The FAQ notes that, “A U.S. Post Office mailbox is located outside bag claim in the lower level of Terminal 2.”
The terminal map link seems to corroborate this; they locate it outside between “Charter Services” and the smoking area.
Note that there are no mail drops in Terminal 1, the terminal that serves Southwest Airlines. You must cross the huge parking structure and lots to move between the terminals, or use an inter-terminal bus if there is one. Moving between terminals might take a little bit of time to do.
Robert emailed on 9/8/2017 to first notify me that a mailbox was located, “Curbside ground level outside baggage claim in front of terminal 2.” Thanks Robert!
Last Updated 2 November 2017