You know those column width are adjustable. You click on the divider and drag the column to the width you like. But you can't use more than the total width of the pane, so you will probably find you needs to trim some columns to get what you desire, like the width of the subject column.

Thanks, Matt. The first column on the left just says either "read" or "new." The next column is date and then size and then subject. I wonder if somewhere on the toolbar there is a way to change a column to "sender?" I just got Thunderbird yesterday, so I am just learning it. I expanded the whole window and played with columns, but could not find any column for sender...??

Click the icon on the right end of the header bar and turn on or off any column you like.

Thanks...I did not know what that little icon was for. I unchecked several boxes and checked "from" and "recipient." Voila...sender now shows. Thanks.

Just an FYI. Correspondent is a more dynamic column, showing an incoming/outgoing arrow so you can merge sent mail with incoming mail in the same folder and still get a meaningful list entry.