Welcome back to the latest update on our progress with Thunderbird Pro, a set of additional subscription services designed to enhance the email client you know, while providing a powerful open-source alternative to many of the big tech offerings available today. These services include Appointment, an easy to use scheduling tool; Send, which offers end-to-end encrypted file sharing; and Thundermail, an email service from the Thunderbird team. If you’d like more information on the broader details of each service and the road to getting here you can read our past series of updates here. Do you want to receive these and other updates and be the first to know when Thunderbird Pro is available? Be sure to sign up for the waitlist.
With that said, here’s how progress has shaped up on Thunderbird Pro since the last update.
Current Progress
Thundermail
It took a lot of work to get here, but Thundermail accounts are now in production testing. Internal testing with our own team members has begun, ensuring everything is in place for support and onboarding of the Early Bird wave of users. On the visual side, we’ve implemented improved designs for the new Thundermail dashboard, where users can view and edit their settings, including adding custom domains and aliases.
The new Thunderbird Pro add-on now features support for Thundermail, which will allow future users who sign-up through the add-on to automatically add their Thundermail account in Thunderbird. Work to boost infrastructure and security has also continued, and we’ve migrated our data hosting from the Americas to Germany and the EU where possible. We’ve also been improving our email delivery to reduce the chances of Thundermail messages landing in spam folders.
Appointment
The team has been busy with design work, getting Zoom and CalDAV better integrated, and addressing workflow, infrastructure, and bugs. Appointment received a major visual update in the past few months, which is being applied across all of Thunderbird Pro. While some of these updates have already been implemented, there’s still lots of remodelling happening and under discussion – all in preparation for the Early Bird beta release.
Send
One of the main focuses for Send has been migrating it from its own add-on to the new Thunderbird Pro add-on, which will make using it in Thunderbird desktop much smoother. Progress continues on improving file safety through better reporting and prevention of illegal uploads. Our security review is now complete, with an external assessor validating all issues scheduled for fixing and once finalized, this report will be shared publicly with our community. Finally, we’ve refined the Send user experience by optimizing mobile performance, improving upload and download speeds, enhancing the first-time user flow, and much more.
Bringing it all together
Our new Thunderbird Pro website is now live, marking a major milestone in bringing the project to life. The website offers more details about Thunderbird Pro and serves as the first step for users to sign up, sign in and access their accounts.
Our initial subscription tier, the Early Bird Plan, priced at $9 per month, will include all three services: Thundermail, Send, and Appointment. Email hosting, file storage, and the security behind all of this come at a cost, and Thunderbird Pro will never be funded by selling user data, showing ads, or compromising its independence. This introductory rate directly supports Thunderbird Pro’s early development and growth, positioning it for long-term sustainability. We will also be actively listening to your feedback and reviewing the pricing and plans we offer. Once the rough edges are smoothed out and we’re ready to open the doors to everyone, we plan to introduce additional tiers to better meet the needs of all our users.
What’s next
Thunderbird Pro is now awaiting its initial closed test run which will include a core group of community contributors. This group will help conduct a broader test and identify critical issues before we gradually open Early Bird access to our waitlist subscribers in waves. While these services will still be considered under active development, with your help this early release will continue to test and refine them for all future users. Be sure you sign up for our Early Bird waitlist at tb.pro and help us shape the future of Thunderbird Pro. See you soon!
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.
In April of this year we announced Thunderbird Pro, additional subscription services from Thunderbird meant to help you get more done with the app you already use and love. These services include a first ever email service from Thunderbird, called Thundermail. They also include Appointment, for scheduling meetings and appointments and Send, an end-to-end encrypted filesharing tool. Each of these services are open source, repositories are linked down below.
Thunderbird Pro services are being built as part of the broader Thunderbird product ecosystem. These services are enhancements to the current Thunderbird application experience. They are optional, designed to enhance productivity for users who need features like scheduling, file sharing and email hosting, without relying on the alternate platforms. For users who opt in, the goal is for these services to be smoothly integrated into the Thunderbird app, providing a natural extension of the familiar experience they already enjoy, enhanced with additional capabilities they may be looking for. For updates on Thunderbird Pro development and beta access availability, sign up for the mailing list at thundermail.com.
Progress So Far
Thundermail
Development has been moving steadily forward and community interest in Thundermail has been strong. The upcoming email hosting service from Thunderbird will support IMAP, SMTP and JMAP out of the box, making it compatible with the Thunderbird app and many other email clients. If you have your own domain, you’ll be able to bring it in and host it with us. Alternatively, grab an email address provided by Thunderbird with your choice of @thundermail.com or @tb.pro as the domains. The servers hosting Thundermail will initially be located in Germany with more countries to follow in the future. Thunderbird’s investment in offering an email service reflects our broader goal of strengthening support for open standards and giving users the option to keep their entire email experience within Thunderbird.
We originally developed the scheduling tool as a standalone web app. On the current roadmap, however, we’re tightly integrating Appointment into the Thunderbird app through the compose window, allowing users to insert scheduling links without leaving the email workflow. It will be easy for organizations and individuals to self-host, fork and adapt the tool to their own needs. The future is for Appointment to support multiple meeting types, like Zoom calls, phone meetings, or in-person coffee chats. Each of these will have its own settings and scheduling rules.
One of the most requested future features is group scheduling, which would allow multiple team members to offer shared availability via a single link. The current calendar protocols don’t fully support this flow, however Thunderbird is participating in discussions around open standards like VPOLL to help move things forward. Usability studies are helping refine the MVP and community feedback is shaping the roadmap.
A secure, end-to-end encrypted file sharing tool, built on Thunderbird app’s existing Filelink feature. It supports large file transfers directly from the email client. This allows users to bypass platforms like Google Drive or OneDrive. Pro users will receive 500 GB of storage to start, with no individual file size limit, only constrained by their total quota. We’re planning support for chunked uploads and encryption to ensure reliability and data protection. We’ll deliver Send as a system add-on which lets the team push updates faster. This also avoids locking new capabilities behind major Thunderbird release cycles.
All Thunderbird Pro tools are open source and self-hostable. For users who prefer to run their own infrastructure or work in regulated environments, both Send and Appointment can be deployed independently. Thunderbird will continue to support these users with documentation and open APIs.
A Look Ahead
Thunderbird is exploring additional Pro features beyond the current lineup. While we’ve made no commitments yet, there is strong interest in adding markdown based Notes functionality, especially as lightweight personal knowledge management becomes more popular. Heavier lifts like collaborative docs or spreadsheets may follow, depending on adoption and sustainability.
Another worthy mention: a fourth, previously announced service called Assist, which will eventually enable users to take advantage of AI features in their day-to-day email tasks, is still in the research and development phase. It will not be part of the initial lineup of services. This initiative is a bigger undertaking as we ensure we get it right for user privacy and make sure the features included are actually things our users want. More to come on this as the project progresses.
To improve transparency and invite community collaboration, Thunderbird is also preparing a public roadmap covering desktop, mobile and Pro services. We’re developing the roadmap in collaboration with the Thunderbird Council. Our goal is to encourage participation from contributors and users alike.
Free vs Paid
Adding these additional subscription services will never compromise the features, stability or functionality our users are accustomed to in the free Thunderbird desktop and mobile applications. These services come with real costs, especially storage and bandwidth. Charging for them helps ensure that users who benefit from these tools help cover their cost, instead of donors footing the bill.
Thunderbird Pro is a completely optional suite of (open source) services designed to provide additional productivity capabilities to the Thunderbird app and never to replace them. The current Thunderbird desktop and mobile applications are, and always will be, free. They will still heavily rely on ongoing donations for both development and independence.
If you haven’t already, join our waiting list to be one of the early beta testers for Thunderbird Pro. While we don’t have a specific timeline just yet, we will be sharing ongoing updates as development progresses.
—
Ryan Sipes Managing Director, Product Mozilla Thunderbird
Today we’re pleased to announce what many in our open source contributor community already know. The Thunderbird team is working on an email service called “Thundermail” as well as file sharing, calendar scheduling and other helpful cloud-based services that as a bundle we have been calling “Thunderbird Pro.”
First, a point of clarification: Thunderbird, the email app, is and always will be free. We will never place features that can be delivered through the Thunderbird app behind a paywall. If something can be done directly on your device, it should be. However, there are things that can’t be done on your computer or phone that many people have come to expect from their email suites. This is what we are setting out to solve with our cloud-based services.
All of these new services are (or soon will be) open source software under true open source licenses. That’s how Thunderbird does things and we believe it is our super power. It is also a major reason we exist: to create open source communication and productivity software that respects our users. Because you can see how it works, you can know that it is doing the right thing.
The Why for offering these services is simple. Thunderbird loses users each day to rich ecosystems that are both products and services, such as Gmail and Office365. These ecosystems have both hard vendor lock-ins (through interoperability issues with 3rd-party clients) and soft lock-ins (through convenience and integration between their clients and services). It is our goal to eventually have a similar offering so that a 100% open source, freedom-respecting alternative ecosystem is available for those who want it. We don’t even care if you use our services with Thunderbird apps, go use them with any mail client. No lock-in, no restrictions – all open standards. That is freedom.
What Are The Services?
Thunderbird Appointment
Appointment is a scheduling tool that allows you to send a link to someone, allowing them to pick a time on your calendar to meet. The repository for Appointment has been public for a while and has seen pretty remarkable development so far. It is currently in a closed Beta and we are letting more users in each day.
Appointment has been developed to make meeting with others easier. We weren’t happy with the existing tools as they were either proprietary or too bloated, so we started building Appointment.
Thunderbird Send
Send is an end-to-end encrypted file sharing service that allows you to upload large files to the service and share links to download those files with others. Many Thunderbird users have expressed interest in the ability to share large files in a privacy-respecting way – and it was a problem we were eager to solve.
Thunderbird Send is the rebirth of Firefox Send – well, kind of. At this point, we have a bit of a Ship of Theseus situation – having rebuilt much of the project to allow for a more direct method of sharing files (from user-to-user without the need to share a link). We opened up the repo to the public earlier this week. So we encourage everyone interested to go and check it out.
Thunderbird Send is currently in Alpha testing, and will move to a closed Beta very soon.
Thunderbird Assist
Assist is an experiment, developed in partnership with Flower AI, a flexible open-source framework for scalable, privacy-preserving federated learning, that will enable users to take advantage of AI features. The hope is that processing can be done on devices that can support the models, and for devices that are not powerful enough to run the language models locally, we are making use of Flower Confidential Remote Compute in order to ensure private remote processing (very similar to Apple’s Private Cloud Compute).
Given some users’ sensitivity to this, these types of features will always be optional and something that users will have to opt into. As a reminder, Thunderbird will never train AI with your data. The repo for Assist is not public yet, but it will be soon.
Thundermail
Thundermail is an email service (with calendars and contacts as well). We want to provide email accounts to those who love Thunderbird, and we believe that we are capable of providing a better service than the other providers out there. Email that aligns with our values of privacy, freedom and respect of our users. No ads, no selling or training AI on your data – just your email and it is youremail.
With Thundermail, it is our goal to create a next generation email experience that is completely, 100% open source and built by all of us, our contributors and users. Unlike the other services, there will not be a single repository where this work is done. But we will try and share relevant places to contribute in future posts like this.
The email domain for Thundermail will be Thundermail.com or tb.pro. Additionally, you will be able to bring your own domain on day 1 of the service.
Heading to thundermail.com you will see a sign up page for the beta waitlist. Please join it!
Final Thoughts
Don’t services cost money to run?
You may be thinking: “this all sounds expensive, how will Thunderbird be able to pay for it?” And that’s a great question! Services such as Send are actually quite expensive (storage is costly). So here is the plan: at the beginning, there will be paid subscription plans at a few different tiers. Once we have a sufficiently strong base of paying users to sustainably support our services, we plan to introduce a limited free tier to the public. You see this with other providers: limitations are standard as free email and file sharing are prone to abuse.
It’s also important to highlight again that Thunderbird Pro will be a completely separate offering from the Thunderbird you already use. While Thunderbird and the additional new services may work together and complement each other for those who opt in, they will never replace, compromise, or interfere with the core features or free availability of Thunderbird. Nothing about your current Thunderbird experience will change unless you choose to opt in and sign up with Thunderbird Pro. None of these features will be automatically integrated into Thunderbird desktop or mobile or activated without your knowledge.
The Realization of a Dream
This has been a long time coming. It is my conviction that all of this should have been a part of the Thunderbird universe a decade ago. But it’s better late than never. Just like our Android client has expanded what Thunderbird is (as will our iOS client), so too will these services.
Thunderbird is unique in the world. Our focus on open source, open standards, privacy and respect for our users is something that should be expressed in multiple forms. The absence of Thunderbird web services means that our users must make compromises that are often uncomfortable ones. This is how we correct that.
I hope that all of you will check out this work and share your thoughts and test these things out. What’s exciting is that you can run Send or Appointment today, on your own server. Everything that we do will be out in the open and you can come and help us build it! Together we can create amazing experiences that enhance how we manage our email, calendars, contacts and beyond.
Thank you for being on this journey with us.
—
Ryan Sipes Managing Director of Product Thunderbird
FreshRSS 
