[Exim] bouncing spamming to certain addresses

Hello!

First, lemme explain the situation, we're being spammed by several spammers
from a ISP that did nothing about it. As a persuasion, i want spam coming
from certain addreses to be redirected to several accounts. The best way to
do this, IMHO, is to redirect mails comming from this addreses to a procmail
filter and let procmail do the job. Another way would be to use exim
filters, but i have no experience on that. If anyone can drop me a few
guidelines on doing this i will really appreciate it.