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A new mailbox may be on your to-do list, whether you just moved into your home or you’re sprucing it up and want to improve your curb appeal. Whatever the reason, it’s a good idea to brush up on mailbox rules and regulations before you begin to shop for a new one or are building one from scratch.

What are the Curbside Mailbox Requirements?

You’ll typically find curbside mailboxes in areas where the mail carrier delivers mail from a vehicle. A curbside mailbox must meet United States Postal Service specifications for size and construction standards. When purchasing a new curbside box, make sure it has the Postmaster General’s seal of approval. If you want to make your own mailbox, you can order plans from the USPS Engineering Department or take your own designs to the local postmaster for approval.

According to postal regulations, all curbside mailboxes must “easily accept a test gauge measuring 18 ½ inches long by 5 inches wide by 6 inches high when inserted with the 6-inch dimension perpendicular to the mailbox floor.”

Otherwise, the minimum and maximum measurements are as follows:

  • Length: 18 9/16 to 22 13/16 inches
  • Width: 6 ¼ to 11 inches
  • Height: 6 to 15 inches

When installing your mailbox at the roadside, use a stable support that will yield or bend if hit by a vehicle. Avoid using concrete or brick pillars or heavy metal posts. The Federal Highway Administration recommends a 4x4-inch wooden post or a 2-inch steel or aluminum pipe, buried no more than 24 inches into the ground. Install the mailbox on the same side of the road as your adjacent neighbors’ boxes. If you’re moving into a new subdivision and there are no other boxes installed yet, check with your local postmaster for placement.

Steps to Replacing a Mailbox and Post:

  1. Before doing any digging, dial 811 to call your local utility locating service to mark underground pipes and wires.
  2. Use post hole diggers to dig a hole 2 feet deep.
  3. Cut the 4x4 post to 4 feet long. Insert two feet into the mailbox post and leave two feet exposed.
  4. Attach the mailbox post to the pressure-treated post using the supplied lag screws and the socket wrench.
  5. Attach the mailbox to the post with the supplied screws.
  6. Position the box so the mail carrier can reach it from inside the vehicle. Set the face of the mailbox 6-8” from the edge of the road and 41-45” higher than the road. If you live where there are no raised curbs, consult with your local postmaster.
  7. Put your house or apartment number on the side of the box, using numbers at least 1-inch tall, so the mail carrier will easily see it when approaching.
  8. If your box is on a street different from your address, put your full address on the side of the box.
  9. Mix the concrete with water in the wheelbarrow.
  10. Hold the mailbox in place and fill around the post in the hole with concrete. Keep the concrete 4” from the surface.
  11. Fill the remainder of the hole with topsoil.

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Tips for Installing Door Slots and Wall Mailboxes

In areas where mail carriers deliver the mail on foot, door slots or wall-mounted boxes are used. For these, the standards are different.

Door slots should measure a minimum of 1 ½ x 7 inches with the bottom of the slot at least 30 inches above the floor. Horizontal slots require a flap hinged at the top and the flaps must swing inward.

A hood over the slot on the interior of the door prevents people from seeing into your home. If you choose to install a hood on a horizontal slot, it shouldn’t project more than 2 1/16 inches beyond the inside of the door. You can find USPS mailbox standards, including those for vertical mail slots, here.

Can You Lock Your Mailbox?

Mail theft is a growing concern in urban and suburban settings alike. If you want the peace of mind a locking mailbox affords, there are a few things to know. Your mail carrier cannot accept a key to your box. So, choose a style that allows them to still deliver your mail. Also, make sure the slot in the box is at least 1.75 inches high by 10 inches wide to accommodate a large volume of mail and the various sized packages you want to secure.

If a locking mailbox isn’t an option, here are a few tips to keeping your mail safe:

  • If you’re going out of town, stop your delivery while you’re away.
  • Don’t leave packages unattended. Remain home when you’re expecting a delivery or ask a trusted neighbor to accept the package for you.
  • Set your phone to receive notifications when packages from retailers like Amazon are delivered.
  • If you have a home security system, set your camera to capture activity at your door and mailbox. If you don’t already have a security camera, consider installing one.
  • Sign up for Informed Delivery. This service sends you notifications each day with photographs of every piece of mail left at your address.

Mailbox Maintenance

Each spring, check your mailbox for damage and wear. Tighten loose hinges and parts. Make sure the post is sturdy and the door closes tightly to protect your mail from rain. Replace any missing numbers or letters and repaint if rust is apparent. Also, periodically check your mailbox for offensive creatures like spiders, ants, or wasps. And always be sure to keep the path to your mailbox clear for your carrier’s ease of access.