Emailing from an Office Application using Remote Desktop Connection

We have setup a Win2003 Server running Terminal Services which our users connect to via RDC. The user opens a MS Access database on the Terminal Server. Part of the database’s functionality is to send out email notifications. The user’s Outlook Express account has been setup on the Terminal Server and can successfully send email. But the user can’t send emails from the database. An error of “Error 2287 – can’t start the mail session” occurs. It seems to be something to do with permissions as I’m able to get it to work, but I’m a Domain Admin, but the user is just a RDC User. Any suggestions?
Thanks Trevor