Preventing users from registering with xxx@yyy format email address Drupal seems to let users register with emails like xxx@yyy

I heard that this kind of email address can exist.
But I want users to register with only emails like xxx@yyy.zzz

Is there any way to validate this type of email format and prevent users from registering with it?
There is a core function named: function valid_email_address that will check that the syntax is valid.

Example of use:

$mail = $form_state['values']['submitted_tree']['email_address'];
if (!valid_email_address($mail)) {
  form_set_error('[submitted][email_address]', t('The email address appears to be invalid.'));
}