If you want to know how to open EML files in Outlook so I recommend you eSoftTools EML to PST converter this tool because the key features of this software are amazing you can add unlimited EML & EMLX files for migration to PST files and also multiple files and protect your email attachments in a good format. Gives you a naming convention option, and shows you the preview of EML files. You can take the benefits of a free demo which is free of cost.