Warning: By selecting this option, you confirm that this computer complies with your organization's security policy. The Light client provides fewer features and is sometimes faster. Use the Light client if you are on a slow connection or using a computer with unusually strict browser security settings. If you are using a browser other than Internet Explorer 6 or later, you can only use the Light client. Connected to Microsoft Exchange.
Note that your web browser or display does not fully support the Advanced version. We strongly recommend that you use the Standard client. The leader in open source messaging and collaboration : Zimbra Blog.