Outlook Email View.
In Outlook, I prefer to have my emails grouped by receive date, as shown at right.
One day, I somehow changed it so that each individual day was displayed, and clicking on that day would expand that day's emails. This was very irritating.
Several days later, I finally figured out how to get Outlook back to my preferred view: with emails visible and displayed under headlines such as Today, Yesterday, Last Week, Two Weeks ago, ect. Under the View menu, choose Arrange By, and check both Date and Show in Groups.