Spammers are a pain. How do we deal?
spamd
tarpit where black listed hosts get stuck - answers 1 byte at the time, tunable interval (-s option)
Grey-lists unknowns using 45n (temporary local error), well behaved ones are let through within a reasonable time
Introduced in OpenBSD 3.3 (May 2003)
Since OpenBSD 4.1, spamd runs in greylisting mode by default