Sounds like a BIG FAT scam to me with a PO Bx no less!I'd email them back and ask them to see a copy of the vet records and they could be forged too. So I'd then call 411 and see if that is a real vet and ask them.
There are so many scammers out there! I guess they think we are all sitting around smoking crack and are all stupid.People are just so mean with these scams. If you found out its a scam you could in return call or write the post master in that town. I guess I have to much time on my hands. I'm always hunting down scammers it just pisses me off.  
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(¸.·´ (¸ ;.♥·'.♥ Teri
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