10% OFF & FREE SHIPPING*   ON ALL ORDERS IN JUNE                                                        Main image Hover image

Salsbury Mailbox Blog

Best Mailboxes for Multifamily Housing

December 20, 2021

Are you in the market for a mailbox for your multifamily development? Here’s the information you need to determine which one is right for you.

Multifamily Mailboxes

When purchasing a mailbox, it can be difficult to decide which type will best suit your needs. Things get even trickier as you try to figure out whether the mailbox you want fits USPS regulations for your building. If you own a multifamily building, you will be particularly concerned with keeping both your tenants and mail carriers happy.

Here is a roadmap that will hopefully make your choices a bit easier.

USPS Mailbox Regulations for Multifamily Housing

Multifamily housing simply refers to a single building that houses more than one family at a time. A multifamily building could be a duplex, or it could contain 200 apartments. The most common type of multifamily building you’ll find is an apartment building.

Not surprisingly, mail delivery gets a bit more complicated when the mail carrier is delivering mail for several families rather than just one. Centralized mail delivery is used for multifamily housing, which means that the letter carrier will deliver mail for multiple residences to one centralized location—a multifamily mailbox. The equipment for centralized delivery is referred to as a “clustered” type mailbox. These multifamily mailboxes can be any type of free-standing, pedestal-mounted cluster box unit, or a cluster mailbox mounted in a wall, shelter, or kiosk.

In 2005, new cluster box unit specifications became the standard for every manufacturer. Since 2007, it has been mandatory for manufacturers to be approved and licensed by the USPS to manufacture cluster box units.

Multifamily mailboxes that are USPS approved

All Salsbury multifamily mailboxes are USPS approved and meet or exceed USPS requirements and specifications. Here are the different types of USPS approved Salsbury multifamily mailboxes to choose from to suit your specific needs.



Cluster Box Units

Salsbury Cluster Box Units (CBUs) are free-standing and include a pedestal. This makes installation extremely simple and also looks very attractive. You will have a wide array of options when it comes to both model and color. CBUs come with 4, 8, 12, 13, or 16 mailbox compartments with one, two (2), or four (4) fully integrated parcel lockers. Each model is available in sandstone, bronze, white, green, black, and gray (for replacement units only). If you want to add a real touch of elegance to your apartment building, check out our Regency Decorative Cluster Mailboxes.

The CBU access door is equipped for a USPS-issued master arrow lock or a private commercial lock. Each unit comes equipped with an outgoing mail slot that will make sending mail convenient for your tenants, and collection convenient for your mail carriers. Mail carriers will also appreciate the fact that the CBU’s master doors open up, which makes mail and package delivery fast and simple. Each tenant compartment can fit large envelopes, small parcels, and check boxes. A CBU will not only make your tenants’ and mail carrier’s lives easier, but yours as well. Since they are free-standing, installation will be a breeze.

These heavy-duty aluminum multifamily mailboxes will put your tenants’ worries about mail and package theft at ease. The rear of each mail slot has an anti-fish plate that prevents any tampering with outgoing mail, which will make your tenants feel secure. Each tenant door also comes with a heavy-duty cam lock and includes three keys. With parcel lockers, tenants will be able to securely receive packages that won’t fit in their compartments. The mail carrier simply leaves the parcel locker key in a tenant’s compartment, and then the key capture system locks the parcel locker key in place after the tenant removes their parcel. After that, the parcel locker key can only be removed with the USPS control key.


4C Horizontal Mailboxes

Salsbury Industries manufactures USPS STD-4C horizontal mailboxes that are required for new construction and major renovations. A “major renovation” refers to any situation in which the condition of the wall is being modified where the existing wall-mounted mailboxes are currently installed. 4C Horizontal mailboxes are ideal for indoor and outdoor use. They are extremely durable and come in a variety of sizes and colors (aluminum, bronze, sandstone, and black). Configurations vary in the number of compartments and parcel lockers, which will allow you to find the perfect size for your building. With the 4C horizontal multifamily mailbox, you have the choice between a front loading or rear loading unit. The rear loading unit features a heavy access door(s) that includes heavy-duty latches and continuous hinges.

4C horizontal mailboxes include many of the same conveniences as CBUs, including an outgoing mail slot with an anti-fish plate, heavy-duty cam locks for each tenant door with three keys, spacious compartments, and secure parcel lockers. In addition to the CBUs, the 4C Free-Standing Mailboxes feature an enclosure that meets USPS height requirements. With the 4C horizontal mailbox’s high-security design and quality construction, you will be able to enjoy many years of maintenance-free service.


Check out our 4C Configurator to help you figure out the ideal number of mailboxes and parcel lockers for your multifamily building. 

Mailboxes that are USPS approved for replacement retrofit installations

Before October 6, 2006, multifamily buildings typically used USPS Standard 4B horizontal and vertical mailboxes. But with new USPS 4C standards, you can only use 4B horizontal and vertical mailboxes for direct one-to-one replacements. So if you don’t have to make any changes to the rough opening where the existing wall-mounted mailboxes are currently installed, 4B horizontal or vertical mailboxes can be used (though you should always check with your local Post Office to be sure). Otherwise, “4C” rated mailboxes must be used. If you’re simply replacing your mailbox with the same type of mailbox or doing repairs, 4B mailboxes are designed for replacement and retrofit installations.


Salsbury mailboxes are known for their durability, and their 4B multifamily mailboxes are no exception. The 3500 series 4B vertical mailboxes have a powder coated finish available in aluminum, bronze or sandstone. You can choose between a surface mounted vertical mailbox or one that is recessed mounted. Surface mounted units are designed to be mounted on a wall or other flat surface while recessed mounted units fit into a rough opening—which makes installation very simple.

Meanwhile, 3600 series 4B horizontal mailboxes are recessed mounted and you have the option to purchase a front loading unit or rear loading unit. If you have unique requirements when it comes to the mailbox and parcel locker door size in your unit, you are able to customize your 4B custom horizontal mailbox to your specifications. Custom colors are also available as an option upon request.

Best Salsbury mailboxes for multifamily developments

There is no question that Salsbury is the best way to go if you want strong, secure cluster mailboxes for your multifamily building. The only question is—which one do you need? 

If you are replacing an older mailbox without making any changes to the rough opening in the wall, a 4B vertical or 4B horizontal mailbox is the one for you. A custom 4B horizontal multifamily mailbox gives you the option to customize compartment and parcel locker sizes should you need to do so, and comes in a wide variety of custom colors.

If you are installing a new mailbox or making a major renovation, there are two types of mailboxes that will work best for your multifamily development—CBUs and 4C horizontal mailboxes. If you have the space for free-standing mailboxes, the Cluster Box Unit is an attractive, durable option that will add a touch of class to your multifamily development. But if a recessed mounted or surface mounted mailbox would better suit your space, then there are several fantastic 4C horizontal multifamily mailbox options for you to choose from.

No matter what your needs are, Salsbury will help to ensure that mail delivery in your multifamily building is convenient, secure, and hassle-free. Click below to explore Salsbury mailboxes for multifamily developments.