[MM3-users] Removing a mail addresses and users

Hello.

I tried to remove random email address signing ups (which I signed up while testing) via admin panel. After removing I tried to sign up again, but I am getting,

'A user is already registered with this e-mail address'

Combing through the database, I found auth_user table in mailman3web db still contain those mail address. How to wipe email address entirely from the db so I can signup again without the 'forget password' method

--abhijith