To convert OST to PST without losing emails and attachments, you should avoid manual export methods, especially if the OST file is orphaned or Outlook is not properly connected to Exchange. Manual methods can sometimes skip attachments, disrupt folder structure, or fail midway with large files.

The safer way to convert OST to PST is by using a reliable standalone converter such as Sysinfo OST to PST Converter. This type of tool scans the OST file in read-only mode, which means it does not modify the original data. It allows you to preview emails, attachments, contacts, calendars, and other mailbox items before starting the conversion.
Read more: https://www.sysinfotools.com/ost-to-pst-converter.php