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Why can’t I open encrypted emails in Outlook Classic after the January 2026 update?
Microsoft confirmed a significant issue affecting Outlook Classic users on January 6, 2026. If you recently updated Microsoft Outlook 365 to Version 2511 (Build 19426.20218), you may lose the ability to open emails designated as “Encrypt Only.”
Instead of the email content, you will see a notification in the reading pane stating: “This message with restricted permissions can only be viewed in the reading pane after you have confirmed your credentials.” Upon opening the item, the actual body text remains inaccessible. You will only see a file attachment labeled message_v2.rpmsg.
The Cause: Specific Encryption Pathways
This error stems from how the email is encrypted during the sending process. The bug triggers specifically when a user applies encryption via the File > Encrypt menu in the email file dialog box. The current software build fails to decrypt messages sent through this specific pathway.
Immediate Workaround for Senders
You can bypass this bug by altering your sending workflow. Do not use the File menu. Instead, navigate to the Options tab in your message window. Select Encrypt, then choose either Encrypt or Do Not Forward. Messages sent using this method remain readable to recipients on the current version.
Technical Solution: Version Rollback
If your workflow relies on the affected features, Microsoft recommends downgrading your Office installation to a previous stable build. This requires administrative privileges.
Run the following command to revert your Click-To-Run installation to Version 16.0.19426.20186:
"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.19426.20186
This incident marks a recurring pattern of instability regarding Outlook’s encryption handling. In September 2025, a similar update caused the Outlook Classic client to crash entirely when interacting with encrypted mail. Further reports in November 2025 indicated intermittent access issues. Given this trend, IT administrators should exercise caution when deploying immediate updates to Outlook 365 until Microsoft stabilizes the encryption protocols. The Outlook team is currently investigating a permanent patch.