Clicking a link in Thunderbird opens Firefox instead of the default browser

Question

I am using KDE on Fedora 21 x86_64. I recently switched my default browser from Firefox to Chromium, and this worked out very well...except for Thunderbird, which still insists on attempting to open links with Firefox.

To attempt to resolve this problem, I have:

• Read the Mozilla wiki entry which explains how to set your default browser on various platforms. (Of course it is horribly out of date, so...) My results are below:

• Checked the default browser in KDE System Settings. It is set to chromium and appears to work fine. Using xdg-open http://www.google.com/ from the command line opens Google in Chromium. But Thunderbird opens links in Firefox.

  

• Set the network.protocol-handler.app.* settings within Thunderbird's about:config. Despite these being explicitly set to chromium, Thunderbird still opens links with Firefox. Even after setting these to /usr/bin/xdg-open Thunderbird still opens Firefox, leading me to believe that these settings are actually being ignored.

  

• Checked the mimeTypes.rdf file. Its relevant entries were set to open Google Chrome; no reference to Firefox appeared anywhere within it. In addition, the referenced Thunderbird configuration entries for network.protocol-handler.warn-external.* were already set:

  

I have also tried:

• Checked the ~/.local/share/applications/mimeapps.list file. It does not appear to reference Firefox in any way.

  [Added Associations]
  application/x-extension-eml=userapp-Thunderbird-93GZAX.desktop;mozilla-thunderbird.desktop;
  audio/mpeg=vlc.desktop;
  message/rfc822=userapp-Thunderbird-93GZAX.desktop;mozilla-thunderbird.desktop;
  text/html=chromium-browser.desktop;
  x-scheme-handler/mailto=userapp-Thunderbird-93GZAX.desktop;mozilla-thunderbird.desktop;
  
  [Default Applications]
  application/x-extension-eml=mozilla-thunderbird.desktop
  message/rfc822=mozilla-thunderbird.desktop
  text/html=chromium-browser.desktop
  x-scheme-handler/mailto=mozilla-thunderbird.desktop
  

I just might be losing my mind here. What have I missed?

Answer 1

I still haven't figured out why Thunderbird does what it does, (though jason C's comment seems likely) but I have managed to get it working.

I simply stopped Thunderbird, deleted the mimeTypes.rdf file from the profile directory, and restarted Thunderbird. Then it prompted me for the browser to use and I was able to change it to chromium successfully.

Thunderbird then created a new mimeTypes.rdf file which references chromium.

Now looking for a new mail client that isn't utterly absurd, but that's a post for another site...