I am sharing my experience after several hours hunting root cause. So this is not a question, but purely sharing my problem and the solution, that might help others.

System:
* Windows Server 2016 running Exchange 2016
* Windows 10 client computers using Internet Explorer and Edge browsers

Symptoms:
* Accessing OWA from client computers with Internet Explorer and Edge at address "https://mail.contoso.com/owa" ends with error "Cant reach this page" at URL "https://mail.contoso.com/owa/auth/errorFE.aspx?httpCode=500" (domain is replaced with mail.contoso.com for privacy reasons).
* Using "https://[Server Name].[Domain].local/owa" and "https://[Server IP address]/owa" ends with same result.
* Accessing OWA using server and Internet Explorer works all right.
* Accessing OWA externally works all right too.

Tracking down root cause (without positive result):
* Client computer DNS settings was checked and DNS server at the server was checked (according to several posts).
* Server policies was checked.
* Internet Explorer "Security settings" in menu item "Internet options" was checked.
At the same time there was independent errors (the first assumption):
* Accessing Danish public administration sites like borger.dk, skat.dk and virk.dk which all uses nemlog-in.dk for access control failed.
* Using Internet Explorer "F12 Developer tools" showed "SCRIPT5009: '$' is undefined" (java error).

Other browser:
* Accessing OWA using Chrome works without any problems.
* Accessing Danish public administration sites using Chrome also works without any problems.

Server Event Viewer:
* Investigating the server event log shows Event ID 1003 when "https://mail.contoso.com/owa" is accessed from client browser (Internet Explorer or Edge). Event Viewer folder "Windows Logs \ Application":
"[Owa] An internal server error occurred. The unhandled exception was: System.Globalization.CultureNotFoundException: Culture is not supported.
Parameter name: culture
4096 (0x1000) is an invalid culture identifier."
* A google search of the text in logged event above, lead to a German site "kräg's blog" item "Exchange 2016 – 4096 (0x1000) is an invalid culture identifier" http://www.kraeg.de/2017/10/30/excha...re-identifier/


Root cause:
* The Windows 10 client computer has an invalid language setting. In this case "English (en-DK)". In the case in "kräg's blog" "English (en-DE)"


Remedy:
* Change the invalid languages setting to "English (United States)" or another valid language setting.


Validation of fix:
* Accessing OWA from client computers with Internet Explorer and Edge at address "https://mail.contoso.com/owa" leads to the expected OWA login page.
* Further more accessing Danish public administration sites like borger.dk, skat.dk and virk.dk works too.
Attached Files