[exim] Spam testing configuration options?

I am going to be testing multiple forms of spamfilter software/hardware
and I would like to configure our normal mail servers to deliver the
message to both of our spam1/spam2 testing hosts. The 2 spam hosts will
also run exim and need to deliver to local mailboxes on those servers
(for comparison on filtered/unfiltered email).

Has anyone done this before and/or have suggestions on how best to do
this? Perhaps a faq I couldn't find somewhere?

Thank you for any suggestions.
--

Mike Wilson