Procedures for mailbox exports to .pst files in Exchange ...
In the EAC, go to Recipients > Mailboxes > click More options, and select Export to a PST file. The Export to a .pst file wizard opens. On the first page, select the source mailbox, and then select one of these options: Export only the contents of this mailbox. Export only the contents of this mailbox's archive. When you're finished, click Next.