To: Harald.T.Alvestrand@uninett.no
Cc: drums@cs.utk.edu
Subject: Re: support for Postmaster address 
In-Reply-To: Your message of "Thu, 05 Oct 1995 10:25:44 +0100."
             <199510050926.FAA25200@CS.UTK.EDU> 
Date: Thu, 05 Oct 1995 21:27:27 +1000
Message-Id: <22759.812892447@munnari.OZ.AU>
From: Robert Elz <kre@munnari.OZ.AU>


    - Any domain that apperason the right-hand side of the
      @ sign in a valid address MUST have a postmaster

That's fine, provided that we understand that one of the major
uses of postmaster is to query invalid addresses...

    - Any domain that is listed in an MX record MUST have a
      postmaster

This I am not too happy about.  For several reasons, one being
that the target of an MX record need not be any kind of valid
mail address, if we were to require that it would be totally now.
While it has certainly been common to direct MX records to
hosts that already run mailers for other domains (their own
domains), there is no requirement that this be true.  The only
requirement on an MX target are that it have an A record (some
permit even a CNAME that eventually gives an A), that there be
an SMTP server at the address returned, and that that server
process mail for the original address (that for which the MX
record existed).  There has never been a requirement that the
MX value itself be a valid mail address for anyone.

While being able to get to the maintainer of a mail relay site
would be a useful thing to be able to depend upon, I'm not
100% certain that this is really the way to do it.

Also, note that by adding this requirement you're potentially
forcing people (well, MUSTing them) to suport mail to postmaster
for names they really have no intention of ever receiving mail.
ie: if you tell me the name of something with a A record to
which you never want mail delivered, and for which you don't
really want to support postmaster, and I will add an MX that
names that host as its  target .. if your requirement above
were in force, you'd then be requiring yourself to support mail
to that name, and implement a postmaster for it.   This doesn't
seem reasonable to me.

    - Any FQDN that is listed in a Received header SHOULD have a postmaster

I can tolerate that.

kre