Hi hi, noob here. I found this today after clicking 'Easy issues' link. 

Would something like this work?  test_mailbox.py seems to pass. However, I'm not too sure what more needs to be done in the _explain_to. It seems like everything to convert headers/flags between message formats are already there ?


diff -r 63bf3bae20ef Lib/mailbox.py
--- a/Lib/mailbox.py    Wed Sep 14 11:46:17 2011 -0400
+++ b/Lib/mailbox.py    Wed Sep 14 17:12:51 2011 -0700
@@ -1467,8 +1467,7 @@
 
     def _become_message(self, message):
         """Assume the non-format-specific state of message."""
-        for name in ('_headers', '_unixfrom', '_payload', '_charset',
-                     'preamble', 'epilogue', 'defects', '_default_type'):
+        for name in message.__dict__:
             self.__dict__[name] = message.__dict__[name]