Check the default settings configured in the Enterprise Vault Site properties.
In the Administration Console, right-click your Enterprise Vault Site.
Site properties include the following settings that are applicable to archiving from Domino servers. Note that you can override some of these at a lower level. For example, you can override the Site archiving schedule for a particular task by setting the schedule in the task properties. The indexing level can also be set at policy level and the default retention category can be set at provisioning group or policy level.
Click Help on any of the Site properties screens for further information.
Now you can create provisioning groups for the mailboxes that are to be archived.