Microsoft Outlook Classic Missing Copilot Buttons After Update, Temporary Workaround Provided

Microsoft Outlook Classic Missing Copilot Buttons After Update, Temporary Workaround Provided

What Happened — Microsoft confirmed that after upgrading Classic Outlook for Windows to build 20026.20182 (or later), the Copilot and Copilot Chat buttons disappear for users with a Copilot Chat (Basic) or M365 Copilot (Premium) license. The issue stems from Outlook being unable to locate the MAPI property PR_PROFILE_USER_SMTP_EMAIL_ADDRESS_W in the user profile, preventing the Copilot component from persisting.

Why It Matters for Trust & Control Assurance

• Demonstrates the need for continuous configuration monitoring to detect unintended UI or feature regressions after software updates.
• Highlights the importance of maintaining auditable evidence that critical productivity controls (e.g., AI‑assisted features) remain enabled and functional.
• Aligns with the control‑mapping capability that tracks configuration changes across Microsoft 365 tenants, providing a defensible audit trail.

Who Is Affected – Enterprises and professional‑service organizations that rely on Classic Outlook with a Copilot license; the issue also touches users of Kaspersky Antivirus who may experience Outlook crashes.

Recommended Actions

• Enable File → Options → Advanced → “Show Apps in Outlook” as a temporary fix.
• Create a new Outlook profile or switch to the new Outlook client/Outlook Web Access, which are not impacted.
• Document the change in your configuration‑management system and add the missing MAPI property check to your post‑update validation checklist.
• Monitor Microsoft 365 release notes for the permanent fix and update your control‑mapping inventory accordingly.

Source: BleepingComputer

Technical Notes

• Root cause: Outlook cannot locate the PR_PROFILE_USER_SMTP_EMAIL_ADDRESS_W property in the null profile section after the update.
• Impact: Copilot UI elements are hidden; functionality remains accessible via Outlook on the web or the standalone Copilot app.
• Related bug: Outlook crashes on systems running Kaspersky Antivirus (event 1000, mcou.dll).

Source: Microsoft advisory, BleepingComputer