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.

That worked for me thank you.

How am I supposed to see the tiny zoom slider when its too small to see with my eyesight... Hello!!! this doesn't solve any problems. SMH

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?

I found a workaround double-click on a message that will be opened as a "full" window to read the message click on Zoom change the percent to your desired value and click on Remember my preference.
this should change and remember the zoom level for the reading pane

I tried this but no dialogue window popped up for me. So still waiting for answers to how to permanently increase the font size.