Mozilla has just unveiled Thunderbird version 140 of its widely adopted free and open-source desktop email client, now available for download. The key thing here is that this is an ESR (Extended Support Release) release.
In other words, designed with enterprise users, institutions, and conservative users in mind, it offers a stable, long-term support cycle for those prioritizing stability and reliability over rapid feature changes.
Among the most notable new additions is enhanced control over notifications, allowing users to directly perform actions such as “Mark as Read,” “Delete,” “Mark as Spam,” and “Mark as Starred” right from the notification itself, providing quick and intuitive interactions without the need to open the main application window.
Additionally, Thunderbird 140 ESR brings a highly requested dark mode feature, which includes support for dark reader in the message pane. Messages now automatically adapt to dark mode through an easily accessible toggle in the header, significantly reducing eye strain and improving readability, especially in low-light conditions.
A newly implemented enterprise policy also gives enterprise users more refined controls, enabling granular management of in-app notifications to better align with organizational preferences.
Further enhancing usability, this new ESR version introduces horizontal scrolling in the thread pane and customizable row counts for Cards View within the revamped “Appearance” settings.
Plus, users have greater flexibility to manually sort folders directly from the folder pane and globally control message threading and sorting preferences through an improved UI.
Significant changes have been made under the hood as well. Thunderbird now uses unified OAuth2 code for both CardDAV address books and calendars, improving consistency and security. Obsolete preferences and buttons, such as the IMAP subscribe/unsubscribe feature, have been removed to simplify the interface.
This release also addresses a comprehensive list of bug fixes, tackling stability issues such as crashes during folder compaction and message header handling, resolving performance bottlenecks when moving bulk messages, and rectifying multiple problems with IMAP and POP3 mail handling.
OpenPGP users will particularly appreciate fixes that address dual signing and key import issues.
Lastly, while Thunderbird 140 ESR delivers robust enhancements and fixes, users should be aware of an unresolved issue where passwords are not remembered in 32-bit MAPI usage without a compose window. The Thunderbird team is actively working to address this in future updates.
For more information, see the announcement. Those eager to immediately download the latest Thunderbird ESR version can do so directly from Mozilla’s server. Apart from it, the regular 140 release is also available, which you can download here.
