Content-Type: multipart/mixed;
 boundary=bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

--bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit

This is a message with a base64 encoded attached email
--bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Content-Disposition: attachment; filename="attached_email.eml"
Content-Type: message/rfc822
Content-Transfer-Encoding: base64
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--bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb--
---- EXPECTED STRUCTURE ----{
  "headers_rfc": {
    "content_type": {
      "ContentType": {
        "c_type": "multipart",
        "c_subtype": "mixed",
        "attributes": {
          "boundary": "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
        }
      }
    }
  },
  "html_body": [
    0
  ],
  "text_body": [
    0
  ],
  "attachments": [
    1
  ],
  "parts": [
    {
      "Text": {
        "headers_rfc": {
          "content_transfer_encoding": {
            "Text": "7bit"
          },
          "content_type": {
            "ContentType": {
              "c_type": "text",
              "c_subtype": "plain",
              "attributes": {
                "charset": "utf-8"
              }
            }
          }
        },
        "is_encoding_problem": false,
        "body": "This is a message with a base64 encoded attached email"
      }
    },
    {
      "Message": {
        "headers_rfc": {
          "content_type": {
            "ContentType": {
              "c_type": "message",
              "c_subtype": "rfc822",
              "attributes": null
            }
          },
          "content_transfer_encoding": {
            "Text": "base64"
          },
          "content_disposition": {
            "ContentType": {
              "c_type": "attachment",
              "c_subtype": null,
              "attributes": {
                "filename": "attached_email.eml"
              }
            }
          }
        },
        "is_encoding_problem": false,
        "body": {
          "headers_rfc": {
            "from": {
              "Address": {
                "name": "Name",
                "address": "email@example.com"
              }
            },
            "content_language": {
              "Text": "en-US"
            },
            "to": {
              "Address": {
                "name": "email@example.com",
                "address": "email@example.com"
              }
            },
            "subject": {
              "Text": "HTML test"
            },
            "message_id": {
              "Text": "random-message-id@example.com"
            },
            "date": {
              "DateTime": {
                "year": 2021,
                "month": 12,
                "day": 14,
                "hour": 11,
                "minute": 48,
                "second": 25,
                "tz_before_gmt": false,
                "tz_hour": 1,
                "tz_minute": 0
              }
            },
            "content_type": {
              "ContentType": {
                "c_type": "multipart",
                "c_subtype": "alternative",
                "attributes": {
                  "boundary": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
                }
              }
            },
            "mime_version": {
              "Text": "1.0"
            }
          },
          "html_body": [
            1
          ],
          "text_body": [
            0
          ],
          "attachments": [],
          "parts": [
            {
              "Text": {
                "headers_rfc": {
                  "content_transfer_encoding": {
                    "Text": "7bit"
                  },
                  "content_type": {
                    "ContentType": {
                      "c_type": "text",
                      "c_subtype": "plain",
                      "attributes": {
                        "charset": "utf-8",
                        "format": "flowed"
                      }
                    }
                  }
                },
                "is_encoding_problem": false,
                "body": "This is an *HTML* test message"
              }
            },
            {
              "Html": {
                "headers_rfc": {
                  "content_transfer_encoding": {
                    "Text": "7bit"
                  },
                  "content_type": {
                    "ContentType": {
                      "c_type": "text",
                      "c_subtype": "html",
                      "attributes": {
                        "charset": "utf-8"
                      }
                    }
                  }
                },
                "is_encoding_problem": false,
                "body": "<html>\r\n  <head>\r\n    <meta http-equiv=\"content-type\" content=\"text/html; charset=UTF-8\">\r\n  </head>\r\n  <body>\r\n    This is an <b>HTML</b> test message\r\n  </body>\r\n</html>\r\n"
              }
            }
          ],
          "structure": {
            "List": [
              {
                "Part": 0
              },
              {
                "Part": 1
              }
            ]
          },
          "offset_header": 0,
          "offset_body": 319,
          "offset_end": 870
        }
      }
    }
  ],
  "structure": {
    "List": [
      {
        "Part": 0
      },
      {
        "Part": 1
      }
    ]
  },
  "offset_header": 0,
  "offset_body": 83,
  "offset_end": 1648
}