To ensure electronic mail according to the reception data of the electronic mail and the preserving period of the electronic mail, and to improve the using efficiency of a storage medium for storing the electronic mail or data of a client.

This electronic mail management system for electronic mail by a client terminal is provided with a file deleting means for periodically deleting long term preserved open files other than invalid date files or undeletable files of each electronic mail from a disk resource for preserving plural electronic mails. Thus, when this use rate exceeds a preliminarily set disk use rate, the undeletable files are compressed, the disk resource can be ensured.