subject: primary subject content-type : multipart/(co\m\)ment)mumble mumble; boundary = "ab\cd ef" mumble abcdef prolog --abcd ef content-type: message/rfc822; mumble subject: nested subject content-type: multipart/mumble; boundary(comment)="pqrs" content-transfer-encoding: base64 pqrs prolog --pqrs header: pqrs part 01 body pqrs part 01 --pqrs header: pqrs part 02 body pqrs part 02 --bogus-boundary header: wietse body asdasads --abcd ef header: abcdef part 02 body abcdef part 02 --abcd ef-- epilog