A dearly departed member of one of my e-mail lists reported that years ago, an ancestor of his received a package from OVERSEAS that was addressed thus (I’ll give the real name since everyone involved is long dead):
ISSERLIS [the person’s surname]
ENGLAND
“I’m sorry Mr. and Mrs. Doe, but I have to object. You’re free to call your children whatever you like, but I think naming your son John is just going to lead to problems.”
Some people out there seem to relish teasing the post office by doing things like that. Playboy knew they had national recognition when a letter to them arrive addressed solely with their rabbit head logo.
I used to be able to send letters to a friend who lived in a small town in northern NH by just putting the ZIP Code on the envelope, no name or other identifying information. The post office knew that anything really odd was for Nelson.
Anyone remember the USPS commercial (I may be misremembering details but not the punchline) with a bunch of envelopes talking about where they were headed, but there was one cocky envelope that had no ZIP code, who got dropped through a trapdoor, and one of the other letters lamented, “There he goes…off to the no-ZIP sorting bin.”
Anyone? Anyone?
I still remember some of the envelopes the old Games magazine used to feature, sent by their readers. Very creative addressing and the USPS delivered them just fine.
The post offices of most civilized countries pride themselves on delivering absolutely every piece of mail for which it’s at all humanly possible to determine the intended recipient. That doesn’t mean that they like it, though, and it also doesn’t mean that it’s fast.
Including the street, city and zip code probably has something to do with redundancy.
So why do I sometimes get multiple cities listed for a single 5-digit ZIP code when I am trying to prepare a shipping label on FedEx’s website?
There can be more than one acceptable place name (although only one will be preferred), but they’re all for the entire ZIP code. “Anywhere, ST 99999” and “Anyplace, ST 99999” mean the same thing.
Zip codes were originally specific to post offices, not cities.
For example, in the "W"s northeast of Cleveland
Willowick, OH has a post office on E 312th St. and a zip code of 44095.
Willoughby, OH has a post office on Erie St and Zip code of 44094.
Wickliffe, OH has a post office on Lloyd Rd. and a Zip code of 44092.
(Adjacent cities are Willoughy Hills and Waite Hill, but they are not germane to this example except that Willoughby Hills is also served by two post offices, 44092 and 44094.)
However, Willowick has a rather twisty set of borders and there are houses in the city of Willowick that are served by either the Willoughby or Wickliffe Post Offices, thus a Zip code of 44094 may be delivered to either Willoughby or Willowick while a Zip code of 44092 may be delivered to either Wickliffe or Willowick.
In recent years, with financial pressures placed on the USPS, even the “Zip Code = Post Office” rule has lost its firm stance. The Chagrin Falls Post Office, Zip Code 44022, originally handled mail for Chagrin Falls, (in Cuyahoga County) as well as South Russell Village, Bainbridge Township, and Auburn Township (in Geauga County). Twenty years ago, or so, a new post office “annex” was built to serve the two townships and assigned the Zip Code 44023. (The mailing city name for the two townships remained Chagrin Falls, as there is an actual village of Bainbridge in south central Ohio and two other Auburn Townships in the state.) Recently, that “annex” was closed under financial pressures, but the Zip Codes for those locations has not reverted to 44022, so one Post Office now has two Zip Codes.
I get annoyed when the credit card phone support person asks for my address WITH zip code as an ‘authentication measure’.
Me: “xxxx X. XXX Ave, Chicago”
Them: “I need the state and zip code for authentication”
They might as well be asking for my time zone. They have the address and city. There’s only one state and there’s only one zip for that address. What kind of thief scammer has my credit card number, name, address and city but NOT the zip code and state?!?
I use the Zip as a shortcut when writing a return address, because it’s less likely to be needed.
Example:
Jones
1234 Road X
90210
I think they could figure it out.
And we nee redundancy because people are stupid. I mean, half of them are below average!
Zip codes are computer friendly, cities and street addresses are not. If the address associated with your credit card is 123 Main St. Apt 4, Saint Louis, MO, a computer may not match it with 123 Main Street, #4, St. Louis, MO.
They want to verify that you know the zip code. As a security measure against stolen or found cards.
The medical term for that is diphallia.
I read long ago in Games that the post office told them that they just delivered any wacky envelopes to the Games offices. 
It never would have occurred to me that the US Postal Service prides itself on anything.
If it’s an apartment complex you’d still need someway to reference the z-axis. Floor number, distance from a reference point (not counting the first two you already gave, perpendicular feet from the ground directly below would be nice), upper/lower designation if it only has two levels etc.