Voicemail systems are often associated with office telephone systems or PBXs. They may also be associated with public telephone network services such as residential phones or cellular phones. Mobile phones generally have voicemail as a standard network feature. The most modern implementations of voicemail support fax delivery to personal voice mailboxes and retrieval via printers, are integrated into e-mail systems for shared directories and shared message storage (also called Unified Messaging), and use touch tone voice user interfaces (VUI), speech technologies, and/or visual, screen-based graphical user interfaces (GUI) user interfaces.