This article relates to a paid Microsoft Copilot feature rather than one that is universally available
When you receive an email, there is the option for a Copilot summary. Click on "Summary by Copilot"
Copilot will generate a summary automatically:
If you click the "Ask Copilot" button then you can interogate the email further. Copilot will respond based on what it knows about you.
And Co-Pilot will respond and also give some buttons you can click for quick action: