A mail slot (American and Canadian usage) or letterbox (British 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 offer 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.
Wall-mounted or attached mailboxes may also be used in place of mail slots, usually located close to the front door of the residence. They are known as full-service mailboxes, since most have provisions for securing outgoing as well as incoming mail. Attached wall-mounted mailboxes are still used in older urban and suburban neighbourhoods in North America. They are especially common in urban and suburban areas of Canada, where the curbside mailbox is rarely seen except in rural areas. Attached mailboxes are less common in newer urban and suburban developments and in rural areas of the United States, where curbside delivery or delivery to a community mail station (cluster mailbox, known as a bank of post boxes in the UK) is generally used.
Rural and some suburban areas of North America may utilize curbside mailboxes, also known as rural mailboxes. These receptacles generally consist of a large metal box mounted on a support designed primarily to receive large quantities of incoming mail, often with an attached flag to signal the presence of outgoing mail to the mail carrier. In the U.S. and Canada, rural curbside mailboxes may be found grouped together at property boundaries or road/driveway intersections, depending upon conditions. Although the United States Postal Service (USPS) has general regulations stating the distance a letter box may be from the road surface, these requirements may be changed by the local postmaster according to local environment and road conditions.1
At one time, nearly 843,000 rural Canadian residents used rural (curbside) mailboxes for private mail delivery, though Canada Post has since required the installation of community mailbox stations for many rural residents.2
In the U.S., wall-mounted or curbside mailboxes that are only designed for receiving incoming mail are known as limited-service mailboxes, while mailboxes equipped with a mechanism for notifying the postman to collect outgoing mail from the mailbox are known as full service mailboxes.
A number of designs of letterboxes and mailboxes have been patented, particularly in the United States. One design was the visible mailbox (because it was made of transparent glass) with a flip-up aluminum lid produced during the first part of the 20th century by George F. Collins of the Barlet-Collins Glass Company in Sapulpa, Oklahoma.Read more