HERE IS THE BEST TIME SAVING / EMAIL ORGANIZING EVER:
When you read an email simply delete it (if junk and completely worthless), reply (if needed), or do nothing. That's it. DO NOT CREATE FOLDERS for emails and try to have some structure of organizing based on folders. When email client programs (Outlook, etc.) became the fad, I noticed that people were spending WAY too much time sorting.
I'd hear them ask questions like "I had an old email from Bob at Acme Inc. regarding Product X-123 that was used the Falcon Project. - Did I have that filed in the Bob folder, the Acme folder, the X-123 folder or the Falcon folder?"
Why? The email search function works fine. Just keep them in your inbox (not folders) and let the search function do its job. Eventually some company began to promote the same concept (esp. Google).
The only issue with this is inbox size capacity limits.