I'd get a locking metal mailbox.

When I was a kid the mail was delivered through a slot with a flap in the front door.

If your area had curbside mailboxes, I'd talk to the post office about how to get a locking metal delivery box.

Kids like to hit my mailbox. Recently I had to straighten it out a bit. A few years ago I had a plastic box and they kept tearing the door off of it, then sail it away. I would find it in the yard next door. Kids come and go and some grow up. If you tell the police about this they make extra rounds in your area watching for this and other mischief.

In the UK we very few people have mail boxes, for the greater part mail is dropped into your house through a postal flap, ( like a cat flap ) in your front door.

It makes it very hard to steal mail, though we did have a criminal fashion for putting nasty things like dog dirt, and even worse petrol, though the flap, but that fashion seems to have died now. In part because someone designed an inner fireproof box with drains to the outside, so that any liquid poured in just splashes onto the criminals feet, and if they intended arson, when the strike the match, they can go up in flames, but the house is safe.

My mom's mailbox kept getting exploded by kids tossing in cherry bombs from their car. My brother bought 2 mailboxes so one fit inside the other with about 2" all around, and filled the space with concrete.
Then he jury-rigged a very flimsy door.....explosions Do Not like to be contained......

My mail was stolen. Then I began getting bills from stores in three counties. I notified the police and postmaster. Got a locked mailbox.

The thief didn't know who he was dealing with. He used the name "Kevin Miller" and my address. When I got a bill for Kevin Miller, I didn't open it. On the envelope, I wrote the case number, detective's name and phone number and "return to sender."

Eventually WalMart got tired of it. They had him arrested at the checkout stand.

The thief was 31. In his apartment, police found machines to make checks, drivers licenses and credit cards. And thousands of fake checks using bank accounts of people in three counties.

He was convicted of identity theft for the third time. The prosecutor used my documentation. SLAM DUNK.

He was sentenced to life in prison under the "Three Strikes and You're Out" law. (NOTE: This law was thrown out later. I didn't follow his case after that.)

I don't feel the least bit sorry for the jerk. If he ruined his clothes, that's all on him!