Personal folder (.pst) files may or may not be an issue for your organization. If the goal is to recentralize end user's .pst files onto the new target system, it might be reasonable to propose the relocation of .pst files on the new platform as part of the migration.
One potential solution is for end users to upload their .pst files (in non-encrypted form) to a shared file system before the migration takes place. Operators performing the migration reload the .pst files in a special place of a slave Microsoft Exchange server and apply the migration tool with a special mode. End users then receive their .pst files in an `archive' folder hierarchy, which is printable and lists folders in a special area of the Messaging Server.
Other alternatives are possible. Consult with your Sun representative for more information.