I have tried many free programs, but they were either too slow or didn't enable batch processing. I would recommend the WholeClear EML Converter. It supports multiple output formats, keeps the folder structure, and works well for batch conversion. It changes EML files into PST, MBOX MSG, PDF, and other file formats. It also works with a number of email applications, such as Outlook Express, Windows Live Mail, Mozilla Thunderbird, and others. It works well on all versions of Windows. It also has a free trial, which is great for trying it out before buying.

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