[Mailman-Users] Virtual hosts

[Stephen J. Turnbull]

Brad Knowles writes:

[[ Aside:
 > I was on the DRUMS working group for a while,

Thank you!
]]

 > The MTA needs to rewrite headers that the MTA needs to rewrite.  The 
 > question is which headers should the MTA be rewriting?

RFC 2821 section 3.8.4 (IIRC) mandates that gateways rewrite non-FQDN
addresses in RFC 2822 headers.  But in the cases in point, we already
have FQDNs most of the time or can trivially generate them (eg, for
locally generated mail append the host's domain name).  My take would
be that MTAs should *translate* FQDNs to primary hostnames for use in
SMTP commands, but that there should be no need to rewrite headers
that are supplied to it, as the remote MTA as an MTA shouldn't care
about the content (including the RFC 2822 headers) of the message.

To the extent that some policy mechanism (which of course is most
efficiently implemented by the MTA, eg a Sendmail milter) is analyzing
the headers, the local MTA is obviously in the best position to check
and if appropriate rewrite addresses in the headers to conform with
policy (at least to the extent that making thing look consistent with
the DNS are going to help).  But that's going to depend on what common
policies are, and what policies any given user will encounter.  AFAIK
there are as yet no BCPs, let alone standards, for that.