
Thunderbird either marks ALL unread messages whether or not I preview them (when automatically mark is set) or doesn't mark them at all even when opened.
This is a brand-new (5/19/2019) install of Thunderbird with no add-ons.
When I set the option in Display to "automatically mark messages as read, immediately on display," it marks all of my new messages at once, even if I have not previewed them.
When I uncheck this option, it will not mark any messages as read even if I open them in a separate tab or window. I can only mark messages as read if I click the mark button or select mark from a menu.
The functionality I am looking for is for messages to be marked individually when they are read in the preview window below the message list. Previous versions of Thunderbird appeared to do this by default.