We use ePPN as the unique identifier because a person's ePPN remains the same regardless of any changes to the person; it is unique and persistent. Email address is not ideal because it changes frequently as people move to different jobs across the campus, change their names, etc. Also, for student workers, they may have several email addresses (e.g. official school email, work email, preferred contact email) and the email address for Single Sign On may not the one for notifications related to SmartSuite tasks. It'll be helpful to have another field in SmartSuite for users to specify in their preferred email address to get notifications from the system, separate from the identifier for SSO.