Tampering with a mailbox in any way is illegal, reports the United States Postal Service. Mailboxes are only intended for postage-paid mail placed inside by an authorized mail carrier. The Sunday newspaper is the only exception, which is delivered on a day that regular mail does not arrive.
It is a crime to vandalize or tear down any mail receptacle or steal or destroy any mail, according to Federal law, Title 18, U.S. Code, Section 1705, as noted by the Legal Information Institute of Cornell Law University. A person may be fined or jailed for this crime. Anyone who sees someone going from mailbox to mailbox should report the person to a U.S. Postal Inspector, says the United States Postal Service. Uninformed entrepreneurs may try to advertise this way. Nonetheless, criminals easily steal mail with this method.