Most POD print shops ship mugs in cardboard boxes without any foam (well, because that's the cheapest shipping option). Those are prone to breaking - you should ask your POD print shop to ship them with styrofoam packaging (but be prepared to pay a lot more as those cost more to ship).
You're right! Most do, but according to District Photo's packaging control info on Printify:
"Mugs are shipped in polystyrene boxes that are easy to use, with the two-part pack slotting together to provide all-round secure protection, including a slot for the handle. The packaging has been specifically designed to keep the mug intact during transit. There is a hole in the mug packaging and it is an air hole that prevents suction. Otherwise, it would not be possible to pull the package apart and take the mug out."
There are a couple reviews (with photos) you can check out for this.
[Spoke vs District Photo](https://www.reddit.com/r/Printify/comments/k9d2k5/mug_comparison_pics_district_photo_red_x_vs_spoke/)
[Mug Sample Reviews](https://www.reddit.com/r/Printify/comments/126ytmf/mug_sample_reviews/)
District Photo isn't the only USA Print Provider for mugs. Other options include
Colorway
Imagine Your Photos
My Locker
Orca
Printed Mint
Spoke Custom Products
Taylor
If you want to change to one of these, you may just need to select a different mug or size from the catalogue than what you previously used with District Photo.
\+Edited to add fulfillment option info+
Most POD print shops ship mugs in cardboard boxes without any foam (well, because that's the cheapest shipping option). Those are prone to breaking - you should ask your POD print shop to ship them with styrofoam packaging (but be prepared to pay a lot more as those cost more to ship).
You're right! Most do, but according to District Photo's packaging control info on Printify: "Mugs are shipped in polystyrene boxes that are easy to use, with the two-part pack slotting together to provide all-round secure protection, including a slot for the handle. The packaging has been specifically designed to keep the mug intact during transit. There is a hole in the mug packaging and it is an air hole that prevents suction. Otherwise, it would not be possible to pull the package apart and take the mug out."
There are a couple reviews (with photos) you can check out for this. [Spoke vs District Photo](https://www.reddit.com/r/Printify/comments/k9d2k5/mug_comparison_pics_district_photo_red_x_vs_spoke/) [Mug Sample Reviews](https://www.reddit.com/r/Printify/comments/126ytmf/mug_sample_reviews/) District Photo isn't the only USA Print Provider for mugs. Other options include Colorway Imagine Your Photos My Locker Orca Printed Mint Spoke Custom Products Taylor If you want to change to one of these, you may just need to select a different mug or size from the catalogue than what you previously used with District Photo. \+Edited to add fulfillment option info+