I really dislike the amount of misinformation that goes around the forum regarding this. I sent mine via xpresspost to the non-PO Box address. This is a courier service provided by Canada post. It has tracking, and has the option to be signed for.
Just because something is being sent via "Canada Post' doesn't mean it should be sent to the PO Box. You would only send to the PO box for normal/letter mail/non-tracked/non-signed.