Split large PST files with vMail PST Split Tool However, as Outlook data grows over time, users often encounter the challenge of oversized PST (Personal Storage Table) files. Large PST files can lead to performance issues, corruption risks, and difficulties in managing emails, contacts, calendars, and other important data. This is where the vMail PST Split Tool proves invaluable. Split large PST files with vMail PST Split Tool. Why Split PST Files? Outlook PST files store emails, attachments, contacts, calendars, tasks, and notes. As these files grow beyond the recommended size limit (50 GB in Outlook 2019/2016/2013), they become more prone to errors, slow performance, and even data corruption. Splitting PST files into smaller, manageable parts helps users: