i am using thunderbird on Ubuntu 18.04. In my preview pane i get these annoying little icons for example, my wife got an email that had something to do with finger nail polish. well right over the email in the preview pane is an icon of a set of fingers with a finger nail brush. i get all kinds of other icons as well depending on what is in the subject line of the email. I have looked all over in the settings and can't find a way to turn this off. can anyone help?