There have been a rash of particularly irritating viagra related email making it past our spam filters over the past month or so. The most irritating part is that they are spoofing email addresses, meaning putting someone else's email address in the from field even though it did not come from that person. Like spam itself, there is no way to prevent spammers from spoofing. The best thing you can do is educate yourself and know how to spot a fake. This article should be a good place to start. Read more.