Outlook and the like have the sweep feature which makes managing email quite easy. The built in unsubscribe tool works very well.
I think maybe the premise is that people don’t know how to use their existing tools well, but then I don’t have confidence Hey will do a better job. They tried to get me to watch their CEO explain it for 37 minutes.
The other thing I find questionable is how this would work with third-party email clients. Anytime the service tries to ‘reinvent’ email, it ends up breaking standard features, like being able to use your own email client. Look at gmail and how their tags concept translates to e.g. imap
Edit: I assumed DHH was running Hey because he’s been complaining about it so much lately.