Releasing Features like Summarize Email Thread without Microsoft 365 Copilot Licenses is Just Business

Those who are surprised by Microsoft making Copilot features in Office to users without a Microsoft 365 Copilot license don’t understand that it’s simply a matter of business. If Microsoft doesn’t make basic AI features available within Office, ISVs will fill the vacuum by selling add-ons to integrate ChatGPT or other AI with Outlook. If customers buy ChatGPT integrations, it removes opportunity for Microsoft to sell Microsoft 365 Copilot licenses.

Message center notification MC1124564 (updated 12 August 2025, Microsoft 365 Roadmap item 498320) is a good example. This post announces that the option to summarize email threads will be available in Outlook even for users without a Microsoft 365 Copilot license provided Copilot chat is pinned to the navigation bar. The feature is available in Outlook Classic (subscription version), the new Outlook for Windows, and OWA if they have enabled Copilot chat by pinning the app to the navigation bar. This option is controlled by a setting in the Copilot section of the Microsoft 365 admin center (Figure 1).

Targeted release users should see the feature between late August 2025 and mid-September 2025, with general availability following in between mid-September and mid-November 2025.

Summarizing Email Threads

Generative AI always creates the best results when it has a well-defined set of data to process. Just like users who have Microsoft 365 Copilot licenses, Outlook users without a Copilot license will see a Summarize button in the reading pane. Choosing the option calls Copilot to process the email thread to create a summary by extracting the most important points from the thread. Even in a single-item thread, summarization can be valuable by confirming critical issues raised in a message.

Summarizing an email thread doesn’t include other Copilot features like summarizing attachments for a message.

The Business Question

If Microsoft didn’t offer thread summarization in Outlook, customers can find the same functionality available in ISV offerings such as AI MailMaestro (ChatGPT for Outlook), available in the Microsoft app store, which includes the ability to summarize “any email for immediate thread analysis and key points” at a price point where “Copilot is 2.5x more expensive than MailMaestro.”

This is not the only example of an Outlook add-in for ChatGPT (here’s another picked at random). OpenAI has their own connector for Outlook email (and others for Outlook calendar, Teams, and SharePoint Online). Using add-ins and connectors creates security, app management, and compliance questions for Microsoft 365 tenants, but some organizations are happy with the trade-off to gain AI features at reduced cost.

No doubt Microsoft will emphasize to customers that their version of the OpenAI software is specially tailored to the demands of Microsoft 365 in a way that a general-purpose LLM cannot be. However, price is a powerful influence and ChatGPT is a very popular solution.

From a Microsoft perspective, if customers embrace OpenAI-based third-party solutions and deploy add-ins or connectors to extend the Office apps, Microsoft loses some degree of account control and their potential to sell Microsoft 365 Copilot licenses is reduced. Neither outcome is an attractive prospect, especially in large enterprise accounts.

In the context of wanting to protect the Office franchise, it’s understandable why Microsoft should make a limited subset of AI-driven features available to users of the Microsoft 365 enterprise apps (subscription version of Office). Apart from making third-party offerings less attractive, getting Copilot’s proverbial foot in the door is likely to encourage investigation of other Copilot functionality like email prioritization that might lead to future purchases.

Raising the Ante

I’ve nothing against Microsoft adding features to Outlook where it makes sense. Summarizing email threads is an example of where everyone can gain from AI, so it seems sensible to add it to Outlook. The fact that adding the feature helps Microsoft to compete with ISVs might seem regrettable, but it’s just business.

In some scenarios, adding features like this might be deemed anti-competitive, but there is plenty of room for ISVs to compete with Microsoft to exploit AI, and including basic features like summarization rapidly becomes the ante to participate in the market.

So much change, all the time. It’s a challenge to stay abreast of all the updates Microsoft makes across the Microsoft 365 ecosystem. Subscribe to the Office 365 for IT Pros eBook to receive insights updated monthly into what happens within Microsoft 365, why it happens, and what new features and capabilities mean for your tenant.