The Inbox folder is opening in the compact view by default. If the Inbox folder does not display in the compact view, you can click View > Change View > Compact to shift to this view.

The compact view contains the message list and reading pane, and it changes the layout of message list mainly.

In the message list, you will see every email display in three lines:
(1) The first line shows the sender of the email;
(2) The second line indicates the subject and received date of the email;
(3) And you can preview the message body of the email in the third line. The wider the message list is, the longer content you can preview.

Notes:
(1) If the Outlook interface is too narrow, it will hide the message list automatically and display the reading pane only.
(2) If you modify the compact view, says add columns, or change the arrangement style, you can quick restore the default compact view by clicking View > Rest View.

After opening the Inbox folder, you can display it in the single view by clicking View > Change View > Single.

The single view also contains the message list and reading pane too. In the single view, you will get more information about an email from the message list. And this view will be a good choice in a wide screen mode.

In the message list, every email displays in two lines.
(1) The first line shows all kinds of information of an email via columns, including importance status, reminders, attachments, sender, subject, received date, etc. No matter how many columns you have added, they will display in the message list.
(2) And the second line displays the message body of the email. The wider the message list, the more content you can preview.

Notes:
(1) The single view works well with a wide screen. If the Outlook interface is too narrow, it will hide the message list automatically and display the reading pane only.
(2) If you have changed the view settings in the single view, says change the sort order, filter, or arrangement styles, you can click View > Reset View to restore the default single view.

After opening the Inbox folder, you can change its view to preview by clicking View > Change View > Preview.

The preview view is similar as the single view, except turning off the reading pane. It displays the message list in a wide mode.
In the wide message list, every email contains two lines.
(1) The first line shows every field of an email in a column, such as from, subject, received, size, flag, etc. No matter how many columns you have added in this view, they will display in the message list.
(2) You can preview the message body of an email in the second line.

Notes:
(1) The preview view is fit for a wide screen. If you narrow the Outlook interface, the preview view will change the compact view without reading pane automatically.
(2) If you have changed the view settings in the preview view, says change the sort order, filter, or arrangement styles, you can click View > Reset View to restore the default preview view.