Source-code can be found here.
Seems pretty cool, although the UI design is a bit too Microsoftish for my taste. Seems to support pgp encryption and CalDAV/CardDav sync.
Last release is a bit older, but the main developer’s blog has some interesting details on new features in the development version.
It used to do it with the Enigmail AddOn, TB 78 and later doesn’t, and maybe it will never do it, does TB support autocrypt?:
You have to manually keep [un]specifying you wan to encrypt/decrypt, depending on how you set things, but it’s all manual. And it seems TB doesn’t like autocrypt at all, and if they don’t, they won’t include it… That along with not using GPG, makes me sad I’m still using TB, lacking really working alternative applications…
god damn them. Really, why remove features when they work well?
I… I can’t even.