High CPU usage when typing a message in Outlook

I only use an external monitor (2.560x1.440), and my integrated display (which I don't use in dock) has the same resolution.

According to DXDiag, I have DirectX 12, the main driver is dated 20210820, and no problems had been detected.

I'm quite sure that it's not a question of versions, options etc., because 2405 has not this bug, but later versions have.

So far, I cannot cause the GPU to spike. I tested switching mail to calendar and otherwise. Does this happen on the primary monitor or is it secondary or does it matter?

In the past when we looked into graphics issues engineers would get a DXDiag report, Which version of DirectX is on your PC? - Microsoft Support. This will show you the driver date which could help indicate if the driver is old and needs to be updated.

Another thing to test if it would help is the option File, Options, General, User interface options, Office support for high definition displays - Microsoft Support. Test with best appearance and optimize for compatibility.

Dear Gabriel,

the GPU (not CPU) bug happens too often now: I cannot restart Outlook 5-10 times times every day to stop the GPU from running perpetually, so that I preferred to do the rollback to 2405 again instead of SemiAnnual Channel. My productivity went down too much checking and taking care all the time of this bug.

2405 reacts really very much quicker than the later versions incl. SemiAnnual Channel 2408 which have been slowed down extremely: When you switch from mailbox to calendar or from inbox to sent mails, for example, it takes nearly a few seconds for each click (and sometimes the GPU starts running with high load without any end [Task DWM.exe in Task Manager], until you quit Outlook - or put other windows over Outlook, but as soon as Outlook is on top again, the CPU load continues), whereas 2405 reacts on the spot without delay.

This seems to be a separate bug, because even SemiAnnual Channel, which has not the CPU bug, is concerned by the GPU bug.

Dear Gabriel,

thank you very much, so I will re-enable updates for SemiAnnual Channel.

I can see the GPU spike when I switch from mailbox to calendar in classic Outlook - then suddenly GPU load rises to and stays between 30-60%, and it does not drop afterwards, but stays high until I quit and restart Outlook. But this happens not every time, only quite often. My graphics driver is up to date.

I did some more follow up for Semi Annual Channel. It turns out after all that the change that causes the CPU spike is not at that channel. My tests are not exactly perfect because my VMs are very resource constricted. Comparing SAC to Current Channel I see a huge noticeable difference. Regular typing does not spike SAC for me like it does on CC or MEC. If you are on SAC you can stay there to avoid seeing this bug again.

I also tested my VMs for the GPU spike you mentioned and so far, I cannot cause that issue. If you are doing anything unique where you see that spike please let me know so I can test further. The main thing to check there is that you have the latest graphics drivers. I will keep monitoring though to see if there are other reports with GPU.

Since SAC does not have the bug I am updating the Known Issue again to suggest it as the best workaround for now, CPU spikes when typing in classic Outlook for Windows - Microsoft Support.