Yes, you will need a separate email address for every applicant that you plan to order a TransUnion Full Credit report for.
Many landlords choose to run a background report on each tenant applicant that is 18 years or older.
If you have an applicant that is married and also has a 24-year-old child living with them you'd want to get the email address of the applicant, spouse, and adult child.
This way you can be assured that each adult living in the home has a clean background and is not a risk for your rental property.