I am not sure you have an idea how large the icon set of eM Client is. It is roughly 500 icons in 7 different resolutions + vector variants of all of them. I don’t think there is any available set you would be able to simply “exchange it for” even if we implement such an option. The thing I agree with you is that with super hi-res displays (such as 5k displays), the icons are too narrow and hardly visible (especially in dark mode). This is a known issue we work on and it’ll be fixed for the official release.