To make it easier for Google Apps admins to locate specific emails in Google Vault search, Gmail labels are now included in search results. Admins can now view both system labels―i.e. the status of the message as viewed by the user – Unread, Inbox, Spam, Sent, etc―and user-applied labels:
To view Gmail labels and basic header information for a message, click show details in your Vault search results.
Gmail user label metadata will also now be included in XML file exports to aid with deeper analysis.
Reference : Google apps