I am doing this because so many use too small a box when shipping eggs! THe 12'X12'X8" box is perfect and it's free!
You will have to set up an account with USPS, but that's free too!
Also I believe that wrapping eggs in BUBBLE WRAP is BAD since it seals off air that the egg needs. Paper towels, shredded paper is better! I personally have had better hatch rates from eggs I've bought and had mailed to me wrapped in paper!
I also believe strongly that a box BRIGHTLY MARKED IN BIG LETTERS is treated with care and respect from postal employees! (I think this is one of the reasons I have good hatch rates on eggs I ship!) Of course I write LIVE EMBRYOS on my boxes with arrows pointing up and the word up under the arrows, ect....