A network management system transmits/receives an email via a network; saves, in a database, first history information including the address of at least one of the destination and the source of the email written in the email; receives transmission information in which access information for accessing a web page via a network is written; saves, in the database, second history information including the access information written in the transmission information; inputs authentication information for identifying a user; and selectively displays the first history information saved in the first saving unit and the second history information saved in the second saving unit in a predetermined display format on a display unit by switching between the first history information and the second history information based on an instruction inputted by a user when the inputted authentication information is identical to previously registered information.