User Configuration > Administrative Templates > Microsoft Outlook 2016 > Outlook Options > Preferences > Calendar Options > Office.com Sharing Service
User
HKCU\software\policies\microsoft\office\16.0\outlook\options\pubcal
This policy setting controls whether Outlook users can publish their calendars to the Office.com Calendar Sharing Service. If you enable this policy setting, Outlook users cannot publish their calendars to Office.com. If you disable do not configure this policy setting, Outlook users can share their calendars with selected others by publishing them to the Microsoft Outlook Calendar Sharing Service. Users can control who can view their calendar and at what level of detail.