There are a couple of ways to interact with the community.
If you have any questions related to K-9 Mail the general purpose mailing list is the right place to ask.
For development talk, the developer mailing list is a low-traffic list covering broad development issues.
For the latest news about the project follow us on Google+.
Use the issue tracker to report bugs or request new features.
The source code is hosted on GitHub. Star the project if you like to keep track of development.