A great tool to open PST files without Outlook is SysInfo Free PST File Viewer. It lets you easily view emails, contacts, calendars, attachments, and more from PST files created by all Outlook versions, including both ANSI and Unicode formats. The software supports opening multiple PST files at once, works with large-sized PSTs without size limits, and preserves your original folder structure and data integrity. It runs on all Windows versions and doesn’t require Outlook to be installed, making it ideal for both personal and professional use.