code: public function getPartDecodedContent(Zend_Mime_Part $mimePart)
      {
          // getRawContent is not available in Zend 1.11 (Magento CE 1.7)
          if (method_exists($mimePart, 'getRawContent')) {
              return $mimePart->getRawContent();
          }
  
          $content = '';
          if (method_exists($mimePart, 'getContent')) {
              $encoding = $mimePart->encoding;
              $mimePart->encoding = 'none';
              $content = $mimePart->getContent();
              $mimePart->encoding = $encoding;
          }
  
          return $content;
      }
docs: Returns raw content of e-mail message. Abstract Zend_Mime_Part interface changes between 1.11.0 and 1.12.0
  
  @param Zend_Mime_Part $mimePart
  @return String