Right now there is no way to delete your account. We do this to keep the load on our database down, because deleting an account is a very intensive process.
The simplest thing to do is to simply stop using the account if you are no longer interested in playing. It will remain there for you, if you should ever decide to use it again. Eventually we will simply consider it inactive.
If you are concerned about email, there are email settings under Options. We promise that if you uncheck all the boxes you will never hear from us again.
If you want to delete your account because you don’t like the class you chose, please see this article.