I always save the cardboard sleeves for exactly that reason - I've even shipped in soft sided envelopes, and had no problems, because the knife is wrapped well enough that there's no chance of poking through.
Yeah, I use bubble mailers for knives all the time. Just need to wrap the blade in a piece of cardboard and tape it. Works great. <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />
