can not sent mail for new user

Hello,
Your question is quite unclear.
Could you please specify what is wrong with the mailing function and who are you trying to mail ?
Does your site has registration form or registration processes to send mail to new user. Or by user you are referring to users with dashboard access?
Because by the look of it, Your website doesn’t seem to have any registration or contact form plus you seem to be using twenty-fifteen theme.
Please contact if you have any queries,

regards,
bplv