I think I can save you some time. FedEx and USPS automaticly check the validity of the address when you enter it. You just have to make sure you have that option selected if you ship via FedEx. FedEx and USPS give you the option of automatic e-mail updates so you can vigilantly track you package, automaticly.. Just have your buyers confirm the shippinng address with their payment. In the end its garbage in garbage out. If they give you a bad address, that is where the package will go. insured with delivery confirmation.