If you find that another resident’s mail is consistently being placed into your mailbox (which might happen when delivery personnel change), the U.S. Postal Service recommends you do the following:
(1) Circle the address and mark it “Incorrectly Delivered”; and
(2) Place that piece of mail into the outgoing mail box.
By doing so, you will inform the Post Office of the need to correct the mistake. Simply placing the misdelivered mail inside the gate of the residence to which it should have been delivered could also cause mail to accumulate at that residence. This would signal that the residence is not occupied, and create the possibility of a security problem.