Do not call the HandlesTarget method. This method is called automatically when the user invokes an object (such as a tool button or menu item) that is linked to this action. The HandlesTarget method provides the action object with an opportunity to indicate whether it is appropriate to execute at this time with the object specified by the Target parameter as a "target". 

HandlesTarget ignores the Target parameter and always returns true, because the ability to send mail is not dependant on the state of the application.