Any air breathing salamander (no gills) can be shipped overnight in small plastic deli containers with a few air holes, lined with moist paper towel or sphagnum moss. The container(s) is placed in a shipping box filled with packing material such as crumpled newspaper or styrofoam "peanuts". I prefer newspaper. If the weather is warm out, either at the sending and/or receiving location, then ice packs should be included in the box as well. It is best to ship when the temps are under 80 F, with cooler temps being preferable. You should make sure that the receiver is at home (or at least someone is) when the box arrives so that it will not have to sit outside. Some shipping services may even require this. All in all I prefer not to ship or receive salamanders during the summer months, although I have received several shipments of various Tylototriton species this summer with no apparent ill effects to the animals. You should definitely not even consider shipping during extreme heat, such as the recent wave that has affected much of the US. Maybe Michael Shrom could chime in with his thoughts.
Chip