Thunderbird 155.0.1 Released

Mozilla has released Thunderbird 155.0.1 just days after the 155.0 feature release landed on September 1. This point release is part of a bigger shift: starting this month, Thunderbird moved from its old six-week release cycle to a fortnightly one, meaning updates for the free, open-source email client will now arrive roughly every two weeks.

What's New in Thunderbird 155.0.1 and 155.0

155.0.1 is a bug-fix release, and its main purpose is stability: it addresses issues that surfaced after 155.0 shipped, keeping the email client running smoothly for users who update promptly.

155.0 itself was the bigger release, and it's worth knowing what came with it since most users will be catching up on both at once:

• Custom OAuth support for IMAP and SMTP servers. The custom OAuth settings panel gained PKCE and external-browser fields, and OAuth add-ons can now override Thunderbird's built-in authentication for specific domains and hostnames, useful if you connect Thunderbird to a self-hosted or less common email provider.
• Simplified account setup. Manual configuration for Exchange, Microsoft Graph, and custom OAuth accounts is now combined into a single setup flow instead of separate paths.
• Two new enterprise policies: DisableQRExport blocks the QR-code export feature (used to transfer settings to Thunderbird for Android), and DisableExperimentalFeatures turns off experimental functionality, both aimed at IT admins managing locked-down deployments.
• Cleaner account removal. Deleting an account now also clears its OAuth token from the password manager, so stale credentials don't linger.
• Roughly 30 additional fixes across crashes, sync failures, and calendar issues shipped alongside the eight headline features.

Download

Thunderbird 155.0.1 is available now for Windows, macOS, and Linux from the official Thunderbird downloads page, or via its UpdateStar listing for update tracking and version history.