Unless they are in snail mail you can ship them like fish...better yet if it is overnight or priority you can stick a dozen or so in a baggie. Just put a detox product t imes double, pack em in popcorn (don't wanna use styro or buy it? Pop some...birds will love it!) and newsprint. Send em away. They don't die in temp drops as long as it isn't extreme. Summer might pose a prob.
Prioity mail and paypal and you are less some snails.
Even I was looking for snails..I can't keep enough. My daughter has very bare tanks for her bettas (as far as live plants go) only breeeding tanks have real plants but half the buggers eat snails. And many of the tanks have botia loaches. And I am not givin up my high price apples for snacks! As it is I ended up having to but expensive ones as big as a fist to keep em safe!