Microsoft users on Windows are facing a fresh Outlook issue after a recent software update broke access to encrypted emails. The company has acknowledged the bug and says a fix is under investigation.

A new over-the-air software patch from Microsoft — build 19426.20218 of the Outlook (Classic) Windows client — has unintentionally introduced a serious bug. After updating, some users are unable to open emails sent with the “encrypt only” setting, according to a report by TechRadar.

The issue affects Outlook (Classic) users on both Windows 10 and Windows 11.

What users are experiencing

After installing the update, attempting to open an encrypted email triggers an error message in Outlook’s Reading Pane. The message states that the email cannot be viewed until the user verifies their credentials.

When users try to open the email manually, Outlook instead generates a blank attachment file named “message_v2.rpmsg”, which cannot be read within the app.

Microsoft acknowledges issue

Microsoft has confirmed the problem on its official support website. In a status update, the company said the Outlook team is actively investigating the issue and will provide updates once more information is available.

For now, no permanent fix has been released.

Temporary workarounds available

Microsoft has shared a temporary workaround for affected users. The company advises navigating to the Options tab in Outlook’s main ribbon, selecting Encrypt, and then choosing Do Not Forward.

This method may allow users to access affected messages in some cases.

If the first workaround does not resolve the issue, Microsoft suggests reverting to a previous version of Outlook from before build 19426.20218. This process involves closing all Office applications and using an elevated Command Prompt to roll back the update.

The company has also outlined a third interim solution for users, though all options are described as temporary until a permanent patch is released.