There's a mailbox that belongs to someone and I'm going to back into it.
For what reason would you back into their mailbox?
They hit my mailbox before and I want revenge on them.
Even though you're angry, it's wrong to destroy property. Rather, you should speak to your neighbor and let them know they should pay for your mailbox repairs and that they should be more careful in the future.
I'd rather hit their mailbox and they won't ask me about it because they won't know I did it.
What your neighbor did was wrong and your anger is valid, but damaging their mailbox is wrong and you could face legal and financial repercussions if you go through with this. You can't guarantee that you won't get caught, not to mention it's a bit petty.