On Wed, Dec 12, 2007 at 03:33:21PM -0700, Trevor Paquette wrote: > I'm currently at odds with a few folks regarding the interpretation of > RFC 2821 and the case of MX records that resolve to CNAMEs. I'm hoping > that those here, who are authoritative when it comes to this RFC, can > shed some light.
I am not authoritative, nevertheless I wish to comment on this. > However, in talking to TrendMicro, they say that this syntax is > perfectly valid and that RFC 2821 overrides the MX to CNAME limitation. > The following website is their stance on this: > http://esupport.trendmicro.com/support/viewxml.do?ContentID=EN-1035667&i > d=EN-1035667 The solution mentions "Section 5" of 2821 which discusses CNAME->MX->mailhost and they (ab)use it to defend MX->CNAME->mailhost which is just not the same, at all. > However, in talking to others, they say that TrendMicro is > misinterpreting the RFC. I'll admit after reading 2821, I could > interpret things both ways. I can see how 3.6 can be interpreted the wrong way, but it does not (IMHO) overrule 2181. Neither does 2821 claim to obsolete or update 2181. 2821 2.3.5 says: Domain names are used as names of hosts and of other entities in the domain name hierarchy. For example, a domain may refer to an alias (label of a CNAME RR) or the label of Mail eXchanger records If these exist: mailrelay.example.com. MX 10 mailhost01.example.com. alias.example.com. CNAME canonicalname.example.com. then 2.3.5 talks about mailrelay and alias, not about mailhost01 or canonicalname. Trendmicro uses it to defend "mailhost01.example.com." being an alias. my 2ct Alex
