'At the end of message, rename the file holding the message to its
final name.
@rtype: L{Deferred} which successfully results in L{bytes}
@return: A deferred which returns the final name of the file.'

def eomReceived(self):

    self.fp.close()
    os.rename(self.name, self.finalName)
    return defer.succeed(self.finalName)
