An IP telephone system includes a source IP telephone apparatus, a destination telephone apparatus, a Web server and an ENUM server. The IP telephone apparatuses are connected to an IP network. The Web server stores control information for controlling an answering machine function. The control information corresponds to a telephone number assigned to the source or destination IP telephone apparatus. The ENUM server stores a NAPTR resource record in which a URI specifies link information related to the control information stored in the Web server. In the IP telephone system, the IP telephone apparatus that has received a call transmits, to the ENUM server, a query for a NAPTR record corresponding to an intended recipient's telephone number. The IP telephone apparatus then transmits, to the Web server, a request for the control information corresponding to the URI included in the obtained NAPTR resource record, and controls the answering machine function according to the obtained control information.