The spammer sends out millions of innocuous e-mails and may get a slightly different response from the mail server if the mail has reached an actual person. Once the spammer has established that certain addresses are valid, he can send his real spam and be sure that he's reaching an inbox.
All of this sounds perfectly reasonable. Spammers are doing bizarro things to get their messages out. But why do I sometimes get a spam with the subject line "$subject"? Why would I ever be fooled into thinking that was a piece of legitimate e-mail? "That's just some spammer who doesn't know how to use his spamware," Quinlan said. "Sometimes spammers do things that are — for lack of a better word — dumb." SFBG
Annalee Newitz is a surly media nerd who is in recovery from receiving spam.