The 20mm letter thickness is a mechanical limit. The automated letter sort machines can only take a certain thickness. These machines read the envelope address and sort it accordingly down the correct chutes for each mail centre. If letters were semi hand sorted like parcels the cost and delivery time frame would be even higher.


You cannot expect much for a dollar these days and if you can exploit the large letters category, you are still way ahead of the parcel pricing.

Throw on a Priority sticker for extra 50 cents and the letter will reach the buyer faster than a parcel will.