#!/usr/bin/env python
from email.utils import parsedate
import mailbox

def extract_date(email):
    date = email.get('Date')
    return parsedate(date)

the_mailbox = mailbox.mbox('cypherpunks-1999-2015-fixedbetter.mbox')
sorted_mails = sorted(the_mailbox, key=extract_date)
print 'after sorted'
the_mailbox.update(enumerate(sorted_mails))
print 'after update'
the_mailbox.flush()
print 'after flush'