401 Unauthorized while subscribing to push notifications with Exchange service and OAuth

Question

I am trying to access EWS managed API (subscribe to push notifications) with oauth as below:

var authenticationTask = await authenticationContext.AcquireToke         


        

Answer 1

For those struggling with the same issue, we need to get the access token for the registered app by using a certificate (instead of doing it with client secret key). For more details on how to do it please see: https://blogs.msdn.microsoft.com/exchangedev/2015/01/21/building-daemon-or-service-apps-with-office-365-mail-calendar-and-contacts-apis-oauth2-client-credential-flow/