You want to create a Content Filter Rule and apply the rule to all mailboxes on the Exchange Server.
For example, you want to create a content filtering rule to detect a particular category of subject-line violations that are associated with a new threat, and then run the scan immediately.
Content filtering is not picking up violations already in the store, even though the content filtering rule is set to scan "Internal messages (store)."
Content filtering will not be applied against items already in the store unless a scan of some type is triggered against the item.
Create a content filtering rule, and then apply that rule to a manual scan.
To enable content filtering scanning:
To apply content filtering to a manual scan:
Your content filtering rule will be applied to the internal message store as the scan proceeds.