Your view may have been switched and you are missing the preview pane, or the appearance of your Zimbra is… unusual.
If Zimbra looks condensed or the font is not what you are used to seeing, perhaps you can’t access your Local Executive mailbox, or the tabs, buttons and features don’t quite look right – check to see if your view has been switched to HTML and change it back to the Advanced view.
Click on Preferences (the tab shown above with the gear icon to the left).
Next, click the radio button to the left of Advanced (AJAX)
Click SAVE, log out and log back in to Zimbra.