Zimbra as primary - forwarding mail for an account with aliases?

[Yann2]

Hello, as said in one of my previous posts, we are going to put zimbra as primary mail server instead of secondary as it is for now; we have a 500 users licence, and around 200 people on exchange.

We want to put Zimbra as primary so that it works as spam filter for exchange; most of our users have aliases though. So my account, yann, also has 2 aliases y.hamon and yann.hamon.

If I want to do a proper redirection,what should I do:
- create an account for yann, 2 aliases for it called y.hamon and yann.hamon, and do the redirection only for the account yann
- create 3 different accounts, redirecting to exchange...

The 2nd solution seems the most easy to do, but our licence restrict us to 500 users, limit we may exceed if I add all the aliases as different accounts..

Any hint would be appreciated