A user applies a sensitivity label to a .txt file using the Microsoft Purview Information Protection client on Windows. The label is configured with encryption. After applying the label, the user reports the .txt file now has a .ptxt extension and will only open in a viewer application, not in Notepad. What is the correct explanation?
Correct answer: B. This is expected behavior. The client applies native encryption to text files, which changes the extension (.txt to .ptxt) and requires the Information Protection viewer to open them.
When the Information Protection client encrypts standalone file types like .txt with native encryption, the file extension changes: .txt becomes .ptxt, .png becomes .ppng, and so on. These files must be opened in the Information Protection viewer rather than their native applications. This is documented behavior and is operationally relevant: firewalls, proxies, and DLP tools that key on file extensions can break when they encounter these renamed files.
Why the other options are wrong:
- A. This is a bug: the Information Protection client should preserve file extensions when applying encryption. The extension change is intentional and documented, not a bug. Office formats (like .docx) retain their extensions after native encryption, but standalone file types like .txt, .png, and others change extensions.
- C. The .ptxt extension indicates the file received generic (pfile) encryption rather than native encryption. Generic encryption produces a .pfile extension on files it cannot natively encrypt. The .ptxt extension is specific to native encryption of .txt files, which retains the capability to enforce usage rights.
- D. The file extension change occurs only when the label uses Double Key Encryption. Double Key Encryption does not change file extensions. Extension changes occur with native encryption on non-Office standalone file types regardless of the key management approach.
Memory hook: .txt becomes .ptxt, .png becomes .ppng. Native encryption on standalone types changes the extension. Proxies and DLP that key on extensions will choke. Check before deploying.
Microsoft Learn: Information protection client