MacSonik OST Viewer Pro is an enterprise-grade solution for securely opening, viewing, and analyzing Outlook OST files of any size on Mac and Windows. It supports active, orphaned, inaccessible, and password-protected OST files without Outlook. Users can preview mailbox data, export to PST, PDF, EML, MSG, MBOX, and CSV, or migrate directly to Microsoft 365. The tool preserves folder hierarchy, ensures data integrity, and processes all data locally for maximum security.