Currently Notes and Domino can show the attached EML file (sent from Outlook) as an attachment (EML file) if it is mentioned in MIME source as below. You must have the parameter "MIMEAttachNestedMessages=2" set.
Content-type: "message/rfc822 eml"
Content-disposition: attachment; filename="filenamexxxxxxx.eml"
Notice the "eml" at the end of Content-type and name of aattachment is must as per design, since an attachment can't be shown without name.
However if the MIME source generated by the sender is like below which does not specify "eml" in Content-type and no filename is mentioned like this,
Then Notes/Domino can't show attached EML file and the content is assumed as plain text RFC822 and contents are simply shown in body of the mail.
So there is an Enhancement Request that, Notes/Domino should show the attached EML file even if the MIME source is like below (without filename and Content-type set to eml)
This Enhancement will enable the display of EML attachments properly when they are generated from multiple senders irrespective of problem in their generated MIME source.