Don't talk nonsense if you don't even know what courier is. What was the specific instruction that cic gave that disproves what I said?
When cic says send by Canada post to a po box, obviously there will be no receipt signature because it's not delivered to a person, it's delivered to a PO BOX. Do you know what a PO box is? Courier includes xpress post, dhl, FedEx etc, anything that is different from regular mail features I.e speed, signature, tracking etc. Canada post is the only one that delivers regular mail in Canada. Cic will not send it back to you courier except by xpress post.
Now, if you don't know stuff, then watch your mouth and don't come here talking nonsense.