Zimbra Desktop lets you download your mail to your computer, similar to Outlook or Mac Mail. Unlike those programs, Zimbra automatically synchronizes with your webmail. Any changes you make in the program (marking mail as spam, sending a message, deleting mail) will appear in your web mail the next time you go online. This means you can have the security of having your mail saved on your home computer, while also being able to access it from any computer connected to the internet. Check out the article on how to setup Zimbra Desktop in the Help section under Email.