I keep getting mail and packages addressed to an individual who no longer lives at this address.  Today I got a fairly heavy package addressed to this individual.  Can I bring it back to the post office and tell them to stop sending stuff addressed to that individual to this address?  Until now i've just been putting all his mail in a big envelope and sending it to him and didn't care because it was only like $2 to send, but i'm not going to pay to send him this big heavy package...

You can just take it back to the post office as un wanted mail. They will ship it back to the sender at no cost to you

great, thanks for the info

We recently got a letter addressed to the previous occupants of this house.
They moved out in 1993.

Just mark on each piece that the addressee has moved & put it back in the mailbox.  There is no need to take it back to the Post Office.  The carrier will pick it up the next day.