I shipped shrimp from Phoenix for several years. Get some Styrofoam insulation and insulate the boxes. Then just drop them off at the post office. The biggest danger usually seems to be when the post office tries to deliver the packages and they sit in their hot truck. Neos are pretty heat tolerant so they should be fine. Also if you are shipping to someplace with high temps try to get the seller to go the PO to pick up the shrimp so they don't sit in a hot car.