To split large PST files in Outlook, you can either do it manually or use a professional tool. Manually, you can create multiple PST files in Outlook and move data into them or use the Archive feature to separate data by date, but this method is time-consuming and lacks size control. For an easier and more precise solution, try the PST Splitter Tool by MSOutlookHelp. It efficiently splits PST files by size, date, folder, or email ID without data loss and supports both ANSI and Unicode formats, making it a reliable option for managing large Outlook files.