Force regenerate server's SSL certificate

Hello, I'm having a problem when an user try to open webmail from his cPanel account. Scenario: My server hostname is like server.example.com.br I just created DNS entries for it and www. When an user log in his cPanel and try to open webmail of one user, it redirects to: since the user logged in using www.hostname Question: how can I regenerate the main server's certificate? When I regenerate, it will auto-create entries like webmail.hostname? Thanks.