Exchange 2019 not connecting to Office Outlook

Susan Dodds 186 Reputation points

Exchange 2019, Office Outlook 2016/2019.

Rebooted Exchange 2019 after installing a windows server 2019 update (kb5005102).

Incoming/outgoing email was still working. OWA still worked. However, Office Outlook clients were not connecting. Got the credential box, put in the credentials, Outlook opened in offline mode.

No errors in event viewer.

An additional reboot of the server (and router as a precaution) fixed the issue.

However, should this happen again, what additional troubleshooting steps are there, what caused this issue, what Exchange service under services is directly connected to this issue?


Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Xzsssss 8,861 Reputation points Microsoft Vendor

    Hi @Susan Dodds ,

    I've checked the KB5005102 update for Windows Server 2019, and the only thing related with Exchange is that the Cluster Service might fail to start because a Cluster Network Driver is not found, as a known issue, because the the DAG is based on the Cluster service.

    This issue occurs because of an update to the PnP class drivers used by this service. After about 20 minutes, you should be able to restart your device and not encounter this issue.

    Actually I don't think restarting the server or install some Windows Server update patches will cause the crash of the Outlook clients.
    You may try restarting IIS or checking if the Exchange services are running.
    And if the issue still there, check the autodiscover: Right click the Outlook button while pressing CTRL, choose Test Email Autoconfiguration and:

    Or use the official tool to test it:

    Best regards,

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