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From: MRC%PANDA@sumex-aim.arpa (Mark Crispin)
Newsgroups: comp.mail.headers
Subject: Re: Replying to Sender or (gasp) Return-path
Message-ID: <891@brl-adm.ARPA>
Date: Tue, 18-Nov-86 12:32:35 EST
Article-I.D.: brl-adm.891
Posted: Tue Nov 18 12:32:35 1986
Date-Received: Tue, 18-Nov-86 21:22:24 EST
Sender: news@brl-adm.ARPA
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Marshall -

     The Internet mail world is not yet such that it is impossible
to use a mail system that obeys RFC 822 when it comes to the
semantics of replying.  The only reason for adding Return-Path to
your mail user agent's REPLY parser is laziness on the part of the
mail maintainer -- that is, he is unwilling to handle the problems
which occasionally come up and explain the realities of mail to a
user who thinks that the reply address is "always" available in a
Return-Path.

     Various vendors then "validate" their mail software against
this lazy software, since it's located on a Unix and everybody is
running Unix so it must be right...  Then the poor maintainers of
non-Unix software get long, pendantic complaint letters from the
above-mentioned vendors (or their users) stating everything imaginable
about the Internet protocols except the facts.  Wollongong is a
worst case, but not the only case.

     I don't want to argue English semantics, but "be conservative
in what you send" sure means to me that you should be conservative
and not send replies to the Return-Path.  What's more, replying to
the Return-Path is explicitly forbidden by RFC 822.
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