Applications :: Tweaking Settings In Thunderbird Mail Client

I use Thunderbird as my preferred mail client. However, one thing I don't like is how when I am in the inbox, anytime I click on a message it always opens beneath. This is not that big of a deal, but what bugs me is that the message is then counted as a "read message." Therefore, like I'm sure many of you do as well, I constantly have to secondary click --- drag cursor down to "mark" --- then click "as read".

I have to do this in order to mark it as "unread" so I remember to reply to it later. If I single click (or tap) the cursor over and email in my inbox, it will either not open up beneath and not be marked as read, or still be opened up beneath (in the inbox) but not be marked as read? The second option would be preferred, but either would be better than the current default setting I have.