|Content-Type: text/plain; charset=utf-8
      |
      |... contents of file1.txt ...
      |--BbC04y
      |Content-Disposition: file; filename="file2.gif"
      |Content-Transfer-Encoding: binary
      |Content-Type: image/gif
      |
      |... contents of file2.gif ...
      |--BbC04y--
      |
      |--AaB03x--
      |
      """.trimMargin().replace("\n", "\r\n")
    val body =