Need help setting up a Windows mail client to work with Leopard Mail server

I have got my 10.5 server up and running, Mac Mail clients sending and receiving fine.

We have one user that must use Windows and I cannot get him connected to the Mail server at all.

We have CRAM-MD5, Kerberos and SSL enabled as options for secure connections.

Does anyone have a setup you could share that would allow the Windows client to connect securely to the Mail server?

Thank you,
Gary