Great Circle Associates List-Managers
(December 1992)

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Subject: Re: How to deal with bounces
From: Brent Chapman <brent @ GreatCircle . COM>
Date: Mon, 21 Dec 92 13:00:03 -0800
To: list-managers @ GreatCircle . COM
In-reply-to: Your message of Thu, 17 Dec 1992 16:10:07 -0500

#  Note that some SMTP servers accept neither EXPN nor VRFY (the default
# Zmailer configuration, for example).
# 	- cks

Further, even some that do accept EXPN and VRFY don't always tell you
what you want to know.  Actually, they correctly answer they questions
they are asked, but in my experience people often ask the wrong questions.

The example I'm thinking of is a common firewall configuration, where
you have some gateway machine (call it "") that's
the MX forwarder for "".  Mail addressed to
"user @
 company .
 com" isn't actually delivered on that machine, though,
it's handed on in through the firewall to some internal server (call
it "").

The common problem I see is that folks wanting to check
"user @
 company .
 com" TELNET to the gateway machine, then do "vrfy user".
The gateway machine quite rightly returns "no such user", since there
_isn't_ any such user ON THE GATEWAY MACHINE.  If they had instead
done "vrfy user @
 company .
 com", they would have gotten back "address OK"
(which still doesn't tell them whether or not the user actually
exists; it just tells them that the gateway knows how to handle mail
addressed to "* @
 company .

Brent Chapman                                   Great Circle Associates
Brent @
 GreatCircle .
 COM                           1057 West Dana Street
+1 415 962 0841                                 Mountain View, CA  94041

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