I would also appreciate to start with an overview of my 7 accounts and going back to this overview with the back button.
Hiding Accounts is good for my 80yr old dad, but I must handle more accounts.
It IS nice that the general inbox can be deselected within the options. So step 2 would be going back to classic account overview
When a message is selected you can press the closed envelope icon at the top to mark it as unread
It seems that the future is not rosy for my relationship and k9. Bytehamster and cketti seem adamant that their new design (with its extra tapping requirements) and misplaced button positions are definite and the way it is to be, and suggestions to the contrary (by users) are unjust. I will be remaining on 5.600 (avoiding updates by google play by installing it from f-droid).
It’s an email client, not a car. It is to read emails and be secure whilst doing so. Development does not NEED design change to be attractive on the eye at the detriment of intuitive use. It just needs to do what it is designed to do (display emails) and easy to drive (interface and buttons being minimal, useful and easy to access).
No one ever said about an email client, “I love the fancy colours and how difficult and complicated it is to do things”.
What if contact icons are turned off? How do I mark email unread without going into the message first?
Long-press the message
Long press selects the message, doesn’t do anything else.
Once the message is selected you can click on envelope icon to mark mail as read or unread.
What envelope?
The one at the top that my thumb can’t reach?
I fully agree to the criticism above and with the changes, this is not my email client anymore, it is unusable. Too bad, before this design change it was the best mobile email client.
Yes, corrrect. I agree that the icons on the top bar are hard to reach with one hand mode. But the same is (almost) true if the top mail needs to be reached. And this was the case with old UI as well 
This new version drain the mobile’s battery to the bottom after 1-2 hour. That’s not good. I will revert to the earlier version.
That envelope icon is so confusing, especially since previous versino of K9 used an envelope icon for “compose”. Not intuitive at all.
I’m also looking into Open Mail (earlier K9 fork) as mentinoed in this forum on one of the threads talking about downgrading.
K9 went from a powerful and easy to use email client for both simple use and power-users to a “must use both hands”, maybe a bit shinier, average looking and working just like many other email clients, from UI stand point really no longer any better then the basic email client that came with my Samsung phone and specially crafted for users like my dad using his single account, power-users be damned, who cares(?)…
If developers’ position is something like described by @jimimaseye above and won’t take into consideration user feedback, especially from the many users these changes really hurt rather then help, then there can be only 2 choices:
I feel sorry to say, but I see no future for K9 and power users in the direction the development started moving recently.
Totally agree. I have no idea why it was necessary to destroy a good usability, the new version is a complete fail.
Overthat, my server logwatch mails from user “root” are all the sudden shown as “unknown identity”.
Baaahh…
I joined the forum yesterday for a setup problem. However, I am seeing some people don’t like the update. I’ve been using K-9 several years and I agree this new update is more flashy and awkward to use. Do I think it’s “better” or “worse”? Not sure yet. I can say for sure that “better” wasn’t my first impression. I hate when software changes after getting used to it. And I’ll also say I think the front takes up too much real estate on the screen. I also have several accounts setup like someone else and it’s not very easy to use in that respect.
Later…I discovered a easy way to navigate back if you’re looking at your emails is to not use the 3 lines on top left corner to go back…instead put your finger on the left side and slid right…nice.
The same for me.
I got the update to version 5.8 today. I did not know about the UI changes and installed the update.
I spent about 2 hours searching for the account overview. I also could not disable notification sound for received emails.
Then I downgraded to version 5.6. This took me another hour to get it working as before.
Three hours of lifetime just wasted.
I fully agree with all the con posts here. The new UI is a real disadvantage. It requires more taps, gives less overview and seems to have less configuration options.
On the K-9 startpage I read
“The user interface has been redesigned. Some of you will love it, some will hate it. You’re welcome and we’re sorry.”
Kind of arrogant from the author.
I do not like the new user interface.
I never had a problem reaching the top email. I can reach the left of the top email row. I can’t reach the right of the top menu.
I miss the back button function to go back to the beginning and not close the app. Select an email with a swipe instead of holding it. All accounts in 1 page and get al the email at once.