What's the rule these days when your mailbox setup is so stout that when something hits it (be it a car or snowplow) that your mailbox holds up but destroys whatever hit it?
Since most mailboxes are in the right-of-way of the road, I didn't think they were allowed to be so stout.
I think it depends on what kind of road it is on, or at least it does in Texas.
Years ago, after my M-I-L had 3 boxes "hit out of the park", I built her a new setup. It was 2 boxes, one inside the other, and the space in between filled with 150 pounds of concrete, all set on a 6" square cedar post sunk 4 feet in the ground and cemented in place.
It defied everything and everybody for over 10 years. Everybody that is except the Texas Department of Transportation. When her little road was redesignated from a county road to a state road, the first thing that TxDOT did was remove her mailbox (it took 3 men and a backhoe) and replace it with one of their mandated break away type. We're now on the 5th one. The trash pick-up guy clips it at least once a year.