I had a Japanese site verify my address by sending me a postcard by registered mail. If the postcard got delivered they presumed the address was valid, if the post office failed to deliver they knew it was fake. No need for any action on the user's end.

When they Swedish post office started their online portal back in the mid-to-late 90's they would mail your initial password home when you signed up. I guess because postal mail is all they knew?