With over 2 million apartment buildings in the United States, the task of ensuring secure and efficient mail delivery has become a critical priority for developers, builders, and property managers. Traditional curbside mailboxes, while common in single-family developments, are no longer practical—or compliant—for multi-unit residential properties. If you’re developing or renovating an apartment complex, you’ll need to choose a mailbox solution that’s not only user-friendly but also meets current United States Postal Service (USPS) regulations.

Centralized Mailboxes: The Standard Since 2006

In 2006, the USPS updated its regulations to require STD-4C centralized mailboxes for all new multi-unit residential buildings constructed after October 6, 2006. These secure, wall-mounted systems consolidate multiple tenant compartments into a single unit, significantly improving security and delivery efficiency.

Glossary: STD-4C Mailbox
A centralized, USPS-approved mailbox system designed for multi-unit residential buildings. It features secure locking compartments, integrated parcel lockers, and compliance with federal delivery standards.

Instead of installing 20 individual mailboxes for a 20-unit property, a centralized 4C system can house all compartments—and parcel lockers—in one or two modular units. This not only saves space and reduces maintenance but also improves the overall aesthetic of the mail center.

On its website, the USPS highlights several key benefits of the 4C design:

• Enhanced security for incoming and outgoing mail

• Simplified and faster delivery for USPS carriers

• Larger mail compartments to prevent overflow

• ADA-compliant accessibility for residents

Q: Can older mailbox models still be used in apartment buildings?
A: Only buildings constructed before October 6, 2006 may continue using older STD-4B mailboxes. All new developments must use STD-4C units.

Parcel Locker Requirements: Don’t Overlook the Details

In addition to the centralized mailbox units themselves, you'll also need to install parcel lockers for the apartment building. In today’s e-commerce-driven world, accommodating larger packages is just as important as securing letters and small parcels. That’s where parcel lockers come in. These are built into or adjacent to the 4C mailbox systems and allow couriers to deliver boxes and oversized items securely—even when residents aren't home. 

Parcel Locker: a secure, oversized mailbox compartment designed to hold packages that don't fit in standard tenant boxes. Required by USPS regulations in multi-unit settings.

To comply with USPS rules, developers must include at least one parcel locker for every 10 mailbox compartments. That means a 50-unit building requires five parcel lockers at a minimum. If you have 100 mailbox compartments, you'll need 20 parcel lockers to remain compliant. Additionally, the USPS says that parcel lockers must be placed closed to the entrance of apartment buildings, and mail couriers must be allowed to access and use the locker without interference from its doors. These lockers must also be positioned in accessible, centralized areas—preferably near the main entrance—with unimpeded access for USPS mail carriers. 

Q: Where should parcel lockers be located?
A: Parcel lockers must be installed close to building entrances or common mail areas and be easily accessible to both residents and mail carriers.

Neglecting these requirements can delay your certificate of occupancy, lead to failed inspections, or result in mail delivery refusal by the USPS.

Plan Early, Install Smart

If you’re in the planning or design phase, don’t leave mail delivery as an afterthought. Engaging a trusted partner like Forsite Mailboxes and Signs early in your process can help ensure compliance, functionality, and visual cohesion from day one.

Forsite offers a wide range of durable, customizable 4C mailbox systems that blend security and style—plus expert guidance on layout, parcel locker ratios, and USPS approval. Whether you’re outfitting a modern high-rise, garden-style complex, or mixed-use development, our team can help configure the ideal mail center for your residents and your project timeline.

Glossary: Apartment Mail Center
A designated area within a multi-unit residential building for secure, centralized mail and package delivery.