For seamless merging of multiple PST files together in Outlook, it can be done with Regain Outlook PST file Merger. With this tool, it is quite easy to combine several PST files into one, without losing folder structure, email properties, and metadata. It has the support of ANSI and UNICODE PST files, including password-protected PSTs, and no duplicate files are added into the result. The program runs without requiring installation of MS Outlook and is compatible with every version of Outlook and Windows. It is possible to combine PST files with a simple interface even when the user is not technical. Try the free demo version and then purchase the full version for lifetime use.