Installing Daylite software added a panel to the Mail window.

This is a drawer on the left side of the main Apple message viewer window. How can I remove this from the mail app or turn it off?

If you just want it hidden temporarily you can close it with View->Toggle Daylite Drawer, but if you no longer want the Daylite Mail Integration plugin installed you can use the uninstaller, as described here:

http://www.marketcircle.com/kb/idx/0/055/article/