SpamAssassin Rule: DNS_FROM_RFC_DSN
Standard description: Envelope sender in dsn.rfc-ignorant.org
Explanation
The domain of the envelope sender is listed in the DNSBL dsn.rfc-ignorant.org.
The criteria for listing is that the servers listed in the domain's MX records must accept messages with the empty sender address (MAIL FROM:<>) so that Delivery Status Notification (DSN) messages can be delivered. The basis for this is section 5.2.9 of RFC 1123 and section 4.5.5 of RFC 5321
Further Info
The default scores for this rule can be found in the online list of tests.
This rule is disabled in SpamAssassin 3.3.2 (see bug 6526)