-. $Cambridge: exim/doc/doc-src/spec.src,v 1.4 2005/01/26 14:52:08 ph10 Exp $
+. $Cambridge: exim/doc/doc-src/spec.src,v 1.8 2005/02/17 11:58:25 ph10 Exp $
.
.set version "4.50"
.set previousversion "4.40"
.section Mailing lists
.index mailing lists||for Exim users
-The following are the two main Exim mailing lists:
+.em
+The following are the three main Exim mailing lists:
.display rm
.tabs 28
$it{exim-users@@exim.org} $t general discussion list
+$it{exim-dev@@exim.org} $t discussion of bugs, enhancements, etc.
$it{exim-announce@@exim.org} $t moderated, low volume announcements list
.endd
+.nem
You can subscribe to these lists, change your existing subscriptions, and view
or search the archives via the
.if ~~html
.em
As part of its operation, \-bV-\ causes Exim to read and syntax check its
configuration file. However, this is a static check only. It cannot check
-values that to be expanded. You cannot rely on \-bV-\ alone to discover (for
-example) all the typos in the configuration; some realistic testing is needed.
-The \-bh-\ and \-N-\ options provide more dynamic testing facilities.
+values that are to be expanded. For example, although a misspelt ACL verb is
+detected, an error in the verb's arguments is not. You cannot rely on \-bV-\
+alone to discover (for example) all the typos in the configuration; some
+realistic testing is needed. The \-bh-\ and \-N-\ options provide more dynamic
+testing facilities.
.nem
Like \%lsearch%\, the testing is done case-insensitively. The following forms
of wildcard are recognized:
.numberpars "$*$"
-The string may begin with an asterisk to mean `begins with'. For example:
+The string may begin with an asterisk to mean `ends with'. For example:
.display asis
*.a.b.c data for anything.a.b.c
*fish data for anythingfish
.em
.tempindent 0
-\$demime@_$\\*xxx*\: Two variables whose names start with \$demime$\ are
-available when Exim is compiled with the content-scanning extension and the
-obsolete \demime\ condition. For details, see section ~~SECTdemimecond.
+\$demime@_errorlevel$\: This variable is available when Exim is compiled with
+the content-scanning extension and the obsolete \demime\ condition. For
+details, see section ~~SECTdemimecond.
+
+.tempindent 0
+\$demime@_reason$\: This variable is available when Exim is compiled with the
+content-scanning extension and the obsolete \demime\ condition. For details,
+see section ~~SECTdemimecond.
.nem
.index black list (DNS)
.em
.tempindent 0
-\$mime@_$\\*xxx*\:
-A number of variables whose names start with \$mime$\ are available when Exim
-is compiled with the content-scanning extension. For details, see section
-~~SECTscanmimepart.
+\$mime@_$\\*xxx*\: A number of variables whose names start with \$mime$\ are
+available when Exim is compiled with the content-scanning extension. For
+details, see section ~~SECTscanmimepart.
.nem
.tempindent 0
message was received over an encrypted SMTP connection and the client was
successfully authenticated.
-Exim also uses the protocol name `smtps' for the rare situation where the
-client initially used \\EHLO\\, set up an encrypted connection using
-\\STARTTLS\\, and then used \\HELO\\ afterwards to initiate the encrypted
-session.
+Exim uses the protocol name `smtps' for the case when encryption is
+automatically set up on connection without the use of \\STARTTLS\\ (see
+\tls@_on@_connect@_ports\), and the client uses \\HELO\\ to initiate the
+encrypted SMTP session. The name `smtps' is also used for the rare situation
+where the client initially uses \\EHLO\\, sets up an encrypted connection using
+\\STARTTLS\\, and then uses \\HELO\\ afterwards.
The \-oMr-\ option provides a way of specifying a custom protocol name for
messages that are injected locally by trusted callers. This is commonly used to
.em
.section Use of standard output and error by Perl
+.index Perl||standard output and error
You should not write to the standard error or output streams from within your
-Perl code, as it is not defined how these are set up. In versions of Exim up to
-at least 4.50, it is possible for the standard output or error to refer to the
-SMTP connection during message reception. Writing to this stream is likely to
-cause chaos. Something may be done about this in later releases.
-
-Unfortunately, the Perl \warn\ statment writes to the standard error stream,
-and this may be embedded in Perl modules that you use, but over which you have
-no control. One way round this is to ensure that the following Perl magic is
-obeyed before \warn\ is used:
-.display asis
-$SIG{__WARN__} = sub { Exim::log_write($_[0]) };
-.endd
-This causes the output of the \warn\ statement to be written to Exim's log
-file.
+Perl code, as it is not defined how these are set up. In versions of Exim
+before 4.50, it is possible for the standard output or error to refer to the
+SMTP connection during message reception via the daemon. Writing to this stream
+is certain to cause chaos. From Exim 4.50 onwards, the standard output and
+error streams are connected to \(/dev/null)\ in the daemon. The chaos is
+avoided, but the output is lost.
+
+.index Perl||\warn\, use of
+The Perl \warn\ statement writes to the standard error stream by default. Calls
+to \warn\ may be embedded in Perl modules that you use, but over which you have
+no control. When Exim starts up the Perl interpreter, it arranges for output
+from the \warn\ statement to be written to the Exim main log. You can change
+this by including appropriate Perl magic somewhere in your Perl code. For
+example, to discard \warn\ output completely, you need this:
+.display asis
+$SIG{__WARN__} = sub { };
+.endd
+Whenever a \warn\ is obeyed, the anonymous subroutine is called. In this
+example, the code for the subroutine is empty, so it does nothing, but you can
+include any Perl code that you like. The text of the \warn\ message is passed
+as the first subroutine argument.
.nem
.em
-.section Support for the obsolete SSMTP protocol
+.section Support for the obsolete SSMTP (or SMTPS) protocol
.rset SECTsupobssmt "~~chapter.~~section"
.index ssmtp protocol
+.index smtps protocol
.index SMTP||ssmtp protocol
-Exim supports the obsolete SSMTP protocol that was used before the \\STARTTLS\\
-command was standardized for SMTP. Some legacy clients still use this protocol.
-If the \tls@_on@_connect@_ports\ option is set to a list of port numbers,
-connections to those ports must use SSMTP. The most common use of this option
-is expected to be
+.index SMTP||smtps protocol
+Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
+before the \\STARTTLS\\ command was standardized for SMTP. Some legacy clients
+still use this protocol. If the \tls@_on@_connect@_ports\ option is set to a
+list of port numbers, connections to those ports must use SSMTP. The most
+common use of this option is expected to be
.display asis
tls_on_connect_ports = 465
.endd
\tls@_dhparam\ $t$rm{DH parameters for server}
.newline
.em
-\tls@_on@_connect@_ports\ $t$rm{specify SSMTP ports}
+\tls@_on@_connect@_ports\ $t$rm{specify SSMTP (SMTPS) ports}
.nem
.newline
\tls@_privatekey\ $t$rm{location of server private key}
This option defines the ACL that is run when a non-SMTP message is on the point
of being accepted. See chapter ~~CHAPACL for further details.
-.index ~~ACL||on SMTP connection
-.conf acl@_smtp@_connect string$**$ unset
-This option defines the ACL that is run when an SMTP connection is received.
-See chapter ~~CHAPACL for further details.
-
.index ~~ACL||setting up for SMTP commands
.index \\AUTH\\||ACL for
.conf acl@_smtp@_auth string$**$ unset
This option defines the ACL that is run when an SMTP \\AUTH\\ command is
received. See chapter ~~CHAPACL for further details.
+.index ~~ACL||on SMTP connection
+.conf acl@_smtp@_connect string$**$ unset
+This option defines the ACL that is run when an SMTP connection is received.
+See chapter ~~CHAPACL for further details.
+
.index \\DATA\\, ACL for
.conf acl@_smtp@_data string$**$ unset
This option defines the ACL that is run after an SMTP \\DATA\\ command has been
.index queue runner||processing messages in order
If this option is set, queue runs happen in order of message arrival instead of
in an arbitrary order. For this to happen, a complete list of the entire queue
-must be set up before the deliveries start. When the queue is all in a single
-directory (the default), this happens anyway, but if \split@_spool@_directory\
-is set it does not -- for delivery in random order, the sub-directories are
-processed one at a time (in random order), to avoid setting up one huge list.
-Thus, setting \queue@_run@_in@_order\ with \split@_spool@_directory\ may
-degrade performance when the queue is large. In most situations,
-\queue@_run@_in@_order\ should not be set.
+must be set up before the deliveries start. When the queue is all held in a
+single directory (the default),
+.em
+a single list is created for both the ordered and the non-ordered cases.
+However, if \split@_spool@_directory\ is set, a single list is not created when
+\queue@_run@_in@_order\ is false. In this case, the sub-directories are
+processed one at a time (in a random order), and this avoids setting up one
+huge list for the whole queue. Thus, setting \queue@_run@_in@_order\ with
+\split@_spool@_directory\ may degrade performance when the queue is large,
+because of the extra work in setting up the single, large list. In most
+situations, \queue@_run@_in@_order\ should not be set.
+.nem
.conf queue@_run@_max integer 5
.index queue runner||maximum number of
responses. For example, it is used as domain name in the response to an
incoming \\HELO\\ or \\EHLO\\ command.
.em
+It is also used in \\HELO\\ commands for callout verification.
The active hostname is placed in the \$smtp__active__hostname$\ variable, which
is saved with any messages that are received. It is therefore available for use
in routers and transports when the message is later delivered.
.em
.conf tls@_on@_connect@_ports "string list" unset
-This option specifies a list of incoming SSMTP ports that should operate the
-obsolete SSMTP protocol, where a TLS session is immediately set up without
-waiting for the client to issue a \\STARTTLS\\ command. For further details,
-see section ~~SECTsupobssmt.
+This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
+operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
+set up without waiting for the client to issue a \\STARTTLS\\ command. For
+further details, see section ~~SECTsupobssmt.
.nem
.conf tls@_privatekey string$**$ unset
X.Employee: :fail: Gone away, no forwarding address
.endd
In the case of an address that is being verified from an ACL or as the subject
-of a \\VRFY\\ command, the text is included in the SMTP error response by
-default. In an ACL, an explicitly provided message overrides the default, but
-the default message is available in the variable \$acl@_verify@_message$\ and
-can therefore be included in a custom message if this is desired. Exim sends a
-451 SMTP code for a :::defer::, and 550 for :::fail::. In non-SMTP cases the
-text is included in the error message that Exim generates.
+of a
+.index \\VRFY\\||error text, display of
+\\VRFY\\ command, the text is included in the SMTP error response by
+default.
+.em
+.index \\EXPN\\||error text, display of
+The text is not included in the response to an \\EXPN\\ command.
+.nem
+
+In an ACL, an explicitly provided message overrides the default, but the
+default message is available in the variable \$acl@_verify@_message$\ and can
+therefore be included in a custom message if this is desired. Exim sends a 451
+SMTP code for a :::defer::, and 550 for :::fail::. In non-SMTP cases the text
+is included in the error message that Exim generates.
return code that is neither zero nor one of the return codes listed in
\temp@_errors\ (that is, the delivery failed), the first line of output is
written to the main log.
+.em
+This option and \log@_output\ are mutually exclusive. Only one of them may be
+set.
+.nem
.conf log@_output boolean false
If this option is set and the command returns any output, the first line of
output is written to the main log, whatever the return code.
+.em
+This option and \log@_fail@_output\ are mutually exclusive. Only one of them
+may be set.
+.nem
.conf max@_output integer 20K
This specifies the maximum amount of output that the command may produce on its
is, the delivery failed), the output is returned in the bounce message.
However, if the message has a null sender (that is, it is itself a bounce
message), output from the command is discarded.
+.em
+This option and \return@_output\ are mutually exclusive. Only one of them may
+be set.
+.nem
.conf return@_output boolean false
If this option is true, and the command produced any output, the delivery is
However, if the message has a null sender (that is, it is a bounce message),
output from the command is always discarded, whatever the setting of this
option.
+.em
+This option and \return@_fail@_output\ are mutually exclusive. Only one of them
+may be set.
+.nem
.conf temp@_errors "string list" "see below"
.index \%pipe%\ transport||temporary failure
library implementation of the RFC 2222 (`Simple Authentication and Security
Layer'). This library supports a number of authentication mechanisms, including
PLAIN and LOGIN, but also several others that Exim does not support directly.
+In particular, there is support for Kerberos authentication.
+
The \%cyrus@_sasl%\ authenticator provides a gatewaying mechanism directly to
the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
then so can the \%cyrus@_sasl%\ authenticator. By default it uses the public
.em
-.section Support for the legacy `ssmtp' protocol
+.section Support for the legacy `ssmtp' (aka `smtps') protocol
.index ssmtp protocol
+.index smtps protocol
.index SMTP||ssmtp protocol
+.index SMTP||smtps protocol
Early implementations of encrypted SMTP used a different TCP port from normal
SMTP, and expected an encryption negotiation to start immediately, instead of
waiting for a \\STARTTLS\\ command from the client using the standard SMTP
-port. The protocol was called `ssmtp' and port 465 was allocated for this
-purpose.
+port. The protocol was called `ssmtp' or `smtps', and port 465 was allocated
+for this purpose.
This approach was abandoned when encrypted SMTP was standardised, but there are
still some legacy clients that use it. Exim supports these clients by means of
.section ACL verbs
The ACL verbs are as follows:
.numberpars $.
+.index \accept\, ACL verb
\accept\: If all the conditions are met, the ACL returns `accept'. If any of
the conditions are not met, what happens depends on whether \endpass\ appears
among the conditions (for syntax see below). If the failing condition is before
command is accepted if verification succeeds. However, if verification fails,
the ACL yields `deny', because the failing condition is after \endpass\.
.nextp
+.index \defer\, ACL verb
\defer\: If all the conditions are met, the ACL returns `defer' which, in an
SMTP session, causes a 4\*xx*\ response to be given. For a non-SMTP ACL,
\defer\ is the same as \deny\, because there is no way of sending a temporary
\%redirect%\ router and \":defer:"\ while verifying, but the \defer\ verb can
be used in any ACL, and even for a recipient it might be a simpler approach.
.nextp
+.index \deny\, ACL verb
\deny\: If all the conditions are met, the ACL returns `deny'. If any of the
conditions are not met, control is passed to the next ACL statement. For
example,
.endd
rejects commands from hosts that are on a DNS black list.
.nextp
+.index \discard\, ACL verb
\discard\: This verb behaves like \accept\, except that it returns `discard'
from the ACL instead of `accept'. It is permitted only on ACLs that are
concerned with receiving messages, and it causes recipients to be discarded.
\\DATA\\ do not appear in the log line when the \log@_recipients\ log selector
is set.
.nextp
+.index \drop\, ACL verb
\drop\: This verb behaves like \deny\, except that an SMTP connection is
forcibly closed after the 5\*xx*\ error message has been sent. For example:
.display asis
There is no difference between \deny\ and \drop\ for the connect-time ACL. The
connection is always dropped after sending a 550 response.
.nextp
+.index \require\, ACL verb
\require\: If all the conditions are met, control is passed to the next ACL
statement. If any of the conditions are not met, the ACL returns `deny'. For
example, when checking a \\RCPT\\ command,
passes control to subsequent statements only if the message's sender can be
verified. Otherwise, it rejects the command.
.nextp
+.index \warn\, ACL verb
\warn\: If all the conditions are met, a header line is added to an incoming
message and/or a line is written to Exim's main log. In all cases, control
passes to the next ACL statement. The text of the added header line and the log
.startitems
.item "control = <<text>>"
+.index \control\, ACL modifier
.em
This modifier affects the subsequent processing of the SMTP connection or of an
incoming message that is accepted. The effect of the first type of control
.endp
.item "delay = <<time>>"
+.index \delay\, ACL modifier
.index \-bh-\ option
This modifier causes Exim to wait for the time interval before proceeding. The
time is given in the usual Exim notation. This modifier may appear in any ACL.
.endd
.item endpass
+.index \endpass\, ACL modifier
This modifier, which has no argument, is recognized only in \accept\
statements. It marks the boundary between the conditions whose failure causes
control to pass to the next statement, and the conditions whose failure causes
the ACL to return `deny'. See the description of \accept\ above.
.item "log@_message = <<text>>"
+.index \log@_message\, ACL modifier
This modifier sets up a message that is used as part of the log message if the
ACL denies access or a \warn\ statement's conditions are true. For example:
.display asis
logging rejections.
.item "logwrite = <<text>>"
+.index \logwrite\, ACL modifier
.index log||in ACL, immediate
This modifier writes a message to a log file as soon as it is encountered when
processing an ACL. (Compare \log@_message\, which, except in the case of
.endd
.item "message = <<text>>"
+.index \message\, ACL modifier
This modifier sets up a text string that is expanded and used as an error
message if the current statement causes the ACL to deny access. The expansion
happens at the time Exim decides that access is to be denied, not at the time
use a \message\ modifier, or make use of \$acl@_verify@_message$\.
.item "set <<acl@_name>> = <<value>>"
+.index \set\, ACL modifier
This modifier puts a value into one of the ACL variables (see section
~~SECTaclvariables).
.em
.section Use of the control modifier
.rset SECTcontrols "~~chapter.~~section"
-.index \control\ modifier
+.index \control\, ACL modifier
The \control\ modifier supports the following settings:
.startitems
.rset SECTaddheadwarn "~~chapter.~~section"
.index header lines||adding in an ACL
.index header lines||position of added lines
+.index \warn\, ACL verb
+.index \message\, ACL modifier
The \message\ modifier can be used on a \warn\ statement to add an extra header
line to an incoming message, as in this example:
.display asis
.item "acl = <<name of acl or ACL string or file name >>"
.index ~~ACL||nested
.index ~~ACL||indirect
+.index \acl\, ACL condition
The possible values of the argument are the same as for the
\acl@_smtp@_$it{xxx}\ options. The named or inline ACL is run. If it returns
`accept' the condition is true; if it returns `deny' the condition is false. If
commands for different local users or different local domains.
.item "authenticated = <<string list>>"
+.index \authenticated\, ACL condition
.index authentication||ACL checking
.index ~~ACL||testing for authentication
If the SMTP connection is not authenticated, the condition is false. Otherwise,
.endd
.item "condition = <<string>>"
+.index \condition\, ACL condition
.index customizing||ACL condition
.index ~~ACL||customized test
.index ~~ACL||testing, customized
.em
.item "decode = <<location>>"
+.index \decode\, ACL condition
This condition is available only when Exim is compiled with the
content-scanning extension, and it is allowed only the the ACL defined by
\acl@_smtp@_mime\. It causes the current MIME part to be decoded into a file.
.item "dnslists = <<list of domain names and other data>>"
+.index \dnslists\, ACL condition
.index DNS list||in ACL
.index black list (DNS)
.index ~~ACL||testing a DNS list
here. See sections ~~SECTmorednslists--~~SECTmorednslistslast for details.
.item "domains = <<domain list>>"
+.index \domains\, ACL condition
.index domain||ACL checking
.index ~~ACL||testing a recipient domain
This condition is relevant only after a \\RCPT\\ command. It checks that the
until the next \domains\ test.
.item "encrypted = <<string list>>"
+.index \encrypted\, ACL condition
.index encryption||checking in an ACL
.index ~~ACL||testing for encryption
If the SMTP connection is not encrypted, the condition is false. Otherwise, the
.endd
.item "hosts = << host list>>"
+.index \hosts\, ACL condition
.index host||ACL checking
.index ~~ACL||testing the client host
This condition tests that the calling host matches the host list. If you have
which gives a custom error message for each denied host.
.item "local@_parts = <<local part list>>"
+.index \local@_parts\, ACL condition
.index local part||ACL checking
.index ~~ACL||testing a local part
This condition is relevant only after a \\RCPT\\ command. It checks that the
.em
.item "malware = <<option>>"
+.index \malware\, ACL condition
.index ~~ACL||virus scanning
.index ~~ACL||scanning for viruses
This condition is available only when Exim is compiled with the
.em
.item "mime@_regex = <<list of regular expressions>>"
+.index \mime@_regex\, ACL condition
.index ~~ACL||testing by regex matching
This condition is available only when Exim is compiled with the
content-scanning extension, and it is allowed only the the ACL defined by
.item "recipients = <<address list>>"
+.index \recipients\, ACL condition
.index recipient||ACL checking
.index ~~ACL||testing a recipient
This condition is relevant only after a \\RCPT\\ command. It checks the entire
.em
.item "regex = <<list of regular expressions>>"
+.index \regex\, ACL condition
.index ~~ACL||testing by regex matching
This condition is available only when Exim is compiled with the
content-scanning extension. It causes the incoming message to be scanned
.item "sender@_domains = <<domain list>>"
+.index \sender@_domains\, ACL condition
.index sender||ACL checking
.index ~~ACL||testing a sender domain
This condition tests the domain of the sender of the message against the given
be used to influence the sender checking.
.item "senders = <<address list>>"
+.index \senders\, ACL condition
.index sender||ACL checking
.index ~~ACL||testing a sender
This condition tests the sender of the message against the given list. To test
.em
.item "spam = <<username>>"
+.index \spam\, ACL condition
.index ~~ACL||scanning for spam
This condition is available only when Exim is compiled with the
content-scanning extension. It causes the incoming message to be scanned by
.item "verify = certificate"
+.index \verify\, ACL condition
.index TLS||client certificate verification
.index certificate||verification of client
.index ~~ACL||certificate verification
or \tls@_try@_verify@_hosts\ (see chapter ~~CHAPTLS).
.item "verify = header@_sender/<<options>>"
+.index \verify\, ACL condition
.index ~~ACL||verifying sender in the header
.index header lines||verifying the sender in
.index sender||verifying in header
.endd
.item "verify = header@_syntax"
+.index \verify\, ACL condition
.index ~~ACL||verifying header syntax
.index header lines||verifying syntax
.index verifying||header syntax
and this condition can be used to reject such messages.
.item "verify = helo"
+.index \verify\, ACL condition
.index ~~ACL||verifying HELO/EHLO
.index \\HELO\\||verifying
.index \\EHLO\\||verifying
to request it.
.item "verify = recipient/<<options>>"
+.index \verify\, ACL condition
.index ~~ACL||verifying recipient
.index recipient||verifying
.index verifying||recipient
.item "verify = reverse@_host@_lookup"
+.index \verify\, ACL condition
.index ~~ACL||verifying host reverse lookup
.index host||verifying reverse lookup
This condition ensures that a verified host name has been looked up from the IP
.item "verify = sender/<<options>>"
+.index \verify\, ACL condition
.index ~~ACL||verifying sender
.index sender||verifying
.index verifying||sender
~~SECTaddressverification. Exim caches the result of sender verification, to
avoid doing it more than once per message.
-.item "verify = sender=address/<<options>>"
+.item "verify = sender=<<address>>/<<options>>"
+.index \verify\, ACL condition
This is a variation of the previous option, in which a modified address is
verified as a sender.
.index virus scanners||command line interface
\cmdline\: This is the keyword for the generic command line scanner interface.
It can be used to attach virus scanners that are invoked from the shell. This
-scanner type takes 3 mantadory options:
+scanner type takes 3 mandatory options:
.numberpars
The full path and name of the scanner binary, with all command line options,
and a placeholder (%s) for the directory to scan.
git://git.exim.org / users / jgh / exim.git / blobdiff