It is common for people to mark a read message as unread because it requires further attention. However, having all read messages in the same folder can distract from your unread messages. Hide your read messages so that the focus is on the new messages.
Thunderbird Mail – Show only unread email
To see only unread email in Mozilla Thunderbird, follow these steps:
Select the Quick Filter toggle button in the toolbar just above your messages.
The Quick Filter toolbar appears directly below the button.
