From: Alice <alice@example.org>
Subject: With attachment
Date: Sat, 01 Aug 2026 10:00:00 +0000
Message-ID: <att-1@example.org>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="MIX"

--MIX
Content-Type: text/plain; charset=utf-8

see attached
--MIX
Content-Type: text/plain; charset=utf-8; name="notes.txt"
Content-Disposition: attachment; filename="notes.txt"
Content-Transfer-Encoding: quoted-printable

caf=C3=A9 notes
--MIX--
