Delete Application Users
After you add an application user, you can remove the user from the Exchange server as necessary. For example, if you no longer want to create contact records and calendar items for a user, you can delete the application user from the user list.
On the Exchange Server Application Users page, select the double arrows beside the application user name to expand the row and then select Delete. On the confirmation message that appears, select Yes. You return to the Exchange Server Application Users page, and the user no longer appears in the grid.