Hi @admin admin213 ,
Welcome to Microsoft Q&A forum.
Please run a test in EXRCA and be free to post the error information back with personal data covered.
Microsoft Remote Connectivity Analyzer
Check your firewall is forwarding port 443 to your Exchange server.
Also make sure the mobile device has not been blocked or quarantined.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.