Official Information

They have a dedicated page to their USPS drop box locations.

  • Terminal 2 between Doors 5 and 6 on the curb
  • Terminal 3 on the North Curb outside Door 5
  • Terminal 4 on the North Curb on Level 2 outside Door 21

These are very likely to be a standard USPS drop box.

Source

Last updated 9 June 2017