An object of the present invention is to realize an electronic mail system wherein related electronic mail is automatically displayed when a telephone call is placed. The electronic mail system of the invention is constructed by linking an electronic mail system composed of a plurality of terminals and an electronic mail center, with a telephone system composed of a plurality of telephones and a telephone exchange, the telephones being associated in advance with individual users. The electronic mail center is equipped with means for storing a table of correspondence between user IDs and telephone numbers, a terminal interface capable of identifying the users using the terminals, and a status variable management table for managing status variables by which to recognize the mail currently displayed. The telephone exchange notifies the calling and called telephone numbers to the electronic mail center upon the reception of a call request, and the electronic mail center then identifies the user IDs in accordance with the correspondence table and transmits the related electronic mail for display on the terminals of the calling user and called user.