Simon Blake wrote:
We've been using greylisting here for the last six months, and it's made a huge difference to the amount of noise that the downstream spam filters have to deal with. I've had to whitelist one external mail server, and a couple of internal ones, but all in all, I'm well pleased with the results. It's particularly useful to have running over mailman owner addresses to reduce the crap that arrives there.
I would set your timeout to be really low - 15 seconds would be as effective as 30 minutes, as far as I can see.
Greylisting does seem to work - the only problems I've had have been with Gmail not waiting long enough, and handheld devices running Windows Mobile 2003 and 5 timing out because they think the connection's down (probably a design feature that). Easy enough to fix though. It seems particularly good for dealing with virus-generated spam. -- Juha