Exchange access for remote Outlook application

I am in a situation where we have 40-50 users who run around the US, selling contracts for various reasons. This places many of them in hotels, coffee shops, and various locations at a given time.

We currently have POP3 accounts all working for them via our Exchange 2000 Server, although dependent on where they go, they may have to change their outgoing SMTP server due to the ISP shifts. Some can do this, some can't - which leads to personal accountability issues.

We currently use Outlook Web Access (they store messages locally on pst's though), but this is not an 'ideal' solution for the executives. Is there a way to communicate directly from Exchange 2000 to the Outlook client without changing the SMTP and POP3 settings continually? I appreciate your responses.