Email notifications from OEM
Yes, you have to fill in the notification schedule. This site defines to whom the mail will be sent on which time and day. If you shut down your database at a time, where no mail-address is set in the schedule, OEM will not send any mails.

You can fill in multiple mail addresses in the field for the schedule to have multiple persons receiving alert mails.

If you want the same addresses to be used every time, set the start and end so that 24 hours are covered and select all weekdays.

For testing the SMTP-Server, there is a link on the site, where you define one to send a test-mail.

The purpose of the notification schedule is e.g. for having different persons to be notified during working hours than at night.