Deleting messages requires two steps. Thunderbird supports two methods:
Method 1: Using a Trash folder
- Select a message and click Delete from the Toolbar.
- Select Empty Trash from the File menu.
- Select a message and click Delete from the Toolbar. The deleted message is displayed with an X and strikethrough text.
- Select Compact Folders from the File menu. All folders which contain messages flagged for deletion are permanently deleted.