The Outlook mobile app now includes a Copilot feature that can summarize long email threads into a few sentences. This saves time when you are away from your desk and need to quickly understand the key points of a conversation. The summary appears at the top of the thread and is generated by Microsoft 365 Copilot. This article explains what the feature does, how to use it on your phone, and what limits you should know about.
Key Takeaways: Using Copilot to Summarize Threads in Outlook Mobile
- Tap the Copilot icon in the thread header: Opens a summary of the selected email thread directly in the reading pane.
- Requires Microsoft 365 Copilot license: The feature is not available with standard Microsoft 365 Business or Enterprise subscriptions.
- Works on iOS and Android: Supported in the Outlook mobile app version 4.2430 or later.
What the Copilot Summarize Thread Feature Does
The Summarize Thread feature in Outlook mobile uses Microsoft 365 Copilot to read the entire email conversation and produce a short summary. The summary appears as a card at the top of the thread. It lists the main topics, decisions, and action items. You do not need to scroll through dozens of replies to find the important details. The summary is generated on Microsoft servers using your tenant data. No data leaves your organization’s compliance boundary.
To use this feature, you need an active Microsoft 365 Copilot license assigned to your account. The license is separate from your standard Microsoft 365 Business Basic, Standard, or Premium subscription. Your organization must also have the Copilot service enabled by the global admin. The feature works in the Outlook mobile app for iOS and Android. It supports threads that contain at least two messages. Threads with only one message do not produce a summary.
Steps to Summarize an Email Thread in Outlook Mobile
- Open the Outlook mobile app
Make sure you are signed in with your work or school account that has a Copilot license. If you have multiple accounts, switch to the correct one by tapping your profile picture and selecting the account. - Navigate to the email thread you want to summarize
Tap the thread in your Inbox or any folder. The thread must contain at least two messages. The feature works best with threads that have more than five replies. - Tap the Copilot icon in the thread header
Look for the Copilot icon, which looks like a purple or blue sparkle. It appears near the sender name or the subject line at the top of the thread. On some versions, the icon is labeled “Summary” or “Summarize.” - Wait for the summary to load
Copilot processes the thread. This takes a few seconds depending on the length of the conversation. A spinning indicator appears while the summary is generated. - Read the summary card
After processing, a card appears at the top of the thread. It shows a short paragraph that captures the key points. You can scroll down to see the full thread below the summary. - Dismiss or regenerate the summary
Swipe the card to dismiss it. To get a new summary, tap the Copilot icon again. The new summary replaces the previous one.
If the Summarize Feature Does Not Appear or Fails
Copilot icon is missing from the thread header
The icon does not appear if your account does not have a Copilot license. Contact your IT admin to confirm license assignment. The icon also does not show for threads with only one message. Open a thread with at least two messages to see the icon.
Summary shows an error message
Copilot may fail to generate a summary if the thread contains unsupported content such as encrypted messages, rights-protected emails, or messages with digital signatures. The summary also fails if the thread is too long, exceeding approximately 20,000 characters. Try summarizing a shorter thread to verify the feature works.
Summary is inaccurate or incomplete
Copilot summarizes based on the text in the thread. If the conversation contains heavy jargon, abbreviations, or non-English text, the summary may miss details. The feature is optimized for English. You can tap the Copilot icon again to regenerate the summary. If the problem persists, the thread may have too many off-topic replies that confuse the model.
| Item | Outlook Mobile with Copilot | Outlook Desktop with Copilot |
|---|---|---|
| Summary location | Card at top of thread in reading pane | Inline summary in the reading pane or pop-up window |
| Trigger action | Tap Copilot icon in thread header | Click Summarize button on the Home ribbon or from the Copilot pane |
| Minimum thread length | 2 messages | 2 messages |
| Maximum thread size | Approximately 20,000 characters | Approximately 20,000 characters |
| Supported platforms | iOS and Android | Windows and Mac |
| License required | Microsoft 365 Copilot | Microsoft 365 Copilot |
The Summarize Thread feature in Outlook mobile gives you a fast way to catch up on long email conversations without reading every reply. To use it, ensure your account has a Copilot license and the app is updated to version 4.2430 or later. After you generate a summary, you can dismiss it or tap the icon again to refresh it. For threads with sensitive content, remember that Copilot may fail if encryption or rights management is applied. Try summarizing a thread with at least ten replies to see the best results.