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Classic Outlook for Windows Copilot button disappearance and Kaspersky-linked crash issue

Service Disruption
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Last updated
Happening score
H score 0
1 unique sources, 1 articles

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Microsoft is still investigating a Classic Outlook for Windows disruption that makes Copilot and Copilot Chat entry points disappear for some Windows users, with the issue confirmed after upgrading to build 20026.20182 and higher. The bug can block access to Copilot from the ribbon, app bar, and add-ins path, and Microsoft has issued a temporary workaround while it works on a permanent fix. Microsoft also confirmed a separate Outlook crash issue on systems running Kaspersky Antivirus, which can trigger Event 1000 entries.

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Timeline

  1. 16.09.2026 15:16 2 articles · 1h ago

    Microsoft investigates missing Copilot buttons in Classic Outlook and Kaspersky-linked crashes

    Technical Analysis Update

    Microsoft is investigating a Classic Outlook for Windows bug that can make the Copilot and Copilot Chat buttons disappear for some Windows users after upgrading to build 20026.20182 or later, because Outlook cannot locate PR_PROFILE_USER_SMTP_EMAIL_ADDRESS_W in the null profile section. Microsoft also confirmed a separate Outlook crash issue on systems running Kaspersky Antivirus, linked to Event 1000 and Kaspersky Mail Checker (mcou.dll), and advised a temporary workaround using Show Apps in Outlook or alternate clients such as new Outlook, Outlook on the web, OWA, or the Microsoft 365 Copilot standalone app.

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