| 摘要 |
A check is made as to whether a received mail contains a password as a combination of preliminarily registered symbols or letters. When the password is found, a telephone diary in a database is retrieved by using a letter train other than the password contained in the received mail. When a telephone number corresponding to the other letter train is contained in the telephone diary, the corresponding telephone number is mail returned to the source of transmission. When no such telephone number is contained, this fact is mail returned.
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