Microsoft Outlook Security Glitch: New Update Blocks Access to Encrypted Emails

A recent Microsoft Outlook update (Build 19426.20218) is preventing users from opening "Encrypt Only" messages. Learn how to fix the message_v2.rpmsg error and restore access.

Microsoft has officially launched an investigation into a frustrating new bug within the classic Outlook desktop client that is locking users out of their secure communications. Following a recent software rollout, many professionals find themselves unable to read encrypted messages, receiving cryptic error warnings instead of their expected data.

The "Encrypt Only" Roadblock

The glitch specifically targets users who have updated to Current Channel Version 2511 (Build 19426.20218). The primary issue occurs with emails sent using the “Encrypt Only” setting. While this security feature is designed to protect sensitive data while still allowing recipients to copy or print the content, the bug has turned these messages into unreadable files. Instead of the email body, impacted users see a warning in the Reading Pane demanding credential verification. If they try to open the email in a new window, the content vanishes, replaced by a mysterious attachment named message_v2.rpmsg.

How to Restore Access: Temporary Workarounds

While the Outlook engineering team works on a permanent patch, Microsoft has provided two primary ways to bypass the error: Change the Encryption Method: Senders are advised to avoid the File > Encrypt menu. Instead, use the Options tab at the top of the compose window and select either “Encrypt” or “Do Not Forward.” Messages sent this way appear to bypass the bug successfully. Roll Back the Update: For users who cannot wait for a fix, Microsoft suggests reverting Outlook to the previous stable version (Build 19426.20186). This requires closing all Office apps and running a rollback command through an elevated Command Prompt.

A Pattern of Outlook Reliability Issues

This encryption glitch is the latest in a string of technical hurdles for the classic Outlook platform. Over the past few months, Microsoft has had to scramble to fix:

Exchange Online Outages: Which blocked mailbox access entirely for thousands.

Application Crashes: Specifically on Windows systems running the 24H2 update.

Performance Spi

kes: Unusual CPU usage triggered simply by typing a message. Microsoft has not yet provided a specific "Estimated Time of Arrival" (ETA) for the permanent fix. For now, IT administrators and daily users are encouraged to stay on Build 19426.20186 or utilize the Options-tab encryption method to ensure business continuity.