I've moved this post from Roll Call to AntiVirus Discussion as this might be a virus/worm and because people cannot respond to roll call posts. Perhaps you could post the email itself so that people could see it? (Remove any parts you feel necessary for privacy issues -- e.g., emails, ips). Sometimes the wording of the email can be helpful in determining whether it's valid or not.

I have done search for "Caster" in both members and posts and haven't found anything that matches.