Traditionally, Exchange has relied solely on the file extension (e.g., .docx, .pdf) to identify the type of an attachment. However, this approach can be bypassed if a file is renamed with a misleading extension. To address this, we’re enhancing our detection logic to go beyond just the visible file extension.
With this update, even if a file’s extension is altered, Exchange will evaluate the actual content of the file to determine its true type. This ensures that policies based on file type—such as “File extension is…”—remain effective and secure, even in cases of renamed or disguised attachments.
This improvement provides customers with a more robust and reliable way to enforce compliance and security rules around file sharing.
GA date: August CY2025
Preview date: July CY2025