2073783 - Add option to sort messages within a thread from newest to oldest

Status: RESOLVED DUPLICATE of bug 479969

(Thunderbird :: Folder and Message Lists, enhancement)

Description

[Igor]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/152.0.0.0 Safari/537.36

Steps to reproduce:

Currently, when threaded view is enabled (View → Sort by → Threaded), messages within each thread are always displayed in chronological order — from oldest (root message) at the top to newest (latest reply) at the bottom. There is no option to reverse this order so that the newest message appears at the top of the thread.

Actual results:

Currently, when threaded view is enabled (View → Sort by → Threaded), messages within each thread are always displayed in chronological order — from oldest (root message) at the top to newest (latest reply) at the bottom. There is no option to reverse this order so that the newest message appears at the top of the thread.

Expected results:

Users coming from other email clients (e.g., Microsoft Outlook, Apple Mail, Gmail) expect the most recent message in a conversation to be visible immediately — at the top of the thread — without scrolling down. The current implementation forces users to scroll to the bottom of every thread to reach the latest reply, which is particularly painful for long threads (10+ messages).
This affects both display modes:
• Table view: threads expand with oldest message first.
• Cards view: cards stack with oldest message at the top.
Proposed solution:
Add a user-configurable option to reverse the sort order within threads. Specifically:

1. New preference: mail.thread_sort_order with values:
   o 0 — Oldest first (current default behavior, backward-compatible)
   o 1 — Newest first (new option)
2. UI integration: Add a toggle in the "Message List Display Options" menu (the icon with horizontal lines in the thread pane header), under the existing "Threaded" checkbox:
   o [✓] Threaded
   o ○ Oldest first ○ Newest first (radio buttons, enabled only when Threaded is checked)
3. Behavior:
   o When Newest first is selected, the root message stays as the thread anchor, but replies are sorted in reverse chronological order below it: the most recent reply appears directly under the root, older replies follow.
   o Alternatively (simpler implementation): the entire thread is reversed — newest message at the top, oldest at the bottom.
   o The setting should be per-account or global (user preference), consistent with existing sort settings.
   o The setting should persist across restarts and apply to both Table and Cards view modes.
4. Impact on existing features:
   o Sort threads by last message date (existing option) should continue to work independently — it controls inter-thread ordering, while the new option controls intra-thread ordering.
   o Quick Filter bar should remain functional within reversed threads.
   o Collapse/expand behavior should not change.
5. Expected result:
   o User enables Threaded view + "Newest first".
   o Opens a thread with 10 messages.
   o The most recent reply is at the top of the expanded thread (or directly below the root).
   o No scrolling needed to reach the latest message.
   Environment:
   • Thunderbird 156.0 64-bit
   • OS: Windows
   Use case:
   A user receives 20+ replies in a single thread throughout the workday. Each time they open the thread, they must scroll past 19 older messages to read the latest reply. With "Newest first", the latest reply would be immediately visible at the top, saving time and reducing frustration.
   References:
   • Outlook for Windows/Mac displays newest replies at the top of a conversation by default.
   • Gmail web interface shows newest messages at the top of a thread.
   • This has been a long-standing user complaint on the Thunderbird support forums.

Comment 1

[Wayne Mery (:wsmwk)]

Sounds like Bug 479969 - Sort by date/descending, Threaded still sorts within-thread messages by date/ascending