To send e-mails to your users in the registration or to make mailing lists of important news you should:
1. Create a mailbox on your domain. You might read here how to do it.
2. Write a script that will send e-mails. For example:
$to = 'email@example.com'; Who receives $subject = 'test'; E-mail thread $message = 'hello'; Message $headers = 'From: firstname.lastname@example.org' . "\r\n" . Who sends.
IMPORTANT: You should write your mail account from which mail will be sent in the field “WWW domains” – Administrator’s e-mail and also indicate the way through Sendmail (sendmail_path = “/usr/sbin/sendmail -t -i -f email@example.com”) in the file php.ini (folder php-bin) to assure your script working.