All top level threads get sorted as per your 'View' > 'Sort by' settings: eg: Date, descending, threaded

However, all emails contained within a thread are appended in the order received as if a conversation. So in effect newest is always at the bottom.

The quick and easy way to locate new unread mail is to use 'Quick Filter' toolbar. Clickon the 'envelope' icon which has tooltop 'Show only unread messages' After reading, click on same icon again to revert to your normail view.

All top level threads that receive new mails within a thread become underlined to draw attention to the fact they contain unread mail.

So, to answer your question, no they cannot be reversed in order.

However, you can also right click on top level thread and select 'Open' > 'Open message in conversation' This opens in a new tab and shows all the conversation including any replies you may have made which may be of use. In that view you can remove the threads option and sort by Date. Thus putting entire conversation in the order desired. It also helps to see the conversation without all the clutter. Then just close the tab when finished or leave open to return to later.

I understand; thank you for the help. How could I submit a suggestion to implement this change? Thank you again.

I understand; thank you for the help. How could I submit a suggestion to implement this change? Thank you again.

There has been several enhancement requests/bug reports asking for this to be implemented over many years and I can tell you there has not been anything forthcoming from the developers. All the code in Thunderbird has recently been completely rewritten and it was not included.

I get the impression this is not so simple a request as it sounds and they prefer to keep using the 'conversation' mode.

Bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=479969

Okay, thank you for the information. I'll submit a ticket, just in case, but I'll de-thread my e-mails for now. Thank you again.