Abstract: An e-mail communication system, in which bothering e-mails can be prevented to transmit to recipients, is provided. In case that a sender (subscriber) connected to an Internet service provider transmitted an e-mail to recipients (subscribers) connected to the Internet service provider, when the e-mail was an unwelcome e-mail (bothering e-mail) to the recipients, each of the recipients transmit a refusal notice to a data server for addresses transmitted refusal e-mails by using e-mails via an e-mail server provided by the Internet service provider. The data server for addresses transmitted refusal e-mails stores the transmitted refusal notices. When the number of the refusal notices per a unit period exceeded a threshold value, the Internet service provider makes the sender stop transmitting e-mails from now on.