Starting chromium as default browser in thunderbird

Thunderbird seems to always start firefox when a link is clicked.
This is bad behaviour. 
 The following command will start chromium: 
 gconftool-2 --type string -s /desktop/gnome/url-handlers/http/command "/usr/bin/chromium %s" 
 This works also in KDE 
 other solution: jan 2012 
 Nothing helped, so I've found other solution: 
 1) in Thunderbird go to Edit -> Preferences -> Advanced -> General ->

Configuration Edito 
 2) change 
 network.protocol-handler.warn-external.http and  
 network.protocol-handler.warn-external.https 
 to "true" 
 3)Click on any link in tb 
 4) navigate to /usr/bin/google-chrome 
 5) have fun