Feeling verbose, so I'll venture some thoughts on this- others will have more beneficial information to share.
If you want to ship legally, you will probably need to ship with one of the Airlines. US Air has always provided good service for me. It can be expensive---last time I checked, the range was from $65 to $100. US Air has two services..."PDQ", which places the animal on a passenger plane- you actually check the box in at a passenger counter. They will want to view the contents of the box, so don't tape it shut. A crowd will gather and five people will tell you their snake stories while others will consider a run for the exit...it's unavoidable. You can also ship US Air Cargo. I think the prices may vary a little bit.
Whatever you do, you will need to line the box with insulating material. I use the 3/4" styrofoam insulation board that can be purchased at Home Depot or Lowes and cut it to completely line the box (top and bottom as well). I use 40 hour heat packs, which can be purchased at some camping/outdoor stores or purchased via one of the herp supply businesses. I'd worry more about overheating a snake than letting it get cool, so don't use too many heat packs. In a 10"x10"x10" box I will use a couple of packs (possibly a third if it's really cold), and place them in the box away from direct contact with the snake. Tape the packs to the side of the shipping box and be sure to put some wadded up paper or bubble wrap in between. (I usually have snake in a bag, in a box, in the bigger shipping box. Confusing enough?)
So far, in the 20 to 25 times I've shipped, I have no horror stories to share...every snake has arrived in good shape.
There are variables involved that may make some of what I've shared null and void, but hopefully this is helpful- If you have further questions, feel free to e-mail me.
Jim
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There is therefore now no condemnation for those who are in Christ Jesus. Rom 8:1