I'm not sure what you mean by a local client. If you are suggesting that even the Tutanova users are decrypting things using browser crypto, that's absurd. I as

I'm not sure what you mean by a local client. If you are suggesting that even the Tutanova users are decrypting things using browser crypto, that's absurd. I assumed this was all done either with a local client or a browser extension. If you mean that the non Tutanova user should have to install a Tutanova client, I might as well just have them set up PGP. If you mean a local server using the github code, it's a fair enough point - it's more complicated and likely insecure than using PGP, but at least the burden of complexity and security falls on the power user.