Office 356 Autodiscover problem

Question

Good afternoon,

I created an application that uses the EWS to read calendar events from all Exchange users using Application Impersonation. I implemented support for OnPremise (using NTLM) and Office 356 (using OAuth2). While I created the OAuth2 implementation 2 years ago, everything was fine. However, the customers get a lot of problems now setting everything up.

The main problem is the Autodiscover server. I created a new Office 356 developer subscriptions and - well, same problem. I won't get access to the autodiscover server. I always get the following message:

Access has been blocked by Conditional Access policies. The access policy does not allow token issuance.

However, I don't have any conditional access plicies configured. I gave full access right to the impersonation user. If I get the autodiscover URL using the autodiscover.json url, access that site and try to lock in to that, I get the same message. So what's going on? What do I have to do to access the autodiscover using Exchange 356?

Best regards,
Marc Schodermayr

Answer 1

Do you have the security defaults enabled for that tenant?
https://learn.microsoft.com/en-us/azure/active-directory/fundamentals/concept-fundamentals-security-defaults

Answer 2

Oh my gosh... I don't belive it. That's it. Now it works fine. Thank you very much for that precious information!