Exchange 2010 SP1 has a new command to import and export to a PST.
First you need to give yourself permissions to do this with the following command:
New-ManagementRoleAssignment –Role “Mailbox Import Export” –User “<username>”
You will need to close down and open up the console again to gain access to the commands below.
Then you need to run the following to actually Export for a PST
New-MailboxExportRequest -Mailbox user@domain.com -FilePath \\path\to\file.pst
You can check on the progress of the backup with:
Get-MailboxExportRequest
You can clear any old Mailbox requests with:
Remove-MailboxExportRequest -Identity "username\MailboxExport"
Very simple!