Recessed

What Is a Recessed Mailbox?

A recessed mailbox is a mail unit that installs flush into a wall, column, or pilaster, with only the door visible from the outside. Unlike a surface-mount unit, which sits proud of the wall, or a free-standing depot, which sits inside a standalone enclosure, a recessed mount mailbox is framed into a rough opening in the structure. Often called a built-in mailbox, it is the most common format for centralized 4C mail centers, and recessed mailboxes also suit residential brick columns.

Features of Our Recessed Mailboxes

Construction & Materials

Most commercial 4C and 4B recessed units use a heavy-gauge aluminum mailbox body with 300-series stainless steel components, built to hold up in high-traffic apartment and office mailrooms. Salsbury 3700/3800 and Florence Versatile lines carry a weather-resistant powder-coat finish, while Florence 1250 vertical units use striated, anodized aluminum that resists scratches. On the residential side, the Streetscape is a solid brass recessed mailbox, and the Qualarc Manchester has a cast aluminum faceplate with a powder-coat finish.

Doors, Locks & Security

Tenant doors use heavy-duty cam locks: three keys per lock on Salsbury 3700 units and a 5-pin cylinder cam on Florence 1250 vertical boxes, with a dust and rain shield on the Salsbury locks. The carrier access door, or master door, comes prepped for a USPS Arrow lock, installed by the carrier. 4C tenant doors come in MB1 through MB4 sizes (3-1/4″, 6-3/4″, 10-1/4″, and 13-3/4″ high by 12-3/4″ wide). A locking recessed mailbox configuration is standard here: Florence Versatile and Salsbury 3800 parcel compartments use a double-locking mechanism.

Finishes & Color Options

Most commercial recessed units here are a powder coat finish mailbox at the core. Salsbury 4C units ship in four standard finishes: aluminum, bronze, sandstone, and black. Florence Versatile 4C offers eight architectural colors. The Florence 1250 vertical line comes in anodized aluminum. Streetscape units come in a hand-finished Polished Antique Patina, a natural brass finish that darkens over time, and the Qualarc Manchester offers black, antique copper, and bronze.

Outgoing Mail & Carrier Access

Salsbury 3700/3800 units include an outgoing mail compartment with an 11-3/4″ wide by 3/4″ high slot and a weather-protection hood. On USPS-approved units it doubles as the carrier access door, or master door, but cannot be used for distribution. They ship with factory-installed 1″ wide by 1/4″ deep trim and a solid rear cover.

Applications of Recessed Mailboxes (Where They Are Used)

Recessed mailboxes show up anywhere mail gets delivered to a central point. Each commercial mailbox application has a best-fit unit type, and the right choice depends on whether you are building new or replacing an existing system. Here is where each one fits:

• Apartment buildings and condominiums: centralized lobby installs using 4C recessed for new builds, or 4B+ units for replacements. An apartment recessed mailbox suits most multifamily properties.
• Office buildings and corporate mail centers: private-delivery 4C and 4B units placed in interior corridors.
• Military bases and government facilities: STD-4C compliant systems for new-construction military base mailbox installations and government offices.
• University dormitories: private-delivery vertical and 4C horizontal units in lobbies and common areas.
• Residential developments and custom homes: in-column and in-wall residential recessed units (Streetscape, Qualarc Manchester) built for masonry columns and pilasters.
• Hospitality and assisted living: ADA-compliant 4C suites with integrated parcel lockers.

Configuration Options

Door Counts & Column Layout

Vertical 4B+ units come in 3, 4, 5, 6, and 7-door single-column configurations. 4C horizontal systems are far more flexible, available in single column 4C and double column 4C layouts, with suite heights running from 6 doors high up to a 16-door max height mailbox (Max Height). Florence Versatile alone offers twelve suite heights across more than 140 pre-configured modules. Salsbury 3700/3800 standard heights include 6, 10, 11, and Maximum Height.

Parcel Locker Integration & Sizing

USPS STD-4C requires a minimum of one parcel locker for every five tenant compartments, and that parcel locker ratio is the first number to size your project around. A parcel locker mailbox can be integrated directly into a 4C unit or run as a stand-alone bank, and each locker uses a double-locking mechanism for added security. Sizes span PL3, PL4, PL4.5, PL5, and PL6:

Parcel Locker	Door Height
PL3	10-1/4″
PL4	13-3/4″
PL4.5	15-1/2″
PL5	17-1/4″
PL6	20-3/4″

ADA-Compliant Configurations

ADA compliant 4C units are available across the Florence Versatile (ADA Max Height suite) and Salsbury 3700/3800 lines. ADA mounting height drives compliance: when an installation has tenant compartments in the bottom row, the minimum is 28″ above the finished floor (AFF). When the bottom row holds no tenant compartments, an ADA mailbox can sit as low as 15″ AFF. Confirm ADA and Fair Housing requirements during planning, using the ADA Standards for Accessible Design as your reference.

Front-Loading vs Rear-Loading

A front loading mailbox gives tenants and the carrier access from the same side, the standard for interior mailrooms. A rear loading mailbox lets carriers work from a secured back corridor while tenants retrieve mail from the front. Your choice comes down to building layout and how you want to separate carrier and tenant traffic.

Installation Requirements

Wall Depth & Rough Opening

A rough opening recessed mailbox install needs enough wall depth to seat the unit. Florence 1250 vertical 4B+ boxes require a minimum wall depth of 6-3/4″, confirmed against Florence’s engineering drawings, or a surface-mount kit if the wall is shallower. For Salsbury 3700/3800 4C units, the framed wall opening dimensions vary by suite height, so pull the manufacturer cut sheet for the specific model. Each unit mounts into 2×4 wood framing with the hardware Salsbury supplies, per the 3700 install guide. For multi-unit walls, total the stud spacings and subtract 1/4″ for trim allowance.

When You Can’t Recess: Surface-Mount Collar & Free-Standing Depot

If wall depth falls short or you cannot cut into the wall, you have two fallbacks. A 4C surface mount collar (offered by Salsbury and Florence) holds the unit against the wall surface, working as an on-wall mailbox enclosure. Where no wall is available, a free-standing 4C depot cabinet houses the unit indoors or out. One caveat on the 4C depot: a free-standing 4C unit is not USPS-approved for delivery. Recessed installations qualify for USPS service, and some local postmasters permit surface-mount collar units for USPS delivery, so confirm with your postmaster before ordering. The free-standing depot does not.

Mount Type	USPS Approved	Wall Depth Needed	Placement
Recessed	Yes	Full (per cut sheet)	Indoor or outdoor wall
Surface-Mount Collar	Conditional: not approved by default	None	Indoor or outdoor wall
Free-Standing Depot	No	None	Indoor or outdoor, freestanding

Connector Kits for Multi-Unit Installations

When you set multiple recessed 4C units side by side, a 4C connector kit ties them together across one larger rough opening. Salsbury calls this a 4C horizontal mailbox connector kit; Florence calls its version the Multi-Unit Connector Kit, or MUCK. The connector removes the need for wall studs between units and gives you a flush, gapless run across the wall.

USPS Approval & Postmaster Confirmation

STD-4C compliance is mandatory for new construction and major renovations, a rule in effect since October 2006. 4B+ vertical and horizontal units stay USPS-approved for replacement and retrofit only. Before mail service starts, your local postmaster has to approve the installation location and configuration, and USPS installs the Arrow lock on the carrier access door. Always confirm the details with your postmaster before finalizing an order. For outdoor centralized delivery where a wall mount is not an option, USPS-approved cluster mailboxes are the alternative. See USPS-STD-4C for the governing standard.

Types of Recessed Mailboxes We Carry

Our recessed catalog spans four families. Here is the quick map so you can jump to the right group.

4C Horizontal Recessed Mailboxes

Florence Versatile and Salsbury 3700/3800 series, all STD-4C compliant for new construction and major renovations. You get full configuration flexibility: single or double column, integrated parcel lockers, and ADA suites. Both USPS-access and private-delivery variants are in stock. Browse the full range of 4C horizontal mailboxes to compare suites.

4B+ Vertical Recessed Mailboxes

Florence 1250 Series and Salsbury 3500 Series, offered in 3 to 7-door configurations for indoor use. These are USPS-approved for replacement and retrofit only, not new construction. Finishes run from striated anodized aluminum to powder coat, and the units need a minimum wall depth of 6-3/4″. See all vertical mailboxes for replacement projects.

4B Horizontal Recessed Mailboxes

Florence 1400 Series, with tenant doors arranged horizontally and a master door for postal access. USPS-approved for replacement only, these are common in older apartment lobbies. View our 4B horizontal mailboxes for retrofit work.

Residential Recessed & In-Column Mailboxes

Streetscape Gateway and Courtyard solid-brass recessed mailboxes for column and in-wall installations. These are built for brick columns, stucco pilasters, and recessed wall installations on custom homes. Pair them with column mount mailboxes for masonry projects, or look at wall mount mailboxes if a surface install fits better.

Why Choose Our Recessed Mailbox Selection

We carry a vast recessed catalog: 309 SKUs across 4C, 4B horizontal, 4B vertical, and residential units. That breadth means you can spec an entire mail center, from a 6-door retrofit to a double-column 4C suite with parcel lockers, without leaving the page. What you get with a MailboxWorks order:

• Technical drawings available for Florence commercial mailboxes
• Bulk pricing with 24-hour quote turnaround
• Free shipping on orders over $30
• Mailbox experts at (866) 717-4943 for compliance and configuration help

Need help sizing a system? Request a quote or browse our full range of commercial mailboxes.