[Problems to be Solved] The object of the present invention is to permit usage of a character name in a network game for safe free communication with each other in cooperation of the e-mail between inside and outside the game without disclosure of the outside-mail address, which is privacy information. To this end, the present invention is characterized by a step of associating a character name with an Internet e-mail address and recording them in the dedicated server, and a step wherein when the terminal equipment of a mail source is connected to the game, an inside-game mail from the mail source using a character name is received and a character name of a destination is acquired, thereafter if the destination is not playing the game at present and the Internet e-mail address has been registered, then an arrival message is transmitted as the Internet e-mail addressed to the Internet e-mail address and thereafter the inside-game mail is converted to a WEB mail format to perform an external e-mail transmission by a WEB mail addressed to the game character name as required by the destination.