The new stable release, K-9 Mail 6.400, adds customizable swipe actions, introduces swiping between messages, and fixes countless bugs (in reality, it would be quite easy to count them; just a lot of work and not much fun, so we didn’t).
You can read more about the release in the Thunderbird blog: Thunderbird Android Update: K-9 Mail 6.400 Adds Customizable Swipe Actions
Questions?
If you have questions about the new version, please join our support forum.