Alright, so in my current situation I already have a P.O box at the local post office with someone else that I live with. Its the sole way we get our mail due to living in a rural location, and is free because of this. Its actually registered under the other person's name, but I have sent my own mail to that P.O box before. Another tidbit is that my address on my ID does not match the address for that P.O box, and is not associated with the address I'm currently living at in anyway. It is in fact in another part of the city all together.
However, they do not really approve of ordering stuff from the net, so I was planning on purchasing another P.O box at the same post office, but solely under my name. I would try and get some normal packages sent to it first, and I would stay within the lines of only ordering domestically.
Considering they have seen my name on mail going to the other P.O box, would this come off as fishy to the Post office and prompt them to investigate?
I'm Canadian also and I find that a bit paranoid. I think you'll be fine so long as your not under suspicion or ordering large quantities or bulky packages from DNMs. I doubt the post office would be suspicious before having any real reason to be.