+1 to rfioren
Canada Post is not too kind when it comes to DC. As far as I know, the cheapest way to get DC is to use Registered Mail which is an additional $8.25 within Canada and $14.50 to the U.S.A. and internationally. That's if it's lettermail. If you use a bubble mailer, it qualifies as Oversized lettermail and tracking is simply not available. So, if DC is required that would eliminate any small trades due to cost and larger trades requiring bubble mailer don't even have the option. These rules would basically prevent me from trading.
If anyone knows otherwise, I'd love to know.
I believe the gist of the wording is that each sender is responsible for their own delivery, and the only way to prove delivery is to use delivery confirmation.