If you want to use BNFW to disable a default WordPress email, such as the one that is sent to the admin when a user changes their password, all you have to do is to create a notification for the one you want to disable, then set it to ‘Notification Disabled’ in the ‘Save Notification’ metabox in the top right of the screen. In this example, you would create a notification for ‘Password Changed – For Admin’ within BNFW, and then set that ‘Notification Disabled’.
Once this is done, this default WordPress notification should no longer be sent.