Gravity Feed Email
There's no getting away from infrastructure. You don't have to go far in a typical office before you trip over a big knot of ethernet cables or hopelessly out of date install CD's. These semi-secret information pathways have always been there, sometimes quietly clinging to the walls.
Mail drop chutes once dotted many office buildings. Instead of running to street level to find a mailbox, simply drop your letters in the slot, and they'd whisk away to a mysterious spot where they're collected and dispatched. A fine system, except when someone put in mail that was too large or folded. The chutes are often made of glass so you can see when mail is jammed in the tube. I worked in a building with a mail chute, and everyone with a desk near the chute kept a coat hanger nearby to persuade stuck mail to continue its journey.
The Cutler Mail Chute Company is long gone but you can still find mail chutes around, though many are dammed up like the one in the picture.