The mail chute is typically a thin shaft going from the top floor of a building to a box in the
lobby, or street floor. Tenants/workers on each floor would simply toss their mail into the slot on their floor, where it would (one would hope) drop to the lobby box. Chutes can become congested; e.g., 40,000 pieces of mail were stuck in the 50-floor
McGraw-Hill Building. To dislodge it, they had to remove cinder blocks.
It was invented in 1883 by James G. Cutler, an architect, and later, the mayor of Rochester, N.Y.. The Cutler Manufacturing Co. installed 1,600 chutes worldwide by 1905. The Chrysler and old RCA buildings in New York have shut down their chutes, as has Chicago's John Hancock Center, owing mainly to the increase of mail rooms; however, there are more than 900 active chutes in Manhattan and the Bronx, as well as 360 buildings in Chicago.
The National Fire Protection Association has banned mail chutes in new buildings since 1997.
props to the WSJ