We have problems with that here too - and we were getting in trouble for it from the estate for having this big gouge in our lawn even though it was clearly not us making it since our driveway is on the other side of the house (corner block)! I said something to the postie and he ignored me so I had to say something to Australia Post...and they ignored me. I told the estate that it wasn't us it was the postie and that I'd spoken to him personally and Australia Post and it was still happening so if they had a problem with it take it up with AP. A week later, it stopped happening.

But if you ask politely I'm sure they wont mind.