The USPS and your regional D.O.T. has a set of guidelines for safely installing curbside mailboxes. This has been established to minimize liability for homeowners. While these guidelines are widely ignored by the public and often mail delivery persons might still deliver mail to mailboxes that ignore these guidelines, MailboxFast.com follows these directions.
The information is provided at the USPS website as well as the American Association of State Highway and Transportation Officials and can be viewed at the following links: