We're getting evicted from our house and we keep getting letters to us and our old landlord, what should we do?

Our landlord lost our house to a forclosure. We were suppose to be out after 90 days, but have had problems getting a new place since. Now we are getting evicted. I now we are dumb for waiting so long to leave, so I don't need people telling me that because I know!! My question is that the lawyers for the bank evicting and the courthouse itself keep sending letters to myself, my gf, and my old landlord. I have never opened my old landlords letters, but I have returned them to the post office, but they keep coming back to the house. I am leaving the house for good tomorrow, what should I do with the letters that are marked for him? Can I somehow get in trouble for all of this?