Most people don’t manage their inbox effectively. Emails should be treated as a list to do. As you complete a task you can just delete the email.
Your inbox should only contain actionable items. So everything in your Inbox, including subfolders, should be tasks that are actionable items on your to-do list.
So do it now, delete all emails you have done and the ones that aren't tasks.
Note: If you want to keep an email that is not an actionable task (e.g. for future reference), move it to a folder outside your inbox (e.g. "Saved items")
The same applies to email tasks assigned to others. If you need to follow up, store them on a separate folder (e.g. Named "Waiting on others")
✅ Figure: Good example - All inbox items are tasks
In fact, you could say that you should not do anything unless it is captured in an email or a PBI, which is why we send ourselves emails.
Note: In rare cases, very simple tasks can be requested and replied 'done' via IM.