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 > 4C Horizontal Mailboxes

4C Horizontal Mailboxes


4C Mailbox Enclosures (Front Loading)
28 Products
Starting at $526.94
10 Products
Starting at $982.94
28 Products
Starting at $354.94
USPS Approved Front Loading 4C Mailboxes by Overall Height
18 Products
Starting at $482.94
18 Products
Starting at $482.94
18 Products
Starting at $431.94
19 Products
Starting at $427.49
15 Products
Starting at $423.86
17 Products
Starting at $387.53
12 Products
Starting at $405.94
8 Products
Starting at $356.66
15 Products
Starting at $339.03
15 Products
Starting at $321.42
10 Products
Starting at $274.70
14 Products
Starting at $212.97
10 Products
Starting at $177.97
8 Products
Starting at $183.52
8 Products
Starting at $165.91
USPS Approved Rear Loading 4C Mailboxes by Overall Height
Max. Height Rear Loading 4C Mailboxes
12 Products
Starting at $537.65
15 Door High Rear Loading 4C Mailboxes
12 Products
Starting at $530.65
14 Door High Rear Loading 4C Mailboxes
12 Products
Starting at $488.65
13 Door High Rear Loading 4C Mailboxes
13 Products
Starting at $425.97
12 Door High Rear Loading 4C Mailboxes
8 Products
Starting at $423.86
11 Door High Rear Loading 4C Mailboxes
11 Products
Starting at $387.53
10 Door High Rear Loading 4C Mailboxes
6 Products
Starting at $452.30
ADA Max Height 4C Mailboxes Rear Loading
8 Products
Starting at $356.66
9 Door High Rear Loading 4C Mailboxes
9 Products
Starting at $339.03
8 Door High Rear Loading 4C Mailboxes
9 Products
Starting at $321.42
7 Door High Rear Loading 4C Mailboxes
6 Products
Starting at $274.70
6 Door High Rear Loading 4C Mailboxes
10 Products
Starting at $212.97
5 Door High Rear Loading 4C Mailboxes
6 Products
Starting at $177.97
4 Door High Rear Loading 4C Mailboxes
3 Products
Starting at $221.84
3 Door High Rear Loading 4C Mailboxes
8 Products
Starting at $165.91

Understanding USPS 4C Mailboxes (a.k.a., recessed CBU mailboxes)

Effective October 2006, the USPS issued the STD-4C standard for USPS commercial mailboxes. This updated standard applies to all recessed 4C mailboxes and replaces the STD-4B+ horizontal mailbox for every new construction development or project in the U.S.

The biggest improvements from the previous 4B specification are the 4C's door size and overall security. Each tenant door is 12 inches wide by 15 inches deep by 3 inches high, meaning that larger envelopes and magazines arrive flat as they were intended.

The STD-4C standard also requires one (1) parcel locker for every ten (10) tenant compartments -- all of our preconfigured units adhere to this requirement. As for overall mail security, our manufacturers must adhere to the stricter and more thorough lock design requirements.

4C Mailbox Materials & Specifications

Made of aluminum with stainless steel hardware for locks and door mechanisms, these units are ideal for both indoor and outdoor applications.

  • 4C tenant door specifications: 3 in. H x 12 in. W x 15 in. D.
  • Finish & material: heavy gauge aluminum construction available in four color options by Salsbury Industries and eight color options by Auth-Florence.
  • Loading and mounting: available in either front or rear loading configurations (explained in detail below).
  • Tenant doors: include heavy duty, stainless steel dustproof cam locks (each with 3 keys).
  • Parcel lockers: for USPS package delivery. The dual, captive locking system allows the USPS to deliver a package to the locker while leaving the key in the tenant's mailbox. The package is retrieved by the tenant and key is retained securely in the lock. See video below for details.


  • Outgoing mail: all units feature an outgoing mail compartment with a drop-off slot, anti-fish comb for security, and protective hood located above USPS access door for convenient outgoing mail drop-off and collection.
  • Door identification: attractive silver placards with black numbers (1 through 20) are included with every standard configuration. Custom numbering can also be selected prior to checkout.

Front Loading Wall Mount

Between Salsbury Industries and Auth Florence Manufacturing, we offer one of the largest selections of front-loading USPS Approved 4C mailboxes and accessories online with over 150+ preconfigured modules to choose from

Front-loading mailboxes include a Master Loading Door prepared for the USPS Arrow Lock, which provides easy access to all compartments by the US mail carrier.

Front-load units are usually more common as they are immediately accessible from the front (as you might have already guessed), whereas rear loading units require the mail carrier to load and retrieve mail from a secure room located behind the recessed mailbox (more about rear loading below).

Rear Loading Wall Mount

You can probably guess that the rear-loading mailbox is accessed from the back. These mailboxes include hinged and latching rear doors that are accessed by a secure mail room for USPS use. Since there is no locking mechanism on the rear doors, a secure mail room behind mailboxes is required to keep mail secure.

If you still aren't sure whether you need a front or rear loading configuration, contact us and we will help you decide on the best option to fit your specific needs.

4C Pedestal

The 4C pedestal mailbox includes all of the features of the 4C horizontal wall units, but the addition of a pedestal means these units are outside of USPS specifications and therefore for private use only (unless you obtain approval from your local postmaster prior to purchase and installation). If you intend to purchase a 4C pedestal mailbox for U.S. mail delivery, we strongly recommend that you contact your local postmaster for approval.

4C Mailbox Enclosures

On every 4C horizontal product page, we offer the option to purchase with a mail station kiosk specifically designed to house the recessed mailbox being purchase. However, we also list 4C enclosures and surface mount collars as stand-alone products for customers looking to replace existing units.

4C Accessories

Whether you need new door identification tags or replacement locks or keys, we carry the full selection of 4C accessories from both of Salsbury Industries and Auth Florence Manufacturing.

Looking for a specific part number? Search our site or chat with one of our reps and we will help you locate it.

4C Horizontals Categorized by Door Height

4C Horizontal Mailboxes are categorized by door height rather than number of doors. This is because most architectural specifications measure the recessed wall dimensions by the height of the unit rather than the number of doors and also because the number of doors can vary across a wide range of 4Cs in the same height category. For an in-depth look at the different height specifications, click the Door Height Spec banner shown below. Feel free to contact us with any questions.

Frequently Asked Questions
Question: Do you sell curbside parcel locking mailboxes?
Answer: Yes, you can view our Curbside Parcel Locking Mailbox Selection for more details. Call us at (866) 707-0008 for further assistance. Thank you.

Question: I am a manager of a self storage facility. I am interested in some information on mailboxes that could be installed and then rented in the office of my facility.
Answer: You have the option of rear or front loading. The most cost-effective option, if you can use the rear loading, is the aluminum mailboxes. If there is a need for front loading, you will need to go with a 4B Horizontal. Both items are USPS approved.

4C Horizontal Mailboxes
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Wall Mount Mailboxes Locking Mailboxes Commercial Residential