To enable real world letters and electronic mails to be properly used corresponding to the utility of information.

Deliveries in a real world and deliveries in a cyber world are connected together through a network server, so that the deliveries in both the worlds are seamlessly connected. Information can be delivered by designating its addressee without taking a specific single address or an address on a network into consideration. Each user has a plurality of addresses residing in both a real world and a cyber world and is capable of transmitting or receiving information through an optimal method at the spot. A communication sentence residing only in a cyber world is converted to a letter or a post card in a real world, or on the contrary, a letter in a real world is converted to an e-mail in a cyber world and delivered.