The email address is transmitted to Jupyter by the central UHH-Login service of the University of Hamburg.
Jupyter stores the email address in the databases of the enrolled nbgrader courses.
The email address is updated each time you log in. It is not possible to change this manually in Jupyter. This ensures that a valid email address is stored for contact purposes.
Students and employees at the University of Hamburg are each assigned their own email addresses. However, the central UHH-Login service only transmits one email address and prefers the work address.