OT: Howto set Mozilla Firefox mailto links

[Tommy Trussell <tommy.trussell@gmail.com>]

As I just mentioned in another message, I just installed the latest
Mozilla-Thunderbird package from testing.

[Why is there an update-alternatives option to set the mailto links in
Mozilla Firefox? I've used Debian for a few years now but the
Mozilla-Thunderbird package is the first time I've interacted with the
update-alternatives system, so please forgive me if this is old news.]

Here is the technique I just used to make mailto links point from
Firefox to Thunderbird. This is for Firefox 1.0 (don't know about any
others):

1) Launch Firefox and view the configuration strings using the URL
   about:config  

2) using the field at the top, search for
   mailto

3) If you do NOT have network.protocol-handler.app.mailto (normally
you don't), create it using these steps:
  a) right-click
  b) choose New --> String
  c) new string: network.protocol-handler.app.mailto
  d) new value: /usr/bin/mozilla-thunderbird

4) If you already see an entry for
network.protocol-handler.app.mailto, verify the path to the mail
client. Double click the string to set it if necessary. Also be sure
network.protocol-handler.external.mailto is set to true.

P.S. The Evolution package can set Firefox mailto links to launch
Evolution, but I could never find the setting to change it!