[mjl-]

I browsed through the article, but it's not clear to me if they're only encrypting data at rest (that you open up with a login session, but then: their referenced docs mention alice and bob exchanging messages, so that can't be it), or that they're encrypting messages and sending them out (i.e. it is similar to openpgp, but then their own custom thing? how would that interoperate with anyone else?).

Perhaps it makes more sense if you already know how they operate technically. There's a chance I browsed too quickly and missed the explanation... The article reads a bit confusing with the mixing of (a)symmetric concepts.

[NewJazz]

They can interoperate with regular email if you share the password for the email out of band. Basically they get a link to a specialized tuta web client, and enter their password there.

https://www.reddit.com/r/tutanota/comments/i3f6j6/stupid_que...