Your initial email address is your Z-ID@students.niu.edu.
Your initial email address is generally your first initial + last firstname.lastname@example.org
If you do:
Your email alias must be unique within the system. It can contain a-z, A-Z, 0-9, - (dash), _ (underscore) and . (dot).
Step by step instructions to change your email alias - How to Change or Update Directory Information.