Tabarca is the smallest permanently inhabited islet in Spain, located in the Mediterranean Sea, close to the town of Santa Pola (Valencian Country). There are only 17 permanent inhabitants.
I was there last summer, and I was told there wasn't any post office, just the yellow post box that you see on the picture. And I was also told that the post service operates every day.
I sent five postcards from there (I didn't dare to send more!) on 13 July. At least two of them arrived, so I guess the rest did so. One of them was postmarked on 22 July and arrived in the Netherlands a week later (29 July). I am glad it arrived but... What does it mean every day?