diff --git a/Lib/test/data/msg_23.txt b/Lib/test/data/msg_23.txt
new file mode 100644
index 00000000000..bb2e8ec36bb
--- /dev/null
+++ b/Lib/test/data/msg_23.txt
@@ -0,0 +1,8 @@
+From: aperson@dom.ain
+Content-Type: multipart/mixed; boundary="BOUNDARY"
+
+--BOUNDARY
+Content-Type: text/plain
+
+A message part
+--BOUNDARY--