User Configuration > Administrative Templates > Microsoft Outlook 2016 > Folder Home Pages for Outlook Special Folders
User
HKCU\software\policies\microsoft\office\16.0\outlook\webview\calendar
This policy setting allows you to modify the "Show home page by default for this folder" in the Home Page tab of the Calendar Properties dialog box. If you enable this policy setting, you will set the "Show home page by default for this folder" check box. You will also be able to enter a URL, which has a maximum limit of 129 characters. If you disable or do not configure this policy setting, the "Show home page by default for this folder" check box will not be checked.