Change hostname and domain of server

So, I did the perfect setup...on ubuntu feisty...everything is set up and working fine; however, I bought an ssl certificate which is different from the info I used to set up the server...which is fine because port 81 works regardless of which domain. The problem is /mailuser tends to want to go back to the server's hostname and domain and gives the self-signed certificate error. So, my question: is there a simple way to change the server's hostname and domain? And will it affect ispconfig and everything else? If not, is there a way to make it so mailuser doesn't keep trying to use the server's domain?

Thanks.

 

in addition to changing it elsewhere? Or is these the only two places where I need to change it?

 

It still tries to switch back. Where else should I change it? I changed it once in each of the files you posted.

 

Is the value of ServerName correct in /root/ispconfig/httpd/conf/httpd.conf?

 

How to change hostname and domain in fedora 10

System -> Administration -> Network
Select DNS tab and change the fully qualified hostname.
Reboot

 

If you're handling email then you also should change /etc/mailname; in my case ISPConfig / postfix attempted and failed to deliver to users@the old hostname until I changed it in this file.