Drupal8: Send E-mail after node creating.

<?php//Add this line to the top of the MYMODULE.module file.use Drupal\Component\Utility\SafeMarkup;/** * Implements hook_mail(). */function MYMODULE_mail($key, &$message, $params) {    $options = array(            'langcode' => $message['langcode'],    );    switch ($key) {        case 'node_insert_alert':            $message['from'] = \Drupal::config('system.site')->get('mail');            $message['subject'] = t('Ticket created: @title', array('@title' => $params['node_title']), $options);            $message['body'][] = SafeMarkup::checkPlain($params['message']);            break;    }}/** * Implements hook_entity_insert(). */function MYMODULE_entity_insert(Drupal\Core\Entity\EntityInterface $entity) {        if ($entity->getEntityTypeId() !== 'node' || ($entity->getEntityTypeId() === 'node' && $entity->bundle() !== 'CONTENT_TYPE')) {        return;    }            $mailManager = \Drupal::service('plugin.manager.mail');                $module = 'MYMODULE';        $key = 'node_insert_alert';        $to = 'To mail '; // email to be sent to this Email ID                $params['message'] = "Message";                $params['node_title'] = $entity->label();        $langcode = \Drupal::currentUser()->getPreferredLangcode();        $send = true;                $result = $mailManager->mail($module, $key, $to, $langcode, $params, NULL, $send);        if ($result['result'] !== true) {            $message = t('There was a problem sending alert email notification to @email for creating ticket @id.', array('@email' => $to, '@id' => $entity->id()));            //drupal dblog            \Drupal::logger('MYMODULE alert')->error($message);            return;        }                $message = t('An email notification has been sent to @email for creating node @id.', array('@email' => $to, '@id' => $entity->id()));        //drupal dblog         \Drupal::logger('MYMODULE alert')->notice($message);}?>