postbox

/ˈpoʊstˌbɑks/
noun
  1. A public container, often on a street or in a wall, where letters and small packages are deposited for collection and delivery by the postal service.
    • I dropped my letter in the red postbox on the corner before the last collection time.
    • She painted the old postbox a bright blue to match the town's new color scheme.
    • The postbox outside the library is emptied every weekday at noon.