Hi,
Kindly check whether the New user registration mail is sent to the admin and user. If you have issues in that then you have contact your hosting for this issue. If the mail is not sent only in Jomclassifieds component, kindly send the below details to This email address is being protected from spambots. You need JavaScript enabled to view it. . So that we will check and update you.
1. Site URL.
2. Joomla admin username and password.
3. FTP details.
Thanks.