Mail Trains On Worldwide Picture Postcards

Hi Everyone,

I would like to start this thread where you can post your cards used or not , that have mail trains or TPO wagons or even only marked wagons that carry mail.
I am not really sure if mail trains still operate anywhere in the world but I know that they did in past, at least mainly mail carrying trains.
I have only two such postcards and am startig the thread with this Sudan card from the 50s.
It was posted in Khartoum with a single stamp as Airmail to Yugoslavia

I am looking forward to seeing your examples.