If a word mp3 file is sent over SMTP which extension is usend?

When a Word MP3 file is sent over SMTP, it is typically attached with the .mp3 extension. However, if the file is originally a Word document and then converted to an MP3 format (like an audio version of the document), it would still retain the .mp3 extension upon transmission. The email client recognizes the file type based on its extension and MIME type.