I work for the federal government and by putting our webmail's URL into the excahnge server field in AS, I am able to sync with the exchange server. It's fantastic!!! Changed my life when I gained the ability to get real-time meeting updates and check my mail on the fly.
For example, if I'm at home and wanted to access my work account, I go to:
http://webmail.agencyname.gov
On my Axim for server name I put: webmail.agencyname.gov
The only catch was getting my domain name. The first time I did that was by nosing around my Outlook settings at work.
Another thing, in order to sync I was required to set a password and to set it at no longer then one hour inactivity. The server apparently scans my Axim's security settings and won't sync if this is not the case. The first time I tried to sync, it walked me through changing my settings so that I met their requirements. Pretty nifty if you ask me.