I'm a firm believer and practitioner of the 'inbox zero' method of email management. Naming this inbox helper/organizer the same may confuse people. Why did you choose that name? Seems a disservice to the method you're trying to promote.
I can easily see them adding more and more features which improve email and nudge users to inbox zero.
I think this is a decent starting point, and for a repo that is only 5 months old, it looks like they've done a decent job of understanding a good UX, and showing the user the emails they are most likely going to want to archive, etc.
The overall goal of the app is to help manage email better. It could turn into a full fledged email app one day too.