Sounds like something that is pretty common right now. "Someone" hijacks your email address and spam gets sent to everyone in your address book. There is nothing you can do about it. It won't send spam to everyone at the same time .It is a bot program that is doing it. It is not on your computer so cleaning your computer or a virus program will not stop it. Do your best to warn everyone in your address book NOT to open these emails and it they do, they should definitely NOT open any attachments or click on any links. From what I have seen and heard the only true way for this to stop is to close the email account.