alerts - pointing at mail server

Dear All,
I've probably missed something obvious but........
I've set up some basic alerts in my hobbit config. Looking at the logs indicates that they are being triggered and attempting to send mail
to the specified address.
However - no mail arrives. I'm sure the reason is that the server doesn't know where to send them - I can't seem to find anywhere in the hobbit config files where I can tell it about my local smtp server.
Do I need to be configuring sendmail on my hobit server or?
Cheers!
Rich