I've been running sendmail since the beginning of my online time.
1. Did I see that postfix can run sendmail milters? 2. If so, did I read that postfix can run these separately for inbound vs. outbound? 3. Can it run like a rbl blacklist on inbound and not outbound? 4. If the above is true, does this require separate configurations of postfix or is it already set to allow this out of the box?
My reasoning... I've added a few milters which has drastically cut spam due to the extra time spent at the smtp level. For instance, running spamassassin takes a couple or few seconds. This bit of delay does in fact seem to stop many of the slamming spambots sort of like the design of milter-greylist. Except, I don't have to send a temp fail. So, this is a good thing. The negative is it also takes longer for my users to send mail as it is processed the same way during outgoing.
Also, we run the SpamHaus blacklist. This works pretty good for inbound, but from time to time one of our hosting clients winds up on the blocklist because they are on a dynamic IP and someone else has recently used it for spamming. One could argue that my client should then go remove their IP from the blacklist to better insure their email actually makes it through any other level of spam filtering on other ISPs. But, that's a rosey concept! So, I would prefer to do it at the smtp level inbound so I can actually reject that mail while not having the embarrassing blocking going on with our users. Yes, this might sound like a double standard, but we do not provide connection service so only very rarely (never so far) does any virus actually send spam through our systems from client applications and I do actually monitor email all the time and stop any spamming immediately.
Thanks for any input.
John Hinton <who still keeps eyeballing postfix but is so comfortable with sendmail>