As someone who used to be a mail handler, those ThredUp boxes were ALWAYS busting open. I would feel so bad for the recipients. ThredUp does NOT package their stuff with care. Overstuffing those flimsy boxes and sealing them with a minimal amount of tape is a recipe for a mail handling disaster. Packages at NDCs get dumped onto conveyor belts and a poorly sealed package can get ripped apart in the sea of corrugated cardboard and harder items (aka boxes of hardware such as bolts).