When installing a mailbox, residents need to look at a few issues before selecting a location. The safety and convenience of both the mail carrier and the patron must be addressed. A mailbox should not be installed where a person will have to walk along the shoulder of a road for more than 200 feet. The mailbox should also be located in an area visible to motorists, but should not be placed too close to the roadway or the usable shoulder.

It should be placed on the right side of the road in the direction that the postal employee is traveling and on the far side of the patron’s driveway.

Height Standards

The U.S. Postal Service has regulations for mailboxes and mailbox height. It does not have any regulations regarding mailbox installation. The U.S. Postal Service only approves certain mailbox types and requires that the bottom of the box be 42 to 48 inches above the ground. This height is at windshield level and is the main reason for having the mailbox firmly attached to the post. A mailbox that becomes unattached can break through the windshield of a vehicle and possibly injure the occupants.

Weight Standards

The mailbox should be approved by the U.S. Postal Service and should be as lightweight as possible. No more than two mailboxes should be fastened to the same support, and a distance equal to three-quarters the height of the mailbox should be left as a space between the boxes. The mailbox should be attached to the support firmly to prevent it from coming off and possibly injuring motorists and residents.

Support Systems

Improper support systems, such as concrete or sand-filled containers, and thick metal pipes can be hazards to motorists. Supports should be made of lightweight materials that will easily break away. If metal pipes are used, the pipe should not have a diameter greater than two inches. Wood posts should not be greater than four inches square or have a diameter of more than four and one-half inches.

The post should not be more than 24 inches into the ground and should not be set in concrete. By following these guidelines, the mailbox post will either break or be moved rather than be a safety hazard for motorists and residents.


Before installing a mailbox, residents should contact the local permit department to determine if there are any mailbox ordinances in their community. The American Association of State Highway and Transportation Officials (AASHTO) has published a guide for mailbox location and assembly titled, A Guide For Erecting Mailboxes on Highways. AASHTO can be contacted at:
American Association of State Highway and Transportation Officials
Suite 225
444 North Capitol Street, NW
Washington, D.C. 20001
(202) 624-5800