I suspect (but do not know) that if you're running a Windows 2000 AD network, you can use Group Policy to enforce the changes in email setup. However, this will depend on you having clients that are aware of AD - i.e. no NT - and a version of Outlook >=2000.
ISTR that we had a script that a logged-in user could double-click and it would set up a simple Outlook profile connecting them to the Exchange server, based on the currently logged-in user. However, it stopped working in Outlook 2002.
I shall investigate this and let you know.