The office-js API for add-ins provides a method to get a token that can be used for authorization on EWS or Outlook REST API calls - getCallbackTokenAsync. https://docs.microsoft.com/en-us/javascrip...
This is the very same thing I would like to achieve. The additional technical overhead/complexity is something we would like to avoid. We just want to keep it simple. Christian175 any updates from microsoft? Thanks.