Very often, an inadvertent click results in unexpected results, and so it is with Outlook and the grey “Sort By:” selector bar at the top of the list of messages. Before you know it, you cannot find the messages you received today, because the order has changed to be listed by sender or other unwanted sorting order.
This situation can cause endless frustration by users of Microsoft Office 365 who may be new to Outlook or may have been using much older versions before.
Fortunately, there is an easy solution and your Outlook sorting will be back to normal before you know it. You need to right-click the gray Arrange By bar and click on Date in the resulting menu as illustrated below:
Once you have clicked on “Date” and changed the sort order, your messages will be back to the normal sort order and the latest ones will again be on top.