Tim Chown (tjc) writes:
I don't know quite how high a performance you need. If it's just email
spam/viruses you are concerned with, you can run MailScanner for free,
see http://www.mailscanner.info. It's been around for 10 years now and
used by a lot of big organisations, many of which are listed on the
web site. Written by a colleague here at University of Southampton,
hence the plug. If you install and run it yourself, there's a good
community mail list for support and tips.
... or just run amavisd. MailScanner used to do Bad Things with the
Postfix queue, but since then I think they have fixed that, but I will
admit to not having any experience with it.