Provided is an electronic mail system that can ensure that a user can be notified of the contents of an electronic mail even in cases where the electronic mail sent to the user was undeliverable. An electronic mail sending unit (220) sends, to an actual mail address of a user, an electronic mail sent to an alternative mail address of the user, after setting a notification destination employed in cases where the electronic mail becomes undeliverable as a predetermined notification destination. If a notification indicating that the electronic mail sent to the user's actual mail address was undeliverable is received at the predetermined notification destination, an undeliverable mail data saving unit (230) stores undeliverable mail data indicating the undeliverable electronic mail in an undeliverable mail data storage unit (410). An undeliverable mail data sending unit (110) sends, to a terminal device being used by the user, the undeliverable mail data indicating the undeliverable electronic mail which is the electronic mail sent to the user's actual mail address.
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