Mail Archiving

[James]

I was wondering if anyone here knew of a good way to duplicate emails 
for archival purposes.

What i want to do is use a gateway machine that will deliver mail to two 
machines.
one being an active imap/pop3 system and the other being a mail archival 
system

i was thinking that there might be something like editing the transport 
file to do that but that only allows a single destination per domain as 
far as i know.

Any help is appreciated,

Thanks