Recently at work we had a visitor from Tristan da Cunha (basically, our visitor was the Tristan da Cunha post office). If you don't know, Tristan is a British island in the south Atlantic. It has no airport and no scheduled boat service and a population of around 250. The nearest other inhabited place is South Africa, about 1600 miles away. To get there, you flag down a passing fishing boat and the journey is typically at least 2 weeks.
They get one mail delivery (which also hitches on a fishing boat) once every 6 weeks or so. They get a lot of misdelivered mail for Trinidad and Tobago. That mail when it gets returned for redelivery then has to take the 2 week journey back to South Africa and may have been delayed for 9 or 10 weeks by the time it gets to its proper destination.
When the mail arrives at Tristan, it's sorted by family at the post office but not actually delivered on from there - the post office rings a big gong and everyone comes to get their mail.