[chimeracoder]

If you're looking for Boomerang functionality without the security/privacy implications, I wrote an open-source version that is designed to be self-hosted: https://github.com/ChimeraCoder/go-yo

It's written in Go; there's no external dependency except a service that downloads emails to a Mailbox-type directory (I recommend offlineimap).

I've been dogfooding it myself for the last few months - I haven't actually "released" it officially yet, but if anybody is interested in beta testing it, I'd love some feedback.