Implements hook_mail().
function user_mail($key, &$message, $params) {
$langcode = $message['langcode'];
$variables = array(
'user' => $params['account'],
);
$message['subject'] .= _user_mail_text($key . '.subject', $langcode, $variables);
$message['body'][] = _user_mail_text($key . '.body', $langcode, $variables);
}