You can download the code of Telerik Web Mail Demo
from "Help"->"Download source code"
item from the RadMenu.
If you need only the code of the RadPanelBar or RadMenu from this demo, let me know and I will isolate it for you.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items