Google App Engine for Java Incoming Email Service

MimeMessage mimeMessage = new MimeMessage(session, req.getInputStream
());

-------------------------------------------------------------

DataHandler dataHandler = mimeMessage.getDataHandler();
DataSource dataSource = dataHandler.getDataSource();
MimeMultipart mimeMultipart = new MimeMultipart(dataSource);

or

InputStream inputStream = (InputStream)mimeMessage.getContent();
String ContentType = mimeMessage.getContentType();
ByteArrayDataSource byteArrayDataSource = new ByteArrayDataSource
(inputStream,ContentType);
Multipart mimeMultipart = new MimeMultipart(byteArrayDataSource);

-------------------------------------------------------------

  //message parse

  Part part1 = mimeMultipart.getBodyPart(0);
  part1.getContentType();
  ....................
  Part part2 = mimeMultipart.getBodyPart(1);
  part2.getContentType();
  ....................

Try that please