Outlook Express settings on OS X Server

Hello,
I have OSX Server setup as a PDC at my school, which is predominantly windows. Logins etc are working fine. I want staff to use the county's mail service, and they configure Outlook Express for that. Immediately after configuring (and before logging out), the mail client works fine, but after logging out and re-logging OE has lost all the settings (other changes - such as desktop icons - are saved perfectly).
Any help would be much appreciated.

Simon.