Use Microsoft Copilot in Outlook to Summarize Email Threads

What This Does

Instantly summarizes any email thread, no matter how long, into 3-5 bullets with key decisions, open questions, and who said what, so you can brief your manager or respond intelligently without reading 25 emails.

Before You Start

• You have Outlook (desktop app or web, outlook.com or your work account) open
• Your organization's M365 license includes Copilot
• You have a long or complex email thread you need to understand quickly

Steps

1. Open the email thread

In your Inbox, click on any email thread. You can see the message count next to the subject line (e.g., "14 messages"). The more messages in the thread, the more time Copilot saves you.

2. Find the Copilot summary banner

At the top of the email reading pane, look for the Summary by Copilot box and select it. On Mac the box shows a Summarize button; in classic Outlook the option is labeled Summarize.

What you should see: A summary above the email messages with bullet points and numbered citations. Click a citation to jump to the source email.

Troubleshooting: If you don't see the Summary by Copilot box, your account may not have Copilot in Outlook enabled. Check with your IT department.

3. Read the summary

The summary shows: what was requested or decided, who the key participants are and what they said, any outstanding questions or pending responses, and any dates or deadlines mentioned.

What you should see: Bullet points with names and brief summaries, e.g., "Sarah (March 14): Requested vendor contract by end of week. Tom (March 15): Confirmed contract is delayed due to legal review."

4. Use the summary to draft your response

After reading the summary, click Reply, then the Copilot icon in the compose toolbar and choose Draft (labeled Draft with Copilot in classic Outlook) to draft a response that references the thread context. Or just use the summary to brief your manager verbally or in a quick Slack message.

Real Example

Scenario: Your director asks you to catch her up on the vendor dispute thread from last week, a 22-message chain she was cc'd on.

What you do: Click the thread in Outlook → read the Copilot summary at the top (takes 10 seconds) → copy the 4 key bullets → send your director a Teams message: "Quick update on the Jones vendor thread: [paste summary]."

What you get: Your director is fully briefed in 2 minutes instead of you spending 20 minutes reading and synthesizing the whole thread.

Tips

• Use this before responding to any thread longer than 5 messages. It prevents you from accidentally addressing something already resolved or missing a key detail.
• Attachments can be summarized too. Use "Summarize a file" on an attached document to get its key points without opening it.
• The summary is private to you, it doesn't appear to other thread participants. You can use it to prep without anyone knowing you used AI.

Tool interfaces change, if a button has moved, look for similar AI/magic/smart options in the same menu area.