What happens if something is mailed to an address that doesn't exist?

Question

KickBack?

If there is no return address?

Answer 1

If there is a return address, it will be sent back. If no return address, it stays at the post office.

Answer 2

if there is no return address then it will be sent back to the post office and thrown away.

Unless the mail deliverer knows the name (if its someone on their  route and they can deliver it that way.