Microsoft Graph 501 Error - Get Emails

Question

I have authenticated with Azure & OAuth to receive an access token. Now I want to read their Outlook emails through a Microsoft Graph endpoint from a native WPF desktop app using c#. However my request to get the emails, of the currently signed in user, fails with a 501 error. The delegated permissions my app has are:

• View users' email address
• Access user's data anytime
• Sign users in
• Read user mail
• Sign in and read user profile

Here is my network trace. Now I'm getting a 404 too

Answer 1

Based on the quest, were you authenticate the app with external user for the Azure AD?

If I understood correctly, the Microsoft Graph API only support for the users in the tenant.