The Sunport has a dropbox and a couple of other courier services:
For passenger convenience, a USPS mail box, as well as a FedEx envelope and package box, are located outside the building on the east end of the ticketing level.
From the maps, this looks to be around the Southwest skycaps on the departures level (Level 2). Make sure you choose the USPS mail box for letters.
The Sunport isn’t a terribly big airport from personal experience; it probably isn’t more than a 5-8 minute walk from the terminals if you’re connecting. Just make sure to allow for a little time to re-clear security if you choose to exit the secure zone.
Last updated 15 June 2017