ion is EteSync. Posteo is an interesting alternative to both ProtonMail and EteSync, because it supports zero access encryption for not only email, but also contacts and calendars. Finally, there are several files clouds with end-to-end encryption, but only Mega and Filen have open source clients and support Linux. Of the two, Mega is the slightly superior choice as it has an API to integrate with other applications (e.g. FolderSync support for Android), and you can even set up WebDAV if you want.</p>


