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Derek Martin wrote: >>- Grey-list new correspondents for 1 hour (this blocks incoming spewage for >>that long no matter how hard they try). > > I don't know what this means... See: http://projects.puremagic.com/greylisting/ Basically it takes advantage of the fact that many programs built to send spam don't incorporate a queue, so if a message fails on the first try, it never gets sent again. When a message is first received by a server implementing grey-listing the the client IP, envelope sender, and recipient will be recorded in a database, and then the message rejected with a temporary failure. It will continue to be rejected for some timeout period (1 hour in the example above), after which a message with those same parameters will be accepted. (Grey-listing can be supplemented with white lists to avoid delays from known senders.) > ...but I do know that any kind of list can > block legitimate senders. I also know that anyone who wants to > authenticate my e-mail address before receiving mail from me never > gets mail from me again... A legitimate MTA will simply retry sending the message periodically over the span of a few days, and thus aside from the delay for the first message, it is transparent to the end users. No authenticate step required. The real problem with grey-listing is that it teaches spammers that sending more spam (iterating over their mailing list multiple times) will increase their chances of success. And unfortunately, spammers are capable of learning... -Tom
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