User Configuration > Administrative Templates > Microsoft Outlook 2016 > Account Settings > Exchange
User
HKCU\software\policies\microsoft\office\16.0\outlook
This policy setting controls entry points to search in the Hierarchical Address Book (HAB). If you enable this policy setting, all entry points to search features in the HAB will be turned off. If you disable or do not configure this policy setting, all entry points to search features in the HAB will be enabled.