Using Outlook for Android in business environments for email and scheduling
The tech told me to execute a test on https://testconnectivity.microsoft.com/tests/O365Imap/input which ran well with just a warning about certificates on old Windows versions :
The Microsoft Connectivity Analyzer can only validate the certificate chain using the Root Certificate Update functionality from Windows Update. Your certificate may not be trusted on Windows if the Update Root Certificates" feature isn't enabled.
(error id : 1339c33a-8f21-427b-a323-4cee1a13f517)
I think this warning is not related to our problem.
I transmitted the results of the test, now waiting for the next step.