my grandpa had the same problem and he is a stuborn hardass. He dug a 1 ft square hole 3 ft deep and filled it with cement. Then inserted a steel 1/4 in 4x4 post in it. Then welded a 1/2 in steel plate on top and put the smallest mailbox on it ive ever seen. The actual mailbox is about a foot long but only four in tall, which would make it very hard to hit it and no steel. my grandpa has shown me three broken baseball bats he has found in his yard, two wood and one aluminum. It seems to be very effective. lol