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 Greylisting: Next Step in the Spam War

Evan Harris tells us all about fighting spam with Greylisting.

"From this, we now have a unique triplet for identifying a mail "relationship". With this data, we simply follow a basic rule, which is: If we have never seen this triplet before, then refuse this delivery and any others that may come within a certain period of time with a temporary failure.Since SMTP is considered an unreliable transport, the possibility of temporary failures is built into the core spec (see RFC 821). As such, any well behaved message transfer agent (MTA) should attempt retries if given an appropriate temporary failure code for a delivery attempt (see below for discussion of issues concerning non-conforming MTA's)."

 (Submitted by Noel Wed Mar 3, 2004 )


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