A52split,
It all comes down to how Canada Post, a government monopoly beholden to no one, rides roughshod over their customers, the people of Canada. CP has arbitrarily divided the mail into two categories, a highly restrictive Letter category and a very broad Parcel category. Mail in the Letter category cannot exceed 500 g in weight and 20 mm in thickness and international letters may contain only "paper-based" products. Any mail piece outside these specifications is a Parcel. These regulations lead to the absurdity of the Light Packet, used for shipment of non-paper-based products outside Canada. A Light Packet is physically identical (same weight and dimension limits) to a Non-standard or Oversize Letter and is transmitted by the same means (air) but postage rates for the two differ wildly. CP treats Light and Small Packets as Parcels; the Small Packet is not available domestically. CP's regulations lead to exorbitant postage rates, especially for lightweight domestic mail.
The whole crackpot scheme is designed to squeeze money out of the poor unfortunates (us) who have no alternative to CP (because it's a monopoly).
The Universal Postal Union, the UN agency that coordinates the world's postal systems, stipulates two mail categories, Letter Post and Parcel Post. The former includes letters, postcards, printed papers, and Small Packets, up to and including 2 kg in weight. UPU directives are followed by most member nations. For example, Deutsche Post in Germany, has just 5 types of lettermail:
Postcard; Standard Letter (max wt 20 g, max thickness 5 mm); Compact Letter (50 g, 10 mm); Large Letter (500 g, max (length + width + height) 900 mm); Maxi Letter (2 kg, max (L+W+H) 900 mm). Content is immaterial. Simple and easy to understand.
Canada Post thumbs its nose at the UPU and goes its own way. We suffer for it.
Tom
