typo3 4.5 lts send html email

setReturnPath('returnEmail@domain.tld');
$mail->setFrom('fromEmail@domain.tld');
$mail->setTo('recipentEmail@domain.tld');
$mail->setSubject($emailSubject);
$mail->setBody($plainMailContent);
$mail->addPart($htmlMailContent, 'text/html'); //html content
$mail->send();
$success = $mail->isSent();