To merge the PST files in MS-Outlook then trying to use of KDETools PST Merge. It joins Various PST files in MS-Outlook. It Combines PST files such as Emails, Contacts, Calendars, Tasks and all. It supports in all Version of Windows and Outlook. During Joining PST files this tool easily removes the duplicates PST files. It joins only selected PST files or folders. Capable in ANSI and also UNICODE formats. It has not required of MS-Outlook.
More Info: http://www.merge-pst.com/
if you want to merge your multiple PST files into a single one, then use the fastest and safest Merge Outlook PST Tool, which can easily combine your multiple PST files into a single one without any hassle. It preserves original data while combining PST files. Also supports the merger of both ANSI and UNICODE files in Outlook PST. You can also use the trial version of this software. Visit here for more info: https://www.softakensoftware.com/merge-outlook-pst.html