In the small mountain town I grew up in in the US, we didn’t have home mail delivery (they still don’t) because of too much snow not being compatible with mailboxes.
I live where this isn’t a problem, but I know folks who lose mailboxes to plowing. If I lived there, I’d mount the box on a simple farm gate, hinged five or six feet from the road. The hinge would lean toward the road, so gravity would swing the box back to the road. The plowing would brush back the box, but not break it. The box would be out of service for a few days, but when the snow melts, it swings right back into place.
This thread reminded me of an old friend whose mailbox was repeatedly knocked down (by cars, not plows) due to a combination of lousy road planning and poor road maintenance. He eventually decided he had had enough. He mounted a new box on a piece of pipe buried in concrete. The mailbox still got hit, but he was happy knowing that the cars were worse off than the mailbox. AFAIK he never suffered any repercussions.
ETA: thanks to Chimera for the memories! 
you’re in minnesota, where they have REAL snow.
down here in central indiana if we got as much snow as you guys get up there, the whole damn state would shut down. talk about wimps…
I have a suggestion for all of you. I have seen a box that was mounted on an 8" or so I-beam post which was welded to a large and heavy wheel. I bet that sucker weighs 300 pounds. Big enough to resist most attempts at abuse, but would just slide out of the way if hit by a plow.