
Some notes on Google Earth vs. browsers and mail clients:

GNU/Linux, at this time, doesn't have any sort of standardized way to launch
 an email composition window with the user's favorite email client...in fact,
 there isn't even a universal way to figure out what the user's favorite email
 client might be!

There is a loose convention for figuring out the favorite web browser, though.
 Please refer to Eric Raymond's documentation on the $BROWSER variable:
    http://www.catb.org/~esr/BROWSER/

When Google Earth needs to launch a web browser, it uses $BROWSER. If
 $BROWSER isn't set, it tries some reasonable defaults (at least, reasonable
 for February 2006):

    "firefox:opera:mozilla:netscape"

(Yes, we know that 'kfmclient openURL' is missing...there too many people
 with KDE installed that actually use Gnome to make that a safe default. You
 can certainly set $BROWSER to that yourself, though. We tried it; it works.)

For the time being, Google Earth gets around the mail client issue by
 launching the web browser with a "mailto:" URL. This at least lets us
 shrug off responsibility for now, and also empowers the community to cleanly
 manage their own solutions on the open source boundaries.

No two email clients on Linux handle command lines the same for launching
 a composition window. We have provided a collection of perl scripts that
 will convert between our URLs and various popular apps. We have not provided
 one for Evolution, because it happens to work with our URLs out of the box
 (this wasn't intentional on our part, we swear).

Firefox, depending on your installation, may not have mailto: support enabled.
 You will have to set these lines in your prefs.js file, which will launch one
 of our wrapper scripts. You'll have to verify the file paths are correct.

  user_pref("network.protocol-handler.expose.mailto", true);
  user_pref("network.protocol-handler.app.mailto", "/usr/bin/mailto-kmail.pl");

The creative could set their $BROWSER to some simple script that either calls
 mailto-thunderbird.pl (or whatever) if started with a mailto: argument or
 firefox (or whatever) elsewise. This may prevent some extra windows and
 tabs from cluttering your desktop as you use Google Earth.

That should get you going. Also, please encourage your distros and software
 vendors to standardize on ways to handle these things, which could remove the
 need for all this explanation some day. Being able to find the user's
 favorite apps and manipulate them from another program is not only good for
 commercial software, but also Free and open source packages, too. After all,
 stringing together a collection of programs is the Unix Way, isn't it?  :)

Good luck,
--ryan, Google.

