Legal Question in Credit and Debt Law in California

No you cannot be sued by email. It is 99.999% sure they are con artists, probably overseas. It is quite possible they also sent you a virus if you opened their email. You need to run a deep virus scan immediately, and change passwords on your accounts.

In addition, to be sued, you must be personally served with the summons and complaint or, after several tries, they can serve an adult at your residence and mail it to you at the same address. To reassure yourself, go to your local courthouse (or perhaps by computer) and search for a case with your name. Please do the virus scan, too!