Email Notifications on Estimate Approval?

Email Notifications on Estimate Approval?

Is it possible to for the estimate owner (or a fixed email address) to be sent an email notification when a customer approves an estimate?  I have not found a way how.  I created a workflow that is triggered by an estimate being edited and the status field = approved, it sends an email to the estimate owner.  But no email is received.  Does the workflow only work if the estimate is manually edited by a user as opposed to a client approving it?