Dude, they do have one of the cheapest postage in the free world
Yeah yeah. It's not their fault they suck. Average salary of a mail carrier is over 50k a year, and they get paid by the hour.
Here are the steps I'd say would make a big difference:
1. Deliver regular mail M/W/F only. Have PO boxes available for those who need to get mail between those days.
2. Have an opt-in/opt-out system for junk mail. People have to go online and elect to receive junk mail.
3. Pay carriers by the route, not by the hour. Figure out the fastest pace at which a route can be done. Add 20% to that time and have that as the payable rate, then pay 15xpayablerate to start (depending on location), for that route. What do you need to be a carrier? A 3rd grade education and a driver's license, right? I don't intend that to be demeaning, but that's all there is to it. It is one of the simplest jobs in the country.
4. Carriers can go home when they finish their route.
5. Bonuses for fewer errors. Demerits for screw ups.
6. Close down all the unnecessary offices.
7. Use "cluster" mail box systems - instead of having carriers go door to door in tight neighborhood, put up cluster boxes with 100 or more boxes, and cut way down on "walking routes," which are anachronistic and inefficient.
Of course, every one of my suggestions would either eliminate union jobs or decrease the $ paid for work performed, and that is the real sticking point.
For what they do, postal workers are grossly overpaid compared to your average private sector employee doing menial labor.