Re:Greylisting (Score 1)

There are lots of different greylist implementations, with different configuration abilities and defaults.

It should be possible to configure the greylist server to have only a five-minute (or even one-minute) waiting period, which is much more reasonable than 15 minutes.

I have noticed that greylisting isn't quite as effective as it once was, because lots of spammers are actually using real queueing mail senders now. But it still has a lot of effectiveness.

See http://greylisting.org/ for more details on the concept. I personally use postgrey.