If you use bacula for backing up your Linux boxes like I do, you might hit the same problem I did. This is just to record what I found for search engines to find, ‘cos it ain’t obvious and I haven’t seen it noted anywhere else.
In the Messages resource, the “Mail” record must be after the “MailCommand” one, otherwise the director will act as if it didn’t find your lovingly-crafted MailCommand. I was getting lots of emails with the subject of just “Bacula Message” when I could have sworn it should include some more details, like maybe whether the damned thing succeeded or failed. I haven’t found any other configuration resource that has this kind of order dependency.
(Despite this little hitch, I do highly recommend bacula. By the way, this little nugget is true at least in version 1.38, which is what you get in debian etch.)