Resolving CPU Spike Issues in Classic Outlook on Windows

If your computer seems to strain every time you send an email in Classic Outlook, you’re not alone. This annoying Outlook CPU spike bug can cause your system to utilize between 30% to 50% of your CPU, resulting in sluggish performance and overheating. While Microsoft is diligently working on a long-term solution, let’s delve into the nature of this bug, explore temporary fixes, and discuss when you might expect the permanent resolution to roll out.

What is the Classic Outlook CPU Spike Bug?

Picture yourself composing an email only to hear your PC’s fan blaring as if it’s racing an engine — this is a clear sign of the Outlook CPU spike bug. This persistent glitch has been eventuating since November 2024, specifically affecting Classic Outlook version 2406 Build 16726.20126 and newer releases.

During episodes of this issue, users see inexplicably high CPU spikes, often reaching the 30-50% mark in Task Manager. Beyond just annoying performance lags, this bug may lead to system freezes and increased heat, particularly affecting older devices and impacting both Windows 10 and 11 users across all platforms. If you’re experiencing substantial performance issues due to this bug, worry not, as there are solutions available to manage your CPU usage more effectively. You may also find tips useful for other systems like Mac or Linux.

How to Fix the CPU Spike Issue Temporarily

While a permanent fix is on the way, one immediate way to alleviate this issue is by switching to the New Outlook. However, the most reliable workaround involves reverting to an earlier build (2405), effectively eliminating the spike problem.

To revert to Build 2405, you can locate the specific build for your channel here.

Follow these steps to execute the rollback:

Open the Start menu and search for Cmd.
Right-click on Command Prompt, then select Run as Administrator.
Copy and paste the command below into the prompt, replacing any version numbers as necessary, and hit Enter:

"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.17628.20144

After running the command, please be patient as Outlook rolls back to Build 2405. Once completed, restart the application for testing. Alternatively, you can employ the Office Deployment Tool, following Microsoft’s guide on switching between versions.

If you continue to struggle with CPU-heavy applications, you can look into additional methods to manage CPU usage in Windows here.

When will Microsoft Release the Permanent Fix?

Microsoft has targeted May 2025 for the rollout of a comprehensive fix for the Outlook CPU spike issue. Here’s the schedule for updates:

Beta Channel: Early May (Version 2505 Build 18822.15000)
Current Channel Preview: Mid-May (Version 2505 Build 18827.20000)
Current Channel /Everyone: Late May (Version 2505 Build 18827.20000)

To ensure timely access to the update, navigate to File -> Office Account -> Update Options -> Update Now within Outlook.

The initial deployment will be made available to Microsoft Insiders and select testers to evaluate the effectiveness of the fix. Be ready to act when the final rollout occurs to overcome this CPU spike issue.

It’s understandable that the Outlook CPU spike can disrupt your workflow significantly. However, with the provided workaround, you can mitigate its effects while awaiting Microsoft’s permanent solution. Consider trying the New Outlook or experimenting with alternative email clients. If you have a method that has worked for you, please share your insights in the comments!

Frequently Asked Questions

1. What are the symptoms of the Outlook CPU spike bug?

Users typically notice high CPU usage (30-50%) and may experience sluggish performance, system freezes, or excessive overheating of the PC’s fan.

2. How can I revert my Outlook version to fix the CPU spike issue?

You can revert to an earlier version by using Command Prompt or via the Office Deployment Tool to download the desired build, specifically aiming for version 2405.