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Guidelines for Installing a Mailbox

Akshay Chavan Jul 7, 2019
A mailbox owner can end up facing a lawsuit for any injuries caused to motorists in an accident, if the mailbox does not satisfy postal and state regulations. Let's see the requirements and regulations for mailbox installation, including its height, dimensions, and placement.

Did You Know?

Mailboxes account for 70 to 100 road fatalities each year in the US.
The United States Postal Service (USPS) is entrusted with making regulations for the installation and maintenance of mailboxes around the country. While this kind of trepidation over an ordinary mailbox can be surprising. Statistics reveal that a large number of road accidents (including fatalities) can be attributed to improperly installed mailboxes.
A majority of such cases are caused when boxes separate from their posts and come hurtling down at a vehicle's passenger compartment, or because of heavily-built posts that stand their ground during a collision, resulting in extensive damage to both, the vehicle as well as its occupants.
During cleanup operations in storms, snowplows also claim their share of mailboxes, when their side wings ram down boxes that hang low, sending their owners clamoring for a replacement to the local municipality. In a few rare cases, it is the snowplow operator who bears the brunt of a weakly-attached mailbox crashing through his windshield.
Very few owners are aware that if their mailbox does not satisfy USPS regulations, they can, in fact, be sued both, by motorists who received injuries as well as local authorities for any damages incurred during their snowplowing operations. Let us have a look at the related guidelines involving US mailboxes.


All postboxes available in the market should bear the local postmaster's seal. if you plan to construct one by yourself, get the plans approved by the postmaster to ensure that it meets all applicable regulations.
The mailbox should be made of plastic, aluminum, or galvanized steel, with a removable flag, and a door to shield the mail. This door should remain open, without closing by itself, when the carrier is inserting mail into it.
The box should be attached to the post in such a way that, under no circumstances, should it separate from the post when a vehicle collides with it.
The wooden support (post) for the mailbox should be made of such a material, and have dimensions such that, it should break or bend when hit by a vehicle.
The dimensions of the post should not be larger than 4" × 4" when using square wood, or more than 4" in diameter when using cylindrical wood, or have more than 2" of inner diameter when using a steel or aluminum pipe. Besides, steel pipes should not be heavier than 2 pounds per foot.
Building a post out of heavy steel, thick wood, or household and agricultural tools like milk cans filled with concrete, I-beams, plow wings, etc., is prohibited.
It is advisable to construct a cantilevered mailbox system, where a horizontal arm carrying a suspended mailbox extends perpendicular to the post. This allows for the side blade of a snow plow to clear snow under the box, without damaging it.
The mailbox should extend from the end of the post. It should be fixed with screws or double-headed nails, which permit easy removal whenever its height needs to be changed.

The post should not have an anchor flange at its bottom, but can have an anti-twist device which should not go deeper than 10" into the ground. It should not be embedded in concrete.
A post cannot have more than two mailboxes. However, fixing a lightweight newspaper box on the same side as the post and below it is allowed, as long as it does not conceal or touch the box or the house number on it, does not impede mail delivery, and does not extend further from the open door of the box.
Multiple mailboxes should not be closer than a distance equal to ¾ the height of the box. For example, two or more mailboxes installed at a height of 4 feet should be at least 3 feet away from each other.
Both sides of the mailbox should display the owner's house or apartment number, in digits at least 1" tall, and the side facing oncoming traffic should have reflecting material for easy visibility.

When the box is installed on a street away from the owner's property, his entire house address should be displayed on it.
When using a locking mailbox, it should have a horizontal slit of size 1.75" high × 10" wide, to allow delivery without folding of envelopes. If such a box has a flap, it should open inwards.

All mailboxes should satisfy the state and local regulations applicable, which may vary slightly from area to area.


The height requirement of both, suburban and rural mailboxes is between 41" - 45" from the street surface, and not the ground the post is fixed on. This allows the mail carrier to deliver mail from the truck itself, without having to alight.
The post should not be embedded deeper than 2 feet inside the ground, with the permissible depth being 18 to 24".
The front of the box should face the street, and its door, on opening, should not be closer than 6" - 8" from the curb. A greater distance is even more preferable, as it allows the carrier to pull to the side of the road for delivering mail, while allowing traffic flow to continue. If a guard rail fence is present, the box should be installed behind it.
The box should always be installed on the right side of a two-way street, to ensure that the mail carrier does not have to obstruct traffic flow while carrying out a delivery. It can be installed on the left side only on a one-way street.
There should be no impediment in reaching a mailbox, as the postal department has the authority to discontinue any future delivery to such a party.


The owner should apply protective paint to the box and the post to protect the wood from decay.

Inspection should be carried out at least once every year to spot and repair any damage.
The owner should ensure that the approach to the mailbox should not be obstructed by snow, tree overgrowth, etc. Any obstructions should be taken care of.

One should take the approval of the mail carrier when shifting a mailbox to another location.
These guidelines will ensure that your innocuous-looking mailbox does not end up injuring any motorist or knocking down a pedestrian. A mailbox that does not conform to these standards can earn you a notice from the local municipality, demanding its removal.