Emails backup in python 3.2

[TheSaint]

Hello,
I'm looking for an idea how to backup emails retrieved by poplib and save 
them into mailbox.mbox file.
The problem is the received message which is a list of bytes streams, 
mailbox.mbox don't expect a list.
What conversion should I do?
A file type io.StringIO ?
decoding every bytes stream which might not have any declared codec?

As far as python moved into unicode, why doesn't it handle these undecoded 
bytes as it was with strings before?

-- 
goto /dev/null