Paul A Vixie <paul@vix.com> said:
This: [deleted] ...is NOT a variance from RFC1123 or any other specification.
That's true (as far as it goes), and I certainly don't see that bouncing mail with a "mailbox is full" error is a violation of RFC1123 section 5.3.3. But the following piece of evidence was not mentioned before: compuserve.com. MX 10 mailgate.compuserve.com. That MX, in conjunction with the CNAME (which was mentioned before): mailgate.compuserve.com. CNAME mx3.compuserve.com. adds up to a violation of RFC 1034 section 3.6.2: "Domain names in RRs which point at another name should always point at the primary name and not the alias." (which esentially means "If a name appears on the left hand side of a CNAME record then that name should not also appear on the right hand side of any other record").
It is completely appropriate for a mail domain to be a CNAME pointing at a handful of A's. It's not ok to _advertise_ one of these, as for example in an exported "From:" header,
I am not sure that my reading of RFC 1123 section 5.2.2 awould support you there. But anyway, the "compuserve.com" domain *does* get advertised in "From:" headers, so there is clearly a problem. --apb (Alan Barrett)