• Thunderbird

State Of The Bird 2024/25

The past twelve months have been another remarkable chapter in Thunderbird’s journey. Together, we started expanding Thunderbird beyond its strong desktop roots, introducing it to smartphones and web browsers to make it more accessible to more people. Thunderbird for Android arrived in the fall and has been steadily improving thanks to our growing mobile team, as well as feedback and contributions from our growing global family. A few months later, in December 2024, we celebrated an extraordinary milestone: 20 years of Thunderbird! We also looked toward a sustainable future with the announcement of Thunderbird Pro, with one of its first services, Appointment, already finding an audience in closed beta. 

The past year also saw a shift in how Thunderbird evolves. Although we recently released our latest annual ESR update (codenamed Eclipse), the bigger news is that our team built the new Monthly Release channel, which is now the default for most of you. This change means you’ll see more frequent updates that make Thunderbird feel fresher, more responsive, and more in tune with your personalized needs. 
Before diving into all the details, I want to pause and express our deepest gratitude to the incredible global community that makes all of this possible. To the hundreds of thousands of people who donated financially, the volunteers who contributed their time and expertise, and the beta testers who carefully helped us polish each update: thank you! Thunderbird thrives because of you. Every milestone we celebrate is a shared achievement, and a shining example of the power of community-driven, open source software development.

Team and Product Updates

Desktop and release updates

In December 2024, we celebrated Thunderbird’s 20th anniversary. Two decades of proving that email software can be both powerful and principled was not without its ups and downs, but that milestone reaffirmed something we hear so often from our community: Thunderbird continues to matter deeply to people all over the world. 

One of the biggest changes this year was the introduction of a new monthly release channel, simply called “Thunderbird Release.” Making this shift required an enormous amount of coordination and care across our desktop and release teams. Unlike the long-standing Extended Support Release (ESR), which provides a single major update every July, the new Thunderbird Release delivers monthly updates. This approach means we can bring you useful improvements and new features significantly faster, while keeping the stability and reliability you rely on.

Over the past year, our desktop team focused heavily on introducing changes that people have been asking for. Specifically, changes that make Thunderbird feel more efficient, intuitive, and modern. We improved visual consistency across system themes, gave you more ways to control the appearance of your message lists and how they’re organized, modernized notifications with native OS integration and quick actions, and moved closer to full Microsoft Exchange support. 

Many of you who switched from the ESR to the new Thunderbird Release channel started seeing these updates as early as April. For those who stuck with the ESR, the annual update, codenamed Eclipse, arrived in July. Thanks to the solid foundation established in those smaller monthly updates, Eclipse enjoyed the smoothest rollout of any annual release in Thunderbird’s history. 

In-depth details on Desktop development can be found in our monthly Developer Digest updates on our blog. 

Thunderbird Mobile

Android

It took longer than we originally anticipated, but Thunderbird has finally arrived as a true smartphone app. The launch of Thunderbird for Android in October 2024 was one of our most exciting steps forward in years. Releasing it took more than two years of active development, beta testing, and invaluable community feedback. 

​​This milestone was made possible by transforming the much-loved K-9 Mail app into something we could proudly call Thunderbird. That process included a full redesign of the interface, including bringing it up to modern design standards, and building an easy way for people to bring their existing Thunderbird desktop accounts directly into the Android app.

We’ve been encouraged by the enthusiastic response to Thunderbird on Android, but we’re also listening closely to your feedback. Our team, together with community contributors, has one very focused goal: to make Thunderbird the best Android email app available. 

iOS

We’ve also seen the overwhelming demand to build a version of Thunderbird for the iOS community. Unlike the Android app, the iOS app is being built from the ground up. 

Fortunately, Thunderbird for iOS took some major steps forward this year. We published the initial repository (a central location for open-source project files and code) for the Thunderbird mobile team and contributors to work together, and we’re laying the groundwork for public testing. 

Our goal for the first public alpha will be to support manual account setup and basic inbox viewing to meet Apple’s minimum review standards. These early pre-release versions will be distributed through TestFlight, allowing Thunderbird for iOS to benefit from your real-world feedback. 

When we started building Thunderbird for iOS, a core decision was made to use a modern foundation (JMAP) designed for mobile devices. This will allow for, among other advantages, faster mail synchronization and more efficient resource usage. The first pieces of that foundation are already in place, with the basic ability to view folders and messages. We’ve also set up internal tools that will make regular updates, language translations, and community testing possible. 

Thunderbird for iOS is still in the early stages of development, but momentum is strong, our team is growing, and we’re confidently moving toward the first community-accessible release. 

In depth details on mobile development can be found in our monthly Mobile Progress Report on our blog. 

Thundermail and Thunderbird Pro services

It’s no secret we’ve been building additional web services under the Thunderbird Pro name, and 2025 marked a pivotal moment in our vision for a complete, open-source Thunderbird ecosystem. 

This year we announced Thundermail, a dedicated email service by Thunderbird. During the past decade, we’ve seen a large move away from dedicated email clients to products like Gmail, partially because of the robust ecosystem around them. The plan for Thundermail is to eventually offer an alternative webmail solution that protects your privacy, and doesn’t use your messages to train AI or show you ads. 

Here’s what else we’ve been working on in addition to Thundermail: 

During its current beta, Thunderbird Appointment saw great improvements in managing your schedule, with many of the changes focused on reliability and visual polish.

Thunderbird Send, an app for securely sharing encrypted files, also saw forward momentum. Together, these services are steadily moving toward a wider beta launch this fall, and we’re excited to see how you’ll use them to improve your personal and professional lives. 

All of the work going into Thundermail and Thunderbird Pro services is guided by a clear goal: providing you with an ethical alternative to the closed-off “walled gardens” that dominate our digital communication. You shouldn’t have to sacrifice your values and give up your personal data to enjoy convenience and powerful features. 

In depth details on Thunderbird Pro development can be found in our Thunderbird Pro updates on our blog. 

2024 Financial Picture

The generosity of our donors continues to power everything we do, and the importance of these financial contributions cannot be understated. In 2024, the Thunderbird project once again saw continued growth in donations which paved the way for Thundermail and the Thunderbird Pro services you just read about. It also gave us the opportunity to grow our mobile development team, improve our user support outreach, and expand our connections to the community. 

Here’s a detailed breakdown of our donation revenue in 2024, and why many of these statistics are so meaningful. 

Contribution Revenue

In 2024, financial contributions to Thunderbird reached $10.3 million, representing a 19% increase over the previous year. This support came courtesy of more than 539,000 transactions from more than 335,000 individual donors. A healthy 25% of these contributions were given as recurring monthly support.

What makes this so meaningful to us isn’t the total revenue, or the scale of the donations. It’s how those donations break down. The average contribution was $18.88, with a median of $16.66. Among our recurring donors, the average monthly gift was only $6.25. In fact, 53% of all donations were $20 or less, and 94% were $35 or less. Only 17 contributions were $1,000 or more. 

What does this represent when we go beyond the numbers? It means Thunderbird isn’t sustained by a handful of wealthy benefactors or corporate sponsors. Rather, it is sustained by a global community of people who believe in what we’ve built and what we’re still building, and they come together to keep it moving forward.

And that global reach continues to inspire us. We received contributions from more than 200 countries. The top ten contributing countries – Germany, the United States, France, the United Kingdom, Switzerland, the Netherlands, Japan, Italy, Austria, and Canada – accounted for 83% of our total revenue.

But products aren’t just numbers and code. Products are the people that work on them. To support the ambitions of our expanding roadmap, our team grew significantly in 2024. We added 14 new team members throughout the year, closing out 2024 with 43 full-time staff members. Much of this growth strengthened our mobile development, web services, and desktop + release teams. 80% of our staff focuses on technical work – things like product development and infrastructure – but we also added more roles to actively support users, improve community outreach, and smooth out internal operations. 

Expenses

When we talk about how we use financial contributions, we’re really talking about investments in our shared values. The majority of our spending goes to personnel; the talented individuals who write code, design interfaces, test features, and support our users. Infrastructure is the next largest expense, followed by administrative costs to keep operations running smoothly. 

Below is a breakdown of our 2024 expenses:

Community Snapshot

Contributor & Community Growth

For two decades, Thunderbird has survived and thrived because of its dedicated open-source community. In 2024, we continued using our Bitergia dashboard to give our community a clear view of the project’s overall activity across the board. (You can read more about how we collaborated on and use this beneficial tool here.)

This dashboard helps us track participation, identify and celebrate successes, and find areas to improve, which is especially important as we expand the Thunderbird ecosystem with new products and services. 

For this report, we’ve highlighted some of the most notable community metrics and growth milestones from 2024. 

For reference, Github and Bugzilla measure developer contributions. TopicBox measures activity across our many mailing lists. Pontoon measures the activity from volunteers who help us translate and localize Thunderbird. SUMO (the Mozilla support website) measures the impact of Thunderbird’s support volunteers who engage with our users and respond to their varied support questions.

We estimate that in 2024, the total number of people who contributed to Thunderbird – by writing code, answering support questions, providing translations, or other meaningful areas – is more than 20,000. 

It’s especially encouraging to see the number of translation locales increase from 58 to 70, as Thunderbird continues to find new users around the world. 

But there are areas of opportunity, too. For example, making it less complicated for people who want to start contributing to Thunderbird. We’ve started addressing this by recording two Community Office Hours videos, talking about how to write Knowledge Base articles, and how to effectively answer questions on the Mozilla Support website. 

Mozilla Connect is another portal that lets anyone interested in the betterment of Thunderbird suggest ideas, openly discuss them, and vote on them. In 2024, four desktop ideas as well as four of your ideas in our relatively new mobile space were implemented, and we saw more than 500 new thoughtful ideas suggested across mobile and desktop. Our staff and community are watching for your ideas, so keep them coming! 

Thank you

As we close out this year’s State of the Bird, we want to once again shine a light on the incredible global community of Thunderbird supporters. Whether you’ve contributed your valuable time, financial donations, or simply shared Thunderbird with colleagues, friends, and family, your support continues to brighten Thunderbird’s future. 

After all, products aren’t just numbers on a chart. Products are the people who create them, support them, improve them, and believe in crucial concepts like privacy, digital wellbeing, and open standards. 

We’re so very grateful to you.