[HCS-D] New postfix, new spam filtering

Ivan Krstic krstic at hcs.harvard.edu
Sat May 21 12:39:54 EDT 2005

Matt Gline wrote:
> why doesn't the spammer just send mail back to hcs later?

"During the initial testing of Greylisting in mid-2003, it was observed
that the vast majority of spam appears to be sent from applications
designed specifically for spamming. These applications appear to adopt
the "fire-and-forget" methodology. That is, they attempt to send the
spam to one or several MX hosts for a domain, but then never attempt a
true retry as a real MTA would. From our testing, this means that in the
test environment, based on a fairly conservative interpretation of
testing data, we have attained an effectiveness of over 95%, and that is
with no legitimate mail ever being permanently blocked."


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