I've been in my house for about two years and still get mail for the old residents some times. They're still friends with some of the neighbors so we always pass it on that way, but turns out I actually should have been doing this... since it is a federal offense to open or throw away someone else's mail, you should either write "return to sender" or "no longer at this address" then mark out the bar codes and drop it back in the mail. It will come up undeliverable and have to be hand inspected so they will see the issue. Plus, make sure if you move you fill out a change of address form so this doesn't happen to the people who move in after you. Watch the video below to see more.