Letter box
A letter box, letterbox, letter plate, letter hole, deed, mail slot, or mailbox is a receptacle for receiving incoming mail at a private residence or business. For the opposite purpose of collating outgoing mail, a post box is generally used instead.
Letterboxes or mailboxes consist of four primary designs:
A slot in a wall or door through which mail is delivered (through-door delivery)
A box attached directly to the house (door-to-door delivery)
A box mounted at or near the street (curbside delivery)
A centralised mail delivery station consisting of individual mailboxes for an entire building
A centralised mail delivery station consisting of individual mailboxes for multiple recipients at multiple addresses in a particular neighborhood or community
Styles and usage
A 'letter box', or 'mail slot' in American and Canadian usage, is a slot, usually horizontal but sometimes vertical, about 30 cm by 5 cm (12 inches by 2 inches), cut through the middle or lower half of a front door. This style is almost universal in British homes and offices, but in the US is limited primarily to older neighborhoods in a few eastern cities. Most are covered by a flap or seal on the outside for weatherproofing. The flap may be closed by gravity, or sprung to prevent it opening and closing noisily in the wind. Some letterboxes also have a second flap on the inside to provide further protection from the elements. There may also be a small cage or box mounted on the inside of the door to receive the delivered mail. Mail slots are limited to receiving incoming mail, as most have no provision for securing and protecting outgoing mail for pickup by the mail carrier.