A bug enhancement request has been made regarding this issue. It's an old request. No idea why it's not been fixed. https://bugzilla.mozilla.org/show_bug.cgi?id=551363 Currently, if you open email in tab and you leave it open in tab and later need to read email again then select the tab which is already displaying the email. The mail tab - the folder you have selected will always be on the far left which means it's easy to locate when you want to select it to get back to the Folder Pane view. Any tab can be closed by using the 'x' displayed in the tab area or right clickon that tab and select 'Close tab'. You can also close all opened tabs in one go by right clicking on the first tab eg: Inbox and selecting 'Close all other tabs'. For email opened in tab - If you move that email or delete that email and you want the tab to close automatically then check this setting: * Settings > General * scroll down to 'REading and Display' * select checkbox 'Close message window/tab on move or delete.