Microsoft restores missing Copilot buttons in Classic Outlook

Key points

• Microsoft fixed a bug on June 29, 2026 that hid Copilot buttons inside Classic Outlook on Windows.
• The problem hit users on the Copilot Chat (Basic) licence, the entry-level tier of Microsoft's AI assistant.
• Users who still see no buttons should restart Outlook or run Update Now from the File menu.
• A separate crash affecting Outlook on PCs running Kaspersky Antivirus is still under investigation.

Microsoft has fixed a glitch that made the Copilot buttons vanish from Classic Outlook on Windows, leaving people on the Copilot Chat (Basic) licence unable to reach the AI assistant from inside their email.

Copilot is Microsoft's AI helper — the thing that drafts replies, summarises long threads and answers questions inside Office apps. For affected users, the button above the ribbon was gone. The icon in the left-hand app bar was gone too. Trying to add it back through the app menu did nothing, or showed the option greyed out.

Copilot itself still worked. Users could reach it through Outlook on the web or the standalone Microsoft 365 Copilot app. It was only the buttons inside the desktop client that had disappeared.

What should affected users actually do?

Restart Outlook. Microsoft says it pushed a service-side fix on June 29, 2026, and closing and reopening the client should pull the change through immediately.

If the buttons are still missing after a restart, Microsoft recommends updating the app. Click File, then Office Account, then Update Options, then Update Now. That forces the latest build to install.

For anyone who can't update, there are two workarounds. Roll back to the previous Current Channel build, numbered 16.0.20026.20168. Or switch to the new Outlook or Outlook on the web, both of which were never affected.

The bug was first reported by BleepingComputer.

A separate crash on Kaspersky machines

Microsoft is also looking into a different problem: Outlook for Microsoft 365 crashing on computers that run Kaspersky Antivirus, a Russian-made security product widely used by consumers and small businesses.

The crashes trace back to a Kaspersky component called Mail Checker, which scans incoming email for malicious content. The file involved is mcou.dll.

Microsoft's advice for confirming the cause is technical but simple to follow. Open the Windows Event Viewer, look at the Application log, and check for entries labelled "Event 1000" that name OUTLOOK.EXE as the faulting app and MCOU.DLL as the faulting module. If both appear together, this is the bug.

"If you are experiencing this crash, please contact Kaspersky support," the Outlook Team wrote in its guidance. In other words, this one is on Kaspersky to fix, not Microsoft.

Why does this keep happening to Classic Outlook?

Classic Outlook has taken a run of hits this year. Microsoft has recently patched a fault that stopped some users sending mail through Outlook.com, and another that broke the client entirely for people using the Microsoft Teams Meeting Add-in.

The pattern reflects an awkward middle age for the app. Microsoft is nudging users toward the new Outlook and the web version, but millions of businesses still run the classic desktop client, and every service change on the cloud side risks knocking something loose on the desktop.

For ordinary users, none of this is a security incident. No data was exposed. No attacker was involved. It's a reliability story, not a breach story — but a useful reminder that the AI features baked into everyday office software depend on a chain of licences, service flags and client builds all lining up. When one link slips, the button just quietly disappears.