In Germany, you usually don't hand in letters, nor does the postman collect letters at your home. You throw them into a post box on the main street, which is emptied once or twice a day. So by the time the postal worker collects the mail they don't have any means to know who posted which letter.
For really important mail you also have the option to use "Einschreiben" (registered mail) where the recipient has to sign that they received the letter.