Thunderbird wide or other views don't display correctly

It seems to me that actually you open a message with a double-click in a '''new window'''. But I wonder how you could open messages by clicking in the "'''folder pane"'''. The only way I know to open a message - whether in the message pane, a new tab oder a new windows - is to click or double-click the message in the '''thread pane ''' ( = message list). Unfortunately I don't know how you displayed and read messages before this "issue". And what do you mean by "''I am offered to display in a browser''" ? I am not familiar with this option... To compare with I include a screen shot of my Thunderbird installation on a Mac, using classic view and table view EDIT: maybe I was entirely wrong with my interpretation of your screen shot, and your '''real''' issue is the display of the '''contents''' of messages. Actually you are using View > Message Body As > Plain Text Probably you were used to '''Original HTML'''