My order of four steelbooks from Amazon - in August this year - was posted in an oversized padded envelope. Result: all four steelbooks arrived dented and bent in multiple ways.
Replacement order was three steelbooks (one was out of stock at the time the replacement was sent) in exactly the same size padded envelope. Result: all three steelbooks were hopelessly ruined. Again
Obviously your mileage may vary. There's always a small chance that steelbooks will arrive undamaged even when sent across the Atlantic in a padded envelope. And they might use a box for shipping - another order of mine earlier this year was two Blu-rays in amaray cases and they were sent in a strong box
As Amazon's customer service always takes care of the customer, I wasn't out of pocket, but using padded envelopes for shipping steelbooks is unbelievably idiotic, especially when shipping multiple items and they can freely move about inside the envelope. Even a preschool age child soon understands that carrying several painted metal toys in a backpack is not a good idea
I did end up ordering The Fog steelbook again (that was the OOS item when my replacement order was sent) with seven other items, and finally got an undamaged copy, as they probably don't have padded envelopes big enough for eight items
Still thinking about ordering new copies of the other three damaged steelbooks as part of an order that would have enough items to guarantee (well, hopefully) shipping in a box.
Amazon US sure takes waiting for steelbook shipments to arrive on a whole new level of excitement
Leaving packaging feedback doesn't seem to make any difference. Nevertheless, I leave it every time.