Rural mail carriers, contract carriers, even rural postmasters who carried mail to another office when it was misdelivered...we carry mail in privately owned vehicles every single day.

Edit: okay, I realized that all of us who were transporting mail in privately-owned vehicles were authorized to do so by virtue of contract or employment, and this might be the distinguishing factor

Rural mail carriers, contract carriers, even rural postmasters who carried mail to another office when it was misdelivered...we carry mail in privately owned vehicles every single day.