If you use Dynamics 365 online, and you want to be notified about any service degredation or online service issues, install the Office 365 Admin mobile app (available for iOSand Android).

Once you install the app (if notifications for the app are turned on), if there is a service notification for Dynamics 365 (or other Office 365 services), you will receive a push notification on your phone.

Tapping the notification will show you the full details.