Can I permanently increase the font size in the reader pane of Outlook?

There IS a permanent way to increase the size in your reading pane.

In the lower left corner of Outlook, manually increase the size using the slider. Once you're at your desired zoom, click on the number (e.g., 120% or whatever you've selected) at the far bottom right. A dialogue window will appear. Click "Remember my preference" and then click OK.

Tried that. That would be nice if the slider isn't grayed out - useless. I'll contact my IT dept about it. Had this problem with excel before and then it magically started working one day (no longer grayed out). Outlook bug?

Looks like that works. TY. :)

An update on January 23, 2024. I was not using view/reading pane in Outlook. I wanted to zoom in permanently after completely opening up an email into a new window pane. Apparently you can zoom in on that message and similar to what CVD_865 suggested, you can also select remember my preferences there so every time a new email is open to a new window, it will retain the zoom strength you specified. This is a great help. But there is no way to zoom the list of emails in a folder if you are not using the reading pane options. Anyway, think I found a way to zoom enough to help tired eyes at the end of the day.

One last update. Windows 11 solved my font size issue! Happy to report I can use magnifier (in Windows setting) to magnify any page - including the Outlook inbox. Still find it funny though the zoom in bottom right still doesn't increase font when looking at the inbox screen, but now I can use magnifier and it has increased the font size. Much better now!