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 server that Outlook Anywhere uses when connecting to Exchange. If you enable this policy setting, Outlook uses only the RPC proxy server that you specify when connecting to Exchange. It ignores the proxy server specified in Autodiscover. If you disable or do not configure this policy setting Outlook uses the RPC proxy server that is specified in Autodiscover.