> I had great results from grey-listing but my users didn't like
> having to wait 30-60-90 minutes for mail, and I understand that. When
> you're on the phone with someone and they say "Just sent it," they
> expect you to have it in a matter of seconds. As I'm often in that
> positition, I had to support that view and remove the grey-list.

I use sa-exim, which means I can greylist after the message has been
scored. So I only greylist a message if it scores over 7 and toss
messages over 20.

This way the vast majority of messages are sent through instantly.
> I've tried aboslute RBL blocking, but I'm happier having RBL as a
> weighted factor counting for or against the spamminess of an email.
> We only process about 5,000 non-spam messages per day (out of about
> 45,000/day total) and are doing OK on a couple of old dual-processor
> systems running it through clamd and spamd with sendmail.

Same here. Sure its more cpu power, but it lowers false positives. CPU
cycles are cheap.