The Belgian Post has come under criticism from the Flemish newspaper Het Nieuwsblad op zondag for distributing mail that did not have the required amount of stamps on it, used worthless foreign stamps, or worse used fake scanned copies of stamps.

Sources : L'Echo : La Poste oblitère tout

That's interesting because I have had my mail returned twice because they considered that my envelope was slightly too big or a few grammes too heavy for the regular stamp rate. This means that some post offices might be too zealous, while others are obviously too careless.

Once, my wife send a letter to Japan, and they managed to send it back to our home address the next day because she had written the 'return address' on the front with the destination address (as is normal in Japan), instead of writing it on the back (as is normal in Europe).