Ideally when using an Microsoft account you would connect via EWS, Exchange Web services.
The exception is if you are using contacts which currently only operates on EAS.
This step has to be performed by the mail administrator of the domain:
- Visit https://admin.microsoft.com/
- Select Users > Active Users
- Select the individual > Mail tab > Manage Email Apps
- Ensure Exchange Web services is enabled:
Test EWS is working by running the following test: https://testconnectivity.microsoft.com/tests/O365EwsTask/input