No, but it is to take their mail or read it. Added: The legal terminology is "TAMPER WITH." Therefore, if your "touch" goes beyond the mere casual placing of your fingertips on the exterior, such as opening it, and it is NOT your mailbox, you have 'tampered' with it.
a rural mailbox is just a mailbox that is attached to a post, so the mailman can just drive up, deliver mail, and drive away. the mailbox will generally have the family's last name and house number on it.
yes Added: Actually it would constitute TWO offenses. (1) It is against the law to threaten someone and, (2) it is against federal law to deposit anything, except mail, in a mailbox intended for the receipt of US Mail.