Microsoft has released an update for Microsoft 365 that finally resolves a frustrating crash in Outlook triggered by the Copilot Compose feature. The bug, which could cause the email client to become unresponsive or terminate unexpectedly, specifically occurred when users started drafting emails using Copilot, either by pressing Alt+I or clicking the Compose button in the Copilot pane. The fix is part of the latest Microsoft 365 Apps update and is being deployed automatically to users, but manual steps can help you get it faster.

The Bug That Made Copilot Completely Unusable

For several weeks, Outlook users who relied on Copilot to draft emails encountered a disruptive issue. When they attempted to start Copilot Compose—whether via the Alt+I keyboard shortcut or the dedicated button in the Copilot sidebar—the application would sometimes crash without warning. This not only interrupted workflows but also risked losing unsaved work. The problem was not universal; it seemed to affect specific configurations or occur under certain conditions, but Microsoft acknowledged the issue publicly and has now addressed it.

According to a Microsoft support document updated recently, the crash occurred due to a flaw in how Outlook handled the initialization of the Copilot drafting interface. When the Compose command was invoked, a specific call failed, leading to an application error. The exact technical details haven’t been disclosed, but the fix likely involves a patch to the underlying code that manages the integration between Outlook’s message composition window and the Copilot AI services.

The update that contains the fix is rolled out as part of the regular Microsoft 365 update channel. While Microsoft hasn’t published a specific KB article exclusively for this issue, it is included in the February 2025 security and quality updates for Microsoft 365 Apps. Users on the Current Channel will receive it automatically through their usual update mechanism. For those who want to verify, the fixed build is one of the latest versions released in the Current Channel, typically build numbers starting with 16.0.18526.20144 or higher for the February 2025 wave. (To check your exact version, go to File > Office Account in Outlook and look under About Outlook.)

It’s important to note that this crash impacted only the desktop version of Outlook on Windows. The web version (Outlook on the web) and the Mac version were not affected, as they handle Copilot integration differently. Users who experienced the crash would see a standard “Microsoft Outlook has stopped working” dialog, and on some occasions, Outlook might restart automatically. However, repeated crashes made the feature unusable for many.

Impact Across Different Audiences

For everyday users: If you’ve been avoiding Copilot Compose or limping along with workarounds, this fix restores full functionality. The feature can save hours each week by turning bullet points into polished messages, adjusting tone, or generating drafts from scratch. Now you can use it without anxiety.

For power users: Those who heavily rely on keyboard shortcuts like Alt+I to speed through email composition can return to their established flow. The crash had forced many to switch to slower mouse-based interactions or abandon Copilot entirely. This update eliminates that friction.

For IT administrators: This fix reduces the burden of support tickets related to Outlook instability. Many organizations had already advised users to disable Copilot or avoided deploying it. Now, the path is clear to enable Copilot in Outlook without fear of downtime. Additionally, the relatively fast turnaround—from first reports in late January to a fix by mid-February—signals that Microsoft is prioritizing Copilot reliability.

A Timeline of Copilot’s Rocky Outlook Integration

Copilot in Outlook began as a limited preview in 2023, initially available only to enterprise customers with specific licenses. Over time, it expanded to more users, adding features like email summarization, coaching, and the Compose tab. The Compose feature, in particular, gained attention because it allowed users to describe the email they wanted to write in natural language and have Copilot generate it. However, the integration, which requires real-time access to Microsoft’s AI models, introduced new dependencies and potential failure points.

This isn’t the first time Outlook has struggled with crashes related to add-ins or cloud features. Historically, Outlook’s stability has been sensitive to third-party COM add-ins, and even native features like the To-Do bar or search have caused issues. Copilot, being a first-party, deeply integrated feature, was expected to be more reliable. Yet, the complexity of threading AI interactions into the composition process—managing context, user permissions, and the asynchronous nature of AI responses—proved challenging.

Reports of the specific Copilot Compose crash began surfacing in Microsoft’s community forums in early February 2025. Users described the crash as reproducible: it would happen consistently when they clicked “Compose” or pressed Alt+I, but only if Copilot was already active in the sidebar. Some workarounds were discovered, such as restarting Outlook in safe mode or disabling and re-enabling the Copilot add-in, but these were temporary. Microsoft acknowledged the issue in its Microsoft 365 admin center under a known-issues advisory, indicating that the product team was investigating and would deliver a fix in an upcoming update. That update has now arrived.

Step-by-Step Guide to Getting the Patch

If you’ve been dealing with crashes or avoiding Copilot Compose, here’s how to ensure you have the patched version:

1. Update Microsoft 365 Apps manually
- Open Outlook (or any Office app like Word).
- Click File > Office Account (or Account in some versions).
- Under Product Information, click Update Options > Update Now.
- Wait for the update to download and install.
- Restart Outlook after the update completes.

2. Verify the update took effect
- After restarting, go back to File > Office Account.
- Under About Outlook, check the build number. The fixed version is part of the February 2025 Current Channel release. Look for a build number like 16.0.18526.20144 or later. If you see an earlier build, repeat the update process or check if updates are deferred by policy.

3. For enterprise users and admins
- The fix is included in the February 2025 monthly enterprise channel update as well (build 16.0.18526.20144 for Monthly Enterprise). Semi-Annual Enterprise Channel users will receive it in the next scheduled release, typically months later, so a workaround is to temporarily move a test machine to Current Channel to verify the fix and plan for broader deployment.
- Use the Microsoft 365 Apps admin center or configuration manager to push the update to affected users.
- If you had implemented a workaround like disabling the Copilot add-in via Group Policy or registry, you can now re-enable it.

4. Confirm the issue is resolved
- Launch Outlook and open the Copilot pane.
- Start a new email and click the Compose button in Copilot, or press Alt+I.
- In earlier affected versions, this would often trigger a crash. Now, the Copilot drafting interface should load smoothly, allowing you to enter a prompt and generate content.

Future-Proofing Your Outlook Experience

While this specific crash is fixed, it’s wise to adopt habits that prevent future disruptions:

  • Keep Office up to date: Regular updates not only bring new features but also security and stability fixes. Set updates to automatic if possible.
  • Monitor the Microsoft 365 service health dashboard: For enterprise environments, this dashboard (accessible via the Microsoft 365 admin center) provides real-time information on known issues, including ones that may not yet have a fix but might have workarounds.
  • Provide feedback: If you encounter new issues with Copilot or any Office feature, use the in-app feedback tool (Help > Feedback) or report through the Microsoft Feedback Portal. Quick reporting helps Microsoft prioritize fixes.
  • Test critical workflows before broad deployment: For IT teams, rolling out new feature updates to a pilot group first can catch bugs like this one before they impact the entire organization.

What to Watch Next: Copilot’s Expanding Role

The Copilot suite continues to grow across Microsoft 365. In the coming months, we expect deeper integrations in Outlook, such as the ability to schedule meetings with Copilot, summarize long threads with more nuance, and even prioritize emails based on your work patterns. All these features increase the surface area for potential glitches. Microsoft’s challenge is to balance rapid innovation with rock-solid reliability.

This crash fix is a positive sign that Microsoft is listening and responding quickly. However, it also serves as a reminder that AI-powered tools are still maturing. Users should embrace Copilot’s utilities but stay vigilant about updates and known issues. For now, if you’ve been waiting to try Copilot Compose or had given up on it, go ahead and update—that particular annoyance is a thing of the past.