The Thunderbird team has officially released Thunderbird 156, bringing another round of new features, security improvements, authentication enhancements, and reliability fixes to the popular open-source email client. Released on September 15, 2026, the update is available for Linux alongside Windows and macOS.

Thunderbird 156 is not a dramatic redesign of the desktop mail client. Instead, it concentrates on improving areas that matter to everyday users and system administrators, including OAuth authentication, OpenPGP, POP3, IMAP, Exchange Web Services, SMTP, attachments, calendars, enterprise policies, and security.

For Linux users in particular, the release delivers several fixes affecting common mail protocols and account configurations while retaining support for Linux environments using GTK+ 3.14 or newer.

Thunderbird 156 Arrives on Linux

Thunderbird 156 follows version 154, which arrived in August with features including optional system tray operation and Microsoft Graph support for Microsoft 365.

Version 156 continues the project's monthly release cycle with a more targeted collection of authentication, security, compatibility, and reliability improvements.

According to Thunderbird's official release notes, version 156 requires:

• Linux: GTK+ 3.14 or newer
• Windows: Windows 10 or newer
• macOS: macOS 10.15 or newer

Thunderbird 156 was officially released on September 15.

Linux distribution availability will vary because distributions can package Thunderbird according to their own schedules. Users receiving Thunderbird through another packaging channel may therefore see version 156 at a different time.

Custom OAuth Support Expands

One of the most significant areas of development in Thunderbird 156 is OAuth authentication.

Thunderbird now supports custom OAuth configurations containing an issuer ID and client secret for IMAP and POP3 accounts. Custom OAuth support has also been extended specifically to POP3.

OAuth has become increasingly important as email providers move away from conventional username-and-password authentication toward token-based authentication.

For Thunderbird, broader custom OAuth support means users and organizations have greater flexibility when connecting the client to mail services that don't fit Thunderbird's predefined provider configurations.

This can be particularly useful in enterprise environments, self-hosted infrastructure, and organizations operating their own identity systems.

Exchange Custom OAuth Setup Fixed

Exchange users receive an important related correction.

The KDE Project has officially released KDE Plasma 6.7.5, delivering another round of bug fixes and stability improvements for the Plasma 6.7 desktop series. Released on September 8, 2026, the update contains roughly a month of fixes and updated translations contributed since Plasma 6.7.4 arrived in early August.

Unlike a major Plasma release, version 6.7.5 doesn't introduce a large collection of new desktop features. Instead, KDE has focused on fixing problems affecting Discover, KWin, Wayland, networking, System Monitor, Plasma Desktop, RPM-OSTree systems, Snap updates, HDR rendering, and several other components.

For users already running Plasma 6.7, this makes version 6.7.5 primarily a maintenance upgrade intended to make the desktop more dependable ahead of the next major Plasma series.

KDE Plasma 6.7.5 Arrives as the September Bugfix Release

KDE describes Plasma 6.7.5 as its September bugfix release for the Plasma 6 desktop.

The broader Plasma 6.7 series originally arrived in June 2026, followed by a succession of maintenance releases:

• Plasma 6.7.1 on June 23
• Plasma 6.7.2 on June 30
• Plasma 6.7.3 on July 14
• Plasma 6.7.4 on August 4
• Plasma 6.7.5 on September 8

KDE's official download infrastructure confirms that the Plasma 6.7.5 source packages became available on September 8.

This slower maintenance cadence later in a Plasma series is normal. Once the most urgent post-release problems have been addressed, KDE generally shifts more development attention toward the next feature release while continuing to provide important fixes for the current branch.

Discover Receives Several Important Fixes

KDE's Discover software center receives some of the most noticeable improvements in Plasma 6.7.5.

One particularly annoying problem could cause Discover to become stuck while checking for updates when its Snap backend was installed but no Snap applications actually had updates available.

That problem has now been corrected.

Discover also behaves more reliably when fwupd, the Linux firmware update service, is unavailable. Previously, a broken or intentionally masked fwupd service could interfere with Discover's normal operation. Plasma 6.7.5 allows the rest of the application to continue functioning correctly in that situation.

This is useful for systems where firmware updating isn't supported, where administrators intentionally disable the service, or where fwupd encounters a configuration problem.

Firmware Updates No Longer Incorrectly Require Reboots

Another Discover correction addresses a regression involving firmware updates.