Date: 1 Jul 1996 02:46:47 -0000
Message-ID: <19960701024647.130.qmail@koobera.math.uic.edu>
From: djb@koobera.math.uic.edu (D. J. Bernstein)
To: drums@cs.utk.edu
Subject: Re: 821bis outstanding issues list -- post Montreal

> First of all, my understanding (albeit from a comment made by Erik Fair at
> the DRUMS session) is that as written, 1123 requires not that you just get
> *an* A record, but that you get the *canonical* A record.

``The domain names ... 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 CNAME.'' (821: ``Whenever
domain names are used in SMTP only the official names are used, the
use of nicknames or aliases is not allowed.'')

Neither ``official name'' nor ``principal name'' is defined, but there's
nothing to suggest that they should mean ``PTR target.''

Doing an A lookup followed by a PTR lookup wouldn't make much sense: it
could give you a domain with an entirely different set of MX records.
Look at phoenix-subnet128.princeton.edu, for example.

> Maybe this is where I misunderstood: I was under the impression that SMTP
> servers simply pass along the "RCPT TO:" envelope unmolested if it is just
> relaying. Is this not the case?

It is not the case, at least for sendmail and qmail.

---Dan