I guarantee that if I was a letter carrier I would never be bit by a dog. I would carry a racket ball racket and when they came after me, I would strain their noses off the back wall.
I got caught between the front fence and a porch when I heard a growl from behind me. It was the biggest German shepard you can imagine. I thought I was a tough guy. I pulled out the spray, aimed, and pressed the button. The liquid dribbled down my wrist. There was no pressure in the can.
I took the mail bag and swung it at the dog.
I got out..but the key is not to let them get close enough to hit.