Since only users registered in a chatting service are subject of friends on the chatting service, unregistered users cannot become friends. A server apparatus controls a message exchanged between registered users who are registered in a chatting service, and controls a message exchanged between a registered user and an unregistered user. Also, the server apparatus manages a friend list of the registered user, and recommends other user to be added to the friend list with respect to the registered user. Also, the server apparatus determines other user to be recommended to the registered user by using a predetermined condition set according to the presence or absence of registration in the chatting service.