Originally posted by pxpaulx Not for a priority mail international package - that requires 4 customs forms, one for the sender, one for the post office where the package is dropped off, and one for each customs port (US and Canada in this case). If he deliberately wrote the wrong addresses, it would be denied for that reason (or should be). The proof is at the point of origin. For first class that is another story, but not priority or express international.
Well, having sent about two dozen international packages in the last year, I can tell you that whether or not they should, they certainly don't check address when you drop of the package. In my experience, they just take the 4 customs forms, stick them in the clear outer envelope, stick the forms to the package and then toss the package into the big bin in the back.
Funny side story, about a year ago I sent a battery grip to someone in Australia. Did everything online to make it easier. Well I must have been in a hurry and I selected "Austria" from the drop-down menu. So the package had the buyers corrected address, except the last line said "New South Wales, Austria". Sure enough the package ended up in Austria, not Australia. Long story shot, the PO told me it would be returned to me so I refunded the buyers money immediately. Then, a week later, the battery grip was delivered to the buyer in Australia. Apparently the customs office in Austria decided to forward it on with the corrected address, despite what the USPS told me. Anyway, makes for a funny story