You may be seeing the "Correspondents" column for the first time. Have you recently updated to a current version of Thunderbird? Many users seem to just leave all their incoming messages in the Inbox and all their sent messages in the Sent folder. In this case, in the Inbox you want to see who a message came from, so you have a "From" column. In the Sent box, you know who sent it (you!) but you need to see where it was sent to and you have a "Recipient" column. My choice is to file associated messages together. For instance, messages to and from my wife or sons are filed in their own folders, and so I have a mix of incoming and outgoing messages in these folders. In this case I'd need both "From" and "Recipients" columns to fully understand the conversational flow, and half of the addresses I saw would be my own and so would be rather a waste of space. The "Correspondents" column is useful because it simply shows the addresses of the other parties in a conversation. It adds an arrow to remind me of the direction of the message; to me or to someone else. If you right-click "Correspondents" , "Date" or any other column headers, you'll get a drop-down dialogue where you can pick which columns you see. You can restore "From" and "Recipients" if that's what suits you. You can also drag columns into different positions and alter their widths.