Microsoft shares fix for Windows' Classic Outlook CPU spike issue

If you have been fuming over CPU usage spikes when typing emails in the Classic Outlook, there’s some good news. Earlier this month, Microsoft confirmed that Classic Outlook users had been noticing a significant spike in CPU usage, as high as 50%, affecting system performance. Well, Microsoft is rolling out a fix for the Classic Outlook CPU usage spike issue to the affected channels.

The fix for CPU usage spikes when typing emails in Classic Outlook is finally rolling out

Previously, Microsoft suggested that users switch to the Semi-Annual Enterprise Channel as a temporary workaround. Now, there’s an update.

Microsoft says the Word team has deployed a fix for the Classic Outlook CPU spike issue. You can expect it to roll out soon to both the Current Channel and the Beta Channel of Office. The company notes:

STATUS: FIXED

The Word Team implemented a fix which will go to the following channels soon:

• Beta Channel (Version 2505 Build 18822.15000) – ETA early May 2025, to check for build, go to Update History for Office Beta Channel – Office release notes.
• Current Channel Preview (Version 2505 18827.20000) – ETA mid May 2025, to check for build, go to Update History for Office Current Channel (Preview) – Office release notes.
• Current Channel (Version 2505 18827.20000) – ETA late May 2025, to check for build, go to Update history for Microsoft 365 Apps (listed by date) – Office release notes.
• Monthly Enterprise Channel (Version 2503 18623.20256) – ETA May 13, 2025, reference Update history for Microsoft 365 Apps (listed by date) – Office release notes.
• Monthly Enterprise Channel (Version 2502 18526.20332) – ETA May 13, 2025, reference Update history for Microsoft 365 Apps (listed by date) – Office release notes.

Some bad news follows, too

While it’s good news for those in the Beta and Current Channel, sadly, the Classic Outlook CPU usage spike issue now shows up in the Semi-Annual Channel. That’s the same channel to which Microsoft advised users to make a switch.

The company is well aware of this issue and has advised Outlook users to roll back to version 2405 if they need an immediate fix for the CPU usage spike. That said, the company also cautions that downgrading should be done only when it’s necessary. The company notes:

We found that the issue now occurs in Semi Annual Channel. If you urgently need to work around the issue the only option would be to revert to Version 2405. This is not recommended since there have been security updates since that version. To make the change do the following:

1. Locate the build of Version 2405 for the respective channel you are on from Update history for Microsoft 365 Apps (listed by date) – Office release notes.
2. Open a Command Prompt (Run as Administrator).
3. Type or past the command below and put the build from Step 1 and then press Enter:
   
   “%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.17628.20144

Alternately you can use the Office Deployment Tool to switch to an earlier version of a channel. For more information, go to How to revert to an earlier version of Office.

Not to forget, Microsoft has also added details about the Monthly Enterprise Channel to the same support page. You can check the support article for the Classic Outlook CPU usage spike issue here.