Chances of you finding a good e-mail server, one that accepts e-mail without logging in or anything are pretty bad, and this isn't really hacking. Also, leviatan is right, after some bombing, you server will probably cut you off, most open smtp servers do. Also, they will most likely have your ip so if your victim gets active and tracks you down, you could be caught. And don't think a dial-up ip will save you, they probably log who got what ip when. So just don't use them.