Regarding to oracle documentation :-
The notification system allows you to notify Enterprise Manager administrators of alerts, policy violations, and the status changes of job executions. In addition to notifying administrators, the notification system can perform actions such as executing operating system commands (including scripts) and PL/SQL procedures when an alert is triggered.
Before Enterprise Manager can send e-mail notifications, you must first specify the Outgoing Mail (SMTP) servers to be used by the notification system. Once set, you can then define e-mail notifications for yourself or, if you have Super Administrator privileges, you can also define notifications for other Enterprise Manager administrators.
For More about E-Mail Notification Read here.
If everything is ready please follow the screen shot :-
Welcome Screen/Login Page