Never used it, so I cannot express an opinion on the specific service, but I'm not so enthusiastic about e2e email services, because they usually break the standard email protocol. E.g. from https://tuta.com/support
> Can I retrieve my Tuta emails via IMAP to another email client?
> This is not possible as we could not guarantee end-to-end encryption for your data. Instead, Tuta offers email desktop clients for Linux, Mac OS and Windows as well as a web client and apps for Android and iOS.
Then the encryption benefit applies only if both parts use it, otherwise Tuta can always read the correspondence.
If i need it, I prefer to manage the encryption on a second independent layer, e.g. GPG or a basic but effective ZIP with password :)