Pressed by increasingly effective anti-spam efforts, senders of unsolicited commercial e-mail are resorting to outright criminality in their efforts to conceal the source of their ill-sent missives, using Trojan horses to turn the computers of innocent netizens into secret spam zombies.
It seems that the blocking of open mail relays and known spam-hosts might actually be working, as spammers are starting to clearly break the law, by utilizing trojans like this one, to reach their targets.
I despise spam and I get way too much of it. Leave an email address on the internet for a couple of days, and you can wave it goodbye.
If you can, sign up for a temporary email address at one of the services that provide those whenever you sign up for something on a somewhat shady website. Or look into something like TMDA.