The best software to split oversized PST files in Outlook is Regain Outlook PST File Splitter Tool. It provides efficient and flexible options to split large PST files by size, date, or sorting emails by sender, recipient, or subject. The tool preserves all important email details, including attachments and timestamps, ensuring data integrity. It’s compatible with both UNICODE and ANSI PST files and works seamlessly with all versions of Outlook. With a simple, user-friendly interface and a free trial available, Regain PST Splitter Tool offers a reliable, cost-effective solution for managing large PST files in Outlook.