In the legacy Yahoo Desktop Mail, there is a toolbar on the right (when message preview is shown below the email preview list) that has buttons for "Contacts, Calendar, Notepad, Help, Settings".
This should be moved to the left column (above or under "Compose") and free up about 25% of the screen real estate. Or at least put in an option to remove the toolbar from view.
This change would be vastly better and an improvement on even the new Mail screen.