Since I prefer to use Evolution, I would really like to completely remove Thunderbird from my PC. I already performed
sudo apt-get purge thunderbird* but
locate thunderbird still lists some hits! How can I completely remove it?
Here is what went wrong in your case.
Removing Thunderbird from Ubuntu is really very simple.
Check this detailed post, with screenshots - http://terminaltwister.com/remove-mozilla-thunderbird-email-client-from-ubuntu-13-04/