[Mimedefang] compare mimedefang to mailscanner

[Cormack, Ken]

> I have been using mimedefang for a couple of years now and just today 
> ran across the mailscanner program. On first glance it appears that the 
> 2 do about the same thing. Have some of the experts here tried both of 
> these and have a comparison as to how they differ? Is it worth my while 
> to spend time trying to configure mailscanner?

The biggest difference between the two is that MIMEDefang, being a milter,
can act on a message DURING the original SMTP conversation thus allowing
rejections, grey/black/whitelisting, and other actions to be taken before
the entire message is even accepted.

If you REJECT a connection while it is in progress, there's no need to
generate a separate bounce notification after the fact, which will likely
just clog up your outbound mail queue.  You just send a rejection to the
connecting server, and drop the connection, effectively slamming the door on
the spammer.

With mail scanner, you've already received the message in full (and said
"thank you very much" to the spammer), before you even begin looking at what
you've just received.

Ken