After adding an email (.eml) as an attachment to a message you are sending with LM the attachment is not received and the log contains rows like:
Found Message-ID in body of list posting, so informing sender (email@example.com)
and discarding mail. where
firstname.lastname@example.org is the sender's email address.
When LM is processing the message the .eml attachment is interpreted as a separate message, not an attachment. In order to deliver the information successfully, convert the .eml file to a PDF or Text file and attach it to your message.