If you are looking for error-free solution to convert EML files to MSG format then I will recommend you try ZOOK EML to MSG Converter tool. The software provide easy EML to MSG migration to convert EML files to MSG format with an attachments. It is completely secure and preserves EML emails formatting during conversion process. Users can preview of EML files just before final EML to MSG conversion. It is fully supportable to Outlook 2019, 2016, 2013, 2010 and all old versions. The free trial version of the software also available for all new users.
For more info- https://www.zooksoftware.com/eml-to-msg/