> > 2: can be bypassed in greylist on that fact #1 >Both of these are addressed by Mailchannels. But what to do when an >"unknown mail server" contacts you is different in the approach. >greylist effectiveness is down to less than 10% effective at this >point, because the botnets know to retry now.
FYI: Use intelligent greylisting with hashing functionality. I even know of a product supporting this. Take a wild guess. :-) And it's effectiveness with greylisting is far beyond 10% even with retrying botnets.
