The mobile mailbox or mobile phone mailbox is an answering machine for mobile devices, for mobile phones, smartphones, PDAs, etc.. It is usually offered by the mobile network provider and can be personalised, e.g. with an announcement. The service of the mobile mailbox is advertised by the operators, since additional mobile usage time and thus higher revenues are associated with its use. In most cases, mobile operators offer an SMS or even e-mail notification service when a message is in the mobile mailbox.