I got recently a 4K screen. Everything works fine except that Kmail seems to insist that the size of the icons should be rescaled (screenshot: https://pli.io/2CjQM9.png)

I'm on Gentoo Linux 4.18.08 with KMail 18.08.02 and Plasma-5.51.0

Please, note that not only the icons are oversized. The Menus also are (there is a huge gap between entries). The icons are set to their minimal resolution (16x16). I can *increase* the icons' size, but not reduce. This is clearly a bug.