Introducing Microsoft Teams Rooms (Updated)

Hello MTR Community,

I come back to you as I encounter a problem of Modern Authentication at a customer’s.

I have been through the different pages on the web to search for info about basic vs modern authent for MTRs but I cannot find the issue I am confronted to now :

https://techcommunity.microsoft.com/t5/microsoft-teams-blog/microsoft-teams-rooms-may-update/ba-p/1387779

https://docs.microsoft.com/en-us/MicrosoftTeams/rooms/rooms-authentication

https://docs.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/enable-or-disable-modern-authentication-in-exchange-online

The MTR is in last version. Modern Authentication has been activated for a while on the MTR. The account works fine since the installation 12 or more months ago. The MTR is granted an E3 licence (nothing is unchecked). The account is full O365 for Exchange, Skype and Teams. The MTR is nor domain-joined nor intune-enrolled or conditional access. There is no MFA on the account.

The customer noticed that despite Modern Authent ON on the device, there is still some Exchange basic authentication running.

For Exchange the OAuth2ClientProfileEnabled is True (taken from the PS command : Get-OrganizationConfig | Format-Table Name,OAuth* -Auto)

The basic authentication towards Exchange online is for the EWS service only.

I made some tests on one of my MTR on an online tenant, deactivating Modern Authentication would only show Autodiscover service as basic authentication. So I can not identify why for this customer the EWS would come in line.

Is there somewhere a detailled workflow connection of an MTR to Online services for Exchange, Skype and Teams ? This would be helpful for troubleshooting sometimes. Is EWS actually implied for MTRs connections ?

Thanks,

Cecile