High CPU usage when typing a message in Outlook

Gabriel's work-around really seems to work and stops the high CPU usage while typing a message in Outlook!

I tried rollbacks to version 2405, build 16.0.17628.20110 (first build of 2405) as well as build 16.0.17628.20164 (latest build of 2405), and with both, the high CPU usage did not appear again up to now. To be verified over the coming days, but this looks very promising!

For the rollback, I would recommend build 16.0.17628.20164 (latest build of 2405), because in comparison to 20110 (first build of 2405) which Gabriel mentioned, 20164 includes some later security fixes and, most of all, it already includes some major user-interface updates (for example the new rounded menu ribbon) which 20110 is missing. So version 2405, build 16.0.17628.20164 has already the same look as the current version 2502, whereas version 2405, build 16.0.17628.20110 still has the older look.

Hopefully, the CPU usage really does not appear again after the rollback. And hopefully, Microsoft will fix this bug very soon so that everybody can receive current updates again.

By the way, there had been a very similar bug already some time ago, from version 2105 to 2301 (it took MS over 1,5 years to finally fix it...). At that time, the high CPU usage appeared when opening attachments in Outlook: https://answers.microsoft.com/en-us/outlook_com/forum/all/outlook-causes-high-cpu-usage-for-2-3-minutes-each/fa903250-4bd2-4517-942c-fe77b4c6f3c3

By the way, for those who speak German, there's another thread for this issue on a German discussion board: https://thinkpad-forum.de/threads/outlook-365-seit-2-3-wochen-pl%C3%B6tzlich-sehr-oft-hohe-cpu-last.230167/page-5#post-2408544

Dear Gabriel,

I did some testing today and although subjective I believe I see the CPU spike more starting with build 17726.20126.

To see if you can confirm this, revert to the build below and test. The build in the steps below is for Current Channel. If you are on a different channel let me know what it is, and I will find the appropriate build. Builds available to revert are on this page, Update history for Microsoft 365 Apps (listed by date) - Office release notes | Microsoft Learn. The revert steps should take about five or so minutes and you will need to close the Office apps.

Steps to revert Office to Current Channel build 17628.20110:

1. Open a Command Prompt in Administrator context.
2. Type or paste the two commands into the Command Prompt window and press Enter after each:

cd %programfiles%\Common Files\Microsoft Shared\ClickToRun

officec2rclient.exe /update user updatetoversion=16.0.17628.20110

Alternate command to those above:

"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.17628.20110

On my system, switching off text predictions and checking spelling and grammar, which I had already tried during the months before, did not solve the problem, but only changed the CPU usage slightly.

I had also some months ago already tried rollbacks of MS 365 incl. Outlook to versions 2410, 2409, 2408 and 2406, with no change concerning this issue.

You now mention build 17726.20126 (version 2406) as starting point of the issue, but build 17628.20110 (version 2405) should be OK. By the way, here's the version history again: https://learn.microsoft.com/de-de/officeupdates/update-history-microsoft365-apps-by-date?redirectSourcePath=%252fen-us%252farticle%252fae942449-1fca-4484-898b-a933ea23def7

And here's the offical rollback how-to: https://support.microsoft.com/en-us/topic/how-to-revert-to-an-earlier-version-of-office-2bd5c457-a917-d57e-35a1-f709e3dda841

So I will try the rollback to 2405 soon and let you know. If it should work, that would be at least a work-around - but the bug must nevertheless be fixed by Microsoft, because we shouldn't stay at an old version too long.

Hi Gabriel, I have the same CPU usage issue running v16.0.18324.20240. I've tried turning off "Check spelling as you type", "Mark grammar errors as you type", and "Check Grammar with spelling" but it hasn't worked. Any other suggestions please?

I followed your instructions to revert to an older version. I'm now on:
Version 2405 (Build 17628.20110 Click-to-Run)

I restarted "Show text predictions while typing" and "Check Spelling while you type"

I restarted Outlook and typed an email and so far it's acting normally, no increased CPU usage for Outlook while typing. Previously, I was seeing CPU usage up to 7% or 8% and loud fans. In this reverted configuration the CPU usage for outlook never went above 1.5% and the fans did not start.

Your help with this is much appreciated, those of us with a hatred of loud fans were suffering!

Let me know what's next, I would hate for this to revert to a new version with an upgrade and restart the issue!

Rich

Thank you for sharing the update. Since you are on Current Channel, if you get a chance please try reverting and test with the prior build if you still see the issue. If you do test that build, please re-enable check spelling and text predictions if you disabled it and restart Outlook after making those settings.