boundary example

 $text->getContent($this->EOL)
                  . $this->EOL
                  . $boundaryLine
                  . $html->getHeaders($this->EOL)
                  . $this->EOL
                  . $html->getContent($this->EOL)
                  . $this->EOL
                  . $boundaryEnd;

            $mp           = new Zend_Mime_Part($body);
            $mp->type     = Zend_Mime::MULTIPART_ALTERNATIVE;
            $mp->boundary = $mime->boundary();

            $this->_isMultipart = true;

            // Ensure first part contains text alternatives             array_unshift($this->_parts, $mp);

            // Get headers             $this->_headers = $this->_mail->getHeaders();
            return;
        }