Users (both staff and students) can login to the NCEdCloud IAM Service without an email address in their account data, however, there may be drawbacks.
Some internal messaging (in the IAM Service) requires an email to operate - e.g. forgot my password
Some Target Applications expect to receive an email address when users login. If it's not present in the source data (e.g. PowerSchool, LINQ HR, HRMS), and therefore not updated in the IAM Service, then the user won't be able to login to the application or some functionality may be limited.
If a PSU wants to opt-in to Alias ID (and use an email address rather than the numeric UID to login), any user without an email address in the IAM Service wouldn't be able to take advantage of that feature.