For combining several PST files in Outlook, Regain Outlook PST Merger is the best tool. All of your vital data, such as contacts, calendars, and emails, are preserved when you use this robust tool to easily merge many PST files into a single, manageable file. It guarantees that the email integrity and original folder structure are preserved and supports both ANSI and UNICODE formats. Installing Microsoft Outlook is not necessary for the software to function, and it removes duplicate emails when merging them. Every version of Windows and Outlook can use it without any issues. You can test out its features with a free sample version.