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Subject: RE: Anti-relay madness
From: Robert A. Rosenberg (bob.rosenbergdigitscorp.com)
Date: Fri Sep 15 2000 - 14:33:31 CDT

At 05:35 PM 09/15/2000 +0200, Martin Mielke wrote:
>Sorry too, I resist to accept that statement. For sure there must exist a
>way to tell Postfix to reject emails with a forged mydomain.com or
>valid-domain.com, unless w.x.y.z is listed somewhere as a valid MX for
>valid-domain ...

That will not fly. It is perfectly valid to be running an SMTP MTA Server
that does not listen to port 25 (but listens to some other port) so that it
acts ONLY as an outgoing mail server. Thus there can be one set of Servers
(listed as MXs) for mail coming in from the Internet and another set for
injecting Email onto the Internet. This set-up allows load-leveling and/or
special purpose Servers (such as ones whose purpose is to handle outgoing
mailing lists and thus are invisible to the Internet as mail receivers
since they are not in a MX chain). One of the problems with Bulk Mail like
Mailings Lists is balancing those messages against "normal" mail. This is
one solution (but it would break if you REQUIRE a MX record to accept mail
from the server).