Prevent Thunderbird from automatic mark "read" while scrolling

On my Lenovo yoga 300-11IBY with a Elan smartpad Touchpad I have the problem, that when I scroll through the email list in my Inbox, the active line follows the visual part of the inbox.

If I scroll down with two fingers on my Touchpad, it seems like inteally thunderbird gets the down-arrow to go down through the list of emails instead of just scrolling through the list.

This is really aoying, cause wherever I stop scrolling, that particular email, where I stop gets marked read!

How do I get back the behaviour like on other mashines, that just the visible area scrolls up and the marked email stays marked (outside of the visible area)?

Note: As a bad workaround, I already set the time up to 5 seconds, after which an email gets marked read and disabled "inertial scrolling" (which was scrolling much too fast and uncontrollable, where it stops)*