SU3 Users unable to change email address...

We are currently using CUA and I have allowed users to modify all profile information including the Internet Mail setting in SCUM; however, when we go to maintain own data (SU3) the email address cannot be modified???? I have searched all over for information regarding this and there seems to be nothing available. Does anyone know anything about this? How can I enable my users to change their email address when necesssary?