Paypal verifies a user's physical address by comparing it with the address provided by their linked credit card. The transaction's payment screen will list the buyer's address as CONFIRMED or UNCONFIRMED.
If you mean email address, then I don't know.
Pretty much. Remember though that if you sell your phone to someone out of america, they probably won't have a confirmed paypal address.
If the buyer does not have a "confirmed" address, it is really not a big deal. If the buyer files a claim with Paypal that they never received the item, and it was shipped to an unconfirmed address, Paypal might not mediate in your favor. Get the buyer to send you an email stating where to ship, then have a way to track the shipment and confirm delivery. That email and tracking record will help with any future mediation (should it become necessary).
I know this is slightly offtopic, but is another Paypal issue. I wonder why it takes so many days to clear funds paid to someones account
https://www.paypal.com/us/verified/pal=stevejobs@apple.com
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