--- D:/apps/Python26/Lib/email/test/test_email-trunk.py	Tue Aug 04 01:17:38 2009
+++ D:/apps/Python26/Lib/email/test/test_email.py	Tue Aug 04 01:16:46 2009
@@ -2270,6 +2270,29 @@
         addrs = Utils.getaddresses(['User ((nested comment)) <foo@bar.com>'])
         eq(addrs[0][1], 'foo@bar.com')
 
+    def test_utils_make_msgid(self):
+        """Test make_msgid uniqueness, even with multiple threads"""
+        NMSGIDS = 10000
+        eq = self.assertEqual
+        try: from threading import Thread
+        except ImportError: from dummy_threading import Thread
+
+        class MsgidsThread(Thread):
+            def run(self):
+                self.msgids = []
+                for i in xrange(NMSGIDS):
+                    self.msgids.append(Utils.make_msgid())
+            
+        threads = [MsgidsThread() for i in range(5)]
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join()
+        for t in threads:
+            eq(len(t.msgids), NMSGIDS)
+            eq(len(set(t.msgids)), NMSGIDS)
+        eq(len(set(sum([t.msgids for t in threads], []))), len(threads)*NMSGIDS)
+
     def test_utils_quote_unquote(self):
         eq = self.assertEqual
         msg = Message()