For the past week/ten days I've been working on a console-based mail client for Linux with built in Lua scripting support.
Although it is not complete browsing maildirs, indexes, and messages now works well enough that I'd be curious if there is any interest.
https://github.com/skx/lumail/ http://lumail.org/
Now that the initial challenges are handled the next step is to wire up more primitives for the lua-scripting, implement "compose", "reply" and view/save attachments.
Then it will be my main mail client.