None! (They were originally proud of this fact.)
I was able to find a location to post letters and postcards!
There is a bank of grey CBUs on the ground level, near the concrete pillar labeled “10”. Walk outside and head towards Terminal C, ensuring that you look up to watch the numbers. Once you pass the one labeled “10”, start looking on your right for the silver boxes. There may be security nearby; show them your letter.
Make sure you use the CBU that accepts US Mail. One of them may not be an official US Mail slot. The correct one is labeled as such.
Here’s the Google Maps picture. It’s grainy, but it’s centered on the boxes (more or less).
Last updated 22 November 2021