Yes, it is technically illegal to attach a magnet or any other item to someone’s mailbox without permission from the United States Postal Service (USPS). According to USPS regulations, mailboxes are considered federal property, and their use is regulated by federal law. The primary purpose of a mailbox is to receive mail that has been processed through the USPS, and the regulations are intended to prevent unauthorized use of this federal property.

Under these regulations, attaching non-postage items such as magnets, flyers, signs, or decorations directly to the mailbox or its flag is prohibited. This rule is in place to ensure unobstructed access for postal carriers, to maintain the security of the mail, and to prevent the mailbox from being used for purposes other than mail delivery by the USPS.

Violating these regulations can result in various consequences, including the removal of the unauthorized items by postal workers. While enforcement may vary, and penalties for minor infractions like attaching a magnet to a mailbox are not commonly severe, it is still advisable to respect the regulations and find alternative methods for distributing materials or conveying messages.

For those looking to distribute advertising materials or communicate with residents, options like door hangers, direct mail through the USPS (with appropriate postage), or digital marketing campaigns offer legal and effective alternatives.