mail·box [mailboxmailboxes] BrE [ˈmeɪlbɒks] NAmE [ˈmeɪlbɑːks] noun 1. (NAmE) (BrE ˈletter box)a small box near the main door of a building or by the road, which mail is delivered to 2. (NAmE) (BrE post·box, ˈletter box)a public box, for example in the street, that you put letters into when you send them 3. the area of a computer's memory where email messages are stored See also: ↑letter box▪ ↑postbox