[Mailman-Users] Hostname in mail headers

Harald Meland Harald.Meland at usit.uio.no
Wed Feb 24 21:36:22 CET 1999

[Marcus C. Gottwald]

> I was sure that none of the involved MTAs that I have control
> over did something like that. But when I was digging into it,
> I found that all mails were addressed to listname at main-fqdn
> although had been sent to listname at some-other-fqdn. This 
> happens when the other fqdn is not a "real" DNS-entry, but a 

Using CNAMEs in mail addresses is Wrong.  So don't.  Cf RFC 1123,
section 5.2.2:

      5.2.2  Canonicalization: RFC-821 Section 3.1

         The domain names that a Sender-SMTP sends in MAIL and RCPT
         commands MUST have been  "canonicalized," i.e., they must be
         fully-qualified principal names or domain literals, not
         nicknames or domain abbreviations.  A canonicalized name either
         identifies a host directly or is an MX name; it cannot be a


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