Firefox and Thunderbird: a fork in the road

Firefox and Thunderbird have reached a fork in the road: it’s now the right time for them to part ways on both a technical and organizational level.

In line with the process we started in 2012, today we’re taking another step towards the independence of Thunderbird. We’re posting a report authored by open source leader Simon Phipps that explores options for a future organizational home for Thunderbird. We’ve also started the process of helping the Thunderbird Council chart a course forward for Thunderbird’s future technical direction, by posting a job specification for a technical architect.

In this post, I want to take the time to go over the origins of Thunderbird and Firefox, the process for Thunderbird’s independence and update you on where we are taking this next. For those close to Mozilla, both the setting and the current process may already be clear. For those who haven’t been following the process, I wanted to write a longer post with all the context. If you are interested in that context, read on.


Much of Mozilla, including the leadership team, believes that focusing on the web through Firefox offers a vastly better chance of moving the Internet industry to a more open place than investing further in Thunderbird—or continuing to attend to both products.

Many of us remain committed Thunderbird users and want to see Thunderbird remain a healthy community and product. But both Firefox and Thunderbird face different challenges, have different goals and different measures of success. Our actions regarding Thunderbird should be viewed in this light.

Success for Firefox means continued relevance in the mass consumer market as a way for people to access, shape and feel safe across many devices. With hundreds of millions of users on both desktop and mobile, we have the raw material for this success. However, if we want Firefox to continue to have an impact on how developers and consumers interact with the Internet, we need to move much more quickly to innovate on mobile and in the cloud. Mozilla is putting the majority of its human and financial resources into Firefox product innovation.

In contrast, success for Thunderbird means remaining a reliable and stable open source desktop email client. While many people still value the security and independence that come with desktop email (I am one of them), the overall number of such people in the world is shrinking. In 2012, around when desktop email first became the exception rather than the rule, Mozilla started to reduce its investment and transitioned Thunderbird into a fully volunteer-run open source project.

Given these different paths, it should be no surprise that tensions have arisen as we’ve tried to maintain Firefox and Thunderbird on top of a common underlying code base and common release engineering system. In December, we started a process to deal with those release engineering issues, and also to find a long-term organizational home for Thunderbird.

The Past

On a technical level, Firefox and Thunderbird have common roots, emerging from the browser and email components of the Mozilla Application Suite nearly 15 years ago. When they were turned into separate products, they also maintained a common set of underlying software components, as well as a shared build and release infrastructure. Both products continue to be intertwined in this manner today.

Firefox and Thunderbird also share common organizational roots. Both were incorporated by the Mozilla Foundation in 2003, and from the beginning, the Foundation aimed to make these products successful in the mainstream consumer Internet market. We believed—and still believe—mass-market open source products are our biggest lever in our efforts to ensure the Internet remains a public resource, open and accessible to all.

Based on this belief, we set up Mozilla Corporation (MoCo) and Mozilla Messaging (MoMo) as commercial subsidiaries of the Mozilla Foundation. These organizations were each charged with innovating and growing a market: one in web access, the other in messaging. We succeeded in making the browser a mass market success, but we were not able to grow the same kind of market for email or messaging.

In 2012, we shut down Mozilla Messaging. That’s when Thunderbird became a purely volunteer-run project.

The Present

Since 2012, we have been doggedly focused on how to take Mozilla’s mission into the future.

In the Mozilla Corporation, we have tried to innovate and sustain Firefox’s relevance in the browser market while breaking into new product categories—first with smartphones, and now in a variety of connected devices.

In the Mozilla Foundation, we have invested in a broader global movement of people who stand for the Internet as a public resource. In 2016, we are focused on becoming a loud and clear champion on open internet issues. This includes significant investments in fuelling the open internet movement and growing a next generation of leaders who will stand up for the web.

These are hard and important things to do—and we have not yet succeeded at them to the level that we need to.

During these shifts, we invested less and less of Mozilla’s resources in Thunderbird, with the volunteer community developing and sustaining the product. MoCo continues to provide the underlying code and build and release infrastructure, but there are no dedicated staff focused on Thunderbird.

Many people who work on Firefox care about Thunderbird and do everything they can to accommodate Thunderbird as they evolve the code base, which slows down Firefox development when it needs to be speeding up. People in the Thunderbird community also remain committed to building on the Firefox codebase. This puts pressure on a small, dedicated group of volunteer coders who struggle to keep up. And people in the Mozilla Foundation feel similar pressure to help the Thunderbird community with donations and community management, which distracts them from the education and advocacy work that’s needed to grow the open internet movement on a global level.

Everyone has the right motivations, and yet everyone is stretched thin and frustrated. And Mozilla’s strategic priorities are elsewhere.

The Future

In late 2015, Mozilla leadership and the Thunderbird Council jointly agreed to:

a) take a new approach to release engineering, as a first step towards putting Thunderbird on the path towards technical independence from Firefox; and

b) identify the organizational home that will best allow Thunderbird to thrive as a volunteer-run project.

Mozilla has already posted a proposal for separating Thunderbird from Firefox release engineering infrastructure. In order to move the technical part of this plan further ahead and address some of the other challenges Thunderbird faces, we agreed to contract for a short period of time with a technical architect who can support the Thunderbird community as they decide what path Thunderbird should take. We have a request for proposals for this position here.

On the organizational front, we hired open source leader Simon Phipps to look at different long-term options for a home for Thunderbird, including: The Document Foundation, Gnome, Mozilla Foundation, and The Software Freedom Conservancy. Simon’s initial report will be posted today in the Thunderbird Planning online forum and is currently being reviewed by both Mozilla and the Thunderbird Council.

With the right technical and organizational paths forward, both Firefox and Thunderbird will have a better chance at success. We believe Firefox will evolve into something consumers need and love for a long time—a way to take the browser into experiences across all devices. But we need to move fast to be effective.

We also believe there’s still a place for stable desktop email, especially if it includes encryption. The Thunderbird community will attract new volunteers and funders, and we’re digging in to help make that happen. We will provide more updates as things progress further.


  1. Paul Boddie replied on | Reply

    I’ve made my opinions quite clear elsewhere about the way Thunderbird appears to have been managed, but I can easily add them here, too. As someone who has an interest in developing or improving Thunderbird, the whole “volunteer” experience is incoherent and frustrating. Just trying to find the canonical resources to get started is a challenge. Most Free Software projects these days lead you to the code very quickly, but Mozilla’s assets are just an unmaintained mess: not exactly what one would expect from such a well-resourced “Web company”; it’s probably easier to start from a GNU/Linux distribution package and follow the links to the upstream repository.

    The Mozilla organisation seems to put vision ahead of the little things that, if done right, would go a long way to deal with the viability problems Thunderbird development is said to have. Should Mozilla be less well-resourced in future, its other products will suffer the same way unless the organisation learns how to focus on the basics.

  2. JimR replied on | Reply

    What can I do to help? I am not a star developer, but I have a long history on computers, from mainframes to building my own pico, and everything in between. I am a DBA by vocation, and a hacker (in the good sense) by avocation. I have used Thunderbird since it was known as Netscape Navigator.

  3. Thunderbird User replied on | Reply

    I feel sad that Thunderbird didn’t really evolve for several years. Calendaring with MS Exchange is still a major pain to deal with (regardless of external addons or applications used). Encryption, as pointed out in this post, is also dear to many. Having an email client that could do encryption with a good user experience, with additions for encrypted chats and other communication would’ve made Thunderbird attractive.

  4. Pete replied on | Reply

    Rewrite Thunderbird in Rust.

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