Microsoft fixing strange Outlook bug where documents open blank or "corrupt" themselves

Microsoft is fixing a strange Outlook bug causing blank Office files; update rolls out tomorrow but workarounds are available.

Earlier this week, Microsoft released its latest Patch Tuesday update and while there are no known issues, the company explained that certain applications like backup apps won't work properly due to a specific recent addition.

However, things haven't been as great on the Microsoft 365 front as the company confirmed it's working on an issue wherein Office documents could go blank. The problem has been affecting users of Classic Outlook when accessing shared files hosted on SharePoint or OneDrive. In some cases, clicking a document link in an email forced the file to open in a desktop application, even when user preferences were set to open files in a web browser. Additionally, some documents appeared blank or triggered error messages indicating that the file was corrupted and required repair.

Microsoft stated that the issue is being addressed through a service-side update such that users don't need to install client-side patches. The fix is scheduled to roll out beginning tomorrow (May 4, 2026) and following the installation, users may need to restart their Outlook client for the update to take effect. Aside from that, no further action should be required once the update is fully deployed.

While the fix is being deployed, Microsoft has outlined several temporary workarounds for affected users. These include adjusting Outlook settings to open files directly in desktop applications, manually opening links in a browser via right-click options, or copying and pasting links into a browser address bar. Other suggested measures include accessing files directly through SharePoint or using Outlook on the web. The company also noted that advanced users could modify system registry settings to alter how links open, though such steps are typically recommended for experienced users or IT admins.

Microsoft writes: "To work around the issue, use one of these options that best suits your requirements:

• Change classic Outlook to open links in the Desktop apps. Go to File > Options > Advanced > File and browser preferences > "Open Word, Excel, and PowerPoint files using: Desktop".
• If you need the file to open in a browser, right-click the link in the body of the Outlook message, select Open with, then choose your browser.
• To force the links to open in the browser you can set this registry key:

  • HKEY_CURRENT_USER\Software\Microsoft\office\16.0\Common\Internet

  • DWORD: OpenDirectlyInApp

  • Value: 0

• Copy the link from the email message and paste it into the browser address bar.
• Open files directly from SharePoint instead of from the Outlook email.
• Open links in Outlook Web App (OWA).

You can check out the official support article here on Microsoft's website. Meanwhile, a similar issue also affects Word wherein EUDC characters are displayed as blank squares.

For anyone wondering, EUDC or End-user-defined characters are custom characters based on the Unicode Private Use Area, enabling users, manufacturers, or organizations to represent symbols that are absent from standard fonts. Thus they support names or terms otherwise unrenderable in default character sets. The company wrote: "Users may see EUDC characters displayed as a blank square ("□") in Word after updating to version 2603 (build 19822.20180 or newer)." Microsoft is investigating the bug and is working on a fix.

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Posted Sunday 3 May 2026 at 4:43 pm AEST (my time).

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