K-9 supports IMAP push, light and dark themes, message tagging, multi-account settings, etc., therefore, it can meet the basic mail sending and receiving needs of users. It is a good choice to replace other non-open source and advertising clients. This app is currently available for download directly from the Play Store.
Open-source email client K-9 will be the Android version of Thunderbird
Thunderbird, owned by the Mozilla Foundation, is an open-source free email client dedicated to security, privacy, and an ad-free experience. However, Thunderbird has developed very slowly over the years, and the lack of a mobile app is one of the big problems. But that will soon change, the well-known open-source mail client K-9 announced the merger with Thunderbird. Next, the K-9 client will become Thunderbird’s Android client, so that Android users can also get a better experience.
So why did Thunderbird choose to incorporate K-9? This turned out to be a bit unexpected. Back in 2018, Thunderbird product managers discussed with the maintainers of K-9. The discussion turned out to be how these two separate products can come together to create an awesome, seamless email experience across platforms.
Of course, this does not mean that Mozilla and K-9 will develop new mail clients. In fact they are focusing on Thunderbird at the same time. In the future, K-9 should also be renamed Thunderbird. However, this requires the maintainers on both sides to continue to work.
Additionally, K-9 maintainer Ketterer has joined the Thunderbird team full-time, which should make the transition and integration quicker.