This object reports the maximum number of subscribers licensed specifically for unified messaging, which combines voicemail with email and other messaging types. An admin enabling unified messaging for a growing group of employees needs to watch this separate license ceiling, since it can be lower than the general subscriber license. If a department wants unified messaging enabled but ciscoUnityLicUMSubscribersMax has already been reached, those users must wait for a license increase even if general voicemail licenses remain available.