Article from the Reg about useful extras

"The easiest way to get this code – and several other useful extras – is by adding a new repository from a project called Medibuntu. The Medibuntu instructions are on the site, but in brief, copy this and paste it into your command prompt:

sudo wget --output-document=/etc/apt/sources.list.d/medibuntu.list http://www.medibuntu.org/sources.list.d/$(lsb_release -cs).list && sudo apt-get --quiet update && sudo apt-get --yes --quiet --allow-unauthenticated install medibuntu-keyring && sudo apt-get --quiet update

After this, you can just install the last few bits:

sudo apt-get install app-install-data-medibuntu apport-hooks-medibuntu libdvdcss2 w32codecs"

From: http://www.theregister.co.uk/2010/06/24/reg_linux_guide_3/page2.html

Delete (or change) the envelope icon from the indicator applet panel

Navigate to
/usr/share/indicators/messages/applications
Delete the evolution file or anything else you want.
If you want to add a new icon to the indicator applet, thunderbird for example, create a new text file in that folder, name it thunderbird and put
/usr/share/applications/thunderbird.desktop
in it. Restart the gnome panel and... there you go.