--- /dev/null
+/**
+ * Implements hook_mail_alter().
+ */
+function {{ machine_name }}_mail_alter(&$message) {
+ if ($message['id'] == 'modulename_messagekey') {
+ if (!example_notifications_optin($message['to'], $message['id'])) {
+ // If the recipient has opted to not receive such messages, cancel
+ // sending.
+ $message['send'] = FALSE;
+ return;
+ }
+ $message['body'][] = "--\nMail sent out from " . \Drupal::config('system.site')->get('name');
+ }
+}