Trying to fix listing of messages in Outlook email

Question

Hello!

In Outlook email, when I have up to 15 messages open, they are shown in icons across the bottom of the screen. More than that, they're listed vertically, as shown in the attachment.

I find it incredibly distracting to have it switch back and forth, and I'd like for Outlook to always list the items vertically--which is how it used to be, a few versions ago.

How can I get it to list message vertically all the time, no matter how many or how few I have open?

Thanks!