Subject: multipart/related with a text/plain root
From: root@localhost
To: rt@example.com
Content-Type: multipart/related; boundary="=_related_boundary_42"

This is a multipart message in MIME format.

--=_related_boundary_42
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit

UNIQUEPLAINBODY this is the plain text body of a multipart/related message that
has no text/html alternative part. It must still be displayed.

--=_related_boundary_42
Content-Type: application/octet-stream; name="data1.bin"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="data1.bin"

aGVsbG8gd29ybGQK

--=_related_boundary_42
Content-Type: application/octet-stream; name="data2.bin"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="data2.bin"

Z29vZGJ5ZSB3b3JsZAo=

--=_related_boundary_42--
