For a long while now, e-mail spammers have attempted to bypass rules and filters, whether they be in place directly on your mail server, or set within your own application (Outlook, Eudora etc.) by using images, most commonly JPGs and GIFs that have their message pictured.
Even if I did dabble in the stock markets, I do not think I would ever take un-solicited advice on where to invest, but each spam takes time out of my day, and until recently, used up some of my monthly ADSL download as well.
Sadly, although spam prevention schemes have now started to be able to detect such image based spam, the spammers themselves have already moved on to other methods. PDF spam is their new attack system. BorderWare however are on the ball, and have already got their systems in place to deal with such spam. In fact, the system is able to monitor the trends in unsolicited commercial mail in real time, making sure your privacy and time remains guarded. If you are at all interested in the services they offer, you may also like to know that they help to protect you from web & Instant Messaging threats as well.