Subject: Inline draft
From: Alice <alice@example.com>
To: Bob <bob@example.com>
MIME-Version: 1.0
Content-Type: multipart/related; boundary=rel

--rel
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 7bit

<div>hello<img src="cid:logo"></div>
--rel
Content-Type: image/png; name=logo.png
Content-Disposition: inline; filename=logo.png
Content-ID: <logo>
Content-Transfer-Encoding: base64

iVBORw0KGgo=
--rel--