This are the simple steps to enable it.
1) Run SQL Server Surface Area Configuration - > Surface Area Configuration for features ->
Select Database Mail - > Check Enable Database mail stored procedures.
2) Open SQL Management Studio - > Management - > Database mail - > Configure SMTP Settings.
3) Go to SQL Server Agent - > Operators - > Create New Operator
4) Go to SQL Job - > In the Notifications, Check email and select the Operator. You can either
select the option to send notification if job fails / succeeds/ completed.
Lastly, don't forget to restart the SQL Agent.