Impact

University of Alberta - Roughly a million total smtp connections a day. Initially running sendmail milter would bring a relatively beefy machine to it's knees. (lots of mysql).

OpenBSD spamd was a huge relief on that load. Greylist size 50,000 to 70,000 tuples every 4 hours.

Well chosen spamtraps, (some of them reactivated "old" domains) and initial stuttering reduce that to typically 10000 to 15000 tuples every 4 hours. 

Whitelist hovers around 120,000 entries.

Huge reduction in processed mail volume (60%)