If those letters are addressed to you personaly, and if you don't have a return address, and if you don't like the letters that you are receiving. What i often do if i know the post mark, or even if there is an address on the back of the envelope, you can do several things. 1. cover your name and address, write on the envelope back and front, 2. iether return to sender, or not known at this address send no more, written in Large Bold RED. 3. Moved away. Just treat as unsolicited mail, and put into you local letter/mail box. 4. Just wait  and collect a big bundle of them, do the above and put into your local mail box. this will be sure to PEE the other party right off. But, be sure that you DO NOT OPEN THEM. On the other hand you could arrange for your local sorting office to stop these letters, but that will cost money, probably quite a lot, and it isn't worth it, unless they are threatening letters, but then you would just report it to your police station. If you do any of 1 to 4, then that would probably do the trick, as it costs them money and not yourself. I hope i have been of some help. Good luck.