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Revealed: Our Plans For Thunderbird On Android

For years, we’ve wanted to extend Thunderbird beyond the desktop, and the path to delivering a great Thunderbird on Android™ experience started in 2018.

That’s when Thunderbird Product Manager Ryan Lee Sipes first met up with Christian Ketterer (aka “cketti”), the project maintainer for open-source Android email client K-9 Mail. The two instantly wanted to find a way for the two projects to collaborate. Throughout the following few years, the conversation evolved into how to create an awesome, seamless email experience across platforms.

But Ryan and cketti both agreed that the final product had to reflect the shared values of both projects. It had to be open source, respect the user, and be a perfect fit for power users who crave customization and a rich feature set.

“Ultimately,” Sipes says, “it made sense to work together instead of developing a mobile client from scratch.”

K-9 Mail Joins The Thunderbird Family

To that end, we’re thrilled to announce that today, K-9 Mail officially joins the Thunderbird family. And cketti has already joined the full-time Thunderbird staff, bringing along his valuable expertise and experience with mobile platforms.

Ultimately, K-9 Mail will transform into Thunderbird on Android.

That means the name itself will change and adopt Thunderbird branding. Before that happens, we need to reach certain development milestones that will bring K-9 Mail into alignment with Thunderbird’s feature set and visual appearance.

To accomplish that, we’ll devote finances and development time to continually improving K-9 Mail. We’ll be adding brand new features and introducing quality-of-life enhancements.

K-9 Mail and Thunderbird are both community-funded projects. If you want to help us improve and expand K-9 Mail faster, please consider donating at

Here’s a glimpse into our features roadmap:

“Joining the Thunderbird family allows K-9 Mail to become more sustainable and gives us the resources to implement long-requested features and fixes that our users want,” cketti says. “In other words, K-9 Mail will soar to greater heights with the help of Thunderbird.”

Thunderbird On Android: Join The Journey

Thunderbird users have long been asking for Thunderbird on their Android and iOS devices. This move allows Thunderbird users to have a powerful, privacy-respecting email experience today on Android. Plus, it lets the community help shape the transition of K-9 Mail into a fully-featured mobile Thunderbird experience.

This is only the beginning, but it’s a very exciting first step.

Want to talk directly with the Thunderbird team about it? Join us for a Twitter Spaces chat (via @MozThunderbird) on Wednesday, June 15 at 10am PDT / 1pm EDT / 7pm CEST). I’ll be there alongside cketti and Ryan to answer your questions, and discuss the future of Thunderbird on mobile devices.

Additional Links And Resources

FAQ: Frequently Asked Questions

We’ve published a separate FAQ here, addressing many of the community’s questions and concerns. Check back there from time to time, as we plan to update the FAQ as this collaboration progresses.

Thunderbird is the leading open-source, cross-platform email and calendaring client, free for business and personal use. We want it to stay secure and become even better. A donation will allow us to hire more developers, pay for infrastructure, expand our userbase, and continue to improve.

Click here to make a donation

30 responses

Stephan wrote on

That awesome! I use Thunderbird on my Linux desktop and K9 on mobile. Perfekt match. I find K9 has way too many settings and options. It could be easier to use. Also easy backups and syncing would be great to have.

Open source android email client K-9 Mail to become Thunderbird on Android - Liliputing wrote on

[…] A month after announcing plans to launch a mobile version of the the open source Thunderbird email client, the folks at Thunderbird have explained how they plan to do that. […]

Thunderbird und K-9 Mail gehen zusammen - LinuxNews wrote on

[…] wurden dann im Thunderbird-Blog nähere Einzelheiten bekannt. Demnach gehen Thunderbird und der bekannte Android-E-Mail-Client K9 […]

MMeinesz wrote on

Great move, people. Happy to help you financially, we will happily sponsor you.

Overall it’s good to see some “merging” in FOSS, there seems to be too much “branching” going on.

Jason Evangelho wrote on

Thank you for your feedback, and we agree. Why spend more of the money you donate to build a client from scratch, when we can take an established open-source app and bring the developer’s expertise along for the ride? We’re looking forward to taking this all to the next level!

Nicolas wrote on

I use k9 on android for a few years. I hope transition to this thunderbird will be smooth !

Jason Evangelho wrote on

We will do nothing short of our best.

Lukasz wrote on

I love this news!

Luna bittin Jernberg wrote on

Installed K-9 Mail and setup it with Gmail on my Android phone today to help out and try it out 🙂
also will help out with Swedish translation for the Android version too

Micke wrote on

I am a finacial supporter, and long time user, of K-9, and I hope this move will be benificial for both projects, eventually merging into one. I used thunderbird as well for a long time, but felt that it had slowed down and threatened to fall behind in the last couple of years. I have been very happy to see thunderbird pick up pace again, and I will definatly give it a go again, as the alternatives will be left in the dust once again 🙂

Dave D. wrote on

I smiled as soon as I saw the graphic at the top of the post. K-9 Mail is already an outstanding app, and it will only benefit from the colaboration.

Doktor Snake wrote on

Overjoyed at this! I’ve used Thunderbird from the very beginning. Still do. You just can’t beat it. I have also used K-9, on and off, on my phone… mostly just used the Fastmail app, though. Really this is a glorious day, bringing the honorable open source ethos to Android… the more of that the better. I’ll be installing it.

Ian wrote on

My favourite desktop e-mail client and my favourite mobile client joining forces!

I wish you all the best, and hope this helps both teams spend more time creating features and fighting bugs and less time re-inventing the wheel.

Pontus wrote on

Thunderbird and K9 is already what Im using. Really hope there’ll be some good way of syncing your settings so I dont have to set up filters again. That process is not super smooth on desktop even, so it feels like it might be a challenge.

Either way it’s exciting news! I’ve been using email less and less because of all the spam, but Thunderbird makes it usable again thanks to powerful filtering. I’m looking forward to seeing that on mobile as well.

I’ll take the opportunity to mention a feature request. Would be great with an easy way to copy all the text content of an email to paste it into a note.

Ryan Sipes wrote on

Great feature request idea! Convert to note is a feature I want to! So it’ll probably happen.

Ryan, Product Manager for Thunderbird.

Randall wrote on

Stoked for this mash-up! Long time user of both, and I feel integration is just going to make two already great products into one much better product.

Happy to support (financially – not a coder…)

(FWIW, I use the Portable version of Thunderbird)

CharlesV wrote on

VERY exciting! Having used Thunderbird and K-9 Mail for years… this is one of the best things I have read!!

Great work!

Suprateeka R Hegde wrote on

Have been a decade long Thunderbird’er and making heartfelt donations since a few years. All I request you is a great widget for Android, something like what Nine provides. Primarily a widget that provides a single combined view of “All Mails”, that is mails from all folders of all accounts, with at least an optional “Unread” filter. Imagine I get to see all unread e-Mails from all folders of all accounts in one view! Wow!

The above is in addition to all the great feature already existing on Desktop, especially for IMAP folders.


Blort wrote on

Already using both, but super excited that K9 will be getting more visibility, funding and FILTERS! Yes!!!

Felicia P wrote on

Truly awesome news Already use Thunderbird and K9 mail so what a perfect fit! Thanks you guys for continuing to work on great e-mail products!

Jason Price wrote on

I used K9 for many years, and have used Thunderbird for even longer. My breaking point for K9 was when it started silently failing to send emails to Gmail users. This lasted for months, for both myself and a friend, resulting in a number of issues from sent email never arriving. I hope the K9 team can fix that

Jason Evangelho wrote on

Hey Jason, it sounds like maybe you’re talking about the OAuth issue? If so, a fix has been developed and is just waiting for approval by Google.

Brian Vaughan wrote on

As a regular user of Thunderbird on desktop and K9 on my phone, I’m happy to hear this.

Barry C wrote on

Great news – my favorite email clients coming together!

Please bring back the accounts overview screen and PIN / fingerprint entry would be useful. Thanks!

Axel wrote on

I love Thunderbird, as well as K-9 Mail. This works perfectly for me. I can use Thunderbird on Android, while also not “abandoning” K-9 Mail, which has served me well.

Alastair Gordon wrote on

Great news! I have always been happy to pay for Thunderbird going back many years. A few questions:

1. Will Thunderbird for Windows and Thunderbird for Android be fully synchronized, including messages, read/unread status (per device), folders, message filters, address book, server settings, etc?

2. If so, will the syncing be automatic and transparent, or will it require a periodic sync request from the user?

3. In other words, except for the different screen sizes, will everything work the same in Windows and Android?

4. Another answered question mentioned, I believe, a syncing add-on for Firefox? How does Firefox come into the picture? Won’t I have a Thunderbird app for my Windows 11 PC and a Thunderbird app for my Android device? Why is there any browser involved?

5. How great it will be to dump the Gmail UI, with its idiotic “labels” instead of intuitive Thunderbird folders? Am I right that Thunderbird for Windows and Thunderbird for Android will both use the current FOLDERS paradigm?

Please forgive if some of my questions are nonsensical or obvious. And thanks again for the great news!

Enrico Migliore wrote on

Can’t wait to install it on my Nokia G50 new smartphone.

Randall wrote on

Oh, I hope that comes through soon!

James wrote on

That’s a good/bad move ..What happen in Mozilla some day bought by google?

Barry R wrote on

Usually when I hear of one software organisation taking over / merging with another I groan – it’s almost always not good news for users. This is completely different – I’m a long time user of both Thunderbird and K9 and I can only think that a merging of these two projects is going to be a big step forward for everyone.

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