Here is another interesting looking letterbox which I came across recently. It is original and shows two birds which resemble pigeons and one of the birds is carrying an envelope in its beak. I suppose it is an old take on the role of carrier pigeons which were used to carry messages.
"A carrier pigeon is a homing pigeon (specifically a domesticated rock pigeon, Columba livia) that is used to carry messages. Using pigeons to carry messages is generally called "pigeon post". Most homing or racing type varieties are used to carry messages. There is no specific breed actually called "carrier pigeon". Carrier pigeons that are the basic Racing Homer were used to carry messages in World War I and World War II." http://en.wikipedia.org/wiki/Carrier_pigeon