Hi there, I´m Ivania. I´m an Independent Advisor and a Microsoft user like you. I´ll be glad to help you today.
Outlook marks a message as read when you select it. To change this behavior:
1.Select File> Options> Advanced.
2.In Outlook panes, select Reading pane 3. Uncheck the boxes to Mark items as read when viewed in the Reading Pane and Mark item as read when the selection changes.
4.Click OK twice to return to Outlook.
Note: Alternatively, you can also specify options as follows: (1) check Mark items as read when viewed in the Reading Pane, (2) enter the average time you spend reading an email, and (3) uncheck Mark the item as read when the selection changes the option.
https://support.microsoft.com/office/59b44298-0...
my best regards