From: wayne <wayne(_at_)midwestcs(_dot_)com>
... However, it was my understanding that qmail
didn't do much validation on the RCPT TO, the validation would come
much later.
Also in common sendmail configurations, such as when you want to
excempt some recipients such as postmaster from access_DB filters.
See http://www.google.com/search?q=sendmail+delay+checks
Anyway, my points were that reporting errors was important because you
want false positives to be reported and it doesn't hurt the spammer
much by not reporting errors. Also, validating early is better
because you waste less bandwidth, and you can force the sending MTA to
do the bounce.
If the sending MTA is standards compliant, you can force it to do the
bounce provided you say 5yz at any time in the transaction including
the very last bits of the transaction.
If you count bits including the DNS lookups for the IP address, HELO
value, Mail_From domain name, and Rctp_To domain names, any IDENT
checks, and DNS blacklists, you often find that the bandwidth required
to process that DATA command and receive the body is less than half
of the total. Stopping before the DATA command is often not much of
a bandwidth savings except for worms and legitimate mail, and you can't
stop the first before the DATA command and don't want to stop at all
for the second.
Vernon Schryver vjs(_at_)rhyolite(_dot_)com
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