-. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.23 2007/08/25 12:33:01 magnus Exp $
+. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.24 2007/08/29 13:37:28 ph10 Exp $
.
. /////////////////////////////////////////////////////////////////////////////
. This is the primary source of the Exim Manual. It is an xfpt document that is
. converted into DocBook XML for subsequent conversion into printing and online
. formats. The markup used herein is "standard" xfpt markup, with some extras.
. The markup is summarized in a file called Markup.txt.
+.
+. WARNING: When you use the .new macro, make sure it appears *before* any
+. adjacent index items; otherwise you get an empty "paragraph" which causes
+. unwanted vertical space.
. /////////////////////////////////////////////////////////////////////////////
.include stdflags
foot_right_recto="&chaptertitle; (&chapternumber;)"
foot_right_verso="&chaptertitle; (&chapternumber;)"
toc_chapter_blanks="yes,yes"
- table_warn_soft_overflow="no"
+ table_warn_overflow="overprint"
?>
.literal off
. the <bookinfo> element must also be updated for each new edition.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.66"
-.set version "4.67"
+.set previousversion "4.67"
+.set version "4.68"
.set ACL "access control lists (ACLs)"
.set I " "
<bookinfo>
<title>Specification of the Exim Mail Transfer Agent</title>
<titleabbrev>The Exim MTA</titleabbrev>
-<date>10 April 2007</date>
+<date>23 August 2007</date>
<author><firstname>Philip</firstname><surname>Hazel</surname></author>
<authorinitials>PH</authorinitials>
<affiliation><orgname>University of Cambridge Computing Service</orgname></affiliation>
<address>New Museums Site, Pembroke Street, Cambridge CB2 3QH, England</address>
<revhistory><revision>
- <revnumber>4.67</revnumber>
- <date>10 April 2007</date>
+ <revnumber>4.68</revnumber>
+ <date>23 August 2007</date>
<authorinitials>PH</authorinitials>
</revision></revhistory>
<copyright><year>2007</year><holder>University of Cambridge</holder></copyright>
</indexterm>
<indexterm role="concept">
<primary>maximum</primary>
- <see><emphasis>limit</emphasis></see>
+ <seealso><emphasis>limit</emphasis></seealso>
</indexterm>
<indexterm role="concept">
<primary>monitor</primary>
.cindex "books about Exim"
An &"easier"& discussion of Exim which provides more in-depth explanatory,
introductory, and tutorial material can be found in a book entitled &'The Exim
-SMTP Mail Server'&, published by UIT Cambridge
+SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
(&url(http://www.uit.co.uk/exim-book/)).
This book also contains a chapter that gives a general introduction to SMTP and
.cindex "wiki"
.cindex "FAQ"
-.new
As well as Exim distribution tar files, the Exim web site contains a number of
differently formatted versions of the documentation. A recent addition to the
-online information is the Exim wiki (&url(http://www.exim.org/eximwiki/)),
+online information is the Exim wiki &new("(&url(http://wiki.exim.org))"),
which contains what used to be a separate FAQ, as well as various other
examples, tips, and know-how that have been contributed by Exim users.
.cindex Bugzilla
-An Exim Bugzilla exists at &url(http://www.exim.org/bugzilla/). You can use
+An Exim Bugzilla exists at &new("&url(http://bugs.exim.org)"). You can use
this to report bugs, and also to add items to the wish list. Please search
first to check that you are not duplicating a previous entry.
-.wen
.section "Mailing lists" "SECID3"
.cindex "mailing lists" "for Exim users"
-.new
The following Exim mailing lists exist:
.table2 140pt
.row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
.row &'exim-future@exim.org'& "Discussion of long-term development"
.endtable
-.wen
You can subscribe to these lists, change your existing subscriptions, and view
or search the archives via the mailing lists link on the Exim home page.
lists.
.section "Exim training" "SECID4"
+.new
.cindex "training courses"
-From time to time (approximately annually at the time of writing), training
-courses are run by the author of Exim in Cambridge, UK. Details of any
-forthcoming courses can be found on the web site
-&url(http://www-tus.csx.cam.ac.uk/courses/exim/).
-
+Training courses in Cambridge (UK) used to be run annually by the author of
+Exim, before he retired. At the time of writing, there are no plans to run
+further Exim courses in Cambridge. However, if that changes, relevant
+information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
+.wen
.section "Bug reports" "SECID5"
.cindex "bug reports"
.cindex "reporting bugs"
-Reports of obvious bugs should be emailed to &'bugs@exim.org'&. However, if you
-are unsure whether some behaviour is a bug or not, the best thing to do is to
-post a message to the &'exim-dev'& mailing list and have it discussed.
+Reports of obvious bugs &new("can be emailed to &'bugs@exim.org'& or reported
+via the Bugzilla (&url(http://bugs.exim.org)).") However, if you are unsure
+whether some behaviour is a bug or not, the best thing to do is to post a
+message to the &'exim-dev'& mailing list and have it discussed.
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
-
This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
the spec and sample code for cdb can be obtained from
&url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
output just states whether a given recipient address from a given host is
acceptable or not. See section &<<SECTcheckaccess>>&.
-.new
Features such as authentication and encryption, where the client input is not
plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
specialized SMTP test program such as
&url(http://jetmore.org/john/code/#swaks,swaks).
-.wen
.vitem &%-bhc%&&~<&'IP&~address'&>
.oindex "&%-bhc%&"
.vitem &%-bP%&
.oindex "&%-bP%&"
-.cindex "configuration options, extracting"
+.cindex "configuration options" "extracting"
.cindex "options" "configuration &-- extracting"
If this option is given with no arguments, it causes the values of all Exim's
main configuration options to be written to the standard output. The values
.code
exim -bP qualify_domain hold_domains
.endd
-.oindex "&%hide%&"
+.cindex "hiding configuration option values"
+.cindex "configuration options" "hiding value of"
+.cindex "options" "hiding value of"
However, any option setting that is preceded by the word &"hide"& in the
configuration file is not shown in full, except to an admin user. For other
users, the output is as in this example:
.cindex "testing" "addresses"
.cindex "address" "testing"
This option runs Exim in address testing mode, in which each argument is taken
-as a &new(recipient) address to be tested for deliverability. The results are
+as a recipient address to be tested for deliverability. The results are
written to the standard output. If a test fails, and the caller is not an admin
user, no details of the failure are output, because these might contain
sensitive information such as usernames and passwords for database lookups.
.cindex "verifying address" "using &%-bv%&"
.cindex "address" "verification"
This option runs Exim in address verification mode, in which each argument is
-taken as a &new(recipient) address to be verified by the routers. (This does
+taken as a recipient address to be verified by the routers. (This does
not involve any verification callouts). During normal operation, verification
happens mostly as a consequence processing a &%verify%& condition in an ACL
(see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
This option causes the contents of the message body (-D) spool file to be
written to the standard output. This option can be used only by an admin user.
+.new
+.vitem &%-Mvc%&&~<&'message&~id'&>
+.oindex "&%-Mvc%&"
+.cindex "message" "listing in RFC 2822 format"
+.cindex "listing" "message in RFC 2922 format"
+This option causes a copy of the complete message (header lines plus body) to
+be written to the standard output in RFC 2822 format. This option can be used
+only by an admin user.
+.wen
+
.vitem &%-Mvh%&&~<&'message&~id'&>
.oindex "&%-Mvh%&"
.cindex "listing" "message headers"
optional parts are:
.ilist
-&'ACL'&: Access control lists for controlling incoming SMTP mail.
+&'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
+&<<CHAPACL>>&).
.next
.cindex "AUTH" "configuration"
&'authenticators'&: Configuration settings for the authenticator drivers. These
are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
.next
&'routers'&: Configuration settings for the router drivers. Routers process
-addresses and determine how the message is to be delivered.
+addresses and determine how the message is to be delivered (see chapters
+&<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
.next
&'transports'&: Configuration settings for the transport drivers. Transports
-define mechanisms for copying messages to destinations.
+define mechanisms for copying messages to destinations (see chapters
+&<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
.next
-&'retry'&: Retry rules, for use when a message cannot be immediately delivered.
+.new
+&'retry'&: Retry rules, for use when a message cannot be delivered immediately.
+If there is no retry section, or if it is empty (that is, no retry rules are
+defined), Exim will not retry deliveries. In this situation, temporary errors
+are treated the same as permanent errors. Retry rules are discussed in chapter
+&<<CHAPretry>>&.
+.wen
.next
&'rewrite'&: Global address rewriting rules, for use when a message arrives and
-when new addresses are generated during delivery.
+when new addresses are generated during delivery. Rewriting is discussed in
+chapter &<<CHAPrewrite>>&.
.next
&'local_scan'&: Private options for the &[local_scan()]& function. If you
want to use this feature, you must set
.code
LOCAL_SCAN_HAS_OPTIONS=yes
.endd
-in &_Local/Makefile_& before building Exim. Full details of the
-&[local_scan()]& facility are given in chapter &<<CHAPlocalscan>>&.
+in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
+facility are given in chapter &<<CHAPlocalscan>>&.
.endlist
.cindex "configuration file" "leading white space in"
.code
qualify_domain = mydomain.example.com
.endd
-.oindex "&%hide%&"
-.cindex "configuration file" "hiding sensitive data"
-.cindex "options" "hiding from extraction"
+.cindex "hiding configuration option values"
+.cindex "configuration options" "hiding value of"
+.cindex "options" "hiding value of"
Some option settings may contain sensitive data, for example, passwords for
accessing databases. To stop non-admin users from using the &%-bP%& command
line option to read these values, you can precede the option settings with the
.section "Integer values" "SECID48"
.cindex "integer configuration values"
.cindex "format" "integer"
-.new
If an option's type is given as &"integer"&, the value can be given in decimal,
hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
number is assumed. Otherwise, it is treated as an octal number unless it starts
with the characters &"0x"&, in which case the remainder is interpreted as a
hexadecimal number.
-.wen
If an integer value is followed by the letter K, it is multiplied by 1024; if
it is followed by the letter M, it is multiplied by 1024x1024. When the values
.section "Octal integer values" "SECID49"
.cindex "integer format"
.cindex "format" "octal integer"
-.new
If an option's type is given as &"octal integer"&, its value is always
interpreted as an octal number, whether or not it starts with the digit zero.
Such options are always output in octal.
-.wen
.section "Fixed point numbers" "SECID50"
.cindex "fixed point configuration values"
.cindex "format" "fixed point"
-.new
If an option's type is given as &"fixed-point"&, its value must be a decimal
integer, optionally followed by a decimal point and up to three further digits.
-.wen
.section "String values" "SECTstrings"
.cindex "string" "format of configuration values"
.cindex "format" "string"
-.new
If an option's type is specified as &"string"&, the value can be specified with
or without double-quotes. If it does not start with a double-quote, the value
consists of the remainder of the line plus any continuation lines, starting at
Exim removes comment lines (those beginning with #) at an early stage, they can
appear in the middle of a multi-line string. The following two settings are
therefore equivalent:
-.wen
.code
trusted_users = uucp:mail
trusted_users = uucp:\
colon in the example above is necessary. If it were not there, the list would
be interpreted as the two items 127.0.0.1:: and 1.
-.new
.section "Changing list separators" "SECID53"
.cindex "list separator" "changing"
.cindex "IPv6" "addresses in lists"
-.wen
Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
introduced to allow the separator character to be changed. If a list begins
with a left angle bracket, followed by any punctuation character, that
&%log_file_path%&. It is recommended that the use of non-colon separators be
confined to circumstances where they really are needed.
-.new
.cindex "list separator" "newline as"
-.cindex "newline as list separator"
+.cindex "newline" "as list separator"
It is also possible to use newline and other control characters (those with
code values less than 32, plus DEL) as separators in lists. Such separators
must be provided literally at the time the list is processed. For options that
doubling, it is not possible to include a control character as data when it is
set as the separator. Two such characters in succession are interpreted as
enclosing an empty list item.
-.wen
1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
is not delivered after 4 days of temporary failure, it is bounced.
+.new
+If the retry section is removed from the configuration, or is empty (that is,
+if no retry rules are defined), Exim will not retry deliveries. This turns
+temporary errors into permanent errors.
+.wen
.section "Rewriting configuration" "SECID58"
utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
.next
+.new
.cindex "lookup" "dsearch"
.cindex "dsearch lookup type"
-&(dsearch)&: The given file must be a directory; this is searched for a file
-whose name is the key. The key may not contain any forward slash characters.
-The result of a successful lookup is the name of the file. An example of how
-this lookup can be used to support virtual domains is given in section
+&(dsearch)&: The given file must be a directory; this is searched for an entry
+whose name is the key by calling the &[lstat()]& function. The key may not
+contain any forward slash characters. If &[lstat()]& succeeds, the result of
+the lookup is the name of the entry, which may be a file, directory,
+symbolic link, or any other kind of directory entry. An example of how this
+lookup can be used to support virtual domains is given in section
&<<SECTvirtualdomains>>&.
+.wen
.next
.cindex "lookup" "iplsearch"
.cindex "iplsearch lookup type"
.next
.cindex "whoson lookup type"
.cindex "lookup" "whoson"
-.new
&(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
allows a server to check whether a particular (dynamically allocated) IP
address is currently allocated to a known (trusted) user and, optionally, to
the authenticated user, which is stored in the variable &$value$&. However, in
this example, the data in &$value$& is not used; the result of the lookup is
one of the fixed strings &"yes"& or &"no"&.
-.wen
.endlist
.section "SQL lookups" "SECTsql"
.cindex "SQL lookup types"
+.cindex "MySQL" "lookup type"
+.cindex "PostgreSQL lookup type"
+.cindex "lookup" "MySQL"
+.cindex "lookup" "PostgreSQL"
+.cindex "Oracle" "lookup type"
+.cindex "lookup" "Oracle"
+.cindex "InterBase lookup type"
+.cindex "lookup" "InterBase"
Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
databases. Queries for these databases contain SQL statements, so an example
might be
If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
&%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
option (as appropriate) must be set to a colon-separated list of server
-information. Each item in the list is a slash-separated list of four items:
-host name, database name, user name, and password. In the case of Oracle, the
-host name field is used for the &"service name"&, and the database name field
-is not used and should be empty. For example:
+information.
+&new("(For MySQL and PostgreSQL only, the global option need not be set if all
+queries contain their own server information &-- see section
+&<<SECTspeserque>>&.)") Each item in the list is a slash-separated list of four
+items: host name, database name, user name, and password. In the case of
+Oracle, the host name field is used for the &"service name"&, and the database
+name field is not used and should be empty. For example:
.code
hide oracle_servers = oracle.plc.example//userx/abcdwxyz
.endd
hide mysql_servers = localhost/users/root/secret:\
otherhost/users/root/othersecret
.endd
+.new
For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
because this is a colon-separated list, the colon has to be doubled. For each
-query, these parameter groups are tried in order until a connection and a query
-succeeds.
+query, these parameter groups are tried in order until a connection is made and
+a query is successfully processed. The result of a query may be that no data is
+found, but that is still a successful query. In other words, the list of
+servers provides a backup facility, not a list of different places to look.
+.wen
The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
for MySQL because these escapes are not recognized in contexts where these
characters are not special.
+.new
+.section "Specifying the server in the query" "SECTspeserque"
+For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
+it is possible to specify a list of servers with an individual query. This is
+done by starting the query with
+.display
+&`servers=`&&'server1:server2:server3:...'&&`;`&
+.endd
+Each item in the list may take one of two forms:
+.olist
+If it contains no slashes it is assumed to be just a host name. The appropriate
+global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
+of the same name, and the remaining parameters (database, user, password) are
+taken from there.
+.next
+If it contains any slashes, it is taken as a complete parameter set.
+.endlist
+The list of servers is used in exactly the same way as the global list.
+Once a connection to a server has happened and a query has been
+successfully executed, processing of the lookup ceases.
+
+This feature is intended for use in master/slave situations where updates
+are occurring and you want to update the master rather than a slave. If the
+master is in the list as a backup for reading, you might have a global setting
+like this:
+.code
+mysql_servers = slave1/db/name/pw:\
+ slave2/db/name/pw:\
+ master/db/name/pw
+.endd
+In an updating lookup, you could then write:
+.code
+${lookup mysql{servers=master; UPDATE ...}
+.endd
+That query would then be sent only to the master server. If, on the other hand,
+the master is not to be used for reading, and so is not present in the global
+option, you can still update it by a query of this form:
+.code
+${lookup pgsql{servers=master/db/name/pw; UPDATE ...}
+.endd
+.wen
+
.section "Special MySQL features" "SECID73"
For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
possible to use the same configuration file on several different hosts that
differ only in their names.
.next
+.new
.cindex "@[] in a domain list"
.cindex "domain list" "matching local IP interfaces"
.cindex "domain literal"
-If a pattern consists of the string &`@[]`& it matches any local IP interface
-address, enclosed in square brackets, as in an email address that contains a
-domain literal.
+If a pattern consists of the string &`@[]`& it matches an IP address enclosed
+in square brackets (as in an email address that contains a domain literal), but
+only if that IP address is recognized as local for email routing purposes. The
+&%local_interfaces%& and &%extra_local_interfaces%& options can be used to
+control which of a host's several IP addresses are treated as local.
In today's Internet, the use of domain literals is controversial.
+.wen
.next
.cindex "@mx_any"
.cindex "@mx_primary"
&'cipher.key.ex'&.
.next
+.new
.cindex "regular expressions" "in domain list"
.cindex "domain list" "matching regular expression"
If a pattern starts with a circumflex character, it is treated as a regular
expression, and matched against the domain using a regular expression matching
function. The circumflex is treated as part of the regular expression.
-References to descriptions of the syntax of regular expressions are given in
-chapter &<<CHAPregexp>>&.
+Email domains are case-independent, so this regular expression match is by
+default case-independent, but you can make it case-dependent by starting it
+with &`(?-i)`&. References to descriptions of the syntax of regular expressions
+are given in chapter &<<CHAPregexp>>&.
+.wen
&*Warning*&: Because domain lists are expanded before being processed, you
must escape any backslash and dollar characters in the regular expression, or
length. A textual string is constructed from the masked value, followed by the
mask, and this is used as the lookup key. For example, if the host's IP address
is 192.168.34.6, the key that is looked up for the above example is
-&"192.168.34.0/24"&. IPv6 addresses are converted to a text value using lower
-case letters and dots as separators instead of the more usual colon, because
-colon is the key terminator in &(lsearch)& files. Full, unabbreviated IPv6
+&"192.168.34.0/24"&.
+
+.new
+When an IPv6 address is converted to a string, dots are normally used instead
+of colons, so that keys in &(lsearch)& files need not contain colons (which
+terminate &(lsearch)& keys). This was implemented some time before the ability
+to quote keys was made available in &(lsearch)& files. However, the more
+recently implemented &(iplsearch)& files do require colons in IPv6 keys
+(notated using the quoting facility) so as to distinguish them from IPv4 keys.
+For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
+converted using colons and not dots. In all cases, full, unabbreviated IPv6
addresses are always used.
+Ideally, it would be nice to tidy up this anomalous situation by changing to
+colons in all cases, given that quoting is now available for &(lsearch)&.
+However, this would be an incompatible change that might break some existing
+configurations.
+.wen
+
&*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
IPv6 address) is not the same as specifying just &%net-%& without a number. In
the former case the key strings include the mask value, whereas in the latter
requirement. Other kinds of wildcarding require the use of a regular
expression.
.next
+.new
.cindex "regular expressions" "in host list"
.cindex "host list" "regular expression in"
If the item starts with &"^"& it is taken to be a regular expression which is
-matched against the host name. For example,
+matched against the host name. Host names are case-independent, so this regular
+expression match is by default case-independent, but you can make it
+case-dependent by starting it with &`(?-i)`&. References to descriptions of the
+syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
+example,
+.wen
.code
^(a|b)\.c\.d$
.endd
.section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
-.cindex "host" "lookup failures"
+.cindex "host" "lookup failures, permanent"
While processing a host list, Exim may need to look up an IP address from a
name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
behaviour when it fails to find the information it is seeking is the same.
+.new
+&*Note*&: This section applies to permanent lookup failures. It does &'not'&
+apply to temporary DNS errors, whose handling is described in the next section.
+.wen
+
.cindex "&`+include_unknown`&"
.cindex "&`+ignore_unknown`&"
By default, Exim behaves as if the host does not match the list. This may not
list. The effect of each one lasts until the next, or until the end of the
list.
-&*Note*&: This section applies to permanent lookup failures. It does &'not'&
-apply to temporary DNS errors. They always cause a defer action (except when
-&%dns_again_means_nonexist%& converts them into permanent errors).
+
+.new
+.section "Temporary DNS errors when looking up host information" &&&
+ "SECTtemdnserr"
+.cindex "host" "lookup failures, temporary"
+.cindex "&`+include_defer`&"
+.cindex "&`+ignore_defer`&"
+A temporary DNS lookup failure normally causes a defer action (except when
+&%dns_again_means_nonexist%& converts it into a permanent error). However,
+host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
+&`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
+section. These options should be used with care, probably only in non-critical
+host lists such as whitelists.
+.wen
.section "Host list patterns for single-key lookups by host name" &&&
"SECThoslispatnamsk"
-.cindex "host" "lookup failures"
.cindex "unknown host name"
.cindex "host list" "matching host name"
If a pattern is of the form
one argument, because it reduces the number of braces and therefore makes the
string easier to understand.
+.vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
+This item inserts &"basic"& header lines. It is described with the &%header%&
+expansion item below.
+
.vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
{*&<&'arg'&>&*}...}*&"
.cindex &%dlfunc%&
empty (for example, the fifth field above).
-.new
.vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
.cindex "list" "selecting by condition"
.cindex "expansion" "selecting from list by condition"
.endd
yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
to what it was before. See also the &*map*& and &*reduce*& expansion items.
-.wen
.vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.endd
.vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
- &*$h_*&<&'header&~name'&>&*:*&"
-See &*$rheader*& below.
-
-.vitem "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
- &*$bh_*&<&'header&~name'&>&*:*&"
-See &*$rheader*& below.
-
-.vitem "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
+ &*$h_*&<&'header&~name'&>&*:*&" &&&
+ "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
+ &*$bh_*&<&'header&~name'&>&*:*&" &&&
+ "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
&*$rh_*&<&'header&~name'&>&*:*&"
.cindex "expansion" "header insertion"
.vindex "&$header_$&"
.endd
-.new
.vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
.cindex "expansion" "list creation"
.vindex "&$item$&"
expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
value of &$item$& is restored to what it was before. See also the &*filter*&
and &*reduce*& expansion items.
-.wen
.vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "expansion" "numeric hash"
locks out the use of this expansion item in filter files.
-.new
.vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "expansion" "reducing a list to a scalar"
.cindex "list" "reducing to a scalar"
At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
restored to what they were before. See also the &*filter*& and &*map*&
expansion items.
-.wen
-.vitem &*$rheader_*&<&'header&~name'&>&*:&~or&~$rh_*&<&'header&~name'&>&*:*&
+.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
This item inserts &"raw"& header lines. It is described with the &%header%&
expansion item above.
not parse successfully, the result is empty.
-.new
.vitem &*${addresses:*&<&'string'&>&*}*&
.cindex "expansion" "RFC 2822 address handling"
.cindex "&%addresses%& expansion item"
expansion item, which extracts the working address from a single RFC2822
address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
processing lists.
-.wen
.vitem &*${base62:*&<&'digits'&>&*}*&
characters.
-.new
.vitem &*${rfc2047d:*&<&'string'&>&*}*&
.cindex "expansion" "RFC 2047"
.cindex "RFC 2047" "decoding"
bytes are replaced by question marks. Characters are converted into the
character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
not recognized unless &%check_rfc2047_length%& is set false.
+
+.new
+&*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
+access a header line, RFC 2047 decoding is done automatically. You do not need
+to use this operator as well.
.wen
attempt. It is false during any subsequent delivery attempts.
-.new
.vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
"&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
.cindex "list" "iterative conditions"
.endd
The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
being processed, to enable these expansion items to be nested.
-.wen
.vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
.cindex "&%isip6%& expansion condition"
The substring is first expanded, and then tested to see if it has the form of
an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
-&%isip4%& and &%isip6%& test just for IPv4 or IPv6 addresses, respectively. For
-example, you could use
+&%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
+
+.new
+For an IPv4 address, the test is for four dot-separated components, each of
+which consists of from one to three digits. For an IPv6 address, up to eight
+colon-separated components are permitted, each containing from one to four
+hexadecimal digits. There may be fewer than eight components if an empty
+component (adjacent colons) is present. Only one empty component is permitted.
+
+&*Note*&: The checks are just on the form of the address; actual numerical
+values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
+check. The main use of these tests is to distinguish between IP addresses and
+host names, or between IPv4 and IPv6 addresses. For example, you could use
.code
${if isip4{$sender_host_address}...
.endd
-to test which version of IP an incoming SMTP connection is using.
-
+to test which IP version an incoming SMTP connection is using.
+.wen
.vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
.cindex "LDAP" "use for authentication"
.next
The item @[] matches any of the local host's interface addresses.
.next
-.new
Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
even if &`net-`& is not specified. There is never any attempt to turn the IP
address into a host name. The most common type of linear search for
.code
${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
.endd
-.wen
.endlist ilist
Consult section &<<SECThoslispatip>>& for further details of these patterns.
.vlist
.vitem "&$0$&, &$1$&, etc"
.cindex "numerical variables (&$1$& &$2$& etc)"
-.new
When a &%match%& expansion condition succeeds, these variables contain the
captured substrings identified by the regular expression during subsequent
processing of the success string of the containing &%if%& expansion item.
precedes the expansion of the string. For example, the commands available in
Exim filter files include an &%if%& command with its own regular expression
matching condition.
-.wen
-.new
.vitem "&$acl_c...$&"
Values can be placed in these variables by the &%set%& modifier in an ACL. They
can be given any name that starts with &$acl_c$& and is at least six characters
message is received, the values of these variables are saved with the message,
and can be accessed by filters, routers, and transports during subsequent
delivery.
-.wen
.vitem &$acl_verify_message$&
.vindex "&$acl_verify_message$&"
content-scanning extension and the obsolete &%demime%& condition. For details,
see section &<<SECTdemimecond>>&.
-
-.vitem &$dnslist_domain$&
-.cindex "black list (DNS)"
+.new
+.vitem &$dnslist_domain$& &&&
+ &$dnslist_matched$& &&&
+ &$dnslist_text$& &&&
+ &$dnslist_value$&
.vindex "&$dnslist_domain$&"
-When a client host is found to be on a DNS (black) list,
-the list's domain name is put into this variable so that it can be included in
-the rejection message.
-
-.vitem &$dnslist_text$&
+.vindex "&$dnslist_matched$&"
.vindex "&$dnslist_text$&"
-When a client host is found to be on a DNS (black) list, the
-contents of any associated TXT record are placed in this variable.
-
-.vitem &$dnslist_value$&
.vindex "&$dnslist_value$&"
-When a client host is found to be on a DNS (black) list,
-the IP address from the resource record is placed in this variable.
-If there are multiple records, all the addresses are included, comma-space
-separated.
+.cindex "black list (DNS)"
+When a DNS (black) list lookup succeeds, these variables are set to contain
+the following data from the lookup: the list's domain name, the key that was
+looked up, the contents of any associated TXT record, and the value from the
+main A record. See section &<<SECID204>>& for more details.
+.wen
.vitem &$domain$&
.vindex "&$domain$&"
.vindex "&$interface_port$&"
This is an obsolete name for &$received_port$&.
-.new
.vitem &$item$&
.vindex "&$item$&"
This variable is used during the expansion of &*forall*& and &*forany*&
conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*man*&, and
&*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
empty.
-.wen
.vitem &$ldap_dn$&
.vindex "&$ldap_dn$&"
content-scanning extension. It is set to the name of the virus that was found
when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
+.new
+.vitem &$max_received_linelength$&
+.vindex "&$max_received_linelength$&"
+.cindex "maximum" "line length"
+.cindex "line length" "maximum"
+This variable contains the number of bytes in the longest line that was
+received as part of the message, not counting the line termination
+character(s).
+.wen
.vitem &$message_age$&
.cindex "message" "age of"
.cindex "message body" "in expansion"
.cindex "binary zero" "in message body"
.vindex "&$message_body$&"
-This variable contains the initial portion of a message's
-body while it is being delivered, and is intended mainly for use in filter
-files. The maximum number of characters of the body that are put into the
-variable is set by the &%message_body_visible%& configuration option; the
-default is 500. Newlines are converted into spaces to make it easier to search
-for phrases that might be split over a line break.
-Binary zeros are also converted into spaces.
+.oindex "&%message_body_visible%&"
+This variable contains the initial portion of a message's body while it is
+being delivered, and is intended mainly for use in filter files. The maximum
+number of characters of the body that are put into the variable is set by the
+&%message_body_visible%& configuration option; the default is 500.
+
+.new
+.oindex "&%message_body_newlines%&"
+By default, newlines are converted into spaces in &$message_body$&, to make it
+easier to search for phrases that might be split over a line break. However,
+this can be disabled by setting &%message_body_newlines%& to be true. Binary
+zeros are always converted into spaces.
+.wen
.vitem &$message_body_end$&
.cindex "body of message" "expansion variable"
&%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
&%acl_not_smtp_mime%&.
.next
-.new
From within a &[local_scan()]& function.
-.wen
.endlist
about the failure. The details are the same as for
&$recipient_verify_failure$&.
-.new
.vitem &$sending_ip_address$&
.vindex "&$sending_ip_address$&"
This variable is set whenever an outgoing SMTP connection to another host has
This variable is set whenever an outgoing SMTP connection to another host has
been set up. It contains the local port that is being used. For incoming
connections, see &$received_port$&.
-.wen
.vitem &$smtp_active_hostname$&
.vindex "&$smtp_active_hostname$&"
space removed. Following the introduction of &$smtp_command$&, this variable is
somewhat redundant, but is retained for backwards compatibility.
-.new
.vitem &$smtp_count_at_connection_start$&
.vindex "&$smtp_count_at_connection_start$&"
This variable is set greater than zero only in processes spawned by the Exim
there actually are, because many other connections may come and go while a
single connection is being processed. When a child process terminates, the
daemon decrements its copy of the variable.
-.wen
.vitem "&$sn0$& &-- &$sn9$&"
These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
message was received, and &"0"& otherwise.
.vitem &$tls_cipher$&
+.new
.vindex "&$tls_cipher$&"
When a message is received from a remote host over an encrypted SMTP
connection, this variable is set to the cipher suite that was negotiated, for
example DES-CBC3-SHA. In other circumstances, in particular, for message
-received over unencrypted connections, the variable is empty. See chapter
-&<<CHAPTLS>>& for details of TLS support.
+received over unencrypted connections, the variable is empty. Testing
+&$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
+non-encrypted connections during ACL processing.
+
+The &$tls_cipher$& variable retains its value during message delivery, except
+when an outward SMTP delivery takes place via the &(smtp)& transport. In this
+case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made,
+and then set to the outgoing cipher suite if one is negotiated. See chapter
+&<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
+details of the &(smtp)& transport.
+.wen
.vitem &$tls_peerdn$&
.vindex "&$tls_peerdn$&"
When a message is received from a remote host over an encrypted SMTP
connection, and Exim is configured to request a certificate from the client,
the value of the Distinguished Name of the certificate is made available in the
-&$tls_peerdn$& during subsequent processing.
+&$tls_peerdn$& during subsequent processing. &new("Like &$tls_cipher$&, the
+value is retained during message delivery, except during outbound SMTP
+deliveries.")
.vitem &$tod_bsdinbox$&
.vindex "&$tod_bsdinbox$&"
.vitem &$value$&
.vindex "&$value$&"
This variable contains the result of an expansion lookup, extraction operation,
-or external command, as described above. &new("It is also used during a
-&*reduce*& expansion.")
+or external command, as described above. It is also used during a
+&*reduce*& expansion.
.vitem &$version_number$&
.vindex "&$version_number$&"
.row &%disable_ipv6%& "do no IPv6 processing"
.row &%keep_malformed%& "for broken files &-- should not happen"
.row &%localhost_number%& "for unique message ids in clusters"
+.row &new(&%message_body_newlines%&) "retain newlines in &$message_body$&"
.row &%message_body_visible%& "how much to show in &$message_body$&"
.row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
.row &%print_topbitchars%& "top-bit characters are printing"
.section "Data lookups" "SECID101"
.table2
+.row &new(&%ibase_servers%&) "InterBase servers"
.row &%ldap_default_servers%& "used if no server in query"
.row &%ldap_version%& "set protocol version"
.row &%lookup_open_max%& "lookup files held open"
-.row &%mysql_servers%& "as it says"
-.row &%oracle_servers%& "as it says"
-.row &%pgsql_servers%& "as it says"
+.row &new(&%mysql_servers%&) "default MySQL servers"
+.row &new(&%oracle_servers%&) "Oracle servers"
+.row &new(&%pgsql_servers%&) "default PostgreSQL servers"
.row &%sqlite_lock_timeout%& "as it says"
.endtable
.row &%check_spool_space%& "before accepting a message"
.row &%deliver_queue_load_max%& "no queue deliveries if load high"
.row &%queue_only_load%& "queue incoming if load high"
+.row &new(&%queue_only_load_latch%&) "don't re-evaluate load for each message"
.row &%queue_run_max%& "maximum simultaneous queue runners"
.row &%remote_max_parallel%& "parallel SMTP delivery per message"
.row &%smtp_accept_max%& "simultaneous incoming connections"
.section "TLS" "SECID108"
.table2
-.row &new(&%gnutls_require_kx%&) "control GnuTLS key exchanges"
-.row &new(&%gnutls_require_mac%&) "control GnuTLS MAC algorithms"
-.row &new(&%gnutls_require_protocols%&) "control GnuTLS protocols"
+.row &%gnutls_require_kx%& "control GnuTLS key exchanges"
+.row &%gnutls_require_mac%& "control GnuTLS MAC algorithms"
+.row &%gnutls_require_protocols%& "control GnuTLS protocols"
.row &%tls_advertise_hosts%& "advertise TLS to these hosts"
.row &%tls_certificate%& "location of server certificate"
.row &%tls_crl%& "certificate revocation list"
.row &%queue_only%& "no immediate delivery at all"
.row &%queue_only_file%& "no immediate delivery if file exists"
.row &%queue_only_load%& "no immediate delivery if load is high"
+.row &new(&%queue_only_load_latch%&) "don't re-evaluate load for each message"
.row &%queue_only_override%& "allow command line to override"
.row &%queue_run_in_order%& "order of arrival"
.row &%queue_run_max%& "of simultaneous queue runners"
.row &%bounce_return_message%& "include original message in bounce"
.row &%bounce_return_size_limit%& "limit on returned message"
.row &%bounce_sender_authentication%& "send authenticated sender with bounce"
-.row &new(&%dsn_from%&) "set &'From:'& contents in bounces"
+.row &%dsn_from%& "set &'From:'& contents in bounces"
.row &%errors_copy%& "copy bounce messages"
.row &%errors_reply_to%& "&'Reply-to:'& in bounces"
.row &%delay_warning%& "time schedule"
removed at the time the message is received, to avoid any problems that might
occur when a delivered message is subsequently sent on to some other recipient.
-.new
.option disable_fsync main boolean false
.cindex "&[fsync()]&, disabling"
This option is available only if Exim was built with the compile-time option
updated files' data to be written to disc before continuing. Unexpected events
such as crashes and power outages may cause data to be lost or scrambled.
Here be Dragons. &*Beware.*&
-.wen
.option disable_ipv6 main boolean false
(?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
.endd
which permits only letters, digits, slashes, and hyphens in components, but
-they must start and end with a letter or digit. Hyphens are not, in fact,
+they must start and end with a letter or digit. &new(Slashes) are not, in fact,
permitted in host names, but they are found in certain NS records (which can be
accessed in Exim by using a &%dnsdb%& lookup). If you set
&%allow_utf8_domains%&, you must modify this pattern, or set the option to an
handled CR and LF characters in incoming messages. What happens now is
described in section &<<SECTlineendings>>&.
-.new
.option dsn_from main "string&!!" "see below"
.cindex "&'From:'& header line" "in bounces"
.cindex "bounce messages" "&'From:'& line, specifying"
.endd
The value is expanded every time it is needed. If the expansion fails, a
panic is logged, and the default value is used.
-.wen
.option envelope_to_remove main boolean true
.cindex "&'Envelope-to:'& header line"
See &%gecos_name%& above.
-.new
.option gnutls_require_kx main string unset
This option controls the key exchange mechanisms when GnuTLS is used in an Exim
server. For details, see section &<<SECTreqciphgnu>>&.
.option gnutls_require_protocols main string unset
This option controls the protocols when GnuTLS is used in an Exim
server. For details, see section &<<SECTreqciphgnu>>&.
-.wen
.option headers_charset main string "see below"
interfaces and recognizing the local host.
+.new
+.option ibase_servers main "string list" unset
+.cindex "InterBase" "server list"
+This option provides a list of InterBase servers and associated connection data,
+to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
+The option is available only if Exim has been built with InterBase support.
+.wen
+
+
+
.option ignore_bounce_errors_after main time 10w
.cindex "bounce message" "discarding"
.cindex "discarding bounce message"
an argument that is longer behaves as if &[getpwnam()]& failed.
+.new
+.option message_body_newlines main bool false
+.cindex "message body" "newlines in variables"
+.cindex "newline" "in message body variables"
+.vindex "&$message_body$&"
+.vindex "&$message_body_end$&"
+By default, newlines in the message body are replaced by spaces when setting
+the &$message_body$& and &$message_body_end$& expansion variables. If this
+option is set true, this no longer happens.
+.wen
+
.option message_body_visible main integer 500
.cindex "body of message" "visible size"
.option mysql_servers main "string list" unset
.cindex "MySQL" "server list"
This option provides a list of MySQL servers and associated connection data, to
-be used in conjunction with &(mysql)& lookups (see section &<<SECTsql>>&). The
+be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
option is available only if Exim has been built with MySQL support.
.option oracle_servers main "string list" unset
.cindex "Oracle" "server list"
This option provides a list of Oracle servers and associated connection data,
-to be used in conjunction with &(oracle)& lookups (see section &<<SECTsql>>&).
+to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
The option is available only if Exim has been built with Oracle support.
.cindex "PostgreSQL lookup type" "server list"
This option provides a list of PostgreSQL servers and associated connection
data, to be used in conjunction with &(pgsql)& lookups (see section
-&<<SECTsql>>&). The option is available only if Exim has been built with
+&<<SECID72>>&). The option is available only if Exim has been built with
PostgreSQL support.
.option pipelining_advertise_hosts main "host list&!!" *
.cindex "PIPELINING" "suppressing advertising"
This option can be used to suppress the advertisement of the SMTP
-PIPELINING extension to specific hosts. &new("See also the &*no_pipelining*&
-control in section &<<SECTcontrols>>&.") When PIPELINING is not advertised and
+PIPELINING extension to specific hosts. See also the &*no_pipelining*&
+control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
&%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
for each SMTP command and response. When PIPELINING is advertised, Exim assumes
that clients will use it; &"out of order"& commands that are &"expected"& do
.option queue_only_load main fixed-point unset
+.new
.cindex "load average"
.cindex "queueing incoming messages"
.cindex "message" "queueing by load"
If the system load average is higher than this value, incoming messages from
all sources are queued, and no automatic deliveries are started. If this
-happens during local or remote SMTP input, all subsequent messages on the same
-connection are queued. Deliveries will subsequently be performed by queue
-runner processes. This option has no effect on ancient operating systems on
-which Exim cannot determine the load average. See also
-&%deliver_queue_load_max%& and &%smtp_load_reserve%&.
+happens during local or remote SMTP input, all subsequent messages received on
+the same SMTP connection are queued by default, whatever happens to the load in
+the meantime, but this can be changed by setting &%queue_only_load_latch%&
+false.
+.wen
+
+Deliveries will subsequently be performed by queue runner processes. This
+option has no effect on ancient operating systems on which Exim cannot
+determine the load average. See also &%deliver_queue_load_max%& and
+&%smtp_load_reserve%&.
+
+
+.new
+.option queue_only_load_latch main boolean true
+.cindex "load average" "re-evaluating per message"
+When this option is true (the default), once one message has been queued
+because the load average is higher than the value set by &%queue_only_load%&,
+all subsequent messages received on the same SMTP connection are also queued.
+This is a deliberate choice; even though the load average may fall below the
+threshold, it doesn't seem right to deliver later messages on the same
+connection when not delivering earlier ones. However, there are special
+circumstances such as very long-lived connections from scanning appliances
+where this is not the best strategy. In such cases, &%queue_only_load_latch%&
+should be set false. This causes the value of the load average to be
+re-evaluated for each message.
+.wen
.option queue_only_override main boolean true
non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
-.new
A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
that limit has not been reached for the client host, &%smtp_accept_reserve%&
and &%smtp_load_reserve%& are then checked before accepting the connection.
-.wen
.option smtp_accept_max_nonmail main integer 10
.option smtp_accept_max_per_host main string&!! unset
.cindex "limit" "SMTP connections from one host"
.cindex "host" "limiting SMTP connections from"
-.new
This option restricts the number of simultaneous IP connections from a single
host (strictly, from a single IP address) to the Exim daemon. The option is
expanded, to enable different limits to be applied to different hosts by
is entirely independent of &%smtp_accept_reserve%&. The option's default value
of zero imposes no limit. If this option is set greater than zero, it is
required that &%smtp_accept_max%& be non-zero.
-.wen
&*Warning*&: When setting this option you should not use any expansion
constructions that take an appreciable amount of time. The expansion and test
.option smtp_accept_queue main integer 0
+.new
.cindex "SMTP" "incoming connection count"
.cindex "queueing incoming messages"
.cindex "message" "queueing by SMTP connection count"
-If the number of simultaneous incoming SMTP calls handled via the listening
-daemon exceeds this value, messages received by SMTP are just placed on the
-queue; no delivery processes are started automatically. A value of zero implies
-no limit, and clearly any non-zero value is useful only if it is less than the
-&%smtp_accept_max%& value (unless that is zero). See also &%queue_only%&,
-&%queue_only_load%&, &%queue_smtp_domains%&, and the various &%-od%&&'x'&
-command line options.
+If the number of simultaneous incoming SMTP connections being handled via the
+listening daemon exceeds this value, messages received by SMTP are just placed
+on the queue; no delivery processes are started automatically. The count is
+fixed at the start of an SMTP connection. It cannot be updated in the
+subprocess that receives messages, and so the queueing or not queueing applies
+to all messages received in the same connection.
+.wen
+
+A value of zero implies no limit, and clearly any non-zero value is useful only
+if it is less than the &%smtp_accept_max%& value (unless that is zero). See
+also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
+various &%-od%&&'x'& command line options.
. Allow this long option name to split; give it unsplit as a fifth argument
&%smtp_accept_max%& includes this reserve pool. The specified hosts are not
restricted to this number of connections; the option specifies a minimum number
of connection slots for them, not a maximum. It is a guarantee that this group
-of hosts can always get at least &%smtp_accept_reserve%& connections.
-&new("However, the limit specified by &%smtp_accept_max_per_host%& is still
-applied to each individual host.")
+of hosts can always get at least &%smtp_accept_reserve%& connections. However,
+the limit specified by &%smtp_accept_max_per_host%& is still applied to each
+individual host.
For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
set to 5, once there are 45 active connections (from any hosts), new
connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
-&new("provided the other criteria for acceptance are met.")
+provided the other criteria for acceptance are met.
.option smtp_active_hostname main string&!! unset
.cindex "TLS" "client certificate verification"
.cindex "certificate" "verification of client"
This option, along with &%tls_try_verify_hosts%&, controls the checking of
-certificates from clients.
-The expected certificates are defined by &%tls_verify_certificates%&, which
-must be set. A configuration error occurs if either &%tls_verify_hosts%& or
-&%tls_try_verify_hosts%& is set and &%tls_verify_certificates%& is not set.
+certificates from clients. The expected certificates are defined by
+&%tls_verify_certificates%&, which must be set. A configuration error occurs if
+either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
+&%tls_verify_certificates%& is not set.
+.new
Any client that matches &%tls_verify_hosts%& is constrained by
-&%tls_verify_certificates%&. The client must present one of the listed
-certificates. If it does not, the connection is aborted.
+&%tls_verify_certificates%&. When the client initiates a TLS session, it must
+present one of the listed certificates. If it does not, the connection is
+aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
+the host to use TLS. It can still send SMTP commands through unencrypted
+connections. Forcing a client to use TLS has to be done separately using an
+ACL to reject inappropriate commands when the connection is not encrypted.
+.wen
A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
matches this option (but not &%tls_verify_hosts%&), Exim requests a
This makes the configuration file less messy, and also reduces the number of
lookups (though Exim does cache lookups).
-The &%address_data%& facility is also useful as a means of passing information
-from one router to another, and from a router to a transport. In addition, if
.vindex "&$sender_address_data$&"
.vindex "&$address_data$&"
-&$address_data$& is set by a router when verifying a recipient address
-from an ACL, it remains available for use in the rest of the ACL statement.
-After verifying a sender, the value is transferred to &$sender_address_data$&.
-
+The &%address_data%& facility is also useful as a means of passing information
+from one router to another, and from a router to a transport. In addition, if
+&$address_data$& is set by a router when verifying a recipient address from an
+ACL, it remains available for use in the rest of the ACL statement. After
+verifying a sender, the value is transferred to &$sender_address_data$&.
&*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
router that has the &%one_time%& option set.
-.new
.cindex "duplicate addresses"
.oindex "&%unseen%&"
&*Warning 2*&: If the &%unseen%& option is set on the router, all header
circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
which of the duplicates is discarded, so this ambiguous situation should be
avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
-.wen
&*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
router that has the &%one_time%& option set.
-.new
&*Warning 2*&: If the &%unseen%& option is set on the router, all header
removal requests are deleted when the address is passed on to subsequent
routers, and this can lead to problems with duplicates -- see the similar
warning for &%headers_add%& above.
-.wen
.option ignore_target_hosts routers "host list&!!" unset
check_local_user
transport = local_delivery
.endd
+.new
+For security, it would probably be a good idea to restrict the use of this
+router to locally-generated messages, using a condition such as this:
+.code
+ condition = ${if match {$sender_host_address}\
+ {\N^(|127\.0\.0\.1)$\N}}
+.endd
+.wen
+
If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
both conditions must be met if not optional. Care must be taken if wildcards
are used in both a prefix and a suffix on the same router. Different
.option pass_router routers string unset
+.new
.cindex "router" "go to after &""pass""&"
-When a router returns &"pass"&, the address is normally handed on to the next
+Routers that recognize the generic &%self%& option (&(dnslookup)&,
+&(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
+routing to continue, and overriding a false setting of &%more%&. When one of
+these routers returns &"pass"&, the address is normally handed on to the next
router in sequence. This can be changed by setting &%pass_router%& to the name
of another router. However (unlike &%redirect_router%&) the named router must
be below the current router, to avoid loops. Note that this option applies only
to the special case of &"pass"&. It does not apply when a router returns
-&"decline"&.
+&"decline"& because it cannot handle an address.
+.wen
the value of &%unseen%& contains expansion items (and therefore, presumably, is
sometimes true and sometimes false).
-.new
.cindex "copy of message (&%unseen%& option)"
Setting the &%unseen%& option has a similar effect to the &%unseen%& command
qualifier in filter files. It can be used to cause copies of messages to be
Unlike the handling of header modifications, any data that was set by the
&%address_data%& option in the current or previous routers &'is'& passed on to
subsequent routers.
-.wen
.option user routers string&!! "see below"
.cindex "options" "&(manualroute)& router"
The private options for the &(manualroute)& router are as follows:
-.new
.option host_all_ignored manualroute string defer
See &%host_find_failed%&.
The &%host_find_failed%& option applies only to a definite &"does not exist"&
state; if a host lookup gets a temporary error, delivery is deferred unless the
generic &%pass_on_timeout%& option is set.
-.wen
.option hosts_randomize manualroute boolean false
.next
It can cause an automatic reply to be generated.
.next
-.new
It can be forced to fail, optionally with a custom error message.
.next
It can be temporarily deferred, optionally with a custom message.
-.wen
.next
It can be discarded.
.endlist
local_part_prefix = real-
transport = local_delivery
.endd
+.new
+For security, it would probably be a good idea to restrict the use of this
+router to locally-generated messages, using a condition such as this:
+.code
+ condition = ${if match {$sender_host_address}\
+ {\N^(|127\.0\.0\.1)$\N}}
+.endd
+.wen
+
.option syntax_errors_text redirect string&!! unset
See &%skip_syntax_errors%& above.
message_prefix = "From ${if def:return_path{$return_path}\
{MAILER-DAEMON}} $tod_bsdinbox\n"
.endd
-
+.new
+&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
+&`\n`& to &`\r\n`& in &%message_prefix%&.
+.wen
.option message_suffix appendfile string&!! "see below"
The string specified here is expanded and output at the end of every message.
.code
message_suffix =
.endd
+.new
+&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
+&`\n`& to &`\r\n`& in &%message_suffix%&.
+.wen
.option mode appendfile "octal integer" 0600
If the output file is created, it is given this mode. If it already exists and
of batched SMTP, the byte sequence written to the file is then an exact image
of what would be sent down a real SMTP connection.
-The contents of the &%message_prefix%& and &%message_suffix%& options are
-written verbatim, so must contain their own carriage return characters if these
-are needed. In cases where these options have non-empty defaults, the values
-end with a single linefeed, so they must be changed to end with &`\r\n`& if
-&%use_crlf%& is set.
+.new
+&*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
+(which are used to supply the traditional &"From&~"& and blank line separators
+in Berkeley-style mailboxes) are written verbatim, so must contain their own
+carriage return characters if these are needed. In cases where these options
+have non-empty defaults, the values end with a single linefeed, so they must be
+changed to end with &`\r\n`& if &%use_crlf%& is set.
+.wen
.option use_fcntl_lock appendfile boolean "see below"
.option timeout lmtp time 5m
The transport is aborted if the created process or Unix domain socket does not
-respond to LMTP commands or message input within this timeout. Here is an
-example of a typical LMTP transport:
+respond to LMTP commands or message input within this timeout. &new("Delivery
+is deferred, and will be tried again later.") Here is an example of a typical
+LMTP transport:
.code
lmtp:
driver = lmtp
.code
message_prefix =
.endd
+.new
+&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
+&`\n`& to &`\r\n`& in &%message_prefix%&.
+.wen
+
.option message_suffix pipe string&!! "see below"
The string specified here is expanded and output at the end of every message.
.code
message_suffix =
.endd
+.new
+&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
+&`\n`& to &`\r\n`& in &%message_suffix%&.
+.wen
+
.option path pipe string "see below"
This option specifies the string that is set up in the PATH environment
of batched SMTP, the byte sequence written to the pipe is then an exact image
of what would be sent down a real SMTP connection.
+.new
The contents of the &%message_prefix%& and &%message_suffix%& options are
written verbatim, so must contain their own carriage return characters if these
-are needed. Since the default values for both &%message_prefix%& and
-&%message_suffix%& end with a single linefeed, their values must be changed to
-end with &`\r\n`& if &%use_crlf%& is set.
+are needed. When &%use_bsmtp%& is not set, the default values for both
+&%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
+values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
+.wen
.option use_shell pipe boolean false
-.section "Use of the $host variable" "SECID145"
+.section "Use of the $host and $host_address variables" "SECID145"
.vindex "&$host$&"
.vindex "&$host_address$&"
At the start of a run of the &(smtp)& transport, the values of &$host$& and
&%serialize_hosts%&, and the various TLS options are expanded.
+.new
+.section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
+.vindex &$tls_cipher$&
+.vindex &$tls_peerdn$&
+At the start of a run of the &(smtp)& transport, the values of &$tls_cipher$&
+and &$tls_peerdn$& are the values that were set when the message was received.
+These are the values that are used for options that are expanded before any
+SMTP connections are made. Just before each connection is made, these two
+variables are emptied. If TLS is subsequently started, they are set to the
+appropriate values for the outgoing connection, and these are the values that
+are in force when any authenticators are run and when the
+&%authenticated_sender%& option is expanded.
+.wen
+
.section "Private options for smtp" "SECID146"
.cindex "options" "&(smtp)& transport"
to be deferred. If the result of expansion is an empty string, that is also
ignored.
+.new
+The expansion happens after the outgoing connection has been made and TLS
+started, if required. This means that the &$host$&, &$host_address$&,
+&$tls_cipher$&, and &$tls_peerdn$& variables are set according to the
+particular connection.
+.wen
+
If the SMTP session is not authenticated, the expansion of
&%authenticated_sender%& still happens (and can cause the delivery to be
deferred if it fails), but no AUTH= item is added to MAIL commands
instead of using the DNS. Of course, that function may in fact use the DNS, but
it may also consult other sources of information such as &_/etc/hosts_&.
-.new
.option gnutls_require_kx main string unset
This option controls the key exchange mechanisms when GnuTLS is used in an Exim
client. For details, see section &<<SECTreqciphgnu>>&.
.option gnutls_require_protocols main string unset
This option controls the protocols when GnuTLS is used in an Exim
client. For details, see section &<<SECTreqciphgnu>>&.
-.wen
-.new
.option helo_data smtp string&!! "see below"
.cindex "HELO" "argument, setting"
.cindex "EHLO" "argument, setting"
During the expansion, the variables &$host$& and &$host_address$& are set to
the identity of the remote host, and the variables &$sending_ip_address$& and
&$sending_port$& are set to the local IP address and port number that are being
-used. These variables can be therefore used to generate different values for
-different servers or different local IP addresses. For example, if you want the
-string that is used for &%helo_data%& to be obtained by a DNS lookup of the
-outgoing interface address, you could use this:
+used. These variables can be used to generate different values for different
+servers or different local IP addresses. For example, if you want the string
+that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
+interface address, you could use this:
.code
helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
{$primary_hostname}}
.endd
The use of &%helo_data%& applies both to sending messages and when doing
callouts.
-.wen
.option hosts smtp "string list&!!" unset
Hosts are associated with an address by a router such as &(dnslookup)&, which
facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
-.new
.option hosts_avoid_pipelining smtp "host list&!!" unset
.cindex "PIPELINING" "avoiding the use of"
Exim will not use the SMTP PIPELINING extension when delivering to any host
that matches this list, even if the server host advertises PIPELINING support.
-.wen
.option hosts_avoid_tls smtp "host list&!!" unset
.vindex "&$host$&"
.vindex "&$host_address$&"
This option specifies which interface to bind to when making an outgoing SMTP
-call. &*Note:*& Do not confuse this with the interface address that was used
-when a message was received, which is in &$received_ip_address$&, formerly
-known as &$interface_address$&. The name was changed to minimize confusion with
-the outgoing interface address. There is no variable that contains an outgoing
+call. &new("The value is an IP address, not an interface name such as
+&`eth0`&.") Do not confuse this with the interface address that was used when a
+message was received, which is in &$received_ip_address$&, formerly known as
+&$interface_address$&. The name was changed to minimize confusion with the
+outgoing interface address. There is no variable that contains an outgoing
interface address because, unless it is set by this option, its value is
unknown.
.chapter "Retry configuration" "CHAPretry"
.scindex IIDretconf1 "retry" "configuration, description of"
.scindex IIDregconf2 "configuration file" "retry section"
-The &"retry"& section of the run time configuration file contains a list of
+.new
+The &"retry"& section of the runtime configuration file contains a list of
retry rules that control how often Exim tries to deliver messages that cannot
-be delivered at the first attempt. If there are no retry rules, temporary
-errors are treated as permanent. The &%-brt%& command line option can be used
-to test which retry rule will be used for a given address, domain and error.
+be delivered at the first attempt. If there are no retry rules (the section is
+empty or not present), there are no retries. In this situation, temporary
+errors are treated as permanent. The default configuration contains a single,
+general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
+line option can be used to test which retry rule will be used for a given
+address, domain and error.
+.wen
The most common cause of retries is temporary failure to deliver to a remote
host because the host is down, or inaccessible because of a network problem.
&`$ `&&*&`telnet server.example 25`&*&
&`Trying 192.168.34.25...`&
&`Connected to server.example.`&
-&`Escape character is '^]'.`&
+&`Escape character is '^]'.`&
&`220 server.example ESMTP Exim 4.20 ...`&
&*&`ehlo client.example`&*&
&`250-server.example Hello client.example [10.8.4.5]`&
.cindex "authentication" "generic options"
.cindex "options" "generic; for authenticators"
+.new
+.option client_condition authenticators string&!! unset
+When Exim is authenticating as a client, it skips any authenticator whose
+&%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
+used, for example, to skip plain text authenticators when the connection is not
+encrypted by a setting such as:
+.code
+client_condition = ${if !eq{$tls_cipher}{}}
+.endd
+(Older documentation incorrectly states that &$tls_cipher$& contains the cipher
+used for incoming messages. In fact, during SMTP delivery, it contains the
+cipher used for the delivery.)
+.wen
+
.option driver authenticators string unset
This option must always be set. It specifies which of the available
of these options, Exim (as a client) tries to authenticate as follows:
.ilist
-.new
For each authenticator that is configured as a client, in the order in which
they are defined in the configuration, it searches the authentication
mechanisms announced by the server for one whose name matches the public name
of the authenticator.
-.wen
.next
.vindex "&$host$&"
.vindex "&$host_address$&"
&$received_ip_address$& (that is, the connection is local), the &"secured"&
option is passed in the Dovecot authentication command. If, for a TLS
connection, a client certificate has been verified, the &"valid-client-cert"&
-option is passed. &new("When authentication succeeds, the identity of the user
-who authenticated is placed in &$auth1$&.")
+option is passed. When authentication succeeds, the identity of the user
+who authenticated is placed in &$auth1$&.
.ecindex IIDdcotauth1
.ecindex IIDdcotauth2
-.new
.section "Requiring specific ciphers or other parameters in GnuTLS" &&&
"SECTreqciphgnu"
.cindex "GnuTLS" "specifying parameters for"
order for the cipher algorithms. The first one in the client's list that is
also advertised by the server is tried first. The default order is as listed
above.
-.wen
also included in the log line that records a message's arrival, keyed by
&"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
condition can be used to test for specific cipher suites in ACLs.
+&new("(For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section
+&<<SECID185>>&.)")
-The ACLs that run for subsequent SMTP commands can check the name of the cipher
-suite and vary their actions accordingly. The cipher suite names are those used
-by OpenSSL. These may differ from the names used elsewhere. For example,
-OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts
-is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL
+.new
+Once TLS has been established, the ACLs that run for subsequent SMTP commands
+can check the name of the cipher suite and vary their actions accordingly. The
+cipher suite names vary, depending on which TLS library is being used. For
+example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
+contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
documentation for more details.
-
+.wen
.section "Requesting and verifying client certificates" "SECID183"
unknown state), opens a new one to the same host, and then tries the delivery
unencrypted.
-
The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
transport provide the client with a certificate, which is passed to the server
if it requests it. If the server is Exim, it will request a certificate only if
which the client is connected. Forced failure of an expansion causes Exim to
behave as if the relevant option were unset.
+.new
+.vindex &$tls_cipher$&
+.vindex &$tls_peerdn$&
+Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$&
+variables are emptied. (Until the first connection, they contain the values
+that were set when the message was received.) If STARTTLS is subsequently
+successfully obeyed, these variables are set to the relevant values for the
+outgoing connection.
+.wen
+
.section "Multiple messages on the same encrypted TCP/IP connection" &&&
.irow &%acl_smtp_mail%& "ACL for MAIL"
.irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
.irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
+.irow &new(&%acl_smtp_notquit%&) "ACL for non-QUIT terminations"
.irow &%acl_smtp_predata%& "ACL at start of DATA command"
.irow &%acl_smtp_quit%& "ACL for QUIT"
.irow &%acl_smtp_rcpt%& "ACL for RCPT"
The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
non-SMTP message, before any of the message has been read. (This is the
-analogue of the &%acl_smtp_predata%& ACL for SMTP input.) &new("In the case of
-batched SMTP input, it runs after the DATA command has been reached.") The
+analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
+batched SMTP input, it runs after the DATA command has been reached. The
result of this ACL is ignored; it cannot be used to reject a message. If you
really need to, you could set a value in an ACL variable here and reject based
on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
+.new
+.section "The not-QUIT ACL" "SECTNOTQUITACL"
+The not-QUIT ACL, specified by &%smtp_notquit_acl%&, is run in most cases when
+an SMTP session ends without sending QUIT. However, when Exim itself is is bad
+trouble, such as being unable to write to its log files, this ACL is not run,
+because it might try to do things (such as write to log files) that make the
+situation even worse.
+
+Like the QUIT ACL, this ACL is provided to make it possible to do customized
+logging or to gather statistics, and its outcome is ignored. The &%delay%&
+modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
+and &%warn%&.
+
+.vindex &$smtp_notquit_reason$&
+When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
+to a string that indicates the reason for the termination of the SMTP
+connection. The possible values are:
+.table2
+.irow &`acl-drop`& "Another ACL issued a &%drop%& command"
+.irow &`bad-commands`& "Too many unknown or non-mail commands"
+.irow &`command-timeout`& "Timeout while reading SMTP commands"
+.irow &`connection-lost`& "The SMTP connection has been lost"
+.irow &`data-timeout`& "Timeout while reading message data"
+.irow &`local-scan-error`& "The &[local_scan()]& function crashed"
+.irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
+.irow &`signal-exit`& "SIGTERM or SIGINT"
+.irow &`synchronization-error`& "SMTP synchronization error"
+.irow &`tls-failed`& "TLS failed to start"
+.endtable
+In most cases when an SMTP connection is closed without having received QUIT,
+Exim sends an SMTP response message before actually closing the connection.
+With the exception of the &`acl-drop`& case, the default message can be
+overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
+&%drop%& verb in another ACL, it is the message from the other ACL that is
+used.
+.wen
+
+
.section "Finding an ACL to use" "SECID195"
.cindex "&ACL;" "finding which to use"
The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
SMTP command is accepted. For example, in a RCPT ACL you could have:
.display
&`accept `&<&'some conditions'&>
-&` message = OK, I'll allow you through today`&
+&` message = OK, I will allow you through today`&
.endd
You can specify an SMTP response code, optionally followed by an &"extended
response code"& at the start of the message, but the first digit must be the
statement. If any of the conditions are not met, the ACL returns &"deny"&. For
example, when checking a RCPT command,
.code
-.new
require message = Sender did not verify
verify = sender
-.wen
.endd
passes control to subsequent statements only if the message's sender can be
-verified. Otherwise, it rejects the command. &new("Note the positioning of the
+verified. Otherwise, it rejects the command. Note the positioning of the
&%message%& modifier, before the &%verify%& condition. The reason for this is
-discussed in section &<<SECTcondmodproc>>&.")
+discussed in section &<<SECTcondmodproc>>&.
.next
.cindex "&%warn%& ACL verb"
incoming message, assuming, of course, that the message is ultimately
accepted. For details, see section &<<SECTaddheadacl>>&.
-.new
.vitem &*continue*&&~=&~<&'text'&>
.cindex "&%continue%& ACL modifier"
.cindex "database" "updating in ACL"
.display
&`continue = `&<&'some expansion'&>
.endd
-.wen
.vitem &*control*&&~=&~<&'text'&>
.cindex "&%control%& ACL modifier"
.vitem &*delay*&&~=&~<&'time'&>
.cindex "&%delay%& ACL modifier"
.oindex "&%-bh%&"
-.new
This modifier may appear in any ACL. It causes Exim to wait for the time
interval before proceeding. However, when testing Exim using the &%-bh%&
option, the delay is not actually imposed (an appropriate message is output
instead). The time is given in the usual Exim notation, and the delay happens
as soon as the modifier is processed. In an SMTP session, pending output is
flushed before the delay is imposed.
-.wen
Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
example:
accept ...
.endd
-.new
If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
responses to several commands are no longer buffered and sent in one packet (as
they would normally be) because all output is flushed before imposing the
appear to the client as one large aggregated delay that might provoke an
unwanted timeout. You can, however, disable output flushing for &%delay%& by
using a &%control%& modifier to set &%no_delay_flush%&.
-.wen
.vitem &*endpass*&
is told about the freezing), provided all the &*control=freeze*& modifiers that
are obeyed for the current message have the &`/no_tell`& option.
-.new
.vitem &*control&~=&~no_delay_flush*&
.cindex "SMTP" "output flushing, disabling for delay"
Exim normally flushes SMTP output before implementing a delay in an ACL, to
avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
use. This control, as long as it is encountered before the &%verify%& condition
that causes the callout, disables such output flushing.
-.wen
.vitem &*control&~=&~no_mbox_unspool*&
This control is available when Exim is compiled with the content scanning
The setting of the switch can, of course, be made conditional on the
calling host. Its effect lasts until the end of the SMTP connection.
-.new
.vitem &*control&~=&~no_pipelining*&
.cindex "PIPELINING" "suppressing advertising"
This control turns off the advertising of the PIPELINING extension to SMTP in
response to an EHLO command. Therefore, it should normally appear in an ACL
controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
&%pipelining_advertise_hosts%&.
-.wen
.vitem &*control&~=&~queue_only*&
.oindex "&%queue_only%&"
and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
data is read.
-.new
&*Note:*& This control applies only to the current message, not to any others
that are being submitted at the same time using &%-bs%& or &%-bS%&.
-.wen
.endlist vlist
This condition is available only when Exim is compiled with the
content-scanning extension, and it is allowed only in the ACL defined by
&%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
-&new("If all goes well, the condition is true. It is false only if there are
+If all goes well, the condition is true. It is false only if there are
problems such as a syntax error or a memory shortage. For more details, see
-chapter &<<CHAPexiscan>>&.")
+chapter &<<CHAPexiscan>>&.
.vitem &*demime&~=&~*&<&'extension&~list'&>
.cindex "&%demime%& ACL condition"
&"RBL lists"&, after the original Realtime Blackhole List, but note that the
use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
different variants of this condition to describe briefly here. See sections
-&<<SECTmorednslists>>&--&<<SECTmorednslistslast>>& for details.
+&<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
.vitem &*domains&~=&~*&<&'domain&~list'&>
.cindex "&%domains%& ACL condition"
Thus, this example checks whether or not the IP addresses of the sender
domain's mail servers are on the Spamhaus black list.
+.new
+The key that was used for a successful DNS list lookup is put into the variable
+&$dnslist_matched$& (see section &<<SECID204>>&).
+.wen
.endd
Section &<<SECTaddmatcon>>& below describes how you can distinguish between
different values. Some DNS lists may return more than one address record;
-&new("see section &<<SECThanmuldnsrec>>& for details of how they are checked.")
+see section &<<SECThanmuldnsrec>>& for details of how they are checked.
+
.section "Variables set from DNS lists" "SECID204"
+.new
+.cindex "expansion" "variables, set from DNS list"
.cindex "DNS list" "variables set from"
.vindex "&$dnslist_domain$&"
+.vindex "&$dnslist_matched$&"
.vindex "&$dnslist_text$&"
.vindex "&$dnslist_value$&"
-When an entry is found in a DNS list, the variable &$dnslist_domain$&
-contains the name of the domain that matched, and &$dnslist_value$& contains
-the data from the entry. If more than one address record is returned by the DNS
-lookup, all the IP addresses are included in &$dnslist_value$&, separated by
-commas and spaces. The variable &$dnslist_text$& contains the contents of any
-associated TXT record. For lists such as RBL+ the TXT record for a merged entry
-is often not very meaningful. See section &<<SECTmordetinf>>& for a way of
-obtaining more information.
+When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
+the name of the overall domain that matched (for example,
+&`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
+(for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
+the DNS record. When the key is an IP address, it is not reversed in
+&$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
+cases, for example:
+.code
+deny dnslists = spamhaus.example
+.endd
+the key is also available in another variable (in this case,
+&$sender_host_address$&). In more complicated cases, however, this is not true.
+For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
+might generate a dnslists lookup like this:
+.code
+deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
+.endd
+If this condition succeeds, the value in &$dnslist_matched$& might be
+&`192.168.6.7`& (for example).
+.wen
+
+If more than one address record is returned by the DNS lookup, all the IP
+addresses are included in &$dnslist_value$&, separated by commas and spaces.
+The variable &$dnslist_text$& contains the contents of any associated TXT
+record. For lists such as RBL+ the TXT record for a merged entry is often not
+very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
+information.
You can use the DNS list variables in &%message%& or &%log_message%& modifiers
&-- although these appear before the condition in the ACL, they are not
deny dnslists = rblplus.mail-abuse.org=127.0.0.2
.endd
rejects only those hosts that yield 127.0.0.2. Without this additional data,
-any address record is considered to be a match. &new("For the moment, we assume
+any address record is considered to be a match. For the moment, we assume
that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
-describes how multiple records are handled.")
+describes how multiple records are handled.
More than one IP address may be given for checking, using a comma as a
separator. These are alternatives &-- if any one of them matches, the
-.new
.section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
thereby providing more than one IP address. When an item in a &%dnslists%& list
.endlist
When the DNS lookup yields only a single IP address, there is no difference
between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
-.wen
dnslists = some.list.example
.endd
-.section "Rate limiting senders" "SECTratelimiting"
+.section "Rate limiting incoming messages" "SECTratelimiting"
.cindex "rate limiting" "client sending"
.cindex "limiting client sending rates"
.oindex "&%smtp_ratelimit_*%&"
example, &$authenticated_id$& is only meaningful if the client has
authenticated, and you can check with the &%authenticated%& ACL condition.
+.new
+If you want to limit the rate at which a recipient receives messages, you can
+use the key &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in
+a RCPT ACL.
+.wen
+
Internally, Exim includes the smoothing constant &'p'& and the options in the
lookup key because they alter the meaning of the stored data. This is not true
for the limit &'m'&, so you can alter the configured maximum rate and Exim will
still remember clients' past behaviour, but if you alter the other ratelimit
parameters Exim forgets past behaviour.
-Each &%ratelimit%& condition can have up to two options. The first option
+.new
+Each &%ratelimit%& condition can have up to three options. One option
specifies what Exim measures the rate of, and the second specifies how Exim
-handles excessively fast clients. The options are separated by a slash, like
-the other parameters.
+handles excessively fast clients. The third option can be &`noupdate`&, to
+disable updating of the ratelimiting database (see section &<<rearatdat>>&).
+The options are separated by a slash, like the other parameters. They may
+appear in any order.
+.wen
+.section "Ratelimit options for what is being measured" "ratoptmea"
The &%per_conn%& option limits the client's connection rate.
The &%per_mail%& option limits the client's rate of sending messages. This is
accepted. Note that in this case the rate limiting engine will see a message
with many recipients as a large high-speed burst.
+.section "Ratelimit options for handling fast clients" "ratophanfas"
If a client's average rate is greater than the maximum, the rate limiting
engine can react in two possible ways, depending on the presence of the
&%strict%& or &%leaky%& options. This is independent of the other
The &%strict%& option means that the client's recorded rate is always updated.
The effect of this is that Exim measures the client's average rate of attempts
-to send email, which can be much higher than the maximum. If the client is over
-the limit it will be subjected to counter-measures until it slows down below
-the maximum rate. The smoothing period determines the time it takes for a high
-sending rate to decay exponentially to 37% of its peak value, which means that
-you can work out the time (the number of smoothing periods) that a client is
-subjected to counter-measures after an over-limit burst with this formula:
+to send email, which can be much higher than the maximum &new("it is actually
+allowed. If the client is over the limit it may be subjected to
+counter-measures in the ACL until it slows down below the maximum rate.") The
+smoothing period determines the time it takes for a high sending rate to decay
+exponentially to 37% of its peak value, which means that you can work out the
+time (the number of smoothing periods) that a client is subjected to
+counter-measures after an over-limit burst with this formula:
.code
ln(peakrate/maxrate)
.endd
-The &%leaky%& option means that the client's recorded rate is not updated if it
-is above the limit. The effect of this is that Exim measures the client's
-average rate of successfully sent email, which cannot be greater than the
-maximum. If the client is over the limit it may suffer some
+The &%leaky%& (default) option means that the client's recorded rate is not
+updated if it is above the limit. The effect of this is that Exim measures the
+client's average rate of successfully sent email, which cannot be greater than
+the maximum allowed. If the client is over the limit it may suffer some
counter-measures (as specified in the ACL), but it will still be able to send
email at the configured maximum rate, whatever the rate of its attempts. This
is generally the better choice if you have clients that retry automatically.
+.section "Using rate limiting" "useratlim"
Exim's other ACL facilities are used to define what counter-measures are taken
when the rate limit is exceeded. This might be anything from logging a warning
(for example, while measuring existing sending rates in order to define
hints, the callout cache, and ratelimit data).
+.new
+.section "Reading ratelimit data without updating" "rearatdat"
+.cindex "rate limitint" "reading data without updating"
+If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim
+computes the rate and checks the limit as normal, but it does not update the
+saved data. This means that, in relevant ACLs, it is possible to lookup the
+existence of a specified (or auto-generated) ratelimit key without incrementing
+the ratelimit counter for that key. In order for this to be useful, another ACL
+entry must set the rate for the same key (otherwise it will always be zero).
+For example:
+.code
+acl_check_connect:
+ deny ratelimit = 100 / 5m / strict / noupdate
+ log_message = RATE: $sender_rate/$sender_rate_period \
+ (max $sender_rate_limit)
+.endd
+.display
+&'... some other logic and tests...'&
+.endd
+.code
+acl_check_mail:
+ warn ratelimit = 100 / 5m / strict / per_cmd
+ condition = ${if le{$sender_rate}{$sender_rate_limit}}
+ logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \
+ (max $sender_rate_limit)
+.endd
+In this example, the rate is tested and used to deny access (when it is too
+high) in the connect ACL, but the actual computation of the remembered rate
+happens later, on a per-command basis, in another ACL.
+.wen
+
+
+
.section "Address verification" "SECTaddressverification"
.cindex "verifying address" "options for"
.cindex "policy control" "address verification"
hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
&%callout%& option is given, in which case the condition is forced to succeed.
-.new
.cindex "SMTP" "output flushing, disabling for callout"
A callout may take a little time. For this reason, Exim normally flushes SMTP
output before performing a callout in an ACL, to avoid unexpected timeouts in
clients when the SMTP PIPELINING extension is in use. The flushing can be
disabled by using a &%control%& modifier to set &%no_callout_flush%&.
-.wen
options may both refer to the same ACL if you want the same processing in both
cases.
-These ACLs are called (possibly many times) just before the
-&%acl_smtp_data%& ACL in the case of an SMTP message, or just before the
-&%acl_not_smtp%& ACL in the case of a non-SMTP message. However, a MIME ACL
-is called only if the message contains a &'MIME-Version:'& header line. When a
-call to a MIME ACL does not yield &"accept"&, ACL processing is aborted and the
-appropriate result code is sent to the client. In the case of an SMTP message,
-the &%acl_smtp_data%& ACL is not called when this happens.
+These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
+ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
+the case of a non-SMTP message. However, a MIME ACL is called only if the
+message contains a &new(&'Content-Type:'&) header line. When a call to a MIME
+ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
+result code is sent to the client. In the case of an SMTP message, the
+&%acl_smtp_data%& ACL is not called when this happens.
You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
If the string does not start with a slash, it is used as the
filename, and the default path is then used.
.endlist
-&new("The &%decode%& condition normally succeeds. It is only false for syntax
-errors or unusual circumstances such as memory shortages.")
-You can easily decode a file with its original, proposed filename using
+The &%decode%& condition normally succeeds. It is only false for syntax
+errors or unusual circumstances such as memory shortages. You can easily decode
+a file with its original, proposed filename using
.code
decode = $mime_filename
.endd
.section "Available Exim variables" "SECID208"
+.new
.cindex "&[local_scan()]& function" "available Exim variables"
The header &_local_scan.h_& gives you access to a number of C variables. These
are the only ones that are guaranteed to be maintained from release to release.
-Note, however, that you can obtain the value of any Exim variable,
-&new("including &$recipients$&,") by calling &'expand_string()'&. The exported
-variables are as follows:
+Note, however, that you can obtain the value of any Exim expansion variable,
+including &$recipients$&, by calling &'expand_string()'&. The exported
+C variables are as follows:
+.wen
.vlist
+.vitem &*int&~body_linecount*&
+.new
+This variable contains the number of lines in the message's body.
+
+.vitem &*int&~body_zerocount*&
+This variable contains the number of binary zero bytes in the message's body.
+.wen
+
.vitem &*unsigned&~int&~debug_selector*&
This variable is set to zero when no debugging is taking place. Otherwise, it
is a bitmap of debugging selectors. Two bits are identified for use in
No retry data is maintained, and any retry rules are ignored.
.next
A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
-true, &%max_rcpt%& in the smtp transport is forced to &"unlimited"&,
+true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
&%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
.endlist
.endd
.endlist
-.new
.cindex "log" "process ids in"
.cindex "pid (process id)" "in log lines"
Exim does not include its process id in log lines by default, but you can
request that it does so by specifying the &`pid`& log selector (see section
&<<SECTlogselector>>&). When this is set, the process id is output, in square
brackets, immediately after the time and date.
-.wen
.display
&`A `& authenticator name (and optional id)
&`C `& SMTP confirmation on delivery
-.new
&` `& command list for &"no mail in SMTP session"&
-.wen
&`CV `& certificate verification status
-.new
&`D `& duration of &"no mail in SMTP session"&
-.wen
&`DN `& distinguished name from peer certificate
&`DT `& on &`=>`& lines: time taken for a delivery
&`F `& sender address (on delivery lines)
&`*queue_run `& start and end queue runs
&` queue_time `& time on queue for one recipient
&` queue_time_overall `& time on queue for whole message
-.new
&` pid `& Exim process id
-.wen
&` received_recipients `& recipients on <= lines
&` received_sender `& sender on <= lines
&`*rejected_header `& header contents on reject log
&` smtp_confirmation `& SMTP confirmation on => lines
&` smtp_connection `& SMTP connections
&` smtp_incomplete_transaction`& incomplete SMTP transactions
-.new
&` smtp_no_mail `& session with no MAIL commands
-.wen
&` smtp_protocol_error `& SMTP protocol errors
&` smtp_syntax_error `& SMTP syntax errors
&` subject `& contents of &'Subject:'& on <= lines
the default setting, because for most ordinary configurations, the remote port
number is always 25 (the SMTP port).
.next
-.new
.cindex "log" "process ids in"
.cindex "pid (process id)" "in log lines"
&%pid%&: The current process id is added to every log line, in square brackets,
immediately after the time and date.
-.wen
.next
.cindex "log" "queue run"
.cindex "queue runner" "logging"
and the message sender plus any accepted recipients are included in the log
line. This can provide evidence of dictionary attacks.
.next
-.new
.cindex "log" "non-MAIL SMTP sessions"
.cindex "MAIL" "logging session without"
&%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
the last 20 are listed, preceded by &"..."&. However, with the default
setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
have been aborted before 20 non-mail commands are processed.
-.wen
.next
.cindex "log" "SMTP protocol error"
.cindex "SMTP" "logging protocol error"
match the pattern. Thus, &'exigrep'& can extract complete log entries for a
given message, or all mail for a given user, or for a given host, for example.
The input files can be in Exim log format or syslog format.
-.new
If a matching log line is not associated with a specific message, it is
included in &'exigrep'&'s output without any additional lines. The usage is:
.display
The &%-v%& option inverts the matching condition. That is, a line is selected
if it does &'not'& match the pattern.
-.wen
If the location of a &'zcat'& command is known from the definition of
ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
If the message is cryptographically signed, any change will invalidate the
signature.
.endlist
-.new
All in all, modifying -D files is fraught with danger.
-.wen
-.new
Files whose names end with -J may also be seen in the &_input_& directory (or
its subdirectories when &%split_spool_directory%& is set). These are journal
files, used to record addresses to which the message has been delivered during
file remains in existence. When Exim next processes the message, it notices the
-J file and uses it to update the -H file before starting the next delivery
attempt.
-.wen
.section "Format of the -H file" "SECID282"
.cindex "uid (user id)" "in spool file"
The second line of the -H file contains the login name for the uid of the
process that called Exim to read the message, followed by the numerical uid and
gid. For a locally generated message, this is normally the user who sent the
-message. For a message received over TCP/IP &new("via the daemon"), it is
+message. For a message received over TCP/IP via the daemon, it is
normally the Exim user.
The third line of the file contains the address of the message's sender as
git://git.exim.org / exim.git / commitdiff