[Exim] Checking Unknown Local Parts & De-Routing

Hello,

I want to do a simple thing to help stop against spam attackers that send
e-mail to random generic names to mail servers, which cause both bandwidth
load and server load as well as annoy many users that they successfully
guess.

Is anyone doing anything to check what uknown local part messages they receive
(and how many) and then de-routeing or firewalling the senders IP addresses?
If so can you please let me know how you are doing this or maybe provide a
sample script?

Thanks in advance..

-Vextor
(who's sick of spammers).