According to the present invention, an SMTP server sending a mail having a predetermined mail address as a recipient to a server that receives and manages the mail having the predetermined mail address, includes: an advertisement information memory operable to store advertisement information to be added to the mail; an advertisement information detector operable to detect the advertisement information to be added to the mail from the advertisement information memory based on at least one of user information about a user having the mail address of the recipient of the mail, user information about a user having a mail address of a sender of the mail and a sentence included in the mail; an advertisement information adding portion operable to add the advertisement information to the mail; and a sending portion operable to send the mail to the server.