I'm using Outlook 2016 on my work computer. Last Friday I noticed an issue. Normally when you click on an email it becomes highlighted. Then it displays in the preview pane, for me on the right. since Friday, this happens but if i click inside the preview pane, the highlighted item in the email list disappears. Very strange. I have used Outlook for 15-20 years, and never noticed anything like this before. It creates confusion because if there are many emails or worst many replies and forwards, you don't know which email it is attached to.