In OpenBSD 3.8 - Greytrapping, and Initial Stuttering

Greytrapping

Greytrapping was added to OpenBSD 3.8 spamd. It allows you to specify spamtrap addresses that greylisted hosts may not mail to

A greylisted host that mails to a spamtrap address is removed from the greylist, and blacklisted for 24 hours. 

spamtrap addresses are added to /var/db/spamd with the spamdb(8) command

spamd automatically blacklists and un-blacklists offending hosts.

At ualberta.ca, During Oct 23-26 2006,we whitelisted 14,000 new hosts, but trapped 30,000 during the same period