Minnesota Statute 169.072 requires the removal of unauthorized mailbox installations, which explains the use of a wood post or small metal pipe for mailbox posts. These posts need to bend or breakaway if a vehicle hits them to decrease the likelihood of the collision causing major damage or injury to the driver or passengers. 
See Mailbox Installation Guidelines.
Unauthorized mailboxes and posts could be dangerous to the motorists on county highways. As vehicles travel, they could veer to the right and ride on the shoulder of the road. If that happens, the vehicle could hit a large mailbox or unauthorized post. The mailbox owner could become responsible for the damages and injuries that occur as a result of this collision because of the placement of an unauthorized mailbox structure. Authorized mailbox structures help to ensure the safety along the county road for the traveling public.
If you have any comments or questions, contact the Dakota County Transportation Department.
Damaged mailboxes
Dakota County will replace mailboxes with a standard size mailbox only when the box was installed at the proper height and location and when actually hit by snowplowing equipment. Dakota County will replace mailboxes damaged by snow coming off the plow when the mailbox have been installed on a swing or pivot support, according to drawings available from the Transportation Department.
For questions, please call 952-891-7900.