Outlook is unable to function with large numbers of EML files at once, although some email clients can. You can open single EML file at a time, but it's difficult to manage a lot of them. One of the easiest method to use them in Outlook is to convert EML files into PST files which Outlook uses. After you change the email you can open it in Outlook by navigating to File, then Open & Export and then Open Outlook Data File. Your emails will be in folders in Outlook. If you have batch EML files a conversion tool can help you keep them organized and save you time. Some users mentioned programs like Softaken EML to PST Converter can help with this, especially when moving many emails into Outlook
Visit here: https://www.softakensoft...o-outlook-converter.html 

To use EML emails in Microsoft Outlook, you can convert them into PST format. PST is the default Outlook data file that stores emails, contacts, calendars, and more. By converting EML to PST, you can easily import and access all your emails in Outlook without losing attachments or formatting. MailsDaddy EML to PST Converter helps users batch convert EML files into PST format with complete data accuracy and an easy-to-use interface.