n. A public box for deposit of mail, where it is later picked up by the postal authority for delivery.n. A private box to recieve delivery of mail. The term is used both for boxes receiving mail delivered by the public postal authority, or by a private services, such as for mail to employees in large corporations.n. A location within a computer storage device where electronic mail is held until it is retrieved by the addressee. Creation and use of an electronic mailbox requires special software as well as a data storage device.