Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi,
I have had the exact same problem and tried the above.
I was able to fix the issue by setting the scaling (settings/display/scale and layout) to 200%, logging off, then logging on. I then set the scale to the required level and log off and on and the issue was resolved. I found it on the link below.
"OS Scaling settings can sometimes get "stuck". Outlook, because of the many different UI elements and how they interact with scaling and other aspects of the display, seems, in my experience, to experience more issues with scaling than other applications.
The simplest fix is to change the system scaling setting to any other value, log off and back on, and then set them back to the desired value and, again, log off and back on.
If this doesn't resolve the problem, removing the graphics driver by deleting the Display Adapter from the Device Manager, and then restarting the computer and either allowing Windows to find and install the current driver, or finding the most recent driver, and downloading and installing it, should resolve the issue."
https://superuser.com/questions/1429306/office-365-outlook-has-huge-fonts-how-to-make-smaller