Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to open or preview PDF attachments in the new Outlook desktop experience – RESOLVED

11/08/2025 08:56:00 AM

NHSmail Reference: INC46600592

Microsoft Reference: EX1131606

Issue Status: RESOLVED

Issue Description: Users may be unable to open or preview PDF attachments in the new Outlook desktop experience.

More info: Impact can manifest when previewing and downloading the PDF file. Some users may see a “Something went wrong while the document preview was being created. Please try again later.” error message in Outlook, or a they can’t open this file. Something went wrong.” error message when the attachment is attempting to open through Microsoft Edge. Users can avoid this issue by accessing the PDF files through the classic Outlook desktop experience.

Final Update: 15/08/2025 08:21:00 AM – Microsoft’s deployment of the previously mentioned fix to bypass the offline caching of attachments is complete, and they have monitored their service health telemetry to confirm that the impact is remediated.

Scope of impact: This issue can potentially affect any New Outlook desktop experience user who is attempting to preview or download PDF files.

Root cause: Some portion of a recent service update, intended to implement a new PDF viewer, isn’t compatible with the offline caching of attachments.

Next Steps: Microsoft are reviewing their Exchange Online update procedures pertaining to the service components responsible for facilitating PDF viewer functionality to prevent similar impact in future updates.