The predecessor to email was the pneumatic tube system. This was how messages were send quickly from one end of a building to the other. You've used one of these systems at the bank drive-through but the one in Building 41 required 3 miles of steel tubing. By August 1951, it connected 21 departments, which meant there were 42 tubes coming into the central station on the mezzanine. I remember in the early 1980s looking into this room in amazement at the engineering this system required. A connection was even added in Building 259, which opened in 1982. Control used to send out hand-signed lot dispositions to Planning using it. As electronic systems advanced during the 1980s the tube system became redundant and was removed. At least one of the plastic and leather carriers survives in the collection of John Shabushnig.  There was also a pneumatic tube system in the Downtown Kalamazoo complex (last two photos below).