URL Dispatching on Linux
Mozilla Thunderbird 0.4 now supports the ability to dispatch browser urls to your default browser on Linux. However, this feature does not work out of the box yet. The following instructions should help get url dispatching up and running for your installation of Thunderbird.
X-Remote Client
Make sure you are using the x-remote client that ships with Thunderbird 0.4 or the x-remote client that ships with any Mozilla browser released after November 22nd, 2003. The mozilla x-remote client had to be modified in order to work with multiple applications. You need to make sure you are using that version.
Shell Script to Launch The Browser
You need a shell script which can be used to launch your default browser. For instance, if your browser is Mozilla Firefox you could use something like this:
#!/bin/sh
export MOZILLA_FIVE_HOME="/opt/firefox-builds/current"
url="$1"
if [ "x$url" = "x" ]; then
url="about:blank"
fi
if $MOZILLA_FIVE_HOME/mozilla-xremote-client openURL\("$url"\); then
exit 0
fi
exec $MOZILLA_FIVE_HOME/firefox "$url"
Registering The Default Browser
If you use GNOME2 you can go to: GNOME Control Centre> Advanced> Preferred Applications and configure your default browser. If you choose Custom Web Browser for the command field, use:
/path/to/the_shell_script %s
Mozilla Firebird and Thunderbird will eventually have UI to do this directly, but for now you you have to do it manually.
Alternatively, you can explicitly tell Mozilla Thunderbird which shell script should be run for particular urls by setting the following user preferences to Thunderbird (don't forget to change the path and name to point to your shell script):
user_pref("network.protocol-handler.app.http", "/path/to/the_shell_script");
Repeat for each protocol you want Thunderbird to dispatch (https, ftp, etc.).
Many thanks to Darin Fisher and Brian Ryner and Christian Biesinger for making this feature happen!