It is quite tedious to backup and restore individual mailboxs in exchange server. Reason being that there is one database file for the whole mailbox store. There are two types of mail box stores, one is the private one that holds most of the mailboxs and then there is a public mailbox store.
In order to restore a single mailbox store, one has to go through the process of restoring the whole mailbox store on a separate exchange server and then extracting the specific mailbox to a .pst file which is then retored on a separate email account.
The details of this process can be found on the microsoft site at
in addition details are listed at this link also