[Mailman-Users] Virtual hosts

[Stephen J. Turnbull]

Mark Sapiro writes:

 > It isn't AFAICT. I was going to add it, but I am looking for a specific
 > RFC reference. I have looked at several RFCs and I don't see anything
 > that talks about rewriting domains in headers. All I found was RFC
 > 1123 (STD 3), sec 5.2.2

As Lucy van Pelt ("The Doctor is 'In'") used to say to Charlie Brown,

                           THAT'S IT!!!!!!

<wink>

If you look at RFC 2821, you will discover that in section 2.3.5, it
specifically allows CNAME aliases in the "domain name" part of a
mailbox.  I conclude that only the EHLO (HELO) command (and possibly
the server's greeting messages) has the restriction.  The rationale is
that it is an error-reporting mechanism, which needs to be more
carefully specified since the system is known to be in a problem
state.  See section 4.1.1, which specifies that the host specified by
a domain in EHLO should have a reverse mapping.  Since a CNAME can't
have a corresponding PTR, the restriction in STD 3 follows.

"MX names" are also allowed, for what it is worth.