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Problem Overview: Outlook Classic CPU Spikes While Typing
A significant and frustrating bug has emerged in Microsoft Outlook Classic (Office 365, Version 2406, Build 17726.20126 and later), causing CPU usage to spike dramatically—often between 30% and 50%—when users type emails. This issue leads to sluggish performance, increased power consumption, and, in some cases, dangerously high CPU temperatures, even on high-end systems. The bug affects users on the Current Channel, Monthly Enterprise Channel, and Insider Channels, and has been observed on both Windows 10 and Windows 11.
Symptoms:
- Noticeable lag and slow response in Outlook Classic when typing emails
- CPU usage jumps to 30–50% (visible in Task Manager)
- Increased power consumption and potential system overheating (reports of CPUs reaching 95°C)
- Ineffective fixes: Disabling add-ins, graphics acceleration, or spell-check does not resolve the problem
Solution: Temporary Workaround Until Permanent Fix
Microsoft has acknowledged the problem and is actively investigating, but no permanent fix is available yet. However, a reliable workaround exists: switching Outlook to the Semi-Annual Channel, where the bug has not been observed.
Method 1: Registry Command (For Individual Users) yo Switch to Semi-Annual Channel
- Press Windows Key, type cmd, right-click on Command Prompt, and select Run as administrator.
- Enter the Registry Command: reg add HKLM\Software\Policies\Microsoft\office\16.0\common\officeupdate /v updatebranch /t REG_SZ /d SemiAnnual
- Open Outlook.
- Go to File > Office Account > Update Options > Update Now.
Method 2: Office Deployment Tool (For Organizations)
Use the Office Deployment Tool or Microsoft Configuration Manager to change the update channel for multiple devices. Follow Microsoft’s official guide for enterprise deployments.
Additional Notes & Recommendations
- This bug is only present in Office 365 builds on the Current, Monthly, and Insider Channels. Perpetual license versions (Office 2019, 2021, 2024) are not affected.
- Temporary Alternatives: If switching channels is not possible, consider composing emails in another application (like Notepad or Thunderbird) and pasting them into Outlook as a short-term measure.
- Monitor for Updates: Microsoft is expected to release a permanent fix. Keep your Office installation updated and monitor the official support article for news.
- Backup Important Work: Due to the risk of system instability, regularly save your work and consider frequent backups to avoid data loss.
While this bug is undeniably disruptive, the workaround is effective and straightforward. By switching to the Semi-Annual Channel, you can restore Outlook’s performance and avoid unnecessary CPU strain until Microsoft delivers a permanent solution.
You’re not alone in this struggle—thousands are affected, and Microsoft is working on a fix. Apply the workaround above, and you’ll be back to productive, frustration-free emailing in no time!