Is it illegal to put flyers or business cards in mailboxes?

Yes. In the United States, federal law (Title 18, Section 1708) prohibits placing any unstamped material inside a mailbox. Mailboxes are reserved for USPS mail, and that applies to flyers, business cards, menus, and any other printed marketing piece.

• What is off limits: anything without postage tucked into, on top of, or hung from a residential or business mailbox.
• The risk: violations can carry fines assessed per item, which adds up fast on a large drop.

Legal distribution methods that reach the same doors include:

• Door hangers placed on the doorknob.
• Hand-to-hand distribution at events or storefronts.
• Direct mail sent through USPS with proper postage.