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Please Note: Not all mailboxes are USPS Approved for all applications. Please consult your local postmaster for approval.

Example: The 4B compliant 1400 Series 4B Horizontal mailboxes and Vertical mailboxes are only USPS Approved for replacement applications. For any mailbox project that will require USPS mail delivery, we recommend you consult your local Postmaster prior to ordering.

All new construction and renovation designs require USPS STD-4C compliant mailbox systems, such as standard CBUs and 4C Horizontal units.

What is a USPS Approved Mailbox?

A USPS Approved mailbox refers to any commercial or residential mailbox that is pre-approved by the Post Office prior to proper installation. An approved Cluster or 4C Horizontal unit will be prepped for the U.S. Postal Carrier to install their arrow lock for the master door (this allows the postal carrier to deliver mail to all individual units within the mailbox cluster).

The following mailboxes are considered USPS approved for New Construction:

1. Cluster Mailboxes

2. 4C Horizontal Mailboxes

The following mailboxes are considered USPS approved for Renovation or Replacement Use:

1. 4B Horizontal Mailboxes

2. Vertical Mailboxes

In addition to these types of units, the DVault brand curbside locking mailboxes are also Approved for curbside mail delivery. These boxes can be used either for residential or commercial applications. Likewise, Mail Boss products are approved for commercial or residential delivery. Mail Drops are also approved provided they are installed in a location the mailman can easily access. If you have any questions about whether a mailbox will meet postal requirements, we recommend you discuss the installation with your local post office prior to purchase.

How to purchase a USPS Approved Mailbox

As of October 5, 2006, all new construction and renovation designs require USPS STD-4C compliant mailbox systems, such as Cluster Mailboxes or Recessed 4C Mailboxes.

If you have an existing commercial mailbox that meets USPS specifications, call your local postmaster for approval. If you need to purchase, we sell new USPS approved mailboxes for new buildings or locations that are renovating. Shop our selection or reach out to our product experts.

USPS Approved Mailbox Specifications

In order to avoid delays and prevent problems, the USPS regulates the types and styles of mailboxes allowed for residential and commercial use. But not to worry: we make the process easy by offering a wide selection of USPS approved mailboxes for both residential and commercial locations.

All STD-4C Regulations

All new designs approved for new construction and major renovation require USPS compliance. The most common USPS commercial mailbox specifications include:

  • Minimum size requirement of 12 in. w x 15 in. d x 3 in. h
  • Minimum number of parcel lockers based on a 1:10 parcel locker to customer compartment ratio
  • Improved security requirements for entire receptacle
  • Standardization and improved tenant compartment lock design
  • Adds testing requirements to verify indoor/outdoor use
  • Meets Americans with Disabilities Act (ADA) standards
Getting a USPS approved mailbox from us is simple. Request a quote or shop our selection to begin.

Our Most Common Pre-Approved Mailboxes

Below is a detailed overview of some of the most common pre-approved mailboxes for USPS delivery.

USPS Cluster Mailboxes

Cluster Box Units are perhaps the most popular products for customers looking for an outdoor, centralized delivery application. They are ideal for office and apartment complexes, but can be used in residential subdivisions as well. The most popular color choices for the CBU are shown below in Sandstone, Bronze, Gray, and Black.


4C Horizontal (for Indoor or Kiosk Installation)

Like the Cluster Box Unit, the 4C Horizontal unit is an ideal application for centralized mail delivery. Where the 4C differs from the cluster box is that, whereas the CBU is for outdoor mail delivery, the 4C is typically used for indoor applications. That being said, the 4C Mailbox can be installed in an outdoor kiosk like the ones listed on this Vario Depot page.

20 tenant doors 2 parcel lockers front load usps approved 4c horizontal mailbox
maximum height usps 4c mailbox rear loading
20 tenant doors 2 parcel units front loading usps approved 4c mailboxes
4c horizontal mailbox maximum height unit

DVault Curbside

If you are looking for a more secure option, DVault locking curbside mailboxes are ideal for either commercial (office, business, industrial) use or residential mail delivery. DVault boxes are known for their anti-theft features, such as the Anti-Pry Posi-Lock access doors and hopper teeth to keep mail thieves from accessing the inside of the box. We offer DVault in post-mount and column mount options for curbside mail delivery.

delivery vault junior full service lockable curbside mailbox sand
delivery vault junior full service lockable curbside mailbox white
delivery vault junior full service lockable curbside mailbox black
delivery vault junior full service lockable curbside mailbox

Mail Boss Locking

Like the Dvault products above, the Mail Boss Locking mailbox is known for its high-security features like anti-pry mechanisms and its commercial grade anti-pick lock system. Made of 14-gauge and 16-gauge welded electro-galvanized steel, these boxes are nearly indestructible (check out this Video for proof). And if you need more than one, we offer Mail Boss packages in two, three, and four unit clusters.

Mail Boss USPS high security locking mailbox
granite ultimate high security locking single mailbox post package
granite ultimate high security locking double mailbox package
granite ultimate high security locking triple mailbox post package

Mail Drops & Receptacles

Properly installed according to postal specifications, Mail Drops & Receptacles can be used for mail delivery but are also appropriate for private use applications. If you have any questions about installing a mail drop for U.S. Postal Service mail delivery, simply give us a call at (866) 707-0008 or reach out to your local post office with details regarding the specific mail drop you are considering for purchase.

Customer Questions & Answers about USPS approval

How do I get USPS Approval?

The best way is to purchase a mailbox pre-approved for USPS delivery. But if you need something more unique for your application, you can view mailboxes with USPS delivery options and contact your local postmaster for approval (prior to purchase). Contact us if you have any questions.

How or where do I find pre-approved mailboxes?

The easiest way is to shop our selection of outdoor pedestal cluster mailboxes or recessed 4c mailboxes, or submit a quote request, or give us a call.

Where do I find pre-approved mailboxes for Apartments?

All of our pedestal mounted cluster mailboxes labeled for USPS delivery and the vast majority of 4C mailboxes (both linked above) are USPS approved for apartment complexes.

Are vertical or 4B horizontal mailboxes USPS approved?

If you are purchasing a vertical or 4B for replacement purposes, yes. In any case, we strongly recommend you get postmaster approval before purchasing.

Who is the manufacturer of USPS approved mailboxes?

We sell USPS mailboxes from an array of well-established brands, with Florence Corp. and Salsbury Industries being the most common.

What are USPS approved mailbox compartment sizes?

The minimum compartment size requirement is: 12 in. w x 15 in. d x 3 in. h. However, in some cases, compartments are made more spacious to accommodate larger parcels.

Related Articles:

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USPS Mailbox Key Replacement Cost

Customers Who Trusted Us With Their Projects

Major League Baseball
Harvard University
JP Morgan
U.S. Department of Defense
U.S. Department of State
USPS Approved
Balfour Beatty
Oregon Tech
Syracuse University