Postal communication in the General Government

Postal communication in the General Government, previously provided by the Polish Post (Poczta Polska), were taken over by the German postal service (Reichspost) after the invasion of Poland and the establishment of the General Government in 1939, and then in 1941 in additional areas of eastern Poland. The laws and regulations that governed postal communication varied widely, depending on which group an individual belonged to, as well as where the individual was located.

Source: Wikipedia — Postal communication in the General Government (CC BY-SA 4.0)