Ben , thank you for all the input, it is very educating.
so you got unlucky
well, I’m still not quite sure if the “system” has decided that my home address under the “Return to” was the “Send to” address. Because in this case it would mean that the “system” has granted me a free delivery from an unknown sender and why would it do that?
It looks more like it tried to figure out a “send to” block, failed, gave up, desided that even a mighty Human would not be able to help in such a critical situation and simply has returned the letter back perfectly knowing what does “Return to” mean.
But to be completely honest, I don’t really care one way or another. What is imprtant is you do X and you might have Y in result, which I wanted folk to be aware of.