I’ve just installed postgrey at webthing. So I’m (experimentally) greylisting incoming mail.
Since people say greylisting is so effective, I’m also dropping the more fallible part of my existing spam filtering as part of the experiment. Blacklist access restrictions and sbl-rbl remain in effect, along with basic SMTP well-formedness checking. But all pattern-matching on message headers and bodies is suspended, as part of the experiment.
If greylisting is as effective as many folks claim for it, I’ll make that a permanent change. Time will tell!