Also known as: 郵便受け
A physical receptacle outside a home or business where mail is delivered by a postal carrier. Also known as a letterbox, letter plate, letter hole, mail slot, etc.
Some mailboxes feature an arm that can be flipped up to indicate that there is some outgoing mail within for the postal carrier to retrieve when they come by delivering mail.
For the public box where outgoing mail is dropped, see Postbox (Outgoing Mail).