Zimbra Desktop attempts to combine the familiarity and power of Webmail with the convenience of conventional desktop e-mail clients, such as Outlook Express or Mozilla Thunderbird. It installs as two major components. The first is a desktop application that provides a UI similar to the standard Zimbra Web-based e-mail client. The second is a server that runs in the background, silently caching messages from your e-mail providers to the local disk.

When your PC has access to the Internet, Zimbra Desktop works pretty much just like an ordinary Webmail service. You can access messages from your AOL, GMail, Yahoo Mail, or any other POP/IMAP accounts, just as you would normally.

The difference is revealed when you lose your network connection. Because of the local cache, you can view previously-received messages just the same as if you were online. You can even compose new messages and Zimbra Desktop will synchronize them with the server the next time you’re online.