Growing up our mailbox had the snowplow enemy. My dad fixed that by welding a metal wagon wheel onto another metal wagon wheel (forming a L shape with the wheels if you can picture). He had the wagon axel and he dug in a 55 gallon drum, sunk the axle into drum filled with concrete, mounted the wheel on the axle and put the mailbox on the vertical wheel. When it was hit it spun around. He made sure the height and distance from the road met all of the post office requirements.