X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/0b23848a94f10065be92d0e06382cff4236dcb89..a2e4e31dae3c20aa9e64427190ab49bd2d315217:/doc/doc-docbook/spec.xfpt
diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 7b5d5c44a..6a1d7ce12 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -1,4 +1,4 @@
-. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.50 2009/06/11 14:07:57 tom Exp $
+. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.72 2010/03/05 16:26:46 nm4 Exp $
.
. /////////////////////////////////////////////////////////////////////////////
. This is the primary source of the Exim Manual. It is an xfpt document that is
@@ -48,7 +48,7 @@
. /////////////////////////////////////////////////////////////////////////////
.set previousversion "4.69"
-.set version "4.70"
+.set version "4.71"
.set ACL "access control lists (ACLs)"
.set I " "
@@ -172,17 +172,15 @@
Specification of the Exim Mail Transfer Agent
The Exim MTA
-23 August 2007
-PhilipHazel
-PH
-University of Cambridge Computing Service
-New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
+5 November 2009
+EximMaintainers
+EM
- 4.68
- 23 August 2007
- PH
+ 4.71
+ 5 November 2009
+ EM
-2007University of Cambridge
+2009University of Cambridge
.literal off
@@ -2975,6 +2973,7 @@ local part) and outputs what it finds.
.cindex "options" "router &-- extracting"
.cindex "options" "transport &-- extracting"
+.cindex "options" "authenticator &-- extracting"
If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
followed by the name of an appropriate driver instance, the option settings for
that driver are output. For example:
@@ -2988,6 +2987,11 @@ using one of the words &%router_list%&, &%transport_list%&, or
settings can be obtained by using &%routers%&, &%transports%&, or
&%authenticators%&.
+.cindex "options" "macro &-- extracting"
+If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
+are available, similarly to the drivers. Because macros are sometimes used
+for storing passwords, this option is restricted.
+The output format is one item per line.
.vitem &%-bp%&
.oindex "&%-bp%&"
@@ -5885,6 +5889,10 @@ password are correct. In the examples it just produces an error message.
To make the authenticators work, you can use a string expansion
expression like one of the examples in &<>&.
+Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
+usercode and password are in different positions. &<>&
+covers both.
+
.ecindex IIDconfiwal
@@ -6128,7 +6136,7 @@ IPv6 addresses must be enclosed in quotes to prevent the first internal colon
being interpreted as a key terminator. For example:
.code
1.2.3.4: data for 1.2.3.4
-192.168.0.0/16 data for 192.168.0.0/16
+192.168.0.0/16: data for 192.168.0.0/16
"abcd::cdab": data for abcd::cdab
"abcd:abcd::/32" data for abcd:abcd::/32
.endd
@@ -9571,6 +9579,17 @@ For single-key lookup types, no quoting is ever necessary and this operator
yields an unchanged string.
+.vitem &*${randint:*&<&'n'&>&*}*&
+.cindex "random number"
+This operator returns a somewhat random number which is less than the
+supplied number and is at least 0. The quality of this randomness depends
+on how Exim was built; the values are not suitable for keying material.
+If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
+Otherwise, the implementation may be arc4random(), random() seeded by
+srandomdev() or srandom(), or a custom implementation even weaker than
+random().
+
+
.vitem &*${rfc2047:*&<&'string'&>&*}*&
.cindex "expansion" "RFC 2047"
.cindex "RFC 2047" "expansion operator"
@@ -9732,6 +9751,22 @@ lower case), signifying multiplication by 1024 or 1024*1024, respectively.
As a special case, the numerical value of an empty string is taken as
zero.
+.vitem &*bool&~{*&<&'string'&>&*}*&
+.cindex "expansion" "boolean parsing"
+.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,
+false if zero. Leading whitespace is ignored.
+All other string values will result in expansion failure.
+
+When combined with ACL variables, this expansion condition will let you
+make decisions in one place and act on those decisions in another place.
+For example,
+.code
+${if bool{$acl_m_privileged_sender} ...
+.endd
+
.vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
.cindex "expansion" "encrypted comparison"
.cindex "encrypted strings, comparing"
@@ -10183,6 +10218,10 @@ configuration, you might have this:
.code
server_condition = ${if pwcheck{$auth1:$auth2}}
.endd
+Again, for a PLAIN authenticator configuration, this would be:
+.code
+server_condition = ${if pwcheck{$auth2:$auth3}}
+.endd
.vitem &*queue_running*&
.cindex "queue runner" "detecting when delivering from"
.cindex "expansion" "queue runner test"
@@ -10970,7 +11009,7 @@ precise size of the file that has been written. See also
&$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
.cindex "RCPT" "value of &$message_size$&"
-While running an ACL at the time of an SMTP RCPT command, &$message_size$&
+While running a per message ACL (mail/rcpt/predata), &$message_size$&
contains the size supplied on the MAIL command, or -1 if no size was given. The
value may not, of course, be truthful.
@@ -12338,6 +12377,7 @@ listed in more than one group.
.row &%gnutls_require_kx%& "control GnuTLS key exchanges"
.row &%gnutls_require_mac%& "control GnuTLS MAC algorithms"
.row &%gnutls_require_protocols%& "control GnuTLS protocols"
+.row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
.row &%tls_advertise_hosts%& "advertise TLS to these hosts"
.row &%tls_certificate%& "location of server certificate"
.row &%tls_crl%& "certificate revocation list"
@@ -13337,6 +13377,10 @@ server. For details, see section &<>&.
This option controls the protocols when GnuTLS is used in an Exim
server. For details, see section &<>&.
+.option gnutls_compat_mode main boolean unset
+This option controls whether GnuTLS is used in compatibility mode in an Exim
+server. This reduces security slightly, but improves interworking with older
+implementations of TLS.
.option headers_charset main string "see below"
This option sets a default character set for translating from encoded MIME
@@ -13408,10 +13452,10 @@ do.
By default, Exim just checks the syntax of HELO and EHLO commands (see
&%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
to do more extensive checking of the data supplied by these commands. The ACL
-condition &`verify`& &`=`& &`helo`& is provided to make this possible.
+condition &`verify = helo`& is provided to make this possible.
Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
to force the check to occur. From release 4.53 onwards, this is no longer
-necessary. If the check has not been done before &`verify`& &`=`& &`helo`& is
+necessary. If the check has not been done before &`verify = helo`& is
encountered, it is done at that time. Consequently, this option is obsolete.
Its specification is retained here for backwards compatibility.
@@ -13433,7 +13477,7 @@ available) yields the calling host address.
However, the EHLO or HELO command is not rejected if any of the checks
fail. Processing continues, but the result of the check is remembered, and can
-be detected later in an ACL by the &`verify`& &`=`& &`helo`& condition.
+be detected later in an ACL by the &`verify = helo`& condition.
.option helo_verify_hosts main "host list&!!" unset
.cindex "HELO verifying" "mandatory"
@@ -13489,8 +13533,8 @@ this check fails, Exim behaves as if the name lookup failed.
.vindex "&$sender_host_name$&"
After any kind of failure, the host name (in &$sender_host_name$&) remains
unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
-&%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and &`verify`& &`=`&
-&`reverse_host_lookup`& in ACLs.
+&%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
+&`verify = reverse_host_lookup`& in ACLs.
.option host_lookup_order main "string list" &`bydns:byaddr`&
@@ -17810,10 +17854,10 @@ redirection items of the form
:defer:
:fail:
.endd
-respectively. When a redirection list contains such an item, it applies to the
-entire redirection; any other items in the list are ignored (&':blackhole:'& is
-different). Any text following &':fail:'& or &':defer:'& is placed in the error
-text associated with the failure. For example, an alias file might contain:
+respectively. When a redirection list contains such an item, it applies
+to the entire redirection; any other items in the list are ignored. Any
+text following &':fail:'& or &':defer:'& is placed in the error text
+associated with the failure. For example, an alias file might contain:
.code
X.Employee: :fail: Gone away, no forwarding address
.endd
@@ -21126,6 +21170,7 @@ procmail_pipe:
envelope_to_add
check_string = "From "
escape_string = ">From "
+ umask = 077
user = $local_part
group = mail
@@ -21425,18 +21470,23 @@ being used, names are looked up using &[gethostbyname()]&
instead of using the DNS. Of course, that function may in fact use the DNS, but
it may also consult other sources of information such as &_/etc/hosts_&.
-.option gnutls_require_kx main string unset
+.option gnutls_require_kx smtp string unset
This option controls the key exchange mechanisms when GnuTLS is used in an Exim
client. For details, see section &<>&.
-.option gnutls_require_mac main string unset
+.option gnutls_require_mac smtp string unset
This option controls the MAC algorithms when GnuTLS is used in an Exim
client. For details, see section &<>&.
-.option gnutls_require_protocols main string unset
+.option gnutls_require_protocols smtp string unset
This option controls the protocols when GnuTLS is used in an Exim
client. For details, see section &<>&.
+.option gnutls_compat_mode smtp boolean unset
+This option controls whether GnuTLS is used in compatibility mode in an Exim
+server. This reduces security slightly, but improves interworking with older
+implementations of TLS.
+
.option helo_data smtp string&!! "see below"
.cindex "HELO" "argument, setting"
.cindex "EHLO" "argument, setting"
@@ -23538,7 +23588,6 @@ the password conform to the Exim syntax. At the LDAP level, the password is an
uninterpreted string.
-
.section "Support for different kinds of authentication" "SECID174"
A number of string expansion features are provided for the purpose of
interfacing to different ways of user authentication. These include checking
@@ -23797,7 +23846,7 @@ sasl_cram_md5:
sasl_plain:
driver = cyrus_sasl
public_name = PLAIN
- server_set_id = $auth1
+ server_set_id = $auth2
.endd
Cyrus SASL does implement the LOGIN authentication method, even though it is
not a standard method. It is disabled by default in the source distribution,
@@ -23830,7 +23879,7 @@ dovecot_plain:
driver = dovecot
public_name = PLAIN
server_socket = /var/run/dovecot/auth-client
- server_set_id = $auth1
+ server_set_id = $auth2
dovecot_ntlm:
driver = dovecot
@@ -24413,13 +24462,10 @@ unencrypted.
The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
transport provide the client with a certificate, which is passed to the server
if it requests it. If the server is Exim, it will request a certificate only if
-&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&:
-These options must be set in the &(smtp)& transport for Exim to use TLS when it
-is operating as a client. Exim does not assume that a server certificate (set
-by the global options of the same name) should also be used when operating as a
-client.
+&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
-If &%tls_verify_certificates%& is set, it must name a file or,
+If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
+must name a file or,
for OpenSSL only (not GnuTLS), a directory, that contains a collection of
expected server certificates. The client verifies the server's certificate
against this collection, taking into account any revoked certificates that are
@@ -24431,6 +24477,12 @@ list of permitted cipher suites. If either of these checks fails, delivery to
the current host is abandoned, and the &(smtp)& transport tries to deliver to
alternative hosts, if any.
+ &*Note*&:
+These options must be set in the &(smtp)& transport for Exim to use TLS when it
+is operating as a client. Exim does not assume that a server certificate (set
+by the global options of the same name) should also be used when operating as a
+client.
+
.vindex "&$host$&"
.vindex "&$host_address$&"
All the TLS options in the &(smtp)& transport are expanded before use, with
@@ -24765,7 +24817,6 @@ client are given temporary error responses until QUIT is received or the
connection is closed. In these special cases, the QUIT ACL does not run.
-
.section "The not-QUIT ACL" "SECTNOTQUITACL"
.vindex &$acl_smtp_notquit$&
The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
@@ -25766,7 +25817,7 @@ This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
the current message is a submission from a local MUA. In this case, Exim
operates in &"submission mode"&, and applies certain fixups to the message if
-necessary. For example, it add a &'Date:'& header line if one is not present.
+necessary. For example, it adds a &'Date:'& header line if one is not present.
This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
late (the message has already been created).
@@ -25779,7 +25830,7 @@ that may be received in the same SMTP connection.
.vitem &*control&~=&~suppress_local_fixups*&
.cindex "submission fixups, suppressing"
This control applies to locally submitted (non TCP/IP) messages, and is the
-complement of &`control`& &`=`& &`submission`&. It disables the fixups that are
+complement of &`control = submission`&. It disables the fixups that are
normally applied to locally-submitted messages. Specifically:
.ilist
@@ -25808,12 +25859,12 @@ All four possibilities for message fixups can be specified:
.ilist
Locally submitted, fixups applied: the default.
.next
-Locally submitted, no fixups applied: use &`control`& &`=`&
-&`suppress_local_fixups`&.
+Locally submitted, no fixups applied: use
+&`control = suppress_local_fixups`&.
.next
Remotely submitted, no fixups applied: the default.
.next
-Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&.
+Remotely submitted, fixups applied: use &`control = submission`&.
.endlist
@@ -26959,7 +27010,7 @@ entry must set the rate for the same key (otherwise it will always be zero).
For example:
.code
acl_check_connect:
- deny ratelimit = 100 / 5m / strict / noupdate
+ deny ratelimit = 100 / 5m / strict / per_cmd / noupdate
log_message = RATE: $sender_rate/$sender_rate_period \
(max $sender_rate_limit)
.endd
@@ -30257,8 +30308,8 @@ If a message contains a number of different addresses, all those with the same
characteristics (for example, the same envelope sender) that resolve to the
same set of hosts, in the same order, are sent in a single SMTP transaction,
even if they are for different domains, unless there are more than the setting
-of the &%max_rcpts%& option in the &(smtp)& transport allows, in which case
-they are split into groups containing no more than &%max_rcpts%& addresses
+of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
+they are split into groups containing no more than &%max_rcpt%&s addresses
each. If &%remote_max_parallel%& is greater than one, such groups may be sent
in parallel sessions. The order of hosts with identical MX values is not
significant when checking whether addresses can be batched in this way.
@@ -34287,56 +34338,245 @@ ACL (acl_smtp_dkim), which can be called several times per message, with
different signature context.
.endlist
+In typical Exim style, the verification implementation does not include any
+default "policy". Instead it enables you to build your own policy using
+Exim's standard controls.
+
+Please note that verification of DKIM signatures in incoming mail is turned
+on by default for logging purposes. For each signature in incoming email,
+exim will log a line displaying the most important signature details, and the
+signature status. Here is an example:
+.code
+2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: d=facebookmail.com s=q1-2009b c=relaxed/relaxed a=rsa-sha1 i=@facebookmail.com t=1252484542 [verification succeeded]
+.endd
+You might want to turn off DKIM verification processing entirely for internal
+or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
+control modifier. This should typically be done in the RCPT ACL, at points
+where you accept mail from relay sources (internal hosts or authenticated
+senders).
+
+
.section "Signing outgoing messages" "SECID513"
.cindex "DKIM" "signing"
Signing is implemented by setting private options on the SMTP transport.
These options take (expandable) strings as arguments.
-.vitem &%dkim_domain = [MANDATORY]%&
+.option dkim_domain smtp string&!! unset
+MANDATORY
The domain you want to sign with. The result of this expanded
-option is put into the $dkim_domain expansion variable.
+option is put into the &%$dkim_domain%& expansion variable.
-.vitem &%dkim_selector = [MANDATORY]%&
-This sets the key selector string. You can use the $dkim_domain expansion
+.option dkim_selector smtp string&!! unset
+MANDATORY
+This sets the key selector string. You can use the &%$dkim_domain%& expansion
variable to look up a matching selector. The result is put in the expansion
-variable $dkim_selector which should be used in the dkim_private_key option
-along with $dkim_domain.
+variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
+option along with &%$dkim_domain%&.
-.vitem &%dkim_private_key = [MANDATORY]%&
-This sets the private key to use. You can use the $dkim_domain and
-$dkim_selector expansion variables to determine the private key to use.
+.option dkim_private_key smtp string&!! unset
+MANDATORY
+This sets the private key to use. You can use the &%$dkim_domain%& and
+&%$dkim_selector%& expansion variables to determine the private key to use.
The result can either
-.ulist
+.ilist
be a valid RSA private key in ASCII armor, including line breaks.
.next
start with a slash, in which case it is treated as a file that contains
the private key.
.next
be "0", "false" or the empty string, in which case the message will not
-be signed. This case will not result in an error, even if dkim_strict is set.
+be signed. This case will not result in an error, even if &%dkim_strict%&
+is set.
.endlist
-.vitem &%dkim_canon = [OPTIONAL]%&
+.option dkim_canon smtp string&!! unset
+OPTIONAL
This option sets the canonicalization method used when signing a message.
The DKIM RFC currently supports two methods: "simple" and "relaxed".
The option defaults to "relaxed" when unset. Note: the current implementation
-only support using the same canonicalization method for both headers and body.
+only supports using the same canonicalization method for both headers and body.
-.vitem &%dkim_strict = [OPTIONAL]%&
+.option dkim_strict smtp string&!! unset
+OPTIONAL
This option defines how Exim behaves when signing a message that
should be signed fails for some reason. When the expansion evaluates to
either "1" or "true", Exim will defer. Otherwise Exim will send the message
-unsigned. You can use the $dkim_domain and $dkim_selector expansion
+unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
variables here.
-.vitem &%dkim_sign_headers = [OPTIONAL]%&
+.option dkim_sign_headers smtp string&!! unset
+OPTIONAL
When set, this option must expand to (or be specified as) a colon-separated
-list of header names. These headers will be included in the message
-signature. When unspecified, the headers recommended in RFC4871 will be used.
+list of header names. Headers with these names will be included in the message
+signature. When unspecified, the header names recommended in RFC4871 will be
+used.
+
+.section "Verifying DKIM signatures in incoming mail" "SECID514"
+.cindex "DKIM" "verification"
+Verification of DKIM signatures in incoming email is implemented via the
+&%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
+syntactically(!) correct signature in the incoming message.
+To evaluate the signature in the ACL a large number of expansion variables
+containing the signature status and its details are set up during the
+runtime of the ACL.
+
+Calling the ACL only for existing signatures is not sufficient to build
+more advanced policies. For that reason, the global option
+&%dkim_verify_signers%&, and a global expansion variable
+&%$dkim_signers%& exist.
+
+The global option &%dkim_verify_signers%& can be set to a colon-separated
+list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
+called. It is expanded when the message has been received. At this point,
+the expansion variable &%$dkim_signers%& already contains a colon-
+separated list of signer domains and identities for the message. When
+&%dkim_verify_signers%& is not specified in the main configuration,
+it defaults as:
+.code
+dkim_verify_signers = $dkim_signers
+.endd
+This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
+DKIM signature in the message. Current DKIM verifiers may want to explicitly
+call the ACL for known domains or identities. This would be achieved as follows:
+.code
+dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
+.endd
+This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
+and "ebay.com", plus all domains and identities that have signatures in the message.
+You can also be more creative in constructing your policy. Example:
+.code
+dkim_verify_signers = $sender_address_domain:$dkim_signers
+.endd
+
+If a domain or identity is listed several times in the (expanded) value of
+&%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
+
+
+Inside the &%acl_smtp_dkim%&, the following expansion variables are
+available (from most to least important):
+
+.vlist
+.vitem &%$dkim_cur_signer%&
+The signer that is being evaluated in this ACL run. This can be domain or
+an identity. This is one of the list items from the expanded main option
+&%dkim_verify_signers%& (see above).
+.vitem &%$dkim_verify_status%&
+A string describing the general status of the signature. One of
+.ilist
+&%none%&: There is no signature in the message for the current domain or
+identity (as reflected by &%$dkim_cur_signer%&).
+.next
+&%invalid%&: The signature could not be verified due to a processing error.
+More detail is available in &%$dkim_verify_reason%&.
+.next
+&%fail%&: Verification of the signature failed. More detail is
+available in &%$dkim_verify_reason%&.
+.next
+&%pass%&: The signature passed verification. It is valid.
+.endlist
+.vitem &%$dkim_verify_reason%&
+A string giving a litte bit more detail when &%$dkim_verify_status%& is either
+"fail" or "invalid". One of
+.ilist
+&%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
+key for the domain could not be retrieved. This may be a temporary problem.
+.next
+&%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
+record for the domain is syntactically invalid.
+.next
+&%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
+body hash does not match the one specified in the signature header. This
+means that the message body was modified in transit.
+.next
+&%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
+could not be verified. This may mean that headers were modified,
+re-written or otherwise changed in a way which is incompatible with
+DKIM verification. It may of course also mean that the signature is forged.
+.endlist
+.vitem &%$dkim_domain%&
+The signing domain. IMPORTANT: This variable is only populated if there is
+an actual signature in the message for the current domain or identity (as
+reflected by &%$dkim_cur_signer%&).
+.vitem &%$dkim_identity%&
+The signing identity, if present. IMPORTANT: This variable is only populated
+if there is an actual signature in the message for the current domain or
+identity (as reflected by &%$dkim_cur_signer%&).
+.vitem &%$dkim_selector%&
+The key record selector string
+.vitem &%$dkim_algo%&
+The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
+.vitem &%$dkim_canon_body%&
+The body canonicalization method. One of 'relaxed' or 'simple'.
+.vitem &%dkim_canon_headers%&
+The header canonicalization method. One of 'relaxed' or 'simple'.
+.vitem &%$dkim_copiedheaders%&
+A transcript of headers and their values which are included in the signature
+(copied from the 'z=' tag of the signature).
+.vitem &%$dkim_bodylength%&
+The number of signed body bytes. If zero ("0"), the body is unsigned. If no
+limit was set by the signer, "9999999999999" is returned. This makes sure
+that this variable always expands to an integer value.
+.vitem &%$dkim_created%&
+UNIX timestamp reflecting the date and time when the signature was created.
+When this was not specified by the signer, "0" is returned.
+.vitem &%$dkim_expires%&
+UNIX timestamp reflecting the date and time when the signer wants the
+signature to be treated as "expired". When this was not specified by the
+signer, "9999999999999" is returned. This makes it possible to do useful
+integer size comparisons against this value.
+.vitem &%$dkim_headernames%&
+A colon-separated list of names of headers included in the signature.
+.vitem &%$dkim_key_testing%&
+"1" if the key record has the "testing" flag set, "0" if not.
+.vitem &%$dkim_key_nosubdomaining%&
+"1" if the key record forbids subdomaining, "0" otherwise.
+.vitem &%$dkim_key_srvtype%&
+Service type (tag s=) from the key record. Defaults to "*" if not specified
+in the key record.
+.vitem &%$dkim_key_granularity%&
+Key granularity (tag g=) from the key record. Defaults to "*" if not specified
+in the key record.
+.vitem &%$dkim_key_notes%&
+Notes from the key record (tag n=)
+.endlist
+
+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 &%$dkim_cur_signer%&). This is typically used to restrict an ACL
+verb to a group of domains or identities, like:
+
+.code
+# Warn when message apparently from GMail has no signature at all
+warn log_message = GMail sender without DKIM signature
+ sender_domains = gmail.com
+ dkim_signers = gmail.com
+ dkim_status = none
+.endd
+
+.vitem &%dkim_status%&
+ACL condition that checks a colon-separated list of possible DKIM verification
+results agains the actual result of verification. This is typically used
+to restrict an ACL verb to a list of verification outcomes, like:
+
+.code
+deny message = Message from Paypal with invalid or missing signature
+ sender_domains = paypal.com:paypal.de
+ dkim_signers = paypal.com:paypal.de
+ dkim_status = none:invalid:fail
+.endd
+
+The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
+see the documentation of the &%$dkim_verify_status%& expansion variable above
+for more information of what they mean.
+.endlist
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////