From the U.S. Postal Inspector’s website:
“Mailboxes are considered federal property, and federal law (Title 18, United States Code, Section 1705), makes it a crime to vandalize them (or to injure, deface or destroy any mail deposited in them). Violators can be fined up to $250,000, or imprisoned for up to three years, for each act of vandalism.”
Source(s):
This only relates to Post Office Boxes in post offices.
When I buy a mailbox at Home Depot and plant it at the end of my driveway; that is MY personal property; not my governments.
Not that many decades ago, most people in small towns got their mail at their post office in their own post office box. I can remember ours from about 1960 or so.