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 printing 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 generate the outermost <book> element that wraps then 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 "4.80"
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 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 . --- the 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 the program,
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 the 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, the 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(http://www.uit.co.uk/exim-book/)).
397 This 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 the program 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 the program (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"
441 The main specification and the specification of the filtering language are also
442 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
443 &<<SECTavail>>& below tells you how to get hold of these.
447 .section "FTP and web sites" "SECID2"
450 The primary site for Exim source distributions is currently the University of
451 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
452 distribution'& below. In addition, there is a web site and an FTP site at
453 &%exim.org%&. These are now also hosted at the University of Cambridge. The
454 &%exim.org%& site was previously hosted for a number of years by Energis
455 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
459 As well as Exim distribution tar files, the Exim web site contains a number of
460 differently formatted versions of the documentation. A recent addition to the
461 online information is the Exim wiki (&url(http://wiki.exim.org)),
462 which contains what used to be a separate FAQ, as well as various other
463 examples, tips, and know-how that have been contributed by Exim users.
466 An Exim Bugzilla exists at &url(http://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.
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(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on this list and not on the general Exim
495 .section "Exim training" "SECID4"
496 .cindex "training courses"
497 Training courses in Cambridge (UK) used to be run annually by the author of
498 Exim, before he retired. At the time of writing, there are no plans to run
499 further Exim courses in Cambridge. However, if that changes, relevant
500 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
502 .section "Bug reports" "SECID5"
503 .cindex "bug reports"
504 .cindex "reporting bugs"
505 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
506 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
507 whether some behaviour is a bug or not, the best thing to do is to post a
508 message to the &'exim-dev'& mailing list and have it discussed.
512 .section "Where to find the Exim distribution" "SECTavail"
514 .cindex "distribution" "ftp site"
515 The master ftp site for the Exim distribution is
517 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
521 &*ftp://ftp.exim.org/pub/exim*&
523 The file references that follow are relative to the &_exim_& directories at
524 these sites. There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
527 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
533 &_exim-n.nn.tar.bz2_&
535 where &'n.nn'& is the highest such version number in the directory. The two
536 files contain identical data; the only difference is the type of compression.
537 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
539 .cindex "distribution" "signing details"
540 .cindex "distribution" "public key"
541 .cindex "public key for signed distribution"
542 The distributions will be PGP signed by an individual key of the Release
543 Coordinator. This key will have a uid containing an email address in the
544 &'exim.org'& domain and will have signatures from other people, including
545 other Exim maintainers. We expect that the key will be in the "strong set" of
546 PGP keys. There should be a trust path to that key from Nigel Metheringham's
547 PGP key, a version of which can be found in the release directory in the file
548 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
549 such as &'pool.sks-keyservers.net'&.
551 At time of last update, releases were being made by Phil Pennock and signed with
552 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
553 A trust path from Nigel's key to Phil's can be observed at
554 &url(https://www.security.spodhuis.org/exim-trustpath).
556 Releases have also been authorized to be performed by Todd Lyons who signs with
557 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
558 Pennock and Todd Lyons through a common associate.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.gz.asc_&
563 &_exim-n.nn.tar.bz2.asc_&
565 For each released version, the log of changes is made separately available in a
566 separate file in the directory &_ChangeLogs_& so that it is possible to
567 find out what has changed without having to download the entire distribution.
569 .cindex "documentation" "available formats"
570 The main distribution contains ASCII versions of this specification and other
571 documentation; other formats of the documents are available in separate files
572 inside the &_exim4_& directory of the FTP site:
574 &_exim-html-n.nn.tar.gz_&
575 &_exim-pdf-n.nn.tar.gz_&
576 &_exim-postscript-n.nn.tar.gz_&
577 &_exim-texinfo-n.nn.tar.gz_&
579 These tar files contain only the &_doc_& directory, not the complete
580 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
583 .section "Limitations" "SECID6"
585 .cindex "limitations of Exim"
586 .cindex "bang paths" "not handled by Exim"
587 Exim is designed for use as an Internet MTA, and therefore handles addresses in
588 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
589 simple two-component bang paths can be converted by a straightforward rewriting
590 configuration. This restriction does not prevent Exim from being interfaced to
591 UUCP as a transport mechanism, provided that domain addresses are used.
593 .cindex "domainless addresses"
594 .cindex "address" "without domain"
595 Exim insists that every address it handles has a domain attached. For incoming
596 local messages, domainless addresses are automatically qualified with a
597 configured domain value. Configuration options specify from which remote
598 systems unqualified addresses are acceptable. These are then qualified on
601 .cindex "transport" "external"
602 .cindex "external transports"
603 The only external transport mechanisms that are currently implemented are SMTP
604 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
605 transport is available, and there are facilities for writing messages to files
606 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
607 to send messages to other transport mechanisms such as UUCP, provided they can
608 handle domain-style addresses. Batched SMTP input is also catered for.
610 Exim is not designed for storing mail for dial-in hosts. When the volumes of
611 such mail are large, it is better to get the messages &"delivered"& into files
612 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
615 Although Exim does have basic facilities for scanning incoming messages, these
616 are not comprehensive enough to do full virus or spam scanning. Such operations
617 are best carried out using additional specialized software packages. If you
618 compile Exim with the content-scanning extension, straightforward interfaces to
619 a number of common scanners are provided.
623 .section "Run time configuration" "SECID7"
624 Exim's run time configuration is held in a single text file that is divided
625 into a number of sections. The entries in this file consist of keywords and
626 values, in the style of Smail 3 configuration files. A default configuration
627 file which is suitable for simple online installations is provided in the
628 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
631 .section "Calling interface" "SECID8"
632 .cindex "Sendmail compatibility" "command line interface"
633 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
634 can be a straight replacement for &_/usr/lib/sendmail_& or
635 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
636 about Sendmail in order to run Exim. For actions other than sending messages,
637 Sendmail-compatible options also exist, but those that produce output (for
638 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
639 format. There are also some additional options that are compatible with Smail
640 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
641 documents all Exim's command line options. This information is automatically
642 made into the man page that forms part of the Exim distribution.
644 Control of messages on the queue can be done via certain privileged command
645 line options. There is also an optional monitor program called &'eximon'&,
646 which displays current information in an X window, and which contains a menu
647 interface to Exim's command line administration options.
651 .section "Terminology" "SECID9"
652 .cindex "terminology definitions"
653 .cindex "body of message" "definition of"
654 The &'body'& of a message is the actual data that the sender wants to transmit.
655 It is the last part of a message, and is separated from the &'header'& (see
656 below) by a blank line.
658 .cindex "bounce message" "definition of"
659 When a message cannot be delivered, it is normally returned to the sender in a
660 delivery failure message or a &"non-delivery report"& (NDR). The term
661 &'bounce'& is commonly used for this action, and the error reports are often
662 called &'bounce messages'&. This is a convenient shorthand for &"delivery
663 failure error report"&. Such messages have an empty sender address in the
664 message's &'envelope'& (see below) to ensure that they cannot themselves give
665 rise to further bounce messages.
667 The term &'default'& appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
672 The term &'defer'& is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
677 The word &'domain'& is sometimes used to mean all but the first component of a
678 host's name. It is &'not'& used in that sense here, where it normally refers to
679 the part of an email address following the @ sign.
681 .cindex "envelope, definition of"
682 .cindex "sender" "definition of"
683 A message in transit has an associated &'envelope'&, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
690 .cindex "message" "header, definition of"
691 .cindex "header section" "definition of"
692 The &'header'& of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
694 &'Subject:'&, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
698 .cindex "local part" "definition of"
699 .cindex "domain" "definition of"
700 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @ sign. The part that follows the
702 @ sign is called the &'domain'& or &'mail domain'&.
704 .cindex "local delivery" "definition of"
705 .cindex "remote delivery, definition of"
706 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
709 host it is running on are &'remote'&.
711 .cindex "return path" "definition of"
712 &'Return path'& is another name that is used for the sender address in a
715 .cindex "queue" "definition of"
716 The term &'queue'& is used to refer to the set of messages awaiting delivery,
717 because this term is in widespread use in the context of MTAs. However, in
718 Exim's case the reality is more like a pool than a queue, because there is
719 normally no ordering of waiting messages.
721 .cindex "queue runner" "definition of"
722 The term &'queue runner'& is used to describe a process that scans the queue
723 and attempts to deliver those messages whose retry times have come. This term
724 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
725 the waiting messages are normally processed in an unpredictable order.
727 .cindex "spool directory" "definition of"
728 The term &'spool directory'& is used for a directory in which Exim keeps the
729 messages on its queue &-- that is, those that it is in the process of
730 delivering. This should not be confused with the directory in which local
731 mailboxes are stored, which is called a &"spool directory"& by some people. In
732 the Exim documentation, &"spool"& is always used in the first sense.
739 . ////////////////////////////////////////////////////////////////////////////
740 . ////////////////////////////////////////////////////////////////////////////
742 .chapter "Incorporated code" "CHID2"
743 .cindex "incorporated code"
744 .cindex "regular expressions" "library"
747 A number of pieces of external code are included in the Exim distribution.
750 Regular expressions are supported in the main Exim program and in the
751 Exim monitor using the freely-distributable PCRE library, copyright
752 © University of Cambridge. The source to PCRE is no longer shipped with
753 Exim, so you will need to use the version of PCRE shipped with your system,
754 or obtain and install the full version of the library from
755 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
757 .cindex "cdb" "acknowledgment"
758 Support for the cdb (Constant DataBase) lookup method is provided by code
759 contributed by Nigel Metheringham of (at the time he contributed it) Planet
760 Online Ltd. The implementation is completely contained within the code of Exim.
761 It does not link against an external cdb library. The code contains the
762 following statements:
765 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
767 This program is free software; you can redistribute it and/or modify it under
768 the terms of the GNU General Public License as published by the Free Software
769 Foundation; either version 2 of the License, or (at your option) any later
771 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
772 the spec and sample code for cdb can be obtained from
773 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
774 some code from Dan Bernstein's implementation (which has no license
775 restrictions applied to it).
778 .cindex "SPA authentication"
779 .cindex "Samba project"
780 .cindex "Microsoft Secure Password Authentication"
781 Client support for Microsoft's &'Secure Password Authentication'& is provided
782 by code contributed by Marc Prud'hommeaux. Server support was contributed by
783 Tom Kistner. This includes code taken from the Samba project, which is released
787 .cindex "&'pwcheck'& daemon"
788 .cindex "&'pwauthd'& daemon"
789 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
790 by code taken from the Cyrus-SASL library and adapted by Alexander S.
791 Sabourenkov. The permission notice appears below, in accordance with the
792 conditions expressed therein.
795 Copyright © 2001 Carnegie Mellon University. All rights reserved.
797 Redistribution and use in source and binary forms, with or without
798 modification, are permitted provided that the following conditions
802 Redistributions of source code must retain the above copyright
803 notice, this list of conditions and the following disclaimer.
805 Redistributions in binary form must reproduce the above copyright
806 notice, this list of conditions and the following disclaimer in
807 the documentation and/or other materials provided with the
810 The name &"Carnegie Mellon University"& must not be used to
811 endorse or promote products derived from this software without
812 prior written permission. For permission or any other legal
813 details, please contact
815 Office of Technology Transfer
816 Carnegie Mellon University
818 Pittsburgh, PA 15213-3890
819 (412) 268-4387, fax: (412) 268-7395
820 tech-transfer@andrew.cmu.edu
823 Redistributions of any form whatsoever must retain the following
826 &"This product includes software developed by Computing Services
827 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
829 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
830 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
831 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
832 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
833 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
834 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
835 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
840 .cindex "Exim monitor" "acknowledgment"
843 The Exim Monitor program, which is an X-Window application, includes
844 modified versions of the Athena StripChart and TextPop widgets.
845 This code is copyright by DEC and MIT, and their permission notice appears
846 below, in accordance with the conditions expressed therein.
849 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
850 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
854 Permission to use, copy, modify, and distribute this software and its
855 documentation for any purpose and without fee is hereby granted,
856 provided that the above copyright notice appear in all copies and that
857 both that copyright notice and this permission notice appear in
858 supporting documentation, and that the names of Digital or MIT not be
859 used in advertising or publicity pertaining to distribution of the
860 software without specific, written prior permission.
862 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
863 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
864 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
865 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
866 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
867 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
872 .cindex "opendmarc" "acknowledgment"
873 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
874 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
875 derived code are indicated in the respective source files. The full OpenDMARC
876 license is provided in the LICENSE.opendmarc file contained in the distributed
880 Many people have contributed code fragments, some large, some small, that were
881 not covered by any specific licence requirements. It is assumed that the
882 contributors are happy to see their code incorporated into Exim under the GPL.
889 . ////////////////////////////////////////////////////////////////////////////
890 . ////////////////////////////////////////////////////////////////////////////
892 .chapter "How Exim receives and delivers mail" "CHID11" &&&
893 "Receiving and delivering mail"
896 .section "Overall philosophy" "SECID10"
897 .cindex "design philosophy"
898 Exim is designed to work efficiently on systems that are permanently connected
899 to the Internet and are handling a general mix of mail. In such circumstances,
900 most messages can be delivered immediately. Consequently, Exim does not
901 maintain independent queues of messages for specific domains or hosts, though
902 it does try to send several messages in a single SMTP connection after a host
903 has been down, and it also maintains per-host retry information.
906 .section "Policy control" "SECID11"
907 .cindex "policy control" "overview"
908 Policy controls are now an important feature of MTAs that are connected to the
909 Internet. Perhaps their most important job is to stop MTAs being abused as
910 &"open relays"& by misguided individuals who send out vast amounts of
911 unsolicited junk, and want to disguise its source. Exim provides flexible
912 facilities for specifying policy controls on incoming mail:
915 .cindex "&ACL;" "introduction"
916 Exim 4 (unlike previous versions of Exim) implements policy controls on
917 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
918 series of statements that may either grant or deny access. ACLs can be used at
919 several places in the SMTP dialogue while receiving a message from a remote
920 host. However, the most common places are after each RCPT command, and at the
921 very end of the message. The sysadmin can specify conditions for accepting or
922 rejecting individual recipients or the entire message, respectively, at these
923 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
926 An ACL is also available for locally generated, non-SMTP messages. In this
927 case, the only available actions are to accept or deny the entire message.
929 When Exim is compiled with the content-scanning extension, facilities are
930 provided in the ACL mechanism for passing the message to external virus and/or
931 spam scanning software. The result of such a scan is passed back to the ACL,
932 which can then use it to decide what to do with the message.
934 When a message has been received, either from a remote host or from the local
935 host, but before the final acknowledgment has been sent, a locally supplied C
936 function called &[local_scan()]& can be run to inspect the message and decide
937 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
938 is accepted, the list of recipients can be modified by the function.
940 Using the &[local_scan()]& mechanism is another way of calling external scanner
941 software. The &%SA-Exim%& add-on package works this way. It does not require
942 Exim to be compiled with the content-scanning extension.
944 After a message has been accepted, a further checking mechanism is available in
945 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
946 runs at the start of every delivery process.
951 .section "User filters" "SECID12"
952 .cindex "filter" "introduction"
953 .cindex "Sieve filter"
954 In a conventional Exim configuration, users are able to run private filters by
955 setting up appropriate &_.forward_& files in their home directories. See
956 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
957 configuration needed to support this, and the separate document entitled
958 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
959 of filtering are available:
962 Sieve filters are written in the standard filtering language that is defined
965 Exim filters are written in a syntax that is unique to Exim, but which is more
966 powerful than Sieve, which it pre-dates.
969 User filters are run as part of the routing process, described below.
973 .section "Message identification" "SECTmessiden"
974 .cindex "message ids" "details of format"
975 .cindex "format" "of message id"
976 .cindex "id of message"
981 Every message handled by Exim is given a &'message id'& which is sixteen
982 characters long. It is divided into three parts, separated by hyphens, for
983 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
984 normally encoding numbers in base 62. However, in the Darwin operating
985 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
986 (avoiding the use of lower case letters) is used instead, because the message
987 id is used to construct file names, and the names of files in those systems are
988 not always case-sensitive.
990 .cindex "pid (process id)" "re-use of"
991 The detail of the contents of the message id have changed as Exim has evolved.
992 Earlier versions relied on the operating system not re-using a process id (pid)
993 within one second. On modern operating systems, this assumption can no longer
994 be made, so the algorithm had to be changed. To retain backward compatibility,
995 the format of the message id was retained, which is why the following rules are
999 The first six characters of the message id are the time at which the message
1000 started to be received, to a granularity of one second. That is, this field
1001 contains the number of seconds since the start of the epoch (the normal Unix
1002 way of representing the date and time of day).
1004 After the first hyphen, the next six characters are the id of the process that
1005 received the message.
1007 There are two different possibilities for the final two characters:
1009 .oindex "&%localhost_number%&"
1010 If &%localhost_number%& is not set, this value is the fractional part of the
1011 time of reception, normally in units of 1/2000 of a second, but for systems
1012 that must use base 36 instead of base 62 (because of case-insensitive file
1013 systems), the units are 1/1000 of a second.
1015 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1016 the fractional part of the time, which in this case is in units of 1/200
1017 (1/100) of a second.
1021 After a message has been received, Exim waits for the clock to tick at the
1022 appropriate resolution before proceeding, so that if another message is
1023 received by the same process, or by another process with the same (re-used)
1024 pid, it is guaranteed that the time will be different. In most cases, the clock
1025 will already have ticked while the message was being received.
1028 .section "Receiving mail" "SECID13"
1029 .cindex "receiving mail"
1030 .cindex "message" "reception"
1031 The only way Exim can receive mail from another host is using SMTP over
1032 TCP/IP, in which case the sender and recipient addresses are transferred using
1033 SMTP commands. However, from a locally running process (such as a user's MUA),
1034 there are several possibilities:
1037 If the process runs Exim with the &%-bm%& option, the message is read
1038 non-interactively (usually via a pipe), with the recipients taken from the
1039 command line, or from the body of the message if &%-t%& is also used.
1041 If the process runs Exim with the &%-bS%& option, the message is also read
1042 non-interactively, but in this case the recipients are listed at the start of
1043 the message in a series of SMTP RCPT commands, terminated by a DATA
1044 command. This is so-called &"batch SMTP"& format,
1045 but it isn't really SMTP. The SMTP commands are just another way of passing
1046 envelope addresses in a non-interactive submission.
1048 If the process runs Exim with the &%-bs%& option, the message is read
1049 interactively, using the SMTP protocol. A two-way pipe is normally used for
1050 passing data between the local process and the Exim process.
1051 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1052 example, the ACLs for SMTP commands are used for this form of submission.
1054 A local process may also make a TCP/IP call to the host's loopback address
1055 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1056 does not treat the loopback address specially. It treats all such connections
1057 in the same way as connections from other hosts.
1061 .cindex "message sender, constructed by Exim"
1062 .cindex "sender" "constructed by Exim"
1063 In the three cases that do not involve TCP/IP, the sender address is
1064 constructed from the login name of the user that called Exim and a default
1065 qualification domain (which can be set by the &%qualify_domain%& configuration
1066 option). For local or batch SMTP, a sender address that is passed using the
1067 SMTP MAIL command is ignored. However, the system administrator may allow
1068 certain users (&"trusted users"&) to specify a different sender address
1069 unconditionally, or all users to specify certain forms of different sender
1070 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1071 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1072 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1073 users to change sender addresses.
1075 Messages received by either of the non-interactive mechanisms are subject to
1076 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1077 (either over TCP/IP, or interacting with a local process) can be checked by a
1078 number of ACLs that operate at different times during the SMTP session. Either
1079 individual recipients, or the entire message, can be rejected if local policy
1080 requirements are not met. The &[local_scan()]& function (see chapter
1081 &<<CHAPlocalscan>>&) is run for all incoming messages.
1083 Exim can be configured not to start a delivery process when a message is
1084 received; this can be unconditional, or depend on the number of incoming SMTP
1085 connections or the system load. In these situations, new messages wait on the
1086 queue until a queue runner process picks them up. However, in standard
1087 configurations under normal conditions, delivery is started as soon as a
1088 message is received.
1094 .section "Handling an incoming message" "SECID14"
1095 .cindex "spool directory" "files that hold a message"
1096 .cindex "file" "how a message is held"
1097 When Exim accepts a message, it writes two files in its spool directory. The
1098 first contains the envelope information, the current status of the message, and
1099 the header lines, and the second contains the body of the message. The names of
1100 the two spool files consist of the message id, followed by &`-H`& for the
1101 file containing the envelope and header, and &`-D`& for the data file.
1103 .cindex "spool directory" "&_input_& sub-directory"
1104 By default all these message files are held in a single directory called
1105 &_input_& inside the general Exim spool directory. Some operating systems do
1106 not perform very well if the number of files in a directory gets large; to
1107 improve performance in such cases, the &%split_spool_directory%& option can be
1108 used. This causes Exim to split up the input files into 62 sub-directories
1109 whose names are single letters or digits. When this is done, the queue is
1110 processed one sub-directory at a time instead of all at once, which can improve
1111 overall performance even when there are not enough files in each directory to
1112 affect file system performance.
1114 The envelope information consists of the address of the message's sender and
1115 the addresses of the recipients. This information is entirely separate from
1116 any addresses contained in the header lines. The status of the message includes
1117 a list of recipients who have already received the message. The format of the
1118 first spool file is described in chapter &<<CHAPspool>>&.
1120 .cindex "rewriting" "addresses"
1121 Address rewriting that is specified in the rewrite section of the configuration
1122 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1123 both in the header lines and the envelope, at the time the message is accepted.
1124 If during the course of delivery additional addresses are generated (for
1125 example, via aliasing), these new addresses are rewritten as soon as they are
1126 generated. At the time a message is actually delivered (transported) further
1127 rewriting can take place; because this is a transport option, it can be
1128 different for different forms of delivery. It is also possible to specify the
1129 addition or removal of certain header lines at the time the message is
1130 delivered (see chapters &<<CHAProutergeneric>>& and
1131 &<<CHAPtransportgeneric>>&).
1135 .section "Life of a message" "SECID15"
1136 .cindex "message" "life of"
1137 .cindex "message" "frozen"
1138 A message remains in the spool directory until it is completely delivered to
1139 its recipients or to an error address, or until it is deleted by an
1140 administrator or by the user who originally created it. In cases when delivery
1141 cannot proceed &-- for example, when a message can neither be delivered to its
1142 recipients nor returned to its sender, the message is marked &"frozen"& on the
1143 spool, and no more deliveries are attempted.
1145 .cindex "frozen messages" "thawing"
1146 .cindex "message" "thawing frozen"
1147 An administrator can &"thaw"& such messages when the problem has been
1148 corrected, and can also freeze individual messages by hand if necessary. In
1149 addition, an administrator can force a delivery error, causing a bounce message
1152 .oindex "&%timeout_frozen_after%&"
1153 .oindex "&%ignore_bounce_errors_after%&"
1154 There are options called &%ignore_bounce_errors_after%& and
1155 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1156 The first applies only to frozen bounces, the second to any frozen messages.
1158 .cindex "message" "log file for"
1159 .cindex "log" "file for each message"
1160 While Exim is working on a message, it writes information about each delivery
1161 attempt to its main log file. This includes successful, unsuccessful, and
1162 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1163 lines are also written to a separate &'message log'& file for each message.
1164 These logs are solely for the benefit of the administrator, and are normally
1165 deleted along with the spool files when processing of a message is complete.
1166 The use of individual message logs can be disabled by setting
1167 &%no_message_logs%&; this might give an improvement in performance on very busy
1170 .cindex "journal file"
1171 .cindex "file" "journal"
1172 All the information Exim itself needs to set up a delivery is kept in the first
1173 spool file, along with the header lines. When a successful delivery occurs, the
1174 address is immediately written at the end of a journal file, whose name is the
1175 message id followed by &`-J`&. At the end of a delivery run, if there are some
1176 addresses left to be tried again later, the first spool file (the &`-H`& file)
1177 is updated to indicate which these are, and the journal file is then deleted.
1178 Updating the spool file is done by writing a new file and renaming it, to
1179 minimize the possibility of data loss.
1181 Should the system or the program crash after a successful delivery but before
1182 the spool file has been updated, the journal is left lying around. The next
1183 time Exim attempts to deliver the message, it reads the journal file and
1184 updates the spool file before proceeding. This minimizes the chances of double
1185 deliveries caused by crashes.
1189 .section "Processing an address for delivery" "SECTprocaddress"
1190 .cindex "drivers" "definition of"
1191 .cindex "router" "definition of"
1192 .cindex "transport" "definition of"
1193 The main delivery processing elements of Exim are called &'routers'& and
1194 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1195 number of them is provided in the source distribution, and compile-time options
1196 specify which ones are included in the binary. Run time options specify which
1197 ones are actually used for delivering messages.
1199 .cindex "drivers" "instance definition"
1200 Each driver that is specified in the run time configuration is an &'instance'&
1201 of that particular driver type. Multiple instances are allowed; for example,
1202 you can set up several different &(smtp)& transports, each with different
1203 option values that might specify different ports or different timeouts. Each
1204 instance has its own identifying name. In what follows we will normally use the
1205 instance name when discussing one particular instance (that is, one specific
1206 configuration of the driver), and the generic driver name when discussing
1207 the driver's features in general.
1209 A &'router'& is a driver that operates on an address, either determining how
1210 its delivery should happen, by assigning it to a specific transport, or
1211 converting the address into one or more new addresses (for example, via an
1212 alias file). A router may also explicitly choose to fail an address, causing it
1215 A &'transport'& is a driver that transmits a copy of the message from Exim's
1216 spool to some destination. There are two kinds of transport: for a &'local'&
1217 transport, the destination is a file or a pipe on the local host, whereas for a
1218 &'remote'& transport the destination is some other host. A message is passed
1219 to a specific transport as a result of successful routing. If a message has
1220 several recipients, it may be passed to a number of different transports.
1222 .cindex "preconditions" "definition of"
1223 An address is processed by passing it to each configured router instance in
1224 turn, subject to certain preconditions, until a router accepts the address or
1225 specifies that it should be bounced. We will describe this process in more
1226 detail shortly. First, as a simple example, we consider how each recipient
1227 address in a message is processed in a small configuration of three routers.
1229 To make this a more concrete example, it is described in terms of some actual
1230 routers, but remember, this is only an example. You can configure Exim's
1231 routers in many different ways, and there may be any number of routers in a
1234 The first router that is specified in a configuration is often one that handles
1235 addresses in domains that are not recognized specially by the local host. These
1236 are typically addresses for arbitrary domains on the Internet. A precondition
1237 is set up which looks for the special domains known to the host (for example,
1238 its own domain name), and the router is run for addresses that do &'not'&
1239 match. Typically, this is a router that looks up domains in the DNS in order to
1240 find the hosts to which this address routes. If it succeeds, the address is
1241 assigned to a suitable SMTP transport; if it does not succeed, the router is
1242 configured to fail the address.
1244 The second router is reached only when the domain is recognized as one that
1245 &"belongs"& to the local host. This router does redirection &-- also known as
1246 aliasing and forwarding. When it generates one or more new addresses from the
1247 original, each of them is routed independently from the start. Otherwise, the
1248 router may cause an address to fail, or it may simply decline to handle the
1249 address, in which case the address is passed to the next router.
1251 The final router in many configurations is one that checks to see if the
1252 address belongs to a local mailbox. The precondition may involve a check to
1253 see if the local part is the name of a login account, or it may look up the
1254 local part in a file or a database. If its preconditions are not met, or if
1255 the router declines, we have reached the end of the routers. When this happens,
1256 the address is bounced.
1260 .section "Processing an address for verification" "SECID16"
1261 .cindex "router" "for verification"
1262 .cindex "verifying address" "overview"
1263 As well as being used to decide how to deliver to an address, Exim's routers
1264 are also used for &'address verification'&. Verification can be requested as
1265 one of the checks to be performed in an ACL for incoming messages, on both
1266 sender and recipient addresses, and it can be tested using the &%-bv%& and
1267 &%-bvs%& command line options.
1269 When an address is being verified, the routers are run in &"verify mode"&. This
1270 does not affect the way the routers work, but it is a state that can be
1271 detected. By this means, a router can be skipped or made to behave differently
1272 when verifying. A common example is a configuration in which the first router
1273 sends all messages to a message-scanning program, unless they have been
1274 previously scanned. Thus, the first router accepts all addresses without any
1275 checking, making it useless for verifying. Normally, the &%no_verify%& option
1276 would be set for such a router, causing it to be skipped in verify mode.
1281 .section "Running an individual router" "SECTrunindrou"
1282 .cindex "router" "running details"
1283 .cindex "preconditions" "checking"
1284 .cindex "router" "result of running"
1285 As explained in the example above, a number of preconditions are checked before
1286 running a router. If any are not met, the router is skipped, and the address is
1287 passed to the next router. When all the preconditions on a router &'are'& met,
1288 the router is run. What happens next depends on the outcome, which is one of
1292 &'accept'&: The router accepts the address, and either assigns it to a
1293 transport, or generates one or more &"child"& addresses. Processing the
1294 original address ceases,
1295 .oindex "&%unseen%&"
1296 unless the &%unseen%& option is set on the router. This option
1297 can be used to set up multiple deliveries with different routing (for example,
1298 for keeping archive copies of messages). When &%unseen%& is set, the address is
1299 passed to the next router. Normally, however, an &'accept'& return marks the
1302 Any child addresses generated by the router are processed independently,
1303 starting with the first router by default. It is possible to change this by
1304 setting the &%redirect_router%& option to specify which router to start at for
1305 child addresses. Unlike &%pass_router%& (see below) the router specified by
1306 &%redirect_router%& may be anywhere in the router configuration.
1308 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1309 requests that the address be passed to another router. By default the address
1310 is passed to the next router, but this can be changed by setting the
1311 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1312 must be below the current router (to avoid loops).
1314 &'decline'&: The router declines to accept the address because it does not
1315 recognize it at all. By default, the address is passed to the next router, but
1316 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1317 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1318 &'decline'& into &'fail'&.
1320 &'fail'&: The router determines that the address should fail, and queues it for
1321 the generation of a bounce message. There is no further processing of the
1322 original address unless &%unseen%& is set on the router.
1324 &'defer'&: The router cannot handle the address at the present time. (A
1325 database may be offline, or a DNS lookup may have timed out.) No further
1326 processing of the address happens in this delivery attempt. It is tried again
1327 next time the message is considered for delivery.
1329 &'error'&: There is some error in the router (for example, a syntax error in
1330 its configuration). The action is as for defer.
1333 If an address reaches the end of the routers without having been accepted by
1334 any of them, it is bounced as unrouteable. The default error message in this
1335 situation is &"unrouteable address"&, but you can set your own message by
1336 making use of the &%cannot_route_message%& option. This can be set for any
1337 router; the value from the last router that &"saw"& the address is used.
1339 Sometimes while routing you want to fail a delivery when some conditions are
1340 met but others are not, instead of passing the address on for further routing.
1341 You can do this by having a second router that explicitly fails the delivery
1342 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1343 facility for this purpose.
1346 .section "Duplicate addresses" "SECID17"
1347 .cindex "case of local parts"
1348 .cindex "address duplicate, discarding"
1349 .cindex "duplicate addresses"
1350 Once routing is complete, Exim scans the addresses that are assigned to local
1351 and remote transports, and discards any duplicates that it finds. During this
1352 check, local parts are treated as case-sensitive. This happens only when
1353 actually delivering a message; when testing routers with &%-bt%&, all the
1354 routed addresses are shown.
1358 .section "Router preconditions" "SECTrouprecon"
1359 .cindex "router" "preconditions, order of processing"
1360 .cindex "preconditions" "order of processing"
1361 The preconditions that are tested for each router are listed below, in the
1362 order in which they are tested. The individual configuration options are
1363 described in more detail in chapter &<<CHAProutergeneric>>&.
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 If the &%local_parts%& option is set, the local part of the address must be in
1403 the set of local parts that it defines. If &%local_part_prefix%& or
1404 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1405 part before this check. If you want to do precondition tests on local parts
1406 that include affixes, you can do so by using a &%condition%& option (see below)
1407 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1408 &$local_part_suffix$& as necessary.
1410 .vindex "&$local_user_uid$&"
1411 .vindex "&$local_user_gid$&"
1413 If the &%check_local_user%& option is set, the local part must be the name of
1414 an account on the local host. If this check succeeds, the uid and gid of the
1415 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1416 user's home directory is placed in &$home$&; these values can be used in the
1417 remaining preconditions.
1419 If the &%router_home_directory%& option is set, it is expanded at this point,
1420 because it overrides the value of &$home$&. If this expansion were left till
1421 later, the value of &$home$& as set by &%check_local_user%& would be used in
1422 subsequent tests. Having two different values of &$home$& in the same router
1423 could lead to confusion.
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1428 If the &%require_files%& option is set, the existence or non-existence of
1429 specified files is tested.
1431 .cindex "customizing" "precondition"
1432 If the &%condition%& option is set, it is evaluated and tested. This option
1433 uses an expanded string to allow you to set up your own custom preconditions.
1434 Expanded strings are described in chapter &<<CHAPexpand>>&.
1438 Note that &%require_files%& comes near the end of the list, so you cannot use
1439 it to check for the existence of a file in which to lookup up a domain, local
1440 part, or sender. However, as these options are all expanded, you can use the
1441 &%exists%& expansion condition to make such tests within each condition. The
1442 &%require_files%& option is intended for checking files that the router may be
1443 going to use internally, or which are needed by a specific transport (for
1444 example, &_.procmailrc_&).
1448 .section "Delivery in detail" "SECID18"
1449 .cindex "delivery" "in detail"
1450 When a message is to be delivered, the sequence of events is as follows:
1453 If a system-wide filter file is specified, the message is passed to it. The
1454 filter may add recipients to the message, replace the recipients, discard the
1455 message, cause a new message to be generated, or cause the message delivery to
1456 fail. The format of the system filter file is the same as for Exim user filter
1457 files, described in the separate document entitled &'Exim's interfaces to mail
1459 .cindex "Sieve filter" "not available for system filter"
1460 (&*Note*&: Sieve cannot be used for system filter files.)
1462 Some additional features are available in system filters &-- see chapter
1463 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1464 filter only once per delivery attempt, however many recipients it has. However,
1465 if there are several delivery attempts because one or more addresses could not
1466 be immediately delivered, the system filter is run each time. The filter
1467 condition &%first_delivery%& can be used to detect the first run of the system
1470 Each recipient address is offered to each configured router in turn, subject to
1471 its preconditions, until one is able to handle it. If no router can handle the
1472 address, that is, if they all decline, the address is failed. Because routers
1473 can be targeted at particular domains, several locally handled domains can be
1474 processed entirely independently of each other.
1476 .cindex "routing" "loops in"
1477 .cindex "loop" "while routing"
1478 A router that accepts an address may assign it to a local or a remote
1479 transport. However, the transport is not run at this time. Instead, the address
1480 is placed on a list for the particular transport, which will be run later.
1481 Alternatively, the router may generate one or more new addresses (typically
1482 from alias, forward, or filter files). New addresses are fed back into this
1483 process from the top, but in order to avoid loops, a router ignores any address
1484 which has an identically-named ancestor that was processed by itself.
1486 When all the routing has been done, addresses that have been successfully
1487 handled are passed to their assigned transports. When local transports are
1488 doing real local deliveries, they handle only one address at a time, but if a
1489 local transport is being used as a pseudo-remote transport (for example, to
1490 collect batched SMTP messages for transmission by some other means) multiple
1491 addresses can be handled. Remote transports can always handle more than one
1492 address at a time, but can be configured not to do so, or to restrict multiple
1493 addresses to the same domain.
1495 Each local delivery to a file or a pipe runs in a separate process under a
1496 non-privileged uid, and these deliveries are run one at a time. Remote
1497 deliveries also run in separate processes, normally under a uid that is private
1498 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1499 run in parallel. The maximum number of simultaneous remote deliveries for any
1500 one message is set by the &%remote_max_parallel%& option.
1501 The order in which deliveries are done is not defined, except that all local
1502 deliveries happen before any remote deliveries.
1504 .cindex "queue runner"
1505 When it encounters a local delivery during a queue run, Exim checks its retry
1506 database to see if there has been a previous temporary delivery failure for the
1507 address before running the local transport. If there was a previous failure,
1508 Exim does not attempt a new delivery until the retry time for the address is
1509 reached. However, this happens only for delivery attempts that are part of a
1510 queue run. Local deliveries are always attempted when delivery immediately
1511 follows message reception, even if retry times are set for them. This makes for
1512 better behaviour if one particular message is causing problems (for example,
1513 causing quota overflow, or provoking an error in a filter file).
1515 .cindex "delivery" "retry in remote transports"
1516 Remote transports do their own retry handling, since an address may be
1517 deliverable to one of a number of hosts, each of which may have a different
1518 retry time. If there have been previous temporary failures and no host has
1519 reached its retry time, no delivery is attempted, whether in a queue run or
1520 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1522 If there were any permanent errors, a bounce message is returned to an
1523 appropriate address (the sender in the common case), with details of the error
1524 for each failing address. Exim can be configured to send copies of bounce
1525 messages to other addresses.
1527 .cindex "delivery" "deferral"
1528 If one or more addresses suffered a temporary failure, the message is left on
1529 the queue, to be tried again later. Delivery of these addresses is said to be
1532 When all the recipient addresses have either been delivered or bounced,
1533 handling of the message is complete. The spool files and message log are
1534 deleted, though the message log can optionally be preserved if required.
1540 .section "Retry mechanism" "SECID19"
1541 .cindex "delivery" "retry mechanism"
1542 .cindex "retry" "description of mechanism"
1543 .cindex "queue runner"
1544 Exim's mechanism for retrying messages that fail to get delivered at the first
1545 attempt is the queue runner process. You must either run an Exim daemon that
1546 uses the &%-q%& option with a time interval to start queue runners at regular
1547 intervals, or use some other means (such as &'cron'&) to start them. If you do
1548 not arrange for queue runners to be run, messages that fail temporarily at the
1549 first attempt will remain on your queue for ever. A queue runner process works
1550 its way through the queue, one message at a time, trying each delivery that has
1551 passed its retry time.
1552 You can run several queue runners at once.
1554 Exim uses a set of configured rules to determine when next to retry the failing
1555 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1556 should give up trying to deliver to the address, at which point it generates a
1557 bounce message. If no retry rules are set for a particular host, address, and
1558 error combination, no retries are attempted, and temporary errors are treated
1563 .section "Temporary delivery failure" "SECID20"
1564 .cindex "delivery" "temporary failure"
1565 There are many reasons why a message may not be immediately deliverable to a
1566 particular address. Failure to connect to a remote machine (because it, or the
1567 connection to it, is down) is one of the most common. Temporary failures may be
1568 detected during routing as well as during the transport stage of delivery.
1569 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1570 is on a file system where the user is over quota. Exim can be configured to
1571 impose its own quotas on local mailboxes; where system quotas are set they will
1574 If a host is unreachable for a period of time, a number of messages may be
1575 waiting for it by the time it recovers, and sending them in a single SMTP
1576 connection is clearly beneficial. Whenever a delivery to a remote host is
1578 .cindex "hints database"
1579 Exim makes a note in its hints database, and whenever a successful
1580 SMTP delivery has happened, it looks to see if any other messages are waiting
1581 for the same host. If any are found, they are sent over the same SMTP
1582 connection, subject to a configuration limit as to the maximum number in any
1587 .section "Permanent delivery failure" "SECID21"
1588 .cindex "delivery" "permanent failure"
1589 .cindex "bounce message" "when generated"
1590 When a message cannot be delivered to some or all of its intended recipients, a
1591 bounce message is generated. Temporary delivery failures turn into permanent
1592 errors when their timeout expires. All the addresses that fail in a given
1593 delivery attempt are listed in a single message. If the original message has
1594 many recipients, it is possible for some addresses to fail in one delivery
1595 attempt and others to fail subsequently, giving rise to more than one bounce
1596 message. The wording of bounce messages can be customized by the administrator.
1597 See chapter &<<CHAPemsgcust>>& for details.
1599 .cindex "&'X-Failed-Recipients:'& header line"
1600 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1601 failed addresses, for the benefit of programs that try to analyse such messages
1604 .cindex "bounce message" "recipient of"
1605 A bounce message is normally sent to the sender of the original message, as
1606 obtained from the message's envelope. For incoming SMTP messages, this is the
1607 address given in the MAIL command. However, when an address is expanded via a
1608 forward or alias file, an alternative address can be specified for delivery
1609 failures of the generated addresses. For a mailing list expansion (see section
1610 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1615 .section "Failures to deliver bounce messages" "SECID22"
1616 .cindex "bounce message" "failure to deliver"
1617 If a bounce message (either locally generated or received from a remote host)
1618 itself suffers a permanent delivery failure, the message is left on the queue,
1619 but it is frozen, awaiting the attention of an administrator. There are options
1620 that can be used to make Exim discard such failed messages, or to keep them
1621 for only a short time (see &%timeout_frozen_after%& and
1622 &%ignore_bounce_errors_after%&).
1628 . ////////////////////////////////////////////////////////////////////////////
1629 . ////////////////////////////////////////////////////////////////////////////
1631 .chapter "Building and installing Exim" "CHID3"
1632 .scindex IIDbuex "building Exim"
1634 .section "Unpacking" "SECID23"
1635 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1636 creates a directory with the name of the current release (for example,
1637 &_exim-&version()_&) into which the following files are placed:
1640 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1641 .irow &_CHANGES_& "contains a reference to where changes are &&&
1643 .irow &_LICENCE_& "the GNU General Public Licence"
1644 .irow &_Makefile_& "top-level make file"
1645 .irow &_NOTICE_& "conditions for the use of Exim"
1646 .irow &_README_& "list of files, directories and simple build &&&
1650 Other files whose names begin with &_README_& may also be present. The
1651 following subdirectories are created:
1654 .irow &_Local_& "an empty directory for local configuration files"
1655 .irow &_OS_& "OS-specific files"
1656 .irow &_doc_& "documentation files"
1657 .irow &_exim_monitor_& "source files for the Exim monitor"
1658 .irow &_scripts_& "scripts used in the build process"
1659 .irow &_src_& "remaining source files"
1660 .irow &_util_& "independent utilities"
1663 The main utility programs are contained in the &_src_& directory, and are built
1664 with the Exim binary. The &_util_& directory contains a few optional scripts
1665 that may be useful to some sites.
1668 .section "Multiple machine architectures and operating systems" "SECID24"
1669 .cindex "building Exim" "multiple OS/architectures"
1670 The building process for Exim is arranged to make it easy to build binaries for
1671 a number of different architectures and operating systems from the same set of
1672 source files. Compilation does not take place in the &_src_& directory.
1673 Instead, a &'build directory'& is created for each architecture and operating
1675 .cindex "symbolic link" "to build directory"
1676 Symbolic links to the sources are installed in this directory, which is where
1677 the actual building takes place. In most cases, Exim can discover the machine
1678 architecture and operating system for itself, but the defaults can be
1679 overridden if necessary.
1682 .section "PCRE library" "SECTpcre"
1683 .cindex "PCRE library"
1684 Exim no longer has an embedded PCRE library as the vast majority of
1685 modern systems include PCRE as a system library, although you may need
1686 to install the PCRE or PCRE development package for your operating
1687 system. If your system has a normal PCRE installation the Exim build
1688 process will need no further configuration. If the library or the
1689 headers are in an unusual location you will need to either set the PCRE_LIBS
1690 and INCLUDE directives appropriately,
1691 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1692 If your operating system has no
1693 PCRE support then you will need to obtain and build the current PCRE
1694 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1695 More information on PCRE is available at &url(http://www.pcre.org/).
1697 .section "DBM libraries" "SECTdb"
1698 .cindex "DBM libraries" "discussion of"
1699 .cindex "hints database" "DBM files used for"
1700 Even if you do not use any DBM files in your configuration, Exim still needs a
1701 DBM library in order to operate, because it uses indexed files for its hints
1702 databases. Unfortunately, there are a number of DBM libraries in existence, and
1703 different operating systems often have different ones installed.
1705 .cindex "Solaris" "DBM library for"
1706 .cindex "IRIX, DBM library for"
1707 .cindex "BSD, DBM library for"
1708 .cindex "Linux, DBM library for"
1709 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1710 Linux distribution, the DBM configuration should happen automatically, and you
1711 may be able to ignore this section. Otherwise, you may have to learn more than
1712 you would like about DBM libraries from what follows.
1714 .cindex "&'ndbm'& DBM library"
1715 Licensed versions of Unix normally contain a library of DBM functions operating
1716 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1717 versions of Unix seem to vary in what they contain as standard. In particular,
1718 some early versions of Linux have no default DBM library, and different
1719 distributors have chosen to bundle different libraries with their packaged
1720 versions. However, the more recent releases seem to have standardized on the
1721 Berkeley DB library.
1723 Different DBM libraries have different conventions for naming the files they
1724 use. When a program opens a file called &_dbmfile_&, there are several
1728 A traditional &'ndbm'& implementation, such as that supplied as part of
1729 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1731 .cindex "&'gdbm'& DBM library"
1732 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1733 compatibility interface it makes two different hard links to it with names
1734 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1735 file name is used unmodified.
1737 .cindex "Berkeley DB library"
1738 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1739 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1740 programmer exactly the same as the traditional &'ndbm'& implementation.
1742 If the Berkeley package is used in its native mode, it operates on a single
1743 file called &_dbmfile_&; the programmer's interface is somewhat different to
1744 the traditional &'ndbm'& interface.
1746 To complicate things further, there are several very different versions of the
1747 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1748 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1749 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1750 versions of Berkeley DB can be obtained from
1751 &url(http://www.sleepycat.com/).
1753 .cindex "&'tdb'& DBM library"
1754 Yet another DBM library, called &'tdb'&, is available from
1755 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1756 operates on a single file.
1760 .cindex "DBM libraries" "configuration for building"
1761 Exim and its utilities can be compiled to use any of these interfaces. In order
1762 to use any version of the Berkeley DB package in native mode, you must set
1763 USE_DB in an appropriate configuration file (typically
1764 &_Local/Makefile_&). For example:
1768 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1769 error is diagnosed if you set more than one of these.
1771 At the lowest level, the build-time configuration sets none of these options,
1772 thereby assuming an interface of type (1). However, some operating system
1773 configuration files (for example, those for the BSD operating systems and
1774 Linux) assume type (4) by setting USE_DB as their default, and the
1775 configuration files for Cygwin set USE_GDBM. Anything you set in
1776 &_Local/Makefile_&, however, overrides these system defaults.
1778 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1779 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1780 in one of these lines:
1785 Settings like that will work if the DBM library is installed in the standard
1786 place. Sometimes it is not, and the library's header file may also not be in
1787 the default path. You may need to set INCLUDE to specify where the header
1788 file is, and to specify the path to the library more fully in DBMLIB, as in
1791 INCLUDE=-I/usr/local/include/db-4.1
1792 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1794 There is further detailed discussion about the various DBM libraries in the
1795 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1799 .section "Pre-building configuration" "SECID25"
1800 .cindex "building Exim" "pre-building configuration"
1801 .cindex "configuration for building Exim"
1802 .cindex "&_Local/Makefile_&"
1803 .cindex "&_src/EDITME_&"
1804 Before building Exim, a local configuration file that specifies options
1805 independent of any operating system has to be created with the name
1806 &_Local/Makefile_&. A template for this file is supplied as the file
1807 &_src/EDITME_&, and it contains full descriptions of all the option settings
1808 therein. These descriptions are therefore not repeated here. If you are
1809 building Exim for the first time, the simplest thing to do is to copy
1810 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1812 There are three settings that you must supply, because Exim will not build
1813 without them. They are the location of the run time configuration file
1814 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1815 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1816 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1817 a colon-separated list of file names; Exim uses the first of them that exists.
1819 There are a few other parameters that can be specified either at build time or
1820 at run time, to enable the same binary to be used on a number of different
1821 machines. However, if the locations of Exim's spool directory and log file
1822 directory (if not within the spool directory) are fixed, it is recommended that
1823 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1824 detected early in Exim's execution (such as a malformed configuration file) can
1827 .cindex "content scanning" "specifying at build time"
1828 Exim's interfaces for calling virus and spam scanning software directly from
1829 access control lists are not compiled by default. If you want to include these
1830 facilities, you need to set
1832 WITH_CONTENT_SCAN=yes
1834 in your &_Local/Makefile_&. For details of the facilities themselves, see
1835 chapter &<<CHAPexiscan>>&.
1838 .cindex "&_Local/eximon.conf_&"
1839 .cindex "&_exim_monitor/EDITME_&"
1840 If you are going to build the Exim monitor, a similar configuration process is
1841 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1842 your installation and saved under the name &_Local/eximon.conf_&. If you are
1843 happy with the default settings described in &_exim_monitor/EDITME_&,
1844 &_Local/eximon.conf_& can be empty, but it must exist.
1846 This is all the configuration that is needed in straightforward cases for known
1847 operating systems. However, the building process is set up so that it is easy
1848 to override options that are set by default or by operating-system-specific
1849 configuration files, for example to change the name of the C compiler, which
1850 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1855 .section "Support for iconv()" "SECID26"
1856 .cindex "&[iconv()]& support"
1858 The contents of header lines in messages may be encoded according to the rules
1859 described RFC 2047. This makes it possible to transmit characters that are not
1860 in the ASCII character set, and to label them as being in a particular
1861 character set. When Exim is inspecting header lines by means of the &%$h_%&
1862 mechanism, it decodes them, and translates them into a specified character set
1863 (default ISO-8859-1). The translation is possible only if the operating system
1864 supports the &[iconv()]& function.
1866 However, some of the operating systems that supply &[iconv()]& do not support
1867 very many conversions. The GNU &%libiconv%& library (available from
1868 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1869 systems to remedy this deficiency, as well as on systems that do not supply
1870 &[iconv()]& at all. After installing &%libiconv%&, you should add
1874 to your &_Local/Makefile_& and rebuild Exim.
1878 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1879 .cindex "TLS" "including support for TLS"
1880 .cindex "encryption" "including support for"
1881 .cindex "SUPPORT_TLS"
1882 .cindex "OpenSSL" "building Exim with"
1883 .cindex "GnuTLS" "building Exim with"
1884 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1885 command as per RFC 2487. It can also support legacy clients that expect to
1886 start a TLS session immediately on connection to a non-standard port (see the
1887 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1890 If you want to build Exim with TLS support, you must first install either the
1891 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1894 If OpenSSL is installed, you should set
1897 TLS_LIBS=-lssl -lcrypto
1899 in &_Local/Makefile_&. You may also need to specify the locations of the
1900 OpenSSL library and include files. For example:
1903 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1904 TLS_INCLUDE=-I/usr/local/openssl/include/
1906 .cindex "pkg-config" "OpenSSL"
1907 If you have &'pkg-config'& available, then instead you can just use:
1910 USE_OPENSSL_PC=openssl
1912 .cindex "USE_GNUTLS"
1913 If GnuTLS is installed, you should set
1917 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1919 in &_Local/Makefile_&, and again you may need to specify the locations of the
1920 library and include files. For example:
1924 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1925 TLS_INCLUDE=-I/usr/gnu/include
1927 .cindex "pkg-config" "GnuTLS"
1928 If you have &'pkg-config'& available, then instead you can just use:
1932 USE_GNUTLS_PC=gnutls
1935 You do not need to set TLS_INCLUDE if the relevant directory is already
1936 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1937 given in chapter &<<CHAPTLS>>&.
1942 .section "Use of tcpwrappers" "SECID27"
1944 .cindex "tcpwrappers, building Exim to support"
1945 .cindex "USE_TCP_WRAPPERS"
1946 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1947 .cindex "tcp_wrappers_daemon_name"
1948 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1949 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1950 alternative to Exim's own checking facilities for installations that are
1951 already making use of &'tcpwrappers'& for other purposes. To do this, you
1952 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1953 &_tcpd.h_& to be available at compile time, and also ensure that the library
1954 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1955 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1958 USE_TCP_WRAPPERS=yes
1959 CFLAGS=-O -I/usr/local/include
1960 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1962 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1963 files is &"exim"&. For example, the line
1965 exim : LOCAL 192.168.1. .friendly.domain.example
1967 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1968 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1969 All other connections are denied. The daemon name used by &'tcpwrappers'&
1970 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1971 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1972 configure file. Consult the &'tcpwrappers'& documentation for
1976 .section "Including support for IPv6" "SECID28"
1977 .cindex "IPv6" "including support for"
1978 Exim contains code for use on systems that have IPv6 support. Setting
1979 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1980 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1981 where the IPv6 support is not fully integrated into the normal include and
1984 Two different types of DNS record for handling IPv6 addresses have been
1985 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1986 currently seen as the mainstream. Another record type called A6 was proposed
1987 as better than AAAA because it had more flexibility. However, it was felt to be
1988 over-complex, and its status was reduced to &"experimental"&. It is not known
1989 if anyone is actually using A6 records. Exim has support for A6 records, but
1990 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1991 support has not been tested for some time.
1995 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1996 .cindex "lookup modules"
1997 .cindex "dynamic modules"
1998 .cindex ".so building"
1999 On some platforms, Exim supports not compiling all lookup types directly into
2000 the main binary, instead putting some into external modules which can be loaded
2002 This permits packagers to build Exim with support for lookups with extensive
2003 library dependencies without requiring all users to install all of those
2005 Most, but not all, lookup types can be built this way.
2007 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2008 installed; Exim will only load modules from that directory, as a security
2009 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2010 for your OS; see &_OS/Makefile-Linux_& for an example.
2011 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2012 see &_src/EDITME_& for details.
2014 Then, for each module to be loaded dynamically, define the relevant
2015 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2016 For example, this will build in lsearch but load sqlite and mysql support
2025 .section "The building process" "SECID29"
2026 .cindex "build directory"
2027 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2028 created, run &'make'& at the top level. It determines the architecture and
2029 operating system types, and creates a build directory if one does not exist.
2030 For example, on a Sun system running Solaris 8, the directory
2031 &_build-SunOS5-5.8-sparc_& is created.
2032 .cindex "symbolic link" "to source files"
2033 Symbolic links to relevant source files are installed in the build directory.
2035 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
2036 building process fails if it is set.
2038 If this is the first time &'make'& has been run, it calls a script that builds
2039 a make file inside the build directory, using the configuration files from the
2040 &_Local_& directory. The new make file is then passed to another instance of
2041 &'make'&. This does the real work, building a number of utility scripts, and
2042 then compiling and linking the binaries for the Exim monitor (if configured), a
2043 number of utility programs, and finally Exim itself. The command &`make
2044 makefile`& can be used to force a rebuild of the make file in the build
2045 directory, should this ever be necessary.
2047 If you have problems building Exim, check for any comments there may be in the
2048 &_README_& file concerning your operating system, and also take a look at the
2049 FAQ, where some common problems are covered.
2053 .section 'Output from &"make"&' "SECID283"
2054 The output produced by the &'make'& process for compile lines is often very
2055 unreadable, because these lines can be very long. For this reason, the normal
2056 output is suppressed by default, and instead output similar to that which
2057 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2058 each module that is being compiled or linked. However, it is still possible to
2059 get the full output, by calling &'make'& like this:
2063 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2064 command reflection in &'make'&. When you ask for the full output, it is
2065 given in addition to the short output.
2069 .section "Overriding build-time options for Exim" "SECToverride"
2070 .cindex "build-time options, overriding"
2071 The main make file that is created at the beginning of the building process
2072 consists of the concatenation of a number of files which set configuration
2073 values, followed by a fixed set of &'make'& instructions. If a value is set
2074 more than once, the last setting overrides any previous ones. This provides a
2075 convenient way of overriding defaults. The files that are concatenated are, in
2078 &_OS/Makefile-Default_&
2079 &_OS/Makefile-_&<&'ostype'&>
2081 &_Local/Makefile-_&<&'ostype'&>
2082 &_Local/Makefile-_&<&'archtype'&>
2083 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2084 &_OS/Makefile-Base_&
2086 .cindex "&_Local/Makefile_&"
2087 .cindex "building Exim" "operating system type"
2088 .cindex "building Exim" "architecture type"
2089 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2090 architecture type. &_Local/Makefile_& is required to exist, and the building
2091 process fails if it is absent. The other three &_Local_& files are optional,
2092 and are often not needed.
2094 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2095 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2096 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2097 values are used, thereby providing a means of forcing particular settings.
2098 Otherwise, the scripts try to get values from the &%uname%& command. If this
2099 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2100 of &'ad hoc'& transformations are then applied, to produce the standard names
2101 that Exim expects. You can run these scripts directly from the shell in order
2102 to find out what values are being used on your system.
2105 &_OS/Makefile-Default_& contains comments about the variables that are set
2106 therein. Some (but not all) are mentioned below. If there is something that
2107 needs changing, review the contents of this file and the contents of the make
2108 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2112 .cindex "building Exim" "overriding default settings"
2113 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2114 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2115 need to change the original files. Instead, you should make the changes by
2116 putting the new values in an appropriate &_Local_& file. For example,
2117 .cindex "Tru64-Unix build-time settings"
2118 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2119 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2120 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2121 called with the option &%-std1%&, to make it recognize some of the features of
2122 Standard C that Exim uses. (Most other compilers recognize Standard C by
2123 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2124 containing the lines
2129 If you are compiling for just one operating system, it may be easier to put
2130 these lines directly into &_Local/Makefile_&.
2132 Keeping all your local configuration settings separate from the distributed
2133 files makes it easy to transfer them to new versions of Exim simply by copying
2134 the contents of the &_Local_& directory.
2137 .cindex "NIS lookup type" "including support for"
2138 .cindex "NIS+ lookup type" "including support for"
2139 .cindex "LDAP" "including support for"
2140 .cindex "lookup" "inclusion in binary"
2141 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2142 lookup, but not all systems have these components installed, so the default is
2143 not to include the relevant code in the binary. All the different kinds of file
2144 and database lookup that Exim supports are implemented as separate code modules
2145 which are included only if the relevant compile-time options are set. In the
2146 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2152 and similar settings apply to the other lookup types. They are all listed in
2153 &_src/EDITME_&. In many cases the relevant include files and interface
2154 libraries need to be installed before compiling Exim.
2155 .cindex "cdb" "including support for"
2156 However, there are some optional lookup types (such as cdb) for which
2157 the code is entirely contained within Exim, and no external include
2158 files or libraries are required. When a lookup type is not included in the
2159 binary, attempts to configure Exim to use it cause run time configuration
2162 .cindex "pkg-config" "lookups"
2163 .cindex "pkg-config" "authenticators"
2164 Many systems now use a tool called &'pkg-config'& to encapsulate information
2165 about how to compile against a library; Exim has some initial support for
2166 being able to use pkg-config for lookups and authenticators. For any given
2167 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2168 variable with the &`_PC`& suffix in the name and assign as the value the
2169 name of the package to be queried. The results of querying via the
2170 &'pkg-config'& command will be added to the appropriate Makefile variables
2171 with &`+=`& directives, so your version of &'make'& will need to support that
2172 syntax. For instance:
2175 LOOKUP_SQLITE_PC=sqlite3
2177 AUTH_GSASL_PC=libgsasl
2178 AUTH_HEIMDAL_GSSAPI=yes
2179 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2182 .cindex "Perl" "including support for"
2183 Exim can be linked with an embedded Perl interpreter, allowing Perl
2184 subroutines to be called during string expansion. To enable this facility,
2188 must be defined in &_Local/Makefile_&. Details of this facility are given in
2189 chapter &<<CHAPperl>>&.
2191 .cindex "X11 libraries, location of"
2192 The location of the X11 libraries is something that varies a lot between
2193 operating systems, and there may be different versions of X11 to cope
2194 with. Exim itself makes no use of X11, but if you are compiling the Exim
2195 monitor, the X11 libraries must be available.
2196 The following three variables are set in &_OS/Makefile-Default_&:
2199 XINCLUDE=-I$(X11)/include
2200 XLFLAGS=-L$(X11)/lib
2202 These are overridden in some of the operating-system configuration files. For
2203 example, in &_OS/Makefile-SunOS5_& there is
2206 XINCLUDE=-I$(X11)/include
2207 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2209 If you need to override the default setting for your operating system, place a
2210 definition of all three of these variables into your
2211 &_Local/Makefile-<ostype>_& file.
2214 If you need to add any extra libraries to the link steps, these can be put in a
2215 variable called EXTRALIBS, which appears in all the link commands, but by
2216 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2217 command for linking the main Exim binary, and not for any associated utilities.
2219 .cindex "DBM libraries" "configuration for building"
2220 There is also DBMLIB, which appears in the link commands for binaries that
2221 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2222 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2223 binary, and which can be used, for example, to include additional X11
2226 .cindex "configuration file" "editing"
2227 The make file copes with rebuilding Exim correctly if any of the configuration
2228 files are edited. However, if an optional configuration file is deleted, it is
2229 necessary to touch the associated non-optional file (that is,
2230 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2233 .section "OS-specific header files" "SECID30"
2235 .cindex "building Exim" "OS-specific C header files"
2236 The &_OS_& directory contains a number of files with names of the form
2237 &_os.h-<ostype>_&. These are system-specific C header files that should not
2238 normally need to be changed. There is a list of macro settings that are
2239 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2240 are porting Exim to a new operating system.
2244 .section "Overriding build-time options for the monitor" "SECID31"
2245 .cindex "building Eximon"
2246 A similar process is used for overriding things when building the Exim monitor,
2247 where the files that are involved are
2249 &_OS/eximon.conf-Default_&
2250 &_OS/eximon.conf-_&<&'ostype'&>
2251 &_Local/eximon.conf_&
2252 &_Local/eximon.conf-_&<&'ostype'&>
2253 &_Local/eximon.conf-_&<&'archtype'&>
2254 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2256 .cindex "&_Local/eximon.conf_&"
2257 As with Exim itself, the final three files need not exist, and in this case the
2258 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2259 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2260 variables of the same name, preceded by EXIMON_. For example, setting
2261 EXIMON_LOG_DEPTH in the environment overrides the value of
2262 LOG_DEPTH at run time.
2266 .section "Installing Exim binaries and scripts" "SECID32"
2267 .cindex "installing Exim"
2268 .cindex "BIN_DIRECTORY"
2269 The command &`make install`& runs the &(exim_install)& script with no
2270 arguments. The script copies binaries and utility scripts into the directory
2271 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2272 .cindex "setuid" "installing Exim with"
2273 The install script copies files only if they are newer than the files they are
2274 going to replace. The Exim binary is required to be owned by root and have the
2275 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2276 install`& as root so that it can set up the Exim binary in this way. However, in
2277 some special situations (for example, if a host is doing no local deliveries)
2278 it may be possible to run Exim without making the binary setuid root (see
2279 chapter &<<CHAPsecurity>>& for details).
2281 .cindex "CONFIGURE_FILE"
2282 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2283 in &_Local/Makefile_&. If this names a single file, and the file does not
2284 exist, the default configuration file &_src/configure.default_& is copied there
2285 by the installation script. If a run time configuration file already exists, it
2286 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2287 alternative files, no default is installed.
2289 .cindex "system aliases file"
2290 .cindex "&_/etc/aliases_&"
2291 One change is made to the default configuration file when it is installed: the
2292 default configuration contains a router that references a system aliases file.
2293 The path to this file is set to the value specified by
2294 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2295 If the system aliases file does not exist, the installation script creates it,
2296 and outputs a comment to the user.
2298 The created file contains no aliases, but it does contain comments about the
2299 aliases a site should normally have. Mail aliases have traditionally been
2300 kept in &_/etc/aliases_&. However, some operating systems are now using
2301 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2302 Exim's configuration if necessary.
2304 The default configuration uses the local host's name as the only local domain,
2305 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2306 running as the local user. System aliases and &_.forward_& files in users' home
2307 directories are supported, but no NIS or NIS+ support is configured. Domains
2308 other than the name of the local host are routed using the DNS, with delivery
2311 It is possible to install Exim for special purposes (such as building a binary
2312 distribution) in a private part of the file system. You can do this by a
2315 make DESTDIR=/some/directory/ install
2317 This has the effect of pre-pending the specified directory to all the file
2318 paths, except the name of the system aliases file that appears in the default
2319 configuration. (If a default alias file is created, its name &'is'& modified.)
2320 For backwards compatibility, ROOT is used if DESTDIR is not set,
2321 but this usage is deprecated.
2323 .cindex "installing Exim" "what is not installed"
2324 Running &'make install'& does not copy the Exim 4 conversion script
2325 &'convert4r4'&. You will probably run this only once if you are
2326 upgrading from Exim 3. None of the documentation files in the &_doc_&
2327 directory are copied, except for the info files when you have set
2328 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2330 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2331 to their names. The Exim binary itself, however, is handled differently. It is
2332 installed under a name that includes the version number and the compile number,
2333 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2334 called &_exim_& to point to the binary. If you are updating a previous version
2335 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2336 from the directory (as seen by other processes).
2338 .cindex "installing Exim" "testing the script"
2339 If you want to see what the &'make install'& will do before running it for
2340 real, you can pass the &%-n%& option to the installation script by this
2343 make INSTALL_ARG=-n install
2345 The contents of the variable INSTALL_ARG are passed to the installation
2346 script. You do not need to be root to run this test. Alternatively, you can run
2347 the installation script directly, but this must be from within the build
2348 directory. For example, from the top-level Exim directory you could use this
2351 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2353 .cindex "installing Exim" "install script options"
2354 There are two other options that can be supplied to the installation script.
2357 &%-no_chown%& bypasses the call to change the owner of the installed binary
2358 to root, and the call to make it a setuid binary.
2360 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2364 INSTALL_ARG can be used to pass these options to the script. For example:
2366 make INSTALL_ARG=-no_symlink install
2368 The installation script can also be given arguments specifying which files are
2369 to be copied. For example, to install just the Exim binary, and nothing else,
2370 without creating the symbolic link, you could use:
2372 make INSTALL_ARG='-no_symlink exim' install
2377 .section "Installing info documentation" "SECTinsinfdoc"
2378 .cindex "installing Exim" "&'info'& documentation"
2379 Not all systems use the GNU &'info'& system for documentation, and for this
2380 reason, the Texinfo source of Exim's documentation is not included in the main
2381 distribution. Instead it is available separately from the ftp site (see section
2384 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2385 source of the documentation is found in the source tree, running &`make
2386 install`& automatically builds the info files and installs them.
2390 .section "Setting up the spool directory" "SECID33"
2391 .cindex "spool directory" "creating"
2392 When it starts up, Exim tries to create its spool directory if it does not
2393 exist. The Exim uid and gid are used for the owner and group of the spool
2394 directory. Sub-directories are automatically created in the spool directory as
2400 .section "Testing" "SECID34"
2401 .cindex "testing" "installation"
2402 Having installed Exim, you can check that the run time configuration file is
2403 syntactically valid by running the following command, which assumes that the
2404 Exim binary directory is within your PATH environment variable:
2408 If there are any errors in the configuration file, Exim outputs error messages.
2409 Otherwise it outputs the version number and build date,
2410 the DBM library that is being used, and information about which drivers and
2411 other optional code modules are included in the binary.
2412 Some simple routing tests can be done by using the address testing option. For
2415 &`exim -bt`& <&'local username'&>
2417 should verify that it recognizes a local mailbox, and
2419 &`exim -bt`& <&'remote address'&>
2421 a remote one. Then try getting it to deliver mail, both locally and remotely.
2422 This can be done by passing messages directly to Exim, without going through a
2423 user agent. For example:
2425 exim -v postmaster@your.domain.example
2426 From: user@your.domain.example
2427 To: postmaster@your.domain.example
2428 Subject: Testing Exim
2430 This is a test message.
2433 The &%-v%& option causes Exim to output some verification of what it is doing.
2434 In this case you should see copies of three log lines, one for the message's
2435 arrival, one for its delivery, and one containing &"Completed"&.
2437 .cindex "delivery" "problems with"
2438 If you encounter problems, look at Exim's log files (&'mainlog'& and
2439 &'paniclog'&) to see if there is any relevant information there. Another source
2440 of information is running Exim with debugging turned on, by specifying the
2441 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2442 with debugging turned on by a command of the form
2444 &`exim -d -M`& <&'exim-message-id'&>
2446 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2447 produces rather a lot of output, but you can cut this down to specific areas.
2448 For example, if you use &%-d-all+route%& only the debugging information
2449 relevant to routing is included. (See the &%-d%& option in chapter
2450 &<<CHAPcommandline>>& for more details.)
2452 .cindex '&"sticky"& bit'
2453 .cindex "lock files"
2454 One specific problem that has shown up on some sites is the inability to do
2455 local deliveries into a shared mailbox directory, because it does not have the
2456 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2457 writing to a mailbox file, and if it cannot create the lock file, the delivery
2458 is deferred. You can get round this either by setting the &"sticky bit"& on the
2459 directory, or by setting a specific group for local deliveries and allowing
2460 that group to create files in the directory (see the comments above the
2461 &(local_delivery)& transport in the default configuration file). Another
2462 approach is to configure Exim not to use lock files, but just to rely on
2463 &[fcntl()]& locking instead. However, you should do this only if all user
2464 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2465 see chapter &<<CHAPappendfile>>&.
2467 One thing that cannot be tested on a system that is already running an MTA is
2468 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2469 &%-oX%& option can be used to run an Exim daemon that listens on some other
2470 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2471 &'exim_checkaccess'& utility can be used to check out policy controls on
2474 Testing a new version on a system that is already running Exim can most easily
2475 be done by building a binary with a different CONFIGURE_FILE setting. From
2476 within the run time configuration, all other file and directory names
2477 that Exim uses can be altered, in order to keep it entirely clear of the
2481 .section "Replacing another MTA with Exim" "SECID35"
2482 .cindex "replacing another MTA"
2483 Building and installing Exim for the first time does not of itself put it in
2484 general use. The name by which the system's MTA is called by mail user agents
2485 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2486 operating system), and it is necessary to make this name point to the &'exim'&
2487 binary in order to get the user agents to pass messages to Exim. This is
2488 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2489 or &_/usr/lib/sendmail_&
2490 .cindex "symbolic link" "to &'exim'& binary"
2491 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2492 privilege and executable status from the old MTA. It is then necessary to stop
2493 and restart the mailer daemon, if one is running.
2495 .cindex "FreeBSD, MTA indirection"
2496 .cindex "&_/etc/mail/mailer.conf_&"
2497 Some operating systems have introduced alternative ways of switching MTAs. For
2498 example, if you are running FreeBSD, you need to edit the file
2499 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2500 described. A typical example of the contents of this file for running Exim is
2503 sendmail /usr/exim/bin/exim
2504 send-mail /usr/exim/bin/exim
2505 mailq /usr/exim/bin/exim -bp
2506 newaliases /usr/bin/true
2508 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2509 your Exim installation is &"live"&. Check it by sending a message from your
2510 favourite user agent.
2512 You should consider what to tell your users about the change of MTA. Exim may
2513 have different capabilities to what was previously running, and there are
2514 various operational differences such as the text of messages produced by
2515 command line options and in bounce messages. If you allow your users to make
2516 use of Exim's filtering capabilities, you should make the document entitled
2517 &'Exim's interface to mail filtering'& available to them.
2521 .section "Upgrading Exim" "SECID36"
2522 .cindex "upgrading Exim"
2523 If you are already running Exim on your host, building and installing a new
2524 version automatically makes it available to MUAs, or any other programs that
2525 call the MTA directly. However, if you are running an Exim daemon, you do need
2526 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2527 new binary. You do not need to stop processing mail in order to install a new
2528 version of Exim. The install script does not modify an existing runtime
2534 .section "Stopping the Exim daemon on Solaris" "SECID37"
2535 .cindex "Solaris" "stopping Exim on"
2536 The standard command for stopping the mailer daemon on Solaris is
2538 /etc/init.d/sendmail stop
2540 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2541 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2542 for the text &"sendmail"&; this is not present because the actual program name
2543 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2544 solution is to replace the line that finds the process id with something like
2546 pid=`cat /var/spool/exim/exim-daemon.pid`
2548 to obtain the daemon's pid directly from the file that Exim saves it in.
2550 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2551 still be received from local processes, and if automatic delivery is configured
2552 (the normal case), deliveries will still occur.
2557 . ////////////////////////////////////////////////////////////////////////////
2558 . ////////////////////////////////////////////////////////////////////////////
2560 .chapter "The Exim command line" "CHAPcommandline"
2561 .scindex IIDclo1 "command line" "options"
2562 .scindex IIDclo2 "options" "command line"
2563 Exim's command line takes the standard Unix form of a sequence of options,
2564 each starting with a hyphen character, followed by a number of arguments. The
2565 options are compatible with the main options of Sendmail, and there are also
2566 some additional options, some of which are compatible with Smail 3. Certain
2567 combinations of options do not make sense, and provoke an error if used.
2568 The form of the arguments depends on which options are set.
2571 .section "Setting options by program name" "SECID38"
2573 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2574 were present before any other options.
2575 The &%-bp%& option requests a listing of the contents of the mail queue on the
2577 This feature is for compatibility with some systems that contain a command of
2578 that name in one of the standard libraries, symbolically linked to
2579 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2582 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2583 were present before any other options, for compatibility with Smail. The
2584 &%-bS%& option is used for reading in a number of messages in batched SMTP
2588 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2589 &%-oee%& options were present before any other options, for compatibility with
2590 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2593 .cindex "queue runner"
2594 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2595 were present before any other options, for compatibility with Smail. The &%-q%&
2596 option causes a single queue runner process to be started.
2598 .cindex "&'newaliases'&"
2599 .cindex "alias file" "building"
2600 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2601 If Exim is called under the name &'newaliases'& it behaves as if the option
2602 &%-bi%& were present before any other options, for compatibility with Sendmail.
2603 This option is used for rebuilding Sendmail's alias file. Exim does not have
2604 the concept of a single alias file, but can be configured to run a given
2605 command if called with the &%-bi%& option.
2608 .section "Trusted and admin users" "SECTtrustedadmin"
2609 Some Exim options are available only to &'trusted users'& and others are
2610 available only to &'admin users'&. In the description below, the phrases &"Exim
2611 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2612 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2613 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2616 .cindex "trusted users" "definition of"
2617 .cindex "user" "trusted definition of"
2618 The trusted users are root, the Exim user, any user listed in the
2619 &%trusted_users%& configuration option, and any user whose current group or any
2620 supplementary group is one of those listed in the &%trusted_groups%&
2621 configuration option. Note that the Exim group is not automatically trusted.
2623 .cindex '&"From"& line'
2624 .cindex "envelope sender"
2625 Trusted users are always permitted to use the &%-f%& option or a leading
2626 &"From&~"& line to specify the envelope sender of a message that is passed to
2627 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2628 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2629 users to set envelope senders.
2631 .cindex "&'From:'& header line"
2632 .cindex "&'Sender:'& header line"
2633 For a trusted user, there is never any check on the contents of the &'From:'&
2634 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2635 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2637 Trusted users may also specify a host name, host address, interface address,
2638 protocol name, ident value, and authentication data when submitting a message
2639 locally. Thus, they are able to insert messages into Exim's queue locally that
2640 have the characteristics of messages received from a remote host. Untrusted
2641 users may in some circumstances use &%-f%&, but can never set the other values
2642 that are available to trusted users.
2644 .cindex "user" "admin definition of"
2645 .cindex "admin user" "definition of"
2646 The admin users are root, the Exim user, and any user that is a member of the
2647 Exim group or of any group listed in the &%admin_groups%& configuration option.
2648 The current group does not have to be one of these groups.
2650 Admin users are permitted to list the queue, and to carry out certain
2651 operations on messages, for example, to force delivery failures. It is also
2652 necessary to be an admin user in order to see the full information provided by
2653 the Exim monitor, and full debugging output.
2655 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2656 Exim to attempt delivery of messages on its queue is restricted to admin users.
2657 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2658 option false (that is, specifying &%no_prod_requires_admin%&).
2660 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2661 is restricted to admin users unless &%queue_list_requires_admin%& is set
2666 &*Warning*&: If you configure your system so that admin users are able to
2667 edit Exim's configuration file, you are giving those users an easy way of
2668 getting root. There is further discussion of this issue at the start of chapter
2674 .section "Command line options" "SECID39"
2675 Exim's command line options are described in alphabetical order below. If none
2676 of the options that specifies a specific action (such as starting the daemon or
2677 a queue runner, or testing an address, or receiving a message in a specific
2678 format, or listing the queue) are present, and there is at least one argument
2679 on the command line, &%-bm%& (accept a local message on the standard input,
2680 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2681 outputs a brief message about itself and exits.
2683 . ////////////////////////////////////////////////////////////////////////////
2684 . Insert a stylized XML comment here, to identify the start of the command line
2685 . options. This is for the benefit of the Perl script that automatically
2686 . creates a man page for the options.
2687 . ////////////////////////////////////////////////////////////////////////////
2690 <!-- === Start of command line options === -->
2697 .cindex "options" "command line; terminating"
2698 This is a pseudo-option whose only purpose is to terminate the options and
2699 therefore to cause subsequent command line items to be treated as arguments
2700 rather than options, even if they begin with hyphens.
2703 .oindex "&%--help%&"
2704 This option causes Exim to output a few sentences stating what it is.
2705 The same output is generated if the Exim binary is called with no options and
2708 .vitem &%--version%&
2709 .oindex "&%--version%&"
2710 This option is an alias for &%-bV%& and causes version information to be
2717 These options are used by Sendmail for selecting configuration files and are
2720 .vitem &%-B%&<&'type'&>
2722 .cindex "8-bit characters"
2723 .cindex "Sendmail compatibility" "8-bit characters"
2724 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2725 clean; it ignores this option.
2730 .cindex "SMTP" "listener"
2731 .cindex "queue runner"
2732 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2733 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2734 that the daemon should also initiate periodic queue runs.
2736 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2737 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2738 disconnect from the controlling terminal. When running this way, it can be
2739 stopped by pressing ctrl-C.
2741 By default, Exim listens for incoming connections to the standard SMTP port on
2742 all the host's running interfaces. However, it is possible to listen on other
2743 ports, on multiple ports, and only on specific interfaces. Chapter
2744 &<<CHAPinterfaces>>& contains a description of the options that control this.
2746 When a listening daemon
2747 .cindex "daemon" "process id (pid)"
2748 .cindex "pid (process id)" "of daemon"
2749 is started without the use of &%-oX%& (that is, without overriding the normal
2750 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2751 in Exim's spool directory. This location can be overridden by setting
2752 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2755 When &%-oX%& is used on the command line to start a listening daemon, the
2756 process id is not written to the normal pid file path. However, &%-oP%& can be
2757 used to specify a path on the command line if a pid file is required.
2761 .cindex "daemon" "restarting"
2762 can be used to cause the daemon to re-execute itself. This should be done
2763 whenever Exim's configuration file, or any file that is incorporated into it by
2764 means of the &%.include%& facility, is changed, and also whenever a new version
2765 of Exim is installed. It is not necessary to do this when other files that are
2766 referenced from the configuration (for example, alias files) are changed,
2767 because these are reread each time they are used.
2771 This option has the same effect as &%-bd%& except that it never disconnects
2772 from the controlling terminal, even when no debugging is specified.
2776 .cindex "testing" "string expansion"
2777 .cindex "expansion" "testing"
2778 Run Exim in expansion testing mode. Exim discards its root privilege, to
2779 prevent ordinary users from using this mode to read otherwise inaccessible
2780 files. If no arguments are given, Exim runs interactively, prompting for lines
2781 of data. Otherwise, it processes each argument in turn.
2783 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2784 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2785 used without command line arguments. If successful, it uses the &[readline()]&
2786 function, which provides extensive line-editing facilities, for reading the
2787 test data. A line history is supported.
2789 Long expansion expressions can be split over several lines by using backslash
2790 continuations. As in Exim's run time configuration, white space at the start of
2791 continuation lines is ignored. Each argument or data line is passed through the
2792 string expansion mechanism, and the result is output. Variable values from the
2793 configuration file (for example, &$qualify_domain$&) are available, but no
2794 message-specific values (such as &$sender_domain$&) are set, because no message
2795 is being processed (but see &%-bem%& and &%-Mset%&).
2797 &*Note*&: If you use this mechanism to test lookups, and you change the data
2798 files or databases you are using, you must exit and restart Exim before trying
2799 the same lookup again. Otherwise, because each Exim process caches the results
2800 of lookups, you will just get the same result as before.
2802 .vitem &%-bem%&&~<&'filename'&>
2804 .cindex "testing" "string expansion"
2805 .cindex "expansion" "testing"
2806 This option operates like &%-be%& except that it must be followed by the name
2807 of a file. For example:
2809 exim -bem /tmp/testmessage
2811 The file is read as a message (as if receiving a locally-submitted non-SMTP
2812 message) before any of the test expansions are done. Thus, message-specific
2813 variables such as &$message_size$& and &$header_from:$& are available. However,
2814 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2815 recipients are read from the headers in the normal way, and are shown in the
2816 &$recipients$& variable. Note that recipients cannot be given on the command
2817 line, because further arguments are taken as strings to expand (just like
2820 .vitem &%-bF%&&~<&'filename'&>
2822 .cindex "system filter" "testing"
2823 .cindex "testing" "system filter"
2824 This option is the same as &%-bf%& except that it assumes that the filter being
2825 tested is a system filter. The additional commands that are available only in
2826 system filters are recognized.
2828 .vitem &%-bf%&&~<&'filename'&>
2830 .cindex "filter" "testing"
2831 .cindex "testing" "filter file"
2832 .cindex "forward file" "testing"
2833 .cindex "testing" "forward file"
2834 .cindex "Sieve filter" "testing"
2835 This option runs Exim in user filter testing mode; the file is the filter file
2836 to be tested, and a test message must be supplied on the standard input. If
2837 there are no message-dependent tests in the filter, an empty file can be
2840 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2841 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2842 filter and a user filter in the same run. For example:
2844 exim -bF /system/filter -bf /user/filter </test/message
2846 This is helpful when the system filter adds header lines or sets filter
2847 variables that are used by the user filter.
2849 If the test filter file does not begin with one of the special lines
2854 it is taken to be a normal &_.forward_& file, and is tested for validity under
2855 that interpretation. See sections &<<SECTitenonfilred>>& to
2856 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2859 The result of an Exim command that uses &%-bf%&, provided no errors are
2860 detected, is a list of the actions that Exim would try to take if presented
2861 with the message for real. More details of filter testing are given in the
2862 separate document entitled &'Exim's interfaces to mail filtering'&.
2864 When testing a filter file,
2865 .cindex "&""From""& line"
2866 .cindex "envelope sender"
2867 .oindex "&%-f%&" "for filter testing"
2868 the envelope sender can be set by the &%-f%& option,
2869 or by a &"From&~"& line at the start of the test message. Various parameters
2870 that would normally be taken from the envelope recipient address of the message
2871 can be set by means of additional command line options (see the next four
2874 .vitem &%-bfd%&&~<&'domain'&>
2876 .vindex "&$qualify_domain$&"
2877 This sets the domain of the recipient address when a filter file is being
2878 tested by means of the &%-bf%& option. The default is the value of
2881 .vitem &%-bfl%&&~<&'local&~part'&>
2883 This sets the local part of the recipient address when a filter file is being
2884 tested by means of the &%-bf%& option. The default is the username of the
2885 process that calls Exim. A local part should be specified with any prefix or
2886 suffix stripped, because that is how it appears to the filter when a message is
2887 actually being delivered.
2889 .vitem &%-bfp%&&~<&'prefix'&>
2891 This sets the prefix of the local part of the recipient address when a filter
2892 file is being tested by means of the &%-bf%& option. The default is an empty
2895 .vitem &%-bfs%&&~<&'suffix'&>
2897 This sets the suffix of the local part of the recipient address when a filter
2898 file is being tested by means of the &%-bf%& option. The default is an empty
2901 .vitem &%-bh%&&~<&'IP&~address'&>
2903 .cindex "testing" "incoming SMTP"
2904 .cindex "SMTP" "testing incoming"
2905 .cindex "testing" "relay control"
2906 .cindex "relaying" "testing configuration"
2907 .cindex "policy control" "testing"
2908 .cindex "debugging" "&%-bh%& option"
2909 This option runs a fake SMTP session as if from the given IP address, using the
2910 standard input and output. The IP address may include a port number at the end,
2911 after a full stop. For example:
2913 exim -bh 10.9.8.7.1234
2914 exim -bh fe80::a00:20ff:fe86:a061.5678
2916 When an IPv6 address is given, it is converted into canonical form. In the case
2917 of the second example above, the value of &$sender_host_address$& after
2918 conversion to the canonical form is
2919 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2921 Comments as to what is going on are written to the standard error file. These
2922 include lines beginning with &"LOG"& for anything that would have been logged.
2923 This facility is provided for testing configuration options for incoming
2924 messages, to make sure they implement the required policy. For example, you can
2925 test your relay controls using &%-bh%&.
2929 You can test features of the configuration that rely on ident (RFC 1413)
2930 information by using the &%-oMt%& option. However, Exim cannot actually perform
2931 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2934 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2935 are also skipped when testing using &%-bh%&. If you want these callouts to
2936 occur, use &%-bhc%& instead.
2938 Messages supplied during the testing session are discarded, and nothing is
2939 written to any of the real log files. There may be pauses when DNS (and other)
2940 lookups are taking place, and of course these may time out. The &%-oMi%& option
2941 can be used to specify a specific IP interface and port if this is important,
2942 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2943 session were authenticated.
2945 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2946 output just states whether a given recipient address from a given host is
2947 acceptable or not. See section &<<SECTcheckaccess>>&.
2949 Features such as authentication and encryption, where the client input is not
2950 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2951 specialized SMTP test program such as
2952 &url(http://jetmore.org/john/code/#swaks,swaks).
2954 .vitem &%-bhc%&&~<&'IP&~address'&>
2956 This option operates in the same way as &%-bh%&, except that address
2957 verification callouts are performed if required. This includes consulting and
2958 updating the callout cache database.
2962 .cindex "alias file" "building"
2963 .cindex "building alias file"
2964 .cindex "Sendmail compatibility" "&%-bi%& option"
2965 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2966 Exim does not have the concept of a single alias file, and so it cannot mimic
2967 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2968 tend to appear in various scripts such as NIS make files, so the option must be
2971 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2972 configuration option is run, under the uid and gid of the caller of Exim. If
2973 the &%-oA%& option is used, its value is passed to the command as an argument.
2974 The command set by &%bi_command%& may not contain arguments. The command can
2975 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2976 if this is required. If the &%bi_command%& option is not set, calling Exim with
2979 . // Keep :help first, then the rest in alphabetical order
2981 .oindex "&%-bI:help%&"
2982 .cindex "querying exim information"
2983 We shall provide various options starting &`-bI:`& for querying Exim for
2984 information. The output of many of these will be intended for machine
2985 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2986 synopsis of supported options beginning &`-bI:`&. Use of any of these
2987 options shall cause Exim to exit after producing the requested output.
2990 .oindex "&%-bI:dscp%&"
2991 .cindex "DSCP" "values"
2992 This option causes Exim to emit an alphabetically sorted list of all
2993 recognised DSCP names.
2995 .vitem &%-bI:sieve%&
2996 .oindex "&%-bI:sieve%&"
2997 .cindex "Sieve filter" "capabilities"
2998 This option causes Exim to emit an alphabetically sorted list of all supported
2999 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3000 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3001 &`SIEVE`& capability response line. As the precise list may depend upon
3002 compile-time build options, which this option will adapt to, this is the only
3003 way to guarantee a correct response.
3007 .cindex "local message reception"
3008 This option runs an Exim receiving process that accepts an incoming,
3009 locally-generated message on the standard input. The recipients are given as the
3010 command arguments (except when &%-t%& is also present &-- see below). Each
3011 argument can be a comma-separated list of RFC 2822 addresses. This is the
3012 default option for selecting the overall action of an Exim call; it is assumed
3013 if no other conflicting option is present.
3015 If any addresses in the message are unqualified (have no domain), they are
3016 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3017 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3018 suppressing this for special cases.
3020 Policy checks on the contents of local messages can be enforced by means of
3021 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3023 .cindex "return code" "for &%-bm%&"
3024 The return code is zero if the message is successfully accepted. Otherwise, the
3025 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3028 .cindex "message" "format"
3029 .cindex "format" "message"
3030 .cindex "&""From""& line"
3031 .cindex "UUCP" "&""From""& line"
3032 .cindex "Sendmail compatibility" "&""From""& line"
3033 of the message must be as defined in RFC 2822, except that, for
3034 compatibility with Sendmail and Smail, a line in one of the forms
3036 From sender Fri Jan 5 12:55 GMT 1997
3037 From sender Fri, 5 Jan 97 12:55:01
3039 (with the weekday optional, and possibly with additional text after the date)
3040 is permitted to appear at the start of the message. There appears to be no
3041 authoritative specification of the format of this line. Exim recognizes it by
3042 matching against the regular expression defined by the &%uucp_from_pattern%&
3043 option, which can be changed if necessary.
3045 .oindex "&%-f%&" "overriding &""From""& line"
3046 The specified sender is treated as if it were given as the argument to the
3047 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3048 preference to the address taken from the message. The caller of Exim must be a
3049 trusted user for the sender of a message to be set in this way.
3051 .vitem &%-bmalware%&&~<&'filename'&>
3052 .oindex "&%-bmalware%&"
3053 .cindex "testing", "malware"
3054 .cindex "malware scan test"
3055 This debugging option causes Exim to scan the given file,
3056 using the malware scanning framework. The option of &%av_scanner%& influences
3057 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3058 the expansion should have defaults which apply to this invocation. ACLs are
3059 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3060 will never be populated and &%-bmalware%& will fail.
3062 Exim will have changed working directory before resolving the filename, so
3063 using fully qualified pathnames is advisable. Exim will be running as the Exim
3064 user when it tries to open the file, rather than as the invoking user.
3065 This option requires admin privileges.
3067 The &%-bmalware%& option will not be extended to be more generally useful,
3068 there are better tools for file-scanning. This option exists to help
3069 administrators verify their Exim and AV scanner configuration.
3073 .cindex "address qualification, suppressing"
3074 By default, Exim automatically qualifies unqualified addresses (those
3075 without domains) that appear in messages that are submitted locally (that
3076 is, not over TCP/IP). This qualification applies both to addresses in
3077 envelopes, and addresses in header lines. Sender addresses are qualified using
3078 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3079 defaults to the value of &%qualify_domain%&).
3081 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3082 being used to re-submit messages that originally came from remote hosts after
3083 content scanning, you probably do not want to qualify unqualified addresses in
3084 header lines. (Such lines will be present only if you have not enabled a header
3085 syntax check in the appropriate ACL.)
3087 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3088 messages that originate on the local host. When this is used, unqualified
3089 addresses in the envelope provoke errors (causing message rejection) and
3090 unqualified addresses in header lines are left alone.
3095 .cindex "configuration options" "extracting"
3096 .cindex "options" "configuration &-- extracting"
3097 If this option is given with no arguments, it causes the values of all Exim's
3098 main configuration options to be written to the standard output. The values
3099 of one or more specific options can be requested by giving their names as
3100 arguments, for example:
3102 exim -bP qualify_domain hold_domains
3104 .cindex "hiding configuration option values"
3105 .cindex "configuration options" "hiding value of"
3106 .cindex "options" "hiding value of"
3107 However, any option setting that is preceded by the word &"hide"& in the
3108 configuration file is not shown in full, except to an admin user. For other
3109 users, the output is as in this example:
3111 mysql_servers = <value not displayable>
3113 If &%configure_file%& is given as an argument, the name of the run time
3114 configuration file is output.
3115 If a list of configuration files was supplied, the value that is output here
3116 is the name of the file that was actually used.
3118 .cindex "options" "hiding name of"
3119 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3120 name will not be output.
3122 .cindex "daemon" "process id (pid)"
3123 .cindex "pid (process id)" "of daemon"
3124 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3125 directories where log files and daemon pid files are written are output,
3126 respectively. If these values are unset, log files are written in a
3127 sub-directory of the spool directory called &%log%&, and the pid file is
3128 written directly into the spool directory.
3130 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3132 exim -bP +local_domains
3134 it searches for a matching named list of any type (domain, host, address, or
3135 local part) and outputs what it finds.
3137 .cindex "options" "router &-- extracting"
3138 .cindex "options" "transport &-- extracting"
3139 .cindex "options" "authenticator &-- extracting"
3140 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3141 followed by the name of an appropriate driver instance, the option settings for
3142 that driver are output. For example:
3144 exim -bP transport local_delivery
3146 The generic driver options are output first, followed by the driver's private
3147 options. A list of the names of drivers of a particular type can be obtained by
3148 using one of the words &%router_list%&, &%transport_list%&, or
3149 &%authenticator_list%&, and a complete list of all drivers with their option
3150 settings can be obtained by using &%routers%&, &%transports%&, or
3153 .cindex "options" "macro &-- extracting"
3154 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3155 are available, similarly to the drivers. Because macros are sometimes used
3156 for storing passwords, this option is restricted.
3157 The output format is one item per line.
3161 .cindex "queue" "listing messages on"
3162 .cindex "listing" "messages on the queue"
3163 This option requests a listing of the contents of the mail queue on the
3164 standard output. If the &%-bp%& option is followed by a list of message ids,
3165 just those messages are listed. By default, this option can be used only by an
3166 admin user. However, the &%queue_list_requires_admin%& option can be set false
3167 to allow any user to see the queue.
3169 Each message on the queue is displayed as in the following example:
3171 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3172 red.king@looking-glass.fict.example
3175 .cindex "message" "size in queue listing"
3176 .cindex "size" "of message"
3177 The first line contains the length of time the message has been on the queue
3178 (in this case 25 minutes), the size of the message (2.9K), the unique local
3179 identifier for the message, and the message sender, as contained in the
3180 envelope. For bounce messages, the sender address is empty, and appears as
3181 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3182 the default sender address, the user's login name is shown in parentheses
3183 before the sender address.
3185 .cindex "frozen messages" "in queue listing"
3186 If the message is frozen (attempts to deliver it are suspended) then the text
3187 &"*** frozen ***"& is displayed at the end of this line.
3189 The recipients of the message (taken from the envelope, not the headers) are
3190 displayed on subsequent lines. Those addresses to which the message has already
3191 been delivered are marked with the letter D. If an original address gets
3192 expanded into several addresses via an alias or forward file, the original is
3193 displayed with a D only when deliveries for all of its child addresses are
3199 This option operates like &%-bp%&, but in addition it shows delivered addresses
3200 that were generated from the original top level address(es) in each message by
3201 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3207 .cindex "queue" "count of messages on"
3208 This option counts the number of messages on the queue, and writes the total
3209 to the standard output. It is restricted to admin users, unless
3210 &%queue_list_requires_admin%& is set false.
3215 This option operates like &%-bp%&, but the output is not sorted into
3216 chronological order of message arrival. This can speed it up when there are
3217 lots of messages on the queue, and is particularly useful if the output is
3218 going to be post-processed in a way that doesn't need the sorting.
3222 This option is a combination of &%-bpr%& and &%-bpa%&.
3226 This option is a combination of &%-bpr%& and &%-bpu%&.
3231 This option operates like &%-bp%& but shows only undelivered top-level
3232 addresses for each message displayed. Addresses generated by aliasing or
3233 forwarding are not shown, unless the message was deferred after processing by a
3234 router with the &%one_time%& option set.
3239 .cindex "testing" "retry configuration"
3240 .cindex "retry" "configuration testing"
3241 This option is for testing retry rules, and it must be followed by up to three
3242 arguments. It causes Exim to look for a retry rule that matches the values
3243 and to write it to the standard output. For example:
3245 exim -brt bach.comp.mus.example
3246 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3248 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3249 argument, which is required, can be a complete address in the form
3250 &'local_part@domain'&, or it can be just a domain name. If the second argument
3251 contains a dot, it is interpreted as an optional second domain name; if no
3252 retry rule is found for the first argument, the second is tried. This ties in
3253 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3254 rule is found that matches the host, one that matches the mail domain is
3255 sought. Finally, an argument that is the name of a specific delivery error, as
3256 used in setting up retry rules, can be given. For example:
3258 exim -brt haydn.comp.mus.example quota_3d
3259 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3264 .cindex "testing" "rewriting"
3265 .cindex "rewriting" "testing"
3266 This option is for testing address rewriting rules, and it must be followed by
3267 a single argument, consisting of either a local part without a domain, or a
3268 complete address with a fully qualified domain. Exim outputs how this address
3269 would be rewritten for each possible place it might appear. See chapter
3270 &<<CHAPrewrite>>& for further details.
3274 .cindex "SMTP" "batched incoming"
3275 .cindex "batched SMTP input"
3276 This option is used for batched SMTP input, which is an alternative interface
3277 for non-interactive local message submission. A number of messages can be
3278 submitted in a single run. However, despite its name, this is not really SMTP
3279 input. Exim reads each message's envelope from SMTP commands on the standard
3280 input, but generates no responses. If the caller is trusted, or
3281 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3282 believed; otherwise the sender is always the caller of Exim.
3284 The message itself is read from the standard input, in SMTP format (leading
3285 dots doubled), terminated by a line containing just a single dot. An error is
3286 provoked if the terminating dot is missing. A further message may then follow.
3288 As for other local message submissions, the contents of incoming batch SMTP
3289 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3290 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3291 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3293 Some other SMTP commands are recognized in the input. HELO and EHLO act
3294 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3295 QUIT quits, ignoring the rest of the standard input.
3297 .cindex "return code" "for &%-bS%&"
3298 If any error is encountered, reports are written to the standard output and
3299 error streams, and Exim gives up immediately. The return code is 0 if no error
3300 was detected; it is 1 if one or more messages were accepted before the error
3301 was detected; otherwise it is 2.
3303 More details of input using batched SMTP are given in section
3304 &<<SECTincomingbatchedSMTP>>&.
3308 .cindex "SMTP" "local input"
3309 .cindex "local SMTP input"
3310 This option causes Exim to accept one or more messages by reading SMTP commands
3311 on the standard input, and producing SMTP replies on the standard output. SMTP
3312 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3313 Some user agents use this interface as a way of passing locally-generated
3314 messages to the MTA.
3317 .cindex "sender" "source of"
3318 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3319 set, the senders of messages are taken from the SMTP MAIL commands.
3320 Otherwise the content of these commands is ignored and the sender is set up as
3321 the calling user. Unqualified addresses are automatically qualified using
3322 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3323 &%-bnq%& option is used.
3327 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3328 using a listening daemon. Exim can distinguish the two cases by checking
3329 whether the standard input is a TCP/IP socket. When Exim is called from
3330 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3331 above concerning senders and qualification do not apply. In this situation,
3332 Exim behaves in exactly the same way as it does when receiving a message via
3333 the listening daemon.
3337 .cindex "testing" "addresses"
3338 .cindex "address" "testing"
3339 This option runs Exim in address testing mode, in which each argument is taken
3340 as a recipient address to be tested for deliverability. The results are
3341 written to the standard output. If a test fails, and the caller is not an admin
3342 user, no details of the failure are output, because these might contain
3343 sensitive information such as usernames and passwords for database lookups.
3345 If no arguments are given, Exim runs in an interactive manner, prompting with a
3346 right angle bracket for addresses to be tested.
3348 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3349 &[readline()]& function, because it is running as &'root'& and there are
3352 Each address is handled as if it were the recipient address of a message
3353 (compare the &%-bv%& option). It is passed to the routers and the result is
3354 written to the standard output. However, any router that has
3355 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3356 genuine routing tests if your first router passes everything to a scanner
3359 .cindex "return code" "for &%-bt%&"
3360 The return code is 2 if any address failed outright; it is 1 if no address
3361 failed outright but at least one could not be resolved for some reason. Return
3362 code 0 is given only when all addresses succeed.
3364 .cindex "duplicate addresses"
3365 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3366 addresses after routing is complete, so that only one delivery takes place.
3367 This does not happen when testing with &%-bt%&; the full results of routing are
3370 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3371 routers in the configuration makes any tests on the sender address of a
3373 .oindex "&%-f%&" "for address testing"
3374 you can use the &%-f%& option to set an appropriate sender when running
3375 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3376 default qualifying domain. However, if you have set up (for example) routers
3377 whose behaviour depends on the contents of an incoming message, you cannot test
3378 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3383 .cindex "version number of Exim"
3384 This option causes Exim to write the current version number, compilation
3385 number, and compilation date of the &'exim'& binary to the standard output.
3386 It also lists the DBM library that is being used, the optional modules (such as
3387 specific lookup types), the drivers that are included in the binary, and the
3388 name of the run time configuration file that is in use.
3390 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3391 configuration file. However, this is a static check only. It cannot check
3392 values that are to be expanded. For example, although a misspelt ACL verb is
3393 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3394 alone to discover (for example) all the typos in the configuration; some
3395 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3396 dynamic testing facilities.
3400 .cindex "verifying address" "using &%-bv%&"
3401 .cindex "address" "verification"
3402 This option runs Exim in address verification mode, in which each argument is
3403 taken as a recipient address to be verified by the routers. (This does
3404 not involve any verification callouts). During normal operation, verification
3405 happens mostly as a consequence processing a &%verify%& condition in an ACL
3406 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3407 including callouts, see the &%-bh%& and &%-bhc%& options.
3409 If verification fails, and the caller is not an admin user, no details of the
3410 failure are output, because these might contain sensitive information such as
3411 usernames and passwords for database lookups.
3413 If no arguments are given, Exim runs in an interactive manner, prompting with a
3414 right angle bracket for addresses to be verified.
3416 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3417 &[readline()]& function, because it is running as &'exim'& and there are
3420 Verification differs from address testing (the &%-bt%& option) in that routers
3421 that have &%no_verify%& set are skipped, and if the address is accepted by a
3422 router that has &%fail_verify%& set, verification fails. The address is
3423 verified as a recipient if &%-bv%& is used; to test verification for a sender
3424 address, &%-bvs%& should be used.
3426 If the &%-v%& option is not set, the output consists of a single line for each
3427 address, stating whether it was verified or not, and giving a reason in the
3428 latter case. Without &%-v%&, generating more than one address by redirection
3429 causes verification to end successfully, without considering the generated
3430 addresses. However, if just one address is generated, processing continues,
3431 and the generated address must verify successfully for the overall verification
3434 When &%-v%& is set, more details are given of how the address has been handled,
3435 and in the case of address redirection, all the generated addresses are also
3436 considered. Verification may succeed for some and fail for others.
3439 .cindex "return code" "for &%-bv%&"
3440 return code is 2 if any address failed outright; it is 1 if no address
3441 failed outright but at least one could not be resolved for some reason. Return
3442 code 0 is given only when all addresses succeed.
3444 If any of the routers in the configuration makes any tests on the sender
3445 address of a message, you should use the &%-f%& option to set an appropriate
3446 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3447 calling user at the default qualifying domain.
3451 This option acts like &%-bv%&, but verifies the address as a sender rather
3452 than a recipient address. This affects any rewriting and qualification that
3459 .cindex "inetd" "wait mode"
3460 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3461 similarly to the &%-bd%& option. All port specifications on the command-line
3462 and in the configuration file are ignored. Queue-running may not be specified.
3464 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3465 listening for connections. This permits the system to start up and have
3466 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3467 each port only when the first connection is received.
3469 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3470 which the daemon will exit, which should cause inetd to listen once more.
3472 .vitem &%-C%&&~<&'filelist'&>
3474 .cindex "configuration file" "alternate"
3475 .cindex "CONFIGURE_FILE"
3476 .cindex "alternate configuration file"
3477 This option causes Exim to find the run time configuration file from the given
3478 list instead of from the list specified by the CONFIGURE_FILE
3479 compile-time setting. Usually, the list will consist of just a single file
3480 name, but it can be a colon-separated list of names. In this case, the first
3481 file that exists is used. Failure to open an existing file stops Exim from
3482 proceeding any further along the list, and an error is generated.
3484 When this option is used by a caller other than root, and the list is different
3485 from the compiled-in list, Exim gives up its root privilege immediately, and
3486 runs with the real and effective uid and gid set to those of the caller.
3487 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3488 file contains a list of full pathnames, one per line, for configuration files
3489 which are trusted. Root privilege is retained for any configuration file so
3490 listed, as long as the caller is the Exim user (or the user specified in the
3491 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3492 not writeable by inappropriate users or groups.
3494 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3495 configuration using &%-C%& right through message reception and delivery,
3496 even if the caller is root. The reception works, but by that time, Exim is
3497 running as the Exim user, so when it re-executes to regain privilege for the
3498 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3499 test reception and delivery using two separate commands (one to put a message
3500 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3502 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3503 prefix string with which any file named in a &%-C%& command line option
3504 must start. In addition, the file name must not contain the sequence &`/../`&.
3505 However, if the value of the &%-C%& option is identical to the value of
3506 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3507 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3508 unset, any file name can be used with &%-C%&.
3510 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3511 to a directory to which only root has access. This prevents someone who has
3512 broken into the Exim account from running a privileged Exim with an arbitrary
3515 The &%-C%& facility is useful for ensuring that configuration files are
3516 syntactically correct, but cannot be used for test deliveries, unless the
3517 caller is privileged, or unless it is an exotic configuration that does not
3518 require privilege. No check is made on the owner or group of the files
3519 specified by this option.
3522 .vitem &%-D%&<&'macro'&>=<&'value'&>
3524 .cindex "macro" "setting on command line"
3525 This option can be used to override macro definitions in the configuration file
3526 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3527 unprivileged caller, it causes Exim to give up its root privilege.
3528 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3529 completely disabled, and its use causes an immediate error exit.
3531 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3532 colon-separated list of macros which are considered safe and, if &%-D%& only
3533 supplies macros from this list, and the values are acceptable, then Exim will
3534 not give up root privilege if the caller is root, the Exim run-time user, or
3535 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3536 to be removed in the future. Acceptable values for the macros satisfy the
3537 regexp: &`^[A-Za-z0-9_/.-]*$`&
3539 The entire option (including equals sign if present) must all be within one
3540 command line item. &%-D%& can be used to set the value of a macro to the empty
3541 string, in which case the equals sign is optional. These two commands are
3547 To include spaces in a macro definition item, quotes must be used. If you use
3548 quotes, spaces are permitted around the macro name and the equals sign. For
3551 exim '-D ABC = something' ...
3553 &%-D%& may be repeated up to 10 times on a command line.
3556 .vitem &%-d%&<&'debug&~options'&>
3558 .cindex "debugging" "list of selectors"
3559 .cindex "debugging" "&%-d%& option"
3560 This option causes debugging information to be written to the standard
3561 error stream. It is restricted to admin users because debugging output may show
3562 database queries that contain password information. Also, the details of users'
3563 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3564 writes an error message to the standard error stream and exits with a non-zero
3567 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3568 standard debugging data is output. This can be reduced, or increased to include
3569 some more rarely needed information, by directly following &%-d%& with a string
3570 made up of names preceded by plus or minus characters. These add or remove sets
3571 of debugging data, respectively. For example, &%-d+filter%& adds filter
3572 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3573 no spaces are allowed in the debug setting. The available debugging categories
3576 &`acl `& ACL interpretation
3577 &`auth `& authenticators
3578 &`deliver `& general delivery logic
3579 &`dns `& DNS lookups (see also resolver)
3580 &`dnsbl `& DNS black list (aka RBL) code
3581 &`exec `& arguments for &[execv()]& calls
3582 &`expand `& detailed debugging for string expansions
3583 &`filter `& filter handling
3584 &`hints_lookup `& hints data lookups
3585 &`host_lookup `& all types of name-to-IP address handling
3586 &`ident `& ident lookup
3587 &`interface `& lists of local interfaces
3588 &`lists `& matching things in lists
3589 &`load `& system load checks
3590 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3591 &<<CHAPlocalscan>>&)
3592 &`lookup `& general lookup code and all lookups
3593 &`memory `& memory handling
3594 &`pid `& add pid to debug output lines
3595 &`process_info `& setting info for the process log
3596 &`queue_run `& queue runs
3597 &`receive `& general message reception logic
3598 &`resolver `& turn on the DNS resolver's debugging output
3599 &`retry `& retry handling
3600 &`rewrite `& address rewriting
3601 &`route `& address routing
3602 &`timestamp `& add timestamp to debug output lines
3604 &`transport `& transports
3605 &`uid `& changes of uid/gid and looking up uid/gid
3606 &`verify `& address verification logic
3607 &`all `& almost all of the above (see below), and also &%-v%&
3609 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3610 for &`-all`&. The reason for this is that &`+all`& is something that people
3611 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3612 is included, an awful lot of output that is very rarely of interest is
3613 generated, so it now has to be explicitly requested. However, &`-all`& does
3614 turn everything off.
3616 .cindex "resolver, debugging output"
3617 .cindex "DNS resolver, debugging output"
3618 The &`resolver`& option produces output only if the DNS resolver was compiled
3619 with DEBUG enabled. This is not the case in some operating systems. Also,
3620 unfortunately, debugging output from the DNS resolver is written to stdout
3623 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3624 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3625 However, the &`pid`& selector is forced when debugging is turned on for a
3626 daemon, which then passes it on to any re-executed Exims. Exim also
3627 automatically adds the pid to debug lines when several remote deliveries are
3630 The &`timestamp`& selector causes the current time to be inserted at the start
3631 of all debug output lines. This can be useful when trying to track down delays
3634 If the &%debug_print%& option is set in any driver, it produces output whenever
3635 any debugging is selected, or if &%-v%& is used.
3637 .vitem &%-dd%&<&'debug&~options'&>
3639 This option behaves exactly like &%-d%& except when used on a command that
3640 starts a daemon process. In that case, debugging is turned off for the
3641 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3642 behaviour of the daemon without creating as much output as full debugging does.
3645 .oindex "&%-dropcr%&"
3646 This is an obsolete option that is now a no-op. It used to affect the way Exim
3647 handled CR and LF characters in incoming messages. What happens now is
3648 described in section &<<SECTlineendings>>&.
3652 .cindex "bounce message" "generating"
3653 This option specifies that an incoming message is a locally-generated delivery
3654 failure report. It is used internally by Exim when handling delivery failures
3655 and is not intended for external use. Its only effect is to stop Exim
3656 generating certain messages to the postmaster, as otherwise message cascades
3657 could occur in some situations. As part of the same option, a message id may
3658 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3659 new message contains the id, following &"R="&, as a cross-reference.
3662 .oindex "&%-e%&&'x'&"
3663 There are a number of Sendmail options starting with &%-oe%& which seem to be
3664 called by various programs without the leading &%o%& in the option. For
3665 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3666 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3668 .vitem &%-F%&&~<&'string'&>
3670 .cindex "sender" "name"
3671 .cindex "name" "of sender"
3672 This option sets the sender's full name for use when a locally-generated
3673 message is being accepted. In the absence of this option, the user's &'gecos'&
3674 entry from the password data is used. As users are generally permitted to alter
3675 their &'gecos'& entries, no security considerations are involved. White space
3676 between &%-F%& and the <&'string'&> is optional.
3678 .vitem &%-f%&&~<&'address'&>
3680 .cindex "sender" "address"
3681 .cindex "address" "sender"
3682 .cindex "trusted users"
3683 .cindex "envelope sender"
3684 .cindex "user" "trusted"
3685 This option sets the address of the envelope sender of a locally-generated
3686 message (also known as the return path). The option can normally be used only
3687 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3690 Processes running as root or the Exim user are always trusted. Other
3691 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3692 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3693 of a local message is set to the caller's login name at the default qualify
3696 There is one exception to the restriction on the use of &%-f%&: an empty sender
3697 can be specified by any user, trusted or not, to create a message that can
3698 never provoke a bounce. An empty sender can be specified either as an empty
3699 string, or as a pair of angle brackets with nothing between them, as in these
3700 examples of shell commands:
3702 exim -f '<>' user@domain
3703 exim -f "" user@domain
3705 In addition, the use of &%-f%& is not restricted when testing a filter file
3706 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3709 Allowing untrusted users to change the sender address does not of itself make
3710 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3711 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3712 though this can be overridden by setting &%no_local_from_check%&.
3715 .cindex "&""From""& line"
3716 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3717 given as two arguments or one combined argument). The sender of a
3718 locally-generated message can also be set (when permitted) by an initial
3719 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3720 if &%-f%& is also present, it overrides &"From&~"&.
3724 .cindex "submission fixups, suppressing (command-line)"
3725 This option is equivalent to an ACL applying:
3727 control = suppress_local_fixups
3729 for every message received. Note that Sendmail will complain about such
3730 bad formatting, where Exim silently just does not fix it up. This may change
3733 As this affects audit information, the caller must be a trusted user to use
3736 .vitem &%-h%&&~<&'number'&>
3738 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3739 This option is accepted for compatibility with Sendmail, but has no effect. (In
3740 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3745 .cindex "Solaris" "&'mail'& command"
3746 .cindex "dot" "in incoming non-SMTP message"
3747 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3748 line by itself should not terminate an incoming, non-SMTP message. I can find
3749 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3750 command in Solaris 2.4 uses it. See also &%-ti%&.
3752 .vitem &%-L%&&~<&'tag'&>
3754 .cindex "syslog" "process name; set with flag"
3755 This option is equivalent to setting &%syslog_processname%& in the config
3756 file and setting &%log_file_path%& to &`syslog`&.
3757 Its use is restricted to administrators. The configuration file has to be
3758 read and parsed, to determine access rights, before this is set and takes
3759 effect, so early configuration file errors will not honour this flag.
3761 The tag should not be longer than 32 characters.
3763 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3765 .cindex "forcing delivery"
3766 .cindex "delivery" "forcing attempt"
3767 .cindex "frozen messages" "forcing delivery"
3768 This option requests Exim to run a delivery attempt on each message in turn. If
3769 any of the messages are frozen, they are automatically thawed before the
3770 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3771 and &%hold_domains%& are ignored.
3774 .cindex "hints database" "overriding retry hints"
3775 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3776 the normal retry time has not yet been reached. This option requires the caller
3777 to be an admin user. However, there is an option called &%prod_requires_admin%&
3778 which can be set false to relax this restriction (and also the same requirement
3779 for the &%-q%&, &%-R%&, and &%-S%& options).
3781 The deliveries happen synchronously, that is, the original Exim process does
3782 not terminate until all the delivery attempts have finished. No output is
3783 produced unless there is a serious error. If you want to see what is happening,
3784 use the &%-v%& option as well, or inspect Exim's main log.
3786 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3788 .cindex "message" "adding recipients"
3789 .cindex "recipient" "adding"
3790 This option requests Exim to add the addresses to the list of recipients of the
3791 message (&"ar"& for &"add recipients"&). The first argument must be a message
3792 id, and the remaining ones must be email addresses. However, if the message is
3793 active (in the middle of a delivery attempt), it is not altered. This option
3794 can be used only by an admin user.
3796 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3797 &~<&'message&~id'&>"
3799 .cindex "SMTP" "passed connection"
3800 .cindex "SMTP" "multiple deliveries"
3801 .cindex "multiple SMTP deliveries"
3802 This option is not intended for use by external callers. It is used internally
3803 by Exim to invoke another instance of itself to deliver a waiting message using
3804 an existing SMTP connection, which is passed as the standard input. Details are
3805 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3806 must be root or the Exim user in order to use it.
3810 This option is not intended for use by external callers. It is used internally
3811 by Exim in conjunction with the &%-MC%& option. It signifies that the
3812 connection to the remote host has been authenticated.
3816 This option is not intended for use by external callers. It is used internally
3817 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3818 which Exim is connected supports pipelining.
3820 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3822 This option is not intended for use by external callers. It is used internally
3823 by Exim in conjunction with the &%-MC%& option when the original delivery was
3824 started by a queue runner. It passes on the process id of the queue runner,
3825 together with the file descriptor number of an open pipe. Closure of the pipe
3826 signals the final completion of the sequence of processes that are passing
3827 messages through the same SMTP connection.
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3833 SMTP SIZE option should be used on messages delivered down the existing
3838 This option is not intended for use by external callers. It is used internally
3839 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3840 host to which Exim is connected supports TLS encryption.
3842 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3844 .cindex "hints database" "not overridden by &%-Mc%&"
3845 .cindex "delivery" "manually started &-- not forced"
3846 This option requests Exim to run a delivery attempt on each message in turn,
3847 but unlike the &%-M%& option, it does check for retry hints, and respects any
3848 that are found. This option is not very useful to external callers. It is
3849 provided mainly for internal use by Exim when it needs to re-invoke itself in
3850 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3851 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3852 respects retry times and other options such as &%hold_domains%& that are
3853 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3854 If you want to run a specific delivery as if in a queue run, you should use
3855 &%-q%& with a message id argument. A distinction between queue run deliveries
3856 and other deliveries is made in one or two places.
3858 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3860 .cindex "message" "changing sender"
3861 .cindex "sender" "changing"
3862 This option requests Exim to change the sender address in the message to the
3863 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3864 &"edit sender"&). There must be exactly two arguments. The first argument must
3865 be a message id, and the second one an email address. However, if the message
3866 is active (in the middle of a delivery attempt), its status is not altered.
3867 This option can be used only by an admin user.
3869 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3871 .cindex "freezing messages"
3872 .cindex "message" "manually freezing"
3873 This option requests Exim to mark each listed message as &"frozen"&. This
3874 prevents any delivery attempts taking place until the message is &"thawed"&,
3875 either manually or as a result of the &%auto_thaw%& configuration option.
3876 However, if any of the messages are active (in the middle of a delivery
3877 attempt), their status is not altered. This option can be used only by an admin
3880 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3882 .cindex "giving up on messages"
3883 .cindex "message" "abandoning delivery attempts"
3884 .cindex "delivery" "abandoning further attempts"
3885 This option requests Exim to give up trying to deliver the listed messages,
3886 including any that are frozen. However, if any of the messages are active,
3887 their status is not altered. For non-bounce messages, a delivery error message
3888 is sent to the sender, containing the text &"cancelled by administrator"&.
3889 Bounce messages are just discarded. This option can be used only by an admin
3892 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3894 .cindex "delivery" "cancelling all"
3895 This option requests Exim to mark all the recipient addresses in the messages
3896 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3897 message is active (in the middle of a delivery attempt), its status is not
3898 altered. This option can be used only by an admin user.
3900 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3902 .cindex "delivery" "cancelling by address"
3903 .cindex "recipient" "removing"
3904 .cindex "removing recipients"
3905 This option requests Exim to mark the given addresses as already delivered
3906 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3907 the remaining ones must be email addresses. These are matched to recipient
3908 addresses in the message in a case-sensitive manner. If the message is active
3909 (in the middle of a delivery attempt), its status is not altered. This option
3910 can be used only by an admin user.
3912 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3914 .cindex "removing messages"
3915 .cindex "abandoning mail"
3916 .cindex "message" "manually discarding"
3917 This option requests Exim to remove the given messages from the queue. No
3918 bounce messages are sent; each message is simply forgotten. However, if any of
3919 the messages are active, their status is not altered. This option can be used
3920 only by an admin user or by the user who originally caused the message to be
3921 placed on the queue.
3923 .vitem &%-Mset%&&~<&'message&~id'&>
3925 .cindex "testing" "string expansion"
3926 .cindex "expansion" "testing"
3927 This option is useful only in conjunction with &%-be%& (that is, when testing
3928 string expansions). Exim loads the given message from its spool before doing
3929 the test expansions, thus setting message-specific variables such as
3930 &$message_size$& and the header variables. The &$recipients$& variable is made
3931 available. This feature is provided to make it easier to test expansions that
3932 make use of these variables. However, this option can be used only by an admin
3933 user. See also &%-bem%&.
3935 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3937 .cindex "thawing messages"
3938 .cindex "unfreezing messages"
3939 .cindex "frozen messages" "thawing"
3940 .cindex "message" "thawing frozen"
3941 This option requests Exim to &"thaw"& any of the listed messages that are
3942 &"frozen"&, so that delivery attempts can resume. However, if any of the
3943 messages are active, their status is not altered. This option can be used only
3946 .vitem &%-Mvb%&&~<&'message&~id'&>
3948 .cindex "listing" "message body"
3949 .cindex "message" "listing body of"
3950 This option causes the contents of the message body (-D) spool file to be
3951 written to the standard output. This option can be used only by an admin user.
3953 .vitem &%-Mvc%&&~<&'message&~id'&>
3955 .cindex "message" "listing in RFC 2822 format"
3956 .cindex "listing" "message in RFC 2822 format"
3957 This option causes a copy of the complete message (header lines plus body) to
3958 be written to the standard output in RFC 2822 format. This option can be used
3959 only by an admin user.
3961 .vitem &%-Mvh%&&~<&'message&~id'&>
3963 .cindex "listing" "message headers"
3964 .cindex "header lines" "listing"
3965 .cindex "message" "listing header lines"
3966 This option causes the contents of the message headers (-H) spool file to be
3967 written to the standard output. This option can be used only by an admin user.
3969 .vitem &%-Mvl%&&~<&'message&~id'&>
3971 .cindex "listing" "message log"
3972 .cindex "message" "listing message log"
3973 This option causes the contents of the message log spool file to be written to
3974 the standard output. This option can be used only by an admin user.
3978 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3979 treats it that way too.
3983 .cindex "debugging" "&%-N%& option"
3984 .cindex "debugging" "suppressing delivery"
3985 This is a debugging option that inhibits delivery of a message at the transport
3986 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3987 it just doesn't actually transport the message, but instead behaves as if it
3988 had successfully done so. However, it does not make any updates to the retry
3989 database, and the log entries for deliveries are flagged with &"*>"& rather
3992 Because &%-N%& discards any message to which it applies, only root or the Exim
3993 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3994 words, an ordinary user can use it only when supplying an incoming message to
3995 which it will apply. Although transportation never fails when &%-N%& is set, an
3996 address may be deferred because of a configuration problem on a transport, or a
3997 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3998 the message, and applies to any subsequent delivery attempts that may happen
4003 This option is interpreted by Sendmail to mean &"no aliasing"&.
4004 For normal modes of operation, it is ignored by Exim.
4005 When combined with &%-bP%& it suppresses the name of an option from being output.
4007 .vitem &%-O%&&~<&'data'&>
4009 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4012 .vitem &%-oA%&&~<&'file&~name'&>
4014 .cindex "Sendmail compatibility" "&%-oA%& option"
4015 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4016 alternative alias file name. Exim handles &%-bi%& differently; see the
4019 .vitem &%-oB%&&~<&'n'&>
4021 .cindex "SMTP" "passed connection"
4022 .cindex "SMTP" "multiple deliveries"
4023 .cindex "multiple SMTP deliveries"
4024 This is a debugging option which limits the maximum number of messages that can
4025 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4026 transport. If <&'n'&> is omitted, the limit is set to 1.
4030 .cindex "background delivery"
4031 .cindex "delivery" "in the background"
4032 This option applies to all modes in which Exim accepts incoming messages,
4033 including the listening daemon. It requests &"background"& delivery of such
4034 messages, which means that the accepting process automatically starts a
4035 delivery process for each message received, but does not wait for the delivery
4036 processes to finish.
4038 When all the messages have been received, the reception process exits,
4039 leaving the delivery processes to finish in their own time. The standard output
4040 and error streams are closed at the start of each delivery process.
4041 This is the default action if none of the &%-od%& options are present.
4043 If one of the queueing options in the configuration file
4044 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4045 overrides it if &%queue_only_override%& is set true, which is the default
4046 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4050 .cindex "foreground delivery"
4051 .cindex "delivery" "in the foreground"
4052 This option requests &"foreground"& (synchronous) delivery when Exim has
4053 accepted a locally-generated message. (For the daemon it is exactly the same as
4054 &%-odb%&.) A delivery process is automatically started to deliver the message,
4055 and Exim waits for it to complete before proceeding.
4057 The original Exim reception process does not finish until the delivery
4058 process for the final message has ended. The standard error stream is left open
4061 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4062 false and one of the queueing options in the configuration file is in effect.
4064 If there is a temporary delivery error during foreground delivery, the
4065 message is left on the queue for later delivery, and the original reception
4066 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4067 restricted configuration that never queues messages.
4072 This option is synonymous with &%-odf%&. It is provided for compatibility with
4077 .cindex "non-immediate delivery"
4078 .cindex "delivery" "suppressing immediate"
4079 .cindex "queueing incoming messages"
4080 This option applies to all modes in which Exim accepts incoming messages,
4081 including the listening daemon. It specifies that the accepting process should
4082 not automatically start a delivery process for each message received. Messages
4083 are placed on the queue, and remain there until a subsequent queue runner
4084 process encounters them. There are several configuration options (such as
4085 &%queue_only%&) that can be used to queue incoming messages under certain
4086 conditions. This option overrides all of them and also &%-odqs%&. It always
4091 .cindex "SMTP" "delaying delivery"
4092 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4093 However, like &%-odb%& and &%-odi%&, this option has no effect if
4094 &%queue_only_override%& is false and one of the queueing options in the
4095 configuration file is in effect.
4097 When &%-odqs%& does operate, a delivery process is started for each incoming
4098 message, in the background by default, but in the foreground if &%-odi%& is
4099 also present. The recipient addresses are routed, and local deliveries are done
4100 in the normal way. However, if any SMTP deliveries are required, they are not
4101 done at this time, so the message remains on the queue until a subsequent queue
4102 runner process encounters it. Because routing was done, Exim knows which
4103 messages are waiting for which hosts, and so a number of messages for the same
4104 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4105 configuration option has the same effect for specific domains. See also the
4110 .cindex "error" "reporting"
4111 If an error is detected while a non-SMTP message is being received (for
4112 example, a malformed address), the error is reported to the sender in a mail
4115 .cindex "return code" "for &%-oee%&"
4117 this error message is successfully sent, the Exim receiving process
4118 exits with a return code of zero. If not, the return code is 2 if the problem
4119 is that the original message has no recipients, or 1 for any other error.
4120 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4124 .cindex "error" "reporting"
4125 .cindex "return code" "for &%-oem%&"
4126 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4127 return code, whether or not the error message was successfully sent.
4128 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4132 .cindex "error" "reporting"
4133 If an error is detected while a non-SMTP message is being received, the
4134 error is reported by writing a message to the standard error file (stderr).
4135 .cindex "return code" "for &%-oep%&"
4136 The return code is 1 for all errors.
4140 .cindex "error" "reporting"
4141 This option is supported for compatibility with Sendmail, but has the same
4146 .cindex "error" "reporting"
4147 This option is supported for compatibility with Sendmail, but has the same
4152 .cindex "dot" "in incoming non-SMTP message"
4153 This option, which has the same effect as &%-i%&, specifies that a dot on a
4154 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4155 single dot does terminate, though Exim does no special processing for other
4156 lines that start with a dot. This option is set by default if Exim is called as
4157 &'rmail'&. See also &%-ti%&.
4160 .oindex "&%-oitrue%&"
4161 This option is treated as synonymous with &%-oi%&.
4163 .vitem &%-oMa%&&~<&'host&~address'&>
4165 .cindex "sender" "host address, specifying for local message"
4166 A number of options starting with &%-oM%& can be used to set values associated
4167 with remote hosts on locally-submitted messages (that is, messages not received
4168 over TCP/IP). These options can be used by any caller in conjunction with the
4169 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4170 other circumstances, they are ignored unless the caller is trusted.
4172 The &%-oMa%& option sets the sender host address. This may include a port
4173 number at the end, after a full stop (period). For example:
4175 exim -bs -oMa 10.9.8.7.1234
4177 An alternative syntax is to enclose the IP address in square brackets,
4178 followed by a colon and the port number:
4180 exim -bs -oMa [10.9.8.7]:1234
4182 The IP address is placed in the &$sender_host_address$& variable, and the
4183 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4184 are present on the command line, the sender host IP address is taken from
4185 whichever one is last.
4187 .vitem &%-oMaa%&&~<&'name'&>
4189 .cindex "authentication" "name, specifying for local message"
4190 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4191 option sets the value of &$sender_host_authenticated$& (the authenticator
4192 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4193 This option can be used with &%-bh%& and &%-bs%& to set up an
4194 authenticated SMTP session without actually using the SMTP AUTH command.
4196 .vitem &%-oMai%&&~<&'string'&>
4198 .cindex "authentication" "id, specifying for local message"
4199 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4200 option sets the value of &$authenticated_id$& (the id that was authenticated).
4201 This overrides the default value (the caller's login id, except with &%-bh%&,
4202 where there is no default) for messages from local sources. See chapter
4203 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4205 .vitem &%-oMas%&&~<&'address'&>
4207 .cindex "authentication" "sender, specifying for local message"
4208 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4209 option sets the authenticated sender value in &$authenticated_sender$&. It
4210 overrides the sender address that is created from the caller's login id for
4211 messages from local sources, except when &%-bh%& is used, when there is no
4212 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4213 specified on a MAIL command overrides this value. See chapter
4214 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4216 .vitem &%-oMi%&&~<&'interface&~address'&>
4218 .cindex "interface" "address, specifying for local message"
4219 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4220 option sets the IP interface address value. A port number may be included,
4221 using the same syntax as for &%-oMa%&. The interface address is placed in
4222 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4224 .vitem &%-oMr%&&~<&'protocol&~name'&>
4226 .cindex "protocol, specifying for local message"
4227 .vindex "&$received_protocol$&"
4228 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4229 option sets the received protocol value that is stored in
4230 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4231 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4232 SMTP protocol names (see the description of &$received_protocol$& in section
4233 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4234 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4237 .vitem &%-oMs%&&~<&'host&~name'&>
4239 .cindex "sender" "host name, specifying for local message"
4240 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4241 option sets the sender host name in &$sender_host_name$&. When this option is
4242 present, Exim does not attempt to look up a host name from an IP address; it
4243 uses the name it is given.
4245 .vitem &%-oMt%&&~<&'ident&~string'&>
4247 .cindex "sender" "ident string, specifying for local message"
4248 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4249 option sets the sender ident value in &$sender_ident$&. The default setting for
4250 local callers is the login id of the calling process, except when &%-bh%& is
4251 used, when there is no default.
4255 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4256 In Sendmail, this option means &"me too"&, indicating that the sender of a
4257 message should receive a copy of the message if the sender appears in an alias
4258 expansion. Exim always does this, so the option does nothing.
4262 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4263 This option is ignored. In Sendmail it specifies &"old style headers"&,
4264 whatever that means.
4266 .vitem &%-oP%&&~<&'path'&>
4268 .cindex "pid (process id)" "of daemon"
4269 .cindex "daemon" "process id (pid)"
4270 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4271 value. The option specifies the file to which the process id of the daemon is
4272 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4273 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4274 because in those cases, the normal pid file is not used.
4276 .vitem &%-or%&&~<&'time'&>
4278 .cindex "timeout" "for non-SMTP input"
4279 This option sets a timeout value for incoming non-SMTP messages. If it is not
4280 set, Exim will wait forever for the standard input. The value can also be set
4281 by the &%receive_timeout%& option. The format used for specifying times is
4282 described in section &<<SECTtimeformat>>&.
4284 .vitem &%-os%&&~<&'time'&>
4286 .cindex "timeout" "for SMTP input"
4287 .cindex "SMTP" "input timeout"
4288 This option sets a timeout value for incoming SMTP messages. The timeout
4289 applies to each SMTP command and block of data. The value can also be set by
4290 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4291 for specifying times is described in section &<<SECTtimeformat>>&.
4295 This option has exactly the same effect as &%-v%&.
4297 .vitem &%-oX%&&~<&'number&~or&~string'&>
4299 .cindex "TCP/IP" "setting listening ports"
4300 .cindex "TCP/IP" "setting listening interfaces"
4301 .cindex "port" "receiving TCP/IP"
4302 This option is relevant only when the &%-bd%& (start listening daemon) option
4303 is also given. It controls which ports and interfaces the daemon uses. Details
4304 of the syntax, and how it interacts with configuration file options, are given
4305 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4306 file is written unless &%-oP%& is also present to specify a pid file name.
4310 .cindex "Perl" "starting the interpreter"
4311 This option applies when an embedded Perl interpreter is linked with Exim (see
4312 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4313 option, forcing the starting of the interpreter to be delayed until it is
4318 .cindex "Perl" "starting the interpreter"
4319 This option applies when an embedded Perl interpreter is linked with Exim (see
4320 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4321 option, forcing the starting of the interpreter to occur as soon as Exim is
4324 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4326 For compatibility with Sendmail, this option is equivalent to
4328 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4330 It sets the incoming protocol and host name (for trusted callers). The
4331 host name and its colon can be omitted when only the protocol is to be set.
4332 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4333 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4334 or &`s`& using this option (but that does not seem a real limitation).
4338 .cindex "queue runner" "starting manually"
4339 This option is normally restricted to admin users. However, there is a
4340 configuration option called &%prod_requires_admin%& which can be set false to
4341 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4342 and &%-S%& options).
4344 .cindex "queue runner" "description of operation"
4345 The &%-q%& option starts one queue runner process. This scans the queue of
4346 waiting messages, and runs a delivery process for each one in turn. It waits
4347 for each delivery process to finish before starting the next one. A delivery
4348 process may not actually do any deliveries if the retry times for the addresses
4349 have not been reached. Use &%-qf%& (see below) if you want to override this.
4352 .cindex "SMTP" "passed connection"
4353 .cindex "SMTP" "multiple deliveries"
4354 .cindex "multiple SMTP deliveries"
4355 the delivery process spawns other processes to deliver other messages down
4356 passed SMTP connections, the queue runner waits for these to finish before
4359 When all the queued messages have been considered, the original queue runner
4360 process terminates. In other words, a single pass is made over the waiting
4361 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4362 this to be repeated periodically.
4364 Exim processes the waiting messages in an unpredictable order. It isn't very
4365 random, but it is likely to be different each time, which is all that matters.
4366 If one particular message screws up a remote MTA, other messages to the same
4367 MTA have a chance of getting through if they get tried first.
4369 It is possible to cause the messages to be processed in lexical message id
4370 order, which is essentially the order in which they arrived, by setting the
4371 &%queue_run_in_order%& option, but this is not recommended for normal use.
4373 .vitem &%-q%&<&'qflags'&>
4374 The &%-q%& option may be followed by one or more flag letters that change its
4375 behaviour. They are all optional, but if more than one is present, they must
4376 appear in the correct order. Each flag is described in a separate item below.
4380 .cindex "queue" "double scanning"
4381 .cindex "queue" "routing"
4382 .cindex "routing" "whole queue before delivery"
4383 An option starting with &%-qq%& requests a two-stage queue run. In the first
4384 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4385 every domain. Addresses are routed, local deliveries happen, but no remote
4388 .cindex "hints database" "remembering routing"
4389 The hints database that remembers which messages are waiting for specific hosts
4390 is updated, as if delivery to those hosts had been deferred. After this is
4391 complete, a second, normal queue scan happens, with routing and delivery taking
4392 place as normal. Messages that are routed to the same host should mostly be
4393 delivered down a single SMTP
4394 .cindex "SMTP" "passed connection"
4395 .cindex "SMTP" "multiple deliveries"
4396 .cindex "multiple SMTP deliveries"
4397 connection because of the hints that were set up during the first queue scan.
4398 This option may be useful for hosts that are connected to the Internet
4401 .vitem &%-q[q]i...%&
4403 .cindex "queue" "initial delivery"
4404 If the &'i'& flag is present, the queue runner runs delivery processes only for
4405 those messages that haven't previously been tried. (&'i'& stands for &"initial
4406 delivery"&.) This can be helpful if you are putting messages on the queue using
4407 &%-odq%& and want a queue runner just to process the new messages.
4409 .vitem &%-q[q][i]f...%&
4411 .cindex "queue" "forcing delivery"
4412 .cindex "delivery" "forcing in queue run"
4413 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4414 message, whereas without &'f'& only those non-frozen addresses that have passed
4415 their retry times are tried.
4417 .vitem &%-q[q][i]ff...%&
4419 .cindex "frozen messages" "forcing delivery"
4420 If &'ff'& is present, a delivery attempt is forced for every message, whether
4423 .vitem &%-q[q][i][f[f]]l%&
4425 .cindex "queue" "local deliveries only"
4426 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4427 be done. If a message requires any remote deliveries, it remains on the queue
4430 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4431 .cindex "queue" "delivering specific messages"
4432 When scanning the queue, Exim can be made to skip over messages whose ids are
4433 lexically less than a given value by following the &%-q%& option with a
4434 starting message id. For example:
4436 exim -q 0t5C6f-0000c8-00
4438 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4439 second message id is given, messages whose ids are lexically greater than it
4440 are also skipped. If the same id is given twice, for example,
4442 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4444 just one delivery process is started, for that message. This differs from
4445 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4446 that it counts as a delivery from a queue run. Note that the selection
4447 mechanism does not affect the order in which the messages are scanned. There
4448 are also other ways of selecting specific sets of messages for delivery in a
4449 queue run &-- see &%-R%& and &%-S%&.
4451 .vitem &%-q%&<&'qflags'&><&'time'&>
4452 .cindex "queue runner" "starting periodically"
4453 .cindex "periodic queue running"
4454 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4455 starting a queue runner process at intervals specified by the given time value
4456 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4457 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4458 single daemon process handles both functions. A common way of starting up a
4459 combined daemon at system boot time is to use a command such as
4461 /usr/exim/bin/exim -bd -q30m
4463 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4464 process every 30 minutes.
4466 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4467 pid file is written unless one is explicitly requested by the &%-oP%& option.
4469 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4471 This option is synonymous with &%-R%&. It is provided for Sendmail
4474 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4476 This option is synonymous with &%-S%&.
4478 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4480 .cindex "queue runner" "for specific recipients"
4481 .cindex "delivery" "to given domain"
4482 .cindex "domain" "delivery to"
4483 The <&'rsflags'&> may be empty, in which case the white space before the string
4484 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4485 which are the possible values for <&'rsflags'&>. White space is required if
4486 <&'rsflags'&> is not empty.
4488 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4489 perform a single queue run, except that, when scanning the messages on the
4490 queue, Exim processes only those that have at least one undelivered recipient
4491 address containing the given string, which is checked in a case-independent
4492 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4493 regular expression; otherwise it is a literal string.
4495 If you want to do periodic queue runs for messages with specific recipients,
4496 you can combine &%-R%& with &%-q%& and a time value. For example:
4498 exim -q25m -R @special.domain.example
4500 This example does a queue run for messages with recipients in the given domain
4501 every 25 minutes. Any additional flags that are specified with &%-q%& are
4502 applied to each queue run.
4504 Once a message is selected for delivery by this mechanism, all its addresses
4505 are processed. For the first selected message, Exim overrides any retry
4506 information and forces a delivery attempt for each undelivered address. This
4507 means that if delivery of any address in the first message is successful, any
4508 existing retry information is deleted, and so delivery attempts for that
4509 address in subsequently selected messages (which are processed without forcing)
4510 will run. However, if delivery of any address does not succeed, the retry
4511 information is updated, and in subsequently selected messages, the failing
4512 address will be skipped.
4514 .cindex "frozen messages" "forcing delivery"
4515 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4516 all selected messages, not just the first; frozen messages are included when
4519 The &%-R%& option makes it straightforward to initiate delivery of all messages
4520 to a given domain after a host has been down for some time. When the SMTP
4521 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4522 effect is to run Exim with the &%-R%& option, but it can be configured to run
4523 an arbitrary command instead.
4527 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4529 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4531 .cindex "delivery" "from given sender"
4532 .cindex "queue runner" "for specific senders"
4533 This option acts like &%-R%& except that it checks the string against each
4534 message's sender instead of against the recipients. If &%-R%& is also set, both
4535 conditions must be met for a message to be selected. If either of the options
4536 has &'f'& or &'ff'& in its flags, the associated action is taken.
4538 .vitem &%-Tqt%&&~<&'times'&>
4540 This is an option that is exclusively for use by the Exim testing suite. It is not
4541 recognized when Exim is run normally. It allows for the setting up of explicit
4542 &"queue times"& so that various warning/retry features can be tested.
4546 .cindex "recipient" "extracting from header lines"
4547 .cindex "&'Bcc:'& header line"
4548 .cindex "&'Cc:'& header line"
4549 .cindex "&'To:'& header line"
4550 When Exim is receiving a locally-generated, non-SMTP message on its standard
4551 input, the &%-t%& option causes the recipients of the message to be obtained
4552 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4553 from the command arguments. The addresses are extracted before any rewriting
4554 takes place and the &'Bcc:'& header line, if present, is then removed.
4556 .cindex "Sendmail compatibility" "&%-t%& option"
4557 If the command has any arguments, they specify addresses to which the message
4558 is &'not'& to be delivered. That is, the argument addresses are removed from
4559 the recipients list obtained from the headers. This is compatible with Smail 3
4560 and in accordance with the documented behaviour of several versions of
4561 Sendmail, as described in man pages on a number of operating systems (e.g.
4562 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4563 argument addresses to those obtained from the headers, and the O'Reilly
4564 Sendmail book documents it that way. Exim can be made to add argument addresses
4565 instead of subtracting them by setting the option
4566 &%extract_addresses_remove_arguments%& false.
4568 .cindex "&%Resent-%& header lines" "with &%-t%&"
4569 If there are any &%Resent-%& header lines in the message, Exim extracts
4570 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4571 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4572 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4573 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4575 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4576 message is resent several times). The RFC also specifies that they should be
4577 added at the front of the message, and separated by &'Received:'& lines. It is
4578 not at all clear how &%-t%& should operate in the present of multiple sets,
4579 nor indeed exactly what constitutes a &"set"&.
4580 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4581 are often added at the end of the header, and if a message is resent more than
4582 once, it is common for the original set of &%Resent-%& headers to be renamed as
4583 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4587 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4588 compatibility with Sendmail.
4590 .vitem &%-tls-on-connect%&
4591 .oindex "&%-tls-on-connect%&"
4592 .cindex "TLS" "use without STARTTLS"
4593 .cindex "TLS" "automatic start"
4594 This option is available when Exim is compiled with TLS support. It forces all
4595 incoming SMTP connections to behave as if the incoming port is listed in the
4596 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4597 &<<CHAPTLS>>& for further details.
4602 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4603 Sendmail uses this option for &"initial message submission"&, and its
4604 documentation states that in future releases, it may complain about
4605 syntactically invalid messages rather than fixing them when this flag is not
4606 set. Exim ignores this option.
4610 This option causes Exim to write information to the standard error stream,
4611 describing what it is doing. In particular, it shows the log lines for
4612 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4613 dialogue is shown. Some of the log lines shown may not actually be written to
4614 the log if the setting of &%log_selector%& discards them. Any relevant
4615 selectors are shown with each log line. If none are shown, the logging is
4620 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4621 National Language Support extended characters in the body of the mail item"&).
4622 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4625 .vitem &%-X%&&~<&'logfile'&>
4627 This option is interpreted by Sendmail to cause debug information to be sent
4628 to the named file. It is ignored by Exim.
4635 . ////////////////////////////////////////////////////////////////////////////
4636 . Insert a stylized DocBook comment here, to identify the end of the command
4637 . line options. This is for the benefit of the Perl script that automatically
4638 . creates a man page for the options.
4639 . ////////////////////////////////////////////////////////////////////////////
4642 <!-- === End of command line options === -->
4649 . ////////////////////////////////////////////////////////////////////////////
4650 . ////////////////////////////////////////////////////////////////////////////
4653 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4654 "The runtime configuration file"
4656 .cindex "run time configuration"
4657 .cindex "configuration file" "general description"
4658 .cindex "CONFIGURE_FILE"
4659 .cindex "configuration file" "errors in"
4660 .cindex "error" "in configuration file"
4661 .cindex "return code" "for bad configuration"
4662 Exim uses a single run time configuration file that is read whenever an Exim
4663 binary is executed. Note that in normal operation, this happens frequently,
4664 because Exim is designed to operate in a distributed manner, without central
4667 If a syntax error is detected while reading the configuration file, Exim
4668 writes a message on the standard error, and exits with a non-zero return code.
4669 The message is also written to the panic log. &*Note*&: Only simple syntax
4670 errors can be detected at this time. The values of any expanded options are
4671 not checked until the expansion happens, even when the expansion does not
4672 actually alter the string.
4674 The name of the configuration file is compiled into the binary for security
4675 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4676 most configurations, this specifies a single file. However, it is permitted to
4677 give a colon-separated list of file names, in which case Exim uses the first
4678 existing file in the list.
4681 .cindex "EXIM_GROUP"
4682 .cindex "CONFIGURE_OWNER"
4683 .cindex "CONFIGURE_GROUP"
4684 .cindex "configuration file" "ownership"
4685 .cindex "ownership" "configuration file"
4686 The run time configuration file must be owned by root or by the user that is
4687 specified at compile time by the CONFIGURE_OWNER option (if set). The
4688 configuration file must not be world-writeable, or group-writeable unless its
4689 group is the root group or the one specified at compile time by the
4690 CONFIGURE_GROUP option.
4692 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4693 to root, anybody who is able to edit the run time configuration file has an
4694 easy way to run commands as root. If you specify a user or group in the
4695 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4696 who are members of that group will trivially be able to obtain root privileges.
4698 Up to Exim version 4.72, the run time configuration file was also permitted to
4699 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4700 since it offered a simple privilege escalation for any attacker who managed to
4701 compromise the Exim user account.
4703 A default configuration file, which will work correctly in simple situations,
4704 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4705 defines just one file name, the installation process copies the default
4706 configuration to a new file of that name if it did not previously exist. If
4707 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4708 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4713 .section "Using a different configuration file" "SECID40"
4714 .cindex "configuration file" "alternate"
4715 A one-off alternate configuration can be specified by the &%-C%& command line
4716 option, which may specify a single file or a list of files. However, when
4717 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4718 unless the argument for &%-C%& is identical to the built-in value from
4719 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4720 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4721 is useful mainly for checking the syntax of configuration files before
4722 installing them. No owner or group checks are done on a configuration file
4723 specified by &%-C%&, if root privilege has been dropped.
4725 Even the Exim user is not trusted to specify an arbitrary configuration file
4726 with the &%-C%& option to be used with root privileges, unless that file is
4727 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4728 testing a configuration using &%-C%& right through message reception and
4729 delivery, even if the caller is root. The reception works, but by that time,
4730 Exim is running as the Exim user, so when it re-execs to regain privilege for
4731 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4732 can test reception and delivery using two separate commands (one to put a
4733 message on the queue, using &%-odq%&, and another to do the delivery, using
4736 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4737 prefix string with which any file named in a &%-C%& command line option must
4738 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4739 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4740 name can be used with &%-C%&.
4742 One-off changes to a configuration can be specified by the &%-D%& command line
4743 option, which defines and overrides values for macros used inside the
4744 configuration file. However, like &%-C%&, the use of this option by a
4745 non-privileged user causes Exim to discard its root privilege.
4746 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4747 completely disabled, and its use causes an immediate error exit.
4749 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4750 to declare certain macro names trusted, such that root privilege will not
4751 necessarily be discarded.
4752 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4753 considered safe and, if &%-D%& only supplies macros from this list, and the
4754 values are acceptable, then Exim will not give up root privilege if the caller
4755 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4756 transition mechanism and is expected to be removed in the future. Acceptable
4757 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4759 Some sites may wish to use the same Exim binary on different machines that
4760 share a file system, but to use different configuration files on each machine.
4761 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4762 looks for a file whose name is the configuration file name followed by a dot
4763 and the machine's node name, as obtained from the &[uname()]& function. If this
4764 file does not exist, the standard name is tried. This processing occurs for
4765 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4767 In some esoteric situations different versions of Exim may be run under
4768 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4769 help with this. See the comments in &_src/EDITME_& for details.
4773 .section "Configuration file format" "SECTconffilfor"
4774 .cindex "configuration file" "format of"
4775 .cindex "format" "configuration file"
4776 Exim's configuration file is divided into a number of different parts. General
4777 option settings must always appear at the start of the file. The other parts
4778 are all optional, and may appear in any order. Each part other than the first
4779 is introduced by the word &"begin"& followed by the name of the part. The
4783 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4786 .cindex "AUTH" "configuration"
4787 &'authenticators'&: Configuration settings for the authenticator drivers. These
4788 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4790 &'routers'&: Configuration settings for the router drivers. Routers process
4791 addresses and determine how the message is to be delivered (see chapters
4792 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4794 &'transports'&: Configuration settings for the transport drivers. Transports
4795 define mechanisms for copying messages to destinations (see chapters
4796 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4798 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4799 If there is no retry section, or if it is empty (that is, no retry rules are
4800 defined), Exim will not retry deliveries. In this situation, temporary errors
4801 are treated the same as permanent errors. Retry rules are discussed in chapter
4804 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4805 when new addresses are generated during delivery. Rewriting is discussed in
4806 chapter &<<CHAPrewrite>>&.
4808 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4809 want to use this feature, you must set
4811 LOCAL_SCAN_HAS_OPTIONS=yes
4813 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4814 facility are given in chapter &<<CHAPlocalscan>>&.
4817 .cindex "configuration file" "leading white space in"
4818 .cindex "configuration file" "trailing white space in"
4819 .cindex "white space" "in configuration file"
4820 Leading and trailing white space in configuration lines is always ignored.
4822 Blank lines in the file, and lines starting with a # character (ignoring
4823 leading white space) are treated as comments and are ignored. &*Note*&: A
4824 # character other than at the beginning of a line is not treated specially,
4825 and does not introduce a comment.
4827 Any non-comment line can be continued by ending it with a backslash. Note that
4828 the general rule for white space means that trailing white space after the
4829 backslash and leading white space at the start of continuation
4830 lines is ignored. Comment lines beginning with # (but not empty lines) may
4831 appear in the middle of a sequence of continuation lines.
4833 A convenient way to create a configuration file is to start from the
4834 default, which is supplied in &_src/configure.default_&, and add, delete, or
4835 change settings as required.
4837 The ACLs, retry rules, and rewriting rules have their own syntax which is
4838 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4839 respectively. The other parts of the configuration file have some syntactic
4840 items in common, and these are described below, from section &<<SECTcos>>&
4841 onwards. Before that, the inclusion, macro, and conditional facilities are
4846 .section "File inclusions in the configuration file" "SECID41"
4847 .cindex "inclusions in configuration file"
4848 .cindex "configuration file" "including other files"
4849 .cindex "&`.include`& in configuration file"
4850 .cindex "&`.include_if_exists`& in configuration file"
4851 You can include other files inside Exim's run time configuration file by
4854 &`.include`& <&'file name'&>
4855 &`.include_if_exists`& <&'file name'&>
4857 on a line by itself. Double quotes round the file name are optional. If you use
4858 the first form, a configuration error occurs if the file does not exist; the
4859 second form does nothing for non-existent files. In all cases, an absolute file
4862 Includes may be nested to any depth, but remember that Exim reads its
4863 configuration file often, so it is a good idea to keep them to a minimum.
4864 If you change the contents of an included file, you must HUP the daemon,
4865 because an included file is read only when the configuration itself is read.
4867 The processing of inclusions happens early, at a physical line level, so, like
4868 comment lines, an inclusion can be used in the middle of an option setting,
4871 hosts_lookup = a.b.c \
4874 Include processing happens after macro processing (see below). Its effect is to
4875 process the lines of the included file as if they occurred inline where the
4880 .section "Macros in the configuration file" "SECTmacrodefs"
4881 .cindex "macro" "description of"
4882 .cindex "configuration file" "macros"
4883 If a line in the main part of the configuration (that is, before the first
4884 &"begin"& line) begins with an upper case letter, it is taken as a macro
4885 definition, and must be of the form
4887 <&'name'&> = <&'rest of line'&>
4889 The name must consist of letters, digits, and underscores, and need not all be
4890 in upper case, though that is recommended. The rest of the line, including any
4891 continuations, is the replacement text, and has leading and trailing white
4892 space removed. Quotes are not removed. The replacement text can never end with
4893 a backslash character, but this doesn't seem to be a serious limitation.
4895 Macros may also be defined between router, transport, authenticator, or ACL
4896 definitions. They may not, however, be defined within an individual driver or
4897 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4899 .section "Macro substitution" "SECID42"
4900 Once a macro is defined, all subsequent lines in the file (and any included
4901 files) are scanned for the macro name; if there are several macros, the line is
4902 scanned for each in turn, in the order in which the macros are defined. The
4903 replacement text is not re-scanned for the current macro, though it is scanned
4904 for subsequently defined macros. For this reason, a macro name may not contain
4905 the name of a previously defined macro as a substring. You could, for example,
4908 &`ABCD_XYZ = `&<&'something'&>
4909 &`ABCD = `&<&'something else'&>
4911 but putting the definitions in the opposite order would provoke a configuration
4912 error. Macro expansion is applied to individual physical lines from the file,
4913 before checking for line continuation or file inclusion (see above). If a line
4914 consists solely of a macro name, and the expansion of the macro is empty, the
4915 line is ignored. A macro at the start of a line may turn the line into a
4916 comment line or a &`.include`& line.
4919 .section "Redefining macros" "SECID43"
4920 Once defined, the value of a macro can be redefined later in the configuration
4921 (or in an included file). Redefinition is specified by using &'=='& instead of
4926 MAC == updated value
4928 Redefinition does not alter the order in which the macros are applied to the
4929 subsequent lines of the configuration file. It is still the same order in which
4930 the macros were originally defined. All that changes is the macro's value.
4931 Redefinition makes it possible to accumulate values. For example:
4935 MAC == MAC and something added
4937 This can be helpful in situations where the configuration file is built
4938 from a number of other files.
4940 .section "Overriding macro values" "SECID44"
4941 The values set for macros in the configuration file can be overridden by the
4942 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4943 used, unless called by root or the Exim user. A definition on the command line
4944 using the &%-D%& option causes all definitions and redefinitions within the
4949 .section "Example of macro usage" "SECID45"
4950 As an example of macro usage, consider a configuration where aliases are looked
4951 up in a MySQL database. It helps to keep the file less cluttered if long
4952 strings such as SQL statements are defined separately as macros, for example:
4954 ALIAS_QUERY = select mailbox from user where \
4955 login='${quote_mysql:$local_part}';
4957 This can then be used in a &(redirect)& router setting like this:
4959 data = ${lookup mysql{ALIAS_QUERY}}
4961 In earlier versions of Exim macros were sometimes used for domain, host, or
4962 address lists. In Exim 4 these are handled better by named lists &-- see
4963 section &<<SECTnamedlists>>&.
4966 .section "Conditional skips in the configuration file" "SECID46"
4967 .cindex "configuration file" "conditional skips"
4968 .cindex "&`.ifdef`&"
4969 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4970 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4971 portions of the configuration file. The processing happens whenever the file is
4972 read (that is, when an Exim binary starts to run).
4974 The implementation is very simple. Instances of the first four directives must
4975 be followed by text that includes the names of one or macros. The condition
4976 that is tested is whether or not any macro substitution has taken place in the
4980 message_size_limit = 50M
4982 message_size_limit = 100M
4985 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4986 otherwise. If there is more than one macro named on the line, the condition
4987 is true if any of them are defined. That is, it is an &"or"& condition. To
4988 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4990 Although you can use a macro expansion to generate one of these directives,
4991 it is not very useful, because the condition &"there was a macro substitution
4992 in this line"& will always be true.
4994 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4995 to clarify complicated nestings.
4999 .section "Common option syntax" "SECTcos"
5000 .cindex "common option syntax"
5001 .cindex "syntax of common options"
5002 .cindex "configuration file" "common option syntax"
5003 For the main set of options, driver options, and &[local_scan()]& options,
5004 each setting is on a line by itself, and starts with a name consisting of
5005 lower-case letters and underscores. Many options require a data value, and in
5006 these cases the name must be followed by an equals sign (with optional white
5007 space) and then the value. For example:
5009 qualify_domain = mydomain.example.com
5011 .cindex "hiding configuration option values"
5012 .cindex "configuration options" "hiding value of"
5013 .cindex "options" "hiding value of"
5014 Some option settings may contain sensitive data, for example, passwords for
5015 accessing databases. To stop non-admin users from using the &%-bP%& command
5016 line option to read these values, you can precede the option settings with the
5017 word &"hide"&. For example:
5019 hide mysql_servers = localhost/users/admin/secret-password
5021 For non-admin users, such options are displayed like this:
5023 mysql_servers = <value not displayable>
5025 If &"hide"& is used on a driver option, it hides the value of that option on
5026 all instances of the same driver.
5028 The following sections describe the syntax used for the different data types
5029 that are found in option settings.
5032 .section "Boolean options" "SECID47"
5033 .cindex "format" "boolean"
5034 .cindex "boolean configuration values"
5035 .oindex "&%no_%&&'xxx'&"
5036 .oindex "&%not_%&&'xxx'&"
5037 Options whose type is given as boolean are on/off switches. There are two
5038 different ways of specifying such options: with and without a data value. If
5039 the option name is specified on its own without data, the switch is turned on;
5040 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5041 boolean options may be followed by an equals sign and one of the words
5042 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5043 the following two settings have exactly the same effect:
5048 The following two lines also have the same (opposite) effect:
5053 You can use whichever syntax you prefer.
5058 .section "Integer values" "SECID48"
5059 .cindex "integer configuration values"
5060 .cindex "format" "integer"
5061 If an option's type is given as &"integer"&, the value can be given in decimal,
5062 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5063 number is assumed. Otherwise, it is treated as an octal number unless it starts
5064 with the characters &"0x"&, in which case the remainder is interpreted as a
5067 If an integer value is followed by the letter K, it is multiplied by 1024; if
5068 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5069 of integer option settings are output, values which are an exact multiple of
5070 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5071 and M. The printing style is independent of the actual input format that was
5075 .section "Octal integer values" "SECID49"
5076 .cindex "integer format"
5077 .cindex "format" "octal integer"
5078 If an option's type is given as &"octal integer"&, its value is always
5079 interpreted as an octal number, whether or not it starts with the digit zero.
5080 Such options are always output in octal.
5083 .section "Fixed point numbers" "SECID50"
5084 .cindex "fixed point configuration values"
5085 .cindex "format" "fixed point"
5086 If an option's type is given as &"fixed-point"&, its value must be a decimal
5087 integer, optionally followed by a decimal point and up to three further digits.
5091 .section "Time intervals" "SECTtimeformat"
5092 .cindex "time interval" "specifying in configuration"
5093 .cindex "format" "time interval"
5094 A time interval is specified as a sequence of numbers, each followed by one of
5095 the following letters, with no intervening white space:
5105 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5106 intervals are output in the same format. Exim does not restrict the values; it
5107 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5111 .section "String values" "SECTstrings"
5112 .cindex "string" "format of configuration values"
5113 .cindex "format" "string"
5114 If an option's type is specified as &"string"&, the value can be specified with
5115 or without double-quotes. If it does not start with a double-quote, the value
5116 consists of the remainder of the line plus any continuation lines, starting at
5117 the first character after any leading white space, with trailing white space
5118 removed, and with no interpretation of the characters in the string. Because
5119 Exim removes comment lines (those beginning with #) at an early stage, they can
5120 appear in the middle of a multi-line string. The following two settings are
5121 therefore equivalent:
5123 trusted_users = uucp:mail
5124 trusted_users = uucp:\
5125 # This comment line is ignored
5128 .cindex "string" "quoted"
5129 .cindex "escape characters in quoted strings"
5130 If a string does start with a double-quote, it must end with a closing
5131 double-quote, and any backslash characters other than those used for line
5132 continuation are interpreted as escape characters, as follows:
5135 .irow &`\\`& "single backslash"
5136 .irow &`\n`& "newline"
5137 .irow &`\r`& "carriage return"
5139 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5140 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5144 If a backslash is followed by some other character, including a double-quote
5145 character, that character replaces the pair.
5147 Quoting is necessary only if you want to make use of the backslash escapes to
5148 insert special characters, or if you need to specify a value with leading or
5149 trailing spaces. These cases are rare, so quoting is almost never needed in
5150 current versions of Exim. In versions of Exim before 3.14, quoting was required
5151 in order to continue lines, so you may come across older configuration files
5152 and examples that apparently quote unnecessarily.
5155 .section "Expanded strings" "SECID51"
5156 .cindex "expansion" "definition of"
5157 Some strings in the configuration file are subjected to &'string expansion'&,
5158 by which means various parts of the string may be changed according to the
5159 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5160 is as just described; in particular, the handling of backslashes in quoted
5161 strings is done as part of the input process, before expansion takes place.
5162 However, backslash is also an escape character for the expander, so any
5163 backslashes that are required for that reason must be doubled if they are
5164 within a quoted configuration string.
5167 .section "User and group names" "SECID52"
5168 .cindex "user name" "format of"
5169 .cindex "format" "user name"
5170 .cindex "groups" "name format"
5171 .cindex "format" "group name"
5172 User and group names are specified as strings, using the syntax described
5173 above, but the strings are interpreted specially. A user or group name must
5174 either consist entirely of digits, or be a name that can be looked up using the
5175 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5178 .section "List construction" "SECTlistconstruct"
5179 .cindex "list" "syntax of in configuration"
5180 .cindex "format" "list item in configuration"
5181 .cindex "string" "list, definition of"
5182 The data for some configuration options is a list of items, with colon as the
5183 default separator. Many of these options are shown with type &"string list"& in
5184 the descriptions later in this document. Others are listed as &"domain list"&,
5185 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5186 are all the same; however, those other than &"string list"& are subject to
5187 particular kinds of interpretation, as described in chapter
5188 &<<CHAPdomhosaddlists>>&.
5190 In all these cases, the entire list is treated as a single string as far as the
5191 input syntax is concerned. The &%trusted_users%& setting in section
5192 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5193 in a list, it must be entered as two colons. Leading and trailing white space
5194 on each item in a list is ignored. This makes it possible to include items that
5195 start with a colon, and in particular, certain forms of IPv6 address. For
5198 local_interfaces = 127.0.0.1 : ::::1
5200 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5202 &*Note*&: Although leading and trailing white space is ignored in individual
5203 list items, it is not ignored when parsing the list. The space after the first
5204 colon in the example above is necessary. If it were not there, the list would
5205 be interpreted as the two items 127.0.0.1:: and 1.
5207 .section "Changing list separators" "SECID53"
5208 .cindex "list separator" "changing"
5209 .cindex "IPv6" "addresses in lists"
5210 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5211 introduced to allow the separator character to be changed. If a list begins
5212 with a left angle bracket, followed by any punctuation character, that
5213 character is used instead of colon as the list separator. For example, the list
5214 above can be rewritten to use a semicolon separator like this:
5216 local_interfaces = <; 127.0.0.1 ; ::1
5218 This facility applies to all lists, with the exception of the list in
5219 &%log_file_path%&. It is recommended that the use of non-colon separators be
5220 confined to circumstances where they really are needed.
5222 .cindex "list separator" "newline as"
5223 .cindex "newline" "as list separator"
5224 It is also possible to use newline and other control characters (those with
5225 code values less than 32, plus DEL) as separators in lists. Such separators
5226 must be provided literally at the time the list is processed. For options that
5227 are string-expanded, you can write the separator using a normal escape
5228 sequence. This will be processed by the expander before the string is
5229 interpreted as a list. For example, if a newline-separated list of domains is
5230 generated by a lookup, you can process it directly by a line such as this:
5232 domains = <\n ${lookup mysql{.....}}
5234 This avoids having to change the list separator in such data. You are unlikely
5235 to want to use a control character as a separator in an option that is not
5236 expanded, because the value is literal text. However, it can be done by giving
5237 the value in quotes. For example:
5239 local_interfaces = "<\n 127.0.0.1 \n ::1"
5241 Unlike printing character separators, which can be included in list items by
5242 doubling, it is not possible to include a control character as data when it is
5243 set as the separator. Two such characters in succession are interpreted as
5244 enclosing an empty list item.
5248 .section "Empty items in lists" "SECTempitelis"
5249 .cindex "list" "empty item in"
5250 An empty item at the end of a list is always ignored. In other words, trailing
5251 separator characters are ignored. Thus, the list in
5253 senders = user@domain :
5255 contains only a single item. If you want to include an empty string as one item
5256 in a list, it must not be the last item. For example, this list contains three
5257 items, the second of which is empty:
5259 senders = user1@domain : : user2@domain
5261 &*Note*&: There must be white space between the two colons, as otherwise they
5262 are interpreted as representing a single colon data character (and the list
5263 would then contain just one item). If you want to specify a list that contains
5264 just one, empty item, you can do it as in this example:
5268 In this case, the first item is empty, and the second is discarded because it
5269 is at the end of the list.
5274 .section "Format of driver configurations" "SECTfordricon"
5275 .cindex "drivers" "configuration format"
5276 There are separate parts in the configuration for defining routers, transports,
5277 and authenticators. In each part, you are defining a number of driver
5278 instances, each with its own set of options. Each driver instance is defined by
5279 a sequence of lines like this:
5281 <&'instance name'&>:
5286 In the following example, the instance name is &(localuser)&, and it is
5287 followed by three options settings:
5292 transport = local_delivery
5294 For each driver instance, you specify which Exim code module it uses &-- by the
5295 setting of the &%driver%& option &-- and (optionally) some configuration
5296 settings. For example, in the case of transports, if you want a transport to
5297 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5298 a local file you would use the &(appendfile)& driver. Each of the drivers is
5299 described in detail in its own separate chapter later in this manual.
5301 You can have several routers, transports, or authenticators that are based on
5302 the same underlying driver (each must have a different instance name).
5304 The order in which routers are defined is important, because addresses are
5305 passed to individual routers one by one, in order. The order in which
5306 transports are defined does not matter at all. The order in which
5307 authenticators are defined is used only when Exim, as a client, is searching
5308 them to find one that matches an authentication mechanism offered by the
5311 .cindex "generic options"
5312 .cindex "options" "generic &-- definition of"
5313 Within a driver instance definition, there are two kinds of option: &'generic'&
5314 and &'private'&. The generic options are those that apply to all drivers of the
5315 same type (that is, all routers, all transports or all authenticators). The
5316 &%driver%& option is a generic option that must appear in every definition.
5317 .cindex "private options"
5318 The private options are special for each driver, and none need appear, because
5319 they all have default values.
5321 The options may appear in any order, except that the &%driver%& option must
5322 precede any private options, since these depend on the particular driver. For
5323 this reason, it is recommended that &%driver%& always be the first option.
5325 Driver instance names, which are used for reference in log entries and
5326 elsewhere, can be any sequence of letters, digits, and underscores (starting
5327 with a letter) and must be unique among drivers of the same type. A router and
5328 a transport (for example) can each have the same name, but no two router
5329 instances can have the same name. The name of a driver instance should not be
5330 confused with the name of the underlying driver module. For example, the
5331 configuration lines:
5336 create an instance of the &(smtp)& transport driver whose name is
5337 &(remote_smtp)&. The same driver code can be used more than once, with
5338 different instance names and different option settings each time. A second
5339 instance of the &(smtp)& transport, with different options, might be defined
5345 command_timeout = 10s
5347 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5348 these transport instances from routers, and these names would appear in log
5351 Comment lines may be present in the middle of driver specifications. The full
5352 list of option settings for any particular driver instance, including all the
5353 defaulted values, can be extracted by making use of the &%-bP%& command line
5361 . ////////////////////////////////////////////////////////////////////////////
5362 . ////////////////////////////////////////////////////////////////////////////
5364 .chapter "The default configuration file" "CHAPdefconfil"
5365 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5366 .cindex "default" "configuration file &""walk through""&"
5367 The default configuration file supplied with Exim as &_src/configure.default_&
5368 is sufficient for a host with simple mail requirements. As an introduction to
5369 the way Exim is configured, this chapter &"walks through"& the default
5370 configuration, giving brief explanations of the settings. Detailed descriptions
5371 of the options are given in subsequent chapters. The default configuration file
5372 itself contains extensive comments about ways you might want to modify the
5373 initial settings. However, note that there are many options that are not
5374 mentioned at all in the default configuration.
5378 .section "Main configuration settings" "SECTdefconfmain"
5379 The main (global) configuration option settings must always come first in the
5380 file. The first thing you'll see in the file, after some initial comments, is
5383 # primary_hostname =
5385 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5386 to know the official, fully qualified name of your host, and this is where you
5387 can specify it. However, in most cases you do not need to set this option. When
5388 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5390 The first three non-comment configuration lines are as follows:
5392 domainlist local_domains = @
5393 domainlist relay_to_domains =
5394 hostlist relay_from_hosts = 127.0.0.1
5396 These are not, in fact, option settings. They are definitions of two named
5397 domain lists and one named host list. Exim allows you to give names to lists of
5398 domains, hosts, and email addresses, in order to make it easier to manage the
5399 configuration file (see section &<<SECTnamedlists>>&).
5401 The first line defines a domain list called &'local_domains'&; this is used
5402 later in the configuration to identify domains that are to be delivered
5405 .cindex "@ in a domain list"
5406 There is just one item in this list, the string &"@"&. This is a special form
5407 of entry which means &"the name of the local host"&. Thus, if the local host is
5408 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5409 be delivered locally. Because the local host's name is referenced indirectly,
5410 the same configuration file can be used on different hosts.
5412 The second line defines a domain list called &'relay_to_domains'&, but the
5413 list itself is empty. Later in the configuration we will come to the part that
5414 controls mail relaying through the local host; it allows relaying to any
5415 domains in this list. By default, therefore, no relaying on the basis of a mail
5416 domain is permitted.
5418 The third line defines a host list called &'relay_from_hosts'&. This list is
5419 used later in the configuration to permit relaying from any host or IP address
5420 that matches the list. The default contains just the IP address of the IPv4
5421 loopback interface, which means that processes on the local host are able to
5422 submit mail for relaying by sending it over TCP/IP to that interface. No other
5423 hosts are permitted to submit messages for relaying.
5425 Just to be sure there's no misunderstanding: at this point in the configuration
5426 we aren't actually setting up any controls. We are just defining some domains
5427 and hosts that will be used in the controls that are specified later.
5429 The next two configuration lines are genuine option settings:
5431 acl_smtp_rcpt = acl_check_rcpt
5432 acl_smtp_data = acl_check_data
5434 These options specify &'Access Control Lists'& (ACLs) that are to be used
5435 during an incoming SMTP session for every recipient of a message (every RCPT
5436 command), and after the contents of the message have been received,
5437 respectively. The names of the lists are &'acl_check_rcpt'& and
5438 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5439 section of the configuration. The RCPT ACL controls which recipients are
5440 accepted for an incoming message &-- if a configuration does not provide an ACL
5441 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5442 contents of a message to be checked.
5444 Two commented-out option settings are next:
5446 # av_scanner = clamd:/tmp/clamd
5447 # spamd_address = 127.0.0.1 783
5449 These are example settings that can be used when Exim is compiled with the
5450 content-scanning extension. The first specifies the interface to the virus
5451 scanner, and the second specifies the interface to SpamAssassin. Further
5452 details are given in chapter &<<CHAPexiscan>>&.
5454 Three more commented-out option settings follow:
5456 # tls_advertise_hosts = *
5457 # tls_certificate = /etc/ssl/exim.crt
5458 # tls_privatekey = /etc/ssl/exim.pem
5460 These are example settings that can be used when Exim is compiled with
5461 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5462 first one specifies the list of clients that are allowed to use TLS when
5463 connecting to this server; in this case the wildcard means all clients. The
5464 other options specify where Exim should find its TLS certificate and private
5465 key, which together prove the server's identity to any clients that connect.
5466 More details are given in chapter &<<CHAPTLS>>&.
5468 Another two commented-out option settings follow:
5470 # daemon_smtp_ports = 25 : 465 : 587
5471 # tls_on_connect_ports = 465
5473 .cindex "port" "465 and 587"
5474 .cindex "port" "for message submission"
5475 .cindex "message" "submission, ports for"
5476 .cindex "ssmtp protocol"
5477 .cindex "smtps protocol"
5478 .cindex "SMTP" "ssmtp protocol"
5479 .cindex "SMTP" "smtps protocol"
5480 These options provide better support for roaming users who wish to use this
5481 server for message submission. They are not much use unless you have turned on
5482 TLS (as described in the previous paragraph) and authentication (about which
5483 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5484 on end-user networks, so RFC 4409 specifies that message submission should use
5485 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5486 configured to use port 587 correctly, so these settings also enable the
5487 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5488 &<<SECTsupobssmt>>&).
5490 Two more commented-out options settings follow:
5493 # qualify_recipient =
5495 The first of these specifies a domain that Exim uses when it constructs a
5496 complete email address from a local login name. This is often needed when Exim
5497 receives a message from a local process. If you do not set &%qualify_domain%&,
5498 the value of &%primary_hostname%& is used. If you set both of these options,
5499 you can have different qualification domains for sender and recipient
5500 addresses. If you set only the first one, its value is used in both cases.
5502 .cindex "domain literal" "recognizing format"
5503 The following line must be uncommented if you want Exim to recognize
5504 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5505 (an IP address within square brackets) instead of a named domain.
5507 # allow_domain_literals
5509 The RFCs still require this form, but many people think that in the modern
5510 Internet it makes little sense to permit mail to be sent to specific hosts by
5511 quoting their IP addresses. This ancient format has been used by people who
5512 try to abuse hosts by using them for unwanted relaying. However, some
5513 people believe there are circumstances (for example, messages addressed to
5514 &'postmaster'&) where domain literals are still useful.
5516 The next configuration line is a kind of trigger guard:
5520 It specifies that no delivery must ever be run as the root user. The normal
5521 convention is to set up &'root'& as an alias for the system administrator. This
5522 setting is a guard against slips in the configuration.
5523 The list of users specified by &%never_users%& is not, however, the complete
5524 list; the build-time configuration in &_Local/Makefile_& has an option called
5525 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5526 contents of &%never_users%& are added to this list. By default
5527 FIXED_NEVER_USERS also specifies root.
5529 When a remote host connects to Exim in order to send mail, the only information
5530 Exim has about the host's identity is its IP address. The next configuration
5535 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5536 in order to get a host name. This improves the quality of the logging
5537 information, but if you feel it is too expensive, you can remove it entirely,
5538 or restrict the lookup to hosts on &"nearby"& networks.
5539 Note that it is not always possible to find a host name from an IP address,
5540 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5543 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5544 1413 (hence their names):
5547 rfc1413_query_timeout = 5s
5549 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5550 You can limit the hosts to which these calls are made, or change the timeout
5551 that is used. If you set the timeout to zero, all ident calls are disabled.
5552 Although they are cheap and can provide useful information for tracing problem
5553 messages, some hosts and firewalls have problems with ident calls. This can
5554 result in a timeout instead of an immediate refused connection, leading to
5555 delays on starting up an incoming SMTP session.
5557 When Exim receives messages over SMTP connections, it expects all addresses to
5558 be fully qualified with a domain, as required by the SMTP definition. However,
5559 if you are running a server to which simple clients submit messages, you may
5560 find that they send unqualified addresses. The two commented-out options:
5562 # sender_unqualified_hosts =
5563 # recipient_unqualified_hosts =
5565 show how you can specify hosts that are permitted to send unqualified sender
5566 and recipient addresses, respectively.
5568 The &%percent_hack_domains%& option is also commented out:
5570 # percent_hack_domains =
5572 It provides a list of domains for which the &"percent hack"& is to operate.
5573 This is an almost obsolete form of explicit email routing. If you do not know
5574 anything about it, you can safely ignore this topic.
5576 The last two settings in the main part of the default configuration are
5577 concerned with messages that have been &"frozen"& on Exim's queue. When a
5578 message is frozen, Exim no longer continues to try to deliver it. Freezing
5579 occurs when a bounce message encounters a permanent failure because the sender
5580 address of the original message that caused the bounce is invalid, so the
5581 bounce cannot be delivered. This is probably the most common case, but there
5582 are also other conditions that cause freezing, and frozen messages are not
5583 always bounce messages.
5585 ignore_bounce_errors_after = 2d
5586 timeout_frozen_after = 7d
5588 The first of these options specifies that failing bounce messages are to be
5589 discarded after 2 days on the queue. The second specifies that any frozen
5590 message (whether a bounce message or not) is to be timed out (and discarded)
5591 after a week. In this configuration, the first setting ensures that no failing
5592 bounce message ever lasts a week.
5596 .section "ACL configuration" "SECID54"
5597 .cindex "default" "ACLs"
5598 .cindex "&ACL;" "default configuration"
5599 In the default configuration, the ACL section follows the main configuration.
5600 It starts with the line
5604 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5605 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5606 and &%acl_smtp_data%& above.
5608 .cindex "RCPT" "ACL for"
5609 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5610 RCPT command specifies one of the message's recipients. The ACL statements
5611 are considered in order, until the recipient address is either accepted or
5612 rejected. The RCPT command is then accepted or rejected, according to the
5613 result of the ACL processing.
5617 This line, consisting of a name terminated by a colon, marks the start of the
5622 This ACL statement accepts the recipient if the sending host matches the list.
5623 But what does that strange list mean? It doesn't actually contain any host
5624 names or IP addresses. The presence of the colon puts an empty item in the
5625 list; Exim matches this only if the incoming message did not come from a remote
5626 host, because in that case, the remote hostname is empty. The colon is
5627 important. Without it, the list itself is empty, and can never match anything.
5629 What this statement is doing is to accept unconditionally all recipients in
5630 messages that are submitted by SMTP from local processes using the standard
5631 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5634 deny message = Restricted characters in address
5635 domains = +local_domains
5636 local_parts = ^[.] : ^.*[@%!/|]
5638 deny message = Restricted characters in address
5639 domains = !+local_domains
5640 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5642 These statements are concerned with local parts that contain any of the
5643 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5644 Although these characters are entirely legal in local parts (in the case of
5645 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5646 in Internet mail addresses.
5648 The first three have in the past been associated with explicitly routed
5649 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5650 option). Addresses containing these characters are regularly tried by spammers
5651 in an attempt to bypass relaying restrictions, and also by open relay testing
5652 programs. Unless you really need them it is safest to reject these characters
5653 at this early stage. This configuration is heavy-handed in rejecting these
5654 characters for all messages it accepts from remote hosts. This is a deliberate
5655 policy of being as safe as possible.
5657 The first rule above is stricter, and is applied to messages that are addressed
5658 to one of the local domains handled by this host. This is implemented by the
5659 first condition, which restricts it to domains that are listed in the
5660 &'local_domains'& domain list. The &"+"& character is used to indicate a
5661 reference to a named list. In this configuration, there is just one domain in
5662 &'local_domains'&, but in general there may be many.
5664 The second condition on the first statement uses two regular expressions to
5665 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5666 or &"|"&. If you have local accounts that include these characters, you will
5667 have to modify this rule.
5669 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5670 allows them because they have been encountered in practice. (Consider the
5671 common convention of local parts constructed as
5672 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5673 the author of Exim, who has no second initial.) However, a local part starting
5674 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5675 file name (for example, for a mailing list). This is also true for local parts
5676 that contain slashes. A pipe symbol can also be troublesome if the local part
5677 is incorporated unthinkingly into a shell command line.
5679 The second rule above applies to all other domains, and is less strict. This
5680 allows your own users to send outgoing messages to sites that use slashes
5681 and vertical bars in their local parts. It blocks local parts that begin
5682 with a dot, slash, or vertical bar, but allows these characters within the
5683 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5684 and &"!"& is blocked, as before. The motivation here is to prevent your users
5685 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5687 accept local_parts = postmaster
5688 domains = +local_domains
5690 This statement, which has two conditions, accepts an incoming address if the
5691 local part is &'postmaster'& and the domain is one of those listed in the
5692 &'local_domains'& domain list. The &"+"& character is used to indicate a
5693 reference to a named list. In this configuration, there is just one domain in
5694 &'local_domains'&, but in general there may be many.
5696 The presence of this statement means that mail to postmaster is never blocked
5697 by any of the subsequent tests. This can be helpful while sorting out problems
5698 in cases where the subsequent tests are incorrectly denying access.
5700 require verify = sender
5702 This statement requires the sender address to be verified before any subsequent
5703 ACL statement can be used. If verification fails, the incoming recipient
5704 address is refused. Verification consists of trying to route the address, to
5705 see if a bounce message could be delivered to it. In the case of remote
5706 addresses, basic verification checks only the domain, but &'callouts'& can be
5707 used for more verification if required. Section &<<SECTaddressverification>>&
5708 discusses the details of address verification.
5710 accept hosts = +relay_from_hosts
5711 control = submission
5713 This statement accepts the address if the message is coming from one of the
5714 hosts that are defined as being allowed to relay through this host. Recipient
5715 verification is omitted here, because in many cases the clients are dumb MUAs
5716 that do not cope well with SMTP error responses. For the same reason, the
5717 second line specifies &"submission mode"& for messages that are accepted. This
5718 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5719 messages that are deficient in some way, for example, because they lack a
5720 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5721 probably add recipient verification here, and disable submission mode.
5723 accept authenticated = *
5724 control = submission
5726 This statement accepts the address if the client host has authenticated itself.
5727 Submission mode is again specified, on the grounds that such messages are most
5728 likely to come from MUAs. The default configuration does not define any
5729 authenticators, though it does include some nearly complete commented-out
5730 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5731 fact authenticate until you complete the authenticator definitions.
5733 require message = relay not permitted
5734 domains = +local_domains : +relay_to_domains
5736 This statement rejects the address if its domain is neither a local domain nor
5737 one of the domains for which this host is a relay.
5739 require verify = recipient
5741 This statement requires the recipient address to be verified; if verification
5742 fails, the address is rejected.
5744 # deny message = rejected because $sender_host_address \
5745 # is in a black list at $dnslist_domain\n\
5747 # dnslists = black.list.example
5749 # warn dnslists = black.list.example
5750 # add_header = X-Warning: $sender_host_address is in \
5751 # a black list at $dnslist_domain
5752 # log_message = found in $dnslist_domain
5754 These commented-out lines are examples of how you could configure Exim to check
5755 sending hosts against a DNS black list. The first statement rejects messages
5756 from blacklisted hosts, whereas the second just inserts a warning header
5759 # require verify = csa
5761 This commented-out line is an example of how you could turn on client SMTP
5762 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5767 The final statement in the first ACL unconditionally accepts any recipient
5768 address that has successfully passed all the previous tests.
5772 This line marks the start of the second ACL, and names it. Most of the contents
5773 of this ACL are commented out:
5776 # message = This message contains a virus \
5779 These lines are examples of how to arrange for messages to be scanned for
5780 viruses when Exim has been compiled with the content-scanning extension, and a
5781 suitable virus scanner is installed. If the message is found to contain a
5782 virus, it is rejected with the given custom error message.
5784 # warn spam = nobody
5785 # message = X-Spam_score: $spam_score\n\
5786 # X-Spam_score_int: $spam_score_int\n\
5787 # X-Spam_bar: $spam_bar\n\
5788 # X-Spam_report: $spam_report
5790 These lines are an example of how to arrange for messages to be scanned by
5791 SpamAssassin when Exim has been compiled with the content-scanning extension,
5792 and SpamAssassin has been installed. The SpamAssassin check is run with
5793 &`nobody`& as its user parameter, and the results are added to the message as a
5794 series of extra header line. In this case, the message is not rejected,
5795 whatever the spam score.
5799 This final line in the DATA ACL accepts the message unconditionally.
5802 .section "Router configuration" "SECID55"
5803 .cindex "default" "routers"
5804 .cindex "routers" "default"
5805 The router configuration comes next in the default configuration, introduced
5810 Routers are the modules in Exim that make decisions about where to send
5811 messages. An address is passed to each router in turn, until it is either
5812 accepted, or failed. This means that the order in which you define the routers
5813 matters. Each router is fully described in its own chapter later in this
5814 manual. Here we give only brief overviews.
5817 # driver = ipliteral
5818 # domains = !+local_domains
5819 # transport = remote_smtp
5821 .cindex "domain literal" "default router"
5822 This router is commented out because the majority of sites do not want to
5823 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5824 you uncomment this router, you also need to uncomment the setting of
5825 &%allow_domain_literals%& in the main part of the configuration.
5829 domains = ! +local_domains
5830 transport = remote_smtp
5831 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5834 The first uncommented router handles addresses that do not involve any local
5835 domains. This is specified by the line
5837 domains = ! +local_domains
5839 The &%domains%& option lists the domains to which this router applies, but the
5840 exclamation mark is a negation sign, so the router is used only for domains
5841 that are not in the domain list called &'local_domains'& (which was defined at
5842 the start of the configuration). The plus sign before &'local_domains'&
5843 indicates that it is referring to a named list. Addresses in other domains are
5844 passed on to the following routers.
5846 The name of the router driver is &(dnslookup)&,
5847 and is specified by the &%driver%& option. Do not be confused by the fact that
5848 the name of this router instance is the same as the name of the driver. The
5849 instance name is arbitrary, but the name set in the &%driver%& option must be
5850 one of the driver modules that is in the Exim binary.
5852 The &(dnslookup)& router routes addresses by looking up their domains in the
5853 DNS in order to obtain a list of hosts to which the address is routed. If the
5854 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5855 specified by the &%transport%& option. If the router does not find the domain
5856 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5857 the address fails and is bounced.
5859 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5860 be entirely ignored. This option is present because a number of cases have been
5861 encountered where MX records in the DNS point to host names
5862 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5863 Completely ignoring these IP addresses causes Exim to fail to route the
5864 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5865 continue to try to deliver the message periodically until the address timed
5872 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5874 file_transport = address_file
5875 pipe_transport = address_pipe
5877 Control reaches this and subsequent routers only for addresses in the local
5878 domains. This router checks to see whether the local part is defined as an
5879 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5880 data that it looks up from that file. If no data is found for the local part,
5881 the value of the &%data%& option is empty, causing the address to be passed to
5884 &_/etc/aliases_& is a conventional name for the system aliases file that is
5885 often used. That is why it is referenced by from the default configuration
5886 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5887 &_Local/Makefile_& before building Exim.
5892 # local_part_suffix = +* : -*
5893 # local_part_suffix_optional
5894 file = $home/.forward
5899 file_transport = address_file
5900 pipe_transport = address_pipe
5901 reply_transport = address_reply
5903 This is the most complicated router in the default configuration. It is another
5904 redirection router, but this time it is looking for forwarding data set up by
5905 individual users. The &%check_local_user%& setting specifies a check that the
5906 local part of the address is the login name of a local user. If it is not, the
5907 router is skipped. The two commented options that follow &%check_local_user%&,
5910 # local_part_suffix = +* : -*
5911 # local_part_suffix_optional
5913 .vindex "&$local_part_suffix$&"
5914 show how you can specify the recognition of local part suffixes. If the first
5915 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5916 by any sequence of characters, is removed from the local part and placed in the
5917 variable &$local_part_suffix$&. The second suffix option specifies that the
5918 presence of a suffix in the local part is optional. When a suffix is present,
5919 the check for a local login uses the local part with the suffix removed.
5921 When a local user account is found, the file called &_.forward_& in the user's
5922 home directory is consulted. If it does not exist, or is empty, the router
5923 declines. Otherwise, the contents of &_.forward_& are interpreted as
5924 redirection data (see chapter &<<CHAPredirect>>& for more details).
5926 .cindex "Sieve filter" "enabling in default router"
5927 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5928 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5929 is commented out by default), the contents of the file are interpreted as a set
5930 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5931 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5932 separate document entitled &'Exim's interfaces to mail filtering'&.
5934 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5935 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5936 There are two reasons for doing this:
5939 Whether or not a local user has a &_.forward_& file is not really relevant when
5940 checking an address for validity; it makes sense not to waste resources doing
5943 More importantly, when Exim is verifying addresses or handling an EXPN
5944 command during an SMTP session, it is running as the Exim user, not as root.
5945 The group is the Exim group, and no additional groups are set up.
5946 It may therefore not be possible for Exim to read users' &_.forward_& files at
5950 The setting of &%check_ancestor%& prevents the router from generating a new
5951 address that is the same as any previous address that was redirected. (This
5952 works round a problem concerning a bad interaction between aliasing and
5953 forwarding &-- see section &<<SECTredlocmai>>&).
5955 The final three option settings specify the transports that are to be used when
5956 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5957 auto-reply, respectively. For example, if a &_.forward_& file contains
5959 a.nother@elsewhere.example, /home/spqr/archive
5961 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5967 # local_part_suffix = +* : -*
5968 # local_part_suffix_optional
5969 transport = local_delivery
5971 The final router sets up delivery into local mailboxes, provided that the local
5972 part is the name of a local login, by accepting the address and assigning it to
5973 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5974 routers, so the address is bounced. The commented suffix settings fulfil the
5975 same purpose as they do for the &(userforward)& router.
5978 .section "Transport configuration" "SECID56"
5979 .cindex "default" "transports"
5980 .cindex "transports" "default"
5981 Transports define mechanisms for actually delivering messages. They operate
5982 only when referenced from routers, so the order in which they are defined does
5983 not matter. The transports section of the configuration starts with
5987 One remote transport and four local transports are defined.
5992 This transport is used for delivering messages over SMTP connections. All its
5993 options are defaulted. The list of remote hosts comes from the router.
5997 file = /var/mail/$local_part
6004 This &(appendfile)& transport is used for local delivery to user mailboxes in
6005 traditional BSD mailbox format. By default it runs under the uid and gid of the
6006 local user, which requires the sticky bit to be set on the &_/var/mail_&
6007 directory. Some systems use the alternative approach of running mail deliveries
6008 under a particular group instead of using the sticky bit. The commented options
6009 show how this can be done.
6011 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6012 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6013 similarly-named options above.
6019 This transport is used for handling deliveries to pipes that are generated by
6020 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6021 option specifies that any output generated by the pipe is to be returned to the
6030 This transport is used for handling deliveries to files that are generated by
6031 redirection. The name of the file is not specified in this instance of
6032 &(appendfile)&, because it comes from the &(redirect)& router.
6037 This transport is used for handling automatic replies generated by users'
6042 .section "Default retry rule" "SECID57"
6043 .cindex "retry" "default rule"
6044 .cindex "default" "retry rule"
6045 The retry section of the configuration file contains rules which affect the way
6046 Exim retries deliveries that cannot be completed at the first attempt. It is
6047 introduced by the line
6051 In the default configuration, there is just one rule, which applies to all
6054 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6056 This causes any temporarily failing address to be retried every 15 minutes for
6057 2 hours, then at intervals starting at one hour and increasing by a factor of
6058 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6059 is not delivered after 4 days of temporary failure, it is bounced.
6061 If the retry section is removed from the configuration, or is empty (that is,
6062 if no retry rules are defined), Exim will not retry deliveries. This turns
6063 temporary errors into permanent errors.
6066 .section "Rewriting configuration" "SECID58"
6067 The rewriting section of the configuration, introduced by
6071 contains rules for rewriting addresses in messages as they arrive. There are no
6072 rewriting rules in the default configuration file.
6076 .section "Authenticators configuration" "SECTdefconfauth"
6077 .cindex "AUTH" "configuration"
6078 The authenticators section of the configuration, introduced by
6080 begin authenticators
6082 defines mechanisms for the use of the SMTP AUTH command. The default
6083 configuration file contains two commented-out example authenticators
6084 which support plaintext username/password authentication using the
6085 standard PLAIN mechanism and the traditional but non-standard LOGIN
6086 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6087 to support most MUA software.
6089 The example PLAIN authenticator looks like this:
6092 # driver = plaintext
6093 # server_set_id = $auth2
6094 # server_prompts = :
6095 # server_condition = Authentication is not yet configured
6096 # server_advertise_condition = ${if def:tls_in_cipher }
6098 And the example LOGIN authenticator looks like this:
6101 # driver = plaintext
6102 # server_set_id = $auth1
6103 # server_prompts = <| Username: | Password:
6104 # server_condition = Authentication is not yet configured
6105 # server_advertise_condition = ${if def:tls_in_cipher }
6108 The &%server_set_id%& option makes Exim remember the authenticated username
6109 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6110 &%server_prompts%& option configures the &(plaintext)& authenticator so
6111 that it implements the details of the specific authentication mechanism,
6112 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6113 when Exim offers authentication to clients; in the examples, this is only
6114 when TLS or SSL has been started, so to enable the authenticators you also
6115 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6117 The &%server_condition%& setting defines how to verify that the username and
6118 password are correct. In the examples it just produces an error message.
6119 To make the authenticators work, you can use a string expansion
6120 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6122 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6123 usercode and password are in different positions.
6124 Chapter &<<CHAPplaintext>>& covers both.
6126 .ecindex IIDconfiwal
6130 . ////////////////////////////////////////////////////////////////////////////
6131 . ////////////////////////////////////////////////////////////////////////////
6133 .chapter "Regular expressions" "CHAPregexp"
6135 .cindex "regular expressions" "library"
6137 Exim supports the use of regular expressions in many of its options. It
6138 uses the PCRE regular expression library; this provides regular expression
6139 matching that is compatible with Perl 5. The syntax and semantics of
6140 regular expressions is discussed in many Perl reference books, and also in
6141 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6142 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6144 The documentation for the syntax and semantics of the regular expressions that
6145 are supported by PCRE is included in the PCRE distribution, and no further
6146 description is included here. The PCRE functions are called from Exim using
6147 the default option settings (that is, with no PCRE options set), except that
6148 the PCRE_CASELESS option is set when the matching is required to be
6151 In most cases, when a regular expression is required in an Exim configuration,
6152 it has to start with a circumflex, in order to distinguish it from plain text
6153 or an &"ends with"& wildcard. In this example of a configuration setting, the
6154 second item in the colon-separated list is a regular expression.
6156 domains = a.b.c : ^\\d{3} : *.y.z : ...
6158 The doubling of the backslash is required because of string expansion that
6159 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6160 of this issue, and a way of avoiding the need for doubling backslashes. The
6161 regular expression that is eventually used in this example contains just one
6162 backslash. The circumflex is included in the regular expression, and has the
6163 normal effect of &"anchoring"& it to the start of the string that is being
6166 There are, however, two cases where a circumflex is not required for the
6167 recognition of a regular expression: these are the &%match%& condition in a
6168 string expansion, and the &%matches%& condition in an Exim filter file. In
6169 these cases, the relevant string is always treated as a regular expression; if
6170 it does not start with a circumflex, the expression is not anchored, and can
6171 match anywhere in the subject string.
6173 In all cases, if you want a regular expression to match at the end of a string,
6174 you must code the $ metacharacter to indicate this. For example:
6176 domains = ^\\d{3}\\.example
6178 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6181 domains = ^\\d{3}\\.example\$
6183 if you want &'example'& to be the top-level domain. The backslash before the
6184 $ is needed because string expansion also interprets dollar characters.
6188 . ////////////////////////////////////////////////////////////////////////////
6189 . ////////////////////////////////////////////////////////////////////////////
6191 .chapter "File and database lookups" "CHAPfdlookup"
6192 .scindex IIDfidalo1 "file" "lookups"
6193 .scindex IIDfidalo2 "database" "lookups"
6194 .cindex "lookup" "description of"
6195 Exim can be configured to look up data in files or databases as it processes
6196 messages. Two different kinds of syntax are used:
6199 A string that is to be expanded may contain explicit lookup requests. These
6200 cause parts of the string to be replaced by data that is obtained from the
6201 lookup. Lookups of this type are conditional expansion items. Different results
6202 can be defined for the cases of lookup success and failure. See chapter
6203 &<<CHAPexpand>>&, where string expansions are described in detail.
6205 Lists of domains, hosts, and email addresses can contain lookup requests as a
6206 way of avoiding excessively long linear lists. In this case, the data that is
6207 returned by the lookup is often (but not always) discarded; whether the lookup
6208 succeeds or fails is what really counts. These kinds of list are described in
6209 chapter &<<CHAPdomhosaddlists>>&.
6212 String expansions, lists, and lookups interact with each other in such a way
6213 that there is no order in which to describe any one of them that does not
6214 involve references to the others. Each of these three chapters makes more sense
6215 if you have read the other two first. If you are reading this for the first
6216 time, be aware that some of it will make a lot more sense after you have read
6217 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6219 .section "Examples of different lookup syntax" "SECID60"
6220 It is easy to confuse the two different kinds of lookup, especially as the
6221 lists that may contain the second kind are always expanded before being
6222 processed as lists. Therefore, they may also contain lookups of the first kind.
6223 Be careful to distinguish between the following two examples:
6225 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6226 domains = lsearch;/some/file
6228 The first uses a string expansion, the result of which must be a domain list.
6229 No strings have been specified for a successful or a failing lookup; the
6230 defaults in this case are the looked-up data and an empty string, respectively.
6231 The expansion takes place before the string is processed as a list, and the
6232 file that is searched could contain lines like this:
6234 192.168.3.4: domain1:domain2:...
6235 192.168.1.9: domain3:domain4:...
6237 When the lookup succeeds, the result of the expansion is a list of domains (and
6238 possibly other types of item that are allowed in domain lists).
6240 In the second example, the lookup is a single item in a domain list. It causes
6241 Exim to use a lookup to see if the domain that is being processed can be found
6242 in the file. The file could contains lines like this:
6247 Any data that follows the keys is not relevant when checking that the domain
6248 matches the list item.
6250 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6251 Consider a file containing lines like this:
6253 192.168.5.6: lsearch;/another/file
6255 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6256 first &%domains%& setting above generates the second setting, which therefore
6257 causes a second lookup to occur.
6259 The rest of this chapter describes the different lookup types that are
6260 available. Any of them can be used in any part of the configuration where a
6261 lookup is permitted.
6264 .section "Lookup types" "SECID61"
6265 .cindex "lookup" "types of"
6266 .cindex "single-key lookup" "definition of"
6267 Two different types of data lookup are implemented:
6270 The &'single-key'& type requires the specification of a file in which to look,
6271 and a single key to search for. The key must be a non-empty string for the
6272 lookup to succeed. The lookup type determines how the file is searched.
6274 .cindex "query-style lookup" "definition of"
6275 The &'query-style'& type accepts a generalized database query. No particular
6276 key value is assumed by Exim for query-style lookups. You can use whichever
6277 Exim variables you need to construct the database query.
6280 The code for each lookup type is in a separate source file that is included in
6281 the binary of Exim only if the corresponding compile-time option is set. The
6282 default settings in &_src/EDITME_& are:
6287 which means that only linear searching and DBM lookups are included by default.
6288 For some types of lookup (e.g. SQL databases), you need to install appropriate
6289 libraries and header files before building Exim.
6294 .section "Single-key lookup types" "SECTsinglekeylookups"
6295 .cindex "lookup" "single-key types"
6296 .cindex "single-key lookup" "list of types"
6297 The following single-key lookup types are implemented:
6300 .cindex "cdb" "description of"
6301 .cindex "lookup" "cdb"
6302 .cindex "binary zero" "in lookup key"
6303 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6304 string without a terminating binary zero. The cdb format is designed for
6305 indexed files that are read frequently and never updated, except by total
6306 re-creation. As such, it is particularly suitable for large files containing
6307 aliases or other indexed data referenced by an MTA. Information about cdb can
6308 be found in several places:
6310 &url(http://www.pobox.com/~djb/cdb.html)
6311 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6312 &url(http://packages.debian.org/stable/utils/freecdb.html)
6314 A cdb distribution is not needed in order to build Exim with cdb support,
6315 because the code for reading cdb files is included directly in Exim itself.
6316 However, no means of building or testing cdb files is provided with Exim, so
6317 you need to obtain a cdb distribution in order to do this.
6319 .cindex "DBM" "lookup type"
6320 .cindex "lookup" "dbm"
6321 .cindex "binary zero" "in lookup key"
6322 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6323 DBM file by looking up the record with the given key. A terminating binary
6324 zero is included in the key that is passed to the DBM library. See section
6325 &<<SECTdb>>& for a discussion of DBM libraries.
6327 .cindex "Berkeley DB library" "file format"
6328 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6329 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6330 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6331 the DB_UNKNOWN option. This enables it to handle any of the types of database
6332 that the library supports, and can be useful for accessing DBM files created by
6333 other applications. (For earlier DB versions, DB_HASH is always used.)
6335 .cindex "lookup" "dbmjz"
6336 .cindex "lookup" "dbm &-- embedded NULs"
6338 .cindex "dbmjz lookup type"
6339 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6340 interpreted as an Exim list; the elements of the list are joined together with
6341 ASCII NUL characters to form the lookup key. An example usage would be to
6342 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6343 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6344 &(cram_md5)& authenticator.
6346 .cindex "lookup" "dbmnz"
6347 .cindex "lookup" "dbm &-- terminating zero"
6348 .cindex "binary zero" "in lookup key"
6350 .cindex "&_/etc/userdbshadow.dat_&"
6351 .cindex "dbmnz lookup type"
6352 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6353 is not included in the key that is passed to the DBM library. You may need this
6354 if you want to look up data in files that are created by or shared with some
6355 other application that does not use terminating zeros. For example, you need to
6356 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6357 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6358 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6359 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6361 .cindex "lookup" "dsearch"
6362 .cindex "dsearch lookup type"
6363 &(dsearch)&: The given file must be a directory; this is searched for an entry
6364 whose name is the key by calling the &[lstat()]& function. The key may not
6365 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6366 the lookup is the name of the entry, which may be a file, directory,
6367 symbolic link, or any other kind of directory entry. An example of how this
6368 lookup can be used to support virtual domains is given in section
6369 &<<SECTvirtualdomains>>&.
6371 .cindex "lookup" "iplsearch"
6372 .cindex "iplsearch lookup type"
6373 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6374 terminated by a colon or white space or the end of the line. The keys in the
6375 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6376 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6377 being interpreted as a key terminator. For example:
6379 1.2.3.4: data for 1.2.3.4
6380 192.168.0.0/16: data for 192.168.0.0/16
6381 "abcd::cdab": data for abcd::cdab
6382 "abcd:abcd::/32" data for abcd:abcd::/32
6384 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6385 file is searched linearly, using the CIDR masks where present, until a matching
6386 key is found. The first key that matches is used; there is no attempt to find a
6387 &"best"& match. Apart from the way the keys are matched, the processing for
6388 &(iplsearch)& is the same as for &(lsearch)&.
6390 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6391 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6392 lookup types support only literal keys.
6394 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6395 the implicit key is the host's IP address rather than its name (see section
6396 &<<SECThoslispatsikey>>&).
6398 .cindex "linear search"
6399 .cindex "lookup" "lsearch"
6400 .cindex "lsearch lookup type"
6401 .cindex "case sensitivity" "in lsearch lookup"
6402 &(lsearch)&: The given file is a text file that is searched linearly for a
6403 line beginning with the search key, terminated by a colon or white space or the
6404 end of the line. The search is case-insensitive; that is, upper and lower case
6405 letters are treated as the same. The first occurrence of the key that is found
6406 in the file is used.
6408 White space between the key and the colon is permitted. The remainder of the
6409 line, with leading and trailing white space removed, is the data. This can be
6410 continued onto subsequent lines by starting them with any amount of white
6411 space, but only a single space character is included in the data at such a
6412 junction. If the data begins with a colon, the key must be terminated by a
6417 Empty lines and lines beginning with # are ignored, even if they occur in the
6418 middle of an item. This is the traditional textual format of alias files. Note
6419 that the keys in an &(lsearch)& file are literal strings. There is no
6420 wildcarding of any kind.
6422 .cindex "lookup" "lsearch &-- colons in keys"
6423 .cindex "white space" "in lsearch key"
6424 In most &(lsearch)& files, keys are not required to contain colons or #
6425 characters, or white space. However, if you need this feature, it is available.
6426 If a key begins with a doublequote character, it is terminated only by a
6427 matching quote (or end of line), and the normal escaping rules apply to its
6428 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6429 quoted keys (exactly as for unquoted keys). There is no special handling of
6430 quotes for the data part of an &(lsearch)& line.
6433 .cindex "NIS lookup type"
6434 .cindex "lookup" "NIS"
6435 .cindex "binary zero" "in lookup key"
6436 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6437 the given key, without a terminating binary zero. There is a variant called
6438 &(nis0)& which does include the terminating binary zero in the key. This is
6439 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6440 aliases; the full map names must be used.
6443 .cindex "wildlsearch lookup type"
6444 .cindex "lookup" "wildlsearch"
6445 .cindex "nwildlsearch lookup type"
6446 .cindex "lookup" "nwildlsearch"
6447 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6448 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6449 the file may be wildcarded. The difference between these two lookup types is
6450 that for &(wildlsearch)&, each key in the file is string-expanded before being
6451 used, whereas for &(nwildlsearch)&, no expansion takes place.
6453 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6454 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6455 file that are regular expressions can be made case-sensitive by the use of
6456 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6458 . ==== As this is a nested list, any displays it contains must be indented
6459 . ==== as otherwise they are too far to the left.
6462 The string may begin with an asterisk to mean &"ends with"&. For example:
6464 *.a.b.c data for anything.a.b.c
6465 *fish data for anythingfish
6468 The string may begin with a circumflex to indicate a regular expression. For
6469 example, for &(wildlsearch)&:
6471 ^\N\d+\.a\.b\N data for <digits>.a.b
6473 Note the use of &`\N`& to disable expansion of the contents of the regular
6474 expression. If you are using &(nwildlsearch)&, where the keys are not
6475 string-expanded, the equivalent entry is:
6477 ^\d+\.a\.b data for <digits>.a.b
6479 The case-insensitive flag is set at the start of compiling the regular
6480 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6481 For example, to make the entire pattern case-sensitive:
6483 ^(?-i)\d+\.a\.b data for <digits>.a.b
6486 If the regular expression contains white space or colon characters, you must
6487 either quote it (see &(lsearch)& above), or represent these characters in other
6488 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6489 colon. This may be easier than quoting, because if you quote, you have to
6490 escape all the backslashes inside the quotes.
6492 &*Note*&: It is not possible to capture substrings in a regular expression
6493 match for later use, because the results of all lookups are cached. If a lookup
6494 is repeated, the result is taken from the cache, and no actual pattern matching
6495 takes place. The values of all the numeric variables are unset after a
6496 &((n)wildlsearch)& match.
6499 Although I cannot see it being of much use, the general matching function that
6500 is used to implement &((n)wildlsearch)& means that the string may begin with a
6501 lookup name terminated by a semicolon, and followed by lookup data. For
6504 cdb;/some/file data for keys that match the file
6506 The data that is obtained from the nested lookup is discarded.
6509 Keys that do not match any of these patterns are interpreted literally. The
6510 continuation rules for the data are the same as for &(lsearch)&, and keys may
6511 be followed by optional colons.
6513 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6514 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6515 lookup types support only literal keys.
6519 .section "Query-style lookup types" "SECID62"
6520 .cindex "lookup" "query-style types"
6521 .cindex "query-style lookup" "list of types"
6522 The supported query-style lookup types are listed below. Further details about
6523 many of them are given in later sections.
6526 .cindex "DNS" "as a lookup type"
6527 .cindex "lookup" "DNS"
6528 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6529 are given in the supplied query. The resulting data is the contents of the
6530 records. See section &<<SECTdnsdb>>&.
6532 .cindex "InterBase lookup type"
6533 .cindex "lookup" "InterBase"
6534 &(ibase)&: This does a lookup in an InterBase database.
6536 .cindex "LDAP" "lookup type"
6537 .cindex "lookup" "LDAP"
6538 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6539 returns attributes from a single entry. There is a variant called &(ldapm)&
6540 that permits values from multiple entries to be returned. A third variant
6541 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6542 any attribute values. See section &<<SECTldap>>&.
6544 .cindex "MySQL" "lookup type"
6545 .cindex "lookup" "MySQL"
6546 &(mysql)&: The format of the query is an SQL statement that is passed to a
6547 MySQL database. See section &<<SECTsql>>&.
6549 .cindex "NIS+ lookup type"
6550 .cindex "lookup" "NIS+"
6551 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6552 the field to be returned. See section &<<SECTnisplus>>&.
6554 .cindex "Oracle" "lookup type"
6555 .cindex "lookup" "Oracle"
6556 &(oracle)&: The format of the query is an SQL statement that is passed to an
6557 Oracle database. See section &<<SECTsql>>&.
6559 .cindex "lookup" "passwd"
6560 .cindex "passwd lookup type"
6561 .cindex "&_/etc/passwd_&"
6562 &(passwd)& is a query-style lookup with queries that are just user names. The
6563 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6564 success, the result string is the same as you would get from an &(lsearch)&
6565 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6566 password value. For example:
6568 *:42:42:King Rat:/home/kr:/bin/bash
6571 .cindex "PostgreSQL lookup type"
6572 .cindex "lookup" "PostgreSQL"
6573 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6574 PostgreSQL database. See section &<<SECTsql>>&.
6577 .cindex "sqlite lookup type"
6578 .cindex "lookup" "sqlite"
6579 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6580 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6583 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6584 not likely to be useful in normal operation.
6586 .cindex "whoson lookup type"
6587 .cindex "lookup" "whoson"
6588 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6589 allows a server to check whether a particular (dynamically allocated) IP
6590 address is currently allocated to a known (trusted) user and, optionally, to
6591 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6592 at one time for &"POP before SMTP"& authentication, but that approach has been
6593 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6594 &"POP before SMTP"& checking using ACL statements such as
6596 require condition = \
6597 ${lookup whoson {$sender_host_address}{yes}{no}}
6599 The query consists of a single IP address. The value returned is the name of
6600 the authenticated user, which is stored in the variable &$value$&. However, in
6601 this example, the data in &$value$& is not used; the result of the lookup is
6602 one of the fixed strings &"yes"& or &"no"&.
6607 .section "Temporary errors in lookups" "SECID63"
6608 .cindex "lookup" "temporary error in"
6609 Lookup functions can return temporary error codes if the lookup cannot be
6610 completed. For example, an SQL or LDAP database might be unavailable. For this
6611 reason, it is not advisable to use a lookup that might do this for critical
6612 options such as a list of local domains.
6614 When a lookup cannot be completed in a router or transport, delivery
6615 of the message (to the relevant address) is deferred, as for any other
6616 temporary error. In other circumstances Exim may assume the lookup has failed,
6617 or may give up altogether.
6621 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6622 .cindex "wildcard lookups"
6623 .cindex "lookup" "default values"
6624 .cindex "lookup" "wildcard"
6625 .cindex "lookup" "* added to type"
6626 .cindex "default" "in single-key lookups"
6627 In this context, a &"default value"& is a value specified by the administrator
6628 that is to be used if a lookup fails.
6630 &*Note:*& This section applies only to single-key lookups. For query-style
6631 lookups, the facilities of the query language must be used. An attempt to
6632 specify a default for a query-style lookup provokes an error.
6634 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6635 and the initial lookup fails, the key &"*"& is looked up in the file to
6636 provide a default value. See also the section on partial matching below.
6638 .cindex "*@ with single-key lookup"
6639 .cindex "lookup" "*@ added to type"
6640 .cindex "alias file" "per-domain default"
6641 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6642 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6643 character, a second lookup is done with everything before the last @ replaced
6644 by *. This makes it possible to provide per-domain defaults in alias files
6645 that include the domains in the keys. If the second lookup fails (or doesn't
6646 take place because there is no @ in the key), &"*"& is looked up.
6647 For example, a &(redirect)& router might contain:
6649 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6651 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6652 looks up these keys, in this order:
6658 The data is taken from whichever key it finds first. &*Note*&: In an
6659 &(lsearch)& file, this does not mean the first of these keys in the file. A
6660 complete scan is done for each key, and only if it is not found at all does
6661 Exim move on to try the next key.
6665 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6666 .cindex "partial matching"
6667 .cindex "wildcard lookups"
6668 .cindex "lookup" "partial matching"
6669 .cindex "lookup" "wildcard"
6670 .cindex "asterisk" "in search type"
6671 The normal operation of a single-key lookup is to search the file for an exact
6672 match with the given key. However, in a number of situations where domains are
6673 being looked up, it is useful to be able to do partial matching. In this case,
6674 information in the file that has a key starting with &"*."& is matched by any
6675 domain that ends with the components that follow the full stop. For example, if
6676 a key in a DBM file is
6678 *.dates.fict.example
6680 then when partial matching is enabled this is matched by (amongst others)
6681 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6682 by &'dates.fict.example'&, if that does not appear as a separate key in the
6685 &*Note*&: Partial matching is not available for query-style lookups. It is
6686 also not available for any lookup items in address lists (see section
6687 &<<SECTaddresslist>>&).
6689 Partial matching is implemented by doing a series of separate lookups using
6690 keys constructed by modifying the original subject key. This means that it can
6691 be used with any of the single-key lookup types, provided that
6692 partial matching keys
6693 beginning with a special prefix (default &"*."&) are included in the data file.
6694 Keys in the file that do not begin with the prefix are matched only by
6695 unmodified subject keys when partial matching is in use.
6697 Partial matching is requested by adding the string &"partial-"& to the front of
6698 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6699 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6700 is added at the start of the subject key, and it is looked up again. If that
6701 fails, further lookups are tried with dot-separated components removed from the
6702 start of the subject key, one-by-one, and &"*."& added on the front of what
6705 A minimum number of two non-* components are required. This can be adjusted
6706 by including a number before the hyphen in the search type. For example,
6707 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6708 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6709 subject key is &'2250.dates.fict.example'& then the following keys are looked
6710 up when the minimum number of non-* components is two:
6712 2250.dates.fict.example
6713 *.2250.dates.fict.example
6714 *.dates.fict.example
6717 As soon as one key in the sequence is successfully looked up, the lookup
6720 .cindex "lookup" "partial matching &-- changing prefix"
6721 .cindex "prefix" "for partial matching"
6722 The use of &"*."& as the partial matching prefix is a default that can be
6723 changed. The motivation for this feature is to allow Exim to operate with file
6724 formats that are used by other MTAs. A different prefix can be supplied in
6725 parentheses instead of the hyphen after &"partial"&. For example:
6727 domains = partial(.)lsearch;/some/file
6729 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6730 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6731 components is unchanged). The prefix may consist of any punctuation characters
6732 other than a closing parenthesis. It may be empty, for example:
6734 domains = partial1()cdb;/some/file
6736 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6737 &`a.b.c`&, &`b.c`&, and &`c`&.
6739 If &"partial0"& is specified, what happens at the end (when the lookup with
6740 just one non-wild component has failed, and the original key is shortened right
6741 down to the null string) depends on the prefix:
6744 If the prefix has zero length, the whole lookup fails.
6746 If the prefix has length 1, a lookup for just the prefix is done. For
6747 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6749 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6750 remainder is looked up. With the default prefix, therefore, the final lookup is
6751 for &"*"& on its own.
6753 Otherwise, the whole prefix is looked up.
6757 If the search type ends in &"*"& or &"*@"& (see section
6758 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6759 this implies happens after all partial lookups have failed. If &"partial0"& is
6760 specified, adding &"*"& to the search type has no effect with the default
6761 prefix, because the &"*"& key is already included in the sequence of partial
6762 lookups. However, there might be a use for lookup types such as
6763 &"partial0(.)lsearch*"&.
6765 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6766 in domain lists and the like. Partial matching works only in terms of
6767 dot-separated components; a key such as &`*fict.example`&
6768 in a database file is useless, because the asterisk in a partial matching
6769 subject key is always followed by a dot.
6774 .section "Lookup caching" "SECID64"
6775 .cindex "lookup" "caching"
6776 .cindex "caching" "lookup data"
6777 Exim caches all lookup results in order to avoid needless repetition of
6778 lookups. However, because (apart from the daemon) Exim operates as a collection
6779 of independent, short-lived processes, this caching applies only within a
6780 single Exim process. There is no inter-process lookup caching facility.
6782 For single-key lookups, Exim keeps the relevant files open in case there is
6783 another lookup that needs them. In some types of configuration this can lead to
6784 many files being kept open for messages with many recipients. To avoid hitting
6785 the operating system limit on the number of simultaneously open files, Exim
6786 closes the least recently used file when it needs to open more files than its
6787 own internal limit, which can be changed via the &%lookup_open_max%& option.
6789 The single-key lookup files are closed and the lookup caches are flushed at
6790 strategic points during delivery &-- for example, after all routing is
6796 .section "Quoting lookup data" "SECID65"
6797 .cindex "lookup" "quoting"
6798 .cindex "quoting" "in lookups"
6799 When data from an incoming message is included in a query-style lookup, there
6800 is the possibility of special characters in the data messing up the syntax of
6801 the query. For example, a NIS+ query that contains
6805 will be broken if the local part happens to contain a closing square bracket.
6806 For NIS+, data can be enclosed in double quotes like this:
6808 [name="$local_part"]
6810 but this still leaves the problem of a double quote in the data. The rule for
6811 NIS+ is that double quotes must be doubled. Other lookup types have different
6812 rules, and to cope with the differing requirements, an expansion operator
6813 of the following form is provided:
6815 ${quote_<lookup-type>:<string>}
6817 For example, the safest way to write the NIS+ query is
6819 [name="${quote_nisplus:$local_part}"]
6821 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6822 operator can be used for all lookup types, but has no effect for single-key
6823 lookups, since no quoting is ever needed in their key strings.
6828 .section "More about dnsdb" "SECTdnsdb"
6829 .cindex "dnsdb lookup"
6830 .cindex "lookup" "dnsdb"
6831 .cindex "DNS" "as a lookup type"
6832 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6833 of a record type and a domain name, separated by an equals sign. For example,
6834 an expansion string could contain:
6836 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6838 If the lookup succeeds, the result is placed in &$value$&, which in this case
6839 is used on its own as the result. If the lookup does not succeed, the
6840 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6841 &<<SECTforexpfai>>& for an explanation of what this means.
6843 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT,
6844 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6845 configured). If no type is given, TXT is assumed. When the type is PTR,
6846 the data can be an IP address, written as normal; inversion and the addition of
6847 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6849 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6851 If the data for a PTR record is not a syntactically valid IP address, it is not
6852 altered and nothing is added.
6854 .cindex "MX record" "in &(dnsdb)& lookup"
6855 .cindex "SRV record" "in &(dnsdb)& lookup"
6856 For an MX lookup, both the preference value and the host name are returned for
6857 each record, separated by a space. For an SRV lookup, the priority, weight,
6858 port, and host name are returned for each record, separated by spaces.
6860 For any record type, if multiple records are found (or, for A6 lookups, if a
6861 single record leads to multiple addresses), the data is returned as a
6862 concatenation, with newline as the default separator. The order, of course,
6863 depends on the DNS resolver. You can specify a different separator character
6864 between multiple records by putting a right angle-bracket followed immediately
6865 by the new separator at the start of the query. For example:
6867 ${lookup dnsdb{>: a=host1.example}}
6869 It is permitted to specify a space as the separator character. Further
6870 white space is ignored.
6872 .cindex "TXT record" "in &(dnsdb)& lookup"
6873 .cindex "SPF record" "in &(dnsdb)& lookup"
6874 For TXT records with multiple items of data, only the first item is returned,
6875 unless a separator for them is specified using a comma after the separator
6876 character followed immediately by the TXT record item separator. To concatenate
6877 items without a separator, use a semicolon instead. For SPF records the
6878 default behaviour is to concatenate multiple items without using a separator.
6880 ${lookup dnsdb{>\n,: txt=a.b.example}}
6881 ${lookup dnsdb{>\n; txt=a.b.example}}
6882 ${lookup dnsdb{spf=example.org}}
6884 It is permitted to specify a space as the separator character. Further
6885 white space is ignored.
6887 .section "Pseudo dnsdb record types" "SECID66"
6888 .cindex "MX record" "in &(dnsdb)& lookup"
6889 By default, both the preference value and the host name are returned for
6890 each MX record, separated by a space. If you want only host names, you can use
6891 the pseudo-type MXH:
6893 ${lookup dnsdb{mxh=a.b.example}}
6895 In this case, the preference values are omitted, and just the host names are
6898 .cindex "name server for enclosing domain"
6899 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6900 records on the given domain, but if none are found, it removes the first
6901 component of the domain name, and tries again. This process continues until NS
6902 records are found or there are no more components left (or there is a DNS
6903 error). In other words, it may return the name servers for a top-level domain,
6904 but it never returns the root name servers. If there are no NS records for the
6905 top-level domain, the lookup fails. Consider these examples:
6907 ${lookup dnsdb{zns=xxx.quercite.com}}
6908 ${lookup dnsdb{zns=xxx.edu}}
6910 Assuming that in each case there are no NS records for the full domain name,
6911 the first returns the name servers for &%quercite.com%&, and the second returns
6912 the name servers for &%edu%&.
6914 You should be careful about how you use this lookup because, unless the
6915 top-level domain does not exist, the lookup always returns some host names. The
6916 sort of use to which this might be put is for seeing if the name servers for a
6917 given domain are on a blacklist. You can probably assume that the name servers
6918 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6921 .cindex "CSA" "in &(dnsdb)& lookup"
6922 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6923 records according to the CSA rules, which are described in section
6924 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6925 not sufficient because of the extra parent domain search behaviour of CSA. The
6926 result of a successful lookup such as:
6928 ${lookup dnsdb {csa=$sender_helo_name}}
6930 has two space-separated fields: an authorization code and a target host name.
6931 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6932 authorization required but absent, or &"?"& for unknown.
6934 .cindex "A+" "in &(dnsdb)& lookup"
6935 The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA
6936 and then an A lookup. All results are returned; defer processing
6937 (see below) is handled separately for each lookup. Example:
6939 ${lookup dnsdb {>; a+=$sender_helo_name}}
6943 .section "Multiple dnsdb lookups" "SECID67"
6944 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6945 However, you can specify a list of domains or IP addresses in a single
6946 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6947 the default separator, but with the ability to change this. For example:
6949 ${lookup dnsdb{one.domain.com:two.domain.com}}
6950 ${lookup dnsdb{a=one.host.com:two.host.com}}
6951 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6953 In order to retain backwards compatibility, there is one special case: if
6954 the lookup type is PTR and no change of separator is specified, Exim looks
6955 to see if the rest of the string is precisely one IPv6 address. In this
6956 case, it does not treat it as a list.
6958 The data from each lookup is concatenated, with newline separators by default,
6959 in the same way that multiple DNS records for a single item are handled. A
6960 different separator can be specified, as described above.
6962 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6963 temporary DNS error for any of them, the behaviour is controlled by
6964 an optional keyword followed by a comma that may appear before the record
6965 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6966 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6967 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6968 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6969 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6970 error causes the whole lookup to defer only if none of the other lookups
6971 succeed. The default is &"lax"&, so the following lookups are equivalent:
6973 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6974 ${lookup dnsdb{a=one.host.com:two.host.com}}
6976 Thus, in the default case, as long as at least one of the DNS lookups
6977 yields some data, the lookup succeeds.
6982 .section "More about LDAP" "SECTldap"
6983 .cindex "LDAP" "lookup, more about"
6984 .cindex "lookup" "LDAP"
6985 .cindex "Solaris" "LDAP"
6986 The original LDAP implementation came from the University of Michigan; this has
6987 become &"Open LDAP"&, and there are now two different releases. Another
6988 implementation comes from Netscape, and Solaris 7 and subsequent releases
6989 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6990 the lookup function level, their error handling is different. For this reason
6991 it is necessary to set a compile-time variable when building Exim with LDAP, to
6992 indicate which LDAP library is in use. One of the following should appear in
6993 your &_Local/Makefile_&:
6995 LDAP_LIB_TYPE=UMICHIGAN
6996 LDAP_LIB_TYPE=OPENLDAP1
6997 LDAP_LIB_TYPE=OPENLDAP2
6998 LDAP_LIB_TYPE=NETSCAPE
6999 LDAP_LIB_TYPE=SOLARIS
7001 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7002 same interface as the University of Michigan version.
7004 There are three LDAP lookup types in Exim. These behave slightly differently in
7005 the way they handle the results of a query:
7008 &(ldap)& requires the result to contain just one entry; if there are more, it
7011 &(ldapdn)& also requires the result to contain just one entry, but it is the
7012 Distinguished Name that is returned rather than any attribute values.
7014 &(ldapm)& permits the result to contain more than one entry; the attributes
7015 from all of them are returned.
7019 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7020 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7021 the data returned by a successful lookup is described in the next section.
7022 First we explain how LDAP queries are coded.
7025 .section "Format of LDAP queries" "SECTforldaque"
7026 .cindex "LDAP" "query format"
7027 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7028 the configuration of a &(redirect)& router one might have this setting:
7030 data = ${lookup ldap \
7031 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7032 c=UK?mailbox?base?}}
7034 .cindex "LDAP" "with TLS"
7035 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7036 secure (encrypted) LDAP connections. The second of these ensures that an
7037 encrypted TLS connection is used.
7039 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7040 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7041 See the &%ldap_start_tls%& option.
7044 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7045 controlled. Every part of the TLS configuration can be configured by settings in
7046 &_exim.conf_&. Depending on the version of the client libraries installed on
7047 your system, some of the initialization may have required setting options in
7048 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7049 certificates. This revealed a nuance where the current UID that exim was
7050 running as could affect which config files it read. With Exim 4.83, these
7051 methods become optional, only taking effect if not specifically set in
7056 .section "LDAP quoting" "SECID68"
7057 .cindex "LDAP" "quoting"
7058 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7059 and the second because the LDAP query is represented as a URL. Furthermore,
7060 within an LDAP query, two different kinds of quoting are required. For this
7061 reason, there are two different LDAP-specific quoting operators.
7063 The &%quote_ldap%& operator is designed for use on strings that are part of
7064 filter specifications. Conceptually, it first does the following conversions on
7072 in accordance with RFC 2254. The resulting string is then quoted according
7073 to the rules for URLs, that is, all non-alphanumeric characters except
7077 are converted to their hex values, preceded by a percent sign. For example:
7079 ${quote_ldap: a(bc)*, a<yz>; }
7083 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7085 Removing the URL quoting, this is (with a leading and a trailing space):
7087 a\28bc\29\2A, a<yz>;
7089 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7090 base DN specifications in queries. Conceptually, it first converts the string
7091 by inserting a backslash in front of any of the following characters:
7095 It also inserts a backslash before any leading spaces or # characters, and
7096 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7097 is then quoted according to the rules for URLs. For example:
7099 ${quote_ldap_dn: a(bc)*, a<yz>; }
7103 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7105 Removing the URL quoting, this is (with a trailing space):
7107 \ a(bc)*\, a\<yz\>\;\
7109 There are some further comments about quoting in the section on LDAP
7110 authentication below.
7113 .section "LDAP connections" "SECID69"
7114 .cindex "LDAP" "connections"
7115 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7116 is in use, via a Unix domain socket. The example given above does not specify
7117 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7120 ldap://<hostname>:<port>/...
7122 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7123 used. When no server is specified in a query, a list of default servers is
7124 taken from the &%ldap_default_servers%& configuration option. This supplies a
7125 colon-separated list of servers which are tried in turn until one successfully
7126 handles a query, or there is a serious error. Successful handling either
7127 returns the requested data, or indicates that it does not exist. Serious errors
7128 are syntactical, or multiple values when only a single value is expected.
7129 Errors which cause the next server to be tried are connection failures, bind
7130 failures, and timeouts.
7132 For each server name in the list, a port number can be given. The standard way
7133 of specifying a host and port is to use a colon separator (RFC 1738). Because
7134 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7135 doubled. For example
7137 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7139 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7140 to the LDAP library with no server name, and the library's default (normally
7141 the local host) is used.
7143 If you are using the OpenLDAP library, you can connect to an LDAP server using
7144 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7145 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7146 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7149 For this type of connection, instead of a host name for the server, a pathname
7150 for the socket is required, and the port number is not relevant. The pathname
7151 can be specified either as an item in &%ldap_default_servers%&, or inline in
7152 the query. In the former case, you can have settings such as
7154 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7156 When the pathname is given in the query, you have to escape the slashes as
7157 &`%2F`& to fit in with the LDAP URL syntax. For example:
7159 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7161 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7162 a pathname, it uses the Unix domain socket code, even if the query actually
7163 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7164 socket connection. This behaviour means that you can use a setting of
7165 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7166 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7167 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7170 If an explicit &`ldapi`& type is given in a query when a host name is
7171 specified, an error is diagnosed. However, if there are more items in
7172 &%ldap_default_servers%&, they are tried. In other words:
7175 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7178 Using &`ldapi`& with a host name causes an error.
7182 Using &`ldapi`& with no host or path in the query, and no setting of
7183 &%ldap_default_servers%&, does whatever the library does by default.
7187 .section "LDAP authentication and control information" "SECID70"
7188 .cindex "LDAP" "authentication"
7189 The LDAP URL syntax provides no way of passing authentication and other control
7190 information to the server. To make this possible, the URL in an LDAP query may
7191 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7192 spaces. If a value contains spaces it must be enclosed in double quotes, and
7193 when double quotes are used, backslash is interpreted in the usual way inside
7194 them. The following names are recognized:
7196 &`DEREFERENCE`& set the dereferencing parameter
7197 &`NETTIME `& set a timeout for a network operation
7198 &`USER `& set the DN, for authenticating the LDAP bind
7199 &`PASS `& set the password, likewise
7200 &`REFERRALS `& set the referrals parameter
7201 &`SIZE `& set the limit for the number of entries returned
7202 &`TIME `& set the maximum waiting time for a query
7204 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7205 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7206 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7207 library from trying to follow referrals issued by the LDAP server.
7209 The name CONNECT is an obsolete name for NETTIME, retained for
7210 backwards compatibility. This timeout (specified as a number of seconds) is
7211 enforced from the client end for operations that can be carried out over a
7212 network. Specifically, it applies to network connections and calls to the
7213 &'ldap_result()'& function. If the value is greater than zero, it is used if
7214 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7215 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7216 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7217 Netscape SDK; for OpenLDAP no action is taken.
7219 The TIME parameter (also a number of seconds) is passed to the server to
7220 set a server-side limit on the time taken to complete a search.
7223 Here is an example of an LDAP query in an Exim lookup that uses some of these
7224 values. This is a single line, folded to fit on the page:
7227 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7228 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7231 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7232 any of the auxiliary data. Exim configuration settings that include lookups
7233 which contain password information should be preceded by &"hide"& to prevent
7234 non-admin users from using the &%-bP%& option to see their values.
7236 The auxiliary data items may be given in any order. The default is no
7237 connection timeout (the system timeout is used), no user or password, no limit
7238 on the number of entries returned, and no time limit on queries.
7240 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7241 removes any URL quoting that it may contain before passing it LDAP. Apparently
7242 some libraries do this for themselves, but some do not. Removing the URL
7243 quoting has two advantages:
7246 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7247 DNs as with DNs inside actual queries.
7249 It permits spaces inside USER= DNs.
7252 For example, a setting such as
7254 USER=cn=${quote_ldap_dn:$1}
7256 should work even if &$1$& contains spaces.
7258 Expanded data for the PASS= value should be quoted using the &%quote%&
7259 expansion operator, rather than the LDAP quote operators. The only reason this
7260 field needs quoting is to ensure that it conforms to the Exim syntax, which
7261 does not allow unquoted spaces. For example:
7265 The LDAP authentication mechanism can be used to check passwords as part of
7266 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7271 .section "Format of data returned by LDAP" "SECID71"
7272 .cindex "LDAP" "returned data formats"
7273 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7274 as a sequence of values, for example
7276 cn=manager, o=University of Cambridge, c=UK
7278 The &(ldap)& lookup type generates an error if more than one entry matches the
7279 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7280 the result between the data from different entries. It is possible for multiple
7281 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7282 you know that whatever values are returned all came from a single entry in the
7285 In the common case where you specify a single attribute in your LDAP query, the
7286 result is not quoted, and does not contain the attribute name. If the attribute
7287 has multiple values, they are separated by commas.
7289 If you specify multiple attributes, the result contains space-separated, quoted
7290 strings, each preceded by the attribute name and an equals sign. Within the
7291 quotes, the quote character, backslash, and newline are escaped with
7292 backslashes, and commas are used to separate multiple values for the attribute.
7293 Apart from the escaping, the string within quotes takes the same form as the
7294 output when a single attribute is requested. Specifying no attributes is the
7295 same as specifying all of an entry's attributes.
7297 Here are some examples of the output format. The first line of each pair is an
7298 LDAP query, and the second is the data that is returned. The attribute called
7299 &%attr1%& has two values, whereas &%attr2%& has only one value:
7301 ldap:///o=base?attr1?sub?(uid=fred)
7304 ldap:///o=base?attr2?sub?(uid=fred)
7307 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7308 attr1="value1.1, value1.2" attr2="value two"
7310 ldap:///o=base??sub?(uid=fred)
7311 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7313 The &%extract%& operator in string expansions can be used to pick out
7314 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7315 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7316 results of LDAP lookups.
7321 .section "More about NIS+" "SECTnisplus"
7322 .cindex "NIS+ lookup type"
7323 .cindex "lookup" "NIS+"
7324 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7325 and field name. If this is given, the result of a successful query is the
7326 contents of the named field; otherwise the result consists of a concatenation
7327 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7328 values containing spaces are quoted. For example, the query
7330 [name=mg1456],passwd.org_dir
7332 might return the string
7334 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7335 home=/home/mg1456 shell=/bin/bash shadow=""
7337 (split over two lines here to fit on the page), whereas
7339 [name=mg1456],passwd.org_dir:gcos
7345 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7346 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7347 operator is to double any quote characters within the text.
7351 .section "SQL lookups" "SECTsql"
7352 .cindex "SQL lookup types"
7353 .cindex "MySQL" "lookup type"
7354 .cindex "PostgreSQL lookup type"
7355 .cindex "lookup" "MySQL"
7356 .cindex "lookup" "PostgreSQL"
7357 .cindex "Oracle" "lookup type"
7358 .cindex "lookup" "Oracle"
7359 .cindex "InterBase lookup type"
7360 .cindex "lookup" "InterBase"
7361 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7362 databases. Queries for these databases contain SQL statements, so an example
7365 ${lookup mysql{select mailbox from users where id='userx'}\
7368 If the result of the query contains more than one field, the data for each
7369 field in the row is returned, preceded by its name, so the result of
7371 ${lookup pgsql{select home,name from users where id='userx'}\
7376 home=/home/userx name="Mister X"
7378 Empty values and values containing spaces are double quoted, with embedded
7379 quotes escaped by a backslash. If the result of the query contains just one
7380 field, the value is passed back verbatim, without a field name, for example:
7384 If the result of the query yields more than one row, it is all concatenated,
7385 with a newline between the data for each row.
7388 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7389 .cindex "MySQL" "lookup type"
7390 .cindex "PostgreSQL lookup type"
7391 .cindex "lookup" "MySQL"
7392 .cindex "lookup" "PostgreSQL"
7393 .cindex "Oracle" "lookup type"
7394 .cindex "lookup" "Oracle"
7395 .cindex "InterBase lookup type"
7396 .cindex "lookup" "InterBase"
7397 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7398 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7399 option (as appropriate) must be set to a colon-separated list of server
7401 (For MySQL and PostgreSQL only, the global option need not be set if all
7402 queries contain their own server information &-- see section
7403 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7404 items: host name, database name, user name, and password. In the case of
7405 Oracle, the host name field is used for the &"service name"&, and the database
7406 name field is not used and should be empty. For example:
7408 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7410 Because password data is sensitive, you should always precede the setting with
7411 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7412 option. Here is an example where two MySQL servers are listed:
7414 hide mysql_servers = localhost/users/root/secret:\
7415 otherhost/users/root/othersecret
7417 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7418 because this is a colon-separated list, the colon has to be doubled. For each
7419 query, these parameter groups are tried in order until a connection is made and
7420 a query is successfully processed. The result of a query may be that no data is
7421 found, but that is still a successful query. In other words, the list of
7422 servers provides a backup facility, not a list of different places to look.
7424 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7425 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7426 respectively, and the characters single-quote, double-quote, and backslash
7427 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7428 addition, escapes the percent and underscore characters. This cannot be done
7429 for MySQL because these escapes are not recognized in contexts where these
7430 characters are not special.
7432 .section "Specifying the server in the query" "SECTspeserque"
7433 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7434 it is possible to specify a list of servers with an individual query. This is
7435 done by starting the query with
7437 &`servers=`&&'server1:server2:server3:...'&&`;`&
7439 Each item in the list may take one of two forms:
7441 If it contains no slashes it is assumed to be just a host name. The appropriate
7442 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7443 of the same name, and the remaining parameters (database, user, password) are
7446 If it contains any slashes, it is taken as a complete parameter set.
7448 The list of servers is used in exactly the same way as the global list.
7449 Once a connection to a server has happened and a query has been
7450 successfully executed, processing of the lookup ceases.
7452 This feature is intended for use in master/slave situations where updates
7453 are occurring and you want to update the master rather than a slave. If the
7454 master is in the list as a backup for reading, you might have a global setting
7457 mysql_servers = slave1/db/name/pw:\
7461 In an updating lookup, you could then write:
7463 ${lookup mysql{servers=master; UPDATE ...} }
7465 That query would then be sent only to the master server. If, on the other hand,
7466 the master is not to be used for reading, and so is not present in the global
7467 option, you can still update it by a query of this form:
7469 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7473 .section "Special MySQL features" "SECID73"
7474 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7475 causes a connection to the server on the local host by means of a Unix domain
7476 socket. An alternate socket can be specified in parentheses. The full syntax of
7477 each item in &%mysql_servers%& is:
7479 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7480 <&'user'&>/<&'password'&>
7482 Any of the three sub-parts of the first field can be omitted. For normal use on
7483 the local host it can be left blank or set to just &"localhost"&.
7485 No database need be supplied &-- but if it is absent here, it must be given in
7488 If a MySQL query is issued that does not request any data (an insert, update,
7489 or delete command), the result of the lookup is the number of rows affected.
7491 &*Warning*&: This can be misleading. If an update does not actually change
7492 anything (for example, setting a field to the value it already has), the result
7493 is zero because no rows are affected.
7496 .section "Special PostgreSQL features" "SECID74"
7497 PostgreSQL lookups can also use Unix domain socket connections to the database.
7498 This is usually faster and costs less CPU time than a TCP/IP connection.
7499 However it can be used only if the mail server runs on the same machine as the
7500 database server. A configuration line for PostgreSQL via Unix domain sockets
7503 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7505 In other words, instead of supplying a host name, a path to the socket is
7506 given. The path name is enclosed in parentheses so that its slashes aren't
7507 visually confused with the delimiters for the other server parameters.
7509 If a PostgreSQL query is issued that does not request any data (an insert,
7510 update, or delete command), the result of the lookup is the number of rows
7513 .section "More about SQLite" "SECTsqlite"
7514 .cindex "lookup" "SQLite"
7515 .cindex "sqlite lookup type"
7516 SQLite is different to the other SQL lookups because a file name is required in
7517 addition to the SQL query. An SQLite database is a single file, and there is no
7518 daemon as in the other SQL databases. The interface to Exim requires the name
7519 of the file, as an absolute path, to be given at the start of the query. It is
7520 separated from the query by white space. This means that the path name cannot
7521 contain white space. Here is a lookup expansion example:
7523 ${lookup sqlite {/some/thing/sqlitedb \
7524 select name from aliases where id='userx';}}
7526 In a list, the syntax is similar. For example:
7528 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7529 select * from relays where ip='$sender_host_address';
7531 The only character affected by the &%quote_sqlite%& operator is a single
7532 quote, which it doubles.
7534 The SQLite library handles multiple simultaneous accesses to the database
7535 internally. Multiple readers are permitted, but only one process can
7536 update at once. Attempts to access the database while it is being updated
7537 are rejected after a timeout period, during which the SQLite library
7538 waits for the lock to be released. In Exim, the default timeout is set
7539 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7545 . ////////////////////////////////////////////////////////////////////////////
7546 . ////////////////////////////////////////////////////////////////////////////
7548 .chapter "Domain, host, address, and local part lists" &&&
7549 "CHAPdomhosaddlists" &&&
7550 "Domain, host, and address lists"
7551 .scindex IIDdohoadli "lists of domains; hosts; etc."
7552 A number of Exim configuration options contain lists of domains, hosts,
7553 email addresses, or local parts. For example, the &%hold_domains%& option
7554 contains a list of domains whose delivery is currently suspended. These lists
7555 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7556 arguments to expansion conditions such as &%match_domain%&.
7558 Each item in one of these lists is a pattern to be matched against a domain,
7559 host, email address, or local part, respectively. In the sections below, the
7560 different types of pattern for each case are described, but first we cover some
7561 general facilities that apply to all four kinds of list.
7565 .section "Expansion of lists" "SECID75"
7566 .cindex "expansion" "of lists"
7567 Each list is expanded as a single string before it is used. The result of
7568 expansion must be a list, possibly containing empty items, which is split up
7569 into separate items for matching. By default, colon is the separator character,
7570 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7571 &<<SECTempitelis>>& for details of the list syntax; the second of these
7572 discusses the way to specify empty list items.
7575 If the string expansion is forced to fail, Exim behaves as if the item it is
7576 testing (domain, host, address, or local part) is not in the list. Other
7577 expansion failures cause temporary errors.
7579 If an item in a list is a regular expression, backslashes, dollars and possibly
7580 other special characters in the expression must be protected against
7581 misinterpretation by the string expander. The easiest way to do this is to use
7582 the &`\N`& expansion feature to indicate that the contents of the regular
7583 expression should not be expanded. For example, in an ACL you might have:
7585 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7586 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7588 The first item is a regular expression that is protected from expansion by
7589 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7590 senders based on the receiving domain.
7595 .section "Negated items in lists" "SECID76"
7596 .cindex "list" "negation"
7597 .cindex "negation" "in lists"
7598 Items in a list may be positive or negative. Negative items are indicated by a
7599 leading exclamation mark, which may be followed by optional white space. A list
7600 defines a set of items (domains, etc). When Exim processes one of these lists,
7601 it is trying to find out whether a domain, host, address, or local part
7602 (respectively) is in the set that is defined by the list. It works like this:
7604 The list is scanned from left to right. If a positive item is matched, the
7605 subject that is being checked is in the set; if a negative item is matched, the
7606 subject is not in the set. If the end of the list is reached without the
7607 subject having matched any of the patterns, it is in the set if the last item
7608 was a negative one, but not if it was a positive one. For example, the list in
7610 domainlist relay_to_domains = !a.b.c : *.b.c
7612 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7613 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7614 list is positive. However, if the setting were
7616 domainlist relay_to_domains = !a.b.c
7618 then all domains other than &'a.b.c'& would match because the last item in the
7619 list is negative. In other words, a list that ends with a negative item behaves
7620 as if it had an extra item &`:*`& on the end.
7622 Another way of thinking about positive and negative items in lists is to read
7623 the connector as &"or"& after a positive item and as &"and"& after a negative
7628 .section "File names in lists" "SECTfilnamlis"
7629 .cindex "list" "file name in"
7630 If an item in a domain, host, address, or local part list is an absolute file
7631 name (beginning with a slash character), each line of the file is read and
7632 processed as if it were an independent item in the list, except that further
7633 file names are not allowed,
7634 and no expansion of the data from the file takes place.
7635 Empty lines in the file are ignored, and the file may also contain comment
7639 For domain and host lists, if a # character appears anywhere in a line of the
7640 file, it and all following characters are ignored.
7642 Because local parts may legitimately contain # characters, a comment in an
7643 address list or local part list file is recognized only if # is preceded by
7644 white space or the start of the line. For example:
7646 not#comment@x.y.z # but this is a comment
7650 Putting a file name in a list has the same effect as inserting each line of the
7651 file as an item in the list (blank lines and comments excepted). However, there
7652 is one important difference: the file is read each time the list is processed,
7653 so if its contents vary over time, Exim's behaviour changes.
7655 If a file name is preceded by an exclamation mark, the sense of any match
7656 within the file is inverted. For example, if
7658 hold_domains = !/etc/nohold-domains
7660 and the file contains the lines
7665 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7666 any domain matching &`*.b.c`& is not.
7670 .section "An lsearch file is not an out-of-line list" "SECID77"
7671 As will be described in the sections that follow, lookups can be used in lists
7672 to provide indexed methods of checking list membership. There has been some
7673 confusion about the way &(lsearch)& lookups work in lists. Because
7674 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7675 sometimes thought that it is allowed to contain wild cards and other kinds of
7676 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7677 always fixed strings, just as for any other single-key lookup type.
7679 If you want to use a file to contain wild-card patterns that form part of a
7680 list, just give the file name on its own, without a search type, as described
7681 in the previous section. You could also use the &(wildlsearch)& or
7682 &(nwildlsearch)&, but there is no advantage in doing this.
7687 .section "Named lists" "SECTnamedlists"
7688 .cindex "named lists"
7689 .cindex "list" "named"
7690 A list of domains, hosts, email addresses, or local parts can be given a name
7691 which is then used to refer to the list elsewhere in the configuration. This is
7692 particularly convenient if the same list is required in several different
7693 places. It also allows lists to be given meaningful names, which can improve
7694 the readability of the configuration. For example, it is conventional to define
7695 a domain list called &'local_domains'& for all the domains that are handled
7696 locally on a host, using a configuration line such as
7698 domainlist local_domains = localhost:my.dom.example
7700 Named lists are referenced by giving their name preceded by a plus sign, so,
7701 for example, a router that is intended to handle local domains would be
7702 configured with the line
7704 domains = +local_domains
7706 The first router in a configuration is often one that handles all domains
7707 except the local ones, using a configuration with a negated item like this:
7711 domains = ! +local_domains
7712 transport = remote_smtp
7715 The four kinds of named list are created by configuration lines starting with
7716 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7717 respectively. Then there follows the name that you are defining, followed by an
7718 equals sign and the list itself. For example:
7720 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7721 addresslist bad_senders = cdb;/etc/badsenders
7723 A named list may refer to other named lists:
7725 domainlist dom1 = first.example : second.example
7726 domainlist dom2 = +dom1 : third.example
7727 domainlist dom3 = fourth.example : +dom2 : fifth.example
7729 &*Warning*&: If the last item in a referenced list is a negative one, the
7730 effect may not be what you intended, because the negation does not propagate
7731 out to the higher level. For example, consider:
7733 domainlist dom1 = !a.b
7734 domainlist dom2 = +dom1 : *.b
7736 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7737 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7738 means it matches the second list as well. The effect is not the same as
7740 domainlist dom2 = !a.b : *.b
7742 where &'x.y'& does not match. It's best to avoid negation altogether in
7743 referenced lists if you can.
7745 Named lists may have a performance advantage. When Exim is routing an
7746 address or checking an incoming message, it caches the result of tests on named
7747 lists. So, if you have a setting such as
7749 domains = +local_domains
7751 on several of your routers
7752 or in several ACL statements,
7753 the actual test is done only for the first one. However, the caching works only
7754 if there are no expansions within the list itself or any sublists that it
7755 references. In other words, caching happens only for lists that are known to be
7756 the same each time they are referenced.
7758 By default, there may be up to 16 named lists of each type. This limit can be
7759 extended by changing a compile-time variable. The use of domain and host lists
7760 is recommended for concepts such as local domains, relay domains, and relay
7761 hosts. The default configuration is set up like this.
7765 .section "Named lists compared with macros" "SECID78"
7766 .cindex "list" "named compared with macro"
7767 .cindex "macro" "compared with named list"
7768 At first sight, named lists might seem to be no different from macros in the
7769 configuration file. However, macros are just textual substitutions. If you
7772 ALIST = host1 : host2
7773 auth_advertise_hosts = !ALIST
7775 it probably won't do what you want, because that is exactly the same as
7777 auth_advertise_hosts = !host1 : host2
7779 Notice that the second host name is not negated. However, if you use a host
7782 hostlist alist = host1 : host2
7783 auth_advertise_hosts = ! +alist
7785 the negation applies to the whole list, and so that is equivalent to
7787 auth_advertise_hosts = !host1 : !host2
7791 .section "Named list caching" "SECID79"
7792 .cindex "list" "caching of named"
7793 .cindex "caching" "named lists"
7794 While processing a message, Exim caches the result of checking a named list if
7795 it is sure that the list is the same each time. In practice, this means that
7796 the cache operates only if the list contains no $ characters, which guarantees
7797 that it will not change when it is expanded. Sometimes, however, you may have
7798 an expanded list that you know will be the same each time within a given
7799 message. For example:
7801 domainlist special_domains = \
7802 ${lookup{$sender_host_address}cdb{/some/file}}
7804 This provides a list of domains that depends only on the sending host's IP
7805 address. If this domain list is referenced a number of times (for example,
7806 in several ACL lines, or in several routers) the result of the check is not
7807 cached by default, because Exim does not know that it is going to be the
7808 same list each time.
7810 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7811 cache the result anyway. For example:
7813 domainlist_cache special_domains = ${lookup{...
7815 If you do this, you should be absolutely sure that caching is going to do
7816 the right thing in all cases. When in doubt, leave it out.
7820 .section "Domain lists" "SECTdomainlist"
7821 .cindex "domain list" "patterns for"
7822 .cindex "list" "domain list"
7823 Domain lists contain patterns that are to be matched against a mail domain.
7824 The following types of item may appear in domain lists:
7827 .cindex "primary host name"
7828 .cindex "host name" "matched in domain list"
7829 .oindex "&%primary_hostname%&"
7830 .cindex "domain list" "matching primary host name"
7831 .cindex "@ in a domain list"
7832 If a pattern consists of a single @ character, it matches the local host name,
7833 as set by the &%primary_hostname%& option (or defaulted). This makes it
7834 possible to use the same configuration file on several different hosts that
7835 differ only in their names.
7837 .cindex "@[] in a domain list"
7838 .cindex "domain list" "matching local IP interfaces"
7839 .cindex "domain literal"
7840 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7841 in square brackets (as in an email address that contains a domain literal), but
7842 only if that IP address is recognized as local for email routing purposes. The
7843 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7844 control which of a host's several IP addresses are treated as local.
7845 In today's Internet, the use of domain literals is controversial.
7848 .cindex "@mx_primary"
7849 .cindex "@mx_secondary"
7850 .cindex "domain list" "matching MX pointers to local host"
7851 If a pattern consists of the string &`@mx_any`& it matches any domain that
7852 has an MX record pointing to the local host or to any host that is listed in
7853 .oindex "&%hosts_treat_as_local%&"
7854 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7855 are similar, except that the first matches only when a primary MX target is the
7856 local host, and the second only when no primary MX target is the local host,
7857 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7858 preference value &-- there may of course be more than one of them.
7860 The MX lookup that takes place when matching a pattern of this type is
7861 performed with the resolver options for widening names turned off. Thus, for
7862 example, a single-component domain will &'not'& be expanded by adding the
7863 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7864 options of the &(dnslookup)& router for a discussion of domain widening.
7866 Sometimes you may want to ignore certain IP addresses when using one of these
7867 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7868 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7869 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7870 on a router). For example:
7872 domains = @mx_any/ignore=127.0.0.1
7874 This example matches any domain that has an MX record pointing to one of
7875 the local host's IP addresses other than 127.0.0.1.
7877 The list of IP addresses is in fact processed by the same code that processes
7878 host lists, so it may contain CIDR-coded network specifications and it may also
7879 contain negative items.
7881 Because the list of IP addresses is a sublist within a domain list, you have to
7882 be careful about delimiters if there is more than one address. Like any other
7883 list, the default delimiter can be changed. Thus, you might have:
7885 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7886 an.other.domain : ...
7888 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7889 involved, it is easiest to change the delimiter for the main list as well:
7891 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7892 an.other.domain ? ...
7895 .cindex "asterisk" "in domain list"
7896 .cindex "domain list" "asterisk in"
7897 .cindex "domain list" "matching &""ends with""&"
7898 If a pattern starts with an asterisk, the remaining characters of the pattern
7899 are compared with the terminating characters of the domain. The use of &"*"& in
7900 domain lists differs from its use in partial matching lookups. In a domain
7901 list, the character following the asterisk need not be a dot, whereas partial
7902 matching works only in terms of dot-separated components. For example, a domain
7903 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7907 .cindex "regular expressions" "in domain list"
7908 .cindex "domain list" "matching regular expression"
7909 If a pattern starts with a circumflex character, it is treated as a regular
7910 expression, and matched against the domain using a regular expression matching
7911 function. The circumflex is treated as part of the regular expression.
7912 Email domains are case-independent, so this regular expression match is by
7913 default case-independent, but you can make it case-dependent by starting it
7914 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7915 are given in chapter &<<CHAPregexp>>&.
7917 &*Warning*&: Because domain lists are expanded before being processed, you
7918 must escape any backslash and dollar characters in the regular expression, or
7919 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7920 it is not to be expanded (unless you really do want to build a regular
7921 expression by expansion, of course).
7923 .cindex "lookup" "in domain list"
7924 .cindex "domain list" "matching by lookup"
7925 If a pattern starts with the name of a single-key lookup type followed by a
7926 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7927 must be a file name in a suitable format for the lookup type. For example, for
7928 &"cdb;"& it must be an absolute path:
7930 domains = cdb;/etc/mail/local_domains.cdb
7932 The appropriate type of lookup is done on the file using the domain name as the
7933 key. In most cases, the data that is looked up is not used; Exim is interested
7934 only in whether or not the key is present in the file. However, when a lookup
7935 is used for the &%domains%& option on a router
7936 or a &%domains%& condition in an ACL statement, the data is preserved in the
7937 &$domain_data$& variable and can be referred to in other router options or
7938 other statements in the same ACL.
7941 Any of the single-key lookup type names may be preceded by
7942 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7944 domains = partial-dbm;/partial/domains
7946 This causes partial matching logic to be invoked; a description of how this
7947 works is given in section &<<SECTpartiallookup>>&.
7950 .cindex "asterisk" "in lookup type"
7951 Any of the single-key lookup types may be followed by an asterisk. This causes
7952 a default lookup for a key consisting of a single asterisk to be done if the
7953 original lookup fails. This is not a useful feature when using a domain list to
7954 select particular domains (because any domain would match), but it might have
7955 value if the result of the lookup is being used via the &$domain_data$&
7958 If the pattern starts with the name of a query-style lookup type followed by a
7959 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7960 pattern must be an appropriate query for the lookup type, as described in
7961 chapter &<<CHAPfdlookup>>&. For example:
7963 hold_domains = mysql;select domain from holdlist \
7964 where domain = '${quote_mysql:$domain}';
7966 In most cases, the data that is looked up is not used (so for an SQL query, for
7967 example, it doesn't matter what field you select). Exim is interested only in
7968 whether or not the query succeeds. However, when a lookup is used for the
7969 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7970 variable and can be referred to in other options.
7972 .cindex "domain list" "matching literal domain name"
7973 If none of the above cases apply, a caseless textual comparison is made
7974 between the pattern and the domain.
7977 Here is an example that uses several different kinds of pattern:
7979 domainlist funny_domains = \
7982 *.foundation.fict.example : \
7983 \N^[1-2]\d{3}\.fict\.example$\N : \
7984 partial-dbm;/opt/data/penguin/book : \
7985 nis;domains.byname : \
7986 nisplus;[name=$domain,status=local],domains.org_dir
7988 There are obvious processing trade-offs among the various matching modes. Using
7989 an asterisk is faster than a regular expression, and listing a few names
7990 explicitly probably is too. The use of a file or database lookup is expensive,
7991 but may be the only option if hundreds of names are required. Because the
7992 patterns are tested in order, it makes sense to put the most commonly matched
7997 .section "Host lists" "SECThostlist"
7998 .cindex "host list" "patterns in"
7999 .cindex "list" "host list"
8000 Host lists are used to control what remote hosts are allowed to do. For
8001 example, some hosts may be allowed to use the local host as a relay, and some
8002 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8003 two different ways, by name or by IP address. In a host list, some types of
8004 pattern are matched to a host name, and some are matched to an IP address.
8005 You need to be particularly careful with this when single-key lookups are
8006 involved, to ensure that the right value is being used as the key.
8009 .section "Special host list patterns" "SECID80"
8010 .cindex "empty item in hosts list"
8011 .cindex "host list" "empty string in"
8012 If a host list item is the empty string, it matches only when no remote host is
8013 involved. This is the case when a message is being received from a local
8014 process using SMTP on the standard input, that is, when a TCP/IP connection is
8017 .cindex "asterisk" "in host list"
8018 The special pattern &"*"& in a host list matches any host or no host. Neither
8019 the IP address nor the name is actually inspected.
8023 .section "Host list patterns that match by IP address" "SECThoslispatip"
8024 .cindex "host list" "matching IP addresses"
8025 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8026 the incoming address actually appears in the IPv6 host as
8027 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8028 list, it is converted into a traditional IPv4 address first. (Not all operating
8029 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8032 The following types of pattern in a host list check the remote host by
8033 inspecting its IP address:
8036 If the pattern is a plain domain name (not a regular expression, not starting
8037 with *, not a lookup of any kind), Exim calls the operating system function
8038 to find the associated IP address(es). Exim uses the newer
8039 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8040 This typically causes a forward DNS lookup of the name. The result is compared
8041 with the IP address of the subject host.
8043 If there is a temporary problem (such as a DNS timeout) with the host name
8044 lookup, a temporary error occurs. For example, if the list is being used in an
8045 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8046 temporary SMTP error code. If no IP address can be found for the host name,
8047 what happens is described in section &<<SECTbehipnot>>& below.
8050 .cindex "@ in a host list"
8051 If the pattern is &"@"&, the primary host name is substituted and used as a
8052 domain name, as just described.
8055 If the pattern is an IP address, it is matched against the IP address of the
8056 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8057 IPv6 addresses can be given in colon-separated format, but the colons have to
8058 be doubled so as not to be taken as item separators when the default list
8059 separator is used. IPv6 addresses are recognized even when Exim is compiled
8060 without IPv6 support. This means that if they appear in a host list on an
8061 IPv4-only host, Exim will not treat them as host names. They are just addresses
8062 that can never match a client host.
8065 .cindex "@[] in a host list"
8066 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8067 the local host. For example, if the local host is an IPv4 host with one
8068 interface address 10.45.23.56, these two ACL statements have the same effect:
8070 accept hosts = 127.0.0.1 : 10.45.23.56
8074 .cindex "CIDR notation"
8075 If the pattern is an IP address followed by a slash and a mask length (for
8076 example 10.11.42.0/24), it is matched against the IP address of the subject
8077 host under the given mask. This allows, an entire network of hosts to be
8078 included (or excluded) by a single item. The mask uses CIDR notation; it
8079 specifies the number of address bits that must match, starting from the most
8080 significant end of the address.
8082 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8083 of a range of addresses. It is the number of bits in the network portion of the
8084 address. The above example specifies a 24-bit netmask, so it matches all 256
8085 addresses in the 10.11.42.0 network. An item such as
8089 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8090 32 for an IPv4 address is the same as no mask at all; just a single address
8093 Here is another example which shows an IPv4 and an IPv6 network:
8095 recipient_unqualified_hosts = 192.168.0.0/16: \
8096 3ffe::ffff::836f::::/48
8098 The doubling of list separator characters applies only when these items
8099 appear inline in a host list. It is not required when indirecting via a file.
8102 recipient_unqualified_hosts = /opt/exim/unqualnets
8104 could make use of a file containing
8109 to have exactly the same effect as the previous example. When listing IPv6
8110 addresses inline, it is usually more convenient to use the facility for
8111 changing separator characters. This list contains the same two networks:
8113 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8116 The separator is changed to semicolon by the leading &"<;"& at the start of the
8122 .section "Host list patterns for single-key lookups by host address" &&&
8123 "SECThoslispatsikey"
8124 .cindex "host list" "lookup of IP address"
8125 When a host is to be identified by a single-key lookup of its complete IP
8126 address, the pattern takes this form:
8128 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8132 hosts_lookup = net-cdb;/hosts-by-ip.db
8134 The text form of the IP address of the subject host is used as the lookup key.
8135 IPv6 addresses are converted to an unabbreviated form, using lower case
8136 letters, with dots as separators because colon is the key terminator in
8137 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8138 quoting the keys, but this is a facility that was added later.] The data
8139 returned by the lookup is not used.
8141 .cindex "IP address" "masking"
8142 .cindex "host list" "masked IP address"
8143 Single-key lookups can also be performed using masked IP addresses, using
8144 patterns of this form:
8146 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8150 net24-dbm;/networks.db
8152 The IP address of the subject host is masked using <&'number'&> as the mask
8153 length. A textual string is constructed from the masked value, followed by the
8154 mask, and this is used as the lookup key. For example, if the host's IP address
8155 is 192.168.34.6, the key that is looked up for the above example is
8156 &"192.168.34.0/24"&.
8158 When an IPv6 address is converted to a string, dots are normally used instead
8159 of colons, so that keys in &(lsearch)& files need not contain colons (which
8160 terminate &(lsearch)& keys). This was implemented some time before the ability
8161 to quote keys was made available in &(lsearch)& files. However, the more
8162 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8163 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8164 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8165 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8166 addresses are always used.
8168 Ideally, it would be nice to tidy up this anomalous situation by changing to
8169 colons in all cases, given that quoting is now available for &(lsearch)&.
8170 However, this would be an incompatible change that might break some existing
8173 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8174 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8175 the former case the key strings include the mask value, whereas in the latter
8176 case the IP address is used on its own.
8180 .section "Host list patterns that match by host name" "SECThoslispatnam"
8181 .cindex "host" "lookup failures"
8182 .cindex "unknown host name"
8183 .cindex "host list" "matching host name"
8184 There are several types of pattern that require Exim to know the name of the
8185 remote host. These are either wildcard patterns or lookups by name. (If a
8186 complete hostname is given without any wildcarding, it is used to find an IP
8187 address to match against, as described in section &<<SECThoslispatip>>&
8190 If the remote host name is not already known when Exim encounters one of these
8191 patterns, it has to be found from the IP address.
8192 Although many sites on the Internet are conscientious about maintaining reverse
8193 DNS data for their hosts, there are also many that do not do this.
8194 Consequently, a name cannot always be found, and this may lead to unwanted
8195 effects. Take care when configuring host lists with wildcarded name patterns.
8196 Consider what will happen if a name cannot be found.
8198 Because of the problems of determining host names from IP addresses, matching
8199 against host names is not as common as matching against IP addresses.
8201 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8202 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8203 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8204 are done can be changed by setting the &%host_lookup_order%& option. For
8205 security, once Exim has found one or more names, it looks up the IP addresses
8206 for these names and compares them with the IP address that it started with.
8207 Only those names whose IP addresses match are accepted. Any other names are
8208 discarded. If no names are left, Exim behaves as if the host name cannot be
8209 found. In the most common case there is only one name and one IP address.
8211 There are some options that control what happens if a host name cannot be
8212 found. These are described in section &<<SECTbehipnot>>& below.
8214 .cindex "host" "alias for"
8215 .cindex "alias for host"
8216 As a result of aliasing, hosts may have more than one name. When processing any
8217 of the following types of pattern, all the host's names are checked:
8220 .cindex "asterisk" "in host list"
8221 If a pattern starts with &"*"& the remainder of the item must match the end of
8222 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8223 &'.b.c'&. This special simple form is provided because this is a very common
8224 requirement. Other kinds of wildcarding require the use of a regular
8227 .cindex "regular expressions" "in host list"
8228 .cindex "host list" "regular expression in"
8229 If the item starts with &"^"& it is taken to be a regular expression which is
8230 matched against the host name. Host names are case-independent, so this regular
8231 expression match is by default case-independent, but you can make it
8232 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8233 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8238 is a regular expression that matches either of the two hosts &'a.c.d'& or
8239 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8240 that backslash and dollar characters are not misinterpreted as part of the
8241 string expansion. The simplest way to do this is to use &`\N`& to mark that
8242 part of the string as non-expandable. For example:
8244 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8246 &*Warning*&: If you want to match a complete host name, you must include the
8247 &`$`& terminating metacharacter in the regular expression, as in the above
8248 example. Without it, a match at the start of the host name is all that is
8255 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8256 .cindex "host" "lookup failures, permanent"
8257 While processing a host list, Exim may need to look up an IP address from a
8258 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8259 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8260 behaviour when it fails to find the information it is seeking is the same.
8262 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8263 apply to temporary DNS errors, whose handling is described in the next section.
8265 .cindex "&`+include_unknown`&"
8266 .cindex "&`+ignore_unknown`&"
8267 Exim parses a host list from left to right. If it encounters a permanent
8268 lookup failure in any item in the host list before it has found a match,
8269 Exim treats it as a failure and the default behavior is as if the host
8270 does not match the list. This may not always be what you want to happen.
8271 To change Exim's behaviour, the special items &`+include_unknown`& or
8272 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8273 not recognized in an indirected file).
8276 If any item that follows &`+include_unknown`& requires information that
8277 cannot found, Exim behaves as if the host does match the list. For example,
8279 host_reject_connection = +include_unknown:*.enemy.ex
8281 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8282 any hosts whose name it cannot find.
8285 If any item that follows &`+ignore_unknown`& requires information that cannot
8286 be found, Exim ignores that item and proceeds to the rest of the list. For
8289 accept hosts = +ignore_unknown : friend.example : \
8292 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8293 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8294 name can be found for 192.168.4.5, it is rejected.
8297 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8298 list. The effect of each one lasts until the next, or until the end of the
8301 To explain the host/ip processing logic a different way for the same ACL:
8304 If you have name lookups or wildcarded host names and
8305 IP addresses in the same host list, you should normally put the IP
8306 addresses first. For example, in an ACL you could have:
8308 accept hosts = 10.9.8.7 : *.friend.example
8310 The reason you normally would order it this way lies in the
8311 left-to-right way that Exim processes lists. It can test IP addresses
8312 without doing any DNS lookups, but when it reaches an item that requires
8313 a host name, it fails if it cannot find a host name to compare with the
8314 pattern. If the above list is given in the opposite order, the
8315 &%accept%& statement fails for a host whose name cannot be found, even
8316 if its IP address is 10.9.8.7.
8319 If you really do want to do the name check first, and still recognize the IP
8320 address, you can rewrite the ACL like this:
8322 accept hosts = *.friend.example
8323 accept hosts = 10.9.8.7
8325 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8326 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8327 &`+ignore_unknown`&, which was discussed in depth in the first example in
8333 .section "Temporary DNS errors when looking up host information" &&&
8335 .cindex "host" "lookup failures, temporary"
8336 .cindex "&`+include_defer`&"
8337 .cindex "&`+ignore_defer`&"
8338 A temporary DNS lookup failure normally causes a defer action (except when
8339 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8340 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8341 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8342 section. These options should be used with care, probably only in non-critical
8343 host lists such as whitelists.
8347 .section "Host list patterns for single-key lookups by host name" &&&
8348 "SECThoslispatnamsk"
8349 .cindex "unknown host name"
8350 .cindex "host list" "matching host name"
8351 If a pattern is of the form
8353 <&'single-key-search-type'&>;<&'search-data'&>
8357 dbm;/host/accept/list
8359 a single-key lookup is performed, using the host name as its key. If the
8360 lookup succeeds, the host matches the item. The actual data that is looked up
8363 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8364 keys in the file, not IP addresses. If you want to do lookups based on IP
8365 addresses, you must precede the search type with &"net-"& (see section
8366 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8367 two items in the same list, one doing an address lookup and one doing a name
8368 lookup, both using the same file.
8372 .section "Host list patterns for query-style lookups" "SECID81"
8373 If a pattern is of the form
8375 <&'query-style-search-type'&>;<&'query'&>
8377 the query is obeyed, and if it succeeds, the host matches the item. The actual
8378 data that is looked up is not used. The variables &$sender_host_address$& and
8379 &$sender_host_name$& can be used in the query. For example:
8381 hosts_lookup = pgsql;\
8382 select ip from hostlist where ip='$sender_host_address'
8384 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8385 can use the &%sg%& expansion item to change this if you need to. If you want to
8386 use masked IP addresses in database queries, you can use the &%mask%& expansion
8389 If the query contains a reference to &$sender_host_name$&, Exim automatically
8390 looks up the host name if it has not already done so. (See section
8391 &<<SECThoslispatnam>>& for comments on finding host names.)
8393 Historical note: prior to release 4.30, Exim would always attempt to find a
8394 host name before running the query, unless the search type was preceded by
8395 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8396 still recognized for query-style lookups, but its presence or absence has no
8397 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8398 See section &<<SECThoslispatsikey>>&.)
8402 .section "Mixing wildcarded host names and addresses in host lists" &&&
8404 .cindex "host list" "mixing names and addresses in"
8405 If you have name lookups or wildcarded host names and IP addresses in the same
8406 host list, you should normally put the IP addresses first. For example, in an
8409 accept hosts = 10.9.8.7 : *.friend.example
8411 The reason for this lies in the left-to-right way that Exim processes lists.
8412 It can test IP addresses without doing any DNS lookups, but when it reaches an
8413 item that requires a host name, it fails if it cannot find a host name to
8414 compare with the pattern. If the above list is given in the opposite order, the
8415 &%accept%& statement fails for a host whose name cannot be found, even if its
8416 IP address is 10.9.8.7.
8418 If you really do want to do the name check first, and still recognize the IP
8419 address, you can rewrite the ACL like this:
8421 accept hosts = *.friend.example
8422 accept hosts = 10.9.8.7
8424 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8425 &<<CHAPACL>>& for details of ACLs.
8431 .section "Address lists" "SECTaddresslist"
8432 .cindex "list" "address list"
8433 .cindex "address list" "empty item"
8434 .cindex "address list" "patterns"
8435 Address lists contain patterns that are matched against mail addresses. There
8436 is one special case to be considered: the sender address of a bounce message is
8437 always empty. You can test for this by providing an empty item in an address
8438 list. For example, you can set up a router to process bounce messages by
8439 using this option setting:
8443 The presence of the colon creates an empty item. If you do not provide any
8444 data, the list is empty and matches nothing. The empty sender can also be
8445 detected by a regular expression that matches an empty string,
8446 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8448 Non-empty items in an address list can be straightforward email addresses. For
8451 senders = jbc@askone.example : hs@anacreon.example
8453 A certain amount of wildcarding is permitted. If a pattern contains an @
8454 character, but is not a regular expression and does not begin with a
8455 semicolon-terminated lookup type (described below), the local part of the
8456 subject address is compared with the local part of the pattern, which may start
8457 with an asterisk. If the local parts match, the domain is checked in exactly
8458 the same way as for a pattern in a domain list. For example, the domain can be
8459 wildcarded, refer to a named list, or be a lookup:
8461 deny senders = *@*.spamming.site:\
8462 *@+hostile_domains:\
8463 bozo@partial-lsearch;/list/of/dodgy/sites:\
8464 *@dbm;/bad/domains.db
8466 .cindex "local part" "starting with !"
8467 .cindex "address list" "local part starting with !"
8468 If a local part that begins with an exclamation mark is required, it has to be
8469 specified using a regular expression, because otherwise the exclamation mark is
8470 treated as a sign of negation, as is standard in lists.
8472 If a non-empty pattern that is not a regular expression or a lookup does not
8473 contain an @ character, it is matched against the domain part of the subject
8474 address. The only two formats that are recognized this way are a literal
8475 domain, or a domain pattern that starts with *. In both these cases, the effect
8476 is the same as if &`*@`& preceded the pattern. For example:
8478 deny senders = enemy.domain : *.enemy.domain
8481 The following kinds of more complicated address list pattern can match any
8482 address, including the empty address that is characteristic of bounce message
8486 .cindex "regular expressions" "in address list"
8487 .cindex "address list" "regular expression in"
8488 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8489 done against the complete address, with the pattern as the regular expression.
8490 You must take care that backslash and dollar characters are not misinterpreted
8491 as part of the string expansion. The simplest way to do this is to use &`\N`&
8492 to mark that part of the string as non-expandable. For example:
8494 deny senders = \N^.*this.*@example\.com$\N : \
8495 \N^\d{8}.+@spamhaus.example$\N : ...
8497 The &`\N`& sequences are removed by the expansion, so these items do indeed
8498 start with &"^"& by the time they are being interpreted as address patterns.
8501 .cindex "address list" "lookup for complete address"
8502 Complete addresses can be looked up by using a pattern that starts with a
8503 lookup type terminated by a semicolon, followed by the data for the lookup. For
8506 deny senders = cdb;/etc/blocked.senders : \
8507 mysql;select address from blocked where \
8508 address='${quote_mysql:$sender_address}'
8510 Both query-style and single-key lookup types can be used. For a single-key
8511 lookup type, Exim uses the complete address as the key. However, empty keys are
8512 not supported for single-key lookups, so a match against the empty address
8513 always fails. This restriction does not apply to query-style lookups.
8515 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8516 cannot be used, and is ignored if specified, with an entry being written to the
8518 .cindex "*@ with single-key lookup"
8519 However, you can configure lookup defaults, as described in section
8520 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8521 default. For example, with this lookup:
8523 accept senders = lsearch*@;/some/file
8525 the file could contains lines like this:
8527 user1@domain1.example
8530 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8533 nimrod@jaeger.example
8537 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8538 would mean that every address matches, thus rendering the test useless.
8540 &*Warning 2*&: Do not confuse these two kinds of item:
8542 deny recipients = dbm*@;/some/file
8543 deny recipients = *@dbm;/some/file
8545 The first does a whole address lookup, with defaulting, as just described,
8546 because it starts with a lookup type. The second matches the local part and
8547 domain independently, as described in a bullet point below.
8551 The following kinds of address list pattern can match only non-empty addresses.
8552 If the subject address is empty, a match against any of these pattern types
8557 .cindex "@@ with single-key lookup"
8558 .cindex "address list" "@@ lookup type"
8559 .cindex "address list" "split local part and domain"
8560 If a pattern starts with &"@@"& followed by a single-key lookup item
8561 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8562 split into a local part and a domain. The domain is looked up in the file. If
8563 it is not found, there is no match. If it is found, the data that is looked up
8564 from the file is treated as a colon-separated list of local part patterns, each
8565 of which is matched against the subject local part in turn.
8567 .cindex "asterisk" "in address list"
8568 The lookup may be a partial one, and/or one involving a search for a default
8569 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8570 patterns that are looked up can be regular expressions or begin with &"*"&, or
8571 even be further lookups. They may also be independently negated. For example,
8574 deny senders = @@dbm;/etc/reject-by-domain
8576 the data from which the DBM file is built could contain lines like
8578 baddomain.com: !postmaster : *
8580 to reject all senders except &%postmaster%& from that domain.
8582 .cindex "local part" "starting with !"
8583 If a local part that actually begins with an exclamation mark is required, it
8584 has to be specified using a regular expression. In &(lsearch)& files, an entry
8585 may be split over several lines by indenting the second and subsequent lines,
8586 but the separating colon must still be included at line breaks. White space
8587 surrounding the colons is ignored. For example:
8589 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8592 As in all colon-separated lists in Exim, a colon can be included in an item by
8595 If the last item in the list starts with a right angle-bracket, the remainder
8596 of the item is taken as a new key to look up in order to obtain a continuation
8597 list of local parts. The new key can be any sequence of characters. Thus one
8598 might have entries like
8600 aol.com: spammer1 : spammer 2 : >*
8601 xyz.com: spammer3 : >*
8604 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8605 local parts for all domains, in addition to the specific local parts listed for
8606 each domain. Of course, using this feature costs another lookup each time a
8607 chain is followed, but the effort needed to maintain the data is reduced.
8609 .cindex "loop" "in lookups"
8610 It is possible to construct loops using this facility, and in order to catch
8611 them, the chains may be no more than fifty items long.
8614 The @@<&'lookup'&> style of item can also be used with a query-style
8615 lookup, but in this case, the chaining facility is not available. The lookup
8616 can only return a single list of local parts.
8619 &*Warning*&: There is an important difference between the address list items
8620 in these two examples:
8623 senders = *@+my_list
8625 In the first one, &`my_list`& is a named address list, whereas in the second
8626 example it is a named domain list.
8631 .section "Case of letters in address lists" "SECTcasletadd"
8632 .cindex "case of local parts"
8633 .cindex "address list" "case forcing"
8634 .cindex "case forcing in address lists"
8635 Domains in email addresses are always handled caselessly, but for local parts
8636 case may be significant on some systems (see &%caseful_local_part%& for how
8637 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8638 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8639 blocking lists should be done in a case-independent manner. Since most address
8640 lists in Exim are used for this kind of control, Exim attempts to do this by
8643 The domain portion of an address is always lowercased before matching it to an
8644 address list. The local part is lowercased by default, and any string
8645 comparisons that take place are done caselessly. This means that the data in
8646 the address list itself, in files included as plain file names, and in any file
8647 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8648 keys in files that are looked up by a search type other than &(lsearch)& (which
8649 works caselessly) must be in lower case, because these lookups are not
8652 .cindex "&`+caseful`&"
8653 To allow for the possibility of caseful address list matching, if an item in
8654 an address list is the string &"+caseful"&, the original case of the local
8655 part is restored for any comparisons that follow, and string comparisons are no
8656 longer case-independent. This does not affect the domain, which remains in
8657 lower case. However, although independent matches on the domain alone are still
8658 performed caselessly, regular expressions that match against an entire address
8659 become case-sensitive after &"+caseful"& has been seen.
8663 .section "Local part lists" "SECTlocparlis"
8664 .cindex "list" "local part list"
8665 .cindex "local part" "list"
8666 Case-sensitivity in local part lists is handled in the same way as for address
8667 lists, as just described. The &"+caseful"& item can be used if required. In a
8668 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8669 set false, the subject is lowercased and the matching is initially
8670 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8671 matching in the local part list, but not elsewhere in the router. If
8672 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8673 option is case-sensitive from the start.
8675 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8676 comments are handled in the same way as address lists &-- they are recognized
8677 only if the # is preceded by white space or the start of the line.
8678 Otherwise, local part lists are matched in the same way as domain lists, except
8679 that the special items that refer to the local host (&`@`&, &`@[]`&,
8680 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8681 Refer to section &<<SECTdomainlist>>& for details of the other available item
8683 .ecindex IIDdohoadli
8688 . ////////////////////////////////////////////////////////////////////////////
8689 . ////////////////////////////////////////////////////////////////////////////
8691 .chapter "String expansions" "CHAPexpand"
8692 .scindex IIDstrexp "expansion" "of strings"
8693 Many strings in Exim's run time configuration are expanded before use. Some of
8694 them are expanded every time they are used; others are expanded only once.
8696 When a string is being expanded it is copied verbatim from left to right except
8697 when a dollar or backslash character is encountered. A dollar specifies the
8698 start of a portion of the string that is interpreted and replaced as described
8699 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8700 escape character, as described in the following section.
8702 Whether a string is expanded depends upon the context. Usually this is solely
8703 dependent upon the option for which a value is sought; in this documentation,
8704 options for which string expansion is performed are marked with † after
8705 the data type. ACL rules always expand strings. A couple of expansion
8706 conditions do not expand some of the brace-delimited branches, for security
8711 .section "Literal text in expanded strings" "SECTlittext"
8712 .cindex "expansion" "including literal text"
8713 An uninterpreted dollar can be included in an expanded string by putting a
8714 backslash in front of it. A backslash can be used to prevent any special
8715 character being treated specially in an expansion, including backslash itself.
8716 If the string appears in quotes in the configuration file, two backslashes are
8717 required because the quotes themselves cause interpretation of backslashes when
8718 the string is read in (see section &<<SECTstrings>>&).
8720 .cindex "expansion" "non-expandable substrings"
8721 A portion of the string can specified as non-expandable by placing it between
8722 two occurrences of &`\N`&. This is particularly useful for protecting regular
8723 expressions, which often contain backslashes and dollar signs. For example:
8725 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8727 On encountering the first &`\N`&, the expander copies subsequent characters
8728 without interpretation until it reaches the next &`\N`& or the end of the
8733 .section "Character escape sequences in expanded strings" "SECID82"
8734 .cindex "expansion" "escape sequences"
8735 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8736 expanded string is recognized as an escape sequence for the character newline,
8737 carriage return, or tab, respectively. A backslash followed by up to three
8738 octal digits is recognized as an octal encoding for a single character, and a
8739 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8742 These escape sequences are also recognized in quoted strings when they are read
8743 in. Their interpretation in expansions as well is useful for unquoted strings,
8744 and for other cases such as looked-up strings that are then expanded.
8747 .section "Testing string expansions" "SECID83"
8748 .cindex "expansion" "testing"
8749 .cindex "testing" "string expansion"
8751 Many expansions can be tested by calling Exim with the &%-be%& option. This
8752 takes the command arguments, or lines from the standard input if there are no
8753 arguments, runs them through the string expansion code, and writes the results
8754 to the standard output. Variables based on configuration values are set up, but
8755 since no message is being processed, variables such as &$local_part$& have no
8756 value. Nevertheless the &%-be%& option can be useful for checking out file and
8757 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8760 Exim gives up its root privilege when it is called with the &%-be%& option, and
8761 instead runs under the uid and gid it was called with, to prevent users from
8762 using &%-be%& for reading files to which they do not have access.
8765 If you want to test expansions that include variables whose values are taken
8766 from a message, there are two other options that can be used. The &%-bem%&
8767 option is like &%-be%& except that it is followed by a file name. The file is
8768 read as a message before doing the test expansions. For example:
8770 exim -bem /tmp/test.message '$h_subject:'
8772 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8773 Exim message identifier. For example:
8775 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8777 This loads the message from Exim's spool before doing the test expansions, and
8778 is therefore restricted to admin users.
8781 .section "Forced expansion failure" "SECTforexpfai"
8782 .cindex "expansion" "forced failure"
8783 A number of expansions that are described in the following section have
8784 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8785 (which are sometimes called &"curly brackets"&). Which of the two strings is
8786 used depends on some condition that is evaluated as part of the expansion. If,
8787 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8788 the entire string expansion fails in a way that can be detected by the code
8789 that requested the expansion. This is called &"forced expansion failure"&, and
8790 its consequences depend on the circumstances. In some cases it is no different
8791 from any other expansion failure, but in others a different action may be
8792 taken. Such variations are mentioned in the documentation of the option that is
8798 .section "Expansion items" "SECTexpansionitems"
8799 The following items are recognized in expanded strings. White space may be used
8800 between sub-items that are keywords or substrings enclosed in braces inside an
8801 outer set of braces, to improve readability. &*Warning*&: Within braces,
8802 white space is significant.
8805 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8806 .cindex "expansion" "variables"
8807 Substitute the contents of the named variable, for example:
8812 The second form can be used to separate the name from subsequent alphanumeric
8813 characters. This form (using braces) is available only for variables; it does
8814 &'not'& apply to message headers. The names of the variables are given in
8815 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8816 given, the expansion fails.
8818 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8819 .cindex "expansion" "operators"
8820 The string is first itself expanded, and then the operation specified by
8821 <&'op'&> is applied to it. For example:
8825 The string starts with the first character after the colon, which may be
8826 leading white space. A list of operators is given in section &<<SECTexpop>>&
8827 below. The operator notation is used for simple expansion items that have just
8828 one argument, because it reduces the number of braces and therefore makes the
8829 string easier to understand.
8831 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8832 This item inserts &"basic"& header lines. It is described with the &%header%&
8833 expansion item below.
8836 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8837 .cindex "expansion" "calling an acl"
8838 .cindex "&%acl%&" "call from expansion"
8839 The name and zero to nine argument strings are first expanded separately. The expanded
8840 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8841 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8842 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8843 and may use the variables; if another acl expansion is used the values
8844 are restored after it returns. If the ACL sets
8845 a value using a "message =" modifier and returns accept or deny, the value becomes
8846 the result of the expansion.
8847 If no message is set and the ACL returns accept or deny
8848 the expansion result is an empty string.
8849 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8852 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8853 {*&<&'arg'&>&*}...}*&"
8855 This expansion dynamically loads and then calls a locally-written C function.
8856 This functionality is available only if Exim is compiled with
8860 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8861 object so that it doesn't reload the same object file in the same Exim process
8862 (but of course Exim does start new processes frequently).
8864 There may be from zero to eight arguments to the function. When compiling
8865 a local function that is to be called in this way, &_local_scan.h_& should be
8866 included. The Exim variables and functions that are defined by that API
8867 are also available for dynamically loaded functions. The function itself
8868 must have the following type:
8870 int dlfunction(uschar **yield, int argc, uschar *argv[])
8872 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8873 function should return one of the following values:
8875 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8876 into the expanded string that is being built.
8878 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8879 from &'yield'&, if it is set.
8881 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8882 taken from &'yield'& if it is set.
8884 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8886 When compiling a function that is to be used in this way with gcc,
8887 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8888 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8890 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8891 {*&<&'string3'&>&*}}*&"
8892 .cindex "expansion" "extracting substrings by key"
8893 .cindex "&%extract%&" "substrings by key"
8894 The key and <&'string1'&> are first expanded separately. Leading and trailing
8895 white space is removed from the key (but not from any of the strings). The key
8896 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8899 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8902 where the equals signs and spaces (but not both) are optional. If any of the
8903 values contain white space, they must be enclosed in double quotes, and any
8904 values that are enclosed in double quotes are subject to escape processing as
8905 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8906 for the value that corresponds to the key. The search is case-insensitive. If
8907 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8908 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8909 variable &$value$& contains the value that has been extracted. Afterwards, it
8910 is restored to any previous value it might have had.
8912 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8913 key is not found. If {<&'string2'&>} is also omitted, the value that was
8914 extracted is used. Thus, for example, these two expansions are identical, and
8917 ${extract{gid}{uid=1984 gid=2001}}
8918 ${extract{gid}{uid=1984 gid=2001}{$value}}
8920 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8921 appear, for example:
8923 ${extract{Z}{A=... B=...}{$value} fail }
8925 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8926 {<&'string2'&>} must be present for &"fail"& to be recognized.
8929 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8930 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8931 .cindex "expansion" "extracting substrings by number"
8932 .cindex "&%extract%&" "substrings by number"
8933 The <&'number'&> argument must consist entirely of decimal digits,
8934 apart from leading and trailing white space, which is ignored.
8935 This is what distinguishes this form of &%extract%& from the previous kind. It
8936 behaves in the same way, except that, instead of extracting a named field, it
8937 extracts from <&'string1'&> the field whose number is given as the first
8938 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8939 <&'string3'&> as before.
8941 The fields in the string are separated by any one of the characters in the
8942 separator string. These may include space or tab characters.
8943 The first field is numbered one. If the number is negative, the fields are
8944 counted from the end of the string, with the rightmost one numbered -1. If the
8945 number given is zero, the entire string is returned. If the modulus of the
8946 number is greater than the number of fields in the string, the result is the
8947 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8948 provided. For example:
8950 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8954 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8956 yields &"99"&. Two successive separators mean that the field between them is
8957 empty (for example, the fifth field above).
8960 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8961 .cindex "list" "selecting by condition"
8962 .cindex "expansion" "selecting from list by condition"
8964 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8965 default, but the separator can be changed in the usual way. For each item
8966 in this list, its value is place in &$item$&, and then the condition is
8967 evaluated. If the condition is true, &$item$& is added to the output as an
8968 item in a new list; if the condition is false, the item is discarded. The
8969 separator used for the output list is the same as the one used for the
8970 input, but a separator setting is not included in the output. For example:
8972 ${filter{a:b:c}{!eq{$item}{b}}
8974 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
8975 to what it was before. See also the &*map*& and &*reduce*& expansion items.
8978 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8979 .cindex "hash function" "textual"
8980 .cindex "expansion" "textual hash"
8981 This is a textual hashing function, and was the first to be implemented in
8982 early versions of Exim. In current releases, there are other hashing functions
8983 (numeric, MD5, and SHA-1), which are described below.
8985 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8986 <&'n'&>. If you are using fixed values for these numbers, that is, if
8987 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8988 use the simpler operator notation that avoids some of the braces:
8990 ${hash_<n>_<m>:<string>}
8992 The second number is optional (in both notations). If <&'n'&> is greater than
8993 or equal to the length of the string, the expansion item returns the string.
8994 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8995 function to the string. The new string consists of characters taken from the
8996 first <&'m'&> characters of the string
8998 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9000 If <&'m'&> is not present the value 26 is used, so that only lower case
9001 letters appear. For example:
9003 &`$hash{3}{monty}} `& yields &`jmg`&
9004 &`$hash{5}{monty}} `& yields &`monty`&
9005 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9008 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9009 &*$h_*&<&'header&~name'&>&*:*&" &&&
9010 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9011 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9012 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9013 &*$rh_*&<&'header&~name'&>&*:*&"
9014 .cindex "expansion" "header insertion"
9015 .vindex "&$header_$&"
9016 .vindex "&$bheader_$&"
9017 .vindex "&$rheader_$&"
9018 .cindex "header lines" "in expansion strings"
9019 .cindex "header lines" "character sets"
9020 .cindex "header lines" "decoding"
9021 Substitute the contents of the named message header line, for example
9025 The newline that terminates a header line is not included in the expansion, but
9026 internal newlines (caused by splitting the header line over several physical
9027 lines) may be present.
9029 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9030 the data in the header line is interpreted.
9033 .cindex "white space" "in header lines"
9034 &%rheader%& gives the original &"raw"& content of the header line, with no
9035 processing at all, and without the removal of leading and trailing white space.
9038 .cindex "base64 encoding" "in header lines"
9039 &%bheader%& removes leading and trailing white space, and then decodes base64
9040 or quoted-printable MIME &"words"& within the header text, but does no
9041 character set translation. If decoding of what looks superficially like a MIME
9042 &"word"& fails, the raw string is returned. If decoding
9043 .cindex "binary zero" "in header line"
9044 produces a binary zero character, it is replaced by a question mark &-- this is
9045 what Exim does for binary zeros that are actually received in header lines.
9048 &%header%& tries to translate the string as decoded by &%bheader%& to a
9049 standard character set. This is an attempt to produce the same string as would
9050 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9051 returned. Translation is attempted only on operating systems that support the
9052 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9053 a system Makefile or in &_Local/Makefile_&.
9056 In a filter file, the target character set for &%header%& can be specified by a
9057 command of the following form:
9059 headers charset "UTF-8"
9061 This command affects all references to &$h_$& (or &$header_$&) expansions in
9062 subsequently obeyed filter commands. In the absence of this command, the target
9063 character set in a filter is taken from the setting of the &%headers_charset%&
9064 option in the runtime configuration. The value of this option defaults to the
9065 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9068 Header names follow the syntax of RFC 2822, which states that they may contain
9069 any printing characters except space and colon. Consequently, curly brackets
9070 &'do not'& terminate header names, and should not be used to enclose them as
9071 if they were variables. Attempting to do so causes a syntax error.
9073 Only header lines that are common to all copies of a message are visible to
9074 this mechanism. These are the original header lines that are received with the
9075 message, and any that are added by an ACL statement or by a system
9076 filter. Header lines that are added to a particular copy of a message by a
9077 router or transport are not accessible.
9079 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9080 before the DATA ACL, because the header structure is not set up until the
9081 message is received. Header lines that are added in a RCPT ACL (for example)
9082 are saved until the message's incoming header lines are available, at which
9083 point they are added. When a DATA ACL is running, however, header lines added
9084 by earlier ACLs are visible.
9086 Upper case and lower case letters are synonymous in header names. If the
9087 following character is white space, the terminating colon may be omitted, but
9088 this is not recommended, because you may then forget it when it is needed. When
9089 white space terminates the header name, it is included in the expanded string.
9090 If the message does not contain the given header, the expansion item is
9091 replaced by an empty string. (See the &%def%& condition in section
9092 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
9094 If there is more than one header with the same name, they are all concatenated
9095 to form the substitution string, up to a maximum length of 64K. Unless
9096 &%rheader%& is being used, leading and trailing white space is removed from
9097 each header before concatenation, and a completely empty header is ignored. A
9098 newline character is then inserted between non-empty headers, but there is no
9099 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9100 those headers that contain lists of addresses, a comma is also inserted at the
9101 junctions between headers. This does not happen for the &%rheader%& expansion.
9104 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9105 .cindex "expansion" "hmac hashing"
9107 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9108 shared secret and some text into a message authentication code, as specified in
9109 RFC 2104. This differs from &`${md5:secret_text...}`& or
9110 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9111 cryptographic hash, allowing for authentication that is not possible with MD5
9112 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9113 present. For example:
9115 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9117 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9120 dd97e3ba5d1a61b5006108f8c8252953
9122 As an example of how this might be used, you might put in the main part of
9123 an Exim configuration:
9125 SPAMSCAN_SECRET=cohgheeLei2thahw
9127 In a router or a transport you could then have:
9130 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9131 ${hmac{md5}{SPAMSCAN_SECRET}\
9132 {${primary_hostname},${message_exim_id},$h_message-id:}}
9134 Then given a message, you can check where it was scanned by looking at the
9135 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9136 this header line is authentic by recomputing the authentication code from the
9137 host name, message ID and the &'Message-id:'& header line. This can be done
9138 using Exim's &%-be%& option, or by other means, for example by using the
9139 &'hmac_md5_hex()'& function in Perl.
9142 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9143 .cindex "expansion" "conditional"
9144 .cindex "&%if%&, expansion item"
9145 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9146 item; otherwise <&'string2'&> is used. The available conditions are described
9147 in section &<<SECTexpcond>>& below. For example:
9149 ${if eq {$local_part}{postmaster} {yes}{no} }
9151 The second string need not be present; if it is not and the condition is not
9152 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9153 be present instead of the second string (without any curly brackets). In this
9154 case, the expansion is forced to fail if the condition is not true (see section
9155 &<<SECTforexpfai>>&).
9157 If both strings are omitted, the result is the string &`true`& if the condition
9158 is true, and the empty string if the condition is false. This makes it less
9159 cumbersome to write custom ACL and router conditions. For example, instead of
9161 condition = ${if >{$acl_m4}{3}{true}{false}}
9165 condition = ${if >{$acl_m4}{3}}
9168 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9169 .cindex "expansion" "string truncation"
9170 .cindex "&%length%& expansion item"
9171 The &%length%& item is used to extract the initial portion of a string. Both
9172 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9173 you are using a fixed value for the number, that is, if <&'string1'&> does not
9174 change when expanded, you can use the simpler operator notation that avoids
9177 ${length_<n>:<string>}
9179 The result of this item is either the first <&'n'&> characters or the whole
9180 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9181 &%strlen%&, which gives the length of a string.
9184 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9185 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9186 .cindex "expansion" "extracting list elements by number"
9187 .cindex "&%listextract%&" "extract list elements by number"
9188 .cindex "list" "extracting elements by number"
9189 The <&'number'&> argument must consist entirely of decimal digits,
9190 apart from an optional leading minus,
9191 and leading and trailing white space (which is ignored).
9193 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9194 default, but the separator can be changed in the usual way.
9196 The first field of the list is numbered one.
9197 If the number is negative, the fields are
9198 counted from the end of the list, with the rightmost one numbered -1.
9199 The numbered element of the list is extracted and placed in &$value$&,
9200 then <&'string2'&> is expanded as the result.
9202 If the modulus of the
9203 number is zero or greater than the number of fields in the string,
9204 the result is the expansion of <&'string3'&>.
9208 ${listextract{2}{x:42:99}}
9212 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9214 yields &"result: 99"&.
9216 If {<&'string3'&>} is omitted, an empty string is used for string3.
9217 If {<&'string2'&>} is also omitted, the value that was
9219 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9222 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9223 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9224 This is the first of one of two different types of lookup item, which are both
9225 described in the next item.
9227 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9228 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9229 .cindex "expansion" "lookup in"
9230 .cindex "file" "lookups"
9231 .cindex "lookup" "in expanded string"
9232 The two forms of lookup item specify data lookups in files and databases, as
9233 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9234 lookups, and the second is used for query-style lookups. The <&'key'&>,
9235 <&'file'&>, and <&'query'&> strings are expanded before use.
9237 If there is any white space in a lookup item which is part of a filter command,
9238 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9239 other place where white space is significant, the lookup item must be enclosed
9240 in double quotes. The use of data lookups in users' filter files may be locked
9241 out by the system administrator.
9244 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9245 During its expansion, the variable &$value$& contains the data returned by the
9246 lookup. Afterwards it reverts to the value it had previously (at the outer
9247 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9248 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9249 string on failure. If <&'string2'&> is provided, it can itself be a nested
9250 lookup, thus providing a mechanism for looking up a default value when the
9251 original lookup fails.
9253 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9254 data for the outer lookup while the parameters of the second lookup are
9255 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9256 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9257 appear, and in this case, if the lookup fails, the entire expansion is forced
9258 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9259 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9260 successful lookup, and nothing in the case of failure.
9262 For single-key lookups, the string &"partial"& is permitted to precede the
9263 search type in order to do partial matching, and * or *@ may follow a search
9264 type to request default lookups if the key does not match (see sections
9265 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9267 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9268 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9269 and non-wild parts of the key during the expansion of the replacement text.
9270 They return to their previous values at the end of the lookup item.
9272 This example looks up the postmaster alias in the conventional alias file:
9274 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9276 This example uses NIS+ to look up the full name of the user corresponding to
9277 the local part of an address, forcing the expansion to fail if it is not found:
9279 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9284 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9285 .cindex "expansion" "list creation"
9287 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9288 default, but the separator can be changed in the usual way. For each item
9289 in this list, its value is place in &$item$&, and then <&'string2'&> is
9290 expanded and added to the output as an item in a new list. The separator used
9291 for the output list is the same as the one used for the input, but a separator
9292 setting is not included in the output. For example:
9294 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9296 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9297 value of &$item$& is restored to what it was before. See also the &*filter*&
9298 and &*reduce*& expansion items.
9300 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9301 .cindex "expansion" "numeric hash"
9302 .cindex "hash function" "numeric"
9303 The three strings are expanded; the first two must yield numbers. Call them
9304 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9305 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9306 can use the simpler operator notation that avoids some of the braces:
9308 ${nhash_<n>_<m>:<string>}
9310 The second number is optional (in both notations). If there is only one number,
9311 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9312 processed by a div/mod hash function that returns two numbers, separated by a
9313 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9316 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9318 returns the string &"6/33"&.
9322 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9323 .cindex "Perl" "use in expanded string"
9324 .cindex "expansion" "calling Perl from"
9325 This item is available only if Exim has been built to include an embedded Perl
9326 interpreter. The subroutine name and the arguments are first separately
9327 expanded, and then the Perl subroutine is called with those arguments. No
9328 additional arguments need be given; the maximum number permitted, including the
9329 name of the subroutine, is nine.
9331 The return value of the subroutine is inserted into the expanded string, unless
9332 the return value is &%undef%&. In that case, the expansion fails in the same
9333 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9334 Whatever you return is evaluated in a scalar context. For example, if you
9335 return the name of a Perl vector, the return value is the size of the vector,
9338 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9339 with the error message that was passed to &%die%&. More details of the embedded
9340 Perl facility are given in chapter &<<CHAPperl>>&.
9342 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9343 out the use of this expansion item in filter files.
9346 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9347 .cindex "&%prvs%& expansion item"
9348 The first argument is a complete email address and the second is secret
9349 keystring. The third argument, specifying a key number, is optional. If absent,
9350 it defaults to 0. The result of the expansion is a prvs-signed email address,
9351 to be typically used with the &%return_path%& option on an &(smtp)& transport
9352 as part of a bounce address tag validation (BATV) scheme. For more discussion
9353 and an example, see section &<<SECTverifyPRVS>>&.
9355 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9356 {*&<&'string'&>&*}}*&"
9357 .cindex "&%prvscheck%& expansion item"
9358 This expansion item is the complement of the &%prvs%& item. It is used for
9359 checking prvs-signed addresses. If the expansion of the first argument does not
9360 yield a syntactically valid prvs-signed address, the whole item expands to the
9361 empty string. When the first argument does expand to a syntactically valid
9362 prvs-signed address, the second argument is expanded, with the prvs-decoded
9363 version of the address and the key number extracted from the address in the
9364 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9366 These two variables can be used in the expansion of the second argument to
9367 retrieve the secret. The validity of the prvs-signed address is then checked
9368 against the secret. The result is stored in the variable &$prvscheck_result$&,
9369 which is empty for failure or &"1"& for success.
9371 The third argument is optional; if it is missing, it defaults to an empty
9372 string. This argument is now expanded. If the result is an empty string, the
9373 result of the expansion is the decoded version of the address. This is the case
9374 whether or not the signature was valid. Otherwise, the result of the expansion
9375 is the expansion of the third argument.
9377 All three variables can be used in the expansion of the third argument.
9378 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9379 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9381 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9382 .cindex "expansion" "inserting an entire file"
9383 .cindex "file" "inserting into expansion"
9384 .cindex "&%readfile%& expansion item"
9385 The file name and end-of-line string are first expanded separately. The file is
9386 then read, and its contents replace the entire item. All newline characters in
9387 the file are replaced by the end-of-line string if it is present. Otherwise,
9388 newlines are left in the string.
9389 String expansion is not applied to the contents of the file. If you want this,
9390 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9391 the string expansion fails.
9393 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9394 locks out the use of this expansion item in filter files.
9398 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9399 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9400 .cindex "expansion" "inserting from a socket"
9401 .cindex "socket, use of in expansion"
9402 .cindex "&%readsocket%& expansion item"
9403 This item inserts data from a Unix domain or Internet socket into the expanded
9404 string. The minimal way of using it uses just two arguments, as in these
9407 ${readsocket{/socket/name}{request string}}
9408 ${readsocket{inet:some.host:1234}{request string}}
9410 For a Unix domain socket, the first substring must be the path to the socket.
9411 For an Internet socket, the first substring must contain &`inet:`& followed by
9412 a host name or IP address, followed by a colon and a port, which can be a
9413 number or the name of a TCP port in &_/etc/services_&. An IP address may
9414 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9417 ${readsocket{inet:[::1]:1234}{request string}}
9419 Only a single host name may be given, but if looking it up yields more than
9420 one IP address, they are each tried in turn until a connection is made. For
9421 both kinds of socket, Exim makes a connection, writes the request string
9422 (unless it is an empty string) and reads from the socket until an end-of-file
9423 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9424 extend what can be done. Firstly, you can vary the timeout. For example:
9426 ${readsocket{/socket/name}{request string}{3s}}
9428 A fourth argument allows you to change any newlines that are in the data
9429 that is read, in the same way as for &%readfile%& (see above). This example
9430 turns them into spaces:
9432 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9434 As with all expansions, the substrings are expanded before the processing
9435 happens. Errors in these sub-expansions cause the expansion to fail. In
9436 addition, the following errors can occur:
9439 Failure to create a socket file descriptor;
9441 Failure to connect the socket;
9443 Failure to write the request string;
9445 Timeout on reading from the socket.
9448 By default, any of these errors causes the expansion to fail. However, if
9449 you supply a fifth substring, it is expanded and used when any of the above
9450 errors occurs. For example:
9452 ${readsocket{/socket/name}{request string}{3s}{\n}\
9455 You can test for the existence of a Unix domain socket by wrapping this
9456 expansion in &`${if exists`&, but there is a race condition between that test
9457 and the actual opening of the socket, so it is safer to use the fifth argument
9458 if you want to be absolutely sure of avoiding an expansion error for a
9459 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9461 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9462 locks out the use of this expansion item in filter files.
9465 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9466 .cindex "expansion" "reducing a list to a scalar"
9467 .cindex "list" "reducing to a scalar"
9470 This operation reduces a list to a single, scalar string. After expansion,
9471 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9472 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9473 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9474 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9475 them. The result of that expansion is assigned to &$value$& before the next
9476 iteration. When the end of the list is reached, the final value of &$value$& is
9477 added to the expansion output. The &*reduce*& expansion item can be used in a
9478 number of ways. For example, to add up a list of numbers:
9480 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9482 The result of that expansion would be &`6`&. The maximum of a list of numbers
9485 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9487 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9488 restored to what they were before. See also the &*filter*& and &*map*&
9491 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9492 This item inserts &"raw"& header lines. It is described with the &%header%&
9493 expansion item above.
9495 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9496 {*&<&'string2'&>&*}}*&"
9497 .cindex "expansion" "running a command"
9498 .cindex "&%run%& expansion item"
9499 The command and its arguments are first expanded separately, and then the
9500 command is run in a separate process, but under the same uid and gid. As in
9501 other command executions from Exim, a shell is not used by default. If you want
9502 a shell, you must explicitly code it.
9504 The standard input for the command exists, but is empty. The standard output
9505 and standard error are set to the same file descriptor.
9506 .cindex "return code" "from &%run%& expansion"
9508 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9509 and replaces the entire item; during this expansion, the standard output/error
9510 from the command is in the variable &$value$&. If the command fails,
9511 <&'string2'&>, if present, is expanded and used. Once again, during the
9512 expansion, the standard output/error from the command is in the variable
9515 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9516 can be the word &"fail"& (not in braces) to force expansion failure if the
9517 command does not succeed. If both strings are omitted, the result is contents
9518 of the standard output/error on success, and nothing on failure.
9520 .vindex "&$run_in_acl$&"
9521 The standard output/error of the command is put in the variable &$value$&.
9522 In this ACL example, the output of a command is logged for the admin to
9525 warn condition = ${run{/usr/bin/id}{yes}{no}}
9526 log_message = Output of id: $value
9528 If the command requires shell idioms, such as the > redirect operator, the
9529 shell must be invoked directly, such as with:
9531 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9535 The return code from the command is put in the variable &$runrc$&, and this
9536 remains set afterwards, so in a filter file you can do things like this:
9538 if "${run{x y z}{}}$runrc" is 1 then ...
9539 elif $runrc is 2 then ...
9543 If execution of the command fails (for example, the command does not exist),
9544 the return code is 127 &-- the same code that shells use for non-existent
9547 &*Warning*&: In a router or transport, you cannot assume the order in which
9548 option values are expanded, except for those preconditions whose order of
9549 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9550 by the expansion of one option, and use it in another.
9552 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9553 out the use of this expansion item in filter files.
9556 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9557 .cindex "expansion" "string substitution"
9558 .cindex "&%sg%& expansion item"
9559 This item works like Perl's substitution operator (s) with the global (/g)
9560 option; hence its name. However, unlike the Perl equivalent, Exim does not
9561 modify the subject string; instead it returns the modified string for insertion
9562 into the overall expansion. The item takes three arguments: the subject string,
9563 a regular expression, and a substitution string. For example:
9565 ${sg{abcdefabcdef}{abc}{xyz}}
9567 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9568 if any $ or \ characters are required in the regular expression or in the
9569 substitution string, they have to be escaped. For example:
9571 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9573 yields &"defabc"&, and
9575 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9577 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9578 the regular expression from string expansion.
9582 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9583 .cindex "&%substr%& expansion item"
9584 .cindex "substring extraction"
9585 .cindex "expansion" "substring extraction"
9586 The three strings are expanded; the first two must yield numbers. Call them
9587 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9588 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9589 can use the simpler operator notation that avoids some of the braces:
9591 ${substr_<n>_<m>:<string>}
9593 The second number is optional (in both notations).
9594 If it is absent in the simpler format, the preceding underscore must also be
9597 The &%substr%& item can be used to extract more general substrings than
9598 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9599 length required. For example
9601 ${substr{3}{2}{$local_part}}
9603 If the starting offset is greater than the string length the result is the
9604 null string; if the length plus starting offset is greater than the string
9605 length, the result is the right-hand part of the string, starting from the
9606 given offset. The first character in the string has offset zero.
9608 The &%substr%& expansion item can take negative offset values to count
9609 from the right-hand end of its operand. The last character is offset -1, the
9610 second-last is offset -2, and so on. Thus, for example,
9612 ${substr{-5}{2}{1234567}}
9614 yields &"34"&. If the absolute value of a negative offset is greater than the
9615 length of the string, the substring starts at the beginning of the string, and
9616 the length is reduced by the amount of overshoot. Thus, for example,
9618 ${substr{-5}{2}{12}}
9620 yields an empty string, but
9622 ${substr{-3}{2}{12}}
9626 When the second number is omitted from &%substr%&, the remainder of the string
9627 is taken if the offset is positive. If it is negative, all characters in the
9628 string preceding the offset point are taken. For example, an offset of -1 and
9629 no length, as in these semantically identical examples:
9632 ${substr{-1}{abcde}}
9634 yields all but the last character of the string, that is, &"abcd"&.
9638 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9639 {*&<&'replacements'&>&*}}*&"
9640 .cindex "expansion" "character translation"
9641 .cindex "&%tr%& expansion item"
9642 This item does single-character translation on its subject string. The second
9643 argument is a list of characters to be translated in the subject string. Each
9644 matching character is replaced by the corresponding character from the
9645 replacement list. For example
9647 ${tr{abcdea}{ac}{13}}
9649 yields &`1b3de1`&. If there are duplicates in the second character string, the
9650 last occurrence is used. If the third string is shorter than the second, its
9651 last character is replicated. However, if it is empty, no translation takes
9657 .section "Expansion operators" "SECTexpop"
9658 .cindex "expansion" "operators"
9659 For expansion items that perform transformations on a single argument string,
9660 the &"operator"& notation is used because it is simpler and uses fewer braces.
9661 The substring is first expanded before the operation is applied to it. The
9662 following operations can be performed:
9665 .vitem &*${address:*&<&'string'&>&*}*&
9666 .cindex "expansion" "RFC 2822 address handling"
9667 .cindex "&%address%& expansion item"
9668 The string is interpreted as an RFC 2822 address, as it might appear in a
9669 header line, and the effective address is extracted from it. If the string does
9670 not parse successfully, the result is empty.
9673 .vitem &*${addresses:*&<&'string'&>&*}*&
9674 .cindex "expansion" "RFC 2822 address handling"
9675 .cindex "&%addresses%& expansion item"
9676 The string (after expansion) is interpreted as a list of addresses in RFC
9677 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9678 operative address (&'local-part@domain'&) is extracted from each item, and the
9679 result of the expansion is a colon-separated list, with appropriate
9680 doubling of colons should any happen to be present in the email addresses.
9681 Syntactically invalid RFC2822 address items are omitted from the output.
9683 It is possible to specify a character other than colon for the output
9684 separator by starting the string with > followed by the new separator
9685 character. For example:
9687 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9689 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9690 expansion item, which extracts the working address from a single RFC2822
9691 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9694 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9695 a strict interpretation of header line formatting. Exim parses the bare,
9696 unquoted portion of an email address and if it finds a comma, treats it as an
9697 email address seperator. For the example header line:
9699 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9701 The first example below demonstrates that Q-encoded email addresses are parsed
9702 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9703 It does not see the comma because it's still encoded as "=2C". The second
9704 example below is passed the contents of &`$header_from:`&, meaning it gets
9705 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9706 The third example shows that the presence of a comma is skipped when it is
9709 # exim -be '${addresses:From: \
9710 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9712 # exim -be '${addresses:From: Last, First <user@example.com>}'
9713 Last:user@example.com
9714 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9718 .vitem &*${base62:*&<&'digits'&>&*}*&
9719 .cindex "&%base62%& expansion item"
9720 .cindex "expansion" "conversion to base 62"
9721 The string must consist entirely of decimal digits. The number is converted to
9722 base 62 and output as a string of six characters, including leading zeros. In
9723 the few operating environments where Exim uses base 36 instead of base 62 for
9724 its message identifiers (because those systems do not have case-sensitive file
9725 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9726 be absolutely clear: this is &'not'& base64 encoding.
9728 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9729 .cindex "&%base62d%& expansion item"
9730 .cindex "expansion" "conversion to base 62"
9731 The string must consist entirely of base-62 digits, or, in operating
9732 environments where Exim uses base 36 instead of base 62 for its message
9733 identifiers, base-36 digits. The number is converted to decimal and output as a
9737 .vitem &*${domain:*&<&'string'&>&*}*&
9738 .cindex "domain" "extraction"
9739 .cindex "expansion" "domain extraction"
9740 The string is interpreted as an RFC 2822 address and the domain is extracted
9741 from it. If the string does not parse successfully, the result is empty.
9744 .vitem &*${escape:*&<&'string'&>&*}*&
9745 .cindex "expansion" "escaping non-printing characters"
9746 .cindex "&%escape%& expansion item"
9747 If the string contains any non-printing characters, they are converted to
9748 escape sequences starting with a backslash. Whether characters with the most
9749 significant bit set (so-called &"8-bit characters"&) count as printing or not
9750 is controlled by the &%print_topbitchars%& option.
9753 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9754 .cindex "expansion" "expression evaluation"
9755 .cindex "expansion" "arithmetic expression"
9756 .cindex "&%eval%& expansion item"
9757 These items supports simple arithmetic and bitwise logical operations in
9758 expansion strings. The string (after expansion) must be a conventional
9759 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9760 logical operators, and parentheses. All operations are carried out using
9761 integer arithmetic. The operator priorities are as follows (the same as in the
9762 C programming language):
9764 .irow &'highest:'& "not (~), negate (-)"
9765 .irow "" "multiply (*), divide (/), remainder (%)"
9766 .irow "" "plus (+), minus (-)"
9767 .irow "" "shift-left (<<), shift-right (>>)"
9770 .irow &'lowest:'& "or (|)"
9772 Binary operators with the same priority are evaluated from left to right. White
9773 space is permitted before or after operators.
9775 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9776 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9777 decimal, even if they start with a leading zero; hexadecimal numbers are not
9778 permitted. This can be useful when processing numbers extracted from dates or
9779 times, which often do have leading zeros.
9781 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
9783 respectively. Negative numbers are supported. The result of the computation is
9784 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
9787 &`${eval:1+1} `& yields 2
9788 &`${eval:1+2*3} `& yields 7
9789 &`${eval:(1+2)*3} `& yields 9
9790 &`${eval:2+42%5} `& yields 4
9791 &`${eval:0xc&5} `& yields 4
9792 &`${eval:0xc|5} `& yields 13
9793 &`${eval:0xc^5} `& yields 9
9794 &`${eval:0xc>>1} `& yields 6
9795 &`${eval:0xc<<1} `& yields 24
9796 &`${eval:~255&0x1234} `& yields 4608
9797 &`${eval:-(~255&0x1234)} `& yields -4608
9800 As a more realistic example, in an ACL you might have
9802 deny message = Too many bad recipients
9805 {>{$rcpt_count}{10}} \
9808 {$recipients_count} \
9809 {${eval:$rcpt_count/2}} \
9813 The condition is true if there have been more than 10 RCPT commands and
9814 fewer than half of them have resulted in a valid recipient.
9817 .vitem &*${expand:*&<&'string'&>&*}*&
9818 .cindex "expansion" "re-expansion of substring"
9819 The &%expand%& operator causes a string to be expanded for a second time. For
9822 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9824 first looks up a string in a file while expanding the operand for &%expand%&,
9825 and then re-expands what it has found.
9828 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9830 .cindex "UTF-8" "conversion from"
9831 .cindex "expansion" "UTF-8 conversion"
9832 .cindex "&%from_utf8%& expansion item"
9833 The world is slowly moving towards Unicode, although there are no standards for
9834 email yet. However, other applications (including some databases) are starting
9835 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9836 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9837 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9838 the result is an undefined sequence of bytes.
9840 Unicode code points with values less than 256 are compatible with ASCII and
9841 ISO-8859-1 (also known as Latin-1).
9842 For example, character 169 is the copyright symbol in both cases, though the
9843 way it is encoded is different. In UTF-8, more than one byte is needed for
9844 characters with code values greater than 127, whereas ISO-8859-1 is a
9845 single-byte encoding (but thereby limited to 256 characters). This makes
9846 translation from UTF-8 to ISO-8859-1 straightforward.
9849 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9850 .cindex "hash function" "textual"
9851 .cindex "expansion" "textual hash"
9852 The &%hash%& operator is a simpler interface to the hashing function that can
9853 be used when the two parameters are fixed numbers (as opposed to strings that
9854 change when expanded). The effect is the same as
9856 ${hash{<n>}{<m>}{<string>}}
9858 See the description of the general &%hash%& item above for details. The
9859 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9863 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9864 .cindex "base64 encoding" "conversion from hex"
9865 .cindex "expansion" "hex to base64"
9866 .cindex "&%hex2b64%& expansion item"
9867 This operator converts a hex string into one that is base64 encoded. This can
9868 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9872 .vitem &*${hexquote:*&<&'string'&>&*}*&
9873 .cindex "quoting" "hex-encoded unprintable characters"
9874 .cindex "&%hexquote%& expansion item"
9875 This operator converts non-printable characters in a string into a hex
9876 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
9877 as is, and other byte values are converted to &`\xNN`&, for example a
9878 byte value 127 is converted to &`\x7f`&.
9881 .vitem &*${lc:*&<&'string'&>&*}*&
9882 .cindex "case forcing in strings"
9883 .cindex "string" "case forcing"
9884 .cindex "lower casing"
9885 .cindex "expansion" "case forcing"
9886 .cindex "&%lc%& expansion item"
9887 This forces the letters in the string into lower-case, for example:
9892 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9893 .cindex "expansion" "string truncation"
9894 .cindex "&%length%& expansion item"
9895 The &%length%& operator is a simpler interface to the &%length%& function that
9896 can be used when the parameter is a fixed number (as opposed to a string that
9897 changes when expanded). The effect is the same as
9899 ${length{<number>}{<string>}}
9901 See the description of the general &%length%& item above for details. Note that
9902 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9903 when &%length%& is used as an operator.
9906 .vitem &*${listcount:*&<&'string'&>&*}*&
9907 .cindex "expansion" "list item count"
9908 .cindex "list" "item count"
9909 .cindex "list" "count of items"
9910 .cindex "&%listcount%& expansion item"
9911 The string is interpreted as a list and the number of items is returned.
9914 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
9915 .cindex "expansion" "named list"
9916 .cindex "&%listnamed%& expansion item"
9917 The name is interpreted as a named list and the content of the list is returned,
9918 expanding any referenced lists, re-quoting as needed for colon-separation.
9919 If the optional type is given it must be one of "a", "d", "h" or "l"
9920 and selects address-, domain-, host- or localpart- lists to search among respectively.
9921 Otherwise all types are searched in an undefined order and the first
9922 matching list is returned.
9925 .vitem &*${local_part:*&<&'string'&>&*}*&
9926 .cindex "expansion" "local part extraction"
9927 .cindex "&%local_part%& expansion item"
9928 The string is interpreted as an RFC 2822 address and the local part is
9929 extracted from it. If the string does not parse successfully, the result is
9933 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9934 .cindex "masked IP address"
9935 .cindex "IP address" "masking"
9936 .cindex "CIDR notation"
9937 .cindex "expansion" "IP address masking"
9938 .cindex "&%mask%& expansion item"
9939 If the form of the string to be operated on is not an IP address followed by a
9940 slash and an integer (that is, a network address in CIDR notation), the
9941 expansion fails. Otherwise, this operator converts the IP address to binary,
9942 masks off the least significant bits according to the bit count, and converts
9943 the result back to text, with mask appended. For example,
9945 ${mask:10.111.131.206/28}
9947 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9948 be mostly used for looking up masked addresses in files, the result for an IPv6
9949 address uses dots to separate components instead of colons, because colon
9950 terminates a key string in lsearch files. So, for example,
9952 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9956 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9958 Letters in IPv6 addresses are always output in lower case.
9961 .vitem &*${md5:*&<&'string'&>&*}*&
9963 .cindex "expansion" "MD5 hash"
9964 .cindex "&%md5%& expansion item"
9965 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9966 as a 32-digit hexadecimal number, in which any letters are in lower case.
9969 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9970 .cindex "expansion" "numeric hash"
9971 .cindex "hash function" "numeric"
9972 The &%nhash%& operator is a simpler interface to the numeric hashing function
9973 that can be used when the two parameters are fixed numbers (as opposed to
9974 strings that change when expanded). The effect is the same as
9976 ${nhash{<n>}{<m>}{<string>}}
9978 See the description of the general &%nhash%& item above for details.
9981 .vitem &*${quote:*&<&'string'&>&*}*&
9982 .cindex "quoting" "in string expansions"
9983 .cindex "expansion" "quoting"
9984 .cindex "&%quote%& expansion item"
9985 The &%quote%& operator puts its argument into double quotes if it
9986 is an empty string or
9987 contains anything other than letters, digits, underscores, dots, and hyphens.
9988 Any occurrences of double quotes and backslashes are escaped with a backslash.
9989 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9990 respectively For example,
9998 The place where this is useful is when the argument is a substitution from a
9999 variable or a message header.
10001 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10002 .cindex "&%quote_local_part%& expansion item"
10003 This operator is like &%quote%&, except that it quotes the string only if
10004 required to do so by the rules of RFC 2822 for quoting local parts. For
10005 example, a plus sign would not cause quoting (but it would for &%quote%&).
10006 If you are creating a new email address from the contents of &$local_part$&
10007 (or any other unknown data), you should always use this operator.
10010 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10011 .cindex "quoting" "lookup-specific"
10012 This operator applies lookup-specific quoting rules to the string. Each
10013 query-style lookup type has its own quoting rules which are described with
10014 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10016 ${quote_ldap:two * two}
10022 For single-key lookup types, no quoting is ever necessary and this operator
10023 yields an unchanged string.
10026 .vitem &*${randint:*&<&'n'&>&*}*&
10027 .cindex "random number"
10028 This operator returns a somewhat random number which is less than the
10029 supplied number and is at least 0. The quality of this randomness depends
10030 on how Exim was built; the values are not suitable for keying material.
10031 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10032 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10033 for versions of GnuTLS with that function.
10034 Otherwise, the implementation may be arc4random(), random() seeded by
10035 srandomdev() or srandom(), or a custom implementation even weaker than
10039 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10040 .cindex "expansion" "IP address"
10041 This operator reverses an IP address; for IPv4 addresses, the result is in
10042 dotted-quad decimal form, while for IPv6 addreses the result is in
10043 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10044 for DNS. For example,
10046 ${reverse_ip:192.0.2.4}
10047 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10052 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10056 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10057 .cindex "expansion" "RFC 2047"
10058 .cindex "RFC 2047" "expansion operator"
10059 .cindex "&%rfc2047%& expansion item"
10060 This operator encodes text according to the rules of RFC 2047. This is an
10061 encoding that is used in header lines to encode non-ASCII characters. It is
10062 assumed that the input string is in the encoding specified by the
10063 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
10064 contains only characters in the range 33&--126, and no instances of the
10067 ? = ( ) < > @ , ; : \ " . [ ] _
10069 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10070 string, using as many &"encoded words"& as necessary to encode all the
10074 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10075 .cindex "expansion" "RFC 2047"
10076 .cindex "RFC 2047" "decoding"
10077 .cindex "&%rfc2047d%& expansion item"
10078 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10079 bytes are replaced by question marks. Characters are converted into the
10080 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10081 not recognized unless &%check_rfc2047_length%& is set false.
10083 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10084 access a header line, RFC 2047 decoding is done automatically. You do not need
10085 to use this operator as well.
10089 .vitem &*${rxquote:*&<&'string'&>&*}*&
10090 .cindex "quoting" "in regular expressions"
10091 .cindex "regular expressions" "quoting"
10092 .cindex "&%rxquote%& expansion item"
10093 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10094 characters in its argument. This is useful when substituting the values of
10095 variables or headers inside regular expressions.
10098 .vitem &*${sha1:*&<&'string'&>&*}*&
10099 .cindex "SHA-1 hash"
10100 .cindex "expansion" "SHA-1 hashing"
10101 .cindex "&%sha2%& expansion item"
10102 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10103 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10106 .vitem &*${stat:*&<&'string'&>&*}*&
10107 .cindex "expansion" "statting a file"
10108 .cindex "file" "extracting characteristics"
10109 .cindex "&%stat%& expansion item"
10110 The string, after expansion, must be a file path. A call to the &[stat()]&
10111 function is made for this path. If &[stat()]& fails, an error occurs and the
10112 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10113 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10114 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10115 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10116 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10117 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10118 can extract individual fields using the &%extract%& expansion item.
10120 The use of the &%stat%& expansion in users' filter files can be locked out by
10121 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10122 systems for files larger than 2GB.
10124 .vitem &*${str2b64:*&<&'string'&>&*}*&
10125 .cindex "expansion" "base64 encoding"
10126 .cindex "base64 encoding" "in string expansion"
10127 .cindex "&%str2b64%& expansion item"
10128 This operator converts a string into one that is base64 encoded.
10132 .vitem &*${strlen:*&<&'string'&>&*}*&
10133 .cindex "expansion" "string length"
10134 .cindex "string" "length in expansion"
10135 .cindex "&%strlen%& expansion item"
10136 The item is replace by the length of the expanded string, expressed as a
10137 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10140 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10141 .cindex "&%substr%& expansion item"
10142 .cindex "substring extraction"
10143 .cindex "expansion" "substring expansion"
10144 The &%substr%& operator is a simpler interface to the &%substr%& function that
10145 can be used when the two parameters are fixed numbers (as opposed to strings
10146 that change when expanded). The effect is the same as
10148 ${substr{<start>}{<length>}{<string>}}
10150 See the description of the general &%substr%& item above for details. The
10151 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10153 .vitem &*${time_eval:*&<&'string'&>&*}*&
10154 .cindex "&%time_eval%& expansion item"
10155 .cindex "time interval" "decoding"
10156 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10159 .vitem &*${time_interval:*&<&'string'&>&*}*&
10160 .cindex "&%time_interval%& expansion item"
10161 .cindex "time interval" "formatting"
10162 The argument (after sub-expansion) must be a sequence of decimal digits that
10163 represents an interval of time as a number of seconds. It is converted into a
10164 number of larger units and output in Exim's normal time format, for example,
10167 .vitem &*${uc:*&<&'string'&>&*}*&
10168 .cindex "case forcing in strings"
10169 .cindex "string" "case forcing"
10170 .cindex "upper casing"
10171 .cindex "expansion" "case forcing"
10172 .cindex "&%uc%& expansion item"
10173 This forces the letters in the string into upper-case.
10175 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10176 .cindex "correction of invalid utf-8 sequences in strings"
10177 .cindex "utf-8" "utf-8 sequences"
10178 .cindex "incorrect utf-8"
10179 .cindex "expansion" "utf-8 forcing"
10180 .cindex "&%utf8clean%& expansion item"
10181 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10189 .section "Expansion conditions" "SECTexpcond"
10190 .scindex IIDexpcond "expansion" "conditions"
10191 The following conditions are available for testing by the &%${if%& construct
10192 while expanding strings:
10195 .vitem &*!*&<&'condition'&>
10196 .cindex "expansion" "negating a condition"
10197 .cindex "negation" "in expansion condition"
10198 Preceding any condition with an exclamation mark negates the result of the
10201 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10202 .cindex "numeric comparison"
10203 .cindex "expansion" "numeric comparison"
10204 There are a number of symbolic operators for doing numeric comparisons. They
10210 &`>= `& greater or equal
10212 &`<= `& less or equal
10216 ${if >{$message_size}{10M} ...
10218 Note that the general negation operator provides for inequality testing. The
10219 two strings must take the form of optionally signed decimal integers,
10220 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10221 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10222 As a special case, the numerical value of an empty string is taken as
10225 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10226 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10227 10M, not if 10M is larger than &$message_size$&.
10230 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10231 {*&<&'arg2'&>&*}...}*&
10232 .cindex "expansion" "calling an acl"
10233 .cindex "&%acl%&" "expansion condition"
10234 The name and zero to nine argument strings are first expanded separately. The expanded
10235 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10236 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10237 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10238 and may use the variables; if another acl expansion is used the values
10239 are restored after it returns. If the ACL sets
10240 a value using a "message =" modifier the variable $value becomes
10241 the result of the expansion, otherwise it is empty.
10242 If the ACL returns accept the condition is true; if deny, false.
10243 If the ACL returns defer the result is a forced-fail.
10245 .vitem &*bool&~{*&<&'string'&>&*}*&
10246 .cindex "expansion" "boolean parsing"
10247 .cindex "&%bool%& expansion condition"
10248 This condition turns a string holding a true or false representation into
10249 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10250 (case-insensitively); also positive integer numbers map to true if non-zero,
10252 An empty string is treated as false.
10253 Leading and trailing whitespace is ignored;
10254 thus a string consisting only of whitespace is false.
10255 All other string values will result in expansion failure.
10257 When combined with ACL variables, this expansion condition will let you
10258 make decisions in one place and act on those decisions in another place.
10261 ${if bool{$acl_m_privileged_sender} ...
10265 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10266 .cindex "expansion" "boolean parsing"
10267 .cindex "&%bool_lax%& expansion condition"
10268 Like &%bool%&, this condition turns a string into a boolean state. But
10269 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10270 loose definition that the Router &%condition%& option uses. The empty string
10271 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10272 true. Leading and trailing whitespace is ignored.
10274 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10276 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10277 .cindex "expansion" "encrypted comparison"
10278 .cindex "encrypted strings, comparing"
10279 .cindex "&%crypteq%& expansion condition"
10280 This condition is included in the Exim binary if it is built to support any
10281 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10282 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10283 included in the binary.
10285 The &%crypteq%& condition has two arguments. The first is encrypted and
10286 compared against the second, which is already encrypted. The second string may
10287 be in the LDAP form for storing encrypted strings, which starts with the
10288 encryption type in curly brackets, followed by the data. If the second string
10289 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10290 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10291 Typically this will be a field from a password file. An example of an encrypted
10292 string in LDAP form is:
10294 {md5}CY9rzUYh03PK3k6DJie09g==
10296 If such a string appears directly in an expansion, the curly brackets have to
10297 be quoted, because they are part of the expansion syntax. For example:
10299 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10301 The following encryption types (whose names are matched case-independently) are
10306 .cindex "base64 encoding" "in encrypted password"
10307 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10308 printable characters to compare with the remainder of the second string. If the
10309 length of the comparison string is 24, Exim assumes that it is base64 encoded
10310 (as in the above example). If the length is 32, Exim assumes that it is a
10311 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10315 .cindex "SHA-1 hash"
10316 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10317 printable characters to compare with the remainder of the second string. If the
10318 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10319 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10320 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10323 .cindex "&[crypt()]&"
10324 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10325 only the first eight characters of the password. However, in modern operating
10326 systems this is no longer true, and in many cases the entire password is used,
10327 whatever its length.
10330 .cindex "&[crypt16()]&"
10331 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10332 use up to 16 characters of the password in some operating systems. Again, in
10333 modern operating systems, more characters may be used.
10335 Exim has its own version of &[crypt16()]&, which is just a double call to
10336 &[crypt()]&. For operating systems that have their own version, setting
10337 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10338 operating system version instead of its own. This option is set by default in
10339 the OS-dependent &_Makefile_& for those operating systems that are known to
10340 support &[crypt16()]&.
10342 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10343 it was not using the same algorithm as some operating systems' versions. It
10344 turns out that as well as &[crypt16()]& there is a function called
10345 &[bigcrypt()]& in some operating systems. This may or may not use the same
10346 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10348 However, since there is now a move away from the traditional &[crypt()]&
10349 functions towards using SHA1 and other algorithms, tidying up this area of
10350 Exim is seen as very low priority.
10352 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10353 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10354 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10355 default is &`{crypt}`&. Whatever the default, you can always use either
10356 function by specifying it explicitly in curly brackets.
10358 .vitem &*def:*&<&'variable&~name'&>
10359 .cindex "expansion" "checking for empty variable"
10360 .cindex "&%def%& expansion condition"
10361 The &%def%& condition must be followed by the name of one of the expansion
10362 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10363 variable does not contain the empty string. For example:
10365 ${if def:sender_ident {from $sender_ident}}
10367 Note that the variable name is given without a leading &%$%& character. If the
10368 variable does not exist, the expansion fails.
10370 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10371 &~&*def:h_*&<&'header&~name'&>&*:*&"
10372 .cindex "expansion" "checking header line existence"
10373 This condition is true if a message is being processed and the named header
10374 exists in the message. For example,
10376 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10378 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10379 the header name must be terminated by a colon if white space does not follow.
10381 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10382 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10383 .cindex "string" "comparison"
10384 .cindex "expansion" "string comparison"
10385 .cindex "&%eq%& expansion condition"
10386 .cindex "&%eqi%& expansion condition"
10387 The two substrings are first expanded. The condition is true if the two
10388 resulting strings are identical. For &%eq%& the comparison includes the case of
10389 letters, whereas for &%eqi%& the comparison is case-independent.
10391 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10392 .cindex "expansion" "file existence test"
10393 .cindex "file" "existence test"
10394 .cindex "&%exists%&, expansion condition"
10395 The substring is first expanded and then interpreted as an absolute path. The
10396 condition is true if the named file (or directory) exists. The existence test
10397 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10398 users' filter files may be locked out by the system administrator.
10400 .vitem &*first_delivery*&
10401 .cindex "delivery" "first"
10402 .cindex "first delivery"
10403 .cindex "expansion" "first delivery test"
10404 .cindex "&%first_delivery%& expansion condition"
10405 This condition, which has no data, is true during a message's first delivery
10406 attempt. It is false during any subsequent delivery attempts.
10409 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10410 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10411 .cindex "list" "iterative conditions"
10412 .cindex "expansion" "&*forall*& condition"
10413 .cindex "expansion" "&*forany*& condition"
10415 These conditions iterate over a list. The first argument is expanded to form
10416 the list. By default, the list separator is a colon, but it can be changed by
10417 the normal method. The second argument is interpreted as a condition that is to
10418 be applied to each item in the list in turn. During the interpretation of the
10419 condition, the current list item is placed in a variable called &$item$&.
10421 For &*forany*&, interpretation stops if the condition is true for any item, and
10422 the result of the whole condition is true. If the condition is false for all
10423 items in the list, the overall condition is false.
10425 For &*forall*&, interpretation stops if the condition is false for any item,
10426 and the result of the whole condition is false. If the condition is true for
10427 all items in the list, the overall condition is true.
10429 Note that negation of &*forany*& means that the condition must be false for all
10430 items for the overall condition to succeed, and negation of &*forall*& means
10431 that the condition must be false for at least one item. In this example, the
10432 list separator is changed to a comma:
10434 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10436 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10437 being processed, to enable these expansion items to be nested.
10439 To scan a named list, expand it with the &*listnamed*& operator.
10442 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10443 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10444 .cindex "string" "comparison"
10445 .cindex "expansion" "string comparison"
10446 .cindex "&%ge%& expansion condition"
10447 .cindex "&%gei%& expansion condition"
10448 The two substrings are first expanded. The condition is true if the first
10449 string is lexically greater than or equal to the second string. For &%ge%& the
10450 comparison includes the case of letters, whereas for &%gei%& the comparison is
10453 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10454 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10455 .cindex "string" "comparison"
10456 .cindex "expansion" "string comparison"
10457 .cindex "&%gt%& expansion condition"
10458 .cindex "&%gti%& expansion condition"
10459 The two substrings are first expanded. The condition is true if the first
10460 string is lexically greater than the second string. For &%gt%& the comparison
10461 includes the case of letters, whereas for &%gti%& the comparison is
10464 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10465 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10466 .cindex "string" "comparison"
10467 .cindex "list" "iterative conditions"
10468 Both strings are expanded; the second string is treated as a list of simple
10469 strings; if the first string is a member of the second, then the condition
10472 These are simpler to use versions of the more powerful &*forany*& condition.
10473 Examples, and the &*forany*& equivalents:
10475 ${if inlist{needle}{foo:needle:bar}}
10476 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10477 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10478 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10481 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10482 &*isip4&~{*&<&'string'&>&*}*& &&&
10483 &*isip6&~{*&<&'string'&>&*}*&
10484 .cindex "IP address" "testing string format"
10485 .cindex "string" "testing for IP address"
10486 .cindex "&%isip%& expansion condition"
10487 .cindex "&%isip4%& expansion condition"
10488 .cindex "&%isip6%& expansion condition"
10489 The substring is first expanded, and then tested to see if it has the form of
10490 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10491 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10493 For an IPv4 address, the test is for four dot-separated components, each of
10494 which consists of from one to three digits. For an IPv6 address, up to eight
10495 colon-separated components are permitted, each containing from one to four
10496 hexadecimal digits. There may be fewer than eight components if an empty
10497 component (adjacent colons) is present. Only one empty component is permitted.
10499 &*Note*&: The checks are just on the form of the address; actual numerical
10500 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10501 check. The main use of these tests is to distinguish between IP addresses and
10502 host names, or between IPv4 and IPv6 addresses. For example, you could use
10504 ${if isip4{$sender_host_address}...
10506 to test which IP version an incoming SMTP connection is using.
10508 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10509 .cindex "LDAP" "use for authentication"
10510 .cindex "expansion" "LDAP authentication test"
10511 .cindex "&%ldapauth%& expansion condition"
10512 This condition supports user authentication using LDAP. See section
10513 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10514 queries. For this use, the query must contain a user name and password. The
10515 query itself is not used, and can be empty. The condition is true if the
10516 password is not empty, and the user name and password are accepted by the LDAP
10517 server. An empty password is rejected without calling LDAP because LDAP binds
10518 with an empty password are considered anonymous regardless of the username, and
10519 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10520 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10524 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10525 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10526 .cindex "string" "comparison"
10527 .cindex "expansion" "string comparison"
10528 .cindex "&%le%& expansion condition"
10529 .cindex "&%lei%& expansion condition"
10530 The two substrings are first expanded. The condition is true if the first
10531 string is lexically less than or equal to the second string. For &%le%& the
10532 comparison includes the case of letters, whereas for &%lei%& the comparison is
10535 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10536 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10537 .cindex "string" "comparison"
10538 .cindex "expansion" "string comparison"
10539 .cindex "&%lt%& expansion condition"
10540 .cindex "&%lti%& expansion condition"
10541 The two substrings are first expanded. The condition is true if the first
10542 string is lexically less than the second string. For &%lt%& the comparison
10543 includes the case of letters, whereas for &%lti%& the comparison is
10547 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10548 .cindex "expansion" "regular expression comparison"
10549 .cindex "regular expressions" "match in expanded string"
10550 .cindex "&%match%& expansion condition"
10551 The two substrings are first expanded. The second is then treated as a regular
10552 expression and applied to the first. Because of the pre-expansion, if the
10553 regular expression contains dollar, or backslash characters, they must be
10554 escaped. Care must also be taken if the regular expression contains braces
10555 (curly brackets). A closing brace must be escaped so that it is not taken as a
10556 premature termination of <&'string2'&>. The easiest approach is to use the
10557 &`\N`& feature to disable expansion of the regular expression.
10560 ${if match {$local_part}{\N^\d{3}\N} ...
10562 If the whole expansion string is in double quotes, further escaping of
10563 backslashes is also required.
10565 The condition is true if the regular expression match succeeds.
10566 The regular expression is not required to begin with a circumflex
10567 metacharacter, but if there is no circumflex, the expression is not anchored,
10568 and it may match anywhere in the subject, not just at the start. If you want
10569 the pattern to match at the end of the subject, you must include the &`$`&
10570 metacharacter at an appropriate point.
10572 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10573 At the start of an &%if%& expansion the values of the numeric variable
10574 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10575 succeeds causes them to be reset to the substrings of that condition and they
10576 will have these values during the expansion of the success string. At the end
10577 of the &%if%& expansion, the previous values are restored. After testing a
10578 combination of conditions using &%or%&, the subsequent values of the numeric
10579 variables are those of the condition that succeeded.
10581 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10582 .cindex "&%match_address%& expansion condition"
10583 See &*match_local_part*&.
10585 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10586 .cindex "&%match_domain%& expansion condition"
10587 See &*match_local_part*&.
10589 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10590 .cindex "&%match_ip%& expansion condition"
10591 This condition matches an IP address to a list of IP address patterns. It must
10592 be followed by two argument strings. The first (after expansion) must be an IP
10593 address or an empty string. The second (not expanded) is a restricted host
10594 list that can match only an IP address, not a host name. For example:
10596 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10598 The specific types of host list item that are permitted in the list are:
10601 An IP address, optionally with a CIDR mask.
10603 A single asterisk, which matches any IP address.
10605 An empty item, which matches only if the IP address is empty. This could be
10606 useful for testing for a locally submitted message or one from specific hosts
10607 in a single test such as
10608 . ==== As this is a nested list, any displays it contains must be indented
10609 . ==== as otherwise they are too far to the left. This comment applies to
10610 . ==== the use of xmlto plus fop. There's no problem when formatting with
10611 . ==== sdop, with or without the extra indent.
10613 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10615 where the first item in the list is the empty string.
10617 The item @[] matches any of the local host's interface addresses.
10619 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10620 even if &`net-`& is not specified. There is never any attempt to turn the IP
10621 address into a host name. The most common type of linear search for
10622 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10623 masks. For example:
10625 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10627 It is of course possible to use other kinds of lookup, and in such a case, you
10628 do need to specify the &`net-`& prefix if you want to specify a specific
10629 address mask, for example:
10631 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10633 However, unless you are combining a &%match_ip%& condition with others, it is
10634 just as easy to use the fact that a lookup is itself a condition, and write:
10636 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10640 Note that <&'string2'&> is not itself subject to string expansion, unless
10641 Exim was built with the EXPAND_LISTMATCH_RHS option.
10643 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10645 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10646 .cindex "domain list" "in expansion condition"
10647 .cindex "address list" "in expansion condition"
10648 .cindex "local part" "list, in expansion condition"
10649 .cindex "&%match_local_part%& expansion condition"
10650 This condition, together with &%match_address%& and &%match_domain%&, make it
10651 possible to test domain, address, and local part lists within expansions. Each
10652 condition requires two arguments: an item and a list to match. A trivial
10655 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10657 In each case, the second argument may contain any of the allowable items for a
10658 list of the appropriate type. Also, because the second argument (after
10659 expansion) is a standard form of list, it is possible to refer to a named list.
10660 Thus, you can use conditions like this:
10662 ${if match_domain{$domain}{+local_domains}{...
10664 .cindex "&`+caseful`&"
10665 For address lists, the matching starts off caselessly, but the &`+caseful`&
10666 item can be used, as in all address lists, to cause subsequent items to
10667 have their local parts matched casefully. Domains are always matched
10670 Note that <&'string2'&> is not itself subject to string expansion, unless
10671 Exim was built with the EXPAND_LISTMATCH_RHS option.
10673 &*Note*&: Host lists are &'not'& supported in this way. This is because
10674 hosts have two identities: a name and an IP address, and it is not clear
10675 how to specify cleanly how such a test would work. However, IP addresses can be
10676 matched using &%match_ip%&.
10678 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10679 .cindex "PAM authentication"
10680 .cindex "AUTH" "with PAM"
10681 .cindex "Solaris" "PAM support"
10682 .cindex "expansion" "PAM authentication test"
10683 .cindex "&%pam%& expansion condition"
10684 &'Pluggable Authentication Modules'&
10685 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10686 available in the latest releases of Solaris and in some GNU/Linux
10687 distributions. The Exim support, which is intended for use in conjunction with
10688 the SMTP AUTH command, is available only if Exim is compiled with
10692 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10693 in some releases of GNU/Linux &%-ldl%& is also needed.
10695 The argument string is first expanded, and the result must be a
10696 colon-separated list of strings. Leading and trailing white space is ignored.
10697 The PAM module is initialized with the service name &"exim"& and the user name
10698 taken from the first item in the colon-separated data string (<&'string1'&>).
10699 The remaining items in the data string are passed over in response to requests
10700 from the authentication function. In the simple case there will only be one
10701 request, for a password, so the data consists of just two strings.
10703 There can be problems if any of the strings are permitted to contain colon
10704 characters. In the usual way, these have to be doubled to avoid being taken as
10705 separators. If the data is being inserted from a variable, the &%sg%& expansion
10706 item can be used to double any existing colons. For example, the configuration
10707 of a LOGIN authenticator might contain this setting:
10709 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10711 For a PLAIN authenticator you could use:
10713 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10715 In some operating systems, PAM authentication can be done only from a process
10716 running as root. Since Exim is running as the Exim user when receiving
10717 messages, this means that PAM cannot be used directly in those systems.
10718 A patched version of the &'pam_unix'& module that comes with the
10719 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10720 The patched module allows one special uid/gid combination, in addition to root,
10721 to authenticate. If you build the patched module to allow the Exim user and
10722 group, PAM can then be used from an Exim authenticator.
10725 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10726 .cindex "&'pwcheck'& daemon"
10728 .cindex "expansion" "&'pwcheck'& authentication test"
10729 .cindex "&%pwcheck%& expansion condition"
10730 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10731 This is one way of making it possible for passwords to be checked by a process
10732 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10733 deprecated. Its replacement is &'saslauthd'& (see below).
10735 The pwcheck support is not included in Exim by default. You need to specify
10736 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10737 building Exim. For example:
10739 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10741 You do not need to install the full Cyrus software suite in order to use
10742 the pwcheck daemon. You can compile and install just the daemon alone
10743 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10744 access to the &_/var/pwcheck_& directory.
10746 The &%pwcheck%& condition takes one argument, which must be the user name and
10747 password, separated by a colon. For example, in a LOGIN authenticator
10748 configuration, you might have this:
10750 server_condition = ${if pwcheck{$auth1:$auth2}}
10752 Again, for a PLAIN authenticator configuration, this would be:
10754 server_condition = ${if pwcheck{$auth2:$auth3}}
10756 .vitem &*queue_running*&
10757 .cindex "queue runner" "detecting when delivering from"
10758 .cindex "expansion" "queue runner test"
10759 .cindex "&%queue_running%& expansion condition"
10760 This condition, which has no data, is true during delivery attempts that are
10761 initiated by queue runner processes, and false otherwise.
10764 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10766 .cindex "expansion" "Radius authentication"
10767 .cindex "&%radius%& expansion condition"
10768 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10769 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10770 the Radius client configuration file in order to build Exim with Radius
10773 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10774 library, using the original API. If you are using release 0.4.0 or later of
10775 this library, you need to set
10777 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10779 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10780 &%libradius%& library that comes with FreeBSD. To do this, set
10782 RADIUS_LIB_TYPE=RADLIB
10784 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10785 You may also have to supply a suitable setting in EXTRALIBS so that the
10786 Radius library can be found when Exim is linked.
10788 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10789 Radius client library, which calls the Radius server. The condition is true if
10790 the authentication is successful. For example:
10792 server_condition = ${if radius{<arguments>}}
10796 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10797 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10798 .cindex "&'saslauthd'& daemon"
10800 .cindex "expansion" "&'saslauthd'& authentication test"
10801 .cindex "&%saslauthd%& expansion condition"
10802 This condition supports user authentication using the Cyrus &'saslauthd'&
10803 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10804 Using this daemon is one way of making it possible for passwords to be checked
10805 by a process that is not running as root.
10807 The saslauthd support is not included in Exim by default. You need to specify
10808 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10809 building Exim. For example:
10811 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10813 You do not need to install the full Cyrus software suite in order to use
10814 the saslauthd daemon. You can compile and install just the daemon alone
10815 from the Cyrus SASL library.
10817 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10818 two are mandatory. For example:
10820 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10822 The service and the realm are optional (which is why the arguments are enclosed
10823 in their own set of braces). For details of the meaning of the service and
10824 realm, and how to run the daemon, consult the Cyrus documentation.
10829 .section "Combining expansion conditions" "SECID84"
10830 .cindex "expansion" "combining conditions"
10831 Several conditions can be tested at once by combining them using the &%and%&
10832 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10833 conditions on their own, and precede their lists of sub-conditions. Each
10834 sub-condition must be enclosed in braces within the overall braces that contain
10835 the list. No repetition of &%if%& is used.
10839 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10840 .cindex "&""or""& expansion condition"
10841 .cindex "expansion" "&""or""& of conditions"
10842 The sub-conditions are evaluated from left to right. The condition is true if
10843 any one of the sub-conditions is true.
10846 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10848 When a true sub-condition is found, the following ones are parsed but not
10849 evaluated. If there are several &"match"& sub-conditions the values of the
10850 numeric variables afterwards are taken from the first one that succeeds.
10852 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10853 .cindex "&""and""& expansion condition"
10854 .cindex "expansion" "&""and""& of conditions"
10855 The sub-conditions are evaluated from left to right. The condition is true if
10856 all of the sub-conditions are true. If there are several &"match"&
10857 sub-conditions, the values of the numeric variables afterwards are taken from
10858 the last one. When a false sub-condition is found, the following ones are
10859 parsed but not evaluated.
10861 .ecindex IIDexpcond
10866 .section "Expansion variables" "SECTexpvar"
10867 .cindex "expansion" "variables, list of"
10868 This section contains an alphabetical list of all the expansion variables. Some
10869 of them are available only when Exim is compiled with specific options such as
10870 support for TLS or the content scanning extension.
10873 .vitem "&$0$&, &$1$&, etc"
10874 .cindex "numerical variables (&$1$& &$2$& etc)"
10875 When a &%match%& expansion condition succeeds, these variables contain the
10876 captured substrings identified by the regular expression during subsequent
10877 processing of the success string of the containing &%if%& expansion item.
10878 However, they do not retain their values afterwards; in fact, their previous
10879 values are restored at the end of processing an &%if%& item. The numerical
10880 variables may also be set externally by some other matching process which
10881 precedes the expansion of the string. For example, the commands available in
10882 Exim filter files include an &%if%& command with its own regular expression
10883 matching condition.
10885 .vitem "&$acl_c...$&"
10886 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10887 can be given any name that starts with &$acl_c$& and is at least six characters
10888 long, but the sixth character must be either a digit or an underscore. For
10889 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10890 variables persist throughout the lifetime of an SMTP connection. They can be
10891 used to pass information between ACLs and between different invocations of the
10892 same ACL. When a message is received, the values of these variables are saved
10893 with the message, and can be accessed by filters, routers, and transports
10894 during subsequent delivery.
10896 .vitem "&$acl_m...$&"
10897 These variables are like the &$acl_c...$& variables, except that their values
10898 are reset after a message has been received. Thus, if several messages are
10899 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10900 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10901 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10902 message is received, the values of these variables are saved with the message,
10903 and can be accessed by filters, routers, and transports during subsequent
10906 .vitem &$acl_verify_message$&
10907 .vindex "&$acl_verify_message$&"
10908 After an address verification has failed, this variable contains the failure
10909 message. It retains its value for use in subsequent modifiers. The message can
10910 be preserved by coding like this:
10912 warn !verify = sender
10913 set acl_m0 = $acl_verify_message
10915 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10916 &%log_message%& modifiers, to include information about the verification
10919 .vitem &$address_data$&
10920 .vindex "&$address_data$&"
10921 This variable is set by means of the &%address_data%& option in routers. The
10922 value then remains with the address while it is processed by subsequent routers
10923 and eventually a transport. If the transport is handling multiple addresses,
10924 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10925 for more details. &*Note*&: The contents of &$address_data$& are visible in
10928 If &$address_data$& is set when the routers are called from an ACL to verify
10929 a recipient address, the final value is still in the variable for subsequent
10930 conditions and modifiers of the ACL statement. If routing the address caused it
10931 to be redirected to just one address, the child address is also routed as part
10932 of the verification, and in this case the final value of &$address_data$& is
10933 from the child's routing.
10935 If &$address_data$& is set when the routers are called from an ACL to verify a
10936 sender address, the final value is also preserved, but this time in
10937 &$sender_address_data$&, to distinguish it from data from a recipient
10940 In both cases (recipient and sender verification), the value does not persist
10941 after the end of the current ACL statement. If you want to preserve
10942 these values for longer, you can save them in ACL variables.
10944 .vitem &$address_file$&
10945 .vindex "&$address_file$&"
10946 When, as a result of aliasing, forwarding, or filtering, a message is directed
10947 to a specific file, this variable holds the name of the file when the transport
10948 is running. At other times, the variable is empty. For example, using the
10949 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10951 /home/r2d2/savemail
10953 then when the &(address_file)& transport is running, &$address_file$&
10954 contains the text string &`/home/r2d2/savemail`&.
10955 .cindex "Sieve filter" "value of &$address_file$&"
10956 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10957 then up to the transport configuration to generate an appropriate absolute path
10958 to the relevant file.
10960 .vitem &$address_pipe$&
10961 .vindex "&$address_pipe$&"
10962 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10963 this variable holds the pipe command when the transport is running.
10965 .vitem "&$auth1$& &-- &$auth3$&"
10966 .vindex "&$auth1$&, &$auth2$&, etc"
10967 These variables are used in SMTP authenticators (see chapters
10968 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10970 .vitem &$authenticated_id$&
10971 .cindex "authentication" "id"
10972 .vindex "&$authenticated_id$&"
10973 When a server successfully authenticates a client it may be configured to
10974 preserve some of the authentication information in the variable
10975 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
10976 user/password authenticator configuration might preserve the user name for use
10977 in the routers. Note that this is not the same information that is saved in
10978 &$sender_host_authenticated$&.
10979 When a message is submitted locally (that is, not over a TCP connection)
10980 the value of &$authenticated_id$& is normally the login name of the calling
10981 process. However, a trusted user can override this by means of the &%-oMai%&
10982 command line option.
10984 .vitem &$authenticated_fail_id$&
10985 .cindex "authentication" "fail" "id"
10986 .vindex "&$authenticated_fail_id$&"
10987 When an authentication attempt fails, the variable &$authenticated_fail_id$&
10988 will contain the failed authentication id. If more than one authentication
10989 id is attempted, it will contain only the last one. The variable is
10990 available for processing in the ACL's, generally the quit or notquit ACL.
10991 A message to a local recipient could still be accepted without requiring
10992 authentication, which means this variable could also be visible in all of
10996 .vitem &$authenticated_sender$&
10997 .cindex "sender" "authenticated"
10998 .cindex "authentication" "sender"
10999 .cindex "AUTH" "on MAIL command"
11000 .vindex "&$authenticated_sender$&"
11001 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11002 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11003 described in section &<<SECTauthparamail>>&. Unless the data is the string
11004 &"<>"&, it is set as the authenticated sender of the message, and the value is
11005 available during delivery in the &$authenticated_sender$& variable. If the
11006 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11008 .vindex "&$qualify_domain$&"
11009 When a message is submitted locally (that is, not over a TCP connection), the
11010 value of &$authenticated_sender$& is an address constructed from the login
11011 name of the calling process and &$qualify_domain$&, except that a trusted user
11012 can override this by means of the &%-oMas%& command line option.
11015 .vitem &$authentication_failed$&
11016 .cindex "authentication" "failure"
11017 .vindex "&$authentication_failed$&"
11018 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11019 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11020 possible to distinguish between &"did not try to authenticate"&
11021 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11022 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11023 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11024 negative response to an AUTH command, including (for example) an attempt to use
11025 an undefined mechanism.
11027 .vitem &$av_failed$&
11028 .cindex "content scanning" "AV scanner failure"
11029 This variable is available when Exim is compiled with the content-scanning
11030 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11031 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11032 the ACL malware condition.
11034 .vitem &$body_linecount$&
11035 .cindex "message body" "line count"
11036 .cindex "body of message" "line count"
11037 .vindex "&$body_linecount$&"
11038 When a message is being received or delivered, this variable contains the
11039 number of lines in the message's body. See also &$message_linecount$&.
11041 .vitem &$body_zerocount$&
11042 .cindex "message body" "binary zero count"
11043 .cindex "body of message" "binary zero count"
11044 .cindex "binary zero" "in message body"
11045 .vindex "&$body_zerocount$&"
11046 When a message is being received or delivered, this variable contains the
11047 number of binary zero bytes (ASCII NULs) in the message's body.
11049 .vitem &$bounce_recipient$&
11050 .vindex "&$bounce_recipient$&"
11051 This is set to the recipient address of a bounce message while Exim is creating
11052 it. It is useful if a customized bounce message text file is in use (see
11053 chapter &<<CHAPemsgcust>>&).
11055 .vitem &$bounce_return_size_limit$&
11056 .vindex "&$bounce_return_size_limit$&"
11057 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11058 up to a multiple of 1000. It is useful when a customized error message text
11059 file is in use (see chapter &<<CHAPemsgcust>>&).
11061 .vitem &$caller_gid$&
11062 .cindex "gid (group id)" "caller"
11063 .vindex "&$caller_gid$&"
11064 The real group id under which the process that called Exim was running. This is
11065 not the same as the group id of the originator of a message (see
11066 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11067 incarnation normally contains the Exim gid.
11069 .vitem &$caller_uid$&
11070 .cindex "uid (user id)" "caller"
11071 .vindex "&$caller_uid$&"
11072 The real user id under which the process that called Exim was running. This is
11073 not the same as the user id of the originator of a message (see
11074 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11075 incarnation normally contains the Exim uid.
11077 .vitem &$compile_date$&
11078 .vindex "&$compile_date$&"
11079 The date on which the Exim binary was compiled.
11081 .vitem &$compile_number$&
11082 .vindex "&$compile_number$&"
11083 The building process for Exim keeps a count of the number
11084 of times it has been compiled. This serves to distinguish different
11085 compilations of the same version of the program.
11087 .vitem &$demime_errorlevel$&
11088 .vindex "&$demime_errorlevel$&"
11089 This variable is available when Exim is compiled with
11090 the content-scanning extension and the obsolete &%demime%& condition. For
11091 details, see section &<<SECTdemimecond>>&.
11093 .vitem &$demime_reason$&
11094 .vindex "&$demime_reason$&"
11095 This variable is available when Exim is compiled with the
11096 content-scanning extension and the obsolete &%demime%& condition. For details,
11097 see section &<<SECTdemimecond>>&.
11099 .vitem &$dnslist_domain$& &&&
11100 &$dnslist_matched$& &&&
11101 &$dnslist_text$& &&&
11103 .vindex "&$dnslist_domain$&"
11104 .vindex "&$dnslist_matched$&"
11105 .vindex "&$dnslist_text$&"
11106 .vindex "&$dnslist_value$&"
11107 .cindex "black list (DNS)"
11108 When a DNS (black) list lookup succeeds, these variables are set to contain
11109 the following data from the lookup: the list's domain name, the key that was
11110 looked up, the contents of any associated TXT record, and the value from the
11111 main A record. See section &<<SECID204>>& for more details.
11114 .vindex "&$domain$&"
11115 When an address is being routed, or delivered on its own, this variable
11116 contains the domain. Uppercase letters in the domain are converted into lower
11117 case for &$domain$&.
11119 Global address rewriting happens when a message is received, so the value of
11120 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11121 is set during user filtering, but not during system filtering, because a
11122 message may have many recipients and the system filter is called just once.
11124 When more than one address is being delivered at once (for example, several
11125 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11126 have the same domain. Transports can be restricted to handling only one domain
11127 at a time if the value of &$domain$& is required at transport time &-- this is
11128 the default for local transports. For further details of the environment in
11129 which local transports are run, see chapter &<<CHAPenvironment>>&.
11131 .oindex "&%delay_warning_condition%&"
11132 At the end of a delivery, if all deferred addresses have the same domain, it is
11133 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11135 The &$domain$& variable is also used in some other circumstances:
11138 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11139 the recipient address. The domain of the &'sender'& address is in
11140 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11141 normally set during the running of the MAIL ACL. However, if the sender address
11142 is verified with a callout during the MAIL ACL, the sender domain is placed in
11143 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11144 the &(smtp)& transport.
11147 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11148 &$domain$& contains the domain portion of the address that is being rewritten;
11149 it can be used in the expansion of the replacement address, for example, to
11150 rewrite domains by file lookup.
11153 With one important exception, whenever a domain list is being scanned,
11154 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11155 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11156 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11157 that, in a RCPT ACL, the sender domain list can be dependent on the
11158 recipient domain (which is what is in &$domain$& at this time).
11161 .cindex "ETRN" "value of &$domain$&"
11162 .oindex "&%smtp_etrn_command%&"
11163 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11164 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11168 .vitem &$domain_data$&
11169 .vindex "&$domain_data$&"
11170 When the &%domains%& option on a router matches a domain by
11171 means of a lookup, the data read by the lookup is available during the running
11172 of the router as &$domain_data$&. In addition, if the driver routes the
11173 address to a transport, the value is available in that transport. If the
11174 transport is handling multiple addresses, the value from the first address is
11177 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11178 domain by means of a lookup. The data read by the lookup is available during
11179 the rest of the ACL statement. In all other situations, this variable expands
11182 .vitem &$exim_gid$&
11183 .vindex "&$exim_gid$&"
11184 This variable contains the numerical value of the Exim group id.
11186 .vitem &$exim_path$&
11187 .vindex "&$exim_path$&"
11188 This variable contains the path to the Exim binary.
11190 .vitem &$exim_uid$&
11191 .vindex "&$exim_uid$&"
11192 This variable contains the numerical value of the Exim user id.
11194 .vitem &$found_extension$&
11195 .vindex "&$found_extension$&"
11196 This variable is available when Exim is compiled with the
11197 content-scanning extension and the obsolete &%demime%& condition. For details,
11198 see section &<<SECTdemimecond>>&.
11200 .vitem &$header_$&<&'name'&>
11201 This is not strictly an expansion variable. It is expansion syntax for
11202 inserting the message header line with the given name. Note that the name must
11203 be terminated by colon or white space, because it may contain a wide variety of
11204 characters. Note also that braces must &'not'& be used.
11206 .vitem &$headers_added$&
11207 .vindex "&$headers_added$&"
11208 Within an ACL this variable contains the headers added so far by
11209 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11210 The headers are a newline-separated list.
11214 When the &%check_local_user%& option is set for a router, the user's home
11215 directory is placed in &$home$& when the check succeeds. In particular, this
11216 means it is set during the running of users' filter files. A router may also
11217 explicitly set a home directory for use by a transport; this can be overridden
11218 by a setting on the transport itself.
11220 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11221 of the environment variable HOME.
11225 If a router assigns an address to a transport (any transport), and passes a
11226 list of hosts with the address, the value of &$host$& when the transport starts
11227 to run is the name of the first host on the list. Note that this applies both
11228 to local and remote transports.
11230 .cindex "transport" "filter"
11231 .cindex "filter" "transport filter"
11232 For the &(smtp)& transport, if there is more than one host, the value of
11233 &$host$& changes as the transport works its way through the list. In
11234 particular, when the &(smtp)& transport is expanding its options for encryption
11235 using TLS, or for specifying a transport filter (see chapter
11236 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11239 When used in the client part of an authenticator configuration (see chapter
11240 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11241 client is connected.
11244 .vitem &$host_address$&
11245 .vindex "&$host_address$&"
11246 This variable is set to the remote host's IP address whenever &$host$& is set
11247 for a remote connection. It is also set to the IP address that is being checked
11248 when the &%ignore_target_hosts%& option is being processed.
11250 .vitem &$host_data$&
11251 .vindex "&$host_data$&"
11252 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11253 result of the lookup is made available in the &$host_data$& variable. This
11254 allows you, for example, to do things like this:
11256 deny hosts = net-lsearch;/some/file
11257 message = $host_data
11259 .vitem &$host_lookup_deferred$&
11260 .cindex "host name" "lookup, failure of"
11261 .vindex "&$host_lookup_deferred$&"
11262 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11263 message comes from a remote host and there is an attempt to look up the host's
11264 name from its IP address, and the attempt is not successful, one of these
11265 variables is set to &"1"&.
11268 If the lookup receives a definite negative response (for example, a DNS lookup
11269 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11272 If there is any kind of problem during the lookup, such that Exim cannot
11273 tell whether or not the host name is defined (for example, a timeout for a DNS
11274 lookup), &$host_lookup_deferred$& is set to &"1"&.
11277 Looking up a host's name from its IP address consists of more than just a
11278 single reverse lookup. Exim checks that a forward lookup of at least one of the
11279 names it receives from a reverse lookup yields the original IP address. If this
11280 is not the case, Exim does not accept the looked up name(s), and
11281 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11282 IP address (for example, the existence of a PTR record in the DNS) is not
11283 sufficient on its own for the success of a host name lookup. If the reverse
11284 lookup succeeds, but there is a lookup problem such as a timeout when checking
11285 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11286 &"1"&. See also &$sender_host_name$&.
11288 .vitem &$host_lookup_failed$&
11289 .vindex "&$host_lookup_failed$&"
11290 See &$host_lookup_deferred$&.
11294 .vindex "&$inode$&"
11295 The only time this variable is set is while expanding the &%directory_file%&
11296 option in the &(appendfile)& transport. The variable contains the inode number
11297 of the temporary file which is about to be renamed. It can be used to construct
11298 a unique name for the file.
11300 .vitem &$interface_address$&
11301 .vindex "&$interface_address$&"
11302 This is an obsolete name for &$received_ip_address$&.
11304 .vitem &$interface_port$&
11305 .vindex "&$interface_port$&"
11306 This is an obsolete name for &$received_port$&.
11310 This variable is used during the expansion of &*forall*& and &*forany*&
11311 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11312 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11316 .vindex "&$ldap_dn$&"
11317 This variable, which is available only when Exim is compiled with LDAP support,
11318 contains the DN from the last entry in the most recently successful LDAP
11321 .vitem &$load_average$&
11322 .vindex "&$load_average$&"
11323 This variable contains the system load average, multiplied by 1000 so that it
11324 is an integer. For example, if the load average is 0.21, the value of the
11325 variable is 210. The value is recomputed every time the variable is referenced.
11327 .vitem &$local_part$&
11328 .vindex "&$local_part$&"
11329 When an address is being routed, or delivered on its own, this
11330 variable contains the local part. When a number of addresses are being
11331 delivered together (for example, multiple RCPT commands in an SMTP
11332 session), &$local_part$& is not set.
11334 Global address rewriting happens when a message is received, so the value of
11335 &$local_part$& during routing and delivery is the value after rewriting.
11336 &$local_part$& is set during user filtering, but not during system filtering,
11337 because a message may have many recipients and the system filter is called just
11340 .vindex "&$local_part_prefix$&"
11341 .vindex "&$local_part_suffix$&"
11342 If a local part prefix or suffix has been recognized, it is not included in the
11343 value of &$local_part$& during routing and subsequent delivery. The values of
11344 any prefix or suffix are in &$local_part_prefix$& and
11345 &$local_part_suffix$&, respectively.
11347 When a message is being delivered to a file, pipe, or autoreply transport as a
11348 result of aliasing or forwarding, &$local_part$& is set to the local part of
11349 the parent address, not to the file name or command (see &$address_file$& and
11352 When an ACL is running for a RCPT command, &$local_part$& contains the
11353 local part of the recipient address.
11355 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11356 &$local_part$& contains the local part of the address that is being rewritten;
11357 it can be used in the expansion of the replacement address, for example.
11359 In all cases, all quoting is removed from the local part. For example, for both
11362 "abc:xyz"@test.example
11363 abc\:xyz@test.example
11365 the value of &$local_part$& is
11369 If you use &$local_part$& to create another address, you should always wrap it
11370 inside a quoting operator. For example, in a &(redirect)& router you could
11373 data = ${quote_local_part:$local_part}@new.domain.example
11375 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11376 to process local parts in a case-dependent manner in a router, you can set the
11377 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11379 .vitem &$local_part_data$&
11380 .vindex "&$local_part_data$&"
11381 When the &%local_parts%& option on a router matches a local part by means of a
11382 lookup, the data read by the lookup is available during the running of the
11383 router as &$local_part_data$&. In addition, if the driver routes the address
11384 to a transport, the value is available in that transport. If the transport is
11385 handling multiple addresses, the value from the first address is used.
11387 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11388 matches a local part by means of a lookup. The data read by the lookup is
11389 available during the rest of the ACL statement. In all other situations, this
11390 variable expands to nothing.
11392 .vitem &$local_part_prefix$&
11393 .vindex "&$local_part_prefix$&"
11394 When an address is being routed or delivered, and a
11395 specific prefix for the local part was recognized, it is available in this
11396 variable, having been removed from &$local_part$&.
11398 .vitem &$local_part_suffix$&
11399 .vindex "&$local_part_suffix$&"
11400 When an address is being routed or delivered, and a
11401 specific suffix for the local part was recognized, it is available in this
11402 variable, having been removed from &$local_part$&.
11404 .vitem &$local_scan_data$&
11405 .vindex "&$local_scan_data$&"
11406 This variable contains the text returned by the &[local_scan()]& function when
11407 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11409 .vitem &$local_user_gid$&
11410 .vindex "&$local_user_gid$&"
11411 See &$local_user_uid$&.
11413 .vitem &$local_user_uid$&
11414 .vindex "&$local_user_uid$&"
11415 This variable and &$local_user_gid$& are set to the uid and gid after the
11416 &%check_local_user%& router precondition succeeds. This means that their values
11417 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11418 and &%condition%&), for the &%address_data%& expansion, and for any
11419 router-specific expansions. At all other times, the values in these variables
11420 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11422 .vitem &$localhost_number$&
11423 .vindex "&$localhost_number$&"
11424 This contains the expanded value of the
11425 &%localhost_number%& option. The expansion happens after the main options have
11428 .vitem &$log_inodes$&
11429 .vindex "&$log_inodes$&"
11430 The number of free inodes in the disk partition where Exim's
11431 log files are being written. The value is recalculated whenever the variable is
11432 referenced. If the relevant file system does not have the concept of inodes,
11433 the value of is -1. See also the &%check_log_inodes%& option.
11435 .vitem &$log_space$&
11436 .vindex "&$log_space$&"
11437 The amount of free space (as a number of kilobytes) in the disk
11438 partition where Exim's log files are being written. The value is recalculated
11439 whenever the variable is referenced. If the operating system does not have the
11440 ability to find the amount of free space (only true for experimental systems),
11441 the space value is -1. See also the &%check_log_space%& option.
11444 .vitem &$mailstore_basename$&
11445 .vindex "&$mailstore_basename$&"
11446 This variable is set only when doing deliveries in &"mailstore"& format in the
11447 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11448 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11449 contains the basename of the files that are being written, that is, the name
11450 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11453 .vitem &$malware_name$&
11454 .vindex "&$malware_name$&"
11455 This variable is available when Exim is compiled with the
11456 content-scanning extension. It is set to the name of the virus that was found
11457 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11459 .vitem &$max_received_linelength$&
11460 .vindex "&$max_received_linelength$&"
11461 .cindex "maximum" "line length"
11462 .cindex "line length" "maximum"
11463 This variable contains the number of bytes in the longest line that was
11464 received as part of the message, not counting the line termination
11467 .vitem &$message_age$&
11468 .cindex "message" "age of"
11469 .vindex "&$message_age$&"
11470 This variable is set at the start of a delivery attempt to contain the number
11471 of seconds since the message was received. It does not change during a single
11474 .vitem &$message_body$&
11475 .cindex "body of message" "expansion variable"
11476 .cindex "message body" "in expansion"
11477 .cindex "binary zero" "in message body"
11478 .vindex "&$message_body$&"
11479 .oindex "&%message_body_visible%&"
11480 This variable contains the initial portion of a message's body while it is
11481 being delivered, and is intended mainly for use in filter files. The maximum
11482 number of characters of the body that are put into the variable is set by the
11483 &%message_body_visible%& configuration option; the default is 500.
11485 .oindex "&%message_body_newlines%&"
11486 By default, newlines are converted into spaces in &$message_body$&, to make it
11487 easier to search for phrases that might be split over a line break. However,
11488 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11489 zeros are always converted into spaces.
11491 .vitem &$message_body_end$&
11492 .cindex "body of message" "expansion variable"
11493 .cindex "message body" "in expansion"
11494 .vindex "&$message_body_end$&"
11495 This variable contains the final portion of a message's
11496 body while it is being delivered. The format and maximum size are as for
11499 .vitem &$message_body_size$&
11500 .cindex "body of message" "size"
11501 .cindex "message body" "size"
11502 .vindex "&$message_body_size$&"
11503 When a message is being delivered, this variable contains the size of the body
11504 in bytes. The count starts from the character after the blank line that
11505 separates the body from the header. Newlines are included in the count. See
11506 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11508 .vitem &$message_exim_id$&
11509 .vindex "&$message_exim_id$&"
11510 When a message is being received or delivered, this variable contains the
11511 unique message id that is generated and used by Exim to identify the message.
11512 An id is not created for a message until after its header has been successfully
11513 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11514 line; it is the local id that Exim assigns to the message, for example:
11515 &`1BXTIK-0001yO-VA`&.
11517 .vitem &$message_headers$&
11518 .vindex &$message_headers$&
11519 This variable contains a concatenation of all the header lines when a message
11520 is being processed, except for lines added by routers or transports. The header
11521 lines are separated by newline characters. Their contents are decoded in the
11522 same way as a header line that is inserted by &%bheader%&.
11524 .vitem &$message_headers_raw$&
11525 .vindex &$message_headers_raw$&
11526 This variable is like &$message_headers$& except that no processing of the
11527 contents of header lines is done.
11529 .vitem &$message_id$&
11530 This is an old name for &$message_exim_id$&, which is now deprecated.
11532 .vitem &$message_linecount$&
11533 .vindex "&$message_linecount$&"
11534 This variable contains the total number of lines in the header and body of the
11535 message. Compare &$body_linecount$&, which is the count for the body only.
11536 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11537 number of lines received. Before delivery happens (that is, before filters,
11538 routers, and transports run) the count is increased to include the
11539 &'Received:'& header line that Exim standardly adds, and also any other header
11540 lines that are added by ACLs. The blank line that separates the message header
11541 from the body is not counted.
11543 As with the special case of &$message_size$&, during the expansion of the
11544 appendfile transport's maildir_tag option in maildir format, the value of
11545 &$message_linecount$& is the precise size of the number of newlines in the
11546 file that has been written (minus one for the blank line between the
11547 header and the body).
11549 Here is an example of the use of this variable in a DATA ACL:
11551 deny message = Too many lines in message header
11553 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11555 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11556 message has not yet been received.
11558 .vitem &$message_size$&
11559 .cindex "size" "of message"
11560 .cindex "message" "size"
11561 .vindex "&$message_size$&"
11562 When a message is being processed, this variable contains its size in bytes. In
11563 most cases, the size includes those headers that were received with the
11564 message, but not those (such as &'Envelope-to:'&) that are added to individual
11565 deliveries as they are written. However, there is one special case: during the
11566 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11567 doing a delivery in maildir format, the value of &$message_size$& is the
11568 precise size of the file that has been written. See also
11569 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11571 .cindex "RCPT" "value of &$message_size$&"
11572 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11573 contains the size supplied on the MAIL command, or -1 if no size was given. The
11574 value may not, of course, be truthful.
11576 .vitem &$mime_$&&'xxx'&
11577 A number of variables whose names start with &$mime$& are
11578 available when Exim is compiled with the content-scanning extension. For
11579 details, see section &<<SECTscanmimepart>>&.
11581 .vitem "&$n0$& &-- &$n9$&"
11582 These variables are counters that can be incremented by means
11583 of the &%add%& command in filter files.
11585 .vitem &$original_domain$&
11586 .vindex "&$domain$&"
11587 .vindex "&$original_domain$&"
11588 When a top-level address is being processed for delivery, this contains the
11589 same value as &$domain$&. However, if a &"child"& address (for example,
11590 generated by an alias, forward, or filter file) is being processed, this
11591 variable contains the domain of the original address (lower cased). This
11592 differs from &$parent_domain$& only when there is more than one level of
11593 aliasing or forwarding. When more than one address is being delivered in a
11594 single transport run, &$original_domain$& is not set.
11596 If a new address is created by means of a &%deliver%& command in a system
11597 filter, it is set up with an artificial &"parent"& address. This has the local
11598 part &'system-filter'& and the default qualify domain.
11600 .vitem &$original_local_part$&
11601 .vindex "&$local_part$&"
11602 .vindex "&$original_local_part$&"
11603 When a top-level address is being processed for delivery, this contains the
11604 same value as &$local_part$&, unless a prefix or suffix was removed from the
11605 local part, because &$original_local_part$& always contains the full local
11606 part. When a &"child"& address (for example, generated by an alias, forward, or
11607 filter file) is being processed, this variable contains the full local part of
11608 the original address.
11610 If the router that did the redirection processed the local part
11611 case-insensitively, the value in &$original_local_part$& is in lower case.
11612 This variable differs from &$parent_local_part$& only when there is more than
11613 one level of aliasing or forwarding. When more than one address is being
11614 delivered in a single transport run, &$original_local_part$& is not set.
11616 If a new address is created by means of a &%deliver%& command in a system
11617 filter, it is set up with an artificial &"parent"& address. This has the local
11618 part &'system-filter'& and the default qualify domain.
11620 .vitem &$originator_gid$&
11621 .cindex "gid (group id)" "of originating user"
11622 .cindex "sender" "gid"
11623 .vindex "&$caller_gid$&"
11624 .vindex "&$originator_gid$&"
11625 This variable contains the value of &$caller_gid$& that was set when the
11626 message was received. For messages received via the command line, this is the
11627 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11628 normally the gid of the Exim user.
11630 .vitem &$originator_uid$&
11631 .cindex "uid (user id)" "of originating user"
11632 .cindex "sender" "uid"
11633 .vindex "&$caller_uid$&"
11634 .vindex "&$originaltor_uid$&"
11635 The value of &$caller_uid$& that was set when the message was received. For
11636 messages received via the command line, this is the uid of the sending user.
11637 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11640 .vitem &$parent_domain$&
11641 .vindex "&$parent_domain$&"
11642 This variable is similar to &$original_domain$& (see
11643 above), except that it refers to the immediately preceding parent address.
11645 .vitem &$parent_local_part$&
11646 .vindex "&$parent_local_part$&"
11647 This variable is similar to &$original_local_part$&
11648 (see above), except that it refers to the immediately preceding parent address.
11651 .cindex "pid (process id)" "of current process"
11653 This variable contains the current process id.
11655 .vitem &$pipe_addresses$&
11656 .cindex "filter" "transport filter"
11657 .cindex "transport" "filter"
11658 .vindex "&$pipe_addresses$&"
11659 This is not an expansion variable, but is mentioned here because the string
11660 &`$pipe_addresses`& is handled specially in the command specification for the
11661 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11662 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11663 It cannot be used in general expansion strings, and provokes an &"unknown
11664 variable"& error if encountered.
11666 .vitem &$primary_hostname$&
11667 .vindex "&$primary_hostname$&"
11668 This variable contains the value set by &%primary_hostname%& in the
11669 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11670 a single-component name, Exim calls &[gethostbyname()]& (or
11671 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11672 qualified host name. See also &$smtp_active_hostname$&.
11675 .vitem &$prvscheck_address$&
11676 This variable is used in conjunction with the &%prvscheck%& expansion item,
11677 which is described in sections &<<SECTexpansionitems>>& and
11678 &<<SECTverifyPRVS>>&.
11680 .vitem &$prvscheck_keynum$&
11681 This variable is used in conjunction with the &%prvscheck%& expansion item,
11682 which is described in sections &<<SECTexpansionitems>>& and
11683 &<<SECTverifyPRVS>>&.
11685 .vitem &$prvscheck_result$&
11686 This variable is used in conjunction with the &%prvscheck%& expansion item,
11687 which is described in sections &<<SECTexpansionitems>>& and
11688 &<<SECTverifyPRVS>>&.
11690 .vitem &$qualify_domain$&
11691 .vindex "&$qualify_domain$&"
11692 The value set for the &%qualify_domain%& option in the configuration file.
11694 .vitem &$qualify_recipient$&
11695 .vindex "&$qualify_recipient$&"
11696 The value set for the &%qualify_recipient%& option in the configuration file,
11697 or if not set, the value of &$qualify_domain$&.
11699 .vitem &$rcpt_count$&
11700 .vindex "&$rcpt_count$&"
11701 When a message is being received by SMTP, this variable contains the number of
11702 RCPT commands received for the current message. If this variable is used in a
11703 RCPT ACL, its value includes the current command.
11705 .vitem &$rcpt_defer_count$&
11706 .vindex "&$rcpt_defer_count$&"
11707 .cindex "4&'xx'& responses" "count of"
11708 When a message is being received by SMTP, this variable contains the number of
11709 RCPT commands in the current message that have previously been rejected with a
11710 temporary (4&'xx'&) response.
11712 .vitem &$rcpt_fail_count$&
11713 .vindex "&$rcpt_fail_count$&"
11714 When a message is being received by SMTP, this variable contains the number of
11715 RCPT commands in the current message that have previously been rejected with a
11716 permanent (5&'xx'&) response.
11718 .vitem &$received_count$&
11719 .vindex "&$received_count$&"
11720 This variable contains the number of &'Received:'& header lines in the message,
11721 including the one added by Exim (so its value is always greater than zero). It
11722 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11725 .vitem &$received_for$&
11726 .vindex "&$received_for$&"
11727 If there is only a single recipient address in an incoming message, this
11728 variable contains that address when the &'Received:'& header line is being
11729 built. The value is copied after recipient rewriting has happened, but before
11730 the &[local_scan()]& function is run.
11732 .vitem &$received_ip_address$&
11733 .vindex "&$received_ip_address$&"
11734 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11735 variable is set to the address of the local IP interface, and &$received_port$&
11736 is set to the local port number. (The remote IP address and port are in
11737 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11738 the port value is -1 unless it has been set using the &%-oMi%& command line
11741 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11742 could be used, for example, to make the file name for a TLS certificate depend
11743 on which interface and/or port is being used for the incoming connection. The
11744 values of &$received_ip_address$& and &$received_port$& are saved with any
11745 messages that are received, thus making these variables available at delivery
11748 &*Note:*& There are no equivalent variables for outgoing connections, because
11749 the values are unknown (unless they are explicitly set by options of the
11750 &(smtp)& transport).
11752 .vitem &$received_port$&
11753 .vindex "&$received_port$&"
11754 See &$received_ip_address$&.
11756 .vitem &$received_protocol$&
11757 .vindex "&$received_protocol$&"
11758 When a message is being processed, this variable contains the name of the
11759 protocol by which it was received. Most of the names used by Exim are defined
11760 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11761 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11762 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11763 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11764 connection and the client was successfully authenticated.
11766 Exim uses the protocol name &"smtps"& for the case when encryption is
11767 automatically set up on connection without the use of STARTTLS (see
11768 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11769 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11770 where the client initially uses EHLO, sets up an encrypted connection using
11771 STARTTLS, and then uses HELO afterwards.
11773 The &%-oMr%& option provides a way of specifying a custom protocol name for
11774 messages that are injected locally by trusted callers. This is commonly used to
11775 identify messages that are being re-injected after some kind of scanning.
11777 .vitem &$received_time$&
11778 .vindex "&$received_time$&"
11779 This variable contains the date and time when the current message was received,
11780 as a number of seconds since the start of the Unix epoch.
11782 .vitem &$recipient_data$&
11783 .vindex "&$recipient_data$&"
11784 This variable is set after an indexing lookup success in an ACL &%recipients%&
11785 condition. It contains the data from the lookup, and the value remains set
11786 until the next &%recipients%& test. Thus, you can do things like this:
11788 &`require recipients = cdb*@;/some/file`&
11789 &`deny `&&'some further test involving'& &`$recipient_data`&
11791 &*Warning*&: This variable is set only when a lookup is used as an indexing
11792 method in the address list, using the semicolon syntax as in the example above.
11793 The variable is not set for a lookup that is used as part of the string
11794 expansion that all such lists undergo before being interpreted.
11796 .vitem &$recipient_verify_failure$&
11797 .vindex "&$recipient_verify_failure$&"
11798 In an ACL, when a recipient verification fails, this variable contains
11799 information about the failure. It is set to one of the following words:
11802 &"qualify"&: The address was unqualified (no domain), and the message
11803 was neither local nor came from an exempted host.
11806 &"route"&: Routing failed.
11809 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11810 or before the MAIL command (that is, on initial connection, HELO, or
11814 &"recipient"&: The RCPT command in a callout was rejected.
11817 &"postmaster"&: The postmaster check in a callout was rejected.
11820 The main use of this variable is expected to be to distinguish between
11821 rejections of MAIL and rejections of RCPT.
11823 .vitem &$recipients$&
11824 .vindex "&$recipients$&"
11825 This variable contains a list of envelope recipients for a message. A comma and
11826 a space separate the addresses in the replacement text. However, the variable
11827 is not generally available, to prevent exposure of Bcc recipients in
11828 unprivileged users' filter files. You can use &$recipients$& only in these
11832 In a system filter file.
11834 In the ACLs associated with the DATA command and with non-SMTP messages, that
11835 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11836 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11837 &%acl_not_smtp_mime%&.
11839 From within a &[local_scan()]& function.
11843 .vitem &$recipients_count$&
11844 .vindex "&$recipients_count$&"
11845 When a message is being processed, this variable contains the number of
11846 envelope recipients that came with the message. Duplicates are not excluded
11847 from the count. While a message is being received over SMTP, the number
11848 increases for each accepted recipient. It can be referenced in an ACL.
11851 .vitem &$regex_match_string$&
11852 .vindex "&$regex_match_string$&"
11853 This variable is set to contain the matching regular expression after a
11854 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11857 .vitem &$reply_address$&
11858 .vindex "&$reply_address$&"
11859 When a message is being processed, this variable contains the contents of the
11860 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11861 contents of the &'From:'& header line. Apart from the removal of leading
11862 white space, the value is not processed in any way. In particular, no RFC 2047
11863 decoding or character code translation takes place.
11865 .vitem &$return_path$&
11866 .vindex "&$return_path$&"
11867 When a message is being delivered, this variable contains the return path &--
11868 the sender field that will be sent as part of the envelope. It is not enclosed
11869 in <> characters. At the start of routing an address, &$return_path$& has the
11870 same value as &$sender_address$&, but if, for example, an incoming message to a
11871 mailing list has been expanded by a router which specifies a different address
11872 for bounce messages, &$return_path$& subsequently contains the new bounce
11873 address, whereas &$sender_address$& always contains the original sender address
11874 that was received with the message. In other words, &$sender_address$& contains
11875 the incoming envelope sender, and &$return_path$& contains the outgoing
11878 .vitem &$return_size_limit$&
11879 .vindex "&$return_size_limit$&"
11880 This is an obsolete name for &$bounce_return_size_limit$&.
11882 .vitem &$router_name$&
11883 .cindex "router" "name"
11884 .cindex "name" "of router"
11885 .vindex "&$router_name$&"
11886 During the running of a router this variable contains its name.
11889 .cindex "return code" "from &%run%& expansion"
11890 .vindex "&$runrc$&"
11891 This variable contains the return code from a command that is run by the
11892 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11893 assume the order in which option values are expanded, except for those
11894 preconditions whose order of testing is documented. Therefore, you cannot
11895 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11898 .vitem &$self_hostname$&
11899 .oindex "&%self%&" "value of host name"
11900 .vindex "&$self_hostname$&"
11901 When an address is routed to a supposedly remote host that turns out to be the
11902 local host, what happens is controlled by the &%self%& generic router option.
11903 One of its values causes the address to be passed to another router. When this
11904 happens, &$self_hostname$& is set to the name of the local host that the
11905 original router encountered. In other circumstances its contents are null.
11907 .vitem &$sender_address$&
11908 .vindex "&$sender_address$&"
11909 When a message is being processed, this variable contains the sender's address
11910 that was received in the message's envelope. The case of letters in the address
11911 is retained, in both the local part and the domain. For bounce messages, the
11912 value of this variable is the empty string. See also &$return_path$&.
11914 .vitem &$sender_address_data$&
11915 .vindex "&$address_data$&"
11916 .vindex "&$sender_address_data$&"
11917 If &$address_data$& is set when the routers are called from an ACL to verify a
11918 sender address, the final value is preserved in &$sender_address_data$&, to
11919 distinguish it from data from a recipient address. The value does not persist
11920 after the end of the current ACL statement. If you want to preserve it for
11921 longer, you can save it in an ACL variable.
11923 .vitem &$sender_address_domain$&
11924 .vindex "&$sender_address_domain$&"
11925 The domain portion of &$sender_address$&.
11927 .vitem &$sender_address_local_part$&
11928 .vindex "&$sender_address_local_part$&"
11929 The local part portion of &$sender_address$&.
11931 .vitem &$sender_data$&
11932 .vindex "&$sender_data$&"
11933 This variable is set after a lookup success in an ACL &%senders%& condition or
11934 in a router &%senders%& option. It contains the data from the lookup, and the
11935 value remains set until the next &%senders%& test. Thus, you can do things like
11938 &`require senders = cdb*@;/some/file`&
11939 &`deny `&&'some further test involving'& &`$sender_data`&
11941 &*Warning*&: This variable is set only when a lookup is used as an indexing
11942 method in the address list, using the semicolon syntax as in the example above.
11943 The variable is not set for a lookup that is used as part of the string
11944 expansion that all such lists undergo before being interpreted.
11946 .vitem &$sender_fullhost$&
11947 .vindex "&$sender_fullhost$&"
11948 When a message is received from a remote host, this variable contains the host
11949 name and IP address in a single string. It ends with the IP address in square
11950 brackets, followed by a colon and a port number if the logging of ports is
11951 enabled. The format of the rest of the string depends on whether the host
11952 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11953 looking up its IP address. (Looking up the IP address can be forced by the
11954 &%host_lookup%& option, independent of verification.) A plain host name at the
11955 start of the string is a verified host name; if this is not present,
11956 verification either failed or was not requested. A host name in parentheses is
11957 the argument of a HELO or EHLO command. This is omitted if it is identical to
11958 the verified host name or to the host's IP address in square brackets.
11960 .vitem &$sender_helo_name$&
11961 .vindex "&$sender_helo_name$&"
11962 When a message is received from a remote host that has issued a HELO or EHLO
11963 command, the argument of that command is placed in this variable. It is also
11964 set if HELO or EHLO is used when a message is received using SMTP locally via
11965 the &%-bs%& or &%-bS%& options.
11967 .vitem &$sender_host_address$&
11968 .vindex "&$sender_host_address$&"
11969 When a message is received from a remote host, this variable contains that
11970 host's IP address. For locally submitted messages, it is empty.
11972 .vitem &$sender_host_authenticated$&
11973 .vindex "&$sender_host_authenticated$&"
11974 This variable contains the name (not the public name) of the authenticator
11975 driver that successfully authenticated the client from which the message was
11976 received. It is empty if there was no successful authentication. See also
11977 &$authenticated_id$&.
11979 .vitem &$sender_host_dnssec$&
11980 .vindex "&$sender_host_dnssec$&"
11981 If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or
11982 otherwise) then this boolean will have been set true if, and only if, the
11983 resolver library states that the reverse DNS was authenticated data. At all
11984 other times, this variable is false.
11986 It is likely that you will need to coerce DNSSEC support on in the resolver
11987 library, by setting:
11992 Exim does not perform DNSSEC validation itself, instead leaving that to a
11993 validating resolver (eg, unbound, or bind with suitable configuration).
11995 Exim does not (currently) check to see if the forward DNS was also secured
11996 with DNSSEC, only the reverse DNS.
11998 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
11999 mechanism in the list, then this variable will be false.
12002 .vitem &$sender_host_name$&
12003 .vindex "&$sender_host_name$&"
12004 When a message is received from a remote host, this variable contains the
12005 host's name as obtained by looking up its IP address. For messages received by
12006 other means, this variable is empty.
12008 .vindex "&$host_lookup_failed$&"
12009 If the host name has not previously been looked up, a reference to
12010 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12011 A looked up name is accepted only if it leads back to the original IP address
12012 via a forward lookup. If either the reverse or the forward lookup fails to find
12013 any data, or if the forward lookup does not yield the original IP address,
12014 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12016 .vindex "&$host_lookup_deferred$&"
12017 However, if either of the lookups cannot be completed (for example, there is a
12018 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12019 &$host_lookup_failed$& remains set to &"0"&.
12021 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12022 host name again if there is a subsequent reference to &$sender_host_name$&
12023 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12026 Exim does not automatically look up every calling host's name. If you want
12027 maximum efficiency, you should arrange your configuration so that it avoids
12028 these lookups altogether. The lookup happens only if one or more of the
12029 following are true:
12032 A string containing &$sender_host_name$& is expanded.
12034 The calling host matches the list in &%host_lookup%&. In the default
12035 configuration, this option is set to *, so it must be changed if lookups are
12036 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12038 Exim needs the host name in order to test an item in a host list. The items
12039 that require this are described in sections &<<SECThoslispatnam>>& and
12040 &<<SECThoslispatnamsk>>&.
12042 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12043 In this case, the host name is required to compare with the name quoted in any
12044 EHLO or HELO commands that the client issues.
12046 The remote host issues a EHLO or HELO command that quotes one of the
12047 domains in &%helo_lookup_domains%&. The default value of this option is
12048 . ==== As this is a nested list, any displays it contains must be indented
12049 . ==== as otherwise they are too far to the left.
12051 helo_lookup_domains = @ : @[]
12053 which causes a lookup if a remote host (incorrectly) gives the server's name or
12054 IP address in an EHLO or HELO command.
12058 .vitem &$sender_host_port$&
12059 .vindex "&$sender_host_port$&"
12060 When a message is received from a remote host, this variable contains the port
12061 number that was used on the remote host.
12063 .vitem &$sender_ident$&
12064 .vindex "&$sender_ident$&"
12065 When a message is received from a remote host, this variable contains the
12066 identification received in response to an RFC 1413 request. When a message has
12067 been received locally, this variable contains the login name of the user that
12070 .vitem &$sender_rate_$&&'xxx'&
12071 A number of variables whose names begin &$sender_rate_$& are set as part of the
12072 &%ratelimit%& ACL condition. Details are given in section
12073 &<<SECTratelimiting>>&.
12075 .vitem &$sender_rcvhost$&
12076 .cindex "DNS" "reverse lookup"
12077 .cindex "reverse DNS lookup"
12078 .vindex "&$sender_rcvhost$&"
12079 This is provided specifically for use in &'Received:'& headers. It starts with
12080 either the verified host name (as obtained from a reverse DNS lookup) or, if
12081 there is no verified host name, the IP address in square brackets. After that
12082 there may be text in parentheses. When the first item is a verified host name,
12083 the first thing in the parentheses is the IP address in square brackets,
12084 followed by a colon and a port number if port logging is enabled. When the
12085 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12088 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12089 was used and its argument was not identical to the real host name or IP
12090 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12091 all three items are present in the parentheses, a newline and tab are inserted
12092 into the string, to improve the formatting of the &'Received:'& header.
12094 .vitem &$sender_verify_failure$&
12095 .vindex "&$sender_verify_failure$&"
12096 In an ACL, when a sender verification fails, this variable contains information
12097 about the failure. The details are the same as for
12098 &$recipient_verify_failure$&.
12100 .vitem &$sending_ip_address$&
12101 .vindex "&$sending_ip_address$&"
12102 This variable is set whenever an outgoing SMTP connection to another host has
12103 been set up. It contains the IP address of the local interface that is being
12104 used. This is useful if a host that has more than one IP address wants to take
12105 on different personalities depending on which one is being used. For incoming
12106 connections, see &$received_ip_address$&.
12108 .vitem &$sending_port$&
12109 .vindex "&$sending_port$&"
12110 This variable is set whenever an outgoing SMTP connection to another host has
12111 been set up. It contains the local port that is being used. For incoming
12112 connections, see &$received_port$&.
12114 .vitem &$smtp_active_hostname$&
12115 .vindex "&$smtp_active_hostname$&"
12116 During an incoming SMTP session, this variable contains the value of the active
12117 host name, as specified by the &%smtp_active_hostname%& option. The value of
12118 &$smtp_active_hostname$& is saved with any message that is received, so its
12119 value can be consulted during routing and delivery.
12121 .vitem &$smtp_command$&
12122 .vindex "&$smtp_command$&"
12123 During the processing of an incoming SMTP command, this variable contains the
12124 entire command. This makes it possible to distinguish between HELO and EHLO in
12125 the HELO ACL, and also to distinguish between commands such as these:
12130 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12131 command, the address in &$smtp_command$& is the original address before any
12132 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12133 the address after SMTP-time rewriting.
12135 .vitem &$smtp_command_argument$&
12136 .cindex "SMTP" "command, argument for"
12137 .vindex "&$smtp_command_argument$&"
12138 While an ACL is running to check an SMTP command, this variable contains the
12139 argument, that is, the text that follows the command name, with leading white
12140 space removed. Following the introduction of &$smtp_command$&, this variable is
12141 somewhat redundant, but is retained for backwards compatibility.
12143 .vitem &$smtp_count_at_connection_start$&
12144 .vindex "&$smtp_count_at_connection_start$&"
12145 This variable is set greater than zero only in processes spawned by the Exim
12146 daemon for handling incoming SMTP connections. The name is deliberately long,
12147 in order to emphasize what the contents are. When the daemon accepts a new
12148 connection, it increments this variable. A copy of the variable is passed to
12149 the child process that handles the connection, but its value is fixed, and
12150 never changes. It is only an approximation of how many incoming connections
12151 there actually are, because many other connections may come and go while a
12152 single connection is being processed. When a child process terminates, the
12153 daemon decrements its copy of the variable.
12155 .vitem "&$sn0$& &-- &$sn9$&"
12156 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12157 that were current at the end of the system filter file. This allows a system
12158 filter file to set values that can be tested in users' filter files. For
12159 example, a system filter could set a value indicating how likely it is that a
12160 message is junk mail.
12162 .vitem &$spam_$&&'xxx'&
12163 A number of variables whose names start with &$spam$& are available when Exim
12164 is compiled with the content-scanning extension. For details, see section
12165 &<<SECTscanspamass>>&.
12168 .vitem &$spool_directory$&
12169 .vindex "&$spool_directory$&"
12170 The name of Exim's spool directory.
12172 .vitem &$spool_inodes$&
12173 .vindex "&$spool_inodes$&"
12174 The number of free inodes in the disk partition where Exim's spool files are
12175 being written. The value is recalculated whenever the variable is referenced.
12176 If the relevant file system does not have the concept of inodes, the value of
12177 is -1. See also the &%check_spool_inodes%& option.
12179 .vitem &$spool_space$&
12180 .vindex "&$spool_space$&"
12181 The amount of free space (as a number of kilobytes) in the disk partition where
12182 Exim's spool files are being written. The value is recalculated whenever the
12183 variable is referenced. If the operating system does not have the ability to
12184 find the amount of free space (only true for experimental systems), the space
12185 value is -1. For example, to check in an ACL that there is at least 50
12186 megabytes free on the spool, you could write:
12188 condition = ${if > {$spool_space}{50000}}
12190 See also the &%check_spool_space%& option.
12193 .vitem &$thisaddress$&
12194 .vindex "&$thisaddress$&"
12195 This variable is set only during the processing of the &%foranyaddress%&
12196 command in a filter file. Its use is explained in the description of that
12197 command, which can be found in the separate document entitled &'Exim's
12198 interfaces to mail filtering'&.
12200 .vitem &$tls_in_bits$&
12201 .vindex "&$tls_in_bits$&"
12202 Contains an approximation of the TLS cipher's bit-strength
12203 on the inbound connection; the meaning of
12204 this depends upon the TLS implementation used.
12205 If TLS has not been negotiated, the value will be 0.
12206 The value of this is automatically fed into the Cyrus SASL authenticator
12207 when acting as a server, to specify the "external SSF" (a SASL term).
12209 The deprecated &$tls_bits$& variable refers to the inbound side
12210 except when used in the context of an outbound SMTP delivery, when it refers to
12213 .vitem &$tls_out_bits$&
12214 .vindex "&$tls_out_bits$&"
12215 Contains an approximation of the TLS cipher's bit-strength
12216 on an outbound SMTP connection; the meaning of
12217 this depends upon the TLS implementation used.
12218 If TLS has not been negotiated, the value will be 0.
12220 .vitem &$tls_in_certificate_verified$&
12221 .vindex "&$tls_in_certificate_verified$&"
12222 This variable is set to &"1"& if a TLS certificate was verified when the
12223 message was received, and &"0"& otherwise.
12225 The deprecated &$tls_certificate_verfied$& variable refers to the inbound side
12226 except when used in the context of an outbound SMTP delivery, when it refers to
12229 .vitem &$tls_out_certificate_verified$&
12230 .vindex "&$tls_out_certificate_verified$&"
12231 This variable is set to &"1"& if a TLS certificate was verified when an
12232 outbound SMTP connection was made,
12233 and &"0"& otherwise.
12235 .vitem &$tls_in_cipher$&
12236 .vindex "&$tls_in_cipher$&"
12237 .vindex "&$tls_cipher$&"
12238 When a message is received from a remote host over an encrypted SMTP
12239 connection, this variable is set to the cipher suite that was negotiated, for
12240 example DES-CBC3-SHA. In other circumstances, in particular, for message
12241 received over unencrypted connections, the variable is empty. Testing
12242 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12243 non-encrypted connections during ACL processing.
12245 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12246 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12247 becomes the same as &$tls_out_cipher$&.
12249 .vitem &$tls_out_cipher$&
12250 .vindex "&$tls_out_cipher$&"
12252 cleared before any outgoing SMTP connection is made,
12253 and then set to the outgoing cipher suite if one is negotiated. See chapter
12254 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12255 details of the &(smtp)& transport.
12257 .vitem &$tls_in_peerdn$&
12258 .vindex "&$tls_in_peerdn$&"
12259 .vindex "&$tls_peerdn$&"
12260 When a message is received from a remote host over an encrypted SMTP
12261 connection, and Exim is configured to request a certificate from the client,
12262 the value of the Distinguished Name of the certificate is made available in the
12263 &$tls_in_peerdn$& during subsequent processing.
12265 The deprecated &$tls_peerdn$& variable refers to the inbound side
12266 except when used in the context of an outbound SMTP delivery, when it refers to
12269 .vitem &$tls_out_peerdn$&
12270 .vindex "&$tls_out_peerdn$&"
12271 When a message is being delivered to a remote host over an encrypted SMTP
12272 connection, and Exim is configured to request a certificate from the server,
12273 the value of the Distinguished Name of the certificate is made available in the
12274 &$tls_out_peerdn$& during subsequent processing.
12276 .vitem &$tls_in_sni$&
12277 .vindex "&$tls_in_sni$&"
12278 .vindex "&$tls_sni$&"
12279 .cindex "TLS" "Server Name Indication"
12280 When a TLS session is being established, if the client sends the Server
12281 Name Indication extension, the value will be placed in this variable.
12282 If the variable appears in &%tls_certificate%& then this option and
12283 some others, described in &<<SECTtlssni>>&,
12284 will be re-expanded early in the TLS session, to permit
12285 a different certificate to be presented (and optionally a different key to be
12286 used) to the client, based upon the value of the SNI extension.
12288 The deprecated &$tls_sni$& variable refers to the inbound side
12289 except when used in the context of an outbound SMTP delivery, when it refers to
12292 .vitem &$tls_out_sni$&
12293 .vindex "&$tls_out_sni$&"
12294 .cindex "TLS" "Server Name Indication"
12296 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12299 .vitem &$tod_bsdinbox$&
12300 .vindex "&$tod_bsdinbox$&"
12301 The time of day and the date, in the format required for BSD-style mailbox
12302 files, for example: Thu Oct 17 17:14:09 1995.
12304 .vitem &$tod_epoch$&
12305 .vindex "&$tod_epoch$&"
12306 The time and date as a number of seconds since the start of the Unix epoch.
12308 .vitem &$tod_epoch_l$&
12309 .vindex "&$tod_epoch_l$&"
12310 The time and date as a number of microseconds since the start of the Unix epoch.
12312 .vitem &$tod_full$&
12313 .vindex "&$tod_full$&"
12314 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12315 +0100. The timezone is always given as a numerical offset from UTC, with
12316 positive values used for timezones that are ahead (east) of UTC, and negative
12317 values for those that are behind (west).
12320 .vindex "&$tod_log$&"
12321 The time and date in the format used for writing Exim's log files, for example:
12322 1995-10-12 15:32:29, but without a timezone.
12324 .vitem &$tod_logfile$&
12325 .vindex "&$tod_logfile$&"
12326 This variable contains the date in the format yyyymmdd. This is the format that
12327 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12330 .vitem &$tod_zone$&
12331 .vindex "&$tod_zone$&"
12332 This variable contains the numerical value of the local timezone, for example:
12335 .vitem &$tod_zulu$&
12336 .vindex "&$tod_zulu$&"
12337 This variable contains the UTC date and time in &"Zulu"& format, as specified
12338 by ISO 8601, for example: 20030221154023Z.
12340 .vitem &$transport_name$&
12341 .cindex "transport" "name"
12342 .cindex "name" "of transport"
12343 .vindex "&$transport_name$&"
12344 During the running of a transport, this variable contains its name.
12347 .vindex "&$value$&"
12348 This variable contains the result of an expansion lookup, extraction operation,
12349 or external command, as described above. It is also used during a
12350 &*reduce*& expansion.
12352 .vitem &$version_number$&
12353 .vindex "&$version_number$&"
12354 The version number of Exim.
12356 .vitem &$warn_message_delay$&
12357 .vindex "&$warn_message_delay$&"
12358 This variable is set only during the creation of a message warning about a
12359 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12361 .vitem &$warn_message_recipients$&
12362 .vindex "&$warn_message_recipients$&"
12363 This variable is set only during the creation of a message warning about a
12364 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12370 . ////////////////////////////////////////////////////////////////////////////
12371 . ////////////////////////////////////////////////////////////////////////////
12373 .chapter "Embedded Perl" "CHAPperl"
12374 .scindex IIDperl "Perl" "calling from Exim"
12375 Exim can be built to include an embedded Perl interpreter. When this is done,
12376 Perl subroutines can be called as part of the string expansion process. To make
12377 use of the Perl support, you need version 5.004 or later of Perl installed on
12378 your system. To include the embedded interpreter in the Exim binary, include
12383 in your &_Local/Makefile_& and then build Exim in the normal way.
12386 .section "Setting up so Perl can be used" "SECID85"
12387 .oindex "&%perl_startup%&"
12388 Access to Perl subroutines is via a global configuration option called
12389 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12390 no &%perl_startup%& option in the Exim configuration file then no Perl
12391 interpreter is started and there is almost no overhead for Exim (since none of
12392 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12393 option then the associated value is taken to be Perl code which is executed in
12394 a newly created Perl interpreter.
12396 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12397 need backslashes before any characters to escape special meanings. The option
12398 should usually be something like
12400 perl_startup = do '/etc/exim.pl'
12402 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12403 use from Exim. Exim can be configured either to start up a Perl interpreter as
12404 soon as it is entered, or to wait until the first time it is needed. Starting
12405 the interpreter at the beginning ensures that it is done while Exim still has
12406 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12407 fact used in a particular run. Also, note that this does not mean that Exim is
12408 necessarily running as root when Perl is called at a later time. By default,
12409 the interpreter is started only when it is needed, but this can be changed in
12413 .oindex "&%perl_at_start%&"
12414 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12415 a startup when Exim is entered.
12417 The command line option &%-ps%& also requests a startup when Exim is entered,
12418 overriding the setting of &%perl_at_start%&.
12421 There is also a command line option &%-pd%& (for delay) which suppresses the
12422 initial startup, even if &%perl_at_start%& is set.
12425 .section "Calling Perl subroutines" "SECID86"
12426 When the configuration file includes a &%perl_startup%& option you can make use
12427 of the string expansion item to call the Perl subroutines that are defined
12428 by the &%perl_startup%& code. The operator is used in any of the following
12432 ${perl{foo}{argument}}
12433 ${perl{foo}{argument1}{argument2} ... }
12435 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12436 arguments may be passed. Passing more than this results in an expansion failure
12437 with an error message of the form
12439 Too many arguments passed to Perl subroutine "foo" (max is 8)
12441 The return value of the Perl subroutine is evaluated in a scalar context before
12442 it is passed back to Exim to be inserted into the expanded string. If the
12443 return value is &'undef'&, the expansion is forced to fail in the same way as
12444 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12445 by obeying Perl's &%die%& function, the expansion fails with the error message
12446 that was passed to &%die%&.
12449 .section "Calling Exim functions from Perl" "SECID87"
12450 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12451 is available to call back into Exim's string expansion function. For example,
12454 my $lp = Exim::expand_string('$local_part');
12456 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12457 Note those are single quotes and not double quotes to protect against
12458 &$local_part$& being interpolated as a Perl variable.
12460 If the string expansion is forced to fail by a &"fail"& item, the result of
12461 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12462 expansion string, the Perl call from the original expansion string fails with
12463 an appropriate error message, in the same way as if &%die%& were used.
12465 .cindex "debugging" "from embedded Perl"
12466 .cindex "log" "writing from embedded Perl"
12467 Two other Exim functions are available for use from within Perl code.
12468 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12469 debugging is enabled. If you want a newline at the end, you must supply it.
12470 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12471 timestamp. In this case, you should not supply a terminating newline.
12474 .section "Use of standard output and error by Perl" "SECID88"
12475 .cindex "Perl" "standard output and error"
12476 You should not write to the standard error or output streams from within your
12477 Perl code, as it is not defined how these are set up. In versions of Exim
12478 before 4.50, it is possible for the standard output or error to refer to the
12479 SMTP connection during message reception via the daemon. Writing to this stream
12480 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12481 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12482 avoided, but the output is lost.
12484 .cindex "Perl" "use of &%warn%&"
12485 The Perl &%warn%& statement writes to the standard error stream by default.
12486 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12487 you have no control. When Exim starts up the Perl interpreter, it arranges for
12488 output from the &%warn%& statement to be written to the Exim main log. You can
12489 change this by including appropriate Perl magic somewhere in your Perl code.
12490 For example, to discard &%warn%& output completely, you need this:
12492 $SIG{__WARN__} = sub { };
12494 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12495 example, the code for the subroutine is empty, so it does nothing, but you can
12496 include any Perl code that you like. The text of the &%warn%& message is passed
12497 as the first subroutine argument.
12501 . ////////////////////////////////////////////////////////////////////////////
12502 . ////////////////////////////////////////////////////////////////////////////
12504 .chapter "Starting the daemon and the use of network interfaces" &&&
12505 "CHAPinterfaces" &&&
12506 "Starting the daemon"
12507 .cindex "daemon" "starting"
12508 .cindex "interface" "listening"
12509 .cindex "network interface"
12510 .cindex "interface" "network"
12511 .cindex "IP address" "for listening"
12512 .cindex "daemon" "listening IP addresses"
12513 .cindex "TCP/IP" "setting listening interfaces"
12514 .cindex "TCP/IP" "setting listening ports"
12515 A host that is connected to a TCP/IP network may have one or more physical
12516 hardware network interfaces. Each of these interfaces may be configured as one
12517 or more &"logical"& interfaces, which are the entities that a program actually
12518 works with. Each of these logical interfaces is associated with an IP address.
12519 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12520 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12521 knowledge about the host's interfaces for use in three different circumstances:
12524 When a listening daemon is started, Exim needs to know which interfaces
12525 and ports to listen on.
12527 When Exim is routing an address, it needs to know which IP addresses
12528 are associated with local interfaces. This is required for the correct
12529 processing of MX lists by removing the local host and others with the
12530 same or higher priority values. Also, Exim needs to detect cases
12531 when an address is routed to an IP address that in fact belongs to the
12532 local host. Unless the &%self%& router option or the &%allow_localhost%&
12533 option of the smtp transport is set (as appropriate), this is treated
12534 as an error situation.
12536 When Exim connects to a remote host, it may need to know which interface to use
12537 for the outgoing connection.
12541 Exim's default behaviour is likely to be appropriate in the vast majority
12542 of cases. If your host has only one interface, and you want all its IP
12543 addresses to be treated in the same way, and you are using only the
12544 standard SMTP port, you should not need to take any special action. The
12545 rest of this chapter does not apply to you.
12547 In a more complicated situation you may want to listen only on certain
12548 interfaces, or on different ports, and for this reason there are a number of
12549 options that can be used to influence Exim's behaviour. The rest of this
12550 chapter describes how they operate.
12552 When a message is received over TCP/IP, the interface and port that were
12553 actually used are set in &$received_ip_address$& and &$received_port$&.
12557 .section "Starting a listening daemon" "SECID89"
12558 When a listening daemon is started (by means of the &%-bd%& command line
12559 option), the interfaces and ports on which it listens are controlled by the
12563 &%daemon_smtp_ports%& contains a list of default ports. (For backward
12564 compatibility, this option can also be specified in the singular.)
12566 &%local_interfaces%& contains list of interface IP addresses on which to
12567 listen. Each item may optionally also specify a port.
12570 The default list separator in both cases is a colon, but this can be changed as
12571 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12572 it is usually best to change the separator to avoid having to double all the
12573 colons. For example:
12575 local_interfaces = <; 127.0.0.1 ; \
12578 3ffe:ffff:836f::fe86:a061
12580 There are two different formats for specifying a port along with an IP address
12581 in &%local_interfaces%&:
12584 The port is added onto the address with a dot separator. For example, to listen
12585 on port 1234 on two different IP addresses:
12587 local_interfaces = <; 192.168.23.65.1234 ; \
12588 3ffe:ffff:836f::fe86:a061.1234
12591 The IP address is enclosed in square brackets, and the port is added
12592 with a colon separator, for example:
12594 local_interfaces = <; [192.168.23.65]:1234 ; \
12595 [3ffe:ffff:836f::fe86:a061]:1234
12599 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
12600 default setting contains just one port:
12602 daemon_smtp_ports = smtp
12604 If more than one port is listed, each interface that does not have its own port
12605 specified listens on all of them. Ports that are listed in
12606 &%daemon_smtp_ports%& can be identified either by name (defined in
12607 &_/etc/services_&) or by number. However, when ports are given with individual
12608 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12612 .section "Special IP listening addresses" "SECID90"
12613 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12614 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12615 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12616 instead of setting up separate listening sockets for each interface. The
12617 default value of &%local_interfaces%& is
12619 local_interfaces = 0.0.0.0
12621 when Exim is built without IPv6 support; otherwise it is:
12623 local_interfaces = <; ::0 ; 0.0.0.0
12625 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12629 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12630 The &%-oX%& command line option can be used to override the values of
12631 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12632 instance. Another way of doing this would be to use macros and the &%-D%&
12633 option. However, &%-oX%& can be used by any admin user, whereas modification of
12634 the runtime configuration by &%-D%& is allowed only when the caller is root or
12637 The value of &%-oX%& is a list of items. The default colon separator can be
12638 changed in the usual way if required. If there are any items that do not
12639 contain dots or colons (that is, are not IP addresses), the value of
12640 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12641 items that do contain dots or colons, the value of &%local_interfaces%& is
12642 replaced by those items. Thus, for example,
12646 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12649 -oX 192.168.34.5.1125
12651 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12652 (However, since &%local_interfaces%& now contains no items without ports, the
12653 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12657 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12658 .cindex "ssmtp protocol"
12659 .cindex "smtps protocol"
12660 .cindex "SMTP" "ssmtp protocol"
12661 .cindex "SMTP" "smtps protocol"
12662 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12663 before the STARTTLS command was standardized for SMTP. Some legacy clients
12664 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12665 list of port numbers, connections to those ports must use SSMTP. The most
12666 common use of this option is expected to be
12668 tls_on_connect_ports = 465
12670 because 465 is the usual port number used by the legacy clients. There is also
12671 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12672 this way when a daemon is started.
12674 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12675 daemon to listen on those ports. You must still specify them in
12676 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12677 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12678 connections via the daemon.)
12683 .section "IPv6 address scopes" "SECID92"
12684 .cindex "IPv6" "address scopes"
12685 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12686 can, in principle, have the same link-local IPv6 address on different
12687 interfaces. Thus, additional information is needed, over and above the IP
12688 address, to distinguish individual interfaces. A convention of using a
12689 percent sign followed by something (often the interface name) has been
12690 adopted in some cases, leading to addresses like this:
12692 fe80::202:b3ff:fe03:45c1%eth0
12694 To accommodate this usage, a percent sign followed by an arbitrary string is
12695 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12696 to convert a textual IPv6 address for actual use. This function recognizes the
12697 percent convention in operating systems that support it, and it processes the
12698 address appropriately. Unfortunately, some older libraries have problems with
12699 &[getaddrinfo()]&. If
12701 IPV6_USE_INET_PTON=yes
12703 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12704 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12705 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12706 function.) Of course, this means that the additional functionality of
12707 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12709 .section "Disabling IPv6" "SECID93"
12710 .cindex "IPv6" "disabling"
12711 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12712 run on a host whose kernel does not support IPv6. The binary will fall back to
12713 using IPv4, but it may waste resources looking up AAAA records, and trying to
12714 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12715 .oindex "&%disable_ipv6%&"
12716 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12717 activities take place. AAAA records are never looked up, and any IPv6 addresses
12718 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12719 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12720 to handle IPv6 literal addresses.
12722 On the other hand, when IPv6 is in use, there may be times when you want to
12723 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12724 option to globally suppress the lookup of AAAA records for specified domains,
12725 and you can use the &%ignore_target_hosts%& generic router option to ignore
12726 IPv6 addresses in an individual router.
12730 .section "Examples of starting a listening daemon" "SECID94"
12731 The default case in an IPv6 environment is
12733 daemon_smtp_ports = smtp
12734 local_interfaces = <; ::0 ; 0.0.0.0
12736 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12737 Either one or two sockets may be used, depending on the characteristics of
12738 the TCP/IP stack. (This is complicated and messy; for more information,
12739 read the comments in the &_daemon.c_& source file.)
12741 To specify listening on ports 25 and 26 on all interfaces:
12743 daemon_smtp_ports = 25 : 26
12745 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12747 local_interfaces = <; ::0.25 ; ::0.26 \
12748 0.0.0.0.25 ; 0.0.0.0.26
12750 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12751 IPv4 loopback address only:
12753 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12755 To specify listening on the default port on specific interfaces only:
12757 local_interfaces = 10.0.0.67 : 192.168.34.67
12759 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12763 .section "Recognizing the local host" "SECTreclocipadd"
12764 The &%local_interfaces%& option is also used when Exim needs to determine
12765 whether or not an IP address refers to the local host. That is, the IP
12766 addresses of all the interfaces on which a daemon is listening are always
12769 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12770 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12771 available interfaces from the operating system, and extracts the relevant
12772 (that is, IPv4 or IPv6) addresses to use for checking.
12774 Some systems set up large numbers of virtual interfaces in order to provide
12775 many virtual web servers. In this situation, you may want to listen for
12776 email on only a few of the available interfaces, but nevertheless treat all
12777 interfaces as local when routing. You can do this by setting
12778 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12779 &"all"& wildcard values. These addresses are recognized as local, but are not
12780 used for listening. Consider this example:
12782 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12784 3ffe:2101:12:1:a00:20ff:fe86:a061
12786 extra_local_interfaces = <; ::0 ; 0.0.0.0
12788 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12789 address, but all available interface addresses are treated as local when
12792 In some environments the local host name may be in an MX list, but with an IP
12793 address that is not assigned to any local interface. In other cases it may be
12794 desirable to treat other host names as if they referred to the local host. Both
12795 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12796 This contains host names rather than IP addresses. When a host is referenced
12797 during routing, either via an MX record or directly, it is treated as the local
12798 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12799 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12803 .section "Delivering to a remote host" "SECID95"
12804 Delivery to a remote host is handled by the smtp transport. By default, it
12805 allows the system's TCP/IP functions to choose which interface to use (if
12806 there is more than one) when connecting to a remote host. However, the
12807 &%interface%& option can be set to specify which interface is used. See the
12808 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12814 . ////////////////////////////////////////////////////////////////////////////
12815 . ////////////////////////////////////////////////////////////////////////////
12817 .chapter "Main configuration" "CHAPmainconfig"
12818 .scindex IIDconfima "configuration file" "main section"
12819 .scindex IIDmaiconf "main configuration"
12820 The first part of the run time configuration file contains three types of item:
12823 Macro definitions: These lines start with an upper case letter. See section
12824 &<<SECTmacrodefs>>& for details of macro processing.
12826 Named list definitions: These lines start with one of the words &"domainlist"&,
12827 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12828 section &<<SECTnamedlists>>&.
12830 Main configuration settings: Each setting occupies one line of the file
12831 (with possible continuations). If any setting is preceded by the word
12832 &"hide"&, the &%-bP%& command line option displays its value to admin users
12833 only. See section &<<SECTcos>>& for a description of the syntax of these option
12837 This chapter specifies all the main configuration options, along with their
12838 types and default values. For ease of finding a particular option, they appear
12839 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12840 are now so many options, they are first listed briefly in functional groups, as
12841 an aid to finding the name of the option you are looking for. Some options are
12842 listed in more than one group.
12844 .section "Miscellaneous" "SECID96"
12846 .row &%bi_command%& "to run for &%-bi%& command line option"
12847 .row &%disable_ipv6%& "do no IPv6 processing"
12848 .row &%keep_malformed%& "for broken files &-- should not happen"
12849 .row &%localhost_number%& "for unique message ids in clusters"
12850 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12851 .row &%message_body_visible%& "how much to show in &$message_body$&"
12852 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12853 .row &%print_topbitchars%& "top-bit characters are printing"
12854 .row &%timezone%& "force time zone"
12858 .section "Exim parameters" "SECID97"
12860 .row &%exim_group%& "override compiled-in value"
12861 .row &%exim_path%& "override compiled-in value"
12862 .row &%exim_user%& "override compiled-in value"
12863 .row &%primary_hostname%& "default from &[uname()]&"
12864 .row &%split_spool_directory%& "use multiple directories"
12865 .row &%spool_directory%& "override compiled-in value"
12870 .section "Privilege controls" "SECID98"
12872 .row &%admin_groups%& "groups that are Exim admin users"
12873 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12874 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12875 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12876 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12877 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12878 .row &%never_users%& "do not run deliveries as these"
12879 .row &%prod_requires_admin%& "forced delivery requires admin user"
12880 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12881 .row &%trusted_groups%& "groups that are trusted"
12882 .row &%trusted_users%& "users that are trusted"
12887 .section "Logging" "SECID99"
12889 .row &%hosts_connection_nolog%& "exemption from connect logging"
12890 .row &%log_file_path%& "override compiled-in value"
12891 .row &%log_selector%& "set/unset optional logging"
12892 .row &%log_timezone%& "add timezone to log lines"
12893 .row &%message_logs%& "create per-message logs"
12894 .row &%preserve_message_logs%& "after message completion"
12895 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12896 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12897 .row &%syslog_facility%& "set syslog &""facility""& field"
12898 .row &%syslog_processname%& "set syslog &""ident""& field"
12899 .row &%syslog_timestamp%& "timestamp syslog lines"
12900 .row &%write_rejectlog%& "control use of message log"
12905 .section "Frozen messages" "SECID100"
12907 .row &%auto_thaw%& "sets time for retrying frozen messages"
12908 .row &%freeze_tell%& "send message when freezing"
12909 .row &%move_frozen_messages%& "to another directory"
12910 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12915 .section "Data lookups" "SECID101"
12917 .row &%ibase_servers%& "InterBase servers"
12918 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
12919 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
12920 .row &%ldap_cert_file%& "client cert file for LDAP"
12921 .row &%ldap_cert_key%& "client key file for LDAP"
12922 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
12923 .row &%ldap_default_servers%& "used if no server in query"
12924 .row &%ldap_require_cert%& "action to take without LDAP server cert"
12925 .row &%ldap_start_tls%& "require TLS within LDAP"
12926 .row &%ldap_version%& "set protocol version"
12927 .row &%lookup_open_max%& "lookup files held open"
12928 .row &%mysql_servers%& "default MySQL servers"
12929 .row &%oracle_servers%& "Oracle servers"
12930 .row &%pgsql_servers%& "default PostgreSQL servers"
12931 .row &%sqlite_lock_timeout%& "as it says"
12936 .section "Message ids" "SECID102"
12938 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12939 .row &%message_id_header_text%& "ditto"
12944 .section "Embedded Perl Startup" "SECID103"
12946 .row &%perl_at_start%& "always start the interpreter"
12947 .row &%perl_startup%& "code to obey when starting Perl"
12952 .section "Daemon" "SECID104"
12954 .row &%daemon_smtp_ports%& "default ports"
12955 .row &%daemon_startup_retries%& "number of times to retry"
12956 .row &%daemon_startup_sleep%& "time to sleep between tries"
12957 .row &%extra_local_interfaces%& "not necessarily listened on"
12958 .row &%local_interfaces%& "on which to listen, with optional ports"
12959 .row &%pid_file_path%& "override compiled-in value"
12960 .row &%queue_run_max%& "maximum simultaneous queue runners"
12965 .section "Resource control" "SECID105"
12967 .row &%check_log_inodes%& "before accepting a message"
12968 .row &%check_log_space%& "before accepting a message"
12969 .row &%check_spool_inodes%& "before accepting a message"
12970 .row &%check_spool_space%& "before accepting a message"
12971 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
12972 .row &%queue_only_load%& "queue incoming if load high"
12973 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12974 .row &%queue_run_max%& "maximum simultaneous queue runners"
12975 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12976 .row &%smtp_accept_max%& "simultaneous incoming connections"
12977 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12978 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12979 .row &%smtp_accept_max_per_connection%& "messages per connection"
12980 .row &%smtp_accept_max_per_host%& "connections from one host"
12981 .row &%smtp_accept_queue%& "queue mail if more connections"
12982 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12984 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12985 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12986 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12987 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
12988 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12993 .section "Policy controls" "SECID106"
12995 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
12996 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
12997 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
12998 .row &%acl_smtp_auth%& "ACL for AUTH"
12999 .row &%acl_smtp_connect%& "ACL for connection"
13000 .row &%acl_smtp_data%& "ACL for DATA"
13001 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13002 .row &%acl_smtp_etrn%& "ACL for ETRN"
13003 .row &%acl_smtp_expn%& "ACL for EXPN"
13004 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13005 .row &%acl_smtp_mail%& "ACL for MAIL"
13006 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13007 .row &%acl_smtp_mime%& "ACL for MIME parts"
13008 .row &%acl_smtp_predata%& "ACL for start of data"
13009 .row &%acl_smtp_quit%& "ACL for QUIT"
13010 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13011 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13012 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13013 .row &%av_scanner%& "specify virus scanner"
13014 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13016 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13017 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13018 .row &%header_maxsize%& "total size of message header"
13019 .row &%header_line_maxsize%& "individual header line limit"
13020 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13021 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13022 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13023 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13024 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13025 .row &%host_lookup%& "host name looked up for these hosts"
13026 .row &%host_lookup_order%& "order of DNS and local name lookups"
13027 .row &%host_reject_connection%& "reject connection from these hosts"
13028 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13029 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13030 .row &%message_size_limit%& "for all messages"
13031 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13032 .row &%spamd_address%& "set interface to SpamAssassin"
13033 .row &%strict_acl_vars%& "object to unset ACL variables"
13038 .section "Callout cache" "SECID107"
13040 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13042 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13044 .row &%callout_negative_expire%& "timeout for negative address cache item"
13045 .row &%callout_positive_expire%& "timeout for positive address cache item"
13046 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13051 .section "TLS" "SECID108"
13053 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13054 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13055 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13056 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13057 .row &%tls_certificate%& "location of server certificate"
13058 .row &%tls_crl%& "certificate revocation list"
13059 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13060 .row &%tls_dhparam%& "DH parameters for server"
13061 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13062 .row &%tls_privatekey%& "location of server private key"
13063 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13064 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13065 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13066 .row &%tls_verify_certificates%& "expected client certificates"
13067 .row &%tls_verify_hosts%& "insist on client certificate verify"
13072 .section "Local user handling" "SECID109"
13074 .row &%finduser_retries%& "useful in NIS environments"
13075 .row &%gecos_name%& "used when creating &'Sender:'&"
13076 .row &%gecos_pattern%& "ditto"
13077 .row &%max_username_length%& "for systems that truncate"
13078 .row &%unknown_login%& "used when no login name found"
13079 .row &%unknown_username%& "ditto"
13080 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13081 .row &%uucp_from_sender%& "ditto"
13086 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13088 .row &%header_maxsize%& "total size of message header"
13089 .row &%header_line_maxsize%& "individual header line limit"
13090 .row &%message_size_limit%& "applies to all messages"
13091 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13092 .row &%received_header_text%& "expanded to make &'Received:'&"
13093 .row &%received_headers_max%& "for mail loop detection"
13094 .row &%recipients_max%& "limit per message"
13095 .row &%recipients_max_reject%& "permanently reject excess recipients"
13101 .section "Non-SMTP incoming messages" "SECID111"
13103 .row &%receive_timeout%& "for non-SMTP messages"
13110 .section "Incoming SMTP messages" "SECID112"
13111 See also the &'Policy controls'& section above.
13114 .row &%host_lookup%& "host name looked up for these hosts"
13115 .row &%host_lookup_order%& "order of DNS and local name lookups"
13116 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13117 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13118 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13119 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13120 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13121 .row &%smtp_accept_max%& "simultaneous incoming connections"
13122 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13123 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13124 .row &%smtp_accept_max_per_connection%& "messages per connection"
13125 .row &%smtp_accept_max_per_host%& "connections from one host"
13126 .row &%smtp_accept_queue%& "queue mail if more connections"
13127 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13129 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13130 .row &%smtp_active_hostname%& "host name to use in messages"
13131 .row &%smtp_banner%& "text for welcome banner"
13132 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13133 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13134 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13135 .row &%smtp_etrn_command%& "what to run for ETRN"
13136 .row &%smtp_etrn_serialize%& "only one at once"
13137 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13138 .row &%smtp_max_unknown_commands%& "before dropping connection"
13139 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13140 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13141 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13142 .row &%smtp_receive_timeout%& "per command or data line"
13143 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13144 .row &%smtp_return_error_details%& "give detail on rejections"
13149 .section "SMTP extensions" "SECID113"
13151 .row &%accept_8bitmime%& "advertise 8BITMIME"
13152 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13153 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13154 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13155 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13156 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13161 .section "Processing messages" "SECID114"
13163 .row &%allow_domain_literals%& "recognize domain literal syntax"
13164 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13165 .row &%allow_utf8_domains%& "in addresses"
13166 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13168 .row &%delivery_date_remove%& "from incoming messages"
13169 .row &%envelope_to_remove%& "from incoming messages"
13170 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13171 .row &%headers_charset%& "default for translations"
13172 .row &%qualify_domain%& "default for senders"
13173 .row &%qualify_recipient%& "default for recipients"
13174 .row &%return_path_remove%& "from incoming messages"
13175 .row &%strip_excess_angle_brackets%& "in addresses"
13176 .row &%strip_trailing_dot%& "at end of addresses"
13177 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13182 .section "System filter" "SECID115"
13184 .row &%system_filter%& "locate system filter"
13185 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13187 .row &%system_filter_file_transport%& "transport for delivery to a file"
13188 .row &%system_filter_group%& "group for filter running"
13189 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13190 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13191 .row &%system_filter_user%& "user for filter running"
13196 .section "Routing and delivery" "SECID116"
13198 .row &%disable_ipv6%& "do no IPv6 processing"
13199 .row &%dns_again_means_nonexist%& "for broken domains"
13200 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13201 .row &%dns_dnssec_ok%& "parameter for resolver"
13202 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13203 .row &%dns_retrans%& "parameter for resolver"
13204 .row &%dns_retry%& "parameter for resolver"
13205 .row &%dns_use_edns0%& "parameter for resolver"
13206 .row &%hold_domains%& "hold delivery for these domains"
13207 .row &%local_interfaces%& "for routing checks"
13208 .row &%queue_domains%& "no immediate delivery for these"
13209 .row &%queue_only%& "no immediate delivery at all"
13210 .row &%queue_only_file%& "no immediate delivery if file exists"
13211 .row &%queue_only_load%& "no immediate delivery if load is high"
13212 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13213 .row &%queue_only_override%& "allow command line to override"
13214 .row &%queue_run_in_order%& "order of arrival"
13215 .row &%queue_run_max%& "of simultaneous queue runners"
13216 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13217 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13218 .row &%remote_sort_domains%& "order of remote deliveries"
13219 .row &%retry_data_expire%& "timeout for retry data"
13220 .row &%retry_interval_max%& "safety net for retry rules"
13225 .section "Bounce and warning messages" "SECID117"
13227 .row &%bounce_message_file%& "content of bounce"
13228 .row &%bounce_message_text%& "content of bounce"
13229 .row &%bounce_return_body%& "include body if returning message"
13230 .row &%bounce_return_message%& "include original message in bounce"
13231 .row &%bounce_return_size_limit%& "limit on returned message"
13232 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13233 .row &%dsn_from%& "set &'From:'& contents in bounces"
13234 .row &%errors_copy%& "copy bounce messages"
13235 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13236 .row &%delay_warning%& "time schedule"
13237 .row &%delay_warning_condition%& "condition for warning messages"
13238 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13239 .row &%smtp_return_error_details%& "give detail on rejections"
13240 .row &%warn_message_file%& "content of warning message"
13245 .section "Alphabetical list of main options" "SECTalomo"
13246 Those options that undergo string expansion before use are marked with
13249 .option accept_8bitmime main boolean true
13251 .cindex "8-bit characters"
13252 .cindex "log" "selectors"
13253 .cindex "log" "8BITMIME"
13254 This option causes Exim to send 8BITMIME in its response to an SMTP
13255 EHLO command, and to accept the BODY= parameter on MAIL commands.
13256 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13257 takes no steps to do anything special with messages received by this route.
13259 Historically Exim kept this option off by default, but the maintainers
13260 feel that in today's Internet, this causes more problems than it solves.
13261 It now defaults to true.
13262 A more detailed analysis of the issues is provided by Dan Bernstein:
13264 &url(http://cr.yp.to/smtp/8bitmime.html)
13267 To log received 8BITMIME status use
13269 log_selector = +8bitmime
13272 .option acl_not_smtp main string&!! unset
13273 .cindex "&ACL;" "for non-SMTP messages"
13274 .cindex "non-SMTP messages" "ACLs for"
13275 This option defines the ACL that is run when a non-SMTP message has been
13276 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13279 .option acl_not_smtp_mime main string&!! unset
13280 This option defines the ACL that is run for individual MIME parts of non-SMTP
13281 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13284 .option acl_not_smtp_start main string&!! unset
13285 .cindex "&ACL;" "at start of non-SMTP message"
13286 .cindex "non-SMTP messages" "ACLs for"
13287 This option defines the ACL that is run before Exim starts reading a
13288 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13290 .option acl_smtp_auth main string&!! unset
13291 .cindex "&ACL;" "setting up for SMTP commands"
13292 .cindex "AUTH" "ACL for"
13293 This option defines the ACL that is run when an SMTP AUTH command is
13294 received. See chapter &<<CHAPACL>>& for further details.
13296 .option acl_smtp_connect main string&!! unset
13297 .cindex "&ACL;" "on SMTP connection"
13298 This option defines the ACL that is run when an SMTP connection is received.
13299 See chapter &<<CHAPACL>>& for further details.
13301 .option acl_smtp_data main string&!! unset
13302 .cindex "DATA" "ACL for"
13303 This option defines the ACL that is run after an SMTP DATA command has been
13304 processed and the message itself has been received, but before the final
13305 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13307 .option acl_smtp_etrn main string&!! unset
13308 .cindex "ETRN" "ACL for"
13309 This option defines the ACL that is run when an SMTP ETRN command is
13310 received. See chapter &<<CHAPACL>>& for further details.
13312 .option acl_smtp_expn main string&!! unset
13313 .cindex "EXPN" "ACL for"
13314 This option defines the ACL that is run when an SMTP EXPN command is
13315 received. See chapter &<<CHAPACL>>& for further details.
13317 .option acl_smtp_helo main string&!! unset
13318 .cindex "EHLO" "ACL for"
13319 .cindex "HELO" "ACL for"
13320 This option defines the ACL that is run when an SMTP EHLO or HELO
13321 command is received. See chapter &<<CHAPACL>>& for further details.
13324 .option acl_smtp_mail main string&!! unset
13325 .cindex "MAIL" "ACL for"
13326 This option defines the ACL that is run when an SMTP MAIL command is
13327 received. See chapter &<<CHAPACL>>& for further details.
13329 .option acl_smtp_mailauth main string&!! unset
13330 .cindex "AUTH" "on MAIL command"
13331 This option defines the ACL that is run when there is an AUTH parameter on
13332 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13333 &<<CHAPSMTPAUTH>>& for details of authentication.
13335 .option acl_smtp_mime main string&!! unset
13336 .cindex "MIME content scanning" "ACL for"
13337 This option is available when Exim is built with the content-scanning
13338 extension. It defines the ACL that is run for each MIME part in a message. See
13339 section &<<SECTscanmimepart>>& for details.
13341 .option acl_smtp_predata main string&!! unset
13342 This option defines the ACL that is run when an SMTP DATA command is
13343 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13346 .option acl_smtp_quit main string&!! unset
13347 .cindex "QUIT, ACL for"
13348 This option defines the ACL that is run when an SMTP QUIT command is
13349 received. See chapter &<<CHAPACL>>& for further details.
13351 .option acl_smtp_rcpt main string&!! unset
13352 .cindex "RCPT" "ACL for"
13353 This option defines the ACL that is run when an SMTP RCPT command is
13354 received. See chapter &<<CHAPACL>>& for further details.
13356 .option acl_smtp_starttls main string&!! unset
13357 .cindex "STARTTLS, ACL for"
13358 This option defines the ACL that is run when an SMTP STARTTLS command is
13359 received. See chapter &<<CHAPACL>>& for further details.
13361 .option acl_smtp_vrfy main string&!! unset
13362 .cindex "VRFY" "ACL for"
13363 This option defines the ACL that is run when an SMTP VRFY command is
13364 received. See chapter &<<CHAPACL>>& for further details.
13366 .option admin_groups main "string list&!!" unset
13367 .cindex "admin user"
13368 This option is expanded just once, at the start of Exim's processing. If the
13369 current group or any of the supplementary groups of an Exim caller is in this
13370 colon-separated list, the caller has admin privileges. If all your system
13371 programmers are in a specific group, for example, you can give them all Exim
13372 admin privileges by putting that group in &%admin_groups%&. However, this does
13373 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13374 To permit this, you have to add individuals to the Exim group.
13376 .option allow_domain_literals main boolean false
13377 .cindex "domain literal"
13378 If this option is set, the RFC 2822 domain literal format is permitted in
13379 email addresses. The option is not set by default, because the domain literal
13380 format is not normally required these days, and few people know about it. It
13381 has, however, been exploited by mail abusers.
13383 Unfortunately, it seems that some DNS black list maintainers are using this
13384 format to report black listing to postmasters. If you want to accept messages
13385 addressed to your hosts by IP address, you need to set
13386 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13387 domains (defined in the named domain list &%local_domains%& in the default
13388 configuration). This &"magic string"& matches the domain literal form of all
13389 the local host's IP addresses.
13392 .option allow_mx_to_ip main boolean false
13393 .cindex "MX record" "pointing to IP address"
13394 It appears that more and more DNS zone administrators are breaking the rules
13395 and putting domain names that look like IP addresses on the right hand side of
13396 MX records. Exim follows the rules and rejects this, giving an error message
13397 that explains the mis-configuration. However, some other MTAs support this
13398 practice, so to avoid &"Why can't Exim do this?"& complaints,
13399 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13400 recommended, except when you have no other choice.
13402 .option allow_utf8_domains main boolean false
13403 .cindex "domain" "UTF-8 characters in"
13404 .cindex "UTF-8" "in domain name"
13405 Lots of discussion is going on about internationalized domain names. One
13406 camp is strongly in favour of just using UTF-8 characters, and it seems
13407 that at least two other MTAs permit this. This option allows Exim users to
13408 experiment if they wish.
13410 If it is set true, Exim's domain parsing function allows valid
13411 UTF-8 multicharacters to appear in domain name components, in addition to
13412 letters, digits, and hyphens. However, just setting this option is not
13413 enough; if you want to look up these domain names in the DNS, you must also
13414 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13415 suitable setting is:
13417 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13418 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13420 Alternatively, you can just disable this feature by setting
13422 dns_check_names_pattern =
13424 That is, set the option to an empty string so that no check is done.
13427 .option auth_advertise_hosts main "host list&!!" *
13428 .cindex "authentication" "advertising"
13429 .cindex "AUTH" "advertising"
13430 If any server authentication mechanisms are configured, Exim advertises them in
13431 response to an EHLO command only if the calling host matches this list.
13432 Otherwise, Exim does not advertise AUTH.
13433 Exim does not accept AUTH commands from clients to which it has not
13434 advertised the availability of AUTH. The advertising of individual
13435 authentication mechanisms can be controlled by the use of the
13436 &%server_advertise_condition%& generic authenticator option on the individual
13437 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13439 Certain mail clients (for example, Netscape) require the user to provide a name
13440 and password for authentication if AUTH is advertised, even though it may
13441 not be needed (the host may accept messages from hosts on its local LAN without
13442 authentication, for example). The &%auth_advertise_hosts%& option can be used
13443 to make these clients more friendly by excluding them from the set of hosts to
13444 which Exim advertises AUTH.
13446 .cindex "AUTH" "advertising when encrypted"
13447 If you want to advertise the availability of AUTH only when the connection
13448 is encrypted using TLS, you can make use of the fact that the value of this
13449 option is expanded, with a setting like this:
13451 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13453 .vindex "&$tls_in_cipher$&"
13454 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13455 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13456 expansion is *, which matches all hosts.
13459 .option auto_thaw main time 0s
13460 .cindex "thawing messages"
13461 .cindex "unfreezing messages"
13462 If this option is set to a time greater than zero, a queue runner will try a
13463 new delivery attempt on any frozen message, other than a bounce message, if
13464 this much time has passed since it was frozen. This may result in the message
13465 being re-frozen if nothing has changed since the last attempt. It is a way of
13466 saying &"keep on trying, even though there are big problems"&.
13468 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13469 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13470 thought to be very useful any more, and its use should probably be avoided.
13473 .option av_scanner main string "see below"
13474 This option is available if Exim is built with the content-scanning extension.
13475 It specifies which anti-virus scanner to use. The default value is:
13477 sophie:/var/run/sophie
13479 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13480 before use. See section &<<SECTscanvirus>>& for further details.
13483 .option bi_command main string unset
13485 This option supplies the name of a command that is run when Exim is called with
13486 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13487 just the command name, it is not a complete command line. If an argument is
13488 required, it must come from the &%-oA%& command line option.
13491 .option bounce_message_file main string unset
13492 .cindex "bounce message" "customizing"
13493 .cindex "customizing" "bounce message"
13494 This option defines a template file containing paragraphs of text to be used
13495 for constructing bounce messages. Details of the file's contents are given in
13496 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13499 .option bounce_message_text main string unset
13500 When this option is set, its contents are included in the default bounce
13501 message immediately after &"This message was created automatically by mail
13502 delivery software."& It is not used if &%bounce_message_file%& is set.
13504 .option bounce_return_body main boolean true
13505 .cindex "bounce message" "including body"
13506 This option controls whether the body of an incoming message is included in a
13507 bounce message when &%bounce_return_message%& is true. The default setting
13508 causes the entire message, both header and body, to be returned (subject to the
13509 value of &%bounce_return_size_limit%&). If this option is false, only the
13510 message header is included. In the case of a non-SMTP message containing an
13511 error that is detected during reception, only those header lines preceding the
13512 point at which the error was detected are returned.
13513 .cindex "bounce message" "including original"
13515 .option bounce_return_message main boolean true
13516 If this option is set false, none of the original message is included in
13517 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13518 &%bounce_return_body%&.
13521 .option bounce_return_size_limit main integer 100K
13522 .cindex "size" "of bounce, limit"
13523 .cindex "bounce message" "size limit"
13524 .cindex "limit" "bounce message size"
13525 This option sets a limit in bytes on the size of messages that are returned to
13526 senders as part of bounce messages when &%bounce_return_message%& is true. The
13527 limit should be less than the value of the global &%message_size_limit%& and of
13528 any &%message_size_limit%& settings on transports, to allow for the bounce text
13529 that Exim generates. If this option is set to zero there is no limit.
13531 When the body of any message that is to be included in a bounce message is
13532 greater than the limit, it is truncated, and a comment pointing this out is
13533 added at the top. The actual cutoff may be greater than the value given, owing
13534 to the use of buffering for transferring the message in chunks (typically 8K in
13535 size). The idea is to save bandwidth on those undeliverable 15-megabyte
13538 .option bounce_sender_authentication main string unset
13539 .cindex "bounce message" "sender authentication"
13540 .cindex "authentication" "bounce message"
13541 .cindex "AUTH" "on bounce message"
13542 This option provides an authenticated sender address that is sent with any
13543 bounce messages generated by Exim that are sent over an authenticated SMTP
13544 connection. A typical setting might be:
13546 bounce_sender_authentication = mailer-daemon@my.domain.example
13548 which would cause bounce messages to be sent using the SMTP command:
13550 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
13552 The value of &%bounce_sender_authentication%& must always be a complete email
13555 .option callout_domain_negative_expire main time 3h
13556 .cindex "caching" "callout timeouts"
13557 .cindex "callout" "caching timeouts"
13558 This option specifies the expiry time for negative callout cache data for a
13559 domain. See section &<<SECTcallver>>& for details of callout verification, and
13560 section &<<SECTcallvercache>>& for details of the caching.
13563 .option callout_domain_positive_expire main time 7d
13564 This option specifies the expiry time for positive callout cache data for a
13565 domain. See section &<<SECTcallver>>& for details of callout verification, and
13566 section &<<SECTcallvercache>>& for details of the caching.
13569 .option callout_negative_expire main time 2h
13570 This option specifies the expiry time for negative callout cache data for an
13571 address. See section &<<SECTcallver>>& for details of callout verification, and
13572 section &<<SECTcallvercache>>& for details of the caching.
13575 .option callout_positive_expire main time 24h
13576 This option specifies the expiry time for positive callout cache data for an
13577 address. See section &<<SECTcallver>>& for details of callout verification, and
13578 section &<<SECTcallvercache>>& for details of the caching.
13581 .option callout_random_local_part main string&!! "see below"
13582 This option defines the &"random"& local part that can be used as part of
13583 callout verification. The default value is
13585 $primary_hostname-$tod_epoch-testing
13587 See section &<<CALLaddparcall>>& for details of how this value is used.
13590 .option check_log_inodes main integer 0
13591 See &%check_spool_space%& below.
13594 .option check_log_space main integer 0
13595 See &%check_spool_space%& below.
13597 .oindex "&%check_rfc2047_length%&"
13598 .cindex "RFC 2047" "disabling length check"
13599 .option check_rfc2047_length main boolean true
13600 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
13601 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
13602 word; strings to be encoded that exceed this length are supposed to use
13603 multiple encoded words. By default, Exim does not recognize encoded words that
13604 exceed the maximum length. However, it seems that some software, in violation
13605 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
13606 set false, Exim recognizes encoded words of any length.
13609 .option check_spool_inodes main integer 0
13610 See &%check_spool_space%& below.
13613 .option check_spool_space main integer 0
13614 .cindex "checking disk space"
13615 .cindex "disk space, checking"
13616 .cindex "spool directory" "checking space"
13617 The four &%check_...%& options allow for checking of disk resources before a
13618 message is accepted.
13620 .vindex "&$log_inodes$&"
13621 .vindex "&$log_space$&"
13622 .vindex "&$spool_inodes$&"
13623 .vindex "&$spool_space$&"
13624 When any of these options are set, they apply to all incoming messages. If you
13625 want to apply different checks to different kinds of message, you can do so by
13626 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
13627 &$spool_space$& in an ACL with appropriate additional conditions.
13630 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13631 either value is greater than zero, for example:
13633 check_spool_space = 10M
13634 check_spool_inodes = 100
13636 The spool partition is the one that contains the directory defined by
13637 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13640 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13641 files are written if either is greater than zero. These should be set only if
13642 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13644 If there is less space or fewer inodes than requested, Exim refuses to accept
13645 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13646 error response to the MAIL command. If ESMTP is in use and there was a
13647 SIZE parameter on the MAIL command, its value is added to the
13648 &%check_spool_space%& value, and the check is performed even if
13649 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13651 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13652 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13654 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13655 failure a message is written to stderr and Exim exits with a non-zero code, as
13656 it obviously cannot send an error message of any kind.
13658 .option daemon_smtp_ports main string &`smtp`&
13659 .cindex "port" "for daemon"
13660 .cindex "TCP/IP" "setting listening ports"
13661 This option specifies one or more default SMTP ports on which the Exim daemon
13662 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13663 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13665 .option daemon_startup_retries main integer 9
13666 .cindex "daemon startup, retrying"
13667 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13668 the daemon at startup when it cannot immediately bind a listening socket
13669 (typically because the socket is already in use): &%daemon_startup_retries%&
13670 defines the number of retries after the first failure, and
13671 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13673 .option daemon_startup_sleep main time 30s
13674 See &%daemon_startup_retries%&.
13676 .option delay_warning main "time list" 24h
13677 .cindex "warning of delay"
13678 .cindex "delay warning, specifying"
13679 When a message is delayed, Exim sends a warning message to the sender at
13680 intervals specified by this option. The data is a colon-separated list of times
13681 after which to send warning messages. If the value of the option is an empty
13682 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13683 message has been on the queue for longer than the last time, the last interval
13684 between the times is used to compute subsequent warning times. For example,
13687 delay_warning = 4h:8h:24h
13689 the first message is sent after 4 hours, the second after 8 hours, and
13690 the third one after 24 hours. After that, messages are sent every 16 hours,
13691 because that is the interval between the last two times on the list. If you set
13692 just one time, it specifies the repeat interval. For example, with:
13696 messages are repeated every six hours. To stop warnings after a given time, set
13697 a very large time at the end of the list. For example:
13699 delay_warning = 2h:12h:99d
13701 Note that the option is only evaluated at the time a delivery attempt fails,
13702 which depends on retry and queue-runner configuration.
13703 Typically retries will be configured more frequently than warning messages.
13705 .option delay_warning_condition main string&!! "see below"
13706 .vindex "&$domain$&"
13707 The string is expanded at the time a warning message might be sent. If all the
13708 deferred addresses have the same domain, it is set in &$domain$& during the
13709 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13710 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13711 &"false"& (the comparison being done caselessly) then the warning message is
13712 not sent. The default is:
13714 delay_warning_condition = ${if or {\
13715 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13716 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13717 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13720 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13721 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13722 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13723 &"auto-replied"& in an &'Auto-Submitted:'& header.
13725 .option deliver_drop_privilege main boolean false
13726 .cindex "unprivileged delivery"
13727 .cindex "delivery" "unprivileged"
13728 If this option is set true, Exim drops its root privilege at the start of a
13729 delivery process, and runs as the Exim user throughout. This severely restricts
13730 the kinds of local delivery that are possible, but is viable in certain types
13731 of configuration. There is a discussion about the use of root privilege in
13732 chapter &<<CHAPsecurity>>&.
13734 .option deliver_queue_load_max main fixed-point unset
13735 .cindex "load average"
13736 .cindex "queue runner" "abandoning"
13737 When this option is set, a queue run is abandoned if the system load average
13738 becomes greater than the value of the option. The option has no effect on
13739 ancient operating systems on which Exim cannot determine the load average.
13740 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13743 .option delivery_date_remove main boolean true
13744 .cindex "&'Delivery-date:'& header line"
13745 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13746 message when it is delivered, in exactly the same way as &'Return-path:'& is
13747 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13748 should not be present in incoming messages, and this option causes them to be
13749 removed at the time the message is received, to avoid any problems that might
13750 occur when a delivered message is subsequently sent on to some other recipient.
13752 .option disable_fsync main boolean false
13753 .cindex "&[fsync()]&, disabling"
13754 This option is available only if Exim was built with the compile-time option
13755 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13756 a runtime configuration generates an &"unknown option"& error. You should not
13757 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13758 really, really, really understand what you are doing. &'No pre-compiled
13759 distributions of Exim should ever make this option available.'&
13761 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13762 updated files' data to be written to disc before continuing. Unexpected events
13763 such as crashes and power outages may cause data to be lost or scrambled.
13764 Here be Dragons. &*Beware.*&
13767 .option disable_ipv6 main boolean false
13768 .cindex "IPv6" "disabling"
13769 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13770 activities take place. AAAA records are never looked up, and any IPv6 addresses
13771 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13772 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13773 to handle IPv6 literal addresses.
13776 .option dns_again_means_nonexist main "domain list&!!" unset
13777 .cindex "DNS" "&""try again""& response; overriding"
13778 DNS lookups give a &"try again"& response for the DNS errors
13779 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13780 keep trying to deliver a message, or to give repeated temporary errors to
13781 incoming mail. Sometimes the effect is caused by a badly set up name server and
13782 may persist for a long time. If a domain which exhibits this problem matches
13783 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13784 This option should be used with care. You can make it apply to reverse lookups
13785 by a setting such as this:
13787 dns_again_means_nonexist = *.in-addr.arpa
13789 This option applies to all DNS lookups that Exim does. It also applies when the
13790 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13791 since these are most likely to be caused by DNS lookup problems. The
13792 &(dnslookup)& router has some options of its own for controlling what happens
13793 when lookups for MX or SRV records give temporary errors. These more specific
13794 options are applied after this global option.
13796 .option dns_check_names_pattern main string "see below"
13797 .cindex "DNS" "pre-check of name syntax"
13798 When this option is set to a non-empty string, it causes Exim to check domain
13799 names for characters that are not allowed in host names before handing them to
13800 the DNS resolver, because some resolvers give temporary errors for names that
13801 contain unusual characters. If a domain name contains any unwanted characters,
13802 a &"not found"& result is forced, and the resolver is not called. The check is
13803 done by matching the domain name against a regular expression, which is the
13804 value of this option. The default pattern is
13806 dns_check_names_pattern = \
13807 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13809 which permits only letters, digits, slashes, and hyphens in components, but
13810 they must start and end with a letter or digit. Slashes are not, in fact,
13811 permitted in host names, but they are found in certain NS records (which can be
13812 accessed in Exim by using a &%dnsdb%& lookup). If you set
13813 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13816 .option dns_csa_search_limit main integer 5
13817 This option controls the depth of parental searching for CSA SRV records in the
13818 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13820 .option dns_csa_use_reverse main boolean true
13821 This option controls whether or not an IP address, given as a CSA domain, is
13822 reversed and looked up in the reverse DNS, as described in more detail in
13823 section &<<SECTverifyCSA>>&.
13826 .option dns_dnssec_ok main integer -1
13827 .cindex "DNS" "resolver options"
13828 .cindex "DNS" "DNSSEC"
13829 If this option is set to a non-negative number then Exim will initialise the
13830 DNS resolver library to either use or not use DNSSEC, overriding the system
13831 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
13833 If the resolver library does not support DNSSEC then this option has no effect.
13836 .option dns_ipv4_lookup main "domain list&!!" unset
13837 .cindex "IPv6" "DNS lookup for AAAA records"
13838 .cindex "DNS" "IPv6 lookup for AAAA records"
13839 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13840 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13841 (A records) when trying to find IP addresses for hosts, unless the host's
13842 domain matches this list.
13844 This is a fudge to help with name servers that give big delays or otherwise do
13845 not work for the AAAA record type. In due course, when the world's name
13846 servers have all been upgraded, there should be no need for this option.
13849 .option dns_retrans main time 0s
13850 .cindex "DNS" "resolver options"
13851 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13852 retransmission and retry parameters for DNS lookups. Values of zero (the
13853 defaults) leave the system default settings unchanged. The first value is the
13854 time between retries, and the second is the number of retries. It isn't
13855 totally clear exactly how these settings affect the total time a DNS lookup may
13856 take. I haven't found any documentation about timeouts on DNS lookups; these
13857 parameter values are available in the external resolver interface structure,
13858 but nowhere does it seem to describe how they are used or what you might want
13862 .option dns_retry main integer 0
13863 See &%dns_retrans%& above.
13866 .option dns_use_edns0 main integer -1
13867 .cindex "DNS" "resolver options"
13868 .cindex "DNS" "EDNS0"
13869 If this option is set to a non-negative number then Exim will initialise the
13870 DNS resolver library to either use or not use EDNS0 extensions, overriding
13871 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
13874 If the resolver library does not support EDNS0 then this option has no effect.
13877 .option drop_cr main boolean false
13878 This is an obsolete option that is now a no-op. It used to affect the way Exim
13879 handled CR and LF characters in incoming messages. What happens now is
13880 described in section &<<SECTlineendings>>&.
13882 .option dsn_from main "string&!!" "see below"
13883 .cindex "&'From:'& header line" "in bounces"
13884 .cindex "bounce messages" "&'From:'& line, specifying"
13885 This option can be used to vary the contents of &'From:'& header lines in
13886 bounces and other automatically generated messages (&"Delivery Status
13887 Notifications"& &-- hence the name of the option). The default setting is:
13889 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13891 The value is expanded every time it is needed. If the expansion fails, a
13892 panic is logged, and the default value is used.
13894 .option envelope_to_remove main boolean true
13895 .cindex "&'Envelope-to:'& header line"
13896 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13897 message when it is delivered, in exactly the same way as &'Return-path:'& is
13898 handled. &'Envelope-to:'& records the original recipient address from the
13899 messages's envelope that caused the delivery to happen. Such headers should not
13900 be present in incoming messages, and this option causes them to be removed at
13901 the time the message is received, to avoid any problems that might occur when a
13902 delivered message is subsequently sent on to some other recipient.
13905 .option errors_copy main "string list&!!" unset
13906 .cindex "bounce message" "copy to other address"
13907 .cindex "copy of bounce message"
13908 Setting this option causes Exim to send bcc copies of bounce messages that it
13909 generates to other addresses. &*Note*&: This does not apply to bounce messages
13910 coming from elsewhere. The value of the option is a colon-separated list of
13911 items. Each item consists of a pattern, terminated by white space, followed by
13912 a comma-separated list of email addresses. If a pattern contains spaces, it
13913 must be enclosed in double quotes.
13915 Each pattern is processed in the same way as a single item in an address list
13916 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13917 the bounce message, the message is copied to the addresses on the list. The
13918 items are scanned in order, and once a matching one is found, no further items
13919 are examined. For example:
13921 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13922 rqps@mydomain hostmaster@mydomain.example,\
13923 postmaster@mydomain.example
13925 .vindex "&$domain$&"
13926 .vindex "&$local_part$&"
13927 The address list is expanded before use. The expansion variables &$local_part$&
13928 and &$domain$& are set from the original recipient of the error message, and if
13929 there was any wildcard matching in the pattern, the expansion
13930 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13931 variables &$0$&, &$1$&, etc. are set in the normal way.
13934 .option errors_reply_to main string unset
13935 .cindex "bounce message" "&'Reply-to:'& in"
13936 By default, Exim's bounce and delivery warning messages contain the header line
13938 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13940 .oindex &%quota_warn_message%&
13941 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13942 A warning message that is generated by the &%quota_warn_message%& option in an
13943 &(appendfile)& transport may contain its own &'From:'& header line that
13944 overrides the default.
13946 Experience shows that people reply to bounce messages. If the
13947 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13948 and warning messages. For example:
13950 errors_reply_to = postmaster@my.domain.example
13952 The value of the option is not expanded. It must specify a valid RFC 2822
13953 address. However, if a warning message that is generated by the
13954 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13955 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13959 .option exim_group main string "compile-time configured"
13960 .cindex "gid (group id)" "Exim's own"
13961 .cindex "Exim group"
13962 This option changes the gid under which Exim runs when it gives up root
13963 privilege. The default value is compiled into the binary. The value of this
13964 option is used only when &%exim_user%& is also set. Unless it consists entirely
13965 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
13966 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
13970 .option exim_path main string "see below"
13971 .cindex "Exim binary, path name"
13972 This option specifies the path name of the Exim binary, which is used when Exim
13973 needs to re-exec itself. The default is set up to point to the file &'exim'& in
13974 the directory configured at compile time by the BIN_DIRECTORY setting. It
13975 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
13977 &*Warning*&: Do not use a macro to define the value of this option, because
13978 you will break those Exim utilities that scan the configuration file to find
13979 where the binary is. (They then use the &%-bP%& option to extract option
13980 settings such as the value of &%spool_directory%&.)
13983 .option exim_user main string "compile-time configured"
13984 .cindex "uid (user id)" "Exim's own"
13985 .cindex "Exim user"
13986 This option changes the uid under which Exim runs when it gives up root
13987 privilege. The default value is compiled into the binary. Ownership of the run
13988 time configuration file and the use of the &%-C%& and &%-D%& command line
13989 options is checked against the values in the binary, not what is set here.
13991 Unless it consists entirely of digits, the string is looked up using
13992 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
13993 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
13994 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
13997 .option extra_local_interfaces main "string list" unset
13998 This option defines network interfaces that are to be considered local when
13999 routing, but which are not used for listening by the daemon. See section
14000 &<<SECTreclocipadd>>& for details.
14003 . Allow this long option name to split; give it unsplit as a fifth argument
14004 . for the automatic .oindex that is generated by .option.
14006 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
14007 extract_addresses_remove_arguments
14009 .cindex "command line" "addresses with &%-t%&"
14010 .cindex "Sendmail compatibility" "&%-t%& option"
14011 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14012 are present on the command line when the &%-t%& option is used to build an
14013 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14014 line addresses are removed from the recipients list. This is also how Smail
14015 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14016 command line addresses are added to those obtained from the header lines. When
14017 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14018 argument headers. If it is set false, Exim adds rather than removes argument
14022 .option finduser_retries main integer 0
14023 .cindex "NIS, retrying user lookups"
14024 On systems running NIS or other schemes in which user and group information is
14025 distributed from a remote system, there can be times when &[getpwnam()]& and
14026 related functions fail, even when given valid data, because things time out.
14027 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14028 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14029 many extra times to find a user or a group, waiting for one second between
14032 .cindex "&_/etc/passwd_&" "multiple reading of"
14033 You should not set this option greater than zero if your user information is in
14034 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14035 search the file multiple times for non-existent users, and also cause delay.
14039 .option freeze_tell main "string list, comma separated" unset
14040 .cindex "freezing messages" "sending a message when freezing"
14041 On encountering certain errors, or when configured to do so in a system filter,
14042 ACL, or special router, Exim freezes a message. This means that no further
14043 delivery attempts take place until an administrator thaws the message, or the
14044 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14045 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14046 warning message whenever it freezes something, unless the message it is
14047 freezing is a locally-generated bounce message. (Without this exception there
14048 is the possibility of looping.) The warning message is sent to the addresses
14049 supplied as the comma-separated value of this option. If several of the
14050 message's addresses cause freezing, only a single message is sent. If the
14051 freezing was automatic, the reason(s) for freezing can be found in the message
14052 log. If you configure freezing in a filter or ACL, you must arrange for any
14053 logging that you require.
14056 .option gecos_name main string&!! unset
14058 .cindex "&""gecos""& field, parsing"
14059 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14060 password file to hold other information in addition to users' real names. Exim
14061 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14062 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14063 of the field are used unchanged, except that, if an ampersand is encountered,
14064 it is replaced by the user's login name with the first character forced to
14065 upper case, since this is a convention that is observed on many systems.
14067 When these options are set, &%gecos_pattern%& is treated as a regular
14068 expression that is to be applied to the field (again with && replaced by the
14069 login name), and if it matches, &%gecos_name%& is expanded and used as the
14072 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14073 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14074 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14075 name terminates at the first comma, the following can be used:
14077 gecos_pattern = ([^,]*)
14081 .option gecos_pattern main string unset
14082 See &%gecos_name%& above.
14085 .option gnutls_compat_mode main boolean unset
14086 This option controls whether GnuTLS is used in compatibility mode in an Exim
14087 server. This reduces security slightly, but improves interworking with older
14088 implementations of TLS.
14091 option gnutls_allow_auto_pkcs11 main boolean unset
14092 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14093 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14096 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14101 .option headers_charset main string "see below"
14102 This option sets a default character set for translating from encoded MIME
14103 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14104 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14105 ultimate default is ISO-8859-1. For more details see the description of header
14106 insertions in section &<<SECTexpansionitems>>&.
14110 .option header_maxsize main integer "see below"
14111 .cindex "header section" "maximum size of"
14112 .cindex "limit" "size of message header section"
14113 This option controls the overall maximum size of a message's header
14114 section. The default is the value of HEADER_MAXSIZE in
14115 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14116 sections are rejected.
14119 .option header_line_maxsize main integer 0
14120 .cindex "header lines" "maximum size of"
14121 .cindex "limit" "size of one header line"
14122 This option limits the length of any individual header line in a message, after
14123 all the continuations have been joined together. Messages with individual
14124 header lines that are longer than the limit are rejected. The default value of
14125 zero means &"no limit"&.
14130 .option helo_accept_junk_hosts main "host list&!!" unset
14131 .cindex "HELO" "accepting junk data"
14132 .cindex "EHLO" "accepting junk data"
14133 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14134 mail, and gives an error response for invalid data. Unfortunately, there are
14135 some SMTP clients that send syntactic junk. They can be accommodated by setting
14136 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14137 if you want to do semantic checking.
14138 See also &%helo_allow_chars%& for a way of extending the permitted character
14142 .option helo_allow_chars main string unset
14143 .cindex "HELO" "underscores in"
14144 .cindex "EHLO" "underscores in"
14145 .cindex "underscore in EHLO/HELO"
14146 This option can be set to a string of rogue characters that are permitted in
14147 all EHLO and HELO names in addition to the standard letters, digits,
14148 hyphens, and dots. If you really must allow underscores, you can set
14150 helo_allow_chars = _
14152 Note that the value is one string, not a list.
14155 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14156 .cindex "HELO" "forcing reverse lookup"
14157 .cindex "EHLO" "forcing reverse lookup"
14158 If the domain given by a client in a HELO or EHLO command matches this
14159 list, a reverse lookup is done in order to establish the host's true name. The
14160 default forces a lookup if the client host gives the server's name or any of
14161 its IP addresses (in brackets), something that broken clients have been seen to
14165 .option helo_try_verify_hosts main "host list&!!" unset
14166 .cindex "HELO verifying" "optional"
14167 .cindex "EHLO" "verifying, optional"
14168 By default, Exim just checks the syntax of HELO and EHLO commands (see
14169 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14170 to do more extensive checking of the data supplied by these commands. The ACL
14171 condition &`verify = helo`& is provided to make this possible.
14172 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14173 to force the check to occur. From release 4.53 onwards, this is no longer
14174 necessary. If the check has not been done before &`verify = helo`& is
14175 encountered, it is done at that time. Consequently, this option is obsolete.
14176 Its specification is retained here for backwards compatibility.
14178 When an EHLO or HELO command is received, if the calling host matches
14179 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14180 EHLO command either:
14183 is an IP literal matching the calling address of the host, or
14185 .cindex "DNS" "reverse lookup"
14186 .cindex "reverse DNS lookup"
14187 matches the host name that Exim obtains by doing a reverse lookup of the
14188 calling host address, or
14190 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
14191 available) yields the calling host address.
14194 However, the EHLO or HELO command is not rejected if any of the checks
14195 fail. Processing continues, but the result of the check is remembered, and can
14196 be detected later in an ACL by the &`verify = helo`& condition.
14198 .option helo_verify_hosts main "host list&!!" unset
14199 .cindex "HELO verifying" "mandatory"
14200 .cindex "EHLO" "verifying, mandatory"
14201 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14202 backwards compatibility. For hosts that match this option, Exim checks the host
14203 name given in the HELO or EHLO in the same way as for
14204 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14205 rejected with a 550 error, and entries are written to the main and reject logs.
14206 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14209 .option hold_domains main "domain list&!!" unset
14210 .cindex "domain" "delaying delivery"
14211 .cindex "delivery" "delaying certain domains"
14212 This option allows mail for particular domains to be held on the queue
14213 manually. The option is overridden if a message delivery is forced with the
14214 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14215 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14216 item in &%hold_domains%&, no routing or delivery for that address is done, and
14217 it is deferred every time the message is looked at.
14219 This option is intended as a temporary operational measure for delaying the
14220 delivery of mail while some problem is being sorted out, or some new
14221 configuration tested. If you just want to delay the processing of some
14222 domains until a queue run occurs, you should use &%queue_domains%& or
14223 &%queue_smtp_domains%&, not &%hold_domains%&.
14225 A setting of &%hold_domains%& does not override Exim's code for removing
14226 messages from the queue if they have been there longer than the longest retry
14227 time in any retry rule. If you want to hold messages for longer than the normal
14228 retry times, insert a dummy retry rule with a long retry time.
14231 .option host_lookup main "host list&!!" unset
14232 .cindex "host name" "lookup, forcing"
14233 Exim does not look up the name of a calling host from its IP address unless it
14234 is required to compare against some host list, or the host matches
14235 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14236 option (which normally contains IP addresses rather than host names). The
14237 default configuration file contains
14241 which causes a lookup to happen for all hosts. If the expense of these lookups
14242 is felt to be too great, the setting can be changed or removed.
14244 After a successful reverse lookup, Exim does a forward lookup on the name it
14245 has obtained, to verify that it yields the IP address that it started with. If
14246 this check fails, Exim behaves as if the name lookup failed.
14248 .vindex "&$host_lookup_failed$&"
14249 .vindex "&$sender_host_name$&"
14250 After any kind of failure, the host name (in &$sender_host_name$&) remains
14251 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14252 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14253 &`verify = reverse_host_lookup`& in ACLs.
14256 .option host_lookup_order main "string list" &`bydns:byaddr`&
14257 This option specifies the order of different lookup methods when Exim is trying
14258 to find a host name from an IP address. The default is to do a DNS lookup
14259 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14260 if that fails. You can change the order of these lookups, or omit one entirely,
14263 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14264 multiple PTR records in the DNS and the IP address is not listed in
14265 &_/etc/hosts_&. Different operating systems give different results in this
14266 case. That is why the default tries a DNS lookup first.
14270 .option host_reject_connection main "host list&!!" unset
14271 .cindex "host" "rejecting connections from"
14272 If this option is set, incoming SMTP calls from the hosts listed are rejected
14273 as soon as the connection is made.
14274 This option is obsolete, and retained only for backward compatibility, because
14275 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14276 connections immediately.
14278 The ability to give an immediate rejection (either by this option or using an
14279 ACL) is provided for use in unusual cases. Many hosts will just try again,
14280 sometimes without much delay. Normally, it is better to use an ACL to reject
14281 incoming messages at a later stage, such as after RCPT commands. See
14282 chapter &<<CHAPACL>>&.
14285 .option hosts_connection_nolog main "host list&!!" unset
14286 .cindex "host" "not logging connections from"
14287 This option defines a list of hosts for which connection logging does not
14288 happen, even though the &%smtp_connection%& log selector is set. For example,
14289 you might want not to log SMTP connections from local processes, or from
14290 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14291 the daemon; you should therefore strive to restrict its value to a short inline
14292 list of IP addresses and networks. To disable logging SMTP connections from
14293 local processes, you must create a host list with an empty item. For example:
14295 hosts_connection_nolog = :
14297 If the &%smtp_connection%& log selector is not set, this option has no effect.
14301 .option hosts_treat_as_local main "domain list&!!" unset
14302 .cindex "local host" "domains treated as"
14303 .cindex "host" "treated as local"
14304 If this option is set, any host names that match the domain list are treated as
14305 if they were the local host when Exim is scanning host lists obtained from MX
14307 or other sources. Note that the value of this option is a domain list, not a
14308 host list, because it is always used to check host names, not IP addresses.
14310 This option also applies when Exim is matching the special items
14311 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14312 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14313 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14314 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14315 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14316 interfaces and recognizing the local host.
14319 .option ibase_servers main "string list" unset
14320 .cindex "InterBase" "server list"
14321 This option provides a list of InterBase servers and associated connection data,
14322 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14323 The option is available only if Exim has been built with InterBase support.
14327 .option ignore_bounce_errors_after main time 10w
14328 .cindex "bounce message" "discarding"
14329 .cindex "discarding bounce message"
14330 This option affects the processing of bounce messages that cannot be delivered,
14331 that is, those that suffer a permanent delivery failure. (Bounce messages that
14332 suffer temporary delivery failures are of course retried in the usual way.)
14334 After a permanent delivery failure, bounce messages are frozen,
14335 because there is no sender to whom they can be returned. When a frozen bounce
14336 message has been on the queue for more than the given time, it is unfrozen at
14337 the next queue run, and a further delivery is attempted. If delivery fails
14338 again, the bounce message is discarded. This makes it possible to keep failed
14339 bounce messages around for a shorter time than the normal maximum retry time
14340 for frozen messages. For example,
14342 ignore_bounce_errors_after = 12h
14344 retries failed bounce message deliveries after 12 hours, discarding any further
14345 failures. If the value of this option is set to a zero time period, bounce
14346 failures are discarded immediately. Setting a very long time (as in the default
14347 value) has the effect of disabling this option. For ways of automatically
14348 dealing with other kinds of frozen message, see &%auto_thaw%& and
14349 &%timeout_frozen_after%&.
14352 .option ignore_fromline_hosts main "host list&!!" unset
14353 .cindex "&""From""& line"
14354 .cindex "UUCP" "&""From""& line"
14355 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14356 the headers of a message. By default this is treated as the start of the
14357 message's body, which means that any following headers are not recognized as
14358 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14359 match those hosts that insist on sending it. If the sender is actually a local
14360 process rather than a remote host, and is using &%-bs%& to inject the messages,
14361 &%ignore_fromline_local%& must be set to achieve this effect.
14364 .option ignore_fromline_local main boolean false
14365 See &%ignore_fromline_hosts%& above.
14368 .option keep_malformed main time 4d
14369 This option specifies the length of time to keep messages whose spool files
14370 have been corrupted in some way. This should, of course, never happen. At the
14371 next attempt to deliver such a message, it gets removed. The incident is
14375 .option ldap_ca_cert_dir main string unset
14376 .cindex "LDAP", "TLS CA certificate directory"
14377 This option indicates which directory contains CA certificates for verifying
14378 a TLS certificate presented by an LDAP server.
14379 While Exim does not provide a default value, your SSL library may.
14380 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14381 and constrained to be a directory.
14384 .option ldap_ca_cert_file main string unset
14385 .cindex "LDAP", "TLS CA certificate file"
14386 This option indicates which file contains CA certificates for verifying
14387 a TLS certificate presented by an LDAP server.
14388 While Exim does not provide a default value, your SSL library may.
14389 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14390 and constrained to be a file.
14393 .option ldap_cert_file main string unset
14394 .cindex "LDAP" "TLS client certificate file"
14395 This option indicates which file contains an TLS client certificate which
14396 Exim should present to the LDAP server during TLS negotiation.
14397 Should be used together with &%ldap_cert_key%&.
14400 .option ldap_cert_key main string unset
14401 .cindex "LDAP" "TLS client key file"
14402 This option indicates which file contains the secret/private key to use
14403 to prove identity to the LDAP server during TLS negotiation.
14404 Should be used together with &%ldap_cert_file%&, which contains the
14405 identity to be proven.
14408 .option ldap_cipher_suite main string unset
14409 .cindex "LDAP" "TLS cipher suite"
14410 This controls the TLS cipher-suite negotiation during TLS negotiation with
14411 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14412 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14415 .option ldap_default_servers main "string list" unset
14416 .cindex "LDAP" "default servers"
14417 This option provides a list of LDAP servers which are tried in turn when an
14418 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14419 details of LDAP queries. This option is available only when Exim has been built
14423 .option ldap_require_cert main string unset.
14424 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14425 This should be one of the values "hard", "demand", "allow", "try" or "never".
14426 A value other than one of these is interpreted as "never".
14427 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14428 Although Exim does not set a default, the LDAP library probably defaults
14432 .option ldap_start_tls main boolean false
14433 .cindex "LDAP" "whether or not to negotiate TLS"
14434 If set, Exim will attempt to negotiate TLS with the LDAP server when
14435 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14436 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14438 In the event of failure to negotiate TLS, the action taken is controlled
14439 by &%ldap_require_cert%&.
14442 .option ldap_version main integer unset
14443 .cindex "LDAP" "protocol version, forcing"
14444 This option can be used to force Exim to set a specific protocol version for
14445 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14446 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14447 the LDAP headers; otherwise it is 2. This option is available only when Exim
14448 has been built with LDAP support.
14452 .option local_from_check main boolean true
14453 .cindex "&'Sender:'& header line" "disabling addition of"
14454 .cindex "&'From:'& header line" "disabling checking of"
14455 When a message is submitted locally (that is, not over a TCP/IP connection) by
14456 an untrusted user, Exim removes any existing &'Sender:'& header line, and
14457 checks that the &'From:'& header line matches the login of the calling user and
14458 the domain specified by &%qualify_domain%&.
14460 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
14461 locally submitted message is automatically qualified by Exim, unless the
14462 &%-bnq%& command line option is used.
14464 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
14465 on the local part. If the &'From:'& header line does not match, Exim adds a
14466 &'Sender:'& header with an address constructed from the calling user's login
14467 and the default qualify domain.
14469 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
14470 and no &'Sender:'& header is ever added. If, in addition, you want to retain
14471 &'Sender:'& header lines supplied by untrusted users, you must also set
14472 &%local_sender_retain%& to be true.
14474 .cindex "envelope sender"
14475 These options affect only the header lines in the message. The envelope sender
14476 is still forced to be the login id at the qualify domain unless
14477 &%untrusted_set_sender%& permits the user to supply an envelope sender.
14479 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
14480 request similar header line checking. See section &<<SECTthesenhea>>&, which
14481 has more details about &'Sender:'& processing.
14486 .option local_from_prefix main string unset
14487 When Exim checks the &'From:'& header line of locally submitted messages for
14488 matching the login id (see &%local_from_check%& above), it can be configured to
14489 ignore certain prefixes and suffixes in the local part of the address. This is
14490 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
14491 appropriate lists, in the same form as the &%local_part_prefix%& and
14492 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
14495 local_from_prefix = *-
14497 is set, a &'From:'& line containing
14499 From: anything-user@your.domain.example
14501 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
14502 matches the actual sender address that is constructed from the login name and
14506 .option local_from_suffix main string unset
14507 See &%local_from_prefix%& above.
14510 .option local_interfaces main "string list" "see below"
14511 This option controls which network interfaces are used by the daemon for
14512 listening; they are also used to identify the local host when routing. Chapter
14513 &<<CHAPinterfaces>>& contains a full description of this option and the related
14514 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
14515 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
14516 &%local_interfaces%& is
14518 local_interfaces = 0.0.0.0
14520 when Exim is built without IPv6 support; otherwise it is
14522 local_interfaces = <; ::0 ; 0.0.0.0
14525 .option local_scan_timeout main time 5m
14526 .cindex "timeout" "for &[local_scan()]& function"
14527 .cindex "&[local_scan()]& function" "timeout"
14528 This timeout applies to the &[local_scan()]& function (see chapter
14529 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
14530 the incoming message is rejected with a temporary error if it is an SMTP
14531 message. For a non-SMTP message, the message is dropped and Exim ends with a
14532 non-zero code. The incident is logged on the main and reject logs.
14536 .option local_sender_retain main boolean false
14537 .cindex "&'Sender:'& header line" "retaining from local submission"
14538 When a message is submitted locally (that is, not over a TCP/IP connection) by
14539 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
14540 do not want this to happen, you must set &%local_sender_retain%&, and you must
14541 also set &%local_from_check%& to be false (Exim will complain if you do not).
14542 See also the ACL modifier &`control = suppress_local_fixups`&. Section
14543 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
14548 .option localhost_number main string&!! unset
14549 .cindex "host" "locally unique number for"
14550 .cindex "message ids" "with multiple hosts"
14551 .vindex "&$localhost_number$&"
14552 Exim's message ids are normally unique only within the local host. If
14553 uniqueness among a set of hosts is required, each host must set a different
14554 value for the &%localhost_number%& option. The string is expanded immediately
14555 after reading the configuration file (so that a number can be computed from the
14556 host name, for example) and the result of the expansion must be a number in the
14557 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
14558 systems). This is available in subsequent string expansions via the variable
14559 &$localhost_number$&. When &%localhost_number is set%&, the final two
14560 characters of the message id, instead of just being a fractional part of the
14561 time, are computed from the time and the local host number as described in
14562 section &<<SECTmessiden>>&.
14566 .option log_file_path main "string list&!!" "set at compile time"
14567 .cindex "log" "file path for"
14568 This option sets the path which is used to determine the names of Exim's log
14569 files, or indicates that logging is to be to syslog, or both. It is expanded
14570 when Exim is entered, so it can, for example, contain a reference to the host
14571 name. If no specific path is set for the log files at compile or run time, they
14572 are written in a sub-directory called &_log_& in Exim's spool directory.
14573 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
14574 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
14575 used. If this string is fixed at your installation (contains no expansion
14576 variables) it is recommended that you do not set this option in the
14577 configuration file, but instead supply the path using LOG_FILE_PATH in
14578 &_Local/Makefile_& so that it is available to Exim for logging errors detected
14579 early on &-- in particular, failure to read the configuration file.
14582 .option log_selector main string unset
14583 .cindex "log" "selectors"
14584 This option can be used to reduce or increase the number of things that Exim
14585 writes to its log files. Its argument is made up of names preceded by plus or
14586 minus characters. For example:
14588 log_selector = +arguments -retry_defer
14590 A list of possible names and what they control is given in the chapter on
14591 logging, in section &<<SECTlogselector>>&.
14594 .option log_timezone main boolean false
14595 .cindex "log" "timezone for entries"
14596 .vindex "&$tod_log$&"
14597 .vindex "&$tod_zone$&"
14598 By default, the timestamps on log lines are in local time without the
14599 timezone. This means that if your timezone changes twice a year, the timestamps
14600 in log lines are ambiguous for an hour when the clocks go back. One way of
14601 avoiding this problem is to set the timezone to UTC. An alternative is to set
14602 &%log_timezone%& true. This turns on the addition of the timezone offset to
14603 timestamps in log lines. Turning on this option can add quite a lot to the size
14604 of log files because each line is extended by 6 characters. Note that the
14605 &$tod_log$& variable contains the log timestamp without the zone, but there is
14606 another variable called &$tod_zone$& that contains just the timezone offset.
14609 .option lookup_open_max main integer 25
14610 .cindex "too many open files"
14611 .cindex "open files, too many"
14612 .cindex "file" "too many open"
14613 .cindex "lookup" "maximum open files"
14614 .cindex "limit" "open files for lookups"
14615 This option limits the number of simultaneously open files for single-key
14616 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
14617 Exim normally keeps these files open during routing, because often the same
14618 file is required several times. If the limit is reached, Exim closes the least
14619 recently used file. Note that if you are using the &'ndbm'& library, it
14620 actually opens two files for each logical DBM database, though it still counts
14621 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
14622 open files"& errors with NDBM, you need to reduce the value of
14623 &%lookup_open_max%&.
14626 .option max_username_length main integer 0
14627 .cindex "length of login name"
14628 .cindex "user name" "maximum length"
14629 .cindex "limit" "user name length"
14630 Some operating systems are broken in that they truncate long arguments to
14631 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
14632 this option is set greater than zero, any attempt to call &[getpwnam()]& with
14633 an argument that is longer behaves as if &[getpwnam()]& failed.
14636 .option message_body_newlines main bool false
14637 .cindex "message body" "newlines in variables"
14638 .cindex "newline" "in message body variables"
14639 .vindex "&$message_body$&"
14640 .vindex "&$message_body_end$&"
14641 By default, newlines in the message body are replaced by spaces when setting
14642 the &$message_body$& and &$message_body_end$& expansion variables. If this
14643 option is set true, this no longer happens.
14646 .option message_body_visible main integer 500
14647 .cindex "body of message" "visible size"
14648 .cindex "message body" "visible size"
14649 .vindex "&$message_body$&"
14650 .vindex "&$message_body_end$&"
14651 This option specifies how much of a message's body is to be included in the
14652 &$message_body$& and &$message_body_end$& expansion variables.
14655 .option message_id_header_domain main string&!! unset
14656 .cindex "&'Message-ID:'& header line"
14657 If this option is set, the string is expanded and used as the right hand side
14658 (domain) of the &'Message-ID:'& header that Exim creates if a
14659 locally-originated incoming message does not have one. &"Locally-originated"&
14660 means &"not received over TCP/IP."&
14661 Otherwise, the primary host name is used.
14662 Only letters, digits, dot and hyphen are accepted; any other characters are
14663 replaced by hyphens. If the expansion is forced to fail, or if the result is an
14664 empty string, the option is ignored.
14667 .option message_id_header_text main string&!! unset
14668 If this variable is set, the string is expanded and used to augment the text of
14669 the &'Message-id:'& header that Exim creates if a locally-originated incoming
14670 message does not have one. The text of this header is required by RFC 2822 to
14671 take the form of an address. By default, Exim uses its internal message id as
14672 the local part, and the primary host name as the domain. If this option is set,
14673 it is expanded, and provided the expansion is not forced to fail, and does not
14674 yield an empty string, the result is inserted into the header immediately
14675 before the @, separated from the internal message id by a dot. Any characters
14676 that are illegal in an address are automatically converted into hyphens. This
14677 means that variables such as &$tod_log$& can be used, because the spaces and
14678 colons will become hyphens.
14681 .option message_logs main boolean true
14682 .cindex "message logs" "disabling"
14683 .cindex "log" "message log; disabling"
14684 If this option is turned off, per-message log files are not created in the
14685 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
14686 Exim, by reducing the number of files involved in handling a message from a
14687 minimum of four (header spool file, body spool file, delivery journal, and
14688 per-message log) to three. The other major I/O activity is Exim's main log,
14689 which is not affected by this option.
14692 .option message_size_limit main string&!! 50M
14693 .cindex "message" "size limit"
14694 .cindex "limit" "message size"
14695 .cindex "size" "of message, limit"
14696 This option limits the maximum size of message that Exim will process. The
14697 value is expanded for each incoming connection so, for example, it can be made
14698 to depend on the IP address of the remote host for messages arriving via
14699 TCP/IP. After expansion, the value must be a sequence of decimal digits,
14700 optionally followed by K or M.
14702 &*Note*&: This limit cannot be made to depend on a message's sender or any
14703 other properties of an individual message, because it has to be advertised in
14704 the server's response to EHLO. String expansion failure causes a temporary
14705 error. A value of zero means no limit, but its use is not recommended. See also
14706 &%bounce_return_size_limit%&.
14708 Incoming SMTP messages are failed with a 552 error if the limit is
14709 exceeded; locally-generated messages either get a stderr message or a delivery
14710 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14711 an oversized message is logged in both the main and the reject logs. See also
14712 the generic transport option &%message_size_limit%&, which limits the size of
14713 message that an individual transport can process.
14715 If you use a virus-scanner and set this option to to a value larger than the
14716 maximum size that your virus-scanner is configured to support, you may get
14717 failures triggered by large mails. The right size to configure for the
14718 virus-scanner depends upon what data is passed and the options in use but it's
14719 probably safest to just set it to a little larger than this value. Eg, with a
14720 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14721 some problems may result.
14723 A value of 0 will disable size limit checking; Exim will still advertise the
14724 SIZE extension in an EHLO response, but without a limit, so as to permit
14725 SMTP clients to still indicate the message size along with the MAIL verb.
14728 .option move_frozen_messages main boolean false
14729 .cindex "frozen messages" "moving"
14730 This option, which is available only if Exim has been built with the setting
14732 SUPPORT_MOVE_FROZEN_MESSAGES=yes
14734 in &_Local/Makefile_&, causes frozen messages and their message logs to be
14735 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
14736 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
14737 standard utilities for handling such moved messages, and they do not show up in
14738 lists generated by &%-bp%& or by the Exim monitor.
14741 .option mua_wrapper main boolean false
14742 Setting this option true causes Exim to run in a very restrictive mode in which
14743 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
14744 contains a full description of this facility.
14748 .option mysql_servers main "string list" unset
14749 .cindex "MySQL" "server list"
14750 This option provides a list of MySQL servers and associated connection data, to
14751 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
14752 option is available only if Exim has been built with MySQL support.
14755 .option never_users main "string list&!!" unset
14756 This option is expanded just once, at the start of Exim's processing. Local
14757 message deliveries are normally run in processes that are setuid to the
14758 recipient, and remote deliveries are normally run under Exim's own uid and gid.
14759 It is usually desirable to prevent any deliveries from running as root, as a
14762 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
14763 list of users that must not be used for local deliveries. This list is fixed in
14764 the binary and cannot be overridden by the configuration file. By default, it
14765 contains just the single user name &"root"&. The &%never_users%& runtime option
14766 can be used to add more users to the fixed list.
14768 If a message is to be delivered as one of the users on the fixed list or the
14769 &%never_users%& list, an error occurs, and delivery is deferred. A common
14772 never_users = root:daemon:bin
14774 Including root is redundant if it is also on the fixed list, but it does no
14775 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
14779 .option openssl_options main "string list" "+no_sslv2"
14780 .cindex "OpenSSL "compatibility options"
14781 This option allows an administrator to adjust the SSL options applied
14782 by OpenSSL to connections. It is given as a space-separated list of items,
14783 each one to be +added or -subtracted from the current value.
14785 This option is only available if Exim is built against OpenSSL. The values
14786 available for this option vary according to the age of your OpenSSL install.
14787 The &"all"& value controls a subset of flags which are available, typically
14788 the bug workaround options. The &'SSL_CTX_set_options'& man page will
14789 list the values known on your system and Exim should support all the
14790 &"bug workaround"& options and many of the &"modifying"& options. The Exim
14791 names lose the leading &"SSL_OP_"& and are lower-cased.
14793 Note that adjusting the options can have severe impact upon the security of
14794 SSL as used by Exim. It is possible to disable safety checks and shoot
14795 yourself in the foot in various unpleasant ways. This option should not be
14796 adjusted lightly. An unrecognised item will be detected at startup, by
14797 invoking Exim with the &%-bV%& flag.
14799 Historical note: prior to release 4.80, Exim defaulted this value to
14800 "+dont_insert_empty_fragments", which may still be needed for compatibility
14801 with some clients, but which lowers security by increasing exposure to
14802 some now infamous attacks.
14806 # Make both old MS and old Eudora happy:
14807 openssl_options = -all +microsoft_big_sslv3_buffer \
14808 +dont_insert_empty_fragments
14811 Possible options may include:
14815 &`allow_unsafe_legacy_renegotiation`&
14817 &`cipher_server_preference`&
14819 &`dont_insert_empty_fragments`&
14823 &`legacy_server_connect`&
14825 &`microsoft_big_sslv3_buffer`&
14827 &`microsoft_sess_id_bug`&
14829 &`msie_sslv2_rsa_padding`&
14831 &`netscape_challenge_bug`&
14833 &`netscape_reuse_cipher_change_bug`&
14837 &`no_session_resumption_on_renegotiation`&
14851 &`safari_ecdhe_ecdsa_bug`&
14855 &`single_ecdh_use`&
14857 &`ssleay_080_client_dh_bug`&
14859 &`sslref2_reuse_cert_type_bug`&
14861 &`tls_block_padding_bug`&
14865 &`tls_rollback_bug`&
14868 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
14869 all clients connecting using the MacOS SecureTransport TLS facility prior
14870 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
14871 to negotiate TLS then this option value might help, provided that your OpenSSL
14872 release is new enough to contain this work-around. This may be a situation
14873 where you have to upgrade OpenSSL to get buggy clients working.
14876 .option oracle_servers main "string list" unset
14877 .cindex "Oracle" "server list"
14878 This option provides a list of Oracle servers and associated connection data,
14879 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
14880 The option is available only if Exim has been built with Oracle support.
14883 .option percent_hack_domains main "domain list&!!" unset
14884 .cindex "&""percent hack""&"
14885 .cindex "source routing" "in email address"
14886 .cindex "address" "source-routed"
14887 The &"percent hack"& is the convention whereby a local part containing a
14888 percent sign is re-interpreted as a new email address, with the percent
14889 replaced by @. This is sometimes called &"source routing"&, though that term is
14890 also applied to RFC 2822 addresses that begin with an @ character. If this
14891 option is set, Exim implements the percent facility for those domains listed,
14892 but no others. This happens before an incoming SMTP address is tested against
14895 &*Warning*&: The &"percent hack"& has often been abused by people who are
14896 trying to get round relaying restrictions. For this reason, it is best avoided
14897 if at all possible. Unfortunately, a number of less security-conscious MTAs
14898 implement it unconditionally. If you are running Exim on a gateway host, and
14899 routing mail through to internal MTAs without processing the local parts, it is
14900 a good idea to reject recipient addresses with percent characters in their
14901 local parts. Exim's default configuration does this.
14904 .option perl_at_start main boolean false
14905 This option is available only when Exim is built with an embedded Perl
14906 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14909 .option perl_startup main string unset
14910 This option is available only when Exim is built with an embedded Perl
14911 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14914 .option pgsql_servers main "string list" unset
14915 .cindex "PostgreSQL lookup type" "server list"
14916 This option provides a list of PostgreSQL servers and associated connection
14917 data, to be used in conjunction with &(pgsql)& lookups (see section
14918 &<<SECID72>>&). The option is available only if Exim has been built with
14919 PostgreSQL support.
14922 .option pid_file_path main string&!! "set at compile time"
14923 .cindex "daemon" "pid file path"
14924 .cindex "pid file, path for"
14925 This option sets the name of the file to which the Exim daemon writes its
14926 process id. The string is expanded, so it can contain, for example, references
14929 pid_file_path = /var/log/$primary_hostname/exim.pid
14931 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14933 The value set by the option can be overridden by the &%-oP%& command line
14934 option. A pid file is not written if a &"non-standard"& daemon is run by means
14935 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14938 .option pipelining_advertise_hosts main "host list&!!" *
14939 .cindex "PIPELINING" "suppressing advertising"
14940 This option can be used to suppress the advertisement of the SMTP
14941 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14942 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14943 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14944 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14945 that clients will use it; &"out of order"& commands that are &"expected"& do
14946 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14949 .option preserve_message_logs main boolean false
14950 .cindex "message logs" "preserving"
14951 If this option is set, message log files are not deleted when messages are
14952 completed. Instead, they are moved to a sub-directory of the spool directory
14953 called &_msglog.OLD_&, where they remain available for statistical or debugging
14954 purposes. This is a dangerous option to set on systems with any appreciable
14955 volume of mail. Use with care!
14958 .option primary_hostname main string "see below"
14959 .cindex "name" "of local host"
14960 .cindex "host" "name of local"
14961 .cindex "local host" "name of"
14962 .vindex "&$primary_hostname$&"
14963 This specifies the name of the current host. It is used in the default EHLO or
14964 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
14965 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
14966 The value is also used by default in some SMTP response messages from an Exim
14967 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
14969 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
14970 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
14971 contains only one component, Exim passes it to &[gethostbyname()]& (or
14972 &[getipnodebyname()]& when available) in order to obtain the fully qualified
14973 version. The variable &$primary_hostname$& contains the host name, whether set
14974 explicitly by this option, or defaulted.
14977 .option print_topbitchars main boolean false
14978 .cindex "printing characters"
14979 .cindex "8-bit characters"
14980 By default, Exim considers only those characters whose codes lie in the range
14981 32&--126 to be printing characters. In a number of circumstances (for example,
14982 when writing log entries) non-printing characters are converted into escape
14983 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
14984 is set, code values of 128 and above are also considered to be printing
14987 This option also affects the header syntax checks performed by the
14988 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
14989 the user's full name when constructing From: and Sender: addresses (as
14990 described in section &<<SECTconstr>>&). Setting this option can cause
14991 Exim to generate eight bit message headers that do not conform to the
14995 .option process_log_path main string unset
14996 .cindex "process log path"
14997 .cindex "log" "process log"
14998 .cindex "&'exiwhat'&"
14999 This option sets the name of the file to which an Exim process writes its
15000 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15001 utility script. If this option is unset, the file called &_exim-process.info_&
15002 in Exim's spool directory is used. The ability to specify the name explicitly
15003 can be useful in environments where two different Exims are running, using
15004 different spool directories.
15007 .option prod_requires_admin main boolean true
15011 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15012 admin user unless &%prod_requires_admin%& is set false. See also
15013 &%queue_list_requires_admin%&.
15016 .option qualify_domain main string "see below"
15017 .cindex "domain" "for qualifying addresses"
15018 .cindex "address" "qualification"
15019 This option specifies the domain name that is added to any envelope sender
15020 addresses that do not have a domain qualification. It also applies to
15021 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15022 are accepted by default only for locally-generated messages. Qualification is
15023 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15024 locally-generated messages, unless the &%-bnq%& command line option is used.
15026 Messages from external sources must always contain fully qualified addresses,
15027 unless the sending host matches &%sender_unqualified_hosts%& or
15028 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15029 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15030 necessary. Internally, Exim always works with fully qualified envelope
15031 addresses. If &%qualify_domain%& is not set, it defaults to the
15032 &%primary_hostname%& value.
15035 .option qualify_recipient main string "see below"
15036 This option allows you to specify a different domain for qualifying recipient
15037 addresses to the one that is used for senders. See &%qualify_domain%& above.
15041 .option queue_domains main "domain list&!!" unset
15042 .cindex "domain" "specifying non-immediate delivery"
15043 .cindex "queueing incoming messages"
15044 .cindex "message" "queueing certain domains"
15045 This option lists domains for which immediate delivery is not required.
15046 A delivery process is started whenever a message is received, but only those
15047 domains that do not match are processed. All other deliveries wait until the
15048 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15051 .option queue_list_requires_admin main boolean true
15053 The &%-bp%& command-line option, which lists the messages that are on the
15054 queue, requires the caller to be an admin user unless
15055 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15058 .option queue_only main boolean false
15059 .cindex "queueing incoming messages"
15060 .cindex "message" "queueing unconditionally"
15061 If &%queue_only%& is set, a delivery process is not automatically started
15062 whenever a message is received. Instead, the message waits on the queue for the
15063 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15064 delivered immediately when certain conditions (such as heavy load) occur.
15066 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15067 and &%-odi%& command line options override &%queue_only%& unless
15068 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15069 &%queue_only_load%&, and &%smtp_accept_queue%&.
15072 .option queue_only_file main string unset
15073 .cindex "queueing incoming messages"
15074 .cindex "message" "queueing by file existence"
15075 This option can be set to a colon-separated list of absolute path names, each
15076 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15077 it tests for the existence of each listed path using a call to &[stat()]&. For
15078 each path that exists, the corresponding queueing option is set.
15079 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15080 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15082 queue_only_file = smtp/some/file
15084 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15085 &_/some/file_& exists.
15088 .option queue_only_load main fixed-point unset
15089 .cindex "load average"
15090 .cindex "queueing incoming messages"
15091 .cindex "message" "queueing by load"
15092 If the system load average is higher than this value, incoming messages from
15093 all sources are queued, and no automatic deliveries are started. If this
15094 happens during local or remote SMTP input, all subsequent messages received on
15095 the same SMTP connection are queued by default, whatever happens to the load in
15096 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15099 Deliveries will subsequently be performed by queue runner processes. This
15100 option has no effect on ancient operating systems on which Exim cannot
15101 determine the load average. See also &%deliver_queue_load_max%& and
15102 &%smtp_load_reserve%&.
15105 .option queue_only_load_latch main boolean true
15106 .cindex "load average" "re-evaluating per message"
15107 When this option is true (the default), once one message has been queued
15108 because the load average is higher than the value set by &%queue_only_load%&,
15109 all subsequent messages received on the same SMTP connection are also queued.
15110 This is a deliberate choice; even though the load average may fall below the
15111 threshold, it doesn't seem right to deliver later messages on the same
15112 connection when not delivering earlier ones. However, there are special
15113 circumstances such as very long-lived connections from scanning appliances
15114 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15115 should be set false. This causes the value of the load average to be
15116 re-evaluated for each message.
15119 .option queue_only_override main boolean true
15120 .cindex "queueing incoming messages"
15121 When this option is true, the &%-od%&&'x'& command line options override the
15122 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15123 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15124 to override; they are accepted, but ignored.
15127 .option queue_run_in_order main boolean false
15128 .cindex "queue runner" "processing messages in order"
15129 If this option is set, queue runs happen in order of message arrival instead of
15130 in an arbitrary order. For this to happen, a complete list of the entire queue
15131 must be set up before the deliveries start. When the queue is all held in a
15132 single directory (the default), a single list is created for both the ordered
15133 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15134 single list is not created when &%queue_run_in_order%& is false. In this case,
15135 the sub-directories are processed one at a time (in a random order), and this
15136 avoids setting up one huge list for the whole queue. Thus, setting
15137 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15138 when the queue is large, because of the extra work in setting up the single,
15139 large list. In most situations, &%queue_run_in_order%& should not be set.
15143 .option queue_run_max main integer 5
15144 .cindex "queue runner" "maximum number of"
15145 This controls the maximum number of queue runner processes that an Exim daemon
15146 can run simultaneously. This does not mean that it starts them all at once,
15147 but rather that if the maximum number are still running when the time comes to
15148 start another one, it refrains from starting another one. This can happen with
15149 very large queues and/or very sluggish deliveries. This option does not,
15150 however, interlock with other processes, so additional queue runners can be
15151 started by other means, or by killing and restarting the daemon.
15153 Setting this option to zero does not suppress queue runs; rather, it disables
15154 the limit, allowing any number of simultaneous queue runner processes to be
15155 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15156 the daemon's command line.
15158 .option queue_smtp_domains main "domain list&!!" unset
15159 .cindex "queueing incoming messages"
15160 .cindex "message" "queueing remote deliveries"
15161 When this option is set, a delivery process is started whenever a message is
15162 received, routing is performed, and local deliveries take place.
15163 However, if any SMTP deliveries are required for domains that match
15164 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15165 message waits on the queue for the next queue run. Since routing of the message
15166 has taken place, Exim knows to which remote hosts it must be delivered, and so
15167 when the queue run happens, multiple messages for the same host are delivered
15168 over a single SMTP connection. The &%-odqs%& command line option causes all
15169 SMTP deliveries to be queued in this way, and is equivalent to setting
15170 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15174 .option receive_timeout main time 0s
15175 .cindex "timeout" "for non-SMTP input"
15176 This option sets the timeout for accepting a non-SMTP message, that is, the
15177 maximum time that Exim waits when reading a message on the standard input. If
15178 the value is zero, it will wait for ever. This setting is overridden by the
15179 &%-or%& command line option. The timeout for incoming SMTP messages is
15180 controlled by &%smtp_receive_timeout%&.
15182 .option received_header_text main string&!! "see below"
15183 .cindex "customizing" "&'Received:'& header"
15184 .cindex "&'Received:'& header line" "customizing"
15185 This string defines the contents of the &'Received:'& message header that is
15186 added to each message, except for the timestamp, which is automatically added
15187 on at the end (preceded by a semicolon). The string is expanded each time it is
15188 used. If the expansion yields an empty string, no &'Received:'& header line is
15189 added to the message. Otherwise, the string should start with the text
15190 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15191 header lines. The default setting is:
15194 received_header_text = Received: \
15195 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15196 {${if def:sender_ident \
15197 {from ${quote_local_part:$sender_ident} }}\
15198 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15199 by $primary_hostname \
15200 ${if def:received_protocol {with $received_protocol}} \
15201 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15202 (Exim $version_number)\n\t\
15203 ${if def:sender_address \
15204 {(envelope-from <$sender_address>)\n\t}}\
15205 id $message_exim_id\
15206 ${if def:received_for {\n\tfor $received_for}}
15209 The reference to the TLS cipher is omitted when Exim is built without TLS
15210 support. The use of conditional expansions ensures that this works for both
15211 locally generated messages and messages received from remote hosts, giving
15212 header lines such as the following:
15214 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15215 by marley.carol.example with esmtp (Exim 4.00)
15216 (envelope-from <bob@carol.example>)
15217 id 16IOWa-00019l-00
15218 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15219 Received: by scrooge.carol.example with local (Exim 4.00)
15220 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15222 Until the body of the message has been received, the timestamp is the time when
15223 the message started to be received. Once the body has arrived, and all policy
15224 checks have taken place, the timestamp is updated to the time at which the
15225 message was accepted.
15228 .option received_headers_max main integer 30
15229 .cindex "loop" "prevention"
15230 .cindex "mail loop prevention"
15231 .cindex "&'Received:'& header line" "counting"
15232 When a message is to be delivered, the number of &'Received:'& headers is
15233 counted, and if it is greater than this parameter, a mail loop is assumed to
15234 have occurred, the delivery is abandoned, and an error message is generated.
15235 This applies to both local and remote deliveries.
15238 .option recipient_unqualified_hosts main "host list&!!" unset
15239 .cindex "unqualified addresses"
15240 .cindex "host" "unqualified addresses from"
15241 This option lists those hosts from which Exim is prepared to accept unqualified
15242 recipient addresses in message envelopes. The addresses are made fully
15243 qualified by the addition of the &%qualify_recipient%& value. This option also
15244 affects message header lines. Exim does not reject unqualified recipient
15245 addresses in headers, but it qualifies them only if the message came from a
15246 host that matches &%recipient_unqualified_hosts%&,
15247 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15248 option was not set.
15251 .option recipients_max main integer 0
15252 .cindex "limit" "number of recipients"
15253 .cindex "recipient" "maximum number"
15254 If this option is set greater than zero, it specifies the maximum number of
15255 original recipients for any message. Additional recipients that are generated
15256 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15257 all recipients over the limit; earlier recipients are delivered as normal.
15258 Non-SMTP messages with too many recipients are failed, and no deliveries are
15261 .cindex "RCPT" "maximum number of incoming"
15262 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15263 RCPT commands in a single message.
15266 .option recipients_max_reject main boolean false
15267 If this option is set true, Exim rejects SMTP messages containing too many
15268 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15269 error to the eventual DATA command. Otherwise (the default) it gives a 452
15270 error to the surplus RCPT commands and accepts the message on behalf of the
15271 initial set of recipients. The remote server should then re-send the message
15272 for the remaining recipients at a later time.
15275 .option remote_max_parallel main integer 2
15276 .cindex "delivery" "parallelism for remote"
15277 This option controls parallel delivery of one message to a number of remote
15278 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15279 does all the remote deliveries for a message one by one. Otherwise, if a single
15280 message has to be delivered to more than one remote host, or if several copies
15281 have to be sent to the same remote host, up to &%remote_max_parallel%&
15282 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15283 deliveries are required, the maximum number of processes are started, and as
15284 each one finishes, another is begun. The order of starting processes is the
15285 same as if sequential delivery were being done, and can be controlled by the
15286 &%remote_sort_domains%& option. If parallel delivery takes place while running
15287 with debugging turned on, the debugging output from each delivery process is
15288 tagged with its process id.
15290 This option controls only the maximum number of parallel deliveries for one
15291 message in one Exim delivery process. Because Exim has no central queue
15292 manager, there is no way of controlling the total number of simultaneous
15293 deliveries if the configuration allows a delivery attempt as soon as a message
15296 .cindex "number of deliveries"
15297 .cindex "delivery" "maximum number of"
15298 If you want to control the total number of deliveries on the system, you
15299 need to set the &%queue_only%& option. This ensures that all incoming messages
15300 are added to the queue without starting a delivery process. Then set up an Exim
15301 daemon to start queue runner processes at appropriate intervals (probably
15302 fairly often, for example, every minute), and limit the total number of queue
15303 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15304 delivers only one message at a time, the maximum number of deliveries that can
15305 then take place at once is &%queue_run_max%& multiplied by
15306 &%remote_max_parallel%&.
15308 If it is purely remote deliveries you want to control, use
15309 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15310 doing the SMTP routing before queueing, so that several messages for the same
15311 host will eventually get delivered down the same connection.
15314 .option remote_sort_domains main "domain list&!!" unset
15315 .cindex "sorting remote deliveries"
15316 .cindex "delivery" "sorting remote"
15317 When there are a number of remote deliveries for a message, they are sorted by
15318 domain into the order given by this list. For example,
15320 remote_sort_domains = *.cam.ac.uk:*.uk
15322 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15323 then to those in the &%uk%& domain, then to any others.
15326 .option retry_data_expire main time 7d
15327 .cindex "hints database" "data expiry"
15328 This option sets a &"use before"& time on retry information in Exim's hints
15329 database. Any older retry data is ignored. This means that, for example, once a
15330 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15334 .option retry_interval_max main time 24h
15335 .cindex "retry" "limit on interval"
15336 .cindex "limit" "on retry interval"
15337 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15338 intervals between delivery attempts for messages that cannot be delivered
15339 straight away. This option sets an overall limit to the length of time between
15340 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15344 .option return_path_remove main boolean true
15345 .cindex "&'Return-path:'& header line" "removing"
15346 RFC 2821, section 4.4, states that an SMTP server must insert a
15347 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15348 The &'Return-path:'& header preserves the sender address as received in the
15349 MAIL command. This description implies that this header should not be present
15350 in an incoming message. If &%return_path_remove%& is true, any existing
15351 &'Return-path:'& headers are removed from messages at the time they are
15352 received. Exim's transports have options for adding &'Return-path:'& headers at
15353 the time of delivery. They are normally used only for final local deliveries.
15356 .option return_size_limit main integer 100K
15357 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15360 .option rfc1413_hosts main "host list&!!" *
15362 .cindex "host" "for RFC 1413 calls"
15363 RFC 1413 identification calls are made to any client host which matches an item
15366 .option rfc1413_query_timeout main time 5s
15367 .cindex "RFC 1413" "query timeout"
15368 .cindex "timeout" "for RFC 1413 call"
15369 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15370 no RFC 1413 calls are ever made.
15373 .option sender_unqualified_hosts main "host list&!!" unset
15374 .cindex "unqualified addresses"
15375 .cindex "host" "unqualified addresses from"
15376 This option lists those hosts from which Exim is prepared to accept unqualified
15377 sender addresses. The addresses are made fully qualified by the addition of
15378 &%qualify_domain%&. This option also affects message header lines. Exim does
15379 not reject unqualified addresses in headers that contain sender addresses, but
15380 it qualifies them only if the message came from a host that matches
15381 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15382 using TCP/IP), and the &%-bnq%& option was not set.
15385 .option smtp_accept_keepalive main boolean true
15386 .cindex "keepalive" "on incoming connection"
15387 This option controls the setting of the SO_KEEPALIVE option on incoming
15388 TCP/IP socket connections. When set, it causes the kernel to probe idle
15389 connections periodically, by sending packets with &"old"& sequence numbers. The
15390 other end of the connection should send an acknowledgment if the connection is
15391 still okay or a reset if the connection has been aborted. The reason for doing
15392 this is that it has the beneficial effect of freeing up certain types of
15393 connection that can get stuck when the remote host is disconnected without
15394 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15395 hours to detect unreachable hosts.
15399 .option smtp_accept_max main integer 20
15400 .cindex "limit" "incoming SMTP connections"
15401 .cindex "SMTP" "incoming connection count"
15403 This option specifies the maximum number of simultaneous incoming SMTP calls
15404 that Exim will accept. It applies only to the listening daemon; there is no
15405 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15406 value is set to zero, no limit is applied. However, it is required to be
15407 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15408 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15410 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15411 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15412 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15413 and &%smtp_load_reserve%& are then checked before accepting the connection.
15416 .option smtp_accept_max_nonmail main integer 10
15417 .cindex "limit" "non-mail SMTP commands"
15418 .cindex "SMTP" "limiting non-mail commands"
15419 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
15420 the connection if there are too many. This option defines &"too many"&. The
15421 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
15422 client looping sending EHLO, for example. The check is applied only if the
15423 client host matches &%smtp_accept_max_nonmail_hosts%&.
15425 When a new message is expected, one occurrence of RSET is not counted. This
15426 allows a client to send one RSET between messages (this is not necessary,
15427 but some clients do it). Exim also allows one uncounted occurrence of HELO
15428 or EHLO, and one occurrence of STARTTLS between messages. After
15429 starting up a TLS session, another EHLO is expected, and so it too is not
15430 counted. The first occurrence of AUTH in a connection, or immediately
15431 following STARTTLS is not counted. Otherwise, all commands other than
15432 MAIL, RCPT, DATA, and QUIT are counted.
15435 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
15436 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
15437 check by setting this option. The default value makes it apply to all hosts. By
15438 changing the value, you can exclude any badly-behaved hosts that you have to
15442 . Allow this long option name to split; give it unsplit as a fifth argument
15443 . for the automatic .oindex that is generated by .option.
15444 . We insert " &~&~" which is both pretty nasty visually and results in
15445 . non-searchable text. HowItWorks.txt mentions an option for inserting
15446 . zero-width-space, which would be nicer visually and results in (at least)
15447 . html that Firefox will split on when it's forced to reflow (rather than
15448 . inserting a horizontal scrollbar). However, the text is still not
15449 . searchable. NM changed this occurrence for bug 1197 to no longer allow
15450 . the option name to split.
15452 .option "smtp_accept_max_per_connection" main integer 1000 &&&
15453 smtp_accept_max_per_connection
15454 .cindex "SMTP" "limiting incoming message count"
15455 .cindex "limit" "messages per SMTP connection"
15456 The value of this option limits the number of MAIL commands that Exim is
15457 prepared to accept over a single SMTP connection, whether or not each command
15458 results in the transfer of a message. After the limit is reached, a 421
15459 response is given to subsequent MAIL commands. This limit is a safety
15460 precaution against a client that goes mad (incidents of this type have been
15464 .option smtp_accept_max_per_host main string&!! unset
15465 .cindex "limit" "SMTP connections from one host"
15466 .cindex "host" "limiting SMTP connections from"
15467 This option restricts the number of simultaneous IP connections from a single
15468 host (strictly, from a single IP address) to the Exim daemon. The option is
15469 expanded, to enable different limits to be applied to different hosts by
15470 reference to &$sender_host_address$&. Once the limit is reached, additional
15471 connection attempts from the same host are rejected with error code 421. This
15472 is entirely independent of &%smtp_accept_reserve%&. The option's default value
15473 of zero imposes no limit. If this option is set greater than zero, it is
15474 required that &%smtp_accept_max%& be non-zero.
15476 &*Warning*&: When setting this option you should not use any expansion
15477 constructions that take an appreciable amount of time. The expansion and test
15478 happen in the main daemon loop, in order to reject additional connections
15479 without forking additional processes (otherwise a denial-of-service attack
15480 could cause a vast number or processes to be created). While the daemon is
15481 doing this processing, it cannot accept any other incoming connections.
15485 .option smtp_accept_queue main integer 0
15486 .cindex "SMTP" "incoming connection count"
15487 .cindex "queueing incoming messages"
15488 .cindex "message" "queueing by SMTP connection count"
15489 If the number of simultaneous incoming SMTP connections being handled via the
15490 listening daemon exceeds this value, messages received by SMTP are just placed
15491 on the queue; no delivery processes are started automatically. The count is
15492 fixed at the start of an SMTP connection. It cannot be updated in the
15493 subprocess that receives messages, and so the queueing or not queueing applies
15494 to all messages received in the same connection.
15496 A value of zero implies no limit, and clearly any non-zero value is useful only
15497 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
15498 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
15499 various &%-od%&&'x'& command line options.
15502 . See the comment on smtp_accept_max_per_connection
15504 .option "smtp_accept_queue_per_connection" main integer 10 &&&
15505 smtp_accept_queue_per_connection
15506 .cindex "queueing incoming messages"
15507 .cindex "message" "queueing by message count"
15508 This option limits the number of delivery processes that Exim starts
15509 automatically when receiving messages via SMTP, whether via the daemon or by
15510 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
15511 and the number of messages received in a single SMTP session exceeds this
15512 number, subsequent messages are placed on the queue, but no delivery processes
15513 are started. This helps to limit the number of Exim processes when a server
15514 restarts after downtime and there is a lot of mail waiting for it on other
15515 systems. On large systems, the default should probably be increased, and on
15516 dial-in client systems it should probably be set to zero (that is, disabled).
15519 .option smtp_accept_reserve main integer 0
15520 .cindex "SMTP" "incoming call count"
15521 .cindex "host" "reserved"
15522 When &%smtp_accept_max%& is set greater than zero, this option specifies a
15523 number of SMTP connections that are reserved for connections from the hosts
15524 that are specified in &%smtp_reserve_hosts%&. The value set in
15525 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
15526 restricted to this number of connections; the option specifies a minimum number
15527 of connection slots for them, not a maximum. It is a guarantee that this group
15528 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
15529 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
15532 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
15533 set to 5, once there are 45 active connections (from any hosts), new
15534 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
15535 provided the other criteria for acceptance are met.
15538 .option smtp_active_hostname main string&!! unset
15539 .cindex "host" "name in SMTP responses"
15540 .cindex "SMTP" "host name in responses"
15541 .vindex "&$primary_hostname$&"
15542 This option is provided for multi-homed servers that want to masquerade as
15543 several different hosts. At the start of an incoming SMTP connection, its value
15544 is expanded and used instead of the value of &$primary_hostname$& in SMTP
15545 responses. For example, it is used as domain name in the response to an
15546 incoming HELO or EHLO command.
15548 .vindex "&$smtp_active_hostname$&"
15549 The active hostname is placed in the &$smtp_active_hostname$& variable, which
15550 is saved with any messages that are received. It is therefore available for use
15551 in routers and transports when the message is later delivered.
15553 If this option is unset, or if its expansion is forced to fail, or if the
15554 expansion results in an empty string, the value of &$primary_hostname$& is
15555 used. Other expansion failures cause a message to be written to the main and
15556 panic logs, and the SMTP command receives a temporary error. Typically, the
15557 value of &%smtp_active_hostname%& depends on the incoming interface address.
15560 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
15561 {cox.mydomain}{box.mydomain}}
15564 Although &$smtp_active_hostname$& is primarily concerned with incoming
15565 messages, it is also used as the default for HELO commands in callout
15566 verification if there is no remote transport from which to obtain a
15567 &%helo_data%& value.
15569 .option smtp_banner main string&!! "see below"
15570 .cindex "SMTP" "welcome banner"
15571 .cindex "banner for SMTP"
15572 .cindex "welcome banner for SMTP"
15573 .cindex "customizing" "SMTP banner"
15574 This string, which is expanded every time it is used, is output as the initial
15575 positive response to an SMTP connection. The default setting is:
15577 smtp_banner = $smtp_active_hostname ESMTP Exim \
15578 $version_number $tod_full
15580 Failure to expand the string causes a panic error. If you want to create a
15581 multiline response to the initial SMTP connection, use &"\n"& in the string at
15582 appropriate points, but not at the end. Note that the 220 code is not included
15583 in this string. Exim adds it automatically (several times in the case of a
15584 multiline response).
15587 .option smtp_check_spool_space main boolean true
15588 .cindex "checking disk space"
15589 .cindex "disk space, checking"
15590 .cindex "spool directory" "checking space"
15591 When this option is set, if an incoming SMTP session encounters the SIZE
15592 option on a MAIL command, it checks that there is enough space in the
15593 spool directory's partition to accept a message of that size, while still
15594 leaving free the amount specified by &%check_spool_space%& (even if that value
15595 is zero). If there isn't enough space, a temporary error code is returned.
15598 .option smtp_connect_backlog main integer 20
15599 .cindex "connection backlog"
15600 .cindex "SMTP" "connection backlog"
15601 .cindex "backlog of connections"
15602 This option specifies a maximum number of waiting SMTP connections. Exim passes
15603 this value to the TCP/IP system when it sets up its listener. Once this number
15604 of connections are waiting for the daemon's attention, subsequent connection
15605 attempts are refused at the TCP/IP level. At least, that is what the manuals
15606 say; in some circumstances such connection attempts have been observed to time
15607 out instead. For large systems it is probably a good idea to increase the
15608 value (to 50, say). It also gives some protection against denial-of-service
15609 attacks by SYN flooding.
15612 .option smtp_enforce_sync main boolean true
15613 .cindex "SMTP" "synchronization checking"
15614 .cindex "synchronization checking in SMTP"
15615 The SMTP protocol specification requires the client to wait for a response from
15616 the server at certain points in the dialogue. Without PIPELINING these
15617 synchronization points are after every command; with PIPELINING they are
15618 fewer, but they still exist.
15620 Some spamming sites send out a complete set of SMTP commands without waiting
15621 for any response. Exim protects against this by rejecting a message if the
15622 client has sent further input when it should not have. The error response &"554
15623 SMTP synchronization error"& is sent, and the connection is dropped. Testing
15624 for this error cannot be perfect because of transmission delays (unexpected
15625 input may be on its way but not yet received when Exim checks). However, it
15626 does detect many instances.
15628 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
15629 If you want to disable the check selectively (for example, only for certain
15630 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
15631 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
15635 .option smtp_etrn_command main string&!! unset
15636 .cindex "ETRN" "command to be run"
15637 .vindex "&$domain$&"
15638 If this option is set, the given command is run whenever an SMTP ETRN
15639 command is received from a host that is permitted to issue such commands (see
15640 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
15641 are independently expanded. The expansion variable &$domain$& is set to the
15642 argument of the ETRN command, and no syntax checking is done on it. For
15645 smtp_etrn_command = /etc/etrn_command $domain \
15646 $sender_host_address
15648 A new process is created to run the command, but Exim does not wait for it to
15649 complete. Consequently, its status cannot be checked. If the command cannot be
15650 run, a line is written to the panic log, but the ETRN caller still receives
15651 a 250 success response. Exim is normally running under its own uid when
15652 receiving SMTP, so it is not possible for it to change the uid before running
15656 .option smtp_etrn_serialize main boolean true
15657 .cindex "ETRN" "serializing"
15658 When this option is set, it prevents the simultaneous execution of more than
15659 one identical command as a result of ETRN in an SMTP connection. See
15660 section &<<SECTETRN>>& for details.
15663 .option smtp_load_reserve main fixed-point unset
15664 .cindex "load average"
15665 If the system load average ever gets higher than this, incoming SMTP calls are
15666 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
15667 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
15668 the load is over the limit. The option has no effect on ancient operating
15669 systems on which Exim cannot determine the load average. See also
15670 &%deliver_queue_load_max%& and &%queue_only_load%&.
15674 .option smtp_max_synprot_errors main integer 3
15675 .cindex "SMTP" "limiting syntax and protocol errors"
15676 .cindex "limit" "SMTP syntax and protocol errors"
15677 Exim rejects SMTP commands that contain syntax or protocol errors. In
15678 particular, a syntactically invalid email address, as in this command:
15680 RCPT TO:<abc xyz@a.b.c>
15682 causes immediate rejection of the command, before any other tests are done.
15683 (The ACL cannot be run if there is no valid address to set up for it.) An
15684 example of a protocol error is receiving RCPT before MAIL. If there are
15685 too many syntax or protocol errors in one SMTP session, the connection is
15686 dropped. The limit is set by this option.
15688 .cindex "PIPELINING" "expected errors"
15689 When the PIPELINING extension to SMTP is in use, some protocol errors are
15690 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
15691 Exim assumes that PIPELINING will be used if it advertises it (see
15692 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
15693 not count towards the limit.
15697 .option smtp_max_unknown_commands main integer 3
15698 .cindex "SMTP" "limiting unknown commands"
15699 .cindex "limit" "unknown SMTP commands"
15700 If there are too many unrecognized commands in an incoming SMTP session, an
15701 Exim server drops the connection. This is a defence against some kinds of abuse
15704 into making connections to SMTP ports; in these circumstances, a number of
15705 non-SMTP command lines are sent first.
15709 .option smtp_ratelimit_hosts main "host list&!!" unset
15710 .cindex "SMTP" "rate limiting"
15711 .cindex "limit" "rate of message arrival"
15712 .cindex "RCPT" "rate limiting"
15713 Some sites find it helpful to be able to limit the rate at which certain hosts
15714 can send them messages, and the rate at which an individual message can specify
15717 Exim has two rate-limiting facilities. This section describes the older
15718 facility, which can limit rates within a single connection. The newer
15719 &%ratelimit%& ACL condition can limit rates across all connections. See section
15720 &<<SECTratelimiting>>& for details of the newer facility.
15722 When a host matches &%smtp_ratelimit_hosts%&, the values of
15723 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
15724 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
15725 respectively. Each option, if set, must contain a set of four comma-separated
15729 A threshold, before which there is no rate limiting.
15731 An initial time delay. Unlike other times in Exim, numbers with decimal
15732 fractional parts are allowed here.
15734 A factor by which to increase the delay each time.
15736 A maximum value for the delay. This should normally be less than 5 minutes,
15737 because after that time, the client is liable to timeout the SMTP command.
15740 For example, these settings have been used successfully at the site which
15741 first suggested this feature, for controlling mail from their customers:
15743 smtp_ratelimit_mail = 2,0.5s,1.05,4m
15744 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
15746 The first setting specifies delays that are applied to MAIL commands after
15747 two have been received over a single connection. The initial delay is 0.5
15748 seconds, increasing by a factor of 1.05 each time. The second setting applies
15749 delays to RCPT commands when more than four occur in a single message.
15752 .option smtp_ratelimit_mail main string unset
15753 See &%smtp_ratelimit_hosts%& above.
15756 .option smtp_ratelimit_rcpt main string unset
15757 See &%smtp_ratelimit_hosts%& above.
15760 .option smtp_receive_timeout main time 5m
15761 .cindex "timeout" "for SMTP input"
15762 .cindex "SMTP" "input timeout"
15763 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
15764 input, including batch SMTP. If a line of input (either an SMTP command or a
15765 data line) is not received within this time, the SMTP connection is dropped and
15766 the message is abandoned.
15767 A line is written to the log containing one of the following messages:
15769 SMTP command timeout on connection from...
15770 SMTP data timeout on connection from...
15772 The former means that Exim was expecting to read an SMTP command; the latter
15773 means that it was in the DATA phase, reading the contents of a message.
15777 The value set by this option can be overridden by the
15778 &%-os%& command-line option. A setting of zero time disables the timeout, but
15779 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
15780 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
15781 timeout is controlled by &%receive_timeout%& and &%-or%&.
15784 .option smtp_reserve_hosts main "host list&!!" unset
15785 This option defines hosts for which SMTP connections are reserved; see
15786 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
15789 .option smtp_return_error_details main boolean false
15790 .cindex "SMTP" "details policy failures"
15791 .cindex "policy control" "rejection, returning details"
15792 In the default state, Exim uses bland messages such as
15793 &"Administrative prohibition"& when it rejects SMTP commands for policy
15794 reasons. Many sysadmins like this because it gives away little information
15795 to spammers. However, some other sysadmins who are applying strict checking
15796 policies want to give out much fuller information about failures. Setting
15797 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
15798 example, instead of &"Administrative prohibition"&, it might give:
15800 550-Rejected after DATA: '>' missing at end of address:
15801 550 failing address in "From" header is: <user@dom.ain
15804 .option spamd_address main string "see below"
15805 This option is available when Exim is compiled with the content-scanning
15806 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
15807 The default value is
15811 See section &<<SECTscanspamass>>& for more details.
15815 .option split_spool_directory main boolean false
15816 .cindex "multiple spool directories"
15817 .cindex "spool directory" "split"
15818 .cindex "directories, multiple"
15819 If this option is set, it causes Exim to split its input directory into 62
15820 subdirectories, each with a single alphanumeric character as its name. The
15821 sixth character of the message id is used to allocate messages to
15822 subdirectories; this is the least significant base-62 digit of the time of
15823 arrival of the message.
15825 Splitting up the spool in this way may provide better performance on systems
15826 where there are long mail queues, by reducing the number of files in any one
15827 directory. The msglog directory is also split up in a similar way to the input
15828 directory; however, if &%preserve_message_logs%& is set, all old msglog files
15829 are still placed in the single directory &_msglog.OLD_&.
15831 It is not necessary to take any special action for existing messages when
15832 changing &%split_spool_directory%&. Exim notices messages that are in the
15833 &"wrong"& place, and continues to process them. If the option is turned off
15834 after a period of being on, the subdirectories will eventually empty and be
15835 automatically deleted.
15837 When &%split_spool_directory%& is set, the behaviour of queue runner processes
15838 changes. Instead of creating a list of all messages in the queue, and then
15839 trying to deliver each one in turn, it constructs a list of those in one
15840 sub-directory and tries to deliver them, before moving on to the next
15841 sub-directory. The sub-directories are processed in a random order. This
15842 spreads out the scanning of the input directories, and uses less memory. It is
15843 particularly beneficial when there are lots of messages on the queue. However,
15844 if &%queue_run_in_order%& is set, none of this new processing happens. The
15845 entire queue has to be scanned and sorted before any deliveries can start.
15848 .option spool_directory main string&!! "set at compile time"
15849 .cindex "spool directory" "path to"
15850 This defines the directory in which Exim keeps its spool, that is, the messages
15851 it is waiting to deliver. The default value is taken from the compile-time
15852 configuration setting, if there is one. If not, this option must be set. The
15853 string is expanded, so it can contain, for example, a reference to
15854 &$primary_hostname$&.
15856 If the spool directory name is fixed on your installation, it is recommended
15857 that you set it at build time rather than from this option, particularly if the
15858 log files are being written to the spool directory (see &%log_file_path%&).
15859 Otherwise log files cannot be used for errors that are detected early on, such
15860 as failures in the configuration file.
15862 By using this option to override the compiled-in path, it is possible to run
15863 tests of Exim without using the standard spool.
15865 .option sqlite_lock_timeout main time 5s
15866 .cindex "sqlite lookup type" "lock timeout"
15867 This option controls the timeout that the &(sqlite)& lookup uses when trying to
15868 access an SQLite database. See section &<<SECTsqlite>>& for more details.
15870 .option strict_acl_vars main boolean false
15871 .cindex "&ACL;" "variables, handling unset"
15872 This option controls what happens if a syntactically valid but undefined ACL
15873 variable is referenced. If it is false (the default), an empty string
15874 is substituted; if it is true, an error is generated. See section
15875 &<<SECTaclvariables>>& for details of ACL variables.
15877 .option strip_excess_angle_brackets main boolean false
15878 .cindex "angle brackets, excess"
15879 If this option is set, redundant pairs of angle brackets round &"route-addr"&
15880 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
15881 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
15882 passed on to another MTA, the excess angle brackets are not passed on. If this
15883 option is not set, multiple pairs of angle brackets cause a syntax error.
15886 .option strip_trailing_dot main boolean false
15887 .cindex "trailing dot on domain"
15888 .cindex "dot" "trailing on domain"
15889 If this option is set, a trailing dot at the end of a domain in an address is
15890 ignored. If this is in the envelope and the message is passed on to another
15891 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
15892 domain causes a syntax error.
15893 However, addresses in header lines are checked only when an ACL requests header
15897 .option syslog_duplication main boolean true
15898 .cindex "syslog" "duplicate log lines; suppressing"
15899 When Exim is logging to syslog, it writes the log lines for its three
15900 separate logs at different syslog priorities so that they can in principle
15901 be separated on the logging hosts. Some installations do not require this
15902 separation, and in those cases, the duplication of certain log lines is a
15903 nuisance. If &%syslog_duplication%& is set false, only one copy of any
15904 particular log line is written to syslog. For lines that normally go to
15905 both the main log and the reject log, the reject log version (possibly
15906 containing message header lines) is written, at LOG_NOTICE priority.
15907 Lines that normally go to both the main and the panic log are written at
15908 the LOG_ALERT priority.
15911 .option syslog_facility main string unset
15912 .cindex "syslog" "facility; setting"
15913 This option sets the syslog &"facility"& name, used when Exim is logging to
15914 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
15915 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
15916 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
15917 details of Exim's logging.
15921 .option syslog_processname main string &`exim`&
15922 .cindex "syslog" "process name; setting"
15923 This option sets the syslog &"ident"& name, used when Exim is logging to
15924 syslog. The value must be no longer than 32 characters. See chapter
15925 &<<CHAPlog>>& for details of Exim's logging.
15929 .option syslog_timestamp main boolean true
15930 .cindex "syslog" "timestamps"
15931 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
15932 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
15933 details of Exim's logging.
15936 .option system_filter main string&!! unset
15937 .cindex "filter" "system filter"
15938 .cindex "system filter" "specifying"
15939 .cindex "Sieve filter" "not available for system filter"
15940 This option specifies an Exim filter file that is applied to all messages at
15941 the start of each delivery attempt, before any routing is done. System filters
15942 must be Exim filters; they cannot be Sieve filters. If the system filter
15943 generates any deliveries to files or pipes, or any new mail messages, the
15944 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15945 which transports are to be used. Details of this facility are given in chapter
15946 &<<CHAPsystemfilter>>&.
15949 .option system_filter_directory_transport main string&!! unset
15950 .vindex "&$address_file$&"
15951 This sets the name of the transport driver that is to be used when the
15952 &%save%& command in a system message filter specifies a path ending in &"/"&,
15953 implying delivery of each message into a separate file in some directory.
15954 During the delivery, the variable &$address_file$& contains the path name.
15957 .option system_filter_file_transport main string&!! unset
15958 .cindex "file" "transport for system filter"
15959 This sets the name of the transport driver that is to be used when the &%save%&
15960 command in a system message filter specifies a path not ending in &"/"&. During
15961 the delivery, the variable &$address_file$& contains the path name.
15963 .option system_filter_group main string unset
15964 .cindex "gid (group id)" "system filter"
15965 This option is used only when &%system_filter_user%& is also set. It sets the
15966 gid under which the system filter is run, overriding any gid that is associated
15967 with the user. The value may be numerical or symbolic.
15969 .option system_filter_pipe_transport main string&!! unset
15970 .cindex "&(pipe)& transport" "for system filter"
15971 .vindex "&$address_pipe$&"
15972 This specifies the transport driver that is to be used when a &%pipe%& command
15973 is used in a system filter. During the delivery, the variable &$address_pipe$&
15974 contains the pipe command.
15977 .option system_filter_reply_transport main string&!! unset
15978 .cindex "&(autoreply)& transport" "for system filter"
15979 This specifies the transport driver that is to be used when a &%mail%& command
15980 is used in a system filter.
15983 .option system_filter_user main string unset
15984 .cindex "uid (user id)" "system filter"
15985 If this option is set to root, the system filter is run in the main Exim
15986 delivery process, as root. Otherwise, the system filter runs in a separate
15987 process, as the given user, defaulting to the Exim run-time user.
15988 Unless the string consists entirely of digits, it
15989 is looked up in the password data. Failure to find the named user causes a
15990 configuration error. The gid is either taken from the password data, or
15991 specified by &%system_filter_group%&. When the uid is specified numerically,
15992 &%system_filter_group%& is required to be set.
15994 If the system filter generates any pipe, file, or reply deliveries, the uid
15995 under which the filter is run is used when transporting them, unless a
15996 transport option overrides.
15999 .option tcp_nodelay main boolean true
16000 .cindex "daemon" "TCP_NODELAY on sockets"
16001 .cindex "Nagle algorithm"
16002 .cindex "TCP_NODELAY on listening sockets"
16003 If this option is set false, it stops the Exim daemon setting the
16004 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16005 turns off the &"Nagle algorithm"&, which is a way of improving network
16006 performance in interactive (character-by-character) situations. Turning it off
16007 should improve Exim's performance a bit, so that is what happens by default.
16008 However, it appears that some broken clients cannot cope, and time out. Hence
16009 this option. It affects only those sockets that are set up for listening by the
16010 daemon. Sockets created by the smtp transport for delivering mail always set
16014 .option timeout_frozen_after main time 0s
16015 .cindex "frozen messages" "timing out"
16016 .cindex "timeout" "frozen messages"
16017 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16018 message of any kind that has been on the queue for longer than the given time
16019 is automatically cancelled at the next queue run. If the frozen message is a
16020 bounce message, it is just discarded; otherwise, a bounce is sent to the
16021 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16022 If you want to timeout frozen bounce messages earlier than other kinds of
16023 frozen message, see &%ignore_bounce_errors_after%&.
16025 &*Note:*& the default value of zero means no timeouts; with this setting,
16026 frozen messages remain on the queue forever (except for any frozen bounce
16027 messages that are released by &%ignore_bounce_errors_after%&).
16030 .option timezone main string unset
16031 .cindex "timezone, setting"
16032 The value of &%timezone%& is used to set the environment variable TZ while
16033 running Exim (if it is different on entry). This ensures that all timestamps
16034 created by Exim are in the required timezone. If you want all your timestamps
16035 to be in UTC (aka GMT) you should set
16039 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16040 or, if that is not set, from the value of the TZ environment variable when Exim
16041 is built. If &%timezone%& is set to the empty string, either at build or run
16042 time, any existing TZ variable is removed from the environment when Exim
16043 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16044 unfortunately not all, operating systems.
16047 .option tls_advertise_hosts main "host list&!!" unset
16048 .cindex "TLS" "advertising"
16049 .cindex "encryption" "on SMTP connection"
16050 .cindex "SMTP" "encrypted connection"
16051 When Exim is built with support for TLS encrypted connections, the availability
16052 of the STARTTLS command to set up an encrypted session is advertised in
16053 response to EHLO only to those client hosts that match this option. See
16054 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16057 .option tls_certificate main string&!! unset
16058 .cindex "TLS" "server certificate; location of"
16059 .cindex "certificate" "server, location of"
16060 The value of this option is expanded, and must then be the absolute path to a
16061 file which contains the server's certificates. The server's private key is also
16062 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16063 &<<CHAPTLS>>& for further details.
16065 &*Note*&: The certificates defined by this option are used only when Exim is
16066 receiving incoming messages as a server. If you want to supply certificates for
16067 use when sending messages as a client, you must set the &%tls_certificate%&
16068 option in the relevant &(smtp)& transport.
16070 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16071 if the OpenSSL build supports TLS extensions and the TLS client sends the
16072 Server Name Indication extension, then this option and others documented in
16073 &<<SECTtlssni>>& will be re-expanded.
16075 .option tls_crl main string&!! unset
16076 .cindex "TLS" "server certificate revocation list"
16077 .cindex "certificate" "revocation list for server"
16078 This option specifies a certificate revocation list. The expanded value must
16079 be the name of a file that contains a CRL in PEM format.
16081 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16084 .option tls_dh_max_bits main integer 2236
16085 .cindex "TLS" "D-H bit count"
16086 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16087 the chosen TLS library. That value might prove to be too high for
16088 interoperability. This option provides a maximum clamp on the value
16089 suggested, trading off security for interoperability.
16091 The value must be at least 1024.
16093 The value 2236 was chosen because, at time of adding the option, it was the
16094 hard-coded maximum value supported by the NSS cryptographic library, as used
16095 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16097 If you prefer more security and are willing to break some clients, raise this
16100 Note that the value passed to GnuTLS for *generating* a new prime may be a
16101 little less than this figure, because GnuTLS is inexact and may produce a
16102 larger prime than requested.
16105 .option tls_dhparam main string&!! unset
16106 .cindex "TLS" "D-H parameters for server"
16107 The value of this option is expanded and indicates the source of DH parameters
16108 to be used by Exim.
16110 If it is a filename starting with a &`/`&, then it names a file from which DH
16111 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16112 PKCS#3 representation of the DH prime. If the file does not exist, for
16113 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16114 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16115 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16116 and treated as though the &%tls_dhparam%& were set to "none".
16118 If this option expands to the string "none", then no DH parameters will be
16121 If this option expands to the string "historic" and Exim is using GnuTLS, then
16122 Exim will attempt to load a file from inside the spool directory. If the file
16123 does not exist, Exim will attempt to create it.
16124 See section &<<SECTgnutlsparam>>& for further details.
16126 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16127 a default DH prime; the default is the 2048 bit prime described in section
16128 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16129 in IKE is assigned number 23.
16131 Otherwise, the option must expand to the name used by Exim for any of a number
16132 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16133 "ike" followed by the number used by IKE, of "default" which corresponds to
16136 The available primes are:
16137 &`ike1`&, &`ike2`&, &`ike5`&,
16138 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16139 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16141 Some of these will be too small to be accepted by clients.
16142 Some may be too large to be accepted by clients.
16144 The TLS protocol does not negotiate an acceptable size for this; clients tend
16145 to hard-drop connections if what is offered by the server is unacceptable,
16146 whether too large or too small, and there's no provision for the client to
16147 tell the server what these constraints are. Thus, as a server operator, you
16148 need to make an educated guess as to what is most likely to work for your
16151 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16152 is most likely to maximise interoperability. The upper bound comes from
16153 applications using the Mozilla Network Security Services (NSS) library, which
16154 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16155 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16156 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16157 acceptable bound from 1024 to 2048.
16160 .option tls_on_connect_ports main "string list" unset
16161 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16162 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16163 set up without waiting for the client to issue a STARTTLS command. For
16164 further details, see section &<<SECTsupobssmt>>&.
16168 .option tls_privatekey main string&!! unset
16169 .cindex "TLS" "server private key; location of"
16170 The value of this option is expanded, and must then be the absolute path to a
16171 file which contains the server's private key. If this option is unset, or if
16172 the expansion is forced to fail, or the result is an empty string, the private
16173 key is assumed to be in the same file as the server's certificates. See chapter
16174 &<<CHAPTLS>>& for further details.
16176 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16179 .option tls_remember_esmtp main boolean false
16180 .cindex "TLS" "esmtp state; remembering"
16181 .cindex "TLS" "broken clients"
16182 If this option is set true, Exim violates the RFCs by remembering that it is in
16183 &"esmtp"& state after successfully negotiating a TLS session. This provides
16184 support for broken clients that fail to send a new EHLO after starting a
16188 .option tls_require_ciphers main string&!! unset
16189 .cindex "TLS" "requiring specific ciphers"
16190 .cindex "cipher" "requiring specific"
16191 This option controls which ciphers can be used for incoming TLS connections.
16192 The &(smtp)& transport has an option of the same name for controlling outgoing
16193 connections. This option is expanded for each connection, so can be varied for
16194 different clients if required. The value of this option must be a list of
16195 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16196 in somewhat different ways. If GnuTLS is being used, the client controls the
16197 preference order of the available ciphers. Details are given in sections
16198 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16201 .option tls_try_verify_hosts main "host list&!!" unset
16202 .cindex "TLS" "client certificate verification"
16203 .cindex "certificate" "verification of client"
16204 See &%tls_verify_hosts%& below.
16207 .option tls_verify_certificates main string&!! unset
16208 .cindex "TLS" "client certificate verification"
16209 .cindex "certificate" "verification of client"
16210 The value of this option is expanded, and must then be the absolute path to
16211 a file containing permitted certificates for clients that
16212 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
16213 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
16214 directory containing certificate files. This does not work with GnuTLS; the
16215 option must be set to the name of a single file if you are using GnuTLS.
16217 These certificates should be for the certificate authorities trusted, rather
16218 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16219 the value is a file then the certificates are sent by Exim as a server to
16220 connecting clients, defining the list of accepted certificate authorities.
16221 Thus the values defined should be considered public data. To avoid this,
16222 use OpenSSL with a directory.
16224 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16226 A forced expansion failure or setting to an empty string is equivalent to
16230 .option tls_verify_hosts main "host list&!!" unset
16231 .cindex "TLS" "client certificate verification"
16232 .cindex "certificate" "verification of client"
16233 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16234 certificates from clients. The expected certificates are defined by
16235 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16236 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16237 &%tls_verify_certificates%& is not set.
16239 Any client that matches &%tls_verify_hosts%& is constrained by
16240 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16241 present one of the listed certificates. If it does not, the connection is
16242 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16243 the host to use TLS. It can still send SMTP commands through unencrypted
16244 connections. Forcing a client to use TLS has to be done separately using an
16245 ACL to reject inappropriate commands when the connection is not encrypted.
16247 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16248 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16249 certificate and checks it against &%tls_verify_certificates%&, but does not
16250 abort the connection if there is no certificate or if it does not match. This
16251 state can be detected in an ACL, which makes it possible to implement policies
16252 such as &"accept for relay only if a verified certificate has been received,
16253 but accept for local delivery if encrypted, even without a verified
16256 Client hosts that match neither of these lists are not asked to present
16260 .option trusted_groups main "string list&!!" unset
16261 .cindex "trusted groups"
16262 .cindex "groups" "trusted"
16263 This option is expanded just once, at the start of Exim's processing. If this
16264 option is set, any process that is running in one of the listed groups, or
16265 which has one of them as a supplementary group, is trusted. The groups can be
16266 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16267 details of what trusted callers are permitted to do. If neither
16268 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16271 .option trusted_users main "string list&!!" unset
16272 .cindex "trusted users"
16273 .cindex "user" "trusted"
16274 This option is expanded just once, at the start of Exim's processing. If this
16275 option is set, any process that is running as one of the listed users is
16276 trusted. The users can be specified numerically or by name. See section
16277 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16278 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16279 Exim user are trusted.
16281 .option unknown_login main string&!! unset
16282 .cindex "uid (user id)" "unknown caller"
16283 .vindex "&$caller_uid$&"
16284 This is a specialized feature for use in unusual configurations. By default, if
16285 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16286 gives up. The &%unknown_login%& option can be used to set a login name to be
16287 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16288 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16289 is used for the user's real name (gecos field), unless this has been set by the
16292 .option unknown_username main string unset
16293 See &%unknown_login%&.
16295 .option untrusted_set_sender main "address list&!!" unset
16296 .cindex "trusted users"
16297 .cindex "sender" "setting by untrusted user"
16298 .cindex "untrusted user setting sender"
16299 .cindex "user" "untrusted setting sender"
16300 .cindex "envelope sender"
16301 When an untrusted user submits a message to Exim using the standard input, Exim
16302 normally creates an envelope sender address from the user's login and the
16303 default qualification domain. Data from the &%-f%& option (for setting envelope
16304 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16305 is used) is ignored.
16307 However, untrusted users are permitted to set an empty envelope sender address,
16308 to declare that a message should never generate any bounces. For example:
16310 exim -f '<>' user@domain.example
16312 .vindex "&$sender_ident$&"
16313 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16314 other envelope sender addresses in a controlled way. When it is set, untrusted
16315 users are allowed to set envelope sender addresses that match any of the
16316 patterns in the list. Like all address lists, the string is expanded. The
16317 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16318 users to setting senders that start with their login ids
16319 followed by a hyphen
16320 by a setting like this:
16322 untrusted_set_sender = ^$sender_ident-
16324 If you want to allow untrusted users to set envelope sender addresses without
16325 restriction, you can use
16327 untrusted_set_sender = *
16329 The &%untrusted_set_sender%& option applies to all forms of local input, but
16330 only to the setting of the envelope sender. It does not permit untrusted users
16331 to use the other options which trusted user can use to override message
16332 parameters. Furthermore, it does not stop Exim from removing an existing
16333 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
16334 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
16335 overriding these actions. The handling of the &'Sender:'& header is also
16336 described in section &<<SECTthesenhea>>&.
16338 The log line for a message's arrival shows the envelope sender following
16339 &"<="&. For local messages, the user's login always follows, after &"U="&. In
16340 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
16341 envelope sender address, the user's login is shown in parentheses after the
16345 .option uucp_from_pattern main string "see below"
16346 .cindex "&""From""& line"
16347 .cindex "UUCP" "&""From""& line"
16348 Some applications that pass messages to an MTA via a command line interface use
16349 an initial line starting with &"From&~"& to pass the envelope sender. In
16350 particular, this is used by UUCP software. Exim recognizes such a line by means
16351 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
16352 matches, the sender address is constructed by expanding the contents of
16353 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
16354 default pattern recognizes lines in the following two forms:
16356 From ph10 Fri Jan 5 12:35 GMT 1996
16357 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16359 The pattern can be seen by running
16361 exim -bP uucp_from_pattern
16363 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16364 year in the second case. The first word after &"From&~"& is matched in the
16365 regular expression by a parenthesized subpattern. The default value for
16366 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16367 (&"ph10"& in the example above) as the message's sender. See also
16368 &%ignore_fromline_hosts%&.
16371 .option uucp_from_sender main string&!! &`$1`&
16372 See &%uucp_from_pattern%& above.
16375 .option warn_message_file main string unset
16376 .cindex "warning of delay" "customizing the message"
16377 .cindex "customizing" "warning message"
16378 This option defines a template file containing paragraphs of text to be used
16379 for constructing the warning message which is sent by Exim when a message has
16380 been on the queue for a specified amount of time, as specified by
16381 &%delay_warning%&. Details of the file's contents are given in chapter
16382 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
16385 .option write_rejectlog main boolean true
16386 .cindex "reject log" "disabling"
16387 If this option is set false, Exim no longer writes anything to the reject log.
16388 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
16389 .ecindex IIDconfima
16390 .ecindex IIDmaiconf
16395 . ////////////////////////////////////////////////////////////////////////////
16396 . ////////////////////////////////////////////////////////////////////////////
16398 .chapter "Generic options for routers" "CHAProutergeneric"
16399 .scindex IIDgenoprou1 "options" "generic; for routers"
16400 .scindex IIDgenoprou2 "generic options" "router"
16401 This chapter describes the generic options that apply to all routers.
16402 Those that are preconditions are marked with ‡ in the &"use"& field.
16404 For a general description of how a router operates, see sections
16405 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
16406 which the preconditions are tested. The order of expansion of the options that
16407 provide data for a transport is: &%errors_to%&, &%headers_add%&,
16408 &%headers_remove%&, &%transport%&.
16412 .option address_data routers string&!! unset
16413 .cindex "router" "data attached to address"
16414 The string is expanded just before the router is run, that is, after all the
16415 precondition tests have succeeded. If the expansion is forced to fail, the
16416 router declines, the value of &%address_data%& remains unchanged, and the
16417 &%more%& option controls what happens next. Other expansion failures cause
16418 delivery of the address to be deferred.
16420 .vindex "&$address_data$&"
16421 When the expansion succeeds, the value is retained with the address, and can be
16422 accessed using the variable &$address_data$& in the current router, subsequent
16423 routers, and the eventual transport.
16425 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
16426 that runs a user's filter file, the contents of &$address_data$& are accessible
16427 in the filter. This is not normally a problem, because such data is usually
16428 either not confidential or it &"belongs"& to the current user, but if you do
16429 put confidential data into &$address_data$& you need to remember this point.
16431 Even if the router declines or passes, the value of &$address_data$& remains
16432 with the address, though it can be changed by another &%address_data%& setting
16433 on a subsequent router. If a router generates child addresses, the value of
16434 &$address_data$& propagates to them. This also applies to the special kind of
16435 &"child"& that is generated by a router with the &%unseen%& option.
16437 The idea of &%address_data%& is that you can use it to look up a lot of data
16438 for the address once, and then pick out parts of the data later. For example,
16439 you could use a single LDAP lookup to return a string of the form
16441 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
16443 In the transport you could pick out the mailbox by a setting such as
16445 file = ${extract{mailbox}{$address_data}}
16447 This makes the configuration file less messy, and also reduces the number of
16448 lookups (though Exim does cache lookups).
16450 .vindex "&$sender_address_data$&"
16451 .vindex "&$address_data$&"
16452 The &%address_data%& facility is also useful as a means of passing information
16453 from one router to another, and from a router to a transport. In addition, if
16454 &$address_data$& is set by a router when verifying a recipient address from an
16455 ACL, it remains available for use in the rest of the ACL statement. After
16456 verifying a sender, the value is transferred to &$sender_address_data$&.
16460 .option address_test routers&!? boolean true
16462 .cindex "router" "skipping when address testing"
16463 If this option is set false, the router is skipped when routing is being tested
16464 by means of the &%-bt%& command line option. This can be a convenience when
16465 your first router sends messages to an external scanner, because it saves you
16466 having to set the &"already scanned"& indicator when testing real address
16471 .option cannot_route_message routers string&!! unset
16472 .cindex "router" "customizing &""cannot route""& message"
16473 .cindex "customizing" "&""cannot route""& message"
16474 This option specifies a text message that is used when an address cannot be
16475 routed because Exim has run out of routers. The default message is
16476 &"Unrouteable address"&. This option is useful only on routers that have
16477 &%more%& set false, or on the very last router in a configuration, because the
16478 value that is used is taken from the last router that is considered. This
16479 includes a router that is skipped because its preconditions are not met, as
16480 well as a router that declines. For example, using the default configuration,
16483 cannot_route_message = Remote domain not found in DNS
16485 on the first router, which is a &(dnslookup)& router with &%more%& set false,
16488 cannot_route_message = Unknown local user
16490 on the final router that checks for local users. If string expansion fails for
16491 this option, the default message is used. Unless the expansion failure was
16492 explicitly forced, a message about the failure is written to the main and panic
16493 logs, in addition to the normal message about the routing failure.
16496 .option caseful_local_part routers boolean false
16497 .cindex "case of local parts"
16498 .cindex "router" "case of local parts"
16499 By default, routers handle the local parts of addresses in a case-insensitive
16500 manner, though the actual case is preserved for transmission with the message.
16501 If you want the case of letters to be significant in a router, you must set
16502 this option true. For individual router options that contain address or local
16503 part lists (for example, &%local_parts%&), case-sensitive matching can be
16504 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
16507 .vindex "&$local_part$&"
16508 .vindex "&$original_local_part$&"
16509 .vindex "&$parent_local_part$&"
16510 The value of the &$local_part$& variable is forced to lower case while a
16511 router is running unless &%caseful_local_part%& is set. When a router assigns
16512 an address to a transport, the value of &$local_part$& when the transport runs
16513 is the same as it was in the router. Similarly, when a router generates child
16514 addresses by aliasing or forwarding, the values of &$original_local_part$&
16515 and &$parent_local_part$& are those that were used by the redirecting router.
16517 This option applies to the processing of an address by a router. When a
16518 recipient address is being processed in an ACL, there is a separate &%control%&
16519 modifier that can be used to specify case-sensitive processing within the ACL
16520 (see section &<<SECTcontrols>>&).
16524 .option check_local_user routers&!? boolean false
16525 .cindex "local user, checking in router"
16526 .cindex "router" "checking for local user"
16527 .cindex "&_/etc/passwd_&"
16529 When this option is true, Exim checks that the local part of the recipient
16530 address (with affixes removed if relevant) is the name of an account on the
16531 local system. The check is done by calling the &[getpwnam()]& function rather
16532 than trying to read &_/etc/passwd_& directly. This means that other methods of
16533 holding password data (such as NIS) are supported. If the local part is a local
16534 user, &$home$& is set from the password data, and can be tested in other
16535 preconditions that are evaluated after this one (the order of evaluation is
16536 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
16537 overridden by &%router_home_directory%&. If the local part is not a local user,
16538 the router is skipped.
16540 If you want to check that the local part is either the name of a local user
16541 or matches something else, you cannot combine &%check_local_user%& with a
16542 setting of &%local_parts%&, because that specifies the logical &'and'& of the
16543 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
16544 setting to achieve this. For example:
16546 local_parts = passwd;$local_part : lsearch;/etc/other/users
16548 Note, however, that the side effects of &%check_local_user%& (such as setting
16549 up a home directory) do not occur when a &(passwd)& lookup is used in a
16550 &%local_parts%& (or any other) precondition.
16554 .option condition routers&!? string&!! unset
16555 .cindex "router" "customized precondition"
16556 This option specifies a general precondition test that has to succeed for the
16557 router to be called. The &%condition%& option is the last precondition to be
16558 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
16559 result is a forced failure, or an empty string, or one of the strings &"0"& or
16560 &"no"& or &"false"& (checked without regard to the case of the letters), the
16561 router is skipped, and the address is offered to the next one.
16563 If the result is any other value, the router is run (as this is the last
16564 precondition to be evaluated, all the other preconditions must be true).
16566 This option is unusual in that multiple &%condition%& options may be present.
16567 All &%condition%& options must succeed.
16569 The &%condition%& option provides a means of applying custom conditions to the
16570 running of routers. Note that in the case of a simple conditional expansion,
16571 the default expansion values are exactly what is wanted. For example:
16573 condition = ${if >{$message_age}{600}}
16575 Because of the default behaviour of the string expansion, this is equivalent to
16577 condition = ${if >{$message_age}{600}{true}{}}
16580 A multiple condition example, which succeeds:
16582 condition = ${if >{$message_age}{600}}
16583 condition = ${if !eq{${lc:$local_part}}{postmaster}}
16587 If the expansion fails (other than forced failure) delivery is deferred. Some
16588 of the other precondition options are common special cases that could in fact
16589 be specified using &%condition%&.
16592 .option debug_print routers string&!! unset
16593 .cindex "testing" "variables in drivers"
16594 If this option is set and debugging is enabled (see the &%-d%& command line
16595 option) or in address-testing mode (see the &%-bt%& command line option),
16596 the string is expanded and included in the debugging output.
16597 If expansion of the string fails, the error message is written to the debugging
16598 output, and Exim carries on processing.
16599 This option is provided to help with checking out the values of variables and
16600 so on when debugging router configurations. For example, if a &%condition%&
16601 option appears not to be working, &%debug_print%& can be used to output the
16602 variables it references. The output happens after checks for &%domains%&,
16603 &%local_parts%&, and &%check_local_user%& but before any other preconditions
16604 are tested. A newline is added to the text if it does not end with one.
16605 The variable &$router_name$& contains the name of the router.
16609 .option disable_logging routers boolean false
16610 If this option is set true, nothing is logged for any routing errors
16611 or for any deliveries caused by this router. You should not set this option
16612 unless you really, really know what you are doing. See also the generic
16613 transport option of the same name.
16616 .option domains routers&!? "domain list&!!" unset
16617 .cindex "router" "restricting to specific domains"
16618 .vindex "&$domain_data$&"
16619 If this option is set, the router is skipped unless the current domain matches
16620 the list. If the match is achieved by means of a file lookup, the data that the
16621 lookup returned for the domain is placed in &$domain_data$& for use in string
16622 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
16623 a list of the order in which preconditions are evaluated.
16627 .option driver routers string unset
16628 This option must always be set. It specifies which of the available routers is
16633 .option errors_to routers string&!! unset
16634 .cindex "envelope sender"
16635 .cindex "router" "changing address for errors"
16636 If a router successfully handles an address, it may assign the address to a
16637 transport for delivery or it may generate child addresses. In both cases, if
16638 there is a delivery problem during later processing, the resulting bounce
16639 message is sent to the address that results from expanding this string,
16640 provided that the address verifies successfully. The &%errors_to%& option is
16641 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
16643 The &%errors_to%& setting associated with an address can be overridden if it
16644 subsequently passes through other routers that have their own &%errors_to%&
16645 settings, or if the message is delivered by a transport with a &%return_path%&
16648 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
16649 the expansion fails to verify, the errors address associated with the incoming
16650 address is used. At top level, this is the envelope sender. A non-forced
16651 expansion failure causes delivery to be deferred.
16653 If an address for which &%errors_to%& has been set ends up being delivered over
16654 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
16655 any bounces that are generated by other MTAs on the delivery route are also
16656 sent there. You can set &%errors_to%& to the empty string by either of these
16662 An expansion item that yields an empty string has the same effect. If you do
16663 this, a locally detected delivery error for addresses processed by this router
16664 no longer gives rise to a bounce message; the error is discarded. If the
16665 address is delivered to a remote host, the return path is set to &`<>`&, unless
16666 overridden by the &%return_path%& option on the transport.
16668 .vindex "&$address_data$&"
16669 If for some reason you want to discard local errors, but use a non-empty
16670 MAIL command for remote delivery, you can preserve the original return
16671 path in &$address_data$& in the router, and reinstate it in the transport by
16672 setting &%return_path%&.
16674 The most common use of &%errors_to%& is to direct mailing list bounces to the
16675 manager of the list, as described in section &<<SECTmailinglists>>&, or to
16676 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
16680 .option expn routers&!? boolean true
16681 .cindex "address" "testing"
16682 .cindex "testing" "addresses"
16683 .cindex "EXPN" "router skipping"
16684 .cindex "router" "skipping for EXPN"
16685 If this option is turned off, the router is skipped when testing an address
16686 as a result of processing an SMTP EXPN command. You might, for example,
16687 want to turn it off on a router for users' &_.forward_& files, while leaving it
16688 on for the system alias file.
16689 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16692 The use of the SMTP EXPN command is controlled by an ACL (see chapter
16693 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
16694 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
16698 .option fail_verify routers boolean false
16699 .cindex "router" "forcing verification failure"
16700 Setting this option has the effect of setting both &%fail_verify_sender%& and
16701 &%fail_verify_recipient%& to the same value.
16705 .option fail_verify_recipient routers boolean false
16706 If this option is true and an address is accepted by this router when
16707 verifying a recipient, verification fails.
16711 .option fail_verify_sender routers boolean false
16712 If this option is true and an address is accepted by this router when
16713 verifying a sender, verification fails.
16717 .option fallback_hosts routers "string list" unset
16718 .cindex "router" "fallback hosts"
16719 .cindex "fallback" "hosts specified on router"
16720 String expansion is not applied to this option. The argument must be a
16721 colon-separated list of host names or IP addresses. The list separator can be
16722 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
16723 each name or address. In fact, the format of each item is exactly the same as
16724 defined for the list of hosts in a &(manualroute)& router (see section
16725 &<<SECTformatonehostitem>>&).
16727 If a router queues an address for a remote transport, this host list is
16728 associated with the address, and used instead of the transport's fallback host
16729 list. If &%hosts_randomize%& is set on the transport, the order of the list is
16730 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
16731 transport for further details.
16734 .option group routers string&!! "see below"
16735 .cindex "gid (group id)" "local delivery"
16736 .cindex "local transports" "uid and gid"
16737 .cindex "transport" "local"
16738 .cindex "router" "setting group"
16739 When a router queues an address for a transport, and the transport does not
16740 specify a group, the group given here is used when running the delivery
16742 The group may be specified numerically or by name. If expansion fails, the
16743 error is logged and delivery is deferred.
16744 The default is unset, unless &%check_local_user%& is set, when the default
16745 is taken from the password information. See also &%initgroups%& and &%user%&
16746 and the discussion in chapter &<<CHAPenvironment>>&.
16750 .option headers_add routers string&!! unset
16751 .cindex "header lines" "adding"
16752 .cindex "router" "adding header lines"
16753 This option specifies a string of text that is expanded at routing time, and
16754 associated with any addresses that are accepted by the router. However, this
16755 option has no effect when an address is just being verified. The way in which
16756 the text is used to add header lines at transport time is described in section
16757 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
16758 message is in the process of being transported. This means that references to
16759 header lines in string expansions in the transport's configuration do not
16760 &"see"& the added header lines.
16762 The &%headers_add%& option is expanded after &%errors_to%&, but before
16763 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
16764 the expansion is forced to fail, the option has no effect. Other expansion
16765 failures are treated as configuration errors.
16767 Unlike most options, &%headers_add%& can be specified multiple times
16768 for a router; all listed headers are added.
16770 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
16771 router that has the &%one_time%& option set.
16773 .cindex "duplicate addresses"
16774 .oindex "&%unseen%&"
16775 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16776 additions are deleted when the address is passed on to subsequent routers.
16777 For a &%redirect%& router, if a generated address is the same as the incoming
16778 address, this can lead to duplicate addresses with different header
16779 modifications. Exim does not do duplicate deliveries (except, in certain
16780 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
16781 which of the duplicates is discarded, so this ambiguous situation should be
16782 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
16786 .option headers_remove routers string&!! unset
16787 .cindex "header lines" "removing"
16788 .cindex "router" "removing header lines"
16789 This option specifies a string of text that is expanded at routing time, and
16790 associated with any addresses that are accepted by the router. However, this
16791 option has no effect when an address is just being verified. The way in which
16792 the text is used to remove header lines at transport time is described in
16793 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
16794 the message is in the process of being transported. This means that references
16795 to header lines in string expansions in the transport's configuration still
16796 &"see"& the original header lines.
16798 The &%headers_remove%& option is expanded after &%errors_to%& and
16799 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
16800 the option has no effect. Other expansion failures are treated as configuration
16803 Unlike most options, &%headers_remove%& can be specified multiple times
16804 for a router; all listed headers are removed.
16806 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
16807 router that has the &%one_time%& option set.
16809 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16810 removal requests are deleted when the address is passed on to subsequent
16811 routers, and this can lead to problems with duplicates -- see the similar
16812 warning for &%headers_add%& above.
16815 .option ignore_target_hosts routers "host list&!!" unset
16816 .cindex "IP address" "discarding"
16817 .cindex "router" "discarding IP addresses"
16818 Although this option is a host list, it should normally contain IP address
16819 entries rather than names. If any host that is looked up by the router has an
16820 IP address that matches an item in this list, Exim behaves as if that IP
16821 address did not exist. This option allows you to cope with rogue DNS entries
16824 remote.domain.example. A 127.0.0.1
16828 ignore_target_hosts = 127.0.0.1
16830 on the relevant router. If all the hosts found by a &(dnslookup)& router are
16831 discarded in this way, the router declines. In a conventional configuration, an
16832 attempt to mail to such a domain would normally provoke the &"unrouteable
16833 domain"& error, and an attempt to verify an address in the domain would fail.
16834 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
16835 router declines if presented with one of the listed addresses.
16837 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
16838 means of the first or the second of the following settings, respectively:
16840 ignore_target_hosts = 0.0.0.0/0
16841 ignore_target_hosts = <; 0::0/0
16843 The pattern in the first line matches all IPv4 addresses, whereas the pattern
16844 in the second line matches all IPv6 addresses.
16846 This option may also be useful for ignoring link-local and site-local IPv6
16847 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
16848 is expanded before use as a list, it is possible to make it dependent on the
16849 domain that is being routed.
16851 .vindex "&$host_address$&"
16852 During its expansion, &$host_address$& is set to the IP address that is being
16855 .option initgroups routers boolean false
16856 .cindex "additional groups"
16857 .cindex "groups" "additional"
16858 .cindex "local transports" "uid and gid"
16859 .cindex "transport" "local"
16860 If the router queues an address for a transport, and this option is true, and
16861 the uid supplied by the router is not overridden by the transport, the
16862 &[initgroups()]& function is called when running the transport to ensure that
16863 any additional groups associated with the uid are set up. See also &%group%&
16864 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
16868 .option local_part_prefix routers&!? "string list" unset
16869 .cindex "router" "prefix for local part"
16870 .cindex "prefix" "for local part, used in router"
16871 If this option is set, the router is skipped unless the local part starts with
16872 one of the given strings, or &%local_part_prefix_optional%& is true. See
16873 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
16876 The list is scanned from left to right, and the first prefix that matches is
16877 used. A limited form of wildcard is available; if the prefix begins with an
16878 asterisk, it matches the longest possible sequence of arbitrary characters at
16879 the start of the local part. An asterisk should therefore always be followed by
16880 some character that does not occur in normal local parts.
16881 .cindex "multiple mailboxes"
16882 .cindex "mailbox" "multiple"
16883 Wildcarding can be used to set up multiple user mailboxes, as described in
16884 section &<<SECTmulbox>>&.
16886 .vindex "&$local_part$&"
16887 .vindex "&$local_part_prefix$&"
16888 During the testing of the &%local_parts%& option, and while the router is
16889 running, the prefix is removed from the local part, and is available in the
16890 expansion variable &$local_part_prefix$&. When a message is being delivered, if
16891 the router accepts the address, this remains true during subsequent delivery by
16892 a transport. In particular, the local part that is transmitted in the RCPT
16893 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
16894 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
16895 the relevant transport.
16897 When an address is being verified, &%local_part_prefix%& affects only the
16898 behaviour of the router. If the callout feature of verification is in use, this
16899 means that the full address, including the prefix, will be used during the
16902 The prefix facility is commonly used to handle local parts of the form
16903 &%owner-something%&. Another common use is to support local parts of the form
16904 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
16905 to tell a user their forwarding is broken &-- by placing a router like this one
16906 immediately before the router that handles &_.forward_& files:
16910 local_part_prefix = real-
16912 transport = local_delivery
16914 For security, it would probably be a good idea to restrict the use of this
16915 router to locally-generated messages, using a condition such as this:
16917 condition = ${if match {$sender_host_address}\
16918 {\N^(|127\.0\.0\.1)$\N}}
16921 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
16922 both conditions must be met if not optional. Care must be taken if wildcards
16923 are used in both a prefix and a suffix on the same router. Different
16924 separator characters must be used to avoid ambiguity.
16927 .option local_part_prefix_optional routers boolean false
16928 See &%local_part_prefix%& above.
16932 .option local_part_suffix routers&!? "string list" unset
16933 .cindex "router" "suffix for local part"
16934 .cindex "suffix for local part" "used in router"
16935 This option operates in the same way as &%local_part_prefix%&, except that the
16936 local part must end (rather than start) with the given string, the
16937 &%local_part_suffix_optional%& option determines whether the suffix is
16938 mandatory, and the wildcard * character, if present, must be the last
16939 character of the suffix. This option facility is commonly used to handle local
16940 parts of the form &%something-request%& and multiple user mailboxes of the form
16944 .option local_part_suffix_optional routers boolean false
16945 See &%local_part_suffix%& above.
16949 .option local_parts routers&!? "local part list&!!" unset
16950 .cindex "router" "restricting to specific local parts"
16951 .cindex "local part" "checking in router"
16952 The router is run only if the local part of the address matches the list.
16953 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16955 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
16956 string is expanded, it is possible to make it depend on the domain, for
16959 local_parts = dbm;/usr/local/specials/$domain
16961 .vindex "&$local_part_data$&"
16962 If the match is achieved by a lookup, the data that the lookup returned
16963 for the local part is placed in the variable &$local_part_data$& for use in
16964 expansions of the router's private options. You might use this option, for
16965 example, if you have a large number of local virtual domains, and you want to
16966 send all postmaster mail to the same place without having to set up an alias in
16967 each virtual domain:
16971 local_parts = postmaster
16972 data = postmaster@real.domain.example
16976 .option log_as_local routers boolean "see below"
16977 .cindex "log" "delivery line"
16978 .cindex "delivery" "log line format"
16979 Exim has two logging styles for delivery, the idea being to make local
16980 deliveries stand out more visibly from remote ones. In the &"local"& style, the
16981 recipient address is given just as the local part, without a domain. The use of
16982 this style is controlled by this option. It defaults to true for the &(accept)&
16983 router, and false for all the others. This option applies only when a
16984 router assigns an address to a transport. It has no effect on routers that
16985 redirect addresses.
16989 .option more routers boolean&!! true
16990 The result of string expansion for this option must be a valid boolean value,
16991 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16992 result causes an error, and delivery is deferred. If the expansion is forced to
16993 fail, the default value for the option (true) is used. Other failures cause
16994 delivery to be deferred.
16996 If this option is set false, and the router declines to handle the address, no
16997 further routers are tried, routing fails, and the address is bounced.
16999 However, if the router explicitly passes an address to the following router by
17000 means of the setting
17004 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17005 does not affect the behaviour if one of the precondition tests fails. In that
17006 case, the address is always passed to the next router.
17008 Note that &%address_data%& is not considered to be a precondition. If its
17009 expansion is forced to fail, the router declines, and the value of &%more%&
17010 controls what happens next.
17013 .option pass_on_timeout routers boolean false
17014 .cindex "timeout" "of router"
17015 .cindex "router" "timeout"
17016 If a router times out during a host lookup, it normally causes deferral of the
17017 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17018 router, overriding &%no_more%&. This may be helpful for systems that are
17019 intermittently connected to the Internet, or those that want to pass to a smart
17020 host any messages that cannot immediately be delivered.
17022 There are occasional other temporary errors that can occur while doing DNS
17023 lookups. They are treated in the same way as a timeout, and this option
17024 applies to all of them.
17028 .option pass_router routers string unset
17029 .cindex "router" "go to after &""pass""&"
17030 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17031 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17032 routing to continue, and overriding a false setting of &%more%&. When one of
17033 these routers returns &"pass"&, the address is normally handed on to the next
17034 router in sequence. This can be changed by setting &%pass_router%& to the name
17035 of another router. However (unlike &%redirect_router%&) the named router must
17036 be below the current router, to avoid loops. Note that this option applies only
17037 to the special case of &"pass"&. It does not apply when a router returns
17038 &"decline"& because it cannot handle an address.
17042 .option redirect_router routers string unset
17043 .cindex "router" "start at after redirection"
17044 Sometimes an administrator knows that it is pointless to reprocess addresses
17045 generated from alias or forward files with the same router again. For
17046 example, if an alias file translates real names into login ids there is no
17047 point searching the alias file a second time, especially if it is a large file.
17049 The &%redirect_router%& option can be set to the name of any router instance.
17050 It causes the routing of any generated addresses to start at the named router
17051 instead of at the first router. This option has no effect if the router in
17052 which it is set does not generate new addresses.
17056 .option require_files routers&!? "string list&!!" unset
17057 .cindex "file" "requiring for router"
17058 .cindex "router" "requiring file existence"
17059 This option provides a general mechanism for predicating the running of a
17060 router on the existence or non-existence of certain files or directories.
17061 Before running a router, as one of its precondition tests, Exim works its way
17062 through the &%require_files%& list, expanding each item separately.
17064 Because the list is split before expansion, any colons in expansion items must
17065 be doubled, or the facility for using a different list separator must be used.
17066 If any expansion is forced to fail, the item is ignored. Other expansion
17067 failures cause routing of the address to be deferred.
17069 If any expanded string is empty, it is ignored. Otherwise, except as described
17070 below, each string must be a fully qualified file path, optionally preceded by
17071 &"!"&. The paths are passed to the &[stat()]& function to test for the
17072 existence of the files or directories. The router is skipped if any paths not
17073 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17076 If &[stat()]& cannot determine whether a file exists or not, delivery of
17077 the message is deferred. This can happen when NFS-mounted filesystems are
17080 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17081 options, so you cannot use it to check for the existence of a file in which to
17082 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17083 full list of the order in which preconditions are evaluated.) However, as
17084 these options are all expanded, you can use the &%exists%& expansion condition
17085 to make such tests. The &%require_files%& option is intended for checking files
17086 that the router may be going to use internally, or which are needed by a
17087 transport (for example &_.procmailrc_&).
17089 During delivery, the &[stat()]& function is run as root, but there is a
17090 facility for some checking of the accessibility of a file by another user.
17091 This is not a proper permissions check, but just a &"rough"& check that
17092 operates as follows:
17094 If an item in a &%require_files%& list does not contain any forward slash
17095 characters, it is taken to be the user (and optional group, separated by a
17096 comma) to be checked for subsequent files in the list. If no group is specified
17097 but the user is specified symbolically, the gid associated with the uid is
17100 require_files = mail:/some/file
17101 require_files = $local_part:$home/.procmailrc
17103 If a user or group name in a &%require_files%& list does not exist, the
17104 &%require_files%& condition fails.
17106 Exim performs the check by scanning along the components of the file path, and
17107 checking the access for the given uid and gid. It checks for &"x"& access on
17108 directories, and &"r"& access on the final file. Note that this means that file
17109 access control lists, if the operating system has them, are ignored.
17111 &*Warning 1*&: When the router is being run to verify addresses for an
17112 incoming SMTP message, Exim is not running as root, but under its own uid. This
17113 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17114 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17115 user is not permitted to read one of the directories on the file's path.
17117 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17118 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17119 without root access. In this case, if a check for access by a particular user
17120 is requested, Exim creates a subprocess that runs as that user, and tries the
17121 check again in that process.
17123 The default action for handling an unresolved EACCES is to consider it to
17124 be caused by a configuration error, and routing is deferred because the
17125 existence or non-existence of the file cannot be determined. However, in some
17126 circumstances it may be desirable to treat this condition as if the file did
17127 not exist. If the file name (or the exclamation mark that precedes the file
17128 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17129 as if the file did not exist. For example:
17131 require_files = +/some/file
17133 If the router is not an essential part of verification (for example, it
17134 handles users' &_.forward_& files), another solution is to set the &%verify%&
17135 option false so that the router is skipped when verifying.
17139 .option retry_use_local_part routers boolean "see below"
17140 .cindex "hints database" "retry keys"
17141 .cindex "local part" "in retry keys"
17142 When a delivery suffers a temporary routing failure, a retry record is created
17143 in Exim's hints database. For addresses whose routing depends only on the
17144 domain, the key for the retry record should not involve the local part, but for
17145 other addresses, both the domain and the local part should be included.
17146 Usually, remote routing is of the former kind, and local routing is of the
17149 This option controls whether the local part is used to form the key for retry
17150 hints for addresses that suffer temporary errors while being handled by this
17151 router. The default value is true for any router that has &%check_local_user%&
17152 set, and false otherwise. Note that this option does not apply to hints keys
17153 for transport delays; they are controlled by a generic transport option of the
17156 The setting of &%retry_use_local_part%& applies only to the router on which it
17157 appears. If the router generates child addresses, they are routed
17158 independently; this setting does not become attached to them.
17162 .option router_home_directory routers string&!! unset
17163 .cindex "router" "home directory for"
17164 .cindex "home directory" "for router"
17166 This option sets a home directory for use while the router is running. (Compare
17167 &%transport_home_directory%&, which sets a home directory for later
17168 transporting.) In particular, if used on a &(redirect)& router, this option
17169 sets a value for &$home$& while a filter is running. The value is expanded;
17170 forced expansion failure causes the option to be ignored &-- other failures
17171 cause the router to defer.
17173 Expansion of &%router_home_directory%& happens immediately after the
17174 &%check_local_user%& test (if configured), before any further expansions take
17176 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17178 While the router is running, &%router_home_directory%& overrides the value of
17179 &$home$& that came from &%check_local_user%&.
17181 When a router accepts an address and assigns it to a local transport (including
17182 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17183 delivery), the home directory setting for the transport is taken from the first
17184 of these values that is set:
17187 The &%home_directory%& option on the transport;
17189 The &%transport_home_directory%& option on the router;
17191 The password data if &%check_local_user%& is set on the router;
17193 The &%router_home_directory%& option on the router.
17196 In other words, &%router_home_directory%& overrides the password data for the
17197 router, but not for the transport.
17201 .option self routers string freeze
17202 .cindex "MX record" "pointing to local host"
17203 .cindex "local host" "MX pointing to"
17204 This option applies to those routers that use a recipient address to find a
17205 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17206 and &(manualroute)& routers.
17207 Certain configurations of the &(queryprogram)& router can also specify a list
17209 Usually such routers are configured to send the message to a remote host via an
17210 &(smtp)& transport. The &%self%& option specifies what happens when the first
17211 host on the list turns out to be the local host.
17212 The way in which Exim checks for the local host is described in section
17213 &<<SECTreclocipadd>>&.
17215 Normally this situation indicates either an error in Exim's configuration (for
17216 example, the router should be configured not to process this domain), or an
17217 error in the DNS (for example, the MX should not point to this host). For this
17218 reason, the default action is to log the incident, defer the address, and
17219 freeze the message. The following alternatives are provided for use in special
17224 Delivery of the message is tried again later, but the message is not frozen.
17226 .vitem "&%reroute%&: <&'domain'&>"
17227 The domain is changed to the given domain, and the address is passed back to
17228 be reprocessed by the routers. No rewriting of headers takes place. This
17229 behaviour is essentially a redirection.
17231 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17232 The domain is changed to the given domain, and the address is passed back to be
17233 reprocessed by the routers. Any headers that contain the original domain are
17238 .vindex "&$self_hostname$&"
17239 The router passes the address to the next router, or to the router named in the
17240 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17241 subsequent routing and delivery, the variable &$self_hostname$& contains the
17242 name of the local host that the router encountered. This can be used to
17243 distinguish between different cases for hosts with multiple names. The
17249 ensures that only those addresses that routed to the local host are passed on.
17250 Without &%no_more%&, addresses that were declined for other reasons would also
17251 be passed to the next router.
17254 Delivery fails and an error report is generated.
17257 .cindex "local host" "sending to"
17258 The anomaly is ignored and the address is queued for the transport. This
17259 setting should be used with extreme caution. For an &(smtp)& transport, it
17260 makes sense only in cases where the program that is listening on the SMTP port
17261 is not this version of Exim. That is, it must be some other MTA, or Exim with a
17262 different configuration file that handles the domain in another way.
17267 .option senders routers&!? "address list&!!" unset
17268 .cindex "router" "checking senders"
17269 If this option is set, the router is skipped unless the message's sender
17270 address matches something on the list.
17271 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17274 There are issues concerning verification when the running of routers is
17275 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
17276 setting, it sets the sender to the null string. When using the &%-bt%& option
17277 to check a configuration file, it is necessary also to use the &%-f%& option to
17278 set an appropriate sender. For incoming mail, the sender is unset when
17279 verifying the sender, but is available when verifying any recipients. If the
17280 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
17284 .option translate_ip_address routers string&!! unset
17285 .cindex "IP address" "translating"
17286 .cindex "packet radio"
17287 .cindex "router" "IP address translation"
17288 There exist some rare networking situations (for example, packet radio) where
17289 it is helpful to be able to translate IP addresses generated by normal routing
17290 mechanisms into other IP addresses, thus performing a kind of manual IP
17291 routing. This should be done only if the normal IP routing of the TCP/IP stack
17292 is inadequate or broken. Because this is an extremely uncommon requirement, the
17293 code to support this option is not included in the Exim binary unless
17294 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
17296 .vindex "&$host_address$&"
17297 The &%translate_ip_address%& string is expanded for every IP address generated
17298 by the router, with the generated address set in &$host_address$&. If the
17299 expansion is forced to fail, no action is taken.
17300 For any other expansion error, delivery of the message is deferred.
17301 If the result of the expansion is an IP address, that replaces the original
17302 address; otherwise the result is assumed to be a host name &-- this is looked
17303 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
17304 produce one or more replacement IP addresses. For example, to subvert all IP
17305 addresses in some specific networks, this could be added to a router:
17307 translate_ip_address = \
17308 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
17311 The file would contain lines like
17313 10.2.3.128/26 some.host
17314 10.8.4.34/26 10.44.8.15
17316 You should not make use of this facility unless you really understand what you
17321 .option transport routers string&!! unset
17322 This option specifies the transport to be used when a router accepts an address
17323 and sets it up for delivery. A transport is never needed if a router is used
17324 only for verification. The value of the option is expanded at routing time,
17325 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
17326 and result must be the name of one of the configured transports. If it is not,
17327 delivery is deferred.
17329 The &%transport%& option is not used by the &(redirect)& router, but it does
17330 have some private options that set up transports for pipe and file deliveries
17331 (see chapter &<<CHAPredirect>>&).
17335 .option transport_current_directory routers string&!! unset
17336 .cindex "current directory for local transport"
17337 This option associates a current directory with any address that is routed
17338 to a local transport. This can happen either because a transport is
17339 explicitly configured for the router, or because it generates a delivery to a
17340 file or a pipe. During the delivery process (that is, at transport time), this
17341 option string is expanded and is set as the current directory, unless
17342 overridden by a setting on the transport.
17343 If the expansion fails for any reason, including forced failure, an error is
17344 logged, and delivery is deferred.
17345 See chapter &<<CHAPenvironment>>& for details of the local delivery
17351 .option transport_home_directory routers string&!! "see below"
17352 .cindex "home directory" "for local transport"
17353 This option associates a home directory with any address that is routed to a
17354 local transport. This can happen either because a transport is explicitly
17355 configured for the router, or because it generates a delivery to a file or a
17356 pipe. During the delivery process (that is, at transport time), the option
17357 string is expanded and is set as the home directory, unless overridden by a
17358 setting of &%home_directory%& on the transport.
17359 If the expansion fails for any reason, including forced failure, an error is
17360 logged, and delivery is deferred.
17362 If the transport does not specify a home directory, and
17363 &%transport_home_directory%& is not set for the router, the home directory for
17364 the transport is taken from the password data if &%check_local_user%& is set for
17365 the router. Otherwise it is taken from &%router_home_directory%& if that option
17366 is set; if not, no home directory is set for the transport.
17368 See chapter &<<CHAPenvironment>>& for further details of the local delivery
17374 .option unseen routers boolean&!! false
17375 .cindex "router" "carrying on after success"
17376 The result of string expansion for this option must be a valid boolean value,
17377 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17378 result causes an error, and delivery is deferred. If the expansion is forced to
17379 fail, the default value for the option (false) is used. Other failures cause
17380 delivery to be deferred.
17382 When this option is set true, routing does not cease if the router accepts the
17383 address. Instead, a copy of the incoming address is passed to the next router,
17384 overriding a false setting of &%more%&. There is little point in setting
17385 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
17386 the value of &%unseen%& contains expansion items (and therefore, presumably, is
17387 sometimes true and sometimes false).
17389 .cindex "copy of message (&%unseen%& option)"
17390 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
17391 qualifier in filter files. It can be used to cause copies of messages to be
17392 delivered to some other destination, while also carrying out a normal delivery.
17393 In effect, the current address is made into a &"parent"& that has two children
17394 &-- one that is delivered as specified by this router, and a clone that goes on
17395 to be routed further. For this reason, &%unseen%& may not be combined with the
17396 &%one_time%& option in a &(redirect)& router.
17398 &*Warning*&: Header lines added to the address (or specified for removal) by
17399 this router or by previous routers affect the &"unseen"& copy of the message
17400 only. The clone that continues to be processed by further routers starts with
17401 no added headers and none specified for removal. For a &%redirect%& router, if
17402 a generated address is the same as the incoming address, this can lead to
17403 duplicate addresses with different header modifications. Exim does not do
17404 duplicate deliveries (except, in certain circumstances, to pipes -- see section
17405 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
17406 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
17407 &%redirect%& router may be of help.
17409 Unlike the handling of header modifications, any data that was set by the
17410 &%address_data%& option in the current or previous routers &'is'& passed on to
17411 subsequent routers.
17414 .option user routers string&!! "see below"
17415 .cindex "uid (user id)" "local delivery"
17416 .cindex "local transports" "uid and gid"
17417 .cindex "transport" "local"
17418 .cindex "router" "user for filter processing"
17419 .cindex "filter" "user for processing"
17420 When a router queues an address for a transport, and the transport does not
17421 specify a user, the user given here is used when running the delivery process.
17422 The user may be specified numerically or by name. If expansion fails, the
17423 error is logged and delivery is deferred.
17424 This user is also used by the &(redirect)& router when running a filter file.
17425 The default is unset, except when &%check_local_user%& is set. In this case,
17426 the default is taken from the password information. If the user is specified as
17427 a name, and &%group%& is not set, the group associated with the user is used.
17428 See also &%initgroups%& and &%group%& and the discussion in chapter
17429 &<<CHAPenvironment>>&.
17433 .option verify routers&!? boolean true
17434 Setting this option has the effect of setting &%verify_sender%& and
17435 &%verify_recipient%& to the same value.
17438 .option verify_only routers&!? boolean false
17439 .cindex "EXPN" "with &%verify_only%&"
17441 .cindex "router" "used only when verifying"
17442 If this option is set, the router is used only when verifying an address,
17443 delivering in cutthrough mode or
17444 testing with the &%-bv%& option, not when actually doing a delivery, testing
17445 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
17446 restricted to verifying only senders or recipients by means of
17447 &%verify_sender%& and &%verify_recipient%&.
17449 &*Warning*&: When the router is being run to verify addresses for an incoming
17450 SMTP message, Exim is not running as root, but under its own uid. If the router
17451 accesses any files, you need to make sure that they are accessible to the Exim
17455 .option verify_recipient routers&!? boolean true
17456 If this option is false, the router is skipped when verifying recipient
17458 delivering in cutthrough mode
17459 or testing recipient verification using &%-bv%&.
17460 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17464 .option verify_sender routers&!? boolean true
17465 If this option is false, the router is skipped when verifying sender addresses
17466 or testing sender verification using &%-bvs%&.
17467 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17469 .ecindex IIDgenoprou1
17470 .ecindex IIDgenoprou2
17477 . ////////////////////////////////////////////////////////////////////////////
17478 . ////////////////////////////////////////////////////////////////////////////
17480 .chapter "The accept router" "CHID4"
17481 .cindex "&(accept)& router"
17482 .cindex "routers" "&(accept)&"
17483 The &(accept)& router has no private options of its own. Unless it is being
17484 used purely for verification (see &%verify_only%&) a transport is required to
17485 be defined by the generic &%transport%& option. If the preconditions that are
17486 specified by generic options are met, the router accepts the address and queues
17487 it for the given transport. The most common use of this router is for setting
17488 up deliveries to local mailboxes. For example:
17492 domains = mydomain.example
17494 transport = local_delivery
17496 The &%domains%& condition in this example checks the domain of the address, and
17497 &%check_local_user%& checks that the local part is the login of a local user.
17498 When both preconditions are met, the &(accept)& router runs, and queues the
17499 address for the &(local_delivery)& transport.
17506 . ////////////////////////////////////////////////////////////////////////////
17507 . ////////////////////////////////////////////////////////////////////////////
17509 .chapter "The dnslookup router" "CHAPdnslookup"
17510 .scindex IIDdnsrou1 "&(dnslookup)& router"
17511 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
17512 The &(dnslookup)& router looks up the hosts that handle mail for the
17513 recipient's domain in the DNS. A transport must always be set for this router,
17514 unless &%verify_only%& is set.
17516 If SRV support is configured (see &%check_srv%& below), Exim first searches for
17517 SRV records. If none are found, or if SRV support is not configured,
17518 MX records are looked up. If no MX records exist, address records are sought.
17519 However, &%mx_domains%& can be set to disable the direct use of address
17522 MX records of equal priority are sorted by Exim into a random order. Exim then
17523 looks for address records for the host names obtained from MX or SRV records.
17524 When a host has more than one IP address, they are sorted into a random order,
17525 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
17526 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
17527 generic option, the router declines.
17529 Unless they have the highest priority (lowest MX value), MX records that point
17530 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
17531 are discarded, together with any other MX records of equal or lower priority.
17533 .cindex "MX record" "pointing to local host"
17534 .cindex "local host" "MX pointing to"
17535 .oindex "&%self%&" "in &(dnslookup)& router"
17536 If the host pointed to by the highest priority MX record, or looked up as an
17537 address record, is the local host, or matches &%hosts_treat_as_local%&, what
17538 happens is controlled by the generic &%self%& option.
17541 .section "Problems with DNS lookups" "SECTprowitdnsloo"
17542 There have been problems with DNS servers when SRV records are looked up.
17543 Some mis-behaving servers return a DNS error or timeout when a non-existent
17544 SRV record is sought. Similar problems have in the past been reported for
17545 MX records. The global &%dns_again_means_nonexist%& option can help with this
17546 problem, but it is heavy-handed because it is a global option.
17548 For this reason, there are two options, &%srv_fail_domains%& and
17549 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
17550 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
17551 an attempt to look up an SRV or MX record causes one of these results, and the
17552 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
17553 such record"&. In the case of an SRV lookup, this means that the router
17554 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
17555 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
17556 case routing fails.
17559 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
17560 .cindex "&(dnslookup)& router" "declines"
17561 There are a few cases where a &(dnslookup)& router will decline to accept
17562 an address; if such a router is expected to handle "all remaining non-local
17563 domains", then it is important to set &%no_more%&.
17565 Reasons for a &(dnslookup)& router to decline currently include:
17567 The domain does not exist in DNS
17569 The domain exists but the MX record's host part is just "."; this is a common
17570 convention (borrowed from SRV) used to indicate that there is no such service
17571 for this domain and to not fall back to trying A/AAAA records.
17573 Ditto, but for SRV records, when &%check_srv%& is set on this router.
17575 MX record points to a non-existent host.
17577 MX record points to an IP address and the main section option
17578 &%allow_mx_to_ip%& is not set.
17580 MX records exist and point to valid hosts, but all hosts resolve only to
17581 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
17583 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
17584 &%dns_check_names_pattern%& for handling one variant of this)
17586 &%check_secondary_mx%& is set on this router but the local host can
17587 not be found in the MX records (see below)
17593 .section "Private options for dnslookup" "SECID118"
17594 .cindex "options" "&(dnslookup)& router"
17595 The private options for the &(dnslookup)& router are as follows:
17597 .option check_secondary_mx dnslookup boolean false
17598 .cindex "MX record" "checking for secondary"
17599 If this option is set, the router declines unless the local host is found in
17600 (and removed from) the list of hosts obtained by MX lookup. This can be used to
17601 process domains for which the local host is a secondary mail exchanger
17602 differently to other domains. The way in which Exim decides whether a host is
17603 the local host is described in section &<<SECTreclocipadd>>&.
17606 .option check_srv dnslookup string&!! unset
17607 .cindex "SRV record" "enabling use of"
17608 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
17609 addition to MX and address records. The support is disabled by default. To
17610 enable SRV support, set the &%check_srv%& option to the name of the service
17611 required. For example,
17615 looks for SRV records that refer to the normal smtp service. The option is
17616 expanded, so the service name can vary from message to message or address
17617 to address. This might be helpful if SRV records are being used for a
17618 submission service. If the expansion is forced to fail, the &%check_srv%&
17619 option is ignored, and the router proceeds to look for MX records in the
17622 When the expansion succeeds, the router searches first for SRV records for
17623 the given service (it assumes TCP protocol). A single SRV record with a
17624 host name that consists of just a single dot indicates &"no such service for
17625 this domain"&; if this is encountered, the router declines. If other kinds of
17626 SRV record are found, they are used to construct a host list for delivery
17627 according to the rules of RFC 2782. MX records are not sought in this case.
17629 When no SRV records are found, MX records (and address records) are sought in
17630 the traditional way. In other words, SRV records take precedence over MX
17631 records, just as MX records take precedence over address records. Note that
17632 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
17633 defined it. It is apparently believed that MX records are sufficient for email
17634 and that SRV records should not be used for this purpose. However, SRV records
17635 have an additional &"weight"& feature which some people might find useful when
17636 trying to split an SMTP load between hosts of different power.
17638 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
17639 when there is a DNS lookup error.
17643 .option mx_domains dnslookup "domain list&!!" unset
17644 .cindex "MX record" "required to exist"
17645 .cindex "SRV record" "required to exist"
17646 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
17647 record in order to be recognized. (The name of this option could be improved.)
17648 For example, if all the mail hosts in &'fict.example'& are known to have MX
17649 records, except for those in &'discworld.fict.example'&, you could use this
17652 mx_domains = ! *.discworld.fict.example : *.fict.example
17654 This specifies that messages addressed to a domain that matches the list but
17655 has no MX record should be bounced immediately instead of being routed using
17656 the address record.
17659 .option mx_fail_domains dnslookup "domain list&!!" unset
17660 If the DNS lookup for MX records for one of the domains in this list causes a
17661 DNS lookup error, Exim behaves as if no MX records were found. See section
17662 &<<SECTprowitdnsloo>>& for more discussion.
17667 .option qualify_single dnslookup boolean true
17668 .cindex "DNS" "resolver options"
17669 .cindex "DNS" "qualifying single-component names"
17670 When this option is true, the resolver option RES_DEFNAMES is set for DNS
17671 lookups. Typically, but not standardly, this causes the resolver to qualify
17672 single-component names with the default domain. For example, on a machine
17673 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
17674 &'thesaurus.ref.example'& inside the resolver. For details of what your
17675 resolver actually does, consult your man pages for &'resolver'& and
17680 .option rewrite_headers dnslookup boolean true
17681 .cindex "rewriting" "header lines"
17682 .cindex "header lines" "rewriting"
17683 If the domain name in the address that is being processed is not fully
17684 qualified, it may be expanded to its full form by a DNS lookup. For example, if
17685 an address is specified as &'dormouse@teaparty'&, the domain might be
17686 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
17687 occur as a result of setting the &%widen_domains%& option. If
17688 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
17689 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
17690 header lines of the message are rewritten with the full domain name.
17692 This option should be turned off only when it is known that no message is
17693 ever going to be sent outside an environment where the abbreviation makes
17696 When an MX record is looked up in the DNS and matches a wildcard record, name
17697 servers normally return a record containing the name that has been looked up,
17698 making it impossible to detect whether a wildcard was present or not. However,
17699 some name servers have recently been seen to return the wildcard entry. If the
17700 name returned by a DNS lookup begins with an asterisk, it is not used for
17704 .option same_domain_copy_routing dnslookup boolean false
17705 .cindex "address" "copying routing"
17706 Addresses with the same domain are normally routed by the &(dnslookup)& router
17707 to the same list of hosts. However, this cannot be presumed, because the router
17708 options and preconditions may refer to the local part of the address. By
17709 default, therefore, Exim routes each address in a message independently. DNS
17710 servers run caches, so repeated DNS lookups are not normally expensive, and in
17711 any case, personal messages rarely have more than a few recipients.
17713 If you are running mailing lists with large numbers of subscribers at the same
17714 domain, and you are using a &(dnslookup)& router which is independent of the
17715 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17716 lookups for identical domains in one message. In this case, when &(dnslookup)&
17717 routes an address to a remote transport, any other unrouted addresses in the
17718 message that have the same domain are automatically given the same routing
17719 without processing them independently,
17720 provided the following conditions are met:
17723 No router that processed the address specified &%headers_add%& or
17724 &%headers_remove%&.
17726 The router did not change the address in any way, for example, by &"widening"&
17733 .option search_parents dnslookup boolean false
17734 .cindex "DNS" "resolver options"
17735 When this option is true, the resolver option RES_DNSRCH is set for DNS
17736 lookups. This is different from the &%qualify_single%& option in that it
17737 applies to domains containing dots. Typically, but not standardly, it causes
17738 the resolver to search for the name in the current domain and in parent
17739 domains. For example, on a machine in the &'fict.example'& domain, if looking
17740 up &'teaparty.wonderland'& failed, the resolver would try
17741 &'teaparty.wonderland.fict.example'&. For details of what your resolver
17742 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
17744 Setting this option true can cause problems in domains that have a wildcard MX
17745 record, because any domain that does not have its own MX record matches the
17750 .option srv_fail_domains dnslookup "domain list&!!" unset
17751 If the DNS lookup for SRV records for one of the domains in this list causes a
17752 DNS lookup error, Exim behaves as if no SRV records were found. See section
17753 &<<SECTprowitdnsloo>>& for more discussion.
17758 .option widen_domains dnslookup "string list" unset
17759 .cindex "domain" "partial; widening"
17760 If a DNS lookup fails and this option is set, each of its strings in turn is
17761 added onto the end of the domain, and the lookup is tried again. For example,
17764 widen_domains = fict.example:ref.example
17766 is set and a lookup of &'klingon.dictionary'& fails,
17767 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
17768 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
17769 and &%search_parents%& options can cause some widening to be undertaken inside
17770 the DNS resolver. &%widen_domains%& is not applied to sender addresses
17771 when verifying, unless &%rewrite_headers%& is false (not the default).
17774 .section "Effect of qualify_single and search_parents" "SECID119"
17775 When a domain from an envelope recipient is changed by the resolver as a result
17776 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
17777 corresponding address in the message's header lines unless &%rewrite_headers%&
17778 is set false. Exim then re-routes the address, using the full domain.
17780 These two options affect only the DNS lookup that takes place inside the router
17781 for the domain of the address that is being routed. They do not affect lookups
17782 such as that implied by
17786 that may happen while processing a router precondition before the router is
17787 entered. No widening ever takes place for these lookups.
17788 .ecindex IIDdnsrou1
17789 .ecindex IIDdnsrou2
17799 . ////////////////////////////////////////////////////////////////////////////
17800 . ////////////////////////////////////////////////////////////////////////////
17802 .chapter "The ipliteral router" "CHID5"
17803 .cindex "&(ipliteral)& router"
17804 .cindex "domain literal" "routing"
17805 .cindex "routers" "&(ipliteral)&"
17806 This router has no private options. Unless it is being used purely for
17807 verification (see &%verify_only%&) a transport is required to be defined by the
17808 generic &%transport%& option. The router accepts the address if its domain part
17809 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
17810 router handles the address
17814 by setting up delivery to the host with that IP address. IPv4 domain literals
17815 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
17816 are similar, but the address is preceded by &`ipv6:`&. For example:
17818 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
17820 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
17821 grounds that sooner or later somebody will try it.
17823 .oindex "&%self%&" "in &(ipliteral)& router"
17824 If the IP address matches something in &%ignore_target_hosts%&, the router
17825 declines. If an IP literal turns out to refer to the local host, the generic
17826 &%self%& option determines what happens.
17828 The RFCs require support for domain literals; however, their use is
17829 controversial in today's Internet. If you want to use this router, you must
17830 also set the main configuration option &%allow_domain_literals%&. Otherwise,
17831 Exim will not recognize the domain literal syntax in addresses.
17835 . ////////////////////////////////////////////////////////////////////////////
17836 . ////////////////////////////////////////////////////////////////////////////
17838 .chapter "The iplookup router" "CHID6"
17839 .cindex "&(iplookup)& router"
17840 .cindex "routers" "&(iplookup)&"
17841 The &(iplookup)& router was written to fulfil a specific requirement in
17842 Cambridge University (which in fact no longer exists). For this reason, it is
17843 not included in the binary of Exim by default. If you want to include it, you
17846 ROUTER_IPLOOKUP=yes
17848 in your &_Local/Makefile_& configuration file.
17850 The &(iplookup)& router routes an address by sending it over a TCP or UDP
17851 connection to one or more specific hosts. The host can then return the same or
17852 a different address &-- in effect rewriting the recipient address in the
17853 message's envelope. The new address is then passed on to subsequent routers. If
17854 this process fails, the address can be passed on to other routers, or delivery
17855 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
17856 must not be specified for it.
17858 .cindex "options" "&(iplookup)& router"
17859 .option hosts iplookup string unset
17860 This option must be supplied. Its value is a colon-separated list of host
17861 names. The hosts are looked up using &[gethostbyname()]&
17862 (or &[getipnodebyname()]& when available)
17863 and are tried in order until one responds to the query. If none respond, what
17864 happens is controlled by &%optional%&.
17867 .option optional iplookup boolean false
17868 If &%optional%& is true, if no response is obtained from any host, the address
17869 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
17870 delivery to the address is deferred.
17873 .option port iplookup integer 0
17874 .cindex "port" "&(iplookup)& router"
17875 This option must be supplied. It specifies the port number for the TCP or UDP
17879 .option protocol iplookup string udp
17880 This option can be set to &"udp"& or &"tcp"& to specify which of the two
17881 protocols is to be used.
17884 .option query iplookup string&!! "see below"
17885 This defines the content of the query that is sent to the remote hosts. The
17888 $local_part@$domain $local_part@$domain
17890 The repetition serves as a way of checking that a response is to the correct
17891 query in the default case (see &%response_pattern%& below).
17894 .option reroute iplookup string&!! unset
17895 If this option is not set, the rerouted address is precisely the byte string
17896 returned by the remote host, up to the first white space, if any. If set, the
17897 string is expanded to form the rerouted address. It can include parts matched
17898 in the response by &%response_pattern%& by means of numeric variables such as
17899 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
17900 whether or not a pattern is in use. In all cases, the rerouted address must end
17901 up in the form &'local_part@domain'&.
17904 .option response_pattern iplookup string unset
17905 This option can be set to a regular expression that is applied to the string
17906 returned from the remote host. If the pattern does not match the response, the
17907 router declines. If &%response_pattern%& is not set, no checking of the
17908 response is done, unless the query was defaulted, in which case there is a
17909 check that the text returned after the first white space is the original
17910 address. This checks that the answer that has been received is in response to
17911 the correct question. For example, if the response is just a new domain, the
17912 following could be used:
17914 response_pattern = ^([^@]+)$
17915 reroute = $local_part@$1
17918 .option timeout iplookup time 5s
17919 This specifies the amount of time to wait for a response from the remote
17920 machine. The same timeout is used for the &[connect()]& function for a TCP
17921 call. It does not apply to UDP.
17926 . ////////////////////////////////////////////////////////////////////////////
17927 . ////////////////////////////////////////////////////////////////////////////
17929 .chapter "The manualroute router" "CHID7"
17930 .scindex IIDmanrou1 "&(manualroute)& router"
17931 .scindex IIDmanrou2 "routers" "&(manualroute)&"
17932 .cindex "domain" "manually routing"
17933 The &(manualroute)& router is so-called because it provides a way of manually
17934 routing an address according to its domain. It is mainly used when you want to
17935 route addresses to remote hosts according to your own rules, bypassing the
17936 normal DNS routing that looks up MX records. However, &(manualroute)& can also
17937 route to local transports, a facility that may be useful if you want to save
17938 messages for dial-in hosts in local files.
17940 The &(manualroute)& router compares a list of domain patterns with the domain
17941 it is trying to route. If there is no match, the router declines. Each pattern
17942 has associated with it a list of hosts and some other optional data, which may
17943 include a transport. The combination of a pattern and its data is called a
17944 &"routing rule"&. For patterns that do not have an associated transport, the
17945 generic &%transport%& option must specify a transport, unless the router is
17946 being used purely for verification (see &%verify_only%&).
17949 In the case of verification, matching the domain pattern is sufficient for the
17950 router to accept the address. When actually routing an address for delivery,
17951 an address that matches a domain pattern is queued for the associated
17952 transport. If the transport is not a local one, a host list must be associated
17953 with the pattern; IP addresses are looked up for the hosts, and these are
17954 passed to the transport along with the mail address. For local transports, a
17955 host list is optional. If it is present, it is passed in &$host$& as a single
17958 The list of routing rules can be provided as an inline string in
17959 &%route_list%&, or the data can be obtained by looking up the domain in a file
17960 or database by setting &%route_data%&. Only one of these settings may appear in
17961 any one instance of &(manualroute)&. The format of routing rules is described
17962 below, following the list of private options.
17965 .section "Private options for manualroute" "SECTprioptman"
17967 .cindex "options" "&(manualroute)& router"
17968 The private options for the &(manualroute)& router are as follows:
17970 .option host_all_ignored manualroute string defer
17971 See &%host_find_failed%&.
17973 .option host_find_failed manualroute string freeze
17974 This option controls what happens when &(manualroute)& tries to find an IP
17975 address for a host, and the host does not exist. The option can be set to one
17976 of the following values:
17985 The default (&"freeze"&) assumes that this state is a serious configuration
17986 error. The difference between &"pass"& and &"decline"& is that the former
17987 forces the address to be passed to the next router (or the router defined by
17990 overriding &%no_more%&, whereas the latter passes the address to the next
17991 router only if &%more%& is true.
17993 The value &"ignore"& causes Exim to completely ignore a host whose IP address
17994 cannot be found. If all the hosts in the list are ignored, the behaviour is
17995 controlled by the &%host_all_ignored%& option. This takes the same values
17996 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
17998 The &%host_find_failed%& option applies only to a definite &"does not exist"&
17999 state; if a host lookup gets a temporary error, delivery is deferred unless the
18000 generic &%pass_on_timeout%& option is set.
18003 .option hosts_randomize manualroute boolean false
18004 .cindex "randomized host list"
18005 .cindex "host" "list of; randomized"
18006 If this option is set, the order of the items in a host list in a routing rule
18007 is randomized each time the list is used, unless an option in the routing rule
18008 overrides (see below). Randomizing the order of a host list can be used to do
18009 crude load sharing. However, if more than one mail address is routed by the
18010 same router to the same host list, the host lists are considered to be the same
18011 (even though they may be randomized into different orders) for the purpose of
18012 deciding whether to batch the deliveries into a single SMTP transaction.
18014 When &%hosts_randomize%& is true, a host list may be split
18015 into groups whose order is separately randomized. This makes it possible to
18016 set up MX-like behaviour. The boundaries between groups are indicated by an
18017 item that is just &`+`& in the host list. For example:
18019 route_list = * host1:host2:host3:+:host4:host5
18021 The order of the first three hosts and the order of the last two hosts is
18022 randomized for each use, but the first three always end up before the last two.
18023 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18024 randomized host list is passed to an &(smtp)& transport that also has
18025 &%hosts_randomize set%&, the list is not re-randomized.
18028 .option route_data manualroute string&!! unset
18029 If this option is set, it must expand to yield the data part of a routing rule.
18030 Typically, the expansion string includes a lookup based on the domain. For
18033 route_data = ${lookup{$domain}dbm{/etc/routes}}
18035 If the expansion is forced to fail, or the result is an empty string, the
18036 router declines. Other kinds of expansion failure cause delivery to be
18040 .option route_list manualroute "string list" unset
18041 This string is a list of routing rules, in the form defined below. Note that,
18042 unlike most string lists, the items are separated by semicolons. This is so
18043 that they may contain colon-separated host lists.
18046 .option same_domain_copy_routing manualroute boolean false
18047 .cindex "address" "copying routing"
18048 Addresses with the same domain are normally routed by the &(manualroute)&
18049 router to the same list of hosts. However, this cannot be presumed, because the
18050 router options and preconditions may refer to the local part of the address. By
18051 default, therefore, Exim routes each address in a message independently. DNS
18052 servers run caches, so repeated DNS lookups are not normally expensive, and in
18053 any case, personal messages rarely have more than a few recipients.
18055 If you are running mailing lists with large numbers of subscribers at the same
18056 domain, and you are using a &(manualroute)& router which is independent of the
18057 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18058 lookups for identical domains in one message. In this case, when
18059 &(manualroute)& routes an address to a remote transport, any other unrouted
18060 addresses in the message that have the same domain are automatically given the
18061 same routing without processing them independently. However, this is only done
18062 if &%headers_add%& and &%headers_remove%& are unset.
18067 .section "Routing rules in route_list" "SECID120"
18068 The value of &%route_list%& is a string consisting of a sequence of routing
18069 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18070 entered as two semicolons. Alternatively, the list separator can be changed as
18071 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18072 Empty rules are ignored. The format of each rule is
18074 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18076 The following example contains two rules, each with a simple domain pattern and
18080 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18081 thes.ref.example mail-3.ref.example:mail-4.ref.example
18083 The three parts of a rule are separated by white space. The pattern and the
18084 list of hosts can be enclosed in quotes if necessary, and if they are, the
18085 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18086 single domain pattern, which is the only mandatory item in the rule. The
18087 pattern is in the same format as one item in a domain list (see section
18088 &<<SECTdomainlist>>&),
18089 except that it may not be the name of an interpolated file.
18090 That is, it may be wildcarded, or a regular expression, or a file or database
18091 lookup (with semicolons doubled, because of the use of semicolon as a separator
18092 in a &%route_list%&).
18094 The rules in &%route_list%& are searched in order until one of the patterns
18095 matches the domain that is being routed. The list of hosts and then options are
18096 then used as described below. If there is no match, the router declines. When
18097 &%route_list%& is set, &%route_data%& must not be set.
18101 .section "Routing rules in route_data" "SECID121"
18102 The use of &%route_list%& is convenient when there are only a small number of
18103 routing rules. For larger numbers, it is easier to use a file or database to
18104 hold the routing information, and use the &%route_data%& option instead.
18105 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18106 Most commonly, &%route_data%& is set as a string that contains an
18107 expansion lookup. For example, suppose we place two routing rules in a file
18110 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18111 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18113 This data can be accessed by setting
18115 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18117 Failure of the lookup results in an empty string, causing the router to
18118 decline. However, you do not have to use a lookup in &%route_data%&. The only
18119 requirement is that the result of expanding the string is a list of hosts,
18120 possibly followed by options, separated by white space. The list of hosts must
18121 be enclosed in quotes if it contains white space.
18126 .section "Format of the list of hosts" "SECID122"
18127 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18128 always separately expanded before use. If the expansion fails, the router
18129 declines. The result of the expansion must be a colon-separated list of names
18130 and/or IP addresses, optionally also including ports. The format of each item
18131 in the list is described in the next section. The list separator can be changed
18132 as described in section &<<SECTlistconstruct>>&.
18134 If the list of hosts was obtained from a &%route_list%& item, the following
18135 variables are set during its expansion:
18138 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18139 If the domain was matched against a regular expression, the numeric variables
18140 &$1$&, &$2$&, etc. may be set. For example:
18142 route_list = ^domain(\d+) host-$1.text.example
18145 &$0$& is always set to the entire domain.
18147 &$1$& is also set when partial matching is done in a file lookup.
18150 .vindex "&$value$&"
18151 If the pattern that matched the domain was a lookup item, the data that was
18152 looked up is available in the expansion variable &$value$&. For example:
18154 route_list = lsearch;;/some/file.routes $value
18158 Note the doubling of the semicolon in the pattern that is necessary because
18159 semicolon is the default route list separator.
18163 .section "Format of one host item" "SECTformatonehostitem"
18164 Each item in the list of hosts is either a host name or an IP address,
18165 optionally with an attached port number. When no port is given, an IP address
18166 is not enclosed in brackets. When a port is specified, it overrides the port
18167 specification on the transport. The port is separated from the name or address
18168 by a colon. This leads to some complications:
18171 Because colon is the default separator for the list of hosts, either
18172 the colon that specifies a port must be doubled, or the list separator must
18173 be changed. The following two examples have the same effect:
18175 route_list = * "host1.tld::1225 : host2.tld::1226"
18176 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18179 When IPv6 addresses are involved, it gets worse, because they contain
18180 colons of their own. To make this case easier, it is permitted to
18181 enclose an IP address (either v4 or v6) in square brackets if a port
18182 number follows. For example:
18184 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18188 .section "How the list of hosts is used" "SECThostshowused"
18189 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18190 the hosts is tried, in the order specified, when carrying out the SMTP
18191 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18192 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18195 Hosts may be listed by name or by IP address. An unadorned name in the list of
18196 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18197 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18198 records in the DNS. For example:
18200 route_list = * x.y.z:p.q.r/MX:e.f.g
18202 If this feature is used with a port specifier, the port must come last. For
18205 route_list = * dom1.tld/mx::1225
18207 If the &%hosts_randomize%& option is set, the order of the items in the list is
18208 randomized before any lookups are done. Exim then scans the list; for any name
18209 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18210 be an interface on the local host and the item is not the first in the list,
18211 Exim discards it and any subsequent items. If it is the first item, what
18212 happens is controlled by the
18213 .oindex "&%self%&" "in &(manualroute)& router"
18214 &%self%& option of the router.
18216 A name on the list that is followed by &`/MX`& is replaced with the list of
18217 hosts obtained by looking up MX records for the name. This is always a DNS
18218 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18219 below) are not relevant here. The order of these hosts is determined by the
18220 preference values in the MX records, according to the usual rules. Because
18221 randomizing happens before the MX lookup, it does not affect the order that is
18222 defined by MX preferences.
18224 If the local host is present in the sublist obtained from MX records, but is
18225 not the most preferred host in that list, it and any equally or less
18226 preferred hosts are removed before the sublist is inserted into the main list.
18228 If the local host is the most preferred host in the MX list, what happens
18229 depends on where in the original list of hosts the &`/MX`& item appears. If it
18230 is not the first item (that is, there are previous hosts in the main list),
18231 Exim discards this name and any subsequent items in the main list.
18233 If the MX item is first in the list of hosts, and the local host is the
18234 most preferred host, what happens is controlled by the &%self%& option of the
18237 DNS failures when lookup up the MX records are treated in the same way as DNS
18238 failures when looking up IP addresses: &%pass_on_timeout%& and
18239 &%host_find_failed%& are used when relevant.
18241 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
18242 whether obtained from an MX lookup or not.
18246 .section "How the options are used" "SECThowoptused"
18247 The options are a sequence of words; in practice no more than three are ever
18248 present. One of the words can be the name of a transport; this overrides the
18249 &%transport%& option on the router for this particular routing rule only. The
18250 other words (if present) control randomization of the list of hosts on a
18251 per-rule basis, and how the IP addresses of the hosts are to be found when
18252 routing to a remote transport. These options are as follows:
18255 &%randomize%&: randomize the order of the hosts in this list, overriding the
18256 setting of &%hosts_randomize%& for this routing rule only.
18258 &%no_randomize%&: do not randomize the order of the hosts in this list,
18259 overriding the setting of &%hosts_randomize%& for this routing rule only.
18261 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
18262 find IP addresses. This function may ultimately cause a DNS lookup, but it may
18263 also look in &_/etc/hosts_& or other sources of information.
18265 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
18266 no address records are found. If there is a temporary DNS error (such as a
18267 timeout), delivery is deferred.
18272 route_list = domain1 host1:host2:host3 randomize bydns;\
18273 domain2 host4:host5
18275 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
18276 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
18277 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
18278 or &[gethostbyname()]&, and the result of the lookup is the result of that
18281 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
18282 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
18283 instead of TRY_AGAIN. That is why the default action is to try a DNS
18284 lookup first. Only if that gives a definite &"no such host"& is the local
18289 If no IP address for a host can be found, what happens is controlled by the
18290 &%host_find_failed%& option.
18293 When an address is routed to a local transport, IP addresses are not looked up.
18294 The host list is passed to the transport in the &$host$& variable.
18298 .section "Manualroute examples" "SECID123"
18299 In some of the examples that follow, the presence of the &%remote_smtp%&
18300 transport, as defined in the default configuration file, is assumed:
18303 .cindex "smart host" "example router"
18304 The &(manualroute)& router can be used to forward all external mail to a
18305 &'smart host'&. If you have set up, in the main part of the configuration, a
18306 named domain list that contains your local domains, for example:
18308 domainlist local_domains = my.domain.example
18310 You can arrange for all other domains to be routed to a smart host by making
18311 your first router something like this:
18314 driver = manualroute
18315 domains = !+local_domains
18316 transport = remote_smtp
18317 route_list = * smarthost.ref.example
18319 This causes all non-local addresses to be sent to the single host
18320 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
18321 they are tried in order
18322 (but you can use &%hosts_randomize%& to vary the order each time).
18323 Another way of configuring the same thing is this:
18326 driver = manualroute
18327 transport = remote_smtp
18328 route_list = !+local_domains smarthost.ref.example
18330 There is no difference in behaviour between these two routers as they stand.
18331 However, they behave differently if &%no_more%& is added to them. In the first
18332 example, the router is skipped if the domain does not match the &%domains%&
18333 precondition; the following router is always tried. If the router runs, it
18334 always matches the domain and so can never decline. Therefore, &%no_more%&
18335 would have no effect. In the second case, the router is never skipped; it
18336 always runs. However, if it doesn't match the domain, it declines. In this case
18337 &%no_more%& would prevent subsequent routers from running.
18340 .cindex "mail hub example"
18341 A &'mail hub'& is a host which receives mail for a number of domains via MX
18342 records in the DNS and delivers it via its own private routing mechanism. Often
18343 the final destinations are behind a firewall, with the mail hub being the one
18344 machine that can connect to machines both inside and outside the firewall. The
18345 &(manualroute)& router is usually used on a mail hub to route incoming messages
18346 to the correct hosts. For a small number of domains, the routing can be inline,
18347 using the &%route_list%& option, but for a larger number a file or database
18348 lookup is easier to manage.
18350 If the domain names are in fact the names of the machines to which the mail is
18351 to be sent by the mail hub, the configuration can be quite simple. For
18355 driver = manualroute
18356 transport = remote_smtp
18357 route_list = *.rhodes.tvs.example $domain
18359 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
18360 whose names are the same as the mail domains. A similar approach can be taken
18361 if the host name can be obtained from the domain name by a string manipulation
18362 that the expansion facilities can handle. Otherwise, a lookup based on the
18363 domain can be used to find the host:
18366 driver = manualroute
18367 transport = remote_smtp
18368 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
18370 The result of the lookup must be the name or IP address of the host (or
18371 hosts) to which the address is to be routed. If the lookup fails, the route
18372 data is empty, causing the router to decline. The address then passes to the
18376 .cindex "batched SMTP output example"
18377 .cindex "SMTP" "batched outgoing; example"
18378 You can use &(manualroute)& to deliver messages to pipes or files in batched
18379 SMTP format for onward transportation by some other means. This is one way of
18380 storing mail for a dial-up host when it is not connected. The route list entry
18381 can be as simple as a single domain name in a configuration like this:
18384 driver = manualroute
18385 transport = batchsmtp_appendfile
18386 route_list = saved.domain.example
18388 though often a pattern is used to pick up more than one domain. If there are
18389 several domains or groups of domains with different transport requirements,
18390 different transports can be listed in the routing information:
18393 driver = manualroute
18395 *.saved.domain1.example $domain batch_appendfile; \
18396 *.saved.domain2.example \
18397 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
18400 .vindex "&$domain$&"
18402 The first of these just passes the domain in the &$host$& variable, which
18403 doesn't achieve much (since it is also in &$domain$&), but the second does a
18404 file lookup to find a value to pass, causing the router to decline to handle
18405 the address if the lookup fails.
18408 .cindex "UUCP" "example of router for"
18409 Routing mail directly to UUCP software is a specific case of the use of
18410 &(manualroute)& in a gateway to another mail environment. This is an example of
18411 one way it can be done:
18417 command = /usr/local/bin/uux -r - \
18418 ${substr_-5:$host}!rmail ${local_part}
18419 return_fail_output = true
18424 driver = manualroute
18426 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
18428 The file &_/usr/local/exim/uucphosts_& contains entries like
18430 darksite.ethereal.example: darksite.UUCP
18432 It can be set up more simply without adding and removing &".UUCP"& but this way
18433 makes clear the distinction between the domain name
18434 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
18436 .ecindex IIDmanrou1
18437 .ecindex IIDmanrou2
18446 . ////////////////////////////////////////////////////////////////////////////
18447 . ////////////////////////////////////////////////////////////////////////////
18449 .chapter "The queryprogram router" "CHAPdriverlast"
18450 .scindex IIDquerou1 "&(queryprogram)& router"
18451 .scindex IIDquerou2 "routers" "&(queryprogram)&"
18452 .cindex "routing" "by external program"
18453 The &(queryprogram)& router routes an address by running an external command
18454 and acting on its output. This is an expensive way to route, and is intended
18455 mainly for use in lightly-loaded systems, or for performing experiments.
18456 However, if it is possible to use the precondition options (&%domains%&,
18457 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
18458 be used in special cases, even on a busy host. There are the following private
18460 .cindex "options" "&(queryprogram)& router"
18462 .option command queryprogram string&!! unset
18463 This option must be set. It specifies the command that is to be run. The
18464 command is split up into a command name and arguments, and then each is
18465 expanded separately (exactly as for a &(pipe)& transport, described in chapter
18466 &<<CHAPpipetransport>>&).
18469 .option command_group queryprogram string unset
18470 .cindex "gid (group id)" "in &(queryprogram)& router"
18471 This option specifies a gid to be set when running the command while routing an
18472 address for deliver. It must be set if &%command_user%& specifies a numerical
18473 uid. If it begins with a digit, it is interpreted as the numerical value of the
18474 gid. Otherwise it is looked up using &[getgrnam()]&.
18477 .option command_user queryprogram string unset
18478 .cindex "uid (user id)" "for &(queryprogram)&"
18479 This option must be set. It specifies the uid which is set when running the
18480 command while routing an address for delivery. If the value begins with a digit,
18481 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
18482 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
18483 not set, a value for the gid also.
18485 &*Warning:*& Changing uid and gid is possible only when Exim is running as
18486 root, which it does during a normal delivery in a conventional configuration.
18487 However, when an address is being verified during message reception, Exim is
18488 usually running as the Exim user, not as root. If the &(queryprogram)& router
18489 is called from a non-root process, Exim cannot change uid or gid before running
18490 the command. In this circumstance the command runs under the current uid and
18494 .option current_directory queryprogram string /
18495 This option specifies an absolute path which is made the current directory
18496 before running the command.
18499 .option timeout queryprogram time 1h
18500 If the command does not complete within the timeout period, its process group
18501 is killed and the message is frozen. A value of zero time specifies no
18505 The standard output of the command is connected to a pipe, which is read when
18506 the command terminates. It should consist of a single line of output,
18507 containing up to five fields, separated by white space. The maximum length of
18508 the line is 1023 characters. Longer lines are silently truncated. The first
18509 field is one of the following words (case-insensitive):
18512 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
18515 &'Decline'&: the router declines; pass the address to the next router, unless
18516 &%no_more%& is set.
18518 &'Fail'&: routing failed; do not pass the address to any more routers. Any
18519 subsequent text on the line is an error message. If the router is run as part
18520 of address verification during an incoming SMTP message, the message is
18521 included in the SMTP response.
18523 &'Defer'&: routing could not be completed at this time; try again later. Any
18524 subsequent text on the line is an error message which is logged. It is not
18525 included in any SMTP response.
18527 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
18529 &'Pass'&: pass the address to the next router (or the router specified by
18530 &%pass_router%&), overriding &%no_more%&.
18532 &'Redirect'&: the message is redirected. The remainder of the line is a list of
18533 new addresses, which are routed independently, starting with the first router,
18534 or the router specified by &%redirect_router%&, if set.
18537 When the first word is &'accept'&, the remainder of the line consists of a
18538 number of keyed data values, as follows (split into two lines here, to fit on
18541 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
18542 LOOKUP=byname|bydns DATA=<text>
18544 The data items can be given in any order, and all are optional. If no transport
18545 is included, the transport specified by the generic &%transport%& option is
18546 used. The list of hosts and the lookup type are needed only if the transport is
18547 an &(smtp)& transport that does not itself supply a list of hosts.
18549 The format of the list of hosts is the same as for the &(manualroute)& router.
18550 As well as host names and IP addresses with optional port numbers, as described
18551 in section &<<SECTformatonehostitem>>&, it may contain names followed by
18552 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
18553 (see section &<<SECThostshowused>>&).
18555 If the lookup type is not specified, Exim behaves as follows when trying to
18556 find an IP address for each host: First, a DNS lookup is done. If this yields
18557 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
18558 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
18559 result of the lookup is the result of that call.
18561 .vindex "&$address_data$&"
18562 If the DATA field is set, its value is placed in the &$address_data$&
18563 variable. For example, this return line
18565 accept hosts=x1.y.example:x2.y.example data="rule1"
18567 routes the address to the default transport, passing a list of two hosts. When
18568 the transport runs, the string &"rule1"& is in &$address_data$&.
18569 .ecindex IIDquerou1
18570 .ecindex IIDquerou2
18575 . ////////////////////////////////////////////////////////////////////////////
18576 . ////////////////////////////////////////////////////////////////////////////
18578 .chapter "The redirect router" "CHAPredirect"
18579 .scindex IIDredrou1 "&(redirect)& router"
18580 .scindex IIDredrou2 "routers" "&(redirect)&"
18581 .cindex "alias file" "in a &(redirect)& router"
18582 .cindex "address redirection" "&(redirect)& router"
18583 The &(redirect)& router handles several kinds of address redirection. Its most
18584 common uses are for resolving local part aliases from a central alias file
18585 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
18586 files, but it has many other potential uses. The incoming address can be
18587 redirected in several different ways:
18590 It can be replaced by one or more new addresses which are themselves routed
18593 It can be routed to be delivered to a given file or directory.
18595 It can be routed to be delivered to a specified pipe command.
18597 It can cause an automatic reply to be generated.
18599 It can be forced to fail, optionally with a custom error message.
18601 It can be temporarily deferred, optionally with a custom message.
18603 It can be discarded.
18606 The generic &%transport%& option must not be set for &(redirect)& routers.
18607 However, there are some private options which define transports for delivery to
18608 files and pipes, and for generating autoreplies. See the &%file_transport%&,
18609 &%pipe_transport%& and &%reply_transport%& descriptions below.
18613 .section "Redirection data" "SECID124"
18614 The router operates by interpreting a text string which it obtains either by
18615 expanding the contents of the &%data%& option, or by reading the entire
18616 contents of a file whose name is given in the &%file%& option. These two
18617 options are mutually exclusive. The first is commonly used for handling system
18618 aliases, in a configuration like this:
18622 data = ${lookup{$local_part}lsearch{/etc/aliases}}
18624 If the lookup fails, the expanded string in this example is empty. When the
18625 expansion of &%data%& results in an empty string, the router declines. A forced
18626 expansion failure also causes the router to decline; other expansion failures
18627 cause delivery to be deferred.
18629 A configuration using &%file%& is commonly used for handling users'
18630 &_.forward_& files, like this:
18635 file = $home/.forward
18638 If the file does not exist, or causes no action to be taken (for example, it is
18639 empty or consists only of comments), the router declines. &*Warning*&: This
18640 is not the case when the file contains syntactically valid items that happen to
18641 yield empty addresses, for example, items containing only RFC 2822 address
18646 .section "Forward files and address verification" "SECID125"
18647 .cindex "address redirection" "while verifying"
18648 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
18649 &_.forward_& files, as in the example above. There are two reasons for this:
18652 When Exim is receiving an incoming SMTP message from a remote host, it is
18653 running under the Exim uid, not as root. Exim is unable to change uid to read
18654 the file as the user, and it may not be able to read it as the Exim user. So in
18655 practice the router may not be able to operate.
18657 However, even when the router can operate, the existence of a &_.forward_& file
18658 is unimportant when verifying an address. What should be checked is whether the
18659 local part is a valid user name or not. Cutting out the redirection processing
18660 saves some resources.
18668 .section "Interpreting redirection data" "SECID126"
18669 .cindex "Sieve filter" "specifying in redirection data"
18670 .cindex "filter" "specifying in redirection data"
18671 The contents of the data string, whether obtained from &%data%& or &%file%&,
18672 can be interpreted in two different ways:
18675 If the &%allow_filter%& option is set true, and the data begins with the text
18676 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
18677 &'filtering'& instructions in the form of an Exim or Sieve filter file,
18678 respectively. Details of the syntax and semantics of filter files are described
18679 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
18680 document is intended for use by end users.
18682 Otherwise, the data must be a comma-separated list of redirection items, as
18683 described in the next section.
18686 When a message is redirected to a file (a &"mail folder"&), the file name given
18687 in a non-filter redirection list must always be an absolute path. A filter may
18688 generate a relative path &-- how this is handled depends on the transport's
18689 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
18690 for the &(appendfile)& transport.
18694 .section "Items in a non-filter redirection list" "SECTitenonfilred"
18695 .cindex "address redirection" "non-filter list items"
18696 When the redirection data is not an Exim or Sieve filter, for example, if it
18697 comes from a conventional alias or forward file, it consists of a list of
18698 addresses, file names, pipe commands, or certain special items (see section
18699 &<<SECTspecitredli>>& below). The special items can be individually enabled or
18700 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
18701 depending on their default values. The items in the list are separated by
18702 commas or newlines.
18703 If a comma is required in an item, the entire item must be enclosed in double
18706 Lines starting with a # character are comments, and are ignored, and # may
18707 also appear following a comma, in which case everything between the # and the
18708 next newline character is ignored.
18710 If an item is entirely enclosed in double quotes, these are removed. Otherwise
18711 double quotes are retained because some forms of mail address require their use
18712 (but never to enclose the entire address). In the following description,
18713 &"item"& refers to what remains after any surrounding double quotes have been
18716 .vindex "&$local_part$&"
18717 &*Warning*&: If you use an Exim expansion to construct a redirection address,
18718 and the expansion contains a reference to &$local_part$&, you should make use
18719 of the &%quote_local_part%& expansion operator, in case the local part contains
18720 special characters. For example, to redirect all mail for the domain
18721 &'obsolete.example'&, retaining the existing local part, you could use this
18724 data = ${quote_local_part:$local_part}@newdomain.example
18728 .section "Redirecting to a local mailbox" "SECTredlocmai"
18729 .cindex "routing" "loops in"
18730 .cindex "loop" "while routing, avoidance of"
18731 .cindex "address redirection" "to local mailbox"
18732 A redirection item may safely be the same as the address currently under
18733 consideration. This does not cause a routing loop, because a router is
18734 automatically skipped if any ancestor of the address that is being processed
18735 is the same as the current address and was processed by the current router.
18736 Such an address is therefore passed to the following routers, so it is handled
18737 as if there were no redirection. When making this loop-avoidance test, the
18738 complete local part, including any prefix or suffix, is used.
18740 .cindex "address redirection" "local part without domain"
18741 Specifying the same local part without a domain is a common usage in personal
18742 filter files when the user wants to have messages delivered to the local
18743 mailbox and also forwarded elsewhere. For example, the user whose login is
18744 &'cleo'& might have a &_.forward_& file containing this:
18746 cleo, cleopatra@egypt.example
18748 .cindex "backslash in alias file"
18749 .cindex "alias file" "backslash in"
18750 For compatibility with other MTAs, such unqualified local parts may be
18751 preceded by &"\"&, but this is not a requirement for loop prevention. However,
18752 it does make a difference if more than one domain is being handled
18755 If an item begins with &"\"& and the rest of the item parses as a valid RFC
18756 2822 address that does not include a domain, the item is qualified using the
18757 domain of the incoming address. In the absence of a leading &"\"&, unqualified
18758 addresses are qualified using the value in &%qualify_recipient%&, but you can
18759 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
18761 Care must be taken if there are alias names for local users.
18762 Consider an MTA handling a single local domain where the system alias file
18767 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
18768 messages in the local mailbox, and also forward copies elsewhere. He creates
18771 Sam.Reman, spqr@reme.elsewhere.example
18773 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
18774 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
18775 second time round, because it has previously routed it,
18776 and the following routers presumably cannot handle the alias. The forward file
18777 should really contain
18779 spqr, spqr@reme.elsewhere.example
18781 but because this is such a common error, the &%check_ancestor%& option (see
18782 below) exists to provide a way to get round it. This is normally set on a
18783 &(redirect)& router that is handling users' &_.forward_& files.
18787 .section "Special items in redirection lists" "SECTspecitredli"
18788 In addition to addresses, the following types of item may appear in redirection
18789 lists (that is, in non-filter redirection data):
18792 .cindex "pipe" "in redirection list"
18793 .cindex "address redirection" "to pipe"
18794 An item is treated as a pipe command if it begins with &"|"& and does not parse
18795 as a valid RFC 2822 address that includes a domain. A transport for running the
18796 command must be specified by the &%pipe_transport%& option.
18797 Normally, either the router or the transport specifies a user and a group under
18798 which to run the delivery. The default is to use the Exim user and group.
18800 Single or double quotes can be used for enclosing the individual arguments of
18801 the pipe command; no interpretation of escapes is done for single quotes. If
18802 the command contains a comma character, it is necessary to put the whole item
18803 in double quotes, for example:
18805 "|/some/command ready,steady,go"
18807 since items in redirection lists are terminated by commas. Do not, however,
18808 quote just the command. An item such as
18810 |"/some/command ready,steady,go"
18812 is interpreted as a pipe with a rather strange command name, and no arguments.
18814 Note that the above example assumes that the text comes from a lookup source
18815 of some sort, so that the quotes are part of the data. If composing a
18816 redirect router with a &%data%& option directly specifying this command, the
18817 quotes will be used by the configuration parser to define the extent of one
18818 string, but will not be passed down into the redirect router itself. There
18819 are two main approaches to get around this: escape quotes to be part of the
18820 data itself, or avoid using this mechanism and instead create a custom
18821 transport with the &%command%& option set and reference that transport from
18822 an &%accept%& router.
18825 .cindex "file" "in redirection list"
18826 .cindex "address redirection" "to file"
18827 An item is interpreted as a path name if it begins with &"/"& and does not
18828 parse as a valid RFC 2822 address that includes a domain. For example,
18830 /home/world/minbari
18832 is treated as a file name, but
18834 /s=molari/o=babylon/@x400gate.way
18836 is treated as an address. For a file name, a transport must be specified using
18837 the &%file_transport%& option. However, if the generated path name ends with a
18838 forward slash character, it is interpreted as a directory name rather than a
18839 file name, and &%directory_transport%& is used instead.
18841 Normally, either the router or the transport specifies a user and a group under
18842 which to run the delivery. The default is to use the Exim user and group.
18844 .cindex "&_/dev/null_&"
18845 However, if a redirection item is the path &_/dev/null_&, delivery to it is
18846 bypassed at a high level, and the log entry shows &"**bypassed**"&
18847 instead of a transport name. In this case the user and group are not used.
18850 .cindex "included address list"
18851 .cindex "address redirection" "included external list"
18852 If an item is of the form
18854 :include:<path name>
18856 a list of further items is taken from the given file and included at that
18857 point. &*Note*&: Such a file can not be a filter file; it is just an
18858 out-of-line addition to the list. The items in the included list are separated
18859 by commas or newlines and are not subject to expansion. If this is the first
18860 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
18861 the alias name. This example is incorrect:
18863 list1 :include:/opt/lists/list1
18865 It must be given as
18867 list1: :include:/opt/lists/list1
18870 .cindex "address redirection" "to black hole"
18871 Sometimes you want to throw away mail to a particular local part. Making the
18872 &%data%& option expand to an empty string does not work, because that causes
18873 the router to decline. Instead, the alias item
18874 .cindex "black hole"
18875 .cindex "abandoning mail"
18876 &':blackhole:'& can be used. It does what its name implies. No delivery is
18877 done, and no error message is generated. This has the same effect as specifing
18878 &_/dev/null_& as a destination, but it can be independently disabled.
18880 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
18881 delivery is done for the original local part, even if other redirection items
18882 are present. If you are generating a multi-item list (for example, by reading a
18883 database) and need the ability to provide a no-op item, you must use
18887 .cindex "delivery" "forcing failure"
18888 .cindex "delivery" "forcing deferral"
18889 .cindex "failing delivery" "forcing"
18890 .cindex "deferred delivery, forcing"
18891 .cindex "customizing" "failure message"
18892 An attempt to deliver a particular address can be deferred or forced to fail by
18893 redirection items of the form
18898 respectively. When a redirection list contains such an item, it applies
18899 to the entire redirection; any other items in the list are ignored. Any
18900 text following &':fail:'& or &':defer:'& is placed in the error text
18901 associated with the failure. For example, an alias file might contain:
18903 X.Employee: :fail: Gone away, no forwarding address
18905 In the case of an address that is being verified from an ACL or as the subject
18907 .cindex "VRFY" "error text, display of"
18908 VRFY command, the text is included in the SMTP error response by
18910 .cindex "EXPN" "error text, display of"
18911 The text is not included in the response to an EXPN command. In non-SMTP cases
18912 the text is included in the error message that Exim generates.
18914 .cindex "SMTP" "error codes"
18915 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
18916 &':fail:'&. However, if the message starts with three digits followed by a
18917 space, optionally followed by an extended code of the form &'n.n.n'&, also
18918 followed by a space, and the very first digit is the same as the default error
18919 code, the code from the message is used instead. If the very first digit is
18920 incorrect, a panic error is logged, and the default code is used. You can
18921 suppress the use of the supplied code in a redirect router by setting the
18922 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
18925 .vindex "&$acl_verify_message$&"
18926 In an ACL, an explicitly provided message overrides the default, but the
18927 default message is available in the variable &$acl_verify_message$& and can
18928 therefore be included in a custom message if this is desired.
18930 Normally the error text is the rest of the redirection list &-- a comma does
18931 not terminate it &-- but a newline does act as a terminator. Newlines are not
18932 normally present in alias expansions. In &(lsearch)& lookups they are removed
18933 as part of the continuation process, but they may exist in other kinds of
18934 lookup and in &':include:'& files.
18936 During routing for message delivery (as opposed to verification), a redirection
18937 containing &':fail:'& causes an immediate failure of the incoming address,
18938 whereas &':defer:'& causes the message to remain on the queue so that a
18939 subsequent delivery attempt can happen at a later time. If an address is
18940 deferred for too long, it will ultimately fail, because the normal retry
18944 .cindex "alias file" "exception to default"
18945 Sometimes it is useful to use a single-key search type with a default (see
18946 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
18947 for exceptions to the default. These can be handled by aliasing them to
18948 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
18949 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
18950 results in an empty redirection list has the same effect.
18954 .section "Duplicate addresses" "SECTdupaddr"
18955 .cindex "duplicate addresses"
18956 .cindex "address duplicate, discarding"
18957 .cindex "pipe" "duplicated"
18958 Exim removes duplicate addresses from the list to which it is delivering, so as
18959 to deliver just one copy to each address. This does not apply to deliveries
18960 routed to pipes by different immediate parent addresses, but an indirect
18961 aliasing scheme of the type
18963 pipe: |/some/command $local_part
18967 does not work with a message that is addressed to both local parts, because
18968 when the second is aliased to the intermediate local part &"pipe"& it gets
18969 discarded as being the same as a previously handled address. However, a scheme
18972 localpart1: |/some/command $local_part
18973 localpart2: |/some/command $local_part
18975 does result in two different pipe deliveries, because the immediate parents of
18976 the pipes are distinct.
18980 .section "Repeated redirection expansion" "SECID128"
18981 .cindex "repeated redirection expansion"
18982 .cindex "address redirection" "repeated for each delivery attempt"
18983 When a message cannot be delivered to all of its recipients immediately,
18984 leading to two or more delivery attempts, redirection expansion is carried out
18985 afresh each time for those addresses whose children were not all previously
18986 delivered. If redirection is being used as a mailing list, this can lead to new
18987 members of the list receiving copies of old messages. The &%one_time%& option
18988 can be used to avoid this.
18991 .section "Errors in redirection lists" "SECID129"
18992 .cindex "address redirection" "errors"
18993 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
18994 error is skipped, and an entry is written to the main log. This may be useful
18995 for mailing lists that are automatically managed. Otherwise, if an error is
18996 detected while generating the list of new addresses, the original address is
18997 deferred. See also &%syntax_errors_to%&.
19001 .section "Private options for the redirect router" "SECID130"
19003 .cindex "options" "&(redirect)& router"
19004 The private options for the &(redirect)& router are as follows:
19007 .option allow_defer redirect boolean false
19008 Setting this option allows the use of &':defer:'& in non-filter redirection
19009 data, or the &%defer%& command in an Exim filter file.
19012 .option allow_fail redirect boolean false
19013 .cindex "failing delivery" "from filter"
19014 If this option is true, the &':fail:'& item can be used in a redirection list,
19015 and the &%fail%& command may be used in an Exim filter file.
19018 .option allow_filter redirect boolean false
19019 .cindex "filter" "enabling use of"
19020 .cindex "Sieve filter" "enabling use of"
19021 Setting this option allows Exim to interpret redirection data that starts with
19022 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19023 are some features of Exim filter files that some administrators may wish to
19024 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19026 It is also possible to lock out Exim filters or Sieve filters while allowing
19027 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19030 The filter is run using the uid and gid set by the generic &%user%& and
19031 &%group%& options. These take their defaults from the password data if
19032 &%check_local_user%& is set, so in the normal case of users' personal filter
19033 files, the filter is run as the relevant user. When &%allow_filter%& is set
19034 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19038 .option allow_freeze redirect boolean false
19039 .cindex "freezing messages" "allowing in filter"
19040 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19041 This command is more normally encountered in system filters, and is disabled by
19042 default for redirection filters because it isn't something you usually want to
19043 let ordinary users do.
19047 .option check_ancestor redirect boolean false
19048 This option is concerned with handling generated addresses that are the same
19049 as some address in the list of redirection ancestors of the current address.
19050 Although it is turned off by default in the code, it is set in the default
19051 configuration file for handling users' &_.forward_& files. It is recommended
19052 for this use of the &(redirect)& router.
19054 When &%check_ancestor%& is set, if a generated address (including the domain)
19055 is the same as any ancestor of the current address, it is replaced by a copy of
19056 the current address. This helps in the case where local part A is aliased to B,
19057 and B has a &_.forward_& file pointing back to A. For example, within a single
19058 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19059 &_&~jb/.forward_& contains:
19061 \Joe.Bloggs, <other item(s)>
19063 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19064 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19065 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19066 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19067 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19068 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19069 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19070 original address. See also the &%repeat_use%& option below.
19073 .option check_group redirect boolean "see below"
19074 When the &%file%& option is used, the group owner of the file is checked only
19075 when this option is set. The permitted groups are those listed in the
19076 &%owngroups%& option, together with the user's default group if
19077 &%check_local_user%& is set. If the file has the wrong group, routing is
19078 deferred. The default setting for this option is true if &%check_local_user%&
19079 is set and the &%modemask%& option permits the group write bit, or if the
19080 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19084 .option check_owner redirect boolean "see below"
19085 When the &%file%& option is used, the owner of the file is checked only when
19086 this option is set. If &%check_local_user%& is set, the local user is
19087 permitted; otherwise the owner must be one of those listed in the &%owners%&
19088 option. The default value for this option is true if &%check_local_user%& or
19089 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19092 .option data redirect string&!! unset
19093 This option is mutually exclusive with &%file%&. One or other of them must be
19094 set, but not both. The contents of &%data%& are expanded, and then used as the
19095 list of forwarding items, or as a set of filtering instructions. If the
19096 expansion is forced to fail, or the result is an empty string or a string that
19097 has no effect (consists entirely of comments), the router declines.
19099 When filtering instructions are used, the string must begin with &"#Exim
19100 filter"&, and all comments in the string, including this initial one, must be
19101 terminated with newline characters. For example:
19103 data = #Exim filter\n\
19104 if $h_to: contains Exim then save $home/mail/exim endif
19106 If you are reading the data from a database where newlines cannot be included,
19107 you can use the &${sg}$& expansion item to turn the escape string of your
19108 choice into a newline.
19111 .option directory_transport redirect string&!! unset
19112 A &(redirect)& router sets up a direct delivery to a directory when a path name
19113 ending with a slash is specified as a new &"address"&. The transport used is
19114 specified by this option, which, after expansion, must be the name of a
19115 configured transport. This should normally be an &(appendfile)& transport.
19118 .option file redirect string&!! unset
19119 This option specifies the name of a file that contains the redirection data. It
19120 is mutually exclusive with the &%data%& option. The string is expanded before
19121 use; if the expansion is forced to fail, the router declines. Other expansion
19122 failures cause delivery to be deferred. The result of a successful expansion
19123 must be an absolute path. The entire file is read and used as the redirection
19124 data. If the data is an empty string or a string that has no effect (consists
19125 entirely of comments), the router declines.
19127 .cindex "NFS" "checking for file existence"
19128 If the attempt to open the file fails with a &"does not exist"& error, Exim
19129 runs a check on the containing directory,
19130 unless &%ignore_enotdir%& is true (see below).
19131 If the directory does not appear to exist, delivery is deferred. This can
19132 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19133 is a mount problem. If the containing directory does exist, but the file does
19134 not, the router declines.
19137 .option file_transport redirect string&!! unset
19138 .vindex "&$address_file$&"
19139 A &(redirect)& router sets up a direct delivery to a file when a path name not
19140 ending in a slash is specified as a new &"address"&. The transport used is
19141 specified by this option, which, after expansion, must be the name of a
19142 configured transport. This should normally be an &(appendfile)& transport. When
19143 it is running, the file name is in &$address_file$&.
19146 .option filter_prepend_home redirect boolean true
19147 When this option is true, if a &(save)& command in an Exim filter specifies a
19148 relative path, and &$home$& is defined, it is automatically prepended to the
19149 relative path. If this option is set false, this action does not happen. The
19150 relative path is then passed to the transport unmodified.
19153 .option forbid_blackhole redirect boolean false
19154 If this option is true, the &':blackhole:'& item may not appear in a
19158 .option forbid_exim_filter redirect boolean false
19159 If this option is set true, only Sieve filters are permitted when
19160 &%allow_filter%& is true.
19165 .option forbid_file redirect boolean false
19166 .cindex "delivery" "to file; forbidding"
19167 .cindex "Sieve filter" "forbidding delivery to a file"
19168 .cindex "Sieve filter" "&""keep""& facility; disabling"
19169 If this option is true, this router may not generate a new address that
19170 specifies delivery to a local file or directory, either from a filter or from a
19171 conventional forward file. This option is forced to be true if &%one_time%& is
19172 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19173 locks out the Sieve's &"keep"& facility.
19176 .option forbid_filter_dlfunc redirect boolean false
19177 .cindex "filter" "locking out certain features"
19178 If this option is true, string expansions in Exim filters are not allowed to
19179 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19182 .option forbid_filter_existstest redirect boolean false
19183 .cindex "expansion" "statting a file"
19184 If this option is true, string expansions in Exim filters are not allowed to
19185 make use of the &%exists%& condition or the &%stat%& expansion item.
19187 .option forbid_filter_logwrite redirect boolean false
19188 If this option is true, use of the logging facility in Exim filters is not
19189 permitted. Logging is in any case available only if the filter is being run
19190 under some unprivileged uid (which is normally the case for ordinary users'
19191 &_.forward_& files).
19194 .option forbid_filter_lookup redirect boolean false
19195 If this option is true, string expansions in Exim filter files are not allowed
19196 to make use of &%lookup%& items.
19199 .option forbid_filter_perl redirect boolean false
19200 This option has an effect only if Exim is built with embedded Perl support. If
19201 it is true, string expansions in Exim filter files are not allowed to make use
19202 of the embedded Perl support.
19205 .option forbid_filter_readfile redirect boolean false
19206 If this option is true, string expansions in Exim filter files are not allowed
19207 to make use of &%readfile%& items.
19210 .option forbid_filter_readsocket redirect boolean false
19211 If this option is true, string expansions in Exim filter files are not allowed
19212 to make use of &%readsocket%& items.
19215 .option forbid_filter_reply redirect boolean false
19216 If this option is true, this router may not generate an automatic reply
19217 message. Automatic replies can be generated only from Exim or Sieve filter
19218 files, not from traditional forward files. This option is forced to be true if
19219 &%one_time%& is set.
19222 .option forbid_filter_run redirect boolean false
19223 If this option is true, string expansions in Exim filter files are not allowed
19224 to make use of &%run%& items.
19227 .option forbid_include redirect boolean false
19228 If this option is true, items of the form
19230 :include:<path name>
19232 are not permitted in non-filter redirection lists.
19235 .option forbid_pipe redirect boolean false
19236 .cindex "delivery" "to pipe; forbidding"
19237 If this option is true, this router may not generate a new address which
19238 specifies delivery to a pipe, either from an Exim filter or from a conventional
19239 forward file. This option is forced to be true if &%one_time%& is set.
19242 .option forbid_sieve_filter redirect boolean false
19243 If this option is set true, only Exim filters are permitted when
19244 &%allow_filter%& is true.
19247 .cindex "SMTP" "error codes"
19248 .option forbid_smtp_code redirect boolean false
19249 If this option is set true, any SMTP error codes that are present at the start
19250 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
19251 the default codes (451 and 550, respectively) are always used.
19256 .option hide_child_in_errmsg redirect boolean false
19257 .cindex "bounce message" "redirection details; suppressing"
19258 If this option is true, it prevents Exim from quoting a child address if it
19259 generates a bounce or delay message for it. Instead it says &"an address
19260 generated from <&'the top level address'&>"&. Of course, this applies only to
19261 bounces generated locally. If a message is forwarded to another host, &'its'&
19262 bounce may well quote the generated address.
19265 .option ignore_eacces redirect boolean false
19267 If this option is set and an attempt to open a redirection file yields the
19268 EACCES error (permission denied), the &(redirect)& router behaves as if the
19269 file did not exist.
19272 .option ignore_enotdir redirect boolean false
19274 If this option is set and an attempt to open a redirection file yields the
19275 ENOTDIR error (something on the path is not a directory), the &(redirect)&
19276 router behaves as if the file did not exist.
19278 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
19279 router that has the &%file%& option set discovers that the file does not exist
19280 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
19281 against unmounted NFS directories. If the parent can not be statted, delivery
19282 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
19283 is set, because that option tells Exim to ignore &"something on the path is not
19284 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
19285 that some operating systems give ENOENT where others give ENOTDIR.
19289 .option include_directory redirect string unset
19290 If this option is set, the path names of any &':include:'& items in a
19291 redirection list must start with this directory.
19294 .option modemask redirect "octal integer" 022
19295 This specifies mode bits which must not be set for a file specified by the
19296 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
19299 .option one_time redirect boolean false
19300 .cindex "one-time aliasing/forwarding expansion"
19301 .cindex "alias file" "one-time expansion"
19302 .cindex "forward file" "one-time expansion"
19303 .cindex "mailing lists" "one-time expansion"
19304 .cindex "address redirection" "one-time expansion"
19305 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
19306 files each time it tries to deliver a message causes a problem when one or more
19307 of the generated addresses fails be delivered at the first attempt. The problem
19308 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
19309 but of what happens when the redirection list changes during the time that the
19310 message is on Exim's queue. This is particularly true in the case of mailing
19311 lists, where new subscribers might receive copies of messages that were posted
19312 before they subscribed.
19314 If &%one_time%& is set and any addresses generated by the router fail to
19315 deliver at the first attempt, the failing addresses are added to the message as
19316 &"top level"& addresses, and the parent address that generated them is marked
19317 &"delivered"&. Thus, redirection does not happen again at the next delivery
19320 &*Warning 1*&: Any header line addition or removal that is specified by this
19321 router would be lost if delivery did not succeed at the first attempt. For this
19322 reason, the &%headers_add%& and &%headers_remove%& generic options are not
19323 permitted when &%one_time%& is set.
19325 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
19326 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
19327 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
19329 &*Warning 3*&: The &%unseen%& generic router option may not be set with
19332 The original top-level address is remembered with each of the generated
19333 addresses, and is output in any log messages. However, any intermediate parent
19334 addresses are not recorded. This makes a difference to the log only if
19335 &%all_parents%& log selector is set. It is expected that &%one_time%& will
19336 typically be used for mailing lists, where there is normally just one level of
19340 .option owners redirect "string list" unset
19341 .cindex "ownership" "alias file"
19342 .cindex "ownership" "forward file"
19343 .cindex "alias file" "ownership"
19344 .cindex "forward file" "ownership"
19345 This specifies a list of permitted owners for the file specified by &%file%&.
19346 This list is in addition to the local user when &%check_local_user%& is set.
19347 See &%check_owner%& above.
19350 .option owngroups redirect "string list" unset
19351 This specifies a list of permitted groups for the file specified by &%file%&.
19352 The list is in addition to the local user's primary group when
19353 &%check_local_user%& is set. See &%check_group%& above.
19356 .option pipe_transport redirect string&!! unset
19357 .vindex "&$address_pipe$&"
19358 A &(redirect)& router sets up a direct delivery to a pipe when a string
19359 starting with a vertical bar character is specified as a new &"address"&. The
19360 transport used is specified by this option, which, after expansion, must be the
19361 name of a configured transport. This should normally be a &(pipe)& transport.
19362 When the transport is run, the pipe command is in &$address_pipe$&.
19365 .option qualify_domain redirect string&!! unset
19366 .vindex "&$qualify_recipient$&"
19367 If this option is set, and an unqualified address (one without a domain) is
19368 generated, and that address would normally be qualified by the global setting
19369 in &%qualify_recipient%&, it is instead qualified with the domain specified by
19370 expanding this string. If the expansion fails, the router declines. If you want
19371 to revert to the default, you can have the expansion generate
19372 &$qualify_recipient$&.
19374 This option applies to all unqualified addresses generated by Exim filters,
19375 but for traditional &_.forward_& files, it applies only to addresses that are
19376 not preceded by a backslash. Sieve filters cannot generate unqualified
19379 .option qualify_preserve_domain redirect boolean false
19380 .cindex "domain" "in redirection; preserving"
19381 .cindex "preserving domain in redirection"
19382 .cindex "address redirection" "domain; preserving"
19383 If this option is set, the router's local &%qualify_domain%& option must not be
19384 set (a configuration error occurs if it is). If an unqualified address (one
19385 without a domain) is generated, it is qualified with the domain of the parent
19386 address (the immediately preceding ancestor) instead of the global
19387 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
19388 this applies whether or not the address is preceded by a backslash.
19391 .option repeat_use redirect boolean true
19392 If this option is set false, the router is skipped for a child address that has
19393 any ancestor that was routed by this router. This test happens before any of
19394 the other preconditions are tested. Exim's default anti-looping rules skip
19395 only when the ancestor is the same as the current address. See also
19396 &%check_ancestor%& above and the generic &%redirect_router%& option.
19399 .option reply_transport redirect string&!! unset
19400 A &(redirect)& router sets up an automatic reply when a &%mail%& or
19401 &%vacation%& command is used in a filter file. The transport used is specified
19402 by this option, which, after expansion, must be the name of a configured
19403 transport. This should normally be an &(autoreply)& transport. Other transports
19404 are unlikely to do anything sensible or useful.
19407 .option rewrite redirect boolean true
19408 .cindex "address redirection" "disabling rewriting"
19409 If this option is set false, addresses generated by the router are not
19410 subject to address rewriting. Otherwise, they are treated like new addresses
19411 and are rewritten according to the global rewriting rules.
19414 .option sieve_subaddress redirect string&!! unset
19415 The value of this option is passed to a Sieve filter to specify the
19416 :subaddress part of an address.
19418 .option sieve_useraddress redirect string&!! unset
19419 The value of this option is passed to a Sieve filter to specify the :user part
19420 of an address. However, if it is unset, the entire original local part
19421 (including any prefix or suffix) is used for :user.
19424 .option sieve_vacation_directory redirect string&!! unset
19425 .cindex "Sieve filter" "vacation directory"
19426 To enable the &"vacation"& extension for Sieve filters, you must set
19427 &%sieve_vacation_directory%& to the directory where vacation databases are held
19428 (do not put anything else in that directory), and ensure that the
19429 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
19430 needs their own directory; Exim will create it if necessary.
19434 .option skip_syntax_errors redirect boolean false
19435 .cindex "forward file" "broken"
19436 .cindex "address redirection" "broken files"
19437 .cindex "alias file" "broken"
19438 .cindex "broken alias or forward files"
19439 .cindex "ignoring faulty addresses"
19440 .cindex "skipping faulty addresses"
19441 .cindex "error" "skipping bad syntax"
19442 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
19443 non-filter redirection data are skipped, and each failing address is logged. If
19444 &%syntax_errors_to%& is set, a message is sent to the address it defines,
19445 giving details of the failures. If &%syntax_errors_text%& is set, its contents
19446 are expanded and placed at the head of the error message generated by
19447 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
19448 be the same address as the generic &%errors_to%& option. The
19449 &%skip_syntax_errors%& option is often used when handling mailing lists.
19451 If all the addresses in a redirection list are skipped because of syntax
19452 errors, the router declines to handle the original address, and it is passed to
19453 the following routers.
19455 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
19456 error in the filter causes filtering to be abandoned without any action being
19457 taken. The incident is logged, and the router declines to handle the address,
19458 so it is passed to the following routers.
19460 .cindex "Sieve filter" "syntax errors in"
19461 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
19462 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
19463 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
19465 &%skip_syntax_errors%& can be used to specify that errors in users' forward
19466 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
19467 option, used with an address that does not get redirected, can be used to
19468 notify users of these errors, by means of a router like this:
19474 file = $home/.forward
19475 file_transport = address_file
19476 pipe_transport = address_pipe
19477 reply_transport = address_reply
19480 syntax_errors_to = real-$local_part@$domain
19481 syntax_errors_text = \
19482 This is an automatically generated message. An error has\n\
19483 been found in your .forward file. Details of the error are\n\
19484 reported below. While this error persists, you will receive\n\
19485 a copy of this message for every message that is addressed\n\
19486 to you. If your .forward file is a filter file, or if it is\n\
19487 a non-filter file containing no valid forwarding addresses,\n\
19488 a copy of each incoming message will be put in your normal\n\
19489 mailbox. If a non-filter file contains at least one valid\n\
19490 forwarding address, forwarding to the valid addresses will\n\
19491 happen, and those will be the only deliveries that occur.
19493 You also need a router to ensure that local addresses that are prefixed by
19494 &`real-`& are recognized, but not forwarded or filtered. For example, you could
19495 put this immediately before the &(userforward)& router:
19500 local_part_prefix = real-
19501 transport = local_delivery
19503 For security, it would probably be a good idea to restrict the use of this
19504 router to locally-generated messages, using a condition such as this:
19506 condition = ${if match {$sender_host_address}\
19507 {\N^(|127\.0\.0\.1)$\N}}
19511 .option syntax_errors_text redirect string&!! unset
19512 See &%skip_syntax_errors%& above.
19515 .option syntax_errors_to redirect string unset
19516 See &%skip_syntax_errors%& above.
19517 .ecindex IIDredrou1
19518 .ecindex IIDredrou2
19525 . ////////////////////////////////////////////////////////////////////////////
19526 . ////////////////////////////////////////////////////////////////////////////
19528 .chapter "Environment for running local transports" "CHAPenvironment" &&&
19529 "Environment for local transports"
19530 .scindex IIDenvlotra1 "local transports" "environment for"
19531 .scindex IIDenvlotra2 "environment for local transports"
19532 .scindex IIDenvlotra3 "transport" "local; environment for"
19533 Local transports handle deliveries to files and pipes. (The &(autoreply)&
19534 transport can be thought of as similar to a pipe.) Exim always runs transports
19535 in subprocesses, under specified uids and gids. Typical deliveries to local
19536 mailboxes run under the uid and gid of the local user.
19538 Exim also sets a specific current directory while running the transport; for
19539 some transports a home directory setting is also relevant. The &(pipe)&
19540 transport is the only one that sets up environment variables; see section
19541 &<<SECTpipeenv>>& for details.
19543 The values used for the uid, gid, and the directories may come from several
19544 different places. In many cases, the router that handles the address associates
19545 settings with that address as a result of its &%check_local_user%&, &%group%&,
19546 or &%user%& options. However, values may also be given in the transport's own
19547 configuration, and these override anything that comes from the router.
19551 .section "Concurrent deliveries" "SECID131"
19552 .cindex "concurrent deliveries"
19553 .cindex "simultaneous deliveries"
19554 If two different messages for the same local recipient arrive more or less
19555 simultaneously, the two delivery processes are likely to run concurrently. When
19556 the &(appendfile)& transport is used to write to a file, Exim applies locking
19557 rules to stop concurrent processes from writing to the same file at the same
19560 However, when you use a &(pipe)& transport, it is up to you to arrange any
19561 locking that is needed. Here is a silly example:
19565 command = /bin/sh -c 'cat >>/some/file'
19567 This is supposed to write the message at the end of the file. However, if two
19568 messages arrive at the same time, the file will be scrambled. You can use the
19569 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
19570 file using the same algorithm that Exim itself uses.
19575 .section "Uids and gids" "SECTenvuidgid"
19576 .cindex "local transports" "uid and gid"
19577 .cindex "transport" "local; uid and gid"
19578 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
19579 overrides any group that the router set in the address, even if &%user%& is not
19580 set for the transport. This makes it possible, for example, to run local mail
19581 delivery under the uid of the recipient (set by the router), but in a special
19582 group (set by the transport). For example:
19585 # User/group are set by check_local_user in this router
19589 transport = group_delivery
19592 # This transport overrides the group
19594 driver = appendfile
19595 file = /var/spool/mail/$local_part
19598 If &%user%& is set for a transport, its value overrides what is set in the
19599 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
19600 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
19603 .oindex "&%initgroups%&"
19604 When the uid is taken from the transport's configuration, the &[initgroups()]&
19605 function is called for the groups associated with that uid if the
19606 &%initgroups%& option is set for the transport. When the uid is not specified
19607 by the transport, but is associated with the address by a router, the option
19608 for calling &[initgroups()]& is taken from the router configuration.
19610 .cindex "&(pipe)& transport" "uid for"
19611 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
19612 is set and &%user%& is not set, the uid of the process that called Exim to
19613 receive the message is used, and if &%group%& is not set, the corresponding
19614 original gid is also used.
19616 This is the detailed preference order for obtaining a gid; the first of the
19617 following that is set is used:
19620 A &%group%& setting of the transport;
19622 A &%group%& setting of the router;
19624 A gid associated with a user setting of the router, either as a result of
19625 &%check_local_user%& or an explicit non-numeric &%user%& setting;
19627 The group associated with a non-numeric &%user%& setting of the transport;
19629 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
19630 the uid is the creator's uid;
19632 The Exim gid if the Exim uid is being used as a default.
19635 If, for example, the user is specified numerically on the router and there are
19636 no group settings, no gid is available. In this situation, an error occurs.
19637 This is different for the uid, for which there always is an ultimate default.
19638 The first of the following that is set is used:
19641 A &%user%& setting of the transport;
19643 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
19645 A &%user%& setting of the router;
19647 A &%check_local_user%& setting of the router;
19652 Of course, an error will still occur if the uid that is chosen is on the
19653 &%never_users%& list.
19659 .section "Current and home directories" "SECID132"
19660 .cindex "current directory for local transport"
19661 .cindex "home directory" "for local transport"
19662 .cindex "transport" "local; home directory for"
19663 .cindex "transport" "local; current directory for"
19664 Routers may set current and home directories for local transports by means of
19665 the &%transport_current_directory%& and &%transport_home_directory%& options.
19666 However, if the transport's &%current_directory%& or &%home_directory%& options
19667 are set, they override the router's values. In detail, the home directory
19668 for a local transport is taken from the first of these values that is set:
19671 The &%home_directory%& option on the transport;
19673 The &%transport_home_directory%& option on the router;
19675 The password data if &%check_local_user%& is set on the router;
19677 The &%router_home_directory%& option on the router.
19680 The current directory is taken from the first of these values that is set:
19683 The &%current_directory%& option on the transport;
19685 The &%transport_current_directory%& option on the router.
19689 If neither the router nor the transport sets a current directory, Exim uses the
19690 value of the home directory, if it is set. Otherwise it sets the current
19691 directory to &_/_& before running a local transport.
19695 .section "Expansion variables derived from the address" "SECID133"
19696 .vindex "&$domain$&"
19697 .vindex "&$local_part$&"
19698 .vindex "&$original_domain$&"
19699 Normally a local delivery is handling a single address, and in that case the
19700 variables such as &$domain$& and &$local_part$& are set during local
19701 deliveries. However, in some circumstances more than one address may be handled
19702 at once (for example, while writing batch SMTP for onward transmission by some
19703 other means). In this case, the variables associated with the local part are
19704 never set, &$domain$& is set only if all the addresses have the same domain,
19705 and &$original_domain$& is never set.
19706 .ecindex IIDenvlotra1
19707 .ecindex IIDenvlotra2
19708 .ecindex IIDenvlotra3
19716 . ////////////////////////////////////////////////////////////////////////////
19717 . ////////////////////////////////////////////////////////////////////////////
19719 .chapter "Generic options for transports" "CHAPtransportgeneric"
19720 .scindex IIDgenoptra1 "generic options" "transport"
19721 .scindex IIDgenoptra2 "options" "generic; for transports"
19722 .scindex IIDgenoptra3 "transport" "generic options for"
19723 The following generic options apply to all transports:
19726 .option body_only transports boolean false
19727 .cindex "transport" "body only"
19728 .cindex "message" "transporting body only"
19729 .cindex "body of message" "transporting"
19730 If this option is set, the message's headers are not transported. It is
19731 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
19732 or &(pipe)& transports, the settings of &%message_prefix%& and
19733 &%message_suffix%& should be checked, because this option does not
19734 automatically suppress them.
19737 .option current_directory transports string&!! unset
19738 .cindex "transport" "current directory for"
19739 This specifies the current directory that is to be set while running the
19740 transport, overriding any value that may have been set by the router.
19741 If the expansion fails for any reason, including forced failure, an error is
19742 logged, and delivery is deferred.
19745 .option disable_logging transports boolean false
19746 If this option is set true, nothing is logged for any
19747 deliveries by the transport or for any
19748 transport errors. You should not set this option unless you really, really know
19749 what you are doing.
19752 .option debug_print transports string&!! unset
19753 .cindex "testing" "variables in drivers"
19754 If this option is set and debugging is enabled (see the &%-d%& command line
19755 option), the string is expanded and included in the debugging output when the
19757 If expansion of the string fails, the error message is written to the debugging
19758 output, and Exim carries on processing.
19759 This facility is provided to help with checking out the values of variables and
19760 so on when debugging driver configurations. For example, if a &%headers_add%&
19761 option is not working properly, &%debug_print%& could be used to output the
19762 variables it references. A newline is added to the text if it does not end with
19764 The variables &$transport_name$& and &$router_name$& contain the name of the
19765 transport and the router that called it.
19767 .option delivery_date_add transports boolean false
19768 .cindex "&'Delivery-date:'& header line"
19769 If this option is true, a &'Delivery-date:'& header is added to the message.
19770 This gives the actual time the delivery was made. As this is not a standard
19771 header, Exim has a configuration option (&%delivery_date_remove%&) which
19772 requests its removal from incoming messages, so that delivered messages can
19773 safely be resent to other recipients.
19776 .option driver transports string unset
19777 This specifies which of the available transport drivers is to be used.
19778 There is no default, and this option must be set for every transport.
19781 .option envelope_to_add transports boolean false
19782 .cindex "&'Envelope-to:'& header line"
19783 If this option is true, an &'Envelope-to:'& header is added to the message.
19784 This gives the original address(es) in the incoming envelope that caused this
19785 delivery to happen. More than one address may be present if the transport is
19786 configured to handle several addresses at once, or if more than one original
19787 address was redirected to the same final address. As this is not a standard
19788 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
19789 its removal from incoming messages, so that delivered messages can safely be
19790 resent to other recipients.
19793 .option group transports string&!! "Exim group"
19794 .cindex "transport" "group; specifying"
19795 This option specifies a gid for running the transport process, overriding any
19796 value that the router supplies, and also overriding any value associated with
19797 &%user%& (see below).
19800 .option headers_add transports string&!! unset
19801 .cindex "header lines" "adding in transport"
19802 .cindex "transport" "header lines; adding"
19803 This option specifies a string of text that is expanded and added to the header
19804 portion of a message as it is transported, as described in section
19805 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
19806 routers. If the result of the expansion is an empty string, or if the expansion
19807 is forced to fail, no action is taken. Other expansion failures are treated as
19808 errors and cause the delivery to be deferred.
19810 Unlike most options, &%headers_add%& can be specified multiple times
19811 for a transport; all listed headers are added.
19814 .option headers_only transports boolean false
19815 .cindex "transport" "header lines only"
19816 .cindex "message" "transporting headers only"
19817 .cindex "header lines" "transporting"
19818 If this option is set, the message's body is not transported. It is mutually
19819 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
19820 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
19821 checked, since this option does not automatically suppress them.
19824 .option headers_remove transports string&!! unset
19825 .cindex "header lines" "removing"
19826 .cindex "transport" "header lines; removing"
19827 This option specifies a string that is expanded into a list of header names;
19828 these headers are omitted from the message as it is transported, as described
19829 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
19830 routers. If the result of the expansion is an empty string, or if the expansion
19831 is forced to fail, no action is taken. Other expansion failures are treated as
19832 errors and cause the delivery to be deferred.
19834 Unlike most options, &%headers_remove%& can be specified multiple times
19835 for a router; all listed headers are added.
19839 .option headers_rewrite transports string unset
19840 .cindex "transport" "header lines; rewriting"
19841 .cindex "rewriting" "at transport time"
19842 This option allows addresses in header lines to be rewritten at transport time,
19843 that is, as the message is being copied to its destination. The contents of the
19844 option are a colon-separated list of rewriting rules. Each rule is in exactly
19845 the same form as one of the general rewriting rules that are applied when a
19846 message is received. These are described in chapter &<<CHAPrewrite>>&. For
19849 headers_rewrite = a@b c@d f : \
19852 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
19853 &'w@z'& in all address-bearing header lines. The rules are applied to the
19854 header lines just before they are written out at transport time, so they affect
19855 only those copies of the message that pass through the transport. However, only
19856 the message's original header lines, and any that were added by a system
19857 filter, are rewritten. If a router or transport adds header lines, they are not
19858 affected by this option. These rewriting rules are &'not'& applied to the
19859 envelope. You can change the return path using &%return_path%&, but you cannot
19860 change envelope recipients at this time.
19863 .option home_directory transports string&!! unset
19864 .cindex "transport" "home directory for"
19866 This option specifies a home directory setting for a local transport,
19867 overriding any value that may be set by the router. The home directory is
19868 placed in &$home$& while expanding the transport's private options. It is also
19869 used as the current directory if no current directory is set by the
19870 &%current_directory%& option on the transport or the
19871 &%transport_current_directory%& option on the router. If the expansion fails
19872 for any reason, including forced failure, an error is logged, and delivery is
19876 .option initgroups transports boolean false
19877 .cindex "additional groups"
19878 .cindex "groups" "additional"
19879 .cindex "transport" "group; additional"
19880 If this option is true and the uid for the delivery process is provided by the
19881 transport, the &[initgroups()]& function is called when running the transport
19882 to ensure that any additional groups associated with the uid are set up.
19885 .option message_size_limit transports string&!! 0
19886 .cindex "limit" "message size per transport"
19887 .cindex "size" "of message, limit"
19888 .cindex "transport" "message size; limiting"
19889 This option controls the size of messages passed through the transport. It is
19890 expanded before use; the result of the expansion must be a sequence of decimal
19891 digits, optionally followed by K or M. If the expansion fails for any reason,
19892 including forced failure, or if the result is not of the required form,
19893 delivery is deferred. If the value is greater than zero and the size of a
19894 message exceeds this limit, the address is failed. If there is any chance that
19895 the resulting bounce message could be routed to the same transport, you should
19896 ensure that &%return_size_limit%& is less than the transport's
19897 &%message_size_limit%&, as otherwise the bounce message will fail to get
19902 .option rcpt_include_affixes transports boolean false
19903 .cindex "prefix" "for local part, including in envelope"
19904 .cindex "suffix for local part" "including in envelope"
19905 .cindex "local part" "prefix"
19906 .cindex "local part" "suffix"
19907 When this option is false (the default), and an address that has had any
19908 affixes (prefixes or suffixes) removed from the local part is delivered by any
19909 form of SMTP or LMTP, the affixes are not included. For example, if a router
19912 local_part_prefix = *-
19914 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
19917 RCPT TO:<xyz@some.domain>
19919 This is also the case when an ACL-time callout is being used to verify a
19920 recipient address. However, if &%rcpt_include_affixes%& is set true, the
19921 whole local part is included in the RCPT command. This option applies to BSMTP
19922 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
19923 &(lmtp)& and &(smtp)& transports.
19926 .option retry_use_local_part transports boolean "see below"
19927 .cindex "hints database" "retry keys"
19928 When a delivery suffers a temporary failure, a retry record is created
19929 in Exim's hints database. For remote deliveries, the key for the retry record
19930 is based on the name and/or IP address of the failing remote host. For local
19931 deliveries, the key is normally the entire address, including both the local
19932 part and the domain. This is suitable for most common cases of local delivery
19933 temporary failure &-- for example, exceeding a mailbox quota should delay only
19934 deliveries to that mailbox, not to the whole domain.
19936 However, in some special cases you may want to treat a temporary local delivery
19937 as a failure associated with the domain, and not with a particular local part.
19938 (For example, if you are storing all mail for some domain in files.) You can do
19939 this by setting &%retry_use_local_part%& false.
19941 For all the local transports, its default value is true. For remote transports,
19942 the default value is false for tidiness, but changing the value has no effect
19943 on a remote transport in the current implementation.
19946 .option return_path transports string&!! unset
19947 .cindex "envelope sender"
19948 .cindex "transport" "return path; changing"
19949 .cindex "return path" "changing in transport"
19950 If this option is set, the string is expanded at transport time and replaces
19951 the existing return path (envelope sender) value in the copy of the message
19952 that is being delivered. An empty return path is permitted. This feature is
19953 designed for remote deliveries, where the value of this option is used in the
19954 SMTP MAIL command. If you set &%return_path%& for a local transport, the
19955 only effect is to change the address that is placed in the &'Return-path:'&
19956 header line, if one is added to the message (see the next option).
19958 &*Note:*& A changed return path is not logged unless you add
19959 &%return_path_on_delivery%& to the log selector.
19961 .vindex "&$return_path$&"
19962 The expansion can refer to the existing value via &$return_path$&. This is
19963 either the message's envelope sender, or an address set by the
19964 &%errors_to%& option on a router. If the expansion is forced to fail, no
19965 replacement occurs; if it fails for another reason, delivery is deferred. This
19966 option can be used to support VERP (Variable Envelope Return Paths) &-- see
19967 section &<<SECTverp>>&.
19969 &*Note*&: If a delivery error is detected locally, including the case when a
19970 remote server rejects a message at SMTP time, the bounce message is not sent to
19971 the value of this option. It is sent to the previously set errors address.
19972 This defaults to the incoming sender address, but can be changed by setting
19973 &%errors_to%& in a router.
19977 .option return_path_add transports boolean false
19978 .cindex "&'Return-path:'& header line"
19979 If this option is true, a &'Return-path:'& header is added to the message.
19980 Although the return path is normally available in the prefix line of BSD
19981 mailboxes, this is commonly not displayed by MUAs, and so the user does not
19982 have easy access to it.
19984 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
19985 the delivery SMTP server makes the final delivery"&. This implies that this
19986 header should not be present in incoming messages. Exim has a configuration
19987 option, &%return_path_remove%&, which requests removal of this header from
19988 incoming messages, so that delivered messages can safely be resent to other
19992 .option shadow_condition transports string&!! unset
19993 See &%shadow_transport%& below.
19996 .option shadow_transport transports string unset
19997 .cindex "shadow transport"
19998 .cindex "transport" "shadow"
19999 A local transport may set the &%shadow_transport%& option to the name of
20000 another local transport. Shadow remote transports are not supported.
20002 Whenever a delivery to the main transport succeeds, and either
20003 &%shadow_condition%& is unset, or its expansion does not result in the empty
20004 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20005 passed to the shadow transport, with the same delivery address or addresses. If
20006 expansion fails, no action is taken except that non-forced expansion failures
20007 cause a log line to be written.
20009 The result of the shadow transport is discarded and does not affect the
20010 subsequent processing of the message. Only a single level of shadowing is
20011 provided; the &%shadow_transport%& option is ignored on any transport when it
20012 is running as a shadow. Options concerned with output from pipes are also
20013 ignored. The log line for the successful delivery has an item added on the end,
20016 ST=<shadow transport name>
20018 If the shadow transport did not succeed, the error message is put in
20019 parentheses afterwards. Shadow transports can be used for a number of different
20020 purposes, including keeping more detailed log information than Exim normally
20021 provides, and implementing automatic acknowledgment policies based on message
20022 headers that some sites insist on.
20025 .option transport_filter transports string&!! unset
20026 .cindex "transport" "filter"
20027 .cindex "filter" "transport filter"
20028 This option sets up a filtering (in the Unix shell sense) process for messages
20029 at transport time. It should not be confused with mail filtering as set up by
20030 individual users or via a system filter.
20032 When the message is about to be written out, the command specified by
20033 &%transport_filter%& is started up in a separate, parallel process, and
20034 the entire message, including the header lines, is passed to it on its standard
20035 input (this in fact is done from a third process, to avoid deadlock). The
20036 command must be specified as an absolute path.
20038 The lines of the message that are written to the transport filter are
20039 terminated by newline (&"\n"&). The message is passed to the filter before any
20040 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20041 lines beginning with a dot, and also before any processing implied by the
20042 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20043 &(pipe)& transports.
20045 The standard error for the filter process is set to the same destination as its
20046 standard output; this is read and written to the message's ultimate
20047 destination. The process that writes the message to the filter, the
20048 filter itself, and the original process that reads the result and delivers it
20049 are all run in parallel, like a shell pipeline.
20051 The filter can perform any transformations it likes, but of course should take
20052 care not to break RFC 2822 syntax. Exim does not check the result, except to
20053 test for a final newline when SMTP is in use. All messages transmitted over
20054 SMTP must end with a newline, so Exim supplies one if it is missing.
20056 .cindex "content scanning" "per user"
20057 A transport filter can be used to provide content-scanning on a per-user basis
20058 at delivery time if the only required effect of the scan is to modify the
20059 message. For example, a content scan could insert a new header line containing
20060 a spam score. This could be interpreted by a filter in the user's MUA. It is
20061 not possible to discard a message at this stage.
20063 .cindex "SMTP" "SIZE"
20064 A problem might arise if the filter increases the size of a message that is
20065 being sent down an SMTP connection. If the receiving SMTP server has indicated
20066 support for the SIZE parameter, Exim will have sent the size of the message
20067 at the start of the SMTP session. If what is actually sent is substantially
20068 more, the server might reject the message. This can be worked round by setting
20069 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20070 additions to the message, or to disable the use of SIZE altogether.
20072 .vindex "&$pipe_addresses$&"
20073 The value of the &%transport_filter%& option is the command string for starting
20074 the filter, which is run directly from Exim, not under a shell. The string is
20075 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20076 Exim breaks it up into arguments and then expands each argument separately (see
20077 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20078 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20079 of arguments, one for each address that applies to this delivery. (This isn't
20080 an ideal name for this feature here, but as it was already implemented for the
20081 &(pipe)& transport, it seemed sensible not to change it.)
20084 .vindex "&$host_address$&"
20085 The expansion variables &$host$& and &$host_address$& are available when the
20086 transport is a remote one. They contain the name and IP address of the host to
20087 which the message is being sent. For example:
20089 transport_filter = /some/directory/transport-filter.pl \
20090 $host $host_address $sender_address $pipe_addresses
20093 Two problems arise if you want to use more complicated expansion items to
20094 generate transport filter commands, both of which due to the fact that the
20095 command is split up &'before'& expansion.
20097 If an expansion item contains white space, you must quote it, so that it is all
20098 part of the same command item. If the entire option setting is one such
20099 expansion item, you have to take care what kind of quoting you use. For
20102 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20104 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20105 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20106 stripped by Exim when it read the option's value. When the value is used, if
20107 the single quotes were missing, the line would be split into two items,
20108 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20109 Exim tried to expand the first one.
20111 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20112 expansion cannot generate multiple arguments, or a command name followed by
20113 arguments. Consider this example:
20115 transport_filter = ${lookup{$host}lsearch{/a/file}\
20116 {$value}{/bin/cat}}
20118 The result of the lookup is interpreted as the name of the command, even
20119 if it contains white space. The simplest way round this is to use a shell:
20121 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20122 {$value}{/bin/cat}}
20126 The filter process is run under the same uid and gid as the normal delivery.
20127 For remote deliveries this is the Exim uid/gid by default. The command should
20128 normally yield a zero return code. Transport filters are not supposed to fail.
20129 A non-zero code is taken to mean that the transport filter encountered some
20130 serious problem. Delivery of the message is deferred; the message remains on
20131 the queue and is tried again later. It is not possible to cause a message to be
20132 bounced from a transport filter.
20134 If a transport filter is set on an autoreply transport, the original message is
20135 passed through the filter as it is being copied into the newly generated
20136 message, which happens if the &%return_message%& option is set.
20139 .option transport_filter_timeout transports time 5m
20140 .cindex "transport" "filter, timeout"
20141 When Exim is reading the output of a transport filter, it applies a timeout
20142 that can be set by this option. Exceeding the timeout is normally treated as a
20143 temporary delivery failure. However, if a transport filter is used with a
20144 &(pipe)& transport, a timeout in the transport filter is treated in the same
20145 way as a timeout in the pipe command itself. By default, a timeout is a hard
20146 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20147 becomes a temporary error.
20150 .option user transports string&!! "Exim user"
20151 .cindex "uid (user id)" "local delivery"
20152 .cindex "transport" "user, specifying"
20153 This option specifies the user under whose uid the delivery process is to be
20154 run, overriding any uid that may have been set by the router. If the user is
20155 given as a name, the uid is looked up from the password data, and the
20156 associated group is taken as the value of the gid to be used if the &%group%&
20159 For deliveries that use local transports, a user and group are normally
20160 specified explicitly or implicitly (for example, as a result of
20161 &%check_local_user%&) by the router or transport.
20163 .cindex "hints database" "access by remote transport"
20164 For remote transports, you should leave this option unset unless you really are
20165 sure you know what you are doing. When a remote transport is running, it needs
20166 to be able to access Exim's hints databases, because each host may have its own
20168 .ecindex IIDgenoptra1
20169 .ecindex IIDgenoptra2
20170 .ecindex IIDgenoptra3
20177 . ////////////////////////////////////////////////////////////////////////////
20178 . ////////////////////////////////////////////////////////////////////////////
20180 .chapter "Address batching in local transports" "CHAPbatching" &&&
20182 .cindex "transport" "local; address batching in"
20183 The only remote transport (&(smtp)&) is normally configured to handle more than
20184 one address at a time, so that when several addresses are routed to the same
20185 remote host, just one copy of the message is sent. Local transports, however,
20186 normally handle one address at a time. That is, a separate instance of the
20187 transport is run for each address that is routed to the transport. A separate
20188 copy of the message is delivered each time.
20190 .cindex "batched local delivery"
20191 .oindex "&%batch_max%&"
20192 .oindex "&%batch_id%&"
20193 In special cases, it may be desirable to handle several addresses at once in a
20194 local transport, for example:
20197 In an &(appendfile)& transport, when storing messages in files for later
20198 delivery by some other means, a single copy of the message with multiple
20199 recipients saves space.
20201 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
20202 a single copy saves time, and is the normal way LMTP is expected to work.
20204 In a &(pipe)& transport, when passing the message
20205 to a scanner program or
20206 to some other delivery mechanism such as UUCP, multiple recipients may be
20210 These three local transports all have the same options for controlling multiple
20211 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
20212 repeating the information for each transport, these options are described here.
20214 The &%batch_max%& option specifies the maximum number of addresses that can be
20215 delivered together in a single run of the transport. Its default value is one
20216 (no batching). When more than one address is routed to a transport that has a
20217 &%batch_max%& value greater than one, the addresses are delivered in a batch
20218 (that is, in a single run of the transport with multiple recipients), subject
20219 to certain conditions:
20222 .vindex "&$local_part$&"
20223 If any of the transport's options contain a reference to &$local_part$&, no
20224 batching is possible.
20226 .vindex "&$domain$&"
20227 If any of the transport's options contain a reference to &$domain$&, only
20228 addresses with the same domain are batched.
20230 .cindex "customizing" "batching condition"
20231 If &%batch_id%& is set, it is expanded for each address, and only those
20232 addresses with the same expanded value are batched. This allows you to specify
20233 customized batching conditions. Failure of the expansion for any reason,
20234 including forced failure, disables batching, but it does not stop the delivery
20237 Batched addresses must also have the same errors address (where to send
20238 delivery errors), the same header additions and removals, the same user and
20239 group for the transport, and if a host list is present, the first host must
20243 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
20244 both when the file or pipe command is specified in the transport, and when it
20245 is specified by a &(redirect)& router, but all the batched addresses must of
20246 course be routed to the same file or pipe command. These two transports have an
20247 option called &%use_bsmtp%&, which causes them to deliver the message in
20248 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
20249 &%check_string%& and &%escape_string%& options are forced to the values
20252 escape_string = ".."
20254 when batched SMTP is in use. A full description of the batch SMTP mechanism is
20255 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
20256 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
20258 .cindex "&'Envelope-to:'& header line"
20259 If the generic &%envelope_to_add%& option is set for a batching transport, the
20260 &'Envelope-to:'& header that is added to the message contains all the addresses
20261 that are being processed together. If you are using a batching &(appendfile)&
20262 transport without &%use_bsmtp%&, the only way to preserve the recipient
20263 addresses is to set the &%envelope_to_add%& option.
20265 .cindex "&(pipe)& transport" "with multiple addresses"
20266 .vindex "&$pipe_addresses$&"
20267 If you are using a &(pipe)& transport without BSMTP, and setting the
20268 transport's &%command%& option, you can include &$pipe_addresses$& as part of
20269 the command. This is not a true variable; it is a bit of magic that causes each
20270 of the recipient addresses to be inserted into the command as a separate
20271 argument. This provides a way of accessing all the addresses that are being
20272 delivered in the batch. &*Note:*& This is not possible for pipe commands that
20273 are specified by a &(redirect)& router.
20278 . ////////////////////////////////////////////////////////////////////////////
20279 . ////////////////////////////////////////////////////////////////////////////
20281 .chapter "The appendfile transport" "CHAPappendfile"
20282 .scindex IIDapptra1 "&(appendfile)& transport"
20283 .scindex IIDapptra2 "transports" "&(appendfile)&"
20284 .cindex "directory creation"
20285 .cindex "creating directories"
20286 The &(appendfile)& transport delivers a message by appending it to an existing
20287 file, or by creating an entirely new file in a specified directory. Single
20288 files to which messages are appended can be in the traditional Unix mailbox
20289 format, or optionally in the MBX format supported by the Pine MUA and
20290 University of Washington IMAP daemon, &'inter alia'&. When each message is
20291 being delivered as a separate file, &"maildir"& format can optionally be used
20292 to give added protection against failures that happen part-way through the
20293 delivery. A third form of separate-file delivery known as &"mailstore"& is also
20294 supported. For all file formats, Exim attempts to create as many levels of
20295 directory as necessary, provided that &%create_directory%& is set.
20297 The code for the optional formats is not included in the Exim binary by
20298 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
20299 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
20302 .cindex "quota" "system"
20303 Exim recognizes system quota errors, and generates an appropriate message. Exim
20304 also supports its own quota control within the transport, for use when the
20305 system facility is unavailable or cannot be used for some reason.
20307 If there is an error while appending to a file (for example, quota exceeded or
20308 partition filled), Exim attempts to reset the file's length and last
20309 modification time back to what they were before. If there is an error while
20310 creating an entirely new file, the new file is removed.
20312 Before appending to a file, a number of security checks are made, and the
20313 file is locked. A detailed description is given below, after the list of
20316 The &(appendfile)& transport is most commonly used for local deliveries to
20317 users' mailboxes. However, it can also be used as a pseudo-remote transport for
20318 putting messages into files for remote delivery by some means other than Exim.
20319 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
20324 .section "The file and directory options" "SECTfildiropt"
20325 The &%file%& option specifies a single file, to which the message is appended;
20326 the &%directory%& option specifies a directory, in which a new file containing
20327 the message is created. Only one of these two options can be set, and for
20328 normal deliveries to mailboxes, one of them &'must'& be set.
20330 .vindex "&$address_file$&"
20331 .vindex "&$local_part$&"
20332 However, &(appendfile)& is also used for delivering messages to files or
20333 directories whose names (or parts of names) are obtained from alias,
20334 forwarding, or filtering operations (for example, a &%save%& command in a
20335 user's Exim filter). When such a transport is running, &$local_part$& contains
20336 the local part that was aliased or forwarded, and &$address_file$& contains the
20337 name (or partial name) of the file or directory generated by the redirection
20338 operation. There are two cases:
20341 If neither &%file%& nor &%directory%& is set, the redirection operation
20342 must specify an absolute path (one that begins with &`/`&). This is the most
20343 common case when users with local accounts use filtering to sort mail into
20344 different folders. See for example, the &(address_file)& transport in the
20345 default configuration. If the path ends with a slash, it is assumed to be the
20346 name of a directory. A delivery to a directory can also be forced by setting
20347 &%maildir_format%& or &%mailstore_format%&.
20349 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
20350 used to determine the file or directory name for the delivery. Normally, the
20351 contents of &$address_file$& are used in some way in the string expansion.
20355 .cindex "Sieve filter" "configuring &(appendfile)&"
20356 .cindex "Sieve filter" "relative mailbox path handling"
20357 As an example of the second case, consider an environment where users do not
20358 have home directories. They may be permitted to use Exim filter commands of the
20363 or Sieve filter commands of the form:
20365 require "fileinto";
20366 fileinto "folder23";
20368 In this situation, the expansion of &%file%& or &%directory%& in the transport
20369 must transform the relative path into an appropriate absolute file name. In the
20370 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
20371 is used as a result of a &"keep"& action in the filter. This example shows one
20372 way of handling this requirement:
20374 file = ${if eq{$address_file}{inbox} \
20375 {/var/mail/$local_part} \
20376 {${if eq{${substr_0_1:$address_file}}{/} \
20378 {$home/mail/$address_file} \
20382 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
20383 location, absolute paths are used without change, and other folders are in the
20384 &_mail_& directory within the home directory.
20386 &*Note 1*&: While processing an Exim filter, a relative path such as
20387 &_folder23_& is turned into an absolute path if a home directory is known to
20388 the router. In particular, this is the case if &%check_local_user%& is set. If
20389 you want to prevent this happening at routing time, you can set
20390 &%router_home_directory%& empty. This forces the router to pass the relative
20391 path to the transport.
20393 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
20394 the &%file%& or &%directory%& option is still used if it is set.
20399 .section "Private options for appendfile" "SECID134"
20400 .cindex "options" "&(appendfile)& transport"
20404 .option allow_fifo appendfile boolean false
20405 .cindex "fifo (named pipe)"
20406 .cindex "named pipe (fifo)"
20407 .cindex "pipe" "named (fifo)"
20408 Setting this option permits delivery to named pipes (FIFOs) as well as to
20409 regular files. If no process is reading the named pipe at delivery time, the
20410 delivery is deferred.
20413 .option allow_symlink appendfile boolean false
20414 .cindex "symbolic link" "to mailbox"
20415 .cindex "mailbox" "symbolic link"
20416 By default, &(appendfile)& will not deliver if the path name for the file is
20417 that of a symbolic link. Setting this option relaxes that constraint, but there
20418 are security issues involved in the use of symbolic links. Be sure you know
20419 what you are doing if you set this. Details of exactly what this option affects
20420 are included in the discussion which follows this list of options.
20423 .option batch_id appendfile string&!! unset
20424 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20425 However, batching is automatically disabled for &(appendfile)& deliveries that
20426 happen as a result of forwarding or aliasing or other redirection directly to a
20430 .option batch_max appendfile integer 1
20431 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20434 .option check_group appendfile boolean false
20435 When this option is set, the group owner of the file defined by the &%file%&
20436 option is checked to see that it is the same as the group under which the
20437 delivery process is running. The default setting is false because the default
20438 file mode is 0600, which means that the group is irrelevant.
20441 .option check_owner appendfile boolean true
20442 When this option is set, the owner of the file defined by the &%file%& option
20443 is checked to ensure that it is the same as the user under which the delivery
20444 process is running.
20447 .option check_string appendfile string "see below"
20448 .cindex "&""From""& line"
20449 As &(appendfile)& writes the message, the start of each line is tested for
20450 matching &%check_string%&, and if it does, the initial matching characters are
20451 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
20452 a literal string, not a regular expression, and the case of any letters it
20453 contains is significant.
20455 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
20456 are forced to &"."& and &".."& respectively, and any settings in the
20457 configuration are ignored. Otherwise, they default to &"From&~"& and
20458 &">From&~"& when the &%file%& option is set, and unset when any of the
20459 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
20461 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
20462 suitable for traditional &"BSD"& mailboxes, where a line beginning with
20463 &"From&~"& indicates the start of a new message. All four options need changing
20464 if another format is used. For example, to deliver to mailboxes in MMDF format:
20465 .cindex "MMDF format mailbox"
20466 .cindex "mailbox" "MMDF format"
20468 check_string = "\1\1\1\1\n"
20469 escape_string = "\1\1\1\1 \n"
20470 message_prefix = "\1\1\1\1\n"
20471 message_suffix = "\1\1\1\1\n"
20473 .option create_directory appendfile boolean true
20474 .cindex "directory creation"
20475 When this option is true, Exim attempts to create any missing superior
20476 directories for the file that it is about to write. A created directory's mode
20477 is given by the &%directory_mode%& option.
20479 The group ownership of a newly created directory is highly dependent on the
20480 operating system (and possibly the file system) that is being used. For
20481 example, in Solaris, if the parent directory has the setgid bit set, its group
20482 is propagated to the child; if not, the currently set group is used. However,
20483 in FreeBSD, the parent's group is always used.
20487 .option create_file appendfile string anywhere
20488 This option constrains the location of files and directories that are created
20489 by this transport. It applies to files defined by the &%file%& option and
20490 directories defined by the &%directory%& option. In the case of maildir
20491 delivery, it applies to the top level directory, not the maildir directories
20494 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
20495 &"belowhome"&. In the second and third cases, a home directory must have been
20496 set for the transport. This option is not useful when an explicit file name is
20497 given for normal mailbox deliveries. It is intended for the case when file
20498 names are generated from users' &_.forward_& files. These are usually handled
20499 by an &(appendfile)& transport called &%address_file%&. See also
20500 &%file_must_exist%&.
20503 .option directory appendfile string&!! unset
20504 This option is mutually exclusive with the &%file%& option, but one of &%file%&
20505 or &%directory%& must be set, unless the delivery is the direct result of a
20506 redirection (see section &<<SECTfildiropt>>&).
20508 When &%directory%& is set, the string is expanded, and the message is delivered
20509 into a new file or files in or below the given directory, instead of being
20510 appended to a single mailbox file. A number of different formats are provided
20511 (see &%maildir_format%& and &%mailstore_format%&), and see section
20512 &<<SECTopdir>>& for further details of this form of delivery.
20515 .option directory_file appendfile string&!! "see below"
20517 .vindex "&$inode$&"
20518 When &%directory%& is set, but neither &%maildir_format%& nor
20519 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
20520 whose name is obtained by expanding this string. The default value is:
20522 q${base62:$tod_epoch}-$inode
20524 This generates a unique name from the current time, in base 62 form, and the
20525 inode of the file. The variable &$inode$& is available only when expanding this
20529 .option directory_mode appendfile "octal integer" 0700
20530 If &(appendfile)& creates any directories as a result of the
20531 &%create_directory%& option, their mode is specified by this option.
20534 .option escape_string appendfile string "see description"
20535 See &%check_string%& above.
20538 .option file appendfile string&!! unset
20539 This option is mutually exclusive with the &%directory%& option, but one of
20540 &%file%& or &%directory%& must be set, unless the delivery is the direct result
20541 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
20542 specifies a single file, to which the message is appended. One or more of
20543 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
20546 .cindex "NFS" "lock file"
20547 .cindex "locking files"
20548 .cindex "lock files"
20549 If you are using more than one host to deliver over NFS into the same
20550 mailboxes, you should always use lock files.
20552 The string value is expanded for each delivery, and must yield an absolute
20553 path. The most common settings of this option are variations on one of these
20556 file = /var/spool/mail/$local_part
20557 file = /home/$local_part/inbox
20560 .cindex "&""sticky""& bit"
20561 In the first example, all deliveries are done into the same directory. If Exim
20562 is configured to use lock files (see &%use_lockfile%& below) it must be able to
20563 create a file in the directory, so the &"sticky"& bit must be turned on for
20564 deliveries to be possible, or alternatively the &%group%& option can be used to
20565 run the delivery under a group id which has write access to the directory.
20569 .option file_format appendfile string unset
20570 .cindex "file" "mailbox; checking existing format"
20571 This option requests the transport to check the format of an existing file
20572 before adding to it. The check consists of matching a specific string at the
20573 start of the file. The value of the option consists of an even number of
20574 colon-separated strings. The first of each pair is the test string, and the
20575 second is the name of a transport. If the transport associated with a matched
20576 string is not the current transport, control is passed over to the other
20577 transport. For example, suppose the standard &(local_delivery)& transport has
20580 file_format = "From : local_delivery :\
20581 \1\1\1\1\n : local_mmdf_delivery"
20583 Mailboxes that begin with &"From"& are still handled by this transport, but if
20584 a mailbox begins with four binary ones followed by a newline, control is passed
20585 to a transport called &%local_mmdf_delivery%&, which presumably is configured
20586 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
20587 is assumed to match the current transport. If the start of a mailbox doesn't
20588 match any string, or if the transport named for a given string is not defined,
20589 delivery is deferred.
20592 .option file_must_exist appendfile boolean false
20593 If this option is true, the file specified by the &%file%& option must exist.
20594 A temporary error occurs if it does not, causing delivery to be deferred.
20595 If this option is false, the file is created if it does not exist.
20598 .option lock_fcntl_timeout appendfile time 0s
20599 .cindex "timeout" "mailbox locking"
20600 .cindex "mailbox" "locking, blocking and non-blocking"
20601 .cindex "locking files"
20602 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
20603 when locking an open mailbox file. If the call fails, the delivery process
20604 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
20605 Non-blocking calls are used so that the file is not kept open during the wait
20606 for the lock; the reason for this is to make it as safe as possible for
20607 deliveries over NFS in the case when processes might be accessing an NFS
20608 mailbox without using a lock file. This should not be done, but
20609 misunderstandings and hence misconfigurations are not unknown.
20611 On a busy system, however, the performance of a non-blocking lock approach is
20612 not as good as using a blocking lock with a timeout. In this case, the waiting
20613 is done inside the system call, and Exim's delivery process acquires the lock
20614 and can proceed as soon as the previous lock holder releases it.
20616 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
20617 timeout, are used. There may still be some retrying: the maximum number of
20620 (lock_retries * lock_interval) / lock_fcntl_timeout
20622 rounded up to the next whole number. In other words, the total time during
20623 which &(appendfile)& is trying to get a lock is roughly the same, unless
20624 &%lock_fcntl_timeout%& is set very large.
20626 You should consider setting this option if you are getting a lot of delayed
20627 local deliveries because of errors of the form
20629 failed to lock mailbox /some/file (fcntl)
20632 .option lock_flock_timeout appendfile time 0s
20633 This timeout applies to file locking when using &[flock()]& (see
20634 &%use_flock%&); the timeout operates in a similar manner to
20635 &%lock_fcntl_timeout%&.
20638 .option lock_interval appendfile time 3s
20639 This specifies the time to wait between attempts to lock the file. See below
20640 for details of locking.
20643 .option lock_retries appendfile integer 10
20644 This specifies the maximum number of attempts to lock the file. A value of zero
20645 is treated as 1. See below for details of locking.
20648 .option lockfile_mode appendfile "octal integer" 0600
20649 This specifies the mode of the created lock file, when a lock file is being
20650 used (see &%use_lockfile%& and &%use_mbx_lock%&).
20653 .option lockfile_timeout appendfile time 30m
20654 .cindex "timeout" "mailbox locking"
20655 When a lock file is being used (see &%use_lockfile%&), if a lock file already
20656 exists and is older than this value, it is assumed to have been left behind by
20657 accident, and Exim attempts to remove it.
20660 .option mailbox_filecount appendfile string&!! unset
20661 .cindex "mailbox" "specifying size of"
20662 .cindex "size" "of mailbox"
20663 If this option is set, it is expanded, and the result is taken as the current
20664 number of files in the mailbox. It must be a decimal number, optionally
20665 followed by K or M. This provides a way of obtaining this information from an
20666 external source that maintains the data.
20669 .option mailbox_size appendfile string&!! unset
20670 .cindex "mailbox" "specifying size of"
20671 .cindex "size" "of mailbox"
20672 If this option is set, it is expanded, and the result is taken as the current
20673 size the mailbox. It must be a decimal number, optionally followed by K or M.
20674 This provides a way of obtaining this information from an external source that
20675 maintains the data. This is likely to be helpful for maildir deliveries where
20676 it is computationally expensive to compute the size of a mailbox.
20680 .option maildir_format appendfile boolean false
20681 .cindex "maildir format" "specifying"
20682 If this option is set with the &%directory%& option, the delivery is into a new
20683 file, in the &"maildir"& format that is used by other mail software. When the
20684 transport is activated directly from a &(redirect)& router (for example, the
20685 &(address_file)& transport in the default configuration), setting
20686 &%maildir_format%& causes the path received from the router to be treated as a
20687 directory, whether or not it ends with &`/`&. This option is available only if
20688 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
20689 &<<SECTmaildirdelivery>>& below for further details.
20692 .option maildir_quota_directory_regex appendfile string "See below"
20693 .cindex "maildir format" "quota; directories included in"
20694 .cindex "quota" "maildir; directories included in"
20695 This option is relevant only when &%maildir_use_size_file%& is set. It defines
20696 a regular expression for specifying directories, relative to the quota
20697 directory (see &%quota_directory%&), that should be included in the quota
20698 calculation. The default value is:
20700 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
20702 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
20703 (directories whose names begin with a dot). If you want to exclude the
20705 folder from the count (as some sites do), you need to change this setting to
20707 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
20709 This uses a negative lookahead in the regular expression to exclude the
20710 directory whose name is &_.Trash_&. When a directory is excluded from quota
20711 calculations, quota processing is bypassed for any messages that are delivered
20712 directly into that directory.
20715 .option maildir_retries appendfile integer 10
20716 This option specifies the number of times to retry when writing a file in
20717 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
20720 .option maildir_tag appendfile string&!! unset
20721 This option applies only to deliveries in maildir format, and is described in
20722 section &<<SECTmaildirdelivery>>& below.
20725 .option maildir_use_size_file appendfile&!! boolean false
20726 .cindex "maildir format" "&_maildirsize_& file"
20727 The result of string expansion for this option must be a valid boolean value.
20728 If it is true, it enables support for &_maildirsize_& files. Exim
20729 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
20730 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
20731 value is zero. See &%maildir_quota_directory_regex%& above and section
20732 &<<SECTmaildirdelivery>>& below for further details.
20734 .option maildirfolder_create_regex appendfile string unset
20735 .cindex "maildir format" "&_maildirfolder_& file"
20736 .cindex "&_maildirfolder_&, creating"
20737 The value of this option is a regular expression. If it is unset, it has no
20738 effect. Otherwise, before a maildir delivery takes place, the pattern is
20739 matched against the name of the maildir directory, that is, the directory
20740 containing the &_new_& and &_tmp_& subdirectories that will be used for the
20741 delivery. If there is a match, Exim checks for the existence of a file called
20742 &_maildirfolder_& in the directory, and creates it if it does not exist.
20743 See section &<<SECTmaildirdelivery>>& for more details.
20746 .option mailstore_format appendfile boolean false
20747 .cindex "mailstore format" "specifying"
20748 If this option is set with the &%directory%& option, the delivery is into two
20749 new files in &"mailstore"& format. The option is available only if
20750 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
20751 below for further details.
20754 .option mailstore_prefix appendfile string&!! unset
20755 This option applies only to deliveries in mailstore format, and is described in
20756 section &<<SECTopdir>>& below.
20759 .option mailstore_suffix appendfile string&!! unset
20760 This option applies only to deliveries in mailstore format, and is described in
20761 section &<<SECTopdir>>& below.
20764 .option mbx_format appendfile boolean false
20765 .cindex "locking files"
20766 .cindex "file" "locking"
20767 .cindex "file" "MBX format"
20768 .cindex "MBX format, specifying"
20769 This option is available only if Exim has been compiled with SUPPORT_MBX
20770 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
20771 the message is appended to the mailbox file in MBX format instead of
20772 traditional Unix format. This format is supported by Pine4 and its associated
20773 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
20775 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
20776 automatically changed by the use of &%mbx_format%&. They should normally be set
20777 empty when using MBX format, so this option almost always appears in this
20784 If none of the locking options are mentioned in the configuration,
20785 &%use_mbx_lock%& is assumed and the other locking options default to false. It
20786 is possible to specify the other kinds of locking with &%mbx_format%&, but
20787 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
20788 interworks with &'c-client'&, providing for shared access to the mailbox. It
20789 should not be used if any program that does not use this form of locking is
20790 going to access the mailbox, nor should it be used if the mailbox file is NFS
20791 mounted, because it works only when the mailbox is accessed from a single host.
20793 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
20794 the standard version of &'c-client'&, because as long as it has a mailbox open
20795 (this means for the whole of a Pine or IMAP session), Exim will not be able to
20796 append messages to it.
20799 .option message_prefix appendfile string&!! "see below"
20800 .cindex "&""From""& line"
20801 The string specified here is expanded and output at the start of every message.
20802 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
20803 in which case it is:
20805 message_prefix = "From ${if def:return_path{$return_path}\
20806 {MAILER-DAEMON}} $tod_bsdinbox\n"
20808 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20809 &`\n`& to &`\r\n`& in &%message_prefix%&.
20811 .option message_suffix appendfile string&!! "see below"
20812 The string specified here is expanded and output at the end of every message.
20813 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
20814 in which case it is a single newline character. The suffix can be suppressed by
20819 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20820 &`\n`& to &`\r\n`& in &%message_suffix%&.
20822 .option mode appendfile "octal integer" 0600
20823 If the output file is created, it is given this mode. If it already exists and
20824 has wider permissions, they are reduced to this mode. If it has narrower
20825 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
20826 if the delivery is the result of a &%save%& command in a filter file specifying
20827 a particular mode, the mode of the output file is always forced to take that
20828 value, and this option is ignored.
20831 .option mode_fail_narrower appendfile boolean true
20832 This option applies in the case when an existing mailbox file has a narrower
20833 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
20834 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
20835 continues with the delivery attempt, using the existing mode of the file.
20838 .option notify_comsat appendfile boolean false
20839 If this option is true, the &'comsat'& daemon is notified after every
20840 successful delivery to a user mailbox. This is the daemon that notifies logged
20841 on users about incoming mail.
20844 .option quota appendfile string&!! unset
20845 .cindex "quota" "imposed by Exim"
20846 This option imposes a limit on the size of the file to which Exim is appending,
20847 or to the total space used in the directory tree when the &%directory%& option
20848 is set. In the latter case, computation of the space used is expensive, because
20849 all the files in the directory (and any sub-directories) have to be
20850 individually inspected and their sizes summed. (See &%quota_size_regex%& and
20851 &%maildir_use_size_file%& for ways to avoid this in environments where users
20852 have no shell access to their mailboxes).
20854 As there is no interlock against two simultaneous deliveries into a
20855 multi-file mailbox, it is possible for the quota to be overrun in this case.
20856 For single-file mailboxes, of course, an interlock is a necessity.
20858 A file's size is taken as its &'used'& value. Because of blocking effects, this
20859 may be a lot less than the actual amount of disk space allocated to the file.
20860 If the sizes of a number of files are being added up, the rounding effect can
20861 become quite noticeable, especially on systems that have large block sizes.
20862 Nevertheless, it seems best to stick to the &'used'& figure, because this is
20863 the obvious value which users understand most easily.
20865 The value of the option is expanded, and must then be a numerical value
20866 (decimal point allowed), optionally followed by one of the letters K, M, or G,
20867 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
20868 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
20871 &*Note*&: A value of zero is interpreted as &"no quota"&.
20873 The expansion happens while Exim is running as root, before it changes uid for
20874 the delivery. This means that files that are inaccessible to the end user can
20875 be used to hold quota values that are looked up in the expansion. When delivery
20876 fails because this quota is exceeded, the handling of the error is as for
20877 system quota failures.
20879 By default, Exim's quota checking mimics system quotas, and restricts the
20880 mailbox to the specified maximum size, though the value is not accurate to the
20881 last byte, owing to separator lines and additional headers that may get added
20882 during message delivery. When a mailbox is nearly full, large messages may get
20883 refused even though small ones are accepted, because the size of the current
20884 message is added to the quota when the check is made. This behaviour can be
20885 changed by setting &%quota_is_inclusive%& false. When this is done, the check
20886 for exceeding the quota does not include the current message. Thus, deliveries
20887 continue until the quota has been exceeded; thereafter, no further messages are
20888 delivered. See also &%quota_warn_threshold%&.
20891 .option quota_directory appendfile string&!! unset
20892 This option defines the directory to check for quota purposes when delivering
20893 into individual files. The default is the delivery directory, or, if a file
20894 called &_maildirfolder_& exists in a maildir directory, the parent of the
20895 delivery directory.
20898 .option quota_filecount appendfile string&!! 0
20899 This option applies when the &%directory%& option is set. It limits the total
20900 number of files in the directory (compare the inode limit in system quotas). It
20901 can only be used if &%quota%& is also set. The value is expanded; an expansion
20902 failure causes delivery to be deferred. A value of zero is interpreted as
20906 .option quota_is_inclusive appendfile boolean true
20907 See &%quota%& above.
20910 .option quota_size_regex appendfile string unset
20911 This option applies when one of the delivery modes that writes a separate file
20912 for each message is being used. When Exim wants to find the size of one of
20913 these files in order to test the quota, it first checks &%quota_size_regex%&.
20914 If this is set to a regular expression that matches the file name, and it
20915 captures one string, that string is interpreted as a representation of the
20916 file's size. The value of &%quota_size_regex%& is not expanded.
20918 This feature is useful only when users have no shell access to their mailboxes
20919 &-- otherwise they could defeat the quota simply by renaming the files. This
20920 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
20921 the file length to the file name. For example:
20923 maildir_tag = ,S=$message_size
20924 quota_size_regex = ,S=(\d+)
20926 An alternative to &$message_size$& is &$message_linecount$&, which contains the
20927 number of lines in the message.
20929 The regular expression should not assume that the length is at the end of the
20930 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
20931 sometimes add other information onto the ends of message file names.
20933 Section &<<SECID136>>& contains further information.
20936 .option quota_warn_message appendfile string&!! "see below"
20937 See below for the use of this option. If it is not set when
20938 &%quota_warn_threshold%& is set, it defaults to
20940 quota_warn_message = "\
20941 To: $local_part@$domain\n\
20942 Subject: Your mailbox\n\n\
20943 This message is automatically created \
20944 by mail delivery software.\n\n\
20945 The size of your mailbox has exceeded \
20946 a warning threshold that is\n\
20947 set by the system administrator.\n"
20951 .option quota_warn_threshold appendfile string&!! 0
20952 .cindex "quota" "warning threshold"
20953 .cindex "mailbox" "size warning"
20954 .cindex "size" "of mailbox"
20955 This option is expanded in the same way as &%quota%& (see above). If the
20956 resulting value is greater than zero, and delivery of the message causes the
20957 size of the file or total space in the directory tree to cross the given
20958 threshold, a warning message is sent. If &%quota%& is also set, the threshold
20959 may be specified as a percentage of it by following the value with a percent
20963 quota_warn_threshold = 75%
20965 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
20966 percent sign is ignored.
20968 The warning message itself is specified by the &%quota_warn_message%& option,
20969 and it must start with a &'To:'& header line containing the recipient(s) of the
20970 warning message. These do not necessarily have to include the recipient(s) of
20971 the original message. A &'Subject:'& line should also normally be supplied. You
20972 can include any other header lines that you want. If you do not include a
20973 &'From:'& line, the default is:
20975 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
20977 .oindex &%errors_reply_to%&
20978 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
20981 The &%quota%& option does not have to be set in order to use this option; they
20982 are independent of one another except when the threshold is specified as a
20986 .option use_bsmtp appendfile boolean false
20987 .cindex "envelope sender"
20988 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
20989 format, with the envelope sender and recipient(s) included as SMTP commands. If
20990 you want to include a leading HELO command with such messages, you can do
20991 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
20992 for details of batch SMTP.
20995 .option use_crlf appendfile boolean false
20996 .cindex "carriage return"
20998 This option causes lines to be terminated with the two-character CRLF sequence
20999 (carriage return, linefeed) instead of just a linefeed character. In the case
21000 of batched SMTP, the byte sequence written to the file is then an exact image
21001 of what would be sent down a real SMTP connection.
21003 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21004 (which are used to supply the traditional &"From&~"& and blank line separators
21005 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21006 carriage return characters if these are needed. In cases where these options
21007 have non-empty defaults, the values end with a single linefeed, so they must be
21008 changed to end with &`\r\n`& if &%use_crlf%& is set.
21011 .option use_fcntl_lock appendfile boolean "see below"
21012 This option controls the use of the &[fcntl()]& function to lock a file for
21013 exclusive use when a message is being appended. It is set by default unless
21014 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21015 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21016 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21019 .option use_flock_lock appendfile boolean false
21020 This option is provided to support the use of &[flock()]& for file locking, for
21021 the few situations where it is needed. Most modern operating systems support
21022 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21023 each other. Exim uses &[fcntl()]& locking by default.
21025 This option is required only if you are using an operating system where
21026 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21027 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21028 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21030 .cindex "Solaris" "&[flock()]& support"
21031 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21032 have it (and some, I think, provide a not quite right version built on top of
21033 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21034 the ability to use it, and any attempt to do so will cause a configuration
21037 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21038 is just being mapped onto &[fcntl()]& by the OS).
21041 .option use_lockfile appendfile boolean "see below"
21042 If this option is turned off, Exim does not attempt to create a lock file when
21043 appending to a mailbox file. In this situation, the only locking is by
21044 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21045 sure that every MUA that is ever going to look at your users' mailboxes uses
21046 &[fcntl()]& rather than a lock file, and even then only when you are not
21047 delivering over NFS from more than one host.
21049 .cindex "NFS" "lock file"
21050 In order to append to an NFS file safely from more than one host, it is
21051 necessary to take out a lock &'before'& opening the file, and the lock file
21052 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21055 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21056 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21057 except when &%mbx_format%& is set.
21060 .option use_mbx_lock appendfile boolean "see below"
21061 This option is available only if Exim has been compiled with SUPPORT_MBX
21062 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21063 locking rules be used. It is set by default if &%mbx_format%& is set and none
21064 of the locking options are mentioned in the configuration. The locking rules
21065 are the same as are used by the &'c-client'& library that underlies Pine and
21066 the IMAP4 and POP daemons that come with it (see the discussion below). The
21067 rules allow for shared access to the mailbox. However, this kind of locking
21068 does not work when the mailbox is NFS mounted.
21070 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21071 &%use_flock_lock%& to control what kind of locking is used in implementing the
21072 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21073 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21078 .section "Operational details for appending" "SECTopappend"
21079 .cindex "appending to a file"
21080 .cindex "file" "appending"
21081 Before appending to a file, the following preparations are made:
21084 If the name of the file is &_/dev/null_&, no action is taken, and a success
21088 .cindex "directory creation"
21089 If any directories on the file's path are missing, Exim creates them if the
21090 &%create_directory%& option is set. A created directory's mode is given by the
21091 &%directory_mode%& option.
21094 If &%file_format%& is set, the format of an existing file is checked. If this
21095 indicates that a different transport should be used, control is passed to that
21099 .cindex "file" "locking"
21100 .cindex "locking files"
21101 .cindex "NFS" "lock file"
21102 If &%use_lockfile%& is set, a lock file is built in a way that will work
21103 reliably over NFS, as follows:
21106 Create a &"hitching post"& file whose name is that of the lock file with the
21107 current time, primary host name, and process id added, by opening for writing
21108 as a new file. If this fails with an access error, delivery is deferred.
21110 Close the hitching post file, and hard link it to the lock file name.
21112 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21113 Unlink the hitching post name.
21115 Otherwise, use &[stat()]& to get information about the hitching post file, and
21116 then unlink hitching post name. If the number of links is exactly two, creation
21117 of the lock file succeeded but something (for example, an NFS server crash and
21118 restart) caused this fact not to be communicated to the &[link()]& call.
21120 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21121 up to &%lock_retries%& times. However, since any program that writes to a
21122 mailbox should complete its task very quickly, it is reasonable to time out old
21123 lock files that are normally the result of user agent and system crashes. If an
21124 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21125 it before trying again.
21129 A call is made to &[lstat()]& to discover whether the main file exists, and if
21130 so, what its characteristics are. If &[lstat()]& fails for any reason other
21131 than non-existence, delivery is deferred.
21134 .cindex "symbolic link" "to mailbox"
21135 .cindex "mailbox" "symbolic link"
21136 If the file does exist and is a symbolic link, delivery is deferred, unless the
21137 &%allow_symlink%& option is set, in which case the ownership of the link is
21138 checked, and then &[stat()]& is called to find out about the real file, which
21139 is then subjected to the checks below. The check on the top-level link
21140 ownership prevents one user creating a link for another's mailbox in a sticky
21141 directory, though allowing symbolic links in this case is definitely not a good
21142 idea. If there is a chain of symbolic links, the intermediate ones are not
21146 If the file already exists but is not a regular file, or if the file's owner
21147 and group (if the group is being checked &-- see &%check_group%& above) are
21148 different from the user and group under which the delivery is running,
21149 delivery is deferred.
21152 If the file's permissions are more generous than specified, they are reduced.
21153 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21154 is set false, in which case the delivery is tried using the existing
21158 The file's inode number is saved, and the file is then opened for appending.
21159 If this fails because the file has vanished, &(appendfile)& behaves as if it
21160 hadn't existed (see below). For any other failures, delivery is deferred.
21163 If the file is opened successfully, check that the inode number hasn't
21164 changed, that it is still a regular file, and that the owner and permissions
21165 have not changed. If anything is wrong, defer delivery and freeze the message.
21168 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21169 option is set. Otherwise, check that the file is being created in a permitted
21170 directory if the &%create_file%& option is set (deferring on failure), and then
21171 open for writing as a new file, with the O_EXCL and O_CREAT options,
21172 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21173 set). In this case, which can happen if the link points to a non-existent file,
21174 the file is opened for writing using O_CREAT but not O_EXCL, because
21175 that prevents link following.
21178 .cindex "loop" "while file testing"
21179 If opening fails because the file exists, obey the tests given above for
21180 existing files. However, to avoid looping in a situation where the file is
21181 being continuously created and destroyed, the exists/not-exists loop is broken
21182 after 10 repetitions, and the message is then frozen.
21185 If opening fails with any other error, defer delivery.
21188 .cindex "file" "locking"
21189 .cindex "locking files"
21190 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
21191 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
21192 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
21193 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
21194 file, and an exclusive lock on the file whose name is
21196 /tmp/.<device-number>.<inode-number>
21198 using the device and inode numbers of the open mailbox file, in accordance with
21199 the MBX locking rules. This file is created with a mode that is specified by
21200 the &%lockfile_mode%& option.
21202 If Exim fails to lock the file, there are two possible courses of action,
21203 depending on the value of the locking timeout. This is obtained from
21204 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
21206 If the timeout value is zero, the file is closed, Exim waits for
21207 &%lock_interval%&, and then goes back and re-opens the file as above and tries
21208 to lock it again. This happens up to &%lock_retries%& times, after which the
21209 delivery is deferred.
21211 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
21212 &[flock()]& are used (with the given timeout), so there has already been some
21213 waiting involved by the time locking fails. Nevertheless, Exim does not give up
21214 immediately. It retries up to
21216 (lock_retries * lock_interval) / <timeout>
21218 times (rounded up).
21221 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
21222 and/or &[flock()]& locks) and then deletes the lock file if one was created.
21225 .section "Operational details for delivery to a new file" "SECTopdir"
21226 .cindex "delivery" "to single file"
21227 .cindex "&""From""& line"
21228 When the &%directory%& option is set instead of &%file%&, each message is
21229 delivered into a newly-created file or set of files. When &(appendfile)& is
21230 activated directly from a &(redirect)& router, neither &%file%& nor
21231 &%directory%& is normally set, because the path for delivery is supplied by the
21232 router. (See for example, the &(address_file)& transport in the default
21233 configuration.) In this case, delivery is to a new file if either the path name
21234 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
21236 No locking is required while writing the message to a new file, so the various
21237 locking options of the transport are ignored. The &"From"& line that by default
21238 separates messages in a single file is not normally needed, nor is the escaping
21239 of message lines that start with &"From"&, and there is no need to ensure a
21240 newline at the end of each message. Consequently, the default values for
21241 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
21242 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
21244 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
21245 the files in the delivery directory by default. However, you can specify a
21246 different directory by setting &%quota_directory%&. Also, for maildir
21247 deliveries (see below) the &_maildirfolder_& convention is honoured.
21250 .cindex "maildir format"
21251 .cindex "mailstore format"
21252 There are three different ways in which delivery to individual files can be
21253 done, controlled by the settings of the &%maildir_format%& and
21254 &%mailstore_format%& options. Note that code to support maildir or mailstore
21255 formats is not included in the binary unless SUPPORT_MAILDIR or
21256 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
21258 .cindex "directory creation"
21259 In all three cases an attempt is made to create the directory and any necessary
21260 sub-directories if they do not exist, provided that the &%create_directory%&
21261 option is set (the default). The location of a created directory can be
21262 constrained by setting &%create_file%&. A created directory's mode is given by
21263 the &%directory_mode%& option. If creation fails, or if the
21264 &%create_directory%& option is not set when creation is required, delivery is
21269 .section "Maildir delivery" "SECTmaildirdelivery"
21270 .cindex "maildir format" "description of"
21271 If the &%maildir_format%& option is true, Exim delivers each message by writing
21272 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
21273 directory that is defined by the &%directory%& option (the &"delivery
21274 directory"&). If the delivery is successful, the file is renamed into the
21275 &_new_& subdirectory.
21277 In the file name, <&'stime'&> is the current time of day in seconds, and
21278 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
21279 Exim checks that the time-of-day clock has moved on by at least one microsecond
21280 before terminating the delivery process. This guarantees uniqueness for the
21281 file name. However, as a precaution, Exim calls &[stat()]& for the file before
21282 opening it. If any response other than ENOENT (does not exist) is given,
21283 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
21285 Before Exim carries out a maildir delivery, it ensures that subdirectories
21286 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
21287 do not exist, Exim tries to create them and any superior directories in their
21288 path, subject to the &%create_directory%& and &%create_file%& options. If the
21289 &%maildirfolder_create_regex%& option is set, and the regular expression it
21290 contains matches the delivery directory, Exim also ensures that a file called
21291 &_maildirfolder_& exists in the delivery directory. If a missing directory or
21292 &_maildirfolder_& file cannot be created, delivery is deferred.
21294 These features make it possible to use Exim to create all the necessary files
21295 and directories in a maildir mailbox, including subdirectories for maildir++
21296 folders. Consider this example:
21298 maildir_format = true
21299 directory = /var/mail/$local_part\
21300 ${if eq{$local_part_suffix}{}{}\
21301 {/.${substr_1:$local_part_suffix}}}
21302 maildirfolder_create_regex = /\.[^/]+$
21304 If &$local_part_suffix$& is empty (there was no suffix for the local part),
21305 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
21306 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
21307 not match this name, so Exim will not look for or create the file
21308 &_/var/mail/pimbo/maildirfolder_&, though it will create
21309 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
21311 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
21312 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
21313 does match &%maildirfolder_create_regex%&. In this case, Exim will create
21314 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
21315 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
21317 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
21318 not inadvertently match the toplevel maildir directory, because a
21319 &_maildirfolder_& file at top level would completely break quota calculations.
21321 .cindex "quota" "in maildir delivery"
21322 .cindex "maildir++"
21323 If Exim is required to check a &%quota%& setting before a maildir delivery, and
21324 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
21325 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
21326 Exim assumes the directory is a maildir++ folder directory, which is one level
21327 down from the user's top level mailbox directory. This causes it to start at
21328 the parent directory instead of the current directory when calculating the
21329 amount of space used.
21331 One problem with delivering into a multi-file mailbox is that it is
21332 computationally expensive to compute the size of the mailbox for quota
21333 checking. Various approaches have been taken to reduce the amount of work
21334 needed. The next two sections describe two of them. A third alternative is to
21335 use some external process for maintaining the size data, and use the expansion
21336 of the &%mailbox_size%& option as a way of importing it into Exim.
21341 .section "Using tags to record message sizes" "SECID135"
21342 If &%maildir_tag%& is set, the string is expanded for each delivery.
21343 When the maildir file is renamed into the &_new_& sub-directory, the
21344 tag is added to its name. However, if adding the tag takes the length of the
21345 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
21346 the tag is dropped and the maildir file is created with no tag.
21349 .vindex "&$message_size$&"
21350 Tags can be used to encode the size of files in their names; see
21351 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
21352 happens after the message has been written. The value of the &$message_size$&
21353 variable is set to the number of bytes actually written. If the expansion is
21354 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
21355 be deferred. The expanded tag may contain any printing characters except &"/"&.
21356 Non-printing characters in the string are ignored; if the resulting string is
21357 empty, it is ignored. If it starts with an alphanumeric character, a leading
21358 colon is inserted; this default has not proven to be the path that popular
21359 maildir implementations have chosen (but changing it in Exim would break
21360 backwards compatibility).
21362 For one common implementation, you might set:
21364 maildir_tag = ,S=${message_size}
21366 but you should check the documentation of the other software to be sure.
21368 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
21369 as this allows Exim to extract the size from your tag, instead of having to
21370 &[stat()]& each message file.
21373 .section "Using a maildirsize file" "SECID136"
21374 .cindex "quota" "in maildir delivery"
21375 .cindex "maildir format" "&_maildirsize_& file"
21376 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
21377 storing quota and message size information in a file called &_maildirsize_&
21378 within the toplevel maildir directory. If this file does not exist, Exim
21379 creates it, setting the quota from the &%quota%& option of the transport. If
21380 the maildir directory itself does not exist, it is created before any attempt
21381 to write a &_maildirsize_& file.
21383 The &_maildirsize_& file is used to hold information about the sizes of
21384 messages in the maildir, thus speeding up quota calculations. The quota value
21385 in the file is just a cache; if the quota is changed in the transport, the new
21386 value overrides the cached value when the next message is delivered. The cache
21387 is maintained for the benefit of other programs that access the maildir and
21388 need to know the quota.
21390 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
21391 file is maintained (with a zero quota setting), but no quota is imposed.
21393 A regular expression is available for controlling which directories in the
21394 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
21395 See the description of the &%maildir_quota_directory_regex%& option above for
21399 .section "Mailstore delivery" "SECID137"
21400 .cindex "mailstore format" "description of"
21401 If the &%mailstore_format%& option is true, each message is written as two
21402 files in the given directory. A unique base name is constructed from the
21403 message id and the current delivery process, and the files that are written use
21404 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
21405 contains the message's envelope, and the &_.msg_& file contains the message
21406 itself. The base name is placed in the variable &$mailstore_basename$&.
21408 During delivery, the envelope is first written to a file with the suffix
21409 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
21410 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
21411 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
21412 file before accessing either of them. An alternative approach is to wait for
21413 the absence of a &_.tmp_& file.
21415 The envelope file starts with any text defined by the &%mailstore_prefix%&
21416 option, expanded and terminated by a newline if there isn't one. Then follows
21417 the sender address on one line, then all the recipient addresses, one per line.
21418 There can be more than one recipient only if the &%batch_max%& option is set
21419 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
21420 appended to the file, followed by a newline if it does not end with one.
21422 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
21423 failure, it is ignored. Other expansion errors are treated as serious
21424 configuration errors, and delivery is deferred. The variable
21425 &$mailstore_basename$& is available for use during these expansions.
21428 .section "Non-special new file delivery" "SECID138"
21429 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
21430 file is created directly in the named directory. For example, when delivering
21431 messages into files in batched SMTP format for later delivery to some host (see
21432 section &<<SECTbatchSMTP>>&), a setting such as
21434 directory = /var/bsmtp/$host
21436 might be used. A message is written to a file with a temporary name, which is
21437 then renamed when the delivery is complete. The final name is obtained by
21438 expanding the contents of the &%directory_file%& option.
21439 .ecindex IIDapptra1
21440 .ecindex IIDapptra2
21447 . ////////////////////////////////////////////////////////////////////////////
21448 . ////////////////////////////////////////////////////////////////////////////
21450 .chapter "The autoreply transport" "CHID8"
21451 .scindex IIDauttra1 "transports" "&(autoreply)&"
21452 .scindex IIDauttra2 "&(autoreply)& transport"
21453 The &(autoreply)& transport is not a true transport in that it does not cause
21454 the message to be transmitted. Instead, it generates a new mail message as an
21455 automatic reply to the incoming message. &'References:'& and
21456 &'Auto-Submitted:'& header lines are included. These are constructed according
21457 to the rules in RFCs 2822 and 3834, respectively.
21459 If the router that passes the message to this transport does not have the
21460 &%unseen%& option set, the original message (for the current recipient) is not
21461 delivered anywhere. However, when the &%unseen%& option is set on the router
21462 that passes the message to this transport, routing of the address continues, so
21463 another router can set up a normal message delivery.
21466 The &(autoreply)& transport is usually run as the result of mail filtering, a
21467 &"vacation"& message being the standard example. However, it can also be run
21468 directly from a router like any other transport. To reduce the possibility of
21469 message cascades, messages created by the &(autoreply)& transport always have
21470 empty envelope sender addresses, like bounce messages.
21472 The parameters of the message to be sent can be specified in the configuration
21473 by options described below. However, these are used only when the address
21474 passed to the transport does not contain its own reply information. When the
21475 transport is run as a consequence of a
21477 or &%vacation%& command in a filter file, the parameters of the message are
21478 supplied by the filter, and passed with the address. The transport's options
21479 that define the message are then ignored (so they are not usually set in this
21480 case). The message is specified entirely by the filter or by the transport; it
21481 is never built from a mixture of options. However, the &%file_optional%&,
21482 &%mode%&, and &%return_message%& options apply in all cases.
21484 &(Autoreply)& is implemented as a local transport. When used as a result of a
21485 command in a user's filter file, &(autoreply)& normally runs under the uid and
21486 gid of the user, and with appropriate current and home directories (see chapter
21487 &<<CHAPenvironment>>&).
21489 There is a subtle difference between routing a message to a &(pipe)& transport
21490 that generates some text to be returned to the sender, and routing it to an
21491 &(autoreply)& transport. This difference is noticeable only if more than one
21492 address from the same message is so handled. In the case of a pipe, the
21493 separate outputs from the different addresses are gathered up and returned to
21494 the sender in a single message, whereas if &(autoreply)& is used, a separate
21495 message is generated for each address that is passed to it.
21497 Non-printing characters are not permitted in the header lines generated for the
21498 message that &(autoreply)& creates, with the exception of newlines that are
21499 immediately followed by white space. If any non-printing characters are found,
21500 the transport defers.
21501 Whether characters with the top bit set count as printing characters or not is
21502 controlled by the &%print_topbitchars%& global option.
21504 If any of the generic options for manipulating headers (for example,
21505 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
21506 of the original message that is included in the generated message when
21507 &%return_message%& is set. They do not apply to the generated message itself.
21509 .vindex "&$sender_address$&"
21510 If the &(autoreply)& transport receives return code 2 from Exim when it submits
21511 the message, indicating that there were no recipients, it does not treat this
21512 as an error. This means that autoreplies sent to &$sender_address$& when this
21513 is empty (because the incoming message is a bounce message) do not cause
21514 problems. They are just discarded.
21518 .section "Private options for autoreply" "SECID139"
21519 .cindex "options" "&(autoreply)& transport"
21521 .option bcc autoreply string&!! unset
21522 This specifies the addresses that are to receive &"blind carbon copies"& of the
21523 message when the message is specified by the transport.
21526 .option cc autoreply string&!! unset
21527 This specifies recipients of the message and the contents of the &'Cc:'& header
21528 when the message is specified by the transport.
21531 .option file autoreply string&!! unset
21532 The contents of the file are sent as the body of the message when the message
21533 is specified by the transport. If both &%file%& and &%text%& are set, the text
21534 string comes first.
21537 .option file_expand autoreply boolean false
21538 If this is set, the contents of the file named by the &%file%& option are
21539 subjected to string expansion as they are added to the message.
21542 .option file_optional autoreply boolean false
21543 If this option is true, no error is generated if the file named by the &%file%&
21544 option or passed with the address does not exist or cannot be read.
21547 .option from autoreply string&!! unset
21548 This specifies the contents of the &'From:'& header when the message is
21549 specified by the transport.
21552 .option headers autoreply string&!! unset
21553 This specifies additional RFC 2822 headers that are to be added to the message
21554 when the message is specified by the transport. Several can be given by using
21555 &"\n"& to separate them. There is no check on the format.
21558 .option log autoreply string&!! unset
21559 This option names a file in which a record of every message sent is logged when
21560 the message is specified by the transport.
21563 .option mode autoreply "octal integer" 0600
21564 If either the log file or the &"once"& file has to be created, this mode is
21568 .option never_mail autoreply "address list&!!" unset
21569 If any run of the transport creates a message with a recipient that matches any
21570 item in the list, that recipient is quietly discarded. If all recipients are
21571 discarded, no message is created. This applies both when the recipients are
21572 generated by a filter and when they are specified in the transport.
21576 .option once autoreply string&!! unset
21577 This option names a file or DBM database in which a record of each &'To:'&
21578 recipient is kept when the message is specified by the transport. &*Note*&:
21579 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
21581 If &%once%& is unset, or is set to an empty string, the message is always sent.
21582 By default, if &%once%& is set to a non-empty file name, the message
21583 is not sent if a potential recipient is already listed in the database.
21584 However, if the &%once_repeat%& option specifies a time greater than zero, the
21585 message is sent if that much time has elapsed since a message was last sent to
21586 this recipient. A setting of zero time for &%once_repeat%& (the default)
21587 prevents a message from being sent a second time &-- in this case, zero means
21590 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
21591 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
21592 greater than zero, it changes the way Exim implements the &%once%& option.
21593 Instead of using a DBM file to record every recipient it sends to, it uses a
21594 regular file, whose size will never get larger than the given value.
21596 In the file, Exim keeps a linear list of recipient addresses and the times at
21597 which they were sent messages. If the file is full when a new address needs to
21598 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
21599 means that a given recipient may receive multiple messages, but at
21600 unpredictable intervals that depend on the rate of turnover of addresses in the
21601 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
21604 .option once_file_size autoreply integer 0
21605 See &%once%& above.
21608 .option once_repeat autoreply time&!! 0s
21609 See &%once%& above.
21610 After expansion, the value of this option must be a valid time value.
21613 .option reply_to autoreply string&!! unset
21614 This specifies the contents of the &'Reply-To:'& header when the message is
21615 specified by the transport.
21618 .option return_message autoreply boolean false
21619 If this is set, a copy of the original message is returned with the new
21620 message, subject to the maximum size set in the &%return_size_limit%& global
21621 configuration option.
21624 .option subject autoreply string&!! unset
21625 This specifies the contents of the &'Subject:'& header when the message is
21626 specified by the transport. It is tempting to quote the original subject in
21627 automatic responses. For example:
21629 subject = Re: $h_subject:
21631 There is a danger in doing this, however. It may allow a third party to
21632 subscribe your users to an opt-in mailing list, provided that the list accepts
21633 bounce messages as subscription confirmations. Well-managed lists require a
21634 non-bounce message to confirm a subscription, so the danger is relatively
21639 .option text autoreply string&!! unset
21640 This specifies a single string to be used as the body of the message when the
21641 message is specified by the transport. If both &%text%& and &%file%& are set,
21642 the text comes first.
21645 .option to autoreply string&!! unset
21646 This specifies recipients of the message and the contents of the &'To:'& header
21647 when the message is specified by the transport.
21648 .ecindex IIDauttra1
21649 .ecindex IIDauttra2
21654 . ////////////////////////////////////////////////////////////////////////////
21655 . ////////////////////////////////////////////////////////////////////////////
21657 .chapter "The lmtp transport" "CHAPLMTP"
21658 .cindex "transports" "&(lmtp)&"
21659 .cindex "&(lmtp)& transport"
21660 .cindex "LMTP" "over a pipe"
21661 .cindex "LMTP" "over a socket"
21662 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
21664 or by interacting with a Unix domain socket.
21665 This transport is something of a cross between the &(pipe)& and &(smtp)&
21666 transports. Exim also has support for using LMTP over TCP/IP; this is
21667 implemented as an option for the &(smtp)& transport. Because LMTP is expected
21668 to be of minority interest, the default build-time configure in &_src/EDITME_&
21669 has it commented out. You need to ensure that
21673 .cindex "options" "&(lmtp)& transport"
21674 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
21675 included in the Exim binary. The private options of the &(lmtp)& transport are
21678 .option batch_id lmtp string&!! unset
21679 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21682 .option batch_max lmtp integer 1
21683 This limits the number of addresses that can be handled in a single delivery.
21684 Most LMTP servers can handle several addresses at once, so it is normally a
21685 good idea to increase this value. See the description of local delivery
21686 batching in chapter &<<CHAPbatching>>&.
21689 .option command lmtp string&!! unset
21690 This option must be set if &%socket%& is not set. The string is a command which
21691 is run in a separate process. It is split up into a command name and list of
21692 arguments, each of which is separately expanded (so expansion cannot change the
21693 number of arguments). The command is run directly, not via a shell. The message
21694 is passed to the new process using the standard input and output to operate the
21697 .option ignore_quota lmtp boolean false
21698 .cindex "LMTP" "ignoring quota errors"
21699 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
21700 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
21701 in its response to the LHLO command.
21703 .option socket lmtp string&!! unset
21704 This option must be set if &%command%& is not set. The result of expansion must
21705 be the name of a Unix domain socket. The transport connects to the socket and
21706 delivers the message to it using the LMTP protocol.
21709 .option timeout lmtp time 5m
21710 The transport is aborted if the created process or Unix domain socket does not
21711 respond to LMTP commands or message input within this timeout. Delivery
21712 is deferred, and will be tried again later. Here is an example of a typical
21717 command = /some/local/lmtp/delivery/program
21721 This delivers up to 20 addresses at a time, in a mixture of domains if
21722 necessary, running as the user &'exim'&.
21726 . ////////////////////////////////////////////////////////////////////////////
21727 . ////////////////////////////////////////////////////////////////////////////
21729 .chapter "The pipe transport" "CHAPpipetransport"
21730 .scindex IIDpiptra1 "transports" "&(pipe)&"
21731 .scindex IIDpiptra2 "&(pipe)& transport"
21732 The &(pipe)& transport is used to deliver messages via a pipe to a command
21733 running in another process. One example is the use of &(pipe)& as a
21734 pseudo-remote transport for passing messages to some other delivery mechanism
21735 (such as UUCP). Another is the use by individual users to automatically process
21736 their incoming messages. The &(pipe)& transport can be used in one of the
21740 .vindex "&$local_part$&"
21741 A router routes one address to a transport in the normal way, and the
21742 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
21743 contains the local part of the address (as usual), and the command that is run
21744 is specified by the &%command%& option on the transport.
21746 .vindex "&$pipe_addresses$&"
21747 If the &%batch_max%& option is set greater than 1 (the default is 1), the
21748 transport can handle more than one address in a single run. In this case, when
21749 more than one address is routed to the transport, &$local_part$& is not set
21750 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
21751 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
21752 that are routed to the transport.
21754 .vindex "&$address_pipe$&"
21755 A router redirects an address directly to a pipe command (for example, from an
21756 alias or forward file). In this case, &$address_pipe$& contains the text of the
21757 pipe command, and the &%command%& option on the transport is ignored unless
21758 &%force_command%& is set. If only one address is being transported
21759 (&%batch_max%& is not greater than one, or only one address was redirected to
21760 this pipe command), &$local_part$& contains the local part that was redirected.
21764 The &(pipe)& transport is a non-interactive delivery method. Exim can also
21765 deliver messages over pipes using the LMTP interactive protocol. This is
21766 implemented by the &(lmtp)& transport.
21768 In the case when &(pipe)& is run as a consequence of an entry in a local user's
21769 &_.forward_& file, the command runs under the uid and gid of that user. In
21770 other cases, the uid and gid have to be specified explicitly, either on the
21771 transport or on the router that handles the address. Current and &"home"&
21772 directories are also controllable. See chapter &<<CHAPenvironment>>& for
21773 details of the local delivery environment and chapter &<<CHAPbatching>>&
21774 for a discussion of local delivery batching.
21777 .section "Concurrent delivery" "SECID140"
21778 If two messages arrive at almost the same time, and both are routed to a pipe
21779 delivery, the two pipe transports may be run concurrently. You must ensure that
21780 any pipe commands you set up are robust against this happening. If the commands
21781 write to a file, the &%exim_lock%& utility might be of use.
21786 .section "Returned status and data" "SECID141"
21787 .cindex "&(pipe)& transport" "returned data"
21788 If the command exits with a non-zero return code, the delivery is deemed to
21789 have failed, unless either the &%ignore_status%& option is set (in which case
21790 the return code is treated as zero), or the return code is one of those listed
21791 in the &%temp_errors%& option, which are interpreted as meaning &"try again
21792 later"&. In this case, delivery is deferred. Details of a permanent failure are
21793 logged, but are not included in the bounce message, which merely contains
21794 &"local delivery failed"&.
21796 If the command exits on a signal and the &%freeze_signal%& option is set then
21797 the message will be frozen in the queue. If that option is not set, a bounce
21798 will be sent as normal.
21800 If the return code is greater than 128 and the command being run is a shell
21801 script, it normally means that the script was terminated by a signal whose
21802 value is the return code minus 128. The &%freeze_signal%& option does not
21803 apply in this case.
21805 If Exim is unable to run the command (that is, if &[execve()]& fails), the
21806 return code is set to 127. This is the value that a shell returns if it is
21807 asked to run a non-existent command. The wording for the log line suggests that
21808 a non-existent command may be the problem.
21810 The &%return_output%& option can affect the result of a pipe delivery. If it is
21811 set and the command produces any output on its standard output or standard
21812 error streams, the command is considered to have failed, even if it gave a zero
21813 return code or if &%ignore_status%& is set. The output from the command is
21814 included as part of the bounce message. The &%return_fail_output%& option is
21815 similar, except that output is returned only when the command exits with a
21816 failure return code, that is, a value other than zero or a code that matches
21821 .section "How the command is run" "SECThowcommandrun"
21822 .cindex "&(pipe)& transport" "path for command"
21823 The command line is (by default) broken down into a command name and arguments
21824 by the &(pipe)& transport itself. The &%allow_commands%& and
21825 &%restrict_to_path%& options can be used to restrict the commands that may be
21828 .cindex "quoting" "in pipe command"
21829 Unquoted arguments are delimited by white space. If an argument appears in
21830 double quotes, backslash is interpreted as an escape character in the usual
21831 way. If an argument appears in single quotes, no escaping is done.
21833 String expansion is applied to the command line except when it comes from a
21834 traditional &_.forward_& file (commands from a filter file are expanded). The
21835 expansion is applied to each argument in turn rather than to the whole line.
21836 For this reason, any string expansion item that contains white space must be
21837 quoted so as to be contained within a single argument. A setting such as
21839 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
21841 will not work, because the expansion item gets split between several
21842 arguments. You have to write
21844 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
21846 to ensure that it is all in one argument. The expansion is done in this way,
21847 argument by argument, so that the number of arguments cannot be changed as a
21848 result of expansion, and quotes or backslashes in inserted variables do not
21849 interact with external quoting. However, this leads to problems if you want to
21850 generate multiple arguments (or the command name plus arguments) from a single
21851 expansion. In this situation, the simplest solution is to use a shell. For
21854 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
21857 .cindex "transport" "filter"
21858 .cindex "filter" "transport filter"
21859 .vindex "&$pipe_addresses$&"
21860 Special handling takes place when an argument consists of precisely the text
21861 &`$pipe_addresses`&. This is not a general expansion variable; the only
21862 place this string is recognized is when it appears as an argument for a pipe or
21863 transport filter command. It causes each address that is being handled to be
21864 inserted in the argument list at that point &'as a separate argument'&. This
21865 avoids any problems with spaces or shell metacharacters, and is of use when a
21866 &(pipe)& transport is handling groups of addresses in a batch.
21868 If &%force_command%& is enabled on the transport, Special handling takes place
21869 for an argument that consists of precisely the text &`$address_pipe`&. It
21870 is handled similarly to &$pipe_addresses$& above. It is expanded and each
21871 argument is inserted in the argument list at that point
21872 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
21873 the only item in the argument; in fact, if it were then &%force_command%&
21874 should behave as a no-op. Rather, it should be used to adjust the command
21875 run while preserving the argument vector separation.
21877 After splitting up into arguments and expansion, the resulting command is run
21878 in a subprocess directly from the transport, &'not'& under a shell. The
21879 message that is being delivered is supplied on the standard input, and the
21880 standard output and standard error are both connected to a single pipe that is
21881 read by Exim. The &%max_output%& option controls how much output the command
21882 may produce, and the &%return_output%& and &%return_fail_output%& options
21883 control what is done with it.
21885 Not running the command under a shell (by default) lessens the security risks
21886 in cases when a command from a user's filter file is built out of data that was
21887 taken from an incoming message. If a shell is required, it can of course be
21888 explicitly specified as the command to be run. However, there are circumstances
21889 where existing commands (for example, in &_.forward_& files) expect to be run
21890 under a shell and cannot easily be modified. To allow for these cases, there is
21891 an option called &%use_shell%&, which changes the way the &(pipe)& transport
21892 works. Instead of breaking up the command line as just described, it expands it
21893 as a single string and passes the result to &_/bin/sh_&. The
21894 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
21895 with &%use_shell%&, and the whole mechanism is inherently less secure.
21899 .section "Environment variables" "SECTpipeenv"
21900 .cindex "&(pipe)& transport" "environment for command"
21901 .cindex "environment for pipe transport"
21902 The environment variables listed below are set up when the command is invoked.
21903 This list is a compromise for maximum compatibility with other MTAs. Note that
21904 the &%environment%& option can be used to add additional variables to this
21907 &`DOMAIN `& the domain of the address
21908 &`HOME `& the home directory, if set
21909 &`HOST `& the host name when called from a router (see below)
21910 &`LOCAL_PART `& see below
21911 &`LOCAL_PART_PREFIX `& see below
21912 &`LOCAL_PART_SUFFIX `& see below
21913 &`LOGNAME `& see below
21914 &`MESSAGE_ID `& Exim's local ID for the message
21915 &`PATH `& as specified by the &%path%& option below
21916 &`QUALIFY_DOMAIN `& the sender qualification domain
21917 &`RECIPIENT `& the complete recipient address
21918 &`SENDER `& the sender of the message (empty if a bounce)
21919 &`SHELL `& &`/bin/sh`&
21920 &`TZ `& the value of the &%timezone%& option, if set
21921 &`USER `& see below
21923 When a &(pipe)& transport is called directly from (for example) an &(accept)&
21924 router, LOCAL_PART is set to the local part of the address. When it is
21925 called as a result of a forward or alias expansion, LOCAL_PART is set to
21926 the local part of the address that was expanded. In both cases, any affixes are
21927 removed from the local part, and made available in LOCAL_PART_PREFIX and
21928 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
21929 same value as LOCAL_PART for compatibility with other MTAs.
21932 HOST is set only when a &(pipe)& transport is called from a router that
21933 associates hosts with an address, typically when using &(pipe)& as a
21934 pseudo-remote transport. HOST is set to the first host name specified by
21938 If the transport's generic &%home_directory%& option is set, its value is used
21939 for the HOME environment variable. Otherwise, a home directory may be set
21940 by the router's &%transport_home_directory%& option, which defaults to the
21941 user's home directory if &%check_local_user%& is set.
21944 .section "Private options for pipe" "SECID142"
21945 .cindex "options" "&(pipe)& transport"
21949 .option allow_commands pipe "string list&!!" unset
21950 .cindex "&(pipe)& transport" "permitted commands"
21951 The string is expanded, and is then interpreted as a colon-separated list of
21952 permitted commands. If &%restrict_to_path%& is not set, the only commands
21953 permitted are those in the &%allow_commands%& list. They need not be absolute
21954 paths; the &%path%& option is still used for relative paths. If
21955 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
21956 in the &%allow_commands%& list, or a name without any slashes that is found on
21957 the path. In other words, if neither &%allow_commands%& nor
21958 &%restrict_to_path%& is set, there is no restriction on the command, but
21959 otherwise only commands that are permitted by one or the other are allowed. For
21962 allow_commands = /usr/bin/vacation
21964 and &%restrict_to_path%& is not set, the only permitted command is
21965 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
21966 &%use_shell%& is set.
21969 .option batch_id pipe string&!! unset
21970 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21973 .option batch_max pipe integer 1
21974 This limits the number of addresses that can be handled in a single delivery.
21975 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21978 .option check_string pipe string unset
21979 As &(pipe)& writes the message, the start of each line is tested for matching
21980 &%check_string%&, and if it does, the initial matching characters are replaced
21981 by the contents of &%escape_string%&, provided both are set. The value of
21982 &%check_string%& is a literal string, not a regular expression, and the case of
21983 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
21984 of &%check_string%& and &%escape_string%& are forced to values that implement
21985 the SMTP escaping protocol. Any settings made in the configuration file are
21989 .option command pipe string&!! unset
21990 This option need not be set when &(pipe)& is being used to deliver to pipes
21991 obtained directly from address redirections. In other cases, the option must be
21992 set, to provide a command to be run. It need not yield an absolute path (see
21993 the &%path%& option below). The command is split up into separate arguments by
21994 Exim, and each argument is separately expanded, as described in section
21995 &<<SECThowcommandrun>>& above.
21998 .option environment pipe string&!! unset
21999 .cindex "&(pipe)& transport" "environment for command"
22000 .cindex "environment for &(pipe)& transport"
22001 This option is used to add additional variables to the environment in which the
22002 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22003 a string which is expanded, and then interpreted as a colon-separated list of
22004 environment settings of the form <&'name'&>=<&'value'&>.
22007 .option escape_string pipe string unset
22008 See &%check_string%& above.
22011 .option freeze_exec_fail pipe boolean false
22012 .cindex "exec failure"
22013 .cindex "failure of exec"
22014 .cindex "&(pipe)& transport" "failure of exec"
22015 Failure to exec the command in a pipe transport is by default treated like
22016 any other failure while running the command. However, if &%freeze_exec_fail%&
22017 is set, failure to exec is treated specially, and causes the message to be
22018 frozen, whatever the setting of &%ignore_status%&.
22021 .option freeze_signal pipe boolean false
22022 .cindex "signal exit"
22023 .cindex "&(pipe)& transport", "signal exit"
22024 Normally if the process run by a command in a pipe transport exits on a signal,
22025 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22026 frozen in Exim's queue instead.
22029 .option force_command pipe boolean false
22030 .cindex "force command"
22031 .cindex "&(pipe)& transport", "force command"
22032 Normally when a router redirects an address directly to a pipe command
22033 the &%command%& option on the transport is ignored. If &%force_command%&
22034 is set, the &%command%& option will used. This is especially
22035 useful for forcing a wrapper or additional argument to be added to the
22036 command. For example:
22038 command = /usr/bin/remote_exec myhost -- $address_pipe
22042 Note that &$address_pipe$& is handled specially in &%command%& when
22043 &%force_command%& is set, expanding out to the original argument vector as
22044 separate items, similarly to a Unix shell &`"$@"`& construct.
22046 .option ignore_status pipe boolean false
22047 If this option is true, the status returned by the subprocess that is set up to
22048 run the command is ignored, and Exim behaves as if zero had been returned.
22049 Otherwise, a non-zero status or termination by signal causes an error return
22050 from the transport unless the status value is one of those listed in
22051 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22053 &*Note*&: This option does not apply to timeouts, which do not return a status.
22054 See the &%timeout_defer%& option for how timeouts are handled.
22056 .option log_defer_output pipe boolean false
22057 .cindex "&(pipe)& transport" "logging output"
22058 If this option is set, and the status returned by the command is
22059 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22060 and any output was produced, the first line of it is written to the main log.
22063 .option log_fail_output pipe boolean false
22064 If this option is set, and the command returns any output, and also ends with a
22065 return code that is neither zero nor one of the return codes listed in
22066 &%temp_errors%& (that is, the delivery failed), the first line of output is
22067 written to the main log. This option and &%log_output%& are mutually exclusive.
22068 Only one of them may be set.
22072 .option log_output pipe boolean false
22073 If this option is set and the command returns any output, the first line of
22074 output is written to the main log, whatever the return code. This option and
22075 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
22079 .option max_output pipe integer 20K
22080 This specifies the maximum amount of output that the command may produce on its
22081 standard output and standard error file combined. If the limit is exceeded, the
22082 process running the command is killed. This is intended as a safety measure to
22083 catch runaway processes. The limit is applied independently of the settings of
22084 the options that control what is done with such output (for example,
22085 &%return_output%&). Because of buffering effects, the amount of output may
22086 exceed the limit by a small amount before Exim notices.
22089 .option message_prefix pipe string&!! "see below"
22090 The string specified here is expanded and output at the start of every message.
22091 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22094 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22098 .cindex "&%tmail%&"
22099 .cindex "&""From""& line"
22100 This is required by the commonly used &_/usr/bin/vacation_& program.
22101 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22102 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22107 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22108 &`\n`& to &`\r\n`& in &%message_prefix%&.
22111 .option message_suffix pipe string&!! "see below"
22112 The string specified here is expanded and output at the end of every message.
22113 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22114 The suffix can be suppressed by setting
22118 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22119 &`\n`& to &`\r\n`& in &%message_suffix%&.
22122 .option path pipe string "see below"
22123 This option specifies the string that is set up in the PATH environment
22124 variable of the subprocess. The default is:
22128 If the &%command%& option does not yield an absolute path name, the command is
22129 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22130 apply to a command specified as a transport filter.
22133 .option permit_coredump pipe boolean false
22134 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22135 a core-dump of a pipe command, enable this command. This enables core-dumps
22136 during delivery and affects both the Exim binary and the pipe command run.
22137 It is recommended that this option remain off unless and until you have a need
22138 for it and that this only be enabled when needed, as the risk of excessive
22139 resource consumption can be quite high. Note also that Exim is typically
22140 installed as a setuid binary and most operating systems will inhibit coredumps
22141 of these by default, so further OS-specific action may be required.
22144 .option pipe_as_creator pipe boolean false
22145 .cindex "uid (user id)" "local delivery"
22146 If the generic &%user%& option is not set and this option is true, the delivery
22147 process is run under the uid that was in force when Exim was originally called
22148 to accept the message. If the group id is not otherwise set (via the generic
22149 &%group%& option), the gid that was in force when Exim was originally called to
22150 accept the message is used.
22153 .option restrict_to_path pipe boolean false
22154 When this option is set, any command name not listed in &%allow_commands%& must
22155 contain no slashes. The command is searched for only in the directories listed
22156 in the &%path%& option. This option is intended for use in the case when a pipe
22157 command has been generated from a user's &_.forward_& file. This is usually
22158 handled by a &(pipe)& transport called &%address_pipe%&.
22161 .option return_fail_output pipe boolean false
22162 If this option is true, and the command produced any output and ended with a
22163 return code other than zero or one of the codes listed in &%temp_errors%& (that
22164 is, the delivery failed), the output is returned in the bounce message.
22165 However, if the message has a null sender (that is, it is itself a bounce
22166 message), output from the command is discarded. This option and
22167 &%return_output%& are mutually exclusive. Only one of them may be set.
22171 .option return_output pipe boolean false
22172 If this option is true, and the command produced any output, the delivery is
22173 deemed to have failed whatever the return code from the command, and the output
22174 is returned in the bounce message. Otherwise, the output is just discarded.
22175 However, if the message has a null sender (that is, it is a bounce message),
22176 output from the command is always discarded, whatever the setting of this
22177 option. This option and &%return_fail_output%& are mutually exclusive. Only one
22178 of them may be set.
22182 .option temp_errors pipe "string list" "see below"
22183 .cindex "&(pipe)& transport" "temporary failure"
22184 This option contains either a colon-separated list of numbers, or a single
22185 asterisk. If &%ignore_status%& is false
22186 and &%return_output%& is not set,
22187 and the command exits with a non-zero return code, the failure is treated as
22188 temporary and the delivery is deferred if the return code matches one of the
22189 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
22190 codes are treated as permanent errors. The default setting contains the codes
22191 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
22192 compiled on a system that does not define these macros, it assumes values of 75
22193 and 73, respectively.
22196 .option timeout pipe time 1h
22197 If the command fails to complete within this time, it is killed. This normally
22198 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
22199 specifies no timeout. In order to ensure that any subprocesses created by the
22200 command are also killed, Exim makes the initial process a process group leader,
22201 and kills the whole process group on a timeout. However, this can be defeated
22202 if one of the processes starts a new process group.
22204 .option timeout_defer pipe boolean false
22205 A timeout in a &(pipe)& transport, either in the command that the transport
22206 runs, or in a transport filter that is associated with it, is by default
22207 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
22208 is set true, both kinds of timeout become temporary errors, causing the
22209 delivery to be deferred.
22211 .option umask pipe "octal integer" 022
22212 This specifies the umask setting for the subprocess that runs the command.
22215 .option use_bsmtp pipe boolean false
22216 .cindex "envelope sender"
22217 If this option is set true, the &(pipe)& transport writes messages in &"batch
22218 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
22219 commands. If you want to include a leading HELO command with such messages,
22220 you can do so by setting the &%message_prefix%& option. See section
22221 &<<SECTbatchSMTP>>& for details of batch SMTP.
22223 .option use_classresources pipe boolean false
22224 .cindex "class resources (BSD)"
22225 This option is available only when Exim is running on FreeBSD, NetBSD, or
22226 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
22227 resource limits when a &(pipe)& transport is run to perform a delivery. The
22228 limits for the uid under which the pipe is to run are obtained from the login
22232 .option use_crlf pipe boolean false
22233 .cindex "carriage return"
22235 This option causes lines to be terminated with the two-character CRLF sequence
22236 (carriage return, linefeed) instead of just a linefeed character. In the case
22237 of batched SMTP, the byte sequence written to the pipe is then an exact image
22238 of what would be sent down a real SMTP connection.
22240 The contents of the &%message_prefix%& and &%message_suffix%& options are
22241 written verbatim, so must contain their own carriage return characters if these
22242 are needed. When &%use_bsmtp%& is not set, the default values for both
22243 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
22244 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
22247 .option use_shell pipe boolean false
22248 .vindex "&$pipe_addresses$&"
22249 If this option is set, it causes the command to be passed to &_/bin/sh_&
22250 instead of being run directly from the transport, as described in section
22251 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
22252 where the command is expected to be run under a shell and cannot easily be
22253 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
22254 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
22255 command is expanded as a single string, and handed to &_/bin/sh_& as data for
22260 .section "Using an external local delivery agent" "SECID143"
22261 .cindex "local delivery" "using an external agent"
22262 .cindex "&'procmail'&"
22263 .cindex "external local delivery"
22264 .cindex "delivery" "&'procmail'&"
22265 .cindex "delivery" "by external agent"
22266 The &(pipe)& transport can be used to pass all messages that require local
22267 delivery to a separate local delivery agent such as &%procmail%&. When doing
22268 this, care must be taken to ensure that the pipe is run under an appropriate
22269 uid and gid. In some configurations one wants this to be a uid that is trusted
22270 by the delivery agent to supply the correct sender of the message. It may be
22271 necessary to recompile or reconfigure the delivery agent so that it trusts an
22272 appropriate user. The following is an example transport and router
22273 configuration for &%procmail%&:
22278 command = /usr/local/bin/procmail -d $local_part
22282 check_string = "From "
22283 escape_string = ">From "
22292 transport = procmail_pipe
22294 In this example, the pipe is run as the local user, but with the group set to
22295 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
22296 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
22297 user to supply a correct sender address. If you do not specify either a
22298 &%group%& or a &%user%& option, the pipe command is run as the local user. The
22299 home directory is the user's home directory by default.
22301 &*Note*&: The command that the pipe transport runs does &'not'& begin with
22305 as shown in some &%procmail%& documentation, because Exim does not by default
22306 use a shell to run pipe commands.
22309 The next example shows a transport and a router for a system where local
22310 deliveries are handled by the Cyrus IMAP server.
22313 local_delivery_cyrus:
22315 command = /usr/cyrus/bin/deliver \
22316 -m ${substr_1:$local_part_suffix} -- $local_part
22328 local_part_suffix = .*
22329 transport = local_delivery_cyrus
22331 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
22332 &%return_output%& to cause any text written by Cyrus to be returned to the
22334 .ecindex IIDpiptra1
22335 .ecindex IIDpiptra2
22338 . ////////////////////////////////////////////////////////////////////////////
22339 . ////////////////////////////////////////////////////////////////////////////
22341 .chapter "The smtp transport" "CHAPsmtptrans"
22342 .scindex IIDsmttra1 "transports" "&(smtp)&"
22343 .scindex IIDsmttra2 "&(smtp)& transport"
22344 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
22345 or LMTP protocol. The list of hosts to try can either be taken from the address
22346 that is being processed (having been set up by the router), or specified
22347 explicitly for the transport. Timeout and retry processing (see chapter
22348 &<<CHAPretry>>&) is applied to each IP address independently.
22351 .section "Multiple messages on a single connection" "SECID144"
22352 The sending of multiple messages over a single TCP/IP connection can arise in
22356 If a message contains more than &%max_rcpt%& (see below) addresses that are
22357 routed to the same host, more than one copy of the message has to be sent to
22358 that host. In this situation, multiple copies may be sent in a single run of
22359 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
22360 does when it has too many addresses to send in one message also depends on the
22361 value of the global &%remote_max_parallel%& option. Details are given in
22362 section &<<SECToutSMTPTCP>>&.)
22364 .cindex "hints database" "remembering routing"
22365 When a message has been successfully delivered over a TCP/IP connection, Exim
22366 looks in its hints database to see if there are any other messages awaiting a
22367 connection to the same host. If there are, a new delivery process is started
22368 for one of them, and the current TCP/IP connection is passed on to it. The new
22369 process may in turn send multiple copies and possibly create yet another
22374 For each copy sent over the same TCP/IP connection, a sequence counter is
22375 incremented, and if it ever gets to the value of &%connection_max_messages%&,
22376 no further messages are sent over that connection.
22380 .section "Use of the $host and $host_address variables" "SECID145"
22382 .vindex "&$host_address$&"
22383 At the start of a run of the &(smtp)& transport, the values of &$host$& and
22384 &$host_address$& are the name and IP address of the first host on the host list
22385 passed by the router. However, when the transport is about to connect to a
22386 specific host, and while it is connected to that host, &$host$& and
22387 &$host_address$& are set to the values for that host. These are the values
22388 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
22389 &%serialize_hosts%&, and the various TLS options are expanded.
22392 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
22393 .vindex &$tls_bits$&
22394 .vindex &$tls_cipher$&
22395 .vindex &$tls_peerdn$&
22396 .vindex &$tls_sni$&
22397 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
22398 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
22399 are the values that were set when the message was received.
22400 These are the values that are used for options that are expanded before any
22401 SMTP connections are made. Just before each connection is made, these four
22402 variables are emptied. If TLS is subsequently started, they are set to the
22403 appropriate values for the outgoing connection, and these are the values that
22404 are in force when any authenticators are run and when the
22405 &%authenticated_sender%& option is expanded.
22407 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
22408 and will be removed in a future release.
22411 .section "Private options for smtp" "SECID146"
22412 .cindex "options" "&(smtp)& transport"
22413 The private options of the &(smtp)& transport are as follows:
22416 .option address_retry_include_sender smtp boolean true
22417 .cindex "4&'xx'& responses" "retrying after"
22418 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
22419 is the combination of sender and recipient that is delayed in subsequent queue
22420 runs until the retry time is reached. You can delay the recipient without
22421 reference to the sender (which is what earlier versions of Exim did), by
22422 setting &%address_retry_include_sender%& false. However, this can lead to
22423 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
22425 .option allow_localhost smtp boolean false
22426 .cindex "local host" "sending to"
22427 .cindex "fallback" "hosts specified on transport"
22428 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
22429 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
22430 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
22431 the delivery anyway. This should be used only in special cases when the
22432 configuration ensures that no looping will result (for example, a differently
22433 configured Exim is listening on the port to which the message is sent).
22436 .option authenticated_sender smtp string&!! unset
22438 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
22439 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
22440 overriding any existing authenticated sender value. If the string expansion is
22441 forced to fail, the option is ignored. Other expansion failures cause delivery
22442 to be deferred. If the result of expansion is an empty string, that is also
22445 The expansion happens after the outgoing connection has been made and TLS
22446 started, if required. This means that the &$host$&, &$host_address$&,
22447 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
22448 particular connection.
22450 If the SMTP session is not authenticated, the expansion of
22451 &%authenticated_sender%& still happens (and can cause the delivery to be
22452 deferred if it fails), but no AUTH= item is added to MAIL commands
22453 unless &%authenticated_sender_force%& is true.
22455 This option allows you to use the &(smtp)& transport in LMTP mode to
22456 deliver mail to Cyrus IMAP and provide the proper local part as the
22457 &"authenticated sender"&, via a setting such as:
22459 authenticated_sender = $local_part
22461 This removes the need for IMAP subfolders to be assigned special ACLs to
22462 allow direct delivery to those subfolders.
22464 Because of expected uses such as that just described for Cyrus (when no
22465 domain is involved), there is no checking on the syntax of the provided
22469 .option authenticated_sender_force smtp boolean false
22470 If this option is set true, the &%authenticated_sender%& option's value
22471 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
22472 authenticated as a client.
22475 .option command_timeout smtp time 5m
22476 This sets a timeout for receiving a response to an SMTP command that has been
22477 sent out. It is also used when waiting for the initial banner line from the
22478 remote host. Its value must not be zero.
22481 .option connect_timeout smtp time 5m
22482 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
22483 to a remote host. A setting of zero allows the system timeout (typically
22484 several minutes) to act. To have any effect, the value of this option must be
22485 less than the system timeout. However, it has been observed that on some
22486 systems there is no system timeout, which is why the default value for this
22487 option is 5 minutes, a value recommended by RFC 1123.
22490 .option connection_max_messages smtp integer 500
22491 .cindex "SMTP" "passed connection"
22492 .cindex "SMTP" "multiple deliveries"
22493 .cindex "multiple SMTP deliveries"
22494 This controls the maximum number of separate message deliveries that are sent
22495 over a single TCP/IP connection. If the value is zero, there is no limit.
22496 For testing purposes, this value can be overridden by the &%-oB%& command line
22500 .option data_timeout smtp time 5m
22501 This sets a timeout for the transmission of each block in the data portion of
22502 the message. As a result, the overall timeout for a message depends on the size
22503 of the message. Its value must not be zero. See also &%final_timeout%&.
22506 .option delay_after_cutoff smtp boolean true
22507 This option controls what happens when all remote IP addresses for a given
22508 domain have been inaccessible for so long that they have passed their retry
22511 In the default state, if the next retry time has not been reached for any of
22512 them, the address is bounced without trying any deliveries. In other words,
22513 Exim delays retrying an IP address after the final cutoff time until a new
22514 retry time is reached, and can therefore bounce an address without ever trying
22515 a delivery, when machines have been down for a long time. Some people are
22516 unhappy at this prospect, so...
22518 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22519 addresses are past their final cutoff time, Exim tries to deliver to those
22520 IP addresses that have not been tried since the message arrived. If there are
22521 none, of if they all fail, the address is bounced. In other words, it does not
22522 delay when a new message arrives, but immediately tries those expired IP
22523 addresses that haven't been tried since the message arrived. If there is a
22524 continuous stream of messages for the dead hosts, unsetting
22525 &%delay_after_cutoff%& means that there will be many more attempts to deliver
22529 .option dns_qualify_single smtp boolean true
22530 If the &%hosts%& or &%fallback_hosts%& option is being used,
22531 and the &%gethostbyname%& option is false,
22532 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
22533 in chapter &<<CHAPdnslookup>>& for more details.
22536 .option dns_search_parents smtp boolean false
22537 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
22538 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
22539 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
22543 .option dscp smtp string&!! unset
22544 .cindex "DCSP" "outbound"
22545 This option causes the DSCP value associated with a socket to be set to one
22546 of a number of fixed strings or to numeric value.
22547 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
22548 Common values include &`throughput`&, &`mincost`&, and on newer systems
22549 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
22551 The outbound packets from Exim will be marked with this value in the header
22552 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
22553 that these values will have any effect, not be stripped by networking
22554 equipment, or do much of anything without cooperation with your Network
22555 Engineer and those of all network operators between the source and destination.
22558 .option fallback_hosts smtp "string list" unset
22559 .cindex "fallback" "hosts specified on transport"
22560 String expansion is not applied to this option. The argument must be a
22561 colon-separated list of host names or IP addresses, optionally also including
22562 port numbers, though the separator can be changed, as described in section
22563 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22564 item in a &%route_list%& setting for the &(manualroute)& router, as described
22565 in section &<<SECTformatonehostitem>>&.
22567 Fallback hosts can also be specified on routers, which associate them with the
22568 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
22569 &%fallback_hosts%& specified on the transport is used only if the address does
22570 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
22571 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
22572 However, &%hosts_randomize%& does apply to fallback host lists.
22574 If Exim is unable to deliver to any of the hosts for a particular address, and
22575 the errors are not permanent rejections, the address is put on a separate
22576 transport queue with its host list replaced by the fallback hosts, unless the
22577 address was routed via MX records and the current host was in the original MX
22578 list. In that situation, the fallback host list is not used.
22580 Once normal deliveries are complete, the fallback queue is delivered by
22581 re-running the same transports with the new host lists. If several failing
22582 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
22583 copy of the message is sent.
22585 The resolution of the host names on the fallback list is controlled by the
22586 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
22587 both to cases when the host list comes with the address and when it is taken
22588 from &%hosts%&. This option provides a &"use a smart host only if delivery
22592 .option final_timeout smtp time 10m
22593 This is the timeout that applies while waiting for the response to the final
22594 line containing just &"."& that terminates a message. Its value must not be
22597 .option gethostbyname smtp boolean false
22598 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
22599 being used, names are looked up using &[gethostbyname()]&
22600 (or &[getipnodebyname()]& when available)
22601 instead of using the DNS. Of course, that function may in fact use the DNS, but
22602 it may also consult other sources of information such as &_/etc/hosts_&.
22604 .option gnutls_compat_mode smtp boolean unset
22605 This option controls whether GnuTLS is used in compatibility mode in an Exim
22606 server. This reduces security slightly, but improves interworking with older
22607 implementations of TLS.
22609 .option helo_data smtp string&!! "see below"
22610 .cindex "HELO" "argument, setting"
22611 .cindex "EHLO" "argument, setting"
22612 .cindex "LHLO argument setting"
22613 The value of this option is expanded after a connection to a another host has
22614 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
22615 command that starts the outgoing SMTP or LMTP session. The default value of the
22620 During the expansion, the variables &$host$& and &$host_address$& are set to
22621 the identity of the remote host, and the variables &$sending_ip_address$& and
22622 &$sending_port$& are set to the local IP address and port number that are being
22623 used. These variables can be used to generate different values for different
22624 servers or different local IP addresses. For example, if you want the string
22625 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
22626 interface address, you could use this:
22628 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
22629 {$primary_hostname}}
22631 The use of &%helo_data%& applies both to sending messages and when doing
22634 .option hosts smtp "string list&!!" unset
22635 Hosts are associated with an address by a router such as &(dnslookup)&, which
22636 finds the hosts by looking up the address domain in the DNS, or by
22637 &(manualroute)&, which has lists of hosts in its configuration. However,
22638 email addresses can be passed to the &(smtp)& transport by any router, and not
22639 all of them can provide an associated list of hosts.
22641 The &%hosts%& option specifies a list of hosts to be used if the address being
22642 processed does not have any hosts associated with it. The hosts specified by
22643 &%hosts%& are also used, whether or not the address has its own hosts, if
22644 &%hosts_override%& is set.
22646 The string is first expanded, before being interpreted as a colon-separated
22647 list of host names or IP addresses, possibly including port numbers. The
22648 separator may be changed to something other than colon, as described in section
22649 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22650 item in a &%route_list%& setting for the &(manualroute)& router, as described
22651 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
22652 of the &(manualroute)& router is not available here.
22654 If the expansion fails, delivery is deferred. Unless the failure was caused by
22655 the inability to complete a lookup, the error is logged to the panic log as
22656 well as the main log. Host names are looked up either by searching directly for
22657 address records in the DNS or by calling &[gethostbyname()]& (or
22658 &[getipnodebyname()]& when available), depending on the setting of the
22659 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
22660 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
22663 During delivery, the hosts are tried in order, subject to their retry status,
22664 unless &%hosts_randomize%& is set.
22667 .option hosts_avoid_esmtp smtp "host list&!!" unset
22668 .cindex "ESMTP, avoiding use of"
22669 .cindex "HELO" "forcing use of"
22670 .cindex "EHLO" "avoiding use of"
22671 .cindex "PIPELINING" "avoiding the use of"
22672 This option is for use with broken hosts that announce ESMTP facilities (for
22673 example, PIPELINING) and then fail to implement them properly. When a host
22674 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
22675 start of the SMTP session. This means that it cannot use any of the ESMTP
22676 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
22679 .option hosts_avoid_pipelining smtp "host list&!!" unset
22680 .cindex "PIPELINING" "avoiding the use of"
22681 Exim will not use the SMTP PIPELINING extension when delivering to any host
22682 that matches this list, even if the server host advertises PIPELINING support.
22685 .option hosts_avoid_tls smtp "host list&!!" unset
22686 .cindex "TLS" "avoiding for certain hosts"
22687 Exim will not try to start a TLS session when delivering to any host that
22688 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22690 .option hosts_verify_avoid_tls smtp "host list&!!" *
22691 .cindex "TLS" "avoiding for certain hosts"
22692 Exim will not try to start a TLS session for a verify callout,
22693 or when delivering in cutthrough mode,
22694 to any host that matches this list.
22695 Note that the default is to not use TLS.
22698 .option hosts_max_try smtp integer 5
22699 .cindex "host" "maximum number to try"
22700 .cindex "limit" "number of hosts tried"
22701 .cindex "limit" "number of MX tried"
22702 .cindex "MX record" "maximum tried"
22703 This option limits the number of IP addresses that are tried for any one
22704 delivery in cases where there are temporary delivery errors. Section
22705 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
22708 .option hosts_max_try_hardlimit smtp integer 50
22709 This is an additional check on the maximum number of IP addresses that Exim
22710 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
22715 .option hosts_nopass_tls smtp "host list&!!" unset
22716 .cindex "TLS" "passing connection"
22717 .cindex "multiple SMTP deliveries"
22718 .cindex "TLS" "multiple message deliveries"
22719 For any host that matches this list, a connection on which a TLS session has
22720 been started will not be passed to a new delivery process for sending another
22721 message on the same connection. See section &<<SECTmulmessam>>& for an
22722 explanation of when this might be needed.
22725 .option hosts_override smtp boolean false
22726 If this option is set and the &%hosts%& option is also set, any hosts that are
22727 attached to the address are ignored, and instead the hosts specified by the
22728 &%hosts%& option are always used. This option does not apply to
22729 &%fallback_hosts%&.
22732 .option hosts_randomize smtp boolean false
22733 .cindex "randomized host list"
22734 .cindex "host" "list of; randomized"
22735 .cindex "fallback" "randomized hosts"
22736 If this option is set, and either the list of hosts is taken from the
22737 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
22738 were not obtained from MX records (this includes fallback hosts from the
22739 router), and were not randomized by the router, the order of trying the hosts
22740 is randomized each time the transport runs. Randomizing the order of a host
22741 list can be used to do crude load sharing.
22743 When &%hosts_randomize%& is true, a host list may be split into groups whose
22744 order is separately randomized. This makes it possible to set up MX-like
22745 behaviour. The boundaries between groups are indicated by an item that is just
22746 &`+`& in the host list. For example:
22748 hosts = host1:host2:host3:+:host4:host5
22750 The order of the first three hosts and the order of the last two hosts is
22751 randomized for each use, but the first three always end up before the last two.
22752 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
22754 .option hosts_require_auth smtp "host list&!!" unset
22755 .cindex "authentication" "required by client"
22756 This option provides a list of servers for which authentication must succeed
22757 before Exim will try to transfer a message. If authentication fails for
22758 servers which are not in this list, Exim tries to send unauthenticated. If
22759 authentication fails for one of these servers, delivery is deferred. This
22760 temporary error is detectable in the retry rules, so it can be turned into a
22761 hard failure if required. See also &%hosts_try_auth%&, and chapter
22762 &<<CHAPSMTPAUTH>>& for details of authentication.
22765 .option hosts_require_tls smtp "host list&!!" unset
22766 .cindex "TLS" "requiring for certain servers"
22767 Exim will insist on using a TLS session when delivering to any host that
22768 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22769 &*Note*&: This option affects outgoing mail only. To insist on TLS for
22770 incoming messages, use an appropriate ACL.
22772 .option hosts_try_auth smtp "host list&!!" unset
22773 .cindex "authentication" "optional in client"
22774 This option provides a list of servers to which, provided they announce
22775 authentication support, Exim will attempt to authenticate as a client when it
22776 connects. If authentication fails, Exim will try to transfer the message
22777 unauthenticated. See also &%hosts_require_auth%&, and chapter
22778 &<<CHAPSMTPAUTH>>& for details of authentication.
22780 .option interface smtp "string list&!!" unset
22781 .cindex "bind IP address"
22782 .cindex "IP address" "binding"
22784 .vindex "&$host_address$&"
22785 This option specifies which interface to bind to when making an outgoing SMTP
22786 call. The value is an IP address, not an interface name such as
22787 &`eth0`&. Do not confuse this with the interface address that was used when a
22788 message was received, which is in &$received_ip_address$&, formerly known as
22789 &$interface_address$&. The name was changed to minimize confusion with the
22790 outgoing interface address. There is no variable that contains an outgoing
22791 interface address because, unless it is set by this option, its value is
22794 During the expansion of the &%interface%& option the variables &$host$& and
22795 &$host_address$& refer to the host to which a connection is about to be made
22796 during the expansion of the string. Forced expansion failure, or an empty
22797 string result causes the option to be ignored. Otherwise, after expansion, the
22798 string must be a list of IP addresses, colon-separated by default, but the
22799 separator can be changed in the usual way. For example:
22801 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
22803 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
22804 connection. If none of them are the correct type, the option is ignored. If
22805 &%interface%& is not set, or is ignored, the system's IP functions choose which
22806 interface to use if the host has more than one.
22809 .option keepalive smtp boolean true
22810 .cindex "keepalive" "on outgoing connection"
22811 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
22812 connections. When set, it causes the kernel to probe idle connections
22813 periodically, by sending packets with &"old"& sequence numbers. The other end
22814 of the connection should send a acknowledgment if the connection is still okay
22815 or a reset if the connection has been aborted. The reason for doing this is
22816 that it has the beneficial effect of freeing up certain types of connection
22817 that can get stuck when the remote host is disconnected without tidying up the
22818 TCP/IP call properly. The keepalive mechanism takes several hours to detect
22822 .option lmtp_ignore_quota smtp boolean false
22823 .cindex "LMTP" "ignoring quota errors"
22824 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
22825 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
22826 has advertised support for IGNOREQUOTA in its response to the LHLO command.
22828 .option max_rcpt smtp integer 100
22829 .cindex "RCPT" "maximum number of outgoing"
22830 This option limits the number of RCPT commands that are sent in a single
22831 SMTP message transaction. Each set of addresses is treated independently, and
22832 so can cause parallel connections to the same host if &%remote_max_parallel%&
22836 .option multi_domain smtp boolean true
22837 .vindex "&$domain$&"
22838 When this option is set, the &(smtp)& transport can handle a number of
22839 addresses containing a mixture of different domains provided they all resolve
22840 to the same list of hosts. Turning the option off restricts the transport to
22841 handling only one domain at a time. This is useful if you want to use
22842 &$domain$& in an expansion for the transport, because it is set only when there
22843 is a single domain involved in a remote delivery.
22846 .option port smtp string&!! "see below"
22847 .cindex "port" "sending TCP/IP"
22848 .cindex "TCP/IP" "setting outgoing port"
22849 This option specifies the TCP/IP port on the server to which Exim connects.
22850 &*Note:*& Do not confuse this with the port that was used when a message was
22851 received, which is in &$received_port$&, formerly known as &$interface_port$&.
22852 The name was changed to minimize confusion with the outgoing port. There is no
22853 variable that contains an outgoing port.
22855 If the value of this option begins with a digit it is taken as a port number;
22856 otherwise it is looked up using &[getservbyname()]&. The default value is
22857 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
22858 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
22863 .option protocol smtp string smtp
22864 .cindex "LMTP" "over TCP/IP"
22865 .cindex "ssmtp protocol" "outbound"
22866 .cindex "TLS" "SSL-on-connect outbound"
22868 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
22869 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
22870 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
22871 deliveries into closed message stores. Exim also has support for running LMTP
22872 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
22874 If this option is set to &"smtps"&, the default vaule for the &%port%& option
22875 changes to &"smtps"&, and the transport initiates TLS immediately after
22876 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
22877 The Internet standards bodies strongly discourage use of this mode.
22880 .option retry_include_ip_address smtp boolean true
22881 Exim normally includes both the host name and the IP address in the key it
22882 constructs for indexing retry data after a temporary delivery failure. This
22883 means that when one of several IP addresses for a host is failing, it gets
22884 tried periodically (controlled by the retry rules), but use of the other IP
22885 addresses is not affected.
22887 However, in some dialup environments hosts are assigned a different IP address
22888 each time they connect. In this situation the use of the IP address as part of
22889 the retry key leads to undesirable behaviour. Setting this option false causes
22890 Exim to use only the host name. This should normally be done on a separate
22891 instance of the &(smtp)& transport, set up specially to handle the dialup
22895 .option serialize_hosts smtp "host list&!!" unset
22896 .cindex "serializing connections"
22897 .cindex "host" "serializing connections"
22898 Because Exim operates in a distributed manner, if several messages for the same
22899 host arrive at around the same time, more than one simultaneous connection to
22900 the remote host can occur. This is not usually a problem except when there is a
22901 slow link between the hosts. In that situation it may be helpful to restrict
22902 Exim to one connection at a time. This can be done by setting
22903 &%serialize_hosts%& to match the relevant hosts.
22905 .cindex "hints database" "serializing deliveries to a host"
22906 Exim implements serialization by means of a hints database in which a record is
22907 written whenever a process connects to one of the restricted hosts. The record
22908 is deleted when the connection is completed. Obviously there is scope for
22909 records to get left lying around if there is a system or program crash. To
22910 guard against this, Exim ignores any records that are more than six hours old.
22912 If you set up this kind of serialization, you should also arrange to delete the
22913 relevant hints database whenever your system reboots. The names of the files
22914 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22915 may be one or two files, depending on the type of DBM in use. The same files
22916 are used for ETRN serialization.
22919 .option size_addition smtp integer 1024
22920 .cindex "SMTP" "SIZE"
22921 .cindex "message" "size issue for transport filter"
22922 .cindex "size" "of message"
22923 .cindex "transport" "filter"
22924 .cindex "filter" "transport filter"
22925 If a remote SMTP server indicates that it supports the SIZE option of the
22926 MAIL command, Exim uses this to pass over the message size at the start of
22927 an SMTP transaction. It adds the value of &%size_addition%& to the value it
22928 sends, to allow for headers and other text that may be added during delivery by
22929 configuration options or in a transport filter. It may be necessary to increase
22930 this if a lot of text is added to messages.
22932 Alternatively, if the value of &%size_addition%& is set negative, it disables
22933 the use of the SIZE option altogether.
22936 .option tls_certificate smtp string&!! unset
22937 .cindex "TLS" "client certificate, location of"
22938 .cindex "certificate" "client, location of"
22940 .vindex "&$host_address$&"
22941 The value of this option must be the absolute path to a file which contains the
22942 client's certificate, for possible use when sending a message over an encrypted
22943 connection. The values of &$host$& and &$host_address$& are set to the name and
22944 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
22947 &*Note*&: This option must be set if you want Exim to be able to use a TLS
22948 certificate when sending messages as a client. The global option of the same
22949 name specifies the certificate for Exim as a server; it is not automatically
22950 assumed that the same certificate should be used when Exim is operating as a
22954 .option tls_crl smtp string&!! unset
22955 .cindex "TLS" "client certificate revocation list"
22956 .cindex "certificate" "revocation list for client"
22957 This option specifies a certificate revocation list. The expanded value must
22958 be the name of a file that contains a CRL in PEM format.
22961 .option tls_dh_min_bits smtp integer 1024
22962 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
22963 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
22964 key agreement is negotiated, the server will provide a large prime number
22965 for use. This option establishes the minimum acceptable size of that number.
22966 If the parameter offered by the server is too small, then the TLS handshake
22969 Only supported when using GnuTLS.
22972 .option tls_privatekey smtp string&!! unset
22973 .cindex "TLS" "client private key, location of"
22975 .vindex "&$host_address$&"
22976 The value of this option must be the absolute path to a file which contains the
22977 client's private key. This is used when sending a message over an encrypted
22978 connection using a client certificate. The values of &$host$& and
22979 &$host_address$& are set to the name and address of the server during the
22980 expansion. If this option is unset, or the expansion is forced to fail, or the
22981 result is an empty string, the private key is assumed to be in the same file as
22982 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
22985 .option tls_require_ciphers smtp string&!! unset
22986 .cindex "TLS" "requiring specific ciphers"
22987 .cindex "cipher" "requiring specific"
22989 .vindex "&$host_address$&"
22990 The value of this option must be a list of permitted cipher suites, for use
22991 when setting up an outgoing encrypted connection. (There is a global option of
22992 the same name for controlling incoming connections.) The values of &$host$& and
22993 &$host_address$& are set to the name and address of the server during the
22994 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
22995 is used in different ways by OpenSSL and GnuTLS (see sections
22996 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
22997 ciphers is a preference order.
23001 .option tls_sni smtp string&!! unset
23002 .cindex "TLS" "Server Name Indication"
23003 .vindex "&$tls_sni$&"
23004 If this option is set then it sets the $tls_out_sni variable and causes any
23005 TLS session to pass this value as the Server Name Indication extension to
23006 the remote side, which can be used by the remote side to select an appropriate
23007 certificate and private key for the session.
23009 See &<<SECTtlssni>>& for more information.
23011 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23017 .option tls_tempfail_tryclear smtp boolean true
23018 .cindex "4&'xx'& responses" "to STARTTLS"
23019 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23020 setting up a TLS session, this option determines whether or not Exim should try
23021 to deliver the message unencrypted. If it is set false, delivery to the
23022 current host is deferred; if there are other hosts, they are tried. If this
23023 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23024 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23025 TLS negotiation fails, Exim closes the current connection (because it is in an
23026 unknown state), opens a new one to the same host, and then tries the delivery
23030 .option tls_try_verify_hosts smtp "host list&!! unset
23031 .cindex "TLS" "server certificate verification"
23032 .cindex "certificate" "verification of server"
23033 For OpenSSL only, this option gives a list of hosts for which, on encrypted connections,
23034 certificate verification will be tried but need not succeed.
23035 The &%tls_verify_certificates%& option must also be set.
23038 .option tls_verify_certificates smtp string&!! unset
23039 .cindex "TLS" "server certificate verification"
23040 .cindex "certificate" "verification of server"
23042 .vindex "&$host_address$&"
23043 The value of this option must be the absolute path to a file containing
23044 permitted server certificates, for use when setting up an encrypted connection.
23045 Alternatively, if you are using OpenSSL, you can set
23046 &%tls_verify_certificates%& to the name of a directory containing certificate
23047 files. This does not work with GnuTLS; the option must be set to the name of a
23048 single file if you are using GnuTLS. The values of &$host$& and
23049 &$host_address$& are set to the name and address of the server during the
23050 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23052 For back-compatability, or when GnuTLS is used,
23053 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23054 and certificate verification fails the TLS connection is closed.
23057 .option tls_verify_hosts smtp "host list&!! unset
23058 .cindex "TLS" "server certificate verification"
23059 .cindex "certificate" "verification of server"
23060 For OpenSSL only, this option gives a list of hosts for which. on encrypted connections,
23061 certificate verification must succeed.
23062 The &%tls_verify_certificates%& option must also be set.
23063 If both this option and &%tls_try_verify_hosts%& are unset
23064 operation is as if this option selected all hosts.
23069 .section "How the limits for the number of hosts to try are used" &&&
23071 .cindex "host" "maximum number to try"
23072 .cindex "limit" "hosts; maximum number tried"
23073 There are two options that are concerned with the number of hosts that are
23074 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23075 &%hosts_max_try_hardlimit%&.
23078 The &%hosts_max_try%& option limits the number of hosts that are tried
23079 for a single delivery. However, despite the term &"host"& in its name, the
23080 option actually applies to each IP address independently. In other words, a
23081 multihomed host is treated as several independent hosts, just as it is for
23084 Many of the larger ISPs have multiple MX records which often point to
23085 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
23086 created as a result of routing one of these domains.
23088 Trying every single IP address on such a long list does not seem sensible; if
23089 several at the top of the list fail, it is reasonable to assume there is some
23090 problem that is likely to affect all of them. Roughly speaking, the value of
23091 &%hosts_max_try%& is the maximum number that are tried before deferring the
23092 delivery. However, the logic cannot be quite that simple.
23094 Firstly, IP addresses that are skipped because their retry times have not
23095 arrived do not count, and in addition, addresses that are past their retry
23096 limits are also not counted, even when they are tried. This means that when
23097 some IP addresses are past their retry limits, more than the value of
23098 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
23099 that all IP addresses are considered before timing out an email address (but
23100 see below for an exception).
23102 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
23103 list to see if there is a subsequent host with a different (higher valued) MX.
23104 If there is, that host is considered next, and the current IP address is used
23105 but not counted. This behaviour helps in the case of a domain with a retry rule
23106 that hardly ever delays any hosts, as is now explained:
23108 Consider the case of a long list of hosts with one MX value, and a few with a
23109 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
23110 hosts at the top of the list are tried at first. With the default retry rule,
23111 which specifies increasing retry times, the higher MX hosts are eventually
23112 tried when those at the top of the list are skipped because they have not
23113 reached their retry times.
23115 However, it is common practice to put a fixed short retry time on domains for
23116 large ISPs, on the grounds that their servers are rarely down for very long.
23117 Unfortunately, these are exactly the domains that tend to resolve to long lists
23118 of hosts. The short retry time means that the lowest MX hosts are tried every
23119 time. The attempts may be in a different order because of random sorting, but
23120 without the special MX check, the higher MX hosts would never be tried until
23121 all the lower MX hosts had timed out (which might be several days), because
23122 there are always some lower MX hosts that have reached their retry times. With
23123 the special check, Exim considers at least one IP address from each MX value at
23124 every delivery attempt, even if the &%hosts_max_try%& limit has already been
23127 The above logic means that &%hosts_max_try%& is not a hard limit, and in
23128 particular, Exim normally eventually tries all the IP addresses before timing
23129 out an email address. When &%hosts_max_try%& was implemented, this seemed a
23130 reasonable thing to do. Recently, however, some lunatic DNS configurations have
23131 been set up with hundreds of IP addresses for some domains. It can
23132 take a very long time indeed for an address to time out in these cases.
23134 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
23135 Exim never tries more than this number of IP addresses; if it hits this limit
23136 and they are all timed out, the email address is bounced, even though not all
23137 possible IP addresses have been tried.
23138 .ecindex IIDsmttra1
23139 .ecindex IIDsmttra2
23145 . ////////////////////////////////////////////////////////////////////////////
23146 . ////////////////////////////////////////////////////////////////////////////
23148 .chapter "Address rewriting" "CHAPrewrite"
23149 .scindex IIDaddrew "rewriting" "addresses"
23150 There are some circumstances in which Exim automatically rewrites domains in
23151 addresses. The two most common are when an address is given without a domain
23152 (referred to as an &"unqualified address"&) or when an address contains an
23153 abbreviated domain that is expanded by DNS lookup.
23155 Unqualified envelope addresses are accepted only for locally submitted
23156 messages, or for messages that are received from hosts matching
23157 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
23158 appropriate. Unqualified addresses in header lines are qualified if they are in
23159 locally submitted messages, or messages from hosts that are permitted to send
23160 unqualified envelope addresses. Otherwise, unqualified addresses in header
23161 lines are neither qualified nor rewritten.
23163 One situation in which Exim does &'not'& automatically rewrite a domain is
23164 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
23165 such a domain should be rewritten using the &"canonical"& name, and some MTAs
23166 do this. The new RFCs do not contain this suggestion.
23169 .section "Explicitly configured address rewriting" "SECID147"
23170 This chapter describes the rewriting rules that can be used in the
23171 main rewrite section of the configuration file, and also in the generic
23172 &%headers_rewrite%& option that can be set on any transport.
23174 Some people believe that configured address rewriting is a Mortal Sin.
23175 Others believe that life is not possible without it. Exim provides the
23176 facility; you do not have to use it.
23178 The main rewriting rules that appear in the &"rewrite"& section of the
23179 configuration file are applied to addresses in incoming messages, both envelope
23180 addresses and addresses in header lines. Each rule specifies the types of
23181 address to which it applies.
23183 Whether or not addresses in header lines are rewritten depends on the origin of
23184 the headers and the type of rewriting. Global rewriting, that is, rewriting
23185 rules from the rewrite section of the configuration file, is applied only to
23186 those headers that were received with the message. Header lines that are added
23187 by ACLs or by a system filter or by individual routers or transports (which
23188 are specific to individual recipient addresses) are not rewritten by the global
23191 Rewriting at transport time, by means of the &%headers_rewrite%& option,
23192 applies all headers except those added by routers and transports. That is, as
23193 well as the headers that were received with the message, it also applies to
23194 headers that were added by an ACL or a system filter.
23197 In general, rewriting addresses from your own system or domain has some
23198 legitimacy. Rewriting other addresses should be done only with great care and
23199 in special circumstances. The author of Exim believes that rewriting should be
23200 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
23201 Although it can sometimes be used as a routing tool, this is very strongly
23204 There are two commonly encountered circumstances where rewriting is used, as
23205 illustrated by these examples:
23208 The company whose domain is &'hitch.fict.example'& has a number of hosts that
23209 exchange mail with each other behind a firewall, but there is only a single
23210 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
23211 &'hitch.fict.example'& when sending mail off-site.
23213 A host rewrites the local parts of its own users so that, for example,
23214 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
23219 .section "When does rewriting happen?" "SECID148"
23220 .cindex "rewriting" "timing of"
23221 .cindex "&ACL;" "rewriting addresses in"
23222 Configured address rewriting can take place at several different stages of a
23223 message's processing.
23225 .vindex "&$sender_address$&"
23226 At the start of an ACL for MAIL, the sender address may have been rewritten
23227 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
23228 ordinary rewrite rules have yet been applied. If, however, the sender address
23229 is verified in the ACL, it is rewritten before verification, and remains
23230 rewritten thereafter. The subsequent value of &$sender_address$& is the
23231 rewritten address. This also applies if sender verification happens in a
23232 RCPT ACL. Otherwise, when the sender address is not verified, it is
23233 rewritten as soon as a message's header lines have been received.
23235 .vindex "&$domain$&"
23236 .vindex "&$local_part$&"
23237 Similarly, at the start of an ACL for RCPT, the current recipient's address
23238 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
23239 rewrite rules have yet been applied to it. However, the behaviour is different
23240 from the sender address when a recipient is verified. The address is rewritten
23241 for the verification, but the rewriting is not remembered at this stage. The
23242 value of &$local_part$& and &$domain$& after verification are always the same
23243 as they were before (that is, they contain the unrewritten &-- except for
23244 SMTP-time rewriting &-- address).
23246 As soon as a message's header lines have been received, all the envelope
23247 recipient addresses are permanently rewritten, and rewriting is also applied to
23248 the addresses in the header lines (if configured). This happens before adding
23249 any header lines that were specified in MAIL or RCPT ACLs, and
23250 .cindex "&[local_scan()]& function" "address rewriting; timing of"
23251 before the DATA ACL and &[local_scan()]& functions are run.
23253 When an address is being routed, either for delivery or for verification,
23254 rewriting is applied immediately to child addresses that are generated by
23255 redirection, unless &%no_rewrite%& is set on the router.
23257 .cindex "envelope sender" "rewriting at transport time"
23258 .cindex "rewriting" "at transport time"
23259 .cindex "header lines" "rewriting at transport time"
23260 At transport time, additional rewriting of addresses in header lines can be
23261 specified by setting the generic &%headers_rewrite%& option on a transport.
23262 This option contains rules that are identical in form to those in the rewrite
23263 section of the configuration file. They are applied to the original message
23264 header lines and any that were added by ACLs or a system filter. They are not
23265 applied to header lines that are added by routers or the transport.
23267 The outgoing envelope sender can be rewritten by means of the &%return_path%&
23268 transport option. However, it is not possible to rewrite envelope recipients at
23274 .section "Testing the rewriting rules that apply on input" "SECID149"
23275 .cindex "rewriting" "testing"
23276 .cindex "testing" "rewriting"
23277 Exim's input rewriting configuration appears in a part of the run time
23278 configuration file headed by &"begin rewrite"&. It can be tested by the
23279 &%-brw%& command line option. This takes an address (which can be a full RFC
23280 2822 address) as its argument. The output is a list of how the address would be
23281 transformed by the rewriting rules for each of the different places it might
23282 appear in an incoming message, that is, for each different header and for the
23283 envelope sender and recipient fields. For example,
23285 exim -brw ph10@exim.workshop.example
23287 might produce the output
23289 sender: Philip.Hazel@exim.workshop.example
23290 from: Philip.Hazel@exim.workshop.example
23291 to: ph10@exim.workshop.example
23292 cc: ph10@exim.workshop.example
23293 bcc: ph10@exim.workshop.example
23294 reply-to: Philip.Hazel@exim.workshop.example
23295 env-from: Philip.Hazel@exim.workshop.example
23296 env-to: ph10@exim.workshop.example
23298 which shows that rewriting has been set up for that address when used in any of
23299 the source fields, but not when it appears as a recipient address. At the
23300 present time, there is no equivalent way of testing rewriting rules that are
23301 set for a particular transport.
23304 .section "Rewriting rules" "SECID150"
23305 .cindex "rewriting" "rules"
23306 The rewrite section of the configuration file consists of lines of rewriting
23309 <&'source pattern'&> <&'replacement'&> <&'flags'&>
23311 Rewriting rules that are specified for the &%headers_rewrite%& generic
23312 transport option are given as a colon-separated list. Each item in the list
23313 takes the same form as a line in the main rewriting configuration (except that
23314 any colons must be doubled, of course).
23316 The formats of source patterns and replacement strings are described below.
23317 Each is terminated by white space, unless enclosed in double quotes, in which
23318 case normal quoting conventions apply inside the quotes. The flags are single
23319 characters which may appear in any order. Spaces and tabs between them are
23322 For each address that could potentially be rewritten, the rules are scanned in
23323 order, and replacements for the address from earlier rules can themselves be
23324 replaced by later rules (but see the &"q"& and &"R"& flags).
23326 The order in which addresses are rewritten is undefined, may change between
23327 releases, and must not be relied on, with one exception: when a message is
23328 received, the envelope sender is always rewritten first, before any header
23329 lines are rewritten. For example, the replacement string for a rewrite of an
23330 address in &'To:'& must not assume that the message's address in &'From:'& has
23331 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
23332 that the envelope sender has already been rewritten.
23334 .vindex "&$domain$&"
23335 .vindex "&$local_part$&"
23336 The variables &$local_part$& and &$domain$& can be used in the replacement
23337 string to refer to the address that is being rewritten. Note that lookup-driven
23338 rewriting can be done by a rule of the form
23342 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
23343 refer to the address that is being rewritten.
23346 .section "Rewriting patterns" "SECID151"
23347 .cindex "rewriting" "patterns"
23348 .cindex "address list" "in a rewriting pattern"
23349 The source pattern in a rewriting rule is any item which may appear in an
23350 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
23351 single-item address list, which means that it is expanded before being tested
23352 against the address. As always, if you use a regular expression as a pattern,
23353 you must take care to escape dollar and backslash characters, or use the &`\N`&
23354 facility to suppress string expansion within the regular expression.
23356 Domains in patterns should be given in lower case. Local parts in patterns are
23357 case-sensitive. If you want to do case-insensitive matching of local parts, you
23358 can use a regular expression that starts with &`^(?i)`&.
23360 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
23361 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
23362 depending on the type of match which occurred. These can be used in the
23363 replacement string to insert portions of the incoming address. &$0$& always
23364 refers to the complete incoming address. When a regular expression is used, the
23365 numerical variables are set from its capturing subexpressions. For other types
23366 of pattern they are set as follows:
23369 If a local part or domain starts with an asterisk, the numerical variables
23370 refer to the character strings matched by asterisks, with &$1$& associated with
23371 the first asterisk, and &$2$& with the second, if present. For example, if the
23374 *queen@*.fict.example
23376 is matched against the address &'hearts-queen@wonderland.fict.example'& then
23378 $0 = hearts-queen@wonderland.fict.example
23382 Note that if the local part does not start with an asterisk, but the domain
23383 does, it is &$1$& that contains the wild part of the domain.
23386 If the domain part of the pattern is a partial lookup, the wild and fixed parts
23387 of the domain are placed in the next available numerical variables. Suppose,
23388 for example, that the address &'foo@bar.baz.example'& is processed by a
23389 rewriting rule of the form
23391 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
23393 and the key in the file that matches the domain is &`*.baz.example`&. Then
23399 If the address &'foo@baz.example'& is looked up, this matches the same
23400 wildcard file entry, and in this case &$2$& is set to the empty string, but
23401 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
23402 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
23403 whole domain. For non-partial domain lookups, no numerical variables are set.
23407 .section "Rewriting replacements" "SECID152"
23408 .cindex "rewriting" "replacements"
23409 If the replacement string for a rule is a single asterisk, addresses that
23410 match the pattern and the flags are &'not'& rewritten, and no subsequent
23411 rewriting rules are scanned. For example,
23413 hatta@lookingglass.fict.example * f
23415 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
23418 .vindex "&$domain$&"
23419 .vindex "&$local_part$&"
23420 If the replacement string is not a single asterisk, it is expanded, and must
23421 yield a fully qualified address. Within the expansion, the variables
23422 &$local_part$& and &$domain$& refer to the address that is being rewritten.
23423 Any letters they contain retain their original case &-- they are not lower
23424 cased. The numerical variables are set up according to the type of pattern that
23425 matched the address, as described above. If the expansion is forced to fail by
23426 the presence of &"fail"& in a conditional or lookup item, rewriting by the
23427 current rule is abandoned, but subsequent rules may take effect. Any other
23428 expansion failure causes the entire rewriting operation to be abandoned, and an
23429 entry written to the panic log.
23433 .section "Rewriting flags" "SECID153"
23434 There are three different kinds of flag that may appear on rewriting rules:
23437 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
23440 A flag that specifies rewriting at SMTP time: S.
23442 Flags that control the rewriting process: Q, q, R, w.
23445 For rules that are part of the &%headers_rewrite%& generic transport option,
23446 E, F, T, and S are not permitted.
23450 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
23452 .cindex "rewriting" "flags"
23453 If none of the following flag letters, nor the &"S"& flag (see section
23454 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
23455 and to both the sender and recipient fields of the envelope, whereas a
23456 transport-time rewriting rule just applies to all headers. Otherwise, the
23457 rewriting rule is skipped unless the relevant addresses are being processed.
23459 &`E`& rewrite all envelope fields
23460 &`F`& rewrite the envelope From field
23461 &`T`& rewrite the envelope To field
23462 &`b`& rewrite the &'Bcc:'& header
23463 &`c`& rewrite the &'Cc:'& header
23464 &`f`& rewrite the &'From:'& header
23465 &`h`& rewrite all headers
23466 &`r`& rewrite the &'Reply-To:'& header
23467 &`s`& rewrite the &'Sender:'& header
23468 &`t`& rewrite the &'To:'& header
23470 "All headers" means all of the headers listed above that can be selected
23471 individually, plus their &'Resent-'& versions. It does not include
23472 other headers such as &'Subject:'& etc.
23474 You should be particularly careful about rewriting &'Sender:'& headers, and
23475 restrict this to special known cases in your own domains.
23478 .section "The SMTP-time rewriting flag" "SECTrewriteS"
23479 .cindex "SMTP" "rewriting malformed addresses"
23480 .cindex "RCPT" "rewriting argument of"
23481 .cindex "MAIL" "rewriting argument of"
23482 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
23483 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
23484 before any other processing; even before syntax checking. The pattern is
23485 required to be a regular expression, and it is matched against the whole of the
23486 data for the command, including any surrounding angle brackets.
23488 .vindex "&$domain$&"
23489 .vindex "&$local_part$&"
23490 This form of rewrite rule allows for the handling of addresses that are not
23491 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
23492 input). Because the input is not required to be a syntactically valid address,
23493 the variables &$local_part$& and &$domain$& are not available during the
23494 expansion of the replacement string. The result of rewriting replaces the
23495 original address in the MAIL or RCPT command.
23498 .section "Flags controlling the rewriting process" "SECID155"
23499 There are four flags which control the way the rewriting process works. These
23500 take effect only when a rule is invoked, that is, when the address is of the
23501 correct type (matches the flags) and matches the pattern:
23504 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
23505 unqualified local part. It is qualified with &%qualify_recipient%&. In the
23506 absence of &"Q"& the rewritten address must always include a domain.
23508 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
23509 even if no rewriting actually takes place because of a &"fail"& in the
23510 expansion. The &"q"& flag is not effective if the address is of the wrong type
23511 (does not match the flags) or does not match the pattern.
23513 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
23514 address, up to ten times. It can be combined with the &"q"& flag, to stop
23515 rewriting once it fails to match (after at least one successful rewrite).
23517 .cindex "rewriting" "whole addresses"
23518 When an address in a header is rewritten, the rewriting normally applies only
23519 to the working part of the address, with any comments and RFC 2822 &"phrase"&
23520 left unchanged. For example, rewriting might change
23522 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
23526 From: Ford Prefect <prefectf@hitch.fict.example>
23529 Sometimes there is a need to replace the whole address item, and this can be
23530 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
23531 causes an address in a header line to be rewritten, the entire address is
23532 replaced, not just the working part. The replacement must be a complete RFC
23533 2822 address, including the angle brackets if necessary. If text outside angle
23534 brackets contains a character whose value is greater than 126 or less than 32
23535 (except for tab), the text is encoded according to RFC 2047. The character set
23536 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
23538 When the &"w"& flag is set on a rule that causes an envelope address to be
23539 rewritten, all but the working part of the replacement address is discarded.
23543 .section "Rewriting examples" "SECID156"
23544 Here is an example of the two common rewriting paradigms:
23546 *@*.hitch.fict.example $1@hitch.fict.example
23547 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
23548 {$value}fail}@hitch.fict.example bctfrF
23550 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
23551 the string expansion to fail if the lookup does not succeed. In this context it
23552 has the effect of leaving the original address unchanged, but Exim goes on to
23553 consider subsequent rewriting rules, if any, because the &"q"& flag is not
23554 present in that rule. An alternative to &"fail"& would be to supply &$1$&
23555 explicitly, which would cause the rewritten address to be the same as before,
23556 at the cost of a small bit of processing. Not supplying either of these is an
23557 error, since the rewritten address would then contain no local part.
23559 The first example above replaces the domain with a superior, more general
23560 domain. This may not be desirable for certain local parts. If the rule
23562 root@*.hitch.fict.example *
23564 were inserted before the first rule, rewriting would be suppressed for the
23565 local part &'root'& at any domain ending in &'hitch.fict.example'&.
23567 Rewriting can be made conditional on a number of tests, by making use of
23568 &${if$& in the expansion item. For example, to apply a rewriting rule only to
23569 messages that originate outside the local host:
23571 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
23572 {$1@hitch.fict.example}fail}"
23574 The replacement string is quoted in this example because it contains white
23577 .cindex "rewriting" "bang paths"
23578 .cindex "bang paths" "rewriting"
23579 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
23580 an address it treats it as an unqualified local part which it qualifies with
23581 the local qualification domain (if the source of the message is local or if the
23582 remote host is permitted to send unqualified addresses). Rewriting can
23583 sometimes be used to handle simple bang paths with a fixed number of
23584 components. For example, the rule
23586 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
23588 rewrites a two-component bang path &'host.name!user'& as the domain address
23589 &'user@host.name'&. However, there is a security implication in using this as
23590 a global rewriting rule for envelope addresses. It can provide a backdoor
23591 method for using your system as a relay, because the incoming addresses appear
23592 to be local. If the bang path addresses are received via SMTP, it is safer to
23593 use the &"S"& flag to rewrite them as they are received, so that relay checking
23594 can be done on the rewritten addresses.
23601 . ////////////////////////////////////////////////////////////////////////////
23602 . ////////////////////////////////////////////////////////////////////////////
23604 .chapter "Retry configuration" "CHAPretry"
23605 .scindex IIDretconf1 "retry" "configuration, description of"
23606 .scindex IIDregconf2 "configuration file" "retry section"
23607 The &"retry"& section of the runtime configuration file contains a list of
23608 retry rules that control how often Exim tries to deliver messages that cannot
23609 be delivered at the first attempt. If there are no retry rules (the section is
23610 empty or not present), there are no retries. In this situation, temporary
23611 errors are treated as permanent. The default configuration contains a single,
23612 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
23613 line option can be used to test which retry rule will be used for a given
23614 address, domain and error.
23616 The most common cause of retries is temporary failure to deliver to a remote
23617 host because the host is down, or inaccessible because of a network problem.
23618 Exim's retry processing in this case is applied on a per-host (strictly, per IP
23619 address) basis, not on a per-message basis. Thus, if one message has recently
23620 been delayed, delivery of a new message to the same host is not immediately
23621 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
23622 log selector is set, the message
23623 .cindex "retry" "time not reached"
23624 &"retry time not reached"& is written to the main log whenever a delivery is
23625 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
23626 the handling of errors during remote deliveries.
23628 Retry processing applies to routing as well as to delivering, except as covered
23629 in the next paragraph. The retry rules do not distinguish between these
23630 actions. It is not possible, for example, to specify different behaviour for
23631 failures to route the domain &'snark.fict.example'& and failures to deliver to
23632 the host &'snark.fict.example'&. I didn't think anyone would ever need this
23633 added complication, so did not implement it. However, although they share the
23634 same retry rule, the actual retry times for routing and transporting a given
23635 domain are maintained independently.
23637 When a delivery is not part of a queue run (typically an immediate delivery on
23638 receipt of a message), the routers are always run, and local deliveries are
23639 always attempted, even if retry times are set for them. This makes for better
23640 behaviour if one particular message is causing problems (for example, causing
23641 quota overflow, or provoking an error in a filter file). If such a delivery
23642 suffers a temporary failure, the retry data is updated as normal, and
23643 subsequent delivery attempts from queue runs occur only when the retry time for
23644 the local address is reached.
23646 .section "Changing retry rules" "SECID157"
23647 If you change the retry rules in your configuration, you should consider
23648 whether or not to delete the retry data that is stored in Exim's spool area in
23649 files with names like &_db/retry_&. Deleting any of Exim's hints files is
23650 always safe; that is why they are called &"hints"&.
23652 The hints retry data contains suggested retry times based on the previous
23653 rules. In the case of a long-running problem with a remote host, it might
23654 record the fact that the host has timed out. If your new rules increase the
23655 timeout time for such a host, you should definitely remove the old retry data
23656 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
23657 messages that it should now be retaining.
23661 .section "Format of retry rules" "SECID158"
23662 .cindex "retry" "rules"
23663 Each retry rule occupies one line and consists of three or four parts,
23664 separated by white space: a pattern, an error name, an optional list of sender
23665 addresses, and a list of retry parameters. The pattern and sender lists must be
23666 enclosed in double quotes if they contain white space. The rules are searched
23667 in order until one is found where the pattern, error name, and sender list (if
23668 present) match the failing host or address, the error that occurred, and the
23669 message's sender, respectively.
23672 The pattern is any single item that may appear in an address list (see section
23673 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
23674 which means that it is expanded before being tested against the address that
23675 has been delayed. A negated address list item is permitted. Address
23676 list processing treats a plain domain name as if it were preceded by &"*@"&,
23677 which makes it possible for many retry rules to start with just a domain. For
23680 lookingglass.fict.example * F,24h,30m;
23682 provides a rule for any address in the &'lookingglass.fict.example'& domain,
23685 alice@lookingglass.fict.example * F,24h,30m;
23687 applies only to temporary failures involving the local part &%alice%&.
23688 In practice, almost all rules start with a domain name pattern without a local
23691 .cindex "regular expressions" "in retry rules"
23692 &*Warning*&: If you use a regular expression in a retry rule pattern, it
23693 must match a complete address, not just a domain, because that is how regular
23694 expressions work in address lists.
23696 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
23697 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
23701 .section "Choosing which retry rule to use for address errors" "SECID159"
23702 When Exim is looking for a retry rule after a routing attempt has failed (for
23703 example, after a DNS timeout), each line in the retry configuration is tested
23704 against the complete address only if &%retry_use_local_part%& is set for the
23705 router. Otherwise, only the domain is used, except when matching against a
23706 regular expression, when the local part of the address is replaced with &"*"&.
23707 A domain on its own can match a domain pattern, or a pattern that starts with
23708 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
23709 &%check_local_user%& is true, and false for other routers.
23711 Similarly, when Exim is looking for a retry rule after a local delivery has
23712 failed (for example, after a mailbox full error), each line in the retry
23713 configuration is tested against the complete address only if
23714 &%retry_use_local_part%& is set for the transport (it defaults true for all
23717 .cindex "4&'xx'& responses" "retry rules for"
23718 However, when Exim is looking for a retry rule after a remote delivery attempt
23719 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
23720 whole address is always used as the key when searching the retry rules. The
23721 rule that is found is used to create a retry time for the combination of the
23722 failing address and the message's sender. It is the combination of sender and
23723 recipient that is delayed in subsequent queue runs until its retry time is
23724 reached. You can delay the recipient without regard to the sender by setting
23725 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
23726 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
23731 .section "Choosing which retry rule to use for host and message errors" &&&
23733 For a temporary error that is not related to an individual address (for
23734 example, a connection timeout), each line in the retry configuration is checked
23735 twice. First, the name of the remote host is used as a domain name (preceded by
23736 &"*@"& when matching a regular expression). If this does not match the line,
23737 the domain from the email address is tried in a similar fashion. For example,
23738 suppose the MX records for &'a.b.c.example'& are
23740 a.b.c.example MX 5 x.y.z.example
23744 and the retry rules are
23746 p.q.r.example * F,24h,30m;
23747 a.b.c.example * F,4d,45m;
23749 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
23750 first rule matches neither the host nor the domain, so Exim looks at the second
23751 rule. This does not match the host, but it does match the domain, so it is used
23752 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
23753 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
23754 first retry rule is used, because it matches the host.
23756 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
23757 first rule to determine retry times, but for all the other hosts for the domain
23758 &'a.b.c.example'&, the second rule is used. The second rule is also used if
23759 routing to &'a.b.c.example'& suffers a temporary failure.
23761 &*Note*&: The host name is used when matching the patterns, not its IP address.
23762 However, if a message is routed directly to an IP address without the use of a
23763 host name, for example, if a &(manualroute)& router contains a setting such as:
23765 route_list = *.a.example 192.168.34.23
23767 then the &"host name"& that is used when searching for a retry rule is the
23768 textual form of the IP address.
23770 .section "Retry rules for specific errors" "SECID161"
23771 .cindex "retry" "specific errors; specifying"
23772 The second field in a retry rule is the name of a particular error, or an
23773 asterisk, which matches any error. The errors that can be tested for are:
23776 .vitem &%auth_failed%&
23777 Authentication failed when trying to send to a host in the
23778 &%hosts_require_auth%& list in an &(smtp)& transport.
23780 .vitem &%data_4xx%&
23781 A 4&'xx'& error was received for an outgoing DATA command, either immediately
23782 after the command, or after sending the message's data.
23784 .vitem &%mail_4xx%&
23785 A 4&'xx'& error was received for an outgoing MAIL command.
23787 .vitem &%rcpt_4xx%&
23788 A 4&'xx'& error was received for an outgoing RCPT command.
23791 For the three 4&'xx'& errors, either the first or both of the x's can be given
23792 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
23793 recognize 452 errors given to RCPT commands for addresses in a certain domain,
23794 and have retries every ten minutes with a one-hour timeout, you could set up a
23795 retry rule of this form:
23797 the.domain.name rcpt_452 F,1h,10m
23799 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
23800 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
23803 .vitem &%lost_connection%&
23804 A server unexpectedly closed the SMTP connection. There may, of course,
23805 legitimate reasons for this (host died, network died), but if it repeats a lot
23806 for the same host, it indicates something odd.
23808 .vitem &%refused_MX%&
23809 A connection to a host obtained from an MX record was refused.
23811 .vitem &%refused_A%&
23812 A connection to a host not obtained from an MX record was refused.
23815 A connection was refused.
23817 .vitem &%timeout_connect_MX%&
23818 A connection attempt to a host obtained from an MX record timed out.
23820 .vitem &%timeout_connect_A%&
23821 A connection attempt to a host not obtained from an MX record timed out.
23823 .vitem &%timeout_connect%&
23824 A connection attempt timed out.
23826 .vitem &%timeout_MX%&
23827 There was a timeout while connecting or during an SMTP session with a host
23828 obtained from an MX record.
23830 .vitem &%timeout_A%&
23831 There was a timeout while connecting or during an SMTP session with a host not
23832 obtained from an MX record.
23835 There was a timeout while connecting or during an SMTP session.
23837 .vitem &%tls_required%&
23838 The server was required to use TLS (it matched &%hosts_require_tls%& in the
23839 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
23840 to STARTTLS, or there was a problem setting up the TLS connection.
23843 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
23846 .vitem &%quota_%&<&'time'&>
23847 .cindex "quota" "error testing in retry rule"
23848 .cindex "retry" "quota error testing"
23849 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
23850 transport, and the mailbox has not been accessed for <&'time'&>. For example,
23851 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
23855 .cindex "mailbox" "time of last read"
23856 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
23857 timeouts when the mailbox is full and is not being read by its owner. Ideally,
23858 it should be based on the last time that the user accessed the mailbox.
23859 However, it is not always possible to determine this. Exim uses the following
23863 If the mailbox is a single file, the time of last access (the &"atime"&) is
23864 used. As no new messages are being delivered (because the mailbox is over
23865 quota), Exim does not access the file, so this is the time of last user access.
23867 .cindex "maildir format" "time of last read"
23868 For a maildir delivery, the time of last modification of the &_new_&
23869 subdirectory is used. As the mailbox is over quota, no new files are created in
23870 the &_new_& subdirectory, because no new messages are being delivered. Any
23871 change to the &_new_& subdirectory is therefore assumed to be the result of an
23872 MUA moving a new message to the &_cur_& directory when it is first read. The
23873 time that is used is therefore the last time that the user read a new message.
23875 For other kinds of multi-file mailbox, the time of last access cannot be
23876 obtained, so a retry rule that uses this type of error field is never matched.
23879 The quota errors apply both to system-enforced quotas and to Exim's own quota
23880 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
23881 when a local delivery is deferred because a partition is full (the ENOSPC
23886 .section "Retry rules for specified senders" "SECID162"
23887 .cindex "retry" "rules; sender-specific"
23888 You can specify retry rules that apply only when the failing message has a
23889 specific sender. In particular, this can be used to define retry rules that
23890 apply only to bounce messages. The third item in a retry rule can be of this
23893 &`senders=`&<&'address list'&>
23895 The retry timings themselves are then the fourth item. For example:
23897 * rcpt_4xx senders=: F,1h,30m
23899 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
23900 host. If the address list contains white space, it must be enclosed in quotes.
23903 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
23905 &*Warning*&: This facility can be unhelpful if it is used for host errors
23906 (which do not depend on the recipient). The reason is that the sender is used
23907 only to match the retry rule. Once the rule has been found for a host error,
23908 its contents are used to set a retry time for the host, and this will apply to
23909 all messages, not just those with specific senders.
23911 When testing retry rules using &%-brt%&, you can supply a sender using the
23912 &%-f%& command line option, like this:
23914 exim -f "" -brt user@dom.ain
23916 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
23917 list is never matched.
23923 .section "Retry parameters" "SECID163"
23924 .cindex "retry" "parameters in rules"
23925 The third (or fourth, if a senders list is present) field in a retry rule is a
23926 sequence of retry parameter sets, separated by semicolons. Each set consists of
23928 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
23930 The letter identifies the algorithm for computing a new retry time; the cutoff
23931 time is the time beyond which this algorithm no longer applies, and the
23932 arguments vary the algorithm's action. The cutoff time is measured from the
23933 time that the first failure for the domain (combined with the local part if
23934 relevant) was detected, not from the time the message was received.
23936 .cindex "retry" "algorithms"
23937 .cindex "retry" "fixed intervals"
23938 .cindex "retry" "increasing intervals"
23939 .cindex "retry" "random intervals"
23940 The available algorithms are:
23943 &'F'&: retry at fixed intervals. There is a single time parameter specifying
23946 &'G'&: retry at geometrically increasing intervals. The first argument
23947 specifies a starting value for the interval, and the second a multiplier, which
23948 is used to increase the size of the interval at each retry.
23950 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
23951 retry, the previous interval is multiplied by the factor in order to get a
23952 maximum for the next interval. The minimum interval is the first argument of
23953 the parameter, and an actual interval is chosen randomly between them. Such a
23954 rule has been found to be helpful in cluster configurations when all the
23955 members of the cluster restart at once, and may therefore synchronize their
23956 queue processing times.
23959 When computing the next retry time, the algorithm definitions are scanned in
23960 order until one whose cutoff time has not yet passed is reached. This is then
23961 used to compute a new retry time that is later than the current time. In the
23962 case of fixed interval retries, this simply means adding the interval to the
23963 current time. For geometrically increasing intervals, retry intervals are
23964 computed from the rule's parameters until one that is greater than the previous
23965 interval is found. The main configuration variable
23966 .cindex "limit" "retry interval"
23967 .cindex "retry" "interval, maximum"
23968 .oindex "&%retry_interval_max%&"
23969 &%retry_interval_max%& limits the maximum interval between retries. It
23970 cannot be set greater than &`24h`&, which is its default value.
23972 A single remote domain may have a number of hosts associated with it, and each
23973 host may have more than one IP address. Retry algorithms are selected on the
23974 basis of the domain name, but are applied to each IP address independently. If,
23975 for example, a host has two IP addresses and one is unusable, Exim will
23976 generate retry times for it and will not try to use it until its next retry
23977 time comes. Thus the good IP address is likely to be tried first most of the
23980 .cindex "hints database" "use for retrying"
23981 Retry times are hints rather than promises. Exim does not make any attempt to
23982 run deliveries exactly at the computed times. Instead, a queue runner process
23983 starts delivery processes for delayed messages periodically, and these attempt
23984 new deliveries only for those addresses that have passed their next retry time.
23985 If a new message arrives for a deferred address, an immediate delivery attempt
23986 occurs only if the address has passed its retry time. In the absence of new
23987 messages, the minimum time between retries is the interval between queue runner
23988 processes. There is not much point in setting retry times of five minutes if
23989 your queue runners happen only once an hour, unless there are a significant
23990 number of incoming messages (which might be the case on a system that is
23991 sending everything to a smart host, for example).
23993 The data in the retry hints database can be inspected by using the
23994 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
23995 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
23996 &'exinext'& utility script can be used to find out what the next retry times
23997 are for the hosts associated with a particular mail domain, and also for local
23998 deliveries that have been deferred.
24001 .section "Retry rule examples" "SECID164"
24002 Here are some example retry rules:
24004 alice@wonderland.fict.example quota_5d F,7d,3h
24005 wonderland.fict.example quota_5d
24006 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24007 lookingglass.fict.example * F,24h,30m;
24008 * refused_A F,2h,20m;
24009 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24011 The first rule sets up special handling for mail to
24012 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24013 mailbox has not been read for at least 5 days. Retries continue every three
24014 hours for 7 days. The second rule handles over-quota errors for all other local
24015 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24016 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24017 fail are bounced immediately if the mailbox has not been read for at least 5
24020 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24021 happen every 15 minutes for an hour, then with geometrically increasing
24022 intervals until two days have passed since a delivery first failed. After the
24023 first hour there is a delay of one hour, then two hours, then four hours, and
24024 so on (this is a rather extreme example).
24026 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24027 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24028 all other domains, with special action for connection refusal from hosts that
24029 were not obtained from an MX record.
24031 The final rule in a retry configuration should always have asterisks in the
24032 first two fields so as to provide a general catch-all for any addresses that do
24033 not have their own special handling. This example tries every 15 minutes for 2
24034 hours, then with intervals starting at one hour and increasing by a factor of
24035 1.5 up to 16 hours, then every 8 hours up to 5 days.
24039 .section "Timeout of retry data" "SECID165"
24040 .cindex "timeout" "of retry data"
24041 .oindex "&%retry_data_expire%&"
24042 .cindex "hints database" "data expiry"
24043 .cindex "retry" "timeout of data"
24044 Exim timestamps the data that it writes to its retry hints database. When it
24045 consults the data during a delivery it ignores any that is older than the value
24046 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24047 been tried for 7 days, Exim will try to deliver to it immediately a message
24048 arrives, and if that fails, it will calculate a retry time as if it were
24049 failing for the first time.
24051 This improves the behaviour for messages routed to rarely-used hosts such as MX
24052 backups. If such a host was down at one time, and happens to be down again when
24053 Exim tries a month later, using the old retry data would imply that it had been
24054 down all the time, which is not a justified assumption.
24056 If a host really is permanently dead, this behaviour causes a burst of retries
24057 every now and again, but only if messages routed to it are rare. If there is a
24058 message at least once every 7 days the retry data never expires.
24063 .section "Long-term failures" "SECID166"
24064 .cindex "delivery failure, long-term"
24065 .cindex "retry" "after long-term failure"
24066 Special processing happens when an email address has been failing for so long
24067 that the cutoff time for the last algorithm is reached. For example, using the
24068 default retry rule:
24070 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24072 the cutoff time is four days. Reaching the retry cutoff is independent of how
24073 long any specific message has been failing; it is the length of continuous
24074 failure for the recipient address that counts.
24076 When the cutoff time is reached for a local delivery, or for all the IP
24077 addresses associated with a remote delivery, a subsequent delivery failure
24078 causes Exim to give up on the address, and a bounce message is generated.
24079 In order to cater for new messages that use the failing address, a next retry
24080 time is still computed from the final algorithm, and is used as follows:
24082 For local deliveries, one delivery attempt is always made for any subsequent
24083 messages. If this delivery fails, the address fails immediately. The
24084 post-cutoff retry time is not used.
24086 If the delivery is remote, there are two possibilities, controlled by the
24087 .oindex "&%delay_after_cutoff%&"
24088 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
24089 default. Until the post-cutoff retry time for one of the IP addresses is
24090 reached, the failing email address is bounced immediately, without a delivery
24091 attempt taking place. After that time, one new delivery attempt is made to
24092 those IP addresses that are past their retry times, and if that still fails,
24093 the address is bounced and new retry times are computed.
24095 In other words, when all the hosts for a given email address have been failing
24096 for a long time, Exim bounces rather then defers until one of the hosts' retry
24097 times is reached. Then it tries once, and bounces if that attempt fails. This
24098 behaviour ensures that few resources are wasted in repeatedly trying to deliver
24099 to a broken destination, but if the host does recover, Exim will eventually
24102 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24103 addresses are past their final cutoff time, Exim tries to deliver to those IP
24104 addresses that have not been tried since the message arrived. If there are
24105 no suitable IP addresses, or if they all fail, the address is bounced. In other
24106 words, it does not delay when a new message arrives, but tries the expired
24107 addresses immediately, unless they have been tried since the message arrived.
24108 If there is a continuous stream of messages for the failing domains, setting
24109 &%delay_after_cutoff%& false means that there will be many more attempts to
24110 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
24113 .section "Deliveries that work intermittently" "SECID167"
24114 .cindex "retry" "intermittently working deliveries"
24115 Some additional logic is needed to cope with cases where a host is
24116 intermittently available, or when a message has some attribute that prevents
24117 its delivery when others to the same address get through. In this situation,
24118 because some messages are successfully delivered, the &"retry clock"& for the
24119 host or address keeps getting reset by the successful deliveries, and so
24120 failing messages remain on the queue for ever because the cutoff time is never
24123 Two exceptional actions are applied to prevent this happening. The first
24124 applies to errors that are related to a message rather than a remote host.
24125 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
24126 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
24127 commands, and quota failures. For this type of error, if a message's arrival
24128 time is earlier than the &"first failed"& time for the error, the earlier time
24129 is used when scanning the retry rules to decide when to try next and when to
24130 time out the address.
24132 The exceptional second action applies in all cases. If a message has been on
24133 the queue for longer than the cutoff time of any applicable retry rule for a
24134 given address, a delivery is attempted for that address, even if it is not yet
24135 time, and if this delivery fails, the address is timed out. A new retry time is
24136 not computed in this case, so that other messages for the same address are
24137 considered immediately.
24138 .ecindex IIDretconf1
24139 .ecindex IIDregconf2
24146 . ////////////////////////////////////////////////////////////////////////////
24147 . ////////////////////////////////////////////////////////////////////////////
24149 .chapter "SMTP authentication" "CHAPSMTPAUTH"
24150 .scindex IIDauthconf1 "SMTP" "authentication configuration"
24151 .scindex IIDauthconf2 "authentication"
24152 The &"authenticators"& section of Exim's run time configuration is concerned
24153 with SMTP authentication. This facility is an extension to the SMTP protocol,
24154 described in RFC 2554, which allows a client SMTP host to authenticate itself
24155 to a server. This is a common way for a server to recognize clients that are
24156 permitted to use it as a relay. SMTP authentication is not of relevance to the
24157 transfer of mail between servers that have no managerial connection with each
24160 .cindex "AUTH" "description of"
24161 Very briefly, the way SMTP authentication works is as follows:
24164 The server advertises a number of authentication &'mechanisms'& in response to
24165 the client's EHLO command.
24167 The client issues an AUTH command, naming a specific mechanism. The command
24168 may, optionally, contain some authentication data.
24170 The server may issue one or more &'challenges'&, to which the client must send
24171 appropriate responses. In simple authentication mechanisms, the challenges are
24172 just prompts for user names and passwords. The server does not have to issue
24173 any challenges &-- in some mechanisms the relevant data may all be transmitted
24174 with the AUTH command.
24176 The server either accepts or denies authentication.
24178 If authentication succeeds, the client may optionally make use of the AUTH
24179 option on the MAIL command to pass an authenticated sender in subsequent
24180 mail transactions. Authentication lasts for the remainder of the SMTP
24183 If authentication fails, the client may give up, or it may try a different
24184 authentication mechanism, or it may try transferring mail over the
24185 unauthenticated connection.
24188 If you are setting up a client, and want to know which authentication
24189 mechanisms the server supports, you can use Telnet to connect to port 25 (the
24190 SMTP port) on the server, and issue an EHLO command. The response to this
24191 includes the list of supported mechanisms. For example:
24193 &`$ `&&*&`telnet server.example 25`&*&
24194 &`Trying 192.168.34.25...`&
24195 &`Connected to server.example.`&
24196 &`Escape character is '^]'.`&
24197 &`220 server.example ESMTP Exim 4.20 ...`&
24198 &*&`ehlo client.example`&*&
24199 &`250-server.example Hello client.example [10.8.4.5]`&
24200 &`250-SIZE 52428800`&
24205 The second-last line of this example output shows that the server supports
24206 authentication using the PLAIN mechanism. In Exim, the different authentication
24207 mechanisms are configured by specifying &'authenticator'& drivers. Like the
24208 routers and transports, which authenticators are included in the binary is
24209 controlled by build-time definitions. The following are currently available,
24210 included by setting
24213 AUTH_CYRUS_SASL=yes
24216 AUTH_HEIMDAL_GSSAPI=yes
24220 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
24221 authentication mechanism (RFC 2195), and the second provides an interface to
24222 the Cyrus SASL authentication library.
24223 The third is an interface to Dovecot's authentication system, delegating the
24224 work via a socket interface.
24225 The fourth provides an interface to the GNU SASL authentication library, which
24226 provides mechanisms but typically not data sources.
24227 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
24228 supporting setting a server keytab.
24229 The sixth can be configured to support
24230 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
24231 not formally documented, but used by several MUAs. The seventh authenticator
24232 supports Microsoft's &'Secure Password Authentication'& mechanism.
24234 The authenticators are configured using the same syntax as other drivers (see
24235 section &<<SECTfordricon>>&). If no authenticators are required, no
24236 authentication section need be present in the configuration file. Each
24237 authenticator can in principle have both server and client functions. When Exim
24238 is receiving SMTP mail, it is acting as a server; when it is sending out
24239 messages over SMTP, it is acting as a client. Authenticator configuration
24240 options are provided for use in both these circumstances.
24242 To make it clear which options apply to which situation, the prefixes
24243 &%server_%& and &%client_%& are used on option names that are specific to
24244 either the server or the client function, respectively. Server and client
24245 functions are disabled if none of their options are set. If an authenticator is
24246 to be used for both server and client functions, a single definition, using
24247 both sets of options, is required. For example:
24251 public_name = CRAM-MD5
24252 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
24254 client_secret = secret2
24256 The &%server_%& option is used when Exim is acting as a server, and the
24257 &%client_%& options when it is acting as a client.
24259 Descriptions of the individual authenticators are given in subsequent chapters.
24260 The remainder of this chapter covers the generic options for the
24261 authenticators, followed by general discussion of the way authentication works
24264 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
24265 per-mechanism basis. Please read carefully to determine which variables hold
24266 account labels such as usercodes and which hold passwords or other
24267 authenticating data.
24269 Note that some mechanisms support two different identifiers for accounts: the
24270 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
24271 and &'authz'& are commonly encountered. The American spelling is standard here.
24272 Conceptually, authentication data such as passwords are tied to the identifier
24273 used to authenticate; servers may have rules to permit one user to act as a
24274 second user, so that after login the session is treated as though that second
24275 user had logged in. That second user is the &'authorization id'&. A robust
24276 configuration might confirm that the &'authz'& field is empty or matches the
24277 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
24278 as verified data, the &'authz'& as an unverified request which the server might
24281 A &'realm'& is a text string, typically a domain name, presented by a server
24282 to a client to help it select an account and credentials to use. In some
24283 mechanisms, the client and server provably agree on the realm, but clients
24284 typically can not treat the realm as secure data to be blindly trusted.
24288 .section "Generic options for authenticators" "SECID168"
24289 .cindex "authentication" "generic options"
24290 .cindex "options" "generic; for authenticators"
24292 .option client_condition authenticators string&!! unset
24293 When Exim is authenticating as a client, it skips any authenticator whose
24294 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
24295 used, for example, to skip plain text authenticators when the connection is not
24296 encrypted by a setting such as:
24298 client_condition = ${if !eq{$tls_out_cipher}{}}
24302 .option client_set_id authenticators string&!! unset
24303 When client authentication succeeds, this condition is expanded; the
24304 result is used in the log lines for outbound messasges.
24305 Typically it will be the user name used for authentication.
24308 .option driver authenticators string unset
24309 This option must always be set. It specifies which of the available
24310 authenticators is to be used.
24313 .option public_name authenticators string unset
24314 This option specifies the name of the authentication mechanism that the driver
24315 implements, and by which it is known to the outside world. These names should
24316 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
24317 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
24318 defaults to the driver's instance name.
24321 .option server_advertise_condition authenticators string&!! unset
24322 When a server is about to advertise an authentication mechanism, the condition
24323 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
24324 mechanism is not advertised.
24325 If the expansion fails, the mechanism is not advertised. If the failure was not
24326 forced, and was not caused by a lookup defer, the incident is logged.
24327 See section &<<SECTauthexiser>>& below for further discussion.
24330 .option server_condition authenticators string&!! unset
24331 This option must be set for a &%plaintext%& server authenticator, where it
24332 is used directly to control authentication. See section &<<SECTplainserver>>&
24335 For the &(gsasl)& authenticator, this option is required for various
24336 mechanisms; see chapter &<<CHAPgsasl>>& for details.
24338 For the other authenticators, &%server_condition%& can be used as an additional
24339 authentication or authorization mechanism that is applied after the other
24340 authenticator conditions succeed. If it is set, it is expanded when the
24341 authenticator would otherwise return a success code. If the expansion is forced
24342 to fail, authentication fails. Any other expansion failure causes a temporary
24343 error code to be returned. If the result of a successful expansion is an empty
24344 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24345 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
24346 other result, a temporary error code is returned, with the expanded string as
24350 .option server_debug_print authenticators string&!! unset
24351 If this option is set and authentication debugging is enabled (see the &%-d%&
24352 command line option), the string is expanded and included in the debugging
24353 output when the authenticator is run as a server. This can help with checking
24354 out the values of variables.
24355 If expansion of the string fails, the error message is written to the debugging
24356 output, and Exim carries on processing.
24359 .option server_set_id authenticators string&!! unset
24360 .vindex "&$authenticated_id$&"
24361 When an Exim server successfully authenticates a client, this string is
24362 expanded using data from the authentication, and preserved for any incoming
24363 messages in the variable &$authenticated_id$&. It is also included in the log
24364 lines for incoming messages. For example, a user/password authenticator
24365 configuration might preserve the user name that was used to authenticate, and
24366 refer to it subsequently during delivery of the message.
24367 If expansion fails, the option is ignored.
24370 .option server_mail_auth_condition authenticators string&!! unset
24371 This option allows a server to discard authenticated sender addresses supplied
24372 as part of MAIL commands in SMTP connections that are authenticated by the
24373 driver on which &%server_mail_auth_condition%& is set. The option is not used
24374 as part of the authentication process; instead its (unexpanded) value is
24375 remembered for later use.
24376 How it is used is described in the following section.
24382 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
24383 .cindex "authentication" "sender; authenticated"
24384 .cindex "AUTH" "on MAIL command"
24385 When a client supplied an AUTH= item on a MAIL command, Exim applies
24386 the following checks before accepting it as the authenticated sender of the
24390 If the connection is not using extended SMTP (that is, HELO was used rather
24391 than EHLO), the use of AUTH= is a syntax error.
24393 If the value of the AUTH= parameter is &"<>"&, it is ignored.
24395 .vindex "&$authenticated_sender$&"
24396 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
24397 running, the value of &$authenticated_sender$& is set to the value obtained
24398 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
24399 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
24400 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
24401 given for the MAIL command.
24403 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
24404 is accepted and placed in &$authenticated_sender$& only if the client has
24407 If the AUTH= value was accepted by either of the two previous rules, and
24408 the client has authenticated, and the authenticator has a setting for the
24409 &%server_mail_auth_condition%&, the condition is checked at this point. The
24410 valued that was saved from the authenticator is expanded. If the expansion
24411 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
24412 &$authenticated_sender$& is deleted. If the expansion yields any other value,
24413 the value of &$authenticated_sender$& is retained and passed on with the
24418 When &$authenticated_sender$& is set for a message, it is passed on to other
24419 hosts to which Exim authenticates as a client. Do not confuse this value with
24420 &$authenticated_id$&, which is a string obtained from the authentication
24421 process, and which is not usually a complete email address.
24423 .vindex "&$sender_address$&"
24424 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
24425 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
24426 therefore make use of &$authenticated_sender$&. The converse is not true: the
24427 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
24432 .section "Authentication on an Exim server" "SECTauthexiser"
24433 .cindex "authentication" "on an Exim server"
24434 When Exim receives an EHLO command, it advertises the public names of those
24435 authenticators that are configured as servers, subject to the following
24439 The client host must match &%auth_advertise_hosts%& (default *).
24441 It the &%server_advertise_condition%& option is set, its expansion must not
24442 yield the empty string, &"0"&, &"no"&, or &"false"&.
24445 The order in which the authenticators are defined controls the order in which
24446 the mechanisms are advertised.
24448 Some mail clients (for example, some versions of Netscape) require the user to
24449 provide a name and password for authentication whenever AUTH is advertised,
24450 even though authentication may not in fact be needed (for example, Exim may be
24451 set up to allow unconditional relaying from the client by an IP address check).
24452 You can make such clients more friendly by not advertising AUTH to them.
24453 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
24454 that runs for RCPT) to relay without authentication, you should set
24456 auth_advertise_hosts = ! 10.9.8.0/24
24458 so that no authentication mechanisms are advertised to them.
24460 The &%server_advertise_condition%& controls the advertisement of individual
24461 authentication mechanisms. For example, it can be used to restrict the
24462 advertisement of a particular mechanism to encrypted connections, by a setting
24465 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
24467 .vindex "&$tls_in_cipher$&"
24468 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
24469 yields &"yes"&, which allows the advertisement to happen.
24471 When an Exim server receives an AUTH command from a client, it rejects it
24472 immediately if AUTH was not advertised in response to an earlier EHLO
24473 command. This is the case if
24476 The client host does not match &%auth_advertise_hosts%&; or
24478 No authenticators are configured with server options; or
24480 Expansion of &%server_advertise_condition%& blocked the advertising of all the
24481 server authenticators.
24485 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
24486 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
24487 AUTH is accepted from any client host.
24489 If AUTH is not rejected by the ACL, Exim searches its configuration for a
24490 server authentication mechanism that was advertised in response to EHLO and
24491 that matches the one named in the AUTH command. If it finds one, it runs
24492 the appropriate authentication protocol, and authentication either succeeds or
24493 fails. If there is no matching advertised mechanism, the AUTH command is
24494 rejected with a 504 error.
24496 .vindex "&$received_protocol$&"
24497 .vindex "&$sender_host_authenticated$&"
24498 When a message is received from an authenticated host, the value of
24499 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
24500 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
24501 public name) of the authenticator driver that successfully authenticated the
24502 client from which the message was received. This variable is empty if there was
24503 no successful authentication.
24508 .section "Testing server authentication" "SECID169"
24509 .cindex "authentication" "testing a server"
24510 .cindex "AUTH" "testing a server"
24511 .cindex "base64 encoding" "creating authentication test data"
24512 Exim's &%-bh%& option can be useful for testing server authentication
24513 configurations. The data for the AUTH command has to be sent using base64
24514 encoding. A quick way to produce such data for testing is the following Perl
24518 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
24520 .cindex "binary zero" "in authentication data"
24521 This interprets its argument as a Perl string, and then encodes it. The
24522 interpretation as a Perl string allows binary zeros, which are required for
24523 some kinds of authentication, to be included in the data. For example, a
24524 command line to run this script on such data might be
24526 encode '\0user\0password'
24528 Note the use of single quotes to prevent the shell interpreting the
24529 backslashes, so that they can be interpreted by Perl to specify characters
24530 whose code value is zero.
24532 &*Warning 1*&: If either of the user or password strings starts with an octal
24533 digit, you must use three zeros instead of one after the leading backslash. If
24534 you do not, the octal digit that starts your string will be incorrectly
24535 interpreted as part of the code for the first character.
24537 &*Warning 2*&: If there are characters in the strings that Perl interprets
24538 specially, you must use a Perl escape to prevent them being misinterpreted. For
24539 example, a command such as
24541 encode '\0user@domain.com\0pas$$word'
24543 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
24545 If you have the &%mimencode%& command installed, another way to do produce
24546 base64-encoded strings is to run the command
24548 echo -e -n `\0user\0password' | mimencode
24550 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
24551 in the argument, and the &%-n%& option specifies no newline at the end of its
24552 output. However, not all versions of &%echo%& recognize these options, so you
24553 should check your version before relying on this suggestion.
24557 .section "Authentication by an Exim client" "SECID170"
24558 .cindex "authentication" "on an Exim client"
24559 The &(smtp)& transport has two options called &%hosts_require_auth%& and
24560 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
24561 announces support for authentication, and the host matches an entry in either
24562 of these options, Exim (as a client) tries to authenticate as follows:
24565 For each authenticator that is configured as a client, in the order in which
24566 they are defined in the configuration, it searches the authentication
24567 mechanisms announced by the server for one whose name matches the public name
24568 of the authenticator.
24571 .vindex "&$host_address$&"
24572 When it finds one that matches, it runs the authenticator's client code. The
24573 variables &$host$& and &$host_address$& are available for any string expansions
24574 that the client might do. They are set to the server's name and IP address. If
24575 any expansion is forced to fail, the authentication attempt is abandoned, and
24576 Exim moves on to the next authenticator. Otherwise an expansion failure causes
24577 delivery to be deferred.
24579 If the result of the authentication attempt is a temporary error or a timeout,
24580 Exim abandons trying to send the message to the host for the moment. It will
24581 try again later. If there are any backup hosts available, they are tried in the
24584 If the response to authentication is a permanent error (5&'xx'& code), Exim
24585 carries on searching the list of authenticators and tries another one if
24586 possible. If all authentication attempts give permanent errors, or if there are
24587 no attempts because no mechanisms match (or option expansions force failure),
24588 what happens depends on whether the host matches &%hosts_require_auth%& or
24589 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
24590 delivery is deferred. The error can be detected in the retry rules, and thereby
24591 turned into a permanent error if you wish. In the second case, Exim tries to
24592 deliver the message unauthenticated.
24595 .cindex "AUTH" "on MAIL command"
24596 When Exim has authenticated itself to a remote server, it adds the AUTH
24597 parameter to the MAIL commands it sends, if it has an authenticated sender for
24598 the message. If the message came from a remote host, the authenticated sender
24599 is the one that was receiving on an incoming MAIL command, provided that the
24600 incoming connection was authenticated and the &%server_mail_auth%& condition
24601 allowed the authenticated sender to be retained. If a local process calls Exim
24602 to send a message, the sender address that is built from the login name and
24603 &%qualify_domain%& is treated as authenticated. However, if the
24604 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
24605 the authenticated sender that was received with the message.
24606 .ecindex IIDauthconf1
24607 .ecindex IIDauthconf2
24614 . ////////////////////////////////////////////////////////////////////////////
24615 . ////////////////////////////////////////////////////////////////////////////
24617 .chapter "The plaintext authenticator" "CHAPplaintext"
24618 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
24619 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
24620 The &(plaintext)& authenticator can be configured to support the PLAIN and
24621 LOGIN authentication mechanisms, both of which transfer authentication data as
24622 plain (unencrypted) text (though base64 encoded). The use of plain text is a
24623 security risk; you are strongly advised to insist on the use of SMTP encryption
24624 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
24625 use unencrypted plain text, you should not use the same passwords for SMTP
24626 connections as you do for login accounts.
24628 .section "Plaintext options" "SECID171"
24629 .cindex "options" "&(plaintext)& authenticator (server)"
24630 When configured as a server, &(plaintext)& uses the following options:
24632 .option server_condition authenticators string&!! unset
24633 This is actually a global authentication option, but it must be set in order to
24634 configure the &(plaintext)& driver as a server. Its use is described below.
24636 .option server_prompts plaintext string&!! unset
24637 The contents of this option, after expansion, must be a colon-separated list of
24638 prompt strings. If expansion fails, a temporary authentication rejection is
24641 .section "Using plaintext in a server" "SECTplainserver"
24642 .cindex "AUTH" "in &(plaintext)& authenticator"
24643 .cindex "binary zero" "in &(plaintext)& authenticator"
24644 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
24645 "in &(plaintext)& authenticator"
24646 .vindex "&$auth1$&, &$auth2$&, etc"
24647 .cindex "base64 encoding" "in &(plaintext)& authenticator"
24649 When running as a server, &(plaintext)& performs the authentication test by
24650 expanding a string. The data sent by the client with the AUTH command, or in
24651 response to subsequent prompts, is base64 encoded, and so may contain any byte
24652 values when decoded. If any data is supplied with the command, it is treated as
24653 a list of strings, separated by NULs (binary zeros), the first three of which
24654 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
24655 (neither LOGIN nor PLAIN uses more than three strings).
24657 For compatibility with previous releases of Exim, the values are also placed in
24658 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
24659 variables for this purpose is now deprecated, as it can lead to confusion in
24660 string expansions that also use them for other things.
24662 If there are more strings in &%server_prompts%& than the number of strings
24663 supplied with the AUTH command, the remaining prompts are used to obtain more
24664 data. Each response from the client may be a list of NUL-separated strings.
24666 .vindex "&$authenticated_id$&"
24667 Once a sufficient number of data strings have been received,
24668 &%server_condition%& is expanded. If the expansion is forced to fail,
24669 authentication fails. Any other expansion failure causes a temporary error code
24670 to be returned. If the result of a successful expansion is an empty string,
24671 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24672 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
24673 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
24674 For any other result, a temporary error code is returned, with the expanded
24675 string as the error text
24677 &*Warning*&: If you use a lookup in the expansion to find the user's
24678 password, be sure to make the authentication fail if the user is unknown.
24679 There are good and bad examples at the end of the next section.
24683 .section "The PLAIN authentication mechanism" "SECID172"
24684 .cindex "PLAIN authentication mechanism"
24685 .cindex "authentication" "PLAIN mechanism"
24686 .cindex "binary zero" "in &(plaintext)& authenticator"
24687 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
24688 sent as one item of data (that is, one combined string containing two NUL
24689 separators). The data is sent either as part of the AUTH command, or
24690 subsequently in response to an empty prompt from the server.
24692 The second and third strings are a user name and a corresponding password.
24693 Using a single fixed user name and password as an example, this could be
24694 configured as follows:
24698 public_name = PLAIN
24700 server_condition = \
24701 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
24702 server_set_id = $auth2
24704 Note that the default result strings from &%if%& (&"true"& or an empty string)
24705 are exactly what we want here, so they need not be specified. Obviously, if the
24706 password contains expansion-significant characters such as dollar, backslash,
24707 or closing brace, they have to be escaped.
24709 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
24710 the end of a string list are ignored). If all the data comes as part of the
24711 AUTH command, as is commonly the case, the prompt is not used. This
24712 authenticator is advertised in the response to EHLO as
24716 and a client host can authenticate itself by sending the command
24718 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
24720 As this contains three strings (more than the number of prompts), no further
24721 data is required from the client. Alternatively, the client may just send
24725 to initiate authentication, in which case the server replies with an empty
24726 prompt. The client must respond with the combined data string.
24728 The data string is base64 encoded, as required by the RFC. This example,
24729 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
24730 represents a zero byte. This is split up into three strings, the first of which
24731 is empty. The &%server_condition%& option in the authenticator checks that the
24732 second two are &`username`& and &`mysecret`& respectively.
24734 Having just one fixed user name and password, as in this example, is not very
24735 realistic, though for a small organization with only a handful of
24736 authenticating clients it could make sense.
24738 A more sophisticated instance of this authenticator could use the user name in
24739 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
24740 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
24741 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
24742 This is an incorrect example:
24744 server_condition = \
24745 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
24747 The expansion uses the user name (&$auth2$&) as the key to look up a password,
24748 which it then compares to the supplied password (&$auth3$&). Why is this example
24749 incorrect? It works fine for existing users, but consider what happens if a
24750 non-existent user name is given. The lookup fails, but as no success/failure
24751 strings are given for the lookup, it yields an empty string. Thus, to defeat
24752 the authentication, all a client has to do is to supply a non-existent user
24753 name and an empty password. The correct way of writing this test is:
24755 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
24756 {${if eq{$value}{$auth3}}} {false}}
24758 In this case, if the lookup succeeds, the result is checked; if the lookup
24759 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
24760 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
24761 always fails if its second argument is empty. However, the second way of
24762 writing the test makes the logic clearer.
24765 .section "The LOGIN authentication mechanism" "SECID173"
24766 .cindex "LOGIN authentication mechanism"
24767 .cindex "authentication" "LOGIN mechanism"
24768 The LOGIN authentication mechanism is not documented in any RFC, but is in use
24769 in a number of programs. No data is sent with the AUTH command. Instead, a
24770 user name and password are supplied separately, in response to prompts. The
24771 plaintext authenticator can be configured to support this as in this example:
24775 public_name = LOGIN
24776 server_prompts = User Name : Password
24777 server_condition = \
24778 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
24779 server_set_id = $auth1
24781 Because of the way plaintext operates, this authenticator accepts data supplied
24782 with the AUTH command (in contravention of the specification of LOGIN), but
24783 if the client does not supply it (as is the case for LOGIN clients), the prompt
24784 strings are used to obtain two data items.
24786 Some clients are very particular about the precise text of the prompts. For
24787 example, Outlook Express is reported to recognize only &"Username:"& and
24788 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
24789 strings. It uses the &%ldapauth%& expansion condition to check the user
24790 name and password by binding to an LDAP server:
24794 public_name = LOGIN
24795 server_prompts = Username:: : Password::
24796 server_condition = ${if and{{ \
24799 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
24800 pass=${quote:$auth2} \
24801 ldap://ldap.example.org/} }} }
24802 server_set_id = uid=$auth1,ou=people,o=example.org
24804 We have to check that the username is not empty before using it, because LDAP
24805 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
24806 operator to correctly quote the DN for authentication. However, the basic
24807 &%quote%& operator, rather than any of the LDAP quoting operators, is the
24808 correct one to use for the password, because quoting is needed only to make
24809 the password conform to the Exim syntax. At the LDAP level, the password is an
24810 uninterpreted string.
24813 .section "Support for different kinds of authentication" "SECID174"
24814 A number of string expansion features are provided for the purpose of
24815 interfacing to different ways of user authentication. These include checking
24816 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
24817 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
24823 .section "Using plaintext in a client" "SECID175"
24824 .cindex "options" "&(plaintext)& authenticator (client)"
24825 The &(plaintext)& authenticator has two client options:
24827 .option client_ignore_invalid_base64 plaintext boolean false
24828 If the client receives a server prompt that is not a valid base64 string,
24829 authentication is abandoned by default. However, if this option is set true,
24830 the error in the challenge is ignored and the client sends the response as
24833 .option client_send plaintext string&!! unset
24834 The string is a colon-separated list of authentication data strings. Each
24835 string is independently expanded before being sent to the server. The first
24836 string is sent with the AUTH command; any more strings are sent in response
24837 to prompts from the server. Before each string is expanded, the value of the
24838 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
24839 with &$auth1$& for the first prompt. Up to three prompts are stored in this
24840 way. Thus, the prompt that is received in response to sending the first string
24841 (with the AUTH command) can be used in the expansion of the second string, and
24842 so on. If an invalid base64 string is received when
24843 &%client_ignore_invalid_base64%& is set, an empty string is put in the
24844 &$auth$&<&'n'&> variable.
24846 &*Note*&: You cannot use expansion to create multiple strings, because
24847 splitting takes priority and happens first.
24849 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
24850 the data, further processing is applied to each string before it is sent. If
24851 there are any single circumflex characters in the string, they are converted to
24852 NULs. Should an actual circumflex be required as data, it must be doubled in
24855 This is an example of a client configuration that implements the PLAIN
24856 authentication mechanism with a fixed user name and password:
24860 public_name = PLAIN
24861 client_send = ^username^mysecret
24863 The lack of colons means that the entire text is sent with the AUTH
24864 command, with the circumflex characters converted to NULs. A similar example
24865 that uses the LOGIN mechanism is:
24869 public_name = LOGIN
24870 client_send = : username : mysecret
24872 The initial colon means that the first string is empty, so no data is sent with
24873 the AUTH command itself. The remaining strings are sent in response to
24875 .ecindex IIDplaiauth1
24876 .ecindex IIDplaiauth2
24881 . ////////////////////////////////////////////////////////////////////////////
24882 . ////////////////////////////////////////////////////////////////////////////
24884 .chapter "The cram_md5 authenticator" "CHID9"
24885 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
24886 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
24887 .cindex "CRAM-MD5 authentication mechanism"
24888 .cindex "authentication" "CRAM-MD5 mechanism"
24889 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
24890 sends a challenge string to the client, and the response consists of a user
24891 name and the CRAM-MD5 digest of the challenge string combined with a secret
24892 string (password) which is known to both server and client. Thus, the secret
24893 is not sent over the network as plain text, which makes this authenticator more
24894 secure than &(plaintext)&. However, the downside is that the secret has to be
24895 available in plain text at either end.
24898 .section "Using cram_md5 as a server" "SECID176"
24899 .cindex "options" "&(cram_md5)& authenticator (server)"
24900 This authenticator has one server option, which must be set to configure the
24901 authenticator as a server:
24903 .option server_secret cram_md5 string&!! unset
24904 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
24905 When the server receives the client's response, the user name is placed in
24906 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
24907 obtain the password for that user. The server then computes the CRAM-MD5 digest
24908 that the client should have sent, and checks that it received the correct
24909 string. If the expansion of &%server_secret%& is forced to fail, authentication
24910 fails. If the expansion fails for some other reason, a temporary error code is
24911 returned to the client.
24913 For compatibility with previous releases of Exim, the user name is also placed
24914 in &$1$&. However, the use of this variables for this purpose is now
24915 deprecated, as it can lead to confusion in string expansions that also use
24916 numeric variables for other things.
24918 For example, the following authenticator checks that the user name given by the
24919 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
24920 user name, authentication fails.
24924 public_name = CRAM-MD5
24925 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
24926 server_set_id = $auth1
24928 .vindex "&$authenticated_id$&"
24929 If authentication succeeds, the setting of &%server_set_id%& preserves the user
24930 name in &$authenticated_id$&. A more typical configuration might look up the
24931 secret string in a file, using the user name as the key. For example:
24935 public_name = CRAM-MD5
24936 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
24938 server_set_id = $auth1
24940 Note that this expansion explicitly forces failure if the lookup fails
24941 because &$auth1$& contains an unknown user name.
24943 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
24944 using the relevant libraries, you need to know the realm to specify in the
24945 lookup and then ask for the &"userPassword"& attribute for that user in that
24950 public_name = CRAM-MD5
24951 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
24952 dbmjz{/etc/sasldb2}}
24953 server_set_id = $auth1
24956 .section "Using cram_md5 as a client" "SECID177"
24957 .cindex "options" "&(cram_md5)& authenticator (client)"
24958 When used as a client, the &(cram_md5)& authenticator has two options:
24962 .option client_name cram_md5 string&!! "the primary host name"
24963 This string is expanded, and the result used as the user name data when
24964 computing the response to the server's challenge.
24967 .option client_secret cram_md5 string&!! unset
24968 This option must be set for the authenticator to work as a client. Its value is
24969 expanded and the result used as the secret string when computing the response.
24973 .vindex "&$host_address$&"
24974 Different user names and secrets can be used for different servers by referring
24975 to &$host$& or &$host_address$& in the options. Forced failure of either
24976 expansion string is treated as an indication that this authenticator is not
24977 prepared to handle this case. Exim moves on to the next configured client
24978 authenticator. Any other expansion failure causes Exim to give up trying to
24979 send the message to the current server.
24981 A simple example configuration of a &(cram_md5)& authenticator, using fixed
24986 public_name = CRAM-MD5
24988 client_secret = secret
24990 .ecindex IIDcramauth1
24991 .ecindex IIDcramauth2
24995 . ////////////////////////////////////////////////////////////////////////////
24996 . ////////////////////////////////////////////////////////////////////////////
24998 .chapter "The cyrus_sasl authenticator" "CHID10"
24999 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25000 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25001 .cindex "Cyrus" "SASL library"
25003 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25004 Digital Ltd (&url(http://www.aldigital.co.uk)).
25006 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25007 library implementation of the RFC 2222 (&"Simple Authentication and Security
25008 Layer"&). This library supports a number of authentication mechanisms,
25009 including PLAIN and LOGIN, but also several others that Exim does not support
25010 directly. In particular, there is support for Kerberos authentication.
25012 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25013 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25014 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25015 name of the driver to determine which mechanism to support.
25017 Where access to some kind of secret file is required, for example in GSSAPI
25018 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25019 user, and that the Cyrus SASL library has no way of escalating privileges
25020 by default. You may also find you need to set environment variables,
25021 depending on the driver you are using.
25023 The application name provided by Exim is &"exim"&, so various SASL options may
25024 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25025 Kerberos, note that because of limitations in the GSSAPI interface,
25026 changing the server keytab might need to be communicated down to the Kerberos
25027 layer independently. The mechanism for doing so is dependent upon the Kerberos
25030 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25031 may be set to point to an alternative keytab file. Exim will pass this
25032 variable through from its own inherited environment when started as root or the
25033 Exim user. The keytab file needs to be readable by the Exim user.
25034 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25035 environment variable. In practice, for those releases, the Cyrus authenticator
25036 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25037 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25040 .section "Using cyrus_sasl as a server" "SECID178"
25041 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25042 (on a successful authentication) into &$auth1$&. For compatibility with
25043 previous releases of Exim, the username is also placed in &$1$&. However, the
25044 use of this variable for this purpose is now deprecated, as it can lead to
25045 confusion in string expansions that also use numeric variables for other
25049 .option server_hostname cyrus_sasl string&!! "see below"
25050 This option selects the hostname that is used when communicating with the
25051 library. The default value is &`$primary_hostname`&. It is up to the underlying
25052 SASL plug-in what it does with this data.
25055 .option server_mech cyrus_sasl string "see below"
25056 This option selects the authentication mechanism this driver should use. The
25057 default is the value of the generic &%public_name%& option. This option allows
25058 you to use a different underlying mechanism from the advertised name. For
25062 driver = cyrus_sasl
25063 public_name = X-ANYTHING
25064 server_mech = CRAM-MD5
25065 server_set_id = $auth1
25068 .option server_realm cyrus_sasl string&!! unset
25069 This specifies the SASL realm that the server claims to be in.
25072 .option server_service cyrus_sasl string &`smtp`&
25073 This is the SASL service that the server claims to implement.
25076 For straightforward cases, you do not need to set any of the authenticator's
25077 private options. All you need to do is to specify an appropriate mechanism as
25078 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
25079 PLAIN, you could have two authenticators as follows:
25082 driver = cyrus_sasl
25083 public_name = CRAM-MD5
25084 server_set_id = $auth1
25087 driver = cyrus_sasl
25088 public_name = PLAIN
25089 server_set_id = $auth2
25091 Cyrus SASL does implement the LOGIN authentication method, even though it is
25092 not a standard method. It is disabled by default in the source distribution,
25093 but it is present in many binary distributions.
25094 .ecindex IIDcyrauth1
25095 .ecindex IIDcyrauth2
25100 . ////////////////////////////////////////////////////////////////////////////
25101 . ////////////////////////////////////////////////////////////////////////////
25102 .chapter "The dovecot authenticator" "CHAPdovecot"
25103 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
25104 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
25105 This authenticator is an interface to the authentication facility of the
25106 Dovecot POP/IMAP server, which can support a number of authentication methods.
25107 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
25108 to use the same mechanisms for SMTP authentication. This is a server
25109 authenticator only. There is only one option:
25111 .option server_socket dovecot string unset
25113 This option must specify the socket that is the interface to Dovecot
25114 authentication. The &%public_name%& option must specify an authentication
25115 mechanism that Dovecot is configured to support. You can have several
25116 authenticators for different mechanisms. For example:
25120 public_name = PLAIN
25121 server_socket = /var/run/dovecot/auth-client
25122 server_set_id = $auth2
25127 server_socket = /var/run/dovecot/auth-client
25128 server_set_id = $auth1
25130 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
25131 &$received_ip_address$& (that is, the connection is local), the &"secured"&
25132 option is passed in the Dovecot authentication command. If, for a TLS
25133 connection, a client certificate has been verified, the &"valid-client-cert"&
25134 option is passed. When authentication succeeds, the identity of the user
25135 who authenticated is placed in &$auth1$&.
25136 .ecindex IIDdcotauth1
25137 .ecindex IIDdcotauth2
25140 . ////////////////////////////////////////////////////////////////////////////
25141 . ////////////////////////////////////////////////////////////////////////////
25142 .chapter "The gsasl authenticator" "CHAPgsasl"
25143 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
25144 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
25145 .cindex "authentication" "GNU SASL"
25146 .cindex "authentication" "SASL"
25147 .cindex "authentication" "EXTERNAL"
25148 .cindex "authentication" "ANONYMOUS"
25149 .cindex "authentication" "PLAIN"
25150 .cindex "authentication" "LOGIN"
25151 .cindex "authentication" "DIGEST-MD5"
25152 .cindex "authentication" "CRAM-MD5"
25153 .cindex "authentication" "SCRAM-SHA-1"
25154 The &(gsasl)& authenticator provides server integration for the GNU SASL
25155 library and the mechanisms it provides. This is new as of the 4.80 release
25156 and there are a few areas where the library does not let Exim smoothly
25157 scale to handle future authentication mechanisms, so no guarantee can be
25158 made that any particular new authentication mechanism will be supported
25159 without code changes in Exim.
25162 .option server_channelbinding gsasl boolean false
25163 Some authentication mechanisms are able to use external context at both ends
25164 of the session to bind the authentication to that context, and fail the
25165 authentication process if that context differs. Specifically, some TLS
25166 ciphersuites can provide identifying information about the cryptographic
25169 This means that certificate identity and verification becomes a non-issue,
25170 as a man-in-the-middle attack will cause the correct client and server to
25171 see different identifiers and authentication will fail.
25173 This is currently only supported when using the GnuTLS library. This is
25174 only usable by mechanisms which support "channel binding"; at time of
25175 writing, that's the SCRAM family.
25177 This defaults off to ensure smooth upgrade across Exim releases, in case
25178 this option causes some clients to start failing. Some future release
25179 of Exim may switch the default to be true.
25182 .option server_hostname gsasl string&!! "see below"
25183 This option selects the hostname that is used when communicating with the
25184 library. The default value is &`$primary_hostname`&.
25185 Some mechanisms will use this data.
25188 .option server_mech gsasl string "see below"
25189 This option selects the authentication mechanism this driver should use. The
25190 default is the value of the generic &%public_name%& option. This option allows
25191 you to use a different underlying mechanism from the advertised name. For
25196 public_name = X-ANYTHING
25197 server_mech = CRAM-MD5
25198 server_set_id = $auth1
25202 .option server_password gsasl string&!! unset
25203 Various mechanisms need access to the cleartext password on the server, so
25204 that proof-of-possession can be demonstrated on the wire, without sending
25205 the password itself.
25207 The data available for lookup varies per mechanism.
25208 In all cases, &$auth1$& is set to the &'authentication id'&.
25209 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
25210 if available, else the empty string.
25211 The &$auth3$& variable will always be the &'realm'& if available,
25212 else the empty string.
25214 A forced failure will cause authentication to defer.
25216 If using this option, it may make sense to set the &%server_condition%&
25217 option to be simply "true".
25220 .option server_realm gsasl string&!! unset
25221 This specifies the SASL realm that the server claims to be in.
25222 Some mechanisms will use this data.
25225 .option server_scram_iter gsasl string&!! unset
25226 This option provides data for the SCRAM family of mechanisms.
25227 &$auth1$& is not available at evaluation time.
25228 (This may change, as we receive feedback on use)
25231 .option server_scram_salt gsasl string&!! unset
25232 This option provides data for the SCRAM family of mechanisms.
25233 &$auth1$& is not available at evaluation time.
25234 (This may change, as we receive feedback on use)
25237 .option server_service gsasl string &`smtp`&
25238 This is the SASL service that the server claims to implement.
25239 Some mechanisms will use this data.
25242 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
25243 .vindex "&$auth1$&, &$auth2$&, etc"
25244 These may be set when evaluating specific options, as detailed above.
25245 They will also be set when evaluating &%server_condition%&.
25247 Unless otherwise stated below, the &(gsasl)& integration will use the following
25248 meanings for these variables:
25251 .vindex "&$auth1$&"
25252 &$auth1$&: the &'authentication id'&
25254 .vindex "&$auth2$&"
25255 &$auth2$&: the &'authorization id'&
25257 .vindex "&$auth3$&"
25258 &$auth3$&: the &'realm'&
25261 On a per-mechanism basis:
25264 .cindex "authentication" "EXTERNAL"
25265 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
25266 the &%server_condition%& option must be present.
25268 .cindex "authentication" "ANONYMOUS"
25269 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
25270 the &%server_condition%& option must be present.
25272 .cindex "authentication" "GSSAPI"
25273 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
25274 &$auth2$& will be set to the &'authorization id'&,
25275 the &%server_condition%& option must be present.
25278 An &'anonymous token'& is something passed along as an unauthenticated
25279 identifier; this is analogous to FTP anonymous authentication passing an
25280 email address, or software-identifier@, as the "password".
25283 An example showing the password having the realm specified in the callback
25284 and demonstrating a Cyrus SASL to GSASL migration approach is:
25286 gsasl_cyrusless_crammd5:
25288 public_name = CRAM-MD5
25289 server_realm = imap.example.org
25290 server_password = ${lookup{$auth1:$auth3:userPassword}\
25291 dbmjz{/etc/sasldb2}{$value}fail}
25292 server_set_id = ${quote:$auth1}
25293 server_condition = yes
25297 . ////////////////////////////////////////////////////////////////////////////
25298 . ////////////////////////////////////////////////////////////////////////////
25300 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
25301 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
25302 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
25303 .cindex "authentication" "GSSAPI"
25304 .cindex "authentication" "Kerberos"
25305 The &(heimdal_gssapi)& authenticator provides server integration for the
25306 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
25309 .option server_hostname heimdal_gssapi string&!! "see below"
25310 This option selects the hostname that is used, with &%server_service%&,
25311 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
25312 identifier. The default value is &`$primary_hostname`&.
25314 .option server_keytab heimdal_gssapi string&!! unset
25315 If set, then Heimdal will not use the system default keytab (typically
25316 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
25317 The value should be a pathname, with no &"file:"& prefix.
25319 .option server_service heimdal_gssapi string&!! "smtp"
25320 This option specifies the service identifier used, in conjunction with
25321 &%server_hostname%&, for building the identifer for finding credentials
25325 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
25326 Beware that these variables will typically include a realm, thus will appear
25327 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
25328 not verified, so a malicious client can set it to anything.
25330 The &$auth1$& field should be safely trustable as a value from the Key
25331 Distribution Center. Note that these are not quite email addresses.
25332 Each identifier is for a role, and so the left-hand-side may include a
25333 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
25335 .vindex "&$auth1$&, &$auth2$&, etc"
25337 .vindex "&$auth1$&"
25338 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
25340 .vindex "&$auth2$&"
25341 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
25342 authentication. If that was empty, this will also be set to the
25347 . ////////////////////////////////////////////////////////////////////////////
25348 . ////////////////////////////////////////////////////////////////////////////
25350 .chapter "The spa authenticator" "CHAPspa"
25351 .scindex IIDspaauth1 "&(spa)& authenticator"
25352 .scindex IIDspaauth2 "authenticators" "&(spa)&"
25353 .cindex "authentication" "Microsoft Secure Password"
25354 .cindex "authentication" "NTLM"
25355 .cindex "Microsoft Secure Password Authentication"
25356 .cindex "NTLM authentication"
25357 The &(spa)& authenticator provides client support for Microsoft's &'Secure
25358 Password Authentication'& mechanism,
25359 which is also sometimes known as NTLM (NT LanMan). The code for client side of
25360 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
25361 taken from the Samba project (&url(http://www.samba.org)). The code for the
25362 server side was subsequently contributed by Tom Kistner. The mechanism works as
25366 After the AUTH command has been accepted, the client sends an SPA
25367 authentication request based on the user name and optional domain.
25369 The server sends back a challenge.
25371 The client builds a challenge response which makes use of the user's password
25372 and sends it to the server, which then accepts or rejects it.
25375 Encryption is used to protect the password in transit.
25379 .section "Using spa as a server" "SECID179"
25380 .cindex "options" "&(spa)& authenticator (server)"
25381 The &(spa)& authenticator has just one server option:
25383 .option server_password spa string&!! unset
25384 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
25385 This option is expanded, and the result must be the cleartext password for the
25386 authenticating user, whose name is at this point in &$auth1$&. For
25387 compatibility with previous releases of Exim, the user name is also placed in
25388 &$1$&. However, the use of this variable for this purpose is now deprecated, as
25389 it can lead to confusion in string expansions that also use numeric variables
25390 for other things. For example:
25395 server_password = \
25396 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
25398 If the expansion is forced to fail, authentication fails. Any other expansion
25399 failure causes a temporary error code to be returned.
25405 .section "Using spa as a client" "SECID180"
25406 .cindex "options" "&(spa)& authenticator (client)"
25407 The &(spa)& authenticator has the following client options:
25411 .option client_domain spa string&!! unset
25412 This option specifies an optional domain for the authentication.
25415 .option client_password spa string&!! unset
25416 This option specifies the user's password, and must be set.
25419 .option client_username spa string&!! unset
25420 This option specifies the user name, and must be set. Here is an example of a
25421 configuration of this authenticator for use with the mail servers at
25427 client_username = msn/msn_username
25428 client_password = msn_plaintext_password
25429 client_domain = DOMAIN_OR_UNSET
25431 .ecindex IIDspaauth1
25432 .ecindex IIDspaauth2
25438 . ////////////////////////////////////////////////////////////////////////////
25439 . ////////////////////////////////////////////////////////////////////////////
25441 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
25442 "Encrypted SMTP connections"
25443 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
25444 .scindex IIDencsmtp2 "SMTP" "encryption"
25445 .cindex "TLS" "on SMTP connection"
25448 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
25449 Sockets Layer), is implemented by making use of the OpenSSL library or the
25450 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
25451 cryptographic code in the Exim distribution itself for implementing TLS. In
25452 order to use this feature you must install OpenSSL or GnuTLS, and then build a
25453 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
25454 You also need to understand the basic concepts of encryption at a managerial
25455 level, and in particular, the way that public keys, private keys, and
25456 certificates are used.
25458 RFC 3207 defines how SMTP connections can make use of encryption. Once a
25459 connection is established, the client issues a STARTTLS command. If the
25460 server accepts this, the client and the server negotiate an encryption
25461 mechanism. If the negotiation succeeds, the data that subsequently passes
25462 between them is encrypted.
25464 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
25465 and if so, what cipher suite is in use, whether the client supplied a
25466 certificate, and whether or not that certificate was verified. This makes it
25467 possible for an Exim server to deny or accept certain commands based on the
25470 &*Warning*&: Certain types of firewall and certain anti-virus products can
25471 disrupt TLS connections. You need to turn off SMTP scanning for these products
25472 in order to get TLS to work.
25476 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
25478 .cindex "ssmtp protocol"
25479 .cindex "smtps protocol"
25480 .cindex "SMTP" "ssmtp protocol"
25481 .cindex "SMTP" "smtps protocol"
25482 Early implementations of encrypted SMTP used a different TCP port from normal
25483 SMTP, and expected an encryption negotiation to start immediately, instead of
25484 waiting for a STARTTLS command from the client using the standard SMTP
25485 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
25486 allocated for this purpose.
25488 This approach was abandoned when encrypted SMTP was standardized, but there are
25489 still some legacy clients that use it. Exim supports these clients by means of
25490 the &%tls_on_connect_ports%& global option. Its value must be a list of port
25491 numbers; the most common use is expected to be:
25493 tls_on_connect_ports = 465
25495 The port numbers specified by this option apply to all SMTP connections, both
25496 via the daemon and via &'inetd'&. You still need to specify all the ports that
25497 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
25498 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
25499 an extra port &-- rather, it specifies different behaviour on a port that is
25502 There is also a &%-tls-on-connect%& command line option. This overrides
25503 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
25510 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
25511 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
25512 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
25513 followed later, when the first versions of GnuTLS were released. To build Exim
25514 to use GnuTLS, you need to set
25518 in Local/Makefile, in addition to
25522 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
25523 include files and libraries for GnuTLS can be found.
25525 There are some differences in usage when using GnuTLS instead of OpenSSL:
25528 The &%tls_verify_certificates%& option must contain the name of a file, not the
25529 name of a directory (for OpenSSL it can be either).
25531 The default value for &%tls_dhparam%& differs for historical reasons.
25533 .vindex "&$tls_in_peerdn$&"
25534 .vindex "&$tls_out_peerdn$&"
25535 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
25536 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
25537 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
25539 OpenSSL identifies cipher suites using hyphens as separators, for example:
25540 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
25541 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
25542 in a cipher list. To make life simpler, Exim changes underscores to hyphens
25543 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
25544 to handle its own older variants) when processing lists of cipher suites in the
25545 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
25548 The &%tls_require_ciphers%& options operate differently, as described in the
25549 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
25551 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
25552 When using OpenSSL, this option is ignored.
25553 (If an API is found to let OpenSSL be configured in this way,
25554 let the Exim Maintainers know and we'll likely use it).
25556 Some other recently added features may only be available in one or the other.
25557 This should be documented with the feature. If the documentation does not
25558 explicitly state that the feature is infeasible in the other TLS
25559 implementation, then patches are welcome.
25563 .section "GnuTLS parameter computation" "SECTgnutlsparam"
25564 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
25565 an explicit path; if the latter, then the text about generation still applies,
25566 but not the chosen filename.
25567 By default, as of Exim 4.80 a hard-coded D-H prime is used.
25568 See the documentation of &%tls_dhparam%& for more information.
25570 GnuTLS uses D-H parameters that may take a substantial amount of time
25571 to compute. It is unreasonable to re-compute them for every TLS session.
25572 Therefore, Exim keeps this data in a file in its spool directory, called
25573 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
25575 The file is owned by the Exim user and is readable only by
25576 its owner. Every Exim process that start up GnuTLS reads the D-H
25577 parameters from this file. If the file does not exist, the first Exim process
25578 that needs it computes the data and writes it to a temporary file which is
25579 renamed once it is complete. It does not matter if several Exim processes do
25580 this simultaneously (apart from wasting a few resources). Once a file is in
25581 place, new Exim processes immediately start using it.
25583 For maximum security, the parameters that are stored in this file should be
25584 recalculated periodically, the frequency depending on your paranoia level.
25585 If you are avoiding using the fixed D-H primes published in RFCs, then you
25586 are concerned about some advanced attacks and will wish to do this; if you do
25587 not regenerate then you might as well stick to the standard primes.
25589 Arranging this is easy in principle; just delete the file when you want new
25590 values to be computed. However, there may be a problem. The calculation of new
25591 parameters needs random numbers, and these are obtained from &_/dev/random_&.
25592 If the system is not very active, &_/dev/random_& may delay returning data
25593 until enough randomness (entropy) is available. This may cause Exim to hang for
25594 a substantial amount of time, causing timeouts on incoming connections.
25596 The solution is to generate the parameters externally to Exim. They are stored
25597 in &_gnutls-params-N_& in PEM format, which means that they can be
25598 generated externally using the &(certtool)& command that is part of GnuTLS.
25600 To replace the parameters with new ones, instead of deleting the file
25601 and letting Exim re-create it, you can generate new parameters using
25602 &(certtool)& and, when this has been done, replace Exim's cache file by
25603 renaming. The relevant commands are something like this:
25606 [ look for file; assume gnutls-params-2236 is the most recent ]
25609 # chown exim:exim new-params
25610 # chmod 0600 new-params
25611 # certtool --generate-dh-params --bits 2236 >>new-params
25612 # openssl dhparam -noout -text -in new-params | head
25613 [ check the first line, make sure it's not more than 2236;
25614 if it is, then go back to the start ("rm") and repeat
25615 until the size generated is at most the size requested ]
25616 # chmod 0400 new-params
25617 # mv new-params gnutls-params-2236
25619 If Exim never has to generate the parameters itself, the possibility of
25620 stalling is removed.
25622 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
25623 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
25624 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
25625 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
25626 and Exim does so. This attempt to remove Exim from TLS policy decisions
25627 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
25628 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
25629 which applies to all D-H usage, client or server. If the value returned by
25630 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
25631 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
25632 limit, which is still much higher than Exim historically used.
25634 The filename and bits used will change as the GnuTLS maintainers change the
25635 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
25636 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
25637 2432 bits, while NSS is limited to 2236 bits.
25639 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
25640 increase the chance of the generated prime actually being within acceptable
25641 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
25642 procedure above. There is no sane procedure available to Exim to double-check
25643 the size of the generated prime, so it might still be too large.
25646 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
25647 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
25648 .oindex "&%tls_require_ciphers%&" "OpenSSL"
25649 There is a function in the OpenSSL library that can be passed a list of cipher
25650 suites before the cipher negotiation takes place. This specifies which ciphers
25651 are acceptable. The list is colon separated and may contain names like
25652 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
25653 directly to this function call.
25654 Many systems will install the OpenSSL manual-pages, so you may have
25655 &'ciphers(1)'& available to you.
25656 The following quotation from the OpenSSL
25657 documentation specifies what forms of item are allowed in the cipher string:
25660 It can consist of a single cipher suite such as RC4-SHA.
25662 It can represent a list of cipher suites containing a certain algorithm,
25663 or cipher suites of a certain type. For example SHA1 represents all
25664 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
25667 Lists of cipher suites can be combined in a single cipher string using
25668 the + character. This is used as a logical and operation. For example
25669 SHA1+DES represents all cipher suites containing the SHA1 and the DES
25673 Each cipher string can be optionally preceded by one of the characters &`!`&,
25676 If &`!`& is used, the ciphers are permanently deleted from the list. The
25677 ciphers deleted can never reappear in the list even if they are explicitly
25680 If &`-`& is used, the ciphers are deleted from the list, but some or all
25681 of the ciphers can be added again by later options.
25683 If &`+`& is used, the ciphers are moved to the end of the list. This
25684 option does not add any new ciphers; it just moves matching existing ones.
25687 If none of these characters is present, the string is interpreted as
25688 a list of ciphers to be appended to the current preference list. If the list
25689 includes any ciphers already present they will be ignored: that is, they will
25690 not be moved to the end of the list.
25693 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
25696 # note single-quotes to get ! past any shell history expansion
25697 $ openssl ciphers 'HIGH:!MD5:!SHA1'
25700 This example will let the library defaults be permitted on the MX port, where
25701 there's probably no identity verification anyway, but ups the ante on the
25702 submission ports where the administrator might have some influence on the
25703 choice of clients used:
25705 # OpenSSL variant; see man ciphers(1)
25706 tls_require_ciphers = ${if =={$received_port}{25}\
25713 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
25715 .cindex "GnuTLS" "specifying parameters for"
25716 .cindex "TLS" "specifying ciphers (GnuTLS)"
25717 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
25718 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
25719 .cindex "TLS" "specifying protocols (GnuTLS)"
25720 .cindex "TLS" "specifying priority string (GnuTLS)"
25721 .oindex "&%tls_require_ciphers%&" "GnuTLS"
25722 The GnuTLS library allows the caller to provide a "priority string", documented
25723 as part of the &[gnutls_priority_init]& function. This is very similar to the
25724 ciphersuite specification in OpenSSL.
25726 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string.
25728 The &%tls_require_ciphers%& option is available both as an global option,
25729 controlling how Exim behaves as a server, and also as an option of the
25730 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
25731 the value is string expanded. The resulting string is not an Exim list and
25732 the string is given to the GnuTLS library, so that Exim does not need to be
25733 aware of future feature enhancements of GnuTLS.
25735 Documentation of the strings accepted may be found in the GnuTLS manual, under
25736 "Priority strings". This is online as
25737 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
25738 but beware that this relates to GnuTLS 3, which may be newer than the version
25739 installed on your system. If you are using GnuTLS 3,
25740 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
25741 on that site can be used to test a given string.
25743 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
25744 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
25745 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
25747 This example will let the library defaults be permitted on the MX port, where
25748 there's probably no identity verification anyway, and lowers security further
25749 by increasing compatibility; but this ups the ante on the submission ports
25750 where the administrator might have some influence on the choice of clients
25754 tls_require_ciphers = ${if =={$received_port}{25}\
25760 .section "Configuring an Exim server to use TLS" "SECID182"
25761 .cindex "TLS" "configuring an Exim server"
25762 When Exim has been built with TLS support, it advertises the availability of
25763 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
25764 but not to any others. The default value of this option is unset, which means
25765 that STARTTLS is not advertised at all. This default is chosen because you
25766 need to set some other options in order to make TLS available, and also it is
25767 sensible for systems that want to use TLS only as a client.
25769 If a client issues a STARTTLS command and there is some configuration
25770 problem in the server, the command is rejected with a 454 error. If the client
25771 persists in trying to issue SMTP commands, all except QUIT are rejected
25774 554 Security failure
25776 If a STARTTLS command is issued within an existing TLS session, it is
25777 rejected with a 554 error code.
25779 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
25780 match some hosts. You can, of course, set it to * to match all hosts.
25781 However, this is not all you need to do. TLS sessions to a server won't work
25782 without some further configuration at the server end.
25784 It is rumoured that all existing clients that support TLS/SSL use RSA
25785 encryption. To make this work you need to set, in the server,
25787 tls_certificate = /some/file/name
25788 tls_privatekey = /some/file/name
25790 These options are, in fact, expanded strings, so you can make them depend on
25791 the identity of the client that is connected if you wish. The first file
25792 contains the server's X509 certificate, and the second contains the private key
25793 that goes with it. These files need to be readable by the Exim user, and must
25794 always be given as full path names. They can be the same file if both the
25795 certificate and the key are contained within it. If &%tls_privatekey%& is not
25796 set, or if its expansion is forced to fail or results in an empty string, this
25797 is assumed to be the case. The certificate file may also contain intermediate
25798 certificates that need to be sent to the client to enable it to authenticate
25799 the server's certificate.
25801 If you do not understand about certificates and keys, please try to find a
25802 source of this background information, which is not Exim-specific. (There are a
25803 few comments below in section &<<SECTcerandall>>&.)
25805 &*Note*&: These options do not apply when Exim is operating as a client &--
25806 they apply only in the case of a server. If you need to use a certificate in an
25807 Exim client, you must set the options of the same names in an &(smtp)&
25810 With just these options, an Exim server will be able to use TLS. It does not
25811 require the client to have a certificate (but see below for how to insist on
25812 this). There is one other option that may be needed in other situations. If
25814 tls_dhparam = /some/file/name
25816 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
25817 with the parameters contained in the file.
25818 Set this to &`none`& to disable use of DH entirely, by making no prime
25823 This may also be set to a string identifying a standard prime to be used for
25824 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
25825 used is &`ike23`&. There are a few standard primes available, see the
25826 documentation for &%tls_dhparam%& for the complete list.
25832 for a way of generating file data.
25834 The strings supplied for these three options are expanded every time a client
25835 host connects. It is therefore possible to use different certificates and keys
25836 for different hosts, if you so wish, by making use of the client's IP address
25837 in &$sender_host_address$& to control the expansion. If a string expansion is
25838 forced to fail, Exim behaves as if the option is not set.
25840 .cindex "cipher" "logging"
25841 .cindex "log" "TLS cipher"
25842 .vindex "&$tls_in_cipher$&"
25843 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
25844 an incoming TLS connection. It is included in the &'Received:'& header of an
25845 incoming message (by default &-- you can, of course, change this), and it is
25846 also included in the log line that records a message's arrival, keyed by
25847 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
25848 condition can be used to test for specific cipher suites in ACLs.
25850 Once TLS has been established, the ACLs that run for subsequent SMTP commands
25851 can check the name of the cipher suite and vary their actions accordingly. The
25852 cipher suite names vary, depending on which TLS library is being used. For
25853 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
25854 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
25855 documentation for more details.
25857 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
25858 (again depending on the &%tls_cipher%& log selector).
25861 .section "Requesting and verifying client certificates" "SECID183"
25862 .cindex "certificate" "verification of client"
25863 .cindex "TLS" "client certificate verification"
25864 If you want an Exim server to request a certificate when negotiating a TLS
25865 session with a client, you must set either &%tls_verify_hosts%& or
25866 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
25867 apply to all TLS connections. For any host that matches one of these options,
25868 Exim requests a certificate as part of the setup of the TLS session. The
25869 contents of the certificate are verified by comparing it with a list of
25870 expected certificates. These must be available in a file or,
25871 for OpenSSL only (not GnuTLS), a directory, identified by
25872 &%tls_verify_certificates%&.
25874 A file can contain multiple certificates, concatenated end to end. If a
25877 each certificate must be in a separate file, with a name (or a symbolic link)
25878 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
25879 certificate. You can compute the relevant hash by running the command
25881 openssl x509 -hash -noout -in /cert/file
25883 where &_/cert/file_& contains a single certificate.
25885 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
25886 what happens if the client does not supply a certificate, or if the certificate
25887 does not match any of the certificates in the collection named by
25888 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
25889 attempt to set up a TLS session is aborted, and the incoming connection is
25890 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
25891 session continues. ACLs that run for subsequent SMTP commands can detect the
25892 fact that no certificate was verified, and vary their actions accordingly. For
25893 example, you can insist on a certificate before accepting a message for
25894 relaying, but not when the message is destined for local delivery.
25896 .vindex "&$tls_in_peerdn$&"
25897 When a client supplies a certificate (whether it verifies or not), the value of
25898 the Distinguished Name of the certificate is made available in the variable
25899 &$tls_in_peerdn$& during subsequent processing of the message.
25901 .cindex "log" "distinguished name"
25902 Because it is often a long text string, it is not included in the log line or
25903 &'Received:'& header by default. You can arrange for it to be logged, keyed by
25904 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
25905 &%received_header_text%& to change the &'Received:'& header. When no
25906 certificate is supplied, &$tls_in_peerdn$& is empty.
25909 .section "Revoked certificates" "SECID184"
25910 .cindex "TLS" "revoked certificates"
25911 .cindex "revocation list"
25912 .cindex "certificate" "revocation list"
25913 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
25914 certificates are revoked. If you have such a list, you can pass it to an Exim
25915 server using the global option called &%tls_crl%& and to an Exim client using
25916 an identically named option for the &(smtp)& transport. In each case, the value
25917 of the option is expanded and must then be the name of a file that contains a
25921 .section "Configuring an Exim client to use TLS" "SECID185"
25922 .cindex "cipher" "logging"
25923 .cindex "log" "TLS cipher"
25924 .cindex "log" "distinguished name"
25925 .cindex "TLS" "configuring an Exim client"
25926 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
25927 deliveries as well as to incoming, the latter one causing logging of the
25928 server certificate's DN. The remaining client configuration for TLS is all
25929 within the &(smtp)& transport.
25931 It is not necessary to set any options to have TLS work in the &(smtp)&
25932 transport. If Exim is built with TLS support, and TLS is advertised by a
25933 server, the &(smtp)& transport always tries to start a TLS session. However,
25934 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
25935 transport) to a list of server hosts for which TLS should not be used.
25937 If you do not want Exim to attempt to send messages unencrypted when an attempt
25938 to set up an encrypted connection fails in any way, you can set
25939 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
25940 those hosts, delivery is always deferred if an encrypted connection cannot be
25941 set up. If there are any other hosts for the address, they are tried in the
25944 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
25945 the message unencrypted. It always does this if the response to STARTTLS is
25946 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
25947 session after a success response code, what happens is controlled by the
25948 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
25949 delivery to this host is deferred, and other hosts (if available) are tried. If
25950 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
25951 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
25952 negotiation fails, Exim closes the current connection (because it is in an
25953 unknown state), opens a new one to the same host, and then tries the delivery
25956 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
25957 transport provide the client with a certificate, which is passed to the server
25958 if it requests it. If the server is Exim, it will request a certificate only if
25959 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
25961 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
25962 must name a file or,
25963 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
25964 expected server certificates. The client verifies the server's certificate
25965 against this collection, taking into account any revoked certificates that are
25966 in the list defined by &%tls_crl%&.
25967 Failure to verify fails the TLS connection unless either of the
25968 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
25970 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
25971 certificate verification to the listed servers. Verification either must
25972 or need not succeed respectively.
25975 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
25976 list of permitted cipher suites. If either of these checks fails, delivery to
25977 the current host is abandoned, and the &(smtp)& transport tries to deliver to
25978 alternative hosts, if any.
25981 These options must be set in the &(smtp)& transport for Exim to use TLS when it
25982 is operating as a client. Exim does not assume that a server certificate (set
25983 by the global options of the same name) should also be used when operating as a
25987 .vindex "&$host_address$&"
25988 All the TLS options in the &(smtp)& transport are expanded before use, with
25989 &$host$& and &$host_address$& containing the name and address of the server to
25990 which the client is connected. Forced failure of an expansion causes Exim to
25991 behave as if the relevant option were unset.
25993 .vindex &$tls_out_bits$&
25994 .vindex &$tls_out_cipher$&
25995 .vindex &$tls_out_peerdn$&
25996 .vindex &$tls_out_sni$&
25997 Before an SMTP connection is established, the
25998 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
25999 variables are emptied. (Until the first connection, they contain the values
26000 that were set when the message was received.) If STARTTLS is subsequently
26001 successfully obeyed, these variables are set to the relevant values for the
26002 outgoing connection.
26006 .section "Use of TLS Server Name Indication" "SECTtlssni"
26007 .cindex "TLS" "Server Name Indication"
26008 .vindex "&$tls_in_sni$&"
26009 .oindex "&%tls_in_sni%&"
26010 With TLS1.0 or above, there is an extension mechanism by which extra
26011 information can be included at various points in the protocol. One of these
26012 extensions, documented in RFC 6066 (and before that RFC 4366) is
26013 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
26014 client in the initial handshake, so that the server can examine the servername
26015 within and possibly choose to use different certificates and keys (and more)
26018 This is analagous to HTTP's &"Host:"& header, and is the main mechanism by
26019 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
26022 With SMTP to MX, there are the same problems here as in choosing the identity
26023 against which to validate a certificate: you can't rely on insecure DNS to
26024 provide the identity which you then cryptographically verify. So this will
26025 be of limited use in that environment.
26027 With SMTP to Submission, there is a well-defined hostname which clients are
26028 connecting to and can validate certificates against. Thus clients &*can*&
26029 choose to include this information in the TLS negotiation. If this becomes
26030 wide-spread, then hosters can choose to present different certificates to
26031 different clients. Or even negotiate different cipher suites.
26033 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
26034 if not empty, will be sent on a TLS session as part of the handshake. There's
26035 nothing more to it. Choosing a sensible value not derived insecurely is the
26036 only point of caution. The &$tls_out_sni$& variable will be set to this string
26037 for the lifetime of the client connection (including during authentication).
26039 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
26040 received from a client.
26041 It can be logged with the &%log_selector%& item &`+tls_sni`&.
26043 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
26044 option (prior to expansion) then the following options will be re-expanded
26045 during TLS session handshake, to permit alternative values to be chosen:
26048 .vindex "&%tls_certificate%&"
26049 &%tls_certificate%&
26051 .vindex "&%tls_crl%&"
26054 .vindex "&%tls_privatekey%&"
26057 .vindex "&%tls_verify_certificates%&"
26058 &%tls_verify_certificates%&
26061 Great care should be taken to deal with matters of case, various injection
26062 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
26063 can always be referenced; it is important to remember that &$tls_sni$& is
26064 arbitrary unverified data provided prior to authentication.
26066 The Exim developers are proceeding cautiously and so far no other TLS options
26069 When Exim is built againt OpenSSL, OpenSSL must have been built with support
26070 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
26071 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
26072 see &`-servername`& in the output, then OpenSSL has support.
26074 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
26075 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
26076 built, then you have SNI support).
26080 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
26082 .cindex "multiple SMTP deliveries with TLS"
26083 .cindex "TLS" "multiple message deliveries"
26084 Exim sends multiple messages down the same TCP/IP connection by starting up
26085 an entirely new delivery process for each message, passing the socket from
26086 one process to the next. This implementation does not fit well with the use
26087 of TLS, because there is quite a lot of state information associated with a TLS
26088 connection, not just a socket identification. Passing all the state information
26089 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
26090 session before passing the socket to a new process. The new process may then
26091 try to start a new TLS session, and if successful, may try to re-authenticate
26092 if AUTH is in use, before sending the next message.
26094 The RFC is not clear as to whether or not an SMTP session continues in clear
26095 after TLS has been shut down, or whether TLS may be restarted again later, as
26096 just described. However, if the server is Exim, this shutdown and
26097 reinitialization works. It is not known which (if any) other servers operate
26098 successfully if the client closes a TLS session and continues with unencrypted
26099 SMTP, but there are certainly some that do not work. For such servers, Exim
26100 should not pass the socket to another process, because the failure of the
26101 subsequent attempt to use it would cause Exim to record a temporary host error,
26102 and delay other deliveries to that host.
26104 To test for this case, Exim sends an EHLO command to the server after
26105 closing down the TLS session. If this fails in any way, the connection is
26106 closed instead of being passed to a new delivery process, but no retry
26107 information is recorded.
26109 There is also a manual override; you can set &%hosts_nopass_tls%& on the
26110 &(smtp)& transport to match those hosts for which Exim should not pass
26111 connections to new processes if TLS has been used.
26116 .section "Certificates and all that" "SECTcerandall"
26117 .cindex "certificate" "references to discussion"
26118 In order to understand fully how TLS works, you need to know about
26119 certificates, certificate signing, and certificate authorities. This is not the
26120 place to give a tutorial, especially as I do not know very much about it
26121 myself. Some helpful introduction can be found in the FAQ for the SSL addition
26122 to Apache, currently at
26124 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
26126 Other parts of the &'modssl'& documentation are also helpful, and have
26127 links to further files.
26128 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
26129 0-201-61598-3), contains both introductory and more in-depth descriptions.
26130 Some sample programs taken from the book are available from
26132 &url(http://www.rtfm.com/openssl-examples/)
26136 .section "Certificate chains" "SECID186"
26137 The file named by &%tls_certificate%& may contain more than one
26138 certificate. This is useful in the case where the certificate that is being
26139 sent is validated by an intermediate certificate which the other end does
26140 not have. Multiple certificates must be in the correct order in the file.
26141 First the host's certificate itself, then the first intermediate
26142 certificate to validate the issuer of the host certificate, then the next
26143 intermediate certificate to validate the issuer of the first intermediate
26144 certificate, and so on, until finally (optionally) the root certificate.
26145 The root certificate must already be trusted by the recipient for
26146 validation to succeed, of course, but if it's not preinstalled, sending the
26147 root certificate along with the rest makes it available for the user to
26148 install if the receiving end is a client MUA that can interact with a user.
26150 Note that certificates using MD5 are unlikely to work on today's Internet;
26151 even if your libraries allow loading them for use in Exim when acting as a
26152 server, increasingly clients will not accept such certificates. The error
26153 diagnostics in such a case can be frustratingly vague.
26157 .section "Self-signed certificates" "SECID187"
26158 .cindex "certificate" "self-signed"
26159 You can create a self-signed certificate using the &'req'& command provided
26160 with OpenSSL, like this:
26161 . ==== Do not shorten the duration here without reading and considering
26162 . ==== the text below. Please leave it at 9999 days.
26164 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
26167 &_file1_& and &_file2_& can be the same file; the key and the certificate are
26168 delimited and so can be identified independently. The &%-days%& option
26169 specifies a period for which the certificate is valid. The &%-nodes%& option is
26170 important: if you do not set it, the key is encrypted with a passphrase
26171 that you are prompted for, and any use that is made of the key causes more
26172 prompting for the passphrase. This is not helpful if you are going to use
26173 this certificate and key in an MTA, where prompting is not possible.
26175 . ==== I expect to still be working 26 years from now. The less technical
26176 . ==== debt I create, in terms of storing up trouble for my later years, the
26177 . ==== happier I will be then. We really have reached the point where we
26178 . ==== should start, at the very least, provoking thought and making folks
26179 . ==== pause before proceeding, instead of leaving all the fixes until two
26180 . ==== years before 2^31 seconds after the 1970 Unix epoch.
26182 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
26183 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
26184 the above command might produce a date in the past. Think carefully about
26185 the lifetime of the systems you're deploying, and either reduce the duration
26186 of the certificate or reconsider your platform deployment. (At time of
26187 writing, reducing the duration is the most likely choice, but the inexorable
26188 progression of time takes us steadily towards an era where this will not
26189 be a sensible resolution).
26191 A self-signed certificate made in this way is sufficient for testing, and
26192 may be adequate for all your requirements if you are mainly interested in
26193 encrypting transfers, and not in secure identification.
26195 However, many clients require that the certificate presented by the server be a
26196 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
26197 certificate. In this situation, the self-signed certificate described above
26198 must be installed on the client host as a trusted root &'certification
26199 authority'& (CA), and the certificate used by Exim must be a user certificate
26200 signed with that self-signed certificate.
26202 For information on creating self-signed CA certificates and using them to sign
26203 user certificates, see the &'General implementation overview'& chapter of the
26204 Open-source PKI book, available online at
26205 &url(http://ospkibook.sourceforge.net/).
26206 .ecindex IIDencsmtp1
26207 .ecindex IIDencsmtp2
26211 . ////////////////////////////////////////////////////////////////////////////
26212 . ////////////////////////////////////////////////////////////////////////////
26214 .chapter "Access control lists" "CHAPACL"
26215 .scindex IIDacl "&ACL;" "description"
26216 .cindex "control of incoming mail"
26217 .cindex "message" "controlling incoming"
26218 .cindex "policy control" "access control lists"
26219 Access Control Lists (ACLs) are defined in a separate section of the run time
26220 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
26221 name, terminated by a colon. Here is a complete ACL section that contains just
26222 one very small ACL:
26226 accept hosts = one.host.only
26228 You can have as many lists as you like in the ACL section, and the order in
26229 which they appear does not matter. The lists are self-terminating.
26231 The majority of ACLs are used to control Exim's behaviour when it receives
26232 certain SMTP commands. This applies both to incoming TCP/IP connections, and
26233 when a local process submits a message using SMTP by specifying the &%-bs%&
26234 option. The most common use is for controlling which recipients are accepted
26235 in incoming messages. In addition, you can define an ACL that is used to check
26236 local non-SMTP messages. The default configuration file contains an example of
26237 a realistic ACL for checking RCPT commands. This is discussed in chapter
26238 &<<CHAPdefconfil>>&.
26241 .section "Testing ACLs" "SECID188"
26242 The &%-bh%& command line option provides a way of testing your ACL
26243 configuration locally by running a fake SMTP session with which you interact.
26244 The host &'relay-test.mail-abuse.org'& provides a service for checking your
26245 relaying configuration (see section &<<SECTcheralcon>>& for more details).
26249 .section "Specifying when ACLs are used" "SECID189"
26250 .cindex "&ACL;" "options for specifying"
26251 In order to cause an ACL to be used, you have to name it in one of the relevant
26252 options in the main part of the configuration. These options are:
26253 .cindex "AUTH" "ACL for"
26254 .cindex "DATA" "ACLs for"
26255 .cindex "ETRN" "ACL for"
26256 .cindex "EXPN" "ACL for"
26257 .cindex "HELO" "ACL for"
26258 .cindex "EHLO" "ACL for"
26259 .cindex "MAIL" "ACL for"
26260 .cindex "QUIT, ACL for"
26261 .cindex "RCPT" "ACL for"
26262 .cindex "STARTTLS, ACL for"
26263 .cindex "VRFY" "ACL for"
26264 .cindex "SMTP" "connection, ACL for"
26265 .cindex "non-SMTP messages" "ACLs for"
26266 .cindex "MIME content scanning" "ACL for"
26269 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
26270 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
26271 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
26272 .irow &%acl_smtp_auth%& "ACL for AUTH"
26273 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
26274 .irow &%acl_smtp_data%& "ACL after DATA is complete"
26275 .irow &%acl_smtp_etrn%& "ACL for ETRN"
26276 .irow &%acl_smtp_expn%& "ACL for EXPN"
26277 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
26278 .irow &%acl_smtp_mail%& "ACL for MAIL"
26279 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
26280 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
26281 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
26282 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
26283 .irow &%acl_smtp_quit%& "ACL for QUIT"
26284 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
26285 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
26286 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
26289 For example, if you set
26291 acl_smtp_rcpt = small_acl
26293 the little ACL defined above is used whenever Exim receives a RCPT command
26294 in an SMTP dialogue. The majority of policy tests on incoming messages can be
26295 done when RCPT commands arrive. A rejection of RCPT should cause the
26296 sending MTA to give up on the recipient address contained in the RCPT
26297 command, whereas rejection at other times may cause the client MTA to keep on
26298 trying to deliver the message. It is therefore recommended that you do as much
26299 testing as possible at RCPT time.
26302 .section "The non-SMTP ACLs" "SECID190"
26303 .cindex "non-SMTP messages" "ACLs for"
26304 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
26305 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
26306 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
26307 the state of the SMTP connection such as encryption and authentication) are not
26308 relevant and are forbidden in these ACLs. However, the sender and recipients
26309 are known, so the &%senders%& and &%sender_domains%& conditions and the
26310 &$sender_address$& and &$recipients$& variables can be used. Variables such as
26311 &$authenticated_sender$& are also available. You can specify added header lines
26312 in any of these ACLs.
26314 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
26315 non-SMTP message, before any of the message has been read. (This is the
26316 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
26317 batched SMTP input, it runs after the DATA command has been reached. The
26318 result of this ACL is ignored; it cannot be used to reject a message. If you
26319 really need to, you could set a value in an ACL variable here and reject based
26320 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
26321 controls, and in particular, it can be used to set
26323 control = suppress_local_fixups
26325 This cannot be used in the other non-SMTP ACLs because by the time they are
26326 run, it is too late.
26328 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
26329 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26331 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
26332 kind of rejection is treated as permanent, because there is no way of sending a
26333 temporary error for these kinds of message.
26336 .section "The SMTP connect ACL" "SECID191"
26337 .cindex "SMTP" "connection, ACL for"
26338 .oindex &%smtp_banner%&
26339 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
26340 session, after the test specified by &%host_reject_connection%& (which is now
26341 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
26342 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
26343 the message override the banner message that is otherwise specified by the
26344 &%smtp_banner%& option.
26347 .section "The EHLO/HELO ACL" "SECID192"
26348 .cindex "EHLO" "ACL for"
26349 .cindex "HELO" "ACL for"
26350 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
26351 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
26352 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
26353 Note that a client may issue more than one EHLO or HELO command in an SMTP
26354 session, and indeed is required to issue a new EHLO or HELO after successfully
26355 setting up encryption following a STARTTLS command.
26357 If the command is accepted by an &%accept%& verb that has a &%message%&
26358 modifier, the message may not contain more than one line (it will be truncated
26359 at the first newline and a panic logged if it does). Such a message cannot
26360 affect the EHLO options that are listed on the second and subsequent lines of
26364 .section "The DATA ACLs" "SECID193"
26365 .cindex "DATA" "ACLs for"
26366 Two ACLs are associated with the DATA command, because it is two-stage
26367 command, with two responses being sent to the client.
26368 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
26369 is obeyed. This gives you control after all the RCPT commands, but before
26370 the message itself is received. It offers the opportunity to give a negative
26371 response to the DATA command before the data is transmitted. Header lines
26372 added by MAIL or RCPT ACLs are not visible at this time, but any that
26373 are defined here are visible when the &%acl_smtp_data%& ACL is run.
26375 You cannot test the contents of the message, for example, to verify addresses
26376 in the headers, at RCPT time or when the DATA command is received. Such
26377 tests have to appear in the ACL that is run after the message itself has been
26378 received, before the final response to the DATA command is sent. This is
26379 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
26380 associated with the DATA command.
26382 For both of these ACLs, it is not possible to reject individual recipients. An
26383 error response rejects the entire message. Unfortunately, it is known that some
26384 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
26385 before or after the data) correctly &-- they keep the message on their queues
26386 and try again later, but that is their problem, though it does waste some of
26389 The &%acl_smtp_data%& ACL is run after both the &%acl_smtp_dkim%& and
26390 the &%acl_smtp_mime%& ACLs.
26392 .section "The SMTP DKIM ACL" "SECTDKIMACL"
26393 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
26394 enabled (which is the default).
26396 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
26397 received, and is executed for each DKIM signature found in a message. If not
26398 otherwise specified, the default action is to accept.
26400 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
26402 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
26405 .section "The SMTP MIME ACL" "SECID194"
26406 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
26407 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26409 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
26412 .section "The QUIT ACL" "SECTQUITACL"
26413 .cindex "QUIT, ACL for"
26414 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
26415 does not affect the response code to QUIT, which is always 221. Thus, the ACL
26416 does not in fact control any access. For this reason, the only verbs that are
26417 permitted are &%accept%& and &%warn%&.
26419 This ACL can be used for tasks such as custom logging at the end of an SMTP
26420 session. For example, you can use ACL variables in other ACLs to count
26421 messages, recipients, etc., and log the totals at QUIT time using one or
26422 more &%logwrite%& modifiers on a &%warn%& verb.
26424 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
26425 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
26427 You do not need to have a final &%accept%&, but if you do, you can use a
26428 &%message%& modifier to specify custom text that is sent as part of the 221
26431 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
26432 failure (for example, failure to open a log file, or when Exim is bombing out
26433 because it has detected an unrecoverable error), all SMTP commands from the
26434 client are given temporary error responses until QUIT is received or the
26435 connection is closed. In these special cases, the QUIT ACL does not run.
26438 .section "The not-QUIT ACL" "SECTNOTQUITACL"
26439 .vindex &$acl_smtp_notquit$&
26440 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
26441 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
26442 trouble, such as being unable to write to its log files, this ACL is not run,
26443 because it might try to do things (such as write to log files) that make the
26444 situation even worse.
26446 Like the QUIT ACL, this ACL is provided to make it possible to do customized
26447 logging or to gather statistics, and its outcome is ignored. The &%delay%&
26448 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
26451 .vindex &$smtp_notquit_reason$&
26452 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
26453 to a string that indicates the reason for the termination of the SMTP
26454 connection. The possible values are:
26456 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
26457 .irow &`bad-commands`& "Too many unknown or non-mail commands"
26458 .irow &`command-timeout`& "Timeout while reading SMTP commands"
26459 .irow &`connection-lost`& "The SMTP connection has been lost"
26460 .irow &`data-timeout`& "Timeout while reading message data"
26461 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
26462 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
26463 .irow &`signal-exit`& "SIGTERM or SIGINT"
26464 .irow &`synchronization-error`& "SMTP synchronization error"
26465 .irow &`tls-failed`& "TLS failed to start"
26467 In most cases when an SMTP connection is closed without having received QUIT,
26468 Exim sends an SMTP response message before actually closing the connection.
26469 With the exception of the &`acl-drop`& case, the default message can be
26470 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
26471 &%drop%& verb in another ACL, it is the message from the other ACL that is
26475 .section "Finding an ACL to use" "SECID195"
26476 .cindex "&ACL;" "finding which to use"
26477 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
26478 you can use different ACLs in different circumstances. For example,
26480 acl_smtp_rcpt = ${if ={25}{$interface_port} \
26481 {acl_check_rcpt} {acl_check_rcpt_submit} }
26483 In the default configuration file there are some example settings for
26484 providing an RFC 4409 message submission service on port 587 and a
26485 non-standard &"smtps"& service on port 465. You can use a string
26486 expansion like this to choose an ACL for MUAs on these ports which is
26487 more appropriate for this purpose than the default ACL on port 25.
26489 The expanded string does not have to be the name of an ACL in the
26490 configuration file; there are other possibilities. Having expanded the
26491 string, Exim searches for an ACL as follows:
26494 If the string begins with a slash, Exim uses it as a file name, and reads its
26495 contents as an ACL. The lines are processed in the same way as lines in the
26496 Exim configuration file. In particular, continuation lines are supported, blank
26497 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
26498 If the file does not exist or cannot be read, an error occurs (typically
26499 causing a temporary failure of whatever caused the ACL to be run). For example:
26501 acl_smtp_data = /etc/acls/\
26502 ${lookup{$sender_host_address}lsearch\
26503 {/etc/acllist}{$value}{default}}
26505 This looks up an ACL file to use on the basis of the host's IP address, falling
26506 back to a default if the lookup fails. If an ACL is successfully read from a
26507 file, it is retained in memory for the duration of the Exim process, so that it
26508 can be re-used without having to re-read the file.
26510 If the string does not start with a slash, and does not contain any spaces,
26511 Exim searches the ACL section of the configuration for an ACL whose name
26512 matches the string.
26514 If no named ACL is found, or if the string contains spaces, Exim parses
26515 the string as an inline ACL. This can save typing in cases where you just
26516 want to have something like
26518 acl_smtp_vrfy = accept
26520 in order to allow free use of the VRFY command. Such a string may contain
26521 newlines; it is processed in the same way as an ACL that is read from a file.
26527 .section "ACL return codes" "SECID196"
26528 .cindex "&ACL;" "return codes"
26529 Except for the QUIT ACL, which does not affect the SMTP return code (see
26530 section &<<SECTQUITACL>>& above), the result of running an ACL is either
26531 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
26532 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
26533 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
26534 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
26535 This also causes a 4&'xx'& return code.
26537 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
26538 &"deny"&, because there is no mechanism for passing temporary errors to the
26539 submitters of non-SMTP messages.
26542 ACLs that are relevant to message reception may also return &"discard"&. This
26543 has the effect of &"accept"&, but causes either the entire message or an
26544 individual recipient address to be discarded. In other words, it is a
26545 blackholing facility. Use it with care.
26547 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
26548 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
26549 RCPT ACL is to discard just the one recipient address. If there are no
26550 recipients left when the message's data is received, the DATA ACL is not
26551 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
26552 remaining recipients. The &"discard"& return is not permitted for the
26553 &%acl_smtp_predata%& ACL.
26556 .cindex "&[local_scan()]& function" "when all recipients discarded"
26557 The &[local_scan()]& function is always run, even if there are no remaining
26558 recipients; it may create new recipients.
26562 .section "Unset ACL options" "SECID197"
26563 .cindex "&ACL;" "unset options"
26564 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
26565 all the same. &*Note*&: These defaults apply only when the relevant ACL is
26566 not defined at all. For any defined ACL, the default action when control
26567 reaches the end of the ACL statements is &"deny"&.
26569 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
26570 these two are ACLs that are used only for their side effects. They cannot be
26571 used to accept or reject anything.
26573 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
26574 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
26575 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
26576 when the ACL is not defined is &"accept"&.
26578 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
26579 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
26580 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
26581 messages over an SMTP connection. For an example, see the ACL in the default
26582 configuration file.
26587 .section "Data for message ACLs" "SECID198"
26588 .cindex "&ACL;" "data for message ACL"
26590 .vindex &$local_part$&
26591 .vindex &$sender_address$&
26592 .vindex &$sender_host_address$&
26593 .vindex &$smtp_command$&
26594 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
26595 that contain information about the host and the message's sender (for example,
26596 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
26597 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
26598 &$local_part$& are set from the argument address. The entire SMTP command
26599 is available in &$smtp_command$&.
26601 When an ACL for the AUTH parameter of MAIL is running, the variables that
26602 contain information about the host are set, but &$sender_address$& is not yet
26603 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
26606 .vindex "&$message_size$&"
26607 The &$message_size$& variable is set to the value of the SIZE parameter on
26608 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
26609 that parameter is not given. The value is updated to the true message size by
26610 the time the final DATA ACL is run (after the message data has been
26613 .vindex "&$rcpt_count$&"
26614 .vindex "&$recipients_count$&"
26615 The &$rcpt_count$& variable increases by one for each RCPT command received.
26616 The &$recipients_count$& variable increases by one each time a RCPT command is
26617 accepted, so while an ACL for RCPT is being processed, it contains the number
26618 of previously accepted recipients. At DATA time (for both the DATA ACLs),
26619 &$rcpt_count$& contains the total number of RCPT commands, and
26620 &$recipients_count$& contains the total number of accepted recipients.
26626 .section "Data for non-message ACLs" "SECTdatfornon"
26627 .cindex "&ACL;" "data for non-message ACL"
26628 .vindex &$smtp_command_argument$&
26629 .vindex &$smtp_command$&
26630 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
26631 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
26632 and the entire SMTP command is available in &$smtp_command$&.
26633 These variables can be tested using a &%condition%& condition. For example,
26634 here is an ACL for use with AUTH, which insists that either the session is
26635 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
26636 does not permit authentication methods that use cleartext passwords on
26637 unencrypted connections.
26640 accept encrypted = *
26641 accept condition = ${if eq{${uc:$smtp_command_argument}}\
26643 deny message = TLS encryption or CRAM-MD5 required
26645 (Another way of applying this restriction is to arrange for the authenticators
26646 that use cleartext passwords not to be advertised when the connection is not
26647 encrypted. You can use the generic &%server_advertise_condition%& authenticator
26648 option to do this.)
26652 .section "Format of an ACL" "SECID199"
26653 .cindex "&ACL;" "format of"
26654 .cindex "&ACL;" "verbs, definition of"
26655 An individual ACL consists of a number of statements. Each statement starts
26656 with a verb, optionally followed by a number of conditions and &"modifiers"&.
26657 Modifiers can change the way the verb operates, define error and log messages,
26658 set variables, insert delays, and vary the processing of accepted messages.
26660 If all the conditions are met, the verb is obeyed. The same condition may be
26661 used (with different arguments) more than once in the same statement. This
26662 provides a means of specifying an &"and"& conjunction between conditions. For
26665 deny dnslists = list1.example
26666 dnslists = list2.example
26668 If there are no conditions, the verb is always obeyed. Exim stops evaluating
26669 the conditions and modifiers when it reaches a condition that fails. What
26670 happens then depends on the verb (and in one case, on a special modifier). Not
26671 all the conditions make sense at every testing point. For example, you cannot
26672 test a sender address in the ACL that is run for a VRFY command.
26675 .section "ACL verbs" "SECID200"
26676 The ACL verbs are as follows:
26679 .cindex "&%accept%& ACL verb"
26680 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
26681 of the conditions are not met, what happens depends on whether &%endpass%&
26682 appears among the conditions (for syntax see below). If the failing condition
26683 is before &%endpass%&, control is passed to the next ACL statement; if it is
26684 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
26685 check a RCPT command:
26687 accept domains = +local_domains
26691 If the recipient domain does not match the &%domains%& condition, control
26692 passes to the next statement. If it does match, the recipient is verified, and
26693 the command is accepted if verification succeeds. However, if verification
26694 fails, the ACL yields &"deny"&, because the failing condition is after
26697 The &%endpass%& feature has turned out to be confusing to many people, so its
26698 use is not recommended nowadays. It is always possible to rewrite an ACL so
26699 that &%endpass%& is not needed, and it is no longer used in the default
26702 .cindex "&%message%& ACL modifier" "with &%accept%&"
26703 If a &%message%& modifier appears on an &%accept%& statement, its action
26704 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
26705 (when an &%accept%& verb either accepts or passes control to the next
26706 statement), &%message%& can be used to vary the message that is sent when an
26707 SMTP command is accepted. For example, in a RCPT ACL you could have:
26709 &`accept `&<&'some conditions'&>
26710 &` message = OK, I will allow you through today`&
26712 You can specify an SMTP response code, optionally followed by an &"extended
26713 response code"& at the start of the message, but the first digit must be the
26714 same as would be sent by default, which is 2 for an &%accept%& verb.
26716 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
26717 an error message that is used when access is denied. This behaviour is retained
26718 for backward compatibility, but current &"best practice"& is to avoid the use
26723 .cindex "&%defer%& ACL verb"
26724 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
26725 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
26726 &%defer%& is the same as &%deny%&, because there is no way of sending a
26727 temporary error. For a RCPT command, &%defer%& is much the same as using a
26728 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
26729 be used in any ACL, and even for a recipient it might be a simpler approach.
26733 .cindex "&%deny%& ACL verb"
26734 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
26735 the conditions are not met, control is passed to the next ACL statement. For
26738 deny dnslists = blackholes.mail-abuse.org
26740 rejects commands from hosts that are on a DNS black list.
26744 .cindex "&%discard%& ACL verb"
26745 &%discard%&: This verb behaves like &%accept%&, except that it returns
26746 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
26747 that are concerned with receiving messages. When all the conditions are true,
26748 the sending entity receives a &"success"& response. However, &%discard%& causes
26749 recipients to be discarded. If it is used in an ACL for RCPT, just the one
26750 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
26751 message's recipients are discarded. Recipients that are discarded before DATA
26752 do not appear in the log line when the &%received_recipients%& log selector is set.
26754 If the &%log_message%& modifier is set when &%discard%& operates,
26755 its contents are added to the line that is automatically written to the log.
26756 The &%message%& modifier operates exactly as it does for &%accept%&.
26760 .cindex "&%drop%& ACL verb"
26761 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
26762 forcibly closed after the 5&'xx'& error message has been sent. For example:
26764 drop message = I don't take more than 20 RCPTs
26765 condition = ${if > {$rcpt_count}{20}}
26767 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
26768 The connection is always dropped after sending a 550 response.
26771 .cindex "&%require%& ACL verb"
26772 &%require%&: If all the conditions are met, control is passed to the next ACL
26773 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
26774 example, when checking a RCPT command,
26776 require message = Sender did not verify
26779 passes control to subsequent statements only if the message's sender can be
26780 verified. Otherwise, it rejects the command. Note the positioning of the
26781 &%message%& modifier, before the &%verify%& condition. The reason for this is
26782 discussed in section &<<SECTcondmodproc>>&.
26785 .cindex "&%warn%& ACL verb"
26786 &%warn%&: If all the conditions are true, a line specified by the
26787 &%log_message%& modifier is written to Exim's main log. Control always passes
26788 to the next ACL statement. If any condition is false, the log line is not
26789 written. If an identical log line is requested several times in the same
26790 message, only one copy is actually written to the log. If you want to force
26791 duplicates to be written, use the &%logwrite%& modifier instead.
26793 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
26794 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
26795 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
26796 first failing condition. There is more about adding header lines in section
26797 &<<SECTaddheadacl>>&.
26799 If any condition on a &%warn%& statement cannot be completed (that is, there is
26800 some sort of defer), the log line specified by &%log_message%& is not written.
26801 This does not include the case of a forced failure from a lookup, which
26802 is considered to be a successful completion. After a defer, no further
26803 conditions or modifiers in the &%warn%& statement are processed. The incident
26804 is logged, and the ACL continues to be processed, from the next statement
26808 .vindex "&$acl_verify_message$&"
26809 When one of the &%warn%& conditions is an address verification that fails, the
26810 text of the verification failure message is in &$acl_verify_message$&. If you
26811 want this logged, you must set it up explicitly. For example:
26813 warn !verify = sender
26814 log_message = sender verify failed: $acl_verify_message
26818 At the end of each ACL there is an implicit unconditional &%deny%&.
26820 As you can see from the examples above, the conditions and modifiers are
26821 written one to a line, with the first one on the same line as the verb, and
26822 subsequent ones on following lines. If you have a very long condition, you can
26823 continue it onto several physical lines by the usual backslash continuation
26824 mechanism. It is conventional to align the conditions vertically.
26828 .section "ACL variables" "SECTaclvariables"
26829 .cindex "&ACL;" "variables"
26830 There are some special variables that can be set during ACL processing. They
26831 can be used to pass information between different ACLs, different invocations
26832 of the same ACL in the same SMTP connection, and between ACLs and the routers,
26833 transports, and filters that are used to deliver a message. The names of these
26834 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
26835 an underscore, but the remainder of the name can be any sequence of
26836 alphanumeric characters and underscores that you choose. There is no limit on
26837 the number of ACL variables. The two sets act as follows:
26839 The values of those variables whose names begin with &$acl_c$& persist
26840 throughout an SMTP connection. They are never reset. Thus, a value that is set
26841 while receiving one message is still available when receiving the next message
26842 on the same SMTP connection.
26844 The values of those variables whose names begin with &$acl_m$& persist only
26845 while a message is being received. They are reset afterwards. They are also
26846 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
26849 When a message is accepted, the current values of all the ACL variables are
26850 preserved with the message and are subsequently made available at delivery
26851 time. The ACL variables are set by a modifier called &%set%&. For example:
26853 accept hosts = whatever
26854 set acl_m4 = some value
26855 accept authenticated = *
26856 set acl_c_auth = yes
26858 &*Note*&: A leading dollar sign is not used when naming a variable that is to
26859 be set. If you want to set a variable without taking any action, you can use a
26860 &%warn%& verb without any other modifiers or conditions.
26862 .oindex &%strict_acl_vars%&
26863 What happens if a syntactically valid but undefined ACL variable is
26864 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
26865 false (the default), an empty string is substituted; if it is true, an
26866 error is generated.
26868 Versions of Exim before 4.64 have a limited set of numbered variables, but
26869 their names are compatible, so there is no problem with upgrading.
26872 .section "Condition and modifier processing" "SECTcondmodproc"
26873 .cindex "&ACL;" "conditions; processing"
26874 .cindex "&ACL;" "modifiers; processing"
26875 An exclamation mark preceding a condition negates its result. For example:
26877 deny domains = *.dom.example
26878 !verify = recipient
26880 causes the ACL to return &"deny"& if the recipient domain ends in
26881 &'dom.example'& and the recipient address cannot be verified. Sometimes
26882 negation can be used on the right-hand side of a condition. For example, these
26883 two statements are equivalent:
26885 deny hosts = !192.168.3.4
26886 deny !hosts = 192.168.3.4
26888 However, for many conditions (&%verify%& being a good example), only left-hand
26889 side negation of the whole condition is possible.
26891 The arguments of conditions and modifiers are expanded. A forced failure
26892 of an expansion causes a condition to be ignored, that is, it behaves as if the
26893 condition is true. Consider these two statements:
26895 accept senders = ${lookup{$host_name}lsearch\
26896 {/some/file}{$value}fail}
26897 accept senders = ${lookup{$host_name}lsearch\
26898 {/some/file}{$value}{}}
26900 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
26901 the returned list is searched, but if the lookup fails the behaviour is
26902 different in the two cases. The &%fail%& in the first statement causes the
26903 condition to be ignored, leaving no further conditions. The &%accept%& verb
26904 therefore succeeds. The second statement, however, generates an empty list when
26905 the lookup fails. No sender can match an empty list, so the condition fails,
26906 and therefore the &%accept%& also fails.
26908 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
26909 specify actions that are taken as the conditions for a statement are checked;
26910 others specify text for messages that are used when access is denied or a
26911 warning is generated. The &%control%& modifier affects the way an incoming
26912 message is handled.
26914 The positioning of the modifiers in an ACL statement is important, because the
26915 processing of a verb ceases as soon as its outcome is known. Only those
26916 modifiers that have already been encountered will take effect. For example,
26917 consider this use of the &%message%& modifier:
26919 require message = Can't verify sender
26921 message = Can't verify recipient
26923 message = This message cannot be used
26925 If sender verification fails, Exim knows that the result of the statement is
26926 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
26927 so its text is used as the error message. If sender verification succeeds, but
26928 recipient verification fails, the second message is used. If recipient
26929 verification succeeds, the third message becomes &"current"&, but is never used
26930 because there are no more conditions to cause failure.
26932 For the &%deny%& verb, on the other hand, it is always the last &%message%&
26933 modifier that is used, because all the conditions must be true for rejection to
26934 happen. Specifying more than one &%message%& modifier does not make sense, and
26935 the message can even be specified after all the conditions. For example:
26938 !senders = *@my.domain.example
26939 message = Invalid sender from client host
26941 The &"deny"& result does not happen until the end of the statement is reached,
26942 by which time Exim has set up the message.
26946 .section "ACL modifiers" "SECTACLmodi"
26947 .cindex "&ACL;" "modifiers; list of"
26948 The ACL modifiers are as follows:
26951 .vitem &*add_header*&&~=&~<&'text'&>
26952 This modifier specifies one or more header lines that are to be added to an
26953 incoming message, assuming, of course, that the message is ultimately
26954 accepted. For details, see section &<<SECTaddheadacl>>&.
26956 .vitem &*continue*&&~=&~<&'text'&>
26957 .cindex "&%continue%& ACL modifier"
26958 .cindex "database" "updating in ACL"
26959 This modifier does nothing of itself, and processing of the ACL always
26960 continues with the next condition or modifier. The value of &%continue%& is in
26961 the side effects of expanding its argument. Typically this could be used to
26962 update a database. It is really just a syntactic tidiness, to avoid having to
26963 write rather ugly lines like this:
26965 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
26967 Instead, all you need is
26969 &`continue = `&<&'some expansion'&>
26972 .vitem &*control*&&~=&~<&'text'&>
26973 .cindex "&%control%& ACL modifier"
26974 This modifier affects the subsequent processing of the SMTP connection or of an
26975 incoming message that is accepted. The effect of the first type of control
26976 lasts for the duration of the connection, whereas the effect of the second type
26977 lasts only until the current message has been received. The message-specific
26978 controls always apply to the whole message, not to individual recipients,
26979 even if the &%control%& modifier appears in a RCPT ACL.
26981 As there are now quite a few controls that can be applied, they are described
26982 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
26983 in several different ways. For example:
26985 . ==== As this is a nested list, any displays it contains must be indented
26986 . ==== as otherwise they are too far to the left. That comment applies only
26987 . ==== when xmlto and fop are used; formatting with sdop gets it right either
26991 It can be at the end of an &%accept%& statement:
26993 accept ...some conditions
26994 control = queue_only
26996 In this case, the control is applied when this statement yields &"accept"&, in
26997 other words, when the conditions are all true.
27000 It can be in the middle of an &%accept%& statement:
27002 accept ...some conditions...
27003 control = queue_only
27004 ...some more conditions...
27006 If the first set of conditions are true, the control is applied, even if the
27007 statement does not accept because one of the second set of conditions is false.
27008 In this case, some subsequent statement must yield &"accept"& for the control
27012 It can be used with &%warn%& to apply the control, leaving the
27013 decision about accepting or denying to a subsequent verb. For
27016 warn ...some conditions...
27020 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
27021 &%logwrite%&, so it does not add anything to the message and does not write a
27025 If you want to apply a control unconditionally, you can use it with a
27026 &%require%& verb. For example:
27028 require control = no_multiline_responses
27032 .vitem &*delay*&&~=&~<&'time'&>
27033 .cindex "&%delay%& ACL modifier"
27035 This modifier may appear in any ACL except notquit. It causes Exim to wait for
27036 the time interval before proceeding. However, when testing Exim using the
27037 &%-bh%& option, the delay is not actually imposed (an appropriate message is
27038 output instead). The time is given in the usual Exim notation, and the delay
27039 happens as soon as the modifier is processed. In an SMTP session, pending
27040 output is flushed before the delay is imposed.
27042 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
27045 deny ...some conditions...
27048 The delay happens if all the conditions are true, before the statement returns
27049 &"deny"&. Compare this with:
27052 ...some conditions...
27054 which waits for 30s before processing the conditions. The &%delay%& modifier
27055 can also be used with &%warn%& and together with &%control%&:
27057 warn ...some conditions...
27063 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
27064 responses to several commands are no longer buffered and sent in one packet (as
27065 they would normally be) because all output is flushed before imposing the
27066 delay. This optimization is disabled so that a number of small delays do not
27067 appear to the client as one large aggregated delay that might provoke an
27068 unwanted timeout. You can, however, disable output flushing for &%delay%& by
27069 using a &%control%& modifier to set &%no_delay_flush%&.
27073 .cindex "&%endpass%& ACL modifier"
27074 This modifier, which has no argument, is recognized only in &%accept%& and
27075 &%discard%& statements. It marks the boundary between the conditions whose
27076 failure causes control to pass to the next statement, and the conditions whose
27077 failure causes the ACL to return &"deny"&. This concept has proved to be
27078 confusing to some people, so the use of &%endpass%& is no longer recommended as
27079 &"best practice"&. See the description of &%accept%& above for more details.
27082 .vitem &*log_message*&&~=&~<&'text'&>
27083 .cindex "&%log_message%& ACL modifier"
27084 This modifier sets up a message that is used as part of the log message if the
27085 ACL denies access or a &%warn%& statement's conditions are true. For example:
27087 require log_message = wrong cipher suite $tls_in_cipher
27088 encrypted = DES-CBC3-SHA
27090 &%log_message%& is also used when recipients are discarded by &%discard%&. For
27093 &`discard `&<&'some conditions'&>
27094 &` log_message = Discarded $local_part@$domain because...`&
27096 When access is denied, &%log_message%& adds to any underlying error message
27097 that may exist because of a condition failure. For example, while verifying a
27098 recipient address, a &':fail:'& redirection might have already set up a
27101 The message may be defined before the conditions to which it applies, because
27102 the string expansion does not happen until Exim decides that access is to be
27103 denied. This means that any variables that are set by the condition are
27104 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
27105 variables are set after a DNS black list lookup succeeds. If the expansion of
27106 &%log_message%& fails, or if the result is an empty string, the modifier is
27109 .vindex "&$acl_verify_message$&"
27110 If you want to use a &%warn%& statement to log the result of an address
27111 verification, you can use &$acl_verify_message$& to include the verification
27114 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
27115 the start of the logged message. If the same warning log message is requested
27116 more than once while receiving a single email message, only one copy is
27117 actually logged. If you want to log multiple copies, use &%logwrite%& instead
27118 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
27119 is logged for a successful &%warn%& statement.
27121 If &%log_message%& is not present and there is no underlying error message (for
27122 example, from the failure of address verification), but &%message%& is present,
27123 the &%message%& text is used for logging rejections. However, if any text for
27124 logging contains newlines, only the first line is logged. In the absence of
27125 both &%log_message%& and &%message%&, a default built-in message is used for
27126 logging rejections.
27129 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
27130 .cindex "&%log_reject_target%& ACL modifier"
27131 .cindex "logging in ACL" "specifying which log"
27132 This modifier makes it possible to specify which logs are used for messages
27133 about ACL rejections. Its argument is a colon-separated list of words that can
27134 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
27135 may be empty, in which case a rejection is not logged at all. For example, this
27136 ACL fragment writes no logging information when access is denied:
27138 &`deny `&<&'some conditions'&>
27139 &` log_reject_target =`&
27141 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
27142 permanent and temporary rejections. Its effect lasts for the rest of the
27146 .vitem &*logwrite*&&~=&~<&'text'&>
27147 .cindex "&%logwrite%& ACL modifier"
27148 .cindex "logging in ACL" "immediate"
27149 This modifier writes a message to a log file as soon as it is encountered when
27150 processing an ACL. (Compare &%log_message%&, which, except in the case of
27151 &%warn%& and &%discard%&, is used only if the ACL statement denies
27152 access.) The &%logwrite%& modifier can be used to log special incidents in
27155 &`accept `&<&'some special conditions'&>
27156 &` control = freeze`&
27157 &` logwrite = froze message because ...`&
27159 By default, the message is written to the main log. However, it may begin
27160 with a colon, followed by a comma-separated list of log names, and then
27161 another colon, to specify exactly which logs are to be written. For
27164 logwrite = :main,reject: text for main and reject logs
27165 logwrite = :panic: text for panic log only
27169 .vitem &*message*&&~=&~<&'text'&>
27170 .cindex "&%message%& ACL modifier"
27171 This modifier sets up a text string that is expanded and used as a response
27172 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
27173 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
27174 there is some complication if &%endpass%& is involved; see the description of
27175 &%accept%& for details.)
27177 The expansion of the message happens at the time Exim decides that the ACL is
27178 to end, not at the time it processes &%message%&. If the expansion fails, or
27179 generates an empty string, the modifier is ignored. Here is an example where
27180 &%message%& must be specified first, because the ACL ends with a rejection if
27181 the &%hosts%& condition fails:
27183 require message = Host not recognized
27186 (Once a condition has failed, no further conditions or modifiers are
27189 .cindex "SMTP" "error codes"
27190 .oindex "&%smtp_banner%&
27191 For ACLs that are triggered by SMTP commands, the message is returned as part
27192 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
27193 is meaningful only for SMTP, as no message is returned when a non-SMTP message
27194 is accepted. In the case of the connect ACL, accepting with a message modifier
27195 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
27196 accept message may not contain more than one line (otherwise it will be
27197 truncated at the first newline and a panic logged), and it cannot affect the
27200 When SMTP is involved, the message may begin with an overriding response code,
27201 consisting of three digits optionally followed by an &"extended response code"&
27202 of the form &'n.n.n'&, each code being followed by a space. For example:
27204 deny message = 599 1.2.3 Host not welcome
27205 hosts = 192.168.34.0/24
27207 The first digit of the supplied response code must be the same as would be sent
27208 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
27209 access, but for the predata ACL, note that the default success code is 354, not
27212 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
27213 the message modifier cannot override the 221 response code.
27215 The text in a &%message%& modifier is literal; any quotes are taken as
27216 literals, but because the string is expanded, backslash escapes are processed
27217 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
27220 .vindex "&$acl_verify_message$&"
27221 If &%message%& is used on a statement that verifies an address, the message
27222 specified overrides any message that is generated by the verification process.
27223 However, the original message is available in the variable
27224 &$acl_verify_message$&, so you can incorporate it into your message if you
27225 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
27226 routers to be passed back as part of the SMTP response, you should either not
27227 use a &%message%& modifier, or make use of &$acl_verify_message$&.
27229 For compatibility with previous releases of Exim, a &%message%& modifier that
27230 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
27231 modifier, but this usage is now deprecated. However, &%message%& acts only when
27232 all the conditions are true, wherever it appears in an ACL command, whereas
27233 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
27234 &%warn%& in an ACL that is not concerned with receiving a message, it has no
27238 .vitem &*remove_header*&&~=&~<&'text'&>
27239 This modifier specifies one or more header names in a colon-separated list
27240 that are to be removed from an incoming message, assuming, of course, that
27241 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
27244 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
27245 .cindex "&%set%& ACL modifier"
27246 This modifier puts a value into one of the ACL variables (see section
27247 &<<SECTaclvariables>>&).
27250 .vitem &*udpsend*&&~=&~<&'parameters'&>
27251 This modifier sends a UDP packet, for purposes such as statistics
27252 collection or behaviour monitoring. The parameters are expanded, and
27253 the result of the expansion must be a colon-separated list consisting
27254 of a destination server, port number, and the packet contents. The
27255 server can be specified as a host name or IPv4 or IPv6 address. The
27256 separator can be changed with the usual angle bracket syntax. For
27257 example, you might want to collect information on which hosts connect
27260 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
27261 $tod_zulu $sender_host_address
27268 .section "Use of the control modifier" "SECTcontrols"
27269 .cindex "&%control%& ACL modifier"
27270 The &%control%& modifier supports the following settings:
27273 .vitem &*control&~=&~allow_auth_unadvertised*&
27274 This modifier allows a client host to use the SMTP AUTH command even when it
27275 has not been advertised in response to EHLO. Furthermore, because there are
27276 apparently some really broken clients that do this, Exim will accept AUTH after
27277 HELO (rather than EHLO) when this control is set. It should be used only if you
27278 really need it, and you should limit its use to those broken clients that do
27279 not work without it. For example:
27281 warn hosts = 192.168.34.25
27282 control = allow_auth_unadvertised
27284 Normally, when an Exim server receives an AUTH command, it checks the name of
27285 the authentication mechanism that is given in the command to ensure that it
27286 matches an advertised mechanism. When this control is set, the check that a
27287 mechanism has been advertised is bypassed. Any configured mechanism can be used
27288 by the client. This control is permitted only in the connection and HELO ACLs.
27291 .vitem &*control&~=&~caseful_local_part*& &&&
27292 &*control&~=&~caselower_local_part*&
27293 .cindex "&ACL;" "case of local part in"
27294 .cindex "case of local parts"
27295 .vindex "&$local_part$&"
27296 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
27297 (that is, during RCPT processing). By default, the contents of &$local_part$&
27298 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
27299 any uppercase letters in the original local part are restored in &$local_part$&
27300 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
27303 These controls affect only the current recipient. Moreover, they apply only to
27304 local part handling that takes place directly in the ACL (for example, as a key
27305 in lookups). If a test to verify the recipient is obeyed, the case-related
27306 handling of the local part during the verification is controlled by the router
27307 configuration (see the &%caseful_local_part%& generic router option).
27309 This facility could be used, for example, to add a spam score to local parts
27310 containing upper case letters. For example, using &$acl_m4$& to accumulate the
27313 warn control = caseful_local_part
27314 set acl_m4 = ${eval:\
27316 ${if match{$local_part}{[A-Z]}{1}{0}}\
27318 control = caselower_local_part
27320 Notice that we put back the lower cased version afterwards, assuming that
27321 is what is wanted for subsequent tests.
27324 .vitem &*control&~=&~cutthrough_delivery*&
27325 .cindex "&ACL;" "cutthrough routing"
27326 .cindex "cutthrough" "requesting"
27327 This option requests delivery be attempted while the item is being received.
27328 It is usable in the RCPT ACL and valid only for single-recipient mails forwarded
27329 from one SMTP connection to another. If a recipient-verify callout connection is
27330 requested in the same ACL it is held open and used for the data, otherwise one is made
27331 after the ACL completes.
27333 Note that routers are used in verify mode,
27334 and cannot depend on content of received headers.
27335 Note also that headers cannot be
27336 modified by any of the post-data ACLs (DATA, MIME and DKIM).
27337 Headers may be modified by routers (subject to the above) and transports.
27339 Cutthrough delivery is not supported via transport-filters or when DKIM signing
27340 of outgoing messages is done, because it sends data to the ultimate destination
27341 before the entire message has been received from the source.
27343 Should the ultimate destination system positively accept or reject the mail,
27344 a corresponding indication is given to the source system and nothing is queued.
27345 If there is a temporary error the item is queued for later delivery in the
27346 usual fashion. If the item is successfully delivered in cutthrough mode the log line
27347 is tagged with ">>" rather than "=>" and appears before the acceptance "<="
27350 Delivery in this mode avoids the generation of a bounce mail to a (possibly faked)
27351 sender when the destination system is doing content-scan based rejection.
27354 .vitem &*control&~=&~debug/*&<&'options'&>
27355 .cindex "&ACL;" "enabling debug logging"
27356 .cindex "debugging" "enabling from an ACL"
27357 This control turns on debug logging, almost as though Exim had been invoked
27358 with &`-d`&, with the output going to a new logfile, by default called
27359 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
27360 may access any variables already defined. The logging may be adjusted with
27361 the &'opts'& option, which takes the same values as the &`-d`& command-line
27362 option. Some examples (which depend on variables that don't exist in all
27366 control = debug/tag=.$sender_host_address
27367 control = debug/opts=+expand+acl
27368 control = debug/tag=.$message_exim_id/opts=+expand
27372 .vitem &*control&~=&~dkim_disable_verify*&
27373 .cindex "disable DKIM verify"
27374 .cindex "DKIM" "disable verify"
27375 This control turns off DKIM verification processing entirely. For details on
27376 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
27379 .vitem &*control&~=&~dscp/*&<&'value'&>
27380 .cindex "&ACL;" "setting DSCP value"
27381 .cindex "DSCP" "inbound"
27382 This option causes the DSCP value associated with the socket for the inbound
27383 connection to be adjusted to a given value, given as one of a number of fixed
27384 strings or to numeric value.
27385 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
27386 Common values include &`throughput`&, &`mincost`&, and on newer systems
27387 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
27389 The outbound packets from Exim will be marked with this value in the header
27390 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
27391 that these values will have any effect, not be stripped by networking
27392 equipment, or do much of anything without cooperation with your Network
27393 Engineer and those of all network operators between the source and destination.
27396 .vitem &*control&~=&~enforce_sync*& &&&
27397 &*control&~=&~no_enforce_sync*&
27398 .cindex "SMTP" "synchronization checking"
27399 .cindex "synchronization checking in SMTP"
27400 These controls make it possible to be selective about when SMTP synchronization
27401 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
27402 state of the switch (it is true by default). See the description of this option
27403 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
27405 The effect of these two controls lasts for the remainder of the SMTP
27406 connection. They can appear in any ACL except the one for the non-SMTP
27407 messages. The most straightforward place to put them is in the ACL defined by
27408 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
27409 before the first synchronization check. The expected use is to turn off the
27410 synchronization checks for badly-behaved hosts that you nevertheless need to
27414 .vitem &*control&~=&~fakedefer/*&<&'message'&>
27415 .cindex "fake defer"
27416 .cindex "defer, fake"
27417 This control works in exactly the same way as &%fakereject%& (described below)
27418 except that it causes an SMTP 450 response after the message data instead of a
27419 550 response. You must take care when using &%fakedefer%& because it causes the
27420 messages to be duplicated when the sender retries. Therefore, you should not
27421 use &%fakedefer%& if the message is to be delivered normally.
27423 .vitem &*control&~=&~fakereject/*&<&'message'&>
27424 .cindex "fake rejection"
27425 .cindex "rejection, fake"
27426 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
27427 words, only when an SMTP message is being received. If Exim accepts the
27428 message, instead the final 250 response, a 550 rejection message is sent.
27429 However, Exim proceeds to deliver the message as normal. The control applies
27430 only to the current message, not to any subsequent ones that may be received in
27431 the same SMTP connection.
27433 The text for the 550 response is taken from the &%control%& modifier. If no
27434 message is supplied, the following is used:
27436 550-Your message has been rejected but is being
27437 550-kept for evaluation.
27438 550-If it was a legitimate message, it may still be
27439 550 delivered to the target recipient(s).
27441 This facility should be used with extreme caution.
27443 .vitem &*control&~=&~freeze*&
27444 .cindex "frozen messages" "forcing in ACL"
27445 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27446 other words, only when a message is being received. If the message is accepted,
27447 it is placed on Exim's queue and frozen. The control applies only to the
27448 current message, not to any subsequent ones that may be received in the same
27451 This modifier can optionally be followed by &`/no_tell`&. If the global option
27452 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
27453 is told about the freezing), provided all the &*control=freeze*& modifiers that
27454 are obeyed for the current message have the &`/no_tell`& option.
27456 .vitem &*control&~=&~no_delay_flush*&
27457 .cindex "SMTP" "output flushing, disabling for delay"
27458 Exim normally flushes SMTP output before implementing a delay in an ACL, to
27459 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
27460 use. This control, as long as it is encountered before the &%delay%& modifier,
27461 disables such output flushing.
27463 .vitem &*control&~=&~no_callout_flush*&
27464 .cindex "SMTP" "output flushing, disabling for callout"
27465 Exim normally flushes SMTP output before performing a callout in an ACL, to
27466 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
27467 use. This control, as long as it is encountered before the &%verify%& condition
27468 that causes the callout, disables such output flushing.
27470 .vitem &*control&~=&~no_mbox_unspool*&
27471 This control is available when Exim is compiled with the content scanning
27472 extension. Content scanning may require a copy of the current message, or parts
27473 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
27474 or spam scanner. Normally, such copies are deleted when they are no longer
27475 needed. If this control is set, the copies are not deleted. The control applies
27476 only to the current message, not to any subsequent ones that may be received in
27477 the same SMTP connection. It is provided for debugging purposes and is unlikely
27478 to be useful in production.
27480 .vitem &*control&~=&~no_multiline_responses*&
27481 .cindex "multiline responses, suppressing"
27482 This control is permitted for any ACL except the one for non-SMTP messages.
27483 It seems that there are broken clients in use that cannot handle multiline
27484 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
27486 If this control is set, multiline SMTP responses from ACL rejections are
27487 suppressed. One way of doing this would have been to put out these responses as
27488 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
27489 (&"use multiline responses for more"& it says &-- ha!), and some of the
27490 responses might get close to that. So this facility, which is after all only a
27491 sop to broken clients, is implemented by doing two very easy things:
27494 Extra information that is normally output as part of a rejection caused by
27495 sender verification failure is omitted. Only the final line (typically &"sender
27496 verification failed"&) is sent.
27498 If a &%message%& modifier supplies a multiline response, only the first
27502 The setting of the switch can, of course, be made conditional on the
27503 calling host. Its effect lasts until the end of the SMTP connection.
27505 .vitem &*control&~=&~no_pipelining*&
27506 .cindex "PIPELINING" "suppressing advertising"
27507 This control turns off the advertising of the PIPELINING extension to SMTP in
27508 the current session. To be useful, it must be obeyed before Exim sends its
27509 response to an EHLO command. Therefore, it should normally appear in an ACL
27510 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
27511 &%pipelining_advertise_hosts%&.
27513 .vitem &*control&~=&~queue_only*&
27514 .oindex "&%queue_only%&"
27515 .cindex "queueing incoming messages"
27516 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27517 other words, only when a message is being received. If the message is accepted,
27518 it is placed on Exim's queue and left there for delivery by a subsequent queue
27519 runner. No immediate delivery process is started. In other words, it has the
27520 effect as the &%queue_only%& global option. However, the control applies only
27521 to the current message, not to any subsequent ones that may be received in the
27522 same SMTP connection.
27524 .vitem &*control&~=&~submission/*&<&'options'&>
27525 .cindex "message" "submission"
27526 .cindex "submission mode"
27527 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
27528 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
27529 the current message is a submission from a local MUA. In this case, Exim
27530 operates in &"submission mode"&, and applies certain fixups to the message if
27531 necessary. For example, it adds a &'Date:'& header line if one is not present.
27532 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
27533 late (the message has already been created).
27535 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
27536 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
27537 submission mode; the available options for this control are described there.
27538 The control applies only to the current message, not to any subsequent ones
27539 that may be received in the same SMTP connection.
27541 .vitem &*control&~=&~suppress_local_fixups*&
27542 .cindex "submission fixups, suppressing"
27543 This control applies to locally submitted (non TCP/IP) messages, and is the
27544 complement of &`control = submission`&. It disables the fixups that are
27545 normally applied to locally-submitted messages. Specifically:
27548 Any &'Sender:'& header line is left alone (in this respect, it is a
27549 dynamic version of &%local_sender_retain%&).
27551 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
27553 There is no check that &'From:'& corresponds to the actual sender.
27556 This control may be useful when a remotely-originated message is accepted,
27557 passed to some scanning program, and then re-submitted for delivery. It can be
27558 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
27559 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
27562 &*Note:*& This control applies only to the current message, not to any others
27563 that are being submitted at the same time using &%-bs%& or &%-bS%&.
27567 .section "Summary of message fixup control" "SECTsummesfix"
27568 All four possibilities for message fixups can be specified:
27571 Locally submitted, fixups applied: the default.
27573 Locally submitted, no fixups applied: use
27574 &`control = suppress_local_fixups`&.
27576 Remotely submitted, no fixups applied: the default.
27578 Remotely submitted, fixups applied: use &`control = submission`&.
27583 .section "Adding header lines in ACLs" "SECTaddheadacl"
27584 .cindex "header lines" "adding in an ACL"
27585 .cindex "header lines" "position of added lines"
27586 .cindex "&%add_header%& ACL modifier"
27587 The &%add_header%& modifier can be used to add one or more extra header lines
27588 to an incoming message, as in this example:
27590 warn dnslists = sbl.spamhaus.org : \
27591 dialup.mail-abuse.org
27592 add_header = X-blacklisted-at: $dnslist_domain
27594 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27595 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
27596 receiving a message). The message must ultimately be accepted for
27597 &%add_header%& to have any significant effect. You can use &%add_header%& with
27598 any ACL verb, including &%deny%& (though this is potentially useful only in a
27601 Headers will not be added to the message if the modifier is used in
27602 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
27604 Leading and trailing newlines are removed from
27605 the data for the &%add_header%& modifier; if it then
27606 contains one or more newlines that
27607 are not followed by a space or a tab, it is assumed to contain multiple header
27608 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
27609 front of any line that is not a valid header line.
27611 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
27612 They are added to the message before processing the DATA and MIME ACLs.
27613 However, if an identical header line is requested more than once, only one copy
27614 is actually added to the message. Further header lines may be accumulated
27615 during the DATA and MIME ACLs, after which they are added to the message, again
27616 with duplicates suppressed. Thus, it is possible to add two identical header
27617 lines to an SMTP message, but only if one is added before DATA and one after.
27618 In the case of non-SMTP messages, new headers are accumulated during the
27619 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
27620 message is rejected after DATA or by the non-SMTP ACL, all added header lines
27621 are included in the entry that is written to the reject log.
27623 .cindex "header lines" "added; visibility of"
27624 Header lines are not visible in string expansions
27626 until they are added to the
27627 message. It follows that header lines defined in the MAIL, RCPT, and predata
27628 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
27629 header lines that are added by the DATA or MIME ACLs are not visible in those
27630 ACLs. Because of this restriction, you cannot use header lines as a way of
27631 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
27632 this, you can use ACL variables, as described in section
27633 &<<SECTaclvariables>>&.
27635 The list of headers yet to be added is given by the &%$headers_added%& variable.
27637 The &%add_header%& modifier acts immediately as it is encountered during the
27638 processing of an ACL. Notice the difference between these two cases:
27640 &`accept add_header = ADDED: some text`&
27641 &` `&<&'some condition'&>
27643 &`accept `&<&'some condition'&>
27644 &` add_header = ADDED: some text`&
27646 In the first case, the header line is always added, whether or not the
27647 condition is true. In the second case, the header line is added only if the
27648 condition is true. Multiple occurrences of &%add_header%& may occur in the same
27649 ACL statement. All those that are encountered before a condition fails are
27652 .cindex "&%warn%& ACL verb"
27653 For compatibility with previous versions of Exim, a &%message%& modifier for a
27654 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
27655 effect only if all the conditions are true, even if it appears before some of
27656 them. Furthermore, only the last occurrence of &%message%& is honoured. This
27657 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
27658 are present on a &%warn%& verb, both are processed according to their
27661 By default, new header lines are added to a message at the end of the existing
27662 header lines. However, you can specify that any particular header line should
27663 be added right at the start (before all the &'Received:'& lines), immediately
27664 after the first block of &'Received:'& lines, or immediately before any line
27665 that is not a &'Received:'& or &'Resent-something:'& header.
27667 This is done by specifying &":at_start:"&, &":after_received:"&, or
27668 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
27669 header line, respectively. (Header text cannot start with a colon, as there has
27670 to be a header name first.) For example:
27672 warn add_header = \
27673 :after_received:X-My-Header: something or other...
27675 If more than one header line is supplied in a single &%add_header%& modifier,
27676 each one is treated independently and can therefore be placed differently. If
27677 you add more than one line at the start, or after the Received: block, they end
27678 up in reverse order.
27680 &*Warning*&: This facility currently applies only to header lines that are
27681 added in an ACL. It does NOT work for header lines that are added in a
27682 system filter or in a router or transport.
27686 .section "Removing header lines in ACLs" "SECTremoveheadacl"
27687 .cindex "header lines" "removing in an ACL"
27688 .cindex "header lines" "position of removed lines"
27689 .cindex "&%remove_header%& ACL modifier"
27690 The &%remove_header%& modifier can be used to remove one or more header lines
27691 from an incoming message, as in this example:
27693 warn message = Remove internal headers
27694 remove_header = x-route-mail1 : x-route-mail2
27696 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27697 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
27698 receiving a message). The message must ultimately be accepted for
27699 &%remove_header%& to have any significant effect. You can use &%remove_header%&
27700 with any ACL verb, including &%deny%&, though this is really not useful for
27701 any verb that doesn't result in a delivered message.
27703 Headers will not be removed to the message if the modifier is used in
27704 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
27706 More than one header can be removed at the same time by using a colon separated
27707 list of header names. The header matching is case insensitive. Wildcards are
27708 not permitted, nor is list expansion performed, so you cannot use hostlists to
27709 create a list of headers, however both connection and message variable expansion
27710 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
27712 warn hosts = +internal_hosts
27713 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
27714 warn message = Remove internal headers
27715 remove_header = $acl_c_ihdrs
27717 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
27718 They are removed from the message before processing the DATA and MIME ACLs.
27719 There is no harm in attempting to remove the same header twice nor is removing
27720 a non-existent header. Further header lines to be removed may be accumulated
27721 during the DATA and MIME ACLs, after which they are removed from the message,
27722 if present. In the case of non-SMTP messages, headers to be removed are
27723 accumulated during the non-SMTP ACLs, and are removed from the message after
27724 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
27725 ACL, there really is no effect because there is no logging of what headers
27726 would have been removed.
27728 .cindex "header lines" "removed; visibility of"
27729 Header lines are not visible in string expansions until the DATA phase when it
27730 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
27731 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
27732 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
27733 this restriction, you cannot use header lines as a way of controlling data
27734 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
27735 you should instead use ACL variables, as described in section
27736 &<<SECTaclvariables>>&.
27738 The &%remove_header%& modifier acts immediately as it is encountered during the
27739 processing of an ACL. Notice the difference between these two cases:
27741 &`accept remove_header = X-Internal`&
27742 &` `&<&'some condition'&>
27744 &`accept `&<&'some condition'&>
27745 &` remove_header = X-Internal`&
27747 In the first case, the header line is always removed, whether or not the
27748 condition is true. In the second case, the header line is removed only if the
27749 condition is true. Multiple occurrences of &%remove_header%& may occur in the
27750 same ACL statement. All those that are encountered before a condition fails
27753 &*Warning*&: This facility currently applies only to header lines that are
27754 present during ACL processing. It does NOT remove header lines that are added
27755 in a system filter or in a router or transport.
27760 .section "ACL conditions" "SECTaclconditions"
27761 .cindex "&ACL;" "conditions; list of"
27762 Some of the conditions listed in this section are available only when Exim is
27763 compiled with the content-scanning extension. They are included here briefly
27764 for completeness. More detailed descriptions can be found in the discussion on
27765 content scanning in chapter &<<CHAPexiscan>>&.
27767 Not all conditions are relevant in all circumstances. For example, testing
27768 senders and recipients does not make sense in an ACL that is being run as the
27769 result of the arrival of an ETRN command, and checks on message headers can be
27770 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
27771 can use the same condition (with different parameters) more than once in the
27772 same ACL statement. This provides a way of specifying an &"and"& conjunction.
27773 The conditions are as follows:
27777 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
27778 .cindex "&ACL;" "nested"
27779 .cindex "&ACL;" "indirect"
27780 .cindex "&ACL;" "arguments"
27781 .cindex "&%acl%& ACL condition"
27782 The possible values of the argument are the same as for the
27783 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
27784 &"accept"& the condition is true; if it returns &"deny"& the condition is
27785 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
27786 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
27787 condition false. This means that further processing of the &%warn%& verb
27788 ceases, but processing of the ACL continues.
27790 If the argument is a named ACL, up to nine space-separated optional values
27791 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
27792 and $acl_narg is set to the count of values.
27793 Previous values of these variables are restored after the call returns.
27794 The name and values are expanded separately.
27796 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
27797 the connection is dropped. If it returns &"discard"&, the verb must be
27798 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
27799 conditions are tested.
27801 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
27802 loops. This condition allows you to use different ACLs in different
27803 circumstances. For example, different ACLs can be used to handle RCPT commands
27804 for different local users or different local domains.
27806 .vitem &*authenticated&~=&~*&<&'string&~list'&>
27807 .cindex "&%authenticated%& ACL condition"
27808 .cindex "authentication" "ACL checking"
27809 .cindex "&ACL;" "testing for authentication"
27810 If the SMTP connection is not authenticated, the condition is false. Otherwise,
27811 the name of the authenticator is tested against the list. To test for
27812 authentication by any authenticator, you can set
27817 .vitem &*condition&~=&~*&<&'string'&>
27818 .cindex "&%condition%& ACL condition"
27819 .cindex "customizing" "ACL condition"
27820 .cindex "&ACL;" "customized test"
27821 .cindex "&ACL;" "testing, customized"
27822 This feature allows you to make up custom conditions. If the result of
27823 expanding the string is an empty string, the number zero, or one of the strings
27824 &"no"& or &"false"&, the condition is false. If the result is any non-zero
27825 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
27826 any other value, some error is assumed to have occurred, and the ACL returns
27827 &"defer"&. However, if the expansion is forced to fail, the condition is
27828 ignored. The effect is to treat it as true, whether it is positive or
27831 .vitem &*decode&~=&~*&<&'location'&>
27832 .cindex "&%decode%& ACL condition"
27833 This condition is available only when Exim is compiled with the
27834 content-scanning extension, and it is allowed only in the ACL defined by
27835 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
27836 If all goes well, the condition is true. It is false only if there are
27837 problems such as a syntax error or a memory shortage. For more details, see
27838 chapter &<<CHAPexiscan>>&.
27840 .vitem &*demime&~=&~*&<&'extension&~list'&>
27841 .cindex "&%demime%& ACL condition"
27842 This condition is available only when Exim is compiled with the
27843 content-scanning extension. Its use is described in section
27844 &<<SECTdemimecond>>&.
27846 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
27847 .cindex "&%dnslists%& ACL condition"
27848 .cindex "DNS list" "in ACL"
27849 .cindex "black list (DNS)"
27850 .cindex "&ACL;" "testing a DNS list"
27851 This condition checks for entries in DNS black lists. These are also known as
27852 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
27853 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
27854 different variants of this condition to describe briefly here. See sections
27855 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
27857 .vitem &*domains&~=&~*&<&'domain&~list'&>
27858 .cindex "&%domains%& ACL condition"
27859 .cindex "domain" "ACL checking"
27860 .cindex "&ACL;" "testing a recipient domain"
27861 .vindex "&$domain_data$&"
27862 This condition is relevant only after a RCPT command. It checks that the domain
27863 of the recipient address is in the domain list. If percent-hack processing is
27864 enabled, it is done before this test is done. If the check succeeds with a
27865 lookup, the result of the lookup is placed in &$domain_data$& until the next
27868 &*Note carefully*& (because many people seem to fall foul of this): you cannot
27869 use &%domains%& in a DATA ACL.
27872 .vitem &*encrypted&~=&~*&<&'string&~list'&>
27873 .cindex "&%encrypted%& ACL condition"
27874 .cindex "encryption" "checking in an ACL"
27875 .cindex "&ACL;" "testing for encryption"
27876 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
27877 name of the cipher suite in use is tested against the list. To test for
27878 encryption without testing for any specific cipher suite(s), set
27884 .vitem &*hosts&~=&~*&<&'host&~list'&>
27885 .cindex "&%hosts%& ACL condition"
27886 .cindex "host" "ACL checking"
27887 .cindex "&ACL;" "testing the client host"
27888 This condition tests that the calling host matches the host list. If you have
27889 name lookups or wildcarded host names and IP addresses in the same host list,
27890 you should normally put the IP addresses first. For example, you could have:
27892 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
27894 The lookup in this example uses the host name for its key. This is implied by
27895 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
27896 and it wouldn't matter which way round you had these two items.)
27898 The reason for the problem with host names lies in the left-to-right way that
27899 Exim processes lists. It can test IP addresses without doing any DNS lookups,
27900 but when it reaches an item that requires a host name, it fails if it cannot
27901 find a host name to compare with the pattern. If the above list is given in the
27902 opposite order, the &%accept%& statement fails for a host whose name cannot be
27903 found, even if its IP address is 10.9.8.7.
27905 If you really do want to do the name check first, and still recognize the IP
27906 address even if the name lookup fails, you can rewrite the ACL like this:
27908 accept hosts = dbm;/etc/friendly/hosts
27909 accept hosts = 10.9.8.7
27911 The default action on failing to find the host name is to assume that the host
27912 is not in the list, so the first &%accept%& statement fails. The second
27913 statement can then check the IP address.
27915 .vindex "&$host_data$&"
27916 If a &%hosts%& condition is satisfied by means of a lookup, the result
27917 of the lookup is made available in the &$host_data$& variable. This
27918 allows you, for example, to set up a statement like this:
27920 deny hosts = net-lsearch;/some/file
27921 message = $host_data
27923 which gives a custom error message for each denied host.
27925 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
27926 .cindex "&%local_parts%& ACL condition"
27927 .cindex "local part" "ACL checking"
27928 .cindex "&ACL;" "testing a local part"
27929 .vindex "&$local_part_data$&"
27930 This condition is relevant only after a RCPT command. It checks that the local
27931 part of the recipient address is in the list. If percent-hack processing is
27932 enabled, it is done before this test. If the check succeeds with a lookup, the
27933 result of the lookup is placed in &$local_part_data$&, which remains set until
27934 the next &%local_parts%& test.
27936 .vitem &*malware&~=&~*&<&'option'&>
27937 .cindex "&%malware%& ACL condition"
27938 .cindex "&ACL;" "virus scanning"
27939 .cindex "&ACL;" "scanning for viruses"
27940 This condition is available only when Exim is compiled with the
27941 content-scanning extension. It causes the incoming message to be scanned for
27942 viruses. For details, see chapter &<<CHAPexiscan>>&.
27944 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
27945 .cindex "&%mime_regex%& ACL condition"
27946 .cindex "&ACL;" "testing by regex matching"
27947 This condition is available only when Exim is compiled with the
27948 content-scanning extension, and it is allowed only in the ACL defined by
27949 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
27950 with any of the regular expressions. For details, see chapter
27953 .vitem &*ratelimit&~=&~*&<&'parameters'&>
27954 .cindex "rate limiting"
27955 This condition can be used to limit the rate at which a user or host submits
27956 messages. Details are given in section &<<SECTratelimiting>>&.
27958 .vitem &*recipients&~=&~*&<&'address&~list'&>
27959 .cindex "&%recipients%& ACL condition"
27960 .cindex "recipient" "ACL checking"
27961 .cindex "&ACL;" "testing a recipient"
27962 This condition is relevant only after a RCPT command. It checks the entire
27963 recipient address against a list of recipients.
27965 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
27966 .cindex "&%regex%& ACL condition"
27967 .cindex "&ACL;" "testing by regex matching"
27968 This condition is available only when Exim is compiled with the
27969 content-scanning extension, and is available only in the DATA, MIME, and
27970 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
27971 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
27973 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
27974 .cindex "&%sender_domains%& ACL condition"
27975 .cindex "sender" "ACL checking"
27976 .cindex "&ACL;" "testing a sender domain"
27977 .vindex "&$domain$&"
27978 .vindex "&$sender_address_domain$&"
27979 This condition tests the domain of the sender of the message against the given
27980 domain list. &*Note*&: The domain of the sender address is in
27981 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
27982 of this condition. This is an exception to the general rule for testing domain
27983 lists. It is done this way so that, if this condition is used in an ACL for a
27984 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
27985 influence the sender checking.
27987 &*Warning*&: It is a bad idea to use this condition on its own as a control on
27988 relaying, because sender addresses are easily, and commonly, forged.
27990 .vitem &*senders&~=&~*&<&'address&~list'&>
27991 .cindex "&%senders%& ACL condition"
27992 .cindex "sender" "ACL checking"
27993 .cindex "&ACL;" "testing a sender"
27994 This condition tests the sender of the message against the given list. To test
27995 for a bounce message, which has an empty sender, set
27999 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28000 relaying, because sender addresses are easily, and commonly, forged.
28002 .vitem &*spam&~=&~*&<&'username'&>
28003 .cindex "&%spam%& ACL condition"
28004 .cindex "&ACL;" "scanning for spam"
28005 This condition is available only when Exim is compiled with the
28006 content-scanning extension. It causes the incoming message to be scanned by
28007 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
28009 .vitem &*verify&~=&~certificate*&
28010 .cindex "&%verify%& ACL condition"
28011 .cindex "TLS" "client certificate verification"
28012 .cindex "certificate" "verification of client"
28013 .cindex "&ACL;" "certificate verification"
28014 .cindex "&ACL;" "testing a TLS certificate"
28015 This condition is true in an SMTP session if the session is encrypted, and a
28016 certificate was received from the client, and the certificate was verified. The
28017 server requests a certificate only if the client matches &%tls_verify_hosts%&
28018 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
28020 .vitem &*verify&~=&~csa*&
28021 .cindex "CSA verification"
28022 This condition checks whether the sending host (the client) is authorized to
28023 send email. Details of how this works are given in section
28024 &<<SECTverifyCSA>>&.
28027 .vitem &*verify&~=&~header_names_ascii*&
28028 .cindex "&%verify%& ACL condition"
28029 .cindex "&ACL;" "verifying header names only ASCII"
28030 .cindex "header lines" "verifying header names only ASCII"
28031 .cindex "verifying" "header names only ASCII"
28032 This condition is relevant only in an ACL that is run after a message has been
28033 received, that is, in an ACL specified by &%acl_smtp_data%& or
28034 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
28035 there are no non-ASCII characters, also excluding control characters. The
28036 allowable characters are decimal ASCII values 33 through 126.
28038 Exim itself will handle headers with non-ASCII characters, but it can cause
28039 problems for downstream applications, so this option will allow their
28040 detection and rejection in the DATA ACL's.
28043 .vitem &*verify&~=&~header_sender/*&<&'options'&>
28044 .cindex "&%verify%& ACL condition"
28045 .cindex "&ACL;" "verifying sender in the header"
28046 .cindex "header lines" "verifying the sender in"
28047 .cindex "sender" "verifying in header"
28048 .cindex "verifying" "sender in header"
28049 This condition is relevant only in an ACL that is run after a message has been
28050 received, that is, in an ACL specified by &%acl_smtp_data%& or
28051 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
28052 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
28053 is loosely thought of as a &"sender"& address (hence the name of the test).
28054 However, an address that appears in one of these headers need not be an address
28055 that accepts bounce messages; only sender addresses in envelopes are required
28056 to accept bounces. Therefore, if you use the callout option on this check, you
28057 might want to arrange for a non-empty address in the MAIL command.
28059 Details of address verification and the options are given later, starting at
28060 section &<<SECTaddressverification>>& (callouts are described in section
28061 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
28062 condition to restrict it to bounce messages only:
28065 message = A valid sender header is required for bounces
28066 !verify = header_sender
28069 .vitem &*verify&~=&~header_syntax*&
28070 .cindex "&%verify%& ACL condition"
28071 .cindex "&ACL;" "verifying header syntax"
28072 .cindex "header lines" "verifying syntax"
28073 .cindex "verifying" "header syntax"
28074 This condition is relevant only in an ACL that is run after a message has been
28075 received, that is, in an ACL specified by &%acl_smtp_data%& or
28076 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
28077 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
28078 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
28079 permitted only in locally generated messages and from hosts that match
28080 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
28083 Note that this condition is a syntax check only. However, a common spamming
28084 ploy used to be to send syntactically invalid headers such as
28088 and this condition can be used to reject such messages, though they are not as
28089 common as they used to be.
28091 .vitem &*verify&~=&~helo*&
28092 .cindex "&%verify%& ACL condition"
28093 .cindex "&ACL;" "verifying HELO/EHLO"
28094 .cindex "HELO" "verifying"
28095 .cindex "EHLO" "verifying"
28096 .cindex "verifying" "EHLO"
28097 .cindex "verifying" "HELO"
28098 This condition is true if a HELO or EHLO command has been received from the
28099 client host, and its contents have been verified. If there has been no previous
28100 attempt to verify the HELO/EHLO contents, it is carried out when this
28101 condition is encountered. See the description of the &%helo_verify_hosts%& and
28102 &%helo_try_verify_hosts%& options for details of how to request verification
28103 independently of this condition.
28105 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
28106 option), this condition is always true.
28109 .vitem &*verify&~=&~not_blind*&
28110 .cindex "verifying" "not blind"
28111 .cindex "bcc recipients, verifying none"
28112 This condition checks that there are no blind (bcc) recipients in the message.
28113 Every envelope recipient must appear either in a &'To:'& header line or in a
28114 &'Cc:'& header line for this condition to be true. Local parts are checked
28115 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
28116 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
28117 used only in a DATA or non-SMTP ACL.
28119 There are, of course, many legitimate messages that make use of blind (bcc)
28120 recipients. This check should not be used on its own for blocking messages.
28123 .vitem &*verify&~=&~recipient/*&<&'options'&>
28124 .cindex "&%verify%& ACL condition"
28125 .cindex "&ACL;" "verifying recipient"
28126 .cindex "recipient" "verifying"
28127 .cindex "verifying" "recipient"
28128 .vindex "&$address_data$&"
28129 This condition is relevant only after a RCPT command. It verifies the current
28130 recipient. Details of address verification are given later, starting at section
28131 &<<SECTaddressverification>>&. After a recipient has been verified, the value
28132 of &$address_data$& is the last value that was set while routing the address.
28133 This applies even if the verification fails. When an address that is being
28134 verified is redirected to a single address, verification continues with the new
28135 address, and in that case, the subsequent value of &$address_data$& is the
28136 value for the child address.
28138 .vitem &*verify&~=&~reverse_host_lookup*&
28139 .cindex "&%verify%& ACL condition"
28140 .cindex "&ACL;" "verifying host reverse lookup"
28141 .cindex "host" "verifying reverse lookup"
28142 This condition ensures that a verified host name has been looked up from the IP
28143 address of the client host. (This may have happened already if the host name
28144 was needed for checking a host list, or if the host matched &%host_lookup%&.)
28145 Verification ensures that the host name obtained from a reverse DNS lookup, or
28146 one of its aliases, does, when it is itself looked up in the DNS, yield the
28147 original IP address.
28149 If this condition is used for a locally generated message (that is, when there
28150 is no client host involved), it always succeeds.
28152 .vitem &*verify&~=&~sender/*&<&'options'&>
28153 .cindex "&%verify%& ACL condition"
28154 .cindex "&ACL;" "verifying sender"
28155 .cindex "sender" "verifying"
28156 .cindex "verifying" "sender"
28157 This condition is relevant only after a MAIL or RCPT command, or after a
28158 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
28159 the message's sender is empty (that is, this is a bounce message), the
28160 condition is true. Otherwise, the sender address is verified.
28162 .vindex "&$address_data$&"
28163 .vindex "&$sender_address_data$&"
28164 If there is data in the &$address_data$& variable at the end of routing, its
28165 value is placed in &$sender_address_data$& at the end of verification. This
28166 value can be used in subsequent conditions and modifiers in the same ACL
28167 statement. It does not persist after the end of the current statement. If you
28168 want to preserve the value for longer, you can save it in an ACL variable.
28170 Details of verification are given later, starting at section
28171 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
28172 to avoid doing it more than once per message.
28174 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
28175 .cindex "&%verify%& ACL condition"
28176 This is a variation of the previous option, in which a modified address is
28177 verified as a sender.
28182 .section "Using DNS lists" "SECTmorednslists"
28183 .cindex "DNS list" "in ACL"
28184 .cindex "black list (DNS)"
28185 .cindex "&ACL;" "testing a DNS list"
28186 In its simplest form, the &%dnslists%& condition tests whether the calling host
28187 is on at least one of a number of DNS lists by looking up the inverted IP
28188 address in one or more DNS domains. (Note that DNS list domains are not mail
28189 domains, so the &`+`& syntax for named lists doesn't work - it is used for
28190 special options instead.) For example, if the calling host's IP
28191 address is 192.168.62.43, and the ACL statement is
28193 deny dnslists = blackholes.mail-abuse.org : \
28194 dialups.mail-abuse.org
28196 the following records are looked up:
28198 43.62.168.192.blackholes.mail-abuse.org
28199 43.62.168.192.dialups.mail-abuse.org
28201 As soon as Exim finds an existing DNS record, processing of the list stops.
28202 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
28203 to test that a host is on more than one list (an &"and"& conjunction), you can
28204 use two separate conditions:
28206 deny dnslists = blackholes.mail-abuse.org
28207 dnslists = dialups.mail-abuse.org
28209 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
28210 behaves as if the host does not match the list item, that is, as if the DNS
28211 record does not exist. If there are further items in the DNS list, they are
28214 This is usually the required action when &%dnslists%& is used with &%deny%&
28215 (which is the most common usage), because it prevents a DNS failure from
28216 blocking mail. However, you can change this behaviour by putting one of the
28217 following special items in the list:
28219 &`+include_unknown `& behave as if the item is on the list
28220 &`+exclude_unknown `& behave as if the item is not on the list (default)
28221 &`+defer_unknown `& give a temporary error
28223 .cindex "&`+include_unknown`&"
28224 .cindex "&`+exclude_unknown`&"
28225 .cindex "&`+defer_unknown`&"
28226 Each of these applies to any subsequent items on the list. For example:
28228 deny dnslists = +defer_unknown : foo.bar.example
28230 Testing the list of domains stops as soon as a match is found. If you want to
28231 warn for one list and block for another, you can use two different statements:
28233 deny dnslists = blackholes.mail-abuse.org
28234 warn message = X-Warn: sending host is on dialups list
28235 dnslists = dialups.mail-abuse.org
28237 DNS list lookups are cached by Exim for the duration of the SMTP session,
28238 so a lookup based on the IP address is done at most once for any incoming
28239 connection. Exim does not share information between multiple incoming
28240 connections (but your local name server cache should be active).
28244 .section "Specifying the IP address for a DNS list lookup" "SECID201"
28245 .cindex "DNS list" "keyed by explicit IP address"
28246 By default, the IP address that is used in a DNS list lookup is the IP address
28247 of the calling host. However, you can specify another IP address by listing it
28248 after the domain name, introduced by a slash. For example:
28250 deny dnslists = black.list.tld/192.168.1.2
28252 This feature is not very helpful with explicit IP addresses; it is intended for
28253 use with IP addresses that are looked up, for example, the IP addresses of the
28254 MX hosts or nameservers of an email sender address. For an example, see section
28255 &<<SECTmulkeyfor>>& below.
28260 .section "DNS lists keyed on domain names" "SECID202"
28261 .cindex "DNS list" "keyed by domain name"
28262 There are some lists that are keyed on domain names rather than inverted IP
28263 addresses (see for example the &'domain based zones'& link at
28264 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
28265 with these lists. You can change the name that is looked up in a DNS list by
28266 listing it after the domain name, introduced by a slash. For example,
28268 deny message = Sender's domain is listed at $dnslist_domain
28269 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
28271 This particular example is useful only in ACLs that are obeyed after the
28272 RCPT or DATA commands, when a sender address is available. If (for
28273 example) the message's sender is &'user@tld.example'& the name that is looked
28274 up by this example is
28276 tld.example.dsn.rfc-ignorant.org
28278 A single &%dnslists%& condition can contain entries for both names and IP
28279 addresses. For example:
28281 deny dnslists = sbl.spamhaus.org : \
28282 dsn.rfc-ignorant.org/$sender_address_domain
28284 The first item checks the sending host's IP address; the second checks a domain
28285 name. The whole condition is true if either of the DNS lookups succeeds.
28290 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
28291 .cindex "DNS list" "multiple keys for"
28292 The syntax described above for looking up explicitly-defined values (either
28293 names or IP addresses) in a DNS blacklist is a simplification. After the domain
28294 name for the DNS list, what follows the slash can in fact be a list of items.
28295 As with all lists in Exim, the default separator is a colon. However, because
28296 this is a sublist within the list of DNS blacklist domains, it is necessary
28297 either to double the separators like this:
28299 dnslists = black.list.tld/name.1::name.2
28301 or to change the separator character, like this:
28303 dnslists = black.list.tld/<;name.1;name.2
28305 If an item in the list is an IP address, it is inverted before the DNS
28306 blacklist domain is appended. If it is not an IP address, no inversion
28307 occurs. Consider this condition:
28309 dnslists = black.list.tld/<;192.168.1.2;a.domain
28311 The DNS lookups that occur are:
28313 2.1.168.192.black.list.tld
28314 a.domain.black.list.tld
28316 Once a DNS record has been found (that matches a specific IP return
28317 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
28318 are done. If there is a temporary DNS error, the rest of the sublist of domains
28319 or IP addresses is tried. A temporary error for the whole dnslists item occurs
28320 only if no other DNS lookup in this sublist succeeds. In other words, a
28321 successful lookup for any of the items in the sublist overrides a temporary
28322 error for a previous item.
28324 The ability to supply a list of items after the slash is in some sense just a
28325 syntactic convenience. These two examples have the same effect:
28327 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
28328 dnslists = black.list.tld/a.domain::b.domain
28330 However, when the data for the list is obtained from a lookup, the second form
28331 is usually much more convenient. Consider this example:
28333 deny message = The mail servers for the domain \
28334 $sender_address_domain \
28335 are listed at $dnslist_domain ($dnslist_value); \
28337 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
28338 ${lookup dnsdb {>|mxh=\
28339 $sender_address_domain} }} }
28341 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
28342 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
28343 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
28344 of expanding the condition might be something like this:
28346 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
28348 Thus, this example checks whether or not the IP addresses of the sender
28349 domain's mail servers are on the Spamhaus black list.
28351 The key that was used for a successful DNS list lookup is put into the variable
28352 &$dnslist_matched$& (see section &<<SECID204>>&).
28357 .section "Data returned by DNS lists" "SECID203"
28358 .cindex "DNS list" "data returned from"
28359 DNS lists are constructed using address records in the DNS. The original RBL
28360 just used the address 127.0.0.1 on the right hand side of each record, but the
28361 RBL+ list and some other lists use a number of values with different meanings.
28362 The values used on the RBL+ list are:
28366 127.1.0.3 DUL and RBL
28368 127.1.0.5 RSS and RBL
28369 127.1.0.6 RSS and DUL
28370 127.1.0.7 RSS and DUL and RBL
28372 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
28373 different values. Some DNS lists may return more than one address record;
28374 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
28377 .section "Variables set from DNS lists" "SECID204"
28378 .cindex "expansion" "variables, set from DNS list"
28379 .cindex "DNS list" "variables set from"
28380 .vindex "&$dnslist_domain$&"
28381 .vindex "&$dnslist_matched$&"
28382 .vindex "&$dnslist_text$&"
28383 .vindex "&$dnslist_value$&"
28384 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
28385 the name of the overall domain that matched (for example,
28386 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
28387 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
28388 the DNS record. When the key is an IP address, it is not reversed in
28389 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
28390 cases, for example:
28392 deny dnslists = spamhaus.example
28394 the key is also available in another variable (in this case,
28395 &$sender_host_address$&). In more complicated cases, however, this is not true.
28396 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
28397 might generate a dnslists lookup like this:
28399 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
28401 If this condition succeeds, the value in &$dnslist_matched$& might be
28402 &`192.168.6.7`& (for example).
28404 If more than one address record is returned by the DNS lookup, all the IP
28405 addresses are included in &$dnslist_value$&, separated by commas and spaces.
28406 The variable &$dnslist_text$& contains the contents of any associated TXT
28407 record. For lists such as RBL+ the TXT record for a merged entry is often not
28408 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
28411 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
28412 &-- although these appear before the condition in the ACL, they are not
28413 expanded until after it has failed. For example:
28415 deny hosts = !+local_networks
28416 message = $sender_host_address is listed \
28418 dnslists = rbl-plus.mail-abuse.example
28423 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
28424 .cindex "DNS list" "matching specific returned data"
28425 You can add an equals sign and an IP address after a &%dnslists%& domain name
28426 in order to restrict its action to DNS records with a matching right hand side.
28429 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
28431 rejects only those hosts that yield 127.0.0.2. Without this additional data,
28432 any address record is considered to be a match. For the moment, we assume
28433 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
28434 describes how multiple records are handled.
28436 More than one IP address may be given for checking, using a comma as a
28437 separator. These are alternatives &-- if any one of them matches, the
28438 &%dnslists%& condition is true. For example:
28440 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
28442 If you want to specify a constraining address list and also specify names or IP
28443 addresses to be looked up, the constraining address list must be specified
28444 first. For example:
28446 deny dnslists = dsn.rfc-ignorant.org\
28447 =127.0.0.2/$sender_address_domain
28450 If the character &`&&`& is used instead of &`=`&, the comparison for each
28451 listed IP address is done by a bitwise &"and"& instead of by an equality test.
28452 In other words, the listed addresses are used as bit masks. The comparison is
28453 true if all the bits in the mask are present in the address that is being
28454 tested. For example:
28456 dnslists = a.b.c&0.0.0.3
28458 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
28459 want to test whether one bit or another bit is present (as opposed to both
28460 being present), you must use multiple values. For example:
28462 dnslists = a.b.c&0.0.0.1,0.0.0.2
28464 matches if the final component of the address is an odd number or two times
28469 .section "Negated DNS matching conditions" "SECID205"
28470 You can supply a negative list of IP addresses as part of a &%dnslists%&
28473 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
28475 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
28476 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
28478 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
28480 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
28481 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
28482 words, the result of the test is inverted if an exclamation mark appears before
28483 the &`=`& (or the &`&&`&) sign.
28485 &*Note*&: This kind of negation is not the same as negation in a domain,
28486 host, or address list (which is why the syntax is different).
28488 If you are using just one list, the negation syntax does not gain you much. The
28489 previous example is precisely equivalent to
28491 deny dnslists = a.b.c
28492 !dnslists = a.b.c=127.0.0.2,127.0.0.3
28494 However, if you are using multiple lists, the negation syntax is clearer.
28495 Consider this example:
28497 deny dnslists = sbl.spamhaus.org : \
28499 dnsbl.njabl.org!=127.0.0.3 : \
28502 Using only positive lists, this would have to be:
28504 deny dnslists = sbl.spamhaus.org : \
28506 deny dnslists = dnsbl.njabl.org
28507 !dnslists = dnsbl.njabl.org=127.0.0.3
28508 deny dnslists = relays.ordb.org
28510 which is less clear, and harder to maintain.
28515 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
28516 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
28517 thereby providing more than one IP address. When an item in a &%dnslists%& list
28518 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
28519 the match to specific results from the DNS lookup, there are two ways in which
28520 the checking can be handled. For example, consider the condition:
28522 dnslists = a.b.c=127.0.0.1
28524 What happens if the DNS lookup for the incoming IP address yields both
28525 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
28526 condition true because at least one given value was found, or is it false
28527 because at least one of the found values was not listed? And how does this
28528 affect negated conditions? Both possibilities are provided for with the help of
28529 additional separators &`==`& and &`=&&`&.
28532 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
28533 IP addresses matches one of the listed addresses. For the example above, the
28534 condition is true because 127.0.0.1 matches.
28536 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
28537 looked up IP addresses matches one of the listed addresses. If the condition is
28540 dnslists = a.b.c==127.0.0.1
28542 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28543 false because 127.0.0.2 is not listed. You would need to have:
28545 dnslists = a.b.c==127.0.0.1,127.0.0.2
28547 for the condition to be true.
28550 When &`!`& is used to negate IP address matching, it inverts the result, giving
28551 the precise opposite of the behaviour above. Thus:
28553 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
28554 addresses matches one of the listed addresses. Consider:
28556 dnslists = a.b.c!&0.0.0.1
28558 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28559 false because 127.0.0.1 matches.
28561 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
28562 looked up IP address that does not match. Consider:
28564 dnslists = a.b.c!=&0.0.0.1
28566 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28567 true, because 127.0.0.2 does not match. You would need to have:
28569 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
28571 for the condition to be false.
28573 When the DNS lookup yields only a single IP address, there is no difference
28574 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
28579 .section "Detailed information from merged DNS lists" "SECTmordetinf"
28580 .cindex "DNS list" "information from merged"
28581 When the facility for restricting the matching IP values in a DNS list is used,
28582 the text from the TXT record that is set in &$dnslist_text$& may not reflect
28583 the true reason for rejection. This happens when lists are merged and the IP
28584 address in the A record is used to distinguish them; unfortunately there is
28585 only one TXT record. One way round this is not to use merged lists, but that
28586 can be inefficient because it requires multiple DNS lookups where one would do
28587 in the vast majority of cases when the host of interest is not on any of the
28590 A less inefficient way of solving this problem is available. If
28591 two domain names, comma-separated, are given, the second is used first to
28592 do an initial check, making use of any IP value restrictions that are set.
28593 If there is a match, the first domain is used, without any IP value
28594 restrictions, to get the TXT record. As a byproduct of this, there is also
28595 a check that the IP being tested is indeed on the first list. The first
28596 domain is the one that is put in &$dnslist_domain$&. For example:
28599 rejected because $sender_host_address is blacklisted \
28600 at $dnslist_domain\n$dnslist_text
28602 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
28603 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
28605 For the first blacklist item, this starts by doing a lookup in
28606 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
28607 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
28608 value, and as long as something is found, it looks for the corresponding TXT
28609 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
28610 The second blacklist item is processed similarly.
28612 If you are interested in more than one merged list, the same list must be
28613 given several times, but because the results of the DNS lookups are cached,
28614 the DNS calls themselves are not repeated. For example:
28616 reject dnslists = \
28617 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
28618 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
28619 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
28620 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
28622 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
28623 values matches (or if no record is found), this is the only lookup that is
28624 done. Only if there is a match is one of the more specific lists consulted.
28628 .section "DNS lists and IPv6" "SECTmorednslistslast"
28629 .cindex "IPv6" "DNS black lists"
28630 .cindex "DNS list" "IPv6 usage"
28631 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
28632 nibble by nibble. For example, if the calling host's IP address is
28633 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
28635 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
28636 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
28638 (split over two lines here to fit on the page). Unfortunately, some of the DNS
28639 lists contain wildcard records, intended for IPv4, that interact badly with
28640 IPv6. For example, the DNS entry
28642 *.3.some.list.example. A 127.0.0.1
28644 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
28645 Unfortunately, it also matches the entire 3::/4 IPv6 network.
28647 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
28648 &%condition%& condition, as in this example:
28650 deny condition = ${if isip4{$sender_host_address}}
28651 dnslists = some.list.example
28654 If an explicit key is being used for a DNS lookup and it may be an IPv6
28655 address you should specify alternate list separators for both the outer
28656 (DNS list name) list and inner (lookup keys) list:
28658 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
28661 .section "Rate limiting incoming messages" "SECTratelimiting"
28662 .cindex "rate limiting" "client sending"
28663 .cindex "limiting client sending rates"
28664 .oindex "&%smtp_ratelimit_*%&"
28665 The &%ratelimit%& ACL condition can be used to measure and control the rate at
28666 which clients can send email. This is more powerful than the
28667 &%smtp_ratelimit_*%& options, because those options control the rate of
28668 commands in a single SMTP session only, whereas the &%ratelimit%& condition
28669 works across all connections (concurrent and sequential) from the same client
28670 host. The syntax of the &%ratelimit%& condition is:
28672 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
28674 If the average client sending rate is less than &'m'& messages per time
28675 period &'p'& then the condition is false; otherwise it is true.
28677 As a side-effect, the &%ratelimit%& condition sets the expansion variable
28678 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
28679 configured value of &'m'&, and &$sender_rate_period$& to the configured value
28682 The parameter &'p'& is the smoothing time constant, in the form of an Exim
28683 time interval, for example, &`8h`& for eight hours. A larger time constant
28684 means that it takes Exim longer to forget a client's past behaviour. The
28685 parameter &'m'& is the maximum number of messages that a client is permitted to
28686 send in each time interval. It also specifies the number of messages permitted
28687 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
28688 constant, you can allow a client to send more messages in a burst without
28689 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
28690 both small, messages must be sent at an even rate.
28692 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
28693 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
28694 when deploying the &%ratelimit%& ACL condition. The script prints usage
28695 instructions when it is run with no arguments.
28697 The key is used to look up the data for calculating the client's average
28698 sending rate. This data is stored in Exim's spool directory, alongside the
28699 retry and other hints databases. The default key is &$sender_host_address$&,
28700 which means Exim computes the sending rate of each client host IP address.
28701 By changing the key you can change how Exim identifies clients for the purpose
28702 of ratelimiting. For example, to limit the sending rate of each authenticated
28703 user, independent of the computer they are sending from, set the key to
28704 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
28705 example, &$authenticated_id$& is only meaningful if the client has
28706 authenticated (which you can check with the &%authenticated%& ACL condition).
28708 The lookup key does not have to identify clients: If you want to limit the
28709 rate at which a recipient receives messages, you can use the key
28710 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
28713 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
28714 specifies what Exim measures the rate of, for example messages or recipients
28715 or bytes. You can adjust the measurement using the &%unique=%& and/or
28716 &%count=%& options. You can also control when Exim updates the recorded rate
28717 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
28718 separated by a slash, like the other parameters. They may appear in any order.
28720 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
28721 any options that alter the meaning of the stored data. The limit &'m'& is not
28722 stored, so you can alter the configured maximum rate and Exim will still
28723 remember clients' past behaviour. If you change the &%per_*%& mode or add or
28724 remove the &%unique=%& option, the lookup key changes so Exim will forget past
28725 behaviour. The lookup key is not affected by changes to the update mode and
28726 the &%count=%& option.
28729 .section "Ratelimit options for what is being measured" "ratoptmea"
28730 .cindex "rate limiting" "per_* options"
28731 The &%per_conn%& option limits the client's connection rate. It is not
28732 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
28733 &%acl_not_smtp_start%& ACLs.
28735 The &%per_mail%& option limits the client's rate of sending messages. This is
28736 the default if none of the &%per_*%& options is specified. It can be used in
28737 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
28738 &%acl_smtp_data%&, or &%acl_not_smtp%&.
28740 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
28741 the same ACLs as the &%per_mail%& option, though it is best to use this option
28742 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
28743 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
28744 in its MAIL command, which may be inaccurate or completely missing. You can
28745 follow the limit &'m'& in the configuration with K, M, or G to specify limits
28746 in kilobytes, megabytes, or gigabytes, respectively.
28748 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
28749 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28750 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
28751 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
28752 ACLs the rate is updated with the total recipient count in one go. Note that
28753 in either case the rate limiting engine will see a message with many
28754 recipients as a large high-speed burst.
28756 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
28757 number of different recipients that the client has sent messages to in the
28758 last time period. That is, if the client repeatedly sends messages to the same
28759 recipient, its measured rate is not increased. This option can only be used in
28762 The &%per_cmd%& option causes Exim to recompute the rate every time the
28763 condition is processed. This can be used to limit the rate of any SMTP
28764 command. If it is used in multiple ACLs it can limit the aggregate rate of
28765 multiple different commands.
28767 The &%count=%& option can be used to alter how much Exim adds to the client's
28768 measured rate. For example, the &%per_byte%& option is equivalent to
28769 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
28770 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
28771 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
28773 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
28776 .section "Ratelimit update modes" "ratoptupd"
28777 .cindex "rate limiting" "reading data without updating"
28778 You can specify one of three options with the &%ratelimit%& condition to
28779 control when its database is updated. This section describes the &%readonly%&
28780 mode, and the next section describes the &%strict%& and &%leaky%& modes.
28782 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
28783 previously-computed rate to check against the limit.
28785 For example, you can test the client's sending rate and deny it access (when
28786 it is too fast) in the connect ACL. If the client passes this check then it
28787 can go on to send a message, in which case its recorded rate will be updated
28788 in the MAIL ACL. Subsequent connections from the same client will check this
28792 deny ratelimit = 100 / 5m / readonly
28793 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
28794 (max $sender_rate_limit)
28797 warn ratelimit = 100 / 5m / strict
28798 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
28799 (max $sender_rate_limit)
28802 If Exim encounters multiple &%ratelimit%& conditions with the same key when
28803 processing a message then it may increase the client's measured rate more than
28804 it should. For example, this will happen if you check the &%per_rcpt%& option
28805 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
28806 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
28807 multiple update problems by using the &%readonly%& option on later ratelimit
28810 The &%per_*%& options described above do not make sense in some ACLs. If you
28811 use a &%per_*%& option in an ACL where it is not normally permitted then the
28812 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
28813 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
28814 next section) so you must specify the &%readonly%& option explicitly.
28817 .section "Ratelimit options for handling fast clients" "ratoptfast"
28818 .cindex "rate limiting" "strict and leaky modes"
28819 If a client's average rate is greater than the maximum, the rate limiting
28820 engine can react in two possible ways, depending on the presence of the
28821 &%strict%& or &%leaky%& update modes. This is independent of the other
28822 counter-measures (such as rejecting the message) that may be specified by the
28825 The &%leaky%& (default) option means that the client's recorded rate is not
28826 updated if it is above the limit. The effect of this is that Exim measures the
28827 client's average rate of successfully sent email, which cannot be greater than
28828 the maximum allowed. If the client is over the limit it may suffer some
28829 counter-measures (as specified in the ACL), but it will still be able to send
28830 email at the configured maximum rate, whatever the rate of its attempts. This
28831 is generally the better choice if you have clients that retry automatically.
28832 For example, it does not prevent a sender with an over-aggressive retry rate
28833 from getting any email through.
28835 The &%strict%& option means that the client's recorded rate is always
28836 updated. The effect of this is that Exim measures the client's average rate
28837 of attempts to send email, which can be much higher than the maximum it is
28838 actually allowed. If the client is over the limit it may be subjected to
28839 counter-measures by the ACL. It must slow down and allow sufficient time to
28840 pass that its computed rate falls below the maximum before it can send email
28841 again. The time (the number of smoothing periods) it must wait and not
28842 attempt to send mail can be calculated with this formula:
28844 ln(peakrate/maxrate)
28848 .section "Limiting the rate of different events" "ratoptuniq"
28849 .cindex "rate limiting" "counting unique events"
28850 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
28851 rate of different events. For example, the &%per_addr%& option uses this
28852 mechanism to count the number of different recipients that the client has
28853 sent messages to in the last time period; it is equivalent to
28854 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
28855 measure the rate that a client uses different sender addresses with the
28856 options &`per_mail/unique=$sender_address`&.
28858 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
28859 has seen for that key. The whole set is thrown away when it is older than the
28860 rate smoothing period &'p'&, so each different event is counted at most once
28861 per period. In the &%leaky%& update mode, an event that causes the client to
28862 go over the limit is not added to the set, in the same way that the client's
28863 recorded rate is not updated in the same situation.
28865 When you combine the &%unique=%& and &%readonly%& options, the specific
28866 &%unique=%& value is ignored, and Exim just retrieves the client's stored
28869 The &%unique=%& mechanism needs more space in the ratelimit database than the
28870 other &%ratelimit%& options in order to store the event set. The number of
28871 unique values is potentially as large as the rate limit, so the extra space
28872 required increases with larger limits.
28874 The uniqueification is not perfect: there is a small probability that Exim
28875 will think a new event has happened before. If the sender's rate is less than
28876 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
28877 the measured rate can go above the limit, in which case Exim may under-count
28878 events by a significant margin. Fortunately, if the rate is high enough (2.7
28879 times the limit) that the false positive rate goes above 9%, then Exim will
28880 throw away the over-full event set before the measured rate falls below the
28881 limit. Therefore the only harm should be that exceptionally high sending rates
28882 are logged incorrectly; any countermeasures you configure will be as effective
28886 .section "Using rate limiting" "useratlim"
28887 Exim's other ACL facilities are used to define what counter-measures are taken
28888 when the rate limit is exceeded. This might be anything from logging a warning
28889 (for example, while measuring existing sending rates in order to define
28890 policy), through time delays to slow down fast senders, up to rejecting the
28891 message. For example:
28893 # Log all senders' rates
28894 warn ratelimit = 0 / 1h / strict
28895 log_message = Sender rate $sender_rate / $sender_rate_period
28897 # Slow down fast senders; note the need to truncate $sender_rate
28898 # at the decimal point.
28899 warn ratelimit = 100 / 1h / per_rcpt / strict
28900 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
28901 $sender_rate_limit }s
28903 # Keep authenticated users under control
28904 deny authenticated = *
28905 ratelimit = 100 / 1d / strict / $authenticated_id
28907 # System-wide rate limit
28908 defer message = Sorry, too busy. Try again later.
28909 ratelimit = 10 / 1s / $primary_hostname
28911 # Restrict incoming rate from each host, with a default
28912 # set using a macro and special cases looked up in a table.
28913 defer message = Sender rate exceeds $sender_rate_limit \
28914 messages per $sender_rate_period
28915 ratelimit = ${lookup {$sender_host_address} \
28916 cdb {DB/ratelimits.cdb} \
28917 {$value} {RATELIMIT} }
28919 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
28920 especially with the &%per_rcpt%& option, you may suffer from a performance
28921 bottleneck caused by locking on the ratelimit hints database. Apart from
28922 making your ACLs less complicated, you can reduce the problem by using a
28923 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
28924 this means that Exim will lose its hints data after a reboot (including retry
28925 hints, the callout cache, and ratelimit data).
28929 .section "Address verification" "SECTaddressverification"
28930 .cindex "verifying address" "options for"
28931 .cindex "policy control" "address verification"
28932 Several of the &%verify%& conditions described in section
28933 &<<SECTaclconditions>>& cause addresses to be verified. Section
28934 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
28935 The verification conditions can be followed by options that modify the
28936 verification process. The options are separated from the keyword and from each
28937 other by slashes, and some of them contain parameters. For example:
28939 verify = sender/callout
28940 verify = recipient/defer_ok/callout=10s,defer_ok
28942 The first stage of address verification, which always happens, is to run the
28943 address through the routers, in &"verify mode"&. Routers can detect the
28944 difference between verification and routing for delivery, and their actions can
28945 be varied by a number of generic options such as &%verify%& and &%verify_only%&
28946 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
28947 The available options are as follows:
28950 If the &%callout%& option is specified, successful routing to one or more
28951 remote hosts is followed by a &"callout"& to those hosts as an additional
28952 check. Callouts and their sub-options are discussed in the next section.
28954 If there is a defer error while doing verification routing, the ACL
28955 normally returns &"defer"&. However, if you include &%defer_ok%& in the
28956 options, the condition is forced to be true instead. Note that this is a main
28957 verification option as well as a suboption for callouts.
28959 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
28960 discusses the reporting of sender address verification failures.
28962 The &%success_on_redirect%& option causes verification always to succeed
28963 immediately after a successful redirection. By default, if a redirection
28964 generates just one address, that address is also verified. See further
28965 discussion in section &<<SECTredirwhilveri>>&.
28968 .cindex "verifying address" "differentiating failures"
28969 .vindex "&$recipient_verify_failure$&"
28970 .vindex "&$sender_verify_failure$&"
28971 .vindex "&$acl_verify_message$&"
28972 After an address verification failure, &$acl_verify_message$& contains the
28973 error message that is associated with the failure. It can be preserved by
28976 warn !verify = sender
28977 set acl_m0 = $acl_verify_message
28979 If you are writing your own custom rejection message or log message when
28980 denying access, you can use this variable to include information about the
28981 verification failure.
28983 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
28984 appropriate) contains one of the following words:
28987 &%qualify%&: The address was unqualified (no domain), and the message
28988 was neither local nor came from an exempted host.
28990 &%route%&: Routing failed.
28992 &%mail%&: Routing succeeded, and a callout was attempted; rejection
28993 occurred at or before the MAIL command (that is, on initial
28994 connection, HELO, or MAIL).
28996 &%recipient%&: The RCPT command in a callout was rejected.
28998 &%postmaster%&: The postmaster check in a callout was rejected.
29001 The main use of these variables is expected to be to distinguish between
29002 rejections of MAIL and rejections of RCPT in callouts.
29007 .section "Callout verification" "SECTcallver"
29008 .cindex "verifying address" "by callout"
29009 .cindex "callout" "verification"
29010 .cindex "SMTP" "callout verification"
29011 For non-local addresses, routing verifies the domain, but is unable to do any
29012 checking of the local part. There are situations where some means of verifying
29013 the local part is desirable. One way this can be done is to make an SMTP
29014 &'callback'& to a delivery host for the sender address or a &'callforward'& to
29015 a subsequent host for a recipient address, to see if the host accepts the
29016 address. We use the term &'callout'& to cover both cases. Note that for a
29017 sender address, the callback is not to the client host that is trying to
29018 deliver the message, but to one of the hosts that accepts incoming mail for the
29021 Exim does not do callouts by default. If you want them to happen, you must
29022 request them by setting appropriate options on the &%verify%& condition, as
29023 described below. This facility should be used with care, because it can add a
29024 lot of resource usage to the cost of verifying an address. However, Exim does
29025 cache the results of callouts, which helps to reduce the cost. Details of
29026 caching are in section &<<SECTcallvercache>>&.
29028 Recipient callouts are usually used only between hosts that are controlled by
29029 the same administration. For example, a corporate gateway host could use
29030 callouts to check for valid recipients on an internal mailserver. A successful
29031 callout does not guarantee that a real delivery to the address would succeed;
29032 on the other hand, a failing callout does guarantee that a delivery would fail.
29034 If the &%callout%& option is present on a condition that verifies an address, a
29035 second stage of verification occurs if the address is successfully routed to
29036 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
29037 &(manualroute)& router, where the router specifies the hosts. However, if a
29038 router that does not set up hosts routes to an &(smtp)& transport with a
29039 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
29040 &%hosts_override%& set, its hosts are always used, whether or not the router
29041 supplies a host list.
29043 The port that is used is taken from the transport, if it is specified and is a
29044 remote transport. (For routers that do verification only, no transport need be
29045 specified.) Otherwise, the default SMTP port is used. If a remote transport
29046 specifies an outgoing interface, this is used; otherwise the interface is not
29047 specified. Likewise, the text that is used for the HELO command is taken from
29048 the transport's &%helo_data%& option; if there is no transport, the value of
29049 &$smtp_active_hostname$& is used.
29051 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
29052 test whether a bounce message could be delivered to the sender address. The
29053 following SMTP commands are sent:
29055 &`HELO `&<&'local host name'&>
29057 &`RCPT TO:`&<&'the address to be tested'&>
29060 LHLO is used instead of HELO if the transport's &%protocol%& option is
29063 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
29066 A recipient callout check is similar. By default, it also uses an empty address
29067 for the sender. This default is chosen because most hosts do not make use of
29068 the sender address when verifying a recipient. Using the same address means
29069 that a single cache entry can be used for each recipient. Some sites, however,
29070 do make use of the sender address when verifying. These are catered for by the
29071 &%use_sender%& and &%use_postmaster%& options, described in the next section.
29073 If the response to the RCPT command is a 2&'xx'& code, the verification
29074 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
29075 Exim tries the next host, if any. If there is a problem with all the remote
29076 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
29077 &%callout%& option is given, in which case the condition is forced to succeed.
29079 .cindex "SMTP" "output flushing, disabling for callout"
29080 A callout may take a little time. For this reason, Exim normally flushes SMTP
29081 output before performing a callout in an ACL, to avoid unexpected timeouts in
29082 clients when the SMTP PIPELINING extension is in use. The flushing can be
29083 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
29088 .section "Additional parameters for callouts" "CALLaddparcall"
29089 .cindex "callout" "additional parameters for"
29090 The &%callout%& option can be followed by an equals sign and a number of
29091 optional parameters, separated by commas. For example:
29093 verify = recipient/callout=10s,defer_ok
29095 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
29096 separate verify options, is retained for backwards compatibility, but is now
29097 deprecated. The additional parameters for &%callout%& are as follows:
29101 .vitem <&'a&~time&~interval'&>
29102 .cindex "callout" "timeout, specifying"
29103 This specifies the timeout that applies for the callout attempt to each host.
29106 verify = sender/callout=5s
29108 The default is 30 seconds. The timeout is used for each response from the
29109 remote host. It is also used for the initial connection, unless overridden by
29110 the &%connect%& parameter.
29113 .vitem &*connect&~=&~*&<&'time&~interval'&>
29114 .cindex "callout" "connection timeout, specifying"
29115 This parameter makes it possible to set a different (usually smaller) timeout
29116 for making the SMTP connection. For example:
29118 verify = sender/callout=5s,connect=1s
29120 If not specified, this timeout defaults to the general timeout value.
29122 .vitem &*defer_ok*&
29123 .cindex "callout" "defer, action on"
29124 When this parameter is present, failure to contact any host, or any other kind
29125 of temporary error, is treated as success by the ACL. However, the cache is not
29126 updated in this circumstance.
29128 .vitem &*fullpostmaster*&
29129 .cindex "callout" "full postmaster check"
29130 This operates like the &%postmaster%& option (see below), but if the check for
29131 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
29132 accordance with the specification in RFC 2821. The RFC states that the
29133 unqualified address &'postmaster'& should be accepted.
29136 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
29137 .cindex "callout" "sender when verifying header"
29138 When verifying addresses in header lines using the &%header_sender%&
29139 verification option, Exim behaves by default as if the addresses are envelope
29140 sender addresses from a message. Callout verification therefore tests to see
29141 whether a bounce message could be delivered, by using an empty address in the
29142 MAIL command. However, it is arguable that these addresses might never be used
29143 as envelope senders, and could therefore justifiably reject bounce messages
29144 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
29145 address to use in the MAIL command. For example:
29147 require verify = header_sender/callout=mailfrom=abcd@x.y.z
29149 This parameter is available only for the &%header_sender%& verification option.
29152 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
29153 .cindex "callout" "overall timeout, specifying"
29154 This parameter sets an overall timeout for performing a callout verification.
29157 verify = sender/callout=5s,maxwait=30s
29159 This timeout defaults to four times the callout timeout for individual SMTP
29160 commands. The overall timeout applies when there is more than one host that can
29161 be tried. The timeout is checked before trying the next host. This prevents
29162 very long delays if there are a large number of hosts and all are timing out
29163 (for example, when network connections are timing out).
29166 .vitem &*no_cache*&
29167 .cindex "callout" "cache, suppressing"
29168 .cindex "caching callout, suppressing"
29169 When this parameter is given, the callout cache is neither read nor updated.
29171 .vitem &*postmaster*&
29172 .cindex "callout" "postmaster; checking"
29173 When this parameter is set, a successful callout check is followed by a similar
29174 check for the local part &'postmaster'& at the same domain. If this address is
29175 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
29176 the postmaster check is recorded in a cache record; if it is a failure, this is
29177 used to fail subsequent callouts for the domain without a connection being
29178 made, until the cache record expires.
29180 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
29181 The postmaster check uses an empty sender in the MAIL command by default.
29182 You can use this parameter to do a postmaster check using a different address.
29185 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
29187 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
29188 one overrides. The &%postmaster%& parameter is equivalent to this example:
29190 require verify = sender/callout=postmaster_mailfrom=
29192 &*Warning*&: The caching arrangements for postmaster checking do not take
29193 account of the sender address. It is assumed that either the empty address or
29194 a fixed non-empty address will be used. All that Exim remembers is that the
29195 postmaster check for the domain succeeded or failed.
29199 .cindex "callout" "&""random""& check"
29200 When this parameter is set, before doing the normal callout check, Exim does a
29201 check for a &"random"& local part at the same domain. The local part is not
29202 really random &-- it is defined by the expansion of the option
29203 &%callout_random_local_part%&, which defaults to
29205 $primary_hostname-$tod_epoch-testing
29207 The idea here is to try to determine whether the remote host accepts all local
29208 parts without checking. If it does, there is no point in doing callouts for
29209 specific local parts. If the &"random"& check succeeds, the result is saved in
29210 a cache record, and used to force the current and subsequent callout checks to
29211 succeed without a connection being made, until the cache record expires.
29213 .vitem &*use_postmaster*&
29214 .cindex "callout" "sender for recipient check"
29215 This parameter applies to recipient callouts only. For example:
29217 deny !verify = recipient/callout=use_postmaster
29219 .vindex "&$qualify_domain$&"
29220 It causes a non-empty postmaster address to be used in the MAIL command when
29221 performing the callout for the recipient, and also for a &"random"& check if
29222 that is configured. The local part of the address is &`postmaster`& and the
29223 domain is the contents of &$qualify_domain$&.
29225 .vitem &*use_sender*&
29226 This option applies to recipient callouts only. For example:
29228 require verify = recipient/callout=use_sender
29230 It causes the message's actual sender address to be used in the MAIL
29231 command when performing the callout, instead of an empty address. There is no
29232 need to use this option unless you know that the called hosts make use of the
29233 sender when checking recipients. If used indiscriminately, it reduces the
29234 usefulness of callout caching.
29237 If you use any of the parameters that set a non-empty sender for the MAIL
29238 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
29239 &%use_sender%&), you should think about possible loops. Recipient checking is
29240 usually done between two hosts that are under the same management, and the host
29241 that receives the callouts is not normally configured to do callouts itself.
29242 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
29243 these circumstances.
29245 However, if you use a non-empty sender address for a callout to an arbitrary
29246 host, there is the likelihood that the remote host will itself initiate a
29247 callout check back to your host. As it is checking what appears to be a message
29248 sender, it is likely to use an empty address in MAIL, thus avoiding a
29249 callout loop. However, to be on the safe side it would be best to set up your
29250 own ACLs so that they do not do sender verification checks when the recipient
29251 is the address you use for header sender or postmaster callout checking.
29253 Another issue to think about when using non-empty senders for callouts is
29254 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
29255 by the sender/recipient combination; thus, for any given recipient, many more
29256 actual callouts are performed than when an empty sender or postmaster is used.
29261 .section "Callout caching" "SECTcallvercache"
29262 .cindex "hints database" "callout cache"
29263 .cindex "callout" "cache, description of"
29264 .cindex "caching" "callout"
29265 Exim caches the results of callouts in order to reduce the amount of resources
29266 used, unless you specify the &%no_cache%& parameter with the &%callout%&
29267 option. A hints database called &"callout"& is used for the cache. Two
29268 different record types are used: one records the result of a callout check for
29269 a specific address, and the other records information that applies to the
29270 entire domain (for example, that it accepts the local part &'postmaster'&).
29272 When an original callout fails, a detailed SMTP error message is given about
29273 the failure. However, for subsequent failures use the cache data, this message
29276 The expiry times for negative and positive address cache records are
29277 independent, and can be set by the global options &%callout_negative_expire%&
29278 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
29280 If a host gives a negative response to an SMTP connection, or rejects any
29281 commands up to and including
29285 (but not including the MAIL command with a non-empty address),
29286 any callout attempt is bound to fail. Exim remembers such failures in a
29287 domain cache record, which it uses to fail callouts for the domain without
29288 making new connections, until the domain record times out. There are two
29289 separate expiry times for domain cache records:
29290 &%callout_domain_negative_expire%& (default 3h) and
29291 &%callout_domain_positive_expire%& (default 7d).
29293 Domain records expire when the negative expiry time is reached if callouts
29294 cannot be made for the domain, or if the postmaster check failed.
29295 Otherwise, they expire when the positive expiry time is reached. This
29296 ensures that, for example, a host that stops accepting &"random"& local parts
29297 will eventually be noticed.
29299 The callout caching mechanism is based on the domain of the address that is
29300 being tested. If the domain routes to several hosts, it is assumed that their
29301 behaviour will be the same.
29305 .section "Sender address verification reporting" "SECTsenaddver"
29306 .cindex "verifying" "suppressing error details"
29307 See section &<<SECTaddressverification>>& for a general discussion of
29308 verification. When sender verification fails in an ACL, the details of the
29309 failure are given as additional output lines before the 550 response to the
29310 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
29313 MAIL FROM:<xyz@abc.example>
29315 RCPT TO:<pqr@def.example>
29316 550-Verification failed for <xyz@abc.example>
29317 550-Called: 192.168.34.43
29318 550-Sent: RCPT TO:<xyz@abc.example>
29319 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
29320 550 Sender verification failed
29322 If more than one RCPT command fails in the same way, the details are given
29323 only for the first of them. However, some administrators do not want to send
29324 out this much information. You can suppress the details by adding
29325 &`/no_details`& to the ACL statement that requests sender verification. For
29328 verify = sender/no_details
29331 .section "Redirection while verifying" "SECTredirwhilveri"
29332 .cindex "verifying" "redirection while"
29333 .cindex "address redirection" "while verifying"
29334 A dilemma arises when a local address is redirected by aliasing or forwarding
29335 during verification: should the generated addresses themselves be verified,
29336 or should the successful expansion of the original address be enough to verify
29337 it? By default, Exim takes the following pragmatic approach:
29340 When an incoming address is redirected to just one child address, verification
29341 continues with the child address, and if that fails to verify, the original
29342 verification also fails.
29344 When an incoming address is redirected to more than one child address,
29345 verification does not continue. A success result is returned.
29348 This seems the most reasonable behaviour for the common use of aliasing as a
29349 way of redirecting different local parts to the same mailbox. It means, for
29350 example, that a pair of alias entries of the form
29353 aw123: :fail: Gone away, no forwarding address
29355 work as expected, with both local parts causing verification failure. When a
29356 redirection generates more than one address, the behaviour is more like a
29357 mailing list, where the existence of the alias itself is sufficient for
29358 verification to succeed.
29360 It is possible, however, to change the default behaviour so that all successful
29361 redirections count as successful verifications, however many new addresses are
29362 generated. This is specified by the &%success_on_redirect%& verification
29363 option. For example:
29365 require verify = recipient/success_on_redirect/callout=10s
29367 In this example, verification succeeds if a router generates a new address, and
29368 the callout does not occur, because no address was routed to a remote host.
29370 When verification is being tested via the &%-bv%& option, the treatment of
29371 redirections is as just described, unless the &%-v%& or any debugging option is
29372 also specified. In that case, full verification is done for every generated
29373 address and a report is output for each of them.
29377 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
29378 .cindex "CSA" "verifying"
29379 Client SMTP Authorization is a system that allows a site to advertise
29380 which machines are and are not permitted to send email. This is done by placing
29381 special SRV records in the DNS; these are looked up using the client's HELO
29382 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
29383 Authorization checks in Exim are performed by the ACL condition:
29387 This fails if the client is not authorized. If there is a DNS problem, or if no
29388 valid CSA SRV record is found, or if the client is authorized, the condition
29389 succeeds. These three cases can be distinguished using the expansion variable
29390 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
29391 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
29392 be likely to cause problems for legitimate email.
29394 The error messages produced by the CSA code include slightly more
29395 detail. If &$csa_status$& is &"defer"&, this may be because of problems
29396 looking up the CSA SRV record, or problems looking up the CSA target
29397 address record. There are four reasons for &$csa_status$& being &"fail"&:
29400 The client's host name is explicitly not authorized.
29402 The client's IP address does not match any of the CSA target IP addresses.
29404 The client's host name is authorized but it has no valid target IP addresses
29405 (for example, the target's addresses are IPv6 and the client is using IPv4).
29407 The client's host name has no CSA SRV record but a parent domain has asserted
29408 that all subdomains must be explicitly authorized.
29411 The &%csa%& verification condition can take an argument which is the domain to
29412 use for the DNS query. The default is:
29414 verify = csa/$sender_helo_name
29416 This implementation includes an extension to CSA. If the query domain
29417 is an address literal such as [192.0.2.95], or if it is a bare IP
29418 address, Exim searches for CSA SRV records in the reverse DNS as if
29419 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
29422 verify = csa/$sender_host_address
29424 In fact, this is the check that Exim performs if the client does not say HELO.
29425 This extension can be turned off by setting the main configuration option
29426 &%dns_csa_use_reverse%& to be false.
29428 If a CSA SRV record is not found for the domain itself, a search
29429 is performed through its parent domains for a record which might be
29430 making assertions about subdomains. The maximum depth of this search is limited
29431 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
29432 default. Exim does not look for CSA SRV records in a top level domain, so the
29433 default settings handle HELO domains as long as seven
29434 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
29435 of legitimate HELO domains.
29437 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
29438 direct SRV lookups, this is not sufficient because of the extra parent domain
29439 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
29440 addresses into lookups in the reverse DNS space. The result of a successful
29443 ${lookup dnsdb {csa=$sender_helo_name}}
29445 has two space-separated fields: an authorization code and a target host name.
29446 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
29447 authorization required but absent, or &"?"& for unknown.
29452 .section "Bounce address tag validation" "SECTverifyPRVS"
29453 .cindex "BATV, verifying"
29454 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
29455 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
29456 Genuine incoming bounce messages should therefore always be addressed to
29457 recipients that have a valid tag. This scheme is a way of detecting unwanted
29458 bounce messages caused by sender address forgeries (often called &"collateral
29459 spam"&), because the recipients of such messages do not include valid tags.
29461 There are two expansion items to help with the implementation of the BATV
29462 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
29463 the original envelope sender address by using a simple key to add a hash of the
29464 address and some time-based randomizing information. The &%prvs%& expansion
29465 item creates a signed address, and the &%prvscheck%& expansion item checks one.
29466 The syntax of these expansion items is described in section
29467 &<<SECTexpansionitems>>&.
29469 As an example, suppose the secret per-address keys are stored in an MySQL
29470 database. A query to look up the key for an address could be defined as a macro
29473 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
29474 WHERE sender='${quote_mysql:$prvscheck_address}'\
29477 Suppose also that the senders who make use of BATV are defined by an address
29478 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
29481 # Bounces: drop unsigned addresses for BATV senders
29482 deny message = This address does not send an unsigned reverse path
29484 recipients = +batv_senders
29486 # Bounces: In case of prvs-signed address, check signature.
29487 deny message = Invalid reverse path signature.
29489 condition = ${prvscheck {$local_part@$domain}\
29490 {PRVSCHECK_SQL}{1}}
29491 !condition = $prvscheck_result
29493 The first statement rejects recipients for bounce messages that are addressed
29494 to plain BATV sender addresses, because it is known that BATV senders do not
29495 send out messages with plain sender addresses. The second statement rejects
29496 recipients that are prvs-signed, but with invalid signatures (either because
29497 the key is wrong, or the signature has timed out).
29499 A non-prvs-signed address is not rejected by the second statement, because the
29500 &%prvscheck%& expansion yields an empty string if its first argument is not a
29501 prvs-signed address, thus causing the &%condition%& condition to be false. If
29502 the first argument is a syntactically valid prvs-signed address, the yield is
29503 the third string (in this case &"1"&), whether or not the cryptographic and
29504 timeout checks succeed. The &$prvscheck_result$& variable contains the result
29505 of the checks (empty for failure, &"1"& for success).
29507 There is one more issue you must consider when implementing prvs-signing:
29508 you have to ensure that the routers accept prvs-signed addresses and
29509 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
29510 router to remove the signature with a configuration along these lines:
29514 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
29516 This works because, if the third argument of &%prvscheck%& is empty, the result
29517 of the expansion of a prvs-signed address is the decoded value of the original
29518 address. This router should probably be the first of your routers that handles
29521 To create BATV-signed addresses in the first place, a transport of this form
29524 external_smtp_batv:
29526 return_path = ${prvs {$return_path} \
29527 {${lookup mysql{SELECT \
29528 secret FROM batv_prvs WHERE \
29529 sender='${quote_mysql:$sender_address}'} \
29532 If no key can be found for the existing return path, no signing takes place.
29536 .section "Using an ACL to control relaying" "SECTrelaycontrol"
29537 .cindex "&ACL;" "relay control"
29538 .cindex "relaying" "control by ACL"
29539 .cindex "policy control" "relay control"
29540 An MTA is said to &'relay'& a message if it receives it from some host and
29541 delivers it directly to another host as a result of a remote address contained
29542 within it. Redirecting a local address via an alias or forward file and then
29543 passing the message on to another host is not relaying,
29544 .cindex "&""percent hack""&"
29545 but a redirection as a result of the &"percent hack"& is.
29547 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
29548 A host which is acting as a gateway or an MX backup is concerned with incoming
29549 relaying from arbitrary hosts to a specific set of domains. On the other hand,
29550 a host which is acting as a smart host for a number of clients is concerned
29551 with outgoing relaying from those clients to the Internet at large. Often the
29552 same host is fulfilling both functions,
29554 . as illustrated in the diagram below,
29556 but in principle these two kinds of relaying are entirely independent. What is
29557 not wanted is the transmission of mail from arbitrary remote hosts through your
29558 system to arbitrary domains.
29561 You can implement relay control by means of suitable statements in the ACL that
29562 runs for each RCPT command. For convenience, it is often easiest to use
29563 Exim's named list facility to define the domains and hosts involved. For
29564 example, suppose you want to do the following:
29567 Deliver a number of domains to mailboxes on the local host (or process them
29568 locally in some other way). Let's say these are &'my.dom1.example'& and
29569 &'my.dom2.example'&.
29571 Relay mail for a number of other domains for which you are the secondary MX.
29572 These might be &'friend1.example'& and &'friend2.example'&.
29574 Relay mail from the hosts on your local LAN, to whatever domains are involved.
29575 Suppose your LAN is 192.168.45.0/24.
29579 In the main part of the configuration, you put the following definitions:
29581 domainlist local_domains = my.dom1.example : my.dom2.example
29582 domainlist relay_to_domains = friend1.example : friend2.example
29583 hostlist relay_from_hosts = 192.168.45.0/24
29585 Now you can use these definitions in the ACL that is run for every RCPT
29589 accept domains = +local_domains : +relay_to_domains
29590 accept hosts = +relay_from_hosts
29592 The first statement accepts any RCPT command that contains an address in
29593 the local or relay domains. For any other domain, control passes to the second
29594 statement, which accepts the command only if it comes from one of the relay
29595 hosts. In practice, you will probably want to make your ACL more sophisticated
29596 than this, for example, by including sender and recipient verification. The
29597 default configuration includes a more comprehensive example, which is described
29598 in chapter &<<CHAPdefconfil>>&.
29602 .section "Checking a relay configuration" "SECTcheralcon"
29603 .cindex "relaying" "checking control of"
29604 You can check the relay characteristics of your configuration in the same way
29605 that you can test any ACL behaviour for an incoming SMTP connection, by using
29606 the &%-bh%& option to run a fake SMTP session with which you interact.
29608 For specifically testing for unwanted relaying, the host
29609 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
29610 host from the host on which Exim is running, using the normal telnet port, you
29611 will see a normal telnet connection message and then quite a long delay. Be
29612 patient. The remote host is making an SMTP connection back to your host, and
29613 trying a number of common probes to test for open relay vulnerability. The
29614 results of the tests will eventually appear on your terminal.
29619 . ////////////////////////////////////////////////////////////////////////////
29620 . ////////////////////////////////////////////////////////////////////////////
29622 .chapter "Content scanning at ACL time" "CHAPexiscan"
29623 .scindex IIDcosca "content scanning" "at ACL time"
29624 The extension of Exim to include content scanning at ACL time, formerly known
29625 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
29626 was integrated into the main source for Exim release 4.50, and Tom continues to
29627 maintain it. Most of the wording of this chapter is taken from Tom's
29630 It is also possible to scan the content of messages at other times. The
29631 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
29632 scanning after all the ACLs have run. A transport filter can be used to scan
29633 messages at delivery time (see the &%transport_filter%& option, described in
29634 chapter &<<CHAPtransportgeneric>>&).
29636 If you want to include the ACL-time content-scanning features when you compile
29637 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
29638 &_Local/Makefile_&. When you do that, the Exim binary is built with:
29641 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
29642 for all MIME parts for SMTP and non-SMTP messages, respectively.
29644 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
29645 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
29646 run at the end of message reception (the &%acl_smtp_data%& ACL).
29648 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
29649 of messages, or parts of messages, for debugging purposes.
29651 Additional expansion variables that are set in the new ACL and by the new
29654 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
29657 There is another content-scanning configuration option for &_Local/Makefile_&,
29658 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
29659 condition is compiled, in addition to all the other content-scanning features.
29661 Content-scanning is continually evolving, and new features are still being
29662 added. While such features are still unstable and liable to incompatible
29663 changes, they are made available in Exim by setting options whose names begin
29664 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
29665 this manual. You can find out about them by reading the file called
29666 &_doc/experimental.txt_&.
29668 All the content-scanning facilities work on a MBOX copy of the message that is
29669 temporarily created in a file called:
29671 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
29673 The &_.eml_& extension is a friendly hint to virus scanners that they can
29674 expect an MBOX-like structure inside that file. The file is created when the
29675 first content scanning facility is called. Subsequent calls to content
29676 scanning conditions open the same file again. The directory is recursively
29677 removed when the &%acl_smtp_data%& ACL has finished running, unless
29679 control = no_mbox_unspool
29681 has been encountered. When the MIME ACL decodes files, they are put into the
29682 same directory by default.
29686 .section "Scanning for viruses" "SECTscanvirus"
29687 .cindex "virus scanning"
29688 .cindex "content scanning" "for viruses"
29689 .cindex "content scanning" "the &%malware%& condition"
29690 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
29691 It supports a &"generic"& interface to scanners called via the shell, and
29692 specialized interfaces for &"daemon"& type virus scanners, which are resident
29693 in memory and thus are much faster.
29696 .oindex "&%av_scanner%&"
29697 You can set the &%av_scanner%& option in first part of the Exim configuration
29698 file to specify which scanner to use, together with any additional options that
29699 are needed. The basic syntax is as follows:
29701 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
29703 If you do not set &%av_scanner%&, it defaults to
29705 av_scanner = sophie:/var/run/sophie
29707 If the value of &%av_scanner%& starts with a dollar character, it is expanded
29709 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
29710 The following scanner types are supported in this release:
29713 .vitem &%aveserver%&
29714 .cindex "virus scanners" "Kaspersky"
29715 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
29716 at &url(http://www.kaspersky.com). This scanner type takes one option,
29717 which is the path to the daemon's UNIX socket. The default is shown in this
29720 av_scanner = aveserver:/var/run/aveserver
29725 .cindex "virus scanners" "clamd"
29726 This daemon-type scanner is GPL and free. You can get it at
29727 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
29728 unpack MIME containers, so it used to be recommended to unpack MIME attachments
29729 in the MIME ACL. This no longer believed to be necessary. One option is
29730 required: either the path and name of a UNIX socket file, or a hostname or IP
29731 number, and a port, separated by space, as in the second of these examples:
29733 av_scanner = clamd:/opt/clamd/socket
29734 av_scanner = clamd:192.0.2.3 1234
29735 av_scanner = clamd:192.0.2.3 1234:local
29736 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
29738 If the value of av_scanner points to a UNIX socket file or contains the local
29739 keyword, then the ClamAV interface will pass a filename containing the data
29740 to be scanned, which will should normally result in less I/O happening and be
29741 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
29742 Exim does not assume that there is a common filesystem with the remote host.
29743 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
29744 you be running a version of ClamAV prior to 0.95.
29746 The final example shows that multiple TCP targets can be specified. Exim will
29747 randomly use one for each incoming email (i.e. it load balances them). Note
29748 that only TCP targets may be used if specifying a list of scanners; a UNIX
29749 socket cannot be mixed in with TCP targets. If one of the servers becomes
29750 unavailable, Exim will try the remaining one(s) until it finds one that works.
29751 When a clamd server becomes unreachable, Exim will log a message. Exim does
29752 not keep track of scanner state between multiple messages, and the scanner
29753 selection is random, so the message will get logged in the mainlog for each
29754 email that the down scanner gets chosen first (message wrapped to be readable):
29756 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
29757 clamd: connection to localhost, port 3310 failed
29758 (Connection refused)
29761 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
29762 contributing the code for this scanner.
29765 .cindex "virus scanners" "command line interface"
29766 This is the keyword for the generic command line scanner interface. It can be
29767 used to attach virus scanners that are invoked from the shell. This scanner
29768 type takes 3 mandatory options:
29771 The full path and name of the scanner binary, with all command line options,
29772 and a placeholder (&`%s`&) for the directory to scan.
29775 A regular expression to match against the STDOUT and STDERR output of the
29776 virus scanner. If the expression matches, a virus was found. You must make
29777 absolutely sure that this expression matches on &"virus found"&. This is called
29778 the &"trigger"& expression.
29781 Another regular expression, containing exactly one pair of parentheses, to
29782 match the name of the virus found in the scanners output. This is called the
29783 &"name"& expression.
29786 For example, Sophos Sweep reports a virus on a line like this:
29788 Virus 'W32/Magistr-B' found in file ./those.bat
29790 For the trigger expression, we can match the phrase &"found in file"&. For the
29791 name expression, we want to extract the W32/Magistr-B string, so we can match
29792 for the single quotes left and right of it. Altogether, this makes the
29793 configuration setting:
29795 av_scanner = cmdline:\
29796 /path/to/sweep -ss -all -rec -archive %s:\
29797 found in file:'(.+)'
29800 .cindex "virus scanners" "DrWeb"
29801 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
29802 argument, either a full path to a UNIX socket, or an IP address and port
29803 separated by white space, as in these examples:
29805 av_scanner = drweb:/var/run/drwebd.sock
29806 av_scanner = drweb:192.168.2.20 31337
29808 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
29809 is used. Thanks to Alex Miller for contributing the code for this scanner.
29812 .cindex "virus scanners" "F-Secure"
29813 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
29814 argument which is the path to a UNIX socket. For example:
29816 av_scanner = fsecure:/path/to/.fsav
29818 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
29819 Thelmen for contributing the code for this scanner.
29821 .vitem &%kavdaemon%&
29822 .cindex "virus scanners" "Kaspersky"
29823 This is the scanner daemon of Kaspersky Version 4. This version of the
29824 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
29825 scanner type takes one option, which is the path to the daemon's UNIX socket.
29828 av_scanner = kavdaemon:/opt/AVP/AvpCtl
29830 The default path is &_/var/run/AvpCtl_&.
29833 .cindex "virus scanners" "mksd"
29834 This is a daemon type scanner that is aimed mainly at Polish users, though some
29835 parts of documentation are now available in English. You can get it at
29836 &url(http://linux.mks.com.pl/). The only option for this scanner type is
29837 the maximum number of processes used simultaneously to scan the attachments,
29838 provided that the demime facility is employed and also provided that mksd has
29839 been run with at least the same number of child processes. For example:
29841 av_scanner = mksd:2
29843 You can safely omit this option (the default value is 1).
29846 .cindex "virus scanners" "simple socket-connected"
29847 This is a general-purpose way of talking to simple scanner daemons
29848 running on the local machine.
29849 There are four options:
29850 an address (which may be an IP addres and port, or the path of a Unix socket),
29851 a commandline to send (may include a single %s which will be replaced with
29852 the path to the mail file to be scanned),
29853 an RE to trigger on from the returned data,
29854 an RE to extract malware_name from the returned data.
29857 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
29859 Default for the socket specifier is &_/tmp/malware.sock_&.
29860 Default for the commandline is &_%s\n_&.
29861 Both regular-expressions are required.
29864 .cindex "virus scanners" "Sophos and Sophie"
29865 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
29866 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
29867 for this scanner type is the path to the UNIX socket that Sophie uses for
29868 client communication. For example:
29870 av_scanner = sophie:/tmp/sophie
29872 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
29876 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
29877 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
29880 The &%av_scanner%& option is expanded each time &%malware%& is called. This
29881 makes it possible to use different scanners. See further below for an example.
29882 The &%malware%& condition caches its results, so when you use it multiple times
29883 for the same message, the actual scanning process is only carried out once.
29884 However, using expandable items in &%av_scanner%& disables this caching, in
29885 which case each use of the &%malware%& condition causes a new scan of the
29888 The &%malware%& condition takes a right-hand argument that is expanded before
29889 use. It can then be one of
29892 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
29893 The condition succeeds if a virus was found, and fail otherwise. This is the
29896 &"false"& or &"0"& or an empty string, in which case no scanning is done and
29897 the condition fails immediately.
29899 A regular expression, in which case the message is scanned for viruses. The
29900 condition succeeds if a virus is found and its name matches the regular
29901 expression. This allows you to take special actions on certain types of virus.
29904 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
29905 even if there is a problem with the virus scanner. Otherwise, such a problem
29906 causes the ACL to defer.
29908 .vindex "&$malware_name$&"
29909 When a virus is found, the condition sets up an expansion variable called
29910 &$malware_name$& that contains the name of the virus. You can use it in a
29911 &%message%& modifier that specifies the error returned to the sender, and/or in
29914 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
29915 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
29916 &%malware%& condition.
29918 Beware the interaction of Exim's &%message_size_limit%& with any size limits
29919 imposed by your anti-virus scanner.
29921 Here is a very simple scanning example:
29923 deny message = This message contains malware ($malware_name)
29927 The next example accepts messages when there is a problem with the scanner:
29929 deny message = This message contains malware ($malware_name)
29931 malware = */defer_ok
29933 The next example shows how to use an ACL variable to scan with both sophie and
29934 aveserver. It assumes you have set:
29936 av_scanner = $acl_m0
29938 in the main Exim configuration.
29940 deny message = This message contains malware ($malware_name)
29941 set acl_m0 = sophie
29944 deny message = This message contains malware ($malware_name)
29945 set acl_m0 = aveserver
29950 .section "Scanning with SpamAssassin" "SECTscanspamass"
29951 .cindex "content scanning" "for spam"
29952 .cindex "spam scanning"
29953 .cindex "SpamAssassin"
29954 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
29955 score and a report for the message. You can get SpamAssassin at
29956 &url(http://www.spamassassin.org), or, if you have a working Perl
29957 installation, you can use CPAN by running:
29959 perl -MCPAN -e 'install Mail::SpamAssassin'
29961 SpamAssassin has its own set of configuration files. Please review its
29962 documentation to see how you can tweak it. The default installation should work
29965 .oindex "&%spamd_address%&"
29966 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
29967 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
29968 port for &%spamd%&, you must set the &%spamd_address%& option in the global
29969 part of the Exim configuration as follows (example):
29971 spamd_address = 192.168.99.45 387
29973 You do not need to set this option if you use the default. As of version 2.60,
29974 &%spamd%& also supports communication over UNIX sockets. If you want to use
29975 these, supply &%spamd_address%& with an absolute file name instead of a
29978 spamd_address = /var/run/spamd_socket
29980 You can have multiple &%spamd%& servers to improve scalability. These can
29981 reside on other hardware reachable over the network. To specify multiple
29982 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
29983 option, separated with colons:
29985 spamd_address = 192.168.2.10 783 : \
29986 192.168.2.11 783 : \
29989 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
29990 fashion. When a server fails to respond to the connection attempt, all other
29991 servers are tried until one succeeds. If no server responds, the &%spam%&
29994 &*Warning*&: It is not possible to use the UNIX socket connection method with
29995 multiple &%spamd%& servers.
29997 The &%spamd_address%& variable is expanded before use if it starts with
29998 a dollar sign. In this case, the expansion may return a string that is
29999 used as the list so that multiple spamd servers can be the result of an
30002 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
30003 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
30005 deny message = This message was classified as SPAM
30008 The right-hand side of the &%spam%& condition specifies a name. This is
30009 relevant if you have set up multiple SpamAssassin profiles. If you do not want
30010 to scan using a specific profile, but rather use the SpamAssassin system-wide
30011 default profile, you can scan for an unknown name, or simply use &"nobody"&.
30012 However, you must put something on the right-hand side.
30014 The name allows you to use per-domain or per-user antispam profiles in
30015 principle, but this is not straightforward in practice, because a message may
30016 have multiple recipients, not necessarily all in the same domain. Because the
30017 &%spam%& condition has to be called from a DATA ACL in order to be able to
30018 read the contents of the message, the variables &$local_part$& and &$domain$&
30021 The right-hand side of the &%spam%& condition is expanded before being used, so
30022 you can put lookups or conditions there. When the right-hand side evaluates to
30023 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
30026 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
30027 large ones may cause significant performance degradation. As most spam messages
30028 are quite small, it is recommended that you do not scan the big ones. For
30031 deny message = This message was classified as SPAM
30032 condition = ${if < {$message_size}{10K}}
30036 The &%spam%& condition returns true if the threshold specified in the user's
30037 SpamAssassin profile has been matched or exceeded. If you want to use the
30038 &%spam%& condition for its side effects (see the variables below), you can make
30039 it always return &"true"& by appending &`:true`& to the username.
30041 .cindex "spam scanning" "returned variables"
30042 When the &%spam%& condition is run, it sets up a number of expansion
30043 variables. These variables are saved with the received message, thus they are
30044 available for use at delivery time.
30047 .vitem &$spam_score$&
30048 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
30049 for inclusion in log or reject messages.
30051 .vitem &$spam_score_int$&
30052 The spam score of the message, multiplied by ten, as an integer value. For
30053 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
30054 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
30055 The integer value is useful for numeric comparisons in conditions.
30057 .vitem &$spam_bar$&
30058 A string consisting of a number of &"+"& or &"-"& characters, representing the
30059 integer part of the spam score value. A spam score of 4.4 would have a
30060 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
30061 headers, since MUAs can match on such strings.
30063 .vitem &$spam_report$&
30064 A multiline text table, containing the full SpamAssassin report for the
30065 message. Useful for inclusion in headers or reject messages.
30068 The &%spam%& condition caches its results unless expansion in
30069 spamd_address was used. If you call it again with the same user name, it
30070 does not scan again, but rather returns the same values as before.
30072 The &%spam%& condition returns DEFER if there is any error while running
30073 the message through SpamAssassin or if the expansion of spamd_address
30074 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
30075 statement block), append &`/defer_ok`& to the right-hand side of the
30076 spam condition, like this:
30078 deny message = This message was classified as SPAM
30079 spam = joe/defer_ok
30081 This causes messages to be accepted even if there is a problem with &%spamd%&.
30083 Here is a longer, commented example of the use of the &%spam%&
30086 # put headers in all messages (no matter if spam or not)
30087 warn spam = nobody:true
30088 add_header = X-Spam-Score: $spam_score ($spam_bar)
30089 add_header = X-Spam-Report: $spam_report
30091 # add second subject line with *SPAM* marker when message
30092 # is over threshold
30094 add_header = Subject: *SPAM* $h_Subject:
30096 # reject spam at high scores (> 12)
30097 deny message = This message scored $spam_score spam points.
30099 condition = ${if >{$spam_score_int}{120}{1}{0}}
30104 .section "Scanning MIME parts" "SECTscanmimepart"
30105 .cindex "content scanning" "MIME parts"
30106 .cindex "MIME content scanning"
30107 .oindex "&%acl_smtp_mime%&"
30108 .oindex "&%acl_not_smtp_mime%&"
30109 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
30110 each MIME part of an SMTP message, including multipart types, in the sequence
30111 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
30112 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
30113 options may both refer to the same ACL if you want the same processing in both
30116 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
30117 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
30118 the case of a non-SMTP message. However, a MIME ACL is called only if the
30119 message contains a &'Content-Type:'& header line. When a call to a MIME
30120 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
30121 result code is sent to the client. In the case of an SMTP message, the
30122 &%acl_smtp_data%& ACL is not called when this happens.
30124 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
30125 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
30126 condition to match against the raw MIME part. You can also use the
30127 &%mime_regex%& condition to match against the decoded MIME part (see section
30128 &<<SECTscanregex>>&).
30130 At the start of a MIME ACL, a number of variables are set from the header
30131 information for the relevant MIME part. These are described below. The contents
30132 of the MIME part are not by default decoded into a disk file except for MIME
30133 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
30134 part into a disk file, you can use the &%decode%& condition. The general
30137 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
30139 The right hand side is expanded before use. After expansion,
30143 &"0"& or &"false"&, in which case no decoding is done.
30145 The string &"default"&. In that case, the file is put in the temporary
30146 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
30147 a sequential file name consisting of the message id and a sequence number. The
30148 full path and name is available in &$mime_decoded_filename$& after decoding.
30150 A full path name starting with a slash. If the full name is an existing
30151 directory, it is used as a replacement for the default directory. The filename
30152 is then sequentially assigned. If the path does not exist, it is used as
30153 the full path and file name.
30155 If the string does not start with a slash, it is used as the
30156 filename, and the default path is then used.
30158 The &%decode%& condition normally succeeds. It is only false for syntax
30159 errors or unusual circumstances such as memory shortages. You can easily decode
30160 a file with its original, proposed filename using
30162 decode = $mime_filename
30164 However, you should keep in mind that &$mime_filename$& might contain
30165 anything. If you place files outside of the default path, they are not
30166 automatically unlinked.
30168 For RFC822 attachments (these are messages attached to messages, with a
30169 content-type of &"message/rfc822"&), the ACL is called again in the same manner
30170 as for the primary message, only that the &$mime_is_rfc822$& expansion
30171 variable is set (see below). Attached messages are always decoded to disk
30172 before being checked, and the files are unlinked once the check is done.
30174 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
30175 used to match regular expressions against raw and decoded MIME parts,
30176 respectively. They are described in section &<<SECTscanregex>>&.
30178 .cindex "MIME content scanning" "returned variables"
30179 The following list describes all expansion variables that are
30180 available in the MIME ACL:
30183 .vitem &$mime_boundary$&
30184 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
30185 have a boundary string, which is stored in this variable. If the current part
30186 has no boundary parameter in the &'Content-Type:'& header, this variable
30187 contains the empty string.
30189 .vitem &$mime_charset$&
30190 This variable contains the character set identifier, if one was found in the
30191 &'Content-Type:'& header. Examples for charset identifiers are:
30197 Please note that this value is not normalized, so you should do matches
30198 case-insensitively.
30200 .vitem &$mime_content_description$&
30201 This variable contains the normalized content of the &'Content-Description:'&
30202 header. It can contain a human-readable description of the parts content. Some
30203 implementations repeat the filename for attachments here, but they are usually
30204 only used for display purposes.
30206 .vitem &$mime_content_disposition$&
30207 This variable contains the normalized content of the &'Content-Disposition:'&
30208 header. You can expect strings like &"attachment"& or &"inline"& here.
30210 .vitem &$mime_content_id$&
30211 This variable contains the normalized content of the &'Content-ID:'& header.
30212 This is a unique ID that can be used to reference a part from another part.
30214 .vitem &$mime_content_size$&
30215 This variable is set only after the &%decode%& modifier (see above) has been
30216 successfully run. It contains the size of the decoded part in kilobytes. The
30217 size is always rounded up to full kilobytes, so only a completely empty part
30218 has a &$mime_content_size$& of zero.
30220 .vitem &$mime_content_transfer_encoding$&
30221 This variable contains the normalized content of the
30222 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
30223 type. Typical values are &"base64"& and &"quoted-printable"&.
30225 .vitem &$mime_content_type$&
30226 If the MIME part has a &'Content-Type:'& header, this variable contains its
30227 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
30228 are some examples of popular MIME types, as they may appear in this variable:
30232 application/octet-stream
30236 If the MIME part has no &'Content-Type:'& header, this variable contains the
30239 .vitem &$mime_decoded_filename$&
30240 This variable is set only after the &%decode%& modifier (see above) has been
30241 successfully run. It contains the full path and file name of the file
30242 containing the decoded data.
30247 .vitem &$mime_filename$&
30248 This is perhaps the most important of the MIME variables. It contains a
30249 proposed filename for an attachment, if one was found in either the
30250 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
30251 RFC2047 decoded, but no additional sanity checks are done. If no filename was
30252 found, this variable contains the empty string.
30254 .vitem &$mime_is_coverletter$&
30255 This variable attempts to differentiate the &"cover letter"& of an e-mail from
30256 attached data. It can be used to clamp down on flashy or unnecessarily encoded
30257 content in the cover letter, while not restricting attachments at all.
30259 The variable contains 1 (true) for a MIME part believed to be part of the
30260 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
30264 The outermost MIME part of a message is always a cover letter.
30267 If a multipart/alternative or multipart/related MIME part is a cover letter,
30268 so are all MIME subparts within that multipart.
30271 If any other multipart is a cover letter, the first subpart is a cover letter,
30272 and the rest are attachments.
30275 All parts contained within an attachment multipart are attachments.
30278 As an example, the following will ban &"HTML mail"& (including that sent with
30279 alternative plain text), while allowing HTML files to be attached. HTML
30280 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
30282 deny message = HTML mail is not accepted here
30283 !condition = $mime_is_rfc822
30284 condition = $mime_is_coverletter
30285 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
30287 .vitem &$mime_is_multipart$&
30288 This variable has the value 1 (true) when the current part has the main type
30289 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
30290 Since multipart entities only serve as containers for other parts, you may not
30291 want to carry out specific actions on them.
30293 .vitem &$mime_is_rfc822$&
30294 This variable has the value 1 (true) if the current part is not a part of the
30295 checked message itself, but part of an attached message. Attached message
30296 decoding is fully recursive.
30298 .vitem &$mime_part_count$&
30299 This variable is a counter that is raised for each processed MIME part. It
30300 starts at zero for the very first part (which is usually a multipart). The
30301 counter is per-message, so it is reset when processing RFC822 attachments (see
30302 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
30303 complete, so you can use it in the DATA ACL to determine the number of MIME
30304 parts of a message. For non-MIME messages, this variable contains the value -1.
30309 .section "Scanning with regular expressions" "SECTscanregex"
30310 .cindex "content scanning" "with regular expressions"
30311 .cindex "regular expressions" "content scanning with"
30312 You can specify your own custom regular expression matches on the full body of
30313 the message, or on individual MIME parts.
30315 The &%regex%& condition takes one or more regular expressions as arguments and
30316 matches them against the full message (when called in the DATA ACL) or a raw
30317 MIME part (when called in the MIME ACL). The &%regex%& condition matches
30318 linewise, with a maximum line length of 32K characters. That means you cannot
30319 have multiline matches with the &%regex%& condition.
30321 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
30322 to 32K of decoded content (the whole content at once, not linewise). If the
30323 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
30324 is decoded automatically when &%mime_regex%& is executed (using default path
30325 and filename values). If the decoded data is larger than 32K, only the first
30326 32K characters are checked.
30328 The regular expressions are passed as a colon-separated list. To include a
30329 literal colon, you must double it. Since the whole right-hand side string is
30330 expanded before being used, you must also escape dollar signs and backslashes
30331 with more backslashes, or use the &`\N`& facility to disable expansion.
30332 Here is a simple example that contains two regular expressions:
30334 deny message = contains blacklisted regex ($regex_match_string)
30335 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
30337 The conditions returns true if any one of the regular expressions matches. The
30338 &$regex_match_string$& expansion variable is then set up and contains the
30339 matching regular expression.
30341 &*Warning*&: With large messages, these conditions can be fairly
30347 .section "The demime condition" "SECTdemimecond"
30348 .cindex "content scanning" "MIME checking"
30349 .cindex "MIME content scanning"
30350 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
30351 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
30352 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
30353 ACL functionality, but provides no additional facilities. Please note that this
30354 condition is deprecated and kept only for backward compatibility. You must set
30355 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
30356 use the &%demime%& condition.
30358 The &%demime%& condition unpacks MIME containers in the message. It detects
30359 errors in MIME containers and can match file extensions found in the message
30360 against a list. Using this facility produces files containing the unpacked MIME
30361 parts of the message in the temporary scan directory. If you do antivirus
30362 scanning, it is recommended that you use the &%demime%& condition before the
30363 antivirus (&%malware%&) condition.
30365 On the right-hand side of the &%demime%& condition you can pass a
30366 colon-separated list of file extensions that it should match against. For
30369 deny message = Found blacklisted file attachment
30370 demime = vbs:com:bat:pif:prf:lnk
30372 If one of the file extensions is found, the condition is true, otherwise it is
30373 false. If there is a temporary error while demimeing (for example, &"disk
30374 full"&), the condition defers, and the message is temporarily rejected (unless
30375 the condition is on a &%warn%& verb).
30377 The right-hand side is expanded before being treated as a list, so you can have
30378 conditions and lookups there. If it expands to an empty string, &"false"&, or
30379 zero (&"0"&), no demimeing is done and the condition is false.
30381 The &%demime%& condition set the following variables:
30384 .vitem &$demime_errorlevel$&
30385 .vindex "&$demime_errorlevel$&"
30386 When an error is detected in a MIME container, this variable contains the
30387 severity of the error, as an integer number. The higher the value, the more
30388 severe the error (the current maximum value is 3). If this variable is unset or
30389 zero, no error occurred.
30391 .vitem &$demime_reason$&
30392 .vindex "&$demime_reason$&"
30393 When &$demime_errorlevel$& is greater than zero, this variable contains a
30394 human-readable text string describing the MIME error that occurred.
30398 .vitem &$found_extension$&
30399 .vindex "&$found_extension$&"
30400 When the &%demime%& condition is true, this variable contains the file
30401 extension it found.
30404 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
30405 the &%demime%& condition, and are not changed on subsequent calls.
30407 If you do not want to check for file extensions, but rather use the &%demime%&
30408 condition for unpacking or error checking purposes, pass &"*"& as the
30409 right-hand side value. Here is a more elaborate example of how to use this
30412 # Reject messages with serious MIME container errors
30413 deny message = Found MIME error ($demime_reason).
30415 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
30417 # Reject known virus spreading file extensions.
30418 # Accepting these is pretty much braindead.
30419 deny message = contains $found_extension file (blacklisted).
30420 demime = com:vbs:bat:pif:scr
30422 # Freeze .exe and .doc files. Postmaster can
30423 # examine them and eventually thaw them.
30424 deny log_message = Another $found_extension file.
30433 . ////////////////////////////////////////////////////////////////////////////
30434 . ////////////////////////////////////////////////////////////////////////////
30436 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
30437 "Local scan function"
30438 .scindex IIDlosca "&[local_scan()]& function" "description of"
30439 .cindex "customizing" "input scan using C function"
30440 .cindex "policy control" "by local scan function"
30441 In these days of email worms, viruses, and ever-increasing spam, some sites
30442 want to apply a lot of checking to messages before accepting them.
30444 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
30445 passing messages to external virus and spam scanning software. You can also do
30446 a certain amount in Exim itself through string expansions and the &%condition%&
30447 condition in the ACL that runs after the SMTP DATA command or the ACL for
30448 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
30450 To allow for further customization to a site's own requirements, there is the
30451 possibility of linking Exim with a private message scanning function, written
30452 in C. If you want to run code that is written in something other than C, you
30453 can of course use a little C stub to call it.
30455 The local scan function is run once for every incoming message, at the point
30456 when Exim is just about to accept the message.
30457 It can therefore be used to control non-SMTP messages from local processes as
30458 well as messages arriving via SMTP.
30460 Exim applies a timeout to calls of the local scan function, and there is an
30461 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
30462 Zero means &"no timeout"&.
30463 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
30464 before calling the local scan function, so that the most common types of crash
30465 are caught. If the timeout is exceeded or one of those signals is caught, the
30466 incoming message is rejected with a temporary error if it is an SMTP message.
30467 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
30468 code. The incident is logged on the main and reject logs.
30472 .section "Building Exim to use a local scan function" "SECID207"
30473 .cindex "&[local_scan()]& function" "building Exim to use"
30474 To make use of the local scan function feature, you must tell Exim where your
30475 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
30476 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
30477 directory, so you might set
30479 LOCAL_SCAN_SOURCE=Local/local_scan.c
30481 for example. The function must be called &[local_scan()]&. It is called by
30482 Exim after it has received a message, when the success return code is about to
30483 be sent. This is after all the ACLs have been run. The return code from your
30484 function controls whether the message is actually accepted or not. There is a
30485 commented template function (that just accepts the message) in the file
30486 _src/local_scan.c_.
30488 If you want to make use of Exim's run time configuration file to set options
30489 for your &[local_scan()]& function, you must also set
30491 LOCAL_SCAN_HAS_OPTIONS=yes
30493 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
30498 .section "API for local_scan()" "SECTapiforloc"
30499 .cindex "&[local_scan()]& function" "API description"
30500 You must include this line near the start of your code:
30502 #include "local_scan.h"
30504 This header file defines a number of variables and other values, and the
30505 prototype for the function itself. Exim is coded to use unsigned char values
30506 almost exclusively, and one of the things this header defines is a shorthand
30507 for &`unsigned char`& called &`uschar`&.
30508 It also contains the following macro definitions, to simplify casting character
30509 strings and pointers to character strings:
30511 #define CS (char *)
30512 #define CCS (const char *)
30513 #define CSS (char **)
30514 #define US (unsigned char *)
30515 #define CUS (const unsigned char *)
30516 #define USS (unsigned char **)
30518 The function prototype for &[local_scan()]& is:
30520 extern int local_scan(int fd, uschar **return_text);
30522 The arguments are as follows:
30525 &%fd%& is a file descriptor for the file that contains the body of the message
30526 (the -D file). The file is open for reading and writing, but updating it is not
30527 recommended. &*Warning*&: You must &'not'& close this file descriptor.
30529 The descriptor is positioned at character 19 of the file, which is the first
30530 character of the body itself, because the first 19 characters are the message
30531 id followed by &`-D`& and a newline. If you rewind the file, you should use the
30532 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
30533 case this changes in some future version.
30535 &%return_text%& is an address which you can use to return a pointer to a text
30536 string at the end of the function. The value it points to on entry is NULL.
30539 The function must return an &%int%& value which is one of the following macros:
30542 .vitem &`LOCAL_SCAN_ACCEPT`&
30543 .vindex "&$local_scan_data$&"
30544 The message is accepted. If you pass back a string of text, it is saved with
30545 the message, and made available in the variable &$local_scan_data$&. No
30546 newlines are permitted (if there are any, they are turned into spaces) and the
30547 maximum length of text is 1000 characters.
30549 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
30550 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
30551 queued without immediate delivery, and is frozen.
30553 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
30554 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
30555 queued without immediate delivery.
30557 .vitem &`LOCAL_SCAN_REJECT`&
30558 The message is rejected; the returned text is used as an error message which is
30559 passed back to the sender and which is also logged. Newlines are permitted &--
30560 they cause a multiline response for SMTP rejections, but are converted to
30561 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
30564 .vitem &`LOCAL_SCAN_TEMPREJECT`&
30565 The message is temporarily rejected; the returned text is used as an error
30566 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
30569 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
30570 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
30571 message is not written to the reject log. It has the effect of unsetting the
30572 &%rejected_header%& log selector for just this rejection. If
30573 &%rejected_header%& is already unset (see the discussion of the
30574 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
30575 same as LOCAL_SCAN_REJECT.
30577 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
30578 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
30579 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
30582 If the message is not being received by interactive SMTP, rejections are
30583 reported by writing to &%stderr%& or by sending an email, as configured by the
30584 &%-oe%& command line options.
30588 .section "Configuration options for local_scan()" "SECTconoptloc"
30589 .cindex "&[local_scan()]& function" "configuration options"
30590 It is possible to have option settings in the main configuration file
30591 that set values in static variables in the &[local_scan()]& module. If you
30592 want to do this, you must have the line
30594 LOCAL_SCAN_HAS_OPTIONS=yes
30596 in your &_Local/Makefile_& when you build Exim. (This line is in
30597 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
30598 file, you must define static variables to hold the option values, and a table
30601 The table must be a vector called &%local_scan_options%&, of type
30602 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
30603 and a pointer to the variable that holds the value. The entries must appear in
30604 alphabetical order. Following &%local_scan_options%& you must also define a
30605 variable called &%local_scan_options_count%& that contains the number of
30606 entries in the table. Here is a short example, showing two kinds of option:
30608 static int my_integer_option = 42;
30609 static uschar *my_string_option = US"a default string";
30611 optionlist local_scan_options[] = {
30612 { "my_integer", opt_int, &my_integer_option },
30613 { "my_string", opt_stringptr, &my_string_option }
30616 int local_scan_options_count =
30617 sizeof(local_scan_options)/sizeof(optionlist);
30619 The values of the variables can now be changed from Exim's runtime
30620 configuration file by including a local scan section as in this example:
30624 my_string = some string of text...
30626 The available types of option data are as follows:
30629 .vitem &*opt_bool*&
30630 This specifies a boolean (true/false) option. The address should point to a
30631 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
30632 that are defined as &"1"& and &"0"&, respectively. If you want to detect
30633 whether such a variable has been set at all, you can initialize it to
30634 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
30637 .vitem &*opt_fixed*&
30638 This specifies a fixed point number, such as is used for load averages.
30639 The address should point to a variable of type &`int`&. The value is stored
30640 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
30643 This specifies an integer; the address should point to a variable of type
30644 &`int`&. The value may be specified in any of the integer formats accepted by
30647 .vitem &*opt_mkint*&
30648 This is the same as &%opt_int%&, except that when such a value is output in a
30649 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
30650 printed with the suffix K or M.
30652 .vitem &*opt_octint*&
30653 This also specifies an integer, but the value is always interpreted as an
30654 octal integer, whether or not it starts with the digit zero, and it is
30655 always output in octal.
30657 .vitem &*opt_stringptr*&
30658 This specifies a string value; the address must be a pointer to a
30659 variable that points to a string (for example, of type &`uschar *`&).
30661 .vitem &*opt_time*&
30662 This specifies a time interval value. The address must point to a variable of
30663 type &`int`&. The value that is placed there is a number of seconds.
30666 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
30667 out the values of all the &[local_scan()]& options.
30671 .section "Available Exim variables" "SECID208"
30672 .cindex "&[local_scan()]& function" "available Exim variables"
30673 The header &_local_scan.h_& gives you access to a number of C variables. These
30674 are the only ones that are guaranteed to be maintained from release to release.
30675 Note, however, that you can obtain the value of any Exim expansion variable,
30676 including &$recipients$&, by calling &'expand_string()'&. The exported
30677 C variables are as follows:
30680 .vitem &*int&~body_linecount*&
30681 This variable contains the number of lines in the message's body.
30683 .vitem &*int&~body_zerocount*&
30684 This variable contains the number of binary zero bytes in the message's body.
30686 .vitem &*unsigned&~int&~debug_selector*&
30687 This variable is set to zero when no debugging is taking place. Otherwise, it
30688 is a bitmap of debugging selectors. Two bits are identified for use in
30689 &[local_scan()]&; they are defined as macros:
30692 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
30693 testing option that is not privileged &-- any caller may set it. All the
30694 other selector bits can be set only by admin users.
30697 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
30698 by the &`+local_scan`& debug selector. It is not included in the default set
30702 Thus, to write to the debugging output only when &`+local_scan`& has been
30703 selected, you should use code like this:
30705 if ((debug_selector & D_local_scan) != 0)
30706 debug_printf("xxx", ...);
30708 .vitem &*uschar&~*expand_string_message*&
30709 After a failing call to &'expand_string()'& (returned value NULL), the
30710 variable &%expand_string_message%& contains the error message, zero-terminated.
30712 .vitem &*header_line&~*header_list*&
30713 A pointer to a chain of header lines. The &%header_line%& structure is
30716 .vitem &*header_line&~*header_last*&
30717 A pointer to the last of the header lines.
30719 .vitem &*uschar&~*headers_charset*&
30720 The value of the &%headers_charset%& configuration option.
30722 .vitem &*BOOL&~host_checking*&
30723 This variable is TRUE during a host checking session that is initiated by the
30724 &%-bh%& command line option.
30726 .vitem &*uschar&~*interface_address*&
30727 The IP address of the interface that received the message, as a string. This
30728 is NULL for locally submitted messages.
30730 .vitem &*int&~interface_port*&
30731 The port on which this message was received. When testing with the &%-bh%&
30732 command line option, the value of this variable is -1 unless a port has been
30733 specified via the &%-oMi%& option.
30735 .vitem &*uschar&~*message_id*&
30736 This variable contains Exim's message id for the incoming message (the value of
30737 &$message_exim_id$&) as a zero-terminated string.
30739 .vitem &*uschar&~*received_protocol*&
30740 The name of the protocol by which the message was received.
30742 .vitem &*int&~recipients_count*&
30743 The number of accepted recipients.
30745 .vitem &*recipient_item&~*recipients_list*&
30746 .cindex "recipient" "adding in local scan"
30747 .cindex "recipient" "removing in local scan"
30748 The list of accepted recipients, held in a vector of length
30749 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
30750 can add additional recipients by calling &'receive_add_recipient()'& (see
30751 below). You can delete recipients by removing them from the vector and
30752 adjusting the value in &%recipients_count%&. In particular, by setting
30753 &%recipients_count%& to zero you remove all recipients. If you then return the
30754 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
30755 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
30756 and then call &'receive_add_recipient()'& as often as needed.
30758 .vitem &*uschar&~*sender_address*&
30759 The envelope sender address. For bounce messages this is the empty string.
30761 .vitem &*uschar&~*sender_host_address*&
30762 The IP address of the sending host, as a string. This is NULL for
30763 locally-submitted messages.
30765 .vitem &*uschar&~*sender_host_authenticated*&
30766 The name of the authentication mechanism that was used, or NULL if the message
30767 was not received over an authenticated SMTP connection.
30769 .vitem &*uschar&~*sender_host_name*&
30770 The name of the sending host, if known.
30772 .vitem &*int&~sender_host_port*&
30773 The port on the sending host.
30775 .vitem &*BOOL&~smtp_input*&
30776 This variable is TRUE for all SMTP input, including BSMTP.
30778 .vitem &*BOOL&~smtp_batched_input*&
30779 This variable is TRUE for BSMTP input.
30781 .vitem &*int&~store_pool*&
30782 The contents of this variable control which pool of memory is used for new
30783 requests. See section &<<SECTmemhanloc>>& for details.
30787 .section "Structure of header lines" "SECID209"
30788 The &%header_line%& structure contains the members listed below.
30789 You can add additional header lines by calling the &'header_add()'& function
30790 (see below). You can cause header lines to be ignored (deleted) by setting
30795 .vitem &*struct&~header_line&~*next*&
30796 A pointer to the next header line, or NULL for the last line.
30798 .vitem &*int&~type*&
30799 A code identifying certain headers that Exim recognizes. The codes are printing
30800 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
30801 Notice in particular that any header line whose type is * is not transmitted
30802 with the message. This flagging is used for header lines that have been
30803 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
30804 lines.) Effectively, * means &"deleted"&.
30806 .vitem &*int&~slen*&
30807 The number of characters in the header line, including the terminating and any
30810 .vitem &*uschar&~*text*&
30811 A pointer to the text of the header. It always ends with a newline, followed by
30812 a zero byte. Internal newlines are preserved.
30817 .section "Structure of recipient items" "SECID210"
30818 The &%recipient_item%& structure contains these members:
30821 .vitem &*uschar&~*address*&
30822 This is a pointer to the recipient address as it was received.
30824 .vitem &*int&~pno*&
30825 This is used in later Exim processing when top level addresses are created by
30826 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
30827 and must always contain -1 at this stage.
30829 .vitem &*uschar&~*errors_to*&
30830 If this value is not NULL, bounce messages caused by failing to deliver to the
30831 recipient are sent to the address it contains. In other words, it overrides the
30832 envelope sender for this one recipient. (Compare the &%errors_to%& generic
30833 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
30834 an unqualified address, Exim qualifies it using the domain from
30835 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
30836 is NULL for all recipients.
30841 .section "Available Exim functions" "SECID211"
30842 .cindex "&[local_scan()]& function" "available Exim functions"
30843 The header &_local_scan.h_& gives you access to a number of Exim functions.
30844 These are the only ones that are guaranteed to be maintained from release to
30848 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
30849 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
30851 This function creates a child process that runs the command specified by
30852 &%argv%&. The environment for the process is specified by &%envp%&, which can
30853 be NULL if no environment variables are to be passed. A new umask is supplied
30854 for the process in &%newumask%&.
30856 Pipes to the standard input and output of the new process are set up
30857 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
30858 standard error is cloned to the standard output. If there are any file
30859 descriptors &"in the way"& in the new process, they are closed. If the final
30860 argument is TRUE, the new process is made into a process group leader.
30862 The function returns the pid of the new process, or -1 if things go wrong.
30864 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
30865 This function waits for a child process to terminate, or for a timeout (in
30866 seconds) to expire. A timeout value of zero means wait as long as it takes. The
30867 return value is as follows:
30872 The process terminated by a normal exit and the value is the process
30878 The process was terminated by a signal and the value is the negation of the
30884 The process timed out.
30888 The was some other error in wait(); &%errno%& is still set.
30891 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
30892 This function provide you with a means of submitting a new message to
30893 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
30894 want, but this packages it all up for you.) The function creates a pipe,
30895 forks a subprocess that is running
30897 exim -t -oem -oi -f <>
30899 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
30900 that is connected to the standard input. The yield of the function is the PID
30901 of the subprocess. You can then write a message to the file descriptor, with
30902 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
30904 When you have finished, call &'child_close()'& to wait for the process to
30905 finish and to collect its ending status. A timeout value of zero is usually
30906 fine in this circumstance. Unless you have made a mistake with the recipient
30907 addresses, you should get a return code of zero.
30910 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
30911 *sender_authentication)*&
30912 This function is a more sophisticated version of &'child_open()'&. The command
30915 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
30917 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
30920 .vitem &*void&~debug_printf(char&~*,&~...)*&
30921 This is Exim's debugging function, with arguments as for &'(printf()'&. The
30922 output is written to the standard error stream. If no debugging is selected,
30923 calls to &'debug_printf()'& have no effect. Normally, you should make calls
30924 conditional on the &`local_scan`& debug selector by coding like this:
30926 if ((debug_selector & D_local_scan) != 0)
30927 debug_printf("xxx", ...);
30930 .vitem &*uschar&~*expand_string(uschar&~*string)*&
30931 This is an interface to Exim's string expansion code. The return value is the
30932 expanded string, or NULL if there was an expansion failure.
30933 The C variable &%expand_string_message%& contains an error message after an
30934 expansion failure. If expansion does not change the string, the return value is
30935 the pointer to the input string. Otherwise, the return value points to a new
30936 block of memory that was obtained by a call to &'store_get()'&. See section
30937 &<<SECTmemhanloc>>& below for a discussion of memory handling.
30939 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
30940 This function allows you to an add additional header line at the end of the
30941 existing ones. The first argument is the type, and should normally be a space
30942 character. The second argument is a format string and any number of
30943 substitution arguments as for &[sprintf()]&. You may include internal newlines
30944 if you want, and you must ensure that the string ends with a newline.
30946 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
30947 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
30948 This function adds a new header line at a specified point in the header
30949 chain. The header itself is specified as for &'header_add()'&.
30951 If &%name%& is NULL, the new header is added at the end of the chain if
30952 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
30953 NULL, the header lines are searched for the first non-deleted header that
30954 matches the name. If one is found, the new header is added before it if
30955 &%after%& is false. If &%after%& is true, the new header is added after the
30956 found header and any adjacent subsequent ones with the same name (even if
30957 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
30958 option controls where the header is added. If it is true, addition is at the
30959 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
30960 headers, or at the top if there are no &'Received:'& headers, you could use
30962 header_add_at_position(TRUE, US"Received", TRUE,
30963 ' ', "X-xxx: ...");
30965 Normally, there is always at least one non-deleted &'Received:'& header, but
30966 there may not be if &%received_header_text%& expands to an empty string.
30969 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
30970 This function removes header lines. If &%occurrence%& is zero or negative, all
30971 occurrences of the header are removed. If occurrence is greater than zero, that
30972 particular instance of the header is removed. If no header(s) can be found that
30973 match the specification, the function does nothing.
30976 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
30977 int&~length,&~BOOL&~notdel)*&"
30978 This function tests whether the given header has the given name. It is not just
30979 a string comparison, because white space is permitted between the name and the
30980 colon. If the &%notdel%& argument is true, a false return is forced for all
30981 &"deleted"& headers; otherwise they are not treated specially. For example:
30983 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
30985 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
30986 .cindex "base64 encoding" "functions for &[local_scan()]& use"
30987 This function base64-encodes a string, which is passed by address and length.
30988 The text may contain bytes of any value, including zero. The result is passed
30989 back in dynamic memory that is obtained by calling &'store_get()'&. It is
30992 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
30993 This function decodes a base64-encoded string. Its arguments are a
30994 zero-terminated base64-encoded string and the address of a variable that is set
30995 to point to the result, which is in dynamic memory. The length of the decoded
30996 string is the yield of the function. If the input is invalid base64 data, the
30997 yield is -1. A zero byte is added to the end of the output string to make it
30998 easy to interpret as a C string (assuming it contains no zeros of its own). The
30999 added zero byte is not included in the returned count.
31001 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
31002 This function checks for a match in a domain list. Domains are always
31003 matched caselessly. The return value is one of the following:
31005 &`OK `& match succeeded
31006 &`FAIL `& match failed
31007 &`DEFER `& match deferred
31009 DEFER is usually caused by some kind of lookup defer, such as the
31010 inability to contact a database.
31012 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
31014 This function checks for a match in a local part list. The third argument
31015 controls case-sensitivity. The return values are as for
31016 &'lss_match_domain()'&.
31018 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
31020 This function checks for a match in an address list. The third argument
31021 controls the case-sensitivity of the local part match. The domain is always
31022 matched caselessly. The return values are as for &'lss_match_domain()'&.
31024 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
31026 This function checks for a match in a host list. The most common usage is
31029 lss_match_host(sender_host_name, sender_host_address, ...)
31031 .vindex "&$sender_host_address$&"
31032 An empty address field matches an empty item in the host list. If the host name
31033 is NULL, the name corresponding to &$sender_host_address$& is automatically
31034 looked up if a host name is required to match an item in the list. The return
31035 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
31036 returns ERROR in the case when it had to look up a host name, but the lookup
31039 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
31041 This function writes to Exim's log files. The first argument should be zero (it
31042 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
31043 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
31044 them. It specifies to which log or logs the message is written. The remaining
31045 arguments are a format and relevant insertion arguments. The string should not
31046 contain any newlines, not even at the end.
31049 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
31050 This function adds an additional recipient to the message. The first argument
31051 is the recipient address. If it is unqualified (has no domain), it is qualified
31052 with the &%qualify_recipient%& domain. The second argument must always be -1.
31054 This function does not allow you to specify a private &%errors_to%& address (as
31055 described with the structure of &%recipient_item%& above), because it pre-dates
31056 the addition of that field to the structure. However, it is easy to add such a
31057 value afterwards. For example:
31059 receive_add_recipient(US"monitor@mydom.example", -1);
31060 recipients_list[recipients_count-1].errors_to =
31061 US"postmaster@mydom.example";
31064 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
31065 This is a convenience function to remove a named recipient from the list of
31066 recipients. It returns true if a recipient was removed, and false if no
31067 matching recipient could be found. The argument must be a complete email
31074 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
31075 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
31076 This function decodes strings that are encoded according to RFC 2047. Typically
31077 these are the contents of header lines. First, each &"encoded word"& is decoded
31078 from the Q or B encoding into a byte-string. Then, if provided with the name of
31079 a charset encoding, and if the &[iconv()]& function is available, an attempt is
31080 made to translate the result to the named character set. If this fails, the
31081 binary string is returned with an error message.
31083 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
31084 maximum MIME word length is enforced. The third argument is the target
31085 encoding, or NULL if no translation is wanted.
31087 .cindex "binary zero" "in RFC 2047 decoding"
31088 .cindex "RFC 2047" "binary zero in"
31089 If a binary zero is encountered in the decoded string, it is replaced by the
31090 contents of the &%zeroval%& argument. For use with Exim headers, the value must
31091 not be 0 because header lines are handled as zero-terminated strings.
31093 The function returns the result of processing the string, zero-terminated; if
31094 &%lenptr%& is not NULL, the length of the result is set in the variable to
31095 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
31097 If an error is encountered, the function returns NULL and uses the &%error%&
31098 argument to return an error message. The variable pointed to by &%error%& is
31099 set to NULL if there is no error; it may be set non-NULL even when the function
31100 returns a non-NULL value if decoding was successful, but there was a problem
31104 .vitem &*int&~smtp_fflush(void)*&
31105 This function is used in conjunction with &'smtp_printf()'&, as described
31108 .vitem &*void&~smtp_printf(char&~*,&~...)*&
31109 The arguments of this function are like &[printf()]&; it writes to the SMTP
31110 output stream. You should use this function only when there is an SMTP output
31111 stream, that is, when the incoming message is being received via interactive
31112 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
31113 is FALSE. If you want to test for an incoming message from another host (as
31114 opposed to a local process that used the &%-bs%& command line option), you can
31115 test the value of &%sender_host_address%&, which is non-NULL when a remote host
31118 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
31119 output function, so it can be used for all forms of SMTP connection.
31121 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
31122 must start with an appropriate response code: 550 if you are going to return
31123 LOCAL_SCAN_REJECT, 451 if you are going to return
31124 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
31125 initial lines of a multi-line response, the code must be followed by a hyphen
31126 to indicate that the line is not the final response line. You must also ensure
31127 that the lines you write terminate with CRLF. For example:
31129 smtp_printf("550-this is some extra info\r\n");
31130 return LOCAL_SCAN_REJECT;
31132 Note that you can also create multi-line responses by including newlines in
31133 the data returned via the &%return_text%& argument. The added value of using
31134 &'smtp_printf()'& is that, for instance, you could introduce delays between
31135 multiple output lines.
31137 The &'smtp_printf()'& function does not return any error indication, because it
31138 does not automatically flush pending output, and therefore does not test
31139 the state of the stream. (In the main code of Exim, flushing and error
31140 detection is done when Exim is ready for the next SMTP input command.) If
31141 you want to flush the output and check for an error (for example, the
31142 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
31143 arguments. It flushes the output stream, and returns a non-zero value if there
31146 .vitem &*void&~*store_get(int)*&
31147 This function accesses Exim's internal store (memory) manager. It gets a new
31148 chunk of memory whose size is given by the argument. Exim bombs out if it ever
31149 runs out of memory. See the next section for a discussion of memory handling.
31151 .vitem &*void&~*store_get_perm(int)*&
31152 This function is like &'store_get()'&, but it always gets memory from the
31153 permanent pool. See the next section for a discussion of memory handling.
31155 .vitem &*uschar&~*string_copy(uschar&~*string)*&
31158 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
31161 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
31162 These three functions create strings using Exim's dynamic memory facilities.
31163 The first makes a copy of an entire string. The second copies up to a maximum
31164 number of characters, indicated by the second argument. The third uses a format
31165 and insertion arguments to create a new string. In each case, the result is a
31166 pointer to a new string in the current memory pool. See the next section for
31172 .section "More about Exim's memory handling" "SECTmemhanloc"
31173 .cindex "&[local_scan()]& function" "memory handling"
31174 No function is provided for freeing memory, because that is never needed.
31175 The dynamic memory that Exim uses when receiving a message is automatically
31176 recycled if another message is received by the same process (this applies only
31177 to incoming SMTP connections &-- other input methods can supply only one
31178 message at a time). After receiving the last message, a reception process
31181 Because it is recycled, the normal dynamic memory cannot be used for holding
31182 data that must be preserved over a number of incoming messages on the same SMTP
31183 connection. However, Exim in fact uses two pools of dynamic memory; the second
31184 one is not recycled, and can be used for this purpose.
31186 If you want to allocate memory that remains available for subsequent messages
31187 in the same SMTP connection, you should set
31189 store_pool = POOL_PERM
31191 before calling the function that does the allocation. There is no need to
31192 restore the value if you do not need to; however, if you do want to revert to
31193 the normal pool, you can either restore the previous value of &%store_pool%& or
31194 set it explicitly to POOL_MAIN.
31196 The pool setting applies to all functions that get dynamic memory, including
31197 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
31198 There is also a convenience function called &'store_get_perm()'& that gets a
31199 block of memory from the permanent pool while preserving the value of
31206 . ////////////////////////////////////////////////////////////////////////////
31207 . ////////////////////////////////////////////////////////////////////////////
31209 .chapter "System-wide message filtering" "CHAPsystemfilter"
31210 .scindex IIDsysfil1 "filter" "system filter"
31211 .scindex IIDsysfil2 "filtering all mail"
31212 .scindex IIDsysfil3 "system filter"
31213 The previous chapters (on ACLs and the local scan function) describe checks
31214 that can be applied to messages before they are accepted by a host. There is
31215 also a mechanism for checking messages once they have been received, but before
31216 they are delivered. This is called the &'system filter'&.
31218 The system filter operates in a similar manner to users' filter files, but it
31219 is run just once per message (however many recipients the message has).
31220 It should not normally be used as a substitute for routing, because &%deliver%&
31221 commands in a system router provide new envelope recipient addresses.
31222 The system filter must be an Exim filter. It cannot be a Sieve filter.
31224 The system filter is run at the start of a delivery attempt, before any routing
31225 is done. If a message fails to be completely delivered at the first attempt,
31226 the system filter is run again at the start of every retry.
31227 If you want your filter to do something only once per message, you can make use
31228 of the &%first_delivery%& condition in an &%if%& command in the filter to
31229 prevent it happening on retries.
31231 .vindex "&$domain$&"
31232 .vindex "&$local_part$&"
31233 &*Warning*&: Because the system filter runs just once, variables that are
31234 specific to individual recipient addresses, such as &$local_part$& and
31235 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
31236 you want to run a centrally-specified filter for each recipient address
31237 independently, you can do so by setting up a suitable &(redirect)& router, as
31238 described in section &<<SECTperaddfil>>& below.
31241 .section "Specifying a system filter" "SECID212"
31242 .cindex "uid (user id)" "system filter"
31243 .cindex "gid (group id)" "system filter"
31244 The name of the file that contains the system filter must be specified by
31245 setting &%system_filter%&. If you want the filter to run under a uid and gid
31246 other than root, you must also set &%system_filter_user%& and
31247 &%system_filter_group%& as appropriate. For example:
31249 system_filter = /etc/mail/exim.filter
31250 system_filter_user = exim
31252 If a system filter generates any deliveries directly to files or pipes (via the
31253 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
31254 specified by setting &%system_filter_file_transport%& and
31255 &%system_filter_pipe_transport%&, respectively. Similarly,
31256 &%system_filter_reply_transport%& must be set to handle any messages generated
31257 by the &%reply%& command.
31260 .section "Testing a system filter" "SECID213"
31261 You can run simple tests of a system filter in the same way as for a user
31262 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
31263 are permitted only in system filters are recognized.
31265 If you want to test the combined effect of a system filter and a user filter,
31266 you can use both &%-bF%& and &%-bf%& on the same command line.
31270 .section "Contents of a system filter" "SECID214"
31271 The language used to specify system filters is the same as for users' filter
31272 files. It is described in the separate end-user document &'Exim's interface to
31273 mail filtering'&. However, there are some additional features that are
31274 available only in system filters; these are described in subsequent sections.
31275 If they are encountered in a user's filter file or when testing with &%-bf%&,
31278 .cindex "frozen messages" "manual thaw; testing in filter"
31279 There are two special conditions which, though available in users' filter
31280 files, are designed for use in system filters. The condition &%first_delivery%&
31281 is true only for the first attempt at delivering a message, and
31282 &%manually_thawed%& is true only if the message has been frozen, and
31283 subsequently thawed by an admin user. An explicit forced delivery counts as a
31284 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
31286 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
31287 specify an &"unseen"& (non-significant) delivery, and that delivery does not
31288 succeed, it will not be tried again.
31289 If you want Exim to retry an unseen delivery until it succeeds, you should
31290 arrange to set it up every time the filter runs.
31292 When a system filter finishes running, the values of the variables &$n0$& &--
31293 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
31294 users' filter files. Thus a system filter can, for example, set up &"scores"&
31295 to which users' filter files can refer.
31299 .section "Additional variable for system filters" "SECID215"
31300 .vindex "&$recipients$&"
31301 The expansion variable &$recipients$&, containing a list of all the recipients
31302 of the message (separated by commas and white space), is available in system
31303 filters. It is not available in users' filters for privacy reasons.
31307 .section "Defer, freeze, and fail commands for system filters" "SECID216"
31308 .cindex "freezing messages"
31309 .cindex "message" "freezing"
31310 .cindex "message" "forced failure"
31311 .cindex "&%fail%&" "in system filter"
31312 .cindex "&%freeze%& in system filter"
31313 .cindex "&%defer%& in system filter"
31314 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
31315 always available in system filters, but are not normally enabled in users'
31316 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
31317 for the &(redirect)& router.) These commands can optionally be followed by the
31318 word &%text%& and a string containing an error message, for example:
31320 fail text "this message looks like spam to me"
31322 The keyword &%text%& is optional if the next character is a double quote.
31324 The &%defer%& command defers delivery of the original recipients of the
31325 message. The &%fail%& command causes all the original recipients to be failed,
31326 and a bounce message to be created. The &%freeze%& command suspends all
31327 delivery attempts for the original recipients. In all cases, any new deliveries
31328 that are specified by the filter are attempted as normal after the filter has
31331 The &%freeze%& command is ignored if the message has been manually unfrozen and
31332 not manually frozen since. This means that automatic freezing by a system
31333 filter can be used as a way of checking out suspicious messages. If a message
31334 is found to be all right, manually unfreezing it allows it to be delivered.
31336 .cindex "log" "&%fail%& command log line"
31337 .cindex "&%fail%&" "log line; reducing"
31338 The text given with a fail command is used as part of the bounce message as
31339 well as being written to the log. If the message is quite long, this can fill
31340 up a lot of log space when such failures are common. To reduce the size of the
31341 log message, Exim interprets the text in a special way if it starts with the
31342 two characters &`<<`& and contains &`>>`& later. The text between these two
31343 strings is written to the log, and the rest of the text is used in the bounce
31344 message. For example:
31346 fail "<<filter test 1>>Your message is rejected \
31347 because it contains attachments that we are \
31348 not prepared to receive."
31351 .cindex "loop" "caused by &%fail%&"
31352 Take great care with the &%fail%& command when basing the decision to fail on
31353 the contents of the message, because the bounce message will of course include
31354 the contents of the original message and will therefore trigger the &%fail%&
31355 command again (causing a mail loop) unless steps are taken to prevent this.
31356 Testing the &%error_message%& condition is one way to prevent this. You could
31359 if $message_body contains "this is spam" and not error_message
31360 then fail text "spam is not wanted here" endif
31362 though of course that might let through unwanted bounce messages. The
31363 alternative is clever checking of the body and/or headers to detect bounces
31364 generated by the filter.
31366 The interpretation of a system filter file ceases after a
31368 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
31369 set up earlier in the filter file are honoured, so you can use a sequence such
31375 to send a specified message when the system filter is freezing (or deferring or
31376 failing) a message. The normal deliveries for the message do not, of course,
31381 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
31382 .cindex "header lines" "adding; in system filter"
31383 .cindex "header lines" "removing; in system filter"
31384 .cindex "filter" "header lines; adding/removing"
31385 Two filter commands that are available only in system filters are:
31387 headers add <string>
31388 headers remove <string>
31390 The argument for the &%headers add%& is a string that is expanded and then
31391 added to the end of the message's headers. It is the responsibility of the
31392 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
31393 space is ignored, and if the string is otherwise empty, or if the expansion is
31394 forced to fail, the command has no effect.
31396 You can use &"\n"& within the string, followed by white space, to specify
31397 continued header lines. More than one header may be added in one command by
31398 including &"\n"& within the string without any following white space. For
31401 headers add "X-header-1: ....\n \
31402 continuation of X-header-1 ...\n\
31405 Note that the header line continuation white space after the first newline must
31406 be placed before the backslash that continues the input string, because white
31407 space after input continuations is ignored.
31409 The argument for &%headers remove%& is a colon-separated list of header names.
31410 This command applies only to those headers that are stored with the message;
31411 those that are added at delivery time (such as &'Envelope-To:'& and
31412 &'Return-Path:'&) cannot be removed by this means. If there is more than one
31413 header with the same name, they are all removed.
31415 The &%headers%& command in a system filter makes an immediate change to the set
31416 of header lines that was received with the message (with possible additions
31417 from ACL processing). Subsequent commands in the system filter operate on the
31418 modified set, which also forms the basis for subsequent message delivery.
31419 Unless further modified during routing or transporting, this set of headers is
31420 used for all recipients of the message.
31422 During routing and transporting, the variables that refer to the contents of
31423 header lines refer only to those lines that are in this set. Thus, header lines
31424 that are added by a system filter are visible to users' filter files and to all
31425 routers and transports. This contrasts with the manipulation of header lines by
31426 routers and transports, which is not immediate, but which instead is saved up
31427 until the message is actually being written (see section
31428 &<<SECTheadersaddrem>>&).
31430 If the message is not delivered at the first attempt, header lines that were
31431 added by the system filter are stored with the message, and so are still
31432 present at the next delivery attempt. Header lines that were removed are still
31433 present, but marked &"deleted"& so that they are not transported with the
31434 message. For this reason, it is usual to make the &%headers%& command
31435 conditional on &%first_delivery%& so that the set of header lines is not
31436 modified more than once.
31438 Because header modification in a system filter acts immediately, you have to
31439 use an indirect approach if you want to modify the contents of a header line.
31442 headers add "Old-Subject: $h_subject:"
31443 headers remove "Subject"
31444 headers add "Subject: new subject (was: $h_old-subject:)"
31445 headers remove "Old-Subject"
31450 .section "Setting an errors address in a system filter" "SECID217"
31451 .cindex "envelope sender"
31452 In a system filter, if a &%deliver%& command is followed by
31454 errors_to <some address>
31456 in order to change the envelope sender (and hence the error reporting) for that
31457 delivery, any address may be specified. (In a user filter, only the current
31458 user's address can be set.) For example, if some mail is being monitored, you
31461 unseen deliver monitor@spying.example errors_to root@local.example
31463 to take a copy which would not be sent back to the normal error reporting
31464 address if its delivery failed.
31468 .section "Per-address filtering" "SECTperaddfil"
31469 .vindex "&$domain$&"
31470 .vindex "&$local_part$&"
31471 In contrast to the system filter, which is run just once per message for each
31472 delivery attempt, it is also possible to set up a system-wide filtering
31473 operation that runs once for each recipient address. In this case, variables
31474 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
31475 filter file could be made dependent on them. This is an example of a router
31476 which implements such a filter:
31481 domains = +local_domains
31482 file = /central/filters/$local_part
31487 The filter is run in a separate process under its own uid. Therefore, either
31488 &%check_local_user%& must be set (as above), in which case the filter is run as
31489 the local user, or the &%user%& option must be used to specify which user to
31490 use. If both are set, &%user%& overrides.
31492 Care should be taken to ensure that none of the commands in the filter file
31493 specify a significant delivery if the message is to go on to be delivered to
31494 its intended recipient. The router will not then claim to have dealt with the
31495 address, so it will be passed on to subsequent routers to be delivered in the
31497 .ecindex IIDsysfil1
31498 .ecindex IIDsysfil2
31499 .ecindex IIDsysfil3
31506 . ////////////////////////////////////////////////////////////////////////////
31507 . ////////////////////////////////////////////////////////////////////////////
31509 .chapter "Message processing" "CHAPmsgproc"
31510 .scindex IIDmesproc "message" "general processing"
31511 Exim performs various transformations on the sender and recipient addresses of
31512 all messages that it handles, and also on the messages' header lines. Some of
31513 these are optional and configurable, while others always take place. All of
31514 this processing, except rewriting as a result of routing, and the addition or
31515 removal of header lines while delivering, happens when a message is received,
31516 before it is placed on Exim's queue.
31518 Some of the automatic processing takes place by default only for
31519 &"locally-originated"& messages. This adjective is used to describe messages
31520 that are not received over TCP/IP, but instead are passed to an Exim process on
31521 its standard input. This includes the interactive &"local SMTP"& case that is
31522 set up by the &%-bs%& command line option.
31524 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
31525 or ::1) are not considered to be locally-originated. Exim does not treat the
31526 loopback interface specially in any way.
31528 If you want the loopback interface to be treated specially, you must ensure
31529 that there are appropriate entries in your ACLs.
31534 .section "Submission mode for non-local messages" "SECTsubmodnon"
31535 .cindex "message" "submission"
31536 .cindex "submission mode"
31537 Processing that happens automatically for locally-originated messages (unless
31538 &%suppress_local_fixups%& is set) can also be requested for messages that are
31539 received over TCP/IP. The term &"submission mode"& is used to describe this
31540 state. Submission mode is set by the modifier
31542 control = submission
31544 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
31545 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
31546 a local submission, and is normally used when the source of the message is
31547 known to be an MUA running on a client host (as opposed to an MTA). For
31548 example, to set submission mode for messages originating on the IPv4 loopback
31549 interface, you could include the following in the MAIL ACL:
31551 warn hosts = 127.0.0.1
31552 control = submission
31554 .cindex "&%sender_retain%& submission option"
31555 There are some options that can be used when setting submission mode. A slash
31556 is used to separate options. For example:
31558 control = submission/sender_retain
31560 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
31561 true and &%local_from_check%& false for the current incoming message. The first
31562 of these allows an existing &'Sender:'& header in the message to remain, and
31563 the second suppresses the check to ensure that &'From:'& matches the
31564 authenticated sender. With this setting, Exim still fixes up messages by adding
31565 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
31566 attempt to check sender authenticity in header lines.
31568 When &%sender_retain%& is not set, a submission mode setting may specify a
31569 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
31572 control = submission/domain=some.domain
31574 The domain may be empty. How this value is used is described in sections
31575 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
31576 that allows you to specify the user's full name for inclusion in a created
31577 &'Sender:'& or &'From:'& header line. For example:
31579 accept authenticated = *
31580 control = submission/domain=wonderland.example/\
31581 name=${lookup {$authenticated_id} \
31582 lsearch {/etc/exim/namelist}}
31584 Because the name may contain any characters, including slashes, the &%name%&
31585 option must be given last. The remainder of the string is used as the name. For
31586 the example above, if &_/etc/exim/namelist_& contains:
31588 bigegg: Humpty Dumpty
31590 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
31593 Sender: Humpty Dumpty <bigegg@wonderland.example>
31595 .cindex "return path" "in submission mode"
31596 By default, submission mode forces the return path to the same address as is
31597 used to create the &'Sender:'& header. However, if &%sender_retain%& is
31598 specified, the return path is also left unchanged.
31600 &*Note*&: The changes caused by submission mode take effect after the predata
31601 ACL. This means that any sender checks performed before the fix-ups use the
31602 untrusted sender address specified by the user, not the trusted sender address
31603 specified by submission mode. Although this might be slightly unexpected, it
31604 does mean that you can configure ACL checks to spot that a user is trying to
31605 spoof another's address.
31607 .section "Line endings" "SECTlineendings"
31608 .cindex "line endings"
31609 .cindex "carriage return"
31611 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
31612 linefeed) is the line ending for messages transmitted over the Internet using
31613 SMTP over TCP/IP. However, within individual operating systems, different
31614 conventions are used. For example, Unix-like systems use just LF, but others
31615 use CRLF or just CR.
31617 Exim was designed for Unix-like systems, and internally, it stores messages
31618 using the system's convention of a single LF as a line terminator. When
31619 receiving a message, all line endings are translated to this standard format.
31620 Originally, it was thought that programs that passed messages directly to an
31621 MTA within an operating system would use that system's convention. Experience
31622 has shown that this is not the case; for example, there are Unix applications
31623 that use CRLF in this circumstance. For this reason, and for compatibility with
31624 other MTAs, the way Exim handles line endings for all messages is now as
31628 LF not preceded by CR is treated as a line ending.
31630 CR is treated as a line ending; if it is immediately followed by LF, the LF
31633 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
31634 nor a local message in the state where a line containing only a dot is a
31637 If a bare CR is encountered within a header line, an extra space is added after
31638 the line terminator so as not to end the header line. The reasoning behind this
31639 is that bare CRs in header lines are most likely either to be mistakes, or
31640 people trying to play silly games.
31642 If the first header line received in a message ends with CRLF, a subsequent
31643 bare LF in a header line is treated in the same way as a bare CR in a header
31651 .section "Unqualified addresses" "SECID218"
31652 .cindex "unqualified addresses"
31653 .cindex "address" "qualification"
31654 By default, Exim expects every envelope address it receives from an external
31655 host to be fully qualified. Unqualified addresses cause negative responses to
31656 SMTP commands. However, because SMTP is used as a means of transporting
31657 messages from MUAs running on personal workstations, there is sometimes a
31658 requirement to accept unqualified addresses from specific hosts or IP networks.
31660 Exim has two options that separately control which hosts may send unqualified
31661 sender or recipient addresses in SMTP commands, namely
31662 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
31663 cases, if an unqualified address is accepted, it is qualified by adding the
31664 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
31666 .oindex "&%qualify_domain%&"
31667 .oindex "&%qualify_recipient%&"
31668 Unqualified addresses in header lines are automatically qualified for messages
31669 that are locally originated, unless the &%-bnq%& option is given on the command
31670 line. For messages received over SMTP, unqualified addresses in header lines
31671 are qualified only if unqualified addresses are permitted in SMTP commands. In
31672 other words, such qualification is also controlled by
31673 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
31678 .section "The UUCP From line" "SECID219"
31679 .cindex "&""From""& line"
31680 .cindex "UUCP" "&""From""& line"
31681 .cindex "sender" "address"
31682 .oindex "&%uucp_from_pattern%&"
31683 .oindex "&%uucp_from_sender%&"
31684 .cindex "envelope sender"
31685 .cindex "Sendmail compatibility" "&""From""& line"
31686 Messages that have come from UUCP (and some other applications) often begin
31687 with a line containing the envelope sender and a timestamp, following the word
31688 &"From"&. Examples of two common formats are:
31690 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
31691 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
31693 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
31694 Exim recognizes such lines at the start of messages that are submitted to it
31695 via the command line (that is, on the standard input). It does not recognize
31696 such lines in incoming SMTP messages, unless the sending host matches
31697 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
31698 and &%ignore_fromline_local%& is set. The recognition is controlled by a
31699 regular expression that is defined by the &%uucp_from_pattern%& option, whose
31700 default value matches the two common cases shown above and puts the address
31701 that follows &"From"& into &$1$&.
31703 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
31704 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
31705 a trusted user, the message's sender address is constructed by expanding the
31706 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
31707 then parsed as an RFC 2822 address. If there is no domain, the local part is
31708 qualified with &%qualify_domain%& unless it is the empty string. However, if
31709 the command line &%-f%& option is used, it overrides the &"From"& line.
31711 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
31712 sender address is not changed. This is also the case for incoming SMTP messages
31713 that are permitted to contain &"From"& lines.
31715 Only one &"From"& line is recognized. If there is more than one, the second is
31716 treated as a data line that starts the body of the message, as it is not valid
31717 as a header line. This also happens if a &"From"& line is present in an
31718 incoming SMTP message from a source that is not permitted to send them.
31722 .section "Resent- header lines" "SECID220"
31723 .cindex "&%Resent-%& header lines"
31724 RFC 2822 makes provision for sets of header lines starting with the string
31725 &`Resent-`& to be added to a message when it is resent by the original
31726 recipient to somebody else. These headers are &'Resent-Date:'&,
31727 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
31728 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
31731 &'Resent fields are strictly informational. They MUST NOT be used in the normal
31732 processing of replies or other such automatic actions on messages.'&
31735 This leaves things a bit vague as far as other processing actions such as
31736 address rewriting are concerned. Exim treats &%Resent-%& header lines as
31740 A &'Resent-From:'& line that just contains the login id of the submitting user
31741 is automatically rewritten in the same way as &'From:'& (see below).
31743 If there's a rewriting rule for a particular header line, it is also applied to
31744 &%Resent-%& header lines of the same type. For example, a rule that rewrites
31745 &'From:'& also rewrites &'Resent-From:'&.
31747 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
31750 For a locally-submitted message,
31751 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
31752 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
31753 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
31754 included in log lines in this case.
31756 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
31757 &%Resent-%& header lines are present.
31763 .section "The Auto-Submitted: header line" "SECID221"
31764 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
31765 includes the header line:
31767 Auto-Submitted: auto-replied
31770 .section "The Bcc: header line" "SECID222"
31771 .cindex "&'Bcc:'& header line"
31772 If Exim is called with the &%-t%& option, to take recipient addresses from a
31773 message's header, it removes any &'Bcc:'& header line that may exist (after
31774 extracting its addresses). If &%-t%& is not present on the command line, any
31775 existing &'Bcc:'& is not removed.
31778 .section "The Date: header line" "SECID223"
31779 .cindex "&'Date:'& header line"
31780 If a locally-generated or submission-mode message has no &'Date:'& header line,
31781 Exim adds one, using the current date and time, unless the
31782 &%suppress_local_fixups%& control has been specified.
31784 .section "The Delivery-date: header line" "SECID224"
31785 .cindex "&'Delivery-date:'& header line"
31786 .oindex "&%delivery_date_remove%&"
31787 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
31788 set. Exim can be configured to add them to the final delivery of messages. (See
31789 the generic &%delivery_date_add%& transport option.) They should not be present
31790 in messages in transit. If the &%delivery_date_remove%& configuration option is
31791 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
31795 .section "The Envelope-to: header line" "SECID225"
31796 .cindex "&'Envelope-to:'& header line"
31797 .oindex "&%envelope_to_remove%&"
31798 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
31799 Exim can be configured to add them to the final delivery of messages. (See the
31800 generic &%envelope_to_add%& transport option.) They should not be present in
31801 messages in transit. If the &%envelope_to_remove%& configuration option is set
31802 (the default), Exim removes &'Envelope-to:'& header lines from incoming
31806 .section "The From: header line" "SECTthefrohea"
31807 .cindex "&'From:'& header line"
31808 .cindex "Sendmail compatibility" "&""From""& line"
31809 .cindex "message" "submission"
31810 .cindex "submission mode"
31811 If a submission-mode message does not contain a &'From:'& header line, Exim
31812 adds one if either of the following conditions is true:
31815 The envelope sender address is not empty (that is, this is not a bounce
31816 message). The added header line copies the envelope sender address.
31818 .vindex "&$authenticated_id$&"
31819 The SMTP session is authenticated and &$authenticated_id$& is not empty.
31821 .vindex "&$qualify_domain$&"
31822 If no domain is specified by the submission control, the local part is
31823 &$authenticated_id$& and the domain is &$qualify_domain$&.
31825 If a non-empty domain is specified by the submission control, the local
31826 part is &$authenticated_id$&, and the domain is the specified domain.
31828 If an empty domain is specified by the submission control,
31829 &$authenticated_id$& is assumed to be the complete address.
31833 A non-empty envelope sender takes precedence.
31835 If a locally-generated incoming message does not contain a &'From:'& header
31836 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
31837 containing the sender's address. The calling user's login name and full name
31838 are used to construct the address, as described in section &<<SECTconstr>>&.
31839 They are obtained from the password data by calling &[getpwuid()]& (but see the
31840 &%unknown_login%& configuration option). The address is qualified with
31841 &%qualify_domain%&.
31843 For compatibility with Sendmail, if an incoming, non-SMTP message has a
31844 &'From:'& header line containing just the unqualified login name of the calling
31845 user, this is replaced by an address containing the user's login name and full
31846 name as described in section &<<SECTconstr>>&.
31849 .section "The Message-ID: header line" "SECID226"
31850 .cindex "&'Message-ID:'& header line"
31851 .cindex "message" "submission"
31852 .oindex "&%message_id_header_text%&"
31853 If a locally-generated or submission-mode incoming message does not contain a
31854 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
31855 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
31856 to the message. If there are any &'Resent-:'& headers in the message, it
31857 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
31858 message id, preceded by the letter E to ensure it starts with a letter, and
31859 followed by @ and the primary host name. Additional information can be included
31860 in this header line by setting the &%message_id_header_text%& and/or
31861 &%message_id_header_domain%& options.
31864 .section "The Received: header line" "SECID227"
31865 .cindex "&'Received:'& header line"
31866 A &'Received:'& header line is added at the start of every message. The
31867 contents are defined by the &%received_header_text%& configuration option, and
31868 Exim automatically adds a semicolon and a timestamp to the configured string.
31870 The &'Received:'& header is generated as soon as the message's header lines
31871 have been received. At this stage, the timestamp in the &'Received:'& header
31872 line is the time that the message started to be received. This is the value
31873 that is seen by the DATA ACL and by the &[local_scan()]& function.
31875 Once a message is accepted, the timestamp in the &'Received:'& header line is
31876 changed to the time of acceptance, which is (apart from a small delay while the
31877 -H spool file is written) the earliest time at which delivery could start.
31880 .section "The References: header line" "SECID228"
31881 .cindex "&'References:'& header line"
31882 Messages created by the &(autoreply)& transport include a &'References:'&
31883 header line. This is constructed according to the rules that are described in
31884 section 3.64 of RFC 2822 (which states that replies should contain such a
31885 header line), and section 3.14 of RFC 3834 (which states that automatic
31886 responses are not different in this respect). However, because some mail
31887 processing software does not cope well with very long header lines, no more
31888 than 12 message IDs are copied from the &'References:'& header line in the
31889 incoming message. If there are more than 12, the first one and then the final
31890 11 are copied, before adding the message ID of the incoming message.
31894 .section "The Return-path: header line" "SECID229"
31895 .cindex "&'Return-path:'& header line"
31896 .oindex "&%return_path_remove%&"
31897 &'Return-path:'& header lines are defined as something an MTA may insert when
31898 it does the final delivery of messages. (See the generic &%return_path_add%&
31899 transport option.) Therefore, they should not be present in messages in
31900 transit. If the &%return_path_remove%& configuration option is set (the
31901 default), Exim removes &'Return-path:'& header lines from incoming messages.
31905 .section "The Sender: header line" "SECTthesenhea"
31906 .cindex "&'Sender:'& header line"
31907 .cindex "message" "submission"
31908 For a locally-originated message from an untrusted user, Exim may remove an
31909 existing &'Sender:'& header line, and it may add a new one. You can modify
31910 these actions by setting the &%local_sender_retain%& option true, the
31911 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
31914 When a local message is received from an untrusted user and
31915 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
31916 control has not been set, a check is made to see if the address given in the
31917 &'From:'& header line is the correct (local) sender of the message. The address
31918 that is expected has the login name as the local part and the value of
31919 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
31920 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
31921 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
31922 line is added to the message.
31924 If you set &%local_from_check%& false, this checking does not occur. However,
31925 the removal of an existing &'Sender:'& line still happens, unless you also set
31926 &%local_sender_retain%& to be true. It is not possible to set both of these
31927 options true at the same time.
31929 .cindex "submission mode"
31930 By default, no processing of &'Sender:'& header lines is done for messages
31931 received over TCP/IP or for messages submitted by trusted users. However, when
31932 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
31933 not specified on the submission control, the following processing takes place:
31935 .vindex "&$authenticated_id$&"
31936 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
31937 authenticated, and &$authenticated_id$& is not empty, a sender address is
31938 created as follows:
31941 .vindex "&$qualify_domain$&"
31942 If no domain is specified by the submission control, the local part is
31943 &$authenticated_id$& and the domain is &$qualify_domain$&.
31945 If a non-empty domain is specified by the submission control, the local part
31946 is &$authenticated_id$&, and the domain is the specified domain.
31948 If an empty domain is specified by the submission control,
31949 &$authenticated_id$& is assumed to be the complete address.
31952 This address is compared with the address in the &'From:'& header line. If they
31953 are different, a &'Sender:'& header line containing the created address is
31954 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
31955 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
31957 .cindex "return path" "created from &'Sender:'&"
31958 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
31959 the message (the envelope sender address) is changed to be the same address,
31960 except in the case of submission mode when &%sender_retain%& is specified.
31964 .section "Adding and removing header lines in routers and transports" &&&
31965 "SECTheadersaddrem"
31966 .cindex "header lines" "adding; in router or transport"
31967 .cindex "header lines" "removing; in router or transport"
31968 When a message is delivered, the addition and removal of header lines can be
31969 specified in a system filter, or on any of the routers and transports that
31970 process the message. Section &<<SECTaddremheasys>>& contains details about
31971 modifying headers in a system filter. Header lines can also be added in an ACL
31972 as a message is received (see section &<<SECTaddheadacl>>&).
31974 In contrast to what happens in a system filter, header modifications that are
31975 specified on routers and transports apply only to the particular recipient
31976 addresses that are being processed by those routers and transports. These
31977 changes do not actually take place until a copy of the message is being
31978 transported. Therefore, they do not affect the basic set of header lines, and
31979 they do not affect the values of the variables that refer to header lines.
31981 &*Note*&: In particular, this means that any expansions in the configuration of
31982 the transport cannot refer to the modified header lines, because such
31983 expansions all occur before the message is actually transported.
31985 For both routers and transports, the result of expanding a &%headers_add%&
31986 option must be in the form of one or more RFC 2822 header lines, separated by
31987 newlines (coded as &"\n"&). For example:
31989 headers_add = X-added-header: added by $primary_hostname\n\
31990 X-added-second: another added header line
31992 Exim does not check the syntax of these added header lines.
31994 Multiple &%headers_add%& options for a single router or transport can be
31995 specified; the values will be concatenated (with a separating newline
31996 added) before expansion.
31998 The result of expanding &%headers_remove%& must consist of a colon-separated
31999 list of header names. This is confusing, because header names themselves are
32000 often terminated by colons. In this case, the colons are the list separators,
32001 not part of the names. For example:
32003 headers_remove = return-receipt-to:acknowledge-to
32006 Multiple &%headers_remove%& options for a single router or transport can be
32007 specified; the values will be concatenated (with a separating colon
32008 added) before expansion.
32010 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
32011 is expanded at routing time, and then associated with all addresses that are
32012 accepted by that router, and also with any new addresses that it generates. If
32013 an address passes through several routers as a result of aliasing or
32014 forwarding, the changes are cumulative.
32016 .oindex "&%unseen%&"
32017 However, this does not apply to multiple routers that result from the use of
32018 the &%unseen%& option. Any header modifications that were specified by the
32019 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
32021 Addresses that end up with different &%headers_add%& or &%headers_remove%&
32022 settings cannot be delivered together in a batch, so a transport is always
32023 dealing with a set of addresses that have the same header-processing
32026 The transport starts by writing the original set of header lines that arrived
32027 with the message, possibly modified by the system filter. As it writes out
32028 these lines, it consults the list of header names that were attached to the
32029 recipient address(es) by &%headers_remove%& options in routers, and it also
32030 consults the transport's own &%headers_remove%& option. Header lines whose
32031 names are on either of these lists are not written out. If there are multiple
32032 instances of any listed header, they are all skipped.
32034 After the remaining original header lines have been written, new header
32035 lines that were specified by routers' &%headers_add%& options are written, in
32036 the order in which they were attached to the address. These are followed by any
32037 header lines specified by the transport's &%headers_add%& option.
32039 This way of handling header line modifications in routers and transports has
32040 the following consequences:
32043 The original set of header lines, possibly modified by the system filter,
32044 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
32045 to it, at all times.
32047 Header lines that are added by a router's
32048 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
32049 expansion syntax in subsequent routers or the transport.
32051 Conversely, header lines that are specified for removal by &%headers_remove%&
32052 in a router remain visible to subsequent routers and the transport.
32054 Headers added to an address by &%headers_add%& in a router cannot be removed by
32055 a later router or by a transport.
32057 An added header can refer to the contents of an original header that is to be
32058 removed, even it has the same name as the added header. For example:
32060 headers_remove = subject
32061 headers_add = Subject: new subject (was: $h_subject:)
32065 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
32066 for a &(redirect)& router that has the &%one_time%& option set.
32072 .section "Constructed addresses" "SECTconstr"
32073 .cindex "address" "constructed"
32074 .cindex "constructed address"
32075 When Exim constructs a sender address for a locally-generated message, it uses
32078 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
32082 Zaphod Beeblebrox <zaphod@end.univ.example>
32084 The user name is obtained from the &%-F%& command line option if set, or
32085 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
32086 &"gecos"& field from the password entry. If the &"gecos"& field contains an
32087 ampersand character, this is replaced by the login name with the first letter
32088 upper cased, as is conventional in a number of operating systems. See the
32089 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
32090 The &%unknown_username%& option can be used to specify user names in cases when
32091 there is no password file entry.
32094 In all cases, the user name is made to conform to RFC 2822 by quoting all or
32095 parts of it if necessary. In addition, if it contains any non-printing
32096 characters, it is encoded as described in RFC 2047, which defines a way of
32097 including non-ASCII characters in header lines. The value of the
32098 &%headers_charset%& option specifies the name of the encoding that is used (the
32099 characters are assumed to be in this encoding). The setting of
32100 &%print_topbitchars%& controls whether characters with the top bit set (that
32101 is, with codes greater than 127) count as printing characters or not.
32105 .section "Case of local parts" "SECID230"
32106 .cindex "case of local parts"
32107 .cindex "local part" "case of"
32108 RFC 2822 states that the case of letters in the local parts of addresses cannot
32109 be assumed to be non-significant. Exim preserves the case of local parts of
32110 addresses, but by default it uses a lower-cased form when it is routing,
32111 because on most Unix systems, usernames are in lower case and case-insensitive
32112 routing is required. However, any particular router can be made to use the
32113 original case for local parts by setting the &%caseful_local_part%& generic
32116 .cindex "mixed-case login names"
32117 If you must have mixed-case user names on your system, the best way to proceed,
32118 assuming you want case-independent handling of incoming email, is to set up
32119 your first router to convert incoming local parts in your domains to the
32120 correct case by means of a file lookup. For example:
32124 domains = +local_domains
32125 data = ${lookup{$local_part}cdb\
32126 {/etc/usercased.cdb}{$value}fail}\
32129 For this router, the local part is forced to lower case by the default action
32130 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
32131 up a new local part in the correct case. If you then set &%caseful_local_part%&
32132 on any subsequent routers which process your domains, they will operate on
32133 local parts with the correct case in a case-sensitive manner.
32137 .section "Dots in local parts" "SECID231"
32138 .cindex "dot" "in local part"
32139 .cindex "local part" "dots in"
32140 RFC 2822 forbids empty components in local parts. That is, an unquoted local
32141 part may not begin or end with a dot, nor have two consecutive dots in the
32142 middle. However, it seems that many MTAs do not enforce this, so Exim permits
32143 empty components for compatibility.
32147 .section "Rewriting addresses" "SECID232"
32148 .cindex "rewriting" "addresses"
32149 Rewriting of sender and recipient addresses, and addresses in headers, can
32150 happen automatically, or as the result of configuration options, as described
32151 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
32152 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
32154 Automatic rewriting includes qualification, as mentioned above. The other case
32155 in which it can happen is when an incomplete non-local domain is given. The
32156 routing process may cause this to be expanded into the full domain name. For
32157 example, a header such as
32161 might get rewritten as
32163 To: hare@teaparty.wonderland.fict.example
32165 Rewriting as a result of routing is the one kind of message processing that
32166 does not happen at input time, as it cannot be done until the address has
32169 Strictly, one should not do &'any'& deliveries of a message until all its
32170 addresses have been routed, in case any of the headers get changed as a
32171 result of routing. However, doing this in practice would hold up many
32172 deliveries for unreasonable amounts of time, just because one address could not
32173 immediately be routed. Exim therefore does not delay other deliveries when
32174 routing of one or more addresses is deferred.
32175 .ecindex IIDmesproc
32179 . ////////////////////////////////////////////////////////////////////////////
32180 . ////////////////////////////////////////////////////////////////////////////
32182 .chapter "SMTP processing" "CHAPSMTP"
32183 .scindex IIDsmtpproc1 "SMTP" "processing details"
32184 .scindex IIDsmtpproc2 "LMTP" "processing details"
32185 Exim supports a number of different ways of using the SMTP protocol, and its
32186 LMTP variant, which is an interactive protocol for transferring messages into a
32187 closed mail store application. This chapter contains details of how SMTP is
32188 processed. For incoming mail, the following are available:
32191 SMTP over TCP/IP (Exim daemon or &'inetd'&);
32193 SMTP over the standard input and output (the &%-bs%& option);
32195 Batched SMTP on the standard input (the &%-bS%& option).
32198 For mail delivery, the following are available:
32201 SMTP over TCP/IP (the &(smtp)& transport);
32203 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
32206 LMTP over a pipe to a process running in the local host (the &(lmtp)&
32209 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
32210 the &%use_bsmtp%& option set).
32213 &'Batched SMTP'& is the name for a process in which batches of messages are
32214 stored in or read from files (or pipes), in a format in which SMTP commands are
32215 used to contain the envelope information.
32219 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
32220 .cindex "SMTP" "outgoing over TCP/IP"
32221 .cindex "outgoing SMTP over TCP/IP"
32222 .cindex "LMTP" "over TCP/IP"
32223 .cindex "outgoing LMTP over TCP/IP"
32226 .cindex "SIZE option on MAIL command"
32227 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
32228 The &%protocol%& option selects which protocol is to be used, but the actual
32229 processing is the same in both cases.
32231 If, in response to its EHLO command, Exim is told that the SIZE
32232 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
32233 command. The value of <&'n'&> is the message size plus the value of the
32234 &%size_addition%& option (default 1024) to allow for additions to the message
32235 such as per-transport header lines, or changes made in a
32236 .cindex "transport" "filter"
32237 .cindex "filter" "transport filter"
32238 transport filter. If &%size_addition%& is set negative, the use of SIZE is
32241 If the remote server advertises support for PIPELINING, Exim uses the
32242 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
32243 required for the transaction.
32245 If the remote server advertises support for the STARTTLS command, and Exim
32246 was built to support TLS encryption, it tries to start a TLS session unless the
32247 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
32248 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
32249 is called for verification.
32251 If the remote server advertises support for the AUTH command, Exim scans
32252 the authenticators configuration for any suitable client settings, as described
32253 in chapter &<<CHAPSMTPAUTH>>&.
32255 .cindex "carriage return"
32257 Responses from the remote host are supposed to be terminated by CR followed by
32258 LF. However, there are known to be hosts that do not send CR characters, so in
32259 order to be able to interwork with such hosts, Exim treats LF on its own as a
32262 If a message contains a number of different addresses, all those with the same
32263 characteristics (for example, the same envelope sender) that resolve to the
32264 same set of hosts, in the same order, are sent in a single SMTP transaction,
32265 even if they are for different domains, unless there are more than the setting
32266 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
32267 they are split into groups containing no more than &%max_rcpt%&s addresses
32268 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
32269 in parallel sessions. The order of hosts with identical MX values is not
32270 significant when checking whether addresses can be batched in this way.
32272 When the &(smtp)& transport suffers a temporary failure that is not
32273 message-related, Exim updates its transport-specific database, which contains
32274 records indexed by host name that remember which messages are waiting for each
32275 particular host. It also updates the retry database with new retry times.
32277 .cindex "hints database" "retry keys"
32278 Exim's retry hints are based on host name plus IP address, so if one address of
32279 a multi-homed host is broken, it will soon be skipped most of the time.
32280 See the next section for more detail about error handling.
32282 .cindex "SMTP" "passed connection"
32283 .cindex "SMTP" "batching over TCP/IP"
32284 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
32285 looks in the hints database for the transport to see if there are any queued
32286 messages waiting for the host to which it is connected. If it finds one, it
32287 creates a new Exim process using the &%-MC%& option (which can only be used by
32288 a process running as root or the Exim user) and passes the TCP/IP socket to it
32289 so that it can deliver another message using the same socket. The new process
32290 does only those deliveries that are routed to the connected host, and may in
32291 turn pass the socket on to a third process, and so on.
32293 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
32294 limit the number of messages sent down a single TCP/IP connection.
32296 .cindex "asterisk" "after IP address"
32297 The second and subsequent messages delivered down an existing connection are
32298 identified in the main log by the addition of an asterisk after the closing
32299 square bracket of the IP address.
32304 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
32305 .cindex "error" "in outgoing SMTP"
32306 .cindex "SMTP" "errors in outgoing"
32307 .cindex "host" "error"
32308 Three different kinds of error are recognized for outgoing SMTP: host errors,
32309 message errors, and recipient errors.
32312 .vitem "&*Host errors*&"
32313 A host error is not associated with a particular message or with a
32314 particular recipient of a message. The host errors are:
32317 Connection refused or timed out,
32319 Any error response code on connection,
32321 Any error response code to EHLO or HELO,
32323 Loss of connection at any time, except after &"."&,
32325 I/O errors at any time,
32327 Timeouts during the session, other than in response to MAIL, RCPT or
32328 the &"."& at the end of the data.
32331 For a host error, a permanent error response on connection, or in response to
32332 EHLO, causes all addresses routed to the host to be failed. Any other host
32333 error causes all addresses to be deferred, and retry data to be created for the
32334 host. It is not tried again, for any message, until its retry time arrives. If
32335 the current set of addresses are not all delivered in this run (to some
32336 alternative host), the message is added to the list of those waiting for this
32337 host, so if it is still undelivered when a subsequent successful delivery is
32338 made to the host, it will be sent down the same SMTP connection.
32340 .vitem "&*Message errors*&"
32341 .cindex "message" "error"
32342 A message error is associated with a particular message when sent to a
32343 particular host, but not with a particular recipient of the message. The
32344 message errors are:
32347 Any error response code to MAIL, DATA, or the &"."& that terminates
32350 Timeout after MAIL,
32352 Timeout or loss of connection after the &"."& that terminates the data. A
32353 timeout after the DATA command itself is treated as a host error, as is loss of
32354 connection at any other time.
32357 For a message error, a permanent error response (5&'xx'&) causes all addresses
32358 to be failed, and a delivery error report to be returned to the sender. A
32359 temporary error response (4&'xx'&), or one of the timeouts, causes all
32360 addresses to be deferred. Retry data is not created for the host, but instead,
32361 a retry record for the combination of host plus message id is created. The
32362 message is not added to the list of those waiting for this host. This ensures
32363 that the failing message will not be sent to this host again until the retry
32364 time arrives. However, other messages that are routed to the host are not
32365 affected, so if it is some property of the message that is causing the error,
32366 it will not stop the delivery of other mail.
32368 If the remote host specified support for the SIZE parameter in its response
32369 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
32370 over-large message will cause a message error because the error arrives as a
32373 .vitem "&*Recipient errors*&"
32374 .cindex "recipient" "error"
32375 A recipient error is associated with a particular recipient of a message. The
32376 recipient errors are:
32379 Any error response to RCPT,
32381 Timeout after RCPT.
32384 For a recipient error, a permanent error response (5&'xx'&) causes the
32385 recipient address to be failed, and a bounce message to be returned to the
32386 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
32387 address to be deferred, and routing retry data to be created for it. This is
32388 used to delay processing of the address in subsequent queue runs, until its
32389 routing retry time arrives. This applies to all messages, but because it
32390 operates only in queue runs, one attempt will be made to deliver a new message
32391 to the failing address before the delay starts to operate. This ensures that,
32392 if the failure is really related to the message rather than the recipient
32393 (&"message too big for this recipient"& is a possible example), other messages
32394 have a chance of getting delivered. If a delivery to the address does succeed,
32395 the retry information gets cleared, so all stuck messages get tried again, and
32396 the retry clock is reset.
32398 The message is not added to the list of those waiting for this host. Use of the
32399 host for other messages is unaffected, and except in the case of a timeout,
32400 other recipients are processed independently, and may be successfully delivered
32401 in the current SMTP session. After a timeout it is of course impossible to
32402 proceed with the session, so all addresses get deferred. However, those other
32403 than the one that failed do not suffer any subsequent retry delays. Therefore,
32404 if one recipient is causing trouble, the others have a chance of getting
32405 through when a subsequent delivery attempt occurs before the failing
32406 recipient's retry time.
32409 In all cases, if there are other hosts (or IP addresses) available for the
32410 current set of addresses (for example, from multiple MX records), they are
32411 tried in this run for any undelivered addresses, subject of course to their
32412 own retry data. In other words, recipient error retry data does not take effect
32413 until the next delivery attempt.
32415 Some hosts have been observed to give temporary error responses to every
32416 MAIL command at certain times (&"insufficient space"& has been seen). It
32417 would be nice if such circumstances could be recognized, and defer data for the
32418 host itself created, but this is not possible within the current Exim design.
32419 What actually happens is that retry data for every (host, message) combination
32422 The reason that timeouts after MAIL and RCPT are treated specially is that
32423 these can sometimes arise as a result of the remote host's verification
32424 procedures. Exim makes this assumption, and treats them as if a temporary error
32425 response had been received. A timeout after &"."& is treated specially because
32426 it is known that some broken implementations fail to recognize the end of the
32427 message if the last character of the last line is a binary zero. Thus, it is
32428 helpful to treat this case as a message error.
32430 Timeouts at other times are treated as host errors, assuming a problem with the
32431 host, or the connection to it. If a timeout after MAIL, RCPT,
32432 or &"."& is really a connection problem, the assumption is that at the next try
32433 the timeout is likely to occur at some other point in the dialogue, causing it
32434 then to be treated as a host error.
32436 There is experimental evidence that some MTAs drop the connection after the
32437 terminating &"."& if they do not like the contents of the message for some
32438 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
32439 should be given. That is why Exim treats this case as a message rather than a
32440 host error, in order not to delay other messages to the same host.
32445 .section "Incoming SMTP messages over TCP/IP" "SECID233"
32446 .cindex "SMTP" "incoming over TCP/IP"
32447 .cindex "incoming SMTP over TCP/IP"
32450 Incoming SMTP messages can be accepted in one of two ways: by running a
32451 listening daemon, or by using &'inetd'&. In the latter case, the entry in
32452 &_/etc/inetd.conf_& should be like this:
32454 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
32456 Exim distinguishes between this case and the case of a locally running user
32457 agent using the &%-bs%& option by checking whether or not the standard input is
32458 a socket. When it is, either the port must be privileged (less than 1024), or
32459 the caller must be root or the Exim user. If any other user passes a socket
32460 with an unprivileged port number, Exim prints a message on the standard error
32461 stream and exits with an error code.
32463 By default, Exim does not make a log entry when a remote host connects or
32464 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
32465 unexpected. It can be made to write such log entries by setting the
32466 &%smtp_connection%& log selector.
32468 .cindex "carriage return"
32470 Commands from the remote host are supposed to be terminated by CR followed by
32471 LF. However, there are known to be hosts that do not send CR characters. In
32472 order to be able to interwork with such hosts, Exim treats LF on its own as a
32474 Furthermore, because common code is used for receiving messages from all
32475 sources, a CR on its own is also interpreted as a line terminator. However, the
32476 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
32478 .cindex "EHLO" "invalid data"
32479 .cindex "HELO" "invalid data"
32480 One area that sometimes gives rise to problems concerns the EHLO or
32481 HELO commands. Some clients send syntactically invalid versions of these
32482 commands, which Exim rejects by default. (This is nothing to do with verifying
32483 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
32484 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
32485 match the broken hosts that send invalid commands.
32487 .cindex "SIZE option on MAIL command"
32488 .cindex "MAIL" "SIZE option"
32489 The amount of disk space available is checked whenever SIZE is received on
32490 a MAIL command, independently of whether &%message_size_limit%& or
32491 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
32492 false. A temporary error is given if there is not enough space. If
32493 &%check_spool_space%& is set, the check is for that amount of space plus the
32494 value given with SIZE, that is, it checks that the addition of the incoming
32495 message will not reduce the space below the threshold.
32497 When a message is successfully received, Exim includes the local message id in
32498 its response to the final &"."& that terminates the data. If the remote host
32499 logs this text it can help with tracing what has happened to a message.
32501 The Exim daemon can limit the number of simultaneous incoming connections it is
32502 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
32503 number of simultaneous incoming connections from a single remote host (see the
32504 &%smtp_accept_max_per_host%& option). Additional connection attempts are
32505 rejected using the SMTP temporary error code 421.
32507 The Exim daemon does not rely on the SIGCHLD signal to detect when a
32508 subprocess has finished, as this can get lost at busy times. Instead, it looks
32509 for completed subprocesses every time it wakes up. Provided there are other
32510 things happening (new incoming calls, starts of queue runs), completed
32511 processes will be noticed and tidied away. On very quiet systems you may
32512 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
32513 it will be noticed when the daemon next wakes up.
32515 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
32516 and can also be set up to reject SMTP calls from non-reserved hosts at times of
32517 high system load &-- for details see the &%smtp_accept_reserve%&,
32518 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
32519 applies in both the daemon and &'inetd'& cases.
32521 Exim normally starts a delivery process for each message received, though this
32522 can be varied by means of the &%-odq%& command line option and the
32523 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
32524 number of simultaneously running delivery processes started in this way from
32525 SMTP input can be limited by the &%smtp_accept_queue%& and
32526 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
32527 subsequently received messages are just put on the input queue without starting
32528 a delivery process.
32530 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
32531 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
32532 started up from the &'inetd'& daemon, because in that case each connection is
32533 handled by an entirely independent Exim process. Control by load average is,
32534 however, available with &'inetd'&.
32536 Exim can be configured to verify addresses in incoming SMTP commands as they
32537 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
32538 to rewrite addresses at this time &-- before any syntax checking is done. See
32539 section &<<SECTrewriteS>>&.
32541 Exim can also be configured to limit the rate at which a client host submits
32542 MAIL and RCPT commands in a single SMTP session. See the
32543 &%smtp_ratelimit_hosts%& option.
32547 .section "Unrecognized SMTP commands" "SECID234"
32548 .cindex "SMTP" "unrecognized commands"
32549 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
32550 commands during a single SMTP connection, it drops the connection after sending
32551 the error response to the last command. The default value for
32552 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
32553 abuse that subvert web servers into making connections to SMTP ports; in these
32554 circumstances, a number of non-SMTP lines are sent first.
32557 .section "Syntax and protocol errors in SMTP commands" "SECID235"
32558 .cindex "SMTP" "syntax errors"
32559 .cindex "SMTP" "protocol errors"
32560 A syntax error is detected if an SMTP command is recognized, but there is
32561 something syntactically wrong with its data, for example, a malformed email
32562 address in a RCPT command. Protocol errors include invalid command
32563 sequencing such as RCPT before MAIL. If Exim receives more than
32564 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
32565 drops the connection after sending the error response to the last command. The
32566 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
32567 broken clients that loop sending bad commands (yes, it has been seen).
32571 .section "Use of non-mail SMTP commands" "SECID236"
32572 .cindex "SMTP" "non-mail commands"
32573 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
32574 DATA. Exim counts such commands, and drops the connection if there are too
32575 many of them in a single SMTP session. This action catches some
32576 denial-of-service attempts and things like repeated failing AUTHs, or a mad
32577 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
32578 defines what &"too many"& means. Its default value is 10.
32580 When a new message is expected, one occurrence of RSET is not counted. This
32581 allows a client to send one RSET between messages (this is not necessary,
32582 but some clients do it). Exim also allows one uncounted occurrence of HELO
32583 or EHLO, and one occurrence of STARTTLS between messages. After
32584 starting up a TLS session, another EHLO is expected, and so it too is not
32587 The first occurrence of AUTH in a connection, or immediately following
32588 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
32589 RCPT, DATA, and QUIT are counted.
32591 You can control which hosts are subject to the limit set by
32592 &%smtp_accept_max_nonmail%& by setting
32593 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
32594 the limit apply to all hosts. This option means that you can exclude any
32595 specific badly-behaved hosts that you have to live with.
32600 .section "The VRFY and EXPN commands" "SECID237"
32601 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
32602 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
32603 appropriate) in order to decide whether the command should be accepted or not.
32604 If no ACL is defined, the command is rejected.
32606 .cindex "VRFY" "processing"
32607 When VRFY is accepted, it runs exactly the same code as when Exim is
32608 called with the &%-bv%& option.
32610 .cindex "EXPN" "processing"
32611 When EXPN is accepted, a single-level expansion of the address is done.
32612 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
32613 than a verification (the &%-bv%& option). If an unqualified local part is given
32614 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
32615 of VRFY and EXPN commands are logged on the main and reject logs, and
32616 VRFY verification failures are logged on the main log for consistency with
32621 .section "The ETRN command" "SECTETRN"
32622 .cindex "ETRN" "processing"
32623 RFC 1985 describes an SMTP command called ETRN that is designed to
32624 overcome the security problems of the TURN command (which has fallen into
32625 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
32626 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
32627 should be accepted or not. If no ACL is defined, the command is rejected.
32629 The ETRN command is concerned with &"releasing"& messages that are awaiting
32630 delivery to certain hosts. As Exim does not organize its message queue by host,
32631 the only form of ETRN that is supported by default is the one where the
32632 text starts with the &"#"& prefix, in which case the remainder of the text is
32633 specific to the SMTP server. A valid ETRN command causes a run of Exim with
32634 the &%-R%& option to happen, with the remainder of the ETRN text as its
32635 argument. For example,
32643 which causes a delivery attempt on all messages with undelivered addresses
32644 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
32645 default), Exim prevents the simultaneous execution of more than one queue run
32646 for the same argument string as a result of an ETRN command. This stops
32647 a misbehaving client from starting more than one queue runner at once.
32649 .cindex "hints database" "ETRN serialization"
32650 Exim implements the serialization by means of a hints database in which a
32651 record is written whenever a process is started by ETRN, and deleted when
32652 the process completes. However, Exim does not keep the SMTP session waiting for
32653 the ETRN process to complete. Once ETRN is accepted, the client is sent
32654 a &"success"& return code. Obviously there is scope for hints records to get
32655 left lying around if there is a system or program crash. To guard against this,
32656 Exim ignores any records that are more than six hours old.
32658 .oindex "&%smtp_etrn_command%&"
32659 For more control over what ETRN does, the &%smtp_etrn_command%& option can
32660 used. This specifies a command that is run whenever ETRN is received,
32661 whatever the form of its argument. For
32664 smtp_etrn_command = /etc/etrn_command $domain \
32665 $sender_host_address
32667 .vindex "&$domain$&"
32668 The string is split up into arguments which are independently expanded. The
32669 expansion variable &$domain$& is set to the argument of the ETRN command,
32670 and no syntax checking is done on the contents of this argument. Exim does not
32671 wait for the command to complete, so its status code is not checked. Exim runs
32672 under its own uid and gid when receiving incoming SMTP, so it is not possible
32673 for it to change them before running the command.
32677 .section "Incoming local SMTP" "SECID238"
32678 .cindex "SMTP" "local incoming"
32679 Some user agents use SMTP to pass messages to their local MTA using the
32680 standard input and output, as opposed to passing the envelope on the command
32681 line and writing the message to the standard input. This is supported by the
32682 &%-bs%& option. This form of SMTP is handled in the same way as incoming
32683 messages over TCP/IP (including the use of ACLs), except that the envelope
32684 sender given in a MAIL command is ignored unless the caller is trusted. In
32685 an ACL you can detect this form of SMTP input by testing for an empty host
32686 identification. It is common to have this as the first line in the ACL that
32687 runs for RCPT commands:
32691 This accepts SMTP messages from local processes without doing any other tests.
32695 .section "Outgoing batched SMTP" "SECTbatchSMTP"
32696 .cindex "SMTP" "batched outgoing"
32697 .cindex "batched SMTP output"
32698 Both the &(appendfile)& and &(pipe)& transports can be used for handling
32699 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
32700 be output in BSMTP format. No SMTP responses are possible for this form of
32701 delivery. All it is doing is using SMTP commands as a way of transmitting the
32702 envelope along with the message.
32704 The message is written to the file or pipe preceded by the SMTP commands
32705 MAIL and RCPT, and followed by a line containing a single dot. Lines in
32706 the message that start with a dot have an extra dot added. The SMTP command
32707 HELO is not normally used. If it is required, the &%message_prefix%& option
32708 can be used to specify it.
32710 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
32711 one recipient address at a time by default. However, you can arrange for them
32712 to handle several addresses at once by setting the &%batch_max%& option. When
32713 this is done for BSMTP, messages may contain multiple RCPT commands. See
32714 chapter &<<CHAPbatching>>& for more details.
32717 When one or more addresses are routed to a BSMTP transport by a router that
32718 sets up a host list, the name of the first host on the list is available to the
32719 transport in the variable &$host$&. Here is an example of such a transport and
32724 driver = manualroute
32725 transport = smtp_appendfile
32726 route_list = domain.example batch.host.example
32730 driver = appendfile
32731 directory = /var/bsmtp/$host
32736 This causes messages addressed to &'domain.example'& to be written in BSMTP
32737 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
32738 message (unless there are more than 1000 recipients).
32742 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
32743 .cindex "SMTP" "batched incoming"
32744 .cindex "batched SMTP input"
32745 The &%-bS%& command line option causes Exim to accept one or more messages by
32746 reading SMTP on the standard input, but to generate no responses. If the caller
32747 is trusted, the senders in the MAIL commands are believed; otherwise the
32748 sender is always the caller of Exim. Unqualified senders and receivers are not
32749 rejected (there seems little point) but instead just get qualified. HELO
32750 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
32751 as NOOP; QUIT quits.
32753 Minimal policy checking is done for BSMTP input. Only the non-SMTP
32754 ACL is run in the same way as for non-SMTP local input.
32756 If an error is detected while reading a message, including a missing &"."& at
32757 the end, Exim gives up immediately. It writes details of the error to the
32758 standard output in a stylized way that the calling program should be able to
32759 make some use of automatically, for example:
32761 554 Unexpected end of file
32762 Transaction started in line 10
32763 Error detected in line 14
32765 It writes a more verbose version, for human consumption, to the standard error
32768 An error was detected while processing a file of BSMTP input.
32769 The error message was:
32771 501 '>' missing at end of address
32773 The SMTP transaction started in line 10.
32774 The error was detected in line 12.
32775 The SMTP command at fault was:
32777 rcpt to:<malformed@in.com.plete
32779 1 previous message was successfully processed.
32780 The rest of the batch was abandoned.
32782 The return code from Exim is zero only if there were no errors. It is 1 if some
32783 messages were accepted before an error was detected, and 2 if no messages were
32785 .ecindex IIDsmtpproc1
32786 .ecindex IIDsmtpproc2
32790 . ////////////////////////////////////////////////////////////////////////////
32791 . ////////////////////////////////////////////////////////////////////////////
32793 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
32794 "Customizing messages"
32795 When a message fails to be delivered, or remains on the queue for more than a
32796 configured amount of time, Exim sends a message to the original sender, or
32797 to an alternative configured address. The text of these messages is built into
32798 the code of Exim, but it is possible to change it, either by adding a single
32799 string, or by replacing each of the paragraphs by text supplied in a file.
32801 The &'From:'& and &'To:'& header lines are automatically generated; you can
32802 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
32803 option. Exim also adds the line
32805 Auto-Submitted: auto-generated
32807 to all warning and bounce messages,
32810 .section "Customizing bounce messages" "SECID239"
32811 .cindex "customizing" "bounce message"
32812 .cindex "bounce message" "customizing"
32813 If &%bounce_message_text%& is set, its contents are included in the default
32814 message immediately after &"This message was created automatically by mail
32815 delivery software."& The string is not expanded. It is not used if
32816 &%bounce_message_file%& is set.
32818 When &%bounce_message_file%& is set, it must point to a template file for
32819 constructing error messages. The file consists of a series of text items,
32820 separated by lines consisting of exactly four asterisks. If the file cannot be
32821 opened, default text is used and a message is written to the main and panic
32822 logs. If any text item in the file is empty, default text is used for that
32825 .vindex "&$bounce_recipient$&"
32826 .vindex "&$bounce_return_size_limit$&"
32827 Each item of text that is read from the file is expanded, and there are two
32828 expansion variables which can be of use here: &$bounce_recipient$& is set to
32829 the recipient of an error message while it is being created, and
32830 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
32831 option, rounded to a whole number.
32833 The items must appear in the file in the following order:
32836 The first item is included in the headers, and should include at least a
32837 &'Subject:'& header. Exim does not check the syntax of these headers.
32839 The second item forms the start of the error message. After it, Exim lists the
32840 failing addresses with their error messages.
32842 The third item is used to introduce any text from pipe transports that is to be
32843 returned to the sender. It is omitted if there is no such text.
32845 The fourth item is used to introduce the copy of the message that is returned
32846 as part of the error report.
32848 The fifth item is added after the fourth one if the returned message is
32849 truncated because it is bigger than &%return_size_limit%&.
32851 The sixth item is added after the copy of the original message.
32854 The default state (&%bounce_message_file%& unset) is equivalent to the
32855 following file, in which the sixth item is empty. The &'Subject:'& and some
32856 other lines have been split in order to fit them on the page:
32858 Subject: Mail delivery failed
32859 ${if eq{$sender_address}{$bounce_recipient}
32860 {: returning message to sender}}
32862 This message was created automatically by mail delivery software.
32864 A message ${if eq{$sender_address}{$bounce_recipient}
32865 {that you sent }{sent by
32869 }}could not be delivered to all of its recipients.
32870 This is a permanent error. The following address(es) failed:
32872 The following text was generated during the delivery attempt(s):
32874 ------ This is a copy of the message, including all the headers.
32877 ------ The body of the message is $message_size characters long;
32879 ------ $bounce_return_size_limit or so are included here.
32882 .section "Customizing warning messages" "SECTcustwarn"
32883 .cindex "customizing" "warning message"
32884 .cindex "warning of delay" "customizing the message"
32885 The option &%warn_message_file%& can be pointed at a template file for use when
32886 warnings about message delays are created. In this case there are only three
32890 The first item is included in the headers, and should include at least a
32891 &'Subject:'& header. Exim does not check the syntax of these headers.
32893 The second item forms the start of the warning message. After it, Exim lists
32894 the delayed addresses.
32896 The third item then ends the message.
32899 The default state is equivalent to the following file, except that some lines
32900 have been split here, in order to fit them on the page:
32902 Subject: Warning: message $message_exim_id delayed
32903 $warn_message_delay
32905 This message was created automatically by mail delivery software.
32907 A message ${if eq{$sender_address}{$warn_message_recipients}
32908 {that you sent }{sent by
32912 }}has not been delivered to all of its recipients after
32913 more than $warn_message_delay on the queue on $primary_hostname.
32915 The message identifier is: $message_exim_id
32916 The subject of the message is: $h_subject
32917 The date of the message is: $h_date
32919 The following address(es) have not yet been delivered:
32921 No action is required on your part. Delivery attempts will
32922 continue for some time, and this warning may be repeated at
32923 intervals if the message remains undelivered. Eventually the
32924 mail delivery software will give up, and when that happens,
32925 the message will be returned to you.
32927 .vindex "&$warn_message_delay$&"
32928 .vindex "&$warn_message_recipients$&"
32929 However, in the default state the subject and date lines are omitted if no
32930 appropriate headers exist. During the expansion of this file,
32931 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
32932 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
32933 of recipients for the warning message. There may be more than one if there are
32934 multiple addresses with different &%errors_to%& settings on the routers that
32940 . ////////////////////////////////////////////////////////////////////////////
32941 . ////////////////////////////////////////////////////////////////////////////
32943 .chapter "Some common configuration settings" "CHAPcomconreq"
32944 This chapter discusses some configuration settings that seem to be fairly
32945 common. More examples and discussion can be found in the Exim book.
32949 .section "Sending mail to a smart host" "SECID240"
32950 .cindex "smart host" "example router"
32951 If you want to send all mail for non-local domains to a &"smart host"&, you
32952 should replace the default &(dnslookup)& router with a router which does the
32953 routing explicitly:
32955 send_to_smart_host:
32956 driver = manualroute
32957 route_list = !+local_domains smart.host.name
32958 transport = remote_smtp
32960 You can use the smart host's IP address instead of the name if you wish.
32961 If you are using Exim only to submit messages to a smart host, and not for
32962 receiving incoming messages, you can arrange for it to do the submission
32963 synchronously by setting the &%mua_wrapper%& option (see chapter
32964 &<<CHAPnonqueueing>>&).
32969 .section "Using Exim to handle mailing lists" "SECTmailinglists"
32970 .cindex "mailing lists"
32971 Exim can be used to run simple mailing lists, but for large and/or complicated
32972 requirements, the use of additional specialized mailing list software such as
32973 Majordomo or Mailman is recommended.
32975 The &(redirect)& router can be used to handle mailing lists where each list
32976 is maintained in a separate file, which can therefore be managed by an
32977 independent manager. The &%domains%& router option can be used to run these
32978 lists in a separate domain from normal mail. For example:
32982 domains = lists.example
32983 file = /usr/lists/$local_part
32986 errors_to = $local_part-request@lists.example
32989 This router is skipped for domains other than &'lists.example'&. For addresses
32990 in that domain, it looks for a file that matches the local part. If there is no
32991 such file, the router declines, but because &%no_more%& is set, no subsequent
32992 routers are tried, and so the whole delivery fails.
32994 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
32995 expanded into a file name or a pipe delivery, which is usually inappropriate in
32998 .oindex "&%errors_to%&"
32999 The &%errors_to%& option specifies that any delivery errors caused by addresses
33000 taken from a mailing list are to be sent to the given address rather than the
33001 original sender of the message. However, before acting on this, Exim verifies
33002 the error address, and ignores it if verification fails.
33004 For example, using the configuration above, mail sent to
33005 &'dicts@lists.example'& is passed on to those addresses contained in
33006 &_/usr/lists/dicts_&, with error reports directed to
33007 &'dicts-request@lists.example'&, provided that this address can be verified.
33008 There could be a file called &_/usr/lists/dicts-request_& containing
33009 the address(es) of this particular list's manager(s), but other approaches,
33010 such as setting up an earlier router (possibly using the &%local_part_prefix%&
33011 or &%local_part_suffix%& options) to handle addresses of the form
33012 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
33016 .section "Syntax errors in mailing lists" "SECID241"
33017 .cindex "mailing lists" "syntax errors in"
33018 If an entry in redirection data contains a syntax error, Exim normally defers
33019 delivery of the original address. That means that a syntax error in a mailing
33020 list holds up all deliveries to the list. This may not be appropriate when a
33021 list is being maintained automatically from data supplied by users, and the
33022 addresses are not rigorously checked.
33024 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
33025 entries that fail to parse, noting the incident in the log. If in addition
33026 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
33027 whenever a broken address is skipped. It is usually appropriate to set
33028 &%syntax_errors_to%& to the same address as &%errors_to%&.
33032 .section "Re-expansion of mailing lists" "SECID242"
33033 .cindex "mailing lists" "re-expansion of"
33034 Exim remembers every individual address to which a message has been delivered,
33035 in order to avoid duplication, but it normally stores only the original
33036 recipient addresses with a message. If all the deliveries to a mailing list
33037 cannot be done at the first attempt, the mailing list is re-expanded when the
33038 delivery is next tried. This means that alterations to the list are taken into
33039 account at each delivery attempt, so addresses that have been added to
33040 the list since the message arrived will therefore receive a copy of the
33041 message, even though it pre-dates their subscription.
33043 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
33044 on the &(redirect)& router. If this is done, any addresses generated by the
33045 router that fail to deliver at the first attempt are added to the message as
33046 &"top level"& addresses, and the parent address that generated them is marked
33047 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
33048 subsequent delivery attempts. The disadvantage of this is that if any of the
33049 failing addresses are incorrect, correcting them in the file has no effect on
33050 pre-existing messages.
33052 The original top-level address is remembered with each of the generated
33053 addresses, and is output in any log messages. However, any intermediate parent
33054 addresses are not recorded. This makes a difference to the log only if the
33055 &%all_parents%& selector is set, but for mailing lists there is normally only
33056 one level of expansion anyway.
33060 .section "Closed mailing lists" "SECID243"
33061 .cindex "mailing lists" "closed"
33062 The examples so far have assumed open mailing lists, to which anybody may
33063 send mail. It is also possible to set up closed lists, where mail is accepted
33064 from specified senders only. This is done by making use of the generic
33065 &%senders%& option to restrict the router that handles the list.
33067 The following example uses the same file as a list of recipients and as a list
33068 of permitted senders. It requires three routers:
33072 domains = lists.example
33073 local_part_suffix = -request
33074 file = /usr/lists/$local_part$local_part_suffix
33079 domains = lists.example
33080 senders = ${if exists {/usr/lists/$local_part}\
33081 {lsearch;/usr/lists/$local_part}{*}}
33082 file = /usr/lists/$local_part
33085 errors_to = $local_part-request@lists.example
33090 domains = lists.example
33092 data = :fail: $local_part@lists.example is a closed mailing list
33094 All three routers have the same &%domains%& setting, so for any other domains,
33095 they are all skipped. The first router runs only if the local part ends in
33096 &%-request%&. It handles messages to the list manager(s) by means of an open
33099 The second router runs only if the &%senders%& precondition is satisfied. It
33100 checks for the existence of a list that corresponds to the local part, and then
33101 checks that the sender is on the list by means of a linear search. It is
33102 necessary to check for the existence of the file before trying to search it,
33103 because otherwise Exim thinks there is a configuration error. If the file does
33104 not exist, the expansion of &%senders%& is *, which matches all senders. This
33105 means that the router runs, but because there is no list, declines, and
33106 &%no_more%& ensures that no further routers are run. The address fails with an
33107 &"unrouteable address"& error.
33109 The third router runs only if the second router is skipped, which happens when
33110 a mailing list exists, but the sender is not on it. This router forcibly fails
33111 the address, giving a suitable error message.
33116 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
33118 .cindex "Variable Envelope Return Paths"
33119 .cindex "envelope sender"
33120 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
33121 are a way of helping mailing list administrators discover which subscription
33122 address is the cause of a particular delivery failure. The idea is to encode
33123 the original recipient address in the outgoing envelope sender address, so that
33124 if the message is forwarded by another host and then subsequently bounces, the
33125 original recipient can be extracted from the recipient address of the bounce.
33127 .oindex &%errors_to%&
33128 .oindex &%return_path%&
33129 Envelope sender addresses can be modified by Exim using two different
33130 facilities: the &%errors_to%& option on a router (as shown in previous mailing
33131 list examples), or the &%return_path%& option on a transport. The second of
33132 these is effective only if the message is successfully delivered to another
33133 host; it is not used for errors detected on the local host (see the description
33134 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
33135 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
33141 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33142 {$1-request+$local_part=$domain@your.dom.example}fail}
33144 This has the effect of rewriting the return path (envelope sender) on outgoing
33145 SMTP messages, if the local part of the original return path ends in
33146 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
33147 local part and domain of the recipient into the return path. Suppose, for
33148 example, that a message whose return path has been set to
33149 &'somelist-request@your.dom.example'& is sent to
33150 &'subscriber@other.dom.example'&. In the transport, the return path is
33153 somelist-request+subscriber=other.dom.example@your.dom.example
33155 .vindex "&$local_part$&"
33156 For this to work, you must tell Exim to send multiple copies of messages that
33157 have more than one recipient, so that each copy has just one recipient. This is
33158 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
33159 might be sent to several different recipients in the same domain, in which case
33160 &$local_part$& is not available in the transport, because it is not unique.
33162 Unless your host is doing nothing but mailing list deliveries, you should
33163 probably use a separate transport for the VERP deliveries, so as not to use
33164 extra resources in making one-per-recipient copies for other deliveries. This
33165 can easily be done by expanding the &%transport%& option in the router:
33169 domains = ! +local_domains
33171 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33172 {verp_smtp}{remote_smtp}}
33175 If you want to change the return path using &%errors_to%& in a router instead
33176 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
33177 routers that handle mailing list addresses. This will ensure that all delivery
33178 errors, including those detected on the local host, are sent to the VERP
33181 On a host that does no local deliveries and has no manual routing, only the
33182 &(dnslookup)& router needs to be changed. A special transport is not needed for
33183 SMTP deliveries. Every mailing list recipient has its own return path value,
33184 and so Exim must hand them to the transport one at a time. Here is an example
33185 of a &(dnslookup)& router that implements VERP:
33189 domains = ! +local_domains
33190 transport = remote_smtp
33192 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
33193 {$1-request+$local_part=$domain@your.dom.example}fail}
33196 Before you start sending out messages with VERPed return paths, you must also
33197 configure Exim to accept the bounce messages that come back to those paths.
33198 Typically this is done by setting a &%local_part_suffix%& option for a
33199 router, and using this to route the messages to wherever you want to handle
33202 The overhead incurred in using VERP depends very much on the size of the
33203 message, the number of recipient addresses that resolve to the same remote
33204 host, and the speed of the connection over which the message is being sent. If
33205 a lot of addresses resolve to the same host and the connection is slow, sending
33206 a separate copy of the message for each address may take substantially longer
33207 than sending a single copy with many recipients (for which VERP cannot be
33215 .section "Virtual domains" "SECTvirtualdomains"
33216 .cindex "virtual domains"
33217 .cindex "domain" "virtual"
33218 The phrase &'virtual domain'& is unfortunately used with two rather different
33222 A domain for which there are no real mailboxes; all valid local parts are
33223 aliases for other email addresses. Common examples are organizational
33224 top-level domains and &"vanity"& domains.
33226 One of a number of independent domains that are all handled by the same host,
33227 with mailboxes on that host, but where the mailbox owners do not necessarily
33228 have login accounts on that host.
33231 The first usage is probably more common, and does seem more &"virtual"& than
33232 the second. This kind of domain can be handled in Exim with a straightforward
33233 aliasing router. One approach is to create a separate alias file for each
33234 virtual domain. Exim can test for the existence of the alias file to determine
33235 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
33236 to a router of this form:
33240 domains = dsearch;/etc/mail/virtual
33241 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
33244 The &%domains%& option specifies that the router is to be skipped, unless there
33245 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
33246 domain that is being processed. When the router runs, it looks up the local
33247 part in the file to find a new address (or list of addresses). The &%no_more%&
33248 setting ensures that if the lookup fails (leading to &%data%& being an empty
33249 string), Exim gives up on the address without trying any subsequent routers.
33251 This one router can handle all the virtual domains because the alias file names
33252 follow a fixed pattern. Permissions can be arranged so that appropriate people
33253 can edit the different alias files. A successful aliasing operation results in
33254 a new envelope recipient address, which is then routed from scratch.
33256 The other kind of &"virtual"& domain can also be handled in a straightforward
33257 way. One approach is to create a file for each domain containing a list of
33258 valid local parts, and use it in a router like this:
33262 domains = dsearch;/etc/mail/domains
33263 local_parts = lsearch;/etc/mail/domains/$domain
33264 transport = my_mailboxes
33266 The address is accepted if there is a file for the domain, and the local part
33267 can be found in the file. The &%domains%& option is used to check for the
33268 file's existence because &%domains%& is tested before the &%local_parts%&
33269 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
33270 because that option is tested after &%local_parts%&. The transport is as
33274 driver = appendfile
33275 file = /var/mail/$domain/$local_part
33278 This uses a directory of mailboxes for each domain. The &%user%& setting is
33279 required, to specify which uid is to be used for writing to the mailboxes.
33281 The configuration shown here is just one example of how you might support this
33282 requirement. There are many other ways this kind of configuration can be set
33283 up, for example, by using a database instead of separate files to hold all the
33284 information about the domains.
33288 .section "Multiple user mailboxes" "SECTmulbox"
33289 .cindex "multiple mailboxes"
33290 .cindex "mailbox" "multiple"
33291 .cindex "local part" "prefix"
33292 .cindex "local part" "suffix"
33293 Heavy email users often want to operate with multiple mailboxes, into which
33294 incoming mail is automatically sorted. A popular way of handling this is to
33295 allow users to use multiple sender addresses, so that replies can easily be
33296 identified. Users are permitted to add prefixes or suffixes to their local
33297 parts for this purpose. The wildcard facility of the generic router options
33298 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
33299 example, consider this router:
33304 file = $home/.forward
33305 local_part_suffix = -*
33306 local_part_suffix_optional
33309 .vindex "&$local_part_suffix$&"
33310 It runs a user's &_.forward_& file for all local parts of the form
33311 &'username-*'&. Within the filter file the user can distinguish different
33312 cases by testing the variable &$local_part_suffix$&. For example:
33314 if $local_part_suffix contains -special then
33315 save /home/$local_part/Mail/special
33318 If the filter file does not exist, or does not deal with such addresses, they
33319 fall through to subsequent routers, and, assuming no subsequent use of the
33320 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
33321 control over which suffixes are valid.
33323 Alternatively, a suffix can be used to trigger the use of a different
33324 &_.forward_& file &-- which is the way a similar facility is implemented in
33330 file = $home/.forward$local_part_suffix
33331 local_part_suffix = -*
33332 local_part_suffix_optional
33335 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
33336 example, &_.forward-special_& is used. Once again, if the appropriate file
33337 does not exist, or does not deal with the address, it is passed on to
33338 subsequent routers, which could, if required, look for an unqualified
33339 &_.forward_& file to use as a default.
33343 .section "Simplified vacation processing" "SECID244"
33344 .cindex "vacation processing"
33345 The traditional way of running the &'vacation'& program is for a user to set up
33346 a pipe command in a &_.forward_& file
33347 (see section &<<SECTspecitredli>>& for syntax details).
33348 This is prone to error by inexperienced users. There are two features of Exim
33349 that can be used to make this process simpler for users:
33352 A local part prefix such as &"vacation-"& can be specified on a router which
33353 can cause the message to be delivered directly to the &'vacation'& program, or
33354 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
33355 &_.forward_& file are then much simpler. For example:
33357 spqr, vacation-spqr
33360 The &%require_files%& generic router option can be used to trigger a
33361 vacation delivery by checking for the existence of a certain file in the
33362 user's home directory. The &%unseen%& generic option should also be used, to
33363 ensure that the original delivery also proceeds. In this case, all the user has
33364 to do is to create a file called, say, &_.vacation_&, containing a vacation
33368 Another advantage of both these methods is that they both work even when the
33369 use of arbitrary pipes by users is locked out.
33373 .section "Taking copies of mail" "SECID245"
33374 .cindex "message" "copying every"
33375 Some installations have policies that require archive copies of all messages to
33376 be made. A single copy of each message can easily be taken by an appropriate
33377 command in a system filter, which could, for example, use a different file for
33378 each day's messages.
33380 There is also a shadow transport mechanism that can be used to take copies of
33381 messages that are successfully delivered by local transports, one copy per
33382 delivery. This could be used, &'inter alia'&, to implement automatic
33383 notification of delivery by sites that insist on doing such things.
33387 .section "Intermittently connected hosts" "SECID246"
33388 .cindex "intermittently connected hosts"
33389 It has become quite common (because it is cheaper) for hosts to connect to the
33390 Internet periodically rather than remain connected all the time. The normal
33391 arrangement is that mail for such hosts accumulates on a system that is
33392 permanently connected.
33394 Exim was designed for use on permanently connected hosts, and so it is not
33395 particularly well-suited to use in an intermittently connected environment.
33396 Nevertheless there are some features that can be used.
33399 .section "Exim on the upstream server host" "SECID247"
33400 It is tempting to arrange for incoming mail for the intermittently connected
33401 host to remain on Exim's queue until the client connects. However, this
33402 approach does not scale very well. Two different kinds of waiting message are
33403 being mixed up in the same queue &-- those that cannot be delivered because of
33404 some temporary problem, and those that are waiting for their destination host
33405 to connect. This makes it hard to manage the queue, as well as wasting
33406 resources, because each queue runner scans the entire queue.
33408 A better approach is to separate off those messages that are waiting for an
33409 intermittently connected host. This can be done by delivering these messages
33410 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
33411 format, from where they are transmitted by other software when their
33412 destination connects. This makes it easy to collect all the mail for one host
33413 in a single directory, and to apply local timeout rules on a per-message basis
33416 On a very small scale, leaving the mail on Exim's queue can be made to work. If
33417 you are doing this, you should configure Exim with a long retry period for the
33418 intermittent host. For example:
33420 cheshire.wonderland.fict.example * F,5d,24h
33422 This stops a lot of failed delivery attempts from occurring, but Exim remembers
33423 which messages it has queued up for that host. Once the intermittent host comes
33424 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
33425 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
33426 causes all the queued up messages to be delivered, often down a single SMTP
33427 connection. While the host remains connected, any new messages get delivered
33430 If the connecting hosts do not have fixed IP addresses, that is, if a host is
33431 issued with a different IP address each time it connects, Exim's retry
33432 mechanisms on the holding host get confused, because the IP address is normally
33433 used as part of the key string for holding retry information. This can be
33434 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
33435 Since this has disadvantages for permanently connected hosts, it is best to
33436 arrange a separate transport for the intermittently connected ones.
33440 .section "Exim on the intermittently connected client host" "SECID248"
33441 The value of &%smtp_accept_queue_per_connection%& should probably be
33442 increased, or even set to zero (that is, disabled) on the intermittently
33443 connected host, so that all incoming messages down a single connection get
33444 delivered immediately.
33446 .cindex "SMTP" "passed connection"
33447 .cindex "SMTP" "multiple deliveries"
33448 .cindex "multiple SMTP deliveries"
33449 Mail waiting to be sent from an intermittently connected host will probably
33450 not have been routed, because without a connection DNS lookups are not
33451 possible. This means that if a normal queue run is done at connection time,
33452 each message is likely to be sent in a separate SMTP session. This can be
33453 avoided by starting the queue run with a command line option beginning with
33454 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
33455 first pass, routing is done but no deliveries take place. The second pass is a
33456 normal queue run; since all the messages have been previously routed, those
33457 destined for the same host are likely to get sent as multiple deliveries in a
33458 single SMTP connection.
33462 . ////////////////////////////////////////////////////////////////////////////
33463 . ////////////////////////////////////////////////////////////////////////////
33465 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
33466 "Exim as a non-queueing client"
33467 .cindex "client, non-queueing"
33468 .cindex "smart host" "suppressing queueing"
33469 On a personal computer, it is a common requirement for all
33470 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
33471 configured to operate that way, for all the popular operating systems.
33472 However, there are some MUAs for Unix-like systems that cannot be so
33473 configured: they submit messages using the command line interface of
33474 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
33477 If the personal computer runs continuously, there is no problem, because it can
33478 run a conventional MTA that handles delivery to the smart host, and deal with
33479 any delays via its queueing mechanism. However, if the computer does not run
33480 continuously or runs different operating systems at different times, queueing
33481 email is not desirable.
33483 There is therefore a requirement for something that can provide the
33484 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
33485 any queueing or retrying facilities. Furthermore, the delivery to the smart
33486 host should be synchronous, so that if it fails, the sending MUA is immediately
33487 informed. In other words, we want something that extends an MUA that submits
33488 to a local MTA via the command line so that it behaves like one that submits
33489 to a remote smart host using TCP/SMTP.
33491 There are a number of applications (for example, there is one called &'ssmtp'&)
33492 that do this job. However, people have found them to be lacking in various
33493 ways. For instance, you might want to allow aliasing and forwarding to be done
33494 before sending a message to the smart host.
33496 Exim already had the necessary infrastructure for doing this job. Just a few
33497 tweaks were needed to make it behave as required, though it is somewhat of an
33498 overkill to use a fully-featured MTA for this purpose.
33500 .oindex "&%mua_wrapper%&"
33501 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
33502 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
33503 assumes that it is being used to &"wrap"& a command-line MUA in the manner
33504 just described. As well as setting &%mua_wrapper%&, you also need to provide a
33505 compatible router and transport configuration. Typically there will be just one
33506 router and one transport, sending everything to a smart host.
33508 When run in MUA wrapping mode, the behaviour of Exim changes in the
33512 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
33513 In other words, the only way to submit messages is via the command line.
33515 Each message is synchronously delivered as soon as it is received (&%-odi%& is
33516 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
33517 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
33518 does not finish until the delivery attempt is complete. If the delivery is
33519 successful, a zero return code is given.
33521 Address redirection is permitted, but the final routing for all addresses must
33522 be to the same remote transport, and to the same list of hosts. Furthermore,
33523 the return address (envelope sender) must be the same for all recipients, as
33524 must any added or deleted header lines. In other words, it must be possible to
33525 deliver the message in a single SMTP transaction, however many recipients there
33528 If these conditions are not met, or if routing any address results in a
33529 failure or defer status, or if Exim is unable to deliver all the recipients
33530 successfully to one of the smart hosts, delivery of the entire message fails.
33532 Because no queueing is allowed, all failures are treated as permanent; there
33533 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
33534 smart host. Furthermore, because only a single yes/no response can be given to
33535 the caller, it is not possible to deliver to some recipients and not others. If
33536 there is an error (temporary or permanent) for any recipient, all are failed.
33538 If more than one smart host is listed, Exim will try another host after a
33539 connection failure or a timeout, in the normal way. However, if this kind of
33540 failure happens for all the hosts, the delivery fails.
33542 When delivery fails, an error message is written to the standard error stream
33543 (as well as to Exim's log), and Exim exits to the caller with a return code
33544 value 1. The message is expunged from Exim's spool files. No bounce messages
33545 are ever generated.
33547 No retry data is maintained, and any retry rules are ignored.
33549 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
33550 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
33551 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
33554 The overall effect is that Exim makes a single synchronous attempt to deliver
33555 the message, failing if there is any kind of problem. Because no local
33556 deliveries are done and no daemon can be run, Exim does not need root
33557 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
33558 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
33559 the advantages and disadvantages of running without root privilege.
33564 . ////////////////////////////////////////////////////////////////////////////
33565 . ////////////////////////////////////////////////////////////////////////////
33567 .chapter "Log files" "CHAPlog"
33568 .scindex IIDloggen "log" "general description"
33569 .cindex "log" "types of"
33570 Exim writes three different logs, referred to as the main log, the reject log,
33575 The main log records the arrival of each message and each delivery in a single
33576 line in each case. The format is as compact as possible, in an attempt to keep
33577 down the size of log files. Two-character flag sequences make it easy to pick
33578 out these lines. A number of other events are recorded in the main log. Some of
33579 them are optional, in which case the &%log_selector%& option controls whether
33580 they are included or not. A Perl script called &'eximstats'&, which does simple
33581 analysis of main log files, is provided in the Exim distribution (see section
33582 &<<SECTmailstat>>&).
33584 .cindex "reject log"
33585 The reject log records information from messages that are rejected as a result
33586 of a configuration option (that is, for policy reasons).
33587 The first line of each rejection is a copy of the line that is also written to
33588 the main log. Then, if the message's header has been read at the time the log
33589 is written, its contents are written to this log. Only the original header
33590 lines are available; header lines added by ACLs are not logged. You can use the
33591 reject log to check that your policy controls are working correctly; on a busy
33592 host this may be easier than scanning the main log for rejection messages. You
33593 can suppress the writing of the reject log by setting &%write_rejectlog%&
33596 .cindex "panic log"
33597 .cindex "system log"
33598 When certain serious errors occur, Exim writes entries to its panic log. If the
33599 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
33600 are usually written to the main log as well, but can get lost amid the mass of
33601 other entries. The panic log should be empty under normal circumstances. It is
33602 therefore a good idea to check it (or to have a &'cron'& script check it)
33603 regularly, in order to become aware of any problems. When Exim cannot open its
33604 panic log, it tries as a last resort to write to the system log (syslog). This
33605 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
33606 message itself is written at priority LOG_CRIT.
33609 Every log line starts with a timestamp, in the format shown in the following
33610 example. Note that many of the examples shown in this chapter are line-wrapped.
33611 In the log file, this would be all on one line:
33613 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
33616 By default, the timestamps are in the local timezone. There are two
33617 ways of changing this:
33620 You can set the &%timezone%& option to a different time zone; in particular, if
33625 the timestamps will be in UTC (aka GMT).
33627 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
33630 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
33634 .cindex "log" "process ids in"
33635 .cindex "pid (process id)" "in log lines"
33636 Exim does not include its process id in log lines by default, but you can
33637 request that it does so by specifying the &`pid`& log selector (see section
33638 &<<SECTlogselector>>&). When this is set, the process id is output, in square
33639 brackets, immediately after the time and date.
33644 .section "Where the logs are written" "SECTwhelogwri"
33645 .cindex "log" "destination"
33646 .cindex "log" "to file"
33647 .cindex "log" "to syslog"
33649 The logs may be written to local files, or to syslog, or both. However, it
33650 should be noted that many syslog implementations use UDP as a transport, and
33651 are therefore unreliable in the sense that messages are not guaranteed to
33652 arrive at the loghost, nor is the ordering of messages necessarily maintained.
33653 It has also been reported that on large log files (tens of megabytes) you may
33654 need to tweak syslog to prevent it syncing the file with each write &-- on
33655 Linux this has been seen to make syslog take 90% plus of CPU time.
33657 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
33658 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
33659 configuration. This latter string is expanded, so it can contain, for example,
33660 references to the host name:
33662 log_file_path = /var/log/$primary_hostname/exim_%slog
33664 It is generally advisable, however, to set the string in &_Local/Makefile_&
33665 rather than at run time, because then the setting is available right from the
33666 start of Exim's execution. Otherwise, if there's something it wants to log
33667 before it has read the configuration file (for example, an error in the
33668 configuration file) it will not use the path you want, and may not be able to
33671 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
33672 list, currently limited to at most two items. This is one option where the
33673 facility for changing a list separator may not be used. The list must always be
33674 colon-separated. If an item in the list is &"syslog"& then syslog is used;
33675 otherwise the item must either be an absolute path, containing &`%s`& at the
33676 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
33677 implying the use of a default path.
33679 When Exim encounters an empty item in the list, it searches the list defined by
33680 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
33681 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
33682 mean &"use the path specified at build time"&. It no such item exists, log
33683 files are written in the &_log_& subdirectory of the spool directory. This is
33684 equivalent to the setting:
33686 log_file_path = $spool_directory/log/%slog
33688 If you do not specify anything at build time or run time, that is where the
33691 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
33692 are in use &-- see section &<<SECTdatlogfil>>& below.
33694 Here are some examples of possible settings:
33696 &`LOG_FILE_PATH=syslog `& syslog only
33697 &`LOG_FILE_PATH=:syslog `& syslog and default path
33698 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
33699 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
33701 If there are more than two paths in the list, the first is used and a panic
33706 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
33707 .cindex "log" "cycling local files"
33708 .cindex "cycling logs"
33709 .cindex "&'exicyclog'&"
33710 .cindex "log" "local files; writing to"
33711 Some operating systems provide centralized and standardized methods for cycling
33712 log files. For those that do not, a utility script called &'exicyclog'& is
33713 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
33714 main and reject logs each time it is called. The maximum number of old logs to
33715 keep can be set. It is suggested this script is run as a daily &'cron'& job.
33717 An Exim delivery process opens the main log when it first needs to write to it,
33718 and it keeps the file open in case subsequent entries are required &-- for
33719 example, if a number of different deliveries are being done for the same
33720 message. However, remote SMTP deliveries can take a long time, and this means
33721 that the file may be kept open long after it is renamed if &'exicyclog'& or
33722 something similar is being used to rename log files on a regular basis. To
33723 ensure that a switch of log files is noticed as soon as possible, Exim calls
33724 &[stat()]& on the main log's name before reusing an open file, and if the file
33725 does not exist, or its inode has changed, the old file is closed and Exim
33726 tries to open the main log from scratch. Thus, an old log file may remain open
33727 for quite some time, but no Exim processes should write to it once it has been
33732 .section "Datestamped log files" "SECTdatlogfil"
33733 .cindex "log" "datestamped files"
33734 Instead of cycling the main and reject log files by renaming them
33735 periodically, some sites like to use files whose names contain a datestamp,
33736 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
33737 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
33738 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
33739 point where the datestamp is required. For example:
33741 log_file_path = /var/spool/exim/log/%slog-%D
33742 log_file_path = /var/log/exim-%s-%D.log
33743 log_file_path = /var/spool/exim/log/%D-%slog
33744 log_file_path = /var/log/exim/%s.%M
33746 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
33747 examples of names generated by the above examples:
33749 /var/spool/exim/log/mainlog-20021225
33750 /var/log/exim-reject-20021225.log
33751 /var/spool/exim/log/20021225-mainlog
33752 /var/log/exim/main.200212
33754 When this form of log file is specified, Exim automatically switches to new
33755 files at midnight. It does not make any attempt to compress old logs; you
33756 will need to write your own script if you require this. You should not
33757 run &'exicyclog'& with this form of logging.
33759 The location of the panic log is also determined by &%log_file_path%&, but it
33760 is not datestamped, because rotation of the panic log does not make sense.
33761 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
33762 the string. In addition, if it immediately follows a slash, a following
33763 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
33764 character is removed. Thus, the four examples above would give these panic
33767 /var/spool/exim/log/paniclog
33768 /var/log/exim-panic.log
33769 /var/spool/exim/log/paniclog
33770 /var/log/exim/panic
33774 .section "Logging to syslog" "SECID249"
33775 .cindex "log" "syslog; writing to"
33776 The use of syslog does not change what Exim logs or the format of its messages,
33777 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
33778 Exim's log lines are omitted when these lines are sent to syslog. Apart from
33779 that, the same strings are written to syslog as to log files. The syslog
33780 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
33781 by default, but you can change these by setting the &%syslog_facility%& and
33782 &%syslog_processname%& options, respectively. If Exim was compiled with
33783 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
33784 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
33785 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
33786 the time and host name to each line.
33787 The three log streams are mapped onto syslog priorities as follows:
33790 &'mainlog'& is mapped to LOG_INFO
33792 &'rejectlog'& is mapped to LOG_NOTICE
33794 &'paniclog'& is mapped to LOG_ALERT
33797 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
33798 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
33799 these are routed by syslog to the same place. You can suppress this duplication
33800 by setting &%syslog_duplication%& false.
33802 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
33803 entries contain multiple lines when headers are included. To cope with both
33804 these cases, entries written to syslog are split into separate &[syslog()]&
33805 calls at each internal newline, and also after a maximum of
33806 870 data characters. (This allows for a total syslog line length of 1024, when
33807 additions such as timestamps are added.) If you are running a syslog
33808 replacement that can handle lines longer than the 1024 characters allowed by
33809 RFC 3164, you should set
33811 SYSLOG_LONG_LINES=yes
33813 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
33814 lines, but it still splits at internal newlines in &'reject'& log entries.
33816 To make it easy to re-assemble split lines later, each component of a split
33817 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
33818 where <&'n'&> is the component number and <&'m'&> is the total number of
33819 components in the entry. The / delimiter is used when the line was split
33820 because it was too long; if it was split because of an internal newline, the \
33821 delimiter is used. For example, supposing the length limit to be 50 instead of
33822 870, the following would be the result of a typical rejection message to
33823 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
33824 name, and pid as added by syslog:
33826 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
33827 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
33828 [3/5] when scanning for sender: missing or malformed lo
33829 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
33832 The same error might cause the following lines to be written to &"rejectlog"&
33835 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
33836 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
33837 [3/18] er when scanning for sender: missing or malformed
33838 [4/18] local part in "<>" (envelope sender is <ph10@cam
33840 [6\18] Recipients: ph10@some.domain.cam.example
33841 [7\18] P Received: from [127.0.0.1] (ident=ph10)
33842 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
33843 [9\18] id 16RdAL-0006pc-00
33844 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
33845 [11\18] 09:43 +0100
33847 [13\18] Subject: this is a test header
33848 [18\18] X-something: this is another header
33849 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
33852 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
33854 Log lines that are neither too long nor contain newlines are written to syslog
33855 without modification.
33857 If only syslog is being used, the Exim monitor is unable to provide a log tail
33858 display, unless syslog is routing &'mainlog'& to a file on the local host and
33859 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
33864 .section "Log line flags" "SECID250"
33865 One line is written to the main log for each message received, and for each
33866 successful, unsuccessful, and delayed delivery. These lines can readily be
33867 picked out by the distinctive two-character flags that immediately follow the
33868 timestamp. The flags are:
33870 &`<=`& message arrival
33871 &`=>`& normal message delivery
33872 &`->`& additional address in same delivery
33873 &`>>`& cutthrough message delivery
33874 &`*>`& delivery suppressed by &%-N%&
33875 &`**`& delivery failed; address bounced
33876 &`==`& delivery deferred; temporary problem
33880 .section "Logging message reception" "SECID251"
33881 .cindex "log" "reception line"
33882 The format of the single-line entry in the main log that is written for every
33883 message received is shown in the basic example below, which is split over
33884 several lines in order to fit it on the page:
33886 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
33887 H=mailer.fict.example [192.168.123.123] U=exim
33888 P=smtp S=5678 id=<incoming message id>
33890 The address immediately following &"<="& is the envelope sender address. A
33891 bounce message is shown with the sender address &"<>"&, and if it is locally
33892 generated, this is followed by an item of the form
33896 which is a reference to the message that caused the bounce to be sent.
33900 For messages from other hosts, the H and U fields identify the remote host and
33901 record the RFC 1413 identity of the user that sent the message, if one was
33902 received. The number given in square brackets is the IP address of the sending
33903 host. If there is a single, unparenthesized host name in the H field, as
33904 above, it has been verified to correspond to the IP address (see the
33905 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
33906 by the remote host in the SMTP HELO or EHLO command, and has not been
33907 verified. If verification yields a different name to that given for HELO or
33908 EHLO, the verified name appears first, followed by the HELO or EHLO
33909 name in parentheses.
33911 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
33912 without brackets, in the HELO or EHLO command, leading to entries in
33913 the log containing text like these examples:
33915 H=(10.21.32.43) [192.168.8.34]
33916 H=([10.21.32.43]) [192.168.8.34]
33918 This can be confusing. Only the final address in square brackets can be relied
33921 For locally generated messages (that is, messages not received over TCP/IP),
33922 the H field is omitted, and the U field contains the login name of the caller
33925 .cindex "authentication" "logging"
33926 .cindex "AUTH" "logging"
33927 For all messages, the P field specifies the protocol used to receive the
33928 message. This is the value that is stored in &$received_protocol$&. In the case
33929 of incoming SMTP messages, the value indicates whether or not any SMTP
33930 extensions (ESMTP), encryption, or authentication were used. If the SMTP
33931 session was encrypted, there is an additional X field that records the cipher
33932 suite that was used.
33934 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
33935 hosts that have authenticated themselves using the SMTP AUTH command. The first
33936 value is used when the SMTP connection was encrypted (&"secure"&). In this case
33937 there is an additional item A= followed by the name of the authenticator that
33938 was used. If an authenticated identification was set up by the authenticator's
33939 &%server_set_id%& option, this is logged too, separated by a colon from the
33940 authenticator name.
33942 .cindex "size" "of message"
33943 The id field records the existing message id, if present. The size of the
33944 received message is given by the S field. When the message is delivered,
33945 headers may be removed or added, so that the size of delivered copies of the
33946 message may not correspond with this value (and indeed may be different to each
33949 The &%log_selector%& option can be used to request the logging of additional
33950 data when a message is received. See section &<<SECTlogselector>>& below.
33954 .section "Logging deliveries" "SECID252"
33955 .cindex "log" "delivery line"
33956 The format of the single-line entry in the main log that is written for every
33957 delivery is shown in one of the examples below, for local and remote
33958 deliveries, respectively. Each example has been split into two lines in order
33959 to fit it on the page:
33961 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
33962 <marv@hitch.fict.example> R=localuser T=local_delivery
33963 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
33964 monk@holistic.fict.example R=dnslookup T=remote_smtp
33965 H=holistic.fict.example [192.168.234.234]
33967 For ordinary local deliveries, the original address is given in angle brackets
33968 after the final delivery address, which might be a pipe or a file. If
33969 intermediate address(es) exist between the original and the final address, the
33970 last of these is given in parentheses after the final address. The R and T
33971 fields record the router and transport that were used to process the address.
33973 If SMTP AUTH was used for the delivery there is an additional item A=
33974 followed by the name of the authenticator that was used.
33975 If an authenticated identification was set up by the authenticator's &%client_set_id%&
33976 option, this is logged too, separated by a colon from the authenticator name.
33978 If a shadow transport was run after a successful local delivery, the log line
33979 for the successful delivery has an item added on the end, of the form
33981 &`ST=<`&&'shadow transport name'&&`>`&
33983 If the shadow transport did not succeed, the error message is put in
33984 parentheses afterwards.
33986 .cindex "asterisk" "after IP address"
33987 When more than one address is included in a single delivery (for example, two
33988 SMTP RCPT commands in one transaction) the second and subsequent addresses are
33989 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
33990 down a single SMTP connection, an asterisk follows the IP address in the log
33991 lines for the second and subsequent messages.
33993 .cindex "delivery" "cutthrough; logging"
33994 .cindex "cutthrough" "logging"
33995 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
33996 line precedes the reception line, since cutthrough waits for a possible
33997 rejection from the destination in case it can reject the sourced item.
33999 The generation of a reply message by a filter file gets logged as a
34000 &"delivery"& to the addressee, preceded by &">"&.
34002 The &%log_selector%& option can be used to request the logging of additional
34003 data when a message is delivered. See section &<<SECTlogselector>>& below.
34006 .section "Discarded deliveries" "SECID253"
34007 .cindex "discarded messages"
34008 .cindex "message" "discarded"
34009 .cindex "delivery" "discarded; logging"
34010 When a message is discarded as a result of the command &"seen finish"& being
34011 obeyed in a filter file which generates no deliveries, a log entry of the form
34013 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
34014 <low.club@bridge.example> R=userforward
34016 is written, to record why no deliveries are logged. When a message is discarded
34017 because it is aliased to &":blackhole:"& the log line is like this:
34019 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
34020 <hole@nowhere.example> R=blackhole_router
34024 .section "Deferred deliveries" "SECID254"
34025 When a delivery is deferred, a line of the following form is logged:
34027 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
34028 R=dnslookup T=smtp defer (146): Connection refused
34030 In the case of remote deliveries, the error is the one that was given for the
34031 last IP address that was tried. Details of individual SMTP failures are also
34032 written to the log, so the above line would be preceded by something like
34034 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
34035 mail1.endrest.example [192.168.239.239]: Connection refused
34037 When a deferred address is skipped because its retry time has not been reached,
34038 a message is written to the log, but this can be suppressed by setting an
34039 appropriate value in &%log_selector%&.
34043 .section "Delivery failures" "SECID255"
34044 .cindex "delivery" "failure; logging"
34045 If a delivery fails because an address cannot be routed, a line of the
34046 following form is logged:
34048 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
34049 <jim@trek99.example>: unknown mail domain
34051 If a delivery fails at transport time, the router and transport are shown, and
34052 the response from the remote host is included, as in this example:
34054 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
34055 R=dnslookup T=remote_smtp: SMTP error from remote mailer
34056 after pipelined RCPT TO:<ace400@pb.example>: host
34057 pbmail3.py.example [192.168.63.111]: 553 5.3.0
34058 <ace400@pb.example>...Addressee unknown
34060 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
34061 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
34062 disabling PIPELINING. The log lines for all forms of delivery failure are
34063 flagged with &`**`&.
34067 .section "Fake deliveries" "SECID256"
34068 .cindex "delivery" "fake; logging"
34069 If a delivery does not actually take place because the &%-N%& option has been
34070 used to suppress it, a normal delivery line is written to the log, except that
34071 &"=>"& is replaced by &"*>"&.
34075 .section "Completion" "SECID257"
34078 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
34080 is written to the main log when a message is about to be removed from the spool
34081 at the end of its processing.
34086 .section "Summary of Fields in Log Lines" "SECID258"
34087 .cindex "log" "summary of fields"
34088 A summary of the field identifiers that are used in log lines is shown in
34089 the following table:
34091 &`A `& authenticator name (and optional id and sender)
34092 &`C `& SMTP confirmation on delivery
34093 &` `& command list for &"no mail in SMTP session"&
34094 &`CV `& certificate verification status
34095 &`D `& duration of &"no mail in SMTP session"&
34096 &`DN `& distinguished name from peer certificate
34097 &`DT `& on &`=>`& lines: time taken for a delivery
34098 &`F `& sender address (on delivery lines)
34099 &`H `& host name and IP address
34100 &`I `& local interface used
34101 &`id `& message id for incoming message
34102 &`P `& on &`<=`& lines: protocol used
34103 &` `& on &`=>`& and &`**`& lines: return path
34104 &`QT `& on &`=>`& lines: time spent on queue so far
34105 &` `& on &"Completed"& lines: time spent on queue
34106 &`R `& on &`<=`& lines: reference for local bounce
34107 &` `& on &`=>`& &`**`& and &`==`& lines: router name
34108 &`S `& size of message
34109 &`SNI `& server name indication from TLS client hello
34110 &`ST `& shadow transport name
34111 &`T `& on &`<=`& lines: message subject (topic)
34112 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
34113 &`U `& local user or RFC 1413 identity
34114 &`X `& TLS cipher suite
34118 .section "Other log entries" "SECID259"
34119 Various other types of log entry are written from time to time. Most should be
34120 self-explanatory. Among the more common are:
34123 .cindex "retry" "time not reached"
34124 &'retry time not reached'&&~&~An address previously suffered a temporary error
34125 during routing or local delivery, and the time to retry has not yet arrived.
34126 This message is not written to an individual message log file unless it happens
34127 during the first delivery attempt.
34129 &'retry time not reached for any host'&&~&~An address previously suffered
34130 temporary errors during remote delivery, and the retry time has not yet arrived
34131 for any of the hosts to which it is routed.
34133 .cindex "spool directory" "file locked"
34134 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
34135 some other Exim process is already working on the message. This can be quite
34136 common if queue running processes are started at frequent intervals. The
34137 &'exiwhat'& utility script can be used to find out what Exim processes are
34140 .cindex "error" "ignored"
34141 &'error ignored'&&~&~There are several circumstances that give rise to this
34144 Exim failed to deliver a bounce message whose age was greater than
34145 &%ignore_bounce_errors_after%&. The bounce was discarded.
34147 A filter file set up a delivery using the &"noerror"& option, and the delivery
34148 failed. The delivery was discarded.
34150 A delivery set up by a router configured with
34151 . ==== As this is a nested list, any displays it contains must be indented
34152 . ==== as otherwise they are too far to the left.
34156 failed. The delivery was discarded.
34164 .section "Reducing or increasing what is logged" "SECTlogselector"
34165 .cindex "log" "selectors"
34166 By setting the &%log_selector%& global option, you can disable some of Exim's
34167 default logging, or you can request additional logging. The value of
34168 &%log_selector%& is made up of names preceded by plus or minus characters. For
34171 log_selector = +arguments -retry_defer
34173 The list of optional log items is in the following table, with the default
34174 selection marked by asterisks:
34176 &` 8bitmime `& received 8BITMIME status
34177 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
34178 &` address_rewrite `& address rewriting
34179 &` all_parents `& all parents in => lines
34180 &` arguments `& command line arguments
34181 &`*connection_reject `& connection rejections
34182 &`*delay_delivery `& immediate delivery delayed
34183 &` deliver_time `& time taken to perform delivery
34184 &` delivery_size `& add &`S=`&&'nnn'& to => lines
34185 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
34186 &`*etrn `& ETRN commands
34187 &`*host_lookup_failed `& as it says
34188 &` ident_timeout `& timeout for ident connection
34189 &` incoming_interface `& incoming interface on <= lines
34190 &` incoming_port `& incoming port on <= lines
34191 &`*lost_incoming_connection `& as it says (includes timeouts)
34192 &` outgoing_port `& add remote port to => lines
34193 &`*queue_run `& start and end queue runs
34194 &` queue_time `& time on queue for one recipient
34195 &` queue_time_overall `& time on queue for whole message
34196 &` pid `& Exim process id
34197 &` received_recipients `& recipients on <= lines
34198 &` received_sender `& sender on <= lines
34199 &`*rejected_header `& header contents on reject log
34200 &`*retry_defer `& &"retry time not reached"&
34201 &` return_path_on_delivery `& put return path on => and ** lines
34202 &` sender_on_delivery `& add sender to => lines
34203 &`*sender_verify_fail `& sender verification failures
34204 &`*size_reject `& rejection because too big
34205 &`*skip_delivery `& delivery skipped in a queue run
34206 &`*smtp_confirmation `& SMTP confirmation on => lines
34207 &` smtp_connection `& SMTP connections
34208 &` smtp_incomplete_transaction`& incomplete SMTP transactions
34209 &` smtp_mailauth `& AUTH argument to MAIL commands
34210 &` smtp_no_mail `& session with no MAIL commands
34211 &` smtp_protocol_error `& SMTP protocol errors
34212 &` smtp_syntax_error `& SMTP syntax errors
34213 &` subject `& contents of &'Subject:'& on <= lines
34214 &` tls_certificate_verified `& certificate verification status
34215 &`*tls_cipher `& TLS cipher suite on <= and => lines
34216 &` tls_peerdn `& TLS peer DN on <= and => lines
34217 &` tls_sni `& TLS SNI on <= lines
34218 &` unknown_in_list `& DNS lookup failed in list match
34220 &` all `& all of the above
34222 More details on each of these items follows:
34226 .cindex "log" "8BITMIME"
34227 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
34228 which may help in tracking down interoperability issues with ancient MTAs
34229 that are not 8bit clean. This is added to the &"<="& line, tagged with
34230 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
34231 &`7BIT`& and &`8BITMIME`& respectively.
34233 .cindex "&%warn%& ACL verb" "log when skipping"
34234 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
34235 its conditions cannot be evaluated, a log line to this effect is written if
34236 this log selector is set.
34238 .cindex "log" "rewriting"
34239 .cindex "rewriting" "logging"
34240 &%address_rewrite%&: This applies both to global rewrites and per-transport
34241 rewrites, but not to rewrites in filters run as an unprivileged user (because
34242 such users cannot access the log).
34244 .cindex "log" "full parentage"
34245 &%all_parents%&: Normally only the original and final addresses are logged on
34246 delivery lines; with this selector, intermediate parents are given in
34247 parentheses between them.
34249 .cindex "log" "Exim arguments"
34250 .cindex "Exim arguments, logging"
34251 &%arguments%&: This causes Exim to write the arguments with which it was called
34252 to the main log, preceded by the current working directory. This is a debugging
34253 feature, added to make it easier to find out how certain MUAs call
34254 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
34255 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
34256 that are empty or that contain white space are quoted. Non-printing characters
34257 are shown as escape sequences. This facility cannot log unrecognized arguments,
34258 because the arguments are checked before the configuration file is read. The
34259 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
34260 between the caller and Exim.
34262 .cindex "log" "connection rejections"
34263 &%connection_reject%&: A log entry is written whenever an incoming SMTP
34264 connection is rejected, for whatever reason.
34266 .cindex "log" "delayed delivery"
34267 .cindex "delayed delivery, logging"
34268 &%delay_delivery%&: A log entry is written whenever a delivery process is not
34269 started for an incoming message because the load is too high or too many
34270 messages were received on one connection. Logging does not occur if no delivery
34271 process is started because &%queue_only%& is set or &%-odq%& was used.
34273 .cindex "log" "delivery duration"
34274 &%deliver_time%&: For each delivery, the amount of real time it has taken to
34275 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
34277 .cindex "log" "message size on delivery"
34278 .cindex "size" "of message"
34279 &%delivery_size%&: For each delivery, the size of message delivered is added to
34280 the &"=>"& line, tagged with S=.
34282 .cindex "log" "dnslist defer"
34283 .cindex "DNS list" "logging defer"
34284 .cindex "black list (DNS)"
34285 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
34286 DNS black list suffers a temporary error.
34288 .cindex "log" "ETRN commands"
34289 .cindex "ETRN" "logging"
34290 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
34291 is run to determine whether or not it is actually accepted. An invalid ETRN
34292 command, or one received within a message transaction is not logged by this
34293 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
34295 .cindex "log" "host lookup failure"
34296 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
34297 any addresses, or when a lookup of an IP address fails to find a host name, a
34298 log line is written. This logging does not apply to direct DNS lookups when
34299 routing email addresses, but it does apply to &"byname"& lookups.
34301 .cindex "log" "ident timeout"
34302 .cindex "RFC 1413" "logging timeout"
34303 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
34304 client's ident port times out.
34306 .cindex "log" "incoming interface"
34307 .cindex "interface" "logging"
34308 &%incoming_interface%&: The interface on which a message was received is added
34309 to the &"<="& line as an IP address in square brackets, tagged by I= and
34310 followed by a colon and the port number. The local interface and port are also
34311 added to other SMTP log lines, for example &"SMTP connection from"&, and to
34314 .cindex "log" "incoming remote port"
34315 .cindex "port" "logging remote"
34316 .cindex "TCP/IP" "logging incoming remote port"
34317 .vindex "&$sender_fullhost$&"
34318 .vindex "&$sender_rcvhost$&"
34319 &%incoming_port%&: The remote port number from which a message was received is
34320 added to log entries and &'Received:'& header lines, following the IP address
34321 in square brackets, and separated from it by a colon. This is implemented by
34322 changing the value that is put in the &$sender_fullhost$& and
34323 &$sender_rcvhost$& variables. Recording the remote port number has become more
34324 important with the widening use of NAT (see RFC 2505).
34326 .cindex "log" "dropped connection"
34327 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
34328 connection is unexpectedly dropped.
34330 .cindex "log" "outgoing remote port"
34331 .cindex "port" "logging outgoint remote"
34332 .cindex "TCP/IP" "logging ougtoing remote port"
34333 &%outgoing_port%&: The remote port number is added to delivery log lines (those
34334 containing => tags) following the IP address. This option is not included in
34335 the default setting, because for most ordinary configurations, the remote port
34336 number is always 25 (the SMTP port).
34338 .cindex "log" "process ids in"
34339 .cindex "pid (process id)" "in log lines"
34340 &%pid%&: The current process id is added to every log line, in square brackets,
34341 immediately after the time and date.
34343 .cindex "log" "queue run"
34344 .cindex "queue runner" "logging"
34345 &%queue_run%&: The start and end of every queue run are logged.
34347 .cindex "log" "queue time"
34348 &%queue_time%&: The amount of time the message has been in the queue on the
34349 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
34350 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
34351 includes reception time as well as the delivery time for the current address.
34352 This means that it may be longer than the difference between the arrival and
34353 delivery log line times, because the arrival log line is not written until the
34354 message has been successfully received.
34356 &%queue_time_overall%&: The amount of time the message has been in the queue on
34357 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
34358 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
34359 message, so it includes reception time as well as the total delivery time.
34361 .cindex "log" "recipients"
34362 &%received_recipients%&: The recipients of a message are listed in the main log
34363 as soon as the message is received. The list appears at the end of the log line
34364 that is written when a message is received, preceded by the word &"for"&. The
34365 addresses are listed after they have been qualified, but before any rewriting
34367 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
34370 .cindex "log" "sender reception"
34371 &%received_sender%&: The unrewritten original sender of a message is added to
34372 the end of the log line that records the message's arrival, after the word
34373 &"from"& (before the recipients if &%received_recipients%& is also set).
34375 .cindex "log" "header lines for rejection"
34376 &%rejected_header%&: If a message's header has been received at the time a
34377 rejection is written to the reject log, the complete header is added to the
34378 log. Header logging can be turned off individually for messages that are
34379 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
34381 .cindex "log" "retry defer"
34382 &%retry_defer%&: A log line is written if a delivery is deferred because a
34383 retry time has not yet been reached. However, this &"retry time not reached"&
34384 message is always omitted from individual message logs after the first delivery
34387 .cindex "log" "return path"
34388 &%return_path_on_delivery%&: The return path that is being transmitted with
34389 the message is included in delivery and bounce lines, using the tag P=.
34390 This is omitted if no delivery actually happens, for example, if routing fails,
34391 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
34393 .cindex "log" "sender on delivery"
34394 &%sender_on_delivery%&: The message's sender address is added to every delivery
34395 and bounce line, tagged by F= (for &"from"&).
34396 This is the original sender that was received with the message; it is not
34397 necessarily the same as the outgoing return path.
34399 .cindex "log" "sender verify failure"
34400 &%sender_verify_fail%&: If this selector is unset, the separate log line that
34401 gives details of a sender verification failure is not written. Log lines for
34402 the rejection of SMTP commands contain just &"sender verify failed"&, so some
34405 .cindex "log" "size rejection"
34406 &%size_reject%&: A log line is written whenever a message is rejected because
34409 .cindex "log" "frozen messages; skipped"
34410 .cindex "frozen messages" "logging skipping"
34411 &%skip_delivery%&: A log line is written whenever a message is skipped during a
34412 queue run because it is frozen or because another process is already delivering
34414 .cindex "&""spool file is locked""&"
34415 The message that is written is &"spool file is locked"&.
34417 .cindex "log" "smtp confirmation"
34418 .cindex "SMTP" "logging confirmation"
34419 .cindex "LMTP" "logging confirmation"
34420 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
34421 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
34422 A number of MTAs (including Exim) return an identifying string in this
34425 .cindex "log" "SMTP connections"
34426 .cindex "SMTP" "logging connections"
34427 &%smtp_connection%&: A log line is written whenever an SMTP connection is
34428 established or closed, unless the connection is from a host that matches
34429 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
34430 only when the closure is unexpected.) This applies to connections from local
34431 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
34432 dropped in the middle of a message, a log line is always written, whether or
34433 not this selector is set, but otherwise nothing is written at the start and end
34434 of connections unless this selector is enabled.
34436 For TCP/IP connections to an Exim daemon, the current number of connections is
34437 included in the log message for each new connection, but note that the count is
34438 reset if the daemon is restarted.
34439 Also, because connections are closed (and the closure is logged) in
34440 subprocesses, the count may not include connections that have been closed but
34441 whose termination the daemon has not yet noticed. Thus, while it is possible to
34442 match up the opening and closing of connections in the log, the value of the
34443 logged counts may not be entirely accurate.
34445 .cindex "log" "SMTP transaction; incomplete"
34446 .cindex "SMTP" "logging incomplete transactions"
34447 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
34448 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
34449 and the message sender plus any accepted recipients are included in the log
34450 line. This can provide evidence of dictionary attacks.
34452 .cindex "log" "non-MAIL SMTP sessions"
34453 .cindex "MAIL" "logging session without"
34454 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
34455 connection terminates without having issued a MAIL command. This includes both
34456 the case when the connection is dropped, and the case when QUIT is used. It
34457 does not include cases where the connection is rejected right at the start (by
34458 an ACL, or because there are too many connections, or whatever). These cases
34459 already have their own log lines.
34461 The log line that is written contains the identity of the client in the usual
34462 way, followed by D= and a time, which records the duration of the connection.
34463 If the connection was authenticated, this fact is logged exactly as it is for
34464 an incoming message, with an A= item. If the connection was encrypted, CV=,
34465 DN=, and X= items may appear as they do for an incoming message, controlled by
34466 the same logging options.
34468 Finally, if any SMTP commands were issued during the connection, a C= item
34469 is added to the line, listing the commands that were used. For example,
34473 shows that the client issued QUIT straight after EHLO. If there were fewer
34474 than 20 commands, they are all listed. If there were more than 20 commands,
34475 the last 20 are listed, preceded by &"..."&. However, with the default
34476 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
34477 have been aborted before 20 non-mail commands are processed.
34479 &%smtp_mailauth%&: A third subfield with the authenticated sender,
34480 colon-separated, is appended to the A= item for a message arrival or delivery
34481 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
34482 was accepted or used.
34484 .cindex "log" "SMTP protocol error"
34485 .cindex "SMTP" "logging protocol error"
34486 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
34487 encountered. Exim does not have perfect detection of all protocol errors
34488 because of transmission delays and the use of pipelining. If PIPELINING has
34489 been advertised to a client, an Exim server assumes that the client will use
34490 it, and therefore it does not count &"expected"& errors (for example, RCPT
34491 received after rejecting MAIL) as protocol errors.
34493 .cindex "SMTP" "logging syntax errors"
34494 .cindex "SMTP" "syntax errors; logging"
34495 .cindex "SMTP" "unknown command; logging"
34496 .cindex "log" "unknown SMTP command"
34497 .cindex "log" "SMTP syntax error"
34498 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
34499 encountered. An unrecognized command is treated as a syntax error. For an
34500 external connection, the host identity is given; for an internal connection
34501 using &%-bs%& the sender identification (normally the calling user) is given.
34503 .cindex "log" "subject"
34504 .cindex "subject, logging"
34505 &%subject%&: The subject of the message is added to the arrival log line,
34506 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
34507 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
34508 specifies whether characters with values greater than 127 should be logged
34509 unchanged, or whether they should be rendered as escape sequences.
34511 .cindex "log" "certificate verification"
34512 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
34513 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
34514 verified, and &`CV=no`& if not.
34516 .cindex "log" "TLS cipher"
34517 .cindex "TLS" "logging cipher"
34518 &%tls_cipher%&: When a message is sent or received over an encrypted
34519 connection, the cipher suite used is added to the log line, preceded by X=.
34521 .cindex "log" "TLS peer DN"
34522 .cindex "TLS" "logging peer DN"
34523 &%tls_peerdn%&: When a message is sent or received over an encrypted
34524 connection, and a certificate is supplied by the remote host, the peer DN is
34525 added to the log line, preceded by DN=.
34527 .cindex "log" "TLS SNI"
34528 .cindex "TLS" "logging SNI"
34529 &%tls_sni%&: When a message is received over an encrypted connection, and
34530 the remote host provided the Server Name Indication extension, the SNI is
34531 added to the log line, preceded by SNI=.
34533 .cindex "log" "DNS failure in list"
34534 &%unknown_in_list%&: This setting causes a log entry to be written when the
34535 result of a list match is failure because a DNS lookup failed.
34539 .section "Message log" "SECID260"
34540 .cindex "message" "log file for"
34541 .cindex "log" "message log; description of"
34542 .cindex "&_msglog_& directory"
34543 .oindex "&%preserve_message_logs%&"
34544 In addition to the general log files, Exim writes a log file for each message
34545 that it handles. The names of these per-message logs are the message ids, and
34546 they are kept in the &_msglog_& sub-directory of the spool directory. Each
34547 message log contains copies of the log lines that apply to the message. This
34548 makes it easier to inspect the status of an individual message without having
34549 to search the main log. A message log is deleted when processing of the message
34550 is complete, unless &%preserve_message_logs%& is set, but this should be used
34551 only with great care because they can fill up your disk very quickly.
34553 On a heavily loaded system, it may be desirable to disable the use of
34554 per-message logs, in order to reduce disk I/O. This can be done by setting the
34555 &%message_logs%& option false.
34561 . ////////////////////////////////////////////////////////////////////////////
34562 . ////////////////////////////////////////////////////////////////////////////
34564 .chapter "Exim utilities" "CHAPutils"
34565 .scindex IIDutils "utilities"
34566 A number of utility scripts and programs are supplied with Exim and are
34567 described in this chapter. There is also the Exim Monitor, which is covered in
34568 the next chapter. The utilities described here are:
34570 .itable none 0 0 3 7* left 15* left 40* left
34571 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
34572 "list what Exim processes are doing"
34573 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
34574 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
34575 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
34576 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
34578 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
34579 .irow &<<SECTmailstat>>& &'eximstats'& &&&
34580 "extract statistics from the log"
34581 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
34582 "check address acceptance from given IP"
34583 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
34584 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
34585 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
34586 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
34587 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
34588 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
34591 Another utility that might be of use to sites with many MTAs is Tom Kistner's
34592 &'exilog'&. It provides log visualizations across multiple Exim servers. See
34593 &url(http://duncanthrax.net/exilog/) for details.
34598 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
34599 .cindex "&'exiwhat'&"
34600 .cindex "process, querying"
34602 On operating systems that can restart a system call after receiving a signal
34603 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
34604 a line describing what it is doing to the file &_exim-process.info_& in the
34605 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
34606 processes it can find, having first emptied the file. It then waits for one
34607 second to allow the Exim processes to react before displaying the results. In
34608 order to run &'exiwhat'& successfully you have to have sufficient privilege to
34609 send the signal to the Exim processes, so it is normally run as root.
34611 &*Warning*&: This is not an efficient process. It is intended for occasional
34612 use by system administrators. It is not sensible, for example, to set up a
34613 script that sends SIGUSR1 signals to Exim processes at short intervals.
34616 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
34617 varies in different operating systems. Not only are different options used,
34618 but the format of the output is different. For this reason, there are some
34619 system configuration options that configure exactly how &'exiwhat'& works. If
34620 it doesn't seem to be working for you, check the following compile-time
34623 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
34624 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
34625 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
34626 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
34628 An example of typical output from &'exiwhat'& is
34630 164 daemon: -q1h, listening on port 25
34631 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
34632 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
34633 [10.19.42.42] (editor@ref.example)
34634 10592 handling incoming call from [192.168.243.242]
34635 10628 accepting a local non-SMTP message
34637 The first number in the output line is the process number. The third line has
34638 been split here, in order to fit it on the page.
34642 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
34643 .cindex "&'exiqgrep'&"
34644 .cindex "queue" "grepping"
34645 This utility is a Perl script contributed by Matt Hubbard. It runs
34649 to obtain a queue listing with undelivered recipients only, and then greps the
34650 output to select messages that match given criteria. The following selection
34651 options are available:
34654 .vitem &*-f*&&~<&'regex'&>
34655 Match the sender address using a case-insensitive search. The field that is
34656 tested is enclosed in angle brackets, so you can test for bounce messages with
34660 .vitem &*-r*&&~<&'regex'&>
34661 Match a recipient address using a case-insensitve search. The field that is
34662 tested is not enclosed in angle brackets.
34664 .vitem &*-s*&&~<&'regex'&>
34665 Match against the size field.
34667 .vitem &*-y*&&~<&'seconds'&>
34668 Match messages that are younger than the given time.
34670 .vitem &*-o*&&~<&'seconds'&>
34671 Match messages that are older than the given time.
34674 Match only frozen messages.
34677 Match only non-frozen messages.
34680 The following options control the format of the output:
34684 Display only the count of matching messages.
34687 Long format &-- display the full message information as output by Exim. This is
34691 Display message ids only.
34694 Brief format &-- one line per message.
34697 Display messages in reverse order.
34700 There is one more option, &%-h%&, which outputs a list of options.
34704 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
34705 .cindex "&'exiqsumm'&"
34706 .cindex "queue" "summary"
34707 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
34708 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
34709 running a command such as
34711 exim -bp | exiqsumm
34713 The output consists of one line for each domain that has messages waiting for
34714 it, as in the following example:
34716 3 2322 74m 66m msn.com.example
34718 Each line lists the number of pending deliveries for a domain, their total
34719 volume, and the length of time that the oldest and the newest messages have
34720 been waiting. Note that the number of pending deliveries is greater than the
34721 number of messages when messages have more than one recipient.
34723 A summary line is output at the end. By default the output is sorted on the
34724 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
34725 the output to be sorted by oldest message and by count of messages,
34726 respectively. There are also three options that split the messages for each
34727 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
34728 separates frozen messages, and &%-s%& separates messages according to their
34731 The output of &'exim -bp'& contains the original addresses in the message, so
34732 this also applies to the output from &'exiqsumm'&. No domains from addresses
34733 generated by aliasing or forwarding are included (unless the &%one_time%&
34734 option of the &(redirect)& router has been used to convert them into &"top
34735 level"& addresses).
34740 .section "Extracting specific information from the log (exigrep)" &&&
34742 .cindex "&'exigrep'&"
34743 .cindex "log" "extracts; grepping for"
34744 The &'exigrep'& utility is a Perl script that searches one or more main log
34745 files for entries that match a given pattern. When it finds a match, it
34746 extracts all the log entries for the relevant message, not just those that
34747 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
34748 given message, or all mail for a given user, or for a given host, for example.
34749 The input files can be in Exim log format or syslog format.
34750 If a matching log line is not associated with a specific message, it is
34751 included in &'exigrep'&'s output without any additional lines. The usage is:
34753 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
34755 If no log file names are given on the command line, the standard input is read.
34757 The &%-t%& argument specifies a number of seconds. It adds an additional
34758 condition for message selection. Messages that are complete are shown only if
34759 they spent more than <&'n'&> seconds on the queue.
34761 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
34762 makes it case-sensitive. This may give a performance improvement when searching
34763 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
34764 option; with &%-I%& they do not. In both cases it is possible to change the
34765 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
34767 The &%-l%& option means &"literal"&, that is, treat all characters in the
34768 pattern as standing for themselves. Otherwise the pattern must be a Perl
34769 regular expression.
34771 The &%-v%& option inverts the matching condition. That is, a line is selected
34772 if it does &'not'& match the pattern.
34774 If the location of a &'zcat'& command is known from the definition of
34775 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
34776 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
34779 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
34780 .cindex "&'exipick'&"
34781 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
34782 lists messages from the queue according to a variety of criteria. For details
34783 of &'exipick'&'s facilities, visit the web page at
34784 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
34785 the &%--help%& option.
34788 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
34789 .cindex "log" "cycling local files"
34790 .cindex "cycling logs"
34791 .cindex "&'exicyclog'&"
34792 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
34793 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
34794 you are using log files with datestamps in their names (see section
34795 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
34796 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
34797 There are two command line options for &'exicyclog'&:
34799 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
34800 default that is set when Exim is built. The default default is 10.
34802 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
34803 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
34804 overriding the script's default, which is to find the setting from Exim's
34808 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
34809 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
34810 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
34811 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
34812 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
34813 logs are handled similarly.
34815 If the limit is greater than 99, the script uses 3-digit numbers such as
34816 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
34817 to one that is greater, or &'vice versa'&, you will have to fix the names of
34818 any existing log files.
34820 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
34821 the end are deleted. All files with numbers greater than 01 are compressed,
34822 using a compression command which is configured by the COMPRESS_COMMAND
34823 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
34824 root &%crontab%& entry of the form
34826 1 0 * * * su exim -c /usr/exim/bin/exicyclog
34828 assuming you have used the name &"exim"& for the Exim user. You can run
34829 &'exicyclog'& as root if you wish, but there is no need.
34833 .section "Mail statistics (eximstats)" "SECTmailstat"
34834 .cindex "statistics"
34835 .cindex "&'eximstats'&"
34836 A Perl script called &'eximstats'& is provided for extracting statistical
34837 information from log files. The output is either plain text, or HTML.
34838 Exim log files are also supported by the &'Lire'& system produced by the
34839 LogReport Foundation &url(http://www.logreport.org).
34841 The &'eximstats'& script has been hacked about quite a bit over time. The
34842 latest version is the result of some extensive revision by Steve Campbell. A
34843 lot of information is given by default, but there are options for suppressing
34844 various parts of it. Following any options, the arguments to the script are a
34845 list of files, which should be main log files. For example:
34847 eximstats -nr /var/spool/exim/log/mainlog.01
34849 By default, &'eximstats'& extracts information about the number and volume of
34850 messages received from or delivered to various hosts. The information is sorted
34851 both by message count and by volume, and the top fifty hosts in each category
34852 are listed on the standard output. Similar information, based on email
34853 addresses or domains instead of hosts can be requested by means of various
34854 options. For messages delivered and received locally, similar statistics are
34855 also produced per user.
34857 The output also includes total counts and statistics about delivery errors, and
34858 histograms showing the number of messages received and deliveries made in each
34859 hour of the day. A delivery with more than one address in its envelope (for
34860 example, an SMTP transaction with more than one RCPT command) is counted
34861 as a single delivery by &'eximstats'&.
34863 Though normally more deliveries than receipts are reported (as messages may
34864 have multiple recipients), it is possible for &'eximstats'& to report more
34865 messages received than delivered, even though the queue is empty at the start
34866 and end of the period in question. If an incoming message contains no valid
34867 recipients, no deliveries are recorded for it. A bounce message is handled as
34868 an entirely separate message.
34870 &'eximstats'& always outputs a grand total summary giving the volume and number
34871 of messages received and deliveries made, and the number of hosts involved in
34872 each case. It also outputs the number of messages that were delayed (that is,
34873 not completely delivered at the first attempt), and the number that had at
34874 least one address that failed.
34876 The remainder of the output is in sections that can be independently disabled
34877 or modified by various options. It consists of a summary of deliveries by
34878 transport, histograms of messages received and delivered per time interval
34879 (default per hour), information about the time messages spent on the queue,
34880 a list of relayed messages, lists of the top fifty sending hosts, local
34881 senders, destination hosts, and destination local users by count and by volume,
34882 and a list of delivery errors that occurred.
34884 The relay information lists messages that were actually relayed, that is, they
34885 came from a remote host and were directly delivered to some other remote host,
34886 without being processed (for example, for aliasing or forwarding) locally.
34888 There are quite a few options for &'eximstats'& to control exactly what it
34889 outputs. These are documented in the Perl script itself, and can be extracted
34890 by running the command &(perldoc)& on the script. For example:
34892 perldoc /usr/exim/bin/eximstats
34895 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
34896 .cindex "&'exim_checkaccess'&"
34897 .cindex "policy control" "checking access"
34898 .cindex "checking access"
34899 The &%-bh%& command line argument allows you to run a fake SMTP session with
34900 debugging output, in order to check what Exim is doing when it is applying
34901 policy controls to incoming SMTP mail. However, not everybody is sufficiently
34902 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
34903 sometimes you just want to answer the question &"Does this address have
34904 access?"& without bothering with any further details.
34906 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
34907 two arguments, an IP address and an email address:
34909 exim_checkaccess 10.9.8.7 A.User@a.domain.example
34911 The utility runs a call to Exim with the &%-bh%& option, to test whether the
34912 given email address would be accepted in a RCPT command in a TCP/IP
34913 connection from the host with the given IP address. The output of the utility
34914 is either the word &"accepted"&, or the SMTP error response, for example:
34917 550 Relay not permitted
34919 When running this test, the utility uses &`<>`& as the envelope sender address
34920 for the MAIL command, but you can change this by providing additional
34921 options. These are passed directly to the Exim command. For example, to specify
34922 that the test is to be run with the sender address &'himself@there.example'&
34925 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
34926 -f himself@there.example
34928 Note that these additional Exim command line items must be given after the two
34929 mandatory arguments.
34931 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
34932 while running its checks. You can run checks that include callouts by using
34933 &%-bhc%&, but this is not yet available in a &"packaged"& form.
34937 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
34938 .cindex "DBM" "building dbm files"
34939 .cindex "building DBM files"
34940 .cindex "&'exim_dbmbuild'&"
34941 .cindex "lower casing"
34942 .cindex "binary zero" "in lookup key"
34943 The &'exim_dbmbuild'& program reads an input file containing keys and data in
34944 the format used by the &(lsearch)& lookup (see section
34945 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
34946 names as keys and the remainder of the information as data. The lower-casing
34947 can be prevented by calling the program with the &%-nolc%& option.
34949 A terminating zero is included as part of the key string. This is expected by
34950 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
34951 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
34952 strings or the data strings. The &(dbmnz)& lookup type can be used with such
34955 The program requires two arguments: the name of the input file (which can be a
34956 single hyphen to indicate the standard input), and the name of the output file.
34957 It creates the output under a temporary name, and then renames it if all went
34961 If the native DB interface is in use (USE_DB is set in a compile-time
34962 configuration file &-- this is common in free versions of Unix) the two file
34963 names must be different, because in this mode the Berkeley DB functions create
34964 a single output file using exactly the name given. For example,
34966 exim_dbmbuild /etc/aliases /etc/aliases.db
34968 reads the system alias file and creates a DBM version of it in
34969 &_/etc/aliases.db_&.
34971 In systems that use the &'ndbm'& routines (mostly proprietary versions of
34972 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
34973 environment, the suffixes are added to the second argument of
34974 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
34975 when the Berkeley functions are used in compatibility mode (though this is not
34976 recommended), because in that case it adds a &_.db_& suffix to the file name.
34978 If a duplicate key is encountered, the program outputs a warning, and when it
34979 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
34980 option is used. By default, only the first of a set of duplicates is used &--
34981 this makes it compatible with &(lsearch)& lookups. There is an option
34982 &%-lastdup%& which causes it to use the data for the last duplicate instead.
34983 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
34984 &%stderr%&. For other errors, where it doesn't actually make a new file, the
34990 .section "Finding individual retry times (exinext)" "SECTfinindret"
34991 .cindex "retry" "times"
34992 .cindex "&'exinext'&"
34993 A utility called &'exinext'& (mostly a Perl script) provides the ability to
34994 fish specific information out of the retry database. Given a mail domain (or a
34995 complete address), it looks up the hosts for that domain, and outputs any retry
34996 information for the hosts or for the domain. At present, the retry information
34997 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
34998 output. For example:
35000 $ exinext piglet@milne.fict.example
35001 kanga.milne.example:192.168.8.1 error 146: Connection refused
35002 first failed: 21-Feb-1996 14:57:34
35003 last tried: 21-Feb-1996 14:57:34
35004 next try at: 21-Feb-1996 15:02:34
35005 roo.milne.example:192.168.8.3 error 146: Connection refused
35006 first failed: 20-Jan-1996 13:12:08
35007 last tried: 21-Feb-1996 11:42:03
35008 next try at: 21-Feb-1996 19:42:03
35009 past final cutoff time
35011 You can also give &'exinext'& a local part, without a domain, and it
35012 will give any retry information for that local part in your default domain.
35013 A message id can be used to obtain retry information pertaining to a specific
35014 message. This exists only when an attempt to deliver a message to a remote host
35015 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
35016 &'exinext'& is not particularly efficient, but then it is not expected to be
35019 The &'exinext'& utility calls Exim to find out information such as the location
35020 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
35021 passed on to the &'exim'& commands. The first specifies an alternate Exim
35022 configuration file, and the second sets macros for use within the configuration
35023 file. These features are mainly to help in testing, but might also be useful in
35024 environments where more than one configuration file is in use.
35028 .section "Hints database maintenance" "SECThindatmai"
35029 .cindex "hints database" "maintenance"
35030 .cindex "maintaining Exim's hints database"
35031 Three utility programs are provided for maintaining the DBM files that Exim
35032 uses to contain its delivery hint information. Each program requires two
35033 arguments. The first specifies the name of Exim's spool directory, and the
35034 second is the name of the database it is to operate on. These are as follows:
35037 &'retry'&: the database of retry information
35039 &'wait-'&<&'transport name'&>: databases of information about messages waiting
35042 &'callout'&: the callout cache
35044 &'ratelimit'&: the data for implementing the ratelimit ACL condition
35046 &'misc'&: other hints data
35049 The &'misc'& database is used for
35052 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
35054 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
35055 &(smtp)& transport)
35060 .section "exim_dumpdb" "SECID261"
35061 .cindex "&'exim_dumpdb'&"
35062 The entire contents of a database are written to the standard output by the
35063 &'exim_dumpdb'& program, which has no options or arguments other than the
35064 spool and database names. For example, to dump the retry database:
35066 exim_dumpdb /var/spool/exim retry
35068 Two lines of output are produced for each entry:
35070 T:mail.ref.example:192.168.242.242 146 77 Connection refused
35071 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
35073 The first item on the first line is the key of the record. It starts with one
35074 of the letters R, or T, depending on whether it refers to a routing or
35075 transport retry. For a local delivery, the next part is the local address; for
35076 a remote delivery it is the name of the remote host, followed by its failing IP
35077 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
35078 transport). If the remote port is not the standard one (port 25), it is added
35079 to the IP address. Then there follows an error code, an additional error code,
35080 and a textual description of the error.
35082 The three times on the second line are the time of first failure, the time of
35083 the last delivery attempt, and the computed time for the next attempt. The line
35084 ends with an asterisk if the cutoff time for the last retry rule has been
35087 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
35088 consists of a host name followed by a list of ids for messages that are or were
35089 waiting to be delivered to that host. If there are a very large number for any
35090 one host, continuation records, with a sequence number added to the host name,
35091 may be seen. The data in these records is often out of date, because a message
35092 may be routed to several alternative hosts, and Exim makes no effort to keep
35097 .section "exim_tidydb" "SECID262"
35098 .cindex "&'exim_tidydb'&"
35099 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
35100 database. If run with no options, it removes all records that are more than 30
35101 days old. The age is calculated from the date and time that the record was last
35102 updated. Note that, in the case of the retry database, it is &'not'& the time
35103 since the first delivery failure. Information about a host that has been down
35104 for more than 30 days will remain in the database, provided that the record is
35105 updated sufficiently often.
35107 The cutoff date can be altered by means of the &%-t%& option, which must be
35108 followed by a time. For example, to remove all records older than a week from
35109 the retry database:
35111 exim_tidydb -t 7d /var/spool/exim retry
35113 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
35114 message ids. In the former these appear as data in records keyed by host &--
35115 they were messages that were waiting for that host &-- and in the latter they
35116 are the keys for retry information for messages that have suffered certain
35117 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
35118 message ids in database records are those of messages that are still on the
35119 queue. Message ids for messages that no longer exist are removed from
35120 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
35121 For the &'retry'& database, records whose keys are non-existent message ids are
35122 removed. The &'exim_tidydb'& utility outputs comments on the standard output
35123 whenever it removes information from the database.
35125 Certain records are automatically removed by Exim when they are no longer
35126 needed, but others are not. For example, if all the MX hosts for a domain are
35127 down, a retry record is created for each one. If the primary MX host comes back
35128 first, its record is removed when Exim successfully delivers to it, but the
35129 records for the others remain because Exim has not tried to use those hosts.
35131 It is important, therefore, to run &'exim_tidydb'& periodically on all the
35132 hints databases. You should do this at a quiet time of day, because it requires
35133 a database to be locked (and therefore inaccessible to Exim) while it does its
35134 work. Removing records from a DBM file does not normally make the file smaller,
35135 but all the common DBM libraries are able to re-use the space that is released.
35136 After an initial phase of increasing in size, the databases normally reach a
35137 point at which they no longer get any bigger, as long as they are regularly
35140 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
35141 databases is likely to keep on increasing.
35146 .section "exim_fixdb" "SECID263"
35147 .cindex "&'exim_fixdb'&"
35148 The &'exim_fixdb'& program is a utility for interactively modifying databases.
35149 Its main use is for testing Exim, but it might also be occasionally useful for
35150 getting round problems in a live system. It has no options, and its interface
35151 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
35152 key of a database record can then be entered, and the data for that record is
35155 If &"d"& is typed at the next prompt, the entire record is deleted. For all
35156 except the &'retry'& database, that is the only operation that can be carried
35157 out. For the &'retry'& database, each field is output preceded by a number, and
35158 data for individual fields can be changed by typing the field number followed
35159 by new data, for example:
35163 resets the time of the next delivery attempt. Time values are given as a
35164 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
35165 used as optional separators.
35170 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
35171 .cindex "mailbox" "maintenance"
35172 .cindex "&'exim_lock'&"
35173 .cindex "locking mailboxes"
35174 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
35175 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
35176 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
35177 a user agent while investigating a problem. The utility requires the name of
35178 the file as its first argument. If the locking is successful, the second
35179 argument is run as a command (using C's &[system()]& function); if there is no
35180 second argument, the value of the SHELL environment variable is used; if this
35181 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
35182 is unlocked and the utility ends. The following options are available:
35186 Use &[fcntl()]& locking on the open mailbox.
35189 Use &[flock()]& locking on the open mailbox, provided the operating system
35192 .vitem &%-interval%&
35193 This must be followed by a number, which is a number of seconds; it sets the
35194 interval to sleep between retries (default 3).
35196 .vitem &%-lockfile%&
35197 Create a lock file before opening the mailbox.
35200 Lock the mailbox using MBX rules.
35203 Suppress verification output.
35205 .vitem &%-retries%&
35206 This must be followed by a number; it sets the number of times to try to get
35207 the lock (default 10).
35209 .vitem &%-restore_time%&
35210 This option causes &%exim_lock%& to restore the modified and read times to the
35211 locked file before exiting. This allows you to access a locked mailbox (for
35212 example, to take a backup copy) without disturbing the times that the user
35215 .vitem &%-timeout%&
35216 This must be followed by a number, which is a number of seconds; it sets a
35217 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
35218 default), a non-blocking call is used.
35221 Generate verbose output.
35224 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
35225 default is to create a lock file and also to use &[fcntl()]& locking on the
35226 mailbox, which is the same as Exim's default. The use of &%-flock%& or
35227 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
35228 requires that the directory containing the file be writeable. Locking by lock
35229 file does not last for ever; Exim assumes that a lock file is expired if it is
35230 more than 30 minutes old.
35232 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
35233 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
35234 to be taken out on the open mailbox, and an exclusive lock on the file
35235 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
35236 number of the mailbox file. When the locking is released, if an exclusive lock
35237 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
35239 The default output contains verification of the locking that takes place. The
35240 &%-v%& option causes some additional information to be given. The &%-q%& option
35241 suppresses all output except error messages.
35245 exim_lock /var/spool/mail/spqr
35247 runs an interactive shell while the file is locked, whereas
35249 &`exim_lock -q /var/spool/mail/spqr <<End`&
35250 <&'some commands'&>
35253 runs a specific non-interactive sequence of commands while the file is locked,
35254 suppressing all verification output. A single command can be run by a command
35257 exim_lock -q /var/spool/mail/spqr \
35258 "cp /var/spool/mail/spqr /some/where"
35260 Note that if a command is supplied, it must be entirely contained within the
35261 second argument &-- hence the quotes.
35265 . ////////////////////////////////////////////////////////////////////////////
35266 . ////////////////////////////////////////////////////////////////////////////
35268 .chapter "The Exim monitor" "CHAPeximon"
35269 .scindex IIDeximon "Exim monitor" "description"
35270 .cindex "X-windows"
35271 .cindex "&'eximon'&"
35272 .cindex "Local/eximon.conf"
35273 .cindex "&_exim_monitor/EDITME_&"
35274 The Exim monitor is an application which displays in an X window information
35275 about the state of Exim's queue and what Exim is doing. An admin user can
35276 perform certain operations on messages from this GUI interface; however all
35277 such facilities are also available from the command line, and indeed, the
35278 monitor itself makes use of the command line to perform any actions requested.
35282 .section "Running the monitor" "SECID264"
35283 The monitor is started by running the script called &'eximon'&. This is a shell
35284 script that sets up a number of environment variables, and then runs the
35285 binary called &_eximon.bin_&. The default appearance of the monitor window can
35286 be changed by editing the &_Local/eximon.conf_& file created by editing
35287 &_exim_monitor/EDITME_&. Comments in that file describe what the various
35288 parameters are for.
35290 The parameters that get built into the &'eximon'& script can be overridden for
35291 a particular invocation by setting up environment variables of the same names,
35292 preceded by &`EXIMON_`&. For example, a shell command such as
35294 EXIMON_LOG_DEPTH=400 eximon
35296 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
35297 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
35298 overrides the Exim log file configuration. This makes it possible to have
35299 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
35300 syslog messages are routed to a file on the local host.
35302 X resources can be used to change the appearance of the window in the normal
35303 way. For example, a resource setting of the form
35305 Eximon*background: gray94
35307 changes the colour of the background to light grey rather than white. The
35308 stripcharts are drawn with both the data lines and the reference lines in
35309 black. This means that the reference lines are not visible when on top of the
35310 data. However, their colour can be changed by setting a resource called
35311 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
35312 For example, if your X server is running Unix, you could set up lighter
35313 reference lines in the stripcharts by obeying
35316 Eximon*highlight: gray
35319 .cindex "admin user"
35320 In order to see the contents of messages on the queue, and to operate on them,
35321 &'eximon'& must either be run as root or by an admin user.
35323 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
35324 contain X11 resource parameters interpreted by the X11 library. In addition,
35325 if the first parameter starts with the string "gdb" then it is removed and the
35326 binary is invoked under gdb (the parameter is used as the gdb command-name, so
35327 versioned variants of gdb can be invoked).
35329 The monitor's window is divided into three parts. The first contains one or
35330 more stripcharts and two action buttons, the second contains a &"tail"& of the
35331 main log file, and the third is a display of the queue of messages awaiting
35332 delivery, with two more action buttons. The following sections describe these
35333 different parts of the display.
35338 .section "The stripcharts" "SECID265"
35339 .cindex "stripchart"
35340 The first stripchart is always a count of messages on the queue. Its name can
35341 be configured by setting QUEUE_STRIPCHART_NAME in the
35342 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
35343 configuration script by regular expression matches on log file entries, making
35344 it possible to display, for example, counts of messages delivered to certain
35345 hosts or using certain transports. The supplied defaults display counts of
35346 received and delivered messages, and of local and SMTP deliveries. The default
35347 period between stripchart updates is one minute; this can be adjusted by a
35348 parameter in the &_Local/eximon.conf_& file.
35350 The stripchart displays rescale themselves automatically as the value they are
35351 displaying changes. There are always 10 horizontal lines in each chart; the
35352 title string indicates the value of each division when it is greater than one.
35353 For example, &"x2"& means that each division represents a value of 2.
35355 It is also possible to have a stripchart which shows the percentage fullness of
35356 a particular disk partition, which is useful when local deliveries are confined
35357 to a single partition.
35359 .cindex "&%statvfs%& function"
35360 This relies on the availability of the &[statvfs()]& function or equivalent in
35361 the operating system. Most, but not all versions of Unix that support Exim have
35362 this. For this particular stripchart, the top of the chart always represents
35363 100%, and the scale is given as &"x10%"&. This chart is configured by setting
35364 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
35365 &_Local/eximon.conf_& file.
35370 .section "Main action buttons" "SECID266"
35371 .cindex "size" "of monitor window"
35372 .cindex "Exim monitor" "window size"
35373 .cindex "window size"
35374 Below the stripcharts there is an action button for quitting the monitor. Next
35375 to this is another button marked &"Size"&. They are placed here so that
35376 shrinking the window to its default minimum size leaves just the queue count
35377 stripchart and these two buttons visible. Pressing the &"Size"& button causes
35378 the window to expand to its maximum size, unless it is already at the maximum,
35379 in which case it is reduced to its minimum.
35381 When expanding to the maximum, if the window cannot be fully seen where it
35382 currently is, it is moved back to where it was the last time it was at full
35383 size. When it is expanding from its minimum size, the old position is
35384 remembered, and next time it is reduced to the minimum it is moved back there.
35386 The idea is that you can keep a reduced window just showing one or two
35387 stripcharts at a convenient place on your screen, easily expand it to show
35388 the full window when required, and just as easily put it back to what it was.
35389 The idea is copied from what the &'twm'& window manager does for its
35390 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
35391 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
35393 Normally, the monitor starts up with the window at its full size, but it can be
35394 built so that it starts up with the window at its smallest size, by setting
35395 START_SMALL=yes in &_Local/eximon.conf_&.
35399 .section "The log display" "SECID267"
35400 .cindex "log" "tail of; in monitor"
35401 The second section of the window is an area in which a display of the tail of
35402 the main log is maintained.
35403 To save space on the screen, the timestamp on each log line is shortened by
35404 removing the date and, if &%log_timezone%& is set, the timezone.
35405 The log tail is not available when the only destination for logging data is
35406 syslog, unless the syslog lines are routed to a local file whose name is passed
35407 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
35409 The log sub-window has a scroll bar at its lefthand side which can be used to
35410 move back to look at earlier text, and the up and down arrow keys also have a
35411 scrolling effect. The amount of log that is kept depends on the setting of
35412 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
35413 to use. When this is full, the earlier 50% of data is discarded &-- this is
35414 much more efficient than throwing it away line by line. The sub-window also has
35415 a horizontal scroll bar for accessing the ends of long log lines. This is the
35416 only means of horizontal scrolling; the right and left arrow keys are not
35417 available. Text can be cut from this part of the window using the mouse in the
35418 normal way. The size of this subwindow is controlled by parameters in the
35419 configuration file &_Local/eximon.conf_&.
35421 Searches of the text in the log window can be carried out by means of the ^R
35422 and ^S keystrokes, which default to a reverse and a forward search,
35423 respectively. The search covers only the text that is displayed in the window.
35424 It cannot go further back up the log.
35426 The point from which the search starts is indicated by a caret marker. This is
35427 normally at the end of the text in the window, but can be positioned explicitly
35428 by pointing and clicking with the left mouse button, and is moved automatically
35429 by a successful search. If new text arrives in the window when it is scrolled
35430 back, the caret remains where it is, but if the window is not scrolled back,
35431 the caret is moved to the end of the new text.
35433 Pressing ^R or ^S pops up a window into which the search text can be typed.
35434 There are buttons for selecting forward or reverse searching, for carrying out
35435 the search, and for cancelling. If the &"Search"& button is pressed, the search
35436 happens and the window remains so that further searches can be done. If the
35437 &"Return"& key is pressed, a single search is done and the window is closed. If
35438 ^C is typed the search is cancelled.
35440 The searching facility is implemented using the facilities of the Athena text
35441 widget. By default this pops up a window containing both &"search"& and
35442 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
35443 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
35444 However, the linkers in BSDI and HP-UX seem unable to handle an externally
35445 provided version of &%TextPop%& when the remaining parts of the text widget
35446 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
35447 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
35448 on these systems, at the expense of having unwanted items in the search popup
35453 .section "The queue display" "SECID268"
35454 .cindex "queue" "display in monitor"
35455 The bottom section of the monitor window contains a list of all messages that
35456 are on the queue, which includes those currently being received or delivered,
35457 as well as those awaiting delivery. The size of this subwindow is controlled by
35458 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
35459 at which it is updated is controlled by another parameter in the same file &--
35460 the default is 5 minutes, since queue scans can be quite expensive. However,
35461 there is an &"Update"& action button just above the display which can be used
35462 to force an update of the queue display at any time.
35464 When a host is down for some time, a lot of pending mail can build up for it,
35465 and this can make it hard to deal with other messages on the queue. To help
35466 with this situation there is a button next to &"Update"& called &"Hide"&. If
35467 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
35468 type anything in here and press &"Return"&, the text is added to a chain of
35469 such texts, and if every undelivered address in a message matches at least one
35470 of the texts, the message is not displayed.
35472 If there is an address that does not match any of the texts, all the addresses
35473 are displayed as normal. The matching happens on the ends of addresses so, for
35474 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
35475 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
35476 has been set up, a button called &"Unhide"& is displayed. If pressed, it
35477 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
35478 a hide request is automatically cancelled after one hour.
35480 While the dialogue box is displayed, you can't press any buttons or do anything
35481 else to the monitor window. For this reason, if you want to cut text from the
35482 queue display to use in the dialogue box, you have to do the cutting before
35483 pressing the &"Hide"& button.
35485 The queue display contains, for each unhidden queued message, the length of
35486 time it has been on the queue, the size of the message, the message id, the
35487 message sender, and the first undelivered recipient, all on one line. If it is
35488 a bounce message, the sender is shown as &"<>"&. If there is more than one
35489 recipient to which the message has not yet been delivered, subsequent ones are
35490 listed on additional lines, up to a maximum configured number, following which
35491 an ellipsis is displayed. Recipients that have already received the message are
35494 .cindex "frozen messages" "display"
35495 If a message is frozen, an asterisk is displayed at the left-hand side.
35497 The queue display has a vertical scroll bar, and can also be scrolled by means
35498 of the arrow keys. Text can be cut from it using the mouse in the normal way.
35499 The text searching facilities, as described above for the log window, are also
35500 available, but the caret is always moved to the end of the text when the queue
35501 display is updated.
35505 .section "The queue menu" "SECID269"
35506 .cindex "queue" "menu in monitor"
35507 If the &%shift%& key is held down and the left button is clicked when the mouse
35508 pointer is over the text for any message, an action menu pops up, and the first
35509 line of the queue display for the message is highlighted. This does not affect
35512 If you want to use some other event for popping up the menu, you can set the
35513 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
35514 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
35515 value set in this parameter is a standard X event description. For example, to
35516 run eximon using &%ctrl%& rather than &%shift%& you could use
35518 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
35520 The title of the menu is the message id, and it contains entries which act as
35524 &'message log'&: The contents of the message log for the message are displayed
35525 in a new text window.
35527 &'headers'&: Information from the spool file that contains the envelope
35528 information and headers is displayed in a new text window. See chapter
35529 &<<CHAPspool>>& for a description of the format of spool files.
35531 &'body'&: The contents of the spool file containing the body of the message are
35532 displayed in a new text window. There is a default limit of 20,000 bytes to the
35533 amount of data displayed. This can be changed by setting the BODY_MAX
35534 option at compile time, or the EXIMON_BODY_MAX option at run time.
35536 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
35537 delivery of the message. This causes an automatic thaw if the message is
35538 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
35539 a new text window. The delivery is run in a separate process, to avoid holding
35540 up the monitor while the delivery proceeds.
35542 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
35543 that the message be frozen.
35545 .cindex "thawing messages"
35546 .cindex "unfreezing messages"
35547 .cindex "frozen messages" "thawing"
35548 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
35549 that the message be thawed.
35551 .cindex "delivery" "forcing failure"
35552 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
35553 that Exim gives up trying to deliver the message. A bounce message is generated
35554 for any remaining undelivered addresses.
35556 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
35557 that the message be deleted from the system without generating a bounce
35560 &'add recipient'&: A dialog box is displayed into which a recipient address can
35561 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
35562 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
35563 Otherwise it must be entered as a fully qualified address. Pressing RETURN
35564 causes a call to Exim to be made using the &%-Mar%& option to request that an
35565 additional recipient be added to the message, unless the entry box is empty, in
35566 which case no action is taken.
35568 &'mark delivered'&: A dialog box is displayed into which a recipient address
35569 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
35570 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
35571 Otherwise it must be entered as a fully qualified address. Pressing RETURN
35572 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
35573 recipient address as already delivered, unless the entry box is empty, in which
35574 case no action is taken.
35576 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
35577 mark all recipient addresses as already delivered.
35579 &'edit sender'&: A dialog box is displayed initialized with the current
35580 sender's address. Pressing RETURN causes a call to Exim to be made using the
35581 &%-Mes%& option to replace the sender address, unless the entry box is empty,
35582 in which case no action is taken. If you want to set an empty sender (as in
35583 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
35584 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
35585 the address is qualified with that domain.
35588 When a delivery is forced, a window showing the &%-v%& output is displayed. In
35589 other cases when a call to Exim is made, if there is any output from Exim (in
35590 particular, if the command fails) a window containing the command and the
35591 output is displayed. Otherwise, the results of the action are normally apparent
35592 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
35593 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
35594 if no output is generated.
35596 The queue display is automatically updated for actions such as freezing and
35597 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
35598 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
35599 force an update of the display after one of these actions.
35601 In any text window that is displayed as result of a menu action, the normal
35602 cut-and-paste facility is available, and searching can be carried out using ^R
35603 and ^S, as described above for the log tail window.
35610 . ////////////////////////////////////////////////////////////////////////////
35611 . ////////////////////////////////////////////////////////////////////////////
35613 .chapter "Security considerations" "CHAPsecurity"
35614 .scindex IIDsecurcon "security" "discussion of"
35615 This chapter discusses a number of issues concerned with security, some of
35616 which are also covered in other parts of this manual.
35618 For reasons that this author does not understand, some people have promoted
35619 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
35620 existence of this chapter in the documentation. However, the intent of the
35621 chapter is simply to describe the way Exim works in relation to certain
35622 security concerns, not to make any specific claims about the effectiveness of
35623 its security as compared with other MTAs.
35625 What follows is a description of the way Exim is supposed to be. Best efforts
35626 have been made to try to ensure that the code agrees with the theory, but an
35627 absence of bugs can never be guaranteed. Any that are reported will get fixed
35628 as soon as possible.
35631 .section "Building a more &""hardened""& Exim" "SECID286"
35632 .cindex "security" "build-time features"
35633 There are a number of build-time options that can be set in &_Local/Makefile_&
35634 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
35635 Exim administrator who does not have the root password, or by someone who has
35636 penetrated the Exim (but not the root) account. These options are as follows:
35639 ALT_CONFIG_PREFIX can be set to a string that is required to match the
35640 start of any file names used with the &%-C%& option. When it is set, these file
35641 names are also not allowed to contain the sequence &"/../"&. (However, if the
35642 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
35643 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
35644 default setting for &%ALT_CONFIG_PREFIX%&.
35646 If the permitted configuration files are confined to a directory to
35647 which only root has access, this guards against someone who has broken
35648 into the Exim account from running a privileged Exim with an arbitrary
35649 configuration file, and using it to break into other accounts.
35652 If a non-trusted configuration file (i.e. not the default configuration file
35653 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
35654 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
35655 the next item), then root privilege is retained only if the caller of Exim is
35656 root. This locks out the possibility of testing a configuration using &%-C%&
35657 right through message reception and delivery, even if the caller is root. The
35658 reception works, but by that time, Exim is running as the Exim user, so when
35659 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
35660 privilege to be lost. However, root can test reception and delivery using two
35664 The WHITELIST_D_MACROS build option declares some macros to be safe to override
35665 with &%-D%& if the real uid is one of root, the Exim run-time user or the
35666 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
35667 requiring the run-time value supplied to &%-D%& to match a regex that errs on
35668 the restrictive side. Requiring build-time selection of safe macros is onerous
35669 but this option is intended solely as a transition mechanism to permit
35670 previously-working configurations to continue to work after release 4.73.
35672 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
35675 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
35676 never to be used for any deliveries. This is like the &%never_users%& runtime
35677 option, but it cannot be overridden; the runtime option adds additional users
35678 to the list. The default setting is &"root"&; this prevents a non-root user who
35679 is permitted to modify the runtime file from using Exim as a way to get root.
35684 .section "Root privilege" "SECID270"
35686 .cindex "root privilege"
35687 The Exim binary is normally setuid to root, which means that it gains root
35688 privilege (runs as root) when it starts execution. In some special cases (for
35689 example, when the daemon is not in use and there are no local deliveries), it
35690 may be possible to run Exim setuid to some user other than root. This is
35691 discussed in the next section. However, in most installations, root privilege
35692 is required for two things:
35695 To set up a socket connected to the standard SMTP port (25) when initialising
35696 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
35699 To be able to change uid and gid in order to read users' &_.forward_& files and
35700 perform local deliveries as the receiving user or as specified in the
35704 It is not necessary to be root to do any of the other things Exim does, such as
35705 receiving messages and delivering them externally over SMTP, and it is
35706 obviously more secure if Exim does not run as root except when necessary.
35707 For this reason, a user and group for Exim to use must be defined in
35708 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
35709 group"&. Their values can be changed by the run time configuration, though this
35710 is not recommended. Often a user called &'exim'& is used, but some sites use
35711 &'mail'& or another user name altogether.
35713 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
35714 abdication; the process cannot regain root afterwards. Prior to release 4.00,
35715 &[seteuid()]& was used in some circumstances, but this is no longer the case.
35717 After a new Exim process has interpreted its command line options, it changes
35718 uid and gid in the following cases:
35723 If the &%-C%& option is used to specify an alternate configuration file, or if
35724 the &%-D%& option is used to define macro values for the configuration, and the
35725 calling process is not running as root, the uid and gid are changed to those of
35726 the calling process.
35727 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
35728 option may not be used at all.
35729 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
35730 can be supplied if the calling process is running as root, the Exim run-time
35731 user or CONFIGURE_OWNER, if defined.
35736 If the expansion test option (&%-be%&) or one of the filter testing options
35737 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
35740 If the process is not a daemon process or a queue runner process or a delivery
35741 process or a process for testing address routing (started with &%-bt%&), the
35742 uid and gid are changed to the Exim user and group. This means that Exim always
35743 runs under its own uid and gid when receiving messages. This also applies when
35744 testing address verification
35747 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
35750 For a daemon, queue runner, delivery, or address testing process, the uid
35751 remains as root at this stage, but the gid is changed to the Exim group.
35754 The processes that initially retain root privilege behave as follows:
35757 A daemon process changes the gid to the Exim group and the uid to the Exim
35758 user after setting up one or more listening sockets. The &[initgroups()]&
35759 function is called, so that if the Exim user is in any additional groups, they
35760 will be used during message reception.
35762 A queue runner process retains root privilege throughout its execution. Its
35763 job is to fork a controlled sequence of delivery processes.
35765 A delivery process retains root privilege throughout most of its execution,
35766 but any actual deliveries (that is, the transports themselves) are run in
35767 subprocesses which always change to a non-root uid and gid. For local
35768 deliveries this is typically the uid and gid of the owner of the mailbox; for
35769 remote deliveries, the Exim uid and gid are used. Once all the delivery
35770 subprocesses have been run, a delivery process changes to the Exim uid and gid
35771 while doing post-delivery tidying up such as updating the retry database and
35772 generating bounce and warning messages.
35774 While the recipient addresses in a message are being routed, the delivery
35775 process runs as root. However, if a user's filter file has to be processed,
35776 this is done in a subprocess that runs under the individual user's uid and
35777 gid. A system filter is run as root unless &%system_filter_user%& is set.
35779 A process that is testing addresses (the &%-bt%& option) runs as root so that
35780 the routing is done in the same environment as a message delivery.
35786 .section "Running Exim without privilege" "SECTrunexiwitpri"
35787 .cindex "privilege, running without"
35788 .cindex "unprivileged running"
35789 .cindex "root privilege" "running without"
35790 Some installations like to run Exim in an unprivileged state for more of its
35791 operation, for added security. Support for this mode of operation is provided
35792 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
35793 gid are changed to the Exim user and group at the start of a delivery process
35794 (and also queue runner and address testing processes). This means that address
35795 routing is no longer run as root, and the deliveries themselves cannot change
35799 .cindex "daemon" "restarting"
35800 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
35801 that the daemon can still be started in the usual way, and it can respond
35802 correctly to SIGHUP because the re-invocation regains root privilege.
35804 An alternative approach is to make Exim setuid to the Exim user and also setgid
35805 to the Exim group. If you do this, the daemon must be started from a root
35806 process. (Calling Exim from a root process makes it behave in the way it does
35807 when it is setuid root.) However, the daemon cannot restart itself after a
35808 SIGHUP signal because it cannot regain privilege.
35810 It is still useful to set &%deliver_drop_privilege%& in this case, because it
35811 stops Exim from trying to re-invoke itself to do a delivery after a message has
35812 been received. Such a re-invocation is a waste of resources because it has no
35815 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
35816 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
35817 to the Exim user seems a clean approach, but there is one complication:
35819 In this style of operation, Exim is running with the real uid and gid set to
35820 those of the calling process, and the effective uid/gid set to Exim's values.
35821 Ideally, any association with the calling process' uid/gid should be dropped,
35822 that is, the real uid/gid should be reset to the effective values so as to
35823 discard any privileges that the caller may have. While some operating systems
35824 have a function that permits this action for a non-root effective uid, quite a
35825 number of them do not. Because of this lack of standardization, Exim does not
35826 address this problem at this time.
35828 For this reason, the recommended approach for &"mostly unprivileged"& running
35829 is to keep the Exim binary setuid to root, and to set
35830 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
35831 be used in the most straightforward way.
35833 If you configure Exim not to run delivery processes as root, there are a
35834 number of restrictions on what you can do:
35837 You can deliver only as the Exim user/group. You should explicitly use the
35838 &%user%& and &%group%& options to override routers or local transports that
35839 normally deliver as the recipient. This makes sure that configurations that
35840 work in this mode function the same way in normal mode. Any implicit or
35841 explicit specification of another user causes an error.
35843 Use of &_.forward_& files is severely restricted, such that it is usually
35844 not worthwhile to include them in the configuration.
35846 Users who wish to use &_.forward_& would have to make their home directory and
35847 the file itself accessible to the Exim user. Pipe and append-to-file entries,
35848 and their equivalents in Exim filters, cannot be used. While they could be
35849 enabled in the Exim user's name, that would be insecure and not very useful.
35851 Unless the local user mailboxes are all owned by the Exim user (possible in
35852 some POP3 or IMAP-only environments):
35855 They must be owned by the Exim group and be writeable by that group. This
35856 implies you must set &%mode%& in the appendfile configuration, as well as the
35857 mode of the mailbox files themselves.
35859 You must set &%no_check_owner%&, since most or all of the files will not be
35860 owned by the Exim user.
35862 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
35863 on a newly created mailbox when unprivileged. This also implies that new
35864 mailboxes need to be created manually.
35869 These restrictions severely restrict what can be done in local deliveries.
35870 However, there are no restrictions on remote deliveries. If you are running a
35871 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
35872 gives more security at essentially no cost.
35874 If you are using the &%mua_wrapper%& facility (see chapter
35875 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
35880 .section "Delivering to local files" "SECID271"
35881 Full details of the checks applied by &(appendfile)& before it writes to a file
35882 are given in chapter &<<CHAPappendfile>>&.
35886 .section "Running local commands" "SECTsecconslocalcmds"
35887 .cindex "security" "local commands"
35888 .cindex "security" "command injection attacks"
35889 There are a number of ways in which an administrator can configure Exim to run
35890 commands based upon received, untrustworthy, data. Further, in some
35891 configurations a user who can control a &_.forward_& file can also arrange to
35892 run commands. Configuration to check includes, but is not limited to:
35895 Use of &%use_shell%& in the pipe transport: various forms of shell command
35896 injection may be possible with this option present. It is dangerous and should
35897 be used only with considerable caution. Consider constraints which whitelist
35898 allowed characters in a variable which is to be used in a pipe transport that
35899 has &%use_shell%& enabled.
35901 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
35902 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
35903 &_.forward_& files in a redirect router. If Exim is running on a central mail
35904 hub to which ordinary users do not have shell access, but home directories are
35905 NFS mounted (for instance) then administrators should review the list of these
35906 forbid options available, and should bear in mind that the options that may
35907 need forbidding can change as new features are added between releases.
35909 The &%${run...}%& expansion item does not use a shell by default, but
35910 administrators can configure use of &_/bin/sh_& as part of the command.
35911 Such invocations should be viewed with prejudicial suspicion.
35913 Administrators who use embedded Perl are advised to explore how Perl's
35914 taint checking might apply to their usage.
35916 Use of &%${expand...}%& is somewhat analagous to shell's eval builtin and
35917 administrators are well advised to view its use with suspicion, in case (for
35918 instance) it allows a local-part to contain embedded Exim directives.
35920 Use of &%${match_local_part...}%& and friends becomes more dangerous if
35921 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
35922 each can reference arbitrary lists and files, rather than just being a list
35924 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
35925 real-world security vulnerabilities caused by its use with untrustworthy data
35926 injected in, for SQL injection attacks.
35927 Consider the use of the &%inlisti%& expansion condition instead.
35933 .section "Trust in configuration data" "SECTsecconfdata"
35934 .cindex "security" "data sources"
35935 .cindex "security" "regular expressions"
35936 .cindex "regular expressions" "security"
35937 .cindex "PCRE" "security"
35938 If configuration data for Exim can come from untrustworthy sources, there
35939 are some issues to be aware of:
35942 Use of &%${expand...}%& may provide a path for shell injection attacks.
35944 Letting untrusted data provide a regular expression is unwise.
35946 Using &%${match...}%& to apply a fixed regular expression against untrusted
35947 data may result in pathological behaviour within PCRE. Be aware of what
35948 "backtracking" means and consider options for being more strict with a regular
35949 expression. Avenues to explore include limiting what can match (avoiding &`.`&
35950 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
35951 possessive quantifiers or just not using regular expressions against untrusted
35954 It can be important to correctly use &%${quote:...}%&,
35955 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
35956 items to ensure that data is correctly constructed.
35958 Some lookups might return multiple results, even though normal usage is only
35959 expected to yield one result.
35965 .section "IPv4 source routing" "SECID272"
35966 .cindex "source routing" "in IP packets"
35967 .cindex "IP source routing"
35968 Many operating systems suppress IP source-routed packets in the kernel, but
35969 some cannot be made to do this, so Exim does its own check. It logs incoming
35970 IPv4 source-routed TCP calls, and then drops them. Things are all different in
35971 IPv6. No special checking is currently done.
35975 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
35976 Support for these SMTP commands is disabled by default. If required, they can
35977 be enabled by defining suitable ACLs.
35982 .section "Privileged users" "SECID274"
35983 .cindex "trusted users"
35984 .cindex "admin user"
35985 .cindex "privileged user"
35986 .cindex "user" "trusted"
35987 .cindex "user" "admin"
35988 Exim recognizes two sets of users with special privileges. Trusted users are
35989 able to submit new messages to Exim locally, but supply their own sender
35990 addresses and information about a sending host. For other users submitting
35991 local messages, Exim sets up the sender address from the uid, and doesn't
35992 permit a remote host to be specified.
35995 However, an untrusted user is permitted to use the &%-f%& command line option
35996 in the special form &%-f <>%& to indicate that a delivery failure for the
35997 message should not cause an error report. This affects the message's envelope,
35998 but it does not affect the &'Sender:'& header. Untrusted users may also be
35999 permitted to use specific forms of address with the &%-f%& option by setting
36000 the &%untrusted_set_sender%& option.
36002 Trusted users are used to run processes that receive mail messages from some
36003 other mail domain and pass them on to Exim for delivery either locally, or over
36004 the Internet. Exim trusts a caller that is running as root, as the Exim user,
36005 as any user listed in the &%trusted_users%& configuration option, or under any
36006 group listed in the &%trusted_groups%& option.
36008 Admin users are permitted to do things to the messages on Exim's queue. They
36009 can freeze or thaw messages, cause them to be returned to their senders, remove
36010 them entirely, or modify them in various ways. In addition, admin users can run
36011 the Exim monitor and see all the information it is capable of providing, which
36012 includes the contents of files on the spool.
36016 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
36017 delivery of messages on its queue is restricted to admin users. This
36018 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
36019 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
36020 queue is also restricted to admin users. This restriction can be relaxed by
36021 setting &%no_queue_list_requires_admin%&.
36023 Exim recognizes an admin user if the calling process is running as root or as
36024 the Exim user or if any of the groups associated with the calling process is
36025 the Exim group. It is not necessary actually to be running under the Exim
36026 group. However, if admin users who are not root or the Exim user are to access
36027 the contents of files on the spool via the Exim monitor (which runs
36028 unprivileged), Exim must be built to allow group read access to its spool
36033 .section "Spool files" "SECID275"
36034 .cindex "spool directory" "files"
36035 Exim's spool directory and everything it contains is owned by the Exim user and
36036 set to the Exim group. The mode for spool files is defined in the
36037 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
36038 any user who is a member of the Exim group can access these files.
36042 .section "Use of argv[0]" "SECID276"
36043 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
36044 of specific strings, Exim assumes certain options. For example, calling Exim
36045 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
36046 to calling it with the option &%-bS%&. There are no security implications in
36051 .section "Use of %f formatting" "SECID277"
36052 The only use made of &"%f"& by Exim is in formatting load average values. These
36053 are actually stored in integer variables as 1000 times the load average.
36054 Consequently, their range is limited and so therefore is the length of the
36059 .section "Embedded Exim path" "SECID278"
36060 Exim uses its own path name, which is embedded in the code, only when it needs
36061 to re-exec in order to regain root privilege. Therefore, it is not root when it
36062 does so. If some bug allowed the path to get overwritten, it would lead to an
36063 arbitrary program's being run as exim, not as root.
36067 .section "Dynamic module directory" "SECTdynmoddir"
36068 Any dynamically loadable modules must be installed into the directory
36069 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
36073 .section "Use of sprintf()" "SECID279"
36074 .cindex "&[sprintf()]&"
36075 A large number of occurrences of &"sprintf"& in the code are actually calls to
36076 &'string_sprintf()'&, a function that returns the result in malloc'd store.
36077 The intermediate formatting is done into a large fixed buffer by a function
36078 that runs through the format string itself, and checks the length of each
36079 conversion before performing it, thus preventing buffer overruns.
36081 The remaining uses of &[sprintf()]& happen in controlled circumstances where
36082 the output buffer is known to be sufficiently long to contain the converted
36087 .section "Use of debug_printf() and log_write()" "SECID280"
36088 Arbitrary strings are passed to both these functions, but they do their
36089 formatting by calling the function &'string_vformat()'&, which runs through
36090 the format string itself, and checks the length of each conversion.
36094 .section "Use of strcat() and strcpy()" "SECID281"
36095 These are used only in cases where the output buffer is known to be large
36096 enough to hold the result.
36097 .ecindex IIDsecurcon
36102 . ////////////////////////////////////////////////////////////////////////////
36103 . ////////////////////////////////////////////////////////////////////////////
36105 .chapter "Format of spool files" "CHAPspool"
36106 .scindex IIDforspo1 "format" "spool files"
36107 .scindex IIDforspo2 "spool directory" "format of files"
36108 .scindex IIDforspo3 "spool files" "format of"
36109 .cindex "spool files" "editing"
36110 A message on Exim's queue consists of two files, whose names are the message id
36111 followed by -D and -H, respectively. The data portion of the message is kept in
36112 the -D file on its own. The message's envelope, status, and headers are all
36113 kept in the -H file, whose format is described in this chapter. Each of these
36114 two files contains the final component of its own name as its first line. This
36115 is insurance against disk crashes where the directory is lost but the files
36116 themselves are recoverable.
36118 Some people are tempted into editing -D files in order to modify messages. You
36119 need to be extremely careful if you do this; it is not recommended and you are
36120 on your own if you do it. Here are some of the pitfalls:
36123 You must ensure that Exim does not try to deliver the message while you are
36124 fiddling with it. The safest way is to take out a write lock on the -D file,
36125 which is what Exim itself does, using &[fcntl()]&. If you update the file in
36126 place, the lock will be retained. If you write a new file and rename it, the
36127 lock will be lost at the instant of rename.
36129 .vindex "&$body_linecount$&"
36130 If you change the number of lines in the file, the value of
36131 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
36132 present, this value is not used by Exim, but there is no guarantee that this
36133 will always be the case.
36135 If the message is in MIME format, you must take care not to break it.
36137 If the message is cryptographically signed, any change will invalidate the
36140 All in all, modifying -D files is fraught with danger.
36142 Files whose names end with -J may also be seen in the &_input_& directory (or
36143 its subdirectories when &%split_spool_directory%& is set). These are journal
36144 files, used to record addresses to which the message has been delivered during
36145 the course of a delivery attempt. If there are still undelivered recipients at
36146 the end, the -H file is updated, and the -J file is deleted. If, however, there
36147 is some kind of crash (for example, a power outage) before this happens, the -J
36148 file remains in existence. When Exim next processes the message, it notices the
36149 -J file and uses it to update the -H file before starting the next delivery
36152 .section "Format of the -H file" "SECID282"
36153 .cindex "uid (user id)" "in spool file"
36154 .cindex "gid (group id)" "in spool file"
36155 The second line of the -H file contains the login name for the uid of the
36156 process that called Exim to read the message, followed by the numerical uid and
36157 gid. For a locally generated message, this is normally the user who sent the
36158 message. For a message received over TCP/IP via the daemon, it is
36159 normally the Exim user.
36161 The third line of the file contains the address of the message's sender as
36162 transmitted in the envelope, contained in angle brackets. The sender address is
36163 empty for bounce messages. For incoming SMTP mail, the sender address is given
36164 in the MAIL command. For locally generated mail, the sender address is
36165 created by Exim from the login name of the current user and the configured
36166 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
36167 leading &"From&~"& line if the caller is trusted, or if the supplied address is
36168 &"<>"& or an address that matches &%untrusted_set_senders%&.
36170 The fourth line contains two numbers. The first is the time that the message
36171 was received, in the conventional Unix form &-- the number of seconds since the
36172 start of the epoch. The second number is a count of the number of messages
36173 warning of delayed delivery that have been sent to the sender.
36175 There follow a number of lines starting with a hyphen. These can appear in any
36176 order, and are omitted when not relevant:
36179 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
36180 This item is obsolete, and is not generated from Exim release 4.61 onwards;
36181 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
36182 recognized, to provide backward compatibility. In the old format, a line of
36183 this form is present for every ACL variable that is not empty. The number
36184 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
36185 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
36186 the data string for the variable. The string itself starts at the beginning of
36187 the next line, and is followed by a newline character. It may contain internal
36190 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
36191 A line of this form is present for every ACL connection variable that is
36192 defined. Note that there is a space between &%-aclc%& and the rest of the name.
36193 The length is the length of the data string for the variable. The string itself
36194 starts at the beginning of the next line, and is followed by a newline
36195 character. It may contain internal newlines.
36197 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
36198 A line of this form is present for every ACL message variable that is defined.
36199 Note that there is a space between &%-aclm%& and the rest of the name. The
36200 length is the length of the data string for the variable. The string itself
36201 starts at the beginning of the next line, and is followed by a newline
36202 character. It may contain internal newlines.
36204 .vitem "&%-active_hostname%&&~<&'hostname'&>"
36205 This is present if, when the message was received over SMTP, the value of
36206 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
36208 .vitem &%-allow_unqualified_recipient%&
36209 This is present if unqualified recipient addresses are permitted in header
36210 lines (to stop such addresses from being qualified if rewriting occurs at
36211 transport time). Local messages that were input using &%-bnq%& and remote
36212 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
36214 .vitem &%-allow_unqualified_sender%&
36215 This is present if unqualified sender addresses are permitted in header lines
36216 (to stop such addresses from being qualified if rewriting occurs at transport
36217 time). Local messages that were input using &%-bnq%& and remote messages from
36218 hosts that match &%sender_unqualified_hosts%& set this flag.
36220 .vitem "&%-auth_id%&&~<&'text'&>"
36221 The id information for a message received on an authenticated SMTP connection
36222 &-- the value of the &$authenticated_id$& variable.
36224 .vitem "&%-auth_sender%&&~<&'address'&>"
36225 The address of an authenticated sender &-- the value of the
36226 &$authenticated_sender$& variable.
36228 .vitem "&%-body_linecount%&&~<&'number'&>"
36229 This records the number of lines in the body of the message, and is always
36232 .vitem "&%-body_zerocount%&&~<&'number'&>"
36233 This records the number of binary zero bytes in the body of the message, and is
36234 present if the number is greater than zero.
36236 .vitem &%-deliver_firsttime%&
36237 This is written when a new message is first added to the spool. When the spool
36238 file is updated after a deferral, it is omitted.
36240 .vitem "&%-frozen%&&~<&'time'&>"
36241 .cindex "frozen messages" "spool data"
36242 The message is frozen, and the freezing happened at <&'time'&>.
36244 .vitem "&%-helo_name%&&~<&'text'&>"
36245 This records the host name as specified by a remote host in a HELO or EHLO
36248 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
36249 This records the IP address of the host from which the message was received and
36250 the remote port number that was used. It is omitted for locally generated
36253 .vitem "&%-host_auth%&&~<&'text'&>"
36254 If the message was received on an authenticated SMTP connection, this records
36255 the name of the authenticator &-- the value of the
36256 &$sender_host_authenticated$& variable.
36258 .vitem &%-host_lookup_failed%&
36259 This is present if an attempt to look up the sending host's name from its IP
36260 address failed. It corresponds to the &$host_lookup_failed$& variable.
36262 .vitem "&%-host_name%&&~<&'text'&>"
36263 .cindex "reverse DNS lookup"
36264 .cindex "DNS" "reverse lookup"
36265 This records the name of the remote host from which the message was received,
36266 if the host name was looked up from the IP address when the message was being
36267 received. It is not present if no reverse lookup was done.
36269 .vitem "&%-ident%&&~<&'text'&>"
36270 For locally submitted messages, this records the login of the originating user,
36271 unless it was a trusted user and the &%-oMt%& option was used to specify an
36272 ident value. For messages received over TCP/IP, this records the ident string
36273 supplied by the remote host, if any.
36275 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
36276 This records the IP address of the local interface and the port number through
36277 which a message was received from a remote host. It is omitted for locally
36278 generated messages.
36281 The message is from a local sender.
36283 .vitem &%-localerror%&
36284 The message is a locally-generated bounce message.
36286 .vitem "&%-local_scan%&&~<&'string'&>"
36287 This records the data string that was returned by the &[local_scan()]& function
36288 when the message was received &-- the value of the &$local_scan_data$&
36289 variable. It is omitted if no data was returned.
36291 .vitem &%-manual_thaw%&
36292 The message was frozen but has been thawed manually, that is, by an explicit
36293 Exim command rather than via the auto-thaw process.
36296 A testing delivery process was started using the &%-N%& option to suppress any
36297 actual deliveries, but delivery was deferred. At any further delivery attempts,
36300 .vitem &%-received_protocol%&
36301 This records the value of the &$received_protocol$& variable, which contains
36302 the name of the protocol by which the message was received.
36304 .vitem &%-sender_set_untrusted%&
36305 The envelope sender of this message was set by an untrusted local caller (used
36306 to ensure that the caller is displayed in queue listings).
36308 .vitem "&%-spam_score_int%&&~<&'number'&>"
36309 If a message was scanned by SpamAssassin, this is present. It records the value
36310 of &$spam_score_int$&.
36312 .vitem &%-tls_certificate_verified%&
36313 A TLS certificate was received from the client that sent this message, and the
36314 certificate was verified by the server.
36316 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
36317 When the message was received over an encrypted connection, this records the
36318 name of the cipher suite that was used.
36320 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
36321 When the message was received over an encrypted connection, and a certificate
36322 was received from the client, this records the Distinguished Name from that
36326 Following the options there is a list of those addresses to which the message
36327 is not to be delivered. This set of addresses is initialized from the command
36328 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
36329 is set; otherwise it starts out empty. Whenever a successful delivery is made,
36330 the address is added to this set. The addresses are kept internally as a
36331 balanced binary tree, and it is a representation of that tree which is written
36332 to the spool file. If an address is expanded via an alias or forward file, the
36333 original address is added to the tree when deliveries to all its child
36334 addresses are complete.
36336 If the tree is empty, there is a single line in the spool file containing just
36337 the text &"XX"&. Otherwise, each line consists of two letters, which are either
36338 Y or N, followed by an address. The address is the value for the node of the
36339 tree, and the letters indicate whether the node has a left branch and/or a
36340 right branch attached to it, respectively. If branches exist, they immediately
36341 follow. Here is an example of a three-node tree:
36343 YY darcy@austen.fict.example
36344 NN alice@wonderland.fict.example
36345 NN editor@thesaurus.ref.example
36347 After the non-recipients tree, there is a list of the message's recipients.
36348 This is a simple list, preceded by a count. It includes all the original
36349 recipients of the message, including those to whom the message has already been
36350 delivered. In the simplest case, the list contains one address per line. For
36354 editor@thesaurus.ref.example
36355 darcy@austen.fict.example
36357 alice@wonderland.fict.example
36359 However, when a child address has been added to the top-level addresses as a
36360 result of the use of the &%one_time%& option on a &(redirect)& router, each
36361 line is of the following form:
36363 <&'top-level address'&> <&'errors_to address'&> &&&
36364 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
36366 The 01 flag bit indicates the presence of the three other fields that follow
36367 the top-level address. Other bits may be used in future to support additional
36368 fields. The <&'parent number'&> is the offset in the recipients list of the
36369 original parent of the &"one time"& address. The first two fields are the
36370 envelope sender that is associated with this address and its length. If the
36371 length is zero, there is no special envelope sender (there are then two space
36372 characters in the line). A non-empty field can arise from a &(redirect)& router
36373 that has an &%errors_to%& setting.
36376 A blank line separates the envelope and status information from the headers
36377 which follow. A header may occupy several lines of the file, and to save effort
36378 when reading it in, each header is preceded by a number and an identifying
36379 character. The number is the number of characters in the header, including any
36380 embedded newlines and the terminating newline. The character is one of the
36384 .row <&'blank'&> "header in which Exim has no special interest"
36385 .row &`B`& "&'Bcc:'& header"
36386 .row &`C`& "&'Cc:'& header"
36387 .row &`F`& "&'From:'& header"
36388 .row &`I`& "&'Message-id:'& header"
36389 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
36390 .row &`R`& "&'Reply-To:'& header"
36391 .row &`S`& "&'Sender:'& header"
36392 .row &`T`& "&'To:'& header"
36393 .row &`*`& "replaced or deleted header"
36396 Deleted or replaced (rewritten) headers remain in the spool file for debugging
36397 purposes. They are not transmitted when the message is delivered. Here is a
36398 typical set of headers:
36400 111P Received: by hobbit.fict.example with local (Exim 4.00)
36401 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
36402 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
36403 038* X-rewrote-sender: bb@hobbit.fict.example
36404 042* From: Bilbo Baggins <bb@hobbit.fict.example>
36405 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
36406 099* To: alice@wonderland.fict.example, rdo@foundation,
36407 darcy@austen.fict.example, editor@thesaurus.ref.example
36408 104T To: alice@wonderland.fict.example, rdo@foundation.example,
36409 darcy@austen.fict.example, editor@thesaurus.ref.example
36410 038 Date: Fri, 11 May 2001 10:28:59 +0100
36412 The asterisked headers indicate that the envelope sender, &'From:'& header, and
36413 &'To:'& header have been rewritten, the last one because routing expanded the
36414 unqualified domain &'foundation'&.
36415 .ecindex IIDforspo1
36416 .ecindex IIDforspo2
36417 .ecindex IIDforspo3
36419 . ////////////////////////////////////////////////////////////////////////////
36420 . ////////////////////////////////////////////////////////////////////////////
36422 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
36426 DKIM is a mechanism by which messages sent by some entity can be provably
36427 linked to a domain which that entity controls. It permits reputation to
36428 be tracked on a per-domain basis, rather than merely upon source IP address.
36429 DKIM is documented in RFC 4871.
36431 Since version 4.70, DKIM support is compiled into Exim by default. It can be
36432 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
36434 Exim's DKIM implementation allows to
36436 Sign outgoing messages: This function is implemented in the SMTP transport.
36437 It can co-exist with all other Exim features
36438 (including transport filters)
36439 except cutthrough delivery.
36441 Verify signatures in incoming messages: This is implemented by an additional
36442 ACL (acl_smtp_dkim), which can be called several times per message, with
36443 different signature contexts.
36446 In typical Exim style, the verification implementation does not include any
36447 default "policy". Instead it enables you to build your own policy using
36448 Exim's standard controls.
36450 Please note that verification of DKIM signatures in incoming mail is turned
36451 on by default for logging purposes. For each signature in incoming email,
36452 exim will log a line displaying the most important signature details, and the
36453 signature status. Here is an example (with line-breaks added for clarity):
36455 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
36456 d=facebookmail.com s=q1-2009b
36457 c=relaxed/relaxed a=rsa-sha1
36458 i=@facebookmail.com t=1252484542 [verification succeeded]
36460 You might want to turn off DKIM verification processing entirely for internal
36461 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
36462 control modifier. This should typically be done in the RCPT ACL, at points
36463 where you accept mail from relay sources (internal hosts or authenticated
36467 .section "Signing outgoing messages" "SECID513"
36468 .cindex "DKIM" "signing"
36470 Signing is implemented by setting private options on the SMTP transport.
36471 These options take (expandable) strings as arguments.
36473 .option dkim_domain smtp string&!! unset
36475 The domain you want to sign with. The result of this expanded
36476 option is put into the &%$dkim_domain%& expansion variable.
36478 .option dkim_selector smtp string&!! unset
36480 This sets the key selector string. You can use the &%$dkim_domain%& expansion
36481 variable to look up a matching selector. The result is put in the expansion
36482 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
36483 option along with &%$dkim_domain%&.
36485 .option dkim_private_key smtp string&!! unset
36487 This sets the private key to use. You can use the &%$dkim_domain%& and
36488 &%$dkim_selector%& expansion variables to determine the private key to use.
36489 The result can either
36491 be a valid RSA private key in ASCII armor, including line breaks.
36493 start with a slash, in which case it is treated as a file that contains
36496 be "0", "false" or the empty string, in which case the message will not
36497 be signed. This case will not result in an error, even if &%dkim_strict%&
36501 .option dkim_canon smtp string&!! unset
36503 This option sets the canonicalization method used when signing a message.
36504 The DKIM RFC currently supports two methods: "simple" and "relaxed".
36505 The option defaults to "relaxed" when unset. Note: the current implementation
36506 only supports using the same canonicalization method for both headers and body.
36508 .option dkim_strict smtp string&!! unset
36510 This option defines how Exim behaves when signing a message that
36511 should be signed fails for some reason. When the expansion evaluates to
36512 either "1" or "true", Exim will defer. Otherwise Exim will send the message
36513 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
36516 .option dkim_sign_headers smtp string&!! unset
36518 When set, this option must expand to (or be specified as) a colon-separated
36519 list of header names. Headers with these names will be included in the message
36520 signature. When unspecified, the header names recommended in RFC4871 will be
36524 .section "Verifying DKIM signatures in incoming mail" "SECID514"
36525 .cindex "DKIM" "verification"
36527 Verification of DKIM signatures in incoming email is implemented via the
36528 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
36529 syntactically(!) correct signature in the incoming message.
36530 A missing ACL definition defaults to accept.
36531 If any ACL call does not acccept, the message is not accepted.
36532 If a cutthrough delivery was in progress for the message it is
36533 summarily dropped (having wasted the transmission effort).
36535 To evaluate the signature in the ACL a large number of expansion variables
36536 containing the signature status and its details are set up during the
36537 runtime of the ACL.
36539 Calling the ACL only for existing signatures is not sufficient to build
36540 more advanced policies. For that reason, the global option
36541 &%dkim_verify_signers%&, and a global expansion variable
36542 &%$dkim_signers%& exist.
36544 The global option &%dkim_verify_signers%& can be set to a colon-separated
36545 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
36546 called. It is expanded when the message has been received. At this point,
36547 the expansion variable &%$dkim_signers%& already contains a colon-separated
36548 list of signer domains and identities for the message. When
36549 &%dkim_verify_signers%& is not specified in the main configuration,
36552 dkim_verify_signers = $dkim_signers
36554 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
36555 DKIM signature in the message. Current DKIM verifiers may want to explicitly
36556 call the ACL for known domains or identities. This would be achieved as follows:
36558 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
36560 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
36561 and "ebay.com", plus all domains and identities that have signatures in the message.
36562 You can also be more creative in constructing your policy. For example:
36564 dkim_verify_signers = $sender_address_domain:$dkim_signers
36567 If a domain or identity is listed several times in the (expanded) value of
36568 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
36571 Inside the &%acl_smtp_dkim%&, the following expansion variables are
36572 available (from most to least important):
36576 .vitem &%$dkim_cur_signer%&
36577 The signer that is being evaluated in this ACL run. This can be a domain or
36578 an identity. This is one of the list items from the expanded main option
36579 &%dkim_verify_signers%& (see above).
36580 .vitem &%$dkim_verify_status%&
36581 A string describing the general status of the signature. One of
36583 &%none%&: There is no signature in the message for the current domain or
36584 identity (as reflected by &%$dkim_cur_signer%&).
36586 &%invalid%&: The signature could not be verified due to a processing error.
36587 More detail is available in &%$dkim_verify_reason%&.
36589 &%fail%&: Verification of the signature failed. More detail is
36590 available in &%$dkim_verify_reason%&.
36592 &%pass%&: The signature passed verification. It is valid.
36594 .vitem &%$dkim_verify_reason%&
36595 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
36596 "fail" or "invalid". One of
36598 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
36599 key for the domain could not be retrieved. This may be a temporary problem.
36601 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
36602 record for the domain is syntactically invalid.
36604 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
36605 body hash does not match the one specified in the signature header. This
36606 means that the message body was modified in transit.
36608 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
36609 could not be verified. This may mean that headers were modified,
36610 re-written or otherwise changed in a way which is incompatible with
36611 DKIM verification. It may of course also mean that the signature is forged.
36613 .vitem &%$dkim_domain%&
36614 The signing domain. IMPORTANT: This variable is only populated if there is
36615 an actual signature in the message for the current domain or identity (as
36616 reflected by &%$dkim_cur_signer%&).
36617 .vitem &%$dkim_identity%&
36618 The signing identity, if present. IMPORTANT: This variable is only populated
36619 if there is an actual signature in the message for the current domain or
36620 identity (as reflected by &%$dkim_cur_signer%&).
36621 .vitem &%$dkim_selector%&
36622 The key record selector string.
36623 .vitem &%$dkim_algo%&
36624 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
36625 .vitem &%$dkim_canon_body%&
36626 The body canonicalization method. One of 'relaxed' or 'simple'.
36627 .vitem &%dkim_canon_headers%&
36628 The header canonicalization method. One of 'relaxed' or 'simple'.
36629 .vitem &%$dkim_copiedheaders%&
36630 A transcript of headers and their values which are included in the signature
36631 (copied from the 'z=' tag of the signature).
36632 .vitem &%$dkim_bodylength%&
36633 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
36634 limit was set by the signer, "9999999999999" is returned. This makes sure
36635 that this variable always expands to an integer value.
36636 .vitem &%$dkim_created%&
36637 UNIX timestamp reflecting the date and time when the signature was created.
36638 When this was not specified by the signer, "0" is returned.
36639 .vitem &%$dkim_expires%&
36640 UNIX timestamp reflecting the date and time when the signer wants the
36641 signature to be treated as "expired". When this was not specified by the
36642 signer, "9999999999999" is returned. This makes it possible to do useful
36643 integer size comparisons against this value.
36644 .vitem &%$dkim_headernames%&
36645 A colon-separated list of names of headers included in the signature.
36646 .vitem &%$dkim_key_testing%&
36647 "1" if the key record has the "testing" flag set, "0" if not.
36648 .vitem &%$dkim_key_nosubdomains%&
36649 "1" if the key record forbids subdomaining, "0" otherwise.
36650 .vitem &%$dkim_key_srvtype%&
36651 Service type (tag s=) from the key record. Defaults to "*" if not specified
36653 .vitem &%$dkim_key_granularity%&
36654 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
36656 .vitem &%$dkim_key_notes%&
36657 Notes from the key record (tag n=).
36660 In addition, two ACL conditions are provided:
36663 .vitem &%dkim_signers%&
36664 ACL condition that checks a colon-separated list of domains or identities
36665 for a match against the domain or identity that the ACL is currently verifying
36666 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
36667 verb to a group of domains or identities. For example:
36670 # Warn when Mail purportedly from GMail has no signature at all
36671 warn log_message = GMail sender without DKIM signature
36672 sender_domains = gmail.com
36673 dkim_signers = gmail.com
36677 .vitem &%dkim_status%&
36678 ACL condition that checks a colon-separated list of possible DKIM verification
36679 results against the actual result of verification. This is typically used
36680 to restrict an ACL verb to a list of verification outcomes, for example:
36683 deny message = Mail from Paypal with invalid/missing signature
36684 sender_domains = paypal.com:paypal.de
36685 dkim_signers = paypal.com:paypal.de
36686 dkim_status = none:invalid:fail
36689 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
36690 see the documentation of the &%$dkim_verify_status%& expansion variable above
36691 for more information of what they mean.
36694 . ////////////////////////////////////////////////////////////////////////////
36695 . ////////////////////////////////////////////////////////////////////////////
36697 .chapter "Adding new drivers or lookup types" "CHID13" &&&
36698 "Adding drivers or lookups"
36699 .cindex "adding drivers"
36700 .cindex "new drivers, adding"
36701 .cindex "drivers" "adding new"
36702 The following actions have to be taken in order to add a new router, transport,
36703 authenticator, or lookup type to Exim:
36706 Choose a name for the driver or lookup type that does not conflict with any
36707 existing name; I will use &"newdriver"& in what follows.
36709 Add to &_src/EDITME_& the line:
36711 <&'type'&>&`_NEWDRIVER=yes`&
36713 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
36714 code is not to be included in the binary by default, comment this line out. You
36715 should also add any relevant comments about the driver or lookup type.
36717 Add to &_src/config.h.defaults_& the line:
36719 #define <type>_NEWDRIVER
36722 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
36723 and create a table entry as is done for all the other drivers and lookup types.
36725 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
36726 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
36727 Add your &`NEWDRIVER`& to that list.
36728 As long as the dynamic module would be named &_newdriver.so_&, you can use the
36729 simple form that most lookups have.
36731 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
36732 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
36733 driver or lookup type and add it to the definition of OBJ.
36735 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
36738 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
36739 as for other drivers and lookups.
36742 Then all you need to do is write the code! A good way to start is to make a
36743 proforma by copying an existing module of the same type, globally changing all
36744 occurrences of the name, and cutting out most of the code. Note that any
36745 options you create must be listed in alphabetical order, because the tables are
36746 searched using a binary chop procedure.
36748 There is a &_README_& file in each of the sub-directories of &_src_& describing
36749 the interface that is expected.
36754 . ////////////////////////////////////////////////////////////////////////////
36755 . ////////////////////////////////////////////////////////////////////////////
36757 . /////////////////////////////////////////////////////////////////////////////
36758 . These lines are processing instructions for the Simple DocBook Processor that
36759 . Philip Hazel has developed as a less cumbersome way of making PostScript and
36760 . PDFs than using xmlto and fop. They will be ignored by all other XML
36762 . /////////////////////////////////////////////////////////////////////////////
36767 foot_right_recto="&chaptertitle;"
36768 foot_right_verso="&chaptertitle;"
36772 .makeindex "Options index" "option"
36773 .makeindex "Variables index" "variable"
36774 .makeindex "Concept index" "concept"
36777 . /////////////////////////////////////////////////////////////////////////////
36778 . /////////////////////////////////////////////////////////////////////////////