supports, including LDAP, Postgres, MySQL, etc, as long as the
result is a list of colon-separated strings.
+Performing the check sets up information used by the
+${authresults } expansion item.
+
Several expansion variables are set before the DATA ACL is
processed, and you can use them in this ACL. The following
expansion variables are available:
warn dmarc_status = accept : none : off
!authenticated = *
log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
- add_header = $dmarc_ar_header
warn dmarc_status = !accept
!authenticated = *
!authenticated = *
message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
+ warn add_header = :at_start:${authresults {$primary_hostname}}
+
DSN extra information
The transport only takes one option:
* directory - This is used to specify the directory messages should be
-copied to
+copied to. Expanded.
The generic transport options (body_only, current_directory, disable_logging,
debug_print, delivery_date_add, envelope_to_add, event_action, group,
An option on the smtp transport, which constructs and prepends to the message
an ARC set of headers. The textually-first Authentication-Results: header
is used as a basis (you must have added one on entry to the ADMD).
-Expanded; if unset, empty or forced-failure then no signing is done.
+Expanded as a whole; if unset, empty or forced-failure then no signing is done.
+If it is set, all three elements must be non-empty.
+
+Caveats:
+ * There must be an Authentication-Results header, presumably added by an ACL
+ while receiving the message, for the same ADMD, for arc_sign to succeed.
+ This requires careful coordination between inbound and outbound logic.
+ * If passing a message to another system, such as a mailing-list manager
+ (MLM), between receipt and sending, be wary of manipulations to headers made
+ by the MLM.
+ + For instance, Mailman with REMOVE_DKIM_HEADERS==3 might improve
+ deliverability in a pre-ARC world, but that option also renames the
+ Authentication-Results header, which breaks signing.
+ * Even if you use multiple DKIM keys for different domains, the ARC concept
+ should try to stick to one ADMD, so pick a primary domain and use that for
+ AR headers and outbound signing.
+
+Signing is not compatible with cutthrough delivery; any (before expansion)
+value set for the option will result in cutthrough delivery not being
+used via the transport in question.