mailboxPronunciation: /ˈmeɪlbɒks/Translate mailbox | into French | into German | into Italian | into Spanish Definition of mailbox noun North American a box into which mail is delivered, especially one mounted on a post at the entrance to a person’s property. North American a postbox. a computer file in which email messages received by a particular user are stored. mailbox in other Oxford dictionaries Definition of mailbox in the US English dictionary