Alert on Job Failure (email alert)

I have had such luck getting a single failure alert to happen.  Here’s what I did.
I presume you have an email account set up in SQL Server.

Right-click SQL Server Agent –> Properties

Select Alert System.
Turn on Enable mail Profile and click OK. 
Then repeat by turning it off! Then turn it back on.

Then, I created a job called fail that would force to fail.
Right-click the ill-fated job –> Properties
 
select Notifications
don’t mess with Alerts (they annoy me at times; my ignorance shows).

Make the ill-fated-job  run so it can fail; check your mail.  If you have enabled mail properly, (turn off + turn on SQL Alert system) you typically won’t have any problems