when click on open email from digsby it opens my outlook, but I've not configured that account on outlook, I want it should open up my gmail account on browser not on outlook :)
What is your default email handler? ie. What opens when you click on a mailto: link on the web?
If it is not Gmail, you can make it so using the settings in the Google Toolbar, or if you do not use that, GTalk (you obviously use Digsby instead), or the Gmail Notifier.