A second email address can be added to a single user in smart tuition, and set to 'mirror' all communications.
This can be done by:
  1. Navigate to Families> Manage Families
  2. Search for and select the family
  3. Click on the blue tab at left
  4. Select 'More Options'
  5. Select 'Update Parent & Student Info'
  6. Enter a 'Secondary Email'
  7. Select 'Mirror'
  8. Scroll the the bottom and click 'Save Changes'
Secondary Email

Additional information can be found here: What is the difference between Mirror and Supplemental for email addresses?