Here all version of my system :
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.2 LTS"
Plasma Version 5.8.7
KDE Frameworks Version 5.36.0
QT version : 5.6.1
Kernel Version 4.4.0-83-generic
My kmail version is 5.2.3 and I can not get any search result in my mail folders.
I posted a bug tracking and the support told me I've to upgrade kmail as these kind of buggies had been fixed. My system seems to be up to date like a LTS version. I installed the backports package listing as recommended is this page : https://community.kde.org/Plasma/Packages
What did I miss?
Thank