On Sun, 2005-02-06 at 14:40 -0600, Jay Moore wrote: > AFAIK, all greylisting implementations use pretty much the same logic: > if the tuple (ip addr, from:, to:) is not in the "whitelist", return a > tempfail (450). A server is automatically "whitelisted" if he tries the > same tuple after a designated time has elapsed (e.g. 30 minutes). It is > effective apparently 'cause most spammers don't retry their connections. --- the entire point of spam is low cost. If the 'cost' is raised, it makes it less attractive. If a spam server has to keep retrying connections (the tempfail), it becomes expensive and reduces the amount of mail xfers that any one computer or server can deliver. The most effective tools have always revolved around 'tar pits' of some kind, designed to elevate the cost of delivery. Managing one of these tar pits has a cost too, as you must have some backend database to handle the the tuple attempts and whitelisting or even blacklisting. The cost however seems insignificant compared to the cost of checking each and every one with spamassassin. Craig
