I don’t remember much about it but hopefully somebody will post suggestions which I will look up on Youtube.
I saw a few episodes of this on a UK channel while staying in a hotel in Germany, between 7-10 years ago. No idea how contemporary it was to the time of viewing.
Here is what I remember: the series was about two sisters, who corresponded by mail. At least one of them was married. I seem to remember that the letters contained “smoothed over” reports of things that had happened, with the sisters trying to one- up each other perhaps, or trying to spin embarrassing incidents in more “dignified” manner - like being a bit competitive and not losing face.
The title of the show may or may not have been a phrase one uses in a letter, such as “Yours truly” or something like that.
Ring a bell for anybody?