Microsoft Outlook 2002 and earlier versions support ANSI file format that has a size limitation of 2 GB. On the other hand, Microsoft Outlook 2003 and later versions support Unicode file format that has a size limitation 20 GB to 50 GB. If you're looking for a way to upgrade PST file from ANSI format to Unicode format, refer to this article -
Upgrade Outlook PST – ANSI to Unicode & Unicode to ANSIIn the above article, you'll learn how to upgrade PST file manually without using any paid software. I hope the shared information would be helpful here.
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