SUMMARY Kmail already has many options to customize the interface and that's amazing! But there's almost nothing to customize the part where the basic headers of an email are displayed, like sender, recipient, subject, etc. Options to change which items should be displayed, list all headers, see the source of the email, would be very useful. Another necessary modification would be the possibility to move the reply buttons, forward, and other useful ones to that same place. In my opinion it makes more sense that these buttons stay in the header. Currently, they only stay on the top menu and you can move it to one of the sides or keep it "floating". Something like what I tried to do in this image: https://i.imgur.com/etvJlxE.png SOFTWARE/OS VERSIONS Linux/KDE Plasma: Archlinux 5.6.6 KDE Plasma Version: 5.18.4 KDE Frameworks Version: 5.69.0 Qt Version: 5.15.0