Alert threshold - Low balance notification is not come in email history.

Steps to reproduce :

 1. Login in customer

 2. Go to my account

 3. Click on alert threshold

 4. Fill up details and save

 5. Customer balance is low then alert notification is not come

 6. Login in admin

 7. Verify email history in notification is not come

Expected result :

 > Customer balance is low should be notification is come in email history.