REALLY misleading. They created this feature for Mr. Robot, the TV show, too:
https://protonmail.com/blog/protonmail-mr-robot-secure-email...
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> Liam, October 14, 2015 at 10:30 PM
> But https://protonmail.com/security-details page says “No tracking or logging of personally identifiable information. Unlike competing services, we do not save any tracking information. We do not record metadata such as the IP addresses used to log into accounts.” So, now it turns to be that you introduced tracking and logging? Is this data encrypted as well?
> Admin, October 17, 2015 at 9:14 PM
> We don’t save any of this data by default, the user must explicitly turn it on for us to save it.
There should be a reasonable assumption that given they have end-to-end encryption for the service, they just encrypt the logging for the user and store it encrypted without the key themselves like they do the emails.
Also to note, they at least have an onion link to use their email service.