According to a reference list - published 1927 - from the German company Mix & Genest AG, Abteilung Rohrpost und Förderanlagen in Berlin-Schöneberg, the Italian city of Milan had access to a Pneumatic Tube Mail system with 6 stations and a tube length of 10 kilometers.
Reference list Mix & Genest - June 1927First Day Cover Posta Pneumatica Milan 15 March 1966
Pneumatic Tube, Rohrpost, Buizenpost