I've spent a good part of the day trying to arrange that thunderbird is invoked when I click on a mailto link in the firefox. I created the file ~/.mozilla/firefox/qi0tjy0b.default/user.js containing the line user_pref("network.protocol-handler.app.mailto","/home/peter/firefox.mailto.sh"); Yet about:config in firefox lacks the network.protocol-handler.app.mailto record. Any ideas? Thanks, Peter Easthope