I am using 11.04. I prefer Thunderbird to Evolution as a mail client. This is mostly because all I have to do with my numerous gmail accounts is type in my user name and password and thunderbird autoconfigures everything whereas Evolution never connects to more than three or four of my accounts without some kind of error. ANYWAY... In the upper right hand corner of the menu bar on the UNITY desktop it has the little envelope icon and I have not been able to change the default of that applet to Thunderbird rather than Evolution. I followed this suggestion:
But at the crucial step where you download and install the thunderbird indicator it says "this app is not compatible with firefox 5"
So, in the upper right hand corner of the Unity desktop I want that mail envelope on the menu bar to connect to Thunderbird rather than Evolution. I tried uninstalling Evolution once but it disasterously took chunks of the desktop with it and left my computer in an usable state...
(As an alternative I would be satisfied with a suggestion that explained how to remove that envelope on the menu bar from the menu bar without decimating all of the icons in the whole bar as it seems to do when you try to remove it.)