Outlook 2016 Exchange 2019 on-Prem - ExcludeExplicitO365Endpoint NOT WORKING

[David.Kiernan]

May 2019 and this is still an issue.

Exchange 2016 on-premise
Outlook 2016 v1094

I cannot get Outlook 2016 to NOT try connecting to o365 and prompting for creds.

I have a laptop NOT joined to the AD Domain of the Exchange 2016 Server.
Outlook 2016 v1904 build 11601.20144

For devices AD-joined, it seems to work with just the ExcludeScpLookup and ExcludeExplicitO365Endpoint

Test Email Autoconfiguration (from system tray) goes to https://outlook.office365.com/autodiscover/autodiscover.xml

I have added the ExcludeExplicitO365Endpoint to both:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\AutoDiscover

I've also added the other keys I've found to both of these locations:

• PreferLocalXML
• ExcludeHttpRedirect
• ExcludeScpLookup
• ExcludeLastKnownGoodURL(only applies to Outlook 2010 version 14.0.7140.5001 and later versions)
• ExcludeExplicitO365Endpoint (only applies to Outlook 2016 version

I've rebooted after every attempt.

I've also added a key mentioned somewhere about WAMoverride.

Autodiscover tests fine on testExchangeConnectivity site.

Is there anything else I can try?

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