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 "4.85"
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"&.
1991 have a compile option for including A6 record support but this has now been
1997 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1998 .cindex "lookup modules"
1999 .cindex "dynamic modules"
2000 .cindex ".so building"
2001 On some platforms, Exim supports not compiling all lookup types directly into
2002 the main binary, instead putting some into external modules which can be loaded
2004 This permits packagers to build Exim with support for lookups with extensive
2005 library dependencies without requiring all users to install all of those
2007 Most, but not all, lookup types can be built this way.
2009 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2010 installed; Exim will only load modules from that directory, as a security
2011 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2012 for your OS; see &_OS/Makefile-Linux_& for an example.
2013 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2014 see &_src/EDITME_& for details.
2016 Then, for each module to be loaded dynamically, define the relevant
2017 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2018 For example, this will build in lsearch but load sqlite and mysql support
2027 .section "The building process" "SECID29"
2028 .cindex "build directory"
2029 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2030 created, run &'make'& at the top level. It determines the architecture and
2031 operating system types, and creates a build directory if one does not exist.
2032 For example, on a Sun system running Solaris 8, the directory
2033 &_build-SunOS5-5.8-sparc_& is created.
2034 .cindex "symbolic link" "to source files"
2035 Symbolic links to relevant source files are installed in the build directory.
2037 If this is the first time &'make'& has been run, it calls a script that builds
2038 a make file inside the build directory, using the configuration files from the
2039 &_Local_& directory. The new make file is then passed to another instance of
2040 &'make'&. This does the real work, building a number of utility scripts, and
2041 then compiling and linking the binaries for the Exim monitor (if configured), a
2042 number of utility programs, and finally Exim itself. The command &`make
2043 makefile`& can be used to force a rebuild of the make file in the build
2044 directory, should this ever be necessary.
2046 If you have problems building Exim, check for any comments there may be in the
2047 &_README_& file concerning your operating system, and also take a look at the
2048 FAQ, where some common problems are covered.
2052 .section 'Output from &"make"&' "SECID283"
2053 The output produced by the &'make'& process for compile lines is often very
2054 unreadable, because these lines can be very long. For this reason, the normal
2055 output is suppressed by default, and instead output similar to that which
2056 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2057 each module that is being compiled or linked. However, it is still possible to
2058 get the full output, by calling &'make'& like this:
2062 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2063 command reflection in &'make'&. When you ask for the full output, it is
2064 given in addition to the short output.
2068 .section "Overriding build-time options for Exim" "SECToverride"
2069 .cindex "build-time options, overriding"
2070 The main make file that is created at the beginning of the building process
2071 consists of the concatenation of a number of files which set configuration
2072 values, followed by a fixed set of &'make'& instructions. If a value is set
2073 more than once, the last setting overrides any previous ones. This provides a
2074 convenient way of overriding defaults. The files that are concatenated are, in
2077 &_OS/Makefile-Default_&
2078 &_OS/Makefile-_&<&'ostype'&>
2080 &_Local/Makefile-_&<&'ostype'&>
2081 &_Local/Makefile-_&<&'archtype'&>
2082 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2083 &_OS/Makefile-Base_&
2085 .cindex "&_Local/Makefile_&"
2086 .cindex "building Exim" "operating system type"
2087 .cindex "building Exim" "architecture type"
2088 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2089 architecture type. &_Local/Makefile_& is required to exist, and the building
2090 process fails if it is absent. The other three &_Local_& files are optional,
2091 and are often not needed.
2093 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2094 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2095 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2096 values are used, thereby providing a means of forcing particular settings.
2097 Otherwise, the scripts try to get values from the &%uname%& command. If this
2098 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2099 of &'ad hoc'& transformations are then applied, to produce the standard names
2100 that Exim expects. You can run these scripts directly from the shell in order
2101 to find out what values are being used on your system.
2104 &_OS/Makefile-Default_& contains comments about the variables that are set
2105 therein. Some (but not all) are mentioned below. If there is something that
2106 needs changing, review the contents of this file and the contents of the make
2107 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2111 .cindex "building Exim" "overriding default settings"
2112 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2113 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2114 need to change the original files. Instead, you should make the changes by
2115 putting the new values in an appropriate &_Local_& file. For example,
2116 .cindex "Tru64-Unix build-time settings"
2117 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2118 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2119 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2120 called with the option &%-std1%&, to make it recognize some of the features of
2121 Standard C that Exim uses. (Most other compilers recognize Standard C by
2122 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2123 containing the lines
2128 If you are compiling for just one operating system, it may be easier to put
2129 these lines directly into &_Local/Makefile_&.
2131 Keeping all your local configuration settings separate from the distributed
2132 files makes it easy to transfer them to new versions of Exim simply by copying
2133 the contents of the &_Local_& directory.
2136 .cindex "NIS lookup type" "including support for"
2137 .cindex "NIS+ lookup type" "including support for"
2138 .cindex "LDAP" "including support for"
2139 .cindex "lookup" "inclusion in binary"
2140 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2141 lookup, but not all systems have these components installed, so the default is
2142 not to include the relevant code in the binary. All the different kinds of file
2143 and database lookup that Exim supports are implemented as separate code modules
2144 which are included only if the relevant compile-time options are set. In the
2145 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2151 and similar settings apply to the other lookup types. They are all listed in
2152 &_src/EDITME_&. In many cases the relevant include files and interface
2153 libraries need to be installed before compiling Exim.
2154 .cindex "cdb" "including support for"
2155 However, there are some optional lookup types (such as cdb) for which
2156 the code is entirely contained within Exim, and no external include
2157 files or libraries are required. When a lookup type is not included in the
2158 binary, attempts to configure Exim to use it cause run time configuration
2161 .cindex "pkg-config" "lookups"
2162 .cindex "pkg-config" "authenticators"
2163 Many systems now use a tool called &'pkg-config'& to encapsulate information
2164 about how to compile against a library; Exim has some initial support for
2165 being able to use pkg-config for lookups and authenticators. For any given
2166 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2167 variable with the &`_PC`& suffix in the name and assign as the value the
2168 name of the package to be queried. The results of querying via the
2169 &'pkg-config'& command will be added to the appropriate Makefile variables
2170 with &`+=`& directives, so your version of &'make'& will need to support that
2171 syntax. For instance:
2174 LOOKUP_SQLITE_PC=sqlite3
2176 AUTH_GSASL_PC=libgsasl
2177 AUTH_HEIMDAL_GSSAPI=yes
2178 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2181 .cindex "Perl" "including support for"
2182 Exim can be linked with an embedded Perl interpreter, allowing Perl
2183 subroutines to be called during string expansion. To enable this facility,
2187 must be defined in &_Local/Makefile_&. Details of this facility are given in
2188 chapter &<<CHAPperl>>&.
2190 .cindex "X11 libraries, location of"
2191 The location of the X11 libraries is something that varies a lot between
2192 operating systems, and there may be different versions of X11 to cope
2193 with. Exim itself makes no use of X11, but if you are compiling the Exim
2194 monitor, the X11 libraries must be available.
2195 The following three variables are set in &_OS/Makefile-Default_&:
2198 XINCLUDE=-I$(X11)/include
2199 XLFLAGS=-L$(X11)/lib
2201 These are overridden in some of the operating-system configuration files. For
2202 example, in &_OS/Makefile-SunOS5_& there is
2205 XINCLUDE=-I$(X11)/include
2206 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2208 If you need to override the default setting for your operating system, place a
2209 definition of all three of these variables into your
2210 &_Local/Makefile-<ostype>_& file.
2213 If you need to add any extra libraries to the link steps, these can be put in a
2214 variable called EXTRALIBS, which appears in all the link commands, but by
2215 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2216 command for linking the main Exim binary, and not for any associated utilities.
2218 .cindex "DBM libraries" "configuration for building"
2219 There is also DBMLIB, which appears in the link commands for binaries that
2220 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2221 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2222 binary, and which can be used, for example, to include additional X11
2225 .cindex "configuration file" "editing"
2226 The make file copes with rebuilding Exim correctly if any of the configuration
2227 files are edited. However, if an optional configuration file is deleted, it is
2228 necessary to touch the associated non-optional file (that is,
2229 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2232 .section "OS-specific header files" "SECID30"
2234 .cindex "building Exim" "OS-specific C header files"
2235 The &_OS_& directory contains a number of files with names of the form
2236 &_os.h-<ostype>_&. These are system-specific C header files that should not
2237 normally need to be changed. There is a list of macro settings that are
2238 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2239 are porting Exim to a new operating system.
2243 .section "Overriding build-time options for the monitor" "SECID31"
2244 .cindex "building Eximon"
2245 A similar process is used for overriding things when building the Exim monitor,
2246 where the files that are involved are
2248 &_OS/eximon.conf-Default_&
2249 &_OS/eximon.conf-_&<&'ostype'&>
2250 &_Local/eximon.conf_&
2251 &_Local/eximon.conf-_&<&'ostype'&>
2252 &_Local/eximon.conf-_&<&'archtype'&>
2253 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2255 .cindex "&_Local/eximon.conf_&"
2256 As with Exim itself, the final three files need not exist, and in this case the
2257 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2258 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2259 variables of the same name, preceded by EXIMON_. For example, setting
2260 EXIMON_LOG_DEPTH in the environment overrides the value of
2261 LOG_DEPTH at run time.
2265 .section "Installing Exim binaries and scripts" "SECID32"
2266 .cindex "installing Exim"
2267 .cindex "BIN_DIRECTORY"
2268 The command &`make install`& runs the &(exim_install)& script with no
2269 arguments. The script copies binaries and utility scripts into the directory
2270 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2271 .cindex "setuid" "installing Exim with"
2272 The install script copies files only if they are newer than the files they are
2273 going to replace. The Exim binary is required to be owned by root and have the
2274 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2275 install`& as root so that it can set up the Exim binary in this way. However, in
2276 some special situations (for example, if a host is doing no local deliveries)
2277 it may be possible to run Exim without making the binary setuid root (see
2278 chapter &<<CHAPsecurity>>& for details).
2280 .cindex "CONFIGURE_FILE"
2281 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2282 in &_Local/Makefile_&. If this names a single file, and the file does not
2283 exist, the default configuration file &_src/configure.default_& is copied there
2284 by the installation script. If a run time configuration file already exists, it
2285 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2286 alternative files, no default is installed.
2288 .cindex "system aliases file"
2289 .cindex "&_/etc/aliases_&"
2290 One change is made to the default configuration file when it is installed: the
2291 default configuration contains a router that references a system aliases file.
2292 The path to this file is set to the value specified by
2293 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2294 If the system aliases file does not exist, the installation script creates it,
2295 and outputs a comment to the user.
2297 The created file contains no aliases, but it does contain comments about the
2298 aliases a site should normally have. Mail aliases have traditionally been
2299 kept in &_/etc/aliases_&. However, some operating systems are now using
2300 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2301 Exim's configuration if necessary.
2303 The default configuration uses the local host's name as the only local domain,
2304 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2305 running as the local user. System aliases and &_.forward_& files in users' home
2306 directories are supported, but no NIS or NIS+ support is configured. Domains
2307 other than the name of the local host are routed using the DNS, with delivery
2310 It is possible to install Exim for special purposes (such as building a binary
2311 distribution) in a private part of the file system. You can do this by a
2314 make DESTDIR=/some/directory/ install
2316 This has the effect of pre-pending the specified directory to all the file
2317 paths, except the name of the system aliases file that appears in the default
2318 configuration. (If a default alias file is created, its name &'is'& modified.)
2319 For backwards compatibility, ROOT is used if DESTDIR is not set,
2320 but this usage is deprecated.
2322 .cindex "installing Exim" "what is not installed"
2323 Running &'make install'& does not copy the Exim 4 conversion script
2324 &'convert4r4'&. You will probably run this only once if you are
2325 upgrading from Exim 3. None of the documentation files in the &_doc_&
2326 directory are copied, except for the info files when you have set
2327 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2329 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2330 to their names. The Exim binary itself, however, is handled differently. It is
2331 installed under a name that includes the version number and the compile number,
2332 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2333 called &_exim_& to point to the binary. If you are updating a previous version
2334 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2335 from the directory (as seen by other processes).
2337 .cindex "installing Exim" "testing the script"
2338 If you want to see what the &'make install'& will do before running it for
2339 real, you can pass the &%-n%& option to the installation script by this
2342 make INSTALL_ARG=-n install
2344 The contents of the variable INSTALL_ARG are passed to the installation
2345 script. You do not need to be root to run this test. Alternatively, you can run
2346 the installation script directly, but this must be from within the build
2347 directory. For example, from the top-level Exim directory you could use this
2350 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2352 .cindex "installing Exim" "install script options"
2353 There are two other options that can be supplied to the installation script.
2356 &%-no_chown%& bypasses the call to change the owner of the installed binary
2357 to root, and the call to make it a setuid binary.
2359 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2363 INSTALL_ARG can be used to pass these options to the script. For example:
2365 make INSTALL_ARG=-no_symlink install
2367 The installation script can also be given arguments specifying which files are
2368 to be copied. For example, to install just the Exim binary, and nothing else,
2369 without creating the symbolic link, you could use:
2371 make INSTALL_ARG='-no_symlink exim' install
2376 .section "Installing info documentation" "SECTinsinfdoc"
2377 .cindex "installing Exim" "&'info'& documentation"
2378 Not all systems use the GNU &'info'& system for documentation, and for this
2379 reason, the Texinfo source of Exim's documentation is not included in the main
2380 distribution. Instead it is available separately from the ftp site (see section
2383 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2384 source of the documentation is found in the source tree, running &`make
2385 install`& automatically builds the info files and installs them.
2389 .section "Setting up the spool directory" "SECID33"
2390 .cindex "spool directory" "creating"
2391 When it starts up, Exim tries to create its spool directory if it does not
2392 exist. The Exim uid and gid are used for the owner and group of the spool
2393 directory. Sub-directories are automatically created in the spool directory as
2399 .section "Testing" "SECID34"
2400 .cindex "testing" "installation"
2401 Having installed Exim, you can check that the run time configuration file is
2402 syntactically valid by running the following command, which assumes that the
2403 Exim binary directory is within your PATH environment variable:
2407 If there are any errors in the configuration file, Exim outputs error messages.
2408 Otherwise it outputs the version number and build date,
2409 the DBM library that is being used, and information about which drivers and
2410 other optional code modules are included in the binary.
2411 Some simple routing tests can be done by using the address testing option. For
2414 &`exim -bt`& <&'local username'&>
2416 should verify that it recognizes a local mailbox, and
2418 &`exim -bt`& <&'remote address'&>
2420 a remote one. Then try getting it to deliver mail, both locally and remotely.
2421 This can be done by passing messages directly to Exim, without going through a
2422 user agent. For example:
2424 exim -v postmaster@your.domain.example
2425 From: user@your.domain.example
2426 To: postmaster@your.domain.example
2427 Subject: Testing Exim
2429 This is a test message.
2432 The &%-v%& option causes Exim to output some verification of what it is doing.
2433 In this case you should see copies of three log lines, one for the message's
2434 arrival, one for its delivery, and one containing &"Completed"&.
2436 .cindex "delivery" "problems with"
2437 If you encounter problems, look at Exim's log files (&'mainlog'& and
2438 &'paniclog'&) to see if there is any relevant information there. Another source
2439 of information is running Exim with debugging turned on, by specifying the
2440 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2441 with debugging turned on by a command of the form
2443 &`exim -d -M`& <&'exim-message-id'&>
2445 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2446 produces rather a lot of output, but you can cut this down to specific areas.
2447 For example, if you use &%-d-all+route%& only the debugging information
2448 relevant to routing is included. (See the &%-d%& option in chapter
2449 &<<CHAPcommandline>>& for more details.)
2451 .cindex '&"sticky"& bit'
2452 .cindex "lock files"
2453 One specific problem that has shown up on some sites is the inability to do
2454 local deliveries into a shared mailbox directory, because it does not have the
2455 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2456 writing to a mailbox file, and if it cannot create the lock file, the delivery
2457 is deferred. You can get round this either by setting the &"sticky bit"& on the
2458 directory, or by setting a specific group for local deliveries and allowing
2459 that group to create files in the directory (see the comments above the
2460 &(local_delivery)& transport in the default configuration file). Another
2461 approach is to configure Exim not to use lock files, but just to rely on
2462 &[fcntl()]& locking instead. However, you should do this only if all user
2463 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2464 see chapter &<<CHAPappendfile>>&.
2466 One thing that cannot be tested on a system that is already running an MTA is
2467 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2468 &%-oX%& option can be used to run an Exim daemon that listens on some other
2469 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2470 &'exim_checkaccess'& utility can be used to check out policy controls on
2473 Testing a new version on a system that is already running Exim can most easily
2474 be done by building a binary with a different CONFIGURE_FILE setting. From
2475 within the run time configuration, all other file and directory names
2476 that Exim uses can be altered, in order to keep it entirely clear of the
2480 .section "Replacing another MTA with Exim" "SECID35"
2481 .cindex "replacing another MTA"
2482 Building and installing Exim for the first time does not of itself put it in
2483 general use. The name by which the system's MTA is called by mail user agents
2484 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2485 operating system), and it is necessary to make this name point to the &'exim'&
2486 binary in order to get the user agents to pass messages to Exim. This is
2487 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2488 or &_/usr/lib/sendmail_&
2489 .cindex "symbolic link" "to &'exim'& binary"
2490 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2491 privilege and executable status from the old MTA. It is then necessary to stop
2492 and restart the mailer daemon, if one is running.
2494 .cindex "FreeBSD, MTA indirection"
2495 .cindex "&_/etc/mail/mailer.conf_&"
2496 Some operating systems have introduced alternative ways of switching MTAs. For
2497 example, if you are running FreeBSD, you need to edit the file
2498 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2499 described. A typical example of the contents of this file for running Exim is
2502 sendmail /usr/exim/bin/exim
2503 send-mail /usr/exim/bin/exim
2504 mailq /usr/exim/bin/exim -bp
2505 newaliases /usr/bin/true
2507 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2508 your Exim installation is &"live"&. Check it by sending a message from your
2509 favourite user agent.
2511 You should consider what to tell your users about the change of MTA. Exim may
2512 have different capabilities to what was previously running, and there are
2513 various operational differences such as the text of messages produced by
2514 command line options and in bounce messages. If you allow your users to make
2515 use of Exim's filtering capabilities, you should make the document entitled
2516 &'Exim's interface to mail filtering'& available to them.
2520 .section "Upgrading Exim" "SECID36"
2521 .cindex "upgrading Exim"
2522 If you are already running Exim on your host, building and installing a new
2523 version automatically makes it available to MUAs, or any other programs that
2524 call the MTA directly. However, if you are running an Exim daemon, you do need
2525 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2526 new binary. You do not need to stop processing mail in order to install a new
2527 version of Exim. The install script does not modify an existing runtime
2533 .section "Stopping the Exim daemon on Solaris" "SECID37"
2534 .cindex "Solaris" "stopping Exim on"
2535 The standard command for stopping the mailer daemon on Solaris is
2537 /etc/init.d/sendmail stop
2539 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2540 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2541 for the text &"sendmail"&; this is not present because the actual program name
2542 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2543 solution is to replace the line that finds the process id with something like
2545 pid=`cat /var/spool/exim/exim-daemon.pid`
2547 to obtain the daemon's pid directly from the file that Exim saves it in.
2549 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2550 still be received from local processes, and if automatic delivery is configured
2551 (the normal case), deliveries will still occur.
2556 . ////////////////////////////////////////////////////////////////////////////
2557 . ////////////////////////////////////////////////////////////////////////////
2559 .chapter "The Exim command line" "CHAPcommandline"
2560 .scindex IIDclo1 "command line" "options"
2561 .scindex IIDclo2 "options" "command line"
2562 Exim's command line takes the standard Unix form of a sequence of options,
2563 each starting with a hyphen character, followed by a number of arguments. The
2564 options are compatible with the main options of Sendmail, and there are also
2565 some additional options, some of which are compatible with Smail 3. Certain
2566 combinations of options do not make sense, and provoke an error if used.
2567 The form of the arguments depends on which options are set.
2570 .section "Setting options by program name" "SECID38"
2572 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2573 were present before any other options.
2574 The &%-bp%& option requests a listing of the contents of the mail queue on the
2576 This feature is for compatibility with some systems that contain a command of
2577 that name in one of the standard libraries, symbolically linked to
2578 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2581 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2582 were present before any other options, for compatibility with Smail. The
2583 &%-bS%& option is used for reading in a number of messages in batched SMTP
2587 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2588 &%-oee%& options were present before any other options, for compatibility with
2589 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2592 .cindex "queue runner"
2593 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2594 were present before any other options, for compatibility with Smail. The &%-q%&
2595 option causes a single queue runner process to be started.
2597 .cindex "&'newaliases'&"
2598 .cindex "alias file" "building"
2599 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2600 If Exim is called under the name &'newaliases'& it behaves as if the option
2601 &%-bi%& were present before any other options, for compatibility with Sendmail.
2602 This option is used for rebuilding Sendmail's alias file. Exim does not have
2603 the concept of a single alias file, but can be configured to run a given
2604 command if called with the &%-bi%& option.
2607 .section "Trusted and admin users" "SECTtrustedadmin"
2608 Some Exim options are available only to &'trusted users'& and others are
2609 available only to &'admin users'&. In the description below, the phrases &"Exim
2610 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2611 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2612 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2615 .cindex "trusted users" "definition of"
2616 .cindex "user" "trusted definition of"
2617 The trusted users are root, the Exim user, any user listed in the
2618 &%trusted_users%& configuration option, and any user whose current group or any
2619 supplementary group is one of those listed in the &%trusted_groups%&
2620 configuration option. Note that the Exim group is not automatically trusted.
2622 .cindex '&"From"& line'
2623 .cindex "envelope sender"
2624 Trusted users are always permitted to use the &%-f%& option or a leading
2625 &"From&~"& line to specify the envelope sender of a message that is passed to
2626 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2627 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2628 users to set envelope senders.
2630 .cindex "&'From:'& header line"
2631 .cindex "&'Sender:'& header line"
2632 For a trusted user, there is never any check on the contents of the &'From:'&
2633 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2634 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2636 Trusted users may also specify a host name, host address, interface address,
2637 protocol name, ident value, and authentication data when submitting a message
2638 locally. Thus, they are able to insert messages into Exim's queue locally that
2639 have the characteristics of messages received from a remote host. Untrusted
2640 users may in some circumstances use &%-f%&, but can never set the other values
2641 that are available to trusted users.
2643 .cindex "user" "admin definition of"
2644 .cindex "admin user" "definition of"
2645 The admin users are root, the Exim user, and any user that is a member of the
2646 Exim group or of any group listed in the &%admin_groups%& configuration option.
2647 The current group does not have to be one of these groups.
2649 Admin users are permitted to list the queue, and to carry out certain
2650 operations on messages, for example, to force delivery failures. It is also
2651 necessary to be an admin user in order to see the full information provided by
2652 the Exim monitor, and full debugging output.
2654 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2655 Exim to attempt delivery of messages on its queue is restricted to admin users.
2656 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2657 option false (that is, specifying &%no_prod_requires_admin%&).
2659 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2660 is restricted to admin users unless &%queue_list_requires_admin%& is set
2665 &*Warning*&: If you configure your system so that admin users are able to
2666 edit Exim's configuration file, you are giving those users an easy way of
2667 getting root. There is further discussion of this issue at the start of chapter
2673 .section "Command line options" "SECID39"
2674 Exim's command line options are described in alphabetical order below. If none
2675 of the options that specifies a specific action (such as starting the daemon or
2676 a queue runner, or testing an address, or receiving a message in a specific
2677 format, or listing the queue) are present, and there is at least one argument
2678 on the command line, &%-bm%& (accept a local message on the standard input,
2679 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2680 outputs a brief message about itself and exits.
2682 . ////////////////////////////////////////////////////////////////////////////
2683 . Insert a stylized XML comment here, to identify the start of the command line
2684 . options. This is for the benefit of the Perl script that automatically
2685 . creates a man page for the options.
2686 . ////////////////////////////////////////////////////////////////////////////
2689 <!-- === Start of command line options === -->
2696 .cindex "options" "command line; terminating"
2697 This is a pseudo-option whose only purpose is to terminate the options and
2698 therefore to cause subsequent command line items to be treated as arguments
2699 rather than options, even if they begin with hyphens.
2702 .oindex "&%--help%&"
2703 This option causes Exim to output a few sentences stating what it is.
2704 The same output is generated if the Exim binary is called with no options and
2707 .vitem &%--version%&
2708 .oindex "&%--version%&"
2709 This option is an alias for &%-bV%& and causes version information to be
2716 These options are used by Sendmail for selecting configuration files and are
2719 .vitem &%-B%&<&'type'&>
2721 .cindex "8-bit characters"
2722 .cindex "Sendmail compatibility" "8-bit characters"
2723 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2724 clean; it ignores this option.
2729 .cindex "SMTP" "listener"
2730 .cindex "queue runner"
2731 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2732 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2733 that the daemon should also initiate periodic queue runs.
2735 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2736 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2737 disconnect from the controlling terminal. When running this way, it can be
2738 stopped by pressing ctrl-C.
2740 By default, Exim listens for incoming connections to the standard SMTP port on
2741 all the host's running interfaces. However, it is possible to listen on other
2742 ports, on multiple ports, and only on specific interfaces. Chapter
2743 &<<CHAPinterfaces>>& contains a description of the options that control this.
2745 When a listening daemon
2746 .cindex "daemon" "process id (pid)"
2747 .cindex "pid (process id)" "of daemon"
2748 is started without the use of &%-oX%& (that is, without overriding the normal
2749 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2750 in Exim's spool directory. This location can be overridden by setting
2751 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2754 When &%-oX%& is used on the command line to start a listening daemon, the
2755 process id is not written to the normal pid file path. However, &%-oP%& can be
2756 used to specify a path on the command line if a pid file is required.
2760 .cindex "daemon" "restarting"
2761 can be used to cause the daemon to re-execute itself. This should be done
2762 whenever Exim's configuration file, or any file that is incorporated into it by
2763 means of the &%.include%& facility, is changed, and also whenever a new version
2764 of Exim is installed. It is not necessary to do this when other files that are
2765 referenced from the configuration (for example, alias files) are changed,
2766 because these are reread each time they are used.
2770 This option has the same effect as &%-bd%& except that it never disconnects
2771 from the controlling terminal, even when no debugging is specified.
2775 .cindex "testing" "string expansion"
2776 .cindex "expansion" "testing"
2777 Run Exim in expansion testing mode. Exim discards its root privilege, to
2778 prevent ordinary users from using this mode to read otherwise inaccessible
2779 files. If no arguments are given, Exim runs interactively, prompting for lines
2780 of data. Otherwise, it processes each argument in turn.
2782 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2783 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2784 used without command line arguments. If successful, it uses the &[readline()]&
2785 function, which provides extensive line-editing facilities, for reading the
2786 test data. A line history is supported.
2788 Long expansion expressions can be split over several lines by using backslash
2789 continuations. As in Exim's run time configuration, white space at the start of
2790 continuation lines is ignored. Each argument or data line is passed through the
2791 string expansion mechanism, and the result is output. Variable values from the
2792 configuration file (for example, &$qualify_domain$&) are available, but no
2793 message-specific values (such as &$sender_domain$&) are set, because no message
2794 is being processed (but see &%-bem%& and &%-Mset%&).
2796 &*Note*&: If you use this mechanism to test lookups, and you change the data
2797 files or databases you are using, you must exit and restart Exim before trying
2798 the same lookup again. Otherwise, because each Exim process caches the results
2799 of lookups, you will just get the same result as before.
2801 .vitem &%-bem%&&~<&'filename'&>
2803 .cindex "testing" "string expansion"
2804 .cindex "expansion" "testing"
2805 This option operates like &%-be%& except that it must be followed by the name
2806 of a file. For example:
2808 exim -bem /tmp/testmessage
2810 The file is read as a message (as if receiving a locally-submitted non-SMTP
2811 message) before any of the test expansions are done. Thus, message-specific
2812 variables such as &$message_size$& and &$header_from:$& are available. However,
2813 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2814 recipients are read from the headers in the normal way, and are shown in the
2815 &$recipients$& variable. Note that recipients cannot be given on the command
2816 line, because further arguments are taken as strings to expand (just like
2819 .vitem &%-bF%&&~<&'filename'&>
2821 .cindex "system filter" "testing"
2822 .cindex "testing" "system filter"
2823 This option is the same as &%-bf%& except that it assumes that the filter being
2824 tested is a system filter. The additional commands that are available only in
2825 system filters are recognized.
2827 .vitem &%-bf%&&~<&'filename'&>
2829 .cindex "filter" "testing"
2830 .cindex "testing" "filter file"
2831 .cindex "forward file" "testing"
2832 .cindex "testing" "forward file"
2833 .cindex "Sieve filter" "testing"
2834 This option runs Exim in user filter testing mode; the file is the filter file
2835 to be tested, and a test message must be supplied on the standard input. If
2836 there are no message-dependent tests in the filter, an empty file can be
2839 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2840 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2841 filter and a user filter in the same run. For example:
2843 exim -bF /system/filter -bf /user/filter </test/message
2845 This is helpful when the system filter adds header lines or sets filter
2846 variables that are used by the user filter.
2848 If the test filter file does not begin with one of the special lines
2853 it is taken to be a normal &_.forward_& file, and is tested for validity under
2854 that interpretation. See sections &<<SECTitenonfilred>>& to
2855 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2858 The result of an Exim command that uses &%-bf%&, provided no errors are
2859 detected, is a list of the actions that Exim would try to take if presented
2860 with the message for real. More details of filter testing are given in the
2861 separate document entitled &'Exim's interfaces to mail filtering'&.
2863 When testing a filter file,
2864 .cindex "&""From""& line"
2865 .cindex "envelope sender"
2866 .oindex "&%-f%&" "for filter testing"
2867 the envelope sender can be set by the &%-f%& option,
2868 or by a &"From&~"& line at the start of the test message. Various parameters
2869 that would normally be taken from the envelope recipient address of the message
2870 can be set by means of additional command line options (see the next four
2873 .vitem &%-bfd%&&~<&'domain'&>
2875 .vindex "&$qualify_domain$&"
2876 This sets the domain of the recipient address when a filter file is being
2877 tested by means of the &%-bf%& option. The default is the value of
2880 .vitem &%-bfl%&&~<&'local&~part'&>
2882 This sets the local part of the recipient address when a filter file is being
2883 tested by means of the &%-bf%& option. The default is the username of the
2884 process that calls Exim. A local part should be specified with any prefix or
2885 suffix stripped, because that is how it appears to the filter when a message is
2886 actually being delivered.
2888 .vitem &%-bfp%&&~<&'prefix'&>
2890 This sets the prefix of the local part of the recipient address when a filter
2891 file is being tested by means of the &%-bf%& option. The default is an empty
2894 .vitem &%-bfs%&&~<&'suffix'&>
2896 This sets the suffix of the local part of the recipient address when a filter
2897 file is being tested by means of the &%-bf%& option. The default is an empty
2900 .vitem &%-bh%&&~<&'IP&~address'&>
2902 .cindex "testing" "incoming SMTP"
2903 .cindex "SMTP" "testing incoming"
2904 .cindex "testing" "relay control"
2905 .cindex "relaying" "testing configuration"
2906 .cindex "policy control" "testing"
2907 .cindex "debugging" "&%-bh%& option"
2908 This option runs a fake SMTP session as if from the given IP address, using the
2909 standard input and output. The IP address may include a port number at the end,
2910 after a full stop. For example:
2912 exim -bh 10.9.8.7.1234
2913 exim -bh fe80::a00:20ff:fe86:a061.5678
2915 When an IPv6 address is given, it is converted into canonical form. In the case
2916 of the second example above, the value of &$sender_host_address$& after
2917 conversion to the canonical form is
2918 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2920 Comments as to what is going on are written to the standard error file. These
2921 include lines beginning with &"LOG"& for anything that would have been logged.
2922 This facility is provided for testing configuration options for incoming
2923 messages, to make sure they implement the required policy. For example, you can
2924 test your relay controls using &%-bh%&.
2928 You can test features of the configuration that rely on ident (RFC 1413)
2929 information by using the &%-oMt%& option. However, Exim cannot actually perform
2930 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2933 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2934 are also skipped when testing using &%-bh%&. If you want these callouts to
2935 occur, use &%-bhc%& instead.
2937 Messages supplied during the testing session are discarded, and nothing is
2938 written to any of the real log files. There may be pauses when DNS (and other)
2939 lookups are taking place, and of course these may time out. The &%-oMi%& option
2940 can be used to specify a specific IP interface and port if this is important,
2941 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2942 session were authenticated.
2944 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2945 output just states whether a given recipient address from a given host is
2946 acceptable or not. See section &<<SECTcheckaccess>>&.
2948 Features such as authentication and encryption, where the client input is not
2949 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2950 specialized SMTP test program such as
2951 &url(http://jetmore.org/john/code/#swaks,swaks).
2953 .vitem &%-bhc%&&~<&'IP&~address'&>
2955 This option operates in the same way as &%-bh%&, except that address
2956 verification callouts are performed if required. This includes consulting and
2957 updating the callout cache database.
2961 .cindex "alias file" "building"
2962 .cindex "building alias file"
2963 .cindex "Sendmail compatibility" "&%-bi%& option"
2964 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2965 Exim does not have the concept of a single alias file, and so it cannot mimic
2966 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2967 tend to appear in various scripts such as NIS make files, so the option must be
2970 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2971 configuration option is run, under the uid and gid of the caller of Exim. If
2972 the &%-oA%& option is used, its value is passed to the command as an argument.
2973 The command set by &%bi_command%& may not contain arguments. The command can
2974 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2975 if this is required. If the &%bi_command%& option is not set, calling Exim with
2978 . // Keep :help first, then the rest in alphabetical order
2980 .oindex "&%-bI:help%&"
2981 .cindex "querying exim information"
2982 We shall provide various options starting &`-bI:`& for querying Exim for
2983 information. The output of many of these will be intended for machine
2984 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2985 synopsis of supported options beginning &`-bI:`&. Use of any of these
2986 options shall cause Exim to exit after producing the requested output.
2989 .oindex "&%-bI:dscp%&"
2990 .cindex "DSCP" "values"
2991 This option causes Exim to emit an alphabetically sorted list of all
2992 recognised DSCP names.
2994 .vitem &%-bI:sieve%&
2995 .oindex "&%-bI:sieve%&"
2996 .cindex "Sieve filter" "capabilities"
2997 This option causes Exim to emit an alphabetically sorted list of all supported
2998 Sieve protocol extensions on stdout, one per line. This is anticipated to be
2999 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3000 &`SIEVE`& capability response line. As the precise list may depend upon
3001 compile-time build options, which this option will adapt to, this is the only
3002 way to guarantee a correct response.
3006 .cindex "local message reception"
3007 This option runs an Exim receiving process that accepts an incoming,
3008 locally-generated message on the standard input. The recipients are given as the
3009 command arguments (except when &%-t%& is also present &-- see below). Each
3010 argument can be a comma-separated list of RFC 2822 addresses. This is the
3011 default option for selecting the overall action of an Exim call; it is assumed
3012 if no other conflicting option is present.
3014 If any addresses in the message are unqualified (have no domain), they are
3015 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3016 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3017 suppressing this for special cases.
3019 Policy checks on the contents of local messages can be enforced by means of
3020 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3022 .cindex "return code" "for &%-bm%&"
3023 The return code is zero if the message is successfully accepted. Otherwise, the
3024 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3027 .cindex "message" "format"
3028 .cindex "format" "message"
3029 .cindex "&""From""& line"
3030 .cindex "UUCP" "&""From""& line"
3031 .cindex "Sendmail compatibility" "&""From""& line"
3032 of the message must be as defined in RFC 2822, except that, for
3033 compatibility with Sendmail and Smail, a line in one of the forms
3035 From sender Fri Jan 5 12:55 GMT 1997
3036 From sender Fri, 5 Jan 97 12:55:01
3038 (with the weekday optional, and possibly with additional text after the date)
3039 is permitted to appear at the start of the message. There appears to be no
3040 authoritative specification of the format of this line. Exim recognizes it by
3041 matching against the regular expression defined by the &%uucp_from_pattern%&
3042 option, which can be changed if necessary.
3044 .oindex "&%-f%&" "overriding &""From""& line"
3045 The specified sender is treated as if it were given as the argument to the
3046 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3047 preference to the address taken from the message. The caller of Exim must be a
3048 trusted user for the sender of a message to be set in this way.
3050 .vitem &%-bmalware%&&~<&'filename'&>
3051 .oindex "&%-bmalware%&"
3052 .cindex "testing", "malware"
3053 .cindex "malware scan test"
3054 This debugging option causes Exim to scan the given file,
3055 using the malware scanning framework. The option of &%av_scanner%& influences
3056 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3057 the expansion should have defaults which apply to this invocation. ACLs are
3058 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3059 will never be populated and &%-bmalware%& will fail.
3061 Exim will have changed working directory before resolving the filename, so
3062 using fully qualified pathnames is advisable. Exim will be running as the Exim
3063 user when it tries to open the file, rather than as the invoking user.
3064 This option requires admin privileges.
3066 The &%-bmalware%& option will not be extended to be more generally useful,
3067 there are better tools for file-scanning. This option exists to help
3068 administrators verify their Exim and AV scanner configuration.
3072 .cindex "address qualification, suppressing"
3073 By default, Exim automatically qualifies unqualified addresses (those
3074 without domains) that appear in messages that are submitted locally (that
3075 is, not over TCP/IP). This qualification applies both to addresses in
3076 envelopes, and addresses in header lines. Sender addresses are qualified using
3077 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3078 defaults to the value of &%qualify_domain%&).
3080 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3081 being used to re-submit messages that originally came from remote hosts after
3082 content scanning, you probably do not want to qualify unqualified addresses in
3083 header lines. (Such lines will be present only if you have not enabled a header
3084 syntax check in the appropriate ACL.)
3086 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3087 messages that originate on the local host. When this is used, unqualified
3088 addresses in the envelope provoke errors (causing message rejection) and
3089 unqualified addresses in header lines are left alone.
3094 .cindex "configuration options" "extracting"
3095 .cindex "options" "configuration &-- extracting"
3096 If this option is given with no arguments, it causes the values of all Exim's
3097 main configuration options to be written to the standard output. The values
3098 of one or more specific options can be requested by giving their names as
3099 arguments, for example:
3101 exim -bP qualify_domain hold_domains
3103 .cindex "hiding configuration option values"
3104 .cindex "configuration options" "hiding value of"
3105 .cindex "options" "hiding value of"
3106 However, any option setting that is preceded by the word &"hide"& in the
3107 configuration file is not shown in full, except to an admin user. For other
3108 users, the output is as in this example:
3110 mysql_servers = <value not displayable>
3112 If &%configure_file%& is given as an argument, the name of the run time
3113 configuration file is output.
3114 If a list of configuration files was supplied, the value that is output here
3115 is the name of the file that was actually used.
3117 .cindex "options" "hiding name of"
3118 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3119 name will not be output.
3121 .cindex "daemon" "process id (pid)"
3122 .cindex "pid (process id)" "of daemon"
3123 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3124 directories where log files and daemon pid files are written are output,
3125 respectively. If these values are unset, log files are written in a
3126 sub-directory of the spool directory called &%log%&, and the pid file is
3127 written directly into the spool directory.
3129 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3131 exim -bP +local_domains
3133 it searches for a matching named list of any type (domain, host, address, or
3134 local part) and outputs what it finds.
3136 .cindex "options" "router &-- extracting"
3137 .cindex "options" "transport &-- extracting"
3138 .cindex "options" "authenticator &-- extracting"
3139 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3140 followed by the name of an appropriate driver instance, the option settings for
3141 that driver are output. For example:
3143 exim -bP transport local_delivery
3145 The generic driver options are output first, followed by the driver's private
3146 options. A list of the names of drivers of a particular type can be obtained by
3147 using one of the words &%router_list%&, &%transport_list%&, or
3148 &%authenticator_list%&, and a complete list of all drivers with their option
3149 settings can be obtained by using &%routers%&, &%transports%&, or
3152 .cindex "environment"
3153 If &%environment%& is given as an argument, the set of environment
3154 variables is output, line by line. Using the &%-n%& flag supresses the value of the
3157 .cindex "options" "macro &-- extracting"
3158 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3159 are available, similarly to the drivers. Because macros are sometimes used
3160 for storing passwords, this option is restricted.
3161 The output format is one item per line.
3165 .cindex "queue" "listing messages on"
3166 .cindex "listing" "messages on the queue"
3167 This option requests a listing of the contents of the mail queue on the
3168 standard output. If the &%-bp%& option is followed by a list of message ids,
3169 just those messages are listed. By default, this option can be used only by an
3170 admin user. However, the &%queue_list_requires_admin%& option can be set false
3171 to allow any user to see the queue.
3173 Each message on the queue is displayed as in the following example:
3175 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3176 red.king@looking-glass.fict.example
3179 .cindex "message" "size in queue listing"
3180 .cindex "size" "of message"
3181 The first line contains the length of time the message has been on the queue
3182 (in this case 25 minutes), the size of the message (2.9K), the unique local
3183 identifier for the message, and the message sender, as contained in the
3184 envelope. For bounce messages, the sender address is empty, and appears as
3185 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3186 the default sender address, the user's login name is shown in parentheses
3187 before the sender address.
3189 .cindex "frozen messages" "in queue listing"
3190 If the message is frozen (attempts to deliver it are suspended) then the text
3191 &"*** frozen ***"& is displayed at the end of this line.
3193 The recipients of the message (taken from the envelope, not the headers) are
3194 displayed on subsequent lines. Those addresses to which the message has already
3195 been delivered are marked with the letter D. If an original address gets
3196 expanded into several addresses via an alias or forward file, the original is
3197 displayed with a D only when deliveries for all of its child addresses are
3203 This option operates like &%-bp%&, but in addition it shows delivered addresses
3204 that were generated from the original top level address(es) in each message by
3205 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3211 .cindex "queue" "count of messages on"
3212 This option counts the number of messages on the queue, and writes the total
3213 to the standard output. It is restricted to admin users, unless
3214 &%queue_list_requires_admin%& is set false.
3219 This option operates like &%-bp%&, but the output is not sorted into
3220 chronological order of message arrival. This can speed it up when there are
3221 lots of messages on the queue, and is particularly useful if the output is
3222 going to be post-processed in a way that doesn't need the sorting.
3226 This option is a combination of &%-bpr%& and &%-bpa%&.
3230 This option is a combination of &%-bpr%& and &%-bpu%&.
3235 This option operates like &%-bp%& but shows only undelivered top-level
3236 addresses for each message displayed. Addresses generated by aliasing or
3237 forwarding are not shown, unless the message was deferred after processing by a
3238 router with the &%one_time%& option set.
3243 .cindex "testing" "retry configuration"
3244 .cindex "retry" "configuration testing"
3245 This option is for testing retry rules, and it must be followed by up to three
3246 arguments. It causes Exim to look for a retry rule that matches the values
3247 and to write it to the standard output. For example:
3249 exim -brt bach.comp.mus.example
3250 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3252 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3253 argument, which is required, can be a complete address in the form
3254 &'local_part@domain'&, or it can be just a domain name. If the second argument
3255 contains a dot, it is interpreted as an optional second domain name; if no
3256 retry rule is found for the first argument, the second is tried. This ties in
3257 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3258 rule is found that matches the host, one that matches the mail domain is
3259 sought. Finally, an argument that is the name of a specific delivery error, as
3260 used in setting up retry rules, can be given. For example:
3262 exim -brt haydn.comp.mus.example quota_3d
3263 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3268 .cindex "testing" "rewriting"
3269 .cindex "rewriting" "testing"
3270 This option is for testing address rewriting rules, and it must be followed by
3271 a single argument, consisting of either a local part without a domain, or a
3272 complete address with a fully qualified domain. Exim outputs how this address
3273 would be rewritten for each possible place it might appear. See chapter
3274 &<<CHAPrewrite>>& for further details.
3278 .cindex "SMTP" "batched incoming"
3279 .cindex "batched SMTP input"
3280 This option is used for batched SMTP input, which is an alternative interface
3281 for non-interactive local message submission. A number of messages can be
3282 submitted in a single run. However, despite its name, this is not really SMTP
3283 input. Exim reads each message's envelope from SMTP commands on the standard
3284 input, but generates no responses. If the caller is trusted, or
3285 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3286 believed; otherwise the sender is always the caller of Exim.
3288 The message itself is read from the standard input, in SMTP format (leading
3289 dots doubled), terminated by a line containing just a single dot. An error is
3290 provoked if the terminating dot is missing. A further message may then follow.
3292 As for other local message submissions, the contents of incoming batch SMTP
3293 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3294 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3295 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3297 Some other SMTP commands are recognized in the input. HELO and EHLO act
3298 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3299 QUIT quits, ignoring the rest of the standard input.
3301 .cindex "return code" "for &%-bS%&"
3302 If any error is encountered, reports are written to the standard output and
3303 error streams, and Exim gives up immediately. The return code is 0 if no error
3304 was detected; it is 1 if one or more messages were accepted before the error
3305 was detected; otherwise it is 2.
3307 More details of input using batched SMTP are given in section
3308 &<<SECTincomingbatchedSMTP>>&.
3312 .cindex "SMTP" "local input"
3313 .cindex "local SMTP input"
3314 This option causes Exim to accept one or more messages by reading SMTP commands
3315 on the standard input, and producing SMTP replies on the standard output. SMTP
3316 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3317 Some user agents use this interface as a way of passing locally-generated
3318 messages to the MTA.
3321 .cindex "sender" "source of"
3322 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3323 set, the senders of messages are taken from the SMTP MAIL commands.
3324 Otherwise the content of these commands is ignored and the sender is set up as
3325 the calling user. Unqualified addresses are automatically qualified using
3326 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3327 &%-bnq%& option is used.
3331 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3332 using a listening daemon. Exim can distinguish the two cases by checking
3333 whether the standard input is a TCP/IP socket. When Exim is called from
3334 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3335 above concerning senders and qualification do not apply. In this situation,
3336 Exim behaves in exactly the same way as it does when receiving a message via
3337 the listening daemon.
3341 .cindex "testing" "addresses"
3342 .cindex "address" "testing"
3343 This option runs Exim in address testing mode, in which each argument is taken
3344 as a recipient address to be tested for deliverability. The results are
3345 written to the standard output. If a test fails, and the caller is not an admin
3346 user, no details of the failure are output, because these might contain
3347 sensitive information such as usernames and passwords for database lookups.
3349 If no arguments are given, Exim runs in an interactive manner, prompting with a
3350 right angle bracket for addresses to be tested.
3352 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3353 &[readline()]& function, because it is running as &'root'& and there are
3356 Each address is handled as if it were the recipient address of a message
3357 (compare the &%-bv%& option). It is passed to the routers and the result is
3358 written to the standard output. However, any router that has
3359 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3360 genuine routing tests if your first router passes everything to a scanner
3363 .cindex "return code" "for &%-bt%&"
3364 The return code is 2 if any address failed outright; it is 1 if no address
3365 failed outright but at least one could not be resolved for some reason. Return
3366 code 0 is given only when all addresses succeed.
3368 .cindex "duplicate addresses"
3369 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3370 addresses after routing is complete, so that only one delivery takes place.
3371 This does not happen when testing with &%-bt%&; the full results of routing are
3374 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3375 routers in the configuration makes any tests on the sender address of a
3377 .oindex "&%-f%&" "for address testing"
3378 you can use the &%-f%& option to set an appropriate sender when running
3379 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3380 default qualifying domain. However, if you have set up (for example) routers
3381 whose behaviour depends on the contents of an incoming message, you cannot test
3382 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3387 .cindex "version number of Exim"
3388 This option causes Exim to write the current version number, compilation
3389 number, and compilation date of the &'exim'& binary to the standard output.
3390 It also lists the DBM library that is being used, the optional modules (such as
3391 specific lookup types), the drivers that are included in the binary, and the
3392 name of the run time configuration file that is in use.
3394 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3395 configuration file. However, this is a static check only. It cannot check
3396 values that are to be expanded. For example, although a misspelt ACL verb is
3397 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3398 alone to discover (for example) all the typos in the configuration; some
3399 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3400 dynamic testing facilities.
3404 .cindex "verifying address" "using &%-bv%&"
3405 .cindex "address" "verification"
3406 This option runs Exim in address verification mode, in which each argument is
3407 taken as a recipient address to be verified by the routers. (This does
3408 not involve any verification callouts). During normal operation, verification
3409 happens mostly as a consequence processing a &%verify%& condition in an ACL
3410 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3411 including callouts, see the &%-bh%& and &%-bhc%& options.
3413 If verification fails, and the caller is not an admin user, no details of the
3414 failure are output, because these might contain sensitive information such as
3415 usernames and passwords for database lookups.
3417 If no arguments are given, Exim runs in an interactive manner, prompting with a
3418 right angle bracket for addresses to be verified.
3420 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3421 &[readline()]& function, because it is running as &'exim'& and there are
3424 Verification differs from address testing (the &%-bt%& option) in that routers
3425 that have &%no_verify%& set are skipped, and if the address is accepted by a
3426 router that has &%fail_verify%& set, verification fails. The address is
3427 verified as a recipient if &%-bv%& is used; to test verification for a sender
3428 address, &%-bvs%& should be used.
3430 If the &%-v%& option is not set, the output consists of a single line for each
3431 address, stating whether it was verified or not, and giving a reason in the
3432 latter case. Without &%-v%&, generating more than one address by redirection
3433 causes verification to end successfully, without considering the generated
3434 addresses. However, if just one address is generated, processing continues,
3435 and the generated address must verify successfully for the overall verification
3438 When &%-v%& is set, more details are given of how the address has been handled,
3439 and in the case of address redirection, all the generated addresses are also
3440 considered. Verification may succeed for some and fail for others.
3443 .cindex "return code" "for &%-bv%&"
3444 return code is 2 if any address failed outright; it is 1 if no address
3445 failed outright but at least one could not be resolved for some reason. Return
3446 code 0 is given only when all addresses succeed.
3448 If any of the routers in the configuration makes any tests on the sender
3449 address of a message, you should use the &%-f%& option to set an appropriate
3450 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3451 calling user at the default qualifying domain.
3455 This option acts like &%-bv%&, but verifies the address as a sender rather
3456 than a recipient address. This affects any rewriting and qualification that
3463 .cindex "inetd" "wait mode"
3464 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3465 similarly to the &%-bd%& option. All port specifications on the command-line
3466 and in the configuration file are ignored. Queue-running may not be specified.
3468 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3469 listening for connections. This permits the system to start up and have
3470 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3471 each port only when the first connection is received.
3473 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3474 which the daemon will exit, which should cause inetd to listen once more.
3476 .vitem &%-C%&&~<&'filelist'&>
3478 .cindex "configuration file" "alternate"
3479 .cindex "CONFIGURE_FILE"
3480 .cindex "alternate configuration file"
3481 This option causes Exim to find the run time configuration file from the given
3482 list instead of from the list specified by the CONFIGURE_FILE
3483 compile-time setting. Usually, the list will consist of just a single file
3484 name, but it can be a colon-separated list of names. In this case, the first
3485 file that exists is used. Failure to open an existing file stops Exim from
3486 proceeding any further along the list, and an error is generated.
3488 The file names need to be absolute names.
3490 When this option is used by a caller other than root, and the list is different
3491 from the compiled-in list, Exim gives up its root privilege immediately, and
3492 runs with the real and effective uid and gid set to those of the caller.
3493 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3494 file contains a list of full pathnames, one per line, for configuration files
3495 which are trusted. Root privilege is retained for any configuration file so
3496 listed, as long as the caller is the Exim user (or the user specified in the
3497 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3498 not writeable by inappropriate users or groups.
3500 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3501 configuration using &%-C%& right through message reception and delivery,
3502 even if the caller is root. The reception works, but by that time, Exim is
3503 running as the Exim user, so when it re-executes to regain privilege for the
3504 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3505 test reception and delivery using two separate commands (one to put a message
3506 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3508 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3509 prefix string with which any file named in a &%-C%& command line option
3510 must start. In addition, the file name must not contain the sequence &`/../`&.
3511 However, if the value of the &%-C%& option is identical to the value of
3512 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3513 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3514 unset, any file name can be used with &%-C%&.
3516 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3517 to a directory to which only root has access. This prevents someone who has
3518 broken into the Exim account from running a privileged Exim with an arbitrary
3521 The &%-C%& facility is useful for ensuring that configuration files are
3522 syntactically correct, but cannot be used for test deliveries, unless the
3523 caller is privileged, or unless it is an exotic configuration that does not
3524 require privilege. No check is made on the owner or group of the files
3525 specified by this option.
3528 .vitem &%-D%&<&'macro'&>=<&'value'&>
3530 .cindex "macro" "setting on command line"
3531 This option can be used to override macro definitions in the configuration file
3532 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3533 unprivileged caller, it causes Exim to give up its root privilege.
3534 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3535 completely disabled, and its use causes an immediate error exit.
3537 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3538 colon-separated list of macros which are considered safe and, if &%-D%& only
3539 supplies macros from this list, and the values are acceptable, then Exim will
3540 not give up root privilege if the caller is root, the Exim run-time user, or
3541 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3542 to be removed in the future. Acceptable values for the macros satisfy the
3543 regexp: &`^[A-Za-z0-9_/.-]*$`&
3545 The entire option (including equals sign if present) must all be within one
3546 command line item. &%-D%& can be used to set the value of a macro to the empty
3547 string, in which case the equals sign is optional. These two commands are
3553 To include spaces in a macro definition item, quotes must be used. If you use
3554 quotes, spaces are permitted around the macro name and the equals sign. For
3557 exim '-D ABC = something' ...
3559 &%-D%& may be repeated up to 10 times on a command line.
3562 .vitem &%-d%&<&'debug&~options'&>
3564 .cindex "debugging" "list of selectors"
3565 .cindex "debugging" "&%-d%& option"
3566 This option causes debugging information to be written to the standard
3567 error stream. It is restricted to admin users because debugging output may show
3568 database queries that contain password information. Also, the details of users'
3569 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3570 writes an error message to the standard error stream and exits with a non-zero
3573 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3574 standard debugging data is output. This can be reduced, or increased to include
3575 some more rarely needed information, by directly following &%-d%& with a string
3576 made up of names preceded by plus or minus characters. These add or remove sets
3577 of debugging data, respectively. For example, &%-d+filter%& adds filter
3578 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3579 no spaces are allowed in the debug setting. The available debugging categories
3582 &`acl `& ACL interpretation
3583 &`auth `& authenticators
3584 &`deliver `& general delivery logic
3585 &`dns `& DNS lookups (see also resolver)
3586 &`dnsbl `& DNS black list (aka RBL) code
3587 &`exec `& arguments for &[execv()]& calls
3588 &`expand `& detailed debugging for string expansions
3589 &`filter `& filter handling
3590 &`hints_lookup `& hints data lookups
3591 &`host_lookup `& all types of name-to-IP address handling
3592 &`ident `& ident lookup
3593 &`interface `& lists of local interfaces
3594 &`lists `& matching things in lists
3595 &`load `& system load checks
3596 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3597 &<<CHAPlocalscan>>&)
3598 &`lookup `& general lookup code and all lookups
3599 &`memory `& memory handling
3600 &`pid `& add pid to debug output lines
3601 &`process_info `& setting info for the process log
3602 &`queue_run `& queue runs
3603 &`receive `& general message reception logic
3604 &`resolver `& turn on the DNS resolver's debugging output
3605 &`retry `& retry handling
3606 &`rewrite `& address rewriting
3607 &`route `& address routing
3608 &`timestamp `& add timestamp to debug output lines
3610 &`transport `& transports
3611 &`uid `& changes of uid/gid and looking up uid/gid
3612 &`verify `& address verification logic
3613 &`all `& almost all of the above (see below), and also &%-v%&
3615 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3616 for &`-all`&. The reason for this is that &`+all`& is something that people
3617 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3618 is included, an awful lot of output that is very rarely of interest is
3619 generated, so it now has to be explicitly requested. However, &`-all`& does
3620 turn everything off.
3622 .cindex "resolver, debugging output"
3623 .cindex "DNS resolver, debugging output"
3624 The &`resolver`& option produces output only if the DNS resolver was compiled
3625 with DEBUG enabled. This is not the case in some operating systems. Also,
3626 unfortunately, debugging output from the DNS resolver is written to stdout
3629 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3630 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3631 However, the &`pid`& selector is forced when debugging is turned on for a
3632 daemon, which then passes it on to any re-executed Exims. Exim also
3633 automatically adds the pid to debug lines when several remote deliveries are
3636 The &`timestamp`& selector causes the current time to be inserted at the start
3637 of all debug output lines. This can be useful when trying to track down delays
3640 If the &%debug_print%& option is set in any driver, it produces output whenever
3641 any debugging is selected, or if &%-v%& is used.
3643 .vitem &%-dd%&<&'debug&~options'&>
3645 This option behaves exactly like &%-d%& except when used on a command that
3646 starts a daemon process. In that case, debugging is turned off for the
3647 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3648 behaviour of the daemon without creating as much output as full debugging does.
3651 .oindex "&%-dropcr%&"
3652 This is an obsolete option that is now a no-op. It used to affect the way Exim
3653 handled CR and LF characters in incoming messages. What happens now is
3654 described in section &<<SECTlineendings>>&.
3658 .cindex "bounce message" "generating"
3659 This option specifies that an incoming message is a locally-generated delivery
3660 failure report. It is used internally by Exim when handling delivery failures
3661 and is not intended for external use. Its only effect is to stop Exim
3662 generating certain messages to the postmaster, as otherwise message cascades
3663 could occur in some situations. As part of the same option, a message id may
3664 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3665 new message contains the id, following &"R="&, as a cross-reference.
3668 .oindex "&%-e%&&'x'&"
3669 There are a number of Sendmail options starting with &%-oe%& which seem to be
3670 called by various programs without the leading &%o%& in the option. For
3671 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3672 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3674 .vitem &%-F%&&~<&'string'&>
3676 .cindex "sender" "name"
3677 .cindex "name" "of sender"
3678 This option sets the sender's full name for use when a locally-generated
3679 message is being accepted. In the absence of this option, the user's &'gecos'&
3680 entry from the password data is used. As users are generally permitted to alter
3681 their &'gecos'& entries, no security considerations are involved. White space
3682 between &%-F%& and the <&'string'&> is optional.
3684 .vitem &%-f%&&~<&'address'&>
3686 .cindex "sender" "address"
3687 .cindex "address" "sender"
3688 .cindex "trusted users"
3689 .cindex "envelope sender"
3690 .cindex "user" "trusted"
3691 This option sets the address of the envelope sender of a locally-generated
3692 message (also known as the return path). The option can normally be used only
3693 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3696 Processes running as root or the Exim user are always trusted. Other
3697 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3698 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3699 of a local message is set to the caller's login name at the default qualify
3702 There is one exception to the restriction on the use of &%-f%&: an empty sender
3703 can be specified by any user, trusted or not, to create a message that can
3704 never provoke a bounce. An empty sender can be specified either as an empty
3705 string, or as a pair of angle brackets with nothing between them, as in these
3706 examples of shell commands:
3708 exim -f '<>' user@domain
3709 exim -f "" user@domain
3711 In addition, the use of &%-f%& is not restricted when testing a filter file
3712 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3715 Allowing untrusted users to change the sender address does not of itself make
3716 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3717 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3718 though this can be overridden by setting &%no_local_from_check%&.
3721 .cindex "&""From""& line"
3722 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3723 given as two arguments or one combined argument). The sender of a
3724 locally-generated message can also be set (when permitted) by an initial
3725 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3726 if &%-f%& is also present, it overrides &"From&~"&.
3730 .cindex "submission fixups, suppressing (command-line)"
3731 This option is equivalent to an ACL applying:
3733 control = suppress_local_fixups
3735 for every message received. Note that Sendmail will complain about such
3736 bad formatting, where Exim silently just does not fix it up. This may change
3739 As this affects audit information, the caller must be a trusted user to use
3742 .vitem &%-h%&&~<&'number'&>
3744 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3745 This option is accepted for compatibility with Sendmail, but has no effect. (In
3746 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3751 .cindex "Solaris" "&'mail'& command"
3752 .cindex "dot" "in incoming non-SMTP message"
3753 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3754 line by itself should not terminate an incoming, non-SMTP message. I can find
3755 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3756 command in Solaris 2.4 uses it. See also &%-ti%&.
3758 .vitem &%-L%&&~<&'tag'&>
3760 .cindex "syslog" "process name; set with flag"
3761 This option is equivalent to setting &%syslog_processname%& in the config
3762 file and setting &%log_file_path%& to &`syslog`&.
3763 Its use is restricted to administrators. The configuration file has to be
3764 read and parsed, to determine access rights, before this is set and takes
3765 effect, so early configuration file errors will not honour this flag.
3767 The tag should not be longer than 32 characters.
3769 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3771 .cindex "forcing delivery"
3772 .cindex "delivery" "forcing attempt"
3773 .cindex "frozen messages" "forcing delivery"
3774 This option requests Exim to run a delivery attempt on each message in turn. If
3775 any of the messages are frozen, they are automatically thawed before the
3776 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3777 and &%hold_domains%& are ignored.
3780 .cindex "hints database" "overriding retry hints"
3781 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3782 the normal retry time has not yet been reached. This option requires the caller
3783 to be an admin user. However, there is an option called &%prod_requires_admin%&
3784 which can be set false to relax this restriction (and also the same requirement
3785 for the &%-q%&, &%-R%&, and &%-S%& options).
3787 The deliveries happen synchronously, that is, the original Exim process does
3788 not terminate until all the delivery attempts have finished. No output is
3789 produced unless there is a serious error. If you want to see what is happening,
3790 use the &%-v%& option as well, or inspect Exim's main log.
3792 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3794 .cindex "message" "adding recipients"
3795 .cindex "recipient" "adding"
3796 This option requests Exim to add the addresses to the list of recipients of the
3797 message (&"ar"& for &"add recipients"&). The first argument must be a message
3798 id, and the remaining ones must be email addresses. However, if the message is
3799 active (in the middle of a delivery attempt), it is not altered. This option
3800 can be used only by an admin user.
3802 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3803 &~<&'message&~id'&>"
3805 .cindex "SMTP" "passed connection"
3806 .cindex "SMTP" "multiple deliveries"
3807 .cindex "multiple SMTP deliveries"
3808 This option is not intended for use by external callers. It is used internally
3809 by Exim to invoke another instance of itself to deliver a waiting message using
3810 an existing SMTP connection, which is passed as the standard input. Details are
3811 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3812 must be root or the Exim user in order to use it.
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
3818 connection to the remote host has been authenticated.
3823 This option is not intended for use by external callers. It is used internally
3824 by Exim in conjunction with the &%-MC%& option. It signifies that the
3825 remote host supports the ESMTP &_DSN_& extension.
3830 This option is not intended for use by external callers. It is used internally
3831 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3832 which Exim is connected supports pipelining.
3834 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3836 This option is not intended for use by external callers. It is used internally
3837 by Exim in conjunction with the &%-MC%& option when the original delivery was
3838 started by a queue runner. It passes on the process id of the queue runner,
3839 together with the file descriptor number of an open pipe. Closure of the pipe
3840 signals the final completion of the sequence of processes that are passing
3841 messages through the same SMTP connection.
3845 This option is not intended for use by external callers. It is used internally
3846 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3847 SMTP SIZE option should be used on messages delivered down the existing
3852 This option is not intended for use by external callers. It is used internally
3853 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3854 host to which Exim is connected supports TLS encryption.
3856 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3858 .cindex "hints database" "not overridden by &%-Mc%&"
3859 .cindex "delivery" "manually started &-- not forced"
3860 This option requests Exim to run a delivery attempt on each message in turn,
3861 but unlike the &%-M%& option, it does check for retry hints, and respects any
3862 that are found. This option is not very useful to external callers. It is
3863 provided mainly for internal use by Exim when it needs to re-invoke itself in
3864 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3865 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3866 respects retry times and other options such as &%hold_domains%& that are
3867 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3868 If you want to run a specific delivery as if in a queue run, you should use
3869 &%-q%& with a message id argument. A distinction between queue run deliveries
3870 and other deliveries is made in one or two places.
3872 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3874 .cindex "message" "changing sender"
3875 .cindex "sender" "changing"
3876 This option requests Exim to change the sender address in the message to the
3877 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3878 &"edit sender"&). There must be exactly two arguments. The first argument must
3879 be a message id, and the second one an email address. However, if the message
3880 is active (in the middle of a delivery attempt), its status is not altered.
3881 This option can be used only by an admin user.
3883 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3885 .cindex "freezing messages"
3886 .cindex "message" "manually freezing"
3887 This option requests Exim to mark each listed message as &"frozen"&. This
3888 prevents any delivery attempts taking place until the message is &"thawed"&,
3889 either manually or as a result of the &%auto_thaw%& configuration option.
3890 However, if any of the messages are active (in the middle of a delivery
3891 attempt), their status is not altered. This option can be used only by an admin
3894 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3896 .cindex "giving up on messages"
3897 .cindex "message" "abandoning delivery attempts"
3898 .cindex "delivery" "abandoning further attempts"
3899 This option requests Exim to give up trying to deliver the listed messages,
3900 including any that are frozen. However, if any of the messages are active,
3901 their status is not altered. For non-bounce messages, a delivery error message
3902 is sent to the sender, containing the text &"cancelled by administrator"&.
3903 Bounce messages are just discarded. This option can be used only by an admin
3906 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3908 .cindex "delivery" "cancelling all"
3909 This option requests Exim to mark all the recipient addresses in the messages
3910 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3911 message is active (in the middle of a delivery attempt), its status is not
3912 altered. This option can be used only by an admin user.
3914 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3916 .cindex "delivery" "cancelling by address"
3917 .cindex "recipient" "removing"
3918 .cindex "removing recipients"
3919 This option requests Exim to mark the given addresses as already delivered
3920 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3921 the remaining ones must be email addresses. These are matched to recipient
3922 addresses in the message in a case-sensitive manner. If the message is active
3923 (in the middle of a delivery attempt), its status is not altered. This option
3924 can be used only by an admin user.
3926 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3928 .cindex "removing messages"
3929 .cindex "abandoning mail"
3930 .cindex "message" "manually discarding"
3931 This option requests Exim to remove the given messages from the queue. No
3932 bounce messages are sent; each message is simply forgotten. However, if any of
3933 the messages are active, their status is not altered. This option can be used
3934 only by an admin user or by the user who originally caused the message to be
3935 placed on the queue.
3937 .vitem &%-Mset%&&~<&'message&~id'&>
3939 .cindex "testing" "string expansion"
3940 .cindex "expansion" "testing"
3941 This option is useful only in conjunction with &%-be%& (that is, when testing
3942 string expansions). Exim loads the given message from its spool before doing
3943 the test expansions, thus setting message-specific variables such as
3944 &$message_size$& and the header variables. The &$recipients$& variable is made
3945 available. This feature is provided to make it easier to test expansions that
3946 make use of these variables. However, this option can be used only by an admin
3947 user. See also &%-bem%&.
3949 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3951 .cindex "thawing messages"
3952 .cindex "unfreezing messages"
3953 .cindex "frozen messages" "thawing"
3954 .cindex "message" "thawing frozen"
3955 This option requests Exim to &"thaw"& any of the listed messages that are
3956 &"frozen"&, so that delivery attempts can resume. However, if any of the
3957 messages are active, their status is not altered. This option can be used only
3960 .vitem &%-Mvb%&&~<&'message&~id'&>
3962 .cindex "listing" "message body"
3963 .cindex "message" "listing body of"
3964 This option causes the contents of the message body (-D) spool file to be
3965 written to the standard output. This option can be used only by an admin user.
3967 .vitem &%-Mvc%&&~<&'message&~id'&>
3969 .cindex "message" "listing in RFC 2822 format"
3970 .cindex "listing" "message in RFC 2822 format"
3971 This option causes a copy of the complete message (header lines plus body) to
3972 be written to the standard output in RFC 2822 format. This option can be used
3973 only by an admin user.
3975 .vitem &%-Mvh%&&~<&'message&~id'&>
3977 .cindex "listing" "message headers"
3978 .cindex "header lines" "listing"
3979 .cindex "message" "listing header lines"
3980 This option causes the contents of the message headers (-H) spool file to be
3981 written to the standard output. This option can be used only by an admin user.
3983 .vitem &%-Mvl%&&~<&'message&~id'&>
3985 .cindex "listing" "message log"
3986 .cindex "message" "listing message log"
3987 This option causes the contents of the message log spool file to be written to
3988 the standard output. This option can be used only by an admin user.
3992 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3993 treats it that way too.
3997 .cindex "debugging" "&%-N%& option"
3998 .cindex "debugging" "suppressing delivery"
3999 This is a debugging option that inhibits delivery of a message at the transport
4000 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4001 it just doesn't actually transport the message, but instead behaves as if it
4002 had successfully done so. However, it does not make any updates to the retry
4003 database, and the log entries for deliveries are flagged with &"*>"& rather
4006 Because &%-N%& discards any message to which it applies, only root or the Exim
4007 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4008 words, an ordinary user can use it only when supplying an incoming message to
4009 which it will apply. Although transportation never fails when &%-N%& is set, an
4010 address may be deferred because of a configuration problem on a transport, or a
4011 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4012 the message, and applies to any subsequent delivery attempts that may happen
4017 This option is interpreted by Sendmail to mean &"no aliasing"&.
4018 For normal modes of operation, it is ignored by Exim.
4019 When combined with &%-bP%& it suppresses the name of an option from being output.
4021 .vitem &%-O%&&~<&'data'&>
4023 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4026 .vitem &%-oA%&&~<&'file&~name'&>
4028 .cindex "Sendmail compatibility" "&%-oA%& option"
4029 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4030 alternative alias file name. Exim handles &%-bi%& differently; see the
4033 .vitem &%-oB%&&~<&'n'&>
4035 .cindex "SMTP" "passed connection"
4036 .cindex "SMTP" "multiple deliveries"
4037 .cindex "multiple SMTP deliveries"
4038 This is a debugging option which limits the maximum number of messages that can
4039 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4040 transport. If <&'n'&> is omitted, the limit is set to 1.
4044 .cindex "background delivery"
4045 .cindex "delivery" "in the background"
4046 This option applies to all modes in which Exim accepts incoming messages,
4047 including the listening daemon. It requests &"background"& delivery of such
4048 messages, which means that the accepting process automatically starts a
4049 delivery process for each message received, but does not wait for the delivery
4050 processes to finish.
4052 When all the messages have been received, the reception process exits,
4053 leaving the delivery processes to finish in their own time. The standard output
4054 and error streams are closed at the start of each delivery process.
4055 This is the default action if none of the &%-od%& options are present.
4057 If one of the queueing options in the configuration file
4058 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4059 overrides it if &%queue_only_override%& is set true, which is the default
4060 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4064 .cindex "foreground delivery"
4065 .cindex "delivery" "in the foreground"
4066 This option requests &"foreground"& (synchronous) delivery when Exim has
4067 accepted a locally-generated message. (For the daemon it is exactly the same as
4068 &%-odb%&.) A delivery process is automatically started to deliver the message,
4069 and Exim waits for it to complete before proceeding.
4071 The original Exim reception process does not finish until the delivery
4072 process for the final message has ended. The standard error stream is left open
4075 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4076 false and one of the queueing options in the configuration file is in effect.
4078 If there is a temporary delivery error during foreground delivery, the
4079 message is left on the queue for later delivery, and the original reception
4080 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4081 restricted configuration that never queues messages.
4086 This option is synonymous with &%-odf%&. It is provided for compatibility with
4091 .cindex "non-immediate delivery"
4092 .cindex "delivery" "suppressing immediate"
4093 .cindex "queueing incoming messages"
4094 This option applies to all modes in which Exim accepts incoming messages,
4095 including the listening daemon. It specifies that the accepting process should
4096 not automatically start a delivery process for each message received. Messages
4097 are placed on the queue, and remain there until a subsequent queue runner
4098 process encounters them. There are several configuration options (such as
4099 &%queue_only%&) that can be used to queue incoming messages under certain
4100 conditions. This option overrides all of them and also &%-odqs%&. It always
4105 .cindex "SMTP" "delaying delivery"
4106 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4107 However, like &%-odb%& and &%-odi%&, this option has no effect if
4108 &%queue_only_override%& is false and one of the queueing options in the
4109 configuration file is in effect.
4111 When &%-odqs%& does operate, a delivery process is started for each incoming
4112 message, in the background by default, but in the foreground if &%-odi%& is
4113 also present. The recipient addresses are routed, and local deliveries are done
4114 in the normal way. However, if any SMTP deliveries are required, they are not
4115 done at this time, so the message remains on the queue until a subsequent queue
4116 runner process encounters it. Because routing was done, Exim knows which
4117 messages are waiting for which hosts, and so a number of messages for the same
4118 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4119 configuration option has the same effect for specific domains. See also the
4124 .cindex "error" "reporting"
4125 If an error is detected while a non-SMTP message is being received (for
4126 example, a malformed address), the error is reported to the sender in a mail
4129 .cindex "return code" "for &%-oee%&"
4131 this error message is successfully sent, the Exim receiving process
4132 exits with a return code of zero. If not, the return code is 2 if the problem
4133 is that the original message has no recipients, or 1 for any other error.
4134 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4138 .cindex "error" "reporting"
4139 .cindex "return code" "for &%-oem%&"
4140 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4141 return code, whether or not the error message was successfully sent.
4142 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4146 .cindex "error" "reporting"
4147 If an error is detected while a non-SMTP message is being received, the
4148 error is reported by writing a message to the standard error file (stderr).
4149 .cindex "return code" "for &%-oep%&"
4150 The return code is 1 for all errors.
4154 .cindex "error" "reporting"
4155 This option is supported for compatibility with Sendmail, but has the same
4160 .cindex "error" "reporting"
4161 This option is supported for compatibility with Sendmail, but has the same
4166 .cindex "dot" "in incoming non-SMTP message"
4167 This option, which has the same effect as &%-i%&, specifies that a dot on a
4168 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4169 single dot does terminate, though Exim does no special processing for other
4170 lines that start with a dot. This option is set by default if Exim is called as
4171 &'rmail'&. See also &%-ti%&.
4174 .oindex "&%-oitrue%&"
4175 This option is treated as synonymous with &%-oi%&.
4177 .vitem &%-oMa%&&~<&'host&~address'&>
4179 .cindex "sender" "host address, specifying for local message"
4180 A number of options starting with &%-oM%& can be used to set values associated
4181 with remote hosts on locally-submitted messages (that is, messages not received
4182 over TCP/IP). These options can be used by any caller in conjunction with the
4183 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4184 other circumstances, they are ignored unless the caller is trusted.
4186 The &%-oMa%& option sets the sender host address. This may include a port
4187 number at the end, after a full stop (period). For example:
4189 exim -bs -oMa 10.9.8.7.1234
4191 An alternative syntax is to enclose the IP address in square brackets,
4192 followed by a colon and the port number:
4194 exim -bs -oMa [10.9.8.7]:1234
4196 The IP address is placed in the &$sender_host_address$& variable, and the
4197 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4198 are present on the command line, the sender host IP address is taken from
4199 whichever one is last.
4201 .vitem &%-oMaa%&&~<&'name'&>
4203 .cindex "authentication" "name, specifying for local message"
4204 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4205 option sets the value of &$sender_host_authenticated$& (the authenticator
4206 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4207 This option can be used with &%-bh%& and &%-bs%& to set up an
4208 authenticated SMTP session without actually using the SMTP AUTH command.
4210 .vitem &%-oMai%&&~<&'string'&>
4212 .cindex "authentication" "id, specifying for local message"
4213 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4214 option sets the value of &$authenticated_id$& (the id that was authenticated).
4215 This overrides the default value (the caller's login id, except with &%-bh%&,
4216 where there is no default) for messages from local sources. See chapter
4217 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4219 .vitem &%-oMas%&&~<&'address'&>
4221 .cindex "authentication" "sender, specifying for local message"
4222 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4223 option sets the authenticated sender value in &$authenticated_sender$&. It
4224 overrides the sender address that is created from the caller's login id for
4225 messages from local sources, except when &%-bh%& is used, when there is no
4226 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4227 specified on a MAIL command overrides this value. See chapter
4228 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4230 .vitem &%-oMi%&&~<&'interface&~address'&>
4232 .cindex "interface" "address, specifying for local message"
4233 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4234 option sets the IP interface address value. A port number may be included,
4235 using the same syntax as for &%-oMa%&. The interface address is placed in
4236 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4238 .vitem &%-oMm%&&~<&'message&~reference'&>
4240 .cindex "message reference" "message reference, specifying for local message"
4241 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4242 option sets the message reference, e.g. message-id, and is logged during
4243 delivery. This is useful when some kind of audit trail is required to tie
4244 messages together. The format of the message reference is checked and will
4245 abort if the format is invalid. The option will only be accepted if exim is
4246 running in trusted mode, not as any regular user.
4248 The best example of a message reference is when Exim sends a bounce message.
4249 The message reference is the message-id of the original message for which Exim
4250 is sending the bounce.
4252 .vitem &%-oMr%&&~<&'protocol&~name'&>
4254 .cindex "protocol, specifying for local message"
4255 .vindex "&$received_protocol$&"
4256 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4257 option sets the received protocol value that is stored in
4258 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4259 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4260 SMTP protocol names (see the description of &$received_protocol$& in section
4261 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4262 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4265 .vitem &%-oMs%&&~<&'host&~name'&>
4267 .cindex "sender" "host name, specifying for local message"
4268 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4269 option sets the sender host name in &$sender_host_name$&. When this option is
4270 present, Exim does not attempt to look up a host name from an IP address; it
4271 uses the name it is given.
4273 .vitem &%-oMt%&&~<&'ident&~string'&>
4275 .cindex "sender" "ident string, specifying for local message"
4276 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4277 option sets the sender ident value in &$sender_ident$&. The default setting for
4278 local callers is the login id of the calling process, except when &%-bh%& is
4279 used, when there is no default.
4283 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4284 In Sendmail, this option means &"me too"&, indicating that the sender of a
4285 message should receive a copy of the message if the sender appears in an alias
4286 expansion. Exim always does this, so the option does nothing.
4290 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4291 This option is ignored. In Sendmail it specifies &"old style headers"&,
4292 whatever that means.
4294 .vitem &%-oP%&&~<&'path'&>
4296 .cindex "pid (process id)" "of daemon"
4297 .cindex "daemon" "process id (pid)"
4298 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4299 value. The option specifies the file to which the process id of the daemon is
4300 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4301 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4302 because in those cases, the normal pid file is not used.
4304 .vitem &%-or%&&~<&'time'&>
4306 .cindex "timeout" "for non-SMTP input"
4307 This option sets a timeout value for incoming non-SMTP messages. If it is not
4308 set, Exim will wait forever for the standard input. The value can also be set
4309 by the &%receive_timeout%& option. The format used for specifying times is
4310 described in section &<<SECTtimeformat>>&.
4312 .vitem &%-os%&&~<&'time'&>
4314 .cindex "timeout" "for SMTP input"
4315 .cindex "SMTP" "input timeout"
4316 This option sets a timeout value for incoming SMTP messages. The timeout
4317 applies to each SMTP command and block of data. The value can also be set by
4318 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4319 for specifying times is described in section &<<SECTtimeformat>>&.
4323 This option has exactly the same effect as &%-v%&.
4325 .vitem &%-oX%&&~<&'number&~or&~string'&>
4327 .cindex "TCP/IP" "setting listening ports"
4328 .cindex "TCP/IP" "setting listening interfaces"
4329 .cindex "port" "receiving TCP/IP"
4330 This option is relevant only when the &%-bd%& (start listening daemon) option
4331 is also given. It controls which ports and interfaces the daemon uses. Details
4332 of the syntax, and how it interacts with configuration file options, are given
4333 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4334 file is written unless &%-oP%& is also present to specify a pid file name.
4338 .cindex "Perl" "starting the interpreter"
4339 This option applies when an embedded Perl interpreter is linked with Exim (see
4340 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4341 option, forcing the starting of the interpreter to be delayed until it is
4346 .cindex "Perl" "starting the interpreter"
4347 This option applies when an embedded Perl interpreter is linked with Exim (see
4348 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4349 option, forcing the starting of the interpreter to occur as soon as Exim is
4352 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4354 For compatibility with Sendmail, this option is equivalent to
4356 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4358 It sets the incoming protocol and host name (for trusted callers). The
4359 host name and its colon can be omitted when only the protocol is to be set.
4360 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4361 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4362 or &`s`& using this option (but that does not seem a real limitation).
4366 .cindex "queue runner" "starting manually"
4367 This option is normally restricted to admin users. However, there is a
4368 configuration option called &%prod_requires_admin%& which can be set false to
4369 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4370 and &%-S%& options).
4372 .cindex "queue runner" "description of operation"
4373 The &%-q%& option starts one queue runner process. This scans the queue of
4374 waiting messages, and runs a delivery process for each one in turn. It waits
4375 for each delivery process to finish before starting the next one. A delivery
4376 process may not actually do any deliveries if the retry times for the addresses
4377 have not been reached. Use &%-qf%& (see below) if you want to override this.
4380 .cindex "SMTP" "passed connection"
4381 .cindex "SMTP" "multiple deliveries"
4382 .cindex "multiple SMTP deliveries"
4383 the delivery process spawns other processes to deliver other messages down
4384 passed SMTP connections, the queue runner waits for these to finish before
4387 When all the queued messages have been considered, the original queue runner
4388 process terminates. In other words, a single pass is made over the waiting
4389 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4390 this to be repeated periodically.
4392 Exim processes the waiting messages in an unpredictable order. It isn't very
4393 random, but it is likely to be different each time, which is all that matters.
4394 If one particular message screws up a remote MTA, other messages to the same
4395 MTA have a chance of getting through if they get tried first.
4397 It is possible to cause the messages to be processed in lexical message id
4398 order, which is essentially the order in which they arrived, by setting the
4399 &%queue_run_in_order%& option, but this is not recommended for normal use.
4401 .vitem &%-q%&<&'qflags'&>
4402 The &%-q%& option may be followed by one or more flag letters that change its
4403 behaviour. They are all optional, but if more than one is present, they must
4404 appear in the correct order. Each flag is described in a separate item below.
4408 .cindex "queue" "double scanning"
4409 .cindex "queue" "routing"
4410 .cindex "routing" "whole queue before delivery"
4411 An option starting with &%-qq%& requests a two-stage queue run. In the first
4412 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4413 every domain. Addresses are routed, local deliveries happen, but no remote
4416 .cindex "hints database" "remembering routing"
4417 The hints database that remembers which messages are waiting for specific hosts
4418 is updated, as if delivery to those hosts had been deferred. After this is
4419 complete, a second, normal queue scan happens, with routing and delivery taking
4420 place as normal. Messages that are routed to the same host should mostly be
4421 delivered down a single SMTP
4422 .cindex "SMTP" "passed connection"
4423 .cindex "SMTP" "multiple deliveries"
4424 .cindex "multiple SMTP deliveries"
4425 connection because of the hints that were set up during the first queue scan.
4426 This option may be useful for hosts that are connected to the Internet
4429 .vitem &%-q[q]i...%&
4431 .cindex "queue" "initial delivery"
4432 If the &'i'& flag is present, the queue runner runs delivery processes only for
4433 those messages that haven't previously been tried. (&'i'& stands for &"initial
4434 delivery"&.) This can be helpful if you are putting messages on the queue using
4435 &%-odq%& and want a queue runner just to process the new messages.
4437 .vitem &%-q[q][i]f...%&
4439 .cindex "queue" "forcing delivery"
4440 .cindex "delivery" "forcing in queue run"
4441 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4442 message, whereas without &'f'& only those non-frozen addresses that have passed
4443 their retry times are tried.
4445 .vitem &%-q[q][i]ff...%&
4447 .cindex "frozen messages" "forcing delivery"
4448 If &'ff'& is present, a delivery attempt is forced for every message, whether
4451 .vitem &%-q[q][i][f[f]]l%&
4453 .cindex "queue" "local deliveries only"
4454 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4455 be done. If a message requires any remote deliveries, it remains on the queue
4458 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4459 .cindex "queue" "delivering specific messages"
4460 When scanning the queue, Exim can be made to skip over messages whose ids are
4461 lexically less than a given value by following the &%-q%& option with a
4462 starting message id. For example:
4464 exim -q 0t5C6f-0000c8-00
4466 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4467 second message id is given, messages whose ids are lexically greater than it
4468 are also skipped. If the same id is given twice, for example,
4470 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4472 just one delivery process is started, for that message. This differs from
4473 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4474 that it counts as a delivery from a queue run. Note that the selection
4475 mechanism does not affect the order in which the messages are scanned. There
4476 are also other ways of selecting specific sets of messages for delivery in a
4477 queue run &-- see &%-R%& and &%-S%&.
4479 .vitem &%-q%&<&'qflags'&><&'time'&>
4480 .cindex "queue runner" "starting periodically"
4481 .cindex "periodic queue running"
4482 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4483 starting a queue runner process at intervals specified by the given time value
4484 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4485 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4486 single daemon process handles both functions. A common way of starting up a
4487 combined daemon at system boot time is to use a command such as
4489 /usr/exim/bin/exim -bd -q30m
4491 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4492 process every 30 minutes.
4494 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4495 pid file is written unless one is explicitly requested by the &%-oP%& option.
4497 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4499 This option is synonymous with &%-R%&. It is provided for Sendmail
4502 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4504 This option is synonymous with &%-S%&.
4506 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4508 .cindex "queue runner" "for specific recipients"
4509 .cindex "delivery" "to given domain"
4510 .cindex "domain" "delivery to"
4511 The <&'rsflags'&> may be empty, in which case the white space before the string
4512 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4513 which are the possible values for <&'rsflags'&>. White space is required if
4514 <&'rsflags'&> is not empty.
4516 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4517 perform a single queue run, except that, when scanning the messages on the
4518 queue, Exim processes only those that have at least one undelivered recipient
4519 address containing the given string, which is checked in a case-independent
4520 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4521 regular expression; otherwise it is a literal string.
4523 If you want to do periodic queue runs for messages with specific recipients,
4524 you can combine &%-R%& with &%-q%& and a time value. For example:
4526 exim -q25m -R @special.domain.example
4528 This example does a queue run for messages with recipients in the given domain
4529 every 25 minutes. Any additional flags that are specified with &%-q%& are
4530 applied to each queue run.
4532 Once a message is selected for delivery by this mechanism, all its addresses
4533 are processed. For the first selected message, Exim overrides any retry
4534 information and forces a delivery attempt for each undelivered address. This
4535 means that if delivery of any address in the first message is successful, any
4536 existing retry information is deleted, and so delivery attempts for that
4537 address in subsequently selected messages (which are processed without forcing)
4538 will run. However, if delivery of any address does not succeed, the retry
4539 information is updated, and in subsequently selected messages, the failing
4540 address will be skipped.
4542 .cindex "frozen messages" "forcing delivery"
4543 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4544 all selected messages, not just the first; frozen messages are included when
4547 The &%-R%& option makes it straightforward to initiate delivery of all messages
4548 to a given domain after a host has been down for some time. When the SMTP
4549 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4550 effect is to run Exim with the &%-R%& option, but it can be configured to run
4551 an arbitrary command instead.
4555 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4557 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4559 .cindex "delivery" "from given sender"
4560 .cindex "queue runner" "for specific senders"
4561 This option acts like &%-R%& except that it checks the string against each
4562 message's sender instead of against the recipients. If &%-R%& is also set, both
4563 conditions must be met for a message to be selected. If either of the options
4564 has &'f'& or &'ff'& in its flags, the associated action is taken.
4566 .vitem &%-Tqt%&&~<&'times'&>
4568 This is an option that is exclusively for use by the Exim testing suite. It is not
4569 recognized when Exim is run normally. It allows for the setting up of explicit
4570 &"queue times"& so that various warning/retry features can be tested.
4574 .cindex "recipient" "extracting from header lines"
4575 .cindex "&'Bcc:'& header line"
4576 .cindex "&'Cc:'& header line"
4577 .cindex "&'To:'& header line"
4578 When Exim is receiving a locally-generated, non-SMTP message on its standard
4579 input, the &%-t%& option causes the recipients of the message to be obtained
4580 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4581 from the command arguments. The addresses are extracted before any rewriting
4582 takes place and the &'Bcc:'& header line, if present, is then removed.
4584 .cindex "Sendmail compatibility" "&%-t%& option"
4585 If the command has any arguments, they specify addresses to which the message
4586 is &'not'& to be delivered. That is, the argument addresses are removed from
4587 the recipients list obtained from the headers. This is compatible with Smail 3
4588 and in accordance with the documented behaviour of several versions of
4589 Sendmail, as described in man pages on a number of operating systems (e.g.
4590 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4591 argument addresses to those obtained from the headers, and the O'Reilly
4592 Sendmail book documents it that way. Exim can be made to add argument addresses
4593 instead of subtracting them by setting the option
4594 &%extract_addresses_remove_arguments%& false.
4596 .cindex "&%Resent-%& header lines" "with &%-t%&"
4597 If there are any &%Resent-%& header lines in the message, Exim extracts
4598 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4599 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4600 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4601 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4603 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4604 message is resent several times). The RFC also specifies that they should be
4605 added at the front of the message, and separated by &'Received:'& lines. It is
4606 not at all clear how &%-t%& should operate in the present of multiple sets,
4607 nor indeed exactly what constitutes a &"set"&.
4608 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4609 are often added at the end of the header, and if a message is resent more than
4610 once, it is common for the original set of &%Resent-%& headers to be renamed as
4611 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4615 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4616 compatibility with Sendmail.
4618 .vitem &%-tls-on-connect%&
4619 .oindex "&%-tls-on-connect%&"
4620 .cindex "TLS" "use without STARTTLS"
4621 .cindex "TLS" "automatic start"
4622 This option is available when Exim is compiled with TLS support. It forces all
4623 incoming SMTP connections to behave as if the incoming port is listed in the
4624 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4625 &<<CHAPTLS>>& for further details.
4630 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4631 Sendmail uses this option for &"initial message submission"&, and its
4632 documentation states that in future releases, it may complain about
4633 syntactically invalid messages rather than fixing them when this flag is not
4634 set. Exim ignores this option.
4638 This option causes Exim to write information to the standard error stream,
4639 describing what it is doing. In particular, it shows the log lines for
4640 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4641 dialogue is shown. Some of the log lines shown may not actually be written to
4642 the log if the setting of &%log_selector%& discards them. Any relevant
4643 selectors are shown with each log line. If none are shown, the logging is
4648 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4649 National Language Support extended characters in the body of the mail item"&).
4650 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4653 .vitem &%-X%&&~<&'logfile'&>
4655 This option is interpreted by Sendmail to cause debug information to be sent
4656 to the named file. It is ignored by Exim.
4659 .vitem &%-z%&&~<&'log-line'&>
4661 This option writes its argument to Exim's logfile.
4662 Use is restricted to administrators; the intent is for operational notes.
4663 Quotes should be used to maintain a multi-word item as a single argument,
4672 . ////////////////////////////////////////////////////////////////////////////
4673 . Insert a stylized DocBook comment here, to identify the end of the command
4674 . line options. This is for the benefit of the Perl script that automatically
4675 . creates a man page for the options.
4676 . ////////////////////////////////////////////////////////////////////////////
4679 <!-- === End of command line options === -->
4686 . ////////////////////////////////////////////////////////////////////////////
4687 . ////////////////////////////////////////////////////////////////////////////
4690 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4691 "The runtime configuration file"
4693 .cindex "run time configuration"
4694 .cindex "configuration file" "general description"
4695 .cindex "CONFIGURE_FILE"
4696 .cindex "configuration file" "errors in"
4697 .cindex "error" "in configuration file"
4698 .cindex "return code" "for bad configuration"
4699 Exim uses a single run time configuration file that is read whenever an Exim
4700 binary is executed. Note that in normal operation, this happens frequently,
4701 because Exim is designed to operate in a distributed manner, without central
4704 If a syntax error is detected while reading the configuration file, Exim
4705 writes a message on the standard error, and exits with a non-zero return code.
4706 The message is also written to the panic log. &*Note*&: Only simple syntax
4707 errors can be detected at this time. The values of any expanded options are
4708 not checked until the expansion happens, even when the expansion does not
4709 actually alter the string.
4711 The name of the configuration file is compiled into the binary for security
4712 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4713 most configurations, this specifies a single file. However, it is permitted to
4714 give a colon-separated list of file names, in which case Exim uses the first
4715 existing file in the list.
4718 .cindex "EXIM_GROUP"
4719 .cindex "CONFIGURE_OWNER"
4720 .cindex "CONFIGURE_GROUP"
4721 .cindex "configuration file" "ownership"
4722 .cindex "ownership" "configuration file"
4723 The run time configuration file must be owned by root or by the user that is
4724 specified at compile time by the CONFIGURE_OWNER option (if set). The
4725 configuration file must not be world-writeable, or group-writeable unless its
4726 group is the root group or the one specified at compile time by the
4727 CONFIGURE_GROUP option.
4729 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4730 to root, anybody who is able to edit the run time configuration file has an
4731 easy way to run commands as root. If you specify a user or group in the
4732 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4733 who are members of that group will trivially be able to obtain root privileges.
4735 Up to Exim version 4.72, the run time configuration file was also permitted to
4736 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4737 since it offered a simple privilege escalation for any attacker who managed to
4738 compromise the Exim user account.
4740 A default configuration file, which will work correctly in simple situations,
4741 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4742 defines just one file name, the installation process copies the default
4743 configuration to a new file of that name if it did not previously exist. If
4744 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4745 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4750 .section "Using a different configuration file" "SECID40"
4751 .cindex "configuration file" "alternate"
4752 A one-off alternate configuration can be specified by the &%-C%& command line
4753 option, which may specify a single file or a list of files. However, when
4754 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4755 unless the argument for &%-C%& is identical to the built-in value from
4756 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4757 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4758 is useful mainly for checking the syntax of configuration files before
4759 installing them. No owner or group checks are done on a configuration file
4760 specified by &%-C%&, if root privilege has been dropped.
4762 Even the Exim user is not trusted to specify an arbitrary configuration file
4763 with the &%-C%& option to be used with root privileges, unless that file is
4764 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4765 testing a configuration using &%-C%& right through message reception and
4766 delivery, even if the caller is root. The reception works, but by that time,
4767 Exim is running as the Exim user, so when it re-execs to regain privilege for
4768 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4769 can test reception and delivery using two separate commands (one to put a
4770 message on the queue, using &%-odq%&, and another to do the delivery, using
4773 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4774 prefix string with which any file named in a &%-C%& command line option must
4775 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4776 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4777 name can be used with &%-C%&.
4779 One-off changes to a configuration can be specified by the &%-D%& command line
4780 option, which defines and overrides values for macros used inside the
4781 configuration file. However, like &%-C%&, the use of this option by a
4782 non-privileged user causes Exim to discard its root privilege.
4783 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4784 completely disabled, and its use causes an immediate error exit.
4786 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4787 to declare certain macro names trusted, such that root privilege will not
4788 necessarily be discarded.
4789 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4790 considered safe and, if &%-D%& only supplies macros from this list, and the
4791 values are acceptable, then Exim will not give up root privilege if the caller
4792 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4793 transition mechanism and is expected to be removed in the future. Acceptable
4794 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4796 Some sites may wish to use the same Exim binary on different machines that
4797 share a file system, but to use different configuration files on each machine.
4798 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4799 looks for a file whose name is the configuration file name followed by a dot
4800 and the machine's node name, as obtained from the &[uname()]& function. If this
4801 file does not exist, the standard name is tried. This processing occurs for
4802 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4804 In some esoteric situations different versions of Exim may be run under
4805 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4806 help with this. See the comments in &_src/EDITME_& for details.
4810 .section "Configuration file format" "SECTconffilfor"
4811 .cindex "configuration file" "format of"
4812 .cindex "format" "configuration file"
4813 Exim's configuration file is divided into a number of different parts. General
4814 option settings must always appear at the start of the file. The other parts
4815 are all optional, and may appear in any order. Each part other than the first
4816 is introduced by the word &"begin"& followed by the name of the part. The
4820 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4823 .cindex "AUTH" "configuration"
4824 &'authenticators'&: Configuration settings for the authenticator drivers. These
4825 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4827 &'routers'&: Configuration settings for the router drivers. Routers process
4828 addresses and determine how the message is to be delivered (see chapters
4829 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4831 &'transports'&: Configuration settings for the transport drivers. Transports
4832 define mechanisms for copying messages to destinations (see chapters
4833 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4835 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4836 If there is no retry section, or if it is empty (that is, no retry rules are
4837 defined), Exim will not retry deliveries. In this situation, temporary errors
4838 are treated the same as permanent errors. Retry rules are discussed in chapter
4841 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4842 when new addresses are generated during delivery. Rewriting is discussed in
4843 chapter &<<CHAPrewrite>>&.
4845 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4846 want to use this feature, you must set
4848 LOCAL_SCAN_HAS_OPTIONS=yes
4850 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4851 facility are given in chapter &<<CHAPlocalscan>>&.
4854 .cindex "configuration file" "leading white space in"
4855 .cindex "configuration file" "trailing white space in"
4856 .cindex "white space" "in configuration file"
4857 Leading and trailing white space in configuration lines is always ignored.
4859 Blank lines in the file, and lines starting with a # character (ignoring
4860 leading white space) are treated as comments and are ignored. &*Note*&: A
4861 # character other than at the beginning of a line is not treated specially,
4862 and does not introduce a comment.
4864 Any non-comment line can be continued by ending it with a backslash. Note that
4865 the general rule for white space means that trailing white space after the
4866 backslash and leading white space at the start of continuation
4867 lines is ignored. Comment lines beginning with # (but not empty lines) may
4868 appear in the middle of a sequence of continuation lines.
4870 A convenient way to create a configuration file is to start from the
4871 default, which is supplied in &_src/configure.default_&, and add, delete, or
4872 change settings as required.
4874 The ACLs, retry rules, and rewriting rules have their own syntax which is
4875 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4876 respectively. The other parts of the configuration file have some syntactic
4877 items in common, and these are described below, from section &<<SECTcos>>&
4878 onwards. Before that, the inclusion, macro, and conditional facilities are
4883 .section "File inclusions in the configuration file" "SECID41"
4884 .cindex "inclusions in configuration file"
4885 .cindex "configuration file" "including other files"
4886 .cindex "&`.include`& in configuration file"
4887 .cindex "&`.include_if_exists`& in configuration file"
4888 You can include other files inside Exim's run time configuration file by
4891 &`.include`& <&'file name'&>
4892 &`.include_if_exists`& <&'file name'&>
4894 on a line by itself. Double quotes round the file name are optional. If you use
4895 the first form, a configuration error occurs if the file does not exist; the
4896 second form does nothing for non-existent files. In all cases, an absolute file
4899 Includes may be nested to any depth, but remember that Exim reads its
4900 configuration file often, so it is a good idea to keep them to a minimum.
4901 If you change the contents of an included file, you must HUP the daemon,
4902 because an included file is read only when the configuration itself is read.
4904 The processing of inclusions happens early, at a physical line level, so, like
4905 comment lines, an inclusion can be used in the middle of an option setting,
4908 hosts_lookup = a.b.c \
4911 Include processing happens after macro processing (see below). Its effect is to
4912 process the lines of the included file as if they occurred inline where the
4917 .section "Macros in the configuration file" "SECTmacrodefs"
4918 .cindex "macro" "description of"
4919 .cindex "configuration file" "macros"
4920 If a line in the main part of the configuration (that is, before the first
4921 &"begin"& line) begins with an upper case letter, it is taken as a macro
4922 definition, and must be of the form
4924 <&'name'&> = <&'rest of line'&>
4926 The name must consist of letters, digits, and underscores, and need not all be
4927 in upper case, though that is recommended. The rest of the line, including any
4928 continuations, is the replacement text, and has leading and trailing white
4929 space removed. Quotes are not removed. The replacement text can never end with
4930 a backslash character, but this doesn't seem to be a serious limitation.
4932 Macros may also be defined between router, transport, authenticator, or ACL
4933 definitions. They may not, however, be defined within an individual driver or
4934 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4936 .section "Macro substitution" "SECID42"
4937 Once a macro is defined, all subsequent lines in the file (and any included
4938 files) are scanned for the macro name; if there are several macros, the line is
4939 scanned for each in turn, in the order in which the macros are defined. The
4940 replacement text is not re-scanned for the current macro, though it is scanned
4941 for subsequently defined macros. For this reason, a macro name may not contain
4942 the name of a previously defined macro as a substring. You could, for example,
4945 &`ABCD_XYZ = `&<&'something'&>
4946 &`ABCD = `&<&'something else'&>
4948 but putting the definitions in the opposite order would provoke a configuration
4949 error. Macro expansion is applied to individual physical lines from the file,
4950 before checking for line continuation or file inclusion (see above). If a line
4951 consists solely of a macro name, and the expansion of the macro is empty, the
4952 line is ignored. A macro at the start of a line may turn the line into a
4953 comment line or a &`.include`& line.
4956 .section "Redefining macros" "SECID43"
4957 Once defined, the value of a macro can be redefined later in the configuration
4958 (or in an included file). Redefinition is specified by using &'=='& instead of
4963 MAC == updated value
4965 Redefinition does not alter the order in which the macros are applied to the
4966 subsequent lines of the configuration file. It is still the same order in which
4967 the macros were originally defined. All that changes is the macro's value.
4968 Redefinition makes it possible to accumulate values. For example:
4972 MAC == MAC and something added
4974 This can be helpful in situations where the configuration file is built
4975 from a number of other files.
4977 .section "Overriding macro values" "SECID44"
4978 The values set for macros in the configuration file can be overridden by the
4979 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4980 used, unless called by root or the Exim user. A definition on the command line
4981 using the &%-D%& option causes all definitions and redefinitions within the
4986 .section "Example of macro usage" "SECID45"
4987 As an example of macro usage, consider a configuration where aliases are looked
4988 up in a MySQL database. It helps to keep the file less cluttered if long
4989 strings such as SQL statements are defined separately as macros, for example:
4991 ALIAS_QUERY = select mailbox from user where \
4992 login='${quote_mysql:$local_part}';
4994 This can then be used in a &(redirect)& router setting like this:
4996 data = ${lookup mysql{ALIAS_QUERY}}
4998 In earlier versions of Exim macros were sometimes used for domain, host, or
4999 address lists. In Exim 4 these are handled better by named lists &-- see
5000 section &<<SECTnamedlists>>&.
5003 .section "Conditional skips in the configuration file" "SECID46"
5004 .cindex "configuration file" "conditional skips"
5005 .cindex "&`.ifdef`&"
5006 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5007 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5008 portions of the configuration file. The processing happens whenever the file is
5009 read (that is, when an Exim binary starts to run).
5011 The implementation is very simple. Instances of the first four directives must
5012 be followed by text that includes the names of one or macros. The condition
5013 that is tested is whether or not any macro substitution has taken place in the
5017 message_size_limit = 50M
5019 message_size_limit = 100M
5022 sets a message size limit of 50M if the macro &`AAA`& is defined
5023 (or &`A`& or &`AA`&), and 100M
5024 otherwise. If there is more than one macro named on the line, the condition
5025 is true if any of them are defined. That is, it is an &"or"& condition. To
5026 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5028 Although you can use a macro expansion to generate one of these directives,
5029 it is not very useful, because the condition &"there was a macro substitution
5030 in this line"& will always be true.
5032 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5033 to clarify complicated nestings.
5037 .section "Common option syntax" "SECTcos"
5038 .cindex "common option syntax"
5039 .cindex "syntax of common options"
5040 .cindex "configuration file" "common option syntax"
5041 For the main set of options, driver options, and &[local_scan()]& options,
5042 each setting is on a line by itself, and starts with a name consisting of
5043 lower-case letters and underscores. Many options require a data value, and in
5044 these cases the name must be followed by an equals sign (with optional white
5045 space) and then the value. For example:
5047 qualify_domain = mydomain.example.com
5049 .cindex "hiding configuration option values"
5050 .cindex "configuration options" "hiding value of"
5051 .cindex "options" "hiding value of"
5052 Some option settings may contain sensitive data, for example, passwords for
5053 accessing databases. To stop non-admin users from using the &%-bP%& command
5054 line option to read these values, you can precede the option settings with the
5055 word &"hide"&. For example:
5057 hide mysql_servers = localhost/users/admin/secret-password
5059 For non-admin users, such options are displayed like this:
5061 mysql_servers = <value not displayable>
5063 If &"hide"& is used on a driver option, it hides the value of that option on
5064 all instances of the same driver.
5066 The following sections describe the syntax used for the different data types
5067 that are found in option settings.
5070 .section "Boolean options" "SECID47"
5071 .cindex "format" "boolean"
5072 .cindex "boolean configuration values"
5073 .oindex "&%no_%&&'xxx'&"
5074 .oindex "&%not_%&&'xxx'&"
5075 Options whose type is given as boolean are on/off switches. There are two
5076 different ways of specifying such options: with and without a data value. If
5077 the option name is specified on its own without data, the switch is turned on;
5078 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5079 boolean options may be followed by an equals sign and one of the words
5080 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5081 the following two settings have exactly the same effect:
5086 The following two lines also have the same (opposite) effect:
5091 You can use whichever syntax you prefer.
5096 .section "Integer values" "SECID48"
5097 .cindex "integer configuration values"
5098 .cindex "format" "integer"
5099 If an option's type is given as &"integer"&, the value can be given in decimal,
5100 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5101 number is assumed. Otherwise, it is treated as an octal number unless it starts
5102 with the characters &"0x"&, in which case the remainder is interpreted as a
5105 If an integer value is followed by the letter K, it is multiplied by 1024; if
5106 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5107 of integer option settings are output, values which are an exact multiple of
5108 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5109 and M. The printing style is independent of the actual input format that was
5113 .section "Octal integer values" "SECID49"
5114 .cindex "integer format"
5115 .cindex "format" "octal integer"
5116 If an option's type is given as &"octal integer"&, its value is always
5117 interpreted as an octal number, whether or not it starts with the digit zero.
5118 Such options are always output in octal.
5121 .section "Fixed point numbers" "SECID50"
5122 .cindex "fixed point configuration values"
5123 .cindex "format" "fixed point"
5124 If an option's type is given as &"fixed-point"&, its value must be a decimal
5125 integer, optionally followed by a decimal point and up to three further digits.
5129 .section "Time intervals" "SECTtimeformat"
5130 .cindex "time interval" "specifying in configuration"
5131 .cindex "format" "time interval"
5132 A time interval is specified as a sequence of numbers, each followed by one of
5133 the following letters, with no intervening white space:
5143 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5144 intervals are output in the same format. Exim does not restrict the values; it
5145 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5149 .section "String values" "SECTstrings"
5150 .cindex "string" "format of configuration values"
5151 .cindex "format" "string"
5152 If an option's type is specified as &"string"&, the value can be specified with
5153 or without double-quotes. If it does not start with a double-quote, the value
5154 consists of the remainder of the line plus any continuation lines, starting at
5155 the first character after any leading white space, with trailing white space
5156 removed, and with no interpretation of the characters in the string. Because
5157 Exim removes comment lines (those beginning with #) at an early stage, they can
5158 appear in the middle of a multi-line string. The following two settings are
5159 therefore equivalent:
5161 trusted_users = uucp:mail
5162 trusted_users = uucp:\
5163 # This comment line is ignored
5166 .cindex "string" "quoted"
5167 .cindex "escape characters in quoted strings"
5168 If a string does start with a double-quote, it must end with a closing
5169 double-quote, and any backslash characters other than those used for line
5170 continuation are interpreted as escape characters, as follows:
5173 .irow &`\\`& "single backslash"
5174 .irow &`\n`& "newline"
5175 .irow &`\r`& "carriage return"
5177 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5178 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5182 If a backslash is followed by some other character, including a double-quote
5183 character, that character replaces the pair.
5185 Quoting is necessary only if you want to make use of the backslash escapes to
5186 insert special characters, or if you need to specify a value with leading or
5187 trailing spaces. These cases are rare, so quoting is almost never needed in
5188 current versions of Exim. In versions of Exim before 3.14, quoting was required
5189 in order to continue lines, so you may come across older configuration files
5190 and examples that apparently quote unnecessarily.
5193 .section "Expanded strings" "SECID51"
5194 .cindex "expansion" "definition of"
5195 Some strings in the configuration file are subjected to &'string expansion'&,
5196 by which means various parts of the string may be changed according to the
5197 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5198 is as just described; in particular, the handling of backslashes in quoted
5199 strings is done as part of the input process, before expansion takes place.
5200 However, backslash is also an escape character for the expander, so any
5201 backslashes that are required for that reason must be doubled if they are
5202 within a quoted configuration string.
5205 .section "User and group names" "SECID52"
5206 .cindex "user name" "format of"
5207 .cindex "format" "user name"
5208 .cindex "groups" "name format"
5209 .cindex "format" "group name"
5210 User and group names are specified as strings, using the syntax described
5211 above, but the strings are interpreted specially. A user or group name must
5212 either consist entirely of digits, or be a name that can be looked up using the
5213 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5216 .section "List construction" "SECTlistconstruct"
5217 .cindex "list" "syntax of in configuration"
5218 .cindex "format" "list item in configuration"
5219 .cindex "string" "list, definition of"
5220 The data for some configuration options is a list of items, with colon as the
5221 default separator. Many of these options are shown with type &"string list"& in
5222 the descriptions later in this document. Others are listed as &"domain list"&,
5223 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5224 are all the same; however, those other than &"string list"& are subject to
5225 particular kinds of interpretation, as described in chapter
5226 &<<CHAPdomhosaddlists>>&.
5228 In all these cases, the entire list is treated as a single string as far as the
5229 input syntax is concerned. The &%trusted_users%& setting in section
5230 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5231 in a list, it must be entered as two colons. Leading and trailing white space
5232 on each item in a list is ignored. This makes it possible to include items that
5233 start with a colon, and in particular, certain forms of IPv6 address. For
5236 local_interfaces = 127.0.0.1 : ::::1
5238 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5240 &*Note*&: Although leading and trailing white space is ignored in individual
5241 list items, it is not ignored when parsing the list. The space after the first
5242 colon in the example above is necessary. If it were not there, the list would
5243 be interpreted as the two items 127.0.0.1:: and 1.
5245 .section "Changing list separators" "SECTlistsepchange"
5246 .cindex "list separator" "changing"
5247 .cindex "IPv6" "addresses in lists"
5248 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5249 introduced to allow the separator character to be changed. If a list begins
5250 with a left angle bracket, followed by any punctuation character, that
5251 character is used instead of colon as the list separator. For example, the list
5252 above can be rewritten to use a semicolon separator like this:
5254 local_interfaces = <; 127.0.0.1 ; ::1
5256 This facility applies to all lists, with the exception of the list in
5257 &%log_file_path%&. It is recommended that the use of non-colon separators be
5258 confined to circumstances where they really are needed.
5260 .cindex "list separator" "newline as"
5261 .cindex "newline" "as list separator"
5262 It is also possible to use newline and other control characters (those with
5263 code values less than 32, plus DEL) as separators in lists. Such separators
5264 must be provided literally at the time the list is processed. For options that
5265 are string-expanded, you can write the separator using a normal escape
5266 sequence. This will be processed by the expander before the string is
5267 interpreted as a list. For example, if a newline-separated list of domains is
5268 generated by a lookup, you can process it directly by a line such as this:
5270 domains = <\n ${lookup mysql{.....}}
5272 This avoids having to change the list separator in such data. You are unlikely
5273 to want to use a control character as a separator in an option that is not
5274 expanded, because the value is literal text. However, it can be done by giving
5275 the value in quotes. For example:
5277 local_interfaces = "<\n 127.0.0.1 \n ::1"
5279 Unlike printing character separators, which can be included in list items by
5280 doubling, it is not possible to include a control character as data when it is
5281 set as the separator. Two such characters in succession are interpreted as
5282 enclosing an empty list item.
5286 .section "Empty items in lists" "SECTempitelis"
5287 .cindex "list" "empty item in"
5288 An empty item at the end of a list is always ignored. In other words, trailing
5289 separator characters are ignored. Thus, the list in
5291 senders = user@domain :
5293 contains only a single item. If you want to include an empty string as one item
5294 in a list, it must not be the last item. For example, this list contains three
5295 items, the second of which is empty:
5297 senders = user1@domain : : user2@domain
5299 &*Note*&: There must be white space between the two colons, as otherwise they
5300 are interpreted as representing a single colon data character (and the list
5301 would then contain just one item). If you want to specify a list that contains
5302 just one, empty item, you can do it as in this example:
5306 In this case, the first item is empty, and the second is discarded because it
5307 is at the end of the list.
5312 .section "Format of driver configurations" "SECTfordricon"
5313 .cindex "drivers" "configuration format"
5314 There are separate parts in the configuration for defining routers, transports,
5315 and authenticators. In each part, you are defining a number of driver
5316 instances, each with its own set of options. Each driver instance is defined by
5317 a sequence of lines like this:
5319 <&'instance name'&>:
5324 In the following example, the instance name is &(localuser)&, and it is
5325 followed by three options settings:
5330 transport = local_delivery
5332 For each driver instance, you specify which Exim code module it uses &-- by the
5333 setting of the &%driver%& option &-- and (optionally) some configuration
5334 settings. For example, in the case of transports, if you want a transport to
5335 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5336 a local file you would use the &(appendfile)& driver. Each of the drivers is
5337 described in detail in its own separate chapter later in this manual.
5339 You can have several routers, transports, or authenticators that are based on
5340 the same underlying driver (each must have a different instance name).
5342 The order in which routers are defined is important, because addresses are
5343 passed to individual routers one by one, in order. The order in which
5344 transports are defined does not matter at all. The order in which
5345 authenticators are defined is used only when Exim, as a client, is searching
5346 them to find one that matches an authentication mechanism offered by the
5349 .cindex "generic options"
5350 .cindex "options" "generic &-- definition of"
5351 Within a driver instance definition, there are two kinds of option: &'generic'&
5352 and &'private'&. The generic options are those that apply to all drivers of the
5353 same type (that is, all routers, all transports or all authenticators). The
5354 &%driver%& option is a generic option that must appear in every definition.
5355 .cindex "private options"
5356 The private options are special for each driver, and none need appear, because
5357 they all have default values.
5359 The options may appear in any order, except that the &%driver%& option must
5360 precede any private options, since these depend on the particular driver. For
5361 this reason, it is recommended that &%driver%& always be the first option.
5363 Driver instance names, which are used for reference in log entries and
5364 elsewhere, can be any sequence of letters, digits, and underscores (starting
5365 with a letter) and must be unique among drivers of the same type. A router and
5366 a transport (for example) can each have the same name, but no two router
5367 instances can have the same name. The name of a driver instance should not be
5368 confused with the name of the underlying driver module. For example, the
5369 configuration lines:
5374 create an instance of the &(smtp)& transport driver whose name is
5375 &(remote_smtp)&. The same driver code can be used more than once, with
5376 different instance names and different option settings each time. A second
5377 instance of the &(smtp)& transport, with different options, might be defined
5383 command_timeout = 10s
5385 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5386 these transport instances from routers, and these names would appear in log
5389 Comment lines may be present in the middle of driver specifications. The full
5390 list of option settings for any particular driver instance, including all the
5391 defaulted values, can be extracted by making use of the &%-bP%& command line
5399 . ////////////////////////////////////////////////////////////////////////////
5400 . ////////////////////////////////////////////////////////////////////////////
5402 .chapter "The default configuration file" "CHAPdefconfil"
5403 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5404 .cindex "default" "configuration file &""walk through""&"
5405 The default configuration file supplied with Exim as &_src/configure.default_&
5406 is sufficient for a host with simple mail requirements. As an introduction to
5407 the way Exim is configured, this chapter &"walks through"& the default
5408 configuration, giving brief explanations of the settings. Detailed descriptions
5409 of the options are given in subsequent chapters. The default configuration file
5410 itself contains extensive comments about ways you might want to modify the
5411 initial settings. However, note that there are many options that are not
5412 mentioned at all in the default configuration.
5416 .section "Main configuration settings" "SECTdefconfmain"
5417 The main (global) configuration option settings must always come first in the
5418 file. The first thing you'll see in the file, after some initial comments, is
5421 # primary_hostname =
5423 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5424 to know the official, fully qualified name of your host, and this is where you
5425 can specify it. However, in most cases you do not need to set this option. When
5426 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5428 The first three non-comment configuration lines are as follows:
5430 domainlist local_domains = @
5431 domainlist relay_to_domains =
5432 hostlist relay_from_hosts = 127.0.0.1
5434 These are not, in fact, option settings. They are definitions of two named
5435 domain lists and one named host list. Exim allows you to give names to lists of
5436 domains, hosts, and email addresses, in order to make it easier to manage the
5437 configuration file (see section &<<SECTnamedlists>>&).
5439 The first line defines a domain list called &'local_domains'&; this is used
5440 later in the configuration to identify domains that are to be delivered
5443 .cindex "@ in a domain list"
5444 There is just one item in this list, the string &"@"&. This is a special form
5445 of entry which means &"the name of the local host"&. Thus, if the local host is
5446 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5447 be delivered locally. Because the local host's name is referenced indirectly,
5448 the same configuration file can be used on different hosts.
5450 The second line defines a domain list called &'relay_to_domains'&, but the
5451 list itself is empty. Later in the configuration we will come to the part that
5452 controls mail relaying through the local host; it allows relaying to any
5453 domains in this list. By default, therefore, no relaying on the basis of a mail
5454 domain is permitted.
5456 The third line defines a host list called &'relay_from_hosts'&. This list is
5457 used later in the configuration to permit relaying from any host or IP address
5458 that matches the list. The default contains just the IP address of the IPv4
5459 loopback interface, which means that processes on the local host are able to
5460 submit mail for relaying by sending it over TCP/IP to that interface. No other
5461 hosts are permitted to submit messages for relaying.
5463 Just to be sure there's no misunderstanding: at this point in the configuration
5464 we aren't actually setting up any controls. We are just defining some domains
5465 and hosts that will be used in the controls that are specified later.
5467 The next two configuration lines are genuine option settings:
5469 acl_smtp_rcpt = acl_check_rcpt
5470 acl_smtp_data = acl_check_data
5472 These options specify &'Access Control Lists'& (ACLs) that are to be used
5473 during an incoming SMTP session for every recipient of a message (every RCPT
5474 command), and after the contents of the message have been received,
5475 respectively. The names of the lists are &'acl_check_rcpt'& and
5476 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5477 section of the configuration. The RCPT ACL controls which recipients are
5478 accepted for an incoming message &-- if a configuration does not provide an ACL
5479 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5480 contents of a message to be checked.
5482 Two commented-out option settings are next:
5484 # av_scanner = clamd:/tmp/clamd
5485 # spamd_address = 127.0.0.1 783
5487 These are example settings that can be used when Exim is compiled with the
5488 content-scanning extension. The first specifies the interface to the virus
5489 scanner, and the second specifies the interface to SpamAssassin. Further
5490 details are given in chapter &<<CHAPexiscan>>&.
5492 Three more commented-out option settings follow:
5494 # tls_advertise_hosts = *
5495 # tls_certificate = /etc/ssl/exim.crt
5496 # tls_privatekey = /etc/ssl/exim.pem
5498 These are example settings that can be used when Exim is compiled with
5499 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5500 first one specifies the list of clients that are allowed to use TLS when
5501 connecting to this server; in this case the wildcard means all clients. The
5502 other options specify where Exim should find its TLS certificate and private
5503 key, which together prove the server's identity to any clients that connect.
5504 More details are given in chapter &<<CHAPTLS>>&.
5506 Another two commented-out option settings follow:
5508 # daemon_smtp_ports = 25 : 465 : 587
5509 # tls_on_connect_ports = 465
5511 .cindex "port" "465 and 587"
5512 .cindex "port" "for message submission"
5513 .cindex "message" "submission, ports for"
5514 .cindex "ssmtp protocol"
5515 .cindex "smtps protocol"
5516 .cindex "SMTP" "ssmtp protocol"
5517 .cindex "SMTP" "smtps protocol"
5518 These options provide better support for roaming users who wish to use this
5519 server for message submission. They are not much use unless you have turned on
5520 TLS (as described in the previous paragraph) and authentication (about which
5521 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5522 on end-user networks, so RFC 4409 specifies that message submission should use
5523 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5524 configured to use port 587 correctly, so these settings also enable the
5525 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5526 &<<SECTsupobssmt>>&).
5528 Two more commented-out options settings follow:
5531 # qualify_recipient =
5533 The first of these specifies a domain that Exim uses when it constructs a
5534 complete email address from a local login name. This is often needed when Exim
5535 receives a message from a local process. If you do not set &%qualify_domain%&,
5536 the value of &%primary_hostname%& is used. If you set both of these options,
5537 you can have different qualification domains for sender and recipient
5538 addresses. If you set only the first one, its value is used in both cases.
5540 .cindex "domain literal" "recognizing format"
5541 The following line must be uncommented if you want Exim to recognize
5542 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5543 (an IP address within square brackets) instead of a named domain.
5545 # allow_domain_literals
5547 The RFCs still require this form, but many people think that in the modern
5548 Internet it makes little sense to permit mail to be sent to specific hosts by
5549 quoting their IP addresses. This ancient format has been used by people who
5550 try to abuse hosts by using them for unwanted relaying. However, some
5551 people believe there are circumstances (for example, messages addressed to
5552 &'postmaster'&) where domain literals are still useful.
5554 The next configuration line is a kind of trigger guard:
5558 It specifies that no delivery must ever be run as the root user. The normal
5559 convention is to set up &'root'& as an alias for the system administrator. This
5560 setting is a guard against slips in the configuration.
5561 The list of users specified by &%never_users%& is not, however, the complete
5562 list; the build-time configuration in &_Local/Makefile_& has an option called
5563 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5564 contents of &%never_users%& are added to this list. By default
5565 FIXED_NEVER_USERS also specifies root.
5567 When a remote host connects to Exim in order to send mail, the only information
5568 Exim has about the host's identity is its IP address. The next configuration
5573 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5574 in order to get a host name. This improves the quality of the logging
5575 information, but if you feel it is too expensive, you can remove it entirely,
5576 or restrict the lookup to hosts on &"nearby"& networks.
5577 Note that it is not always possible to find a host name from an IP address,
5578 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5581 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5582 1413 (hence their names):
5585 rfc1413_query_timeout = 0s
5587 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5588 Few hosts offer RFC1413 service these days; calls have to be
5589 terminated by a timeout and this needlessly delays the startup
5590 of an incoming SMTP connection.
5591 If you have hosts for which you trust RFC1413 and need this
5592 information, you can change this.
5594 This line enables an efficiency SMTP option. It is negotiated by clients
5595 and not expected to cause problems but can be disabled if needed.
5600 When Exim receives messages over SMTP connections, it expects all addresses to
5601 be fully qualified with a domain, as required by the SMTP definition. However,
5602 if you are running a server to which simple clients submit messages, you may
5603 find that they send unqualified addresses. The two commented-out options:
5605 # sender_unqualified_hosts =
5606 # recipient_unqualified_hosts =
5608 show how you can specify hosts that are permitted to send unqualified sender
5609 and recipient addresses, respectively.
5612 The &%log_selector%& option is used to increase the detail of logging
5615 log_selector = +smtp_protocol_error +smtp_syntax_error \
5616 +tls_certificate_verified
5620 The &%percent_hack_domains%& option is also commented out:
5622 # percent_hack_domains =
5624 It provides a list of domains for which the &"percent hack"& is to operate.
5625 This is an almost obsolete form of explicit email routing. If you do not know
5626 anything about it, you can safely ignore this topic.
5628 The last two settings in the main part of the default configuration are
5629 concerned with messages that have been &"frozen"& on Exim's queue. When a
5630 message is frozen, Exim no longer continues to try to deliver it. Freezing
5631 occurs when a bounce message encounters a permanent failure because the sender
5632 address of the original message that caused the bounce is invalid, so the
5633 bounce cannot be delivered. This is probably the most common case, but there
5634 are also other conditions that cause freezing, and frozen messages are not
5635 always bounce messages.
5637 ignore_bounce_errors_after = 2d
5638 timeout_frozen_after = 7d
5640 The first of these options specifies that failing bounce messages are to be
5641 discarded after 2 days on the queue. The second specifies that any frozen
5642 message (whether a bounce message or not) is to be timed out (and discarded)
5643 after a week. In this configuration, the first setting ensures that no failing
5644 bounce message ever lasts a week.
5648 .section "ACL configuration" "SECID54"
5649 .cindex "default" "ACLs"
5650 .cindex "&ACL;" "default configuration"
5651 In the default configuration, the ACL section follows the main configuration.
5652 It starts with the line
5656 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5657 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5658 and &%acl_smtp_data%& above.
5660 .cindex "RCPT" "ACL for"
5661 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5662 RCPT command specifies one of the message's recipients. The ACL statements
5663 are considered in order, until the recipient address is either accepted or
5664 rejected. The RCPT command is then accepted or rejected, according to the
5665 result of the ACL processing.
5669 This line, consisting of a name terminated by a colon, marks the start of the
5674 This ACL statement accepts the recipient if the sending host matches the list.
5675 But what does that strange list mean? It doesn't actually contain any host
5676 names or IP addresses. The presence of the colon puts an empty item in the
5677 list; Exim matches this only if the incoming message did not come from a remote
5678 host, because in that case, the remote hostname is empty. The colon is
5679 important. Without it, the list itself is empty, and can never match anything.
5681 What this statement is doing is to accept unconditionally all recipients in
5682 messages that are submitted by SMTP from local processes using the standard
5683 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5686 deny message = Restricted characters in address
5687 domains = +local_domains
5688 local_parts = ^[.] : ^.*[@%!/|]
5690 deny message = Restricted characters in address
5691 domains = !+local_domains
5692 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5694 These statements are concerned with local parts that contain any of the
5695 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5696 Although these characters are entirely legal in local parts (in the case of
5697 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5698 in Internet mail addresses.
5700 The first three have in the past been associated with explicitly routed
5701 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5702 option). Addresses containing these characters are regularly tried by spammers
5703 in an attempt to bypass relaying restrictions, and also by open relay testing
5704 programs. Unless you really need them it is safest to reject these characters
5705 at this early stage. This configuration is heavy-handed in rejecting these
5706 characters for all messages it accepts from remote hosts. This is a deliberate
5707 policy of being as safe as possible.
5709 The first rule above is stricter, and is applied to messages that are addressed
5710 to one of the local domains handled by this host. This is implemented by the
5711 first condition, which restricts it to domains that are listed in the
5712 &'local_domains'& domain list. The &"+"& character is used to indicate a
5713 reference to a named list. In this configuration, there is just one domain in
5714 &'local_domains'&, but in general there may be many.
5716 The second condition on the first statement uses two regular expressions to
5717 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5718 or &"|"&. If you have local accounts that include these characters, you will
5719 have to modify this rule.
5721 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5722 allows them because they have been encountered in practice. (Consider the
5723 common convention of local parts constructed as
5724 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5725 the author of Exim, who has no second initial.) However, a local part starting
5726 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5727 file name (for example, for a mailing list). This is also true for local parts
5728 that contain slashes. A pipe symbol can also be troublesome if the local part
5729 is incorporated unthinkingly into a shell command line.
5731 The second rule above applies to all other domains, and is less strict. This
5732 allows your own users to send outgoing messages to sites that use slashes
5733 and vertical bars in their local parts. It blocks local parts that begin
5734 with a dot, slash, or vertical bar, but allows these characters within the
5735 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5736 and &"!"& is blocked, as before. The motivation here is to prevent your users
5737 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5739 accept local_parts = postmaster
5740 domains = +local_domains
5742 This statement, which has two conditions, accepts an incoming address if the
5743 local part is &'postmaster'& and the domain is one of those listed in the
5744 &'local_domains'& domain list. The &"+"& character is used to indicate a
5745 reference to a named list. In this configuration, there is just one domain in
5746 &'local_domains'&, but in general there may be many.
5748 The presence of this statement means that mail to postmaster is never blocked
5749 by any of the subsequent tests. This can be helpful while sorting out problems
5750 in cases where the subsequent tests are incorrectly denying access.
5752 require verify = sender
5754 This statement requires the sender address to be verified before any subsequent
5755 ACL statement can be used. If verification fails, the incoming recipient
5756 address is refused. Verification consists of trying to route the address, to
5757 see if a bounce message could be delivered to it. In the case of remote
5758 addresses, basic verification checks only the domain, but &'callouts'& can be
5759 used for more verification if required. Section &<<SECTaddressverification>>&
5760 discusses the details of address verification.
5762 accept hosts = +relay_from_hosts
5763 control = submission
5765 This statement accepts the address if the message is coming from one of the
5766 hosts that are defined as being allowed to relay through this host. Recipient
5767 verification is omitted here, because in many cases the clients are dumb MUAs
5768 that do not cope well with SMTP error responses. For the same reason, the
5769 second line specifies &"submission mode"& for messages that are accepted. This
5770 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5771 messages that are deficient in some way, for example, because they lack a
5772 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5773 probably add recipient verification here, and disable submission mode.
5775 accept authenticated = *
5776 control = submission
5778 This statement accepts the address if the client host has authenticated itself.
5779 Submission mode is again specified, on the grounds that such messages are most
5780 likely to come from MUAs. The default configuration does not define any
5781 authenticators, though it does include some nearly complete commented-out
5782 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5783 fact authenticate until you complete the authenticator definitions.
5785 require message = relay not permitted
5786 domains = +local_domains : +relay_to_domains
5788 This statement rejects the address if its domain is neither a local domain nor
5789 one of the domains for which this host is a relay.
5791 require verify = recipient
5793 This statement requires the recipient address to be verified; if verification
5794 fails, the address is rejected.
5796 # deny message = rejected because $sender_host_address \
5797 # is in a black list at $dnslist_domain\n\
5799 # dnslists = black.list.example
5801 # warn dnslists = black.list.example
5802 # add_header = X-Warning: $sender_host_address is in \
5803 # a black list at $dnslist_domain
5804 # log_message = found in $dnslist_domain
5806 These commented-out lines are examples of how you could configure Exim to check
5807 sending hosts against a DNS black list. The first statement rejects messages
5808 from blacklisted hosts, whereas the second just inserts a warning header
5811 # require verify = csa
5813 This commented-out line is an example of how you could turn on client SMTP
5814 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5819 The final statement in the first ACL unconditionally accepts any recipient
5820 address that has successfully passed all the previous tests.
5824 This line marks the start of the second ACL, and names it. Most of the contents
5825 of this ACL are commented out:
5828 # message = This message contains a virus \
5831 These lines are examples of how to arrange for messages to be scanned for
5832 viruses when Exim has been compiled with the content-scanning extension, and a
5833 suitable virus scanner is installed. If the message is found to contain a
5834 virus, it is rejected with the given custom error message.
5836 # warn spam = nobody
5837 # message = X-Spam_score: $spam_score\n\
5838 # X-Spam_score_int: $spam_score_int\n\
5839 # X-Spam_bar: $spam_bar\n\
5840 # X-Spam_report: $spam_report
5842 These lines are an example of how to arrange for messages to be scanned by
5843 SpamAssassin when Exim has been compiled with the content-scanning extension,
5844 and SpamAssassin has been installed. The SpamAssassin check is run with
5845 &`nobody`& as its user parameter, and the results are added to the message as a
5846 series of extra header line. In this case, the message is not rejected,
5847 whatever the spam score.
5851 This final line in the DATA ACL accepts the message unconditionally.
5854 .section "Router configuration" "SECID55"
5855 .cindex "default" "routers"
5856 .cindex "routers" "default"
5857 The router configuration comes next in the default configuration, introduced
5862 Routers are the modules in Exim that make decisions about where to send
5863 messages. An address is passed to each router in turn, until it is either
5864 accepted, or failed. This means that the order in which you define the routers
5865 matters. Each router is fully described in its own chapter later in this
5866 manual. Here we give only brief overviews.
5869 # driver = ipliteral
5870 # domains = !+local_domains
5871 # transport = remote_smtp
5873 .cindex "domain literal" "default router"
5874 This router is commented out because the majority of sites do not want to
5875 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5876 you uncomment this router, you also need to uncomment the setting of
5877 &%allow_domain_literals%& in the main part of the configuration.
5881 domains = ! +local_domains
5882 transport = remote_smtp
5883 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5886 The first uncommented router handles addresses that do not involve any local
5887 domains. This is specified by the line
5889 domains = ! +local_domains
5891 The &%domains%& option lists the domains to which this router applies, but the
5892 exclamation mark is a negation sign, so the router is used only for domains
5893 that are not in the domain list called &'local_domains'& (which was defined at
5894 the start of the configuration). The plus sign before &'local_domains'&
5895 indicates that it is referring to a named list. Addresses in other domains are
5896 passed on to the following routers.
5898 The name of the router driver is &(dnslookup)&,
5899 and is specified by the &%driver%& option. Do not be confused by the fact that
5900 the name of this router instance is the same as the name of the driver. The
5901 instance name is arbitrary, but the name set in the &%driver%& option must be
5902 one of the driver modules that is in the Exim binary.
5904 The &(dnslookup)& router routes addresses by looking up their domains in the
5905 DNS in order to obtain a list of hosts to which the address is routed. If the
5906 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5907 specified by the &%transport%& option. If the router does not find the domain
5908 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5909 the address fails and is bounced.
5911 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5912 be entirely ignored. This option is present because a number of cases have been
5913 encountered where MX records in the DNS point to host names
5914 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5915 Completely ignoring these IP addresses causes Exim to fail to route the
5916 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5917 continue to try to deliver the message periodically until the address timed
5924 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5926 file_transport = address_file
5927 pipe_transport = address_pipe
5929 Control reaches this and subsequent routers only for addresses in the local
5930 domains. This router checks to see whether the local part is defined as an
5931 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5932 data that it looks up from that file. If no data is found for the local part,
5933 the value of the &%data%& option is empty, causing the address to be passed to
5936 &_/etc/aliases_& is a conventional name for the system aliases file that is
5937 often used. That is why it is referenced by from the default configuration
5938 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5939 &_Local/Makefile_& before building Exim.
5944 # local_part_suffix = +* : -*
5945 # local_part_suffix_optional
5946 file = $home/.forward
5951 file_transport = address_file
5952 pipe_transport = address_pipe
5953 reply_transport = address_reply
5955 This is the most complicated router in the default configuration. It is another
5956 redirection router, but this time it is looking for forwarding data set up by
5957 individual users. The &%check_local_user%& setting specifies a check that the
5958 local part of the address is the login name of a local user. If it is not, the
5959 router is skipped. The two commented options that follow &%check_local_user%&,
5962 # local_part_suffix = +* : -*
5963 # local_part_suffix_optional
5965 .vindex "&$local_part_suffix$&"
5966 show how you can specify the recognition of local part suffixes. If the first
5967 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5968 by any sequence of characters, is removed from the local part and placed in the
5969 variable &$local_part_suffix$&. The second suffix option specifies that the
5970 presence of a suffix in the local part is optional. When a suffix is present,
5971 the check for a local login uses the local part with the suffix removed.
5973 When a local user account is found, the file called &_.forward_& in the user's
5974 home directory is consulted. If it does not exist, or is empty, the router
5975 declines. Otherwise, the contents of &_.forward_& are interpreted as
5976 redirection data (see chapter &<<CHAPredirect>>& for more details).
5978 .cindex "Sieve filter" "enabling in default router"
5979 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5980 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5981 is commented out by default), the contents of the file are interpreted as a set
5982 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5983 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5984 separate document entitled &'Exim's interfaces to mail filtering'&.
5986 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5987 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5988 There are two reasons for doing this:
5991 Whether or not a local user has a &_.forward_& file is not really relevant when
5992 checking an address for validity; it makes sense not to waste resources doing
5995 More importantly, when Exim is verifying addresses or handling an EXPN
5996 command during an SMTP session, it is running as the Exim user, not as root.
5997 The group is the Exim group, and no additional groups are set up.
5998 It may therefore not be possible for Exim to read users' &_.forward_& files at
6002 The setting of &%check_ancestor%& prevents the router from generating a new
6003 address that is the same as any previous address that was redirected. (This
6004 works round a problem concerning a bad interaction between aliasing and
6005 forwarding &-- see section &<<SECTredlocmai>>&).
6007 The final three option settings specify the transports that are to be used when
6008 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6009 auto-reply, respectively. For example, if a &_.forward_& file contains
6011 a.nother@elsewhere.example, /home/spqr/archive
6013 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6019 # local_part_suffix = +* : -*
6020 # local_part_suffix_optional
6021 transport = local_delivery
6023 The final router sets up delivery into local mailboxes, provided that the local
6024 part is the name of a local login, by accepting the address and assigning it to
6025 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6026 routers, so the address is bounced. The commented suffix settings fulfil the
6027 same purpose as they do for the &(userforward)& router.
6030 .section "Transport configuration" "SECID56"
6031 .cindex "default" "transports"
6032 .cindex "transports" "default"
6033 Transports define mechanisms for actually delivering messages. They operate
6034 only when referenced from routers, so the order in which they are defined does
6035 not matter. The transports section of the configuration starts with
6039 One remote transport and four local transports are defined.
6045 This transport is used for delivering messages over SMTP connections.
6046 The list of remote hosts comes from the router.
6047 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6048 It is negotiated between client and server
6049 and not expected to cause problems but can be disabled if needed.
6050 All other options are defaulted.
6054 file = /var/mail/$local_part
6061 This &(appendfile)& transport is used for local delivery to user mailboxes in
6062 traditional BSD mailbox format. By default it runs under the uid and gid of the
6063 local user, which requires the sticky bit to be set on the &_/var/mail_&
6064 directory. Some systems use the alternative approach of running mail deliveries
6065 under a particular group instead of using the sticky bit. The commented options
6066 show how this can be done.
6068 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6069 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6070 similarly-named options above.
6076 This transport is used for handling deliveries to pipes that are generated by
6077 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6078 option specifies that any output generated by the pipe is to be returned to the
6087 This transport is used for handling deliveries to files that are generated by
6088 redirection. The name of the file is not specified in this instance of
6089 &(appendfile)&, because it comes from the &(redirect)& router.
6094 This transport is used for handling automatic replies generated by users'
6099 .section "Default retry rule" "SECID57"
6100 .cindex "retry" "default rule"
6101 .cindex "default" "retry rule"
6102 The retry section of the configuration file contains rules which affect the way
6103 Exim retries deliveries that cannot be completed at the first attempt. It is
6104 introduced by the line
6108 In the default configuration, there is just one rule, which applies to all
6111 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6113 This causes any temporarily failing address to be retried every 15 minutes for
6114 2 hours, then at intervals starting at one hour and increasing by a factor of
6115 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6116 is not delivered after 4 days of temporary failure, it is bounced.
6118 If the retry section is removed from the configuration, or is empty (that is,
6119 if no retry rules are defined), Exim will not retry deliveries. This turns
6120 temporary errors into permanent errors.
6123 .section "Rewriting configuration" "SECID58"
6124 The rewriting section of the configuration, introduced by
6128 contains rules for rewriting addresses in messages as they arrive. There are no
6129 rewriting rules in the default configuration file.
6133 .section "Authenticators configuration" "SECTdefconfauth"
6134 .cindex "AUTH" "configuration"
6135 The authenticators section of the configuration, introduced by
6137 begin authenticators
6139 defines mechanisms for the use of the SMTP AUTH command. The default
6140 configuration file contains two commented-out example authenticators
6141 which support plaintext username/password authentication using the
6142 standard PLAIN mechanism and the traditional but non-standard LOGIN
6143 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6144 to support most MUA software.
6146 The example PLAIN authenticator looks like this:
6149 # driver = plaintext
6150 # server_set_id = $auth2
6151 # server_prompts = :
6152 # server_condition = Authentication is not yet configured
6153 # server_advertise_condition = ${if def:tls_in_cipher }
6155 And the example LOGIN authenticator looks like this:
6158 # driver = plaintext
6159 # server_set_id = $auth1
6160 # server_prompts = <| Username: | Password:
6161 # server_condition = Authentication is not yet configured
6162 # server_advertise_condition = ${if def:tls_in_cipher }
6165 The &%server_set_id%& option makes Exim remember the authenticated username
6166 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6167 &%server_prompts%& option configures the &(plaintext)& authenticator so
6168 that it implements the details of the specific authentication mechanism,
6169 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6170 when Exim offers authentication to clients; in the examples, this is only
6171 when TLS or SSL has been started, so to enable the authenticators you also
6172 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6174 The &%server_condition%& setting defines how to verify that the username and
6175 password are correct. In the examples it just produces an error message.
6176 To make the authenticators work, you can use a string expansion
6177 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6179 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6180 usercode and password are in different positions.
6181 Chapter &<<CHAPplaintext>>& covers both.
6183 .ecindex IIDconfiwal
6187 . ////////////////////////////////////////////////////////////////////////////
6188 . ////////////////////////////////////////////////////////////////////////////
6190 .chapter "Regular expressions" "CHAPregexp"
6192 .cindex "regular expressions" "library"
6194 Exim supports the use of regular expressions in many of its options. It
6195 uses the PCRE regular expression library; this provides regular expression
6196 matching that is compatible with Perl 5. The syntax and semantics of
6197 regular expressions is discussed in many Perl reference books, and also in
6198 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6199 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6201 The documentation for the syntax and semantics of the regular expressions that
6202 are supported by PCRE is included in the PCRE distribution, and no further
6203 description is included here. The PCRE functions are called from Exim using
6204 the default option settings (that is, with no PCRE options set), except that
6205 the PCRE_CASELESS option is set when the matching is required to be
6208 In most cases, when a regular expression is required in an Exim configuration,
6209 it has to start with a circumflex, in order to distinguish it from plain text
6210 or an &"ends with"& wildcard. In this example of a configuration setting, the
6211 second item in the colon-separated list is a regular expression.
6213 domains = a.b.c : ^\\d{3} : *.y.z : ...
6215 The doubling of the backslash is required because of string expansion that
6216 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6217 of this issue, and a way of avoiding the need for doubling backslashes. The
6218 regular expression that is eventually used in this example contains just one
6219 backslash. The circumflex is included in the regular expression, and has the
6220 normal effect of &"anchoring"& it to the start of the string that is being
6223 There are, however, two cases where a circumflex is not required for the
6224 recognition of a regular expression: these are the &%match%& condition in a
6225 string expansion, and the &%matches%& condition in an Exim filter file. In
6226 these cases, the relevant string is always treated as a regular expression; if
6227 it does not start with a circumflex, the expression is not anchored, and can
6228 match anywhere in the subject string.
6230 In all cases, if you want a regular expression to match at the end of a string,
6231 you must code the $ metacharacter to indicate this. For example:
6233 domains = ^\\d{3}\\.example
6235 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6238 domains = ^\\d{3}\\.example\$
6240 if you want &'example'& to be the top-level domain. The backslash before the
6241 $ is needed because string expansion also interprets dollar characters.
6245 . ////////////////////////////////////////////////////////////////////////////
6246 . ////////////////////////////////////////////////////////////////////////////
6248 .chapter "File and database lookups" "CHAPfdlookup"
6249 .scindex IIDfidalo1 "file" "lookups"
6250 .scindex IIDfidalo2 "database" "lookups"
6251 .cindex "lookup" "description of"
6252 Exim can be configured to look up data in files or databases as it processes
6253 messages. Two different kinds of syntax are used:
6256 A string that is to be expanded may contain explicit lookup requests. These
6257 cause parts of the string to be replaced by data that is obtained from the
6258 lookup. Lookups of this type are conditional expansion items. Different results
6259 can be defined for the cases of lookup success and failure. See chapter
6260 &<<CHAPexpand>>&, where string expansions are described in detail.
6262 Lists of domains, hosts, and email addresses can contain lookup requests as a
6263 way of avoiding excessively long linear lists. In this case, the data that is
6264 returned by the lookup is often (but not always) discarded; whether the lookup
6265 succeeds or fails is what really counts. These kinds of list are described in
6266 chapter &<<CHAPdomhosaddlists>>&.
6269 String expansions, lists, and lookups interact with each other in such a way
6270 that there is no order in which to describe any one of them that does not
6271 involve references to the others. Each of these three chapters makes more sense
6272 if you have read the other two first. If you are reading this for the first
6273 time, be aware that some of it will make a lot more sense after you have read
6274 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6276 .section "Examples of different lookup syntax" "SECID60"
6277 It is easy to confuse the two different kinds of lookup, especially as the
6278 lists that may contain the second kind are always expanded before being
6279 processed as lists. Therefore, they may also contain lookups of the first kind.
6280 Be careful to distinguish between the following two examples:
6282 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6283 domains = lsearch;/some/file
6285 The first uses a string expansion, the result of which must be a domain list.
6286 No strings have been specified for a successful or a failing lookup; the
6287 defaults in this case are the looked-up data and an empty string, respectively.
6288 The expansion takes place before the string is processed as a list, and the
6289 file that is searched could contain lines like this:
6291 192.168.3.4: domain1:domain2:...
6292 192.168.1.9: domain3:domain4:...
6294 When the lookup succeeds, the result of the expansion is a list of domains (and
6295 possibly other types of item that are allowed in domain lists).
6297 In the second example, the lookup is a single item in a domain list. It causes
6298 Exim to use a lookup to see if the domain that is being processed can be found
6299 in the file. The file could contains lines like this:
6304 Any data that follows the keys is not relevant when checking that the domain
6305 matches the list item.
6307 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6308 Consider a file containing lines like this:
6310 192.168.5.6: lsearch;/another/file
6312 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6313 first &%domains%& setting above generates the second setting, which therefore
6314 causes a second lookup to occur.
6316 The rest of this chapter describes the different lookup types that are
6317 available. Any of them can be used in any part of the configuration where a
6318 lookup is permitted.
6321 .section "Lookup types" "SECID61"
6322 .cindex "lookup" "types of"
6323 .cindex "single-key lookup" "definition of"
6324 Two different types of data lookup are implemented:
6327 The &'single-key'& type requires the specification of a file in which to look,
6328 and a single key to search for. The key must be a non-empty string for the
6329 lookup to succeed. The lookup type determines how the file is searched.
6331 .cindex "query-style lookup" "definition of"
6332 The &'query-style'& type accepts a generalized database query. No particular
6333 key value is assumed by Exim for query-style lookups. You can use whichever
6334 Exim variables you need to construct the database query.
6337 The code for each lookup type is in a separate source file that is included in
6338 the binary of Exim only if the corresponding compile-time option is set. The
6339 default settings in &_src/EDITME_& are:
6344 which means that only linear searching and DBM lookups are included by default.
6345 For some types of lookup (e.g. SQL databases), you need to install appropriate
6346 libraries and header files before building Exim.
6351 .section "Single-key lookup types" "SECTsinglekeylookups"
6352 .cindex "lookup" "single-key types"
6353 .cindex "single-key lookup" "list of types"
6354 The following single-key lookup types are implemented:
6357 .cindex "cdb" "description of"
6358 .cindex "lookup" "cdb"
6359 .cindex "binary zero" "in lookup key"
6360 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6361 string without a terminating binary zero. The cdb format is designed for
6362 indexed files that are read frequently and never updated, except by total
6363 re-creation. As such, it is particularly suitable for large files containing
6364 aliases or other indexed data referenced by an MTA. Information about cdb can
6365 be found in several places:
6367 &url(http://www.pobox.com/~djb/cdb.html)
6368 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6369 &url(http://packages.debian.org/stable/utils/freecdb.html)
6371 A cdb distribution is not needed in order to build Exim with cdb support,
6372 because the code for reading cdb files is included directly in Exim itself.
6373 However, no means of building or testing cdb files is provided with Exim, so
6374 you need to obtain a cdb distribution in order to do this.
6376 .cindex "DBM" "lookup type"
6377 .cindex "lookup" "dbm"
6378 .cindex "binary zero" "in lookup key"
6379 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6380 DBM file by looking up the record with the given key. A terminating binary
6381 zero is included in the key that is passed to the DBM library. See section
6382 &<<SECTdb>>& for a discussion of DBM libraries.
6384 .cindex "Berkeley DB library" "file format"
6385 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6386 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6387 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6388 the DB_UNKNOWN option. This enables it to handle any of the types of database
6389 that the library supports, and can be useful for accessing DBM files created by
6390 other applications. (For earlier DB versions, DB_HASH is always used.)
6392 .cindex "lookup" "dbmjz"
6393 .cindex "lookup" "dbm &-- embedded NULs"
6395 .cindex "dbmjz lookup type"
6396 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6397 interpreted as an Exim list; the elements of the list are joined together with
6398 ASCII NUL characters to form the lookup key. An example usage would be to
6399 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6400 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6401 &(cram_md5)& authenticator.
6403 .cindex "lookup" "dbmnz"
6404 .cindex "lookup" "dbm &-- terminating zero"
6405 .cindex "binary zero" "in lookup key"
6407 .cindex "&_/etc/userdbshadow.dat_&"
6408 .cindex "dbmnz lookup type"
6409 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6410 is not included in the key that is passed to the DBM library. You may need this
6411 if you want to look up data in files that are created by or shared with some
6412 other application that does not use terminating zeros. For example, you need to
6413 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6414 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6415 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6416 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6418 .cindex "lookup" "dsearch"
6419 .cindex "dsearch lookup type"
6420 &(dsearch)&: The given file must be a directory; this is searched for an entry
6421 whose name is the key by calling the &[lstat()]& function. The key may not
6422 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6423 the lookup is the name of the entry, which may be a file, directory,
6424 symbolic link, or any other kind of directory entry. An example of how this
6425 lookup can be used to support virtual domains is given in section
6426 &<<SECTvirtualdomains>>&.
6428 .cindex "lookup" "iplsearch"
6429 .cindex "iplsearch lookup type"
6430 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6431 terminated by a colon or white space or the end of the line. The keys in the
6432 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6433 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6434 being interpreted as a key terminator. For example:
6436 1.2.3.4: data for 1.2.3.4
6437 192.168.0.0/16: data for 192.168.0.0/16
6438 "abcd::cdab": data for abcd::cdab
6439 "abcd:abcd::/32" data for abcd:abcd::/32
6441 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6442 file is searched linearly, using the CIDR masks where present, until a matching
6443 key is found. The first key that matches is used; there is no attempt to find a
6444 &"best"& match. Apart from the way the keys are matched, the processing for
6445 &(iplsearch)& is the same as for &(lsearch)&.
6447 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6448 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6449 lookup types support only literal keys.
6451 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6452 the implicit key is the host's IP address rather than its name (see section
6453 &<<SECThoslispatsikey>>&).
6455 .cindex "linear search"
6456 .cindex "lookup" "lsearch"
6457 .cindex "lsearch lookup type"
6458 .cindex "case sensitivity" "in lsearch lookup"
6459 &(lsearch)&: The given file is a text file that is searched linearly for a
6460 line beginning with the search key, terminated by a colon or white space or the
6461 end of the line. The search is case-insensitive; that is, upper and lower case
6462 letters are treated as the same. The first occurrence of the key that is found
6463 in the file is used.
6465 White space between the key and the colon is permitted. The remainder of the
6466 line, with leading and trailing white space removed, is the data. This can be
6467 continued onto subsequent lines by starting them with any amount of white
6468 space, but only a single space character is included in the data at such a
6469 junction. If the data begins with a colon, the key must be terminated by a
6474 Empty lines and lines beginning with # are ignored, even if they occur in the
6475 middle of an item. This is the traditional textual format of alias files. Note
6476 that the keys in an &(lsearch)& file are literal strings. There is no
6477 wildcarding of any kind.
6479 .cindex "lookup" "lsearch &-- colons in keys"
6480 .cindex "white space" "in lsearch key"
6481 In most &(lsearch)& files, keys are not required to contain colons or #
6482 characters, or white space. However, if you need this feature, it is available.
6483 If a key begins with a doublequote character, it is terminated only by a
6484 matching quote (or end of line), and the normal escaping rules apply to its
6485 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6486 quoted keys (exactly as for unquoted keys). There is no special handling of
6487 quotes for the data part of an &(lsearch)& line.
6490 .cindex "NIS lookup type"
6491 .cindex "lookup" "NIS"
6492 .cindex "binary zero" "in lookup key"
6493 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6494 the given key, without a terminating binary zero. There is a variant called
6495 &(nis0)& which does include the terminating binary zero in the key. This is
6496 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6497 aliases; the full map names must be used.
6500 .cindex "wildlsearch lookup type"
6501 .cindex "lookup" "wildlsearch"
6502 .cindex "nwildlsearch lookup type"
6503 .cindex "lookup" "nwildlsearch"
6504 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6505 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6506 the file may be wildcarded. The difference between these two lookup types is
6507 that for &(wildlsearch)&, each key in the file is string-expanded before being
6508 used, whereas for &(nwildlsearch)&, no expansion takes place.
6510 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6511 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6512 file that are regular expressions can be made case-sensitive by the use of
6513 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6515 . ==== As this is a nested list, any displays it contains must be indented
6516 . ==== as otherwise they are too far to the left.
6519 The string may begin with an asterisk to mean &"ends with"&. For example:
6521 *.a.b.c data for anything.a.b.c
6522 *fish data for anythingfish
6525 The string may begin with a circumflex to indicate a regular expression. For
6526 example, for &(wildlsearch)&:
6528 ^\N\d+\.a\.b\N data for <digits>.a.b
6530 Note the use of &`\N`& to disable expansion of the contents of the regular
6531 expression. If you are using &(nwildlsearch)&, where the keys are not
6532 string-expanded, the equivalent entry is:
6534 ^\d+\.a\.b data for <digits>.a.b
6536 The case-insensitive flag is set at the start of compiling the regular
6537 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6538 For example, to make the entire pattern case-sensitive:
6540 ^(?-i)\d+\.a\.b data for <digits>.a.b
6543 If the regular expression contains white space or colon characters, you must
6544 either quote it (see &(lsearch)& above), or represent these characters in other
6545 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6546 colon. This may be easier than quoting, because if you quote, you have to
6547 escape all the backslashes inside the quotes.
6549 &*Note*&: It is not possible to capture substrings in a regular expression
6550 match for later use, because the results of all lookups are cached. If a lookup
6551 is repeated, the result is taken from the cache, and no actual pattern matching
6552 takes place. The values of all the numeric variables are unset after a
6553 &((n)wildlsearch)& match.
6556 Although I cannot see it being of much use, the general matching function that
6557 is used to implement &((n)wildlsearch)& means that the string may begin with a
6558 lookup name terminated by a semicolon, and followed by lookup data. For
6561 cdb;/some/file data for keys that match the file
6563 The data that is obtained from the nested lookup is discarded.
6566 Keys that do not match any of these patterns are interpreted literally. The
6567 continuation rules for the data are the same as for &(lsearch)&, and keys may
6568 be followed by optional colons.
6570 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6571 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6572 lookup types support only literal keys.
6576 .section "Query-style lookup types" "SECID62"
6577 .cindex "lookup" "query-style types"
6578 .cindex "query-style lookup" "list of types"
6579 The supported query-style lookup types are listed below. Further details about
6580 many of them are given in later sections.
6583 .cindex "DNS" "as a lookup type"
6584 .cindex "lookup" "DNS"
6585 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6586 are given in the supplied query. The resulting data is the contents of the
6587 records. See section &<<SECTdnsdb>>&.
6589 .cindex "InterBase lookup type"
6590 .cindex "lookup" "InterBase"
6591 &(ibase)&: This does a lookup in an InterBase database.
6593 .cindex "LDAP" "lookup type"
6594 .cindex "lookup" "LDAP"
6595 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6596 returns attributes from a single entry. There is a variant called &(ldapm)&
6597 that permits values from multiple entries to be returned. A third variant
6598 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6599 any attribute values. See section &<<SECTldap>>&.
6601 .cindex "MySQL" "lookup type"
6602 .cindex "lookup" "MySQL"
6603 &(mysql)&: The format of the query is an SQL statement that is passed to a
6604 MySQL database. See section &<<SECTsql>>&.
6606 .cindex "NIS+ lookup type"
6607 .cindex "lookup" "NIS+"
6608 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6609 the field to be returned. See section &<<SECTnisplus>>&.
6611 .cindex "Oracle" "lookup type"
6612 .cindex "lookup" "Oracle"
6613 &(oracle)&: The format of the query is an SQL statement that is passed to an
6614 Oracle database. See section &<<SECTsql>>&.
6616 .cindex "lookup" "passwd"
6617 .cindex "passwd lookup type"
6618 .cindex "&_/etc/passwd_&"
6619 &(passwd)& is a query-style lookup with queries that are just user names. The
6620 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6621 success, the result string is the same as you would get from an &(lsearch)&
6622 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6623 password value. For example:
6625 *:42:42:King Rat:/home/kr:/bin/bash
6628 .cindex "PostgreSQL lookup type"
6629 .cindex "lookup" "PostgreSQL"
6630 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6631 PostgreSQL database. See section &<<SECTsql>>&.
6634 .cindex "sqlite lookup type"
6635 .cindex "lookup" "sqlite"
6636 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6637 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6640 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6641 not likely to be useful in normal operation.
6643 .cindex "whoson lookup type"
6644 .cindex "lookup" "whoson"
6645 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6646 allows a server to check whether a particular (dynamically allocated) IP
6647 address is currently allocated to a known (trusted) user and, optionally, to
6648 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6649 at one time for &"POP before SMTP"& authentication, but that approach has been
6650 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6651 &"POP before SMTP"& checking using ACL statements such as
6653 require condition = \
6654 ${lookup whoson {$sender_host_address}{yes}{no}}
6656 The query consists of a single IP address. The value returned is the name of
6657 the authenticated user, which is stored in the variable &$value$&. However, in
6658 this example, the data in &$value$& is not used; the result of the lookup is
6659 one of the fixed strings &"yes"& or &"no"&.
6664 .section "Temporary errors in lookups" "SECID63"
6665 .cindex "lookup" "temporary error in"
6666 Lookup functions can return temporary error codes if the lookup cannot be
6667 completed. For example, an SQL or LDAP database might be unavailable. For this
6668 reason, it is not advisable to use a lookup that might do this for critical
6669 options such as a list of local domains.
6671 When a lookup cannot be completed in a router or transport, delivery
6672 of the message (to the relevant address) is deferred, as for any other
6673 temporary error. In other circumstances Exim may assume the lookup has failed,
6674 or may give up altogether.
6678 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6679 .cindex "wildcard lookups"
6680 .cindex "lookup" "default values"
6681 .cindex "lookup" "wildcard"
6682 .cindex "lookup" "* added to type"
6683 .cindex "default" "in single-key lookups"
6684 In this context, a &"default value"& is a value specified by the administrator
6685 that is to be used if a lookup fails.
6687 &*Note:*& This section applies only to single-key lookups. For query-style
6688 lookups, the facilities of the query language must be used. An attempt to
6689 specify a default for a query-style lookup provokes an error.
6691 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6692 and the initial lookup fails, the key &"*"& is looked up in the file to
6693 provide a default value. See also the section on partial matching below.
6695 .cindex "*@ with single-key lookup"
6696 .cindex "lookup" "*@ added to type"
6697 .cindex "alias file" "per-domain default"
6698 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6699 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6700 character, a second lookup is done with everything before the last @ replaced
6701 by *. This makes it possible to provide per-domain defaults in alias files
6702 that include the domains in the keys. If the second lookup fails (or doesn't
6703 take place because there is no @ in the key), &"*"& is looked up.
6704 For example, a &(redirect)& router might contain:
6706 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6708 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6709 looks up these keys, in this order:
6715 The data is taken from whichever key it finds first. &*Note*&: In an
6716 &(lsearch)& file, this does not mean the first of these keys in the file. A
6717 complete scan is done for each key, and only if it is not found at all does
6718 Exim move on to try the next key.
6722 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6723 .cindex "partial matching"
6724 .cindex "wildcard lookups"
6725 .cindex "lookup" "partial matching"
6726 .cindex "lookup" "wildcard"
6727 .cindex "asterisk" "in search type"
6728 The normal operation of a single-key lookup is to search the file for an exact
6729 match with the given key. However, in a number of situations where domains are
6730 being looked up, it is useful to be able to do partial matching. In this case,
6731 information in the file that has a key starting with &"*."& is matched by any
6732 domain that ends with the components that follow the full stop. For example, if
6733 a key in a DBM file is
6735 *.dates.fict.example
6737 then when partial matching is enabled this is matched by (amongst others)
6738 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6739 by &'dates.fict.example'&, if that does not appear as a separate key in the
6742 &*Note*&: Partial matching is not available for query-style lookups. It is
6743 also not available for any lookup items in address lists (see section
6744 &<<SECTaddresslist>>&).
6746 Partial matching is implemented by doing a series of separate lookups using
6747 keys constructed by modifying the original subject key. This means that it can
6748 be used with any of the single-key lookup types, provided that
6749 partial matching keys
6750 beginning with a special prefix (default &"*."&) are included in the data file.
6751 Keys in the file that do not begin with the prefix are matched only by
6752 unmodified subject keys when partial matching is in use.
6754 Partial matching is requested by adding the string &"partial-"& to the front of
6755 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6756 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6757 is added at the start of the subject key, and it is looked up again. If that
6758 fails, further lookups are tried with dot-separated components removed from the
6759 start of the subject key, one-by-one, and &"*."& added on the front of what
6762 A minimum number of two non-* components are required. This can be adjusted
6763 by including a number before the hyphen in the search type. For example,
6764 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6765 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6766 subject key is &'2250.dates.fict.example'& then the following keys are looked
6767 up when the minimum number of non-* components is two:
6769 2250.dates.fict.example
6770 *.2250.dates.fict.example
6771 *.dates.fict.example
6774 As soon as one key in the sequence is successfully looked up, the lookup
6777 .cindex "lookup" "partial matching &-- changing prefix"
6778 .cindex "prefix" "for partial matching"
6779 The use of &"*."& as the partial matching prefix is a default that can be
6780 changed. The motivation for this feature is to allow Exim to operate with file
6781 formats that are used by other MTAs. A different prefix can be supplied in
6782 parentheses instead of the hyphen after &"partial"&. For example:
6784 domains = partial(.)lsearch;/some/file
6786 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6787 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6788 components is unchanged). The prefix may consist of any punctuation characters
6789 other than a closing parenthesis. It may be empty, for example:
6791 domains = partial1()cdb;/some/file
6793 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6794 &`a.b.c`&, &`b.c`&, and &`c`&.
6796 If &"partial0"& is specified, what happens at the end (when the lookup with
6797 just one non-wild component has failed, and the original key is shortened right
6798 down to the null string) depends on the prefix:
6801 If the prefix has zero length, the whole lookup fails.
6803 If the prefix has length 1, a lookup for just the prefix is done. For
6804 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6806 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6807 remainder is looked up. With the default prefix, therefore, the final lookup is
6808 for &"*"& on its own.
6810 Otherwise, the whole prefix is looked up.
6814 If the search type ends in &"*"& or &"*@"& (see section
6815 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6816 this implies happens after all partial lookups have failed. If &"partial0"& is
6817 specified, adding &"*"& to the search type has no effect with the default
6818 prefix, because the &"*"& key is already included in the sequence of partial
6819 lookups. However, there might be a use for lookup types such as
6820 &"partial0(.)lsearch*"&.
6822 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6823 in domain lists and the like. Partial matching works only in terms of
6824 dot-separated components; a key such as &`*fict.example`&
6825 in a database file is useless, because the asterisk in a partial matching
6826 subject key is always followed by a dot.
6831 .section "Lookup caching" "SECID64"
6832 .cindex "lookup" "caching"
6833 .cindex "caching" "lookup data"
6834 Exim caches all lookup results in order to avoid needless repetition of
6835 lookups. However, because (apart from the daemon) Exim operates as a collection
6836 of independent, short-lived processes, this caching applies only within a
6837 single Exim process. There is no inter-process lookup caching facility.
6839 For single-key lookups, Exim keeps the relevant files open in case there is
6840 another lookup that needs them. In some types of configuration this can lead to
6841 many files being kept open for messages with many recipients. To avoid hitting
6842 the operating system limit on the number of simultaneously open files, Exim
6843 closes the least recently used file when it needs to open more files than its
6844 own internal limit, which can be changed via the &%lookup_open_max%& option.
6846 The single-key lookup files are closed and the lookup caches are flushed at
6847 strategic points during delivery &-- for example, after all routing is
6853 .section "Quoting lookup data" "SECID65"
6854 .cindex "lookup" "quoting"
6855 .cindex "quoting" "in lookups"
6856 When data from an incoming message is included in a query-style lookup, there
6857 is the possibility of special characters in the data messing up the syntax of
6858 the query. For example, a NIS+ query that contains
6862 will be broken if the local part happens to contain a closing square bracket.
6863 For NIS+, data can be enclosed in double quotes like this:
6865 [name="$local_part"]
6867 but this still leaves the problem of a double quote in the data. The rule for
6868 NIS+ is that double quotes must be doubled. Other lookup types have different
6869 rules, and to cope with the differing requirements, an expansion operator
6870 of the following form is provided:
6872 ${quote_<lookup-type>:<string>}
6874 For example, the safest way to write the NIS+ query is
6876 [name="${quote_nisplus:$local_part}"]
6878 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6879 operator can be used for all lookup types, but has no effect for single-key
6880 lookups, since no quoting is ever needed in their key strings.
6885 .section "More about dnsdb" "SECTdnsdb"
6886 .cindex "dnsdb lookup"
6887 .cindex "lookup" "dnsdb"
6888 .cindex "DNS" "as a lookup type"
6889 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6890 of a record type and a domain name, separated by an equals sign. For example,
6891 an expansion string could contain:
6893 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6895 If the lookup succeeds, the result is placed in &$value$&, which in this case
6896 is used on its own as the result. If the lookup does not succeed, the
6897 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6898 &<<SECTforexpfai>>& for an explanation of what this means.
6901 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
6902 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
6903 If no type is given, TXT is assumed.
6906 For any record type, if multiple records are found, the data is returned as a
6907 concatenation, with newline as the default separator. The order, of course,
6908 depends on the DNS resolver. You can specify a different separator character
6909 between multiple records by putting a right angle-bracket followed immediately
6910 by the new separator at the start of the query. For example:
6912 ${lookup dnsdb{>: a=host1.example}}
6914 It is permitted to specify a space as the separator character. Further
6915 white space is ignored.
6916 For lookup types that return multiple fields per record,
6917 an alternate field separator can be specified using a comma after the main
6918 separator character, followed immediately by the field separator.
6920 .cindex "PTR record" "in &(dnsdb)& lookup"
6921 When the type is PTR,
6922 the data can be an IP address, written as normal; inversion and the addition of
6923 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6925 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6927 If the data for a PTR record is not a syntactically valid IP address, it is not
6928 altered and nothing is added.
6930 .cindex "MX record" "in &(dnsdb)& lookup"
6931 .cindex "SRV record" "in &(dnsdb)& lookup"
6932 For an MX lookup, both the preference value and the host name are returned for
6933 each record, separated by a space. For an SRV lookup, the priority, weight,
6934 port, and host name are returned for each record, separated by spaces.
6935 The field separator can be modified as above.
6937 .cindex "TXT record" "in &(dnsdb)& lookup"
6938 .cindex "SPF record" "in &(dnsdb)& lookup"
6939 For TXT records with multiple items of data, only the first item is returned,
6940 unless a field separator is specified.
6941 To concatenate items without a separator, use a semicolon instead.
6943 default behaviour is to concatenate multiple items without using a separator.
6945 ${lookup dnsdb{>\n,: txt=a.b.example}}
6946 ${lookup dnsdb{>\n; txt=a.b.example}}
6947 ${lookup dnsdb{spf=example.org}}
6949 It is permitted to specify a space as the separator character. Further
6950 white space is ignored.
6953 .cindex "SOA record" "in &(dnsdb)& lookup"
6954 For an SOA lookup, while no result is obtained the lookup is redone with
6955 successively more leading components dropped from the given domain.
6956 Only the primary-nameserver field is returned unless a field separator is
6959 ${lookup dnsdb{>:,; soa=a.b.example.com}}
6963 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
6964 .cindex "dnsdb modifiers"
6965 .cindex "modifiers" "dnsdb"
6966 .cindex "options" "dnsdb"
6967 Modifiers for &(dnsdb)& lookups are given by optional keywords,
6968 each followed by a comma,
6969 that may appear before the record type.
6971 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6972 temporary DNS error for any of them, the behaviour is controlled by
6973 a defer-option modifier.
6974 The possible keywords are
6975 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6976 With &"strict"& behaviour, any temporary DNS error causes the
6977 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6978 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6979 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6980 error causes the whole lookup to defer only if none of the other lookups
6981 succeed. The default is &"lax"&, so the following lookups are equivalent:
6983 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6984 ${lookup dnsdb{a=one.host.com:two.host.com}}
6986 Thus, in the default case, as long as at least one of the DNS lookups
6987 yields some data, the lookup succeeds.
6989 .cindex "DNSSEC" "dns lookup"
6990 Use of &(DNSSEC)& is controlled by a dnssec modifier.
6991 The possible keywords are
6992 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
6993 With &"strict"& or &"lax"& DNSSEC information is requested
6995 With &"strict"& a response from the DNS resolver that
6996 is not labelled as authenticated data
6997 is treated as equivalent to a temporary DNS error.
6998 The default is &"never"&.
7000 See also the &$lookup_dnssec_authenticated$& variable.
7003 .cindex timeout "dns lookup"
7004 .cindex "DNS" timeout
7005 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7006 The form is &"retrans_VAL"& where VAL is an Exim time specification
7008 The default value is set by the main configuration option &%dns_retrans%&.
7010 Retries for the dnsdb lookup can be controlled by a retry modifier.
7011 The form if &"retry_VAL"& where VAL is an integer.
7012 The default count is set by the main configuration option &%dns_retry%&.
7016 .section "Pseudo dnsdb record types" "SECID66"
7017 .cindex "MX record" "in &(dnsdb)& lookup"
7018 By default, both the preference value and the host name are returned for
7019 each MX record, separated by a space. If you want only host names, you can use
7020 the pseudo-type MXH:
7022 ${lookup dnsdb{mxh=a.b.example}}
7024 In this case, the preference values are omitted, and just the host names are
7027 .cindex "name server for enclosing domain"
7028 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7029 records on the given domain, but if none are found, it removes the first
7030 component of the domain name, and tries again. This process continues until NS
7031 records are found or there are no more components left (or there is a DNS
7032 error). In other words, it may return the name servers for a top-level domain,
7033 but it never returns the root name servers. If there are no NS records for the
7034 top-level domain, the lookup fails. Consider these examples:
7036 ${lookup dnsdb{zns=xxx.quercite.com}}
7037 ${lookup dnsdb{zns=xxx.edu}}
7039 Assuming that in each case there are no NS records for the full domain name,
7040 the first returns the name servers for &%quercite.com%&, and the second returns
7041 the name servers for &%edu%&.
7043 You should be careful about how you use this lookup because, unless the
7044 top-level domain does not exist, the lookup always returns some host names. The
7045 sort of use to which this might be put is for seeing if the name servers for a
7046 given domain are on a blacklist. You can probably assume that the name servers
7047 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7050 .cindex "CSA" "in &(dnsdb)& lookup"
7051 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7052 records according to the CSA rules, which are described in section
7053 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7054 not sufficient because of the extra parent domain search behaviour of CSA. The
7055 result of a successful lookup such as:
7057 ${lookup dnsdb {csa=$sender_helo_name}}
7059 has two space-separated fields: an authorization code and a target host name.
7060 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7061 authorization required but absent, or &"?"& for unknown.
7063 .cindex "A+" "in &(dnsdb)& lookup"
7064 The pseudo-type A+ performs an AAAA
7065 and then an A lookup. All results are returned; defer processing
7066 (see below) is handled separately for each lookup. Example:
7068 ${lookup dnsdb {>; a+=$sender_helo_name}}
7072 .section "Multiple dnsdb lookups" "SECID67"
7073 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7074 However, you can specify a list of domains or IP addresses in a single
7075 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7076 the default separator, but with the ability to change this. For example:
7078 ${lookup dnsdb{one.domain.com:two.domain.com}}
7079 ${lookup dnsdb{a=one.host.com:two.host.com}}
7080 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7082 In order to retain backwards compatibility, there is one special case: if
7083 the lookup type is PTR and no change of separator is specified, Exim looks
7084 to see if the rest of the string is precisely one IPv6 address. In this
7085 case, it does not treat it as a list.
7087 The data from each lookup is concatenated, with newline separators by default,
7088 in the same way that multiple DNS records for a single item are handled. A
7089 different separator can be specified, as described above.
7094 .section "More about LDAP" "SECTldap"
7095 .cindex "LDAP" "lookup, more about"
7096 .cindex "lookup" "LDAP"
7097 .cindex "Solaris" "LDAP"
7098 The original LDAP implementation came from the University of Michigan; this has
7099 become &"Open LDAP"&, and there are now two different releases. Another
7100 implementation comes from Netscape, and Solaris 7 and subsequent releases
7101 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7102 the lookup function level, their error handling is different. For this reason
7103 it is necessary to set a compile-time variable when building Exim with LDAP, to
7104 indicate which LDAP library is in use. One of the following should appear in
7105 your &_Local/Makefile_&:
7107 LDAP_LIB_TYPE=UMICHIGAN
7108 LDAP_LIB_TYPE=OPENLDAP1
7109 LDAP_LIB_TYPE=OPENLDAP2
7110 LDAP_LIB_TYPE=NETSCAPE
7111 LDAP_LIB_TYPE=SOLARIS
7113 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7114 same interface as the University of Michigan version.
7116 There are three LDAP lookup types in Exim. These behave slightly differently in
7117 the way they handle the results of a query:
7120 &(ldap)& requires the result to contain just one entry; if there are more, it
7123 &(ldapdn)& also requires the result to contain just one entry, but it is the
7124 Distinguished Name that is returned rather than any attribute values.
7126 &(ldapm)& permits the result to contain more than one entry; the attributes
7127 from all of them are returned.
7131 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7132 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7133 the data returned by a successful lookup is described in the next section.
7134 First we explain how LDAP queries are coded.
7137 .section "Format of LDAP queries" "SECTforldaque"
7138 .cindex "LDAP" "query format"
7139 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7140 the configuration of a &(redirect)& router one might have this setting:
7142 data = ${lookup ldap \
7143 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7144 c=UK?mailbox?base?}}
7146 .cindex "LDAP" "with TLS"
7147 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7148 secure (encrypted) LDAP connections. The second of these ensures that an
7149 encrypted TLS connection is used.
7151 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7152 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7153 See the &%ldap_start_tls%& option.
7155 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7156 controlled. Every part of the TLS configuration can be configured by settings in
7157 &_exim.conf_&. Depending on the version of the client libraries installed on
7158 your system, some of the initialization may have required setting options in
7159 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7160 certificates. This revealed a nuance where the current UID that exim was
7161 running as could affect which config files it read. With Exim 4.83, these
7162 methods become optional, only taking effect if not specifically set in
7166 .section "LDAP quoting" "SECID68"
7167 .cindex "LDAP" "quoting"
7168 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7169 and the second because the LDAP query is represented as a URL. Furthermore,
7170 within an LDAP query, two different kinds of quoting are required. For this
7171 reason, there are two different LDAP-specific quoting operators.
7173 The &%quote_ldap%& operator is designed for use on strings that are part of
7174 filter specifications. Conceptually, it first does the following conversions on
7182 in accordance with RFC 2254. The resulting string is then quoted according
7183 to the rules for URLs, that is, all non-alphanumeric characters except
7187 are converted to their hex values, preceded by a percent sign. For example:
7189 ${quote_ldap: a(bc)*, a<yz>; }
7193 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7195 Removing the URL quoting, this is (with a leading and a trailing space):
7197 a\28bc\29\2A, a<yz>;
7199 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7200 base DN specifications in queries. Conceptually, it first converts the string
7201 by inserting a backslash in front of any of the following characters:
7205 It also inserts a backslash before any leading spaces or # characters, and
7206 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7207 is then quoted according to the rules for URLs. For example:
7209 ${quote_ldap_dn: a(bc)*, a<yz>; }
7213 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7215 Removing the URL quoting, this is (with a trailing space):
7217 \ a(bc)*\, a\<yz\>\;\
7219 There are some further comments about quoting in the section on LDAP
7220 authentication below.
7223 .section "LDAP connections" "SECID69"
7224 .cindex "LDAP" "connections"
7225 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7226 is in use, via a Unix domain socket. The example given above does not specify
7227 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7230 ldap://<hostname>:<port>/...
7232 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7233 used. When no server is specified in a query, a list of default servers is
7234 taken from the &%ldap_default_servers%& configuration option. This supplies a
7235 colon-separated list of servers which are tried in turn until one successfully
7236 handles a query, or there is a serious error. Successful handling either
7237 returns the requested data, or indicates that it does not exist. Serious errors
7238 are syntactical, or multiple values when only a single value is expected.
7239 Errors which cause the next server to be tried are connection failures, bind
7240 failures, and timeouts.
7242 For each server name in the list, a port number can be given. The standard way
7243 of specifying a host and port is to use a colon separator (RFC 1738). Because
7244 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7245 doubled. For example
7247 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7249 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7250 to the LDAP library with no server name, and the library's default (normally
7251 the local host) is used.
7253 If you are using the OpenLDAP library, you can connect to an LDAP server using
7254 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7255 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7256 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7259 For this type of connection, instead of a host name for the server, a pathname
7260 for the socket is required, and the port number is not relevant. The pathname
7261 can be specified either as an item in &%ldap_default_servers%&, or inline in
7262 the query. In the former case, you can have settings such as
7264 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7266 When the pathname is given in the query, you have to escape the slashes as
7267 &`%2F`& to fit in with the LDAP URL syntax. For example:
7269 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7271 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7272 a pathname, it uses the Unix domain socket code, even if the query actually
7273 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7274 socket connection. This behaviour means that you can use a setting of
7275 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7276 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7277 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7280 If an explicit &`ldapi`& type is given in a query when a host name is
7281 specified, an error is diagnosed. However, if there are more items in
7282 &%ldap_default_servers%&, they are tried. In other words:
7285 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7288 Using &`ldapi`& with a host name causes an error.
7292 Using &`ldapi`& with no host or path in the query, and no setting of
7293 &%ldap_default_servers%&, does whatever the library does by default.
7297 .section "LDAP authentication and control information" "SECID70"
7298 .cindex "LDAP" "authentication"
7299 The LDAP URL syntax provides no way of passing authentication and other control
7300 information to the server. To make this possible, the URL in an LDAP query may
7301 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7302 spaces. If a value contains spaces it must be enclosed in double quotes, and
7303 when double quotes are used, backslash is interpreted in the usual way inside
7304 them. The following names are recognized:
7306 &`DEREFERENCE`& set the dereferencing parameter
7307 &`NETTIME `& set a timeout for a network operation
7308 &`USER `& set the DN, for authenticating the LDAP bind
7309 &`PASS `& set the password, likewise
7310 &`REFERRALS `& set the referrals parameter
7311 &`SERVERS `& set alternate server list for this query only
7312 &`SIZE `& set the limit for the number of entries returned
7313 &`TIME `& set the maximum waiting time for a query
7315 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7316 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7317 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7318 library from trying to follow referrals issued by the LDAP server.
7320 The name CONNECT is an obsolete name for NETTIME, retained for
7321 backwards compatibility. This timeout (specified as a number of seconds) is
7322 enforced from the client end for operations that can be carried out over a
7323 network. Specifically, it applies to network connections and calls to the
7324 &'ldap_result()'& function. If the value is greater than zero, it is used if
7325 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7326 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7327 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7328 Netscape SDK; for OpenLDAP no action is taken.
7330 The TIME parameter (also a number of seconds) is passed to the server to
7331 set a server-side limit on the time taken to complete a search.
7333 The SERVERS parameter allows you to specify an alternate list of ldap servers
7334 to use for an individual lookup. The global ldap_servers option provides a
7335 default list of ldap servers, and a single lookup can specify a single ldap
7336 server to use. But when you need to do a lookup with a list of servers that is
7337 different than the default list (maybe different order, maybe a completely
7338 different set of servers), the SERVERS parameter allows you to specify this
7339 alternate list (colon-separated).
7341 Here is an example of an LDAP query in an Exim lookup that uses some of these
7342 values. This is a single line, folded to fit on the page:
7345 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7346 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7349 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7350 any of the auxiliary data. Exim configuration settings that include lookups
7351 which contain password information should be preceded by &"hide"& to prevent
7352 non-admin users from using the &%-bP%& option to see their values.
7354 The auxiliary data items may be given in any order. The default is no
7355 connection timeout (the system timeout is used), no user or password, no limit
7356 on the number of entries returned, and no time limit on queries.
7358 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7359 removes any URL quoting that it may contain before passing it LDAP. Apparently
7360 some libraries do this for themselves, but some do not. Removing the URL
7361 quoting has two advantages:
7364 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7365 DNs as with DNs inside actual queries.
7367 It permits spaces inside USER= DNs.
7370 For example, a setting such as
7372 USER=cn=${quote_ldap_dn:$1}
7374 should work even if &$1$& contains spaces.
7376 Expanded data for the PASS= value should be quoted using the &%quote%&
7377 expansion operator, rather than the LDAP quote operators. The only reason this
7378 field needs quoting is to ensure that it conforms to the Exim syntax, which
7379 does not allow unquoted spaces. For example:
7383 The LDAP authentication mechanism can be used to check passwords as part of
7384 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7389 .section "Format of data returned by LDAP" "SECID71"
7390 .cindex "LDAP" "returned data formats"
7391 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7392 as a sequence of values, for example
7394 cn=manager, o=University of Cambridge, c=UK
7396 The &(ldap)& lookup type generates an error if more than one entry matches the
7397 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7398 the result between the data from different entries. It is possible for multiple
7399 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7400 you know that whatever values are returned all came from a single entry in the
7403 In the common case where you specify a single attribute in your LDAP query, the
7404 result is not quoted, and does not contain the attribute name. If the attribute
7405 has multiple values, they are separated by commas.
7407 If you specify multiple attributes, the result contains space-separated, quoted
7408 strings, each preceded by the attribute name and an equals sign. Within the
7409 quotes, the quote character, backslash, and newline are escaped with
7410 backslashes, and commas are used to separate multiple values for the attribute.
7411 Any commas in attribute values are doubled
7412 (permitting treatment of the values as a comma-separated list).
7413 Apart from the escaping, the string within quotes takes the same form as the
7414 output when a single attribute is requested. Specifying no attributes is the
7415 same as specifying all of an entry's attributes.
7417 Here are some examples of the output format. The first line of each pair is an
7418 LDAP query, and the second is the data that is returned. The attribute called
7419 &%attr1%& has two values, one of them with an embedded comma, whereas
7420 &%attr2%& has only one value:
7422 ldap:///o=base?attr1?sub?(uid=fred)
7425 ldap:///o=base?attr2?sub?(uid=fred)
7428 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7429 attr1="value1.1,value1,,2" attr2="value two"
7431 ldap:///o=base??sub?(uid=fred)
7432 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7435 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7436 results of LDAP lookups.
7437 The &%extract%& operator in string expansions can be used to pick out
7438 individual fields from data that consists of &'key'&=&'value'& pairs.
7439 The &%listextract%& operator should be used to pick out individual values
7440 of attributes, even when only a single value is expected.
7441 The doubling of embedded commas allows you to use the returned data as a
7442 comma separated list (using the "<," syntax for changing the input list separator).
7447 .section "More about NIS+" "SECTnisplus"
7448 .cindex "NIS+ lookup type"
7449 .cindex "lookup" "NIS+"
7450 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7451 and field name. If this is given, the result of a successful query is the
7452 contents of the named field; otherwise the result consists of a concatenation
7453 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7454 values containing spaces are quoted. For example, the query
7456 [name=mg1456],passwd.org_dir
7458 might return the string
7460 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7461 home=/home/mg1456 shell=/bin/bash shadow=""
7463 (split over two lines here to fit on the page), whereas
7465 [name=mg1456],passwd.org_dir:gcos
7471 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7472 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7473 operator is to double any quote characters within the text.
7477 .section "SQL lookups" "SECTsql"
7478 .cindex "SQL lookup types"
7479 .cindex "MySQL" "lookup type"
7480 .cindex "PostgreSQL lookup type"
7481 .cindex "lookup" "MySQL"
7482 .cindex "lookup" "PostgreSQL"
7483 .cindex "Oracle" "lookup type"
7484 .cindex "lookup" "Oracle"
7485 .cindex "InterBase lookup type"
7486 .cindex "lookup" "InterBase"
7487 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7488 databases. Queries for these databases contain SQL statements, so an example
7491 ${lookup mysql{select mailbox from users where id='userx'}\
7494 If the result of the query contains more than one field, the data for each
7495 field in the row is returned, preceded by its name, so the result of
7497 ${lookup pgsql{select home,name from users where id='userx'}\
7502 home=/home/userx name="Mister X"
7504 Empty values and values containing spaces are double quoted, with embedded
7505 quotes escaped by a backslash. If the result of the query contains just one
7506 field, the value is passed back verbatim, without a field name, for example:
7510 If the result of the query yields more than one row, it is all concatenated,
7511 with a newline between the data for each row.
7514 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7515 .cindex "MySQL" "lookup type"
7516 .cindex "PostgreSQL lookup type"
7517 .cindex "lookup" "MySQL"
7518 .cindex "lookup" "PostgreSQL"
7519 .cindex "Oracle" "lookup type"
7520 .cindex "lookup" "Oracle"
7521 .cindex "InterBase lookup type"
7522 .cindex "lookup" "InterBase"
7523 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7524 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7525 option (as appropriate) must be set to a colon-separated list of server
7527 (For MySQL and PostgreSQL only, the global option need not be set if all
7528 queries contain their own server information &-- see section
7529 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7530 items: host name, database name, user name, and password. In the case of
7531 Oracle, the host name field is used for the &"service name"&, and the database
7532 name field is not used and should be empty. For example:
7534 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7536 Because password data is sensitive, you should always precede the setting with
7537 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7538 option. Here is an example where two MySQL servers are listed:
7540 hide mysql_servers = localhost/users/root/secret:\
7541 otherhost/users/root/othersecret
7543 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7544 because this is a colon-separated list, the colon has to be doubled. For each
7545 query, these parameter groups are tried in order until a connection is made and
7546 a query is successfully processed. The result of a query may be that no data is
7547 found, but that is still a successful query. In other words, the list of
7548 servers provides a backup facility, not a list of different places to look.
7550 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7551 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7552 respectively, and the characters single-quote, double-quote, and backslash
7553 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7554 addition, escapes the percent and underscore characters. This cannot be done
7555 for MySQL because these escapes are not recognized in contexts where these
7556 characters are not special.
7558 .section "Specifying the server in the query" "SECTspeserque"
7559 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7560 it is possible to specify a list of servers with an individual query. This is
7561 done by starting the query with
7563 &`servers=`&&'server1:server2:server3:...'&&`;`&
7565 Each item in the list may take one of two forms:
7567 If it contains no slashes it is assumed to be just a host name. The appropriate
7568 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7569 of the same name, and the remaining parameters (database, user, password) are
7572 If it contains any slashes, it is taken as a complete parameter set.
7574 The list of servers is used in exactly the same way as the global list.
7575 Once a connection to a server has happened and a query has been
7576 successfully executed, processing of the lookup ceases.
7578 This feature is intended for use in master/slave situations where updates
7579 are occurring and you want to update the master rather than a slave. If the
7580 master is in the list as a backup for reading, you might have a global setting
7583 mysql_servers = slave1/db/name/pw:\
7587 In an updating lookup, you could then write:
7589 ${lookup mysql{servers=master; UPDATE ...} }
7591 That query would then be sent only to the master server. If, on the other hand,
7592 the master is not to be used for reading, and so is not present in the global
7593 option, you can still update it by a query of this form:
7595 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7599 .section "Special MySQL features" "SECID73"
7600 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7601 causes a connection to the server on the local host by means of a Unix domain
7602 socket. An alternate socket can be specified in parentheses. The full syntax of
7603 each item in &%mysql_servers%& is:
7605 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7606 <&'user'&>/<&'password'&>
7608 Any of the three sub-parts of the first field can be omitted. For normal use on
7609 the local host it can be left blank or set to just &"localhost"&.
7611 No database need be supplied &-- but if it is absent here, it must be given in
7614 If a MySQL query is issued that does not request any data (an insert, update,
7615 or delete command), the result of the lookup is the number of rows affected.
7617 &*Warning*&: This can be misleading. If an update does not actually change
7618 anything (for example, setting a field to the value it already has), the result
7619 is zero because no rows are affected.
7622 .section "Special PostgreSQL features" "SECID74"
7623 PostgreSQL lookups can also use Unix domain socket connections to the database.
7624 This is usually faster and costs less CPU time than a TCP/IP connection.
7625 However it can be used only if the mail server runs on the same machine as the
7626 database server. A configuration line for PostgreSQL via Unix domain sockets
7629 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7631 In other words, instead of supplying a host name, a path to the socket is
7632 given. The path name is enclosed in parentheses so that its slashes aren't
7633 visually confused with the delimiters for the other server parameters.
7635 If a PostgreSQL query is issued that does not request any data (an insert,
7636 update, or delete command), the result of the lookup is the number of rows
7639 .section "More about SQLite" "SECTsqlite"
7640 .cindex "lookup" "SQLite"
7641 .cindex "sqlite lookup type"
7642 SQLite is different to the other SQL lookups because a file name is required in
7643 addition to the SQL query. An SQLite database is a single file, and there is no
7644 daemon as in the other SQL databases. The interface to Exim requires the name
7645 of the file, as an absolute path, to be given at the start of the query. It is
7646 separated from the query by white space. This means that the path name cannot
7647 contain white space. Here is a lookup expansion example:
7649 ${lookup sqlite {/some/thing/sqlitedb \
7650 select name from aliases where id='userx';}}
7652 In a list, the syntax is similar. For example:
7654 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7655 select * from relays where ip='$sender_host_address';
7657 The only character affected by the &%quote_sqlite%& operator is a single
7658 quote, which it doubles.
7660 The SQLite library handles multiple simultaneous accesses to the database
7661 internally. Multiple readers are permitted, but only one process can
7662 update at once. Attempts to access the database while it is being updated
7663 are rejected after a timeout period, during which the SQLite library
7664 waits for the lock to be released. In Exim, the default timeout is set
7665 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7671 . ////////////////////////////////////////////////////////////////////////////
7672 . ////////////////////////////////////////////////////////////////////////////
7674 .chapter "Domain, host, address, and local part lists" &&&
7675 "CHAPdomhosaddlists" &&&
7676 "Domain, host, and address lists"
7677 .scindex IIDdohoadli "lists of domains; hosts; etc."
7678 A number of Exim configuration options contain lists of domains, hosts,
7679 email addresses, or local parts. For example, the &%hold_domains%& option
7680 contains a list of domains whose delivery is currently suspended. These lists
7681 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7682 arguments to expansion conditions such as &%match_domain%&.
7684 Each item in one of these lists is a pattern to be matched against a domain,
7685 host, email address, or local part, respectively. In the sections below, the
7686 different types of pattern for each case are described, but first we cover some
7687 general facilities that apply to all four kinds of list.
7690 Note that other parts of Exim use a &'string list'& which does not
7691 support all the complexity available in
7692 domain, host, address and local part lists.
7697 .section "Expansion of lists" "SECTlistexpand"
7698 .cindex "expansion" "of lists"
7699 Each list is expanded as a single string before it is used. The result of
7700 expansion must be a list, possibly containing empty items, which is split up
7701 into separate items for matching. By default, colon is the separator character,
7702 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7703 &<<SECTempitelis>>& for details of the list syntax; the second of these
7704 discusses the way to specify empty list items.
7707 If the string expansion is forced to fail, Exim behaves as if the item it is
7708 testing (domain, host, address, or local part) is not in the list. Other
7709 expansion failures cause temporary errors.
7711 If an item in a list is a regular expression, backslashes, dollars and possibly
7712 other special characters in the expression must be protected against
7713 misinterpretation by the string expander. The easiest way to do this is to use
7714 the &`\N`& expansion feature to indicate that the contents of the regular
7715 expression should not be expanded. For example, in an ACL you might have:
7717 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7718 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7720 The first item is a regular expression that is protected from expansion by
7721 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7722 senders based on the receiving domain.
7727 .section "Negated items in lists" "SECID76"
7728 .cindex "list" "negation"
7729 .cindex "negation" "in lists"
7730 Items in a list may be positive or negative. Negative items are indicated by a
7731 leading exclamation mark, which may be followed by optional white space. A list
7732 defines a set of items (domains, etc). When Exim processes one of these lists,
7733 it is trying to find out whether a domain, host, address, or local part
7734 (respectively) is in the set that is defined by the list. It works like this:
7736 The list is scanned from left to right. If a positive item is matched, the
7737 subject that is being checked is in the set; if a negative item is matched, the
7738 subject is not in the set. If the end of the list is reached without the
7739 subject having matched any of the patterns, it is in the set if the last item
7740 was a negative one, but not if it was a positive one. For example, the list in
7742 domainlist relay_to_domains = !a.b.c : *.b.c
7744 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7745 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7746 list is positive. However, if the setting were
7748 domainlist relay_to_domains = !a.b.c
7750 then all domains other than &'a.b.c'& would match because the last item in the
7751 list is negative. In other words, a list that ends with a negative item behaves
7752 as if it had an extra item &`:*`& on the end.
7754 Another way of thinking about positive and negative items in lists is to read
7755 the connector as &"or"& after a positive item and as &"and"& after a negative
7760 .section "File names in lists" "SECTfilnamlis"
7761 .cindex "list" "file name in"
7762 If an item in a domain, host, address, or local part list is an absolute file
7763 name (beginning with a slash character), each line of the file is read and
7764 processed as if it were an independent item in the list, except that further
7765 file names are not allowed,
7766 and no expansion of the data from the file takes place.
7767 Empty lines in the file are ignored, and the file may also contain comment
7771 For domain and host lists, if a # character appears anywhere in a line of the
7772 file, it and all following characters are ignored.
7774 Because local parts may legitimately contain # characters, a comment in an
7775 address list or local part list file is recognized only if # is preceded by
7776 white space or the start of the line. For example:
7778 not#comment@x.y.z # but this is a comment
7782 Putting a file name in a list has the same effect as inserting each line of the
7783 file as an item in the list (blank lines and comments excepted). However, there
7784 is one important difference: the file is read each time the list is processed,
7785 so if its contents vary over time, Exim's behaviour changes.
7787 If a file name is preceded by an exclamation mark, the sense of any match
7788 within the file is inverted. For example, if
7790 hold_domains = !/etc/nohold-domains
7792 and the file contains the lines
7797 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7798 any domain matching &`*.b.c`& is not.
7802 .section "An lsearch file is not an out-of-line list" "SECID77"
7803 As will be described in the sections that follow, lookups can be used in lists
7804 to provide indexed methods of checking list membership. There has been some
7805 confusion about the way &(lsearch)& lookups work in lists. Because
7806 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7807 sometimes thought that it is allowed to contain wild cards and other kinds of
7808 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7809 always fixed strings, just as for any other single-key lookup type.
7811 If you want to use a file to contain wild-card patterns that form part of a
7812 list, just give the file name on its own, without a search type, as described
7813 in the previous section. You could also use the &(wildlsearch)& or
7814 &(nwildlsearch)&, but there is no advantage in doing this.
7819 .section "Named lists" "SECTnamedlists"
7820 .cindex "named lists"
7821 .cindex "list" "named"
7822 A list of domains, hosts, email addresses, or local parts can be given a name
7823 which is then used to refer to the list elsewhere in the configuration. This is
7824 particularly convenient if the same list is required in several different
7825 places. It also allows lists to be given meaningful names, which can improve
7826 the readability of the configuration. For example, it is conventional to define
7827 a domain list called &'local_domains'& for all the domains that are handled
7828 locally on a host, using a configuration line such as
7830 domainlist local_domains = localhost:my.dom.example
7832 Named lists are referenced by giving their name preceded by a plus sign, so,
7833 for example, a router that is intended to handle local domains would be
7834 configured with the line
7836 domains = +local_domains
7838 The first router in a configuration is often one that handles all domains
7839 except the local ones, using a configuration with a negated item like this:
7843 domains = ! +local_domains
7844 transport = remote_smtp
7847 The four kinds of named list are created by configuration lines starting with
7848 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7849 respectively. Then there follows the name that you are defining, followed by an
7850 equals sign and the list itself. For example:
7852 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7853 addresslist bad_senders = cdb;/etc/badsenders
7855 A named list may refer to other named lists:
7857 domainlist dom1 = first.example : second.example
7858 domainlist dom2 = +dom1 : third.example
7859 domainlist dom3 = fourth.example : +dom2 : fifth.example
7861 &*Warning*&: If the last item in a referenced list is a negative one, the
7862 effect may not be what you intended, because the negation does not propagate
7863 out to the higher level. For example, consider:
7865 domainlist dom1 = !a.b
7866 domainlist dom2 = +dom1 : *.b
7868 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7869 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7870 means it matches the second list as well. The effect is not the same as
7872 domainlist dom2 = !a.b : *.b
7874 where &'x.y'& does not match. It's best to avoid negation altogether in
7875 referenced lists if you can.
7877 Named lists may have a performance advantage. When Exim is routing an
7878 address or checking an incoming message, it caches the result of tests on named
7879 lists. So, if you have a setting such as
7881 domains = +local_domains
7883 on several of your routers
7884 or in several ACL statements,
7885 the actual test is done only for the first one. However, the caching works only
7886 if there are no expansions within the list itself or any sublists that it
7887 references. In other words, caching happens only for lists that are known to be
7888 the same each time they are referenced.
7890 By default, there may be up to 16 named lists of each type. This limit can be
7891 extended by changing a compile-time variable. The use of domain and host lists
7892 is recommended for concepts such as local domains, relay domains, and relay
7893 hosts. The default configuration is set up like this.
7897 .section "Named lists compared with macros" "SECID78"
7898 .cindex "list" "named compared with macro"
7899 .cindex "macro" "compared with named list"
7900 At first sight, named lists might seem to be no different from macros in the
7901 configuration file. However, macros are just textual substitutions. If you
7904 ALIST = host1 : host2
7905 auth_advertise_hosts = !ALIST
7907 it probably won't do what you want, because that is exactly the same as
7909 auth_advertise_hosts = !host1 : host2
7911 Notice that the second host name is not negated. However, if you use a host
7914 hostlist alist = host1 : host2
7915 auth_advertise_hosts = ! +alist
7917 the negation applies to the whole list, and so that is equivalent to
7919 auth_advertise_hosts = !host1 : !host2
7923 .section "Named list caching" "SECID79"
7924 .cindex "list" "caching of named"
7925 .cindex "caching" "named lists"
7926 While processing a message, Exim caches the result of checking a named list if
7927 it is sure that the list is the same each time. In practice, this means that
7928 the cache operates only if the list contains no $ characters, which guarantees
7929 that it will not change when it is expanded. Sometimes, however, you may have
7930 an expanded list that you know will be the same each time within a given
7931 message. For example:
7933 domainlist special_domains = \
7934 ${lookup{$sender_host_address}cdb{/some/file}}
7936 This provides a list of domains that depends only on the sending host's IP
7937 address. If this domain list is referenced a number of times (for example,
7938 in several ACL lines, or in several routers) the result of the check is not
7939 cached by default, because Exim does not know that it is going to be the
7940 same list each time.
7942 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7943 cache the result anyway. For example:
7945 domainlist_cache special_domains = ${lookup{...
7947 If you do this, you should be absolutely sure that caching is going to do
7948 the right thing in all cases. When in doubt, leave it out.
7952 .section "Domain lists" "SECTdomainlist"
7953 .cindex "domain list" "patterns for"
7954 .cindex "list" "domain list"
7955 Domain lists contain patterns that are to be matched against a mail domain.
7956 The following types of item may appear in domain lists:
7959 .cindex "primary host name"
7960 .cindex "host name" "matched in domain list"
7961 .oindex "&%primary_hostname%&"
7962 .cindex "domain list" "matching primary host name"
7963 .cindex "@ in a domain list"
7964 If a pattern consists of a single @ character, it matches the local host name,
7965 as set by the &%primary_hostname%& option (or defaulted). This makes it
7966 possible to use the same configuration file on several different hosts that
7967 differ only in their names.
7969 .cindex "@[] in a domain list"
7970 .cindex "domain list" "matching local IP interfaces"
7971 .cindex "domain literal"
7972 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7973 in square brackets (as in an email address that contains a domain literal), but
7974 only if that IP address is recognized as local for email routing purposes. The
7975 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7976 control which of a host's several IP addresses are treated as local.
7977 In today's Internet, the use of domain literals is controversial.
7980 .cindex "@mx_primary"
7981 .cindex "@mx_secondary"
7982 .cindex "domain list" "matching MX pointers to local host"
7983 If a pattern consists of the string &`@mx_any`& it matches any domain that
7984 has an MX record pointing to the local host or to any host that is listed in
7985 .oindex "&%hosts_treat_as_local%&"
7986 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7987 are similar, except that the first matches only when a primary MX target is the
7988 local host, and the second only when no primary MX target is the local host,
7989 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7990 preference value &-- there may of course be more than one of them.
7992 The MX lookup that takes place when matching a pattern of this type is
7993 performed with the resolver options for widening names turned off. Thus, for
7994 example, a single-component domain will &'not'& be expanded by adding the
7995 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7996 options of the &(dnslookup)& router for a discussion of domain widening.
7998 Sometimes you may want to ignore certain IP addresses when using one of these
7999 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8000 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8001 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8002 on a router). For example:
8004 domains = @mx_any/ignore=127.0.0.1
8006 This example matches any domain that has an MX record pointing to one of
8007 the local host's IP addresses other than 127.0.0.1.
8009 The list of IP addresses is in fact processed by the same code that processes
8010 host lists, so it may contain CIDR-coded network specifications and it may also
8011 contain negative items.
8013 Because the list of IP addresses is a sublist within a domain list, you have to
8014 be careful about delimiters if there is more than one address. Like any other
8015 list, the default delimiter can be changed. Thus, you might have:
8017 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8018 an.other.domain : ...
8020 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8021 involved, it is easiest to change the delimiter for the main list as well:
8023 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8024 an.other.domain ? ...
8027 .cindex "asterisk" "in domain list"
8028 .cindex "domain list" "asterisk in"
8029 .cindex "domain list" "matching &""ends with""&"
8030 If a pattern starts with an asterisk, the remaining characters of the pattern
8031 are compared with the terminating characters of the domain. The use of &"*"& in
8032 domain lists differs from its use in partial matching lookups. In a domain
8033 list, the character following the asterisk need not be a dot, whereas partial
8034 matching works only in terms of dot-separated components. For example, a domain
8035 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8039 .cindex "regular expressions" "in domain list"
8040 .cindex "domain list" "matching regular expression"
8041 If a pattern starts with a circumflex character, it is treated as a regular
8042 expression, and matched against the domain using a regular expression matching
8043 function. The circumflex is treated as part of the regular expression.
8044 Email domains are case-independent, so this regular expression match is by
8045 default case-independent, but you can make it case-dependent by starting it
8046 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8047 are given in chapter &<<CHAPregexp>>&.
8049 &*Warning*&: Because domain lists are expanded before being processed, you
8050 must escape any backslash and dollar characters in the regular expression, or
8051 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8052 it is not to be expanded (unless you really do want to build a regular
8053 expression by expansion, of course).
8055 .cindex "lookup" "in domain list"
8056 .cindex "domain list" "matching by lookup"
8057 If a pattern starts with the name of a single-key lookup type followed by a
8058 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8059 must be a file name in a suitable format for the lookup type. For example, for
8060 &"cdb;"& it must be an absolute path:
8062 domains = cdb;/etc/mail/local_domains.cdb
8064 The appropriate type of lookup is done on the file using the domain name as the
8065 key. In most cases, the data that is looked up is not used; Exim is interested
8066 only in whether or not the key is present in the file. However, when a lookup
8067 is used for the &%domains%& option on a router
8068 or a &%domains%& condition in an ACL statement, the data is preserved in the
8069 &$domain_data$& variable and can be referred to in other router options or
8070 other statements in the same ACL.
8073 Any of the single-key lookup type names may be preceded by
8074 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8076 domains = partial-dbm;/partial/domains
8078 This causes partial matching logic to be invoked; a description of how this
8079 works is given in section &<<SECTpartiallookup>>&.
8082 .cindex "asterisk" "in lookup type"
8083 Any of the single-key lookup types may be followed by an asterisk. This causes
8084 a default lookup for a key consisting of a single asterisk to be done if the
8085 original lookup fails. This is not a useful feature when using a domain list to
8086 select particular domains (because any domain would match), but it might have
8087 value if the result of the lookup is being used via the &$domain_data$&
8090 If the pattern starts with the name of a query-style lookup type followed by a
8091 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8092 pattern must be an appropriate query for the lookup type, as described in
8093 chapter &<<CHAPfdlookup>>&. For example:
8095 hold_domains = mysql;select domain from holdlist \
8096 where domain = '${quote_mysql:$domain}';
8098 In most cases, the data that is looked up is not used (so for an SQL query, for
8099 example, it doesn't matter what field you select). Exim is interested only in
8100 whether or not the query succeeds. However, when a lookup is used for the
8101 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8102 variable and can be referred to in other options.
8104 .cindex "domain list" "matching literal domain name"
8105 If none of the above cases apply, a caseless textual comparison is made
8106 between the pattern and the domain.
8109 Here is an example that uses several different kinds of pattern:
8111 domainlist funny_domains = \
8114 *.foundation.fict.example : \
8115 \N^[1-2]\d{3}\.fict\.example$\N : \
8116 partial-dbm;/opt/data/penguin/book : \
8117 nis;domains.byname : \
8118 nisplus;[name=$domain,status=local],domains.org_dir
8120 There are obvious processing trade-offs among the various matching modes. Using
8121 an asterisk is faster than a regular expression, and listing a few names
8122 explicitly probably is too. The use of a file or database lookup is expensive,
8123 but may be the only option if hundreds of names are required. Because the
8124 patterns are tested in order, it makes sense to put the most commonly matched
8129 .section "Host lists" "SECThostlist"
8130 .cindex "host list" "patterns in"
8131 .cindex "list" "host list"
8132 Host lists are used to control what remote hosts are allowed to do. For
8133 example, some hosts may be allowed to use the local host as a relay, and some
8134 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8135 two different ways, by name or by IP address. In a host list, some types of
8136 pattern are matched to a host name, and some are matched to an IP address.
8137 You need to be particularly careful with this when single-key lookups are
8138 involved, to ensure that the right value is being used as the key.
8141 .section "Special host list patterns" "SECID80"
8142 .cindex "empty item in hosts list"
8143 .cindex "host list" "empty string in"
8144 If a host list item is the empty string, it matches only when no remote host is
8145 involved. This is the case when a message is being received from a local
8146 process using SMTP on the standard input, that is, when a TCP/IP connection is
8149 .cindex "asterisk" "in host list"
8150 The special pattern &"*"& in a host list matches any host or no host. Neither
8151 the IP address nor the name is actually inspected.
8155 .section "Host list patterns that match by IP address" "SECThoslispatip"
8156 .cindex "host list" "matching IP addresses"
8157 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8158 the incoming address actually appears in the IPv6 host as
8159 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8160 list, it is converted into a traditional IPv4 address first. (Not all operating
8161 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8164 The following types of pattern in a host list check the remote host by
8165 inspecting its IP address:
8168 If the pattern is a plain domain name (not a regular expression, not starting
8169 with *, not a lookup of any kind), Exim calls the operating system function
8170 to find the associated IP address(es). Exim uses the newer
8171 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8172 This typically causes a forward DNS lookup of the name. The result is compared
8173 with the IP address of the subject host.
8175 If there is a temporary problem (such as a DNS timeout) with the host name
8176 lookup, a temporary error occurs. For example, if the list is being used in an
8177 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8178 temporary SMTP error code. If no IP address can be found for the host name,
8179 what happens is described in section &<<SECTbehipnot>>& below.
8182 .cindex "@ in a host list"
8183 If the pattern is &"@"&, the primary host name is substituted and used as a
8184 domain name, as just described.
8187 If the pattern is an IP address, it is matched against the IP address of the
8188 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8189 IPv6 addresses can be given in colon-separated format, but the colons have to
8190 be doubled so as not to be taken as item separators when the default list
8191 separator is used. IPv6 addresses are recognized even when Exim is compiled
8192 without IPv6 support. This means that if they appear in a host list on an
8193 IPv4-only host, Exim will not treat them as host names. They are just addresses
8194 that can never match a client host.
8197 .cindex "@[] in a host list"
8198 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8199 the local host. For example, if the local host is an IPv4 host with one
8200 interface address 10.45.23.56, these two ACL statements have the same effect:
8202 accept hosts = 127.0.0.1 : 10.45.23.56
8206 .cindex "CIDR notation"
8207 If the pattern is an IP address followed by a slash and a mask length (for
8208 example 10.11.42.0/24), it is matched against the IP address of the subject
8209 host under the given mask. This allows, an entire network of hosts to be
8210 included (or excluded) by a single item. The mask uses CIDR notation; it
8211 specifies the number of address bits that must match, starting from the most
8212 significant end of the address.
8214 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8215 of a range of addresses. It is the number of bits in the network portion of the
8216 address. The above example specifies a 24-bit netmask, so it matches all 256
8217 addresses in the 10.11.42.0 network. An item such as
8221 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8222 32 for an IPv4 address is the same as no mask at all; just a single address
8225 Here is another example which shows an IPv4 and an IPv6 network:
8227 recipient_unqualified_hosts = 192.168.0.0/16: \
8228 3ffe::ffff::836f::::/48
8230 The doubling of list separator characters applies only when these items
8231 appear inline in a host list. It is not required when indirecting via a file.
8234 recipient_unqualified_hosts = /opt/exim/unqualnets
8236 could make use of a file containing
8241 to have exactly the same effect as the previous example. When listing IPv6
8242 addresses inline, it is usually more convenient to use the facility for
8243 changing separator characters. This list contains the same two networks:
8245 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8248 The separator is changed to semicolon by the leading &"<;"& at the start of the
8254 .section "Host list patterns for single-key lookups by host address" &&&
8255 "SECThoslispatsikey"
8256 .cindex "host list" "lookup of IP address"
8257 When a host is to be identified by a single-key lookup of its complete IP
8258 address, the pattern takes this form:
8260 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8264 hosts_lookup = net-cdb;/hosts-by-ip.db
8266 The text form of the IP address of the subject host is used as the lookup key.
8267 IPv6 addresses are converted to an unabbreviated form, using lower case
8268 letters, with dots as separators because colon is the key terminator in
8269 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8270 quoting the keys, but this is a facility that was added later.] The data
8271 returned by the lookup is not used.
8273 .cindex "IP address" "masking"
8274 .cindex "host list" "masked IP address"
8275 Single-key lookups can also be performed using masked IP addresses, using
8276 patterns of this form:
8278 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8282 net24-dbm;/networks.db
8284 The IP address of the subject host is masked using <&'number'&> as the mask
8285 length. A textual string is constructed from the masked value, followed by the
8286 mask, and this is used as the lookup key. For example, if the host's IP address
8287 is 192.168.34.6, the key that is looked up for the above example is
8288 &"192.168.34.0/24"&.
8290 When an IPv6 address is converted to a string, dots are normally used instead
8291 of colons, so that keys in &(lsearch)& files need not contain colons (which
8292 terminate &(lsearch)& keys). This was implemented some time before the ability
8293 to quote keys was made available in &(lsearch)& files. However, the more
8294 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8295 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8296 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8297 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8298 addresses are always used.
8300 Ideally, it would be nice to tidy up this anomalous situation by changing to
8301 colons in all cases, given that quoting is now available for &(lsearch)&.
8302 However, this would be an incompatible change that might break some existing
8305 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8306 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8307 the former case the key strings include the mask value, whereas in the latter
8308 case the IP address is used on its own.
8312 .section "Host list patterns that match by host name" "SECThoslispatnam"
8313 .cindex "host" "lookup failures"
8314 .cindex "unknown host name"
8315 .cindex "host list" "matching host name"
8316 There are several types of pattern that require Exim to know the name of the
8317 remote host. These are either wildcard patterns or lookups by name. (If a
8318 complete hostname is given without any wildcarding, it is used to find an IP
8319 address to match against, as described in section &<<SECThoslispatip>>&
8322 If the remote host name is not already known when Exim encounters one of these
8323 patterns, it has to be found from the IP address.
8324 Although many sites on the Internet are conscientious about maintaining reverse
8325 DNS data for their hosts, there are also many that do not do this.
8326 Consequently, a name cannot always be found, and this may lead to unwanted
8327 effects. Take care when configuring host lists with wildcarded name patterns.
8328 Consider what will happen if a name cannot be found.
8330 Because of the problems of determining host names from IP addresses, matching
8331 against host names is not as common as matching against IP addresses.
8333 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8334 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8335 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8336 are done can be changed by setting the &%host_lookup_order%& option. For
8337 security, once Exim has found one or more names, it looks up the IP addresses
8338 for these names and compares them with the IP address that it started with.
8339 Only those names whose IP addresses match are accepted. Any other names are
8340 discarded. If no names are left, Exim behaves as if the host name cannot be
8341 found. In the most common case there is only one name and one IP address.
8343 There are some options that control what happens if a host name cannot be
8344 found. These are described in section &<<SECTbehipnot>>& below.
8346 .cindex "host" "alias for"
8347 .cindex "alias for host"
8348 As a result of aliasing, hosts may have more than one name. When processing any
8349 of the following types of pattern, all the host's names are checked:
8352 .cindex "asterisk" "in host list"
8353 If a pattern starts with &"*"& the remainder of the item must match the end of
8354 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8355 &'.b.c'&. This special simple form is provided because this is a very common
8356 requirement. Other kinds of wildcarding require the use of a regular
8359 .cindex "regular expressions" "in host list"
8360 .cindex "host list" "regular expression in"
8361 If the item starts with &"^"& it is taken to be a regular expression which is
8362 matched against the host name. Host names are case-independent, so this regular
8363 expression match is by default case-independent, but you can make it
8364 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8365 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8370 is a regular expression that matches either of the two hosts &'a.c.d'& or
8371 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8372 that backslash and dollar characters are not misinterpreted as part of the
8373 string expansion. The simplest way to do this is to use &`\N`& to mark that
8374 part of the string as non-expandable. For example:
8376 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8378 &*Warning*&: If you want to match a complete host name, you must include the
8379 &`$`& terminating metacharacter in the regular expression, as in the above
8380 example. Without it, a match at the start of the host name is all that is
8387 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8388 .cindex "host" "lookup failures, permanent"
8389 While processing a host list, Exim may need to look up an IP address from a
8390 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8391 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8392 behaviour when it fails to find the information it is seeking is the same.
8394 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8395 apply to temporary DNS errors, whose handling is described in the next section.
8397 .cindex "&`+include_unknown`&"
8398 .cindex "&`+ignore_unknown`&"
8399 Exim parses a host list from left to right. If it encounters a permanent
8400 lookup failure in any item in the host list before it has found a match,
8401 Exim treats it as a failure and the default behavior is as if the host
8402 does not match the list. This may not always be what you want to happen.
8403 To change Exim's behaviour, the special items &`+include_unknown`& or
8404 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8405 not recognized in an indirected file).
8408 If any item that follows &`+include_unknown`& requires information that
8409 cannot found, Exim behaves as if the host does match the list. For example,
8411 host_reject_connection = +include_unknown:*.enemy.ex
8413 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8414 any hosts whose name it cannot find.
8417 If any item that follows &`+ignore_unknown`& requires information that cannot
8418 be found, Exim ignores that item and proceeds to the rest of the list. For
8421 accept hosts = +ignore_unknown : friend.example : \
8424 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8425 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8426 name can be found for 192.168.4.5, it is rejected.
8429 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8430 list. The effect of each one lasts until the next, or until the end of the
8433 .section "Mixing wildcarded host names and addresses in host lists" &&&
8435 .cindex "host list" "mixing names and addresses in"
8437 This section explains the host/ip processing logic with the same concepts
8438 as the previous section, but specifically addresses what happens when a
8439 wildcarded hostname is one of the items in the hostlist.
8442 If you have name lookups or wildcarded host names and
8443 IP addresses in the same host list, you should normally put the IP
8444 addresses first. For example, in an ACL you could have:
8446 accept hosts = 10.9.8.7 : *.friend.example
8448 The reason you normally would order it this way lies in the
8449 left-to-right way that Exim processes lists. It can test IP addresses
8450 without doing any DNS lookups, but when it reaches an item that requires
8451 a host name, it fails if it cannot find a host name to compare with the
8452 pattern. If the above list is given in the opposite order, the
8453 &%accept%& statement fails for a host whose name cannot be found, even
8454 if its IP address is 10.9.8.7.
8457 If you really do want to do the name check first, and still recognize the IP
8458 address, you can rewrite the ACL like this:
8460 accept hosts = *.friend.example
8461 accept hosts = 10.9.8.7
8463 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8464 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8465 &`+ignore_unknown`&, which was discussed in depth in the first example in
8470 .section "Temporary DNS errors when looking up host information" &&&
8472 .cindex "host" "lookup failures, temporary"
8473 .cindex "&`+include_defer`&"
8474 .cindex "&`+ignore_defer`&"
8475 A temporary DNS lookup failure normally causes a defer action (except when
8476 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8477 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8478 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8479 section. These options should be used with care, probably only in non-critical
8480 host lists such as whitelists.
8484 .section "Host list patterns for single-key lookups by host name" &&&
8485 "SECThoslispatnamsk"
8486 .cindex "unknown host name"
8487 .cindex "host list" "matching host name"
8488 If a pattern is of the form
8490 <&'single-key-search-type'&>;<&'search-data'&>
8494 dbm;/host/accept/list
8496 a single-key lookup is performed, using the host name as its key. If the
8497 lookup succeeds, the host matches the item. The actual data that is looked up
8500 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8501 keys in the file, not IP addresses. If you want to do lookups based on IP
8502 addresses, you must precede the search type with &"net-"& (see section
8503 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8504 two items in the same list, one doing an address lookup and one doing a name
8505 lookup, both using the same file.
8509 .section "Host list patterns for query-style lookups" "SECID81"
8510 If a pattern is of the form
8512 <&'query-style-search-type'&>;<&'query'&>
8514 the query is obeyed, and if it succeeds, the host matches the item. The actual
8515 data that is looked up is not used. The variables &$sender_host_address$& and
8516 &$sender_host_name$& can be used in the query. For example:
8518 hosts_lookup = pgsql;\
8519 select ip from hostlist where ip='$sender_host_address'
8521 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8522 can use the &%sg%& expansion item to change this if you need to. If you want to
8523 use masked IP addresses in database queries, you can use the &%mask%& expansion
8526 If the query contains a reference to &$sender_host_name$&, Exim automatically
8527 looks up the host name if it has not already done so. (See section
8528 &<<SECThoslispatnam>>& for comments on finding host names.)
8530 Historical note: prior to release 4.30, Exim would always attempt to find a
8531 host name before running the query, unless the search type was preceded by
8532 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8533 still recognized for query-style lookups, but its presence or absence has no
8534 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8535 See section &<<SECThoslispatsikey>>&.)
8541 .section "Address lists" "SECTaddresslist"
8542 .cindex "list" "address list"
8543 .cindex "address list" "empty item"
8544 .cindex "address list" "patterns"
8545 Address lists contain patterns that are matched against mail addresses. There
8546 is one special case to be considered: the sender address of a bounce message is
8547 always empty. You can test for this by providing an empty item in an address
8548 list. For example, you can set up a router to process bounce messages by
8549 using this option setting:
8553 The presence of the colon creates an empty item. If you do not provide any
8554 data, the list is empty and matches nothing. The empty sender can also be
8555 detected by a regular expression that matches an empty string,
8556 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8558 Non-empty items in an address list can be straightforward email addresses. For
8561 senders = jbc@askone.example : hs@anacreon.example
8563 A certain amount of wildcarding is permitted. If a pattern contains an @
8564 character, but is not a regular expression and does not begin with a
8565 semicolon-terminated lookup type (described below), the local part of the
8566 subject address is compared with the local part of the pattern, which may start
8567 with an asterisk. If the local parts match, the domain is checked in exactly
8568 the same way as for a pattern in a domain list. For example, the domain can be
8569 wildcarded, refer to a named list, or be a lookup:
8571 deny senders = *@*.spamming.site:\
8572 *@+hostile_domains:\
8573 bozo@partial-lsearch;/list/of/dodgy/sites:\
8574 *@dbm;/bad/domains.db
8576 .cindex "local part" "starting with !"
8577 .cindex "address list" "local part starting with !"
8578 If a local part that begins with an exclamation mark is required, it has to be
8579 specified using a regular expression, because otherwise the exclamation mark is
8580 treated as a sign of negation, as is standard in lists.
8582 If a non-empty pattern that is not a regular expression or a lookup does not
8583 contain an @ character, it is matched against the domain part of the subject
8584 address. The only two formats that are recognized this way are a literal
8585 domain, or a domain pattern that starts with *. In both these cases, the effect
8586 is the same as if &`*@`& preceded the pattern. For example:
8588 deny senders = enemy.domain : *.enemy.domain
8591 The following kinds of more complicated address list pattern can match any
8592 address, including the empty address that is characteristic of bounce message
8596 .cindex "regular expressions" "in address list"
8597 .cindex "address list" "regular expression in"
8598 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8599 done against the complete address, with the pattern as the regular expression.
8600 You must take care that backslash and dollar characters are not misinterpreted
8601 as part of the string expansion. The simplest way to do this is to use &`\N`&
8602 to mark that part of the string as non-expandable. For example:
8604 deny senders = \N^.*this.*@example\.com$\N : \
8605 \N^\d{8}.+@spamhaus.example$\N : ...
8607 The &`\N`& sequences are removed by the expansion, so these items do indeed
8608 start with &"^"& by the time they are being interpreted as address patterns.
8611 .cindex "address list" "lookup for complete address"
8612 Complete addresses can be looked up by using a pattern that starts with a
8613 lookup type terminated by a semicolon, followed by the data for the lookup. For
8616 deny senders = cdb;/etc/blocked.senders : \
8617 mysql;select address from blocked where \
8618 address='${quote_mysql:$sender_address}'
8620 Both query-style and single-key lookup types can be used. For a single-key
8621 lookup type, Exim uses the complete address as the key. However, empty keys are
8622 not supported for single-key lookups, so a match against the empty address
8623 always fails. This restriction does not apply to query-style lookups.
8625 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8626 cannot be used, and is ignored if specified, with an entry being written to the
8628 .cindex "*@ with single-key lookup"
8629 However, you can configure lookup defaults, as described in section
8630 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8631 default. For example, with this lookup:
8633 accept senders = lsearch*@;/some/file
8635 the file could contains lines like this:
8637 user1@domain1.example
8640 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8643 nimrod@jaeger.example
8647 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8648 would mean that every address matches, thus rendering the test useless.
8650 &*Warning 2*&: Do not confuse these two kinds of item:
8652 deny recipients = dbm*@;/some/file
8653 deny recipients = *@dbm;/some/file
8655 The first does a whole address lookup, with defaulting, as just described,
8656 because it starts with a lookup type. The second matches the local part and
8657 domain independently, as described in a bullet point below.
8661 The following kinds of address list pattern can match only non-empty addresses.
8662 If the subject address is empty, a match against any of these pattern types
8667 .cindex "@@ with single-key lookup"
8668 .cindex "address list" "@@ lookup type"
8669 .cindex "address list" "split local part and domain"
8670 If a pattern starts with &"@@"& followed by a single-key lookup item
8671 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8672 split into a local part and a domain. The domain is looked up in the file. If
8673 it is not found, there is no match. If it is found, the data that is looked up
8674 from the file is treated as a colon-separated list of local part patterns, each
8675 of which is matched against the subject local part in turn.
8677 .cindex "asterisk" "in address list"
8678 The lookup may be a partial one, and/or one involving a search for a default
8679 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8680 patterns that are looked up can be regular expressions or begin with &"*"&, or
8681 even be further lookups. They may also be independently negated. For example,
8684 deny senders = @@dbm;/etc/reject-by-domain
8686 the data from which the DBM file is built could contain lines like
8688 baddomain.com: !postmaster : *
8690 to reject all senders except &%postmaster%& from that domain.
8692 .cindex "local part" "starting with !"
8693 If a local part that actually begins with an exclamation mark is required, it
8694 has to be specified using a regular expression. In &(lsearch)& files, an entry
8695 may be split over several lines by indenting the second and subsequent lines,
8696 but the separating colon must still be included at line breaks. White space
8697 surrounding the colons is ignored. For example:
8699 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8702 As in all colon-separated lists in Exim, a colon can be included in an item by
8705 If the last item in the list starts with a right angle-bracket, the remainder
8706 of the item is taken as a new key to look up in order to obtain a continuation
8707 list of local parts. The new key can be any sequence of characters. Thus one
8708 might have entries like
8710 aol.com: spammer1 : spammer 2 : >*
8711 xyz.com: spammer3 : >*
8714 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8715 local parts for all domains, in addition to the specific local parts listed for
8716 each domain. Of course, using this feature costs another lookup each time a
8717 chain is followed, but the effort needed to maintain the data is reduced.
8719 .cindex "loop" "in lookups"
8720 It is possible to construct loops using this facility, and in order to catch
8721 them, the chains may be no more than fifty items long.
8724 The @@<&'lookup'&> style of item can also be used with a query-style
8725 lookup, but in this case, the chaining facility is not available. The lookup
8726 can only return a single list of local parts.
8729 &*Warning*&: There is an important difference between the address list items
8730 in these two examples:
8733 senders = *@+my_list
8735 In the first one, &`my_list`& is a named address list, whereas in the second
8736 example it is a named domain list.
8741 .section "Case of letters in address lists" "SECTcasletadd"
8742 .cindex "case of local parts"
8743 .cindex "address list" "case forcing"
8744 .cindex "case forcing in address lists"
8745 Domains in email addresses are always handled caselessly, but for local parts
8746 case may be significant on some systems (see &%caseful_local_part%& for how
8747 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8748 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8749 blocking lists should be done in a case-independent manner. Since most address
8750 lists in Exim are used for this kind of control, Exim attempts to do this by
8753 The domain portion of an address is always lowercased before matching it to an
8754 address list. The local part is lowercased by default, and any string
8755 comparisons that take place are done caselessly. This means that the data in
8756 the address list itself, in files included as plain file names, and in any file
8757 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8758 keys in files that are looked up by a search type other than &(lsearch)& (which
8759 works caselessly) must be in lower case, because these lookups are not
8762 .cindex "&`+caseful`&"
8763 To allow for the possibility of caseful address list matching, if an item in
8764 an address list is the string &"+caseful"&, the original case of the local
8765 part is restored for any comparisons that follow, and string comparisons are no
8766 longer case-independent. This does not affect the domain, which remains in
8767 lower case. However, although independent matches on the domain alone are still
8768 performed caselessly, regular expressions that match against an entire address
8769 become case-sensitive after &"+caseful"& has been seen.
8773 .section "Local part lists" "SECTlocparlis"
8774 .cindex "list" "local part list"
8775 .cindex "local part" "list"
8776 Case-sensitivity in local part lists is handled in the same way as for address
8777 lists, as just described. The &"+caseful"& item can be used if required. In a
8778 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8779 set false, the subject is lowercased and the matching is initially
8780 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8781 matching in the local part list, but not elsewhere in the router. If
8782 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8783 option is case-sensitive from the start.
8785 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8786 comments are handled in the same way as address lists &-- they are recognized
8787 only if the # is preceded by white space or the start of the line.
8788 Otherwise, local part lists are matched in the same way as domain lists, except
8789 that the special items that refer to the local host (&`@`&, &`@[]`&,
8790 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8791 Refer to section &<<SECTdomainlist>>& for details of the other available item
8793 .ecindex IIDdohoadli
8798 . ////////////////////////////////////////////////////////////////////////////
8799 . ////////////////////////////////////////////////////////////////////////////
8801 .chapter "String expansions" "CHAPexpand"
8802 .scindex IIDstrexp "expansion" "of strings"
8803 Many strings in Exim's run time configuration are expanded before use. Some of
8804 them are expanded every time they are used; others are expanded only once.
8806 When a string is being expanded it is copied verbatim from left to right except
8807 when a dollar or backslash character is encountered. A dollar specifies the
8808 start of a portion of the string that is interpreted and replaced as described
8809 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8810 escape character, as described in the following section.
8812 Whether a string is expanded depends upon the context. Usually this is solely
8813 dependent upon the option for which a value is sought; in this documentation,
8814 options for which string expansion is performed are marked with † after
8815 the data type. ACL rules always expand strings. A couple of expansion
8816 conditions do not expand some of the brace-delimited branches, for security
8821 .section "Literal text in expanded strings" "SECTlittext"
8822 .cindex "expansion" "including literal text"
8823 An uninterpreted dollar can be included in an expanded string by putting a
8824 backslash in front of it. A backslash can be used to prevent any special
8825 character being treated specially in an expansion, including backslash itself.
8826 If the string appears in quotes in the configuration file, two backslashes are
8827 required because the quotes themselves cause interpretation of backslashes when
8828 the string is read in (see section &<<SECTstrings>>&).
8830 .cindex "expansion" "non-expandable substrings"
8831 A portion of the string can specified as non-expandable by placing it between
8832 two occurrences of &`\N`&. This is particularly useful for protecting regular
8833 expressions, which often contain backslashes and dollar signs. For example:
8835 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8837 On encountering the first &`\N`&, the expander copies subsequent characters
8838 without interpretation until it reaches the next &`\N`& or the end of the
8843 .section "Character escape sequences in expanded strings" "SECID82"
8844 .cindex "expansion" "escape sequences"
8845 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8846 expanded string is recognized as an escape sequence for the character newline,
8847 carriage return, or tab, respectively. A backslash followed by up to three
8848 octal digits is recognized as an octal encoding for a single character, and a
8849 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8852 These escape sequences are also recognized in quoted strings when they are read
8853 in. Their interpretation in expansions as well is useful for unquoted strings,
8854 and for other cases such as looked-up strings that are then expanded.
8857 .section "Testing string expansions" "SECID83"
8858 .cindex "expansion" "testing"
8859 .cindex "testing" "string expansion"
8861 Many expansions can be tested by calling Exim with the &%-be%& option. This
8862 takes the command arguments, or lines from the standard input if there are no
8863 arguments, runs them through the string expansion code, and writes the results
8864 to the standard output. Variables based on configuration values are set up, but
8865 since no message is being processed, variables such as &$local_part$& have no
8866 value. Nevertheless the &%-be%& option can be useful for checking out file and
8867 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8870 Exim gives up its root privilege when it is called with the &%-be%& option, and
8871 instead runs under the uid and gid it was called with, to prevent users from
8872 using &%-be%& for reading files to which they do not have access.
8875 If you want to test expansions that include variables whose values are taken
8876 from a message, there are two other options that can be used. The &%-bem%&
8877 option is like &%-be%& except that it is followed by a file name. The file is
8878 read as a message before doing the test expansions. For example:
8880 exim -bem /tmp/test.message '$h_subject:'
8882 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8883 Exim message identifier. For example:
8885 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8887 This loads the message from Exim's spool before doing the test expansions, and
8888 is therefore restricted to admin users.
8891 .section "Forced expansion failure" "SECTforexpfai"
8892 .cindex "expansion" "forced failure"
8893 A number of expansions that are described in the following section have
8894 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8895 (which are sometimes called &"curly brackets"&). Which of the two strings is
8896 used depends on some condition that is evaluated as part of the expansion. If,
8897 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8898 the entire string expansion fails in a way that can be detected by the code
8899 that requested the expansion. This is called &"forced expansion failure"&, and
8900 its consequences depend on the circumstances. In some cases it is no different
8901 from any other expansion failure, but in others a different action may be
8902 taken. Such variations are mentioned in the documentation of the option that is
8908 .section "Expansion items" "SECTexpansionitems"
8909 The following items are recognized in expanded strings. White space may be used
8910 between sub-items that are keywords or substrings enclosed in braces inside an
8911 outer set of braces, to improve readability. &*Warning*&: Within braces,
8912 white space is significant.
8915 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8916 .cindex "expansion" "variables"
8917 Substitute the contents of the named variable, for example:
8922 The second form can be used to separate the name from subsequent alphanumeric
8923 characters. This form (using braces) is available only for variables; it does
8924 &'not'& apply to message headers. The names of the variables are given in
8925 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8926 given, the expansion fails.
8928 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8929 .cindex "expansion" "operators"
8930 The string is first itself expanded, and then the operation specified by
8931 <&'op'&> is applied to it. For example:
8935 The string starts with the first character after the colon, which may be
8936 leading white space. A list of operators is given in section &<<SECTexpop>>&
8937 below. The operator notation is used for simple expansion items that have just
8938 one argument, because it reduces the number of braces and therefore makes the
8939 string easier to understand.
8941 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8942 This item inserts &"basic"& header lines. It is described with the &%header%&
8943 expansion item below.
8946 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8947 .cindex "expansion" "calling an acl"
8948 .cindex "&%acl%&" "call from expansion"
8949 The name and zero to nine argument strings are first expanded separately. The expanded
8950 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8951 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8952 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8953 and may use the variables; if another acl expansion is used the values
8954 are restored after it returns. If the ACL sets
8955 a value using a "message =" modifier and returns accept or deny, the value becomes
8956 the result of the expansion.
8957 If no message is set and the ACL returns accept or deny
8958 the expansion result is an empty string.
8959 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8962 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
8963 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8964 .cindex "expansion" "extracting cerificate fields"
8965 .cindex "&%certextract%&" "certificate fields"
8966 .cindex "certificate" "extracting fields"
8967 The <&'certificate'&> must be a variable of type certificate.
8968 The field name is expanded and used to retrieve the relevant field from
8969 the certificate. Supported fields are:
8973 &`subject `& RFC4514 DN
8974 &`issuer `& RFC4514 DN
8979 &`subj_altname `& tagged list
8983 If the field is found,
8984 <&'string2'&> is expanded, and replaces the whole item;
8985 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8986 variable &$value$& contains the value that has been extracted. Afterwards, it
8987 is restored to any previous value it might have had.
8989 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8990 key is not found. If {<&'string2'&>} is also omitted, the value that was
8993 Some field names take optional modifiers, appended and separated by commas.
8995 The field selectors marked as "RFC4514" above
8996 output a Distinguished Name string which is
8998 parseable by Exim as a comma-separated tagged list
8999 (the exceptions being elements containing commas).
9000 RDN elements of a single type may be selected by
9001 a modifier of the type label; if so the expansion
9002 result is a list (newline-separated by default).
9003 The separator may be changed by another modifier of
9004 a right angle-bracket followed immediately by the new separator.
9005 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9007 The field selectors marked as "time" above
9008 take an optional modifier of "int"
9009 for which the result is the number of seconds since epoch.
9010 Otherwise the result is a human-readable string
9011 in the timezone selected by the main "timezone" option.
9013 The field selectors marked as "list" above return a list,
9014 newline-separated by default,
9015 (embedded separator characters in elements are doubled).
9016 The separator may be changed by a modifier of
9017 a right angle-bracket followed immediately by the new separator.
9019 The field selectors marked as "tagged" above
9020 prefix each list element with a type string and an equals sign.
9021 Elements of only one type may be selected by a modifier
9022 which is one of "dns", "uri" or "mail";
9023 if so the element tags are omitted.
9025 If not otherwise noted field values are presented in human-readable form.
9027 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9028 {*&<&'arg'&>&*}...}*&"
9030 This expansion dynamically loads and then calls a locally-written C function.
9031 This functionality is available only if Exim is compiled with
9035 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9036 object so that it doesn't reload the same object file in the same Exim process
9037 (but of course Exim does start new processes frequently).
9039 There may be from zero to eight arguments to the function. When compiling
9040 a local function that is to be called in this way, &_local_scan.h_& should be
9041 included. The Exim variables and functions that are defined by that API
9042 are also available for dynamically loaded functions. The function itself
9043 must have the following type:
9045 int dlfunction(uschar **yield, int argc, uschar *argv[])
9047 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9048 function should return one of the following values:
9050 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9051 into the expanded string that is being built.
9053 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9054 from &'yield'&, if it is set.
9056 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9057 taken from &'yield'& if it is set.
9059 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9061 When compiling a function that is to be used in this way with gcc,
9062 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9063 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9067 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9068 .cindex "expansion" "extracting value from environment"
9069 .cindex "environment" "value from"
9070 The key is first expanded separately, and leading and trailing white space
9072 This is then searched for as a name in the environment.
9073 If a variable is found then its value is placed in &$value$&
9074 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9076 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9077 appear, for example:
9079 ${env{USER}{$value} fail }
9081 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9082 {<&'string1'&>} must be present for &"fail"& to be recognized.
9084 If {<&'string2'&>} is omitted an empty string is substituted on
9086 If {<&'string1'&>} is omitted the search result is substituted on
9091 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9092 {*&<&'string3'&>&*}}*&"
9093 .cindex "expansion" "extracting substrings by key"
9094 .cindex "&%extract%&" "substrings by key"
9095 The key and <&'string1'&> are first expanded separately. Leading and trailing
9096 white space is removed from the key (but not from any of the strings). The key
9097 must not consist entirely of digits. The expanded <&'string1'&> must be of the
9100 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9103 where the equals signs and spaces (but not both) are optional. If any of the
9104 values contain white space, they must be enclosed in double quotes, and any
9105 values that are enclosed in double quotes are subject to escape processing as
9106 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9107 for the value that corresponds to the key. The search is case-insensitive. If
9108 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9109 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9110 variable &$value$& contains the value that has been extracted. Afterwards, it
9111 is restored to any previous value it might have had.
9113 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9114 key is not found. If {<&'string2'&>} is also omitted, the value that was
9115 extracted is used. Thus, for example, these two expansions are identical, and
9118 ${extract{gid}{uid=1984 gid=2001}}
9119 ${extract{gid}{uid=1984 gid=2001}{$value}}
9121 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9122 appear, for example:
9124 ${extract{Z}{A=... B=...}{$value} fail }
9126 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9127 {<&'string2'&>} must be present for &"fail"& to be recognized.
9130 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9131 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9132 .cindex "expansion" "extracting substrings by number"
9133 .cindex "&%extract%&" "substrings by number"
9134 The <&'number'&> argument must consist entirely of decimal digits,
9135 apart from leading and trailing white space, which is ignored.
9136 This is what distinguishes this form of &%extract%& from the previous kind. It
9137 behaves in the same way, except that, instead of extracting a named field, it
9138 extracts from <&'string1'&> the field whose number is given as the first
9139 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9140 <&'string3'&> as before.
9142 The fields in the string are separated by any one of the characters in the
9143 separator string. These may include space or tab characters.
9144 The first field is numbered one. If the number is negative, the fields are
9145 counted from the end of the string, with the rightmost one numbered -1. If the
9146 number given is zero, the entire string is returned. If the modulus of the
9147 number is greater than the number of fields in the string, the result is the
9148 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9149 provided. For example:
9151 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9155 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9157 yields &"99"&. Two successive separators mean that the field between them is
9158 empty (for example, the fifth field above).
9161 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9162 .cindex "list" "selecting by condition"
9163 .cindex "expansion" "selecting from list by condition"
9165 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9166 default, but the separator can be changed in the usual way. For each item
9167 in this list, its value is place in &$item$&, and then the condition is
9168 evaluated. If the condition is true, &$item$& is added to the output as an
9169 item in a new list; if the condition is false, the item is discarded. The
9170 separator used for the output list is the same as the one used for the
9171 input, but a separator setting is not included in the output. For example:
9173 ${filter{a:b:c}{!eq{$item}{b}}
9175 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9176 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9179 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9180 .cindex "hash function" "textual"
9181 .cindex "expansion" "textual hash"
9182 This is a textual hashing function, and was the first to be implemented in
9183 early versions of Exim. In current releases, there are other hashing functions
9184 (numeric, MD5, and SHA-1), which are described below.
9186 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9187 <&'n'&>. If you are using fixed values for these numbers, that is, if
9188 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9189 use the simpler operator notation that avoids some of the braces:
9191 ${hash_<n>_<m>:<string>}
9193 The second number is optional (in both notations). If <&'n'&> is greater than
9194 or equal to the length of the string, the expansion item returns the string.
9195 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9196 function to the string. The new string consists of characters taken from the
9197 first <&'m'&> characters of the string
9199 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9201 If <&'m'&> is not present the value 26 is used, so that only lower case
9202 letters appear. For example:
9204 &`$hash{3}{monty}} `& yields &`jmg`&
9205 &`$hash{5}{monty}} `& yields &`monty`&
9206 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9209 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9210 &*$h_*&<&'header&~name'&>&*:*&" &&&
9211 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9212 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9213 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9214 &*$rh_*&<&'header&~name'&>&*:*&"
9215 .cindex "expansion" "header insertion"
9216 .vindex "&$header_$&"
9217 .vindex "&$bheader_$&"
9218 .vindex "&$rheader_$&"
9219 .cindex "header lines" "in expansion strings"
9220 .cindex "header lines" "character sets"
9221 .cindex "header lines" "decoding"
9222 Substitute the contents of the named message header line, for example
9226 The newline that terminates a header line is not included in the expansion, but
9227 internal newlines (caused by splitting the header line over several physical
9228 lines) may be present.
9230 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9231 the data in the header line is interpreted.
9234 .cindex "white space" "in header lines"
9235 &%rheader%& gives the original &"raw"& content of the header line, with no
9236 processing at all, and without the removal of leading and trailing white space.
9239 .cindex "base64 encoding" "in header lines"
9240 &%bheader%& removes leading and trailing white space, and then decodes base64
9241 or quoted-printable MIME &"words"& within the header text, but does no
9242 character set translation. If decoding of what looks superficially like a MIME
9243 &"word"& fails, the raw string is returned. If decoding
9244 .cindex "binary zero" "in header line"
9245 produces a binary zero character, it is replaced by a question mark &-- this is
9246 what Exim does for binary zeros that are actually received in header lines.
9249 &%header%& tries to translate the string as decoded by &%bheader%& to a
9250 standard character set. This is an attempt to produce the same string as would
9251 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9252 returned. Translation is attempted only on operating systems that support the
9253 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9254 a system Makefile or in &_Local/Makefile_&.
9257 In a filter file, the target character set for &%header%& can be specified by a
9258 command of the following form:
9260 headers charset "UTF-8"
9262 This command affects all references to &$h_$& (or &$header_$&) expansions in
9263 subsequently obeyed filter commands. In the absence of this command, the target
9264 character set in a filter is taken from the setting of the &%headers_charset%&
9265 option in the runtime configuration. The value of this option defaults to the
9266 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9269 Header names follow the syntax of RFC 2822, which states that they may contain
9270 any printing characters except space and colon. Consequently, curly brackets
9271 &'do not'& terminate header names, and should not be used to enclose them as
9272 if they were variables. Attempting to do so causes a syntax error.
9274 Only header lines that are common to all copies of a message are visible to
9275 this mechanism. These are the original header lines that are received with the
9276 message, and any that are added by an ACL statement or by a system
9277 filter. Header lines that are added to a particular copy of a message by a
9278 router or transport are not accessible.
9280 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9281 before the DATA ACL, because the header structure is not set up until the
9282 message is received. Header lines that are added in a RCPT ACL (for example)
9283 are saved until the message's incoming header lines are available, at which
9284 point they are added. When a DATA ACL is running, however, header lines added
9285 by earlier ACLs are visible.
9287 Upper case and lower case letters are synonymous in header names. If the
9288 following character is white space, the terminating colon may be omitted, but
9289 this is not recommended, because you may then forget it when it is needed. When
9290 white space terminates the header name, it is included in the expanded string.
9291 If the message does not contain the given header, the expansion item is
9292 replaced by an empty string. (See the &%def%& condition in section
9293 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
9295 If there is more than one header with the same name, they are all concatenated
9296 to form the substitution string, up to a maximum length of 64K. Unless
9297 &%rheader%& is being used, leading and trailing white space is removed from
9298 each header before concatenation, and a completely empty header is ignored. A
9299 newline character is then inserted between non-empty headers, but there is no
9300 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9301 those headers that contain lists of addresses, a comma is also inserted at the
9302 junctions between headers. This does not happen for the &%rheader%& expansion.
9305 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9306 .cindex "expansion" "hmac hashing"
9308 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9309 shared secret and some text into a message authentication code, as specified in
9310 RFC 2104. This differs from &`${md5:secret_text...}`& or
9311 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9312 cryptographic hash, allowing for authentication that is not possible with MD5
9313 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9314 present. For example:
9316 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9318 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9321 dd97e3ba5d1a61b5006108f8c8252953
9323 As an example of how this might be used, you might put in the main part of
9324 an Exim configuration:
9326 SPAMSCAN_SECRET=cohgheeLei2thahw
9328 In a router or a transport you could then have:
9331 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9332 ${hmac{md5}{SPAMSCAN_SECRET}\
9333 {${primary_hostname},${message_exim_id},$h_message-id:}}
9335 Then given a message, you can check where it was scanned by looking at the
9336 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9337 this header line is authentic by recomputing the authentication code from the
9338 host name, message ID and the &'Message-id:'& header line. This can be done
9339 using Exim's &%-be%& option, or by other means, for example by using the
9340 &'hmac_md5_hex()'& function in Perl.
9343 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9344 .cindex "expansion" "conditional"
9345 .cindex "&%if%&, expansion item"
9346 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9347 item; otherwise <&'string2'&> is used. The available conditions are described
9348 in section &<<SECTexpcond>>& below. For example:
9350 ${if eq {$local_part}{postmaster} {yes}{no} }
9352 The second string need not be present; if it is not and the condition is not
9353 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9354 be present instead of the second string (without any curly brackets). In this
9355 case, the expansion is forced to fail if the condition is not true (see section
9356 &<<SECTforexpfai>>&).
9358 If both strings are omitted, the result is the string &`true`& if the condition
9359 is true, and the empty string if the condition is false. This makes it less
9360 cumbersome to write custom ACL and router conditions. For example, instead of
9362 condition = ${if >{$acl_m4}{3}{true}{false}}
9366 condition = ${if >{$acl_m4}{3}}
9369 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9370 .cindex "expansion" "string truncation"
9371 .cindex "&%length%& expansion item"
9372 The &%length%& item is used to extract the initial portion of a string. Both
9373 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9374 you are using a fixed value for the number, that is, if <&'string1'&> does not
9375 change when expanded, you can use the simpler operator notation that avoids
9378 ${length_<n>:<string>}
9380 The result of this item is either the first <&'n'&> characters or the whole
9381 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9382 &%strlen%&, which gives the length of a string.
9385 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9386 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9387 .cindex "expansion" "extracting list elements by number"
9388 .cindex "&%listextract%&" "extract list elements by number"
9389 .cindex "list" "extracting elements by number"
9390 The <&'number'&> argument must consist entirely of decimal digits,
9391 apart from an optional leading minus,
9392 and leading and trailing white space (which is ignored).
9394 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9395 default, but the separator can be changed in the usual way.
9397 The first field of the list is numbered one.
9398 If the number is negative, the fields are
9399 counted from the end of the list, with the rightmost one numbered -1.
9400 The numbered element of the list is extracted and placed in &$value$&,
9401 then <&'string2'&> is expanded as the result.
9403 If the modulus of the
9404 number is zero or greater than the number of fields in the string,
9405 the result is the expansion of <&'string3'&>.
9409 ${listextract{2}{x:42:99}}
9413 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9415 yields &"result: 99"&.
9417 If {<&'string3'&>} is omitted, an empty string is used for string3.
9418 If {<&'string2'&>} is also omitted, the value that was
9420 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9423 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9424 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9425 This is the first of one of two different types of lookup item, which are both
9426 described in the next item.
9428 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9429 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9430 .cindex "expansion" "lookup in"
9431 .cindex "file" "lookups"
9432 .cindex "lookup" "in expanded string"
9433 The two forms of lookup item specify data lookups in files and databases, as
9434 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9435 lookups, and the second is used for query-style lookups. The <&'key'&>,
9436 <&'file'&>, and <&'query'&> strings are expanded before use.
9438 If there is any white space in a lookup item which is part of a filter command,
9439 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9440 other place where white space is significant, the lookup item must be enclosed
9441 in double quotes. The use of data lookups in users' filter files may be locked
9442 out by the system administrator.
9445 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9446 During its expansion, the variable &$value$& contains the data returned by the
9447 lookup. Afterwards it reverts to the value it had previously (at the outer
9448 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9449 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9450 string on failure. If <&'string2'&> is provided, it can itself be a nested
9451 lookup, thus providing a mechanism for looking up a default value when the
9452 original lookup fails.
9454 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9455 data for the outer lookup while the parameters of the second lookup are
9456 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9457 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9458 appear, and in this case, if the lookup fails, the entire expansion is forced
9459 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9460 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9461 successful lookup, and nothing in the case of failure.
9463 For single-key lookups, the string &"partial"& is permitted to precede the
9464 search type in order to do partial matching, and * or *@ may follow a search
9465 type to request default lookups if the key does not match (see sections
9466 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9468 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9469 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9470 and non-wild parts of the key during the expansion of the replacement text.
9471 They return to their previous values at the end of the lookup item.
9473 This example looks up the postmaster alias in the conventional alias file:
9475 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9477 This example uses NIS+ to look up the full name of the user corresponding to
9478 the local part of an address, forcing the expansion to fail if it is not found:
9480 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9485 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9486 .cindex "expansion" "list creation"
9488 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9489 default, but the separator can be changed in the usual way. For each item
9490 in this list, its value is place in &$item$&, and then <&'string2'&> is
9491 expanded and added to the output as an item in a new list. The separator used
9492 for the output list is the same as the one used for the input, but a separator
9493 setting is not included in the output. For example:
9495 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9497 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9498 value of &$item$& is restored to what it was before. See also the &*filter*&
9499 and &*reduce*& expansion items.
9501 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9502 .cindex "expansion" "numeric hash"
9503 .cindex "hash function" "numeric"
9504 The three strings are expanded; the first two must yield numbers. Call them
9505 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9506 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9507 can use the simpler operator notation that avoids some of the braces:
9509 ${nhash_<n>_<m>:<string>}
9511 The second number is optional (in both notations). If there is only one number,
9512 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9513 processed by a div/mod hash function that returns two numbers, separated by a
9514 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9517 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9519 returns the string &"6/33"&.
9523 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9524 .cindex "Perl" "use in expanded string"
9525 .cindex "expansion" "calling Perl from"
9526 This item is available only if Exim has been built to include an embedded Perl
9527 interpreter. The subroutine name and the arguments are first separately
9528 expanded, and then the Perl subroutine is called with those arguments. No
9529 additional arguments need be given; the maximum number permitted, including the
9530 name of the subroutine, is nine.
9532 The return value of the subroutine is inserted into the expanded string, unless
9533 the return value is &%undef%&. In that case, the expansion fails in the same
9534 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9535 Whatever you return is evaluated in a scalar context. For example, if you
9536 return the name of a Perl vector, the return value is the size of the vector,
9539 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9540 with the error message that was passed to &%die%&. More details of the embedded
9541 Perl facility are given in chapter &<<CHAPperl>>&.
9543 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9544 out the use of this expansion item in filter files.
9547 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9548 .cindex "&%prvs%& expansion item"
9549 The first argument is a complete email address and the second is secret
9550 keystring. The third argument, specifying a key number, is optional. If absent,
9551 it defaults to 0. The result of the expansion is a prvs-signed email address,
9552 to be typically used with the &%return_path%& option on an &(smtp)& transport
9553 as part of a bounce address tag validation (BATV) scheme. For more discussion
9554 and an example, see section &<<SECTverifyPRVS>>&.
9556 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9557 {*&<&'string'&>&*}}*&"
9558 .cindex "&%prvscheck%& expansion item"
9559 This expansion item is the complement of the &%prvs%& item. It is used for
9560 checking prvs-signed addresses. If the expansion of the first argument does not
9561 yield a syntactically valid prvs-signed address, the whole item expands to the
9562 empty string. When the first argument does expand to a syntactically valid
9563 prvs-signed address, the second argument is expanded, with the prvs-decoded
9564 version of the address and the key number extracted from the address in the
9565 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9567 These two variables can be used in the expansion of the second argument to
9568 retrieve the secret. The validity of the prvs-signed address is then checked
9569 against the secret. The result is stored in the variable &$prvscheck_result$&,
9570 which is empty for failure or &"1"& for success.
9572 The third argument is optional; if it is missing, it defaults to an empty
9573 string. This argument is now expanded. If the result is an empty string, the
9574 result of the expansion is the decoded version of the address. This is the case
9575 whether or not the signature was valid. Otherwise, the result of the expansion
9576 is the expansion of the third argument.
9578 All three variables can be used in the expansion of the third argument.
9579 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9580 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9582 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9583 .cindex "expansion" "inserting an entire file"
9584 .cindex "file" "inserting into expansion"
9585 .cindex "&%readfile%& expansion item"
9586 The file name and end-of-line string are first expanded separately. The file is
9587 then read, and its contents replace the entire item. All newline characters in
9588 the file are replaced by the end-of-line string if it is present. Otherwise,
9589 newlines are left in the string.
9590 String expansion is not applied to the contents of the file. If you want this,
9591 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9592 the string expansion fails.
9594 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9595 locks out the use of this expansion item in filter files.
9599 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9600 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9601 .cindex "expansion" "inserting from a socket"
9602 .cindex "socket, use of in expansion"
9603 .cindex "&%readsocket%& expansion item"
9604 This item inserts data from a Unix domain or TCP socket into the expanded
9605 string. The minimal way of using it uses just two arguments, as in these
9608 ${readsocket{/socket/name}{request string}}
9609 ${readsocket{inet:some.host:1234}{request string}}
9611 For a Unix domain socket, the first substring must be the path to the socket.
9612 For an Internet socket, the first substring must contain &`inet:`& followed by
9613 a host name or IP address, followed by a colon and a port, which can be a
9614 number or the name of a TCP port in &_/etc/services_&. An IP address may
9615 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9618 ${readsocket{inet:[::1]:1234}{request string}}
9620 Only a single host name may be given, but if looking it up yields more than
9621 one IP address, they are each tried in turn until a connection is made. For
9622 both kinds of socket, Exim makes a connection, writes the request string
9623 (unless it is an empty string) and reads from the socket until an end-of-file
9624 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9625 extend what can be done. Firstly, you can vary the timeout. For example:
9627 ${readsocket{/socket/name}{request string}{3s}}
9629 A fourth argument allows you to change any newlines that are in the data
9630 that is read, in the same way as for &%readfile%& (see above). This example
9631 turns them into spaces:
9633 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9635 As with all expansions, the substrings are expanded before the processing
9636 happens. Errors in these sub-expansions cause the expansion to fail. In
9637 addition, the following errors can occur:
9640 Failure to create a socket file descriptor;
9642 Failure to connect the socket;
9644 Failure to write the request string;
9646 Timeout on reading from the socket.
9649 By default, any of these errors causes the expansion to fail. However, if
9650 you supply a fifth substring, it is expanded and used when any of the above
9651 errors occurs. For example:
9653 ${readsocket{/socket/name}{request string}{3s}{\n}\
9656 You can test for the existence of a Unix domain socket by wrapping this
9657 expansion in &`${if exists`&, but there is a race condition between that test
9658 and the actual opening of the socket, so it is safer to use the fifth argument
9659 if you want to be absolutely sure of avoiding an expansion error for a
9660 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9662 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9663 locks out the use of this expansion item in filter files.
9666 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9667 .cindex "expansion" "reducing a list to a scalar"
9668 .cindex "list" "reducing to a scalar"
9671 This operation reduces a list to a single, scalar string. After expansion,
9672 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9673 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9674 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9675 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9676 them. The result of that expansion is assigned to &$value$& before the next
9677 iteration. When the end of the list is reached, the final value of &$value$& is
9678 added to the expansion output. The &*reduce*& expansion item can be used in a
9679 number of ways. For example, to add up a list of numbers:
9681 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9683 The result of that expansion would be &`6`&. The maximum of a list of numbers
9686 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9688 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9689 restored to what they were before. See also the &*filter*& and &*map*&
9692 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9693 This item inserts &"raw"& header lines. It is described with the &%header%&
9694 expansion item above.
9696 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9697 {*&<&'string2'&>&*}}*&"
9698 .cindex "expansion" "running a command"
9699 .cindex "&%run%& expansion item"
9700 The command and its arguments are first expanded as one string. The string is
9701 split apart into individual arguments by spaces, and then the command is run
9702 in a separate process, but under the same uid and gid. As in other command
9703 executions from Exim, a shell is not used by default. If the command requires
9704 a shell, you must explicitly code it.
9706 Since the arguments are split by spaces, when there is a variable expansion
9707 which has an empty result, it will cause the situation that the argument will
9708 simply be omitted when the program is actually executed by Exim. If the
9709 script/program requires a specific number of arguments and the expanded
9710 variable could possibly result in this empty expansion, the variable must be
9711 quoted. This is more difficult if the expanded variable itself could result
9712 in a string containing quotes, because it would interfere with the quotes
9713 around the command arguments. A possible guard against this is to wrap the
9714 variable in the &%sg%& operator to change any quote marks to some other
9717 The standard input for the command exists, but is empty. The standard output
9718 and standard error are set to the same file descriptor.
9719 .cindex "return code" "from &%run%& expansion"
9721 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9722 and replaces the entire item; during this expansion, the standard output/error
9723 from the command is in the variable &$value$&. If the command fails,
9724 <&'string2'&>, if present, is expanded and used. Once again, during the
9725 expansion, the standard output/error from the command is in the variable
9728 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9729 can be the word &"fail"& (not in braces) to force expansion failure if the
9730 command does not succeed. If both strings are omitted, the result is contents
9731 of the standard output/error on success, and nothing on failure.
9733 .vindex "&$run_in_acl$&"
9734 The standard output/error of the command is put in the variable &$value$&.
9735 In this ACL example, the output of a command is logged for the admin to
9738 warn condition = ${run{/usr/bin/id}{yes}{no}}
9739 log_message = Output of id: $value
9741 If the command requires shell idioms, such as the > redirect operator, the
9742 shell must be invoked directly, such as with:
9744 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9748 The return code from the command is put in the variable &$runrc$&, and this
9749 remains set afterwards, so in a filter file you can do things like this:
9751 if "${run{x y z}{}}$runrc" is 1 then ...
9752 elif $runrc is 2 then ...
9756 If execution of the command fails (for example, the command does not exist),
9757 the return code is 127 &-- the same code that shells use for non-existent
9760 &*Warning*&: In a router or transport, you cannot assume the order in which
9761 option values are expanded, except for those preconditions whose order of
9762 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9763 by the expansion of one option, and use it in another.
9765 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9766 out the use of this expansion item in filter files.
9769 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9770 .cindex "expansion" "string substitution"
9771 .cindex "&%sg%& expansion item"
9772 This item works like Perl's substitution operator (s) with the global (/g)
9773 option; hence its name. However, unlike the Perl equivalent, Exim does not
9774 modify the subject string; instead it returns the modified string for insertion
9775 into the overall expansion. The item takes three arguments: the subject string,
9776 a regular expression, and a substitution string. For example:
9778 ${sg{abcdefabcdef}{abc}{xyz}}
9780 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9781 if any $ or \ characters are required in the regular expression or in the
9782 substitution string, they have to be escaped. For example:
9784 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9786 yields &"defabc"&, and
9788 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9790 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9791 the regular expression from string expansion.
9795 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9796 .cindex sorting "a list"
9797 .cindex list sorting
9798 .cindex expansion "list sorting"
9799 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9800 default, but the separator can be changed in the usual way.
9801 The <&'comparator'&> argument is interpreted as the operator
9802 of a two-argument expansion condition.
9803 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9804 The comparison should return true when applied to two values
9805 if the first value should sort before the second value.
9806 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9807 the element being placed in &$item$&,
9808 to give values for comparison.
9810 The item result is a sorted list,
9811 with the original list separator,
9812 of the list elements (in full) of the original.
9816 ${sort{3:2:1:4}{<}{$item}}
9818 sorts a list of numbers, and
9820 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
9822 will sort an MX lookup into priority order.
9825 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9826 .cindex "&%substr%& expansion item"
9827 .cindex "substring extraction"
9828 .cindex "expansion" "substring extraction"
9829 The three strings are expanded; the first two must yield numbers. Call them
9830 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9831 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9832 can use the simpler operator notation that avoids some of the braces:
9834 ${substr_<n>_<m>:<string>}
9836 The second number is optional (in both notations).
9837 If it is absent in the simpler format, the preceding underscore must also be
9840 The &%substr%& item can be used to extract more general substrings than
9841 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9842 length required. For example
9844 ${substr{3}{2}{$local_part}}
9846 If the starting offset is greater than the string length the result is the
9847 null string; if the length plus starting offset is greater than the string
9848 length, the result is the right-hand part of the string, starting from the
9849 given offset. The first character in the string has offset zero.
9851 The &%substr%& expansion item can take negative offset values to count
9852 from the right-hand end of its operand. The last character is offset -1, the
9853 second-last is offset -2, and so on. Thus, for example,
9855 ${substr{-5}{2}{1234567}}
9857 yields &"34"&. If the absolute value of a negative offset is greater than the
9858 length of the string, the substring starts at the beginning of the string, and
9859 the length is reduced by the amount of overshoot. Thus, for example,
9861 ${substr{-5}{2}{12}}
9863 yields an empty string, but
9865 ${substr{-3}{2}{12}}
9869 When the second number is omitted from &%substr%&, the remainder of the string
9870 is taken if the offset is positive. If it is negative, all characters in the
9871 string preceding the offset point are taken. For example, an offset of -1 and
9872 no length, as in these semantically identical examples:
9875 ${substr{-1}{abcde}}
9877 yields all but the last character of the string, that is, &"abcd"&.
9881 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9882 {*&<&'replacements'&>&*}}*&"
9883 .cindex "expansion" "character translation"
9884 .cindex "&%tr%& expansion item"
9885 This item does single-character translation on its subject string. The second
9886 argument is a list of characters to be translated in the subject string. Each
9887 matching character is replaced by the corresponding character from the
9888 replacement list. For example
9890 ${tr{abcdea}{ac}{13}}
9892 yields &`1b3de1`&. If there are duplicates in the second character string, the
9893 last occurrence is used. If the third string is shorter than the second, its
9894 last character is replicated. However, if it is empty, no translation takes
9900 .section "Expansion operators" "SECTexpop"
9901 .cindex "expansion" "operators"
9902 For expansion items that perform transformations on a single argument string,
9903 the &"operator"& notation is used because it is simpler and uses fewer braces.
9904 The substring is first expanded before the operation is applied to it. The
9905 following operations can be performed:
9908 .vitem &*${address:*&<&'string'&>&*}*&
9909 .cindex "expansion" "RFC 2822 address handling"
9910 .cindex "&%address%& expansion item"
9911 The string is interpreted as an RFC 2822 address, as it might appear in a
9912 header line, and the effective address is extracted from it. If the string does
9913 not parse successfully, the result is empty.
9916 .vitem &*${addresses:*&<&'string'&>&*}*&
9917 .cindex "expansion" "RFC 2822 address handling"
9918 .cindex "&%addresses%& expansion item"
9919 The string (after expansion) is interpreted as a list of addresses in RFC
9920 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9921 operative address (&'local-part@domain'&) is extracted from each item, and the
9922 result of the expansion is a colon-separated list, with appropriate
9923 doubling of colons should any happen to be present in the email addresses.
9924 Syntactically invalid RFC2822 address items are omitted from the output.
9926 It is possible to specify a character other than colon for the output
9927 separator by starting the string with > followed by the new separator
9928 character. For example:
9930 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9932 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9933 expansion item, which extracts the working address from a single RFC2822
9934 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9937 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9938 a strict interpretation of header line formatting. Exim parses the bare,
9939 unquoted portion of an email address and if it finds a comma, treats it as an
9940 email address separator. For the example header line:
9942 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9944 The first example below demonstrates that Q-encoded email addresses are parsed
9945 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9946 It does not see the comma because it's still encoded as "=2C". The second
9947 example below is passed the contents of &`$header_from:`&, meaning it gets
9948 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9949 The third example shows that the presence of a comma is skipped when it is
9952 # exim -be '${addresses:From: \
9953 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9955 # exim -be '${addresses:From: Last, First <user@example.com>}'
9956 Last:user@example.com
9957 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9961 .vitem &*${base62:*&<&'digits'&>&*}*&
9962 .cindex "&%base62%& expansion item"
9963 .cindex "expansion" "conversion to base 62"
9964 The string must consist entirely of decimal digits. The number is converted to
9965 base 62 and output as a string of six characters, including leading zeros. In
9966 the few operating environments where Exim uses base 36 instead of base 62 for
9967 its message identifiers (because those systems do not have case-sensitive file
9968 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9969 be absolutely clear: this is &'not'& base64 encoding.
9971 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9972 .cindex "&%base62d%& expansion item"
9973 .cindex "expansion" "conversion to base 62"
9974 The string must consist entirely of base-62 digits, or, in operating
9975 environments where Exim uses base 36 instead of base 62 for its message
9976 identifiers, base-36 digits. The number is converted to decimal and output as a
9980 .vitem &*${domain:*&<&'string'&>&*}*&
9981 .cindex "domain" "extraction"
9982 .cindex "expansion" "domain extraction"
9983 The string is interpreted as an RFC 2822 address and the domain is extracted
9984 from it. If the string does not parse successfully, the result is empty.
9987 .vitem &*${escape:*&<&'string'&>&*}*&
9988 .cindex "expansion" "escaping non-printing characters"
9989 .cindex "&%escape%& expansion item"
9990 If the string contains any non-printing characters, they are converted to
9991 escape sequences starting with a backslash. Whether characters with the most
9992 significant bit set (so-called &"8-bit characters"&) count as printing or not
9993 is controlled by the &%print_topbitchars%& option.
9996 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9997 .cindex "expansion" "expression evaluation"
9998 .cindex "expansion" "arithmetic expression"
9999 .cindex "&%eval%& expansion item"
10000 These items supports simple arithmetic and bitwise logical operations in
10001 expansion strings. The string (after expansion) must be a conventional
10002 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10003 logical operators, and parentheses. All operations are carried out using
10004 integer arithmetic. The operator priorities are as follows (the same as in the
10005 C programming language):
10007 .irow &'highest:'& "not (~), negate (-)"
10008 .irow "" "multiply (*), divide (/), remainder (%)"
10009 .irow "" "plus (+), minus (-)"
10010 .irow "" "shift-left (<<), shift-right (>>)"
10011 .irow "" "and (&&)"
10013 .irow &'lowest:'& "or (|)"
10015 Binary operators with the same priority are evaluated from left to right. White
10016 space is permitted before or after operators.
10018 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10019 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10020 decimal, even if they start with a leading zero; hexadecimal numbers are not
10021 permitted. This can be useful when processing numbers extracted from dates or
10022 times, which often do have leading zeros.
10024 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10026 respectively. Negative numbers are supported. The result of the computation is
10027 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10030 &`${eval:1+1} `& yields 2
10031 &`${eval:1+2*3} `& yields 7
10032 &`${eval:(1+2)*3} `& yields 9
10033 &`${eval:2+42%5} `& yields 4
10034 &`${eval:0xc&5} `& yields 4
10035 &`${eval:0xc|5} `& yields 13
10036 &`${eval:0xc^5} `& yields 9
10037 &`${eval:0xc>>1} `& yields 6
10038 &`${eval:0xc<<1} `& yields 24
10039 &`${eval:~255&0x1234} `& yields 4608
10040 &`${eval:-(~255&0x1234)} `& yields -4608
10043 As a more realistic example, in an ACL you might have
10045 deny message = Too many bad recipients
10048 {>{$rcpt_count}{10}} \
10051 {$recipients_count} \
10052 {${eval:$rcpt_count/2}} \
10056 The condition is true if there have been more than 10 RCPT commands and
10057 fewer than half of them have resulted in a valid recipient.
10060 .vitem &*${expand:*&<&'string'&>&*}*&
10061 .cindex "expansion" "re-expansion of substring"
10062 The &%expand%& operator causes a string to be expanded for a second time. For
10065 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10067 first looks up a string in a file while expanding the operand for &%expand%&,
10068 and then re-expands what it has found.
10071 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10073 .cindex "UTF-8" "conversion from"
10074 .cindex "expansion" "UTF-8 conversion"
10075 .cindex "&%from_utf8%& expansion item"
10076 The world is slowly moving towards Unicode, although there are no standards for
10077 email yet. However, other applications (including some databases) are starting
10078 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10079 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10080 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10081 the result is an undefined sequence of bytes.
10083 Unicode code points with values less than 256 are compatible with ASCII and
10084 ISO-8859-1 (also known as Latin-1).
10085 For example, character 169 is the copyright symbol in both cases, though the
10086 way it is encoded is different. In UTF-8, more than one byte is needed for
10087 characters with code values greater than 127, whereas ISO-8859-1 is a
10088 single-byte encoding (but thereby limited to 256 characters). This makes
10089 translation from UTF-8 to ISO-8859-1 straightforward.
10092 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10093 .cindex "hash function" "textual"
10094 .cindex "expansion" "textual hash"
10095 The &%hash%& operator is a simpler interface to the hashing function that can
10096 be used when the two parameters are fixed numbers (as opposed to strings that
10097 change when expanded). The effect is the same as
10099 ${hash{<n>}{<m>}{<string>}}
10101 See the description of the general &%hash%& item above for details. The
10102 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10106 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10107 .cindex "base64 encoding" "conversion from hex"
10108 .cindex "expansion" "hex to base64"
10109 .cindex "&%hex2b64%& expansion item"
10110 This operator converts a hex string into one that is base64 encoded. This can
10111 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10115 .vitem &*${hexquote:*&<&'string'&>&*}*&
10116 .cindex "quoting" "hex-encoded unprintable characters"
10117 .cindex "&%hexquote%& expansion item"
10118 This operator converts non-printable characters in a string into a hex
10119 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10120 as is, and other byte values are converted to &`\xNN`&, for example a
10121 byte value 127 is converted to &`\x7f`&.
10124 .vitem &*${lc:*&<&'string'&>&*}*&
10125 .cindex "case forcing in strings"
10126 .cindex "string" "case forcing"
10127 .cindex "lower casing"
10128 .cindex "expansion" "case forcing"
10129 .cindex "&%lc%& expansion item"
10130 This forces the letters in the string into lower-case, for example:
10135 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10136 .cindex "expansion" "string truncation"
10137 .cindex "&%length%& expansion item"
10138 The &%length%& operator is a simpler interface to the &%length%& function that
10139 can be used when the parameter is a fixed number (as opposed to a string that
10140 changes when expanded). The effect is the same as
10142 ${length{<number>}{<string>}}
10144 See the description of the general &%length%& item above for details. Note that
10145 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10146 when &%length%& is used as an operator.
10149 .vitem &*${listcount:*&<&'string'&>&*}*&
10150 .cindex "expansion" "list item count"
10151 .cindex "list" "item count"
10152 .cindex "list" "count of items"
10153 .cindex "&%listcount%& expansion item"
10154 The string is interpreted as a list and the number of items is returned.
10157 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10158 .cindex "expansion" "named list"
10159 .cindex "&%listnamed%& expansion item"
10160 The name is interpreted as a named list and the content of the list is returned,
10161 expanding any referenced lists, re-quoting as needed for colon-separation.
10162 If the optional type is given it must be one of "a", "d", "h" or "l"
10163 and selects address-, domain-, host- or localpart- lists to search among respectively.
10164 Otherwise all types are searched in an undefined order and the first
10165 matching list is returned.
10168 .vitem &*${local_part:*&<&'string'&>&*}*&
10169 .cindex "expansion" "local part extraction"
10170 .cindex "&%local_part%& expansion item"
10171 The string is interpreted as an RFC 2822 address and the local part is
10172 extracted from it. If the string does not parse successfully, the result is
10176 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10177 .cindex "masked IP address"
10178 .cindex "IP address" "masking"
10179 .cindex "CIDR notation"
10180 .cindex "expansion" "IP address masking"
10181 .cindex "&%mask%& expansion item"
10182 If the form of the string to be operated on is not an IP address followed by a
10183 slash and an integer (that is, a network address in CIDR notation), the
10184 expansion fails. Otherwise, this operator converts the IP address to binary,
10185 masks off the least significant bits according to the bit count, and converts
10186 the result back to text, with mask appended. For example,
10188 ${mask:10.111.131.206/28}
10190 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10191 be mostly used for looking up masked addresses in files, the result for an IPv6
10192 address uses dots to separate components instead of colons, because colon
10193 terminates a key string in lsearch files. So, for example,
10195 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10199 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10201 Letters in IPv6 addresses are always output in lower case.
10204 .vitem &*${md5:*&<&'string'&>&*}*&
10206 .cindex "expansion" "MD5 hash"
10207 .cindex "certificate fingerprint"
10208 .cindex "&%md5%& expansion item"
10209 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10210 as a 32-digit hexadecimal number, in which any letters are in lower case.
10213 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10214 .cindex "expansion" "numeric hash"
10215 .cindex "hash function" "numeric"
10216 The &%nhash%& operator is a simpler interface to the numeric hashing function
10217 that can be used when the two parameters are fixed numbers (as opposed to
10218 strings that change when expanded). The effect is the same as
10220 ${nhash{<n>}{<m>}{<string>}}
10222 See the description of the general &%nhash%& item above for details.
10225 .vitem &*${quote:*&<&'string'&>&*}*&
10226 .cindex "quoting" "in string expansions"
10227 .cindex "expansion" "quoting"
10228 .cindex "&%quote%& expansion item"
10229 The &%quote%& operator puts its argument into double quotes if it
10230 is an empty string or
10231 contains anything other than letters, digits, underscores, dots, and hyphens.
10232 Any occurrences of double quotes and backslashes are escaped with a backslash.
10233 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10234 respectively For example,
10242 The place where this is useful is when the argument is a substitution from a
10243 variable or a message header.
10245 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10246 .cindex "&%quote_local_part%& expansion item"
10247 This operator is like &%quote%&, except that it quotes the string only if
10248 required to do so by the rules of RFC 2822 for quoting local parts. For
10249 example, a plus sign would not cause quoting (but it would for &%quote%&).
10250 If you are creating a new email address from the contents of &$local_part$&
10251 (or any other unknown data), you should always use this operator.
10254 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10255 .cindex "quoting" "lookup-specific"
10256 This operator applies lookup-specific quoting rules to the string. Each
10257 query-style lookup type has its own quoting rules which are described with
10258 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10260 ${quote_ldap:two * two}
10266 For single-key lookup types, no quoting is ever necessary and this operator
10267 yields an unchanged string.
10270 .vitem &*${randint:*&<&'n'&>&*}*&
10271 .cindex "random number"
10272 This operator returns a somewhat random number which is less than the
10273 supplied number and is at least 0. The quality of this randomness depends
10274 on how Exim was built; the values are not suitable for keying material.
10275 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10276 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10277 for versions of GnuTLS with that function.
10278 Otherwise, the implementation may be arc4random(), random() seeded by
10279 srandomdev() or srandom(), or a custom implementation even weaker than
10283 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10284 .cindex "expansion" "IP address"
10285 This operator reverses an IP address; for IPv4 addresses, the result is in
10286 dotted-quad decimal form, while for IPv6 addresses the result is in
10287 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10288 for DNS. For example,
10290 ${reverse_ip:192.0.2.4}
10291 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10296 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10300 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10301 .cindex "expansion" "RFC 2047"
10302 .cindex "RFC 2047" "expansion operator"
10303 .cindex "&%rfc2047%& expansion item"
10304 This operator encodes text according to the rules of RFC 2047. This is an
10305 encoding that is used in header lines to encode non-ASCII characters. It is
10306 assumed that the input string is in the encoding specified by the
10307 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
10308 contains only characters in the range 33&--126, and no instances of the
10311 ? = ( ) < > @ , ; : \ " . [ ] _
10313 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10314 string, using as many &"encoded words"& as necessary to encode all the
10318 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10319 .cindex "expansion" "RFC 2047"
10320 .cindex "RFC 2047" "decoding"
10321 .cindex "&%rfc2047d%& expansion item"
10322 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10323 bytes are replaced by question marks. Characters are converted into the
10324 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10325 not recognized unless &%check_rfc2047_length%& is set false.
10327 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10328 access a header line, RFC 2047 decoding is done automatically. You do not need
10329 to use this operator as well.
10333 .vitem &*${rxquote:*&<&'string'&>&*}*&
10334 .cindex "quoting" "in regular expressions"
10335 .cindex "regular expressions" "quoting"
10336 .cindex "&%rxquote%& expansion item"
10337 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10338 characters in its argument. This is useful when substituting the values of
10339 variables or headers inside regular expressions.
10342 .vitem &*${sha1:*&<&'string'&>&*}*&
10343 .cindex "SHA-1 hash"
10344 .cindex "expansion" "SHA-1 hashing"
10345 .cindex "certificate fingerprint"
10346 .cindex "&%sha2%& expansion item"
10347 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10348 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10351 .vitem &*${sha256:*&<&'certificate'&>&*}*&
10352 .cindex "SHA-256 hash"
10353 .cindex "certificate fingerprint"
10354 .cindex "expansion" "SHA-256 hashing"
10355 .cindex "&%sha256%& expansion item"
10356 The &%sha256%& operator computes the SHA-256 hash fingerprint of the
10359 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10360 Only arguments which are a single variable of certificate type are supported.
10363 .vitem &*${stat:*&<&'string'&>&*}*&
10364 .cindex "expansion" "statting a file"
10365 .cindex "file" "extracting characteristics"
10366 .cindex "&%stat%& expansion item"
10367 The string, after expansion, must be a file path. A call to the &[stat()]&
10368 function is made for this path. If &[stat()]& fails, an error occurs and the
10369 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10370 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10371 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10372 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10373 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10374 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10375 can extract individual fields using the &%extract%& expansion item.
10377 The use of the &%stat%& expansion in users' filter files can be locked out by
10378 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10379 systems for files larger than 2GB.
10381 .vitem &*${str2b64:*&<&'string'&>&*}*&
10382 .cindex "expansion" "base64 encoding"
10383 .cindex "base64 encoding" "in string expansion"
10384 .cindex "&%str2b64%& expansion item"
10385 This operator converts a string into one that is base64 encoded.
10389 .vitem &*${strlen:*&<&'string'&>&*}*&
10390 .cindex "expansion" "string length"
10391 .cindex "string" "length in expansion"
10392 .cindex "&%strlen%& expansion item"
10393 The item is replace by the length of the expanded string, expressed as a
10394 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10397 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10398 .cindex "&%substr%& expansion item"
10399 .cindex "substring extraction"
10400 .cindex "expansion" "substring expansion"
10401 The &%substr%& operator is a simpler interface to the &%substr%& function that
10402 can be used when the two parameters are fixed numbers (as opposed to strings
10403 that change when expanded). The effect is the same as
10405 ${substr{<start>}{<length>}{<string>}}
10407 See the description of the general &%substr%& item above for details. The
10408 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10410 .vitem &*${time_eval:*&<&'string'&>&*}*&
10411 .cindex "&%time_eval%& expansion item"
10412 .cindex "time interval" "decoding"
10413 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10416 .vitem &*${time_interval:*&<&'string'&>&*}*&
10417 .cindex "&%time_interval%& expansion item"
10418 .cindex "time interval" "formatting"
10419 The argument (after sub-expansion) must be a sequence of decimal digits that
10420 represents an interval of time as a number of seconds. It is converted into a
10421 number of larger units and output in Exim's normal time format, for example,
10424 .vitem &*${uc:*&<&'string'&>&*}*&
10425 .cindex "case forcing in strings"
10426 .cindex "string" "case forcing"
10427 .cindex "upper casing"
10428 .cindex "expansion" "case forcing"
10429 .cindex "&%uc%& expansion item"
10430 This forces the letters in the string into upper-case.
10432 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10433 .cindex "correction of invalid utf-8 sequences in strings"
10434 .cindex "utf-8" "utf-8 sequences"
10435 .cindex "incorrect utf-8"
10436 .cindex "expansion" "utf-8 forcing"
10437 .cindex "&%utf8clean%& expansion item"
10438 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10446 .section "Expansion conditions" "SECTexpcond"
10447 .scindex IIDexpcond "expansion" "conditions"
10448 The following conditions are available for testing by the &%${if%& construct
10449 while expanding strings:
10452 .vitem &*!*&<&'condition'&>
10453 .cindex "expansion" "negating a condition"
10454 .cindex "negation" "in expansion condition"
10455 Preceding any condition with an exclamation mark negates the result of the
10458 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10459 .cindex "numeric comparison"
10460 .cindex "expansion" "numeric comparison"
10461 There are a number of symbolic operators for doing numeric comparisons. They
10467 &`>= `& greater or equal
10469 &`<= `& less or equal
10473 ${if >{$message_size}{10M} ...
10475 Note that the general negation operator provides for inequality testing. The
10476 two strings must take the form of optionally signed decimal integers,
10477 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10478 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10479 As a special case, the numerical value of an empty string is taken as
10482 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10483 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10484 10M, not if 10M is larger than &$message_size$&.
10487 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10488 {*&<&'arg2'&>&*}...}*&
10489 .cindex "expansion" "calling an acl"
10490 .cindex "&%acl%&" "expansion condition"
10491 The name and zero to nine argument strings are first expanded separately. The expanded
10492 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10493 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10494 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10495 and may use the variables; if another acl expansion is used the values
10496 are restored after it returns. If the ACL sets
10497 a value using a "message =" modifier the variable $value becomes
10498 the result of the expansion, otherwise it is empty.
10499 If the ACL returns accept the condition is true; if deny, false.
10500 If the ACL returns defer the result is a forced-fail.
10502 .vitem &*bool&~{*&<&'string'&>&*}*&
10503 .cindex "expansion" "boolean parsing"
10504 .cindex "&%bool%& expansion condition"
10505 This condition turns a string holding a true or false representation into
10506 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10507 (case-insensitively); also integer numbers map to true if non-zero,
10509 An empty string is treated as false.
10510 Leading and trailing whitespace is ignored;
10511 thus a string consisting only of whitespace is false.
10512 All other string values will result in expansion failure.
10514 When combined with ACL variables, this expansion condition will let you
10515 make decisions in one place and act on those decisions in another place.
10518 ${if bool{$acl_m_privileged_sender} ...
10522 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10523 .cindex "expansion" "boolean parsing"
10524 .cindex "&%bool_lax%& expansion condition"
10525 Like &%bool%&, this condition turns a string into a boolean state. But
10526 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10527 loose definition that the Router &%condition%& option uses. The empty string
10528 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10529 true. Leading and trailing whitespace is ignored.
10531 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10533 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10534 .cindex "expansion" "encrypted comparison"
10535 .cindex "encrypted strings, comparing"
10536 .cindex "&%crypteq%& expansion condition"
10537 This condition is included in the Exim binary if it is built to support any
10538 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10539 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10540 included in the binary.
10542 The &%crypteq%& condition has two arguments. The first is encrypted and
10543 compared against the second, which is already encrypted. The second string may
10544 be in the LDAP form for storing encrypted strings, which starts with the
10545 encryption type in curly brackets, followed by the data. If the second string
10546 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10547 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10548 Typically this will be a field from a password file. An example of an encrypted
10549 string in LDAP form is:
10551 {md5}CY9rzUYh03PK3k6DJie09g==
10553 If such a string appears directly in an expansion, the curly brackets have to
10554 be quoted, because they are part of the expansion syntax. For example:
10556 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10558 The following encryption types (whose names are matched case-independently) are
10563 .cindex "base64 encoding" "in encrypted password"
10564 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10565 printable characters to compare with the remainder of the second string. If the
10566 length of the comparison string is 24, Exim assumes that it is base64 encoded
10567 (as in the above example). If the length is 32, Exim assumes that it is a
10568 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10572 .cindex "SHA-1 hash"
10573 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10574 printable characters to compare with the remainder of the second string. If the
10575 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10576 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10577 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10580 .cindex "&[crypt()]&"
10581 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10582 only the first eight characters of the password. However, in modern operating
10583 systems this is no longer true, and in many cases the entire password is used,
10584 whatever its length.
10587 .cindex "&[crypt16()]&"
10588 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10589 use up to 16 characters of the password in some operating systems. Again, in
10590 modern operating systems, more characters may be used.
10592 Exim has its own version of &[crypt16()]&, which is just a double call to
10593 &[crypt()]&. For operating systems that have their own version, setting
10594 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10595 operating system version instead of its own. This option is set by default in
10596 the OS-dependent &_Makefile_& for those operating systems that are known to
10597 support &[crypt16()]&.
10599 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10600 it was not using the same algorithm as some operating systems' versions. It
10601 turns out that as well as &[crypt16()]& there is a function called
10602 &[bigcrypt()]& in some operating systems. This may or may not use the same
10603 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10605 However, since there is now a move away from the traditional &[crypt()]&
10606 functions towards using SHA1 and other algorithms, tidying up this area of
10607 Exim is seen as very low priority.
10609 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10610 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10611 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10612 default is &`{crypt}`&. Whatever the default, you can always use either
10613 function by specifying it explicitly in curly brackets.
10615 .vitem &*def:*&<&'variable&~name'&>
10616 .cindex "expansion" "checking for empty variable"
10617 .cindex "&%def%& expansion condition"
10618 The &%def%& condition must be followed by the name of one of the expansion
10619 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10620 variable does not contain the empty string. For example:
10622 ${if def:sender_ident {from $sender_ident}}
10624 Note that the variable name is given without a leading &%$%& character. If the
10625 variable does not exist, the expansion fails.
10627 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10628 &~&*def:h_*&<&'header&~name'&>&*:*&"
10629 .cindex "expansion" "checking header line existence"
10630 This condition is true if a message is being processed and the named header
10631 exists in the message. For example,
10633 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10635 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10636 the header name must be terminated by a colon if white space does not follow.
10638 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10639 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10640 .cindex "string" "comparison"
10641 .cindex "expansion" "string comparison"
10642 .cindex "&%eq%& expansion condition"
10643 .cindex "&%eqi%& expansion condition"
10644 The two substrings are first expanded. The condition is true if the two
10645 resulting strings are identical. For &%eq%& the comparison includes the case of
10646 letters, whereas for &%eqi%& the comparison is case-independent.
10648 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10649 .cindex "expansion" "file existence test"
10650 .cindex "file" "existence test"
10651 .cindex "&%exists%&, expansion condition"
10652 The substring is first expanded and then interpreted as an absolute path. The
10653 condition is true if the named file (or directory) exists. The existence test
10654 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10655 users' filter files may be locked out by the system administrator.
10657 .vitem &*first_delivery*&
10658 .cindex "delivery" "first"
10659 .cindex "first delivery"
10660 .cindex "expansion" "first delivery test"
10661 .cindex "&%first_delivery%& expansion condition"
10662 This condition, which has no data, is true during a message's first delivery
10663 attempt. It is false during any subsequent delivery attempts.
10666 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10667 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10668 .cindex "list" "iterative conditions"
10669 .cindex "expansion" "&*forall*& condition"
10670 .cindex "expansion" "&*forany*& condition"
10672 These conditions iterate over a list. The first argument is expanded to form
10673 the list. By default, the list separator is a colon, but it can be changed by
10674 the normal method. The second argument is interpreted as a condition that is to
10675 be applied to each item in the list in turn. During the interpretation of the
10676 condition, the current list item is placed in a variable called &$item$&.
10678 For &*forany*&, interpretation stops if the condition is true for any item, and
10679 the result of the whole condition is true. If the condition is false for all
10680 items in the list, the overall condition is false.
10682 For &*forall*&, interpretation stops if the condition is false for any item,
10683 and the result of the whole condition is false. If the condition is true for
10684 all items in the list, the overall condition is true.
10686 Note that negation of &*forany*& means that the condition must be false for all
10687 items for the overall condition to succeed, and negation of &*forall*& means
10688 that the condition must be false for at least one item. In this example, the
10689 list separator is changed to a comma:
10691 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10693 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10694 being processed, to enable these expansion items to be nested.
10696 To scan a named list, expand it with the &*listnamed*& operator.
10699 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10700 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10701 .cindex "string" "comparison"
10702 .cindex "expansion" "string comparison"
10703 .cindex "&%ge%& expansion condition"
10704 .cindex "&%gei%& expansion condition"
10705 The two substrings are first expanded. The condition is true if the first
10706 string is lexically greater than or equal to the second string. For &%ge%& the
10707 comparison includes the case of letters, whereas for &%gei%& the comparison is
10710 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10711 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10712 .cindex "string" "comparison"
10713 .cindex "expansion" "string comparison"
10714 .cindex "&%gt%& expansion condition"
10715 .cindex "&%gti%& expansion condition"
10716 The two substrings are first expanded. The condition is true if the first
10717 string is lexically greater than the second string. For &%gt%& the comparison
10718 includes the case of letters, whereas for &%gti%& the comparison is
10721 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10722 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10723 .cindex "string" "comparison"
10724 .cindex "list" "iterative conditions"
10725 Both strings are expanded; the second string is treated as a list of simple
10726 strings; if the first string is a member of the second, then the condition
10729 These are simpler to use versions of the more powerful &*forany*& condition.
10730 Examples, and the &*forany*& equivalents:
10732 ${if inlist{needle}{foo:needle:bar}}
10733 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10734 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10735 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10738 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10739 &*isip4&~{*&<&'string'&>&*}*& &&&
10740 &*isip6&~{*&<&'string'&>&*}*&
10741 .cindex "IP address" "testing string format"
10742 .cindex "string" "testing for IP address"
10743 .cindex "&%isip%& expansion condition"
10744 .cindex "&%isip4%& expansion condition"
10745 .cindex "&%isip6%& expansion condition"
10746 The substring is first expanded, and then tested to see if it has the form of
10747 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10748 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10750 For an IPv4 address, the test is for four dot-separated components, each of
10751 which consists of from one to three digits. For an IPv6 address, up to eight
10752 colon-separated components are permitted, each containing from one to four
10753 hexadecimal digits. There may be fewer than eight components if an empty
10754 component (adjacent colons) is present. Only one empty component is permitted.
10756 &*Note*&: The checks are just on the form of the address; actual numerical
10757 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10758 check. The main use of these tests is to distinguish between IP addresses and
10759 host names, or between IPv4 and IPv6 addresses. For example, you could use
10761 ${if isip4{$sender_host_address}...
10763 to test which IP version an incoming SMTP connection is using.
10765 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10766 .cindex "LDAP" "use for authentication"
10767 .cindex "expansion" "LDAP authentication test"
10768 .cindex "&%ldapauth%& expansion condition"
10769 This condition supports user authentication using LDAP. See section
10770 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10771 queries. For this use, the query must contain a user name and password. The
10772 query itself is not used, and can be empty. The condition is true if the
10773 password is not empty, and the user name and password are accepted by the LDAP
10774 server. An empty password is rejected without calling LDAP because LDAP binds
10775 with an empty password are considered anonymous regardless of the username, and
10776 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10777 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10781 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10782 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10783 .cindex "string" "comparison"
10784 .cindex "expansion" "string comparison"
10785 .cindex "&%le%& expansion condition"
10786 .cindex "&%lei%& expansion condition"
10787 The two substrings are first expanded. The condition is true if the first
10788 string is lexically less than or equal to the second string. For &%le%& the
10789 comparison includes the case of letters, whereas for &%lei%& the comparison is
10792 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10793 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10794 .cindex "string" "comparison"
10795 .cindex "expansion" "string comparison"
10796 .cindex "&%lt%& expansion condition"
10797 .cindex "&%lti%& expansion condition"
10798 The two substrings are first expanded. The condition is true if the first
10799 string is lexically less than the second string. For &%lt%& the comparison
10800 includes the case of letters, whereas for &%lti%& the comparison is
10804 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10805 .cindex "expansion" "regular expression comparison"
10806 .cindex "regular expressions" "match in expanded string"
10807 .cindex "&%match%& expansion condition"
10808 The two substrings are first expanded. The second is then treated as a regular
10809 expression and applied to the first. Because of the pre-expansion, if the
10810 regular expression contains dollar, or backslash characters, they must be
10811 escaped. Care must also be taken if the regular expression contains braces
10812 (curly brackets). A closing brace must be escaped so that it is not taken as a
10813 premature termination of <&'string2'&>. The easiest approach is to use the
10814 &`\N`& feature to disable expansion of the regular expression.
10817 ${if match {$local_part}{\N^\d{3}\N} ...
10819 If the whole expansion string is in double quotes, further escaping of
10820 backslashes is also required.
10822 The condition is true if the regular expression match succeeds.
10823 The regular expression is not required to begin with a circumflex
10824 metacharacter, but if there is no circumflex, the expression is not anchored,
10825 and it may match anywhere in the subject, not just at the start. If you want
10826 the pattern to match at the end of the subject, you must include the &`$`&
10827 metacharacter at an appropriate point.
10829 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10830 At the start of an &%if%& expansion the values of the numeric variable
10831 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10832 succeeds causes them to be reset to the substrings of that condition and they
10833 will have these values during the expansion of the success string. At the end
10834 of the &%if%& expansion, the previous values are restored. After testing a
10835 combination of conditions using &%or%&, the subsequent values of the numeric
10836 variables are those of the condition that succeeded.
10838 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10839 .cindex "&%match_address%& expansion condition"
10840 See &*match_local_part*&.
10842 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10843 .cindex "&%match_domain%& expansion condition"
10844 See &*match_local_part*&.
10846 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10847 .cindex "&%match_ip%& expansion condition"
10848 This condition matches an IP address to a list of IP address patterns. It must
10849 be followed by two argument strings. The first (after expansion) must be an IP
10850 address or an empty string. The second (not expanded) is a restricted host
10851 list that can match only an IP address, not a host name. For example:
10853 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10855 The specific types of host list item that are permitted in the list are:
10858 An IP address, optionally with a CIDR mask.
10860 A single asterisk, which matches any IP address.
10862 An empty item, which matches only if the IP address is empty. This could be
10863 useful for testing for a locally submitted message or one from specific hosts
10864 in a single test such as
10865 . ==== As this is a nested list, any displays it contains must be indented
10866 . ==== as otherwise they are too far to the left. This comment applies to
10867 . ==== the use of xmlto plus fop. There's no problem when formatting with
10868 . ==== sdop, with or without the extra indent.
10870 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10872 where the first item in the list is the empty string.
10874 The item @[] matches any of the local host's interface addresses.
10876 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10877 even if &`net-`& is not specified. There is never any attempt to turn the IP
10878 address into a host name. The most common type of linear search for
10879 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10880 masks. For example:
10882 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10884 It is of course possible to use other kinds of lookup, and in such a case, you
10885 do need to specify the &`net-`& prefix if you want to specify a specific
10886 address mask, for example:
10888 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10890 However, unless you are combining a &%match_ip%& condition with others, it is
10891 just as easy to use the fact that a lookup is itself a condition, and write:
10893 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10897 Note that <&'string2'&> is not itself subject to string expansion, unless
10898 Exim was built with the EXPAND_LISTMATCH_RHS option.
10900 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10902 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10903 .cindex "domain list" "in expansion condition"
10904 .cindex "address list" "in expansion condition"
10905 .cindex "local part" "list, in expansion condition"
10906 .cindex "&%match_local_part%& expansion condition"
10907 This condition, together with &%match_address%& and &%match_domain%&, make it
10908 possible to test domain, address, and local part lists within expansions. Each
10909 condition requires two arguments: an item and a list to match. A trivial
10912 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10914 In each case, the second argument may contain any of the allowable items for a
10915 list of the appropriate type. Also, because the second argument (after
10916 expansion) is a standard form of list, it is possible to refer to a named list.
10917 Thus, you can use conditions like this:
10919 ${if match_domain{$domain}{+local_domains}{...
10921 .cindex "&`+caseful`&"
10922 For address lists, the matching starts off caselessly, but the &`+caseful`&
10923 item can be used, as in all address lists, to cause subsequent items to
10924 have their local parts matched casefully. Domains are always matched
10927 Note that <&'string2'&> is not itself subject to string expansion, unless
10928 Exim was built with the EXPAND_LISTMATCH_RHS option.
10930 &*Note*&: Host lists are &'not'& supported in this way. This is because
10931 hosts have two identities: a name and an IP address, and it is not clear
10932 how to specify cleanly how such a test would work. However, IP addresses can be
10933 matched using &%match_ip%&.
10935 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10936 .cindex "PAM authentication"
10937 .cindex "AUTH" "with PAM"
10938 .cindex "Solaris" "PAM support"
10939 .cindex "expansion" "PAM authentication test"
10940 .cindex "&%pam%& expansion condition"
10941 &'Pluggable Authentication Modules'&
10942 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10943 available in the latest releases of Solaris and in some GNU/Linux
10944 distributions. The Exim support, which is intended for use in conjunction with
10945 the SMTP AUTH command, is available only if Exim is compiled with
10949 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10950 in some releases of GNU/Linux &%-ldl%& is also needed.
10952 The argument string is first expanded, and the result must be a
10953 colon-separated list of strings. Leading and trailing white space is ignored.
10954 The PAM module is initialized with the service name &"exim"& and the user name
10955 taken from the first item in the colon-separated data string (<&'string1'&>).
10956 The remaining items in the data string are passed over in response to requests
10957 from the authentication function. In the simple case there will only be one
10958 request, for a password, so the data consists of just two strings.
10960 There can be problems if any of the strings are permitted to contain colon
10961 characters. In the usual way, these have to be doubled to avoid being taken as
10962 separators. If the data is being inserted from a variable, the &%sg%& expansion
10963 item can be used to double any existing colons. For example, the configuration
10964 of a LOGIN authenticator might contain this setting:
10966 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10968 For a PLAIN authenticator you could use:
10970 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10972 In some operating systems, PAM authentication can be done only from a process
10973 running as root. Since Exim is running as the Exim user when receiving
10974 messages, this means that PAM cannot be used directly in those systems.
10975 A patched version of the &'pam_unix'& module that comes with the
10976 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10977 The patched module allows one special uid/gid combination, in addition to root,
10978 to authenticate. If you build the patched module to allow the Exim user and
10979 group, PAM can then be used from an Exim authenticator.
10982 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10983 .cindex "&'pwcheck'& daemon"
10985 .cindex "expansion" "&'pwcheck'& authentication test"
10986 .cindex "&%pwcheck%& expansion condition"
10987 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10988 This is one way of making it possible for passwords to be checked by a process
10989 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10990 deprecated. Its replacement is &'saslauthd'& (see below).
10992 The pwcheck support is not included in Exim by default. You need to specify
10993 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10994 building Exim. For example:
10996 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10998 You do not need to install the full Cyrus software suite in order to use
10999 the pwcheck daemon. You can compile and install just the daemon alone
11000 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11001 access to the &_/var/pwcheck_& directory.
11003 The &%pwcheck%& condition takes one argument, which must be the user name and
11004 password, separated by a colon. For example, in a LOGIN authenticator
11005 configuration, you might have this:
11007 server_condition = ${if pwcheck{$auth1:$auth2}}
11009 Again, for a PLAIN authenticator configuration, this would be:
11011 server_condition = ${if pwcheck{$auth2:$auth3}}
11013 .vitem &*queue_running*&
11014 .cindex "queue runner" "detecting when delivering from"
11015 .cindex "expansion" "queue runner test"
11016 .cindex "&%queue_running%& expansion condition"
11017 This condition, which has no data, is true during delivery attempts that are
11018 initiated by queue runner processes, and false otherwise.
11021 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11023 .cindex "expansion" "Radius authentication"
11024 .cindex "&%radius%& expansion condition"
11025 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11026 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11027 the Radius client configuration file in order to build Exim with Radius
11030 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11031 library, using the original API. If you are using release 0.4.0 or later of
11032 this library, you need to set
11034 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11036 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11037 &%libradius%& library that comes with FreeBSD. To do this, set
11039 RADIUS_LIB_TYPE=RADLIB
11041 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11042 You may also have to supply a suitable setting in EXTRALIBS so that the
11043 Radius library can be found when Exim is linked.
11045 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11046 Radius client library, which calls the Radius server. The condition is true if
11047 the authentication is successful. For example:
11049 server_condition = ${if radius{<arguments>}}
11053 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11054 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11055 .cindex "&'saslauthd'& daemon"
11057 .cindex "expansion" "&'saslauthd'& authentication test"
11058 .cindex "&%saslauthd%& expansion condition"
11059 This condition supports user authentication using the Cyrus &'saslauthd'&
11060 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11061 Using this daemon is one way of making it possible for passwords to be checked
11062 by a process that is not running as root.
11064 The saslauthd support is not included in Exim by default. You need to specify
11065 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11066 building Exim. For example:
11068 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11070 You do not need to install the full Cyrus software suite in order to use
11071 the saslauthd daemon. You can compile and install just the daemon alone
11072 from the Cyrus SASL library.
11074 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11075 two are mandatory. For example:
11077 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11079 The service and the realm are optional (which is why the arguments are enclosed
11080 in their own set of braces). For details of the meaning of the service and
11081 realm, and how to run the daemon, consult the Cyrus documentation.
11086 .section "Combining expansion conditions" "SECID84"
11087 .cindex "expansion" "combining conditions"
11088 Several conditions can be tested at once by combining them using the &%and%&
11089 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11090 conditions on their own, and precede their lists of sub-conditions. Each
11091 sub-condition must be enclosed in braces within the overall braces that contain
11092 the list. No repetition of &%if%& is used.
11096 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11097 .cindex "&""or""& expansion condition"
11098 .cindex "expansion" "&""or""& of conditions"
11099 The sub-conditions are evaluated from left to right. The condition is true if
11100 any one of the sub-conditions is true.
11103 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11105 When a true sub-condition is found, the following ones are parsed but not
11106 evaluated. If there are several &"match"& sub-conditions the values of the
11107 numeric variables afterwards are taken from the first one that succeeds.
11109 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11110 .cindex "&""and""& expansion condition"
11111 .cindex "expansion" "&""and""& of conditions"
11112 The sub-conditions are evaluated from left to right. The condition is true if
11113 all of the sub-conditions are true. If there are several &"match"&
11114 sub-conditions, the values of the numeric variables afterwards are taken from
11115 the last one. When a false sub-condition is found, the following ones are
11116 parsed but not evaluated.
11118 .ecindex IIDexpcond
11123 .section "Expansion variables" "SECTexpvar"
11124 .cindex "expansion" "variables, list of"
11125 This section contains an alphabetical list of all the expansion variables. Some
11126 of them are available only when Exim is compiled with specific options such as
11127 support for TLS or the content scanning extension.
11130 .vitem "&$0$&, &$1$&, etc"
11131 .cindex "numerical variables (&$1$& &$2$& etc)"
11132 When a &%match%& expansion condition succeeds, these variables contain the
11133 captured substrings identified by the regular expression during subsequent
11134 processing of the success string of the containing &%if%& expansion item.
11135 However, they do not retain their values afterwards; in fact, their previous
11136 values are restored at the end of processing an &%if%& item. The numerical
11137 variables may also be set externally by some other matching process which
11138 precedes the expansion of the string. For example, the commands available in
11139 Exim filter files include an &%if%& command with its own regular expression
11140 matching condition.
11142 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11143 Within an acl condition, expansion condition or expansion item
11144 any arguments are copied to these variables,
11145 any unused variables being made empty.
11147 .vitem "&$acl_c...$&"
11148 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11149 can be given any name that starts with &$acl_c$& and is at least six characters
11150 long, but the sixth character must be either a digit or an underscore. For
11151 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11152 variables persist throughout the lifetime of an SMTP connection. They can be
11153 used to pass information between ACLs and between different invocations of the
11154 same ACL. When a message is received, the values of these variables are saved
11155 with the message, and can be accessed by filters, routers, and transports
11156 during subsequent delivery.
11158 .vitem "&$acl_m...$&"
11159 These variables are like the &$acl_c...$& variables, except that their values
11160 are reset after a message has been received. Thus, if several messages are
11161 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11162 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11163 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11164 message is received, the values of these variables are saved with the message,
11165 and can be accessed by filters, routers, and transports during subsequent
11168 .vitem &$acl_narg$&
11169 Within an acl condition, expansion condition or expansion item
11170 this variable has the number of arguments.
11172 .vitem &$acl_verify_message$&
11173 .vindex "&$acl_verify_message$&"
11174 After an address verification has failed, this variable contains the failure
11175 message. It retains its value for use in subsequent modifiers. The message can
11176 be preserved by coding like this:
11178 warn !verify = sender
11179 set acl_m0 = $acl_verify_message
11181 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11182 &%log_message%& modifiers, to include information about the verification
11185 .vitem &$address_data$&
11186 .vindex "&$address_data$&"
11187 This variable is set by means of the &%address_data%& option in routers. The
11188 value then remains with the address while it is processed by subsequent routers
11189 and eventually a transport. If the transport is handling multiple addresses,
11190 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11191 for more details. &*Note*&: The contents of &$address_data$& are visible in
11194 If &$address_data$& is set when the routers are called from an ACL to verify
11195 a recipient address, the final value is still in the variable for subsequent
11196 conditions and modifiers of the ACL statement. If routing the address caused it
11197 to be redirected to just one address, the child address is also routed as part
11198 of the verification, and in this case the final value of &$address_data$& is
11199 from the child's routing.
11201 If &$address_data$& is set when the routers are called from an ACL to verify a
11202 sender address, the final value is also preserved, but this time in
11203 &$sender_address_data$&, to distinguish it from data from a recipient
11206 In both cases (recipient and sender verification), the value does not persist
11207 after the end of the current ACL statement. If you want to preserve
11208 these values for longer, you can save them in ACL variables.
11210 .vitem &$address_file$&
11211 .vindex "&$address_file$&"
11212 When, as a result of aliasing, forwarding, or filtering, a message is directed
11213 to a specific file, this variable holds the name of the file when the transport
11214 is running. At other times, the variable is empty. For example, using the
11215 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11217 /home/r2d2/savemail
11219 then when the &(address_file)& transport is running, &$address_file$&
11220 contains the text string &`/home/r2d2/savemail`&.
11221 .cindex "Sieve filter" "value of &$address_file$&"
11222 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11223 then up to the transport configuration to generate an appropriate absolute path
11224 to the relevant file.
11226 .vitem &$address_pipe$&
11227 .vindex "&$address_pipe$&"
11228 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11229 this variable holds the pipe command when the transport is running.
11231 .vitem "&$auth1$& &-- &$auth3$&"
11232 .vindex "&$auth1$&, &$auth2$&, etc"
11233 These variables are used in SMTP authenticators (see chapters
11234 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
11236 .vitem &$authenticated_id$&
11237 .cindex "authentication" "id"
11238 .vindex "&$authenticated_id$&"
11239 When a server successfully authenticates a client it may be configured to
11240 preserve some of the authentication information in the variable
11241 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11242 user/password authenticator configuration might preserve the user name for use
11243 in the routers. Note that this is not the same information that is saved in
11244 &$sender_host_authenticated$&.
11245 When a message is submitted locally (that is, not over a TCP connection)
11246 the value of &$authenticated_id$& is normally the login name of the calling
11247 process. However, a trusted user can override this by means of the &%-oMai%&
11248 command line option.
11250 .vitem &$authenticated_fail_id$&
11251 .cindex "authentication" "fail" "id"
11252 .vindex "&$authenticated_fail_id$&"
11253 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11254 will contain the failed authentication id. If more than one authentication
11255 id is attempted, it will contain only the last one. The variable is
11256 available for processing in the ACL's, generally the quit or notquit ACL.
11257 A message to a local recipient could still be accepted without requiring
11258 authentication, which means this variable could also be visible in all of
11262 .vitem &$authenticated_sender$&
11263 .cindex "sender" "authenticated"
11264 .cindex "authentication" "sender"
11265 .cindex "AUTH" "on MAIL command"
11266 .vindex "&$authenticated_sender$&"
11267 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11268 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11269 described in section &<<SECTauthparamail>>&. Unless the data is the string
11270 &"<>"&, it is set as the authenticated sender of the message, and the value is
11271 available during delivery in the &$authenticated_sender$& variable. If the
11272 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11274 .vindex "&$qualify_domain$&"
11275 When a message is submitted locally (that is, not over a TCP connection), the
11276 value of &$authenticated_sender$& is an address constructed from the login
11277 name of the calling process and &$qualify_domain$&, except that a trusted user
11278 can override this by means of the &%-oMas%& command line option.
11281 .vitem &$authentication_failed$&
11282 .cindex "authentication" "failure"
11283 .vindex "&$authentication_failed$&"
11284 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11285 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11286 possible to distinguish between &"did not try to authenticate"&
11287 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11288 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11289 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11290 negative response to an AUTH command, including (for example) an attempt to use
11291 an undefined mechanism.
11293 .vitem &$av_failed$&
11294 .cindex "content scanning" "AV scanner failure"
11295 This variable is available when Exim is compiled with the content-scanning
11296 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11297 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11298 the ACL malware condition.
11300 .vitem &$body_linecount$&
11301 .cindex "message body" "line count"
11302 .cindex "body of message" "line count"
11303 .vindex "&$body_linecount$&"
11304 When a message is being received or delivered, this variable contains the
11305 number of lines in the message's body. See also &$message_linecount$&.
11307 .vitem &$body_zerocount$&
11308 .cindex "message body" "binary zero count"
11309 .cindex "body of message" "binary zero count"
11310 .cindex "binary zero" "in message body"
11311 .vindex "&$body_zerocount$&"
11312 When a message is being received or delivered, this variable contains the
11313 number of binary zero bytes (ASCII NULs) in the message's body.
11315 .vitem &$bounce_recipient$&
11316 .vindex "&$bounce_recipient$&"
11317 This is set to the recipient address of a bounce message while Exim is creating
11318 it. It is useful if a customized bounce message text file is in use (see
11319 chapter &<<CHAPemsgcust>>&).
11321 .vitem &$bounce_return_size_limit$&
11322 .vindex "&$bounce_return_size_limit$&"
11323 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11324 up to a multiple of 1000. It is useful when a customized error message text
11325 file is in use (see chapter &<<CHAPemsgcust>>&).
11327 .vitem &$caller_gid$&
11328 .cindex "gid (group id)" "caller"
11329 .vindex "&$caller_gid$&"
11330 The real group id under which the process that called Exim was running. This is
11331 not the same as the group id of the originator of a message (see
11332 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11333 incarnation normally contains the Exim gid.
11335 .vitem &$caller_uid$&
11336 .cindex "uid (user id)" "caller"
11337 .vindex "&$caller_uid$&"
11338 The real user id under which the process that called Exim was running. This is
11339 not the same as the user id of the originator of a message (see
11340 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11341 incarnation normally contains the Exim uid.
11343 .vitem &$compile_date$&
11344 .vindex "&$compile_date$&"
11345 The date on which the Exim binary was compiled.
11347 .vitem &$compile_number$&
11348 .vindex "&$compile_number$&"
11349 The building process for Exim keeps a count of the number
11350 of times it has been compiled. This serves to distinguish different
11351 compilations of the same version of the program.
11354 .vitem &$config_dir$&
11355 .vindex "&$config_dir$&"
11356 The directory name of the main configuration file. That is, the content of
11357 &$config_file$& with the last component stripped. The value does not
11358 contain the trailing slash. If &$config_file$& does not contain a slash,
11359 &$config_dir$& is ".".
11361 .vitem &$config_file$&
11362 .vindex "&$config_file$&"
11363 The name of the main configuration file Exim is using.
11366 .vitem &$demime_errorlevel$&
11367 .vindex "&$demime_errorlevel$&"
11368 This variable is available when Exim is compiled with
11369 the content-scanning extension and the obsolete &%demime%& condition. For
11370 details, see section &<<SECTdemimecond>>&.
11372 .vitem &$demime_reason$&
11373 .vindex "&$demime_reason$&"
11374 This variable is available when Exim is compiled with the
11375 content-scanning extension and the obsolete &%demime%& condition. For details,
11376 see section &<<SECTdemimecond>>&.
11379 .vitem &$dkim_cur_signer$& &&&
11380 &$dkim_verify_status$& &&&
11381 &$dkim_verify_reason$& &&&
11382 &$dkim_domain$& &&&
11383 &$dkim_identity$& &&&
11384 &$dkim_selector$& &&&
11386 &$dkim_canon_body$& &&&
11387 &$dkim_canon_headers$& &&&
11388 &$dkim_copiedheaders$& &&&
11389 &$dkim_bodylength$& &&&
11390 &$dkim_created$& &&&
11391 &$dkim_expires$& &&&
11392 &$dkim_headernames$& &&&
11393 &$dkim_key_testing$& &&&
11394 &$dkim_key_nosubdomains$& &&&
11395 &$dkim_key_srvtype$& &&&
11396 &$dkim_key_granularity$& &&&
11398 These variables are only available within the DKIM ACL.
11399 For details see chapter &<<CHAPdkim>>&.
11401 .vitem &$dkim_signers$&
11402 .vindex &$dkim_signers$&
11403 When a message has been received this variable contains
11404 a colon-separated list of signer domains and identities for the message.
11405 For details see chapter &<<CHAPdkim>>&.
11408 .vitem &$dnslist_domain$& &&&
11409 &$dnslist_matched$& &&&
11410 &$dnslist_text$& &&&
11412 .vindex "&$dnslist_domain$&"
11413 .vindex "&$dnslist_matched$&"
11414 .vindex "&$dnslist_text$&"
11415 .vindex "&$dnslist_value$&"
11416 .cindex "black list (DNS)"
11417 When a DNS (black) list lookup succeeds, these variables are set to contain
11418 the following data from the lookup: the list's domain name, the key that was
11419 looked up, the contents of any associated TXT record, and the value from the
11420 main A record. See section &<<SECID204>>& for more details.
11423 .vindex "&$domain$&"
11424 When an address is being routed, or delivered on its own, this variable
11425 contains the domain. Uppercase letters in the domain are converted into lower
11426 case for &$domain$&.
11428 Global address rewriting happens when a message is received, so the value of
11429 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11430 is set during user filtering, but not during system filtering, because a
11431 message may have many recipients and the system filter is called just once.
11433 When more than one address is being delivered at once (for example, several
11434 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11435 have the same domain. Transports can be restricted to handling only one domain
11436 at a time if the value of &$domain$& is required at transport time &-- this is
11437 the default for local transports. For further details of the environment in
11438 which local transports are run, see chapter &<<CHAPenvironment>>&.
11440 .oindex "&%delay_warning_condition%&"
11441 At the end of a delivery, if all deferred addresses have the same domain, it is
11442 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11444 The &$domain$& variable is also used in some other circumstances:
11447 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11448 the recipient address. The domain of the &'sender'& address is in
11449 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11450 normally set during the running of the MAIL ACL. However, if the sender address
11451 is verified with a callout during the MAIL ACL, the sender domain is placed in
11452 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11453 the &(smtp)& transport.
11456 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11457 &$domain$& contains the domain portion of the address that is being rewritten;
11458 it can be used in the expansion of the replacement address, for example, to
11459 rewrite domains by file lookup.
11462 With one important exception, whenever a domain list is being scanned,
11463 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11464 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11465 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11466 that, in a RCPT ACL, the sender domain list can be dependent on the
11467 recipient domain (which is what is in &$domain$& at this time).
11470 .cindex "ETRN" "value of &$domain$&"
11471 .oindex "&%smtp_etrn_command%&"
11472 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11473 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11477 .vitem &$domain_data$&
11478 .vindex "&$domain_data$&"
11479 When the &%domains%& option on a router matches a domain by
11480 means of a lookup, the data read by the lookup is available during the running
11481 of the router as &$domain_data$&. In addition, if the driver routes the
11482 address to a transport, the value is available in that transport. If the
11483 transport is handling multiple addresses, the value from the first address is
11486 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11487 domain by means of a lookup. The data read by the lookup is available during
11488 the rest of the ACL statement. In all other situations, this variable expands
11491 .vitem &$exim_gid$&
11492 .vindex "&$exim_gid$&"
11493 This variable contains the numerical value of the Exim group id.
11495 .vitem &$exim_path$&
11496 .vindex "&$exim_path$&"
11497 This variable contains the path to the Exim binary.
11499 .vitem &$exim_uid$&
11500 .vindex "&$exim_uid$&"
11501 This variable contains the numerical value of the Exim user id.
11504 .vitem &$exim_version$&
11505 .vindex "&$exim_version$&"
11506 This variable contains the version string of the Exim build.
11507 The first character is a major version number, currently 4.
11508 Then after a dot, the next group of digits is a minor version number.
11509 There may be other characters following the minor version.
11512 .vitem &$found_extension$&
11513 .vindex "&$found_extension$&"
11514 This variable is available when Exim is compiled with the
11515 content-scanning extension and the obsolete &%demime%& condition. For details,
11516 see section &<<SECTdemimecond>>&.
11518 .vitem &$header_$&<&'name'&>
11519 This is not strictly an expansion variable. It is expansion syntax for
11520 inserting the message header line with the given name. Note that the name must
11521 be terminated by colon or white space, because it may contain a wide variety of
11522 characters. Note also that braces must &'not'& be used.
11524 .vitem &$headers_added$&
11525 .vindex "&$headers_added$&"
11526 Within an ACL this variable contains the headers added so far by
11527 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11528 The headers are a newline-separated list.
11532 When the &%check_local_user%& option is set for a router, the user's home
11533 directory is placed in &$home$& when the check succeeds. In particular, this
11534 means it is set during the running of users' filter files. A router may also
11535 explicitly set a home directory for use by a transport; this can be overridden
11536 by a setting on the transport itself.
11538 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11539 of the environment variable HOME.
11543 If a router assigns an address to a transport (any transport), and passes a
11544 list of hosts with the address, the value of &$host$& when the transport starts
11545 to run is the name of the first host on the list. Note that this applies both
11546 to local and remote transports.
11548 .cindex "transport" "filter"
11549 .cindex "filter" "transport filter"
11550 For the &(smtp)& transport, if there is more than one host, the value of
11551 &$host$& changes as the transport works its way through the list. In
11552 particular, when the &(smtp)& transport is expanding its options for encryption
11553 using TLS, or for specifying a transport filter (see chapter
11554 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11557 When used in the client part of an authenticator configuration (see chapter
11558 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11559 client is connected.
11562 .vitem &$host_address$&
11563 .vindex "&$host_address$&"
11564 This variable is set to the remote host's IP address whenever &$host$& is set
11565 for a remote connection. It is also set to the IP address that is being checked
11566 when the &%ignore_target_hosts%& option is being processed.
11568 .vitem &$host_data$&
11569 .vindex "&$host_data$&"
11570 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11571 result of the lookup is made available in the &$host_data$& variable. This
11572 allows you, for example, to do things like this:
11574 deny hosts = net-lsearch;/some/file
11575 message = $host_data
11577 .vitem &$host_lookup_deferred$&
11578 .cindex "host name" "lookup, failure of"
11579 .vindex "&$host_lookup_deferred$&"
11580 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11581 message comes from a remote host and there is an attempt to look up the host's
11582 name from its IP address, and the attempt is not successful, one of these
11583 variables is set to &"1"&.
11586 If the lookup receives a definite negative response (for example, a DNS lookup
11587 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11590 If there is any kind of problem during the lookup, such that Exim cannot
11591 tell whether or not the host name is defined (for example, a timeout for a DNS
11592 lookup), &$host_lookup_deferred$& is set to &"1"&.
11595 Looking up a host's name from its IP address consists of more than just a
11596 single reverse lookup. Exim checks that a forward lookup of at least one of the
11597 names it receives from a reverse lookup yields the original IP address. If this
11598 is not the case, Exim does not accept the looked up name(s), and
11599 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11600 IP address (for example, the existence of a PTR record in the DNS) is not
11601 sufficient on its own for the success of a host name lookup. If the reverse
11602 lookup succeeds, but there is a lookup problem such as a timeout when checking
11603 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11604 &"1"&. See also &$sender_host_name$&.
11606 .vitem &$host_lookup_failed$&
11607 .vindex "&$host_lookup_failed$&"
11608 See &$host_lookup_deferred$&.
11610 .vitem &$host_port$&
11611 .vindex "&$host_port$&"
11612 This variable is set to the remote host's TCP port whenever &$host$& is set
11613 for an outbound connection.
11617 .vindex "&$inode$&"
11618 The only time this variable is set is while expanding the &%directory_file%&
11619 option in the &(appendfile)& transport. The variable contains the inode number
11620 of the temporary file which is about to be renamed. It can be used to construct
11621 a unique name for the file.
11623 .vitem &$interface_address$&
11624 .vindex "&$interface_address$&"
11625 This is an obsolete name for &$received_ip_address$&.
11627 .vitem &$interface_port$&
11628 .vindex "&$interface_port$&"
11629 This is an obsolete name for &$received_port$&.
11633 This variable is used during the expansion of &*forall*& and &*forany*&
11634 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11635 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11639 .vindex "&$ldap_dn$&"
11640 This variable, which is available only when Exim is compiled with LDAP support,
11641 contains the DN from the last entry in the most recently successful LDAP
11644 .vitem &$load_average$&
11645 .vindex "&$load_average$&"
11646 This variable contains the system load average, multiplied by 1000 so that it
11647 is an integer. For example, if the load average is 0.21, the value of the
11648 variable is 210. The value is recomputed every time the variable is referenced.
11650 .vitem &$local_part$&
11651 .vindex "&$local_part$&"
11652 When an address is being routed, or delivered on its own, this
11653 variable contains the local part. When a number of addresses are being
11654 delivered together (for example, multiple RCPT commands in an SMTP
11655 session), &$local_part$& is not set.
11657 Global address rewriting happens when a message is received, so the value of
11658 &$local_part$& during routing and delivery is the value after rewriting.
11659 &$local_part$& is set during user filtering, but not during system filtering,
11660 because a message may have many recipients and the system filter is called just
11663 .vindex "&$local_part_prefix$&"
11664 .vindex "&$local_part_suffix$&"
11665 If a local part prefix or suffix has been recognized, it is not included in the
11666 value of &$local_part$& during routing and subsequent delivery. The values of
11667 any prefix or suffix are in &$local_part_prefix$& and
11668 &$local_part_suffix$&, respectively.
11670 When a message is being delivered to a file, pipe, or autoreply transport as a
11671 result of aliasing or forwarding, &$local_part$& is set to the local part of
11672 the parent address, not to the file name or command (see &$address_file$& and
11675 When an ACL is running for a RCPT command, &$local_part$& contains the
11676 local part of the recipient address.
11678 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11679 &$local_part$& contains the local part of the address that is being rewritten;
11680 it can be used in the expansion of the replacement address, for example.
11682 In all cases, all quoting is removed from the local part. For example, for both
11685 "abc:xyz"@test.example
11686 abc\:xyz@test.example
11688 the value of &$local_part$& is
11692 If you use &$local_part$& to create another address, you should always wrap it
11693 inside a quoting operator. For example, in a &(redirect)& router you could
11696 data = ${quote_local_part:$local_part}@new.domain.example
11698 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11699 to process local parts in a case-dependent manner in a router, you can set the
11700 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11702 .vitem &$local_part_data$&
11703 .vindex "&$local_part_data$&"
11704 When the &%local_parts%& option on a router matches a local part by means of a
11705 lookup, the data read by the lookup is available during the running of the
11706 router as &$local_part_data$&. In addition, if the driver routes the address
11707 to a transport, the value is available in that transport. If the transport is
11708 handling multiple addresses, the value from the first address is used.
11710 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11711 matches a local part by means of a lookup. The data read by the lookup is
11712 available during the rest of the ACL statement. In all other situations, this
11713 variable expands to nothing.
11715 .vitem &$local_part_prefix$&
11716 .vindex "&$local_part_prefix$&"
11717 When an address is being routed or delivered, and a
11718 specific prefix for the local part was recognized, it is available in this
11719 variable, having been removed from &$local_part$&.
11721 .vitem &$local_part_suffix$&
11722 .vindex "&$local_part_suffix$&"
11723 When an address is being routed or delivered, and a
11724 specific suffix for the local part was recognized, it is available in this
11725 variable, having been removed from &$local_part$&.
11727 .vitem &$local_scan_data$&
11728 .vindex "&$local_scan_data$&"
11729 This variable contains the text returned by the &[local_scan()]& function when
11730 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11732 .vitem &$local_user_gid$&
11733 .vindex "&$local_user_gid$&"
11734 See &$local_user_uid$&.
11736 .vitem &$local_user_uid$&
11737 .vindex "&$local_user_uid$&"
11738 This variable and &$local_user_gid$& are set to the uid and gid after the
11739 &%check_local_user%& router precondition succeeds. This means that their values
11740 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11741 and &%condition%&), for the &%address_data%& expansion, and for any
11742 router-specific expansions. At all other times, the values in these variables
11743 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11745 .vitem &$localhost_number$&
11746 .vindex "&$localhost_number$&"
11747 This contains the expanded value of the
11748 &%localhost_number%& option. The expansion happens after the main options have
11751 .vitem &$log_inodes$&
11752 .vindex "&$log_inodes$&"
11753 The number of free inodes in the disk partition where Exim's
11754 log files are being written. The value is recalculated whenever the variable is
11755 referenced. If the relevant file system does not have the concept of inodes,
11756 the value of is -1. See also the &%check_log_inodes%& option.
11758 .vitem &$log_space$&
11759 .vindex "&$log_space$&"
11760 The amount of free space (as a number of kilobytes) in the disk
11761 partition where Exim's log files are being written. The value is recalculated
11762 whenever the variable is referenced. If the operating system does not have the
11763 ability to find the amount of free space (only true for experimental systems),
11764 the space value is -1. See also the &%check_log_space%& option.
11767 .vitem &$lookup_dnssec_authenticated$&
11768 .vindex "&$lookup_dnssec_authenticated$&"
11769 This variable is set after a DNS lookup done by
11770 a dnsdb lookup expansion, dnslookup router or smtp transport.
11771 .cindex "DNS" "DNSSEC"
11772 It will be empty if &(DNSSEC)& was not requested,
11773 &"no"& if the result was not labelled as authenticated data
11774 and &"yes"& if it was.
11776 Results that are labelled as authoritative answer that match
11777 the &%dns_trust_aa%& configuration variable count also
11778 as authenticated data.
11781 .vitem &$mailstore_basename$&
11782 .vindex "&$mailstore_basename$&"
11783 This variable is set only when doing deliveries in &"mailstore"& format in the
11784 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11785 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11786 contains the basename of the files that are being written, that is, the name
11787 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11790 .vitem &$malware_name$&
11791 .vindex "&$malware_name$&"
11792 This variable is available when Exim is compiled with the
11793 content-scanning extension. It is set to the name of the virus that was found
11794 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11796 .vitem &$max_received_linelength$&
11797 .vindex "&$max_received_linelength$&"
11798 .cindex "maximum" "line length"
11799 .cindex "line length" "maximum"
11800 This variable contains the number of bytes in the longest line that was
11801 received as part of the message, not counting the line termination
11804 .vitem &$message_age$&
11805 .cindex "message" "age of"
11806 .vindex "&$message_age$&"
11807 This variable is set at the start of a delivery attempt to contain the number
11808 of seconds since the message was received. It does not change during a single
11811 .vitem &$message_body$&
11812 .cindex "body of message" "expansion variable"
11813 .cindex "message body" "in expansion"
11814 .cindex "binary zero" "in message body"
11815 .vindex "&$message_body$&"
11816 .oindex "&%message_body_visible%&"
11817 This variable contains the initial portion of a message's body while it is
11818 being delivered, and is intended mainly for use in filter files. The maximum
11819 number of characters of the body that are put into the variable is set by the
11820 &%message_body_visible%& configuration option; the default is 500.
11822 .oindex "&%message_body_newlines%&"
11823 By default, newlines are converted into spaces in &$message_body$&, to make it
11824 easier to search for phrases that might be split over a line break. However,
11825 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11826 zeros are always converted into spaces.
11828 .vitem &$message_body_end$&
11829 .cindex "body of message" "expansion variable"
11830 .cindex "message body" "in expansion"
11831 .vindex "&$message_body_end$&"
11832 This variable contains the final portion of a message's
11833 body while it is being delivered. The format and maximum size are as for
11836 .vitem &$message_body_size$&
11837 .cindex "body of message" "size"
11838 .cindex "message body" "size"
11839 .vindex "&$message_body_size$&"
11840 When a message is being delivered, this variable contains the size of the body
11841 in bytes. The count starts from the character after the blank line that
11842 separates the body from the header. Newlines are included in the count. See
11843 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11845 .vitem &$message_exim_id$&
11846 .vindex "&$message_exim_id$&"
11847 When a message is being received or delivered, this variable contains the
11848 unique message id that is generated and used by Exim to identify the message.
11849 An id is not created for a message until after its header has been successfully
11850 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11851 line; it is the local id that Exim assigns to the message, for example:
11852 &`1BXTIK-0001yO-VA`&.
11854 .vitem &$message_headers$&
11855 .vindex &$message_headers$&
11856 This variable contains a concatenation of all the header lines when a message
11857 is being processed, except for lines added by routers or transports. The header
11858 lines are separated by newline characters. Their contents are decoded in the
11859 same way as a header line that is inserted by &%bheader%&.
11861 .vitem &$message_headers_raw$&
11862 .vindex &$message_headers_raw$&
11863 This variable is like &$message_headers$& except that no processing of the
11864 contents of header lines is done.
11866 .vitem &$message_id$&
11867 This is an old name for &$message_exim_id$&. It is now deprecated.
11869 .vitem &$message_linecount$&
11870 .vindex "&$message_linecount$&"
11871 This variable contains the total number of lines in the header and body of the
11872 message. Compare &$body_linecount$&, which is the count for the body only.
11873 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11874 number of lines received. Before delivery happens (that is, before filters,
11875 routers, and transports run) the count is increased to include the
11876 &'Received:'& header line that Exim standardly adds, and also any other header
11877 lines that are added by ACLs. The blank line that separates the message header
11878 from the body is not counted.
11880 As with the special case of &$message_size$&, during the expansion of the
11881 appendfile transport's maildir_tag option in maildir format, the value of
11882 &$message_linecount$& is the precise size of the number of newlines in the
11883 file that has been written (minus one for the blank line between the
11884 header and the body).
11886 Here is an example of the use of this variable in a DATA ACL:
11888 deny message = Too many lines in message header
11890 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11892 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11893 message has not yet been received.
11895 .vitem &$message_size$&
11896 .cindex "size" "of message"
11897 .cindex "message" "size"
11898 .vindex "&$message_size$&"
11899 When a message is being processed, this variable contains its size in bytes. In
11900 most cases, the size includes those headers that were received with the
11901 message, but not those (such as &'Envelope-to:'&) that are added to individual
11902 deliveries as they are written. However, there is one special case: during the
11903 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11904 doing a delivery in maildir format, the value of &$message_size$& is the
11905 precise size of the file that has been written. See also
11906 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11908 .cindex "RCPT" "value of &$message_size$&"
11909 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11910 contains the size supplied on the MAIL command, or -1 if no size was given. The
11911 value may not, of course, be truthful.
11913 .vitem &$mime_$&&'xxx'&
11914 A number of variables whose names start with &$mime$& are
11915 available when Exim is compiled with the content-scanning extension. For
11916 details, see section &<<SECTscanmimepart>>&.
11918 .vitem "&$n0$& &-- &$n9$&"
11919 These variables are counters that can be incremented by means
11920 of the &%add%& command in filter files.
11922 .vitem &$original_domain$&
11923 .vindex "&$domain$&"
11924 .vindex "&$original_domain$&"
11925 When a top-level address is being processed for delivery, this contains the
11926 same value as &$domain$&. However, if a &"child"& address (for example,
11927 generated by an alias, forward, or filter file) is being processed, this
11928 variable contains the domain of the original address (lower cased). This
11929 differs from &$parent_domain$& only when there is more than one level of
11930 aliasing or forwarding. When more than one address is being delivered in a
11931 single transport run, &$original_domain$& is not set.
11933 If a new address is created by means of a &%deliver%& command in a system
11934 filter, it is set up with an artificial &"parent"& address. This has the local
11935 part &'system-filter'& and the default qualify domain.
11937 .vitem &$original_local_part$&
11938 .vindex "&$local_part$&"
11939 .vindex "&$original_local_part$&"
11940 When a top-level address is being processed for delivery, this contains the
11941 same value as &$local_part$&, unless a prefix or suffix was removed from the
11942 local part, because &$original_local_part$& always contains the full local
11943 part. When a &"child"& address (for example, generated by an alias, forward, or
11944 filter file) is being processed, this variable contains the full local part of
11945 the original address.
11947 If the router that did the redirection processed the local part
11948 case-insensitively, the value in &$original_local_part$& is in lower case.
11949 This variable differs from &$parent_local_part$& only when there is more than
11950 one level of aliasing or forwarding. When more than one address is being
11951 delivered in a single transport run, &$original_local_part$& is not set.
11953 If a new address is created by means of a &%deliver%& command in a system
11954 filter, it is set up with an artificial &"parent"& address. This has the local
11955 part &'system-filter'& and the default qualify domain.
11957 .vitem &$originator_gid$&
11958 .cindex "gid (group id)" "of originating user"
11959 .cindex "sender" "gid"
11960 .vindex "&$caller_gid$&"
11961 .vindex "&$originator_gid$&"
11962 This variable contains the value of &$caller_gid$& that was set when the
11963 message was received. For messages received via the command line, this is the
11964 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11965 normally the gid of the Exim user.
11967 .vitem &$originator_uid$&
11968 .cindex "uid (user id)" "of originating user"
11969 .cindex "sender" "uid"
11970 .vindex "&$caller_uid$&"
11971 .vindex "&$originaltor_uid$&"
11972 The value of &$caller_uid$& that was set when the message was received. For
11973 messages received via the command line, this is the uid of the sending user.
11974 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11977 .vitem &$parent_domain$&
11978 .vindex "&$parent_domain$&"
11979 This variable is similar to &$original_domain$& (see
11980 above), except that it refers to the immediately preceding parent address.
11982 .vitem &$parent_local_part$&
11983 .vindex "&$parent_local_part$&"
11984 This variable is similar to &$original_local_part$&
11985 (see above), except that it refers to the immediately preceding parent address.
11988 .cindex "pid (process id)" "of current process"
11990 This variable contains the current process id.
11992 .vitem &$pipe_addresses$&
11993 .cindex "filter" "transport filter"
11994 .cindex "transport" "filter"
11995 .vindex "&$pipe_addresses$&"
11996 This is not an expansion variable, but is mentioned here because the string
11997 &`$pipe_addresses`& is handled specially in the command specification for the
11998 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11999 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12000 It cannot be used in general expansion strings, and provokes an &"unknown
12001 variable"& error if encountered.
12003 .vitem &$primary_hostname$&
12004 .vindex "&$primary_hostname$&"
12005 This variable contains the value set by &%primary_hostname%& in the
12006 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12007 a single-component name, Exim calls &[gethostbyname()]& (or
12008 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12009 qualified host name. See also &$smtp_active_hostname$&.
12012 .vitem &$prvscheck_address$&
12013 This variable is used in conjunction with the &%prvscheck%& expansion item,
12014 which is described in sections &<<SECTexpansionitems>>& and
12015 &<<SECTverifyPRVS>>&.
12017 .vitem &$prvscheck_keynum$&
12018 This variable is used in conjunction with the &%prvscheck%& expansion item,
12019 which is described in sections &<<SECTexpansionitems>>& and
12020 &<<SECTverifyPRVS>>&.
12022 .vitem &$prvscheck_result$&
12023 This variable is used in conjunction with the &%prvscheck%& expansion item,
12024 which is described in sections &<<SECTexpansionitems>>& and
12025 &<<SECTverifyPRVS>>&.
12027 .vitem &$qualify_domain$&
12028 .vindex "&$qualify_domain$&"
12029 The value set for the &%qualify_domain%& option in the configuration file.
12031 .vitem &$qualify_recipient$&
12032 .vindex "&$qualify_recipient$&"
12033 The value set for the &%qualify_recipient%& option in the configuration file,
12034 or if not set, the value of &$qualify_domain$&.
12036 .vitem &$rcpt_count$&
12037 .vindex "&$rcpt_count$&"
12038 When a message is being received by SMTP, this variable contains the number of
12039 RCPT commands received for the current message. If this variable is used in a
12040 RCPT ACL, its value includes the current command.
12042 .vitem &$rcpt_defer_count$&
12043 .vindex "&$rcpt_defer_count$&"
12044 .cindex "4&'xx'& responses" "count of"
12045 When a message is being received by SMTP, this variable contains the number of
12046 RCPT commands in the current message that have previously been rejected with a
12047 temporary (4&'xx'&) response.
12049 .vitem &$rcpt_fail_count$&
12050 .vindex "&$rcpt_fail_count$&"
12051 When a message is being received by SMTP, this variable contains the number of
12052 RCPT commands in the current message that have previously been rejected with a
12053 permanent (5&'xx'&) response.
12055 .vitem &$received_count$&
12056 .vindex "&$received_count$&"
12057 This variable contains the number of &'Received:'& header lines in the message,
12058 including the one added by Exim (so its value is always greater than zero). It
12059 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12062 .vitem &$received_for$&
12063 .vindex "&$received_for$&"
12064 If there is only a single recipient address in an incoming message, this
12065 variable contains that address when the &'Received:'& header line is being
12066 built. The value is copied after recipient rewriting has happened, but before
12067 the &[local_scan()]& function is run.
12069 .vitem &$received_ip_address$&
12070 .vindex "&$received_ip_address$&"
12071 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12072 variable is set to the address of the local IP interface, and &$received_port$&
12073 is set to the local port number. (The remote IP address and port are in
12074 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12075 the port value is -1 unless it has been set using the &%-oMi%& command line
12078 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12079 could be used, for example, to make the file name for a TLS certificate depend
12080 on which interface and/or port is being used for the incoming connection. The
12081 values of &$received_ip_address$& and &$received_port$& are saved with any
12082 messages that are received, thus making these variables available at delivery
12084 For outbound connections see &$sending_ip_address$&.
12086 .vitem &$received_port$&
12087 .vindex "&$received_port$&"
12088 See &$received_ip_address$&.
12090 .vitem &$received_protocol$&
12091 .vindex "&$received_protocol$&"
12092 When a message is being processed, this variable contains the name of the
12093 protocol by which it was received. Most of the names used by Exim are defined
12094 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12095 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12096 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12097 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12098 connection and the client was successfully authenticated.
12100 Exim uses the protocol name &"smtps"& for the case when encryption is
12101 automatically set up on connection without the use of STARTTLS (see
12102 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12103 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12104 where the client initially uses EHLO, sets up an encrypted connection using
12105 STARTTLS, and then uses HELO afterwards.
12107 The &%-oMr%& option provides a way of specifying a custom protocol name for
12108 messages that are injected locally by trusted callers. This is commonly used to
12109 identify messages that are being re-injected after some kind of scanning.
12111 .vitem &$received_time$&
12112 .vindex "&$received_time$&"
12113 This variable contains the date and time when the current message was received,
12114 as a number of seconds since the start of the Unix epoch.
12116 .vitem &$recipient_data$&
12117 .vindex "&$recipient_data$&"
12118 This variable is set after an indexing lookup success in an ACL &%recipients%&
12119 condition. It contains the data from the lookup, and the value remains set
12120 until the next &%recipients%& test. Thus, you can do things like this:
12122 &`require recipients = cdb*@;/some/file`&
12123 &`deny `&&'some further test involving'& &`$recipient_data`&
12125 &*Warning*&: This variable is set only when a lookup is used as an indexing
12126 method in the address list, using the semicolon syntax as in the example above.
12127 The variable is not set for a lookup that is used as part of the string
12128 expansion that all such lists undergo before being interpreted.
12130 .vitem &$recipient_verify_failure$&
12131 .vindex "&$recipient_verify_failure$&"
12132 In an ACL, when a recipient verification fails, this variable contains
12133 information about the failure. It is set to one of the following words:
12136 &"qualify"&: The address was unqualified (no domain), and the message
12137 was neither local nor came from an exempted host.
12140 &"route"&: Routing failed.
12143 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12144 or before the MAIL command (that is, on initial connection, HELO, or
12148 &"recipient"&: The RCPT command in a callout was rejected.
12151 &"postmaster"&: The postmaster check in a callout was rejected.
12154 The main use of this variable is expected to be to distinguish between
12155 rejections of MAIL and rejections of RCPT.
12157 .vitem &$recipients$&
12158 .vindex "&$recipients$&"
12159 This variable contains a list of envelope recipients for a message. A comma and
12160 a space separate the addresses in the replacement text. However, the variable
12161 is not generally available, to prevent exposure of Bcc recipients in
12162 unprivileged users' filter files. You can use &$recipients$& only in these
12166 In a system filter file.
12168 In the ACLs associated with the DATA command and with non-SMTP messages, that
12169 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12170 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12171 &%acl_not_smtp_mime%&.
12173 From within a &[local_scan()]& function.
12177 .vitem &$recipients_count$&
12178 .vindex "&$recipients_count$&"
12179 When a message is being processed, this variable contains the number of
12180 envelope recipients that came with the message. Duplicates are not excluded
12181 from the count. While a message is being received over SMTP, the number
12182 increases for each accepted recipient. It can be referenced in an ACL.
12185 .vitem &$regex_match_string$&
12186 .vindex "&$regex_match_string$&"
12187 This variable is set to contain the matching regular expression after a
12188 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12191 .vitem &$reply_address$&
12192 .vindex "&$reply_address$&"
12193 When a message is being processed, this variable contains the contents of the
12194 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12195 contents of the &'From:'& header line. Apart from the removal of leading
12196 white space, the value is not processed in any way. In particular, no RFC 2047
12197 decoding or character code translation takes place.
12199 .vitem &$return_path$&
12200 .vindex "&$return_path$&"
12201 When a message is being delivered, this variable contains the return path &--
12202 the sender field that will be sent as part of the envelope. It is not enclosed
12203 in <> characters. At the start of routing an address, &$return_path$& has the
12204 same value as &$sender_address$&, but if, for example, an incoming message to a
12205 mailing list has been expanded by a router which specifies a different address
12206 for bounce messages, &$return_path$& subsequently contains the new bounce
12207 address, whereas &$sender_address$& always contains the original sender address
12208 that was received with the message. In other words, &$sender_address$& contains
12209 the incoming envelope sender, and &$return_path$& contains the outgoing
12212 .vitem &$return_size_limit$&
12213 .vindex "&$return_size_limit$&"
12214 This is an obsolete name for &$bounce_return_size_limit$&.
12216 .vitem &$router_name$&
12217 .cindex "router" "name"
12218 .cindex "name" "of router"
12219 .vindex "&$router_name$&"
12220 During the running of a router this variable contains its name.
12223 .cindex "return code" "from &%run%& expansion"
12224 .vindex "&$runrc$&"
12225 This variable contains the return code from a command that is run by the
12226 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12227 assume the order in which option values are expanded, except for those
12228 preconditions whose order of testing is documented. Therefore, you cannot
12229 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12232 .vitem &$self_hostname$&
12233 .oindex "&%self%&" "value of host name"
12234 .vindex "&$self_hostname$&"
12235 When an address is routed to a supposedly remote host that turns out to be the
12236 local host, what happens is controlled by the &%self%& generic router option.
12237 One of its values causes the address to be passed to another router. When this
12238 happens, &$self_hostname$& is set to the name of the local host that the
12239 original router encountered. In other circumstances its contents are null.
12241 .vitem &$sender_address$&
12242 .vindex "&$sender_address$&"
12243 When a message is being processed, this variable contains the sender's address
12244 that was received in the message's envelope. The case of letters in the address
12245 is retained, in both the local part and the domain. For bounce messages, the
12246 value of this variable is the empty string. See also &$return_path$&.
12248 .vitem &$sender_address_data$&
12249 .vindex "&$address_data$&"
12250 .vindex "&$sender_address_data$&"
12251 If &$address_data$& is set when the routers are called from an ACL to verify a
12252 sender address, the final value is preserved in &$sender_address_data$&, to
12253 distinguish it from data from a recipient address. The value does not persist
12254 after the end of the current ACL statement. If you want to preserve it for
12255 longer, you can save it in an ACL variable.
12257 .vitem &$sender_address_domain$&
12258 .vindex "&$sender_address_domain$&"
12259 The domain portion of &$sender_address$&.
12261 .vitem &$sender_address_local_part$&
12262 .vindex "&$sender_address_local_part$&"
12263 The local part portion of &$sender_address$&.
12265 .vitem &$sender_data$&
12266 .vindex "&$sender_data$&"
12267 This variable is set after a lookup success in an ACL &%senders%& condition or
12268 in a router &%senders%& option. It contains the data from the lookup, and the
12269 value remains set until the next &%senders%& test. Thus, you can do things like
12272 &`require senders = cdb*@;/some/file`&
12273 &`deny `&&'some further test involving'& &`$sender_data`&
12275 &*Warning*&: This variable is set only when a lookup is used as an indexing
12276 method in the address list, using the semicolon syntax as in the example above.
12277 The variable is not set for a lookup that is used as part of the string
12278 expansion that all such lists undergo before being interpreted.
12280 .vitem &$sender_fullhost$&
12281 .vindex "&$sender_fullhost$&"
12282 When a message is received from a remote host, this variable contains the host
12283 name and IP address in a single string. It ends with the IP address in square
12284 brackets, followed by a colon and a port number if the logging of ports is
12285 enabled. The format of the rest of the string depends on whether the host
12286 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12287 looking up its IP address. (Looking up the IP address can be forced by the
12288 &%host_lookup%& option, independent of verification.) A plain host name at the
12289 start of the string is a verified host name; if this is not present,
12290 verification either failed or was not requested. A host name in parentheses is
12291 the argument of a HELO or EHLO command. This is omitted if it is identical to
12292 the verified host name or to the host's IP address in square brackets.
12295 .vitem &$sender_helo_dnssec$&
12296 .vindex "&$sender_helo_dnssec$&"
12297 This boolean variable is true if a successful HELO verification was
12298 .cindex "DNS" "DNSSEC"
12299 done using DNS information the resolver library stated was authenticated data.
12302 .vitem &$sender_helo_name$&
12303 .vindex "&$sender_helo_name$&"
12304 When a message is received from a remote host that has issued a HELO or EHLO
12305 command, the argument of that command is placed in this variable. It is also
12306 set if HELO or EHLO is used when a message is received using SMTP locally via
12307 the &%-bs%& or &%-bS%& options.
12309 .vitem &$sender_host_address$&
12310 .vindex "&$sender_host_address$&"
12311 When a message is received from a remote host using SMTP,
12312 this variable contains that
12313 host's IP address. For locally non-SMTP submitted messages, it is empty.
12315 .vitem &$sender_host_authenticated$&
12316 .vindex "&$sender_host_authenticated$&"
12317 This variable contains the name (not the public name) of the authenticator
12318 driver that successfully authenticated the client from which the message was
12319 received. It is empty if there was no successful authentication. See also
12320 &$authenticated_id$&.
12322 .vitem &$sender_host_dnssec$&
12323 .vindex "&$sender_host_dnssec$&"
12324 If an attempt to populate &$sender_host_name$& has been made
12325 (by reference, &%hosts_lookup%& or
12326 otherwise) then this boolean will have been set true if, and only if, the
12327 resolver library states that both
12328 the reverse and forward DNS were authenticated data. At all
12329 other times, this variable is false.
12331 .cindex "DNS" "DNSSEC"
12332 It is likely that you will need to coerce DNSSEC support on in the resolver
12333 library, by setting:
12338 Exim does not perform DNSSEC validation itself, instead leaving that to a
12339 validating resolver (e.g. unbound, or bind with suitable configuration).
12341 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12342 mechanism in the list, then this variable will be false.
12345 .vitem &$sender_host_name$&
12346 .vindex "&$sender_host_name$&"
12347 When a message is received from a remote host, this variable contains the
12348 host's name as obtained by looking up its IP address. For messages received by
12349 other means, this variable is empty.
12351 .vindex "&$host_lookup_failed$&"
12352 If the host name has not previously been looked up, a reference to
12353 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12354 A looked up name is accepted only if it leads back to the original IP address
12355 via a forward lookup. If either the reverse or the forward lookup fails to find
12356 any data, or if the forward lookup does not yield the original IP address,
12357 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12359 .vindex "&$host_lookup_deferred$&"
12360 However, if either of the lookups cannot be completed (for example, there is a
12361 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12362 &$host_lookup_failed$& remains set to &"0"&.
12364 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12365 host name again if there is a subsequent reference to &$sender_host_name$&
12366 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12369 Exim does not automatically look up every calling host's name. If you want
12370 maximum efficiency, you should arrange your configuration so that it avoids
12371 these lookups altogether. The lookup happens only if one or more of the
12372 following are true:
12375 A string containing &$sender_host_name$& is expanded.
12377 The calling host matches the list in &%host_lookup%&. In the default
12378 configuration, this option is set to *, so it must be changed if lookups are
12379 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12381 Exim needs the host name in order to test an item in a host list. The items
12382 that require this are described in sections &<<SECThoslispatnam>>& and
12383 &<<SECThoslispatnamsk>>&.
12385 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12386 In this case, the host name is required to compare with the name quoted in any
12387 EHLO or HELO commands that the client issues.
12389 The remote host issues a EHLO or HELO command that quotes one of the
12390 domains in &%helo_lookup_domains%&. The default value of this option is
12391 . ==== As this is a nested list, any displays it contains must be indented
12392 . ==== as otherwise they are too far to the left.
12394 helo_lookup_domains = @ : @[]
12396 which causes a lookup if a remote host (incorrectly) gives the server's name or
12397 IP address in an EHLO or HELO command.
12401 .vitem &$sender_host_port$&
12402 .vindex "&$sender_host_port$&"
12403 When a message is received from a remote host, this variable contains the port
12404 number that was used on the remote host.
12406 .vitem &$sender_ident$&
12407 .vindex "&$sender_ident$&"
12408 When a message is received from a remote host, this variable contains the
12409 identification received in response to an RFC 1413 request. When a message has
12410 been received locally, this variable contains the login name of the user that
12413 .vitem &$sender_rate_$&&'xxx'&
12414 A number of variables whose names begin &$sender_rate_$& are set as part of the
12415 &%ratelimit%& ACL condition. Details are given in section
12416 &<<SECTratelimiting>>&.
12418 .vitem &$sender_rcvhost$&
12419 .cindex "DNS" "reverse lookup"
12420 .cindex "reverse DNS lookup"
12421 .vindex "&$sender_rcvhost$&"
12422 This is provided specifically for use in &'Received:'& headers. It starts with
12423 either the verified host name (as obtained from a reverse DNS lookup) or, if
12424 there is no verified host name, the IP address in square brackets. After that
12425 there may be text in parentheses. When the first item is a verified host name,
12426 the first thing in the parentheses is the IP address in square brackets,
12427 followed by a colon and a port number if port logging is enabled. When the
12428 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12431 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12432 was used and its argument was not identical to the real host name or IP
12433 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12434 all three items are present in the parentheses, a newline and tab are inserted
12435 into the string, to improve the formatting of the &'Received:'& header.
12437 .vitem &$sender_verify_failure$&
12438 .vindex "&$sender_verify_failure$&"
12439 In an ACL, when a sender verification fails, this variable contains information
12440 about the failure. The details are the same as for
12441 &$recipient_verify_failure$&.
12443 .vitem &$sending_ip_address$&
12444 .vindex "&$sending_ip_address$&"
12445 This variable is set whenever an outgoing SMTP connection to another host has
12446 been set up. It contains the IP address of the local interface that is being
12447 used. This is useful if a host that has more than one IP address wants to take
12448 on different personalities depending on which one is being used. For incoming
12449 connections, see &$received_ip_address$&.
12451 .vitem &$sending_port$&
12452 .vindex "&$sending_port$&"
12453 This variable is set whenever an outgoing SMTP connection to another host has
12454 been set up. It contains the local port that is being used. For incoming
12455 connections, see &$received_port$&.
12457 .vitem &$smtp_active_hostname$&
12458 .vindex "&$smtp_active_hostname$&"
12459 During an incoming SMTP session, this variable contains the value of the active
12460 host name, as specified by the &%smtp_active_hostname%& option. The value of
12461 &$smtp_active_hostname$& is saved with any message that is received, so its
12462 value can be consulted during routing and delivery.
12464 .vitem &$smtp_command$&
12465 .vindex "&$smtp_command$&"
12466 During the processing of an incoming SMTP command, this variable contains the
12467 entire command. This makes it possible to distinguish between HELO and EHLO in
12468 the HELO ACL, and also to distinguish between commands such as these:
12473 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12474 command, the address in &$smtp_command$& is the original address before any
12475 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12476 the address after SMTP-time rewriting.
12478 .vitem &$smtp_command_argument$&
12479 .cindex "SMTP" "command, argument for"
12480 .vindex "&$smtp_command_argument$&"
12481 While an ACL is running to check an SMTP command, this variable contains the
12482 argument, that is, the text that follows the command name, with leading white
12483 space removed. Following the introduction of &$smtp_command$&, this variable is
12484 somewhat redundant, but is retained for backwards compatibility.
12486 .vitem &$smtp_count_at_connection_start$&
12487 .vindex "&$smtp_count_at_connection_start$&"
12488 This variable is set greater than zero only in processes spawned by the Exim
12489 daemon for handling incoming SMTP connections. The name is deliberately long,
12490 in order to emphasize what the contents are. When the daemon accepts a new
12491 connection, it increments this variable. A copy of the variable is passed to
12492 the child process that handles the connection, but its value is fixed, and
12493 never changes. It is only an approximation of how many incoming connections
12494 there actually are, because many other connections may come and go while a
12495 single connection is being processed. When a child process terminates, the
12496 daemon decrements its copy of the variable.
12498 .vitem "&$sn0$& &-- &$sn9$&"
12499 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12500 that were current at the end of the system filter file. This allows a system
12501 filter file to set values that can be tested in users' filter files. For
12502 example, a system filter could set a value indicating how likely it is that a
12503 message is junk mail.
12505 .vitem &$spam_$&&'xxx'&
12506 A number of variables whose names start with &$spam$& are available when Exim
12507 is compiled with the content-scanning extension. For details, see section
12508 &<<SECTscanspamass>>&.
12511 .vitem &$spool_directory$&
12512 .vindex "&$spool_directory$&"
12513 The name of Exim's spool directory.
12515 .vitem &$spool_inodes$&
12516 .vindex "&$spool_inodes$&"
12517 The number of free inodes in the disk partition where Exim's spool files are
12518 being written. The value is recalculated whenever the variable is referenced.
12519 If the relevant file system does not have the concept of inodes, the value of
12520 is -1. See also the &%check_spool_inodes%& option.
12522 .vitem &$spool_space$&
12523 .vindex "&$spool_space$&"
12524 The amount of free space (as a number of kilobytes) in the disk partition where
12525 Exim's spool files are being written. The value is recalculated whenever the
12526 variable is referenced. If the operating system does not have the ability to
12527 find the amount of free space (only true for experimental systems), the space
12528 value is -1. For example, to check in an ACL that there is at least 50
12529 megabytes free on the spool, you could write:
12531 condition = ${if > {$spool_space}{50000}}
12533 See also the &%check_spool_space%& option.
12536 .vitem &$thisaddress$&
12537 .vindex "&$thisaddress$&"
12538 This variable is set only during the processing of the &%foranyaddress%&
12539 command in a filter file. Its use is explained in the description of that
12540 command, which can be found in the separate document entitled &'Exim's
12541 interfaces to mail filtering'&.
12543 .vitem &$tls_in_bits$&
12544 .vindex "&$tls_in_bits$&"
12545 Contains an approximation of the TLS cipher's bit-strength
12546 on the inbound connection; the meaning of
12547 this depends upon the TLS implementation used.
12548 If TLS has not been negotiated, the value will be 0.
12549 The value of this is automatically fed into the Cyrus SASL authenticator
12550 when acting as a server, to specify the "external SSF" (a SASL term).
12552 The deprecated &$tls_bits$& variable refers to the inbound side
12553 except when used in the context of an outbound SMTP delivery, when it refers to
12556 .vitem &$tls_out_bits$&
12557 .vindex "&$tls_out_bits$&"
12558 Contains an approximation of the TLS cipher's bit-strength
12559 on an outbound SMTP connection; the meaning of
12560 this depends upon the TLS implementation used.
12561 If TLS has not been negotiated, the value will be 0.
12563 .vitem &$tls_in_ourcert$&
12564 .vindex "&$tls_in_ourcert$&"
12565 This variable refers to the certificate presented to the peer of an
12566 inbound connection when the message was received.
12567 It is only useful as the argument of a
12568 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12569 or a &%def%& condition.
12571 .vitem &$tls_in_peercert$&
12572 .vindex "&$tls_in_peercert$&"
12573 This variable refers to the certificate presented by the peer of an
12574 inbound connection when the message was received.
12575 It is only useful as the argument of a
12576 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12577 or a &%def%& condition.
12579 If certificate verification fails it may refer to a failing chain element
12580 which is not the leaf.
12583 .vitem &$tls_out_ourcert$&
12584 .vindex "&$tls_out_ourcert$&"
12585 This variable refers to the certificate presented to the peer of an
12586 outbound connection. It is only useful as the argument of a
12587 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12588 or a &%def%& condition.
12590 .vitem &$tls_out_peercert$&
12591 .vindex "&$tls_out_peercert$&"
12592 This variable refers to the certificate presented by the peer of an
12593 outbound connection. It is only useful as the argument of a
12594 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12595 or a &%def%& condition.
12597 If certificate verification fails it may refer to a failing chain element
12598 which is not the leaf.
12601 .vitem &$tls_in_certificate_verified$&
12602 .vindex "&$tls_in_certificate_verified$&"
12603 This variable is set to &"1"& if a TLS certificate was verified when the
12604 message was received, and &"0"& otherwise.
12606 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12607 except when used in the context of an outbound SMTP delivery, when it refers to
12610 .vitem &$tls_out_certificate_verified$&
12611 .vindex "&$tls_out_certificate_verified$&"
12612 This variable is set to &"1"& if a TLS certificate was verified when an
12613 outbound SMTP connection was made,
12614 and &"0"& otherwise.
12616 .vitem &$tls_in_cipher$&
12617 .vindex "&$tls_in_cipher$&"
12618 .vindex "&$tls_cipher$&"
12619 When a message is received from a remote host over an encrypted SMTP
12620 connection, this variable is set to the cipher suite that was negotiated, for
12621 example DES-CBC3-SHA. In other circumstances, in particular, for message
12622 received over unencrypted connections, the variable is empty. Testing
12623 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12624 non-encrypted connections during ACL processing.
12626 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12627 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12628 becomes the same as &$tls_out_cipher$&.
12630 .vitem &$tls_out_cipher$&
12631 .vindex "&$tls_out_cipher$&"
12633 cleared before any outgoing SMTP connection is made,
12634 and then set to the outgoing cipher suite if one is negotiated. See chapter
12635 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12636 details of the &(smtp)& transport.
12638 .vitem &$tls_in_ocsp$&
12639 .vindex "&$tls_in_ocsp$&"
12640 When a message is received from a remote client connection
12641 the result of any OCSP request from the client is encoded in this variable:
12643 0 OCSP proof was not requested (default value)
12644 1 No response to request
12645 2 Response not verified
12646 3 Verification failed
12647 4 Verification succeeded
12650 .vitem &$tls_out_ocsp$&
12651 .vindex "&$tls_out_ocsp$&"
12652 When a message is sent to a remote host connection
12653 the result of any OCSP request made is encoded in this variable.
12654 See &$tls_in_ocsp$& for values.
12656 .vitem &$tls_in_peerdn$&
12657 .vindex "&$tls_in_peerdn$&"
12658 .vindex "&$tls_peerdn$&"
12659 When a message is received from a remote host over an encrypted SMTP
12660 connection, and Exim is configured to request a certificate from the client,
12661 the value of the Distinguished Name of the certificate is made available in the
12662 &$tls_in_peerdn$& during subsequent processing.
12664 If certificate verification fails it may refer to a failing chain element
12665 which is not the leaf.
12668 The deprecated &$tls_peerdn$& variable refers to the inbound side
12669 except when used in the context of an outbound SMTP delivery, when it refers to
12672 .vitem &$tls_out_peerdn$&
12673 .vindex "&$tls_out_peerdn$&"
12674 When a message is being delivered to a remote host over an encrypted SMTP
12675 connection, and Exim is configured to request a certificate from the server,
12676 the value of the Distinguished Name of the certificate is made available in the
12677 &$tls_out_peerdn$& during subsequent processing.
12679 If certificate verification fails it may refer to a failing chain element
12680 which is not the leaf.
12683 .vitem &$tls_in_sni$&
12684 .vindex "&$tls_in_sni$&"
12685 .vindex "&$tls_sni$&"
12686 .cindex "TLS" "Server Name Indication"
12687 When a TLS session is being established, if the client sends the Server
12688 Name Indication extension, the value will be placed in this variable.
12689 If the variable appears in &%tls_certificate%& then this option and
12690 some others, described in &<<SECTtlssni>>&,
12691 will be re-expanded early in the TLS session, to permit
12692 a different certificate to be presented (and optionally a different key to be
12693 used) to the client, based upon the value of the SNI extension.
12695 The deprecated &$tls_sni$& variable refers to the inbound side
12696 except when used in the context of an outbound SMTP delivery, when it refers to
12699 .vitem &$tls_out_sni$&
12700 .vindex "&$tls_out_sni$&"
12701 .cindex "TLS" "Server Name Indication"
12703 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12706 .vitem &$tod_bsdinbox$&
12707 .vindex "&$tod_bsdinbox$&"
12708 The time of day and the date, in the format required for BSD-style mailbox
12709 files, for example: Thu Oct 17 17:14:09 1995.
12711 .vitem &$tod_epoch$&
12712 .vindex "&$tod_epoch$&"
12713 The time and date as a number of seconds since the start of the Unix epoch.
12715 .vitem &$tod_epoch_l$&
12716 .vindex "&$tod_epoch_l$&"
12717 The time and date as a number of microseconds since the start of the Unix epoch.
12719 .vitem &$tod_full$&
12720 .vindex "&$tod_full$&"
12721 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12722 +0100. The timezone is always given as a numerical offset from UTC, with
12723 positive values used for timezones that are ahead (east) of UTC, and negative
12724 values for those that are behind (west).
12727 .vindex "&$tod_log$&"
12728 The time and date in the format used for writing Exim's log files, for example:
12729 1995-10-12 15:32:29, but without a timezone.
12731 .vitem &$tod_logfile$&
12732 .vindex "&$tod_logfile$&"
12733 This variable contains the date in the format yyyymmdd. This is the format that
12734 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12737 .vitem &$tod_zone$&
12738 .vindex "&$tod_zone$&"
12739 This variable contains the numerical value of the local timezone, for example:
12742 .vitem &$tod_zulu$&
12743 .vindex "&$tod_zulu$&"
12744 This variable contains the UTC date and time in &"Zulu"& format, as specified
12745 by ISO 8601, for example: 20030221154023Z.
12747 .vitem &$transport_name$&
12748 .cindex "transport" "name"
12749 .cindex "name" "of transport"
12750 .vindex "&$transport_name$&"
12751 During the running of a transport, this variable contains its name.
12754 .vindex "&$value$&"
12755 This variable contains the result of an expansion lookup, extraction operation,
12756 or external command, as described above. It is also used during a
12757 &*reduce*& expansion.
12759 .vitem &$verify_mode$&
12760 .vindex "&$verify_mode$&"
12761 While a router or transport is being run in verify mode
12762 or for cutthrough delivery,
12763 contains "S" for sender-verification or "R" for recipient-verification.
12766 .vitem &$version_number$&
12767 .vindex "&$version_number$&"
12768 The version number of Exim.
12770 .vitem &$warn_message_delay$&
12771 .vindex "&$warn_message_delay$&"
12772 This variable is set only during the creation of a message warning about a
12773 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12775 .vitem &$warn_message_recipients$&
12776 .vindex "&$warn_message_recipients$&"
12777 This variable is set only during the creation of a message warning about a
12778 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12784 . ////////////////////////////////////////////////////////////////////////////
12785 . ////////////////////////////////////////////////////////////////////////////
12787 .chapter "Embedded Perl" "CHAPperl"
12788 .scindex IIDperl "Perl" "calling from Exim"
12789 Exim can be built to include an embedded Perl interpreter. When this is done,
12790 Perl subroutines can be called as part of the string expansion process. To make
12791 use of the Perl support, you need version 5.004 or later of Perl installed on
12792 your system. To include the embedded interpreter in the Exim binary, include
12797 in your &_Local/Makefile_& and then build Exim in the normal way.
12800 .section "Setting up so Perl can be used" "SECID85"
12801 .oindex "&%perl_startup%&"
12802 Access to Perl subroutines is via a global configuration option called
12803 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12804 no &%perl_startup%& option in the Exim configuration file then no Perl
12805 interpreter is started and there is almost no overhead for Exim (since none of
12806 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12807 option then the associated value is taken to be Perl code which is executed in
12808 a newly created Perl interpreter.
12810 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12811 need backslashes before any characters to escape special meanings. The option
12812 should usually be something like
12814 perl_startup = do '/etc/exim.pl'
12816 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12817 use from Exim. Exim can be configured either to start up a Perl interpreter as
12818 soon as it is entered, or to wait until the first time it is needed. Starting
12819 the interpreter at the beginning ensures that it is done while Exim still has
12820 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12821 fact used in a particular run. Also, note that this does not mean that Exim is
12822 necessarily running as root when Perl is called at a later time. By default,
12823 the interpreter is started only when it is needed, but this can be changed in
12827 .oindex "&%perl_at_start%&"
12828 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12829 a startup when Exim is entered.
12831 The command line option &%-ps%& also requests a startup when Exim is entered,
12832 overriding the setting of &%perl_at_start%&.
12835 There is also a command line option &%-pd%& (for delay) which suppresses the
12836 initial startup, even if &%perl_at_start%& is set.
12839 .section "Calling Perl subroutines" "SECID86"
12840 When the configuration file includes a &%perl_startup%& option you can make use
12841 of the string expansion item to call the Perl subroutines that are defined
12842 by the &%perl_startup%& code. The operator is used in any of the following
12846 ${perl{foo}{argument}}
12847 ${perl{foo}{argument1}{argument2} ... }
12849 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12850 arguments may be passed. Passing more than this results in an expansion failure
12851 with an error message of the form
12853 Too many arguments passed to Perl subroutine "foo" (max is 8)
12855 The return value of the Perl subroutine is evaluated in a scalar context before
12856 it is passed back to Exim to be inserted into the expanded string. If the
12857 return value is &'undef'&, the expansion is forced to fail in the same way as
12858 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12859 by obeying Perl's &%die%& function, the expansion fails with the error message
12860 that was passed to &%die%&.
12863 .section "Calling Exim functions from Perl" "SECID87"
12864 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12865 is available to call back into Exim's string expansion function. For example,
12868 my $lp = Exim::expand_string('$local_part');
12870 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12871 Note those are single quotes and not double quotes to protect against
12872 &$local_part$& being interpolated as a Perl variable.
12874 If the string expansion is forced to fail by a &"fail"& item, the result of
12875 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12876 expansion string, the Perl call from the original expansion string fails with
12877 an appropriate error message, in the same way as if &%die%& were used.
12879 .cindex "debugging" "from embedded Perl"
12880 .cindex "log" "writing from embedded Perl"
12881 Two other Exim functions are available for use from within Perl code.
12882 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12883 debugging is enabled. If you want a newline at the end, you must supply it.
12884 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12885 timestamp. In this case, you should not supply a terminating newline.
12888 .section "Use of standard output and error by Perl" "SECID88"
12889 .cindex "Perl" "standard output and error"
12890 You should not write to the standard error or output streams from within your
12891 Perl code, as it is not defined how these are set up. In versions of Exim
12892 before 4.50, it is possible for the standard output or error to refer to the
12893 SMTP connection during message reception via the daemon. Writing to this stream
12894 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12895 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12896 avoided, but the output is lost.
12898 .cindex "Perl" "use of &%warn%&"
12899 The Perl &%warn%& statement writes to the standard error stream by default.
12900 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12901 you have no control. When Exim starts up the Perl interpreter, it arranges for
12902 output from the &%warn%& statement to be written to the Exim main log. You can
12903 change this by including appropriate Perl magic somewhere in your Perl code.
12904 For example, to discard &%warn%& output completely, you need this:
12906 $SIG{__WARN__} = sub { };
12908 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12909 example, the code for the subroutine is empty, so it does nothing, but you can
12910 include any Perl code that you like. The text of the &%warn%& message is passed
12911 as the first subroutine argument.
12915 . ////////////////////////////////////////////////////////////////////////////
12916 . ////////////////////////////////////////////////////////////////////////////
12918 .chapter "Starting the daemon and the use of network interfaces" &&&
12919 "CHAPinterfaces" &&&
12920 "Starting the daemon"
12921 .cindex "daemon" "starting"
12922 .cindex "interface" "listening"
12923 .cindex "network interface"
12924 .cindex "interface" "network"
12925 .cindex "IP address" "for listening"
12926 .cindex "daemon" "listening IP addresses"
12927 .cindex "TCP/IP" "setting listening interfaces"
12928 .cindex "TCP/IP" "setting listening ports"
12929 A host that is connected to a TCP/IP network may have one or more physical
12930 hardware network interfaces. Each of these interfaces may be configured as one
12931 or more &"logical"& interfaces, which are the entities that a program actually
12932 works with. Each of these logical interfaces is associated with an IP address.
12933 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12934 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12935 knowledge about the host's interfaces for use in three different circumstances:
12938 When a listening daemon is started, Exim needs to know which interfaces
12939 and ports to listen on.
12941 When Exim is routing an address, it needs to know which IP addresses
12942 are associated with local interfaces. This is required for the correct
12943 processing of MX lists by removing the local host and others with the
12944 same or higher priority values. Also, Exim needs to detect cases
12945 when an address is routed to an IP address that in fact belongs to the
12946 local host. Unless the &%self%& router option or the &%allow_localhost%&
12947 option of the smtp transport is set (as appropriate), this is treated
12948 as an error situation.
12950 When Exim connects to a remote host, it may need to know which interface to use
12951 for the outgoing connection.
12955 Exim's default behaviour is likely to be appropriate in the vast majority
12956 of cases. If your host has only one interface, and you want all its IP
12957 addresses to be treated in the same way, and you are using only the
12958 standard SMTP port, you should not need to take any special action. The
12959 rest of this chapter does not apply to you.
12961 In a more complicated situation you may want to listen only on certain
12962 interfaces, or on different ports, and for this reason there are a number of
12963 options that can be used to influence Exim's behaviour. The rest of this
12964 chapter describes how they operate.
12966 When a message is received over TCP/IP, the interface and port that were
12967 actually used are set in &$received_ip_address$& and &$received_port$&.
12971 .section "Starting a listening daemon" "SECID89"
12972 When a listening daemon is started (by means of the &%-bd%& command line
12973 option), the interfaces and ports on which it listens are controlled by the
12977 &%daemon_smtp_ports%& contains a list of default ports
12979 (For backward compatibility, this option can also be specified in the singular.)
12981 &%local_interfaces%& contains list of interface IP addresses on which to
12982 listen. Each item may optionally also specify a port.
12985 The default list separator in both cases is a colon, but this can be changed as
12986 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12987 it is usually best to change the separator to avoid having to double all the
12988 colons. For example:
12990 local_interfaces = <; 127.0.0.1 ; \
12993 3ffe:ffff:836f::fe86:a061
12995 There are two different formats for specifying a port along with an IP address
12996 in &%local_interfaces%&:
12999 The port is added onto the address with a dot separator. For example, to listen
13000 on port 1234 on two different IP addresses:
13002 local_interfaces = <; 192.168.23.65.1234 ; \
13003 3ffe:ffff:836f::fe86:a061.1234
13006 The IP address is enclosed in square brackets, and the port is added
13007 with a colon separator, for example:
13009 local_interfaces = <; [192.168.23.65]:1234 ; \
13010 [3ffe:ffff:836f::fe86:a061]:1234
13014 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13015 default setting contains just one port:
13017 daemon_smtp_ports = smtp
13019 If more than one port is listed, each interface that does not have its own port
13020 specified listens on all of them. Ports that are listed in
13021 &%daemon_smtp_ports%& can be identified either by name (defined in
13022 &_/etc/services_&) or by number. However, when ports are given with individual
13023 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13027 .section "Special IP listening addresses" "SECID90"
13028 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13029 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13030 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13031 instead of setting up separate listening sockets for each interface. The
13032 default value of &%local_interfaces%& is
13034 local_interfaces = 0.0.0.0
13036 when Exim is built without IPv6 support; otherwise it is:
13038 local_interfaces = <; ::0 ; 0.0.0.0
13040 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13044 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13045 The &%-oX%& command line option can be used to override the values of
13046 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13047 instance. Another way of doing this would be to use macros and the &%-D%&
13048 option. However, &%-oX%& can be used by any admin user, whereas modification of
13049 the runtime configuration by &%-D%& is allowed only when the caller is root or
13052 The value of &%-oX%& is a list of items. The default colon separator can be
13053 changed in the usual way if required. If there are any items that do not
13054 contain dots or colons (that is, are not IP addresses), the value of
13055 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13056 items that do contain dots or colons, the value of &%local_interfaces%& is
13057 replaced by those items. Thus, for example,
13061 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13064 -oX 192.168.34.5.1125
13066 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13067 (However, since &%local_interfaces%& now contains no items without ports, the
13068 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13072 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13073 .cindex "ssmtp protocol"
13074 .cindex "smtps protocol"
13075 .cindex "SMTP" "ssmtp protocol"
13076 .cindex "SMTP" "smtps protocol"
13077 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13078 before the STARTTLS command was standardized for SMTP. Some legacy clients
13079 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13080 list of port numbers or service names,
13081 connections to those ports must use SSMTP. The most
13082 common use of this option is expected to be
13084 tls_on_connect_ports = 465
13086 because 465 is the usual port number used by the legacy clients. There is also
13087 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13088 this way when a daemon is started.
13090 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13091 daemon to listen on those ports. You must still specify them in
13092 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13093 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13094 connections via the daemon.)
13099 .section "IPv6 address scopes" "SECID92"
13100 .cindex "IPv6" "address scopes"
13101 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13102 can, in principle, have the same link-local IPv6 address on different
13103 interfaces. Thus, additional information is needed, over and above the IP
13104 address, to distinguish individual interfaces. A convention of using a
13105 percent sign followed by something (often the interface name) has been
13106 adopted in some cases, leading to addresses like this:
13108 fe80::202:b3ff:fe03:45c1%eth0
13110 To accommodate this usage, a percent sign followed by an arbitrary string is
13111 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13112 to convert a textual IPv6 address for actual use. This function recognizes the
13113 percent convention in operating systems that support it, and it processes the
13114 address appropriately. Unfortunately, some older libraries have problems with
13115 &[getaddrinfo()]&. If
13117 IPV6_USE_INET_PTON=yes
13119 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13120 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13121 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13122 function.) Of course, this means that the additional functionality of
13123 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13125 .section "Disabling IPv6" "SECID93"
13126 .cindex "IPv6" "disabling"
13127 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13128 run on a host whose kernel does not support IPv6. The binary will fall back to
13129 using IPv4, but it may waste resources looking up AAAA records, and trying to
13130 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13131 .oindex "&%disable_ipv6%&"
13132 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13133 activities take place. AAAA records are never looked up, and any IPv6 addresses
13134 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13135 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13136 to handle IPv6 literal addresses.
13138 On the other hand, when IPv6 is in use, there may be times when you want to
13139 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13140 option to globally suppress the lookup of AAAA records for specified domains,
13141 and you can use the &%ignore_target_hosts%& generic router option to ignore
13142 IPv6 addresses in an individual router.
13146 .section "Examples of starting a listening daemon" "SECID94"
13147 The default case in an IPv6 environment is
13149 daemon_smtp_ports = smtp
13150 local_interfaces = <; ::0 ; 0.0.0.0
13152 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13153 Either one or two sockets may be used, depending on the characteristics of
13154 the TCP/IP stack. (This is complicated and messy; for more information,
13155 read the comments in the &_daemon.c_& source file.)
13157 To specify listening on ports 25 and 26 on all interfaces:
13159 daemon_smtp_ports = 25 : 26
13161 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13163 local_interfaces = <; ::0.25 ; ::0.26 \
13164 0.0.0.0.25 ; 0.0.0.0.26
13166 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13167 IPv4 loopback address only:
13169 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13171 To specify listening on the default port on specific interfaces only:
13173 local_interfaces = 10.0.0.67 : 192.168.34.67
13175 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13179 .section "Recognizing the local host" "SECTreclocipadd"
13180 The &%local_interfaces%& option is also used when Exim needs to determine
13181 whether or not an IP address refers to the local host. That is, the IP
13182 addresses of all the interfaces on which a daemon is listening are always
13185 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13186 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13187 available interfaces from the operating system, and extracts the relevant
13188 (that is, IPv4 or IPv6) addresses to use for checking.
13190 Some systems set up large numbers of virtual interfaces in order to provide
13191 many virtual web servers. In this situation, you may want to listen for
13192 email on only a few of the available interfaces, but nevertheless treat all
13193 interfaces as local when routing. You can do this by setting
13194 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13195 &"all"& wildcard values. These addresses are recognized as local, but are not
13196 used for listening. Consider this example:
13198 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13200 3ffe:2101:12:1:a00:20ff:fe86:a061
13202 extra_local_interfaces = <; ::0 ; 0.0.0.0
13204 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13205 address, but all available interface addresses are treated as local when
13208 In some environments the local host name may be in an MX list, but with an IP
13209 address that is not assigned to any local interface. In other cases it may be
13210 desirable to treat other host names as if they referred to the local host. Both
13211 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13212 This contains host names rather than IP addresses. When a host is referenced
13213 during routing, either via an MX record or directly, it is treated as the local
13214 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13215 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13219 .section "Delivering to a remote host" "SECID95"
13220 Delivery to a remote host is handled by the smtp transport. By default, it
13221 allows the system's TCP/IP functions to choose which interface to use (if
13222 there is more than one) when connecting to a remote host. However, the
13223 &%interface%& option can be set to specify which interface is used. See the
13224 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13230 . ////////////////////////////////////////////////////////////////////////////
13231 . ////////////////////////////////////////////////////////////////////////////
13233 .chapter "Main configuration" "CHAPmainconfig"
13234 .scindex IIDconfima "configuration file" "main section"
13235 .scindex IIDmaiconf "main configuration"
13236 The first part of the run time configuration file contains three types of item:
13239 Macro definitions: These lines start with an upper case letter. See section
13240 &<<SECTmacrodefs>>& for details of macro processing.
13242 Named list definitions: These lines start with one of the words &"domainlist"&,
13243 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13244 section &<<SECTnamedlists>>&.
13246 Main configuration settings: Each setting occupies one line of the file
13247 (with possible continuations). If any setting is preceded by the word
13248 &"hide"&, the &%-bP%& command line option displays its value to admin users
13249 only. See section &<<SECTcos>>& for a description of the syntax of these option
13253 This chapter specifies all the main configuration options, along with their
13254 types and default values. For ease of finding a particular option, they appear
13255 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13256 are now so many options, they are first listed briefly in functional groups, as
13257 an aid to finding the name of the option you are looking for. Some options are
13258 listed in more than one group.
13260 .section "Miscellaneous" "SECID96"
13262 .row &%bi_command%& "to run for &%-bi%& command line option"
13263 .row &%disable_ipv6%& "do no IPv6 processing"
13264 .row &%keep_malformed%& "for broken files &-- should not happen"
13265 .row &%localhost_number%& "for unique message ids in clusters"
13266 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13267 .row &%message_body_visible%& "how much to show in &$message_body$&"
13268 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13269 .row &%print_topbitchars%& "top-bit characters are printing"
13270 .row &%timezone%& "force time zone"
13274 .section "Exim parameters" "SECID97"
13276 .row &%exim_group%& "override compiled-in value"
13277 .row &%exim_path%& "override compiled-in value"
13278 .row &%exim_user%& "override compiled-in value"
13279 .row &%primary_hostname%& "default from &[uname()]&"
13280 .row &%split_spool_directory%& "use multiple directories"
13281 .row &%spool_directory%& "override compiled-in value"
13286 .section "Privilege controls" "SECID98"
13288 .row &%admin_groups%& "groups that are Exim admin users"
13289 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13290 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13291 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13292 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13293 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13294 .row &%never_users%& "do not run deliveries as these"
13295 .row &%prod_requires_admin%& "forced delivery requires admin user"
13296 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13297 .row &%trusted_groups%& "groups that are trusted"
13298 .row &%trusted_users%& "users that are trusted"
13303 .section "Logging" "SECID99"
13305 .row &%hosts_connection_nolog%& "exemption from connect logging"
13306 .row &%log_file_path%& "override compiled-in value"
13307 .row &%log_selector%& "set/unset optional logging"
13308 .row &%log_timezone%& "add timezone to log lines"
13309 .row &%message_logs%& "create per-message logs"
13310 .row &%preserve_message_logs%& "after message completion"
13311 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13312 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13313 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13314 .row &%syslog_facility%& "set syslog &""facility""& field"
13315 .row &%syslog_processname%& "set syslog &""ident""& field"
13316 .row &%syslog_timestamp%& "timestamp syslog lines"
13317 .row &%write_rejectlog%& "control use of message log"
13322 .section "Frozen messages" "SECID100"
13324 .row &%auto_thaw%& "sets time for retrying frozen messages"
13325 .row &%freeze_tell%& "send message when freezing"
13326 .row &%move_frozen_messages%& "to another directory"
13327 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13332 .section "Data lookups" "SECID101"
13334 .row &%ibase_servers%& "InterBase servers"
13335 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13336 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13337 .row &%ldap_cert_file%& "client cert file for LDAP"
13338 .row &%ldap_cert_key%& "client key file for LDAP"
13339 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13340 .row &%ldap_default_servers%& "used if no server in query"
13341 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13342 .row &%ldap_start_tls%& "require TLS within LDAP"
13343 .row &%ldap_version%& "set protocol version"
13344 .row &%lookup_open_max%& "lookup files held open"
13345 .row &%mysql_servers%& "default MySQL servers"
13346 .row &%oracle_servers%& "Oracle servers"
13347 .row &%pgsql_servers%& "default PostgreSQL servers"
13348 .row &%sqlite_lock_timeout%& "as it says"
13353 .section "Message ids" "SECID102"
13355 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13356 .row &%message_id_header_text%& "ditto"
13361 .section "Embedded Perl Startup" "SECID103"
13363 .row &%perl_at_start%& "always start the interpreter"
13364 .row &%perl_startup%& "code to obey when starting Perl"
13369 .section "Daemon" "SECID104"
13371 .row &%daemon_smtp_ports%& "default ports"
13372 .row &%daemon_startup_retries%& "number of times to retry"
13373 .row &%daemon_startup_sleep%& "time to sleep between tries"
13374 .row &%extra_local_interfaces%& "not necessarily listened on"
13375 .row &%local_interfaces%& "on which to listen, with optional ports"
13376 .row &%pid_file_path%& "override compiled-in value"
13377 .row &%queue_run_max%& "maximum simultaneous queue runners"
13382 .section "Resource control" "SECID105"
13384 .row &%check_log_inodes%& "before accepting a message"
13385 .row &%check_log_space%& "before accepting a message"
13386 .row &%check_spool_inodes%& "before accepting a message"
13387 .row &%check_spool_space%& "before accepting a message"
13388 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13389 .row &%queue_only_load%& "queue incoming if load high"
13390 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13391 .row &%queue_run_max%& "maximum simultaneous queue runners"
13392 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13393 .row &%smtp_accept_max%& "simultaneous incoming connections"
13394 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13395 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13396 .row &%smtp_accept_max_per_connection%& "messages per connection"
13397 .row &%smtp_accept_max_per_host%& "connections from one host"
13398 .row &%smtp_accept_queue%& "queue mail if more connections"
13399 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13401 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13402 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13403 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13404 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13405 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13410 .section "Policy controls" "SECID106"
13412 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13413 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13414 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13415 .row &%acl_smtp_auth%& "ACL for AUTH"
13416 .row &%acl_smtp_connect%& "ACL for connection"
13417 .row &%acl_smtp_data%& "ACL for DATA"
13418 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13419 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13420 .row &%acl_smtp_etrn%& "ACL for ETRN"
13421 .row &%acl_smtp_expn%& "ACL for EXPN"
13422 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13423 .row &%acl_smtp_mail%& "ACL for MAIL"
13424 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13425 .row &%acl_smtp_mime%& "ACL for MIME parts"
13426 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13427 .row &%acl_smtp_predata%& "ACL for start of data"
13428 .row &%acl_smtp_quit%& "ACL for QUIT"
13429 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13430 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13431 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13432 .row &%av_scanner%& "specify virus scanner"
13433 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13435 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13436 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13437 .row &%header_maxsize%& "total size of message header"
13438 .row &%header_line_maxsize%& "individual header line limit"
13439 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13440 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13441 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13442 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13443 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13444 .row &%host_lookup%& "host name looked up for these hosts"
13445 .row &%host_lookup_order%& "order of DNS and local name lookups"
13446 .row &%host_reject_connection%& "reject connection from these hosts"
13447 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13448 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13449 .row &%message_size_limit%& "for all messages"
13450 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13451 .row &%spamd_address%& "set interface to SpamAssassin"
13452 .row &%strict_acl_vars%& "object to unset ACL variables"
13457 .section "Callout cache" "SECID107"
13459 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13461 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13463 .row &%callout_negative_expire%& "timeout for negative address cache item"
13464 .row &%callout_positive_expire%& "timeout for positive address cache item"
13465 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13470 .section "TLS" "SECID108"
13472 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13473 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13474 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13475 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13476 .row &%tls_certificate%& "location of server certificate"
13477 .row &%tls_crl%& "certificate revocation list"
13478 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13479 .row &%tls_dhparam%& "DH parameters for server"
13480 .row &%tls_eccurve%& "EC curve selection for server"
13481 .row &%tls_ocsp_file%& "location of server certificate status proof"
13482 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13483 .row &%tls_privatekey%& "location of server private key"
13484 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13485 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13486 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13487 .row &%tls_verify_certificates%& "expected client certificates"
13488 .row &%tls_verify_hosts%& "insist on client certificate verify"
13493 .section "Local user handling" "SECID109"
13495 .row &%finduser_retries%& "useful in NIS environments"
13496 .row &%gecos_name%& "used when creating &'Sender:'&"
13497 .row &%gecos_pattern%& "ditto"
13498 .row &%max_username_length%& "for systems that truncate"
13499 .row &%unknown_login%& "used when no login name found"
13500 .row &%unknown_username%& "ditto"
13501 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13502 .row &%uucp_from_sender%& "ditto"
13507 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13509 .row &%header_maxsize%& "total size of message header"
13510 .row &%header_line_maxsize%& "individual header line limit"
13511 .row &%message_size_limit%& "applies to all messages"
13512 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13513 .row &%received_header_text%& "expanded to make &'Received:'&"
13514 .row &%received_headers_max%& "for mail loop detection"
13515 .row &%recipients_max%& "limit per message"
13516 .row &%recipients_max_reject%& "permanently reject excess recipients"
13522 .section "Non-SMTP incoming messages" "SECID111"
13524 .row &%receive_timeout%& "for non-SMTP messages"
13531 .section "Incoming SMTP messages" "SECID112"
13532 See also the &'Policy controls'& section above.
13535 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13536 .row &%host_lookup%& "host name looked up for these hosts"
13537 .row &%host_lookup_order%& "order of DNS and local name lookups"
13538 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13539 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13540 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13541 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13542 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13543 .row &%smtp_accept_max%& "simultaneous incoming connections"
13544 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13545 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13546 .row &%smtp_accept_max_per_connection%& "messages per connection"
13547 .row &%smtp_accept_max_per_host%& "connections from one host"
13548 .row &%smtp_accept_queue%& "queue mail if more connections"
13549 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13551 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13552 .row &%smtp_active_hostname%& "host name to use in messages"
13553 .row &%smtp_banner%& "text for welcome banner"
13554 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13555 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13556 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13557 .row &%smtp_etrn_command%& "what to run for ETRN"
13558 .row &%smtp_etrn_serialize%& "only one at once"
13559 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13560 .row &%smtp_max_unknown_commands%& "before dropping connection"
13561 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13562 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13563 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13564 .row &%smtp_receive_timeout%& "per command or data line"
13565 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13566 .row &%smtp_return_error_details%& "give detail on rejections"
13571 .section "SMTP extensions" "SECID113"
13573 .row &%accept_8bitmime%& "advertise 8BITMIME"
13574 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13575 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13576 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13577 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13578 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13579 .row &%prdr_enable%& "advertise PRDR to all hosts"
13580 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13585 .section "Processing messages" "SECID114"
13587 .row &%allow_domain_literals%& "recognize domain literal syntax"
13588 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13589 .row &%allow_utf8_domains%& "in addresses"
13590 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13592 .row &%delivery_date_remove%& "from incoming messages"
13593 .row &%envelope_to_remove%& "from incoming messages"
13594 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13595 .row &%headers_charset%& "default for translations"
13596 .row &%qualify_domain%& "default for senders"
13597 .row &%qualify_recipient%& "default for recipients"
13598 .row &%return_path_remove%& "from incoming messages"
13599 .row &%strip_excess_angle_brackets%& "in addresses"
13600 .row &%strip_trailing_dot%& "at end of addresses"
13601 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13606 .section "System filter" "SECID115"
13608 .row &%system_filter%& "locate system filter"
13609 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13611 .row &%system_filter_file_transport%& "transport for delivery to a file"
13612 .row &%system_filter_group%& "group for filter running"
13613 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13614 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13615 .row &%system_filter_user%& "user for filter running"
13620 .section "Routing and delivery" "SECID116"
13622 .row &%disable_ipv6%& "do no IPv6 processing"
13623 .row &%dns_again_means_nonexist%& "for broken domains"
13624 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13625 .row &%dns_dnssec_ok%& "parameter for resolver"
13626 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13627 .row &%dns_retrans%& "parameter for resolver"
13628 .row &%dns_retry%& "parameter for resolver"
13629 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13630 .row &%dns_use_edns0%& "parameter for resolver"
13631 .row &%hold_domains%& "hold delivery for these domains"
13632 .row &%local_interfaces%& "for routing checks"
13633 .row &%queue_domains%& "no immediate delivery for these"
13634 .row &%queue_only%& "no immediate delivery at all"
13635 .row &%queue_only_file%& "no immediate delivery if file exists"
13636 .row &%queue_only_load%& "no immediate delivery if load is high"
13637 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13638 .row &%queue_only_override%& "allow command line to override"
13639 .row &%queue_run_in_order%& "order of arrival"
13640 .row &%queue_run_max%& "of simultaneous queue runners"
13641 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13642 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13643 .row &%remote_sort_domains%& "order of remote deliveries"
13644 .row &%retry_data_expire%& "timeout for retry data"
13645 .row &%retry_interval_max%& "safety net for retry rules"
13650 .section "Bounce and warning messages" "SECID117"
13652 .row &%bounce_message_file%& "content of bounce"
13653 .row &%bounce_message_text%& "content of bounce"
13654 .row &%bounce_return_body%& "include body if returning message"
13655 .row &%bounce_return_message%& "include original message in bounce"
13656 .row &%bounce_return_size_limit%& "limit on returned message"
13657 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13658 .row &%dsn_from%& "set &'From:'& contents in bounces"
13659 .row &%errors_copy%& "copy bounce messages"
13660 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13661 .row &%delay_warning%& "time schedule"
13662 .row &%delay_warning_condition%& "condition for warning messages"
13663 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13664 .row &%smtp_return_error_details%& "give detail on rejections"
13665 .row &%warn_message_file%& "content of warning message"
13670 .section "Alphabetical list of main options" "SECTalomo"
13671 Those options that undergo string expansion before use are marked with
13674 .option accept_8bitmime main boolean true
13676 .cindex "8-bit characters"
13677 .cindex "log" "selectors"
13678 .cindex "log" "8BITMIME"
13679 This option causes Exim to send 8BITMIME in its response to an SMTP
13680 EHLO command, and to accept the BODY= parameter on MAIL commands.
13681 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13682 takes no steps to do anything special with messages received by this route.
13684 Historically Exim kept this option off by default, but the maintainers
13685 feel that in today's Internet, this causes more problems than it solves.
13686 It now defaults to true.
13687 A more detailed analysis of the issues is provided by Dan Bernstein:
13689 &url(http://cr.yp.to/smtp/8bitmime.html)
13692 To log received 8BITMIME status use
13694 log_selector = +8bitmime
13697 .option acl_not_smtp main string&!! unset
13698 .cindex "&ACL;" "for non-SMTP messages"
13699 .cindex "non-SMTP messages" "ACLs for"
13700 This option defines the ACL that is run when a non-SMTP message has been
13701 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13704 .option acl_not_smtp_mime main string&!! unset
13705 This option defines the ACL that is run for individual MIME parts of non-SMTP
13706 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13709 .option acl_not_smtp_start main string&!! unset
13710 .cindex "&ACL;" "at start of non-SMTP message"
13711 .cindex "non-SMTP messages" "ACLs for"
13712 This option defines the ACL that is run before Exim starts reading a
13713 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13715 .option acl_smtp_auth main string&!! unset
13716 .cindex "&ACL;" "setting up for SMTP commands"
13717 .cindex "AUTH" "ACL for"
13718 This option defines the ACL that is run when an SMTP AUTH command is
13719 received. See chapter &<<CHAPACL>>& for further details.
13721 .option acl_smtp_connect main string&!! unset
13722 .cindex "&ACL;" "on SMTP connection"
13723 This option defines the ACL that is run when an SMTP connection is received.
13724 See chapter &<<CHAPACL>>& for further details.
13726 .option acl_smtp_data main string&!! unset
13727 .cindex "DATA" "ACL for"
13728 This option defines the ACL that is run after an SMTP DATA command has been
13729 processed and the message itself has been received, but before the final
13730 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13733 .option acl_smtp_data_prdr main string&!! accept
13734 .cindex "PRDR" "ACL for"
13735 .cindex "DATA" "PRDR ACL for"
13736 .cindex "&ACL;" "PRDR-related"
13737 .cindex "&ACL;" "per-user data processing"
13739 This option defines the ACL that,
13740 if the PRDR feature has been negotiated,
13741 is run for each recipient after an SMTP DATA command has been
13742 processed and the message itself has been received, but before the
13743 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13746 .option acl_smtp_dkim main string&!! unset
13747 .cindex DKIM "ACL for"
13748 This option defines the ACL that is run for each DKIM signature
13749 of a received message.
13750 See chapter &<<CHAPdkim>>& for further details.
13753 .option acl_smtp_etrn main string&!! unset
13754 .cindex "ETRN" "ACL for"
13755 This option defines the ACL that is run when an SMTP ETRN command is
13756 received. See chapter &<<CHAPACL>>& for further details.
13758 .option acl_smtp_expn main string&!! unset
13759 .cindex "EXPN" "ACL for"
13760 This option defines the ACL that is run when an SMTP EXPN command is
13761 received. See chapter &<<CHAPACL>>& for further details.
13763 .option acl_smtp_helo main string&!! unset
13764 .cindex "EHLO" "ACL for"
13765 .cindex "HELO" "ACL for"
13766 This option defines the ACL that is run when an SMTP EHLO or HELO
13767 command is received. See chapter &<<CHAPACL>>& for further details.
13770 .option acl_smtp_mail main string&!! unset
13771 .cindex "MAIL" "ACL for"
13772 This option defines the ACL that is run when an SMTP MAIL command is
13773 received. See chapter &<<CHAPACL>>& for further details.
13775 .option acl_smtp_mailauth main string&!! unset
13776 .cindex "AUTH" "on MAIL command"
13777 This option defines the ACL that is run when there is an AUTH parameter on
13778 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13779 &<<CHAPSMTPAUTH>>& for details of authentication.
13781 .option acl_smtp_mime main string&!! unset
13782 .cindex "MIME content scanning" "ACL for"
13783 This option is available when Exim is built with the content-scanning
13784 extension. It defines the ACL that is run for each MIME part in a message. See
13785 section &<<SECTscanmimepart>>& for details.
13788 .option acl_smtp_notquit main string&!! unset
13789 .cindex "not-QUIT, ACL for"
13790 This option defines the ACL that is run when an SMTP session
13791 ends without a QUIT command being received.
13792 See chapter &<<CHAPACL>>& for further details.
13795 .option acl_smtp_predata main string&!! unset
13796 This option defines the ACL that is run when an SMTP DATA command is
13797 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13800 .option acl_smtp_quit main string&!! unset
13801 .cindex "QUIT, ACL for"
13802 This option defines the ACL that is run when an SMTP QUIT command is
13803 received. See chapter &<<CHAPACL>>& for further details.
13805 .option acl_smtp_rcpt main string&!! unset
13806 .cindex "RCPT" "ACL for"
13807 This option defines the ACL that is run when an SMTP RCPT command is
13808 received. See chapter &<<CHAPACL>>& for further details.
13810 .option acl_smtp_starttls main string&!! unset
13811 .cindex "STARTTLS, ACL for"
13812 This option defines the ACL that is run when an SMTP STARTTLS command is
13813 received. See chapter &<<CHAPACL>>& for further details.
13815 .option acl_smtp_vrfy main string&!! unset
13816 .cindex "VRFY" "ACL for"
13817 This option defines the ACL that is run when an SMTP VRFY command is
13818 received. See chapter &<<CHAPACL>>& for further details.
13821 .option add_environment main "string list" empty
13822 .cindex "environment" "inherited"
13823 This option allows to set individual environment variables that the
13824 currently linked libraries and programs in child processes use. The
13825 default list is empty,
13828 .option admin_groups main "string list&!!" unset
13829 .cindex "admin user"
13830 This option is expanded just once, at the start of Exim's processing. If the
13831 current group or any of the supplementary groups of an Exim caller is in this
13832 colon-separated list, the caller has admin privileges. If all your system
13833 programmers are in a specific group, for example, you can give them all Exim
13834 admin privileges by putting that group in &%admin_groups%&. However, this does
13835 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13836 To permit this, you have to add individuals to the Exim group.
13838 .option allow_domain_literals main boolean false
13839 .cindex "domain literal"
13840 If this option is set, the RFC 2822 domain literal format is permitted in
13841 email addresses. The option is not set by default, because the domain literal
13842 format is not normally required these days, and few people know about it. It
13843 has, however, been exploited by mail abusers.
13845 Unfortunately, it seems that some DNS black list maintainers are using this
13846 format to report black listing to postmasters. If you want to accept messages
13847 addressed to your hosts by IP address, you need to set
13848 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13849 domains (defined in the named domain list &%local_domains%& in the default
13850 configuration). This &"magic string"& matches the domain literal form of all
13851 the local host's IP addresses.
13854 .option allow_mx_to_ip main boolean false
13855 .cindex "MX record" "pointing to IP address"
13856 It appears that more and more DNS zone administrators are breaking the rules
13857 and putting domain names that look like IP addresses on the right hand side of
13858 MX records. Exim follows the rules and rejects this, giving an error message
13859 that explains the misconfiguration. However, some other MTAs support this
13860 practice, so to avoid &"Why can't Exim do this?"& complaints,
13861 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13862 recommended, except when you have no other choice.
13864 .option allow_utf8_domains main boolean false
13865 .cindex "domain" "UTF-8 characters in"
13866 .cindex "UTF-8" "in domain name"
13867 Lots of discussion is going on about internationalized domain names. One
13868 camp is strongly in favour of just using UTF-8 characters, and it seems
13869 that at least two other MTAs permit this. This option allows Exim users to
13870 experiment if they wish.
13872 If it is set true, Exim's domain parsing function allows valid
13873 UTF-8 multicharacters to appear in domain name components, in addition to
13874 letters, digits, and hyphens. However, just setting this option is not
13875 enough; if you want to look up these domain names in the DNS, you must also
13876 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13877 suitable setting is:
13879 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13880 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13882 Alternatively, you can just disable this feature by setting
13884 dns_check_names_pattern =
13886 That is, set the option to an empty string so that no check is done.
13889 .option auth_advertise_hosts main "host list&!!" *
13890 .cindex "authentication" "advertising"
13891 .cindex "AUTH" "advertising"
13892 If any server authentication mechanisms are configured, Exim advertises them in
13893 response to an EHLO command only if the calling host matches this list.
13894 Otherwise, Exim does not advertise AUTH.
13895 Exim does not accept AUTH commands from clients to which it has not
13896 advertised the availability of AUTH. The advertising of individual
13897 authentication mechanisms can be controlled by the use of the
13898 &%server_advertise_condition%& generic authenticator option on the individual
13899 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13901 Certain mail clients (for example, Netscape) require the user to provide a name
13902 and password for authentication if AUTH is advertised, even though it may
13903 not be needed (the host may accept messages from hosts on its local LAN without
13904 authentication, for example). The &%auth_advertise_hosts%& option can be used
13905 to make these clients more friendly by excluding them from the set of hosts to
13906 which Exim advertises AUTH.
13908 .cindex "AUTH" "advertising when encrypted"
13909 If you want to advertise the availability of AUTH only when the connection
13910 is encrypted using TLS, you can make use of the fact that the value of this
13911 option is expanded, with a setting like this:
13913 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13915 .vindex "&$tls_in_cipher$&"
13916 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13917 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13918 expansion is *, which matches all hosts.
13921 .option auto_thaw main time 0s
13922 .cindex "thawing messages"
13923 .cindex "unfreezing messages"
13924 If this option is set to a time greater than zero, a queue runner will try a
13925 new delivery attempt on any frozen message, other than a bounce message, if
13926 this much time has passed since it was frozen. This may result in the message
13927 being re-frozen if nothing has changed since the last attempt. It is a way of
13928 saying &"keep on trying, even though there are big problems"&.
13930 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13931 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13932 thought to be very useful any more, and its use should probably be avoided.
13935 .option av_scanner main string "see below"
13936 This option is available if Exim is built with the content-scanning extension.
13937 It specifies which anti-virus scanner to use. The default value is:
13939 sophie:/var/run/sophie
13941 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13942 before use. See section &<<SECTscanvirus>>& for further details.
13945 .option bi_command main string unset
13947 This option supplies the name of a command that is run when Exim is called with
13948 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13949 just the command name, it is not a complete command line. If an argument is
13950 required, it must come from the &%-oA%& command line option.
13953 .option bounce_message_file main string unset
13954 .cindex "bounce message" "customizing"
13955 .cindex "customizing" "bounce message"
13956 This option defines a template file containing paragraphs of text to be used
13957 for constructing bounce messages. Details of the file's contents are given in
13958 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13961 .option bounce_message_text main string unset
13962 When this option is set, its contents are included in the default bounce
13963 message immediately after &"This message was created automatically by mail
13964 delivery software."& It is not used if &%bounce_message_file%& is set.
13966 .option bounce_return_body main boolean true
13967 .cindex "bounce message" "including body"
13968 This option controls whether the body of an incoming message is included in a
13969 bounce message when &%bounce_return_message%& is true. The default setting
13970 causes the entire message, both header and body, to be returned (subject to the
13971 value of &%bounce_return_size_limit%&). If this option is false, only the
13972 message header is included. In the case of a non-SMTP message containing an
13973 error that is detected during reception, only those header lines preceding the
13974 point at which the error was detected are returned.
13975 .cindex "bounce message" "including original"
13977 .option bounce_return_message main boolean true
13978 If this option is set false, none of the original message is included in
13979 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13980 &%bounce_return_body%&.
13983 .option bounce_return_size_limit main integer 100K
13984 .cindex "size" "of bounce, limit"
13985 .cindex "bounce message" "size limit"
13986 .cindex "limit" "bounce message size"
13987 This option sets a limit in bytes on the size of messages that are returned to
13988 senders as part of bounce messages when &%bounce_return_message%& is true. The
13989 limit should be less than the value of the global &%message_size_limit%& and of
13990 any &%message_size_limit%& settings on transports, to allow for the bounce text
13991 that Exim generates. If this option is set to zero there is no limit.
13993 When the body of any message that is to be included in a bounce message is
13994 greater than the limit, it is truncated, and a comment pointing this out is
13995 added at the top. The actual cutoff may be greater than the value given, owing
13996 to the use of buffering for transferring the message in chunks (typically 8K in
13997 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14000 .option bounce_sender_authentication main string unset
14001 .cindex "bounce message" "sender authentication"
14002 .cindex "authentication" "bounce message"
14003 .cindex "AUTH" "on bounce message"
14004 This option provides an authenticated sender address that is sent with any
14005 bounce messages generated by Exim that are sent over an authenticated SMTP
14006 connection. A typical setting might be:
14008 bounce_sender_authentication = mailer-daemon@my.domain.example
14010 which would cause bounce messages to be sent using the SMTP command:
14012 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14014 The value of &%bounce_sender_authentication%& must always be a complete email
14017 .option callout_domain_negative_expire main time 3h
14018 .cindex "caching" "callout timeouts"
14019 .cindex "callout" "caching timeouts"
14020 This option specifies the expiry time for negative callout cache data for a
14021 domain. See section &<<SECTcallver>>& for details of callout verification, and
14022 section &<<SECTcallvercache>>& for details of the caching.
14025 .option callout_domain_positive_expire main time 7d
14026 This option specifies the expiry time for positive callout cache data for a
14027 domain. See section &<<SECTcallver>>& for details of callout verification, and
14028 section &<<SECTcallvercache>>& for details of the caching.
14031 .option callout_negative_expire main time 2h
14032 This option specifies the expiry time for negative callout cache data for an
14033 address. See section &<<SECTcallver>>& for details of callout verification, and
14034 section &<<SECTcallvercache>>& for details of the caching.
14037 .option callout_positive_expire main time 24h
14038 This option specifies the expiry time for positive callout cache data for an
14039 address. See section &<<SECTcallver>>& for details of callout verification, and
14040 section &<<SECTcallvercache>>& for details of the caching.
14043 .option callout_random_local_part main string&!! "see below"
14044 This option defines the &"random"& local part that can be used as part of
14045 callout verification. The default value is
14047 $primary_hostname-$tod_epoch-testing
14049 See section &<<CALLaddparcall>>& for details of how this value is used.
14052 .option check_log_inodes main integer 0
14053 See &%check_spool_space%& below.
14056 .option check_log_space main integer 0
14057 See &%check_spool_space%& below.
14059 .oindex "&%check_rfc2047_length%&"
14060 .cindex "RFC 2047" "disabling length check"
14061 .option check_rfc2047_length main boolean true
14062 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14063 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14064 word; strings to be encoded that exceed this length are supposed to use
14065 multiple encoded words. By default, Exim does not recognize encoded words that
14066 exceed the maximum length. However, it seems that some software, in violation
14067 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14068 set false, Exim recognizes encoded words of any length.
14071 .option check_spool_inodes main integer 0
14072 See &%check_spool_space%& below.
14075 .option check_spool_space main integer 0
14076 .cindex "checking disk space"
14077 .cindex "disk space, checking"
14078 .cindex "spool directory" "checking space"
14079 The four &%check_...%& options allow for checking of disk resources before a
14080 message is accepted.
14082 .vindex "&$log_inodes$&"
14083 .vindex "&$log_space$&"
14084 .vindex "&$spool_inodes$&"
14085 .vindex "&$spool_space$&"
14086 When any of these options are set, they apply to all incoming messages. If you
14087 want to apply different checks to different kinds of message, you can do so by
14088 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14089 &$spool_space$& in an ACL with appropriate additional conditions.
14092 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14093 either value is greater than zero, for example:
14095 check_spool_space = 10M
14096 check_spool_inodes = 100
14098 The spool partition is the one that contains the directory defined by
14099 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14102 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14103 files are written if either is greater than zero. These should be set only if
14104 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14106 If there is less space or fewer inodes than requested, Exim refuses to accept
14107 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14108 error response to the MAIL command. If ESMTP is in use and there was a
14109 SIZE parameter on the MAIL command, its value is added to the
14110 &%check_spool_space%& value, and the check is performed even if
14111 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14113 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14114 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
14116 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14117 failure a message is written to stderr and Exim exits with a non-zero code, as
14118 it obviously cannot send an error message of any kind.
14120 .option daemon_smtp_ports main string &`smtp`&
14121 .cindex "port" "for daemon"
14122 .cindex "TCP/IP" "setting listening ports"
14123 This option specifies one or more default SMTP ports on which the Exim daemon
14124 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14125 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14127 .option daemon_startup_retries main integer 9
14128 .cindex "daemon startup, retrying"
14129 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14130 the daemon at startup when it cannot immediately bind a listening socket
14131 (typically because the socket is already in use): &%daemon_startup_retries%&
14132 defines the number of retries after the first failure, and
14133 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14135 .option daemon_startup_sleep main time 30s
14136 See &%daemon_startup_retries%&.
14138 .option delay_warning main "time list" 24h
14139 .cindex "warning of delay"
14140 .cindex "delay warning, specifying"
14141 When a message is delayed, Exim sends a warning message to the sender at
14142 intervals specified by this option. The data is a colon-separated list of times
14143 after which to send warning messages. If the value of the option is an empty
14144 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14145 message has been on the queue for longer than the last time, the last interval
14146 between the times is used to compute subsequent warning times. For example,
14149 delay_warning = 4h:8h:24h
14151 the first message is sent after 4 hours, the second after 8 hours, and
14152 the third one after 24 hours. After that, messages are sent every 16 hours,
14153 because that is the interval between the last two times on the list. If you set
14154 just one time, it specifies the repeat interval. For example, with:
14158 messages are repeated every six hours. To stop warnings after a given time, set
14159 a very large time at the end of the list. For example:
14161 delay_warning = 2h:12h:99d
14163 Note that the option is only evaluated at the time a delivery attempt fails,
14164 which depends on retry and queue-runner configuration.
14165 Typically retries will be configured more frequently than warning messages.
14167 .option delay_warning_condition main string&!! "see below"
14168 .vindex "&$domain$&"
14169 The string is expanded at the time a warning message might be sent. If all the
14170 deferred addresses have the same domain, it is set in &$domain$& during the
14171 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14172 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14173 &"false"& (the comparison being done caselessly) then the warning message is
14174 not sent. The default is:
14176 delay_warning_condition = ${if or {\
14177 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14178 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14179 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14182 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14183 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14184 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14185 &"auto-replied"& in an &'Auto-Submitted:'& header.
14187 .option deliver_drop_privilege main boolean false
14188 .cindex "unprivileged delivery"
14189 .cindex "delivery" "unprivileged"
14190 If this option is set true, Exim drops its root privilege at the start of a
14191 delivery process, and runs as the Exim user throughout. This severely restricts
14192 the kinds of local delivery that are possible, but is viable in certain types
14193 of configuration. There is a discussion about the use of root privilege in
14194 chapter &<<CHAPsecurity>>&.
14196 .option deliver_queue_load_max main fixed-point unset
14197 .cindex "load average"
14198 .cindex "queue runner" "abandoning"
14199 When this option is set, a queue run is abandoned if the system load average
14200 becomes greater than the value of the option. The option has no effect on
14201 ancient operating systems on which Exim cannot determine the load average.
14202 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14205 .option delivery_date_remove main boolean true
14206 .cindex "&'Delivery-date:'& header line"
14207 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14208 message when it is delivered, in exactly the same way as &'Return-path:'& is
14209 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14210 should not be present in incoming messages, and this option causes them to be
14211 removed at the time the message is received, to avoid any problems that might
14212 occur when a delivered message is subsequently sent on to some other recipient.
14214 .option disable_fsync main boolean false
14215 .cindex "&[fsync()]&, disabling"
14216 This option is available only if Exim was built with the compile-time option
14217 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14218 a runtime configuration generates an &"unknown option"& error. You should not
14219 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14220 really, really, really understand what you are doing. &'No pre-compiled
14221 distributions of Exim should ever make this option available.'&
14223 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14224 updated files' data to be written to disc before continuing. Unexpected events
14225 such as crashes and power outages may cause data to be lost or scrambled.
14226 Here be Dragons. &*Beware.*&
14229 .option disable_ipv6 main boolean false
14230 .cindex "IPv6" "disabling"
14231 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14232 activities take place. AAAA records are never looked up, and any IPv6 addresses
14233 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14234 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14235 to handle IPv6 literal addresses.
14239 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14240 .cindex DKIM "controlling calls to the ACL"
14241 This option gives a list of DKIM domains for which the DKIM ACL is run.
14242 It is expanded after the message is received; by default it runs
14243 the ACL once for each signature in the message.
14244 See chapter &<<CHAPdkim>>&.
14248 .option dns_again_means_nonexist main "domain list&!!" unset
14249 .cindex "DNS" "&""try again""& response; overriding"
14250 DNS lookups give a &"try again"& response for the DNS errors
14251 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14252 keep trying to deliver a message, or to give repeated temporary errors to
14253 incoming mail. Sometimes the effect is caused by a badly set up name server and
14254 may persist for a long time. If a domain which exhibits this problem matches
14255 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14256 This option should be used with care. You can make it apply to reverse lookups
14257 by a setting such as this:
14259 dns_again_means_nonexist = *.in-addr.arpa
14261 This option applies to all DNS lookups that Exim does. It also applies when the
14262 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14263 since these are most likely to be caused by DNS lookup problems. The
14264 &(dnslookup)& router has some options of its own for controlling what happens
14265 when lookups for MX or SRV records give temporary errors. These more specific
14266 options are applied after this global option.
14268 .option dns_check_names_pattern main string "see below"
14269 .cindex "DNS" "pre-check of name syntax"
14270 When this option is set to a non-empty string, it causes Exim to check domain
14271 names for characters that are not allowed in host names before handing them to
14272 the DNS resolver, because some resolvers give temporary errors for names that
14273 contain unusual characters. If a domain name contains any unwanted characters,
14274 a &"not found"& result is forced, and the resolver is not called. The check is
14275 done by matching the domain name against a regular expression, which is the
14276 value of this option. The default pattern is
14278 dns_check_names_pattern = \
14279 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14281 which permits only letters, digits, slashes, and hyphens in components, but
14282 they must start and end with a letter or digit. Slashes are not, in fact,
14283 permitted in host names, but they are found in certain NS records (which can be
14284 accessed in Exim by using a &%dnsdb%& lookup). If you set
14285 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14288 .option dns_csa_search_limit main integer 5
14289 This option controls the depth of parental searching for CSA SRV records in the
14290 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14292 .option dns_csa_use_reverse main boolean true
14293 This option controls whether or not an IP address, given as a CSA domain, is
14294 reversed and looked up in the reverse DNS, as described in more detail in
14295 section &<<SECTverifyCSA>>&.
14298 .option dns_dnssec_ok main integer -1
14299 .cindex "DNS" "resolver options"
14300 .cindex "DNS" "DNSSEC"
14301 If this option is set to a non-negative number then Exim will initialise the
14302 DNS resolver library to either use or not use DNSSEC, overriding the system
14303 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14305 If the resolver library does not support DNSSEC then this option has no effect.
14308 .option dns_ipv4_lookup main "domain list&!!" unset
14309 .cindex "IPv6" "DNS lookup for AAAA records"
14310 .cindex "DNS" "IPv6 lookup for AAAA records"
14311 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14312 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14313 (A records) when trying to find IP addresses for hosts, unless the host's
14314 domain matches this list.
14316 This is a fudge to help with name servers that give big delays or otherwise do
14317 not work for the AAAA record type. In due course, when the world's name
14318 servers have all been upgraded, there should be no need for this option.
14321 .option dns_retrans main time 0s
14322 .cindex "DNS" "resolver options"
14323 .cindex timeout "dns lookup"
14324 .cindex "DNS" timeout
14325 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14326 retransmission and retry parameters for DNS lookups. Values of zero (the
14327 defaults) leave the system default settings unchanged. The first value is the
14328 time between retries, and the second is the number of retries. It isn't
14329 totally clear exactly how these settings affect the total time a DNS lookup may
14330 take. I haven't found any documentation about timeouts on DNS lookups; these
14331 parameter values are available in the external resolver interface structure,
14332 but nowhere does it seem to describe how they are used or what you might want
14335 See also the &%slow_lookup_log%& option.
14339 .option dns_retry main integer 0
14340 See &%dns_retrans%& above.
14344 .option dns_trust_aa main "domain list&!!" unset
14345 .cindex "DNS" "resolver options"
14346 .cindex "DNS" "DNSSEC"
14347 If this option is set then lookup results marked with the AA bit
14348 (Authoritative Answer) are trusted the same way as if they were
14349 DNSSEC-verified. The authority section's name of the answer must
14350 match with this expanded domain list.
14352 Use this option only if you talk directly to a resolver that is
14353 authoritative for some zones and does not set the AD (Authentic Data)
14354 bit in the answer. Some DNS servers may have an configuration option to
14355 mark the answers from their own zones as verified (they set the AD bit).
14356 Others do not have this option. It is considered as poor practice using
14357 a resolver that is an authoritative server for some zones.
14359 Use this option only if you really have to (e.g. if you want
14360 to use DANE for remote delivery to a server that is listed in the DNS
14361 zones that your resolver is authoritative for).
14363 If the DNS answer packet has the AA bit set and contains resource record
14364 in the answer section, the name of the first NS record appearing in the
14365 authority section is compared against the list. If the answer packet is
14366 authoritative but the answer section is empty, the name of the first SOA
14367 record in the authoritative section is used instead.
14370 .cindex "DNS" "resolver options"
14371 .option dns_use_edns0 main integer -1
14372 .cindex "DNS" "resolver options"
14373 .cindex "DNS" "EDNS0"
14374 If this option is set to a non-negative number then Exim will initialise the
14375 DNS resolver library to either use or not use EDNS0 extensions, overriding
14376 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14379 If the resolver library does not support EDNS0 then this option has no effect.
14382 .option drop_cr main boolean false
14383 This is an obsolete option that is now a no-op. It used to affect the way Exim
14384 handled CR and LF characters in incoming messages. What happens now is
14385 described in section &<<SECTlineendings>>&.
14388 .option dsn_advertise_hosts main "host list&!!" unset
14389 .cindex "bounce messages" "success"
14390 .cindex "DSN" "success"
14391 .cindex "Delivery Status Notification" "success"
14392 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14393 and accepted from, these hosts.
14394 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14395 and RET and ORCPT options on MAIL FROM commands.
14396 A NOTIFY=SUCCESS option requests success-DSN messages.
14397 A NOTIFY= option with no argument requests that no delay or failure DSNs
14401 .option dsn_from main "string&!!" "see below"
14402 .cindex "&'From:'& header line" "in bounces"
14403 .cindex "bounce messages" "&'From:'& line, specifying"
14404 This option can be used to vary the contents of &'From:'& header lines in
14405 bounces and other automatically generated messages (&"Delivery Status
14406 Notifications"& &-- hence the name of the option). The default setting is:
14408 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14410 The value is expanded every time it is needed. If the expansion fails, a
14411 panic is logged, and the default value is used.
14413 .option envelope_to_remove main boolean true
14414 .cindex "&'Envelope-to:'& header line"
14415 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14416 message when it is delivered, in exactly the same way as &'Return-path:'& is
14417 handled. &'Envelope-to:'& records the original recipient address from the
14418 message's envelope that caused the delivery to happen. Such headers should not
14419 be present in incoming messages, and this option causes them to be removed at
14420 the time the message is received, to avoid any problems that might occur when a
14421 delivered message is subsequently sent on to some other recipient.
14424 .option errors_copy main "string list&!!" unset
14425 .cindex "bounce message" "copy to other address"
14426 .cindex "copy of bounce message"
14427 Setting this option causes Exim to send bcc copies of bounce messages that it
14428 generates to other addresses. &*Note*&: This does not apply to bounce messages
14429 coming from elsewhere. The value of the option is a colon-separated list of
14430 items. Each item consists of a pattern, terminated by white space, followed by
14431 a comma-separated list of email addresses. If a pattern contains spaces, it
14432 must be enclosed in double quotes.
14434 Each pattern is processed in the same way as a single item in an address list
14435 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14436 the bounce message, the message is copied to the addresses on the list. The
14437 items are scanned in order, and once a matching one is found, no further items
14438 are examined. For example:
14440 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14441 rqps@mydomain hostmaster@mydomain.example,\
14442 postmaster@mydomain.example
14444 .vindex "&$domain$&"
14445 .vindex "&$local_part$&"
14446 The address list is expanded before use. The expansion variables &$local_part$&
14447 and &$domain$& are set from the original recipient of the error message, and if
14448 there was any wildcard matching in the pattern, the expansion
14449 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14450 variables &$0$&, &$1$&, etc. are set in the normal way.
14453 .option errors_reply_to main string unset
14454 .cindex "bounce message" "&'Reply-to:'& in"
14455 By default, Exim's bounce and delivery warning messages contain the header line
14457 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14459 .oindex &%quota_warn_message%&
14460 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14461 A warning message that is generated by the &%quota_warn_message%& option in an
14462 &(appendfile)& transport may contain its own &'From:'& header line that
14463 overrides the default.
14465 Experience shows that people reply to bounce messages. If the
14466 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14467 and warning messages. For example:
14469 errors_reply_to = postmaster@my.domain.example
14471 The value of the option is not expanded. It must specify a valid RFC 2822
14472 address. However, if a warning message that is generated by the
14473 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14474 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14478 .option exim_group main string "compile-time configured"
14479 .cindex "gid (group id)" "Exim's own"
14480 .cindex "Exim group"
14481 This option changes the gid under which Exim runs when it gives up root
14482 privilege. The default value is compiled into the binary. The value of this
14483 option is used only when &%exim_user%& is also set. Unless it consists entirely
14484 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14485 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14489 .option exim_path main string "see below"
14490 .cindex "Exim binary, path name"
14491 This option specifies the path name of the Exim binary, which is used when Exim
14492 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14493 the directory configured at compile time by the BIN_DIRECTORY setting. It
14494 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14496 &*Warning*&: Do not use a macro to define the value of this option, because
14497 you will break those Exim utilities that scan the configuration file to find
14498 where the binary is. (They then use the &%-bP%& option to extract option
14499 settings such as the value of &%spool_directory%&.)
14502 .option exim_user main string "compile-time configured"
14503 .cindex "uid (user id)" "Exim's own"
14504 .cindex "Exim user"
14505 This option changes the uid under which Exim runs when it gives up root
14506 privilege. The default value is compiled into the binary. Ownership of the run
14507 time configuration file and the use of the &%-C%& and &%-D%& command line
14508 options is checked against the values in the binary, not what is set here.
14510 Unless it consists entirely of digits, the string is looked up using
14511 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14512 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14513 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14516 .option extra_local_interfaces main "string list" unset
14517 This option defines network interfaces that are to be considered local when
14518 routing, but which are not used for listening by the daemon. See section
14519 &<<SECTreclocipadd>>& for details.
14522 . Allow this long option name to split; give it unsplit as a fifth argument
14523 . for the automatic .oindex that is generated by .option.
14525 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
14526 extract_addresses_remove_arguments
14528 .cindex "command line" "addresses with &%-t%&"
14529 .cindex "Sendmail compatibility" "&%-t%& option"
14530 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14531 are present on the command line when the &%-t%& option is used to build an
14532 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14533 line addresses are removed from the recipients list. This is also how Smail
14534 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14535 command line addresses are added to those obtained from the header lines. When
14536 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14537 argument headers. If it is set false, Exim adds rather than removes argument
14541 .option finduser_retries main integer 0
14542 .cindex "NIS, retrying user lookups"
14543 On systems running NIS or other schemes in which user and group information is
14544 distributed from a remote system, there can be times when &[getpwnam()]& and
14545 related functions fail, even when given valid data, because things time out.
14546 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14547 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14548 many extra times to find a user or a group, waiting for one second between
14551 .cindex "&_/etc/passwd_&" "multiple reading of"
14552 You should not set this option greater than zero if your user information is in
14553 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14554 search the file multiple times for non-existent users, and also cause delay.
14558 .option freeze_tell main "string list, comma separated" unset
14559 .cindex "freezing messages" "sending a message when freezing"
14560 On encountering certain errors, or when configured to do so in a system filter,
14561 ACL, or special router, Exim freezes a message. This means that no further
14562 delivery attempts take place until an administrator thaws the message, or the
14563 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14564 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14565 warning message whenever it freezes something, unless the message it is
14566 freezing is a locally-generated bounce message. (Without this exception there
14567 is the possibility of looping.) The warning message is sent to the addresses
14568 supplied as the comma-separated value of this option. If several of the
14569 message's addresses cause freezing, only a single message is sent. If the
14570 freezing was automatic, the reason(s) for freezing can be found in the message
14571 log. If you configure freezing in a filter or ACL, you must arrange for any
14572 logging that you require.
14575 .option gecos_name main string&!! unset
14577 .cindex "&""gecos""& field, parsing"
14578 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14579 password file to hold other information in addition to users' real names. Exim
14580 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14581 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14582 of the field are used unchanged, except that, if an ampersand is encountered,
14583 it is replaced by the user's login name with the first character forced to
14584 upper case, since this is a convention that is observed on many systems.
14586 When these options are set, &%gecos_pattern%& is treated as a regular
14587 expression that is to be applied to the field (again with && replaced by the
14588 login name), and if it matches, &%gecos_name%& is expanded and used as the
14591 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14592 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14593 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14594 name terminates at the first comma, the following can be used:
14596 gecos_pattern = ([^,]*)
14600 .option gecos_pattern main string unset
14601 See &%gecos_name%& above.
14604 .option gnutls_compat_mode main boolean unset
14605 This option controls whether GnuTLS is used in compatibility mode in an Exim
14606 server. This reduces security slightly, but improves interworking with older
14607 implementations of TLS.
14610 option gnutls_allow_auto_pkcs11 main boolean unset
14611 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14612 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14615 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14620 .option headers_charset main string "see below"
14621 This option sets a default character set for translating from encoded MIME
14622 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14623 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14624 ultimate default is ISO-8859-1. For more details see the description of header
14625 insertions in section &<<SECTexpansionitems>>&.
14629 .option header_maxsize main integer "see below"
14630 .cindex "header section" "maximum size of"
14631 .cindex "limit" "size of message header section"
14632 This option controls the overall maximum size of a message's header
14633 section. The default is the value of HEADER_MAXSIZE in
14634 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14635 sections are rejected.
14638 .option header_line_maxsize main integer 0
14639 .cindex "header lines" "maximum size of"
14640 .cindex "limit" "size of one header line"
14641 This option limits the length of any individual header line in a message, after
14642 all the continuations have been joined together. Messages with individual
14643 header lines that are longer than the limit are rejected. The default value of
14644 zero means &"no limit"&.
14649 .option helo_accept_junk_hosts main "host list&!!" unset
14650 .cindex "HELO" "accepting junk data"
14651 .cindex "EHLO" "accepting junk data"
14652 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14653 mail, and gives an error response for invalid data. Unfortunately, there are
14654 some SMTP clients that send syntactic junk. They can be accommodated by setting
14655 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14656 if you want to do semantic checking.
14657 See also &%helo_allow_chars%& for a way of extending the permitted character
14661 .option helo_allow_chars main string unset
14662 .cindex "HELO" "underscores in"
14663 .cindex "EHLO" "underscores in"
14664 .cindex "underscore in EHLO/HELO"
14665 This option can be set to a string of rogue characters that are permitted in
14666 all EHLO and HELO names in addition to the standard letters, digits,
14667 hyphens, and dots. If you really must allow underscores, you can set
14669 helo_allow_chars = _
14671 Note that the value is one string, not a list.
14674 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14675 .cindex "HELO" "forcing reverse lookup"
14676 .cindex "EHLO" "forcing reverse lookup"
14677 If the domain given by a client in a HELO or EHLO command matches this
14678 list, a reverse lookup is done in order to establish the host's true name. The
14679 default forces a lookup if the client host gives the server's name or any of
14680 its IP addresses (in brackets), something that broken clients have been seen to
14684 .option helo_try_verify_hosts main "host list&!!" unset
14685 .cindex "HELO verifying" "optional"
14686 .cindex "EHLO" "verifying, optional"
14687 By default, Exim just checks the syntax of HELO and EHLO commands (see
14688 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14689 to do more extensive checking of the data supplied by these commands. The ACL
14690 condition &`verify = helo`& is provided to make this possible.
14691 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14692 to force the check to occur. From release 4.53 onwards, this is no longer
14693 necessary. If the check has not been done before &`verify = helo`& is
14694 encountered, it is done at that time. Consequently, this option is obsolete.
14695 Its specification is retained here for backwards compatibility.
14697 When an EHLO or HELO command is received, if the calling host matches
14698 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14699 EHLO command either:
14702 is an IP literal matching the calling address of the host, or
14704 .cindex "DNS" "reverse lookup"
14705 .cindex "reverse DNS lookup"
14706 matches the host name that Exim obtains by doing a reverse lookup of the
14707 calling host address, or
14709 when looked up in DNS yields the calling host address.
14712 However, the EHLO or HELO command is not rejected if any of the checks
14713 fail. Processing continues, but the result of the check is remembered, and can
14714 be detected later in an ACL by the &`verify = helo`& condition.
14716 If DNS was used for successful verification, the variable
14717 .cindex "DNS" "DNSSEC"
14718 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
14720 .option helo_verify_hosts main "host list&!!" unset
14721 .cindex "HELO verifying" "mandatory"
14722 .cindex "EHLO" "verifying, mandatory"
14723 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14724 backwards compatibility. For hosts that match this option, Exim checks the host
14725 name given in the HELO or EHLO in the same way as for
14726 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14727 rejected with a 550 error, and entries are written to the main and reject logs.
14728 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14731 .option hold_domains main "domain list&!!" unset
14732 .cindex "domain" "delaying delivery"
14733 .cindex "delivery" "delaying certain domains"
14734 This option allows mail for particular domains to be held on the queue
14735 manually. The option is overridden if a message delivery is forced with the
14736 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14737 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14738 item in &%hold_domains%&, no routing or delivery for that address is done, and
14739 it is deferred every time the message is looked at.
14741 This option is intended as a temporary operational measure for delaying the
14742 delivery of mail while some problem is being sorted out, or some new
14743 configuration tested. If you just want to delay the processing of some
14744 domains until a queue run occurs, you should use &%queue_domains%& or
14745 &%queue_smtp_domains%&, not &%hold_domains%&.
14747 A setting of &%hold_domains%& does not override Exim's code for removing
14748 messages from the queue if they have been there longer than the longest retry
14749 time in any retry rule. If you want to hold messages for longer than the normal
14750 retry times, insert a dummy retry rule with a long retry time.
14753 .option host_lookup main "host list&!!" unset
14754 .cindex "host name" "lookup, forcing"
14755 Exim does not look up the name of a calling host from its IP address unless it
14756 is required to compare against some host list, or the host matches
14757 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14758 option (which normally contains IP addresses rather than host names). The
14759 default configuration file contains
14763 which causes a lookup to happen for all hosts. If the expense of these lookups
14764 is felt to be too great, the setting can be changed or removed.
14766 After a successful reverse lookup, Exim does a forward lookup on the name it
14767 has obtained, to verify that it yields the IP address that it started with. If
14768 this check fails, Exim behaves as if the name lookup failed.
14770 .vindex "&$host_lookup_failed$&"
14771 .vindex "&$sender_host_name$&"
14772 After any kind of failure, the host name (in &$sender_host_name$&) remains
14773 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14774 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14775 &`verify = reverse_host_lookup`& in ACLs.
14778 .option host_lookup_order main "string list" &`bydns:byaddr`&
14779 This option specifies the order of different lookup methods when Exim is trying
14780 to find a host name from an IP address. The default is to do a DNS lookup
14781 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14782 if that fails. You can change the order of these lookups, or omit one entirely,
14785 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14786 multiple PTR records in the DNS and the IP address is not listed in
14787 &_/etc/hosts_&. Different operating systems give different results in this
14788 case. That is why the default tries a DNS lookup first.
14792 .option host_reject_connection main "host list&!!" unset
14793 .cindex "host" "rejecting connections from"
14794 If this option is set, incoming SMTP calls from the hosts listed are rejected
14795 as soon as the connection is made.
14796 This option is obsolete, and retained only for backward compatibility, because
14797 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14798 connections immediately.
14800 The ability to give an immediate rejection (either by this option or using an
14801 ACL) is provided for use in unusual cases. Many hosts will just try again,
14802 sometimes without much delay. Normally, it is better to use an ACL to reject
14803 incoming messages at a later stage, such as after RCPT commands. See
14804 chapter &<<CHAPACL>>&.
14807 .option hosts_connection_nolog main "host list&!!" unset
14808 .cindex "host" "not logging connections from"
14809 This option defines a list of hosts for which connection logging does not
14810 happen, even though the &%smtp_connection%& log selector is set. For example,
14811 you might want not to log SMTP connections from local processes, or from
14812 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14813 the daemon; you should therefore strive to restrict its value to a short inline
14814 list of IP addresses and networks. To disable logging SMTP connections from
14815 local processes, you must create a host list with an empty item. For example:
14817 hosts_connection_nolog = :
14819 If the &%smtp_connection%& log selector is not set, this option has no effect.
14823 .option hosts_treat_as_local main "domain list&!!" unset
14824 .cindex "local host" "domains treated as"
14825 .cindex "host" "treated as local"
14826 If this option is set, any host names that match the domain list are treated as
14827 if they were the local host when Exim is scanning host lists obtained from MX
14829 or other sources. Note that the value of this option is a domain list, not a
14830 host list, because it is always used to check host names, not IP addresses.
14832 This option also applies when Exim is matching the special items
14833 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14834 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14835 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14836 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14837 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14838 interfaces and recognizing the local host.
14841 .option ibase_servers main "string list" unset
14842 .cindex "InterBase" "server list"
14843 This option provides a list of InterBase servers and associated connection data,
14844 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14845 The option is available only if Exim has been built with InterBase support.
14849 .option ignore_bounce_errors_after main time 10w
14850 .cindex "bounce message" "discarding"
14851 .cindex "discarding bounce message"
14852 This option affects the processing of bounce messages that cannot be delivered,
14853 that is, those that suffer a permanent delivery failure. (Bounce messages that
14854 suffer temporary delivery failures are of course retried in the usual way.)
14856 After a permanent delivery failure, bounce messages are frozen,
14857 because there is no sender to whom they can be returned. When a frozen bounce
14858 message has been on the queue for more than the given time, it is unfrozen at
14859 the next queue run, and a further delivery is attempted. If delivery fails
14860 again, the bounce message is discarded. This makes it possible to keep failed
14861 bounce messages around for a shorter time than the normal maximum retry time
14862 for frozen messages. For example,
14864 ignore_bounce_errors_after = 12h
14866 retries failed bounce message deliveries after 12 hours, discarding any further
14867 failures. If the value of this option is set to a zero time period, bounce
14868 failures are discarded immediately. Setting a very long time (as in the default
14869 value) has the effect of disabling this option. For ways of automatically
14870 dealing with other kinds of frozen message, see &%auto_thaw%& and
14871 &%timeout_frozen_after%&.
14874 .option ignore_fromline_hosts main "host list&!!" unset
14875 .cindex "&""From""& line"
14876 .cindex "UUCP" "&""From""& line"
14877 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14878 the headers of a message. By default this is treated as the start of the
14879 message's body, which means that any following headers are not recognized as
14880 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14881 match those hosts that insist on sending it. If the sender is actually a local
14882 process rather than a remote host, and is using &%-bs%& to inject the messages,
14883 &%ignore_fromline_local%& must be set to achieve this effect.
14886 .option ignore_fromline_local main boolean false
14887 See &%ignore_fromline_hosts%& above.
14890 .option keep_environment main "string list" unset
14891 .cindex "environment" "inherited"
14892 This option contains a string list of environment variables to keep.
14893 You have to trust these variables or you have to be sure that
14894 these variables do not impose any security risk. Keep in mind that
14895 during the startup phase Exim is running with an effective UID 0 in most
14896 installations. As the default value is an empty list, the default
14897 environment for using libraries, running embedded Perl code, or running
14898 external binaries is empty, and does not not even contain PATH or HOME.
14900 Actually the list is interpreted as a list of patterns
14901 (&<<SECTlistexpand>>&), except that it is not expanded first.
14903 WARNING: Macro substitution is still done first, so having a macro
14904 FOO and having FOO_HOME in your &%keep_environment%& option may have
14905 unexpected results. You may work around this using a regular expression
14906 that does not match the macro name: ^[F]OO_HOME$.
14908 Current versions of Exim issue a warning during startupif you do not mention
14909 &%keep_environment%& or &%add_environment%& in your runtime configuration
14914 .option keep_malformed main time 4d
14915 This option specifies the length of time to keep messages whose spool files
14916 have been corrupted in some way. This should, of course, never happen. At the
14917 next attempt to deliver such a message, it gets removed. The incident is
14921 .option ldap_ca_cert_dir main string unset
14922 .cindex "LDAP", "TLS CA certificate directory"
14923 This option indicates which directory contains CA certificates for verifying
14924 a TLS certificate presented by an LDAP server.
14925 While Exim does not provide a default value, your SSL library may.
14926 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14927 and constrained to be a directory.
14930 .option ldap_ca_cert_file main string unset
14931 .cindex "LDAP", "TLS CA certificate file"
14932 This option indicates which file contains CA certificates for verifying
14933 a TLS certificate presented by an LDAP server.
14934 While Exim does not provide a default value, your SSL library may.
14935 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14936 and constrained to be a file.
14939 .option ldap_cert_file main string unset
14940 .cindex "LDAP" "TLS client certificate file"
14941 This option indicates which file contains an TLS client certificate which
14942 Exim should present to the LDAP server during TLS negotiation.
14943 Should be used together with &%ldap_cert_key%&.
14946 .option ldap_cert_key main string unset
14947 .cindex "LDAP" "TLS client key file"
14948 This option indicates which file contains the secret/private key to use
14949 to prove identity to the LDAP server during TLS negotiation.
14950 Should be used together with &%ldap_cert_file%&, which contains the
14951 identity to be proven.
14954 .option ldap_cipher_suite main string unset
14955 .cindex "LDAP" "TLS cipher suite"
14956 This controls the TLS cipher-suite negotiation during TLS negotiation with
14957 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14958 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14961 .option ldap_default_servers main "string list" unset
14962 .cindex "LDAP" "default servers"
14963 This option provides a list of LDAP servers which are tried in turn when an
14964 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14965 details of LDAP queries. This option is available only when Exim has been built
14969 .option ldap_require_cert main string unset.
14970 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14971 This should be one of the values "hard", "demand", "allow", "try" or "never".
14972 A value other than one of these is interpreted as "never".
14973 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14974 Although Exim does not set a default, the LDAP library probably defaults
14978 .option ldap_start_tls main boolean false
14979 .cindex "LDAP" "whether or not to negotiate TLS"
14980 If set, Exim will attempt to negotiate TLS with the LDAP server when
14981 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14982 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14984 In the event of failure to negotiate TLS, the action taken is controlled
14985 by &%ldap_require_cert%&.
14988 .option ldap_version main integer unset
14989 .cindex "LDAP" "protocol version, forcing"
14990 This option can be used to force Exim to set a specific protocol version for
14991 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14992 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14993 the LDAP headers; otherwise it is 2. This option is available only when Exim
14994 has been built with LDAP support.
14998 .option local_from_check main boolean true
14999 .cindex "&'Sender:'& header line" "disabling addition of"
15000 .cindex "&'From:'& header line" "disabling checking of"
15001 When a message is submitted locally (that is, not over a TCP/IP connection) by
15002 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15003 checks that the &'From:'& header line matches the login of the calling user and
15004 the domain specified by &%qualify_domain%&.
15006 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15007 locally submitted message is automatically qualified by Exim, unless the
15008 &%-bnq%& command line option is used.
15010 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15011 on the local part. If the &'From:'& header line does not match, Exim adds a
15012 &'Sender:'& header with an address constructed from the calling user's login
15013 and the default qualify domain.
15015 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15016 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15017 &'Sender:'& header lines supplied by untrusted users, you must also set
15018 &%local_sender_retain%& to be true.
15020 .cindex "envelope sender"
15021 These options affect only the header lines in the message. The envelope sender
15022 is still forced to be the login id at the qualify domain unless
15023 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15025 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15026 request similar header line checking. See section &<<SECTthesenhea>>&, which
15027 has more details about &'Sender:'& processing.
15032 .option local_from_prefix main string unset
15033 When Exim checks the &'From:'& header line of locally submitted messages for
15034 matching the login id (see &%local_from_check%& above), it can be configured to
15035 ignore certain prefixes and suffixes in the local part of the address. This is
15036 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15037 appropriate lists, in the same form as the &%local_part_prefix%& and
15038 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15041 local_from_prefix = *-
15043 is set, a &'From:'& line containing
15045 From: anything-user@your.domain.example
15047 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15048 matches the actual sender address that is constructed from the login name and
15052 .option local_from_suffix main string unset
15053 See &%local_from_prefix%& above.
15056 .option local_interfaces main "string list" "see below"
15057 This option controls which network interfaces are used by the daemon for
15058 listening; they are also used to identify the local host when routing. Chapter
15059 &<<CHAPinterfaces>>& contains a full description of this option and the related
15060 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15061 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15062 &%local_interfaces%& is
15064 local_interfaces = 0.0.0.0
15066 when Exim is built without IPv6 support; otherwise it is
15068 local_interfaces = <; ::0 ; 0.0.0.0
15071 .option local_scan_timeout main time 5m
15072 .cindex "timeout" "for &[local_scan()]& function"
15073 .cindex "&[local_scan()]& function" "timeout"
15074 This timeout applies to the &[local_scan()]& function (see chapter
15075 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15076 the incoming message is rejected with a temporary error if it is an SMTP
15077 message. For a non-SMTP message, the message is dropped and Exim ends with a
15078 non-zero code. The incident is logged on the main and reject logs.
15082 .option local_sender_retain main boolean false
15083 .cindex "&'Sender:'& header line" "retaining from local submission"
15084 When a message is submitted locally (that is, not over a TCP/IP connection) by
15085 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15086 do not want this to happen, you must set &%local_sender_retain%&, and you must
15087 also set &%local_from_check%& to be false (Exim will complain if you do not).
15088 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15089 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15094 .option localhost_number main string&!! unset
15095 .cindex "host" "locally unique number for"
15096 .cindex "message ids" "with multiple hosts"
15097 .vindex "&$localhost_number$&"
15098 Exim's message ids are normally unique only within the local host. If
15099 uniqueness among a set of hosts is required, each host must set a different
15100 value for the &%localhost_number%& option. The string is expanded immediately
15101 after reading the configuration file (so that a number can be computed from the
15102 host name, for example) and the result of the expansion must be a number in the
15103 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15104 systems). This is available in subsequent string expansions via the variable
15105 &$localhost_number$&. When &%localhost_number is set%&, the final two
15106 characters of the message id, instead of just being a fractional part of the
15107 time, are computed from the time and the local host number as described in
15108 section &<<SECTmessiden>>&.
15112 .option log_file_path main "string list&!!" "set at compile time"
15113 .cindex "log" "file path for"
15114 This option sets the path which is used to determine the names of Exim's log
15115 files, or indicates that logging is to be to syslog, or both. It is expanded
15116 when Exim is entered, so it can, for example, contain a reference to the host
15117 name. If no specific path is set for the log files at compile or run time,
15118 or if the option is unset at run time (i.e. &`log_file_path = `&)
15119 they are written in a sub-directory called &_log_& in Exim's spool directory.
15120 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15121 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15122 used. If this string is fixed at your installation (contains no expansion
15123 variables) it is recommended that you do not set this option in the
15124 configuration file, but instead supply the path using LOG_FILE_PATH in
15125 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15126 early on &-- in particular, failure to read the configuration file.
15129 .option log_selector main string unset
15130 .cindex "log" "selectors"
15131 This option can be used to reduce or increase the number of things that Exim
15132 writes to its log files. Its argument is made up of names preceded by plus or
15133 minus characters. For example:
15135 log_selector = +arguments -retry_defer
15137 A list of possible names and what they control is given in the chapter on
15138 logging, in section &<<SECTlogselector>>&.
15141 .option log_timezone main boolean false
15142 .cindex "log" "timezone for entries"
15143 .vindex "&$tod_log$&"
15144 .vindex "&$tod_zone$&"
15145 By default, the timestamps on log lines are in local time without the
15146 timezone. This means that if your timezone changes twice a year, the timestamps
15147 in log lines are ambiguous for an hour when the clocks go back. One way of
15148 avoiding this problem is to set the timezone to UTC. An alternative is to set
15149 &%log_timezone%& true. This turns on the addition of the timezone offset to
15150 timestamps in log lines. Turning on this option can add quite a lot to the size
15151 of log files because each line is extended by 6 characters. Note that the
15152 &$tod_log$& variable contains the log timestamp without the zone, but there is
15153 another variable called &$tod_zone$& that contains just the timezone offset.
15156 .option lookup_open_max main integer 25
15157 .cindex "too many open files"
15158 .cindex "open files, too many"
15159 .cindex "file" "too many open"
15160 .cindex "lookup" "maximum open files"
15161 .cindex "limit" "open files for lookups"
15162 This option limits the number of simultaneously open files for single-key
15163 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15164 Exim normally keeps these files open during routing, because often the same
15165 file is required several times. If the limit is reached, Exim closes the least
15166 recently used file. Note that if you are using the &'ndbm'& library, it
15167 actually opens two files for each logical DBM database, though it still counts
15168 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15169 open files"& errors with NDBM, you need to reduce the value of
15170 &%lookup_open_max%&.
15173 .option max_username_length main integer 0
15174 .cindex "length of login name"
15175 .cindex "user name" "maximum length"
15176 .cindex "limit" "user name length"
15177 Some operating systems are broken in that they truncate long arguments to
15178 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15179 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15180 an argument that is longer behaves as if &[getpwnam()]& failed.
15183 .option message_body_newlines main bool false
15184 .cindex "message body" "newlines in variables"
15185 .cindex "newline" "in message body variables"
15186 .vindex "&$message_body$&"
15187 .vindex "&$message_body_end$&"
15188 By default, newlines in the message body are replaced by spaces when setting
15189 the &$message_body$& and &$message_body_end$& expansion variables. If this
15190 option is set true, this no longer happens.
15193 .option message_body_visible main integer 500
15194 .cindex "body of message" "visible size"
15195 .cindex "message body" "visible size"
15196 .vindex "&$message_body$&"
15197 .vindex "&$message_body_end$&"
15198 This option specifies how much of a message's body is to be included in the
15199 &$message_body$& and &$message_body_end$& expansion variables.
15202 .option message_id_header_domain main string&!! unset
15203 .cindex "&'Message-ID:'& header line"
15204 If this option is set, the string is expanded and used as the right hand side
15205 (domain) of the &'Message-ID:'& header that Exim creates if a
15206 locally-originated incoming message does not have one. &"Locally-originated"&
15207 means &"not received over TCP/IP."&
15208 Otherwise, the primary host name is used.
15209 Only letters, digits, dot and hyphen are accepted; any other characters are
15210 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15211 empty string, the option is ignored.
15214 .option message_id_header_text main string&!! unset
15215 If this variable is set, the string is expanded and used to augment the text of
15216 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15217 message does not have one. The text of this header is required by RFC 2822 to
15218 take the form of an address. By default, Exim uses its internal message id as
15219 the local part, and the primary host name as the domain. If this option is set,
15220 it is expanded, and provided the expansion is not forced to fail, and does not
15221 yield an empty string, the result is inserted into the header immediately
15222 before the @, separated from the internal message id by a dot. Any characters
15223 that are illegal in an address are automatically converted into hyphens. This
15224 means that variables such as &$tod_log$& can be used, because the spaces and
15225 colons will become hyphens.
15228 .option message_logs main boolean true
15229 .cindex "message logs" "disabling"
15230 .cindex "log" "message log; disabling"
15231 If this option is turned off, per-message log files are not created in the
15232 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15233 Exim, by reducing the number of files involved in handling a message from a
15234 minimum of four (header spool file, body spool file, delivery journal, and
15235 per-message log) to three. The other major I/O activity is Exim's main log,
15236 which is not affected by this option.
15239 .option message_size_limit main string&!! 50M
15240 .cindex "message" "size limit"
15241 .cindex "limit" "message size"
15242 .cindex "size" "of message, limit"
15243 This option limits the maximum size of message that Exim will process. The
15244 value is expanded for each incoming connection so, for example, it can be made
15245 to depend on the IP address of the remote host for messages arriving via
15246 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15247 optionally followed by K or M.
15249 &*Note*&: This limit cannot be made to depend on a message's sender or any
15250 other properties of an individual message, because it has to be advertised in
15251 the server's response to EHLO. String expansion failure causes a temporary
15252 error. A value of zero means no limit, but its use is not recommended. See also
15253 &%bounce_return_size_limit%&.
15255 Incoming SMTP messages are failed with a 552 error if the limit is
15256 exceeded; locally-generated messages either get a stderr message or a delivery
15257 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15258 an oversized message is logged in both the main and the reject logs. See also
15259 the generic transport option &%message_size_limit%&, which limits the size of
15260 message that an individual transport can process.
15262 If you use a virus-scanner and set this option to to a value larger than the
15263 maximum size that your virus-scanner is configured to support, you may get
15264 failures triggered by large mails. The right size to configure for the
15265 virus-scanner depends upon what data is passed and the options in use but it's
15266 probably safest to just set it to a little larger than this value. E.g., with a
15267 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15268 some problems may result.
15270 A value of 0 will disable size limit checking; Exim will still advertise the
15271 SIZE extension in an EHLO response, but without a limit, so as to permit
15272 SMTP clients to still indicate the message size along with the MAIL verb.
15275 .option move_frozen_messages main boolean false
15276 .cindex "frozen messages" "moving"
15277 This option, which is available only if Exim has been built with the setting
15279 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15281 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15282 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15283 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15284 standard utilities for handling such moved messages, and they do not show up in
15285 lists generated by &%-bp%& or by the Exim monitor.
15288 .option mua_wrapper main boolean false
15289 Setting this option true causes Exim to run in a very restrictive mode in which
15290 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15291 contains a full description of this facility.
15295 .option mysql_servers main "string list" unset
15296 .cindex "MySQL" "server list"
15297 This option provides a list of MySQL servers and associated connection data, to
15298 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15299 option is available only if Exim has been built with MySQL support.
15302 .option never_users main "string list&!!" unset
15303 This option is expanded just once, at the start of Exim's processing. Local
15304 message deliveries are normally run in processes that are setuid to the
15305 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15306 It is usually desirable to prevent any deliveries from running as root, as a
15309 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15310 list of users that must not be used for local deliveries. This list is fixed in
15311 the binary and cannot be overridden by the configuration file. By default, it
15312 contains just the single user name &"root"&. The &%never_users%& runtime option
15313 can be used to add more users to the fixed list.
15315 If a message is to be delivered as one of the users on the fixed list or the
15316 &%never_users%& list, an error occurs, and delivery is deferred. A common
15319 never_users = root:daemon:bin
15321 Including root is redundant if it is also on the fixed list, but it does no
15322 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15326 .option openssl_options main "string list" "+no_sslv2"
15327 .cindex "OpenSSL "compatibility options"
15328 This option allows an administrator to adjust the SSL options applied
15329 by OpenSSL to connections. It is given as a space-separated list of items,
15330 each one to be +added or -subtracted from the current value.
15332 This option is only available if Exim is built against OpenSSL. The values
15333 available for this option vary according to the age of your OpenSSL install.
15334 The &"all"& value controls a subset of flags which are available, typically
15335 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15336 list the values known on your system and Exim should support all the
15337 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15338 names lose the leading &"SSL_OP_"& and are lower-cased.
15340 Note that adjusting the options can have severe impact upon the security of
15341 SSL as used by Exim. It is possible to disable safety checks and shoot
15342 yourself in the foot in various unpleasant ways. This option should not be
15343 adjusted lightly. An unrecognised item will be detected at startup, by
15344 invoking Exim with the &%-bV%& flag.
15346 The option affects Exim operating both as a server and as a client.
15348 Historical note: prior to release 4.80, Exim defaulted this value to
15349 "+dont_insert_empty_fragments", which may still be needed for compatibility
15350 with some clients, but which lowers security by increasing exposure to
15351 some now infamous attacks.
15355 # Make both old MS and old Eudora happy:
15356 openssl_options = -all +microsoft_big_sslv3_buffer \
15357 +dont_insert_empty_fragments
15359 # Disable older protocol versions:
15360 openssl_options = +no_sslv2 +no_sslv3
15363 Possible options may include:
15367 &`allow_unsafe_legacy_renegotiation`&
15369 &`cipher_server_preference`&
15371 &`dont_insert_empty_fragments`&
15375 &`legacy_server_connect`&
15377 &`microsoft_big_sslv3_buffer`&
15379 &`microsoft_sess_id_bug`&
15381 &`msie_sslv2_rsa_padding`&
15383 &`netscape_challenge_bug`&
15385 &`netscape_reuse_cipher_change_bug`&
15389 &`no_session_resumption_on_renegotiation`&
15403 &`safari_ecdhe_ecdsa_bug`&
15407 &`single_ecdh_use`&
15409 &`ssleay_080_client_dh_bug`&
15411 &`sslref2_reuse_cert_type_bug`&
15413 &`tls_block_padding_bug`&
15417 &`tls_rollback_bug`&
15420 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15421 all clients connecting using the MacOS SecureTransport TLS facility prior
15422 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15423 to negotiate TLS then this option value might help, provided that your OpenSSL
15424 release is new enough to contain this work-around. This may be a situation
15425 where you have to upgrade OpenSSL to get buggy clients working.
15428 .option oracle_servers main "string list" unset
15429 .cindex "Oracle" "server list"
15430 This option provides a list of Oracle servers and associated connection data,
15431 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15432 The option is available only if Exim has been built with Oracle support.
15435 .option percent_hack_domains main "domain list&!!" unset
15436 .cindex "&""percent hack""&"
15437 .cindex "source routing" "in email address"
15438 .cindex "address" "source-routed"
15439 The &"percent hack"& is the convention whereby a local part containing a
15440 percent sign is re-interpreted as a new email address, with the percent
15441 replaced by @. This is sometimes called &"source routing"&, though that term is
15442 also applied to RFC 2822 addresses that begin with an @ character. If this
15443 option is set, Exim implements the percent facility for those domains listed,
15444 but no others. This happens before an incoming SMTP address is tested against
15447 &*Warning*&: The &"percent hack"& has often been abused by people who are
15448 trying to get round relaying restrictions. For this reason, it is best avoided
15449 if at all possible. Unfortunately, a number of less security-conscious MTAs
15450 implement it unconditionally. If you are running Exim on a gateway host, and
15451 routing mail through to internal MTAs without processing the local parts, it is
15452 a good idea to reject recipient addresses with percent characters in their
15453 local parts. Exim's default configuration does this.
15456 .option perl_at_start main boolean false
15457 This option is available only when Exim is built with an embedded Perl
15458 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15461 .option perl_startup main string unset
15462 This option is available only when Exim is built with an embedded Perl
15463 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15466 .option pgsql_servers main "string list" unset
15467 .cindex "PostgreSQL lookup type" "server list"
15468 This option provides a list of PostgreSQL servers and associated connection
15469 data, to be used in conjunction with &(pgsql)& lookups (see section
15470 &<<SECID72>>&). The option is available only if Exim has been built with
15471 PostgreSQL support.
15474 .option pid_file_path main string&!! "set at compile time"
15475 .cindex "daemon" "pid file path"
15476 .cindex "pid file, path for"
15477 This option sets the name of the file to which the Exim daemon writes its
15478 process id. The string is expanded, so it can contain, for example, references
15481 pid_file_path = /var/log/$primary_hostname/exim.pid
15483 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15485 The value set by the option can be overridden by the &%-oP%& command line
15486 option. A pid file is not written if a &"non-standard"& daemon is run by means
15487 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15490 .option pipelining_advertise_hosts main "host list&!!" *
15491 .cindex "PIPELINING" "suppressing advertising"
15492 This option can be used to suppress the advertisement of the SMTP
15493 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15494 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15495 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15496 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15497 that clients will use it; &"out of order"& commands that are &"expected"& do
15498 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15501 .option prdr_enable main boolean false
15502 .cindex "PRDR" "enabling on server"
15503 This option can be used to enable the Per-Recipient Data Response extension
15504 to SMTP, defined by Eric Hall.
15505 If the option is set, PRDR is advertised by Exim when operating as a server.
15506 If the client requests PRDR, and more than one recipient, for a message
15507 an additional ACL is called for each recipient after the message content
15508 is received. See section &<<SECTPRDRACL>>&.
15510 .option preserve_message_logs main boolean false
15511 .cindex "message logs" "preserving"
15512 If this option is set, message log files are not deleted when messages are
15513 completed. Instead, they are moved to a sub-directory of the spool directory
15514 called &_msglog.OLD_&, where they remain available for statistical or debugging
15515 purposes. This is a dangerous option to set on systems with any appreciable
15516 volume of mail. Use with care!
15519 .option primary_hostname main string "see below"
15520 .cindex "name" "of local host"
15521 .cindex "host" "name of local"
15522 .cindex "local host" "name of"
15523 .vindex "&$primary_hostname$&"
15524 This specifies the name of the current host. It is used in the default EHLO or
15525 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15526 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15527 The value is also used by default in some SMTP response messages from an Exim
15528 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15530 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15531 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15532 contains only one component, Exim passes it to &[gethostbyname()]& (or
15533 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15534 version. The variable &$primary_hostname$& contains the host name, whether set
15535 explicitly by this option, or defaulted.
15538 .option print_topbitchars main boolean false
15539 .cindex "printing characters"
15540 .cindex "8-bit characters"
15541 By default, Exim considers only those characters whose codes lie in the range
15542 32&--126 to be printing characters. In a number of circumstances (for example,
15543 when writing log entries) non-printing characters are converted into escape
15544 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15545 is set, code values of 128 and above are also considered to be printing
15548 This option also affects the header syntax checks performed by the
15549 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15550 the user's full name when constructing From: and Sender: addresses (as
15551 described in section &<<SECTconstr>>&). Setting this option can cause
15552 Exim to generate eight bit message headers that do not conform to the
15556 .option process_log_path main string unset
15557 .cindex "process log path"
15558 .cindex "log" "process log"
15559 .cindex "&'exiwhat'&"
15560 This option sets the name of the file to which an Exim process writes its
15561 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15562 utility script. If this option is unset, the file called &_exim-process.info_&
15563 in Exim's spool directory is used. The ability to specify the name explicitly
15564 can be useful in environments where two different Exims are running, using
15565 different spool directories.
15568 .option prod_requires_admin main boolean true
15572 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15573 admin user unless &%prod_requires_admin%& is set false. See also
15574 &%queue_list_requires_admin%&.
15577 .option qualify_domain main string "see below"
15578 .cindex "domain" "for qualifying addresses"
15579 .cindex "address" "qualification"
15580 This option specifies the domain name that is added to any envelope sender
15581 addresses that do not have a domain qualification. It also applies to
15582 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15583 are accepted by default only for locally-generated messages. Qualification is
15584 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15585 locally-generated messages, unless the &%-bnq%& command line option is used.
15587 Messages from external sources must always contain fully qualified addresses,
15588 unless the sending host matches &%sender_unqualified_hosts%& or
15589 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15590 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15591 necessary. Internally, Exim always works with fully qualified envelope
15592 addresses. If &%qualify_domain%& is not set, it defaults to the
15593 &%primary_hostname%& value.
15596 .option qualify_recipient main string "see below"
15597 This option allows you to specify a different domain for qualifying recipient
15598 addresses to the one that is used for senders. See &%qualify_domain%& above.
15602 .option queue_domains main "domain list&!!" unset
15603 .cindex "domain" "specifying non-immediate delivery"
15604 .cindex "queueing incoming messages"
15605 .cindex "message" "queueing certain domains"
15606 This option lists domains for which immediate delivery is not required.
15607 A delivery process is started whenever a message is received, but only those
15608 domains that do not match are processed. All other deliveries wait until the
15609 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15612 .option queue_list_requires_admin main boolean true
15614 The &%-bp%& command-line option, which lists the messages that are on the
15615 queue, requires the caller to be an admin user unless
15616 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15619 .option queue_only main boolean false
15620 .cindex "queueing incoming messages"
15621 .cindex "message" "queueing unconditionally"
15622 If &%queue_only%& is set, a delivery process is not automatically started
15623 whenever a message is received. Instead, the message waits on the queue for the
15624 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15625 delivered immediately when certain conditions (such as heavy load) occur.
15627 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15628 and &%-odi%& command line options override &%queue_only%& unless
15629 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15630 &%queue_only_load%&, and &%smtp_accept_queue%&.
15633 .option queue_only_file main string unset
15634 .cindex "queueing incoming messages"
15635 .cindex "message" "queueing by file existence"
15636 This option can be set to a colon-separated list of absolute path names, each
15637 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15638 it tests for the existence of each listed path using a call to &[stat()]&. For
15639 each path that exists, the corresponding queueing option is set.
15640 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15641 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15643 queue_only_file = smtp/some/file
15645 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15646 &_/some/file_& exists.
15649 .option queue_only_load main fixed-point unset
15650 .cindex "load average"
15651 .cindex "queueing incoming messages"
15652 .cindex "message" "queueing by load"
15653 If the system load average is higher than this value, incoming messages from
15654 all sources are queued, and no automatic deliveries are started. If this
15655 happens during local or remote SMTP input, all subsequent messages received on
15656 the same SMTP connection are queued by default, whatever happens to the load in
15657 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15660 Deliveries will subsequently be performed by queue runner processes. This
15661 option has no effect on ancient operating systems on which Exim cannot
15662 determine the load average. See also &%deliver_queue_load_max%& and
15663 &%smtp_load_reserve%&.
15666 .option queue_only_load_latch main boolean true
15667 .cindex "load average" "re-evaluating per message"
15668 When this option is true (the default), once one message has been queued
15669 because the load average is higher than the value set by &%queue_only_load%&,
15670 all subsequent messages received on the same SMTP connection are also queued.
15671 This is a deliberate choice; even though the load average may fall below the
15672 threshold, it doesn't seem right to deliver later messages on the same
15673 connection when not delivering earlier ones. However, there are special
15674 circumstances such as very long-lived connections from scanning appliances
15675 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15676 should be set false. This causes the value of the load average to be
15677 re-evaluated for each message.
15680 .option queue_only_override main boolean true
15681 .cindex "queueing incoming messages"
15682 When this option is true, the &%-od%&&'x'& command line options override the
15683 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15684 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15685 to override; they are accepted, but ignored.
15688 .option queue_run_in_order main boolean false
15689 .cindex "queue runner" "processing messages in order"
15690 If this option is set, queue runs happen in order of message arrival instead of
15691 in an arbitrary order. For this to happen, a complete list of the entire queue
15692 must be set up before the deliveries start. When the queue is all held in a
15693 single directory (the default), a single list is created for both the ordered
15694 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15695 single list is not created when &%queue_run_in_order%& is false. In this case,
15696 the sub-directories are processed one at a time (in a random order), and this
15697 avoids setting up one huge list for the whole queue. Thus, setting
15698 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15699 when the queue is large, because of the extra work in setting up the single,
15700 large list. In most situations, &%queue_run_in_order%& should not be set.
15704 .option queue_run_max main integer 5
15705 .cindex "queue runner" "maximum number of"
15706 This controls the maximum number of queue runner processes that an Exim daemon
15707 can run simultaneously. This does not mean that it starts them all at once,
15708 but rather that if the maximum number are still running when the time comes to
15709 start another one, it refrains from starting another one. This can happen with
15710 very large queues and/or very sluggish deliveries. This option does not,
15711 however, interlock with other processes, so additional queue runners can be
15712 started by other means, or by killing and restarting the daemon.
15714 Setting this option to zero does not suppress queue runs; rather, it disables
15715 the limit, allowing any number of simultaneous queue runner processes to be
15716 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15717 the daemon's command line.
15719 .option queue_smtp_domains main "domain list&!!" unset
15720 .cindex "queueing incoming messages"
15721 .cindex "message" "queueing remote deliveries"
15722 When this option is set, a delivery process is started whenever a message is
15723 received, routing is performed, and local deliveries take place.
15724 However, if any SMTP deliveries are required for domains that match
15725 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15726 message waits on the queue for the next queue run. Since routing of the message
15727 has taken place, Exim knows to which remote hosts it must be delivered, and so
15728 when the queue run happens, multiple messages for the same host are delivered
15729 over a single SMTP connection. The &%-odqs%& command line option causes all
15730 SMTP deliveries to be queued in this way, and is equivalent to setting
15731 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15735 .option receive_timeout main time 0s
15736 .cindex "timeout" "for non-SMTP input"
15737 This option sets the timeout for accepting a non-SMTP message, that is, the
15738 maximum time that Exim waits when reading a message on the standard input. If
15739 the value is zero, it will wait for ever. This setting is overridden by the
15740 &%-or%& command line option. The timeout for incoming SMTP messages is
15741 controlled by &%smtp_receive_timeout%&.
15743 .option received_header_text main string&!! "see below"
15744 .cindex "customizing" "&'Received:'& header"
15745 .cindex "&'Received:'& header line" "customizing"
15746 This string defines the contents of the &'Received:'& message header that is
15747 added to each message, except for the timestamp, which is automatically added
15748 on at the end (preceded by a semicolon). The string is expanded each time it is
15749 used. If the expansion yields an empty string, no &'Received:'& header line is
15750 added to the message. Otherwise, the string should start with the text
15751 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15752 header lines. The default setting is:
15755 received_header_text = Received: \
15756 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15757 {${if def:sender_ident \
15758 {from ${quote_local_part:$sender_ident} }}\
15759 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15760 by $primary_hostname \
15761 ${if def:received_protocol {with $received_protocol}} \
15762 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15763 (Exim $version_number)\n\t\
15764 ${if def:sender_address \
15765 {(envelope-from <$sender_address>)\n\t}}\
15766 id $message_exim_id\
15767 ${if def:received_for {\n\tfor $received_for}}
15770 The reference to the TLS cipher is omitted when Exim is built without TLS
15771 support. The use of conditional expansions ensures that this works for both
15772 locally generated messages and messages received from remote hosts, giving
15773 header lines such as the following:
15775 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15776 by marley.carol.example with esmtp (Exim 4.00)
15777 (envelope-from <bob@carol.example>)
15778 id 16IOWa-00019l-00
15779 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15780 Received: by scrooge.carol.example with local (Exim 4.00)
15781 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15783 Until the body of the message has been received, the timestamp is the time when
15784 the message started to be received. Once the body has arrived, and all policy
15785 checks have taken place, the timestamp is updated to the time at which the
15786 message was accepted.
15789 .option received_headers_max main integer 30
15790 .cindex "loop" "prevention"
15791 .cindex "mail loop prevention"
15792 .cindex "&'Received:'& header line" "counting"
15793 When a message is to be delivered, the number of &'Received:'& headers is
15794 counted, and if it is greater than this parameter, a mail loop is assumed to
15795 have occurred, the delivery is abandoned, and an error message is generated.
15796 This applies to both local and remote deliveries.
15799 .option recipient_unqualified_hosts main "host list&!!" unset
15800 .cindex "unqualified addresses"
15801 .cindex "host" "unqualified addresses from"
15802 This option lists those hosts from which Exim is prepared to accept unqualified
15803 recipient addresses in message envelopes. The addresses are made fully
15804 qualified by the addition of the &%qualify_recipient%& value. This option also
15805 affects message header lines. Exim does not reject unqualified recipient
15806 addresses in headers, but it qualifies them only if the message came from a
15807 host that matches &%recipient_unqualified_hosts%&,
15808 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15809 option was not set.
15812 .option recipients_max main integer 0
15813 .cindex "limit" "number of recipients"
15814 .cindex "recipient" "maximum number"
15815 If this option is set greater than zero, it specifies the maximum number of
15816 original recipients for any message. Additional recipients that are generated
15817 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15818 all recipients over the limit; earlier recipients are delivered as normal.
15819 Non-SMTP messages with too many recipients are failed, and no deliveries are
15822 .cindex "RCPT" "maximum number of incoming"
15823 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15824 RCPT commands in a single message.
15827 .option recipients_max_reject main boolean false
15828 If this option is set true, Exim rejects SMTP messages containing too many
15829 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15830 error to the eventual DATA command. Otherwise (the default) it gives a 452
15831 error to the surplus RCPT commands and accepts the message on behalf of the
15832 initial set of recipients. The remote server should then re-send the message
15833 for the remaining recipients at a later time.
15836 .option remote_max_parallel main integer 2
15837 .cindex "delivery" "parallelism for remote"
15838 This option controls parallel delivery of one message to a number of remote
15839 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15840 does all the remote deliveries for a message one by one. Otherwise, if a single
15841 message has to be delivered to more than one remote host, or if several copies
15842 have to be sent to the same remote host, up to &%remote_max_parallel%&
15843 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15844 deliveries are required, the maximum number of processes are started, and as
15845 each one finishes, another is begun. The order of starting processes is the
15846 same as if sequential delivery were being done, and can be controlled by the
15847 &%remote_sort_domains%& option. If parallel delivery takes place while running
15848 with debugging turned on, the debugging output from each delivery process is
15849 tagged with its process id.
15851 This option controls only the maximum number of parallel deliveries for one
15852 message in one Exim delivery process. Because Exim has no central queue
15853 manager, there is no way of controlling the total number of simultaneous
15854 deliveries if the configuration allows a delivery attempt as soon as a message
15857 .cindex "number of deliveries"
15858 .cindex "delivery" "maximum number of"
15859 If you want to control the total number of deliveries on the system, you
15860 need to set the &%queue_only%& option. This ensures that all incoming messages
15861 are added to the queue without starting a delivery process. Then set up an Exim
15862 daemon to start queue runner processes at appropriate intervals (probably
15863 fairly often, for example, every minute), and limit the total number of queue
15864 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15865 delivers only one message at a time, the maximum number of deliveries that can
15866 then take place at once is &%queue_run_max%& multiplied by
15867 &%remote_max_parallel%&.
15869 If it is purely remote deliveries you want to control, use
15870 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15871 doing the SMTP routing before queueing, so that several messages for the same
15872 host will eventually get delivered down the same connection.
15875 .option remote_sort_domains main "domain list&!!" unset
15876 .cindex "sorting remote deliveries"
15877 .cindex "delivery" "sorting remote"
15878 When there are a number of remote deliveries for a message, they are sorted by
15879 domain into the order given by this list. For example,
15881 remote_sort_domains = *.cam.ac.uk:*.uk
15883 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15884 then to those in the &%uk%& domain, then to any others.
15887 .option retry_data_expire main time 7d
15888 .cindex "hints database" "data expiry"
15889 This option sets a &"use before"& time on retry information in Exim's hints
15890 database. Any older retry data is ignored. This means that, for example, once a
15891 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15895 .option retry_interval_max main time 24h
15896 .cindex "retry" "limit on interval"
15897 .cindex "limit" "on retry interval"
15898 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15899 intervals between delivery attempts for messages that cannot be delivered
15900 straight away. This option sets an overall limit to the length of time between
15901 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15905 .option return_path_remove main boolean true
15906 .cindex "&'Return-path:'& header line" "removing"
15907 RFC 2821, section 4.4, states that an SMTP server must insert a
15908 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15909 The &'Return-path:'& header preserves the sender address as received in the
15910 MAIL command. This description implies that this header should not be present
15911 in an incoming message. If &%return_path_remove%& is true, any existing
15912 &'Return-path:'& headers are removed from messages at the time they are
15913 received. Exim's transports have options for adding &'Return-path:'& headers at
15914 the time of delivery. They are normally used only for final local deliveries.
15917 .option return_size_limit main integer 100K
15918 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15922 .option rfc1413_hosts main "host list&!!" @[]
15924 .cindex "host" "for RFC 1413 calls"
15925 RFC 1413 identification calls are made to any client host which matches
15926 an item in the list.
15927 The default value specifies just this host, being any local interface
15932 .option rfc1413_query_timeout main time 0s
15934 .cindex "RFC 1413" "query timeout"
15935 .cindex "timeout" "for RFC 1413 call"
15936 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15937 no RFC 1413 calls are ever made.
15940 .option sender_unqualified_hosts main "host list&!!" unset
15941 .cindex "unqualified addresses"
15942 .cindex "host" "unqualified addresses from"
15943 This option lists those hosts from which Exim is prepared to accept unqualified
15944 sender addresses. The addresses are made fully qualified by the addition of
15945 &%qualify_domain%&. This option also affects message header lines. Exim does
15946 not reject unqualified addresses in headers that contain sender addresses, but
15947 it qualifies them only if the message came from a host that matches
15948 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15949 using TCP/IP), and the &%-bnq%& option was not set.
15951 .option set_environment main "string list" empty
15952 .cindex "environment"
15953 This option allows to set individual environment variables that the
15954 currently linked libraries and programs in child processes use. The
15955 default list is empty,
15959 .option slow_lookup_log main integer 0
15960 .cindex "logging" "slow lookups"
15961 .cindex "dns" "logging slow lookups"
15962 This option controls logging of slow lookups.
15963 If the value is nonzero it is taken as a number of milliseconds
15964 and lookups taking longer than this are logged.
15965 Currently this applies only to DNS lookups.
15970 .option smtp_accept_keepalive main boolean true
15971 .cindex "keepalive" "on incoming connection"
15972 This option controls the setting of the SO_KEEPALIVE option on incoming
15973 TCP/IP socket connections. When set, it causes the kernel to probe idle
15974 connections periodically, by sending packets with &"old"& sequence numbers. The
15975 other end of the connection should send an acknowledgment if the connection is
15976 still okay or a reset if the connection has been aborted. The reason for doing
15977 this is that it has the beneficial effect of freeing up certain types of
15978 connection that can get stuck when the remote host is disconnected without
15979 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15980 hours to detect unreachable hosts.
15984 .option smtp_accept_max main integer 20
15985 .cindex "limit" "incoming SMTP connections"
15986 .cindex "SMTP" "incoming connection count"
15988 This option specifies the maximum number of simultaneous incoming SMTP calls
15989 that Exim will accept. It applies only to the listening daemon; there is no
15990 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15991 value is set to zero, no limit is applied. However, it is required to be
15992 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15993 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15995 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15996 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15997 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15998 and &%smtp_load_reserve%& are then checked before accepting the connection.
16001 .option smtp_accept_max_nonmail main integer 10
16002 .cindex "limit" "non-mail SMTP commands"
16003 .cindex "SMTP" "limiting non-mail commands"
16004 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16005 the connection if there are too many. This option defines &"too many"&. The
16006 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16007 client looping sending EHLO, for example. The check is applied only if the
16008 client host matches &%smtp_accept_max_nonmail_hosts%&.
16010 When a new message is expected, one occurrence of RSET is not counted. This
16011 allows a client to send one RSET between messages (this is not necessary,
16012 but some clients do it). Exim also allows one uncounted occurrence of HELO
16013 or EHLO, and one occurrence of STARTTLS between messages. After
16014 starting up a TLS session, another EHLO is expected, and so it too is not
16015 counted. The first occurrence of AUTH in a connection, or immediately
16016 following STARTTLS is not counted. Otherwise, all commands other than
16017 MAIL, RCPT, DATA, and QUIT are counted.
16020 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16021 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16022 check by setting this option. The default value makes it apply to all hosts. By
16023 changing the value, you can exclude any badly-behaved hosts that you have to
16027 . Allow this long option name to split; give it unsplit as a fifth argument
16028 . for the automatic .oindex that is generated by .option.
16029 . We insert " &~&~" which is both pretty nasty visually and results in
16030 . non-searchable text. HowItWorks.txt mentions an option for inserting
16031 . zero-width-space, which would be nicer visually and results in (at least)
16032 . html that Firefox will split on when it's forced to reflow (rather than
16033 . inserting a horizontal scrollbar). However, the text is still not
16034 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16035 . the option name to split.
16037 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16038 smtp_accept_max_per_connection
16039 .cindex "SMTP" "limiting incoming message count"
16040 .cindex "limit" "messages per SMTP connection"
16041 The value of this option limits the number of MAIL commands that Exim is
16042 prepared to accept over a single SMTP connection, whether or not each command
16043 results in the transfer of a message. After the limit is reached, a 421
16044 response is given to subsequent MAIL commands. This limit is a safety
16045 precaution against a client that goes mad (incidents of this type have been
16049 .option smtp_accept_max_per_host main string&!! unset
16050 .cindex "limit" "SMTP connections from one host"
16051 .cindex "host" "limiting SMTP connections from"
16052 This option restricts the number of simultaneous IP connections from a single
16053 host (strictly, from a single IP address) to the Exim daemon. The option is
16054 expanded, to enable different limits to be applied to different hosts by
16055 reference to &$sender_host_address$&. Once the limit is reached, additional
16056 connection attempts from the same host are rejected with error code 421. This
16057 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16058 of zero imposes no limit. If this option is set greater than zero, it is
16059 required that &%smtp_accept_max%& be non-zero.
16061 &*Warning*&: When setting this option you should not use any expansion
16062 constructions that take an appreciable amount of time. The expansion and test
16063 happen in the main daemon loop, in order to reject additional connections
16064 without forking additional processes (otherwise a denial-of-service attack
16065 could cause a vast number or processes to be created). While the daemon is
16066 doing this processing, it cannot accept any other incoming connections.
16070 .option smtp_accept_queue main integer 0
16071 .cindex "SMTP" "incoming connection count"
16072 .cindex "queueing incoming messages"
16073 .cindex "message" "queueing by SMTP connection count"
16074 If the number of simultaneous incoming SMTP connections being handled via the
16075 listening daemon exceeds this value, messages received by SMTP are just placed
16076 on the queue; no delivery processes are started automatically. The count is
16077 fixed at the start of an SMTP connection. It cannot be updated in the
16078 subprocess that receives messages, and so the queueing or not queueing applies
16079 to all messages received in the same connection.
16081 A value of zero implies no limit, and clearly any non-zero value is useful only
16082 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16083 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16084 various &%-od%&&'x'& command line options.
16087 . See the comment on smtp_accept_max_per_connection
16089 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16090 smtp_accept_queue_per_connection
16091 .cindex "queueing incoming messages"
16092 .cindex "message" "queueing by message count"
16093 This option limits the number of delivery processes that Exim starts
16094 automatically when receiving messages via SMTP, whether via the daemon or by
16095 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16096 and the number of messages received in a single SMTP session exceeds this
16097 number, subsequent messages are placed on the queue, but no delivery processes
16098 are started. This helps to limit the number of Exim processes when a server
16099 restarts after downtime and there is a lot of mail waiting for it on other
16100 systems. On large systems, the default should probably be increased, and on
16101 dial-in client systems it should probably be set to zero (that is, disabled).
16104 .option smtp_accept_reserve main integer 0
16105 .cindex "SMTP" "incoming call count"
16106 .cindex "host" "reserved"
16107 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16108 number of SMTP connections that are reserved for connections from the hosts
16109 that are specified in &%smtp_reserve_hosts%&. The value set in
16110 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16111 restricted to this number of connections; the option specifies a minimum number
16112 of connection slots for them, not a maximum. It is a guarantee that this group
16113 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16114 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16117 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16118 set to 5, once there are 45 active connections (from any hosts), new
16119 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16120 provided the other criteria for acceptance are met.
16123 .option smtp_active_hostname main string&!! unset
16124 .cindex "host" "name in SMTP responses"
16125 .cindex "SMTP" "host name in responses"
16126 .vindex "&$primary_hostname$&"
16127 This option is provided for multi-homed servers that want to masquerade as
16128 several different hosts. At the start of an incoming SMTP connection, its value
16129 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16130 responses. For example, it is used as domain name in the response to an
16131 incoming HELO or EHLO command.
16133 .vindex "&$smtp_active_hostname$&"
16134 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16135 is saved with any messages that are received. It is therefore available for use
16136 in routers and transports when the message is later delivered.
16138 If this option is unset, or if its expansion is forced to fail, or if the
16139 expansion results in an empty string, the value of &$primary_hostname$& is
16140 used. Other expansion failures cause a message to be written to the main and
16141 panic logs, and the SMTP command receives a temporary error. Typically, the
16142 value of &%smtp_active_hostname%& depends on the incoming interface address.
16145 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16146 {cox.mydomain}{box.mydomain}}
16149 Although &$smtp_active_hostname$& is primarily concerned with incoming
16150 messages, it is also used as the default for HELO commands in callout
16151 verification if there is no remote transport from which to obtain a
16152 &%helo_data%& value.
16154 .option smtp_banner main string&!! "see below"
16155 .cindex "SMTP" "welcome banner"
16156 .cindex "banner for SMTP"
16157 .cindex "welcome banner for SMTP"
16158 .cindex "customizing" "SMTP banner"
16159 This string, which is expanded every time it is used, is output as the initial
16160 positive response to an SMTP connection. The default setting is:
16162 smtp_banner = $smtp_active_hostname ESMTP Exim \
16163 $version_number $tod_full
16165 Failure to expand the string causes a panic error. If you want to create a
16166 multiline response to the initial SMTP connection, use &"\n"& in the string at
16167 appropriate points, but not at the end. Note that the 220 code is not included
16168 in this string. Exim adds it automatically (several times in the case of a
16169 multiline response).
16172 .option smtp_check_spool_space main boolean true
16173 .cindex "checking disk space"
16174 .cindex "disk space, checking"
16175 .cindex "spool directory" "checking space"
16176 When this option is set, if an incoming SMTP session encounters the SIZE
16177 option on a MAIL command, it checks that there is enough space in the
16178 spool directory's partition to accept a message of that size, while still
16179 leaving free the amount specified by &%check_spool_space%& (even if that value
16180 is zero). If there isn't enough space, a temporary error code is returned.
16183 .option smtp_connect_backlog main integer 20
16184 .cindex "connection backlog"
16185 .cindex "SMTP" "connection backlog"
16186 .cindex "backlog of connections"
16187 This option specifies a maximum number of waiting SMTP connections. Exim passes
16188 this value to the TCP/IP system when it sets up its listener. Once this number
16189 of connections are waiting for the daemon's attention, subsequent connection
16190 attempts are refused at the TCP/IP level. At least, that is what the manuals
16191 say; in some circumstances such connection attempts have been observed to time
16192 out instead. For large systems it is probably a good idea to increase the
16193 value (to 50, say). It also gives some protection against denial-of-service
16194 attacks by SYN flooding.
16197 .option smtp_enforce_sync main boolean true
16198 .cindex "SMTP" "synchronization checking"
16199 .cindex "synchronization checking in SMTP"
16200 The SMTP protocol specification requires the client to wait for a response from
16201 the server at certain points in the dialogue. Without PIPELINING these
16202 synchronization points are after every command; with PIPELINING they are
16203 fewer, but they still exist.
16205 Some spamming sites send out a complete set of SMTP commands without waiting
16206 for any response. Exim protects against this by rejecting a message if the
16207 client has sent further input when it should not have. The error response &"554
16208 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16209 for this error cannot be perfect because of transmission delays (unexpected
16210 input may be on its way but not yet received when Exim checks). However, it
16211 does detect many instances.
16213 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16214 If you want to disable the check selectively (for example, only for certain
16215 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16216 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16220 .option smtp_etrn_command main string&!! unset
16221 .cindex "ETRN" "command to be run"
16222 .vindex "&$domain$&"
16223 If this option is set, the given command is run whenever an SMTP ETRN
16224 command is received from a host that is permitted to issue such commands (see
16225 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16226 are independently expanded. The expansion variable &$domain$& is set to the
16227 argument of the ETRN command, and no syntax checking is done on it. For
16230 smtp_etrn_command = /etc/etrn_command $domain \
16231 $sender_host_address
16233 A new process is created to run the command, but Exim does not wait for it to
16234 complete. Consequently, its status cannot be checked. If the command cannot be
16235 run, a line is written to the panic log, but the ETRN caller still receives
16236 a 250 success response. Exim is normally running under its own uid when
16237 receiving SMTP, so it is not possible for it to change the uid before running
16241 .option smtp_etrn_serialize main boolean true
16242 .cindex "ETRN" "serializing"
16243 When this option is set, it prevents the simultaneous execution of more than
16244 one identical command as a result of ETRN in an SMTP connection. See
16245 section &<<SECTETRN>>& for details.
16248 .option smtp_load_reserve main fixed-point unset
16249 .cindex "load average"
16250 If the system load average ever gets higher than this, incoming SMTP calls are
16251 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16252 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16253 the load is over the limit. The option has no effect on ancient operating
16254 systems on which Exim cannot determine the load average. See also
16255 &%deliver_queue_load_max%& and &%queue_only_load%&.
16259 .option smtp_max_synprot_errors main integer 3
16260 .cindex "SMTP" "limiting syntax and protocol errors"
16261 .cindex "limit" "SMTP syntax and protocol errors"
16262 Exim rejects SMTP commands that contain syntax or protocol errors. In
16263 particular, a syntactically invalid email address, as in this command:
16265 RCPT TO:<abc xyz@a.b.c>
16267 causes immediate rejection of the command, before any other tests are done.
16268 (The ACL cannot be run if there is no valid address to set up for it.) An
16269 example of a protocol error is receiving RCPT before MAIL. If there are
16270 too many syntax or protocol errors in one SMTP session, the connection is
16271 dropped. The limit is set by this option.
16273 .cindex "PIPELINING" "expected errors"
16274 When the PIPELINING extension to SMTP is in use, some protocol errors are
16275 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16276 Exim assumes that PIPELINING will be used if it advertises it (see
16277 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16278 not count towards the limit.
16282 .option smtp_max_unknown_commands main integer 3
16283 .cindex "SMTP" "limiting unknown commands"
16284 .cindex "limit" "unknown SMTP commands"
16285 If there are too many unrecognized commands in an incoming SMTP session, an
16286 Exim server drops the connection. This is a defence against some kinds of abuse
16289 into making connections to SMTP ports; in these circumstances, a number of
16290 non-SMTP command lines are sent first.
16294 .option smtp_ratelimit_hosts main "host list&!!" unset
16295 .cindex "SMTP" "rate limiting"
16296 .cindex "limit" "rate of message arrival"
16297 .cindex "RCPT" "rate limiting"
16298 Some sites find it helpful to be able to limit the rate at which certain hosts
16299 can send them messages, and the rate at which an individual message can specify
16302 Exim has two rate-limiting facilities. This section describes the older
16303 facility, which can limit rates within a single connection. The newer
16304 &%ratelimit%& ACL condition can limit rates across all connections. See section
16305 &<<SECTratelimiting>>& for details of the newer facility.
16307 When a host matches &%smtp_ratelimit_hosts%&, the values of
16308 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16309 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16310 respectively. Each option, if set, must contain a set of four comma-separated
16314 A threshold, before which there is no rate limiting.
16316 An initial time delay. Unlike other times in Exim, numbers with decimal
16317 fractional parts are allowed here.
16319 A factor by which to increase the delay each time.
16321 A maximum value for the delay. This should normally be less than 5 minutes,
16322 because after that time, the client is liable to timeout the SMTP command.
16325 For example, these settings have been used successfully at the site which
16326 first suggested this feature, for controlling mail from their customers:
16328 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16329 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16331 The first setting specifies delays that are applied to MAIL commands after
16332 two have been received over a single connection. The initial delay is 0.5
16333 seconds, increasing by a factor of 1.05 each time. The second setting applies
16334 delays to RCPT commands when more than four occur in a single message.
16337 .option smtp_ratelimit_mail main string unset
16338 See &%smtp_ratelimit_hosts%& above.
16341 .option smtp_ratelimit_rcpt main string unset
16342 See &%smtp_ratelimit_hosts%& above.
16345 .option smtp_receive_timeout main time&!! 5m
16346 .cindex "timeout" "for SMTP input"
16347 .cindex "SMTP" "input timeout"
16348 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16349 input, including batch SMTP. If a line of input (either an SMTP command or a
16350 data line) is not received within this time, the SMTP connection is dropped and
16351 the message is abandoned.
16352 A line is written to the log containing one of the following messages:
16354 SMTP command timeout on connection from...
16355 SMTP data timeout on connection from...
16357 The former means that Exim was expecting to read an SMTP command; the latter
16358 means that it was in the DATA phase, reading the contents of a message.
16361 If the first character of the option is a &"$"& the option is
16362 expanded before use and may depend on
16363 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16368 The value set by this option can be overridden by the
16369 &%-os%& command-line option. A setting of zero time disables the timeout, but
16370 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16371 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16372 timeout is controlled by &%receive_timeout%& and &%-or%&.
16375 .option smtp_reserve_hosts main "host list&!!" unset
16376 This option defines hosts for which SMTP connections are reserved; see
16377 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16380 .option smtp_return_error_details main boolean false
16381 .cindex "SMTP" "details policy failures"
16382 .cindex "policy control" "rejection, returning details"
16383 In the default state, Exim uses bland messages such as
16384 &"Administrative prohibition"& when it rejects SMTP commands for policy
16385 reasons. Many sysadmins like this because it gives away little information
16386 to spammers. However, some other sysadmins who are applying strict checking
16387 policies want to give out much fuller information about failures. Setting
16388 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16389 example, instead of &"Administrative prohibition"&, it might give:
16391 550-Rejected after DATA: '>' missing at end of address:
16392 550 failing address in "From" header is: <user@dom.ain
16395 .option spamd_address main string "see below"
16396 This option is available when Exim is compiled with the content-scanning
16397 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16398 The default value is
16402 See section &<<SECTscanspamass>>& for more details.
16406 .option split_spool_directory main boolean false
16407 .cindex "multiple spool directories"
16408 .cindex "spool directory" "split"
16409 .cindex "directories, multiple"
16410 If this option is set, it causes Exim to split its input directory into 62
16411 subdirectories, each with a single alphanumeric character as its name. The
16412 sixth character of the message id is used to allocate messages to
16413 subdirectories; this is the least significant base-62 digit of the time of
16414 arrival of the message.
16416 Splitting up the spool in this way may provide better performance on systems
16417 where there are long mail queues, by reducing the number of files in any one
16418 directory. The msglog directory is also split up in a similar way to the input
16419 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16420 are still placed in the single directory &_msglog.OLD_&.
16422 It is not necessary to take any special action for existing messages when
16423 changing &%split_spool_directory%&. Exim notices messages that are in the
16424 &"wrong"& place, and continues to process them. If the option is turned off
16425 after a period of being on, the subdirectories will eventually empty and be
16426 automatically deleted.
16428 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16429 changes. Instead of creating a list of all messages in the queue, and then
16430 trying to deliver each one in turn, it constructs a list of those in one
16431 sub-directory and tries to deliver them, before moving on to the next
16432 sub-directory. The sub-directories are processed in a random order. This
16433 spreads out the scanning of the input directories, and uses less memory. It is
16434 particularly beneficial when there are lots of messages on the queue. However,
16435 if &%queue_run_in_order%& is set, none of this new processing happens. The
16436 entire queue has to be scanned and sorted before any deliveries can start.
16439 .option spool_directory main string&!! "set at compile time"
16440 .cindex "spool directory" "path to"
16441 This defines the directory in which Exim keeps its spool, that is, the messages
16442 it is waiting to deliver. The default value is taken from the compile-time
16443 configuration setting, if there is one. If not, this option must be set. The
16444 string is expanded, so it can contain, for example, a reference to
16445 &$primary_hostname$&.
16447 If the spool directory name is fixed on your installation, it is recommended
16448 that you set it at build time rather than from this option, particularly if the
16449 log files are being written to the spool directory (see &%log_file_path%&).
16450 Otherwise log files cannot be used for errors that are detected early on, such
16451 as failures in the configuration file.
16453 By using this option to override the compiled-in path, it is possible to run
16454 tests of Exim without using the standard spool.
16456 .option sqlite_lock_timeout main time 5s
16457 .cindex "sqlite lookup type" "lock timeout"
16458 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16459 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16461 .option strict_acl_vars main boolean false
16462 .cindex "&ACL;" "variables, handling unset"
16463 This option controls what happens if a syntactically valid but undefined ACL
16464 variable is referenced. If it is false (the default), an empty string
16465 is substituted; if it is true, an error is generated. See section
16466 &<<SECTaclvariables>>& for details of ACL variables.
16468 .option strip_excess_angle_brackets main boolean false
16469 .cindex "angle brackets, excess"
16470 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16471 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16472 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16473 passed on to another MTA, the excess angle brackets are not passed on. If this
16474 option is not set, multiple pairs of angle brackets cause a syntax error.
16477 .option strip_trailing_dot main boolean false
16478 .cindex "trailing dot on domain"
16479 .cindex "dot" "trailing on domain"
16480 If this option is set, a trailing dot at the end of a domain in an address is
16481 ignored. If this is in the envelope and the message is passed on to another
16482 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16483 domain causes a syntax error.
16484 However, addresses in header lines are checked only when an ACL requests header
16488 .option syslog_duplication main boolean true
16489 .cindex "syslog" "duplicate log lines; suppressing"
16490 When Exim is logging to syslog, it writes the log lines for its three
16491 separate logs at different syslog priorities so that they can in principle
16492 be separated on the logging hosts. Some installations do not require this
16493 separation, and in those cases, the duplication of certain log lines is a
16494 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16495 particular log line is written to syslog. For lines that normally go to
16496 both the main log and the reject log, the reject log version (possibly
16497 containing message header lines) is written, at LOG_NOTICE priority.
16498 Lines that normally go to both the main and the panic log are written at
16499 the LOG_ALERT priority.
16502 .option syslog_facility main string unset
16503 .cindex "syslog" "facility; setting"
16504 This option sets the syslog &"facility"& name, used when Exim is logging to
16505 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16506 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16507 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16508 details of Exim's logging.
16512 .option syslog_processname main string &`exim`&
16513 .cindex "syslog" "process name; setting"
16514 This option sets the syslog &"ident"& name, used when Exim is logging to
16515 syslog. The value must be no longer than 32 characters. See chapter
16516 &<<CHAPlog>>& for details of Exim's logging.
16520 .option syslog_timestamp main boolean true
16521 .cindex "syslog" "timestamps"
16522 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16523 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16524 details of Exim's logging.
16527 .option system_filter main string&!! unset
16528 .cindex "filter" "system filter"
16529 .cindex "system filter" "specifying"
16530 .cindex "Sieve filter" "not available for system filter"
16531 This option specifies an Exim filter file that is applied to all messages at
16532 the start of each delivery attempt, before any routing is done. System filters
16533 must be Exim filters; they cannot be Sieve filters. If the system filter
16534 generates any deliveries to files or pipes, or any new mail messages, the
16535 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16536 which transports are to be used. Details of this facility are given in chapter
16537 &<<CHAPsystemfilter>>&.
16540 .option system_filter_directory_transport main string&!! unset
16541 .vindex "&$address_file$&"
16542 This sets the name of the transport driver that is to be used when the
16543 &%save%& command in a system message filter specifies a path ending in &"/"&,
16544 implying delivery of each message into a separate file in some directory.
16545 During the delivery, the variable &$address_file$& contains the path name.
16548 .option system_filter_file_transport main string&!! unset
16549 .cindex "file" "transport for system filter"
16550 This sets the name of the transport driver that is to be used when the &%save%&
16551 command in a system message filter specifies a path not ending in &"/"&. During
16552 the delivery, the variable &$address_file$& contains the path name.
16554 .option system_filter_group main string unset
16555 .cindex "gid (group id)" "system filter"
16556 This option is used only when &%system_filter_user%& is also set. It sets the
16557 gid under which the system filter is run, overriding any gid that is associated
16558 with the user. The value may be numerical or symbolic.
16560 .option system_filter_pipe_transport main string&!! unset
16561 .cindex "&(pipe)& transport" "for system filter"
16562 .vindex "&$address_pipe$&"
16563 This specifies the transport driver that is to be used when a &%pipe%& command
16564 is used in a system filter. During the delivery, the variable &$address_pipe$&
16565 contains the pipe command.
16568 .option system_filter_reply_transport main string&!! unset
16569 .cindex "&(autoreply)& transport" "for system filter"
16570 This specifies the transport driver that is to be used when a &%mail%& command
16571 is used in a system filter.
16574 .option system_filter_user main string unset
16575 .cindex "uid (user id)" "system filter"
16576 If this option is set to root, the system filter is run in the main Exim
16577 delivery process, as root. Otherwise, the system filter runs in a separate
16578 process, as the given user, defaulting to the Exim run-time user.
16579 Unless the string consists entirely of digits, it
16580 is looked up in the password data. Failure to find the named user causes a
16581 configuration error. The gid is either taken from the password data, or
16582 specified by &%system_filter_group%&. When the uid is specified numerically,
16583 &%system_filter_group%& is required to be set.
16585 If the system filter generates any pipe, file, or reply deliveries, the uid
16586 under which the filter is run is used when transporting them, unless a
16587 transport option overrides.
16590 .option tcp_nodelay main boolean true
16591 .cindex "daemon" "TCP_NODELAY on sockets"
16592 .cindex "Nagle algorithm"
16593 .cindex "TCP_NODELAY on listening sockets"
16594 If this option is set false, it stops the Exim daemon setting the
16595 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16596 turns off the &"Nagle algorithm"&, which is a way of improving network
16597 performance in interactive (character-by-character) situations. Turning it off
16598 should improve Exim's performance a bit, so that is what happens by default.
16599 However, it appears that some broken clients cannot cope, and time out. Hence
16600 this option. It affects only those sockets that are set up for listening by the
16601 daemon. Sockets created by the smtp transport for delivering mail always set
16605 .option timeout_frozen_after main time 0s
16606 .cindex "frozen messages" "timing out"
16607 .cindex "timeout" "frozen messages"
16608 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16609 message of any kind that has been on the queue for longer than the given time
16610 is automatically cancelled at the next queue run. If the frozen message is a
16611 bounce message, it is just discarded; otherwise, a bounce is sent to the
16612 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16613 If you want to timeout frozen bounce messages earlier than other kinds of
16614 frozen message, see &%ignore_bounce_errors_after%&.
16616 &*Note:*& the default value of zero means no timeouts; with this setting,
16617 frozen messages remain on the queue forever (except for any frozen bounce
16618 messages that are released by &%ignore_bounce_errors_after%&).
16621 .option timezone main string unset
16622 .cindex "timezone, setting"
16623 The value of &%timezone%& is used to set the environment variable TZ while
16624 running Exim (if it is different on entry). This ensures that all timestamps
16625 created by Exim are in the required timezone. If you want all your timestamps
16626 to be in UTC (aka GMT) you should set
16630 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16631 or, if that is not set, from the value of the TZ environment variable when Exim
16632 is built. If &%timezone%& is set to the empty string, either at build or run
16633 time, any existing TZ variable is removed from the environment when Exim
16634 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16635 unfortunately not all, operating systems.
16638 .option tls_advertise_hosts main "host list&!!" unset
16639 .cindex "TLS" "advertising"
16640 .cindex "encryption" "on SMTP connection"
16641 .cindex "SMTP" "encrypted connection"
16642 When Exim is built with support for TLS encrypted connections, the availability
16643 of the STARTTLS command to set up an encrypted session is advertised in
16644 response to EHLO only to those client hosts that match this option. See
16645 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16648 .option tls_certificate main string&!! unset
16649 .cindex "TLS" "server certificate; location of"
16650 .cindex "certificate" "server, location of"
16651 The value of this option is expanded, and must then be the absolute path to a
16652 file which contains the server's certificates. The server's private key is also
16653 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16654 &<<CHAPTLS>>& for further details.
16656 &*Note*&: The certificates defined by this option are used only when Exim is
16657 receiving incoming messages as a server. If you want to supply certificates for
16658 use when sending messages as a client, you must set the &%tls_certificate%&
16659 option in the relevant &(smtp)& transport.
16661 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16662 if the OpenSSL build supports TLS extensions and the TLS client sends the
16663 Server Name Indication extension, then this option and others documented in
16664 &<<SECTtlssni>>& will be re-expanded.
16666 .option tls_crl main string&!! unset
16667 .cindex "TLS" "server certificate revocation list"
16668 .cindex "certificate" "revocation list for server"
16669 This option specifies a certificate revocation list. The expanded value must
16670 be the name of a file that contains a CRL in PEM format.
16672 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16675 .option tls_dh_max_bits main integer 2236
16676 .cindex "TLS" "D-H bit count"
16677 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16678 the chosen TLS library. That value might prove to be too high for
16679 interoperability. This option provides a maximum clamp on the value
16680 suggested, trading off security for interoperability.
16682 The value must be at least 1024.
16684 The value 2236 was chosen because, at time of adding the option, it was the
16685 hard-coded maximum value supported by the NSS cryptographic library, as used
16686 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16688 If you prefer more security and are willing to break some clients, raise this
16691 Note that the value passed to GnuTLS for *generating* a new prime may be a
16692 little less than this figure, because GnuTLS is inexact and may produce a
16693 larger prime than requested.
16696 .option tls_dhparam main string&!! unset
16697 .cindex "TLS" "D-H parameters for server"
16698 The value of this option is expanded and indicates the source of DH parameters
16699 to be used by Exim.
16701 If it is a filename starting with a &`/`&, then it names a file from which DH
16702 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16703 PKCS#3 representation of the DH prime. If the file does not exist, for
16704 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16705 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16706 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16707 and treated as though the &%tls_dhparam%& were set to "none".
16709 If this option expands to the string "none", then no DH parameters will be
16712 If this option expands to the string "historic" and Exim is using GnuTLS, then
16713 Exim will attempt to load a file from inside the spool directory. If the file
16714 does not exist, Exim will attempt to create it.
16715 See section &<<SECTgnutlsparam>>& for further details.
16717 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16718 a default DH prime; the default is the 2048 bit prime described in section
16719 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16720 in IKE is assigned number 23.
16722 Otherwise, the option must expand to the name used by Exim for any of a number
16723 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16724 "ike" followed by the number used by IKE, of "default" which corresponds to
16727 The available primes are:
16728 &`ike1`&, &`ike2`&, &`ike5`&,
16729 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16730 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16732 Some of these will be too small to be accepted by clients.
16733 Some may be too large to be accepted by clients.
16735 The TLS protocol does not negotiate an acceptable size for this; clients tend
16736 to hard-drop connections if what is offered by the server is unacceptable,
16737 whether too large or too small, and there's no provision for the client to
16738 tell the server what these constraints are. Thus, as a server operator, you
16739 need to make an educated guess as to what is most likely to work for your
16742 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16743 is most likely to maximise interoperability. The upper bound comes from
16744 applications using the Mozilla Network Security Services (NSS) library, which
16745 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16746 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16747 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16748 acceptable bound from 1024 to 2048.
16752 .option tls_eccurve main string&!! prime256v1
16753 .cindex TLS "EC cryptography"
16754 If built with a recent-enough version of OpenSSL,
16755 this option selects a EC curve for use by Exim.
16757 Curve names of the form &'prime256v1'& are accepted.
16758 For even more-recent library versions, names of the form &'P-512'&
16759 are also accepted, plus the special value &'auto'&
16760 which tell the library to choose.
16762 If the option is set to an empty string, no EC curves will be enabled.
16766 .option tls_ocsp_file main string&!! unset
16767 .cindex TLS "certificate status"
16768 .cindex TLS "OCSP proof file"
16770 must if set expand to the absolute path to a file which contains a current
16771 status proof for the server's certificate, as obtained from the
16772 Certificate Authority.
16775 .option tls_on_connect_ports main "string list" unset
16778 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16779 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16780 set up without waiting for the client to issue a STARTTLS command. For
16781 further details, see section &<<SECTsupobssmt>>&.
16785 .option tls_privatekey main string&!! unset
16786 .cindex "TLS" "server private key; location of"
16787 The value of this option is expanded, and must then be the absolute path to a
16788 file which contains the server's private key. If this option is unset, or if
16789 the expansion is forced to fail, or the result is an empty string, the private
16790 key is assumed to be in the same file as the server's certificates. See chapter
16791 &<<CHAPTLS>>& for further details.
16793 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16796 .option tls_remember_esmtp main boolean false
16797 .cindex "TLS" "esmtp state; remembering"
16798 .cindex "TLS" "broken clients"
16799 If this option is set true, Exim violates the RFCs by remembering that it is in
16800 &"esmtp"& state after successfully negotiating a TLS session. This provides
16801 support for broken clients that fail to send a new EHLO after starting a
16805 .option tls_require_ciphers main string&!! unset
16806 .cindex "TLS" "requiring specific ciphers"
16807 .cindex "cipher" "requiring specific"
16808 This option controls which ciphers can be used for incoming TLS connections.
16809 The &(smtp)& transport has an option of the same name for controlling outgoing
16810 connections. This option is expanded for each connection, so can be varied for
16811 different clients if required. The value of this option must be a list of
16812 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16813 in somewhat different ways. If GnuTLS is being used, the client controls the
16814 preference order of the available ciphers. Details are given in sections
16815 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16818 .option tls_try_verify_hosts main "host list&!!" unset
16819 .cindex "TLS" "client certificate verification"
16820 .cindex "certificate" "verification of client"
16821 See &%tls_verify_hosts%& below.
16825 .option tls_verify_certificates main string&!! system
16826 .cindex "TLS" "client certificate verification"
16827 .cindex "certificate" "verification of client"
16828 The value of this option is expanded, and must then be either the
16830 or the absolute path to
16831 a file or directory containing permitted certificates for clients that
16832 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
16834 The "system" value for the option will use a
16835 system default location compiled into the SSL library.
16836 This is not available for GnuTLS versions preceding 3.0.20,
16837 and will be taken as empty; an explicit location
16840 The use of a directory for the option value is not available for GnuTLS versions
16841 preceding 3.3.6 and a single file must be used.
16843 With OpenSSL the certificates specified
16845 either by file or directory
16846 are added to those given by the system default location.
16849 These certificates should be for the certificate authorities trusted, rather
16850 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16851 the value is a file then the certificates are sent by Exim as a server to
16852 connecting clients, defining the list of accepted certificate authorities.
16853 Thus the values defined should be considered public data. To avoid this,
16854 use the explicit directory version.
16856 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16858 A forced expansion failure or setting to an empty string is equivalent to
16862 .option tls_verify_hosts main "host list&!!" unset
16863 .cindex "TLS" "client certificate verification"
16864 .cindex "certificate" "verification of client"
16865 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16866 certificates from clients. The expected certificates are defined by
16867 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16868 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16869 &%tls_verify_certificates%& is not set.
16871 Any client that matches &%tls_verify_hosts%& is constrained by
16872 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16873 present one of the listed certificates. If it does not, the connection is
16874 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16875 the host to use TLS. It can still send SMTP commands through unencrypted
16876 connections. Forcing a client to use TLS has to be done separately using an
16877 ACL to reject inappropriate commands when the connection is not encrypted.
16879 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16880 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16881 certificate and checks it against &%tls_verify_certificates%&, but does not
16882 abort the connection if there is no certificate or if it does not match. This
16883 state can be detected in an ACL, which makes it possible to implement policies
16884 such as &"accept for relay only if a verified certificate has been received,
16885 but accept for local delivery if encrypted, even without a verified
16888 Client hosts that match neither of these lists are not asked to present
16892 .option trusted_groups main "string list&!!" unset
16893 .cindex "trusted groups"
16894 .cindex "groups" "trusted"
16895 This option is expanded just once, at the start of Exim's processing. If this
16896 option is set, any process that is running in one of the listed groups, or
16897 which has one of them as a supplementary group, is trusted. The groups can be
16898 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16899 details of what trusted callers are permitted to do. If neither
16900 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16903 .option trusted_users main "string list&!!" unset
16904 .cindex "trusted users"
16905 .cindex "user" "trusted"
16906 This option is expanded just once, at the start of Exim's processing. If this
16907 option is set, any process that is running as one of the listed users is
16908 trusted. The users can be specified numerically or by name. See section
16909 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16910 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16911 Exim user are trusted.
16913 .option unknown_login main string&!! unset
16914 .cindex "uid (user id)" "unknown caller"
16915 .vindex "&$caller_uid$&"
16916 This is a specialized feature for use in unusual configurations. By default, if
16917 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16918 gives up. The &%unknown_login%& option can be used to set a login name to be
16919 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16920 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16921 is used for the user's real name (gecos field), unless this has been set by the
16924 .option unknown_username main string unset
16925 See &%unknown_login%&.
16927 .option untrusted_set_sender main "address list&!!" unset
16928 .cindex "trusted users"
16929 .cindex "sender" "setting by untrusted user"
16930 .cindex "untrusted user setting sender"
16931 .cindex "user" "untrusted setting sender"
16932 .cindex "envelope sender"
16933 When an untrusted user submits a message to Exim using the standard input, Exim
16934 normally creates an envelope sender address from the user's login and the
16935 default qualification domain. Data from the &%-f%& option (for setting envelope
16936 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16937 is used) is ignored.
16939 However, untrusted users are permitted to set an empty envelope sender address,
16940 to declare that a message should never generate any bounces. For example:
16942 exim -f '<>' user@domain.example
16944 .vindex "&$sender_ident$&"
16945 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16946 other envelope sender addresses in a controlled way. When it is set, untrusted
16947 users are allowed to set envelope sender addresses that match any of the
16948 patterns in the list. Like all address lists, the string is expanded. The
16949 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16950 users to setting senders that start with their login ids
16951 followed by a hyphen
16952 by a setting like this:
16954 untrusted_set_sender = ^$sender_ident-
16956 If you want to allow untrusted users to set envelope sender addresses without
16957 restriction, you can use
16959 untrusted_set_sender = *
16961 The &%untrusted_set_sender%& option applies to all forms of local input, but
16962 only to the setting of the envelope sender. It does not permit untrusted users
16963 to use the other options which trusted user can use to override message
16964 parameters. Furthermore, it does not stop Exim from removing an existing
16965 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
16966 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
16967 overriding these actions. The handling of the &'Sender:'& header is also
16968 described in section &<<SECTthesenhea>>&.
16970 The log line for a message's arrival shows the envelope sender following
16971 &"<="&. For local messages, the user's login always follows, after &"U="&. In
16972 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
16973 envelope sender address, the user's login is shown in parentheses after the
16977 .option uucp_from_pattern main string "see below"
16978 .cindex "&""From""& line"
16979 .cindex "UUCP" "&""From""& line"
16980 Some applications that pass messages to an MTA via a command line interface use
16981 an initial line starting with &"From&~"& to pass the envelope sender. In
16982 particular, this is used by UUCP software. Exim recognizes such a line by means
16983 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
16984 matches, the sender address is constructed by expanding the contents of
16985 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
16986 default pattern recognizes lines in the following two forms:
16988 From ph10 Fri Jan 5 12:35 GMT 1996
16989 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16991 The pattern can be seen by running
16993 exim -bP uucp_from_pattern
16995 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16996 year in the second case. The first word after &"From&~"& is matched in the
16997 regular expression by a parenthesized subpattern. The default value for
16998 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16999 (&"ph10"& in the example above) as the message's sender. See also
17000 &%ignore_fromline_hosts%&.
17003 .option uucp_from_sender main string&!! &`$1`&
17004 See &%uucp_from_pattern%& above.
17007 .option warn_message_file main string unset
17008 .cindex "warning of delay" "customizing the message"
17009 .cindex "customizing" "warning message"
17010 This option defines a template file containing paragraphs of text to be used
17011 for constructing the warning message which is sent by Exim when a message has
17012 been on the queue for a specified amount of time, as specified by
17013 &%delay_warning%&. Details of the file's contents are given in chapter
17014 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17017 .option write_rejectlog main boolean true
17018 .cindex "reject log" "disabling"
17019 If this option is set false, Exim no longer writes anything to the reject log.
17020 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17021 .ecindex IIDconfima
17022 .ecindex IIDmaiconf
17027 . ////////////////////////////////////////////////////////////////////////////
17028 . ////////////////////////////////////////////////////////////////////////////
17030 .chapter "Generic options for routers" "CHAProutergeneric"
17031 .scindex IIDgenoprou1 "options" "generic; for routers"
17032 .scindex IIDgenoprou2 "generic options" "router"
17033 This chapter describes the generic options that apply to all routers.
17034 Those that are preconditions are marked with ‡ in the &"use"& field.
17036 For a general description of how a router operates, see sections
17037 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17038 which the preconditions are tested. The order of expansion of the options that
17039 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17040 &%headers_remove%&, &%transport%&.
17044 .option address_data routers string&!! unset
17045 .cindex "router" "data attached to address"
17046 The string is expanded just before the router is run, that is, after all the
17047 precondition tests have succeeded. If the expansion is forced to fail, the
17048 router declines, the value of &%address_data%& remains unchanged, and the
17049 &%more%& option controls what happens next. Other expansion failures cause
17050 delivery of the address to be deferred.
17052 .vindex "&$address_data$&"
17053 When the expansion succeeds, the value is retained with the address, and can be
17054 accessed using the variable &$address_data$& in the current router, subsequent
17055 routers, and the eventual transport.
17057 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17058 that runs a user's filter file, the contents of &$address_data$& are accessible
17059 in the filter. This is not normally a problem, because such data is usually
17060 either not confidential or it &"belongs"& to the current user, but if you do
17061 put confidential data into &$address_data$& you need to remember this point.
17063 Even if the router declines or passes, the value of &$address_data$& remains
17064 with the address, though it can be changed by another &%address_data%& setting
17065 on a subsequent router. If a router generates child addresses, the value of
17066 &$address_data$& propagates to them. This also applies to the special kind of
17067 &"child"& that is generated by a router with the &%unseen%& option.
17069 The idea of &%address_data%& is that you can use it to look up a lot of data
17070 for the address once, and then pick out parts of the data later. For example,
17071 you could use a single LDAP lookup to return a string of the form
17073 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17075 In the transport you could pick out the mailbox by a setting such as
17077 file = ${extract{mailbox}{$address_data}}
17079 This makes the configuration file less messy, and also reduces the number of
17080 lookups (though Exim does cache lookups).
17082 .vindex "&$sender_address_data$&"
17083 .vindex "&$address_data$&"
17084 The &%address_data%& facility is also useful as a means of passing information
17085 from one router to another, and from a router to a transport. In addition, if
17086 &$address_data$& is set by a router when verifying a recipient address from an
17087 ACL, it remains available for use in the rest of the ACL statement. After
17088 verifying a sender, the value is transferred to &$sender_address_data$&.
17092 .option address_test routers&!? boolean true
17094 .cindex "router" "skipping when address testing"
17095 If this option is set false, the router is skipped when routing is being tested
17096 by means of the &%-bt%& command line option. This can be a convenience when
17097 your first router sends messages to an external scanner, because it saves you
17098 having to set the &"already scanned"& indicator when testing real address
17103 .option cannot_route_message routers string&!! unset
17104 .cindex "router" "customizing &""cannot route""& message"
17105 .cindex "customizing" "&""cannot route""& message"
17106 This option specifies a text message that is used when an address cannot be
17107 routed because Exim has run out of routers. The default message is
17108 &"Unrouteable address"&. This option is useful only on routers that have
17109 &%more%& set false, or on the very last router in a configuration, because the
17110 value that is used is taken from the last router that is considered. This
17111 includes a router that is skipped because its preconditions are not met, as
17112 well as a router that declines. For example, using the default configuration,
17115 cannot_route_message = Remote domain not found in DNS
17117 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17120 cannot_route_message = Unknown local user
17122 on the final router that checks for local users. If string expansion fails for
17123 this option, the default message is used. Unless the expansion failure was
17124 explicitly forced, a message about the failure is written to the main and panic
17125 logs, in addition to the normal message about the routing failure.
17128 .option caseful_local_part routers boolean false
17129 .cindex "case of local parts"
17130 .cindex "router" "case of local parts"
17131 By default, routers handle the local parts of addresses in a case-insensitive
17132 manner, though the actual case is preserved for transmission with the message.
17133 If you want the case of letters to be significant in a router, you must set
17134 this option true. For individual router options that contain address or local
17135 part lists (for example, &%local_parts%&), case-sensitive matching can be
17136 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17139 .vindex "&$local_part$&"
17140 .vindex "&$original_local_part$&"
17141 .vindex "&$parent_local_part$&"
17142 The value of the &$local_part$& variable is forced to lower case while a
17143 router is running unless &%caseful_local_part%& is set. When a router assigns
17144 an address to a transport, the value of &$local_part$& when the transport runs
17145 is the same as it was in the router. Similarly, when a router generates child
17146 addresses by aliasing or forwarding, the values of &$original_local_part$&
17147 and &$parent_local_part$& are those that were used by the redirecting router.
17149 This option applies to the processing of an address by a router. When a
17150 recipient address is being processed in an ACL, there is a separate &%control%&
17151 modifier that can be used to specify case-sensitive processing within the ACL
17152 (see section &<<SECTcontrols>>&).
17156 .option check_local_user routers&!? boolean false
17157 .cindex "local user, checking in router"
17158 .cindex "router" "checking for local user"
17159 .cindex "&_/etc/passwd_&"
17161 When this option is true, Exim checks that the local part of the recipient
17162 address (with affixes removed if relevant) is the name of an account on the
17163 local system. The check is done by calling the &[getpwnam()]& function rather
17164 than trying to read &_/etc/passwd_& directly. This means that other methods of
17165 holding password data (such as NIS) are supported. If the local part is a local
17166 user, &$home$& is set from the password data, and can be tested in other
17167 preconditions that are evaluated after this one (the order of evaluation is
17168 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17169 overridden by &%router_home_directory%&. If the local part is not a local user,
17170 the router is skipped.
17172 If you want to check that the local part is either the name of a local user
17173 or matches something else, you cannot combine &%check_local_user%& with a
17174 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17175 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17176 setting to achieve this. For example:
17178 local_parts = passwd;$local_part : lsearch;/etc/other/users
17180 Note, however, that the side effects of &%check_local_user%& (such as setting
17181 up a home directory) do not occur when a &(passwd)& lookup is used in a
17182 &%local_parts%& (or any other) precondition.
17186 .option condition routers&!? string&!! unset
17187 .cindex "router" "customized precondition"
17188 This option specifies a general precondition test that has to succeed for the
17189 router to be called. The &%condition%& option is the last precondition to be
17190 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17191 result is a forced failure, or an empty string, or one of the strings &"0"& or
17192 &"no"& or &"false"& (checked without regard to the case of the letters), the
17193 router is skipped, and the address is offered to the next one.
17195 If the result is any other value, the router is run (as this is the last
17196 precondition to be evaluated, all the other preconditions must be true).
17198 This option is unusual in that multiple &%condition%& options may be present.
17199 All &%condition%& options must succeed.
17201 The &%condition%& option provides a means of applying custom conditions to the
17202 running of routers. Note that in the case of a simple conditional expansion,
17203 the default expansion values are exactly what is wanted. For example:
17205 condition = ${if >{$message_age}{600}}
17207 Because of the default behaviour of the string expansion, this is equivalent to
17209 condition = ${if >{$message_age}{600}{true}{}}
17212 A multiple condition example, which succeeds:
17214 condition = ${if >{$message_age}{600}}
17215 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17219 If the expansion fails (other than forced failure) delivery is deferred. Some
17220 of the other precondition options are common special cases that could in fact
17221 be specified using &%condition%&.
17223 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17224 are far older, and use one set of semantics. ACLs are newer and when
17225 they were created, the ACL &%condition%& process was given far stricter
17226 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17227 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17228 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17229 Router rules processing behavior.
17231 This is best illustrated in an example:
17233 # If used in an ACL condition will fail with a syntax error, but
17234 # in a router condition any extra characters are treated as a string
17236 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17239 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17242 In each example above, the &%if%& statement actually ends after
17243 &"{google.com}}"&. Since no true or false braces were defined, the
17244 default &%if%& behavior is to return a boolean true or a null answer
17245 (which evaluates to false). The rest of the line is then treated as a
17246 string. So the first example resulted in the boolean answer &"true"&
17247 with the string &" {yes} {no}}"& appended to it. The second example
17248 resulted in the null output (indicating false) with the string
17249 &" {yes} {no}}"& appended to it.
17251 In fact you can put excess forward braces in too. In the router
17252 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17253 mean something, like after a &"$"& or when required as part of a
17254 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17257 Thus, in a Router, the above expansion strings will both always evaluate
17258 true, as the result of expansion is a non-empty string which doesn't
17259 match an explicit false value. This can be tricky to debug. By
17260 contrast, in an ACL either of those strings will always result in an
17261 expansion error because the result doesn't look sufficiently boolean.
17264 .option debug_print routers string&!! unset
17265 .cindex "testing" "variables in drivers"
17266 If this option is set and debugging is enabled (see the &%-d%& command line
17267 option) or in address-testing mode (see the &%-bt%& command line option),
17268 the string is expanded and included in the debugging output.
17269 If expansion of the string fails, the error message is written to the debugging
17270 output, and Exim carries on processing.
17271 This option is provided to help with checking out the values of variables and
17272 so on when debugging router configurations. For example, if a &%condition%&
17273 option appears not to be working, &%debug_print%& can be used to output the
17274 variables it references. The output happens after checks for &%domains%&,
17275 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17276 are tested. A newline is added to the text if it does not end with one.
17277 The variable &$router_name$& contains the name of the router.
17281 .option disable_logging routers boolean false
17282 If this option is set true, nothing is logged for any routing errors
17283 or for any deliveries caused by this router. You should not set this option
17284 unless you really, really know what you are doing. See also the generic
17285 transport option of the same name.
17288 .option dnssec_request_domains routers "domain list&!!" unset
17289 .cindex "MX record" "security"
17290 .cindex "DNSSEC" "MX lookup"
17291 .cindex "security" "MX lookup"
17292 .cindex "DNS" "DNSSEC"
17293 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17294 the dnssec request bit set.
17295 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17297 .option dnssec_require_domains routers "domain list&!!" unset
17298 .cindex "MX record" "security"
17299 .cindex "DNSSEC" "MX lookup"
17300 .cindex "security" "MX lookup"
17301 .cindex "DNS" "DNSSEC"
17302 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17303 the dnssec request bit set. Any returns not having the Authenticated Data bit
17304 (AD bit) set will be ignored and logged as a host-lookup failure.
17305 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17309 .option domains routers&!? "domain list&!!" unset
17310 .cindex "router" "restricting to specific domains"
17311 .vindex "&$domain_data$&"
17312 If this option is set, the router is skipped unless the current domain matches
17313 the list. If the match is achieved by means of a file lookup, the data that the
17314 lookup returned for the domain is placed in &$domain_data$& for use in string
17315 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17316 a list of the order in which preconditions are evaluated.
17320 .option driver routers string unset
17321 This option must always be set. It specifies which of the available routers is
17326 .option dsn_lasthop routers boolean false
17327 .cindex "DSN" "success"
17328 .cindex "Delivery Status Notification" "success"
17329 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17330 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17331 instead send a success DSN as if the next hop does not support DSN.
17332 Not effective on redirect routers.
17337 .option errors_to routers string&!! unset
17338 .cindex "envelope sender"
17339 .cindex "router" "changing address for errors"
17340 If a router successfully handles an address, it may assign the address to a
17341 transport for delivery or it may generate child addresses. In both cases, if
17342 there is a delivery problem during later processing, the resulting bounce
17343 message is sent to the address that results from expanding this string,
17344 provided that the address verifies successfully. The &%errors_to%& option is
17345 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17347 The &%errors_to%& setting associated with an address can be overridden if it
17348 subsequently passes through other routers that have their own &%errors_to%&
17349 settings, or if the message is delivered by a transport with a &%return_path%&
17352 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17353 the expansion fails to verify, the errors address associated with the incoming
17354 address is used. At top level, this is the envelope sender. A non-forced
17355 expansion failure causes delivery to be deferred.
17357 If an address for which &%errors_to%& has been set ends up being delivered over
17358 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17359 any bounces that are generated by other MTAs on the delivery route are also
17360 sent there. You can set &%errors_to%& to the empty string by either of these
17366 An expansion item that yields an empty string has the same effect. If you do
17367 this, a locally detected delivery error for addresses processed by this router
17368 no longer gives rise to a bounce message; the error is discarded. If the
17369 address is delivered to a remote host, the return path is set to &`<>`&, unless
17370 overridden by the &%return_path%& option on the transport.
17372 .vindex "&$address_data$&"
17373 If for some reason you want to discard local errors, but use a non-empty
17374 MAIL command for remote delivery, you can preserve the original return
17375 path in &$address_data$& in the router, and reinstate it in the transport by
17376 setting &%return_path%&.
17378 The most common use of &%errors_to%& is to direct mailing list bounces to the
17379 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17380 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17384 .option expn routers&!? boolean true
17385 .cindex "address" "testing"
17386 .cindex "testing" "addresses"
17387 .cindex "EXPN" "router skipping"
17388 .cindex "router" "skipping for EXPN"
17389 If this option is turned off, the router is skipped when testing an address
17390 as a result of processing an SMTP EXPN command. You might, for example,
17391 want to turn it off on a router for users' &_.forward_& files, while leaving it
17392 on for the system alias file.
17393 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17396 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17397 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17398 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17402 .option fail_verify routers boolean false
17403 .cindex "router" "forcing verification failure"
17404 Setting this option has the effect of setting both &%fail_verify_sender%& and
17405 &%fail_verify_recipient%& to the same value.
17409 .option fail_verify_recipient routers boolean false
17410 If this option is true and an address is accepted by this router when
17411 verifying a recipient, verification fails.
17415 .option fail_verify_sender routers boolean false
17416 If this option is true and an address is accepted by this router when
17417 verifying a sender, verification fails.
17421 .option fallback_hosts routers "string list" unset
17422 .cindex "router" "fallback hosts"
17423 .cindex "fallback" "hosts specified on router"
17424 String expansion is not applied to this option. The argument must be a
17425 colon-separated list of host names or IP addresses. The list separator can be
17426 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17427 each name or address. In fact, the format of each item is exactly the same as
17428 defined for the list of hosts in a &(manualroute)& router (see section
17429 &<<SECTformatonehostitem>>&).
17431 If a router queues an address for a remote transport, this host list is
17432 associated with the address, and used instead of the transport's fallback host
17433 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17434 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17435 transport for further details.
17438 .option group routers string&!! "see below"
17439 .cindex "gid (group id)" "local delivery"
17440 .cindex "local transports" "uid and gid"
17441 .cindex "transport" "local"
17442 .cindex "router" "setting group"
17443 When a router queues an address for a transport, and the transport does not
17444 specify a group, the group given here is used when running the delivery
17446 The group may be specified numerically or by name. If expansion fails, the
17447 error is logged and delivery is deferred.
17448 The default is unset, unless &%check_local_user%& is set, when the default
17449 is taken from the password information. See also &%initgroups%& and &%user%&
17450 and the discussion in chapter &<<CHAPenvironment>>&.
17454 .option headers_add routers list&!! unset
17455 .cindex "header lines" "adding"
17456 .cindex "router" "adding header lines"
17457 This option specifies a list of text headers,
17459 newline-separated (by default, changeable in the usual way),
17461 that is associated with any addresses that are accepted by the router.
17462 Each item is separately expanded, at routing time. However, this
17463 option has no effect when an address is just being verified. The way in which
17464 the text is used to add header lines at transport time is described in section
17465 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17466 message is in the process of being transported. This means that references to
17467 header lines in string expansions in the transport's configuration do not
17468 &"see"& the added header lines.
17470 The &%headers_add%& option is expanded after &%errors_to%&, but before
17471 &%headers_remove%& and &%transport%&. If an item is empty, or if
17472 an item expansion is forced to fail, the item has no effect. Other expansion
17473 failures are treated as configuration errors.
17475 Unlike most options, &%headers_add%& can be specified multiple times
17476 for a router; all listed headers are added.
17478 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17479 router that has the &%one_time%& option set.
17481 .cindex "duplicate addresses"
17482 .oindex "&%unseen%&"
17483 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17484 additions are deleted when the address is passed on to subsequent routers.
17485 For a &%redirect%& router, if a generated address is the same as the incoming
17486 address, this can lead to duplicate addresses with different header
17487 modifications. Exim does not do duplicate deliveries (except, in certain
17488 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17489 which of the duplicates is discarded, so this ambiguous situation should be
17490 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17494 .option headers_remove routers list&!! unset
17495 .cindex "header lines" "removing"
17496 .cindex "router" "removing header lines"
17497 This option specifies a list of text headers,
17499 colon-separated (by default, changeable in the usual way),
17501 that is associated with any addresses that are accepted by the router.
17502 Each item is separately expanded, at routing time. However, this
17503 option has no effect when an address is just being verified. The way in which
17504 the text is used to remove header lines at transport time is described in
17505 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17506 the message is in the process of being transported. This means that references
17507 to header lines in string expansions in the transport's configuration still
17508 &"see"& the original header lines.
17510 The &%headers_remove%& option is expanded after &%errors_to%& and
17511 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17512 the item has no effect. Other expansion failures are treated as configuration
17515 Unlike most options, &%headers_remove%& can be specified multiple times
17516 for a router; all listed headers are removed.
17518 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17519 router that has the &%one_time%& option set.
17521 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17522 removal requests are deleted when the address is passed on to subsequent
17523 routers, and this can lead to problems with duplicates -- see the similar
17524 warning for &%headers_add%& above.
17527 &*Warning 3*&: Because of the separate expansion of the list items,
17528 items that contain a list separator must have it doubled.
17529 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17534 .option ignore_target_hosts routers "host list&!!" unset
17535 .cindex "IP address" "discarding"
17536 .cindex "router" "discarding IP addresses"
17537 Although this option is a host list, it should normally contain IP address
17538 entries rather than names. If any host that is looked up by the router has an
17539 IP address that matches an item in this list, Exim behaves as if that IP
17540 address did not exist. This option allows you to cope with rogue DNS entries
17543 remote.domain.example. A 127.0.0.1
17547 ignore_target_hosts = 127.0.0.1
17549 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17550 discarded in this way, the router declines. In a conventional configuration, an
17551 attempt to mail to such a domain would normally provoke the &"unrouteable
17552 domain"& error, and an attempt to verify an address in the domain would fail.
17553 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17554 router declines if presented with one of the listed addresses.
17556 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17557 means of the first or the second of the following settings, respectively:
17559 ignore_target_hosts = 0.0.0.0/0
17560 ignore_target_hosts = <; 0::0/0
17562 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17563 in the second line matches all IPv6 addresses.
17565 This option may also be useful for ignoring link-local and site-local IPv6
17566 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17567 is expanded before use as a list, it is possible to make it dependent on the
17568 domain that is being routed.
17570 .vindex "&$host_address$&"
17571 During its expansion, &$host_address$& is set to the IP address that is being
17574 .option initgroups routers boolean false
17575 .cindex "additional groups"
17576 .cindex "groups" "additional"
17577 .cindex "local transports" "uid and gid"
17578 .cindex "transport" "local"
17579 If the router queues an address for a transport, and this option is true, and
17580 the uid supplied by the router is not overridden by the transport, the
17581 &[initgroups()]& function is called when running the transport to ensure that
17582 any additional groups associated with the uid are set up. See also &%group%&
17583 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17587 .option local_part_prefix routers&!? "string list" unset
17588 .cindex "router" "prefix for local part"
17589 .cindex "prefix" "for local part, used in router"
17590 If this option is set, the router is skipped unless the local part starts with
17591 one of the given strings, or &%local_part_prefix_optional%& is true. See
17592 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17595 The list is scanned from left to right, and the first prefix that matches is
17596 used. A limited form of wildcard is available; if the prefix begins with an
17597 asterisk, it matches the longest possible sequence of arbitrary characters at
17598 the start of the local part. An asterisk should therefore always be followed by
17599 some character that does not occur in normal local parts.
17600 .cindex "multiple mailboxes"
17601 .cindex "mailbox" "multiple"
17602 Wildcarding can be used to set up multiple user mailboxes, as described in
17603 section &<<SECTmulbox>>&.
17605 .vindex "&$local_part$&"
17606 .vindex "&$local_part_prefix$&"
17607 During the testing of the &%local_parts%& option, and while the router is
17608 running, the prefix is removed from the local part, and is available in the
17609 expansion variable &$local_part_prefix$&. When a message is being delivered, if
17610 the router accepts the address, this remains true during subsequent delivery by
17611 a transport. In particular, the local part that is transmitted in the RCPT
17612 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
17613 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
17614 the relevant transport.
17616 When an address is being verified, &%local_part_prefix%& affects only the
17617 behaviour of the router. If the callout feature of verification is in use, this
17618 means that the full address, including the prefix, will be used during the
17621 The prefix facility is commonly used to handle local parts of the form
17622 &%owner-something%&. Another common use is to support local parts of the form
17623 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
17624 to tell a user their forwarding is broken &-- by placing a router like this one
17625 immediately before the router that handles &_.forward_& files:
17629 local_part_prefix = real-
17631 transport = local_delivery
17633 For security, it would probably be a good idea to restrict the use of this
17634 router to locally-generated messages, using a condition such as this:
17636 condition = ${if match {$sender_host_address}\
17637 {\N^(|127\.0\.0\.1)$\N}}
17640 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
17641 both conditions must be met if not optional. Care must be taken if wildcards
17642 are used in both a prefix and a suffix on the same router. Different
17643 separator characters must be used to avoid ambiguity.
17646 .option local_part_prefix_optional routers boolean false
17647 See &%local_part_prefix%& above.
17651 .option local_part_suffix routers&!? "string list" unset
17652 .cindex "router" "suffix for local part"
17653 .cindex "suffix for local part" "used in router"
17654 This option operates in the same way as &%local_part_prefix%&, except that the
17655 local part must end (rather than start) with the given string, the
17656 &%local_part_suffix_optional%& option determines whether the suffix is
17657 mandatory, and the wildcard * character, if present, must be the last
17658 character of the suffix. This option facility is commonly used to handle local
17659 parts of the form &%something-request%& and multiple user mailboxes of the form
17663 .option local_part_suffix_optional routers boolean false
17664 See &%local_part_suffix%& above.
17668 .option local_parts routers&!? "local part list&!!" unset
17669 .cindex "router" "restricting to specific local parts"
17670 .cindex "local part" "checking in router"
17671 The router is run only if the local part of the address matches the list.
17672 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17674 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
17675 string is expanded, it is possible to make it depend on the domain, for
17678 local_parts = dbm;/usr/local/specials/$domain
17680 .vindex "&$local_part_data$&"
17681 If the match is achieved by a lookup, the data that the lookup returned
17682 for the local part is placed in the variable &$local_part_data$& for use in
17683 expansions of the router's private options. You might use this option, for
17684 example, if you have a large number of local virtual domains, and you want to
17685 send all postmaster mail to the same place without having to set up an alias in
17686 each virtual domain:
17690 local_parts = postmaster
17691 data = postmaster@real.domain.example
17695 .option log_as_local routers boolean "see below"
17696 .cindex "log" "delivery line"
17697 .cindex "delivery" "log line format"
17698 Exim has two logging styles for delivery, the idea being to make local
17699 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17700 recipient address is given just as the local part, without a domain. The use of
17701 this style is controlled by this option. It defaults to true for the &(accept)&
17702 router, and false for all the others. This option applies only when a
17703 router assigns an address to a transport. It has no effect on routers that
17704 redirect addresses.
17708 .option more routers boolean&!! true
17709 The result of string expansion for this option must be a valid boolean value,
17710 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17711 result causes an error, and delivery is deferred. If the expansion is forced to
17712 fail, the default value for the option (true) is used. Other failures cause
17713 delivery to be deferred.
17715 If this option is set false, and the router declines to handle the address, no
17716 further routers are tried, routing fails, and the address is bounced.
17718 However, if the router explicitly passes an address to the following router by
17719 means of the setting
17723 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17724 does not affect the behaviour if one of the precondition tests fails. In that
17725 case, the address is always passed to the next router.
17727 Note that &%address_data%& is not considered to be a precondition. If its
17728 expansion is forced to fail, the router declines, and the value of &%more%&
17729 controls what happens next.
17732 .option pass_on_timeout routers boolean false
17733 .cindex "timeout" "of router"
17734 .cindex "router" "timeout"
17735 If a router times out during a host lookup, it normally causes deferral of the
17736 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17737 router, overriding &%no_more%&. This may be helpful for systems that are
17738 intermittently connected to the Internet, or those that want to pass to a smart
17739 host any messages that cannot immediately be delivered.
17741 There are occasional other temporary errors that can occur while doing DNS
17742 lookups. They are treated in the same way as a timeout, and this option
17743 applies to all of them.
17747 .option pass_router routers string unset
17748 .cindex "router" "go to after &""pass""&"
17749 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17750 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17751 routing to continue, and overriding a false setting of &%more%&. When one of
17752 these routers returns &"pass"&, the address is normally handed on to the next
17753 router in sequence. This can be changed by setting &%pass_router%& to the name
17754 of another router. However (unlike &%redirect_router%&) the named router must
17755 be below the current router, to avoid loops. Note that this option applies only
17756 to the special case of &"pass"&. It does not apply when a router returns
17757 &"decline"& because it cannot handle an address.
17761 .option redirect_router routers string unset
17762 .cindex "router" "start at after redirection"
17763 Sometimes an administrator knows that it is pointless to reprocess addresses
17764 generated from alias or forward files with the same router again. For
17765 example, if an alias file translates real names into login ids there is no
17766 point searching the alias file a second time, especially if it is a large file.
17768 The &%redirect_router%& option can be set to the name of any router instance.
17769 It causes the routing of any generated addresses to start at the named router
17770 instead of at the first router. This option has no effect if the router in
17771 which it is set does not generate new addresses.
17775 .option require_files routers&!? "string list&!!" unset
17776 .cindex "file" "requiring for router"
17777 .cindex "router" "requiring file existence"
17778 This option provides a general mechanism for predicating the running of a
17779 router on the existence or non-existence of certain files or directories.
17780 Before running a router, as one of its precondition tests, Exim works its way
17781 through the &%require_files%& list, expanding each item separately.
17783 Because the list is split before expansion, any colons in expansion items must
17784 be doubled, or the facility for using a different list separator must be used.
17785 If any expansion is forced to fail, the item is ignored. Other expansion
17786 failures cause routing of the address to be deferred.
17788 If any expanded string is empty, it is ignored. Otherwise, except as described
17789 below, each string must be a fully qualified file path, optionally preceded by
17790 &"!"&. The paths are passed to the &[stat()]& function to test for the
17791 existence of the files or directories. The router is skipped if any paths not
17792 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17795 If &[stat()]& cannot determine whether a file exists or not, delivery of
17796 the message is deferred. This can happen when NFS-mounted filesystems are
17799 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17800 options, so you cannot use it to check for the existence of a file in which to
17801 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17802 full list of the order in which preconditions are evaluated.) However, as
17803 these options are all expanded, you can use the &%exists%& expansion condition
17804 to make such tests. The &%require_files%& option is intended for checking files
17805 that the router may be going to use internally, or which are needed by a
17806 transport (for example &_.procmailrc_&).
17808 During delivery, the &[stat()]& function is run as root, but there is a
17809 facility for some checking of the accessibility of a file by another user.
17810 This is not a proper permissions check, but just a &"rough"& check that
17811 operates as follows:
17813 If an item in a &%require_files%& list does not contain any forward slash
17814 characters, it is taken to be the user (and optional group, separated by a
17815 comma) to be checked for subsequent files in the list. If no group is specified
17816 but the user is specified symbolically, the gid associated with the uid is
17819 require_files = mail:/some/file
17820 require_files = $local_part:$home/.procmailrc
17822 If a user or group name in a &%require_files%& list does not exist, the
17823 &%require_files%& condition fails.
17825 Exim performs the check by scanning along the components of the file path, and
17826 checking the access for the given uid and gid. It checks for &"x"& access on
17827 directories, and &"r"& access on the final file. Note that this means that file
17828 access control lists, if the operating system has them, are ignored.
17830 &*Warning 1*&: When the router is being run to verify addresses for an
17831 incoming SMTP message, Exim is not running as root, but under its own uid. This
17832 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17833 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17834 user is not permitted to read one of the directories on the file's path.
17836 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17837 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17838 without root access. In this case, if a check for access by a particular user
17839 is requested, Exim creates a subprocess that runs as that user, and tries the
17840 check again in that process.
17842 The default action for handling an unresolved EACCES is to consider it to
17843 be caused by a configuration error, and routing is deferred because the
17844 existence or non-existence of the file cannot be determined. However, in some
17845 circumstances it may be desirable to treat this condition as if the file did
17846 not exist. If the file name (or the exclamation mark that precedes the file
17847 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17848 as if the file did not exist. For example:
17850 require_files = +/some/file
17852 If the router is not an essential part of verification (for example, it
17853 handles users' &_.forward_& files), another solution is to set the &%verify%&
17854 option false so that the router is skipped when verifying.
17858 .option retry_use_local_part routers boolean "see below"
17859 .cindex "hints database" "retry keys"
17860 .cindex "local part" "in retry keys"
17861 When a delivery suffers a temporary routing failure, a retry record is created
17862 in Exim's hints database. For addresses whose routing depends only on the
17863 domain, the key for the retry record should not involve the local part, but for
17864 other addresses, both the domain and the local part should be included.
17865 Usually, remote routing is of the former kind, and local routing is of the
17868 This option controls whether the local part is used to form the key for retry
17869 hints for addresses that suffer temporary errors while being handled by this
17870 router. The default value is true for any router that has &%check_local_user%&
17871 set, and false otherwise. Note that this option does not apply to hints keys
17872 for transport delays; they are controlled by a generic transport option of the
17875 The setting of &%retry_use_local_part%& applies only to the router on which it
17876 appears. If the router generates child addresses, they are routed
17877 independently; this setting does not become attached to them.
17881 .option router_home_directory routers string&!! unset
17882 .cindex "router" "home directory for"
17883 .cindex "home directory" "for router"
17885 This option sets a home directory for use while the router is running. (Compare
17886 &%transport_home_directory%&, which sets a home directory for later
17887 transporting.) In particular, if used on a &(redirect)& router, this option
17888 sets a value for &$home$& while a filter is running. The value is expanded;
17889 forced expansion failure causes the option to be ignored &-- other failures
17890 cause the router to defer.
17892 Expansion of &%router_home_directory%& happens immediately after the
17893 &%check_local_user%& test (if configured), before any further expansions take
17895 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17897 While the router is running, &%router_home_directory%& overrides the value of
17898 &$home$& that came from &%check_local_user%&.
17900 When a router accepts an address and assigns it to a local transport (including
17901 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17902 delivery), the home directory setting for the transport is taken from the first
17903 of these values that is set:
17906 The &%home_directory%& option on the transport;
17908 The &%transport_home_directory%& option on the router;
17910 The password data if &%check_local_user%& is set on the router;
17912 The &%router_home_directory%& option on the router.
17915 In other words, &%router_home_directory%& overrides the password data for the
17916 router, but not for the transport.
17920 .option self routers string freeze
17921 .cindex "MX record" "pointing to local host"
17922 .cindex "local host" "MX pointing to"
17923 This option applies to those routers that use a recipient address to find a
17924 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17925 and &(manualroute)& routers.
17926 Certain configurations of the &(queryprogram)& router can also specify a list
17928 Usually such routers are configured to send the message to a remote host via an
17929 &(smtp)& transport. The &%self%& option specifies what happens when the first
17930 host on the list turns out to be the local host.
17931 The way in which Exim checks for the local host is described in section
17932 &<<SECTreclocipadd>>&.
17934 Normally this situation indicates either an error in Exim's configuration (for
17935 example, the router should be configured not to process this domain), or an
17936 error in the DNS (for example, the MX should not point to this host). For this
17937 reason, the default action is to log the incident, defer the address, and
17938 freeze the message. The following alternatives are provided for use in special
17943 Delivery of the message is tried again later, but the message is not frozen.
17945 .vitem "&%reroute%&: <&'domain'&>"
17946 The domain is changed to the given domain, and the address is passed back to
17947 be reprocessed by the routers. No rewriting of headers takes place. This
17948 behaviour is essentially a redirection.
17950 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17951 The domain is changed to the given domain, and the address is passed back to be
17952 reprocessed by the routers. Any headers that contain the original domain are
17957 .vindex "&$self_hostname$&"
17958 The router passes the address to the next router, or to the router named in the
17959 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17960 subsequent routing and delivery, the variable &$self_hostname$& contains the
17961 name of the local host that the router encountered. This can be used to
17962 distinguish between different cases for hosts with multiple names. The
17968 ensures that only those addresses that routed to the local host are passed on.
17969 Without &%no_more%&, addresses that were declined for other reasons would also
17970 be passed to the next router.
17973 Delivery fails and an error report is generated.
17976 .cindex "local host" "sending to"
17977 The anomaly is ignored and the address is queued for the transport. This
17978 setting should be used with extreme caution. For an &(smtp)& transport, it
17979 makes sense only in cases where the program that is listening on the SMTP port
17980 is not this version of Exim. That is, it must be some other MTA, or Exim with a
17981 different configuration file that handles the domain in another way.
17986 .option senders routers&!? "address list&!!" unset
17987 .cindex "router" "checking senders"
17988 If this option is set, the router is skipped unless the message's sender
17989 address matches something on the list.
17990 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17993 There are issues concerning verification when the running of routers is
17994 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
17995 setting, it sets the sender to the null string. When using the &%-bt%& option
17996 to check a configuration file, it is necessary also to use the &%-f%& option to
17997 set an appropriate sender. For incoming mail, the sender is unset when
17998 verifying the sender, but is available when verifying any recipients. If the
17999 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18003 .option translate_ip_address routers string&!! unset
18004 .cindex "IP address" "translating"
18005 .cindex "packet radio"
18006 .cindex "router" "IP address translation"
18007 There exist some rare networking situations (for example, packet radio) where
18008 it is helpful to be able to translate IP addresses generated by normal routing
18009 mechanisms into other IP addresses, thus performing a kind of manual IP
18010 routing. This should be done only if the normal IP routing of the TCP/IP stack
18011 is inadequate or broken. Because this is an extremely uncommon requirement, the
18012 code to support this option is not included in the Exim binary unless
18013 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18015 .vindex "&$host_address$&"
18016 The &%translate_ip_address%& string is expanded for every IP address generated
18017 by the router, with the generated address set in &$host_address$&. If the
18018 expansion is forced to fail, no action is taken.
18019 For any other expansion error, delivery of the message is deferred.
18020 If the result of the expansion is an IP address, that replaces the original
18021 address; otherwise the result is assumed to be a host name &-- this is looked
18022 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18023 produce one or more replacement IP addresses. For example, to subvert all IP
18024 addresses in some specific networks, this could be added to a router:
18026 translate_ip_address = \
18027 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18030 The file would contain lines like
18032 10.2.3.128/26 some.host
18033 10.8.4.34/26 10.44.8.15
18035 You should not make use of this facility unless you really understand what you
18040 .option transport routers string&!! unset
18041 This option specifies the transport to be used when a router accepts an address
18042 and sets it up for delivery. A transport is never needed if a router is used
18043 only for verification. The value of the option is expanded at routing time,
18044 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18045 and result must be the name of one of the configured transports. If it is not,
18046 delivery is deferred.
18048 The &%transport%& option is not used by the &(redirect)& router, but it does
18049 have some private options that set up transports for pipe and file deliveries
18050 (see chapter &<<CHAPredirect>>&).
18054 .option transport_current_directory routers string&!! unset
18055 .cindex "current directory for local transport"
18056 This option associates a current directory with any address that is routed
18057 to a local transport. This can happen either because a transport is
18058 explicitly configured for the router, or because it generates a delivery to a
18059 file or a pipe. During the delivery process (that is, at transport time), this
18060 option string is expanded and is set as the current directory, unless
18061 overridden by a setting on the transport.
18062 If the expansion fails for any reason, including forced failure, an error is
18063 logged, and delivery is deferred.
18064 See chapter &<<CHAPenvironment>>& for details of the local delivery
18070 .option transport_home_directory routers string&!! "see below"
18071 .cindex "home directory" "for local transport"
18072 This option associates a home directory with any address that is routed to a
18073 local transport. This can happen either because a transport is explicitly
18074 configured for the router, or because it generates a delivery to a file or a
18075 pipe. During the delivery process (that is, at transport time), the option
18076 string is expanded and is set as the home directory, unless overridden by a
18077 setting of &%home_directory%& on the transport.
18078 If the expansion fails for any reason, including forced failure, an error is
18079 logged, and delivery is deferred.
18081 If the transport does not specify a home directory, and
18082 &%transport_home_directory%& is not set for the router, the home directory for
18083 the transport is taken from the password data if &%check_local_user%& is set for
18084 the router. Otherwise it is taken from &%router_home_directory%& if that option
18085 is set; if not, no home directory is set for the transport.
18087 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18093 .option unseen routers boolean&!! false
18094 .cindex "router" "carrying on after success"
18095 The result of string expansion for this option must be a valid boolean value,
18096 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18097 result causes an error, and delivery is deferred. If the expansion is forced to
18098 fail, the default value for the option (false) is used. Other failures cause
18099 delivery to be deferred.
18101 When this option is set true, routing does not cease if the router accepts the
18102 address. Instead, a copy of the incoming address is passed to the next router,
18103 overriding a false setting of &%more%&. There is little point in setting
18104 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18105 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18106 sometimes true and sometimes false).
18108 .cindex "copy of message (&%unseen%& option)"
18109 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18110 qualifier in filter files. It can be used to cause copies of messages to be
18111 delivered to some other destination, while also carrying out a normal delivery.
18112 In effect, the current address is made into a &"parent"& that has two children
18113 &-- one that is delivered as specified by this router, and a clone that goes on
18114 to be routed further. For this reason, &%unseen%& may not be combined with the
18115 &%one_time%& option in a &(redirect)& router.
18117 &*Warning*&: Header lines added to the address (or specified for removal) by
18118 this router or by previous routers affect the &"unseen"& copy of the message
18119 only. The clone that continues to be processed by further routers starts with
18120 no added headers and none specified for removal. For a &%redirect%& router, if
18121 a generated address is the same as the incoming address, this can lead to
18122 duplicate addresses with different header modifications. Exim does not do
18123 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18124 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18125 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18126 &%redirect%& router may be of help.
18128 Unlike the handling of header modifications, any data that was set by the
18129 &%address_data%& option in the current or previous routers &'is'& passed on to
18130 subsequent routers.
18133 .option user routers string&!! "see below"
18134 .cindex "uid (user id)" "local delivery"
18135 .cindex "local transports" "uid and gid"
18136 .cindex "transport" "local"
18137 .cindex "router" "user for filter processing"
18138 .cindex "filter" "user for processing"
18139 When a router queues an address for a transport, and the transport does not
18140 specify a user, the user given here is used when running the delivery process.
18141 The user may be specified numerically or by name. If expansion fails, the
18142 error is logged and delivery is deferred.
18143 This user is also used by the &(redirect)& router when running a filter file.
18144 The default is unset, except when &%check_local_user%& is set. In this case,
18145 the default is taken from the password information. If the user is specified as
18146 a name, and &%group%& is not set, the group associated with the user is used.
18147 See also &%initgroups%& and &%group%& and the discussion in chapter
18148 &<<CHAPenvironment>>&.
18152 .option verify routers&!? boolean true
18153 Setting this option has the effect of setting &%verify_sender%& and
18154 &%verify_recipient%& to the same value.
18157 .option verify_only routers&!? boolean false
18158 .cindex "EXPN" "with &%verify_only%&"
18160 .cindex "router" "used only when verifying"
18161 If this option is set, the router is used only when verifying an address,
18162 delivering in cutthrough mode or
18163 testing with the &%-bv%& option, not when actually doing a delivery, testing
18164 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18165 restricted to verifying only senders or recipients by means of
18166 &%verify_sender%& and &%verify_recipient%&.
18168 &*Warning*&: When the router is being run to verify addresses for an incoming
18169 SMTP message, Exim is not running as root, but under its own uid. If the router
18170 accesses any files, you need to make sure that they are accessible to the Exim
18174 .option verify_recipient routers&!? boolean true
18175 If this option is false, the router is skipped when verifying recipient
18177 delivering in cutthrough mode
18178 or testing recipient verification using &%-bv%&.
18179 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18181 See also the &$verify_mode$& variable.
18184 .option verify_sender routers&!? boolean true
18185 If this option is false, the router is skipped when verifying sender addresses
18186 or testing sender verification using &%-bvs%&.
18187 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18189 See also the &$verify_mode$& variable.
18190 .ecindex IIDgenoprou1
18191 .ecindex IIDgenoprou2
18198 . ////////////////////////////////////////////////////////////////////////////
18199 . ////////////////////////////////////////////////////////////////////////////
18201 .chapter "The accept router" "CHID4"
18202 .cindex "&(accept)& router"
18203 .cindex "routers" "&(accept)&"
18204 The &(accept)& router has no private options of its own. Unless it is being
18205 used purely for verification (see &%verify_only%&) a transport is required to
18206 be defined by the generic &%transport%& option. If the preconditions that are
18207 specified by generic options are met, the router accepts the address and queues
18208 it for the given transport. The most common use of this router is for setting
18209 up deliveries to local mailboxes. For example:
18213 domains = mydomain.example
18215 transport = local_delivery
18217 The &%domains%& condition in this example checks the domain of the address, and
18218 &%check_local_user%& checks that the local part is the login of a local user.
18219 When both preconditions are met, the &(accept)& router runs, and queues the
18220 address for the &(local_delivery)& transport.
18227 . ////////////////////////////////////////////////////////////////////////////
18228 . ////////////////////////////////////////////////////////////////////////////
18230 .chapter "The dnslookup router" "CHAPdnslookup"
18231 .scindex IIDdnsrou1 "&(dnslookup)& router"
18232 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18233 The &(dnslookup)& router looks up the hosts that handle mail for the
18234 recipient's domain in the DNS. A transport must always be set for this router,
18235 unless &%verify_only%& is set.
18237 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18238 SRV records. If none are found, or if SRV support is not configured,
18239 MX records are looked up. If no MX records exist, address records are sought.
18240 However, &%mx_domains%& can be set to disable the direct use of address
18243 MX records of equal priority are sorted by Exim into a random order. Exim then
18244 looks for address records for the host names obtained from MX or SRV records.
18245 When a host has more than one IP address, they are sorted into a random order,
18246 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18247 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18248 generic option, the router declines.
18250 Unless they have the highest priority (lowest MX value), MX records that point
18251 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18252 are discarded, together with any other MX records of equal or lower priority.
18254 .cindex "MX record" "pointing to local host"
18255 .cindex "local host" "MX pointing to"
18256 .oindex "&%self%&" "in &(dnslookup)& router"
18257 If the host pointed to by the highest priority MX record, or looked up as an
18258 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18259 happens is controlled by the generic &%self%& option.
18262 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18263 There have been problems with DNS servers when SRV records are looked up.
18264 Some misbehaving servers return a DNS error or timeout when a non-existent
18265 SRV record is sought. Similar problems have in the past been reported for
18266 MX records. The global &%dns_again_means_nonexist%& option can help with this
18267 problem, but it is heavy-handed because it is a global option.
18269 For this reason, there are two options, &%srv_fail_domains%& and
18270 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18271 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18272 an attempt to look up an SRV or MX record causes one of these results, and the
18273 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18274 such record"&. In the case of an SRV lookup, this means that the router
18275 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18276 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18277 case routing fails.
18280 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18281 .cindex "&(dnslookup)& router" "declines"
18282 There are a few cases where a &(dnslookup)& router will decline to accept
18283 an address; if such a router is expected to handle "all remaining non-local
18284 domains", then it is important to set &%no_more%&.
18287 The router will defer rather than decline if the domain
18288 is found in the &%fail_defer_domains%& router option.
18291 Reasons for a &(dnslookup)& router to decline currently include:
18293 The domain does not exist in DNS
18295 The domain exists but the MX record's host part is just "."; this is a common
18296 convention (borrowed from SRV) used to indicate that there is no such service
18297 for this domain and to not fall back to trying A/AAAA records.
18299 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18301 MX record points to a non-existent host.
18303 MX record points to an IP address and the main section option
18304 &%allow_mx_to_ip%& is not set.
18306 MX records exist and point to valid hosts, but all hosts resolve only to
18307 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18309 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18310 &%dns_check_names_pattern%& for handling one variant of this)
18312 &%check_secondary_mx%& is set on this router but the local host can
18313 not be found in the MX records (see below)
18319 .section "Private options for dnslookup" "SECID118"
18320 .cindex "options" "&(dnslookup)& router"
18321 The private options for the &(dnslookup)& router are as follows:
18323 .option check_secondary_mx dnslookup boolean false
18324 .cindex "MX record" "checking for secondary"
18325 If this option is set, the router declines unless the local host is found in
18326 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18327 process domains for which the local host is a secondary mail exchanger
18328 differently to other domains. The way in which Exim decides whether a host is
18329 the local host is described in section &<<SECTreclocipadd>>&.
18332 .option check_srv dnslookup string&!! unset
18333 .cindex "SRV record" "enabling use of"
18334 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18335 addition to MX and address records. The support is disabled by default. To
18336 enable SRV support, set the &%check_srv%& option to the name of the service
18337 required. For example,
18341 looks for SRV records that refer to the normal smtp service. The option is
18342 expanded, so the service name can vary from message to message or address
18343 to address. This might be helpful if SRV records are being used for a
18344 submission service. If the expansion is forced to fail, the &%check_srv%&
18345 option is ignored, and the router proceeds to look for MX records in the
18348 When the expansion succeeds, the router searches first for SRV records for
18349 the given service (it assumes TCP protocol). A single SRV record with a
18350 host name that consists of just a single dot indicates &"no such service for
18351 this domain"&; if this is encountered, the router declines. If other kinds of
18352 SRV record are found, they are used to construct a host list for delivery
18353 according to the rules of RFC 2782. MX records are not sought in this case.
18355 When no SRV records are found, MX records (and address records) are sought in
18356 the traditional way. In other words, SRV records take precedence over MX
18357 records, just as MX records take precedence over address records. Note that
18358 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18359 defined it. It is apparently believed that MX records are sufficient for email
18360 and that SRV records should not be used for this purpose. However, SRV records
18361 have an additional &"weight"& feature which some people might find useful when
18362 trying to split an SMTP load between hosts of different power.
18364 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18365 when there is a DNS lookup error.
18371 .option fail_defer_domains dnslookup "domain list&!!" unset
18372 .cindex "MX record" "not found"
18373 DNS lookups for domains matching &%fail_defer_domains%&
18374 which find no matching record will cause the router to defer
18375 rather than the default behaviour of decline.
18376 This maybe be useful for queueing messages for a newly created
18377 domain while the DNS configuration is not ready.
18378 However, it will result in any message with mistyped domains
18383 .option mx_domains dnslookup "domain list&!!" unset
18384 .cindex "MX record" "required to exist"
18385 .cindex "SRV record" "required to exist"
18386 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18387 record in order to be recognized. (The name of this option could be improved.)
18388 For example, if all the mail hosts in &'fict.example'& are known to have MX
18389 records, except for those in &'discworld.fict.example'&, you could use this
18392 mx_domains = ! *.discworld.fict.example : *.fict.example
18394 This specifies that messages addressed to a domain that matches the list but
18395 has no MX record should be bounced immediately instead of being routed using
18396 the address record.
18399 .option mx_fail_domains dnslookup "domain list&!!" unset
18400 If the DNS lookup for MX records for one of the domains in this list causes a
18401 DNS lookup error, Exim behaves as if no MX records were found. See section
18402 &<<SECTprowitdnsloo>>& for more discussion.
18407 .option qualify_single dnslookup boolean true
18408 .cindex "DNS" "resolver options"
18409 .cindex "DNS" "qualifying single-component names"
18410 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18411 lookups. Typically, but not standardly, this causes the resolver to qualify
18412 single-component names with the default domain. For example, on a machine
18413 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18414 &'thesaurus.ref.example'& inside the resolver. For details of what your
18415 resolver actually does, consult your man pages for &'resolver'& and
18420 .option rewrite_headers dnslookup boolean true
18421 .cindex "rewriting" "header lines"
18422 .cindex "header lines" "rewriting"
18423 If the domain name in the address that is being processed is not fully
18424 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18425 an address is specified as &'dormouse@teaparty'&, the domain might be
18426 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18427 occur as a result of setting the &%widen_domains%& option. If
18428 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18429 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18430 header lines of the message are rewritten with the full domain name.
18432 This option should be turned off only when it is known that no message is
18433 ever going to be sent outside an environment where the abbreviation makes
18436 When an MX record is looked up in the DNS and matches a wildcard record, name
18437 servers normally return a record containing the name that has been looked up,
18438 making it impossible to detect whether a wildcard was present or not. However,
18439 some name servers have recently been seen to return the wildcard entry. If the
18440 name returned by a DNS lookup begins with an asterisk, it is not used for
18444 .option same_domain_copy_routing dnslookup boolean false
18445 .cindex "address" "copying routing"
18446 Addresses with the same domain are normally routed by the &(dnslookup)& router
18447 to the same list of hosts. However, this cannot be presumed, because the router
18448 options and preconditions may refer to the local part of the address. By
18449 default, therefore, Exim routes each address in a message independently. DNS
18450 servers run caches, so repeated DNS lookups are not normally expensive, and in
18451 any case, personal messages rarely have more than a few recipients.
18453 If you are running mailing lists with large numbers of subscribers at the same
18454 domain, and you are using a &(dnslookup)& router which is independent of the
18455 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18456 lookups for identical domains in one message. In this case, when &(dnslookup)&
18457 routes an address to a remote transport, any other unrouted addresses in the
18458 message that have the same domain are automatically given the same routing
18459 without processing them independently,
18460 provided the following conditions are met:
18463 No router that processed the address specified &%headers_add%& or
18464 &%headers_remove%&.
18466 The router did not change the address in any way, for example, by &"widening"&
18473 .option search_parents dnslookup boolean false
18474 .cindex "DNS" "resolver options"
18475 When this option is true, the resolver option RES_DNSRCH is set for DNS
18476 lookups. This is different from the &%qualify_single%& option in that it
18477 applies to domains containing dots. Typically, but not standardly, it causes
18478 the resolver to search for the name in the current domain and in parent
18479 domains. For example, on a machine in the &'fict.example'& domain, if looking
18480 up &'teaparty.wonderland'& failed, the resolver would try
18481 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18482 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18484 Setting this option true can cause problems in domains that have a wildcard MX
18485 record, because any domain that does not have its own MX record matches the
18490 .option srv_fail_domains dnslookup "domain list&!!" unset
18491 If the DNS lookup for SRV records for one of the domains in this list causes a
18492 DNS lookup error, Exim behaves as if no SRV records were found. See section
18493 &<<SECTprowitdnsloo>>& for more discussion.
18498 .option widen_domains dnslookup "string list" unset
18499 .cindex "domain" "partial; widening"
18500 If a DNS lookup fails and this option is set, each of its strings in turn is
18501 added onto the end of the domain, and the lookup is tried again. For example,
18504 widen_domains = fict.example:ref.example
18506 is set and a lookup of &'klingon.dictionary'& fails,
18507 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18508 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18509 and &%search_parents%& options can cause some widening to be undertaken inside
18510 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18511 when verifying, unless &%rewrite_headers%& is false (not the default).
18514 .section "Effect of qualify_single and search_parents" "SECID119"
18515 When a domain from an envelope recipient is changed by the resolver as a result
18516 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18517 corresponding address in the message's header lines unless &%rewrite_headers%&
18518 is set false. Exim then re-routes the address, using the full domain.
18520 These two options affect only the DNS lookup that takes place inside the router
18521 for the domain of the address that is being routed. They do not affect lookups
18522 such as that implied by
18526 that may happen while processing a router precondition before the router is
18527 entered. No widening ever takes place for these lookups.
18528 .ecindex IIDdnsrou1
18529 .ecindex IIDdnsrou2
18539 . ////////////////////////////////////////////////////////////////////////////
18540 . ////////////////////////////////////////////////////////////////////////////
18542 .chapter "The ipliteral router" "CHID5"
18543 .cindex "&(ipliteral)& router"
18544 .cindex "domain literal" "routing"
18545 .cindex "routers" "&(ipliteral)&"
18546 This router has no private options. Unless it is being used purely for
18547 verification (see &%verify_only%&) a transport is required to be defined by the
18548 generic &%transport%& option. The router accepts the address if its domain part
18549 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18550 router handles the address
18554 by setting up delivery to the host with that IP address. IPv4 domain literals
18555 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18556 are similar, but the address is preceded by &`ipv6:`&. For example:
18558 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18560 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18561 grounds that sooner or later somebody will try it.
18563 .oindex "&%self%&" "in &(ipliteral)& router"
18564 If the IP address matches something in &%ignore_target_hosts%&, the router
18565 declines. If an IP literal turns out to refer to the local host, the generic
18566 &%self%& option determines what happens.
18568 The RFCs require support for domain literals; however, their use is
18569 controversial in today's Internet. If you want to use this router, you must
18570 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18571 Exim will not recognize the domain literal syntax in addresses.
18575 . ////////////////////////////////////////////////////////////////////////////
18576 . ////////////////////////////////////////////////////////////////////////////
18578 .chapter "The iplookup router" "CHID6"
18579 .cindex "&(iplookup)& router"
18580 .cindex "routers" "&(iplookup)&"
18581 The &(iplookup)& router was written to fulfil a specific requirement in
18582 Cambridge University (which in fact no longer exists). For this reason, it is
18583 not included in the binary of Exim by default. If you want to include it, you
18586 ROUTER_IPLOOKUP=yes
18588 in your &_Local/Makefile_& configuration file.
18590 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18591 connection to one or more specific hosts. The host can then return the same or
18592 a different address &-- in effect rewriting the recipient address in the
18593 message's envelope. The new address is then passed on to subsequent routers. If
18594 this process fails, the address can be passed on to other routers, or delivery
18595 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18596 must not be specified for it.
18598 .cindex "options" "&(iplookup)& router"
18599 .option hosts iplookup string unset
18600 This option must be supplied. Its value is a colon-separated list of host
18601 names. The hosts are looked up using &[gethostbyname()]&
18602 (or &[getipnodebyname()]& when available)
18603 and are tried in order until one responds to the query. If none respond, what
18604 happens is controlled by &%optional%&.
18607 .option optional iplookup boolean false
18608 If &%optional%& is true, if no response is obtained from any host, the address
18609 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18610 delivery to the address is deferred.
18613 .option port iplookup integer 0
18614 .cindex "port" "&(iplookup)& router"
18615 This option must be supplied. It specifies the port number for the TCP or UDP
18619 .option protocol iplookup string udp
18620 This option can be set to &"udp"& or &"tcp"& to specify which of the two
18621 protocols is to be used.
18624 .option query iplookup string&!! "see below"
18625 This defines the content of the query that is sent to the remote hosts. The
18628 $local_part@$domain $local_part@$domain
18630 The repetition serves as a way of checking that a response is to the correct
18631 query in the default case (see &%response_pattern%& below).
18634 .option reroute iplookup string&!! unset
18635 If this option is not set, the rerouted address is precisely the byte string
18636 returned by the remote host, up to the first white space, if any. If set, the
18637 string is expanded to form the rerouted address. It can include parts matched
18638 in the response by &%response_pattern%& by means of numeric variables such as
18639 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
18640 whether or not a pattern is in use. In all cases, the rerouted address must end
18641 up in the form &'local_part@domain'&.
18644 .option response_pattern iplookup string unset
18645 This option can be set to a regular expression that is applied to the string
18646 returned from the remote host. If the pattern does not match the response, the
18647 router declines. If &%response_pattern%& is not set, no checking of the
18648 response is done, unless the query was defaulted, in which case there is a
18649 check that the text returned after the first white space is the original
18650 address. This checks that the answer that has been received is in response to
18651 the correct question. For example, if the response is just a new domain, the
18652 following could be used:
18654 response_pattern = ^([^@]+)$
18655 reroute = $local_part@$1
18658 .option timeout iplookup time 5s
18659 This specifies the amount of time to wait for a response from the remote
18660 machine. The same timeout is used for the &[connect()]& function for a TCP
18661 call. It does not apply to UDP.
18666 . ////////////////////////////////////////////////////////////////////////////
18667 . ////////////////////////////////////////////////////////////////////////////
18669 .chapter "The manualroute router" "CHID7"
18670 .scindex IIDmanrou1 "&(manualroute)& router"
18671 .scindex IIDmanrou2 "routers" "&(manualroute)&"
18672 .cindex "domain" "manually routing"
18673 The &(manualroute)& router is so-called because it provides a way of manually
18674 routing an address according to its domain. It is mainly used when you want to
18675 route addresses to remote hosts according to your own rules, bypassing the
18676 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18677 route to local transports, a facility that may be useful if you want to save
18678 messages for dial-in hosts in local files.
18680 The &(manualroute)& router compares a list of domain patterns with the domain
18681 it is trying to route. If there is no match, the router declines. Each pattern
18682 has associated with it a list of hosts and some other optional data, which may
18683 include a transport. The combination of a pattern and its data is called a
18684 &"routing rule"&. For patterns that do not have an associated transport, the
18685 generic &%transport%& option must specify a transport, unless the router is
18686 being used purely for verification (see &%verify_only%&).
18689 In the case of verification, matching the domain pattern is sufficient for the
18690 router to accept the address. When actually routing an address for delivery,
18691 an address that matches a domain pattern is queued for the associated
18692 transport. If the transport is not a local one, a host list must be associated
18693 with the pattern; IP addresses are looked up for the hosts, and these are
18694 passed to the transport along with the mail address. For local transports, a
18695 host list is optional. If it is present, it is passed in &$host$& as a single
18698 The list of routing rules can be provided as an inline string in
18699 &%route_list%&, or the data can be obtained by looking up the domain in a file
18700 or database by setting &%route_data%&. Only one of these settings may appear in
18701 any one instance of &(manualroute)&. The format of routing rules is described
18702 below, following the list of private options.
18705 .section "Private options for manualroute" "SECTprioptman"
18707 .cindex "options" "&(manualroute)& router"
18708 The private options for the &(manualroute)& router are as follows:
18710 .option host_all_ignored manualroute string defer
18711 See &%host_find_failed%&.
18713 .option host_find_failed manualroute string freeze
18714 This option controls what happens when &(manualroute)& tries to find an IP
18715 address for a host, and the host does not exist. The option can be set to one
18716 of the following values:
18725 The default (&"freeze"&) assumes that this state is a serious configuration
18726 error. The difference between &"pass"& and &"decline"& is that the former
18727 forces the address to be passed to the next router (or the router defined by
18730 overriding &%no_more%&, whereas the latter passes the address to the next
18731 router only if &%more%& is true.
18733 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18734 cannot be found. If all the hosts in the list are ignored, the behaviour is
18735 controlled by the &%host_all_ignored%& option. This takes the same values
18736 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18738 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18739 state; if a host lookup gets a temporary error, delivery is deferred unless the
18740 generic &%pass_on_timeout%& option is set.
18743 .option hosts_randomize manualroute boolean false
18744 .cindex "randomized host list"
18745 .cindex "host" "list of; randomized"
18746 If this option is set, the order of the items in a host list in a routing rule
18747 is randomized each time the list is used, unless an option in the routing rule
18748 overrides (see below). Randomizing the order of a host list can be used to do
18749 crude load sharing. However, if more than one mail address is routed by the
18750 same router to the same host list, the host lists are considered to be the same
18751 (even though they may be randomized into different orders) for the purpose of
18752 deciding whether to batch the deliveries into a single SMTP transaction.
18754 When &%hosts_randomize%& is true, a host list may be split
18755 into groups whose order is separately randomized. This makes it possible to
18756 set up MX-like behaviour. The boundaries between groups are indicated by an
18757 item that is just &`+`& in the host list. For example:
18759 route_list = * host1:host2:host3:+:host4:host5
18761 The order of the first three hosts and the order of the last two hosts is
18762 randomized for each use, but the first three always end up before the last two.
18763 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18764 randomized host list is passed to an &(smtp)& transport that also has
18765 &%hosts_randomize set%&, the list is not re-randomized.
18768 .option route_data manualroute string&!! unset
18769 If this option is set, it must expand to yield the data part of a routing rule.
18770 Typically, the expansion string includes a lookup based on the domain. For
18773 route_data = ${lookup{$domain}dbm{/etc/routes}}
18775 If the expansion is forced to fail, or the result is an empty string, the
18776 router declines. Other kinds of expansion failure cause delivery to be
18780 .option route_list manualroute "string list" unset
18781 This string is a list of routing rules, in the form defined below. Note that,
18782 unlike most string lists, the items are separated by semicolons. This is so
18783 that they may contain colon-separated host lists.
18786 .option same_domain_copy_routing manualroute boolean false
18787 .cindex "address" "copying routing"
18788 Addresses with the same domain are normally routed by the &(manualroute)&
18789 router to the same list of hosts. However, this cannot be presumed, because the
18790 router options and preconditions may refer to the local part of the address. By
18791 default, therefore, Exim routes each address in a message independently. DNS
18792 servers run caches, so repeated DNS lookups are not normally expensive, and in
18793 any case, personal messages rarely have more than a few recipients.
18795 If you are running mailing lists with large numbers of subscribers at the same
18796 domain, and you are using a &(manualroute)& router which is independent of the
18797 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18798 lookups for identical domains in one message. In this case, when
18799 &(manualroute)& routes an address to a remote transport, any other unrouted
18800 addresses in the message that have the same domain are automatically given the
18801 same routing without processing them independently. However, this is only done
18802 if &%headers_add%& and &%headers_remove%& are unset.
18807 .section "Routing rules in route_list" "SECID120"
18808 The value of &%route_list%& is a string consisting of a sequence of routing
18809 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18810 entered as two semicolons. Alternatively, the list separator can be changed as
18811 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18812 Empty rules are ignored. The format of each rule is
18814 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18816 The following example contains two rules, each with a simple domain pattern and
18820 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18821 thes.ref.example mail-3.ref.example:mail-4.ref.example
18823 The three parts of a rule are separated by white space. The pattern and the
18824 list of hosts can be enclosed in quotes if necessary, and if they are, the
18825 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18826 single domain pattern, which is the only mandatory item in the rule. The
18827 pattern is in the same format as one item in a domain list (see section
18828 &<<SECTdomainlist>>&),
18829 except that it may not be the name of an interpolated file.
18830 That is, it may be wildcarded, or a regular expression, or a file or database
18831 lookup (with semicolons doubled, because of the use of semicolon as a separator
18832 in a &%route_list%&).
18834 The rules in &%route_list%& are searched in order until one of the patterns
18835 matches the domain that is being routed. The list of hosts and then options are
18836 then used as described below. If there is no match, the router declines. When
18837 &%route_list%& is set, &%route_data%& must not be set.
18841 .section "Routing rules in route_data" "SECID121"
18842 The use of &%route_list%& is convenient when there are only a small number of
18843 routing rules. For larger numbers, it is easier to use a file or database to
18844 hold the routing information, and use the &%route_data%& option instead.
18845 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18846 Most commonly, &%route_data%& is set as a string that contains an
18847 expansion lookup. For example, suppose we place two routing rules in a file
18850 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18851 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18853 This data can be accessed by setting
18855 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18857 Failure of the lookup results in an empty string, causing the router to
18858 decline. However, you do not have to use a lookup in &%route_data%&. The only
18859 requirement is that the result of expanding the string is a list of hosts,
18860 possibly followed by options, separated by white space. The list of hosts must
18861 be enclosed in quotes if it contains white space.
18866 .section "Format of the list of hosts" "SECID122"
18867 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18868 always separately expanded before use. If the expansion fails, the router
18869 declines. The result of the expansion must be a colon-separated list of names
18870 and/or IP addresses, optionally also including ports. The format of each item
18871 in the list is described in the next section. The list separator can be changed
18872 as described in section &<<SECTlistconstruct>>&.
18874 If the list of hosts was obtained from a &%route_list%& item, the following
18875 variables are set during its expansion:
18878 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18879 If the domain was matched against a regular expression, the numeric variables
18880 &$1$&, &$2$&, etc. may be set. For example:
18882 route_list = ^domain(\d+) host-$1.text.example
18885 &$0$& is always set to the entire domain.
18887 &$1$& is also set when partial matching is done in a file lookup.
18890 .vindex "&$value$&"
18891 If the pattern that matched the domain was a lookup item, the data that was
18892 looked up is available in the expansion variable &$value$&. For example:
18894 route_list = lsearch;;/some/file.routes $value
18898 Note the doubling of the semicolon in the pattern that is necessary because
18899 semicolon is the default route list separator.
18903 .section "Format of one host item" "SECTformatonehostitem"
18904 Each item in the list of hosts is either a host name or an IP address,
18905 optionally with an attached port number. When no port is given, an IP address
18906 is not enclosed in brackets. When a port is specified, it overrides the port
18907 specification on the transport. The port is separated from the name or address
18908 by a colon. This leads to some complications:
18911 Because colon is the default separator for the list of hosts, either
18912 the colon that specifies a port must be doubled, or the list separator must
18913 be changed. The following two examples have the same effect:
18915 route_list = * "host1.tld::1225 : host2.tld::1226"
18916 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18919 When IPv6 addresses are involved, it gets worse, because they contain
18920 colons of their own. To make this case easier, it is permitted to
18921 enclose an IP address (either v4 or v6) in square brackets if a port
18922 number follows. For example:
18924 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18928 .section "How the list of hosts is used" "SECThostshowused"
18929 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18930 the hosts is tried, in the order specified, when carrying out the SMTP
18931 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18932 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18935 Hosts may be listed by name or by IP address. An unadorned name in the list of
18936 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18937 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18938 records in the DNS. For example:
18940 route_list = * x.y.z:p.q.r/MX:e.f.g
18942 If this feature is used with a port specifier, the port must come last. For
18945 route_list = * dom1.tld/mx::1225
18947 If the &%hosts_randomize%& option is set, the order of the items in the list is
18948 randomized before any lookups are done. Exim then scans the list; for any name
18949 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18950 be an interface on the local host and the item is not the first in the list,
18951 Exim discards it and any subsequent items. If it is the first item, what
18952 happens is controlled by the
18953 .oindex "&%self%&" "in &(manualroute)& router"
18954 &%self%& option of the router.
18956 A name on the list that is followed by &`/MX`& is replaced with the list of
18957 hosts obtained by looking up MX records for the name. This is always a DNS
18958 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18959 below) are not relevant here. The order of these hosts is determined by the
18960 preference values in the MX records, according to the usual rules. Because
18961 randomizing happens before the MX lookup, it does not affect the order that is
18962 defined by MX preferences.
18964 If the local host is present in the sublist obtained from MX records, but is
18965 not the most preferred host in that list, it and any equally or less
18966 preferred hosts are removed before the sublist is inserted into the main list.
18968 If the local host is the most preferred host in the MX list, what happens
18969 depends on where in the original list of hosts the &`/MX`& item appears. If it
18970 is not the first item (that is, there are previous hosts in the main list),
18971 Exim discards this name and any subsequent items in the main list.
18973 If the MX item is first in the list of hosts, and the local host is the
18974 most preferred host, what happens is controlled by the &%self%& option of the
18977 DNS failures when lookup up the MX records are treated in the same way as DNS
18978 failures when looking up IP addresses: &%pass_on_timeout%& and
18979 &%host_find_failed%& are used when relevant.
18981 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
18982 whether obtained from an MX lookup or not.
18986 .section "How the options are used" "SECThowoptused"
18987 The options are a sequence of words; in practice no more than three are ever
18988 present. One of the words can be the name of a transport; this overrides the
18989 &%transport%& option on the router for this particular routing rule only. The
18990 other words (if present) control randomization of the list of hosts on a
18991 per-rule basis, and how the IP addresses of the hosts are to be found when
18992 routing to a remote transport. These options are as follows:
18995 &%randomize%&: randomize the order of the hosts in this list, overriding the
18996 setting of &%hosts_randomize%& for this routing rule only.
18998 &%no_randomize%&: do not randomize the order of the hosts in this list,
18999 overriding the setting of &%hosts_randomize%& for this routing rule only.
19001 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19002 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19003 also look in &_/etc/hosts_& or other sources of information.
19005 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19006 no address records are found. If there is a temporary DNS error (such as a
19007 timeout), delivery is deferred.
19012 route_list = domain1 host1:host2:host3 randomize bydns;\
19013 domain2 host4:host5
19015 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19016 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19017 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19018 or &[gethostbyname()]&, and the result of the lookup is the result of that
19021 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19022 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19023 instead of TRY_AGAIN. That is why the default action is to try a DNS
19024 lookup first. Only if that gives a definite &"no such host"& is the local
19029 If no IP address for a host can be found, what happens is controlled by the
19030 &%host_find_failed%& option.
19033 When an address is routed to a local transport, IP addresses are not looked up.
19034 The host list is passed to the transport in the &$host$& variable.
19038 .section "Manualroute examples" "SECID123"
19039 In some of the examples that follow, the presence of the &%remote_smtp%&
19040 transport, as defined in the default configuration file, is assumed:
19043 .cindex "smart host" "example router"
19044 The &(manualroute)& router can be used to forward all external mail to a
19045 &'smart host'&. If you have set up, in the main part of the configuration, a
19046 named domain list that contains your local domains, for example:
19048 domainlist local_domains = my.domain.example
19050 You can arrange for all other domains to be routed to a smart host by making
19051 your first router something like this:
19054 driver = manualroute
19055 domains = !+local_domains
19056 transport = remote_smtp
19057 route_list = * smarthost.ref.example
19059 This causes all non-local addresses to be sent to the single host
19060 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19061 they are tried in order
19062 (but you can use &%hosts_randomize%& to vary the order each time).
19063 Another way of configuring the same thing is this:
19066 driver = manualroute
19067 transport = remote_smtp
19068 route_list = !+local_domains smarthost.ref.example
19070 There is no difference in behaviour between these two routers as they stand.
19071 However, they behave differently if &%no_more%& is added to them. In the first
19072 example, the router is skipped if the domain does not match the &%domains%&
19073 precondition; the following router is always tried. If the router runs, it
19074 always matches the domain and so can never decline. Therefore, &%no_more%&
19075 would have no effect. In the second case, the router is never skipped; it
19076 always runs. However, if it doesn't match the domain, it declines. In this case
19077 &%no_more%& would prevent subsequent routers from running.
19080 .cindex "mail hub example"
19081 A &'mail hub'& is a host which receives mail for a number of domains via MX
19082 records in the DNS and delivers it via its own private routing mechanism. Often
19083 the final destinations are behind a firewall, with the mail hub being the one
19084 machine that can connect to machines both inside and outside the firewall. The
19085 &(manualroute)& router is usually used on a mail hub to route incoming messages
19086 to the correct hosts. For a small number of domains, the routing can be inline,
19087 using the &%route_list%& option, but for a larger number a file or database
19088 lookup is easier to manage.
19090 If the domain names are in fact the names of the machines to which the mail is
19091 to be sent by the mail hub, the configuration can be quite simple. For
19095 driver = manualroute
19096 transport = remote_smtp
19097 route_list = *.rhodes.tvs.example $domain
19099 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19100 whose names are the same as the mail domains. A similar approach can be taken
19101 if the host name can be obtained from the domain name by a string manipulation
19102 that the expansion facilities can handle. Otherwise, a lookup based on the
19103 domain can be used to find the host:
19106 driver = manualroute
19107 transport = remote_smtp
19108 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19110 The result of the lookup must be the name or IP address of the host (or
19111 hosts) to which the address is to be routed. If the lookup fails, the route
19112 data is empty, causing the router to decline. The address then passes to the
19116 .cindex "batched SMTP output example"
19117 .cindex "SMTP" "batched outgoing; example"
19118 You can use &(manualroute)& to deliver messages to pipes or files in batched
19119 SMTP format for onward transportation by some other means. This is one way of
19120 storing mail for a dial-up host when it is not connected. The route list entry
19121 can be as simple as a single domain name in a configuration like this:
19124 driver = manualroute
19125 transport = batchsmtp_appendfile
19126 route_list = saved.domain.example
19128 though often a pattern is used to pick up more than one domain. If there are
19129 several domains or groups of domains with different transport requirements,
19130 different transports can be listed in the routing information:
19133 driver = manualroute
19135 *.saved.domain1.example $domain batch_appendfile; \
19136 *.saved.domain2.example \
19137 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19140 .vindex "&$domain$&"
19142 The first of these just passes the domain in the &$host$& variable, which
19143 doesn't achieve much (since it is also in &$domain$&), but the second does a
19144 file lookup to find a value to pass, causing the router to decline to handle
19145 the address if the lookup fails.
19148 .cindex "UUCP" "example of router for"
19149 Routing mail directly to UUCP software is a specific case of the use of
19150 &(manualroute)& in a gateway to another mail environment. This is an example of
19151 one way it can be done:
19157 command = /usr/local/bin/uux -r - \
19158 ${substr_-5:$host}!rmail ${local_part}
19159 return_fail_output = true
19164 driver = manualroute
19166 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19168 The file &_/usr/local/exim/uucphosts_& contains entries like
19170 darksite.ethereal.example: darksite.UUCP
19172 It can be set up more simply without adding and removing &".UUCP"& but this way
19173 makes clear the distinction between the domain name
19174 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19176 .ecindex IIDmanrou1
19177 .ecindex IIDmanrou2
19186 . ////////////////////////////////////////////////////////////////////////////
19187 . ////////////////////////////////////////////////////////////////////////////
19189 .chapter "The queryprogram router" "CHAPdriverlast"
19190 .scindex IIDquerou1 "&(queryprogram)& router"
19191 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19192 .cindex "routing" "by external program"
19193 The &(queryprogram)& router routes an address by running an external command
19194 and acting on its output. This is an expensive way to route, and is intended
19195 mainly for use in lightly-loaded systems, or for performing experiments.
19196 However, if it is possible to use the precondition options (&%domains%&,
19197 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19198 be used in special cases, even on a busy host. There are the following private
19200 .cindex "options" "&(queryprogram)& router"
19202 .option command queryprogram string&!! unset
19203 This option must be set. It specifies the command that is to be run. The
19204 command is split up into a command name and arguments, and then each is
19205 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19206 &<<CHAPpipetransport>>&).
19209 .option command_group queryprogram string unset
19210 .cindex "gid (group id)" "in &(queryprogram)& router"
19211 This option specifies a gid to be set when running the command while routing an
19212 address for deliver. It must be set if &%command_user%& specifies a numerical
19213 uid. If it begins with a digit, it is interpreted as the numerical value of the
19214 gid. Otherwise it is looked up using &[getgrnam()]&.
19217 .option command_user queryprogram string unset
19218 .cindex "uid (user id)" "for &(queryprogram)&"
19219 This option must be set. It specifies the uid which is set when running the
19220 command while routing an address for delivery. If the value begins with a digit,
19221 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19222 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19223 not set, a value for the gid also.
19225 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19226 root, which it does during a normal delivery in a conventional configuration.
19227 However, when an address is being verified during message reception, Exim is
19228 usually running as the Exim user, not as root. If the &(queryprogram)& router
19229 is called from a non-root process, Exim cannot change uid or gid before running
19230 the command. In this circumstance the command runs under the current uid and
19234 .option current_directory queryprogram string /
19235 This option specifies an absolute path which is made the current directory
19236 before running the command.
19239 .option timeout queryprogram time 1h
19240 If the command does not complete within the timeout period, its process group
19241 is killed and the message is frozen. A value of zero time specifies no
19245 The standard output of the command is connected to a pipe, which is read when
19246 the command terminates. It should consist of a single line of output,
19247 containing up to five fields, separated by white space. The maximum length of
19248 the line is 1023 characters. Longer lines are silently truncated. The first
19249 field is one of the following words (case-insensitive):
19252 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19255 &'Decline'&: the router declines; pass the address to the next router, unless
19256 &%no_more%& is set.
19258 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19259 subsequent text on the line is an error message. If the router is run as part
19260 of address verification during an incoming SMTP message, the message is
19261 included in the SMTP response.
19263 &'Defer'&: routing could not be completed at this time; try again later. Any
19264 subsequent text on the line is an error message which is logged. It is not
19265 included in any SMTP response.
19267 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19269 &'Pass'&: pass the address to the next router (or the router specified by
19270 &%pass_router%&), overriding &%no_more%&.
19272 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19273 new addresses, which are routed independently, starting with the first router,
19274 or the router specified by &%redirect_router%&, if set.
19277 When the first word is &'accept'&, the remainder of the line consists of a
19278 number of keyed data values, as follows (split into two lines here, to fit on
19281 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19282 LOOKUP=byname|bydns DATA=<text>
19284 The data items can be given in any order, and all are optional. If no transport
19285 is included, the transport specified by the generic &%transport%& option is
19286 used. The list of hosts and the lookup type are needed only if the transport is
19287 an &(smtp)& transport that does not itself supply a list of hosts.
19289 The format of the list of hosts is the same as for the &(manualroute)& router.
19290 As well as host names and IP addresses with optional port numbers, as described
19291 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19292 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19293 (see section &<<SECThostshowused>>&).
19295 If the lookup type is not specified, Exim behaves as follows when trying to
19296 find an IP address for each host: First, a DNS lookup is done. If this yields
19297 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19298 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19299 result of the lookup is the result of that call.
19301 .vindex "&$address_data$&"
19302 If the DATA field is set, its value is placed in the &$address_data$&
19303 variable. For example, this return line
19305 accept hosts=x1.y.example:x2.y.example data="rule1"
19307 routes the address to the default transport, passing a list of two hosts. When
19308 the transport runs, the string &"rule1"& is in &$address_data$&.
19309 .ecindex IIDquerou1
19310 .ecindex IIDquerou2
19315 . ////////////////////////////////////////////////////////////////////////////
19316 . ////////////////////////////////////////////////////////////////////////////
19318 .chapter "The redirect router" "CHAPredirect"
19319 .scindex IIDredrou1 "&(redirect)& router"
19320 .scindex IIDredrou2 "routers" "&(redirect)&"
19321 .cindex "alias file" "in a &(redirect)& router"
19322 .cindex "address redirection" "&(redirect)& router"
19323 The &(redirect)& router handles several kinds of address redirection. Its most
19324 common uses are for resolving local part aliases from a central alias file
19325 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19326 files, but it has many other potential uses. The incoming address can be
19327 redirected in several different ways:
19330 It can be replaced by one or more new addresses which are themselves routed
19333 It can be routed to be delivered to a given file or directory.
19335 It can be routed to be delivered to a specified pipe command.
19337 It can cause an automatic reply to be generated.
19339 It can be forced to fail, optionally with a custom error message.
19341 It can be temporarily deferred, optionally with a custom message.
19343 It can be discarded.
19346 The generic &%transport%& option must not be set for &(redirect)& routers.
19347 However, there are some private options which define transports for delivery to
19348 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19349 &%pipe_transport%& and &%reply_transport%& descriptions below.
19352 If success DSNs have been requested
19353 .cindex "DSN" "success"
19354 .cindex "Delivery Status Notification" "success"
19355 redirection triggers one and the DSN options are not passed any further.
19360 .section "Redirection data" "SECID124"
19361 The router operates by interpreting a text string which it obtains either by
19362 expanding the contents of the &%data%& option, or by reading the entire
19363 contents of a file whose name is given in the &%file%& option. These two
19364 options are mutually exclusive. The first is commonly used for handling system
19365 aliases, in a configuration like this:
19369 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19371 If the lookup fails, the expanded string in this example is empty. When the
19372 expansion of &%data%& results in an empty string, the router declines. A forced
19373 expansion failure also causes the router to decline; other expansion failures
19374 cause delivery to be deferred.
19376 A configuration using &%file%& is commonly used for handling users'
19377 &_.forward_& files, like this:
19382 file = $home/.forward
19385 If the file does not exist, or causes no action to be taken (for example, it is
19386 empty or consists only of comments), the router declines. &*Warning*&: This
19387 is not the case when the file contains syntactically valid items that happen to
19388 yield empty addresses, for example, items containing only RFC 2822 address
19393 .section "Forward files and address verification" "SECID125"
19394 .cindex "address redirection" "while verifying"
19395 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19396 &_.forward_& files, as in the example above. There are two reasons for this:
19399 When Exim is receiving an incoming SMTP message from a remote host, it is
19400 running under the Exim uid, not as root. Exim is unable to change uid to read
19401 the file as the user, and it may not be able to read it as the Exim user. So in
19402 practice the router may not be able to operate.
19404 However, even when the router can operate, the existence of a &_.forward_& file
19405 is unimportant when verifying an address. What should be checked is whether the
19406 local part is a valid user name or not. Cutting out the redirection processing
19407 saves some resources.
19415 .section "Interpreting redirection data" "SECID126"
19416 .cindex "Sieve filter" "specifying in redirection data"
19417 .cindex "filter" "specifying in redirection data"
19418 The contents of the data string, whether obtained from &%data%& or &%file%&,
19419 can be interpreted in two different ways:
19422 If the &%allow_filter%& option is set true, and the data begins with the text
19423 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19424 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19425 respectively. Details of the syntax and semantics of filter files are described
19426 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19427 document is intended for use by end users.
19429 Otherwise, the data must be a comma-separated list of redirection items, as
19430 described in the next section.
19433 When a message is redirected to a file (a &"mail folder"&), the file name given
19434 in a non-filter redirection list must always be an absolute path. A filter may
19435 generate a relative path &-- how this is handled depends on the transport's
19436 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19437 for the &(appendfile)& transport.
19441 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19442 .cindex "address redirection" "non-filter list items"
19443 When the redirection data is not an Exim or Sieve filter, for example, if it
19444 comes from a conventional alias or forward file, it consists of a list of
19445 addresses, file names, pipe commands, or certain special items (see section
19446 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19447 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19448 depending on their default values. The items in the list are separated by
19449 commas or newlines.
19450 If a comma is required in an item, the entire item must be enclosed in double
19453 Lines starting with a # character are comments, and are ignored, and # may
19454 also appear following a comma, in which case everything between the # and the
19455 next newline character is ignored.
19457 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19458 double quotes are retained because some forms of mail address require their use
19459 (but never to enclose the entire address). In the following description,
19460 &"item"& refers to what remains after any surrounding double quotes have been
19463 .vindex "&$local_part$&"
19464 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19465 and the expansion contains a reference to &$local_part$&, you should make use
19466 of the &%quote_local_part%& expansion operator, in case the local part contains
19467 special characters. For example, to redirect all mail for the domain
19468 &'obsolete.example'&, retaining the existing local part, you could use this
19471 data = ${quote_local_part:$local_part}@newdomain.example
19475 .section "Redirecting to a local mailbox" "SECTredlocmai"
19476 .cindex "routing" "loops in"
19477 .cindex "loop" "while routing, avoidance of"
19478 .cindex "address redirection" "to local mailbox"
19479 A redirection item may safely be the same as the address currently under
19480 consideration. This does not cause a routing loop, because a router is
19481 automatically skipped if any ancestor of the address that is being processed
19482 is the same as the current address and was processed by the current router.
19483 Such an address is therefore passed to the following routers, so it is handled
19484 as if there were no redirection. When making this loop-avoidance test, the
19485 complete local part, including any prefix or suffix, is used.
19487 .cindex "address redirection" "local part without domain"
19488 Specifying the same local part without a domain is a common usage in personal
19489 filter files when the user wants to have messages delivered to the local
19490 mailbox and also forwarded elsewhere. For example, the user whose login is
19491 &'cleo'& might have a &_.forward_& file containing this:
19493 cleo, cleopatra@egypt.example
19495 .cindex "backslash in alias file"
19496 .cindex "alias file" "backslash in"
19497 For compatibility with other MTAs, such unqualified local parts may be
19498 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19499 it does make a difference if more than one domain is being handled
19502 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19503 2822 address that does not include a domain, the item is qualified using the
19504 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19505 addresses are qualified using the value in &%qualify_recipient%&, but you can
19506 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19508 Care must be taken if there are alias names for local users.
19509 Consider an MTA handling a single local domain where the system alias file
19514 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19515 messages in the local mailbox, and also forward copies elsewhere. He creates
19518 Sam.Reman, spqr@reme.elsewhere.example
19520 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19521 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19522 second time round, because it has previously routed it,
19523 and the following routers presumably cannot handle the alias. The forward file
19524 should really contain
19526 spqr, spqr@reme.elsewhere.example
19528 but because this is such a common error, the &%check_ancestor%& option (see
19529 below) exists to provide a way to get round it. This is normally set on a
19530 &(redirect)& router that is handling users' &_.forward_& files.
19534 .section "Special items in redirection lists" "SECTspecitredli"
19535 In addition to addresses, the following types of item may appear in redirection
19536 lists (that is, in non-filter redirection data):
19539 .cindex "pipe" "in redirection list"
19540 .cindex "address redirection" "to pipe"
19541 An item is treated as a pipe command if it begins with &"|"& and does not parse
19542 as a valid RFC 2822 address that includes a domain. A transport for running the
19543 command must be specified by the &%pipe_transport%& option.
19544 Normally, either the router or the transport specifies a user and a group under
19545 which to run the delivery. The default is to use the Exim user and group.
19547 Single or double quotes can be used for enclosing the individual arguments of
19548 the pipe command; no interpretation of escapes is done for single quotes. If
19549 the command contains a comma character, it is necessary to put the whole item
19550 in double quotes, for example:
19552 "|/some/command ready,steady,go"
19554 since items in redirection lists are terminated by commas. Do not, however,
19555 quote just the command. An item such as
19557 |"/some/command ready,steady,go"
19559 is interpreted as a pipe with a rather strange command name, and no arguments.
19561 Note that the above example assumes that the text comes from a lookup source
19562 of some sort, so that the quotes are part of the data. If composing a
19563 redirect router with a &%data%& option directly specifying this command, the
19564 quotes will be used by the configuration parser to define the extent of one
19565 string, but will not be passed down into the redirect router itself. There
19566 are two main approaches to get around this: escape quotes to be part of the
19567 data itself, or avoid using this mechanism and instead create a custom
19568 transport with the &%command%& option set and reference that transport from
19569 an &%accept%& router.
19572 .cindex "file" "in redirection list"
19573 .cindex "address redirection" "to file"
19574 An item is interpreted as a path name if it begins with &"/"& and does not
19575 parse as a valid RFC 2822 address that includes a domain. For example,
19577 /home/world/minbari
19579 is treated as a file name, but
19581 /s=molari/o=babylon/@x400gate.way
19583 is treated as an address. For a file name, a transport must be specified using
19584 the &%file_transport%& option. However, if the generated path name ends with a
19585 forward slash character, it is interpreted as a directory name rather than a
19586 file name, and &%directory_transport%& is used instead.
19588 Normally, either the router or the transport specifies a user and a group under
19589 which to run the delivery. The default is to use the Exim user and group.
19591 .cindex "&_/dev/null_&"
19592 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19593 bypassed at a high level, and the log entry shows &"**bypassed**"&
19594 instead of a transport name. In this case the user and group are not used.
19597 .cindex "included address list"
19598 .cindex "address redirection" "included external list"
19599 If an item is of the form
19601 :include:<path name>
19603 a list of further items is taken from the given file and included at that
19604 point. &*Note*&: Such a file can not be a filter file; it is just an
19605 out-of-line addition to the list. The items in the included list are separated
19606 by commas or newlines and are not subject to expansion. If this is the first
19607 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19608 the alias name. This example is incorrect:
19610 list1 :include:/opt/lists/list1
19612 It must be given as
19614 list1: :include:/opt/lists/list1
19617 .cindex "address redirection" "to black hole"
19618 Sometimes you want to throw away mail to a particular local part. Making the
19619 &%data%& option expand to an empty string does not work, because that causes
19620 the router to decline. Instead, the alias item
19621 .cindex "black hole"
19622 .cindex "abandoning mail"
19623 &':blackhole:'& can be used. It does what its name implies. No delivery is
19624 done, and no error message is generated. This has the same effect as specifying
19625 &_/dev/null_& as a destination, but it can be independently disabled.
19627 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
19628 delivery is done for the original local part, even if other redirection items
19629 are present. If you are generating a multi-item list (for example, by reading a
19630 database) and need the ability to provide a no-op item, you must use
19634 .cindex "delivery" "forcing failure"
19635 .cindex "delivery" "forcing deferral"
19636 .cindex "failing delivery" "forcing"
19637 .cindex "deferred delivery, forcing"
19638 .cindex "customizing" "failure message"
19639 An attempt to deliver a particular address can be deferred or forced to fail by
19640 redirection items of the form
19645 respectively. When a redirection list contains such an item, it applies
19646 to the entire redirection; any other items in the list are ignored. Any
19647 text following &':fail:'& or &':defer:'& is placed in the error text
19648 associated with the failure. For example, an alias file might contain:
19650 X.Employee: :fail: Gone away, no forwarding address
19652 In the case of an address that is being verified from an ACL or as the subject
19654 .cindex "VRFY" "error text, display of"
19655 VRFY command, the text is included in the SMTP error response by
19657 .cindex "EXPN" "error text, display of"
19658 The text is not included in the response to an EXPN command. In non-SMTP cases
19659 the text is included in the error message that Exim generates.
19661 .cindex "SMTP" "error codes"
19662 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
19663 &':fail:'&. However, if the message starts with three digits followed by a
19664 space, optionally followed by an extended code of the form &'n.n.n'&, also
19665 followed by a space, and the very first digit is the same as the default error
19666 code, the code from the message is used instead. If the very first digit is
19667 incorrect, a panic error is logged, and the default code is used. You can
19668 suppress the use of the supplied code in a redirect router by setting the
19669 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
19672 .vindex "&$acl_verify_message$&"
19673 In an ACL, an explicitly provided message overrides the default, but the
19674 default message is available in the variable &$acl_verify_message$& and can
19675 therefore be included in a custom message if this is desired.
19677 Normally the error text is the rest of the redirection list &-- a comma does
19678 not terminate it &-- but a newline does act as a terminator. Newlines are not
19679 normally present in alias expansions. In &(lsearch)& lookups they are removed
19680 as part of the continuation process, but they may exist in other kinds of
19681 lookup and in &':include:'& files.
19683 During routing for message delivery (as opposed to verification), a redirection
19684 containing &':fail:'& causes an immediate failure of the incoming address,
19685 whereas &':defer:'& causes the message to remain on the queue so that a
19686 subsequent delivery attempt can happen at a later time. If an address is
19687 deferred for too long, it will ultimately fail, because the normal retry
19691 .cindex "alias file" "exception to default"
19692 Sometimes it is useful to use a single-key search type with a default (see
19693 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19694 for exceptions to the default. These can be handled by aliasing them to
19695 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19696 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19697 results in an empty redirection list has the same effect.
19701 .section "Duplicate addresses" "SECTdupaddr"
19702 .cindex "duplicate addresses"
19703 .cindex "address duplicate, discarding"
19704 .cindex "pipe" "duplicated"
19705 Exim removes duplicate addresses from the list to which it is delivering, so as
19706 to deliver just one copy to each address. This does not apply to deliveries
19707 routed to pipes by different immediate parent addresses, but an indirect
19708 aliasing scheme of the type
19710 pipe: |/some/command $local_part
19714 does not work with a message that is addressed to both local parts, because
19715 when the second is aliased to the intermediate local part &"pipe"& it gets
19716 discarded as being the same as a previously handled address. However, a scheme
19719 localpart1: |/some/command $local_part
19720 localpart2: |/some/command $local_part
19722 does result in two different pipe deliveries, because the immediate parents of
19723 the pipes are distinct.
19727 .section "Repeated redirection expansion" "SECID128"
19728 .cindex "repeated redirection expansion"
19729 .cindex "address redirection" "repeated for each delivery attempt"
19730 When a message cannot be delivered to all of its recipients immediately,
19731 leading to two or more delivery attempts, redirection expansion is carried out
19732 afresh each time for those addresses whose children were not all previously
19733 delivered. If redirection is being used as a mailing list, this can lead to new
19734 members of the list receiving copies of old messages. The &%one_time%& option
19735 can be used to avoid this.
19738 .section "Errors in redirection lists" "SECID129"
19739 .cindex "address redirection" "errors"
19740 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19741 error is skipped, and an entry is written to the main log. This may be useful
19742 for mailing lists that are automatically managed. Otherwise, if an error is
19743 detected while generating the list of new addresses, the original address is
19744 deferred. See also &%syntax_errors_to%&.
19748 .section "Private options for the redirect router" "SECID130"
19750 .cindex "options" "&(redirect)& router"
19751 The private options for the &(redirect)& router are as follows:
19754 .option allow_defer redirect boolean false
19755 Setting this option allows the use of &':defer:'& in non-filter redirection
19756 data, or the &%defer%& command in an Exim filter file.
19759 .option allow_fail redirect boolean false
19760 .cindex "failing delivery" "from filter"
19761 If this option is true, the &':fail:'& item can be used in a redirection list,
19762 and the &%fail%& command may be used in an Exim filter file.
19765 .option allow_filter redirect boolean false
19766 .cindex "filter" "enabling use of"
19767 .cindex "Sieve filter" "enabling use of"
19768 Setting this option allows Exim to interpret redirection data that starts with
19769 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19770 are some features of Exim filter files that some administrators may wish to
19771 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19773 It is also possible to lock out Exim filters or Sieve filters while allowing
19774 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19777 The filter is run using the uid and gid set by the generic &%user%& and
19778 &%group%& options. These take their defaults from the password data if
19779 &%check_local_user%& is set, so in the normal case of users' personal filter
19780 files, the filter is run as the relevant user. When &%allow_filter%& is set
19781 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19785 .option allow_freeze redirect boolean false
19786 .cindex "freezing messages" "allowing in filter"
19787 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19788 This command is more normally encountered in system filters, and is disabled by
19789 default for redirection filters because it isn't something you usually want to
19790 let ordinary users do.
19794 .option check_ancestor redirect boolean false
19795 This option is concerned with handling generated addresses that are the same
19796 as some address in the list of redirection ancestors of the current address.
19797 Although it is turned off by default in the code, it is set in the default
19798 configuration file for handling users' &_.forward_& files. It is recommended
19799 for this use of the &(redirect)& router.
19801 When &%check_ancestor%& is set, if a generated address (including the domain)
19802 is the same as any ancestor of the current address, it is replaced by a copy of
19803 the current address. This helps in the case where local part A is aliased to B,
19804 and B has a &_.forward_& file pointing back to A. For example, within a single
19805 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19806 &_&~jb/.forward_& contains:
19808 \Joe.Bloggs, <other item(s)>
19810 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19811 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19812 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19813 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19814 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19815 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19816 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19817 original address. See also the &%repeat_use%& option below.
19820 .option check_group redirect boolean "see below"
19821 When the &%file%& option is used, the group owner of the file is checked only
19822 when this option is set. The permitted groups are those listed in the
19823 &%owngroups%& option, together with the user's default group if
19824 &%check_local_user%& is set. If the file has the wrong group, routing is
19825 deferred. The default setting for this option is true if &%check_local_user%&
19826 is set and the &%modemask%& option permits the group write bit, or if the
19827 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19831 .option check_owner redirect boolean "see below"
19832 When the &%file%& option is used, the owner of the file is checked only when
19833 this option is set. If &%check_local_user%& is set, the local user is
19834 permitted; otherwise the owner must be one of those listed in the &%owners%&
19835 option. The default value for this option is true if &%check_local_user%& or
19836 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19839 .option data redirect string&!! unset
19840 This option is mutually exclusive with &%file%&. One or other of them must be
19841 set, but not both. The contents of &%data%& are expanded, and then used as the
19842 list of forwarding items, or as a set of filtering instructions. If the
19843 expansion is forced to fail, or the result is an empty string or a string that
19844 has no effect (consists entirely of comments), the router declines.
19846 When filtering instructions are used, the string must begin with &"#Exim
19847 filter"&, and all comments in the string, including this initial one, must be
19848 terminated with newline characters. For example:
19850 data = #Exim filter\n\
19851 if $h_to: contains Exim then save $home/mail/exim endif
19853 If you are reading the data from a database where newlines cannot be included,
19854 you can use the &${sg}$& expansion item to turn the escape string of your
19855 choice into a newline.
19858 .option directory_transport redirect string&!! unset
19859 A &(redirect)& router sets up a direct delivery to a directory when a path name
19860 ending with a slash is specified as a new &"address"&. The transport used is
19861 specified by this option, which, after expansion, must be the name of a
19862 configured transport. This should normally be an &(appendfile)& transport.
19865 .option file redirect string&!! unset
19866 This option specifies the name of a file that contains the redirection data. It
19867 is mutually exclusive with the &%data%& option. The string is expanded before
19868 use; if the expansion is forced to fail, the router declines. Other expansion
19869 failures cause delivery to be deferred. The result of a successful expansion
19870 must be an absolute path. The entire file is read and used as the redirection
19871 data. If the data is an empty string or a string that has no effect (consists
19872 entirely of comments), the router declines.
19874 .cindex "NFS" "checking for file existence"
19875 If the attempt to open the file fails with a &"does not exist"& error, Exim
19876 runs a check on the containing directory,
19877 unless &%ignore_enotdir%& is true (see below).
19878 If the directory does not appear to exist, delivery is deferred. This can
19879 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19880 is a mount problem. If the containing directory does exist, but the file does
19881 not, the router declines.
19884 .option file_transport redirect string&!! unset
19885 .vindex "&$address_file$&"
19886 A &(redirect)& router sets up a direct delivery to a file when a path name not
19887 ending in a slash is specified as a new &"address"&. The transport used is
19888 specified by this option, which, after expansion, must be the name of a
19889 configured transport. This should normally be an &(appendfile)& transport. When
19890 it is running, the file name is in &$address_file$&.
19893 .option filter_prepend_home redirect boolean true
19894 When this option is true, if a &(save)& command in an Exim filter specifies a
19895 relative path, and &$home$& is defined, it is automatically prepended to the
19896 relative path. If this option is set false, this action does not happen. The
19897 relative path is then passed to the transport unmodified.
19900 .option forbid_blackhole redirect boolean false
19901 If this option is true, the &':blackhole:'& item may not appear in a
19905 .option forbid_exim_filter redirect boolean false
19906 If this option is set true, only Sieve filters are permitted when
19907 &%allow_filter%& is true.
19912 .option forbid_file redirect boolean false
19913 .cindex "delivery" "to file; forbidding"
19914 .cindex "Sieve filter" "forbidding delivery to a file"
19915 .cindex "Sieve filter" "&""keep""& facility; disabling"
19916 If this option is true, this router may not generate a new address that
19917 specifies delivery to a local file or directory, either from a filter or from a
19918 conventional forward file. This option is forced to be true if &%one_time%& is
19919 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19920 locks out the Sieve's &"keep"& facility.
19923 .option forbid_filter_dlfunc redirect boolean false
19924 .cindex "filter" "locking out certain features"
19925 If this option is true, string expansions in Exim filters are not allowed to
19926 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19929 .option forbid_filter_existstest redirect boolean false
19930 .cindex "expansion" "statting a file"
19931 If this option is true, string expansions in Exim filters are not allowed to
19932 make use of the &%exists%& condition or the &%stat%& expansion item.
19934 .option forbid_filter_logwrite redirect boolean false
19935 If this option is true, use of the logging facility in Exim filters is not
19936 permitted. Logging is in any case available only if the filter is being run
19937 under some unprivileged uid (which is normally the case for ordinary users'
19938 &_.forward_& files).
19941 .option forbid_filter_lookup redirect boolean false
19942 If this option is true, string expansions in Exim filter files are not allowed
19943 to make use of &%lookup%& items.
19946 .option forbid_filter_perl redirect boolean false
19947 This option has an effect only if Exim is built with embedded Perl support. If
19948 it is true, string expansions in Exim filter files are not allowed to make use
19949 of the embedded Perl support.
19952 .option forbid_filter_readfile redirect boolean false
19953 If this option is true, string expansions in Exim filter files are not allowed
19954 to make use of &%readfile%& items.
19957 .option forbid_filter_readsocket redirect boolean false
19958 If this option is true, string expansions in Exim filter files are not allowed
19959 to make use of &%readsocket%& items.
19962 .option forbid_filter_reply redirect boolean false
19963 If this option is true, this router may not generate an automatic reply
19964 message. Automatic replies can be generated only from Exim or Sieve filter
19965 files, not from traditional forward files. This option is forced to be true if
19966 &%one_time%& is set.
19969 .option forbid_filter_run redirect boolean false
19970 If this option is true, string expansions in Exim filter files are not allowed
19971 to make use of &%run%& items.
19974 .option forbid_include redirect boolean false
19975 If this option is true, items of the form
19977 :include:<path name>
19979 are not permitted in non-filter redirection lists.
19982 .option forbid_pipe redirect boolean false
19983 .cindex "delivery" "to pipe; forbidding"
19984 If this option is true, this router may not generate a new address which
19985 specifies delivery to a pipe, either from an Exim filter or from a conventional
19986 forward file. This option is forced to be true if &%one_time%& is set.
19989 .option forbid_sieve_filter redirect boolean false
19990 If this option is set true, only Exim filters are permitted when
19991 &%allow_filter%& is true.
19994 .cindex "SMTP" "error codes"
19995 .option forbid_smtp_code redirect boolean false
19996 If this option is set true, any SMTP error codes that are present at the start
19997 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
19998 the default codes (451 and 550, respectively) are always used.
20003 .option hide_child_in_errmsg redirect boolean false
20004 .cindex "bounce message" "redirection details; suppressing"
20005 If this option is true, it prevents Exim from quoting a child address if it
20006 generates a bounce or delay message for it. Instead it says &"an address
20007 generated from <&'the top level address'&>"&. Of course, this applies only to
20008 bounces generated locally. If a message is forwarded to another host, &'its'&
20009 bounce may well quote the generated address.
20012 .option ignore_eacces redirect boolean false
20014 If this option is set and an attempt to open a redirection file yields the
20015 EACCES error (permission denied), the &(redirect)& router behaves as if the
20016 file did not exist.
20019 .option ignore_enotdir redirect boolean false
20021 If this option is set and an attempt to open a redirection file yields the
20022 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20023 router behaves as if the file did not exist.
20025 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20026 router that has the &%file%& option set discovers that the file does not exist
20027 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20028 against unmounted NFS directories. If the parent can not be statted, delivery
20029 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20030 is set, because that option tells Exim to ignore &"something on the path is not
20031 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20032 that some operating systems give ENOENT where others give ENOTDIR.
20036 .option include_directory redirect string unset
20037 If this option is set, the path names of any &':include:'& items in a
20038 redirection list must start with this directory.
20041 .option modemask redirect "octal integer" 022
20042 This specifies mode bits which must not be set for a file specified by the
20043 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20046 .option one_time redirect boolean false
20047 .cindex "one-time aliasing/forwarding expansion"
20048 .cindex "alias file" "one-time expansion"
20049 .cindex "forward file" "one-time expansion"
20050 .cindex "mailing lists" "one-time expansion"
20051 .cindex "address redirection" "one-time expansion"
20052 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20053 files each time it tries to deliver a message causes a problem when one or more
20054 of the generated addresses fails be delivered at the first attempt. The problem
20055 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20056 but of what happens when the redirection list changes during the time that the
20057 message is on Exim's queue. This is particularly true in the case of mailing
20058 lists, where new subscribers might receive copies of messages that were posted
20059 before they subscribed.
20061 If &%one_time%& is set and any addresses generated by the router fail to
20062 deliver at the first attempt, the failing addresses are added to the message as
20063 &"top level"& addresses, and the parent address that generated them is marked
20064 &"delivered"&. Thus, redirection does not happen again at the next delivery
20067 &*Warning 1*&: Any header line addition or removal that is specified by this
20068 router would be lost if delivery did not succeed at the first attempt. For this
20069 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20070 permitted when &%one_time%& is set.
20072 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20073 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20074 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20076 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20079 The original top-level address is remembered with each of the generated
20080 addresses, and is output in any log messages. However, any intermediate parent
20081 addresses are not recorded. This makes a difference to the log only if
20082 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20083 typically be used for mailing lists, where there is normally just one level of
20087 .option owners redirect "string list" unset
20088 .cindex "ownership" "alias file"
20089 .cindex "ownership" "forward file"
20090 .cindex "alias file" "ownership"
20091 .cindex "forward file" "ownership"
20092 This specifies a list of permitted owners for the file specified by &%file%&.
20093 This list is in addition to the local user when &%check_local_user%& is set.
20094 See &%check_owner%& above.
20097 .option owngroups redirect "string list" unset
20098 This specifies a list of permitted groups for the file specified by &%file%&.
20099 The list is in addition to the local user's primary group when
20100 &%check_local_user%& is set. See &%check_group%& above.
20103 .option pipe_transport redirect string&!! unset
20104 .vindex "&$address_pipe$&"
20105 A &(redirect)& router sets up a direct delivery to a pipe when a string
20106 starting with a vertical bar character is specified as a new &"address"&. The
20107 transport used is specified by this option, which, after expansion, must be the
20108 name of a configured transport. This should normally be a &(pipe)& transport.
20109 When the transport is run, the pipe command is in &$address_pipe$&.
20112 .option qualify_domain redirect string&!! unset
20113 .vindex "&$qualify_recipient$&"
20114 If this option is set, and an unqualified address (one without a domain) is
20115 generated, and that address would normally be qualified by the global setting
20116 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20117 expanding this string. If the expansion fails, the router declines. If you want
20118 to revert to the default, you can have the expansion generate
20119 &$qualify_recipient$&.
20121 This option applies to all unqualified addresses generated by Exim filters,
20122 but for traditional &_.forward_& files, it applies only to addresses that are
20123 not preceded by a backslash. Sieve filters cannot generate unqualified
20126 .option qualify_preserve_domain redirect boolean false
20127 .cindex "domain" "in redirection; preserving"
20128 .cindex "preserving domain in redirection"
20129 .cindex "address redirection" "domain; preserving"
20130 If this option is set, the router's local &%qualify_domain%& option must not be
20131 set (a configuration error occurs if it is). If an unqualified address (one
20132 without a domain) is generated, it is qualified with the domain of the parent
20133 address (the immediately preceding ancestor) instead of the global
20134 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20135 this applies whether or not the address is preceded by a backslash.
20138 .option repeat_use redirect boolean true
20139 If this option is set false, the router is skipped for a child address that has
20140 any ancestor that was routed by this router. This test happens before any of
20141 the other preconditions are tested. Exim's default anti-looping rules skip
20142 only when the ancestor is the same as the current address. See also
20143 &%check_ancestor%& above and the generic &%redirect_router%& option.
20146 .option reply_transport redirect string&!! unset
20147 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20148 &%vacation%& command is used in a filter file. The transport used is specified
20149 by this option, which, after expansion, must be the name of a configured
20150 transport. This should normally be an &(autoreply)& transport. Other transports
20151 are unlikely to do anything sensible or useful.
20154 .option rewrite redirect boolean true
20155 .cindex "address redirection" "disabling rewriting"
20156 If this option is set false, addresses generated by the router are not
20157 subject to address rewriting. Otherwise, they are treated like new addresses
20158 and are rewritten according to the global rewriting rules.
20161 .option sieve_subaddress redirect string&!! unset
20162 The value of this option is passed to a Sieve filter to specify the
20163 :subaddress part of an address.
20165 .option sieve_useraddress redirect string&!! unset
20166 The value of this option is passed to a Sieve filter to specify the :user part
20167 of an address. However, if it is unset, the entire original local part
20168 (including any prefix or suffix) is used for :user.
20171 .option sieve_vacation_directory redirect string&!! unset
20172 .cindex "Sieve filter" "vacation directory"
20173 To enable the &"vacation"& extension for Sieve filters, you must set
20174 &%sieve_vacation_directory%& to the directory where vacation databases are held
20175 (do not put anything else in that directory), and ensure that the
20176 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20177 needs their own directory; Exim will create it if necessary.
20181 .option skip_syntax_errors redirect boolean false
20182 .cindex "forward file" "broken"
20183 .cindex "address redirection" "broken files"
20184 .cindex "alias file" "broken"
20185 .cindex "broken alias or forward files"
20186 .cindex "ignoring faulty addresses"
20187 .cindex "skipping faulty addresses"
20188 .cindex "error" "skipping bad syntax"
20189 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20190 non-filter redirection data are skipped, and each failing address is logged. If
20191 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20192 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20193 are expanded and placed at the head of the error message generated by
20194 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20195 be the same address as the generic &%errors_to%& option. The
20196 &%skip_syntax_errors%& option is often used when handling mailing lists.
20198 If all the addresses in a redirection list are skipped because of syntax
20199 errors, the router declines to handle the original address, and it is passed to
20200 the following routers.
20202 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20203 error in the filter causes filtering to be abandoned without any action being
20204 taken. The incident is logged, and the router declines to handle the address,
20205 so it is passed to the following routers.
20207 .cindex "Sieve filter" "syntax errors in"
20208 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20209 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20210 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20212 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20213 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20214 option, used with an address that does not get redirected, can be used to
20215 notify users of these errors, by means of a router like this:
20221 file = $home/.forward
20222 file_transport = address_file
20223 pipe_transport = address_pipe
20224 reply_transport = address_reply
20227 syntax_errors_to = real-$local_part@$domain
20228 syntax_errors_text = \
20229 This is an automatically generated message. An error has\n\
20230 been found in your .forward file. Details of the error are\n\
20231 reported below. While this error persists, you will receive\n\
20232 a copy of this message for every message that is addressed\n\
20233 to you. If your .forward file is a filter file, or if it is\n\
20234 a non-filter file containing no valid forwarding addresses,\n\
20235 a copy of each incoming message will be put in your normal\n\
20236 mailbox. If a non-filter file contains at least one valid\n\
20237 forwarding address, forwarding to the valid addresses will\n\
20238 happen, and those will be the only deliveries that occur.
20240 You also need a router to ensure that local addresses that are prefixed by
20241 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20242 put this immediately before the &(userforward)& router:
20247 local_part_prefix = real-
20248 transport = local_delivery
20250 For security, it would probably be a good idea to restrict the use of this
20251 router to locally-generated messages, using a condition such as this:
20253 condition = ${if match {$sender_host_address}\
20254 {\N^(|127\.0\.0\.1)$\N}}
20258 .option syntax_errors_text redirect string&!! unset
20259 See &%skip_syntax_errors%& above.
20262 .option syntax_errors_to redirect string unset
20263 See &%skip_syntax_errors%& above.
20264 .ecindex IIDredrou1
20265 .ecindex IIDredrou2
20272 . ////////////////////////////////////////////////////////////////////////////
20273 . ////////////////////////////////////////////////////////////////////////////
20275 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20276 "Environment for local transports"
20277 .scindex IIDenvlotra1 "local transports" "environment for"
20278 .scindex IIDenvlotra2 "environment for local transports"
20279 .scindex IIDenvlotra3 "transport" "local; environment for"
20280 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20281 transport can be thought of as similar to a pipe.) Exim always runs transports
20282 in subprocesses, under specified uids and gids. Typical deliveries to local
20283 mailboxes run under the uid and gid of the local user.
20285 Exim also sets a specific current directory while running the transport; for
20286 some transports a home directory setting is also relevant. The &(pipe)&
20287 transport is the only one that sets up environment variables; see section
20288 &<<SECTpipeenv>>& for details.
20290 The values used for the uid, gid, and the directories may come from several
20291 different places. In many cases, the router that handles the address associates
20292 settings with that address as a result of its &%check_local_user%&, &%group%&,
20293 or &%user%& options. However, values may also be given in the transport's own
20294 configuration, and these override anything that comes from the router.
20298 .section "Concurrent deliveries" "SECID131"
20299 .cindex "concurrent deliveries"
20300 .cindex "simultaneous deliveries"
20301 If two different messages for the same local recipient arrive more or less
20302 simultaneously, the two delivery processes are likely to run concurrently. When
20303 the &(appendfile)& transport is used to write to a file, Exim applies locking
20304 rules to stop concurrent processes from writing to the same file at the same
20307 However, when you use a &(pipe)& transport, it is up to you to arrange any
20308 locking that is needed. Here is a silly example:
20312 command = /bin/sh -c 'cat >>/some/file'
20314 This is supposed to write the message at the end of the file. However, if two
20315 messages arrive at the same time, the file will be scrambled. You can use the
20316 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20317 file using the same algorithm that Exim itself uses.
20322 .section "Uids and gids" "SECTenvuidgid"
20323 .cindex "local transports" "uid and gid"
20324 .cindex "transport" "local; uid and gid"
20325 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20326 overrides any group that the router set in the address, even if &%user%& is not
20327 set for the transport. This makes it possible, for example, to run local mail
20328 delivery under the uid of the recipient (set by the router), but in a special
20329 group (set by the transport). For example:
20332 # User/group are set by check_local_user in this router
20336 transport = group_delivery
20339 # This transport overrides the group
20341 driver = appendfile
20342 file = /var/spool/mail/$local_part
20345 If &%user%& is set for a transport, its value overrides what is set in the
20346 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20347 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20350 .oindex "&%initgroups%&"
20351 When the uid is taken from the transport's configuration, the &[initgroups()]&
20352 function is called for the groups associated with that uid if the
20353 &%initgroups%& option is set for the transport. When the uid is not specified
20354 by the transport, but is associated with the address by a router, the option
20355 for calling &[initgroups()]& is taken from the router configuration.
20357 .cindex "&(pipe)& transport" "uid for"
20358 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20359 is set and &%user%& is not set, the uid of the process that called Exim to
20360 receive the message is used, and if &%group%& is not set, the corresponding
20361 original gid is also used.
20363 This is the detailed preference order for obtaining a gid; the first of the
20364 following that is set is used:
20367 A &%group%& setting of the transport;
20369 A &%group%& setting of the router;
20371 A gid associated with a user setting of the router, either as a result of
20372 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20374 The group associated with a non-numeric &%user%& setting of the transport;
20376 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20377 the uid is the creator's uid;
20379 The Exim gid if the Exim uid is being used as a default.
20382 If, for example, the user is specified numerically on the router and there are
20383 no group settings, no gid is available. In this situation, an error occurs.
20384 This is different for the uid, for which there always is an ultimate default.
20385 The first of the following that is set is used:
20388 A &%user%& setting of the transport;
20390 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20392 A &%user%& setting of the router;
20394 A &%check_local_user%& setting of the router;
20399 Of course, an error will still occur if the uid that is chosen is on the
20400 &%never_users%& list.
20406 .section "Current and home directories" "SECID132"
20407 .cindex "current directory for local transport"
20408 .cindex "home directory" "for local transport"
20409 .cindex "transport" "local; home directory for"
20410 .cindex "transport" "local; current directory for"
20411 Routers may set current and home directories for local transports by means of
20412 the &%transport_current_directory%& and &%transport_home_directory%& options.
20413 However, if the transport's &%current_directory%& or &%home_directory%& options
20414 are set, they override the router's values. In detail, the home directory
20415 for a local transport is taken from the first of these values that is set:
20418 The &%home_directory%& option on the transport;
20420 The &%transport_home_directory%& option on the router;
20422 The password data if &%check_local_user%& is set on the router;
20424 The &%router_home_directory%& option on the router.
20427 The current directory is taken from the first of these values that is set:
20430 The &%current_directory%& option on the transport;
20432 The &%transport_current_directory%& option on the router.
20436 If neither the router nor the transport sets a current directory, Exim uses the
20437 value of the home directory, if it is set. Otherwise it sets the current
20438 directory to &_/_& before running a local transport.
20442 .section "Expansion variables derived from the address" "SECID133"
20443 .vindex "&$domain$&"
20444 .vindex "&$local_part$&"
20445 .vindex "&$original_domain$&"
20446 Normally a local delivery is handling a single address, and in that case the
20447 variables such as &$domain$& and &$local_part$& are set during local
20448 deliveries. However, in some circumstances more than one address may be handled
20449 at once (for example, while writing batch SMTP for onward transmission by some
20450 other means). In this case, the variables associated with the local part are
20451 never set, &$domain$& is set only if all the addresses have the same domain,
20452 and &$original_domain$& is never set.
20453 .ecindex IIDenvlotra1
20454 .ecindex IIDenvlotra2
20455 .ecindex IIDenvlotra3
20463 . ////////////////////////////////////////////////////////////////////////////
20464 . ////////////////////////////////////////////////////////////////////////////
20466 .chapter "Generic options for transports" "CHAPtransportgeneric"
20467 .scindex IIDgenoptra1 "generic options" "transport"
20468 .scindex IIDgenoptra2 "options" "generic; for transports"
20469 .scindex IIDgenoptra3 "transport" "generic options for"
20470 The following generic options apply to all transports:
20473 .option body_only transports boolean false
20474 .cindex "transport" "body only"
20475 .cindex "message" "transporting body only"
20476 .cindex "body of message" "transporting"
20477 If this option is set, the message's headers are not transported. It is
20478 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20479 or &(pipe)& transports, the settings of &%message_prefix%& and
20480 &%message_suffix%& should be checked, because this option does not
20481 automatically suppress them.
20484 .option current_directory transports string&!! unset
20485 .cindex "transport" "current directory for"
20486 This specifies the current directory that is to be set while running the
20487 transport, overriding any value that may have been set by the router.
20488 If the expansion fails for any reason, including forced failure, an error is
20489 logged, and delivery is deferred.
20492 .option disable_logging transports boolean false
20493 If this option is set true, nothing is logged for any
20494 deliveries by the transport or for any
20495 transport errors. You should not set this option unless you really, really know
20496 what you are doing.
20499 .option debug_print transports string&!! unset
20500 .cindex "testing" "variables in drivers"
20501 If this option is set and debugging is enabled (see the &%-d%& command line
20502 option), the string is expanded and included in the debugging output when the
20504 If expansion of the string fails, the error message is written to the debugging
20505 output, and Exim carries on processing.
20506 This facility is provided to help with checking out the values of variables and
20507 so on when debugging driver configurations. For example, if a &%headers_add%&
20508 option is not working properly, &%debug_print%& could be used to output the
20509 variables it references. A newline is added to the text if it does not end with
20511 The variables &$transport_name$& and &$router_name$& contain the name of the
20512 transport and the router that called it.
20514 .option delivery_date_add transports boolean false
20515 .cindex "&'Delivery-date:'& header line"
20516 If this option is true, a &'Delivery-date:'& header is added to the message.
20517 This gives the actual time the delivery was made. As this is not a standard
20518 header, Exim has a configuration option (&%delivery_date_remove%&) which
20519 requests its removal from incoming messages, so that delivered messages can
20520 safely be resent to other recipients.
20523 .option driver transports string unset
20524 This specifies which of the available transport drivers is to be used.
20525 There is no default, and this option must be set for every transport.
20528 .option envelope_to_add transports boolean false
20529 .cindex "&'Envelope-to:'& header line"
20530 If this option is true, an &'Envelope-to:'& header is added to the message.
20531 This gives the original address(es) in the incoming envelope that caused this
20532 delivery to happen. More than one address may be present if the transport is
20533 configured to handle several addresses at once, or if more than one original
20534 address was redirected to the same final address. As this is not a standard
20535 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20536 its removal from incoming messages, so that delivered messages can safely be
20537 resent to other recipients.
20540 .option group transports string&!! "Exim group"
20541 .cindex "transport" "group; specifying"
20542 This option specifies a gid for running the transport process, overriding any
20543 value that the router supplies, and also overriding any value associated with
20544 &%user%& (see below).
20547 .option headers_add transports list&!! unset
20548 .cindex "header lines" "adding in transport"
20549 .cindex "transport" "header lines; adding"
20550 This option specifies a list of text headers,
20552 newline-separated (by default, changeable in the usual way),
20554 which are (separately) expanded and added to the header
20555 portion of a message as it is transported, as described in section
20556 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20557 routers. If the result of the expansion is an empty string, or if the expansion
20558 is forced to fail, no action is taken. Other expansion failures are treated as
20559 errors and cause the delivery to be deferred.
20561 Unlike most options, &%headers_add%& can be specified multiple times
20562 for a transport; all listed headers are added.
20565 .option headers_only transports boolean false
20566 .cindex "transport" "header lines only"
20567 .cindex "message" "transporting headers only"
20568 .cindex "header lines" "transporting"
20569 If this option is set, the message's body is not transported. It is mutually
20570 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20571 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20572 checked, since this option does not automatically suppress them.
20575 .option headers_remove transports list&!! unset
20576 .cindex "header lines" "removing"
20577 .cindex "transport" "header lines; removing"
20578 This option specifies a list of header names,
20580 colon-separated (by default, changeable in the usual way);
20582 these headers are omitted from the message as it is transported, as described
20583 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20585 Each list item is separately expanded.
20586 If the result of the expansion is an empty string, or if the expansion
20587 is forced to fail, no action is taken. Other expansion failures are treated as
20588 errors and cause the delivery to be deferred.
20590 Unlike most options, &%headers_remove%& can be specified multiple times
20591 for a router; all listed headers are removed.
20593 &*Warning*&: Because of the separate expansion of the list items,
20594 items that contain a list separator must have it doubled.
20595 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20599 .option headers_rewrite transports string unset
20600 .cindex "transport" "header lines; rewriting"
20601 .cindex "rewriting" "at transport time"
20602 This option allows addresses in header lines to be rewritten at transport time,
20603 that is, as the message is being copied to its destination. The contents of the
20604 option are a colon-separated list of rewriting rules. Each rule is in exactly
20605 the same form as one of the general rewriting rules that are applied when a
20606 message is received. These are described in chapter &<<CHAPrewrite>>&. For
20609 headers_rewrite = a@b c@d f : \
20612 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
20613 &'w@z'& in all address-bearing header lines. The rules are applied to the
20614 header lines just before they are written out at transport time, so they affect
20615 only those copies of the message that pass through the transport. However, only
20616 the message's original header lines, and any that were added by a system
20617 filter, are rewritten. If a router or transport adds header lines, they are not
20618 affected by this option. These rewriting rules are &'not'& applied to the
20619 envelope. You can change the return path using &%return_path%&, but you cannot
20620 change envelope recipients at this time.
20623 .option home_directory transports string&!! unset
20624 .cindex "transport" "home directory for"
20626 This option specifies a home directory setting for a local transport,
20627 overriding any value that may be set by the router. The home directory is
20628 placed in &$home$& while expanding the transport's private options. It is also
20629 used as the current directory if no current directory is set by the
20630 &%current_directory%& option on the transport or the
20631 &%transport_current_directory%& option on the router. If the expansion fails
20632 for any reason, including forced failure, an error is logged, and delivery is
20636 .option initgroups transports boolean false
20637 .cindex "additional groups"
20638 .cindex "groups" "additional"
20639 .cindex "transport" "group; additional"
20640 If this option is true and the uid for the delivery process is provided by the
20641 transport, the &[initgroups()]& function is called when running the transport
20642 to ensure that any additional groups associated with the uid are set up.
20645 .option message_size_limit transports string&!! 0
20646 .cindex "limit" "message size per transport"
20647 .cindex "size" "of message, limit"
20648 .cindex "transport" "message size; limiting"
20649 This option controls the size of messages passed through the transport. It is
20650 expanded before use; the result of the expansion must be a sequence of decimal
20651 digits, optionally followed by K or M. If the expansion fails for any reason,
20652 including forced failure, or if the result is not of the required form,
20653 delivery is deferred. If the value is greater than zero and the size of a
20654 message exceeds this limit, the address is failed. If there is any chance that
20655 the resulting bounce message could be routed to the same transport, you should
20656 ensure that &%return_size_limit%& is less than the transport's
20657 &%message_size_limit%&, as otherwise the bounce message will fail to get
20662 .option rcpt_include_affixes transports boolean false
20663 .cindex "prefix" "for local part, including in envelope"
20664 .cindex "suffix for local part" "including in envelope"
20665 .cindex "local part" "prefix"
20666 .cindex "local part" "suffix"
20667 When this option is false (the default), and an address that has had any
20668 affixes (prefixes or suffixes) removed from the local part is delivered by any
20669 form of SMTP or LMTP, the affixes are not included. For example, if a router
20672 local_part_prefix = *-
20674 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
20677 RCPT TO:<xyz@some.domain>
20679 This is also the case when an ACL-time callout is being used to verify a
20680 recipient address. However, if &%rcpt_include_affixes%& is set true, the
20681 whole local part is included in the RCPT command. This option applies to BSMTP
20682 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
20683 &(lmtp)& and &(smtp)& transports.
20686 .option retry_use_local_part transports boolean "see below"
20687 .cindex "hints database" "retry keys"
20688 When a delivery suffers a temporary failure, a retry record is created
20689 in Exim's hints database. For remote deliveries, the key for the retry record
20690 is based on the name and/or IP address of the failing remote host. For local
20691 deliveries, the key is normally the entire address, including both the local
20692 part and the domain. This is suitable for most common cases of local delivery
20693 temporary failure &-- for example, exceeding a mailbox quota should delay only
20694 deliveries to that mailbox, not to the whole domain.
20696 However, in some special cases you may want to treat a temporary local delivery
20697 as a failure associated with the domain, and not with a particular local part.
20698 (For example, if you are storing all mail for some domain in files.) You can do
20699 this by setting &%retry_use_local_part%& false.
20701 For all the local transports, its default value is true. For remote transports,
20702 the default value is false for tidiness, but changing the value has no effect
20703 on a remote transport in the current implementation.
20706 .option return_path transports string&!! unset
20707 .cindex "envelope sender"
20708 .cindex "transport" "return path; changing"
20709 .cindex "return path" "changing in transport"
20710 If this option is set, the string is expanded at transport time and replaces
20711 the existing return path (envelope sender) value in the copy of the message
20712 that is being delivered. An empty return path is permitted. This feature is
20713 designed for remote deliveries, where the value of this option is used in the
20714 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20715 only effect is to change the address that is placed in the &'Return-path:'&
20716 header line, if one is added to the message (see the next option).
20718 &*Note:*& A changed return path is not logged unless you add
20719 &%return_path_on_delivery%& to the log selector.
20721 .vindex "&$return_path$&"
20722 The expansion can refer to the existing value via &$return_path$&. This is
20723 either the message's envelope sender, or an address set by the
20724 &%errors_to%& option on a router. If the expansion is forced to fail, no
20725 replacement occurs; if it fails for another reason, delivery is deferred. This
20726 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20727 section &<<SECTverp>>&.
20729 &*Note*&: If a delivery error is detected locally, including the case when a
20730 remote server rejects a message at SMTP time, the bounce message is not sent to
20731 the value of this option. It is sent to the previously set errors address.
20732 This defaults to the incoming sender address, but can be changed by setting
20733 &%errors_to%& in a router.
20737 .option return_path_add transports boolean false
20738 .cindex "&'Return-path:'& header line"
20739 If this option is true, a &'Return-path:'& header is added to the message.
20740 Although the return path is normally available in the prefix line of BSD
20741 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20742 have easy access to it.
20744 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20745 the delivery SMTP server makes the final delivery"&. This implies that this
20746 header should not be present in incoming messages. Exim has a configuration
20747 option, &%return_path_remove%&, which requests removal of this header from
20748 incoming messages, so that delivered messages can safely be resent to other
20752 .option shadow_condition transports string&!! unset
20753 See &%shadow_transport%& below.
20756 .option shadow_transport transports string unset
20757 .cindex "shadow transport"
20758 .cindex "transport" "shadow"
20759 A local transport may set the &%shadow_transport%& option to the name of
20760 another local transport. Shadow remote transports are not supported.
20762 Whenever a delivery to the main transport succeeds, and either
20763 &%shadow_condition%& is unset, or its expansion does not result in the empty
20764 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20765 passed to the shadow transport, with the same delivery address or addresses. If
20766 expansion fails, no action is taken except that non-forced expansion failures
20767 cause a log line to be written.
20769 The result of the shadow transport is discarded and does not affect the
20770 subsequent processing of the message. Only a single level of shadowing is
20771 provided; the &%shadow_transport%& option is ignored on any transport when it
20772 is running as a shadow. Options concerned with output from pipes are also
20773 ignored. The log line for the successful delivery has an item added on the end,
20776 ST=<shadow transport name>
20778 If the shadow transport did not succeed, the error message is put in
20779 parentheses afterwards. Shadow transports can be used for a number of different
20780 purposes, including keeping more detailed log information than Exim normally
20781 provides, and implementing automatic acknowledgment policies based on message
20782 headers that some sites insist on.
20785 .option transport_filter transports string&!! unset
20786 .cindex "transport" "filter"
20787 .cindex "filter" "transport filter"
20788 This option sets up a filtering (in the Unix shell sense) process for messages
20789 at transport time. It should not be confused with mail filtering as set up by
20790 individual users or via a system filter.
20792 When the message is about to be written out, the command specified by
20793 &%transport_filter%& is started up in a separate, parallel process, and
20794 the entire message, including the header lines, is passed to it on its standard
20795 input (this in fact is done from a third process, to avoid deadlock). The
20796 command must be specified as an absolute path.
20798 The lines of the message that are written to the transport filter are
20799 terminated by newline (&"\n"&). The message is passed to the filter before any
20800 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20801 lines beginning with a dot, and also before any processing implied by the
20802 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20803 &(pipe)& transports.
20805 The standard error for the filter process is set to the same destination as its
20806 standard output; this is read and written to the message's ultimate
20807 destination. The process that writes the message to the filter, the
20808 filter itself, and the original process that reads the result and delivers it
20809 are all run in parallel, like a shell pipeline.
20811 The filter can perform any transformations it likes, but of course should take
20812 care not to break RFC 2822 syntax. Exim does not check the result, except to
20813 test for a final newline when SMTP is in use. All messages transmitted over
20814 SMTP must end with a newline, so Exim supplies one if it is missing.
20816 .cindex "content scanning" "per user"
20817 A transport filter can be used to provide content-scanning on a per-user basis
20818 at delivery time if the only required effect of the scan is to modify the
20819 message. For example, a content scan could insert a new header line containing
20820 a spam score. This could be interpreted by a filter in the user's MUA. It is
20821 not possible to discard a message at this stage.
20823 .cindex "SMTP" "SIZE"
20824 A problem might arise if the filter increases the size of a message that is
20825 being sent down an SMTP connection. If the receiving SMTP server has indicated
20826 support for the SIZE parameter, Exim will have sent the size of the message
20827 at the start of the SMTP session. If what is actually sent is substantially
20828 more, the server might reject the message. This can be worked round by setting
20829 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20830 additions to the message, or to disable the use of SIZE altogether.
20832 .vindex "&$pipe_addresses$&"
20833 The value of the &%transport_filter%& option is the command string for starting
20834 the filter, which is run directly from Exim, not under a shell. The string is
20835 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20836 Exim breaks it up into arguments and then expands each argument separately (see
20837 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20838 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20839 of arguments, one for each address that applies to this delivery. (This isn't
20840 an ideal name for this feature here, but as it was already implemented for the
20841 &(pipe)& transport, it seemed sensible not to change it.)
20844 .vindex "&$host_address$&"
20845 The expansion variables &$host$& and &$host_address$& are available when the
20846 transport is a remote one. They contain the name and IP address of the host to
20847 which the message is being sent. For example:
20849 transport_filter = /some/directory/transport-filter.pl \
20850 $host $host_address $sender_address $pipe_addresses
20853 Two problems arise if you want to use more complicated expansion items to
20854 generate transport filter commands, both of which due to the fact that the
20855 command is split up &'before'& expansion.
20857 If an expansion item contains white space, you must quote it, so that it is all
20858 part of the same command item. If the entire option setting is one such
20859 expansion item, you have to take care what kind of quoting you use. For
20862 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20864 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20865 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20866 stripped by Exim when it read the option's value. When the value is used, if
20867 the single quotes were missing, the line would be split into two items,
20868 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20869 Exim tried to expand the first one.
20871 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20872 expansion cannot generate multiple arguments, or a command name followed by
20873 arguments. Consider this example:
20875 transport_filter = ${lookup{$host}lsearch{/a/file}\
20876 {$value}{/bin/cat}}
20878 The result of the lookup is interpreted as the name of the command, even
20879 if it contains white space. The simplest way round this is to use a shell:
20881 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20882 {$value}{/bin/cat}}
20886 The filter process is run under the same uid and gid as the normal delivery.
20887 For remote deliveries this is the Exim uid/gid by default. The command should
20888 normally yield a zero return code. Transport filters are not supposed to fail.
20889 A non-zero code is taken to mean that the transport filter encountered some
20890 serious problem. Delivery of the message is deferred; the message remains on
20891 the queue and is tried again later. It is not possible to cause a message to be
20892 bounced from a transport filter.
20894 If a transport filter is set on an autoreply transport, the original message is
20895 passed through the filter as it is being copied into the newly generated
20896 message, which happens if the &%return_message%& option is set.
20899 .option transport_filter_timeout transports time 5m
20900 .cindex "transport" "filter, timeout"
20901 When Exim is reading the output of a transport filter, it applies a timeout
20902 that can be set by this option. Exceeding the timeout is normally treated as a
20903 temporary delivery failure. However, if a transport filter is used with a
20904 &(pipe)& transport, a timeout in the transport filter is treated in the same
20905 way as a timeout in the pipe command itself. By default, a timeout is a hard
20906 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20907 becomes a temporary error.
20910 .option user transports string&!! "Exim user"
20911 .cindex "uid (user id)" "local delivery"
20912 .cindex "transport" "user, specifying"
20913 This option specifies the user under whose uid the delivery process is to be
20914 run, overriding any uid that may have been set by the router. If the user is
20915 given as a name, the uid is looked up from the password data, and the
20916 associated group is taken as the value of the gid to be used if the &%group%&
20919 For deliveries that use local transports, a user and group are normally
20920 specified explicitly or implicitly (for example, as a result of
20921 &%check_local_user%&) by the router or transport.
20923 .cindex "hints database" "access by remote transport"
20924 For remote transports, you should leave this option unset unless you really are
20925 sure you know what you are doing. When a remote transport is running, it needs
20926 to be able to access Exim's hints databases, because each host may have its own
20928 .ecindex IIDgenoptra1
20929 .ecindex IIDgenoptra2
20930 .ecindex IIDgenoptra3
20937 . ////////////////////////////////////////////////////////////////////////////
20938 . ////////////////////////////////////////////////////////////////////////////
20940 .chapter "Address batching in local transports" "CHAPbatching" &&&
20942 .cindex "transport" "local; address batching in"
20943 The only remote transport (&(smtp)&) is normally configured to handle more than
20944 one address at a time, so that when several addresses are routed to the same
20945 remote host, just one copy of the message is sent. Local transports, however,
20946 normally handle one address at a time. That is, a separate instance of the
20947 transport is run for each address that is routed to the transport. A separate
20948 copy of the message is delivered each time.
20950 .cindex "batched local delivery"
20951 .oindex "&%batch_max%&"
20952 .oindex "&%batch_id%&"
20953 In special cases, it may be desirable to handle several addresses at once in a
20954 local transport, for example:
20957 In an &(appendfile)& transport, when storing messages in files for later
20958 delivery by some other means, a single copy of the message with multiple
20959 recipients saves space.
20961 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
20962 a single copy saves time, and is the normal way LMTP is expected to work.
20964 In a &(pipe)& transport, when passing the message
20965 to a scanner program or
20966 to some other delivery mechanism such as UUCP, multiple recipients may be
20970 These three local transports all have the same options for controlling multiple
20971 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
20972 repeating the information for each transport, these options are described here.
20974 The &%batch_max%& option specifies the maximum number of addresses that can be
20975 delivered together in a single run of the transport. Its default value is one
20976 (no batching). When more than one address is routed to a transport that has a
20977 &%batch_max%& value greater than one, the addresses are delivered in a batch
20978 (that is, in a single run of the transport with multiple recipients), subject
20979 to certain conditions:
20982 .vindex "&$local_part$&"
20983 If any of the transport's options contain a reference to &$local_part$&, no
20984 batching is possible.
20986 .vindex "&$domain$&"
20987 If any of the transport's options contain a reference to &$domain$&, only
20988 addresses with the same domain are batched.
20990 .cindex "customizing" "batching condition"
20991 If &%batch_id%& is set, it is expanded for each address, and only those
20992 addresses with the same expanded value are batched. This allows you to specify
20993 customized batching conditions. Failure of the expansion for any reason,
20994 including forced failure, disables batching, but it does not stop the delivery
20997 Batched addresses must also have the same errors address (where to send
20998 delivery errors), the same header additions and removals, the same user and
20999 group for the transport, and if a host list is present, the first host must
21003 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21004 both when the file or pipe command is specified in the transport, and when it
21005 is specified by a &(redirect)& router, but all the batched addresses must of
21006 course be routed to the same file or pipe command. These two transports have an
21007 option called &%use_bsmtp%&, which causes them to deliver the message in
21008 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21009 &%check_string%& and &%escape_string%& options are forced to the values
21012 escape_string = ".."
21014 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21015 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21016 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21018 .cindex "&'Envelope-to:'& header line"
21019 If the generic &%envelope_to_add%& option is set for a batching transport, the
21020 &'Envelope-to:'& header that is added to the message contains all the addresses
21021 that are being processed together. If you are using a batching &(appendfile)&
21022 transport without &%use_bsmtp%&, the only way to preserve the recipient
21023 addresses is to set the &%envelope_to_add%& option.
21025 .cindex "&(pipe)& transport" "with multiple addresses"
21026 .vindex "&$pipe_addresses$&"
21027 If you are using a &(pipe)& transport without BSMTP, and setting the
21028 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21029 the command. This is not a true variable; it is a bit of magic that causes each
21030 of the recipient addresses to be inserted into the command as a separate
21031 argument. This provides a way of accessing all the addresses that are being
21032 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21033 are specified by a &(redirect)& router.
21038 . ////////////////////////////////////////////////////////////////////////////
21039 . ////////////////////////////////////////////////////////////////////////////
21041 .chapter "The appendfile transport" "CHAPappendfile"
21042 .scindex IIDapptra1 "&(appendfile)& transport"
21043 .scindex IIDapptra2 "transports" "&(appendfile)&"
21044 .cindex "directory creation"
21045 .cindex "creating directories"
21046 The &(appendfile)& transport delivers a message by appending it to an existing
21047 file, or by creating an entirely new file in a specified directory. Single
21048 files to which messages are appended can be in the traditional Unix mailbox
21049 format, or optionally in the MBX format supported by the Pine MUA and
21050 University of Washington IMAP daemon, &'inter alia'&. When each message is
21051 being delivered as a separate file, &"maildir"& format can optionally be used
21052 to give added protection against failures that happen part-way through the
21053 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21054 supported. For all file formats, Exim attempts to create as many levels of
21055 directory as necessary, provided that &%create_directory%& is set.
21057 The code for the optional formats is not included in the Exim binary by
21058 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21059 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21062 .cindex "quota" "system"
21063 Exim recognizes system quota errors, and generates an appropriate message. Exim
21064 also supports its own quota control within the transport, for use when the
21065 system facility is unavailable or cannot be used for some reason.
21067 If there is an error while appending to a file (for example, quota exceeded or
21068 partition filled), Exim attempts to reset the file's length and last
21069 modification time back to what they were before. If there is an error while
21070 creating an entirely new file, the new file is removed.
21072 Before appending to a file, a number of security checks are made, and the
21073 file is locked. A detailed description is given below, after the list of
21076 The &(appendfile)& transport is most commonly used for local deliveries to
21077 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21078 putting messages into files for remote delivery by some means other than Exim.
21079 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21084 .section "The file and directory options" "SECTfildiropt"
21085 The &%file%& option specifies a single file, to which the message is appended;
21086 the &%directory%& option specifies a directory, in which a new file containing
21087 the message is created. Only one of these two options can be set, and for
21088 normal deliveries to mailboxes, one of them &'must'& be set.
21090 .vindex "&$address_file$&"
21091 .vindex "&$local_part$&"
21092 However, &(appendfile)& is also used for delivering messages to files or
21093 directories whose names (or parts of names) are obtained from alias,
21094 forwarding, or filtering operations (for example, a &%save%& command in a
21095 user's Exim filter). When such a transport is running, &$local_part$& contains
21096 the local part that was aliased or forwarded, and &$address_file$& contains the
21097 name (or partial name) of the file or directory generated by the redirection
21098 operation. There are two cases:
21101 If neither &%file%& nor &%directory%& is set, the redirection operation
21102 must specify an absolute path (one that begins with &`/`&). This is the most
21103 common case when users with local accounts use filtering to sort mail into
21104 different folders. See for example, the &(address_file)& transport in the
21105 default configuration. If the path ends with a slash, it is assumed to be the
21106 name of a directory. A delivery to a directory can also be forced by setting
21107 &%maildir_format%& or &%mailstore_format%&.
21109 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21110 used to determine the file or directory name for the delivery. Normally, the
21111 contents of &$address_file$& are used in some way in the string expansion.
21115 .cindex "Sieve filter" "configuring &(appendfile)&"
21116 .cindex "Sieve filter" "relative mailbox path handling"
21117 As an example of the second case, consider an environment where users do not
21118 have home directories. They may be permitted to use Exim filter commands of the
21123 or Sieve filter commands of the form:
21125 require "fileinto";
21126 fileinto "folder23";
21128 In this situation, the expansion of &%file%& or &%directory%& in the transport
21129 must transform the relative path into an appropriate absolute file name. In the
21130 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21131 is used as a result of a &"keep"& action in the filter. This example shows one
21132 way of handling this requirement:
21134 file = ${if eq{$address_file}{inbox} \
21135 {/var/mail/$local_part} \
21136 {${if eq{${substr_0_1:$address_file}}{/} \
21138 {$home/mail/$address_file} \
21142 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21143 location, absolute paths are used without change, and other folders are in the
21144 &_mail_& directory within the home directory.
21146 &*Note 1*&: While processing an Exim filter, a relative path such as
21147 &_folder23_& is turned into an absolute path if a home directory is known to
21148 the router. In particular, this is the case if &%check_local_user%& is set. If
21149 you want to prevent this happening at routing time, you can set
21150 &%router_home_directory%& empty. This forces the router to pass the relative
21151 path to the transport.
21153 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21154 the &%file%& or &%directory%& option is still used if it is set.
21159 .section "Private options for appendfile" "SECID134"
21160 .cindex "options" "&(appendfile)& transport"
21164 .option allow_fifo appendfile boolean false
21165 .cindex "fifo (named pipe)"
21166 .cindex "named pipe (fifo)"
21167 .cindex "pipe" "named (fifo)"
21168 Setting this option permits delivery to named pipes (FIFOs) as well as to
21169 regular files. If no process is reading the named pipe at delivery time, the
21170 delivery is deferred.
21173 .option allow_symlink appendfile boolean false
21174 .cindex "symbolic link" "to mailbox"
21175 .cindex "mailbox" "symbolic link"
21176 By default, &(appendfile)& will not deliver if the path name for the file is
21177 that of a symbolic link. Setting this option relaxes that constraint, but there
21178 are security issues involved in the use of symbolic links. Be sure you know
21179 what you are doing if you set this. Details of exactly what this option affects
21180 are included in the discussion which follows this list of options.
21183 .option batch_id appendfile string&!! unset
21184 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21185 However, batching is automatically disabled for &(appendfile)& deliveries that
21186 happen as a result of forwarding or aliasing or other redirection directly to a
21190 .option batch_max appendfile integer 1
21191 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21194 .option check_group appendfile boolean false
21195 When this option is set, the group owner of the file defined by the &%file%&
21196 option is checked to see that it is the same as the group under which the
21197 delivery process is running. The default setting is false because the default
21198 file mode is 0600, which means that the group is irrelevant.
21201 .option check_owner appendfile boolean true
21202 When this option is set, the owner of the file defined by the &%file%& option
21203 is checked to ensure that it is the same as the user under which the delivery
21204 process is running.
21207 .option check_string appendfile string "see below"
21208 .cindex "&""From""& line"
21209 As &(appendfile)& writes the message, the start of each line is tested for
21210 matching &%check_string%&, and if it does, the initial matching characters are
21211 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21212 a literal string, not a regular expression, and the case of any letters it
21213 contains is significant.
21215 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21216 are forced to &"."& and &".."& respectively, and any settings in the
21217 configuration are ignored. Otherwise, they default to &"From&~"& and
21218 &">From&~"& when the &%file%& option is set, and unset when any of the
21219 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21221 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21222 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21223 &"From&~"& indicates the start of a new message. All four options need changing
21224 if another format is used. For example, to deliver to mailboxes in MMDF format:
21225 .cindex "MMDF format mailbox"
21226 .cindex "mailbox" "MMDF format"
21228 check_string = "\1\1\1\1\n"
21229 escape_string = "\1\1\1\1 \n"
21230 message_prefix = "\1\1\1\1\n"
21231 message_suffix = "\1\1\1\1\n"
21233 .option create_directory appendfile boolean true
21234 .cindex "directory creation"
21235 When this option is true, Exim attempts to create any missing superior
21236 directories for the file that it is about to write. A created directory's mode
21237 is given by the &%directory_mode%& option.
21239 The group ownership of a newly created directory is highly dependent on the
21240 operating system (and possibly the file system) that is being used. For
21241 example, in Solaris, if the parent directory has the setgid bit set, its group
21242 is propagated to the child; if not, the currently set group is used. However,
21243 in FreeBSD, the parent's group is always used.
21247 .option create_file appendfile string anywhere
21248 This option constrains the location of files and directories that are created
21249 by this transport. It applies to files defined by the &%file%& option and
21250 directories defined by the &%directory%& option. In the case of maildir
21251 delivery, it applies to the top level directory, not the maildir directories
21254 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21255 &"belowhome"&. In the second and third cases, a home directory must have been
21256 set for the transport. This option is not useful when an explicit file name is
21257 given for normal mailbox deliveries. It is intended for the case when file
21258 names are generated from users' &_.forward_& files. These are usually handled
21259 by an &(appendfile)& transport called &%address_file%&. See also
21260 &%file_must_exist%&.
21263 .option directory appendfile string&!! unset
21264 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21265 or &%directory%& must be set, unless the delivery is the direct result of a
21266 redirection (see section &<<SECTfildiropt>>&).
21268 When &%directory%& is set, the string is expanded, and the message is delivered
21269 into a new file or files in or below the given directory, instead of being
21270 appended to a single mailbox file. A number of different formats are provided
21271 (see &%maildir_format%& and &%mailstore_format%&), and see section
21272 &<<SECTopdir>>& for further details of this form of delivery.
21275 .option directory_file appendfile string&!! "see below"
21277 .vindex "&$inode$&"
21278 When &%directory%& is set, but neither &%maildir_format%& nor
21279 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21280 whose name is obtained by expanding this string. The default value is:
21282 q${base62:$tod_epoch}-$inode
21284 This generates a unique name from the current time, in base 62 form, and the
21285 inode of the file. The variable &$inode$& is available only when expanding this
21289 .option directory_mode appendfile "octal integer" 0700
21290 If &(appendfile)& creates any directories as a result of the
21291 &%create_directory%& option, their mode is specified by this option.
21294 .option escape_string appendfile string "see description"
21295 See &%check_string%& above.
21298 .option file appendfile string&!! unset
21299 This option is mutually exclusive with the &%directory%& option, but one of
21300 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21301 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21302 specifies a single file, to which the message is appended. One or more of
21303 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21306 .cindex "NFS" "lock file"
21307 .cindex "locking files"
21308 .cindex "lock files"
21309 If you are using more than one host to deliver over NFS into the same
21310 mailboxes, you should always use lock files.
21312 The string value is expanded for each delivery, and must yield an absolute
21313 path. The most common settings of this option are variations on one of these
21316 file = /var/spool/mail/$local_part
21317 file = /home/$local_part/inbox
21320 .cindex "&""sticky""& bit"
21321 In the first example, all deliveries are done into the same directory. If Exim
21322 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21323 create a file in the directory, so the &"sticky"& bit must be turned on for
21324 deliveries to be possible, or alternatively the &%group%& option can be used to
21325 run the delivery under a group id which has write access to the directory.
21329 .option file_format appendfile string unset
21330 .cindex "file" "mailbox; checking existing format"
21331 This option requests the transport to check the format of an existing file
21332 before adding to it. The check consists of matching a specific string at the
21333 start of the file. The value of the option consists of an even number of
21334 colon-separated strings. The first of each pair is the test string, and the
21335 second is the name of a transport. If the transport associated with a matched
21336 string is not the current transport, control is passed over to the other
21337 transport. For example, suppose the standard &(local_delivery)& transport has
21340 file_format = "From : local_delivery :\
21341 \1\1\1\1\n : local_mmdf_delivery"
21343 Mailboxes that begin with &"From"& are still handled by this transport, but if
21344 a mailbox begins with four binary ones followed by a newline, control is passed
21345 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21346 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21347 is assumed to match the current transport. If the start of a mailbox doesn't
21348 match any string, or if the transport named for a given string is not defined,
21349 delivery is deferred.
21352 .option file_must_exist appendfile boolean false
21353 If this option is true, the file specified by the &%file%& option must exist.
21354 A temporary error occurs if it does not, causing delivery to be deferred.
21355 If this option is false, the file is created if it does not exist.
21358 .option lock_fcntl_timeout appendfile time 0s
21359 .cindex "timeout" "mailbox locking"
21360 .cindex "mailbox" "locking, blocking and non-blocking"
21361 .cindex "locking files"
21362 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21363 when locking an open mailbox file. If the call fails, the delivery process
21364 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21365 Non-blocking calls are used so that the file is not kept open during the wait
21366 for the lock; the reason for this is to make it as safe as possible for
21367 deliveries over NFS in the case when processes might be accessing an NFS
21368 mailbox without using a lock file. This should not be done, but
21369 misunderstandings and hence misconfigurations are not unknown.
21371 On a busy system, however, the performance of a non-blocking lock approach is
21372 not as good as using a blocking lock with a timeout. In this case, the waiting
21373 is done inside the system call, and Exim's delivery process acquires the lock
21374 and can proceed as soon as the previous lock holder releases it.
21376 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21377 timeout, are used. There may still be some retrying: the maximum number of
21380 (lock_retries * lock_interval) / lock_fcntl_timeout
21382 rounded up to the next whole number. In other words, the total time during
21383 which &(appendfile)& is trying to get a lock is roughly the same, unless
21384 &%lock_fcntl_timeout%& is set very large.
21386 You should consider setting this option if you are getting a lot of delayed
21387 local deliveries because of errors of the form
21389 failed to lock mailbox /some/file (fcntl)
21392 .option lock_flock_timeout appendfile time 0s
21393 This timeout applies to file locking when using &[flock()]& (see
21394 &%use_flock%&); the timeout operates in a similar manner to
21395 &%lock_fcntl_timeout%&.
21398 .option lock_interval appendfile time 3s
21399 This specifies the time to wait between attempts to lock the file. See below
21400 for details of locking.
21403 .option lock_retries appendfile integer 10
21404 This specifies the maximum number of attempts to lock the file. A value of zero
21405 is treated as 1. See below for details of locking.
21408 .option lockfile_mode appendfile "octal integer" 0600
21409 This specifies the mode of the created lock file, when a lock file is being
21410 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21413 .option lockfile_timeout appendfile time 30m
21414 .cindex "timeout" "mailbox locking"
21415 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21416 exists and is older than this value, it is assumed to have been left behind by
21417 accident, and Exim attempts to remove it.
21420 .option mailbox_filecount appendfile string&!! unset
21421 .cindex "mailbox" "specifying size of"
21422 .cindex "size" "of mailbox"
21423 If this option is set, it is expanded, and the result is taken as the current
21424 number of files in the mailbox. It must be a decimal number, optionally
21425 followed by K or M. This provides a way of obtaining this information from an
21426 external source that maintains the data.
21429 .option mailbox_size appendfile string&!! unset
21430 .cindex "mailbox" "specifying size of"
21431 .cindex "size" "of mailbox"
21432 If this option is set, it is expanded, and the result is taken as the current
21433 size the mailbox. It must be a decimal number, optionally followed by K or M.
21434 This provides a way of obtaining this information from an external source that
21435 maintains the data. This is likely to be helpful for maildir deliveries where
21436 it is computationally expensive to compute the size of a mailbox.
21440 .option maildir_format appendfile boolean false
21441 .cindex "maildir format" "specifying"
21442 If this option is set with the &%directory%& option, the delivery is into a new
21443 file, in the &"maildir"& format that is used by other mail software. When the
21444 transport is activated directly from a &(redirect)& router (for example, the
21445 &(address_file)& transport in the default configuration), setting
21446 &%maildir_format%& causes the path received from the router to be treated as a
21447 directory, whether or not it ends with &`/`&. This option is available only if
21448 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21449 &<<SECTmaildirdelivery>>& below for further details.
21452 .option maildir_quota_directory_regex appendfile string "See below"
21453 .cindex "maildir format" "quota; directories included in"
21454 .cindex "quota" "maildir; directories included in"
21455 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21456 a regular expression for specifying directories, relative to the quota
21457 directory (see &%quota_directory%&), that should be included in the quota
21458 calculation. The default value is:
21460 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21462 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21463 (directories whose names begin with a dot). If you want to exclude the
21465 folder from the count (as some sites do), you need to change this setting to
21467 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21469 This uses a negative lookahead in the regular expression to exclude the
21470 directory whose name is &_.Trash_&. When a directory is excluded from quota
21471 calculations, quota processing is bypassed for any messages that are delivered
21472 directly into that directory.
21475 .option maildir_retries appendfile integer 10
21476 This option specifies the number of times to retry when writing a file in
21477 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21480 .option maildir_tag appendfile string&!! unset
21481 This option applies only to deliveries in maildir format, and is described in
21482 section &<<SECTmaildirdelivery>>& below.
21485 .option maildir_use_size_file appendfile&!! boolean false
21486 .cindex "maildir format" "&_maildirsize_& file"
21487 The result of string expansion for this option must be a valid boolean value.
21488 If it is true, it enables support for &_maildirsize_& files. Exim
21489 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21490 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21491 value is zero. See &%maildir_quota_directory_regex%& above and section
21492 &<<SECTmaildirdelivery>>& below for further details.
21494 .option maildirfolder_create_regex appendfile string unset
21495 .cindex "maildir format" "&_maildirfolder_& file"
21496 .cindex "&_maildirfolder_&, creating"
21497 The value of this option is a regular expression. If it is unset, it has no
21498 effect. Otherwise, before a maildir delivery takes place, the pattern is
21499 matched against the name of the maildir directory, that is, the directory
21500 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21501 delivery. If there is a match, Exim checks for the existence of a file called
21502 &_maildirfolder_& in the directory, and creates it if it does not exist.
21503 See section &<<SECTmaildirdelivery>>& for more details.
21506 .option mailstore_format appendfile boolean false
21507 .cindex "mailstore format" "specifying"
21508 If this option is set with the &%directory%& option, the delivery is into two
21509 new files in &"mailstore"& format. The option is available only if
21510 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21511 below for further details.
21514 .option mailstore_prefix appendfile string&!! unset
21515 This option applies only to deliveries in mailstore format, and is described in
21516 section &<<SECTopdir>>& below.
21519 .option mailstore_suffix appendfile string&!! unset
21520 This option applies only to deliveries in mailstore format, and is described in
21521 section &<<SECTopdir>>& below.
21524 .option mbx_format appendfile boolean false
21525 .cindex "locking files"
21526 .cindex "file" "locking"
21527 .cindex "file" "MBX format"
21528 .cindex "MBX format, specifying"
21529 This option is available only if Exim has been compiled with SUPPORT_MBX
21530 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21531 the message is appended to the mailbox file in MBX format instead of
21532 traditional Unix format. This format is supported by Pine4 and its associated
21533 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21535 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21536 automatically changed by the use of &%mbx_format%&. They should normally be set
21537 empty when using MBX format, so this option almost always appears in this
21544 If none of the locking options are mentioned in the configuration,
21545 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21546 is possible to specify the other kinds of locking with &%mbx_format%&, but
21547 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21548 interworks with &'c-client'&, providing for shared access to the mailbox. It
21549 should not be used if any program that does not use this form of locking is
21550 going to access the mailbox, nor should it be used if the mailbox file is NFS
21551 mounted, because it works only when the mailbox is accessed from a single host.
21553 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21554 the standard version of &'c-client'&, because as long as it has a mailbox open
21555 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21556 append messages to it.
21559 .option message_prefix appendfile string&!! "see below"
21560 .cindex "&""From""& line"
21561 The string specified here is expanded and output at the start of every message.
21562 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21563 in which case it is:
21565 message_prefix = "From ${if def:return_path{$return_path}\
21566 {MAILER-DAEMON}} $tod_bsdinbox\n"
21568 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21569 &`\n`& to &`\r\n`& in &%message_prefix%&.
21571 .option message_suffix appendfile string&!! "see below"
21572 The string specified here is expanded and output at the end of every message.
21573 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21574 in which case it is a single newline character. The suffix can be suppressed by
21579 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21580 &`\n`& to &`\r\n`& in &%message_suffix%&.
21582 .option mode appendfile "octal integer" 0600
21583 If the output file is created, it is given this mode. If it already exists and
21584 has wider permissions, they are reduced to this mode. If it has narrower
21585 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
21586 if the delivery is the result of a &%save%& command in a filter file specifying
21587 a particular mode, the mode of the output file is always forced to take that
21588 value, and this option is ignored.
21591 .option mode_fail_narrower appendfile boolean true
21592 This option applies in the case when an existing mailbox file has a narrower
21593 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
21594 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
21595 continues with the delivery attempt, using the existing mode of the file.
21598 .option notify_comsat appendfile boolean false
21599 If this option is true, the &'comsat'& daemon is notified after every
21600 successful delivery to a user mailbox. This is the daemon that notifies logged
21601 on users about incoming mail.
21604 .option quota appendfile string&!! unset
21605 .cindex "quota" "imposed by Exim"
21606 This option imposes a limit on the size of the file to which Exim is appending,
21607 or to the total space used in the directory tree when the &%directory%& option
21608 is set. In the latter case, computation of the space used is expensive, because
21609 all the files in the directory (and any sub-directories) have to be
21610 individually inspected and their sizes summed. (See &%quota_size_regex%& and
21611 &%maildir_use_size_file%& for ways to avoid this in environments where users
21612 have no shell access to their mailboxes).
21614 As there is no interlock against two simultaneous deliveries into a
21615 multi-file mailbox, it is possible for the quota to be overrun in this case.
21616 For single-file mailboxes, of course, an interlock is a necessity.
21618 A file's size is taken as its &'used'& value. Because of blocking effects, this
21619 may be a lot less than the actual amount of disk space allocated to the file.
21620 If the sizes of a number of files are being added up, the rounding effect can
21621 become quite noticeable, especially on systems that have large block sizes.
21622 Nevertheless, it seems best to stick to the &'used'& figure, because this is
21623 the obvious value which users understand most easily.
21625 The value of the option is expanded, and must then be a numerical value
21626 (decimal point allowed), optionally followed by one of the letters K, M, or G,
21627 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
21628 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
21631 &*Note*&: A value of zero is interpreted as &"no quota"&.
21633 The expansion happens while Exim is running as root, before it changes uid for
21634 the delivery. This means that files that are inaccessible to the end user can
21635 be used to hold quota values that are looked up in the expansion. When delivery
21636 fails because this quota is exceeded, the handling of the error is as for
21637 system quota failures.
21639 By default, Exim's quota checking mimics system quotas, and restricts the
21640 mailbox to the specified maximum size, though the value is not accurate to the
21641 last byte, owing to separator lines and additional headers that may get added
21642 during message delivery. When a mailbox is nearly full, large messages may get
21643 refused even though small ones are accepted, because the size of the current
21644 message is added to the quota when the check is made. This behaviour can be
21645 changed by setting &%quota_is_inclusive%& false. When this is done, the check
21646 for exceeding the quota does not include the current message. Thus, deliveries
21647 continue until the quota has been exceeded; thereafter, no further messages are
21648 delivered. See also &%quota_warn_threshold%&.
21651 .option quota_directory appendfile string&!! unset
21652 This option defines the directory to check for quota purposes when delivering
21653 into individual files. The default is the delivery directory, or, if a file
21654 called &_maildirfolder_& exists in a maildir directory, the parent of the
21655 delivery directory.
21658 .option quota_filecount appendfile string&!! 0
21659 This option applies when the &%directory%& option is set. It limits the total
21660 number of files in the directory (compare the inode limit in system quotas). It
21661 can only be used if &%quota%& is also set. The value is expanded; an expansion
21662 failure causes delivery to be deferred. A value of zero is interpreted as
21666 .option quota_is_inclusive appendfile boolean true
21667 See &%quota%& above.
21670 .option quota_size_regex appendfile string unset
21671 This option applies when one of the delivery modes that writes a separate file
21672 for each message is being used. When Exim wants to find the size of one of
21673 these files in order to test the quota, it first checks &%quota_size_regex%&.
21674 If this is set to a regular expression that matches the file name, and it
21675 captures one string, that string is interpreted as a representation of the
21676 file's size. The value of &%quota_size_regex%& is not expanded.
21678 This feature is useful only when users have no shell access to their mailboxes
21679 &-- otherwise they could defeat the quota simply by renaming the files. This
21680 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
21681 the file length to the file name. For example:
21683 maildir_tag = ,S=$message_size
21684 quota_size_regex = ,S=(\d+)
21686 An alternative to &$message_size$& is &$message_linecount$&, which contains the
21687 number of lines in the message.
21689 The regular expression should not assume that the length is at the end of the
21690 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21691 sometimes add other information onto the ends of message file names.
21693 Section &<<SECID136>>& contains further information.
21696 .option quota_warn_message appendfile string&!! "see below"
21697 See below for the use of this option. If it is not set when
21698 &%quota_warn_threshold%& is set, it defaults to
21700 quota_warn_message = "\
21701 To: $local_part@$domain\n\
21702 Subject: Your mailbox\n\n\
21703 This message is automatically created \
21704 by mail delivery software.\n\n\
21705 The size of your mailbox has exceeded \
21706 a warning threshold that is\n\
21707 set by the system administrator.\n"
21711 .option quota_warn_threshold appendfile string&!! 0
21712 .cindex "quota" "warning threshold"
21713 .cindex "mailbox" "size warning"
21714 .cindex "size" "of mailbox"
21715 This option is expanded in the same way as &%quota%& (see above). If the
21716 resulting value is greater than zero, and delivery of the message causes the
21717 size of the file or total space in the directory tree to cross the given
21718 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21719 may be specified as a percentage of it by following the value with a percent
21723 quota_warn_threshold = 75%
21725 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21726 percent sign is ignored.
21728 The warning message itself is specified by the &%quota_warn_message%& option,
21729 and it must start with a &'To:'& header line containing the recipient(s) of the
21730 warning message. These do not necessarily have to include the recipient(s) of
21731 the original message. A &'Subject:'& line should also normally be supplied. You
21732 can include any other header lines that you want. If you do not include a
21733 &'From:'& line, the default is:
21735 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21737 .oindex &%errors_reply_to%&
21738 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21741 The &%quota%& option does not have to be set in order to use this option; they
21742 are independent of one another except when the threshold is specified as a
21746 .option use_bsmtp appendfile boolean false
21747 .cindex "envelope sender"
21748 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21749 format, with the envelope sender and recipient(s) included as SMTP commands. If
21750 you want to include a leading HELO command with such messages, you can do
21751 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21752 for details of batch SMTP.
21755 .option use_crlf appendfile boolean false
21756 .cindex "carriage return"
21758 This option causes lines to be terminated with the two-character CRLF sequence
21759 (carriage return, linefeed) instead of just a linefeed character. In the case
21760 of batched SMTP, the byte sequence written to the file is then an exact image
21761 of what would be sent down a real SMTP connection.
21763 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21764 (which are used to supply the traditional &"From&~"& and blank line separators
21765 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21766 carriage return characters if these are needed. In cases where these options
21767 have non-empty defaults, the values end with a single linefeed, so they must be
21768 changed to end with &`\r\n`& if &%use_crlf%& is set.
21771 .option use_fcntl_lock appendfile boolean "see below"
21772 This option controls the use of the &[fcntl()]& function to lock a file for
21773 exclusive use when a message is being appended. It is set by default unless
21774 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21775 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21776 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21779 .option use_flock_lock appendfile boolean false
21780 This option is provided to support the use of &[flock()]& for file locking, for
21781 the few situations where it is needed. Most modern operating systems support
21782 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21783 each other. Exim uses &[fcntl()]& locking by default.
21785 This option is required only if you are using an operating system where
21786 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21787 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21788 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21790 .cindex "Solaris" "&[flock()]& support"
21791 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21792 have it (and some, I think, provide a not quite right version built on top of
21793 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21794 the ability to use it, and any attempt to do so will cause a configuration
21797 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21798 is just being mapped onto &[fcntl()]& by the OS).
21801 .option use_lockfile appendfile boolean "see below"
21802 If this option is turned off, Exim does not attempt to create a lock file when
21803 appending to a mailbox file. In this situation, the only locking is by
21804 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21805 sure that every MUA that is ever going to look at your users' mailboxes uses
21806 &[fcntl()]& rather than a lock file, and even then only when you are not
21807 delivering over NFS from more than one host.
21809 .cindex "NFS" "lock file"
21810 In order to append to an NFS file safely from more than one host, it is
21811 necessary to take out a lock &'before'& opening the file, and the lock file
21812 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21815 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21816 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21817 except when &%mbx_format%& is set.
21820 .option use_mbx_lock appendfile boolean "see below"
21821 This option is available only if Exim has been compiled with SUPPORT_MBX
21822 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21823 locking rules be used. It is set by default if &%mbx_format%& is set and none
21824 of the locking options are mentioned in the configuration. The locking rules
21825 are the same as are used by the &'c-client'& library that underlies Pine and
21826 the IMAP4 and POP daemons that come with it (see the discussion below). The
21827 rules allow for shared access to the mailbox. However, this kind of locking
21828 does not work when the mailbox is NFS mounted.
21830 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21831 &%use_flock_lock%& to control what kind of locking is used in implementing the
21832 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21833 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21838 .section "Operational details for appending" "SECTopappend"
21839 .cindex "appending to a file"
21840 .cindex "file" "appending"
21841 Before appending to a file, the following preparations are made:
21844 If the name of the file is &_/dev/null_&, no action is taken, and a success
21848 .cindex "directory creation"
21849 If any directories on the file's path are missing, Exim creates them if the
21850 &%create_directory%& option is set. A created directory's mode is given by the
21851 &%directory_mode%& option.
21854 If &%file_format%& is set, the format of an existing file is checked. If this
21855 indicates that a different transport should be used, control is passed to that
21859 .cindex "file" "locking"
21860 .cindex "locking files"
21861 .cindex "NFS" "lock file"
21862 If &%use_lockfile%& is set, a lock file is built in a way that will work
21863 reliably over NFS, as follows:
21866 Create a &"hitching post"& file whose name is that of the lock file with the
21867 current time, primary host name, and process id added, by opening for writing
21868 as a new file. If this fails with an access error, delivery is deferred.
21870 Close the hitching post file, and hard link it to the lock file name.
21872 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21873 Unlink the hitching post name.
21875 Otherwise, use &[stat()]& to get information about the hitching post file, and
21876 then unlink hitching post name. If the number of links is exactly two, creation
21877 of the lock file succeeded but something (for example, an NFS server crash and
21878 restart) caused this fact not to be communicated to the &[link()]& call.
21880 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21881 up to &%lock_retries%& times. However, since any program that writes to a
21882 mailbox should complete its task very quickly, it is reasonable to time out old
21883 lock files that are normally the result of user agent and system crashes. If an
21884 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21885 it before trying again.
21889 A call is made to &[lstat()]& to discover whether the main file exists, and if
21890 so, what its characteristics are. If &[lstat()]& fails for any reason other
21891 than non-existence, delivery is deferred.
21894 .cindex "symbolic link" "to mailbox"
21895 .cindex "mailbox" "symbolic link"
21896 If the file does exist and is a symbolic link, delivery is deferred, unless the
21897 &%allow_symlink%& option is set, in which case the ownership of the link is
21898 checked, and then &[stat()]& is called to find out about the real file, which
21899 is then subjected to the checks below. The check on the top-level link
21900 ownership prevents one user creating a link for another's mailbox in a sticky
21901 directory, though allowing symbolic links in this case is definitely not a good
21902 idea. If there is a chain of symbolic links, the intermediate ones are not
21906 If the file already exists but is not a regular file, or if the file's owner
21907 and group (if the group is being checked &-- see &%check_group%& above) are
21908 different from the user and group under which the delivery is running,
21909 delivery is deferred.
21912 If the file's permissions are more generous than specified, they are reduced.
21913 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21914 is set false, in which case the delivery is tried using the existing
21918 The file's inode number is saved, and the file is then opened for appending.
21919 If this fails because the file has vanished, &(appendfile)& behaves as if it
21920 hadn't existed (see below). For any other failures, delivery is deferred.
21923 If the file is opened successfully, check that the inode number hasn't
21924 changed, that it is still a regular file, and that the owner and permissions
21925 have not changed. If anything is wrong, defer delivery and freeze the message.
21928 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21929 option is set. Otherwise, check that the file is being created in a permitted
21930 directory if the &%create_file%& option is set (deferring on failure), and then
21931 open for writing as a new file, with the O_EXCL and O_CREAT options,
21932 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21933 set). In this case, which can happen if the link points to a non-existent file,
21934 the file is opened for writing using O_CREAT but not O_EXCL, because
21935 that prevents link following.
21938 .cindex "loop" "while file testing"
21939 If opening fails because the file exists, obey the tests given above for
21940 existing files. However, to avoid looping in a situation where the file is
21941 being continuously created and destroyed, the exists/not-exists loop is broken
21942 after 10 repetitions, and the message is then frozen.
21945 If opening fails with any other error, defer delivery.
21948 .cindex "file" "locking"
21949 .cindex "locking files"
21950 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
21951 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
21952 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
21953 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
21954 file, and an exclusive lock on the file whose name is
21956 /tmp/.<device-number>.<inode-number>
21958 using the device and inode numbers of the open mailbox file, in accordance with
21959 the MBX locking rules. This file is created with a mode that is specified by
21960 the &%lockfile_mode%& option.
21962 If Exim fails to lock the file, there are two possible courses of action,
21963 depending on the value of the locking timeout. This is obtained from
21964 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
21966 If the timeout value is zero, the file is closed, Exim waits for
21967 &%lock_interval%&, and then goes back and re-opens the file as above and tries
21968 to lock it again. This happens up to &%lock_retries%& times, after which the
21969 delivery is deferred.
21971 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
21972 &[flock()]& are used (with the given timeout), so there has already been some
21973 waiting involved by the time locking fails. Nevertheless, Exim does not give up
21974 immediately. It retries up to
21976 (lock_retries * lock_interval) / <timeout>
21978 times (rounded up).
21981 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
21982 and/or &[flock()]& locks) and then deletes the lock file if one was created.
21985 .section "Operational details for delivery to a new file" "SECTopdir"
21986 .cindex "delivery" "to single file"
21987 .cindex "&""From""& line"
21988 When the &%directory%& option is set instead of &%file%&, each message is
21989 delivered into a newly-created file or set of files. When &(appendfile)& is
21990 activated directly from a &(redirect)& router, neither &%file%& nor
21991 &%directory%& is normally set, because the path for delivery is supplied by the
21992 router. (See for example, the &(address_file)& transport in the default
21993 configuration.) In this case, delivery is to a new file if either the path name
21994 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
21996 No locking is required while writing the message to a new file, so the various
21997 locking options of the transport are ignored. The &"From"& line that by default
21998 separates messages in a single file is not normally needed, nor is the escaping
21999 of message lines that start with &"From"&, and there is no need to ensure a
22000 newline at the end of each message. Consequently, the default values for
22001 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22002 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22004 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22005 the files in the delivery directory by default. However, you can specify a
22006 different directory by setting &%quota_directory%&. Also, for maildir
22007 deliveries (see below) the &_maildirfolder_& convention is honoured.
22010 .cindex "maildir format"
22011 .cindex "mailstore format"
22012 There are three different ways in which delivery to individual files can be
22013 done, controlled by the settings of the &%maildir_format%& and
22014 &%mailstore_format%& options. Note that code to support maildir or mailstore
22015 formats is not included in the binary unless SUPPORT_MAILDIR or
22016 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22018 .cindex "directory creation"
22019 In all three cases an attempt is made to create the directory and any necessary
22020 sub-directories if they do not exist, provided that the &%create_directory%&
22021 option is set (the default). The location of a created directory can be
22022 constrained by setting &%create_file%&. A created directory's mode is given by
22023 the &%directory_mode%& option. If creation fails, or if the
22024 &%create_directory%& option is not set when creation is required, delivery is
22029 .section "Maildir delivery" "SECTmaildirdelivery"
22030 .cindex "maildir format" "description of"
22031 If the &%maildir_format%& option is true, Exim delivers each message by writing
22032 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22033 directory that is defined by the &%directory%& option (the &"delivery
22034 directory"&). If the delivery is successful, the file is renamed into the
22035 &_new_& subdirectory.
22037 In the file name, <&'stime'&> is the current time of day in seconds, and
22038 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22039 Exim checks that the time-of-day clock has moved on by at least one microsecond
22040 before terminating the delivery process. This guarantees uniqueness for the
22041 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22042 opening it. If any response other than ENOENT (does not exist) is given,
22043 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22045 Before Exim carries out a maildir delivery, it ensures that subdirectories
22046 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22047 do not exist, Exim tries to create them and any superior directories in their
22048 path, subject to the &%create_directory%& and &%create_file%& options. If the
22049 &%maildirfolder_create_regex%& option is set, and the regular expression it
22050 contains matches the delivery directory, Exim also ensures that a file called
22051 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22052 &_maildirfolder_& file cannot be created, delivery is deferred.
22054 These features make it possible to use Exim to create all the necessary files
22055 and directories in a maildir mailbox, including subdirectories for maildir++
22056 folders. Consider this example:
22058 maildir_format = true
22059 directory = /var/mail/$local_part\
22060 ${if eq{$local_part_suffix}{}{}\
22061 {/.${substr_1:$local_part_suffix}}}
22062 maildirfolder_create_regex = /\.[^/]+$
22064 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22065 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22066 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22067 not match this name, so Exim will not look for or create the file
22068 &_/var/mail/pimbo/maildirfolder_&, though it will create
22069 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22071 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22072 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22073 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22074 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22075 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22077 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22078 not inadvertently match the toplevel maildir directory, because a
22079 &_maildirfolder_& file at top level would completely break quota calculations.
22081 .cindex "quota" "in maildir delivery"
22082 .cindex "maildir++"
22083 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22084 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22085 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22086 Exim assumes the directory is a maildir++ folder directory, which is one level
22087 down from the user's top level mailbox directory. This causes it to start at
22088 the parent directory instead of the current directory when calculating the
22089 amount of space used.
22091 One problem with delivering into a multi-file mailbox is that it is
22092 computationally expensive to compute the size of the mailbox for quota
22093 checking. Various approaches have been taken to reduce the amount of work
22094 needed. The next two sections describe two of them. A third alternative is to
22095 use some external process for maintaining the size data, and use the expansion
22096 of the &%mailbox_size%& option as a way of importing it into Exim.
22101 .section "Using tags to record message sizes" "SECID135"
22102 If &%maildir_tag%& is set, the string is expanded for each delivery.
22103 When the maildir file is renamed into the &_new_& sub-directory, the
22104 tag is added to its name. However, if adding the tag takes the length of the
22105 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22106 the tag is dropped and the maildir file is created with no tag.
22109 .vindex "&$message_size$&"
22110 Tags can be used to encode the size of files in their names; see
22111 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22112 happens after the message has been written. The value of the &$message_size$&
22113 variable is set to the number of bytes actually written. If the expansion is
22114 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22115 be deferred. The expanded tag may contain any printing characters except &"/"&.
22116 Non-printing characters in the string are ignored; if the resulting string is
22117 empty, it is ignored. If it starts with an alphanumeric character, a leading
22118 colon is inserted; this default has not proven to be the path that popular
22119 maildir implementations have chosen (but changing it in Exim would break
22120 backwards compatibility).
22122 For one common implementation, you might set:
22124 maildir_tag = ,S=${message_size}
22126 but you should check the documentation of the other software to be sure.
22128 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22129 as this allows Exim to extract the size from your tag, instead of having to
22130 &[stat()]& each message file.
22133 .section "Using a maildirsize file" "SECID136"
22134 .cindex "quota" "in maildir delivery"
22135 .cindex "maildir format" "&_maildirsize_& file"
22136 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22137 storing quota and message size information in a file called &_maildirsize_&
22138 within the toplevel maildir directory. If this file does not exist, Exim
22139 creates it, setting the quota from the &%quota%& option of the transport. If
22140 the maildir directory itself does not exist, it is created before any attempt
22141 to write a &_maildirsize_& file.
22143 The &_maildirsize_& file is used to hold information about the sizes of
22144 messages in the maildir, thus speeding up quota calculations. The quota value
22145 in the file is just a cache; if the quota is changed in the transport, the new
22146 value overrides the cached value when the next message is delivered. The cache
22147 is maintained for the benefit of other programs that access the maildir and
22148 need to know the quota.
22150 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22151 file is maintained (with a zero quota setting), but no quota is imposed.
22153 A regular expression is available for controlling which directories in the
22154 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22155 See the description of the &%maildir_quota_directory_regex%& option above for
22159 .section "Mailstore delivery" "SECID137"
22160 .cindex "mailstore format" "description of"
22161 If the &%mailstore_format%& option is true, each message is written as two
22162 files in the given directory. A unique base name is constructed from the
22163 message id and the current delivery process, and the files that are written use
22164 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22165 contains the message's envelope, and the &_.msg_& file contains the message
22166 itself. The base name is placed in the variable &$mailstore_basename$&.
22168 During delivery, the envelope is first written to a file with the suffix
22169 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22170 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22171 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22172 file before accessing either of them. An alternative approach is to wait for
22173 the absence of a &_.tmp_& file.
22175 The envelope file starts with any text defined by the &%mailstore_prefix%&
22176 option, expanded and terminated by a newline if there isn't one. Then follows
22177 the sender address on one line, then all the recipient addresses, one per line.
22178 There can be more than one recipient only if the &%batch_max%& option is set
22179 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22180 appended to the file, followed by a newline if it does not end with one.
22182 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22183 failure, it is ignored. Other expansion errors are treated as serious
22184 configuration errors, and delivery is deferred. The variable
22185 &$mailstore_basename$& is available for use during these expansions.
22188 .section "Non-special new file delivery" "SECID138"
22189 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22190 file is created directly in the named directory. For example, when delivering
22191 messages into files in batched SMTP format for later delivery to some host (see
22192 section &<<SECTbatchSMTP>>&), a setting such as
22194 directory = /var/bsmtp/$host
22196 might be used. A message is written to a file with a temporary name, which is
22197 then renamed when the delivery is complete. The final name is obtained by
22198 expanding the contents of the &%directory_file%& option.
22199 .ecindex IIDapptra1
22200 .ecindex IIDapptra2
22207 . ////////////////////////////////////////////////////////////////////////////
22208 . ////////////////////////////////////////////////////////////////////////////
22210 .chapter "The autoreply transport" "CHID8"
22211 .scindex IIDauttra1 "transports" "&(autoreply)&"
22212 .scindex IIDauttra2 "&(autoreply)& transport"
22213 The &(autoreply)& transport is not a true transport in that it does not cause
22214 the message to be transmitted. Instead, it generates a new mail message as an
22215 automatic reply to the incoming message. &'References:'& and
22216 &'Auto-Submitted:'& header lines are included. These are constructed according
22217 to the rules in RFCs 2822 and 3834, respectively.
22219 If the router that passes the message to this transport does not have the
22220 &%unseen%& option set, the original message (for the current recipient) is not
22221 delivered anywhere. However, when the &%unseen%& option is set on the router
22222 that passes the message to this transport, routing of the address continues, so
22223 another router can set up a normal message delivery.
22226 The &(autoreply)& transport is usually run as the result of mail filtering, a
22227 &"vacation"& message being the standard example. However, it can also be run
22228 directly from a router like any other transport. To reduce the possibility of
22229 message cascades, messages created by the &(autoreply)& transport always have
22230 empty envelope sender addresses, like bounce messages.
22232 The parameters of the message to be sent can be specified in the configuration
22233 by options described below. However, these are used only when the address
22234 passed to the transport does not contain its own reply information. When the
22235 transport is run as a consequence of a
22237 or &%vacation%& command in a filter file, the parameters of the message are
22238 supplied by the filter, and passed with the address. The transport's options
22239 that define the message are then ignored (so they are not usually set in this
22240 case). The message is specified entirely by the filter or by the transport; it
22241 is never built from a mixture of options. However, the &%file_optional%&,
22242 &%mode%&, and &%return_message%& options apply in all cases.
22244 &(Autoreply)& is implemented as a local transport. When used as a result of a
22245 command in a user's filter file, &(autoreply)& normally runs under the uid and
22246 gid of the user, and with appropriate current and home directories (see chapter
22247 &<<CHAPenvironment>>&).
22249 There is a subtle difference between routing a message to a &(pipe)& transport
22250 that generates some text to be returned to the sender, and routing it to an
22251 &(autoreply)& transport. This difference is noticeable only if more than one
22252 address from the same message is so handled. In the case of a pipe, the
22253 separate outputs from the different addresses are gathered up and returned to
22254 the sender in a single message, whereas if &(autoreply)& is used, a separate
22255 message is generated for each address that is passed to it.
22257 Non-printing characters are not permitted in the header lines generated for the
22258 message that &(autoreply)& creates, with the exception of newlines that are
22259 immediately followed by white space. If any non-printing characters are found,
22260 the transport defers.
22261 Whether characters with the top bit set count as printing characters or not is
22262 controlled by the &%print_topbitchars%& global option.
22264 If any of the generic options for manipulating headers (for example,
22265 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22266 of the original message that is included in the generated message when
22267 &%return_message%& is set. They do not apply to the generated message itself.
22269 .vindex "&$sender_address$&"
22270 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22271 the message, indicating that there were no recipients, it does not treat this
22272 as an error. This means that autoreplies sent to &$sender_address$& when this
22273 is empty (because the incoming message is a bounce message) do not cause
22274 problems. They are just discarded.
22278 .section "Private options for autoreply" "SECID139"
22279 .cindex "options" "&(autoreply)& transport"
22281 .option bcc autoreply string&!! unset
22282 This specifies the addresses that are to receive &"blind carbon copies"& of the
22283 message when the message is specified by the transport.
22286 .option cc autoreply string&!! unset
22287 This specifies recipients of the message and the contents of the &'Cc:'& header
22288 when the message is specified by the transport.
22291 .option file autoreply string&!! unset
22292 The contents of the file are sent as the body of the message when the message
22293 is specified by the transport. If both &%file%& and &%text%& are set, the text
22294 string comes first.
22297 .option file_expand autoreply boolean false
22298 If this is set, the contents of the file named by the &%file%& option are
22299 subjected to string expansion as they are added to the message.
22302 .option file_optional autoreply boolean false
22303 If this option is true, no error is generated if the file named by the &%file%&
22304 option or passed with the address does not exist or cannot be read.
22307 .option from autoreply string&!! unset
22308 This specifies the contents of the &'From:'& header when the message is
22309 specified by the transport.
22312 .option headers autoreply string&!! unset
22313 This specifies additional RFC 2822 headers that are to be added to the message
22314 when the message is specified by the transport. Several can be given by using
22315 &"\n"& to separate them. There is no check on the format.
22318 .option log autoreply string&!! unset
22319 This option names a file in which a record of every message sent is logged when
22320 the message is specified by the transport.
22323 .option mode autoreply "octal integer" 0600
22324 If either the log file or the &"once"& file has to be created, this mode is
22328 .option never_mail autoreply "address list&!!" unset
22329 If any run of the transport creates a message with a recipient that matches any
22330 item in the list, that recipient is quietly discarded. If all recipients are
22331 discarded, no message is created. This applies both when the recipients are
22332 generated by a filter and when they are specified in the transport.
22336 .option once autoreply string&!! unset
22337 This option names a file or DBM database in which a record of each &'To:'&
22338 recipient is kept when the message is specified by the transport. &*Note*&:
22339 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22341 If &%once%& is unset, or is set to an empty string, the message is always sent.
22342 By default, if &%once%& is set to a non-empty file name, the message
22343 is not sent if a potential recipient is already listed in the database.
22344 However, if the &%once_repeat%& option specifies a time greater than zero, the
22345 message is sent if that much time has elapsed since a message was last sent to
22346 this recipient. A setting of zero time for &%once_repeat%& (the default)
22347 prevents a message from being sent a second time &-- in this case, zero means
22350 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22351 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22352 greater than zero, it changes the way Exim implements the &%once%& option.
22353 Instead of using a DBM file to record every recipient it sends to, it uses a
22354 regular file, whose size will never get larger than the given value.
22356 In the file, Exim keeps a linear list of recipient addresses and the times at
22357 which they were sent messages. If the file is full when a new address needs to
22358 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22359 means that a given recipient may receive multiple messages, but at
22360 unpredictable intervals that depend on the rate of turnover of addresses in the
22361 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22364 .option once_file_size autoreply integer 0
22365 See &%once%& above.
22368 .option once_repeat autoreply time&!! 0s
22369 See &%once%& above.
22370 After expansion, the value of this option must be a valid time value.
22373 .option reply_to autoreply string&!! unset
22374 This specifies the contents of the &'Reply-To:'& header when the message is
22375 specified by the transport.
22378 .option return_message autoreply boolean false
22379 If this is set, a copy of the original message is returned with the new
22380 message, subject to the maximum size set in the &%return_size_limit%& global
22381 configuration option.
22384 .option subject autoreply string&!! unset
22385 This specifies the contents of the &'Subject:'& header when the message is
22386 specified by the transport. It is tempting to quote the original subject in
22387 automatic responses. For example:
22389 subject = Re: $h_subject:
22391 There is a danger in doing this, however. It may allow a third party to
22392 subscribe your users to an opt-in mailing list, provided that the list accepts
22393 bounce messages as subscription confirmations. Well-managed lists require a
22394 non-bounce message to confirm a subscription, so the danger is relatively
22399 .option text autoreply string&!! unset
22400 This specifies a single string to be used as the body of the message when the
22401 message is specified by the transport. If both &%text%& and &%file%& are set,
22402 the text comes first.
22405 .option to autoreply string&!! unset
22406 This specifies recipients of the message and the contents of the &'To:'& header
22407 when the message is specified by the transport.
22408 .ecindex IIDauttra1
22409 .ecindex IIDauttra2
22414 . ////////////////////////////////////////////////////////////////////////////
22415 . ////////////////////////////////////////////////////////////////////////////
22417 .chapter "The lmtp transport" "CHAPLMTP"
22418 .cindex "transports" "&(lmtp)&"
22419 .cindex "&(lmtp)& transport"
22420 .cindex "LMTP" "over a pipe"
22421 .cindex "LMTP" "over a socket"
22422 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22424 or by interacting with a Unix domain socket.
22425 This transport is something of a cross between the &(pipe)& and &(smtp)&
22426 transports. Exim also has support for using LMTP over TCP/IP; this is
22427 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22428 to be of minority interest, the default build-time configure in &_src/EDITME_&
22429 has it commented out. You need to ensure that
22433 .cindex "options" "&(lmtp)& transport"
22434 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22435 included in the Exim binary. The private options of the &(lmtp)& transport are
22438 .option batch_id lmtp string&!! unset
22439 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22442 .option batch_max lmtp integer 1
22443 This limits the number of addresses that can be handled in a single delivery.
22444 Most LMTP servers can handle several addresses at once, so it is normally a
22445 good idea to increase this value. See the description of local delivery
22446 batching in chapter &<<CHAPbatching>>&.
22449 .option command lmtp string&!! unset
22450 This option must be set if &%socket%& is not set. The string is a command which
22451 is run in a separate process. It is split up into a command name and list of
22452 arguments, each of which is separately expanded (so expansion cannot change the
22453 number of arguments). The command is run directly, not via a shell. The message
22454 is passed to the new process using the standard input and output to operate the
22457 .option ignore_quota lmtp boolean false
22458 .cindex "LMTP" "ignoring quota errors"
22459 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22460 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22461 in its response to the LHLO command.
22463 .option socket lmtp string&!! unset
22464 This option must be set if &%command%& is not set. The result of expansion must
22465 be the name of a Unix domain socket. The transport connects to the socket and
22466 delivers the message to it using the LMTP protocol.
22469 .option timeout lmtp time 5m
22470 The transport is aborted if the created process or Unix domain socket does not
22471 respond to LMTP commands or message input within this timeout. Delivery
22472 is deferred, and will be tried again later. Here is an example of a typical
22477 command = /some/local/lmtp/delivery/program
22481 This delivers up to 20 addresses at a time, in a mixture of domains if
22482 necessary, running as the user &'exim'&.
22486 . ////////////////////////////////////////////////////////////////////////////
22487 . ////////////////////////////////////////////////////////////////////////////
22489 .chapter "The pipe transport" "CHAPpipetransport"
22490 .scindex IIDpiptra1 "transports" "&(pipe)&"
22491 .scindex IIDpiptra2 "&(pipe)& transport"
22492 The &(pipe)& transport is used to deliver messages via a pipe to a command
22493 running in another process. One example is the use of &(pipe)& as a
22494 pseudo-remote transport for passing messages to some other delivery mechanism
22495 (such as UUCP). Another is the use by individual users to automatically process
22496 their incoming messages. The &(pipe)& transport can be used in one of the
22500 .vindex "&$local_part$&"
22501 A router routes one address to a transport in the normal way, and the
22502 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22503 contains the local part of the address (as usual), and the command that is run
22504 is specified by the &%command%& option on the transport.
22506 .vindex "&$pipe_addresses$&"
22507 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22508 transport can handle more than one address in a single run. In this case, when
22509 more than one address is routed to the transport, &$local_part$& is not set
22510 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22511 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22512 that are routed to the transport.
22514 .vindex "&$address_pipe$&"
22515 A router redirects an address directly to a pipe command (for example, from an
22516 alias or forward file). In this case, &$address_pipe$& contains the text of the
22517 pipe command, and the &%command%& option on the transport is ignored unless
22518 &%force_command%& is set. If only one address is being transported
22519 (&%batch_max%& is not greater than one, or only one address was redirected to
22520 this pipe command), &$local_part$& contains the local part that was redirected.
22524 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22525 deliver messages over pipes using the LMTP interactive protocol. This is
22526 implemented by the &(lmtp)& transport.
22528 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22529 &_.forward_& file, the command runs under the uid and gid of that user. In
22530 other cases, the uid and gid have to be specified explicitly, either on the
22531 transport or on the router that handles the address. Current and &"home"&
22532 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22533 details of the local delivery environment and chapter &<<CHAPbatching>>&
22534 for a discussion of local delivery batching.
22537 .section "Concurrent delivery" "SECID140"
22538 If two messages arrive at almost the same time, and both are routed to a pipe
22539 delivery, the two pipe transports may be run concurrently. You must ensure that
22540 any pipe commands you set up are robust against this happening. If the commands
22541 write to a file, the &%exim_lock%& utility might be of use.
22546 .section "Returned status and data" "SECID141"
22547 .cindex "&(pipe)& transport" "returned data"
22548 If the command exits with a non-zero return code, the delivery is deemed to
22549 have failed, unless either the &%ignore_status%& option is set (in which case
22550 the return code is treated as zero), or the return code is one of those listed
22551 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22552 later"&. In this case, delivery is deferred. Details of a permanent failure are
22553 logged, but are not included in the bounce message, which merely contains
22554 &"local delivery failed"&.
22556 If the command exits on a signal and the &%freeze_signal%& option is set then
22557 the message will be frozen in the queue. If that option is not set, a bounce
22558 will be sent as normal.
22560 If the return code is greater than 128 and the command being run is a shell
22561 script, it normally means that the script was terminated by a signal whose
22562 value is the return code minus 128. The &%freeze_signal%& option does not
22563 apply in this case.
22565 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22566 return code is set to 127. This is the value that a shell returns if it is
22567 asked to run a non-existent command. The wording for the log line suggests that
22568 a non-existent command may be the problem.
22570 The &%return_output%& option can affect the result of a pipe delivery. If it is
22571 set and the command produces any output on its standard output or standard
22572 error streams, the command is considered to have failed, even if it gave a zero
22573 return code or if &%ignore_status%& is set. The output from the command is
22574 included as part of the bounce message. The &%return_fail_output%& option is
22575 similar, except that output is returned only when the command exits with a
22576 failure return code, that is, a value other than zero or a code that matches
22581 .section "How the command is run" "SECThowcommandrun"
22582 .cindex "&(pipe)& transport" "path for command"
22583 The command line is (by default) broken down into a command name and arguments
22584 by the &(pipe)& transport itself. The &%allow_commands%& and
22585 &%restrict_to_path%& options can be used to restrict the commands that may be
22588 .cindex "quoting" "in pipe command"
22589 Unquoted arguments are delimited by white space. If an argument appears in
22590 double quotes, backslash is interpreted as an escape character in the usual
22591 way. If an argument appears in single quotes, no escaping is done.
22593 String expansion is applied to the command line except when it comes from a
22594 traditional &_.forward_& file (commands from a filter file are expanded). The
22595 expansion is applied to each argument in turn rather than to the whole line.
22596 For this reason, any string expansion item that contains white space must be
22597 quoted so as to be contained within a single argument. A setting such as
22599 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
22601 will not work, because the expansion item gets split between several
22602 arguments. You have to write
22604 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
22606 to ensure that it is all in one argument. The expansion is done in this way,
22607 argument by argument, so that the number of arguments cannot be changed as a
22608 result of expansion, and quotes or backslashes in inserted variables do not
22609 interact with external quoting. However, this leads to problems if you want to
22610 generate multiple arguments (or the command name plus arguments) from a single
22611 expansion. In this situation, the simplest solution is to use a shell. For
22614 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
22617 .cindex "transport" "filter"
22618 .cindex "filter" "transport filter"
22619 .vindex "&$pipe_addresses$&"
22620 Special handling takes place when an argument consists of precisely the text
22621 &`$pipe_addresses`&. This is not a general expansion variable; the only
22622 place this string is recognized is when it appears as an argument for a pipe or
22623 transport filter command. It causes each address that is being handled to be
22624 inserted in the argument list at that point &'as a separate argument'&. This
22625 avoids any problems with spaces or shell metacharacters, and is of use when a
22626 &(pipe)& transport is handling groups of addresses in a batch.
22628 If &%force_command%& is enabled on the transport, Special handling takes place
22629 for an argument that consists of precisely the text &`$address_pipe`&. It
22630 is handled similarly to &$pipe_addresses$& above. It is expanded and each
22631 argument is inserted in the argument list at that point
22632 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
22633 the only item in the argument; in fact, if it were then &%force_command%&
22634 should behave as a no-op. Rather, it should be used to adjust the command
22635 run while preserving the argument vector separation.
22637 After splitting up into arguments and expansion, the resulting command is run
22638 in a subprocess directly from the transport, &'not'& under a shell. The
22639 message that is being delivered is supplied on the standard input, and the
22640 standard output and standard error are both connected to a single pipe that is
22641 read by Exim. The &%max_output%& option controls how much output the command
22642 may produce, and the &%return_output%& and &%return_fail_output%& options
22643 control what is done with it.
22645 Not running the command under a shell (by default) lessens the security risks
22646 in cases when a command from a user's filter file is built out of data that was
22647 taken from an incoming message. If a shell is required, it can of course be
22648 explicitly specified as the command to be run. However, there are circumstances
22649 where existing commands (for example, in &_.forward_& files) expect to be run
22650 under a shell and cannot easily be modified. To allow for these cases, there is
22651 an option called &%use_shell%&, which changes the way the &(pipe)& transport
22652 works. Instead of breaking up the command line as just described, it expands it
22653 as a single string and passes the result to &_/bin/sh_&. The
22654 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
22655 with &%use_shell%&, and the whole mechanism is inherently less secure.
22659 .section "Environment variables" "SECTpipeenv"
22660 .cindex "&(pipe)& transport" "environment for command"
22661 .cindex "environment for pipe transport"
22662 The environment variables listed below are set up when the command is invoked.
22663 This list is a compromise for maximum compatibility with other MTAs. Note that
22664 the &%environment%& option can be used to add additional variables to this
22667 &`DOMAIN `& the domain of the address
22668 &`HOME `& the home directory, if set
22669 &`HOST `& the host name when called from a router (see below)
22670 &`LOCAL_PART `& see below
22671 &`LOCAL_PART_PREFIX `& see below
22672 &`LOCAL_PART_SUFFIX `& see below
22673 &`LOGNAME `& see below
22674 &`MESSAGE_ID `& Exim's local ID for the message
22675 &`PATH `& as specified by the &%path%& option below
22676 &`QUALIFY_DOMAIN `& the sender qualification domain
22677 &`RECIPIENT `& the complete recipient address
22678 &`SENDER `& the sender of the message (empty if a bounce)
22679 &`SHELL `& &`/bin/sh`&
22680 &`TZ `& the value of the &%timezone%& option, if set
22681 &`USER `& see below
22683 When a &(pipe)& transport is called directly from (for example) an &(accept)&
22684 router, LOCAL_PART is set to the local part of the address. When it is
22685 called as a result of a forward or alias expansion, LOCAL_PART is set to
22686 the local part of the address that was expanded. In both cases, any affixes are
22687 removed from the local part, and made available in LOCAL_PART_PREFIX and
22688 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
22689 same value as LOCAL_PART for compatibility with other MTAs.
22692 HOST is set only when a &(pipe)& transport is called from a router that
22693 associates hosts with an address, typically when using &(pipe)& as a
22694 pseudo-remote transport. HOST is set to the first host name specified by
22698 If the transport's generic &%home_directory%& option is set, its value is used
22699 for the HOME environment variable. Otherwise, a home directory may be set
22700 by the router's &%transport_home_directory%& option, which defaults to the
22701 user's home directory if &%check_local_user%& is set.
22704 .section "Private options for pipe" "SECID142"
22705 .cindex "options" "&(pipe)& transport"
22709 .option allow_commands pipe "string list&!!" unset
22710 .cindex "&(pipe)& transport" "permitted commands"
22711 The string is expanded, and is then interpreted as a colon-separated list of
22712 permitted commands. If &%restrict_to_path%& is not set, the only commands
22713 permitted are those in the &%allow_commands%& list. They need not be absolute
22714 paths; the &%path%& option is still used for relative paths. If
22715 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22716 in the &%allow_commands%& list, or a name without any slashes that is found on
22717 the path. In other words, if neither &%allow_commands%& nor
22718 &%restrict_to_path%& is set, there is no restriction on the command, but
22719 otherwise only commands that are permitted by one or the other are allowed. For
22722 allow_commands = /usr/bin/vacation
22724 and &%restrict_to_path%& is not set, the only permitted command is
22725 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22726 &%use_shell%& is set.
22729 .option batch_id pipe string&!! unset
22730 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22733 .option batch_max pipe integer 1
22734 This limits the number of addresses that can be handled in a single delivery.
22735 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22738 .option check_string pipe string unset
22739 As &(pipe)& writes the message, the start of each line is tested for matching
22740 &%check_string%&, and if it does, the initial matching characters are replaced
22741 by the contents of &%escape_string%&, provided both are set. The value of
22742 &%check_string%& is a literal string, not a regular expression, and the case of
22743 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22744 of &%check_string%& and &%escape_string%& are forced to values that implement
22745 the SMTP escaping protocol. Any settings made in the configuration file are
22749 .option command pipe string&!! unset
22750 This option need not be set when &(pipe)& is being used to deliver to pipes
22751 obtained directly from address redirections. In other cases, the option must be
22752 set, to provide a command to be run. It need not yield an absolute path (see
22753 the &%path%& option below). The command is split up into separate arguments by
22754 Exim, and each argument is separately expanded, as described in section
22755 &<<SECThowcommandrun>>& above.
22758 .option environment pipe string&!! unset
22759 .cindex "&(pipe)& transport" "environment for command"
22760 .cindex "environment for &(pipe)& transport"
22761 This option is used to add additional variables to the environment in which the
22762 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22763 a string which is expanded, and then interpreted as a colon-separated list of
22764 environment settings of the form <&'name'&>=<&'value'&>.
22767 .option escape_string pipe string unset
22768 See &%check_string%& above.
22771 .option freeze_exec_fail pipe boolean false
22772 .cindex "exec failure"
22773 .cindex "failure of exec"
22774 .cindex "&(pipe)& transport" "failure of exec"
22775 Failure to exec the command in a pipe transport is by default treated like
22776 any other failure while running the command. However, if &%freeze_exec_fail%&
22777 is set, failure to exec is treated specially, and causes the message to be
22778 frozen, whatever the setting of &%ignore_status%&.
22781 .option freeze_signal pipe boolean false
22782 .cindex "signal exit"
22783 .cindex "&(pipe)& transport", "signal exit"
22784 Normally if the process run by a command in a pipe transport exits on a signal,
22785 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22786 frozen in Exim's queue instead.
22789 .option force_command pipe boolean false
22790 .cindex "force command"
22791 .cindex "&(pipe)& transport", "force command"
22792 Normally when a router redirects an address directly to a pipe command
22793 the &%command%& option on the transport is ignored. If &%force_command%&
22794 is set, the &%command%& option will used. This is especially
22795 useful for forcing a wrapper or additional argument to be added to the
22796 command. For example:
22798 command = /usr/bin/remote_exec myhost -- $address_pipe
22802 Note that &$address_pipe$& is handled specially in &%command%& when
22803 &%force_command%& is set, expanding out to the original argument vector as
22804 separate items, similarly to a Unix shell &`"$@"`& construct.
22806 .option ignore_status pipe boolean false
22807 If this option is true, the status returned by the subprocess that is set up to
22808 run the command is ignored, and Exim behaves as if zero had been returned.
22809 Otherwise, a non-zero status or termination by signal causes an error return
22810 from the transport unless the status value is one of those listed in
22811 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22813 &*Note*&: This option does not apply to timeouts, which do not return a status.
22814 See the &%timeout_defer%& option for how timeouts are handled.
22816 .option log_defer_output pipe boolean false
22817 .cindex "&(pipe)& transport" "logging output"
22818 If this option is set, and the status returned by the command is
22819 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22820 and any output was produced, the first line of it is written to the main log.
22823 .option log_fail_output pipe boolean false
22824 If this option is set, and the command returns any output, and also ends with a
22825 return code that is neither zero nor one of the return codes listed in
22826 &%temp_errors%& (that is, the delivery failed), the first line of output is
22827 written to the main log. This option and &%log_output%& are mutually exclusive.
22828 Only one of them may be set.
22832 .option log_output pipe boolean false
22833 If this option is set and the command returns any output, the first line of
22834 output is written to the main log, whatever the return code. This option and
22835 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
22839 .option max_output pipe integer 20K
22840 This specifies the maximum amount of output that the command may produce on its
22841 standard output and standard error file combined. If the limit is exceeded, the
22842 process running the command is killed. This is intended as a safety measure to
22843 catch runaway processes. The limit is applied independently of the settings of
22844 the options that control what is done with such output (for example,
22845 &%return_output%&). Because of buffering effects, the amount of output may
22846 exceed the limit by a small amount before Exim notices.
22849 .option message_prefix pipe string&!! "see below"
22850 The string specified here is expanded and output at the start of every message.
22851 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22854 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22858 .cindex "&%tmail%&"
22859 .cindex "&""From""& line"
22860 This is required by the commonly used &_/usr/bin/vacation_& program.
22861 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22862 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22867 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22868 &`\n`& to &`\r\n`& in &%message_prefix%&.
22871 .option message_suffix pipe string&!! "see below"
22872 The string specified here is expanded and output at the end of every message.
22873 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22874 The suffix can be suppressed by setting
22878 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22879 &`\n`& to &`\r\n`& in &%message_suffix%&.
22882 .option path pipe string "see below"
22883 This option specifies the string that is set up in the PATH environment
22884 variable of the subprocess. The default is:
22888 If the &%command%& option does not yield an absolute path name, the command is
22889 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22890 apply to a command specified as a transport filter.
22893 .option permit_coredump pipe boolean false
22894 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22895 a core-dump of a pipe command, enable this command. This enables core-dumps
22896 during delivery and affects both the Exim binary and the pipe command run.
22897 It is recommended that this option remain off unless and until you have a need
22898 for it and that this only be enabled when needed, as the risk of excessive
22899 resource consumption can be quite high. Note also that Exim is typically
22900 installed as a setuid binary and most operating systems will inhibit coredumps
22901 of these by default, so further OS-specific action may be required.
22904 .option pipe_as_creator pipe boolean false
22905 .cindex "uid (user id)" "local delivery"
22906 If the generic &%user%& option is not set and this option is true, the delivery
22907 process is run under the uid that was in force when Exim was originally called
22908 to accept the message. If the group id is not otherwise set (via the generic
22909 &%group%& option), the gid that was in force when Exim was originally called to
22910 accept the message is used.
22913 .option restrict_to_path pipe boolean false
22914 When this option is set, any command name not listed in &%allow_commands%& must
22915 contain no slashes. The command is searched for only in the directories listed
22916 in the &%path%& option. This option is intended for use in the case when a pipe
22917 command has been generated from a user's &_.forward_& file. This is usually
22918 handled by a &(pipe)& transport called &%address_pipe%&.
22921 .option return_fail_output pipe boolean false
22922 If this option is true, and the command produced any output and ended with a
22923 return code other than zero or one of the codes listed in &%temp_errors%& (that
22924 is, the delivery failed), the output is returned in the bounce message.
22925 However, if the message has a null sender (that is, it is itself a bounce
22926 message), output from the command is discarded. This option and
22927 &%return_output%& are mutually exclusive. Only one of them may be set.
22931 .option return_output pipe boolean false
22932 If this option is true, and the command produced any output, the delivery is
22933 deemed to have failed whatever the return code from the command, and the output
22934 is returned in the bounce message. Otherwise, the output is just discarded.
22935 However, if the message has a null sender (that is, it is a bounce message),
22936 output from the command is always discarded, whatever the setting of this
22937 option. This option and &%return_fail_output%& are mutually exclusive. Only one
22938 of them may be set.
22942 .option temp_errors pipe "string list" "see below"
22943 .cindex "&(pipe)& transport" "temporary failure"
22944 This option contains either a colon-separated list of numbers, or a single
22945 asterisk. If &%ignore_status%& is false
22946 and &%return_output%& is not set,
22947 and the command exits with a non-zero return code, the failure is treated as
22948 temporary and the delivery is deferred if the return code matches one of the
22949 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
22950 codes are treated as permanent errors. The default setting contains the codes
22951 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
22952 compiled on a system that does not define these macros, it assumes values of 75
22953 and 73, respectively.
22956 .option timeout pipe time 1h
22957 If the command fails to complete within this time, it is killed. This normally
22958 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
22959 specifies no timeout. In order to ensure that any subprocesses created by the
22960 command are also killed, Exim makes the initial process a process group leader,
22961 and kills the whole process group on a timeout. However, this can be defeated
22962 if one of the processes starts a new process group.
22964 .option timeout_defer pipe boolean false
22965 A timeout in a &(pipe)& transport, either in the command that the transport
22966 runs, or in a transport filter that is associated with it, is by default
22967 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
22968 is set true, both kinds of timeout become temporary errors, causing the
22969 delivery to be deferred.
22971 .option umask pipe "octal integer" 022
22972 This specifies the umask setting for the subprocess that runs the command.
22975 .option use_bsmtp pipe boolean false
22976 .cindex "envelope sender"
22977 If this option is set true, the &(pipe)& transport writes messages in &"batch
22978 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
22979 commands. If you want to include a leading HELO command with such messages,
22980 you can do so by setting the &%message_prefix%& option. See section
22981 &<<SECTbatchSMTP>>& for details of batch SMTP.
22983 .option use_classresources pipe boolean false
22984 .cindex "class resources (BSD)"
22985 This option is available only when Exim is running on FreeBSD, NetBSD, or
22986 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
22987 resource limits when a &(pipe)& transport is run to perform a delivery. The
22988 limits for the uid under which the pipe is to run are obtained from the login
22992 .option use_crlf pipe boolean false
22993 .cindex "carriage return"
22995 This option causes lines to be terminated with the two-character CRLF sequence
22996 (carriage return, linefeed) instead of just a linefeed character. In the case
22997 of batched SMTP, the byte sequence written to the pipe is then an exact image
22998 of what would be sent down a real SMTP connection.
23000 The contents of the &%message_prefix%& and &%message_suffix%& options are
23001 written verbatim, so must contain their own carriage return characters if these
23002 are needed. When &%use_bsmtp%& is not set, the default values for both
23003 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23004 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23007 .option use_shell pipe boolean false
23008 .vindex "&$pipe_addresses$&"
23009 If this option is set, it causes the command to be passed to &_/bin/sh_&
23010 instead of being run directly from the transport, as described in section
23011 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23012 where the command is expected to be run under a shell and cannot easily be
23013 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23014 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23015 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23020 .section "Using an external local delivery agent" "SECID143"
23021 .cindex "local delivery" "using an external agent"
23022 .cindex "&'procmail'&"
23023 .cindex "external local delivery"
23024 .cindex "delivery" "&'procmail'&"
23025 .cindex "delivery" "by external agent"
23026 The &(pipe)& transport can be used to pass all messages that require local
23027 delivery to a separate local delivery agent such as &%procmail%&. When doing
23028 this, care must be taken to ensure that the pipe is run under an appropriate
23029 uid and gid. In some configurations one wants this to be a uid that is trusted
23030 by the delivery agent to supply the correct sender of the message. It may be
23031 necessary to recompile or reconfigure the delivery agent so that it trusts an
23032 appropriate user. The following is an example transport and router
23033 configuration for &%procmail%&:
23038 command = /usr/local/bin/procmail -d $local_part
23042 check_string = "From "
23043 escape_string = ">From "
23052 transport = procmail_pipe
23054 In this example, the pipe is run as the local user, but with the group set to
23055 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23056 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23057 user to supply a correct sender address. If you do not specify either a
23058 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23059 home directory is the user's home directory by default.
23061 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23065 as shown in some &%procmail%& documentation, because Exim does not by default
23066 use a shell to run pipe commands.
23069 The next example shows a transport and a router for a system where local
23070 deliveries are handled by the Cyrus IMAP server.
23073 local_delivery_cyrus:
23075 command = /usr/cyrus/bin/deliver \
23076 -m ${substr_1:$local_part_suffix} -- $local_part
23088 local_part_suffix = .*
23089 transport = local_delivery_cyrus
23091 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23092 &%return_output%& to cause any text written by Cyrus to be returned to the
23094 .ecindex IIDpiptra1
23095 .ecindex IIDpiptra2
23098 . ////////////////////////////////////////////////////////////////////////////
23099 . ////////////////////////////////////////////////////////////////////////////
23101 .chapter "The smtp transport" "CHAPsmtptrans"
23102 .scindex IIDsmttra1 "transports" "&(smtp)&"
23103 .scindex IIDsmttra2 "&(smtp)& transport"
23104 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23105 or LMTP protocol. The list of hosts to try can either be taken from the address
23106 that is being processed (having been set up by the router), or specified
23107 explicitly for the transport. Timeout and retry processing (see chapter
23108 &<<CHAPretry>>&) is applied to each IP address independently.
23111 .section "Multiple messages on a single connection" "SECID144"
23112 The sending of multiple messages over a single TCP/IP connection can arise in
23116 If a message contains more than &%max_rcpt%& (see below) addresses that are
23117 routed to the same host, more than one copy of the message has to be sent to
23118 that host. In this situation, multiple copies may be sent in a single run of
23119 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23120 does when it has too many addresses to send in one message also depends on the
23121 value of the global &%remote_max_parallel%& option. Details are given in
23122 section &<<SECToutSMTPTCP>>&.)
23124 .cindex "hints database" "remembering routing"
23125 When a message has been successfully delivered over a TCP/IP connection, Exim
23126 looks in its hints database to see if there are any other messages awaiting a
23127 connection to the same host. If there are, a new delivery process is started
23128 for one of them, and the current TCP/IP connection is passed on to it. The new
23129 process may in turn send multiple copies and possibly create yet another
23134 For each copy sent over the same TCP/IP connection, a sequence counter is
23135 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23136 no further messages are sent over that connection.
23140 .section "Use of the $host and $host_address variables" "SECID145"
23142 .vindex "&$host_address$&"
23143 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23144 &$host_address$& are the name and IP address of the first host on the host list
23145 passed by the router. However, when the transport is about to connect to a
23146 specific host, and while it is connected to that host, &$host$& and
23147 &$host_address$& are set to the values for that host. These are the values
23148 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23149 &%serialize_hosts%&, and the various TLS options are expanded.
23152 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23153 .vindex &$tls_bits$&
23154 .vindex &$tls_cipher$&
23155 .vindex &$tls_peerdn$&
23156 .vindex &$tls_sni$&
23157 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23158 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23159 are the values that were set when the message was received.
23160 These are the values that are used for options that are expanded before any
23161 SMTP connections are made. Just before each connection is made, these four
23162 variables are emptied. If TLS is subsequently started, they are set to the
23163 appropriate values for the outgoing connection, and these are the values that
23164 are in force when any authenticators are run and when the
23165 &%authenticated_sender%& option is expanded.
23167 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23168 and will be removed in a future release.
23171 .section "Private options for smtp" "SECID146"
23172 .cindex "options" "&(smtp)& transport"
23173 The private options of the &(smtp)& transport are as follows:
23176 .option address_retry_include_sender smtp boolean true
23177 .cindex "4&'xx'& responses" "retrying after"
23178 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23179 is the combination of sender and recipient that is delayed in subsequent queue
23180 runs until the retry time is reached. You can delay the recipient without
23181 reference to the sender (which is what earlier versions of Exim did), by
23182 setting &%address_retry_include_sender%& false. However, this can lead to
23183 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23185 .option allow_localhost smtp boolean false
23186 .cindex "local host" "sending to"
23187 .cindex "fallback" "hosts specified on transport"
23188 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23189 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23190 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23191 the delivery anyway. This should be used only in special cases when the
23192 configuration ensures that no looping will result (for example, a differently
23193 configured Exim is listening on the port to which the message is sent).
23196 .option authenticated_sender smtp string&!! unset
23198 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23199 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23200 overriding any existing authenticated sender value. If the string expansion is
23201 forced to fail, the option is ignored. Other expansion failures cause delivery
23202 to be deferred. If the result of expansion is an empty string, that is also
23205 The expansion happens after the outgoing connection has been made and TLS
23206 started, if required. This means that the &$host$&, &$host_address$&,
23207 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23208 particular connection.
23210 If the SMTP session is not authenticated, the expansion of
23211 &%authenticated_sender%& still happens (and can cause the delivery to be
23212 deferred if it fails), but no AUTH= item is added to MAIL commands
23213 unless &%authenticated_sender_force%& is true.
23215 This option allows you to use the &(smtp)& transport in LMTP mode to
23216 deliver mail to Cyrus IMAP and provide the proper local part as the
23217 &"authenticated sender"&, via a setting such as:
23219 authenticated_sender = $local_part
23221 This removes the need for IMAP subfolders to be assigned special ACLs to
23222 allow direct delivery to those subfolders.
23224 Because of expected uses such as that just described for Cyrus (when no
23225 domain is involved), there is no checking on the syntax of the provided
23229 .option authenticated_sender_force smtp boolean false
23230 If this option is set true, the &%authenticated_sender%& option's value
23231 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23232 authenticated as a client.
23235 .option command_timeout smtp time 5m
23236 This sets a timeout for receiving a response to an SMTP command that has been
23237 sent out. It is also used when waiting for the initial banner line from the
23238 remote host. Its value must not be zero.
23241 .option connect_timeout smtp time 5m
23242 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23243 to a remote host. A setting of zero allows the system timeout (typically
23244 several minutes) to act. To have any effect, the value of this option must be
23245 less than the system timeout. However, it has been observed that on some
23246 systems there is no system timeout, which is why the default value for this
23247 option is 5 minutes, a value recommended by RFC 1123.
23250 .option connection_max_messages smtp integer 500
23251 .cindex "SMTP" "passed connection"
23252 .cindex "SMTP" "multiple deliveries"
23253 .cindex "multiple SMTP deliveries"
23254 This controls the maximum number of separate message deliveries that are sent
23255 over a single TCP/IP connection. If the value is zero, there is no limit.
23256 For testing purposes, this value can be overridden by the &%-oB%& command line
23260 .option data_timeout smtp time 5m
23261 This sets a timeout for the transmission of each block in the data portion of
23262 the message. As a result, the overall timeout for a message depends on the size
23263 of the message. Its value must not be zero. See also &%final_timeout%&.
23266 .option delay_after_cutoff smtp boolean true
23267 This option controls what happens when all remote IP addresses for a given
23268 domain have been inaccessible for so long that they have passed their retry
23271 In the default state, if the next retry time has not been reached for any of
23272 them, the address is bounced without trying any deliveries. In other words,
23273 Exim delays retrying an IP address after the final cutoff time until a new
23274 retry time is reached, and can therefore bounce an address without ever trying
23275 a delivery, when machines have been down for a long time. Some people are
23276 unhappy at this prospect, so...
23278 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23279 addresses are past their final cutoff time, Exim tries to deliver to those
23280 IP addresses that have not been tried since the message arrived. If there are
23281 none, of if they all fail, the address is bounced. In other words, it does not
23282 delay when a new message arrives, but immediately tries those expired IP
23283 addresses that haven't been tried since the message arrived. If there is a
23284 continuous stream of messages for the dead hosts, unsetting
23285 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23289 .option dns_qualify_single smtp boolean true
23290 If the &%hosts%& or &%fallback_hosts%& option is being used,
23291 and the &%gethostbyname%& option is false,
23292 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23293 in chapter &<<CHAPdnslookup>>& for more details.
23296 .option dns_search_parents smtp boolean false
23297 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23298 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23299 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23303 .option dnssec_request_domains smtp "domain list&!!" unset
23304 .cindex "MX record" "security"
23305 .cindex "DNSSEC" "MX lookup"
23306 .cindex "security" "MX lookup"
23307 .cindex "DNS" "DNSSEC"
23308 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23309 the dnssec request bit set.
23310 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23314 .option dnssec_require_domains smtp "domain list&!!" unset
23315 .cindex "MX record" "security"
23316 .cindex "DNSSEC" "MX lookup"
23317 .cindex "security" "MX lookup"
23318 .cindex "DNS" "DNSSEC"
23319 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23320 the dnssec request bit set. Any returns not having the Authenticated Data bit
23321 (AD bit) set will be ignored and logged as a host-lookup failure.
23322 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23326 .option dscp smtp string&!! unset
23327 .cindex "DCSP" "outbound"
23328 This option causes the DSCP value associated with a socket to be set to one
23329 of a number of fixed strings or to numeric value.
23330 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23331 Common values include &`throughput`&, &`mincost`&, and on newer systems
23332 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23334 The outbound packets from Exim will be marked with this value in the header
23335 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23336 that these values will have any effect, not be stripped by networking
23337 equipment, or do much of anything without cooperation with your Network
23338 Engineer and those of all network operators between the source and destination.
23341 .option fallback_hosts smtp "string list" unset
23342 .cindex "fallback" "hosts specified on transport"
23343 String expansion is not applied to this option. The argument must be a
23344 colon-separated list of host names or IP addresses, optionally also including
23345 port numbers, though the separator can be changed, as described in section
23346 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23347 item in a &%route_list%& setting for the &(manualroute)& router, as described
23348 in section &<<SECTformatonehostitem>>&.
23350 Fallback hosts can also be specified on routers, which associate them with the
23351 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23352 &%fallback_hosts%& specified on the transport is used only if the address does
23353 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23354 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23355 However, &%hosts_randomize%& does apply to fallback host lists.
23357 If Exim is unable to deliver to any of the hosts for a particular address, and
23358 the errors are not permanent rejections, the address is put on a separate
23359 transport queue with its host list replaced by the fallback hosts, unless the
23360 address was routed via MX records and the current host was in the original MX
23361 list. In that situation, the fallback host list is not used.
23363 Once normal deliveries are complete, the fallback queue is delivered by
23364 re-running the same transports with the new host lists. If several failing
23365 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23366 copy of the message is sent.
23368 The resolution of the host names on the fallback list is controlled by the
23369 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23370 both to cases when the host list comes with the address and when it is taken
23371 from &%hosts%&. This option provides a &"use a smart host only if delivery
23375 .option final_timeout smtp time 10m
23376 This is the timeout that applies while waiting for the response to the final
23377 line containing just &"."& that terminates a message. Its value must not be
23380 .option gethostbyname smtp boolean false
23381 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23382 being used, names are looked up using &[gethostbyname()]&
23383 (or &[getipnodebyname()]& when available)
23384 instead of using the DNS. Of course, that function may in fact use the DNS, but
23385 it may also consult other sources of information such as &_/etc/hosts_&.
23387 .option gnutls_compat_mode smtp boolean unset
23388 This option controls whether GnuTLS is used in compatibility mode in an Exim
23389 server. This reduces security slightly, but improves interworking with older
23390 implementations of TLS.
23392 .option helo_data smtp string&!! "see below"
23393 .cindex "HELO" "argument, setting"
23394 .cindex "EHLO" "argument, setting"
23395 .cindex "LHLO argument setting"
23396 The value of this option is expanded after a connection to a another host has
23397 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23398 command that starts the outgoing SMTP or LMTP session. The default value of the
23403 During the expansion, the variables &$host$& and &$host_address$& are set to
23404 the identity of the remote host, and the variables &$sending_ip_address$& and
23405 &$sending_port$& are set to the local IP address and port number that are being
23406 used. These variables can be used to generate different values for different
23407 servers or different local IP addresses. For example, if you want the string
23408 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23409 interface address, you could use this:
23411 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23412 {$primary_hostname}}
23414 The use of &%helo_data%& applies both to sending messages and when doing
23417 .option hosts smtp "string list&!!" unset
23418 Hosts are associated with an address by a router such as &(dnslookup)&, which
23419 finds the hosts by looking up the address domain in the DNS, or by
23420 &(manualroute)&, which has lists of hosts in its configuration. However,
23421 email addresses can be passed to the &(smtp)& transport by any router, and not
23422 all of them can provide an associated list of hosts.
23424 The &%hosts%& option specifies a list of hosts to be used if the address being
23425 processed does not have any hosts associated with it. The hosts specified by
23426 &%hosts%& are also used, whether or not the address has its own hosts, if
23427 &%hosts_override%& is set.
23429 The string is first expanded, before being interpreted as a colon-separated
23430 list of host names or IP addresses, possibly including port numbers. The
23431 separator may be changed to something other than colon, as described in section
23432 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23433 item in a &%route_list%& setting for the &(manualroute)& router, as described
23434 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23435 of the &(manualroute)& router is not available here.
23437 If the expansion fails, delivery is deferred. Unless the failure was caused by
23438 the inability to complete a lookup, the error is logged to the panic log as
23439 well as the main log. Host names are looked up either by searching directly for
23440 address records in the DNS or by calling &[gethostbyname()]& (or
23441 &[getipnodebyname()]& when available), depending on the setting of the
23442 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23443 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23446 During delivery, the hosts are tried in order, subject to their retry status,
23447 unless &%hosts_randomize%& is set.
23450 .option hosts_avoid_esmtp smtp "host list&!!" unset
23451 .cindex "ESMTP, avoiding use of"
23452 .cindex "HELO" "forcing use of"
23453 .cindex "EHLO" "avoiding use of"
23454 .cindex "PIPELINING" "avoiding the use of"
23455 This option is for use with broken hosts that announce ESMTP facilities (for
23456 example, PIPELINING) and then fail to implement them properly. When a host
23457 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23458 start of the SMTP session. This means that it cannot use any of the ESMTP
23459 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23462 .option hosts_avoid_pipelining smtp "host list&!!" unset
23463 .cindex "PIPELINING" "avoiding the use of"
23464 Exim will not use the SMTP PIPELINING extension when delivering to any host
23465 that matches this list, even if the server host advertises PIPELINING support.
23468 .option hosts_avoid_tls smtp "host list&!!" unset
23469 .cindex "TLS" "avoiding for certain hosts"
23470 Exim will not try to start a TLS session when delivering to any host that
23471 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23474 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23475 .cindex "TLS" "avoiding for certain hosts"
23476 Exim will not try to start a TLS session for a verify callout,
23477 or when delivering in cutthrough mode,
23478 to any host that matches this list.
23482 .option hosts_max_try smtp integer 5
23483 .cindex "host" "maximum number to try"
23484 .cindex "limit" "number of hosts tried"
23485 .cindex "limit" "number of MX tried"
23486 .cindex "MX record" "maximum tried"
23487 This option limits the number of IP addresses that are tried for any one
23488 delivery in cases where there are temporary delivery errors. Section
23489 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23492 .option hosts_max_try_hardlimit smtp integer 50
23493 This is an additional check on the maximum number of IP addresses that Exim
23494 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23499 .option hosts_nopass_tls smtp "host list&!!" unset
23500 .cindex "TLS" "passing connection"
23501 .cindex "multiple SMTP deliveries"
23502 .cindex "TLS" "multiple message deliveries"
23503 For any host that matches this list, a connection on which a TLS session has
23504 been started will not be passed to a new delivery process for sending another
23505 message on the same connection. See section &<<SECTmulmessam>>& for an
23506 explanation of when this might be needed.
23509 .option hosts_override smtp boolean false
23510 If this option is set and the &%hosts%& option is also set, any hosts that are
23511 attached to the address are ignored, and instead the hosts specified by the
23512 &%hosts%& option are always used. This option does not apply to
23513 &%fallback_hosts%&.
23516 .option hosts_randomize smtp boolean false
23517 .cindex "randomized host list"
23518 .cindex "host" "list of; randomized"
23519 .cindex "fallback" "randomized hosts"
23520 If this option is set, and either the list of hosts is taken from the
23521 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23522 were not obtained from MX records (this includes fallback hosts from the
23523 router), and were not randomized by the router, the order of trying the hosts
23524 is randomized each time the transport runs. Randomizing the order of a host
23525 list can be used to do crude load sharing.
23527 When &%hosts_randomize%& is true, a host list may be split into groups whose
23528 order is separately randomized. This makes it possible to set up MX-like
23529 behaviour. The boundaries between groups are indicated by an item that is just
23530 &`+`& in the host list. For example:
23532 hosts = host1:host2:host3:+:host4:host5
23534 The order of the first three hosts and the order of the last two hosts is
23535 randomized for each use, but the first three always end up before the last two.
23536 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23538 .option hosts_require_auth smtp "host list&!!" unset
23539 .cindex "authentication" "required by client"
23540 This option provides a list of servers for which authentication must succeed
23541 before Exim will try to transfer a message. If authentication fails for
23542 servers which are not in this list, Exim tries to send unauthenticated. If
23543 authentication fails for one of these servers, delivery is deferred. This
23544 temporary error is detectable in the retry rules, so it can be turned into a
23545 hard failure if required. See also &%hosts_try_auth%&, and chapter
23546 &<<CHAPSMTPAUTH>>& for details of authentication.
23549 .option hosts_request_ocsp smtp "host list&!!" *
23550 .cindex "TLS" "requiring for certain servers"
23551 Exim will request a Certificate Status on a
23552 TLS session for any host that matches this list.
23553 &%tls_verify_certificates%& should also be set for the transport.
23555 .option hosts_require_ocsp smtp "host list&!!" unset
23556 .cindex "TLS" "requiring for certain servers"
23557 Exim will request, and check for a valid Certificate Status being given, on a
23558 TLS session for any host that matches this list.
23559 &%tls_verify_certificates%& should also be set for the transport.
23561 .option hosts_require_tls smtp "host list&!!" unset
23562 .cindex "TLS" "requiring for certain servers"
23563 Exim will insist on using a TLS session when delivering to any host that
23564 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23565 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23566 incoming messages, use an appropriate ACL.
23568 .option hosts_try_auth smtp "host list&!!" unset
23569 .cindex "authentication" "optional in client"
23570 This option provides a list of servers to which, provided they announce
23571 authentication support, Exim will attempt to authenticate as a client when it
23572 connects. If authentication fails, Exim will try to transfer the message
23573 unauthenticated. See also &%hosts_require_auth%&, and chapter
23574 &<<CHAPSMTPAUTH>>& for details of authentication.
23577 .option hosts_try_prdr smtp "host list&!!" *
23578 .cindex "PRDR" "enabling, optional in client"
23579 This option provides a list of servers to which, provided they announce
23580 PRDR support, Exim will attempt to negotiate PRDR
23581 for multi-recipient messages.
23582 The option can usually be left as default.
23585 .option interface smtp "string list&!!" unset
23586 .cindex "bind IP address"
23587 .cindex "IP address" "binding"
23589 .vindex "&$host_address$&"
23590 This option specifies which interface to bind to when making an outgoing SMTP
23591 call. The value is an IP address, not an interface name such as
23592 &`eth0`&. Do not confuse this with the interface address that was used when a
23593 message was received, which is in &$received_ip_address$&, formerly known as
23594 &$interface_address$&. The name was changed to minimize confusion with the
23595 outgoing interface address. There is no variable that contains an outgoing
23596 interface address because, unless it is set by this option, its value is
23599 During the expansion of the &%interface%& option the variables &$host$& and
23600 &$host_address$& refer to the host to which a connection is about to be made
23601 during the expansion of the string. Forced expansion failure, or an empty
23602 string result causes the option to be ignored. Otherwise, after expansion, the
23603 string must be a list of IP addresses, colon-separated by default, but the
23604 separator can be changed in the usual way. For example:
23606 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
23608 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
23609 connection. If none of them are the correct type, the option is ignored. If
23610 &%interface%& is not set, or is ignored, the system's IP functions choose which
23611 interface to use if the host has more than one.
23614 .option keepalive smtp boolean true
23615 .cindex "keepalive" "on outgoing connection"
23616 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
23617 connections. When set, it causes the kernel to probe idle connections
23618 periodically, by sending packets with &"old"& sequence numbers. The other end
23619 of the connection should send a acknowledgment if the connection is still okay
23620 or a reset if the connection has been aborted. The reason for doing this is
23621 that it has the beneficial effect of freeing up certain types of connection
23622 that can get stuck when the remote host is disconnected without tidying up the
23623 TCP/IP call properly. The keepalive mechanism takes several hours to detect
23627 .option lmtp_ignore_quota smtp boolean false
23628 .cindex "LMTP" "ignoring quota errors"
23629 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
23630 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
23631 has advertised support for IGNOREQUOTA in its response to the LHLO command.
23633 .option max_rcpt smtp integer 100
23634 .cindex "RCPT" "maximum number of outgoing"
23635 This option limits the number of RCPT commands that are sent in a single
23636 SMTP message transaction. Each set of addresses is treated independently, and
23637 so can cause parallel connections to the same host if &%remote_max_parallel%&
23641 .option multi_domain smtp boolean&!! true
23642 .vindex "&$domain$&"
23643 When this option is set, the &(smtp)& transport can handle a number of
23644 addresses containing a mixture of different domains provided they all resolve
23645 to the same list of hosts. Turning the option off restricts the transport to
23646 handling only one domain at a time. This is useful if you want to use
23647 &$domain$& in an expansion for the transport, because it is set only when there
23648 is a single domain involved in a remote delivery.
23651 It is expanded per-address and can depend on any of
23652 &$address_data$&, &$domain_data$&, &$local_part_data$&,
23653 &$host$&, &$host_address$& and &$host_port$&.
23656 .option port smtp string&!! "see below"
23657 .cindex "port" "sending TCP/IP"
23658 .cindex "TCP/IP" "setting outgoing port"
23659 This option specifies the TCP/IP port on the server to which Exim connects.
23660 &*Note:*& Do not confuse this with the port that was used when a message was
23661 received, which is in &$received_port$&, formerly known as &$interface_port$&.
23662 The name was changed to minimize confusion with the outgoing port. There is no
23663 variable that contains an outgoing port.
23665 If the value of this option begins with a digit it is taken as a port number;
23666 otherwise it is looked up using &[getservbyname()]&. The default value is
23667 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
23668 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
23673 .option protocol smtp string smtp
23674 .cindex "LMTP" "over TCP/IP"
23675 .cindex "ssmtp protocol" "outbound"
23676 .cindex "TLS" "SSL-on-connect outbound"
23678 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
23679 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
23680 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
23681 deliveries into closed message stores. Exim also has support for running LMTP
23682 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
23684 If this option is set to &"smtps"&, the default value for the &%port%& option
23685 changes to &"smtps"&, and the transport initiates TLS immediately after
23686 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
23687 The Internet standards bodies strongly discourage use of this mode.
23690 .option retry_include_ip_address smtp boolean&!! true
23691 Exim normally includes both the host name and the IP address in the key it
23692 constructs for indexing retry data after a temporary delivery failure. This
23693 means that when one of several IP addresses for a host is failing, it gets
23694 tried periodically (controlled by the retry rules), but use of the other IP
23695 addresses is not affected.
23697 However, in some dialup environments hosts are assigned a different IP address
23698 each time they connect. In this situation the use of the IP address as part of
23699 the retry key leads to undesirable behaviour. Setting this option false causes
23700 Exim to use only the host name.
23702 Since it is expanded it can be made to depend on the host or domain.
23706 .option serialize_hosts smtp "host list&!!" unset
23707 .cindex "serializing connections"
23708 .cindex "host" "serializing connections"
23709 Because Exim operates in a distributed manner, if several messages for the same
23710 host arrive at around the same time, more than one simultaneous connection to
23711 the remote host can occur. This is not usually a problem except when there is a
23712 slow link between the hosts. In that situation it may be helpful to restrict
23713 Exim to one connection at a time. This can be done by setting
23714 &%serialize_hosts%& to match the relevant hosts.
23716 .cindex "hints database" "serializing deliveries to a host"
23717 Exim implements serialization by means of a hints database in which a record is
23718 written whenever a process connects to one of the restricted hosts. The record
23719 is deleted when the connection is completed. Obviously there is scope for
23720 records to get left lying around if there is a system or program crash. To
23721 guard against this, Exim ignores any records that are more than six hours old.
23723 If you set up this kind of serialization, you should also arrange to delete the
23724 relevant hints database whenever your system reboots. The names of the files
23725 start with &_misc_& and they are kept in the &_spool/db_& directory. There
23726 may be one or two files, depending on the type of DBM in use. The same files
23727 are used for ETRN serialization.
23730 .option size_addition smtp integer 1024
23731 .cindex "SMTP" "SIZE"
23732 .cindex "message" "size issue for transport filter"
23733 .cindex "size" "of message"
23734 .cindex "transport" "filter"
23735 .cindex "filter" "transport filter"
23736 If a remote SMTP server indicates that it supports the SIZE option of the
23737 MAIL command, Exim uses this to pass over the message size at the start of
23738 an SMTP transaction. It adds the value of &%size_addition%& to the value it
23739 sends, to allow for headers and other text that may be added during delivery by
23740 configuration options or in a transport filter. It may be necessary to increase
23741 this if a lot of text is added to messages.
23743 Alternatively, if the value of &%size_addition%& is set negative, it disables
23744 the use of the SIZE option altogether.
23747 .option tls_certificate smtp string&!! unset
23748 .cindex "TLS" "client certificate, location of"
23749 .cindex "certificate" "client, location of"
23751 .vindex "&$host_address$&"
23752 The value of this option must be the absolute path to a file which contains the
23753 client's certificate, for possible use when sending a message over an encrypted
23754 connection. The values of &$host$& and &$host_address$& are set to the name and
23755 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23758 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23759 certificate when sending messages as a client. The global option of the same
23760 name specifies the certificate for Exim as a server; it is not automatically
23761 assumed that the same certificate should be used when Exim is operating as a
23765 .option tls_crl smtp string&!! unset
23766 .cindex "TLS" "client certificate revocation list"
23767 .cindex "certificate" "revocation list for client"
23768 This option specifies a certificate revocation list. The expanded value must
23769 be the name of a file that contains a CRL in PEM format.
23772 .option tls_dh_min_bits smtp integer 1024
23773 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23774 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23775 key agreement is negotiated, the server will provide a large prime number
23776 for use. This option establishes the minimum acceptable size of that number.
23777 If the parameter offered by the server is too small, then the TLS handshake
23780 Only supported when using GnuTLS.
23783 .option tls_privatekey smtp string&!! unset
23784 .cindex "TLS" "client private key, location of"
23786 .vindex "&$host_address$&"
23787 The value of this option must be the absolute path to a file which contains the
23788 client's private key. This is used when sending a message over an encrypted
23789 connection using a client certificate. The values of &$host$& and
23790 &$host_address$& are set to the name and address of the server during the
23791 expansion. If this option is unset, or the expansion is forced to fail, or the
23792 result is an empty string, the private key is assumed to be in the same file as
23793 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
23796 .option tls_require_ciphers smtp string&!! unset
23797 .cindex "TLS" "requiring specific ciphers"
23798 .cindex "cipher" "requiring specific"
23800 .vindex "&$host_address$&"
23801 The value of this option must be a list of permitted cipher suites, for use
23802 when setting up an outgoing encrypted connection. (There is a global option of
23803 the same name for controlling incoming connections.) The values of &$host$& and
23804 &$host_address$& are set to the name and address of the server during the
23805 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
23806 is used in different ways by OpenSSL and GnuTLS (see sections
23807 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
23808 ciphers is a preference order.
23812 .option tls_sni smtp string&!! unset
23813 .cindex "TLS" "Server Name Indication"
23814 .vindex "&$tls_sni$&"
23815 If this option is set then it sets the $tls_out_sni variable and causes any
23816 TLS session to pass this value as the Server Name Indication extension to
23817 the remote side, which can be used by the remote side to select an appropriate
23818 certificate and private key for the session.
23820 See &<<SECTtlssni>>& for more information.
23822 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23828 .option tls_tempfail_tryclear smtp boolean true
23829 .cindex "4&'xx'& responses" "to STARTTLS"
23830 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23831 setting up a TLS session, this option determines whether or not Exim should try
23832 to deliver the message unencrypted. If it is set false, delivery to the
23833 current host is deferred; if there are other hosts, they are tried. If this
23834 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23835 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23836 TLS negotiation fails, Exim closes the current connection (because it is in an
23837 unknown state), opens a new one to the same host, and then tries the delivery
23842 .option tls_try_verify_hosts smtp "host list&!!" *
23844 .cindex "TLS" "server certificate verification"
23845 .cindex "certificate" "verification of server"
23846 This option gives a list of hosts for which, on encrypted connections,
23847 certificate verification will be tried but need not succeed.
23848 The &%tls_verify_certificates%& option must also be set.
23849 Note that unless the host is in this list
23850 TLS connections will be denied to hosts using self-signed certificates
23851 when &%tls_verify_certificates%& is matched.
23852 The &$tls_out_certificate_verified$& variable is set when
23853 certificate verification succeeds.
23857 .option tls_verify_cert_hostnames smtp "host list&!!" *
23858 .cindex "TLS" "server certificate hostname verification"
23859 .cindex "certificate" "verification of server"
23860 This option give a list of hosts for which,
23861 while verifying the server certificate,
23862 checks will be included on the host name
23863 (note that this will generally be the result of a DNS MX lookup)
23864 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
23865 limited to being the initial component of a 3-or-more component FQDN.
23867 There is no equivalent checking on client certificates.
23872 .option tls_verify_certificates smtp string&!! system
23873 .cindex "TLS" "server certificate verification"
23874 .cindex "certificate" "verification of server"
23876 .vindex "&$host_address$&"
23877 The value of this option must be either the
23879 or the absolute path to
23880 a file or directory containing permitted certificates for servers,
23881 for use when setting up an encrypted connection.
23883 The "system" value for the option will use a location compiled into the SSL library.
23884 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
23885 is taken as empty and an explicit location
23888 The use of a directory for the option value is not available for GnuTLS versions
23889 preceding 3.3.6 and a single file must be used.
23892 With OpenSSL the certificates specified
23894 either by file or directory
23895 are added to those given by the system default location.
23897 The values of &$host$& and
23898 &$host_address$& are set to the name and address of the server during the
23899 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23901 For back-compatibility,
23902 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23903 (a single-colon empty list counts as being set)
23904 and certificate verification fails the TLS connection is closed.
23907 .option tls_verify_hosts smtp "host list&!!" unset
23908 .cindex "TLS" "server certificate verification"
23909 .cindex "certificate" "verification of server"
23910 This option gives a list of hosts for which. on encrypted connections,
23911 certificate verification must succeed.
23912 The &%tls_verify_certificates%& option must also be set.
23913 If both this option and &%tls_try_verify_hosts%& are unset
23914 operation is as if this option selected all hosts.
23919 .section "How the limits for the number of hosts to try are used" &&&
23921 .cindex "host" "maximum number to try"
23922 .cindex "limit" "hosts; maximum number tried"
23923 There are two options that are concerned with the number of hosts that are
23924 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23925 &%hosts_max_try_hardlimit%&.
23928 The &%hosts_max_try%& option limits the number of hosts that are tried
23929 for a single delivery. However, despite the term &"host"& in its name, the
23930 option actually applies to each IP address independently. In other words, a
23931 multihomed host is treated as several independent hosts, just as it is for
23934 Many of the larger ISPs have multiple MX records which often point to
23935 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
23936 created as a result of routing one of these domains.
23938 Trying every single IP address on such a long list does not seem sensible; if
23939 several at the top of the list fail, it is reasonable to assume there is some
23940 problem that is likely to affect all of them. Roughly speaking, the value of
23941 &%hosts_max_try%& is the maximum number that are tried before deferring the
23942 delivery. However, the logic cannot be quite that simple.
23944 Firstly, IP addresses that are skipped because their retry times have not
23945 arrived do not count, and in addition, addresses that are past their retry
23946 limits are also not counted, even when they are tried. This means that when
23947 some IP addresses are past their retry limits, more than the value of
23948 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
23949 that all IP addresses are considered before timing out an email address (but
23950 see below for an exception).
23952 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
23953 list to see if there is a subsequent host with a different (higher valued) MX.
23954 If there is, that host is considered next, and the current IP address is used
23955 but not counted. This behaviour helps in the case of a domain with a retry rule
23956 that hardly ever delays any hosts, as is now explained:
23958 Consider the case of a long list of hosts with one MX value, and a few with a
23959 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
23960 hosts at the top of the list are tried at first. With the default retry rule,
23961 which specifies increasing retry times, the higher MX hosts are eventually
23962 tried when those at the top of the list are skipped because they have not
23963 reached their retry times.
23965 However, it is common practice to put a fixed short retry time on domains for
23966 large ISPs, on the grounds that their servers are rarely down for very long.
23967 Unfortunately, these are exactly the domains that tend to resolve to long lists
23968 of hosts. The short retry time means that the lowest MX hosts are tried every
23969 time. The attempts may be in a different order because of random sorting, but
23970 without the special MX check, the higher MX hosts would never be tried until
23971 all the lower MX hosts had timed out (which might be several days), because
23972 there are always some lower MX hosts that have reached their retry times. With
23973 the special check, Exim considers at least one IP address from each MX value at
23974 every delivery attempt, even if the &%hosts_max_try%& limit has already been
23977 The above logic means that &%hosts_max_try%& is not a hard limit, and in
23978 particular, Exim normally eventually tries all the IP addresses before timing
23979 out an email address. When &%hosts_max_try%& was implemented, this seemed a
23980 reasonable thing to do. Recently, however, some lunatic DNS configurations have
23981 been set up with hundreds of IP addresses for some domains. It can
23982 take a very long time indeed for an address to time out in these cases.
23984 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
23985 Exim never tries more than this number of IP addresses; if it hits this limit
23986 and they are all timed out, the email address is bounced, even though not all
23987 possible IP addresses have been tried.
23988 .ecindex IIDsmttra1
23989 .ecindex IIDsmttra2
23995 . ////////////////////////////////////////////////////////////////////////////
23996 . ////////////////////////////////////////////////////////////////////////////
23998 .chapter "Address rewriting" "CHAPrewrite"
23999 .scindex IIDaddrew "rewriting" "addresses"
24000 There are some circumstances in which Exim automatically rewrites domains in
24001 addresses. The two most common are when an address is given without a domain
24002 (referred to as an &"unqualified address"&) or when an address contains an
24003 abbreviated domain that is expanded by DNS lookup.
24005 Unqualified envelope addresses are accepted only for locally submitted
24006 messages, or for messages that are received from hosts matching
24007 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24008 appropriate. Unqualified addresses in header lines are qualified if they are in
24009 locally submitted messages, or messages from hosts that are permitted to send
24010 unqualified envelope addresses. Otherwise, unqualified addresses in header
24011 lines are neither qualified nor rewritten.
24013 One situation in which Exim does &'not'& automatically rewrite a domain is
24014 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24015 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24016 do this. The new RFCs do not contain this suggestion.
24019 .section "Explicitly configured address rewriting" "SECID147"
24020 This chapter describes the rewriting rules that can be used in the
24021 main rewrite section of the configuration file, and also in the generic
24022 &%headers_rewrite%& option that can be set on any transport.
24024 Some people believe that configured address rewriting is a Mortal Sin.
24025 Others believe that life is not possible without it. Exim provides the
24026 facility; you do not have to use it.
24028 The main rewriting rules that appear in the &"rewrite"& section of the
24029 configuration file are applied to addresses in incoming messages, both envelope
24030 addresses and addresses in header lines. Each rule specifies the types of
24031 address to which it applies.
24033 Whether or not addresses in header lines are rewritten depends on the origin of
24034 the headers and the type of rewriting. Global rewriting, that is, rewriting
24035 rules from the rewrite section of the configuration file, is applied only to
24036 those headers that were received with the message. Header lines that are added
24037 by ACLs or by a system filter or by individual routers or transports (which
24038 are specific to individual recipient addresses) are not rewritten by the global
24041 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24042 applies all headers except those added by routers and transports. That is, as
24043 well as the headers that were received with the message, it also applies to
24044 headers that were added by an ACL or a system filter.
24047 In general, rewriting addresses from your own system or domain has some
24048 legitimacy. Rewriting other addresses should be done only with great care and
24049 in special circumstances. The author of Exim believes that rewriting should be
24050 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24051 Although it can sometimes be used as a routing tool, this is very strongly
24054 There are two commonly encountered circumstances where rewriting is used, as
24055 illustrated by these examples:
24058 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24059 exchange mail with each other behind a firewall, but there is only a single
24060 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24061 &'hitch.fict.example'& when sending mail off-site.
24063 A host rewrites the local parts of its own users so that, for example,
24064 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24069 .section "When does rewriting happen?" "SECID148"
24070 .cindex "rewriting" "timing of"
24071 .cindex "&ACL;" "rewriting addresses in"
24072 Configured address rewriting can take place at several different stages of a
24073 message's processing.
24075 .vindex "&$sender_address$&"
24076 At the start of an ACL for MAIL, the sender address may have been rewritten
24077 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24078 ordinary rewrite rules have yet been applied. If, however, the sender address
24079 is verified in the ACL, it is rewritten before verification, and remains
24080 rewritten thereafter. The subsequent value of &$sender_address$& is the
24081 rewritten address. This also applies if sender verification happens in a
24082 RCPT ACL. Otherwise, when the sender address is not verified, it is
24083 rewritten as soon as a message's header lines have been received.
24085 .vindex "&$domain$&"
24086 .vindex "&$local_part$&"
24087 Similarly, at the start of an ACL for RCPT, the current recipient's address
24088 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24089 rewrite rules have yet been applied to it. However, the behaviour is different
24090 from the sender address when a recipient is verified. The address is rewritten
24091 for the verification, but the rewriting is not remembered at this stage. The
24092 value of &$local_part$& and &$domain$& after verification are always the same
24093 as they were before (that is, they contain the unrewritten &-- except for
24094 SMTP-time rewriting &-- address).
24096 As soon as a message's header lines have been received, all the envelope
24097 recipient addresses are permanently rewritten, and rewriting is also applied to
24098 the addresses in the header lines (if configured). This happens before adding
24099 any header lines that were specified in MAIL or RCPT ACLs, and
24100 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24101 before the DATA ACL and &[local_scan()]& functions are run.
24103 When an address is being routed, either for delivery or for verification,
24104 rewriting is applied immediately to child addresses that are generated by
24105 redirection, unless &%no_rewrite%& is set on the router.
24107 .cindex "envelope sender" "rewriting at transport time"
24108 .cindex "rewriting" "at transport time"
24109 .cindex "header lines" "rewriting at transport time"
24110 At transport time, additional rewriting of addresses in header lines can be
24111 specified by setting the generic &%headers_rewrite%& option on a transport.
24112 This option contains rules that are identical in form to those in the rewrite
24113 section of the configuration file. They are applied to the original message
24114 header lines and any that were added by ACLs or a system filter. They are not
24115 applied to header lines that are added by routers or the transport.
24117 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24118 transport option. However, it is not possible to rewrite envelope recipients at
24124 .section "Testing the rewriting rules that apply on input" "SECID149"
24125 .cindex "rewriting" "testing"
24126 .cindex "testing" "rewriting"
24127 Exim's input rewriting configuration appears in a part of the run time
24128 configuration file headed by &"begin rewrite"&. It can be tested by the
24129 &%-brw%& command line option. This takes an address (which can be a full RFC
24130 2822 address) as its argument. The output is a list of how the address would be
24131 transformed by the rewriting rules for each of the different places it might
24132 appear in an incoming message, that is, for each different header and for the
24133 envelope sender and recipient fields. For example,
24135 exim -brw ph10@exim.workshop.example
24137 might produce the output
24139 sender: Philip.Hazel@exim.workshop.example
24140 from: Philip.Hazel@exim.workshop.example
24141 to: ph10@exim.workshop.example
24142 cc: ph10@exim.workshop.example
24143 bcc: ph10@exim.workshop.example
24144 reply-to: Philip.Hazel@exim.workshop.example
24145 env-from: Philip.Hazel@exim.workshop.example
24146 env-to: ph10@exim.workshop.example
24148 which shows that rewriting has been set up for that address when used in any of
24149 the source fields, but not when it appears as a recipient address. At the
24150 present time, there is no equivalent way of testing rewriting rules that are
24151 set for a particular transport.
24154 .section "Rewriting rules" "SECID150"
24155 .cindex "rewriting" "rules"
24156 The rewrite section of the configuration file consists of lines of rewriting
24159 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24161 Rewriting rules that are specified for the &%headers_rewrite%& generic
24162 transport option are given as a colon-separated list. Each item in the list
24163 takes the same form as a line in the main rewriting configuration (except that
24164 any colons must be doubled, of course).
24166 The formats of source patterns and replacement strings are described below.
24167 Each is terminated by white space, unless enclosed in double quotes, in which
24168 case normal quoting conventions apply inside the quotes. The flags are single
24169 characters which may appear in any order. Spaces and tabs between them are
24172 For each address that could potentially be rewritten, the rules are scanned in
24173 order, and replacements for the address from earlier rules can themselves be
24174 replaced by later rules (but see the &"q"& and &"R"& flags).
24176 The order in which addresses are rewritten is undefined, may change between
24177 releases, and must not be relied on, with one exception: when a message is
24178 received, the envelope sender is always rewritten first, before any header
24179 lines are rewritten. For example, the replacement string for a rewrite of an
24180 address in &'To:'& must not assume that the message's address in &'From:'& has
24181 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24182 that the envelope sender has already been rewritten.
24184 .vindex "&$domain$&"
24185 .vindex "&$local_part$&"
24186 The variables &$local_part$& and &$domain$& can be used in the replacement
24187 string to refer to the address that is being rewritten. Note that lookup-driven
24188 rewriting can be done by a rule of the form
24192 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24193 refer to the address that is being rewritten.
24196 .section "Rewriting patterns" "SECID151"
24197 .cindex "rewriting" "patterns"
24198 .cindex "address list" "in a rewriting pattern"
24199 The source pattern in a rewriting rule is any item which may appear in an
24200 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24201 single-item address list, which means that it is expanded before being tested
24202 against the address. As always, if you use a regular expression as a pattern,
24203 you must take care to escape dollar and backslash characters, or use the &`\N`&
24204 facility to suppress string expansion within the regular expression.
24206 Domains in patterns should be given in lower case. Local parts in patterns are
24207 case-sensitive. If you want to do case-insensitive matching of local parts, you
24208 can use a regular expression that starts with &`^(?i)`&.
24210 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24211 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24212 depending on the type of match which occurred. These can be used in the
24213 replacement string to insert portions of the incoming address. &$0$& always
24214 refers to the complete incoming address. When a regular expression is used, the
24215 numerical variables are set from its capturing subexpressions. For other types
24216 of pattern they are set as follows:
24219 If a local part or domain starts with an asterisk, the numerical variables
24220 refer to the character strings matched by asterisks, with &$1$& associated with
24221 the first asterisk, and &$2$& with the second, if present. For example, if the
24224 *queen@*.fict.example
24226 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24228 $0 = hearts-queen@wonderland.fict.example
24232 Note that if the local part does not start with an asterisk, but the domain
24233 does, it is &$1$& that contains the wild part of the domain.
24236 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24237 of the domain are placed in the next available numerical variables. Suppose,
24238 for example, that the address &'foo@bar.baz.example'& is processed by a
24239 rewriting rule of the form
24241 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24243 and the key in the file that matches the domain is &`*.baz.example`&. Then
24249 If the address &'foo@baz.example'& is looked up, this matches the same
24250 wildcard file entry, and in this case &$2$& is set to the empty string, but
24251 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24252 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24253 whole domain. For non-partial domain lookups, no numerical variables are set.
24257 .section "Rewriting replacements" "SECID152"
24258 .cindex "rewriting" "replacements"
24259 If the replacement string for a rule is a single asterisk, addresses that
24260 match the pattern and the flags are &'not'& rewritten, and no subsequent
24261 rewriting rules are scanned. For example,
24263 hatta@lookingglass.fict.example * f
24265 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24268 .vindex "&$domain$&"
24269 .vindex "&$local_part$&"
24270 If the replacement string is not a single asterisk, it is expanded, and must
24271 yield a fully qualified address. Within the expansion, the variables
24272 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24273 Any letters they contain retain their original case &-- they are not lower
24274 cased. The numerical variables are set up according to the type of pattern that
24275 matched the address, as described above. If the expansion is forced to fail by
24276 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24277 current rule is abandoned, but subsequent rules may take effect. Any other
24278 expansion failure causes the entire rewriting operation to be abandoned, and an
24279 entry written to the panic log.
24283 .section "Rewriting flags" "SECID153"
24284 There are three different kinds of flag that may appear on rewriting rules:
24287 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24290 A flag that specifies rewriting at SMTP time: S.
24292 Flags that control the rewriting process: Q, q, R, w.
24295 For rules that are part of the &%headers_rewrite%& generic transport option,
24296 E, F, T, and S are not permitted.
24300 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24302 .cindex "rewriting" "flags"
24303 If none of the following flag letters, nor the &"S"& flag (see section
24304 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24305 and to both the sender and recipient fields of the envelope, whereas a
24306 transport-time rewriting rule just applies to all headers. Otherwise, the
24307 rewriting rule is skipped unless the relevant addresses are being processed.
24309 &`E`& rewrite all envelope fields
24310 &`F`& rewrite the envelope From field
24311 &`T`& rewrite the envelope To field
24312 &`b`& rewrite the &'Bcc:'& header
24313 &`c`& rewrite the &'Cc:'& header
24314 &`f`& rewrite the &'From:'& header
24315 &`h`& rewrite all headers
24316 &`r`& rewrite the &'Reply-To:'& header
24317 &`s`& rewrite the &'Sender:'& header
24318 &`t`& rewrite the &'To:'& header
24320 "All headers" means all of the headers listed above that can be selected
24321 individually, plus their &'Resent-'& versions. It does not include
24322 other headers such as &'Subject:'& etc.
24324 You should be particularly careful about rewriting &'Sender:'& headers, and
24325 restrict this to special known cases in your own domains.
24328 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24329 .cindex "SMTP" "rewriting malformed addresses"
24330 .cindex "RCPT" "rewriting argument of"
24331 .cindex "MAIL" "rewriting argument of"
24332 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24333 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24334 before any other processing; even before syntax checking. The pattern is
24335 required to be a regular expression, and it is matched against the whole of the
24336 data for the command, including any surrounding angle brackets.
24338 .vindex "&$domain$&"
24339 .vindex "&$local_part$&"
24340 This form of rewrite rule allows for the handling of addresses that are not
24341 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24342 input). Because the input is not required to be a syntactically valid address,
24343 the variables &$local_part$& and &$domain$& are not available during the
24344 expansion of the replacement string. The result of rewriting replaces the
24345 original address in the MAIL or RCPT command.
24348 .section "Flags controlling the rewriting process" "SECID155"
24349 There are four flags which control the way the rewriting process works. These
24350 take effect only when a rule is invoked, that is, when the address is of the
24351 correct type (matches the flags) and matches the pattern:
24354 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24355 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24356 absence of &"Q"& the rewritten address must always include a domain.
24358 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24359 even if no rewriting actually takes place because of a &"fail"& in the
24360 expansion. The &"q"& flag is not effective if the address is of the wrong type
24361 (does not match the flags) or does not match the pattern.
24363 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24364 address, up to ten times. It can be combined with the &"q"& flag, to stop
24365 rewriting once it fails to match (after at least one successful rewrite).
24367 .cindex "rewriting" "whole addresses"
24368 When an address in a header is rewritten, the rewriting normally applies only
24369 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24370 left unchanged. For example, rewriting might change
24372 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24376 From: Ford Prefect <prefectf@hitch.fict.example>
24379 Sometimes there is a need to replace the whole address item, and this can be
24380 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24381 causes an address in a header line to be rewritten, the entire address is
24382 replaced, not just the working part. The replacement must be a complete RFC
24383 2822 address, including the angle brackets if necessary. If text outside angle
24384 brackets contains a character whose value is greater than 126 or less than 32
24385 (except for tab), the text is encoded according to RFC 2047. The character set
24386 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
24388 When the &"w"& flag is set on a rule that causes an envelope address to be
24389 rewritten, all but the working part of the replacement address is discarded.
24393 .section "Rewriting examples" "SECID156"
24394 Here is an example of the two common rewriting paradigms:
24396 *@*.hitch.fict.example $1@hitch.fict.example
24397 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24398 {$value}fail}@hitch.fict.example bctfrF
24400 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24401 the string expansion to fail if the lookup does not succeed. In this context it
24402 has the effect of leaving the original address unchanged, but Exim goes on to
24403 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24404 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24405 explicitly, which would cause the rewritten address to be the same as before,
24406 at the cost of a small bit of processing. Not supplying either of these is an
24407 error, since the rewritten address would then contain no local part.
24409 The first example above replaces the domain with a superior, more general
24410 domain. This may not be desirable for certain local parts. If the rule
24412 root@*.hitch.fict.example *
24414 were inserted before the first rule, rewriting would be suppressed for the
24415 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24417 Rewriting can be made conditional on a number of tests, by making use of
24418 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24419 messages that originate outside the local host:
24421 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24422 {$1@hitch.fict.example}fail}"
24424 The replacement string is quoted in this example because it contains white
24427 .cindex "rewriting" "bang paths"
24428 .cindex "bang paths" "rewriting"
24429 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24430 an address it treats it as an unqualified local part which it qualifies with
24431 the local qualification domain (if the source of the message is local or if the
24432 remote host is permitted to send unqualified addresses). Rewriting can
24433 sometimes be used to handle simple bang paths with a fixed number of
24434 components. For example, the rule
24436 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24438 rewrites a two-component bang path &'host.name!user'& as the domain address
24439 &'user@host.name'&. However, there is a security implication in using this as
24440 a global rewriting rule for envelope addresses. It can provide a backdoor
24441 method for using your system as a relay, because the incoming addresses appear
24442 to be local. If the bang path addresses are received via SMTP, it is safer to
24443 use the &"S"& flag to rewrite them as they are received, so that relay checking
24444 can be done on the rewritten addresses.
24451 . ////////////////////////////////////////////////////////////////////////////
24452 . ////////////////////////////////////////////////////////////////////////////
24454 .chapter "Retry configuration" "CHAPretry"
24455 .scindex IIDretconf1 "retry" "configuration, description of"
24456 .scindex IIDregconf2 "configuration file" "retry section"
24457 The &"retry"& section of the runtime configuration file contains a list of
24458 retry rules that control how often Exim tries to deliver messages that cannot
24459 be delivered at the first attempt. If there are no retry rules (the section is
24460 empty or not present), there are no retries. In this situation, temporary
24461 errors are treated as permanent. The default configuration contains a single,
24462 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24463 line option can be used to test which retry rule will be used for a given
24464 address, domain and error.
24466 The most common cause of retries is temporary failure to deliver to a remote
24467 host because the host is down, or inaccessible because of a network problem.
24468 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24469 address) basis, not on a per-message basis. Thus, if one message has recently
24470 been delayed, delivery of a new message to the same host is not immediately
24471 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24472 log selector is set, the message
24473 .cindex "retry" "time not reached"
24474 &"retry time not reached"& is written to the main log whenever a delivery is
24475 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24476 the handling of errors during remote deliveries.
24478 Retry processing applies to routing as well as to delivering, except as covered
24479 in the next paragraph. The retry rules do not distinguish between these
24480 actions. It is not possible, for example, to specify different behaviour for
24481 failures to route the domain &'snark.fict.example'& and failures to deliver to
24482 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24483 added complication, so did not implement it. However, although they share the
24484 same retry rule, the actual retry times for routing and transporting a given
24485 domain are maintained independently.
24487 When a delivery is not part of a queue run (typically an immediate delivery on
24488 receipt of a message), the routers are always run, and local deliveries are
24489 always attempted, even if retry times are set for them. This makes for better
24490 behaviour if one particular message is causing problems (for example, causing
24491 quota overflow, or provoking an error in a filter file). If such a delivery
24492 suffers a temporary failure, the retry data is updated as normal, and
24493 subsequent delivery attempts from queue runs occur only when the retry time for
24494 the local address is reached.
24496 .section "Changing retry rules" "SECID157"
24497 If you change the retry rules in your configuration, you should consider
24498 whether or not to delete the retry data that is stored in Exim's spool area in
24499 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24500 always safe; that is why they are called &"hints"&.
24502 The hints retry data contains suggested retry times based on the previous
24503 rules. In the case of a long-running problem with a remote host, it might
24504 record the fact that the host has timed out. If your new rules increase the
24505 timeout time for such a host, you should definitely remove the old retry data
24506 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24507 messages that it should now be retaining.
24511 .section "Format of retry rules" "SECID158"
24512 .cindex "retry" "rules"
24513 Each retry rule occupies one line and consists of three or four parts,
24514 separated by white space: a pattern, an error name, an optional list of sender
24515 addresses, and a list of retry parameters. The pattern and sender lists must be
24516 enclosed in double quotes if they contain white space. The rules are searched
24517 in order until one is found where the pattern, error name, and sender list (if
24518 present) match the failing host or address, the error that occurred, and the
24519 message's sender, respectively.
24522 The pattern is any single item that may appear in an address list (see section
24523 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24524 which means that it is expanded before being tested against the address that
24525 has been delayed. A negated address list item is permitted. Address
24526 list processing treats a plain domain name as if it were preceded by &"*@"&,
24527 which makes it possible for many retry rules to start with just a domain. For
24530 lookingglass.fict.example * F,24h,30m;
24532 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24535 alice@lookingglass.fict.example * F,24h,30m;
24537 applies only to temporary failures involving the local part &%alice%&.
24538 In practice, almost all rules start with a domain name pattern without a local
24541 .cindex "regular expressions" "in retry rules"
24542 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24543 must match a complete address, not just a domain, because that is how regular
24544 expressions work in address lists.
24546 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24547 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
24551 .section "Choosing which retry rule to use for address errors" "SECID159"
24552 When Exim is looking for a retry rule after a routing attempt has failed (for
24553 example, after a DNS timeout), each line in the retry configuration is tested
24554 against the complete address only if &%retry_use_local_part%& is set for the
24555 router. Otherwise, only the domain is used, except when matching against a
24556 regular expression, when the local part of the address is replaced with &"*"&.
24557 A domain on its own can match a domain pattern, or a pattern that starts with
24558 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
24559 &%check_local_user%& is true, and false for other routers.
24561 Similarly, when Exim is looking for a retry rule after a local delivery has
24562 failed (for example, after a mailbox full error), each line in the retry
24563 configuration is tested against the complete address only if
24564 &%retry_use_local_part%& is set for the transport (it defaults true for all
24567 .cindex "4&'xx'& responses" "retry rules for"
24568 However, when Exim is looking for a retry rule after a remote delivery attempt
24569 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
24570 whole address is always used as the key when searching the retry rules. The
24571 rule that is found is used to create a retry time for the combination of the
24572 failing address and the message's sender. It is the combination of sender and
24573 recipient that is delayed in subsequent queue runs until its retry time is
24574 reached. You can delay the recipient without regard to the sender by setting
24575 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
24576 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
24581 .section "Choosing which retry rule to use for host and message errors" &&&
24583 For a temporary error that is not related to an individual address (for
24584 example, a connection timeout), each line in the retry configuration is checked
24585 twice. First, the name of the remote host is used as a domain name (preceded by
24586 &"*@"& when matching a regular expression). If this does not match the line,
24587 the domain from the email address is tried in a similar fashion. For example,
24588 suppose the MX records for &'a.b.c.example'& are
24590 a.b.c.example MX 5 x.y.z.example
24594 and the retry rules are
24596 p.q.r.example * F,24h,30m;
24597 a.b.c.example * F,4d,45m;
24599 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
24600 first rule matches neither the host nor the domain, so Exim looks at the second
24601 rule. This does not match the host, but it does match the domain, so it is used
24602 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
24603 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
24604 first retry rule is used, because it matches the host.
24606 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
24607 first rule to determine retry times, but for all the other hosts for the domain
24608 &'a.b.c.example'&, the second rule is used. The second rule is also used if
24609 routing to &'a.b.c.example'& suffers a temporary failure.
24611 &*Note*&: The host name is used when matching the patterns, not its IP address.
24612 However, if a message is routed directly to an IP address without the use of a
24613 host name, for example, if a &(manualroute)& router contains a setting such as:
24615 route_list = *.a.example 192.168.34.23
24617 then the &"host name"& that is used when searching for a retry rule is the
24618 textual form of the IP address.
24620 .section "Retry rules for specific errors" "SECID161"
24621 .cindex "retry" "specific errors; specifying"
24622 The second field in a retry rule is the name of a particular error, or an
24623 asterisk, which matches any error. The errors that can be tested for are:
24626 .vitem &%auth_failed%&
24627 Authentication failed when trying to send to a host in the
24628 &%hosts_require_auth%& list in an &(smtp)& transport.
24630 .vitem &%data_4xx%&
24631 A 4&'xx'& error was received for an outgoing DATA command, either immediately
24632 after the command, or after sending the message's data.
24634 .vitem &%mail_4xx%&
24635 A 4&'xx'& error was received for an outgoing MAIL command.
24637 .vitem &%rcpt_4xx%&
24638 A 4&'xx'& error was received for an outgoing RCPT command.
24641 For the three 4&'xx'& errors, either the first or both of the x's can be given
24642 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
24643 recognize 452 errors given to RCPT commands for addresses in a certain domain,
24644 and have retries every ten minutes with a one-hour timeout, you could set up a
24645 retry rule of this form:
24647 the.domain.name rcpt_452 F,1h,10m
24649 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
24650 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
24653 .vitem &%lost_connection%&
24654 A server unexpectedly closed the SMTP connection. There may, of course,
24655 legitimate reasons for this (host died, network died), but if it repeats a lot
24656 for the same host, it indicates something odd.
24660 A DNS lookup for a host failed.
24661 Note that a &%dnslookup%& router will need to have matched
24662 its &%fail_defer_domains%& option for this retry type to be usable.
24663 Also note that a &%manualroute%& router will probably need
24664 its &%host_find_failed%& option set to &%defer%&.
24667 .vitem &%refused_MX%&
24668 A connection to a host obtained from an MX record was refused.
24670 .vitem &%refused_A%&
24671 A connection to a host not obtained from an MX record was refused.
24674 A connection was refused.
24676 .vitem &%timeout_connect_MX%&
24677 A connection attempt to a host obtained from an MX record timed out.
24679 .vitem &%timeout_connect_A%&
24680 A connection attempt to a host not obtained from an MX record timed out.
24682 .vitem &%timeout_connect%&
24683 A connection attempt timed out.
24685 .vitem &%timeout_MX%&
24686 There was a timeout while connecting or during an SMTP session with a host
24687 obtained from an MX record.
24689 .vitem &%timeout_A%&
24690 There was a timeout while connecting or during an SMTP session with a host not
24691 obtained from an MX record.
24694 There was a timeout while connecting or during an SMTP session.
24696 .vitem &%tls_required%&
24697 The server was required to use TLS (it matched &%hosts_require_tls%& in the
24698 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
24699 to STARTTLS, or there was a problem setting up the TLS connection.
24702 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24705 .vitem &%quota_%&<&'time'&>
24706 .cindex "quota" "error testing in retry rule"
24707 .cindex "retry" "quota error testing"
24708 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
24709 transport, and the mailbox has not been accessed for <&'time'&>. For example,
24710 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
24714 .cindex "mailbox" "time of last read"
24715 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
24716 timeouts when the mailbox is full and is not being read by its owner. Ideally,
24717 it should be based on the last time that the user accessed the mailbox.
24718 However, it is not always possible to determine this. Exim uses the following
24722 If the mailbox is a single file, the time of last access (the &"atime"&) is
24723 used. As no new messages are being delivered (because the mailbox is over
24724 quota), Exim does not access the file, so this is the time of last user access.
24726 .cindex "maildir format" "time of last read"
24727 For a maildir delivery, the time of last modification of the &_new_&
24728 subdirectory is used. As the mailbox is over quota, no new files are created in
24729 the &_new_& subdirectory, because no new messages are being delivered. Any
24730 change to the &_new_& subdirectory is therefore assumed to be the result of an
24731 MUA moving a new message to the &_cur_& directory when it is first read. The
24732 time that is used is therefore the last time that the user read a new message.
24734 For other kinds of multi-file mailbox, the time of last access cannot be
24735 obtained, so a retry rule that uses this type of error field is never matched.
24738 The quota errors apply both to system-enforced quotas and to Exim's own quota
24739 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
24740 when a local delivery is deferred because a partition is full (the ENOSPC
24745 .section "Retry rules for specified senders" "SECID162"
24746 .cindex "retry" "rules; sender-specific"
24747 You can specify retry rules that apply only when the failing message has a
24748 specific sender. In particular, this can be used to define retry rules that
24749 apply only to bounce messages. The third item in a retry rule can be of this
24752 &`senders=`&<&'address list'&>
24754 The retry timings themselves are then the fourth item. For example:
24756 * rcpt_4xx senders=: F,1h,30m
24758 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
24759 host. If the address list contains white space, it must be enclosed in quotes.
24762 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
24764 &*Warning*&: This facility can be unhelpful if it is used for host errors
24765 (which do not depend on the recipient). The reason is that the sender is used
24766 only to match the retry rule. Once the rule has been found for a host error,
24767 its contents are used to set a retry time for the host, and this will apply to
24768 all messages, not just those with specific senders.
24770 When testing retry rules using &%-brt%&, you can supply a sender using the
24771 &%-f%& command line option, like this:
24773 exim -f "" -brt user@dom.ain
24775 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
24776 list is never matched.
24782 .section "Retry parameters" "SECID163"
24783 .cindex "retry" "parameters in rules"
24784 The third (or fourth, if a senders list is present) field in a retry rule is a
24785 sequence of retry parameter sets, separated by semicolons. Each set consists of
24787 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
24789 The letter identifies the algorithm for computing a new retry time; the cutoff
24790 time is the time beyond which this algorithm no longer applies, and the
24791 arguments vary the algorithm's action. The cutoff time is measured from the
24792 time that the first failure for the domain (combined with the local part if
24793 relevant) was detected, not from the time the message was received.
24795 .cindex "retry" "algorithms"
24796 .cindex "retry" "fixed intervals"
24797 .cindex "retry" "increasing intervals"
24798 .cindex "retry" "random intervals"
24799 The available algorithms are:
24802 &'F'&: retry at fixed intervals. There is a single time parameter specifying
24805 &'G'&: retry at geometrically increasing intervals. The first argument
24806 specifies a starting value for the interval, and the second a multiplier, which
24807 is used to increase the size of the interval at each retry.
24809 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
24810 retry, the previous interval is multiplied by the factor in order to get a
24811 maximum for the next interval. The minimum interval is the first argument of
24812 the parameter, and an actual interval is chosen randomly between them. Such a
24813 rule has been found to be helpful in cluster configurations when all the
24814 members of the cluster restart at once, and may therefore synchronize their
24815 queue processing times.
24818 When computing the next retry time, the algorithm definitions are scanned in
24819 order until one whose cutoff time has not yet passed is reached. This is then
24820 used to compute a new retry time that is later than the current time. In the
24821 case of fixed interval retries, this simply means adding the interval to the
24822 current time. For geometrically increasing intervals, retry intervals are
24823 computed from the rule's parameters until one that is greater than the previous
24824 interval is found. The main configuration variable
24825 .cindex "limit" "retry interval"
24826 .cindex "retry" "interval, maximum"
24827 .oindex "&%retry_interval_max%&"
24828 &%retry_interval_max%& limits the maximum interval between retries. It
24829 cannot be set greater than &`24h`&, which is its default value.
24831 A single remote domain may have a number of hosts associated with it, and each
24832 host may have more than one IP address. Retry algorithms are selected on the
24833 basis of the domain name, but are applied to each IP address independently. If,
24834 for example, a host has two IP addresses and one is unusable, Exim will
24835 generate retry times for it and will not try to use it until its next retry
24836 time comes. Thus the good IP address is likely to be tried first most of the
24839 .cindex "hints database" "use for retrying"
24840 Retry times are hints rather than promises. Exim does not make any attempt to
24841 run deliveries exactly at the computed times. Instead, a queue runner process
24842 starts delivery processes for delayed messages periodically, and these attempt
24843 new deliveries only for those addresses that have passed their next retry time.
24844 If a new message arrives for a deferred address, an immediate delivery attempt
24845 occurs only if the address has passed its retry time. In the absence of new
24846 messages, the minimum time between retries is the interval between queue runner
24847 processes. There is not much point in setting retry times of five minutes if
24848 your queue runners happen only once an hour, unless there are a significant
24849 number of incoming messages (which might be the case on a system that is
24850 sending everything to a smart host, for example).
24852 The data in the retry hints database can be inspected by using the
24853 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
24854 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
24855 &'exinext'& utility script can be used to find out what the next retry times
24856 are for the hosts associated with a particular mail domain, and also for local
24857 deliveries that have been deferred.
24860 .section "Retry rule examples" "SECID164"
24861 Here are some example retry rules:
24863 alice@wonderland.fict.example quota_5d F,7d,3h
24864 wonderland.fict.example quota_5d
24865 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24866 lookingglass.fict.example * F,24h,30m;
24867 * refused_A F,2h,20m;
24868 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24870 The first rule sets up special handling for mail to
24871 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24872 mailbox has not been read for at least 5 days. Retries continue every three
24873 hours for 7 days. The second rule handles over-quota errors for all other local
24874 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24875 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24876 fail are bounced immediately if the mailbox has not been read for at least 5
24879 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24880 happen every 15 minutes for an hour, then with geometrically increasing
24881 intervals until two days have passed since a delivery first failed. After the
24882 first hour there is a delay of one hour, then two hours, then four hours, and
24883 so on (this is a rather extreme example).
24885 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24886 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24887 all other domains, with special action for connection refusal from hosts that
24888 were not obtained from an MX record.
24890 The final rule in a retry configuration should always have asterisks in the
24891 first two fields so as to provide a general catch-all for any addresses that do
24892 not have their own special handling. This example tries every 15 minutes for 2
24893 hours, then with intervals starting at one hour and increasing by a factor of
24894 1.5 up to 16 hours, then every 8 hours up to 5 days.
24898 .section "Timeout of retry data" "SECID165"
24899 .cindex "timeout" "of retry data"
24900 .oindex "&%retry_data_expire%&"
24901 .cindex "hints database" "data expiry"
24902 .cindex "retry" "timeout of data"
24903 Exim timestamps the data that it writes to its retry hints database. When it
24904 consults the data during a delivery it ignores any that is older than the value
24905 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24906 been tried for 7 days, Exim will try to deliver to it immediately a message
24907 arrives, and if that fails, it will calculate a retry time as if it were
24908 failing for the first time.
24910 This improves the behaviour for messages routed to rarely-used hosts such as MX
24911 backups. If such a host was down at one time, and happens to be down again when
24912 Exim tries a month later, using the old retry data would imply that it had been
24913 down all the time, which is not a justified assumption.
24915 If a host really is permanently dead, this behaviour causes a burst of retries
24916 every now and again, but only if messages routed to it are rare. If there is a
24917 message at least once every 7 days the retry data never expires.
24922 .section "Long-term failures" "SECID166"
24923 .cindex "delivery failure, long-term"
24924 .cindex "retry" "after long-term failure"
24925 Special processing happens when an email address has been failing for so long
24926 that the cutoff time for the last algorithm is reached. For example, using the
24927 default retry rule:
24929 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24931 the cutoff time is four days. Reaching the retry cutoff is independent of how
24932 long any specific message has been failing; it is the length of continuous
24933 failure for the recipient address that counts.
24935 When the cutoff time is reached for a local delivery, or for all the IP
24936 addresses associated with a remote delivery, a subsequent delivery failure
24937 causes Exim to give up on the address, and a bounce message is generated.
24938 In order to cater for new messages that use the failing address, a next retry
24939 time is still computed from the final algorithm, and is used as follows:
24941 For local deliveries, one delivery attempt is always made for any subsequent
24942 messages. If this delivery fails, the address fails immediately. The
24943 post-cutoff retry time is not used.
24945 If the delivery is remote, there are two possibilities, controlled by the
24946 .oindex "&%delay_after_cutoff%&"
24947 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
24948 default. Until the post-cutoff retry time for one of the IP addresses is
24949 reached, the failing email address is bounced immediately, without a delivery
24950 attempt taking place. After that time, one new delivery attempt is made to
24951 those IP addresses that are past their retry times, and if that still fails,
24952 the address is bounced and new retry times are computed.
24954 In other words, when all the hosts for a given email address have been failing
24955 for a long time, Exim bounces rather then defers until one of the hosts' retry
24956 times is reached. Then it tries once, and bounces if that attempt fails. This
24957 behaviour ensures that few resources are wasted in repeatedly trying to deliver
24958 to a broken destination, but if the host does recover, Exim will eventually
24961 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24962 addresses are past their final cutoff time, Exim tries to deliver to those IP
24963 addresses that have not been tried since the message arrived. If there are
24964 no suitable IP addresses, or if they all fail, the address is bounced. In other
24965 words, it does not delay when a new message arrives, but tries the expired
24966 addresses immediately, unless they have been tried since the message arrived.
24967 If there is a continuous stream of messages for the failing domains, setting
24968 &%delay_after_cutoff%& false means that there will be many more attempts to
24969 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
24972 .section "Deliveries that work intermittently" "SECID167"
24973 .cindex "retry" "intermittently working deliveries"
24974 Some additional logic is needed to cope with cases where a host is
24975 intermittently available, or when a message has some attribute that prevents
24976 its delivery when others to the same address get through. In this situation,
24977 because some messages are successfully delivered, the &"retry clock"& for the
24978 host or address keeps getting reset by the successful deliveries, and so
24979 failing messages remain on the queue for ever because the cutoff time is never
24982 Two exceptional actions are applied to prevent this happening. The first
24983 applies to errors that are related to a message rather than a remote host.
24984 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
24985 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
24986 commands, and quota failures. For this type of error, if a message's arrival
24987 time is earlier than the &"first failed"& time for the error, the earlier time
24988 is used when scanning the retry rules to decide when to try next and when to
24989 time out the address.
24991 The exceptional second action applies in all cases. If a message has been on
24992 the queue for longer than the cutoff time of any applicable retry rule for a
24993 given address, a delivery is attempted for that address, even if it is not yet
24994 time, and if this delivery fails, the address is timed out. A new retry time is
24995 not computed in this case, so that other messages for the same address are
24996 considered immediately.
24997 .ecindex IIDretconf1
24998 .ecindex IIDregconf2
25005 . ////////////////////////////////////////////////////////////////////////////
25006 . ////////////////////////////////////////////////////////////////////////////
25008 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25009 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25010 .scindex IIDauthconf2 "authentication"
25011 The &"authenticators"& section of Exim's run time configuration is concerned
25012 with SMTP authentication. This facility is an extension to the SMTP protocol,
25013 described in RFC 2554, which allows a client SMTP host to authenticate itself
25014 to a server. This is a common way for a server to recognize clients that are
25015 permitted to use it as a relay. SMTP authentication is not of relevance to the
25016 transfer of mail between servers that have no managerial connection with each
25019 .cindex "AUTH" "description of"
25020 Very briefly, the way SMTP authentication works is as follows:
25023 The server advertises a number of authentication &'mechanisms'& in response to
25024 the client's EHLO command.
25026 The client issues an AUTH command, naming a specific mechanism. The command
25027 may, optionally, contain some authentication data.
25029 The server may issue one or more &'challenges'&, to which the client must send
25030 appropriate responses. In simple authentication mechanisms, the challenges are
25031 just prompts for user names and passwords. The server does not have to issue
25032 any challenges &-- in some mechanisms the relevant data may all be transmitted
25033 with the AUTH command.
25035 The server either accepts or denies authentication.
25037 If authentication succeeds, the client may optionally make use of the AUTH
25038 option on the MAIL command to pass an authenticated sender in subsequent
25039 mail transactions. Authentication lasts for the remainder of the SMTP
25042 If authentication fails, the client may give up, or it may try a different
25043 authentication mechanism, or it may try transferring mail over the
25044 unauthenticated connection.
25047 If you are setting up a client, and want to know which authentication
25048 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25049 SMTP port) on the server, and issue an EHLO command. The response to this
25050 includes the list of supported mechanisms. For example:
25052 &`$ `&&*&`telnet server.example 25`&*&
25053 &`Trying 192.168.34.25...`&
25054 &`Connected to server.example.`&
25055 &`Escape character is '^]'.`&
25056 &`220 server.example ESMTP Exim 4.20 ...`&
25057 &*&`ehlo client.example`&*&
25058 &`250-server.example Hello client.example [10.8.4.5]`&
25059 &`250-SIZE 52428800`&
25064 The second-last line of this example output shows that the server supports
25065 authentication using the PLAIN mechanism. In Exim, the different authentication
25066 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25067 routers and transports, which authenticators are included in the binary is
25068 controlled by build-time definitions. The following are currently available,
25069 included by setting
25072 AUTH_CYRUS_SASL=yes
25075 AUTH_HEIMDAL_GSSAPI=yes
25080 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25081 authentication mechanism (RFC 2195), and the second provides an interface to
25082 the Cyrus SASL authentication library.
25083 The third is an interface to Dovecot's authentication system, delegating the
25084 work via a socket interface.
25085 The fourth provides an interface to the GNU SASL authentication library, which
25086 provides mechanisms but typically not data sources.
25087 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25088 supporting setting a server keytab.
25089 The sixth can be configured to support
25090 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25091 not formally documented, but used by several MUAs. The seventh authenticator
25092 supports Microsoft's &'Secure Password Authentication'& mechanism.
25094 The eighth is an Exim authenticator but not an SMTP one;
25095 instead it can use information from a TLS negotiation.
25098 The authenticators are configured using the same syntax as other drivers (see
25099 section &<<SECTfordricon>>&). If no authenticators are required, no
25100 authentication section need be present in the configuration file. Each
25101 authenticator can in principle have both server and client functions. When Exim
25102 is receiving SMTP mail, it is acting as a server; when it is sending out
25103 messages over SMTP, it is acting as a client. Authenticator configuration
25104 options are provided for use in both these circumstances.
25106 To make it clear which options apply to which situation, the prefixes
25107 &%server_%& and &%client_%& are used on option names that are specific to
25108 either the server or the client function, respectively. Server and client
25109 functions are disabled if none of their options are set. If an authenticator is
25110 to be used for both server and client functions, a single definition, using
25111 both sets of options, is required. For example:
25115 public_name = CRAM-MD5
25116 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25118 client_secret = secret2
25120 The &%server_%& option is used when Exim is acting as a server, and the
25121 &%client_%& options when it is acting as a client.
25123 Descriptions of the individual authenticators are given in subsequent chapters.
25124 The remainder of this chapter covers the generic options for the
25125 authenticators, followed by general discussion of the way authentication works
25128 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25129 per-mechanism basis. Please read carefully to determine which variables hold
25130 account labels such as usercodes and which hold passwords or other
25131 authenticating data.
25133 Note that some mechanisms support two different identifiers for accounts: the
25134 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25135 and &'authz'& are commonly encountered. The American spelling is standard here.
25136 Conceptually, authentication data such as passwords are tied to the identifier
25137 used to authenticate; servers may have rules to permit one user to act as a
25138 second user, so that after login the session is treated as though that second
25139 user had logged in. That second user is the &'authorization id'&. A robust
25140 configuration might confirm that the &'authz'& field is empty or matches the
25141 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25142 as verified data, the &'authz'& as an unverified request which the server might
25145 A &'realm'& is a text string, typically a domain name, presented by a server
25146 to a client to help it select an account and credentials to use. In some
25147 mechanisms, the client and server provably agree on the realm, but clients
25148 typically can not treat the realm as secure data to be blindly trusted.
25152 .section "Generic options for authenticators" "SECID168"
25153 .cindex "authentication" "generic options"
25154 .cindex "options" "generic; for authenticators"
25156 .option client_condition authenticators string&!! unset
25157 When Exim is authenticating as a client, it skips any authenticator whose
25158 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25159 used, for example, to skip plain text authenticators when the connection is not
25160 encrypted by a setting such as:
25162 client_condition = ${if !eq{$tls_out_cipher}{}}
25166 .option client_set_id authenticators string&!! unset
25167 When client authentication succeeds, this condition is expanded; the
25168 result is used in the log lines for outbound messages.
25169 Typically it will be the user name used for authentication.
25172 .option driver authenticators string unset
25173 This option must always be set. It specifies which of the available
25174 authenticators is to be used.
25177 .option public_name authenticators string unset
25178 This option specifies the name of the authentication mechanism that the driver
25179 implements, and by which it is known to the outside world. These names should
25180 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25181 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25182 defaults to the driver's instance name.
25185 .option server_advertise_condition authenticators string&!! unset
25186 When a server is about to advertise an authentication mechanism, the condition
25187 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25188 mechanism is not advertised.
25189 If the expansion fails, the mechanism is not advertised. If the failure was not
25190 forced, and was not caused by a lookup defer, the incident is logged.
25191 See section &<<SECTauthexiser>>& below for further discussion.
25194 .option server_condition authenticators string&!! unset
25195 This option must be set for a &%plaintext%& server authenticator, where it
25196 is used directly to control authentication. See section &<<SECTplainserver>>&
25199 For the &(gsasl)& authenticator, this option is required for various
25200 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25202 For the other authenticators, &%server_condition%& can be used as an additional
25203 authentication or authorization mechanism that is applied after the other
25204 authenticator conditions succeed. If it is set, it is expanded when the
25205 authenticator would otherwise return a success code. If the expansion is forced
25206 to fail, authentication fails. Any other expansion failure causes a temporary
25207 error code to be returned. If the result of a successful expansion is an empty
25208 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25209 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25210 other result, a temporary error code is returned, with the expanded string as
25214 .option server_debug_print authenticators string&!! unset
25215 If this option is set and authentication debugging is enabled (see the &%-d%&
25216 command line option), the string is expanded and included in the debugging
25217 output when the authenticator is run as a server. This can help with checking
25218 out the values of variables.
25219 If expansion of the string fails, the error message is written to the debugging
25220 output, and Exim carries on processing.
25223 .option server_set_id authenticators string&!! unset
25224 .vindex "&$authenticated_id$&"
25225 When an Exim server successfully authenticates a client, this string is
25226 expanded using data from the authentication, and preserved for any incoming
25227 messages in the variable &$authenticated_id$&. It is also included in the log
25228 lines for incoming messages. For example, a user/password authenticator
25229 configuration might preserve the user name that was used to authenticate, and
25230 refer to it subsequently during delivery of the message.
25231 If expansion fails, the option is ignored.
25234 .option server_mail_auth_condition authenticators string&!! unset
25235 This option allows a server to discard authenticated sender addresses supplied
25236 as part of MAIL commands in SMTP connections that are authenticated by the
25237 driver on which &%server_mail_auth_condition%& is set. The option is not used
25238 as part of the authentication process; instead its (unexpanded) value is
25239 remembered for later use.
25240 How it is used is described in the following section.
25246 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25247 .cindex "authentication" "sender; authenticated"
25248 .cindex "AUTH" "on MAIL command"
25249 When a client supplied an AUTH= item on a MAIL command, Exim applies
25250 the following checks before accepting it as the authenticated sender of the
25254 If the connection is not using extended SMTP (that is, HELO was used rather
25255 than EHLO), the use of AUTH= is a syntax error.
25257 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25259 .vindex "&$authenticated_sender$&"
25260 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25261 running, the value of &$authenticated_sender$& is set to the value obtained
25262 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25263 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25264 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25265 given for the MAIL command.
25267 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25268 is accepted and placed in &$authenticated_sender$& only if the client has
25271 If the AUTH= value was accepted by either of the two previous rules, and
25272 the client has authenticated, and the authenticator has a setting for the
25273 &%server_mail_auth_condition%&, the condition is checked at this point. The
25274 valued that was saved from the authenticator is expanded. If the expansion
25275 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25276 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25277 the value of &$authenticated_sender$& is retained and passed on with the
25282 When &$authenticated_sender$& is set for a message, it is passed on to other
25283 hosts to which Exim authenticates as a client. Do not confuse this value with
25284 &$authenticated_id$&, which is a string obtained from the authentication
25285 process, and which is not usually a complete email address.
25287 .vindex "&$sender_address$&"
25288 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25289 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25290 therefore make use of &$authenticated_sender$&. The converse is not true: the
25291 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25296 .section "Authentication on an Exim server" "SECTauthexiser"
25297 .cindex "authentication" "on an Exim server"
25298 When Exim receives an EHLO command, it advertises the public names of those
25299 authenticators that are configured as servers, subject to the following
25303 The client host must match &%auth_advertise_hosts%& (default *).
25305 It the &%server_advertise_condition%& option is set, its expansion must not
25306 yield the empty string, &"0"&, &"no"&, or &"false"&.
25309 The order in which the authenticators are defined controls the order in which
25310 the mechanisms are advertised.
25312 Some mail clients (for example, some versions of Netscape) require the user to
25313 provide a name and password for authentication whenever AUTH is advertised,
25314 even though authentication may not in fact be needed (for example, Exim may be
25315 set up to allow unconditional relaying from the client by an IP address check).
25316 You can make such clients more friendly by not advertising AUTH to them.
25317 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25318 that runs for RCPT) to relay without authentication, you should set
25320 auth_advertise_hosts = ! 10.9.8.0/24
25322 so that no authentication mechanisms are advertised to them.
25324 The &%server_advertise_condition%& controls the advertisement of individual
25325 authentication mechanisms. For example, it can be used to restrict the
25326 advertisement of a particular mechanism to encrypted connections, by a setting
25329 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25331 .vindex "&$tls_in_cipher$&"
25332 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25333 yields &"yes"&, which allows the advertisement to happen.
25335 When an Exim server receives an AUTH command from a client, it rejects it
25336 immediately if AUTH was not advertised in response to an earlier EHLO
25337 command. This is the case if
25340 The client host does not match &%auth_advertise_hosts%&; or
25342 No authenticators are configured with server options; or
25344 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25345 server authenticators.
25349 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25350 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25351 AUTH is accepted from any client host.
25353 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25354 server authentication mechanism that was advertised in response to EHLO and
25355 that matches the one named in the AUTH command. If it finds one, it runs
25356 the appropriate authentication protocol, and authentication either succeeds or
25357 fails. If there is no matching advertised mechanism, the AUTH command is
25358 rejected with a 504 error.
25360 .vindex "&$received_protocol$&"
25361 .vindex "&$sender_host_authenticated$&"
25362 When a message is received from an authenticated host, the value of
25363 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25364 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25365 public name) of the authenticator driver that successfully authenticated the
25366 client from which the message was received. This variable is empty if there was
25367 no successful authentication.
25372 .section "Testing server authentication" "SECID169"
25373 .cindex "authentication" "testing a server"
25374 .cindex "AUTH" "testing a server"
25375 .cindex "base64 encoding" "creating authentication test data"
25376 Exim's &%-bh%& option can be useful for testing server authentication
25377 configurations. The data for the AUTH command has to be sent using base64
25378 encoding. A quick way to produce such data for testing is the following Perl
25382 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25384 .cindex "binary zero" "in authentication data"
25385 This interprets its argument as a Perl string, and then encodes it. The
25386 interpretation as a Perl string allows binary zeros, which are required for
25387 some kinds of authentication, to be included in the data. For example, a
25388 command line to run this script on such data might be
25390 encode '\0user\0password'
25392 Note the use of single quotes to prevent the shell interpreting the
25393 backslashes, so that they can be interpreted by Perl to specify characters
25394 whose code value is zero.
25396 &*Warning 1*&: If either of the user or password strings starts with an octal
25397 digit, you must use three zeros instead of one after the leading backslash. If
25398 you do not, the octal digit that starts your string will be incorrectly
25399 interpreted as part of the code for the first character.
25401 &*Warning 2*&: If there are characters in the strings that Perl interprets
25402 specially, you must use a Perl escape to prevent them being misinterpreted. For
25403 example, a command such as
25405 encode '\0user@domain.com\0pas$$word'
25407 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25409 If you have the &%mimencode%& command installed, another way to do produce
25410 base64-encoded strings is to run the command
25412 echo -e -n `\0user\0password' | mimencode
25414 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25415 in the argument, and the &%-n%& option specifies no newline at the end of its
25416 output. However, not all versions of &%echo%& recognize these options, so you
25417 should check your version before relying on this suggestion.
25421 .section "Authentication by an Exim client" "SECID170"
25422 .cindex "authentication" "on an Exim client"
25423 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25424 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25425 announces support for authentication, and the host matches an entry in either
25426 of these options, Exim (as a client) tries to authenticate as follows:
25429 For each authenticator that is configured as a client, in the order in which
25430 they are defined in the configuration, it searches the authentication
25431 mechanisms announced by the server for one whose name matches the public name
25432 of the authenticator.
25435 .vindex "&$host_address$&"
25436 When it finds one that matches, it runs the authenticator's client code. The
25437 variables &$host$& and &$host_address$& are available for any string expansions
25438 that the client might do. They are set to the server's name and IP address. If
25439 any expansion is forced to fail, the authentication attempt is abandoned, and
25440 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25441 delivery to be deferred.
25443 If the result of the authentication attempt is a temporary error or a timeout,
25444 Exim abandons trying to send the message to the host for the moment. It will
25445 try again later. If there are any backup hosts available, they are tried in the
25448 If the response to authentication is a permanent error (5&'xx'& code), Exim
25449 carries on searching the list of authenticators and tries another one if
25450 possible. If all authentication attempts give permanent errors, or if there are
25451 no attempts because no mechanisms match (or option expansions force failure),
25452 what happens depends on whether the host matches &%hosts_require_auth%& or
25453 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25454 delivery is deferred. The error can be detected in the retry rules, and thereby
25455 turned into a permanent error if you wish. In the second case, Exim tries to
25456 deliver the message unauthenticated.
25459 .cindex "AUTH" "on MAIL command"
25460 When Exim has authenticated itself to a remote server, it adds the AUTH
25461 parameter to the MAIL commands it sends, if it has an authenticated sender for
25462 the message. If the message came from a remote host, the authenticated sender
25463 is the one that was receiving on an incoming MAIL command, provided that the
25464 incoming connection was authenticated and the &%server_mail_auth%& condition
25465 allowed the authenticated sender to be retained. If a local process calls Exim
25466 to send a message, the sender address that is built from the login name and
25467 &%qualify_domain%& is treated as authenticated. However, if the
25468 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25469 the authenticated sender that was received with the message.
25470 .ecindex IIDauthconf1
25471 .ecindex IIDauthconf2
25478 . ////////////////////////////////////////////////////////////////////////////
25479 . ////////////////////////////////////////////////////////////////////////////
25481 .chapter "The plaintext authenticator" "CHAPplaintext"
25482 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25483 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25484 The &(plaintext)& authenticator can be configured to support the PLAIN and
25485 LOGIN authentication mechanisms, both of which transfer authentication data as
25486 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25487 security risk; you are strongly advised to insist on the use of SMTP encryption
25488 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25489 use unencrypted plain text, you should not use the same passwords for SMTP
25490 connections as you do for login accounts.
25492 .section "Plaintext options" "SECID171"
25493 .cindex "options" "&(plaintext)& authenticator (server)"
25494 When configured as a server, &(plaintext)& uses the following options:
25496 .option server_condition authenticators string&!! unset
25497 This is actually a global authentication option, but it must be set in order to
25498 configure the &(plaintext)& driver as a server. Its use is described below.
25500 .option server_prompts plaintext string&!! unset
25501 The contents of this option, after expansion, must be a colon-separated list of
25502 prompt strings. If expansion fails, a temporary authentication rejection is
25505 .section "Using plaintext in a server" "SECTplainserver"
25506 .cindex "AUTH" "in &(plaintext)& authenticator"
25507 .cindex "binary zero" "in &(plaintext)& authenticator"
25508 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25509 "in &(plaintext)& authenticator"
25510 .vindex "&$auth1$&, &$auth2$&, etc"
25511 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25513 When running as a server, &(plaintext)& performs the authentication test by
25514 expanding a string. The data sent by the client with the AUTH command, or in
25515 response to subsequent prompts, is base64 encoded, and so may contain any byte
25516 values when decoded. If any data is supplied with the command, it is treated as
25517 a list of strings, separated by NULs (binary zeros), the first three of which
25518 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25519 (neither LOGIN nor PLAIN uses more than three strings).
25521 For compatibility with previous releases of Exim, the values are also placed in
25522 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25523 variables for this purpose is now deprecated, as it can lead to confusion in
25524 string expansions that also use them for other things.
25526 If there are more strings in &%server_prompts%& than the number of strings
25527 supplied with the AUTH command, the remaining prompts are used to obtain more
25528 data. Each response from the client may be a list of NUL-separated strings.
25530 .vindex "&$authenticated_id$&"
25531 Once a sufficient number of data strings have been received,
25532 &%server_condition%& is expanded. If the expansion is forced to fail,
25533 authentication fails. Any other expansion failure causes a temporary error code
25534 to be returned. If the result of a successful expansion is an empty string,
25535 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25536 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25537 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25538 For any other result, a temporary error code is returned, with the expanded
25539 string as the error text
25541 &*Warning*&: If you use a lookup in the expansion to find the user's
25542 password, be sure to make the authentication fail if the user is unknown.
25543 There are good and bad examples at the end of the next section.
25547 .section "The PLAIN authentication mechanism" "SECID172"
25548 .cindex "PLAIN authentication mechanism"
25549 .cindex "authentication" "PLAIN mechanism"
25550 .cindex "binary zero" "in &(plaintext)& authenticator"
25551 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
25552 sent as one item of data (that is, one combined string containing two NUL
25553 separators). The data is sent either as part of the AUTH command, or
25554 subsequently in response to an empty prompt from the server.
25556 The second and third strings are a user name and a corresponding password.
25557 Using a single fixed user name and password as an example, this could be
25558 configured as follows:
25562 public_name = PLAIN
25564 server_condition = \
25565 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
25566 server_set_id = $auth2
25568 Note that the default result strings from &%if%& (&"true"& or an empty string)
25569 are exactly what we want here, so they need not be specified. Obviously, if the
25570 password contains expansion-significant characters such as dollar, backslash,
25571 or closing brace, they have to be escaped.
25573 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
25574 the end of a string list are ignored). If all the data comes as part of the
25575 AUTH command, as is commonly the case, the prompt is not used. This
25576 authenticator is advertised in the response to EHLO as
25580 and a client host can authenticate itself by sending the command
25582 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
25584 As this contains three strings (more than the number of prompts), no further
25585 data is required from the client. Alternatively, the client may just send
25589 to initiate authentication, in which case the server replies with an empty
25590 prompt. The client must respond with the combined data string.
25592 The data string is base64 encoded, as required by the RFC. This example,
25593 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
25594 represents a zero byte. This is split up into three strings, the first of which
25595 is empty. The &%server_condition%& option in the authenticator checks that the
25596 second two are &`username`& and &`mysecret`& respectively.
25598 Having just one fixed user name and password, as in this example, is not very
25599 realistic, though for a small organization with only a handful of
25600 authenticating clients it could make sense.
25602 A more sophisticated instance of this authenticator could use the user name in
25603 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
25604 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
25605 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
25606 This is an incorrect example:
25608 server_condition = \
25609 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
25611 The expansion uses the user name (&$auth2$&) as the key to look up a password,
25612 which it then compares to the supplied password (&$auth3$&). Why is this example
25613 incorrect? It works fine for existing users, but consider what happens if a
25614 non-existent user name is given. The lookup fails, but as no success/failure
25615 strings are given for the lookup, it yields an empty string. Thus, to defeat
25616 the authentication, all a client has to do is to supply a non-existent user
25617 name and an empty password. The correct way of writing this test is:
25619 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
25620 {${if eq{$value}{$auth3}}} {false}}
25622 In this case, if the lookup succeeds, the result is checked; if the lookup
25623 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
25624 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
25625 always fails if its second argument is empty. However, the second way of
25626 writing the test makes the logic clearer.
25629 .section "The LOGIN authentication mechanism" "SECID173"
25630 .cindex "LOGIN authentication mechanism"
25631 .cindex "authentication" "LOGIN mechanism"
25632 The LOGIN authentication mechanism is not documented in any RFC, but is in use
25633 in a number of programs. No data is sent with the AUTH command. Instead, a
25634 user name and password are supplied separately, in response to prompts. The
25635 plaintext authenticator can be configured to support this as in this example:
25639 public_name = LOGIN
25640 server_prompts = User Name : Password
25641 server_condition = \
25642 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
25643 server_set_id = $auth1
25645 Because of the way plaintext operates, this authenticator accepts data supplied
25646 with the AUTH command (in contravention of the specification of LOGIN), but
25647 if the client does not supply it (as is the case for LOGIN clients), the prompt
25648 strings are used to obtain two data items.
25650 Some clients are very particular about the precise text of the prompts. For
25651 example, Outlook Express is reported to recognize only &"Username:"& and
25652 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
25653 strings. It uses the &%ldapauth%& expansion condition to check the user
25654 name and password by binding to an LDAP server:
25658 public_name = LOGIN
25659 server_prompts = Username:: : Password::
25660 server_condition = ${if and{{ \
25663 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
25664 pass=${quote:$auth2} \
25665 ldap://ldap.example.org/} }} }
25666 server_set_id = uid=$auth1,ou=people,o=example.org
25668 We have to check that the username is not empty before using it, because LDAP
25669 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
25670 operator to correctly quote the DN for authentication. However, the basic
25671 &%quote%& operator, rather than any of the LDAP quoting operators, is the
25672 correct one to use for the password, because quoting is needed only to make
25673 the password conform to the Exim syntax. At the LDAP level, the password is an
25674 uninterpreted string.
25677 .section "Support for different kinds of authentication" "SECID174"
25678 A number of string expansion features are provided for the purpose of
25679 interfacing to different ways of user authentication. These include checking
25680 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
25681 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
25687 .section "Using plaintext in a client" "SECID175"
25688 .cindex "options" "&(plaintext)& authenticator (client)"
25689 The &(plaintext)& authenticator has two client options:
25691 .option client_ignore_invalid_base64 plaintext boolean false
25692 If the client receives a server prompt that is not a valid base64 string,
25693 authentication is abandoned by default. However, if this option is set true,
25694 the error in the challenge is ignored and the client sends the response as
25697 .option client_send plaintext string&!! unset
25698 The string is a colon-separated list of authentication data strings. Each
25699 string is independently expanded before being sent to the server. The first
25700 string is sent with the AUTH command; any more strings are sent in response
25701 to prompts from the server. Before each string is expanded, the value of the
25702 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
25703 with &$auth1$& for the first prompt. Up to three prompts are stored in this
25704 way. Thus, the prompt that is received in response to sending the first string
25705 (with the AUTH command) can be used in the expansion of the second string, and
25706 so on. If an invalid base64 string is received when
25707 &%client_ignore_invalid_base64%& is set, an empty string is put in the
25708 &$auth$&<&'n'&> variable.
25710 &*Note*&: You cannot use expansion to create multiple strings, because
25711 splitting takes priority and happens first.
25713 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
25714 the data, further processing is applied to each string before it is sent. If
25715 there are any single circumflex characters in the string, they are converted to
25716 NULs. Should an actual circumflex be required as data, it must be doubled in
25719 This is an example of a client configuration that implements the PLAIN
25720 authentication mechanism with a fixed user name and password:
25724 public_name = PLAIN
25725 client_send = ^username^mysecret
25727 The lack of colons means that the entire text is sent with the AUTH
25728 command, with the circumflex characters converted to NULs. A similar example
25729 that uses the LOGIN mechanism is:
25733 public_name = LOGIN
25734 client_send = : username : mysecret
25736 The initial colon means that the first string is empty, so no data is sent with
25737 the AUTH command itself. The remaining strings are sent in response to
25739 .ecindex IIDplaiauth1
25740 .ecindex IIDplaiauth2
25745 . ////////////////////////////////////////////////////////////////////////////
25746 . ////////////////////////////////////////////////////////////////////////////
25748 .chapter "The cram_md5 authenticator" "CHID9"
25749 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
25750 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
25751 .cindex "CRAM-MD5 authentication mechanism"
25752 .cindex "authentication" "CRAM-MD5 mechanism"
25753 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
25754 sends a challenge string to the client, and the response consists of a user
25755 name and the CRAM-MD5 digest of the challenge string combined with a secret
25756 string (password) which is known to both server and client. Thus, the secret
25757 is not sent over the network as plain text, which makes this authenticator more
25758 secure than &(plaintext)&. However, the downside is that the secret has to be
25759 available in plain text at either end.
25762 .section "Using cram_md5 as a server" "SECID176"
25763 .cindex "options" "&(cram_md5)& authenticator (server)"
25764 This authenticator has one server option, which must be set to configure the
25765 authenticator as a server:
25767 .option server_secret cram_md5 string&!! unset
25768 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
25769 When the server receives the client's response, the user name is placed in
25770 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
25771 obtain the password for that user. The server then computes the CRAM-MD5 digest
25772 that the client should have sent, and checks that it received the correct
25773 string. If the expansion of &%server_secret%& is forced to fail, authentication
25774 fails. If the expansion fails for some other reason, a temporary error code is
25775 returned to the client.
25777 For compatibility with previous releases of Exim, the user name is also placed
25778 in &$1$&. However, the use of this variables for this purpose is now
25779 deprecated, as it can lead to confusion in string expansions that also use
25780 numeric variables for other things.
25782 For example, the following authenticator checks that the user name given by the
25783 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
25784 user name, authentication fails.
25788 public_name = CRAM-MD5
25789 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
25790 server_set_id = $auth1
25792 .vindex "&$authenticated_id$&"
25793 If authentication succeeds, the setting of &%server_set_id%& preserves the user
25794 name in &$authenticated_id$&. A more typical configuration might look up the
25795 secret string in a file, using the user name as the key. For example:
25799 public_name = CRAM-MD5
25800 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
25802 server_set_id = $auth1
25804 Note that this expansion explicitly forces failure if the lookup fails
25805 because &$auth1$& contains an unknown user name.
25807 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
25808 using the relevant libraries, you need to know the realm to specify in the
25809 lookup and then ask for the &"userPassword"& attribute for that user in that
25814 public_name = CRAM-MD5
25815 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
25816 dbmjz{/etc/sasldb2}{$value}fail}
25817 server_set_id = $auth1
25820 .section "Using cram_md5 as a client" "SECID177"
25821 .cindex "options" "&(cram_md5)& authenticator (client)"
25822 When used as a client, the &(cram_md5)& authenticator has two options:
25826 .option client_name cram_md5 string&!! "the primary host name"
25827 This string is expanded, and the result used as the user name data when
25828 computing the response to the server's challenge.
25831 .option client_secret cram_md5 string&!! unset
25832 This option must be set for the authenticator to work as a client. Its value is
25833 expanded and the result used as the secret string when computing the response.
25837 .vindex "&$host_address$&"
25838 Different user names and secrets can be used for different servers by referring
25839 to &$host$& or &$host_address$& in the options. Forced failure of either
25840 expansion string is treated as an indication that this authenticator is not
25841 prepared to handle this case. Exim moves on to the next configured client
25842 authenticator. Any other expansion failure causes Exim to give up trying to
25843 send the message to the current server.
25845 A simple example configuration of a &(cram_md5)& authenticator, using fixed
25850 public_name = CRAM-MD5
25852 client_secret = secret
25854 .ecindex IIDcramauth1
25855 .ecindex IIDcramauth2
25859 . ////////////////////////////////////////////////////////////////////////////
25860 . ////////////////////////////////////////////////////////////////////////////
25862 .chapter "The cyrus_sasl authenticator" "CHID10"
25863 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25864 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25865 .cindex "Cyrus" "SASL library"
25867 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25868 Digital Ltd (&url(http://www.aldigital.co.uk)).
25870 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25871 library implementation of the RFC 2222 (&"Simple Authentication and Security
25872 Layer"&). This library supports a number of authentication mechanisms,
25873 including PLAIN and LOGIN, but also several others that Exim does not support
25874 directly. In particular, there is support for Kerberos authentication.
25876 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25877 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25878 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25879 name of the driver to determine which mechanism to support.
25881 Where access to some kind of secret file is required, for example in GSSAPI
25882 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25883 user, and that the Cyrus SASL library has no way of escalating privileges
25884 by default. You may also find you need to set environment variables,
25885 depending on the driver you are using.
25887 The application name provided by Exim is &"exim"&, so various SASL options may
25888 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25889 Kerberos, note that because of limitations in the GSSAPI interface,
25890 changing the server keytab might need to be communicated down to the Kerberos
25891 layer independently. The mechanism for doing so is dependent upon the Kerberos
25894 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25895 may be set to point to an alternative keytab file. Exim will pass this
25896 variable through from its own inherited environment when started as root or the
25897 Exim user. The keytab file needs to be readable by the Exim user.
25898 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25899 environment variable. In practice, for those releases, the Cyrus authenticator
25900 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25901 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25904 .section "Using cyrus_sasl as a server" "SECID178"
25905 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25906 (on a successful authentication) into &$auth1$&. For compatibility with
25907 previous releases of Exim, the username is also placed in &$1$&. However, the
25908 use of this variable for this purpose is now deprecated, as it can lead to
25909 confusion in string expansions that also use numeric variables for other
25913 .option server_hostname cyrus_sasl string&!! "see below"
25914 This option selects the hostname that is used when communicating with the
25915 library. The default value is &`$primary_hostname`&. It is up to the underlying
25916 SASL plug-in what it does with this data.
25919 .option server_mech cyrus_sasl string "see below"
25920 This option selects the authentication mechanism this driver should use. The
25921 default is the value of the generic &%public_name%& option. This option allows
25922 you to use a different underlying mechanism from the advertised name. For
25926 driver = cyrus_sasl
25927 public_name = X-ANYTHING
25928 server_mech = CRAM-MD5
25929 server_set_id = $auth1
25932 .option server_realm cyrus_sasl string&!! unset
25933 This specifies the SASL realm that the server claims to be in.
25936 .option server_service cyrus_sasl string &`smtp`&
25937 This is the SASL service that the server claims to implement.
25940 For straightforward cases, you do not need to set any of the authenticator's
25941 private options. All you need to do is to specify an appropriate mechanism as
25942 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
25943 PLAIN, you could have two authenticators as follows:
25946 driver = cyrus_sasl
25947 public_name = CRAM-MD5
25948 server_set_id = $auth1
25951 driver = cyrus_sasl
25952 public_name = PLAIN
25953 server_set_id = $auth2
25955 Cyrus SASL does implement the LOGIN authentication method, even though it is
25956 not a standard method. It is disabled by default in the source distribution,
25957 but it is present in many binary distributions.
25958 .ecindex IIDcyrauth1
25959 .ecindex IIDcyrauth2
25964 . ////////////////////////////////////////////////////////////////////////////
25965 . ////////////////////////////////////////////////////////////////////////////
25966 .chapter "The dovecot authenticator" "CHAPdovecot"
25967 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
25968 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
25969 This authenticator is an interface to the authentication facility of the
25970 Dovecot POP/IMAP server, which can support a number of authentication methods.
25971 Note that Dovecot must be configured to use auth-client not auth-userdb.
25972 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
25973 to use the same mechanisms for SMTP authentication. This is a server
25974 authenticator only. There is only one option:
25976 .option server_socket dovecot string unset
25978 This option must specify the socket that is the interface to Dovecot
25979 authentication. The &%public_name%& option must specify an authentication
25980 mechanism that Dovecot is configured to support. You can have several
25981 authenticators for different mechanisms. For example:
25985 public_name = PLAIN
25986 server_socket = /var/run/dovecot/auth-client
25987 server_set_id = $auth1
25992 server_socket = /var/run/dovecot/auth-client
25993 server_set_id = $auth1
25995 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
25996 &$received_ip_address$& (that is, the connection is local), the &"secured"&
25997 option is passed in the Dovecot authentication command. If, for a TLS
25998 connection, a client certificate has been verified, the &"valid-client-cert"&
25999 option is passed. When authentication succeeds, the identity of the user
26000 who authenticated is placed in &$auth1$&.
26001 .ecindex IIDdcotauth1
26002 .ecindex IIDdcotauth2
26005 . ////////////////////////////////////////////////////////////////////////////
26006 . ////////////////////////////////////////////////////////////////////////////
26007 .chapter "The gsasl authenticator" "CHAPgsasl"
26008 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26009 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26010 .cindex "authentication" "GNU SASL"
26011 .cindex "authentication" "SASL"
26012 .cindex "authentication" "EXTERNAL"
26013 .cindex "authentication" "ANONYMOUS"
26014 .cindex "authentication" "PLAIN"
26015 .cindex "authentication" "LOGIN"
26016 .cindex "authentication" "DIGEST-MD5"
26017 .cindex "authentication" "CRAM-MD5"
26018 .cindex "authentication" "SCRAM-SHA-1"
26019 The &(gsasl)& authenticator provides server integration for the GNU SASL
26020 library and the mechanisms it provides. This is new as of the 4.80 release
26021 and there are a few areas where the library does not let Exim smoothly
26022 scale to handle future authentication mechanisms, so no guarantee can be
26023 made that any particular new authentication mechanism will be supported
26024 without code changes in Exim.
26027 .option server_channelbinding gsasl boolean false
26028 Some authentication mechanisms are able to use external context at both ends
26029 of the session to bind the authentication to that context, and fail the
26030 authentication process if that context differs. Specifically, some TLS
26031 ciphersuites can provide identifying information about the cryptographic
26034 This means that certificate identity and verification becomes a non-issue,
26035 as a man-in-the-middle attack will cause the correct client and server to
26036 see different identifiers and authentication will fail.
26038 This is currently only supported when using the GnuTLS library. This is
26039 only usable by mechanisms which support "channel binding"; at time of
26040 writing, that's the SCRAM family.
26042 This defaults off to ensure smooth upgrade across Exim releases, in case
26043 this option causes some clients to start failing. Some future release
26044 of Exim may switch the default to be true.
26047 .option server_hostname gsasl string&!! "see below"
26048 This option selects the hostname that is used when communicating with the
26049 library. The default value is &`$primary_hostname`&.
26050 Some mechanisms will use this data.
26053 .option server_mech gsasl string "see below"
26054 This option selects the authentication mechanism this driver should use. The
26055 default is the value of the generic &%public_name%& option. This option allows
26056 you to use a different underlying mechanism from the advertised name. For
26061 public_name = X-ANYTHING
26062 server_mech = CRAM-MD5
26063 server_set_id = $auth1
26067 .option server_password gsasl string&!! unset
26068 Various mechanisms need access to the cleartext password on the server, so
26069 that proof-of-possession can be demonstrated on the wire, without sending
26070 the password itself.
26072 The data available for lookup varies per mechanism.
26073 In all cases, &$auth1$& is set to the &'authentication id'&.
26074 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26075 if available, else the empty string.
26076 The &$auth3$& variable will always be the &'realm'& if available,
26077 else the empty string.
26079 A forced failure will cause authentication to defer.
26081 If using this option, it may make sense to set the &%server_condition%&
26082 option to be simply "true".
26085 .option server_realm gsasl string&!! unset
26086 This specifies the SASL realm that the server claims to be in.
26087 Some mechanisms will use this data.
26090 .option server_scram_iter gsasl string&!! unset
26091 This option provides data for the SCRAM family of mechanisms.
26092 &$auth1$& is not available at evaluation time.
26093 (This may change, as we receive feedback on use)
26096 .option server_scram_salt gsasl string&!! unset
26097 This option provides data for the SCRAM family of mechanisms.
26098 &$auth1$& is not available at evaluation time.
26099 (This may change, as we receive feedback on use)
26102 .option server_service gsasl string &`smtp`&
26103 This is the SASL service that the server claims to implement.
26104 Some mechanisms will use this data.
26107 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26108 .vindex "&$auth1$&, &$auth2$&, etc"
26109 These may be set when evaluating specific options, as detailed above.
26110 They will also be set when evaluating &%server_condition%&.
26112 Unless otherwise stated below, the &(gsasl)& integration will use the following
26113 meanings for these variables:
26116 .vindex "&$auth1$&"
26117 &$auth1$&: the &'authentication id'&
26119 .vindex "&$auth2$&"
26120 &$auth2$&: the &'authorization id'&
26122 .vindex "&$auth3$&"
26123 &$auth3$&: the &'realm'&
26126 On a per-mechanism basis:
26129 .cindex "authentication" "EXTERNAL"
26130 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26131 the &%server_condition%& option must be present.
26133 .cindex "authentication" "ANONYMOUS"
26134 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26135 the &%server_condition%& option must be present.
26137 .cindex "authentication" "GSSAPI"
26138 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26139 &$auth2$& will be set to the &'authorization id'&,
26140 the &%server_condition%& option must be present.
26143 An &'anonymous token'& is something passed along as an unauthenticated
26144 identifier; this is analogous to FTP anonymous authentication passing an
26145 email address, or software-identifier@, as the "password".
26148 An example showing the password having the realm specified in the callback
26149 and demonstrating a Cyrus SASL to GSASL migration approach is:
26151 gsasl_cyrusless_crammd5:
26153 public_name = CRAM-MD5
26154 server_realm = imap.example.org
26155 server_password = ${lookup{$auth1:$auth3:userPassword}\
26156 dbmjz{/etc/sasldb2}{$value}fail}
26157 server_set_id = ${quote:$auth1}
26158 server_condition = yes
26162 . ////////////////////////////////////////////////////////////////////////////
26163 . ////////////////////////////////////////////////////////////////////////////
26165 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26166 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26167 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26168 .cindex "authentication" "GSSAPI"
26169 .cindex "authentication" "Kerberos"
26170 The &(heimdal_gssapi)& authenticator provides server integration for the
26171 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26174 .option server_hostname heimdal_gssapi string&!! "see below"
26175 This option selects the hostname that is used, with &%server_service%&,
26176 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26177 identifier. The default value is &`$primary_hostname`&.
26179 .option server_keytab heimdal_gssapi string&!! unset
26180 If set, then Heimdal will not use the system default keytab (typically
26181 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26182 The value should be a pathname, with no &"file:"& prefix.
26184 .option server_service heimdal_gssapi string&!! "smtp"
26185 This option specifies the service identifier used, in conjunction with
26186 &%server_hostname%&, for building the identifier for finding credentials
26190 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26191 Beware that these variables will typically include a realm, thus will appear
26192 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26193 not verified, so a malicious client can set it to anything.
26195 The &$auth1$& field should be safely trustable as a value from the Key
26196 Distribution Center. Note that these are not quite email addresses.
26197 Each identifier is for a role, and so the left-hand-side may include a
26198 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26200 .vindex "&$auth1$&, &$auth2$&, etc"
26202 .vindex "&$auth1$&"
26203 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26205 .vindex "&$auth2$&"
26206 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26207 authentication. If that was empty, this will also be set to the
26212 . ////////////////////////////////////////////////////////////////////////////
26213 . ////////////////////////////////////////////////////////////////////////////
26215 .chapter "The spa authenticator" "CHAPspa"
26216 .scindex IIDspaauth1 "&(spa)& authenticator"
26217 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26218 .cindex "authentication" "Microsoft Secure Password"
26219 .cindex "authentication" "NTLM"
26220 .cindex "Microsoft Secure Password Authentication"
26221 .cindex "NTLM authentication"
26222 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26223 Password Authentication'& mechanism,
26224 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26225 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26226 taken from the Samba project (&url(http://www.samba.org)). The code for the
26227 server side was subsequently contributed by Tom Kistner. The mechanism works as
26231 After the AUTH command has been accepted, the client sends an SPA
26232 authentication request based on the user name and optional domain.
26234 The server sends back a challenge.
26236 The client builds a challenge response which makes use of the user's password
26237 and sends it to the server, which then accepts or rejects it.
26240 Encryption is used to protect the password in transit.
26244 .section "Using spa as a server" "SECID179"
26245 .cindex "options" "&(spa)& authenticator (server)"
26246 The &(spa)& authenticator has just one server option:
26248 .option server_password spa string&!! unset
26249 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26250 This option is expanded, and the result must be the cleartext password for the
26251 authenticating user, whose name is at this point in &$auth1$&. For
26252 compatibility with previous releases of Exim, the user name is also placed in
26253 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26254 it can lead to confusion in string expansions that also use numeric variables
26255 for other things. For example:
26260 server_password = \
26261 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26263 If the expansion is forced to fail, authentication fails. Any other expansion
26264 failure causes a temporary error code to be returned.
26270 .section "Using spa as a client" "SECID180"
26271 .cindex "options" "&(spa)& authenticator (client)"
26272 The &(spa)& authenticator has the following client options:
26276 .option client_domain spa string&!! unset
26277 This option specifies an optional domain for the authentication.
26280 .option client_password spa string&!! unset
26281 This option specifies the user's password, and must be set.
26284 .option client_username spa string&!! unset
26285 This option specifies the user name, and must be set. Here is an example of a
26286 configuration of this authenticator for use with the mail servers at
26292 client_username = msn/msn_username
26293 client_password = msn_plaintext_password
26294 client_domain = DOMAIN_OR_UNSET
26296 .ecindex IIDspaauth1
26297 .ecindex IIDspaauth2
26303 . ////////////////////////////////////////////////////////////////////////////
26304 . ////////////////////////////////////////////////////////////////////////////
26307 .chapter "The tls authenticator" "CHAPtlsauth"
26308 .scindex IIDtlsauth1 "&(tls)& authenticator"
26309 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26310 .cindex "authentication" "Client Certificate"
26311 .cindex "authentication" "X509"
26312 .cindex "Certificate-based authentication"
26313 The &(tls)& authenticator provides server support for
26314 authentication based on client certificates.
26316 It is not an SMTP authentication mechanism and is not
26317 advertised by the server as part of the SMTP EHLO response.
26318 It is an Exim authenticator in the sense that it affects
26319 the protocol element of the log line, can be tested for
26320 by the &%authenticated%& ACL condition, and can set
26321 the &$authenticated_id$& variable.
26323 The client must present a verifiable certificate,
26324 for which it must have been requested via the
26325 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26326 (see &<<CHAPTLS>>&).
26328 If an authenticator of this type is configured it is
26329 run before any SMTP-level communication is done,
26330 and can authenticate the connection.
26331 If it does, SMTP authentication is not offered.
26333 A maximum of one authenticator of this type may be present.
26336 .cindex "options" "&(tls)& authenticator (server)"
26337 The &(tls)& authenticator has three server options:
26339 .option server_param1 tls string&!! unset
26340 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26341 This option is expanded after the TLS negotiation and
26342 the result is placed in &$auth1$&.
26343 If the expansion is forced to fail, authentication fails. Any other expansion
26344 failure causes a temporary error code to be returned.
26346 .option server_param2 tls string&!! unset
26347 .option server_param3 tls string&!! unset
26348 As above, for &$auth2$& and &$auth3$&.
26350 &%server_param1%& may also be spelled &%server_param%&.
26357 server_param1 = ${certextract {subj_altname,mail,>:} \
26358 {$tls_in_peercert}}
26359 server_condition = ${if forany {$auth1} \
26361 {${lookup ldap{ldap:///\
26362 mailname=${quote_ldap_dn:${lc:$item}},\
26363 ou=users,LDAP_DC?mailid} {$value}{0} \
26365 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26367 .ecindex IIDtlsauth1
26368 .ecindex IIDtlsauth2
26372 Note that because authentication is traditionally an SMTP operation,
26373 the &%authenticated%& ACL condition cannot be used in
26374 a connect- or helo-ACL.
26378 . ////////////////////////////////////////////////////////////////////////////
26379 . ////////////////////////////////////////////////////////////////////////////
26381 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26382 "Encrypted SMTP connections"
26383 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26384 .scindex IIDencsmtp2 "SMTP" "encryption"
26385 .cindex "TLS" "on SMTP connection"
26388 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26389 Sockets Layer), is implemented by making use of the OpenSSL library or the
26390 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26391 cryptographic code in the Exim distribution itself for implementing TLS. In
26392 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26393 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26394 You also need to understand the basic concepts of encryption at a managerial
26395 level, and in particular, the way that public keys, private keys, and
26396 certificates are used.
26398 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26399 connection is established, the client issues a STARTTLS command. If the
26400 server accepts this, the client and the server negotiate an encryption
26401 mechanism. If the negotiation succeeds, the data that subsequently passes
26402 between them is encrypted.
26404 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26405 and if so, what cipher suite is in use, whether the client supplied a
26406 certificate, and whether or not that certificate was verified. This makes it
26407 possible for an Exim server to deny or accept certain commands based on the
26410 &*Warning*&: Certain types of firewall and certain anti-virus products can
26411 disrupt TLS connections. You need to turn off SMTP scanning for these products
26412 in order to get TLS to work.
26416 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26418 .cindex "ssmtp protocol"
26419 .cindex "smtps protocol"
26420 .cindex "SMTP" "ssmtp protocol"
26421 .cindex "SMTP" "smtps protocol"
26422 Early implementations of encrypted SMTP used a different TCP port from normal
26423 SMTP, and expected an encryption negotiation to start immediately, instead of
26424 waiting for a STARTTLS command from the client using the standard SMTP
26425 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26426 allocated for this purpose.
26428 This approach was abandoned when encrypted SMTP was standardized, but there are
26429 still some legacy clients that use it. Exim supports these clients by means of
26430 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26431 numbers; the most common use is expected to be:
26433 tls_on_connect_ports = 465
26435 The port numbers specified by this option apply to all SMTP connections, both
26436 via the daemon and via &'inetd'&. You still need to specify all the ports that
26437 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26438 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26439 an extra port &-- rather, it specifies different behaviour on a port that is
26442 There is also a &%-tls-on-connect%& command line option. This overrides
26443 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26450 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26451 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26452 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26453 followed later, when the first versions of GnuTLS were released. To build Exim
26454 to use GnuTLS, you need to set
26458 in Local/Makefile, in addition to
26462 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26463 include files and libraries for GnuTLS can be found.
26465 There are some differences in usage when using GnuTLS instead of OpenSSL:
26468 The &%tls_verify_certificates%& option
26469 cannot be the path of a directory
26470 for GnuTLS versions before 3.3.6
26471 (for later versions, or OpenSSL, it can be either).
26473 The default value for &%tls_dhparam%& differs for historical reasons.
26475 .vindex "&$tls_in_peerdn$&"
26476 .vindex "&$tls_out_peerdn$&"
26477 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26478 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26479 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26481 OpenSSL identifies cipher suites using hyphens as separators, for example:
26482 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26483 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26484 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26485 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26486 to handle its own older variants) when processing lists of cipher suites in the
26487 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26490 The &%tls_require_ciphers%& options operate differently, as described in the
26491 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26493 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26494 When using OpenSSL, this option is ignored.
26495 (If an API is found to let OpenSSL be configured in this way,
26496 let the Exim Maintainers know and we'll likely use it).
26498 Some other recently added features may only be available in one or the other.
26499 This should be documented with the feature. If the documentation does not
26500 explicitly state that the feature is infeasible in the other TLS
26501 implementation, then patches are welcome.
26505 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26506 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26507 an explicit path; if the latter, then the text about generation still applies,
26508 but not the chosen filename.
26509 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26510 See the documentation of &%tls_dhparam%& for more information.
26512 GnuTLS uses D-H parameters that may take a substantial amount of time
26513 to compute. It is unreasonable to re-compute them for every TLS session.
26514 Therefore, Exim keeps this data in a file in its spool directory, called
26515 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26517 The file is owned by the Exim user and is readable only by
26518 its owner. Every Exim process that start up GnuTLS reads the D-H
26519 parameters from this file. If the file does not exist, the first Exim process
26520 that needs it computes the data and writes it to a temporary file which is
26521 renamed once it is complete. It does not matter if several Exim processes do
26522 this simultaneously (apart from wasting a few resources). Once a file is in
26523 place, new Exim processes immediately start using it.
26525 For maximum security, the parameters that are stored in this file should be
26526 recalculated periodically, the frequency depending on your paranoia level.
26527 If you are avoiding using the fixed D-H primes published in RFCs, then you
26528 are concerned about some advanced attacks and will wish to do this; if you do
26529 not regenerate then you might as well stick to the standard primes.
26531 Arranging this is easy in principle; just delete the file when you want new
26532 values to be computed. However, there may be a problem. The calculation of new
26533 parameters needs random numbers, and these are obtained from &_/dev/random_&.
26534 If the system is not very active, &_/dev/random_& may delay returning data
26535 until enough randomness (entropy) is available. This may cause Exim to hang for
26536 a substantial amount of time, causing timeouts on incoming connections.
26538 The solution is to generate the parameters externally to Exim. They are stored
26539 in &_gnutls-params-N_& in PEM format, which means that they can be
26540 generated externally using the &(certtool)& command that is part of GnuTLS.
26542 To replace the parameters with new ones, instead of deleting the file
26543 and letting Exim re-create it, you can generate new parameters using
26544 &(certtool)& and, when this has been done, replace Exim's cache file by
26545 renaming. The relevant commands are something like this:
26548 [ look for file; assume gnutls-params-2236 is the most recent ]
26551 # chown exim:exim new-params
26552 # chmod 0600 new-params
26553 # certtool --generate-dh-params --bits 2236 >>new-params
26554 # openssl dhparam -noout -text -in new-params | head
26555 [ check the first line, make sure it's not more than 2236;
26556 if it is, then go back to the start ("rm") and repeat
26557 until the size generated is at most the size requested ]
26558 # chmod 0400 new-params
26559 # mv new-params gnutls-params-2236
26561 If Exim never has to generate the parameters itself, the possibility of
26562 stalling is removed.
26564 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
26565 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
26566 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
26567 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
26568 and Exim does so. This attempt to remove Exim from TLS policy decisions
26569 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
26570 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
26571 which applies to all D-H usage, client or server. If the value returned by
26572 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
26573 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
26574 limit, which is still much higher than Exim historically used.
26576 The filename and bits used will change as the GnuTLS maintainers change the
26577 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
26578 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
26579 2432 bits, while NSS is limited to 2236 bits.
26581 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
26582 increase the chance of the generated prime actually being within acceptable
26583 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
26584 procedure above. There is no sane procedure available to Exim to double-check
26585 the size of the generated prime, so it might still be too large.
26588 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
26589 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
26590 .oindex "&%tls_require_ciphers%&" "OpenSSL"
26591 There is a function in the OpenSSL library that can be passed a list of cipher
26592 suites before the cipher negotiation takes place. This specifies which ciphers
26593 are acceptable. The list is colon separated and may contain names like
26594 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
26595 directly to this function call.
26596 Many systems will install the OpenSSL manual-pages, so you may have
26597 &'ciphers(1)'& available to you.
26598 The following quotation from the OpenSSL
26599 documentation specifies what forms of item are allowed in the cipher string:
26602 It can consist of a single cipher suite such as RC4-SHA.
26604 It can represent a list of cipher suites containing a certain algorithm,
26605 or cipher suites of a certain type. For example SHA1 represents all
26606 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
26609 Lists of cipher suites can be combined in a single cipher string using
26610 the + character. This is used as a logical and operation. For example
26611 SHA1+DES represents all cipher suites containing the SHA1 and the DES
26615 Each cipher string can be optionally preceded by one of the characters &`!`&,
26618 If &`!`& is used, the ciphers are permanently deleted from the list. The
26619 ciphers deleted can never reappear in the list even if they are explicitly
26622 If &`-`& is used, the ciphers are deleted from the list, but some or all
26623 of the ciphers can be added again by later options.
26625 If &`+`& is used, the ciphers are moved to the end of the list. This
26626 option does not add any new ciphers; it just moves matching existing ones.
26629 If none of these characters is present, the string is interpreted as
26630 a list of ciphers to be appended to the current preference list. If the list
26631 includes any ciphers already present they will be ignored: that is, they will
26632 not be moved to the end of the list.
26635 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
26638 # note single-quotes to get ! past any shell history expansion
26639 $ openssl ciphers 'HIGH:!MD5:!SHA1'
26642 This example will let the library defaults be permitted on the MX port, where
26643 there's probably no identity verification anyway, but ups the ante on the
26644 submission ports where the administrator might have some influence on the
26645 choice of clients used:
26647 # OpenSSL variant; see man ciphers(1)
26648 tls_require_ciphers = ${if =={$received_port}{25}\
26655 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
26657 .cindex "GnuTLS" "specifying parameters for"
26658 .cindex "TLS" "specifying ciphers (GnuTLS)"
26659 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
26660 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
26661 .cindex "TLS" "specifying protocols (GnuTLS)"
26662 .cindex "TLS" "specifying priority string (GnuTLS)"
26663 .oindex "&%tls_require_ciphers%&" "GnuTLS"
26664 The GnuTLS library allows the caller to provide a "priority string", documented
26665 as part of the &[gnutls_priority_init]& function. This is very similar to the
26666 ciphersuite specification in OpenSSL.
26668 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
26669 and controls both protocols and ciphers.
26671 The &%tls_require_ciphers%& option is available both as an global option,
26672 controlling how Exim behaves as a server, and also as an option of the
26673 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
26674 the value is string expanded. The resulting string is not an Exim list and
26675 the string is given to the GnuTLS library, so that Exim does not need to be
26676 aware of future feature enhancements of GnuTLS.
26678 Documentation of the strings accepted may be found in the GnuTLS manual, under
26679 "Priority strings". This is online as
26680 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
26681 but beware that this relates to GnuTLS 3, which may be newer than the version
26682 installed on your system. If you are using GnuTLS 3,
26683 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
26684 on that site can be used to test a given string.
26688 # Disable older versions of protocols
26689 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
26692 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
26693 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
26694 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
26696 This example will let the library defaults be permitted on the MX port, where
26697 there's probably no identity verification anyway, and lowers security further
26698 by increasing compatibility; but this ups the ante on the submission ports
26699 where the administrator might have some influence on the choice of clients
26703 tls_require_ciphers = ${if =={$received_port}{25}\
26709 .section "Configuring an Exim server to use TLS" "SECID182"
26710 .cindex "TLS" "configuring an Exim server"
26711 When Exim has been built with TLS support, it advertises the availability of
26712 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
26713 but not to any others. The default value of this option is unset, which means
26714 that STARTTLS is not advertised at all. This default is chosen because you
26715 need to set some other options in order to make TLS available, and also it is
26716 sensible for systems that want to use TLS only as a client.
26718 If a client issues a STARTTLS command and there is some configuration
26719 problem in the server, the command is rejected with a 454 error. If the client
26720 persists in trying to issue SMTP commands, all except QUIT are rejected
26723 554 Security failure
26725 If a STARTTLS command is issued within an existing TLS session, it is
26726 rejected with a 554 error code.
26728 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
26729 match some hosts. You can, of course, set it to * to match all hosts.
26730 However, this is not all you need to do. TLS sessions to a server won't work
26731 without some further configuration at the server end.
26733 It is rumoured that all existing clients that support TLS/SSL use RSA
26734 encryption. To make this work you need to set, in the server,
26736 tls_certificate = /some/file/name
26737 tls_privatekey = /some/file/name
26739 These options are, in fact, expanded strings, so you can make them depend on
26740 the identity of the client that is connected if you wish. The first file
26741 contains the server's X509 certificate, and the second contains the private key
26742 that goes with it. These files need to be
26743 PEM format and readable by the Exim user, and must
26744 always be given as full path names.
26745 The key must not be password-protected.
26746 They can be the same file if both the
26747 certificate and the key are contained within it. If &%tls_privatekey%& is not
26748 set, or if its expansion is forced to fail or results in an empty string, this
26749 is assumed to be the case. The certificate file may also contain intermediate
26750 certificates that need to be sent to the client to enable it to authenticate
26751 the server's certificate.
26753 If you do not understand about certificates and keys, please try to find a
26754 source of this background information, which is not Exim-specific. (There are a
26755 few comments below in section &<<SECTcerandall>>&.)
26757 &*Note*&: These options do not apply when Exim is operating as a client &--
26758 they apply only in the case of a server. If you need to use a certificate in an
26759 Exim client, you must set the options of the same names in an &(smtp)&
26762 With just these options, an Exim server will be able to use TLS. It does not
26763 require the client to have a certificate (but see below for how to insist on
26764 this). There is one other option that may be needed in other situations. If
26766 tls_dhparam = /some/file/name
26768 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
26769 with the parameters contained in the file.
26770 Set this to &`none`& to disable use of DH entirely, by making no prime
26775 This may also be set to a string identifying a standard prime to be used for
26776 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
26777 used is &`ike23`&. There are a few standard primes available, see the
26778 documentation for &%tls_dhparam%& for the complete list.
26784 for a way of generating file data.
26786 The strings supplied for these three options are expanded every time a client
26787 host connects. It is therefore possible to use different certificates and keys
26788 for different hosts, if you so wish, by making use of the client's IP address
26789 in &$sender_host_address$& to control the expansion. If a string expansion is
26790 forced to fail, Exim behaves as if the option is not set.
26792 .cindex "cipher" "logging"
26793 .cindex "log" "TLS cipher"
26794 .vindex "&$tls_in_cipher$&"
26795 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
26796 an incoming TLS connection. It is included in the &'Received:'& header of an
26797 incoming message (by default &-- you can, of course, change this), and it is
26798 also included in the log line that records a message's arrival, keyed by
26799 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
26800 condition can be used to test for specific cipher suites in ACLs.
26802 Once TLS has been established, the ACLs that run for subsequent SMTP commands
26803 can check the name of the cipher suite and vary their actions accordingly. The
26804 cipher suite names vary, depending on which TLS library is being used. For
26805 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
26806 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
26807 documentation for more details.
26809 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
26810 (again depending on the &%tls_cipher%& log selector).
26813 .section "Requesting and verifying client certificates" "SECID183"
26814 .cindex "certificate" "verification of client"
26815 .cindex "TLS" "client certificate verification"
26816 If you want an Exim server to request a certificate when negotiating a TLS
26817 session with a client, you must set either &%tls_verify_hosts%& or
26818 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
26819 apply to all TLS connections. For any host that matches one of these options,
26820 Exim requests a certificate as part of the setup of the TLS session. The
26821 contents of the certificate are verified by comparing it with a list of
26822 expected certificates.
26824 These may be the system default set (depending on library version),
26826 an explicit file or,
26827 depending on library version, a directory, identified by
26828 &%tls_verify_certificates%&.
26830 A file can contain multiple certificates, concatenated end to end. If a
26833 each certificate must be in a separate file, with a name (or a symbolic link)
26834 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
26835 certificate. You can compute the relevant hash by running the command
26837 openssl x509 -hash -noout -in /cert/file
26839 where &_/cert/file_& contains a single certificate.
26841 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
26842 what happens if the client does not supply a certificate, or if the certificate
26843 does not match any of the certificates in the collection named by
26844 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
26845 attempt to set up a TLS session is aborted, and the incoming connection is
26846 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
26847 session continues. ACLs that run for subsequent SMTP commands can detect the
26848 fact that no certificate was verified, and vary their actions accordingly. For
26849 example, you can insist on a certificate before accepting a message for
26850 relaying, but not when the message is destined for local delivery.
26852 .vindex "&$tls_in_peerdn$&"
26853 When a client supplies a certificate (whether it verifies or not), the value of
26854 the Distinguished Name of the certificate is made available in the variable
26855 &$tls_in_peerdn$& during subsequent processing of the message.
26857 .cindex "log" "distinguished name"
26858 Because it is often a long text string, it is not included in the log line or
26859 &'Received:'& header by default. You can arrange for it to be logged, keyed by
26860 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
26861 &%received_header_text%& to change the &'Received:'& header. When no
26862 certificate is supplied, &$tls_in_peerdn$& is empty.
26865 .section "Revoked certificates" "SECID184"
26866 .cindex "TLS" "revoked certificates"
26867 .cindex "revocation list"
26868 .cindex "certificate" "revocation list"
26869 .cindex "OCSP" "stapling"
26870 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
26871 certificates are revoked. If you have such a list, you can pass it to an Exim
26872 server using the global option called &%tls_crl%& and to an Exim client using
26873 an identically named option for the &(smtp)& transport. In each case, the value
26874 of the option is expanded and must then be the name of a file that contains a
26876 The downside is that clients have to periodically re-download a potentially huge
26877 file from every certificate authority they know of.
26879 The way with most moving parts at query time is Online Certificate
26880 Status Protocol (OCSP), where the client verifies the certificate
26881 against an OCSP server run by the CA. This lets the CA track all
26882 usage of the certs. It requires running software with access to the
26883 private key of the CA, to sign the responses to the OCSP queries. OCSP
26884 is based on HTTP and can be proxied accordingly.
26886 The only widespread OCSP server implementation (known to this writer)
26887 comes as part of OpenSSL and aborts on an invalid request, such as
26888 connecting to the port and then disconnecting. This requires
26889 re-entering the passphrase each time some random client does this.
26891 The third way is OCSP Stapling; in this, the server using a certificate
26892 issued by the CA periodically requests an OCSP proof of validity from
26893 the OCSP server, then serves it up inline as part of the TLS
26894 negotiation. This approach adds no extra round trips, does not let the
26895 CA track users, scales well with number of certs issued by the CA and is
26896 resilient to temporary OCSP server failures, as long as the server
26897 starts retrying to fetch an OCSP proof some time before its current
26898 proof expires. The downside is that it requires server support.
26900 Unless Exim is built with the support disabled,
26901 or with GnuTLS earlier than version 3.1.3,
26902 support for OCSP stapling is included.
26904 There is a global option called &%tls_ocsp_file%&.
26905 The file specified therein is expected to be in DER format, and contain
26906 an OCSP proof. Exim will serve it as part of the TLS handshake. This
26907 option will be re-expanded for SNI, if the &%tls_certificate%& option
26908 contains &`tls_in_sni`&, as per other TLS options.
26910 Exim does not at this time implement any support for fetching a new OCSP
26911 proof. The burden is on the administrator to handle this, outside of
26912 Exim. The file specified should be replaced atomically, so that the
26913 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
26914 on each connection, so a new file will be handled transparently on the
26917 When built with OpenSSL Exim will check for a valid next update timestamp
26918 in the OCSP proof; if not present, or if the proof has expired, it will be
26921 For the client to be able to verify the stapled OCSP the server must
26922 also supply, in its stapled information, any intermediate
26923 certificates for the chain leading to the OCSP proof from the signer
26924 of the server certificate. There may be zero or one such. These
26925 intermediate certificates should be added to the server OCSP stapling
26926 file named by &%tls_ocsp_file%&.
26928 Note that the proof only covers the terminal server certificate,
26929 not any of the chain from CA to it.
26931 There is no current way to staple a proof for a client certificate.
26934 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
26935 OCSP server is supplied. The server URL may be included in the
26936 server certificate, if the CA is helpful.
26938 One failure mode seen was the OCSP Signer cert expiring before the end
26939 of validity of the OCSP proof. The checking done by Exim/OpenSSL
26940 noted this as invalid overall, but the re-fetch script did not.
26946 .section "Configuring an Exim client to use TLS" "SECID185"
26947 .cindex "cipher" "logging"
26948 .cindex "log" "TLS cipher"
26949 .cindex "log" "distinguished name"
26950 .cindex "TLS" "configuring an Exim client"
26951 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
26952 deliveries as well as to incoming, the latter one causing logging of the
26953 server certificate's DN. The remaining client configuration for TLS is all
26954 within the &(smtp)& transport.
26956 It is not necessary to set any options to have TLS work in the &(smtp)&
26957 transport. If Exim is built with TLS support, and TLS is advertised by a
26958 server, the &(smtp)& transport always tries to start a TLS session. However,
26959 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
26960 transport) to a list of server hosts for which TLS should not be used.
26962 If you do not want Exim to attempt to send messages unencrypted when an attempt
26963 to set up an encrypted connection fails in any way, you can set
26964 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
26965 those hosts, delivery is always deferred if an encrypted connection cannot be
26966 set up. If there are any other hosts for the address, they are tried in the
26969 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
26970 the message unencrypted. It always does this if the response to STARTTLS is
26971 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
26972 session after a success response code, what happens is controlled by the
26973 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
26974 delivery to this host is deferred, and other hosts (if available) are tried. If
26975 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
26976 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
26977 negotiation fails, Exim closes the current connection (because it is in an
26978 unknown state), opens a new one to the same host, and then tries the delivery
26981 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
26982 transport provide the client with a certificate, which is passed to the server
26983 if it requests it. If the server is Exim, it will request a certificate only if
26984 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
26986 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
26987 specifies a collection of expected server certificates.
26989 These may be the system default set (depending on library version),
26992 depending on library version, a directory,
26993 must name a file or,
26994 for OpenSSL only (not GnuTLS), a directory.
26995 The client verifies the server's certificate
26996 against this collection, taking into account any revoked certificates that are
26997 in the list defined by &%tls_crl%&.
26998 Failure to verify fails the TLS connection unless either of the
26999 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27001 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27002 certificate verification to the listed servers. Verification either must
27003 or need not succeed respectively.
27005 The &(smtp)& transport has two OCSP-related options:
27006 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27007 is requested and required for the connection to proceed. The default
27009 &%hosts_request_ocsp%&; a host-list for which (additionally)
27010 a Certificate Status is requested (but not necessarily verified). The default
27011 value is "*" meaning that requests are made unless configured
27014 The host(s) should also be in &%hosts_require_tls%&, and
27015 &%tls_verify_certificates%& configured for the transport,
27016 for OCSP to be relevant.
27019 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27020 list of permitted cipher suites. If either of these checks fails, delivery to
27021 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27022 alternative hosts, if any.
27025 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27026 is operating as a client. Exim does not assume that a server certificate (set
27027 by the global options of the same name) should also be used when operating as a
27031 .vindex "&$host_address$&"
27032 All the TLS options in the &(smtp)& transport are expanded before use, with
27033 &$host$& and &$host_address$& containing the name and address of the server to
27034 which the client is connected. Forced failure of an expansion causes Exim to
27035 behave as if the relevant option were unset.
27037 .vindex &$tls_out_bits$&
27038 .vindex &$tls_out_cipher$&
27039 .vindex &$tls_out_peerdn$&
27040 .vindex &$tls_out_sni$&
27041 Before an SMTP connection is established, the
27042 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27043 variables are emptied. (Until the first connection, they contain the values
27044 that were set when the message was received.) If STARTTLS is subsequently
27045 successfully obeyed, these variables are set to the relevant values for the
27046 outgoing connection.
27050 .section "Use of TLS Server Name Indication" "SECTtlssni"
27051 .cindex "TLS" "Server Name Indication"
27052 .vindex "&$tls_in_sni$&"
27053 .oindex "&%tls_in_sni%&"
27054 With TLS1.0 or above, there is an extension mechanism by which extra
27055 information can be included at various points in the protocol. One of these
27056 extensions, documented in RFC 6066 (and before that RFC 4366) is
27057 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27058 client in the initial handshake, so that the server can examine the servername
27059 within and possibly choose to use different certificates and keys (and more)
27062 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27063 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27066 With SMTP to MX, there are the same problems here as in choosing the identity
27067 against which to validate a certificate: you can't rely on insecure DNS to
27068 provide the identity which you then cryptographically verify. So this will
27069 be of limited use in that environment.
27071 With SMTP to Submission, there is a well-defined hostname which clients are
27072 connecting to and can validate certificates against. Thus clients &*can*&
27073 choose to include this information in the TLS negotiation. If this becomes
27074 wide-spread, then hosters can choose to present different certificates to
27075 different clients. Or even negotiate different cipher suites.
27077 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27078 if not empty, will be sent on a TLS session as part of the handshake. There's
27079 nothing more to it. Choosing a sensible value not derived insecurely is the
27080 only point of caution. The &$tls_out_sni$& variable will be set to this string
27081 for the lifetime of the client connection (including during authentication).
27083 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27084 received from a client.
27085 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27087 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27088 option (prior to expansion) then the following options will be re-expanded
27089 during TLS session handshake, to permit alternative values to be chosen:
27092 .vindex "&%tls_certificate%&"
27093 &%tls_certificate%&
27095 .vindex "&%tls_crl%&"
27098 .vindex "&%tls_privatekey%&"
27101 .vindex "&%tls_verify_certificates%&"
27102 &%tls_verify_certificates%&
27104 .vindex "&%tls_ocsp_file%&"
27108 Great care should be taken to deal with matters of case, various injection
27109 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27110 can always be referenced; it is important to remember that &$tls_sni$& is
27111 arbitrary unverified data provided prior to authentication.
27113 The Exim developers are proceeding cautiously and so far no other TLS options
27116 When Exim is built against OpenSSL, OpenSSL must have been built with support
27117 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27118 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27119 see &`-servername`& in the output, then OpenSSL has support.
27121 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27122 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27123 built, then you have SNI support).
27127 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27129 .cindex "multiple SMTP deliveries with TLS"
27130 .cindex "TLS" "multiple message deliveries"
27131 Exim sends multiple messages down the same TCP/IP connection by starting up
27132 an entirely new delivery process for each message, passing the socket from
27133 one process to the next. This implementation does not fit well with the use
27134 of TLS, because there is quite a lot of state information associated with a TLS
27135 connection, not just a socket identification. Passing all the state information
27136 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27137 session before passing the socket to a new process. The new process may then
27138 try to start a new TLS session, and if successful, may try to re-authenticate
27139 if AUTH is in use, before sending the next message.
27141 The RFC is not clear as to whether or not an SMTP session continues in clear
27142 after TLS has been shut down, or whether TLS may be restarted again later, as
27143 just described. However, if the server is Exim, this shutdown and
27144 reinitialization works. It is not known which (if any) other servers operate
27145 successfully if the client closes a TLS session and continues with unencrypted
27146 SMTP, but there are certainly some that do not work. For such servers, Exim
27147 should not pass the socket to another process, because the failure of the
27148 subsequent attempt to use it would cause Exim to record a temporary host error,
27149 and delay other deliveries to that host.
27151 To test for this case, Exim sends an EHLO command to the server after
27152 closing down the TLS session. If this fails in any way, the connection is
27153 closed instead of being passed to a new delivery process, but no retry
27154 information is recorded.
27156 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27157 &(smtp)& transport to match those hosts for which Exim should not pass
27158 connections to new processes if TLS has been used.
27163 .section "Certificates and all that" "SECTcerandall"
27164 .cindex "certificate" "references to discussion"
27165 In order to understand fully how TLS works, you need to know about
27166 certificates, certificate signing, and certificate authorities. This is not the
27167 place to give a tutorial, especially as I do not know very much about it
27168 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27169 to Apache, currently at
27171 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27173 Other parts of the &'modssl'& documentation are also helpful, and have
27174 links to further files.
27175 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27176 0-201-61598-3), contains both introductory and more in-depth descriptions.
27177 Some sample programs taken from the book are available from
27179 &url(http://www.rtfm.com/openssl-examples/)
27183 .section "Certificate chains" "SECID186"
27184 The file named by &%tls_certificate%& may contain more than one
27185 certificate. This is useful in the case where the certificate that is being
27186 sent is validated by an intermediate certificate which the other end does
27187 not have. Multiple certificates must be in the correct order in the file.
27188 First the host's certificate itself, then the first intermediate
27189 certificate to validate the issuer of the host certificate, then the next
27190 intermediate certificate to validate the issuer of the first intermediate
27191 certificate, and so on, until finally (optionally) the root certificate.
27192 The root certificate must already be trusted by the recipient for
27193 validation to succeed, of course, but if it's not preinstalled, sending the
27194 root certificate along with the rest makes it available for the user to
27195 install if the receiving end is a client MUA that can interact with a user.
27197 Note that certificates using MD5 are unlikely to work on today's Internet;
27198 even if your libraries allow loading them for use in Exim when acting as a
27199 server, increasingly clients will not accept such certificates. The error
27200 diagnostics in such a case can be frustratingly vague.
27204 .section "Self-signed certificates" "SECID187"
27205 .cindex "certificate" "self-signed"
27206 You can create a self-signed certificate using the &'req'& command provided
27207 with OpenSSL, like this:
27208 . ==== Do not shorten the duration here without reading and considering
27209 . ==== the text below. Please leave it at 9999 days.
27211 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27214 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27215 delimited and so can be identified independently. The &%-days%& option
27216 specifies a period for which the certificate is valid. The &%-nodes%& option is
27217 important: if you do not set it, the key is encrypted with a passphrase
27218 that you are prompted for, and any use that is made of the key causes more
27219 prompting for the passphrase. This is not helpful if you are going to use
27220 this certificate and key in an MTA, where prompting is not possible.
27222 . ==== I expect to still be working 26 years from now. The less technical
27223 . ==== debt I create, in terms of storing up trouble for my later years, the
27224 . ==== happier I will be then. We really have reached the point where we
27225 . ==== should start, at the very least, provoking thought and making folks
27226 . ==== pause before proceeding, instead of leaving all the fixes until two
27227 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27229 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27230 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27231 the above command might produce a date in the past. Think carefully about
27232 the lifetime of the systems you're deploying, and either reduce the duration
27233 of the certificate or reconsider your platform deployment. (At time of
27234 writing, reducing the duration is the most likely choice, but the inexorable
27235 progression of time takes us steadily towards an era where this will not
27236 be a sensible resolution).
27238 A self-signed certificate made in this way is sufficient for testing, and
27239 may be adequate for all your requirements if you are mainly interested in
27240 encrypting transfers, and not in secure identification.
27242 However, many clients require that the certificate presented by the server be a
27243 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27244 certificate. In this situation, the self-signed certificate described above
27245 must be installed on the client host as a trusted root &'certification
27246 authority'& (CA), and the certificate used by Exim must be a user certificate
27247 signed with that self-signed certificate.
27249 For information on creating self-signed CA certificates and using them to sign
27250 user certificates, see the &'General implementation overview'& chapter of the
27251 Open-source PKI book, available online at
27252 &url(http://ospkibook.sourceforge.net/).
27253 .ecindex IIDencsmtp1
27254 .ecindex IIDencsmtp2
27258 . ////////////////////////////////////////////////////////////////////////////
27259 . ////////////////////////////////////////////////////////////////////////////
27261 .chapter "Access control lists" "CHAPACL"
27262 .scindex IIDacl "&ACL;" "description"
27263 .cindex "control of incoming mail"
27264 .cindex "message" "controlling incoming"
27265 .cindex "policy control" "access control lists"
27266 Access Control Lists (ACLs) are defined in a separate section of the run time
27267 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27268 name, terminated by a colon. Here is a complete ACL section that contains just
27269 one very small ACL:
27273 accept hosts = one.host.only
27275 You can have as many lists as you like in the ACL section, and the order in
27276 which they appear does not matter. The lists are self-terminating.
27278 The majority of ACLs are used to control Exim's behaviour when it receives
27279 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27280 when a local process submits a message using SMTP by specifying the &%-bs%&
27281 option. The most common use is for controlling which recipients are accepted
27282 in incoming messages. In addition, you can define an ACL that is used to check
27283 local non-SMTP messages. The default configuration file contains an example of
27284 a realistic ACL for checking RCPT commands. This is discussed in chapter
27285 &<<CHAPdefconfil>>&.
27288 .section "Testing ACLs" "SECID188"
27289 The &%-bh%& command line option provides a way of testing your ACL
27290 configuration locally by running a fake SMTP session with which you interact.
27291 The host &'relay-test.mail-abuse.org'& provides a service for checking your
27292 relaying configuration (see section &<<SECTcheralcon>>& for more details).
27296 .section "Specifying when ACLs are used" "SECID189"
27297 .cindex "&ACL;" "options for specifying"
27298 In order to cause an ACL to be used, you have to name it in one of the relevant
27299 options in the main part of the configuration. These options are:
27300 .cindex "AUTH" "ACL for"
27301 .cindex "DATA" "ACLs for"
27302 .cindex "ETRN" "ACL for"
27303 .cindex "EXPN" "ACL for"
27304 .cindex "HELO" "ACL for"
27305 .cindex "EHLO" "ACL for"
27306 .cindex "DKIM" "ACL for"
27307 .cindex "MAIL" "ACL for"
27308 .cindex "QUIT, ACL for"
27309 .cindex "RCPT" "ACL for"
27310 .cindex "STARTTLS, ACL for"
27311 .cindex "VRFY" "ACL for"
27312 .cindex "SMTP" "connection, ACL for"
27313 .cindex "non-SMTP messages" "ACLs for"
27314 .cindex "MIME content scanning" "ACL for"
27315 .cindex "PRDR" "ACL for"
27318 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27319 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27320 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27321 .irow &%acl_smtp_auth%& "ACL for AUTH"
27322 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27323 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27324 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27325 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27326 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27327 .irow &%acl_smtp_expn%& "ACL for EXPN"
27328 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27329 .irow &%acl_smtp_mail%& "ACL for MAIL"
27330 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27331 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27332 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27333 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27334 .irow &%acl_smtp_quit%& "ACL for QUIT"
27335 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27336 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27337 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27340 For example, if you set
27342 acl_smtp_rcpt = small_acl
27344 the little ACL defined above is used whenever Exim receives a RCPT command
27345 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27346 done when RCPT commands arrive. A rejection of RCPT should cause the
27347 sending MTA to give up on the recipient address contained in the RCPT
27348 command, whereas rejection at other times may cause the client MTA to keep on
27349 trying to deliver the message. It is therefore recommended that you do as much
27350 testing as possible at RCPT time.
27353 .section "The non-SMTP ACLs" "SECID190"
27354 .cindex "non-SMTP messages" "ACLs for"
27355 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27356 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27357 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27358 the state of the SMTP connection such as encryption and authentication) are not
27359 relevant and are forbidden in these ACLs. However, the sender and recipients
27360 are known, so the &%senders%& and &%sender_domains%& conditions and the
27361 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27362 &$authenticated_sender$& are also available. You can specify added header lines
27363 in any of these ACLs.
27365 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27366 non-SMTP message, before any of the message has been read. (This is the
27367 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27368 batched SMTP input, it runs after the DATA command has been reached. The
27369 result of this ACL is ignored; it cannot be used to reject a message. If you
27370 really need to, you could set a value in an ACL variable here and reject based
27371 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27372 controls, and in particular, it can be used to set
27374 control = suppress_local_fixups
27376 This cannot be used in the other non-SMTP ACLs because by the time they are
27377 run, it is too late.
27379 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27380 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27382 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27383 kind of rejection is treated as permanent, because there is no way of sending a
27384 temporary error for these kinds of message.
27387 .section "The SMTP connect ACL" "SECID191"
27388 .cindex "SMTP" "connection, ACL for"
27389 .oindex &%smtp_banner%&
27390 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27391 session, after the test specified by &%host_reject_connection%& (which is now
27392 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27393 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27394 the message override the banner message that is otherwise specified by the
27395 &%smtp_banner%& option.
27398 .section "The EHLO/HELO ACL" "SECID192"
27399 .cindex "EHLO" "ACL for"
27400 .cindex "HELO" "ACL for"
27401 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27402 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27403 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27404 Note that a client may issue more than one EHLO or HELO command in an SMTP
27405 session, and indeed is required to issue a new EHLO or HELO after successfully
27406 setting up encryption following a STARTTLS command.
27408 If the command is accepted by an &%accept%& verb that has a &%message%&
27409 modifier, the message may not contain more than one line (it will be truncated
27410 at the first newline and a panic logged if it does). Such a message cannot
27411 affect the EHLO options that are listed on the second and subsequent lines of
27415 .section "The DATA ACLs" "SECID193"
27416 .cindex "DATA" "ACLs for"
27417 Two ACLs are associated with the DATA command, because it is two-stage
27418 command, with two responses being sent to the client.
27419 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27420 is obeyed. This gives you control after all the RCPT commands, but before
27421 the message itself is received. It offers the opportunity to give a negative
27422 response to the DATA command before the data is transmitted. Header lines
27423 added by MAIL or RCPT ACLs are not visible at this time, but any that
27424 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27426 You cannot test the contents of the message, for example, to verify addresses
27427 in the headers, at RCPT time or when the DATA command is received. Such
27428 tests have to appear in the ACL that is run after the message itself has been
27429 received, before the final response to the DATA command is sent. This is
27430 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27431 associated with the DATA command.
27433 For both of these ACLs, it is not possible to reject individual recipients. An
27434 error response rejects the entire message. Unfortunately, it is known that some
27435 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27436 before or after the data) correctly &-- they keep the message on their queues
27437 and try again later, but that is their problem, though it does waste some of
27440 The &%acl_smtp_data%& ACL is run after
27441 the &%acl_smtp_data_prdr%&,
27442 the &%acl_smtp_dkim%&
27443 and the &%acl_smtp_mime%& ACLs.
27445 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27446 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27447 enabled (which is the default).
27449 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27450 received, and is executed for each DKIM signature found in a message. If not
27451 otherwise specified, the default action is to accept.
27453 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27455 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27458 .section "The SMTP MIME ACL" "SECID194"
27459 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27460 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27462 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27465 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27466 .cindex "PRDR" "ACL for"
27467 .oindex "&%prdr_enable%&"
27468 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27469 with PRDR support enabled (which is the default).
27470 It becomes active only when the PRDR feature is negotiated between
27471 client and server for a message, and more than one recipient
27474 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27475 has been received, and is executed once for each recipient of the message
27476 with &$local_part$& and &$domain$& valid.
27477 The test may accept, defer or deny for individual recipients.
27478 The &%acl_smtp_data%& will still be called after this ACL and
27479 can reject the message overall, even if this ACL has accepted it
27480 for some or all recipients.
27482 PRDR may be used to support per-user content filtering. Without it
27483 one must defer any recipient after the first that has a different
27484 content-filter configuration. With PRDR, the RCPT-time check
27485 for this can be disabled when the MAIL-time $smtp_command included
27486 "PRDR". Any required difference in behaviour of the main DATA-time
27487 ACL should however depend on the PRDR-time ACL having run, as Exim
27488 will avoid doing so in some situations (e.g. single-recipient mails).
27490 See also the &%prdr_enable%& global option
27491 and the &%hosts_try_prdr%& smtp transport option.
27493 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27494 If the ACL is not defined, processing completes as if
27495 the feature was not requested by the client.
27497 .section "The QUIT ACL" "SECTQUITACL"
27498 .cindex "QUIT, ACL for"
27499 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27500 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27501 does not in fact control any access.
27503 For this reason, it may only accept
27504 or warn as its final result.
27507 This ACL can be used for tasks such as custom logging at the end of an SMTP
27508 session. For example, you can use ACL variables in other ACLs to count
27509 messages, recipients, etc., and log the totals at QUIT time using one or
27510 more &%logwrite%& modifiers on a &%warn%& verb.
27512 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
27513 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
27515 You do not need to have a final &%accept%&, but if you do, you can use a
27516 &%message%& modifier to specify custom text that is sent as part of the 221
27519 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
27520 failure (for example, failure to open a log file, or when Exim is bombing out
27521 because it has detected an unrecoverable error), all SMTP commands from the
27522 client are given temporary error responses until QUIT is received or the
27523 connection is closed. In these special cases, the QUIT ACL does not run.
27526 .section "The not-QUIT ACL" "SECTNOTQUITACL"
27527 .vindex &$acl_smtp_notquit$&
27528 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
27529 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
27530 trouble, such as being unable to write to its log files, this ACL is not run,
27531 because it might try to do things (such as write to log files) that make the
27532 situation even worse.
27534 Like the QUIT ACL, this ACL is provided to make it possible to do customized
27535 logging or to gather statistics, and its outcome is ignored. The &%delay%&
27536 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
27539 .vindex &$smtp_notquit_reason$&
27540 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
27541 to a string that indicates the reason for the termination of the SMTP
27542 connection. The possible values are:
27544 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
27545 .irow &`bad-commands`& "Too many unknown or non-mail commands"
27546 .irow &`command-timeout`& "Timeout while reading SMTP commands"
27547 .irow &`connection-lost`& "The SMTP connection has been lost"
27548 .irow &`data-timeout`& "Timeout while reading message data"
27549 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
27550 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
27551 .irow &`signal-exit`& "SIGTERM or SIGINT"
27552 .irow &`synchronization-error`& "SMTP synchronization error"
27553 .irow &`tls-failed`& "TLS failed to start"
27555 In most cases when an SMTP connection is closed without having received QUIT,
27556 Exim sends an SMTP response message before actually closing the connection.
27557 With the exception of the &`acl-drop`& case, the default message can be
27558 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
27559 &%drop%& verb in another ACL, it is the message from the other ACL that is
27563 .section "Finding an ACL to use" "SECID195"
27564 .cindex "&ACL;" "finding which to use"
27565 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
27566 you can use different ACLs in different circumstances. For example,
27568 acl_smtp_rcpt = ${if ={25}{$interface_port} \
27569 {acl_check_rcpt} {acl_check_rcpt_submit} }
27571 In the default configuration file there are some example settings for
27572 providing an RFC 4409 message submission service on port 587 and a
27573 non-standard &"smtps"& service on port 465. You can use a string
27574 expansion like this to choose an ACL for MUAs on these ports which is
27575 more appropriate for this purpose than the default ACL on port 25.
27577 The expanded string does not have to be the name of an ACL in the
27578 configuration file; there are other possibilities. Having expanded the
27579 string, Exim searches for an ACL as follows:
27582 If the string begins with a slash, Exim uses it as a file name, and reads its
27583 contents as an ACL. The lines are processed in the same way as lines in the
27584 Exim configuration file. In particular, continuation lines are supported, blank
27585 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
27586 If the file does not exist or cannot be read, an error occurs (typically
27587 causing a temporary failure of whatever caused the ACL to be run). For example:
27589 acl_smtp_data = /etc/acls/\
27590 ${lookup{$sender_host_address}lsearch\
27591 {/etc/acllist}{$value}{default}}
27593 This looks up an ACL file to use on the basis of the host's IP address, falling
27594 back to a default if the lookup fails. If an ACL is successfully read from a
27595 file, it is retained in memory for the duration of the Exim process, so that it
27596 can be re-used without having to re-read the file.
27598 If the string does not start with a slash, and does not contain any spaces,
27599 Exim searches the ACL section of the configuration for an ACL whose name
27600 matches the string.
27602 If no named ACL is found, or if the string contains spaces, Exim parses
27603 the string as an inline ACL. This can save typing in cases where you just
27604 want to have something like
27606 acl_smtp_vrfy = accept
27608 in order to allow free use of the VRFY command. Such a string may contain
27609 newlines; it is processed in the same way as an ACL that is read from a file.
27615 .section "ACL return codes" "SECID196"
27616 .cindex "&ACL;" "return codes"
27617 Except for the QUIT ACL, which does not affect the SMTP return code (see
27618 section &<<SECTQUITACL>>& above), the result of running an ACL is either
27619 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
27620 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
27621 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
27622 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
27623 This also causes a 4&'xx'& return code.
27625 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
27626 &"deny"&, because there is no mechanism for passing temporary errors to the
27627 submitters of non-SMTP messages.
27630 ACLs that are relevant to message reception may also return &"discard"&. This
27631 has the effect of &"accept"&, but causes either the entire message or an
27632 individual recipient address to be discarded. In other words, it is a
27633 blackholing facility. Use it with care.
27635 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
27636 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
27637 RCPT ACL is to discard just the one recipient address. If there are no
27638 recipients left when the message's data is received, the DATA ACL is not
27639 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
27640 remaining recipients. The &"discard"& return is not permitted for the
27641 &%acl_smtp_predata%& ACL.
27644 .cindex "&[local_scan()]& function" "when all recipients discarded"
27645 The &[local_scan()]& function is always run, even if there are no remaining
27646 recipients; it may create new recipients.
27650 .section "Unset ACL options" "SECID197"
27651 .cindex "&ACL;" "unset options"
27652 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
27653 all the same. &*Note*&: These defaults apply only when the relevant ACL is
27654 not defined at all. For any defined ACL, the default action when control
27655 reaches the end of the ACL statements is &"deny"&.
27657 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
27658 these two are ACLs that are used only for their side effects. They cannot be
27659 used to accept or reject anything.
27661 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
27662 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
27663 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
27664 when the ACL is not defined is &"accept"&.
27666 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
27667 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
27668 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
27669 messages over an SMTP connection. For an example, see the ACL in the default
27670 configuration file.
27675 .section "Data for message ACLs" "SECID198"
27676 .cindex "&ACL;" "data for message ACL"
27678 .vindex &$local_part$&
27679 .vindex &$sender_address$&
27680 .vindex &$sender_host_address$&
27681 .vindex &$smtp_command$&
27682 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
27683 that contain information about the host and the message's sender (for example,
27684 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
27685 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
27686 &$local_part$& are set from the argument address. The entire SMTP command
27687 is available in &$smtp_command$&.
27689 When an ACL for the AUTH parameter of MAIL is running, the variables that
27690 contain information about the host are set, but &$sender_address$& is not yet
27691 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
27694 .vindex "&$message_size$&"
27695 The &$message_size$& variable is set to the value of the SIZE parameter on
27696 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
27697 that parameter is not given. The value is updated to the true message size by
27698 the time the final DATA ACL is run (after the message data has been
27701 .vindex "&$rcpt_count$&"
27702 .vindex "&$recipients_count$&"
27703 The &$rcpt_count$& variable increases by one for each RCPT command received.
27704 The &$recipients_count$& variable increases by one each time a RCPT command is
27705 accepted, so while an ACL for RCPT is being processed, it contains the number
27706 of previously accepted recipients. At DATA time (for both the DATA ACLs),
27707 &$rcpt_count$& contains the total number of RCPT commands, and
27708 &$recipients_count$& contains the total number of accepted recipients.
27714 .section "Data for non-message ACLs" "SECTdatfornon"
27715 .cindex "&ACL;" "data for non-message ACL"
27716 .vindex &$smtp_command_argument$&
27717 .vindex &$smtp_command$&
27718 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
27719 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
27720 and the entire SMTP command is available in &$smtp_command$&.
27721 These variables can be tested using a &%condition%& condition. For example,
27722 here is an ACL for use with AUTH, which insists that either the session is
27723 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
27724 does not permit authentication methods that use cleartext passwords on
27725 unencrypted connections.
27728 accept encrypted = *
27729 accept condition = ${if eq{${uc:$smtp_command_argument}}\
27731 deny message = TLS encryption or CRAM-MD5 required
27733 (Another way of applying this restriction is to arrange for the authenticators
27734 that use cleartext passwords not to be advertised when the connection is not
27735 encrypted. You can use the generic &%server_advertise_condition%& authenticator
27736 option to do this.)
27740 .section "Format of an ACL" "SECID199"
27741 .cindex "&ACL;" "format of"
27742 .cindex "&ACL;" "verbs, definition of"
27743 An individual ACL consists of a number of statements. Each statement starts
27744 with a verb, optionally followed by a number of conditions and &"modifiers"&.
27745 Modifiers can change the way the verb operates, define error and log messages,
27746 set variables, insert delays, and vary the processing of accepted messages.
27748 If all the conditions are met, the verb is obeyed. The same condition may be
27749 used (with different arguments) more than once in the same statement. This
27750 provides a means of specifying an &"and"& conjunction between conditions. For
27753 deny dnslists = list1.example
27754 dnslists = list2.example
27756 If there are no conditions, the verb is always obeyed. Exim stops evaluating
27757 the conditions and modifiers when it reaches a condition that fails. What
27758 happens then depends on the verb (and in one case, on a special modifier). Not
27759 all the conditions make sense at every testing point. For example, you cannot
27760 test a sender address in the ACL that is run for a VRFY command.
27763 .section "ACL verbs" "SECID200"
27764 The ACL verbs are as follows:
27767 .cindex "&%accept%& ACL verb"
27768 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
27769 of the conditions are not met, what happens depends on whether &%endpass%&
27770 appears among the conditions (for syntax see below). If the failing condition
27771 is before &%endpass%&, control is passed to the next ACL statement; if it is
27772 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
27773 check a RCPT command:
27775 accept domains = +local_domains
27779 If the recipient domain does not match the &%domains%& condition, control
27780 passes to the next statement. If it does match, the recipient is verified, and
27781 the command is accepted if verification succeeds. However, if verification
27782 fails, the ACL yields &"deny"&, because the failing condition is after
27785 The &%endpass%& feature has turned out to be confusing to many people, so its
27786 use is not recommended nowadays. It is always possible to rewrite an ACL so
27787 that &%endpass%& is not needed, and it is no longer used in the default
27790 .cindex "&%message%& ACL modifier" "with &%accept%&"
27791 If a &%message%& modifier appears on an &%accept%& statement, its action
27792 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
27793 (when an &%accept%& verb either accepts or passes control to the next
27794 statement), &%message%& can be used to vary the message that is sent when an
27795 SMTP command is accepted. For example, in a RCPT ACL you could have:
27797 &`accept `&<&'some conditions'&>
27798 &` message = OK, I will allow you through today`&
27800 You can specify an SMTP response code, optionally followed by an &"extended
27801 response code"& at the start of the message, but the first digit must be the
27802 same as would be sent by default, which is 2 for an &%accept%& verb.
27804 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
27805 an error message that is used when access is denied. This behaviour is retained
27806 for backward compatibility, but current &"best practice"& is to avoid the use
27811 .cindex "&%defer%& ACL verb"
27812 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
27813 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
27814 &%defer%& is the same as &%deny%&, because there is no way of sending a
27815 temporary error. For a RCPT command, &%defer%& is much the same as using a
27816 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
27817 be used in any ACL, and even for a recipient it might be a simpler approach.
27821 .cindex "&%deny%& ACL verb"
27822 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
27823 the conditions are not met, control is passed to the next ACL statement. For
27826 deny dnslists = blackholes.mail-abuse.org
27828 rejects commands from hosts that are on a DNS black list.
27832 .cindex "&%discard%& ACL verb"
27833 &%discard%&: This verb behaves like &%accept%&, except that it returns
27834 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
27835 that are concerned with receiving messages. When all the conditions are true,
27836 the sending entity receives a &"success"& response. However, &%discard%& causes
27837 recipients to be discarded. If it is used in an ACL for RCPT, just the one
27838 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
27839 message's recipients are discarded. Recipients that are discarded before DATA
27840 do not appear in the log line when the &%received_recipients%& log selector is set.
27842 If the &%log_message%& modifier is set when &%discard%& operates,
27843 its contents are added to the line that is automatically written to the log.
27844 The &%message%& modifier operates exactly as it does for &%accept%&.
27848 .cindex "&%drop%& ACL verb"
27849 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
27850 forcibly closed after the 5&'xx'& error message has been sent. For example:
27852 drop message = I don't take more than 20 RCPTs
27853 condition = ${if > {$rcpt_count}{20}}
27855 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
27856 The connection is always dropped after sending a 550 response.
27859 .cindex "&%require%& ACL verb"
27860 &%require%&: If all the conditions are met, control is passed to the next ACL
27861 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
27862 example, when checking a RCPT command,
27864 require message = Sender did not verify
27867 passes control to subsequent statements only if the message's sender can be
27868 verified. Otherwise, it rejects the command. Note the positioning of the
27869 &%message%& modifier, before the &%verify%& condition. The reason for this is
27870 discussed in section &<<SECTcondmodproc>>&.
27873 .cindex "&%warn%& ACL verb"
27874 &%warn%&: If all the conditions are true, a line specified by the
27875 &%log_message%& modifier is written to Exim's main log. Control always passes
27876 to the next ACL statement. If any condition is false, the log line is not
27877 written. If an identical log line is requested several times in the same
27878 message, only one copy is actually written to the log. If you want to force
27879 duplicates to be written, use the &%logwrite%& modifier instead.
27881 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
27882 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
27883 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
27884 first failing condition. There is more about adding header lines in section
27885 &<<SECTaddheadacl>>&.
27887 If any condition on a &%warn%& statement cannot be completed (that is, there is
27888 some sort of defer), the log line specified by &%log_message%& is not written.
27889 This does not include the case of a forced failure from a lookup, which
27890 is considered to be a successful completion. After a defer, no further
27891 conditions or modifiers in the &%warn%& statement are processed. The incident
27892 is logged, and the ACL continues to be processed, from the next statement
27896 .vindex "&$acl_verify_message$&"
27897 When one of the &%warn%& conditions is an address verification that fails, the
27898 text of the verification failure message is in &$acl_verify_message$&. If you
27899 want this logged, you must set it up explicitly. For example:
27901 warn !verify = sender
27902 log_message = sender verify failed: $acl_verify_message
27906 At the end of each ACL there is an implicit unconditional &%deny%&.
27908 As you can see from the examples above, the conditions and modifiers are
27909 written one to a line, with the first one on the same line as the verb, and
27910 subsequent ones on following lines. If you have a very long condition, you can
27911 continue it onto several physical lines by the usual backslash continuation
27912 mechanism. It is conventional to align the conditions vertically.
27916 .section "ACL variables" "SECTaclvariables"
27917 .cindex "&ACL;" "variables"
27918 There are some special variables that can be set during ACL processing. They
27919 can be used to pass information between different ACLs, different invocations
27920 of the same ACL in the same SMTP connection, and between ACLs and the routers,
27921 transports, and filters that are used to deliver a message. The names of these
27922 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
27923 an underscore, but the remainder of the name can be any sequence of
27924 alphanumeric characters and underscores that you choose. There is no limit on
27925 the number of ACL variables. The two sets act as follows:
27927 The values of those variables whose names begin with &$acl_c$& persist
27928 throughout an SMTP connection. They are never reset. Thus, a value that is set
27929 while receiving one message is still available when receiving the next message
27930 on the same SMTP connection.
27932 The values of those variables whose names begin with &$acl_m$& persist only
27933 while a message is being received. They are reset afterwards. They are also
27934 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
27937 When a message is accepted, the current values of all the ACL variables are
27938 preserved with the message and are subsequently made available at delivery
27939 time. The ACL variables are set by a modifier called &%set%&. For example:
27941 accept hosts = whatever
27942 set acl_m4 = some value
27943 accept authenticated = *
27944 set acl_c_auth = yes
27946 &*Note*&: A leading dollar sign is not used when naming a variable that is to
27947 be set. If you want to set a variable without taking any action, you can use a
27948 &%warn%& verb without any other modifiers or conditions.
27950 .oindex &%strict_acl_vars%&
27951 What happens if a syntactically valid but undefined ACL variable is
27952 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
27953 false (the default), an empty string is substituted; if it is true, an
27954 error is generated.
27956 Versions of Exim before 4.64 have a limited set of numbered variables, but
27957 their names are compatible, so there is no problem with upgrading.
27960 .section "Condition and modifier processing" "SECTcondmodproc"
27961 .cindex "&ACL;" "conditions; processing"
27962 .cindex "&ACL;" "modifiers; processing"
27963 An exclamation mark preceding a condition negates its result. For example:
27965 deny domains = *.dom.example
27966 !verify = recipient
27968 causes the ACL to return &"deny"& if the recipient domain ends in
27969 &'dom.example'& and the recipient address cannot be verified. Sometimes
27970 negation can be used on the right-hand side of a condition. For example, these
27971 two statements are equivalent:
27973 deny hosts = !192.168.3.4
27974 deny !hosts = 192.168.3.4
27976 However, for many conditions (&%verify%& being a good example), only left-hand
27977 side negation of the whole condition is possible.
27979 The arguments of conditions and modifiers are expanded. A forced failure
27980 of an expansion causes a condition to be ignored, that is, it behaves as if the
27981 condition is true. Consider these two statements:
27983 accept senders = ${lookup{$host_name}lsearch\
27984 {/some/file}{$value}fail}
27985 accept senders = ${lookup{$host_name}lsearch\
27986 {/some/file}{$value}{}}
27988 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
27989 the returned list is searched, but if the lookup fails the behaviour is
27990 different in the two cases. The &%fail%& in the first statement causes the
27991 condition to be ignored, leaving no further conditions. The &%accept%& verb
27992 therefore succeeds. The second statement, however, generates an empty list when
27993 the lookup fails. No sender can match an empty list, so the condition fails,
27994 and therefore the &%accept%& also fails.
27996 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
27997 specify actions that are taken as the conditions for a statement are checked;
27998 others specify text for messages that are used when access is denied or a
27999 warning is generated. The &%control%& modifier affects the way an incoming
28000 message is handled.
28002 The positioning of the modifiers in an ACL statement is important, because the
28003 processing of a verb ceases as soon as its outcome is known. Only those
28004 modifiers that have already been encountered will take effect. For example,
28005 consider this use of the &%message%& modifier:
28007 require message = Can't verify sender
28009 message = Can't verify recipient
28011 message = This message cannot be used
28013 If sender verification fails, Exim knows that the result of the statement is
28014 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
28015 so its text is used as the error message. If sender verification succeeds, but
28016 recipient verification fails, the second message is used. If recipient
28017 verification succeeds, the third message becomes &"current"&, but is never used
28018 because there are no more conditions to cause failure.
28020 For the &%deny%& verb, on the other hand, it is always the last &%message%&
28021 modifier that is used, because all the conditions must be true for rejection to
28022 happen. Specifying more than one &%message%& modifier does not make sense, and
28023 the message can even be specified after all the conditions. For example:
28026 !senders = *@my.domain.example
28027 message = Invalid sender from client host
28029 The &"deny"& result does not happen until the end of the statement is reached,
28030 by which time Exim has set up the message.
28034 .section "ACL modifiers" "SECTACLmodi"
28035 .cindex "&ACL;" "modifiers; list of"
28036 The ACL modifiers are as follows:
28039 .vitem &*add_header*&&~=&~<&'text'&>
28040 This modifier specifies one or more header lines that are to be added to an
28041 incoming message, assuming, of course, that the message is ultimately
28042 accepted. For details, see section &<<SECTaddheadacl>>&.
28044 .vitem &*continue*&&~=&~<&'text'&>
28045 .cindex "&%continue%& ACL modifier"
28046 .cindex "database" "updating in ACL"
28047 This modifier does nothing of itself, and processing of the ACL always
28048 continues with the next condition or modifier. The value of &%continue%& is in
28049 the side effects of expanding its argument. Typically this could be used to
28050 update a database. It is really just a syntactic tidiness, to avoid having to
28051 write rather ugly lines like this:
28053 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28055 Instead, all you need is
28057 &`continue = `&<&'some expansion'&>
28060 .vitem &*control*&&~=&~<&'text'&>
28061 .cindex "&%control%& ACL modifier"
28062 This modifier affects the subsequent processing of the SMTP connection or of an
28063 incoming message that is accepted. The effect of the first type of control
28064 lasts for the duration of the connection, whereas the effect of the second type
28065 lasts only until the current message has been received. The message-specific
28066 controls always apply to the whole message, not to individual recipients,
28067 even if the &%control%& modifier appears in a RCPT ACL.
28069 As there are now quite a few controls that can be applied, they are described
28070 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28071 in several different ways. For example:
28073 . ==== As this is a nested list, any displays it contains must be indented
28074 . ==== as otherwise they are too far to the left. That comment applies only
28075 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28079 It can be at the end of an &%accept%& statement:
28081 accept ...some conditions
28082 control = queue_only
28084 In this case, the control is applied when this statement yields &"accept"&, in
28085 other words, when the conditions are all true.
28088 It can be in the middle of an &%accept%& statement:
28090 accept ...some conditions...
28091 control = queue_only
28092 ...some more conditions...
28094 If the first set of conditions are true, the control is applied, even if the
28095 statement does not accept because one of the second set of conditions is false.
28096 In this case, some subsequent statement must yield &"accept"& for the control
28100 It can be used with &%warn%& to apply the control, leaving the
28101 decision about accepting or denying to a subsequent verb. For
28104 warn ...some conditions...
28108 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28109 &%logwrite%&, so it does not add anything to the message and does not write a
28113 If you want to apply a control unconditionally, you can use it with a
28114 &%require%& verb. For example:
28116 require control = no_multiline_responses
28120 .vitem &*delay*&&~=&~<&'time'&>
28121 .cindex "&%delay%& ACL modifier"
28123 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28124 the time interval before proceeding. However, when testing Exim using the
28125 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28126 output instead). The time is given in the usual Exim notation, and the delay
28127 happens as soon as the modifier is processed. In an SMTP session, pending
28128 output is flushed before the delay is imposed.
28130 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28133 deny ...some conditions...
28136 The delay happens if all the conditions are true, before the statement returns
28137 &"deny"&. Compare this with:
28140 ...some conditions...
28142 which waits for 30s before processing the conditions. The &%delay%& modifier
28143 can also be used with &%warn%& and together with &%control%&:
28145 warn ...some conditions...
28151 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28152 responses to several commands are no longer buffered and sent in one packet (as
28153 they would normally be) because all output is flushed before imposing the
28154 delay. This optimization is disabled so that a number of small delays do not
28155 appear to the client as one large aggregated delay that might provoke an
28156 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28157 using a &%control%& modifier to set &%no_delay_flush%&.
28161 .cindex "&%endpass%& ACL modifier"
28162 This modifier, which has no argument, is recognized only in &%accept%& and
28163 &%discard%& statements. It marks the boundary between the conditions whose
28164 failure causes control to pass to the next statement, and the conditions whose
28165 failure causes the ACL to return &"deny"&. This concept has proved to be
28166 confusing to some people, so the use of &%endpass%& is no longer recommended as
28167 &"best practice"&. See the description of &%accept%& above for more details.
28170 .vitem &*log_message*&&~=&~<&'text'&>
28171 .cindex "&%log_message%& ACL modifier"
28172 This modifier sets up a message that is used as part of the log message if the
28173 ACL denies access or a &%warn%& statement's conditions are true. For example:
28175 require log_message = wrong cipher suite $tls_in_cipher
28176 encrypted = DES-CBC3-SHA
28178 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28181 &`discard `&<&'some conditions'&>
28182 &` log_message = Discarded $local_part@$domain because...`&
28184 When access is denied, &%log_message%& adds to any underlying error message
28185 that may exist because of a condition failure. For example, while verifying a
28186 recipient address, a &':fail:'& redirection might have already set up a
28189 The message may be defined before the conditions to which it applies, because
28190 the string expansion does not happen until Exim decides that access is to be
28191 denied. This means that any variables that are set by the condition are
28192 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28193 variables are set after a DNS black list lookup succeeds. If the expansion of
28194 &%log_message%& fails, or if the result is an empty string, the modifier is
28197 .vindex "&$acl_verify_message$&"
28198 If you want to use a &%warn%& statement to log the result of an address
28199 verification, you can use &$acl_verify_message$& to include the verification
28202 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28203 the start of the logged message. If the same warning log message is requested
28204 more than once while receiving a single email message, only one copy is
28205 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28206 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28207 is logged for a successful &%warn%& statement.
28209 If &%log_message%& is not present and there is no underlying error message (for
28210 example, from the failure of address verification), but &%message%& is present,
28211 the &%message%& text is used for logging rejections. However, if any text for
28212 logging contains newlines, only the first line is logged. In the absence of
28213 both &%log_message%& and &%message%&, a default built-in message is used for
28214 logging rejections.
28217 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28218 .cindex "&%log_reject_target%& ACL modifier"
28219 .cindex "logging in ACL" "specifying which log"
28220 This modifier makes it possible to specify which logs are used for messages
28221 about ACL rejections. Its argument is a colon-separated list of words that can
28222 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28223 may be empty, in which case a rejection is not logged at all. For example, this
28224 ACL fragment writes no logging information when access is denied:
28226 &`deny `&<&'some conditions'&>
28227 &` log_reject_target =`&
28229 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28230 permanent and temporary rejections. Its effect lasts for the rest of the
28234 .vitem &*logwrite*&&~=&~<&'text'&>
28235 .cindex "&%logwrite%& ACL modifier"
28236 .cindex "logging in ACL" "immediate"
28237 This modifier writes a message to a log file as soon as it is encountered when
28238 processing an ACL. (Compare &%log_message%&, which, except in the case of
28239 &%warn%& and &%discard%&, is used only if the ACL statement denies
28240 access.) The &%logwrite%& modifier can be used to log special incidents in
28243 &`accept `&<&'some special conditions'&>
28244 &` control = freeze`&
28245 &` logwrite = froze message because ...`&
28247 By default, the message is written to the main log. However, it may begin
28248 with a colon, followed by a comma-separated list of log names, and then
28249 another colon, to specify exactly which logs are to be written. For
28252 logwrite = :main,reject: text for main and reject logs
28253 logwrite = :panic: text for panic log only
28257 .vitem &*message*&&~=&~<&'text'&>
28258 .cindex "&%message%& ACL modifier"
28259 This modifier sets up a text string that is expanded and used as a response
28260 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28261 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28262 there is some complication if &%endpass%& is involved; see the description of
28263 &%accept%& for details.)
28265 The expansion of the message happens at the time Exim decides that the ACL is
28266 to end, not at the time it processes &%message%&. If the expansion fails, or
28267 generates an empty string, the modifier is ignored. Here is an example where
28268 &%message%& must be specified first, because the ACL ends with a rejection if
28269 the &%hosts%& condition fails:
28271 require message = Host not recognized
28274 (Once a condition has failed, no further conditions or modifiers are
28277 .cindex "SMTP" "error codes"
28278 .oindex "&%smtp_banner%&
28279 For ACLs that are triggered by SMTP commands, the message is returned as part
28280 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28281 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28282 is accepted. In the case of the connect ACL, accepting with a message modifier
28283 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28284 accept message may not contain more than one line (otherwise it will be
28285 truncated at the first newline and a panic logged), and it cannot affect the
28288 When SMTP is involved, the message may begin with an overriding response code,
28289 consisting of three digits optionally followed by an &"extended response code"&
28290 of the form &'n.n.n'&, each code being followed by a space. For example:
28292 deny message = 599 1.2.3 Host not welcome
28293 hosts = 192.168.34.0/24
28295 The first digit of the supplied response code must be the same as would be sent
28296 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28297 access, but for the predata ACL, note that the default success code is 354, not
28300 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28301 the message modifier cannot override the 221 response code.
28303 The text in a &%message%& modifier is literal; any quotes are taken as
28304 literals, but because the string is expanded, backslash escapes are processed
28305 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28308 .vindex "&$acl_verify_message$&"
28309 For ACLs that are called by an &%acl =%& ACL condition, the message is
28310 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28312 If &%message%& is used on a statement that verifies an address, the message
28313 specified overrides any message that is generated by the verification process.
28314 However, the original message is available in the variable
28315 &$acl_verify_message$&, so you can incorporate it into your message if you
28316 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28317 routers to be passed back as part of the SMTP response, you should either not
28318 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28320 For compatibility with previous releases of Exim, a &%message%& modifier that
28321 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28322 modifier, but this usage is now deprecated. However, &%message%& acts only when
28323 all the conditions are true, wherever it appears in an ACL command, whereas
28324 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28325 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28329 .vitem &*remove_header*&&~=&~<&'text'&>
28330 This modifier specifies one or more header names in a colon-separated list
28331 that are to be removed from an incoming message, assuming, of course, that
28332 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28335 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28336 .cindex "&%set%& ACL modifier"
28337 This modifier puts a value into one of the ACL variables (see section
28338 &<<SECTaclvariables>>&).
28341 .vitem &*udpsend*&&~=&~<&'parameters'&>
28342 This modifier sends a UDP packet, for purposes such as statistics
28343 collection or behaviour monitoring. The parameters are expanded, and
28344 the result of the expansion must be a colon-separated list consisting
28345 of a destination server, port number, and the packet contents. The
28346 server can be specified as a host name or IPv4 or IPv6 address. The
28347 separator can be changed with the usual angle bracket syntax. For
28348 example, you might want to collect information on which hosts connect
28351 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28352 $tod_zulu $sender_host_address
28359 .section "Use of the control modifier" "SECTcontrols"
28360 .cindex "&%control%& ACL modifier"
28361 The &%control%& modifier supports the following settings:
28364 .vitem &*control&~=&~allow_auth_unadvertised*&
28365 This modifier allows a client host to use the SMTP AUTH command even when it
28366 has not been advertised in response to EHLO. Furthermore, because there are
28367 apparently some really broken clients that do this, Exim will accept AUTH after
28368 HELO (rather than EHLO) when this control is set. It should be used only if you
28369 really need it, and you should limit its use to those broken clients that do
28370 not work without it. For example:
28372 warn hosts = 192.168.34.25
28373 control = allow_auth_unadvertised
28375 Normally, when an Exim server receives an AUTH command, it checks the name of
28376 the authentication mechanism that is given in the command to ensure that it
28377 matches an advertised mechanism. When this control is set, the check that a
28378 mechanism has been advertised is bypassed. Any configured mechanism can be used
28379 by the client. This control is permitted only in the connection and HELO ACLs.
28382 .vitem &*control&~=&~caseful_local_part*& &&&
28383 &*control&~=&~caselower_local_part*&
28384 .cindex "&ACL;" "case of local part in"
28385 .cindex "case of local parts"
28386 .vindex "&$local_part$&"
28387 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28388 (that is, during RCPT processing). By default, the contents of &$local_part$&
28389 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28390 any uppercase letters in the original local part are restored in &$local_part$&
28391 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28394 These controls affect only the current recipient. Moreover, they apply only to
28395 local part handling that takes place directly in the ACL (for example, as a key
28396 in lookups). If a test to verify the recipient is obeyed, the case-related
28397 handling of the local part during the verification is controlled by the router
28398 configuration (see the &%caseful_local_part%& generic router option).
28400 This facility could be used, for example, to add a spam score to local parts
28401 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28404 warn control = caseful_local_part
28405 set acl_m4 = ${eval:\
28407 ${if match{$local_part}{[A-Z]}{1}{0}}\
28409 control = caselower_local_part
28411 Notice that we put back the lower cased version afterwards, assuming that
28412 is what is wanted for subsequent tests.
28415 .vitem &*control&~=&~cutthrough_delivery*&
28416 .cindex "&ACL;" "cutthrough routing"
28417 .cindex "cutthrough" "requesting"
28418 This option requests delivery be attempted while the item is being received.
28420 The option is usable in the RCPT ACL.
28421 If enabled for a message received via smtp and routed to an smtp transport,
28423 and only one transport, interface, destination host and port combination
28424 is used for all recipients of the message,
28426 then the delivery connection is made while the receiving connection is open
28427 and data is copied from one to the other.
28429 An attempt to set this option for any recipient but the first
28430 for a mail will be quietly ignored.
28431 If a recipient-verify callout connection is subsequently
28432 requested in the same ACL it is held open and used for
28434 any subsequent recipients and the data,
28436 otherwise one is made after the initial RCPT ACL completes.
28438 Note that routers are used in verify mode,
28439 and cannot depend on content of received headers.
28440 Note also that headers cannot be
28441 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28442 Headers may be modified by routers (subject to the above) and transports.
28444 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28445 of outgoing messages is done, because it sends data to the ultimate destination
28446 before the entire message has been received from the source.
28448 It is not supported for messages received with the SMTP PRDR option in use.
28451 Should the ultimate destination system positively accept or reject the mail,
28452 a corresponding indication is given to the source system and nothing is queued.
28453 If there is a temporary error the item is queued for later delivery in the
28454 usual fashion. If the item is successfully delivered in cutthrough mode
28455 the delivery log lines are tagged with ">>" rather than "=>" and appear
28456 before the acceptance "<=" line.
28458 Delivery in this mode avoids the generation of a bounce mail to a
28460 sender when the destination system is doing content-scan based rejection.
28463 .vitem &*control&~=&~debug/*&<&'options'&>
28464 .cindex "&ACL;" "enabling debug logging"
28465 .cindex "debugging" "enabling from an ACL"
28466 This control turns on debug logging, almost as though Exim had been invoked
28467 with &`-d`&, with the output going to a new logfile, by default called
28468 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28469 may access any variables already defined. The logging may be adjusted with
28470 the &'opts'& option, which takes the same values as the &`-d`& command-line
28471 option. Some examples (which depend on variables that don't exist in all
28475 control = debug/tag=.$sender_host_address
28476 control = debug/opts=+expand+acl
28477 control = debug/tag=.$message_exim_id/opts=+expand
28481 .vitem &*control&~=&~dkim_disable_verify*&
28482 .cindex "disable DKIM verify"
28483 .cindex "DKIM" "disable verify"
28484 This control turns off DKIM verification processing entirely. For details on
28485 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
28488 .vitem &*control&~=&~dscp/*&<&'value'&>
28489 .cindex "&ACL;" "setting DSCP value"
28490 .cindex "DSCP" "inbound"
28491 This option causes the DSCP value associated with the socket for the inbound
28492 connection to be adjusted to a given value, given as one of a number of fixed
28493 strings or to numeric value.
28494 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
28495 Common values include &`throughput`&, &`mincost`&, and on newer systems
28496 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
28498 The outbound packets from Exim will be marked with this value in the header
28499 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
28500 that these values will have any effect, not be stripped by networking
28501 equipment, or do much of anything without cooperation with your Network
28502 Engineer and those of all network operators between the source and destination.
28505 .vitem &*control&~=&~enforce_sync*& &&&
28506 &*control&~=&~no_enforce_sync*&
28507 .cindex "SMTP" "synchronization checking"
28508 .cindex "synchronization checking in SMTP"
28509 These controls make it possible to be selective about when SMTP synchronization
28510 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
28511 state of the switch (it is true by default). See the description of this option
28512 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
28514 The effect of these two controls lasts for the remainder of the SMTP
28515 connection. They can appear in any ACL except the one for the non-SMTP
28516 messages. The most straightforward place to put them is in the ACL defined by
28517 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
28518 before the first synchronization check. The expected use is to turn off the
28519 synchronization checks for badly-behaved hosts that you nevertheless need to
28523 .vitem &*control&~=&~fakedefer/*&<&'message'&>
28524 .cindex "fake defer"
28525 .cindex "defer, fake"
28526 This control works in exactly the same way as &%fakereject%& (described below)
28527 except that it causes an SMTP 450 response after the message data instead of a
28528 550 response. You must take care when using &%fakedefer%& because it causes the
28529 messages to be duplicated when the sender retries. Therefore, you should not
28530 use &%fakedefer%& if the message is to be delivered normally.
28532 .vitem &*control&~=&~fakereject/*&<&'message'&>
28533 .cindex "fake rejection"
28534 .cindex "rejection, fake"
28535 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
28536 words, only when an SMTP message is being received. If Exim accepts the
28537 message, instead the final 250 response, a 550 rejection message is sent.
28538 However, Exim proceeds to deliver the message as normal. The control applies
28539 only to the current message, not to any subsequent ones that may be received in
28540 the same SMTP connection.
28542 The text for the 550 response is taken from the &%control%& modifier. If no
28543 message is supplied, the following is used:
28545 550-Your message has been rejected but is being
28546 550-kept for evaluation.
28547 550-If it was a legitimate message, it may still be
28548 550 delivered to the target recipient(s).
28550 This facility should be used with extreme caution.
28552 .vitem &*control&~=&~freeze*&
28553 .cindex "frozen messages" "forcing in ACL"
28554 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28555 other words, only when a message is being received. If the message is accepted,
28556 it is placed on Exim's queue and frozen. The control applies only to the
28557 current message, not to any subsequent ones that may be received in the same
28560 This modifier can optionally be followed by &`/no_tell`&. If the global option
28561 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
28562 is told about the freezing), provided all the &*control=freeze*& modifiers that
28563 are obeyed for the current message have the &`/no_tell`& option.
28565 .vitem &*control&~=&~no_delay_flush*&
28566 .cindex "SMTP" "output flushing, disabling for delay"
28567 Exim normally flushes SMTP output before implementing a delay in an ACL, to
28568 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28569 use. This control, as long as it is encountered before the &%delay%& modifier,
28570 disables such output flushing.
28572 .vitem &*control&~=&~no_callout_flush*&
28573 .cindex "SMTP" "output flushing, disabling for callout"
28574 Exim normally flushes SMTP output before performing a callout in an ACL, to
28575 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
28576 use. This control, as long as it is encountered before the &%verify%& condition
28577 that causes the callout, disables such output flushing.
28579 .vitem &*control&~=&~no_mbox_unspool*&
28580 This control is available when Exim is compiled with the content scanning
28581 extension. Content scanning may require a copy of the current message, or parts
28582 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
28583 or spam scanner. Normally, such copies are deleted when they are no longer
28584 needed. If this control is set, the copies are not deleted. The control applies
28585 only to the current message, not to any subsequent ones that may be received in
28586 the same SMTP connection. It is provided for debugging purposes and is unlikely
28587 to be useful in production.
28589 .vitem &*control&~=&~no_multiline_responses*&
28590 .cindex "multiline responses, suppressing"
28591 This control is permitted for any ACL except the one for non-SMTP messages.
28592 It seems that there are broken clients in use that cannot handle multiline
28593 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
28595 If this control is set, multiline SMTP responses from ACL rejections are
28596 suppressed. One way of doing this would have been to put out these responses as
28597 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
28598 (&"use multiline responses for more"& it says &-- ha!), and some of the
28599 responses might get close to that. So this facility, which is after all only a
28600 sop to broken clients, is implemented by doing two very easy things:
28603 Extra information that is normally output as part of a rejection caused by
28604 sender verification failure is omitted. Only the final line (typically &"sender
28605 verification failed"&) is sent.
28607 If a &%message%& modifier supplies a multiline response, only the first
28611 The setting of the switch can, of course, be made conditional on the
28612 calling host. Its effect lasts until the end of the SMTP connection.
28614 .vitem &*control&~=&~no_pipelining*&
28615 .cindex "PIPELINING" "suppressing advertising"
28616 This control turns off the advertising of the PIPELINING extension to SMTP in
28617 the current session. To be useful, it must be obeyed before Exim sends its
28618 response to an EHLO command. Therefore, it should normally appear in an ACL
28619 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
28620 &%pipelining_advertise_hosts%&.
28622 .vitem &*control&~=&~queue_only*&
28623 .oindex "&%queue_only%&"
28624 .cindex "queueing incoming messages"
28625 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
28626 other words, only when a message is being received. If the message is accepted,
28627 it is placed on Exim's queue and left there for delivery by a subsequent queue
28628 runner. No immediate delivery process is started. In other words, it has the
28629 effect as the &%queue_only%& global option. However, the control applies only
28630 to the current message, not to any subsequent ones that may be received in the
28631 same SMTP connection.
28633 .vitem &*control&~=&~submission/*&<&'options'&>
28634 .cindex "message" "submission"
28635 .cindex "submission mode"
28636 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
28637 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
28638 the current message is a submission from a local MUA. In this case, Exim
28639 operates in &"submission mode"&, and applies certain fixups to the message if
28640 necessary. For example, it adds a &'Date:'& header line if one is not present.
28641 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
28642 late (the message has already been created).
28644 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
28645 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
28646 submission mode; the available options for this control are described there.
28647 The control applies only to the current message, not to any subsequent ones
28648 that may be received in the same SMTP connection.
28650 .vitem &*control&~=&~suppress_local_fixups*&
28651 .cindex "submission fixups, suppressing"
28652 This control applies to locally submitted (non TCP/IP) messages, and is the
28653 complement of &`control = submission`&. It disables the fixups that are
28654 normally applied to locally-submitted messages. Specifically:
28657 Any &'Sender:'& header line is left alone (in this respect, it is a
28658 dynamic version of &%local_sender_retain%&).
28660 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
28662 There is no check that &'From:'& corresponds to the actual sender.
28665 This control may be useful when a remotely-originated message is accepted,
28666 passed to some scanning program, and then re-submitted for delivery. It can be
28667 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28668 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
28671 &*Note:*& This control applies only to the current message, not to any others
28672 that are being submitted at the same time using &%-bs%& or &%-bS%&.
28676 .section "Summary of message fixup control" "SECTsummesfix"
28677 All four possibilities for message fixups can be specified:
28680 Locally submitted, fixups applied: the default.
28682 Locally submitted, no fixups applied: use
28683 &`control = suppress_local_fixups`&.
28685 Remotely submitted, no fixups applied: the default.
28687 Remotely submitted, fixups applied: use &`control = submission`&.
28692 .section "Adding header lines in ACLs" "SECTaddheadacl"
28693 .cindex "header lines" "adding in an ACL"
28694 .cindex "header lines" "position of added lines"
28695 .cindex "&%add_header%& ACL modifier"
28696 The &%add_header%& modifier can be used to add one or more extra header lines
28697 to an incoming message, as in this example:
28699 warn dnslists = sbl.spamhaus.org : \
28700 dialup.mail-abuse.org
28701 add_header = X-blacklisted-at: $dnslist_domain
28703 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28704 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28705 receiving a message). The message must ultimately be accepted for
28706 &%add_header%& to have any significant effect. You can use &%add_header%& with
28707 any ACL verb, including &%deny%& (though this is potentially useful only in a
28710 Headers will not be added to the message if the modifier is used in
28711 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28713 Leading and trailing newlines are removed from
28714 the data for the &%add_header%& modifier; if it then
28715 contains one or more newlines that
28716 are not followed by a space or a tab, it is assumed to contain multiple header
28717 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
28718 front of any line that is not a valid header line.
28720 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28721 They are added to the message before processing the DATA and MIME ACLs.
28722 However, if an identical header line is requested more than once, only one copy
28723 is actually added to the message. Further header lines may be accumulated
28724 during the DATA and MIME ACLs, after which they are added to the message, again
28725 with duplicates suppressed. Thus, it is possible to add two identical header
28726 lines to an SMTP message, but only if one is added before DATA and one after.
28727 In the case of non-SMTP messages, new headers are accumulated during the
28728 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
28729 message is rejected after DATA or by the non-SMTP ACL, all added header lines
28730 are included in the entry that is written to the reject log.
28732 .cindex "header lines" "added; visibility of"
28733 Header lines are not visible in string expansions
28735 until they are added to the
28736 message. It follows that header lines defined in the MAIL, RCPT, and predata
28737 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
28738 header lines that are added by the DATA or MIME ACLs are not visible in those
28739 ACLs. Because of this restriction, you cannot use header lines as a way of
28740 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
28741 this, you can use ACL variables, as described in section
28742 &<<SECTaclvariables>>&.
28744 The list of headers yet to be added is given by the &%$headers_added%& variable.
28746 The &%add_header%& modifier acts immediately as it is encountered during the
28747 processing of an ACL. Notice the difference between these two cases:
28749 &`accept add_header = ADDED: some text`&
28750 &` `&<&'some condition'&>
28752 &`accept `&<&'some condition'&>
28753 &` add_header = ADDED: some text`&
28755 In the first case, the header line is always added, whether or not the
28756 condition is true. In the second case, the header line is added only if the
28757 condition is true. Multiple occurrences of &%add_header%& may occur in the same
28758 ACL statement. All those that are encountered before a condition fails are
28761 .cindex "&%warn%& ACL verb"
28762 For compatibility with previous versions of Exim, a &%message%& modifier for a
28763 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
28764 effect only if all the conditions are true, even if it appears before some of
28765 them. Furthermore, only the last occurrence of &%message%& is honoured. This
28766 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
28767 are present on a &%warn%& verb, both are processed according to their
28770 By default, new header lines are added to a message at the end of the existing
28771 header lines. However, you can specify that any particular header line should
28772 be added right at the start (before all the &'Received:'& lines), immediately
28773 after the first block of &'Received:'& lines, or immediately before any line
28774 that is not a &'Received:'& or &'Resent-something:'& header.
28776 This is done by specifying &":at_start:"&, &":after_received:"&, or
28777 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
28778 header line, respectively. (Header text cannot start with a colon, as there has
28779 to be a header name first.) For example:
28781 warn add_header = \
28782 :after_received:X-My-Header: something or other...
28784 If more than one header line is supplied in a single &%add_header%& modifier,
28785 each one is treated independently and can therefore be placed differently. If
28786 you add more than one line at the start, or after the Received: block, they end
28787 up in reverse order.
28789 &*Warning*&: This facility currently applies only to header lines that are
28790 added in an ACL. It does NOT work for header lines that are added in a
28791 system filter or in a router or transport.
28795 .section "Removing header lines in ACLs" "SECTremoveheadacl"
28796 .cindex "header lines" "removing in an ACL"
28797 .cindex "header lines" "position of removed lines"
28798 .cindex "&%remove_header%& ACL modifier"
28799 The &%remove_header%& modifier can be used to remove one or more header lines
28800 from an incoming message, as in this example:
28802 warn message = Remove internal headers
28803 remove_header = x-route-mail1 : x-route-mail2
28805 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
28806 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
28807 receiving a message). The message must ultimately be accepted for
28808 &%remove_header%& to have any significant effect. You can use &%remove_header%&
28809 with any ACL verb, including &%deny%&, though this is really not useful for
28810 any verb that doesn't result in a delivered message.
28812 Headers will not be removed to the message if the modifier is used in
28813 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
28815 More than one header can be removed at the same time by using a colon separated
28816 list of header names. The header matching is case insensitive. Wildcards are
28817 not permitted, nor is list expansion performed, so you cannot use hostlists to
28818 create a list of headers, however both connection and message variable expansion
28819 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
28821 warn hosts = +internal_hosts
28822 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
28823 warn message = Remove internal headers
28824 remove_header = $acl_c_ihdrs
28826 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
28827 They are removed from the message before processing the DATA and MIME ACLs.
28828 There is no harm in attempting to remove the same header twice nor is removing
28829 a non-existent header. Further header lines to be removed may be accumulated
28830 during the DATA and MIME ACLs, after which they are removed from the message,
28831 if present. In the case of non-SMTP messages, headers to be removed are
28832 accumulated during the non-SMTP ACLs, and are removed from the message after
28833 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
28834 ACL, there really is no effect because there is no logging of what headers
28835 would have been removed.
28837 .cindex "header lines" "removed; visibility of"
28838 Header lines are not visible in string expansions until the DATA phase when it
28839 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
28840 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
28841 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
28842 this restriction, you cannot use header lines as a way of controlling data
28843 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
28844 you should instead use ACL variables, as described in section
28845 &<<SECTaclvariables>>&.
28847 The &%remove_header%& modifier acts immediately as it is encountered during the
28848 processing of an ACL. Notice the difference between these two cases:
28850 &`accept remove_header = X-Internal`&
28851 &` `&<&'some condition'&>
28853 &`accept `&<&'some condition'&>
28854 &` remove_header = X-Internal`&
28856 In the first case, the header line is always removed, whether or not the
28857 condition is true. In the second case, the header line is removed only if the
28858 condition is true. Multiple occurrences of &%remove_header%& may occur in the
28859 same ACL statement. All those that are encountered before a condition fails
28862 &*Warning*&: This facility currently applies only to header lines that are
28863 present during ACL processing. It does NOT remove header lines that are added
28864 in a system filter or in a router or transport.
28869 .section "ACL conditions" "SECTaclconditions"
28870 .cindex "&ACL;" "conditions; list of"
28871 Some of the conditions listed in this section are available only when Exim is
28872 compiled with the content-scanning extension. They are included here briefly
28873 for completeness. More detailed descriptions can be found in the discussion on
28874 content scanning in chapter &<<CHAPexiscan>>&.
28876 Not all conditions are relevant in all circumstances. For example, testing
28877 senders and recipients does not make sense in an ACL that is being run as the
28878 result of the arrival of an ETRN command, and checks on message headers can be
28879 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
28880 can use the same condition (with different parameters) more than once in the
28881 same ACL statement. This provides a way of specifying an &"and"& conjunction.
28882 The conditions are as follows:
28886 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
28887 .cindex "&ACL;" "nested"
28888 .cindex "&ACL;" "indirect"
28889 .cindex "&ACL;" "arguments"
28890 .cindex "&%acl%& ACL condition"
28891 The possible values of the argument are the same as for the
28892 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
28893 &"accept"& the condition is true; if it returns &"deny"& the condition is
28894 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
28895 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
28896 condition false. This means that further processing of the &%warn%& verb
28897 ceases, but processing of the ACL continues.
28899 If the argument is a named ACL, up to nine space-separated optional values
28900 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
28901 and $acl_narg is set to the count of values.
28902 Previous values of these variables are restored after the call returns.
28903 The name and values are expanded separately.
28904 Note that spaces in complex expansions which are used as arguments
28905 will act as argument separators.
28907 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
28908 the connection is dropped. If it returns &"discard"&, the verb must be
28909 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
28910 conditions are tested.
28912 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
28913 loops. This condition allows you to use different ACLs in different
28914 circumstances. For example, different ACLs can be used to handle RCPT commands
28915 for different local users or different local domains.
28917 .vitem &*authenticated&~=&~*&<&'string&~list'&>
28918 .cindex "&%authenticated%& ACL condition"
28919 .cindex "authentication" "ACL checking"
28920 .cindex "&ACL;" "testing for authentication"
28921 If the SMTP connection is not authenticated, the condition is false. Otherwise,
28922 the name of the authenticator is tested against the list. To test for
28923 authentication by any authenticator, you can set
28928 .vitem &*condition&~=&~*&<&'string'&>
28929 .cindex "&%condition%& ACL condition"
28930 .cindex "customizing" "ACL condition"
28931 .cindex "&ACL;" "customized test"
28932 .cindex "&ACL;" "testing, customized"
28933 This feature allows you to make up custom conditions. If the result of
28934 expanding the string is an empty string, the number zero, or one of the strings
28935 &"no"& or &"false"&, the condition is false. If the result is any non-zero
28936 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
28937 any other value, some error is assumed to have occurred, and the ACL returns
28938 &"defer"&. However, if the expansion is forced to fail, the condition is
28939 ignored. The effect is to treat it as true, whether it is positive or
28942 .vitem &*decode&~=&~*&<&'location'&>
28943 .cindex "&%decode%& ACL condition"
28944 This condition is available only when Exim is compiled with the
28945 content-scanning extension, and it is allowed only in the ACL defined by
28946 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
28947 If all goes well, the condition is true. It is false only if there are
28948 problems such as a syntax error or a memory shortage. For more details, see
28949 chapter &<<CHAPexiscan>>&.
28951 .vitem &*demime&~=&~*&<&'extension&~list'&>
28952 .cindex "&%demime%& ACL condition"
28953 This condition is available only when Exim is compiled with the
28954 content-scanning extension. Its use is described in section
28955 &<<SECTdemimecond>>&.
28957 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
28958 .cindex "&%dnslists%& ACL condition"
28959 .cindex "DNS list" "in ACL"
28960 .cindex "black list (DNS)"
28961 .cindex "&ACL;" "testing a DNS list"
28962 This condition checks for entries in DNS black lists. These are also known as
28963 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
28964 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
28965 different variants of this condition to describe briefly here. See sections
28966 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
28968 .vitem &*domains&~=&~*&<&'domain&~list'&>
28969 .cindex "&%domains%& ACL condition"
28970 .cindex "domain" "ACL checking"
28971 .cindex "&ACL;" "testing a recipient domain"
28972 .vindex "&$domain_data$&"
28973 This condition is relevant only after a RCPT command. It checks that the domain
28974 of the recipient address is in the domain list. If percent-hack processing is
28975 enabled, it is done before this test is done. If the check succeeds with a
28976 lookup, the result of the lookup is placed in &$domain_data$& until the next
28979 &*Note carefully*& (because many people seem to fall foul of this): you cannot
28980 use &%domains%& in a DATA ACL.
28983 .vitem &*encrypted&~=&~*&<&'string&~list'&>
28984 .cindex "&%encrypted%& ACL condition"
28985 .cindex "encryption" "checking in an ACL"
28986 .cindex "&ACL;" "testing for encryption"
28987 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
28988 name of the cipher suite in use is tested against the list. To test for
28989 encryption without testing for any specific cipher suite(s), set
28995 .vitem &*hosts&~=&~*&<&'host&~list'&>
28996 .cindex "&%hosts%& ACL condition"
28997 .cindex "host" "ACL checking"
28998 .cindex "&ACL;" "testing the client host"
28999 This condition tests that the calling host matches the host list. If you have
29000 name lookups or wildcarded host names and IP addresses in the same host list,
29001 you should normally put the IP addresses first. For example, you could have:
29003 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
29005 The lookup in this example uses the host name for its key. This is implied by
29006 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
29007 and it wouldn't matter which way round you had these two items.)
29009 The reason for the problem with host names lies in the left-to-right way that
29010 Exim processes lists. It can test IP addresses without doing any DNS lookups,
29011 but when it reaches an item that requires a host name, it fails if it cannot
29012 find a host name to compare with the pattern. If the above list is given in the
29013 opposite order, the &%accept%& statement fails for a host whose name cannot be
29014 found, even if its IP address is 10.9.8.7.
29016 If you really do want to do the name check first, and still recognize the IP
29017 address even if the name lookup fails, you can rewrite the ACL like this:
29019 accept hosts = dbm;/etc/friendly/hosts
29020 accept hosts = 10.9.8.7
29022 The default action on failing to find the host name is to assume that the host
29023 is not in the list, so the first &%accept%& statement fails. The second
29024 statement can then check the IP address.
29026 .vindex "&$host_data$&"
29027 If a &%hosts%& condition is satisfied by means of a lookup, the result
29028 of the lookup is made available in the &$host_data$& variable. This
29029 allows you, for example, to set up a statement like this:
29031 deny hosts = net-lsearch;/some/file
29032 message = $host_data
29034 which gives a custom error message for each denied host.
29036 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
29037 .cindex "&%local_parts%& ACL condition"
29038 .cindex "local part" "ACL checking"
29039 .cindex "&ACL;" "testing a local part"
29040 .vindex "&$local_part_data$&"
29041 This condition is relevant only after a RCPT command. It checks that the local
29042 part of the recipient address is in the list. If percent-hack processing is
29043 enabled, it is done before this test. If the check succeeds with a lookup, the
29044 result of the lookup is placed in &$local_part_data$&, which remains set until
29045 the next &%local_parts%& test.
29047 .vitem &*malware&~=&~*&<&'option'&>
29048 .cindex "&%malware%& ACL condition"
29049 .cindex "&ACL;" "virus scanning"
29050 .cindex "&ACL;" "scanning for viruses"
29051 This condition is available only when Exim is compiled with the
29052 content-scanning extension. It causes the incoming message to be scanned for
29053 viruses. For details, see chapter &<<CHAPexiscan>>&.
29055 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29056 .cindex "&%mime_regex%& ACL condition"
29057 .cindex "&ACL;" "testing by regex matching"
29058 This condition is available only when Exim is compiled with the
29059 content-scanning extension, and it is allowed only in the ACL defined by
29060 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29061 with any of the regular expressions. For details, see chapter
29064 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29065 .cindex "rate limiting"
29066 This condition can be used to limit the rate at which a user or host submits
29067 messages. Details are given in section &<<SECTratelimiting>>&.
29069 .vitem &*recipients&~=&~*&<&'address&~list'&>
29070 .cindex "&%recipients%& ACL condition"
29071 .cindex "recipient" "ACL checking"
29072 .cindex "&ACL;" "testing a recipient"
29073 This condition is relevant only after a RCPT command. It checks the entire
29074 recipient address against a list of recipients.
29076 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29077 .cindex "&%regex%& ACL condition"
29078 .cindex "&ACL;" "testing by regex matching"
29079 This condition is available only when Exim is compiled with the
29080 content-scanning extension, and is available only in the DATA, MIME, and
29081 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29082 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29084 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29085 .cindex "&%sender_domains%& ACL condition"
29086 .cindex "sender" "ACL checking"
29087 .cindex "&ACL;" "testing a sender domain"
29088 .vindex "&$domain$&"
29089 .vindex "&$sender_address_domain$&"
29090 This condition tests the domain of the sender of the message against the given
29091 domain list. &*Note*&: The domain of the sender address is in
29092 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29093 of this condition. This is an exception to the general rule for testing domain
29094 lists. It is done this way so that, if this condition is used in an ACL for a
29095 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29096 influence the sender checking.
29098 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29099 relaying, because sender addresses are easily, and commonly, forged.
29101 .vitem &*senders&~=&~*&<&'address&~list'&>
29102 .cindex "&%senders%& ACL condition"
29103 .cindex "sender" "ACL checking"
29104 .cindex "&ACL;" "testing a sender"
29105 This condition tests the sender of the message against the given list. To test
29106 for a bounce message, which has an empty sender, set
29110 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29111 relaying, because sender addresses are easily, and commonly, forged.
29113 .vitem &*spam&~=&~*&<&'username'&>
29114 .cindex "&%spam%& ACL condition"
29115 .cindex "&ACL;" "scanning for spam"
29116 This condition is available only when Exim is compiled with the
29117 content-scanning extension. It causes the incoming message to be scanned by
29118 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29120 .vitem &*verify&~=&~certificate*&
29121 .cindex "&%verify%& ACL condition"
29122 .cindex "TLS" "client certificate verification"
29123 .cindex "certificate" "verification of client"
29124 .cindex "&ACL;" "certificate verification"
29125 .cindex "&ACL;" "testing a TLS certificate"
29126 This condition is true in an SMTP session if the session is encrypted, and a
29127 certificate was received from the client, and the certificate was verified. The
29128 server requests a certificate only if the client matches &%tls_verify_hosts%&
29129 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29131 .vitem &*verify&~=&~csa*&
29132 .cindex "CSA verification"
29133 This condition checks whether the sending host (the client) is authorized to
29134 send email. Details of how this works are given in section
29135 &<<SECTverifyCSA>>&.
29137 .vitem &*verify&~=&~header_names_ascii*&
29138 .cindex "&%verify%& ACL condition"
29139 .cindex "&ACL;" "verifying header names only ASCII"
29140 .cindex "header lines" "verifying header names only ASCII"
29141 .cindex "verifying" "header names only ASCII"
29142 This condition is relevant only in an ACL that is run after a message has been
29143 received, that is, in an ACL specified by &%acl_smtp_data%& or
29144 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29145 there are no non-ASCII characters, also excluding control characters. The
29146 allowable characters are decimal ASCII values 33 through 126.
29148 Exim itself will handle headers with non-ASCII characters, but it can cause
29149 problems for downstream applications, so this option will allow their
29150 detection and rejection in the DATA ACL's.
29152 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29153 .cindex "&%verify%& ACL condition"
29154 .cindex "&ACL;" "verifying sender in the header"
29155 .cindex "header lines" "verifying the sender in"
29156 .cindex "sender" "verifying in header"
29157 .cindex "verifying" "sender in header"
29158 This condition is relevant only in an ACL that is run after a message has been
29159 received, that is, in an ACL specified by &%acl_smtp_data%& or
29160 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29161 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29162 is loosely thought of as a &"sender"& address (hence the name of the test).
29163 However, an address that appears in one of these headers need not be an address
29164 that accepts bounce messages; only sender addresses in envelopes are required
29165 to accept bounces. Therefore, if you use the callout option on this check, you
29166 might want to arrange for a non-empty address in the MAIL command.
29168 Details of address verification and the options are given later, starting at
29169 section &<<SECTaddressverification>>& (callouts are described in section
29170 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29171 condition to restrict it to bounce messages only:
29174 message = A valid sender header is required for bounces
29175 !verify = header_sender
29178 .vitem &*verify&~=&~header_syntax*&
29179 .cindex "&%verify%& ACL condition"
29180 .cindex "&ACL;" "verifying header syntax"
29181 .cindex "header lines" "verifying syntax"
29182 .cindex "verifying" "header syntax"
29183 This condition is relevant only in an ACL that is run after a message has been
29184 received, that is, in an ACL specified by &%acl_smtp_data%& or
29185 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29186 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29187 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
29188 permitted only in locally generated messages and from hosts that match
29189 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29192 Note that this condition is a syntax check only. However, a common spamming
29193 ploy used to be to send syntactically invalid headers such as
29197 and this condition can be used to reject such messages, though they are not as
29198 common as they used to be.
29200 .vitem &*verify&~=&~helo*&
29201 .cindex "&%verify%& ACL condition"
29202 .cindex "&ACL;" "verifying HELO/EHLO"
29203 .cindex "HELO" "verifying"
29204 .cindex "EHLO" "verifying"
29205 .cindex "verifying" "EHLO"
29206 .cindex "verifying" "HELO"
29207 This condition is true if a HELO or EHLO command has been received from the
29208 client host, and its contents have been verified. If there has been no previous
29209 attempt to verify the HELO/EHLO contents, it is carried out when this
29210 condition is encountered. See the description of the &%helo_verify_hosts%& and
29211 &%helo_try_verify_hosts%& options for details of how to request verification
29212 independently of this condition.
29214 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29215 option), this condition is always true.
29218 .vitem &*verify&~=&~not_blind*&
29219 .cindex "verifying" "not blind"
29220 .cindex "bcc recipients, verifying none"
29221 This condition checks that there are no blind (bcc) recipients in the message.
29222 Every envelope recipient must appear either in a &'To:'& header line or in a
29223 &'Cc:'& header line for this condition to be true. Local parts are checked
29224 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29225 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29226 used only in a DATA or non-SMTP ACL.
29228 There are, of course, many legitimate messages that make use of blind (bcc)
29229 recipients. This check should not be used on its own for blocking messages.
29232 .vitem &*verify&~=&~recipient/*&<&'options'&>
29233 .cindex "&%verify%& ACL condition"
29234 .cindex "&ACL;" "verifying recipient"
29235 .cindex "recipient" "verifying"
29236 .cindex "verifying" "recipient"
29237 .vindex "&$address_data$&"
29238 This condition is relevant only after a RCPT command. It verifies the current
29239 recipient. Details of address verification are given later, starting at section
29240 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29241 of &$address_data$& is the last value that was set while routing the address.
29242 This applies even if the verification fails. When an address that is being
29243 verified is redirected to a single address, verification continues with the new
29244 address, and in that case, the subsequent value of &$address_data$& is the
29245 value for the child address.
29247 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29248 .cindex "&%verify%& ACL condition"
29249 .cindex "&ACL;" "verifying host reverse lookup"
29250 .cindex "host" "verifying reverse lookup"
29251 This condition ensures that a verified host name has been looked up from the IP
29252 address of the client host. (This may have happened already if the host name
29253 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29254 Verification ensures that the host name obtained from a reverse DNS lookup, or
29255 one of its aliases, does, when it is itself looked up in the DNS, yield the
29256 original IP address.
29259 There is one possible option, &`defer_ok`&. If this is present and a
29260 DNS operation returns a temporary error, the verify condition succeeds.
29263 If this condition is used for a locally generated message (that is, when there
29264 is no client host involved), it always succeeds.
29266 .vitem &*verify&~=&~sender/*&<&'options'&>
29267 .cindex "&%verify%& ACL condition"
29268 .cindex "&ACL;" "verifying sender"
29269 .cindex "sender" "verifying"
29270 .cindex "verifying" "sender"
29271 This condition is relevant only after a MAIL or RCPT command, or after a
29272 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29273 the message's sender is empty (that is, this is a bounce message), the
29274 condition is true. Otherwise, the sender address is verified.
29276 .vindex "&$address_data$&"
29277 .vindex "&$sender_address_data$&"
29278 If there is data in the &$address_data$& variable at the end of routing, its
29279 value is placed in &$sender_address_data$& at the end of verification. This
29280 value can be used in subsequent conditions and modifiers in the same ACL
29281 statement. It does not persist after the end of the current statement. If you
29282 want to preserve the value for longer, you can save it in an ACL variable.
29284 Details of verification are given later, starting at section
29285 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29286 to avoid doing it more than once per message.
29288 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29289 .cindex "&%verify%& ACL condition"
29290 This is a variation of the previous option, in which a modified address is
29291 verified as a sender.
29296 .section "Using DNS lists" "SECTmorednslists"
29297 .cindex "DNS list" "in ACL"
29298 .cindex "black list (DNS)"
29299 .cindex "&ACL;" "testing a DNS list"
29300 In its simplest form, the &%dnslists%& condition tests whether the calling host
29301 is on at least one of a number of DNS lists by looking up the inverted IP
29302 address in one or more DNS domains. (Note that DNS list domains are not mail
29303 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29304 special options instead.) For example, if the calling host's IP
29305 address is 192.168.62.43, and the ACL statement is
29307 deny dnslists = blackholes.mail-abuse.org : \
29308 dialups.mail-abuse.org
29310 the following records are looked up:
29312 43.62.168.192.blackholes.mail-abuse.org
29313 43.62.168.192.dialups.mail-abuse.org
29315 As soon as Exim finds an existing DNS record, processing of the list stops.
29316 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29317 to test that a host is on more than one list (an &"and"& conjunction), you can
29318 use two separate conditions:
29320 deny dnslists = blackholes.mail-abuse.org
29321 dnslists = dialups.mail-abuse.org
29323 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29324 behaves as if the host does not match the list item, that is, as if the DNS
29325 record does not exist. If there are further items in the DNS list, they are
29328 This is usually the required action when &%dnslists%& is used with &%deny%&
29329 (which is the most common usage), because it prevents a DNS failure from
29330 blocking mail. However, you can change this behaviour by putting one of the
29331 following special items in the list:
29333 &`+include_unknown `& behave as if the item is on the list
29334 &`+exclude_unknown `& behave as if the item is not on the list (default)
29335 &`+defer_unknown `& give a temporary error
29337 .cindex "&`+include_unknown`&"
29338 .cindex "&`+exclude_unknown`&"
29339 .cindex "&`+defer_unknown`&"
29340 Each of these applies to any subsequent items on the list. For example:
29342 deny dnslists = +defer_unknown : foo.bar.example
29344 Testing the list of domains stops as soon as a match is found. If you want to
29345 warn for one list and block for another, you can use two different statements:
29347 deny dnslists = blackholes.mail-abuse.org
29348 warn message = X-Warn: sending host is on dialups list
29349 dnslists = dialups.mail-abuse.org
29351 DNS list lookups are cached by Exim for the duration of the SMTP session,
29352 so a lookup based on the IP address is done at most once for any incoming
29353 connection. Exim does not share information between multiple incoming
29354 connections (but your local name server cache should be active).
29358 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29359 .cindex "DNS list" "keyed by explicit IP address"
29360 By default, the IP address that is used in a DNS list lookup is the IP address
29361 of the calling host. However, you can specify another IP address by listing it
29362 after the domain name, introduced by a slash. For example:
29364 deny dnslists = black.list.tld/192.168.1.2
29366 This feature is not very helpful with explicit IP addresses; it is intended for
29367 use with IP addresses that are looked up, for example, the IP addresses of the
29368 MX hosts or nameservers of an email sender address. For an example, see section
29369 &<<SECTmulkeyfor>>& below.
29374 .section "DNS lists keyed on domain names" "SECID202"
29375 .cindex "DNS list" "keyed by domain name"
29376 There are some lists that are keyed on domain names rather than inverted IP
29377 addresses (see for example the &'domain based zones'& link at
29378 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29379 with these lists. You can change the name that is looked up in a DNS list by
29380 listing it after the domain name, introduced by a slash. For example,
29382 deny message = Sender's domain is listed at $dnslist_domain
29383 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29385 This particular example is useful only in ACLs that are obeyed after the
29386 RCPT or DATA commands, when a sender address is available. If (for
29387 example) the message's sender is &'user@tld.example'& the name that is looked
29388 up by this example is
29390 tld.example.dsn.rfc-ignorant.org
29392 A single &%dnslists%& condition can contain entries for both names and IP
29393 addresses. For example:
29395 deny dnslists = sbl.spamhaus.org : \
29396 dsn.rfc-ignorant.org/$sender_address_domain
29398 The first item checks the sending host's IP address; the second checks a domain
29399 name. The whole condition is true if either of the DNS lookups succeeds.
29404 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29405 .cindex "DNS list" "multiple keys for"
29406 The syntax described above for looking up explicitly-defined values (either
29407 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29408 name for the DNS list, what follows the slash can in fact be a list of items.
29409 As with all lists in Exim, the default separator is a colon. However, because
29410 this is a sublist within the list of DNS blacklist domains, it is necessary
29411 either to double the separators like this:
29413 dnslists = black.list.tld/name.1::name.2
29415 or to change the separator character, like this:
29417 dnslists = black.list.tld/<;name.1;name.2
29419 If an item in the list is an IP address, it is inverted before the DNS
29420 blacklist domain is appended. If it is not an IP address, no inversion
29421 occurs. Consider this condition:
29423 dnslists = black.list.tld/<;192.168.1.2;a.domain
29425 The DNS lookups that occur are:
29427 2.1.168.192.black.list.tld
29428 a.domain.black.list.tld
29430 Once a DNS record has been found (that matches a specific IP return
29431 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29432 are done. If there is a temporary DNS error, the rest of the sublist of domains
29433 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29434 only if no other DNS lookup in this sublist succeeds. In other words, a
29435 successful lookup for any of the items in the sublist overrides a temporary
29436 error for a previous item.
29438 The ability to supply a list of items after the slash is in some sense just a
29439 syntactic convenience. These two examples have the same effect:
29441 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29442 dnslists = black.list.tld/a.domain::b.domain
29444 However, when the data for the list is obtained from a lookup, the second form
29445 is usually much more convenient. Consider this example:
29447 deny message = The mail servers for the domain \
29448 $sender_address_domain \
29449 are listed at $dnslist_domain ($dnslist_value); \
29451 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29452 ${lookup dnsdb {>|mxh=\
29453 $sender_address_domain} }} }
29455 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29456 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29457 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29458 of expanding the condition might be something like this:
29460 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
29462 Thus, this example checks whether or not the IP addresses of the sender
29463 domain's mail servers are on the Spamhaus black list.
29465 The key that was used for a successful DNS list lookup is put into the variable
29466 &$dnslist_matched$& (see section &<<SECID204>>&).
29471 .section "Data returned by DNS lists" "SECID203"
29472 .cindex "DNS list" "data returned from"
29473 DNS lists are constructed using address records in the DNS. The original RBL
29474 just used the address 127.0.0.1 on the right hand side of each record, but the
29475 RBL+ list and some other lists use a number of values with different meanings.
29476 The values used on the RBL+ list are:
29480 127.1.0.3 DUL and RBL
29482 127.1.0.5 RSS and RBL
29483 127.1.0.6 RSS and DUL
29484 127.1.0.7 RSS and DUL and RBL
29486 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
29487 different values. Some DNS lists may return more than one address record;
29488 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
29491 .section "Variables set from DNS lists" "SECID204"
29492 .cindex "expansion" "variables, set from DNS list"
29493 .cindex "DNS list" "variables set from"
29494 .vindex "&$dnslist_domain$&"
29495 .vindex "&$dnslist_matched$&"
29496 .vindex "&$dnslist_text$&"
29497 .vindex "&$dnslist_value$&"
29498 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
29499 the name of the overall domain that matched (for example,
29500 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
29501 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
29502 the DNS record. When the key is an IP address, it is not reversed in
29503 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
29504 cases, for example:
29506 deny dnslists = spamhaus.example
29508 the key is also available in another variable (in this case,
29509 &$sender_host_address$&). In more complicated cases, however, this is not true.
29510 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
29511 might generate a dnslists lookup like this:
29513 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
29515 If this condition succeeds, the value in &$dnslist_matched$& might be
29516 &`192.168.6.7`& (for example).
29518 If more than one address record is returned by the DNS lookup, all the IP
29519 addresses are included in &$dnslist_value$&, separated by commas and spaces.
29520 The variable &$dnslist_text$& contains the contents of any associated TXT
29521 record. For lists such as RBL+ the TXT record for a merged entry is often not
29522 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
29525 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
29526 &-- although these appear before the condition in the ACL, they are not
29527 expanded until after it has failed. For example:
29529 deny hosts = !+local_networks
29530 message = $sender_host_address is listed \
29532 dnslists = rbl-plus.mail-abuse.example
29537 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
29538 .cindex "DNS list" "matching specific returned data"
29539 You can add an equals sign and an IP address after a &%dnslists%& domain name
29540 in order to restrict its action to DNS records with a matching right hand side.
29543 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
29545 rejects only those hosts that yield 127.0.0.2. Without this additional data,
29546 any address record is considered to be a match. For the moment, we assume
29547 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
29548 describes how multiple records are handled.
29550 More than one IP address may be given for checking, using a comma as a
29551 separator. These are alternatives &-- if any one of them matches, the
29552 &%dnslists%& condition is true. For example:
29554 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29556 If you want to specify a constraining address list and also specify names or IP
29557 addresses to be looked up, the constraining address list must be specified
29558 first. For example:
29560 deny dnslists = dsn.rfc-ignorant.org\
29561 =127.0.0.2/$sender_address_domain
29564 If the character &`&&`& is used instead of &`=`&, the comparison for each
29565 listed IP address is done by a bitwise &"and"& instead of by an equality test.
29566 In other words, the listed addresses are used as bit masks. The comparison is
29567 true if all the bits in the mask are present in the address that is being
29568 tested. For example:
29570 dnslists = a.b.c&0.0.0.3
29572 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
29573 want to test whether one bit or another bit is present (as opposed to both
29574 being present), you must use multiple values. For example:
29576 dnslists = a.b.c&0.0.0.1,0.0.0.2
29578 matches if the final component of the address is an odd number or two times
29583 .section "Negated DNS matching conditions" "SECID205"
29584 You can supply a negative list of IP addresses as part of a &%dnslists%&
29587 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
29589 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29590 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
29592 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
29594 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
29595 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
29596 words, the result of the test is inverted if an exclamation mark appears before
29597 the &`=`& (or the &`&&`&) sign.
29599 &*Note*&: This kind of negation is not the same as negation in a domain,
29600 host, or address list (which is why the syntax is different).
29602 If you are using just one list, the negation syntax does not gain you much. The
29603 previous example is precisely equivalent to
29605 deny dnslists = a.b.c
29606 !dnslists = a.b.c=127.0.0.2,127.0.0.3
29608 However, if you are using multiple lists, the negation syntax is clearer.
29609 Consider this example:
29611 deny dnslists = sbl.spamhaus.org : \
29613 dnsbl.njabl.org!=127.0.0.3 : \
29616 Using only positive lists, this would have to be:
29618 deny dnslists = sbl.spamhaus.org : \
29620 deny dnslists = dnsbl.njabl.org
29621 !dnslists = dnsbl.njabl.org=127.0.0.3
29622 deny dnslists = relays.ordb.org
29624 which is less clear, and harder to maintain.
29629 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
29630 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
29631 thereby providing more than one IP address. When an item in a &%dnslists%& list
29632 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
29633 the match to specific results from the DNS lookup, there are two ways in which
29634 the checking can be handled. For example, consider the condition:
29636 dnslists = a.b.c=127.0.0.1
29638 What happens if the DNS lookup for the incoming IP address yields both
29639 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
29640 condition true because at least one given value was found, or is it false
29641 because at least one of the found values was not listed? And how does this
29642 affect negated conditions? Both possibilities are provided for with the help of
29643 additional separators &`==`& and &`=&&`&.
29646 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
29647 IP addresses matches one of the listed addresses. For the example above, the
29648 condition is true because 127.0.0.1 matches.
29650 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
29651 looked up IP addresses matches one of the listed addresses. If the condition is
29654 dnslists = a.b.c==127.0.0.1
29656 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29657 false because 127.0.0.2 is not listed. You would need to have:
29659 dnslists = a.b.c==127.0.0.1,127.0.0.2
29661 for the condition to be true.
29664 When &`!`& is used to negate IP address matching, it inverts the result, giving
29665 the precise opposite of the behaviour above. Thus:
29667 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
29668 addresses matches one of the listed addresses. Consider:
29670 dnslists = a.b.c!&0.0.0.1
29672 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29673 false because 127.0.0.1 matches.
29675 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
29676 looked up IP address that does not match. Consider:
29678 dnslists = a.b.c!=&0.0.0.1
29680 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
29681 true, because 127.0.0.2 does not match. You would need to have:
29683 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
29685 for the condition to be false.
29687 When the DNS lookup yields only a single IP address, there is no difference
29688 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
29693 .section "Detailed information from merged DNS lists" "SECTmordetinf"
29694 .cindex "DNS list" "information from merged"
29695 When the facility for restricting the matching IP values in a DNS list is used,
29696 the text from the TXT record that is set in &$dnslist_text$& may not reflect
29697 the true reason for rejection. This happens when lists are merged and the IP
29698 address in the A record is used to distinguish them; unfortunately there is
29699 only one TXT record. One way round this is not to use merged lists, but that
29700 can be inefficient because it requires multiple DNS lookups where one would do
29701 in the vast majority of cases when the host of interest is not on any of the
29704 A less inefficient way of solving this problem is available. If
29705 two domain names, comma-separated, are given, the second is used first to
29706 do an initial check, making use of any IP value restrictions that are set.
29707 If there is a match, the first domain is used, without any IP value
29708 restrictions, to get the TXT record. As a byproduct of this, there is also
29709 a check that the IP being tested is indeed on the first list. The first
29710 domain is the one that is put in &$dnslist_domain$&. For example:
29713 rejected because $sender_host_address is blacklisted \
29714 at $dnslist_domain\n$dnslist_text
29716 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
29717 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29719 For the first blacklist item, this starts by doing a lookup in
29720 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
29721 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
29722 value, and as long as something is found, it looks for the corresponding TXT
29723 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
29724 The second blacklist item is processed similarly.
29726 If you are interested in more than one merged list, the same list must be
29727 given several times, but because the results of the DNS lookups are cached,
29728 the DNS calls themselves are not repeated. For example:
29730 reject dnslists = \
29731 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
29732 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
29733 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
29734 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
29736 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
29737 values matches (or if no record is found), this is the only lookup that is
29738 done. Only if there is a match is one of the more specific lists consulted.
29742 .section "DNS lists and IPv6" "SECTmorednslistslast"
29743 .cindex "IPv6" "DNS black lists"
29744 .cindex "DNS list" "IPv6 usage"
29745 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
29746 nibble by nibble. For example, if the calling host's IP address is
29747 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
29749 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
29750 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
29752 (split over two lines here to fit on the page). Unfortunately, some of the DNS
29753 lists contain wildcard records, intended for IPv4, that interact badly with
29754 IPv6. For example, the DNS entry
29756 *.3.some.list.example. A 127.0.0.1
29758 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
29759 Unfortunately, it also matches the entire 3::/4 IPv6 network.
29761 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
29762 &%condition%& condition, as in this example:
29764 deny condition = ${if isip4{$sender_host_address}}
29765 dnslists = some.list.example
29768 If an explicit key is being used for a DNS lookup and it may be an IPv6
29769 address you should specify alternate list separators for both the outer
29770 (DNS list name) list and inner (lookup keys) list:
29772 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
29775 .section "Rate limiting incoming messages" "SECTratelimiting"
29776 .cindex "rate limiting" "client sending"
29777 .cindex "limiting client sending rates"
29778 .oindex "&%smtp_ratelimit_*%&"
29779 The &%ratelimit%& ACL condition can be used to measure and control the rate at
29780 which clients can send email. This is more powerful than the
29781 &%smtp_ratelimit_*%& options, because those options control the rate of
29782 commands in a single SMTP session only, whereas the &%ratelimit%& condition
29783 works across all connections (concurrent and sequential) from the same client
29784 host. The syntax of the &%ratelimit%& condition is:
29786 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
29788 If the average client sending rate is less than &'m'& messages per time
29789 period &'p'& then the condition is false; otherwise it is true.
29791 As a side-effect, the &%ratelimit%& condition sets the expansion variable
29792 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
29793 configured value of &'m'&, and &$sender_rate_period$& to the configured value
29796 The parameter &'p'& is the smoothing time constant, in the form of an Exim
29797 time interval, for example, &`8h`& for eight hours. A larger time constant
29798 means that it takes Exim longer to forget a client's past behaviour. The
29799 parameter &'m'& is the maximum number of messages that a client is permitted to
29800 send in each time interval. It also specifies the number of messages permitted
29801 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
29802 constant, you can allow a client to send more messages in a burst without
29803 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
29804 both small, messages must be sent at an even rate.
29806 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
29807 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
29808 when deploying the &%ratelimit%& ACL condition. The script prints usage
29809 instructions when it is run with no arguments.
29811 The key is used to look up the data for calculating the client's average
29812 sending rate. This data is stored in Exim's spool directory, alongside the
29813 retry and other hints databases. The default key is &$sender_host_address$&,
29814 which means Exim computes the sending rate of each client host IP address.
29815 By changing the key you can change how Exim identifies clients for the purpose
29816 of ratelimiting. For example, to limit the sending rate of each authenticated
29817 user, independent of the computer they are sending from, set the key to
29818 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
29819 example, &$authenticated_id$& is only meaningful if the client has
29820 authenticated (which you can check with the &%authenticated%& ACL condition).
29822 The lookup key does not have to identify clients: If you want to limit the
29823 rate at which a recipient receives messages, you can use the key
29824 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
29827 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
29828 specifies what Exim measures the rate of, for example messages or recipients
29829 or bytes. You can adjust the measurement using the &%unique=%& and/or
29830 &%count=%& options. You can also control when Exim updates the recorded rate
29831 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
29832 separated by a slash, like the other parameters. They may appear in any order.
29834 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
29835 any options that alter the meaning of the stored data. The limit &'m'& is not
29836 stored, so you can alter the configured maximum rate and Exim will still
29837 remember clients' past behaviour. If you change the &%per_*%& mode or add or
29838 remove the &%unique=%& option, the lookup key changes so Exim will forget past
29839 behaviour. The lookup key is not affected by changes to the update mode and
29840 the &%count=%& option.
29843 .section "Ratelimit options for what is being measured" "ratoptmea"
29844 .cindex "rate limiting" "per_* options"
29845 The &%per_conn%& option limits the client's connection rate. It is not
29846 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
29847 &%acl_not_smtp_start%& ACLs.
29849 The &%per_mail%& option limits the client's rate of sending messages. This is
29850 the default if none of the &%per_*%& options is specified. It can be used in
29851 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
29852 &%acl_smtp_data%&, or &%acl_not_smtp%&.
29854 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
29855 the same ACLs as the &%per_mail%& option, though it is best to use this option
29856 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
29857 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
29858 in its MAIL command, which may be inaccurate or completely missing. You can
29859 follow the limit &'m'& in the configuration with K, M, or G to specify limits
29860 in kilobytes, megabytes, or gigabytes, respectively.
29862 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
29863 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29864 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
29865 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
29866 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
29867 in either case the rate limiting engine will see a message with many
29868 recipients as a large high-speed burst.
29870 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
29871 number of different recipients that the client has sent messages to in the
29872 last time period. That is, if the client repeatedly sends messages to the same
29873 recipient, its measured rate is not increased. This option can only be used in
29876 The &%per_cmd%& option causes Exim to recompute the rate every time the
29877 condition is processed. This can be used to limit the rate of any SMTP
29878 command. If it is used in multiple ACLs it can limit the aggregate rate of
29879 multiple different commands.
29881 The &%count=%& option can be used to alter how much Exim adds to the client's
29882 measured rate. For example, the &%per_byte%& option is equivalent to
29883 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
29884 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
29885 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
29887 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
29890 .section "Ratelimit update modes" "ratoptupd"
29891 .cindex "rate limiting" "reading data without updating"
29892 You can specify one of three options with the &%ratelimit%& condition to
29893 control when its database is updated. This section describes the &%readonly%&
29894 mode, and the next section describes the &%strict%& and &%leaky%& modes.
29896 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
29897 previously-computed rate to check against the limit.
29899 For example, you can test the client's sending rate and deny it access (when
29900 it is too fast) in the connect ACL. If the client passes this check then it
29901 can go on to send a message, in which case its recorded rate will be updated
29902 in the MAIL ACL. Subsequent connections from the same client will check this
29906 deny ratelimit = 100 / 5m / readonly
29907 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
29908 (max $sender_rate_limit)
29911 warn ratelimit = 100 / 5m / strict
29912 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
29913 (max $sender_rate_limit)
29916 If Exim encounters multiple &%ratelimit%& conditions with the same key when
29917 processing a message then it may increase the client's measured rate more than
29918 it should. For example, this will happen if you check the &%per_rcpt%& option
29919 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
29920 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
29921 multiple update problems by using the &%readonly%& option on later ratelimit
29924 The &%per_*%& options described above do not make sense in some ACLs. If you
29925 use a &%per_*%& option in an ACL where it is not normally permitted then the
29926 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
29927 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
29928 next section) so you must specify the &%readonly%& option explicitly.
29931 .section "Ratelimit options for handling fast clients" "ratoptfast"
29932 .cindex "rate limiting" "strict and leaky modes"
29933 If a client's average rate is greater than the maximum, the rate limiting
29934 engine can react in two possible ways, depending on the presence of the
29935 &%strict%& or &%leaky%& update modes. This is independent of the other
29936 counter-measures (such as rejecting the message) that may be specified by the
29939 The &%leaky%& (default) option means that the client's recorded rate is not
29940 updated if it is above the limit. The effect of this is that Exim measures the
29941 client's average rate of successfully sent email, which cannot be greater than
29942 the maximum allowed. If the client is over the limit it may suffer some
29943 counter-measures (as specified in the ACL), but it will still be able to send
29944 email at the configured maximum rate, whatever the rate of its attempts. This
29945 is generally the better choice if you have clients that retry automatically.
29946 For example, it does not prevent a sender with an over-aggressive retry rate
29947 from getting any email through.
29949 The &%strict%& option means that the client's recorded rate is always
29950 updated. The effect of this is that Exim measures the client's average rate
29951 of attempts to send email, which can be much higher than the maximum it is
29952 actually allowed. If the client is over the limit it may be subjected to
29953 counter-measures by the ACL. It must slow down and allow sufficient time to
29954 pass that its computed rate falls below the maximum before it can send email
29955 again. The time (the number of smoothing periods) it must wait and not
29956 attempt to send mail can be calculated with this formula:
29958 ln(peakrate/maxrate)
29962 .section "Limiting the rate of different events" "ratoptuniq"
29963 .cindex "rate limiting" "counting unique events"
29964 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
29965 rate of different events. For example, the &%per_addr%& option uses this
29966 mechanism to count the number of different recipients that the client has
29967 sent messages to in the last time period; it is equivalent to
29968 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
29969 measure the rate that a client uses different sender addresses with the
29970 options &`per_mail/unique=$sender_address`&.
29972 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
29973 has seen for that key. The whole set is thrown away when it is older than the
29974 rate smoothing period &'p'&, so each different event is counted at most once
29975 per period. In the &%leaky%& update mode, an event that causes the client to
29976 go over the limit is not added to the set, in the same way that the client's
29977 recorded rate is not updated in the same situation.
29979 When you combine the &%unique=%& and &%readonly%& options, the specific
29980 &%unique=%& value is ignored, and Exim just retrieves the client's stored
29983 The &%unique=%& mechanism needs more space in the ratelimit database than the
29984 other &%ratelimit%& options in order to store the event set. The number of
29985 unique values is potentially as large as the rate limit, so the extra space
29986 required increases with larger limits.
29988 The uniqueification is not perfect: there is a small probability that Exim
29989 will think a new event has happened before. If the sender's rate is less than
29990 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
29991 the measured rate can go above the limit, in which case Exim may under-count
29992 events by a significant margin. Fortunately, if the rate is high enough (2.7
29993 times the limit) that the false positive rate goes above 9%, then Exim will
29994 throw away the over-full event set before the measured rate falls below the
29995 limit. Therefore the only harm should be that exceptionally high sending rates
29996 are logged incorrectly; any countermeasures you configure will be as effective
30000 .section "Using rate limiting" "useratlim"
30001 Exim's other ACL facilities are used to define what counter-measures are taken
30002 when the rate limit is exceeded. This might be anything from logging a warning
30003 (for example, while measuring existing sending rates in order to define
30004 policy), through time delays to slow down fast senders, up to rejecting the
30005 message. For example:
30007 # Log all senders' rates
30008 warn ratelimit = 0 / 1h / strict
30009 log_message = Sender rate $sender_rate / $sender_rate_period
30011 # Slow down fast senders; note the need to truncate $sender_rate
30012 # at the decimal point.
30013 warn ratelimit = 100 / 1h / per_rcpt / strict
30014 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
30015 $sender_rate_limit }s
30017 # Keep authenticated users under control
30018 deny authenticated = *
30019 ratelimit = 100 / 1d / strict / $authenticated_id
30021 # System-wide rate limit
30022 defer message = Sorry, too busy. Try again later.
30023 ratelimit = 10 / 1s / $primary_hostname
30025 # Restrict incoming rate from each host, with a default
30026 # set using a macro and special cases looked up in a table.
30027 defer message = Sender rate exceeds $sender_rate_limit \
30028 messages per $sender_rate_period
30029 ratelimit = ${lookup {$sender_host_address} \
30030 cdb {DB/ratelimits.cdb} \
30031 {$value} {RATELIMIT} }
30033 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
30034 especially with the &%per_rcpt%& option, you may suffer from a performance
30035 bottleneck caused by locking on the ratelimit hints database. Apart from
30036 making your ACLs less complicated, you can reduce the problem by using a
30037 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
30038 this means that Exim will lose its hints data after a reboot (including retry
30039 hints, the callout cache, and ratelimit data).
30043 .section "Address verification" "SECTaddressverification"
30044 .cindex "verifying address" "options for"
30045 .cindex "policy control" "address verification"
30046 Several of the &%verify%& conditions described in section
30047 &<<SECTaclconditions>>& cause addresses to be verified. Section
30048 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30049 The verification conditions can be followed by options that modify the
30050 verification process. The options are separated from the keyword and from each
30051 other by slashes, and some of them contain parameters. For example:
30053 verify = sender/callout
30054 verify = recipient/defer_ok/callout=10s,defer_ok
30056 The first stage of address verification, which always happens, is to run the
30057 address through the routers, in &"verify mode"&. Routers can detect the
30058 difference between verification and routing for delivery, and their actions can
30059 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30060 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30061 The available options are as follows:
30064 If the &%callout%& option is specified, successful routing to one or more
30065 remote hosts is followed by a &"callout"& to those hosts as an additional
30066 check. Callouts and their sub-options are discussed in the next section.
30068 If there is a defer error while doing verification routing, the ACL
30069 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30070 options, the condition is forced to be true instead. Note that this is a main
30071 verification option as well as a suboption for callouts.
30073 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30074 discusses the reporting of sender address verification failures.
30076 The &%success_on_redirect%& option causes verification always to succeed
30077 immediately after a successful redirection. By default, if a redirection
30078 generates just one address, that address is also verified. See further
30079 discussion in section &<<SECTredirwhilveri>>&.
30082 .cindex "verifying address" "differentiating failures"
30083 .vindex "&$recipient_verify_failure$&"
30084 .vindex "&$sender_verify_failure$&"
30085 .vindex "&$acl_verify_message$&"
30086 After an address verification failure, &$acl_verify_message$& contains the
30087 error message that is associated with the failure. It can be preserved by
30090 warn !verify = sender
30091 set acl_m0 = $acl_verify_message
30093 If you are writing your own custom rejection message or log message when
30094 denying access, you can use this variable to include information about the
30095 verification failure.
30097 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30098 appropriate) contains one of the following words:
30101 &%qualify%&: The address was unqualified (no domain), and the message
30102 was neither local nor came from an exempted host.
30104 &%route%&: Routing failed.
30106 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30107 occurred at or before the MAIL command (that is, on initial
30108 connection, HELO, or MAIL).
30110 &%recipient%&: The RCPT command in a callout was rejected.
30112 &%postmaster%&: The postmaster check in a callout was rejected.
30115 The main use of these variables is expected to be to distinguish between
30116 rejections of MAIL and rejections of RCPT in callouts.
30121 .section "Callout verification" "SECTcallver"
30122 .cindex "verifying address" "by callout"
30123 .cindex "callout" "verification"
30124 .cindex "SMTP" "callout verification"
30125 For non-local addresses, routing verifies the domain, but is unable to do any
30126 checking of the local part. There are situations where some means of verifying
30127 the local part is desirable. One way this can be done is to make an SMTP
30128 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30129 a subsequent host for a recipient address, to see if the host accepts the
30130 address. We use the term &'callout'& to cover both cases. Note that for a
30131 sender address, the callback is not to the client host that is trying to
30132 deliver the message, but to one of the hosts that accepts incoming mail for the
30135 Exim does not do callouts by default. If you want them to happen, you must
30136 request them by setting appropriate options on the &%verify%& condition, as
30137 described below. This facility should be used with care, because it can add a
30138 lot of resource usage to the cost of verifying an address. However, Exim does
30139 cache the results of callouts, which helps to reduce the cost. Details of
30140 caching are in section &<<SECTcallvercache>>&.
30142 Recipient callouts are usually used only between hosts that are controlled by
30143 the same administration. For example, a corporate gateway host could use
30144 callouts to check for valid recipients on an internal mailserver. A successful
30145 callout does not guarantee that a real delivery to the address would succeed;
30146 on the other hand, a failing callout does guarantee that a delivery would fail.
30148 If the &%callout%& option is present on a condition that verifies an address, a
30149 second stage of verification occurs if the address is successfully routed to
30150 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30151 &(manualroute)& router, where the router specifies the hosts. However, if a
30152 router that does not set up hosts routes to an &(smtp)& transport with a
30153 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30154 &%hosts_override%& set, its hosts are always used, whether or not the router
30155 supplies a host list.
30156 Callouts are only supported on &(smtp)& transports.
30158 The port that is used is taken from the transport, if it is specified and is a
30159 remote transport. (For routers that do verification only, no transport need be
30160 specified.) Otherwise, the default SMTP port is used. If a remote transport
30161 specifies an outgoing interface, this is used; otherwise the interface is not
30162 specified. Likewise, the text that is used for the HELO command is taken from
30163 the transport's &%helo_data%& option; if there is no transport, the value of
30164 &$smtp_active_hostname$& is used.
30166 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30167 test whether a bounce message could be delivered to the sender address. The
30168 following SMTP commands are sent:
30170 &`HELO `&<&'local host name'&>
30172 &`RCPT TO:`&<&'the address to be tested'&>
30175 LHLO is used instead of HELO if the transport's &%protocol%& option is
30178 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30181 A recipient callout check is similar. By default, it also uses an empty address
30182 for the sender. This default is chosen because most hosts do not make use of
30183 the sender address when verifying a recipient. Using the same address means
30184 that a single cache entry can be used for each recipient. Some sites, however,
30185 do make use of the sender address when verifying. These are catered for by the
30186 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30188 If the response to the RCPT command is a 2&'xx'& code, the verification
30189 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30190 Exim tries the next host, if any. If there is a problem with all the remote
30191 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30192 &%callout%& option is given, in which case the condition is forced to succeed.
30194 .cindex "SMTP" "output flushing, disabling for callout"
30195 A callout may take a little time. For this reason, Exim normally flushes SMTP
30196 output before performing a callout in an ACL, to avoid unexpected timeouts in
30197 clients when the SMTP PIPELINING extension is in use. The flushing can be
30198 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30203 .section "Additional parameters for callouts" "CALLaddparcall"
30204 .cindex "callout" "additional parameters for"
30205 The &%callout%& option can be followed by an equals sign and a number of
30206 optional parameters, separated by commas. For example:
30208 verify = recipient/callout=10s,defer_ok
30210 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30211 separate verify options, is retained for backwards compatibility, but is now
30212 deprecated. The additional parameters for &%callout%& are as follows:
30216 .vitem <&'a&~time&~interval'&>
30217 .cindex "callout" "timeout, specifying"
30218 This specifies the timeout that applies for the callout attempt to each host.
30221 verify = sender/callout=5s
30223 The default is 30 seconds. The timeout is used for each response from the
30224 remote host. It is also used for the initial connection, unless overridden by
30225 the &%connect%& parameter.
30228 .vitem &*connect&~=&~*&<&'time&~interval'&>
30229 .cindex "callout" "connection timeout, specifying"
30230 This parameter makes it possible to set a different (usually smaller) timeout
30231 for making the SMTP connection. For example:
30233 verify = sender/callout=5s,connect=1s
30235 If not specified, this timeout defaults to the general timeout value.
30237 .vitem &*defer_ok*&
30238 .cindex "callout" "defer, action on"
30239 When this parameter is present, failure to contact any host, or any other kind
30240 of temporary error, is treated as success by the ACL. However, the cache is not
30241 updated in this circumstance.
30243 .vitem &*fullpostmaster*&
30244 .cindex "callout" "full postmaster check"
30245 This operates like the &%postmaster%& option (see below), but if the check for
30246 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30247 accordance with the specification in RFC 2821. The RFC states that the
30248 unqualified address &'postmaster'& should be accepted.
30251 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30252 .cindex "callout" "sender when verifying header"
30253 When verifying addresses in header lines using the &%header_sender%&
30254 verification option, Exim behaves by default as if the addresses are envelope
30255 sender addresses from a message. Callout verification therefore tests to see
30256 whether a bounce message could be delivered, by using an empty address in the
30257 MAIL command. However, it is arguable that these addresses might never be used
30258 as envelope senders, and could therefore justifiably reject bounce messages
30259 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30260 address to use in the MAIL command. For example:
30262 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30264 This parameter is available only for the &%header_sender%& verification option.
30267 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30268 .cindex "callout" "overall timeout, specifying"
30269 This parameter sets an overall timeout for performing a callout verification.
30272 verify = sender/callout=5s,maxwait=30s
30274 This timeout defaults to four times the callout timeout for individual SMTP
30275 commands. The overall timeout applies when there is more than one host that can
30276 be tried. The timeout is checked before trying the next host. This prevents
30277 very long delays if there are a large number of hosts and all are timing out
30278 (for example, when network connections are timing out).
30281 .vitem &*no_cache*&
30282 .cindex "callout" "cache, suppressing"
30283 .cindex "caching callout, suppressing"
30284 When this parameter is given, the callout cache is neither read nor updated.
30286 .vitem &*postmaster*&
30287 .cindex "callout" "postmaster; checking"
30288 When this parameter is set, a successful callout check is followed by a similar
30289 check for the local part &'postmaster'& at the same domain. If this address is
30290 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30291 the postmaster check is recorded in a cache record; if it is a failure, this is
30292 used to fail subsequent callouts for the domain without a connection being
30293 made, until the cache record expires.
30295 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30296 The postmaster check uses an empty sender in the MAIL command by default.
30297 You can use this parameter to do a postmaster check using a different address.
30300 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30302 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30303 one overrides. The &%postmaster%& parameter is equivalent to this example:
30305 require verify = sender/callout=postmaster_mailfrom=
30307 &*Warning*&: The caching arrangements for postmaster checking do not take
30308 account of the sender address. It is assumed that either the empty address or
30309 a fixed non-empty address will be used. All that Exim remembers is that the
30310 postmaster check for the domain succeeded or failed.
30314 .cindex "callout" "&""random""& check"
30315 When this parameter is set, before doing the normal callout check, Exim does a
30316 check for a &"random"& local part at the same domain. The local part is not
30317 really random &-- it is defined by the expansion of the option
30318 &%callout_random_local_part%&, which defaults to
30320 $primary_hostname-$tod_epoch-testing
30322 The idea here is to try to determine whether the remote host accepts all local
30323 parts without checking. If it does, there is no point in doing callouts for
30324 specific local parts. If the &"random"& check succeeds, the result is saved in
30325 a cache record, and used to force the current and subsequent callout checks to
30326 succeed without a connection being made, until the cache record expires.
30328 .vitem &*use_postmaster*&
30329 .cindex "callout" "sender for recipient check"
30330 This parameter applies to recipient callouts only. For example:
30332 deny !verify = recipient/callout=use_postmaster
30334 .vindex "&$qualify_domain$&"
30335 It causes a non-empty postmaster address to be used in the MAIL command when
30336 performing the callout for the recipient, and also for a &"random"& check if
30337 that is configured. The local part of the address is &`postmaster`& and the
30338 domain is the contents of &$qualify_domain$&.
30340 .vitem &*use_sender*&
30341 This option applies to recipient callouts only. For example:
30343 require verify = recipient/callout=use_sender
30345 It causes the message's actual sender address to be used in the MAIL
30346 command when performing the callout, instead of an empty address. There is no
30347 need to use this option unless you know that the called hosts make use of the
30348 sender when checking recipients. If used indiscriminately, it reduces the
30349 usefulness of callout caching.
30352 If you use any of the parameters that set a non-empty sender for the MAIL
30353 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30354 &%use_sender%&), you should think about possible loops. Recipient checking is
30355 usually done between two hosts that are under the same management, and the host
30356 that receives the callouts is not normally configured to do callouts itself.
30357 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30358 these circumstances.
30360 However, if you use a non-empty sender address for a callout to an arbitrary
30361 host, there is the likelihood that the remote host will itself initiate a
30362 callout check back to your host. As it is checking what appears to be a message
30363 sender, it is likely to use an empty address in MAIL, thus avoiding a
30364 callout loop. However, to be on the safe side it would be best to set up your
30365 own ACLs so that they do not do sender verification checks when the recipient
30366 is the address you use for header sender or postmaster callout checking.
30368 Another issue to think about when using non-empty senders for callouts is
30369 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30370 by the sender/recipient combination; thus, for any given recipient, many more
30371 actual callouts are performed than when an empty sender or postmaster is used.
30376 .section "Callout caching" "SECTcallvercache"
30377 .cindex "hints database" "callout cache"
30378 .cindex "callout" "cache, description of"
30379 .cindex "caching" "callout"
30380 Exim caches the results of callouts in order to reduce the amount of resources
30381 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30382 option. A hints database called &"callout"& is used for the cache. Two
30383 different record types are used: one records the result of a callout check for
30384 a specific address, and the other records information that applies to the
30385 entire domain (for example, that it accepts the local part &'postmaster'&).
30387 When an original callout fails, a detailed SMTP error message is given about
30388 the failure. However, for subsequent failures use the cache data, this message
30391 The expiry times for negative and positive address cache records are
30392 independent, and can be set by the global options &%callout_negative_expire%&
30393 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30395 If a host gives a negative response to an SMTP connection, or rejects any
30396 commands up to and including
30400 (but not including the MAIL command with a non-empty address),
30401 any callout attempt is bound to fail. Exim remembers such failures in a
30402 domain cache record, which it uses to fail callouts for the domain without
30403 making new connections, until the domain record times out. There are two
30404 separate expiry times for domain cache records:
30405 &%callout_domain_negative_expire%& (default 3h) and
30406 &%callout_domain_positive_expire%& (default 7d).
30408 Domain records expire when the negative expiry time is reached if callouts
30409 cannot be made for the domain, or if the postmaster check failed.
30410 Otherwise, they expire when the positive expiry time is reached. This
30411 ensures that, for example, a host that stops accepting &"random"& local parts
30412 will eventually be noticed.
30414 The callout caching mechanism is based on the domain of the address that is
30415 being tested. If the domain routes to several hosts, it is assumed that their
30416 behaviour will be the same.
30420 .section "Sender address verification reporting" "SECTsenaddver"
30421 .cindex "verifying" "suppressing error details"
30422 See section &<<SECTaddressverification>>& for a general discussion of
30423 verification. When sender verification fails in an ACL, the details of the
30424 failure are given as additional output lines before the 550 response to the
30425 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30428 MAIL FROM:<xyz@abc.example>
30430 RCPT TO:<pqr@def.example>
30431 550-Verification failed for <xyz@abc.example>
30432 550-Called: 192.168.34.43
30433 550-Sent: RCPT TO:<xyz@abc.example>
30434 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30435 550 Sender verification failed
30437 If more than one RCPT command fails in the same way, the details are given
30438 only for the first of them. However, some administrators do not want to send
30439 out this much information. You can suppress the details by adding
30440 &`/no_details`& to the ACL statement that requests sender verification. For
30443 verify = sender/no_details
30446 .section "Redirection while verifying" "SECTredirwhilveri"
30447 .cindex "verifying" "redirection while"
30448 .cindex "address redirection" "while verifying"
30449 A dilemma arises when a local address is redirected by aliasing or forwarding
30450 during verification: should the generated addresses themselves be verified,
30451 or should the successful expansion of the original address be enough to verify
30452 it? By default, Exim takes the following pragmatic approach:
30455 When an incoming address is redirected to just one child address, verification
30456 continues with the child address, and if that fails to verify, the original
30457 verification also fails.
30459 When an incoming address is redirected to more than one child address,
30460 verification does not continue. A success result is returned.
30463 This seems the most reasonable behaviour for the common use of aliasing as a
30464 way of redirecting different local parts to the same mailbox. It means, for
30465 example, that a pair of alias entries of the form
30468 aw123: :fail: Gone away, no forwarding address
30470 work as expected, with both local parts causing verification failure. When a
30471 redirection generates more than one address, the behaviour is more like a
30472 mailing list, where the existence of the alias itself is sufficient for
30473 verification to succeed.
30475 It is possible, however, to change the default behaviour so that all successful
30476 redirections count as successful verifications, however many new addresses are
30477 generated. This is specified by the &%success_on_redirect%& verification
30478 option. For example:
30480 require verify = recipient/success_on_redirect/callout=10s
30482 In this example, verification succeeds if a router generates a new address, and
30483 the callout does not occur, because no address was routed to a remote host.
30485 When verification is being tested via the &%-bv%& option, the treatment of
30486 redirections is as just described, unless the &%-v%& or any debugging option is
30487 also specified. In that case, full verification is done for every generated
30488 address and a report is output for each of them.
30492 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
30493 .cindex "CSA" "verifying"
30494 Client SMTP Authorization is a system that allows a site to advertise
30495 which machines are and are not permitted to send email. This is done by placing
30496 special SRV records in the DNS; these are looked up using the client's HELO
30497 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
30498 Authorization checks in Exim are performed by the ACL condition:
30502 This fails if the client is not authorized. If there is a DNS problem, or if no
30503 valid CSA SRV record is found, or if the client is authorized, the condition
30504 succeeds. These three cases can be distinguished using the expansion variable
30505 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
30506 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
30507 be likely to cause problems for legitimate email.
30509 The error messages produced by the CSA code include slightly more
30510 detail. If &$csa_status$& is &"defer"&, this may be because of problems
30511 looking up the CSA SRV record, or problems looking up the CSA target
30512 address record. There are four reasons for &$csa_status$& being &"fail"&:
30515 The client's host name is explicitly not authorized.
30517 The client's IP address does not match any of the CSA target IP addresses.
30519 The client's host name is authorized but it has no valid target IP addresses
30520 (for example, the target's addresses are IPv6 and the client is using IPv4).
30522 The client's host name has no CSA SRV record but a parent domain has asserted
30523 that all subdomains must be explicitly authorized.
30526 The &%csa%& verification condition can take an argument which is the domain to
30527 use for the DNS query. The default is:
30529 verify = csa/$sender_helo_name
30531 This implementation includes an extension to CSA. If the query domain
30532 is an address literal such as [192.0.2.95], or if it is a bare IP
30533 address, Exim searches for CSA SRV records in the reverse DNS as if
30534 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
30537 verify = csa/$sender_host_address
30539 In fact, this is the check that Exim performs if the client does not say HELO.
30540 This extension can be turned off by setting the main configuration option
30541 &%dns_csa_use_reverse%& to be false.
30543 If a CSA SRV record is not found for the domain itself, a search
30544 is performed through its parent domains for a record which might be
30545 making assertions about subdomains. The maximum depth of this search is limited
30546 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
30547 default. Exim does not look for CSA SRV records in a top level domain, so the
30548 default settings handle HELO domains as long as seven
30549 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
30550 of legitimate HELO domains.
30552 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
30553 direct SRV lookups, this is not sufficient because of the extra parent domain
30554 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
30555 addresses into lookups in the reverse DNS space. The result of a successful
30558 ${lookup dnsdb {csa=$sender_helo_name}}
30560 has two space-separated fields: an authorization code and a target host name.
30561 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
30562 authorization required but absent, or &"?"& for unknown.
30567 .section "Bounce address tag validation" "SECTverifyPRVS"
30568 .cindex "BATV, verifying"
30569 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
30570 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
30571 Genuine incoming bounce messages should therefore always be addressed to
30572 recipients that have a valid tag. This scheme is a way of detecting unwanted
30573 bounce messages caused by sender address forgeries (often called &"collateral
30574 spam"&), because the recipients of such messages do not include valid tags.
30576 There are two expansion items to help with the implementation of the BATV
30577 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
30578 the original envelope sender address by using a simple key to add a hash of the
30579 address and some time-based randomizing information. The &%prvs%& expansion
30580 item creates a signed address, and the &%prvscheck%& expansion item checks one.
30581 The syntax of these expansion items is described in section
30582 &<<SECTexpansionitems>>&.
30584 As an example, suppose the secret per-address keys are stored in an MySQL
30585 database. A query to look up the key for an address could be defined as a macro
30588 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
30589 WHERE sender='${quote_mysql:$prvscheck_address}'\
30592 Suppose also that the senders who make use of BATV are defined by an address
30593 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
30596 # Bounces: drop unsigned addresses for BATV senders
30597 deny message = This address does not send an unsigned reverse path
30599 recipients = +batv_senders
30601 # Bounces: In case of prvs-signed address, check signature.
30602 deny message = Invalid reverse path signature.
30604 condition = ${prvscheck {$local_part@$domain}\
30605 {PRVSCHECK_SQL}{1}}
30606 !condition = $prvscheck_result
30608 The first statement rejects recipients for bounce messages that are addressed
30609 to plain BATV sender addresses, because it is known that BATV senders do not
30610 send out messages with plain sender addresses. The second statement rejects
30611 recipients that are prvs-signed, but with invalid signatures (either because
30612 the key is wrong, or the signature has timed out).
30614 A non-prvs-signed address is not rejected by the second statement, because the
30615 &%prvscheck%& expansion yields an empty string if its first argument is not a
30616 prvs-signed address, thus causing the &%condition%& condition to be false. If
30617 the first argument is a syntactically valid prvs-signed address, the yield is
30618 the third string (in this case &"1"&), whether or not the cryptographic and
30619 timeout checks succeed. The &$prvscheck_result$& variable contains the result
30620 of the checks (empty for failure, &"1"& for success).
30622 There is one more issue you must consider when implementing prvs-signing:
30623 you have to ensure that the routers accept prvs-signed addresses and
30624 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
30625 router to remove the signature with a configuration along these lines:
30629 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
30631 This works because, if the third argument of &%prvscheck%& is empty, the result
30632 of the expansion of a prvs-signed address is the decoded value of the original
30633 address. This router should probably be the first of your routers that handles
30636 To create BATV-signed addresses in the first place, a transport of this form
30639 external_smtp_batv:
30641 return_path = ${prvs {$return_path} \
30642 {${lookup mysql{SELECT \
30643 secret FROM batv_prvs WHERE \
30644 sender='${quote_mysql:$sender_address}'} \
30647 If no key can be found for the existing return path, no signing takes place.
30651 .section "Using an ACL to control relaying" "SECTrelaycontrol"
30652 .cindex "&ACL;" "relay control"
30653 .cindex "relaying" "control by ACL"
30654 .cindex "policy control" "relay control"
30655 An MTA is said to &'relay'& a message if it receives it from some host and
30656 delivers it directly to another host as a result of a remote address contained
30657 within it. Redirecting a local address via an alias or forward file and then
30658 passing the message on to another host is not relaying,
30659 .cindex "&""percent hack""&"
30660 but a redirection as a result of the &"percent hack"& is.
30662 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
30663 A host which is acting as a gateway or an MX backup is concerned with incoming
30664 relaying from arbitrary hosts to a specific set of domains. On the other hand,
30665 a host which is acting as a smart host for a number of clients is concerned
30666 with outgoing relaying from those clients to the Internet at large. Often the
30667 same host is fulfilling both functions,
30669 . as illustrated in the diagram below,
30671 but in principle these two kinds of relaying are entirely independent. What is
30672 not wanted is the transmission of mail from arbitrary remote hosts through your
30673 system to arbitrary domains.
30676 You can implement relay control by means of suitable statements in the ACL that
30677 runs for each RCPT command. For convenience, it is often easiest to use
30678 Exim's named list facility to define the domains and hosts involved. For
30679 example, suppose you want to do the following:
30682 Deliver a number of domains to mailboxes on the local host (or process them
30683 locally in some other way). Let's say these are &'my.dom1.example'& and
30684 &'my.dom2.example'&.
30686 Relay mail for a number of other domains for which you are the secondary MX.
30687 These might be &'friend1.example'& and &'friend2.example'&.
30689 Relay mail from the hosts on your local LAN, to whatever domains are involved.
30690 Suppose your LAN is 192.168.45.0/24.
30694 In the main part of the configuration, you put the following definitions:
30696 domainlist local_domains = my.dom1.example : my.dom2.example
30697 domainlist relay_to_domains = friend1.example : friend2.example
30698 hostlist relay_from_hosts = 192.168.45.0/24
30700 Now you can use these definitions in the ACL that is run for every RCPT
30704 accept domains = +local_domains : +relay_to_domains
30705 accept hosts = +relay_from_hosts
30707 The first statement accepts any RCPT command that contains an address in
30708 the local or relay domains. For any other domain, control passes to the second
30709 statement, which accepts the command only if it comes from one of the relay
30710 hosts. In practice, you will probably want to make your ACL more sophisticated
30711 than this, for example, by including sender and recipient verification. The
30712 default configuration includes a more comprehensive example, which is described
30713 in chapter &<<CHAPdefconfil>>&.
30717 .section "Checking a relay configuration" "SECTcheralcon"
30718 .cindex "relaying" "checking control of"
30719 You can check the relay characteristics of your configuration in the same way
30720 that you can test any ACL behaviour for an incoming SMTP connection, by using
30721 the &%-bh%& option to run a fake SMTP session with which you interact.
30723 For specifically testing for unwanted relaying, the host
30724 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
30725 host from the host on which Exim is running, using the normal telnet port, you
30726 will see a normal telnet connection message and then quite a long delay. Be
30727 patient. The remote host is making an SMTP connection back to your host, and
30728 trying a number of common probes to test for open relay vulnerability. The
30729 results of the tests will eventually appear on your terminal.
30734 . ////////////////////////////////////////////////////////////////////////////
30735 . ////////////////////////////////////////////////////////////////////////////
30737 .chapter "Content scanning at ACL time" "CHAPexiscan"
30738 .scindex IIDcosca "content scanning" "at ACL time"
30739 The extension of Exim to include content scanning at ACL time, formerly known
30740 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
30741 was integrated into the main source for Exim release 4.50, and Tom continues to
30742 maintain it. Most of the wording of this chapter is taken from Tom's
30745 It is also possible to scan the content of messages at other times. The
30746 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
30747 scanning after all the ACLs have run. A transport filter can be used to scan
30748 messages at delivery time (see the &%transport_filter%& option, described in
30749 chapter &<<CHAPtransportgeneric>>&).
30751 If you want to include the ACL-time content-scanning features when you compile
30752 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
30753 &_Local/Makefile_&. When you do that, the Exim binary is built with:
30756 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
30757 for all MIME parts for SMTP and non-SMTP messages, respectively.
30759 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
30760 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
30761 run at the end of message reception (the &%acl_smtp_data%& ACL).
30763 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
30764 of messages, or parts of messages, for debugging purposes.
30766 Additional expansion variables that are set in the new ACL and by the new
30769 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
30772 There is another content-scanning configuration option for &_Local/Makefile_&,
30773 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
30774 condition is compiled, in addition to all the other content-scanning features.
30776 Content-scanning is continually evolving, and new features are still being
30777 added. While such features are still unstable and liable to incompatible
30778 changes, they are made available in Exim by setting options whose names begin
30779 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
30780 this manual. You can find out about them by reading the file called
30781 &_doc/experimental.txt_&.
30783 All the content-scanning facilities work on a MBOX copy of the message that is
30784 temporarily created in a file called:
30786 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
30788 The &_.eml_& extension is a friendly hint to virus scanners that they can
30789 expect an MBOX-like structure inside that file. The file is created when the
30790 first content scanning facility is called. Subsequent calls to content
30791 scanning conditions open the same file again. The directory is recursively
30792 removed when the &%acl_smtp_data%& ACL has finished running, unless
30794 control = no_mbox_unspool
30796 has been encountered. When the MIME ACL decodes files, they are put into the
30797 same directory by default.
30801 .section "Scanning for viruses" "SECTscanvirus"
30802 .cindex "virus scanning"
30803 .cindex "content scanning" "for viruses"
30804 .cindex "content scanning" "the &%malware%& condition"
30805 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
30806 It supports a &"generic"& interface to scanners called via the shell, and
30807 specialized interfaces for &"daemon"& type virus scanners, which are resident
30808 in memory and thus are much faster.
30811 A timeout of 2 minutes is applied to a scanner call (by default);
30812 if it expires then a defer action is taken.
30815 .oindex "&%av_scanner%&"
30816 You can set the &%av_scanner%& option in the main part of the configuration
30817 to specify which scanner to use, together with any additional options that
30818 are needed. The basic syntax is as follows:
30820 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
30822 If you do not set &%av_scanner%&, it defaults to
30824 av_scanner = sophie:/var/run/sophie
30826 If the value of &%av_scanner%& starts with a dollar character, it is expanded
30828 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
30829 The following scanner types are supported in this release:
30834 .cindex "virus scanners" "avast"
30835 This is the scanner daemon of Avast. It has been tested with Avast Core
30836 Security (currently at version 1.1.7).
30837 You can get a trial version at &url(http://www.avast.com) or for Linux
30838 at &url(http://www.avast.com/linux-server-antivirus).
30839 This scanner type takes one option,
30840 which can be either a full path to a UNIX socket,
30841 or host and port specifiers separated by white space.
30842 The host may be a name or an IP address; the port is either a
30843 single number or a pair of numbers with a dash between.
30844 Any further options are given, on separate lines,
30845 to the daemon as options before the main scan command.
30848 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
30849 av_scanner = avast:192.168.2.22 5036
30851 If you omit the argument, the default path
30852 &_/var/run/avast/scan.sock_&
30854 If you use a remote host,
30855 you need to make Exim's spool directory available to it,
30856 as the scanner is passed a file path, not file contents.
30857 For information about available commands and their options you may use
30859 $ socat UNIX:/var/run/avast/scan.sock STDIO:
30867 .vitem &%aveserver%&
30868 .cindex "virus scanners" "Kaspersky"
30869 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
30870 at &url(http://www.kaspersky.com). This scanner type takes one option,
30871 which is the path to the daemon's UNIX socket. The default is shown in this
30874 av_scanner = aveserver:/var/run/aveserver
30879 .cindex "virus scanners" "clamd"
30880 This daemon-type scanner is GPL and free. You can get it at
30881 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
30882 unpack MIME containers, so it used to be recommended to unpack MIME attachments
30883 in the MIME ACL. This is no longer believed to be necessary.
30885 The options are a list of server specifiers, which may be
30886 a UNIX socket specification,
30887 a TCP socket specification,
30888 or a (global) option.
30890 A socket specification consists of a space-separated list.
30891 For a Unix socket the first element is a full path for the socket,
30892 for a TCP socket the first element is the IP address
30893 and the second a port number,
30894 Any further elements are per-server (non-global) options.
30895 These per-server options are supported:
30897 retry=<timespec> Retry on connect fail
30900 The &`retry`& option specifies a time after which a single retry for
30901 a failed connect is made. The default is to not retry.
30903 If a Unix socket file is specified, only one server is supported.
30907 av_scanner = clamd:/opt/clamd/socket
30908 av_scanner = clamd:192.0.2.3 1234
30909 av_scanner = clamd:192.0.2.3 1234:local
30910 av_scanner = clamd:192.0.2.3 1234 retry=10s
30911 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
30913 If the value of av_scanner points to a UNIX socket file or contains the
30915 option, then the ClamAV interface will pass a filename containing the data
30916 to be scanned, which will should normally result in less I/O happening and be
30917 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
30918 Exim does not assume that there is a common filesystem with the remote host.
30919 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
30920 you be running a version of ClamAV prior to 0.95.
30922 The final example shows that multiple TCP targets can be specified. Exim will
30923 randomly use one for each incoming email (i.e. it load balances them). Note
30924 that only TCP targets may be used if specifying a list of scanners; a UNIX
30925 socket cannot be mixed in with TCP targets. If one of the servers becomes
30926 unavailable, Exim will try the remaining one(s) until it finds one that works.
30927 When a clamd server becomes unreachable, Exim will log a message. Exim does
30928 not keep track of scanner state between multiple messages, and the scanner
30929 selection is random, so the message will get logged in the mainlog for each
30930 email that the down scanner gets chosen first (message wrapped to be readable):
30932 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
30933 clamd: connection to localhost, port 3310 failed
30934 (Connection refused)
30937 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
30938 contributing the code for this scanner.
30941 .cindex "virus scanners" "command line interface"
30942 This is the keyword for the generic command line scanner interface. It can be
30943 used to attach virus scanners that are invoked from the shell. This scanner
30944 type takes 3 mandatory options:
30947 The full path and name of the scanner binary, with all command line options,
30948 and a placeholder (&`%s`&) for the directory to scan.
30951 A regular expression to match against the STDOUT and STDERR output of the
30952 virus scanner. If the expression matches, a virus was found. You must make
30953 absolutely sure that this expression matches on &"virus found"&. This is called
30954 the &"trigger"& expression.
30957 Another regular expression, containing exactly one pair of parentheses, to
30958 match the name of the virus found in the scanners output. This is called the
30959 &"name"& expression.
30962 For example, Sophos Sweep reports a virus on a line like this:
30964 Virus 'W32/Magistr-B' found in file ./those.bat
30966 For the trigger expression, we can match the phrase &"found in file"&. For the
30967 name expression, we want to extract the W32/Magistr-B string, so we can match
30968 for the single quotes left and right of it. Altogether, this makes the
30969 configuration setting:
30971 av_scanner = cmdline:\
30972 /path/to/sweep -ss -all -rec -archive %s:\
30973 found in file:'(.+)'
30976 .cindex "virus scanners" "DrWeb"
30977 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
30979 either a full path to a UNIX socket,
30980 or host and port specifiers separated by white space.
30981 The host may be a name or an IP address; the port is either a
30982 single number or a pair of numbers with a dash between.
30985 av_scanner = drweb:/var/run/drwebd.sock
30986 av_scanner = drweb:192.168.2.20 31337
30988 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
30989 is used. Thanks to Alex Miller for contributing the code for this scanner.
30992 .cindex "virus scanners" "f-protd"
30993 The f-protd scanner is accessed via HTTP over TCP.
30994 One argument is taken, being a space-separated hostname and port number
30998 av_scanner = f-protd:localhost 10200-10204
31000 If you omit the argument, the default values show above are used.
31003 .cindex "virus scanners" "F-Secure"
31004 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
31005 argument which is the path to a UNIX socket. For example:
31007 av_scanner = fsecure:/path/to/.fsav
31009 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
31010 Thelmen for contributing the code for this scanner.
31012 .vitem &%kavdaemon%&
31013 .cindex "virus scanners" "Kaspersky"
31014 This is the scanner daemon of Kaspersky Version 4. This version of the
31015 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
31016 scanner type takes one option, which is the path to the daemon's UNIX socket.
31019 av_scanner = kavdaemon:/opt/AVP/AvpCtl
31021 The default path is &_/var/run/AvpCtl_&.
31024 .cindex "virus scanners" "mksd"
31025 This is a daemon type scanner that is aimed mainly at Polish users, though some
31026 parts of documentation are now available in English. You can get it at
31027 &url(http://linux.mks.com.pl/). The only option for this scanner type is
31028 the maximum number of processes used simultaneously to scan the attachments,
31029 provided that the demime facility is employed and also provided that mksd has
31030 been run with at least the same number of child processes. For example:
31032 av_scanner = mksd:2
31034 You can safely omit this option (the default value is 1).
31037 .cindex "virus scanners" "simple socket-connected"
31038 This is a general-purpose way of talking to simple scanner daemons
31039 running on the local machine.
31040 There are four options:
31041 an address (which may be an IP address and port, or the path of a Unix socket),
31042 a commandline to send (may include a single %s which will be replaced with
31043 the path to the mail file to be scanned),
31044 an RE to trigger on from the returned data,
31045 an RE to extract malware_name from the returned data.
31048 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31050 Default for the socket specifier is &_/tmp/malware.sock_&.
31051 Default for the commandline is &_%s\n_&.
31052 Both regular-expressions are required.
31055 .cindex "virus scanners" "Sophos and Sophie"
31056 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31057 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31058 for this scanner type is the path to the UNIX socket that Sophie uses for
31059 client communication. For example:
31061 av_scanner = sophie:/tmp/sophie
31063 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31067 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31068 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31071 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31072 makes it possible to use different scanners. See further below for an example.
31073 The &%malware%& condition caches its results, so when you use it multiple times
31074 for the same message, the actual scanning process is only carried out once.
31075 However, using expandable items in &%av_scanner%& disables this caching, in
31076 which case each use of the &%malware%& condition causes a new scan of the
31079 The &%malware%& condition takes a right-hand argument that is expanded before
31081 use and taken as a list, slash-separated by default.
31083 The first element can then be one of
31086 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31087 The condition succeeds if a virus was found, and fail otherwise. This is the
31090 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31091 the condition fails immediately.
31093 A regular expression, in which case the message is scanned for viruses. The
31094 condition succeeds if a virus is found and its name matches the regular
31095 expression. This allows you to take special actions on certain types of virus.
31097 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31098 unless the separator is changed (in the usual way).
31102 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31103 messages even if there is a problem with the virus scanner.
31104 Otherwise, such a problem causes the ACL to defer.
31107 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31108 specify a non-default timeout. The default is two minutes.
31111 malware = * / defer_ok / tmo=10s
31113 A timeout causes the ACL to defer.
31116 .vindex "&$malware_name$&"
31117 When a virus is found, the condition sets up an expansion variable called
31118 &$malware_name$& that contains the name of the virus. You can use it in a
31119 &%message%& modifier that specifies the error returned to the sender, and/or in
31122 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
31123 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
31124 &%malware%& condition.
31126 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31127 imposed by your anti-virus scanner.
31129 Here is a very simple scanning example:
31131 deny message = This message contains malware ($malware_name)
31135 The next example accepts messages when there is a problem with the scanner:
31137 deny message = This message contains malware ($malware_name)
31139 malware = */defer_ok
31141 The next example shows how to use an ACL variable to scan with both sophie and
31142 aveserver. It assumes you have set:
31144 av_scanner = $acl_m0
31146 in the main Exim configuration.
31148 deny message = This message contains malware ($malware_name)
31149 set acl_m0 = sophie
31152 deny message = This message contains malware ($malware_name)
31153 set acl_m0 = aveserver
31158 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31159 .cindex "content scanning" "for spam"
31160 .cindex "spam scanning"
31161 .cindex "SpamAssassin"
31163 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31164 score and a report for the message.
31166 Support is also provided for Rspamd.
31168 For more information about installation and configuration of SpamAssassin or
31169 Rspamd refer to their respective websites at
31170 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31173 SpamAssassin can be installed with CPAN by running:
31175 perl -MCPAN -e 'install Mail::SpamAssassin'
31177 SpamAssassin has its own set of configuration files. Please review its
31178 documentation to see how you can tweak it. The default installation should work
31181 .oindex "&%spamd_address%&"
31182 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31183 intend to use an instance running on the local host you do not need to set
31184 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31185 you must set the &%spamd_address%& option in the global part of the Exim
31186 configuration as follows (example):
31188 spamd_address = 192.168.99.45 387
31192 To use Rspamd (which by default listens on all local addresses
31194 you should add &%variant=rspamd%& after the address/port pair, for example:
31196 spamd_address = 127.0.0.1 11333 variant=rspamd
31200 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31201 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31202 file name instead of an address/port pair:
31204 spamd_address = /var/run/spamd_socket
31206 You can have multiple &%spamd%& servers to improve scalability. These can
31207 reside on other hardware reachable over the network. To specify multiple
31208 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31209 option, separated with colons (the separator can be changed in the usual way):
31211 spamd_address = 192.168.2.10 783 : \
31212 192.168.2.11 783 : \
31215 Up to 32 &%spamd%& servers are supported.
31216 When a server fails to respond to the connection attempt, all other
31217 servers are tried until one succeeds. If no server responds, the &%spam%&
31221 Unix and TCP socket specifications may be mixed in any order.
31222 Each element of the list is a list itself, space-separated by default
31223 and changeable in the usual way.
31225 For TCP socket specifications a host name or IP (v4 or v6, but
31226 subject to list-separator quoting rules) address can be used,
31227 and the port can be one or a dash-separated pair.
31228 In the latter case, the range is tried in strict order.
31230 Elements after the first for Unix sockets, or second for TCP socket,
31232 The supported option are:
31234 pri=<priority> Selection priority
31235 weight=<value> Selection bias
31236 time=<start>-<end> Use only between these times of day
31237 retry=<timespec> Retry on connect fail
31238 tmo=<timespec> Connection time limit
31239 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31242 The &`pri`& option specifies a priority for the server within the list,
31243 higher values being tried first.
31244 The default priority is 1.
31246 The &`weight`& option specifies a selection bias.
31247 Within a priority set
31248 servers are queried in a random fashion, weighted by this value.
31249 The default value for selection bias is 1.
31251 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31252 in the local time zone; each element being one or more digits.
31253 Either the seconds or both minutes and seconds, plus the leading &`.`&
31254 characters, may be omitted and will be taken as zero.
31256 Timeout specifications for the &`retry`& and &`tmo`& options
31257 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31259 The &`tmo`& option specifies an overall timeout for communication.
31260 The default value is two minutes.
31262 The &`retry`& option specifies a time after which a single retry for
31263 a failed connect is made.
31264 The default is to not retry.
31267 The &%spamd_address%& variable is expanded before use if it starts with
31268 a dollar sign. In this case, the expansion may return a string that is
31269 used as the list so that multiple spamd servers can be the result of an
31272 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31273 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31275 deny message = This message was classified as SPAM
31278 The right-hand side of the &%spam%& condition specifies a name. This is
31279 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31280 to scan using a specific profile, but rather use the SpamAssassin system-wide
31281 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31283 Rspamd does not use this setting. However, you must put something on the
31287 The name allows you to use per-domain or per-user antispam profiles in
31288 principle, but this is not straightforward in practice, because a message may
31289 have multiple recipients, not necessarily all in the same domain. Because the
31290 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31291 read the contents of the message, the variables &$local_part$& and &$domain$&
31294 Careful enforcement of single-recipient messages
31295 (e.g. by responding with defer in the recipient ACL for all recipients
31297 or the use of PRDR,
31298 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31299 are needed to use this feature.
31302 The right-hand side of the &%spam%& condition is expanded before being used, so
31303 you can put lookups or conditions there. When the right-hand side evaluates to
31304 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31307 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31308 large ones may cause significant performance degradation. As most spam messages
31309 are quite small, it is recommended that you do not scan the big ones. For
31312 deny message = This message was classified as SPAM
31313 condition = ${if < {$message_size}{10K}}
31317 The &%spam%& condition returns true if the threshold specified in the user's
31318 SpamAssassin profile has been matched or exceeded. If you want to use the
31319 &%spam%& condition for its side effects (see the variables below), you can make
31320 it always return &"true"& by appending &`:true`& to the username.
31322 .cindex "spam scanning" "returned variables"
31323 When the &%spam%& condition is run, it sets up a number of expansion
31326 Except for &$spam_report$&,
31328 these variables are saved with the received message so are
31329 available for use at delivery time.
31332 .vitem &$spam_score$&
31333 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31334 for inclusion in log or reject messages.
31336 .vitem &$spam_score_int$&
31337 The spam score of the message, multiplied by ten, as an integer value. For
31338 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31339 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31340 The integer value is useful for numeric comparisons in conditions.
31342 .vitem &$spam_bar$&
31343 A string consisting of a number of &"+"& or &"-"& characters, representing the
31344 integer part of the spam score value. A spam score of 4.4 would have a
31345 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31346 headers, since MUAs can match on such strings.
31348 .vitem &$spam_report$&
31349 A multiline text table, containing the full SpamAssassin report for the
31350 message. Useful for inclusion in headers or reject messages.
31352 This variable is only usable in a DATA-time ACL.
31356 .vitem &$spam_action$&
31357 For SpamAssassin either 'reject' or 'no action' depending on the
31358 spam score versus threshold.
31359 For Rspamd, the recommended action.
31364 The &%spam%& condition caches its results unless expansion in
31365 spamd_address was used. If you call it again with the same user name, it
31366 does not scan again, but rather returns the same values as before.
31368 The &%spam%& condition returns DEFER if there is any error while running
31369 the message through SpamAssassin or if the expansion of spamd_address
31370 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31371 statement block), append &`/defer_ok`& to the right-hand side of the
31372 spam condition, like this:
31374 deny message = This message was classified as SPAM
31375 spam = joe/defer_ok
31377 This causes messages to be accepted even if there is a problem with &%spamd%&.
31379 Here is a longer, commented example of the use of the &%spam%&
31382 # put headers in all messages (no matter if spam or not)
31383 warn spam = nobody:true
31384 add_header = X-Spam-Score: $spam_score ($spam_bar)
31385 add_header = X-Spam-Report: $spam_report
31387 # add second subject line with *SPAM* marker when message
31388 # is over threshold
31390 add_header = Subject: *SPAM* $h_Subject:
31392 # reject spam at high scores (> 12)
31393 deny message = This message scored $spam_score spam points.
31395 condition = ${if >{$spam_score_int}{120}{1}{0}}
31400 .section "Scanning MIME parts" "SECTscanmimepart"
31401 .cindex "content scanning" "MIME parts"
31402 .cindex "MIME content scanning"
31403 .oindex "&%acl_smtp_mime%&"
31404 .oindex "&%acl_not_smtp_mime%&"
31405 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31406 each MIME part of an SMTP message, including multipart types, in the sequence
31407 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31408 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31409 options may both refer to the same ACL if you want the same processing in both
31412 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31413 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31414 the case of a non-SMTP message. However, a MIME ACL is called only if the
31415 message contains a &'Content-Type:'& header line. When a call to a MIME
31416 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31417 result code is sent to the client. In the case of an SMTP message, the
31418 &%acl_smtp_data%& ACL is not called when this happens.
31420 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31421 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31422 condition to match against the raw MIME part. You can also use the
31423 &%mime_regex%& condition to match against the decoded MIME part (see section
31424 &<<SECTscanregex>>&).
31426 At the start of a MIME ACL, a number of variables are set from the header
31427 information for the relevant MIME part. These are described below. The contents
31428 of the MIME part are not by default decoded into a disk file except for MIME
31429 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31430 part into a disk file, you can use the &%decode%& condition. The general
31433 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31435 The right hand side is expanded before use. After expansion,
31439 &"0"& or &"false"&, in which case no decoding is done.
31441 The string &"default"&. In that case, the file is put in the temporary
31442 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31443 a sequential file name consisting of the message id and a sequence number. The
31444 full path and name is available in &$mime_decoded_filename$& after decoding.
31446 A full path name starting with a slash. If the full name is an existing
31447 directory, it is used as a replacement for the default directory. The filename
31448 is then sequentially assigned. If the path does not exist, it is used as
31449 the full path and file name.
31451 If the string does not start with a slash, it is used as the
31452 filename, and the default path is then used.
31454 The &%decode%& condition normally succeeds. It is only false for syntax
31455 errors or unusual circumstances such as memory shortages. You can easily decode
31456 a file with its original, proposed filename using
31458 decode = $mime_filename
31460 However, you should keep in mind that &$mime_filename$& might contain
31461 anything. If you place files outside of the default path, they are not
31462 automatically unlinked.
31464 For RFC822 attachments (these are messages attached to messages, with a
31465 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31466 as for the primary message, only that the &$mime_is_rfc822$& expansion
31467 variable is set (see below). Attached messages are always decoded to disk
31468 before being checked, and the files are unlinked once the check is done.
31470 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31471 used to match regular expressions against raw and decoded MIME parts,
31472 respectively. They are described in section &<<SECTscanregex>>&.
31474 .cindex "MIME content scanning" "returned variables"
31475 The following list describes all expansion variables that are
31476 available in the MIME ACL:
31479 .vitem &$mime_boundary$&
31480 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31481 have a boundary string, which is stored in this variable. If the current part
31482 has no boundary parameter in the &'Content-Type:'& header, this variable
31483 contains the empty string.
31485 .vitem &$mime_charset$&
31486 This variable contains the character set identifier, if one was found in the
31487 &'Content-Type:'& header. Examples for charset identifiers are:
31493 Please note that this value is not normalized, so you should do matches
31494 case-insensitively.
31496 .vitem &$mime_content_description$&
31497 This variable contains the normalized content of the &'Content-Description:'&
31498 header. It can contain a human-readable description of the parts content. Some
31499 implementations repeat the filename for attachments here, but they are usually
31500 only used for display purposes.
31502 .vitem &$mime_content_disposition$&
31503 This variable contains the normalized content of the &'Content-Disposition:'&
31504 header. You can expect strings like &"attachment"& or &"inline"& here.
31506 .vitem &$mime_content_id$&
31507 This variable contains the normalized content of the &'Content-ID:'& header.
31508 This is a unique ID that can be used to reference a part from another part.
31510 .vitem &$mime_content_size$&
31511 This variable is set only after the &%decode%& modifier (see above) has been
31512 successfully run. It contains the size of the decoded part in kilobytes. The
31513 size is always rounded up to full kilobytes, so only a completely empty part
31514 has a &$mime_content_size$& of zero.
31516 .vitem &$mime_content_transfer_encoding$&
31517 This variable contains the normalized content of the
31518 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
31519 type. Typical values are &"base64"& and &"quoted-printable"&.
31521 .vitem &$mime_content_type$&
31522 If the MIME part has a &'Content-Type:'& header, this variable contains its
31523 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
31524 are some examples of popular MIME types, as they may appear in this variable:
31528 application/octet-stream
31532 If the MIME part has no &'Content-Type:'& header, this variable contains the
31535 .vitem &$mime_decoded_filename$&
31536 This variable is set only after the &%decode%& modifier (see above) has been
31537 successfully run. It contains the full path and file name of the file
31538 containing the decoded data.
31543 .vitem &$mime_filename$&
31544 This is perhaps the most important of the MIME variables. It contains a
31545 proposed filename for an attachment, if one was found in either the
31546 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
31551 decoded, but no additional sanity checks are done.
31553 found, this variable contains the empty string.
31555 .vitem &$mime_is_coverletter$&
31556 This variable attempts to differentiate the &"cover letter"& of an e-mail from
31557 attached data. It can be used to clamp down on flashy or unnecessarily encoded
31558 content in the cover letter, while not restricting attachments at all.
31560 The variable contains 1 (true) for a MIME part believed to be part of the
31561 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
31565 The outermost MIME part of a message is always a cover letter.
31568 If a multipart/alternative or multipart/related MIME part is a cover letter,
31569 so are all MIME subparts within that multipart.
31572 If any other multipart is a cover letter, the first subpart is a cover letter,
31573 and the rest are attachments.
31576 All parts contained within an attachment multipart are attachments.
31579 As an example, the following will ban &"HTML mail"& (including that sent with
31580 alternative plain text), while allowing HTML files to be attached. HTML
31581 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
31583 deny message = HTML mail is not accepted here
31584 !condition = $mime_is_rfc822
31585 condition = $mime_is_coverletter
31586 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
31588 .vitem &$mime_is_multipart$&
31589 This variable has the value 1 (true) when the current part has the main type
31590 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
31591 Since multipart entities only serve as containers for other parts, you may not
31592 want to carry out specific actions on them.
31594 .vitem &$mime_is_rfc822$&
31595 This variable has the value 1 (true) if the current part is not a part of the
31596 checked message itself, but part of an attached message. Attached message
31597 decoding is fully recursive.
31599 .vitem &$mime_part_count$&
31600 This variable is a counter that is raised for each processed MIME part. It
31601 starts at zero for the very first part (which is usually a multipart). The
31602 counter is per-message, so it is reset when processing RFC822 attachments (see
31603 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
31604 complete, so you can use it in the DATA ACL to determine the number of MIME
31605 parts of a message. For non-MIME messages, this variable contains the value -1.
31610 .section "Scanning with regular expressions" "SECTscanregex"
31611 .cindex "content scanning" "with regular expressions"
31612 .cindex "regular expressions" "content scanning with"
31613 You can specify your own custom regular expression matches on the full body of
31614 the message, or on individual MIME parts.
31616 The &%regex%& condition takes one or more regular expressions as arguments and
31617 matches them against the full message (when called in the DATA ACL) or a raw
31618 MIME part (when called in the MIME ACL). The &%regex%& condition matches
31619 linewise, with a maximum line length of 32K characters. That means you cannot
31620 have multiline matches with the &%regex%& condition.
31622 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
31623 to 32K of decoded content (the whole content at once, not linewise). If the
31624 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
31625 is decoded automatically when &%mime_regex%& is executed (using default path
31626 and filename values). If the decoded data is larger than 32K, only the first
31627 32K characters are checked.
31629 The regular expressions are passed as a colon-separated list. To include a
31630 literal colon, you must double it. Since the whole right-hand side string is
31631 expanded before being used, you must also escape dollar signs and backslashes
31632 with more backslashes, or use the &`\N`& facility to disable expansion.
31633 Here is a simple example that contains two regular expressions:
31635 deny message = contains blacklisted regex ($regex_match_string)
31636 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
31638 The conditions returns true if any one of the regular expressions matches. The
31639 &$regex_match_string$& expansion variable is then set up and contains the
31640 matching regular expression.
31642 &*Warning*&: With large messages, these conditions can be fairly
31648 .section "The demime condition" "SECTdemimecond"
31649 .cindex "content scanning" "MIME checking"
31650 .cindex "MIME content scanning"
31651 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
31652 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
31653 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
31654 ACL functionality, but provides no additional facilities. Please note that this
31655 condition is deprecated and kept only for backward compatibility. You must set
31656 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
31657 use the &%demime%& condition.
31659 The &%demime%& condition unpacks MIME containers in the message. It detects
31660 errors in MIME containers and can match file extensions found in the message
31661 against a list. Using this facility produces files containing the unpacked MIME
31662 parts of the message in the temporary scan directory. If you do antivirus
31663 scanning, it is recommended that you use the &%demime%& condition before the
31664 antivirus (&%malware%&) condition.
31666 On the right-hand side of the &%demime%& condition you can pass a
31667 colon-separated list of file extensions that it should match against. For
31670 deny message = Found blacklisted file attachment
31671 demime = vbs:com:bat:pif:prf:lnk
31673 If one of the file extensions is found, the condition is true, otherwise it is
31674 false. If there is a temporary error while demimeing (for example, &"disk
31675 full"&), the condition defers, and the message is temporarily rejected (unless
31676 the condition is on a &%warn%& verb).
31678 The right-hand side is expanded before being treated as a list, so you can have
31679 conditions and lookups there. If it expands to an empty string, &"false"&, or
31680 zero (&"0"&), no demimeing is done and the condition is false.
31682 The &%demime%& condition set the following variables:
31685 .vitem &$demime_errorlevel$&
31686 .vindex "&$demime_errorlevel$&"
31687 When an error is detected in a MIME container, this variable contains the
31688 severity of the error, as an integer number. The higher the value, the more
31689 severe the error (the current maximum value is 3). If this variable is unset or
31690 zero, no error occurred.
31692 .vitem &$demime_reason$&
31693 .vindex "&$demime_reason$&"
31694 When &$demime_errorlevel$& is greater than zero, this variable contains a
31695 human-readable text string describing the MIME error that occurred.
31699 .vitem &$found_extension$&
31700 .vindex "&$found_extension$&"
31701 When the &%demime%& condition is true, this variable contains the file
31702 extension it found.
31705 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
31706 the &%demime%& condition, and are not changed on subsequent calls.
31708 If you do not want to check for file extensions, but rather use the &%demime%&
31709 condition for unpacking or error checking purposes, pass &"*"& as the
31710 right-hand side value. Here is a more elaborate example of how to use this
31713 # Reject messages with serious MIME container errors
31714 deny message = Found MIME error ($demime_reason).
31716 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
31718 # Reject known virus spreading file extensions.
31719 # Accepting these is pretty much braindead.
31720 deny message = contains $found_extension file (blacklisted).
31721 demime = com:vbs:bat:pif:scr
31723 # Freeze .exe and .doc files. Postmaster can
31724 # examine them and eventually thaw them.
31725 deny log_message = Another $found_extension file.
31734 . ////////////////////////////////////////////////////////////////////////////
31735 . ////////////////////////////////////////////////////////////////////////////
31737 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
31738 "Local scan function"
31739 .scindex IIDlosca "&[local_scan()]& function" "description of"
31740 .cindex "customizing" "input scan using C function"
31741 .cindex "policy control" "by local scan function"
31742 In these days of email worms, viruses, and ever-increasing spam, some sites
31743 want to apply a lot of checking to messages before accepting them.
31745 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
31746 passing messages to external virus and spam scanning software. You can also do
31747 a certain amount in Exim itself through string expansions and the &%condition%&
31748 condition in the ACL that runs after the SMTP DATA command or the ACL for
31749 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
31751 To allow for further customization to a site's own requirements, there is the
31752 possibility of linking Exim with a private message scanning function, written
31753 in C. If you want to run code that is written in something other than C, you
31754 can of course use a little C stub to call it.
31756 The local scan function is run once for every incoming message, at the point
31757 when Exim is just about to accept the message.
31758 It can therefore be used to control non-SMTP messages from local processes as
31759 well as messages arriving via SMTP.
31761 Exim applies a timeout to calls of the local scan function, and there is an
31762 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
31763 Zero means &"no timeout"&.
31764 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
31765 before calling the local scan function, so that the most common types of crash
31766 are caught. If the timeout is exceeded or one of those signals is caught, the
31767 incoming message is rejected with a temporary error if it is an SMTP message.
31768 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
31769 code. The incident is logged on the main and reject logs.
31773 .section "Building Exim to use a local scan function" "SECID207"
31774 .cindex "&[local_scan()]& function" "building Exim to use"
31775 To make use of the local scan function feature, you must tell Exim where your
31776 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
31777 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
31778 directory, so you might set
31780 LOCAL_SCAN_SOURCE=Local/local_scan.c
31782 for example. The function must be called &[local_scan()]&. It is called by
31783 Exim after it has received a message, when the success return code is about to
31784 be sent. This is after all the ACLs have been run. The return code from your
31785 function controls whether the message is actually accepted or not. There is a
31786 commented template function (that just accepts the message) in the file
31787 _src/local_scan.c_.
31789 If you want to make use of Exim's run time configuration file to set options
31790 for your &[local_scan()]& function, you must also set
31792 LOCAL_SCAN_HAS_OPTIONS=yes
31794 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
31799 .section "API for local_scan()" "SECTapiforloc"
31800 .cindex "&[local_scan()]& function" "API description"
31801 You must include this line near the start of your code:
31803 #include "local_scan.h"
31805 This header file defines a number of variables and other values, and the
31806 prototype for the function itself. Exim is coded to use unsigned char values
31807 almost exclusively, and one of the things this header defines is a shorthand
31808 for &`unsigned char`& called &`uschar`&.
31809 It also contains the following macro definitions, to simplify casting character
31810 strings and pointers to character strings:
31812 #define CS (char *)
31813 #define CCS (const char *)
31814 #define CSS (char **)
31815 #define US (unsigned char *)
31816 #define CUS (const unsigned char *)
31817 #define USS (unsigned char **)
31819 The function prototype for &[local_scan()]& is:
31821 extern int local_scan(int fd, uschar **return_text);
31823 The arguments are as follows:
31826 &%fd%& is a file descriptor for the file that contains the body of the message
31827 (the -D file). The file is open for reading and writing, but updating it is not
31828 recommended. &*Warning*&: You must &'not'& close this file descriptor.
31830 The descriptor is positioned at character 19 of the file, which is the first
31831 character of the body itself, because the first 19 characters are the message
31832 id followed by &`-D`& and a newline. If you rewind the file, you should use the
31833 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
31834 case this changes in some future version.
31836 &%return_text%& is an address which you can use to return a pointer to a text
31837 string at the end of the function. The value it points to on entry is NULL.
31840 The function must return an &%int%& value which is one of the following macros:
31843 .vitem &`LOCAL_SCAN_ACCEPT`&
31844 .vindex "&$local_scan_data$&"
31845 The message is accepted. If you pass back a string of text, it is saved with
31846 the message, and made available in the variable &$local_scan_data$&. No
31847 newlines are permitted (if there are any, they are turned into spaces) and the
31848 maximum length of text is 1000 characters.
31850 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
31851 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31852 queued without immediate delivery, and is frozen.
31854 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
31855 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
31856 queued without immediate delivery.
31858 .vitem &`LOCAL_SCAN_REJECT`&
31859 The message is rejected; the returned text is used as an error message which is
31860 passed back to the sender and which is also logged. Newlines are permitted &--
31861 they cause a multiline response for SMTP rejections, but are converted to
31862 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
31865 .vitem &`LOCAL_SCAN_TEMPREJECT`&
31866 The message is temporarily rejected; the returned text is used as an error
31867 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
31870 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
31871 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
31872 message is not written to the reject log. It has the effect of unsetting the
31873 &%rejected_header%& log selector for just this rejection. If
31874 &%rejected_header%& is already unset (see the discussion of the
31875 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
31876 same as LOCAL_SCAN_REJECT.
31878 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
31879 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
31880 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
31883 If the message is not being received by interactive SMTP, rejections are
31884 reported by writing to &%stderr%& or by sending an email, as configured by the
31885 &%-oe%& command line options.
31889 .section "Configuration options for local_scan()" "SECTconoptloc"
31890 .cindex "&[local_scan()]& function" "configuration options"
31891 It is possible to have option settings in the main configuration file
31892 that set values in static variables in the &[local_scan()]& module. If you
31893 want to do this, you must have the line
31895 LOCAL_SCAN_HAS_OPTIONS=yes
31897 in your &_Local/Makefile_& when you build Exim. (This line is in
31898 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
31899 file, you must define static variables to hold the option values, and a table
31902 The table must be a vector called &%local_scan_options%&, of type
31903 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
31904 and a pointer to the variable that holds the value. The entries must appear in
31905 alphabetical order. Following &%local_scan_options%& you must also define a
31906 variable called &%local_scan_options_count%& that contains the number of
31907 entries in the table. Here is a short example, showing two kinds of option:
31909 static int my_integer_option = 42;
31910 static uschar *my_string_option = US"a default string";
31912 optionlist local_scan_options[] = {
31913 { "my_integer", opt_int, &my_integer_option },
31914 { "my_string", opt_stringptr, &my_string_option }
31917 int local_scan_options_count =
31918 sizeof(local_scan_options)/sizeof(optionlist);
31920 The values of the variables can now be changed from Exim's runtime
31921 configuration file by including a local scan section as in this example:
31925 my_string = some string of text...
31927 The available types of option data are as follows:
31930 .vitem &*opt_bool*&
31931 This specifies a boolean (true/false) option. The address should point to a
31932 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
31933 that are defined as &"1"& and &"0"&, respectively. If you want to detect
31934 whether such a variable has been set at all, you can initialize it to
31935 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
31938 .vitem &*opt_fixed*&
31939 This specifies a fixed point number, such as is used for load averages.
31940 The address should point to a variable of type &`int`&. The value is stored
31941 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
31944 This specifies an integer; the address should point to a variable of type
31945 &`int`&. The value may be specified in any of the integer formats accepted by
31948 .vitem &*opt_mkint*&
31949 This is the same as &%opt_int%&, except that when such a value is output in a
31950 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
31951 printed with the suffix K or M.
31953 .vitem &*opt_octint*&
31954 This also specifies an integer, but the value is always interpreted as an
31955 octal integer, whether or not it starts with the digit zero, and it is
31956 always output in octal.
31958 .vitem &*opt_stringptr*&
31959 This specifies a string value; the address must be a pointer to a
31960 variable that points to a string (for example, of type &`uschar *`&).
31962 .vitem &*opt_time*&
31963 This specifies a time interval value. The address must point to a variable of
31964 type &`int`&. The value that is placed there is a number of seconds.
31967 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
31968 out the values of all the &[local_scan()]& options.
31972 .section "Available Exim variables" "SECID208"
31973 .cindex "&[local_scan()]& function" "available Exim variables"
31974 The header &_local_scan.h_& gives you access to a number of C variables. These
31975 are the only ones that are guaranteed to be maintained from release to release.
31976 Note, however, that you can obtain the value of any Exim expansion variable,
31977 including &$recipients$&, by calling &'expand_string()'&. The exported
31978 C variables are as follows:
31981 .vitem &*int&~body_linecount*&
31982 This variable contains the number of lines in the message's body.
31984 .vitem &*int&~body_zerocount*&
31985 This variable contains the number of binary zero bytes in the message's body.
31987 .vitem &*unsigned&~int&~debug_selector*&
31988 This variable is set to zero when no debugging is taking place. Otherwise, it
31989 is a bitmap of debugging selectors. Two bits are identified for use in
31990 &[local_scan()]&; they are defined as macros:
31993 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
31994 testing option that is not privileged &-- any caller may set it. All the
31995 other selector bits can be set only by admin users.
31998 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
31999 by the &`+local_scan`& debug selector. It is not included in the default set
32003 Thus, to write to the debugging output only when &`+local_scan`& has been
32004 selected, you should use code like this:
32006 if ((debug_selector & D_local_scan) != 0)
32007 debug_printf("xxx", ...);
32009 .vitem &*uschar&~*expand_string_message*&
32010 After a failing call to &'expand_string()'& (returned value NULL), the
32011 variable &%expand_string_message%& contains the error message, zero-terminated.
32013 .vitem &*header_line&~*header_list*&
32014 A pointer to a chain of header lines. The &%header_line%& structure is
32017 .vitem &*header_line&~*header_last*&
32018 A pointer to the last of the header lines.
32020 .vitem &*uschar&~*headers_charset*&
32021 The value of the &%headers_charset%& configuration option.
32023 .vitem &*BOOL&~host_checking*&
32024 This variable is TRUE during a host checking session that is initiated by the
32025 &%-bh%& command line option.
32027 .vitem &*uschar&~*interface_address*&
32028 The IP address of the interface that received the message, as a string. This
32029 is NULL for locally submitted messages.
32031 .vitem &*int&~interface_port*&
32032 The port on which this message was received. When testing with the &%-bh%&
32033 command line option, the value of this variable is -1 unless a port has been
32034 specified via the &%-oMi%& option.
32036 .vitem &*uschar&~*message_id*&
32037 This variable contains Exim's message id for the incoming message (the value of
32038 &$message_exim_id$&) as a zero-terminated string.
32040 .vitem &*uschar&~*received_protocol*&
32041 The name of the protocol by which the message was received.
32043 .vitem &*int&~recipients_count*&
32044 The number of accepted recipients.
32046 .vitem &*recipient_item&~*recipients_list*&
32047 .cindex "recipient" "adding in local scan"
32048 .cindex "recipient" "removing in local scan"
32049 The list of accepted recipients, held in a vector of length
32050 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
32051 can add additional recipients by calling &'receive_add_recipient()'& (see
32052 below). You can delete recipients by removing them from the vector and
32053 adjusting the value in &%recipients_count%&. In particular, by setting
32054 &%recipients_count%& to zero you remove all recipients. If you then return the
32055 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
32056 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
32057 and then call &'receive_add_recipient()'& as often as needed.
32059 .vitem &*uschar&~*sender_address*&
32060 The envelope sender address. For bounce messages this is the empty string.
32062 .vitem &*uschar&~*sender_host_address*&
32063 The IP address of the sending host, as a string. This is NULL for
32064 locally-submitted messages.
32066 .vitem &*uschar&~*sender_host_authenticated*&
32067 The name of the authentication mechanism that was used, or NULL if the message
32068 was not received over an authenticated SMTP connection.
32070 .vitem &*uschar&~*sender_host_name*&
32071 The name of the sending host, if known.
32073 .vitem &*int&~sender_host_port*&
32074 The port on the sending host.
32076 .vitem &*BOOL&~smtp_input*&
32077 This variable is TRUE for all SMTP input, including BSMTP.
32079 .vitem &*BOOL&~smtp_batched_input*&
32080 This variable is TRUE for BSMTP input.
32082 .vitem &*int&~store_pool*&
32083 The contents of this variable control which pool of memory is used for new
32084 requests. See section &<<SECTmemhanloc>>& for details.
32088 .section "Structure of header lines" "SECID209"
32089 The &%header_line%& structure contains the members listed below.
32090 You can add additional header lines by calling the &'header_add()'& function
32091 (see below). You can cause header lines to be ignored (deleted) by setting
32096 .vitem &*struct&~header_line&~*next*&
32097 A pointer to the next header line, or NULL for the last line.
32099 .vitem &*int&~type*&
32100 A code identifying certain headers that Exim recognizes. The codes are printing
32101 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32102 Notice in particular that any header line whose type is * is not transmitted
32103 with the message. This flagging is used for header lines that have been
32104 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32105 lines.) Effectively, * means &"deleted"&.
32107 .vitem &*int&~slen*&
32108 The number of characters in the header line, including the terminating and any
32111 .vitem &*uschar&~*text*&
32112 A pointer to the text of the header. It always ends with a newline, followed by
32113 a zero byte. Internal newlines are preserved.
32118 .section "Structure of recipient items" "SECID210"
32119 The &%recipient_item%& structure contains these members:
32122 .vitem &*uschar&~*address*&
32123 This is a pointer to the recipient address as it was received.
32125 .vitem &*int&~pno*&
32126 This is used in later Exim processing when top level addresses are created by
32127 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32128 and must always contain -1 at this stage.
32130 .vitem &*uschar&~*errors_to*&
32131 If this value is not NULL, bounce messages caused by failing to deliver to the
32132 recipient are sent to the address it contains. In other words, it overrides the
32133 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32134 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32135 an unqualified address, Exim qualifies it using the domain from
32136 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32137 is NULL for all recipients.
32142 .section "Available Exim functions" "SECID211"
32143 .cindex "&[local_scan()]& function" "available Exim functions"
32144 The header &_local_scan.h_& gives you access to a number of Exim functions.
32145 These are the only ones that are guaranteed to be maintained from release to
32149 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32150 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32152 This function creates a child process that runs the command specified by
32153 &%argv%&. The environment for the process is specified by &%envp%&, which can
32154 be NULL if no environment variables are to be passed. A new umask is supplied
32155 for the process in &%newumask%&.
32157 Pipes to the standard input and output of the new process are set up
32158 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32159 standard error is cloned to the standard output. If there are any file
32160 descriptors &"in the way"& in the new process, they are closed. If the final
32161 argument is TRUE, the new process is made into a process group leader.
32163 The function returns the pid of the new process, or -1 if things go wrong.
32165 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32166 This function waits for a child process to terminate, or for a timeout (in
32167 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32168 return value is as follows:
32173 The process terminated by a normal exit and the value is the process
32179 The process was terminated by a signal and the value is the negation of the
32185 The process timed out.
32189 The was some other error in wait(); &%errno%& is still set.
32192 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32193 This function provide you with a means of submitting a new message to
32194 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32195 want, but this packages it all up for you.) The function creates a pipe,
32196 forks a subprocess that is running
32198 exim -t -oem -oi -f <>
32200 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32201 that is connected to the standard input. The yield of the function is the PID
32202 of the subprocess. You can then write a message to the file descriptor, with
32203 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32205 When you have finished, call &'child_close()'& to wait for the process to
32206 finish and to collect its ending status. A timeout value of zero is usually
32207 fine in this circumstance. Unless you have made a mistake with the recipient
32208 addresses, you should get a return code of zero.
32211 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32212 *sender_authentication)*&
32213 This function is a more sophisticated version of &'child_open()'&. The command
32216 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32218 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32221 .vitem &*void&~debug_printf(char&~*,&~...)*&
32222 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32223 output is written to the standard error stream. If no debugging is selected,
32224 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32225 conditional on the &`local_scan`& debug selector by coding like this:
32227 if ((debug_selector & D_local_scan) != 0)
32228 debug_printf("xxx", ...);
32231 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32232 This is an interface to Exim's string expansion code. The return value is the
32233 expanded string, or NULL if there was an expansion failure.
32234 The C variable &%expand_string_message%& contains an error message after an
32235 expansion failure. If expansion does not change the string, the return value is
32236 the pointer to the input string. Otherwise, the return value points to a new
32237 block of memory that was obtained by a call to &'store_get()'&. See section
32238 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32240 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32241 This function allows you to an add additional header line at the end of the
32242 existing ones. The first argument is the type, and should normally be a space
32243 character. The second argument is a format string and any number of
32244 substitution arguments as for &[sprintf()]&. You may include internal newlines
32245 if you want, and you must ensure that the string ends with a newline.
32247 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32248 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32249 This function adds a new header line at a specified point in the header
32250 chain. The header itself is specified as for &'header_add()'&.
32252 If &%name%& is NULL, the new header is added at the end of the chain if
32253 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32254 NULL, the header lines are searched for the first non-deleted header that
32255 matches the name. If one is found, the new header is added before it if
32256 &%after%& is false. If &%after%& is true, the new header is added after the
32257 found header and any adjacent subsequent ones with the same name (even if
32258 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32259 option controls where the header is added. If it is true, addition is at the
32260 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32261 headers, or at the top if there are no &'Received:'& headers, you could use
32263 header_add_at_position(TRUE, US"Received", TRUE,
32264 ' ', "X-xxx: ...");
32266 Normally, there is always at least one non-deleted &'Received:'& header, but
32267 there may not be if &%received_header_text%& expands to an empty string.
32270 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32271 This function removes header lines. If &%occurrence%& is zero or negative, all
32272 occurrences of the header are removed. If occurrence is greater than zero, that
32273 particular instance of the header is removed. If no header(s) can be found that
32274 match the specification, the function does nothing.
32277 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32278 int&~length,&~BOOL&~notdel)*&"
32279 This function tests whether the given header has the given name. It is not just
32280 a string comparison, because white space is permitted between the name and the
32281 colon. If the &%notdel%& argument is true, a false return is forced for all
32282 &"deleted"& headers; otherwise they are not treated specially. For example:
32284 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32286 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32287 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32288 This function base64-encodes a string, which is passed by address and length.
32289 The text may contain bytes of any value, including zero. The result is passed
32290 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32293 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32294 This function decodes a base64-encoded string. Its arguments are a
32295 zero-terminated base64-encoded string and the address of a variable that is set
32296 to point to the result, which is in dynamic memory. The length of the decoded
32297 string is the yield of the function. If the input is invalid base64 data, the
32298 yield is -1. A zero byte is added to the end of the output string to make it
32299 easy to interpret as a C string (assuming it contains no zeros of its own). The
32300 added zero byte is not included in the returned count.
32302 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32303 This function checks for a match in a domain list. Domains are always
32304 matched caselessly. The return value is one of the following:
32306 &`OK `& match succeeded
32307 &`FAIL `& match failed
32308 &`DEFER `& match deferred
32310 DEFER is usually caused by some kind of lookup defer, such as the
32311 inability to contact a database.
32313 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32315 This function checks for a match in a local part list. The third argument
32316 controls case-sensitivity. The return values are as for
32317 &'lss_match_domain()'&.
32319 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32321 This function checks for a match in an address list. The third argument
32322 controls the case-sensitivity of the local part match. The domain is always
32323 matched caselessly. The return values are as for &'lss_match_domain()'&.
32325 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32327 This function checks for a match in a host list. The most common usage is
32330 lss_match_host(sender_host_name, sender_host_address, ...)
32332 .vindex "&$sender_host_address$&"
32333 An empty address field matches an empty item in the host list. If the host name
32334 is NULL, the name corresponding to &$sender_host_address$& is automatically
32335 looked up if a host name is required to match an item in the list. The return
32336 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32337 returns ERROR in the case when it had to look up a host name, but the lookup
32340 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32342 This function writes to Exim's log files. The first argument should be zero (it
32343 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32344 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32345 them. It specifies to which log or logs the message is written. The remaining
32346 arguments are a format and relevant insertion arguments. The string should not
32347 contain any newlines, not even at the end.
32350 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32351 This function adds an additional recipient to the message. The first argument
32352 is the recipient address. If it is unqualified (has no domain), it is qualified
32353 with the &%qualify_recipient%& domain. The second argument must always be -1.
32355 This function does not allow you to specify a private &%errors_to%& address (as
32356 described with the structure of &%recipient_item%& above), because it pre-dates
32357 the addition of that field to the structure. However, it is easy to add such a
32358 value afterwards. For example:
32360 receive_add_recipient(US"monitor@mydom.example", -1);
32361 recipients_list[recipients_count-1].errors_to =
32362 US"postmaster@mydom.example";
32365 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32366 This is a convenience function to remove a named recipient from the list of
32367 recipients. It returns true if a recipient was removed, and false if no
32368 matching recipient could be found. The argument must be a complete email
32375 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32376 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32377 This function decodes strings that are encoded according to RFC 2047. Typically
32378 these are the contents of header lines. First, each &"encoded word"& is decoded
32379 from the Q or B encoding into a byte-string. Then, if provided with the name of
32380 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32381 made to translate the result to the named character set. If this fails, the
32382 binary string is returned with an error message.
32384 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32385 maximum MIME word length is enforced. The third argument is the target
32386 encoding, or NULL if no translation is wanted.
32388 .cindex "binary zero" "in RFC 2047 decoding"
32389 .cindex "RFC 2047" "binary zero in"
32390 If a binary zero is encountered in the decoded string, it is replaced by the
32391 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32392 not be 0 because header lines are handled as zero-terminated strings.
32394 The function returns the result of processing the string, zero-terminated; if
32395 &%lenptr%& is not NULL, the length of the result is set in the variable to
32396 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32398 If an error is encountered, the function returns NULL and uses the &%error%&
32399 argument to return an error message. The variable pointed to by &%error%& is
32400 set to NULL if there is no error; it may be set non-NULL even when the function
32401 returns a non-NULL value if decoding was successful, but there was a problem
32405 .vitem &*int&~smtp_fflush(void)*&
32406 This function is used in conjunction with &'smtp_printf()'&, as described
32409 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32410 The arguments of this function are like &[printf()]&; it writes to the SMTP
32411 output stream. You should use this function only when there is an SMTP output
32412 stream, that is, when the incoming message is being received via interactive
32413 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32414 is FALSE. If you want to test for an incoming message from another host (as
32415 opposed to a local process that used the &%-bs%& command line option), you can
32416 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32419 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32420 output function, so it can be used for all forms of SMTP connection.
32422 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32423 must start with an appropriate response code: 550 if you are going to return
32424 LOCAL_SCAN_REJECT, 451 if you are going to return
32425 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32426 initial lines of a multi-line response, the code must be followed by a hyphen
32427 to indicate that the line is not the final response line. You must also ensure
32428 that the lines you write terminate with CRLF. For example:
32430 smtp_printf("550-this is some extra info\r\n");
32431 return LOCAL_SCAN_REJECT;
32433 Note that you can also create multi-line responses by including newlines in
32434 the data returned via the &%return_text%& argument. The added value of using
32435 &'smtp_printf()'& is that, for instance, you could introduce delays between
32436 multiple output lines.
32438 The &'smtp_printf()'& function does not return any error indication, because it
32439 does not automatically flush pending output, and therefore does not test
32440 the state of the stream. (In the main code of Exim, flushing and error
32441 detection is done when Exim is ready for the next SMTP input command.) If
32442 you want to flush the output and check for an error (for example, the
32443 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32444 arguments. It flushes the output stream, and returns a non-zero value if there
32447 .vitem &*void&~*store_get(int)*&
32448 This function accesses Exim's internal store (memory) manager. It gets a new
32449 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32450 runs out of memory. See the next section for a discussion of memory handling.
32452 .vitem &*void&~*store_get_perm(int)*&
32453 This function is like &'store_get()'&, but it always gets memory from the
32454 permanent pool. See the next section for a discussion of memory handling.
32456 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32459 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32462 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32463 These three functions create strings using Exim's dynamic memory facilities.
32464 The first makes a copy of an entire string. The second copies up to a maximum
32465 number of characters, indicated by the second argument. The third uses a format
32466 and insertion arguments to create a new string. In each case, the result is a
32467 pointer to a new string in the current memory pool. See the next section for
32473 .section "More about Exim's memory handling" "SECTmemhanloc"
32474 .cindex "&[local_scan()]& function" "memory handling"
32475 No function is provided for freeing memory, because that is never needed.
32476 The dynamic memory that Exim uses when receiving a message is automatically
32477 recycled if another message is received by the same process (this applies only
32478 to incoming SMTP connections &-- other input methods can supply only one
32479 message at a time). After receiving the last message, a reception process
32482 Because it is recycled, the normal dynamic memory cannot be used for holding
32483 data that must be preserved over a number of incoming messages on the same SMTP
32484 connection. However, Exim in fact uses two pools of dynamic memory; the second
32485 one is not recycled, and can be used for this purpose.
32487 If you want to allocate memory that remains available for subsequent messages
32488 in the same SMTP connection, you should set
32490 store_pool = POOL_PERM
32492 before calling the function that does the allocation. There is no need to
32493 restore the value if you do not need to; however, if you do want to revert to
32494 the normal pool, you can either restore the previous value of &%store_pool%& or
32495 set it explicitly to POOL_MAIN.
32497 The pool setting applies to all functions that get dynamic memory, including
32498 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32499 There is also a convenience function called &'store_get_perm()'& that gets a
32500 block of memory from the permanent pool while preserving the value of
32507 . ////////////////////////////////////////////////////////////////////////////
32508 . ////////////////////////////////////////////////////////////////////////////
32510 .chapter "System-wide message filtering" "CHAPsystemfilter"
32511 .scindex IIDsysfil1 "filter" "system filter"
32512 .scindex IIDsysfil2 "filtering all mail"
32513 .scindex IIDsysfil3 "system filter"
32514 The previous chapters (on ACLs and the local scan function) describe checks
32515 that can be applied to messages before they are accepted by a host. There is
32516 also a mechanism for checking messages once they have been received, but before
32517 they are delivered. This is called the &'system filter'&.
32519 The system filter operates in a similar manner to users' filter files, but it
32520 is run just once per message (however many recipients the message has).
32521 It should not normally be used as a substitute for routing, because &%deliver%&
32522 commands in a system router provide new envelope recipient addresses.
32523 The system filter must be an Exim filter. It cannot be a Sieve filter.
32525 The system filter is run at the start of a delivery attempt, before any routing
32526 is done. If a message fails to be completely delivered at the first attempt,
32527 the system filter is run again at the start of every retry.
32528 If you want your filter to do something only once per message, you can make use
32529 of the &%first_delivery%& condition in an &%if%& command in the filter to
32530 prevent it happening on retries.
32532 .vindex "&$domain$&"
32533 .vindex "&$local_part$&"
32534 &*Warning*&: Because the system filter runs just once, variables that are
32535 specific to individual recipient addresses, such as &$local_part$& and
32536 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32537 you want to run a centrally-specified filter for each recipient address
32538 independently, you can do so by setting up a suitable &(redirect)& router, as
32539 described in section &<<SECTperaddfil>>& below.
32542 .section "Specifying a system filter" "SECID212"
32543 .cindex "uid (user id)" "system filter"
32544 .cindex "gid (group id)" "system filter"
32545 The name of the file that contains the system filter must be specified by
32546 setting &%system_filter%&. If you want the filter to run under a uid and gid
32547 other than root, you must also set &%system_filter_user%& and
32548 &%system_filter_group%& as appropriate. For example:
32550 system_filter = /etc/mail/exim.filter
32551 system_filter_user = exim
32553 If a system filter generates any deliveries directly to files or pipes (via the
32554 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32555 specified by setting &%system_filter_file_transport%& and
32556 &%system_filter_pipe_transport%&, respectively. Similarly,
32557 &%system_filter_reply_transport%& must be set to handle any messages generated
32558 by the &%reply%& command.
32561 .section "Testing a system filter" "SECID213"
32562 You can run simple tests of a system filter in the same way as for a user
32563 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32564 are permitted only in system filters are recognized.
32566 If you want to test the combined effect of a system filter and a user filter,
32567 you can use both &%-bF%& and &%-bf%& on the same command line.
32571 .section "Contents of a system filter" "SECID214"
32572 The language used to specify system filters is the same as for users' filter
32573 files. It is described in the separate end-user document &'Exim's interface to
32574 mail filtering'&. However, there are some additional features that are
32575 available only in system filters; these are described in subsequent sections.
32576 If they are encountered in a user's filter file or when testing with &%-bf%&,
32579 .cindex "frozen messages" "manual thaw; testing in filter"
32580 There are two special conditions which, though available in users' filter
32581 files, are designed for use in system filters. The condition &%first_delivery%&
32582 is true only for the first attempt at delivering a message, and
32583 &%manually_thawed%& is true only if the message has been frozen, and
32584 subsequently thawed by an admin user. An explicit forced delivery counts as a
32585 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
32587 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
32588 specify an &"unseen"& (non-significant) delivery, and that delivery does not
32589 succeed, it will not be tried again.
32590 If you want Exim to retry an unseen delivery until it succeeds, you should
32591 arrange to set it up every time the filter runs.
32593 When a system filter finishes running, the values of the variables &$n0$& &--
32594 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
32595 users' filter files. Thus a system filter can, for example, set up &"scores"&
32596 to which users' filter files can refer.
32600 .section "Additional variable for system filters" "SECID215"
32601 .vindex "&$recipients$&"
32602 The expansion variable &$recipients$&, containing a list of all the recipients
32603 of the message (separated by commas and white space), is available in system
32604 filters. It is not available in users' filters for privacy reasons.
32608 .section "Defer, freeze, and fail commands for system filters" "SECID216"
32609 .cindex "freezing messages"
32610 .cindex "message" "freezing"
32611 .cindex "message" "forced failure"
32612 .cindex "&%fail%&" "in system filter"
32613 .cindex "&%freeze%& in system filter"
32614 .cindex "&%defer%& in system filter"
32615 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
32616 always available in system filters, but are not normally enabled in users'
32617 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
32618 for the &(redirect)& router.) These commands can optionally be followed by the
32619 word &%text%& and a string containing an error message, for example:
32621 fail text "this message looks like spam to me"
32623 The keyword &%text%& is optional if the next character is a double quote.
32625 The &%defer%& command defers delivery of the original recipients of the
32626 message. The &%fail%& command causes all the original recipients to be failed,
32627 and a bounce message to be created. The &%freeze%& command suspends all
32628 delivery attempts for the original recipients. In all cases, any new deliveries
32629 that are specified by the filter are attempted as normal after the filter has
32632 The &%freeze%& command is ignored if the message has been manually unfrozen and
32633 not manually frozen since. This means that automatic freezing by a system
32634 filter can be used as a way of checking out suspicious messages. If a message
32635 is found to be all right, manually unfreezing it allows it to be delivered.
32637 .cindex "log" "&%fail%& command log line"
32638 .cindex "&%fail%&" "log line; reducing"
32639 The text given with a fail command is used as part of the bounce message as
32640 well as being written to the log. If the message is quite long, this can fill
32641 up a lot of log space when such failures are common. To reduce the size of the
32642 log message, Exim interprets the text in a special way if it starts with the
32643 two characters &`<<`& and contains &`>>`& later. The text between these two
32644 strings is written to the log, and the rest of the text is used in the bounce
32645 message. For example:
32647 fail "<<filter test 1>>Your message is rejected \
32648 because it contains attachments that we are \
32649 not prepared to receive."
32652 .cindex "loop" "caused by &%fail%&"
32653 Take great care with the &%fail%& command when basing the decision to fail on
32654 the contents of the message, because the bounce message will of course include
32655 the contents of the original message and will therefore trigger the &%fail%&
32656 command again (causing a mail loop) unless steps are taken to prevent this.
32657 Testing the &%error_message%& condition is one way to prevent this. You could
32660 if $message_body contains "this is spam" and not error_message
32661 then fail text "spam is not wanted here" endif
32663 though of course that might let through unwanted bounce messages. The
32664 alternative is clever checking of the body and/or headers to detect bounces
32665 generated by the filter.
32667 The interpretation of a system filter file ceases after a
32669 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
32670 set up earlier in the filter file are honoured, so you can use a sequence such
32676 to send a specified message when the system filter is freezing (or deferring or
32677 failing) a message. The normal deliveries for the message do not, of course,
32682 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
32683 .cindex "header lines" "adding; in system filter"
32684 .cindex "header lines" "removing; in system filter"
32685 .cindex "filter" "header lines; adding/removing"
32686 Two filter commands that are available only in system filters are:
32688 headers add <string>
32689 headers remove <string>
32691 The argument for the &%headers add%& is a string that is expanded and then
32692 added to the end of the message's headers. It is the responsibility of the
32693 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
32694 space is ignored, and if the string is otherwise empty, or if the expansion is
32695 forced to fail, the command has no effect.
32697 You can use &"\n"& within the string, followed by white space, to specify
32698 continued header lines. More than one header may be added in one command by
32699 including &"\n"& within the string without any following white space. For
32702 headers add "X-header-1: ....\n \
32703 continuation of X-header-1 ...\n\
32706 Note that the header line continuation white space after the first newline must
32707 be placed before the backslash that continues the input string, because white
32708 space after input continuations is ignored.
32710 The argument for &%headers remove%& is a colon-separated list of header names.
32711 This command applies only to those headers that are stored with the message;
32712 those that are added at delivery time (such as &'Envelope-To:'& and
32713 &'Return-Path:'&) cannot be removed by this means. If there is more than one
32714 header with the same name, they are all removed.
32716 The &%headers%& command in a system filter makes an immediate change to the set
32717 of header lines that was received with the message (with possible additions
32718 from ACL processing). Subsequent commands in the system filter operate on the
32719 modified set, which also forms the basis for subsequent message delivery.
32720 Unless further modified during routing or transporting, this set of headers is
32721 used for all recipients of the message.
32723 During routing and transporting, the variables that refer to the contents of
32724 header lines refer only to those lines that are in this set. Thus, header lines
32725 that are added by a system filter are visible to users' filter files and to all
32726 routers and transports. This contrasts with the manipulation of header lines by
32727 routers and transports, which is not immediate, but which instead is saved up
32728 until the message is actually being written (see section
32729 &<<SECTheadersaddrem>>&).
32731 If the message is not delivered at the first attempt, header lines that were
32732 added by the system filter are stored with the message, and so are still
32733 present at the next delivery attempt. Header lines that were removed are still
32734 present, but marked &"deleted"& so that they are not transported with the
32735 message. For this reason, it is usual to make the &%headers%& command
32736 conditional on &%first_delivery%& so that the set of header lines is not
32737 modified more than once.
32739 Because header modification in a system filter acts immediately, you have to
32740 use an indirect approach if you want to modify the contents of a header line.
32743 headers add "Old-Subject: $h_subject:"
32744 headers remove "Subject"
32745 headers add "Subject: new subject (was: $h_old-subject:)"
32746 headers remove "Old-Subject"
32751 .section "Setting an errors address in a system filter" "SECID217"
32752 .cindex "envelope sender"
32753 In a system filter, if a &%deliver%& command is followed by
32755 errors_to <some address>
32757 in order to change the envelope sender (and hence the error reporting) for that
32758 delivery, any address may be specified. (In a user filter, only the current
32759 user's address can be set.) For example, if some mail is being monitored, you
32762 unseen deliver monitor@spying.example errors_to root@local.example
32764 to take a copy which would not be sent back to the normal error reporting
32765 address if its delivery failed.
32769 .section "Per-address filtering" "SECTperaddfil"
32770 .vindex "&$domain$&"
32771 .vindex "&$local_part$&"
32772 In contrast to the system filter, which is run just once per message for each
32773 delivery attempt, it is also possible to set up a system-wide filtering
32774 operation that runs once for each recipient address. In this case, variables
32775 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
32776 filter file could be made dependent on them. This is an example of a router
32777 which implements such a filter:
32782 domains = +local_domains
32783 file = /central/filters/$local_part
32788 The filter is run in a separate process under its own uid. Therefore, either
32789 &%check_local_user%& must be set (as above), in which case the filter is run as
32790 the local user, or the &%user%& option must be used to specify which user to
32791 use. If both are set, &%user%& overrides.
32793 Care should be taken to ensure that none of the commands in the filter file
32794 specify a significant delivery if the message is to go on to be delivered to
32795 its intended recipient. The router will not then claim to have dealt with the
32796 address, so it will be passed on to subsequent routers to be delivered in the
32798 .ecindex IIDsysfil1
32799 .ecindex IIDsysfil2
32800 .ecindex IIDsysfil3
32807 . ////////////////////////////////////////////////////////////////////////////
32808 . ////////////////////////////////////////////////////////////////////////////
32810 .chapter "Message processing" "CHAPmsgproc"
32811 .scindex IIDmesproc "message" "general processing"
32812 Exim performs various transformations on the sender and recipient addresses of
32813 all messages that it handles, and also on the messages' header lines. Some of
32814 these are optional and configurable, while others always take place. All of
32815 this processing, except rewriting as a result of routing, and the addition or
32816 removal of header lines while delivering, happens when a message is received,
32817 before it is placed on Exim's queue.
32819 Some of the automatic processing takes place by default only for
32820 &"locally-originated"& messages. This adjective is used to describe messages
32821 that are not received over TCP/IP, but instead are passed to an Exim process on
32822 its standard input. This includes the interactive &"local SMTP"& case that is
32823 set up by the &%-bs%& command line option.
32825 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
32826 or ::1) are not considered to be locally-originated. Exim does not treat the
32827 loopback interface specially in any way.
32829 If you want the loopback interface to be treated specially, you must ensure
32830 that there are appropriate entries in your ACLs.
32835 .section "Submission mode for non-local messages" "SECTsubmodnon"
32836 .cindex "message" "submission"
32837 .cindex "submission mode"
32838 Processing that happens automatically for locally-originated messages (unless
32839 &%suppress_local_fixups%& is set) can also be requested for messages that are
32840 received over TCP/IP. The term &"submission mode"& is used to describe this
32841 state. Submission mode is set by the modifier
32843 control = submission
32845 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
32846 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
32847 a local submission, and is normally used when the source of the message is
32848 known to be an MUA running on a client host (as opposed to an MTA). For
32849 example, to set submission mode for messages originating on the IPv4 loopback
32850 interface, you could include the following in the MAIL ACL:
32852 warn hosts = 127.0.0.1
32853 control = submission
32855 .cindex "&%sender_retain%& submission option"
32856 There are some options that can be used when setting submission mode. A slash
32857 is used to separate options. For example:
32859 control = submission/sender_retain
32861 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
32862 true and &%local_from_check%& false for the current incoming message. The first
32863 of these allows an existing &'Sender:'& header in the message to remain, and
32864 the second suppresses the check to ensure that &'From:'& matches the
32865 authenticated sender. With this setting, Exim still fixes up messages by adding
32866 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
32867 attempt to check sender authenticity in header lines.
32869 When &%sender_retain%& is not set, a submission mode setting may specify a
32870 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
32873 control = submission/domain=some.domain
32875 The domain may be empty. How this value is used is described in sections
32876 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
32877 that allows you to specify the user's full name for inclusion in a created
32878 &'Sender:'& or &'From:'& header line. For example:
32880 accept authenticated = *
32881 control = submission/domain=wonderland.example/\
32882 name=${lookup {$authenticated_id} \
32883 lsearch {/etc/exim/namelist}}
32885 Because the name may contain any characters, including slashes, the &%name%&
32886 option must be given last. The remainder of the string is used as the name. For
32887 the example above, if &_/etc/exim/namelist_& contains:
32889 bigegg: Humpty Dumpty
32891 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
32894 Sender: Humpty Dumpty <bigegg@wonderland.example>
32896 .cindex "return path" "in submission mode"
32897 By default, submission mode forces the return path to the same address as is
32898 used to create the &'Sender:'& header. However, if &%sender_retain%& is
32899 specified, the return path is also left unchanged.
32901 &*Note*&: The changes caused by submission mode take effect after the predata
32902 ACL. This means that any sender checks performed before the fix-ups use the
32903 untrusted sender address specified by the user, not the trusted sender address
32904 specified by submission mode. Although this might be slightly unexpected, it
32905 does mean that you can configure ACL checks to spot that a user is trying to
32906 spoof another's address.
32908 .section "Line endings" "SECTlineendings"
32909 .cindex "line endings"
32910 .cindex "carriage return"
32912 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
32913 linefeed) is the line ending for messages transmitted over the Internet using
32914 SMTP over TCP/IP. However, within individual operating systems, different
32915 conventions are used. For example, Unix-like systems use just LF, but others
32916 use CRLF or just CR.
32918 Exim was designed for Unix-like systems, and internally, it stores messages
32919 using the system's convention of a single LF as a line terminator. When
32920 receiving a message, all line endings are translated to this standard format.
32921 Originally, it was thought that programs that passed messages directly to an
32922 MTA within an operating system would use that system's convention. Experience
32923 has shown that this is not the case; for example, there are Unix applications
32924 that use CRLF in this circumstance. For this reason, and for compatibility with
32925 other MTAs, the way Exim handles line endings for all messages is now as
32929 LF not preceded by CR is treated as a line ending.
32931 CR is treated as a line ending; if it is immediately followed by LF, the LF
32934 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
32935 nor a local message in the state where a line containing only a dot is a
32938 If a bare CR is encountered within a header line, an extra space is added after
32939 the line terminator so as not to end the header line. The reasoning behind this
32940 is that bare CRs in header lines are most likely either to be mistakes, or
32941 people trying to play silly games.
32943 If the first header line received in a message ends with CRLF, a subsequent
32944 bare LF in a header line is treated in the same way as a bare CR in a header
32952 .section "Unqualified addresses" "SECID218"
32953 .cindex "unqualified addresses"
32954 .cindex "address" "qualification"
32955 By default, Exim expects every envelope address it receives from an external
32956 host to be fully qualified. Unqualified addresses cause negative responses to
32957 SMTP commands. However, because SMTP is used as a means of transporting
32958 messages from MUAs running on personal workstations, there is sometimes a
32959 requirement to accept unqualified addresses from specific hosts or IP networks.
32961 Exim has two options that separately control which hosts may send unqualified
32962 sender or recipient addresses in SMTP commands, namely
32963 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
32964 cases, if an unqualified address is accepted, it is qualified by adding the
32965 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
32967 .oindex "&%qualify_domain%&"
32968 .oindex "&%qualify_recipient%&"
32969 Unqualified addresses in header lines are automatically qualified for messages
32970 that are locally originated, unless the &%-bnq%& option is given on the command
32971 line. For messages received over SMTP, unqualified addresses in header lines
32972 are qualified only if unqualified addresses are permitted in SMTP commands. In
32973 other words, such qualification is also controlled by
32974 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
32979 .section "The UUCP From line" "SECID219"
32980 .cindex "&""From""& line"
32981 .cindex "UUCP" "&""From""& line"
32982 .cindex "sender" "address"
32983 .oindex "&%uucp_from_pattern%&"
32984 .oindex "&%uucp_from_sender%&"
32985 .cindex "envelope sender"
32986 .cindex "Sendmail compatibility" "&""From""& line"
32987 Messages that have come from UUCP (and some other applications) often begin
32988 with a line containing the envelope sender and a timestamp, following the word
32989 &"From"&. Examples of two common formats are:
32991 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
32992 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
32994 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
32995 Exim recognizes such lines at the start of messages that are submitted to it
32996 via the command line (that is, on the standard input). It does not recognize
32997 such lines in incoming SMTP messages, unless the sending host matches
32998 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
32999 and &%ignore_fromline_local%& is set. The recognition is controlled by a
33000 regular expression that is defined by the &%uucp_from_pattern%& option, whose
33001 default value matches the two common cases shown above and puts the address
33002 that follows &"From"& into &$1$&.
33004 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
33005 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
33006 a trusted user, the message's sender address is constructed by expanding the
33007 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
33008 then parsed as an RFC 2822 address. If there is no domain, the local part is
33009 qualified with &%qualify_domain%& unless it is the empty string. However, if
33010 the command line &%-f%& option is used, it overrides the &"From"& line.
33012 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
33013 sender address is not changed. This is also the case for incoming SMTP messages
33014 that are permitted to contain &"From"& lines.
33016 Only one &"From"& line is recognized. If there is more than one, the second is
33017 treated as a data line that starts the body of the message, as it is not valid
33018 as a header line. This also happens if a &"From"& line is present in an
33019 incoming SMTP message from a source that is not permitted to send them.
33023 .section "Resent- header lines" "SECID220"
33024 .cindex "&%Resent-%& header lines"
33025 RFC 2822 makes provision for sets of header lines starting with the string
33026 &`Resent-`& to be added to a message when it is resent by the original
33027 recipient to somebody else. These headers are &'Resent-Date:'&,
33028 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
33029 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
33032 &'Resent fields are strictly informational. They MUST NOT be used in the normal
33033 processing of replies or other such automatic actions on messages.'&
33036 This leaves things a bit vague as far as other processing actions such as
33037 address rewriting are concerned. Exim treats &%Resent-%& header lines as
33041 A &'Resent-From:'& line that just contains the login id of the submitting user
33042 is automatically rewritten in the same way as &'From:'& (see below).
33044 If there's a rewriting rule for a particular header line, it is also applied to
33045 &%Resent-%& header lines of the same type. For example, a rule that rewrites
33046 &'From:'& also rewrites &'Resent-From:'&.
33048 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
33051 For a locally-submitted message,
33052 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
33053 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
33054 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
33055 included in log lines in this case.
33057 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
33058 &%Resent-%& header lines are present.
33064 .section "The Auto-Submitted: header line" "SECID221"
33065 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33066 includes the header line:
33068 Auto-Submitted: auto-replied
33071 .section "The Bcc: header line" "SECID222"
33072 .cindex "&'Bcc:'& header line"
33073 If Exim is called with the &%-t%& option, to take recipient addresses from a
33074 message's header, it removes any &'Bcc:'& header line that may exist (after
33075 extracting its addresses). If &%-t%& is not present on the command line, any
33076 existing &'Bcc:'& is not removed.
33079 .section "The Date: header line" "SECID223"
33080 .cindex "&'Date:'& header line"
33081 If a locally-generated or submission-mode message has no &'Date:'& header line,
33082 Exim adds one, using the current date and time, unless the
33083 &%suppress_local_fixups%& control has been specified.
33085 .section "The Delivery-date: header line" "SECID224"
33086 .cindex "&'Delivery-date:'& header line"
33087 .oindex "&%delivery_date_remove%&"
33088 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33089 set. Exim can be configured to add them to the final delivery of messages. (See
33090 the generic &%delivery_date_add%& transport option.) They should not be present
33091 in messages in transit. If the &%delivery_date_remove%& configuration option is
33092 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33096 .section "The Envelope-to: header line" "SECID225"
33097 .cindex "&'Envelope-to:'& header line"
33098 .oindex "&%envelope_to_remove%&"
33099 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33100 Exim can be configured to add them to the final delivery of messages. (See the
33101 generic &%envelope_to_add%& transport option.) They should not be present in
33102 messages in transit. If the &%envelope_to_remove%& configuration option is set
33103 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33107 .section "The From: header line" "SECTthefrohea"
33108 .cindex "&'From:'& header line"
33109 .cindex "Sendmail compatibility" "&""From""& line"
33110 .cindex "message" "submission"
33111 .cindex "submission mode"
33112 If a submission-mode message does not contain a &'From:'& header line, Exim
33113 adds one if either of the following conditions is true:
33116 The envelope sender address is not empty (that is, this is not a bounce
33117 message). The added header line copies the envelope sender address.
33119 .vindex "&$authenticated_id$&"
33120 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33122 .vindex "&$qualify_domain$&"
33123 If no domain is specified by the submission control, the local part is
33124 &$authenticated_id$& and the domain is &$qualify_domain$&.
33126 If a non-empty domain is specified by the submission control, the local
33127 part is &$authenticated_id$&, and the domain is the specified domain.
33129 If an empty domain is specified by the submission control,
33130 &$authenticated_id$& is assumed to be the complete address.
33134 A non-empty envelope sender takes precedence.
33136 If a locally-generated incoming message does not contain a &'From:'& header
33137 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33138 containing the sender's address. The calling user's login name and full name
33139 are used to construct the address, as described in section &<<SECTconstr>>&.
33140 They are obtained from the password data by calling &[getpwuid()]& (but see the
33141 &%unknown_login%& configuration option). The address is qualified with
33142 &%qualify_domain%&.
33144 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33145 &'From:'& header line containing just the unqualified login name of the calling
33146 user, this is replaced by an address containing the user's login name and full
33147 name as described in section &<<SECTconstr>>&.
33150 .section "The Message-ID: header line" "SECID226"
33151 .cindex "&'Message-ID:'& header line"
33152 .cindex "message" "submission"
33153 .oindex "&%message_id_header_text%&"
33154 If a locally-generated or submission-mode incoming message does not contain a
33155 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33156 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33157 to the message. If there are any &'Resent-:'& headers in the message, it
33158 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33159 message id, preceded by the letter E to ensure it starts with a letter, and
33160 followed by @ and the primary host name. Additional information can be included
33161 in this header line by setting the &%message_id_header_text%& and/or
33162 &%message_id_header_domain%& options.
33165 .section "The Received: header line" "SECID227"
33166 .cindex "&'Received:'& header line"
33167 A &'Received:'& header line is added at the start of every message. The
33168 contents are defined by the &%received_header_text%& configuration option, and
33169 Exim automatically adds a semicolon and a timestamp to the configured string.
33171 The &'Received:'& header is generated as soon as the message's header lines
33172 have been received. At this stage, the timestamp in the &'Received:'& header
33173 line is the time that the message started to be received. This is the value
33174 that is seen by the DATA ACL and by the &[local_scan()]& function.
33176 Once a message is accepted, the timestamp in the &'Received:'& header line is
33177 changed to the time of acceptance, which is (apart from a small delay while the
33178 -H spool file is written) the earliest time at which delivery could start.
33181 .section "The References: header line" "SECID228"
33182 .cindex "&'References:'& header line"
33183 Messages created by the &(autoreply)& transport include a &'References:'&
33184 header line. This is constructed according to the rules that are described in
33185 section 3.64 of RFC 2822 (which states that replies should contain such a
33186 header line), and section 3.14 of RFC 3834 (which states that automatic
33187 responses are not different in this respect). However, because some mail
33188 processing software does not cope well with very long header lines, no more
33189 than 12 message IDs are copied from the &'References:'& header line in the
33190 incoming message. If there are more than 12, the first one and then the final
33191 11 are copied, before adding the message ID of the incoming message.
33195 .section "The Return-path: header line" "SECID229"
33196 .cindex "&'Return-path:'& header line"
33197 .oindex "&%return_path_remove%&"
33198 &'Return-path:'& header lines are defined as something an MTA may insert when
33199 it does the final delivery of messages. (See the generic &%return_path_add%&
33200 transport option.) Therefore, they should not be present in messages in
33201 transit. If the &%return_path_remove%& configuration option is set (the
33202 default), Exim removes &'Return-path:'& header lines from incoming messages.
33206 .section "The Sender: header line" "SECTthesenhea"
33207 .cindex "&'Sender:'& header line"
33208 .cindex "message" "submission"
33209 For a locally-originated message from an untrusted user, Exim may remove an
33210 existing &'Sender:'& header line, and it may add a new one. You can modify
33211 these actions by setting the &%local_sender_retain%& option true, the
33212 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33215 When a local message is received from an untrusted user and
33216 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33217 control has not been set, a check is made to see if the address given in the
33218 &'From:'& header line is the correct (local) sender of the message. The address
33219 that is expected has the login name as the local part and the value of
33220 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33221 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33222 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33223 line is added to the message.
33225 If you set &%local_from_check%& false, this checking does not occur. However,
33226 the removal of an existing &'Sender:'& line still happens, unless you also set
33227 &%local_sender_retain%& to be true. It is not possible to set both of these
33228 options true at the same time.
33230 .cindex "submission mode"
33231 By default, no processing of &'Sender:'& header lines is done for messages
33232 received over TCP/IP or for messages submitted by trusted users. However, when
33233 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33234 not specified on the submission control, the following processing takes place:
33236 .vindex "&$authenticated_id$&"
33237 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33238 authenticated, and &$authenticated_id$& is not empty, a sender address is
33239 created as follows:
33242 .vindex "&$qualify_domain$&"
33243 If no domain is specified by the submission control, the local part is
33244 &$authenticated_id$& and the domain is &$qualify_domain$&.
33246 If a non-empty domain is specified by the submission control, the local part
33247 is &$authenticated_id$&, and the domain is the specified domain.
33249 If an empty domain is specified by the submission control,
33250 &$authenticated_id$& is assumed to be the complete address.
33253 This address is compared with the address in the &'From:'& header line. If they
33254 are different, a &'Sender:'& header line containing the created address is
33255 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33256 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33258 .cindex "return path" "created from &'Sender:'&"
33259 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33260 the message (the envelope sender address) is changed to be the same address,
33261 except in the case of submission mode when &%sender_retain%& is specified.
33265 .section "Adding and removing header lines in routers and transports" &&&
33266 "SECTheadersaddrem"
33267 .cindex "header lines" "adding; in router or transport"
33268 .cindex "header lines" "removing; in router or transport"
33269 When a message is delivered, the addition and removal of header lines can be
33270 specified in a system filter, or on any of the routers and transports that
33271 process the message. Section &<<SECTaddremheasys>>& contains details about
33272 modifying headers in a system filter. Header lines can also be added in an ACL
33273 as a message is received (see section &<<SECTaddheadacl>>&).
33275 In contrast to what happens in a system filter, header modifications that are
33276 specified on routers and transports apply only to the particular recipient
33277 addresses that are being processed by those routers and transports. These
33278 changes do not actually take place until a copy of the message is being
33279 transported. Therefore, they do not affect the basic set of header lines, and
33280 they do not affect the values of the variables that refer to header lines.
33282 &*Note*&: In particular, this means that any expansions in the configuration of
33283 the transport cannot refer to the modified header lines, because such
33284 expansions all occur before the message is actually transported.
33286 For both routers and transports, the argument of a &%headers_add%&
33287 option must be in the form of one or more RFC 2822 header lines, separated by
33288 newlines (coded as &"\n"&). For example:
33290 headers_add = X-added-header: added by $primary_hostname\n\
33291 X-added-second: another added header line
33293 Exim does not check the syntax of these added header lines.
33295 Multiple &%headers_add%& options for a single router or transport can be
33296 specified; the values will append to a single list of header lines.
33297 Each header-line is separately expanded.
33299 The argument of a &%headers_remove%& option must consist of a colon-separated
33300 list of header names. This is confusing, because header names themselves are
33301 often terminated by colons. In this case, the colons are the list separators,
33302 not part of the names. For example:
33304 headers_remove = return-receipt-to:acknowledge-to
33307 Multiple &%headers_remove%& options for a single router or transport can be
33308 specified; the arguments will append to a single header-names list.
33309 Each item is separately expanded.
33310 Note that colons in complex expansions which are used to
33311 form all or part of a &%headers_remove%& list
33312 will act as list separators.
33314 When &%headers_add%& or &%headers_remove%& is specified on a router,
33315 items are expanded at routing time,
33316 and then associated with all addresses that are
33317 accepted by that router, and also with any new addresses that it generates. If
33318 an address passes through several routers as a result of aliasing or
33319 forwarding, the changes are cumulative.
33321 .oindex "&%unseen%&"
33322 However, this does not apply to multiple routers that result from the use of
33323 the &%unseen%& option. Any header modifications that were specified by the
33324 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33326 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33327 settings cannot be delivered together in a batch, so a transport is always
33328 dealing with a set of addresses that have the same header-processing
33331 The transport starts by writing the original set of header lines that arrived
33332 with the message, possibly modified by the system filter. As it writes out
33333 these lines, it consults the list of header names that were attached to the
33334 recipient address(es) by &%headers_remove%& options in routers, and it also
33335 consults the transport's own &%headers_remove%& option. Header lines whose
33336 names are on either of these lists are not written out. If there are multiple
33337 instances of any listed header, they are all skipped.
33339 After the remaining original header lines have been written, new header
33340 lines that were specified by routers' &%headers_add%& options are written, in
33341 the order in which they were attached to the address. These are followed by any
33342 header lines specified by the transport's &%headers_add%& option.
33344 This way of handling header line modifications in routers and transports has
33345 the following consequences:
33348 The original set of header lines, possibly modified by the system filter,
33349 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33350 to it, at all times.
33352 Header lines that are added by a router's
33353 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33354 expansion syntax in subsequent routers or the transport.
33356 Conversely, header lines that are specified for removal by &%headers_remove%&
33357 in a router remain visible to subsequent routers and the transport.
33359 Headers added to an address by &%headers_add%& in a router cannot be removed by
33360 a later router or by a transport.
33362 An added header can refer to the contents of an original header that is to be
33363 removed, even it has the same name as the added header. For example:
33365 headers_remove = subject
33366 headers_add = Subject: new subject (was: $h_subject:)
33370 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33371 for a &(redirect)& router that has the &%one_time%& option set.
33377 .section "Constructed addresses" "SECTconstr"
33378 .cindex "address" "constructed"
33379 .cindex "constructed address"
33380 When Exim constructs a sender address for a locally-generated message, it uses
33383 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33387 Zaphod Beeblebrox <zaphod@end.univ.example>
33389 The user name is obtained from the &%-F%& command line option if set, or
33390 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33391 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33392 ampersand character, this is replaced by the login name with the first letter
33393 upper cased, as is conventional in a number of operating systems. See the
33394 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33395 The &%unknown_username%& option can be used to specify user names in cases when
33396 there is no password file entry.
33399 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33400 parts of it if necessary. In addition, if it contains any non-printing
33401 characters, it is encoded as described in RFC 2047, which defines a way of
33402 including non-ASCII characters in header lines. The value of the
33403 &%headers_charset%& option specifies the name of the encoding that is used (the
33404 characters are assumed to be in this encoding). The setting of
33405 &%print_topbitchars%& controls whether characters with the top bit set (that
33406 is, with codes greater than 127) count as printing characters or not.
33410 .section "Case of local parts" "SECID230"
33411 .cindex "case of local parts"
33412 .cindex "local part" "case of"
33413 RFC 2822 states that the case of letters in the local parts of addresses cannot
33414 be assumed to be non-significant. Exim preserves the case of local parts of
33415 addresses, but by default it uses a lower-cased form when it is routing,
33416 because on most Unix systems, usernames are in lower case and case-insensitive
33417 routing is required. However, any particular router can be made to use the
33418 original case for local parts by setting the &%caseful_local_part%& generic
33421 .cindex "mixed-case login names"
33422 If you must have mixed-case user names on your system, the best way to proceed,
33423 assuming you want case-independent handling of incoming email, is to set up
33424 your first router to convert incoming local parts in your domains to the
33425 correct case by means of a file lookup. For example:
33429 domains = +local_domains
33430 data = ${lookup{$local_part}cdb\
33431 {/etc/usercased.cdb}{$value}fail}\
33434 For this router, the local part is forced to lower case by the default action
33435 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33436 up a new local part in the correct case. If you then set &%caseful_local_part%&
33437 on any subsequent routers which process your domains, they will operate on
33438 local parts with the correct case in a case-sensitive manner.
33442 .section "Dots in local parts" "SECID231"
33443 .cindex "dot" "in local part"
33444 .cindex "local part" "dots in"
33445 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33446 part may not begin or end with a dot, nor have two consecutive dots in the
33447 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33448 empty components for compatibility.
33452 .section "Rewriting addresses" "SECID232"
33453 .cindex "rewriting" "addresses"
33454 Rewriting of sender and recipient addresses, and addresses in headers, can
33455 happen automatically, or as the result of configuration options, as described
33456 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33457 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33459 Automatic rewriting includes qualification, as mentioned above. The other case
33460 in which it can happen is when an incomplete non-local domain is given. The
33461 routing process may cause this to be expanded into the full domain name. For
33462 example, a header such as
33466 might get rewritten as
33468 To: hare@teaparty.wonderland.fict.example
33470 Rewriting as a result of routing is the one kind of message processing that
33471 does not happen at input time, as it cannot be done until the address has
33474 Strictly, one should not do &'any'& deliveries of a message until all its
33475 addresses have been routed, in case any of the headers get changed as a
33476 result of routing. However, doing this in practice would hold up many
33477 deliveries for unreasonable amounts of time, just because one address could not
33478 immediately be routed. Exim therefore does not delay other deliveries when
33479 routing of one or more addresses is deferred.
33480 .ecindex IIDmesproc
33484 . ////////////////////////////////////////////////////////////////////////////
33485 . ////////////////////////////////////////////////////////////////////////////
33487 .chapter "SMTP processing" "CHAPSMTP"
33488 .scindex IIDsmtpproc1 "SMTP" "processing details"
33489 .scindex IIDsmtpproc2 "LMTP" "processing details"
33490 Exim supports a number of different ways of using the SMTP protocol, and its
33491 LMTP variant, which is an interactive protocol for transferring messages into a
33492 closed mail store application. This chapter contains details of how SMTP is
33493 processed. For incoming mail, the following are available:
33496 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33498 SMTP over the standard input and output (the &%-bs%& option);
33500 Batched SMTP on the standard input (the &%-bS%& option).
33503 For mail delivery, the following are available:
33506 SMTP over TCP/IP (the &(smtp)& transport);
33508 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33511 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33514 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33515 the &%use_bsmtp%& option set).
33518 &'Batched SMTP'& is the name for a process in which batches of messages are
33519 stored in or read from files (or pipes), in a format in which SMTP commands are
33520 used to contain the envelope information.
33524 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33525 .cindex "SMTP" "outgoing over TCP/IP"
33526 .cindex "outgoing SMTP over TCP/IP"
33527 .cindex "LMTP" "over TCP/IP"
33528 .cindex "outgoing LMTP over TCP/IP"
33531 .cindex "SIZE option on MAIL command"
33532 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33533 The &%protocol%& option selects which protocol is to be used, but the actual
33534 processing is the same in both cases.
33536 If, in response to its EHLO command, Exim is told that the SIZE
33537 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33538 command. The value of <&'n'&> is the message size plus the value of the
33539 &%size_addition%& option (default 1024) to allow for additions to the message
33540 such as per-transport header lines, or changes made in a
33541 .cindex "transport" "filter"
33542 .cindex "filter" "transport filter"
33543 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33546 If the remote server advertises support for PIPELINING, Exim uses the
33547 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33548 required for the transaction.
33550 If the remote server advertises support for the STARTTLS command, and Exim
33551 was built to support TLS encryption, it tries to start a TLS session unless the
33552 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33553 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33554 is called for verification.
33556 If the remote server advertises support for the AUTH command, Exim scans
33557 the authenticators configuration for any suitable client settings, as described
33558 in chapter &<<CHAPSMTPAUTH>>&.
33560 .cindex "carriage return"
33562 Responses from the remote host are supposed to be terminated by CR followed by
33563 LF. However, there are known to be hosts that do not send CR characters, so in
33564 order to be able to interwork with such hosts, Exim treats LF on its own as a
33567 If a message contains a number of different addresses, all those with the same
33568 characteristics (for example, the same envelope sender) that resolve to the
33569 same set of hosts, in the same order, are sent in a single SMTP transaction,
33570 even if they are for different domains, unless there are more than the setting
33571 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
33572 they are split into groups containing no more than &%max_rcpt%&s addresses
33573 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
33574 in parallel sessions. The order of hosts with identical MX values is not
33575 significant when checking whether addresses can be batched in this way.
33577 When the &(smtp)& transport suffers a temporary failure that is not
33578 message-related, Exim updates its transport-specific database, which contains
33579 records indexed by host name that remember which messages are waiting for each
33580 particular host. It also updates the retry database with new retry times.
33582 .cindex "hints database" "retry keys"
33583 Exim's retry hints are based on host name plus IP address, so if one address of
33584 a multi-homed host is broken, it will soon be skipped most of the time.
33585 See the next section for more detail about error handling.
33587 .cindex "SMTP" "passed connection"
33588 .cindex "SMTP" "batching over TCP/IP"
33589 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
33590 looks in the hints database for the transport to see if there are any queued
33591 messages waiting for the host to which it is connected. If it finds one, it
33592 creates a new Exim process using the &%-MC%& option (which can only be used by
33593 a process running as root or the Exim user) and passes the TCP/IP socket to it
33594 so that it can deliver another message using the same socket. The new process
33595 does only those deliveries that are routed to the connected host, and may in
33596 turn pass the socket on to a third process, and so on.
33598 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
33599 limit the number of messages sent down a single TCP/IP connection.
33601 .cindex "asterisk" "after IP address"
33602 The second and subsequent messages delivered down an existing connection are
33603 identified in the main log by the addition of an asterisk after the closing
33604 square bracket of the IP address.
33609 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
33610 .cindex "error" "in outgoing SMTP"
33611 .cindex "SMTP" "errors in outgoing"
33612 .cindex "host" "error"
33613 Three different kinds of error are recognized for outgoing SMTP: host errors,
33614 message errors, and recipient errors.
33617 .vitem "&*Host errors*&"
33618 A host error is not associated with a particular message or with a
33619 particular recipient of a message. The host errors are:
33622 Connection refused or timed out,
33624 Any error response code on connection,
33626 Any error response code to EHLO or HELO,
33628 Loss of connection at any time, except after &"."&,
33630 I/O errors at any time,
33632 Timeouts during the session, other than in response to MAIL, RCPT or
33633 the &"."& at the end of the data.
33636 For a host error, a permanent error response on connection, or in response to
33637 EHLO, causes all addresses routed to the host to be failed. Any other host
33638 error causes all addresses to be deferred, and retry data to be created for the
33639 host. It is not tried again, for any message, until its retry time arrives. If
33640 the current set of addresses are not all delivered in this run (to some
33641 alternative host), the message is added to the list of those waiting for this
33642 host, so if it is still undelivered when a subsequent successful delivery is
33643 made to the host, it will be sent down the same SMTP connection.
33645 .vitem "&*Message errors*&"
33646 .cindex "message" "error"
33647 A message error is associated with a particular message when sent to a
33648 particular host, but not with a particular recipient of the message. The
33649 message errors are:
33652 Any error response code to MAIL, DATA, or the &"."& that terminates
33655 Timeout after MAIL,
33657 Timeout or loss of connection after the &"."& that terminates the data. A
33658 timeout after the DATA command itself is treated as a host error, as is loss of
33659 connection at any other time.
33662 For a message error, a permanent error response (5&'xx'&) causes all addresses
33663 to be failed, and a delivery error report to be returned to the sender. A
33664 temporary error response (4&'xx'&), or one of the timeouts, causes all
33665 addresses to be deferred. Retry data is not created for the host, but instead,
33666 a retry record for the combination of host plus message id is created. The
33667 message is not added to the list of those waiting for this host. This ensures
33668 that the failing message will not be sent to this host again until the retry
33669 time arrives. However, other messages that are routed to the host are not
33670 affected, so if it is some property of the message that is causing the error,
33671 it will not stop the delivery of other mail.
33673 If the remote host specified support for the SIZE parameter in its response
33674 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
33675 over-large message will cause a message error because the error arrives as a
33678 .vitem "&*Recipient errors*&"
33679 .cindex "recipient" "error"
33680 A recipient error is associated with a particular recipient of a message. The
33681 recipient errors are:
33684 Any error response to RCPT,
33686 Timeout after RCPT.
33689 For a recipient error, a permanent error response (5&'xx'&) causes the
33690 recipient address to be failed, and a bounce message to be returned to the
33691 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
33692 address to be deferred, and routing retry data to be created for it. This is
33693 used to delay processing of the address in subsequent queue runs, until its
33694 routing retry time arrives. This applies to all messages, but because it
33695 operates only in queue runs, one attempt will be made to deliver a new message
33696 to the failing address before the delay starts to operate. This ensures that,
33697 if the failure is really related to the message rather than the recipient
33698 (&"message too big for this recipient"& is a possible example), other messages
33699 have a chance of getting delivered. If a delivery to the address does succeed,
33700 the retry information gets cleared, so all stuck messages get tried again, and
33701 the retry clock is reset.
33703 The message is not added to the list of those waiting for this host. Use of the
33704 host for other messages is unaffected, and except in the case of a timeout,
33705 other recipients are processed independently, and may be successfully delivered
33706 in the current SMTP session. After a timeout it is of course impossible to
33707 proceed with the session, so all addresses get deferred. However, those other
33708 than the one that failed do not suffer any subsequent retry delays. Therefore,
33709 if one recipient is causing trouble, the others have a chance of getting
33710 through when a subsequent delivery attempt occurs before the failing
33711 recipient's retry time.
33714 In all cases, if there are other hosts (or IP addresses) available for the
33715 current set of addresses (for example, from multiple MX records), they are
33716 tried in this run for any undelivered addresses, subject of course to their
33717 own retry data. In other words, recipient error retry data does not take effect
33718 until the next delivery attempt.
33720 Some hosts have been observed to give temporary error responses to every
33721 MAIL command at certain times (&"insufficient space"& has been seen). It
33722 would be nice if such circumstances could be recognized, and defer data for the
33723 host itself created, but this is not possible within the current Exim design.
33724 What actually happens is that retry data for every (host, message) combination
33727 The reason that timeouts after MAIL and RCPT are treated specially is that
33728 these can sometimes arise as a result of the remote host's verification
33729 procedures. Exim makes this assumption, and treats them as if a temporary error
33730 response had been received. A timeout after &"."& is treated specially because
33731 it is known that some broken implementations fail to recognize the end of the
33732 message if the last character of the last line is a binary zero. Thus, it is
33733 helpful to treat this case as a message error.
33735 Timeouts at other times are treated as host errors, assuming a problem with the
33736 host, or the connection to it. If a timeout after MAIL, RCPT,
33737 or &"."& is really a connection problem, the assumption is that at the next try
33738 the timeout is likely to occur at some other point in the dialogue, causing it
33739 then to be treated as a host error.
33741 There is experimental evidence that some MTAs drop the connection after the
33742 terminating &"."& if they do not like the contents of the message for some
33743 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
33744 should be given. That is why Exim treats this case as a message rather than a
33745 host error, in order not to delay other messages to the same host.
33750 .section "Incoming SMTP messages over TCP/IP" "SECID233"
33751 .cindex "SMTP" "incoming over TCP/IP"
33752 .cindex "incoming SMTP over TCP/IP"
33755 Incoming SMTP messages can be accepted in one of two ways: by running a
33756 listening daemon, or by using &'inetd'&. In the latter case, the entry in
33757 &_/etc/inetd.conf_& should be like this:
33759 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
33761 Exim distinguishes between this case and the case of a locally running user
33762 agent using the &%-bs%& option by checking whether or not the standard input is
33763 a socket. When it is, either the port must be privileged (less than 1024), or
33764 the caller must be root or the Exim user. If any other user passes a socket
33765 with an unprivileged port number, Exim prints a message on the standard error
33766 stream and exits with an error code.
33768 By default, Exim does not make a log entry when a remote host connects or
33769 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
33770 unexpected. It can be made to write such log entries by setting the
33771 &%smtp_connection%& log selector.
33773 .cindex "carriage return"
33775 Commands from the remote host are supposed to be terminated by CR followed by
33776 LF. However, there are known to be hosts that do not send CR characters. In
33777 order to be able to interwork with such hosts, Exim treats LF on its own as a
33779 Furthermore, because common code is used for receiving messages from all
33780 sources, a CR on its own is also interpreted as a line terminator. However, the
33781 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
33783 .cindex "EHLO" "invalid data"
33784 .cindex "HELO" "invalid data"
33785 One area that sometimes gives rise to problems concerns the EHLO or
33786 HELO commands. Some clients send syntactically invalid versions of these
33787 commands, which Exim rejects by default. (This is nothing to do with verifying
33788 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
33789 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
33790 match the broken hosts that send invalid commands.
33792 .cindex "SIZE option on MAIL command"
33793 .cindex "MAIL" "SIZE option"
33794 The amount of disk space available is checked whenever SIZE is received on
33795 a MAIL command, independently of whether &%message_size_limit%& or
33796 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
33797 false. A temporary error is given if there is not enough space. If
33798 &%check_spool_space%& is set, the check is for that amount of space plus the
33799 value given with SIZE, that is, it checks that the addition of the incoming
33800 message will not reduce the space below the threshold.
33802 When a message is successfully received, Exim includes the local message id in
33803 its response to the final &"."& that terminates the data. If the remote host
33804 logs this text it can help with tracing what has happened to a message.
33806 The Exim daemon can limit the number of simultaneous incoming connections it is
33807 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
33808 number of simultaneous incoming connections from a single remote host (see the
33809 &%smtp_accept_max_per_host%& option). Additional connection attempts are
33810 rejected using the SMTP temporary error code 421.
33812 The Exim daemon does not rely on the SIGCHLD signal to detect when a
33813 subprocess has finished, as this can get lost at busy times. Instead, it looks
33814 for completed subprocesses every time it wakes up. Provided there are other
33815 things happening (new incoming calls, starts of queue runs), completed
33816 processes will be noticed and tidied away. On very quiet systems you may
33817 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
33818 it will be noticed when the daemon next wakes up.
33820 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
33821 and can also be set up to reject SMTP calls from non-reserved hosts at times of
33822 high system load &-- for details see the &%smtp_accept_reserve%&,
33823 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
33824 applies in both the daemon and &'inetd'& cases.
33826 Exim normally starts a delivery process for each message received, though this
33827 can be varied by means of the &%-odq%& command line option and the
33828 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
33829 number of simultaneously running delivery processes started in this way from
33830 SMTP input can be limited by the &%smtp_accept_queue%& and
33831 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
33832 subsequently received messages are just put on the input queue without starting
33833 a delivery process.
33835 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
33836 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
33837 started up from the &'inetd'& daemon, because in that case each connection is
33838 handled by an entirely independent Exim process. Control by load average is,
33839 however, available with &'inetd'&.
33841 Exim can be configured to verify addresses in incoming SMTP commands as they
33842 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
33843 to rewrite addresses at this time &-- before any syntax checking is done. See
33844 section &<<SECTrewriteS>>&.
33846 Exim can also be configured to limit the rate at which a client host submits
33847 MAIL and RCPT commands in a single SMTP session. See the
33848 &%smtp_ratelimit_hosts%& option.
33852 .section "Unrecognized SMTP commands" "SECID234"
33853 .cindex "SMTP" "unrecognized commands"
33854 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
33855 commands during a single SMTP connection, it drops the connection after sending
33856 the error response to the last command. The default value for
33857 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
33858 abuse that subvert web servers into making connections to SMTP ports; in these
33859 circumstances, a number of non-SMTP lines are sent first.
33862 .section "Syntax and protocol errors in SMTP commands" "SECID235"
33863 .cindex "SMTP" "syntax errors"
33864 .cindex "SMTP" "protocol errors"
33865 A syntax error is detected if an SMTP command is recognized, but there is
33866 something syntactically wrong with its data, for example, a malformed email
33867 address in a RCPT command. Protocol errors include invalid command
33868 sequencing such as RCPT before MAIL. If Exim receives more than
33869 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
33870 drops the connection after sending the error response to the last command. The
33871 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
33872 broken clients that loop sending bad commands (yes, it has been seen).
33876 .section "Use of non-mail SMTP commands" "SECID236"
33877 .cindex "SMTP" "non-mail commands"
33878 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
33879 DATA. Exim counts such commands, and drops the connection if there are too
33880 many of them in a single SMTP session. This action catches some
33881 denial-of-service attempts and things like repeated failing AUTHs, or a mad
33882 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
33883 defines what &"too many"& means. Its default value is 10.
33885 When a new message is expected, one occurrence of RSET is not counted. This
33886 allows a client to send one RSET between messages (this is not necessary,
33887 but some clients do it). Exim also allows one uncounted occurrence of HELO
33888 or EHLO, and one occurrence of STARTTLS between messages. After
33889 starting up a TLS session, another EHLO is expected, and so it too is not
33892 The first occurrence of AUTH in a connection, or immediately following
33893 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
33894 RCPT, DATA, and QUIT are counted.
33896 You can control which hosts are subject to the limit set by
33897 &%smtp_accept_max_nonmail%& by setting
33898 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
33899 the limit apply to all hosts. This option means that you can exclude any
33900 specific badly-behaved hosts that you have to live with.
33905 .section "The VRFY and EXPN commands" "SECID237"
33906 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
33907 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
33908 appropriate) in order to decide whether the command should be accepted or not.
33909 If no ACL is defined, the command is rejected.
33911 .cindex "VRFY" "processing"
33912 When VRFY is accepted, it runs exactly the same code as when Exim is
33913 called with the &%-bv%& option.
33915 .cindex "EXPN" "processing"
33916 When EXPN is accepted, a single-level expansion of the address is done.
33917 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
33918 than a verification (the &%-bv%& option). If an unqualified local part is given
33919 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
33920 of VRFY and EXPN commands are logged on the main and reject logs, and
33921 VRFY verification failures are logged on the main log for consistency with
33926 .section "The ETRN command" "SECTETRN"
33927 .cindex "ETRN" "processing"
33928 RFC 1985 describes an SMTP command called ETRN that is designed to
33929 overcome the security problems of the TURN command (which has fallen into
33930 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
33931 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
33932 should be accepted or not. If no ACL is defined, the command is rejected.
33934 The ETRN command is concerned with &"releasing"& messages that are awaiting
33935 delivery to certain hosts. As Exim does not organize its message queue by host,
33936 the only form of ETRN that is supported by default is the one where the
33937 text starts with the &"#"& prefix, in which case the remainder of the text is
33938 specific to the SMTP server. A valid ETRN command causes a run of Exim with
33939 the &%-R%& option to happen, with the remainder of the ETRN text as its
33940 argument. For example,
33948 which causes a delivery attempt on all messages with undelivered addresses
33949 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
33950 default), Exim prevents the simultaneous execution of more than one queue run
33951 for the same argument string as a result of an ETRN command. This stops
33952 a misbehaving client from starting more than one queue runner at once.
33954 .cindex "hints database" "ETRN serialization"
33955 Exim implements the serialization by means of a hints database in which a
33956 record is written whenever a process is started by ETRN, and deleted when
33957 the process completes. However, Exim does not keep the SMTP session waiting for
33958 the ETRN process to complete. Once ETRN is accepted, the client is sent
33959 a &"success"& return code. Obviously there is scope for hints records to get
33960 left lying around if there is a system or program crash. To guard against this,
33961 Exim ignores any records that are more than six hours old.
33963 .oindex "&%smtp_etrn_command%&"
33964 For more control over what ETRN does, the &%smtp_etrn_command%& option can
33965 used. This specifies a command that is run whenever ETRN is received,
33966 whatever the form of its argument. For
33969 smtp_etrn_command = /etc/etrn_command $domain \
33970 $sender_host_address
33972 .vindex "&$domain$&"
33973 The string is split up into arguments which are independently expanded. The
33974 expansion variable &$domain$& is set to the argument of the ETRN command,
33975 and no syntax checking is done on the contents of this argument. Exim does not
33976 wait for the command to complete, so its status code is not checked. Exim runs
33977 under its own uid and gid when receiving incoming SMTP, so it is not possible
33978 for it to change them before running the command.
33982 .section "Incoming local SMTP" "SECID238"
33983 .cindex "SMTP" "local incoming"
33984 Some user agents use SMTP to pass messages to their local MTA using the
33985 standard input and output, as opposed to passing the envelope on the command
33986 line and writing the message to the standard input. This is supported by the
33987 &%-bs%& option. This form of SMTP is handled in the same way as incoming
33988 messages over TCP/IP (including the use of ACLs), except that the envelope
33989 sender given in a MAIL command is ignored unless the caller is trusted. In
33990 an ACL you can detect this form of SMTP input by testing for an empty host
33991 identification. It is common to have this as the first line in the ACL that
33992 runs for RCPT commands:
33996 This accepts SMTP messages from local processes without doing any other tests.
34000 .section "Outgoing batched SMTP" "SECTbatchSMTP"
34001 .cindex "SMTP" "batched outgoing"
34002 .cindex "batched SMTP output"
34003 Both the &(appendfile)& and &(pipe)& transports can be used for handling
34004 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
34005 be output in BSMTP format. No SMTP responses are possible for this form of
34006 delivery. All it is doing is using SMTP commands as a way of transmitting the
34007 envelope along with the message.
34009 The message is written to the file or pipe preceded by the SMTP commands
34010 MAIL and RCPT, and followed by a line containing a single dot. Lines in
34011 the message that start with a dot have an extra dot added. The SMTP command
34012 HELO is not normally used. If it is required, the &%message_prefix%& option
34013 can be used to specify it.
34015 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
34016 one recipient address at a time by default. However, you can arrange for them
34017 to handle several addresses at once by setting the &%batch_max%& option. When
34018 this is done for BSMTP, messages may contain multiple RCPT commands. See
34019 chapter &<<CHAPbatching>>& for more details.
34022 When one or more addresses are routed to a BSMTP transport by a router that
34023 sets up a host list, the name of the first host on the list is available to the
34024 transport in the variable &$host$&. Here is an example of such a transport and
34029 driver = manualroute
34030 transport = smtp_appendfile
34031 route_list = domain.example batch.host.example
34035 driver = appendfile
34036 directory = /var/bsmtp/$host
34041 This causes messages addressed to &'domain.example'& to be written in BSMTP
34042 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
34043 message (unless there are more than 1000 recipients).
34047 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
34048 .cindex "SMTP" "batched incoming"
34049 .cindex "batched SMTP input"
34050 The &%-bS%& command line option causes Exim to accept one or more messages by
34051 reading SMTP on the standard input, but to generate no responses. If the caller
34052 is trusted, the senders in the MAIL commands are believed; otherwise the
34053 sender is always the caller of Exim. Unqualified senders and receivers are not
34054 rejected (there seems little point) but instead just get qualified. HELO
34055 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
34056 as NOOP; QUIT quits.
34058 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34059 ACL is run in the same way as for non-SMTP local input.
34061 If an error is detected while reading a message, including a missing &"."& at
34062 the end, Exim gives up immediately. It writes details of the error to the
34063 standard output in a stylized way that the calling program should be able to
34064 make some use of automatically, for example:
34066 554 Unexpected end of file
34067 Transaction started in line 10
34068 Error detected in line 14
34070 It writes a more verbose version, for human consumption, to the standard error
34073 An error was detected while processing a file of BSMTP input.
34074 The error message was:
34076 501 '>' missing at end of address
34078 The SMTP transaction started in line 10.
34079 The error was detected in line 12.
34080 The SMTP command at fault was:
34082 rcpt to:<malformed@in.com.plete
34084 1 previous message was successfully processed.
34085 The rest of the batch was abandoned.
34087 The return code from Exim is zero only if there were no errors. It is 1 if some
34088 messages were accepted before an error was detected, and 2 if no messages were
34090 .ecindex IIDsmtpproc1
34091 .ecindex IIDsmtpproc2
34095 . ////////////////////////////////////////////////////////////////////////////
34096 . ////////////////////////////////////////////////////////////////////////////
34098 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34099 "Customizing messages"
34100 When a message fails to be delivered, or remains on the queue for more than a
34101 configured amount of time, Exim sends a message to the original sender, or
34102 to an alternative configured address. The text of these messages is built into
34103 the code of Exim, but it is possible to change it, either by adding a single
34104 string, or by replacing each of the paragraphs by text supplied in a file.
34106 The &'From:'& and &'To:'& header lines are automatically generated; you can
34107 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34108 option. Exim also adds the line
34110 Auto-Submitted: auto-generated
34112 to all warning and bounce messages,
34115 .section "Customizing bounce messages" "SECID239"
34116 .cindex "customizing" "bounce message"
34117 .cindex "bounce message" "customizing"
34118 If &%bounce_message_text%& is set, its contents are included in the default
34119 message immediately after &"This message was created automatically by mail
34120 delivery software."& The string is not expanded. It is not used if
34121 &%bounce_message_file%& is set.
34123 When &%bounce_message_file%& is set, it must point to a template file for
34124 constructing error messages. The file consists of a series of text items,
34125 separated by lines consisting of exactly four asterisks. If the file cannot be
34126 opened, default text is used and a message is written to the main and panic
34127 logs. If any text item in the file is empty, default text is used for that
34130 .vindex "&$bounce_recipient$&"
34131 .vindex "&$bounce_return_size_limit$&"
34132 Each item of text that is read from the file is expanded, and there are two
34133 expansion variables which can be of use here: &$bounce_recipient$& is set to
34134 the recipient of an error message while it is being created, and
34135 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34136 option, rounded to a whole number.
34138 The items must appear in the file in the following order:
34141 The first item is included in the headers, and should include at least a
34142 &'Subject:'& header. Exim does not check the syntax of these headers.
34144 The second item forms the start of the error message. After it, Exim lists the
34145 failing addresses with their error messages.
34147 The third item is used to introduce any text from pipe transports that is to be
34148 returned to the sender. It is omitted if there is no such text.
34151 The fourth, fifth and sixth items will be ignored and may be empty.
34152 The fields exist for back-compatibility
34156 The default state (&%bounce_message_file%& unset) is equivalent to the
34157 following file, in which the sixth item is empty. The &'Subject:'& and some
34158 other lines have been split in order to fit them on the page:
34160 Subject: Mail delivery failed
34161 ${if eq{$sender_address}{$bounce_recipient}
34162 {: returning message to sender}}
34164 This message was created automatically by mail delivery software.
34166 A message ${if eq{$sender_address}{$bounce_recipient}
34167 {that you sent }{sent by
34171 }}could not be delivered to all of its recipients.
34172 This is a permanent error. The following address(es) failed:
34174 The following text was generated during the delivery attempt(s):
34176 ------ This is a copy of the message, including all the headers.
34179 ------ The body of the message is $message_size characters long;
34181 ------ $bounce_return_size_limit or so are included here.
34184 .section "Customizing warning messages" "SECTcustwarn"
34185 .cindex "customizing" "warning message"
34186 .cindex "warning of delay" "customizing the message"
34187 The option &%warn_message_file%& can be pointed at a template file for use when
34188 warnings about message delays are created. In this case there are only three
34192 The first item is included in the headers, and should include at least a
34193 &'Subject:'& header. Exim does not check the syntax of these headers.
34195 The second item forms the start of the warning message. After it, Exim lists
34196 the delayed addresses.
34198 The third item then ends the message.
34201 The default state is equivalent to the following file, except that some lines
34202 have been split here, in order to fit them on the page:
34204 Subject: Warning: message $message_exim_id delayed
34205 $warn_message_delay
34207 This message was created automatically by mail delivery software.
34209 A message ${if eq{$sender_address}{$warn_message_recipients}
34210 {that you sent }{sent by
34214 }}has not been delivered to all of its recipients after
34215 more than $warn_message_delay on the queue on $primary_hostname.
34217 The message identifier is: $message_exim_id
34218 The subject of the message is: $h_subject
34219 The date of the message is: $h_date
34221 The following address(es) have not yet been delivered:
34223 No action is required on your part. Delivery attempts will
34224 continue for some time, and this warning may be repeated at
34225 intervals if the message remains undelivered. Eventually the
34226 mail delivery software will give up, and when that happens,
34227 the message will be returned to you.
34229 .vindex "&$warn_message_delay$&"
34230 .vindex "&$warn_message_recipients$&"
34231 However, in the default state the subject and date lines are omitted if no
34232 appropriate headers exist. During the expansion of this file,
34233 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34234 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34235 of recipients for the warning message. There may be more than one if there are
34236 multiple addresses with different &%errors_to%& settings on the routers that
34242 . ////////////////////////////////////////////////////////////////////////////
34243 . ////////////////////////////////////////////////////////////////////////////
34245 .chapter "Some common configuration settings" "CHAPcomconreq"
34246 This chapter discusses some configuration settings that seem to be fairly
34247 common. More examples and discussion can be found in the Exim book.
34251 .section "Sending mail to a smart host" "SECID240"
34252 .cindex "smart host" "example router"
34253 If you want to send all mail for non-local domains to a &"smart host"&, you
34254 should replace the default &(dnslookup)& router with a router which does the
34255 routing explicitly:
34257 send_to_smart_host:
34258 driver = manualroute
34259 route_list = !+local_domains smart.host.name
34260 transport = remote_smtp
34262 You can use the smart host's IP address instead of the name if you wish.
34263 If you are using Exim only to submit messages to a smart host, and not for
34264 receiving incoming messages, you can arrange for it to do the submission
34265 synchronously by setting the &%mua_wrapper%& option (see chapter
34266 &<<CHAPnonqueueing>>&).
34271 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34272 .cindex "mailing lists"
34273 Exim can be used to run simple mailing lists, but for large and/or complicated
34274 requirements, the use of additional specialized mailing list software such as
34275 Majordomo or Mailman is recommended.
34277 The &(redirect)& router can be used to handle mailing lists where each list
34278 is maintained in a separate file, which can therefore be managed by an
34279 independent manager. The &%domains%& router option can be used to run these
34280 lists in a separate domain from normal mail. For example:
34284 domains = lists.example
34285 file = /usr/lists/$local_part
34288 errors_to = $local_part-request@lists.example
34291 This router is skipped for domains other than &'lists.example'&. For addresses
34292 in that domain, it looks for a file that matches the local part. If there is no
34293 such file, the router declines, but because &%no_more%& is set, no subsequent
34294 routers are tried, and so the whole delivery fails.
34296 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34297 expanded into a file name or a pipe delivery, which is usually inappropriate in
34300 .oindex "&%errors_to%&"
34301 The &%errors_to%& option specifies that any delivery errors caused by addresses
34302 taken from a mailing list are to be sent to the given address rather than the
34303 original sender of the message. However, before acting on this, Exim verifies
34304 the error address, and ignores it if verification fails.
34306 For example, using the configuration above, mail sent to
34307 &'dicts@lists.example'& is passed on to those addresses contained in
34308 &_/usr/lists/dicts_&, with error reports directed to
34309 &'dicts-request@lists.example'&, provided that this address can be verified.
34310 There could be a file called &_/usr/lists/dicts-request_& containing
34311 the address(es) of this particular list's manager(s), but other approaches,
34312 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34313 or &%local_part_suffix%& options) to handle addresses of the form
34314 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34318 .section "Syntax errors in mailing lists" "SECID241"
34319 .cindex "mailing lists" "syntax errors in"
34320 If an entry in redirection data contains a syntax error, Exim normally defers
34321 delivery of the original address. That means that a syntax error in a mailing
34322 list holds up all deliveries to the list. This may not be appropriate when a
34323 list is being maintained automatically from data supplied by users, and the
34324 addresses are not rigorously checked.
34326 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34327 entries that fail to parse, noting the incident in the log. If in addition
34328 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34329 whenever a broken address is skipped. It is usually appropriate to set
34330 &%syntax_errors_to%& to the same address as &%errors_to%&.
34334 .section "Re-expansion of mailing lists" "SECID242"
34335 .cindex "mailing lists" "re-expansion of"
34336 Exim remembers every individual address to which a message has been delivered,
34337 in order to avoid duplication, but it normally stores only the original
34338 recipient addresses with a message. If all the deliveries to a mailing list
34339 cannot be done at the first attempt, the mailing list is re-expanded when the
34340 delivery is next tried. This means that alterations to the list are taken into
34341 account at each delivery attempt, so addresses that have been added to
34342 the list since the message arrived will therefore receive a copy of the
34343 message, even though it pre-dates their subscription.
34345 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34346 on the &(redirect)& router. If this is done, any addresses generated by the
34347 router that fail to deliver at the first attempt are added to the message as
34348 &"top level"& addresses, and the parent address that generated them is marked
34349 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34350 subsequent delivery attempts. The disadvantage of this is that if any of the
34351 failing addresses are incorrect, correcting them in the file has no effect on
34352 pre-existing messages.
34354 The original top-level address is remembered with each of the generated
34355 addresses, and is output in any log messages. However, any intermediate parent
34356 addresses are not recorded. This makes a difference to the log only if the
34357 &%all_parents%& selector is set, but for mailing lists there is normally only
34358 one level of expansion anyway.
34362 .section "Closed mailing lists" "SECID243"
34363 .cindex "mailing lists" "closed"
34364 The examples so far have assumed open mailing lists, to which anybody may
34365 send mail. It is also possible to set up closed lists, where mail is accepted
34366 from specified senders only. This is done by making use of the generic
34367 &%senders%& option to restrict the router that handles the list.
34369 The following example uses the same file as a list of recipients and as a list
34370 of permitted senders. It requires three routers:
34374 domains = lists.example
34375 local_part_suffix = -request
34376 file = /usr/lists/$local_part$local_part_suffix
34381 domains = lists.example
34382 senders = ${if exists {/usr/lists/$local_part}\
34383 {lsearch;/usr/lists/$local_part}{*}}
34384 file = /usr/lists/$local_part
34387 errors_to = $local_part-request@lists.example
34392 domains = lists.example
34394 data = :fail: $local_part@lists.example is a closed mailing list
34396 All three routers have the same &%domains%& setting, so for any other domains,
34397 they are all skipped. The first router runs only if the local part ends in
34398 &%-request%&. It handles messages to the list manager(s) by means of an open
34401 The second router runs only if the &%senders%& precondition is satisfied. It
34402 checks for the existence of a list that corresponds to the local part, and then
34403 checks that the sender is on the list by means of a linear search. It is
34404 necessary to check for the existence of the file before trying to search it,
34405 because otherwise Exim thinks there is a configuration error. If the file does
34406 not exist, the expansion of &%senders%& is *, which matches all senders. This
34407 means that the router runs, but because there is no list, declines, and
34408 &%no_more%& ensures that no further routers are run. The address fails with an
34409 &"unrouteable address"& error.
34411 The third router runs only if the second router is skipped, which happens when
34412 a mailing list exists, but the sender is not on it. This router forcibly fails
34413 the address, giving a suitable error message.
34418 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34420 .cindex "Variable Envelope Return Paths"
34421 .cindex "envelope sender"
34422 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34423 are a way of helping mailing list administrators discover which subscription
34424 address is the cause of a particular delivery failure. The idea is to encode
34425 the original recipient address in the outgoing envelope sender address, so that
34426 if the message is forwarded by another host and then subsequently bounces, the
34427 original recipient can be extracted from the recipient address of the bounce.
34429 .oindex &%errors_to%&
34430 .oindex &%return_path%&
34431 Envelope sender addresses can be modified by Exim using two different
34432 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34433 list examples), or the &%return_path%& option on a transport. The second of
34434 these is effective only if the message is successfully delivered to another
34435 host; it is not used for errors detected on the local host (see the description
34436 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34437 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34443 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34444 {$1-request+$local_part=$domain@your.dom.example}fail}
34446 This has the effect of rewriting the return path (envelope sender) on outgoing
34447 SMTP messages, if the local part of the original return path ends in
34448 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34449 local part and domain of the recipient into the return path. Suppose, for
34450 example, that a message whose return path has been set to
34451 &'somelist-request@your.dom.example'& is sent to
34452 &'subscriber@other.dom.example'&. In the transport, the return path is
34455 somelist-request+subscriber=other.dom.example@your.dom.example
34457 .vindex "&$local_part$&"
34458 For this to work, you must tell Exim to send multiple copies of messages that
34459 have more than one recipient, so that each copy has just one recipient. This is
34460 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34461 might be sent to several different recipients in the same domain, in which case
34462 &$local_part$& is not available in the transport, because it is not unique.
34464 Unless your host is doing nothing but mailing list deliveries, you should
34465 probably use a separate transport for the VERP deliveries, so as not to use
34466 extra resources in making one-per-recipient copies for other deliveries. This
34467 can easily be done by expanding the &%transport%& option in the router:
34471 domains = ! +local_domains
34473 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34474 {verp_smtp}{remote_smtp}}
34477 If you want to change the return path using &%errors_to%& in a router instead
34478 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34479 routers that handle mailing list addresses. This will ensure that all delivery
34480 errors, including those detected on the local host, are sent to the VERP
34483 On a host that does no local deliveries and has no manual routing, only the
34484 &(dnslookup)& router needs to be changed. A special transport is not needed for
34485 SMTP deliveries. Every mailing list recipient has its own return path value,
34486 and so Exim must hand them to the transport one at a time. Here is an example
34487 of a &(dnslookup)& router that implements VERP:
34491 domains = ! +local_domains
34492 transport = remote_smtp
34494 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34495 {$1-request+$local_part=$domain@your.dom.example}fail}
34498 Before you start sending out messages with VERPed return paths, you must also
34499 configure Exim to accept the bounce messages that come back to those paths.
34500 Typically this is done by setting a &%local_part_suffix%& option for a
34501 router, and using this to route the messages to wherever you want to handle
34504 The overhead incurred in using VERP depends very much on the size of the
34505 message, the number of recipient addresses that resolve to the same remote
34506 host, and the speed of the connection over which the message is being sent. If
34507 a lot of addresses resolve to the same host and the connection is slow, sending
34508 a separate copy of the message for each address may take substantially longer
34509 than sending a single copy with many recipients (for which VERP cannot be
34517 .section "Virtual domains" "SECTvirtualdomains"
34518 .cindex "virtual domains"
34519 .cindex "domain" "virtual"
34520 The phrase &'virtual domain'& is unfortunately used with two rather different
34524 A domain for which there are no real mailboxes; all valid local parts are
34525 aliases for other email addresses. Common examples are organizational
34526 top-level domains and &"vanity"& domains.
34528 One of a number of independent domains that are all handled by the same host,
34529 with mailboxes on that host, but where the mailbox owners do not necessarily
34530 have login accounts on that host.
34533 The first usage is probably more common, and does seem more &"virtual"& than
34534 the second. This kind of domain can be handled in Exim with a straightforward
34535 aliasing router. One approach is to create a separate alias file for each
34536 virtual domain. Exim can test for the existence of the alias file to determine
34537 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34538 to a router of this form:
34542 domains = dsearch;/etc/mail/virtual
34543 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34546 The &%domains%& option specifies that the router is to be skipped, unless there
34547 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34548 domain that is being processed. When the router runs, it looks up the local
34549 part in the file to find a new address (or list of addresses). The &%no_more%&
34550 setting ensures that if the lookup fails (leading to &%data%& being an empty
34551 string), Exim gives up on the address without trying any subsequent routers.
34553 This one router can handle all the virtual domains because the alias file names
34554 follow a fixed pattern. Permissions can be arranged so that appropriate people
34555 can edit the different alias files. A successful aliasing operation results in
34556 a new envelope recipient address, which is then routed from scratch.
34558 The other kind of &"virtual"& domain can also be handled in a straightforward
34559 way. One approach is to create a file for each domain containing a list of
34560 valid local parts, and use it in a router like this:
34564 domains = dsearch;/etc/mail/domains
34565 local_parts = lsearch;/etc/mail/domains/$domain
34566 transport = my_mailboxes
34568 The address is accepted if there is a file for the domain, and the local part
34569 can be found in the file. The &%domains%& option is used to check for the
34570 file's existence because &%domains%& is tested before the &%local_parts%&
34571 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
34572 because that option is tested after &%local_parts%&. The transport is as
34576 driver = appendfile
34577 file = /var/mail/$domain/$local_part
34580 This uses a directory of mailboxes for each domain. The &%user%& setting is
34581 required, to specify which uid is to be used for writing to the mailboxes.
34583 The configuration shown here is just one example of how you might support this
34584 requirement. There are many other ways this kind of configuration can be set
34585 up, for example, by using a database instead of separate files to hold all the
34586 information about the domains.
34590 .section "Multiple user mailboxes" "SECTmulbox"
34591 .cindex "multiple mailboxes"
34592 .cindex "mailbox" "multiple"
34593 .cindex "local part" "prefix"
34594 .cindex "local part" "suffix"
34595 Heavy email users often want to operate with multiple mailboxes, into which
34596 incoming mail is automatically sorted. A popular way of handling this is to
34597 allow users to use multiple sender addresses, so that replies can easily be
34598 identified. Users are permitted to add prefixes or suffixes to their local
34599 parts for this purpose. The wildcard facility of the generic router options
34600 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
34601 example, consider this router:
34606 file = $home/.forward
34607 local_part_suffix = -*
34608 local_part_suffix_optional
34611 .vindex "&$local_part_suffix$&"
34612 It runs a user's &_.forward_& file for all local parts of the form
34613 &'username-*'&. Within the filter file the user can distinguish different
34614 cases by testing the variable &$local_part_suffix$&. For example:
34616 if $local_part_suffix contains -special then
34617 save /home/$local_part/Mail/special
34620 If the filter file does not exist, or does not deal with such addresses, they
34621 fall through to subsequent routers, and, assuming no subsequent use of the
34622 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
34623 control over which suffixes are valid.
34625 Alternatively, a suffix can be used to trigger the use of a different
34626 &_.forward_& file &-- which is the way a similar facility is implemented in
34632 file = $home/.forward$local_part_suffix
34633 local_part_suffix = -*
34634 local_part_suffix_optional
34637 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
34638 example, &_.forward-special_& is used. Once again, if the appropriate file
34639 does not exist, or does not deal with the address, it is passed on to
34640 subsequent routers, which could, if required, look for an unqualified
34641 &_.forward_& file to use as a default.
34645 .section "Simplified vacation processing" "SECID244"
34646 .cindex "vacation processing"
34647 The traditional way of running the &'vacation'& program is for a user to set up
34648 a pipe command in a &_.forward_& file
34649 (see section &<<SECTspecitredli>>& for syntax details).
34650 This is prone to error by inexperienced users. There are two features of Exim
34651 that can be used to make this process simpler for users:
34654 A local part prefix such as &"vacation-"& can be specified on a router which
34655 can cause the message to be delivered directly to the &'vacation'& program, or
34656 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
34657 &_.forward_& file are then much simpler. For example:
34659 spqr, vacation-spqr
34662 The &%require_files%& generic router option can be used to trigger a
34663 vacation delivery by checking for the existence of a certain file in the
34664 user's home directory. The &%unseen%& generic option should also be used, to
34665 ensure that the original delivery also proceeds. In this case, all the user has
34666 to do is to create a file called, say, &_.vacation_&, containing a vacation
34670 Another advantage of both these methods is that they both work even when the
34671 use of arbitrary pipes by users is locked out.
34675 .section "Taking copies of mail" "SECID245"
34676 .cindex "message" "copying every"
34677 Some installations have policies that require archive copies of all messages to
34678 be made. A single copy of each message can easily be taken by an appropriate
34679 command in a system filter, which could, for example, use a different file for
34680 each day's messages.
34682 There is also a shadow transport mechanism that can be used to take copies of
34683 messages that are successfully delivered by local transports, one copy per
34684 delivery. This could be used, &'inter alia'&, to implement automatic
34685 notification of delivery by sites that insist on doing such things.
34689 .section "Intermittently connected hosts" "SECID246"
34690 .cindex "intermittently connected hosts"
34691 It has become quite common (because it is cheaper) for hosts to connect to the
34692 Internet periodically rather than remain connected all the time. The normal
34693 arrangement is that mail for such hosts accumulates on a system that is
34694 permanently connected.
34696 Exim was designed for use on permanently connected hosts, and so it is not
34697 particularly well-suited to use in an intermittently connected environment.
34698 Nevertheless there are some features that can be used.
34701 .section "Exim on the upstream server host" "SECID247"
34702 It is tempting to arrange for incoming mail for the intermittently connected
34703 host to remain on Exim's queue until the client connects. However, this
34704 approach does not scale very well. Two different kinds of waiting message are
34705 being mixed up in the same queue &-- those that cannot be delivered because of
34706 some temporary problem, and those that are waiting for their destination host
34707 to connect. This makes it hard to manage the queue, as well as wasting
34708 resources, because each queue runner scans the entire queue.
34710 A better approach is to separate off those messages that are waiting for an
34711 intermittently connected host. This can be done by delivering these messages
34712 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
34713 format, from where they are transmitted by other software when their
34714 destination connects. This makes it easy to collect all the mail for one host
34715 in a single directory, and to apply local timeout rules on a per-message basis
34718 On a very small scale, leaving the mail on Exim's queue can be made to work. If
34719 you are doing this, you should configure Exim with a long retry period for the
34720 intermittent host. For example:
34722 cheshire.wonderland.fict.example * F,5d,24h
34724 This stops a lot of failed delivery attempts from occurring, but Exim remembers
34725 which messages it has queued up for that host. Once the intermittent host comes
34726 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
34727 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
34728 causes all the queued up messages to be delivered, often down a single SMTP
34729 connection. While the host remains connected, any new messages get delivered
34732 If the connecting hosts do not have fixed IP addresses, that is, if a host is
34733 issued with a different IP address each time it connects, Exim's retry
34734 mechanisms on the holding host get confused, because the IP address is normally
34735 used as part of the key string for holding retry information. This can be
34736 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
34737 Since this has disadvantages for permanently connected hosts, it is best to
34738 arrange a separate transport for the intermittently connected ones.
34742 .section "Exim on the intermittently connected client host" "SECID248"
34743 The value of &%smtp_accept_queue_per_connection%& should probably be
34744 increased, or even set to zero (that is, disabled) on the intermittently
34745 connected host, so that all incoming messages down a single connection get
34746 delivered immediately.
34748 .cindex "SMTP" "passed connection"
34749 .cindex "SMTP" "multiple deliveries"
34750 .cindex "multiple SMTP deliveries"
34751 Mail waiting to be sent from an intermittently connected host will probably
34752 not have been routed, because without a connection DNS lookups are not
34753 possible. This means that if a normal queue run is done at connection time,
34754 each message is likely to be sent in a separate SMTP session. This can be
34755 avoided by starting the queue run with a command line option beginning with
34756 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
34757 first pass, routing is done but no deliveries take place. The second pass is a
34758 normal queue run; since all the messages have been previously routed, those
34759 destined for the same host are likely to get sent as multiple deliveries in a
34760 single SMTP connection.
34764 . ////////////////////////////////////////////////////////////////////////////
34765 . ////////////////////////////////////////////////////////////////////////////
34767 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
34768 "Exim as a non-queueing client"
34769 .cindex "client, non-queueing"
34770 .cindex "smart host" "suppressing queueing"
34771 On a personal computer, it is a common requirement for all
34772 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
34773 configured to operate that way, for all the popular operating systems.
34774 However, there are some MUAs for Unix-like systems that cannot be so
34775 configured: they submit messages using the command line interface of
34776 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
34779 If the personal computer runs continuously, there is no problem, because it can
34780 run a conventional MTA that handles delivery to the smart host, and deal with
34781 any delays via its queueing mechanism. However, if the computer does not run
34782 continuously or runs different operating systems at different times, queueing
34783 email is not desirable.
34785 There is therefore a requirement for something that can provide the
34786 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
34787 any queueing or retrying facilities. Furthermore, the delivery to the smart
34788 host should be synchronous, so that if it fails, the sending MUA is immediately
34789 informed. In other words, we want something that extends an MUA that submits
34790 to a local MTA via the command line so that it behaves like one that submits
34791 to a remote smart host using TCP/SMTP.
34793 There are a number of applications (for example, there is one called &'ssmtp'&)
34794 that do this job. However, people have found them to be lacking in various
34795 ways. For instance, you might want to allow aliasing and forwarding to be done
34796 before sending a message to the smart host.
34798 Exim already had the necessary infrastructure for doing this job. Just a few
34799 tweaks were needed to make it behave as required, though it is somewhat of an
34800 overkill to use a fully-featured MTA for this purpose.
34802 .oindex "&%mua_wrapper%&"
34803 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
34804 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
34805 assumes that it is being used to &"wrap"& a command-line MUA in the manner
34806 just described. As well as setting &%mua_wrapper%&, you also need to provide a
34807 compatible router and transport configuration. Typically there will be just one
34808 router and one transport, sending everything to a smart host.
34810 When run in MUA wrapping mode, the behaviour of Exim changes in the
34814 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
34815 In other words, the only way to submit messages is via the command line.
34817 Each message is synchronously delivered as soon as it is received (&%-odi%& is
34818 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
34819 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
34820 does not finish until the delivery attempt is complete. If the delivery is
34821 successful, a zero return code is given.
34823 Address redirection is permitted, but the final routing for all addresses must
34824 be to the same remote transport, and to the same list of hosts. Furthermore,
34825 the return address (envelope sender) must be the same for all recipients, as
34826 must any added or deleted header lines. In other words, it must be possible to
34827 deliver the message in a single SMTP transaction, however many recipients there
34830 If these conditions are not met, or if routing any address results in a
34831 failure or defer status, or if Exim is unable to deliver all the recipients
34832 successfully to one of the smart hosts, delivery of the entire message fails.
34834 Because no queueing is allowed, all failures are treated as permanent; there
34835 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
34836 smart host. Furthermore, because only a single yes/no response can be given to
34837 the caller, it is not possible to deliver to some recipients and not others. If
34838 there is an error (temporary or permanent) for any recipient, all are failed.
34840 If more than one smart host is listed, Exim will try another host after a
34841 connection failure or a timeout, in the normal way. However, if this kind of
34842 failure happens for all the hosts, the delivery fails.
34844 When delivery fails, an error message is written to the standard error stream
34845 (as well as to Exim's log), and Exim exits to the caller with a return code
34846 value 1. The message is expunged from Exim's spool files. No bounce messages
34847 are ever generated.
34849 No retry data is maintained, and any retry rules are ignored.
34851 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
34852 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
34853 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
34856 The overall effect is that Exim makes a single synchronous attempt to deliver
34857 the message, failing if there is any kind of problem. Because no local
34858 deliveries are done and no daemon can be run, Exim does not need root
34859 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
34860 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
34861 the advantages and disadvantages of running without root privilege.
34866 . ////////////////////////////////////////////////////////////////////////////
34867 . ////////////////////////////////////////////////////////////////////////////
34869 .chapter "Log files" "CHAPlog"
34870 .scindex IIDloggen "log" "general description"
34871 .cindex "log" "types of"
34872 Exim writes three different logs, referred to as the main log, the reject log,
34877 The main log records the arrival of each message and each delivery in a single
34878 line in each case. The format is as compact as possible, in an attempt to keep
34879 down the size of log files. Two-character flag sequences make it easy to pick
34880 out these lines. A number of other events are recorded in the main log. Some of
34881 them are optional, in which case the &%log_selector%& option controls whether
34882 they are included or not. A Perl script called &'eximstats'&, which does simple
34883 analysis of main log files, is provided in the Exim distribution (see section
34884 &<<SECTmailstat>>&).
34886 .cindex "reject log"
34887 The reject log records information from messages that are rejected as a result
34888 of a configuration option (that is, for policy reasons).
34889 The first line of each rejection is a copy of the line that is also written to
34890 the main log. Then, if the message's header has been read at the time the log
34891 is written, its contents are written to this log. Only the original header
34892 lines are available; header lines added by ACLs are not logged. You can use the
34893 reject log to check that your policy controls are working correctly; on a busy
34894 host this may be easier than scanning the main log for rejection messages. You
34895 can suppress the writing of the reject log by setting &%write_rejectlog%&
34898 .cindex "panic log"
34899 .cindex "system log"
34900 When certain serious errors occur, Exim writes entries to its panic log. If the
34901 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
34902 are usually written to the main log as well, but can get lost amid the mass of
34903 other entries. The panic log should be empty under normal circumstances. It is
34904 therefore a good idea to check it (or to have a &'cron'& script check it)
34905 regularly, in order to become aware of any problems. When Exim cannot open its
34906 panic log, it tries as a last resort to write to the system log (syslog). This
34907 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
34908 message itself is written at priority LOG_CRIT.
34911 Every log line starts with a timestamp, in the format shown in the following
34912 example. Note that many of the examples shown in this chapter are line-wrapped.
34913 In the log file, this would be all on one line:
34915 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
34918 By default, the timestamps are in the local timezone. There are two
34919 ways of changing this:
34922 You can set the &%timezone%& option to a different time zone; in particular, if
34927 the timestamps will be in UTC (aka GMT).
34929 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
34932 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
34936 .cindex "log" "process ids in"
34937 .cindex "pid (process id)" "in log lines"
34938 Exim does not include its process id in log lines by default, but you can
34939 request that it does so by specifying the &`pid`& log selector (see section
34940 &<<SECTlogselector>>&). When this is set, the process id is output, in square
34941 brackets, immediately after the time and date.
34946 .section "Where the logs are written" "SECTwhelogwri"
34947 .cindex "log" "destination"
34948 .cindex "log" "to file"
34949 .cindex "log" "to syslog"
34951 The logs may be written to local files, or to syslog, or both. However, it
34952 should be noted that many syslog implementations use UDP as a transport, and
34953 are therefore unreliable in the sense that messages are not guaranteed to
34954 arrive at the loghost, nor is the ordering of messages necessarily maintained.
34955 It has also been reported that on large log files (tens of megabytes) you may
34956 need to tweak syslog to prevent it syncing the file with each write &-- on
34957 Linux this has been seen to make syslog take 90% plus of CPU time.
34959 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
34960 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
34961 configuration. This latter string is expanded, so it can contain, for example,
34962 references to the host name:
34964 log_file_path = /var/log/$primary_hostname/exim_%slog
34966 It is generally advisable, however, to set the string in &_Local/Makefile_&
34967 rather than at run time, because then the setting is available right from the
34968 start of Exim's execution. Otherwise, if there's something it wants to log
34969 before it has read the configuration file (for example, an error in the
34970 configuration file) it will not use the path you want, and may not be able to
34973 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
34974 list, currently limited to at most two items. This is one option where the
34975 facility for changing a list separator may not be used. The list must always be
34976 colon-separated. If an item in the list is &"syslog"& then syslog is used;
34977 otherwise the item must either be an absolute path, containing &`%s`& at the
34978 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
34979 implying the use of a default path.
34981 When Exim encounters an empty item in the list, it searches the list defined by
34982 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
34983 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
34984 mean &"use the path specified at build time"&. It no such item exists, log
34985 files are written in the &_log_& subdirectory of the spool directory. This is
34986 equivalent to the setting:
34988 log_file_path = $spool_directory/log/%slog
34990 If you do not specify anything at build time or run time,
34991 or if you unset the option at run time (i.e. &`log_file_path = `&),
34992 that is where the logs are written.
34994 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
34995 are in use &-- see section &<<SECTdatlogfil>>& below.
34997 Here are some examples of possible settings:
34999 &`LOG_FILE_PATH=syslog `& syslog only
35000 &`LOG_FILE_PATH=:syslog `& syslog and default path
35001 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
35002 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
35004 If there are more than two paths in the list, the first is used and a panic
35009 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
35010 .cindex "log" "cycling local files"
35011 .cindex "cycling logs"
35012 .cindex "&'exicyclog'&"
35013 .cindex "log" "local files; writing to"
35014 Some operating systems provide centralized and standardized methods for cycling
35015 log files. For those that do not, a utility script called &'exicyclog'& is
35016 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
35017 main and reject logs each time it is called. The maximum number of old logs to
35018 keep can be set. It is suggested this script is run as a daily &'cron'& job.
35020 An Exim delivery process opens the main log when it first needs to write to it,
35021 and it keeps the file open in case subsequent entries are required &-- for
35022 example, if a number of different deliveries are being done for the same
35023 message. However, remote SMTP deliveries can take a long time, and this means
35024 that the file may be kept open long after it is renamed if &'exicyclog'& or
35025 something similar is being used to rename log files on a regular basis. To
35026 ensure that a switch of log files is noticed as soon as possible, Exim calls
35027 &[stat()]& on the main log's name before reusing an open file, and if the file
35028 does not exist, or its inode has changed, the old file is closed and Exim
35029 tries to open the main log from scratch. Thus, an old log file may remain open
35030 for quite some time, but no Exim processes should write to it once it has been
35035 .section "Datestamped log files" "SECTdatlogfil"
35036 .cindex "log" "datestamped files"
35037 Instead of cycling the main and reject log files by renaming them
35038 periodically, some sites like to use files whose names contain a datestamp,
35039 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
35040 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
35041 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
35042 point where the datestamp is required. For example:
35044 log_file_path = /var/spool/exim/log/%slog-%D
35045 log_file_path = /var/log/exim-%s-%D.log
35046 log_file_path = /var/spool/exim/log/%D-%slog
35047 log_file_path = /var/log/exim/%s.%M
35049 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
35050 examples of names generated by the above examples:
35052 /var/spool/exim/log/mainlog-20021225
35053 /var/log/exim-reject-20021225.log
35054 /var/spool/exim/log/20021225-mainlog
35055 /var/log/exim/main.200212
35057 When this form of log file is specified, Exim automatically switches to new
35058 files at midnight. It does not make any attempt to compress old logs; you
35059 will need to write your own script if you require this. You should not
35060 run &'exicyclog'& with this form of logging.
35062 The location of the panic log is also determined by &%log_file_path%&, but it
35063 is not datestamped, because rotation of the panic log does not make sense.
35064 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35065 the string. In addition, if it immediately follows a slash, a following
35066 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35067 character is removed. Thus, the four examples above would give these panic
35070 /var/spool/exim/log/paniclog
35071 /var/log/exim-panic.log
35072 /var/spool/exim/log/paniclog
35073 /var/log/exim/panic
35077 .section "Logging to syslog" "SECID249"
35078 .cindex "log" "syslog; writing to"
35079 The use of syslog does not change what Exim logs or the format of its messages,
35080 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35081 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35082 that, the same strings are written to syslog as to log files. The syslog
35083 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35084 by default, but you can change these by setting the &%syslog_facility%& and
35085 &%syslog_processname%& options, respectively. If Exim was compiled with
35086 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35087 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35088 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35089 the time and host name to each line.
35090 The three log streams are mapped onto syslog priorities as follows:
35093 &'mainlog'& is mapped to LOG_INFO
35095 &'rejectlog'& is mapped to LOG_NOTICE
35097 &'paniclog'& is mapped to LOG_ALERT
35100 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35101 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35102 these are routed by syslog to the same place. You can suppress this duplication
35103 by setting &%syslog_duplication%& false.
35105 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35106 entries contain multiple lines when headers are included. To cope with both
35107 these cases, entries written to syslog are split into separate &[syslog()]&
35108 calls at each internal newline, and also after a maximum of
35109 870 data characters. (This allows for a total syslog line length of 1024, when
35110 additions such as timestamps are added.) If you are running a syslog
35111 replacement that can handle lines longer than the 1024 characters allowed by
35112 RFC 3164, you should set
35114 SYSLOG_LONG_LINES=yes
35116 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35117 lines, but it still splits at internal newlines in &'reject'& log entries.
35119 To make it easy to re-assemble split lines later, each component of a split
35120 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35121 where <&'n'&> is the component number and <&'m'&> is the total number of
35122 components in the entry. The / delimiter is used when the line was split
35123 because it was too long; if it was split because of an internal newline, the \
35124 delimiter is used. For example, supposing the length limit to be 50 instead of
35125 870, the following would be the result of a typical rejection message to
35126 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35127 name, and pid as added by syslog:
35129 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35130 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35131 [3/5] when scanning for sender: missing or malformed lo
35132 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35135 The same error might cause the following lines to be written to &"rejectlog"&
35138 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35139 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35140 [3/18] er when scanning for sender: missing or malformed
35141 [4/18] local part in "<>" (envelope sender is <ph10@cam
35143 [6\18] Recipients: ph10@some.domain.cam.example
35144 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35145 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35146 [9\18] id 16RdAL-0006pc-00
35147 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35148 [11\18] 09:43 +0100
35150 [13\18] Subject: this is a test header
35151 [18\18] X-something: this is another header
35152 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35155 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35157 Log lines that are neither too long nor contain newlines are written to syslog
35158 without modification.
35160 If only syslog is being used, the Exim monitor is unable to provide a log tail
35161 display, unless syslog is routing &'mainlog'& to a file on the local host and
35162 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35167 .section "Log line flags" "SECID250"
35168 One line is written to the main log for each message received, and for each
35169 successful, unsuccessful, and delayed delivery. These lines can readily be
35170 picked out by the distinctive two-character flags that immediately follow the
35171 timestamp. The flags are:
35173 &`<=`& message arrival
35174 &`=>`& normal message delivery
35175 &`->`& additional address in same delivery
35176 &`>>`& cutthrough message delivery
35177 &`*>`& delivery suppressed by &%-N%&
35178 &`**`& delivery failed; address bounced
35179 &`==`& delivery deferred; temporary problem
35183 .section "Logging message reception" "SECID251"
35184 .cindex "log" "reception line"
35185 The format of the single-line entry in the main log that is written for every
35186 message received is shown in the basic example below, which is split over
35187 several lines in order to fit it on the page:
35189 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35190 H=mailer.fict.example [192.168.123.123] U=exim
35191 P=smtp S=5678 id=<incoming message id>
35193 The address immediately following &"<="& is the envelope sender address. A
35194 bounce message is shown with the sender address &"<>"&, and if it is locally
35195 generated, this is followed by an item of the form
35199 which is a reference to the message that caused the bounce to be sent.
35203 For messages from other hosts, the H and U fields identify the remote host and
35204 record the RFC 1413 identity of the user that sent the message, if one was
35205 received. The number given in square brackets is the IP address of the sending
35206 host. If there is a single, unparenthesized host name in the H field, as
35207 above, it has been verified to correspond to the IP address (see the
35208 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35209 by the remote host in the SMTP HELO or EHLO command, and has not been
35210 verified. If verification yields a different name to that given for HELO or
35211 EHLO, the verified name appears first, followed by the HELO or EHLO
35212 name in parentheses.
35214 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35215 without brackets, in the HELO or EHLO command, leading to entries in
35216 the log containing text like these examples:
35218 H=(10.21.32.43) [192.168.8.34]
35219 H=([10.21.32.43]) [192.168.8.34]
35221 This can be confusing. Only the final address in square brackets can be relied
35224 For locally generated messages (that is, messages not received over TCP/IP),
35225 the H field is omitted, and the U field contains the login name of the caller
35228 .cindex "authentication" "logging"
35229 .cindex "AUTH" "logging"
35230 For all messages, the P field specifies the protocol used to receive the
35231 message. This is the value that is stored in &$received_protocol$&. In the case
35232 of incoming SMTP messages, the value indicates whether or not any SMTP
35233 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35234 session was encrypted, there is an additional X field that records the cipher
35235 suite that was used.
35237 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35238 hosts that have authenticated themselves using the SMTP AUTH command. The first
35239 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35240 there is an additional item A= followed by the name of the authenticator that
35241 was used. If an authenticated identification was set up by the authenticator's
35242 &%server_set_id%& option, this is logged too, separated by a colon from the
35243 authenticator name.
35245 .cindex "size" "of message"
35246 The id field records the existing message id, if present. The size of the
35247 received message is given by the S field. When the message is delivered,
35248 headers may be removed or added, so that the size of delivered copies of the
35249 message may not correspond with this value (and indeed may be different to each
35252 The &%log_selector%& option can be used to request the logging of additional
35253 data when a message is received. See section &<<SECTlogselector>>& below.
35257 .section "Logging deliveries" "SECID252"
35258 .cindex "log" "delivery line"
35259 The format of the single-line entry in the main log that is written for every
35260 delivery is shown in one of the examples below, for local and remote
35261 deliveries, respectively. Each example has been split into two lines in order
35262 to fit it on the page:
35264 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35265 <marv@hitch.fict.example> R=localuser T=local_delivery
35266 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35267 monk@holistic.fict.example R=dnslookup T=remote_smtp
35268 H=holistic.fict.example [192.168.234.234]
35270 For ordinary local deliveries, the original address is given in angle brackets
35271 after the final delivery address, which might be a pipe or a file. If
35272 intermediate address(es) exist between the original and the final address, the
35273 last of these is given in parentheses after the final address. The R and T
35274 fields record the router and transport that were used to process the address.
35276 If SMTP AUTH was used for the delivery there is an additional item A=
35277 followed by the name of the authenticator that was used.
35278 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35279 option, this is logged too, separated by a colon from the authenticator name.
35281 If a shadow transport was run after a successful local delivery, the log line
35282 for the successful delivery has an item added on the end, of the form
35284 &`ST=<`&&'shadow transport name'&&`>`&
35286 If the shadow transport did not succeed, the error message is put in
35287 parentheses afterwards.
35289 .cindex "asterisk" "after IP address"
35290 When more than one address is included in a single delivery (for example, two
35291 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35292 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35293 down a single SMTP connection, an asterisk follows the IP address in the log
35294 lines for the second and subsequent messages.
35296 .cindex "delivery" "cutthrough; logging"
35297 .cindex "cutthrough" "logging"
35298 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35299 line precedes the reception line, since cutthrough waits for a possible
35300 rejection from the destination in case it can reject the sourced item.
35302 The generation of a reply message by a filter file gets logged as a
35303 &"delivery"& to the addressee, preceded by &">"&.
35305 The &%log_selector%& option can be used to request the logging of additional
35306 data when a message is delivered. See section &<<SECTlogselector>>& below.
35309 .section "Discarded deliveries" "SECID253"
35310 .cindex "discarded messages"
35311 .cindex "message" "discarded"
35312 .cindex "delivery" "discarded; logging"
35313 When a message is discarded as a result of the command &"seen finish"& being
35314 obeyed in a filter file which generates no deliveries, a log entry of the form
35316 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35317 <low.club@bridge.example> R=userforward
35319 is written, to record why no deliveries are logged. When a message is discarded
35320 because it is aliased to &":blackhole:"& the log line is like this:
35322 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35323 <hole@nowhere.example> R=blackhole_router
35327 .section "Deferred deliveries" "SECID254"
35328 When a delivery is deferred, a line of the following form is logged:
35330 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35331 R=dnslookup T=smtp defer (146): Connection refused
35333 In the case of remote deliveries, the error is the one that was given for the
35334 last IP address that was tried. Details of individual SMTP failures are also
35335 written to the log, so the above line would be preceded by something like
35337 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35338 mail1.endrest.example [192.168.239.239]: Connection refused
35340 When a deferred address is skipped because its retry time has not been reached,
35341 a message is written to the log, but this can be suppressed by setting an
35342 appropriate value in &%log_selector%&.
35346 .section "Delivery failures" "SECID255"
35347 .cindex "delivery" "failure; logging"
35348 If a delivery fails because an address cannot be routed, a line of the
35349 following form is logged:
35351 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35352 <jim@trek99.example>: unknown mail domain
35354 If a delivery fails at transport time, the router and transport are shown, and
35355 the response from the remote host is included, as in this example:
35357 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35358 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35359 after pipelined RCPT TO:<ace400@pb.example>: host
35360 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35361 <ace400@pb.example>...Addressee unknown
35363 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35364 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35365 disabling PIPELINING. The log lines for all forms of delivery failure are
35366 flagged with &`**`&.
35370 .section "Fake deliveries" "SECID256"
35371 .cindex "delivery" "fake; logging"
35372 If a delivery does not actually take place because the &%-N%& option has been
35373 used to suppress it, a normal delivery line is written to the log, except that
35374 &"=>"& is replaced by &"*>"&.
35378 .section "Completion" "SECID257"
35381 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35383 is written to the main log when a message is about to be removed from the spool
35384 at the end of its processing.
35389 .section "Summary of Fields in Log Lines" "SECID258"
35390 .cindex "log" "summary of fields"
35391 A summary of the field identifiers that are used in log lines is shown in
35392 the following table:
35394 &`A `& authenticator name (and optional id and sender)
35395 &`C `& SMTP confirmation on delivery
35396 &` `& command list for &"no mail in SMTP session"&
35397 &`CV `& certificate verification status
35398 &`D `& duration of &"no mail in SMTP session"&
35399 &`DN `& distinguished name from peer certificate
35400 &`DT `& on &`=>`& lines: time taken for a delivery
35401 &`F `& sender address (on delivery lines)
35402 &`H `& host name and IP address
35403 &`I `& local interface used
35404 &`id `& message id for incoming message
35405 &`P `& on &`<=`& lines: protocol used
35406 &` `& on &`=>`& and &`**`& lines: return path
35407 &`QT `& on &`=>`& lines: time spent on queue so far
35408 &` `& on &"Completed"& lines: time spent on queue
35409 &`R `& on &`<=`& lines: reference for local bounce
35410 &` `& on &`=>`& &`**`& and &`==`& lines: router name
35411 &`S `& size of message
35412 &`SNI `& server name indication from TLS client hello
35413 &`ST `& shadow transport name
35414 &`T `& on &`<=`& lines: message subject (topic)
35415 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35416 &`U `& local user or RFC 1413 identity
35417 &`X `& TLS cipher suite
35421 .section "Other log entries" "SECID259"
35422 Various other types of log entry are written from time to time. Most should be
35423 self-explanatory. Among the more common are:
35426 .cindex "retry" "time not reached"
35427 &'retry time not reached'&&~&~An address previously suffered a temporary error
35428 during routing or local delivery, and the time to retry has not yet arrived.
35429 This message is not written to an individual message log file unless it happens
35430 during the first delivery attempt.
35432 &'retry time not reached for any host'&&~&~An address previously suffered
35433 temporary errors during remote delivery, and the retry time has not yet arrived
35434 for any of the hosts to which it is routed.
35436 .cindex "spool directory" "file locked"
35437 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35438 some other Exim process is already working on the message. This can be quite
35439 common if queue running processes are started at frequent intervals. The
35440 &'exiwhat'& utility script can be used to find out what Exim processes are
35443 .cindex "error" "ignored"
35444 &'error ignored'&&~&~There are several circumstances that give rise to this
35447 Exim failed to deliver a bounce message whose age was greater than
35448 &%ignore_bounce_errors_after%&. The bounce was discarded.
35450 A filter file set up a delivery using the &"noerror"& option, and the delivery
35451 failed. The delivery was discarded.
35453 A delivery set up by a router configured with
35454 . ==== As this is a nested list, any displays it contains must be indented
35455 . ==== as otherwise they are too far to the left.
35459 failed. The delivery was discarded.
35467 .section "Reducing or increasing what is logged" "SECTlogselector"
35468 .cindex "log" "selectors"
35469 By setting the &%log_selector%& global option, you can disable some of Exim's
35470 default logging, or you can request additional logging. The value of
35471 &%log_selector%& is made up of names preceded by plus or minus characters. For
35474 log_selector = +arguments -retry_defer
35476 The list of optional log items is in the following table, with the default
35477 selection marked by asterisks:
35479 &` 8bitmime `& received 8BITMIME status
35480 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35481 &` address_rewrite `& address rewriting
35482 &` all_parents `& all parents in => lines
35483 &` arguments `& command line arguments
35484 &`*connection_reject `& connection rejections
35485 &`*delay_delivery `& immediate delivery delayed
35486 &` deliver_time `& time taken to perform delivery
35487 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35488 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35489 &`*etrn `& ETRN commands
35490 &`*host_lookup_failed `& as it says
35491 &` ident_timeout `& timeout for ident connection
35493 &` incoming_interface `& local interface on <= and => lines
35495 &` incoming_port `& remote port on <= lines
35496 &`*lost_incoming_connection `& as it says (includes timeouts)
35497 &` outgoing_port `& add remote port to => lines
35498 &`*queue_run `& start and end queue runs
35499 &` queue_time `& time on queue for one recipient
35500 &` queue_time_overall `& time on queue for whole message
35501 &` pid `& Exim process id
35502 &` received_recipients `& recipients on <= lines
35503 &` received_sender `& sender on <= lines
35504 &`*rejected_header `& header contents on reject log
35505 &`*retry_defer `& &"retry time not reached"&
35506 &` return_path_on_delivery `& put return path on => and ** lines
35507 &` sender_on_delivery `& add sender to => lines
35508 &`*sender_verify_fail `& sender verification failures
35509 &`*size_reject `& rejection because too big
35510 &`*skip_delivery `& delivery skipped in a queue run
35511 &`*smtp_confirmation `& SMTP confirmation on => lines
35512 &` smtp_connection `& incoming SMTP connections
35513 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35514 &` smtp_mailauth `& AUTH argument to MAIL commands
35515 &` smtp_no_mail `& session with no MAIL commands
35516 &` smtp_protocol_error `& SMTP protocol errors
35517 &` smtp_syntax_error `& SMTP syntax errors
35518 &` subject `& contents of &'Subject:'& on <= lines
35520 &`*tls_certificate_verified `& certificate verification status
35522 &`*tls_cipher `& TLS cipher suite on <= and => lines
35523 &` tls_peerdn `& TLS peer DN on <= and => lines
35524 &` tls_sni `& TLS SNI on <= lines
35525 &` unknown_in_list `& DNS lookup failed in list match
35527 &` all `& all of the above
35529 More details on each of these items follows:
35533 .cindex "log" "8BITMIME"
35534 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35535 which may help in tracking down interoperability issues with ancient MTAs
35536 that are not 8bit clean. This is added to the &"<="& line, tagged with
35537 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35538 &`7BIT`& and &`8BITMIME`& respectively.
35540 .cindex "&%warn%& ACL verb" "log when skipping"
35541 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35542 its conditions cannot be evaluated, a log line to this effect is written if
35543 this log selector is set.
35545 .cindex "log" "rewriting"
35546 .cindex "rewriting" "logging"
35547 &%address_rewrite%&: This applies both to global rewrites and per-transport
35548 rewrites, but not to rewrites in filters run as an unprivileged user (because
35549 such users cannot access the log).
35551 .cindex "log" "full parentage"
35552 &%all_parents%&: Normally only the original and final addresses are logged on
35553 delivery lines; with this selector, intermediate parents are given in
35554 parentheses between them.
35556 .cindex "log" "Exim arguments"
35557 .cindex "Exim arguments, logging"
35558 &%arguments%&: This causes Exim to write the arguments with which it was called
35559 to the main log, preceded by the current working directory. This is a debugging
35560 feature, added to make it easier to find out how certain MUAs call
35561 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
35562 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
35563 that are empty or that contain white space are quoted. Non-printing characters
35564 are shown as escape sequences. This facility cannot log unrecognized arguments,
35565 because the arguments are checked before the configuration file is read. The
35566 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
35567 between the caller and Exim.
35569 .cindex "log" "connection rejections"
35570 &%connection_reject%&: A log entry is written whenever an incoming SMTP
35571 connection is rejected, for whatever reason.
35573 .cindex "log" "delayed delivery"
35574 .cindex "delayed delivery, logging"
35575 &%delay_delivery%&: A log entry is written whenever a delivery process is not
35576 started for an incoming message because the load is too high or too many
35577 messages were received on one connection. Logging does not occur if no delivery
35578 process is started because &%queue_only%& is set or &%-odq%& was used.
35580 .cindex "log" "delivery duration"
35581 &%deliver_time%&: For each delivery, the amount of real time it has taken to
35582 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
35584 .cindex "log" "message size on delivery"
35585 .cindex "size" "of message"
35586 &%delivery_size%&: For each delivery, the size of message delivered is added to
35587 the &"=>"& line, tagged with S=.
35589 .cindex "log" "dnslist defer"
35590 .cindex "DNS list" "logging defer"
35591 .cindex "black list (DNS)"
35592 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
35593 DNS black list suffers a temporary error.
35595 .cindex "log" "ETRN commands"
35596 .cindex "ETRN" "logging"
35597 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
35598 is run to determine whether or not it is actually accepted. An invalid ETRN
35599 command, or one received within a message transaction is not logged by this
35600 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
35602 .cindex "log" "host lookup failure"
35603 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
35604 any addresses, or when a lookup of an IP address fails to find a host name, a
35605 log line is written. This logging does not apply to direct DNS lookups when
35606 routing email addresses, but it does apply to &"byname"& lookups.
35608 .cindex "log" "ident timeout"
35609 .cindex "RFC 1413" "logging timeout"
35610 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
35611 client's ident port times out.
35613 .cindex "log" "incoming interface"
35614 .cindex "log" "local interface"
35615 .cindex "log" "local address and port"
35616 .cindex "TCP/IP" "logging local address and port"
35617 .cindex "interface" "logging"
35618 &%incoming_interface%&: The interface on which a message was received is added
35619 to the &"<="& line as an IP address in square brackets, tagged by I= and
35620 followed by a colon and the port number. The local interface and port are also
35621 added to other SMTP log lines, for example &"SMTP connection from"& and to
35624 and (despite the name) the local interface is added to &"=>"& lines..
35627 .cindex "log" "incoming remote port"
35628 .cindex "port" "logging remote"
35629 .cindex "TCP/IP" "logging incoming remote port"
35630 .vindex "&$sender_fullhost$&"
35631 .vindex "&$sender_rcvhost$&"
35632 &%incoming_port%&: The remote port number from which a message was received is
35633 added to log entries and &'Received:'& header lines, following the IP address
35634 in square brackets, and separated from it by a colon. This is implemented by
35635 changing the value that is put in the &$sender_fullhost$& and
35636 &$sender_rcvhost$& variables. Recording the remote port number has become more
35637 important with the widening use of NAT (see RFC 2505).
35639 .cindex "log" "dropped connection"
35640 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
35641 connection is unexpectedly dropped.
35643 .cindex "log" "outgoing remote port"
35644 .cindex "port" "logging outgoint remote"
35645 .cindex "TCP/IP" "logging ougtoing remote port"
35646 &%outgoing_port%&: The remote port number is added to delivery log lines (those
35647 containing => tags) following the IP address. This option is not included in
35648 the default setting, because for most ordinary configurations, the remote port
35649 number is always 25 (the SMTP port).
35651 .cindex "log" "process ids in"
35652 .cindex "pid (process id)" "in log lines"
35653 &%pid%&: The current process id is added to every log line, in square brackets,
35654 immediately after the time and date.
35656 .cindex "log" "queue run"
35657 .cindex "queue runner" "logging"
35658 &%queue_run%&: The start and end of every queue run are logged.
35660 .cindex "log" "queue time"
35661 &%queue_time%&: The amount of time the message has been in the queue on the
35662 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
35663 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
35664 includes reception time as well as the delivery time for the current address.
35665 This means that it may be longer than the difference between the arrival and
35666 delivery log line times, because the arrival log line is not written until the
35667 message has been successfully received.
35669 &%queue_time_overall%&: The amount of time the message has been in the queue on
35670 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
35671 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
35672 message, so it includes reception time as well as the total delivery time.
35674 .cindex "log" "recipients"
35675 &%received_recipients%&: The recipients of a message are listed in the main log
35676 as soon as the message is received. The list appears at the end of the log line
35677 that is written when a message is received, preceded by the word &"for"&. The
35678 addresses are listed after they have been qualified, but before any rewriting
35680 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
35683 .cindex "log" "sender reception"
35684 &%received_sender%&: The unrewritten original sender of a message is added to
35685 the end of the log line that records the message's arrival, after the word
35686 &"from"& (before the recipients if &%received_recipients%& is also set).
35688 .cindex "log" "header lines for rejection"
35689 &%rejected_header%&: If a message's header has been received at the time a
35690 rejection is written to the reject log, the complete header is added to the
35691 log. Header logging can be turned off individually for messages that are
35692 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
35694 .cindex "log" "retry defer"
35695 &%retry_defer%&: A log line is written if a delivery is deferred because a
35696 retry time has not yet been reached. However, this &"retry time not reached"&
35697 message is always omitted from individual message logs after the first delivery
35700 .cindex "log" "return path"
35701 &%return_path_on_delivery%&: The return path that is being transmitted with
35702 the message is included in delivery and bounce lines, using the tag P=.
35703 This is omitted if no delivery actually happens, for example, if routing fails,
35704 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
35706 .cindex "log" "sender on delivery"
35707 &%sender_on_delivery%&: The message's sender address is added to every delivery
35708 and bounce line, tagged by F= (for &"from"&).
35709 This is the original sender that was received with the message; it is not
35710 necessarily the same as the outgoing return path.
35712 .cindex "log" "sender verify failure"
35713 &%sender_verify_fail%&: If this selector is unset, the separate log line that
35714 gives details of a sender verification failure is not written. Log lines for
35715 the rejection of SMTP commands contain just &"sender verify failed"&, so some
35718 .cindex "log" "size rejection"
35719 &%size_reject%&: A log line is written whenever a message is rejected because
35722 .cindex "log" "frozen messages; skipped"
35723 .cindex "frozen messages" "logging skipping"
35724 &%skip_delivery%&: A log line is written whenever a message is skipped during a
35725 queue run because it is frozen or because another process is already delivering
35727 .cindex "&""spool file is locked""&"
35728 The message that is written is &"spool file is locked"&.
35730 .cindex "log" "smtp confirmation"
35731 .cindex "SMTP" "logging confirmation"
35732 .cindex "LMTP" "logging confirmation"
35733 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
35734 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
35735 A number of MTAs (including Exim) return an identifying string in this
35738 .cindex "log" "SMTP connections"
35739 .cindex "SMTP" "logging connections"
35740 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
35741 established or closed, unless the connection is from a host that matches
35742 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
35743 only when the closure is unexpected.) This applies to connections from local
35744 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
35745 dropped in the middle of a message, a log line is always written, whether or
35746 not this selector is set, but otherwise nothing is written at the start and end
35747 of connections unless this selector is enabled.
35749 For TCP/IP connections to an Exim daemon, the current number of connections is
35750 included in the log message for each new connection, but note that the count is
35751 reset if the daemon is restarted.
35752 Also, because connections are closed (and the closure is logged) in
35753 subprocesses, the count may not include connections that have been closed but
35754 whose termination the daemon has not yet noticed. Thus, while it is possible to
35755 match up the opening and closing of connections in the log, the value of the
35756 logged counts may not be entirely accurate.
35758 .cindex "log" "SMTP transaction; incomplete"
35759 .cindex "SMTP" "logging incomplete transactions"
35760 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
35761 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
35762 and the message sender plus any accepted recipients are included in the log
35763 line. This can provide evidence of dictionary attacks.
35765 .cindex "log" "non-MAIL SMTP sessions"
35766 .cindex "MAIL" "logging session without"
35767 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
35768 connection terminates without having issued a MAIL command. This includes both
35769 the case when the connection is dropped, and the case when QUIT is used. It
35770 does not include cases where the connection is rejected right at the start (by
35771 an ACL, or because there are too many connections, or whatever). These cases
35772 already have their own log lines.
35774 The log line that is written contains the identity of the client in the usual
35775 way, followed by D= and a time, which records the duration of the connection.
35776 If the connection was authenticated, this fact is logged exactly as it is for
35777 an incoming message, with an A= item. If the connection was encrypted, CV=,
35778 DN=, and X= items may appear as they do for an incoming message, controlled by
35779 the same logging options.
35781 Finally, if any SMTP commands were issued during the connection, a C= item
35782 is added to the line, listing the commands that were used. For example,
35786 shows that the client issued QUIT straight after EHLO. If there were fewer
35787 than 20 commands, they are all listed. If there were more than 20 commands,
35788 the last 20 are listed, preceded by &"..."&. However, with the default
35789 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
35790 have been aborted before 20 non-mail commands are processed.
35792 &%smtp_mailauth%&: A third subfield with the authenticated sender,
35793 colon-separated, is appended to the A= item for a message arrival or delivery
35794 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
35795 was accepted or used.
35797 .cindex "log" "SMTP protocol error"
35798 .cindex "SMTP" "logging protocol error"
35799 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
35800 encountered. Exim does not have perfect detection of all protocol errors
35801 because of transmission delays and the use of pipelining. If PIPELINING has
35802 been advertised to a client, an Exim server assumes that the client will use
35803 it, and therefore it does not count &"expected"& errors (for example, RCPT
35804 received after rejecting MAIL) as protocol errors.
35806 .cindex "SMTP" "logging syntax errors"
35807 .cindex "SMTP" "syntax errors; logging"
35808 .cindex "SMTP" "unknown command; logging"
35809 .cindex "log" "unknown SMTP command"
35810 .cindex "log" "SMTP syntax error"
35811 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
35812 encountered. An unrecognized command is treated as a syntax error. For an
35813 external connection, the host identity is given; for an internal connection
35814 using &%-bs%& the sender identification (normally the calling user) is given.
35816 .cindex "log" "subject"
35817 .cindex "subject, logging"
35818 &%subject%&: The subject of the message is added to the arrival log line,
35819 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
35820 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
35821 specifies whether characters with values greater than 127 should be logged
35822 unchanged, or whether they should be rendered as escape sequences.
35824 .cindex "log" "certificate verification"
35825 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
35826 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
35827 verified, and &`CV=no`& if not.
35829 .cindex "log" "TLS cipher"
35830 .cindex "TLS" "logging cipher"
35831 &%tls_cipher%&: When a message is sent or received over an encrypted
35832 connection, the cipher suite used is added to the log line, preceded by X=.
35834 .cindex "log" "TLS peer DN"
35835 .cindex "TLS" "logging peer DN"
35836 &%tls_peerdn%&: When a message is sent or received over an encrypted
35837 connection, and a certificate is supplied by the remote host, the peer DN is
35838 added to the log line, preceded by DN=.
35840 .cindex "log" "TLS SNI"
35841 .cindex "TLS" "logging SNI"
35842 &%tls_sni%&: When a message is received over an encrypted connection, and
35843 the remote host provided the Server Name Indication extension, the SNI is
35844 added to the log line, preceded by SNI=.
35846 .cindex "log" "DNS failure in list"
35847 &%unknown_in_list%&: This setting causes a log entry to be written when the
35848 result of a list match is failure because a DNS lookup failed.
35852 .section "Message log" "SECID260"
35853 .cindex "message" "log file for"
35854 .cindex "log" "message log; description of"
35855 .cindex "&_msglog_& directory"
35856 .oindex "&%preserve_message_logs%&"
35857 In addition to the general log files, Exim writes a log file for each message
35858 that it handles. The names of these per-message logs are the message ids, and
35859 they are kept in the &_msglog_& sub-directory of the spool directory. Each
35860 message log contains copies of the log lines that apply to the message. This
35861 makes it easier to inspect the status of an individual message without having
35862 to search the main log. A message log is deleted when processing of the message
35863 is complete, unless &%preserve_message_logs%& is set, but this should be used
35864 only with great care because they can fill up your disk very quickly.
35866 On a heavily loaded system, it may be desirable to disable the use of
35867 per-message logs, in order to reduce disk I/O. This can be done by setting the
35868 &%message_logs%& option false.
35874 . ////////////////////////////////////////////////////////////////////////////
35875 . ////////////////////////////////////////////////////////////////////////////
35877 .chapter "Exim utilities" "CHAPutils"
35878 .scindex IIDutils "utilities"
35879 A number of utility scripts and programs are supplied with Exim and are
35880 described in this chapter. There is also the Exim Monitor, which is covered in
35881 the next chapter. The utilities described here are:
35883 .itable none 0 0 3 7* left 15* left 40* left
35884 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
35885 "list what Exim processes are doing"
35886 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
35887 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
35888 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
35889 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
35891 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
35892 .irow &<<SECTmailstat>>& &'eximstats'& &&&
35893 "extract statistics from the log"
35894 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
35895 "check address acceptance from given IP"
35896 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
35897 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
35898 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
35899 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
35900 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
35901 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
35904 Another utility that might be of use to sites with many MTAs is Tom Kistner's
35905 &'exilog'&. It provides log visualizations across multiple Exim servers. See
35906 &url(http://duncanthrax.net/exilog/) for details.
35911 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
35912 .cindex "&'exiwhat'&"
35913 .cindex "process, querying"
35915 On operating systems that can restart a system call after receiving a signal
35916 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
35917 a line describing what it is doing to the file &_exim-process.info_& in the
35918 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
35919 processes it can find, having first emptied the file. It then waits for one
35920 second to allow the Exim processes to react before displaying the results. In
35921 order to run &'exiwhat'& successfully you have to have sufficient privilege to
35922 send the signal to the Exim processes, so it is normally run as root.
35924 &*Warning*&: This is not an efficient process. It is intended for occasional
35925 use by system administrators. It is not sensible, for example, to set up a
35926 script that sends SIGUSR1 signals to Exim processes at short intervals.
35929 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
35930 varies in different operating systems. Not only are different options used,
35931 but the format of the output is different. For this reason, there are some
35932 system configuration options that configure exactly how &'exiwhat'& works. If
35933 it doesn't seem to be working for you, check the following compile-time
35936 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
35937 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
35938 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
35939 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
35941 An example of typical output from &'exiwhat'& is
35943 164 daemon: -q1h, listening on port 25
35944 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
35945 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
35946 [10.19.42.42] (editor@ref.example)
35947 10592 handling incoming call from [192.168.243.242]
35948 10628 accepting a local non-SMTP message
35950 The first number in the output line is the process number. The third line has
35951 been split here, in order to fit it on the page.
35955 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
35956 .cindex "&'exiqgrep'&"
35957 .cindex "queue" "grepping"
35958 This utility is a Perl script contributed by Matt Hubbard. It runs
35962 or (in case &*-a*& switch is specified)
35966 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
35967 contain alternate exim configuration the queue management might be using.
35969 to obtain a queue listing, and then greps the output to select messages
35970 that match given criteria. The following selection options are available:
35973 .vitem &*-f*&&~<&'regex'&>
35974 Match the sender address using a case-insensitive search. The field that is
35975 tested is enclosed in angle brackets, so you can test for bounce messages with
35979 .vitem &*-r*&&~<&'regex'&>
35980 Match a recipient address using a case-insensitive search. The field that is
35981 tested is not enclosed in angle brackets.
35983 .vitem &*-s*&&~<&'regex'&>
35984 Match against the size field.
35986 .vitem &*-y*&&~<&'seconds'&>
35987 Match messages that are younger than the given time.
35989 .vitem &*-o*&&~<&'seconds'&>
35990 Match messages that are older than the given time.
35993 Match only frozen messages.
35996 Match only non-frozen messages.
35999 The following options control the format of the output:
36003 Display only the count of matching messages.
36006 Long format &-- display the full message information as output by Exim. This is
36010 Display message ids only.
36013 Brief format &-- one line per message.
36016 Display messages in reverse order.
36019 Include delivered recipients in queue listing.
36022 There is one more option, &%-h%&, which outputs a list of options.
36026 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
36027 .cindex "&'exiqsumm'&"
36028 .cindex "queue" "summary"
36029 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
36030 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
36031 running a command such as
36033 exim -bp | exiqsumm
36035 The output consists of one line for each domain that has messages waiting for
36036 it, as in the following example:
36038 3 2322 74m 66m msn.com.example
36040 Each line lists the number of pending deliveries for a domain, their total
36041 volume, and the length of time that the oldest and the newest messages have
36042 been waiting. Note that the number of pending deliveries is greater than the
36043 number of messages when messages have more than one recipient.
36045 A summary line is output at the end. By default the output is sorted on the
36046 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36047 the output to be sorted by oldest message and by count of messages,
36048 respectively. There are also three options that split the messages for each
36049 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36050 separates frozen messages, and &%-s%& separates messages according to their
36053 The output of &'exim -bp'& contains the original addresses in the message, so
36054 this also applies to the output from &'exiqsumm'&. No domains from addresses
36055 generated by aliasing or forwarding are included (unless the &%one_time%&
36056 option of the &(redirect)& router has been used to convert them into &"top
36057 level"& addresses).
36062 .section "Extracting specific information from the log (exigrep)" &&&
36064 .cindex "&'exigrep'&"
36065 .cindex "log" "extracts; grepping for"
36066 The &'exigrep'& utility is a Perl script that searches one or more main log
36067 files for entries that match a given pattern. When it finds a match, it
36068 extracts all the log entries for the relevant message, not just those that
36069 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36070 given message, or all mail for a given user, or for a given host, for example.
36071 The input files can be in Exim log format or syslog format.
36072 If a matching log line is not associated with a specific message, it is
36073 included in &'exigrep'&'s output without any additional lines. The usage is:
36075 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36077 If no log file names are given on the command line, the standard input is read.
36079 The &%-t%& argument specifies a number of seconds. It adds an additional
36080 condition for message selection. Messages that are complete are shown only if
36081 they spent more than <&'n'&> seconds on the queue.
36083 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36084 makes it case-sensitive. This may give a performance improvement when searching
36085 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36086 option; with &%-I%& they do not. In both cases it is possible to change the
36087 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36089 The &%-l%& option means &"literal"&, that is, treat all characters in the
36090 pattern as standing for themselves. Otherwise the pattern must be a Perl
36091 regular expression.
36093 The &%-v%& option inverts the matching condition. That is, a line is selected
36094 if it does &'not'& match the pattern.
36096 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36097 that are generated as a result/response to a message that &'exigrep'& matched
36101 user_a sends a message to user_b, which generates a bounce back to user_b. If
36102 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36103 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36104 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36105 when searching for &"user_a"& will show both messages since the bounce is
36106 &"related"& to or a &"result"& of the first message that was found by the
36109 If the location of a &'zcat'& command is known from the definition of
36110 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36111 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36112 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36113 autodetection of some well known compression extensions.
36116 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36117 .cindex "&'exipick'&"
36118 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36119 lists messages from the queue according to a variety of criteria. For details
36120 of &'exipick'&'s facilities, visit the web page at
36121 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36122 the &%--help%& option.
36125 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36126 .cindex "log" "cycling local files"
36127 .cindex "cycling logs"
36128 .cindex "&'exicyclog'&"
36129 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36130 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36131 you are using log files with datestamps in their names (see section
36132 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36133 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36134 There are two command line options for &'exicyclog'&:
36136 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36137 default that is set when Exim is built. The default default is 10.
36139 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36140 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36141 overriding the script's default, which is to find the setting from Exim's
36145 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36146 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36147 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36148 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36149 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36150 logs are handled similarly.
36152 If the limit is greater than 99, the script uses 3-digit numbers such as
36153 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36154 to one that is greater, or &'vice versa'&, you will have to fix the names of
36155 any existing log files.
36157 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36158 the end are deleted. All files with numbers greater than 01 are compressed,
36159 using a compression command which is configured by the COMPRESS_COMMAND
36160 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36161 root &%crontab%& entry of the form
36163 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36165 assuming you have used the name &"exim"& for the Exim user. You can run
36166 &'exicyclog'& as root if you wish, but there is no need.
36170 .section "Mail statistics (eximstats)" "SECTmailstat"
36171 .cindex "statistics"
36172 .cindex "&'eximstats'&"
36173 A Perl script called &'eximstats'& is provided for extracting statistical
36174 information from log files. The output is either plain text, or HTML.
36175 Exim log files are also supported by the &'Lire'& system produced by the
36176 LogReport Foundation &url(http://www.logreport.org).
36178 The &'eximstats'& script has been hacked about quite a bit over time. The
36179 latest version is the result of some extensive revision by Steve Campbell. A
36180 lot of information is given by default, but there are options for suppressing
36181 various parts of it. Following any options, the arguments to the script are a
36182 list of files, which should be main log files. For example:
36184 eximstats -nr /var/spool/exim/log/mainlog.01
36186 By default, &'eximstats'& extracts information about the number and volume of
36187 messages received from or delivered to various hosts. The information is sorted
36188 both by message count and by volume, and the top fifty hosts in each category
36189 are listed on the standard output. Similar information, based on email
36190 addresses or domains instead of hosts can be requested by means of various
36191 options. For messages delivered and received locally, similar statistics are
36192 also produced per user.
36194 The output also includes total counts and statistics about delivery errors, and
36195 histograms showing the number of messages received and deliveries made in each
36196 hour of the day. A delivery with more than one address in its envelope (for
36197 example, an SMTP transaction with more than one RCPT command) is counted
36198 as a single delivery by &'eximstats'&.
36200 Though normally more deliveries than receipts are reported (as messages may
36201 have multiple recipients), it is possible for &'eximstats'& to report more
36202 messages received than delivered, even though the queue is empty at the start
36203 and end of the period in question. If an incoming message contains no valid
36204 recipients, no deliveries are recorded for it. A bounce message is handled as
36205 an entirely separate message.
36207 &'eximstats'& always outputs a grand total summary giving the volume and number
36208 of messages received and deliveries made, and the number of hosts involved in
36209 each case. It also outputs the number of messages that were delayed (that is,
36210 not completely delivered at the first attempt), and the number that had at
36211 least one address that failed.
36213 The remainder of the output is in sections that can be independently disabled
36214 or modified by various options. It consists of a summary of deliveries by
36215 transport, histograms of messages received and delivered per time interval
36216 (default per hour), information about the time messages spent on the queue,
36217 a list of relayed messages, lists of the top fifty sending hosts, local
36218 senders, destination hosts, and destination local users by count and by volume,
36219 and a list of delivery errors that occurred.
36221 The relay information lists messages that were actually relayed, that is, they
36222 came from a remote host and were directly delivered to some other remote host,
36223 without being processed (for example, for aliasing or forwarding) locally.
36225 There are quite a few options for &'eximstats'& to control exactly what it
36226 outputs. These are documented in the Perl script itself, and can be extracted
36227 by running the command &(perldoc)& on the script. For example:
36229 perldoc /usr/exim/bin/eximstats
36232 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36233 .cindex "&'exim_checkaccess'&"
36234 .cindex "policy control" "checking access"
36235 .cindex "checking access"
36236 The &%-bh%& command line argument allows you to run a fake SMTP session with
36237 debugging output, in order to check what Exim is doing when it is applying
36238 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36239 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36240 sometimes you just want to answer the question &"Does this address have
36241 access?"& without bothering with any further details.
36243 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36244 two arguments, an IP address and an email address:
36246 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36248 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36249 given email address would be accepted in a RCPT command in a TCP/IP
36250 connection from the host with the given IP address. The output of the utility
36251 is either the word &"accepted"&, or the SMTP error response, for example:
36254 550 Relay not permitted
36256 When running this test, the utility uses &`<>`& as the envelope sender address
36257 for the MAIL command, but you can change this by providing additional
36258 options. These are passed directly to the Exim command. For example, to specify
36259 that the test is to be run with the sender address &'himself@there.example'&
36262 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36263 -f himself@there.example
36265 Note that these additional Exim command line items must be given after the two
36266 mandatory arguments.
36268 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36269 while running its checks. You can run checks that include callouts by using
36270 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36274 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36275 .cindex "DBM" "building dbm files"
36276 .cindex "building DBM files"
36277 .cindex "&'exim_dbmbuild'&"
36278 .cindex "lower casing"
36279 .cindex "binary zero" "in lookup key"
36280 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36281 the format used by the &(lsearch)& lookup (see section
36282 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36283 names as keys and the remainder of the information as data. The lower-casing
36284 can be prevented by calling the program with the &%-nolc%& option.
36286 A terminating zero is included as part of the key string. This is expected by
36287 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36288 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36289 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36292 The program requires two arguments: the name of the input file (which can be a
36293 single hyphen to indicate the standard input), and the name of the output file.
36294 It creates the output under a temporary name, and then renames it if all went
36298 If the native DB interface is in use (USE_DB is set in a compile-time
36299 configuration file &-- this is common in free versions of Unix) the two file
36300 names must be different, because in this mode the Berkeley DB functions create
36301 a single output file using exactly the name given. For example,
36303 exim_dbmbuild /etc/aliases /etc/aliases.db
36305 reads the system alias file and creates a DBM version of it in
36306 &_/etc/aliases.db_&.
36308 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36309 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36310 environment, the suffixes are added to the second argument of
36311 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36312 when the Berkeley functions are used in compatibility mode (though this is not
36313 recommended), because in that case it adds a &_.db_& suffix to the file name.
36315 If a duplicate key is encountered, the program outputs a warning, and when it
36316 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36317 option is used. By default, only the first of a set of duplicates is used &--
36318 this makes it compatible with &(lsearch)& lookups. There is an option
36319 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36320 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36321 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36327 .section "Finding individual retry times (exinext)" "SECTfinindret"
36328 .cindex "retry" "times"
36329 .cindex "&'exinext'&"
36330 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36331 fish specific information out of the retry database. Given a mail domain (or a
36332 complete address), it looks up the hosts for that domain, and outputs any retry
36333 information for the hosts or for the domain. At present, the retry information
36334 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36335 output. For example:
36337 $ exinext piglet@milne.fict.example
36338 kanga.milne.example:192.168.8.1 error 146: Connection refused
36339 first failed: 21-Feb-1996 14:57:34
36340 last tried: 21-Feb-1996 14:57:34
36341 next try at: 21-Feb-1996 15:02:34
36342 roo.milne.example:192.168.8.3 error 146: Connection refused
36343 first failed: 20-Jan-1996 13:12:08
36344 last tried: 21-Feb-1996 11:42:03
36345 next try at: 21-Feb-1996 19:42:03
36346 past final cutoff time
36348 You can also give &'exinext'& a local part, without a domain, and it
36349 will give any retry information for that local part in your default domain.
36350 A message id can be used to obtain retry information pertaining to a specific
36351 message. This exists only when an attempt to deliver a message to a remote host
36352 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36353 &'exinext'& is not particularly efficient, but then it is not expected to be
36356 The &'exinext'& utility calls Exim to find out information such as the location
36357 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36358 passed on to the &'exim'& commands. The first specifies an alternate Exim
36359 configuration file, and the second sets macros for use within the configuration
36360 file. These features are mainly to help in testing, but might also be useful in
36361 environments where more than one configuration file is in use.
36365 .section "Hints database maintenance" "SECThindatmai"
36366 .cindex "hints database" "maintenance"
36367 .cindex "maintaining Exim's hints database"
36368 Three utility programs are provided for maintaining the DBM files that Exim
36369 uses to contain its delivery hint information. Each program requires two
36370 arguments. The first specifies the name of Exim's spool directory, and the
36371 second is the name of the database it is to operate on. These are as follows:
36374 &'retry'&: the database of retry information
36376 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36379 &'callout'&: the callout cache
36381 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36383 &'misc'&: other hints data
36386 The &'misc'& database is used for
36389 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36391 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36392 &(smtp)& transport)
36397 .section "exim_dumpdb" "SECID261"
36398 .cindex "&'exim_dumpdb'&"
36399 The entire contents of a database are written to the standard output by the
36400 &'exim_dumpdb'& program, which has no options or arguments other than the
36401 spool and database names. For example, to dump the retry database:
36403 exim_dumpdb /var/spool/exim retry
36405 Two lines of output are produced for each entry:
36407 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36408 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36410 The first item on the first line is the key of the record. It starts with one
36411 of the letters R, or T, depending on whether it refers to a routing or
36412 transport retry. For a local delivery, the next part is the local address; for
36413 a remote delivery it is the name of the remote host, followed by its failing IP
36414 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36415 transport). If the remote port is not the standard one (port 25), it is added
36416 to the IP address. Then there follows an error code, an additional error code,
36417 and a textual description of the error.
36419 The three times on the second line are the time of first failure, the time of
36420 the last delivery attempt, and the computed time for the next attempt. The line
36421 ends with an asterisk if the cutoff time for the last retry rule has been
36424 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36425 consists of a host name followed by a list of ids for messages that are or were
36426 waiting to be delivered to that host. If there are a very large number for any
36427 one host, continuation records, with a sequence number added to the host name,
36428 may be seen. The data in these records is often out of date, because a message
36429 may be routed to several alternative hosts, and Exim makes no effort to keep
36434 .section "exim_tidydb" "SECID262"
36435 .cindex "&'exim_tidydb'&"
36436 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36437 database. If run with no options, it removes all records that are more than 30
36438 days old. The age is calculated from the date and time that the record was last
36439 updated. Note that, in the case of the retry database, it is &'not'& the time
36440 since the first delivery failure. Information about a host that has been down
36441 for more than 30 days will remain in the database, provided that the record is
36442 updated sufficiently often.
36444 The cutoff date can be altered by means of the &%-t%& option, which must be
36445 followed by a time. For example, to remove all records older than a week from
36446 the retry database:
36448 exim_tidydb -t 7d /var/spool/exim retry
36450 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36451 message ids. In the former these appear as data in records keyed by host &--
36452 they were messages that were waiting for that host &-- and in the latter they
36453 are the keys for retry information for messages that have suffered certain
36454 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36455 message ids in database records are those of messages that are still on the
36456 queue. Message ids for messages that no longer exist are removed from
36457 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36458 For the &'retry'& database, records whose keys are non-existent message ids are
36459 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36460 whenever it removes information from the database.
36462 Certain records are automatically removed by Exim when they are no longer
36463 needed, but others are not. For example, if all the MX hosts for a domain are
36464 down, a retry record is created for each one. If the primary MX host comes back
36465 first, its record is removed when Exim successfully delivers to it, but the
36466 records for the others remain because Exim has not tried to use those hosts.
36468 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36469 hints databases. You should do this at a quiet time of day, because it requires
36470 a database to be locked (and therefore inaccessible to Exim) while it does its
36471 work. Removing records from a DBM file does not normally make the file smaller,
36472 but all the common DBM libraries are able to re-use the space that is released.
36473 After an initial phase of increasing in size, the databases normally reach a
36474 point at which they no longer get any bigger, as long as they are regularly
36477 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36478 databases is likely to keep on increasing.
36483 .section "exim_fixdb" "SECID263"
36484 .cindex "&'exim_fixdb'&"
36485 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36486 Its main use is for testing Exim, but it might also be occasionally useful for
36487 getting round problems in a live system. It has no options, and its interface
36488 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36489 key of a database record can then be entered, and the data for that record is
36492 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36493 except the &'retry'& database, that is the only operation that can be carried
36494 out. For the &'retry'& database, each field is output preceded by a number, and
36495 data for individual fields can be changed by typing the field number followed
36496 by new data, for example:
36500 resets the time of the next delivery attempt. Time values are given as a
36501 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36502 used as optional separators.
36507 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36508 .cindex "mailbox" "maintenance"
36509 .cindex "&'exim_lock'&"
36510 .cindex "locking mailboxes"
36511 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36512 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36513 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36514 a user agent while investigating a problem. The utility requires the name of
36515 the file as its first argument. If the locking is successful, the second
36516 argument is run as a command (using C's &[system()]& function); if there is no
36517 second argument, the value of the SHELL environment variable is used; if this
36518 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36519 is unlocked and the utility ends. The following options are available:
36523 Use &[fcntl()]& locking on the open mailbox.
36526 Use &[flock()]& locking on the open mailbox, provided the operating system
36529 .vitem &%-interval%&
36530 This must be followed by a number, which is a number of seconds; it sets the
36531 interval to sleep between retries (default 3).
36533 .vitem &%-lockfile%&
36534 Create a lock file before opening the mailbox.
36537 Lock the mailbox using MBX rules.
36540 Suppress verification output.
36542 .vitem &%-retries%&
36543 This must be followed by a number; it sets the number of times to try to get
36544 the lock (default 10).
36546 .vitem &%-restore_time%&
36547 This option causes &%exim_lock%& to restore the modified and read times to the
36548 locked file before exiting. This allows you to access a locked mailbox (for
36549 example, to take a backup copy) without disturbing the times that the user
36552 .vitem &%-timeout%&
36553 This must be followed by a number, which is a number of seconds; it sets a
36554 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
36555 default), a non-blocking call is used.
36558 Generate verbose output.
36561 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
36562 default is to create a lock file and also to use &[fcntl()]& locking on the
36563 mailbox, which is the same as Exim's default. The use of &%-flock%& or
36564 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
36565 requires that the directory containing the file be writeable. Locking by lock
36566 file does not last for ever; Exim assumes that a lock file is expired if it is
36567 more than 30 minutes old.
36569 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
36570 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
36571 to be taken out on the open mailbox, and an exclusive lock on the file
36572 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
36573 number of the mailbox file. When the locking is released, if an exclusive lock
36574 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
36576 The default output contains verification of the locking that takes place. The
36577 &%-v%& option causes some additional information to be given. The &%-q%& option
36578 suppresses all output except error messages.
36582 exim_lock /var/spool/mail/spqr
36584 runs an interactive shell while the file is locked, whereas
36586 &`exim_lock -q /var/spool/mail/spqr <<End`&
36587 <&'some commands'&>
36590 runs a specific non-interactive sequence of commands while the file is locked,
36591 suppressing all verification output. A single command can be run by a command
36594 exim_lock -q /var/spool/mail/spqr \
36595 "cp /var/spool/mail/spqr /some/where"
36597 Note that if a command is supplied, it must be entirely contained within the
36598 second argument &-- hence the quotes.
36602 . ////////////////////////////////////////////////////////////////////////////
36603 . ////////////////////////////////////////////////////////////////////////////
36605 .chapter "The Exim monitor" "CHAPeximon"
36606 .scindex IIDeximon "Exim monitor" "description"
36607 .cindex "X-windows"
36608 .cindex "&'eximon'&"
36609 .cindex "Local/eximon.conf"
36610 .cindex "&_exim_monitor/EDITME_&"
36611 The Exim monitor is an application which displays in an X window information
36612 about the state of Exim's queue and what Exim is doing. An admin user can
36613 perform certain operations on messages from this GUI interface; however all
36614 such facilities are also available from the command line, and indeed, the
36615 monitor itself makes use of the command line to perform any actions requested.
36619 .section "Running the monitor" "SECID264"
36620 The monitor is started by running the script called &'eximon'&. This is a shell
36621 script that sets up a number of environment variables, and then runs the
36622 binary called &_eximon.bin_&. The default appearance of the monitor window can
36623 be changed by editing the &_Local/eximon.conf_& file created by editing
36624 &_exim_monitor/EDITME_&. Comments in that file describe what the various
36625 parameters are for.
36627 The parameters that get built into the &'eximon'& script can be overridden for
36628 a particular invocation by setting up environment variables of the same names,
36629 preceded by &`EXIMON_`&. For example, a shell command such as
36631 EXIMON_LOG_DEPTH=400 eximon
36633 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
36634 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
36635 overrides the Exim log file configuration. This makes it possible to have
36636 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
36637 syslog messages are routed to a file on the local host.
36639 X resources can be used to change the appearance of the window in the normal
36640 way. For example, a resource setting of the form
36642 Eximon*background: gray94
36644 changes the colour of the background to light grey rather than white. The
36645 stripcharts are drawn with both the data lines and the reference lines in
36646 black. This means that the reference lines are not visible when on top of the
36647 data. However, their colour can be changed by setting a resource called
36648 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
36649 For example, if your X server is running Unix, you could set up lighter
36650 reference lines in the stripcharts by obeying
36653 Eximon*highlight: gray
36656 .cindex "admin user"
36657 In order to see the contents of messages on the queue, and to operate on them,
36658 &'eximon'& must either be run as root or by an admin user.
36660 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
36661 contain X11 resource parameters interpreted by the X11 library. In addition,
36662 if the first parameter starts with the string "gdb" then it is removed and the
36663 binary is invoked under gdb (the parameter is used as the gdb command-name, so
36664 versioned variants of gdb can be invoked).
36666 The monitor's window is divided into three parts. The first contains one or
36667 more stripcharts and two action buttons, the second contains a &"tail"& of the
36668 main log file, and the third is a display of the queue of messages awaiting
36669 delivery, with two more action buttons. The following sections describe these
36670 different parts of the display.
36675 .section "The stripcharts" "SECID265"
36676 .cindex "stripchart"
36677 The first stripchart is always a count of messages on the queue. Its name can
36678 be configured by setting QUEUE_STRIPCHART_NAME in the
36679 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
36680 configuration script by regular expression matches on log file entries, making
36681 it possible to display, for example, counts of messages delivered to certain
36682 hosts or using certain transports. The supplied defaults display counts of
36683 received and delivered messages, and of local and SMTP deliveries. The default
36684 period between stripchart updates is one minute; this can be adjusted by a
36685 parameter in the &_Local/eximon.conf_& file.
36687 The stripchart displays rescale themselves automatically as the value they are
36688 displaying changes. There are always 10 horizontal lines in each chart; the
36689 title string indicates the value of each division when it is greater than one.
36690 For example, &"x2"& means that each division represents a value of 2.
36692 It is also possible to have a stripchart which shows the percentage fullness of
36693 a particular disk partition, which is useful when local deliveries are confined
36694 to a single partition.
36696 .cindex "&%statvfs%& function"
36697 This relies on the availability of the &[statvfs()]& function or equivalent in
36698 the operating system. Most, but not all versions of Unix that support Exim have
36699 this. For this particular stripchart, the top of the chart always represents
36700 100%, and the scale is given as &"x10%"&. This chart is configured by setting
36701 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
36702 &_Local/eximon.conf_& file.
36707 .section "Main action buttons" "SECID266"
36708 .cindex "size" "of monitor window"
36709 .cindex "Exim monitor" "window size"
36710 .cindex "window size"
36711 Below the stripcharts there is an action button for quitting the monitor. Next
36712 to this is another button marked &"Size"&. They are placed here so that
36713 shrinking the window to its default minimum size leaves just the queue count
36714 stripchart and these two buttons visible. Pressing the &"Size"& button causes
36715 the window to expand to its maximum size, unless it is already at the maximum,
36716 in which case it is reduced to its minimum.
36718 When expanding to the maximum, if the window cannot be fully seen where it
36719 currently is, it is moved back to where it was the last time it was at full
36720 size. When it is expanding from its minimum size, the old position is
36721 remembered, and next time it is reduced to the minimum it is moved back there.
36723 The idea is that you can keep a reduced window just showing one or two
36724 stripcharts at a convenient place on your screen, easily expand it to show
36725 the full window when required, and just as easily put it back to what it was.
36726 The idea is copied from what the &'twm'& window manager does for its
36727 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
36728 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
36730 Normally, the monitor starts up with the window at its full size, but it can be
36731 built so that it starts up with the window at its smallest size, by setting
36732 START_SMALL=yes in &_Local/eximon.conf_&.
36736 .section "The log display" "SECID267"
36737 .cindex "log" "tail of; in monitor"
36738 The second section of the window is an area in which a display of the tail of
36739 the main log is maintained.
36740 To save space on the screen, the timestamp on each log line is shortened by
36741 removing the date and, if &%log_timezone%& is set, the timezone.
36742 The log tail is not available when the only destination for logging data is
36743 syslog, unless the syslog lines are routed to a local file whose name is passed
36744 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
36746 The log sub-window has a scroll bar at its lefthand side which can be used to
36747 move back to look at earlier text, and the up and down arrow keys also have a
36748 scrolling effect. The amount of log that is kept depends on the setting of
36749 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
36750 to use. When this is full, the earlier 50% of data is discarded &-- this is
36751 much more efficient than throwing it away line by line. The sub-window also has
36752 a horizontal scroll bar for accessing the ends of long log lines. This is the
36753 only means of horizontal scrolling; the right and left arrow keys are not
36754 available. Text can be cut from this part of the window using the mouse in the
36755 normal way. The size of this subwindow is controlled by parameters in the
36756 configuration file &_Local/eximon.conf_&.
36758 Searches of the text in the log window can be carried out by means of the ^R
36759 and ^S keystrokes, which default to a reverse and a forward search,
36760 respectively. The search covers only the text that is displayed in the window.
36761 It cannot go further back up the log.
36763 The point from which the search starts is indicated by a caret marker. This is
36764 normally at the end of the text in the window, but can be positioned explicitly
36765 by pointing and clicking with the left mouse button, and is moved automatically
36766 by a successful search. If new text arrives in the window when it is scrolled
36767 back, the caret remains where it is, but if the window is not scrolled back,
36768 the caret is moved to the end of the new text.
36770 Pressing ^R or ^S pops up a window into which the search text can be typed.
36771 There are buttons for selecting forward or reverse searching, for carrying out
36772 the search, and for cancelling. If the &"Search"& button is pressed, the search
36773 happens and the window remains so that further searches can be done. If the
36774 &"Return"& key is pressed, a single search is done and the window is closed. If
36775 ^C is typed the search is cancelled.
36777 The searching facility is implemented using the facilities of the Athena text
36778 widget. By default this pops up a window containing both &"search"& and
36779 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
36780 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
36781 However, the linkers in BSDI and HP-UX seem unable to handle an externally
36782 provided version of &%TextPop%& when the remaining parts of the text widget
36783 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
36784 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
36785 on these systems, at the expense of having unwanted items in the search popup
36790 .section "The queue display" "SECID268"
36791 .cindex "queue" "display in monitor"
36792 The bottom section of the monitor window contains a list of all messages that
36793 are on the queue, which includes those currently being received or delivered,
36794 as well as those awaiting delivery. The size of this subwindow is controlled by
36795 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
36796 at which it is updated is controlled by another parameter in the same file &--
36797 the default is 5 minutes, since queue scans can be quite expensive. However,
36798 there is an &"Update"& action button just above the display which can be used
36799 to force an update of the queue display at any time.
36801 When a host is down for some time, a lot of pending mail can build up for it,
36802 and this can make it hard to deal with other messages on the queue. To help
36803 with this situation there is a button next to &"Update"& called &"Hide"&. If
36804 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
36805 type anything in here and press &"Return"&, the text is added to a chain of
36806 such texts, and if every undelivered address in a message matches at least one
36807 of the texts, the message is not displayed.
36809 If there is an address that does not match any of the texts, all the addresses
36810 are displayed as normal. The matching happens on the ends of addresses so, for
36811 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
36812 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
36813 has been set up, a button called &"Unhide"& is displayed. If pressed, it
36814 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
36815 a hide request is automatically cancelled after one hour.
36817 While the dialogue box is displayed, you can't press any buttons or do anything
36818 else to the monitor window. For this reason, if you want to cut text from the
36819 queue display to use in the dialogue box, you have to do the cutting before
36820 pressing the &"Hide"& button.
36822 The queue display contains, for each unhidden queued message, the length of
36823 time it has been on the queue, the size of the message, the message id, the
36824 message sender, and the first undelivered recipient, all on one line. If it is
36825 a bounce message, the sender is shown as &"<>"&. If there is more than one
36826 recipient to which the message has not yet been delivered, subsequent ones are
36827 listed on additional lines, up to a maximum configured number, following which
36828 an ellipsis is displayed. Recipients that have already received the message are
36831 .cindex "frozen messages" "display"
36832 If a message is frozen, an asterisk is displayed at the left-hand side.
36834 The queue display has a vertical scroll bar, and can also be scrolled by means
36835 of the arrow keys. Text can be cut from it using the mouse in the normal way.
36836 The text searching facilities, as described above for the log window, are also
36837 available, but the caret is always moved to the end of the text when the queue
36838 display is updated.
36842 .section "The queue menu" "SECID269"
36843 .cindex "queue" "menu in monitor"
36844 If the &%shift%& key is held down and the left button is clicked when the mouse
36845 pointer is over the text for any message, an action menu pops up, and the first
36846 line of the queue display for the message is highlighted. This does not affect
36849 If you want to use some other event for popping up the menu, you can set the
36850 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
36851 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
36852 value set in this parameter is a standard X event description. For example, to
36853 run eximon using &%ctrl%& rather than &%shift%& you could use
36855 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
36857 The title of the menu is the message id, and it contains entries which act as
36861 &'message log'&: The contents of the message log for the message are displayed
36862 in a new text window.
36864 &'headers'&: Information from the spool file that contains the envelope
36865 information and headers is displayed in a new text window. See chapter
36866 &<<CHAPspool>>& for a description of the format of spool files.
36868 &'body'&: The contents of the spool file containing the body of the message are
36869 displayed in a new text window. There is a default limit of 20,000 bytes to the
36870 amount of data displayed. This can be changed by setting the BODY_MAX
36871 option at compile time, or the EXIMON_BODY_MAX option at run time.
36873 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
36874 delivery of the message. This causes an automatic thaw if the message is
36875 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
36876 a new text window. The delivery is run in a separate process, to avoid holding
36877 up the monitor while the delivery proceeds.
36879 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
36880 that the message be frozen.
36882 .cindex "thawing messages"
36883 .cindex "unfreezing messages"
36884 .cindex "frozen messages" "thawing"
36885 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
36886 that the message be thawed.
36888 .cindex "delivery" "forcing failure"
36889 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
36890 that Exim gives up trying to deliver the message. A bounce message is generated
36891 for any remaining undelivered addresses.
36893 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
36894 that the message be deleted from the system without generating a bounce
36897 &'add recipient'&: A dialog box is displayed into which a recipient address can
36898 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36899 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36900 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36901 causes a call to Exim to be made using the &%-Mar%& option to request that an
36902 additional recipient be added to the message, unless the entry box is empty, in
36903 which case no action is taken.
36905 &'mark delivered'&: A dialog box is displayed into which a recipient address
36906 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
36907 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
36908 Otherwise it must be entered as a fully qualified address. Pressing RETURN
36909 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
36910 recipient address as already delivered, unless the entry box is empty, in which
36911 case no action is taken.
36913 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
36914 mark all recipient addresses as already delivered.
36916 &'edit sender'&: A dialog box is displayed initialized with the current
36917 sender's address. Pressing RETURN causes a call to Exim to be made using the
36918 &%-Mes%& option to replace the sender address, unless the entry box is empty,
36919 in which case no action is taken. If you want to set an empty sender (as in
36920 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
36921 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
36922 the address is qualified with that domain.
36925 When a delivery is forced, a window showing the &%-v%& output is displayed. In
36926 other cases when a call to Exim is made, if there is any output from Exim (in
36927 particular, if the command fails) a window containing the command and the
36928 output is displayed. Otherwise, the results of the action are normally apparent
36929 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
36930 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
36931 if no output is generated.
36933 The queue display is automatically updated for actions such as freezing and
36934 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
36935 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
36936 force an update of the display after one of these actions.
36938 In any text window that is displayed as result of a menu action, the normal
36939 cut-and-paste facility is available, and searching can be carried out using ^R
36940 and ^S, as described above for the log tail window.
36947 . ////////////////////////////////////////////////////////////////////////////
36948 . ////////////////////////////////////////////////////////////////////////////
36950 .chapter "Security considerations" "CHAPsecurity"
36951 .scindex IIDsecurcon "security" "discussion of"
36952 This chapter discusses a number of issues concerned with security, some of
36953 which are also covered in other parts of this manual.
36955 For reasons that this author does not understand, some people have promoted
36956 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
36957 existence of this chapter in the documentation. However, the intent of the
36958 chapter is simply to describe the way Exim works in relation to certain
36959 security concerns, not to make any specific claims about the effectiveness of
36960 its security as compared with other MTAs.
36962 What follows is a description of the way Exim is supposed to be. Best efforts
36963 have been made to try to ensure that the code agrees with the theory, but an
36964 absence of bugs can never be guaranteed. Any that are reported will get fixed
36965 as soon as possible.
36968 .section "Building a more &""hardened""& Exim" "SECID286"
36969 .cindex "security" "build-time features"
36970 There are a number of build-time options that can be set in &_Local/Makefile_&
36971 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
36972 Exim administrator who does not have the root password, or by someone who has
36973 penetrated the Exim (but not the root) account. These options are as follows:
36976 ALT_CONFIG_PREFIX can be set to a string that is required to match the
36977 start of any file names used with the &%-C%& option. When it is set, these file
36978 names are also not allowed to contain the sequence &"/../"&. (However, if the
36979 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
36980 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
36981 default setting for &%ALT_CONFIG_PREFIX%&.
36983 If the permitted configuration files are confined to a directory to
36984 which only root has access, this guards against someone who has broken
36985 into the Exim account from running a privileged Exim with an arbitrary
36986 configuration file, and using it to break into other accounts.
36989 If a non-trusted configuration file (i.e. not the default configuration file
36990 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
36991 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
36992 the next item), then root privilege is retained only if the caller of Exim is
36993 root. This locks out the possibility of testing a configuration using &%-C%&
36994 right through message reception and delivery, even if the caller is root. The
36995 reception works, but by that time, Exim is running as the Exim user, so when
36996 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
36997 privilege to be lost. However, root can test reception and delivery using two
37001 The WHITELIST_D_MACROS build option declares some macros to be safe to override
37002 with &%-D%& if the real uid is one of root, the Exim run-time user or the
37003 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
37004 requiring the run-time value supplied to &%-D%& to match a regex that errs on
37005 the restrictive side. Requiring build-time selection of safe macros is onerous
37006 but this option is intended solely as a transition mechanism to permit
37007 previously-working configurations to continue to work after release 4.73.
37009 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
37012 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
37013 never to be used for any deliveries. This is like the &%never_users%& runtime
37014 option, but it cannot be overridden; the runtime option adds additional users
37015 to the list. The default setting is &"root"&; this prevents a non-root user who
37016 is permitted to modify the runtime file from using Exim as a way to get root.
37021 .section "Root privilege" "SECID270"
37023 .cindex "root privilege"
37024 The Exim binary is normally setuid to root, which means that it gains root
37025 privilege (runs as root) when it starts execution. In some special cases (for
37026 example, when the daemon is not in use and there are no local deliveries), it
37027 may be possible to run Exim setuid to some user other than root. This is
37028 discussed in the next section. However, in most installations, root privilege
37029 is required for two things:
37032 To set up a socket connected to the standard SMTP port (25) when initialising
37033 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
37036 To be able to change uid and gid in order to read users' &_.forward_& files and
37037 perform local deliveries as the receiving user or as specified in the
37041 It is not necessary to be root to do any of the other things Exim does, such as
37042 receiving messages and delivering them externally over SMTP, and it is
37043 obviously more secure if Exim does not run as root except when necessary.
37044 For this reason, a user and group for Exim to use must be defined in
37045 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37046 group"&. Their values can be changed by the run time configuration, though this
37047 is not recommended. Often a user called &'exim'& is used, but some sites use
37048 &'mail'& or another user name altogether.
37050 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37051 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37052 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37054 After a new Exim process has interpreted its command line options, it changes
37055 uid and gid in the following cases:
37060 If the &%-C%& option is used to specify an alternate configuration file, or if
37061 the &%-D%& option is used to define macro values for the configuration, and the
37062 calling process is not running as root, the uid and gid are changed to those of
37063 the calling process.
37064 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37065 option may not be used at all.
37066 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37067 can be supplied if the calling process is running as root, the Exim run-time
37068 user or CONFIGURE_OWNER, if defined.
37073 If the expansion test option (&%-be%&) or one of the filter testing options
37074 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37077 If the process is not a daemon process or a queue runner process or a delivery
37078 process or a process for testing address routing (started with &%-bt%&), the
37079 uid and gid are changed to the Exim user and group. This means that Exim always
37080 runs under its own uid and gid when receiving messages. This also applies when
37081 testing address verification
37084 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37087 For a daemon, queue runner, delivery, or address testing process, the uid
37088 remains as root at this stage, but the gid is changed to the Exim group.
37091 The processes that initially retain root privilege behave as follows:
37094 A daemon process changes the gid to the Exim group and the uid to the Exim
37095 user after setting up one or more listening sockets. The &[initgroups()]&
37096 function is called, so that if the Exim user is in any additional groups, they
37097 will be used during message reception.
37099 A queue runner process retains root privilege throughout its execution. Its
37100 job is to fork a controlled sequence of delivery processes.
37102 A delivery process retains root privilege throughout most of its execution,
37103 but any actual deliveries (that is, the transports themselves) are run in
37104 subprocesses which always change to a non-root uid and gid. For local
37105 deliveries this is typically the uid and gid of the owner of the mailbox; for
37106 remote deliveries, the Exim uid and gid are used. Once all the delivery
37107 subprocesses have been run, a delivery process changes to the Exim uid and gid
37108 while doing post-delivery tidying up such as updating the retry database and
37109 generating bounce and warning messages.
37111 While the recipient addresses in a message are being routed, the delivery
37112 process runs as root. However, if a user's filter file has to be processed,
37113 this is done in a subprocess that runs under the individual user's uid and
37114 gid. A system filter is run as root unless &%system_filter_user%& is set.
37116 A process that is testing addresses (the &%-bt%& option) runs as root so that
37117 the routing is done in the same environment as a message delivery.
37123 .section "Running Exim without privilege" "SECTrunexiwitpri"
37124 .cindex "privilege, running without"
37125 .cindex "unprivileged running"
37126 .cindex "root privilege" "running without"
37127 Some installations like to run Exim in an unprivileged state for more of its
37128 operation, for added security. Support for this mode of operation is provided
37129 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37130 gid are changed to the Exim user and group at the start of a delivery process
37131 (and also queue runner and address testing processes). This means that address
37132 routing is no longer run as root, and the deliveries themselves cannot change
37136 .cindex "daemon" "restarting"
37137 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37138 that the daemon can still be started in the usual way, and it can respond
37139 correctly to SIGHUP because the re-invocation regains root privilege.
37141 An alternative approach is to make Exim setuid to the Exim user and also setgid
37142 to the Exim group. If you do this, the daemon must be started from a root
37143 process. (Calling Exim from a root process makes it behave in the way it does
37144 when it is setuid root.) However, the daemon cannot restart itself after a
37145 SIGHUP signal because it cannot regain privilege.
37147 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37148 stops Exim from trying to re-invoke itself to do a delivery after a message has
37149 been received. Such a re-invocation is a waste of resources because it has no
37152 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37153 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37154 to the Exim user seems a clean approach, but there is one complication:
37156 In this style of operation, Exim is running with the real uid and gid set to
37157 those of the calling process, and the effective uid/gid set to Exim's values.
37158 Ideally, any association with the calling process' uid/gid should be dropped,
37159 that is, the real uid/gid should be reset to the effective values so as to
37160 discard any privileges that the caller may have. While some operating systems
37161 have a function that permits this action for a non-root effective uid, quite a
37162 number of them do not. Because of this lack of standardization, Exim does not
37163 address this problem at this time.
37165 For this reason, the recommended approach for &"mostly unprivileged"& running
37166 is to keep the Exim binary setuid to root, and to set
37167 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37168 be used in the most straightforward way.
37170 If you configure Exim not to run delivery processes as root, there are a
37171 number of restrictions on what you can do:
37174 You can deliver only as the Exim user/group. You should explicitly use the
37175 &%user%& and &%group%& options to override routers or local transports that
37176 normally deliver as the recipient. This makes sure that configurations that
37177 work in this mode function the same way in normal mode. Any implicit or
37178 explicit specification of another user causes an error.
37180 Use of &_.forward_& files is severely restricted, such that it is usually
37181 not worthwhile to include them in the configuration.
37183 Users who wish to use &_.forward_& would have to make their home directory and
37184 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37185 and their equivalents in Exim filters, cannot be used. While they could be
37186 enabled in the Exim user's name, that would be insecure and not very useful.
37188 Unless the local user mailboxes are all owned by the Exim user (possible in
37189 some POP3 or IMAP-only environments):
37192 They must be owned by the Exim group and be writeable by that group. This
37193 implies you must set &%mode%& in the appendfile configuration, as well as the
37194 mode of the mailbox files themselves.
37196 You must set &%no_check_owner%&, since most or all of the files will not be
37197 owned by the Exim user.
37199 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37200 on a newly created mailbox when unprivileged. This also implies that new
37201 mailboxes need to be created manually.
37206 These restrictions severely restrict what can be done in local deliveries.
37207 However, there are no restrictions on remote deliveries. If you are running a
37208 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37209 gives more security at essentially no cost.
37211 If you are using the &%mua_wrapper%& facility (see chapter
37212 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37217 .section "Delivering to local files" "SECID271"
37218 Full details of the checks applied by &(appendfile)& before it writes to a file
37219 are given in chapter &<<CHAPappendfile>>&.
37223 .section "Running local commands" "SECTsecconslocalcmds"
37224 .cindex "security" "local commands"
37225 .cindex "security" "command injection attacks"
37226 There are a number of ways in which an administrator can configure Exim to run
37227 commands based upon received, untrustworthy, data. Further, in some
37228 configurations a user who can control a &_.forward_& file can also arrange to
37229 run commands. Configuration to check includes, but is not limited to:
37232 Use of &%use_shell%& in the pipe transport: various forms of shell command
37233 injection may be possible with this option present. It is dangerous and should
37234 be used only with considerable caution. Consider constraints which whitelist
37235 allowed characters in a variable which is to be used in a pipe transport that
37236 has &%use_shell%& enabled.
37238 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37239 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37240 &_.forward_& files in a redirect router. If Exim is running on a central mail
37241 hub to which ordinary users do not have shell access, but home directories are
37242 NFS mounted (for instance) then administrators should review the list of these
37243 forbid options available, and should bear in mind that the options that may
37244 need forbidding can change as new features are added between releases.
37246 The &%${run...}%& expansion item does not use a shell by default, but
37247 administrators can configure use of &_/bin/sh_& as part of the command.
37248 Such invocations should be viewed with prejudicial suspicion.
37250 Administrators who use embedded Perl are advised to explore how Perl's
37251 taint checking might apply to their usage.
37253 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37254 administrators are well advised to view its use with suspicion, in case (for
37255 instance) it allows a local-part to contain embedded Exim directives.
37257 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37258 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37259 each can reference arbitrary lists and files, rather than just being a list
37261 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37262 real-world security vulnerabilities caused by its use with untrustworthy data
37263 injected in, for SQL injection attacks.
37264 Consider the use of the &%inlisti%& expansion condition instead.
37270 .section "Trust in configuration data" "SECTsecconfdata"
37271 .cindex "security" "data sources"
37272 .cindex "security" "regular expressions"
37273 .cindex "regular expressions" "security"
37274 .cindex "PCRE" "security"
37275 If configuration data for Exim can come from untrustworthy sources, there
37276 are some issues to be aware of:
37279 Use of &%${expand...}%& may provide a path for shell injection attacks.
37281 Letting untrusted data provide a regular expression is unwise.
37283 Using &%${match...}%& to apply a fixed regular expression against untrusted
37284 data may result in pathological behaviour within PCRE. Be aware of what
37285 "backtracking" means and consider options for being more strict with a regular
37286 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37287 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37288 possessive quantifiers or just not using regular expressions against untrusted
37291 It can be important to correctly use &%${quote:...}%&,
37292 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37293 items to ensure that data is correctly constructed.
37295 Some lookups might return multiple results, even though normal usage is only
37296 expected to yield one result.
37302 .section "IPv4 source routing" "SECID272"
37303 .cindex "source routing" "in IP packets"
37304 .cindex "IP source routing"
37305 Many operating systems suppress IP source-routed packets in the kernel, but
37306 some cannot be made to do this, so Exim does its own check. It logs incoming
37307 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37308 IPv6. No special checking is currently done.
37312 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37313 Support for these SMTP commands is disabled by default. If required, they can
37314 be enabled by defining suitable ACLs.
37319 .section "Privileged users" "SECID274"
37320 .cindex "trusted users"
37321 .cindex "admin user"
37322 .cindex "privileged user"
37323 .cindex "user" "trusted"
37324 .cindex "user" "admin"
37325 Exim recognizes two sets of users with special privileges. Trusted users are
37326 able to submit new messages to Exim locally, but supply their own sender
37327 addresses and information about a sending host. For other users submitting
37328 local messages, Exim sets up the sender address from the uid, and doesn't
37329 permit a remote host to be specified.
37332 However, an untrusted user is permitted to use the &%-f%& command line option
37333 in the special form &%-f <>%& to indicate that a delivery failure for the
37334 message should not cause an error report. This affects the message's envelope,
37335 but it does not affect the &'Sender:'& header. Untrusted users may also be
37336 permitted to use specific forms of address with the &%-f%& option by setting
37337 the &%untrusted_set_sender%& option.
37339 Trusted users are used to run processes that receive mail messages from some
37340 other mail domain and pass them on to Exim for delivery either locally, or over
37341 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37342 as any user listed in the &%trusted_users%& configuration option, or under any
37343 group listed in the &%trusted_groups%& option.
37345 Admin users are permitted to do things to the messages on Exim's queue. They
37346 can freeze or thaw messages, cause them to be returned to their senders, remove
37347 them entirely, or modify them in various ways. In addition, admin users can run
37348 the Exim monitor and see all the information it is capable of providing, which
37349 includes the contents of files on the spool.
37353 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37354 delivery of messages on its queue is restricted to admin users. This
37355 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37356 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37357 queue is also restricted to admin users. This restriction can be relaxed by
37358 setting &%no_queue_list_requires_admin%&.
37360 Exim recognizes an admin user if the calling process is running as root or as
37361 the Exim user or if any of the groups associated with the calling process is
37362 the Exim group. It is not necessary actually to be running under the Exim
37363 group. However, if admin users who are not root or the Exim user are to access
37364 the contents of files on the spool via the Exim monitor (which runs
37365 unprivileged), Exim must be built to allow group read access to its spool
37370 .section "Spool files" "SECID275"
37371 .cindex "spool directory" "files"
37372 Exim's spool directory and everything it contains is owned by the Exim user and
37373 set to the Exim group. The mode for spool files is defined in the
37374 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37375 any user who is a member of the Exim group can access these files.
37379 .section "Use of argv[0]" "SECID276"
37380 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37381 of specific strings, Exim assumes certain options. For example, calling Exim
37382 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37383 to calling it with the option &%-bS%&. There are no security implications in
37388 .section "Use of %f formatting" "SECID277"
37389 The only use made of &"%f"& by Exim is in formatting load average values. These
37390 are actually stored in integer variables as 1000 times the load average.
37391 Consequently, their range is limited and so therefore is the length of the
37396 .section "Embedded Exim path" "SECID278"
37397 Exim uses its own path name, which is embedded in the code, only when it needs
37398 to re-exec in order to regain root privilege. Therefore, it is not root when it
37399 does so. If some bug allowed the path to get overwritten, it would lead to an
37400 arbitrary program's being run as exim, not as root.
37404 .section "Dynamic module directory" "SECTdynmoddir"
37405 Any dynamically loadable modules must be installed into the directory
37406 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37410 .section "Use of sprintf()" "SECID279"
37411 .cindex "&[sprintf()]&"
37412 A large number of occurrences of &"sprintf"& in the code are actually calls to
37413 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37414 The intermediate formatting is done into a large fixed buffer by a function
37415 that runs through the format string itself, and checks the length of each
37416 conversion before performing it, thus preventing buffer overruns.
37418 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37419 the output buffer is known to be sufficiently long to contain the converted
37424 .section "Use of debug_printf() and log_write()" "SECID280"
37425 Arbitrary strings are passed to both these functions, but they do their
37426 formatting by calling the function &'string_vformat()'&, which runs through
37427 the format string itself, and checks the length of each conversion.
37431 .section "Use of strcat() and strcpy()" "SECID281"
37432 These are used only in cases where the output buffer is known to be large
37433 enough to hold the result.
37434 .ecindex IIDsecurcon
37439 . ////////////////////////////////////////////////////////////////////////////
37440 . ////////////////////////////////////////////////////////////////////////////
37442 .chapter "Format of spool files" "CHAPspool"
37443 .scindex IIDforspo1 "format" "spool files"
37444 .scindex IIDforspo2 "spool directory" "format of files"
37445 .scindex IIDforspo3 "spool files" "format of"
37446 .cindex "spool files" "editing"
37447 A message on Exim's queue consists of two files, whose names are the message id
37448 followed by -D and -H, respectively. The data portion of the message is kept in
37449 the -D file on its own. The message's envelope, status, and headers are all
37450 kept in the -H file, whose format is described in this chapter. Each of these
37451 two files contains the final component of its own name as its first line. This
37452 is insurance against disk crashes where the directory is lost but the files
37453 themselves are recoverable.
37455 Some people are tempted into editing -D files in order to modify messages. You
37456 need to be extremely careful if you do this; it is not recommended and you are
37457 on your own if you do it. Here are some of the pitfalls:
37460 You must ensure that Exim does not try to deliver the message while you are
37461 fiddling with it. The safest way is to take out a write lock on the -D file,
37462 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37463 place, the lock will be retained. If you write a new file and rename it, the
37464 lock will be lost at the instant of rename.
37466 .vindex "&$body_linecount$&"
37467 If you change the number of lines in the file, the value of
37468 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
37469 present, this value is not used by Exim, but there is no guarantee that this
37470 will always be the case.
37472 If the message is in MIME format, you must take care not to break it.
37474 If the message is cryptographically signed, any change will invalidate the
37477 All in all, modifying -D files is fraught with danger.
37479 Files whose names end with -J may also be seen in the &_input_& directory (or
37480 its subdirectories when &%split_spool_directory%& is set). These are journal
37481 files, used to record addresses to which the message has been delivered during
37482 the course of a delivery attempt. If there are still undelivered recipients at
37483 the end, the -H file is updated, and the -J file is deleted. If, however, there
37484 is some kind of crash (for example, a power outage) before this happens, the -J
37485 file remains in existence. When Exim next processes the message, it notices the
37486 -J file and uses it to update the -H file before starting the next delivery
37489 .section "Format of the -H file" "SECID282"
37490 .cindex "uid (user id)" "in spool file"
37491 .cindex "gid (group id)" "in spool file"
37492 The second line of the -H file contains the login name for the uid of the
37493 process that called Exim to read the message, followed by the numerical uid and
37494 gid. For a locally generated message, this is normally the user who sent the
37495 message. For a message received over TCP/IP via the daemon, it is
37496 normally the Exim user.
37498 The third line of the file contains the address of the message's sender as
37499 transmitted in the envelope, contained in angle brackets. The sender address is
37500 empty for bounce messages. For incoming SMTP mail, the sender address is given
37501 in the MAIL command. For locally generated mail, the sender address is
37502 created by Exim from the login name of the current user and the configured
37503 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37504 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37505 &"<>"& or an address that matches &%untrusted_set_senders%&.
37507 The fourth line contains two numbers. The first is the time that the message
37508 was received, in the conventional Unix form &-- the number of seconds since the
37509 start of the epoch. The second number is a count of the number of messages
37510 warning of delayed delivery that have been sent to the sender.
37512 There follow a number of lines starting with a hyphen. These can appear in any
37513 order, and are omitted when not relevant:
37516 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37517 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37518 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37519 recognized, to provide backward compatibility. In the old format, a line of
37520 this form is present for every ACL variable that is not empty. The number
37521 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37522 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37523 the data string for the variable. The string itself starts at the beginning of
37524 the next line, and is followed by a newline character. It may contain internal
37527 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37528 A line of this form is present for every ACL connection variable that is
37529 defined. Note that there is a space between &%-aclc%& and the rest of the name.
37530 The length is the length of the data string for the variable. The string itself
37531 starts at the beginning of the next line, and is followed by a newline
37532 character. It may contain internal newlines.
37534 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
37535 A line of this form is present for every ACL message variable that is defined.
37536 Note that there is a space between &%-aclm%& and the rest of the name. The
37537 length is the length of the data string for the variable. The string itself
37538 starts at the beginning of the next line, and is followed by a newline
37539 character. It may contain internal newlines.
37541 .vitem "&%-active_hostname%&&~<&'hostname'&>"
37542 This is present if, when the message was received over SMTP, the value of
37543 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
37545 .vitem &%-allow_unqualified_recipient%&
37546 This is present if unqualified recipient addresses are permitted in header
37547 lines (to stop such addresses from being qualified if rewriting occurs at
37548 transport time). Local messages that were input using &%-bnq%& and remote
37549 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
37551 .vitem &%-allow_unqualified_sender%&
37552 This is present if unqualified sender addresses are permitted in header lines
37553 (to stop such addresses from being qualified if rewriting occurs at transport
37554 time). Local messages that were input using &%-bnq%& and remote messages from
37555 hosts that match &%sender_unqualified_hosts%& set this flag.
37557 .vitem "&%-auth_id%&&~<&'text'&>"
37558 The id information for a message received on an authenticated SMTP connection
37559 &-- the value of the &$authenticated_id$& variable.
37561 .vitem "&%-auth_sender%&&~<&'address'&>"
37562 The address of an authenticated sender &-- the value of the
37563 &$authenticated_sender$& variable.
37565 .vitem "&%-body_linecount%&&~<&'number'&>"
37566 This records the number of lines in the body of the message, and is always
37569 .vitem "&%-body_zerocount%&&~<&'number'&>"
37570 This records the number of binary zero bytes in the body of the message, and is
37571 present if the number is greater than zero.
37573 .vitem &%-deliver_firsttime%&
37574 This is written when a new message is first added to the spool. When the spool
37575 file is updated after a deferral, it is omitted.
37577 .vitem "&%-frozen%&&~<&'time'&>"
37578 .cindex "frozen messages" "spool data"
37579 The message is frozen, and the freezing happened at <&'time'&>.
37581 .vitem "&%-helo_name%&&~<&'text'&>"
37582 This records the host name as specified by a remote host in a HELO or EHLO
37585 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
37586 This records the IP address of the host from which the message was received and
37587 the remote port number that was used. It is omitted for locally generated
37590 .vitem "&%-host_auth%&&~<&'text'&>"
37591 If the message was received on an authenticated SMTP connection, this records
37592 the name of the authenticator &-- the value of the
37593 &$sender_host_authenticated$& variable.
37595 .vitem &%-host_lookup_failed%&
37596 This is present if an attempt to look up the sending host's name from its IP
37597 address failed. It corresponds to the &$host_lookup_failed$& variable.
37599 .vitem "&%-host_name%&&~<&'text'&>"
37600 .cindex "reverse DNS lookup"
37601 .cindex "DNS" "reverse lookup"
37602 This records the name of the remote host from which the message was received,
37603 if the host name was looked up from the IP address when the message was being
37604 received. It is not present if no reverse lookup was done.
37606 .vitem "&%-ident%&&~<&'text'&>"
37607 For locally submitted messages, this records the login of the originating user,
37608 unless it was a trusted user and the &%-oMt%& option was used to specify an
37609 ident value. For messages received over TCP/IP, this records the ident string
37610 supplied by the remote host, if any.
37612 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
37613 This records the IP address of the local interface and the port number through
37614 which a message was received from a remote host. It is omitted for locally
37615 generated messages.
37618 The message is from a local sender.
37620 .vitem &%-localerror%&
37621 The message is a locally-generated bounce message.
37623 .vitem "&%-local_scan%&&~<&'string'&>"
37624 This records the data string that was returned by the &[local_scan()]& function
37625 when the message was received &-- the value of the &$local_scan_data$&
37626 variable. It is omitted if no data was returned.
37628 .vitem &%-manual_thaw%&
37629 The message was frozen but has been thawed manually, that is, by an explicit
37630 Exim command rather than via the auto-thaw process.
37633 A testing delivery process was started using the &%-N%& option to suppress any
37634 actual deliveries, but delivery was deferred. At any further delivery attempts,
37637 .vitem &%-received_protocol%&
37638 This records the value of the &$received_protocol$& variable, which contains
37639 the name of the protocol by which the message was received.
37641 .vitem &%-sender_set_untrusted%&
37642 The envelope sender of this message was set by an untrusted local caller (used
37643 to ensure that the caller is displayed in queue listings).
37645 .vitem "&%-spam_score_int%&&~<&'number'&>"
37646 If a message was scanned by SpamAssassin, this is present. It records the value
37647 of &$spam_score_int$&.
37649 .vitem &%-tls_certificate_verified%&
37650 A TLS certificate was received from the client that sent this message, and the
37651 certificate was verified by the server.
37653 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
37654 When the message was received over an encrypted connection, this records the
37655 name of the cipher suite that was used.
37657 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
37658 When the message was received over an encrypted connection, and a certificate
37659 was received from the client, this records the Distinguished Name from that
37663 Following the options there is a list of those addresses to which the message
37664 is not to be delivered. This set of addresses is initialized from the command
37665 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
37666 is set; otherwise it starts out empty. Whenever a successful delivery is made,
37667 the address is added to this set. The addresses are kept internally as a
37668 balanced binary tree, and it is a representation of that tree which is written
37669 to the spool file. If an address is expanded via an alias or forward file, the
37670 original address is added to the tree when deliveries to all its child
37671 addresses are complete.
37673 If the tree is empty, there is a single line in the spool file containing just
37674 the text &"XX"&. Otherwise, each line consists of two letters, which are either
37675 Y or N, followed by an address. The address is the value for the node of the
37676 tree, and the letters indicate whether the node has a left branch and/or a
37677 right branch attached to it, respectively. If branches exist, they immediately
37678 follow. Here is an example of a three-node tree:
37680 YY darcy@austen.fict.example
37681 NN alice@wonderland.fict.example
37682 NN editor@thesaurus.ref.example
37684 After the non-recipients tree, there is a list of the message's recipients.
37685 This is a simple list, preceded by a count. It includes all the original
37686 recipients of the message, including those to whom the message has already been
37687 delivered. In the simplest case, the list contains one address per line. For
37691 editor@thesaurus.ref.example
37692 darcy@austen.fict.example
37694 alice@wonderland.fict.example
37696 However, when a child address has been added to the top-level addresses as a
37697 result of the use of the &%one_time%& option on a &(redirect)& router, each
37698 line is of the following form:
37700 <&'top-level address'&> <&'errors_to address'&> &&&
37701 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
37703 The 01 flag bit indicates the presence of the three other fields that follow
37704 the top-level address. Other bits may be used in future to support additional
37705 fields. The <&'parent number'&> is the offset in the recipients list of the
37706 original parent of the &"one time"& address. The first two fields are the
37707 envelope sender that is associated with this address and its length. If the
37708 length is zero, there is no special envelope sender (there are then two space
37709 characters in the line). A non-empty field can arise from a &(redirect)& router
37710 that has an &%errors_to%& setting.
37713 A blank line separates the envelope and status information from the headers
37714 which follow. A header may occupy several lines of the file, and to save effort
37715 when reading it in, each header is preceded by a number and an identifying
37716 character. The number is the number of characters in the header, including any
37717 embedded newlines and the terminating newline. The character is one of the
37721 .row <&'blank'&> "header in which Exim has no special interest"
37722 .row &`B`& "&'Bcc:'& header"
37723 .row &`C`& "&'Cc:'& header"
37724 .row &`F`& "&'From:'& header"
37725 .row &`I`& "&'Message-id:'& header"
37726 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
37727 .row &`R`& "&'Reply-To:'& header"
37728 .row &`S`& "&'Sender:'& header"
37729 .row &`T`& "&'To:'& header"
37730 .row &`*`& "replaced or deleted header"
37733 Deleted or replaced (rewritten) headers remain in the spool file for debugging
37734 purposes. They are not transmitted when the message is delivered. Here is a
37735 typical set of headers:
37737 111P Received: by hobbit.fict.example with local (Exim 4.00)
37738 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
37739 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
37740 038* X-rewrote-sender: bb@hobbit.fict.example
37741 042* From: Bilbo Baggins <bb@hobbit.fict.example>
37742 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
37743 099* To: alice@wonderland.fict.example, rdo@foundation,
37744 darcy@austen.fict.example, editor@thesaurus.ref.example
37745 104T To: alice@wonderland.fict.example, rdo@foundation.example,
37746 darcy@austen.fict.example, editor@thesaurus.ref.example
37747 038 Date: Fri, 11 May 2001 10:28:59 +0100
37749 The asterisked headers indicate that the envelope sender, &'From:'& header, and
37750 &'To:'& header have been rewritten, the last one because routing expanded the
37751 unqualified domain &'foundation'&.
37752 .ecindex IIDforspo1
37753 .ecindex IIDforspo2
37754 .ecindex IIDforspo3
37756 . ////////////////////////////////////////////////////////////////////////////
37757 . ////////////////////////////////////////////////////////////////////////////
37759 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
37763 DKIM is a mechanism by which messages sent by some entity can be provably
37764 linked to a domain which that entity controls. It permits reputation to
37765 be tracked on a per-domain basis, rather than merely upon source IP address.
37766 DKIM is documented in RFC 4871.
37768 Since version 4.70, DKIM support is compiled into Exim by default. It can be
37769 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
37771 Exim's DKIM implementation allows to
37773 Sign outgoing messages: This function is implemented in the SMTP transport.
37774 It can co-exist with all other Exim features
37775 (including transport filters)
37776 except cutthrough delivery.
37778 Verify signatures in incoming messages: This is implemented by an additional
37779 ACL (acl_smtp_dkim), which can be called several times per message, with
37780 different signature contexts.
37783 In typical Exim style, the verification implementation does not include any
37784 default "policy". Instead it enables you to build your own policy using
37785 Exim's standard controls.
37787 Please note that verification of DKIM signatures in incoming mail is turned
37788 on by default for logging purposes. For each signature in incoming email,
37789 exim will log a line displaying the most important signature details, and the
37790 signature status. Here is an example (with line-breaks added for clarity):
37792 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
37793 d=facebookmail.com s=q1-2009b
37794 c=relaxed/relaxed a=rsa-sha1
37795 i=@facebookmail.com t=1252484542 [verification succeeded]
37797 You might want to turn off DKIM verification processing entirely for internal
37798 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
37799 control modifier. This should typically be done in the RCPT ACL, at points
37800 where you accept mail from relay sources (internal hosts or authenticated
37804 .section "Signing outgoing messages" "SECID513"
37805 .cindex "DKIM" "signing"
37807 Signing is implemented by setting private options on the SMTP transport.
37808 These options take (expandable) strings as arguments.
37810 .option dkim_domain smtp string&!! unset
37812 The domain you want to sign with. The result of this expanded
37813 option is put into the &%$dkim_domain%& expansion variable.
37815 .option dkim_selector smtp string&!! unset
37817 This sets the key selector string. You can use the &%$dkim_domain%& expansion
37818 variable to look up a matching selector. The result is put in the expansion
37819 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
37820 option along with &%$dkim_domain%&.
37822 .option dkim_private_key smtp string&!! unset
37824 This sets the private key to use. You can use the &%$dkim_domain%& and
37825 &%$dkim_selector%& expansion variables to determine the private key to use.
37826 The result can either
37828 be a valid RSA private key in ASCII armor, including line breaks.
37830 start with a slash, in which case it is treated as a file that contains
37833 be "0", "false" or the empty string, in which case the message will not
37834 be signed. This case will not result in an error, even if &%dkim_strict%&
37838 .option dkim_canon smtp string&!! unset
37840 This option sets the canonicalization method used when signing a message.
37841 The DKIM RFC currently supports two methods: "simple" and "relaxed".
37842 The option defaults to "relaxed" when unset. Note: the current implementation
37843 only supports using the same canonicalization method for both headers and body.
37845 .option dkim_strict smtp string&!! unset
37847 This option defines how Exim behaves when signing a message that
37848 should be signed fails for some reason. When the expansion evaluates to
37849 either "1" or "true", Exim will defer. Otherwise Exim will send the message
37850 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
37853 .option dkim_sign_headers smtp string&!! unset
37855 When set, this option must expand to (or be specified as) a colon-separated
37856 list of header names. Headers with these names will be included in the message
37857 signature. When unspecified, the header names recommended in RFC4871 will be
37861 .section "Verifying DKIM signatures in incoming mail" "SECID514"
37862 .cindex "DKIM" "verification"
37864 Verification of DKIM signatures in incoming email is implemented via the
37865 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
37866 syntactically(!) correct signature in the incoming message.
37867 A missing ACL definition defaults to accept.
37868 If any ACL call does not accept, the message is not accepted.
37869 If a cutthrough delivery was in progress for the message it is
37870 summarily dropped (having wasted the transmission effort).
37872 To evaluate the signature in the ACL a large number of expansion variables
37873 containing the signature status and its details are set up during the
37874 runtime of the ACL.
37876 Calling the ACL only for existing signatures is not sufficient to build
37877 more advanced policies. For that reason, the global option
37878 &%dkim_verify_signers%&, and a global expansion variable
37879 &%$dkim_signers%& exist.
37881 The global option &%dkim_verify_signers%& can be set to a colon-separated
37882 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
37883 called. It is expanded when the message has been received. At this point,
37884 the expansion variable &%$dkim_signers%& already contains a colon-separated
37885 list of signer domains and identities for the message. When
37886 &%dkim_verify_signers%& is not specified in the main configuration,
37889 dkim_verify_signers = $dkim_signers
37891 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
37892 DKIM signature in the message. Current DKIM verifiers may want to explicitly
37893 call the ACL for known domains or identities. This would be achieved as follows:
37895 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
37897 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
37898 and "ebay.com", plus all domains and identities that have signatures in the message.
37899 You can also be more creative in constructing your policy. For example:
37901 dkim_verify_signers = $sender_address_domain:$dkim_signers
37904 If a domain or identity is listed several times in the (expanded) value of
37905 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
37908 Inside the &%acl_smtp_dkim%&, the following expansion variables are
37909 available (from most to least important):
37913 .vitem &%$dkim_cur_signer%&
37914 The signer that is being evaluated in this ACL run. This can be a domain or
37915 an identity. This is one of the list items from the expanded main option
37916 &%dkim_verify_signers%& (see above).
37917 .vitem &%$dkim_verify_status%&
37918 A string describing the general status of the signature. One of
37920 &%none%&: There is no signature in the message for the current domain or
37921 identity (as reflected by &%$dkim_cur_signer%&).
37923 &%invalid%&: The signature could not be verified due to a processing error.
37924 More detail is available in &%$dkim_verify_reason%&.
37926 &%fail%&: Verification of the signature failed. More detail is
37927 available in &%$dkim_verify_reason%&.
37929 &%pass%&: The signature passed verification. It is valid.
37931 .vitem &%$dkim_verify_reason%&
37932 A string giving a little bit more detail when &%$dkim_verify_status%& is either
37933 "fail" or "invalid". One of
37935 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
37936 key for the domain could not be retrieved. This may be a temporary problem.
37938 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
37939 record for the domain is syntactically invalid.
37941 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
37942 body hash does not match the one specified in the signature header. This
37943 means that the message body was modified in transit.
37945 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
37946 could not be verified. This may mean that headers were modified,
37947 re-written or otherwise changed in a way which is incompatible with
37948 DKIM verification. It may of course also mean that the signature is forged.
37950 .vitem &%$dkim_domain%&
37951 The signing domain. IMPORTANT: This variable is only populated if there is
37952 an actual signature in the message for the current domain or identity (as
37953 reflected by &%$dkim_cur_signer%&).
37954 .vitem &%$dkim_identity%&
37955 The signing identity, if present. IMPORTANT: This variable is only populated
37956 if there is an actual signature in the message for the current domain or
37957 identity (as reflected by &%$dkim_cur_signer%&).
37958 .vitem &%$dkim_selector%&
37959 The key record selector string.
37960 .vitem &%$dkim_algo%&
37961 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
37962 .vitem &%$dkim_canon_body%&
37963 The body canonicalization method. One of 'relaxed' or 'simple'.
37964 .vitem &%dkim_canon_headers%&
37965 The header canonicalization method. One of 'relaxed' or 'simple'.
37966 .vitem &%$dkim_copiedheaders%&
37967 A transcript of headers and their values which are included in the signature
37968 (copied from the 'z=' tag of the signature).
37969 .vitem &%$dkim_bodylength%&
37970 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
37971 limit was set by the signer, "9999999999999" is returned. This makes sure
37972 that this variable always expands to an integer value.
37973 .vitem &%$dkim_created%&
37974 UNIX timestamp reflecting the date and time when the signature was created.
37975 When this was not specified by the signer, "0" is returned.
37976 .vitem &%$dkim_expires%&
37977 UNIX timestamp reflecting the date and time when the signer wants the
37978 signature to be treated as "expired". When this was not specified by the
37979 signer, "9999999999999" is returned. This makes it possible to do useful
37980 integer size comparisons against this value.
37981 .vitem &%$dkim_headernames%&
37982 A colon-separated list of names of headers included in the signature.
37983 .vitem &%$dkim_key_testing%&
37984 "1" if the key record has the "testing" flag set, "0" if not.
37985 .vitem &%$dkim_key_nosubdomains%&
37986 "1" if the key record forbids subdomaining, "0" otherwise.
37987 .vitem &%$dkim_key_srvtype%&
37988 Service type (tag s=) from the key record. Defaults to "*" if not specified
37990 .vitem &%$dkim_key_granularity%&
37991 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
37993 .vitem &%$dkim_key_notes%&
37994 Notes from the key record (tag n=).
37997 In addition, two ACL conditions are provided:
38000 .vitem &%dkim_signers%&
38001 ACL condition that checks a colon-separated list of domains or identities
38002 for a match against the domain or identity that the ACL is currently verifying
38003 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
38004 verb to a group of domains or identities. For example:
38007 # Warn when Mail purportedly from GMail has no signature at all
38008 warn log_message = GMail sender without DKIM signature
38009 sender_domains = gmail.com
38010 dkim_signers = gmail.com
38014 .vitem &%dkim_status%&
38015 ACL condition that checks a colon-separated list of possible DKIM verification
38016 results against the actual result of verification. This is typically used
38017 to restrict an ACL verb to a list of verification outcomes, for example:
38020 deny message = Mail from Paypal with invalid/missing signature
38021 sender_domains = paypal.com:paypal.de
38022 dkim_signers = paypal.com:paypal.de
38023 dkim_status = none:invalid:fail
38026 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
38027 see the documentation of the &%$dkim_verify_status%& expansion variable above
38028 for more information of what they mean.
38031 . ////////////////////////////////////////////////////////////////////////////
38032 . ////////////////////////////////////////////////////////////////////////////
38034 .chapter "Adding new drivers or lookup types" "CHID13" &&&
38035 "Adding drivers or lookups"
38036 .cindex "adding drivers"
38037 .cindex "new drivers, adding"
38038 .cindex "drivers" "adding new"
38039 The following actions have to be taken in order to add a new router, transport,
38040 authenticator, or lookup type to Exim:
38043 Choose a name for the driver or lookup type that does not conflict with any
38044 existing name; I will use &"newdriver"& in what follows.
38046 Add to &_src/EDITME_& the line:
38048 <&'type'&>&`_NEWDRIVER=yes`&
38050 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38051 code is not to be included in the binary by default, comment this line out. You
38052 should also add any relevant comments about the driver or lookup type.
38054 Add to &_src/config.h.defaults_& the line:
38056 #define <type>_NEWDRIVER
38059 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38060 and create a table entry as is done for all the other drivers and lookup types.
38062 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38063 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38064 Add your &`NEWDRIVER`& to that list.
38065 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38066 simple form that most lookups have.
38068 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38069 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38070 driver or lookup type and add it to the definition of OBJ.
38072 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38075 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38076 as for other drivers and lookups.
38079 Then all you need to do is write the code! A good way to start is to make a
38080 proforma by copying an existing module of the same type, globally changing all
38081 occurrences of the name, and cutting out most of the code. Note that any
38082 options you create must be listed in alphabetical order, because the tables are
38083 searched using a binary chop procedure.
38085 There is a &_README_& file in each of the sub-directories of &_src_& describing
38086 the interface that is expected.
38091 . ////////////////////////////////////////////////////////////////////////////
38092 . ////////////////////////////////////////////////////////////////////////////
38094 . /////////////////////////////////////////////////////////////////////////////
38095 . These lines are processing instructions for the Simple DocBook Processor that
38096 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38097 . PDFs than using xmlto and fop. They will be ignored by all other XML
38099 . /////////////////////////////////////////////////////////////////////////////
38104 foot_right_recto="&chaptertitle;"
38105 foot_right_verso="&chaptertitle;"
38109 .makeindex "Options index" "option"
38110 .makeindex "Variables index" "variable"
38111 .makeindex "Concept index" "concept"
38114 . /////////////////////////////////////////////////////////////////////////////
38115 . /////////////////////////////////////////////////////////////////////////////