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We have an Exchange 2019 server configured with a DAG, and we are encountering an issue where our Mac users are unable to connect to the Exchange servers using Outlook. The problem affects all Mac users, and the root cause is unknown.
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Hi @Innocent Heartvoice ，
Before going forward, could you elaborate the things below so that we can understand better about your situation?
You can also have a look at the event viewer on Exchange server and see if there's any potentially relevant event recorded out there.
Thank you for your response.
The Mac users previously had a successful connection with the Exchange server and did not encounter any problems.
However, suddenly, they lost their connectivity to the Exchange server using the Outlook application. Despite no updates or changes being made to the Exchange server, the cause of the issue is unknown and there is no error message appearing on the client Mac OS or in the Outlook connectivity.
The event log did not reveal any information to help identify the root cause of the issue.
Hi @Innocent Heartvoice ，
However, suddenly, they lost their connectivity to the Exchange server using the Outlook application.
How about creating a new Outlook profile in Mac and see if the account can be added to it successfully?
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Configure the Exchange server to support Compatible mode by using the instructions from KB article 980436.
For more detail - https://support.microsoft.com/en-us/topic/outlook-for-mac-clients-cannot-connect-to-exchange-server-bb7690e0-975a-7d95-a29b-b8bf5e787cb3