My preferred settings for the message list pane (not sure if that's what everyone else calls it) include unthreaded, newest at top. From time to time, Thunderbird apparently forgets these settings, and in all my mailboxes and sub-folders, lists messages with the newest at the bottom and threaded. I haven't checked how often this happens and it doesn't seem to be related to updates. Any ideas about why T-bird does this, or even better, whether and how it can be fixed?