1(North American English) (British Englishletter box)a small box near the main door of a building or by the road, which mail is delivered to2(North American English) (British Englishpostbox, letter box)a public box, for example in the street, that you put letters into when you send them3the area of a computer's memory where email messages are stored
ˈmeɪlbɒks
ˈmeɪlbɑːks