I don't think there are any free apps that will turn on the backlight when you receive an SMS/Email. I'm not even sure if there is a free app that will keep your backlight on for an undetermined amount of time.
I do know of other apps that will do what you're looking for, but they are all paid/premium apps. And I could be wrong, but I think you would need more than one app to do it. Leave it On would probably be your best bet. Like I said in the other post, it has a free trial and you could test it out to see if it is something you would be interested in!
Otherwise, you may wanna try searching App World and/or Mobihand for an alternative. New apps are posted all the time so you never know what you may find!
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