A long time user here and as others have said, I certainly appreciate the hard work put into the app. While initially pleased to see that the development of K-9 continues, I’ve downgraded to 5.600 due to the removal of the account overview screen. It’s good that you’re seeking feedback so I’ll try and articulate why.
I rarely need to view folders other than the inbox. I receive far more emails than I write (which I suspect is true for most people) so the inbox is the hub of my interaction with any email client and where I spend most of my time. This is doubly true for a mobile client as I tend to do more writing and account admin on a desktop. K-9’s account overview screen provides quick access to the inbox of each account. This is a bit like Thunderbird’s “Unified” folder view where folders are grouped by name: the inboxes from all accounts are close together so I can move between them easily. In K-9 the small folder icon still gives quick access to the other folders on the rare occasion I do need to access them, and I can get to that list immediately from the account overview screen. The ethos of the account overview seems to be “primarily inbox, but just one tap away from other folders”, and making the inbox special by giving it priority in this way exactly matches the way I interact with folders.
The new UI is more like Thunderbird’s “All” folder view where folders are grouped by account. Except in Thunderbird you can instantly see all the folders without clicking in a menu and selecting each account separately. If you have several accounts it’s cumbersome to use because the inboxes are all separated from each other. In K-9’s new UI this means inboxes are no longer given special priority and instead sit alongside all other folders, even though I mostly want to view just the inbox. In the new UI it’s slightly easier to view another folder in the currently visible account (2 taps vs. 3 or 4), but I rarely do this. In contrast it’s more difficult to perform an action I do more often which is switch to the inbox of a different account, this now requires 4 taps (menu, account dropdown, choose the account, choose the folder) instead of just 2 (back then tap on the account). In summary the new UI no longer gives special priority to the inbox which is what really makes the account overview screen useful, and therefore it no longer matches how I primarily use an email client.
Also, for a right handed user, it’s not only more taps, but also less comfortable: it’s more difficult to get my right thumb up to the top left hand corner of the screen to press then menu button to choose another account than it was to press the back button at the bottom and press on an account on the overview screen that was both lower down and spanned almost all the way to the right edge. This is also true for the new placement of the toolbar at the top when viewing an email.
The alternative approach you mention seems to be the unified inbox, but I do not find it a useful alternative to having easy access to individual inboxes. I have separate email accounts for a reason: to keep different email streams separate. Combining them again largely defeats the point of keeping them separate to begin with. I try to keep work and personal life separate by not viewing business accounts out of hours, but it’s hard if all emails appear side by side. Other accounts are specifically for things like mailing lists or security camera alerts which can sometimes receive dozens or hundreds of emails a day and I usually want to attend to them at different times, so I don’t want them mixed in with general emails. I know I can remove these folders from the unified inbox, but at that point it’s no longer an alternative approach because I’d need to view the individual inbox anyway which is harder in the new UI.
It was only when I downgraded to 5.600 that I even noticed there was also a unified inbox in the old version, I just never used it because I did not find it useful. I can understand that for some users it is useful, but it should not be deemed an alternative to easy access to individual inboxes.
A more general comment about how I use and feel about K-9: I see the account overview screen as the “main” page, it’s the view I see every time I start the app and it’s the foundation or core from which I navigate to all other parts of the app. There’s an important psychological comfort in having this base, it’s like a home you can always go back to, and there’s additional comfort in it showing an overview, which provides a sense of control. In the new UI this core has been ripped out and the replacement does not offer the same psychological comfort: you’re dumped directly into an inbox and there’s nowhere that I can see all accounts at once. Even if you argue that the account overview is redundant or unnecessary (and I don’t think that’s true), I’m a human, and the comfort and sense of control that a feature provides is just as important as its outright utility.
I’m sad to say that I haven’t learned a lot.
I’d also like to make a blunt response to this comment. The fact that hundreds of people have taken the time to comment in favour of the account overview screen with very few in support of its removal means you should have learned that it’s a feature that users like, want, use, find useful and are passionate about, even if they’re not good at explaining WHY they find it useful. Most of us are not UI experts (me included) and would struggle to explain how we use an app, but it doesn’t mean we don’t know what we like. Ultimately many users will have chosen K-9 after trying different apps and deciding we like how K-9 works, even if we didn’t quite know why. Hopefully I’ve persuaded you that there are good reasons why the account overview is preferable and worth keeping, but even if not, don’t dismiss a feature as useless just because users can’t describe objective reasons for keeping it.
Finally I think it would be useful for you to provide some answers to users about the reasons for the removal of the account overview. What do you think was wrong with the account overview? Why did you decide to remove it? Why not keep it as an alternative view? What do you think is improved with the new UI and how are those improvements better for the user? What do you think are suitable “alternative approaches” to the account overview?