Your server username is different from your Slamdot login email address. You will have a server username for each of your hosting plans. Your server username is for your primary email and FTP accounts, as well as your primary database and FrontPage access, whereas your Slamdot login email address is used to login and manage all of your hosting plans.
To find your server username, from your Dashboard look to the right in the “Connection Settings” box. Your server username will be listed here, along with the mail server, FTP server, and IP address.