User Configuration > Administrative Templates > Microsoft Outlook 2016 > Account Settings > Exchange
User
HKCU\software\policies\microsoft\office\16.0\outlook\rpc
This policy setting determines the RPC proxy authentication setting for Outlook Anywhere. If you enable this policy setting, you can specify the proxy authentication setting that Outlook uses, and this overrides any proxy authentication setting specified in Autodiscover. If you do not configure this policy setting Outlook uses the proxy server authentication specified in Autodiscover.