If you open Mozilla Thunderbird in the classic view you are looking at a window that is divided into two areas. The left sidebar contains the email folders while the right window the emails that are contained in the folders and the contents of the selected email.

Thunderbird displays the same icon in the header of the folder and email area to change email display options. The display options can be accessed by left-clicking on the icon which will reveal several display options that can be enabled or disabled with another left-click.

The folder pane offers the three additional display options unread, total and size. Unread will display the unread count of folders, total the total amount of emails in a folder and size the size of that folder on the computer’s hard drive. These options offer several new ways of working with Thunderbird. It is for example possible to see the largest folders or the folders with the highest unread email count on a glance.

The very same display option menu is available in the email list in the right pane. This one contains additional display options that will display the information in additional columns in the same window. This includes sizes, email accounts, recipients, tags and about a dozen more.

These options can again be used to display additional information providing options to display and sort emails by size, recipients or email accounts. The two email display options described in the paragraphs before can for example be used to discover and delete the biggest attachments or emails of a webmail account like Gmail, Yahoo Mail or Live Mail.