I can't seem to find the answer I am looking for so hopefully someone can point me in the right direction.

We are going to upgrade our existing mail server to exchange, and we aren't going to do it all at once. We are going to switch over users little by little to exchange. So we need a gateway machine that can filter the mail based on address and say fake1@fakedomain.com goes to server1 and fake2@fakedomain.com goes to server 2.

I have been mostly looking at postfix but can't seem to find a way to deliver to multiple destinations based on rules. Any help is appreciated.