I implemented this for my email. Each email can have any number of tags. Each tag can have a directory hierarchy. So for instance an email can be tagged fun/sk

I implemented this for my email. Each email can have any number of tags. Each tag can have a directory hierarchy. So for instance an email can be tagged fun/ski, social/facebook/marketplace, money/receipts. If you open the social/facebook/marketplace “folder” you’ll see the email, but also if you open the money/receipts “folder”. You could also see it in the intersection of the social tag and the fun/ski tag, etc.