Users frustrated by massive CPU spikes in the classic version of Outlook for Windows, with Microsoft acknowledging the issue and investigating it.

Reports began surfacing in late 2024 on Microsoft’s help site, with users reporting that Outlook’s CPU usage spikes when typing, and then drops down to roughly 1% when idle. The user who initially reported the issue saw spikes of 16-22%, but others saw spikes of 25%.

Microsoft has finally weighed in, confirming there is an issue. The company’s own testing found the spikes could be much higher, potentially being as high as 50%.

When you write an email in classic Outlook for Windows, you may notice the CPU spikes up to 30 to 50% at some times and increases the power consumption. You can observe this if Task Manager is open while you type.

This issue can occur after updating to Version 2406 Build 17726.20126+ on Current Channel, Monthly Enterprise Channel, or the Insider channels.

The company does not yet have a fix, but does offer a workaround.

The Outlook Team is investigating this issue. We will update this topic when there are any status updates.

To work around the issue, you can switch to Semi Annual Channel where the issue has not been observed.

Given that Microsoft has been working to migrate customers to its subscription and cloud-based software, it’s unclear how high a priority it will be fixing this issue. Only time will if/when it is resolved.