When Thunderbird shows a list of messages, it displays a set of columns that contain attributes of each message, such as the message subject, date, etc.
Add or remove columns
The screenshot above shows the default column layout. Click the column picker button on the far right of the label bar to see a list of the available columns. Alternatively, you can right-click on any column label to display the list.
Click on a checked item in the list to remove a column from the message list. Click on an unchecked item in the list to add a column to the message list.
Move or resize columns
To move a column, click and drag the column heading to the desired position. To resize a column, roll your cursor over the right side of the column heading. When the cursor changes from a single pointer to a double pointer, drag the column edge into the desired position.
Apply column layout to other folders
To apply the column layout to other folders, select Apply columns to from the column list. Select Folder to apply the changes to one specific folder. Select Folder and its children to apply the changes to a selected folder and all sub-folders beneath it. Under Folder and its children, you can select an email address (which will apply the folder configuration to all folders beneath that address) or a specific folder under an email address. Note that if you apply the changes from one folder to another, the column positions and sizes will also be applied.