Thread sorting issue in Thunderbird – incorrect order and date display when grouped by threads

Alzi — Wed, 12 Nov 2025 08:57:00 GMT

Hello Thunderbird team,

I’ve encountered an issue with message sorting in the latest ESR version of Thunderbird (140.4.0, 64-bit).

When messages are sorted by Date (Descending) and Grouped by Thread is enabled, the thread view does not correctly reflect the selected sorting order.
Specifically:

Threads are not reordered according to the newest message within each thread.
The parent (root) message of a thread always stays in the same position, even when new replies are received.
The displayed date for the thread does not match the date of the latest message inside the thread.
Individual messages inside the thread also ignore the descending date order.

Expected behavior:

The main thread entry should represent the newest message within the thread, showing its actual date, and the overall sorting should respect the chosen "Date (Descending)" order.

Here is a screenshot that demonstrates the incorrect order and mismatched dates.

Additional info:

Version: Mozilla Thunderbird 140.4.0esr (64-bit)
OS: Windows 10 22H2 (x64)
Setting: Sort by Date (Descending) + Group by Thread
Config value mailnews.sort_threads_by_root = false
Issue persists even in safe mode (tested with all add-ons disabled)

Thanks for looking into this - it seems to be a regression or sorting logic inconsistency when threaded view is active.

Best regards,
Michal

Re: Thread sorting issue in Thunderbird – incorrect order and date display when grouped by threads

ADRN — Mon, 12 Jan 2026 20:11:38 GMT

Same issue!

Additional info:

Version: Mozilla Thunderbird 140.6.0esr (64 bits) (but existed on my last OS once I installed Nebula)
OS: Linux Mint 22.2 (x64) (my last OS was on Mint 21.3)
Setting: Sort by Date (Descending) + Group by Thread

Also: Sort by Read Status + Group by Thread
Config value mailnews.sort_threads_by_root =??? (I don't know, but the bug appeared when I upgraded to Nebula)

topic Re: Thread sorting issue in Thunderbird – incorrect order and date display when grouped by threads in Firefox Labs

Thread sorting issue in Thunderbird – incorrect order and date display when grouped by threads

Re: Thread sorting issue in Thunderbird – incorrect order and date display when grouped by threads