A client device including a first message receiver that receives a first message from an external device; a second message receiver that receives a second message from the external device; a display unit that displays one of the first message received by the first message receiver and the second message received by the second message receiver; and a controller that determines whether or not a specific address or a specific keyword is stated in the body of the second message received by the second message receiver, and discards the received second message on the basis of the determination result.