Exim supports the use of regular expressions in many of its options. It
uses the PCRE regular expression library; this provides regular expression
matching that is compatible with Perl 5. The syntax and semantics of
-regular expressions is discussed in many Perl reference books, and also in
+regular expressions is discussed in
+.new
+online Perl manpages, in
+.wen
+many Perl reference books, and also in
Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
.vitem &$verify_mode$&
.vindex "&$verify_mode$&"
-While a router or transport is being run in verify mode
-or for cutthrough delivery,
+While a router or transport is being run in verify mode or for cutthrough delivery,
contains "S" for sender-verification or "R" for recipient-verification.
Otherwise, empty.
example:
.code
deny dnslists = list1.example
-dnslists = list2.example
+ dnslists = list2.example
.endd
If there are no conditions, the verb is always obeyed. Exim stops evaluating
the conditions and modifiers when it reaches a condition that fails. What
check a RCPT command:
.code
accept domains = +local_domains
-endpass
-verify = recipient
+ endpass
+ verify = recipient
.endd
If the recipient domain does not match the &%domains%& condition, control
passes to the next statement. If it does match, the recipient is verified, and
is what is wanted for subsequent tests.
-.vitem &*control&~=&~cutthrough_delivery*&
+.vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
.cindex "&ACL;" "cutthrough routing"
.cindex "cutthrough" "requesting"
This option requests delivery be attempted while the item is being received.
Should the ultimate destination system positively accept or reject the mail,
a corresponding indication is given to the source system and nothing is queued.
-If there is a temporary error the item is queued for later delivery in the
-usual fashion. If the item is successfully delivered in cutthrough mode
+If the item is successfully delivered in cutthrough mode
the delivery log lines are tagged with ">>" rather than "=>" and appear
before the acceptance "<=" line.
+.new
+If there is a temporary error the item is queued for later delivery in the
+usual fashion.
+This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
+to the control; the default value is &"spool"& and the alternate value
+&"pass"& copies an SMTP defer response from the target back to the initiator
+and does not queue the message.
+Note that this is independent of any receipient verify conditions in the ACL.
+.wen
+
Delivery in this mode avoids the generation of a bounce mail to a
(possibly faked)
sender when the destination system is doing content-scan based rejection.
DKIM support is compiled into Exim by default if TLS support is present.
It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
-Exim's DKIM implementation allows to
+Exim's DKIM implementation allows for
.olist
-Sign outgoing messages: This function is implemented in the SMTP transport.
+Signing outgoing messages: This function is implemented in the SMTP transport.
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
+Verifying signatures in incoming messages: This is implemented by an additional
ACL (acl_smtp_dkim), which can be called several times per message, with
different signature contexts.
.endlist
The signer that is being evaluated in this ACL run. This can be a domain or
an identity. This is one of the list items from the expanded main option
&%dkim_verify_signers%& (see above).
+
.vitem &%$dkim_verify_status%&
A string describing the general status of the signature. One of
.ilist
.next
&%pass%&: The signature passed verification. It is valid.
.endlist
+
.vitem &%$dkim_verify_reason%&
A string giving a little bit more detail when &%$dkim_verify_status%& is either
"fail" or "invalid". One of
re-written or otherwise changed in a way which is incompatible with
DKIM verification. It may of course also mean that the signature is forged.
.endlist
+
.vitem &%$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 &%$dkim_copiedheaders%&
A transcript of headers and their values which are included in the signature
(copied from the 'z=' tag of the signature).
+.new
+Note that RFC6376 requires that verification fail if the From: header is
+not included in the signature. Exim does not enforce this; sites wishing
+strict enforcement should code the check explicitly.
+.wen
+
.vitem &%$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 &%$dkim_key_nosubdomains%&
"1" if the key record forbids subdomaining, "0" otherwise.
+
.vitem &%$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=).
+
.vitem &%$dkim_key_length%&
Number of bits in the key.
.endlist
verb to a group of domains or identities. For example:
.code
-# Warn when Mail purportedly from GMail has no signature at all
-warn log_message = GMail sender without DKIM signature
+# Warn when Mail purportedly from GMail has no gmail signature
+warn log_message = GMail sender without gmail.com DKIM signature
sender_domains = gmail.com
dkim_signers = gmail.com
dkim_status = none
.endd
+.new
+Note that the above does not check for a total lack of DKIM signing;
+for that check for empty &$h_DKIM-Signature:$& in the data ACL.
+.wen
+
.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
projects / exim.git / blobdiff