When using Intune App Protection I found it hard to find which users are using outlook protected (through Intune) and who not. So this is how you find the reports:

• Go To Intune App Protection in the Azure portal
• In the Overview blade you already see by default the App protection status
• Click on the widget
• Click on Add user and select the user you want to check.

• Go To Intune App Protection in the Azure portal
• Go to App Protection Status
• Click on the Top Protected iOS Apps, or the Android one (you can change this later)
  • Select the Platform: iOS or Android
  • Select the App: Outlook (or any other app)
  • Status: Unprotected

This will show you the list of users.