protected function _encodeHeader($value)
    {
        if (Zend_Mime::isPrintable($value) === false) {
            if ($this->getHeaderEncoding() === Zend_Mime::ENCODING_QUOTEDPRINTABLE) {
                $value = Zend_Mime::encodeQuotedPrintableHeader($value, $this->getCharset(), Zend_Mime::LINELENGTH, Zend_Mime::LINEEND);
            } else {
                $value = Zend_Mime::encodeBase64Header($value, $this->getCharset(), Zend_Mime::LINELENGTH, Zend_Mime::LINEEND);
            }
        }

        return $value;
    }