If you get into a shop in a different country and ask for stamps you’ll expect to get stamps provided by the local post. On Mallorca tourists are often surprised that they can’t throw their postcards into the normal Correos post boxes. That is because of the deregulation of the market and the option of other companies to deliver letters and postcards. And on the island the Swiss post is active.
If you bought stamps from Swiss post just remember that you can only enter them in boxes of Swiss post, colored in orange. Best option is to return the written cards to the store where you bought the stamps. It just feels quite strange to send postcards from Spain with Swiss post. And it slows down the delivery process – postcards to Germany need 14 days. An unnecessary thing caused by global capitalism.
The same is true on nearby Menorca, where the flimsy Swiss Post boxes are a very similar yellow colour to the Correos ones. Ideally, buy your stamps from a real post office, or maybe a tabac, and lock into the more efficient Correos postal network at much the same price.