Mail systems are evolving to match the new volume of email, and users will increasingly see only algorithmically vetted emails. Some other emails may be shown below the vetted email, and the rest will flow away into temporal oblivion, just like uninteresting social posts from a few hours ago.
Email providers may soon sell “promoted emails” where a marketer can target a user in their priority inbox. Users may revolt, but in the end they are getting email for free, so it will be hard to complain. Email has become a stream, and as the adage goes, when you’re not paying, you’re the product.