For fun I once send a postcard to my parents from Spain to Germany without a ZIP code, without the country, misspelling the town and street, and writing "the last house on the right" (in German) as a house number.
I worked a summer as a postal carrier in the US, and I was surprised at how far off from the official address standard you can get and still get delivered.
For reference, our address standard is ## Street Name,<cr> City, State, ZIP.
There was one neighborhood in particular that had a name like "Edgeview Cottages", and instead of getting letters addressed to 20 Apple St, you'd see Edgeview #20. It's crazy how people expect the post office to be able to figure this out.
Embarrassingly, I didn't believe it when I was told USPS OCR rejects less than 5% of hand-written address. I assumed that even if you could read the writing, the format would be too irregular to parse a lot of the time.
Part of the reason I was wrong is that so much of the address is redundant. I think they only use four letters of the street name, for example, before they essentially always can narrow it down to one possibility in their database.
It arrived without problems.