Safco Small Wall-Mounted Mailbox with Lock in Black

Black Locking Mailbox or Locking Drop Box

tl;dr: Adding a lock yourself may not be legal, but you can buy a USPS-approved mailbox with a lock The box will need a mail slot or similar,

mailbox for door slot Mailbox is made of galvanized steel with a tough powder coat finish and features a gray body, red door and black top Incoming mail slot is covered by a steel

mailbox drop slot locked mailbox? I live in condos and that happens once in a while If I find someone else's mail, I stick it in the slot beside their mailbox