As the previous poster alluded to, with Exchange server you are not downloading any mail, Outlook merely acts as an IMAP client that allows you to view the mailbox stored on the Exchange server. Therefore you simply configure each Outlook client in the same way to access the relevant mailbox on the Exchange server. As messages are not downloaded, the mailbox & messages will be viewable by both computers. If they are logging on as the same network user, configure Outlook in exactly the same way on each PC. If you are wanting another user to have access to the original users mailbox you have to:
1. From the first users PC while logged on as the first user, right-click the mailbox folder/s you want the second user to have access to, select properties > permissions and add the second user and assign the relevant permissions (reviewer, author, editor, etc).
2. From the second users PC while logged on as the second user, open Outlook and go to Tools > Services > Exchange Server > Properties > Advanced and add the first users mailbox. This is how it’s done in Outlook 2000, it has changed slightly in Outlook 2003 but if you poke around you will find the Exchange server Advanced tab and be able to ad the first user’s mailbox.