Outlook Sync between Navision and Exchange

Hello,

I'm new in the world of outlook synchronization.
A customer of us works with Exchange 2003 and NAV 5.0 SP1. Some cliënts work with XP and other with Vista.
He wants to work with outlook synchronization between NAV 5.0 SP1 and all outlook clients. I have set up everything so the synchronization of the contacts works between NAV 5.0 SP1 and all LOCAL outlook clients. This works fine.
The customer has a public folder in exchange with all the contacts and it's info. He wants to synchronize between NAV 5.0 SP1 and that public folder. Then it's not neccessary anymore to synchronize to every outlook client.

How is this set up?
Does every client need the outlook addin?

Thanks in advance.