Apartment Mailboxes: USPS-Approved

4C Horizontal Mailboxes for New Construction

USPS STD-4C has been required for all new multi-family construction since 2006, making 4C the default for any new build or major renovation. Units come recessed, surface-mounted, or freestanding, with 4 to 29 compartments and optional built-in parcel lockers. Front-loading is standard; rear-loading suits secure mail rooms. Shop 4C apartment mailboxes by compartment count and mounting type.

CBU Cluster Mailboxes for Outdoor Centralized Delivery

Cluster box units are pedestal-mounted outdoor units that meet USPS STD-4C. Each holds 4 to 16 tenant compartments with one, two, or four integrated parcel lockers, and USPS installs the arrow lock after placement. CBUs suit garden-style and townhome communities without a dedicated indoor mail room. CBU cluster mailboxes come in six finishes: black, bronze, sandstone, white, forest green, and postal grey. Postal grey is approved for replacement installations only.

4B+ Horizontal Mailboxes for Replacement Projects

4B+ horizontal mailboxes are approved for replacement and retrofit only, not new construction. When an older building's rough opening was built to 4B dimensions, a 4B+ unit matches that footprint for far less than rebuilding the wall to 4C. Configurations run 5 to 7 compartments per bank, and local postmaster confirmation is required. 4B+ horizontal apartment mailboxes are the fit when the existing opening is a fixed constraint.

Vertical Mailboxes for Small Building Retrofits

Vertical mailboxes offer 3 to 7 locked doors per unit and are approved for retrofit only, never new construction. They install indoors only and fit small buildings where wall space rules out a recessed 4C. As with 4B+, confirm acceptance with your local postmaster before specifying vertical apartment mailboxes.

How to Choose the Right Apartment Mailbox System

The right apartment building mailboxes come down to six variables. Work through them in order before specifying:

1. New construction or retrofit? New builds require STD-4C compliant units (4C horizontal or CBU). Retrofits may qualify for 4B+ or vertical units depending on the existing rough opening and postmaster acceptance.

2. Tenant unit count. One compartment per unit is the standard. Confirm tenant compartment and rough opening dimensions before ordering, and add a vacancy buffer for new construction.

3. Front or rear access? Front-loading is standard. Rear-loading adds a carrier-security layer in high-traffic buildings with a dedicated mail room.

4. Mounting type. Recessed, surface-mounted, and freestanding are the three mounting options for apartment mailbox installations. Recessed requires confirmed wall depth before framing. CBUs require a concrete pad for outdoor placement.

5. Security specifications. Standard cam locks work for most applications. High-theft locations warrant upgraded anti-pry hardware and high-security lock cylinders.

6. ADA compliance. At least one compartment per bank must fall within the 15 to 48 inch forward reach range. Design for this at the specification stage, not after installation.

When in doubt, request a bulk quote and our team will spec the right system for your unit count and building type.

USPS Approval and ADA Compliance Requirements

Every USPS-approved apartment mailbox system installed in a new multi-family building must comply with USPS STD-4C. For existing buildings, STD-4B+ applies to replacement units where the rough opening dimensions align, and vertical mailboxes require postmaster acceptance on a case-by-case basis. When sourcing USPS-approved units, confirm the STD-4C or STD-4B+ designation in the product specifications before placing any order.

ADA compliance must be designed alongside USPS approval, not added afterward. Retrofitting for ADA after a unit is already installed is significantly more expensive than specifying for it from the start. For apartment mailboxes, USPS approval alone is not enough: the ADA Standards for Accessible Design require the following simultaneously:

• Forward reach range: 15 to 48 inches above finished floor

• At least one tenant compartment per bank must fall within the compliant reach range

• USPS placement requirements and ADA reach range apply at the same time: a unit can pass USPS inspection and still fail ADA if compartment heights fall outside the reach range

• Private delivery setups (non-USPS) are not required to meet STD-4C but should still comply with ADA reach-range standards

Installation Process and Postmaster Approval

The most common mistake in apartment mailbox installation is ordering the unit before contacting the postmaster. USPS approval must come first:

1. Submit your floor plan and compartment count to your local postmaster for approval before purchasing any hardware

2. Specify and order the unit once USPS approves the layout, compartment count, and placement location

3. Install the physical unit: confirm rough-in dimensions for recessed 4C installations before wall framing, and verify concrete pad dimensions and bolt spacing for outdoor CBU placements before pouring

4. USPS installs the arrow lock after placement: the carrier brings master key hardware once the unit is in position and approved

Getting postmaster sign-off before purchasing usps approved apartment mailboxes prevents the most common project delays: unit rejections, required reinstalls, and rough-opening mismatches discovered after the walls are closed. 

Correct Addressing and Tenant Updates

Keeping each apartment mailbox compartment labeled correctly is as important as the installation itself. Mail delivery does not update automatically when residents move: USPS and all other carriers deliver to the name and address on record. The standard format for apartment mail is recipient name + unit number + building street address. Update nameplates before a new tenant moves in, not after. Some buildings manage this at the leasing office; others maintain a label kit at the mailbox unit itself.

How Packages Are Delivered to Apartments

In apartment buildings, how packages get delivered to apartments depends entirely on the carrier and the building setup. Delivery goes to parcel lockers, the leasing office, or the apartment door directly.

How each major carrier handles apartment deliveries:

• USPS places small parcels directly in the tenant compartment. Some units also include an outgoing mail slot for letters and small flats. For larger packages, the carrier deposits the parcel in a parcel locker and leaves a retrieval key in the tenant's compartment. The locker retains that key after pickup, returning it to USPS on the next carrier visit.

• UPS and FedEx do not have access to apartment mailboxes. UPS and FedEx are legally prohibited from placing items inside USPS-controlled mailboxes under the federal Mailbox Restriction Law and deliver to the leasing office, an unsecured common area, or the apartment door instead.

• Amazon Logistics typically delivers to the door with photo confirmation. Amazon Hub Locker or Amazon Key access applies in some buildings.

• Private delivery mailboxes offer a separate secure option for non-USPS carriers in buildings where leasing office hours limit drop-off windows.

When specifying parcel capacity, plan for 1 parcel locker per 5 tenant compartments as a starting point, and add capacity for buildings with high e-commerce volume.

Security and Mail Theft Prevention

Shared apartment spaces create theft risk when systems are outdated or maintenance falls behind. The right hardware reduces that risk for both indoor and outdoor units; operational discipline from management and residents closes the gap.

Hardware features that matter:

• Heavy-duty aluminum doors with anti-pry framing and concealed or continuous hinges: a rigid door and frame resist prying, since a lock is only as strong as the structure behind it

• 5-pin cam locks as the standard configuration

• High-security lock cylinders for high-theft locations or buildings with prior incidents

• Keying configurations confirmed at order: keyed-alike, keyed-different, or master-key setups each serve different management needs

• Stainless steel hardware for coastal or high-humidity environments where powder-coated aluminum degrades faster

Operational practices that complete the picture:

• Collect mail promptly so compartments don't overflow, and don't tamper with a damaged unit while a repair is pending

• Report damaged or non-functioning locks immediately so management can schedule replacement before the next delivery cycle

• Controlled-access lobbies and dedicated mail rooms significantly reduce walk-in theft risk

For properties with a history of theft, high security cluster mailboxes with anti-pry hardware are the strongest option. Outdoor units with integrated parcel lockers also cut porch-piracy by eliminating unsecured front-door deliveries.

Why Choose Our Apartment Mailboxes

Browse apartment mailboxes for sale from the two most widely specified brands in multi-family construction:

• Over 500 USPS-approved units in stock across 4C, CBU, 4B, and vertical configurations

• Florence apartment mailboxes from Florence Manufacturing and Salsbury apartment mailboxes from Salsbury Industries, stocked in the depth that large-scale projects require

• Free shipping on orders over $99

• CBU price match guarantee

• Bulk pricing for multi-unit projects

• 5-star customer reviews across product categories

What Happens to Mail When You Move In or Out

Tenant transitions are one of the most common causes of misdelivered tenant mail. Property managers are responsible for managing both sides of each transition to prevent misdelivery:

• Outgoing tenant files a USPS Change of Address at usps.com/move or in person at a local post office; standard forwarding runs 12 months

• Property manager removes or updates the nameplate on the vacated compartment before the new resident moves in

• Key handover goes through the property manager, not directly between residents: chain-of-custody matters for compartment security

• Lost keys are the property owner's responsibility to replace; USPS does not service or replace tenant lock cylinders 

• Arrow locks are USPS-owned and stay in place during any tenant transition: no action is needed from the property manager for carrier access

• New tenant updates their address with banks, employers, and online retailers within the first week

Find the Right Apartment Mailbox System for Your Building

The right apartment mailboxes for your building depend on three things: build vs. retrofit, tenant unit count, and indoor vs. outdoor installation. The product grid above covers every configuration for self-service browsing. For project-scale orders, request a bulk apartment mailbox quote for volume pricing and specification support, or talk to a specialist if you need help narrowing down the right unit count before committing to an order.