Hi anonymous user
What version of Outlook are you using? From your screenshot it seems to be Outlook 2016.
You can check the version and the build number via File > Office Account > About Outlook.
If you are using Outlook 2016 version 16.0.6741.2017 or some later versions, the issue may be caused by Outlook trying to connect to Microsoft 365.
To confirm it, you may run a Test E-mail Autoconfiguration via the Outlook client and check the results under the log tag to see if autodiscover is working properly.
If it is the cause of the issue, you may need to:
- open registry on client device
- locate HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
- add a DWORD value named "ExcludeExplicitO365Endpoint" and set its value to 1
- restart Outlook and see if the problem persists
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