Had a thought during the night as you do
By the main entrances of airliners of many different companies is the Royal Mail logo, bit like a bugle hanging from a cord.
Ok we know its to state that that A/c is carrying mail.
They dont paint any other logo's to say they are carrying live animals/mod cgo/hazmat etc etc. So why just Mail?
(wonder if the reply on here will be from aviation or post office person?)