SaneBox

SaneBox works on the server side of your email account, so it does not replace your email app. It watches which senders you open and reply to, and moves mail it judges unimportant out of the inbox into a folder called SaneLater. A daily digest lists what was moved so you can rescue anything it got wrong.

You train it by dragging messages between folders: move a sender into the inbox once and SaneBox remembers. Other folders include SaneBlackHole, which unsubscribes you in practice by keeping a sender out of sight, and reminders for messages that get no reply.

It works with Gmail, Outlook, iCloud and most IMAP providers, and with any email app. It needs access to your mail to work; read its privacy notes, and check current pricing on its site.