Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!DECWRL.DEC.COM!dcrocker
From: dcrocker@DECWRL.DEC.COM (Dave Crocker)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Mail Source Routing (was Re: New Host-Requirement RFCs)
Message-ID: <8910282254.AA10351@volition.pa.dec.com>
Date: 28 Oct 89 22:54:50 GMT
References: <2560@munnari.oz.au>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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I have been waiting for someone to observe that static entries in a
data base do not work for routing information..

Thank you.

The MX mechanism is fine for real 'off-net' mail relaying.  It does
NOT work as a means of communicating complex and/or dynamic and/or
alternate routes.

Your scenario exemplifies this limitation.

The %-hack doesn't fix the problem.

It does, however, let knowledgeable users source-route around some of
these types of problems.

That is, if you are a wizard, you can make up for a basic deficiency
in the mail architecture.

Note that IP-level routing can, albeit slowly, discover alternate routes.

d/