The easiest way to import EMLX files into Thunderbird is to convert them into a compatible format like MBOX, which Thunderbird supports. You can do this using the third-party tool Aryson EMLX Converter. This software allows you to convert EMLX files to MBOX and other formats, then easily import them into Thunderbird. The tool also offers features like removing duplicates, excluding attachments, and batch processing, making the migration process smoother. If you prefer a more hands-on approach, you can manually drag EMLX files into Thunderbird, though conversion to MBOX is generally recommended for better compatibility.