Hello @Trent,
Based on my experience, I suggest you try the following methods:
1.Since we change the configuration on server side, so I suggest to create a new Outlook profile to force updating the configuration:
Create an Outlook profile
2.In general, changing the OWA URL will not infect on Outlook client. So I need to know the internal DNS configuration, such as the A record/CNAME record.
3.Please Run Test Email Configuration in Outlook client
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- In Outlook , hold Ctrl key and right click the Outlook icon in the system tray.
- Select Test E-mail AutoConfiguration.
- Only select Use AutoDiscover and click Test.
- Please take a screenshot of the Log and result tab, save it as a .jpg files and upload the images in our forum directly.
4.Check your SSL certificate:
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1.Use IIS Manager to go to your Exchange 2019 server to confirm that the SSL certificate is installed.
2.Check in the binding whether the certificate has been assigned to the HTTPS site.
3.Make sure that all required domain names are included in the SSL certificate, such as 'autodiscover.<yourdomain>' and 'mail.<yourdomain>'.
Internet Information Services (IIS) needs to be restarted after changing settings to ensure all new settings are applied. This can be done by running the command "iisreset" in Command Prompt or PowerShell.