On Mon, 2008-05-26, Robert A. Rosenberg wrote:
One way to eliminate the duplicates if the SMTP server has accepted
and sent the message but the MUA did not hang around to get the
acceptance ACK (or did not send the QUIT) is to save the Message-ID
of messages that the MUA did this for (I assume the retransmission
will have the same MID. If/when it attempts reinjection, compare the
supplied MID against the saved list and reject the attempt with a 5xx
status code (and text saying "You submitted this already and I
accepted and forwarded it"). You can prune the entry after a
designated wait time or when the message is resubmitted (the latter
possibly before the wait time expiration).
Wouldn't it be better to accept the duplicate message, reply with 250, and
route the message to the bit bucket without any further processing?
This tells the sending MTA that the message "got through" (which it did) so
that it will not retry here or elsewhere and allows the receiving MTA to
short circuit the processing that presumably delayed the original reply and
thus respond quickly enough to the sending MTA so as to be within its
timeout.
--
Bill McQuillan <McQuilWP(_at_)pobox(_dot_)com>