How do I get back the missing email content view area on macOS in Mail?

Question

macOS

Presumably, something was pressed on the keyboard or with the mouse and the area for viewing the contents of letters in the Mail program disappeared. By default, this area is displayed to the right of the mail list. The option to shift the border of the area and the list of letters to the right did not work: on another iMac, you can move it all the way and move it apart, and on the problematic one there is not even anything to catch on with the mouse.
Switching to classic view (when the message view area is at the bottom) doesn't help either.
How to get back the missing email content view area?
Or maybe there is some way to reset the state of the window?

Answer 1

After a long search, I found a solution.
It turned out that in the same versions of macOS, the design of the Mail program is slightly different for some reason, namely, in the problematic when the border of the message viewing area is shifted all the way to the right, there is no strip to stretch back (the mouse does not cling, instead it resizes the window), although on the second iMac in the same Mail, this strip is there!
As a result, I had to switch to the classic view mode, then extend the border of the viewport from below (and you need to pull it high, otherwise it doesn’t react - this is also my mistake, because I tried to pull it out before, but apparently I didn’t reach the desired height ). When the area appears, switch to normal view.

Answer 2

He accidentally closed the preview window ...
He climbed all the settings. Didn't find anything. It turned out that it was necessary to take the right edge when the cursor changes, and stretch to the left about 1/3 of the entire width of the Mail application and the area appears. If you stretch less than 1/3, then simply nothing happens.