I was disappointed that Thunderbird does not appear to be part of the Mint 13 KDE distribution and wasn't installed by default like previous Mint KDEs. It wasn't even available in the Synaptic Package Manager. I got it installed after adding http://ppa.launchpad.net/ubuntu-mozilla ... pa/ubuntu/ (both deb and deb-src) to the Software Repositories. Anyway, no problem installing 15.0.1 and using it - it works fine.
However, the issue is that I can't get it to communicate with the Message Indicator system tray icon (it says "No applications running"). I had this same problem on Mint 10 KDE, which I never was able to solve. But with Mint 12 KDE, it just worked from the get-go. I'm assuming the Mint Team did something to get it to work on Mint 12 KDE. I have yet to find the magic package or Thunderbird add-on that I need to make it work with Mint 13 KDE. I tried installing the thunderbird-globalmenu and thunderbird-gnome-support packages, but these didn't make it work. I see the mail-notification package, but that brings a whole bunch of stuff with it (like gnome stuff), so I didn't install this package (and it doesn't appear to be installed on my Mint 12 KDE).