Provided is an e-mail managing apparatus that easily performs a check of the contents of a mail exchange for a specified mail. An HDD (storage device) of an e-mail-managing server stores sent mail and received mail from a user terminal and that includes tags for specifying categories of contents of messages, a mail-managing unit, based on the tags, creates a mail-correlation diagram that indicates contents of mail exchange for a specified mail, and a system-control unit sends the mail-correlation diagram that is created by the mail-managing unit to the user terminal. As a result, by using the mail-correlation diagram it is possible to express the correlation of the contents of the mail exchange.