A mail message pane can be supported eventually. https://kontact.kde.org/assets/img/kontact-kmail.png There can be reasons to work without this widget occasionally. * Its service became broken. See also: Missing content display in the mail pane https://bugs.kde.org/show_bug.cgi?id=427584 * You would like to work with an user interface configuration where more messages should be listed. Thus extra widgets should be excluded from the display for this use case.