When converting large OST files (4 GB and above), you will have to use a 64-bit computer system. All program components required for converting OST to PST must be 64-bit. These include:
This allows you to bypass the limitations on the RAM that can be used by each component and convert OST files of virtually any size.
Once all necessary components have been installed, run Recovery Toolbox for Outlook and perform the following actions:
The process of reading the OST file and then exporting it to PST takes a significant amount of time. The time it takes to convert OST to PST depends on your computer's performance, particularly the speed of your disk subsystem.
Note: When you install Microsoft Office or Microsoft Outlook, the 32-bit version is installed by default. To install Microsoft Outlook 64-bit, read the following article: https://outlook.recoverytoolbox.com/faq-install-microsoft-outlook-64.html.