Email Sync Problems

Fix Blank Attack Simulation Phishing Emails in Classic Outlook

Adam Davis Sep 30, 2026 869 views

Question details

Users need to resolve an issue where Attack Simulation test emails fail to render their contents correctly in the desktop client.

Fix Blank Attack Simulation Phishing Emails in Classic Outlook

Product: Microsoft Outlook (Classic)
Device & OS: Windows
Scenario: Reviewing simulated phishing test emails deployed by an organization within the Classic Outlook desktop client.
Observed behavior: Attack Simulation test emails render completely blank except for a hyperlink in Classic Outlook, despite displaying perfectly in Outlook on the web, New Outlook, and mobile devices.

Before you start

Verify whether the issue occurs consistently or intermittently, and ensure you have administrative access to your Microsoft 365 tenant if you need to run advanced diagnostic traces or submit a support ticket.

Solution 1Recommended

Update Classic Outlook and Rule Out Local Conflicts

Since this is often a version-specific rendering bug (such as in build 16.0.17726.20078), applying the latest updates and disabling third-party add-ins can restore proper message display.

Microsoft frequently patches HTML rendering issues in Classic Outlook. Updating to the latest Microsoft 365 Apps release channel is the primary fix. If the update does not immediately resolve it, third-party security software or Outlook add-ins might be interfering with the message body rendering.

Update Outlook

Open Classic Outlook, navigate to 'File' > 'Office Account', click 'Update Options' under the Product Information section, and select 'Update Now' to fetch the latest build.

Test in Safe Mode

Press the Windows key + R, type 'outlook.exe /safe', and press Enter. This launches Outlook without add-ins. Open the phishing simulation email to see if it renders correctly.

Temporarily Disable Security Software

In accordance with your organization's IT policy, temporarily pause your third-party antivirus email shields to check if they are stripping the HTML content of the test email.

Check the Phishing Indicator: If the phishing indicator selection also appears blank in the affected client, this further confirms a local rendering bug specific to your current Outlook build rather than an issue with the email delivery itself.

Solution 2

Compare Affected Builds and Collect Diagnostic Logs

If updating doesn't work, gathering specific error logs using Microsoft's official diagnostic tools will help pinpoint the rendering failure.

Solution 3

Escalate to Microsoft 365 Support

When the issue is tied to a specific Microsoft 365 cloud environment update affecting multiple users, an administrator must escalate the issue directly to Microsoft.

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Frequently Asked Questions

Why do Attack Simulation emails only appear blank in Classic Outlook?

Classic Outlook uses an older HTML rendering engine (based on Microsoft Word) which sometimes fails to parse specific modern security overlays or HTML structures used in Microsoft 365 Attack Simulations. Modern clients like Outlook on the Web and New Outlook use web-based rendering engines that process these emails correctly.

How can users temporarily read these phishing simulation emails?

Because the rendering issue is specific to the desktop application, users can temporarily read the simulation emails by logging into Outlook on the web (OWA), using the Outlook mobile app, or switching the toggle at the top right of the desktop client to 'Try the new Outlook'.

What details should an IT admin include when opening a support ticket for this issue?

Administrators should include the exact Classic Outlook version and build numbers (e.g., MSO Version 2406, build 16.0.17726.20078 64-bit), the affected user accounts, exact timestamps when the test emails were received, complete message headers, and clear reproduction steps showing the discrepancy between Classic and Web Outlook.

Outlook & Email Problems