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From: MRC%PANDA@SUMEX-AIM.ARPA (Mark Crispin)
Newsgroups: net.mail.headers
Subject: Re: Mail looping
Message-ID: <1310@brl-smoke.ARPA>
Date: Wed, 26-Feb-86 05:23:47 EST
Article-I.D.: brl-smok.1310
Posted: Wed Feb 26 05:23:47 1986
Date-Received: Sun, 2-Mar-86 19:33:00 EST
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Bill Wells -

     You cannot assume that list mail goes from the root to all branches
without going through the same node twice.  This is especially true with
mailers which do not differentiate between "mail exploders", "mail aliases",
and "mail forwardings".  Add to this swamp the large numbers of individuals
who regularly use multiple hosts (I have two primary, two secondary, and
dozens of tertiary Internet hosts in addition to my DEC-20 at home) and
who have "classed mailboxes" and forwardings all over the place and it isn't
hard to see how you can lose big.

     I'd argue that if you really care about loop abatement you will use
what SMTP provides to help you out from this -- the EXPN command.  That is,
the sender fully resolves the destination list.  It isn't hard to detect
loops when you do this.
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