So, aside from hacking milter-greylist itself, is there a way in sendmail.cf to only call a milter when a RBL hits? Is there another milter that can wrap milter-greylist to do this? (ie: sendmail calls milter-rbl-wrapper, and milter-rbl-wrapper conditionally calls milter-greylist)
AFAIK, all milters are always called directly from sendmail (assuming the previous milter accepted the message), so any decision has to be made within a milter, not within sendmail. In this scenario, you would have to hack or replace milter-greylist.
I can't speak for Mailscanner, but I know MIMEDefang has some built-in RBL functions, and people have posted several greylist implementations that work within a MIMEDefang filter. With that setup, you could have MD do the RBL lookup and conditionally run the greylist code.
-- Kelson Vibber SpeedGate Communications <www.speed.net>
