That’s a strange one to be on that list, being in North America and all.
Newfoundlanders hate strange delivery people using their ports.
I actually looked up some info and got some other info from some WWII sites and up until 1943 it was possible to pass letters from Western Allied countries to Axis countries and back. It went through neutral countries and they all were heavily censored. None of the letters was assured of getting through.
I still haven’t been able to find anything about Russian to Axis countries