[kroberton]

Yep: https://github.com/tutao/tutanota/

Devs say they want to publish the app on F-Droid. https://tutanota.com/blog/posts/secure-mail-open-source

[Boulth]

Did I get this right: the client is open source while the service that works in the backend and does 80% of the job is closed source?

[amelius]

So the source isn't of much use except for verifying that the encryption is robust?

How is that for protonmail?

[kroberton]

In Protonmail client is open source, server and apps are not.