Dear Support, we want to intergrade Thunderbird to our Microsoft 365 (Exchange Online), but we have massive problems with the authentication of our users. I have allready configured an the Enterprise Application for Thunderbird in Entra ID and the Clients, excactly as documented in you article: https://support.mozilla.org/en-US/kb/microsoft-oauth-authentication-and-thunderbird-202 We have conditional access policies in out Entra ID, which allow only comliant devices to acess out Exchange Online. The Thunderbird clients are running on these compliant devices (Windows ans macOS), but it seems that the client is not passing this information through the Oauth authentication (see screenshots 01 to 04 - I uploaded the configuration and all the steps of authentication). I searched the internet for more then 3 days, but the only thing that I have found about this problem is this: https://bugzilla.mozilla.org/show_bug.cgi?id=1697805 In our Entra ID, we see in the sign-in logs, what excactly is happening with the conditional access (screenshots 05 to 07) We use the newest client versions of thunderbird. Can you please help me on this? We realy want to continue to use Thunderbird! Kind Regards Ioannis Kyriakidis