Issue add a mailbox with Outlook for MAC

New Contributor

Dear All,


This is my first post on this board.


My client has an Exchange Server 2019 on-premises, configured with full hybrid to Exchange Online. We don't have any mailbox in the Exchange Online organization. The hybrid configuration was necessary since the client is using MS Teams and wants to see the calendar tab in MS Teams pointing to the on-premises calendar. This works fine


The client has some MAC computers. Their exchange mailboxes lost connectivity to the Exchange Server. We are not sure if it is related to the configuration change for full hybrid. Since then I tested a few times to add a mailbox with a MAC client using Outlook for MAC or native MAC Mail. The error message is always "unable to verify credentials"


We don't have any issue with Outlook for Windows clients. They are working fine and adding a mailbox on a test client works without a problem. Using the MS Remote Connectivity Analyzer I ran the Exchange ActiveSync and Outlook Connectivity test. Both are completed successfully. I also checked the virtual directory URL and both the internal and external URIs are looking fine. We use the same URL for internal and external. In addition, I ran the Outlook for Windows autoconfiguration test. It looks fine too. I copied the URL from the OOF line into the address bar of the browser, received the authentication prompt and I was able to log in.


I don't think we have a URL resolution or certificate issue, but MAC clients are unable to add a mailbox. OWA is fine using Safari or Chrome on the MAC


Do you have an idea what it could be?



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