Not sure where you're located, but the US post office provides free LP-shaped boxes when you ship via Priority mail. I've also constructed my own LP mailiers in the past by cutting and folding larger cardboard boxes down to LP size.

American_Nightmare, July 24, 2003; 9:42 PM

If it's an open lp, remove the vinyl and sleeve from the jacket. Place both jacket and lp with paper sleeve in a plastic outer jacket/sleeve. This protects the lp jacket from damage during shipping(the vinyl will tear the seams as it shifts around)

fswric, July 24, 2003; 9:42 PM