Howdy,

Did anyone else see the paper mentioned on slashdot about greylisting?

http://projects.puremagic.com/greylisting/

Basically, for the first time when receiving an e-mail with a given sending IP address, sender and recepient, the server will temporarily fail delivery, asking the sending server to retry.

Most spam software doesn't retry, so most of that spam will be blocked. There are other ways to compensate for greylisting, but that will then make the spammer's efforts more detectable by other methods.

So not a final solution, but perhaps another good tool for the toolbox. Interesting read.