I have had similar experiences to yours on occasion. Yahoo! advice is that, "you should immediately change your email password and that is really about all you can do." (I have YAHOO! email). Changing the email password did stop the infractions and lasted for a couple of years before it happened again. I again changed the password immediately. That has been two or three years ago now. I am of the belief that if the hacker cannot "de-code" your password, they cannot gain access to your account. Are you using a strong password on your email account?