Manual methods for migrating OST files can be quite complex and often require Outlook to be properly configured with the original mailbox profile. They may not work with orphaned OST files and can become time-consuming when dealing with large amounts of data. Instead, I would recommend the CloudXena OST to Office 365 Migration Tool. It allows users to migrate single or multiple OST files directly to Office 365 without Outlook. The software also supports conversion to PST, PDF, MBOX, EML, and other formats. Features like mailbox preview, date-range filtering, duplicate email removal, attachment exclusion, and large file splitting make the migration process much easier. Additionally, it supports migration to Thunderbird, iCloud, and other email platforms and works seamlessly on both Windows and Mac systems.