Remark: This message is used to test examples from RFC 3501 page 56, the
    "example of a complex message".
From: foo@bar.com
Subject: RFC 3501
Content-Type: multipart/mixed; boundary=toplevel

--toplevel
Content-Id: 1
Content-Type: text/plain

Part 1

--toplevel
Content-Id: 2
Content-Type: application/octet-stream

Part 2

--toplevel
Content-Id: 3
Content-Type: message/rfc822

Subject: Part 3
Content-Type: multipart/mixed; boundary=part3

--part3
Content-Id: 3.1
Content-Type: text/plain

Part 3.1

--part3
Content-Id: 3.2
Content-Type: application/octet-stream

Part 3.2

--part3--
--toplevel
Content-Id: 4
Content-Type: multipart/mixed; boundary=part4

--part4
Content-Id: 4.1
Content-Type: image/gif

Part 4.1

--part4
Content-Id: 4.2
Content-Type: message/rfc822

Subject: Part 4.2
Content-Type: multipart/mixed; boundary=subpart42

--subpart42
Content-Id: 4.2.1
Content-Type: text/plain

Part 4.2.1

--subpart42
Content-Id: 4.2.2
Content-Type: multipart/alternative; boundary=subsubpart422

--subsubpart422
Content-Id: 4.2.2.1
Content-Type: text/plain

Part 4.2.2.1

--subsubpart422
Content-Id: 4.2.2.2
Content-Type: text/richtext

Part 4.2.2.2

--subsubpart422--
--subpart42--
--part4--
--toplevel--