SPAM (on list) was:Re: classiccmp list (sort of) help requested
mloewen at cpumagic.scol.pa.us
Fri Dec 15 09:40:07 CST 2006
> It was noted in one of the trade publications I looked at that a very
> effective check on SPAM was to confirm that the stream opened up to
> you (on your port 25) actually did a "conversation" with the remote
Something I've been experimenting with on one of my SMTP servers is
"greylisting", as implemented in a sendmail milter:
On my system, it blocks over 95% of SPAM delivery attempts. Most of
the SPAMbots I've seen attempting to deliver a message don't wait around
for a reply and simply disconnect when they get the temporary reject code.
Those that do often attempt to deliver the next message with a different
"from" address, which starts a new delay timer. I've also enabled it's
DNSRBL feature, with the SORBS list. Anything that is listed in SORBS
gets a longer delay. I can't say how well it scales on a busy system, but
it's a valid concept.
I passed this on to Jay in a private message.
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://ripsaw.cac.psu.edu/~mloewen/Oldtech/
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