| 摘要 |
PROBLEM TO BE SOLVED: To interrupt the delivery of many electronic mails, such as spam mails and issue an alarm to an originating subscriber in the delivery of electronic mails received via a network. SOLUTION: A mail server on a receiving side checks whether or not an unclear delivery destination electronic address exists (S13), and when an electronic mail with an unclear delivery destination does exist, an electronic mail address, transmitting the electronic mail with the unclear delivery destination, is extracted (S14). Then, the number of electronic mails with unclear delivery destinations from the same electronic mails within a predetermined time interval is counted, and it is checked whether or not the count value exceeds a threshold (S15). When the count value exceeds the threshold, a mail server holder is informed thereof (S16), and the delivery of electronic mails from a corresponding originating electronic mail address (S17) is interrupted, and further registers the corresponding electronic mail address on a black list (S18).
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