Check at the top of the site for a file called .htaccess (you may have to enable your FTP client to allow viewing of hidden or dot files). This is the most likely method that the site is being redirected with.
Then it's not a .htaccess file that's doing it if you haven't got one at the site root and it redirects when you browse to http://www.mydomain.com. Next stop would be to have a look in your /etc/httpd/conf/httpd.conf file and search for the <VirtualHost></VirtualHost> directive for the domain incase it's been changed manually. This is usually unlikely as it would be overwritten when/if you modified the site through the UI. You should also check in your /etc/httpd/conf/srm.conf incase anything has been entered there relating to the site.
Thanks for pointing out httpd.conf & srm.conf, which showed me how to fix it. Now I just need to find the right file. Is there a linux command you know of that you can search by a word or phrase in a file? If I could search on command line for "Alias fakename realname", I could then edit my file...
it depends on the editor you are using, if you are using pico then you would use control-w to search for a word/phrase, if you are using vi then you would hit ":" and then type what you are looking for and hit enter.