It is good the sender put down the return address. It is also good the post service did a good job of returning the mail to the sender. We have a good postal service in Hong Kong.
The mail was returned to me as I had made a mistake not putting in the street number. I have mailed it out again (to the correct address).
因我錯誤沒有寫門牌號碼致信件退回給我,現已重新寄出(到正確地址)。