.set I " "
.macro copyyear
-2013
+2014
.endmacro
. /////////////////////////////////////////////////////////////////////////////
using the same syntax as for &%-oMa%&. The interface address is placed in
&$received_ip_address$& and the port number, if present, in &$received_port$&.
+.vitem &%-oMm%&&~<&'message&~reference'&>
+.oindex "&%-oMm%&"
+.cindex "message reference" "message reference, specifying for local message"
+See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
+option sets the message reference, e.g. message-id, and is logged during
+delivery. This is useful when some kind of audit trail is required to tie
+messages together. The format of the message reference is checked and will
+abort if the format is invalid. The option will only be accepted if exim is
+running in trusted mode, not as any regular user.
+
+The best example of a message reference is when Exim sends a bounce message.
+The message reference is the message-id of the original message for which Exim
+is sending the bounce.
+
.vitem &%-oMr%&&~<&'protocol&~name'&>
.oindex "&%-oMr%&"
.cindex "protocol, specifying for local message"
The next two lines are concerned with &'ident'& callbacks, as defined by RFC
1413 (hence their names):
.code
-rfc1413_hosts = *
-rfc1413_query_timeout = 5s
+rfc1413_query_hosts = *
+rfc1413_query_timeout = 0s
+.endd
+These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
+Few hosts offer RFC1413 service these days; calls have to be
+terminated by a timeout and this needlessly delays the startup
+of an incoming SMTP connection.
+If you have hosts for which you trust RFC1413 and need this
+information, you can change this.
+
+This line enables an efficiency SMTP option. It is negociated by clients
+and not expected to cause problems but can be disabled if needed.
+.code
+prdr_enable = true
.endd
-These settings cause Exim to make ident callbacks for all incoming SMTP calls.
-You can limit the hosts to which these calls are made, or change the timeout
-that is used. If you set the timeout to zero, all ident calls are disabled.
-Although they are cheap and can provide useful information for tracing problem
-messages, some hosts and firewalls have problems with ident calls. This can
-result in a timeout instead of an immediate refused connection, leading to
-delays on starting up an incoming SMTP session.
When Exim receives messages over SMTP connections, it expects all addresses to
be fully qualified with a domain, as required by the SMTP definition. However,
.code
remote_smtp:
driver = smtp
+ hosts_try_prdr = *
.endd
-This transport is used for delivering messages over SMTP connections. All its
-options are defaulted. The list of remote hosts comes from the router.
+This transport is used for delivering messages over SMTP connections.
+The list of remote hosts comes from the router.
+The &%hosts_try_prdr%& option enables an efficiency SMTP option.
+It is negotiated between client and server
+and not expected to cause problems but can be disabled if needed.
+All other options are defaulted.
.code
local_delivery:
driver = appendfile
&`fail`& keyword causes a &'forced expansion failure'& &-- see section
&<<SECTforexpfai>>& for an explanation of what this means.
-The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT,
+The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT,
and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
configured). If no type is given, TXT is assumed. When the type is PTR,
the data can be an IP address, written as normal; inversion and the addition of
in the same way that multiple DNS records for a single item are handled. A
different separator can be specified, as described above.
+Modifiers for &(dnsdb)& lookups are givien by optional keywords,
+each followed by a comma,
+that may appear before the record type.
+
The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
temporary DNS error for any of them, the behaviour is controlled by
-an optional keyword followed by a comma that may appear before the record
-type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
-&"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
+a defer-option modifier.
+The possible keywords are
+&"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
+With &"strict"& behaviour, any temporary DNS error causes the
whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
ignored, and the behaviour is as if the DNS lookup failed to find anything.
With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
Thus, in the default case, as long as at least one of the DNS lookups
yields some data, the lookup succeeds.
+.new
+.cindex "DNSSEC" "dns lookup"
+Use of &(DNSSEC)& is controlled by a dnssec modifier.
+The possible keywords are
+&"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
+With &"strict"& or &"lax"& DNSSEC information is requested
+with the lookup.
+With &"strict"& a response from the DNS resolver that
+is not labelled as authenticated data
+is treated as equivalent to a temporary DNS error.
+The default is &"never"&.
+
+See also the &$lookup_dnssec_authenticated$& variable.
+.wen
+
LDAP connections, rather than the SSL-on-connect &`ldaps`&.
See the &%ldap_start_tls%& option.
+.new
+Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
+controlled. Every part of the TLS configuration can be configured by settings in
+&_exim.conf_&. Depending on the version of the client libraries installed on
+your system, some of the initialization may have required setting options in
+&_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
+certificates. This revealed a nuance where the current UID that exim was
+running as could affect which config files it read. With Exim 4.83, these
+methods become optional, only taking effect if not specifically set in
+&_exim.conf_&.
+.wen
+
.section "LDAP quoting" "SECID68"
.cindex "LDAP" "quoting"
&`USER `& set the DN, for authenticating the LDAP bind
&`PASS `& set the password, likewise
&`REFERRALS `& set the referrals parameter
+.new
+&`SERVERS `& set alternate server list for this query only
+.wen
&`SIZE `& set the limit for the number of entries returned
&`TIME `& set the maximum waiting time for a query
.endd
The TIME parameter (also a number of seconds) is passed to the server to
set a server-side limit on the time taken to complete a search.
+.new
+The SERVERS parameter allows you to specify an alternate list of ldap servers
+to use for an individual lookup. The global ldap_servers option provides a
+default list of ldap servers, and a single lookup can specify a single ldap
+server to use. But when you need to do a lookup with a list of servers that is
+different than the default list (maybe different order, maybe a completely
+different set of servers), the SERVERS parameter allows you to specify this
+alternate list.
+.wen
Here is an example of an LDAP query in an Exim lookup that uses some of these
values. This is a single line, folded to fit on the page:
list. The effect of each one lasts until the next, or until the end of the
list.
-To explain the host/ip processing logic a different way for the same ACL:
+.new
+.section "Mixing wildcarded host names and addresses in host lists" &&&
+ "SECTmixwilhos"
+.cindex "host list" "mixing names and addresses in"
+
+This section explains the host/ip processing logic with the same concepts
+as the previous section, but specifically addresses what happens when a
+wildcarded hostname is one of the items in the hostlist.
.ilist
If you have name lookups or wildcarded host names and
&`+ignore_unknown`&, which was discussed in depth in the first example in
this section.
.endlist
-
+.wen
.section "Temporary DNS errors when looking up host information" &&&
-.section "Mixing wildcarded host names and addresses in host lists" &&&
- "SECTmixwilhos"
-.cindex "host list" "mixing names and addresses in"
-If you have name lookups or wildcarded host names and IP addresses in the same
-host list, you should normally put the IP addresses first. For example, in an
-ACL you could have:
-.code
-accept hosts = 10.9.8.7 : *.friend.example
-.endd
-The reason for this lies in the left-to-right way that Exim processes lists.
-It can test IP addresses without doing any DNS lookups, but when it reaches an
-item that requires a host name, it fails if it cannot find a host name to
-compare with the pattern. If the above list is given in the opposite order, the
-&%accept%& statement fails for a host whose name cannot be found, even if its
-IP address is 10.9.8.7.
-
-If you really do want to do the name check first, and still recognize the IP
-address, you can rewrite the ACL like this:
-.code
-accept hosts = *.friend.example
-accept hosts = 10.9.8.7
-.endd
-If the first &%accept%& fails, Exim goes on to try the second one. See chapter
-&<<CHAPACL>>& for details of ACLs.
-
-
-
.section "Address lists" "SECTaddresslist"
If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
+.new
+.vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
+ {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
+.cindex "expansion" "extracting cerificate fields"
+.cindex "&%certextract%&" "certificate fields"
+.cindex "certificate" "extracting fields"
+The <&'certificate'&> must be a variable of type certificate.
+The field name is expanded and used to retrive the relevant field from
+the certificate. Supported fields are:
+.display
+&`version `&
+&`serial_number `&
+&`subject `& RFC4514 DN
+&`issuer `& RFC4514 DN
+&`notbefore `& time
+&`notafter `& time
+&`sig_algorithm `&
+&`signature `&
+&`subj_altname `& tagged list
+&`ocsp_uri `& list
+&`crl_uri `& list
+.endd
+If the field is found,
+<&'string2'&> is expanded, and replaces the whole item;
+otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
+variable &$value$& contains the value that has been extracted. Afterwards, it
+is restored to any previous value it might have had.
+
+If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
+key is not found. If {<&'string2'&>} is also omitted, the value that was
+extracted is used.
+
+Some field names take optional modifiers, appended and separated by commas.
+
+The field selectors marked as "RFC4514" above
+output a Distinguished Name string which is
+not quite
+parseable by Exim as a comma-separated tagged list
+(the exceptions being elements containin commas).
+RDN elements of a single type may be selected by
+a modifier of the type label; if so the expansion
+result is a list (newline-separated by default).
+The separator may be changed by another modifer of
+a right angle-bracket followed immediately by the new separator.
+Recognised RDN type labels include "CN", "O", "OU" and "DC".
+
+The field selectors marked as "time" above
+may output a number of seconds since epoch
+if the modifier "int" is used.
+
+The field selectors marked as "list" above return a list,
+newline-separated by default,
+(embedded separator characters in elements are doubled).
+The separator may be changed by a modifier of
+a right angle-bracket followed immediately by the new separator.
+
+The field selectors marked as "tagged" above
+prefix each list element with a type string and an equals sign.
+Elements of only one type may be selected by a modifier
+which is one of "dns", "uri" or "mail";
+if so the elenment tags are omitted.
+
+If not otherwise noted field values are presented in human-readable form.
+.wen
+
.vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
{*&<&'arg'&>&*}...}*&"
.cindex &%dlfunc%&
&%strlen%&, which gives the length of a string.
+.vitem "&*${listextract{*&<&'number'&>&*}&&&
+ {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
+.cindex "expansion" "extracting list elements by number"
+.cindex "&%listextract%&" "extract list elements by number"
+.cindex "list" "extracting elements by number"
+The <&'number'&> argument must consist entirely of decimal digits,
+apart from an optional leading minus,
+and leading and trailing white space (which is ignored).
+
+After expansion, <&'string1'&> is interpreted as a list, colon-separated by
+default, but the separator can be changed in the usual way.
+
+The first field of the list is numbered one.
+If the number is negative, the fields are
+counted from the end of the list, with the rightmost one numbered -1.
+The numbered element of the list is extracted and placed in &$value$&,
+then <&'string2'&> is expanded as the result.
+
+If the modulus of the
+number is zero or greater than the number of fields in the string,
+the result is the expansion of <&'string3'&>.
+
+For example:
+.code
+${listextract{2}{x:42:99}}
+.endd
+yields &"42"&, and
+.code
+${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
+.endd
+yields &"result: 99"&.
+
+If {<&'string3'&>} is omitted, an empty string is used for string3.
+If {<&'string2'&>} is also omitted, the value that was
+extracted is used.
+You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
+
+
.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
{*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
This is the first of one of two different types of lookup item, which are both
{*&<&'string2'&>&*}}*&"
.cindex "expansion" "running a command"
.cindex "&%run%& expansion item"
-The command and its arguments are first expanded separately, and 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 you want
+.new
+The command and its arguments are first expanded as one string. The string is
+split apart into individual arguments by spaces, and 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 shell, you must explicitly code it.
+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
+script/program requires a specific number of arguments and the expanded
+variable could possibly result in this empty expansion, the variable must be
+quoted. This is more difficult if the expanded variable itself could result
+in a string containing quotes, because it would interfere with the quotes
+around the command arguments. A possible guard against this is to wrap the
+variable in the &%sg%& operator to change any quote marks to some other
+character.
+.wen
+
The standard input for the command exists, but is empty. The standard output
and standard error are set to the same file descriptor.
.cindex "return code" "from &%run%& expansion"
.vitem &*${md5:*&<&'string'&>&*}*&
.cindex "MD5 hash"
.cindex "expansion" "MD5 hash"
+.cindex "certificate fingerprint"
.cindex "&%md5%& expansion item"
The &%md5%& operator computes the MD5 hash value of the string, and returns it
as a 32-digit hexadecimal number, in which any letters are in lower case.
.vitem &*${sha1:*&<&'string'&>&*}*&
.cindex "SHA-1 hash"
.cindex "expansion" "SHA-1 hashing"
+.cindex "certificate fingerprint"
.cindex "&%sha2%& expansion item"
The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
it as a 40-digit hexadecimal number, in which any letters are in upper case.
+.vitem &*${sha256:*&<&'certificate'&>&*}*&
+.cindex "SHA-256 hash"
+.cindex "certificate fingerprint"
+.cindex "expansion" "SHA-256 hashing"
+.cindex "&%sha256%& expansion item"
+The &%sha256%& operator computes the SHA-256 hash fingerprint of the
+certificate,
+and returns
+it as a 64-digit hexadecimal number, in which any letters are in upper case.
+Only arguments which are a single variable of certificate type are supported.
+
+
.vitem &*${stat:*&<&'string'&>&*}*&
.cindex "expansion" "statting a file"
.cindex "file" "extracting characteristics"
.cindex "expansion" "case forcing"
.cindex "&%uc%& expansion item"
This forces the letters in the string into upper-case.
+
+.vitem &*${utf8clean:*&<&'string'&>&*}*&
+.cindex "correction of invalid utf-8 sequences in strings"
+.cindex "utf-8" "utf-8 sequences"
+.cindex "incorrect utf-8"
+.cindex "expansion" "utf-8 forcing"
+.cindex "&%utf8clean%& expansion item"
+This replaces any invalid utf-8 sequence in the string by the character &`?`&.
.endlist
.cindex "&%bool%& expansion condition"
This condition turns a string holding a true or false representation into
a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
-(case-insensitively); also positive integer numbers map to true if non-zero,
+(case-insensitively); also integer numbers map to true if non-zero,
false if zero.
An empty string is treated as false.
Leading and trailing whitespace is ignored;
the space value is -1. See also the &%check_log_space%& option.
+.new
+.vitem &$lookup_dnssec_authenticated$&
+.vindex "&$lookup_dnssec_authenticated$&"
+This variable is set after a DNS lookup done by
+a dnsdb lookup expansion, dnslookup router or smtp transport.
+It will be empty if &(DNSSEC)& was not requested,
+&"no"& if the result was not labelled as authenticated data
+and &"yes"& if it was.
+.wen
+
.vitem &$mailstore_basename$&
.vindex "&$mailstore_basename$&"
This variable is set only when doing deliveries in &"mailstore"& format in the
.vitem &$sender_host_dnssec$&
.vindex "&$sender_host_dnssec$&"
-If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or
+If an attempt to populate &$sender_host_name$& has been made
+(by reference, &%hosts_lookup%& or
otherwise) then this boolean will have been set true if, and only if, the
resolver library states that the reverse DNS was authenticated data. At all
other times, this variable is false.
It is likely that you will need to coerce DNSSEC support on in the resolver
library, by setting:
.code
-dns_use_dnssec = 1
+dns_dnssec_ok = 1
.endd
Exim does not perform DNSSEC validation itself, instead leaving that to a
this depends upon the TLS implementation used.
If TLS has not been negotiated, the value will be 0.
+.new
+.vitem &$tls_in_ourcert$&
+.vindex "&$tls_in_ourcert$&"
+This variable refers to the certificate presented to the peer of an
+inbound connection when the message was received.
+It is only useful as the argument of a
+&%certextract%& expansion item, &%md5%& or &%sha1%& operator,
+or a &%def%& condition.
+.wen
+
+.new
+.vitem &$tls_in_peercert$&
+.vindex "&$tls_in_peercert$&"
+This variable refers to the certificate presented by the peer of an
+inbound connection when the message was received.
+It is only useful as the argument of a
+&%certextract%& expansion item, &%md5%& or &%sha1%& operator,
+or a &%def%& condition.
+.wen
+
+.new
+.vitem &$tls_out_ourcert$&
+.vindex "&$tls_out_ourcert$&"
+This variable refers to the certificate presented to the peer of an
+outbound connection. It is only useful as the argument of a
+&%certextract%& expansion item, &%md5%& or &%sha1%& operator,
+or a &%def%& condition.
+.wen
+
+.new
+.vitem &$tls_out_peercert$&
+.vindex "&$tls_out_peercert$&"
+This variable refers to the certificate presented by the peer of an
+outbound connection. It is only useful as the argument of a
+&%certextract%& expansion item, &%md5%& or &%sha1%& operator,
+or a &%def%& condition.
+.wen
+
.vitem &$tls_in_certificate_verified$&
.vindex "&$tls_in_certificate_verified$&"
This variable is set to &"1"& if a TLS certificate was verified when the
following options:
.ilist
-&%daemon_smtp_ports%& contains a list of default ports. (For backward
-compatibility, this option can also be specified in the singular.)
+&%daemon_smtp_ports%& contains a list of default ports
+or service names.
+(For backward compatibility, this option can also be specified in the singular.)
.next
&%local_interfaces%& contains list of interface IP addresses on which to
listen. Each item may optionally also specify a port.
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
+list of port numbers or service names,
+connections to those ports must use SSMTP. The most
common use of this option is expected to be
.code
tls_on_connect_ports = 465
.row &%acl_smtp_auth%& "ACL for AUTH"
.row &%acl_smtp_connect%& "ACL for connection"
.row &%acl_smtp_data%& "ACL for DATA"
+.row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
.row &%acl_smtp_dkim%& "ACL for DKIM verification"
.row &%acl_smtp_etrn%& "ACL for ETRN"
.row &%acl_smtp_expn%& "ACL for EXPN"
.row &%tls_crl%& "certificate revocation list"
.row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
.row &%tls_dhparam%& "DH parameters for server"
+.row &%tls_ocsp_file%& "location of server certificate status proof"
.row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
.row &%tls_privatekey%& "location of server private key"
.row &%tls_remember_esmtp%& "don't reset after starting TLS"
.row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
.row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
.row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
+.row &%prdr_enable%& "advertise PRDR to all hosts"
.row &%tls_advertise_hosts%& "advertise TLS to these hosts"
.endtable
.row &%disable_ipv6%& "do no IPv6 processing"
.row &%dns_again_means_nonexist%& "for broken domains"
.row &%dns_check_names_pattern%& "pre-DNS syntax check"
+.row &%dns_dnssec_ok%& "parameter for resolver"
.row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
.row &%dns_retrans%& "parameter for resolver"
.row &%dns_retry%& "parameter for resolver"
-.row &%dns_use_dnssec%& "parameter for resolver"
.row &%dns_use_edns0%& "parameter for resolver"
.row &%hold_domains%& "hold delivery for these domains"
.row &%local_interfaces%& "for routing checks"
processed and the message itself has been received, but before the final
acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
+.option acl_smtp_data_prdr main string&!! unset
+.cindex "DATA" "ACL for"
+.cindex "&ACL;" "PRDR-related"
+.cindex "&ACL;" "per-user data processing"
+This option defines the ACL that,
+if the PRDR feature has been negotiated,
+is run for each recipient after an SMTP DATA command has been
+processed and the message itself has been received, but before the
+acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
+
.option acl_smtp_etrn main string&!! unset
.cindex "ETRN" "ACL for"
This option defines the ACL that is run when an SMTP ETRN command is
.code
delay_warning = 2h:12h:99d
.endd
+Note that the option is only evaluated at the time a delivery attempt fails,
+which depends on retry and queue-runner configuration.
+Typically retries will be configured more frequently than warning messages.
.option delay_warning_condition main string&!! "see below"
.vindex "&$domain$&"
reversed and looked up in the reverse DNS, as described in more detail in
section &<<SECTverifyCSA>>&.
+
+.option dns_dnssec_ok main integer -1
+.cindex "DNS" "resolver options"
+.cindex "DNS" "DNSSEC"
+If this option is set to a non-negative number then Exim will initialise the
+DNS resolver library to either use or not use DNSSEC, overriding the system
+default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
+
+If the resolver library does not support DNSSEC then this option has no effect.
+
+
.option dns_ipv4_lookup main "domain list&!!" unset
.cindex "IPv6" "DNS lookup for AAAA records"
.cindex "DNS" "IPv6 lookup for AAAA records"
See &%dns_retrans%& above.
-.option dns_use_dnssec main integer -1
-.cindex "DNS" "resolver options"
-.cindex "DNS" "DNSSEC"
-If this option is set to a non-negative number then Exim will initialise the
-DNS resolver library to either use or not use DNSSEC, overriding the system
-default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
-
-If the resolver library does not support DNSSEC then this option has no effect.
-
-
.option dns_use_edns0 main integer -1
.cindex "DNS" "resolver options"
.cindex "DNS" "EDNS0"
not count as protocol errors (see &%smtp_max_synprot_errors%&).
+.option prdr_enable main boolean false
+.cindex "PRDR" "enabling on server"
+This option can be used to enable the Per-Recipient Data Response extension
+to SMTP, defined by Eric Hall.
+If the option is set, PRDR is advertised by Exim when operating as a server.
+If the client requests PRDR, and more than one recipient, for a message
+an additional ACL is called for each recipient after the message content
+is recieved. See section &<<SECTPRDRACL>>&.
+
.option preserve_message_logs main boolean false
.cindex "message logs" "preserving"
If this option is set, message log files are not deleted when messages are
acceptable bound from 1024 to 2048.
+.option tls_ocsp_file main string&!! unset
+This option
+must if set expand to the absolute path to a file which contains a current
+status proof for the server's certificate, as obtained from the
+Certificate Authority.
+
+
.option tls_on_connect_ports main "string list" unset
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
-.option headers_add routers string&!! unset
+.option headers_add routers list&!! unset
.cindex "header lines" "adding"
.cindex "router" "adding header lines"
-This option specifies a string of text that is expanded at routing time, and
-associated with any addresses that are accepted by the router. However, this
+This option specifies a list of text headers, newline-separated,
+that is associated with any addresses that are accepted by the router.
+Each item is separately expanded, at routing time. However, this
option has no effect when an address is just being verified. The way in which
the text is used to add header lines at transport time is described in section
&<<SECTheadersaddrem>>&. New header lines are not actually added until the
&"see"& the added header lines.
The &%headers_add%& option is expanded after &%errors_to%&, but before
-&%headers_remove%& and &%transport%&. If the expanded string is empty, or if
-the expansion is forced to fail, the option has no effect. Other expansion
+&%headers_remove%& and &%transport%&. If an item is empty, or if
+an item expansion is forced to fail, the item has no effect. Other expansion
failures are treated as configuration errors.
Unlike most options, &%headers_add%& can be specified multiple times
-.option headers_remove routers string&!! unset
+.option headers_remove routers list&!! unset
.cindex "header lines" "removing"
.cindex "router" "removing header lines"
-This option specifies a string of text that is expanded at routing time, and
-associated with any addresses that are accepted by the router. However, this
+This option specifies a list of text headers, colon-separated,
+that is associated with any addresses that are accepted by the router.
+Each item is separately expanded, at routing time. However, this
option has no effect when an address is just being verified. The way in which
the text is used to remove header lines at transport time is described in
section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
&"see"& the original header lines.
The &%headers_remove%& option is expanded after &%errors_to%& and
-&%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
-the option has no effect. Other expansion failures are treated as configuration
+&%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
+the item has no effect. Other expansion failures are treated as configuration
errors.
Unlike most options, &%headers_remove%& can be specified multiple times
+.new
+.option dnssec_request_domains dnslookup "domain list&!!" unset
+.cindex "MX record" "security"
+.cindex "DNSSEC" "MX lookup"
+.cindex "security" "MX lookup"
+.cindex "DNS" "DNSSEC"
+DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+the dnssec request bit set.
+This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+.wen
+
+
+
+.new
+.option dnssec_require_domains dnslookup "domain list&!!" unset
+.cindex "MX record" "security"
+.cindex "DNSSEC" "MX lookup"
+.cindex "security" "MX lookup"
+.cindex "DNS" "DNSSEC"
+DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+the dnssec request bit set. Any returns not having the Authenticated Data bit
+(AD bit) set wil be ignored and logged as a host-lookup failure.
+This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+.wen
+
+
+
.option mx_domains dnslookup "domain list&!!" unset
.cindex "MX record" "required to exist"
.cindex "SRV record" "required to exist"
&%user%& (see below).
-.option headers_add transports string&!! unset
+.option headers_add transports list&!! unset
.cindex "header lines" "adding in transport"
.cindex "transport" "header lines; adding"
-This option specifies a string of text that is expanded and added to the header
+This option specifies a list of text headers, newline-separated,
+which are (separately) expanded and added to the header
portion of a message as it is transported, as described in section
&<<SECTheadersaddrem>>&. Additional header lines can also be specified by
routers. If the result of the expansion is an empty string, or if the expansion
checked, since this option does not automatically suppress them.
-.option headers_remove transports string&!! unset
+.option headers_remove transports list&!! unset
.cindex "header lines" "removing"
.cindex "transport" "header lines; removing"
-This option specifies a string that is expanded into a list of header names;
+This option specifies a list of header names, colon-separated;
these headers are omitted from the message as it is transported, as described
in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
-routers. If the result of the expansion is an empty string, or if the expansion
+routers.
+Each list item is separately expanded.
+If the result of the expansion is an empty string, or if the expansion
is forced to fail, no action is taken. Other expansion failures are treated as
errors and cause the delivery to be deferred.
Unlike most options, &%headers_remove%& can be specified multiple times
-for a router; all listed headers are added.
+for a router; all listed headers are removed.
details.
+.new
+.option dnssec_request_domains smtp "domain list&!!" unset
+.cindex "MX record" "security"
+.cindex "DNSSEC" "MX lookup"
+.cindex "security" "MX lookup"
+.cindex "DNS" "DNSSEC"
+DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+the dnssec request bit set.
+This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+.wen
+
+
+
+.new
+.option dnssec_require_domains smtp "domain list&!!" unset
+.cindex "MX record" "security"
+.cindex "DNSSEC" "MX lookup"
+.cindex "security" "MX lookup"
+.cindex "DNS" "DNSSEC"
+DNS lookups for domains matching &%dnssec_request_domains%& will be done with
+the dnssec request bit set. Any returns not having the Authenticated Data bit
+(AD bit) set wil be ignored and logged as a host-lookup failure.
+This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+.wen
+
+
+
.option dscp smtp string&!! unset
.cindex "DCSP" "outbound"
This option causes the DSCP value associated with a socket to be set to one
&<<CHAPSMTPAUTH>>& for details of authentication.
+.option hosts_request_ocsp smtp "host list&!!" *
+.cindex "TLS" "requiring for certain servers"
+Exim will request a Certificate Status on a
+TLS session for any host that matches this list.
+&%tls_verify_certificates%& should also be set for the transport.
+
+.option hosts_require_ocsp smtp "host list&!!" unset
+.cindex "TLS" "requiring for certain servers"
+Exim will request, and check for a valid Certificate Status being given, on a
+TLS session for any host that matches this list.
+&%tls_verify_certificates%& should also be set for the transport.
+
.option hosts_require_tls smtp "host list&!!" unset
.cindex "TLS" "requiring for certain servers"
Exim will insist on using a TLS session when delivering to any host that
unauthenticated. See also &%hosts_require_auth%&, and chapter
&<<CHAPSMTPAUTH>>& for details of authentication.
+.option hosts_try_prdr smtp "host list&!!" unset
+.cindex "PRDR" "enabling, optional in client"
+This option provides a list of servers to which, provided they announce
+PRDR support, Exim will attempt to negotiate PRDR
+for multi-recipient messages.
+
.option interface smtp "string list&!!" unset
.cindex "bind IP address"
.cindex "IP address" "binding"
in clear.
+.option tls_try_verify_hosts smtp "host list&!! unset
+.cindex "TLS" "server certificate verification"
+.cindex "certificate" "verification of server"
+This option gives a list of hosts for which, on encrypted connections,
+certificate verification will be tried but need not succeed.
+The &%tls_verify_certificates%& option must also be set.
+Note that unless the host is in this list
+TLS connections will be denied to hosts using self-signed certificates
+when &%tls_verify_certificates%& is set.
+The &$tls_out_certificate_verified$& variable is set when
+certificate verification succeeds.
+
+
.option tls_verify_certificates smtp string&!! unset
.cindex "TLS" "server certificate verification"
.cindex "certificate" "verification of server"
&$host_address$& are set to the name and address of the server during the
expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
+For back-compatability,
+if neither tls_verify_hosts nor tls_try_verify_hosts are set
+and certificate verification fails the TLS connection is closed.
+
+
+.option tls_verify_hosts smtp "host list&!! unset
+.cindex "TLS" "server certificate verification"
+.cindex "certificate" "verification of server"
+This option gives a list of hosts for which. on encrypted connections,
+certificate verification must succeed.
+The &%tls_verify_certificates%& option must also be set.
+If both this option and &%tls_try_verify_hosts%& are unset
+operation is as if this option selected all hosts.
+
driver = dovecot
public_name = PLAIN
server_socket = /var/run/dovecot/auth-client
- server_set_id = $auth2
+ server_set_id = $auth1
dovecot_ntlm:
driver = dovecot
.cindex "TLS" "revoked certificates"
.cindex "revocation list"
.cindex "certificate" "revocation list"
+.cindex "OCSP" "stapling"
Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
certificates are revoked. If you have such a list, you can pass it to an Exim
server using the global option called &%tls_crl%& and to an Exim client using
an identically named option for the &(smtp)& transport. In each case, the value
of the option is expanded and must then be the name of a file that contains a
CRL in PEM format.
+The downside is that clients have to periodically re-download a potentially huge
+file from every certificate authority the know of.
+
+The way with most moving parts at query time is Online Certificate
+Status Protocol (OCSP), where the client verifies the certificate
+against an OCSP server run by the CA. This lets the CA track all
+usage of the certs. It requires running software with access to the
+private key of the CA, to sign the responses to the OCSP queries. OCSP
+is based on HTTP and can be proxied accordingly.
+
+The only widespread OCSP server implementation (known to this writer)
+comes as part of OpenSSL and aborts on an invalid request, such as
+connecting to the port and then disconnecting. This requires
+re-entering the passphrase each time some random client does this.
+
+The third way is OCSP Stapling; in this, the server using a certificate
+issued by the CA periodically requests an OCSP proof of validity from
+the OCSP server, then serves it up inline as part of the TLS
+negotiation. This approach adds no extra round trips, does not let the
+CA track users, scales well with number of certs issued by the CA and is
+resilient to temporary OCSP server failures, as long as the server
+starts retrying to fetch an OCSP proof some time before its current
+proof expires. The downside is that it requires server support.
+
+Unless Exim is built with the support disabled,
+or with GnuTLS earlier than version 3.1.3,
+support for OCSP stapling is included.
+
+There is a global option called &%tls_ocsp_file%&.
+The file specified therein is expected to be in DER format, and contain
+an OCSP proof. Exim will serve it as part of the TLS handshake. This
+option will be re-expanded for SNI, if the &%tls_certificate%& option
+contains &`tls_in_sni`&, as per other TLS options.
+
+Exim does not at this time implement any support for fetching a new OCSP
+proof. The burden is on the administrator to handle this, outside of
+Exim. The file specified should be replaced atomically, so that the
+contents are always valid. Exim will expand the &%tls_ocsp_file%& option
+on each connection, so a new file will be handled transparently on the
+next connection.
+
+When built with OpenSSL Exim will check for a valid next update timestamp
+in the OCSP proof; if not present, or if the proof has expired, it will be
+ignored.
+
+For the client to be able to verify the stapled OCSP the server must
+also supply, in its stapled information, any intermediate
+certificates for the chain leading to the OCSP proof from the signer
+of the server certificate. There may be zero or one such. These
+intermediate certificates should be added to the server OCSP stapling
+file named by &%tls_ocsp_file%&.
+
+Note that the proof only covers the terminal server certificate,
+not any of the chain from CA to it.
+
+.code
+ A helper script "ocsp_fetch.pl" for fetching a proof from a CA
+ OCSP server is supplied. The server URL may be included in the
+ server certificate, if the CA is helpful.
+
+ One failure mode seen was the OCSP Signer cert expiring before the end
+ of validity of the OCSP proof. The checking done by Exim/OpenSSL
+ noted this as invalid overall, but the re-fetch script did not.
+.endd
+
+
.section "Configuring an Exim client to use TLS" "SECID185"
expected server certificates. The client verifies the server's certificate
against this collection, taking into account any revoked certificates that are
in the list defined by &%tls_crl%&.
+Failure to verify fails the TLS connection unless either of the
+&%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
+
+The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
+certificate verification to the listed servers. Verification either must
+or need not succeed respectively.
+
+The &(smtp)& transport has two OCSP-related options:
+&%hosts_require_ocsp%&; a host-list for which a Certificate Status
+is requested and required for the connection to proceed. The default
+value is empty.
+&%hosts_request_ocsp%&; a host-list for which (additionally)
+a Certificate Status is requested (but not necessarily verified). The default
+value is "*" meaning that requests are made unless configured
+otherwise.
+
+The host(s) should also be in &%hosts_require_tls%&, and
+&%tls_verify_certificates%& configured for the transport,
+for OCSP to be relevant.
If
&%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
.next
.vindex "&%tls_verify_certificates%&"
&%tls_verify_certificates%&
+.next
+.vindex "&%tls_ocsp_file%&"
+&%tls_verify_certificates%&
.endlist
Great care should be taken to deal with matters of case, various injection
root certificate along with the rest makes it available for the user to
install if the receiving end is a client MUA that can interact with a user.
+Note that certificates using MD5 are unlikely to work on today's Internet;
+even if your libraries allow loading them for use in Exim when acting as a
+server, increasingly clients will not accept such certificates. The error
+diagnostics in such a case can be frustratingly vague.
+
+
.section "Self-signed certificates" "SECID187"
.cindex "certificate" "self-signed"
.cindex "SMTP" "connection, ACL for"
.cindex "non-SMTP messages" "ACLs for"
.cindex "MIME content scanning" "ACL for"
+.cindex "PRDR" "ACL for"
.table2 140pt
.irow &%acl_not_smtp%& "ACL for non-SMTP messages"
.irow &%acl_smtp_auth%& "ACL for AUTH"
.irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
.irow &%acl_smtp_data%& "ACL after DATA is complete"
+.irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
.irow &%acl_smtp_etrn%& "ACL for ETRN"
.irow &%acl_smtp_expn%& "ACL for EXPN"
.irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
and try again later, but that is their problem, though it does waste some of
your resources.
-The &%acl_smtp_data%& ACL is run after both the &%acl_smtp_dkim%& and
-the &%acl_smtp_mime%& ACLs.
+The &%acl_smtp_data%& ACL is run after
+the &%acl_smtp_data_prdr%&,
+the &%acl_smtp_dkim%&
+and the &%acl_smtp_mime%& ACLs.
.section "The SMTP DKIM ACL" "SECTDKIMACL"
The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
+.section "The SMTP PRDR ACL" "SECTPRDRACL"
+.oindex "&%prdr_enable%&"
+The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
+with PRDR support enabled (which is the default).
+It becomes active only when the PRDR feature is negotiated between
+client and server for a message, and more than one recipient
+has been accepted.
+
+The ACL test specfied by &%acl_smtp_data_prdr%& happens after a message
+has been recieved, and is executed for each recipient of the message.
+The test may accept or deny for inividual recipients.
+The &%acl_smtp_data%& will still be called after this ACL and
+can reject the message overall, even if this ACL has accepted it
+for some or all recipients.
+
+PRDR may be used to support per-user content filtering. Without it
+one must defer any recipient after the first that has a different
+content-filter configuration. With PRDR, the RCPT-time check
+for this can be disabled when the MAIL-time $smtp_command included
+"PRDR". Any required difference in behaviour of the main DATA-time
+ACL should however depend on the PRDR-time ACL having run, as Exim
+will avoid doing so in some situations (eg. single-recipient mails).
+
+See also the &%prdr_enable%& global option
+and the &%hosts_try_prdr%& smtp transport option.
+
+This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
+If the ACL is not defined, processing completes as if
+the feature was not requested by the client.
+
.section "The QUIT ACL" "SECTQUITACL"
.cindex "QUIT, ACL for"
The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
from one SMTP connection to another. If a recipient-verify callout connection is
requested in the same ACL it is held open and used for the data, otherwise one is made
after the ACL completes.
-Note that routers are used in verify mode.
+
+Note that routers are used in verify mode,
+and cannot depend on content of received headers.
+Note also that headers cannot be
+modified by any of the post-data ACLs (DATA, MIME and DKIM).
+Headers may be modified by routers (subject to the above) and transports.
+
+Cutthrough delivery is not supported via transport-filters or when DKIM signing
+of outgoing messages is done, because it sends data to the ultimate destination
+before the entire message has been received from the source.
Should the ultimate destination system positively accept or reject the mail,
a corresponding indication is given to the source system and nothing is queued.
add_header = X-blacklisted-at: $dnslist_domain
.endd
The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
-MIME, and non-SMTP ACLs (in other words, those that are concerned with
+MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
receiving a message). The message must ultimately be accepted for
&%add_header%& to have any significant effect. You can use &%add_header%& with
any ACL verb, including &%deny%& (though this is potentially useful only in a
RCPT ACL).
+Headers will not be added to the message if the modifier is used in
+DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
+
Leading and trailing newlines are removed from
the data for the &%add_header%& modifier; if it then
contains one or more newlines that
remove_header = x-route-mail1 : x-route-mail2
.endd
The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
-MIME, and non-SMTP ACLs (in other words, those that are concerned with
+MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
receiving a message). The message must ultimately be accepted for
&%remove_header%& to have any significant effect. You can use &%remove_header%&
with any ACL verb, including &%deny%&, though this is really not useful for
any verb that doesn't result in a delivered message.
+Headers will not be removed to the message if the modifier is used in
+DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
+
More than one header can be removed at the same time by using a colon separated
list of header names. The header matching is case insensitive. Wildcards are
not permitted, nor is list expansion performed, so you cannot use hostlists to
send email. Details of how this works are given in section
&<<SECTverifyCSA>>&.
+.new
+.vitem &*verify&~=&~header_names_ascii*&
+.cindex "&%verify%& ACL condition"
+.cindex "&ACL;" "verifying header names only ASCII"
+.cindex "header lines" "verifying header names only ASCII"
+.cindex "verifying" "header names only ASCII"
+This condition is relevant only in an ACL that is run after a message has been
+received, that is, in an ACL specified by &%acl_smtp_data%& or
+&%acl_not_smtp%&. It checks all header names (not the content) to make sure
+there are no non-ASCII characters, also excluding control characters. The
+allowable characters are decimal ASCII values 33 through 126.
+
+Exim itself will handle headers with non-ASCII characters, but it can cause
+problems for downstream applications, so this option will allow their
+detection and rejection in the DATA ACL's.
+.wen
+
.vitem &*verify&~=&~header_sender/*&<&'options'&>
.cindex "&%verify%& ACL condition"
.cindex "&ACL;" "verifying sender in the header"
dnslists = some.list.example
.endd
+If an explicit key is being used for a DNS lookup and it may be an IPv6
+address you should specify alternate list separators for both the outer
+(DNS list name) list and inner (lookup keys) list:
+.code
+ dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
+.endd
+
.section "Rate limiting incoming messages" "SECTratelimiting"
.cindex "rate limiting" "client sending"
.cindex "limiting client sending rates"
&%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
&%hosts_override%& set, its hosts are always used, whether or not the router
supplies a host list.
+Callouts are only supported on &(smtp)& transports.
The port that is used is taken from the transport, if it is specified and is a
remote transport. (For routers that do verification only, no transport need be
.endd
You can safely omit this option (the default value is 1).
+.vitem &%sock%&
+.cindex "virus scanners" "simple socket-connected"
+This is a general-purpose way of talking to simple scanner daemons
+running on the local machine.
+There are four options:
+an address (which may be an IP addres and port, or the path of a Unix socket),
+a commandline to send (may include a single %s which will be replaced with
+the path to the mail file to be scanned),
+an RE to trigger on from the returned data,
+an RE to extract malware_name from the returned data.
+For example:
+.code
+av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
+.endd
+Default for the socket specifier is &_/tmp/malware.sock_&.
+Default for the commandline is &_%s\n_&.
+Both regular-expressions are required.
+
.vitem &%sophie%&
.cindex "virus scanners" "Sophos and Sophie"
Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
the transport cannot refer to the modified header lines, because such
expansions all occur before the message is actually transported.
-For both routers and transports, the result of expanding a &%headers_add%&
+For both routers and transports, the argument of a &%headers_add%&
option must be in the form of one or more RFC 2822 header lines, separated by
newlines (coded as &"\n"&). For example:
.code
Exim does not check the syntax of these added header lines.
Multiple &%headers_add%& options for a single router or transport can be
-specified; the values will be concatenated (with a separating newline
-added) before expansion.
+specified; the values will append to a single list of header lines.
+Each header-line is separately expanded.
-The result of expanding &%headers_remove%& must consist of a colon-separated
+The argument of a &%headers_remove%& option must consist of a colon-separated
list of header names. This is confusing, because header names themselves are
often terminated by colons. In this case, the colons are the list separators,
not part of the names. For example:
.endd
Multiple &%headers_remove%& options for a single router or transport can be
-specified; the values will be concatenated (with a separating colon
-added) before expansion.
+specified; the arguments will append to a single header-names list.
+Each item is separately expanded.
-When &%headers_add%& or &%headers_remove%& is specified on a router, its value
-is expanded at routing time, and then associated with all addresses that are
+When &%headers_add%& or &%headers_remove%& is specified on a router,
+items are expanded at routing time,
+and then associated with all addresses that are
accepted by that router, and also with any new addresses that it generates. If
an address passes through several routers as a result of aliasing or
forwarding, the changes are cumulative.
&`R `& on &`<=`& lines: reference for local bounce
&` `& on &`=>`& &`**`& and &`==`& lines: router name
&`S `& size of message
+&`SNI `& server name indication from TLS client hello
&`ST `& shadow transport name
&`T `& on &`<=`& lines: message subject (topic)
&` `& on &`=>`& &`**`& and &`==`& lines: transport name
.next
.cindex "log" "smtp confirmation"
.cindex "SMTP" "logging confirmation"
-&%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
+.cindex "LMTP" "logging confirmation"
+&%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
A number of MTAs (including Exim) return an identifying string in this
response.
.code
exim -bpu
.endd
-to obtain a queue listing with undelivered recipients only, and then greps the
-output to select messages that match given criteria. The following selection
-options are available:
+or (in case &*-a*& switch is specified)
+.code
+exim -bp
+.endd
+.new
+The &*-C*& option is used to specify an alternate &_exim.conf_& which might
+contain alternate exim configuration the queue management might be using.
+.wen
+
+to obtain a queue listing, and then greps the output to select messages
+that match given criteria. The following selection options are available:
.vlist
.vitem &*-f*&&~<&'regex'&>
.vitem &*-R*&
Display messages in reverse order.
+
+.vitem &*-a*&
+Include delivered recipients in queue listing.
.endlist
There is one more option, &%-h%&, which outputs a list of options.
Exim's DKIM implementation allows to
.olist
Sign outgoing messages: This function is implemented in the SMTP transport.
-It can co-exist with all other Exim features, including transport filters.
+It can co-exist with all other Exim features
+(including transport filters)
+except cutthrough delivery.
.next
Verify signatures in incoming messages: This is implemented by an additional
ACL (acl_smtp_dkim), which can be called several times per message, with
Verification of DKIM signatures in incoming email is implemented via the
&%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
syntactically(!) correct signature in the incoming message.
+A missing ACL definition defaults to accept.
+If any ACL call does not acccept, the message is not accepted.
+If a cutthrough delivery was in progress for the message it is
+summarily dropped (having wasted the transmission effort).
To evaluate the signature in the ACL a large number of expansion variables
containing the signature status and its details are set up during the
git://git.exim.org / users / heiko / exim.git / blobdiff