You can either remove zimbra completely and start from scratch and enter the correct domain name, you can rename your current domain name to your correct name or you can create a new domain of the correct name and set it as the default and create all your accounts in that. This subject has been covered many times in the forums.
Is it better to rename the domain through the command line or through the web management console? I ask because i tried changing the domain name through the web console and it made ZCS unstable and unusable
Before i make any change and i have to restart from scratch what are the locations i should backup to have all the zimbra files covered in case i need to restore them; and do i need to stop the ZCS services before i start backing them up?