Microsoft has fixed a long-standing issue in classic Outlook that prevented Microsoft 365 users from opening encrypted emails following a December update. The problem specifically affected messages sent using the “Encrypt Only” option—an encryption setting that protects email content without restricting forwarding, copying, or printing.
The bug surfaced after users updated to Current Channel Version 2511 (Build 19426.20218), where encrypted emails failed to render correctly. Instead of readable content, recipients encountered a message_v2.rpmsg attachment, effectively blocking access to the email body. In the Reading Pane, users were shown a prompt stating that the message with restricted permission could not be viewed until credentials were verified, even after opening the item.
Microsoft acknowledged the issue earlier this month and, in a recent update to its support documentation, confirmed that a fix is now available in the Beta Channel. The company said the resolution will roll out to customers on the Current Channel and Current Channel Preview (Build 19725.20000) in February.
According to Microsoft, the issue was limited to emails encrypted with the “Encrypt Only” policy and did not impact messages using other protection settings. However, for organisations that rely heavily on encrypted communications, the bug caused significant disruption, particularly for users who depend on the Reading Pane to review emails quickly.
Until the fix reaches all affected users, Microsoft has outlined two temporary workarounds. The first involves a change at the sender’s end: instead of selecting encryption from the File menu, senders are advised to use the Encrypt option available under the Options ribbon when composing emails. This method, Microsoft said, avoids triggering the rendering issue in affected Outlook builds.
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The second workaround is more technical and applies to users who cannot immediately upgrade to a fixed version. In such cases, Microsoft recommends reverting to an earlier, unaffected Office build. This requires closing all Office applications and running a specific command from an elevated command prompt to downgrade Outlook to a prior version. While effective, the approach may not be practical for all enterprise environments due to update policies and administrative controls.
The latest fix is part of a broader effort by Microsoft to address a series of issues that have affected classic Outlook users over the past year. In 2025, the company resolved bugs that broke email drag-and-drop functionality after certain Windows updates and addressed problems that caused CPU usage spikes while typing messages.
Microsoft has also patched issues that led to Outlook crashes when opening emails or starting new messages and previously shared temporary solutions for errors encountered while opening encrypted emails. More recently, the company released fixes for a critical bug that prevented some Microsoft 365 users from launching classic Outlook on Windows and issued out-of-band Windows updates to resolve Outlook freezes affecting specific configurations.
The recurring nature of these fixes highlights the ongoing challenges Microsoft faces in maintaining stability across multiple Outlook versions while rolling out frequent updates. Although the company has been encouraging users to transition to the new Outlook experience, a large number of enterprises continue to rely on classic Outlook due to compatibility requirements and established workflows.
With the latest patch, Microsoft aims to restore confidence among users who depend on encrypted email for secure communication. The company has advised customers to ensure their Outlook installations are updated to the latest available builds as the February rollout progresses, and to apply the recommended workarounds only if immediate access to encrypted emails is critical.
For organisations handling sensitive information, the fix is expected to remove a key obstacle to encrypted email usage and reduce the risk of operational delays caused by inaccessible messages.
About the author – Ayesha Aayat is a law student and contributor covering cybercrime, online frauds, and digital safety concerns. Her writing aims to raise awareness about evolving cyber threats and legal responses.
