Set-OrganizationConfig -BlockLevelOneFileExtensions ".exe", ".js" Or move an extension to Level 2 (warning only):
Cybersecurity & Messaging Team Document version: 2.0 Last reviewed: April 2026 End of Report outlook unblock attachment
Security should never be permanently sacrificed for convenience. Implement the minimum required unblocking for the shortest necessary duration. | Goal | Command / Action | |------|------------------| | List current Level 1 blocked extensions (Exchange Online) | Get-OrganizationConfig \| fl BlockLevelOneFileExtensions | | Remove .ps1 from Level 1 | Set-OrganizationConfig -BlockLevelOneFileExtensions @Remove=".ps1" | | Add .ps1 to Level 2 | Set-OrganizationConfig -BlockLevelTwoFileExtensions @Add=".ps1" | | Unblock single saved file (Windows) | Right-click → Properties → Check "Unblock" | | Disable all unsafe attachment blocking (local Outlook) | Registry EnableUnsafeAttachmentBlocking = 0 | | Skip Level 1 block for a sender (Transport rule) | Set header X-MS-Exchange-Organization-SkipLevel1AttachmentBlock = true | Set-OrganizationConfig -BlockLevelOneFileExtensions "