To provide an electronic mail arrival ascertaining method which is improved in usability and serviceability so as to watch whether a replying electronic mail is present or not and to enable the other end to automatically transmit an electronic mail.

An electronic mail arrival ascertaining method comprises an ascertaining process of monitoring at the prescribed period electronic mails replying to the electronic mails transmitted by a user through an electronic mail system and ascertaining an originator mail address, a monitor terminating process of stopping monitoring when the originator mail address is coincident with the address of the other end to which the user has transmitted the electronic mail in consideration of the electronic mail as a replying electronic mail, an indicating process of giving an indication to a private branch exchange when no electronic mail is sent from the mail address of the other end after a monitoring operation is carried out for a prescribed period, and a transmission process of enabling the private branch exchange to automatically transmit the prescribed registered electronic mail to the other end on the basis of the above instruction so as to ascertain whether an electronic mail from the other end replying to a user's electronic mail.