. Update the Copyright year (only) when changing content.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.96"
+.set previousversion "4.97"
.include ./local_params
.set ACL "access control lists (ACLs)"
.set drivernamemax "64"
.macro copyyear
-2022
+2023
.endmacro
. /////////////////////////////////////////////////////////////////////////////
way of representing the date and time of day).
.next
After the first hyphen, the next
-.new
eleven
-.wen
characters are the id of the process that received the message.
.next
-.new
There are two different possibilities for the final four characters:
.olist
.oindex "&%localhost_number%&"
500000 (250000) and added to
the fractional part of the time, which in this case is in units of 2 us (4 us).
.endlist
-.wen
.endlist
After a message has been received, Exim waits for the clock to tick at the
referenced from the configuration (for example, alias files) are changed,
because these are reread each time they are used.
-.new
Either a SIGTERM or a SIGINT signal should be used to cause the daemon
to cleanly shut down.
Subprocesses handling recceiving or delivering messages,
or for scanning the queue,
will not be affected by the termination of the daemon process.
-.wen
.cmdopt -bdf
This option has the same effect as &%-bd%& except that it never disconnects
Because macros in the config file are often used for secrets, those are only
available to admin users.
-.new
The word &"set"& at the start of a line, followed by a single space,
is recognised specially as defining a value for a variable.
The syntax is otherwise the same as the ACL modifier &"set ="&.
-.wen
.cmdopt -bem <&'filename'&>
.cindex "testing" "string expansion"
given.
Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
option is also present.
-.new
If this option is given then the socket will not be created. This is required
if the system is running multiple daemons, in which case it should
be used on all.
.next
obtaining a current queue size
.endlist
-.wen
.cmdopt -pd
.cindex "Perl" "starting the interpreter"
.cindex "multiple SMTP deliveries"
connection because of the hints that were set up during the first queue scan.
-.new
Two-phase queue runs should be used on systems which, even intermittently,
have a large queue (such as mailing-list operators).
They may also be useful for hosts that are connected to the Internet
intermittently.
-.wen
.vitem &%-q[q]i...%&
.oindex "&%-qi%&"
Such a daemon listens for incoming SMTP calls, and also starts a queue runner
process every 30 minutes.
-.new
.cindex "named queues" "queue runners"
It is possible to set up runners for multiple named queues within one daemon,
For example:
.code
exim -qGhipri/2m -q10m -qqGmailinglist/1h
.endd
-.wen
When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
pid file is written unless one is explicitly requested by the &%-oP%& option.
[name="${quote_nisplus:$local_part}"]
.endd
.cindex "tainted data" "in lookups"
-.new
&*All*& tainted data used in a query-style lookup must be quoted
using a mechanism appropriate for the lookup type.
-.wen
See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
operator can be used for all lookup types, but has no effect for single-key
lookups, since no quoting is ever needed in their key strings.
database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
and &%nhash%&.
-.new
When reading lines from the standard input,
macros can be defined and ACL variables can be set.
For example:
set acl_m_myvar = bar
.endd
Such macros and variables can then be used in later input lines.
-.wen
Exim gives up its root privilege when it is called with the &%-be%& option, and
instead runs under the uid and gid it was called with, to prevent users from
add_header = :at_start:${authresults {$primary_hostname}}
.endd
This is safe even if no authentication results are available
-.new
and would generally be placed in the DATA ACL.
-.wen
.vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
For each item
in this list, its value is placed in &$item$&, and then the condition is
evaluated.
-.new
Any modification of &$value$& by this evaluation is discarded.
-.wen
If the condition is true, &$item$& is added to the output as an
item in a new list; if the condition is false, the item is discarded. The
separator used for the output list is the same as the one used for the
This item inserts &"raw"& header lines. It is described with the &%header%&
expansion item in section &<<SECTexpansionitems>>& above.
-.vitem "&*${run<&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
+.vitem "&*${run<&'options'&> {*&<&'command&~string'&>&*}{*&<&'string1'&>&*}&&&
{*&<&'string2'&>&*}}*&"
.cindex "expansion" "running a command"
.cindex "&%run%& expansion item"
and without whitespace.
If the option &'preexpand'& is not used,
-the command string is split into individual arguments by spaces
-and then each argument is expanded.
+the command string before expansion is split into individual arguments by spaces
+and then each argument is separately expanded.
Then the command is run
in a separate process, but under the same uid and gid. As in other command
executions from Exim, a shell is not used by default. If the command requires
a careful assessment for security vulnerabilities should be done.
If the option &'preexpand'& is used,
-the command and its arguments are first expanded as one string. The result is
-split apart into individual arguments by spaces, and then the command is run
-as above.
+the command string is first expanded as a whole.
+The expansion result is split apart into individual arguments by spaces,
+and then the command is run as above.
Since the arguments are split by spaces, when there is a variable expansion
which has an empty result, it will cause the situation that the argument will
simply be omitted when the program is actually executed by Exim. If the
-.new
.vitem &*${headerwrap_*&<&'cols'&>&*_*&<&'limit'&>&*:*&<&'string'&>&*}*&
.cindex header "wrapping operator"
.cindex expansion "header wrapping"
Whitespace at a chosen wrap point is removed.
A line-wrap consists of a newline followed by a tab,
and the tab is counted as 8 columns.
-.wen
rejections of MAIL and rejections of RCPT.
.tvar &$recipients$&
-.new
.tvar &$recipients_list$&
These variables both contain the envelope recipients for a message.
this variable is not intended for further processing.
The second is a proper Exim list; colon-separated.
-.wen
However, the variables
are not generally available, to prevent exposure of Bcc recipients in
dns_again_means_nonexist = *.in-addr.arpa
.endd
This option applies to all DNS lookups that Exim does,
-.new
except for TLSA lookups (where knowing about such failures
is security-relevant).
-.wen
It also applies when the
&[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
since these are most likely to be caused by DNS lookup problems. The
nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
connections immediately.
-.new
If the connection is on a TLS-on-connect port then the TCP connection is
just dropped. Otherwise, an SMTP error is sent first.
-.wen
The ability to give an immediate rejection (either by this option or using an
ACL) is provided for use in unusual cases. Many hosts will just try again,
.code
hosts_connection_nolog = :
.endd
-.new
The hosts affected by this option also do not log "no MAIL in SMTP connection"
lines, as may commonly be produced by a monitoring system.
-.wen
.option hosts_require_alpn main "host list&!!" unset
The option is available only if Exim has been built with Oracle support.
-.new
.option panic_coredump main boolean false
This option is rarely needed but can help for some debugging investigations.
If set, when an internal error is detected by Exim which is sufficient
Note that most systems require additional administrative configuration
to permit write a core file for a setuid program, which is Exim's
common installed configuration.
-.wen
.option percent_hack_domains main "domain list&!!" unset
.cindex "&""percent hack""&"
smtp_banner = $smtp_active_hostname ESMTP Exim \
$version_number $tod_full
.endd
-.new
Failure to expand the string causes a panic error;
a forced fail just closes the connection.
-.wen
If you want to create a
multiline response to the initial SMTP connection, use &"\n"& in the string at
appropriate points, but not at the end. Note that the 220 code is not included
&%tls_require_ciphers%& option).
After expansion it must contain
-.new
one or (only for OpenSSL versiona 1.1.1 onwards) more
-.wen
EC curve names, such as &`prime256v1`&, &`secp384r1`&, or &`P-521`&.
Consult your OpenSSL manual for valid curve names.
&`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
&`auto`& tells the library to choose.
-.new
If the option expands to an empty string, the effect is undefined.
-.wen
.option tls_ocsp_file main string&!! unset
When the message is about to be written out, the command specified by
&%transport_filter%& is started up in a separate, parallel process, and
the entire message, including the header lines, is passed to it on its standard
-input (this in fact is done from a third process, to avoid deadlock). The
-command must be specified as an absolute path.
+input (this in fact is done from a third process, to avoid deadlock).
+The command must be specified as an absolute path.
+
+The process run by the command must use its standard input as the message
+data to be transformed, and write the results on its standard output.
The lines of the message that are written to the transport filter are
terminated by newline (&"\n"&). The message is passed to the filter before any
TLS session for any host that matches this list.
&%tls_verify_certificates%& should also be set for the transport.
-.new
The default is &"**"& if DANE is not in use for the connection,
or if DANE-TA us used.
It is empty if DANE-EE is used.
-.wen
.option hosts_require_alpn smtp "host list&!!" unset
.cindex ALPN "require negotiation in client"
.option max_rcpt smtp integer&!! 100
.cindex "RCPT" "maximum number of outgoing"
This option,
-.new
after expansion,
-.wen
limits the number of RCPT commands that are sent in a single
SMTP message transaction.
A value setting of zero disables the limit.
-.new
If a constant is given,
-.wen
each set of addresses is treated independently, and
so can cause parallel connections to the same host if &%remote_max_parallel%&
permits this.
Successful authentication sets up information used by the
&%authresults%& expansion item.
-.new
.cindex authentication "failure event, server"
If an authenticator is run and does not succeed,
an event (see &<<CHAPevents>>&) of type "auth:fail" is raised.
If the event is serviced and a string is returned then the string will be logged
instead of the default log line.
See <<CHAPevents>> for details on events.
-.wen
.section "Testing server authentication" "SECID169"
try again later. If there are any backup hosts available, they are tried in the
usual way.
-.new
.next
.cindex authentication "failure event, client"
If the response to authentication is a permanent error (5&'xx'& code),
will be valid.
If the event is serviced and a string is returned then the string will be logged.
See <<CHAPevents>> for details on events.
-.wen
.next
If the response to authentication is a permanent error (5&'xx'& code), Exim
server_set_id = $auth1
.endd
-.new
&*Note*&: plaintext authentication methods such as PLAIN and LOGIN
should not be advertised on cleartext SMTP connections.
See the discussion in section &<<SECTplain_TLS>>&.
-.wen
If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
&$received_ip_address$& (that is, the connection is local), the &"secured"&
(If an API is found to let OpenSSL be configured in this way,
let the Exim Maintainers know and we'll likely use it).
.next
-With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option, it must be ordered to match the &%tls_certificate%& list.
+With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option,
+it must be ordered to match the &%tls_certificate%& list.
.next
Some other recently added features may only be available in one or the other.
This should be documented with the feature. If the documentation does not
the message override the banner message that is otherwise specified by the
&%smtp_banner%& option.
-.new
For tls-on-connect connections, the ACL is run before the TLS connection
is accepted; if the ACL does not accept then the TCP connection is dropped without
any TLS startup attempt and without any SMTP response being transmitted.
-.wen
.subsection "The EHLO/HELO ACL" SECID192
More than one header can be removed at the same time by using a colon separated
list of header specifiers.
-.new
If a specifier does not start with a circumflex (^)
then it is treated as a header name.
The header name matching is case insensitive.
.code
remove_header = \N^(?i)Authentication-Results\s*::\s*example.org;\N
.endd
-.wen
List expansion is not performed, so you cannot use hostlists to
create a list of headers, however both connection and message variable expansion
between the caller and Exim.
.next
.cindex "log" "connection identifier"
-.new
&%connection_identifier%&: An identifier for the accepted connection is added to
connection start and end lines and to message accept lines.
The identifier is tagged by Ci=.
The value is PID-based, so will reset on reboot and will wrap.
-.wen
.next
.cindex "log" "connection rejections"
&%connection_reject%&: A log entry is written whenever an incoming SMTP
Verification of DKIM signatures in SMTP incoming email is done for all
messages for which an ACL control &%dkim_disable_verify%& has not been set.
+
.cindex DKIM "selecting signature algorithms"
-Individual classes of signature algorithm can be ignored by changing
+Individual classes of DKIM signature algorithm can be ignored by changing
the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
The &%dkim_verify_minimal%& option can be set to cease verification
processing for a message once the first passing signature is found.
of this section can be ignored.
The results of verification are made available to the
-&%acl_smtp_dkim%& ACL, which can examine and modify them.
+&%acl_smtp_dkim%& ACL, which (for complex needs) can examine and modify them.
A missing ACL definition defaults to accept.
By default, the ACL is called once for each
syntactically(!) correct signature in the incoming message.
&%dkim_verify_signers%& (see above).
.vitem &%$dkim_verify_status%&
+So long as a DKIM ACL is defined
+(it need do no more than accept, which is the default),
+after all the DKIM ACL runs have completed, the value becomes a
+colon-separated list of the values after each run.
+The value is maintained for the MIME, PRDR and DATA ACLs.
+
Within the DKIM ACL,
a string describing the general status of the signature. One of
.ilist
set dkim_verify_reason = hash too weak or key too short
.endd
-So long as a DKIM ACL is defined (it need do no more than accept),
-after all the DKIM ACL runs have completed, the value becomes a
-colon-separated list of the values after each run.
-This is maintained for the mime, prdr and data ACLs.
-
.vitem &%$dkim_verify_reason%&
A string giving a little bit more detail when &%$dkim_verify_status%& is either
"fail" or "invalid". One of
.endlist
-In addition, two ACL conditions are provided, usable only in a DKIM ACL:
+In addition, two ACL conditions are provided:
.vlist
.vitem &%dkim_signers%&
ACL condition that checks a colon-separated list of domains or identities
for a match against the domain or identity that the ACL is currently verifying
-(reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
+(reflected by &%$dkim_cur_signer%&).
+This condition is only usable in a DKIM ACL.
+This is typically used to restrict an ACL
verb to a group of domains or identities. For example:
.code
.vitem &%dkim_status%&
ACL condition that checks a colon-separated list of possible DKIM verification
-results against the actual result of verification. This is typically used
+results against the actual result of verification,
+given by &$dkim_verify_status$& if that is non-empty or "none" if empty.
+.new
+This condition may be used in DKIM, MIME, PRDR and DATA ACLs.
+.wen
+
+A basic verification might be:
+.code
+deny !dkim_status = pass:none:invalid
+.endd
+
+A more complex use could be
to restrict an ACL verb to a list of verification outcomes, for example:
.code
The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
see the documentation of the &%$dkim_verify_status%& expansion variable above
for more information of what they mean.
+
+The condition is true if the status
+.new
+(or any of the list of status values)
+.wen
+is any one of the supplied list.
.endlist
If it is, the condition will return true and the variable
&$srs_recipient$& will be set to the decoded (original) value.
-.new
If the second argument is empty then the condition returns true if
the first argument is in valid SRS formet, else false.
The variable &$srs_recipient$& is not set for this case.
-.wen
.endlist
Example usage:
no other use is made of it.
For a tcp:connect event, if the connection is being made to a proxy
-then the &$host_address$& and &$port$& variables will be that of the proxy and not
-the target system.
+then the &$host_address$& and &$host_port$& variables
+will be that of the proxy and not the target system.
For tls:cert events, if GnuTLS is in use this will trigger only per
chain element received on the connection.
git://git.exim.org / exim.git / blobdiff