The Zimbra Web Client is a graphical user interface (GUI) that includes windows, buttons, text entry, and mouse.
With traditional GUIs, leaving a window where you've done some work or made a change causes the application to pop up a dialog asking if you want to save your work. If you've worked with this type of software before, you may be in the habit of expecting the software to remind you to save your changes.
With a GUI that uses Internet browser technology to display and operate the user features, it is not always possible for the application to detect when you have done something that you might want to save.
Within Zimbra, the following rules apply:
If you are in the middle of composing an email message, and you click another portion of the Zimbra screen, you are prompted to save your work. You can subsequently find the message in your Drafts folder.
If you use the browser's Back button (as opposed to the Zimbra Close button), or you use that same browser window to navigate to a different site, you may not be prompted to save your work.
Reloading the Zimbra Web Client from the same browser window will continue your mail session, but you may lose any unsaved changes.