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Pneumatic tubes were used to deliver mail!
(slrpnk.net)
You can read more about the fascinating history here: https://about.usps.com/who-we-are/postal-history/pneumatic-tubes.pdf
Credit: https://hachyderm.io/@miah
We had such a system (with only one pipe) a few decades ago in our company. Purpose was to deliver samples from the production to the laboratory. When I started in the late 90’s it was already not in use anymore. I got told that sometimes the pipe got clogged…