If you are looking for a solution that helps to merge and delete duplicate Outlook contacts, then you can go with the FreeViewer Outlook PST Merge Tool (https://www.freeviewer.org/pst/merge.html). This software works the PST file of Outlook 2019, 2016, 2013, 2010, 2007 and other versions.

It allows the user to combine and delete duplicate entries in Outlook contacts (https://www.freeviewer.org/blog/combine-delete-duplicate-entries-in-outlook-contacts/) without loss of data integrity. The tool supports to merge multiple PST files into a single file with all emails, contacts, and calendars.
 

Today there are many tool for split pst file but trust me i suggest you best ever pst split tool which can instantly convert your pst file without wasting you costlytime. Any type of users can easily split pst file through this tool because you don't need any technical knowledge for this tool. this tool Creates several independent PST files by splitting large PST file. The user can split large PST file according to date, email type and user nameOriginal formatting and order of mails are retained in the new PST file. It supports splitting of PST file which is password protected, i'm telling you again No extra technical skill is required to use this tool as it uses self explanatory graphical interface.

to checkout this free tool click here:- http://www.undeletepcfiles.com/split-pst-file.html

 

What is the best technique to merge multiple PST data files into one?

To split large PST file of MS Outlook 2016, 2013, 2010, 2007 using Split PST Tool. It is the best and comprehensive solution with the help of which you can Break Large PST File into multiple PST files, without harming the original content of the main PST files. It undergoes deep scanning and gives out the new PST files without data alteration. It strongly supports the all versions of Microsoft Outlook and can install and run on any Windows-based operating system.

https://gallery.technet.microsoft.com/office/Split-PST-File-into-1d81cb14

PST Merge to quickly join, add or merge multiple PST file into single PST file including calendars, contacts and address book and other email items. PST Merge allows to combine multiple PST files such as email folders, address book, contacts, journals, notes, calendars, tasks to one single PST file.

https://gallery.technet.microsoft.com/office/Merge-PST-Files-into-One-420741c3

Download PST Merge software which is smart solution that without any data loss merge multiple PST files in single PST file. This PST Merge tool takes less time in merging process and is one of the safe methods that give the advance option to combine PST files i.e. - Merge PST, Join PST and Merge Contacts as well as you can also Remove Duplicate Items and Exclude Deleted Items from PST file.

Read more at:  PST Merge software