/** sendNewsletter()
  *
  * @param mixed string/object recipient
  * @param object oEmailTemplateInstance
  *
  * @return void
  */
 private function sendNewsletter($mRecipient, $oEmailTemplateInstance)
 {
     if (is_object($mRecipient)) {
         $oEmailTemplateInstance->replaceIdentifier('recipient', $mRecipient->getName());
         if ($mRecipient instanceof Subscriber && $this->oUnsubscribePage) {
             $sLanguageId = FrontendManager::shouldIncludeLanguageInLink() ? $this->oNewsletter->getLanguageId() : false;
             if (method_exists($mRecipient, 'getUnsubscribeQueryParams')) {
                 $sUnsubscribeLink = LinkUtil::absoluteLink(LinkUtil::link($this->oUnsubscribePage->getLink(), 'FrontendManager', $mRecipient->getUnsubscribeQueryParams(), $sLanguageId));
                 $oEmailTemplateInstance->replaceIdentifier('unsubscribe_link', $sUnsubscribeLink);
             }
         }
     } else {
         $oEmailTemplateInstance->replaceIdentifier('recipient', $mRecipient);
     }
     // Send newsletter and store invalid emails
     try {
         $sPlainTextMethod = Settings::getSetting('newsletter', 'plain_text_alternative_method', 'markdown');
         $oEMail = null;
         if ($sPlainTextMethod === null || $sPlainTextMethod === false) {
             $oEMail = new EMail($this->oNewsletter->getSubject(), $oEmailTemplateInstance, true);
         } else {
             $oEMail = new EMail($this->oNewsletter->getSubject(), MIMEMultipart::alternativeMultipartForTemplate($oEmailTemplateInstance, null, null, $sPlainTextMethod), true);
         }
         if (is_object($mRecipient)) {
             $oEMail->addRecipient($mRecipient->getEmail(), $mRecipient->getName() === $mRecipient->getEmail() ? null : $mRecipient->getName());
         } else {
             $oEMail->addRecipient($mRecipient);
         }
         $oEMail->setSender($this->sSenderName, $this->sSenderEmailAddress);
         $oEMail->send();
     } catch (Exception $e) {
         $this->aInvalidEmails[] = new NewsletterSendFailure($e, $mRecipient);
     }
 }