protected function decodeContentTransfer($encodedString, $encodingType)
    {
        if (is_array($encodingType)) {
            $encodingType = $encodingType[0];
        }

        $encodingType = strtolower($encodingType);
        if ($encodingType == 'base64') {
            return base64_decode($encodedString);
        } elseif ($encodingType == 'quoted-printable') {
            return quoted_printable_decode($encodedString);
        } else {
            return $encodedString;
        }
    }