You need to use the custom view dialog to customize your view and also to reset views back to their default and there are several ways to access this dialog in Microsoft Outlook.

To access the customize view menu from the message list:

1. Click or right click on the row of field names above the message list. This is the row where it's says "Arrange By:" or lists the different field names, as seen in these two screen shots.



2. Choose Custom (or Customize, if you use a single line view) to open the Customize view dialog. (In Outlook 2010, its called View Settings)

This method works with all Outlook folder types (if you can position the cursor over the "invisible" row of fields names at the top of the Calendar and Card windows), however, it's generally easier to use the View menu in the views that lack a row of field names, like the Calendar and Address Card views.

To access it from any folder:

Including those without a row of field names across the top

1. View menu
2. Arrange by
3. Custom...

In Outlook 2010 or 2013:

Select the View ribbon and click on the Reset View button to reset the view or click on View settings to open the dialog to customize the current view.