A communication management system that manages a plurality of communication terminals transmits, to a request communication terminal, one of operation state information indicating that an operation state of a candidate counterpart communication terminal is unknown or information indicating that a communications protocol of the candidate counterpart communication terminal is different from a communications protocol of the request communication terminal, when the communications protocol is different between the candidate counterpart communication terminal and the request communication terminal. The request communication terminal displays information to a user, which is generated based on the information received from the communication management system.