To solve a problem that conventionally, individual identification of an owner of a mail address is performed by making a user access to a site address carried in a mail text in general, but if the user can not access to the site due to access concentration in a time of disaster or the constraint of a portable telephone contract, he can not use the site, and he can not receive email with a terminal such as a portable telephone which is set not to receive email including a URL because of countermeasures to junk mail of these days, so that individual identification of the mail address owner can not be performed.

After transmitting code having a special meaning for the body and title of email, a user is made to send back email including the code, and thereby identification is performed.

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