Whoever owns your rental house has a set of mailbox keys. We give them to our renters and their mail is forwarded to our mailboxes just like the full time residents. As long as the house address is on the mail and the mailman is aware it's a rental, he puts the mail in the box for them. Since we live right next door to our rental, it's easy to transfer the mailbox keys from renter to renter. So far, none lost.