The kmail documentation says "... you can send a new message to the mailing list via Message → New Message to Mailing-List... or by clicking with the middle mousebutton on the folder in the folder list. http://docs.kde.org/stable/en/kdepim/kmail/kmail.pdf section 3.4.3, Mailing List However, clicking the mousebutton has no effect.
Ok doc is outdated. I remove this entry
Git commit 479c93763075763c4ef2005be98c6b239049b8c6 by Montel Laurent. Committed on 14/05/2013 at 14:09. Pushed by mlaurent into branch 'KDE/4.10'. Fix Bug 319820 - Middle mousebutton on folder in folder list doesn't send new message to mailing list FIXED-IN: 4.10.4 M +1 -3 doc/kmail/using-kmail.docbook http://commits.kde.org/kdepim/479c93763075763c4ef2005be98c6b239049b8c6