In times when Google itself already abandons the terrible hamburger-menu for good reasons, this new update brings it 10 years late only to kill the best feature of k9, the account overview at the start of the app. Plus the bottom navigationbar moved to the top for no one to reach.
WHY? SIMPLY WHY ???
It’s really a shame.
While I appreciate the effort that went into this version I am not happy with it. I have used K-9 for as long as I can remember and the account overview list at the start was a major feature for me as I have 6 emails. Now there are hamburger menus and way too many clicks to get to where I want to be. The back button closing the app is also a step backward. I will give this new version a try but it’s not the clean, simple version I loved.
Please, consider bringing back the account list. Please.
I also agree. Bring back 5.6 UI!
This worked for me, I’m again on 5.6 version, permanently 
I must say that I am a little surprised by the comments in this thread. Apparently most of you consider yourselves “power-users” but none of you installed one of the many pre-releases that appeared on F-Droid and Play?
The new interface has been around more than a year. If you are indeed a power-user who so strongly relies on this app, maybe give one of those versions a try and give feedback early on?
If, on the other hand, you do not expect/want/need any kind of changes to your app, why not just use the old version and stop complaining?
I don’t like all things about the new version, but the comments in this thread are completely out-of-touch. If you have criticism, at least be friendly, you are getting something for free.
Where did you get 5.6?
Sorry, but there were no updates prior to the 5.8 one! If there were, I would have complained earlier!
There is a beta-channel on Play, and F-Droid has shown the newer versions also (although it did’t recommend them).
No, the majority of users don’t install betas or are involved in the developer-process of an app.
They were surprised to see their app completely changed (badly) after a multiple years long update-pause in the Play Store. Thanks, but no thanks.
I well know about beta channels, but I explicitly do not use them on apps I heavily rely on because of stability reasons!
I do help with apps and open source as far as I am able to, but k-9 is a mail client I need to use daily in production!
Being easy to use, fast and productive was what I used k-9 for since 10+ years!
This has nothing to do with “power-users”. The most useful feature of K9 - compared to other mail clients out there - has been removed for no reason. I like the new UI in terms of design but it’s completely unusable without the account overview feature where I can select all unread or starred messages from a specific account with a single click.
Staying on 5.6 as well, the overview is a must-have for me. Otherwise I’d still be using the stock mail app.
@h-2:
but none of you installed one of the many pre-releases that appeared on F-Droid and Play?
The new interface has been around more than a year. If you are indeed a power-user who so strongly relies on this app, maybe give one of those versions a try and give feedback early on?
In the Hitchhiker’s Guide universe, you’d be Mr. Prosser 
Instructions on how to “downgrade” to an earlier version:
Thank you cketti. As an addendum, if you want to prevent the play store from updating it at all you can get the APK from f-droid instead of github (K-9 Mail | F-Droid - Free and Open Source Android App Repository).
No, it’s true, I don’t. Sounds incredibly stressful whatever it is though! 
This is not a point release, this is a major upgrade bordering on new product. I appreciate all the new whiz bang features. Encryption, yay.
But I have to agree that the new UI has made this once streamlined and intuitive application dumbed down click bloat. Removing controls doesn’t streamline the UI, it increases the number of operations required to accomplish a task.
No account summary on opening.
No account summary on ‘back’
No show only starred.
No show only unread.
No unique notification sounds per account.
And that’s after only a couple minutes exposure.
And I don’t know what the heck those “user icon” looking things at the top of the drawer are supposed to do. They seem unconfigurable and arbitrary.
I’m not looking forward to finding out what other subtle changes occurred that will disrupt my workflow.
It’s like someone walked into a pile of Git code without tribal knowledge and just decided to start dancing all Clockwork Orange on it.
I realize the app is free so we really don’t have any standing to complain. Maybe you’ll attract a grand new audience, at the expense of your once loyal following. Maybe that’s the goal. But catering to the lowest common denominator user makes product differentiation difficult.
I hate to see k9 become just another commodity app like Gmail.
I’ve managed to score a 5.6 apk. I’ll wait a little bit to see if the developers respond to users concerns.
If this is truly The New Way™, I’ll go back to 5.6 until it’s obsoleted by android.
This has been an unfortunate kick in the teeth for many, many users.
Most of us had no idea that an essentially ‘dead’ but still useful app was being destroyed.
I’m another user who just reinstalled v5.600 and happy with that.
Actually I DID remove the auto-update on Play Store immediately but last night the app updated anyway!!
BTW: on my Moto G5 plus with Android 8 the new icon background is a circle in a light rose color!!! …transparent would be better…
Me too I will keep an eye on what will happen in the next few months to eventually decide to upgrade or (sigh) remove K9 definitely… Even if I do not know what to use as a replacement since GMail app is not an option…
On a positive note:
I can now show my email passwords.
That’ll make setting up 5.6 again easier.