Copilot Buttons Vanish in Classic Outlook – Microsoft Issues Workaround

Microsoft confirmed that a known issue is still affecting Classic Outlook on Windows. Users with a Copilot Chat (Basic) or paid M365 Copilot (Premium) license report that the Copilot and Copilot Chat buttons no longer appear in the side navigation or above the ribbon after upgrading to build 20026.20182 or higher.

What’s Broken?

• The Copilot button is missing from the top‑right area above the ribbon.
• The Copilot icon is absent from the left app bar or the More Apps area.
• In Add Apps, Copilot shows as available but does nothing when opened.
• Adding Copilot via ribbon customization displays the command as unavailable or grayed out.

Despite the disappearance, Copilot remains reachable through Outlook on the web, the standalone Microsoft 365 Copilot app, or the web experience.

Root Cause

Analysis points to Outlook’s failure to locate the MAPI property PR_PROFILE_USER_SMTP_EMAIL_ADDRESS_W within the null profile section. Without this property, Copilot settings cannot persist, causing the UI entry point to vanish.

Workarounds

• Enable Show Apps in Outlook: File > Options > Advanced > Outlook panes > check "Show Apps in Outlook".
• Create a new Outlook profile.
• Switch to the new Outlook client or use Outlook Web Access (OWA).

Other Related Issues

Microsoft also reported unexpected Outlook crashes on systems with Kaspersky Antivirus, tied to the Kaspersky Mail Checker (mcou.dll). Kaspersky users experiencing crashes should reach out to Kaspersky support.

"The Outlook Team is actively investigating this issue. Current analysis indicates that, in affected environments, Outlook is unable to locate the MAPI property PR_PROFILE_USER_SMTP_EMAIL_ADDRESS_W within the null profile section," Microsoft said.

Microsoft is working on a permanent fix and will update users when it’s available.