High CPU usage when typing a message in Outlook

What Office channel is your Outlook? In Outlook click File, Office Account, under About Outlook.

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

Unfortunately, upon restart of Outlook, the CPU runs at 16% when typing, even though "Check spelling as you type", "Mark grammar errors as you type", "Frequently confused words" and "Check Grammar with spelling" are all unchecked. Tried different combos, but none worked.

Hi all,

There are some run time operations writing an email that will affect performance. I tested on one of my VMs and these two appear to contribute a lot to the CPU. I have not tested yet if this varies between builds/versions and if this has changed any over time. If you test turning these off, restart Outlook after making each change.

1. Text Predictions, Use text predictions in Outlook for Windows - Microsoft Support. (File, Options, Mail, "Show text predictions while typing".
2. Check spelling as you type, Check spelling and grammar in Office - Microsoft Support (File, Options, Mail, Editor Options, "Check spelling as you type".

Dear Matth22,

thank you very much for your posting and the very detailed information, great!

At least we now know that nothing else can be done by us users, but that it's a bug that has to be resolved by Microsoft.

On occasion, merely opening an email prompts the fans of my device to activate. Once I start typing, the fans surge to their maximum speed. This incessant noise is profoundly irritating. I am perplexed as to why Microsoft continues to overlook such issues. I'm also using a brand new Windows 11 PC with i7-14700F 20 core processor, typing an email with Outlook should not be putting a load on this processor.