Originally Posted by
A318neo
Some are run by airport volunteers and are marked that they are not official post office boxes. It's possible that the JFK one is no longer collected. They should weld the slot shut if that's true. I wouldn't chance it.
If you want to use that mail slot a lot, you could mail yourself a post card or letter and see. It would only be worthwhile if you travel to JFK often. An alternative is for you to mail something that you anticipate getting a response and can resend it.
I was surprised to see the slot. On the day I saw the slot (it is NOT a mailbox), I was returning a NETFLIX Red Mailer envelope and needed an on street mailbox which I did find--though the JFK slot would have been more convenient...had I known it existed.
PS: Even though we all know how efficient TSA is in finding explosives

, the removal of mailing drops in airports after security was to prevent a terrorist from detonating a bomb in a mailbox.