That is exactly how it works. Once you highlight the entry in message list, the timer starts. Click on to another message before 5 seconds and it stays marked unread.

Thanks for the reply, but I was looking for an option to turn OFF the automatic mark as read but ONLY for the Message Pane (opened by F8). So that the message must be viewed in a new tab or window in order to automatically be marked as read, while still allowing the preview from the Message Pane window in the Inbox.

Sorry for the misunderstanding if my first post wasn't coherent enough.

The issue is that reading a message in preview pane is still reading it. In fact, many (most?) read their messages that way. If you tend to spend meaningful time when reading in a tab, I suggest you experiment by increasing the minimum number of seconds, maybe trying 30 for a start. That would let you peruse the message in preview, but it would stay unread until you spent a larger time amount.

It could be implemented as a feature with a simple check box in the settings, and Outlook as a mail client already offers this feature and has done for years.

Whether you open in Message Pane, tab or window. The email is opened. So the setting will operate no matter which option you prefer because it functions from the second you open it.

If you do not want any email to open in Message Pane and get marked as read at any point then you either do not use the Message Pane (disable it) or do not enable the automatic mark as read.

So if you do want to open messages in the 'Message Pane' - which is not a preview - it is an opened email, then disable the automatic mark as read and use an alternative option.

Then use any of these alternatives to mark as read:

1. Use the shortcut key - whilst email is selected and displaying in Message Pane or Tab, press 'R' on keyboard.
2. Right click on email in list and select 'Mark as ' > 'Read'
3. Customise the 'Mail Toolbar' to have the 'Mark' button option - saves you doing a right click.