Sounds like I'm not the only one then...
Interesting page that seems to be talking about the same thing
http://www.spamnation.info/stocks/FAQ.html
Short excerpt
"Is there anything I can do?
The best thing is to try to filter the spam. Unfortunately, this isn't easy. Stock spammers try particularly hard to avoid spam filters. Recently, many of them have taken to sending their messages as embedded images accompanied by random 'hashbuster' text in order to get past filtering."