I've always used tons of the shipping supplies that the USPS offers for free on their website, and it surely has saved me money and gotten them more business. I usually try to only use the stuff for what it is meant for, as the boxes say something along the lines of "this is property of the USPS and may only be used for shipping priority/EMS mail and it may be against the law to use these for something else."

It's pretty vague and I've always wondered what exactly the story was regarding this issue. Today I did lots of searching on usps.com, google, and here, yet I couldn't find any more information. They seem to really care about it because all of the newer items are plastered with even more "PRIORITY MAIL" text on them. Only the bigger boxes aren't labeled on the inside.

Is it only illegal to use this stuff to ship items outside of the USPS via UPS/DHL/FedEx, etc? Or would fliping a priority box inside out and sending parcel be "illegal" as well?

One nice thing is that the flat rate boxes that are sized very nicely can still be shipped inside out via priority without violating anything the box says.

Anyone have more insight as to all of this?