Im just going to assume that you have no malicious intent ..But If you plan on doing spamming runs , forget it , it's stupid and illegal . But this is a site where you learn things , so the thing to do to send mail from a different ip would be to first find a wingate , then telnet to a mail server and send it through there. But something like that is probably illegal , so don't bother. And by the way , don't rely on 'progs' to do all the work for you , setup a linux box with a mail server and learn how to use smtp or something.
-N