re : I try to slide/seek another message on the list, And how are you achieving this? Do you left click and hold down cursor on the scroll bar and then drag the scrollbar? Do you use middle wheel on mouse to scroll ? Are you using a touchpad? When you press a key, use mouse clicks, touch the touchpad, signals are sent from that piece of hardware to computer and then computer acts upon those signals in the currently selected program or window. Thunderbird does not control the keyboard nor mouse nor touchpad etc. Sometimes, issues arise with faulty hardware or if hardware is set too sensitive. It is worth seeing if a change in the sensitivity levels can help offer better results. Check settings on computer for eg: mouse Switch off ClickLock if set to test whether it is effecting your scrolling. In Thunderbird there is a settings to do with scrolling, so you could test results if you select different option. Menu icon > Options > Options > Advanced > 'General' tab I am using a keyboard and mouse. I selected the 'Use smooth scrolling' option.