They wear uniforms around here, which often include shorts (or at least our postal worker wears them a lot. He even wears them when it's cold). But they are easy to identify as postal workers.
Our regular carrier wears a uniform and drives a mail truck. The sub mail carrier is about 19 years old, wears a big hoodie, crappy jeans and huge head phones. He scared me the first time he came to my door.
I've seen the postal truck come into our area, but we have community boxes that aren't even on our street so I haven't seen the mailperson in a long time. I have no idea if there is a uniform.
Re: Postal Workers
My mom used to be a postal carrier. If she was doing a rural route with her own car, she wore her own clothes.
Here in civilization, uniforms and mail trucks.