Well if the USPS is looking for a way to save some money and improve their bottom line, how about doing away with mule mail delivery? Yes, I said mules.
According to the Fun Facts section of the USPS website: "Most Unusual Delivery Method -- mule trains in Arizona. Each mule carries about 130 pounds of mail, food, supplies and furniture down the 8-mile trail to the Havasupai Indians at the bottom of the Grand Canyon, averaging 41,000 pounds per week."
I'd like to suggest retiring the mules, attaching all deliverables to parachutes and dropping the items in. They could supply the Havasupai with postal rockets to send them back up for the next delivery. After all, one doesn't have to feed and board parachutes and rockets: Voila, money saved!
Aside from missile and mule mail, there are other strange ways that the U.S. mail has been delivered. Check out 10 of the strangest at Popular Mechanics' Ten Geeky Ways to Deliver Mail: U.S. Postal Service Technology.