A few years back I actually worked for USPS as a walking carrier. When I say it is a tough job - I assure you...it is tough! You are constantly moving, and walking/running to get your deliveries in while your supervisor is breathing down your neck to hurry up and get done in a certain time frame.
You cannot believe the amount of mail that gets moved by just one carrier - my trucks were always filled top to bottom, front to back, and then some.
I worked when it was cold and icy outside. My fingers were constantly numb, but I had to leaf through the letters in a certain manner or else I would get in trouble. I absolutely cannot imagine doing it in the summer heat.
The work environment was harsh, unfriendly, and definitely not what I was expecting. The actual physical demand of carrying the weight of the letters and packages with you were ultimately too much for me to bear. And when I tell you I gave it a shot - I did my best. It did not last long.
That being all said - the postal service has the delivery of mail as their number one top priority above all else. I was really impressed with that. And the letters get scanned in to huge huge machinery in a central area where the do get scanned and then sorted out automatically.
To the person who said the state abbreviation was the most important part of the package - you were misinformed by that clerk. The zip code is what they most care about, though it is all important.
I was definitely not "tough enough" to be a walking carrier (which you have to begin with to work for USPS), but that was the most fascinating experience of my working career, how the system works.
I am not surprised about the Informed Delivery option, and personally like it myself. Thanks for the tips, though. Brought back some...interesting....memories of my time there!