During the course of business, a user's mailbox becomes unavailable because the .ost file is corrupted. The hosting company is asked to recover the mailbox.
The Microsoft Exchange Server 2007 product team recommends backing up mail stores regularly, along with deploying storage management software and "brick-level" restoration capabilities from one of the backup/disaster recovery Independent Software Vendor (ISV) partners of Microsoft.
We recommend that you use recovery storage groups to recover individual mailboxes. For more information, see Exchange Server 2007 Recovery Storage Groups. Recovery storage groups enable you to restore content, extract mailbox content, and recover databases.