Any Free to useEindows based MAPI compatible emal client exists?

We at office having Exchange 2003, and above 3000 licensed users.
same time we have only few hundreds of MS office licenses.
Reason all people cannot access emails using MS Outlook. (they use OWA)
Owa has limits cannot use offline no personal folders etc.
so we are in need of any free to use MAPI compatible email clients.
can any one suggest any thing??
Rgds
HND