Different approach to
merge PST files without creating duplicate copies can be done either manually or by using some particular programs. In Outlook, you can use the import export wizard to create a new PST file by importing items from other PST and you can tick the box that states replace duplicates. But it can be time-consuming particularly if one has many files..
In this case, it is advisable to use a specialised tool for reaching the PST, which would mean that the process will be carried out with the immediate elimination of duplicates. Out of all the merging tools, I suggest
Shoviv PST Merge Tool as it is effective in merging several PST files with high efficiency and ensuring user data is preserved and well-organised.