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From: root@ETN-WLV.EATON.COM (System Root)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: implementation question
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Date: 13 Dec 88 05:24:54 GMT
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  From: "John G. Ata" <Ata@RADC-MULTICS.ARPA>
  Subject:  Re: implementation question

    From:  apple!bionet!lear at BLOOM-BEACON.MIT.EDU (Eliot Lear)
    Subject:  implementation question

    Given a permanent error condition and that you control SMTP server
    code, which do you believe to be the better action?

    [a] Immediately have a server respond with an error to the SMTP client
        leave the client to report the error.

    [b] Receive the message and report the error directly to the sender.

  I believe that [a] is the more efficient way to go.  This is because if
  a SMTP server KNOWS that it cannot deliver the message to the intended
  recipient, it is taking up network bandwidth needlessly by accepting the
  message.  It would seem that the proper thing to do is to reject the
  message at that point, so that the SMTP user can then return the mail
  item to sender.

John, Eliot, et al:

The correct answer is it depends.  There is a tacit assumption in the query
that the recipient exists or that the transmitting station is persistent in
attempting to deliver a message to a non-existent recipient.  In the latter
case, [b] is the correct answer as it will limit the impact on the network
with the response being sent to the "Re-sent from:", "Sender:", or "From:".

In the former case, either [a] or [b] can be the correct answer.  If the
problem is resource related, the answer is [a] if there is a reasonable
expectation that the user can or will free the necessary reources in a
reasonable period of time. (Unlike AFIS/IND ;-))  If the problem is a brain
damaged mailer, [b] is the correct answer--the neat trick is figuring out
whether or not you've seen the message several times before and that you've
seen the same errors that preclude successful delivery of the message.  The
Internet doesn't have an equivalent of an AUTODIN Switching Center which
you an ring up and request that the message be "scrubbed".

Merton