While the technique described in this article is intended for implementation at the MTA level,
My prediction is that this is going to be bad.
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.
Great, so the next wave of spammers will be firing off multiples of every single spam, probably by processing their list twice (to give some time between the two attempts).
Just what we need, a doubling of traffic.
As a temporary stop-gap I'm sure it will be astonishingly effective. long-term it's really gonna suck.
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Because you can't cotton to evil. No Sir. You have to smack evil on the nose with the rolled-up newspaper of justice and say,'Bad evil. bad BAD evil'"
