What sort of exception?
If you have a Canadian Paypal account, you can add several "gift" addresses, but they must all be in Canada.
You cannot add an address in another country.
Sellers who ship to addresses not attached to the PP account they were paid through, forfeit their Seller Protection.
A seller may allow his customer to pay by PP, but then ship to an address that has been arranged elsewhere. Really all he has to do is address the parcel manually and stamp it. Or use stamps.com or even usps.com for a label. But he has to feel confident that the parcel will be delivered and that the customer is not scamming.
Or is the seller's email address in PP not valid?