Postcards and letters up to 250 g including newspapers could be mailed free of charge by the German para-military and military organizations.
All German military branches had its own organic postal administration in charge of receiving and delivering mail.
For Feldpost offices closest to the combat zone a mobile facility usually processed mail for all military branches.
Eventually a series of postal agreements were set up between Germany and the occupied countries providing an extended usage of Feldpost service.
If a soldier wanted to send mail through a civil post office, full postage was collected.