| 摘要 |
PROBLEM TO BE SOLVED: To restore a message even when it is deleted and to prevent a memory capacity from being wasted caused by storage of only unread messages not interested in a user. SOLUTION: A folder means 10 classifies messages stored in a memory 4 into messages in a backup folder that are to be deleted with priority. A memory management means 4 gives a deletion command to a delete means 13 when the idle capacity of the memory 4 is deficient or a set storage period for the messages expires, and the delete means 13 deletes messages in the backup folder with priority over messages stored in other folders. That is, the stored messages are transferred to the backup folder, even unread messages are deleted to reserve a capacity to store newly received messages. The messages stored in the backup folder can be returned to the usual storage folder until the delete processing is conducted.
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