Mozilla Thunderbird ESR is for Windows

Mozilla Thunderbird ESR — Summary

Mozilla Thunderbird ESR is a free, open-source desktop email client built for people who want dependable security fixes and a predictable feature schedule. The Extended Support Release focuses on stability, delivering feature updates less frequently while providing regular maintenance and safety patches. It supports email, calendar, and chat functions, all of which can be tailored through settings and add-ons to suit personal or workplace needs.

Update rhythm and support approach

The ESR channel is intended for users and organizations that prefer fewer feature changes but still require prompt bug and security remediation. Major capabilities are refreshed on an annual cadence, while smaller stability and security updates are applied monthly to reduce disruption and maintain a secure environment.

Core capabilities and customization

• Robust message handling for multiple accounts, including support for IMAP, POP, and RSS feeds.
• Integrated calendar and scheduling tools that sync with popular calendar services.
• Built-in chat and newsgroup features, plus a wide ecosystem of extensions for deeper customization.
• Strong emphasis on security and reliability, with frequent fixes and compatibility with open standards.

Alternatives you may want to evaluate

• Thunderbird (standard release) — the regular release channel delivers new features sooner for users who want the latest functionality.
• DSpeech — a separate text-to-speech utility that some users pair with email clients for accessibility and read-aloud workflows.
• Other modern mail clients (for example, Mailspring or eM Client) — worth exploring if you prefer different user interfaces or commercial support options.