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Path: utzoo!watmath!clyde!burl!hou3c!don.provan@CMU-CS-A.ARPA
From: don.provan@CMU-CS-A.ARPA
Newsgroups: net.mail.headers
Subject: Re: What are SMTP commands "EXPN" and "VRFY" good for?
Message-ID: <17Sep84.133744.DP0N@CMU-CS-A.ARPA>
Date: Mon, 17-Sep-84 13:37:00 EDT
Article-I.D.: hou3c.838
Posted: Mon Sep 17 13:37:00 1984
Date-Received: Thu, 4-Oct-84 02:46:35 EDT
Sender: ka@hou3c.UUCP (Kenneth Almquist)
Lines: 17
To: Rich Wales 
Cc: Header-People@MIT-MC.ARPA
In-Reply-To: "Rich Wales's message of 15 Sep 84 16:39-EST"

i've always assumed that VRFY would be used only in reaction to a
user's request.  in other words, a user would say "verify
jones@cmu-10a" and the program would run out and check on the
existence of such a user.  there are any number of reasons a person
may want to check an address in such a way.  for me, it's usually
because i can't remember whether jones has his mailbox on cmu-10a or
cmu-10b.  VRFY allows me to check this without actually sending mail.

i assume EXPN is for similar purposes.  it's not intended to be used
to deliver mail to the list.  it allows a user to find out who's on
the list.

i didn't have anything to do with designing this protocol, so i'm
guessing when i say "intended", but it certainly seems like the more
obvious use of optional commands.  i'd also like to point out that
i talk big, but none of my software uses or supports these
two commands in any way.