Problem with domain.com

[MichaeLTC]

Hi, i have just recently reinstall the parallel panel. I have received a problem that all xxxx.domain.com on my server is not working. like www.xxxx.domain.com, xxxx.domain.com , ipv4.xxx.domain.com, i keep receiving cannot find server error. Can anyone tell how can i fix this issue?
Extra question: i cannot send email through smtp, i follow the setting in mail section in panel use port 25 or 587 and both doesn't work, i keep getting Failure sending email.

Sorry i am not a tech in this area. Can anyone help? thanks