Microsoft Outlook: Update to default blocked file types in OwaMailboxPolicy

MC1488841 · published Oct 5, 2026 · 0 comments

Outlook on the web and new Outlook for Windows will block .msix and .msixbundle file types by default in OwaMailboxPolicy starting November 2026 to enhance security. Organizations using these file types should whitelist them beforehand; no action is needed if not used.