On Sat, 9 Jun 2018 at 17:36, Andrew C Aitchison <and...@aitchison.me.uk> wrote: > I'm curious. > If a domain has no MX record, do all servers deliver to an AAAA record, > as required by (at least) RFC3974,
required? "This memo provides information for the Internet community. It does not specify an Internet standard of any kind." For sure any server without Ipv6 connectivity won't go to AAAA and Ipv6 connectivity is not mandatory. Any MTA with no support for Ipv6 won't lookup AAAA records. Are you asking if every server with support for Ipv6 and with access to an Ipv6 network actually implement the "implicit MX rule"? BTW rfc5321 "5.2. IPv6 and MX Records" says ----- While RFC3974 discusses some operational experience in mixed environments, it was not comprehensive enough to justify standardization, and some of its recommendations appear to be inconsistent with this specification. ----- > or do some email systems ignore domains with no MX and no A record ? I don't have data but I'd bet every server check MX. Most of them also check A (this is required by rfc, but I saw a lot of implementors forget this)... a very small amount of them will go to AAAA. What I can share is that over a sample of 1 million sent email almost 800 (0.08%) were sent to domains with no MX. Only around 20% (150) were deliverable and I suspect many of them are not real inboxes as rates (opens/clicks/replies) are a lot below the average. Sometimes I think we should "break" the implicit mx rule and stop delivering to domains with no MX as the "non deliverable" part (80%) keeps using resources for many days. No, I won't do that as I care too much about RFC, but I would be happy to see someone doing that!.. and I remember a discussion about the fact that the "implicit MX rule" doesn't have MUST or SHOULD words in the rfc2821/rfc5321 formulation (even if the original rfc974 used a lowercase "should" and the uppercase terms have been defined later in rfc2119). > Does anyone use lack of MX record (for envelope sender domain I guess) > as a marker for spaminess ? I saw rejects because of missing MX records for domains that had valid MX records, so I guess some issue with the DNS lookup: this prove someone does check this not only as a "marker" but as a reject rule. Stefano _______________________________________________ mailop mailing list mailop@mailop.org https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop
