The best way of splitting Outlook PST files is by using third party tool, it's easy and effective, and less time-consuming. But there are some DO IT YOURSELF methods also available. Actually, there are three simple ways to split your Outlook PST file 1. Archive them 2. Import & Export them and 3. Move to Folder There is an article How to Split PST, in this article the both Option has been discussed. I hope this will helps.