Evan Platt wrote (in short):

> I'd like to implement either tarpitting or some method of blocking
> spammers attempting dictionary attempts.
> ....
> I would have liked to block this guy at the second or maybe even third
> attempt. Or perhaps just /dev/null all his traffic. Can postfix
> automatically do something when this occurs?

I'm not sure about postfix (but it probably could). But if it was a
problem I was experiencing I would be tempted to use iptables rate
limiting first.
(e.g. http://penguincares.no-ip.org:9090/mylinuxtips/?p=374)
I would prefer this approach to try to stop or at least slow down the
little bugger well before he got to postfix at all. Actually, maybe
I'd just block the whole ip for a couple of days to see if he goes away
:-).

Good luck!