User Configuration > Administrative Templates > Microsoft Outlook 2016 > Miscellaneous
User
HKCU\software\policies\microsoft\office\16.0\common\drm
By default, IRM license information for e-mail messages is downloaded to the user's local cache when Outlook synchronizes with Exchange. By enabling this setting, you can change this behavior so that licence information is not cached locally and users must connect to the network to retreive license information in order to open rights-managed e-mail messages.