Disclaimer: I haven't used KMail for years, yet I use Thunderbird and Firefox every day. I just want to point out a few things that the KDE team has gotten right, as opposed to the Mozilla team.
Things that I like about KMail and its settings:
- The UI doesn't change every 6 months in an attempt to ape their closest competitor.
- If a settings can be configured, there's a button for it in the settings. I don't have to download a plugin that might get updated at any moment with spyware, or to muck about in the configuration editor. Do you remember that, in order to show http in URLs, you have to change the setting browser.urlbar.trimURLs in about:config? For some reason, I have to look it up in Google every single time I set up a Firefox. If there was a button for it, I would probably remember where it is.
- They are not so utterly reliant on ad money that they set the default tracking setting to "Do not tell sites about my tracking preferences", which is a lame cop-out. Maybe they could cut some of the compensations they are giving to their executives instead.
With all that said, it is true that the settings in KDE and KMail in particular can be confusing to new users. Maybe they could have a "show settings: simple/all" radio button in the corner of their preferences windows, like VLC?