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Salsbury Mailbox Blog

The Ultimate Guide to Cluster Mailboxes

January 20, 2022

Centralized mail is the United States Postal Service’s preferred form of mail delivery. Centralized delivery equipment like cluster mailboxes offer a wide variety of benefits to both mail carriers and the customer. Although door-to-door delivery is still common in many communities, cluster mailboxes have become more common in new developments, subdivisions and multifamily housing. However, navigating the selection and purchase of these mailboxes can be difficult, especially when you’re not already familiar with this type of mailbox.

Here is the ultimate guide to cluster mailboxes, which is sure to make you an expert in no time.

What is a Cluster Mailbox?

A cluster mailbox, or Cluster Box Unit (CBU), is a freestanding, pedestal-mounted mailbox that consists of multiple mailboxes and parcel compartments that can be locked individually. There is one mailbox for each customer on the street, complex, or subdivision. They are simple to install and will make an attractive addition to your community.

Each Salsbury CBU includes 4, 8, 12, 13, or 16 mailbox compartments with one, two (2), or four (4) fully integrated parcel lockers. Every model is available in bronze, sandstone, green, white, black, and gray (for replacement units only). You can add a real touch of sophistication to your community with our Regency Decorative Cluster Mailboxes.



Members of your community will deeply appreciate the spacious mail compartments and parcel lockers that are included with Salsbury CBUs. They won’t have to worry about their large envelopes and small parcels getting crushed or damaged by being wedged into too small a space. The bigger compartments and parcel lockers are convenient for mail carriers as well. There are plenty of reasons why the United States Postal Service prefers this type of mailbox, which we’ll discuss more in the next section.

Why Cluster Mailboxes are Important to USPS

Cluster mailboxes make mail carriers’ lives easier in several ways. The United States Postal Service serves over 150 million homes each day, and an average of one million new delivery points are added to their routes each year. In order to provide the best possible service to customers, it is essential that USPS mail delivery is as efficient as possible.

It is far more efficient for a mail carrier to deliver mail to one centralized location rather than driving from house to house. Neighborhood cluster mailboxes are more fuel-efficient as well, resulting in greener neighborhoods. CBUs also save the U.S. Postal Service money on salaries since each mail carrier will be able to cover more ground.

Using cluster mailboxes instead of individual street-side mailboxes is far more secure, which is a huge benefit for the USPS and the customer. Stolen bills, checks, and packages are no fun for the mail carrier or the customer to deal with, and these mailboxes have multiple safety features that protect against any type of theft.

Read on to learn more about the fantastic durability and security features you’ll enjoy with cluster mailboxes.

The Durability & Security of Cluster Mailboxes


Salsbury CBUs are constructed of heavy-duty aluminum and stainless steel hardware. Their durability and corrosion resistance will help to both deter thieves and save you the hassle and expense of constant maintenance. These mailboxes will also retain their modern, attractive look for years to come.

Durability is not the only feature that will help customers feel safe. The door to each mail compartment comes with a heavy-duty cam lock and includes three keys. There is also an anti-fish plate on the rear of the mail slot to prevent any tampering with outgoing mail.

Package theft is a serious problem many tenants and homeowners face, and the security of parcel lockers will help to put those worries to rest. Whenever a mail carrier delivers a package that won’t fit in a recipient’s mail compartment, they place it in the parcel locker and leave the parcel key in the recipient’s compartment. After the recipient removes their parcel, the key capture system locks the parcel key in place, and it can only be removed with the USPS control key. With cluster mailboxes, customers can say goodbye to concerns about ordering an expensive item for fear that it will be stolen.

USPS Regulations for Cluster Mailboxes

New cluster box unit specifications became the standard for every manufacturer in 2005. Ever since 2007, manufacturers have had to be approved and licensed by the USPS to manufacture cluster box units. All Salsbury Cluster Mailboxes are USPS approved and meet or exceed USPS requirements and specifications.

The builder or property owner is responsible for providing lock and key service for CBUs. The locks and keys for each compartment are provided with the CBU and USPS will furnish the “master access lock” so that mail can be delivered.


You need to choose a safe location for your cluster mailboxes. Also, you need to provide sufficient access to the mailboxes with enough space for both mail carriers and customers to easily access them.

How to Install a Cluster Mailbox


Worried about how to install your new cluster mailbox? This short video will take you through each and every step in the process, showing you exactly what you need to do. It also lists the exact tools you will need to complete the installation. The video provides an in-depth overview of how to install a cluster mailbox and yet it’s only 3 minutes long, which shows what a breeze installation really is.

Though the installation is simple, it is not something you should attempt alone. You will need assistance when it comes to mounting the CBU onto its pedestal and helping to hold the unit steady during installation. Once you’ve installed your cluster mailbox, contact your local Post Authority to get the master arrow lock installed.


Who Repairs Damaged Cluster Mailboxes?

According to USPS regulations, the property owners, builders, or developers are responsible for repairing damaged cluster mailboxes. The USPS’s Postal Operations Manual states, “Purchase, installation, and maintenance of mail receptacles are the responsibility of the customer.” There are occasionally some individual exceptions to this rule, but they are very rare. When in doubt about responsibility, contact your local Post Office.

Who Manufactures Cluster Mailboxes?

Salsbury Industries is the industry leader in the manufacturing of quality commercial and residential mailboxes in the United States and is officially licensed by the USPS to manufacture Cluster Box Units. Ever since Foster Salsbury founded the company way back in 1936, Salsbury Industries has been committed to manufacturing top-quality products.

Now Salsbury Industries operates in over 600,000 square feet of ISO 9001:2015 certified vertically integrated manufacturing facilities in the greater Los Angeles area. ISO 9001:2015 is an internationally recognized Quality Management System that requires a company to identify, define, document, implement, monitor and measure, and continually improve the effectiveness of its processes for the purposes of enhancing Customer Satisfaction. Each Salsbury Industries manufacturing facility has undergone third-party audits by accredited certification boards in order to become ISO 9001:2015 certified. Components are machined, powder coated, assembled, packaged, and shipped from these facilities.


Salsbury Industries utilizes the latest manufacturing methods, state-of-the-art machinery, and computer-aided robotics to manufacture the best products on the market. Some of the high-tech equipment used in Salsbury Industries facilities includes robotic welding, high-speed sawing, precision water jet cutting, press braking, CNC turret punching, milling, drilling, deburring, and a state-of-the-art powder coating line. Salsbury Industries employees assemble all of the products the company manufactures and fully inspect them prior to shipping.

How to Buy Cluster Mailboxes

Now that you have learned more about what a cluster mailbox is, USPS regulations, installation, and the top manufacturer of cluster mailboxes, you can begin the process of selecting and purchasing your CBU with confidence. And if you still feel uncertain moving forward, don’t worry! Salsbury Industries has made it extremely simple to order your cluster mailbox online, through customer service, or request a quote.

First, you can take everything you’ve learned from this guide and use it to choose the cluster mailbox that will best suit your needs. You’ll find each unit’s price on its product page, as well as the volume discounts you will receive if you purchase a certain number of mailboxes. Once you’ve decided on the size and model you want, then it’s as easy as clicking “Add to Cart” and completing the brief checkout process. After that, your order will typically be shipped in just 1-2 days.

If you have any questions, just click the “Live Chat” button on the product page, or call 1-800-MAILBOX to order through Customer Service. Salsbury Industries is known for its top-notch service, and our Customer Service representatives will be sure to help you purchase the right cluster mailbox for your community.

If you’d like to request a quote, there are two easy ways to do so. You can add items to your cart, then click the “Request Quote” button. You can also fill out our Request a Quote form, where you will have the option to attach any relevant documents. Most quotes are processed within 1-2 business days.

Now that you are a bona fide expert, you will be able to navigate the world of cluster mailboxes with ease. You’re now ready to purchase the perfect CBU to make mail delivery in your community efficient, secure, and hassle-free.