Exchange server email on 2 computers and 2 servers

Hi,

We have 2 exchange servers at our company, located in different parts of the city. An employee works in both offices and needs to access his email from both. I set up and exchange mail account in Outlook 2003 at the new office and pointed it to the server. It found his email account on the old exchange server and downloaded his email to outlook. Now when he goes to the other office his email that he recieved out here doesnt show up. I look further and found outlook 2003 is downloading his email into a pst file under inbox instead of the mailbox on the exchange server under inbox. Any ideas what may have caused this as he says he did nothing to change the configuration?