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Path: utzoo!mnetor!uunet!husc6!bloom-beacon!athena.mit.edu!ambar
From: ambar@athena.mit.edu (Jean Marie Diaz)
Newsgroups: comp.mail.misc
Subject: Re: routing in the user agent
Message-ID: <1642@bloom-beacon.MIT.EDU>
Date: Mon, 19-Oct-87 02:23:28 EDT
Article-I.D.: bloom-be.1642
Posted: Mon Oct 19 02:23:28 1987
Date-Received: Tue, 20-Oct-87 00:38:41 EDT
References: <279@minya.UUCP> <7461@g.ms.uky.edu> <287@minya.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: ambar@athena.mit.edu (Jean Marie Diaz)
Organization: Madhouse International Technologies
Lines: 23
Keywords: reversing mail paths
Summary: reversing paths gets you in trouble

In article <287@minya.UUCP> jc@minya.UUCP (John Chambers) writes:
>
>Nonsense.  I have much better info than that.  My mailer extracts the
>paths from all incoming mail and puts it (with a timestamp) into the
>database.  I thus have good info on good paths to those people who
>have sent me mail lately.  This is at worst the same data as is used
>by the mailers; it is usually better.

Er, no.  It is never wise to assume that a mail path works both ways.
An example I saw recently: someone was sending mail from Tektronix to
MIT using the path fragment ..!allegra!eddie!athena!user.  It was their
dumb luck that allegra realized that "eddie" was the same machine as
mit-eddie (aka eddie.mit.edu), AND that eddie  would resolve "athena" as
athena.mit.edu (which is mit-athena in the uucp world).

How did I trip over this one?  The recipient was trying to reverse that
path and send along it.  Oops.   Didn't work.  (mit-athena was looking
for the uucp machine eddie, and losing.)

Don't try this one at home...

				AMBAR
{backbones}!mit-eddie!ambar			ambar@eddie.mit.edu