In Canada, if a copyright holder notices you are downloading something they own the rights to, e.g. because you are using torrent, they cannot ask the ISP for your name or address. The only recourse they have, short of going through the expensive and lengthy court process, is that they can give the ISP a note which they are legally required to forward to the client. It's a simple system. Your privacy remains preserved and you get the messages too. Why not mandate an email forwarding service by registrars if that's what they are after?
What’s wrong with e-mail?
Some people don't check their email so a physical letter can be used as a backup.
Some people don't check their mail either
But you can send a letter with proof of reception so at least they know if you received it or not.