On Wed, June 29, 2005 11:09, Ruud H.G. van Tol said:
<SNIP>
Example of an anti-virus DNSBL:
http://virbl.bit.nl/faq.php
Stalling IP-nrs that are not in a cache with all the most recent
connecting IP-nrs, does also work well. Make newcomers wait for a few
seconds and give them a 4xx temporary error, and put their IP-nr in a
special temporary cache. If they don't come back withing a few hours,
forget about them. If they do come back, only then do all kind of
SMTP-checks possible, and add them to the IP-nr cache only if all OK.
Beware: aol and yahoo don't like 4xx, so again some whitelisting will be
necessary.
I *love* grey-listing, but Yahoo (and AOL too - up to a certain extend)
like to block your emails when there are too many rejects (which they
incorrectly call bounces <G>), even if those are temporary ('soft
bounce'), which they only help maintain by using a different sender
address every single message they deliver! :-/
So far I have 3 domains in my whitelist to circumvent greylisting issues
with those, but it works like a treat! My SPAM reception has gone down
considerably by just this one measure... (No, it's not my only protection,
just one of the most effective! I also use DNSRBLs, ClamAV, SA, SPF, etc.)
Of course it'll - unfortunately - only be a matter of time before the
zombie-worms will circumvent this by retrying on 4xx errors! :-(
--
Francesco Peeters
----
GPG Key = AA69 E7C6 1D8A F148 160C D5C4 9943 6E38 D5E3 7704
If your program doesn't recognize my signature, please visit
http://www.CAcert.org/index.php?id=3 to retrieve the Root CA certificate.
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