 &`CA=dane`& if using a DNS trust anchor,
38680 and &`CV=no`& if not.
38682 .cindex "log" "TLS cipher"
38683 .cindex "TLS" "logging cipher"
38684 &%tls_cipher%&: When a message is sent or received over an encrypted
38685 connection, the cipher suite used is added to the log line, preceded by X=.
38687 .cindex "log" "TLS peer DN"
38688 .cindex "TLS" "logging peer DN"
38689 &%tls_peerdn%&: When a message is sent or received over an encrypted
38690 connection, and a certificate is supplied by the remote host, the peer DN is
38691 added to the log line, preceded by DN=.
38693 .cindex "log" "TLS resumption"
38694 .cindex "TLS" "logging session resumption"
38696 &%tls_resumption%&: When a message is sent or received over an encrypted
38697 connection and the TLS session resumed one used on a previous TCP connection,
38698 an asterisk is appended to the X= cipher field in the log line.
38701 .cindex "log" "TLS SNI"
38702 .cindex "TLS" "logging SNI"
38703 &%tls_sni%&: When a message is received over an encrypted connection, and
38704 the remote host provided the Server Name Indication extension, the SNI is
38705 added to the log line, preceded by SNI=.
38707 .cindex "log" "DNS failure in list"
38708 &%unknown_in_list%&: This setting causes a log entry to be written when the
38709 result of a list match is failure because a DNS lookup failed.
38713 .section "Message log" "SECID260"
38714 .cindex "message" "log file for"
38715 .cindex "log" "message log; description of"
38716 .cindex "&_msglog_& directory"
38717 .oindex "&%preserve_message_logs%&"
38718 In addition to the general log files, Exim writes a log file for each message
38719 that it handles. The names of these per-message logs are the message ids, and
38720 they are kept in the &_msglog_& sub-directory of the spool directory. Each
38721 message log contains copies of the log lines that apply to the message. This
38722 makes it easier to inspect the status of an individual message without having
38723 to search the main log. A message log is deleted when processing of the message
38724 is complete, unless &%preserve_message_logs%& is set, but this should be used
38725 only with great care because they can fill up your disk very quickly.
38727 On a heavily loaded system, it may be desirable to disable the use of
38728 per-message logs, in order to reduce disk I/O. This can be done by setting the
38729 &%message_logs%& option false.
38735 . ////////////////////////////////////////////////////////////////////////////
38736 . ////////////////////////////////////////////////////////////////////////////
38738 .chapter "Exim utilities" "CHAPutils"
38739 .scindex IIDutils "utilities"
38740 A number of utility scripts and programs are supplied with Exim and are
38741 described in this chapter. There is also the Exim Monitor, which is covered in
38742 the next chapter. The utilities described here are:
38744 .itable none 0 0 3 7* left 15* left 40* left
38745 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
38746 "list what Exim processes are doing"
38747 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
38748 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
38749 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
38750 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
38752 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
38753 .irow &<<SECTmailstat>>& &'eximstats'& &&&
38754 "extract statistics from the log"
38755 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
38756 "check address acceptance from given IP"
38757 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
38758 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
38759 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
38760 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
38761 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
38762 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
38765 Another utility that might be of use to sites with many MTAs is Tom Kistner's
38766 &'exilog'&. It provides log visualizations across multiple Exim servers. See
38767 &url(https://duncanthrax.net/exilog/) for details.
38772 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
38773 .cindex "&'exiwhat'&"
38774 .cindex "process, querying"
38776 On operating systems that can restart a system call after receiving a signal
38777 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
38778 a line describing what it is doing to the file &_exim-process.info_& in the
38779 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
38780 processes it can find, having first emptied the file. It then waits for one
38781 second to allow the Exim processes to react before displaying the results. In
38782 order to run &'exiwhat'& successfully you have to have sufficient privilege to
38783 send the signal to the Exim processes, so it is normally run as root.
38785 &*Warning*&: This is not an efficient process. It is intended for occasional
38786 use by system administrators. It is not sensible, for example, to set up a
38787 script that sends SIGUSR1 signals to Exim processes at short intervals.
38790 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
38791 varies in different operating systems. Not only are different options used,
38792 but the format of the output is different. For this reason, there are some
38793 system configuration options that configure exactly how &'exiwhat'& works. If
38794 it doesn't seem to be working for you, check the following compile-time
38797 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
38798 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
38799 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
38800 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
38802 An example of typical output from &'exiwhat'& is
38804 164 daemon: -q1h, listening on port 25
38805 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
38806 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
38807 [10.19.42.42] (editor@ref.example)
38808 10592 handling incoming call from [192.168.243.242]
38809 10628 accepting a local non-SMTP message
38811 The first number in the output line is the process number. The third line has
38812 been split here, in order to fit it on the page.
38816 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
38817 .cindex "&'exiqgrep'&"
38818 .cindex "queue" "grepping"
38819 This utility is a Perl script contributed by Matt Hubbard. It runs
38823 or (in case &*-a*& switch is specified)
38827 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
38828 contain alternate exim configuration the queue management might be using.
38830 to obtain a queue listing, and then greps the output to select messages
38831 that match given criteria. The following selection options are available:
38834 .vitem &*-f*&&~<&'regex'&>
38835 Match the sender address using a case-insensitive search. The field that is
38836 tested is enclosed in angle brackets, so you can test for bounce messages with
38840 .vitem &*-r*&&~<&'regex'&>
38841 Match a recipient address using a case-insensitive search. The field that is
38842 tested is not enclosed in angle brackets.
38844 .vitem &*-s*&&~<&'regex'&>
38845 Match against the size field.
38847 .vitem &*-y*&&~<&'seconds'&>
38848 Match messages that are younger than the given time.
38850 .vitem &*-o*&&~<&'seconds'&>
38851 Match messages that are older than the given time.
38854 Match only frozen messages.
38857 Match only non-frozen messages.
38859 .vitem &*-G*&&~<&'queuename'&>
38860 Match only messages in the given queue. Without this, the default queue is searched.
38863 The following options control the format of the output:
38867 Display only the count of matching messages.
38870 Long format &-- display the full message information as output by Exim. This is
38874 Display message ids only.
38877 Brief format &-- one line per message.
38880 Display messages in reverse order.
38883 Include delivered recipients in queue listing.
38886 There is one more option, &%-h%&, which outputs a list of options.
38890 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
38891 .cindex "&'exiqsumm'&"
38892 .cindex "queue" "summary"
38893 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
38894 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
38895 running a command such as
38897 exim -bp | exiqsumm
38899 The output consists of one line for each domain that has messages waiting for
38900 it, as in the following example:
38902 3 2322 74m 66m msn.com.example
38904 Each line lists the number of pending deliveries for a domain, their total
38905 volume, and the length of time that the oldest and the newest messages have
38906 been waiting. Note that the number of pending deliveries is greater than the
38907 number of messages when messages have more than one recipient.
38909 A summary line is output at the end. By default the output is sorted on the
38910 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
38911 the output to be sorted by oldest message and by count of messages,
38912 respectively. There are also three options that split the messages for each
38913 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
38914 separates frozen messages, and &%-s%& separates messages according to their
38917 The output of &'exim -bp'& contains the original addresses in the message, so
38918 this also applies to the output from &'exiqsumm'&. No domains from addresses
38919 generated by aliasing or forwarding are included (unless the &%one_time%&
38920 option of the &(redirect)& router has been used to convert them into &"top
38921 level"& addresses).
38926 .section "Extracting specific information from the log (exigrep)" &&&
38928 .cindex "&'exigrep'&"
38929 .cindex "log" "extracts; grepping for"
38930 The &'exigrep'& utility is a Perl script that searches one or more main log
38931 files for entries that match a given pattern. When it finds a match, it
38932 extracts all the log entries for the relevant message, not just those that
38933 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
38934 given message, or all mail for a given user, or for a given host, for example.
38935 The input files can be in Exim log format or syslog format.
38936 If a matching log line is not associated with a specific message, it is
38937 included in &'exigrep'&'s output without any additional lines. The usage is:
38939 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
38941 If no log filenames are given on the command line, the standard input is read.
38943 The &%-t%& argument specifies a number of seconds. It adds an additional
38944 condition for message selection. Messages that are complete are shown only if
38945 they spent more than <&'n'&> seconds in the queue.
38947 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
38948 makes it case-sensitive. This may give a performance improvement when searching
38949 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
38950 option; with &%-I%& they do not. In both cases it is possible to change the
38951 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
38953 The &%-l%& option means &"literal"&, that is, treat all characters in the
38954 pattern as standing for themselves. Otherwise the pattern must be a Perl
38955 regular expression.
38957 The &%-v%& option inverts the matching condition. That is, a line is selected
38958 if it does &'not'& match the pattern.
38960 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
38961 that are generated as a result/response to a message that &'exigrep'& matched
38965 user_a sends a message to user_b, which generates a bounce back to user_b. If
38966 &'exigrep'& is used to search for &"user_a"&, only the first message will be
38967 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
38968 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
38969 when searching for &"user_a"& will show both messages since the bounce is
38970 &"related"& to or a &"result"& of the first message that was found by the
38973 If the location of a &'zcat'& command is known from the definition of
38974 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
38975 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
38976 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
38977 autodetection of some well known compression extensions.
38980 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
38981 .cindex "&'exipick'&"
38982 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
38983 lists messages from the queue according to a variety of criteria. For details
38984 of &'exipick'&'s facilities, run &'exipick'& with
38985 the &%--help%& option.
38988 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
38989 .cindex "log" "cycling local files"
38990 .cindex "cycling logs"
38991 .cindex "&'exicyclog'&"
38992 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
38993 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
38994 you are using log files with datestamps in their names (see section
38995 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
38996 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
38997 There are two command line options for &'exicyclog'&:
38999 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39000 default that is set when Exim is built. The default default is 10.
39002 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39003 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39004 overriding the script's default, which is to find the setting from Exim's
39008 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39009 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39010 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39011 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39012 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39013 logs are handled similarly.
39015 If the limit is greater than 99, the script uses 3-digit numbers such as
39016 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39017 to one that is greater, or &'vice versa'&, you will have to fix the names of
39018 any existing log files.
39020 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39021 the end are deleted. All files with numbers greater than 01 are compressed,
39022 using a compression command which is configured by the COMPRESS_COMMAND
39023 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39024 root &%crontab%& entry of the form
39026 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39028 assuming you have used the name &"exim"& for the Exim user. You can run
39029 &'exicyclog'& as root if you wish, but there is no need.
39033 .section "Mail statistics (eximstats)" "SECTmailstat"
39034 .cindex "statistics"
39035 .cindex "&'eximstats'&"
39036 A Perl script called &'eximstats'& is provided for extracting statistical
39037 information from log files. The output is either plain text, or HTML.
39038 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39039 . --- 404 error and everything else points to that.
39041 The &'eximstats'& script has been hacked about quite a bit over time. The
39042 latest version is the result of some extensive revision by Steve Campbell. A
39043 lot of information is given by default, but there are options for suppressing
39044 various parts of it. Following any options, the arguments to the script are a
39045 list of files, which should be main log files. For example:
39047 eximstats -nr /var/spool/exim/log/mainlog.01
39049 By default, &'eximstats'& extracts information about the number and volume of
39050 messages received from or delivered to various hosts. The information is sorted
39051 both by message count and by volume, and the top fifty hosts in each category
39052 are listed on the standard output. Similar information, based on email
39053 addresses or domains instead of hosts can be requested by means of various
39054 options. For messages delivered and received locally, similar statistics are
39055 also produced per user.
39057 The output also includes total counts and statistics about delivery errors, and
39058 histograms showing the number of messages received and deliveries made in each
39059 hour of the day. A delivery with more than one address in its envelope (for
39060 example, an SMTP transaction with more than one RCPT command) is counted
39061 as a single delivery by &'eximstats'&.
39063 Though normally more deliveries than receipts are reported (as messages may
39064 have multiple recipients), it is possible for &'eximstats'& to report more
39065 messages received than delivered, even though the queue is empty at the start
39066 and end of the period in question. If an incoming message contains no valid
39067 recipients, no deliveries are recorded for it. A bounce message is handled as
39068 an entirely separate message.
39070 &'eximstats'& always outputs a grand total summary giving the volume and number
39071 of messages received and deliveries made, and the number of hosts involved in
39072 each case. It also outputs the number of messages that were delayed (that is,
39073 not completely delivered at the first attempt), and the number that had at
39074 least one address that failed.
39076 The remainder of the output is in sections that can be independently disabled
39077 or modified by various options. It consists of a summary of deliveries by
39078 transport, histograms of messages received and delivered per time interval
39079 (default per hour), information about the time messages spent in the queue,
39080 a list of relayed messages, lists of the top fifty sending hosts, local
39081 senders, destination hosts, and destination local users by count and by volume,
39082 and a list of delivery errors that occurred.
39084 The relay information lists messages that were actually relayed, that is, they
39085 came from a remote host and were directly delivered to some other remote host,
39086 without being processed (for example, for aliasing or forwarding) locally.
39088 There are quite a few options for &'eximstats'& to control exactly what it
39089 outputs. These are documented in the Perl script itself, and can be extracted
39090 by running the command &(perldoc)& on the script. For example:
39092 perldoc /usr/exim/bin/eximstats
39095 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39096 .cindex "&'exim_checkaccess'&"
39097 .cindex "policy control" "checking access"
39098 .cindex "checking access"
39099 The &%-bh%& command line argument allows you to run a fake SMTP session with
39100 debugging output, in order to check what Exim is doing when it is applying
39101 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39102 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39103 sometimes you just want to answer the question &"Does this address have
39104 access?"& without bothering with any further details.
39106 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39107 two arguments, an IP address and an email address:
39109 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39111 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39112 given email address would be accepted in a RCPT command in a TCP/IP
39113 connection from the host with the given IP address. The output of the utility
39114 is either the word &"accepted"&, or the SMTP error response, for example:
39117 550 Relay not permitted
39119 When running this test, the utility uses &`<>`& as the envelope sender address
39120 for the MAIL command, but you can change this by providing additional
39121 options. These are passed directly to the Exim command. For example, to specify
39122 that the test is to be run with the sender address &'himself@there.example'&
39125 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39126 -f himself@there.example
39128 Note that these additional Exim command line items must be given after the two
39129 mandatory arguments.
39131 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39132 while running its checks. You can run checks that include callouts by using
39133 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39137 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39138 .cindex "DBM" "building dbm files"
39139 .cindex "building DBM files"
39140 .cindex "&'exim_dbmbuild'&"
39141 .cindex "lower casing"
39142 .cindex "binary zero" "in lookup key"
39143 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39144 the format used by the &(lsearch)& lookup (see section
39145 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39146 names as keys and the remainder of the information as data. The lower-casing
39147 can be prevented by calling the program with the &%-nolc%& option.
39149 A terminating zero is included as part of the key string. This is expected by
39150 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39151 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39152 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39155 The program requires two arguments: the name of the input file (which can be a
39156 single hyphen to indicate the standard input), and the name of the output file.
39157 It creates the output under a temporary name, and then renames it if all went
39161 If the native DB interface is in use (USE_DB is set in a compile-time
39162 configuration file &-- this is common in free versions of Unix) the two
39163 filenames must be different, because in this mode the Berkeley DB functions
39164 create a single output file using exactly the name given. For example,
39166 exim_dbmbuild /etc/aliases /etc/aliases.db
39168 reads the system alias file and creates a DBM version of it in
39169 &_/etc/aliases.db_&.
39171 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39172 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39173 environment, the suffixes are added to the second argument of
39174 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39175 when the Berkeley functions are used in compatibility mode (though this is not
39176 recommended), because in that case it adds a &_.db_& suffix to the filename.
39178 If a duplicate key is encountered, the program outputs a warning, and when it
39179 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39180 option is used. By default, only the first of a set of duplicates is used &--
39181 this makes it compatible with &(lsearch)& lookups. There is an option
39182 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39183 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39184 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39190 .section "Finding individual retry times (exinext)" "SECTfinindret"
39191 .cindex "retry" "times"
39192 .cindex "&'exinext'&"
39193 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39194 fish specific information out of the retry database. Given a mail domain (or a
39195 complete address), it looks up the hosts for that domain, and outputs any retry
39196 information for the hosts or for the domain. At present, the retry information
39197 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39198 output. For example:
39200 $ exinext piglet@milne.fict.example
39201 kanga.milne.example:192.168.8.1 error 146: Connection refused
39202 first failed: 21-Feb-1996 14:57:34
39203 last tried: 21-Feb-1996 14:57:34
39204 next try at: 21-Feb-1996 15:02:34
39205 roo.milne.example:192.168.8.3 error 146: Connection refused
39206 first failed: 20-Jan-1996 13:12:08
39207 last tried: 21-Feb-1996 11:42:03
39208 next try at: 21-Feb-1996 19:42:03
39209 past final cutoff time
39211 You can also give &'exinext'& a local part, without a domain, and it
39212 will give any retry information for that local part in your default domain.
39213 A message id can be used to obtain retry information pertaining to a specific
39214 message. This exists only when an attempt to deliver a message to a remote host
39215 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39216 &'exinext'& is not particularly efficient, but then it is not expected to be
39219 The &'exinext'& utility calls Exim to find out information such as the location
39220 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39221 passed on to the &'exim'& commands. The first specifies an alternate Exim
39222 configuration file, and the second sets macros for use within the configuration
39223 file. These features are mainly to help in testing, but might also be useful in
39224 environments where more than one configuration file is in use.
39228 .section "Hints database maintenance" "SECThindatmai"
39229 .cindex "hints database" "maintenance"
39230 .cindex "maintaining Exim's hints database"
39231 Three utility programs are provided for maintaining the DBM files that Exim
39232 uses to contain its delivery hint information. Each program requires two
39233 arguments. The first specifies the name of Exim's spool directory, and the
39234 second is the name of the database it is to operate on. These are as follows:
39237 &'retry'&: the database of retry information
39239 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39242 &'callout'&: the callout cache
39244 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39247 &'tls'&: TLS session resumption data
39250 &'misc'&: other hints data
39253 The &'misc'& database is used for
39256 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39258 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39259 &(smtp)& transport)
39261 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39267 .section "exim_dumpdb" "SECID261"
39268 .cindex "&'exim_dumpdb'&"
39269 The entire contents of a database are written to the standard output by the
39270 &'exim_dumpdb'& program, which has no options or arguments other than the
39271 spool and database names. For example, to dump the retry database:
39273 exim_dumpdb /var/spool/exim retry
39275 Two lines of output are produced for each entry:
39277 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39278 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39280 The first item on the first line is the key of the record. It starts with one
39281 of the letters R, or T, depending on whether it refers to a routing or
39282 transport retry. For a local delivery, the next part is the local address; for
39283 a remote delivery it is the name of the remote host, followed by its failing IP
39284 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39285 transport). If the remote port is not the standard one (port 25), it is added
39286 to the IP address. Then there follows an error code, an additional error code,
39287 and a textual description of the error.
39289 The three times on the second line are the time of first failure, the time of
39290 the last delivery attempt, and the computed time for the next attempt. The line
39291 ends with an asterisk if the cutoff time for the last retry rule has been
39294 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39295 consists of a host name followed by a list of ids for messages that are or were
39296 waiting to be delivered to that host. If there are a very large number for any
39297 one host, continuation records, with a sequence number added to the host name,
39298 may be seen. The data in these records is often out of date, because a message
39299 may be routed to several alternative hosts, and Exim makes no effort to keep
39304 .section "exim_tidydb" "SECID262"
39305 .cindex "&'exim_tidydb'&"
39306 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39307 database. If run with no options, it removes all records that are more than 30
39308 days old. The age is calculated from the date and time that the record was last
39309 updated. Note that, in the case of the retry database, it is &'not'& the time
39310 since the first delivery failure. Information about a host that has been down
39311 for more than 30 days will remain in the database, provided that the record is
39312 updated sufficiently often.
39314 The cutoff date can be altered by means of the &%-t%& option, which must be
39315 followed by a time. For example, to remove all records older than a week from
39316 the retry database:
39318 exim_tidydb -t 7d /var/spool/exim retry
39320 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39321 message ids. In the former these appear as data in records keyed by host &--
39322 they were messages that were waiting for that host &-- and in the latter they
39323 are the keys for retry information for messages that have suffered certain
39324 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39325 message ids in database records are those of messages that are still on the
39326 queue. Message ids for messages that no longer exist are removed from
39327 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39328 For the &'retry'& database, records whose keys are non-existent message ids are
39329 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39330 whenever it removes information from the database.
39332 Certain records are automatically removed by Exim when they are no longer
39333 needed, but others are not. For example, if all the MX hosts for a domain are
39334 down, a retry record is created for each one. If the primary MX host comes back
39335 first, its record is removed when Exim successfully delivers to it, but the
39336 records for the others remain because Exim has not tried to use those hosts.
39338 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39339 hints databases. You should do this at a quiet time of day, because it requires
39340 a database to be locked (and therefore inaccessible to Exim) while it does its
39341 work. Removing records from a DBM file does not normally make the file smaller,
39342 but all the common DBM libraries are able to re-use the space that is released.
39343 After an initial phase of increasing in size, the databases normally reach a
39344 point at which they no longer get any bigger, as long as they are regularly
39347 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39348 databases is likely to keep on increasing.
39353 .section "exim_fixdb" "SECID263"
39354 .cindex "&'exim_fixdb'&"
39355 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39356 Its main use is for testing Exim, but it might also be occasionally useful for
39357 getting round problems in a live system. It has no options, and its interface
39358 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39359 key of a database record can then be entered, and the data for that record is
39362 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39363 except the &'retry'& database, that is the only operation that can be carried
39364 out. For the &'retry'& database, each field is output preceded by a number, and
39365 data for individual fields can be changed by typing the field number followed
39366 by new data, for example:
39370 resets the time of the next delivery attempt. Time values are given as a
39371 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39372 used as optional separators.
39377 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39378 .cindex "mailbox" "maintenance"
39379 .cindex "&'exim_lock'&"
39380 .cindex "locking mailboxes"
39381 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39382 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39383 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39384 a user agent while investigating a problem. The utility requires the name of
39385 the file as its first argument. If the locking is successful, the second
39386 argument is run as a command (using C's &[system()]& function); if there is no
39387 second argument, the value of the SHELL environment variable is used; if this
39388 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39389 is unlocked and the utility ends. The following options are available:
39393 Use &[fcntl()]& locking on the open mailbox.
39396 Use &[flock()]& locking on the open mailbox, provided the operating system
39399 .vitem &%-interval%&
39400 This must be followed by a number, which is a number of seconds; it sets the
39401 interval to sleep between retries (default 3).
39403 .vitem &%-lockfile%&
39404 Create a lock file before opening the mailbox.
39407 Lock the mailbox using MBX rules.
39410 Suppress verification output.
39412 .vitem &%-retries%&
39413 This must be followed by a number; it sets the number of times to try to get
39414 the lock (default 10).
39416 .vitem &%-restore_time%&
39417 This option causes &%exim_lock%& to restore the modified and read times to the
39418 locked file before exiting. This allows you to access a locked mailbox (for
39419 example, to take a backup copy) without disturbing the times that the user
39422 .vitem &%-timeout%&
39423 This must be followed by a number, which is a number of seconds; it sets a
39424 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39425 default), a non-blocking call is used.
39428 Generate verbose output.
39431 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39432 default is to create a lock file and also to use &[fcntl()]& locking on the
39433 mailbox, which is the same as Exim's default. The use of &%-flock%& or
39434 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
39435 requires that the directory containing the file be writeable. Locking by lock
39436 file does not last forever; Exim assumes that a lock file is expired if it is
39437 more than 30 minutes old.
39439 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
39440 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
39441 to be taken out on the open mailbox, and an exclusive lock on the file
39442 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
39443 number of the mailbox file. When the locking is released, if an exclusive lock
39444 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
39446 The default output contains verification of the locking that takes place. The
39447 &%-v%& option causes some additional information to be given. The &%-q%& option
39448 suppresses all output except error messages.
39452 exim_lock /var/spool/mail/spqr
39454 runs an interactive shell while the file is locked, whereas
39456 &`exim_lock -q /var/spool/mail/spqr <<End`&
39457 <&'some commands'&>
39460 runs a specific non-interactive sequence of commands while the file is locked,
39461 suppressing all verification output. A single command can be run by a command
39464 exim_lock -q /var/spool/mail/spqr \
39465 "cp /var/spool/mail/spqr /some/where"
39467 Note that if a command is supplied, it must be entirely contained within the
39468 second argument &-- hence the quotes.
39472 . ////////////////////////////////////////////////////////////////////////////
39473 . ////////////////////////////////////////////////////////////////////////////
39475 .chapter "The Exim monitor" "CHAPeximon"
39476 .scindex IIDeximon "Exim monitor" "description"
39477 .cindex "X-windows"
39478 .cindex "&'eximon'&"
39479 .cindex "Local/eximon.conf"
39480 .cindex "&_exim_monitor/EDITME_&"
39481 The Exim monitor is an application which displays in an X window information
39482 about the state of Exim's queue and what Exim is doing. An admin user can
39483 perform certain operations on messages from this GUI interface; however all
39484 such facilities are also available from the command line, and indeed, the
39485 monitor itself makes use of the command line to perform any actions requested.
39489 .section "Running the monitor" "SECID264"
39490 The monitor is started by running the script called &'eximon'&. This is a shell
39491 script that sets up a number of environment variables, and then runs the
39492 binary called &_eximon.bin_&. The default appearance of the monitor window can
39493 be changed by editing the &_Local/eximon.conf_& file created by editing
39494 &_exim_monitor/EDITME_&. Comments in that file describe what the various
39495 parameters are for.
39497 The parameters that get built into the &'eximon'& script can be overridden for
39498 a particular invocation by setting up environment variables of the same names,
39499 preceded by &`EXIMON_`&. For example, a shell command such as
39501 EXIMON_LOG_DEPTH=400 eximon
39503 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
39504 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
39505 overrides the Exim log file configuration. This makes it possible to have
39506 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
39507 syslog messages are routed to a file on the local host.
39509 X resources can be used to change the appearance of the window in the normal
39510 way. For example, a resource setting of the form
39512 Eximon*background: gray94
39514 changes the colour of the background to light grey rather than white. The
39515 stripcharts are drawn with both the data lines and the reference lines in
39516 black. This means that the reference lines are not visible when on top of the
39517 data. However, their colour can be changed by setting a resource called
39518 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
39519 For example, if your X server is running Unix, you could set up lighter
39520 reference lines in the stripcharts by obeying
39523 Eximon*highlight: gray
39526 .cindex "admin user"
39527 In order to see the contents of messages in the queue, and to operate on them,
39528 &'eximon'& must either be run as root or by an admin user.
39530 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
39531 contain X11 resource parameters interpreted by the X11 library. In addition,
39532 if the first parameter starts with the string "gdb" then it is removed and the
39533 binary is invoked under gdb (the parameter is used as the gdb command-name, so
39534 versioned variants of gdb can be invoked).
39536 The monitor's window is divided into three parts. The first contains one or
39537 more stripcharts and two action buttons, the second contains a &"tail"& of the
39538 main log file, and the third is a display of the queue of messages awaiting
39539 delivery, with two more action buttons. The following sections describe these
39540 different parts of the display.
39545 .section "The stripcharts" "SECID265"
39546 .cindex "stripchart"
39547 The first stripchart is always a count of messages in the queue. Its name can
39548 be configured by setting QUEUE_STRIPCHART_NAME in the
39549 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
39550 configuration script by regular expression matches on log file entries, making
39551 it possible to display, for example, counts of messages delivered to certain
39552 hosts or using certain transports. The supplied defaults display counts of
39553 received and delivered messages, and of local and SMTP deliveries. The default
39554 period between stripchart updates is one minute; this can be adjusted by a
39555 parameter in the &_Local/eximon.conf_& file.
39557 The stripchart displays rescale themselves automatically as the value they are
39558 displaying changes. There are always 10 horizontal lines in each chart; the
39559 title string indicates the value of each division when it is greater than one.
39560 For example, &"x2"& means that each division represents a value of 2.
39562 It is also possible to have a stripchart which shows the percentage fullness of
39563 a particular disk partition, which is useful when local deliveries are confined
39564 to a single partition.
39566 .cindex "&%statvfs%& function"
39567 This relies on the availability of the &[statvfs()]& function or equivalent in
39568 the operating system. Most, but not all versions of Unix that support Exim have
39569 this. For this particular stripchart, the top of the chart always represents
39570 100%, and the scale is given as &"x10%"&. This chart is configured by setting
39571 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
39572 &_Local/eximon.conf_& file.
39577 .section "Main action buttons" "SECID266"
39578 .cindex "size" "of monitor window"
39579 .cindex "Exim monitor" "window size"
39580 .cindex "window size"
39581 Below the stripcharts there is an action button for quitting the monitor. Next
39582 to this is another button marked &"Size"&. They are placed here so that
39583 shrinking the window to its default minimum size leaves just the queue count
39584 stripchart and these two buttons visible. Pressing the &"Size"& button causes
39585 the window to expand to its maximum size, unless it is already at the maximum,
39586 in which case it is reduced to its minimum.
39588 When expanding to the maximum, if the window cannot be fully seen where it
39589 currently is, it is moved back to where it was the last time it was at full
39590 size. When it is expanding from its minimum size, the old position is
39591 remembered, and next time it is reduced to the minimum it is moved back there.
39593 The idea is that you can keep a reduced window just showing one or two
39594 stripcharts at a convenient place on your screen, easily expand it to show
39595 the full window when required, and just as easily put it back to what it was.
39596 The idea is copied from what the &'twm'& window manager does for its
39597 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
39598 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
39600 Normally, the monitor starts up with the window at its full size, but it can be
39601 built so that it starts up with the window at its smallest size, by setting
39602 START_SMALL=yes in &_Local/eximon.conf_&.
39606 .section "The log display" "SECID267"
39607 .cindex "log" "tail of; in monitor"
39608 The second section of the window is an area in which a display of the tail of
39609 the main log is maintained.
39610 To save space on the screen, the timestamp on each log line is shortened by
39611 removing the date and, if &%log_timezone%& is set, the timezone.
39612 The log tail is not available when the only destination for logging data is
39613 syslog, unless the syslog lines are routed to a local file whose name is passed
39614 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
39616 The log sub-window has a scroll bar at its lefthand side which can be used to
39617 move back to look at earlier text, and the up and down arrow keys also have a
39618 scrolling effect. The amount of log that is kept depends on the setting of
39619 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
39620 to use. When this is full, the earlier 50% of data is discarded &-- this is
39621 much more efficient than throwing it away line by line. The sub-window also has
39622 a horizontal scroll bar for accessing the ends of long log lines. This is the
39623 only means of horizontal scrolling; the right and left arrow keys are not
39624 available. Text can be cut from this part of the window using the mouse in the
39625 normal way. The size of this subwindow is controlled by parameters in the
39626 configuration file &_Local/eximon.conf_&.
39628 Searches of the text in the log window can be carried out by means of the ^R
39629 and ^S keystrokes, which default to a reverse and a forward search,
39630 respectively. The search covers only the text that is displayed in the window.
39631 It cannot go further back up the log.
39633 The point from which the search starts is indicated by a caret marker. This is
39634 normally at the end of the text in the window, but can be positioned explicitly
39635 by pointing and clicking with the left mouse button, and is moved automatically
39636 by a successful search. If new text arrives in the window when it is scrolled
39637 back, the caret remains where it is, but if the window is not scrolled back,
39638 the caret is moved to the end of the new text.
39640 Pressing ^R or ^S pops up a window into which the search text can be typed.
39641 There are buttons for selecting forward or reverse searching, for carrying out
39642 the search, and for cancelling. If the &"Search"& button is pressed, the search
39643 happens and the window remains so that further searches can be done. If the
39644 &"Return"& key is pressed, a single search is done and the window is closed. If
39645 ^C is typed the search is cancelled.
39647 The searching facility is implemented using the facilities of the Athena text
39648 widget. By default this pops up a window containing both &"search"& and
39649 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
39650 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
39651 However, the linkers in BSDI and HP-UX seem unable to handle an externally
39652 provided version of &%TextPop%& when the remaining parts of the text widget
39653 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
39654 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
39655 on these systems, at the expense of having unwanted items in the search popup
39660 .section "The queue display" "SECID268"
39661 .cindex "queue" "display in monitor"
39662 The bottom section of the monitor window contains a list of all messages that
39663 are in the queue, which includes those currently being received or delivered,
39664 as well as those awaiting delivery. The size of this subwindow is controlled by
39665 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
39666 at which it is updated is controlled by another parameter in the same file &--
39667 the default is 5 minutes, since queue scans can be quite expensive. However,
39668 there is an &"Update"& action button just above the display which can be used
39669 to force an update of the queue display at any time.
39671 When a host is down for some time, a lot of pending mail can build up for it,
39672 and this can make it hard to deal with other messages in the queue. To help
39673 with this situation there is a button next to &"Update"& called &"Hide"&. If
39674 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
39675 type anything in here and press &"Return"&, the text is added to a chain of
39676 such texts, and if every undelivered address in a message matches at least one
39677 of the texts, the message is not displayed.
39679 If there is an address that does not match any of the texts, all the addresses
39680 are displayed as normal. The matching happens on the ends of addresses so, for
39681 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
39682 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
39683 has been set up, a button called &"Unhide"& is displayed. If pressed, it
39684 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
39685 a hide request is automatically cancelled after one hour.
39687 While the dialogue box is displayed, you can't press any buttons or do anything
39688 else to the monitor window. For this reason, if you want to cut text from the
39689 queue display to use in the dialogue box, you have to do the cutting before
39690 pressing the &"Hide"& button.
39692 The queue display contains, for each unhidden queued message, the length of
39693 time it has been in the queue, the size of the message, the message id, the
39694 message sender, and the first undelivered recipient, all on one line. If it is
39695 a bounce message, the sender is shown as &"<>"&. If there is more than one
39696 recipient to which the message has not yet been delivered, subsequent ones are
39697 listed on additional lines, up to a maximum configured number, following which
39698 an ellipsis is displayed. Recipients that have already received the message are
39701 .cindex "frozen messages" "display"
39702 If a message is frozen, an asterisk is displayed at the left-hand side.
39704 The queue display has a vertical scroll bar, and can also be scrolled by means
39705 of the arrow keys. Text can be cut from it using the mouse in the normal way.
39706 The text searching facilities, as described above for the log window, are also
39707 available, but the caret is always moved to the end of the text when the queue
39708 display is updated.
39712 .section "The queue menu" "SECID269"
39713 .cindex "queue" "menu in monitor"
39714 If the &%shift%& key is held down and the left button is clicked when the mouse
39715 pointer is over the text for any message, an action menu pops up, and the first
39716 line of the queue display for the message is highlighted. This does not affect
39719 If you want to use some other event for popping up the menu, you can set the
39720 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
39721 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
39722 value set in this parameter is a standard X event description. For example, to
39723 run eximon using &%ctrl%& rather than &%shift%& you could use
39725 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
39727 The title of the menu is the message id, and it contains entries which act as
39731 &'message log'&: The contents of the message log for the message are displayed
39732 in a new text window.
39734 &'headers'&: Information from the spool file that contains the envelope
39735 information and headers is displayed in a new text window. See chapter
39736 &<<CHAPspool>>& for a description of the format of spool files.
39738 &'body'&: The contents of the spool file containing the body of the message are
39739 displayed in a new text window. There is a default limit of 20,000 bytes to the
39740 amount of data displayed. This can be changed by setting the BODY_MAX
39741 option at compile time, or the EXIMON_BODY_MAX option at runtime.
39743 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
39744 delivery of the message. This causes an automatic thaw if the message is
39745 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
39746 a new text window. The delivery is run in a separate process, to avoid holding
39747 up the monitor while the delivery proceeds.
39749 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
39750 that the message be frozen.
39752 .cindex "thawing messages"
39753 .cindex "unfreezing messages"
39754 .cindex "frozen messages" "thawing"
39755 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
39756 that the message be thawed.
39758 .cindex "delivery" "forcing failure"
39759 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
39760 that Exim gives up trying to deliver the message. A bounce message is generated
39761 for any remaining undelivered addresses.
39763 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
39764 that the message be deleted from the system without generating a bounce
39767 &'add recipient'&: A dialog box is displayed into which a recipient address can
39768 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
39769 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
39770 Otherwise it must be entered as a fully qualified address. Pressing RETURN
39771 causes a call to Exim to be made using the &%-Mar%& option to request that an
39772 additional recipient be added to the message, unless the entry box is empty, in
39773 which case no action is taken.
39775 &'mark delivered'&: A dialog box is displayed into which a recipient address
39776 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
39777 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
39778 Otherwise it must be entered as a fully qualified address. Pressing RETURN
39779 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
39780 recipient address as already delivered, unless the entry box is empty, in which
39781 case no action is taken.
39783 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
39784 mark all recipient addresses as already delivered.
39786 &'edit sender'&: A dialog box is displayed initialized with the current
39787 sender's address. Pressing RETURN causes a call to Exim to be made using the
39788 &%-Mes%& option to replace the sender address, unless the entry box is empty,
39789 in which case no action is taken. If you want to set an empty sender (as in
39790 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
39791 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
39792 the address is qualified with that domain.
39795 When a delivery is forced, a window showing the &%-v%& output is displayed. In
39796 other cases when a call to Exim is made, if there is any output from Exim (in
39797 particular, if the command fails) a window containing the command and the
39798 output is displayed. Otherwise, the results of the action are normally apparent
39799 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
39800 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
39801 if no output is generated.
39803 The queue display is automatically updated for actions such as freezing and
39804 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
39805 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
39806 force an update of the display after one of these actions.
39808 In any text window that is displayed as result of a menu action, the normal
39809 cut-and-paste facility is available, and searching can be carried out using ^R
39810 and ^S, as described above for the log tail window.
39817 . ////////////////////////////////////////////////////////////////////////////
39818 . ////////////////////////////////////////////////////////////////////////////
39820 .chapter "Security considerations" "CHAPsecurity"
39821 .scindex IIDsecurcon "security" "discussion of"
39822 This chapter discusses a number of issues concerned with security, some of
39823 which are also covered in other parts of this manual.
39825 For reasons that this author does not understand, some people have promoted
39826 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
39827 existence of this chapter in the documentation. However, the intent of the
39828 chapter is simply to describe the way Exim works in relation to certain
39829 security concerns, not to make any specific claims about the effectiveness of
39830 its security as compared with other MTAs.
39832 What follows is a description of the way Exim is supposed to be. Best efforts
39833 have been made to try to ensure that the code agrees with the theory, but an
39834 absence of bugs can never be guaranteed. Any that are reported will get fixed
39835 as soon as possible.
39838 .section "Building a more &""hardened""& Exim" "SECID286"
39839 .cindex "security" "build-time features"
39840 There are a number of build-time options that can be set in &_Local/Makefile_&
39841 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
39842 Exim administrator who does not have the root password, or by someone who has
39843 penetrated the Exim (but not the root) account. These options are as follows:
39846 ALT_CONFIG_PREFIX can be set to a string that is required to match the
39847 start of any filenames used with the &%-C%& option. When it is set, these
39848 filenames are also not allowed to contain the sequence &"/../"&. (However, if
39849 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
39850 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
39851 default setting for &%ALT_CONFIG_PREFIX%&.
39853 If the permitted configuration files are confined to a directory to
39854 which only root has access, this guards against someone who has broken
39855 into the Exim account from running a privileged Exim with an arbitrary
39856 configuration file, and using it to break into other accounts.
39859 If a non-trusted configuration file (i.e. not the default configuration file
39860 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
39861 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
39862 the next item), then root privilege is retained only if the caller of Exim is
39863 root. This locks out the possibility of testing a configuration using &%-C%&
39864 right through message reception and delivery, even if the caller is root. The
39865 reception works, but by that time, Exim is running as the Exim user, so when
39866 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
39867 privilege to be lost. However, root can test reception and delivery using two
39871 The WHITELIST_D_MACROS build option declares some macros to be safe to override
39872 with &%-D%& if the real uid is one of root, the Exim run-time user or the
39873 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
39874 requiring the run-time value supplied to &%-D%& to match a regex that errs on
39875 the restrictive side. Requiring build-time selection of safe macros is onerous
39876 but this option is intended solely as a transition mechanism to permit
39877 previously-working configurations to continue to work after release 4.73.
39879 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
39882 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
39883 never to be used for any deliveries. This is like the &%never_users%& runtime
39884 option, but it cannot be overridden; the runtime option adds additional users
39885 to the list. The default setting is &"root"&; this prevents a non-root user who
39886 is permitted to modify the runtime file from using Exim as a way to get root.
39891 .section "Root privilege" "SECID270"
39893 .cindex "root privilege"
39894 The Exim binary is normally setuid to root, which means that it gains root
39895 privilege (runs as root) when it starts execution. In some special cases (for
39896 example, when the daemon is not in use and there are no local deliveries), it
39897 may be possible to run Exim setuid to some user other than root. This is
39898 discussed in the next section. However, in most installations, root privilege
39899 is required for two things:
39902 To set up a socket connected to the standard SMTP port (25) when initialising
39903 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
39906 To be able to change uid and gid in order to read users' &_.forward_& files and
39907 perform local deliveries as the receiving user or as specified in the
39911 It is not necessary to be root to do any of the other things Exim does, such as
39912 receiving messages and delivering them externally over SMTP, and it is
39913 obviously more secure if Exim does not run as root except when necessary.
39914 For this reason, a user and group for Exim to use must be defined in
39915 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
39916 group"&. Their values can be changed by the runtime configuration, though this
39917 is not recommended. Often a user called &'exim'& is used, but some sites use
39918 &'mail'& or another user name altogether.
39920 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
39921 abdication; the process cannot regain root afterwards. Prior to release 4.00,
39922 &[seteuid()]& was used in some circumstances, but this is no longer the case.
39924 After a new Exim process has interpreted its command line options, it changes
39925 uid and gid in the following cases:
39930 If the &%-C%& option is used to specify an alternate configuration file, or if
39931 the &%-D%& option is used to define macro values for the configuration, and the
39932 calling process is not running as root, the uid and gid are changed to those of
39933 the calling process.
39934 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
39935 option may not be used at all.
39936 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
39937 can be supplied if the calling process is running as root, the Exim run-time
39938 user or CONFIGURE_OWNER, if defined.
39943 If the expansion test option (&%-be%&) or one of the filter testing options
39944 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
39947 If the process is not a daemon process or a queue runner process or a delivery
39948 process or a process for testing address routing (started with &%-bt%&), the
39949 uid and gid are changed to the Exim user and group. This means that Exim always
39950 runs under its own uid and gid when receiving messages. This also applies when
39951 testing address verification
39954 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
39957 For a daemon, queue runner, delivery, or address testing process, the uid
39958 remains as root at this stage, but the gid is changed to the Exim group.
39961 The processes that initially retain root privilege behave as follows:
39964 A daemon process changes the gid to the Exim group and the uid to the Exim
39965 user after setting up one or more listening sockets. The &[initgroups()]&
39966 function is called, so that if the Exim user is in any additional groups, they
39967 will be used during message reception.
39969 A queue runner process retains root privilege throughout its execution. Its
39970 job is to fork a controlled sequence of delivery processes.
39972 A delivery process retains root privilege throughout most of its execution,
39973 but any actual deliveries (that is, the transports themselves) are run in
39974 subprocesses which always change to a non-root uid and gid. For local
39975 deliveries this is typically the uid and gid of the owner of the mailbox; for
39976 remote deliveries, the Exim uid and gid are used. Once all the delivery
39977 subprocesses have been run, a delivery process changes to the Exim uid and gid
39978 while doing post-delivery tidying up such as updating the retry database and
39979 generating bounce and warning messages.
39981 While the recipient addresses in a message are being routed, the delivery
39982 process runs as root. However, if a user's filter file has to be processed,
39983 this is done in a subprocess that runs under the individual user's uid and
39984 gid. A system filter is run as root unless &%system_filter_user%& is set.
39986 A process that is testing addresses (the &%-bt%& option) runs as root so that
39987 the routing is done in the same environment as a message delivery.
39993 .section "Running Exim without privilege" "SECTrunexiwitpri"
39994 .cindex "privilege, running without"
39995 .cindex "unprivileged running"
39996 .cindex "root privilege" "running without"
39997 Some installations like to run Exim in an unprivileged state for more of its
39998 operation, for added security. Support for this mode of operation is provided
39999 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40000 gid are changed to the Exim user and group at the start of a delivery process
40001 (and also queue runner and address testing processes). This means that address
40002 routing is no longer run as root, and the deliveries themselves cannot change
40006 .cindex "daemon" "restarting"
40007 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40008 that the daemon can still be started in the usual way, and it can respond
40009 correctly to SIGHUP because the re-invocation regains root privilege.
40011 An alternative approach is to make Exim setuid to the Exim user and also setgid
40012 to the Exim group. If you do this, the daemon must be started from a root
40013 process. (Calling Exim from a root process makes it behave in the way it does
40014 when it is setuid root.) However, the daemon cannot restart itself after a
40015 SIGHUP signal because it cannot regain privilege.
40017 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40018 stops Exim from trying to re-invoke itself to do a delivery after a message has
40019 been received. Such a re-invocation is a waste of resources because it has no
40022 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40023 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40024 to the Exim user seems a clean approach, but there is one complication:
40026 In this style of operation, Exim is running with the real uid and gid set to
40027 those of the calling process, and the effective uid/gid set to Exim's values.
40028 Ideally, any association with the calling process' uid/gid should be dropped,
40029 that is, the real uid/gid should be reset to the effective values so as to
40030 discard any privileges that the caller may have. While some operating systems
40031 have a function that permits this action for a non-root effective uid, quite a
40032 number of them do not. Because of this lack of standardization, Exim does not
40033 address this problem at this time.
40035 For this reason, the recommended approach for &"mostly unprivileged"& running
40036 is to keep the Exim binary setuid to root, and to set
40037 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40038 be used in the most straightforward way.
40040 If you configure Exim not to run delivery processes as root, there are a
40041 number of restrictions on what you can do:
40044 You can deliver only as the Exim user/group. You should explicitly use the
40045 &%user%& and &%group%& options to override routers or local transports that
40046 normally deliver as the recipient. This makes sure that configurations that
40047 work in this mode function the same way in normal mode. Any implicit or
40048 explicit specification of another user causes an error.
40050 Use of &_.forward_& files is severely restricted, such that it is usually
40051 not worthwhile to include them in the configuration.
40053 Users who wish to use &_.forward_& would have to make their home directory and
40054 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40055 and their equivalents in Exim filters, cannot be used. While they could be
40056 enabled in the Exim user's name, that would be insecure and not very useful.
40058 Unless the local user mailboxes are all owned by the Exim user (possible in
40059 some POP3 or IMAP-only environments):
40062 They must be owned by the Exim group and be writeable by that group. This
40063 implies you must set &%mode%& in the appendfile configuration, as well as the
40064 mode of the mailbox files themselves.
40066 You must set &%no_check_owner%&, since most or all of the files will not be
40067 owned by the Exim user.
40069 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40070 on a newly created mailbox when unprivileged. This also implies that new
40071 mailboxes need to be created manually.
40076 These restrictions severely restrict what can be done in local deliveries.
40077 However, there are no restrictions on remote deliveries. If you are running a
40078 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40079 gives more security at essentially no cost.
40081 If you are using the &%mua_wrapper%& facility (see chapter
40082 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40087 .section "Delivering to local files" "SECID271"
40088 Full details of the checks applied by &(appendfile)& before it writes to a file
40089 are given in chapter &<<CHAPappendfile>>&.
40093 .section "Running local commands" "SECTsecconslocalcmds"
40094 .cindex "security" "local commands"
40095 .cindex "security" "command injection attacks"
40096 There are a number of ways in which an administrator can configure Exim to run
40097 commands based upon received, untrustworthy, data. Further, in some
40098 configurations a user who can control a &_.forward_& file can also arrange to
40099 run commands. Configuration to check includes, but is not limited to:
40102 Use of &%use_shell%& in the pipe transport: various forms of shell command
40103 injection may be possible with this option present. It is dangerous and should
40104 be used only with considerable caution. Consider constraints which whitelist
40105 allowed characters in a variable which is to be used in a pipe transport that
40106 has &%use_shell%& enabled.
40108 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40109 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40110 &_.forward_& files in a redirect router. If Exim is running on a central mail
40111 hub to which ordinary users do not have shell access, but home directories are
40112 NFS mounted (for instance) then administrators should review the list of these
40113 forbid options available, and should bear in mind that the options that may
40114 need forbidding can change as new features are added between releases.
40116 The &%${run...}%& expansion item does not use a shell by default, but
40117 administrators can configure use of &_/bin/sh_& as part of the command.
40118 Such invocations should be viewed with prejudicial suspicion.
40120 Administrators who use embedded Perl are advised to explore how Perl's
40121 taint checking might apply to their usage.
40123 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40124 administrators are well advised to view its use with suspicion, in case (for
40125 instance) it allows a local-part to contain embedded Exim directives.
40127 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40128 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40129 each can reference arbitrary lists and files, rather than just being a list
40131 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40132 real-world security vulnerabilities caused by its use with untrustworthy data
40133 injected in, for SQL injection attacks.
40134 Consider the use of the &%inlisti%& expansion condition instead.
40140 .section "Trust in configuration data" "SECTsecconfdata"
40141 .cindex "security" "data sources"
40142 .cindex "security" "regular expressions"
40143 .cindex "regular expressions" "security"
40144 .cindex "PCRE" "security"
40145 If configuration data for Exim can come from untrustworthy sources, there
40146 are some issues to be aware of:
40149 Use of &%${expand...}%& may provide a path for shell injection attacks.
40151 Letting untrusted data provide a regular expression is unwise.
40153 Using &%${match...}%& to apply a fixed regular expression against untrusted
40154 data may result in pathological behaviour within PCRE. Be aware of what
40155 "backtracking" means and consider options for being more strict with a regular
40156 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40157 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40158 possessive quantifiers or just not using regular expressions against untrusted
40161 It can be important to correctly use &%${quote:...}%&,
40162 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40163 items to ensure that data is correctly constructed.
40165 Some lookups might return multiple results, even though normal usage is only
40166 expected to yield one result.
40172 .section "IPv4 source routing" "SECID272"
40173 .cindex "source routing" "in IP packets"
40174 .cindex "IP source routing"
40175 Many operating systems suppress IP source-routed packets in the kernel, but
40176 some cannot be made to do this, so Exim does its own check. It logs incoming
40177 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40178 IPv6. No special checking is currently done.
40182 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40183 Support for these SMTP commands is disabled by default. If required, they can
40184 be enabled by defining suitable ACLs.
40189 .section "Privileged users" "SECID274"
40190 .cindex "trusted users"
40191 .cindex "admin user"
40192 .cindex "privileged user"
40193 .cindex "user" "trusted"
40194 .cindex "user" "admin"
40195 Exim recognizes two sets of users with special privileges. Trusted users are
40196 able to submit new messages to Exim locally, but supply their own sender
40197 addresses and information about a sending host. For other users submitting
40198 local messages, Exim sets up the sender address from the uid, and doesn't
40199 permit a remote host to be specified.
40202 However, an untrusted user is permitted to use the &%-f%& command line option
40203 in the special form &%-f <>%& to indicate that a delivery failure for the
40204 message should not cause an error report. This affects the message's envelope,
40205 but it does not affect the &'Sender:'& header. Untrusted users may also be
40206 permitted to use specific forms of address with the &%-f%& option by setting
40207 the &%untrusted_set_sender%& option.
40209 Trusted users are used to run processes that receive mail messages from some
40210 other mail domain and pass them on to Exim for delivery either locally, or over
40211 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40212 as any user listed in the &%trusted_users%& configuration option, or under any
40213 group listed in the &%trusted_groups%& option.
40215 Admin users are permitted to do things to the messages on Exim's queue. They
40216 can freeze or thaw messages, cause them to be returned to their senders, remove
40217 them entirely, or modify them in various ways. In addition, admin users can run
40218 the Exim monitor and see all the information it is capable of providing, which
40219 includes the contents of files on the spool.
40223 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40224 delivery of messages on its queue is restricted to admin users. This
40225 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40226 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40227 queue is also restricted to admin users. This restriction can be relaxed by
40228 setting &%no_queue_list_requires_admin%&.
40230 Exim recognizes an admin user if the calling process is running as root or as
40231 the Exim user or if any of the groups associated with the calling process is
40232 the Exim group. It is not necessary actually to be running under the Exim
40233 group. However, if admin users who are not root or the Exim user are to access
40234 the contents of files on the spool via the Exim monitor (which runs
40235 unprivileged), Exim must be built to allow group read access to its spool
40238 By default, regular users are trusted to perform basic testing and
40239 introspection commands, as themselves. This setting can be tightened by
40240 setting the &%commandline_checks_require_admin%& option.
40241 This affects most of the checking options,
40242 such as &%-be%& and anything else &%-b*%&.
40245 .section "Spool files" "SECID275"
40246 .cindex "spool directory" "files"
40247 Exim's spool directory and everything it contains is owned by the Exim user and
40248 set to the Exim group. The mode for spool files is defined in the
40249 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40250 any user who is a member of the Exim group can access these files.
40254 .section "Use of argv[0]" "SECID276"
40255 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40256 of specific strings, Exim assumes certain options. For example, calling Exim
40257 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40258 to calling it with the option &%-bS%&. There are no security implications in
40263 .section "Use of %f formatting" "SECID277"
40264 The only use made of &"%f"& by Exim is in formatting load average values. These
40265 are actually stored in integer variables as 1000 times the load average.
40266 Consequently, their range is limited and so therefore is the length of the
40271 .section "Embedded Exim path" "SECID278"
40272 Exim uses its own path name, which is embedded in the code, only when it needs
40273 to re-exec in order to regain root privilege. Therefore, it is not root when it
40274 does so. If some bug allowed the path to get overwritten, it would lead to an
40275 arbitrary program's being run as exim, not as root.
40279 .section "Dynamic module directory" "SECTdynmoddir"
40280 Any dynamically loadable modules must be installed into the directory
40281 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40285 .section "Use of sprintf()" "SECID279"
40286 .cindex "&[sprintf()]&"
40287 A large number of occurrences of &"sprintf"& in the code are actually calls to
40288 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40289 The intermediate formatting is done into a large fixed buffer by a function
40290 that runs through the format string itself, and checks the length of each
40291 conversion before performing it, thus preventing buffer overruns.
40293 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40294 the output buffer is known to be sufficiently long to contain the converted
40299 .section "Use of debug_printf() and log_write()" "SECID280"
40300 Arbitrary strings are passed to both these functions, but they do their
40301 formatting by calling the function &'string_vformat()'&, which runs through
40302 the format string itself, and checks the length of each conversion.
40306 .section "Use of strcat() and strcpy()" "SECID281"
40307 These are used only in cases where the output buffer is known to be large
40308 enough to hold the result.
40309 .ecindex IIDsecurcon
40314 . ////////////////////////////////////////////////////////////////////////////
40315 . ////////////////////////////////////////////////////////////////////////////
40317 .chapter "Format of spool files" "CHAPspool"
40318 .scindex IIDforspo1 "format" "spool files"
40319 .scindex IIDforspo2 "spool directory" "format of files"
40320 .scindex IIDforspo3 "spool files" "format of"
40321 .cindex "spool files" "editing"
40322 A message on Exim's queue consists of two files, whose names are the message id
40323 followed by -D and -H, respectively. The data portion of the message is kept in
40324 the -D file on its own. The message's envelope, status, and headers are all
40325 kept in the -H file, whose format is described in this chapter. Each of these
40326 two files contains the final component of its own name as its first line. This
40327 is insurance against disk crashes where the directory is lost but the files
40328 themselves are recoverable.
40330 The file formats may be changed, or new formats added, at any release.
40331 Spool files are not intended as an interface to other programs
40332 and should not be used as such.
40334 Some people are tempted into editing -D files in order to modify messages. You
40335 need to be extremely careful if you do this; it is not recommended and you are
40336 on your own if you do it. Here are some of the pitfalls:
40339 You must ensure that Exim does not try to deliver the message while you are
40340 fiddling with it. The safest way is to take out a write lock on the -D file,
40341 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40342 place, the lock will be retained. If you write a new file and rename it, the
40343 lock will be lost at the instant of rename.
40345 .vindex "&$body_linecount$&"
40346 If you change the number of lines in the file, the value of
40347 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40348 cause incomplete transmission of messages or undeliverable messages.
40350 If the message is in MIME format, you must take care not to break it.
40352 If the message is cryptographically signed, any change will invalidate the
40355 All in all, modifying -D files is fraught with danger.
40357 Files whose names end with -J may also be seen in the &_input_& directory (or
40358 its subdirectories when &%split_spool_directory%& is set). These are journal
40359 files, used to record addresses to which the message has been delivered during
40360 the course of a delivery attempt. If there are still undelivered recipients at
40361 the end, the -H file is updated, and the -J file is deleted. If, however, there
40362 is some kind of crash (for example, a power outage) before this happens, the -J
40363 file remains in existence. When Exim next processes the message, it notices the
40364 -J file and uses it to update the -H file before starting the next delivery
40367 Files whose names end with -K or .eml may also be seen in the spool.
40368 These are temporaries used for DKIM or malware processing, when that is used.
40369 They should be tidied up by normal operations; any old ones are probably
40370 relics of crashes and can be removed.
40372 .section "Format of the -H file" "SECID282"
40373 .cindex "uid (user id)" "in spool file"
40374 .cindex "gid (group id)" "in spool file"
40375 The second line of the -H file contains the login name for the uid of the
40376 process that called Exim to read the message, followed by the numerical uid and
40377 gid. For a locally generated message, this is normally the user who sent the
40378 message. For a message received over TCP/IP via the daemon, it is
40379 normally the Exim user.
40381 The third line of the file contains the address of the message's sender as
40382 transmitted in the envelope, contained in angle brackets. The sender address is
40383 empty for bounce messages. For incoming SMTP mail, the sender address is given
40384 in the MAIL command. For locally generated mail, the sender address is
40385 created by Exim from the login name of the current user and the configured
40386 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40387 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40388 &"<>"& or an address that matches &%untrusted_set_senders%&.
40390 The fourth line contains two numbers. The first is the time that the message
40391 was received, in the conventional Unix form &-- the number of seconds since the
40392 start of the epoch. The second number is a count of the number of messages
40393 warning of delayed delivery that have been sent to the sender.
40395 There follow a number of lines starting with a hyphen. These can appear in any
40396 order, and are omitted when not relevant:
40399 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40400 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40401 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40402 recognized, to provide backward compatibility. In the old format, a line of
40403 this form is present for every ACL variable that is not empty. The number
40404 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40405 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40406 the data string for the variable. The string itself starts at the beginning of
40407 the next line, and is followed by a newline character. It may contain internal
40410 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40411 A line of this form is present for every ACL connection variable that is
40412 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40413 The length is the length of the data string for the variable. The string itself
40414 starts at the beginning of the next line, and is followed by a newline
40415 character. It may contain internal newlines.
40417 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40418 A line of this form is present for every ACL message variable that is defined.
40419 Note that there is a space between &%-aclm%& and the rest of the name. The
40420 length is the length of the data string for the variable. The string itself
40421 starts at the beginning of the next line, and is followed by a newline
40422 character. It may contain internal newlines.
40424 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40425 This is present if, when the message was received over SMTP, the value of
40426 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40428 .vitem &%-allow_unqualified_recipient%&
40429 This is present if unqualified recipient addresses are permitted in header
40430 lines (to stop such addresses from being qualified if rewriting occurs at
40431 transport time). Local messages that were input using &%-bnq%& and remote
40432 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
40434 .vitem &%-allow_unqualified_sender%&
40435 This is present if unqualified sender addresses are permitted in header lines
40436 (to stop such addresses from being qualified if rewriting occurs at transport
40437 time). Local messages that were input using &%-bnq%& and remote messages from
40438 hosts that match &%sender_unqualified_hosts%& set this flag.
40440 .vitem "&%-auth_id%&&~<&'text'&>"
40441 The id information for a message received on an authenticated SMTP connection
40442 &-- the value of the &$authenticated_id$& variable.
40444 .vitem "&%-auth_sender%&&~<&'address'&>"
40445 The address of an authenticated sender &-- the value of the
40446 &$authenticated_sender$& variable.
40448 .vitem "&%-body_linecount%&&~<&'number'&>"
40449 This records the number of lines in the body of the message, and is
40450 present unless &%-spool_file_wireformat%& is.
40452 .vitem "&%-body_zerocount%&&~<&'number'&>"
40453 This records the number of binary zero bytes in the body of the message, and is
40454 present if the number is greater than zero.
40456 .vitem &%-deliver_firsttime%&
40457 This is written when a new message is first added to the spool. When the spool
40458 file is updated after a deferral, it is omitted.
40460 .vitem "&%-frozen%&&~<&'time'&>"
40461 .cindex "frozen messages" "spool data"
40462 The message is frozen, and the freezing happened at <&'time'&>.
40464 .vitem "&%-helo_name%&&~<&'text'&>"
40465 This records the host name as specified by a remote host in a HELO or EHLO
40468 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
40469 This records the IP address of the host from which the message was received and
40470 the remote port number that was used. It is omitted for locally generated
40473 .vitem "&%-host_auth%&&~<&'text'&>"
40474 If the message was received on an authenticated SMTP connection, this records
40475 the name of the authenticator &-- the value of the
40476 &$sender_host_authenticated$& variable.
40478 .vitem &%-host_lookup_failed%&
40479 This is present if an attempt to look up the sending host's name from its IP
40480 address failed. It corresponds to the &$host_lookup_failed$& variable.
40482 .vitem "&%-host_name%&&~<&'text'&>"
40483 .cindex "reverse DNS lookup"
40484 .cindex "DNS" "reverse lookup"
40485 This records the name of the remote host from which the message was received,
40486 if the host name was looked up from the IP address when the message was being
40487 received. It is not present if no reverse lookup was done.
40489 .vitem "&%-ident%&&~<&'text'&>"
40490 For locally submitted messages, this records the login of the originating user,
40491 unless it was a trusted user and the &%-oMt%& option was used to specify an
40492 ident value. For messages received over TCP/IP, this records the ident string
40493 supplied by the remote host, if any.
40495 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
40496 This records the IP address of the local interface and the port number through
40497 which a message was received from a remote host. It is omitted for locally
40498 generated messages.
40501 The message is from a local sender.
40503 .vitem &%-localerror%&
40504 The message is a locally-generated bounce message.
40506 .vitem "&%-local_scan%&&~<&'string'&>"
40507 This records the data string that was returned by the &[local_scan()]& function
40508 when the message was received &-- the value of the &$local_scan_data$&
40509 variable. It is omitted if no data was returned.
40511 .vitem &%-manual_thaw%&
40512 The message was frozen but has been thawed manually, that is, by an explicit
40513 Exim command rather than via the auto-thaw process.
40516 A testing delivery process was started using the &%-N%& option to suppress any
40517 actual deliveries, but delivery was deferred. At any further delivery attempts,
40520 .vitem &%-received_protocol%&
40521 This records the value of the &$received_protocol$& variable, which contains
40522 the name of the protocol by which the message was received.
40524 .vitem &%-sender_set_untrusted%&
40525 The envelope sender of this message was set by an untrusted local caller (used
40526 to ensure that the caller is displayed in queue listings).
40528 .vitem "&%-spam_score_int%&&~<&'number'&>"
40529 If a message was scanned by SpamAssassin, this is present. It records the value
40530 of &$spam_score_int$&.
40532 .vitem &%-spool_file_wireformat%&
40533 The -D file for this message is in wire-format (for ESMTP CHUNKING)
40534 rather than Unix-format.
40535 The line-ending is CRLF rather than newline.
40536 There is still, however, no leading-dot-stuffing.
40538 .vitem &%-tls_certificate_verified%&
40539 A TLS certificate was received from the client that sent this message, and the
40540 certificate was verified by the server.
40542 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
40543 When the message was received over an encrypted connection, this records the
40544 name of the cipher suite that was used.
40546 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
40547 When the message was received over an encrypted connection, and a certificate
40548 was received from the client, this records the Distinguished Name from that
40552 Any of the above may have an extra hyphen prepended, to indicate the the
40553 corresponding data is untrusted.
40555 Following the options there is a list of those addresses to which the message
40556 is not to be delivered. This set of addresses is initialized from the command
40557 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
40558 is set; otherwise it starts out empty. Whenever a successful delivery is made,
40559 the address is added to this set. The addresses are kept internally as a
40560 balanced binary tree, and it is a representation of that tree which is written
40561 to the spool file. If an address is expanded via an alias or forward file, the
40562 original address is added to the tree when deliveries to all its child
40563 addresses are complete.
40565 If the tree is empty, there is a single line in the spool file containing just
40566 the text &"XX"&. Otherwise, each line consists of two letters, which are either
40567 Y or N, followed by an address. The address is the value for the node of the
40568 tree, and the letters indicate whether the node has a left branch and/or a
40569 right branch attached to it, respectively. If branches exist, they immediately
40570 follow. Here is an example of a three-node tree:
40572 YY darcy@austen.fict.example
40573 NN alice@wonderland.fict.example
40574 NN editor@thesaurus.ref.example
40576 After the non-recipients tree, there is a list of the message's recipients.
40577 This is a simple list, preceded by a count. It includes all the original
40578 recipients of the message, including those to whom the message has already been
40579 delivered. In the simplest case, the list contains one address per line. For
40583 editor@thesaurus.ref.example
40584 darcy@austen.fict.example
40586 alice@wonderland.fict.example
40588 However, when a child address has been added to the top-level addresses as a
40589 result of the use of the &%one_time%& option on a &(redirect)& router, each
40590 line is of the following form:
40592 <&'top-level address'&> <&'errors_to address'&> &&&
40593 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
40595 The 01 flag bit indicates the presence of the three other fields that follow
40596 the top-level address. Other bits may be used in future to support additional
40597 fields. The <&'parent number'&> is the offset in the recipients list of the
40598 original parent of the &"one time"& address. The first two fields are the
40599 envelope sender that is associated with this address and its length. If the
40600 length is zero, there is no special envelope sender (there are then two space
40601 characters in the line). A non-empty field can arise from a &(redirect)& router
40602 that has an &%errors_to%& setting.
40605 A blank line separates the envelope and status information from the headers
40606 which follow. A header may occupy several lines of the file, and to save effort
40607 when reading it in, each header is preceded by a number and an identifying
40608 character. The number is the number of characters in the header, including any
40609 embedded newlines and the terminating newline. The character is one of the
40613 .row <&'blank'&> "header in which Exim has no special interest"
40614 .row &`B`& "&'Bcc:'& header"
40615 .row &`C`& "&'Cc:'& header"
40616 .row &`F`& "&'From:'& header"
40617 .row &`I`& "&'Message-id:'& header"
40618 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
40619 .row &`R`& "&'Reply-To:'& header"
40620 .row &`S`& "&'Sender:'& header"
40621 .row &`T`& "&'To:'& header"
40622 .row &`*`& "replaced or deleted header"
40625 Deleted or replaced (rewritten) headers remain in the spool file for debugging
40626 purposes. They are not transmitted when the message is delivered. Here is a
40627 typical set of headers:
40629 111P Received: by hobbit.fict.example with local (Exim 4.00)
40630 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
40631 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
40632 038* X-rewrote-sender: bb@hobbit.fict.example
40633 042* From: Bilbo Baggins <bb@hobbit.fict.example>
40634 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
40635 099* To: alice@wonderland.fict.example, rdo@foundation,
40636 darcy@austen.fict.example, editor@thesaurus.ref.example
40637 104T To: alice@wonderland.fict.example, rdo@foundation.example,
40638 darcy@austen.fict.example, editor@thesaurus.ref.example
40639 038 Date: Fri, 11 May 2001 10:28:59 +0100
40641 The asterisked headers indicate that the envelope sender, &'From:'& header, and
40642 &'To:'& header have been rewritten, the last one because routing expanded the
40643 unqualified domain &'foundation'&.
40644 .ecindex IIDforspo1
40645 .ecindex IIDforspo2
40646 .ecindex IIDforspo3
40648 .section "Format of the -D file" "SECID282a"
40649 The data file is traditionally in Unix-standard format: lines are ended with
40650 an ASCII newline character.
40651 However, when the &%spool_wireformat%& main option is used some -D files
40652 can have an alternate format.
40653 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
40654 The -D file lines (not including the first name-component line) are
40655 suitable for direct copying to the wire when transmitting using the
40656 ESMTP CHUNKING option, meaning lower processing overhead.
40657 Lines are terminated with an ASCII CRLF pair.
40658 There is no dot-stuffing (and no dot-termination).
40660 . ////////////////////////////////////////////////////////////////////////////
40661 . ////////////////////////////////////////////////////////////////////////////
40663 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
40664 "DKIM, SPF, SRS and DMARC Support"
40666 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
40669 DKIM is a mechanism by which messages sent by some entity can be provably
40670 linked to a domain which that entity controls. It permits reputation to
40671 be tracked on a per-domain basis, rather than merely upon source IP address.
40672 DKIM is documented in RFC 6376.
40674 As DKIM relies on the message being unchanged in transit, messages handled
40675 by a mailing-list (which traditionally adds to the message) will not match
40676 any original DKIM signature.
40678 DKIM support is compiled into Exim by default if TLS support is present.
40679 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
40681 Exim's DKIM implementation allows for
40683 Signing outgoing messages: This function is implemented in the SMTP transport.
40684 It can co-exist with all other Exim features
40685 (including transport filters)
40686 except cutthrough delivery.
40688 Verifying signatures in incoming messages: This is implemented by an additional
40689 ACL (acl_smtp_dkim), which can be called several times per message, with
40690 different signature contexts.
40693 In typical Exim style, the verification implementation does not include any
40694 default "policy". Instead it enables you to build your own policy using
40695 Exim's standard controls.
40697 Please note that verification of DKIM signatures in incoming mail is turned
40698 on by default for logging (in the <= line) purposes.
40700 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
40701 When set, for each signature in incoming email,
40702 exim will log a line displaying the most important signature details, and the
40703 signature status. Here is an example (with line-breaks added for clarity):
40705 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
40706 d=facebookmail.com s=q1-2009b
40707 c=relaxed/relaxed a=rsa-sha1
40708 i=@facebookmail.com t=1252484542 [verification succeeded]
40711 You might want to turn off DKIM verification processing entirely for internal
40712 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
40713 control modifier. This should typically be done in the RCPT ACL, at points
40714 where you accept mail from relay sources (internal hosts or authenticated
40718 .section "Signing outgoing messages" "SECDKIMSIGN"
40719 .cindex "DKIM" "signing"
40721 For signing to be usable you must have published a DKIM record in DNS.
40722 Note that RFC 8301 (which does not cover EC keys) says:
40724 rsa-sha1 MUST NOT be used for signing or verifying.
40726 Signers MUST use RSA keys of at least 1024 bits for all keys.
40727 Signers SHOULD use RSA keys of at least 2048 bits.
40730 Note also that the key content (the 'p=' field)
40731 in the DNS record is different between RSA and EC keys;
40732 for the former it is the base64 of the ASN.1 for the RSA public key
40733 (equivalent to the private-key .pem with the header/trailer stripped)
40734 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
40736 Signing is enabled by setting private options on the SMTP transport.
40737 These options take (expandable) strings as arguments.
40739 .option dkim_domain smtp string list&!! unset
40740 The domain(s) you want to sign with.
40741 After expansion, this can be a list.
40742 Each element in turn,
40744 is put into the &%$dkim_domain%& expansion variable
40745 while expanding the remaining signing options.
40746 If it is empty after expansion, DKIM signing is not done,
40747 and no error will result even if &%dkim_strict%& is set.
40749 .option dkim_selector smtp string list&!! unset
40750 This sets the key selector string.
40751 After expansion, which can use &$dkim_domain$&, this can be a list.
40752 Each element in turn is put in the expansion
40753 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
40754 option along with &%$dkim_domain%&.
40755 If the option is empty after expansion, DKIM signing is not done for this domain,
40756 and no error will result even if &%dkim_strict%& is set.
40758 .option dkim_private_key smtp string&!! unset
40759 This sets the private key to use.
40760 You can use the &%$dkim_domain%& and
40761 &%$dkim_selector%& expansion variables to determine the private key to use.
40762 The result can either
40764 be a valid RSA private key in ASCII armor (.pem file), including line breaks
40766 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
40767 be a valid Ed25519 private key (same format as above)
40769 start with a slash, in which case it is treated as a file that contains
40772 be "0", "false" or the empty string, in which case the message will not
40773 be signed. This case will not result in an error, even if &%dkim_strict%&
40777 To generate keys under OpenSSL:
40779 openssl genrsa -out dkim_rsa.private 2048
40780 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
40782 The result file from the first command should be retained, and
40783 this option set to use it.
40784 Take the base-64 lines from the output of the second command, concatenated,
40785 for the DNS TXT record.
40786 See section 3.6 of RFC6376 for the record specification.
40790 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
40791 certtool --load-privkey=dkim_rsa.private --pubkey-info
40794 Note that RFC 8301 says:
40796 Signers MUST use RSA keys of at least 1024 bits for all keys.
40797 Signers SHOULD use RSA keys of at least 2048 bits.
40800 EC keys for DKIM are defined by RFC 8463.
40801 They are considerably smaller than RSA keys for equivalent protection.
40802 As they are a recent development, users should consider dual-signing
40803 (by setting a list of selectors, and an expansion for this option)
40804 for some transition period.
40805 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
40808 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
40810 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
40811 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
40814 To produce the required public key value for a DNS record:
40816 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
40817 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
40820 Exim also supports an alternate format
40821 of Ed25519 keys in DNS which was a candidate during development
40822 of the standard, but not adopted.
40823 A future release will probably drop that support.
40825 .option dkim_hash smtp string&!! sha256
40826 Can be set to any one of the supported hash methods, which are:
40828 &`sha1`& &-- should not be used, is old and insecure
40830 &`sha256`& &-- the default
40832 &`sha512`& &-- possibly more secure but less well supported
40835 Note that RFC 8301 says:
40837 rsa-sha1 MUST NOT be used for signing or verifying.
40840 .option dkim_identity smtp string&!! unset
40841 If set after expansion, the value is used to set an "i=" tag in
40842 the signing header. The DKIM standards restrict the permissible
40843 syntax of this optional tag to a mail address, with possibly-empty
40844 local part, an @, and a domain identical to or subdomain of the "d="
40845 tag value. Note that Exim does not check the value.
40847 .option dkim_canon smtp string&!! unset
40848 This option sets the canonicalization method used when signing a message.
40849 The DKIM RFC currently supports two methods: "simple" and "relaxed".
40850 The option defaults to "relaxed" when unset. Note: the current implementation
40851 only supports signing with the same canonicalization method for both headers and body.
40853 .option dkim_strict smtp string&!! unset
40854 This option defines how Exim behaves when signing a message that
40855 should be signed fails for some reason. When the expansion evaluates to
40856 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
40857 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
40860 .option dkim_sign_headers smtp string&!! "see below"
40861 If set, this option must expand to a colon-separated
40862 list of header names.
40863 Headers with these names, or the absence or such a header, will be included
40864 in the message signature.
40865 When unspecified, the header names listed in RFC4871 will be used,
40866 whether or not each header is present in the message.
40867 The default list is available for the expansion in the macro
40868 &"_DKIM_SIGN_HEADERS"&
40870 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
40873 If a name is repeated, multiple headers by that name (or the absence thereof)
40874 will be signed. The textually later headers in the headers part of the
40875 message are signed first, if there are multiples.
40877 A name can be prefixed with either an &"="& or a &"+"& character.
40878 If an &"="& prefix is used, all headers that are present with this name
40880 If a &"+"& prefix if used, all headers that are present with this name
40881 will be signed, and one signature added for a missing header with the
40882 name will be appended.
40884 .option dkim_timestamps smtp integer&!! unset
40885 This option controls the inclusion of timestamp information in the signature.
40886 If not set, no such information will be included.
40887 Otherwise, must be an unsigned number giving an offset in seconds from the current time
40889 (eg. 1209600 for two weeks);
40890 both creation (t=) and expiry (x=) tags will be included.
40892 RFC 6376 lists these tags as RECOMMENDED.
40895 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
40896 .cindex "DKIM" "verification"
40898 Verification of DKIM signatures in SMTP incoming email is done for all
40899 messages for which an ACL control &%dkim_disable_verify%& has not been set.
40900 .cindex DKIM "selecting signature algorithms"
40901 Individual classes of signature algorithm can be ignored by changing
40902 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
40903 The &%dkim_verify_minimal%& option can be set to cease verification
40904 processing for a message once the first passing signature is found.
40906 .cindex authentication "expansion item"
40907 Performing verification sets up information used by the
40908 &%authresults%& expansion item.
40910 For most purposes the default option settings suffice and the remainder
40911 of this section can be ignored.
40913 The results of verification are made available to the
40914 &%acl_smtp_dkim%& ACL, which can examine and modify them.
40915 A missing ACL definition defaults to accept.
40916 By default, the ACL is called once for each
40917 syntactically(!) correct signature in the incoming message.
40918 If any ACL call does not accept, the message is not accepted.
40919 If a cutthrough delivery was in progress for the message, that is
40920 summarily dropped (having wasted the transmission effort).
40922 To evaluate the verification result in the ACL
40923 a large number of expansion variables
40924 containing the signature status and its details are set up during the
40925 runtime of the ACL.
40927 Calling the ACL only for existing signatures is not sufficient to build
40928 more advanced policies. For that reason, the main option
40929 &%dkim_verify_signers%&, and an expansion variable
40930 &%$dkim_signers%& exist.
40932 The main option &%dkim_verify_signers%& can be set to a colon-separated
40933 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
40934 called. It is expanded when the message has been received. At this point,
40935 the expansion variable &%$dkim_signers%& already contains a colon-separated
40936 list of signer domains and identities for the message. When
40937 &%dkim_verify_signers%& is not specified in the main configuration,
40940 dkim_verify_signers = $dkim_signers
40942 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
40943 DKIM signature in the message. Current DKIM verifiers may want to explicitly
40944 call the ACL for known domains or identities. This would be achieved as follows:
40946 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
40948 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
40949 and "ebay.com", plus all domains and identities that have signatures in the message.
40950 You can also be more creative in constructing your policy. For example:
40952 dkim_verify_signers = $sender_address_domain:$dkim_signers
40955 If a domain or identity is listed several times in the (expanded) value of
40956 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
40958 Note that if the option is set using untrustworthy data
40959 (such as the From: header)
40960 care should be taken to force lowercase for domains
40961 and for the domain part if identities.
40962 The default setting can be regarded as trustworthy in this respect.
40964 If multiple signatures match a domain (or identity), the ACL is called once
40965 for each matching signature.
40968 Inside the DKIM ACL, the following expansion variables are
40969 available (from most to least important):
40973 .vitem &%$dkim_cur_signer%&
40974 The signer that is being evaluated in this ACL run. This can be a domain or
40975 an identity. This is one of the list items from the expanded main option
40976 &%dkim_verify_signers%& (see above).
40978 .vitem &%$dkim_verify_status%&
40979 Within the DKIM ACL,
40980 a string describing the general status of the signature. One of
40982 &%none%&: There is no signature in the message for the current domain or
40983 identity (as reflected by &%$dkim_cur_signer%&).
40985 &%invalid%&: The signature could not be verified due to a processing error.
40986 More detail is available in &%$dkim_verify_reason%&.
40988 &%fail%&: Verification of the signature failed. More detail is
40989 available in &%$dkim_verify_reason%&.
40991 &%pass%&: The signature passed verification. It is valid.
40994 This variable can be overwritten using an ACL 'set' modifier.
40995 This might, for instance, be done to enforce a policy restriction on
40996 hash-method or key-size:
40998 warn condition = ${if eq {$dkim_verify_status}{pass}}
40999 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41000 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41001 {< {$dkim_key_length}{1024}}}}
41002 logwrite = NOTE: forcing DKIM verify fail (was pass)
41003 set dkim_verify_status = fail
41004 set dkim_verify_reason = hash too weak or key too short
41007 So long as a DKIM ACL is defined (it need do no more than accept),
41008 after all the DKIM ACL runs have completed, the value becomes a
41009 colon-separated list of the values after each run.
41010 This is maintained for the mime, prdr and data ACLs.
41012 .vitem &%$dkim_verify_reason%&
41013 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41014 "fail" or "invalid". One of
41016 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41017 key for the domain could not be retrieved. This may be a temporary problem.
41019 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41020 record for the domain is syntactically invalid.
41022 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41023 body hash does not match the one specified in the signature header. This
41024 means that the message body was modified in transit.
41026 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41027 could not be verified. This may mean that headers were modified,
41028 re-written or otherwise changed in a way which is incompatible with
41029 DKIM verification. It may of course also mean that the signature is forged.
41032 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41034 .vitem &%$dkim_domain%&
41035 The signing domain. IMPORTANT: This variable is only populated if there is
41036 an actual signature in the message for the current domain or identity (as
41037 reflected by &%$dkim_cur_signer%&).
41039 .vitem &%$dkim_identity%&
41040 The signing identity, if present. IMPORTANT: This variable is only populated
41041 if there is an actual signature in the message for the current domain or
41042 identity (as reflected by &%$dkim_cur_signer%&).
41044 .vitem &%$dkim_selector%&
41045 The key record selector string.
41047 .vitem &%$dkim_algo%&
41048 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41049 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41050 may also be 'ed25519-sha256'.
41051 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41054 Note that RFC 8301 says:
41056 rsa-sha1 MUST NOT be used for signing or verifying.
41058 DKIM signatures identified as having been signed with historic
41059 algorithms (currently, rsa-sha1) have permanently failed evaluation
41062 To enforce this you must either have a DKIM ACL which checks this variable
41063 and overwrites the &$dkim_verify_status$& variable as discussed above,
41064 or have set the main option &%dkim_verify_hashes%& to exclude
41065 processing of such signatures.
41067 .vitem &%$dkim_canon_body%&
41068 The body canonicalization method. One of 'relaxed' or 'simple'.
41070 .vitem &%$dkim_canon_headers%&
41071 The header canonicalization method. One of 'relaxed' or 'simple'.
41073 .vitem &%$dkim_copiedheaders%&
41074 A transcript of headers and their values which are included in the signature
41075 (copied from the 'z=' tag of the signature).
41076 Note that RFC6376 requires that verification fail if the From: header is
41077 not included in the signature. Exim does not enforce this; sites wishing
41078 strict enforcement should code the check explicitly.
41080 .vitem &%$dkim_bodylength%&
41081 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41082 limit was set by the signer, "9999999999999" is returned. This makes sure
41083 that this variable always expands to an integer value.
41084 &*Note:*& The presence of the signature tag specifying a signing body length
41085 is one possible route to spoofing of valid DKIM signatures.
41086 A paranoid implementation might wish to regard signature where this variable
41087 shows less than the "no limit" return as being invalid.
41089 .vitem &%$dkim_created%&
41090 UNIX timestamp reflecting the date and time when the signature was created.
41091 When this was not specified by the signer, "0" is returned.
41093 .vitem &%$dkim_expires%&
41094 UNIX timestamp reflecting the date and time when the signer wants the
41095 signature to be treated as "expired". When this was not specified by the
41096 signer, "9999999999999" is returned. This makes it possible to do useful
41097 integer size comparisons against this value.
41098 Note that Exim does not check this value.
41100 .vitem &%$dkim_headernames%&
41101 A colon-separated list of names of headers included in the signature.
41103 .vitem &%$dkim_key_testing%&
41104 "1" if the key record has the "testing" flag set, "0" if not.
41106 .vitem &%$dkim_key_nosubdomains%&
41107 "1" if the key record forbids subdomaining, "0" otherwise.
41109 .vitem &%$dkim_key_srvtype%&
41110 Service type (tag s=) from the key record. Defaults to "*" if not specified
41113 .vitem &%$dkim_key_granularity%&
41114 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41117 .vitem &%$dkim_key_notes%&
41118 Notes from the key record (tag n=).
41120 .vitem &%$dkim_key_length%&
41121 Number of bits in the key.
41123 Valid only once the key is loaded, which is at the time the header signature
41124 is verified, which is after the body hash is.
41127 Note that RFC 8301 says:
41129 Verifiers MUST NOT consider signatures using RSA keys of
41130 less than 1024 bits as valid signatures.
41133 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41138 In addition, two ACL conditions are provided:
41141 .vitem &%dkim_signers%&
41142 ACL condition that checks a colon-separated list of domains or identities
41143 for a match against the domain or identity that the ACL is currently verifying
41144 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41145 verb to a group of domains or identities. For example:
41148 # Warn when Mail purportedly from GMail has no gmail signature
41149 warn log_message = GMail sender without gmail.com DKIM signature
41150 sender_domains = gmail.com
41151 dkim_signers = gmail.com
41155 Note that the above does not check for a total lack of DKIM signing;
41156 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41158 .vitem &%dkim_status%&
41159 ACL condition that checks a colon-separated list of possible DKIM verification
41160 results against the actual result of verification. This is typically used
41161 to restrict an ACL verb to a list of verification outcomes, for example:
41164 deny message = Mail from Paypal with invalid/missing signature
41165 sender_domains = paypal.com:paypal.de
41166 dkim_signers = paypal.com:paypal.de
41167 dkim_status = none:invalid:fail
41170 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41171 see the documentation of the &%$dkim_verify_status%& expansion variable above
41172 for more information of what they mean.
41178 .section "SPF (Sender Policy Framework)" SECSPF
41179 .cindex SPF verification
41181 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41182 messages with its domain in the envelope from, documented by RFC 7208.
41183 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41184 the &url(http://openspf.org).
41185 . --- 2019-10-28: still not https, open-spf.org is told to be a
41186 . --- web-archive copy of the now dead openspf.org site
41187 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41190 Messages sent by a system not authorised will fail checking of such assertions.
41191 This includes retransmissions done by traditional forwarders.
41193 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41194 &_Local/Makefile_&. The support uses the &_libspf2_& library
41195 &url(https://www.libspf2.org/).
41196 There is no Exim involvement in the transmission of messages;
41197 publishing certain DNS records is all that is required.
41199 For verification, an ACL condition and an expansion lookup are provided.
41200 .cindex authentication "expansion item"
41201 Performing verification sets up information used by the
41202 &%authresults%& expansion item.
41205 .cindex SPF "ACL condition"
41206 .cindex ACL "spf condition"
41207 The ACL condition "spf" can be used at or after the MAIL ACL.
41208 It takes as an argument a list of strings giving the outcome of the SPF check,
41209 and will succeed for any matching outcome.
41213 The SPF check passed, the sending host is positively verified by SPF.
41216 The SPF check failed, the sending host is NOT allowed to send mail for the
41217 domain in the envelope-from address.
41219 .vitem &%softfail%&
41220 The SPF check failed, but the queried domain can't absolutely confirm that this
41224 The queried domain does not publish SPF records.
41227 The SPF check returned a "neutral" state. This means the queried domain has
41228 published a SPF record, but wants to allow outside servers to send mail under
41229 its domain as well. This should be treated like "none".
41231 .vitem &%permerror%&
41232 This indicates a syntax error in the SPF record of the queried domain.
41233 You may deny messages when this occurs.
41235 .vitem &%temperror%&
41236 This indicates a temporary error during all processing, including Exim's
41237 SPF processing. You may defer messages when this occurs.
41240 You can prefix each string with an exclamation mark to invert
41241 its meaning, for example "!fail" will match all results but
41242 "fail". The string list is evaluated left-to-right, in a
41243 short-circuit fashion.
41248 message = $sender_host_address is not allowed to send mail from \
41249 ${if def:sender_address_domain \
41250 {$sender_address_domain}{$sender_helo_name}}. \
41251 Please see http://www.open-spf.org/Why?scope=\
41252 ${if def:sender_address_domain {mfrom}{helo}};\
41253 identity=${if def:sender_address_domain \
41254 {$sender_address}{$sender_helo_name}};\
41255 ip=$sender_host_address
41258 When the spf condition has run, it sets up several expansion
41261 .cindex SPF "verification variables"
41263 .vitem &$spf_header_comment$&
41264 .vindex &$spf_header_comment$&
41265 This contains a human-readable string describing the outcome
41266 of the SPF check. You can add it to a custom header or use
41267 it for logging purposes.
41269 .vitem &$spf_received$&
41270 .vindex &$spf_received$&
41271 This contains a complete Received-SPF: header that can be
41272 added to the message. Please note that according to the SPF
41273 draft, this header must be added at the top of the header
41274 list. Please see section 10 on how you can do this.
41276 Note: in case of "Best-guess" (see below), the convention is
41277 to put this string in a header called X-SPF-Guess: instead.
41279 .vitem &$spf_result$&
41280 .vindex &$spf_result$&
41281 This contains the outcome of the SPF check in string form,
41282 one of pass, fail, softfail, none, neutral, permerror or
41285 .vitem &$spf_result_guessed$&
41286 .vindex &$spf_result_guessed$&
41287 This boolean is true only if a best-guess operation was used
41288 and required in order to obtain a result.
41290 .vitem &$spf_smtp_comment$&
41291 .vindex &$spf_smtp_comment$&
41292 This contains a string that can be used in a SMTP response
41293 to the calling party. Useful for "fail".
41297 .cindex SPF "ACL condition"
41298 .cindex ACL "spf_guess condition"
41299 .cindex SPF "best guess"
41300 In addition to SPF, you can also perform checks for so-called
41301 "Best-guess". Strictly speaking, "Best-guess" is not standard
41302 SPF, but it is supported by the same framework that enables SPF
41304 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41305 for a description of what it means.
41306 . --- 2019-10-28: still not https:
41308 To access this feature, simply use the spf_guess condition in place
41309 of the spf one. For example:
41312 deny spf_guess = fail
41313 message = $sender_host_address doesn't look trustworthy to me
41316 In case you decide to reject messages based on this check, you
41317 should note that although it uses the same framework, "Best-guess"
41318 is not SPF, and therefore you should not mention SPF at all in your
41321 When the spf_guess condition has run, it sets up the same expansion
41322 variables as when spf condition is run, described above.
41324 Additionally, since Best-guess is not standardized, you may redefine
41325 what "Best-guess" means to you by redefining the main configuration
41326 &%spf_guess%& option.
41327 For example, the following:
41330 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41333 would relax host matching rules to a broader network range.
41336 .cindex SPF "lookup expansion"
41338 A lookup expansion is also available. It takes an email
41339 address as the key and an IP address
41344 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41347 The lookup will return the same result strings as can appear in
41348 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41354 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41355 .cindex SRS "sender rewriting scheme"
41358 SRS can be used to modify sender addresses when forwarding so that
41359 SPF verification does not object to them.
41360 It operates by encoding the original envelope sender in a new
41361 sender local part and using a domain run by the forwarding site
41362 as the new domain for the sender. Any DSN message should be returned
41363 to this new sender at the forwarding site, which can extract the
41364 original sender from the coded local part and forward the DSN to
41367 This is a way of avoiding the breakage that SPF does to forwarding.
41368 The constructed local-part will be longer than the original,
41369 leading to possible problems with very long addresses.
41370 The changing of the sender address also hinders the tracing of mail
41373 Exim can be built to include native SRS support. To do this
41374 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41375 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41377 The support is limited to SRS0-encoding; SRS1 is not supported.
41379 .cindex SRS excoding
41380 To encode an address use this expansion item:
41382 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41383 .cindex "&%srs_encode%& expansion item"
41384 .cindex SRS "expansion item"
41385 The first argument should be a secret known and used by all systems
41386 handling the recipient domain for the original message.
41387 There is no need to periodically change this key; a timestamp is also
41389 The second argument should be given as the envelope sender address before this
41390 encoding operation.
41391 The third argument should be the recipient domain of the message when
41392 it arrived at this system.
41395 .cindex SRS decoding
41396 To decode an address use this expansion condition:
41398 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41399 The first argument should be the recipient local prt as is was received.
41400 The second argument is the site secret.
41402 If the messages is not for an SRS-encoded recipient the condition will
41403 return false. If it is, the condition will return true and the variable
41404 &$srs_recipient$& will be set to the decoded (original) value.
41410 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41416 # if outbound, and forwarding has been done, use an alternate transport
41417 domains = ! +my_domains
41418 transport = ${if eq {$local_part@$domain} \
41419 {$original_local_part@$original_domain} \
41420 {remote_smtp} {remote_forwarded_smtp}}
41425 domains = +my_domains
41426 # detect inbound bounces which are SRS'd, and decode them
41427 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
41428 data = $srs_recipient
41430 inbound_srs_failure:
41433 domains = +my_domains
41434 # detect inbound bounces which look SRS'd but are invalid
41435 condition = ${if inbound_srs {$local_part} {}}
41437 data = :fail: Invalid SRS recipient address
41439 #... further routers here
41442 # transport; should look like the non-forward outbound
41443 # one, plus the max_rcpt and return_path options
41444 remote_forwarded_smtp:
41446 # modify the envelope from, for mails that we forward
41448 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
41456 .section DMARC SECDMARC
41457 .cindex DMARC verification
41459 DMARC combines feedback from SPF, DKIM, and header From: in order
41460 to attempt to provide better indicators of the authenticity of an
41461 email. This document does not explain the fundamentals; you
41462 should read and understand how it works by visiting the website at
41463 &url(http://www.dmarc.org/).
41465 If Exim is built with DMARC support,
41466 the libopendmarc library is used.
41468 For building Exim yourself, obtain the library from
41469 &url(http://sourceforge.net/projects/opendmarc/)
41470 to obtain a copy, or find it in your favorite package
41471 repository. You will need to attend to the local/Makefile feature
41472 SUPPORT_DMARC and the associated LDFLAGS addition.
41473 This description assumes
41474 that headers will be in /usr/local/include, and that the libraries
41475 are in /usr/local/lib.
41479 There are three main-configuration options:
41480 .cindex DMARC "configuration options"
41482 The &%dmarc_tld_file%& option
41483 .oindex &%dmarc_tld_file%&
41484 defines the location of a text file of valid
41485 top level domains the opendmarc library uses
41486 during domain parsing. Maintained by Mozilla,
41487 the most current version can be downloaded
41488 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
41489 See also the util/renew-opendmarc-tlds.sh script.
41491 The default for the option is unset.
41492 If not set, DMARC processing is disabled.
41496 The &%dmarc_history_file%& option, if set
41497 .oindex &%dmarc_history_file%&
41498 defines the location of a file to log results
41499 of dmarc verification on inbound emails. The
41500 contents are importable by the opendmarc tools
41501 which will manage the data, send out DMARC
41502 reports, and expire the data. Make sure the
41503 directory of this file is writable by the user
41505 The default is unset.
41507 The &%dmarc_forensic_sender%& option
41508 .oindex &%dmarc_forensic_sender%&
41509 defines an alternate email address to use when sending a
41510 forensic report detailing alignment failures
41511 if a sender domain's dmarc record specifies it
41512 and you have configured Exim to send them.
41513 If set, this is expanded and used for the
41514 From: header line; the address is extracted
41515 from it and used for the envelope from.
41516 If not set (the default), the From: header is expanded from
41517 the dsn_from option, and <> is used for the
41520 . I wish we had subsections...
41522 .cindex DMARC controls
41523 By default, the DMARC processing will run for any remote,
41524 non-authenticated user. It makes sense to only verify DMARC
41525 status of messages coming from remote, untrusted sources. You can
41526 use standard conditions such as hosts, senders, etc, to decide that
41527 DMARC verification should *not* be performed for them and disable
41528 DMARC with an ACL control modifier:
41530 control = dmarc_disable_verify
41532 A DMARC record can also specify a "forensic address", which gives
41533 exim an email address to submit reports about failed alignment.
41534 Exim does not do this by default because in certain conditions it
41535 results in unintended information leakage (what lists a user might
41536 be subscribed to, etc). You must configure exim to submit forensic
41537 reports to the owner of the domain. If the DMARC record contains a
41538 forensic address and you specify the control statement below, then
41539 exim will send these forensic emails. It is also advised that you
41540 configure a &%dmarc_forensic_sender%& because the default sender address
41541 construction might be inadequate.
41543 control = dmarc_enable_forensic
41545 (AGAIN: You can choose not to send these forensic reports by simply
41546 not putting the dmarc_enable_forensic control line at any point in
41547 your exim config. If you don't tell exim to send them, it will not
41550 There are no options to either control. Both must appear before
41555 DMARC checks cam be run on incoming SMTP messages by using the
41556 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
41557 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
41558 condition. Putting this condition in the ACLs is required in order
41559 for a DMARC check to actually occur. All of the variables are set
41560 up before the DATA ACL, but there is no actual DMARC check that
41561 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
41563 The &"dmarc_status"& condition takes a list of strings on its
41564 right-hand side. These strings describe recommended action based
41565 on the DMARC check. To understand what the policy recommendations
41566 mean, refer to the DMARC website above. Valid strings are:
41568 &'accept '& The DMARC check passed and the library recommends accepting the email.
41569 &'reject '& The DMARC check failed and the library recommends rejecting the email.
41570 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
41571 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
41572 &'norecord '& No policy section in the DMARC record for this sender domain.
41573 &'nofrom '& Unable to determine the domain of the sender.
41574 &'temperror '& Library error or dns error.
41575 &'off '& The DMARC check was disabled for this email.
41577 You can prefix each string with an exclamation mark to invert its
41578 meaning, for example "!accept" will match all results but
41579 "accept". The string list is evaluated left-to-right in a
41580 short-circuit fashion. When a string matches the outcome of the
41581 DMARC check, the condition succeeds. If none of the listed
41582 strings matches the outcome of the DMARC check, the condition
41585 Of course, you can also use any other lookup method that Exim
41586 supports, including LDAP, Postgres, MySQL, etc, as long as the
41587 result is a list of colon-separated strings.
41589 Performing the check sets up information used by the
41590 &%authresults%& expansion item.
41592 Several expansion variables are set before the DATA ACL is
41593 processed, and you can use them in this ACL. The following
41594 expansion variables are available:
41597 .vitem &$dmarc_status$&
41598 .vindex &$dmarc_status$&
41599 .cindex DMARC result
41600 A one word status indicating what the DMARC library
41601 thinks of the email. It is a combination of the results of
41602 DMARC record lookup and the SPF/DKIM/DMARC processing results
41603 (if a DMARC record was found). The actual policy declared
41604 in the DMARC record is in a separate expansion variable.
41606 .vitem &$dmarc_status_text$&
41607 .vindex &$dmarc_status_text$&
41608 Slightly longer, human readable status.
41610 .vitem &$dmarc_used_domain$&
41611 .vindex &$dmarc_used_domain$&
41612 The domain which DMARC used to look up the DMARC policy record.
41614 .vitem &$dmarc_domain_policy$&
41615 .vindex &$dmarc_domain_policy$&
41616 The policy declared in the DMARC record. Valid values
41617 are "none", "reject" and "quarantine". It is blank when there
41618 is any error, including no DMARC record.
41623 By default, Exim's DMARC configuration is intended to be
41624 non-intrusive and conservative. To facilitate this, Exim will not
41625 create any type of logging files without explicit configuration by
41626 you, the admin. Nor will Exim send out any emails/reports about
41627 DMARC issues without explicit configuration by you, the admin (other
41628 than typical bounce messages that may come about due to ACL
41629 processing or failure delivery issues).
41631 In order to log statistics suitable to be imported by the opendmarc
41632 tools, you need to:
41634 Configure the global option &%dmarc_history_file%&
41636 Configure cron jobs to call the appropriate opendmarc history
41637 import scripts and truncating the dmarc_history_file
41640 In order to send forensic reports, you need to:
41642 Configure the global option &%dmarc_forensic_sender%&
41644 Configure, somewhere before the DATA ACL, the control option to
41645 enable sending DMARC forensic reports
41653 warn domains = +local_domains
41654 hosts = +local_hosts
41655 control = dmarc_disable_verify
41657 warn !domains = +screwed_up_dmarc_records
41658 control = dmarc_enable_forensic
41660 warn condition = (lookup if destined to mailing list)
41661 set acl_m_mailing_list = 1
41664 warn dmarc_status = accept : none : off
41666 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
41668 warn dmarc_status = !accept
41670 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
41672 warn dmarc_status = quarantine
41674 set $acl_m_quarantine = 1
41675 # Do something in a transport with this flag variable
41677 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
41678 condition = ${if eq{$acl_m_mailing_list}{1}}
41679 message = Messages from $dmarc_used_domain break mailing lists
41681 deny dmarc_status = reject
41683 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
41685 warn add_header = :at_start:${authresults {$primary_hostname}}
41692 . ////////////////////////////////////////////////////////////////////////////
41693 . ////////////////////////////////////////////////////////////////////////////
41695 .chapter "Proxies" "CHAPproxies" &&&
41697 .cindex "proxy support"
41698 .cindex "proxy" "access via"
41700 A proxy is an intermediate system through which communication is passed.
41701 Proxies may provide a security, availability or load-distribution function.
41704 .section "Inbound proxies" SECTproxyInbound
41705 .cindex proxy inbound
41706 .cindex proxy "server side"
41707 .cindex proxy "Proxy protocol"
41708 .cindex "Proxy protocol" proxy
41710 Exim has support for receiving inbound SMTP connections via a proxy
41711 that uses &"Proxy Protocol"& to speak to it.
41712 To include this support, include &"SUPPORT_PROXY=yes"&
41715 It was built on the HAProxy specification, found at
41716 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
41718 The purpose of this facility is so that an application load balancer,
41719 such as HAProxy, can sit in front of several Exim servers
41720 to distribute load.
41721 Exim uses the local protocol communication with the proxy to obtain
41722 the remote SMTP system IP address and port information.
41723 There is no logging if a host passes or
41724 fails Proxy Protocol negotiation, but it can easily be determined and
41725 recorded in an ACL (example is below).
41727 Use of a proxy is enabled by setting the &%hosts_proxy%&
41728 main configuration option to a hostlist; connections from these
41729 hosts will use Proxy Protocol.
41730 Exim supports both version 1 and version 2 of the Proxy Protocol and
41731 automatically determines which version is in use.
41733 The Proxy Protocol header is the first data received on a TCP connection
41734 and is inserted before any TLS-on-connect handshake from the client; Exim
41735 negotiates TLS between Exim-as-server and the remote client, not between
41736 Exim and the proxy server.
41738 The following expansion variables are usable
41739 (&"internal"& and &"external"& here refer to the interfaces
41742 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
41743 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
41744 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
41745 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
41746 &'proxy_session '& boolean: SMTP connection via proxy
41748 If &$proxy_session$& is set but &$proxy_external_address$& is empty
41749 there was a protocol error.
41750 The variables &$sender_host_address$& and &$sender_host_port$&
41751 will have values for the actual client system, not the proxy.
41753 Since the real connections are all coming from the proxy, and the
41754 per host connection tracking is done before Proxy Protocol is
41755 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
41756 handle all of the parallel volume you expect per inbound proxy.
41757 With the option set so high, you lose the ability
41758 to protect your server from many connections from one IP.
41759 In order to prevent your server from overload, you
41760 need to add a per connection ratelimit to your connect ACL.
41761 A possible solution is:
41763 # Set max number of connections per host
41765 # Or do some kind of IP lookup in a flat file or database
41766 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
41768 defer message = Too many connections from this IP right now
41769 ratelimit = LIMIT / 5s / per_conn / strict
41774 .section "Outbound proxies" SECTproxySOCKS
41775 .cindex proxy outbound
41776 .cindex proxy "client side"
41777 .cindex proxy SOCKS
41778 .cindex SOCKS proxy
41779 Exim has support for sending outbound SMTP via a proxy
41780 using a protocol called SOCKS5 (defined by RFC1928).
41781 The support can be optionally included by defining SUPPORT_SOCKS=yes in
41784 Use of a proxy is enabled by setting the &%socks_proxy%& option
41785 on an smtp transport.
41786 The option value is expanded and should then be a list
41787 (colon-separated by default) of proxy specifiers.
41788 Each proxy specifier is a list
41789 (space-separated by default) where the initial element
41790 is an IP address and any subsequent elements are options.
41792 Options are a string <name>=<value>.
41793 The list of options is in the following table:
41795 &'auth '& authentication method
41796 &'name '& authentication username
41797 &'pass '& authentication password
41799 &'tmo '& connection timeout
41801 &'weight '& selection bias
41804 More details on each of these options follows:
41807 .cindex authentication "to proxy"
41808 .cindex proxy authentication
41809 &%auth%&: Either &"none"& (default) or &"name"&.
41810 Using &"name"& selects username/password authentication per RFC 1929
41811 for access to the proxy.
41812 Default is &"none"&.
41814 &%name%&: sets the username for the &"name"& authentication method.
41817 &%pass%&: sets the password for the &"name"& authentication method.
41820 &%port%&: the TCP port number to use for the connection to the proxy.
41823 &%tmo%&: sets a connection timeout in seconds for this proxy.
41826 &%pri%&: specifies a priority for the proxy within the list,
41827 higher values being tried first.
41828 The default priority is 1.
41830 &%weight%&: specifies a selection bias.
41831 Within a priority set servers are queried in a random fashion,
41832 weighted by this value.
41833 The default value for selection bias is 1.
41836 Proxies from the list are tried according to their priority
41837 and weight settings until one responds. The timeout for the
41838 overall connection applies to the set of proxied attempts.
41840 .section Logging SECTproxyLog
41841 To log the (local) IP of a proxy in the incoming or delivery logline,
41842 add &"+proxy"& to the &%log_selector%& option.
41843 This will add a component tagged with &"PRX="& to the line.
41845 . ////////////////////////////////////////////////////////////////////////////
41846 . ////////////////////////////////////////////////////////////////////////////
41848 .chapter "Internationalisation" "CHAPi18n" &&&
41849 "Internationalisation""
41850 .cindex internationalisation "email address"
41853 .cindex utf8 "mail name handling"
41855 Exim has support for Internationalised mail names.
41856 To include this it must be built with SUPPORT_I18N and the libidn library.
41857 Standards supported are RFCs 2060, 5890, 6530 and 6533.
41859 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
41860 instead of it) then IDNA2008 is supported; this adds an extra library
41861 requirement, upon libidn2.
41863 .section "MTA operations" SECTi18nMTA
41864 .cindex SMTPUTF8 "ESMTP option"
41865 .cindex "ESMTP extensions" SMTPUTF8
41866 The main configuration option &%smtputf8_advertise_hosts%& specifies
41867 a host list. If this matches the sending host and
41868 accept_8bitmime is true (the default) then the ESMTP option
41869 SMTPUTF8 will be advertised.
41871 If the sender specifies the SMTPUTF8 option on a MAIL command
41872 international handling for the message is enabled and
41873 the expansion variable &$message_smtputf8$& will have value TRUE.
41875 The option &%allow_utf8_domains%& is set to true for this
41876 message. All DNS lookups are converted to a-label form
41877 whatever the setting of &%allow_utf8_domains%&
41878 when Exim is built with SUPPORT_I18N.
41880 Both localparts and domain are maintained as the original
41881 UTF-8 form internally; any comparison or regular-expression use will
41882 require appropriate care. Filenames created, eg. by
41883 the appendfile transport, will have UTF-8 names.
41885 HELO names sent by the smtp transport will have any UTF-8
41886 components expanded to a-label form,
41887 and any certificate name checks will be done using the a-label
41890 .cindex log protocol
41891 .cindex SMTPUTF8 logging
41892 .cindex i18n logging
41893 Log lines and Received-by: header lines will acquire a "utf8"
41894 prefix on the protocol element, eg. utf8esmtp.
41896 The following expansion operators can be used:
41898 ${utf8_domain_to_alabel:str}
41899 ${utf8_domain_from_alabel:str}
41900 ${utf8_localpart_to_alabel:str}
41901 ${utf8_localpart_from_alabel:str}
41904 .cindex utf8 "address downconversion"
41905 .cindex i18n "utf8 address downconversion"
41907 may use the following modifier:
41909 control = utf8_downconvert
41910 control = utf8_downconvert/<value>
41912 This sets a flag requiring that envelope addresses are converted to
41913 a-label form before smtp delivery.
41914 This is usually for use in a Message Submission Agent context,
41915 but could be used for any message.
41917 If a value is appended it may be:
41919 &`1 `& mandatory downconversion
41920 &`0 `& no downconversion
41921 &`-1 `& if SMTPUTF8 not supported by destination host
41923 If no value is given, 1 is used.
41925 If mua_wrapper is set, the utf8_downconvert control
41926 is initially set to -1.
41928 The smtp transport has an option &%utf8_downconvert%&.
41929 If set it must expand to one of the three values described above,
41930 or an empty string.
41931 If non-empty it overrides value previously set
41932 (due to mua_wrapper or by an ACL control).
41935 There is no explicit support for VRFY and EXPN.
41936 Configurations supporting these should inspect
41937 &$smtp_command_argument$& for an SMTPUTF8 argument.
41939 There is no support for LMTP on Unix sockets.
41940 Using the "lmtp" protocol option on an smtp transport,
41941 for LMTP over TCP, should work as expected.
41943 There is no support for DSN unitext handling,
41944 and no provision for converting logging from or to UTF-8.
41948 .section "MDA operations" SECTi18nMDA
41949 To aid in constructing names suitable for IMAP folders
41950 the following expansion operator can be used:
41952 ${imapfolder {<string>} {<sep>} {<specials>}}
41955 The string is converted from the charset specified by
41956 the "headers charset" command (in a filter file)
41957 or &%headers_charset%& main configuration option (otherwise),
41959 modified UTF-7 encoding specified by RFC 2060,
41960 with the following exception: All occurrences of <sep>
41961 (which has to be a single character)
41962 are replaced with periods ("."), and all periods and slashes that are not
41963 <sep> and are not in the <specials> string are BASE64 encoded.
41965 The third argument can be omitted, defaulting to an empty string.
41966 The second argument can be omitted, defaulting to "/".
41968 This is the encoding used by Courier for Maildir names on disk, and followed
41969 by many other IMAP servers.
41973 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
41974 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
41975 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
41978 Note that the source charset setting is vital, and also that characters
41979 must be representable in UTF-16.
41982 . ////////////////////////////////////////////////////////////////////////////
41983 . ////////////////////////////////////////////////////////////////////////////
41985 .chapter "Events" "CHAPevents" &&&
41989 The events mechanism in Exim can be used to intercept processing at a number
41990 of points. It was originally invented to give a way to do customised logging
41991 actions (for example, to a database) but can also be used to modify some
41992 processing actions.
41994 Most installations will never need to use Events.
41995 The support can be left out of a build by defining DISABLE_EVENT=yes
41996 in &_Local/Makefile_&.
41998 There are two major classes of events: main and transport.
41999 The main configuration option &%event_action%& controls reception events;
42000 a transport option &%event_action%& controls delivery events.
42002 Both options are a string which is expanded when the event fires.
42003 An example might look like:
42004 .cindex logging custom
42006 event_action = ${if eq {msg:delivery}{$event_name} \
42007 {${lookup pgsql {SELECT * FROM record_Delivery( \
42008 '${quote_pgsql:$sender_address_domain}',\
42009 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42010 '${quote_pgsql:$domain}', \
42011 '${quote_pgsql:${lc:$local_part}}', \
42012 '${quote_pgsql:$host_address}', \
42013 '${quote_pgsql:${lc:$host}}', \
42014 '${quote_pgsql:$message_exim_id}')}} \
42018 Events have names which correspond to the point in process at which they fire.
42019 The name is placed in the variable &$event_name$& and the event action
42020 expansion must check this, as it will be called for every possible event type.
42023 The current list of events is:
42026 &`dane:fail after transport `& per connection
42027 &`msg:complete after main `& per message
42028 &`msg:defer after transport `& per message per delivery try
42029 &`msg:delivery after transport `& per recipient
42030 &`msg:rcpt:host:defer after transport `& per recipient per host
42031 &`msg:rcpt:defer after transport `& per recipient
42032 &`msg:host:defer after transport `& per host per delivery try; host errors
42033 &`msg:fail:delivery after transport `& per recipient
42034 &`msg:fail:internal after main `& per recipient
42035 &`tcp:connect before transport `& per connection
42036 &`tcp:close after transport `& per connection
42037 &`tls:cert before both `& per certificate in verification chain
42038 &`smtp:connect after transport `& per connection
42039 &`smtp:ehlo after transport `& per connection
42041 New event types may be added in future.
42043 The event name is a colon-separated list, defining the type of
42044 event in a tree of possibilities. It may be used as a list
42045 or just matched on as a whole. There will be no spaces in the name.
42047 The second column in the table above describes whether the event fires
42048 before or after the action is associates with. Those which fire before
42049 can be used to affect that action (more on this below).
42051 The third column in the table above says what section of the configuration
42052 should define the event action.
42054 An additional variable, &$event_data$&, is filled with information varying
42055 with the event type:
42057 &`dane:fail `& failure reason
42058 &`msg:defer `& error string
42059 &`msg:delivery `& smtp confirmation message
42060 &`msg:fail:internal `& failure reason
42061 &`msg:fail:delivery `& smtp error message
42062 &`msg:host:defer `& error string
42063 &`msg:rcpt:host:defer `& error string
42064 &`msg:rcpt:defer `& error string
42065 &`tls:cert `& verification chain depth
42066 &`smtp:connect `& smtp banner
42067 &`smtp:ehlo `& smtp ehlo response
42070 The :defer events populate one extra variable: &$event_defer_errno$&.
42072 For complex operations an ACL expansion can be used in &%event_action%&
42073 however due to the multiple contexts that Exim operates in during
42074 the course of its processing:
42076 variables set in transport events will not be visible outside that
42079 acl_m variables in a server context are lost on a new connection,
42080 and after smtp helo/ehlo/mail/starttls/rset commands
42082 Using an ACL expansion with the logwrite modifier can be
42083 a useful way of writing to the main log.
42085 The expansion of the event_action option should normally
42086 return an empty string. Should it return anything else the
42087 following will be forced:
42089 &`tcp:connect `& do not connect
42090 &`tls:cert `& refuse verification
42091 &`smtp:connect `& close connection
42093 All other message types ignore the result string, and
42094 no other use is made of it.
42096 For a tcp:connect event, if the connection is being made to a proxy
42097 then the address and port variables will be that of the proxy and not
42100 For tls:cert events, if GnuTLS is in use this will trigger only per
42101 chain element received on the connection.
42102 For OpenSSL it will trigger for every chain element including those
42105 . ////////////////////////////////////////////////////////////////////////////
42106 . ////////////////////////////////////////////////////////////////////////////
42108 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42109 "Adding drivers or lookups"
42110 .cindex "adding drivers"
42111 .cindex "new drivers, adding"
42112 .cindex "drivers" "adding new"
42113 The following actions have to be taken in order to add a new router, transport,
42114 authenticator, or lookup type to Exim:
42117 Choose a name for the driver or lookup type that does not conflict with any
42118 existing name; I will use &"newdriver"& in what follows.
42120 Add to &_src/EDITME_& the line:
42122 <&'type'&>&`_NEWDRIVER=yes`&
42124 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42125 code is not to be included in the binary by default, comment this line out. You
42126 should also add any relevant comments about the driver or lookup type.
42128 Add to &_src/config.h.defaults_& the line:
42130 #define <type>_NEWDRIVER
42133 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42134 and create a table entry as is done for all the other drivers and lookup types.
42136 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42137 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42138 Add your &`NEWDRIVER`& to that list.
42139 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42140 simple form that most lookups have.
42142 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42143 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42144 driver or lookup type and add it to the definition of OBJ.
42146 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42147 definition of OBJ_MACRO. Add a set of line to do the compile also.
42149 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42152 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42153 as for other drivers and lookups.
42156 Then all you need to do is write the code! A good way to start is to make a
42157 proforma by copying an existing module of the same type, globally changing all
42158 occurrences of the name, and cutting out most of the code. Note that any
42159 options you create must be listed in alphabetical order, because the tables are
42160 searched using a binary chop procedure.
42162 There is a &_README_& file in each of the sub-directories of &_src_& describing
42163 the interface that is expected.
42168 . ////////////////////////////////////////////////////////////////////////////
42169 . ////////////////////////////////////////////////////////////////////////////
42171 . /////////////////////////////////////////////////////////////////////////////
42172 . These lines are processing instructions for the Simple DocBook Processor that
42173 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42174 . PDFs than using xmlto and fop. They will be ignored by all other XML
42176 . /////////////////////////////////////////////////////////////////////////////
42181 foot_right_recto="&chaptertitle;"
42182 foot_right_verso="&chaptertitle;"
42186 .makeindex "Options index" "option"
42187 .makeindex "Variables index" "variable"
42188 .makeindex "Concept index" "concept"
42191 . /////////////////////////////////////////////////////////////////////////////
42192 . /////////////////////////////////////////////////////////////////////////////