Hi
I managed to get it working by allowing the server to relay through itself which is normally locked down, i found this out by checking the event viewer, and noticing relay failure messages from Back up exec to my email address. once i added the ip address of the server in the Relay tab all was well
This was the case on about ten different clients, which are now happily emailing me, whether the relay tab within exchange should be allowing this is debatable, but it lets the emails through which is what i wanted.
Thanks