It’s on the terminal map (PDF), but labeled in English instead of a pictogram.
There is a mail drop (along with FedEx and UPS) on the second floor, pre-security, next to the Delta check-in counter. If you pass the “Hope Reflection Center” or the “Military Lounge”, you’ve wandered too far.
Robert submitted the location, which I was able to confirm via the map.
No pictures, sadly. But they have a Little Free Library!
Last updated 24 December 2018