@champsupertramp , @missveronicatv Thanks all of you. The Activating Email is sending successfully.
I find another place that should be set correctly so that Activating Email can be sent. So totally there are there settings:
First
UM -> Settings -> Appearance -> Registration form -> Registration Default Role
Second
UM -> User Roles ->
Select the user role above defined as “Registration Default Role” -> Edit -> Registration Options -> Registration Status -> Require email activation
Third
UM -> Settings -> Email -> Account Activation Email (edit template and check the box on the screen that appears)-> save change(edit template) -> save change(Settings -> Email)