The contents delivery system is capable of delivering multimedia contents efficiently, securely, easily and economically. In the contents delivery system, a data transmitter transmits the contents, and the data transmitter is connected to a communication network. A data receiver receives the contents, and the data receiver is connected to the communication network. The contents are attached to electronic mail, which is transmitted from the data transmitter to the data receiver. Commands for processing the contents in the data receiver are written in the electronic mail. The data receiver has a unit for executing the commands and processing the contents.