To send e-mails from WordPress you must use a SMTP plug-in. Configure your plug-in (for example Configure SMTP) to use SMTP, not the PHP mail() function, and to set the envelope from address to a working e-mail address on your domain. You will also need to furnish the server, smtp port, user account and password for a working e-mail account on your domain. Configure the plug-in with authentication required set to 'on' or 'true'.
