Thunderbird: how to open links in firefox (or other app)

There is one simple solution to set the right application for handling links in thunderbird. However finding the solution wasn't as easy, so here it is:
 

In TB 5.0 the hyper-links in the messages don’t work, even with the changes like these they do NOT work:
1) To be absolutely sure: make back up using MozBackup http://www.mozbackup.nl/
2) In Thunderbird, go to Preferences / Advanced /Config Editor (it will warn you, say yes)
3) Scroll down to network.protocol-handler.warn-external.http and make sure it’s set to true
4) Do the same for network.protocol-handler.warn-external.https
5) Do the same for network.protocol-handler.warn-external.ftp
6) Do the same for network.protocol-handler.external-default
7) Exit Thunderbird
8) Restart Thunderbird. The first time you try clicking on a link (or sooner) it will ask you to confirm that you’re using an external handler. Say yes and check the “Always do this” checkbox.

Thanks to Charell.

EDIT:
Recently, with thunderbird 31, the above steps are not working.
To change associated application, edit the mimeTypes.rdf file, placed in thunderbird's default profile folder.

Example: in my case, I wanted to change http(s) associated files to be opened with firefox-aurora, instead of firefox, so I've executed:

sed -i.bak 's/\(firefox\)/\1-aurora/g' ~/.thunderbird/m3e8sg0w.default/mimeTypes.rdf