Our plan to bring the Tutanota app to @fdroidorg is making progress: https://tutanota.com/blog/posts/secure-mail-open-source
We have just removed GCM for push from the app, the main requirement to realize the F-Droid publication! 😀 Here are details: https://github.com/tutao/tutanota/commit/449c36eac5755571f4c5d28a74dfdc13c3cdc6df