Add missing "s" from format string.
This closes SourceForge patch #101714.
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index f010777..51aeb30 100755
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -272,7 +272,7 @@
             f = msg.getheader('from') or ""
             s = msg.getheader('subject') or ""
             d = msg.getheader('date') or ""
-            print '-%20.20s   %20.20   %-30.30s'%(f, d[5:], s)
+            print '-%20.20s   %20.20s   %-30.30s'%(f, d[5:], s)
 
 
 if __name__ == '__main__':