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

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

this part never closes