High CPU usage when typing a message in Outlook

I also updated to version 2503 build 18623.20266 (Monthly Enterprise Channel), and I have to report that the GPU (not CPU) bug also still exists. It was not in 2405.

Not always, but quite often Outlook causes the GPU to run permanently with high load. If you quit and restart Outlook, the GPU load is no more permanently, but still much higher than normal every time the mouse cursor moves over Outlook. The only thing that helps (for a while) is to restart the whole PC/Windows.

I still couldn't find a certain trigger for this further bug, but showing certain e-mails or the calendar, especially after longer idle times, seem to be a possible trigger.

Outlook is more and more not for productive work, but for beta testing, also in not-beta channels, and that always again over many months or even years until the bugs get acknowledged at all and fixed (Microsoft makes it nearly impossible for users to report bugs and to be taken serious)... It's a desaster with this piece of software.

Dear Gabriel,

today I experienced the Outlook GPU (not CPU) bug again, as every few days, with Monthly Enterpise Channel 2503 (18623.20266):

• Sometimes suddenly high GPU load of about 30-50% by DWM.exe stays permanently, as long as Outlook is running.
• If you quit and restart Outlook, the permanent GPU load has gone, but as soon as you work with Outlook and move the mouse cursor over things in Outlook, GPU load still much higher than normal. Even if you just mouse-over the close-button of task manager while Outlook is open, GPU load temporarily rises quite high.
• The only way to get rid of Outlook-caused GPU-load for a while is to restart Windows.

This massive GPU load does not make the fan run, as the CPU bug did, but it also slows down the system significantly.

As I told you, I couldn't yet find a 100% working trigger for reproducing this GPU bug in Outlook, but one thing is striking: If you move the mouse cursor over Outlook's e-mail folder list (normally left column in Outlook), GPU load is temporarily very much higher than when you move the mouse cursor over other things like calendar entries in Outlook or objects in other apps than Outlook.

Version 2405 did not yet have this GPU bug.

Gabriel, please can we have an update on this issue?

Outlook's GPU bug appears nearly every day now - especially after longer times of Outlook in idle (for example after lunch break).

It's a bit more difficult to see this bug, because the GPU does not directly make the fan run as the CPU did during the other bug, but the GPU overload just slows down the PC.

It appears only while Outlook is running - as soon as you quit Outlook, it's gone, but if you restart Outlook after it has appeared, it's there again until you restart Windows.

It's a pity that Gabriel seems to have stopped answering here, so that this bug most probably will stay for years again as some bugs before.

I wonder if there is some way to disable using the GPU. The Compatibility tab seems to be intentionally disabled for Outlook.exe but you can add the EXE path to

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers

and maybe try some flags like

DISABLEDWM DISABLETHEMES DISABLEDXMAXIMIZEDWINDOWEDMODE

and see if that has any effect?

Many of them are listed at https://community.revenera.com/s/article/how-to-set-compatibility-flags-for-your-application

Unfortunately I can't reproduce as the users I support are all running Outlook on Remote Desktop Session Hosts without GPUs.