Microsoft is still grappling with a pesky issue that causes Copilot buttons to vanish from Classic Outlook for some users. The problem, which affects Windows customers with specific licenses or subscriptions, has been ongoing since June, when Microsoft announced a fix via a service change.
The affected group includes those with the Copilot Chat (Basic) license or a paid M365 Copilot (Premium) account. These users may experience one or more issues, such as missing Copilot buttons in the top-right area above the ribbon or in the left app bar. Additionally, when trying to add Copilot through ribbon customization, it might appear as unavailable or grayed out.
The reason behind this issue is that Outlook struggles to locate a specific MAPI property (PR_PROFILE_USER_SMTP_EMAIL_ADDRESS_W) within the null profile section. As a result, the Copilot component can’t persist in related settings, making it difficult for users to access the Copilot entry point. Microsoft’s investigation suggests that this problem arises after upgrading Classic Outlook to build 20026.20182 and higher.
To mitigate this issue temporarily, Microsoft has provided a workaround: enabling the “Show Apps in Outlook” option in Classic Outlook settings. To do so, select the File tab, then Options, go to Advanced, and check the box for “Show Apps in Outlook” under “Outlook panes.” Users can also create a new Outlook profile or switch to the new Outlook email client or Outlook Web Access (OWA), which are not affected by this bug.
Interestingly, Microsoft has acknowledged another issue causing unexpected Outlook crashes on systems running Kaspersky Antivirus software. This problem results in “Event 1000” events being recorded in the Application log linked to the Kaspersky Mail Checker (mcou.dll). Although the exact cause is still unknown, Microsoft advises Kaspersky customers experiencing crashes to contact Kaspersky support.
This latest development serves as a reminder that even with the most advanced technology, bugs can persist and cause frustration for users. It’s essential to stay informed about ongoing issues and workarounds to minimize disruptions to productivity.
To protect yourself from similar problems in the future, consider implementing a robust IT infrastructure, including regular software updates and security patches. Additionally, be cautious when introducing new features or services that may interact with your existing systems. By staying vigilant and proactive, you can reduce the likelihood of encountering issues like this one.
Source: Bleeping Computer — 2026-09-16