Aspose.Email can convert 5gb to 10 gb OST file to Different Formats Like PST,MSG, EML, EMLX and MHT etc.
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Aspose.Email has the capability to process large OST files and extract messages from these in MSG, EML, EMLX and MHT formats. In addition, the API has the power to convert OST to PST (and vice verse) with just a single line of code as shown in our online article Read and Convert Outlook OST. Please use the latest version of Aspose.Email for .NET and let us know if we can be of any additional help with respect to your any query in this regard.