Fetch Email address for the user in SU01

Hi. My requirement is to fetch the email address(SU01) of the user name . I know that the email address is in ADR6 table (SMTP_ADDR) and username in usr02 table(bname).. When i checked the usr02 table, it has relationships with TTZZ and USRGRP which is no way releated in fetching the email adress.

Do any one know how the relationships are maintained ???