----- Original Message -----
From: <Valdis(_dot_)Kletnieks(_at_)vt(_dot_)edu>
To: "Hector Santos" <winserver(_dot_)support(_at_)winserver(_dot_)com>
Cc: "IETF-SMTP" <ietf-smtp(_at_)imc(_dot_)org>
Sent: Sunday, January 04, 2004 2:09 PM
Subject: Re: RFC 2821 Address Resolution
Valdis (and Richard),
In regards to RFC2821, section 5, saying:
Multiple MX records contain a preference indication that MUST be used
in sorting (see below). Lower numbers are more preferred than higher
ones. If there are multiple destinations with the same preference
and there is no clear reason to favor one (e.g., by recognition of an
easily-reached address), then the sender-SMTP MUST randomize them to
spread the load across multiple mail exchangers for a specific
organization.
There seems to be a conflict between this and the following itemized rule in
RFC1123:
RFC1123 "Requirements for Internet Hosts -- Application and Support"
5.3.4 Reliable Mail Transmission
...
The following information is to be used to rank the host
addresses:
(1) Multiple MX Records -- these contain a preference
indication that should be used in sorting. If there are
multiple destinations with the same preference and there
is no clear reason to favor one (e.g., by address
preference), then the sender-SMTP SHOULD pick one at
random to spread the load across multiple mail exchanges
for a specific organization; note that this is a
refinement of the procedure in [DNS:3].
RFC2821 seems to suggest to include all equal preference MX records, while
RFC1123 seems to suggest, unless I am reading it wrong, to choose 1 (at
random) of the equal preference MX records. [DNS.3] references RFC974
which is more consistent with RFC2821.
What say you?
--
Hector Santos, Santronics Software, Inc.
http://www.santronics.com