Email coaching gives feedback on an email you wrote yourself. You write the message as usual, select the Copilot icon on the toolbar and choose Coaching by Copilot. It flags points on tone, clarity and the reader's likely reaction. You can select Apply all suggestions to have Copilot regenerate the message, or make your own edits based on what it flagged.
Coaching only sees the draft in front of you, not your mailbox history. It works with work or school accounts and with personal Microsoft accounts on outlook.com, hotmail.com, live.com or msn.com; a Gmail, Yahoo or iCloud address in Outlook gets no Copilot features. On Mac, only the latest Outlook version supports it. Use it to catch a tone you did not intend, not to replace your own judgement about what to say.