This sounds like an easy mod, but I can't for the life of me find out
where to make the change.

Our backup box sends its report emails to root@thebackupmachine
whenever a backup job is completed. However, I just switched the box
from sendmail to postfix so that I could do some internal email stuff
on it unrelated to backups. The problem is, now I'm no longer
receiving email notifications when backup jobs are completed. Can
someone tell me where/ how the mail MTA is specified, and how to
modify it?

Again, I apologize if this is a basic question - I can't seem to find
any info on it.

Thanks,
Matt Emmott