1
subject: primary subject
2
content-type : multipart/(co\m\)ment)mumble mumble; boundary = "ab\cd
8
content-type: message/rfc822; mumble
10
subject: nested subject
11
content-type: multipart/mumble; boundary(comment)="pqrs"
12
content-transfer-encoding: base64
32
header: abcdef part 02