Note: We use a development model where larger changes are made in a development branch. Releases from this branch start with an odd number in the minor version (5.7xx, 5.9xx), are not released to the production channel on Google Play, and are not marked as stable on F-Droid.
Once the features planned for a new version are implemented and newly introduced bugs have been found and fixed, a new stable version will be released. Given our version numbering scheme, this will be K-9 Mail 6.000 (the minor version of stable releases start with an even number, e.g. 5.805, 6.000).
The focus for the next development iteration is fixing notifications. Many users have noticed that some of the notification features that were available previously are no longer there in K-9 Mail 5.8xx. Most notably, custom vibration patterns and a configurable notification LED color. That’s not because these features were removed. They still work like they always have on Android versions prior to 8.0. However, Android 8 has introduced the concept of notification categories. And to be able to publish updates on Google Play apps have to support this new way of doing things. (Old apps, e.g. K-9 Mail 5.600, can still use the old way, even on devices running Android 8 and newer). So what we have to do is re-implement the old features so they work with notification categories.
There are also some long-standing bugs related to notifications that we plan to fix, e.g. notifications not disappearing when they should.
The preliminary plan for K-9 Mail 6.200 is to add an account overview screen. But the focus right now is on fixing notifications.
To help test the beta versions, read the post How do I become a beta tester?