Ubuntu 10.04: Add thunderbird 3.0 in Indicator Applet

I like Ubuntu 10.04 and Thunderbird. But default mail client is
Evolution instead of Thunderbird. So I installed Thunderbird 3.0, but
it's not be shown on Indicator Applet area. To show Thunderbird 3.0 on
that area, I need to add it manually as following:
- Create a file named thunderbird at
/usr/share/indicators/messages/applications/
- Add below line in the file:
/usr/share/applications/thunderbird.desktop

Done!