what is the prompt asking for? just asking for username, password? or is it asking for what the name of the exchange server is? we use scriptlogic desktop authority to set the exchange name so that it does not ask. then it uses their network login to login to exchange. when someone logs in it will check to see if they have a mail profile. if not it creates one and forces it to use the name of our exchange server. it is basically a very high end login script processor. you can setup any number of different scripts in it and point those scripts to a single user or group or everyone if needed.
on the other hand if it is a brand new install of office that no one has opened outlook on before you need to login and open outlook the first time to tell it to use a corporate style of email. then from there on it will work fine.
<i>Use Group Policies to Publish Outlook using a Transform file. The Transform file can be setup with the Exchange server already programmed, and the user details. You can create Transform files using the ORK (Office Resource Kit) for whatever version of Office you are using.</i>