K-9 Mail joins the Thunderbird family

This is the comment thread for the blog post K-9 Mail joins the Thunderbird family.


“Once a certain level of functionality is reached, K-9 Mail will transform into Thunderbird on Android, and will be renamed accordingly.”

This is very disappointing. Nothing wrong with Thunderbird helping out, recommending, or even flat out transforming a project to align with their values, but to fully annex it is wrong. It erases everything that K-9 Mail has accomplished and just turns it into a mere piece of Thunderbird, with no individual recognition or value. I’m saying this as someone who uses both products, has no problems with either of them or their developers, and enjoys the experience of said usage, but this nonetheless is very sad.


I’m genuinely upset about this. I use K9 every day, and to have such a bad company take over pisses me off. It couldve been fine if they had just funded them or even contributed, it would’ve been fine. Taking over a whole project is just uncalled for, they literally could’ve just forked it, that would’ve been fine too!


This is what they’re telling you:

But this is what they’re really thinking:


Guess we’ll have to see how it works out … while I do use Thunderbird on my PC I’m not really a friend of it, but it is the slimmest mail client since M$ ditched Windows Mail.

We can always just keep our Beta apk’s and if it doesn’t work out install 1 of them and stay on it :innocent:

1 Like

It feels natural to put “your” icon first. From the K-9 Mail blog:


I didn’t expect the backlash after this. I thought that the most vocal people here would be happy that more people are going to work on this project after all.

Thunderbird is more of a community project than a Mozilla thing, so that’s not actually an issue.

K-9 has been kinda slow in development, no account overview screen and all. A new redesign is only good, I think

I do however agree that this mail client and its name have some value and it should be somewhat preserved instead of flat out changing its name.


Over the course of the past 12 years the name K-9 has become a synonym for a very good FOSS mail client. I’d also suggest to keep it. What about naming the synergy project simply “Thunderbird K-9”.

cketti, can you ensure us, that there will be no feature loss due to the UI change?
Anyway, looking forward to a bright future!


For me, this sounds very positive, meaning more users, a broader support and more development capacity for K9. Looking forward to Thunderbird for Android alias K9 mail.


This is good news, combining resources to provide a direct competitor to gmail on Android with more developers behind it. I just moved to Thunderbird on Linux after many years with Claws, mainly because of the devs lack of interest in authO and have found Thunderbird much better than I remembered it from years ago.


Interesting news! Here are my takes:

I don’t mind the name change. If the cketti is fine with it, I am fine with it. What matters is that we have a great open source solution. Maybe it can even attract new users.

I use Thunderbird and I mostly like it. I hope k9-mail stays focused on mail and won’t try to handle stuff like calendar or contacts as well.

Synchronization between thunderbird and k9-mail could be nice but I don’t know whether a “thunderbird account” would be the right approach. I’d prefer compatible configuration backup files.


Do you think that with the new resources at hand “Thunderbird for Android” will support the superior JMAP protocol [1] [2] and thus also motivate the server developers for instance of Dovecot to finally follow this road, too? That’d be really great news for the whole ecosystem!

[1] https://jmap.io/
[2] GitHub - iNPUTmice/jmap: A Java 8+ library for the JSON Meta Application Protocol (Java JMAP library)


As far as I know, cketti didn’t name the project tho (please, correct me if I am wrong), not trying to say that as a counter argument tho, just pointing it out.

According to the blog it would be provided via Firefox Sync, which is actually quite great. In desktop you can usually move a .thunderbird directory across computers but that probably will never work on mobile devices and its more of a backup solution rather than real time sync. (Honestly tho, once your setup is done there really isn’t a lot to sync lol)


There’s already rudimentary support for JMAP: k-9/backend/jmap at main · k9mail/k-9 · GitHub (this isn’t included in the app itself).

However, JMAP uses a data model that is a bit different from the other protocols K-9 Mail supports. So to make full use of JMAP’s capabilities the app requires quite a few architectural changes. I’m sure we’ll get there eventually. But it’s definitely not the highest priority.


Oooh yeah, jmap seems to be barely supported, but its getting really good, or so I hear

I will miss K-9 Mail and its cute logo, but I’m sure I’ll get used to a bird instead of a dog on my home screen.

As long as @cketti stays in control I’m quite happy to see K-9 Mail get more funding. If Thunderbird was still part of Mozilla I would’ve had some worries (as Mozilla has had its sad moments like letting go of the Rust team and I don’t want K-9 Mail to die because it’s “not profitable”) but given they’re their own team nowadays I’m not too worried about this “outside influence”.

Let’s see what the future brings :slight_smile:


I’m really excited to hear this! Using Thunderbird on Desktop and K9 on mobile there’s been a few times where I’d have loved tighter integration in the past. (i.e. one example: Mute thread functionality like in thunderbird · Issue #5601 · k9mail/k-9 · GitHub)

So I’m very much looking forward to what the future brings here. :slight_smile:

All the best to @cketti amd I hope you get additional support/community management resources together with the increased attention by the thunderbird brand.

edit: fixed issue link


I’m rather disappointed by this news. I used to enjoy using Thunderbird, but for the last 7 or so months, Thunderbird has not been working properly on my system. During an update around that time, they broke Thunderbird with respect to IMAP folders. Now, I get lots of long-duration freezing while Thunderbird loses track of where emails begins and ends - consequently merging many emails into one. And they can’t figure out what’s going wrong.

This bug is particularly dangerous to privacy, as replying to one of these merged emails can result in sensitive information being sent to the wrong set of eyes. Right now, I am unable to trust Thunderbird.

For the last 7 months, I’ve been relying on K-9 Mail, as it just works.

I am worried that K-9 Mail will go the way of Thunderbird, and I will again experience show-stopping bugs that can’t be fixed.

So yeah, sad days indeed.

couldn’t you just like, remove the email accounts and add them again?

Anyways the codebases are totally different and just a single personal experience does not contribute much. Thunderbird simply works for the majority, and so does K-9 Mail, I just hope they both can help each other out and everything ends up being for the best