Concept: I want to be able to greylist email that matches an RBL. I'd rather not greylist all mail company wide (although I do greylist all mail to this account) due to latency and multi-smarthost site problems. I also can't afford the FPs of outright rejecting mail based on RBLs. However, I can see greylisting all mail that matches an RBL, particularly ones like DULs and XBL. You could even use fairly "aggressive" RBLs in this fashion..
Setup: Sendmail, milter-greylist, MailScanner, SA.
Currently I use sendmail, and have milter-greylist enabled in "test mode" so only my account is greylisted. Based on testing with my account, some MTAs take a few hours (my greylist period is one minute, so any retry will succeed). The delay is fine for me, but there are others here who expect email to be relatively quick unless there's an outage. Certainly multi-hour delays aren't good for some people who are receiving business related files like price quotes, product specs, tech support, etc.
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)
