Hi @William Tey ,
Does your Exchange server version is Exchange 2016 CU19?
Is there a problem with logging in to ECP?
Have you set up a redirect to login OWA URL?
1.Please run the first command below to verify that the url and Authentication method of OWA are correct. You can also run the second command to verify that the authentication method of ECP is the same as that of OWA.
Get-OWAVirtualdirectory | fl *url*,*auth*
Get-ECpVirtualdirectory | fl *url*,*auth*
2.Please check the authentication method of OWA backend in IIS, the following picture is the default setting
3.Please try to recycle the MSExchangeOWAAppPool in Application Pools in IIS. Then run the “IISRESET” in the CMD started by the administrator to reset the IIS.
4.Please run the following commands to remove and re-create the OWA virtual directory. Then run the “IISRESET” in the CMD started by the administrator to reset the IIS.
Remove-OwaVirtualDirectory -Identity <>
New-OwaVirtualDirectory -WebSiteName <> -ExternalUrl <> -InternalUrl <>
For more information : New-OwaVirtualDirectory and Remove-OwaVirtualDirectory
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