Are there any solutions out there (FOSS highly preferred) that convert email into a REST/JSON API? What I really want is a traditional email account but headless (a frontend UI that works would be great, but there are plenty of those around already). I have a bunch of other projects I'm working on at the moment so I haven't built that myself, but I've gotten close a number of times. I would pay $3/month for a small account like that, going up to $10/month for lots of storage (but I won't need much personally).

I've heard that Gmail actually has a pretty good API, but I haven't looked into it. Has anyone tried using gmail from the API?