If you don't want to lose your PST files database while merging PST files that I want to recommend MailsDaddy PST Merge and JoibnTool. It safely combines multiple PST files into a single PST file. Here users can merge password-protected PST files into a new PST file. The software enables users to combine ANSI, Archive, and Unicode PST files into PST files without any changes in the original database. Users can skip the duplicate items while merging PST files. It provides a compatible PST file that can be imported into all Outlook versions.