Go to Jobs on Management Studio, double click your job, and select
Notifications. Perhaps 'When the job completes' is selected. Change it to
'When the job fails'.
Since this job runs daily I would recommend to leave it as it is and receive
that e-mail daily. It could be the case that maybe the job is not running and
you are not receiving the e-mail either, for example, if the SQL Server Agent
is not running, there is a problem with the e-mail, etc.
Hope this helps,
Ben Nevarez