How To Install a New Mailbox and Post

Thinking about a new mailbox? Installing one can boost your curb appeal and help your mail person deliver correctly. Whether you’re replacing an old mailbox or putting in a new one, it’s important to know the rules and steps before you get started. This guide walks you through everything you need to know about choosing and installing a new mailbox and post.

Mailbox Requirements

Before buying or installing a new mailbox, make sure you’re familiar with the USPS guidelines. These rules are in place to make sure your mailbox meets the standards for size, construction, and placement.

Curbside Mailbox Specifications

Curbside mailboxes are common in areas where mail carriers deliver from vehicles. When selecting a new curbside mailbox, keep these specifications in mind:

Look for the Postmaster General’s seal of approval on pre-made mailboxes.
Be sure the mailbox can accommodate a test gauge measuring 18 1/2 inches long, 5 inches wide, and 6 inches high.

The mailbox should adhere to the following size requirements:

Length: 18 9/16–22 13/16 inches
Width: 6 1/4–11 inches
Height: 6–15 inches

If you want to build a custom mailbox, you can order plans from the USPS Engineering Department or submit your design to the local postmaster for approval.

Pro Tips:

For easier nighttime visibility, use reflective letters and numbers on your box. Using reflectors or reflective tape on the post can help.
Persons with hardships or medical problems can apply for door delivery. Write a letter requesting the change to the postmaster of your town and attach a note from your doctor stating you cannot collect mail from the curb or post office. Once approved, you may install a door slot or wall mailbox.
If you receive a substantial volume of mail and small packages, you can upgrade to a USPS-approved extra large mailbox that fits on most standard posts.

Mailbox Post Requirements

The Federal Highway Administration recommends using either a 4-by-4-inch wooden post or a 2-inch steel or aluminum pipe for mailbox support. These materials are designed to yield or bend if struck by a vehicle, making them safer in case of an accident.

When installing the post, follow these steps:

Install the mailbox on the same side of the road as adjacent neighbors’ boxes
Bury it no more than 24 inches into the ground
Avoid using concrete or brick pillars or heavy metal posts

Installing Your New Mailbox and Post

You’ll need the following tools and materials for this project:

Concrete mix
Drill/driver
Level
Measuring tape
Post hole digger
Post level
Screwdriver
Sledgehammer
Socket wrench
Wheelbarrow

Mailbox Placement and Accessibility

Getting your mailbox placement correct is crucial for both you and your mail carriers. Look at these factors when installing your new mailbox:

Make sure the mailbox is easily accessible from the mail carrier’s vehicle.
Clear any obstacles that might block access to the mailbox.
If you live on a corner lot, consult with your local postmaster for the best placement.
If you live on a street different from your mailing address, include your full address on the side of the box.

Step-by-Step Instructions

Follow these steps to install a pre-made mailbox properly. You can use the video above, featuring Ask This Old House landscaper Roger Cook, for a visual of the post portion of the project:

Call 811 to locate underground utilities before digging.
Dig a 2-foot-deep hole using a post hole digger.
Cut a 4-by-4 post to 4 feet long, with 2 feet for the mailbox and 2 feet for below the ground.
Attach the mailbox post to the pressure-treated post using lag screws.
Secure the mailbox to the post with the screws provided with the mailbox.
Position the mailbox 6–8 inches from the road’s edge and 41–45 inches above the road surface.
Add your house number to the side of the box using 1-inch tall numbers.
Mix concrete in a wheelbarrow and fill the hole around the post, leaving 4 inches from the surface.
Top off the hole with soil.

Alternative Mailbox Options

While curbside mailboxes are common, there are other options available depending on your location and needs.

Door Slots and Wall-Mounted Boxes

In areas where mail carriers deliver on foot, homeowners often use door slots or wall-mounted boxes. These options follow different USPS standards:

Door slots should measure at least 1 1/2 inches tall and 7 inches wide.
The bottom of the slot should be at least 30 inches above the floor.
Horizontal slots require a flap hinged at the top that swings inward.
Wall-mounted boxes should be easily accessible and visible.

Locking Mailboxes

If you’re concerned about mail theft, a locking mailbox offers extra protection. When choosing a locking mailbox:

Select a style that allows mail carriers to deliver without a key.
Make sure the slot is at least 1 3/4 inches high and 10 inches wide to accommodate various mail sizes.

Cluster Box Units

In new developments or apartment complexes, cluster box units (CBUs) are common. They consolidate individual mailboxes into a single location, offering benefits like enhanced security and reduced theft.

Mailbox Maintenance and Security

Regular maintenance keeps your mailbox looking good and functioning well. Below are some tips.

Routine Maintenance

Check your mailbox annually for:

Damage and wear
Loose hinges and parts
A sturdy post
A door that closes tightly
Missing numbers or letters
Rust (and repaint if necessary)
Clear paths for easy access

Mail Security

These steps help keep your mail safe:

Stop mail delivery when you’re out of town.
Don’t leave packages unattended.
Set up delivery notifications on your phone.
Install a security camera.
Sign up for USPS Informed Delivery to get daily mail notifications.