The wrong domain name is being shown in my signature files.

It should say http://www.wowhq.com and instead shows http://www.mithan.com

Now, the server was initially configured for Mithan.com, but I have wowhq.com on it and don't use Mithan.com.

How can I fix this?

Example:
http://www.wowhq.com/roster/addons/sigg ... mithan.png