In previous versions up to and including 4.0 customers had wanted the ability to place the email from PST files directly into the mailbox in Archive Manager.
In the previous versions, when you imported a PST, it created a PST type mailbox and associated it to the view for the user. The mail could not be merged using any of the out of box utilities provided by Archive Manager.
The 4.0.5 version of Archive Manager now has the ability in its PST importer to import the mail directly to the users AM mailbox.
Install 4.0.5 and refer to the Archive Manager Administrator Guide on page 95 for instructions.