The same thing has been happening to me. I don't think it's the Sobig Virus. It's been happening for some time now. I have an updated Anti-Viral software installed, and just finished scanning for Viruses. None Found. I don't have the answer to what could be causing this, just that it's a pain just like getting spam. Delete the mail and deal with it I guess. Yes you could block the sender too, but since it already out there, I keep on getting email from different daemons. Oh well!!!