User Configuration > Administrative Templates > Microsoft Outlook 2016 > Security
User
HKCU\software\policies\microsoft\office\16.0\outlook
This policy setting controls the ability of users to export contact information from the address book. If you enable this policy setting, the "Add to Contacts" menu is not configurable in the address book. If you disable or do not configure this policy setting, the "Add to Contacts" menu is configurable.