Reset Docker ID password without email

Hi,my classmate forget his Docker ID’s password,and the email address used for it.
So,how can he reset the Docker ID’s password,or how to get the email address for the Docker ID (his ID is bigbomb)?
The admin can dispaly the email address with abcdxxx@mailhost.com?only display the first 4 characters email account and full emailhost.com?
Thanks a lot.