Microsoft restores missing Copilot buttons in Classic Outlook
A licensing bug wiped the AI assistant's buttons from the desktop email client. Microsoft says a June 29 fix has now landed.
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 and summarises long threads inside Office apps. For affected users, the button above the ribbon was gone, and so was the icon in the left-hand app bar. 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. Only the buttons inside the desktop client had disappeared.
What should affected users actually do?
Restart Outlook. Microsoft pushed a service-side fix on June 29, 2026, and closing and reopening the client should pull the change through immediately.
If buttons are still missing, click File, then Office Account, then Update Options, then Update Now. That forces the latest build to install.
For anyone who cannot update, two workarounds exist. 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 Outlook for Microsoft 365 crashing on computers running Kaspersky Antivirus, a Russian-made security product widely used by consumers and small businesses. Six of our seven Outlook stories in the last 90 days have involved bugs in the desktop client, and this one is different because the fix sits with a third party.
A Kaspersky component called Mail Checker, which scans incoming email for malicious content, appears to be the cause. The file involved is mcou.dll.
To confirm the cause, open 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. Both must appear together.
"If you are experiencing this crash, please contact Kaspersky support," the Outlook Team wrote. Microsoft is pointing users to Kaspersky, not itself, which signals where it believes the fix belongs. We covered a Kaspersky-linked story on 2 July 2026, when the company tied the China-nexus ToddyCat crew to a new Gmail-siphoning tool, a reminder that the vendor's name keeps appearing in enterprise security headlines this summer.
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 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.
None of this is a security incident. No data was exposed and no attacker was involved. It's a reliability story, not a breach story. The real thing to watch is how long enterprises are willing to stay on Classic Outlook as these paper cuts accumulate: at some point the disruption of staying put exceeds the disruption of switching, and Microsoft knows it.
