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The Evolution of Centralized Mailboxes

Tuesday January 04, 2022

Centralized mailboxes have become increasingly common in recent years. They are distinguished from curbside mailboxes by their use of multiple mailbox units. While curbside mailboxes are exclusive to a single home or residence, centralized mailboxes have multiple units. As a result, both the United States Postal Service (USPS) and many property developers prefer them. Centralized mailboxes, however, have evolved. This post explores the evolution of centralized mailboxes and how they came to be.

Cluster Box Units (CBUs)

In the 1960s, the USPS developed Cluster Box Units (CBUs). CBUs were the first type of centralized mailboxes to hit the market. During this time, suburbanization was taking over the United States, which prompted the USPS to develop a new style of mailbox. The USPS ultimately developed a pedestal-style centralized mailbox that was used in place of individual curbside mailboxes. Known as CBUs, they allowed mail couriers to service a single CBU rather than multiple curbside mailboxes.

Neighborhood Delivery Collection Box Units (NDCBUs)

NDCBUs are pedestal-style centralized mailboxes that feature multiple mailbox units. They came several decades after the first generation of CBUs. The USPS developed NDCBUs based on the design of CBUS. They are both types of centralized mailboxes, and they both feature locks for each individual mailbox unit. NDCBUs simply came after the first generation of CBUs. They had several improvements to their design, making them a popular choice.


The USPS developed the STD-4B specification for centralized mailboxes following the development of NDCBUs. STD-4B mailboxes are centralized mailboxes are well. They are available in both wall-mounted and pedestal styles, however. STD-4B mailboxes can be installed as freestanding, pedestal-style units. Alternatively, they can be installed inside of an existing wall.


The latest type of centralized mailbox is STD-4C. STD-4C mailboxes are the successor to STD-4B mailboxes. In 2004, the USPS released the STD-4C mailbox. And in 2006, it began to require all multi-unit buildings to use them. STD-4C mailboxes look like ordinary STD-4B mailboxes, but they feature several changes. According to the USPS's specification, for instance, STD-4C mailboxes must be constructed of a heavier and stronger material, and they must feature a new and improved locking mechanism. Furthermore, all STD-4C mailboxes must be powder-coated to protect against corrosion and other forms of weather-related damage.

In the case of multi-unit buildings, STD-4B mailboxes can now only be used as replacements for existing STD-4B mailboxes. The USPS requires STD-4C mailboxes for multi-unit buildings that don't already have centralized mailboxes.


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