Introduction

Users of Microsoft's classic Outlook application within Office 365 have recently encountered significant typing lag and elevated CPU usage during email composition. This issue, first reported in early November 2024, has led to widespread frustration among users. Microsoft has acknowledged the problem and is actively working on a solution.

Background

Outlook is a cornerstone of Microsoft's Office suite, serving as a primary email client for millions worldwide. Its performance and reliability are crucial for both individual and enterprise users. The emergence of typing lag and high CPU usage has disrupted workflows, prompting users to seek immediate remedies.

Technical Details

The issue manifests as a noticeable delay between keystrokes and their appearance on the screen, accompanied by CPU spikes ranging from 30% to 50%. These symptoms are observed in Outlook Version 2406 Build 17726.20126 and later, affecting users across the Current Channel, Monthly Enterprise Channel, and Insider channels. Microsoft's support document outlines the problem and provides interim solutions. (support.microsoft.com)

Implications and Impact

The performance degradation has several consequences:

  • Reduced Productivity: Typing delays hinder efficient email composition.
  • Increased Power Consumption: Elevated CPU usage leads to higher energy use and potential overheating.
  • System Instability: Prolonged CPU spikes can affect overall system performance.

These issues are particularly concerning for organizations relying on Outlook for daily operations.

Microsoft's Response

Microsoft has acknowledged the issue and is implementing a fix across various update channels:

  • Beta Channel: Version 2505 Build 18822.15000, expected early May 2025.
  • Current Channel Preview: Version 2505 Build 18827.20000, expected mid-May 2025.
  • Current Channel: Version 2505 Build 18827.20000, expected late May 2025.

Users are advised to update their Office applications as these versions become available. (bleepingcomputer.com)

Interim Workarounds

While awaiting the official fix, users can consider the following temporary solutions:

  1. Revert to Previous Version:
  • Identify the build number for Version 2405 from Microsoft's update history.
  • Open Command Prompt as Administrator.
  • Execute the command:

``INLINECODE0 `INLINECODE1 `INLINECODE2 ``

  • Open Outlook, navigate to File > Office Account > Update Options > Update Now.

Detailed instructions are available in Microsoft's support article. (support.microsoft.com)

Conclusion

The typing lag and high CPU usage in Outlook have significantly impacted user experience. Microsoft's prompt acknowledgment and forthcoming updates aim to resolve these issues. Users are encouraged to apply interim workarounds cautiously and stay informed about official updates to ensure optimal performance and security.