User Configuration > Administrative Templates > Microsoft Outlook 2016 > Account Settings > Exchange > Cached Exchange Mode
User
HKCU\software\policies\microsoft\office\16.0\outlook\hybrid
This policy setting allows you to disable Exchange Fast Access, which forces user accounts to access data from a local cache. If you enable this policy setting, Exchange Fast Access is not available to any Exchange Accounts on a computer. If you disable or do not configure this policy setting, Exchange Fast Access is turned on by default for Exchange Accounts in Cached Exchange Mode.