If you need an offline OST to PST converter, especially for an inaccessible or orphaned OST file, WholeClear OST to PST Converter is worth considering. It can convert OST files to PST without requiring Outlook or an Exchange Server connection. The tool provides a preview of mailbox data and allows selective conversion of folders or items, including emails, contacts, calendars, notes, and tasks. It also preserves the original folder hierarchy, email metadata, and attachments during conversion. For larger OST files, the software states that it has no file-size limitation. I would recommend previewing the OST first, converting the required data, and then opening the resulting PST in Outlook to verify emails, attachments, and folders before keeping the converted file as the working copy.
