Following a December update, Microsoft resolved a known problem that made it impossible for users of Microsoft 365 to access encrypted emails in traditional Outlook.
An issue in Outlook for Windows that prevented users from opening emails with “Encrypt Only” permissions has been fixed by Microsoft. After an update in December 2025, the problem appeared, causing receivers to view an attachment called message_v2.rpmsg rather than legible content.
Users who attempt to open encrypted communications with “Encrypt Only” permissions, a policy that does not limit email forwarding, printing, or copying, are impacted by this flaw.
“After updating to Current Channel Version 2511 (Build 19426.20218), recipients may not be able to open ‘Encrypt Only’ emails,” Microsoft stated three weeks ago when it acknowledged the problem.
On affected systems, users are seeing a message_v2.rpmsg attachment instead of readable content, rendering the encrypted message inaccessible.
“This message with restricted permission cannot be viewed in the reading pane until you verify your credentials” may appear in the reading pane. To read the contents and confirm your credentials, open the item.”
Microsoft stated in a Thursday update to the original support article that a patch is currently accessible for users in the Beta Channel and will be made available to users in the Current Channel (Build 19725.20000) and Current Channel Preview (Build 19725.20000) in February.
For users who are unable to switch to a repaired version of Outlook right away, Microsoft also offers two interim fixes. For one of them, senders must use the Encrypt option under the Options ribbon rather than the File dialogue, as explained in this support document.
As an alternative, users must close all Office applications and execute the following command from an elevated command prompt in order to switch back to a software build that is unaffected by this known problem.
Microsoft fixed a number of other problems that affected users of traditional Outlook last year, such as glitches that caused CPU spikes when typing messages and disrupted email drag-and-drop capabilities after downloading Windows 24H2 upgrades.
The Outlook team previously published a temporary patch for a known problem that caused Outlook issues while opening encrypted emails and corrected a bug that caused traditional Outlook crashes when opening emails or starting new messages.
More recently, it delivered urgent, out-of-band Windows upgrades to address classic Outlook freezes and fixed a significant bug that stopped Microsoft 365 users from opening classic Outlook on Windows.
Users of Current Channel and Current Channel Preview (Build 19725.20000) are expected to receive the permanent patch in February 2026.
Microsoft recommends the following techniques to restore access if you are unable to wait for the update:
- Alternative Senders’ Method: Senders can circumvent the flaw by applying encryption via the Options ribbon (by choosing Encrypt > Do Not Forward) rather than the File dialogue.
- Outlook on the Web: Because Outlook Web Access (OWA) and the mobile version of Outlook handle decryption via the cloud, affected emails can still be opened and read normally.
- Revert to Previous Build: Using the Office Deployment Tool or Command Prompt, technical users can go back to a version that was released before Build 19426.20218 (like Build 19426.20186).
In late January 2026, Microsoft also issued an urgent out-of-band update to fix several problems where Outlook would crash or stall when utilising cloud-linked files, such as OneDrive PSTs.
These guidelines address current Microsoft 365 outages and the Outlook problem that affects encrypted emails.