Use Classic Outlook? This Microsoft bug might stop you from opening encrypted emails
There is no fix available
· TechRadarNews By Sead Fadilpašić published 8 January 2026
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- Outlook patch (Build 19426.20218) broke “Encrypt Only” emails, showing unreadable attachments
- Workarounds: use Options ribbon encryption or revert to Build 19426.20186 via Command Prompt
- Microsoft also disabled inline SVGs in Outlook for Web and new Outlook for Windows
Microsoft released a new patch for classic Outlook, and broke how encrypted emails work. It is currently working on a fix, and in the meantime, it offered a few ways to open encrypted emails in the popular client app.
In a short update posted on January 6, Microsoft said that after updating to Current Channel Version 2511 (Build 19426.20218), email recipients may not be able to open “Encrypt Only” messages.
The error manifests in the Reading Pane, where users might get a message saying "This message with restricted permission cannot be viewed in the reading pane until you verify your credentials. Open the item to read its contents and verify your credentials."
Two workarounds
After opening the email, users will find an attachment message_v2.rpmsg and won’t be able to read the contents.
The problem happens for users who encrypt the email using the settings under the email File dialog (File > Encrypt), Microsoft further explained. To prevent the issue, there are two possible workarounds. For the first one, users should select the Options ribbon, then select Encrypt, and choose Encrypt or Do Not Forward.
The second workaround is to revert to a build before the issue started and then send the email. The issue started with build 19426.20218, and the next prior build that works is 19426.20186. To revert Office, users should open an elevated Command Prompt, and run this command:
"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.19426.20186
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