Hi

it might of been the way you have it setup or the view. I use it on my windows 10 machine and have no problems with it.

A while ago I did a audio and also a written tutorial on mozilla thunderbird if you are interested. it can be fund at the following web address at http://www.accessibilitycentral.net
It is called accessible email client mozilla thunderbird. It at least covered the basics of using it.

Gene nz