My tin-hat is defiantly on too tight. But having been browsing around in my spam mailbox I noticed how easily messages could be inserted into spam as meda-data. Random sentences containing messages, either encrypted, or just random ordered words could be sent from any email system, with no accurate return address, to any other destination without arousing suspicion.
It’s almost like shortwave radio, broadcasting from any location to any receiver. The receiver can even acknowledge the receipt by responding to the URL to trigger the acknowledgment.
Update: I never got to my point, sorry, we may all be receiving terrorist emails. 😉 Now, go and recheck your spam.