One of the most important things you need to do when moving is updating your address to all the possible services that might need it. In Finland we have a great system where you can basically update your address to all the government registries and postal office at once. Of course that doesn't cover all the commercial services you might need your address for. Especially the online stores still need to know where to ship your purchases.
When announcing a new address the postal service offers free complimentary address redirection service for a while to ensure you get all your mail to the new address before all the systems have been updated. But that's also for a limited time and after that it's up to whoever lives now on your old address to return the deliveries to the post office and hope they will find your new address. If not, then it's returned to the sender and it's up to them figure out your mistake.
It's easy to remember to update all those often used services at the same time as you do the official address change, but for the services you use rarely, or haven't used for a while it's easy to forget. Especially if you return to one of those services after years and don't even think to check the address. Only to find out you hadn't updated your address after you had already placed the order.