https://www.theregister.co.uk/2019/07/03/superhuman_email_biz/

Superhuman, an email startup betting people who deal with a lot of messages will pay $30 a month for a more organized inbox, has come under fire for not providing privacy by default.

"Superhuman is a surveillance tool that intentionally violates privacy by notifying senders every time their emails have been viewed by recipients," said Mike Davidson, VP at InVision and former design VP at Twitter, in a tweet last week.