I posted in another forum to discover that whilst the Evernote search facility is amazing with notes, attachments like PDFs, JPGs, etc it can not search .eml files.
Its easy to drag and drop an email from Macs Mail program into a note and it shows as an attachment and is easy to open or quick look. But sadly Evernote does not search these .eml files. I am not really sure why.
I know you can email a note - but this makes it tricky if you don't necessarily want to show the whole content of the email "in-line" but may need that info later. Email file attachments sit neatly on your note and if you want to view it its easy to see - but really the search facility on these files is a must?