The official site mentions a mailbox and a FedEx drop, “Between Southwest and American signs outside the main terminal”.
There are no mail facilities at the South terminal.
Robert emailed on 9/12/2017 stating that there is a mail drop, “Curbside second level in front of American Airlines ticket counter”.
A Google Maps search tells me where the FedEx box is, and a satellite image doesn’t appear with it. So note that it is outside around where the FedEx box is, and be mindful to not post items for USPS in the FedEx box.
Last Updated 2 November 2017