Multiple MTAs?

Hi,

I have a Debian server, and was about to install an MTA, when I was stricken by indecision as to which MTA actually to install. I realized that it would probably be best to use Postfix to send/receive mail to/from the Internet (because of its security) and Exim on my internal network (because of its flexibility). My question is, is there a way (short of virtualized servers) of installing multiple MTAs on one computer, so that they could pass mail between them, and so that which one handles a particular message is determined by whence the message came?

-- 
To UNSUBSCRIBE, email to debian-user-REQUEST@lists.debian.org 
with a subject of "unsubscribe". Trouble? Contact listmaster@lists.debian.org