If emitting via email, it will send from email@example.com.
Which is totally invalid for two distinct reasons.
#1 The address yum-updatesd@ is invalid. Use a valid user like root or create an
#2 Host should already have a name. In this case, it is bozo.example.com. And a
properly configured mailer already knows it's name. So the @localhost needs to
be removed entirely. Of course just using @localhost. (with trailing dot) would
be valid too, although less preferred.
Updated the defaults to just be root to let sendmail set the domain itself