A transmission management system receives, from a request source terminal which is an addition request source requesting to add a certain transmission terminal as a destination candidate, an addition request for the destination candidate, identification information of the request source terminal and identification information of a request target terminal which is an addition request target of the destination candidate; and informs the request target terminal of an approval request for requesting the request target terminal to approve the addition request, and the identification of the request source terminal. The system receives an addition request response from the request target terminal in response to the addition request. When the addition request response indicates to approve the addition request, the system additionally associates the identification information of the request target terminal with the identification information of the request source terminal as the identification information of the destination terminal.