**Microsoft** has rolled out a fix for a known issue affecting **Classic Outlook** users on Windows. The problem caused the **Copilot Chat** or **Copilot** buttons to disappear for individuals holding the **Copilot Chat (Basic)** license. ### Copilot Buttons Reappear in Classic Outlook According to a recent support document from **Microsoft**, affected users reported that **Copilot** buttons were missing from both the side navigation and above the ribbon. Specific symptoms included: * The **Copilot** button was absent from the top-right area above the ribbon. * The **Copilot** icon was missing from the left app bar or **More Apps** area. * Selecting **Copilot** in **Add Apps** yielded no action. * Adding **Copilot** via ribbon customization showed the command as unavailable or grayed out. **Microsoft** confirmed that **Copilot** remained accessible through other entry points, such as **Outlook on the web** or the **Microsoft 365 Copilot** standalone app. The **Outlook Team** resolved this issue with a service change implemented on June 29, 2026. Users still experiencing the problem are advised to restart their email client. Updating to the latest build via `File > Office Account > Update Options > Update Now` is also recommended. Temporary workarounds included reverting to the previous **Current Channel** build (16.0.20026.20168) or utilizing the new **Outlook** or **Outlook Web Access (OWA)**. ### Investigating Kaspersky Antivirus Crashes In a separate development, **Microsoft** is actively investigating an issue where **Outlook** unexpectedly crashes on systems running **Kaspersky Antivirus** software. This problem is linked to the **Kaspersky Mail Checker (mcou.dll)**. **Outlook for Microsoft 365** users experiencing these crashes are advised to check their Application logs for "Event 1000" entries, specifically looking for `OUTLOOK.EXE` as the faulting application name and `MCOU.DLL` as the faulting module name. The **Outlook Team** recommends contacting **Kaspersky** support if these conditions are met. These recent fixes follow previous resolutions for other **Classic Outlook** issues, including problems preventing email delivery via **Outlook.com** and client usability issues caused by the **Microsoft Teams Meeting Add-in**.