If you’d like to see a count of how many emails are contained in each folder in Thunderbird, here’s how:
- Tools > Options > Advanced > General
- Check “Show expanded columns in the folder pane”
- Click OK to accept changes.
- At the top of the folder pane, click the column selection icon () and select the columns that you would like to see. You can choose to display Total, Unread, and/or Size.