(insert "To: user@example.com\n")'
sed \
-e s',^User-Agent: Notmuch/.* Emacs/.*,User-Agent: Notmuch/XXX Emacs/XXX,' \
- -e s',^Message-ID: <.*>$,Message-ID: <XXX>,' < sent_message >OUTPUT
+ -e s',^Message-ID: <.*>$,Message-ID: <XXX>,' \
+ -e s',^\(Content-Type: text/plain\); charset=us-ascii$,\1,' < sent_message >OUTPUT
cat <<EOF >EXPECTED
From: Notmuch Test Suite <test_suite@notmuchmail.org>
To: user@example.com
User-Agent: Notmuch/XXX Emacs/XXX
Message-ID: <XXX>
MIME-Version: 1.0
-Content-Type: text/plain; charset=us-ascii
+Content-Type: text/plain
This is a test that messages are sent via SMTP
EOF