I clipped a guys mailbox when I was in high school. Same deal. Got off the road in snow and just smashed it down. I went to the guys door, left him a note waited for the call. Guy only called to thank me for leaving the note.
I used to have the same problem with the mailbox hit with baseball bats & thrown firewood. I moved the mailbox off the road about 6 more inches & moved it closer to a power pole. I haven't seen any evidence (in the past 5 years) of attempts to damage it since it is now within 4 feet of the power pole.
We used to have that happen all the time til my dad took an 8 foot section of 6" pipe, set it in 4' of concrete, and made the mail box out of 1' diameter 3/8" thick pipe! They only hit it once after that..........