In Exchange Server, items are categorized by message class. Enterprise Vault comes with a predefined set of message classes that identify different types of items. This list is defined on the Message Classes page of the Directory properties. You can add or remove message classes on this page. Note that this list of message classes applies across the Directory, not just to the site.
Table: Predefined message classes lists the predefined message classes and indicates which types of messages are archived by default.
Table: Predefined message classes
With the exception of Exchange Journal archiving, Enterprise Vault archives items whose message classes match the text listed. Exchange Journal archiving stores all items that are sent to the journal mailbox, irrespective of the message classes configured.
When adding message classes to the list in the Directory properties, you can use a trailing asterisk as a wildcard. For example, a message class of 'IPM*' would include 'IPM.Appointment', 'IPM.Contact', 'IPM.Document', and so on.
If required, you can customize the message classes to archive in Exchange Public Folder Policies or Exchange Mailbox Policies.