Joy Stratford reminded us of this little-known fact about your box at local post offices. We discovered this ourselves some years back:
Canada Post will not put (junk) mail in your box if you request a red dot. This dot is placed at the interior of the post office for the sorters to see. I have had said dot for years and have greatly reduced my household waste. I tell folk everyday as I get my mail, but my husband suggested I pass this little known fact on to you to spread.Interested people simple approach the desk and ask for a dot and offer their box number, Canada Post does not advertise this because they enjoy the funding junk mail generates.
MORE INFO: See this link from Canada Post about junk mail.