Mobile communication terminal sending and receiving electronic mail and mobile communication system therefor

When sending electronic mail, a user of a mobile phone (10) can add predetermined conditions (or data) to the electronic mail. When the mobile phone receives electronic mail with the conditions added thereto, the received electronic mail can be displayed and deleted according to the aforementioned conditions. The receiver of the electronic mail cannot freely dispose of the received electronic mail. The added conditions are, for example, display date and time, display period, number of displays, retention period.