If you are wondering a 3rd party software/ tool to convert MSG to EML format then I will personally suggest you go with Total Mail Converter This tool helps you to manage your emails outside your email clients. This tool has the following features: 1. Convert MSG or EML to PDF 2. Friendly User Interface 3. Easy to Use 4. Exporting Feature You can give a call here - 1-855-418-2323.
If you are wondering for the easiest way to convert EML to PST, then I personally do recommend you to go with Total Webmail Converter. This converter is easy to use and not only it converts EML to PST but you can also convert several emails and organize emails with new names. If you want to generate a report of your emails - this converter helps you there too. I don't know how much it costs but you can use its 30-day free trial.