A communication system that exchanges electronic mail information based on a mail address including a telephone number of a destination and a domain name of a telecommunication services operator, and that includes a communication device for inputting the telephone number including an operator code and for exchanging the electronic mail information in accordance with the mail address; a storage device which stores a reference table in which the operator code is correlated to the domain name; and a communication management device which uses the operator code as an address to read the domain name of the telecommunication services operator to establish the mail address by combining the telephone number input through the communication device and the domain name read from the storage device.