Mozilla Thunderbird ESR Overview

What is Mozilla Thunderbird ESR?

Mozilla will offer an Extended Support Release (ESR) based on an official release of Thunderbird for desktop for use by organizations including schools, universities, businesses and others who need extended support for mass deployments. You can read more about the plan here.

What does the Mozilla Thunderbird ESR life cycle look like?

Releases will be maintained for approximately one year, with point releases containing security updates coinciding with regular Thunderbird releases. The ESR will also have a two cycle (12 week) overlap between the time of a new release and the end-of-life of the previous release to permit testing and certification prior to deploying a new version.

Thunderbird ESR Release Overview

Maintenance of each ESR, through point releases, is limited to high-risk/high-impact security vulnerabilities and in rare cases may also include off-schedule releases that address live security vulnerabilities. Backports of any functional enhancements and/or stability fixes are not in scope.

At the end of the support period for an ESR version:

  • the release will reach its end-of-life
  • no further updates will be offered for that version
  • an update to the next version will be offered through the application update service

Who should use Mozilla Thunderbird ESR?

Mozilla Thunderbird ESR is meant for organizations that centrally manage their client desktops, including schools, businesses and other institutions that want to offer Thunderbird. Users who want to get the latest features, performance enhancements and technologies in their emailing experience should download Thunderbird, as these improvements will only be available to ESR users several development cycles after being made available in Thunderbird for desktop. If you're not using Thunderbird ESR, you can download Thunderbird from

What does my organization need to do to use Mozilla Thunderbird ESR?

Organizations that deploy Thunderbird ESR are requested to sign up for the Enterprise Working Group mailing list. They are also requested to test advance versions of Thunderbird and ESR Release Candidates. Users can file bugs for issues they may encounter here or follow known bugs here.

How can I learn about the latest Mozilla Thunderbird ESR news?

To learn about the latest Mozilla Thunderbird ESR news, you must be signed up for the Thunderbird Enterprise mailing list. This is where Mozilla communicates the latest information about Thunderbird ESR and product updates. You can read more about Thunderbird Enterprise mailing list here.

What is the Enterprise Working Group?

The Mozilla Enterprise User Working Group is where enterprise developers, IT staff, Thunderbird and Firefox developers discuss best practices for deploying Thunderbird and Firefox in the enterprise. You can learn more about the EWG here.

Where can I get technical support for Mozilla Thunderbird ESR?

Mozilla Thunderbird ESR support can be found through the Thunderbird Enterprise mailing list. As Thunderbird ESR is functionally identical to Thunderbird for desktop, users will be able to find relevant support articles here.

How do I customize Thunderbird to meet my organization’s IT policy/requirements?

There are several methods that can be used to customize Thunderbird and the best place to start is the Thunderbird Enterprise mailing list or the Enterprise Wiki page. There are add-ons available, as well as third-party organizations who provide customizations services, and the Thunderbird Enterprise mailing list is a good place to discuss requirements if you’re just getting started.

Is Mozilla Thunderbird ESR available in my language?

Thunderbird ESR is available in all languages that are supported by the Thunderbird version from which it is taken. Technical support for the ESR is currently limited to English and Japanese; further languages may be added in the future.

Where can I download Mozilla Thunderbird ESR?

You can download Mozilla Thunderbird ESR from here.