If I'm shipping a package with a Mercari USPS Priority mail label is it ok to use this padded envelope? I've seen lots of things about them only accepting certain types of
Shipping Supplies | USPS.com
ReadyPost 8-1/2 x 12-inch Bubble Mailers | USPS.com
6 Things You Can Ship with USPS Padded Envelopes to Save Money
Wrap It Up In ReadyPost
Can I send a nutritional supplement as a "flat" in a padded envelope? : r/ USPS