I tried to reuse one of those boxes last year. If memory serves, I covered everything that said "Priority Mail" with an opaque white label. Then when I got to the post office, they said it couldn't go that way because the blue stripe around the box still showed, and that's how the handlers sort things out. What a bunch of hogwash! I wonder what they do when a box comes through that has any old blue stripe on it. Anyway, somebody there helped me completely cover the blue stripe with more labels, and off it went. It made it to its destination alright.