Some thoughts: "No subject", may have been sent that way. "Undisclosed recipients", this was sent to multiple addresses and sent as BCC (Blind Carbon Copy). Actually I prefer people sending to me in that form since my email address does not get spread around and when a spammer gets the message he will have a bunch of valid addresses to spam to. Look at some of the mail you receive and you may see hundreds of email addresses plainly displayed. Anyone sending mail to me with my address showing with all the others is politely asked to send mine BCC. If not, don't send me any more mail. Amazing how my spam has dropped to zero with my new email address.
"No Message", this could be a test to see if your email address was valid, also a spammer trick.