Content-Type: multipart/mixed; boundary="1234567890123456789012345678901234567890123456789012345678901234567890123456789012"

--1234567890123456789012345678901234567890123456789012345678901234567890123456789012
Content-Type: multipart/mixed; boundary="123456789012345678901234567890123456789012345678901234567890123456789012345678901"

--123456789012345678901234567890123456789012345678901234567890123456789012345678901
Content-Type: multipart/mixed; boundary="12345678901234567890123456789012345678901234567890123456789012345678901234567890"

--12345678901234567890123456789012345678901234567890123456789012345678901234567890
Content-Type: text/plain

1
--1234567890123456789012345678901234567890123456789012345678901234567890123456789012
Content-Type: text/plain

22
--123456789012345678901234567890123456789012345678901234567890123456789012345678901
Content-Type: text/plain

333
--12345678901234567890123456789012345678901234567890123456789012345678901234567890
Content-Type: text/plain

4444

---- EXPECTED STRUCTURE ----
{
  "headers": {
    "content_type": {
      "ContentType": {
        "c_type": "multipart",
        "c_subtype": "mixed",
        "attributes": {
          "boundary": "1234567890123456789012345678901234567890123456789012345678901234567890123456789012"
        }
      }
    }
  },
  "html_body": [
    {
      "contents": "<html><body>1<br/>--1234567890123456789012345678901234567890123456789012345678901234567890123456789012<br/>Content-Type: text/plain<br/><br/>22<br/>--123456789012345678901234567890123456789012345678901234567890123456789012345678901<br/>Content-Type: text/plain<br/><br/>333</body></html>"
    }
  ],
  "text_body": [
    {
      "headers": {
        "content_type": {
          "ContentType": {
            "c_type": "text",
            "c_subtype": "plain"
          }
        }
      },
      "contents": "1\n--1234567890123456789012345678901234567890123456789012345678901234567890123456789012\nContent-Type: text/plain\n\n22\n--123456789012345678901234567890123456789012345678901234567890123456789012345678901\nContent-Type: text/plain\n\n333"
    }
  ],
  "attachments": [
    {
      "Text": {
        "headers": {
          "content_type": {
            "ContentType": {
              "c_type": "text",
              "c_subtype": "plain"
            }
          }
        },
        "contents": "4444\n"
      }
    }
  ]
}