Comment 2 for bug 148008

I have seen this bug too since upgrading from Ubuntu 7.04 to Ubuntu 7.10. To show what's happening I got to 'about:config' and I edit this key

  network.protocol-handler.warn-external.mailto

and set it to 'true' instead of the default (which is false). Next I go to:

  http://www.ianr.unl.edu/internet/mailto.html

And I click one of the links. I get a warning saying that Firefox is going to run the command "mozilla-thunderbird %s". But there is no such program on my system. I believe that "mozilla-thunderbird" was renamed to just "thunderbird" in the latest release, and the Firefox protocol handlers somehow haven't been updated, or perhaps are stored in the user profile and can't be automatically updated...?

In any case, a hacky workaround is

  gksudo gedit /usr/bin/mozilla-thunderbird

Paste in the following text:

#!/usr/bin/env python
import os, sys
prog = "/usr/bin/thunderbird"
os.execvp(prog,tuple([prog]+sys.argv[1:]))

Then save and exit gedit.

Then:

  sudo chmod +x /usr/bin/mozilla-thunderbird

This works for me.