The FAQ doesn’t explicitly state postal services, but it’s at the business center (bolding mine):
Our Business Center, located in the main terminal on the second level, in the hallway leading to Concourse B, provides a variety of useful services for the business traveler. There, you may purchase travelers checks, phone cards, travel insurance, money transfers, and money orders. In addition, you may exchange hundreds of currencies, hire a notary, make copies, send a fax, or check email at the internet kiosks. U.S. mail and FedEx drop-offs are also located at the Business Center; however, there are no shipping or postage services offered. The Business Center is open Monday to Friday, 7 a.m. to 7 p.m., and Saturday and Sunday, 9 a.m. to 5 p.m.
The Terminal Map is somewhat useful here; it’s next to Beaches as you’re going to Terminal B and is marked as the currency exchange.
Robert Confirms it’s pre-security before the Terminal B security checkpoint.
Last updated 19 August 2018