Subject: In parts MIME-Version: 1.0 Content-Type: multipart/mixed; boundary=1 --1 Content-Type: text/plain Content-Transfer-Encoding: binary Hi, this is the fancy thing I was talking about! --1 Content-Type: Message/Partial; number=1; total=5; id="heks68ewe@example.org" X-Weird-Header-1: Bar X-Weird-Header-2: Hello Message-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: base64 dGhpcyBpcyB0aGUgZmlyc3QgcGFydCBvZiB0aGUgbWVzc2FnZQo= --1--