MAIL STORAGE BACKUP SYSTEM AND BACKUP METHOD

PROBLEM TO BE SOLVED: To provide a mail storage backup system and a backup method capable of ensuring, when storing mail, fault resistance and enhancing storage efficiency of the mail.SOLUTION: A mail server 10 determines an importance level of received mail with reference to a mail importance level determination table 300. Then, the mail server 10 refers to a backup server management table 100 to determine the number of backup servers 20 for storing mail in accordance with the determined importance level of mail, and selects backup servers 20 that are to be storage destinations. After that, the mail server 10 transmits the received mail to the selected backup servers 20, and the backup servers 20 store the received mail in a memory unit 230.