Introduction

Microsoft's Classic Outlook for Windows has long been a staple in the realm of email clients, renowned for its robust features and reliability. However, recent reports have surfaced indicating significant CPU usage spikes when composing emails, particularly affecting users on Windows 11. This article delves into the origins of this issue, its implications, and provides detailed solutions to mitigate the problem.

Background

In April 2025, Microsoft acknowledged a performance issue within Classic Outlook for Windows. Users reported CPU usage escalating by 30% to 50% during email composition, leading to increased power consumption and potential system slowdowns. This anomaly was observed following updates to Version 2406 Build 17726.20126 and later, impacting users across the Current Channel, Monthly Enterprise Channel, and Insider channels. (support.microsoft.com)

Technical Analysis

The CPU spikes occur specifically during the typing process in the email composition window. Affected users noted that disabling spell-check options and add-ins did not alleviate the issue, suggesting a deeper underlying problem within the application's processing mechanisms. The exact cause remains under investigation by Microsoft's Outlook Team. (bleepingcomputer.com)

Implications and Impact

For end-users, this issue translates to decreased system performance, faster battery depletion in portable devices, and a suboptimal user experience. Organizations relying on Outlook for critical communications may face productivity setbacks, emphasizing the need for a prompt resolution.

Recommended Workarounds

While awaiting an official fix, Microsoft has proposed the following interim solutions:

1. Switch to the Semi-Annual Channel

The Semi-Annual Channel has not exhibited this issue. To transition:

  1. Using the Office Deployment Tool:
  1. Using a Registry Command:
  • Open Command Prompt with administrative privileges.
  • Execute the following command:

``INLINECODE0 `INLINECODE1 File > Office Account > Update Options > Update NowINLINECODE2 `INLINECODE3 ``

Note: Reverting may expose the system to vulnerabilities addressed in subsequent updates. (bleepingcomputer.com)

Official Resolution Timeline

Microsoft has outlined a phased rollout for the permanent fix:

  • Beta Channel: Version 2505 Build 18822.15000 – Early May 2025
  • Current Channel Preview: Version 2505 Build 18827.20000 – Mid May 2025
  • Current Channel: Version 2505 Build 18827.20000 – Late May 2025

(bleepingcomputer.com)

Conclusion

The CPU spike issue in Classic Outlook for Windows 11 underscores the complexities inherent in software maintenance and the importance of timely updates. Users are advised to implement the recommended workarounds to maintain optimal performance and monitor official channels for the forthcoming fix.