Thanks for using the forums to get this issue with your Online Security looked into, I am sorry if this has been causing some frustration. I would be more than happy to look into this for you. Our Internet Security team are incredibly thorough with their work around spam emails and security, if you've received this letter then all you need to do is follow the instructions to protect yourself.
You mentioned you don't use the email account, is it one of ours? If yes, do you want it removing from the server so it can no longer be used for sending out spam emails?