Lou Picciano wrote:
Can I collect opinions here about favorite/least favorite spam filtering
packages, for use in a dbmail environment?
What have you had luck with? What works best? What's your opinion? Which
should a happy dbmail (postfix) user, now getting too much spam, use for
filtration?
I don't use content based spam filtering at all. The three techniques
that I find work really well combined are:
1) nolisting
http://en.wikipedia.org/wiki/Nolisting
I find it works best when you have at least two dummy high priority
decoys before the real MX, and some lower priority ones, too. Spammers
typically go for either the first one or the last one.
2) RBLs. Spamhaus is probably the best option, and it's free until you
need to query it more than about 400,000 times / day. Stay away from UCE
Protect, their policies are wholly unreasonable.
3) Clamav Milter
I don't really consider this to be optional any more. Fairly trivial to
set up, too.
In that order.
I wouldn't bother with content-based filtering - it's expensive and
prone to false positives, especially if you go as far as scanning image
based spam by extracting images and OCR-ing the pictures.
I get about 3-4 spams/week in my inbox. After decoys that protect me
from 75%+ of the spam, my MTA rejection rates on what's left are between
30 and 50% (RBLs, AV milter).
Last year I switched off my anti-spam defences for a test, and the
torrent of spam was quite staggering - about 100-200/day.
Gordan
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