Bounce Rules

Matt Kettler mkettler at EVI-INC.COM
Thu Oct 27 00:08:48 IST 2005

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Dave Shariff Yadallee - System Administrator a.k.a. The Root of the Problem wrote:
> I did order the book and I do recommend it.
> Question, for bounce rules, ho do I bounce spam > a score of 7.5 ?


Rejecting spam at SMTP delivery time is fine, but don't _ever_ bounce it. I for
one treat it as intentional malicious misconfiguration and will *immediately*
blacklist a network that bounces a joe-jobbed spam to me.

Unfortunately, all of mailscanner is done post-delivery, so you can't do SMTP
time rejects using it.

Of course, the post-delivery scanning part of Mailscanner's design is what makes
it deal with bursty loads so well.

Sadly, you can't have it both ways. Delivery time scanners can reject, but the
fact that they scan at delivery time severely limits your peak delivery rate.
SpamAssassin instances are large, and you'll wind up memory limited in terms of
the number of simultaneous scanners you can have running. Eventually this will
lead to dropped connections which will have to retry delivery later.

Admittedly the average delivery rate is the same, but queue-first-then scan
methods like MailScanner can deal with a short term burst at the expense of
increasing the mail queue depth.

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