I also use greylisting, which blocks about 75% of all incoming mail.
(See FreeBSD ports: /usr/ports/mail/milter-greylist )
<snip/>
I seem to remember you talking about the greylist also. Is it high
maintenance?
*No* maintenance ... once you set it up. milter-greylist is very well
written. It requires no MySQL databases (nothing special, actually). A
good overview of greylisting is at
http://projects.puremagic.com/greylisting/ (I don't use that particular
greylisting package--I did initially, though. Now milter-greylist is my
favorite.) There is also a greylisting website at greylisting.org
The only possible drawback is that when a sender *first* sends an e-mail
to a particular recipient on your server, your server returns a
*temporary* failure response, forcing the sending server to queue the mail
until its next queue run (typically 20-60 minutes). Compliant SMTP servers
will all queue the mail and deliver it within that time period. Windows
trojans and most spam generating programs, OTOH, won't try a second time,
so the the SPAM is never delivered. When the mail is finally delivered,
that sender/recipient/IP-address triple is "remembered" for a
(configurable) period of time--typically 5-30 days--so that subsequent
deliveries are instantaneous.
--
Bennett Lanford <ben@xxxxxxxxxxxxx>