A known issue in Classic Outlook for Windows caused the Copilot Chat or Copilot buttons to disappear for users licensed for Copilot Chat (Basic). This affected the visibility and functionality of Copilot UI elements such as buttons above the ribbon and in the left app bar. Microsoft fixed the problem with a service-side update on June 29, 2026. Users are recommended to update their Outlook client to the latest build or restart the application to receive the fix. Workarounds include reverting to a previous Outlook build or using Outlook Web Access or the new Outlook client. The issue does not affect Copilot availability in web or standalone app contexts. No exploitation or security breach is reported. Separately, Microsoft is investigating Outlook crashes linked to Kaspersky Antivirus software.

The impact is limited to user interface functionality within Classic Outlook on Windows, specifically the disappearance of Copilot buttons for licensed users, which may hinder access to Copilot features. There is no indication of data compromise, privilege escalation, or broader security impact. Copilot remains accessible through other Microsoft platforms and clients. No known exploits are reported in the wild.

Microsoft has implemented a service-side fix as of June 29, 2026. Users should restart their Outlook client to apply the fix immediately and update to the latest build via File > Office Account > Update Options > Update Now. Users unable to upgrade can revert to the previous Current Channel build (16.0.20026.20168) or use Outlook Web Access or the new Outlook client as a workaround. No additional security actions are required. For the separate Outlook crash issue related to Kaspersky Antivirus, affected users should check application logs for specific fault events and contact Kaspersky support.