Yes!  Parablu can backup PSTs, even if they are in use and locked by Outlook.  Parablu is designed to get logically consistent copies of files even if they are in use.  With files such as PSTs, Parablu also uses a special algorithm called a ‘partial file transfer’ to accomplish what the industry refers to as delta-incremental backups.  In this situation, large flies that are changing each day are not backed up in their entirety.  Instead, Parablu tracks which portions of the files have changed and only transmits those for backup.  Ofcourse when the entire file is requested back by the user, Parablu has the smarts to piece together all the right components from the different backup runs, in the right sequence, decrypt and supply the correct file version back to the user.