Maybe this will help too. I only use the bubble wrap manila style envelopes to mail in. I also tape the end closed so as not to open.
The ones that have the fall-apart-in-your-hands junk make-you-sneeze liner are just awful to open, takes very little to rip them open, and I hate the mess when I open them. I always put fabric in a baggie, but now will also put my address or the receivers address because that way it will get to them.