Mail Side Preview column missing? Here's the fix

A longstanding peculiarity in Apple's Mail app is that if you should de-select its Side Preview column, it will not reappear even after re-selecting it.

• The Side Preview is the column that contains a list of email messages containing the message subject in bold text and a few lines of the message body (as many as five lines of text, depending on your Viewing Preferences). That column normally appears between the Mailbox list on the left and the body of the selected email message on the right.

If you don't see that column, first be sure to select Mail's View menu > Show Side Preview. A checkmark should appear adjacent to it, like so:

If that selection is as shown, yet you still don't see the Side Preview column, then proceed as follows.

Position (hover) your cursor over the right side of the Mail window, all the way to the right, whether or not you are using Mail in Full Screen, Split View, or in a traditional window. Provided Show Side Preview is selected in Mail's View menu, the Mac's usual "arrow" cursor will take on an appearance resembling the following:

<-|

When it does, drag that cursor to the left. Nothing will appear to happen at first. Keep dragging it. There will be no visual confirmation of that action until you drag it more than halfway to the opposite edge of the window. The Side Preview column will suddenly appear.

Here's a short movie illustrating what happens:

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