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.