[Mimedefang] Pounded by spam

[Rich West]

We just got the living daylights pounded out of us by a spam host 
running at 69.6.66.103.

While I know it can be easy to simply block the host, I was wondering if 
there was some way to avoid the problem all together by potentially 
identifying hosts attempting to overload the server (Denial Of Service) 
by throttling down the amount of allowed inbound connections (from 
external sources) from a single host.

Admittedly, this is a bit off topic.. Mimedefang.pl was the process that 
was getting hammered (and subsequently drove the CPU load to >16 before 
we shut down email all together), but I do not think that the fault lies 
with mimedefang (in fact, I don't think there is any 'fault' here).. 
it's more a configuration issue at the MTA level (in this case, sendmail).

-Rich