A Clever Way to Reduce Spam Load on an Email Server

At Shel's talk last week Jan Fong mentioned the huge
number of spam messages received by the CalMail servers.

I recently learned about a technique called "Nolisting",
as opposed to "Graylisting". It's described at
http://www.joreybump.com/code/howto/nolisting.html .

The basic idea is that if an email server has multiple MX records,
and you deliberately misconfigure the one with highest
priority to point to an address that has nothing listening
on the SMTP port, most spam senders won't try any of
the other MX records. At worst, legitimate senders will have to retry
messages, but since most legitimate senders use caching
mechanisms the amount of retries is minimal.

One nice result from this approach is that it can substantially
reduce the load on the destination mail server because the
server receives many fewer connections. This also means content-based
spam filters will have less work to do.

I wonder what you Micronetters think of this approach.

Cordially,

-- 
Jon Forrest
forrest_at_ce.berkeley.edu
Computer Resources Manager
Civil and Environmental Engineering Dept.
305 Davis Hall
Univ. of Calif., Berkeley
Berkeley, CA 94720-1710
510-642-0904
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