If you need to 'hold the left arrow' then this tells me you have been opening loads of new tabs, and now there are so many opened tabs, the left and right scroll type arrows have been forced to be displayed in order to move through the various tabs that are in effect 'off screen'. As the last folder you selected in always in the first tab, then this would explain why you are 'holding the left arrow' in order to see it again. Is there are reason why you have so many tabs open ? Have you considered closing tabs after reading the email ? Each tab will have it's own 'x' on tab used to close that tab. You can also right click on tab and select from the options. Most people read the opened email in the 'Message Pane' which is below the 'Thread Pane' (list of emails). They only open new mail in a tab if it eg: a lengthy email. Do you see the Message Pane ? If no: Menu app icon > Customise > Layout > select 'Message Pane' It can also be made visible using F8 key as a shortcut. A single click on email in list will display it in the 'Message Pane' area. This is not a 'preview'. It is an opened email. When you select another email in the list, it will replace the previous one in the Message Pane. A double click will open email in eg: a new tab (default setting but there are other options like a new window). You can move the height of the Message Pane to get a satisfactory balance between the list of emails and the Mesage Pane viewing area. http://kb.mozillazine.org/Window_layout_-_Thunderbird https://support.mozilla.org/en-US/kb/how-change-thunderbird-layout