Host: example.com
Content-Type: multipart/mixed;
     boundary=unique-boundary-1

The preamble of the outer multipart message.
Content readers that understand multipart format
should ignore this preamble.
If you are reading this text, you might want to
consider changing to a content reader that understands
how to properly parse multipart messages.
--unique-boundary-1

Part 1 of the outer message.
[Note that the preceding blank line means
no header fields were given and this is text,
with charset US ASCII. It could have been
done with explicit typing as in the next part.]

--unique-boundary-1
Content-type: text/plain; charset=utf-8

Part 2 of the outer message.
This could have been part of the previous part,
but illustrates explicit versus implicit
typing of body parts.

--unique-boundary-1
Content-Type: multipart/form-data;
    boundary=unique-boundary-2
X-Description: Part 3 of the outer message is multipart!

A one-line preamble for the inner multipart message.
--unique-boundary-2
Content-Type: image/png
Content-Encoding: base64
Content-Disposition: form-data; name="image1"; filename="tengu-2.png"
X-Description: Part 1 of the inner message is a png, "tengu-2.png"

iVBORw0KGgoAAAANSUhEUgAAABUAAAAWCAIAAACg4UBvAAADEklEQVR4nGL4TxlgoKb+f58+fVm0
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btkjLHFYUWaTm+mOWK9Fdkb92ioTDTU3FeX9Q0+7GPr//v/3/umTOTomq7iF9inKbNeQmKEg1Com
0CYrd3rZEmzasZUf1/cdmBkUMk9JZb2Y0CxZgTphvgk2tp/fvsWmHaIf1WXAtPH18+eXd++enjp1
ibf7XF+fG7t3/cWqm8rlFxkAAAAA//8DAB1sApdpwz9dAAAAAElFTkSuQmCC
--unique-boundary-2
Content-Type: image/png
Content-Encoding: base64
Content-Disposition: form-data; name="image2"; filename="oni.png"
X-Description: Part 2 of the inner message is another png, "oni.png"

iVBORw0KGgoAAAANSUhEUgAAABYAAAAUCAIAAAAGHlpnAAADwElEQVR4nGL4TzFgwBT69///lzt3
Xly+8OLp4+dPH71++fzj+7fvb938eOP633//kNT9w27E9+/fjx8/dDY2ZLOVYYy7dYCLaYinZVaQ
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N3PSzetXvn75/O/v3/8YAEupRSoAAAAA//8DABTUSlT+h8PYAAAAAElFTkSuQmCC
--unique-boundary-2--

The epilogue for the inner multipart message.

--unique-boundary-1
Content-type: text/richtext

This is <bold>part 4 of the outer message</bold>
<smaller>as defined in RFC1341</smaller><nl>
<nl>
Isn't it <bigger><bigger>cool?</bigger></bigger>

--unique-boundary-1
Content-Type: message/http; name="/evil/filename";

GET / HTTP/1.1
Host: www.example.org
Content-Type: text/plain; charset=utf-8
Content-Encoding: Quoted-printable

Part 5 of the outer message is itself an http message!

--unique-boundary-1--

The epilogue for the outer message.