I am saddened by the loss.
When I ship i actually use four bands of filament tape around the box, flats, ends and sides. and then use transparent packaging tape to cover the edges and shipping label.
I also put a duplicate address inside the box. Inside the box for content protection, I use "Sill Seal," about a i/4th inch thick high density flexible foam wrapped around each item with the ends of that tube taped shut. It recovers... unlike bubble wrap which gives one save per bubble that is bumped and destroyed.
I did have more than one battered box and letter come into my place. One of which appears to have had the blade winkled out by a carrier.
Flat Rate is cheap and there is no extra charge for the weight of the safety padding and heavily taped protection. Routing info is also a real plus.
Never use an envelope or cheap padding! JMO
sill seal foam gasket Its cheap too!
Better safe than frustrated!
YMMV
~Richard
PS, if you ship liquids, wrap the cap where it joins\s the bottle with #33 electrical tape. It holds the cap and prevents leaks when the bottle is air shipped along the way.