Hallo,
der Hoster ist Netbeat (netbeat.de)
$mail->isSMTP();
$mail->Host = 'smtp.xxxxxxxx.de';
$mail->Username = 'xxxxxxxx.de';
$mail->Password = 'yyyyyyyyyy';
$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
$mail->Port = 587;
$mail->SMTPAuth = true;