Hello Rob,
In order to backup the Exchange resources either local on the Backup Server or on a different server,you must have an Agent for Exchange licence for that.
An additional Remote Agent for Windows Servers licence comes with it, so you could use this licence for backing up any other remote server running on a Windows platform.
==================
NOTE : If we do not receive your reply within two business days, this post would be marked assumed answered and would be moved to answered questions pool.