Microsoft has fixed a critical bug that was causing Copilot buttons to vanish from Classic Outlook for Windows users with a Basic license. The issue, which was affecting thousands of customers, has been resolved through a service change implemented by Microsoft’s Outlook Team on June 29th.
The problem was particularly frustrating for those who rely heavily on the Copilot Chat feature in their daily work. Affected users reported that the Copilot buttons disappeared from the side navigation and above the ribbon, making it difficult to access this essential tool. Moreover, some users experienced additional issues such as being unable to add Copilot through ribbon customization or having it appear as an unavailable app.
Fortunately, Microsoft has taken swift action to address this issue. Users who are still experiencing problems can try restarting their email client to get the change immediately. Additionally, those with access to the latest build should update their Outlook software by selecting File > Office Account > Update Options > Update Now. For users who cannot upgrade their client, there is a workaround: reverting to the previous Current Channel build (16.0.20026.20168) or switching to the new Outlook or Outlook Web Access (OWA).
While this issue has been resolved, Microsoft is now investigating another critical problem that causes unexpected Outlook crashes on systems running Kaspersky Antivirus software. This bug is linked to the Kaspersky Mail Checker (mcou.dll). Affected users are advised to check their Application log for “Event 1000” events with the OUTLOOK.EXE faulting app name and MCOU.DLL faulting module name. If you’re experiencing this crash, it’s recommended that you contact Kaspersky support.
The Copilot bug highlights the importance of keeping software up-to-date and patching vulnerabilities in a timely manner. It’s also essential to have robust security measures in place to prevent such issues from affecting productivity. As the cybersecurity landscape continues to evolve, it’s crucial for organizations to prioritize their security posture and regularly test their systems against potential threats.
In conclusion, users who experienced issues with missing Copilot buttons can breathe a sigh of relief now that Microsoft has fixed this bug. However, it’s essential to remember that this is not an isolated incident, and there may be other vulnerabilities lurking in the shadows. To stay ahead of attackers, organizations must prioritize their security measures and regularly test their systems against potential threats.
Source: Bleeping Computer — 2026-07-02