Steve got a letter delivered from the UK to here in Aus with only a street name as an address.
It’s not international, but back when we were living down at the farm, I’ve had mail delivered which was posted to “Brooks 6326”, the latter being the postcode for Narrikup, the more-or-less shire which delivered our mail back then.
It turns out that there is one other Brooks property in their delivery area, but with nobody living on it at the time (they lived in Albany) all they were getting for the others was formally-addressed official letters, which made it easy to decide what the one word in addition to the postcode indicated.
Either way, I was impressed to get mail with a one-number address correctly delivered. I did hear, years ago, of a lass getting a letter delivered to “<name>, City Beach” delivered. Some postal pixie had also scrawled “try Australia” on this one. I guess Australia counts as WTF-land for mail?
Being postie for Mount Barker (WA) was interesting, as lots of streets had similar names (e.g. Osborne St crossed Ormond Rd) with inevitable results, & Mount Barker (SA) had some similar street names. I learned where to deliver mail with unit numbers on it — addressed to streets without units on them — & to have people on the outer limits of my round treat their mailboxes as RMBs, doing stuff like clipping on pieces of outbound mail for me to pick up as I passed.