These spam messages are usually the result of random email generators, of email address harvesting from somewhere you have published you address or from an unprotected computer which has your address on it. What surprises me is the extent to which spam trying to sell me "enhancement" pills are disguised to get through spam filters. Surely if I was interested in buying these things, I wouldn't be trying to block the emails. I'm also surprised that these products appear to originate from a Canadian company, which if genuine has not been closed down. I haven't yet been targeted with the Undelivered Mail spam, but I'm sure it will happen.