User Configuration > Administrative Templates > Microsoft Outlook 2016 > Outlook Options > Other
User
HKCU\software\policies\microsoft\office\16.0\outlook\preferences
This policy setting allows you to manage whether classic Outlook automatically sets up user accounts and settings in new Outlook. If you enable this policy setting, automatic setup of user accounts and settings in new Outlook is allowed and cannot be changed by the user. If you disable this policy setting, automatic setup of user accounts and settings in new Outlook is not allowed and cannot be changed by the user. If you don't configure this policy setting, users can manage the setting themselves. Automatic setup is enabled by default.