Comes into mind: in Belgium we had a story making nationwide news: one street in a small town had such a long street name it didn't fit on any enveloppe. Those in town wanting to play the lottery or order by mail form didn't have enough boxes to enter the entire street name. I believe the street name was "Parallelweg Kleine Kerkstraat" or something similar. The story made nationwide news due to post delivery going wrong so often. They then decided to shorten the streetname to just "Parallelweg". Even in a country as small as ours (the average US state is much bigger than Belgium) we managed to not get some of our own national courier delivered
Also, just out of curiosity but does the Vatican issue own stamps and have an own postal service, or do they use the Italian one with just a zipcode indicating the difference between Rome and the Vatican state? If a Vatican postal service exists, I can imagine a Vatican stamp being so rare it's worth a lot. Just like the Euro coins issued there with the former Pope's image on the back, there were so few coins issued in the Vatican that a 1 € coin from the Vatican was actually worth a few hundreds euros when selling it on eBay.