PROBLEM TO BE SOLVED: To reduce the number of junk electronic mails received by a recipient and the number of electronic mails transmitted by a user. SOLUTION: The amount of the junk electronic mails received by the user 105 of an electronic mail system is reduced by adding a recipient specifier 121 to an electronic mail message. The recipient specifier 121 is non-address information for further specifying the recipient to actually receive the message inside a group to which the message is sent. The mail filter 109 of the recipient can access information relating to the recipient, uses the information along with the non-address information inside the electronic mail message and judges whether or not to provide the message to the pertinent recipient. In the case that the non-address information and the information relating to the recipient indicate that the recipient is not to receive the message, the filter 109 does not provide it.