If you log in with you email account and password you will be immediately be able to change your settings for that email account.
If you log in with your domain name and password you will see a link to Email. Click it to manage your email accounts.
Once clicked you will see a list of email accounts.
To manage an email account click the wrench and screwdriver.
To delete the account click the garbage can. Be sure you want to delete the account. Once you do, the account and all emails associated with it will be permanently deleted.