To: recipient@example.com
From: sender@example.com
Subject: mhfixmsg pass through on parse error
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="----- =_aaaaaaaaaa0"

------- =_aaaaaaaaaa0
Content-Type: text/plain; charset="iso-8859-1
Content-Disposition: attachment; filename="test1.txt"
Content-Transfer-Encoding: quoted-printable

This is the=
 text/plain part.

------- =_aaaaaaaaaa0--