MIME (
  part  1  (
           part1_1 (
                      part1_1_1 (
                                .............
                                )
                   )

           part1_2 (
                   ...................
                   )
           )
  part  2  (
           part2_1 (
                   )

           part2_2 (
                   )
           )
)

MIME (
part  1  (
  content-type: image/gif;
  content-disposition: attachment;
  )
part  2  (
  content-type: text/plain;
  ....
  )
)